Dunlop Sports Company Limited

Sumitomo Rubber Industries Limited

Ryota Sakamine

Chiemi Mikura

Kazuyoshi Shiga

Hikaru Nagakura

Ayaka Shindo

Takahiro Shigemitsu

Shun Kurihara

Sho Goji

Hiroshi Tadaoka

Katsumi Terakawa

An object of the present invention is to provide a golf ball having an excellent flight performance on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover covering the spherical core, wherein a hardness difference D1 (H75&#x2212;H0) between a hardness H75 at a point radially located at a distance of 75% from a center of the spherical core and a center hardness H0 of the spherical core is 10 or more and 27 or less in Shore C hardness, and a hardness difference D2 (Hs&#x2212;H75) between a surface hardness Hs of the spherical core and the hardness H75 at the point radially located at the distance of 75% from the center of the spherical core is 0 or more and 6.5 or less in Shore C hardness.

Golf ball

An object of the present invention is to provide a method for obtaining a golf ball having excellent impact durability. The present invention provides a method for producing a golf ball, comprising a first step of kneading (a) a base rubber, (b) an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinkable compound having two or more polymerizable unsaturated bonds in a molecule thereof, and (d) a crosslinking initiator to prepare a core rubber composition; a second step of producing the spherical core from the core rubber composition at a molding temperature in a range from 100&#xb0; C. to 150&#xb0; C.; and a third step of molding the at least one cover layer covering the spherical core on the spherical core.

Method for producing golf ball

An object of the present invention is to provide a golf ball having excellent impact durability. The present invention provides a golf ball comprising a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a core rubber composition containing (a) a base rubber, (b) an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinkable compound having two or more polymerizable unsaturated bonds in the molecule, and (d) a crosslinking initiator.

An object of the present invention is to provide a golf ball having excellent shot feeling on driver shots. The present invention provides a golf ball comprising a core and at least one cover covering the core, wherein the core is formed from a core rubber composition containing (a) a base rubber containing a polybutadiene, (b) an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) a terpene-based resin.

An object of the present invention is to provide a golf ball having excellent resilience. The present invention provides a golf ball comprising a spherical core and at least one cover covering the spherical core, wherein the spherical core is formed from a rubber composition containing (a) a base rubber, and (b) a co-crosslinking agent containing (b1) a carboxylic acid represented by a structural formula (1) and/or a metal salt thereof. [In the formula (1), Ato Aeach independently represents a nitrogen atom or a carbon atom. Xrepresents a single bond or a divalent organic group. Rrepresents a hydrogen atom or a monovalent organic group. It is noted that at least one of Ato Ais the carbon atom, and Xand Rbond to the carbon atom. n represents an integer of 0 to 3. When n is 2 or more, a plurality of Rmay be identical to or different from each other, and a plurality of Rmay bond to each other to form a ring structure.]

An object of the present invention is to provide a golf ball traveling a great flight distance. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the golf ball has a ratio (t2/t1) of a time (t2) to a time (t1) of 1.05 or more in a hitting test using a driver (at a head speed of 40 m/sec), wherein the time (t1) is a time taken from a moment that the driver begins to contact with the golf ball to a moment that the golf ball reaches a maximum deformation amount, and the time (t2) is a time taken from the moment that the golf ball reaches the maximum deformation amount to a moment that the golf ball leaves the driver.

A golf ball includes a spherical core, and a cover covering the spherical core. The spherical core is formed from a rubber composition including a base rubber, a co-cross-linking agent, a cross-linking initiator, and an unsaturated fatty acid and/or a metal salt thereof, the co-cross-linking agent includes &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof, the unsaturated fatty acid and/or metal salt thereof excludes an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof, an unsaturated aliphatic carboxylic acid that forms the unsaturated fatty acid and/or metal salt thereof has a functional group other than a carboxy group and a carbon-carbon unsaturated bond, and the rubber composition further includes a metal compound when the co-cross-linking agent is only an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms.

An object of the present invention is to provide a golf ball having an excellent flight performance on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover covering the spherical core, wherein the spherical core is formed from a rubber composition containing (a) a base rubber, (b) an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d) an unsaturated fatty acid and/or a metal salt thereof excluding an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof, and provided that the rubber composition further contains (f) a metal compound if only an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms is present as (b) the co-crosslinking agent.

