This invention relates generally to golf balls, and more specifically, to a multi-layer golf ball and a composition therefore. In particular, this invention relates to a golf ball having a core, a cover and at least one intermediate layer disposed between the core and cover, wherein the intermediate layer is formed from a blend comprising at least one glycidyl polymer. The multi-layer golf balls of the present invention have been found to provide good distance, durability, and desirable playing characteristics.
Conventional golf balls can be divided into two general types or groups: solid balls or wound balls. The difference in play characteristics resulting from these different types of constructions can be quite significant.
Balls having a solid construction are generally most popular with the average recreational golfer because they provide a very durable ball while also providing maximum distance. Solid balls are made with a solid core, usually formed of a crosslinked rubber, which is encased by a cover material. Typically the solid core is formed of polybutadiene which is chemically crosslinked with zinc diacrylate and/or similar crosslinking agents and is covered by a tough, cut-proof blended cover. The cover is generally formed of a material such as SURLYN(copyright), which is a trademark for an ionomer resin produced by DuPont of Wilmington, Del. The combination of the core and cover materials provide a ball that is virtually indestructible by golfers. Further, such a combination imparts a high initial velocity to the ball which results in improved distance. Because the materials of which the ball is formed are very rigid, solid balls generally have a hard xe2x80x9cfeelxe2x80x9d when struck with a club. Likewise, due to their hardness, these balls have a relatively low spin rate which provides greater distance.
Wound balls typically have either a solid rubber or liquid center core around which many yards of a stretched elastic thread or yam are wound. The wound core is then covered with a durable cover material such as a SURLYN(copyright) or similar material or a softer cover such as balata or polyurethane. Wound balls are generally softer and provide more spin than non-wound balls, which enables a skilled golfer to have more control over the ball""s flight and final position. Particularly, with approach shots into the green, the high spin rate of soft, wound balls enables the golfer to stop the ball very near its landing position.
A number of patents have been issued that arc directed towards modifying the properties of a conventional solid ball by altering the typical single layer core and single cover layer construction to provide a multi-layer ball having Such as a dual cover layer, dual core layer and/or a ball having a mantle layer disposed between the cover and the core. The inventions disclosed in the prior art patents arc directed towards improving a variety of golf balls physical properties that help determine xe2x80x9cin-playxe2x80x9d characteristics.
Several patents are directed towards improving the carry distance of such balls. For example, U.S. Pat. No. 4,863,167 relates to a three piece solid golf ball having increased flight distance, wherein the ball has a center portion and an outer layer formed from a rubber composition, wherein the outer layer is harder than the center portion and further contains a gravity-adjusting filler so as to impart a higher specific gravity to the outer layer than that of the center portion. U.S. Pat. No. 5,184,828 relates to a solid three-piece golf ball having improved rebound characteristics and carry distance while maintaining an adequate spin rate, wherein these characteristics are allegedly obtained by controlling the size of the polybutadiene inner core and outer layer as well as their specific gravity and hardness. According to the ""828 patent, the key to obtaining the desired rebound characteristics is that the maximum hardness (42-62 Shore D) must be located at the interface between the core and the mantle and the hardness must then decrease both inwardly and outwardly. U.S. Pat. No. 4,714,253 is also directed towards a three-piece golf ball having an improved rebound coefficient. This golf ball has a core with a Shore C hardness of 57-80 in its center, but not more than 83 at a distance between 5-10 mm from its center and an outer layer with a Shore C hardness of 70-83.
Additionally, there are a number of patents directed towards improving the spin and feel of solid balls while maintaining the distance provided by the solid construction. For example, U.S. Pat. No. 5,072,944 discloses a three-piece solid golf ball having a center layer and an outer layer that are prepared from a rubber composition, wherein it is desirable that the center core layer is softer than the outer layer, the layers having a hardness (Shore C) of 25-50 and 70-90, respectively.
U.S. Pat. No. 4,625,964 relates to a solid golf ball having a polybutadiene rubber core of a diameter not more than 32 mm, a polybutadiene rubber intermediate layer having a specific gravity of lower than that of the core material, and a cover. U.S. Pat. No. 4,650,193 is directed towards a solid golf ball having a core comprising a central portion and an integral outer layer, wherein the core is a curable elastomer such as polybutadiene which is treated with a cure altering agent to soften an outer layer of the core, to produce a central layer with a hardness (Shore C) of greater than 75 and an outer layer with a hardness (Shore A) of less than 80.
