Patent Application
20240207689
The present disclosure relates generally to compositions for use in golf ball cores that produce high compression golf ball cores. More particularly, the present disclosure provides compositions and golf ball cores made from such compositions that provide the ability to tailor and/or improve certain ball performance characteristics when such cores are used in a golf ball. In some respects, the present disclosure relates to golf ball cores with increased compression, resiliency, and rebounding that, when used in golf balls, provide the ability to achieve one or more desired performance characteristics including, for example, spin on driver and short distance shots.
The performance of a golf ball is affected by a variety of factors including the materials, weight, size, dimple pattern, and external shape of the golf ball. As a result, golf ball manufacturers are constantly improving or tweaking the performance of golf balls by adjusting the materials and construction of the ball as well as the dimple pattern and dimple shape.
For example, the resiliency and rebounding (Coefficient of Restitution, or COR) performance of a golf ball are generally driven by the composition and construction of the core. The spin rate and feel of the ball also are important properties that are affected by the composition and construction of the core. The spin rate refers to the rate of rotation of the golf ball after being hit with a club. Two factors that affect the spin rate of a golf ball are the hardness gradient of the core, i.e., the difference in hardness between the geometric center and outer surface of the core, and the compression of the core, i.e., how much the core deflects under a given load. Generally, changing the compression of a golf ball or golf ball core alters the spin rate of the golf ball similarly for both driver shots and short distance shots. For example, increasing the compression of a golf ball or golf ball core may cause a 10 percent increase in spin rates for both short distance and driver shots. In contrast, changing the hardness gradient of the golf ball core may affect the spin rate differently for driver shots and short distance shots. More specifically, an increase in the hardness gradient may result in a 15 percent increase in spin rate on short distance shots but only a 5 percent increase in spin rate on driver shots.
Most professionals and highly skilled amateurs (i.e., those who can control the spin of a golf ball) generally prefer balls with high spin rates to allow for better control in and around the green and draw and fade on approach shots. Indeed, these balls are beneficial for short distance shots made with irons and wedges. In contrast, recreational players who cannot necessarily control the spin of the ball will likely find that it is easier to play with a golf ball with low spin because the spin from a golf ball with a high spin rate can create more shot dispersion, i.e., more stray off to the left or right of the centerline, especially if the ball is hooked or sliced.
Meanwhile, the “feel” of the ball generally refers to the sensation that a player experiences when striking the ball with the club. Most players prefer balls having a soft feel, because the players experience a more natural and comfortable sensation when the club face makes contact with these balls. Balls having a softer feel are particularly desirable when making short shots around the green, because the player senses more with such balls. The feel of the ball primarily depends upon the hardness and compression of the ball.
It is recognized in the art that the use of polyfunctional isocyanates in the rubber formulation of a golf ball core may affect the compression and the COR of the golf ball core. For example, U.S. Pat. No. 4,726,590 explains that adding polyfunctional isocyanates into the rubber formulation of a core increases the compression and COR of a golf ball core. However, it is also recognized that the inclusion of polyfunctional isocyanate in a rubber core formulation results in unpredictable (and sometimes undesirable) changes to the compression and COR of the core. In particular, the activity of the polyfunctional isocyanate in the rubber core formulation is affected by factors such as the moisture level in the raw materials and moisture uptake or loss during storage and manufacturing.
It is also recognized that the compression of a golf ball core can be manipulated by including water in a rubber core formulation. More particularly, adding water to a rubber core formulation has been shown to decrease the compression of the core. For example, U.S. Pat. No. 11,040,251 teaches that adding water to a rubber golf ball core decreases compression and reduces the spin of a golf ball core on driver and approach shots. However, as is understood by those of ordinary skill in the art, it may be undesirable to decrease the compression of a golf ball core in some cases. Thus, when water is added to a rubber core formulation, it may be necessary to also add or increase concentrations of other components to control and/or achieve the desired compression. Moreover, adding water to a rubber core formulation may also be difficult since the base rubber may be non-polar and resist full inclusion of water.
Accordingly, there remains a need in the art for compositions that allow formation of golf ball cores having both increased compression and increased COR. Particularly, there is a need for core compositions and golf ball cores made from such core compositions that can be tailored to have a desired and/or targeted compression and COR. In this respect, it would be advantageous to provide a core composition for use in a core of a golf ball such that the finished golf ball has the desired amount of spin on short distance and driver shots for players having different levels of expertise as well as other advantageous properties, features, and benefits. For example, it would be beneficial to tailor the core composition for use in a core of a golf ball so as to reduce shot dispersion for amateur players. Similarly, it would be advantageous to tailor the core composition for use in a core of a golf ball such that the finished golf ball gives highly skilled players greater control over the shot. The present disclosure provides compositions for use in golf ball cores and golf balls containing such cores that allow for controlled increase of the compression and COR of a golf ball core, and, thus, manipulation or tailoring of desired performance characteristics.
The present disclosure relates to a golf ball that includes a core formed from a rubber formulation including a base rubber, an organic peroxide, a compression agent, and a water-producing agent and a cover of one or more layers disposed about the core, wherein the compression agent is a polyfunctional isocyanate. In some embodiments, the compression agent is a polymethylene polyphenylisocyanate. In other embodiments, the rubber formulation has a compression agent concentration between about 0.1 and about 6.0 parts per hundred rubber. In some aspects, the water producing agent may be a metal salt hydrate. In other aspects, the rubber formulation has a water-producing agent concentration WPAC, and wherein WPAC is between about 0.1 and about 15 parts per hundred rubber. In still other aspects, the rubber formulation has a water content WC and wherein WC is between 0.1 and 3.5 parts per hundred rubber.
The core further includes a geometric center having a hardness, a geometric surface having a hardness, and a hardness gradient equal to the difference in the geometric center hardness and the surface hardness, and wherein the hardness gradient is in the range of about 10 Shore C to about 42 Shore C. In some embodiments, the core further includes a core compression and wherein the core compression is in the range of about 40 DCM to about 100 DCM. In other embodiments, the core further includes a Coefficient of Restitution, wherein the Coefficient of Restitution is in the range of about 0.750 to about 0.830. In still other embodiments, the rubber formulation further includes a co-agent, a filler, a radical scavenger, an initiator, an organosulfur, or a combination thereof. In this aspect, the organosulfur may be present in an amount of about 0.1 to 5 parts per hundred rubber. The base rubber may be polybutadiene rubber, polyisoprene, ethylene propylene rubber, ethylene-propylene-diene rubber, styrene-butadiene rubber, or a blend thereof. The cover layer may include a material selected from the group consisting of polyurethanes, polyureas, and hybrids, copolymers, and blends thereof.
The present disclosure also relates to a golf ball with a core and a cover of at least one layer disposed about the core, where the core is formed from a rubber formulation including a base rubber, a compression agent having a compression agent concentration CAC, and a water-producing agent having a water-producing agent concentration WPAC, wherein the core has a core compression C, and
In some embodiments,
In other embodiments, CAC is about 0.5 to about 5 parts per hundred rubber. In still other embodiments, WPAC is about 0.5 to about 3.5 parts per hundred rubber. In yet other embodiments, the rubber formulation further includes a co-agent, a filler, a radical scavenger, an initiator, an organosulfur, or a combination thereof. In this aspect, the organosulfur may be present in an amount of about 0.1 to 5 parts per hundred rubber.
The present disclosure is also directed to a golf ball including a core and a cover of at least one layer, where the core is formed from a rubber formulation including a base rubber, a compression agent having a compression agent concentration CAC, and a water-producing agent having a water-producing agent concentration WPAC, where the core has a core compression C, and
In some embodiments,
In other embodiments, CAC is about 0.5 to about 5 parts per hundred rubber and wherein WPAC is about 0.5 to about 3.5 parts per hundred rubber. In still other embodiments, the rubber formulation further includes a co-agent, a filler, a radical scavenger, an initiator, an organosulfur, or a combination thereof. In this aspect, the organosulfur may be present in an amount of about 0.1 to 5 parts per hundred rubber.
Further features and advantages of the invention can be ascertained from the following detailed description that is provided in connection with the drawings described below:
The present disclosure relates to compositions that may be used to produce golf cores (or components thereof) with a desired compression, Coefficient of Restitution (COR), and/or hardness gradient, cores including such compositions, and golf balls including such cores. In some respects, the increased compression and increased COR of cores formed in accordance with the present disclosure provide the ability to increase spin when compared to a conventional golf ball hit under the same conditions. In addition, increased compression and COR of cores formed in accordance with the present disclosure may be used to provide greater control on long shots as well as approach shots and greenside play.
