Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-09-26
2003-11-25
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S074000, C473S373000, C473S374000
Reexamination Certificate
active
06653403
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to golf balls and, in particular, to golf balls having a cover of at least two layers, wherein the inner cover layer material includes an ionomeric material, and the outer cover layer includes a blend of at least one grafted metallocene-catalyzed polymer and at least one ionomer resin neutralized with a metal cation. The outer cover layer blend may optionally include a non-grafted metallocene-catalyzed polymer. The golf balls of the present invention can provide low driver spin and high short iron and partial shot spin.
BACKGROUND OF THE INVENTION
Golf ball manufacturers are constantly attempting to construct golf balls having a desirable combination of good “feel,” distance, and durability. One way in which the properties of a golf ball may be adjusted is through the cover composition and construction of the ball. Traditionally, softer feeling golf balls were obtained by providing an outer cover formed with natural or synthetic balata over a liquid center surrounded by a tensioned elastomeric wound layer. Because of its softness, however, balata is susceptible to cuts or other damage to the cover, and, thus, lacks the durability required to withstand the numerous mis-hits produced by the average golfer.
For this reason, amateur golfers typically prefer a golf ball constructed with a harder, more durable cover material, such as an ionomer or ionomer blend. Covers formed of ionomeric materials generally provide a good combination of distance and durability. Because of the hard ionomer cover, these balls are difficult to cut, but have a very hard “feel”, and a lower spin rate, making these balls more difficult to draw or fade. The differences in the spin rate can be attributed to the differences in the composition and construction of both the cover and the core.
Many attempts have been made, therefore, to produce a golf ball with the control and feel of a balata-covered ball and the durability of an ionomer-covered ball. For example, U.S. Pat. No. 4,274,637 discloses two- and three-piece golf balls having covers completely or partially formed from a cellular polymeric material to improve backspin.
U.S. Pat. No. 5,002,281 discloses a three-piece solid golf ball having an ionomer cover and a solid core consisting of a soft inner core and a hard outer shell, where the difference in the hardness of the two parts of the core is at least 10 on the JIS-C scale.
Similarly, U.S. Pat. No. 4,781,383 discloses a solid, three-piece golf ball, having an ionomer cover and a core with inner and outer layers, where the inner layer has a diameter of 24 to 29 mm and a Shore D hardness of 15 to 30, and the outer layer has a diameter of 36 to 41 and a Shore D hardness of 55 to 65. The percentage of the ball surface which contacts the club face when the ball is struck is 27 to 35 percent.
European Patent Application No. 0 633 043 discloses a solid, three-piece golf ball with an ionomer or balata cover, a center core, and an intermediate layer. The center core has a diameter of at least 29 mm and a specific gravity of less than 1.4. The intermediate layer has a thickness of at least 1 mm, a specific gravity of less than 1.2, and a hardness of at least 85 on the JIS-C scale.
U.S. Pat. No. 5,586,950 discloses a golf ball having a core and a cover for covering the core, the cover comprising two ionomeric layers of an inner layer, with a high stiffness modulus of approximately 3,000 kgf/cm
2
(42,000 psi) to 5,500 kgf/cm
2
(78,000 psi) and a thickness of 0.5 to 2.5 mm, and an outer layer with a lower stiffness modulus of approximately 1,000 kgf/cm
2
(14,000 psi) to 2,500 kgf/cm
2
(35,000 psi) and a thickness of 0.5 to 2.5 mm. The base resin of the inner and outer cover layer contains an ionomer neutralized with a zinc ion.
U.S. Pat. No. 5,803,831 discloses a multi-layer golf ball having soft outer cover, preferably having a Shore D hardness of 48 or less, and a thermoplastic inner cover layer, preferably having a Shore D hardness of at least 65. The outer cover preferably includes at least 75 percent of a soft ionomeric neutralized copolymer formed from a polyolefin, an unsaturated carboxylic acid, and a monomer of the acrylate ester class.
U.S. Pat. Nos. 5,984,806 and 6,015,356 are directed to multi-layer golf balls with smaller and lighter cores produced by including metal particles, or other heavy weight filler materials, in the cover compositions. The covers may include an inner layer that includes a material having a flexural modulus of at least about 15,000 psi and a hardness of at least about 60 Shore D and an outer layer that includes a material, such as a blend of high and low ionomers, having a flexural modulus of from about 1,000 to 10,000 psi and a Shore D hardness of about 65 or less.
U.S. Pat. Nos. 5,553,852 and 5,782,707 disclose a three-piece solid golf ball having a center core, an intermediate layer, and a cover. The ionomeric resin intermediate layer can include various fillers. The outer cover layer, preferably a thermoplastic resin base composition, is softer than the intermediate layer. Iron shots and partial swing shots are affected by this cover design.
U.S. Pat. No. 5,919,101 discloses a solid golf ball comprising a core and a cover formed on the core, wherein the cover has a two-layer structure consisting of an inner cover having a flexural modulus of approximately 3,000 kgf/cm
2
(42,000 psi) to 7,000 kgf/cm
2
(99,000 psi) and an outer cover formed on the inner cover having a flexural modulus of approximately 1,000 kgf/cm
2
(14,000 psi) to 2,800 kgf/cm
2
(39,000 psi), and wherein the core is formed from a rubber composition comprising 0.05 to 5 parts by weight of an organic sulfide compound, based on 100 parts by weight of a base rubber. The cover layer can be an ionomer resin, a polyamide, or a nylon.
The above references, however, do not provide an ideal cover material for attaining both good feel and durability. One solution may be golf balls and, in particular, cover layers formed of or blended with metallocene-catalyzed polymers, i.e., polymers produced using single-site metallocene catalysts, which produce polymers with a narrow molecular weight distribution and uniform molecular architecture, so that the order and orientation of the monomers in the polymer, and the amount and type of branching is essentially the same in each polymer chain.
The narrow molecular weight distribution and uniform molecular architecture provides metallocene-catalyzed polymers with properties that are not available with conventional polymers, and allow polymers to be produced having unique properties that are specifically tailored to a particular application. The desired molecular weight distribution and the molecular architecture are obtained by the selection of the appropriate metallocene catalyst and polymerization conditions.
Processes for grafting monomers onto polymers and, in particular, polyolefins, are known in the art. European Patent Application No. 0 266 994 discloses a process for grafting ethylenically unsaturated monomers, such as unsaturated carboxylic acids and anhydrides and derivatives thereof, onto copolymers of ethylene. The disclosed process includes the steps of forming an admixture of the copolymer, monomer, and 25 to 3,000 ppm of an organic peroxide having a half-life of about one minute to 120 minutes at 150° C., and mixing the resultant admixture in an extruder at a temperature above the melting point of the copolymer for a period of time at least four times the half-life of the organic peroxide. The resultant grafted copolymer is then extruded into a shaped article.
U.S. Pat. No. 5,106,916 discloses a process for the catalytic grafting of an ethylenically unsaturated monomer onto a copolymer in which the process of EPA 0 266 994 is modified by the addition of a catalyst comprising water and at least one phosphorous-containing compound selected from the group consisting of compounds of formula HPO(OR
I
)
2
, phosphite compounds of formula P(OR
2
)
3
and formula (OR
3
)P—O—R
4
—O—P(OR
5
)
2
, and di-substitute
Cavallaro Christopher
Dalton Jeffrey L.
Halko Roman D.
Harris Kevin M.
Rajagopalan Murali
Acushnet Company
Buttner David J.
Swidler Berlin Shereff & Friedman, LLP
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