Mantle surface topography for optimum energy transfer in multi-layer golf ball

BACKGROUND OF THE INVENTION

[0002] Generally, golf balls are one of three types. A first type is a multi-piece wound ball wherein a vulcanized rubber thread is wound under tension around a solid or semi-solid core, and thereafter enclosed in a single or multi-layer covering of a tough, protective material. A second type of golf ball is a one-piece ball formed from a solid mass of a resilient material which has been cured to develop the necessary degree of hardness to provide utility. One-piece molded balls do not have a second enclosing cover. A third type of ball is a multi-piece non-wound ball which includes a liquid, gel or solid core of one or more layers and a cover having one or more layers formed over the core.

[0003] Attempts to improve and/or optimize performance characteristics in golf balls are typically directed toward achieving better feel when the ball is struck with a golf club, and also allowing for increased or optimum distance while at the same time adhering to the rules set forth by the United States Golf Association (U.S.G.A.) regarding the physical characteristics and performance properties of golf balls. These rules specify that the weight of a golf ball shall not be greater than 1.620 ounces, the diameter of the ball shall not be less than 1.680 inches and the velocity of the ball shall not be greater than 250 feet per second. The U.S.G.A. rules also specify that the overall distance a golf ball should travel shall not cover an average distance (in carry and roll) greater then 280 yards.

[0004] Over the years, attempts to improve characteristics such as feel and durability have centered around the materials used to form the various layers of a golf ball.

[0005] Improvements in spin and distance characteristics are usually directed toward the actual construction and physical makeup of the golf ball. The use of one or more intermediate layers between a core and a cover layer to achieve such improvements is known in the art. The thickness and/or material hardness of each layer may also be varied in order to achieve a desired property.

[0006] Attempts at improving spin and distance characteristics have included employing a core or inner cover layer that utilize an outer surface with a particular configuration. Specifically, U.S. Pat. No. 5,836,834 and U.S. Pat. No. 5,984,807 describe golf balls that use inner cores with certain shaped projections. Both the '834 patent and the '807 patent also describe forming another core layer around the inner core such that the core is essentially a concentric, smooth surfaced dual core.

[0007] U.S. Pat. No. 5,820,485 describes a golf ball employing an inner cover layer having a collection of projections. An outer cover layer covers the inner layer.

[0008] In general, there is a natural transfer of energy that occurs within a golf ball when the ball is struck by a golf club. Energy is transferred from the club face to the golf ball cover, and then subsequently transferred through each layer beneath the cover. In solid non-wound golf balls employing spherical layers, energy transfer is generally a function of the thickness and material composition of a given layer.

[0009] Therefore, varying either the thickness of a given layer and/or the material from which a layer is made affects the efficiency of energy transfer occurring within a golf ball and consequently affects the overall performance characteristics of that ball.

[0010] There still exists a need for a golf ball design that improves the energy transfer occurring within a golf ball, after being struck by a golf club, such that the design may be varied in order to achieve different, desirable performance characteristics.

SUMMARY OF THE INVENTION

[0011] An object of the present invention is to provide a multi-layer golf ball, in which one or more intermediate layers have a unique surface configuration.

[0012] Another object of the invention is to provide a multi-layer golf ball wherein one or more intermediate layers have a protuberant surface configuration as described herein.

[0013] Yet another object of the invention is to form a multi-layer golf ball, in which one or more mantle layers have a protuberant surface configuration formed by a plurality of outwardly extending projections.

[0014] A further object of the invention is to provide a multi-layer golf ball having one or more mantle layers in which the properties of the ball are optimized by the surface configuration of at least one of the one or more mantle layers and the materials used to construct the ball.

[0015] Still another object of the invention is to optimize the transfer of energy occurring within a multi-layer golf ball, when the ball is struck with a golf club, by providing a surface interface between adjacent layers that results in an efficient transfer of energy between the layers.

[0016] Yet another object of the invention is to provide a golf ball mantle assembly which includes a core and one or more mantle layers disposed about the core, wherein at least one of the one or more mantle layers has a protuberant surface provided by a plurality of projections.

[0017] A further object of the invention is to provide a golf ball having a cover layer disposed about a mantle assembly described above.

[0018] The present invention achieves all of the foregoing noted objectives and provides, in a first aspect, a golf ball mantle assembly comprising a core and one or more mantle layers disposed about the core. At least one of the mantle layers has a protuberant surface that is defined by a plurality of projections extending outward from the mantle layer.

[0019] In another aspect, the present invention provides a mantle assembly comprising a core, a first mantle layer disposed about the core and a second mantle layer disposed about the first mantle layer. Each of the first mantle layer and the second mantle layer have a protuberant surface defined by a plurality of projections.

[0020] In still another aspect, the present invention provides a golf ball comprising a mantle assembly that includes a core and a mantle layer disposed about the core. The mantle layer includes a plurality of outwardly extending projections that define a protuberant surface. The projections exhibit a geometrical shape selected from the group consisting of hemispherical, conical, cylindrical, and angled, having a height of from about 0.02 inches to about 0.06 inches and a base diameter of from about 0.05 inches to about 0.200 inches. The ball further comprises a cover layer disposed about the mantle assembly and immediately adjacent to the protuberant surface.

[0021] In yet another aspect the present invention provides a golf ball comprising a core, a first mantle layer disposed about the core having a protuberant surface defined by a plurality of outward extending projections, a second mantle layer disposed about the first mantle layer, and a cover layer disposed about the second mantle layer. The second mantle layer defines an inner surface layer comprising a plurality of depressions, and an outer surface layer having a protuberant surface defined by a plurality of projections. The cover layer defines an inner surface layer and a dimpled outer surface layer. The inner surface layer comprises a plurality of depressions. The depressions on the inner surface layer of the second mantle layer correspond to the projections of the first mantle layer, and the depressions on the inner surface of the cover layer correspond to the projections of the second mantle layer.

[0022] In a further aspect, the present invention provides a golf ball comprising a core, a mantle layer disposed about the core and a cover layer disposed about the mantle layer. The mantle layer comprises a protuberant surface configuration provided by a plurality of stepped projections.

[0023] Other objects of the present invention will become apparent upon a reading and understanding of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]
FIG. 1 is a cross-section of a conventional prior art non-wound multi-layer golf ball having one intermediate layer;

[0025]
FIG. 2 is a cross-section of a conventional prior art non-wound multi-layer golf ball having two intermediate layers;

[0026]

FIG. 3

a
is a schematic cross-section of a cover and a mantle layer in a conventional prior art golf ball having a smooth interface therebetween;

[0027]

FIG. 3

b
is a diagram showing the transfer of energy occurring between the layers of a conventional prior art golf ball having a smooth interface therebetween;

[0028]

FIG. 4

a
is a schematic cross-section of a cover layer and a mantle layer in a golf ball having a protuberant interface therebetween in accordance with the present invention;

[0029]

FIG. 4

b
is a diagram showing the transfer of energy occurring between the layers of a golf ball having a protuberant interface therebetween in accordance with the present invention;

[0030]

FIG. 5

a
is a cross-sectional view of a hemispherical projection of a protuberant mantle layer;

[0031]

FIG. 5

b
is a top view of the projection in FIG. 5a;

[0032]

FIG. 6

a
is a cross-sectional view of an angled projection of a protuberant mantle layer;

[0033]

FIG. 6

b
is a top view of the projection of FIG. 6a;

[0034]

FIG. 7

a
is a cross-sectional view of a stepped projection of a protuberant mantle layer;

[0035]

FIG. 7

b
is a top view of the projection of FIG. 7a;

[0036]

FIG. 7

c
is the cross-sectional view of FIG. 7a, further illustrating dimensional characteristics of the stepped projection;

[0037]

FIG. 8

a
is a perspective view of a mantle assembly of a first preferred embodiment;

[0038]

FIG. 8

b
is a cross-section of the mantle assembly shown in FIG. 8a;

[0039]

FIG. 9

a
is a perspective view of a mantle assembly of a second preferred embodiment;

[0040]

FIG. 9

b
is a cross-section of the mantle assembly in FIG. 9a;

[0041]
FIG. 10 is a cross-sectional view of a mantle assembly of a third preferred embodiment;

[0042]
FIG. 11 is a cross-sectional view of a mantle assembly of a fourth preferred embodiment;

[0043]
FIG. 12 is a cross-sectional view of a three-piece, non-wound golf ball employing a mantle assembly of the first preferred embodiment;

[0044]
FIG. 13 is a cross-sectional view of a four-piece, non-wound golf ball employing a mantle assembly of the first preferred embodiment;

[0045]
FIG. 14 is a cross-sectional view of a three-piece, non-wound golf ball employing a mantle assembly of the second preferred embodiment;

[0046]
FIG. 15 is a cross-sectional view of a four-piece, non-wound golf ball employing a mantle assembly of the second preferred embodiment;

[0047]
FIG. 16 is a cross-sectional view of a golf ball employing a mantle assembly of the third preferred embodiment; and

[0048]
FIG. 17 is a cross-sectional view of a golf ball employing a mantle assembly of the fourth preferred embodiment.

[0049] The above-referenced figures are not to scale, but are merely illustrative of the enclosed invention. In addition, several of the figures are schematic in nature. Specifically, the figures are for purposes of illustrating the enclosed invention, and not to be construed as limiting the invention described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The present invention is based on the discovery by the inventors that by incorporating a particular surface configuration between adjacent layers of a golf ball, such as between a core and cover layer or, core and intermediate layer or, between an intermediate layer and a cover layer or, between adjacent intermediate layers, desired performance properties may be obtained. In accordance with the present invention, a golf ball is provided that utilizes a surface topography at one or more interior layer interfaces that allows energy to be transferred between regions of the ball efficiently and in a manner such that desirable performance characteristics are achieved.

[0051] Multi-layer golf ball constructions are known in the art. Multi-layer golf balls typically include a core, a dimpled cover layer and one or more mantle layers disposed therebetween. The term “mantle layer” as used herein refers to any intermediate layer disposed between the core and the cover of a golf ball.

[0052]
FIGS. 1 and 2 show cross-sectional views of prior art three-piece and four-piece non-wound golf balls, respectively. FIG. I represents a three-piece, non-wound golf ball 10 having a core 12, a mantle layer 14 disposed about core 12, and dimpled cover layer 16. FIG. 2 represents a four-piece, non-wound golf ball 20 having a core 21, two mantle layers 22 and 23 disposed about core 21 and dimpled cover layer 24.

[0053] Mantle layers are often considered to contribute to a respective layer of a golf ball, i.e., they are typically considered part of the core or the cover layer. Standard convention is to consider a mantle layer a member of a respective layer based on the material from which the mantle layer is constructed. A mantle layer constructed of the same material, or material similar to that, as the core and immediately molded over or otherwise formed about the core would be considered a dual core or core assembly. Likewise, mantle layers constructed of material similar to that of a cover layer are typically considered an inner cover layer.

[0054] Conventional multi-layer golf balls are typically constructed from uniform spherical layers, i.e., layers having a smooth round surface. A smooth surface, as used herein refers to a continuous even surface, i.e., a surface generally free from any disturbances or protrusions in the surface topography. The inner layers, i.e., the core and mantle layers, of golf ball 10 and golf ball 20 shown in FIGS. 1 and 2, respectively, are smooth-surfaced, spherical layers.

[0055] Interfaces occur at surface boundaries where immediately adjacent layers adhere to or are in intimate contact with one another. Inner layers of golf balls 10 and 20 of FIGS. 1 and 2, respectively, have smooth spherical surfaces. Consequently, a smooth surface interface is formed between adjacent layers, in each of the respective golf balls. A smooth interface 17 is formed between core 12 and mantle layer 14 and another smooth interface 18 is formed between mantle layer 14 and cover layer 16 in the golf ball of FIG. 1. Similarly, in FIG. 2, smooth interfaces 25, 26, 27 are formed between core 21 and mantle layer 22, between mantle layer 22 and mantle layer 23, and between mantle layer 23 and cover layer 24, respectively.

[0056] When a golf ball is struck with a golf club, energy is transferred from the face of the club to the cover of the ball and subsequently transferred from the cover to each layer below the cover. Typically, the cover layer material and the mantle layer material differ in both their compositions and physical properties. Therefore, the energy transfer occurring throughout a golf ball must propagate through different materials via one or more smooth interfaces, which affects the transfer of energy within a golf ball. Additionally, different layers typically have different thicknesses, which also affects the transfer of energy within a golf ball.

[0057] In addition to differing compositions and physical properties, the physical arrangement or configuration of the interface between adjacent layers also affects the transfer of energy between respective layers. FIG. 3a represents a schematic cross-section of a golf ball having a cover layer 30 of a particular thickness and modulus (in terms of a particular type of material) and a mantle layer 32 of a different thickness and modulus. A smooth interface 34 is defined between the two layers. The smooth interface 34 represents any of the smooth interfaces 17, 18, 25, 26, 27 of FIGS. 1 and 2, respectively. FIG. 3b in a graph illustrating the transfer of energy occurring between adjacent layers of a golf ball having a smooth interface as represented in FIG. 3a. The transfer of energy from one layer to another in a ball having a smooth interface between the respective layers is very sudden and rather abrupt. It is believed that significant inefficiencies result from such energy transfers across smooth interfaces.

[0058] It is desirable, therefore, to incorporate a structural feature in a golf ball, specifically along the interface between adjacent layers of a golf ball that allows for an efficient and less abrupt transfer of energy between adjacent golf ball layers or interior regions.

Protuberant Surface Configurations

[0059] It has been discovered that changing the surface configuration of a mantle layer so that the mantle layer no longer has a uniformly smooth surface, alters the manner in which energy is transferred between adjacent layers.

[0060] A protuberant surface provides an alternative to a smooth surface. A protuberant surface contains outwardly extending bulges, protrusions or projections creating a surface with a unique contour or topography.

[0061] In a golf ball, a mantle layer having a protuberant surface, referred to herein as a protuberant mantle layer, contains outwardly extending, and preferably radially extending bulges, projections, or protuberances that impart contours or other irregularities to the surface.

[0062] When a golf ball layer is molded over or otherwise formed about a protuberant mantle layer, such as a cover or another mantle layer, the resulting interface between the two layers is not smooth, but rather conforms to the topography of the surface of the protuberant mantle layer. An interface occurring between a protuberant mantle layer and a golf ball layer molded immediately thereon is referred to herein as a protuberant interface.

[0063]

FIG. 4

a
illustrates a representative embodiment of a protuberant surface in accordance with the present invention. In FIG. 4a, mantle layer 42 has a protuberant surface topography created by projections 44. Projections 44, shown in cross-section of FIG. 4a, are representative of cylindrical and/or rectangular projections. A protuberant interface, as illustrated in FIG. 4a, results from the cover 40 being in intimate contact with the protuberant surface of mantle layer 42. Surface 46, extends between the base or side wall of a given projection and the base or side wall of any next nearest projection. Unless otherwise noted, the distance between projections is defined in terms of the distance between the base of a given projection and the base of a next nearest projection.

[0064]

FIG. 4

b
is a graph demonstrating the transfer of energy that occurs across the interface between adjacent layers in which the mantle layer has a protuberant surface topography, thereby providing a protuberant interface between the mantle layer and adjacent layer, such as the interface of FIG. 4a. Energy transfer between adjacent layers having a protuberant interface therebetween is gradual and more efficient over the total thickness of the respective layers than the energy transfer occurring across a smooth interface. FIG. 4b is representative of the typical transfer of energy that occurs between adjacent layers having a protuberant surface therebetween. FIG. 4b is merely illustrative, and not to be considered a limiting example of energy transfer across a protuberant interface. Energy transfer between adjacent layers of a golf ball having a protuberant interface therebetween is a function of several factors including: the thickness of the respective layers; the material used to construct the respective layers; and the surface topography which gives rise to the protuberant interface. A change in any of the noted parameters affects the energy transfer occurring between adjacent layers.

[0065] A protuberant interface occurs at the surface boundary where immediately adjacent layers adhere to and/or are in intimate contact with one another and is created by either of the adjacent layers having a protuberant surface. Preferably, of the two layers, the “lower” or underlying layer exhibits a protuberant surface. A protuberant surface, as previously described herein, is preferably formed by a plurality of outwardly extending bulges, protrusions or projections.

[0066] The outwardly extending bulges, contours, or regions on a protuberant mantle layer according to the present invention are preferably formed by a plurality of projections. Projections are preferably in the form of geometrical shapes selected from the group including, but not limited to, hemispherical, elliptical, conical, pyramidal, rectangular, hexagonal, pentagonal, trapezoidal, and cylindrical.

[0067] In one embodiment, projections are preferably hemispherical. FIG. 5a represents hemispherical projection 50 extending outwardly from surface 52. Surface 52 is representative of the outer surface of a mantle layer. FIG. 5b is a top view of projection 50 displaying the circular base of the hemispherical projection.

[0068] The present invention also contemplates angled projections. Angled projections are substantially conical projections that extend outwardly from the surface (of a mantle layer) and angle toward a single point. However, angled projections differ from conical projections in that angled projections are rounded and/or curved toward the apex of the projection and do not form a single point. FIG. 6a displays an embodiment of an angled projection 60 extending outwardly from surface 62. As illustrated in FIG. 6a, angled projections are substantially conical in that extending the outer angled walls of projection 60, represented by dashed lines 64 and 66, to a single point 65 provides a cone. FIG. 6b is a top view of projection 60 displaying the circular base of the angled projection.

[0069] Protuberant surface configurations may also be provided by stepped projections, as illustrated in FIG. 7a. Stepped projections include a step abutting and extending outwardly from the surface of a mantle layer and at least one step extending therefrom. Preferably stepped projections include a plurality of steps, wherein each step extends outwardly from an immediately adjacent underlying step. Preferably each respective step exhibits a substantially even or flat surface area. FIGS. 7a-7c display stepped projection 70 extending outwardly from surface 72. Stepped projection 70 includes a base step 70a extending directly from surface 72. A plurality of steps (70b-70e) successively extend outward from disc 70a. Each successive step is preferably smaller, in terms of diameter, length and/or width, than the immediately adjacent underlying step from which it extends, i.e., step 70b is smaller than 70a, step 70c is smaller than step 70b, etc. The present invention also contemplates an inverted step arrangement wherein the step abutting the mantle layer is the smallest step and the size of each successive step increases.

[0070]

FIG. 7

b
is a top view of stepped projection 70. According to FIG. 7b, stepped projection 70 is comprised of circular discs 70a-70e, wherein the diameter (and/or radius) of each disc decreases from 70a to 70e, i.e., disc 70e exhibits the smallest diameter. The present invention also contemplates that stepped projections may be formed utilizing geometrical shaped steps, including but not limited to, squares, rectangles, rhombuses, pentagons, hexagons, octagons, triangles, and the like. Stepped projections preferably employ steps having the same shape. However, the present invention contemplates employing different shaped steps to form a stepped projection.

[0071] Projection size is defined in terms of the dimensions of the base of the projection and also the height of the projection. For hemispherical, cylindrical, elliptical, conical and angled projections, base size refers to the diameter of the base of the individual projections. In FIG. 5a, 6a and 7a, the diameter d is defined by the distance between the points at which opposite, i.e., polar, ends of the projection base make contact with the outer surface of a mantle layer. In the case of pyramidal, rectangular, pentagonal, hexagonal, and trapezoidal projections, base size refers to the length and/or width of the base of individual projections, defined by the points at which the base (of each respective side) of the projection contacts the surface of the mantle layer. The base diameter or, in the alternative, the length and/or width is preferably from about 0.05 inches to about 0.20 inches, more preferably from about 0.07 inches to about 0.190 inches, and most preferably from about 0.09 inches to about 0.180 inches.

