Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-02-06
2002-05-28
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C473S371000, C473S372000, C473S373000
Reexamination Certificate
active
06395816
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rubber compound for a golf ball, which is used for a solid core or a solid center (hereinafter, generally referred to as “center core”) of a solid golf ball or a thread wound golf ball, whereby the initial velocity of the center core can be increased, and to a golf ball including a center core made from the above rubber compound, whereby the degree of freedom in design of the golf ball can be enlarged.
In recent years, golf balls have been variously improved. For example, an attempt has been made to adjust the composition of a material for forming a center core used for a solid golf ball or a thread wound golf ball for the purpose of enhancing the feeling of shooting the golf ball and/or increasing the flying performance of the golf ball.
Such improvements of golf balls, however, have been insufficient yet to satisfy various needs of players, and at present, there have been strong demands toward further improvement of golf balls. In particular, it has been required to develop a material capable of forming a center core having a high repulsion.
In particular, a multi-layer golf ball including a cover having two or more layers different in material from each other has been recently proposed. However, such a multi-layer golf ball has a problem that the degree of freedom in design of the golf ball is limited due to the multi-layer structure when it is used as a competition golf ball in accordance with the golf rule, since the diameter and weight of the golf ball are specified under the golf rule.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a rubber compound for a golf ball, which is used for a center core of a solid golf ball or a thread wound golf ball, whereby the initial velocity of the center core can be increased, and to provide a golf ball including a center core made from the above rubber compound, whereby the degree of freedom in design of the golf ball can be enlarged.
To achieve the above object, the present inventor has made studies on a rubber compound for a golf ball. As the result, it has been found that by incorporating synthetic zeolite into a rubber compound comprising a base rubber, a metal salt of an &agr;,&bgr;-unsaturated carboxylic acid and an organic peroxide in an amount of 0.1 to 15 parts by weight on the basis of 100 parts by weight of the base rubber and forming a center core by the rubber compound containing the synthetic zeolite, it is possible to enhance the initial velocity of the center core, although the added amount of the synthetic zeolite is very smaller than that of a usual filler. This may be considered to be due to the fact that the synthetic zeolite suitably captures moisture contained in the center core.
As a result of further study, it has also been found that the center core formed by using the above rubber compound is suitable for a golf ball for competition specified in diameter and weight under a golf rule, and that since the added amount of the filler can be reduced as described above, it is possible to extend the degree of freedom in design of structural parts other than the center core, for example, a cover, and particularly improve the degree of freedom in design of a multi-layer cover, and hence to improve the characteristic of the golf ball.
Accordingly, the present invention provides a rubber compound for a golf ball comprising a base rubber, a metal salt of an &agr;,&bgr;-unsaturated carboxylic acid, an organic peroxide, and synthetic zeolite, wherein the content of the synthetic zeolite is in a range of 0.1 to 15 parts by weight on the basis of 100 parts by weight of the base rubber.
The present invention also provides a golf ball comprising a center core and a cover having at least one cover layer, wherein the center core is made from a rubber compound comprising a base rubber, a metal salt of an &agr;,&bgr;-unsaturated carboxylic acid, an organic peroxide, and synthetic zeolite, the content of the synthetic zeolite being in a range of 0.1 to 15 parts by weight on the basis of 100 parts by weight of the base rubber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A rubber compound for a golf ball according to the present invention contains a base rubber, a metal salt of an &agr;,&bgr;-unsaturated carboxylic acid, an organic peroxide, and synthetic zeolite.
The function of each component of the rubber compound for a golf ball according to the present invention will be described below.
As the base rubber, there may be used polybutadiene generally used as a material for forming a solid core or a solid center, particularly 1,4-cis-polybutadiene, more preferably 1,4-cis-polybutadiene having a cis-structure of at least 40% or more. In addition, natural rubber, polyisoprene rubber, or styrene-butadiene rubber may be suitably added to the polybutadiene as needed.
As the metal salt of an &agr;,&bgr;-unsaturated carboxylic acid, there may be used zinc methacrylate or zinc acrylate. In particular, zinc acrylate is preferably used from the viewpoint of a high repulsion. The added amount of the metal salt of an &agr;,&bgr;-unsaturated carboxylic acid may be in a range of 5 to 45 parts by weight, preferably 15 to 30 parts by weight on the basis of the 100 parts by weight of the base rubber.
As the organic peroxide, there may be used 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane, dicumyl peroxide, di(t-butylperoxy)-meta-diisopropylbenzene, and 2,5-dimethyl-2,5-di-t-butylperoxyhexane. The added amount of the organic peroxide may be in a range of 0.2 to 5 parts by weight, preferably 1 to 2 parts by weight on the basis of 100 parts by weight of the base rubber.
The rubber compound for a golf ball according to the present invention contains synthetic zeolite.
The synthetic zeolite may be used in the form of particles having an average particle size in a range of 0.1 to 6 mm, preferably 0.5 to 3 mm. An average diameter of pores of the synthetic zeolite may be in a range of 1 to 10 Å, preferably, 2 to 6 Å. Such synthetic zeolite is commercially available, for example, by Wako Pure Chemical Industries, Ltd. in the trade name of “Molecular Sieve”.
The rubber compound for a golf ball according to the present invention is specified such that the added amount of the synthetic zeolite to the base rubber is in a range of 0.1 to 15 parts by weight, preferably 0.5 to 10 parts by weight on the basis of the 100 parts by weight of the base rubber. If the added amount of the synthetic zeolite is less than 0.1 part by weight, the capture of moisture by the synthetic zeolite is insufficient, failing to improve the initial velocity of a center core made from the rubber compound, and if it is more than 15 parts by weight, there occur reductions in repulsion and durability of the center core made from the rubber compound.
It should be noted that in addition to the synthetic zeolite, a known filler, typically an inorganic filler such as zinc oxide or barium sulfate may be added insofar as the added amount does not exert adverse effect on the rubber compound.
A golf ball of the present invention includes a center core made from the above-described rubber compound and a cover having at least one cover layer. The golf ball of the present invention can be applied to a solid golf ball (having a solid core as the center core) and a thread wound golf ball (having a solid center as the center core) insofar as the center core is made from the above-described rubber compound.
The solid golf ball according to the present invention has a solid core made from the above-described rubber compound. The solid core can be produced by a known core production method, for example, a method of kneading respective components for a base rubber, forming a core slug, and vulcanizing it.
In the solid core thus produced, which contains synthetic zeolite in a suitable amount, the amount of moisture in the solid core is suitably adjusted since moisture in the solid core is suitably captured by the synthetic zeolite, resulting in that the initial velocity of the solid core can be improv
Bridgestone Sports Co. Ltd.
Buttner David J.
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