Abstract: 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?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?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.

Abstract: A pressurizing device is used for manufacturing a fiber-reinforced resin pipe from a pipe-shaped laminate body prepreg sheets, and comprises a tubular main body. The tubular main body is provided with a helical cut extending helically in the axial direction so as to have a helical cut portion made of a metal. The helical cut portion is arranged inside or outside of the pipe-shaped laminate body. The helical cut portion changes its outer diameter and inner diameter to press the laminate body when a torsional moment and/or a force in the axial direction is applied thereto.

Abstract: 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 ?,?-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° C. to 150° C.; and a third step of molding the at least one cover layer covering the spherical core on the spherical core.

Abstract: 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 ?,?-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.

Abstract: 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 ?,?-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.

Abstract: 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), A1 to A4 each independently represents a nitrogen atom or a carbon atom. X1 represents a single bond or a divalent organic group. R1 represents a hydrogen atom or a monovalent organic group. It is noted that at least one of A1 to A4 is the carbon atom, and X1 and R1 bond to the carbon atom. n represents an integer of 0 to 3. When n is 2 or more, a plurality of R1 may be identical to or different from each other, and a plurality of R1 may bond to each other to form a ring structure.

Abstract: 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.

Abstract: 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 ?,?-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.

Abstract: 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 ?,?-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 ?,?-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 ?,?-unsaturated carboxylic acid having 3 to 8 carbon atoms.

Abstract: 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), A1 to A4 each independently represents a nitrogen atom or a carbon atom. X1 represents a single bond or a divalent organic group. R1 represents a hydrogen atom or a monovalent organic group. It is noted that at least one of A1 to A4 is the carbon atom, and X1 and R1 bond to the carbon atom. n represents an integer of 0 to 3. When n is 2 or more, a plurality of R1 may be identical to or different from each other, and a plurality of R1 may bond to each other to form a ring structure.

Abstract: 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 ?,?-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 ?,?-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 ?,?-unsaturated carboxylic acid having 3 to 8 carbon atoms is present as (b) the co-crosslinking agent.

Abstract: 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 ?,?-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.

Abstract: 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 ?,?-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° C. to 150° C.; and a third step of molding the at least one cover layer covering the spherical core on the spherical core.

Abstract: 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 (R40) ranging from 65.50% to 99.0% at a deformation amount of 7%, and a rebound equivalence energy ratio (R50) ranging from 20.0% to 70.0% at a deformation amount of 19%, in a compression test (measurement temperature: ?70° C., compression speed: 30 mm/min) applying a load to the golf ball along a radial direction of the golf ball.

Abstract: 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?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?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 ?1 or more and 3.5 or less in Shore C hardness, and a hardness difference D3 ((H0+H75)/2?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.

Abstract: 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?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?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 ?1 or more and 3.5 or less in Shore C hardness, and a hardness difference D3 ((H0+H75)/2?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.

Abstract: 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 ?,?-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 ?,?-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 ?,?-unsaturated carboxylic acid having 3 to 8 carbon atoms.

Abstract: 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?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?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.

Abstract: 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.

Abstract: 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 ?,?-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 ?,?-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent.