Games using tangible projectile – Golf – Ball
Reexamination Certificate
2001-04-18
2003-01-21
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S371000, C473S374000, C473S377000, C473S378000, C473S370000, C473S373000, C525S089000, C525S093000
Reexamination Certificate
active
06508725
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to golf ball compositions and, more particularly, to golf ball compositions for use in making golf ball covers and intermediate layers, to optimize ball performance. This invention also relates to methods of manufacture of such ball compositions.
Golf balls generally include a core and at least one layer surrounding the core. Balls can be classified as two-piece, wound, or multi-layer balls. Two-piece balls include a spherical inner core and an outer cover layer. Wound balls include a core, a rubber thread wound under tension around the core to a desired diameter, and a cover layer. Cover layers for wound ball generally are made of balata material. Multi-layer balls include a core, a cover layer, and one or more intermediate layers.
Generally, two-piece balls have good durability and distance when hit, but poor “feel”—the overall sensation transmitted to the golfer while hitting the ball—and low spin rate, which results in poor ball control. Wound balls having balata covers generally have high spin rate, leading to good control, and they also have good feel, but they have poor durability and short distance in comparison to two-piece balls. Multi-layer balls generally have performance characteristics between those of two-piece and wound balls; that is, multi-layer balls exhibit durability and distance inferior to two-piece balls but superior to wound balata balls, and they exhibit feel and spin rate inferior to wound balata balls but superior to two-piece balls.
Material characteristics of the compositions used in the core, cover, and any intermediate layers of golf balls are among the important factors that determine the performance of the balls. In particular, the composition of the cover layer is important in determining the ball's durability, shear-cut resistance, speed, spin rate, hitting sound (the sound made by a golf club head when it hits the ball), and feel. The composition of an intermediate layer is important in determining the ball's spin rate and speed. Various materials having different physical properties are used to make cover and intermediate layers to create a ball having the most desirable performance possible. In particular, cover layers of many commercially available balls are made using soft or hard ionomeric resins, elastomeric resins, or blends of these.
Ionomeric resins used generally are ionomeric copolymers of an olefin and a metal salt of a unsaturated carboxylic acid, or ionomeric terpolymers having a co-monomer within its structure. These resins vary in resiliency, flexural modulus, and hardness. Examples of these resins include those marketed under the trademark SURLYN manufactured by E.I. DuPont de Nemours & Company of Wilmington, Del., and IOTEK manufactured by ExxonMobil Corporation of Irving, Tex. Ionomeric copolymers have been have been particularly favored for use in golf ball covers because they produce ball covers having excellent durability and high resilience. Ionomeric terpolymers are used to produce covers having improved spin and feel, though at the cost of ball speed and durability.
Elastomeric resins used in golf ball covers include a variety of thermoplastic or thermoset elastomers available, such as polyurethane, polyetherester elastomer, and polyamide elastomer. Another elastomeric material considered suitable for use in golf ball compositions is a block polymer having at least one polymer block comprising an aromatic vinyl compound and at least one polymer block comprising a conjugated diene compound, and having a hydroxyl group, or its hydrogenated product. The hydroxyl group can be at the terminal block copolymer or elsewhere in the block copolymer structure. An example of this block copolymer having a hydroxyl group at the terminal block copolymer is sold under the trademark HG-252 by Kuraray Company of Kurashiki, Japan.
Each of the materials discussed above has particular characteristics that can lead to good golf ball properties when used in a golf ball composition, either for making a ball cover or intermediate layer. However, one material generally cannot optimize all of the important properties of a golf ball layer. Properties such as feel, speed, spin rate, resilience, and durability all are important, but improvement of one of these properties by use of a particular material often can lead to worsening of another. For example, ideally, a golf ball cover should have low hardness, high spin rate, and good feel, without sacrificing ball speed, distance, or durability. Despite the broad use of copolymeric ionomers in golf balls, their use alone in, for example, a ball cover can be unsatisfactory. A cover providing good durability, spin, and feel would be difficult to make using only a copolymeric ionomer resin having a high flexural modulus, because the resulting cover, while having good distance and durability, also will have poor feel and low spin rate, leading to reduced controllability of the ball. Also, use of particular elastomeric resins alone can lead to compositions having unsatisfactory properties, such as poor durability and low ball speed.
Therefore, to improve golf ball properties, the materials discussed above can be blended to produce improved ball layers. Prior compositions for golf balls have involved blending high-modulus copolymeric ionomer with, for example, lower-modulus copolymeric ionomer, terpolymeric ionomer, or elastomer, such as the block copolymer discussed above. As discussed above, ideally a golf ball cover should provide high spin rate and good feel, without sacrificing the ball's distance and durability. Therefore, a copolymeric ionomer having a high flexural modulus often is combined in a cover composition with a terpolymeric ionomer or an elastomer having a low flexural modulus. The resulting intermediate-modulus blend possesses a good combination of hardness, spin, and durability. Also, the prior understanding of use of the above-specified block copolymers is that it is essential to use them in combination with ionomers to produce satisfactory golf ball compositions. Use of this material with ionomers in golf ball compositions has previously been disclosed in, for example, U.S. Pat. No. 5,693,711 to Akiba et al. It has been believed that use of the block copolymer in ball cover compositions without blending it with ionomer would result in loss of durability, scuff resistance, and ball speed.
However, even with blending of materials to improve properties, use of the materials and blends discussed above has not been completely satisfactory. Improving one characteristic can lead to worsening another. For example, blending an ionomer having a high flexural modulus with an ionomer having a low flexural modulus can lead to reduced resilience and durability compared to use of the high-modulus ionomer alone. Also, blends of ionomer with the above-specified block copolymer, as described in the Akiba et al. patent, are not completely satisfactory in providing optimal ball cover properties. In general, it is difficult to make a material for a golf ball cover layer that has low hardness, good feel, high speed, high resilience, and good shear durability. Additional compositions meeting these criteria therefore are needed.
In view of the above, it is apparent that golf ball compositions are needed that allow the optimization of many ball performance properties without the worsening of other properties. The ball compositions also should provide little or no processing and preparation difficulties over existing compositions. The present invention fulfills this need and other needs, and provides further related advantages.
SUMMARY OF THE INVENTION
The present invention is embodied a golf ball composition incorporating a block copolymer having a first polymer block comprising an aromatic vinyl compound, a second polymer block comprising a conjugated diene compound, and a hydroxyl group, or its hydrogenation product, wherein the composition is essentially free of ionomer. The composition preferably includes a second polymer having
Caglar Oral
Duong T.
Sewell Paul T.
Sheppard Mullin Richter & Hampton LLP
Taylor Made Golf Company Inc.
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