Patent Application
20120064999
The present invention is directed to novel formulating techniques that eliminate the need for post curing or delay times when utilizing aliphatic chemistries in golf ball covers. More specifically, it achieves this by incorporating amide linkages into either the pre-polymer backbone or the curing agent.
Golf ball components are formed from a variety of compositions. For example, golf ball cores, intermediate layers, and covers may be formed from materials ranging from balata to ionomer resin to polyurethane or polyurea. Manufacturers constantly is experiment with the different materials for use in the various golf ball layers in order to provide a golf ball that has desirable aerodynamic properties, “soft” feel, and increased durability.
For example, balata covered balls are favored by more highly skilled golfers because the softness of the cover allows the player to achieve spin rates sufficient to more precisely control ball direction and distance, particularly on shorter shots. However, balata covered balls lack durability and are therefore easily damaged, thus balata is almost never used today.
Alternative cover compositions have been developed in an attempt to provide balls with spin rates and a feel approaching those of balata covered balls, while also providing a golf ball with a higher durability and overall distance. For instance, ionomer resins have, to a large extent, replaced balata as a cover material. Chemically, ionomer resins are a copolymer of an olefin and an α,β-ethylenically-unsaturated carboxylic acid having 10 to 90 percent of the carboxylic acid groups neutralized by a metal ion, as disclosed in U.S. Pat. No. 3,264,272. Commercially available ionomer resins include, for example, copolymers of ethylene and methacrylic or acrylic acid, neutralized with metal salts. Examples of commercially available ionomer resins include, but are not limited to, SURLYN® from DuPont de Nemours and Company, and ESCOR® and IOTEK® from Exxon Corporation. These ionomer resins are distinguished by the type of metal ion, the amount of acid, and the degree of neutralization.
U.S. Pat. Nos. 3,454,280, 3,819,768, 4,323,247, 4,526,375, 4,884,814, and 4,911,451 all relate to the use of SURLYN®-type compositions in golf ball covers. However, while SURLYN® covered golf balls, as described in the preceding patents, possess virtually cut-proof covers, the spin and feel are inferior compared to balata covered balls.
Polyurethanes have also been recognized as useful materials for golf ball covers since about 1960. For example, U.S. Pat. No. 4,123,061 teaches a golf ball made from a polyurethane prepolymer formed of polyether with diisocyanate that is cured with either a polyol or an amine-type curing agent. U.S. Pat. No. 5,334,673 discloses the use of two categories of polyurethane available on the market, i.e., thermoset and thermoplastic polyurethanes, for forming golf ball covers and, in particular, thermoset is polyurethane covered golf balls made from a composition of polyurethane prepolymer and a slow-reacting amine curing agent, and/or a glycol.
Unlike ionomer resin covered golf balls, polyurethane golf ball covers can be formulated to possess the soft “feel” of balata covered golf balls. However, golf ball covers made from polyurethane have not, to date, fully matched ionomer resin golf balls with respect to resilience or the rebound of the golf ball cover, which is a function of the initial velocity of a golf ball after impact with a golf club.
Polyureas have also been proposed as cover materials for golf balls. For instance, U.S. Pat. No. 5,484,870 discloses a polyurea composition comprising the reaction product of an organic isocyanate and an organic amine, each having at least two functional groups. Once these two ingredients are combined, the polyurea is formed, and thus the ability to vary the physical properties of the composition is limited. And, like polyurethanes, polyureas are not completely comparable to ionomer resin golf balls with respect to resilience or the rebound or damping behavior of the golf ball cover. Moreover, golf ball components cast from polyurethane or polyurea compositions involve complicated ratio and dynamic mixing requirements, which adds to possible waste during manufacturing if the requirements are not met.
Therefore, there remains a continuing need for golf ball components that may be cast using a composition that solves the problems associated with polyurethane and polyurea compositions discussed above, e.g., resilience reduction and complicated ratio and mixing requirements, while still obtaining the soft feel provided by such compositions. In particular, it would be advantageous to provide a composition formed from incorporating aliphatic chemistries, however past efforts to make top quality blemish free aliphatic golf ball covers with aliphatic chemistries required elevated temperature post curing or delay times which were unacceptable.
There is a need in making golf ball covers, for compositions that contain aliphatic chemistries, but in a manner that does not require the added curing times or the higher processing temperature. The present invention describes such compositions and the use of them in a variety of golf ball cover layers.