[0072] Angled projections and conical projections further exhibit and define a conical angle φ, as illustrated in FIG. 6a. Angled projections, as previously described herein, are substantially conical and therefore may be defined by a conical angle. The conical angel φ is preferably from about 75° to about 110°.

[0073] Preferably, particularly with respect to conical, pyramidal, pentagonal, hexagonal, and trapezoidal projections, the diameter, length and/or width of the base of a projection is equal to or greater than the diameter, length, and/or width of the apex, i.e. the top most point, of the projection. Most preferably, the base diameter, length and/or width of a projection is greater than the diameter, length, and/or width of its apex. The present invention also contemplates forming a protuberant mantle layer comprising a plurality of projections wherein the base of a projection has a diameter, length, and/or width less than the diameter, length and/or width of the apex.

[0074] The height or depth of the projection is defined from the surface of the mantle layer to the apex of the projection. Projections reside on or extend outwardly from a curved and/or a substantially spherical surface. Consequently, a surface arc is defined between polar ends on the base of a projection, where each end of the projection makes contact with the outer surface of the mantle layer. The depths of projections is defined by the distance h between the apex of the surface arc and the apex of a given projection, as, for example, is illustrated in FIGS. 5a, 6a and 7a. The depths of projections are at least about 0.020 inches. Preferably, the depths of projections are between about 0.020 inches and 0.060 inches.

[0075] Stepped projections are further defined by the number of steps and the size of each individual step. Steps are defined based upon the shape of each respective step. Cylindrical projections, i.e., disc shaped steps, are defined by the diameter or, alternatively the radius, and the step height. Steps exhibiting other shapes, i.e., square, rectangle, rhombuses, hexagon, pentagon, octagon, triangles etc., are defined by the height, length and/or width of each step. Steps preferably have a diameter, length and/or width of from about 0.05 inches to about 0.130 inches. Preferably, step size, in terms of diameter, length, and/or width, decreases from the base step to the outermost step in uniform increments, i.e., each given step has a diameter, length and/or width less than the diameter, length and/or width of the step immediately therebeneath. The present invention also contemplates stepped projections wherein step size does not decrease from the base step to the outermost step in uniform increments. The size difference, in terms of the diameter, length and/or width, of adjacent steps is preferably from about 0.005 inches to about 0.02 inches.

[0076] Preferably, the height of each respective step, i.e., the height increments, are equal. The present invention also contemplates employing steps of different heights in a stepped projection. Step height increments are preferably from about 0.005 inches to about 0.03 inches.

[0077] Step heights depend upon the number of steps employed in a stepped projection. Stepped projections employ at least two steps. Stepped projections preferably employ from about two steps to about twelve steps, more preferably from about three steps to about eight steps, and most preferably from about four steps to about six steps.

[0078] Projections may be arranged in any manner to form a protuberant surface. Patterns and arrangements of projections are selected as desired to yield various properties and/or characteristics in a final golf ball product. Additionally, projections may be arranged such that the bases of adjacent projections are in contact with one another or such that the bases of adjacent projections are not in contact with another. For example, in FIG. 4a, the base of a given projection does not make contact with the base of any next nearest projection. Subsequently, a region of the given mantle layer is exposed. The exposed region is considered to be a smooth surface region, as would be found in a mantle construction having a smooth surface. Arrangement of projections is more fully described in accordance with the preferred embodiments. Preferably the distance between the bases of adjacent projections is from about 0.010 inches to about 0.250 inches, and more preferably between about 0.020 inches to about 0.200 inches.

[0079] A protuberant mantle layer preferably comprises projections of the same shape and having equal dimensions, i.e., having equal size. When projections of equal dimensions are employed, the apex of the projections are considered to be co-planar with each other. However, the present invention encompasses the use of projections having different dimensions in terms of the height, base diameter, and/or base length and width of the projection.

[0080] The present invention encompasses protuberant mantle layers having a protuberant surface formed by projections of different geometric shapes. Protuberant mantle layers optionally comprise combinations of two or more geometrical shaped or stepped projections. Multiple geometric shapes are arranged in any pattern as desired to provide a mantle layer and/or assembly with a protuberant surface. A non-limiting example of such an embodiment is a protuberant mantle layer formed by hemispherical and angled projections. The projections could be arranged in any manner such that spherical and/or angled projections were repeating, i.e., a projection of a given shape would be immediately adjacent to a projection of the same shape. Additionally, the projections could be arranged in an alternating or generally non-repeating fashion.

[0081] Another non-limiting example of utilizing multiple geometric shapes in accordance with the present invention is a protuberant mantle assembly formed by pyramidal, hexagonal, and trapezoidal projections. Accordingly, the projections may be arranged in a repeating or non-repeating manner, such that desired properties are achieved.

Mantle Assemblies

[0082] Preferably, a protuberant mantle layer, as previously described herein, is part of a mantle assembly. A mantle assembly according to the present invention is comprised of a core and one or more mantle layers disposed about the core, wherein at least one of the one or more mantle layers has a protuberant surface. In a preferred embodiment, the outermost mantle layer of a mantle assembly comprises a plurality of projections that provide the outermost mantle layer with a protuberant surface. Projections, as previously described herein, are most preferably in the form of repeating geometrical shapes. And, it is preferred that the plurality of projections are arranged in a uniform or repeating pattern. However, the present invention encompasses the simultaneous use of multiple geometric shapes and generally non-repeating shapes. And, the present invention includes the use of non-uniform or non-repeating patterns of projections.

[0083] Preferably, a mantle assembly comprising a protuberant mantle layer is generally spherical. While a protuberant mantle layer does not have a uniformly smooth or even surface topography due to the plurality of projections as described herein, in a most preferred form, the overall shape of the layer is generally spherical and/or circular.

[0084]

FIG. 8

a
displays a mantle assembly 80 of a first preferred embodiment mantle assembly in accordance with the present invention. The mantle assembly 80 comprises a mantle layer 81 on its outer surface. Hemispherical projections 82 provide the mantle layer with a protuberant surface. A flat or smooth surface area 84 is formed on the outer mantle layer of the mantle assembly 80 in the first preferred embodiment, and is defined within the region between adjacent projections.

[0085]

FIG. 8

b
is a cross-section of the mantle assembly of FIG. 8a and provides a view of the entire mantle assembly 80 including a mantle layer 81 and a core 86. Projections 82 and smooth surface 84 generally extending between the projections 82 provide mantle layer 81 with a protuberant surface. The projections 82 of the mantle assembly 80 can be of any shape or size described herein.

[0086] A second preferred embodiment of a mantle assembly according to the present invention is illustrated in FIGS. 9a and 9b.

FIG. 9

a displays a mantle assembly 90 having a mantle layer 92. Mantle layer 92 has a protuberant surface configuration provided by a plurality of hemispherical projections 94. The present invention contemplates that projections 94 can be of any shape or size described herein. In the second preferred embodiment, the base of any selected projection makes contact with the base of each projection to which it is immediately adjacent. Therefore, no exposed smooth surfaces exists on the outer surface of the mantle assembly of the second preferred embodiment.

[0087]

FIG. 9

b
is a cross-section of FIG. 9a and shows mantle assembly 90 of the second preferred embodiment. Mantle assembly 90 comprises a mantle layer 92 having a plurality of projections 94 molded over a core 96. The projections 94 of the second preferred embodiment preferably are of equal dimensions.

[0088]

FIG. 9

b
also demonstrates the arrangement of the projections 94, i.e., the base of a projection is in intimate contact with the base of each immediately adjacent projection.

[0089] A third preferred embodiment of a mantle assembly of the present invention is shown in FIG. 10. Multi-layer mantle assembly 100 comprises three layers, a core 102, an inner mantle layer 104 and an outer mantle layer 106. The inner mantle layer 104 is disposed between the core 102 and the outer mantle layer 106.

[0090] The outer mantle layer 106 comprises a plurality of projections 108, which provide the outer mantle layer with a protuberant surface. Projections 108 of the third preferred embodiment exhibit an arrangement similar to the arrangement of the projections according to the second preferred embodiment, i.e., the base of a projection is in immediate contact with the base of each immediately adjacent projection. Alternatively, a smooth surface may extend between the projections 108. Additionally, projections 108 can be of any shape or size as described herein.

[0091]
FIG. 11 a cross-sectional view of a fourth preferred embodiment of a multi-layer mantle assembly 110 according to the present invention. Multi-layer mantle assembly 110 comprises core 111, a first protuberant mantle layer 112 having a plurality of projections 113 disposed about the core 111, and a second protuberant mantle layer 114 having a plurality of projections 115 disposed about the first protuberant mantle layer 112. First protuberant mantle layer 112 exhibits a protuberant surface configuration provided by a plurality of hemispherical projections 113 arranged such that the base of a projection is in immediate contact with the base of each immediately adjacent projection. Second protuberant mantle layer 114 exhibits a protuberant surface provided by a plurality of projections 115 and smooth surface 116 generally extending between the projections.

[0092] Second protuberant mantle layer 114 defines an inner surface that adheres to or makes contact with the outer surface of mantle layer 112. Additionally, first protuberant mantle layer 112 defines an inner surface that adheres to or is in intimate contact with the outer surface of core 111. Depressions are formed on the inner surface of second protuberant mantle layer 114 and are defined by projections 113 on the outer surface of first protuberant mantle layer 112. Specifically, depressions on the inner surface of second protuberant mantle layer 114 exhibit a shape that is the negative shape of a corresponding projection on the outer surface of first protuberant mantle layer 112.

[0093] Depressions are formed on the inner surface of any layer formed immediately over a protuberant mantle layer. Depressions are defined by projections, bulges, or other contours on the surface of the protuberant mantle layer, i.e., depressions are defined by the space and/or volume occupied by a projection, bulge, or contour of the protuberant mantle layer. Consequently, depressions exhibit a shape that is the negative or corresponding inverse of the shape of the corresponding projection, bulge or contour from which it is formed.

[0094] In FIG. 11, for example, the inner surface of outer mantle layer 114, if removed from mantle assembly 110, exhibits depressions corresponding to the projections 113 of mantle layer 112. The inner surface of mantle layer 114 is the region of mantle layer 114 that adheres to or is in contact with the outer surface of mantle layer 112. Specifically, the depressions on the inner surface of mantle layer 114 exhibit shapes that are the negative shapes to a corresponding projection of mantle layer 112.

[0095] The multi-layer mantle assembly 110 is considered to be spherical, preferably comprised of spherical core and spherical protuberant mantle layers 112 and 114. Mantle assemblies comprising two or more protuberant mantle layers are not limited to the mantle assembly according to the fourth preferred embodiment. The present invention encompasses numerous variations and alternative arrangements of a multi-layer mantle assembly comprising two or more protuberant mantle layers. The present invention contemplates a mantle assembly comprising two protuberant mantle layers, wherein the protuberant mantle layers exhibit different surface configurations. Surface configurations of the mantle layers differ with respect to any of the arrangement, shape, and/or size of projections which provide each mantle layer with its respective surface configuration. Additionally, the present invention encompasses multi-layer mantle assemblies comprising two or more protuberant mantle layers wherein each mantle layer exhibits a surface configuration similar to that of the at least one other protuberant mantle layer. In such an embodiment, the surface configurations of each protuberant mantle layer are similar with respect to the size, shape, and arrangement of projections, which provide the mantle layers with a protuberant surface configuration.

[0096] In accordance with the fourth preferred embodiment, the present invention contemplates, as previously described herein, protuberant mantle layers having a protuberant surface provided by projections of different geometric shapes, and optionally comprising combinations of two or more geometrical shaped projections. The present invention further contemplates the arrangement of geometric shapes as desired to provide a mantle layer and/or assembly with a protuberant surface, optionally arranged in a repeating or alternating, i.e., a generally non-repeating fashion.

[0097] A multi-layer mantle assembly according to the present invention is not limited to three layers. That is, the present invention includes a multi-layer mantle assembly comprising a core, and one or more mantle layers disposed about the core, wherein at least one of the one or more mantle layers has a protuberant surface as previously described herein. Preferably, the outermost mantle layer of a multi-layer mantle assembly according to the present invention has a protuberant surface. The present invention also contemplates a multi-layer mantle assembly comprising, a core, an outer mantle layer having a smooth surface, and an inner mantle layer having a protuberant surface disposed therebetween.

[0098] A mantle assembly according to the present invention is constructed by forming a spherical core and then molding one or more mantle layers over the core. At least one of the one or more mantle layers has a protuberant surface provided by a plurality of projections.

[0099] A mantle assembly, specifically the constituent components of a mantle assembly, are formed by any suitable molding method known in the golf ball art. Such methods include, but are not limited to, compression molding, injection molding, blow molding, and reaction injection molding. Preferred methods are described herein.

[0100] To form a mantle layer having a protuberant surface by the above-referenced methods, a mold is employed preferably having a pattern that provides the desired shape, size, and arrangement of projections, such that a protuberant mantle layer having the desired surface topography is formed. A mantle layer having a protuberant surface topography may also be formed by a method described in copending application, “Method of Making Golf Balls Having a Protrusion Center”, Ser. No. 09/737,067, filed on Dec. 14, 2000, incorporated herein by reference.

[0101] Preferably, the outer surface of a given layer in an mantle assembly is in adhesive contact with the inner surface of an immediately adjacent layer. Embodiments comprising a mantle layer disposed immediately over a protuberant mantle layer also preferably exhibit adhesive contact between the two respective layers. Specifically, projections on the outer surface of an underlying mantle layer are in adhesive contact with the resulting depression on the inner surface of the layer formed immediately over the protuberant mantle layer. As previously described herein, depressions in one layer are the negative shape of the corresponding projection.

[0102] Materials suitable for forming the core and one or more mantle layers of a mantle assembly according to the present invention are described in greater detail herein.

[0103] A mantle assembly, as previously described herein, comprises a core and one or more mantle layers disposed about the core, wherein at least one of the one or more mantle layers has a protuberant surface. Therefore, the core of a present invention mantle assembly is preferably constructed from any suitable core material known in the golf ball art. Suitable core materials are more fully described herein.

[0104] It is recognized that the mantle layers in a mantle assembly according to the present invention may be constructed from materials suitable for forming a core, a cover layer, a mantle layer, or combinations thereof. As previously described herein, a mantle layer is often considered to be part of a respective layer, i.e., a core or a cover layer, based on the material from which the mantle is constructed. A mantle layer constructed from the same material, or material similar to that, as the core may be considered a core assembly. Additionally a mantle layer constructed from material conventionally suitable as a cover material is typically considered an inner cover layer. Mantle layers, including protuberant mantle layers, according to the present invention, are preferably constructed of materials suitable for forming golf ball covers.

[0105] For example, in one preferred form of a present invention golf ball, in accordance with FIGS. 8a and 8b, mantle layer 81 is formed by a material suitable as a golf ball core material. Core 86 and mantle layer 81, which are collectively considered a mantle assembly according to the present invention, are therefore considered to be a dual or multi-layer core.

[0106] In an alternative embodiment of a present invention golf ball, in accordance with FIGS. 8a and 8b, mantle layer 81 is constructed from a material suitable as a cover material. Mantle layer 81 is therefore considered to be an inner cover layer. However, mantle layer 81 and core 86 are still collectively considered a mantle assembly according to the present invention.

[0107] The foregoing examples are not to be considered limiting embodiments. Rather the foregoing examples are merely illustrative of possible alternative mantle layer constructions, in terms of materials used to form a mantle layer, and a system for associating mantle layers with a conventional golf ball layer, i.e., either a core or a cover layer. The examples, as described in accordance with FIGS. 8a and 8b, are applicable to any golf ball employing a mantle assembly according to the present invention.

[0108] A multi-layer mantle assembly of the present invention is not limited to the particular shapes and/or arrangements of projections described in the first, second, third, or fourth preferred embodiments. Additionally, any of the one or more mantle layers may have a protuberant surface.

Golf Balls

[0109] Preferably, mantle assemblies, as previously described herein, are utilized to form a golf ball. A golf ball employing a mantle assembly according to the present invention comprises a cover layer disposed about the mantle assembly. The cover may be a single cover layer or optionally a multi-layer cover. The cover layer is constructed from any suitable cover material, known in the golf ball art. Suitable cover materials are more fully described herein. Alternatively, golf balls according to the present invention include a core, a cover layer, and one or more mantle layers disposed between the core and the cover, wherein at least one of the one or more mantle layers exhibits a protuberant surface configuration as previously described herein. In a preferred form, a golf ball employing a mantle assembly according to the present invention has a cover layer molded or otherwise formed immediately over the outer mantle of a mantle assembly, wherein the outer mantle layer has a protuberant surface provided by a plurality of projections. In a most preferred form, a golf ball cover is formed over a mantle assembly comprising a core and a protuberant mantle layer.

[0110]
FIG. 12 is a cross-section of a three-piece, non-wound golf ball 120 employing a mantle assembly according to the first preferred embodiment. A cover layer 122 is molded or otherwise formed over mantle layer 81. A plurality of outwardly extending projections 82 and smooth surface 84 extending therebetween are defined along the outer region of mantle layer 81. Core 86 and mantle layer 81 are collectively considered to comprise mantle assembly 80, as described in accordance with FIGS. 8a and 8b. A protuberant interface is provided where the cover layer adheres to and is in intimate contact with the protuberant surface of the mantle assembly.

[0111] A four-piece, non-wound golf ball 130 employing a mantle assembly according to the first preferred embodiment is shown in FIG. 13, wherein a mantle layer 132 is disposed between the mantle assembly of the first preferred embodiment and a cover layer 134. Core 86 and mantle layer 81 are collectively considered to comprise mantle assembly 80, as described in accordance with FIGS. 8a and 8b. A plurality of outwardly extending projections 82 and smooth surface 84 extending therebetween are defined along the outer region of mantle 81. A protuberant interface is provided where mantle layer 132 adheres to and makes intimate contact with protuberant surface of the mantle assembly.

[0112] A golf ball employing a mantle assembly of the first preferred embodiment is not limited to the above-described golf balls. It is contemplated that any number of mantle layers may be disposed between a cover layer and the mantle assembly.

[0113] Multi-piece, non-wound golf balls employing a mantle assembly of the second preferred embodiment are shown in FIGS. 14 and 15.

[0114]
FIG. 14 is a cross-section of a three-piece, non-wound golf ball 140 having a mantle assembly according to the second preferred embodiment. A cover layer 142 is disposed over the mantle layer 92 of the mantle assembly. Core 96 and mantle layer 92 comprise mantle assembly 90, as described in accordance with FIGS. 9a and 9b. A protuberant interface is provided by the protuberant surface formed by projections 94, where the cover layer adheres to and is in intimate contact with the surface of mantle layer 92 (of the mantle assembly).

[0115] A cross-section of a four-piece, non-wound golf ball 150 employing a mantle assembly according to the second preferred embodiment is shown in FIG. 15, wherein a mantle layer 152 is disposed between mantle layer 92 of the mantle assembly and a cover 154. A plurality of outwardly extending projections 94 are defined along the outer region of mantle layer 92. Core 96 and mantle layer 92 comprise mantle assembly 90, as described in accordance with FIGS. 9a and 9b. A protuberant interface is provided, where the mantle layer 152 adheres to and makes intimate contact with the protuberant surface of mantle layer 92 (of the mantle assembly).

[0116] A golf ball employing a mantle assembly according to the second preferred embodiment is not limited to the above-described golf balls. It is contemplated that any number of mantle layers may be disposed between a cover layer and a mantle assembly of the present invention.

