Games using tangible projectile – Golf – Ball
Reexamination Certificate
2001-05-21
2003-02-18
Mullis, Jeffrey (Department: 1711)
Games using tangible projectile
Golf
Ball
C473S371000, C473S378000, C473S385000, C525S070000, C525S071000, C525S072000, C525S078000
Reexamination Certificate
active
06520869
ABSTRACT:
This invention relates to resin compositions for golf ball having specific comb-like graft copolymers blended therein which have good flow characteristics and moldability. It also relates to high-performance golf balls formed thereof and endowed with outstanding rebound energy and durability.
BACKGROUND OF THE INVENTION
Over the past few years, wide use has been made of ionomer resins in golf ball cover materials. Ionomer resins are ionic copolymers composed of an olefin such as ethylene in combination with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or maleic acid, wherein the acidic groups are partially neutralized with metal ions such as sodium, lithium, zinc or magnesium ions. They have excellent characteristics such as durability, rebound and scuff resistance, making them highly suitable as the base resin in golf ball cover material.
The golf ball cover materials based on ionomer resins, however, have the drawback that the ball gives a poor feel when hit and lacks a softness necessary to receive an appropriate spin to control the ball in flight. This is because ionomer resins are relatively hard. Upon impact, the ball is not fully pressed against the club head surface and thus gains a less spin rate. The use of harder ionomer resins as the cover stock has the problem that the feel of the ball when hit becomes very hard.
There is a need to have a golf ball having good spin properties and pleasant feel that are attractive to experienced low-handicap golfers and professional golfers.
To improve the hitting feel of ionomer cover materials, a number of proposals have been made on the blending of ionomer resins with thermoplastic elastomers to produce cover materials. The thermoplastic elastomers proposed thus far are olefin elastomers (Japanese Patent No. 2,924,706), polyester elastomers (Japanese Patent No. 2,570,587), styrene elastomers (JP-A 8-182776), polyamide elastomers (JP-A 8-155053), and olefin copolymers (JP-A 11-57071 and 9-117532).
In general, cover materials comprising ionomer resins in admixture with thermoplastic elastomers are good in spin performance as compared with prior art cover materials, but suffer from the drawbacks of low resilience and molding fault due to the limited compatibility between ionomer resins and thermoplastic elastomers.
To improve the compatibility between ionomer resins and thermoplastic elastomers, several techniques have been proposed, for example, grafting of acid anhydride to ionomer resins (JP-A 6-157843 and JP-A 6-299052), blending of glycidyl-modified thermoplastic elastomers (JP-A 8-182776), and addition of a compatibilizing agent having a reactive group such as epoxy or acid anhydride group (JP-A 11-57071).
These techniques intend to improve compatibility by reaction of acid anhydride or glycidyl groups in the thermoplastic elastomers or compatibilizing agent with acid groups in the ionomer resins. When such techniques are applied, however, molecular bonds are formed by heating, resulting in a substantial decrease in flow to interfere with molding. Additionally, reaction by-products can substantially degrade physical properties. For this reason, use of these techniques are not recommended.
SUMMARY OF THE INVENTION
An object of the invention is to provide a resin composition for golf ball comprising a thermoplastic resin and a specific comb-like graft copolymer which has good flow characteristics and moldability so that high-performance golf balls endowed with outstanding rebound energy and durability may be produced therefrom. Another object of the invention is to provide a high-performance golf ball formed thereof and having improved rebound and durability.
The above and other objects are achieved by the resin composition for golf ball and the golf ball defined below. It is noted that the term “enclosure” used in conjunction with the golf ball encompasses the cover and/or the intermediate layer that surrounds the core.
In one aspect, the invention provides a resin composition for golf ball comprising, in admixture,
(A) a thermoplastic resin composition comprising at least one thermoplastic resin selected from the group consisting of an olefin-unsaturated carboxylic acid random copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylate ternary copolymer, a metal ion-neutralized product of an olefin-unsaturated carboxylic acid random copolymer, and a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylate ternary copolymer, and
(B) a comb-like graft copolymer comprising (b-1) a non-ionomer thermoplastic elastomer as backbone component and (b-2) a polymeric chain containing a non-olefinic monomer as side chain component,
the thermoplastic resin composition (A) and the comb-like graft copolymer (B) being blended in a weight ratio of from 99:1 to 40:60.
In one preferred embodiment, the thermoplastic resin composition (A) further includes a non-ionomer thermoplastic elastomer. In the comb-like graft copolymer (B), the backbone component (b-1) and the side chain component (b-2) are preferably mixed in a weight ratio of from 99:1 to 40:60. The non-ionomer thermoplastic elastomer in (B) or as the optional component in (A) is preferably an olefin copolymer, an olefin elastomer, a styrene elastomer or a mixture thereof. Also preferably, the side chain component (b-2) contains an unsaturated carboxylic acid as a monomer.
In another aspect, the invention provides a golf ball having a layer formed of a material comprising the resin composition defined above.
A golf ball may also be embodied as comprising a core and a cover formed around the core, the cover being formed of a material comprising the resin composition defined above.
A golf ball may further be embodied as comprising a core and an enclosure formed around the core, the enclosure having a multilayer structure of two or more layers, at least one layer of the enclosure being formed of a material comprising the resin composition defined above.
DESCRIPTION OF PREFERRED EMBODIMENTS
The resin composition for golf ball of the invention is defined as comprising (A) a thermoplastic resin composition and (B) a comb-like graft copolymer in a specific blending ratio.
First referring to the thermoplastic resin composition (A), there is formulated as an essential component at least one thermoplastic resin selected from the group consisting of an olefin-unsaturated carboxylic acid random copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylate ternary copolymer, a metal ion-neutralized product of an olefin-unsaturated carboxylic acid random copolymer, and a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylate ternary copolymer.
In these copolymers, the olefin has at least 2 carbons, but not more than 8 carbons, and preferably not more than 6 carbons. Illustrative examples include ethylene, propylene, butene, pentene, hexene, heptene and octene. Ethylene is especially preferred.
Suitable examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid and fumaric acid. Of these, acrylic acid and methacrylic acid are especially preferred.
The unsaturated carboxylate is preferably a lower alkyl ester of the foregoing unsaturated carboxylic acid. Illustrative examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate and butyl acrylate. Butyl acrylate (n-butyl acrylate or isobutyl acrylate) is especially preferred.
The olefin-unsaturated carboxylic acid random copolymer and olefin-unsaturated carboxylic acid-unsaturated carboxylate ternary copolymer may be prepared by using a known process to carry out copolymerization on the above ingredients in any desired proportion. It is generally recommended that the unsaturated carboxylic acid content within the copolymer be at least 2% by weight, preferably at least 6% by weight, and most preferably at least 8% by weight, but not more than 25% by weight, preferably not more than 20% by weight, and most pr
Ichikawa Yasushi
Takesue Rinya
Bridgestone Sports Co. Ltd.
Mullis Jeffrey
Sughrue & Mion, PLLC
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