Golf ball, golf ball cover material composition and method of manufacturing the composition

Abstract

A golf ball whose core is covered with a cover, wherein the core is constituted of a rubber composition containing polybutadiene rubber and the cover is constituted of a resin composition composed of ionomer resin and diene rubber. A golf ball cover material composition composed of ionomer resin, diene rubber and non-staining antioxidant. A method of manufacturing a golf ball cover material composition constituted by mixing/kneading ionomer resin and diene rubber.

What is claimed is:  
     
         1 . A golf ball whose core is covered with a cover, wherein a ratio of flexural rigidity value of said golf ball to flexural rigidity value of said core is 1.8 or more and less than 3.0, and a thickness of said cover is 1.7 to 2.6 mm.  
     
     
         2 . The golf ball according to  claim 1 , wherein Young's modulus of elasticity of said cover is 100 to 200 MPa.  
     
     
         3 . The golf ball according to  claim 1 , wherein said coyer is composed of a composition, containing ionomer resin and diene rubber, in which the diene rubber is dispersed in the ionomer resin in such a manner that it has a particle diameter of 5 μm or less.  
     
     
         4 . A golf ball whose core is covered with a cover, wherein a ratio of compression value of said golf ball to compression value of said core is 1.2 or more and less than 1.5, and hardness of said cover is Shore D hardness of 62 or less.  
     
     
         5 . The golf ball according to  claim 4 , wherein said cover is composed of the composition, containing 50 to 90 parts by weight of ionomer resin of Shore D hardness of 55 or more and less than 80 and 10 to 50 parts by weight of diene rubber, in which the diene rubber is dispersed in the ionomer resin in such a manner that it has the particle diameter of 5 μm or less.  
     
     
         6 . The golf ball according to  claim 5 , wherein said diene rubber is thermally crosslinked without the use of crosslinking agent.  
     
     
         7 . A golf ball having a core and a cover covering said core, wherein said core is constituted of a rubber composition which is compounded of 100 parts by weight of matrix rubber containing polybutadiene rubber having 40% or more of cis-1,4-structure and 20 to 40 parts by weight of unsaturated carboxylic acid metal salt having an average particle size of 5.0 μm or less, and said cover is constituted of a resin composition which is composed of ionomer resin and diene rubber dispersed in the ionomer resin and which has Shore D hardness of 65 or less.  
     
     
         8 . The golf ball according to  claim 7 , wherein the average particle size of said unsaturated carboxylic acid metal salt is 2.0 to 3.5 μm.  
     
     
         9 . The golf ball according to  claim 7 , wherein said unsaturated carboxylic acid metal salt is zinc diacrylate and/or zinc dimethacrylate.  
     
     
         10 . The golf ball according to  claim 7 , wherein 10 to 30 parts by weight of barium sulfate are further blended with said rubber composition.  
     
     
         11 . The golf ball according to  claim 7  wherein said diene rubber is thermally crosslinked without the use of crosslinking agent.  
     
     
         12 . The golf ball according to  claim 7 , wherein Shore D hardness of said cover is 45 to 62.  
     
     
         13 . A golf ball cover material composition, wherein said composition is composed of 50 to 90 parts by weight of ionomer resin, 10 to 50 parts by weight of diene rubber and 0.1 to 5 parts by weight of non-staining antioxidant, the diene rubber is dispersed in the ionomer resin, and the dispersed diene rubber has a particle diameter of 5.0 um or less.  
     
     
         14 . The golf ball cover material composition according to  claim 13 , wherein said diene rubber is thermally crosslinked without the use of crosslinking agent.  
     
     
         15 . The golf ball cover material composition according to  claim 13 , wherein Shore D hardness of said ionomer resin is equal to or more than 55 and less than 80.  
     
     
         16 . The golf ball cover material composition according to  claim 13 , wherein said non-staining antioxidant is phenol antioxidant and/or phosphite antioxidant.  
     
