Golf ball

Abstract

An object of the present disclosure is to provide a golf ball having improved controllability on iron shots. The present disclosure provides a golf ball 2 comprising a spherical core 4 , an intermediate layer 6 and an outermost cover 8 having a plurality of dimples 10 formed thereon, wherein the spherical core 4 is formed from a rubber composition containing a polybutadiene rubber and a butyl rubber in a predetermined amount, a slab hardness of an intermediate layer composition forming the intermediate layer 6 is greater than a slab hardness of a cover composition forming the outermost cover 8 , a total lower volume of the plurality of dimples 10 is 365 mm 3 or more, and an occupation ratio of a total area of the plurality of dimples 10 in a surface area of a virtual sphere that is assumed to have no dimples on the outermost cover 8 is 75% or more.

1 . A golf ball comprising a spherical core, an intermediate layer covering the spherical core, and an outermost cover positioned outside the intermediate layer and having a plurality of dimples formed thereon, wherein
 the spherical core is formed from a rubber composition containing a base rubber, a co-crosslinking agent, and a crosslinking initiator,   the base rubber contains a polybutadiene rubber and a butyl rubber,   an amount of the butyl rubber ranges from 10 mass % to 60 mass % in 100 mass % of the base rubber,   a slab hardness of an intermediate layer composition forming the intermediate layer is greater than a slab hardness of a cover composition forming the outermost cover,   a total lower volume of the plurality of dimples is 365 mm 3  or more, and   an occupation ratio of a total area of the plurality of dimples in a surface area of a virtual sphere that is assumed to have no dimples on the outermost cover is 75% or more.   
     
     
         2 . The golf ball according to  claim 1 , wherein the total lower volume of the plurality of dimples is 400 mm 3  or more. 
     
     
         3 . The golf ball according to  claim 1 , wherein a center hardness (H0) of the spherical core, a hardness (H 2.5 ) at a point having a radial distance of 2.5 mm from a center of the spherical core, a hardness (H 5.0 ) at a point having a radial distance of 5.0 mm from the center of the spherical core, a hardness (H 7.5 ) at a point having a radial distance of 7.5 mm from the center of the spherical core, a hardness (H 10 ) at a point having a radial distance of 10 mm from the center of the spherical core, a hardness (H 12.5 ) at a point having a radial distance of 12.5 mm from the center of the spherical core, and a hardness (H 15 ) at a point having a radial distance of 15 mm from the center of the spherical core satisfy a relationship of H0<H 2.5 <H 5.0 <H 7.5 <H 10 <H 12.5 <H 15 , and
 a hardness difference (H 10 -H0) between the hardness (H 10 ) at the point having the radial distance of 10 mm from the center of the spherical core and the center hardness (H0) is 10 or more in Shore C hardness.   
     
     
         4 . The golf ball according to  claim 1 , wherein a hardness difference (H 12.5 -H 5.0 ) between the hardness (H 12.5 ) at the point having the radial distance of 12.5 mm from the center of the spherical core and the hardness (H 5.0 ) at the point having the radial distance of 5.0 mm from the center of the spherical core is 5 or more in Shore C hardness. 
     
     
         5 . The golf ball according to  claim 1 , wherein the center hardness (H0) of the spherical core is 60 or less in Shore C hardness. 
     
     
         6 . The golf ball according to  claim 1 , wherein the intermediate layer composition forming the intermediate layer is a resin composition containing an ionomer resin as a base resin, and
 the cover composition forming the outermost cover is a resin composition containing a urethane resin as a base resin.   
     
     
         7 . The golf ball according to  claim 1 , wherein the slab hardness of the cover composition forming the outermost cover is 40 or less in Shore D hardness. 
     
     
         8 . The golf ball according to  claim 1 , wherein the slab hardness of the intermediate layer composition forming the intermediate layer is 50 or more in Shore D hardness. 
     
     
         9 . The golf ball according to  claim 3 , wherein the hardness (H 5.0 ) at the point having the radial distance of 5.0 mm from the center of the spherical core ranges from 56 to 72 in Shore C hardness. 
     
     
         10 . The golf ball according to  claim 3 , wherein the hardness (H 10 ) at the point having the radial distance of 10 mm from the center of the spherical core ranges from 62 to 78 in Shore C hardness. 
     
     
         11 . The golf ball according to  claim 3 , wherein the hardness (H 12.5 ) at the point having the radial distance of 12.5 mm from the center of the spherical core ranges from 66 to 80 in Shore C hardness. 
     
     
         12 . The golf ball according to  claim 3 , wherein the hardness (H 15 ) at the point having the radial distance of 15 mm from the center of the spherical core ranges from 70 to 85 in Shore C hardness. 
     
     
         13 . The golf ball according to  claim 1 , wherein a surface hardness (Hs) of the spherical core ranges from 70 to 85 in Shore C hardness. 
     
     
         14 . The golf ball according to  claim 1 , wherein a hardness difference (Hm-Hc) between the slab hardness (Hm) of the intermediate layer and the slab hardness (Hc) of the cover composition is more than 0 and 50 or less in Shore D hardness. 
     
     
         15 . The golf ball according to  claim 1 , wherein a mass ratio (polybutadiene rubber/butyl rubber) of the polybutadiene rubber to the butyl rubber ranges from 40/60 to 90/10. 
     
     
         16 . The golf ball according to  claim 1 , wherein the butyl rubber has a Mooney viscosity (ML 1+8  (125° C.)) ranging from 28 to 60.