Multi-piece solid golf ball

Abstract

A multi-piece solid golf ball has a core, an intermediate layer encasing the core, and a cover layer which encases the intermediate layer and has a plurality of dimples on an outer surface thereof. The intermediate layer is formed primarily of a material which includes specific amounts of a fatty acid and/or fatty acid derivative having a molecular weight of from 228 to 1500 and a basic inorganic metal compound capable of neutralizing un-neutralized acid groups per 100 parts by weight of a resin component composed primarily of a specific olefin-unsaturated carboxylic acid copolymer, and in which at least 82 mol % of acid groups in the above components are neutralized. The cover layer is formed of a thermoplastic resin composed primarily of an ionomer resin, and has a Shore D hardness of from 50 to 85. This invention makes it possible to achieve both an increased distance owing to a reduced spin rate, and also an improved durability.

1 . A multi-piece solid golf ball comprising a core, an intermediate layer encasing the core, and a cover layer which encases the intermediate layer and has a plurality of dimples on an outer surface thereof, wherein the intermediate layer is formed primarily of a material which is comprised of:
 100 parts by weight of a resin component composed of, in admixture,
 a base resin of (a) an olefin-unsaturated carboxylic acid random copolymer and/or a metal ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer blended with (b) an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random terpolymer and/or a metal ion neutralization product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random terpolymer in a weight ratio between 100:0 and 0:100, and 
 (e) a non-ionomeric thermoplastic elastomer in a weight ratio between 100:0 and 50:50; 
   (c) from 5 to 150 parts by weight of a fatty acid and/or fatty acid derivative having a molecular weight of from 228 to 1500; and   (d) from 0.1 to 17 parts by weight of a basic inorganic metal compound capable of neutralizing un-neutralized acid groups in the base resin and component (c), and in which at least 82 mol % of acid groups in the base resin and component (c) are neutralized; and wherein the cover layer is formed of a thermoplastic resin composed primarily of an ionomer resin and has a Shore D hardness of from 50 to 85.   
     
     
         2 . The multi-piece solid golf ball of  claim 1 , wherein the ionomer resin in the cover layer includes at least 16 wt % of an unsaturated carboxylic acid, and the cover layer includes from 5 to 35 parts by weight of a granular inorganic filler per 100 parts by weight of the thermoplastic resin. 
     
     
         3 . The multi-piece solid golf ball of  claim 1 , which further comprises, between the core and the intermediate layer, an envelope layer composed primarily of a polyester elastomer. 
     
     
         4 . The multi-piece solid golf ball of  claim 1 , wherein the total number of dimples is from 250 to 342.