[0117]
FIG. 16 shows a multi-layer golf ball 160 employing a multi-layer mantle assembly according to the third preferred embodiment. A cover layer 162 is disposed about the outer mantle layer 106 of the multi-layer mantle assembly. A plurality of outwardly extending projections 108 are defined along the outer region of mantle layer 106. Core 102, inner mantle layer 104 and outer mantle layer 106 comprise mantle assembly 100, as described in accordance with FIG. 10. A protuberant interface is provided where the cover layer adheres to and is in intimate contact with the protuberant surface of mantle layer 106 (of the mantle assembly).

[0118]
FIG. 17 is a cross-sectional view of a golf ball 170 employing a mantle assembly of the fourth preferred embodiment. Cover layer 172 is disposed about outer mantle layer 114. Outer mantle 114 exhibits a protuberant surface provided by projections 115 and surface 116 extending between the projections. Core 111, protuberant inner mantle 112, projections 113, and protuberant outer mantle layer 114 collectively comprise mantle assembly 110, as described in accordance with FIG. 11.

[0119] Depressions exist on the inner surface of a cover layer formed immediately over a protuberant mantle layer. As previously described herein, depressions are defined on the inner surface of any layer molded immediately over a protuberant layer by the space and/or volume occupied by projections extending outwardly from the protuberant layer. Depressions exhibit a shape that is the negative of corresponding projections on the surface of the protuberant mantle layer.

[0120] Preferably, the outer surface of a given layer of a golf ball according to the present invention is in adhesive contact with the inner surface of the immediately adjacent layer. Most preferably, projections of a protuberant mantle layer are in adhesive contact with the corresponding depressions on the inner surface of an immediately adjacent layer, which is preferably a cover layer.

[0121] It is contemplated that a golf ball employing a multi-layer mantle assembly according to the present invention may have one or more additional layers disposed between the multi-layer mantle assembly and the cover. Such additional mantle layers are preferably constructed of a golf ball cover material and, thus, would be considered to be part of a multi-layer cover.

[0122] Energy transfer within a golf ball is primarily a function of the thickness of the respective layers, the size, shape and placement of projections, and the materials used to form the respective layers. Physical properties of a golf ball utilizing the present invention may be adjusted and optimized by varying the compositions and thickness of individual layers and also by variations in the surface topography of one or more mantle layers.

[0123] A selected layer of a golf ball according to the present invention preferably is formed from a material suitable for that selected layer. A golf ball core is preferably constructed of any material known in the art suitable as a golf ball core. A cover layer preferably includes a material suitable as a golf ball cover. A mantle layer, including protuberant mantle layers, as previously described herein may be constructed of a material suitable as any of a core or a cover layer. Preferably mantle layers are constructed from materials suitable as a golf ball cover. Suitable materials are described more fully herein.

[0124] In a preferred form of the invention a golf ball layer comprises a selected material in combination with an adjacent layer having another selected material. The selected materials of adjacent layers preferably exhibit different physical properties such as hardness and flexural modulus, and more preferably include different composition. Materials are chosen to provide a particular layer with a desired physical property, and subsequently to contribute to the overall performance of the golf ball.

[0125] Materials are selected such that satisfactory adhesion is obtained between adjacent layers. Specifically, it is preferable that the outer surface of an underlying layer is in adhesive contact with the inner surface of the immediate overlying layer. Adhesive properties between materials of adjacent layers are preferred for a core and an adjacent mantle layer, for adjacent mantle layers, and for a mantle layer and a cover layer adjacent thereto. Adhesive properties between materials is especially preferred when an underlying layer exhibits a protuberant surface configuration as previously described herein.

[0126] A selected layer preferably comprises a material dissimilar from a material of an adjacent layer. A material of one type is considered dissimilar to a material of one another type if the selected materials i) exhibit different chemical compositions; ii) exhibit different physical properties; or iii) exhibit a combination of i and ii. Adjacent layers that utilize materials having the same primary chemical composition most preferably exhibit different physical properties, i.e., hardness, flexural modulus, etc.

[0127] A golf ball according to the present invention preferably utilizes a cover layer of material A in combination with an underlying protuberant mantle layer of material B. More preferably, the golf ball further includes utilizing protuberant mantle layer having material B in combination with a core having material C. As previously described herein, materials A, B, and C preferably exhibit different physical properties and may have comparatively similar or unique compositions. Preferably material A exhibits a flexural modulus from about 1,000 psi to about 100,000 psi, material B exhibits a flexural modulus of from about 1,000 psi to about 400,000 psi, and material C exhibits a flexural modulus of from about 1,000 psi to about 200,000 psi. More preferably material A exhibits a flexural modulus from about 1,000 psi to about 50,000 psi, material B exhibits a flexural modulus from about 10,000 psi to about 200,000 psi, and material C exhibits a flexural modulus from about 1,000 psi to about 150,000 psi. Most preferably material A exhibits a flexural modulus of from about 1,000 psi to about 10,000 psi, material B exhibits a flexural modulus of from about 40,000 psi to about 100,000 psi, and material C exhibits a flexural modulus of from about 1,000 psi to about 100,000 psi.

[0128] In another form of the present invention, a golf ball utilizes a cover of material A in combination with a protuberant mantle layer of material B, and protuberant mantle layer of material B is utilized in combination with a second protuberant mantle layer having material D. The second protuberant mantle layer of material D is preferably used in combination with a core having material C.

[0129] As previously described herein, materials A, B, C and D preferably exhibit different physical properties and may have comparatively similar or unique compositions. Preferably material A exhibits a flexural modulus from about 1,000 psi to about 100,000 psi, material B exhibits a flexural modulus of from about 1,000 psi to about 400,000 psi, material D exhibits a flexural modulus of from about 1,000 psi to about 400,000 psi, and material C exhibits a flexural modulus of from about 1,000 psi to about 200,000 psi. More preferably material A exhibits a flexural modulus from about 1,000 psi to about 50,000 psi, material B exhibits a flexural modulus from about 10,000 psi to about 200,000 psi, material D exhibits a flexural modulus of from about 20,000 psi to about 200,000 psi, and material C exhibits a flexural modulus from about 1,000 psi to about 150,000 psi. Most preferably material A exhibits a flexural modulus of from about 1,000 psi to about 10,000 psi, material B exhibits a flexural modulus of from about 40,000 psi to about 100,000 psi, material D exhibits a flexural modulus of from about 50,000 psi to about 150,000 psi, and material C exhibits a flexural modulus of from about 1,000 psi to about 100,000 psi.

[0130] Any suitable golf ball material may be utilized as materials A, B, C, and D. Materials A, B, and D preferably include any of a low-acid ionomer, a high-acid ionomer, a polyamide-ionomer composition, a polyurethane, and combinations thereof. Material C, i.e., a core material, preferably includes a polybutadiene material, a metallocene polyolefin, a polyurethane and combinations thereof. Materials for a core (material C), a cover layer (material A), and/or one or more protuberant mantle layers (materials B and D) are discussed in greater detail herein with respect to cores, mantle layers, and cover layers.

[0131] In one embodiment according to the present invention, a golf ball comprises a polybutadiene core, a protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0132] In another embodiment according to the present invention, a golf ball comprises a polybutadiene core, a protuberant mantle layer high acid ionomer composition, and a cover layer comprising a blend of a high acid ionomer and a low acid ionomer.

[0133] In a further embodiment, a golf ball according to the present invention comprises a polybutadiene core, a protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a blend of a polyamide and ionomer.

[0134] Still another embodiment of the present invention is a golf ball comprising a polybutadiene core, a protuberant mantle layer comprising a high acid ionomer and a cover layer comprising a polyurethane.

[0135] In another embodiment, a golf ball according to the present invention comprises a polybutadiene core, a protuberant mantle layer comprising a polyurethane, and a cover layer comprising a low acid ionomer.

[0136] Still a further example of an embodiment according to the present invention is a golf ball comprising a polybutadiene core, a polyurethane protuberant mantle layer, and a cover layer comprising a blend of a high acid ionomer and a low acid ionomer.

[0137] Yet another embodiment of the present invention is a golf ball comprising a polybutadiene core, a protuberant mantle layer comprising a polyurethane material, and a cover layer comprising a polyamide-ionomer composition.

[0138] In a further embodiment according to the present invention, a golf ball comprises a polybutadiene core, a protuberant mantle layer comprising a polyurethane material, and a cover layer comprising a polyurethane material.

[0139] Another embodiment of the present invention is a golf ball comprising a core which includes a metallocene polyolefin, a protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0140] Yet another embodiment according to the present invention is a golf ball comprising a core that comprises a metallocene polyolefin, a protuberant mantle layer comprising a high acid ionomer, and a cover layer including a blended composition comprising a high acid ionomer and a low acid ionomer.

[0141] In a further embodiment, a golf ball according to the present invention comprises a core which includes a metallocene polyolefin, a protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a composition which includes a polyamide and ionomer blend.

[0142] In yet a further embodiment, a golf ball according to the present invention comprises a metallocene polyolefin core, a protuberant mantle layer that includes a high acid ionomer, and a polyurethane cover.

[0143] Yet another embodiment of the present invention, is a golf ball that comprises a metallocene polyolefin core, a polyurethane protuberant mantle layer, and a cover layer comprising a low acid ionomer.

[0144] A further embodiment of a golf ball according to the present invention comprises a metallocene polyolefin core, a protuberant mantle layer comprising a polyurethane, and a cover layer comprising a high acid/low acid ionomer blend.

[0145] In another embodiment according to the present invention, a golf ball comprises a metallocene polyolefin core, a protuberant mantle layer comprising a polyurethane, and a cover layer comprising a polyamide-ionomer composition.

[0146] Yet another embodiment of a golf ball according to the present invention includes a metallocene polyolefin core, a protuberant mantle layer comprising a polyurethane, and a cover layer comprising a polyurethane.

[0147] In yet another preferred embodiment, a golf ball according to the present invention includes a polyurethane core, a protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0148] In another preferred embodiment, a golf ball according to the present invention comprises a polyurethane core, a high acid ionomer protuberant mantle layer, and a cover layer comprising a blend of a high acid and a low acid ionomer.

[0149] Still another embodiment according to the present invention is a golf ball comprising a polyurethane core, a high acid ionomer protuberant mantle layer, and a high acid ionomer cover.

[0150] In another embodiment according to the present invention, a golf ball comprises a polyurethane core, protuberant mantle layer comprising a high acid ionomer, and a polyurethane cover.

[0151] Another embodiment according to the present invention is a golf ball comprising a polyurethane core, a protuberant mantle layer comprising a polyurethane, and a polyamide-ionomer cover layer.

[0152] Still another embodiment according to the present invention is a golf ball comprising a polyurethane core, a protuberant mantle layer comprising a polyurethane, and a cover layer comprising a polyurethane.

[0153] In another embodiment, a golf ball according to the present invention comprises a polybutadiene core, a first protuberant mantle layer comprising a polyurethane material, a second protuberant mantle comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0154] Still another embodiment according to the present invention is a golf ball comprising a polybutadiene core, a protuberant mantle layer comprising a polyurethane material, a second protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a blend of a high acid ionomer and a low acid ionomer.

[0155] Yet another embodiment according to the present invention is a golf ball comprising a polybutadiene core, a first mantle layer comprising a polyurethane material, a second mantle layer comprising a polyurethane material, and a cover layer comprising a polyamide ionomer composition, wherein both the first and second mantle layers have a protuberant surface configuration.

[0156] A further embodiment according to the present invention is a golf ball comprising a polybutadiene core, a protuberant mantle layer comprising a high acid ionomer, a second protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0157] Still another embodiment according to the present invention is a golf ball comprising a polybutadiene core, a protuberant mantle layer comprising a polyurethane material, another protuberant mantle layer comprising a polyurethane material, and a polyurethane cover.

[0158] In another embodiment according to the present invention, a golf ball includes a metallocene polyolefin core, a first protuberant mantle layer comprising a high acid ionomer, a second protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0159] Still a further embodiment according to the present invention, is a golf ball including a core which comprises a metallocene polyolefin, a first protuberant mantle layer comprising a high acid ionomer, a second protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a blend of a high acid ionomer with a low acid ionomer.

[0160] Yet another embodiment according to the present invention is a golf ball comprising a metallocene polyolefin core, a protuberant mantle layer comprising a polyamide-ionomer composition, another protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0161] A further embodiment according to the present invention is a golf ball comprising a metallocene polyolefin core, a first protuberant mantle layer comprising a polyamide-ionomer composition, a second protuberant mantle layer comprising a polyurethane, and a polyurethane cover.

[0162] In another embodiment, a golf ball according to the present invention comprises a polyurethane core, a first protuberant mantle layer comprising a polyurethane, a second protuberant mantle layer comprising a high acid ionomer, and a cover layer comprising a low acid ionomer.

[0163] In another embodiment according to the present invention, a golf ball comprises a polyurethane core, a first protuberant mantle layer comprising a polyamide-ionomer composition, a second protuberant mantle layer comprising a polyurethane material, and a cover layer comprising a polyamide-ionomer composition.

[0164] Yet another embodiment according to the present invention is a golf ball comprising a polyurethane core, a first protuberant mantle layer comprising a polyamide-ionomer composition, a second protuberant mantle layer comprising a polyurethane composition, and a cover layer comprising a polyurethane composition.

[0165] Still another embodiment according to the present invention is a golf ball comprising a polyurethane core, a first protuberant mantle layer comprising a polyurethane material, a second protuberant mantle layer comprising a polyurethane material, and a cover layer comprising a polyurethane material.

[0166] Mantle assembly cores according to the present invention may be formed from any suitable core material known in the golf ball art. The core and/or mantle layers may be formed from a thermoset material, a thermoplastic material, or combinations thereof.

[0167] A wide array of thermoset materials can be utilized in a core and/or mantle layers of the present invention. Examples of suitable thermoset materials include butadiene or any natural or synthetic elastomer, including metallocene polyolefins, polyurethanes, silicones, polyamides, polyureas, or virtually any irreversibly cross-linked resin system. Similarly a polybutadiene elastomer could be further used. It is also contemplated that epoxy, phenolic, and an array of unsaturated polyester resins could be utilized.

[0168] The thermoplastic material used in the present invention cores and/or mantle layers includes a wide assortment of thermoplastic materials. Examples of typical thermoplastic materials for incorporation in the golf balls of the present invention include, but are not limited to, ionomers, polyurethane thermoplastic elastomers, and combinations thereof. It is also contemplated that a wide array of other thermoplastic materials could be utilized, such as polysulfones, fluoropolymers, polyamide-imides, polyarylates, polyaryletherketones, polyaryl sulfones/polyether sulfones, polybenzimidazoles, polyether-imides, polyamides, liquid crystal polymers, polyphenylene sulfides; and specialty high-performance resins, which would include fluoropolymers, polybenzimidazole, and ultrahigh molecular weight polyethylenes.

[0169] Additional examples of suitable thermoplastics include metallocenes, polyvinyl chlorides, acrylonitrile-butadiene-styrenes, acrylics, styrene-acrylonitriles, styrene-maleic anhydrides, polyamides (nylons), polycarbonates, polybutylene terephthalates, polyethylene terephthalates, polyphenylene ethers/polyphenylene oxides, reinforced polypropylenes, and high-impact polystyrenes.

[0170] Preferably, the thermoplastic materials have relatively high melting points, such as a melting point of at least about 300° F. Several examples of these preferred thermoplastic materials and which are commercially available include, but are not limited to, Capron® (trademarked by Allied Signal Plastics for a blend of nylon and ionomer), Lexan® (trademarked by General Electric for polycarbonate), Pebax® (trademarked by Elf Atochem for a polyether block amide), and Hytrel® (trademarked by DuPont for a series of polyester elastomers). The polymers or resin system may be cross-linked by a variety of means such as by peroxide agents, sulphur agents, radiation or other cross-linking techniques.

[0171] Any or all of the previously described components in the cores and/or mantle layers of the preferred embodiment golf balls of the present invention may be formed in such a manner, or have suitable fillers added, so that their resulting density is decreased or increased. For example, any of the components in the cores and/or mantle layers could be formed or otherwise produced to be light in weight. For instance, the components could be foamed, either separately or in situ. Related to this, a foamed light weight filler agent may be added. In contrast, any of these components could be mixed with, or otherwise receive, various high density filler agents or other weighting components such as relatively high density fibers or particulate agents in order to increase their mass or weight.

[0172] The following commercially available thermoplastic resins are particularly preferred for use in the noted mantle layers employed in the preferred embodiment golf balls of the present invention: Capron® 8351 (available from Allied Signal Plastics), Lexan® ML5776 (from General Electric), Pebax® 3533 (a polyether block amide from Elf Atochem), and Hytrel® G4074 (from DuPont). Properties of these four preferred thermoplastics are set forth below in Tables 1-4. When forming a golf ball in accordance with the present invention, if the mantle layer is to comprise a thermoplastic material, it is most preferred to utilize Pebax® thermoplastic resin.

1TABLE 1Capron ® 835150%ASTMMechanicalDAMRHTestTensile Strength, Yield, psi (MPa)7,800 (54)—D-638Flexural Strength, psi (MPa)9,500 (65)—D-790Flexural Modulus, psi (MPa)230,000—D-790(1,585)Ultimate Elongation, %200—D-638Notched Izod Impact, ft-lbs/in (J/M)No Break—D-256Drop Weight Impact, ft-lbs (J)150 (200)—D-3029Drop Weight Impact, @ −40° F., ft-lbs (J)150 (200)—D-3029PhysicalSpecific Gravity1.07—D-792ThermalMelting Point, ° F. (° C.)420 (215)—D-789Heat Deflection @ 264 psi ° F. (° C.)140 (60)—D-648

[0173]

2

TABLE 2

Lexan ® ML5776

Typical

ASTM

Property
Data
Unit
Method

Mechanical

Tensile Strength, Yield,
8500
psi
ASTM D-638

Type 1, 0.125″

Tensile Strength, Break
9500
psi
ASTM D-638

Type 1, 0.125″

Tensile Elongation, Yield,
110.0
%
ASTM D-638

Type 1, 0.125″

Flexural Strength, Yield,
12000
psi
ASTM D-790

0.125″

Flexural Modulus,
310000
psi
ASTM D-790

0125″

Impact

Izod Impact, Unnotched, 73 F.
60.0
ft-lbs/ins
ASTM D-4812

Izod Impact, Notched, 73 F.
15.5
ft-lbs/ins
ASTM D-256

Izod Impact, Notches, 73 F.,
12.0
ft-lbs/ins
ASTM D-256

0.250″

Instrumented Impact
48.0
ft-lbs
ASTM D-3763

Energy @ Peak, 73 F.

Thermal

HDT, 264 psi, 0.250″,
257
deg F.
ASTM D-648

Unannealed

Thermal Index, Elec Prop
80
deg C.
UL 7468

Thermal Index, Mech Prep with
80
deg C.
UL 7468

Impact

Thermal Index, Mech Prop
80
deg C.
UL 7468

without Impact

Physical

Specific Gravity, Solid
1.19
—
ASTM D-792

Water Absorption,
0.150
%
ASTM D-570

24 hours @ 73 F.

