Games using tangible projectile – Golf – Ball
Reexamination Certificate
2002-05-24
2004-03-30
Chiu, Raleigh W. (Department: 3711)
Games using tangible projectile
Golf
Ball
C524S432000, C524S526000, C524S534000
Reexamination Certificate
active
06712715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf ball including a molded product obtained from a polybutadiene having a linearity of butadiene rubber molecules, and exhibiting very high resilience.
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 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 insufficient 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 which includes a main rubber containing 10 to 90 mass % of a polybutadiene (a), an unsaturated carboxylic acid and/or a metal salt thereof, and an organic peroxide, wherein the polybutadiene has 60% or more of cis-1,4-bonds, and letting a Mooney viscosity (ML
1+4
(100° C.)) of the polybutadiene be ML and a viscosity of a toluene solution containing 5 mass % of the polybutadiene at 25° C. be (mPa·s), ML and &eegr; satisfy a relationship of &eegr;≧20×ML−600, is advantageous in that a very excellent hot-molded product can be obtained by a synergism effect of the polybutadiene having a very high linearity of rubber molecules and the other components, and that a golf ball having such a hot-molded product has very excellent resilience, thereby increasing the carry of the ball. On the basis of the above knowledge, the present invention has been accomplished.
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, the rubber composition including:
a main rubber containing 10 to 90 mass % of a polybutadiene (a);
an unsaturated carboxylic acid and/or a metal salt thereof; and
an organic peroxide;
wherein the polybutadiene has 60% or more of cis-1,4-bonds; and
letting a Mooney viscosity (ML
1+4
(100° C.)) of the polybutadiene be ML and a viscosity of a toluene solution containing 5 mass % of the polybutadiene at 25° C. be 1(mPa·s), Ml and &eegr; satisfy a relationship of &eegr;≧20×ML−600.
(2) A golf ball according to claim 1, wherein the polybutadiene component (a) is synthesized by using a rare earth element based catalyst.
(3) A golf ball according to claim 1 or 2, wherein the polybutadiene component (a) is synthesized by using a rare earth element based catalyst, and is then reacted with a terminal denaturant.
(4) A golf ball according to any one of claims 1 to 3, wherein the main rubber contains, in addition to the polybutadiene component (a), 90 to 10 mass % of a polybutadiene (b) having a Mooney viscosity of 55 or less.
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 includes a main rubber containing 10 to 90 mass % of a polybutadiene (a), wherein the polybutadiene has 60% or more of cis-1,4-bonds, and letting a Mooney viscosity (ML
1+4
(100° C.)) of the polybutadiene be ML and a viscosity of a toluene solution containing 5 mass % of the polybutadiene at 25° C. be &eegr;(mPa·s), ML and &eegr; satisfy a relationship of &eegr;≧20×ML−600.
The polybutadiene component (a) is required to have 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 polybutadiene component (a) of the present invention is required to be specified such that letting a Mooney viscosity (ML
1+4
(100° C.)) of the polybutadiene be ML and a viscosity of a toluene solution containing 5 mass % of the polybutadiene at 25° C. be &eegr;(mPa·s), ML and &eegr; satisfy a relationship of &eegr;≧20×ML−600, preferably, &eegr;≧20×ML−580, more preferably, &eegr;≧20×ML−560, most preferably, &eegr;≧20×ML−540. Since the polybutadiene with the viscosities &eegr; and ML optimized has a high linearity of polybutadiene molecules, it can give very excellent resilience to a molded-product.
The polybutadiene component (a) of the present invention may be further specified such that the upper limit of the viscosity &eegr; be in a range of &eegr;≦20×ML−100, preferably, &eegr;≦20×ML−150, more preferably, &eegr;≦20×ML−200, most preferably, &eegr;≦20×ML−250.
The viscosity &eegr;(mPa·s) of a toluene solution containing 5 mass % of a polybutadiene at 25° C. used herein is determined by a manner of dissolving 2.28 g of the polybutadiene to be measured in 50 ml of toluene, and measuring a viscosity of the toluene solution under a condition with 25° C. using a viscometer constituting standard solution (JIS Z8809) by a specific viscometer.
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 large rotor (L-type) of the plastimeter, “(1+4)” indicates that a pre-heating time is one minutes and a rotational time of the rotor is four minutes, and “100° C.” indicates a measurement temperature.
The Mooney viscosity [ML
1+4
(100° C.)] of the polybutadiene component (a) is required to be in a range of 20 or more, preferably, 30 or more, more preferably, 40 or more, most preferably, 50 or more, with the upper limit being in a range of 80 or less, preferably, 7
Higuchi Hiroshi
Nanba Atsushi
Bridgestone Sports Co. Ltd.
Chiu Raleigh W.
Duong Tom P
LandOfFree
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