Golf ball

Abstract

In a golf ball having a core of at least one layer and a cover of one or more layer encasing the core, at least one layer of the cover is formed of a resin composition that includes (I) a polyurethane or a polyurea and (II) an aromatic vinyl elastomer which together satisfy certain specific conditions. The golf ball has an excellent controllability on approach shots and is also able to maintain a good scuff resistance.

1 . A golf ball comprising a core of at least one layer and a cover of one or more layer encasing the core, wherein at least one layer of the cover is formed of a resin composition comprising:
 (I) a polyurethane or a polyurea, and   (II) an aromatic vinyl elastomer; and   
       letting HMa (N/mm 2 ) be the Martens hardness of the resin material of component (I), HMb (N/mm 2 ) be the Martens hardness of the cover layer formed of the resin composition containing components (1) and (11) and ηItb (%) be the elastic work recovery of the cover layer, HMa, HMb and ηItb satisfy formulas (1) and (2) below
   1.005≤ HMa/HMb≤ 1.450  (1)
 
   2.00≤η Itb/HMb≤ 7.00  (2).
 
 
     
     
         2 . The golf ball of  claim 1 , wherein HMa/HMb in formula (1) has a lower limit value of 1.007 and an upper limit value of 1.400. 
     
     
         3 . The golf ball of  claim 1 , wherein ηItb/HMb in formula (2) has a lower limit value of 2.50 and an upper limit value of 6.50. 
     
     
         4 . The golf ball of  claim 1  which, letting ηIta (%) be the elastic work recovery of the resin material of component (I), satisfies formula (3) below:
   1.001≤η Ita/ηItb≤ 1.070  (3).
 
 
     
     
         5 . The golf ball of  claim 1 , wherein the content of component (II) is 50 parts by weight or less per 100 parts by weight of component (I). 
     
     
         6 . The golf ball of  claim 1 , wherein component (II) is a hydrogenated aromatic vinyl elastomer. 
     
     
         7 . The golf ball of  claim 1 , wherein component (II) is an elastomer obtained by hydrogenating a polymer comprising a polymer block composed primarily of an aromatic vinyl compound and a random copolymer block of an aromatic vinyl compound and a conjugated diene compound. 
     
     
         8 . The golf ball of  claim 1 , wherein component (II) is a hydrogenated aromatic vinyl elastomer obtained by hydrogenating a polymer comprising, at each of two ends thereof, a polymer block consisting of styrene and, in between, a random copolymer block.