Mold Shrinkage, Flow, 0.125″
5.7
in/in E-3
ASTM D-955

Melt Flow Rate, Nom'l,
7.5
g/10 min
ASTM D-1238

30° C./1.2 kgf (0)

Flame Characteristics

UL File Number, USA
E121562
—
—

94HB Rated (tested thickness)
0.060
inch
UL 94

[0174]

3

TABLE 3

Pebax ® 3533 Resin

ASTM

Property
Test Method
Units
3533

Specific Gravity
D792
1.01

Water Absorption Equilibrium
D570

(20° C., 50% RH.>)

0.5

24 Hr. Immersion

1.2

Hardness
D2240

35D

Tensile Strength, Ultimate
D638
psi
5600

Elongation, Ultimate
D638
%
580

Flexural Modulus
D790
psi
2800

Izod Impact, Notched
D256
ft

20° C.

lb/in
NB

−40° C.

NB

Abrasion Resistance
D1044
Mg/100
104

H18/1000 g

Cycles

Tear Resistance Notched
D624C
lb/in
260

Melting Point
D3418
° F.
306

Vicat Softening Point

° F.
165

HDT 66 psi
D648
° F.
115

Compression Set

(24 hr., 160° F.)
D395A
%
54

[0175]

4

TABLE 4

Hytrel ® G4074

Thermoplastic Elastomer

ASTM

Physical
Test Method

Dens/Sp Gr
ASTM D792

1.1800
sp gr

23/23C

Melt Flow
ASTM D1238
5.20 @ E-190 C/2.16 kg

g/10/min

Wat Abs
ASTM D570

2.100%

Mechanical

Elong @ Brk
ASTM D638

230.0%

Flex Mod
ASTM D790

9500 psi

TnStr @ Brk
ASTM D638

2000 psi

Impact

Notch Izod
ASTM D256
No Break @ 73.0 F.
@ 0.250 inft-lb/in

0.50 @ −40.0 F.
@ 0.2500 inft-lb/in

Shore
ASTM D2240

40 Shore D

DTUL @ 66
ASTM D648

122 F.

Melt Point

338.0 F.

Vicat Soft
ASTM D1525

248 F.

Melt Point

[0176] The cores have a weight of about 25 to 40 grams and preferably about 30 to 40 grams. The cores can be molded from materials noted herein. For example the core can be molded from a slug of uncured or lightly cured elastomer composition comprising a high cis content polybutadiene and a metal salt of an ethylenically unsaturated carboxylic acid such as zinc mono- or diacrylate or methacrylate. To achieve higher coefficients of restitution and/or to increase hardness in the core, the manufacturer may increase the amount of zinc diacrylate co-agent. In addition, larger amounts of metal oxide such as zinc oxide may be included in order to increase the core weight so that the finished ball more closely approaches the U.S.G.A. upper weight limit of 1.620 ounces. Non-limiting examples of other materials which may be used in the core composition include compatible rubbers or ionomers, and low molecular weight fatty acids such as stearic acid. Free radical initiator catalysts such as peroxides are admixed with the core composition so that on the application of heat and pressure, a curing or crosslinking reaction takes place.

[0177] The cores and mantle layers of the present invention are preferably formed by compression molding techniques. However, it is fully contemplated that liquid injection molding, blow molding or transfer molding techniques could be utilized.

[0178] Additionally, the core and/or mantle layer compositions of the invention may be based on polybutadiene, natural rubber, metallocene catalyzed polyolefins such as Exact® (Exxon Chem. Co.) and Engage® (Dow Chem. Co.), polyurethanes, other thermoplastic or thermoset elastomers, and mixtures of one or more of the above materials with each other and/or with other elastomers.

[0179] It is preferred that the base elastomer have a relatively high molecular weight. Polybutadiene has been found to be particularly useful because it imparts to the golf balls a relatively high coefficient of restitution. Polybutadiene can be cured using a free radical initiator such as a peroxide, or it can be sulfur cured. A broad range for the molecular weight of preferred base elastomers is from about 50,000 to about 500,000. A more preferred range for the molecular weight of the base elastomer is from about 100,000 to about 500,000. As a base elastomer for the core composition, cis-1-4-polybutadiene is preferably employed, or a blend of cis-1-4-polybutadiene with other elastomers may also be utilized. Most preferably, cis-1-4-polybutadiene having a weight-average molecular weight of from about 100,000 to about 500,000 is employed. Along this line, it has been found that the high cis-1-4-polybutadienes manufactured and sold by Bayer Corporation, Germany, under the trade name Taktene® 220 or 1220 are particularly preferred. Furthermore, the core may be comprised of a cross linked natural rubber, EPDM, metallocene catalyzed polyolefin, or another crosslinkable elastomer.

[0180] When polybutadiene is used for golf ball cores, it commonly is cross linked with an unsaturated carboxylic acid co-crosslinking agent. The unsaturated carboxylic acid component of the core composition typically is the reaction product of the selected carboxylic acid or acids and an oxide or carbonate of a metal such as zinc, magnesium, barium, calcium, lithium, sodium, potassium, cadmium, lead, tin, and the like. Preferably, the oxides of polyvalent metals such as zinc, magnesium and cadmium are used, and most preferably, the oxide is zinc oxide.

[0181] Exemplary of the unsaturated carboxylic acids which find utility in the core compositions are acrylic acid, methacrylic acid, itaconic acid, crotonic acid, sorbic acid, and the like, and mixtures thereof. Preferably, the acid component is either acrylic or methacrylic acid. Usually, from about 5 to about 40, and preferably from about 15 to about 30 parts by weight of the carboxylic acid salt, such as zinc diacrylate, is included in the core composition. The unsaturated carboxylic acids and metal salts thereof are generally soluble in the elastomeric base, or are readily dispersible.

[0182] The free radical initiator included in the core composition is any known polymerization initiator (a co-crosslinking agent) which decomposes during the cure cycle. The term “free radical initiator” as used herein refers to a chemical which, when added to a mixture of the elastomeric blend and a metal salt of an unsaturated, carboxylic acid, promotes cross linking of the elastomers by the metal salt of the unsaturated carboxylic acid. The amount of the selected initiator present is dictated only by the requirements of catalytic activity as a polymerization initiator. Suitable initiators include peroxides, persulfates, azo compounds and hydrazides. Peroxides, which are readily commercially available, are conveniently used in the present invention, generally in amounts of from about 0.1 to about 10.0 and preferably in amounts of from about 0.3 to about 3.0 parts by weight per each 100 parts of elastomer.

[0183] Exemplary of suitable peroxides for the purposes of the present invention are dicumyl peroxide, n-butyl 4,4′-bis (butylperoxy) valerate, 1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane, di-t-butyl peroxide and 2,5-di-(t-butylperoxy)-2,5 dimethyl hexane and the like, as well as mixtures thereof. It will be understood that the total amount of initiators used will vary depending on the specific end product desired and the particular initiators employed.

[0184] The core compositions of the present invention may additionally contain any other suitable and compatible modifying ingredients including, but not limited to, metal oxides, fatty acids, and diisocyanates and polypropylene powder resin. For example, Papi® 94, a polymeric diisocyanate, commonly available from Dow Chemical Co., Midland, Mich., is an optional component in the rubber compositions. It can range from about 0 to 5 parts by weight per 100 parts by weight rubber (phr) component, and acts as a moisture scavenger. In addition, it has been found that the addition of a polypropylene powder resin results in a core which is hard (i.e., exhibits high PGA compression) and thus allows for a reduction in the amount of cross linking co-agent utilized to soften the core to a normal or below normal compression.

[0185] Furthermore, because polypropylene powder resin can be added to a core composition without an increase in weight of the molded core upon curing, the addition of the polypropylene powder allows for the addition of higher specific gravity fillers, such as mineral fillers. Since the cross linking agents utilized in the polybutadiene core compositions are expensive and/or the higher specific gravity fillers are relatively inexpensive, the addition of the polypropylene powder resin substantially lowers the cost of the golf ball cores while maintaining, or lowering, weight and compression.

[0186] Various activators may also be included in the compositions of the present invention. For example, zinc oxide and/or magnesium oxide are activators for the polybutadiene. The activator can range from about 2 to about 30 parts by weight per 100 parts by weight of the rubbers (phr) component.

[0187] Moreover, reinforcement agents may be added to the core compositions of the present invention. Since the specific gravity of polypropylene powder is very low, and when compounded, the polypropylene powder produces a lighter molded core, when polypropylene is incorporated in the core compositions, relatively large amounts of higher specific gravity fillers may be added so long as the specific core weight limitations are met. As indicated above, additional benefits may be obtained by the incorporation of relatively large amounts of higher specific gravity, inexpensive mineral fillers such as calcium carbonate. Such fillers as are incorporated into the core compositions should be in finely divided form, as for example, in a size generally less than about 30 mesh and preferably less than about 100 mesh U.S. standard size. The amount of additional filler included in the core composition is primarily dictated by weight restrictions and preferably is included in amounts of from about 10 to about 100 parts by weight per 100 parts rubber.

[0188] The preferred fillers are relatively inexpensive and heavy and serve to lower the cost of the ball and to increase the weight of the ball to closely approach the U.S.G.A. weight limit of 1.620 ounces. However, if thicker cover compositions are to be applied to the core to produce larger than normal (i.e., greater than 1.680 inches in diameter) balls, use of such fillers and modifying agents will be limited in order to meet the U.S.G.A. maximum weight limitations of 1.620 ounces. Limestone is ground calcium/magnesium carbonate and is used because it is an inexpensive, heavy filler. Ground flash filler may be incorporated and is preferably 20 mesh ground up center stock from the excess flash from compression molding. It lowers the cost and may increase the hardness of the ball.

[0189] Fatty acids or metallic salts of fatty acids may also be included in the compositions, functioning to improve moldability and processing. Generally, free fatty acids having from about 10 to about 40 carbon atoms, and preferably having from about 15 to about 20 carbon atoms, are used. Exemplary of suitable fatty acids are stearic acid and linoleic acids, as well as mixtures thereof. An example of a suitable metallic salt of a fatty acid is zinc stearate. When included in the core compositions, the metallic salts of fatty acids are present in amounts of from about 1 to about 25, preferably in amounts from about 2 to about 15 parts by weight based on 100 parts rubber (elastomer). It is preferred that the core compositions include stearic acid as the fatty acid adjunct in an amount of from about 2 to about 5 parts by weight per 100 parts of rubber.

[0190] Diisocyanates may also be optionally included in the core compositions. When utilized, the diisocyanates are included in amounts of from about 0.2 to about 5.0 parts by weight based on 100 parts rubber. Exemplary of suitable diisocyanates is 4,4′-diphenylmethane diisocyanate and other polyfunctional isocyanates known in the art.

[0191] Furthermore, the dialkyl tin difatty acids set forth in U.S. Pat. No. 4,844,471, the dispensing agents disclosed in U.S. Pat. No. 4,838,556, and the dithiocarbamates set forth in U.S. Pat. No. 4,852,884 may also be incorporated into the polybutadiene compositions of the present invention. The specific types and amounts of such additives are set forth in the above identified patents, which are incorporated herein by reference.

[0192] Cores according to the present invention can be manufactured using relatively conventional techniques, such as injection molding, blow molding, compression molding and reaction injection molding.

[0193] The covers of golf balls according to the present invention may comprise any material suitable for use as a golf ball cover. Examples of preferred materials include, but are not limited to, ionomer resins, nylon compositions, and polyurethane materials.

[0194] It is appreciated that the following described materials may be used in a multi-layer cover as any of an outer cover layer or an inner cover layer.

[0195] Additionally, the cover materials described herein are also suitable for forming a mantle layer. A mantle layer as presently used includes a mantle layer that is a member of a mantle assembly according to the present invention including a mantle layer having a textured surface topography.

[0196] It is appreciated that the following described materials, while referred with respect to cover layers, are also suitable to form any mantle layer in a mantle assembly according to the present invention.

[0197] A. Ionomer Resins

[0198] With respect to a preferred ionomeric cover composition of the invention, ionomeric resins are polymers containing interchain ionic bonding. As a result of their toughness, durability, and flight characteristics, various ionomeric resins sold by E. I. DuPont de Nemours & Company under the trademark Surlyn® and more recently, by the Exxon Corporation (see U.S. Pat. No. 4,911,451, incorporated herein by reference) under the trademarks Escor® and Iotek®, have become the materials of choice for the construction of golf ball covers over the traditional “balata” (transpolyisoprene, nature or synthetic) rubbers.

[0199] Ionomeric resins are generally ionic copolymers of an olefin, such as ethylene, and a metal salt of an unsaturated carboxylic acid, such as acrylic acid, methacrylic acid or maleic acid. In some instances, an additional softening comonomer such as an acrylate can also be included to form a terpolymer. The pendent ionic groups in the ionomeric resins interact to form ion-rich aggregates contained in a non-polar polymer matrix. The metal ions, such as sodium, zinc, magnesium, lithium, potassium, calcium, etc. are used to neutralize some portion of the acid groups in the copolymer resulting in a thermoplastic elastomer exhibiting enhanced properties, i.e., improved durability, etc., for golf ball construction over balata.

[0200] The ionomeric resins utilized to produce cover compositions can be formulated according to known procedures such as those set forth in U.S. Pat. No. 3,421,766 or British Patent No. 963,380, with neutralization effected according to procedures disclosed in Canadian Patent Nos. 674,595 and 713,631, all of which are hereby incorporated by reference, wherein the ionomer is produced by copolymerizing the olefin and carboxylic acid to produce a copolymer having the acid units randomly distributed along the polymer chain. Broadly, the ionic copolymer generally comprises one or more α-olefins and from about 9 to about 20 weight percent of α,β-ethylenically unsaturated mono- or dicarboxylic acid, the basic copolymer neutralized with metal ions to the extent desired.

[0201] At least about 20% of the carboxylic acid groups of the copolymer are neutralized by the metal ions (such as sodium, potassium, zinc, calcium, magnesium, and the like) and exist in the ionic state. Suitable olefins for use in preparing the ionomeric resins include ethylene, propylene, butene-1, hexene-1 and the like. Unsaturated carboxylic acids include acrylic, methacrylic, ethacrylic, α-chloroacrylic, crotonic, maleic, fumaric, itaconic acids, and the like. The ionomeric resins utilized in the golf ball industry are generally copolymers of ethylene with acrylic (i.e., Escor®) and/or methacrylic (i.e., Surlyn®) acid. In addition, two or more types of ionomeric resins may be blended into the cover compositions in order to produce the desired properties of the resulting golf balls.

[0202] The cover compositions which may be used in making the preferred embodiment golf balls of the present invention are set forth in detail but not limited to those in U.S. Pat. No. 5,688,869, incorporated herein by reference. In short, the cover material is comprised of hard, high stiffness ionomer resins, preferably containing relatively high amounts of acid (i.e., greater than 16 weight percent acid, preferably from about 17 to about 25 weight percent acid, and more preferably from about 18.5 to about 21.5 weight percent) and at least partially neutralized with metal ions (such as sodium, zinc, potassium, calcium, magnesium and the like). The high acid resins are blended and melt processed to produce compositions exhibiting hardness and coefficient of restitution values when compared to low acid ionomers, or blends of low acid ionomer resins containing 16 weight percent acid or less.

[0203] The preferred cover compositions may also be prepared from specific blends of two or more high acid ionomers with other cover additives which do not exhibit the processing, playability, distance and/or durability limitations demonstrated by the prior art. However, as more particularly indicated below, the cover composition can also be comprised of one or more low acid ionomers so long as the molded covers exhibit a hardness of 65 or more on the Shore D scale. These include lithium ionomers or blends of ionomers with harder non-ionic polymers such as nylon, polyphenylene oxide and other compatible thermoplastics. Examples of cover compositions which may be used are set forth in detail in copending U.S. Ser. No. 07/776,803 filed Oct. 15, 1991, and Ser. No. 07/901,660 filed Jun. 19, 1992, now having matured into U.S. Pat. No. 5,688,869, incorporated herein by reference. Of course, the cover compositions are not limited in any way to those compositions set forth in said copending applications.

[0204] The high acid ionomers suitable for use in the preferred embodiment golf balls are ionic copolymers which are the metal, i.e., sodium, zinc, magnesium, etc., salts of the reaction product of an olefin having from about 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from about 3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers of ethylene and either acrylic or methacrylic acid. In some circumstances, an additional comonomer such as an acrylate ester (i.e., iso- or n-butylacrylate, etc.) can also be included to produce a softer terpolymer. The carboxylic acid groups of the copolymer are partially neutralized (i.e., approximately 10-75%, preferably 30-70%) by the metal ions. Each of the high acid ionomer resins included in the cover compositions of the invention contains greater than about 16% by weight of a carboxylic acid, preferably from about 17% to about 25% by weight of a carboxylic acid, more preferably from about 18.5% to about 21.5 % by weight of a carboxylic acid.

[0205] Although an ionomeric cover composition preferably includes a high acid ionomeric resin and the scope of the patent embraces all known high acid ionomeric resins falling within the parameters set forth above, only a relatively limited number of these high acid ionomeric resins are currently available. In this regard, the high acid ionomeric resins available from E. I. DuPont de Nemours Company under the trademark Surlyn®, and the high acid ionomer resins available from Exxon Corporation under the trademarks Escor® or Iotek® are examples of available high acid ionomeric resins which may be utilized in the present invention.

[0206] The high acid ionomeric resins available from Exxon under the designation Escor® and/or Iotek®, are somewhat similar to the high acid ionomeric resins available under the Surlyn® trademark. However, since the Escor®/Iotek® ionomeric resins are sodium or zinc salts of poly(ethylene acrylic acid) and the Surlyn® resins are zinc, sodium, magnesium, etc., salts of poly(ethylene methacrylic acid), distinct differences in properties exist.

[0207] Examples of the high acid methacrylic acid-based ionomers found suitable for use in accordance with this invention include Surlyn® AD-8422 (sodium cation), Surlyn® 8162 (zinc cation), Surlyn® SEP-503-1 (zinc cation), and Surlyn® SEP-503-2 (magnesium cation). According to DuPont, all of these ionomers contain from about 18.5 to about 21.5% by weight methacrylic acid.

[0208] More particularly, Surlyn® AD-8422 is currently commercially available from DuPont in a number of different grades (i.e., Surlyn® AD-8422-2, Surlyn® AD-8422-3, Surlyn® AD-8422-5, etc.) based upon differences in melt index. According to DuPont, Surlyn® AD-8422 offers the following general properties, listed in Table 5, when compared to Surlyn® 8920, which is the stiffest, hardest of all on the low acid grades (referred to as “hard” ionomers in U.S. Pat. No. 4,884,814, incorporated herein by reference):

5TABLE 5Low AcidHigh Acid(15 wt % Acid)(>20 wt % Acid)Surlyn ®Surlyn ®Surlyn ®89208422-28422-3IonomerCationNaNaNaMelt Index1.22.81.0Sodium, Wt %2/31.92.4Base Resin MI606060MP1, ° C.888685FP1, ° C.4748.545Compression Molding2Tensile Break, psi435041905330Yield, psi228036703590Elongation, %315263289Flex Mod, K psi53.276.488.3Shore D hardness6667681DSC second heat, 10° C./min heating rate. 2Samples compression molded at 150° C. annealed 24 hours at 60° C. Surlyn ® 8422-2, −3 were homogenized at 190° C. before molding.

[0209] In comparing Surlyn® 8920 to Surlyn® 8422-2 and Surlyn® 8422-3, it is noted that the high acid Surlyn® ionomers yield, lower elongation, slightly higher Shore D hardness and much higher flexural modulus. Surlyn® 8920 contains 15% weight methacrylic acid and is 59% neutralized with sodium.

