Bridgestone Sports Co., Ltd.

Bridgestone Corporation

Yuichiro Ozawa

Tsuyoshi Nakajima

Yusuke Yamagata

Teppei Mori

Takashi Ohira

Takahiro Iwai

Hideo Takeichi

Satoru Tamaki

Hiroshi Higuchi

Hideo Watanabe

Katsunori Sato

Atsushi Komatsu

Hiroshi Nasu

Daisuke Arai

Hirotaka Shinohara

Daisuke Nakajima

Motoki Furuyama

Tasuku Takita

Kae Yamazaki

Kazufumi Tabata

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 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

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 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 having a core and a cover of at least one layer. The core has a cross-sectional hardness which, letting (H) be a JIS-C hardness at a position 14 mm in from a surface toward a center of the core, (H) be a JIS-C hardness at a position 8 mm in from the surface toward the center of the core, (H) be a JIS-C hardness at a position 6 mm in from the surface toward the center of the core, and (H) be a JIS-C hardness at a position 4 mm in from the surface toward the center of the core, satisfies the formulas (1) H&#x3c;70, (2) H&#x3c;72, (3) H&#x3c;75, and (3) H&#x2212;H&#x3e;8.

A golf ball having a good rebound and excellent flight performance can be obtained using a golf ball composition which contains a diene polymer having an aluminum catalyst residue content of not more than 650 ppm.

Golf ball composition and golf ball

A golf ball having a good rebound and excellent flight performance can be obtained using a golf ball composition which includes a diene polymer containing not more than 1.5% of components having a molecular weight of 30,000 or less.

A golf ball having a good rebound and excellent flight performance can be obtained using a golf ball composition which includes a diene polymer having a molecular weight distribution (Mw/Mn) of less than 1.9.

A golf ball endowed with a good rebound and an excellent flight performance can be obtained using a golf ball composition of good workability which contains a diene polymer having a peak top molecular weight (Mp) on a molecular weight distribution curve measured using gel permeation chromatography (GPC) of at least 40&#xd7;10and not more than 100&#xd7;10.

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Chichibushi, Japan

Yuichiro Ozawa