An object of the present invention is to provide a golf ball having an excellent initial velocity when being hit at a head speed of 50 m/sec and an improved initial velocity when being hit at a head speed of 40 m/sec. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the golf ball has a rebound equivalence energy ratio (R) ranging from 65.50% to 99.0% at a deformation amount of 7%, and a rebound equivalence energy ratio (R) ranging from 20.0% to 70.0% at a deformation amount of 19%, in a compression test (measurement temperature: &#x2212;70&#xb0; C., compression speed: 30 mm/min) applying a load to the golf ball along a radial direction of the golf ball.

An object of the present invention is to provide a golf ball having an excellent flight performance on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover covering the spherical core, wherein a hardness difference D1 (H75&#x2212;H0) between a hardness H75 at a point located at a distance of 75% of a core radius from a center of the spherical core and a center hardness H0 of the spherical core is 15 or more and 35 or less in Shore C hardness, a hardness difference D2 (Hs&#x2212;H75) between a surface hardness Hs of the spherical core and the hardness H75 at the point located at the distance of 75% of the core radius from the center of the spherical core is &#x2212;1 or more and 3.5 or less in Shore C hardness, and a hardness difference D3 ((H0+H75)/2&#x2212;H37.5) between a hardness of (the center hardness H0 of the spherical core+the hardness H75 at the point located at the distance of 75% of the core radius from the center of the spherical core)/2 and a hardness H37.5 at a point located at a distance of 37.5% of the core radius from the center of the spherical core is 0.5 or more and 6.5 or less in Shore C hardness.

An object of the present invention is to provide a golf ball having a low spin rate on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a rubber composition containing (a) base rubber, (b) an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator and (d) a carboxylic acid having a benzene ring and/or a salt thereof, provided that the rubber composition further contains (e) a metal compound in case of containing only (b) the &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent.

An object of the present invention is to provide a golf ball having an excellent initial velocity when being hit at a head speed of 50 m/sec and an improved initial velocity when being hit at a head speed of 40 m/sec. The present invention provides a golf ball comprising a spherical core and at least one cover covering the spherical core, wherein the spherical core is formed from a core rubber composition containing (a) a base rubber, (b) a co-crosslinking agent, (c) a crosslinking initiator and (x) a crosslinked rubber powder, and (x) the crosslinked rubber powder is formed from a rubber composition containing (a1) a base rubber, (b1) a co-crosslinking agent, (c1) a crosslinking initiator and (r) a resin component.

An object of the present invention is to provide a golf ball showing a great flight distance on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover layer covering the spherical core, wherein when JIS-C hardness of the spherical core is measured at points located at distances of 0% (core center), 37.5%, 75.0% and 100% (core surface) from the core center of the spherical core, a hardness difference (Hs&#x2212;Ho) between a surface hardness (Hs) thereof and a center hardness (Ho) thereof is 20 or more, a ratio ((H&#x2212;Ho)/(H&#x2212;Ho)) of a hardness difference (H&#x2212;Ho) to a hardness difference (H&#x2212;Ho) is 0.6 or less, and a compression deformation amount (D (mm)) of the spherical core and the 37.5% point hardness (H) satisfy a relation of H&#x2266;&#x2212;9&#xd7;D+95.

An object of the present invention is to provide a golf ball traveling a great flight distance. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the golf ball has a ratio (t/t) of a time (t) to a time (t) of 1.05 or more in a hitting test using a driver (at a head speed of 40 m/sec), wherein the time (t) is a time taken from a moment that the driver begins to contact with the golf ball to a moment that the golf ball reaches a maximum deformation amount, and the time (t) is a time taken from the moment that the golf ball reaches the maximum deformation amount to a moment that the golf ball leaves the driver.

A method for manufacturing a golf ball showing a great flight distance on driver shots for includes the steps of: preparing a rubber composition containing a base rubber, an &#x3b1;,&#x3b2;-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, a crosslinking initiator and a carboxylic acid and/or a salt thereof; heat pressing the rubber composition at a press temperature ranging from t-40&#xb0; C. to t-15&#xb0; C. to mold a spherical core, wherein t &#xb0; C. is a one-minute half-life temperature of the crosslinking initiator; and forming at least one cover layer covering the spherical core.

Growing community of inventors

Kobe, Japan

Ryota Sakamine