[0210] In addition, Surlyn® SEP-503-1 (zinc cation) and Surlyn® SEP-503-2 (magnesium cation) are high acid zinc and magnesium versions of the Surlyn® AD 8422 high acid ionomers. When compared to the Surlyn® AD 8422 (sometimes referred to herein as Surlyn® 8422 or as 8422) high acid ionomers, the Surlyn® SEP-503-1 and SEP-503-2 ionomers can be defined as follows in Table 6:

6TABLE 6Surlyn ® IonomerIonMelt IndexNeutralization %AD 8422-3Na1.045SEP 503-1Zn0.838SEP 503-2Mg1.843

[0211] Furthermore, Surlyn® 8162 is a zinc cation ionomer resin containing approximately 20% by weight (i.e., 18.5-21.5% weight) methacrylic acid copolymer that has been 30-70% neutralized. Surlyn® 8162 is currently commercially available from DuPont.

[0212] Examples of the high acid acrylic acid-based ionomers suitable for use in the present invention include the Escor® or Iotek® high acid ethylene acrylic acid ionomers produced by Exxon. In this regard, Escor® or Iotek® 959 is a sodium ion neutralized ethylene-acrylic acid copolymer. According to Exxon, Iotek®s 959 and 960 contain from about 19.0 to about 21.0% by weight acrylic acid with approximately 30 to about 70 percent of the acid groups neutralized with sodium and zinc ions, respectively. The physical properties of these high acid acrylic acid-based ionomers are as follows in Table 7:

7TABLE 7Escor ®Escor ®Property(Iotek ® 959)(Iotek ® 960)Melt Index, g/10 min2.01.8CationSodiumZincMelting Point, ° F.172174Vicat Softening Point, ° F.130131Tensile @ Break, psi46003500Elongation @ Break, %325430Hardness, Shore D6657Flexural Modulus, psi66,00027,000

[0213] Furthermore, as a result of the development by the inventors of a number of new high acid ionomers neutralized to various extents by several different types of metal cations, such as by manganese, lithium, potassium, calcium and nickel cations, several new high acid ionomers and/or high acid ionomer blends besides sodium, zinc and magnesium high acid ionomers or ionomer blends are now available for golf ball cover production. It has been found that these new cation neutralized high acid ionomer blends produce cover compositions exhibiting enhanced hardness and resilience due to synergies which occur during processing. Consequently, the metal cation neutralized high acid ionomer resins recently produced can be blended to produce substantially harder covered golf balls having higher C.O.R.'s than those produced by the low acid ionomer covers presently commercially available.

[0214] More particularly, several new metal cation neutralized high acid ionomer resins have been produced by the inventors by neutralizing, to various extents, high acid copolymers of an alpha-olefin and an alpha, beta-unsaturated carboxylic acid with a wide variety of different metal cation salts. This discovery is the subject matter of U.S. application Ser. No. 901,680, incorporated herein by reference. It has been found that numerous new metal cation neutralized high acid ionomer resins can be obtained by reacting a high acid copolymer (i.e., a copolymer containing greater than 16% by weight acid, preferably from about 17 to about 25 weight percent acid, and more preferably about 20 weight percent acid), with a metal cation salt capable of ionizing or neutralizing the copolymer to the extent desired (i.e., from about 10% to 90%).

[0215] The base copolymer is made up of greater than 16% by weight of an alpha, beta-unsaturated carboxylic acid and an alpha-olefin. Optionally, a softening comonomer can be included in the copolymer. Generally, the alpha-olefin has from 2 to 10 carbon atoms and is preferably ethylene, and the unsaturated carboxylic acid is a carboxylic acid having from about 3 to 8 carbons. Examples of such acids include acrylic acid, methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, with acrylic acid being preferred.

[0216] The softening comonomer that can be optionally included in the covers of the preferred embodiment golf balls of the invention may be selected from the group consisting of vinyl esters of aliphatic carboxylic acids wherein the acids have 2 to 10 carbon atoms, vinyl ethers wherein the alkyl groups contain 1 to 10 carbon atoms, and alkyl acrylates or methacrylates wherein the alkyl group contains 1 to 10 carbon atoms. Suitable softening comonomers include vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, or the like.

[0217] Consequently, examples of a number of copolymers suitable for use to produce the high acid ionomers included in the preferred embodiment balls of the present invention include, but are not limited to, high acid embodiments of an ethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer, an ethylene/itaconic acid copolymer, an ethylene/maleic acid copolymer, an ethylene/methacrylic acid/vinyl acetate copolymer, an ethylene/acrylic acid/vinyl alcohol copolymer, etc. The base copolymer broadly contains greater than 16% by weight unsaturated carboxylic acid, from about 30 to about 83% by weight ethylene and from 0 to about 40% by weight of a softening comonomer. Preferably, the copolymer contains about 20% by weight unsaturated carboxylic acid and about 80% by weight ethylene. Most preferably, the copolymer contains about 20% acrylic acid with the remainder being ethylene.

[0218] Along these lines, examples of the preferred high acid base copolymers which fulfill the criteria set forth above, are a series of ethylene-acrylic acid copolymers which are commercially available from The Dow Chemical Company, Midland, Mich., under the Primacor® designation. These high acid base copolymers exhibit the typical properties set forth in Table 8 below:

8TABLE 8Typical Properties of Primacor ® Ethylene-Acrylic Acid CopolymersMeltTensileFlexuralVicatPercentDensity,Index,YD. StModulusSoft PTShore DGradeAcidglccg/10 min(psi)(psi)(° C.)HardnessASTMD-792D-1238D-638D-790D-1525D-2240598020.00.958300.0—48004350599020.00.9551300.0 65026004042599020.00.9551300.0 65032004042598120.00.960300.090032004648598120.00.960300.090032004648598320.00.958500.085031004445599120.00.9532600.0 63526003840

[0219] Due to the high molecular weight of the Primacor® 5981 grade of the ethylene-acrylic acid copolymer, this copolymer is the more preferred grade utilized in the invention.

[0220] The metal cation salts utilized in the invention are those salts which provide the metal cations capable of neutralizing, to various extents, the carboxylic acid groups of the high acid copolymer. These include acetate, oxide or hydroxide salts of lithium, calcium, zinc, sodium, potassium, nickel, magnesium, and manganese.

[0221] Examples of such lithium ion sources are lithium hydroxide monohydrate, lithium hydroxide, lithium oxide and lithium acetate. Sources for the calcium ion include calcium hydroxide, calcium acetate and calcium oxide. Suitable zinc ion sources are zinc acetate dihydrate and zinc acetate, a blend of zinc oxide and acetic acid. Examples of sodium ion sources are sodium hydroxide and sodium acetate. Sources for the potassium ion include potassium hydroxide and potassium acetate. Suitable nickel ion sources are nickel acetate, nickel oxide and nickel hydroxide. Sources of magnesium include magnesium oxide, magnesium hydroxide, and magnesium acetate. Sources of manganese include manganese acetate and manganese oxide.

[0222] The new metal cation neutralized high acid ionomer resins are produced by reacting the high acid base copolymer with various amounts of the metal cation salts above the crystalline melting point of the copolymer, such as at a temperature from about 200° F. to about 500° F., preferably from about 250° F. to about 350° F. under high shear conditions at a pressure of from about 10 psi to 10,000 psi. Other well known blending techniques may also be used. The amount of metal cation salt utilized to produce the new metal cation neutralized high acid-based ionomer resins is the quantity which provides a sufficient amount of the metal cations to neutralize the desired percentage of the carboxylic acid groups in the high acid copolymer. The extent of neutralization is generally from about 10% to about 90%.

[0223] As indicated below in Table 9, and more specifically in Example 1 in U.S. application Ser. No. 901,680, a number of new types of metal cation neutralized high acid ionomers can be obtained from the above indicated process. These include new high acid ionomer resins neutralized to various extents with manganese, lithium, potassium, calcium and nickel cations. In addition, when a high acid ethylene/acrylic acid copolymer is utilized as the base copolymer component of the invention and this component is subsequently neutralized to various extents with the metal cation salts producing acrylic acid based high acid ionomer resins neutralized with cations such as sodium, potassium, lithium, zinc, magnesium, manganese, calcium and nickel, several new cation neutralized acrylic acid based high acid ionomer resins are produced.

9TABLE 9FormulationWt-% CationWt-%MeltShore DNo.SaltNeutralizationIndexC.O.R.Hardness1 (NaOH)6.9867.50.9.804712 (NaOH)5.6654.02.4.806733 (NaOH)3.8435.912.2.612694 (NaOH)2.9127.017.5.812(brittle)5 (MnAc)19.671.77.5.809736 (MnAc)23.18833.5.814777 (MnAc)15.353.07.5.810728 (MnAc)26.51060.7.813(brittle)9 (LiOH)4.5471.30.6.6107410 (LiOH)3.3852.54.2.8187211 (LiOH)2.3435.918.6.8157212 (KOH)5.3036.019.3Broke7013 (KOH)8.2657.97.18.8047014 (KOH)10.777.04.3.8016715 (ZnAc)17.971.50.2.8067116 (ZnAc)13.953.00.9.7976917 (ZnAc)9.9136.13.4.7936718 (MgAC)17.470.72.8.8147419 (MgAC)20.687.11.5.8157620 (MgAC)13.853.84.1.6147421 (CaAc)13.269.21.1.8137422 (CaAc)7.1234.910.1.80870Control:50/50 Blend of loteks ® 8000/7030C.O.R. = .810/65 Shore D HardnessDuPont High Acid Surlyn ® 8422 (Na)C.O.R. = .811/70 Shore D HardnessDuPont High Acid Surlyn ® 8162 (Zn)C.O.R. = .807/65 Shore D HardnessExxon High Acid Iotek ® EX-960 (Zn)C.O.R. = .796/65 Shore D HardnessFormulationWt-%/CationWt-%MeltNo.SaltNeutralizationIndexC.O.R.23 (MgO)2.9153.52.5.81324 (MgO)3 8571.52.8.80825 (MgO)4.7689.31.1.80926 (MgO)1.9635.77.5.815Control for Formulation Nos. 23-26 is 50/50 Iotek ® 8000/7030,C.O.R. = .814, Formulation 26 C.O.R. was normalizedto that control accordinglyFormulationWt-% CationWt-%MeltShore DNo.SaltNeutralizationIndexC.O.R.Hardness27 (NiAc)13.0461.10.2.8027128 (NiAc)10.7148.90.57997229 (NiAc)8.2636.71.8.7966930 (NiAc)5.6624.47.5.7866417 (ZnAc)9.9136.13.4.79367Control for Formulation Nos. 27-30 is 50/50 Iotek ® 8000/7030, C.O.R. = .807

[0224] When compared to low acid versions of similar cation neutralized ionomer resins, the new metal cation neutralized high acid ionomer resins exhibit enhanced hardness, modulus and resilience characteristics.

[0225] When utilized in golf ball cover construction, it has been found that the new acrylic acid based high acid ionomers extend the range of hardness beyond that previously obtainable while maintaining the beneficial properties (i.e., durability, click, feel, etc.) of the softer low acid ionomer covered balls, such as balls produced utilizing the low acid ionomers disclosed in U.S. Pat. Nos. 4,884,814 and 4,911,451, and the recently produced high acid blends disclosed in U.S. Pat. No. 5,688,869, all of which, as previously noted, are herein incorporated by reference.

[0226] Moreover, as a result of the development of a number of new acrylic acid based high acid ionomer resins neutralized to various extents by several different types of metal cations, such as manganese, lithium, potassium, calcium and nickel cations, several new ionomers or ionomer blends are now available for golf ball production. By using these high acid ionomer resins harder, stiffer golf balls having higher C.O.R.s, and thus longer distance, can be obtained.

[0227] Other ionomer resins may be used in the cover compositions, such as low acid ionomer resins, preferably such that the molded cover produces a Shore D hardness of 65 or more.

[0228] The low acid ionomers which may be suitable for use in formulating cover layer compositions are ionic copolymers which are the metal, i.e., sodium, zinc, magnesium, etc., salts of the reaction product of an olefin having from about 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from about 3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers of ethylene and either acrylic or methacrylic acid. In some circumstances, an additional comonomer such as an acrylate ester (i.e., iso- or n-butylacrylate, etc.) can also be included to produce a softer terpolymer. The carboxylic acid groups of the copolymer are partially neutralized (i.e., approximately 10-75%, preferably 30-70%) by the metal ions. Each of the low acid ionomer resins which may be included in the inner layer cover compositions of the invention contains 16% by weight or less of a carboxylic acid.

[0229] Suitable low acid ionomers include, but are not limited to, those developed and sold by E. I. DuPont de Nemours & Company under the trademark Surlyn® and by Exxon Corporation under the trademarks Escor® or Iotek®, or blends thereof.

[0230] The low acid ionomeric resins available from Exxon under the designation Escor® and/or Iotek®, are somewhat similar to the low acid ionomeric resins available under the Surlyn® trademark. However, since the Escor®/Iotek® ionomeric resins are sodium or zinc salts of poly(ethylene-acrylic acid) and the Surlyn® resins are zinc, sodium, magnesium, etc. salts of poly(ethylene-methacrylic acid), distinct differences in properties exist.

[0231] When utilized in the construction of an inner layer of a multi-layered golf ball, it has been found that the low acid ionomer blends extend the range of compression and spin rates beyond that previously obtainable. More preferably, it has been found that when two or more low acid ionomers, particularly blends of sodium and zinc low acid ionomers, are processed to produce the covers of multi-layered golf balls, (i.e., the inner cover layer herein) the resulting golf balls will travel further and at an enhanced spin rate than previously known multi-layered golf balls. Such an improvement is particularly noticeable in enlarged or oversized golf balls.

[0232] For example, the normal size, multi-layer golf ball taught in U.S. Pat. No. 4,650,193 does not incorporate blends of low acid ionomeric resins of the present invention in the inner cover layer. In addition, the multi-layered ball disclosed in the '193 patent suffers substantially in durability in comparison with the present invention.

[0233] Furthermore, use of an inner layer formulated from blends of lower acid ionomers produces multi-layer golf balls having enhanced compression and spin rates. These are the properties desired by the more skilled golfer.

[0234] Regarding multi-layer cover constructions, the outer cover layer is preferably softer than the low acid ionomer blend based inner layer. The softness provides for the enhanced feel and playability characteristics typically associated with balata or balata-blend balls. The outer layer or ply is comprised of a relatively soft, low modulus (about 1,000 psi to about 10,000 psi) and low acid (less than 16 weight percent acid) ionomer, ionomer blend or a non-ionomeric thermoplastic elastomer such as, but not limited to, a polyurethane, a polyester elastomer such as that marketed by DuPont under the trademark Hytrel®, or a polyether amide such as that marketed by Elf Atochem S.A. under the trademark Pebax®. The outer layer is fairly thin (i.e., from about 0.010 to about 0.070 in thickness, more desirably 0.03 to 0.06 inches in thickness for a 1.680 inch ball and 0.04 to 0.07 inches in thickness for a 1.72 inch ball), but thick enough to achieve desired playability characteristics while minimizing expense

[0235] Preferably, an outer layer includes a blend of hard and soft (low acid) ionomer resins such as those described in U.S. Pat. Nos. 4,884,814 and 5,120,791, both incorporated herein by reference. Specifically, a desirable material for use in molding an outer layer comprises a blend of a high modulus (hard), low acid, ionomer with a low modulus (soft), low acid, ionomer to form a base ionomer mixture.

[0236] A high modulus ionomer herein is one which measures from about 15,000 to about 70,000 psi as measured in accordance with ASTM method D-790. The hardness may be defined as at least 50 on the Shore D scale as measured in accordance with ASTM method D-2240.

[0237] The hard ionomer resins utilized to produce an outer cover layer composition comprised of hard/soft blends include ionic copolymers which are the sodium, zinc, magnesium or lithium salts of the reaction product of an olefin having from 2 to 8 carbon atoms and an unsaturated monocarboxylic acid having from 3 to 8 carbon atoms.

[0238] The carboxylic acid groups of the copolymer may be totally or partially (i.e., approximately 15-75%) neutralized.

[0239] The hard ionomeric resins are likely copolymers of ethylene and either acrylic and/or methacrylic acid, with copolymers of ethylene and acrylic acid being the most preferred. Two or more types of hard ionomeric resins may be blended into the outer cover layer compositions in order to produce the desired properties of the resulting golf balls.

[0240] As discussed earlier herein, the hard ionomeric resins introduced under the designation Escor® and sold under the designation Iotek® are somewhat similar to the hard ionomeric resins sold under the Surlyn® trademark. However, since the Iotek® ionomeric resins are sodium or zinc salts of poly(ethylene-acrylic acid) and the Surlyn® resins are zinc or sodium salts of poly(ethylene-methacrylic acid) some distinct differences in properties exist. As more specifically indicated in the data set forth below, the hard Iotek® resins (i.e., the acrylic acid based hard ionomer resins) are the more preferred hard resins for use in formulating the outer layer blends for use in the present invention. In addition, various blends of Iotek® and Surlyn® hard ionomeric resins, as well as other available ionomeric resins, may be utilized in the present invention in a similar manner.

[0241] Examples of commercially available hard ionomeric resins which may be used in the present invention in formulating the inner and outer cover blends include the hard sodium ionic copolymer sold under the trademark Surlyn® 8940 and the hard zinc ionic copolymer sold under the trademark Surlyn® 9910. Surlyn® 8940 is a copolymer of ethylene with methacrylic acid and about 15 weight percent acid which is about 29% neutralized with sodium ions. This resin has an average melt flow index of about 2.8. Surlyn® 9910 is a copolymer of ethylene and methacrylic acid with about 15 weight percent acid which is about 58 percent neutralized with zinc ions. The average melt flow index of Surlyn® 9910 is about 0.7. The typical properties of Surlyn® 9910 and 8940 are set forth below in Table 10:

10TABLE 10Typical Properties of Commercially Available HardSurlyn ® Resins Suitable for Use in the Inner and Outer LayerBlends of the Present InventionASTM D894099108920852699709730Cation TypeSodiumZincSodiumSodiumZincZincMelt flow index, gms/10 min.D-1238280.70.91.314.01.6Specific Gravity, g/cm3D-7920.950.970.950.940.95.095Hardness, Shore DD-2240666466606263Tensile Strength, (kpsi), MPaD-638(4.8)(3.6)(5.4)(4.2)(3.2)(4.1)Elongation, %D-638470290350450460460Flexural Modulus, (kpsi) MPaD-790(51)(48)(55)(32)(28)(30)Tensile Impact (23° C.)D-182251020102086511607601240KJ/m2 (ft.-lbs./in2)(485)(485)(410)(550)(360)(590)Vicat Temperature, ° C.D-1525636258736173

[0242] Examples of the more pertinent acrylic acid based hard ionomer resin suitable for use as an inner and outer cover composition sold under the Iotek® tradename by the Exxon Corporation include Iotek® 4000, Iotek® 4010, Iotek® 8000, Iotek® 8020 and Iotek® 8030. The typical properties of these and other Iotek® hard ionomers suited for use in formulating an inner and/or outer layer cover compositions are listed in Table 11:

11TABLE 11Typical Properties of lotek ® lonomersASTMResin PropertiesMethodUnits40004010800080208030Cation typezinczincsodiumsodiumsodiumMelt indexD-1238g/10 min.251.50.8162.8DensityD-1505kg/m3963963954960960Melting PointD-3417° C.90909087.587.5Crystallization PointD-3417° C.6264565355Vicat Softening PointD-1525° C.6263616467% Weight Acrylic Acid16—11——% of Acid Groups Cation30—40——NeutralizedASTMPlaque PropertiesMethodUnits40004010800080208030(3 mm thick, compressionmolded)Tensile at BreakD-638MPa24263631.528Yield PointD-638MPanonenone212123Elongation at BreakD-638%4204203504103951% Secant ModulusD-638MPa160160300350390Shore Hardness DD-2240—5555615859Film Properties(50 Micron Film 2.2:1ASTMBlow-Up Ratio)MethodUnits40004010800080208030Tensile at Break MDD-882MPa4139425247.4TDD-882MPa3738383840.5Yield Point MDD-882MPa1517172321.6TDD-882MPa1415152120.7Elongation at Break MDD-882%310270260295305TDD-882%3602402803403451% Secant Modulus MDD-882MPa210215390380380TDD-882MPa200225380350345Dart Drop ImpactD-1709g/micron12.412.520.3ASTMResin PropertiesMethodUnits701070207030Cation typezinczinczincMelt indexD-1238g/10 min.0.80.82.5DensityD-1505kg/m3960960960Melting PointD-3417° C.909090Vicat Softening PointD-1525° C.606362.5ASTMPlaque PropertiesMethodUnits701070207030(3 mm thick, compression molded)Tensile at BreakD-638MPa383838Yield PointD-638MPanonenonenoneElongation at BreakD-638%500420395Shore Hardness DD-2240—575555

[0243] Comparatively, soft ionomers are used in formulating the hard/soft blends of inner and outer cover compositions. These ionomers include acrylic acid based soft ionomers. They are generally characterized as comprising sodium or zinc salts of a terpolymer of an olefin having from about 2 to 8 carbon atoms, acrylic acid, and an unsaturated monomer of the acrylate ester class having from 1 to 21 carbon atoms. The soft ionomer is preferably a zinc-based ionomer made from an acrylic acid base polymer in an unsaturated monomer of the acrylate ester class. The soft (low modulus) ionomers have a hardness from about 20 to about 40 as measured on the Shore D scale, as measured in accordance with ASTM method D-2240, and a flexural modulus from about 1,000 to about 10,000, as measured in accordance with ASTM method D-790.

