Bridgestone Sports Co., Ltd.

Bridgestone Corporation

Tsuyoshi Nakajima

Yuichiro Ozawa

Yusuke Yamagata

Teppei Mori

Takashi Ohira

Takahiro Iwai

Hideo Takeichi

Satoru Tamaki

Hideo Watanabe

Jun Shindo

Daisuke Nakajima

Hiroshi Higuchi

Atsuki Kasashima

Akira Kimura

Eiji Takehana

Takuma Nakagawa

Toru Ogawana

Takanori Tago

Kae Yamazaki

Kazufumi Tabata

Ryota Nakamura

Kae Ilzuka

A method of manufacturing golf balls having a core and a cover of at least one layer encasing the core includes the steps of producing a core by molding and vulcanizing a rubber composition containing (A) a base rubber, (B) an &#x3b1;,&#x3b2;-unsaturated carboxylic acid and/or a metal salt thereof, and (C) an organic peroxide; and heat-treating the core for 1 to 24 hours at between 175 and 300&#xb0; C. Golf balls which undergo little energy loss and have a high initial velocity can be obtained by this method.

Golf ball manufacturing method

The invention provides a golf ball having a core and a cover of one or more layer encasing the core, wherein the core has a center core and a foamed outer layer that directly, or indirectly through another layer, envelops the center core. The foamed outer layer is made of a rubber composition that includes a base rubber, a co-crosslinking agent and an organic peroxide. The foamed outer layer has an inside portion facing the ball center and an outside portion facing the outside of the ball that are unfoamed regions, and contains a foamed region in an intermediate portion therebetween. A method of manufacturing such a golf ball is also provided.

Golf ball and method of manufacturing the same

The invention provides a golf ball having a core and a cover of one layer or a plurality of layers, wherein the core is formed of a material molded under heat from a rubber composition containing (A) a base rubber, (B) an organic peroxide, and (C) water and/or a metal monocarboxylate, and has a hysteresis loss of 50% or less when compressed at a load cell speed of 500 mm/min and under a constant load of 5,000 N.

Golf ball

In a multi-piece solid golf ball which includes a core of at least one layer, a cover of at least one layer, and at least one intermediate layer interposed between the core and the cover, the cover is composed primarily of polyurethane and the following parameters are controlled within specific ranges: core deflection, melt flow rate of intermediate layer material, thickness of intermediate layer, thickness and Shore D hardness of cover, combined thickness of intermediate layer and cover, and the value of (Shore D hardness of cover material)&#x2212;(Shore D hardness of intermediate layer material). This golf ball has a good, soft feel at impact and lowers the rate of spin on full shots, achieving a good distance.

Multi-piece solid golf ball

A rubber composition for golf balls includes (A) a base rubber, (B) two different metal salts of &#x3b1;,&#x3b2;-unsaturated carboxylic acids having 3 to 8 carbon atoms, (C) a metal salt in which at least one bonding site is a fatty acid of 9 or more carbon atoms, and (D) a crosslinking initiator. Letting component (B) include (B-1) an unsaturated metal carboxylate in a high compounding weight and (B-2) an unsaturated metal carboxylate in a low compounding weight, the ratio (B-2)/(B-1) is from 4 to 20 wt % and the ratio (B-2)/(C) is from 20 to 115 wt %. By using this rubber composition in a golf ball core, the golf ball can be endowed with both good spin properties and good durability on impact.

Rubber composition for golf ball, and golf ball

The invention provides a golf ball having a core and a cover of one layer or a plurality of layers, the core being formed of a material molded under heat from a rubber composition containing: (A) a base rubber, (B) an organic peroxide, and (C) water and/or a metal monocarboxylate. The core has a hardness profile which satisfies specific relationships between the JIS-C hardness at the core center (Cc), the JIS-C hardness at a position 10 mm from the core center (C10) and the JIS-C hardness at the core surface (Cs).

The invention provides a golf ball having a core and a cover of one or more layer encasing the core, wherein the core is formed of a rubber composition that includes a base rubber, a co-crosslinking agent and an organic peroxide. The core has a center portion and a surface portion that are unfoamed regions, and has an intermediate portion that contains a foamed region. A method of manufacturing such a golf ball is also provided.

Golf ball and method of manufacture

The invention provides a golf ball having a core and a cover of one layer or a plurality of layers, the core being formed of a material molded under heat from a rubber composition which includes (A) a base rubber, (B) an organic peroxide, and (C) water and/or a metal monocarboxylate. The product P&#xd7;E of the difference P (mol/m) in crosslink density between the core surface and the core center, as measured based on a toluene swelling test, multiplied by the deflection E (mm) of the core when compressed under a final load of 1,275 N (130 kgf) from an initial load state of 98 N (10 kgf) is at least 28&#xd7;10mol/m&#xb7;mm.

Golf ball having a core and a cover of one or more layers, the core being formed of a material molded under heat from a rubber composition including a base rubber, an organic peroxide, and water and/or a metal monocarboxylate. Defining the tan &#x3b4; slope as (tan &#x3b4;&#x2212;tan &#x3b4;)/(10%&#x2212;1%), where tan &#x3b4;and tan &#x3b4;are the loss tangents at dynamic strains of, respectively, 1% and 10% when the loss tangents of the core center and the core surface are measured at &#x2212;12&#xb0; C. and 15 Hz, the difference between the tan &#x3b4; slopes at the core surface and the core center is larger than 0.002. Because a core material which undergoes little decrease in resilience over time and experiences little energy loss can be obtained, the golf ball maintains a good rebound, has a reduced spin rate and thus is able to achieve an increased distance.

The invention provides a golf ball that is a one-piece golf ball or a golf ball having a core and a cover of one layer or a plurality of layers, wherein the one-piece golf ball or core is formed of a material molded under heat from a rubber composition containing: The content of component (D) per 100 parts by weight of component (A) is from 30 to 45 parts by weight. The molar ratio (C)/(D) between components (C) and (D) satisfies the formula0.9&#x3c;()/()&#x3c;1.1. The core has an initial velocity Vof at least 72.0 m/s and up to 75.0 m/s.

In a golf ball having, in order, a core, an envelope layer, an intermediate layer and a cover, the following conditions are satisfied: The ball provides an excellent flight performance when struck by the average golfer, a feel that is both soft and solid, and an excellent durability to repeated impact.

The invention provides a golf ball having a core and a cover of at least one layer. The core has a cross-sectional hardness which, letting R (mm) be the radius of the core, A be the JIS-C hardness at a center of the core, B be the JIS-C hardness at a position R/3 mm from the core center, C be the JIS-C hardness at a position R/1.8 mm from the core center, D be the JIS-C hardness at a position R/1.3 mm from the core center, and E be the JIS-C hardness at a surface of the core, satisfies the formulas (1) D&#x2212;C&#x2267;7, (2) C&#x2212;B&#x2266;7, (3) (D&#x2212;C)&#x2212;(C&#x2212;B)&#x2267;7, and (4) E&#x2212;A&#x2267;16.

In a golf ball having a core and a cover, the core is formed of a rubber composition, has center and surface portions which are unfoamed regions and has an intermediate portion containing a foamed region. The core is produced by charging the rubber composition, which contains a blowing agent, into a first curing mold and curing under given conditions, then removing the molded rubber material in a semi-cured state from the first mold, transferring the semi-cured material to a second curing mold and curing under given conditions. The foamed region of the core deforms by a certain degree at the time of impact, decreasing the radius of gyration of the ball and enabling a lower spin rate to be achieved. The decrease in resilience due to expansion of the molded material can be held to a minimum.

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Chichibushi, Japan

Tsuyoshi Nakajima