The present invention is directed to a golf ball including a core and a cover, wherein the cover is cast from a castable reactive aliphatic functional composition consisting essentially of: a methylene dicyclohexyl diisocyanate based prepolymer; at least one polyamine/polyamide functional component used as a backbone of the prepolymer; a free isocyanate group; and a curative. The polyamine/polyamide is formed from the condensation reaction of a polyamine and a polyacid, with the equivalent ratio of polyamine to polyacid ranges from 2:1 to 10:1, preferably the ratio is 3:1, and more preferably 2:1. It is preferable that the polyamine be a Jeffamine series D-2000. The polyacid can be chosen from acids such as maleic, adipic, azelaic or sebacic. It is preferable that the prepolymer be a polyurethane or urea.
The present invention is directed to formulating techniques that eliminate the need for a post cure or delay times when utilizing aliphatic chemistries in golf ball covers. The main inventive concept of the present invention is incorporating amide linkages as the pre-polymer backbone or incorporating them into the curing agent.
Typically, formulations are designed with concern for only the physical properties of the finished materials. The present invention not only formulates for material properties, but teaches towards formulating for ease of material processing, by eliminating the need for additional manufacturing steps to produce blemish-free aliphatic golf ball covers. Utilizing aliphatic chemistries often has required elevated temperature post curing which has been eliminated herein by the present invention.
A polyamine/polyamide is formed by the condensation reaction of a polyacid and a polyamine. The equivalent ration of polyamine to polyacid ranges from 2:1 to 10:1, and a blend of at least two polyacids and/or a blend of at least two polyamines can be used, wherein one has a molecular weight greater than the other. Useful polyamines include, but are not limited to, polyamines such as the Jeffamine series from Huntsman. Polyacids useful for the present invention include, but are not limited to, maleic acid, adipic acid, azelaic acid, and sebacic acid. When the polyacid/polyamine reaction is complete, it can be utilized as a curing agent or in the backbone of an isocyanate based pre-polymer. Other methods of producing polyamides known to those skilled in the art may also be used in the present invention.
Previous attempts at molding defect free aliphatic cover formulations have required additional process steps to the method of the present invention. These steps have included: additional curing time; elevated post cure times; and chilling of the golf ball cores. It has been discovered that the incorporation of amide linkages into the polymer eliminates the need for additional process steps to produce defect free golf ball covers. The present invention allows for the formulator to utilize aliphatic chemistries that would otherwise be prohibited due to manufacturing constraints. The ratio of polyamine/polyacid is the determining factor when trying to balance both physical properties and ease of processing of the formulation.
It should be understood that the examples below are for illustrative purposes only. In no manner is the present invention limited to the specific disclosures therein.
Pre-polymer: 1.0 eq. of Jeffamine D-2000 pre-polymer @ 6.4% NCO
Curative: 0.95 eq. Clearlink 1000 and 3.5% HCC 19584 (white dispersion)
Pre-polymer: Jeffamine D-2000/Adipic acid @ 3:1 ratio @ 6.42% NCO
Curative: 0.95 eq. Clearlink 1000 and 3.5% HCC 19584 (white dispersion)
Pre-polymer: Jeffamine D-2000/Adipic acid @ 2:1 ratio @ 6.4% NCO
Curative: 0.95 eq. Clearlink 1000 and 3.5% HCC 19584 (white dispersion)
Jeffamine® D-2000 is a polyetheramine characterized by repeating oxypropylene units in the backbone and is a difunctional, primary amine with average molecular weight of about 2000. The primary amine groups are located on secondary carbon atoms at the end of the aliphatic polyether chains.
The data in the above chart shows the advantage of utilizing polyamine/polyamide chemistries in the casting of aliphatic golf ball covers. Through the incorporation of amide linkages into the polymer, additional process steps such as post cure times and the chilling of the cores have been eliminated.
The compositions of the invention may be used in cover layers of a variety of golf ball constructions, e.g., one-piece, two-piece, and multilayer balls.
