Golf ball

Abstract

The present invention provides 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) an acid and/or a salt thereof, 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, wherein (d) the acid and/or the salt thereof has a relative solubility parameter to (a) the base rubber and (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or the metal salt thereof ranging from 0.45 to 1.10.

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) an acid and/or a salt thereof, 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, wherein (d) the acid and/or the salt thereof has a relative solubility parameter ranging from 0.45 to 1.10 to (a) the base rubber and (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or the metal salt thereof. 
     
     
         2 . The golf ball according to  claim 1 , wherein (d) the acid and/or the salt thereof has a relative solubility parameter of 0.48 or more. 
     
     
         3 . The golf ball according to  claim 1 , wherein (d) the acid and/or the salt thereof has a relative solubility parameter of 0.52 or more. 
     
     
         4 . The golf ball according to  claim 1 , wherein (d) the acid and/or the salt thereof has a relative solubility parameter of 1.05 or less. 
     
     
         5 . The golf ball according to  claim 1 , wherein (d) the acid and/or the salt thereof has a proton bond dissociation energy of 270 kcal/mole or less. 
     
     
         6 . The golf ball according to  claim 1 , wherein (d) the acid and/or the salt thereof is a carboxylic acid and/or a salt thereof. 
     
     
         7 . The golf ball according to  claim 1 , wherein the rubber composition contains (d) the acid and/or the salt thereof in a content of 2 parts by mass or more and less than 40 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         8 . The golf ball according to  claim 1 , wherein the rubber composition further contains (f) an organic sulfur compound. 
     
     
         9 . The golf ball according to  claim 8 , wherein (f) the organic sulfur compound includes at least one compound selected from the group consisting of thiophenols, diphenyl disulfides, thionaphthols, thiuram disulfides, and metal salts thereof. 
     
     
         10 . The golf ball according to  claim 8 , 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. 
     
     
         11 . 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 by mass to 50 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 the metal salt of (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent. 
     
     
         13 . The golf ball according to  claim 1 , wherein the spherical core has a hardness difference of 20 or more in JIS-C hardness between a surface hardness and a center hardness thereof. 
     
     
         14 . 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 0.93 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. 
     
     
         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, and (d) a carboxylic acid and/or a salt thereof, 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, wherein (d) the carboxylic acid and/or the salt thereof has a relative solubility parameter ranging from 0.48 to 1.05 to (a) the base rubber and (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or the metal salt thereof. 
     
     
         16 . The golf ball according to  claim 15 , wherein (d) the carboxylic acid and/or the salt thereof has a proton bond dissociation energy of 270 kcal/mole or less. 
     
     
         17 . The golf ball according to  claim 15 , wherein the rubber composition contains (d) the carboxylic acid and/or the salt thereof in a content of 2 parts by mass or more and less than 40 parts by mass with respect to 100 parts by mass of (a) the base rubber. 
     
     
         18 . The golf ball according to  claim 15 , wherein the rubber composition further contains (f) an organic sulfur compound. 
     
     
         19 . The golf ball according to  claim 15 , wherein (d) the carboxylic acid and/or the salt thereof includes at least one compound selected from the group consisting of 4-acetoxybenzoic acid, dimethylaminobenzoic acid, benzoic acid, cyclohexane carboxylic acid, suberic acid, dodecanedioic acid, octanoic acid, 2-propylpentanoic acid, neodecanoic acid, lauric acid, decanoic acid, chlorobenzoic acid, myristic acid and salts thereof.