Patent ID: 7976410
Filing Date: 2011-07-12
Classification: A63B,C08K

Abstract:
1. A multi-piece solid golf ball comprising a core, an inner cover layer and an outer cover layer, wherein the core is made of a material obtained by molding under applied heat a rubber composition comprising (a) a base rubber containing polybutadiene having a stress relaxation time (T80), defined as the time in seconds from the moment when rotor rotation is stopped immediately after measurement of the M 1+4 (100° C.) value (the Mooney viscosity measured at 100° C. in accordance with ASTM D-1646-96) that is required for the ML 1+4 value to decrease 80%, of 3.5 or less, (b) an unsaturated carboxylic acid and/or a metal salt thereof, and (c) an organic peroxide; the inner cover layer has a Shore D hardness of from 50 to 80; the outer cover layer has a Shore D hardness of from 35 to 60 which is lower than the Shore D hardness of the inner cover layer; and the outer cover layer is formed primarily of a resin composition obtained by mixing: 100 parts by weight of a base resin of (A) at least one selected from among olefin unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymers, olefin-unsaturated carboxylic acid binary random copolymers and metal salts thereof having a weight-average molecular weight (Mw) of at least 10,000 but less than 80,000, and (B) at least one selected from among olefin unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymers, olefin-unsaturated carboxylic acid binary random copolymers and metal salts thereof having a weight-average molecular weight (Mw) of at least 80,000 but less than 250,000, in a weight ratio A/B therebetween of from 100/0 to 30/70, with (C) from 0.1 to 10 parts by weight of a basic inorganic metal compound capable of neutralizing acid groups within components A and B.