     
         17 . A method of manufacturing a golf ball cover material composition of  claim 13 , wherein 50 to 90 parts by weight of ionomer resin, 10 to 50 parts by weight of diene rubber and 0.1 to 5 parts by weight of non-staining antioxidant are kneaded at a temperature between 130 to 260° C. with the air shut out.  
     
     
         18 . A golf ball whose core is covered with the golf ball cover material composition of  claim 13 .  
     
     
         19 . A method of manufacturing a golf ball cover material composition constituted by kneading ionomer resin and diene rubber and dispersing the diene rubber in the ionomer resin, wherein the ionomer resin and the diene rubber are previously mixed, at a weight ratio (ionomer resin/diene rubber) ranging from 9/1 to 5/5, at such a temperature at which the diene rubber is not crosslinked, and then a resultant mixture is kneaded at such a temperature at which the diene rubber is crosslinked.  
     
     
         20 . The method according to  claim 19 , wherein said previous mixing at the non-crosslinking temperature is performed by a batch mixer at the temperature of 100° C. or more and less than 150° C., and said kneading at the crosslinking temperature is performed by a biaxial extruder at the temperature of 150° C. or more and less than 260° C.  
     
     
         21 . The method according to  claim 19 , wherein Shore D hardness of said ionomer resin is equal to or more than 55 and less than 80.  
     
     
         22 . A golf ball whose core is covered with the golf ball cover material composition obtained by the manufacturing method of  claim 19 .  
     
     
         23 . A method of manufacturing a golf ball cover material composition constituted by kneading ionomer resin and diene rubber and dispersing the diene rubber in the ionomer resin, wherein pellets of the diene rubber whose surface is sprinkled with ionomer resin powder is mixed with the pellets of the ionomer resin, and then a resultant mixture is kneaded at such a temperature at which the diene rubber is crosslinked.  
     
     
         24 . The method according to  claim 23 , wherein said pellets of the diene rubber whose surface is sprinkled with the ionomer resin powder is constituted by mixing one part by weight or more of the ionomer resin powder with one part by weight of the pelletized diene rubber.  
     
     
         25 . The method according to  claim 23 , wherein said kneading at the crosslinking temperature is performed by the twin-screw extruder at the temperature of 150° C. or more and less than 260° C.  
     
     
         26 . The method according to  claim 23 , wherein Shore D hardness of said ionomer resin is equal to or more than 55 and less than 80.  
     
     
         27 . A golf ball whose core is covered with the golf ball cover material composition obtained by the manufacturing method of  claim 23 .  
     
     
         28 . A method of manufacturing a golf ball cover material composition constituted by kneading ionomer resin and diene rubber and dispersing the diene rubber in the ionomer resin, wherein the pellets of the mixture of the ionomer resin powder and the diene rubber is mixed with the pellets of the ionomer resin, and then the resultant mixture is kneaded at such a temperature at which the diene rubber is crosslinked.  
     
     
         29 . The method according to  claim 28 , wherein said kneading at the crosslinking temperature is performed using a twin-screw extruder at the temperature of 150° C. or more and less than 260° C.  
     
     
         30 . The method according to  claim 28 , wherein Shore ‘D’ hardness of said ionomer resin is equal to or more than 55 and less than 80.  
     
     
         31 . A golf ball whose core is covered with the golf ball cover material composition obtained by the manufacturing method of  claim 28 .  
     
     
         32 . A golf ball having a core applied with a cover, wherein the cover has a Shore D hardness (A) of 63 or below and the golf ball has a compression value (B), the Shore D hardness (A) of the cover having a ratio to the compression value (B) of the golf ball, (A)/(B), within a range of 0.49 to 0.6.  
     
     
         33 . A golf ball as claimed in  claim 32 , wherein said cover has a thickness within a range of 2.0 to 2.4 mm.  
     
     
         34 . A golf ball as claimed in  claim 32 , wherein said cover comprises a thermoplastic elastomer composition containing an ionomer resin and a diene rubber.  
     
     
         35 . A golf ball as claimed in  claim 32 , wherein said cover comprises a diene rubber dispersed in a continuous phase comprising an ionomer resin, the diene rubber being thermally crosslinked without the use of a crosslinking agent.