Multi-piece solid golf ball

Abstract

In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the hardness profile at the core interior and the hardness relationships among the various layers are optimized. The ball is endowed with an excellent flight performance on shots with a driver and an excellent controllability in the short game that are acceptable to professionals and other skilled golfers. The ball also has a good feel at impact and an excellent scuff resistance.

1 . A multi-piece solid golf ball comprising a core, an envelope layer encasing the core, an intermediate layer encasing the envelope layer, and a cover which encases the intermediate layer and has formed on a surface thereof a plurality of dimples, wherein the envelope layer is comprised of an inner envelope layer, an intermediate envelope layer and an outer envelope layer; the inner, intermediate and outer envelope layers, the intermediate layer and the cover are each formed primarily of a resin material which may be of the same or different types; the core is formed primarily of a rubber material; the cover has a material hardness (Shore D) and the core has a center hardness (Shore D) and a surface hardness (Shore D) with an arithmetic mean thereof (average core hardness), which cover material hardness and average core hardness satisfy the following condition:
   cover material hardness≦average core hardness;
   one layer from among the envelope layers and the intermediate layer has a material hardness (Shore D) which is higher than either or both of the cover material hardness (Shore D) and the average core hardness (Shore D); and, letting C10 represent a JIS-C cross-sectional hardness at a position 10 mm from a center of the core on a cross-section obtained by cutting the core in half and H represent a JIS-C surface hardness of the core, the hardnesses C10 and H satisfy the following condition:
   10≦( H−C 10)≦30.
 
   
     
     
         2 . The multi-piece solid golf ball of  claim 1 , wherein the intermediate envelope layer is formed so as to be harder than the inner envelope layer and to have a material hardness difference (Shore D) with the inner envelope layer of from 1 to 10, and so as to be softer than the outer envelope layer and to have a material hardness difference (Shore D) with the outer envelope layer of from 1 to 10. 
     
     
         3 . The multi-piece solid golf ball of  claim 1 , wherein the intermediate layer and the cover have thicknesses which satisfy the following condition:
   1.3≦intermediate layer thickness/cover thickness≦4.0.
   
     
     
         4 . The multi-piece solid golf ball of  claim 1 , wherein the inner envelope layer, intermediate envelope layer and outer envelope layer have thicknesses which satisfy the following condition:
   inner envelope layer thickness≦intermediate envelope layer thickness≦outer envelope layer thickness.
   
     
     
         5 . The multi-piece solid golf ball of  claim 1 , wherein the intermediate layer is formed of a material which includes an ionomer resin having an acid content of at least 16 wt %. 
     
     
         6 . The multi-piece solid golf ball of  claim 1 , wherein the core center, outer envelope layer, intermediate layer and cover have hardnesses (Shore D) which satisfy the following condition:
   cover material hardness<intermediate layer material hardness>outer envelope layer material hardness>core center hardness.   
     
     
         7 . The multi-piece solid golf ball of  claim 1 , wherein the core center, inner envelope layer, intermediate envelope layer, outer envelope layer, intermediate layer and cover have hardnesses (Shore D) which satisfy the following condition:
   cover material hardness<intermediate layer material hardness>outer envelope layer material hardness>intermediate envelope layer material hardness>inner envelope layer material hardness>core center hardness.   
     
     
         8 . The multi-piece solid golf ball of  claim 1 , wherein the core, inner envelope layer, intermediate envelope layer, outer envelope layer, intermediate layer and cover have thicknesses which satisfy the following condition:
   cover thickness<intermediate layer thickness<(outer envelope layer thickness+intermediate envelope layer thickness+inner envelope layer thickness)<core diameter.   
     
     
         9 . The multi-piece solid golf ball of  claim 1 , wherein the inner envelope layer, intermediate envelope layer, outer envelope layer, intermediate layer and cover have thicknesses which satisfy the following condition:
   (cover thickness+intermediate layer thickness)<(outer envelope layer thickness+intermediate envelope layer thickness+inner envelope layer thickness).   
     
     
         10 . The multi-piece solid golf ball of  claim 1 , wherein at least one layer from among the inner envelope layer, intermediate envelope layer and outer envelope layer is formed of a material obtained by blending:
 an ionomer resin component of (a) an olefin-unsaturated carboxylic acid random copolymer and/or a metal ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer mixed 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.   
     
     
         11 . The multi-piece solid golf ball of  claim 1 , wherein at least one layer from among the inner envelope layer, intermediate envelope layer and outer envelope layer is formed of a material obtained by blending as essential components:
 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 mixed 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 120 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).   
     
     
         12 . The multi-piece solid golf ball of  claim 11  wherein at least two layers from among the inner envelope layer, intermediate envelope layer and outer envelope layer are formed of the material of  claim 11 . 
     
     
         13 . The multi-piece solid golf ball of  claim 11  wherein the inner envelope layer, intermediate envelope layer and outer envelope layer are all formed of the material of  claim 11 . 
     
     
         14 . The multi-piece solid golf ball of  claim 1 , wherein the core has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load state of 98 N (10 kgf) of at least 1.8 mm but not more than 6.0 mm. 
     
     
         15 . The multi-piece solid golf ball of  claim 1 , wherein the cover is formed by injection molding a resin blend composed primarily of (A) a thermoplastic polyurethane and (B) a polyisocyanate compound, which resin blend contains a polyisocyanate compound in at least some portion of which all the isocyanate groups remain in an unreacted state. 
     
     
         16 . The multi-piece solid golf ball of  claim 1 , wherein, letting C0 represent a JIS-C cross-sectional hardness at the center of the core on a cross-section obtained by cutting the core in half, C4 represent a JIS-C cross-sectional hardness at a position 4 mm from the center of the core, C10 represent a JIS-C cross-sectional hardness at a position 10 mm from the center of the core, and H represent a JIS-C surface hardness of the core, the hardnesses C0, C4, C10 and H satisfy the conditions:
     C 4− C 0≦5,
     3≦ C 10− C 4≦12, and
       C 4− C 0< C 10− C 4< H−C 10.
   
     
     
         17 . The multi-piece solid golf ball of  claim 1 , wherein the core has a single-layer structure.