Representative aliphatic and cycloaliphatic acids suitable for use in this aspect of the invention include, but are not limited to, sebacic acid, 1, 3 or 1,4-cyclohexane dicarboxylic acid, adipic acid, glutaric acid, succinic acid, carbonic acid, oxalic acid, itaconic acid, azelaic acid, diethylmalonic acid, fumaric acid, citraconic acid, allylmalonate acid, 4-cyclohexene-1,2-dicarboxylate acid, pimelic acid, suberic acid, 2,5-diethyladipic acid, 2-ethylsuccinic acid, cyclopentane dicarboxylic acid, 2,2,3,3 tetramethyl succinic acid, decahydro-1,5-(or 2,6-) naphthylene dicarboxylic acid, 4,4′-bicyclohexyl dicarboxylic acid, 4,4′-methylenebis(cyclohexyl carboxylic acid), 3,4-furan dicarboxylate, 1,1-cyclobutane dicarboxylate, and mixtures thereof.
Additional materials other than the main components discussed above may be added to the compositions of the invention including, but not limited to, coloring agents or dyes, optical brighteners, cross-linking agents, whitening agents such as TiO2 and ZnO, UV absorbers, hindered amine light stabilizers, de-foaming agents, processing aids, softening agents, plasticizers, surfactants, impact modifiers, fillers, reinforcing materials, catalysts, compatibilizers, fragrance components, antioxidants and other conventional additives. Those of ordinary skill in the art are aware of the purpose of these additives and the amounts that should be employed to fulfill those purposes.
For example, fillers may be added to the compositions of the invention to affect rheological and mixing properties, the specific gravity (i.e., density-modifying fillers), the modulus, the tear strength, reinforcement, and the like. The fillers are generally inorganic, and suitable fillers include numerous metals, metal oxides and salts, such as zinc oxide and tin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate, zinc carbonate, barium carbonate, clay, tungsten, tungsten carbide, an array of silicas, regrind (recycled core material typically ground to about 30 mesh particle), high-Mooney-viscosity rubber regrind (having a Mooney viscosity of about 55 or greater), and mixtures thereof.
In addition, the compositions of the invention may contain at least one light stabilizing component. As used herein, light stabilizer may be understood to include hindered amine light stabilizers, ultraviolet (UV) absorbers, and antioxidants. Addition of UV absorbers and light stabilizers to any of the above compositions may help to maintain the tensile strength, elongation, and color stability, as well as prevent cover surface fractures due to photodegradation. Suitable light stabilizers include, but are not limited to, TINUVIN® 292, TINUVIN® 328, TINUVIN® 213, TINUVIN® 765, TINUVIN® 770 and TINUVIN® 622. TINUVIN® products are available from Ciba Specialty Chemicals of Tarrytown, N.Y.
Moreover, as discussed above, dyes, as well as optical brighteners and fluorescent pigments may also be included in the golf ball covers produced with polymers formed according to the present invention. Such additional ingredients may be added in any amounts that will achieve their desired purpose. For example, a white dispersion may used in the compositions of the invention, preferably in an amount of about 0.5 percent to about 10 percent by weight of the composition. In one embodiment, the composition of the invention includes about 2 percent to about 8 percent of white dispersion by weight of the composition. In another embodiment, the white dispersion is present in the composition in an amount of about 3 percent to about 6 percent by weight of the composition. In still another embodiment, the white dispersion is present in the composition in an amount of about 3.5 percent to about 5 percent by weight of the composition.
Furthermore, a stabilizing component may be included that is a combination of polyamide and antioxidant. For example, U.S. Pat. No. 3,896,078 discloses a suitable stabilizer for use in the compositions of the invention, the entire disclosure of which is incorporated by reference herein. In particular, such a stabilizing component may be included in the composition in amounts providing up to about 6.5 percent of amide linkages by weight of the composition.
The compositions of the present invention may be used with any type of ball construction. For example, one-piece, two-piece, three-piece, and four-piece golf ball designs are contemplated by the present invention. In addition, golf balls having double cores, intermediate layer(s), and/or double covers are also useful with the present invention. As known to those of ordinary skill in the art, the type of golf ball constructed, i.e., double core, double cover, and the like, depends on the type of performance desired of the ball. As used herein, the term “layer” includes any generally spherical portion of a golf ball, i.e., a golf ball core or center, an intermediate layer, and/or a golf ball cover. As used herein, the term “inner layer” refers to any golf ball layer beneath the outermost structural layer of the golf ball. As used herein, “structural layer” does not include a coating layer, top coat, paint layer, or the like. As used herein, the term “multilayer” means at least two layers.
As discussed, the golf balls of the invention include at least one structural layer that includes compositions of the invention. In addition, as discussed in more detail below, the golf balls of the invention may include core layers, intermediate layers, or cover layers formed from materials known to those of skill in the art. These examples are not exhaustive, as skilled artisans would be aware that a variety of materials might be used to produce a golf ball of the invention with desired performance properties.
