Patent ID: 8030386

Claim:
A golf ball comprising: a core comprising an inner core layer and an outer core layer; and a cover comprising an inner cover layer and an outer cover layer; wherein the inner core layer is formed from a rubber composition comprising: (a) a base rubber; (b) at least 0.05 parts by weight of a free radical initiator per 100 parts of the base rubber; and (c) at least 0.1 parts by weight of a hydroquinone per 100 parts of the base rubber; wherein a ratio (P HQ /P FRI ) of the amount of the hydroquinone present in the rubber composition (P HQ ), measured in parts by weight per 100 parts of the base rubber, to the amount of free radical initiator present in the rubber composition (P FRI ), measured in parts by weight per 100 parts of the base rubber, is from 0.05 to 2; and wherein the inner core layer has a positive hardness gradient wherein the difference between the Shore C hardness of the outer surface of the inner core layer (H INNER CORE OUTER SURFACE ) and the Shore C hardness of the center of the inner core layer (H CENTER )≧5 Shore C units; and wherein the surface hardness of the outer core layer is greater than the material hardness of the inner cover layer.