While the golf ball core is functionally different from the other layers of the golf ball and operates somewhat independently, the core of the present disclosure greatly influences the overall performance of the finished golf ball including such a core. Without being bound by any particular theory, performance characteristics of a finished golf ball that contains the core of the present disclosure may be tailored by changing the core composition. For example, altering the core composition and, thus, the compression and COR, may have a significant effect on long shots, e.g., shots off of a driver, and approach shots, e.g., shots made with irons and wedges. In fact, adjusting the compression and COR of golf ball cores made in accordance with this present disclosure, even in relatively small amounts, can significantly affect how a golf ball performs on long and short distance shots. Similarly, adjusting the compression and COR of the core may allow for tailoring of other properties of the finished golf ball. The inventive core formulations, cores, golf balls, and resulting performance characteristics are discussed in greater detail below.
A golf ball of the present disclosure may contain a single- or multi-layered core. One or more of the layers of the core may comprise a rubber formulation comprising one or more components. Concentrations of components are in parts per hundred (phr) unless otherwise indicated. As used herein, the term, “parts per hundred,” also known as “phr” or “pph” is defined as the number of parts by weight of a particular component present in a mixture, relative to 100 parts by weight of the polymer component. Mathematically, this can be expressed as the weight of an ingredient divided by the total weight of the polymer, multiplied by a factor of 100.
In one embodiment, the rubber formulation includes a base rubber in an amount of about 5 percent to 100 percent by weight based on the total weight of the rubber formulation. In one embodiment, the base rubber is included in the rubber formulation in an amount within a range having a lower limit of about 5 percent or 10 percent or 20 percent or 30 percent or 40 percent or 50 percent or 55 percent and an upper limit of about 60 percent or 70 percent or 80 percent or 90 percent or 95 percent or 100 percent. For example, the base rubber may be present in the rubber formulation in an amount of about 30 percent to about 90 percent or about 40 percent to about 80 percent by weight base rubber based on the total weight of the rubber formulation. In another example, the rubber formulation includes about 50 percent to about 70 percent or about 60 percent to about 70 percent by weight base rubber based on the total weight of the rubber formulation.
The base rubber may be polybutadiene, polyisoprene, ethylene propylene rubber, ethylene-propylene-diene rubber, styrene-butadiene rubber, styrenic block copolymer rubbers, polyalkenamers such as, for example, polyoctenamer, butyl rubber, halobutyl rubber, polystyrene elastomers, polyethylene elastomers, polyurethane elastomers, polyurea elastomers, metallocene-catalyzed elastomers and plastomers, copolymers of isobutylene and p-alkylstyrene, halogenated copolymers of isobutylene and p-alkylstyrene, copolymers of butadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, and blends of two or more thereof. In one embodiment, the rubber formulation includes polybutadiene rubber, butyl rubber, or a blend thereof as the base rubber.
For example, the core may be formed from a rubber formulation that includes polybutadiene as the base rubber. Polybutadiene is a homopolymer of 1,3-butadiene. The double bonds in the 1,3-butadiene monomer are attacked by catalysts to grow the polymer chain and form a polybutadiene polymer having a desired molecular weight. Any suitable catalyst may be used to synthesize the polybutadiene rubber depending upon the desired properties. In one embodiment, a transition metal complex (for example, neodymium, nickel, or cobalt) or an alkyl metal such as alkyl lithium is used as a catalyst. Other catalysts include, but are not limited to, aluminum, boron, lithium, titanium, and combinations thereof. The catalysts produce polybutadiene rubbers having different chemical structures. In a cis-bond configuration, the main internal polymer chain of the polybutadiene appears on the same side of the carbon-carbon double bond contained in the polybutadiene. In a trans-bond configuration, the main internal polymer chain is on opposite sides of the internal carbon-carbon double bond in the polybutadiene. The polybutadiene rubber can have various combinations of cis- and trans-bond structures. For example, the polybutadiene rubber may have a 1,4 cis-bond content of at least 40 percent. In another embodiment, the polybutadiene rubber has a 1,4 cis-bond content of greater than 80 percent. In still another embodiment, the polybutadiene rubber has a 1,4 cis-bond content of greater than 90 percent. In general, polybutadiene rubbers having a high 1,4 cis-bond content have high tensile strength and rebound.
In some embodiments, the rubber formulation of the present disclosure includes a blend of different polybutadiene rubbers. In this embodiment, the rubber formulation may include a blend of a first polybutadiene rubber and a second polybutadiene rubber in a ratio of about 5:95 to about 95:5. For example, the rubber formulation may include a first polybutadiene rubber and a second polybutadiene rubber in a ratio of about 10:90 to about 90:10 or about 15:85 to about 85:15 or about 20:80 to about 80:20 or about 30:70 to about 70:30 or about 40:60 to about 60:40. In other embodiments, the rubber formulation may include a blend of more than two polybutadiene rubbers or a blend of polybutadiene rubbers with any of the other elastomers discussed above.
The polybutadiene rubber may have a relatively high or low Mooney viscosity. Generally, polybutadiene rubbers of higher molecular weight and higher Mooney viscosity have better resiliency than polybutadiene rubbers of lower molecular weight and lower Mooney viscosity. However, as the Mooney viscosity increases, the milling and processing of the polybutadiene rubber generally becomes more difficult. Blends of high and low Mooney viscosity polybutadiene rubbers may be prepared as is described in U.S. Pat. Nos. 6,982,301 and 6,774,187, the disclosures of which are hereby incorporated by reference, and used in accordance with this invention. In general, the lower limit of Mooney viscosity may be about 30 or 35 or 40 or 45 or 50 or 55 or 60 or 70 or 75 and the upper limit may be about 80 or 85 or 90 or 95 or 100 or 105 or 110 or 115 or 120 or 125 or 130. For example, the polybutadiene used in the rubber formulation may have a Mooney viscosity of about 30 to about 80 or about 40 to about 60.
Examples of commercially available polybutadiene rubbers that can be used in rubber formulations in accordance with this invention, include, but are not limited to, BR 01 and BR 1220, available from BST Elastomers of Bangkok, Thailand; SE BR 1220LA and SE BR1203, available from DOW Chemical Co of Midland, Mich.; BUDENE 1207, 1207s, 1208, and 1280 available from Goodyear, Inc of Akron, Ohio; BR 01, 51 and 730, available from Japan Synthetic Rubber (JSR) of Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29 MES, CB 60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221, available from ARLANXEO Performance Polymers of Maastricht, Netherlands; BR1208, available from LG Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B, BR150L, BR230, BR360L, BR710, and VCR617, available from UBE Industries, Ltd. of Tokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60 AF and P30AF, and EUROPRENE BR HV80, available from Polimeri Europa of Rome, Italy; AFDENE 50 and NEODENE BR40, BR45, BR50 and BR60, available from Karbochem (PTY) Ltd. of Bruma, South Africa; KBR 01, NdBr 40, NdBR-45, NdBr 60, KBR 710S, KBR 710H, and KBR 750, available from Kumho Petrochemical Co., Ltd. Of Seoul, South Korea; DIENE 55NF, 70AC, and 320 AC, available from Firestone Polymers of Akron, Ohio; and PBR-Nd Group II and Group III, available from Nizhnekamskneftekhim, Inc. of Nizhnekamsk, Tartarstan Republic.
In another embodiment, the rubber formulation includes butyl rubber. Butyl rubber is an elastomeric copolymer of isobutylene and isoprene. Butyl rubber is an amorphous, non-polar polymer with good oxidative and thermal stability, good permanent flexibility and high moisture and gas resistance. Generally, butyl rubber includes copolymers of about 70 percent to about 99.5 percent by weight of an isoolefin, which has about 4 to 7 carbon atoms, for example, isobutylene, and about 0.5 percent to about 30 percent by weight of a conjugated multiolefin, which has about 4 to 14 carbon atoms, for example, isoprene. The resulting copolymer contains about 85 percent to about 99.8 percent by weight of combined isoolefin and about 0.2 percent to about 15 percent of combined multiolefin. A commercially available butyl rubber includes Bayer Butyl 301 manufactured by Bayer AG.
In still another embodiment, the rubber formulation used to form the core includes a blend of polybutadiene and butyl rubber. In this embodiment, the rubber formulation may include a blend of polybutadiene and butyl rubber in a ratio of about 99:1 to about 80:20. For example, the rubber formulation may include a blend of polybutadiene and butyl rubber in a ratio of about 95:5 to about 85:15 or about 92:8 to about 88:12 or about 90:10. In other embodiments, the rubber formulation may include polybutadiene and/or butyl rubber in a blend with any of the other elastomers discussed above.
The rubber formulations of the present disclosure may include a compression agent. Without being bound to any particular theory, including a compression agent in the rubber formulation of a golf ball core increases the compression and COR of the golf ball core. The compression agent may also be aromatic or aliphatic in nature. As discussed in greater detail below, some compression agents may have increased activity when the rubber formulation also includes a water-producing agent.
In some embodiments, the compression agent is a polyfunctional isocyanate. A polyfunctional isocyanate is an organic compound having two or more isocyanate (—NCO) groups per molecule and may include monomers, polymers, quasi prepolymers, or prepolymers. In some aspects, the compression agent may be a monomeric polyfunctional isocyanate, a polymeric polyfunctional isocyanate, or a blend thereof. The polyfunctional isocyanate may be aromatic or aliphatic in nature. Nonlimiting examples of polyfunctional isocyanates for use as the compression agent with the present invention include methylene diphenyl diisocyanate (“MDI”) and isomers thereof including 4,4′-diphenylmethane diisocyanate (“4,4′-MDI”), polymeric MDI, carbodiimide-modified liquid MDI, 4,4′-dicyclohexylmethane diisocyanate (“H12MDI”), polymethylene polyphenlisocyante containing MDI, p-phenylene diisocyanate (“PPDI”), toluene 3,3′-dimethyl-4,4′-biphenylene diisocyanate (“TDI”), diisocyanate (“TODI”), isophoronediisocyanate (“IPDI”), hexamethylene diisocyanate (“HDI”), naphthalene diisocyanate (“NDI”); xylene diisocyanate (“XDI”); p-methylxylene diisocyanate; m-methylxylene diisocyanate; o-methylxylene diisocyanate; para-tetramethylxylene diisocyanate (“p-TMXDI”); meta-tetramethylxylene diisocyanate (“m-TMXDI”); ethylene diisocyanate; propylene-1,2-diisocyanate; tetramethylene-1,4-diisocyanate; cyclohexyl diisocyanate; 1,6-hexamethylene-diisocyanate (“HDI”); dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate; 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; methyl cyclohexylene diisocyanate; triisocyanate of HDI; triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate (“TMDI”), tetracene diisocyanate, naphthalene diisocyanate, anthracene diisocyanate; and combinations thereof. In one embodiment, the compression agent is a polymethylene polyphenylisocyanate containing MDI. A non-limiting example of a commercially available polyfunctional isocyanate includes PAPI® 94 manufactured by The Dow Chemical Company.
The compression agent may be included in the rubber formulation in varying amounts depending on the desired characteristics of the golf ball core. For example, the compression agent may be used in an amount of 0.1 to about 10 parts by weight per 100 parts of the total rubber. In one embodiment, the rubber formulation of the core includes about 0.2 to about 7 parts by weight polyfunctional isocyanate per 100 parts of the total rubber. In another embodiment, the polyfunctional isocyanate is included in the rubber formulation in an amount of about 0.5 to about 5 or about 0.5 to about 2 or about 0.7 to about 1.3 parts by weight per 100 parts of the total rubber. In yet another embodiment, the rubber formulation includes 0.6 to about 0.9 or about 0.8 to about 1.2 or about 1.1 to about 1.6 parts by weight polyfunctional isocyanate per 100 parts of the total rubber.
The rubber formulations of the present disclosure may also include a water-producing agent. Without being bound to any particular theory, adding water to a rubber formulation containing a compression agent of the present disclosure may generally increase the compression and COR of a golf ball core made from the rubber formulation more than the increase in compression and COR provided by the compression agent alone. In other words, including a compression agent and a water-producing agent in the rubber formulation of a golf ball core produces a synergistic effect that allows for greater increases in the compression and COR of the golf ball core. This starkly contrasts with prior art golf balls, which generally exhibited a decreased compression when a water-producing agent was added to the rubber formulation of the core of the golf ball. Suitable water-producing agents include, but are not limited to, hydrates such as metal salt hydrates. Nonlimiting examples of metal salt hydrates are calcium sulfate hemihydrate, calcium sulfate dihydrate, aluminum sulfate 14-18-hydrate, magnesium sulfate heptahydrate, beryllium sulfate tetrahydrate, zirconium sulfate tetrahydrate, manganese sulfate pentahydrate, iron sulfate heptahydrate, cobalt sulfate heptahydrate, nickel sulfate hexahydrate, cupric sulfate pentahydrate, zinc sulfate heptahydrate, cadmium sulfate octahydrate, indium sulfate nonahydrate, and zinc sulfate dihydrate. Without being bound to any particular theory, using a hydrate as the water-producing agent allows for better inclusion of the water-producing agent into the rubber formulation, which, in turn, allows for greater control of the water content in the rubber formulation.
The water-producing agent may be included in the rubber formulation in varying amounts depending on the desired characteristics of the golf ball core. For example, the water-producing agent may be used in an amount of 0.1 to about 10 parts by weight per 100 parts of the total rubber. In one embodiment, the rubber formulation of the core includes about 0.2 to about 5 parts by weight water-producing agent per 100 parts of the total rubber. In another embodiment, the water-producing agent is included in the rubber formulation in an amount of about 0.5 to about 3.5 or about 0.8 to about 2.2 or about 1 to about 2 parts by weight per 100 parts of the total rubber. In still another embodiment, the rubber formulation includes about 0.7 to about 1.4 or about 1.3 to about 1.7 or about 1.6 to about 2.3 parts by weight water-producing agent per 100 parts of the total rubber.
In some respects, the amount of water-producing agent in the rubber formulation required to produce the desired compression and COR of a golf ball core may differ based on the compound used as the water-producing agent. In particular, the amount of water-producing agent included may depend on the mass percentage and moisture availability in the water-producing agent. The mass percentage of the water in the water-producing agent can be calculated as the mass of water in the water-producing agent divided by the total weight of the water-producing agent. When the water-producing agent has a greater mass percentage of water, less water-producing agent may be needed in the rubber formulation to give the golf ball core the desired performance characteristics. For example, more water-producing agent may be required when the water-producing agent is calcium sulfate dihydrate, which has a moisture content of approximately 21 percent by mass, than if water-producing agent is magnesium sulfate heptahydrate, which has a moisture content of about 51 percent by mass. The moisture availability refers to how readily the water molecules dissociate from the water-producing agent. If the water-producing agent used has a high moisture availability, less water-producing agent may be needed than if the water-producing agent has a low moisture availability.
In some embodiments, it may be desirable to formulate the rubber formulation of the golf ball core based on the water content of the rubber formulation instead of or in addition to the concentration of the water-producing agent. In this aspect, the water content of the rubber formulation can be determined by multiplying the concentration of water-producing agent in parts by weight per 100 parts of the total rubber with the mass percentage of water in the water-producing agent. For example, if the water-producing agent is included in the rubber formulation at about 2 parts by weight per 100 parts of the total rubber and the mass percentage of water in the water-producing agent is 50 percent, the water content of the rubber formulation is 1 part by weight per 100 parts of the total rubber. As such, the desired or targeted water content of the rubber formulation may be used to determine the concentration (and/or type of) water-producing agent.
In some embodiments, the rubber formulation has a water content of about 0.01 to about 10 or about 0.05 to about 5 or about 0.5 to about 5 parts by weight water per 100 parts of the total rubber. In other embodiments, the water content of the rubber formulation is about 0.1 to about 2.5 or about 0.2 to about 2 or about 0.5 to about 1.5 parts by weight per 100 parts of the total rubber. In other embodiments, the water content of the rubber formulation is about 0.05 to about 1 or about 0.1 to about 0.5 or about 0.3 to about 0.8 parts by weight per 100 parts of the total rubber. In further embodiments, the rubber formulation has a water content of about 1 to about 3 or about 1.5 to about 3.5 or about 1 to about 2 parts by weight per 100 parts of the total rubber.
The rubber formulations may further include a reactive cross-linking co-agent. Suitable co-agents include, but are not limited to, metal salts of unsaturated carboxylic acids having from 3 to 8 carbon atoms; unsaturated vinyl compounds and polyfunctional monomers (e.g., trimethylolpropane trimethacrylate); phenylene bismaleimide; and combinations thereof. In one embodiment, the co-agent is one or more metal salts of acrylates, diacrylates, methacrylates, and dimethacrylates, wherein the metal is selected from magnesium, calcium, zinc, aluminum, lithium, and nickel. In another embodiment, the co-agent includes one or more zinc salts of acrylates, diacrylates, methacrylates, and dimethacrylates. For example, the co-agent may be zinc diacrylate (ZDA). In another embodiment, the co-agent may be zinc dimethacrylate (ZDMA). An example of a commercially available zinc diacrylate includes Dymalink® 526 manufactured by Cray Valley.
