Golf ball

Abstract

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 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 and (d) a carboxylic acid having 1 to 14 carbon atoms, provided that the rubber composition further contains (e) a metal compound in 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, and (d) a carboxylic acid having 1 to 14 carbon atoms, provided that the rubber composition further contains (e) 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 1 to 14 carbon atoms in a content ranging from 0.5 part to 13 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 1 to 14 carbon atoms in a content ranging from 1.5 part to 11 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 1 to 12 carbon atoms. 
     
     
         5 . The golf ball according to  claim 1 , wherein (d) the carboxylic acid having 1 to 14 carbon atoms is a fatty acid. 
     
     
         6 . The golf ball according to  claim 1 , wherein (d) the carboxylic acid having 1 to 14 carbon atoms is a saturated fatty acid. 
     
     
         7 . The golf ball according to  claim 1 , wherein the spherical core has a hardness difference of 27 or more in JIS-C hardness between a surface hardness and a center hardness thereof. 
     
     
         8 . The golf ball according to  claim 1 , wherein the spherical core has a hardness difference of 30 or more in JIS-C hardness between a surface hardness and a center hardness thereof. 
     
     
         9 . 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 0.95 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. 
     
     
         10 . The golf ball according to  claim 1 , wherein the rubber composition contains a metal salt of (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. 
     
     
         11 . The golf ball according to  claim 1 , wherein the rubber composition further contains (f) an organic sulfur compound. 
     
     
         12 . The golf ball according to  claim 11 , wherein (f) the organic sulfur compound includes thiophenol or a derivative thereof, diphenyl disulfide or a derivative thereof, thionaphthol or a derivative thereof, thiuram disulfide or a derivative thereof, or a metal salt thereof. 
     
     
         13 . The golf ball according to  claim 11 , wherein the rubber composition contains (f) 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. 
     
     
         14 . The golf ball according to  claim 1 , 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.