U.S. Pat. No. 4,848,770 discloses a solid three-piece golf ball which includes a core of a highly filled synthetic rubber or polymeric material, an intermediate mantle of an unfilled synthetic rubber and a cover. The core and intermediate mantle have a hardness of between 50-95 Shore D. U.S. Pat. No. 5,002,281 is directed towards a three-piece solid golf ball which has an inner core having a hardness of 25-70 (Shore C), an outer shell having a hardness of 80-95 (Shore C) and a cover. Further, the specific gravity of the inner core must be greater than 1.0, but less than or equal to that of the outer shell, which must be less than 1.3.
The prior art discloses a variety of materials other than polybutadiene for use as intermediate layers. For example, U.S. Pat. No. 5,253,871 concerns a golf ball having a three-piece structure comprising an elastomer core, an intermediate layer of a thermoplastic material containing at least 10% of ether block copolymer, preferably blended with an ionomer, and a thermoplastic cover. U.S. Pat. No. 5,681,898 is directed to a multi-layer golf ball having a conventional polybutadiene core, an ionomer cover and an intermediate layer formed from a blend of an ethylene methacrylic acid copolymer and a vulcanizate formed from polybutadiene and a peroxide curing agent. U.S. Pat. Nos. 5,439,227 and 5,556,098 both disclose multi-layer golf balls which have a conventional polybutadiene core, conventional covers and an intermediate layer formed from a polyetherester block copolymer blended with an ionomer.
Further, there are also several patents which are directed to golf balls having multiple cover layers. For example U.S. Pat. No. 4,431,193 relates to a golf ball having a multi-layer cover wherein the inner layer is a hard, high flexural modulus ionomer resin and the outer layer is a soft, low flexural modulus ionomer resin, and wherein either or both layers may comprise a foamed ionomer resin. U.S. Pat. No. 5,314,187 also relates to golf balls having a multiple layer cover, wherein the outer layer is molded over the inner layer and comprises a blend of balata and an elastomer and the inner layer is an ionomer resin. U.S. Pat. No. 4,919,434 is directed towards a golf ball having a cover which comprises an inner layer and an outer layer, each of which comprise a thermoplastic resin. Preferably the layers are comprised of materials that are capable of bonding with each other, for example, by heat, or by other means which are readily known to one of ordinary skill in the art.
Additionally, U.S. Pat. No. 5,631,324 is directed to a golf ball wherein the terpolymer composition of the core, mantle layers, or cover comprises an epoxy (i.e., glycidyl moiety) and an ionomer material. U.S. Pat. No. 5,155,157 provides compositions useful in the manufacture of one-, two-and three-piece golf balls that comprises blends of block copolymers, an ionomer material, and an epoxy-containing compound. U.S. Pat. No. 5,565,524 provides a golf ball having a cover that comprises an ionomer material and a glycidyl-group-containing olefinic copolymer. U.S. Pat. No. 5,543,467 discloses a golf ball having a core and a cover in which the base material of the cover comprises a maleic anhydride-modified olefinic copolymer, an ionomer resin, and a glycidyl-group-containing olefinic copolymer.
However, none of the patents discussed above disclose the multi-layer ball of the current invention that employs the materials, and has the improved golf ball properties, as disclosed herein.
The present invention is directed to a golf ball comprising a core, a cover, and an intermediate layer disposed between the core and the cover, wherein the intermediate layer comprises a glycidyl homo-polymer having the formula: 
wherein R1 is hydrogen, CH3, linear or branched alkyl group having the formula CxH2x+1 where x is an integer from 1 to about 8, aromatic, or alicyclic; R2 is hydrogen, CH3, linear or branched alkyl group having the formula CyH2y+1 where y is an integer from 1 to about 20, aromatic, or alicyclic; and n is an integer ranging from 1 to about 6; or a glydidyl co-polymer having the formula: 
wherein R3, R4, and R5 are hydrogen, CH3, linear or branched alkyl group having the formula CxH2x+1, where x is an integer from 1 to about 8, aromatic, or alicyclic; R6 is hydrogen, CH3, linear or branched alkyl group having the formula CyH2y+1 where y is an integer from 1 to about 20, aromatic, or alicyclic; o ranges from about 1 to about 99 weight percent of the total polymer; p ranges from about 99 to about 1 weight percent of the total polymer; and q is an integer ranging from 1 to about 6.
The glycidyl polymer is preferably a co-polymer of olefin with glycidyl acrylate or glycidyl methacrylate comonomer. Additionally, the glycidyl polymer has a flexural modulus of greater than about 10,000 psi and, preferably, between about 55,000 psi and about 75,000 psi. The glycidyl polymer also may have a Shore D hardness of between about 55 and about 70.