The co-agent may be included in the rubber formulation in varying amounts depending on the desired characteristics of the golf ball core. For example, the co-agent may be used in an amount of about 10 to about 50 parts by weight per 100 parts of the total rubber. In one embodiment, the rubber formulation of the core includes about 15 to about 40 parts by weight co-agent per 100 parts of the total rubber. In another embodiment, the rubber formulation includes about 20 to about 35 or about 22 to about 30 parts by weight co-agent per 100 parts of total rubber. In still another embodiment, the rubber formulation includes about 23 to about 27 or about 25 to about 29 parts by weight co-agent per 100 parts of the total rubber. Without being bound to any particular theory, increasing the concentration of co-agent in the rubber formulation of a golf ball core increases the compression and COR of a golf ball core.
In some respects, the amount of co-agent in the rubber formulation may be altered based on the amount and type of compression agent and water-producing agent included in the rubber formulation. For example, when the rubber formulation includes higher concentrations of compression agent and/or water-producing agent or a more active compression agent and/or water-producing agent, a lower concentration of co-agent may be needed to produce the desired compression and COR. Moreover, if a particular combination of compression agent and water-producing agent has a strong synergistic effect that results in a high increase the compression and COR of the core, a lower concentration of co-agent may be needed to produce the desired compression and COR of the core. For example, in prior art golf ball cores that do not include a compression agent and a water-producing agent, the co-agent may be included in the rubber formulation in amount from about 40 to about 50 parts by weight per 100 parts of the total rubber. In contrast, for a golf ball core of the present disclosure including a compression agent and a water-producing agent, the rubber formulation may include about 20 to about 35 parts co-agent by weight per 100 parts of the total rubber. In one embodiment, the co-agent may be included in an amount of about 20 to about 30 parts by weight per 100 parts of the total rubber. In another embodiment, the rubber formulation may include about 25 to about 35 parts by weight of the co-agent per 100 parts of the total rubber. In still another embodiment, the co-agent may be included in the rubber formulation in an amount of about 22 to about 28 parts by weight of the total rubber. Without being bound to any particular theory, the reduced need for co-agent in the rubber formulation may reduce the cost of manufacturing golf balls that include the golf ball core of the present disclosure.
Radical scavengers such as a halogenated organosulfur, organic disulfide, or inorganic disulfide compounds may also be added to the rubber formulation. In one embodiment, a halogenated organosulfur compound included in the rubber formulation includes, but is not limited to, pentachlorothiophenol (PCTP) and salts of PCTP such as zinc pentachlorothiophenol (Zn-PCTP). In another embodiment, ditolyl disulfide, diphenyl disulfide, dixylyl disulfide, 2-nitroresorcinol, and combinations thereof are added to the rubber formulation.). An example of a commercially available radical scavenger includes Rhenogran® Zn-PTCP-72 manufactured by Rheine Chemie. The radical scavenger may be included in the rubber formulation in an amount of about 0.1 to about 5 part by weight per 100 parts of the total rubber. In one embodiment, the rubber formulation may include about 0.3 to about 2.5 parts by weight radical scavenger compound per 100 parts of the total rubber. In another embodiment, the rubber formulation may include about 0.2 to about 0.5 or about 0.4 to about 0.6 or about 0.5 to about 0.8 parts by weight radical scavenger compound per 100 parts of the total rubber.
The rubber formulation may also include filler(s). Suitable non-limiting examples of fillers include carbon black, clay and nanoclay particles, talc, glass (e.g., glass flake, milled glass, and microglass), mica and mica-based pigments (e.g., Iriodin® pearl luster pigments from The Merck Group), and combinations thereof. Metal oxide and metal sulfate fillers are also contemplated for inclusion in the rubber formulation. Suitable metal fillers include, for example, particulate, powders, flakes, and fibers of copper, steel, brass, tungsten, titanium, aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin, zinc, barium, bismuth, bronze, silver, gold, and platinum, and alloys and combinations thereof. Suitable metal oxide fillers include, for example, zinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium oxide, and zirconium oxide. Suitable metal sulfate fillers include, for example, barium sulfate and strontium sulfate. When included, the fillers may be in an amount of about 1 to about 40 parts by weight per 100 parts of the total rubber. In one embodiment, the rubber formulation includes at least one filler in an amount of about 1 to about 15 or about 3 to about 10 parts by weight per 100 parts of the total rubber. In another embodiment, the rubber formulation includes at least one filler in an amount of about 3 to about 7 or about 5 to about 9 or about 5 to about 7 parts by weight per 100 parts of the total rubber. For example, the rubber formulation may include a metal oxide in any of these amounts. In further embodiments, the rubber formulation includes at least one filler in an amount of about 1 to about 30 or about 5 to about 25 or about 10 to about 20 parts by weight per 100 parts of the total rubber. In yet another embodiment, the rubber formulation includes at least one filler in an amount of about 12 to about 17 or about 13 to about 18 or about 14 to about 16 parts by weight per 100 parts of the total rubber. For example, the rubber formulation may include a metal sulfate in any of these amounts. An example of a commercially available filler suitable for use in accordance with the present disclosure includes PolyWate® 325 manufactured by Cimbar Performance Minerals.
In some respects, the amount of filler in the rubber formulation may be altered based on amount and type of compression agent or water-producing agent included in the rubber formulation. For example, when the rubber formulation includes higher concentrations of compression agent and water-producing agent or a more active compression agent or water-producing agent, a greater concentration of filler may be needed to produce a golf ball with the desired characteristics (core weight, for example). Moreover, if a particular compression agent and water-producing agent combination in the rubber formulation of a golf ball core has a particularly strong effect on the compression and COR of the core, a greater concentration of filler may be needed. For example, in prior art golf ball cores that do not include a compression agent and a water-producing agent, the filler may be included in the rubber formulation in amount from about 4 to about 25 parts by weight per 100 parts of the total rubber. In contrast, in golf balls of the present disclosure, the filler may be included in the rubber formulation, for example, in amount from about 6 to about 35 parts by weight per 100 parts of the total rubber.
In some embodiments, more than one type of filler may be included in the rubber formulation. For example, the rubber formulation may include a first filler in an amount from about 1 to about 15 or about 2 to about 12 parts by weight per 100 parts total rubber and a second filler in an amount from about 1 to about 30 or about 7 to about 22 parts by weight per 100 parts total rubber. In another example, the rubber formulation may include a first filler in an amount from about 3 to about 10 or about 4 to about 8 parts by weight per 100 parts total rubber and a second filler in an amount from about 11 to about 19 or about 13 to about 17 parts by weight per 100 parts total rubber. In yet another example, the rubber formulation may include a first filler in an amount from about 2 to about 6 or about 4 to about 8 parts by weight per 100 parts total rubber and a second filler in an amount from about 11 to about 16 or about 14 to about 19 parts by weight per 100 parts total rubber.
Antioxidants, processing aids, accelerators (for example, tetra methylthiuram), dyes and pigments, wetting agents, surfactants, plasticizers, coloring agents, fluorescent agents, chemical blowing and foaming agents, defoaming agents, stabilizers, softening agents, impact modifiers, antiozonants, as well as other additives known in the art, may also be added to the rubber formulation. Examples of suitable processing aids include, but are not limited to, high molecular weight organic acids and salts thereof. Suitable organic acids are aliphatic organic acids, aromatic organic acids, saturated mono-functional organic acids, unsaturated monofunctional organic acids, multi-unsaturated mono-functional organic acids, and dimerized derivatives thereof. In one embodiment, the organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, linoleic acid, myristic acid, benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid, and dimerized derivatives thereof. The salts of organic acids include the salts of barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin, or calcium, salts of fatty acids, particularly stearic, behenic, erucic, oleic, linoelic or dimerized derivatives thereof.
The rubber formulation may be cured using conventional curing processes. In one embodiment, the curing process employs molding temperatures between about 240° F. to about 400° F. In some aspects, the molding temperature is about 270° F. to about 380° F. In other aspects, the molding temperature is about 290° F. to 350° F. The rubber formulation may be held at the molding temperature for about 5 minutes to about 30 minutes. In one embodiment, the rubber formulation is held at the molding temperature for about 9 minutes to about 25 minutes. In another embodiment, the rubber formulation is held at the molding temperature for about 13 minutes to about 20 minutes.