As used herein, “intermediate layer” includes any layer between the innermost layer of the golf ball and the outermost layer of the golf ball. Therefore, intermediate layers may also be referred to as outer core layers, inner cover layers, and the like. When the golf ball of the present invention includes an intermediate layer, this layer may be formed from the compositions of the invention.
The intermediate layer may also be formed of conventional materials known to those of ordinary skill in the art, including various thermoset and thermoplastic materials, as well as blends thereof. For example, the intermediate layer may be formed, at least in part, from one or more homopolymeric or copolymeric materials, such as vinyl resins, low and high acid ionomer resins, polyolefins, polyurethanes, polyureas, polyamides, acrylic resins, olefinic thermoplastic rubbers, block copolymers of styrene and butadiene, isoprene or ethylene-butylene rubber, copoly(ether-amide), polyphenylene oxide resins, thermoplastic polyesters, ethylene, propylene, 1-butene or 1-hexene based homopolymers or copolymers, and the like.
The intermediate layer may also be formed from highly neutralized polymers such as those disclosed U.S. Pat. Nos. 6,565,455 and 6,565,456, which are incorporated herein in their entirety by express reference thereto; grafted and non-grafted metallocene catalyzed polyolefins and polyamides, polyamide/ionomer blends, and polyamide/nonionomer blends, such as those disclosed in U.S. Pat. No. 6,800,690, which is incorporated by reference herein in its entirety; among other polymers. Examples of other suitable intermediate layer materials include blends of some of the above materials, such as disclosed in U.S. Pat. No. 5,688,181, and of which the entire disclosure is incorporated by reference herein.
The intermediate layer may also be a moisture barrier layer, such as described in U.S. Pat. No. 5,820,488, and which is incorporated in its entirety by reference herein.
The cover provides the interface between the ball and a club. As used herein, the term “cover” means the outermost portion of a golf ball. A cover typically includes at least one layer and may contain indentations such as dimples and/or ridges. Paints and/or laminates are typically disposed about the cover to protect the golf ball during use thereof. The cover may include a plurality of layers, e.g., an inner cover layer disposed about a golf ball center and an outer cover layer formed thereon.
Inner and/or outer cover layers may be formed from the compositions of the invention. Alternatively, both the inner and/or outer cover layers of golf balls of the present invention may be formed of polyurea, polyurethane, or mixtures thereof, as disclosed in U.S. Pat. Nos. 6,835,794 and 7,041,770. The entire disclosures of these publications are incorporated by reference herein.
In addition, cover layers may also be formed of one or more homopolymeric or copolymeric materials, such as vinyl resins, polyolefins, conventional polyurethanes and polyureas, such as the ones disclosed in U.S. Pat. Nos. 5,334,673, and 5,484,870, polyamides, acrylic resins and blends of these resins with poly vinyl chloride, elastomers, and the like, thermoplastic urethanes, olefinic thermoplastic rubbers, block copolymers of styrene and butadiene, polyphenylene oxide resins or blends of polyphenylene oxide with high impact polystyrene, thermoplastic polyesters, ethylene, propylene, 1-butene or 1-hexane based homopolymers or copolymers including functional monomers, methyl acrylate, methyl methacrylate homopolymers and copolymers, low acid ionomers, high acid ionomers, highly neutralized ionomers, alloys, and mixtures thereof.
Additional materials may be included in the core, intermediate layer, and/or cover layer compositions outlined above. For example, catalysts, coloring agents, optical brighteners, cross-linking agents, whitening agents such as TiO2 and ZnO, UV absorbers, hindered amine light stabilizers, defoaming agents, processing aids, surfactants, and other conventional additives may be added to the cover layer compositions of the invention. In addition, antioxidants, stabilizers, softening agents, plasticizers, including internal and external plasticizers, impact modifiers, foaming agents, density-adjusting fillers, reinforcing materials, and compatibilizers may also be added to any of the cover layer compositions. Those of ordinary skill in the art should be aware of the requisite amount for each type of additive to realize the benefits of that particular additive.
The golf balls of the invention may be formed using a variety of application techniques such as compression molding, flip molding, injection molding, retractable pin injection molding, reaction injection molding (RIN), reinforced reaction injection molding (RRIM), retractable pin injection molding (RPIM), casting, vacuum forming, powder coating, flow coating, spin coating, dipping, spraying, and the like depending on the materials used for a specific component. For example, the compositions of the invention are particular useful in injection molding and extrusion applications. Thus, golf ball components including the compositions of the invention may be formed by injection molding and the like.
