Games using tangible projectile – Golf – Ball
Reexamination Certificate
1999-12-16
2001-06-05
Chapman, Jeanette (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S351000
Reexamination Certificate
active
06241625
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf ball, and more particularly to a solid golf ball having an improved shot feeling, resilience on shot and controllability.
2. Description of the Prior Art
Heretofore, balata rubber (natural rubber or synthetic transpolyisoprene rubber) or a mixture of balata rubber and elastomer has been used as a material for covers of so-called high-class golf balls. It is easier to put spin to golf balls having covers made of balata rubber because balata rubber is relatively soft and provides the golf balls with good controllability. Therefore, not only professional golfers but also non-professional but advanced golfers prefer the above type of golf balls. Since durability of balata rubber is rather small, the golf ball having the cover made of balata rubber has suffered from a problem that the golf ball may be broken or damaged when the golfer failed to hit the ball at a proper portion of the ball. Thus, it is highly likely that such a golf ball has a relatively short lifetime.
Recently, there has been widely used an ionomer which is a copolymer of &agr;, &bgr;-unsaturated carboxylic acid and olefin as a material for a cover of a golf ball. Ionomer is superior to balata rubber in terms of durability and flight performance. However, the golf balls with the covers made of such ionomer have suffered from another problem that golfers have a difficulty in putting spin to the balls due to the hardness of ionomer, thus lowering controllability of the golf balls. Also, the hardness of ionomer leads to a poor shot feeling.
In order to improve controllability of the golf ball, Japanese Unexamined Patent Publication Nos. 1-308577 and 5-3931 disclose the idea of using ionomer mixture composed of a hard-type ionomer and a soft-type ionomer. This idea is effective in improving controllability and shot feeling of the golf ball but lowers resilience of the cover because the hardness of the cover decreases as a whole. Consequently, the resilience of the golf ball deteriorates, and the flying distance is lowered.
There has been proposed an idea of reducing the hardness of a core of the ball as well as the idea of reducing the hardness of the cover of the ball in order to improve the shot feeling. However, deterioration of the resilience of the ball as a whole is unavoidable also in the case where the hardness of the core is reduced for the same reason as applied above in the case where the hardness of the cover is reduced.
Also, there have been proposed various techniques of adding a variety of compounds as a material for the core to improve the resilience of the core, as disclosed in, for example, Japanese Examined Patent Publication Nos. 3-1335, 3-1336, 3-1337; and Japanese Unexamined Patent Publication Nos. 2-297384, 4-109970, 8-98901. None of them has proven to be effective in improving the resilience of the core of the ball.
As mentioned above, there has not been known a golf ball with a cover composed of ionomer which attains an improvement in shot feeling, controllability and resilience.
SUMMARY OF THE INVENTION
In view of the above, the present invention has been accomplished. An object of the present invention is to provide a golf ball with a cover made of ionomer which attains improved shot feeling, controllability and resilience.
According to an aspect of the present invention, a golf ball comprises a cover member and a core member. The cover member contains: 3 to 30 parts by weight of a thermoplastic elastomer containing polyamide; 5 to 50 parts by weight of a terpolymer ionomer containing ethylene, (meth)acrylic acid, and (meth)acrylic ester; 30 to 80 parts by weight of a copolymer ionomer containing ethylene and (meth)acrylic acid; and 1 to 20 parts by weight of an epoxidized-diene-based block copolymer. The core member is formed by vulcanizing a rubber composition containing: 100 parts by weight of a base rubber, A parts by weight of an &agr;, &bgr;-unsaturated carboxylic acid or a metal salt thereof, B parts by weight of an organic peroxide, and C parts by weight of a sulfide, where A, B, and C satisfies the relationship:
0.02×A≦B+C≦0.05×A,
and
A lies in the range from 25 to 45.
It should be noted that the term “(meth)acrylic” used throughout the specification indicates acrylic or methacrylic.
DETAILED DESCRIPTION OF THE INVENTION
Prior to filing this application, the present inventors found out the fact that forming a cover of a plurality of kinds of resins provides a golf ball with a good shot feeling, controllability and resilience, as a result of various experiments with an attempt to provide a golf ball having a cover made of ionomer with an improved shot feeling and controllability while maintaining an excellent durability and resilience. The inventors, however, have realized that the above golf ball still needs improvement because the above golf ball had an inferior resilience to those with the covers made of the conventional ionomer resins.
Accordingly, the present inventors have proceeded with further experiments by varying the ratio of each component composing the core in order to solve the above problem. As a result of the experiments, the present inventors found out that setting the ratio of each component of the core at such a value as to satisfy a certain relationship improves the resilience of the golf ball, and thus completed this invention.
A golf ball generally consists of a core member and a cover member. The cover member may consist of a single layer or a plurality of layers. In this embodiment, “cover” indicates the outermost layer constituting the cover member of the golf ball. For example, in the case where the golf ball has a single-layered cover member, the cover member corresponds to the cover in this embodiment, while in the case where the golf ball has a multi-layered cover member such as a 3-piece golf ball and 4-piece golf ball, the outermost layer of the cover member corresponds to the cover in this embodiment.
[Description of Cover]
First, components of a cover of a golf ball as a preferred embodiment of this invention are described. A primary feature of the cover used in this invention is that the cover contains 3 to 30 parts by weight of a thermoplastic elastomer having polyamide as a base material (hereinafter, also simply referred to as “elastomer”), 5 to 50 parts by weight of a terpolymer type ionomer containing ethylene, (meth)acrylic acid, and (meth)acrylic ester (hereinafter, also simply referred to as “terpolymer ionomer”), 30 to 80 parts by weight of a copolymer type ionomer containing ethylene and (meth)acrylic acid (hereinafter, also simply referred to as “copolymer ionomer”), and 1 to 20 parts by weight of an epoxidized diene-based block copolymer.
Specifically, copolymer ionomer has a great hardness and high resilience, and provides the cover with an improved hardness and resilience. In this state, however, the cover can not provide the resulting golf ball with a satisfactory shot feeling and controllability. Adding elastomer having a relatively small hardness and high resilience as a component constituting the cover improves the shot feeling and controllability of the resulting golf ball.
Further, in the case where the hardness of the golf ball is not so highly expected, that is, production of golf balls with substantially the same degree of hardness as the conventional golf balls composed of terpolymer ionomer and copolymer ionomer is expected, it is possible to provide the golf balls with a higher resilience by adding a larger amount of copolymer ionomer than the case of producing golf balls excellent both in hardness and resilience. Adding terpolymer ionomer having a relatively low resilience and low hardness as a component for the cover provides the resulting golf ball with a good shot feeling and controllability.
Terpolymer ionomer exhibits compatibility with elastomer. However, merely adding terpolymer ionomer does not accomplish a desired compatibility of terpolymer ionomer and elastomer. Accordingly, epoxidized d
Iwami Satoshi
Ohama Keiji
Yokota Masatoshi
Birch & Stewart Kolasch & Birch, LLP
Chapman Jeanette
Gorden Raeann
Sumitomo Rubber Industries Ltd.
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