Non-limiting examples of curing processes suitable for use in accordance with the present disclosure include peroxide-curing, sulfur-curing, high-energy radiation, and combinations thereof. In one embodiment, the rubber formulation includes a free-radical initiator selected from organic peroxides, high energy radiation sources capable of generating free-radicals, and combinations thereof. Suitable organic peroxides include, but are not limited to, dicumyl peroxide; n-butyl-4,4-di(t-butylperoxy) valerate; 1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane; 2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide; di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide; 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3; di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoyl peroxide; t-butyl hydroperoxide; and combinations thereof. In a particular embodiment, the free radical initiator is dicumyl peroxide, including, but not limited to Perkadox® BC, commercially available from Akzo Nobel. Peroxide free-radical initiators may be present in the rubber formulation in an amount of at least 0.05 parts by weight per 100 parts of the total rubber, or an amount within the range having a lower limit of 0.05 parts or 0.1 parts or 1 part or 1.25 parts or 1.5 parts or 2.5 parts or 5 parts by weight per 100 parts of the total rubber, and an upper limit of 2.5 parts or 3 parts or 5 parts or 6 parts or 10 parts or 15 parts by weight per 100 parts of the total rubber. For example, the rubber formulation may include peroxide free-radical initiators in an amount of about 0.1 to about 2.5 or about 0.3 to about 1.8 or about 0.5 to about 1.2 parts by weight per 100 parts of the total rubber. In another example, the rubber formulation may include peroxide free-radical initiators in an amount of about 0.5 to about 0.9 or about 0.7 to about 1.2 or about 0.6 to about 1.0 or about 0.7 to about 0.9 parts by weight per 100 parts of the total rubber.
The hardness of the geometric center of the core may be obtained according to the following: the core is first gently pressed into a hemispherical holder having an internal diameter approximately slightly smaller than the diameter of the core, such that the core is held in place in the hemispherical portion of the holder while concurrently leaving the geometric central plane of the center exposed. The core is secured in the holder by friction, such that it will not move during the cutting and grinding steps, but the friction is not so excessive that distortion of the natural shape of the core would result. The core is secured such that the parting line of the center is roughly parallel to the top of the holder. The diameter of the center is measured 90 degrees to this orientation prior to securing. A measurement is also made from the bottom of the holder to the top of the core to provide a reference point for future calculations. A rough cut is made slightly above the exposed geometric center of the core using a band saw or other appropriate cutting tool, making sure that the core does not move in the holder during this step. The remainder of the core, still in the holder, is secured to the base plate of a surface grinding machine. The exposed ‘rough’ surface is ground to a smooth, flat surface, revealing the geometric center of the core, which can be verified by measuring the height from the bottom of the holder to the exposed surface of the core, making sure that exactly half of the original height of the core, as measured above, has been removed to within 0.004 inches. Leaving the core in the holder, the geometric center of the core is confirmed with a center square and carefully marked, and the hardness is measured at the center mark according to ASTM D-2240.
Additional hardness measurements at any distance from the geometric center of the core can then be made by drawing a line radially outward from the geometric center mark and measuring the hardness at any given distance along the line, typically in 2 mm increments from the center of the core. The hardness at a particular distance from the geometric center should be measured along at least two, preferably four, radial arms located 180° apart, or 90° apart, respectively, and then averaged. All hardness measurements performed on a plane passing through the geometric center are performed while the core is still in the holder and without having disturbed its orientation, such that the test surface is constantly parallel to the bottom of the holder, and thus also parallel to the properly aligned foot of the durometer.
The outer surface hardness of the core (or any golf ball layer) is measured on the actual outer surface of the layer and is obtained from the average of a number of measurements taken from opposing hemispheres, taking care to avoid making measurements on the parting line of the core or on surface defects, such as holes or protrusions and preferably making the measurements prior to surrounding the layer of interest with an additional layer. Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface, care must be taken to ensure that the golf ball or golf ball sub-assembly is centered under the durometer indenter before a surface hardness reading is obtained. A calibrated, digital durometer, capable of reading to 0.1 hardness units is used for the hardness measurements. The digital durometer must be attached to, and its foot made parallel to, the base of an automatic stand. The weight on the durometer and attack rate conforms to ASTM D-2240. It is worthwhile to note that, once an additional layer surrounds a layer of interest, the hardness of the layer of interest can be difficult to determine. Therefore, for purposes of the present disclosure, when the hardness of a layer is needed after the inner layer has been surrounded with another layer, the test procedure for measuring a point located 1 mm from an interface is used.
It should also be noted that there is a fundamental difference between “material hardness” and “hardness as measured directly on a golf ball” (or, as used herein, “surface hardness”). For purposes of the present disclosure, material hardness is measured according to ASTM D2240 and generally involves measuring the hardness of a flat “slab” or “button” formed of the material. Surface hardness as measured directly on a golf ball (or other spherical surface) typically results in a different hardness value. The difference in “surface hardness” and “material hardness” values is due to several factors including, but not limited to, ball construction (that is, core type, number of layers, and the like); ball (or ball sub-assembly) diameter; and the material composition of adjacent layers. It also should be understood that the two measurement techniques are not linearly related and, therefore, one hardness value cannot easily be correlated to the other. Shore hardness (for example, Shore C or Shore D hardness) was measured according to the test method ASTM D-2240.
A golf ball core made from the rubber formulation of the present disclosure may have a hardness at the geometric center of the core, referred to herein as HC, that ranges from about 40 to about 80 Shore C or about 50 to about 70 Shore C. In one embodiment, the core has a hardness at its geometric center of about 45 to about 60 Shore C or about 48 to about 56 Shore C or about 51 to about 54 Shore C. In another embodiment, the core has a hardness at its geometric center of about 52 to about 68 Shore C or about 55 to about 64 Shore C or about 58 to about 61 Shore C. In yet another embodiment, the core has a hardness at its geometric center of about 51 to about 66 Shore C or about 54 to about 63 Shore C or about 57 to about 60 Shore C.
The hardness at the surface of the core, referred to herein as HS, may range from about 70 to about 95 Shore C or about 75 to about 90 Shore C. In one embodiment, the hardness at the surface of the core is about 75 to about 85 Shore C or about 77 to about 83 Shore C or about 79 to about 81 Shore C. In another embodiment, the hardness at the surface of the core is about 76 to about 86 Shore C or about 78 to about 84 Shore C or about 80 to about 82 Shore C. In yet another embodiment, the hardness at the surface of the core is about 77 to about 88 Shore C or about 79 to about 86 Shore C or about 81 to about 84 Shore C.
The direction of the hardness gradient is defined by the difference in hardness measurements taken at the geometric center and outer surfaces of the core. The geometric center hardness is readily determined according to the test procedures provided above. For example, the hardness of the outer surface of the core is also readily determined according to the procedures given herein for measuring the outer surface hardness of a golf ball layer, if the measurement is made prior to surrounding the core with additional layers.
While the hardness gradient across the core will vary based on several factors including, but not limited to, the dimensions and formulations of the components, the cure temperature and cure time. In this aspect, cores made according to the present disclosure may have a “positive” or “negative” hardness gradient. For the purposes of this disclosure, a “negative” hardness gradient occurs when the core surface hardness is softer than the geometric center and a “positive” hardness gradient occurs when the geometric center is softer than the outer surface of the core.
In some embodiments, the cores of the present disclosure have a positive hardness gradient. More particularly, the term, “positive hardness gradient” as used herein means a hardness gradient of positive about 2 Shore C or greater, about 4 Shore C or greater, about 6 Shore C or greater, about 8 Shore C or greater, or about 10 Shore C or greater. In general, the hardness gradient may be determined by subtracting the hardness value of the first component being measured (for example, the geometric center of the core, HC) from the hardness value of the second component being measured (for example, the outer surface of the core, HS).
In one embodiment, the core has a positive hardness gradient from the geometric center to the surface of the core of about 10 to about 42 Shore C or about 15 to about 35 Shore C or about 15 to about 30 Shore C. In this aspect, the positive hardness gradient of the core may be about 20 to about 30 Shore C. In one embodiment, the positive hardness gradient of the core is about 16 to about 28 Shore C or about 18 to about 26 Shore C or about 20 to about 24 Shore C. In another embodiment, the positive hardness gradient of the core is about 18 to about 32 Shore C or about 20 to about 28 Shore C or about 23 to about 26 Shore C. In yet another embodiment, the positive hardness gradient of the core may be about 21 to about 36 Shore C or about 24 to about 32 Shore C or about 26 to 30 Shore C. In a further embodiment, the hardness gradient of the core is about 28 to about 42 Shore C or about 30 to about 39 for Shore C or about 33 to about 37 Shore C.
