Multi-piece solid golf ball

Abstract

In a multi-piece solid golf ball having a core, an intermediate layer and a cover, the ball and the intermediate layer have respective surface hardnesses which are set so as to satisfy a specific relationship. Also, the respective initial velocities measured for the core, a sphere composed of the core over which an envelope layer and the intermediate layer have been formed (intermediate layer-encased sphere) and the ball are set so as to satisfy a specific relationship. In addition, the hardness relationship between the surface and the center of the core has been adjusted in a specific range. This golf ball is able to exhibit an excellent flight performance not only when struck by mid head-speed golfers, but even when struck by low head-speed golfers, in addition to which it has both a good feel at impact and an excellent durability to repeated impact.

1 . A multi-piece solid golf ball comprising a core, an intermediate layer and a cover,
 wherein the ball and the intermediate layer have respective surface hardnesses, expressed in terms of Shore D hardness, which satisfy the relationship:
   ball surface hardness>intermediate layer surface hardness; 
   the core and the ball have respective initial velocities which satisfy the relationship:
   −0.6 m/s≦(ball initial velocity−core initial velocity)≦0 m/s;
 
   a sphere composed of the core covered peripherally by the intermediate layer (intermediate layer-encased sphere) and the ball have respective initial velocities which satisfy the relationship:
   −0.4 m/s≦(ball initial velocity−intermediate layer-encased sphere initial velocity)≦0.4 m/s; and
 
   the core has a surface and a center with respective hardnesses, expressed as JIS-C hardnesses, which satisfy the relationship:
   core surface hardness−core center hardness≧21.
 
   
     
     
         2 . The multi-piece solid golf ball of  claim 1 , further comprising an envelope layer between the core and the intermediate layer. 
     
     
         3 . The multi-piece solid golf ball of  claim 2 , wherein the core, the envelope layer, the intermediate layer and the ball have surface hardnesses which satisfy the relationship:
   ball surface hardness>intermediate layer surface hardness>envelope layer surface hardness<core surface hardness.   
     
     
         4 . The multi-piece solid golf ball of  claim 2 , wherein a sphere composed of the core covered peripherally by the envelope layer (envelope layer-encased sphere) and the intermediate layer-encased sphere have respective initial velocities which satisfy the relationship:
   (intermediate layer-encased sphere initial velocity−envelope layer-encased sphere initial velocity)≧−0.2 m/s.
   
     
     
         5 . The multi-piece solid golf ball of  claim 2 , wherein the core surface hardness and the envelope layer surface hardness, expressed as Shore D hardnesses, satisfy the relationship:
   −40≦(envelope layer surface hardness−core surface hardness)≦−5.
   
     
     
         6 . The multi-piece solid golf ball of  claim 2 , wherein the envelope layer surface hardness and the intermediate layer surface hardness, expressed as Shore D hardnesses, satisfy the relationship:
   10≦(intermediate layer surface hardness−envelope layer surface hardness)≦50.
   
     
     
         7 . The multi-piece solid golf ball of  claim 1 , wherein the intermediate layer surface hardness and the ball surface hardness, expressed as Shore D hardnesses, satisfy the relationship:
   5≦(ball surface hardness−intermediate layer surface hardness)≦20.
   
     
     
         8 . The multi-piece solid golf ball of  claim 2 , wherein the envelope layer-encased sphere and the ball have respective initial velocities which satisfy the relationship:
   0.1 m/s≦(ball initial velocity−envelope layer-encased sphere initial velocity)≦0.8m/s; and
   the core initial velocity and the ball initial velocity satisfy the relationship:
   −0.5 m/s≦(ball initial velocity−core initial velocity)≦0 m/s.
 
   
     
     
         9 . The multi-piece solid golf ball of  claim 1 , wherein the envelope layer, the intermediate layer and the cover have respective thicknesses which satisfy the relationship:
   envelope layer thickness≦intermediate layer thickness≦cover thickness.
   
     
     
         10 . The multi-piece solid golf ball of  claim 1 , wherein the intermediate layer and the cover have respective specific gravities which satisfy the relationship:
   cover specific gravity≧intermediate layer specific gravity.
   
     
     
         11 . The multi-piece solid golf ball of  claim 1 , wherein the intermediate layer is formed of a resin composition obtained by blending as essential components:
 100 parts by weight of a resin component composed of, in admixture,
 (A) a base resin of (a-1) an olefin-unsaturated carboxylic acid random copolymer and/or a metal ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer mixed with (a-2) 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 
 (B) a non-ionomeric thermoplastic elastomer in a weight ratio between 100:0 and 50:50; 
 (C) from 5 to 80 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 components A and C. 
   
     
     
         12 . The multi-piece solid golf ball of  claim 2 , wherein the envelope layer is formed of a thermoplastic polyether ester elastomer. 
     
     
         13 . The multi-piece solid golf ball of  claim 1 , wherein the cover is formed of a resin composition obtained by blending together an ionomer resin and a granular inorganic filler. 
     
     
         14 . The multi-piece solid golf ball of  claim 1 , wherein the core is formed of a material molded under heat from a rubber composition comprising as essential components:
 (A) a base rubber,   (B) an organic peroxide, and   (C) water and/or a metal monocarboxylate.