Cores made from thermoset and plasticized thermoplastic materials for golf balls

摘要

Multi-layered golf balls containing a two or three-layered core assembly are provided. In one embodiment, the core assembly includes an inner core (center) comprising a thermoset composition, an intermediate core layer; and surrounding outer core layer. Preferably, the thermoplastic composition comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. A second thermoset composition such as polybutadiene rubber may be used to form the outer core layer. The core layers have different hardness levels. In another embodiment, a two-layered core structure is provided. For example, the inner core and/or outer core layer may be made of the plasticized thermoplastic composition. The core structure and resulting ball have relatively good resiliency at given compressions.

主权项

1. A core assembly for a golf ball, comprising:
i) an inner core layer comprising a first thermoset rubber material, the inner core having an outer surface hardness (Hinner core surface) and a center hardness (Hinner core center), the Hinner core surface being greater than the Hinner core center to provide a positive hardness gradient; ii) an intermediate core layer comprising a thermoplastic material, the intermediate layer being disposed about the inner core and having an outer surface hardness (Houter surface of Inter Core) and a midpoint hardness (Hmidpoint of Inter Core), the Houter surface of the Inter Core being greater than the Hmidpoint of the Inter Core to provide a positive hardness gradient, the thermoplastic material comprising:
a) an acid copolymer of ethylene and an α,β-unsaturated carboxylic acid, optionally including a softening monomer selected from the group consisting of alkyl acrylates and methacrylates;b) a plasticizer; andc) a cation source present in an amount sufficient to neutralize from about 0 to about 100% of all acid groups present in the material; and iii) an outer core layer comprising a second thermoset rubber material, the outer core layer being disposed about the intermediate core layer and having an outer surface hardness (Houter surface of OC) and a midpoint hardness (Hmidpoint of OC), the Houter surface of OC being greater than the Hmidpoint of OC to provide a positive hardness gradient, wherein the center hardness of the inner core (Hinner core center) is in the range of about 10 Shore C to about 70 Shore C and the outer surface hardness of the outer core layer (Houter surface of OC) is in the range of about 20 Shore C to about 95 Shore C to provide a positive hardness gradient across the core assembly.