In one embodiment, the intermediate layer is an outer core layer. It may also be an an inner cover layer. Ideally, the cover comprises a castable thermoset material or a thermoplastic material. The thermoset material may also include a polyurethane, polyurea, epoxy, or a mixture thereof.
In a preferred embodiment, the cover layer comprises the glycidyl homo- or co-polymer. The core of the ball has a compression of less than about 60 and the intermediate layer has a thickness of between about 0.02 inches and about 0.035 inches. In one embodiment, the core comprises a center and an outer core layer and the cover comprises an inner and an outer cover layer. At least one or both of the outer core or inner cover layers are formed of the glycidyl polymer. Preferably, the cover has a Shore D hardness of less than about 60 or, more preferably, less than about 54. Additionally, the core has a compression of less than about 80, preferably less than about 60.
At least one of the intermediate layer or cover has a thickness of less than about 0.05 inches, preferably, less than about 0.035 inches.
The present invention is also directed to a golf ball comprising a core, a cover, and an intermediate layer disposed between the core and the cover, wherein the intermediate layer consists essentially of a glycidyl homo- or co-polymer; and the glycidyl polymer has a flexural modulus of greater than about 10,000 psi.
The glycidyl polymer is preferably a co-polymer of olefin with glycidyl acrylate or glycidyl methacrylate comonomer. Additionally, the glycidyl polymer has a flexural modulus of greater than about 10,000 psi and, preferably, between about 55,000 psi and about 75,000 psi. The glycidyl polymer also may have a Shore D hardness of between about 55 and about 70.
In one embodiment, the intermediate layer is an outer core layer. It may also be an an inner cover layer. Ideally, the cover comprises a castable thermoset material or a thermoplastic material. The thermoset material may also include a polyurethane, polyurea, epoxy, or a mixture thereof.
In a preferred embodiment, the cover layer comprises the glycidyl homo- or co-polymer. The core of the ball has a compression of less than about 60 and the intermediate layer has a thickness of between about 0.02 inches and about 0.035 inches. In one embodiment, the core comprises a center and an outer core layer and the cover comprises an inner and an outer cover layer. At least one or both of the outer core or inner cover layers are formed of the glycidyl polymer. Preferably, the cover has a Shore D hardness of less than about 60 or, more preferably, less than about 54. Additionally, the core has a compression of less than about 80, preferably less than about 60.
At least one of the intermediate layer or cover has a thickness of less than about 0.05 inches, preferably, less than about 0.035 inches.
The following terms that are used in this application are defined in terms of the enumerated ASTM tests: Specific Gravity ASTM D-297, Flexural Modulus ASTM D-790, Shore D Hardness ASTM D-2240, and Shore C Hardness ASTM D-2240. The ASTM D-297 test was carried out in lab conditions where the temperature was controlled to 20-23xc2x0 C.
As used herein, the terns xe2x80x9cpointsxe2x80x9d or xe2x80x9ccompression pointsxe2x80x9d refer to the compression scale or the compression scale based on the ATTI Engineering Compression Tester. This scale, which is well known to those working in this field, is used in determining the relative compression of a core or ball.
As used herein, xe2x80x9cCORxe2x80x9d refers to Coefficient of Restitution, which is obtained by dividing a ball""s rebound velocity by its initial (i.e., incoming) velocity. This test is performed by firing the samples out of an air cannon at a vertical steel plate over a range of test velocities (from 75 to 150 ft/s). A golf ball having a high COR dissipates a smaller fraction of its total energy when colliding with the plate and rebounding therefrom than does a ball with a lower COR. Unless otherwise noted, the COR values reported herein are the values determined at an incoming velocity of 125 ft/s.
As used herein, the term xe2x80x9cglycidyl polymerxe2x80x9d is defined as any homopolymer, copolymer, terpolymer, or mixture thereof, having at least one glycidyl group in at least one of the monomer repeat units in the polymer.
As used herein, the term xe2x80x9ccopolymerxe2x80x9d refers to a polymer which is formed from two or more monomers, wherein said monomers are not identical.
As used herein, the term xe2x80x9cterpolymerxe2x80x9d refers to a polymer which is formed from three monomers, wherein said monomers are not identical.
As used herein, the term xe2x80x9cpphxe2x80x9d in connection with a batch formulation refers parts by weight of the constituent per hundred parts of the base composition (e.g., elastomer).
The term xe2x80x9cabout,xe2x80x9d as used herein in connection with one or more numbers or numerical ranges, should be understood to refer to all such numbers, including all numbers in a range.