Although the molding method for the present invention is casting, one skilled in the art, however, would appreciate that the molding method used may be determined at least partially by the properties of the composition used to form the particular golf ball component. For example, casting or RIM, may be preferred when the material is thermoset, whereas compression molding or injection molding may be preferred for thermoplastic compositions. Compression molding, however, may also be used for thermoset inner ball materials. For example, when cores are formed from a thermoset material, compression molding is a particularly suitable method of forming the core, whereas when the cores are formed of a thermoplastic material, the cores may be injection molded. In addition, the intermediate layer may also be formed from using any suitable method known to those of ordinary skill in the art. For instance, an intermediate layer may be formed by blow molding and covered with a dimpled cover layer formed by injection molding, compression molding, casting, vacuum forming, powder coating, and the like.
The golf balls of the invention are preferably designed with certain flight characteristics in mind. The use of various dimple patterns and profiles provides a relatively effective-way to modify the aerodynamic characteristics of a golf ball. As such, the manner in which the dimples are arranged on the surface of the ball can be by any available method. For instance, the ball may have an icosahedron-based pattern, such as described in U.S. Pat. No. 4,560,168, or an octahedral-based dimple patterns as described in U.S. Pat. No. 4,960,281. Alternatively, the dimple pattern can be arranged according to phyllotactic patterns, such as described in U.S. Pat. No. 6,338,684, or a tubular lattice pattern, such as the one disclosed in U.S. Pat. No. 6,290,615, the disclosures of which are incorporated herein in their entirety.
The golf balls of the present invention may be painted, coated, or surface treated for further benefits. For example, a golf ball of the invention may be treated with a base resin paint composition or the cover composition may contain certain additives to achieve a desired color characteristic. In one embodiment, the golf ball cover composition contains a fluorescent whitening agent to provide improved weather resistance and brightness.
Protective and decorative coating materials, as well as methods of applying such materials to the surface of a golf ball cover are well known in the golf ball art. Generally, such coating materials comprise urethanes, urethane hybrids, epoxies, polyesters and acrylics. If desired, more than one coating layer can be used. The coating layer(s) may be applied by any suitable method known to those of ordinary skill in the art. For example, the coating layer(s) may be applied to the golf ball cover by an in-mold coating process, such as described in U.S. Pat. No. 5,849,168, which is incorporated in its entirety by reference herein. The coating layer may have a thickness of about 0.004 inches or less, more preferably about 0.002 inches or less.
In addition, the golf balls of the invention may be painted or coated with an ultraviolet curable/treatable ink, by using the methods and materials disclosed in U.S. Pat. Nos. 6,500,495, 6,248,804, and 6,099,415, the entire disclosures of which are incorporated by reference herein.
Furthermore, trademarks or other indicia may be stamped, i.e., pad-printed, on the outer surface of the ball cover, and the stamped outer surface is then treated with at least one clear coat to give the ball a glossy finish and protect the indicia stamped on the cover.
The golf balls of the invention may also be subjected to dye sublimation, wherein at least one golf ball component is subjected to at least one sublimating ink that migrates at a depth into the outer surface and forms an indicia. The at least one sublimating ink preferably includes at least one of an azo dye, a nitroarylamine dye, or an anthraquinone dye as disclosed in U.S. Pat. No. 6,935,240, the entire disclosure of which is incorporated by reference herein.
Laser marking of a selected surface portion of a golf ball causing the laser light-irradiated portion to change color is also contemplated for use with the present invention. U.S. Pat. Nos. 5,248,878 and 6,075,223 generally disclose such methods, the entire disclosures of which are incorporated by reference herein. In addition, the golf balls may be subjected to ablation, i.e., directing a beam of laser radiation onto a portion of the cover, irradiating the cover portion, wherein the irradiated cover portion is ablated to form a detectable mark, wherein no significant discoloration of the cover portion results therefrom. Ablation is discussed in U.S. Pat. No. 6,462,303, which is incorporated in its entirety by reference herein.
The properties such as hardness, modulus, core diameter, and layer thickness of the golf balls of the present invention have been found to effect play characteristics such as spin, initial velocity and feel of the present golf balls. For example, the flexural and/or tensile modulus of the intermediate layer are believed to have an effect on the “feel” of the golf balls of the present invention. It should be understood that the ranges herein are meant to be intermixed with each other, i.e., the low end of one range may be combined with a high end of another range.