In some embodiments, the core may be a dual layer core including an inner core layer and an outer core layer. The inner core layer has a geometric center hardness that ranges from about 45 to about 65 Shore C. In one embodiment, the hardness at the geometric center of the inner core layer is about 50 to about 60 Shore C. For example, the inner core layer may have a hardness at its geometric center of about 52 to about 56 Shore C or about 54 to about 58 Shore C. The hardness at the surface of the inner core layer may range from about 65 to about 90 Shore C. In one embodiment, the hardness at the surface of the inner core layer is about 70 to about 85 Shore C or about 70 to about 80 Shore C or about 75 to about 85 Shore C. In another example, the inner core layer may have a surface hardness of about 78 to about 82 Shore C.
The outer layer of the dual layer core has an outer surface hardness that may range from about 80 to about 100 Shore C. For example, the outer layer may have an outer surface hardness of about 75 to about 100 Shore C or about 85 to about 95 Shore C or about 88 to about 92 Shore C. In another example, the outer layer has an outer surface hardness of about 90 to about 100 Shore C or about 93 to about 97 Shore C.
Dual layer core embodiments may also have an overall core gradient, i.e., the hardness gradient from the center of the inner core to the outer surface of the outer core layer. Generally, the geometric hardness of the center is less than the surface hardness of the outer core layer. The overall core gradient may be 25 Shore C or greater or 30 Shore C or greater. In one embodiment, the positive hardness gradient from the geometric center to the surface of the outer core layer is in the range of about 30 to about 50 Shore C or about 30 to 45 Shore C or about 35 to 50 Shore C or about 37 to about 43 Shore C. For example, the overall core gradient may be about 30 to 40 Shore C or 33 to about 37 Shore C or about 31 to about 36 Shore C or about 34 to about 39 Shore C. In another example, the overall core gradient may be about 40 to 50 Shore C or 43 to about 47 Shore C or about 41 to about 46 Shore C or about 44 to about 49 Shore C.
The center itself may also have a positive hardness gradient. In one embodiment, the center has a positive hardness gradient from the geometric center to the surface of the center of about 5 to 40 Shore C. In this aspect, the positive hardness gradient of the center (from the geometric center to the surface of the center) is about 10 to about 30 Shore C. For example, the positive hardness gradient of the center is about 18 to about 25 Shore C. The center may also have a “zero” hardness gradient, i.e., the hardness values of the outer surface of the outer core layer and the geometric center are substantially the same. The term, “zero hardness gradient” as used herein means a hardness gradient of less than about 3 Shore C, preferably less than about 1 Shore C and may have a value of zero. In other embodiments, the outer core layer may have a “zero” hardness gradient within the layer itself (i.e., the hardness values of the inner surface and outer surface of the outer core layer are substantially the same). In still other embodiments, the surface of the center and the inner surface of the outer core layer may have a substantially similar hardness or the same hardness, but the surface of the center and the outer surface of the outer core layer still have hardness values that differ such that a positive hardness gradient as described above is achieved.
In some embodiments, a point or plurality of points measured along a “positive” gradient may be above or below a line fit through the gradient and its outermost and innermost hardness values. In an alternative embodiment, the hardest point along a particular steep “positive” gradient may be higher than the value at the innermost portion of the center (the geometric center) or outer surface of the core—as long as the outermost point (i.e., the outer surface of the core) is greater than the innermost point (i.e., the geometric center of the core), such that the “positive” gradients remain intact.
Several different methods can be used to measure compression, including Atti compression, Riehle compression, load/deflection measurements at a variety of fixed loads and offsets, and effective modulus (see, e.g., Compression by Any Other Name, Science and Golf IV, Proceedings of the World Scientific Congress of Golf (Eric Thain ed., Routledge, 2002) (J. Dalton). For purposes of the present disclosure, compression values are provided as measured by the Dynamic Compression Machine (“DCM”) as well as the Soft Center Deflection Index (“SCDI”). The DCM applies a load to a ball component or a ball and measures the number of inches the core or ball is deflected at measured loads. A crude load/deflection curve is generated that is fit to the Atti compression scale that results in a number being generated that represents an Atti compression. The DCM does this via a load cell attached to the bottom of a hydraulic cylinder that is triggered pneumatically at a fixed rate (typically about 1.0 ft/s) towards a stationary core. Attached to the cylinder is an LVDT that measures the distance the cylinder travels during the testing timeframe. A software-based logarithmic algorithm ensures that measurements are not taken until at least five successive increases in load are detected during the initial phase of the test.
The SCDI is a slight variation of the DCM set up that allows determination of the pounds required to deflect a component or ball 10 percent of its diameter. With the SCDI, the goal is to obtain the pounds of force required to deflect a component or ball a certain amount of inches. That amount of deflection is 10 percent of the component or ball diameter. The DCM is triggered, the cylinder deflects the component or ball by 10 percent of its diameter, and the DCM reports back the pounds of force required (as measured from the attached load cell) to deflect the component or ball by that amount. The SCDI value obtained is a single number in units of pounds.
The compression of a core made from the rubber formulation of the present disclosure may range from about 40 to about 100 DCM. For example, the core compression may be about 55 to about 85 DCM or about 60 to 80 DCM or about 65 to about 75 DCM. In another example, the core compression may range from about 50 to about 70 DCM or about 55 to about 65 DCM or about 60 to 70 DCM. In yet another example, the core compression is about 70 to about 90 DCM or about 70 to about 80 DCM or about 71 to about 77 DCM.
The diameter of the core may vary. In some embodiments, the core diameter may range from about 1.45 to about 1.58 inches. For example, the core may have a diameter of 1.53 to 1.56 inches. In embodiments where the core comprises two or more layers, the diameter of the inner layer of the core may range from about 0.8 to about 1.4 inches or from about 1.0 to about 1.2 inches.
In one embodiment, the concentration of compression agent and concentration of water-producing agent present in the rubber formulation used to form the core are related to the compression (DCM) of the core, according to the relationship shown in Equation I below:
where CAC represents the concentration of the compression agent in the rubber formulation in parts per hundred; WPAC represents the concentration of the water-producing agent in the rubber formulation in parts per hundred; and C represents the compression (DCM) of the core. In another embodiment,
In still another embodiment,
In yet another embodiment,
In another aspect, the concentration of compression agent and concentration of water-producing agent present in the rubber formulation used to form the core is related to the compression (DCM) of the core according to the relationship shown in Equation II below:
where CAC represents the concentration of the compression agent in the rubber formulation in parts per hundred; WPAC represents the concentration of the water-producing agent in the rubber formulation in parts per hundred; and C represents the compression (DCM) of the core. In another embodiment,
In still another embodiment,
In yet another embodiment,
Golf balls having various constructions may be made in accordance with this invention. For example, golf balls having one-piece, two-piece, three-piece, four-piece, and five or more-piece constructions with the term “piece” refer to any core, cover, or intermediate layer of a golf ball construction. Representative illustrations of such golf ball constructions are provided and discussed further below. The term, “layer” as used herein means generally any spherical portion of the golf ball.
In one embodiment, a golf ball of the present disclosure is a one-piece ball where the core and cover form a single integral layer. In another version, shown in
The rubber formulations discussed above are suitable for use in the core or one or more of the core layers if multiple core layers are present. It is also contemplated that the rubber formulations disclosed herein may be used to form one or more of the layers of any of the one, two, three, four, or five, or more-piece (layered) balls described above. That is, any of the core layers, intermediate layers, and/or cover layers may comprise the rubber formulation of this disclosure. The rubber formulations of different layers may be the same or different. The diameter and thickness of the different layers along with properties such as hardness and compression may vary depending upon the construction and desired performance characteristics of the golf ball.
Golf balls made in accordance with this invention can be of any size, although the USGA requires that golf balls used in competition have a diameter of at least 1.68 inches. For play outside of United States Golf Association (USGA) rules, the golf balls can be of a smaller size. In one embodiment, golf balls made in accordance with this invention have a diameter in the range of about 1.68 to about 1.80 inches.
