Patent ID: 7534835

Claim:
A golf ball comprising a material molded under heat from a rubber composition comprised of: (a) a base rubber composed primarily of a mixture of at least 60 wt % of a polybutadiene having a stress relaxation time (T 80 ), defined as the length of time it takes from the moment rotor rotation is stopped immediately after measurement of the ML 1+4 (100° C.) value (the Mooney viscosity measured at 100° C. in accordance with ASTM D1646-96) for the ML 1+4 value to decrease 80%, of less than 4 seconds with up to 40 wt % of a polybutadiene having a stress relaxation time (T 80 ) of at least 4 seconds; (b) an unsaturated carboxylic acid and/or a metal salt thereof; and (c) an organic peroxide; wherein both the polybutadiene having T 80 of less than 4 seconds and the polybutadiene having T 80 of at least 4 seconds are present in the base rubber and both polybutadienes are polymerized using a rare-earth catalyst.