Golf ball incorporating core consisting of: a solid inner core layer consisting of a peroxide cured polybutadiene rubber composition and having a diameter of 1.25 inches or less and a center Shore C hardness (H.sub.center) of 50 or less; and an outer core layer consisting of a thermoplastic composition Tc as defined herein and having a thickness of 0.400 inches or greater and an outer surface Shore C hardness (H.sub.outer surface) of 70 or greater, wherein H.sub.outer surface>H.sub.center, and H.sub.outer surface−H.sub.center≧40. The peroxide cured polybutadiene rubber composition may comprise a reaction product of polybutadiene and a sufficient amount of peroxide to form the solid inner layer having the center Shore C hardness (H.sub.center) of 50 or less. In one embodiment, 100 phr polybutadiene and from about 0.05 phr to about 3.0 phr of peroxide are mixed with at least one of 5 phr or less of a metal oxide; 5 phr or less of a metal coagent; or 5 phr or less of a metal carbonate. Alternatively, the solid inner core layer has a diameter of 1.10 inches or less or less than 1.0 inches.

Multi-piece golf balls containing a multi-layered core structure having layers with different hardness gradients and specific gravities are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity with metal material preferably dispersed in a first thermoset composition. The intermediate core layer is preferably formed from a thermoplastic composition such as an ethylene acid copolymer ionomer resin; and the outer core layer is preferably formed from a second thermoset composition. The resulting ball has high resiliency and good spin control.

An object of the present invention is to provide a golf ball having excellent durability and good shot feeling. The present invention provides a golf ball comprising a core, wherein a difference (crosslinking density at surface of core−crosslinking density at center of core) between a crosslinking density at a surface of the core and a crosslinking density at a center of the core is more than 1.0×10.sup.2 mol/m.sup.3 and less than 9.0×10.sup.2 mol/m.sup.3, and a hardness difference (Hs−Ho) between Hs and Ho is 13.0 or more and 30.0 or less, and the core satisfies H50−Ho>Hs−H50, wherein Hs (Shore C hardness) is a hardness at the surface of the core, Ho (Shore C hardness) is a hardness at the center of the core, and H50 (Shore C hardness) is a hardness at a midpoint between the center of the core and the surface of the core.

Multi-layer golf balls having a hard, high compression center, a relatively soft intermediate layer, and a stiff outer cover layer, are provided. The outer surface hardness of the intermediate layer is less than that of both the center and the outer cover layer.

The invention provides a golf ball having a core and a cover of one layer or a plurality of layers, wherein the core is formed of a material molded under heat from a rubber composition containing (A) a base rubber, (B) an organic peroxide, and (C) water and/or a metal monocarboxylate, and has a hysteresis loss of 50% or less when compressed at a load cell speed of 500 mm/min and under a constant load of 5,000 N.

A golf ball comprising a core and a cover, wherein the core consists of: a solid inner core layer formed from an unfoamed thermoplastic composition and having a diameter of 1.10 inch or less and a center Shore C hardness (H.sub.center) of 50 or less, one or more optional intermediate core layers, and an outer core layer formed from an unfoamed thermoset composition and having a thickness of 0.200 inches or greater and an outer surface Shore C hardness (H.sub.outer surface) of 70 or greater, wherein H.sub.outer surface>H.sub.center, and H.sub.outer surface−H.sub.center≧40.

A golf ball includes a relatively large polymer core and has a soft ball compression. The polymer is, in the illustrated embodiments, a highly neutralized acid polymer. The golf ball may, optionally, include an outer core made of a different material, such as a thermoset polybutadiene rubber. The golf ball may, optionally, include a mantle layer made of an ionomer material. The inner core having a diameter of between 24 mm and 40 mm, and in some designs, between 28 mm and 32 mm, yields increased iron initial velocity and lower iron spin while maintaining driver performance.

Multi-piece golf balls having a solid core made of a foamed silicone composition and a cover are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core structures can be made. Preferably, a dual-core having has a silicone foam inner core (center) and surrounding silicone foam outer core layer is made. The core layers can have different hardness gradients. The silicone foam center and outer core layer have good thermal stability and durability and provide the ball with good resiliency.

Golf balls comprising a multi-layer core and a cover are disclosed. The multi-layer core comprises at least one intermediate core layer formed from a metallic, composite, or inorganic/organic hybrid composition.

Golf balls having multi-layered covers, wherein at least one of the cover layers is substantially transparent, are provided. The cover includes an inner cover layer made of an ionomer composition; an intermediate cover layer made of an aromatic polyurethane composition; and outer cover layer made of an aliphatic polyurethane composition, wherein the total thickness of the multi-layered cover is no greater than 0.110 inches. In one version, the outer cover layer is substantially transparent and the underlying intermediate cover layer is colored. In another version, both the outer and intermediate cover layers are substantially transparent. Light-reflective fillers such as pearlescent pigments, glitter, and metallics may be added to the cover layers. The resulting ball has pleasing decorative effects.