In contrast to the core, the cover of a golf ball plays less of a role on shots off of a driver. However, because the cover plays a large role in generating spin on iron and wedge shots, the cover material and properties are still important. In this aspect, different materials may be used in the construction of the intermediate and cover layers of golf balls according to the present disclosure. For example, a variety of materials may be used for forming the outer cover including, for example, polyurethanes; polyureas; copolymers, blends and hybrids of polyurethane and polyurea; olefin-based copolymer ionomer resins; polyethylene, including, for example, low density polyethylene, linear low density polyethylene, and high density polyethylene; polypropylene; rubber-toughened olefin polymers; acid copolymers, for example, poly(meth)acrylic acid, which do not become part of an ionomeric copolymer; plastomers; flexomers; styrene/butadiene/styrene block copolymers; styrene/ethylene-butylene/styrene block copolymers; dynamically vulcanized elastomers; copolymers of ethylene and vinyl acetates; copolymers of ethylene and methyl acrylates; polyvinyl chloride resins; polyamides, poly(amide-ester) elastomers, and graft copolymers of ionomer; cross-linked trans-polyisoprene and blends thereof; polyester-based thermoplastic elastomers; polyurethane-based thermoplastic elastomers; synthetic or natural vulcanized rubber; and combinations thereof.
In one embodiment, the cover is formed from a polyurethane, polyurea, or hybrid of polyurethane-polyurea. When used as cover layer materials, polyurethanes and polyureas can be thermoset or thermoplastic. Thermoset materials can be formed into golf ball layers by conventional casting or reaction injection molding techniques. Thermoplastic materials can be formed into golf ball layers by conventional compression or injection molding techniques.
Conventional and non-conventional materials may be used for forming intermediate layers of the ball including, for instance, ionomer resins, highly neutralized polymers, polybutadiene, butyl rubber, and other rubber-based core formulations, and the like. In one embodiment, the inner cover layer, i.e., the layer disposed between the core and the outer cover, includes an ionomer. In this aspect, ionomers suitable for use in accordance with the present disclosure may include partially-neutralized ionomers and highly-neutralized ionomers (HNPs), including ionomers formed from blends of two or more partially-neutralized ionomers, blends of two or more highly-neutralized ionomers, and blends of one or more partially-neutralized ionomers with one or more highly-neutralized ionomers. For purposes of the present disclosure, “HNP” refers to an acid copolymer after at least 70 percent of all acid groups present in the composition are neutralized.
Preferred ionomers are salts of O/X- and O/X/Y-type acid copolymers, wherein O is an α-olefin, X is a C3-C8 α, β-ethylenically unsaturated carboxylic acid, and Y is a softening monomer. O is preferably selected from ethylene and propylene. X is preferably selected from methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, and itaconic acid. Methacrylic acid and acrylic acid are particularly preferred. Y is preferably selected from (meth) acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1 to 8 carbon atoms, including, but not limited to, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate.
Preferred O/X and O/X/Y-type copolymers include, without limitation, ethylene acid copolymers, such as ethylene/(meth)acrylic acid, ethylene/(meth)acrylic acid/maleic anhydride, ethylene/(meth)acrylic acid/maleic acid mono-ester, ethylene/maleic acid, ethylene/maleic acid mono-ester, ethylene/(meth)acrylic acid/n-butyl (meth)acrylate, ethylene/(meth)acrylic acid/isobutyl (meth)acrylate, ethylene/(meth)acrylic acid/methyl (meth)acrylate, ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and the like. The term, “copolymer,” as used herein, includes polymers having two types of monomers, those having three types of monomers, and those having more than three types of monomers. Preferred α, B-ethylenically unsaturated mono- or dicarboxylic acids are (meth) acrylic acid, ethacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconic acid. (Meth) acrylic acid is most preferred. As used herein, “(meth) acrylic acid” means methacrylic acid and/or acrylic acid. Likewise, “(meth) acrylate” means methacrylate and/or acrylate.
In a particularly preferred version, highly neutralized E/X- and E/X/Y-type acid copolymers, wherein E is ethylene, X is a C3-C8 α, β-ethylenically unsaturated carboxylic acid, and Y is a softening monomer are used. X is preferably selected from methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, and itaconic acid. Methacrylic acid and acrylic acid are particularly preferred. Y is preferably an acrylate selected from alkyl acrylates and aryl acrylates and preferably selected from (meth) acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1 to 8 carbon atoms, including, but not limited to, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate. Preferred E/X/Y-type copolymers are those wherein X is (meth) acrylic acid and/or Y is selected from (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate. More preferred E/X/Y-type copolymers are ethylene/(meth) acrylic acid/n-butyl acrylate, ethylene/(meth) acrylic acid/methyl acrylate, and ethylene/(meth) acrylic acid/ethyl acrylate.
The amount of ethylene in the acid copolymer may be at least about 15 weight percent, at least about 25 weight percent, at least about 40 weight percent, or at least about 60 weight percent, based on total weight of the copolymer. The amount of C3 to C8 α, β-ethylenically unsaturated mono- or dicarboxylic acid in the acid copolymer is typically from 1 weight percent to 35 weight percent, from 5 weight percent to 30 weight percent, from 5 weight percent to 25 weight percent, or from 10 weight percent to 20 weight percent, based on total weight of the copolymer. The amount of optional softening comonomer in the acid copolymer may be from 0 weight percent to 50 weight percent, from 5 weight percent to 40 weight percent, from 10 weight percent to 35 weight percent, or from 16 weight percent to 30 weight percent, based on total weight of the copolymer.
The various O/X, E/X, O/X/Y, and E/X/Y-type copolymers are at least partially neutralized with a cation source, optionally in the presence of a high molecular weight organic acid, such as those disclosed in U.S. Pat. No. 6,756,436, the entire disclosure of which is hereby incorporated herein by reference. The acid copolymer can be reacted with the optional high molecular weight organic acid and the cation source simultaneously, or prior to the addition of the cation source. Suitable cation sources include, but are not limited to, metal ion sources, such as compounds of alkali metals, alkaline earth metals, transition metals, and rare earth elements; ammonium salts and monoamine salts; and combinations thereof. Preferred cation sources are compounds of magnesium, sodium, potassium, cesium, calcium, barium, manganese, copper, zinc, lead, tin, aluminum, nickel, chromium, lithium, and rare earth metals. The amount of cation used in the composition is readily determined based on desired level of neutralization. As discussed above, for HNP compositions, the acid groups are neutralized to 70 percent or greater, 70 to 100 percent, or 90 to 100 percent. In one embodiment, an excess amount of neutralizing agent, that is, an amount greater than the stoichiometric amount needed to neutralize the acid groups, may be used. That is, the acid groups may be neutralized to 100 percent or greater, for example 110 percent or 120 percent or greater. In other embodiments, partially-neutralized compositions are prepared, wherein 10 percent or greater, normally 30 percent or greater of the acid groups are neutralized. When aluminum is used as the cation source, it is preferably used at low levels with another cation such as zinc, sodium, or lithium, since aluminum has a dramatic effect on melt flow reduction and cannot be used alone at high levels. For example, aluminum is used to neutralize about 10 percent of the acid groups and sodium is added to neutralize an additional 90 percent of the acid groups.
“Low acid” and “high acid” ionomeric polymers, as well as blends of such ionomers, may be used. In general, low acid ionomers are considered to be those containing 16 weight percent or less of acid moieties, whereas high acid ionomers are considered to be those containing greater than 16 weight percent of acid moieties. In one embodiment, the inner cover layer is formed from a composition comprising a high acid ionomer. A suitable high acid ionomer is Surlyn® 8150 (Dow), which is a copolymer of ethylene and methacrylic acid, having an acid content of 19 weight percent, 45 percent neutralized with sodium. In another embodiment, the inner cover layer is formed from a composition comprising a high acid ionomer and a maleic anhydride-grafted non-ionomeric polymer. An example of a suitable maleic anhydride-grafted polymer is Fusabond® 525D (Dow), which is a maleic anhydride-grafted, metallocene-catalyzed ethylene-butene copolymer having about 0.9 weight percent maleic anhydride grafted onto the copolymer. Blends of high acid ionomers with maleic anhydride-grafted polymers are further disclosed, for example, in U.S. Pat. Nos. 6,992,135 and 6,677,401, the entire disclosures of which are hereby incorporated herein by reference.
The inner cover layer also may be formed from a composition comprising a 50/45/5 blend of Surlyn® 8940/Surlyn® 9650/Nucrel® 960. In this aspect, the composition may have a material hardness of from 80 to 85 Shore C. In another embodiment, the inner cover layer is formed from a composition comprising a 50/25/25 blend of Surlyn® 8940/Surlyn® 9650/Surlyn® 9910, having a material hardness of about 85 to 95 Shore C. In yet another embodiment, the inner cover layer is formed from a composition comprising a 50/50 blend of Surlyn® 8940/Surlyn® 9650, having a material hardness of about 82 to 90 Shore C. A composition comprising a 50/50 blend of Surlyn® 8940 and Surlyn® 7940 also may be used.
