Games using tangible projectile – Golf – Ball
Reexamination Certificate
2002-05-24
2004-02-24
Chu, Raleigh W. (Department: 3711)
Games using tangible projectile
Golf
Ball
C524S432000, C524S526000, C524S534000
Reexamination Certificate
active
06695716
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf ball excellent in resilience, which ball is producible with high workability.
2. Prior Art
Conventionally, to give excellent resilience to a golf ball, various attempts have been made to improve the composition of a polybutadiene used as a main rubber for the golf ball.
For example, Japanese Patent Laid-open No. Sho 62-89750 has proposed a rubber composition for a solid golf ball, which contains, as a main rubber, a polybutadiene having a Mooney viscosity ranging from 70 to 100 and synthesized by using an Ni or Co catalyst and a polybutadiene having a Mooney viscosity ranging from 30 to 90 and synthesized by using a lantern based catalyst or a polybutadiene having a Mooney viscosity ranging from 20 to 50 and synthesized by using an Ni or Co catalyst.
The above-described golf ball, however, has been further required to be improved in terms of workability at the time of extrusion of the rubber composition and resilience of the ball.
Japanese Patent Laid-open No. Hei 2-268778 has proposed a golf ball, which is produced from a rubber composition containing a polybutadiene having a Mooney viscosity of less than 50 and synthesized by using a group VIII element catalyst and a polybutadiene having a Mooney viscosity of less than 50 and synthesized by using a lanthanide catalyst. The golf ball thus obtained, however, is poor in resilience.
Japanese Patent Laid-open No. Hei 11-70187 has proposed a multi-piece solid golf ball including an intermediate layer made from a polybutadiene having a low Mooney viscosity; Japanese Patent Laid-open No. Hei 11-319148 has proposed a solid golf ball produced from a rubber composition containing a polybutadiene having a Mooney viscosity ranging from 50 to 60 and synthesized by using an Ni or Co catalyst and a polybutadiene having a Mooney viscosity ranging from 20 to 90 and synthesized by using lanthanoid based catalyst; Japanese Patent Laid-open No. Hei 11-164912 has proposed a solid golf ball produced from a rubber composition in which the amount of 1,2-vinyl bonds is in a range of 2.0% or less and a ratio (Mw/Mn) of a weight-average molecular weight to a number-average molecular weight is in a range of 3.5 or less; Japanese Patent Laid-open No. Sho 63-275356 has proposed a golf ball produced from a rubber composition containing a polybutadiene having a high Mooney viscosity; and Japanese Patent Laid-open No. Hei 3-151985 has proposed a golf ball produced from a rubber composition containing a polybutadiene having a high number-average molecular weight and a polybutadiene having a low number-average molecular weight. Each of these golf balls, however, is disadvantageous in that it is poor in workability at the time of extrusion of the rubber composition and/or low in resilience of the ball.
SUMMARY OF THE INVENTION
In view of the foregoing, the present inventor has earnestly examined and found that a golf ball including, as a composing element, a hot-molded product obtained from a rubber composition, the rubber composition including a polybutadiene obtained by mixing a polybutadiene (a) with a polybutadiene (b) at a mass ratio [(a)/(b)] ranging from 70/30 to 10/90; an unsaturated carboxylic acid and/or a metal salt thereof; and an organic peroxide; wherein said polybutadiene (a) contains 60% or more of cis-1,4-bonds and has a Mooney viscosity [ML
1+4
(100° C.)] of 10 or more and less than 50, and is synthesized by using a group VIII element catalyst, and said polybutadiene (b) contains 60% or more of cis-1,4-bonds and has a Mooney viscosity [ML
1+4
(100° C.)] of 50 or more, and is synthesized by using a rare earth element based catalyst, is advantageous due to a synergism effect of a polybutadiene obtained by mixing two kinds of polybutadienes at a specific ratio and the essential components. In general, a material having a high Mooney viscosity and thereby having a high resilience is poor in moldability, that is, workability in extrusion of a rubber which has been kneaded, whereas a material having a low Mooney viscosity is good in moldability in extrusion of a rubber which has been kneaded but is poor in resilience of the ball. The above-described rubber composition examined by the present inventor can solve such an inconsistent problem. That is to say, the present inventor has found that the above-described rubber composition is good in moldability in extrusion after kneading and also good in resilience of the ball, and thereby a molded product excellent in resilience can be obtained from the rubber composition with good workability, and that a golf ball having excellent resilience can be produced by using the molded product thus obtained as a composing element of the ball.
