Multi-piece solid golf ball

Abstract

A multi-piece solid golf ball has a core, an envelope layer encasing the core, an intermediate layer encasing the envelope layer, and an outer layer which encases the intermediate layer and has formed on a surface thereof a plurality of dimples. The core is made of an elastomer. The envelope layer is formed of an inner envelope layer and an outer envelope layer, and the intermediate layer is formed of an inner intermediate layer and an outer intermediate layer. The outer layer has a hardness which is higher than the average core hardness, and each of the envelope layers and the intermediate layers is softer than the outer layer.

1 . A multi-piece solid golf ball comprising a core, an envelope layer encasing the core, an intermediate layer encasing the envelope layer, and an outer layer which encases the intermediate layer and has formed on a surface thereof a plurality of dimples, wherein the core is made of an elastomer; the envelope layer is formed of an inner envelope layer and an outer envelope layer; the intermediate layer is formed of an inner intermediate layer and an outer intermediate layer; letting the average hardness of the core be expressed by the following formula:
   average core hardness (Shore D)=[core surface hardness (Shore D)+core center hardness (Shore D)]/2,   
       the outer layer has a hardness (Shore D) which is higher than the average core hardness; 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 condition:
   10≦(H−C10)≦30;
 
 
       and each of the envelope layers and the intermediate layers is softer than the outer layer. 
     
     
         2 . The multi-piece solid golf ball of  claim 1 , wherein the envelope layers, the intermediate layers and the outer layer have Shore D hardnesses which satisfy the following relationship:
   outer layer hardness>outer intermediate layer hardness>inner intermediate layer hardness>outer envelope layer hardness>inner envelope layer hardness.   
     
     
         3 . The multi-piece solid golf ball of  claim 1 , wherein the core, the envelope layers, the intermediate layers and the outer layer have Shore D hardnesses which satisfy the following five relationships:
   3≦(outer layer hardness−outer intermediate layer hardness)≦20,
     1≦(outer intermediate layer hardness−inner intermediate layer hardness)≦10,
     1≦(inner intermediate layer hardness−outer envelope layer hardness)≦10,
     1≦(outer envelope layer hardness−inner envelope layer hardness)≦10, and
     5≦(outer layer hardness−average core hardness)≦40.
   
     
     
         4 . The multi-piece solid golf ball of  claim 1 , wherein the envelope layers, the intermediate layers and the outer layer have thicknesses which satisfy the following relationships:
   0.1≦outer layer thickness/(outer intermediate layer thickness+inner intermediate layer thickness+outer envelope layer thickness+inner envelope layer thickness)≦1, and
     1.0 mm≦(outer intermediate layer thickness+inner intermediate layer thickness+outer envelope layer thickness+inner envelope layer thickness)≦10 mm.
   
     
     
         5 . The multi-piece solid golf ball of  claim 1 , wherein the outer layer is formed of a material composed primarily of an ionomer, and the outer layer material includes one or more type of ionomer resin having an acid content of at least 16 wt %. 
     
     
         6 . The multi-piece solid golf ball of  claim 1 , wherein the core, envelope layers, intermediate layers and outer layer have Shore D hardnesses which satisfy the following relationship:
   outer layer hardness>outer intermediate layer hardness>inner intermediate layer hardness>outer envelope layer hardness>inner envelope layer hardness>core center hardness.   
     
     
         7 . The multi-piece solid golf ball of  claim 1 , wherein the envelope layers, intermediate layers and outer layer have thicknesses which satisfy the following relationship:
   outer layer thickness≦(outer intermediate layer thickness+inner intermediate layer thickness+outer envelope layer thickness+inner envelope layer thickness)<core diameter.
   
     
     
         8 . The multi-piece solid golf ball of  claim 1 , wherein at least one layer from among the inner envelope layer, outer envelope layer, inner intermediate layer and outer intermediate 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.   
     
     
         9 . The multi-piece solid golf ball of  claim 1 , wherein at least one layer from among the inner envelope layer, outer envelope layer, inner intermediate layer and outer intermediate layer is formed of a material obtained by blending, as essential ingredients:
 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).   
     
     
         10 . The multi-piece solid golf ball of  claim 9 , wherein at least two layers from among the inner envelope layer, outer envelope layer, inner intermediate layer and outer intermediate layer are formed of the material of  claim 9  which is composed of, as essential ingredients, components (a) to (e). 
     
     
         11 . The multi-piece solid golf ball of  claim 9 , wherein at least three layers from among the inner envelope layer, outer envelope layer, inner intermediate layer and outer intermediate layer are formed of the material of  claim 9  which is composed of, as essential ingredients, components (a) to (e). 
     
     
         12 . The multi-piece solid golf ball of  claim 9 , wherein the inner envelope layer, outer envelope layer, inner intermediate layer and outer intermediate layer are all formed of the material of  claim 9  which is composed of, as essential ingredients, components (a) to (e). 
     
     
         13 . The multi-piece solid golf ball of  claim 1 , wherein the core, envelope layers, intermediate layers and outer layer have thicknesses which satisfy the following four relationships:
   0.75≦(outer intermediate layer thickness+inner intermediate layer thickness)/outer layer thickness≦1.5,
     0.75≦(outer envelope layer thickness+inner envelope layer thickness)/outer layer thickness≦1.5,
     0.75≦(outer intermediate layer thickness+inner intermediate layer thickness)/(outer envelope layer thickness+inner envelope layer thickness)≦1.5, and
     outer layer thickness<(outer intermediate layer thickness+inner intermediate layer thickness+outer envelope layer thickness+inner envelope layer thickness)<core diameter.   
     
     
         14 . 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:
   C4−C0≦5,
     2≦C10−C4≦12, and
     C4−C0≦C10−C4<H−C10.
   
     
     
         15 . The multi-piece solid golf ball of  claim 1 , wherein the core has a single-layer structure.