Patent ID: 8039529

Claim:
A method of manufacturing a golf ball, comprising: (i) pre-preparing a masterbatch of an unsaturated carboxylic acid and/or a metal salt thereof by mixing an unsaturated carboxylic acid and/or a metal salt thereof with a rubber material, (ii) preparing a rubber composition comprising the masterbatch of the unsaturated carboxylic acid and/or a metal salt thereof, and (iii) employing a material obtained by molding the rubber composition under heat as a golf ball component, wherein the masterbatch comprises: (A) from 20 to 80 wt % of a modified polybutadiene obtained by a modification reaction wherein a polybutadiene having a vinyl content of from 0 to 2%, a cis-1,4 bond content of at least 80% and an active end is modified at the active end with at least one type of alkoxysilane compound, (B) from 80 to 20 wt % of a diene rubber other than ingredient A, such that ingredients A and B are included in a combined amount of 100 wt %, and (C) an unsaturated carboxylic acid and/or a metal salt thereof, wherein ingredient C is included in the masterbatch of an unsaturated carboxylic acid and/or a metal salt thereof in an amount of at least 150 parts by weight but not more than 200 parts by weight per 100 parts by weight of rubber ingredients A and B, and wherein the masterbatch is blended with a rubber consisting of the same diene rubber as ingredient B in the step (ii) of preparing the rubber composition.