Dimensions of golf ball components, i.e., thickness and diameter, may vary depending on the desired properties. For the purposes of the invention, any layer thickness may be employed. Non-limiting examples of the various embodiments outlined above are provided here with respect to layer dimensions.
The present invention relates to golf balls of any size. While USGA specifications limit the size of a competition golf ball to more than 1.68 inches in diameter, golf balls of any size can be used for leisure golf play. The preferred diameter of the golf balls is from about 1.68 inches to about 1.8 inches. The more preferred diameter is from about 1.68 inches to about 1.76 inches. A diameter of from about 1.68 inches to about 1.74 inches is most preferred, however diameters anywhere in the range of from 1.7 to about 1.95 inches can be used. Preferably, the overall diameter of the core and all intermediate layers is about 80 percent to about 98 percent of the overall diameter of the finished ball.
The core may have a diameter ranging from about 0.09 inches to about 1.65 inches. In one embodiment, the diameter of the core of the present invention is about 1.2 inches to about 1.630 inches. In another embodiment, the diameter of the core is about 1.3 inches to about 1.6 inches, preferably from about 1.39 inches to about 1.6 inches, and more preferably from about 1.5 inches to about 1.6 inches. In yet another embodiment, the core has a diameter of about 1.55 inches to about 1.65 inches.
The core of the golf ball may also be extremely large in relation to the rest of the ball. For example, in one embodiment, the core makes up about 90 percent to about 98 percent of the ball, preferably about 94 percent to about 96 percent of the ball. In this embodiment, the diameter of the core is preferably about 1.54 inches or greater, preferably about 1.55 inches or greater. In one embodiment, the core diameter is about 1.59 inches or greater. In another embodiment, the diameter of the core is about 1.64 inches or less.
When the core includes an inner core layer and an outer core layer, the inner core layer is preferably about 0.9 inches or greater and the outer core layer preferably has a thickness of about 0.1 inches or greater. In one embodiment, the inner core layer has a diameter from about 0.09 inches to about 1.2 inches and the outer core layer has a thickness from about 0.1 inches to about 0.8 inches. In yet another embodiment, the inner core layer diameter is from about 0.095 inches to about 1.1 inches and the outer core layer has a thickness of about 0.20 inches to about 0.03 inches.
The cover typically has a thickness to provide sufficient strength, good performance characteristics, and durability. The thickness of the outer cover layer may be from about 0.005 inches to about 0.100 inches, preferably about 0.007 inches to about 0.035 inches. In one embodiment, the cover thickness is from about 0.02 inches to about 0.35 inches. In another embodiment, the cover preferably has a thickness of about 0.02 inches to about 0.12 inches, preferably about 0.1 inches or less, more preferably about 0.07 inches or less. In yet another embodiment, the outer cover has a thickness from about 0.02 inches to about 0.07 inches. In still another embodiment, the cover thickness is about 0.05 inches or less, preferably from about 0.02 inches to about 0.05 inches. For example, the outer cover layer may be between about 0.02 inches and about 0.045 inches, preferably about 0.025 inches to about 0.04 inches thick. In one embodiment, the outer cover layer is about 0.03 inches thick.
The range of thicknesses for an intermediate layer of a golf ball is large because of the vast possibilities when using an intermediate layer, i.e., as an outer core layer, an inner cover layer, a wound layer, a moisture/vapor barrier layer. When used in a golf ball of the invention, the intermediate layer, or inner cover layer, may have a thickness about 0.3 inches or less. In one embodiment, the thickness of the intermediate layer is from about 0.002 inches to about 0.1 inches, preferably about 0.01 inches or greater. In one embodiment, the thickness of the intermediate layer is about 0.09 inches or less, preferably about 0.06 inches or less. In another embodiment, the intermediate layer thickness is about 0.05 inches or less, more preferably about 0.01 inches to about 0.045 inches. In one embodiment, the intermediate layer, thickness is about 0.02 inches to about 0.04 inches. In another embodiment, the intermediate layer thickness is from about 0.025 inches to about 0.035 inches. In yet another embodiment, the thickness of the intermediate layer is about 0.035 inches thick. In still another embodiment, the inner cover layer is from about 0.03 inches to about 0.035 inches thick. Varying combinations of these ranges of thickness for the intermediate and outer cover layers may be used in combination with other embodiments described herein.