Accordingly, the present invention provides the following golf balls:
(1) A golf ball including, as a composing element, a hot-molded product obtained from a rubber composition, said rubber composition including:
a polybutadiene obtained by mixing a polybutadiene (a) with a polybutadiene (b) at a mass ratio [(a)/(b)] ranging from 70/30 to 10/90;
an unsaturated carboxylic acid and/or a metal salt thereof; and
an organic peroxide;
wherein said polybutadiene (a) contains 60% or more of cis-1,4-bonds and has a Mooney viscosity [ML
1+4
(100° C.)] of 10 or more and less than 50, and is synthesized by using a group VIII element catalyst, and said polybutadiene (b) contains 60% or more of cis-1,4-bonds and has a Mooney viscosity [ML
1+4
(100° C.)] of 50 or more, and is, synthesized by using a rare earth element based catalyst.
(2) A golf ball according to claim
1
, wherein said golf ball is either a one-piece golf ball or a golf ball including a solid core or a solid center, and a flexural amount of said one-piece solid golf ball, solid core, or solid center, measured by applying a load of 980 N (100 kg) thereto, is in a range of 2.0 to 6.0 mm.
(3) A golf ball according to claim
1
or
2
, wherein letting a weight-average molecular weight be Mw (×10
4
), a number-average molecular weight be Mn (×10
4
), and a ratio of the weight-average molecular weight to the number-average molecular weight be Mw/Mn, the ratio Mw/Mn of said component (a) is in a range of 3.0 to 6.0, and the Mw/Mn of said component (b) is in a range of 2.0 to 4.0.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. A golf ball of the present invention includes a hot-molded product obtained from a rubber composition. The rubber composition contains, as a main rubber, a polybutadiene component obtained by mixing a polybutadiene (a) with a polybutadiene (b). The polybutadiene (a) contains 60% or more of cis-1,4-bonds and has a Mooney viscosity [ML
1+4
(100° C.)] of 10 or more and less than 50, and is synthesized by using a group VIII element catalyst. The polybutadiene (b) contains 60% or more of cis-1,4-bonds and has a Mooney viscosity [ML
1+4
(100° C.)] of 50 or more, and is synthesized by using a rare earth element based catalyst.
The polybutadiene component (a) is added to improve the workability, and is required to contain the cis-1,4-bonds in an amount of 60% or more, preferably, 80% or more, more preferably, 90% or more, most preferably, 95% or more. If the amount of the cis-1,4-bonds is excessively small, the resilience is reduced.
The Mooney viscosity [ML
1+4
(100° C.)] of the polybutadiene component (a) is required to be in a range of 10 or more, preferably, 20 or more, more preferably, 25 or more, most preferably, 30 or more, with the upper limit being in a range of less than 50, preferably, 48 or less, more preferably, 46 or less, most preferably, 44 or less.
The Mooney viscosity used herein is an industrial index of viscosity measured by a Mooney viscometer which is one kind of a rotary plastimeter under JIS-K6300. The Mooney viscosity is expressed in ML
1+4
(100° C.), where M indicates the Mooney viscosity, L indicates a la
Higuchi Hiroshi
Nanba Atsushi
Bridgestone Sports Co. Ltd.
Chu Raleigh W.
Duong Tom
Sughrue & Mion, PLLC
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