Golf ball

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, an unsaturated fatty acid and/or a metal salt thereof, and an aromatic carboxylic acid and/or a metal salt thereof, the co-cross-linking agent includes an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof, the unsaturated fatty acid and metal salt thereof excludes an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof, and the rubber composition includes a metal compound when the co-cross-linking agent contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms.

What is claimed is: 
     
         1 . A golf ball, comprising:
 a spherical core; and   a cover covering the spherical core,   wherein the spherical core is formed from a rubber composition comprising a base rubber, a co-cross-linking agent, a cross-linking initiator, an unsaturated fatty acid and/or a metal salt thereof, and an aromatic carboxylic acid and/or a metal salt thereof, the co-cross-linking agent comprises at least one of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof, the unsaturated fatty acid and metal salt thereof excludes an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof, and the rubber composition further includes a metal compound when the co-cross-linking agent is consisting of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms.   
     
     
         2 . The golf ball according to  claim 1 , wherein the rubber composition includes the unsaturated fatty acid and/or metal salt thereof and the aromatic carboxylic acid and/or metal salt thereof such that a ratio of a total number of moles of carboxy groups and carboxylate groups in the unsaturated fatty acid and/or metal salt thereof to a total number of moles of carboxy groups and carboxylate groups in the aromatic carboxylic acid and/or metal salt thereof is in a range of 0.01 to 18. 
     
     
         3 . The golf ball according to  claim 1 , wherein the unsaturated fatty acid and/or metal salt thereof has a number of carbon-carbon double bonds per unit mass in a range of 1.00 mmol/g to 10.00 mmol/g. 
     
     
         4 . The golf ball according to  claim 1 , wherein the rubber composition includes the unsaturated fatty acid and/or metal salt thereof and the co-cross-linking agent such that a ratio of a total number of moles carbon-carbon double bonds in the unsaturated fatty acid and/or metal salt thereof to a total number of moles of carbon-carbon double bonds of the co-cross-linking agent is in a range of 0.01 to 0.20. 
     
     
         5 . The golf ball according to  claim 1 , wherein the unsaturated fatty acid and/or metal salt thereof is an unsaturated fatty acid having 4 to 33 carbon atoms and/or a metal salt thereof. 
     
     
         6 . The golf ball according to  claim 1 , wherein the unsaturated fatty acid and/or metal salt thereof is an unsaturated fatty acid having one or two carbon-carbon double bonds and/or a metal salt thereof. 
     
     
         7 . The golf ball according to  claim 1 , wherein the unsaturated fatty acid and/or metal salt thereof is an unsaturated fatty acid having 5 or more carbon atoms and having a first carbon-carbon double bond at a fourth or later carbon atom counted from a carboxy group thereof, and/or a metal salt thereof. 
     
     
         8 . The golf ball according to  claim 1 , wherein the unsaturated fatty acid and/or metal salt thereof is an unsaturated fatty acid of formula (1) and/or a metal salt thereof, 
       
         
           
           
               
               
           
         
       
       where R 1  represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 25 carbon atoms, R 2  represents a substituted or unsubstituted alkylene group having 1 to 25 carbon atoms, R 3  represents a substituted or unsubstituted alkylene group having 2 to 25 carbon atoms, m represents a natural number of 0 to 5, and when m is in a range of 2 to 5, R 2  is identical to or different from each other. 
     
     
         9 . The golf ball according to  claim 1 , wherein the unsaturated fatty acid and/or metal salt thereof is a linear unsaturated fatty acid and/or a metal salt thereof. 
     
     
         10 . The golf ball according to  claim 1 , wherein the unsaturated fatty acid and/or metal salt thereof is at least one of an unsaturated fatty acid having a carbon-carbon double bond at a terminal of a hydrocarbon chain and/or a metal salt thereof, and an unsaturated fatty acid having at least one cis-isomerized carbon-carbon double bond and/or a metal salt thereof. 
     
     
         11 . The golf ball according to  claim 1 , wherein the rubber composition includes the unsaturated fatty acid and/or metal salt thereof in a range of 1 part by mass to 35 parts by mass with respect to 100 parts by mass of the base rubber. 
     
     
         12 . The golf ball according to  claim 1 , wherein the rubber composition includes the co-cross-linking agent comprising the metal salt of the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. 
     
     
         13 . The golf ball according to  claim 1 , wherein the rubber composition has a neutralization degree in a range of 100 mol % to 200 mol %. 
     
     
         14 . The golf ball according to  claim 1 , wherein the rubber composition includes an organic sulfur compound. 
     
     
         15 . The golf ball according to  claim 14 , wherein the organic sulfur compound is at least one compound selected from the group consisting of a thiophenol, a diphenyldisulfide, a thionaphthol, a thiuramdisulfide, and a metal salt thereof. 
     
     
         16 . The golf ball according to  claim 14 , wherein the rubber composition includes the organic sulfur compound in a range of 0.05 parts by mass to 5 parts by mass with respect to 100 parts by mass of the base rubber. 
     
     
         17 . The golf ball according to  claim 1 , wherein the rubber composition includes the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or the metal salt thereof in a range of 15 parts by mass to 50 parts by mass with respect to 100 parts by mass of the base rubber. 
     
     
         18 . The golf ball according to  claim 2 , wherein the unsaturated fatty acid and/or metal salt thereof has a number of carbon-carbon double bonds per unit mass in a range of 1.00 mmol/g to 10.00 mmol/g. 
     
     
         19 . The golf ball according to  claim 2 , wherein the rubber composition includes the unsaturated fatty acid and/or metal salt thereof and the co-cross-linking agent such that a ratio of a total number of moles carbon-carbon double bonds in the unsaturated fatty acid and/or metal salt thereof to a total number of moles of carbon-carbon double bonds of the co-cross-linking agent is in a range of 0.01 to 0.20. 
     
     
         20 . The golf ball according to  claim 2 , wherein the unsaturated fatty acid and/or metal salt thereof is an unsaturated fatty acid having 4 to 33 carbon atoms and/or a metal salt thereof.