The compositions used to make the layers outside of the core, e.g., the outer cover layer and, when present, the inner cover layer, may contain a variety of fillers and additives to impart specific properties to the ball. For example, relatively heavy-weight and light-weight metal fillers such as, particulate; powders; flakes; and fibers of copper, steel, brass, tungsten, titanium, aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin, zinc, barium, bismuth, bronze, silver, gold, and platinum, and alloys and combinations thereof may be used to adjust the specific gravity of the ball. Other additives and fillers include, but are not limited to, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, surfactants, processing aids, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, titanium dioxide, clay, mica, talc, glass flakes, milled glass, and mixtures thereof.
The outer cover layer preferably has a material hardness of 85 Shore C or less. The thickness of the outer cover layer is preferably within a range having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of 0.035 or 0.040 or 0.055 or 0.080 inches. Methods for measuring hardness of the layers in the golf ball are described in further detail above. When included, the inner cover layer preferably has a material hardness within a range having a lower limit of 70 or 75 or 80 or 82 Shore C and an upper limit of 85 or 86 or 90 or 92 Shore C. The thickness of the intermediate layer is preferably within a range having a lower limit of 0.010 or 0.015 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.045 or 0.080 or 0.120 inches.
In one embodiment, the golf balls made in accordance with the present disclosure include a core comprising a rubber formulation as described herein, an inner cover layer formed from an ionomeric material, and the outer cover layer is formed from a polyurethane material, and the outer cover layer has a hardness that is less than that of the inner cover layer. For example, the inner cover layer may have a hardness of greater than about 60 Shore D and the outer cover layer may have a hardness of less than about 60 Shore D. In an alternative embodiment, the inner cover layer is comprised of a partially or fully neutralized ionomer, a thermoplastic polyester elastomer, a thermoplastic polyether block amide, or a thermoplastic or thermosetting polyurethane or polyurea, and the outer cover layer is comprised of an ionomeric material. In this alternative embodiment, the inner cover layer may have a hardness of less than about 60 Shore D and the outer cover layer may have a hardness of greater than about 55 Shore D and the inner cover layer hardness is less than the outer cover layer hardness.
When a dual cover is disposed about the core, the inner cover layer may have a thickness of about 0.01 inches to about 0.06 inches, about 0.015 inches to about 0.040 inches, or about 0.02 inches to about 0.035 inches. The outer cover layer may have a thickness of about 0.015 inches to about 0.055 inches, about 0.02 inches to about 0.04 inches, or about 0.025 inches to about 0.035 inches.
The golf balls of the present disclosure may be formed using a variety of application techniques. For example, the golf ball, golf ball core, or any layer of the golf ball may be formed using compression molding, flip molding, injection molding, retractable pin injection molding, reaction injection molding (RIM), liquid injection molding (LIM), casting, vacuum forming, powder coating, flow coating, spin coating, dipping, spraying, and the like. Conventionally, compression molding and injection molding are applied to thermoplastic materials, whereas RIM, liquid injection molding, and casting are employed on thermoset materials. In this aspect, cover layers may be formed over the core using any suitable technique that is associated with the material used to form the layer. Preferably, each cover layer is separately formed over the core. For example, an ethylene acid copolymer ionomer composition may be injection-molded to produce half-shells over the core. Alternatively, the ionomer composition can be placed into a compression mold and molded under sufficient pressure, temperature, and time to produce the hemispherical shells, which may then be placed around the core in a compression mold. An outer cover layer including a polyurethane or polyurea composition over the ball sub-assembly may be formed by using a casting process.
Golf balls made in accordance with the present disclosure may be subjected to finishing steps such as flash-trimming, surface-treatment, marking, coating, and the like using techniques known in the art. In one embodiment, a white-pigmented cover may be surface-treated using a suitable method such as, for example, corona, plasma, or ultraviolet (UV) light-treatment. Indicia such as trademarks, symbols, logos, letters, and the like may be printed on the cover using pad-printing, ink-jet printing, dye-sublimation, or other suitable printing methods. Clear surface coatings (for example, primer and top-coats), which may contain a fluorescent whitening agent, may be applied to the cover. Golf balls may also be painted with one or more paint coatings in a variety of colors. In one embodiment, white primer paint is applied first to the surface of the ball and then a white top-coat of paint may be applied over the primer.
Golf ball spin rate is the amount of spin on the golf ball once the ball is hit and separates from the clubface of the golf club. Spin rate is measured by RPM (revolutions per minute). As described above, the golf balls of the present disclosure combine a core with a positive hardness gradient and increased compression of the core to tailor the spin rate to produce a desired performance on shots off of a driver and on approach shots when compared to a “conventional golf ball.” For the purposes of this disclosure, the “conventional golf ball” used for comparison purposes includes a three-piece golf ball with a polybutadiene core, an inner cover layer formed from ionomer, and a polyurethane outer cover. In particular, for this spin rate comparison exercise, the inner cover and outer cover of the conventional golf ball are the same or substantially the same as the inner and outer cover layers of golf balls of the present disclosure. Additionally, both the conventional golf ball and golf balls of the present disclosure comprised a single core layer. In other words, the only variation between the conventional golf ball and the golf balls made according to the present disclosure (for the purposes of this spin rate comparison exercise) was the rubber formulation of the core.
In this vein, golf ball cores made from the rubber formulations disclosed herein help to increase the spin rate of the golf ball to provide the desired performance when hit with drivers, irons, and wedges.
The invention is further illustrated by the following examples. It should be understood that the examples below are for illustrative purposes only. These examples should not be construed as limiting the scope of the invention.
The following examples provide a comparison of golf ball cores having a single layer (solid sphere) made with and without rubber formulations in accordance with the present invention. Each of the rubber formulations shown in the examples include a base rubber, Buna® CB 1221; a co-agent, zinc diacrylate (ZDA); a first filler, zinc oxide (ZnO); a second filler, PolyWate® 325 (barium sulfate); a radical scavenger, zinc pentachlorothiophenol (Zn-PCTP); an initiator, Perkadox® BC (dicumyl peroxide). Further, some of the rubber formulations shown below include a compression agent, PAPI® 94 (polymethylene polyphenylisocyanate containing MDI) and/or a water-producing agent, calcium sulfate hydrate (CaSO4·2H2O). The compositions and properties of the cores are described in Table 1 below.
As shown in Table 1, the compression and COR generally increases when the compression agent is added to the rubber formulation and further increases when compression agent and water-producing agent are both added to the rubber formulation. The hardness of the core at the surface increases slightly when the compression agent and water-producing agent are included. When the compression agent and water-producing agent are added in, the hardness of the core at the geometric center generally shows greater increases than the hardness at the surface of the core. This results in an overall decrease in the hardness gradient from the core center to the core surface as the compression agent and water-producing agents are added into the rubber formulation.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art of this disclosure. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well known functions or constructions may not be described in detail for brevity or clarity.
The terms “about” and “approximately” shall generally mean an acceptable degree of error or variation for the quantity measured given the nature or precision of the measurements. Numerical quantities given in this description are approximate unless stated otherwise, meaning that the term “about” or “approximately” can be inferred when not expressly stated.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well (i.e., at least one of whatever the article modifies), unless the context clearly indicates otherwise.
The terms “first,” “second,” and the like are used to describe various features or elements, but these features or elements should not be limited by these terms. These terms are only used to distinguish one feature or element from another feature or element. Thus, a first feature or element discussed below could be termed a second feature or element, and similarly, a second feature or element discussed below could be termed a first feature or element without departing from the teachings of the disclosure. Likewise, terms like “top” and “bottom”; “front” and “back”; and “left” and “right” are used to distinguish certain features or elements from each other, but it is expressly contemplated that a top could be a bottom, and vice versa.
The golf balls described and claimed herein are not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are intended as illustrations of several aspects of the disclosure. Any equivalent embodiments are intended to be within the scope of this disclosure. Indeed, various modifications of the device in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. All patents and patent applications cited in the foregoing text are expressly incorporated herein by reference in their entirety. Any section headings herein are provided only for consistency with the suggestions of 37 C.F.R. § 1.77 or otherwise to provide organizational queues. These headings shall not limit or characterize the invention(s) set forth herein.
