Golf ball

Abstract

Golf ball 2 has spherical core 4 , mid layer 6 situated on the external side of the core 4 , and cover 8 situated on the external side of the mid layer 6 . The mid layer 6 is constituted with a resin composition. This resin composition contains 100 parts by weight of an ionomer resin (A) and 25 parts by weight or more and 100 parts by weight or less of a fatty acid metal salt (B). This ionomer resin (A) is a neutralized product of a ternary copolymer of ethylene, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α,β-unsaturated carboxylic acid ester, with a metal ion. The fatty acid metal salt (B) has 18 to 30 carbon atoms. The weight Wm of the mid layer 6 is greater than the weight Wc of the cover 8 . The sum (Tm+Tc) of the thickness Tm of the mid layer 6 and the thickness Tc of the cover 8 is 1.0 mm or greater and 3.0 mm or less.

1 . A golf ball comprising a core, a mid layer situated on the external side of the core, and a cover situated on the external side of the mid layer,
 the weight Wm of the mid layer being greater than the weight Wc of the cover,   the sum (Tm+Tc) of the thickness Tm of the mid layer and the thickness Tc of the cover being 1.0 mm or greater and 3.0 mm or less,   the mid layer being constituted with a resin composition,   the resin composition comprising 100 parts by weight of an ionomer resin (A) and 25 parts by weight or more and 100 parts by weight or less of a fatty acid metal salt (B),   the ionomer resin (A) being a neutralized product of a ternary copolymer of ethylene, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α,β-unsaturated carboxylic acid ester, with a metal ion, and   the fatty acid metal salt (B) having 18 to 30 carbon atoms.   
     
     
         2 . The golf ball according to  claim 1 , wherein the difference (Wm−Wc) between the weight Wm and the weight Wc is 0.1 g or greater and 3 g or less. 
     
     
         3 . The golf ball according to  claim 1 , wherein the difference (Gm−Gc) between the specific gravity Gm of the mid layer and the specific gravity Gc of the cover is greater than 0 and no greater than 1.15. 
     
     
         4 . The golf ball according to  claim 1 , wherein the specific gravity Gm of the mid layer is 1.05 or greater and 2.0 or less. 
     
     
         5 . The golf ball according to  claim 1 , wherein the specific gravity Gc of the cover is 0.90 or greater and 1.05 or less. 
     
     
         6 . The golf ball according to  claim 1 , wherein the volume Vm of the mid layer is less than the volume Vc of the cover. 
     
     
         7 . The golf ball according to  claim 6 , wherein the difference (Vc−Vm) between the volume Vc and the volume Vm is no less than 0.1 cm 3 . 
     
     
         8 . The golf ball according to  claim 1 , wherein:
 the metal ion of the ionomer resin (A) is a magnesium ion, a zinc ion or a sodium ion;   the fatty acid component of the fatty acid metal salt (B) is stearic acid, behenic acid or montanic acid; and   the metal ion of the fatty acid metal salt (B) is a magnesium ion, a calcium ion or a barium ion.   
     
     
         9 . The golf ball according to  claim 1 , wherein the Shore D hardness Hm of the mid layer is 30 or greater and 60 or less. 
     
     
         10 . The golf ball according to  claim 1 , wherein the resin composition of the mid layer has a melt flow rate of 1.0 g/10 min or greater and 50 g/10 min or less. 
     
     
         11 . The golf ball according to  claim 1 , wherein the resin composition of the mid layer has a modulus of flexural rigidity of 100 MPa or greater and 300 MPa or less. 
     
     
         12 . The golf ball according to  claim 1 , wherein the resin composition of the mid layer has a modulus of impact resilience of no less than 40%. 
     
     
         13 . The golf ball according to  claim 1 , wherein the ratio (Pn 2 /Pn 1 ) of the degree of neutralization Pn 2  of the resin composition of the mid layer to the degree of neutralization Pn 1  of the ionomer resin (A) not mixed with the fatty acid metal salt (B) is no less than 1.2. 
     
     
         14 . The golf ball according to  claim 1 , wherein the difference (Hs−Ho) between the JIS-C hardness Hs of the surface of the core and the JIS-C hardness Ho of the central point of the core is no less than 20. 
     
     
         15 . The golf ball according to  claim 1 , wherein the JIS-C hardness Ho of the central point of the core is 25 or greater and 70 or less. 
     
     
         16 . The golf ball according to  claim 1 , wherein the JIS-C hardness Hs of the surface of the core is 60 or greater and 95 or less. 
     
     
         17 . The golf ball according to  claim 1 , wherein the core has a specific gravity of 1.00 or greater and 1.20 or less. 
     
     
         18 . The golf ball according to  claim 1 , wherein the thickness Tc of the cover is no greater than 2.0 mm. 
     
     
         19 . The golf ball according to  claim 1 , wherein the Shore D hardness of the cover is 50 or greater and 75 or less. 
     
     
         20 . The golf ball according to  claim 1 , wherein the core has a center, and an envelope layer situated on the external side of the center.