Golf ball

Abstract

An object of the present disclosure is to provide a golf ball that bends in a great amplitude on short iron shots and rolls in a short distance after landing. The present disclosure provides a golf ball comprising a spherical core, one or more intermediate layer positioned outside 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 rubber component, a co-crosslinking agent, and a crosslinking initiator, the rubber component contains a natural rubber, the co-crosslinking agent contains methacrylic acid and/or a metal salt thereof, a total lower volume Vi (mm 3 ) of the plurality of dimples is less than 365 mm 3 , and an occupation ratio of the dimples is 75% or more.

1 . A golf ball comprising a spherical core, at least one intermediate layer positioned outside 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 rubber component, a co-crosslinking agent, and a crosslinking initiator,   the rubber component contains a natural rubber,   the co-crosslinking agent contains methacrylic acid and/or a metal salt thereof,   a total lower volume Vi (mm 3 ) of the plurality of dimples is less than 365 mm 3 , and   an occupation ratio of the dimples defined by the following formula is 75% or more,   Occupation ratio of dimples (%)=100×total area of all dimples/surface area of a virtual sphere that is assumed to have no dimples on a golf ball surface.   
     
     
         2 . 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 ) at a point having a radial distance of 5 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, a hardness (H 15 ) at a point having a radial distance of 15 mm from the center of the spherical core, and a surface hardness (Hs) of the spherical core satisfy a relationship of H0<H 2.5 <H 5 <H 7.5 <H 10 <H 12.5 <H 15 <Hs. 
     
     
         3 . The golf ball according to  claim 2 , wherein the center hardness (H0), the hardness (H 2.5 ), the hardness (H 5 ), the hardness (H 7.5 ), the hardness (H 10 ), the hardness (H 12.5 ), the hardness (H 15 ) and the surface hardness (Hs) satisfy relationships of
 H 2.5 −H0<4,   H 5 −H 2.5 <4,   H 7.5 −H 5 <4,   H 10 −H 7.5 <4,   H 12.5 −H 10 <4,   H 15 −H 12.5 <4, and   Hs−H 15 <4 in Shore C hardness.   
     
     
         4 . The golf ball according to  claim 2 , wherein a hardness difference (Hs−H0) between the surface hardness (Hs) of the spherical core and the center hardness (H0) of the spherical core is 10 or less in Shore C hardness. 
     
     
         5 . The golf ball according to  claim 1 , wherein the total lower volume Vi (mm 3 ) is 350 mm 3  or less. 
     
     
         6 . The golf ball according to  claim 1 , wherein an amount of the natural rubber is 10 mass % or more and 80 mass % or less in the rubber component. 
     
     
         7 . The golf ball according to  claim 1 , wherein a material hardness Hm of the intermediate layer is greater than a material hardness Hc of the outermost cover. 
     
     
         8 . The golf ball according to  claim 1 , wherein the intermediate layer is formed from an intermediate layer composition having a slab hardness of 50 or more in Shore D hardness and containing an ionomer resin. 
     
     
         9 . The golf ball according to  claim 1 , wherein the outermost cover is formed from a cover composition having a slab hardness of 40 or less in Shore D hardness and containing a polyurethane. 
     
     
         10 . The golf ball according to  claim 2 , wherein the center hardness Ho of the spherical core ranges from 55 to 77 in Shore C hardness. 
     
     
         11 . The golf ball according to  claim 2 , wherein the surface hardness Hs of the spherical core ranges from 60 to 87 in Shore C hardness. 
     
     
         12 . The golf ball according to  claim 4 , wherein the hardness difference (Hs−H0) ranges from 2 to 10 in Shore C hardness. 
     
     
         13 . The golf ball according to  claim 3 , wherein the center hardness (H0), the hardness (H 2.5 ), the hardness (H 5 ), the hardness (H 7.5 ), the hardness (H 10 ), the hardness (H 12.5 ), the hardness (H 15 ) and the surface hardness (Hs) satisfy relationships of
 0.3≤H 2.5 −H0<4,   0.5≤H 5 −H 2.5 <4,   0.5≤H 7.5 −H 5 <4,   0.5≤H 10 −H 7.5 <4,   0.5≤H 12.5 −H 10 <4,   0.1≤H 15 −H 12.5 <4, and   0<Hs−H 15 <4 in Shore C hardness.   
     
     
         14 . The golf ball according to  claim 7 , wherein a difference (Hm−Hc) between the material hardness Hm of the intermediate layer and the material hardness Hc of the outermost cover ranges from 20 to 40 in Shore D hardness. 
     
     
         15 . A golf ball comprising a spherical core, at least one intermediate layer positioned outside 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 rubber component, a co-crosslinking agent, and a crosslinking initiator,   the rubber component contains a natural rubber,   the co-crosslinking agent contains methacrylic acid and/or a metal salt thereof,   a total lower volume Vi (mm 3 ) of the plurality of dimples is less than 365 mm 3 , and   an occupation ratio of the dimples defined by the following formula is 75% or more,   Occupation ratio of dimples (%)=100×total area of all dimples/surface area of a virtual sphere that is assumed to have no dimples on a golf ball surface,   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 ) at a point having a radial distance of 5 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, a hardness (H 15 ) at a point having a radial distance of 15 mm from the center of the spherical core, and a surface hardness (Hs) of the spherical core satisfy relationships of   H0<H 2.5 <H 5 <H 7.5 <H 10 <H 12.5 <H 15 <Hs,   0.3≤H 2.5 −H0<4,   0.5≤H 5 −H 2.5 <4,   0.5≤H 7.5 −H 5 <4,   0.5≤H 10 −H 7.5 <4,   0.5≤H 12.5 −H 10 <4,   0.1≤H 15 −H 12.5 <4, and   0<Hs−H 15 <4 in Shore C hardness, and   a hardness difference (Hs−H0) between the surface hardness (Hs) of the spherical core and the center hardness (H0) of the spherical core is 10 or less in Shore C hardness.   
     
     
         16 . The golf ball according to  claim 15 , wherein the total lower volume Vi (mm 3 ) is 350 mm 3  or less. 
     
     
         17 . The golf ball according to  claim 15 , wherein a material hardness Hm of the intermediate layer is greater than a material hardness Hc of the outermost cover. 
     
     
         18 . The golf ball according to  claim 15 , wherein an amount of the natural rubber is 10 mass % or more and 80 mass % or less in the rubber component. 
     
     
         19 . The golf ball according to  claim 15 , wherein the intermediate layer is formed from an intermediate layer composition having a slab hardness of 50 or more in Shore D hardness and containing an ionomer resin. 
     
     
         20 . The golf ball according to  claim 15 , wherein the outermost cover is formed from a cover composition having a slab hardness of 40 or less in Shore D hardness and containing a polyurethane.