[0244] Certain ethylene-acrylic acid based soft ionomer resins developed by the Exxon Corporation under the designation Iotek® 7520 (referred to experimentally by differences in neutralization and melt indexes as LDX 195, LDX 196, LDX 218 and LDX 219) may be combined with known hard ionomers such as those indicated above to produce the inner and outer cover layers. The combination produces higher C.O.R.s at equal or softer hardness, higher melt flow (which corresponds to improved, more efficient molding, i.e., fewer rejects) as well as significant cost savings versus the inner and outer layers of multi-layer balls produced by other known hard-soft ionomer blends as a result of the lower overall raw materials costs and improved yields.

[0245] While the exact chemical composition of the resins to be sold by Exxon under the designation Iotek® 7520 is considered by Exxon to be confidential and proprietary information, Exxon's experimental product data sheet and Table 12 lists the following physical properties of the ethylene acrylic acid zinc ionomer developed by Exxon:

12TABLE 12Physical Properties of Iotek ® 7520PropertyASTM MethodUnitsTypical ValueMelt IndexD-1238g/10 min.2DensityD-1505kg/m30.962CationzincMelting PointD-341766Crystallization PointD-3417° C.49Vicat SofteningD-1525° C.42Plaque Properties(2 mm thickCompressionMolded Plaques)Tensile at BreakD-638MPa10Yield PointD-638MPaNoneElongation at BreakD-638%7601% Secant ModulusD-638MPa22Shore D HardnessD-224032Flexural ModulusD-790MPa26Zwick ReboundISO 4862%52De Mattia FlexD-430Cycles>5000Resistance

[0246] In addition, test data collected by the inventor indicates that Iotek® 7520 resins have Shore D hardnesses of about 32 to 36 (per ASTM D-2240), melt flow indexes of 3±0.5 g/10 min (at 190° C. per ASTM D-1288), and a flexural modulus of about 2500-3500 psi (per ASTM D-790). Furthermore, testing by an independent testing laboratory by pyrolysis mass spectrometry indicates that Iotek® 7520 resins are generally zinc salts of a terpolymer of ethylene, acrylic acid, and methyl acrylate.

[0247] Furthermore, a newly developed grade of an acrylic acid based soft ionomer available from the Exxon Corporation under the designation Iotek® 7510, is also effective, when combined with the hard ionomers indicated above in producing golf ball covers exhibiting higher C.O.R. values at equal or softer hardness than those produced by known hard-soft ionomer blends. In this regard, Iotek® 7510 has the advantages (i.e., improved flow, higher C.O.R. values at equal hardness, increased clarity, etc.) produced by the Iotek® 7520 resin when compared to the methacrylic acid base soft ionomers known in the art (such as the Surlyn® 8625 and the Surlyn® 8629 combinations disclosed in U.S. Pat. No. 4,884,814).

[0248] In addition, Iotek® 7510, when compared to Iotek® 7520, produces slightly higher C.O.R. valves at equal softness/hardness due to the Iotek® 7510's higher hardness and neutralization. Similarly, Iotek® 7510 produces better release properties (from the mold cavities) due to its slightly higher stiffness and lower flow rate than Iotek® 7520. This is important in production where the soft-covered balls tend to have lower yields caused by sticking in the molds and subsequent punched pin marks from the knockouts.

[0249] According to Exxon, Iotek® 7510 is of similar chemical composition as Iotek® 7520 (i.e., a zinc salt of a terpolymer of ethylene, acrylic acid, and methyl acrylate) but is more highly neutralized. Based upon FTIR analysis Iotek® 7520 is estimated to be about 30-40 wt. -% neutralized and Iotek® 7510 is estimated to be about 40-60 wt.-% neutralized. The typical properties of Iotek® 7510 in comparison of those of Iotek® 7520 are set forth below in Table 13:

13TABLE 13Physical Properties of Iotek ® 7510 in Comparison to Iotek ® 7520Iotek ® 7520Iotek ® 7514MI, g/10 min2.00.8Density, g/cc0.960.97Melting Point, of151149Vicat Softening Point, ° F.108109Flex Modulus, psi38005300Tensile Strength, psi14501750Elongation, %760690Shore D Hardness3235

[0250] It has been determined that when hard/soft ionomer blends are used for the outer cover layer, good results are achieved when the relative combination is in a range of about 90 to about 10 percent hard ionomer and about 10 to about 90 percent soft ionomer. The results are improved by adjusting the range to about 75 to 25 percent hard ionomer and 25 to 75 percent soft ionomer. Even better results are noted at relative ranges of about 60 to 90 percent hard ionomer resin and about 40 to 10 percent soft ionomer resin.

[0251] Specific formulations which may be used in the cover composition are included in the examples set forth in U.S. Pat. Nos. 5,120,791 and 4,884,814. The present invention is in no way limited to those examples.

[0252] Moreover, in alternative embodiments, the outer cover layer formulation may also comprise a soft, low modulus non-ionomeric thermoplastic elastomer including a polyester polyurethane such as B. F. Goodrich Company's Estane® polyester polyurethane X-4517. According to B. F. Goodrich, Estane® X-4517 has the properties listed in Table 14:

14TABLE 14Properties of Estane ® X-4517Tensile 143100% 815200%1024300%1193Elongation 641Youngs Modulus1826Hardness A/D88/39Bayshore Rebound 59Solubility in WaterInsolubleMelt Processing Temperature>350° (>177° C.)Specific Gravity (H2O = 1)1.1-1.3

[0253] In addition to the above noted ionomers, compatible additive materials may also be added to produce the cover compositions of the present invention. These additive materials include dyes (for example, Ultramarine Blue™ sold by Whitaker, Clark, and Daniels of South Painsfield, N.J.), and pigments, i.e., white pigments such as titanium dioxide (for example Unitane™ 0-110) zinc oxide, and zinc sulfate, as well as fluorescent pigments. As indicated in U.S. Pat. No. 4,884,814, the amount of pigment and/or dye used in conjunction with the polymeric cover composition depends on the particular base ionomer mixture utilized and the particular pigment and/or dye utilized. The concentration of the pigment in the polymeric cover composition can be from about 1% to about 10% as based on the weight of the base ionomer mixture. A more preferred range is from about 1% to about 5% as based on the weight of the base ionomer mixture. The most preferred range is from about 1% to about 3% as based on the weight of the base ionomer mixture. The most preferred pigment for use in accordance with this invention is titanium dioxide.

[0254] Moreover, since there are various hues of white, i.e., blue white, yellow white, etc., trace amounts of blue pigment may be added to the cover stock composition to impart a blue white appearance thereto. However, if different hues of the color white are desired, different pigments can be added to the cover composition at the amounts necessary to produce the color desired.

[0255] In addition, it is within the purview of this invention to add to the cover compositions of this invention compatible materials which do not affect the basic novel characteristics of the composition of this invention. Among such materials are antioxidants (i.e., Santonox® R), antistatic agents, stabilizers and processing aids. The cover compositions of the present invention may also contain softening agents, such as plasticizers, etc., and reinforcing materials such as glass fibers and inorganic fillers, as long as the desired properties produced by the golf ball covers of the invention are not impaired.

[0256] Furthermore, optical brighteners, such as those disclosed in U.S. Pat. No. 4,679,795, herein incorporated by reference, may also be included in the cover composition of the invention. Examples of suitable optical brighteners which can be used in accordance with this invention are Uvitex® OB as sold by the Ciba-Geigy Chemical Company, Ardsley, N.Y. Uvitex® OB is thought to be 2,5-Bis(5-tert-butyl-2-benzoxazoly)thiophene. Examples of other optical brighteners suitable for use in accordance with this invention are as follows: Leucopure® EGM as sold by Sandoz, East Hanover, N.J. 07936. Leucopure® EGM is thought to be 7-(2n-naphthol(1,2-d)-triazol 2yl)-3phenyl-coumarin. Phorwhite® K-20G2 is sold by Mobay Chemical Corporation, P.O. Box 385, Union Metro Park, Union, N.J. 07083, and is thought to be a pyrazoline derivative. Eastobrite® OB-1 as sold by Eastman Chemical Products, Inc. Kingsport, Tenn., is thought to be 4,4-Bis(-benzoxazoly)stilbene. The above-mentioned Uvitex® and Eastobrite® OB-1 are preferred optical brighteners for use in accordance with this invention.

[0257] Moreover, since many optical brighteners are colored, the percentage of optical brighteners utilized must not be excessive in order to prevent the optical brightener from functioning as a pigment or dye in its own right.

[0258] Other soft, relatively low modulus non-ionomeric thermoplastic elastomers may also be utilized to produce the outer cover layer as long as the non-ionomeric thermoplastic elastomers produce the playability and durability characteristics desired without adversely effecting the enhanced spin characteristics produced by the low acid ionomer resin compositions. These include, but are not limited to thermoplastic polyurethanes such as: Texin® thermoplastic polyurethanes from Mobay Chemical Co. and the Pellethane® thermoplastic polyurethanes from Dow Chemical Co.; Ionomer/rubber blends such as those in Spalding U.S. Pat. Nos. 4,986,545; 5,098,105 and 5,187,013; and, Hytrel® polyester elastomers from DuPont and Pebax® polyetheramides from Elf Atochem S.A.

[0259] B. Nylon Compositions

[0260] Furthermore, examples of cover compositions for use as inner or outer cover layers include a graft copolymer or blend of a polyamide homopolymer with one or both of an ionomeric terpolymer and an ionomeric copolymer with two types of monomers. Preferred polyamides for use according to the invention are polymers of caprolactam such as polyepsiloncaprolactam (nylon 6), polyhexamethyleneadipamide (nylon 6,6), and copolymers of nylon 6 and nylon 6,6. The ionomeric component of the invention preferably is a copolymer formed from an alpha-olefin having 2 to 8 carbon atoms and an acid which is selected from the group consisting of alpha, beta-ethylenically unsaturated mono- or dicarboxylic acids and is neutralized with cations which include at least one member selected from the group consisting of zinc, lithium, sodium, manganese, calcium, chromium, nickel, aluminum, potassium, barium, tin, copper, and magnesium ions. Preferred cations are zinc, sodium and lithium, and combinations thereof. The copolymer may further be formed from an unsaturated monomer of the acrylate ester class having from 1 to 21 carbon atoms.

[0261] The Shore D hardness of a hard nylon-containing cover layer according to the invention is typically in the range of 65 to 84. Shore D hardness is measured generally in accordance with ASTM D-2240, but measured on the curved surface of the ball. The Shore D hardness of a soft nylon-containing cover layer according to the present invention typically is in the range of 50 to 65. Both hard and soft nylon-containing cover layers preferably are made from resin compositions which have a melt index of from about 0.5 to about 20 g/10 min., more preferably from about 0.5 to about 8 g/10 min., and most preferably from about 1 to about 4 g/10 mins.

[0262] Golf balls according to the invention typically have a coefficient of restitution of at least 0.780 and more preferably at least 0.800, and a PGA compression of 85 to 117, more preferably 90 to 105, and most preferably 90 to 97. High spin golf balls according to the invention typically have a PGA compression of 70 to 100, more preferably 75 to 95, and most preferably 75 to 85.

[0263] An “ionomeric copolymer” as this term is used herein is a copolymer of alpha-olefin and an alpha, beta-ethylenically unsaturated mono- or dicarboxylic acid with at least 3% and preferably at least 10% of the carboxylic acid groups being neutralized with metal ions. The alpha-olefin preferably has 2 to 8 carbon atoms, the carboxylic acid preferably is acrylic acid, methacrylic acid, maleic acid, or the like and the metal ions include at least one cation selected from the group consisting of ions of zinc, magnesium, lithium, barium, potassium, calcium, manganese, nickel, chromium, tin, aluminum, sodium, copper, or the like. Preferably the cation is zinc, sodium or lithium or a combination thereof. The term “copolymer” includes (1) copolymers having two types of monomers which are polymerized together, (2) terpolymers (which are formed by the polymerization of three types of monomers), and (3) copolymers which are formed by the polymerization of more than three types of monomers.

[0264] A “polyamide component” as used herein is a polyamide homopolymer, a polyamide copolymer containing two or more types of amide units, e.g., nylon 6, nylon 12, or a combination of both a polyamide homopolymer and a polyamide copolymer. The polyamide component preferably is a long chain polymer, not an oligomer, which typically is a short chain polymer of 2 to 10 units. An “ionomeric component” is (a) a non-polyamide-containing ionomeric copolymer which is capable of being mixed or blended with the polyamide component, (b) the ionomeric portion of a polyamide-containing ionomeric copolymer, or a combination of both (a) and (b). If the polyamide component and ionomeric component are bonded to one another, the acid portion of the ionomeric component preferably is neutralized before the reaction of the polyamide and ionomeric components, but could also be neutralized after the reaction of the polyamide and ionomeric components.

[0265] The details of interaction between a polyamide and an ionomeric copolymer are not fully understood. A polyamide and an ionomer could, for example, be intimately mixed without any bonding but with specific intermolecular interactions. Furthermore, it is possible, in combining a specific quantity of polyamide with a specific quantity of ionomeric copolymer that portions of the overall quantities of the polyamide component and ionomeric component could be bonded to each other, as in a graft reaction, while other portions of the polyamide component and ionomeric component could form a blend which may have specific intermolecular interactions. Thus, this application is not intended to be limited by the degree of bonding versus intermolecular interaction of the polyamide component and ionomeric component unless specifically indicated.

[0266] Golf balls of the present invention may employ a composition that is the reaction product (“RP”) of a reactive mixture of polyamide, ionomeric copolymer, and an ester. The RP preferably is formed from a reactive mixture of at least one of polyepsiloncaprolactam (Nylon 6) and polyhexamethyleneadipamide (Nylon 6,6), zinc neutralized ethylene/methacrylic acid ionomer copolymer, and ethylene (meth)acrylate. As used herein, the term “(meth)acrylate” includes both acrylates and methacrylates. The polyamide preferably is about 50 wt % to about 90 wt % of the reactive mixture, the ionic copolymer is about 5 to about 50 wt % of the reactive mixture, and the copolymer is about 1 to 20 wt % of the reactive mixture. More preferably, the polyamide is about 60 to about 72 wt % of the reactive mixture, the ionic copolymer is about 26-34 wt % of the reactive mixture, and the ester copolymer, preferably olefin ester copolymer, is about 2-6 wt % of the reactive mixture.

[0267] Commercially available products which are the reaction products of reactive mixtures of polyamide, ionic copolymer, and olefin ester copolymer include Capron® 8351, available from Allied Signal. This reactive mixture, and the processing thereof, is believed to be described in U.S. Pat. No. 4,404,325, the teachings of which are incorporated herein by reference in their entirety. As described therein, the preferred polyamide is polyespiloncaprolactam or polyhexamethyleneadipamide, and most preferably polyespiloncaprolactam. The preferred olefin ester copolymer is ethylene/ethyl acrylate. The preferred ionic copolymer is a zinc neutralized copolymer of ethylene/methacrylic acid available from DuPont under the trade name Surlyn® 9721 (1801). According to claim 7 of U.S. Pat. No. 4,404,325, the polyamide is present in the reactive mixture in an amount of about 60 to about 72 wt %, the ionomeric copolymer is present in an amount of about 26 wt % to about 34 wt %, and the olefin ester copolymer is present in an amount of about 2 to about 6 wt %, based on the total weight of the reactive mixture. It is believed that Capron® 8351 has a nylon backbone with ionomer grafted thereto. Allied Signal indicates that Capron® 8351 is a graft copolymer which has the properties set forth below in Table 15:

15TABLE 15TestPropertyMethod (ASTM)ValueSpecific GravityD-7921.07Yield Tensile Strength, psi (MPa)D-6387800 (54)Ultimate Elongation %D-638200.00Flexural Strength, psi (MPa)D-7909500 (65)Flexural Modulus, psi (MPa)D-790230,000 (1585)Notched Izod Impact ft-lbs/inD-256No BreakDrop Weight Impact ft-lbs/inD-3029150 (200)Drop Weight Impact @−40 F,D-3029150 (200)ft-lbs (J)Heat Deflection TemperatureD-64860.00@264 psi, ° C.Melting Point, ° C.D-789215.00

[0268] Capron® 8351 is the most preferred RP for use in the invention. Variations of Capron® 8351 also may be used. For example, variations of Capron® 8351 which may be used include those which employ polyepsiloncaprolactam or polyhexamethyleneadipamide with olefin ester copolymers such as ethylene/methyl acrylate, ethylene/ethyl methacrylate, and ethylene/methyl methacrylate. Ionic copolymers which may be used in variations of Capron® 8351 include ionic copolymers of an alpha olefin of the formula RCH═CH2 where R is H or alkyl radicals having 1-8 carbons, and an alpha, beta-ethylenically unsaturated carboxylic acid having from 3-8 carbons. The ionic copolymer has at least about 10 wt % of the COOH groups neutralized with metal cations, preferably zinc. Examples of these ionic copolymers include zinc neutralized ethylene/methacrylic acid. In variations of Capron® 8351, the reactive mixture neutralized to produce such variations may include from about 50 wt % to about 90 wt % polyamide, from about 5 wt % to about 50 wt % ionic copolymer, and from about 1 wt % to about 20 wt % olefin ester copolymer, all percents based on the weight of the reactive mixture.

[0269] In another preferred embodiment, golf balls of the invention employ preferably as an inner and/or outer cover layer, a composition that includes RP and at least one terpolymer. Terpolymers which may be employed include olefin/alkyl (meth)acrylate/carboxylic acid terpolymers. These terpolymers typically have from about 50 wt % to about 98 wt % olefin, from about 1 wt % to about 30 wt % alkyl acrylate, and from about 1 wt % to about 20 wt % carboxylic acid. The olefin may be any of ethylene, propylene, butene-1, hexene-,1 and the like, preferably ethylene. The alkyl (meth)acrylate may be any of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, butyl vinyl ether, methyl vinyl ether, and the like, preferably methyl acrylate. The carboxylic acid may be any one of acrylic acid, methacrylic acid, maleic acid, and fumaric acid. Monoesters of diacids such as methyl hydrogen maleate, methyl hydrogen fumarate, ethyl hydrogen fumarate, and maleic anhydride which is considered to be a carboxylic acid may also be used. Preferably, the carboxylic acid is acrylic acid. Useful ethylene/methyl acrylate/acrylic acid terpolymers may comprise from about 50 wt % to about 98 wt %, preferably from about 65 wt % to about 85 wt %, and most preferably about 76 wt % ethylene; from about 1 wt % to about 30 wt % preferably from about 15 wt % to about 20 wt %, and most preferably about 18 wt % methyl acrylate; and about 1 wt % to about 20 wt %, preferably from about 4 wt % to about 10 wt %, and most preferably about 6 wt % acrylic acid.

[0270] Olefin/alkyl(meth)acrylate/carboxylic acid terpolymers which are preferred for use in the compositions employed in the invention are ethylene/methyl acrylate/acrylic acid terpolymers such as those marketed by Exxon Chemical Co. under the name Escor®. Examples of these terpolymers include Escor® ATX 320 and Escor® ATX 325. The properties of Escor® ATX 320 and Escor® ATX 325 as provided by Exxon are set forth below in Table 16:

16TABLE 16Property/ResinESCOR ® ATX-320ESCOR ® ATX-325Melt Index15.0g/10 min20.0g/10 minDensity10.950g/cc0.950g/ccMelting Point169C.67C.Crystallization51C.50C.Temperature1Vicat Softening66C.60C.Temperature 200 g2Tensile Strength @12MPa7.8MPaYield3Hardness434.0030.00Elongation @ Break3>800%>800%1Exxon Method 2ASTM D 1525 3ASTM 638 4Shore D

[0271] Other olefin/alkyl (meth)acrylate/carboxylic acid terpolymers which may be employed with RP in the compositions employed in the invention include but are not limited to:

[0272] ethylene/n-butyl acrylate/acrylic acid,

[0273] ethylene/n-butyl acrylate/methacrylic acid,

[0274] ethylene/2-ethoxyethyl acrylate/acrylic acid,

[0275] ethylene/2-ethoxyethyl acrylate/methacrylic acid,

[0276] ethylene/n-pentyl acrylate/acrylic acid,

[0277] ethylene/n-pentyl acrylate/methacrylic acid,

[0278] ethylene/n-octyl acrylate/acrylic acid,

[0279] ethylene/2-ethyhexyl acrylate/acrylic acid,

[0280] ethylene/n-propyl acrylate/acrylic acid,

[0281] ethylene/n-propyl acrylate/methacrylic acid,

[0282] ethylene/n-heptyl acrylate/acrylic acid,

[0283] ethylene/2-methoxylethyl acrylate/acrylic acid,

[0284] ethylene/3-methoxypropyl acrylate/acrylic acid,

[0285] ethylene/3-ethoxypropyl acrylate/acrylic acid, and

[0286] ethylene/acrylate/acrylic acid.

[0287] Compositions which may be employed to provide golf balls according to this embodiment of the invention include from about 1 wt % to about 90 wt %, preferably from about 1 wt % to about 30 wt %, and most preferably about 15 wt % RP; and from about 99 wt % to about 10 wt % terpolymer, preferably from about 99 wt % to about 70 wt % and most preferably about 85 wt % terpolymer.

[0288] Golf balls of the present invention also employ, preferably as a cover, compositions which include RP and an olefin/alkyl acrylate/carboxylic acid terpolymer ionomer. Typically, the carboxylic acid groups of the terpolymer ionomer are partially (i.e., approximately 5% to 80%) neutralized by metal ions such as lithium, sodium, zinc, manganese, nickel, barium, tin, calcium, magnesium, copper and the like, preferably zinc, sodium or lithium or a combination thereof, and most preferably zinc or lithium or a combination thereof. These terpolymer ionomers usually have a relatively high molecular weight, e.g., a melt index of about 0.1 to 1000 g/10 min., and/or a weight average molecular weight of 5000 up to one million. The ethylene/methyl acrylate/acrylic acid terpolymer ionomer may comprise from about 50 wt % to about 98 wt %, preferably from about 65 wt % to about 85 wt %, and most preferably about 76 wt % ethylene; from about 1 to about 30 wt %, preferably from about 15 to about 20 wt %, and most preferably about 18 wt % methyl acrylate; and from about 1 wt % to about 20 wt %, preferably from about 4 wt % to about 10 wt %, and most preferably about 6 wt % acrylic acid. Useful terpolymer ionomers include, for example, ethylene/methyl acrylate/acrylic acid terpolymer ionomers sold by Exxon Chemical Co. under the designation Iotek®. Preferred terpolymer ionomers for use in the invention include zinc neutralized ethylene/methyl acrylate/acrylic acid terpolymer ionomers such as Iotek® 7520 and Iotek® 7510, and lithium neutralized ionomers such as Escor® ATX-320-Li-80.

[0289] Escor® ATX320 Li-80 is produced by utilizing a 6.0 wt % acrylic acid/18.0 wt % methyl acrylate 76 wt % ethylene terpolymer produced by Exxon Chemical Co. under the designation Escor® ATX 320. The acid groups present in the terpolymer then are neutralized to 80 mol % by using lithium hydroxymonohydrate. Neutralization is performed by adding lithium hydroxymonohydrate and Escor® ATX 320 terpolymer to an intensive mixer (Banbury® type). The lithium salt solubilizes in the ATX 320 terpolymer above the melting temperature of the terpolymer, and a vigorous reaction occurs with foaming as the lithium cation reacts with the acid groups of the terpolymer, and volatile byproducts are evaporated. The reaction is continued until foaming ceases (i.e., about 30 to about 45 minutes at 250° F. to 350° F.) and the batch is removed from the Banbury® mixer. Mixing continues on a hot two-roll mill (175° F. to 250° F.) to complete the neutralization reaction.

[0290] For the purpose of determining the weight percent of neutralization of the acrylic acid groups in the terpolymer ionomer after reacting with the lithium salt, it is assumed that one mol of lithium neutralizes one mol of acrylic acid. The calculations of neutralization are based upon an acrylic acid molecular weight of 72 g/mol, giving 0.067 mols of lithium per 100 grams of the terpolymer.

[0291] Although Escor® ATX 320 terpolymer can be 80 mol % neutralized by lithium, it is to be understood that other degrees of neutralization with lithium, ranging from about 3 mol % to about 90 mol %, may be employed to provide useful ionomers. Thus, for example, ATX 320 that is 20 mol % neutralized by lithium, hereinafter referred to as ATX 320-Li-20 may be employed. In addition, various cation salts such as salts of sodium, potassium, magnesium, manganese, calcium and nickel may be employed in a manner similar to lithium salts to provide various other Escor® ATX 320 type terpolymer ionomers.

[0292] Other terpolymer ionomers which may be used in the compositions employed in this embodiment of the invention include ethylene/alkyl ester/methacrylic acid terpolymer ionomers; such as those disclosed in U.S. Pat. No. 4,690,981, the teachings of which are incorporated by reference in its entirety herein, and which are available from DuPont Corp. under the trade name Surlyn®. Properties of various Surlyn® terpolymer ionomers which may be used in the invention are set forth in Table 17. The terpolymer ionomer may be from about 1 wt % to about 99 wt %, preferably from about 50 wt % to about 99 wt %, and most preferably about 85 wt %, all amounts based on the total weight of the RP-terpolymer ionomer composition. RP may be from about 1 wt % to about 99 wt %, preferably about 1 wt % to about 50 wt %, and most preferably about 15 wt %, all amounts based on the total weight of the composition.

17TABLE 17Resin/Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®PropertyASTM79307940802085288550866081208320CationLiLiNaNaNaNaNaNaMeld Flow IndexD-12381.802.601.001.303.9010.000.900.90(g/10 min)DensityD-7920.940.940.950.940.940.940.940.94Notched IzodD-256NB1NB1NB111.40—16.00——Tensile Impact (23 C)D-1822S140.00220.00630.00550.00795.00345.00235.00213.00ft-lb/in2Flexural Mod (23 C)D-79067.0061.0014.0032.0031.7034.0049.1019.30kpsiYield Strength (kpsi)D-8382.802.20—1.801.601.902.202.30Elongation (%)D-838290.00285.00530.00450.00419.00470.00660.00770.00Hardness, Shore DD-224068.0068.0056.0060.0060.0062.0038.0025.00Vicat TemperatureD-152(C)5-7062.0063.0061.0073.0078.0071.0051.0048.00Rate BResin/Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Surlyn ®Property902093209520965097209730991099509970CationZnZnZnZnZnZnZnZnZnMeld Flow Index (g/101.100.601.105.001.001.600.705.501.40min)Density0.960.940.950.950.950.950.970.950.95Notched IzodNB210.1014.50NB1NB16.60NB1NB1Tensile Impact (23 C) ft-610.00570.00460.00600.00590.00485.00485.00360.00lb/in2Flexural Mod (23 C) kpsi14.003.7038.0032.0036.0030.0048.0037.0028.00Yield Strength (kpsi)—3.501.801.801.701.602.001.801.60Elongation (%)510.00500.00410.00410.00440.00460.00290.00490.00480.00Hardness, Shore D55.0040.0060.0063.0061.0063.0064.0062.0062.00Vicat Temperature (C)57.00454.0074.0071.0071.0073.0062.0068.0061.001Terpolymer ionomers 2No Break

[0293] Other suitable nylon containing compositions include compositions of olefin/carboxylic acid copolymer ionomers made from two types of monomers and RP. Olefin/carboxylic acid copolymer ionomers which may be employed with RP include those wherein the carboxylic acid groups of the copolymer ionomer are partially (i.e., approximately 5% to 80%) neutralized by metal ions such as but not limited to lithium, sodium, zinc and magnesium, and preferably zinc, and/or sodium. Ionic copolymers may be zinc neutralized ethylene/methacrylic acid ionomer copolymer, sodium neutralized ethylene/acrylic acid copolymer ionomers, and mixtures thereof. The zinc neutralized ethylene/acrylic acid copolymer ionomer can be the reaction product of zinc neutralization of an ethylene/acrylic acid copolymer having from about 15 wt % to about 20 wt % acrylic acid and a melt index of about 37 to about 100. These copolymer ionomers usually have a relatively high molecular weight, e.g., a melt index of about 0.1 to 1000 g/10 min., and/or a weight average molecular weight of 5000 up to one million. Useful copolymer ionomers include, for example, ethylene/acrylic acid copolymer ionomers sold by Exxon Chemical Co. under the designation Iotek® such as Iotek® 7030, Iotek® 7020, Iotek® 7010, Iotek® 8030, Iotek® 8020, and Iotek® 8000. Non-limiting examples of preferred Iotek® copolymer ionomers for use in the invention include Iotek® 7010, Iotek® 7030 and Iotek® 8000. Properties of various Iotek® copolymer ionomers are shown in Tables 18 and 19.

18TABLE 18ASTMIotek ®Iotek ®Iotek ®Iotek ®Iotek ®Method40004010701070207030Resin/PropertyCationZnZnZnZnZnMelt Flow Index g/10 min D-12382.501.500.801.502.50Density Point, C.D-792964.00966.00968.00966.00964.00Melting Point, C. D-224085.0084.0083.5084.0085.00Crystallization Point, C.D-63858.0056.0055.0056.0058.00Vicat Softening Point, C.D-63860.0060.0060.0060.0060.00Flexural Mod, MPaD-790155.00175.00190.00175.00155.00Tensile Impact at 23 C., KJ/m2 D-1822480.00520.00550.00520.00480.00(Type S Dumbbell, 2 mmThick Compression Plaques)Plaque Properties(2 mm thickcompression molding)Tensile Strength at BreakD-63822.6023.5024.5023.5022.60MPaYield Point MPaD-63812.0013.0014.0013.0012.00Elongation at Break %D-638460.00450.00440.00450.00460.001% Secant Modulus MPaD-638125.00135.00150.00135.00125.00Shore D Hardness D-224052.0053.0054.0053.0052.00IOTEK ™Iotek ®Iotek ®Iotek ®Iotek ®Iotek ®800080208030752075103110Resin/PropertyCationNaNaNaZnZnNaMelt Flow Index g/10 min0.801.602.802.000.801.30Density Point, C.957.000.96956.00962.00970.00939.00Melting Point, C.83.0084.0087.0067.0067.0095.00Crystallization Point, C.45.0047.0049.0039.0038.0058.00Vicat Softening Point, C.54.0054.5055.5040.0040.0075.00Flexural Mod, MPa320.00340.00355.0030.0035.00260.00Tensile Impact at 23 C., KJ/m2570.00550.00500.00780.00950.00580.00(Type S Dumbbell, 2 mmThick Compression Plaques)Plaque Properties(2 mm thickcompression molding)Tensile Strength at Break33.0032.5032.0012.0015.0028.00MPaYield Point MPa19.0018.5018.004.004.0014.00Elongation at Break %370.00380.00410.00680.00570.00510.001% Secant Modulus MPa280.00280.00280.0022.0027.00210.00Shore D Hardness60.0060.0060.0030.0035.0055.00*Terpolymer ionomer

[0294]

19

TABLE 19

ASTM
EX
EX
EX
EX

Method
1001
1004
1006
1007

Resin/Property

Cation
Exxon
Na
Zn
Na
Zn

Melt Flow Index
D-1238
1.00
2.00
1.30

g/10 min

Melting Point (C.)
D-3417
83.70
82.50
86.00

Crystallization Point (C.)
D-3417
41.30
52.50
47.50
52.30

Plaque Properties

(2 mm thick

compression molding

Tensile Strength at Break
D-638
34.40
20.60
33.50
24.10

MPa

Yield Point MPa
D-638
21.30
14.00
19.30
13.80

Elongation at Break %
D-638
341.00
437.00
421.00
472.00

1% Secant Modulus MPa
D-638
356.00
128.00
314.00
154.00

1% Secant Modulus MPa
D-790
365.00
130.00
290.00
152.00

Shore D Hardness
D-2240
63.00
53.00
58.00
51.00

Vicat Softening Point
D-1525
51.50
55.00
57.00
60.50

[0295] Compositions of nylon homopolymer and/or copolymer and one or more olefin/alkyl acrylate/carboxylic acid terpolymer ionomers are also suitable cover materials in a golf ball according to the present invention. Terpolymer ionomers which may be used with the nylon homopolymers preferably are ethylene/methyl acrylate/acrylic acid terpolymer ionomers. Nylon homopolymers for use in any of the compositions employed in the invention include but are not limited to nylon 6, nylon 6,6, and mixtures or copolymers thereof. Other nylons such as nylon 11, nylon 12, nylon 6,12, nylon 6,6/6 and nylon 46 also can be used as long as sufficient durability is achieved. In the case of nylon 6, a polyamide chain of about 140 to about 222 repeating units is typically useful, but lower and higher molecular weight material may be employed. Capron® 8202, a nylon 6 type polymer available from Allied Signal, is preferred. According to Allied Signal, Capron® 8202 has the properties set forth below in Table 20.

20TABLE 20TestMethodProperty(ASTM)ValueSpecific GravityD-7921.13Yield Tensile Strength, psi (MPa)D-63811500 (80)Ultimate Elongation %D-63870.00Flexural Strength, psi (MPa)D-79015700 (110)Flexural Modulus, psi (MPa)D-790410,000 (2825)Notched Izod Impact, ft-labs/inD-2561.0 (55)Heat Deflection Temperature @ 264 psi, C.D-64865.00Melting Point, C.D-789215.00Rockwell Hardness, R ScaleD-785119.00

[0296] Terpolymer ionomers which may be employed include but are not limited to those having from about 50 wt % to about 98 wt %, preferably from about 65 wt % to about 85 wt %, and most preferably about 76 wt % ethylene; from about 1 wt % to about 30 wt %, preferably from about 15 wt % to about 20 wt %, and most preferably about 18 wt % methyl acrylate, and from about 1 wt % to about 20 wt %, preferably from about 4 wt % to about 10 wt %, and most preferably about 6 wt % acrylic acid, wherein the acrylic acid has been neutralized by zinc, lithium or sodium or combinations thereof. Preferred terpolymer ionomers include Iotek® 7520, Iotek® 7510, Escor® ATX 320-Li-80, or a mixture thereof. The nylon homopolymer may be present in the compositions in an amount of from about 1 wt % to about 99 wt %, preferably from about 1 wt % to about 50 wt %, and most preferably about 15 wt % of the composition. The terpolymer ionomer may be from about 99 wt % to about 1 wt %, preferably from about 90 wt % to about 50 wt %, and most preferably about 85 wt %, all amounts based on total weight of the composition.

[0297] Zytel® 408 is a nylon 66 modified molding compound containing ionomer. It is believed that Zytel® 408 is an intimate mixture of polyamide and an ionomeric terpolymer of an alpha-olefin, an acrylate ester, and an alpha, beta-ethylenically unsaturated mono- or dicarboxylic acid with a portion of the carboxylic acid groups being neutralized with metal ions. It is unknown to the present inventors whether Zytel® 408 is a graft copolymer or a blend; however, Zytel® 408 is believed to be a blend of nylon 6,6 and an ethylene alkylmethacrylate methacrylic acid terpolymer ionomer neutralized with zinc. The properties of Zytel® 408, as provided by DuPont, are shown below in Table 21:

21TABLE 21TestMethodProperty(ASTM)ValueSpecific GravityD-7921/09Tensile Strength (−40° F.)D-63815100 psiTensile Strength (−40° C.)D-638104.1 MPaFlexural Modulus (−40° F.)D-790410,000 psiFlexural Modulus (−40° C.)D-7902827 MPaIzod Impact Strength at −40° F.D-2561.3 ft.lb/in.Izod Impact Strength at −40° C.D-25669 J/mGardner Impact at −30° F.D-3029>320 ft. lbs.Heat Deflection temperature @@D-64875 C.1.8106 PaMelting PointD-789255 C.1Dry as molded, with about 0.2% water

[0298] Other suitable nylon compositions include compositions of polyamide homopolymers or copolymers, and olefin/carboxylic acid copolymer ionomers made from two types of monomers such as Iotek®. The polyamides which can be used in the compositions employed in the invention include but are not limited to nylon 6, nylon 6,6, nylon 11, nylon 12, nylon 6,12, nylon 6,6/6, nylon 46 and mixtures thereof, as long as sufficient durability is achieved. Preferably, the nylon polymer is any of nylon 6 and nylon 6,6, most preferably nylon 6. In the case of nylon 6, a polyamide chain of about 140 to about 222 repeating units is typically useful, but lower and higher molecular weight material may be employed. A preferred polyamide homopolymer is Capron® 8202 available from Allied Signal. Useful copolymer ionomers include copolymer ionomers having from about 99 wt % to about 70 wt %, preferably from about 90 wt % to about 80 wt %, and most preferably 85 wt % ethylene; and from about 1 wt % to about 30 wt %, preferably from about 10 wt % to about 20 wt %, and most preferably 15 wt % acrylic acid. A preferred ethylene/acrylic acid copolymer ionomer is Iotek® 7010 from Exxon Chemical Co. The copolymer ionomer may be present in the composition in an amount of from about 99 wt % to about 1 wt %, preferably from about 95 wt % to about 70 wt %, and most preferably about 80 wt % of the composition. The polyamide homopolymer may be from about 1 wt % to about 99 wt %, preferably from about 5 wt % to about 30 wt %, and most preferably about 20 wt %, wherein all amounts are based on the total weight of the composition.

[0299] Two or more copolymer ionomers may be preblended prior to blending with polyamide homopolymers and/or RP to provide compositions which may be used in the invention. Thus, preblends of hard and soft copolymer ionomers, as well as preblends of high carboxylic acid copolymer ionomers and low carboxylic acid copolymer ionomers may be utilized to provide compositions for use in the invention. An example of such a preblend is a mixture of Iotek® 8000 and Iotek® 7010.

[0300] Cover materials may also be nylon compositions of polyamide homopolymers or copolymers, and olefin/alkyl acrylate/carboxylic acid terpolymers. Useful terpolymers include terpolymers having about from 50 wt % to about 98 wt %, preferably from about 65 wt % to about 85 wt %, and most preferably about 76 wt % olefin, preferably ethylene; from about 1 wt % to about 30 wt %, preferably from about 15 wt % to about 20 wt %, and most preferably about 18 wt % alkyl acrylate, preferably methyl acrylate; and from about 1 wt % to about 20 wt %, preferably from about 4 wt % to about 10 wt %, and most preferably about 6 wt % carboxylic acid, preferably acrylic acid. The terpolymer may be present in the composition in an amount of from about 1 wt % to about 99 wt %, preferably from about 50 wt % to about 99 wt %, and most preferably about 85 wt % of the composition. The polyamide homopolymer may be from about 1 wt % to about 99 wt %, preferably from about 1 wt % to about 50 wt %, and most preferably about 15 wt % wherein all amounts are based on the total weight of the composition. Useful polyamides may be of polyepsiloncaprolactam and polyhexamethyleneadipamide, more preferably nylon 6, nylon 6,6, nylon 11, nylon 12, nylon 6,12, nylon 6,6/6, nylon 46 and mixtures thereof. Preferably, the nylon polymer is any of nylon 6 and nylon 6,6, still more preferably nylon 6, and most preferably the nylon homopolymer sold by Allied Signal under the trade name Capron® 8202. A preferred ethylene/methyl acrylate/acrylic acid terpolymer is Escor® ATX 320 from Exxon Chemical Co.

[0301] Two or more terpolymers may be preblended prior to blending with any of RP or the polyamide homopolymers to provide compositions which may be used in the invention. Thus, preblends of hard and soft terpolymers, as well as preblends of high carboxylic acid terpolymers and low carboxylic acid terpolymers may be utilized to provide compositions for use in the invention.

[0302] C. Polyurethanes

[0303] Polyurethanes are polymers which are used to form a broad range of products. They are generally formed by mixing two primary ingredients during processing. For the most commonly used polyurethanes, the two primary ingredients are a polyisocyanate (for example, diphenyl methane diisocyanate monomer (“MDI”) and toluene diisocyanate (“TDI”) and their derivatives) and a polyol (for example, a polyester polyol or a polyether polyol).

[0304] A wide range of combinations of polyisocyanates and polyols, as well as other ingredients, are available. Furthermore, the end-use properties of polyurethanes can be controlled by the type of polyurethane utilized, i.e., whether the material is thermoset (crosslinked molecular structure) or thermoplastic (linear molecular structure).

[0305] Crosslinking occurs between the isocyanate groups (—NCO) and the polyol's hydroxyl end-groups (—OH). Additionally, the end-use characteristics of polyurethanes can also be controlled by different types of reactive chemicals and processing parameters. For example, catalysts are utilized to control polymerization rates. Depending upon the processing method, reaction rates can be very quick (as in the case for some reaction injection molding systems (“RIM”)) or may be on the order of several hours or longer (as in several coating systems). Consequently, a great variety of polyurethanes are suitable for different end uses.

[0306] Polyurethane has been used for golf balls and other game balls as a cover material. Commercially available polyurethane golf balls have been made of thermoset polyurethanes. A polyurethane becomes irreversibly “set” when a polyurethane prepolymer is cross linked with a polyfunctional curing agent, such as polyamine and polyol. The prepolymer typically is made from polyether or polyester. Diisocyanate polyethers are preferred because of their water resistance.

[0307] The physical properties of thermoset polyurethanes are controlled substantially by the degree of cross linking. Tightly cross linked polyurethanes are fairly rigid and strong. A lower amount of cross linking results in materials that are flexible and resilient. Thermoplastic polyurethanes have some cross linking, but purely by physical means. The crosslinkings bonds can be reversibly broken by increasing temperature, as occurs during molding or extrusion. In this regard, thermoplastic polyurethanes can be injection molded, and extruded as sheet and blown film. They can be used up to about 350° F. and are available in a wide range of hardnesses.

[0308] Polyurethane materials suitable for the present invention are formed by the reaction of a polyisocyanate, a polyol, and optionally one or more chain extending diols. The polyisocyanate is selected, for example, from the group including diphenyl methane diisocyanate (“MDI”); toluene diisocyanate (“TDI”); xylene diisocyanate (“XDI”); methylene bis-(4-cyclohexyl isocyanate) (“HMDI”); hexamethylene diisocyanate; and naphthalene-1,5,-diisocyanate (“NDI”).

[0309] One polyurethane component which can be used in the present invention incorporates meta-tetramethylxylylene diisocyanate (TMXDI)(“META”) aliphatic isocyanate (Cytec Industries, West Paterson, N.J.). Polyurethanes based on meta-tetramethylxylylene diisocyanate can provide improved gloss retention, UV light stability, thermal stability, and hydrolytic stability. Additionally, TMXDI (“META”) aliphatic isocyanate has demonstrated favorable toxicological properties. Furthermore, because it has a low viscosity, it is usable with a wider range of diols (to polyurethane) and diamines (to polyureas). If TMXDI is used, it typically, but not necessarily, is added as a direct replacement for some or all of the other aliphatic isocyanates in accordance with the suggestions of the supplier. Because of slow reactivity of TMXDI, it may be useful or necessary to use catalysts to have practical demolding times. Hardness, tensile strength and elongation can be adjusted by adding further materials in accordance with the supplier's instructions.

[0310] A non-limiting example of a suitable polyurethane is Estane® X4517 from B. F. Goodrich.

[0311] Further examples of suitable polyurethanes include polyurethane systems formed via reaction injection molding (RIM). RIM processing to form various layers of a golf ball is described in detail in pending application U.S. Ser. No. 09/411,690, incorporated herein by reference.

[0312] Non-limiting examples of suitable RIM systems for use in the present invention are Bayflex® elastomeric polyurethane RIM systems, Baydur® GS solid polyurethane RIM systems, Prism® solid polyurethane RIM systems, all from Bayer Corporation (Pittsburgh, Pa.), Spectrim® reaction moldable polyurethane and polyurea systems from Dow Chemical USA (Midland, Mich.), including Spectrim® MM 373-A (isocyanate) and 373-B (polyol), and Elastolit® SR systems from BASF (Parsippany, N.J.). Preferred RIM systems include Bayflex® MP-10000 and Bayflex® 110-50, filled and unfilled. Further preferred examples are polyols, polyamines and isocyanates formed by processes for recycling polyurethanes and polyureas. Peroxides, such as MEK-peroxide and dicumyl peroxide can be used. Furthermore, catalysts or activators such as cobalt octoate 6% can be used.

[0313] The golf balls of the present invention can be produced, at least in part, by molding processes currently known in the golf ball art. Specifically, multi-layer golf balls can be produced by injection molding or compression molding a mantle layer about wound or solid molded cores to produce an intermediate golf ball having a diameter of about 1.50 to 1.67 inches, preferably about 1.620 inches. The cover layer is subsequently molded over the mantle layer to produce a golf ball having a diameter of 1.680 inches or more. Although either solid cores or wound cores can be used in the present invention, as a result of their lower cost and superior performance, solid molded cores are preferred over wound cores.

[0314] In compression molding, the mantle layer composition is formed via injection at about 380° F. to about 450° F. into smooth surfaced hemispherical shells which are then positioned around the core in a mold having the desired mantle layer thickness and subjected to compression molding at 200° F. to 300° F. for about 2 to 10 minutes, followed by cooling at 50° F. to 70° F. for about 2 to 7 minutes to fuse the shells together to form a unitary intermediate ball. In addition, the intermediate balls may be produced by injection molding wherein the mantle layer is injected directly around the core placed at the center of an intermediate ball mold for a period of time at a mold temperature of from 50° F. to about 100° F. An outer layer is molded about the core and the inner layer by similar compression or injection molding techniques to form a dimpled golf ball of a diameter of 1.680 inches or more.

[0315] A preferred method of forming a golf ball according to the present invention is forming one or more layers via a fast-chemical-reaction process.

[0316] A preferred method of forming a polyurethane component for a golf ball according to the invention is by reaction injection molding (“RIM”). RIM is a process by which highly reactive liquids are injected into a closed mold, mixed usually by impingement and/or mechanical mixing in an in-line device such as a “peanut mixer,” where they polymerize primarily in the mold to form a coherent, one-piece molded article. The RIM processes usually involve a rapid reaction between one or more reactive components such as polyether- or polyester-polyol, polyamine, or other material with an active hydrogen, and one or more isocyanate-containing constituents, often in the presence of a catalyst. The constituents are stored in separate tanks prior to molding and may be first mixed in a mix head upstream of a mold and then injected into the mold. The liquid streams are metered in the desired weight to weight ratio and fed into an impingement mix head, with mixing occurring under high pressure, e.g., 1500-3000 psi. The liquid streams impinge upon each other in the mixing chamber of the mix head and the mixture is injected into the mold. One of the liquid streams typically contains a catalyst for the reaction. The constituents react rapidly after mixing to gel and form polyurethane polymers. Polyureas, epoxies, and various unsaturated polyesters also can be molded by RIM.

[0317] RIM differs from non-reaction injection molding in a number of ways. The main distinction is that in RIM a chemical reaction takes place in the mold to transform a monomer or adducts to polymers and the components are in liquid form. Thus, a RIM mold need not be made to withstand the pressures which occur in a conventional injection molding. In contrast, injection molding is conducted at high molding pressures in the mold cavity by melting a solid resin and conveying it into a mold, with the molten resin often being at about 150 to about 350° C. At this elevated temperature, the viscosity of the molten resin usually is in the range of 50,000 to 1,000,000 centipoise, and is typically around 200,000 centipoise. In an injection molding process, the solidification of the resins occurs after about 10 to about 90 seconds, depending upon the size of the molded product, the temperature and heat transfer conditions, and the hardness of the injection molded material. Subsequently, the molded product is removed from the mold. There is no significant chemical reaction taking place in an injection molding process when the thermoplastic resin is introduced into the mold. In contrast, in a RIM process, the chemical reaction typically takes place in less than about two minutes, preferably in under one minute, and in many cases in about 30 seconds or less.

[0318] If plastic products are produced by combining components that are preformed to some extent, subsequent failure can occur at a location on the cover which is along the seam or parting line of the mold. Failure can occur at this location because this interfacial region is intrinsically different from the remainder of the cover layer and can be weaker or more stressed. The developments described herein are believed to provide for improved durability of a golf ball cover layer by providing a uniform or “seamless” cover in which the properties of the cover material in the region along the parting line are generally the same as the properties of the cover material at other locations on the cover, including at the poles. The improvement in durability is believed to be a result of the fact that the reaction mixture is distributed uniformly into a closed mold. This uniform distribution of the injected materials eliminates knit-lines and other molding deficiencies which can be caused by temperature difference and/or reaction difference in the injected materials. The process of the invention results in generally uniform molecular structure, density and stress distribution as compared to conventional injection-molding processes.

[0319] The various cover composition layers of the present invention may be produced according to conventional melt blending procedures. When a blend of hard and soft, low acid ionomer resins are utilized, the hard ionomer resins are blended with the soft ionomeric resins and with a masterbatch containing the desired additives in a Banbury® mixer, two-roll mill, or extruder prior to molding. The blended composition is then formed into slabs and maintained in such a state until molding is desired. Alternatively, a simple dry blend of the pelletized or granulated resins and color masterbatch may be prepared and fed directly into the injection molding machine where homogenization occurs in the mixing section of the barrel prior to injection into the mold. If necessary, further additives such as an inorganic filler, etc., may be added and uniformly mixed before initiation of the molding process. A similar process is utilized to formulate the low acid ionomer resin compositions.

[0320] Preferably, in a golf ball, according to the invention, at least one layer of the golf ball contains at least one part by weight of a filler. Fillers preferably are used to adjust the density, flex modulus, mold release, and/or melt flow index of a layer. More preferably, at least when the filler is for adjustment of density or flex modulus of a layer, it is present in an amount of at least five parts by weight based upon 100 parts by weight of the layer composition. With some fillers, up to about 200 parts by weight probably can be used.

[0321] A density adjusting filler according to the invention preferably is a filler which has a specific gravity which is at least 0.05 and more preferably at least 0.1 higher or lower than the specific gravity of the layer composition. Particularly preferred density adjusting fillers have specific gravities which are higher than the specific gravity of the resin composition by 0.2 or more, even more preferably by 2.0 or more.

[0322] A flex modulus adjusting filler according to the invention is a filler which, when used in an amount of, e.g., 1 to 100 parts by weight based upon 100 parts by weight of resin composition, will raise or lower the flex modulus (ASTM D-790) of the resin composition by at least 1% and preferably at least 5% as compared to the flex modulus of the resin composition without the inclusion of the flex modulus adjusting filler.

[0323] A mold release adjusting filler is a filler which allows for the easier removal of a part from a mold, and eliminates or reduces the need for external release agents which otherwise could be applied to the mold. A mold release adjusting filler typically is used in an amount of up to about 2 weight percent based upon the total weight of the layer.

[0324] A melt flow index adjusting filler is a filler which increases or decreases the melt flow, or ease of processing of the composition.

[0325] The layers may contain coupling agents that increase adhesion of materials within a particular layer, e.g., to couple a filler to a resin composition, or between adjacent layers. Non-limiting examples of coupling agents include titanates, zirconates and silanes. Coupling agents typically are used in amounts of 0.1 to 2 weight percent based upon the total weight of the composition in which the coupling agent is included.

[0326] A density adjusting filler is used to control the moment of inertia, and thus the initial spin rate of the ball and spin decay. The addition in one or more layers, and particularly in the outer cover layer of a filler with a lower specific gravity than the resin composition results in a decrease in moment of inertia and a higher initial spin rate than would result if no filler were used. The addition in one or more of the cover layers, and particularly in the outer cover layer of a filler with a higher specific gravity than the resin composition, results in an increase in moment of inertia and a lower initial spin rate. High specific gravity fillers are preferred as less volume is used to achieve the desired inner cover total weight. Non-reinforcing fillers are also preferred as they have minimal effect on C.O.R. Preferably, the filler does not chemically react with the resin composition to a substantial degree, although some reaction may occur when, for example, zinc oxide is used in a shell layer which contains some ionomer.

[0327] The density-increasing fillers for use in the invention preferably have a specific gravity in the range of 1.0 to 20. The density-reducing fillers for use in the invention preferably have a specific gravity of 0.06 to 1.4, and more preferably 0.06 to 0.90. The flex modulus increasing fillers have a reinforcing or stiffening effect due to their morphology, their interaction with the resin, or their inherent physical properties. The flex modulus reducing fillers have an opposite effect due to their relatively flexible properties compared to the matrix resin. The melt flow index increasing fillers have a flow enhancing effect due to their relatively high melt flow versus the matrix. The melt flow index decreasing fillers have an opposite effect due to their relatively low melt flow index versus the matrix.

[0328] Fillers which may be employed in layers other than the outer cover layer may be or are typically in a finely divided form, for example, in a size generally less than about 20 mesh, preferably less than about 100 mesh U.S. standard size, except for fibers and flock, which are generally elongated. Flock and fiber sizes should be small enough to facilitate processing. Filler particle size will depend upon desired effect, cost, ease of addition, and dusting considerations. The filler preferably is selected from the group consisting of precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates, metals, metal alloys, tungsten carbide, metal oxides, metal stearates, particulate carbonaceous materials, micro balloons, and combinations thereof. Non-limiting examples of suitable fillers, their densities, and their preferred uses are listed in Table 22:

22TABLE 22Filler TypeSpec. Grav.CommentsPrecipitated hydrated silica2.001,2Clay2.621,2Talc2.851,2Asbestos2.501,2Glass fibers2.551,2Aramid fibers (KEVLAR ®)1.441,2Mica2.801,2Calcium metasilicate2.901,2Barium sulfate4.601,2Zinc sulfide4.101,2Lithopone4.2-4.31,2Silicates2.101,2Silicon carbide platelets3.181,2Silicon carbide whiskers3.201,2Tungsten carbide15.601Diatomaceous earth2.301,2Polyvinyl chloride1.411,2CarbonatesCalcium carbonate2.711,2Magnesium carbonate2.201,2Metals and Alloys (Powders)Titanium4.511Tungsten19.351Aluminum2.701Bismuth9.781Nickel8.901Molybdenum10.201Iron7.861Steel7.8-7.91Lead11.401,2Copper8.941Brass8.2-8.41Boron2.341Boron carbide whiskers2.521,2Bronze8.70-8.741Cobalt8.921Beryllium1.841Zinc7.141Tin7.311Metal OxidesZinc oxide5.571,2Iron oxide5.101,2Aluminum oxide4.00Titanium oxide3.9-4.11,2Magnesium oxide3.3-3.51,2Zirconium oxide5.731,2Metal StearatesZinc stearate1.093,4Calcium stearate1.033,4Barium stearate1.233,4Lithium stearate1.013,4Magnesium stearate1.033,4Particulate Carbonaceous MaterialsGraphite1.5-1.81,2Carbon black1.801,2Natural bitumen1.2-1.41,2Cotton flock1.3-1.41,2Cellulose flock1.15-1.5 1,2Leather fiber1.2-1.41,2Micro BalloonsGlass0.15-1.1 1,2Ceramic0.2-0.71,2Fly ash0.6-0.81,2Coupling Agents Adhesion PromotersTitanates0.95-1.17Zirconates0.92-1.11Silane0.95-1.2 Comments 1. Particularly useful for adjusting density of the cover layer. 2. Particularly useful for adjusting flex modulus of the cover layer. 3. Particularly useful for adjusting mold release of the cover layer. 4. Particularly useful for increasing melt flow index of the cover layer. All fillers except for metal stearates would be expected to reduce the melt flow index of an injection molded cover layer. The amount of filler employed is primarily a function of weight requirements and distribution.

[0329] The foregoing description is, at present, considered to be the preferred embodiments of the present invention. However, it is contemplated that various changes and modifications apparent to those skilled in the art, may be made without departing from the present invention. Therefore, the foregoing description is intended to cover all such changes and modifications encompassed within the spirit and scope of the present invention, including all equivalent aspects.

	Number	Date	Country
Parent	08920070	Aug 1997	US
Child	08998243	Dec 1997	US

	Number	Date	Country
Parent	08542793	Oct 1995	US
Child	08920070	Aug 1997	US

	Number	Date	Country
Parent	08998243	Dec 1997	US
Child	09800292	Mar 2001	US
Parent	08070510	Jun 1993	US
Child	08542793	Oct 1995	US

Mantle surface topography for optimum energy transfer in multi-layer golf ball

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