Multi-piece solid golf ball

Abstract

The invention provides a multi-piece solid golf ball having 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. The core is formed primarily of a rubber material and has a diameter of at least 31 mm, the envelope layer and the intermediate layer are each formed primarily of the same or different resin materials, and the cover is formed primarily of polyurethane. The intermediate layer and the cover have thicknesses which satisfy the relationship: cover thickness<intermediate layer thickness. The core has a surface hardness (Durometer D hardness) and the envelope layer, intermediate layer and cover have material hardnesses (Durometer D hardness) which together satisfy the relationship: cover material hardness<intermediate layer material hardness<envelope layer material hardness>core surface hardness. The golf ball of the invention, as a ball for professionals and skilled amateur golfers, has both an excellent controllability and flight as well as an excellent feel on impact, in addition to which it has a good scuff resistance, enabling it to endure harsh conditions of use.

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 core is formed primarily of a rubber material and has a diameter of at least 31 mm, the envelope layer and the intermediate layer are each formed primarily of the same or different resin materials, and the cover is formed primarily of polyurethane; the envelope layer, the intermediate layer and the cover have thicknesses which satisfy the relationship:
 cover thickness<intermediate layer thickness<envelope layer thickness;   and the core has a surface hardness (Durometer D hardness) and the envelope layer, intermediate layer and cover have material hardnesses (Durometer D hardness) which together satisfy the relationship;   cover material hardness<intermediate layer material hardness<envelope layer material hardness<core surface hardness.   
   
   
       2 . (canceled) 
   
   
       3 . The multi-piece solid golf ball of  claim 1 , wherein the resin material which forms the envelope layer comprises an ionomer resin having an acid content of at least 16 wt %. 
   
   
       4 . The multi-piece solid golf ball of  claim 1 , wherein the resin material which forms the cover is composed primarily of:
 (A) a thermoplastic polyurethane material, and   (B) an isocyanate mixture obtained by dispersing (b-1) a compound having two or more isocyanate groups as functional groups per molecule in (b-2) a thermoplastic resin which is substantially non-reactive with isocyanate.   
   
   
       5 . The multi-piece solid golf ball of  claim 1 , wherein the envelope layer, intermediate layer and cover have material hardnesses (Durometer D hardnesses) such that
 60≦envelope layer material hardness≦70,   55≦intermediate layer material hardness≦70, and   30≦cover material hardness≦55.   
   
   
       6 . The multi-piece solid golf ball of  claim 1 , wherein the ball and the core have deflections (mm), when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf), which satisfy the following respective conditions:
 2.0 mm≦ball deflection≦3.0 mm, and   3.5 mm≦core deflection≦6.0 mm.   
   
   
       7 . The multi-piece solid golf ball of  claim 1 , wherein the core surface hardness is lower than the material hardness of the envelope layer by a difference in Durometer D hardness of 5 to 35. 
   
   
       8 . The multi-piece solid golf ball of  claim 1 , wherein the difference between the hardness of the envelope layer material and the hardness of the intermediate layer material is at least 1 but not more than 20 in Durometer D hardness. 
   
   
       9 . The multi-piece solid golf ball of  claim 1 , wherein the surface of the intermediate layer is abraded. 
   
   
       10 . The multi-piece solid golf ball of  claim 9 , wherein a primer is applied to the surface of the intermediate layer after the abrasion. 
   
   
       11 . The multi-piece solid golf ball of  claim 9 , wherein an adhesion reinforcing agent is added to the intermediate layer material after the abrasion. 
   
   
       12 . The multi-piece solid golf ball of  claim 11 , wherein the adhesion reinforcing agent is selected from the group consisting of 1,3-butanediol, trimethylolpropane, polyethylene glycol oligomer and polyhydroxy polyolefin oligomer. 
   
   
       13 . The multi-piece solid golf ball of  claim 1 , wherein the numbers of the dimples arranged on the cover surface is at least 280 but not more than 360. 
   
   
       14 . The multi-piece solid golf ball of  claim 1 , wherein the diameter of the dimples is set to at least about 2.5 mm but not more than about 6.5 mm. 
   
   
       15 . The multi-piece solid golf ball of  claim 1 , wherein the dimple coverage on the spherical surface of the golf ball, which is the sum of the individual dimple surface areas, each defined by the border of the flat plane circumscribed by the edge of the dimple, expressed as a ratio (SR) with respect to the spherical surface area of the ball were it to be free of dimples, is at least 60% but not more than 90%. 
   
   
       16 . The multi-piece solid golf ball of  claim 1 , wherein the value V 0  obtained by dividing the spatial volume of each dimple below the flat plane circumscribed by the edge of that dimple by the volume of a cylinder whose base is the flat plane and whose height from the base to the maximum depth of the dimple is at least 0.35 but not more than 0.80. 
   
   
       17 . The multi-piece solid golf ball of  claim 1 , wherein the VR value, which is the sum of the volumes of individual dimples formed below flat planes circumscribed by the dimple edges, as a percentage of the volume of the ball sphere were it to have no dimples thereon, is at least 0.6% but not more than 1.0%. 
   
   
       18 . The multi-piece solid golf ball of  claim 1 , wherein the ball has deflection of 2.0 to 2.2 mm, when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf).