Golf ball

Abstract

An object of the present invention is to provide a golf ball traveling 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 the spherical core is formed from a rubber composition containing (a) base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, (d) a carboxylic acid having 4 to 30 carbon atoms and/or a salt thereof, and (e) a halogen-substituted thiophenol and/or a metal salt thereof as an organic sulfur compound, provided that the rubber composition further contains (f) a metal compound in the case of containing only (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent.

1 . A golf ball having 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) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, (d) a carboxylic acid having 4 to 30 carbon atoms and/or a salt thereof, and (e) a halogen-substituted thiophenol and/or a metal salt thereof as an organic sulfur compound, provided that the rubber composition further contains (f) a metal compound in the case of containing only (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent. 
     
     
         2 . The golf ball according to  claim 1 , wherein the rubber composition contains (d) the carboxylic acid having 4 to 30 carbon atoms and/or the salt thereof in a content ranging from 0.5 part to 40 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         3 . The golf ball according to  claim 1 , wherein the rubber composition contains (d) the carboxylic acid having 4 to 30 carbon atoms and/or the salt thereof in a content ranging from 5.0 parts to 40 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         4 . The golf ball according to  claim 1 , wherein the rubber composition contains (d) the carboxylic acid having 4 to 30 carbon atoms and/or the salt thereof in a content ranging from 10.0 parts to 40 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         5 . The golf ball according to  claim 1 , wherein (d) the carboxylic acid having 4 to 30 carbon atoms and/or the salt thereof is a fatty acid and/or a fatty acid salt. 
     
     
         6 . The golf ball according to  claim 1 , wherein (d) the carboxylic acid having 4 to 30 carbon atoms and/or the salt thereof is a carboxylic acid having 15 to 30 carbon atoms and/or the salt thereof. 
     
     
         7 . The golf ball according to  claim 1 , wherein (e) the organic sulfur compound is a thiophenol substituted with at least one halogen. 
     
     
         8 . The golf ball according to  claim 1 , wherein (e) the organic sulfur compound is a thiophenol substituted with 1 to 4 halogen. 
     
     
         9 . The golf ball according to  claim 1 , wherein the halogen is chlorine. 
     
     
         10 . The golf ball according to  claim 1 , wherein (e) the organic sulfur compound includes 2,6-dichlorothiophenol or 2,4,5-trichlorothiophenol. 
     
     
         11 . The golf ball according to  claim 1 , wherein the rubber composition contains (e) the organic sulfur compound in a content ranging from 0.05 part to 5 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         12 . The golf ball according to  claim 1 , wherein the rubber composition contains (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or the metal salt thereof in a content ranging from 15 parts to 50 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         13 . The golf ball according to  claim 1 , wherein the spherical core is such that R 2  of a linear approximation curve obtained from a least square method is 0.90 or higher, when JIS-C hardness, which is measured at nine points obtained by dividing a radius of the spherical core into equal parts having 12.5% intervals therebetween, is plotted against distance (%) from a core center. 
     
     
         14 . The golf ball according to  claim 1 , wherein the spherical core has a hardness difference between a surface hardness and a center hardness of 25 or more and 80 or less in JIS-C hardness. 
     
     
         15 . A golf ball having 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) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, (d) a carboxylic acid having 15 to 30 carbon atoms and/or a salt thereof, and (e) a bromine or chlorine-substituted thiophenol and/or a metal salt thereof as an organic sulfur compound, provided that the rubber composition further contains (f) a metal compound in the case of containing only (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent, wherein the rubber composition contains (d) the carboxylic acid having 15 to 30 carbon atoms and/or the salt thereof in a content ranging from 5.0 parts to 40 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         16 . The golf ball according to  claim 15 , wherein the spherical core is such that R 2  of a linear approximation curve obtained from a least square method is 0.90 or higher, when JIS-C hardness, which is measured at nine points obtained by dividing a radius of the spherical core into equal parts having 12.5% intervals therebetween, is plotted against distance (%) from a core center. 
     
     
         17 . The golf ball according to  claim 16 , wherein the spherical core has a hardness difference between a surface hardness and a center hardness of 25 or more and 80 or less in JIS-C hardness. 
     
     
         18 . The golf ball according to  claim 17 , wherein the spherical core is such that R 2  of a linear approximation curve obtained from a least square method is 0.95 or higher.