The ratio of the thickness of the intermediate layer to the outer cover layer is preferably about 10 or less, preferably from about 3 or less. In another embodiment, the ratio of the thickness of the intermediate layer to the outer cover layer is about 1 or less.
Most golf balls consist of layers having different levels of hardness, e.g., hardness gradients, to achieve desired performance characteristics. The present invention contemplates golf balls having hardness gradients between layers, as well as those golf balls with layers having the same hardness.
It should be understood, especially to one of ordinary skill in the art, that there is a fundamental difference between “material hardness” and “hardness, as measured directly on a golf ball.” Material hardness is defined by the procedure set forth in ASTM-D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material of which the hardness is to be measured. Hardness, when measured directly on a golf ball (or other spherical surface) is a completely different measurement and, therefore, results in a different hardness value. This difference results from a number of factors including, but not limited to, ball construction (i.e., core type, number of core and/or cover layers, etc.), ball (or sphere) diameter, and the material composition of adjacent layers. It should also be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other.
The cores of the present invention may have varying grades of hardness depending on the particular golf ball construction. In one embodiment, the core hardness is at least about 15 Shore A, preferably about 30 Shore A, as measured on a formed sphere. In another embodiment, the core has a hardness of about 50 Shore A to about 90 Shore D. In yet another embodiment, the hardness of the core is about 80 Shore D or less. Preferably, the core has a hardness about 30 to about 65 Shore D, and more preferably, the core has a hardness about 35 to about 60 Shore D.
The intermediate layer(s) of the present invention may also vary in hardness depending on the specific construction of the ball. In one embodiment, the hardness of the intermediate layer is about 30 Shore D or greater. In another embodiment, the hardness of the intermediate layer is about 90 Shore D or less, preferably about 80 Shore D or less, and more preferably about 70 Shore D or less. In yet another embodiment, the hardness of the intermediate layer is about 50 Shore D or greater, preferably about 55 Shore D or greater. In one embodiment, the intermediate layer hardness is from about 55 Shore D to about 65 Shore D. The intermediate layer may also be about 65 Shore D or greater.
When the intermediate layer is intended to be harder than the core layer, then the ratio of the intermediate layer hardness to the core hardness is preferably about 2 or less. In one embodiment, the ratio is about 1.8 or less. In yet another embodiment, the ratio is about 1.3 or less.
As with the core and intermediate layers, the cover hardness may vary depending on the construction and desired characteristics of the golf ball. The ratio of cover hardness to inner ball hardness is a primary variable used to control the aerodynamics of a ball and, in particular, the spin of a ball. In general, the harder the inner ball, the greater the driver spin and the softer the cover, the greater the driver spin.
For example, when the intermediate layer is intended to be the hardest point in the ball, e.g., about 50 Shore D to about 75 Shore D, the cover material may have a hardness of about 20 Shore D or greater, preferably about 25 Shore D or greater, and more preferably about 30 Shore D or greater, as measured on the slab. In another embodiment, the cover itself has a hardness of about 30 Shore D or greater. In particular, the cover may be from about 30 Shore D to about 70 Shore D. In one embodiment, the cover has a hardness of about 40 Shore D to about 65 Shore D, and in another embodiment, about 40 Shore to about 55 Shore D. In another aspect of the invention, the cover has a hardness less than about 45 Shore D, preferably less than about 40 Shore D, and more preferably about 25 Shore D to about 40 Shore D. In one embodiment, the cover has a hardness from about 30 Shore D to about 40 Shore D.
In this embodiment when the outer cover layer is softer than the intermediate layer or inner cover layer, the ratio of the Shore D hardness of the outer cover material to the intermediate layer material is about 0.8 or less, preferably about 0.75 or less, and more preferably about 0.7 or less. In another embodiment, the ratio is about 0.5 or less, preferably about 0.45 or less.
In yet another embodiment, the ratio is about 0.1 or less when the cover and intermediate layer each have a hardness that are substantially the same. When the hardness differential between the cover layer and the intermediate layer is not intended to be as significant, the cover may have a hardness of about 55 Shore D to about 65 Shore D. In this embodiment, the ratio of the Shore D hardness of the outer cover to the intermediate layer is about 1.0 or less, preferably about 0.9 or less.
In another embodiment, the cover layer is harder than the intermediate layer. In this design, the ratio of Shore D hardness of the cover layer to the intermediate layer is about 1.33 or less, preferably from about 1.14 or less.
Compression values are dependent on the diameter of the component being measured. Atti compression is typically used to measure the compression of a golf ball. As used herein, the terms “Atti compression” or “compression” are defined as the deflection of an object or material relative to the deflection of a calibrated spring, as measured with an Atti Compression Gauge, that is commercially available from Atti Engineering Corp. of Union City, N.J.
The Atti compression of the core, or portion of the core, of golf balls prepared according to the invention is preferably less than about 80, more preferably less than about 75. In another embodiment, the core compression is from about 40 to about 80, preferably from about 50 to about 70. In yet another embodiment, the core compression is preferably below about 50, and more preferably below about 25. In an alternative, low compression embodiment, the core has a compression less than about 20, more preferably less than about 10, and most preferably, 0. As known to those of ordinary skill in the art, however, the cores generated according to the present invention may be below the measurement of the Atti Compression Gauge.
In one embodiment, golf balls of the invention preferably have an Atti compression of about 55 or greater, preferably from about 60 to about 120. In another embodiment, the Atti compression of the golf balls of the invention is at least about 40, preferably from about 50 to 120, and more preferably from about 60 to 100. In yet another embodiment, the compression of the golf balls of the invention is about 75 or greater and about 95 or less. For example, a preferred golf ball of the invention may have a compression from about 80 to about 95.
There is currently no USGA limit on the COR of a golf ball, but the initial velocity of the golf ball cannot exceed 250.+−.5 feet/second (ft/s). Thus, in one embodiment, the initial velocity is about 245 ft/s or greater and about 255 ft/s or greater. In another embodiment, the initial velocity is about 250 ft/s or greater. In one embodiment, the initial velocity is about 253 ft/s to about 254 ft/s. In yet another embodiment, the initial velocity is about 255 ft/s. While the current rules on initial velocity require that golf ball manufacturers stay within the limit, one of ordinary skill in the art would appreciate that the golf ball of the invention would readily convert into a golf ball with initial velocity outside of this range. For example, a golf ball of the invention may be designed to have an initial velocity of about 220 ft/s or greater, preferably about 225 ft/s or greater.
As a result, of the initial velocity limitation set forth by the USGA, the goal is to maximize COR without violating the 255 ft/s limit. The COR of a ball is measured by taking the ratio of the outbound or rebound velocity to the incoming or inbound velocity. In a one-piece solid golf ball, the COR will depend on a variety of characteristics of the ball, including its composition and hardness. For a given composition, COR will generally increase as hardness is increased. In a two-piece solid golf ball, e.g., a core and a cover, one of the purposes of the cover is to produce a gain in COR over that of the core. When the contribution of the core to high COR is substantial, a lesser contribution is required from the cover. Similarly, when the cover contributes substantially to high COR of the ball, a lesser contribution is needed from the core.
The present invention contemplates golf balls having CORs from about 0.700 to about 0.850 at an inbound velocity of about 125 ft/sec. In one embodiment, the COR is about 0.750 or greater, preferably about 0.780 or greater. In another embodiment, the ball has a COR of about 0.800 or greater. In yet another embodiment, the COR of the balls of the invention is about 0.800 to about 0.815.
As known to those of ordinary skill in the art, the spin rate of a golf ball will vary depending on the golf ball construction. In a multilayer ball, e.g., a core, an intermediate layer, and a cover, wherein the cover is formed from the compositions of the invention, the spin rate of the ball off a driver (“driver spin rate”) may be 1500 rpm or greater. In one embodiment, the driver spin rate is about 2000 rpm to about 3500 rpm. In another embodiment, the driver spin rate is about 2200 rpm to about 3400 rpm. In still another embodiment, the driver spin rate may be less than about 1500 rpm.
Two-piece balls made according to the invention may also have driver spin rates of 1500 rpm and greater. In one embodiment, the driver spin rate is about 2000 rpm to about 3300 rpm. Wound balls made according to the invention preferably have similar spin rates.
Methods of determining the spin rate should be well understood by those of ordinary skill in the art. Examples of methods for determining the spin rate are disclosed in U.S. Pat. Nos. 6,500,073, 6,488,591, 6,286,364, and 6,241,622, which are incorporated by reference herein in their entirety.
The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. All patents and patent applications cited in the foregoing text are expressly incorporate herein by reference in their entirety.
