Multi-piece golf balls containing a dual-layered core are provided. The ball further includes single or multi-layered covers. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, and a surrounding outer core layer. The core layers may have different hardness gradients. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and combinations and alloys thereof preferably dispersed in a thermoplastic polymeric matrix. The outer core layer is preferably formed from a thermoset composition such as polybutadiene. These multi-layered core constructions with metal-containing centers have selective specific gravity relationships between the different layers. This helps provide the ball with good flight distance and spin control. The resulting balls have good resiliency and other playing performance properties.

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.

Multi-piece golf balls containing a multi-layered core structure are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, an intermediate core layer, and a surrounding outer core layer. The layers of the core structure may have different hardness gradients. In one preferred embodiment, each core layer has a positive hardness gradient. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and alloys thereof. The intermediate core layer is preferably formed from a thermoset composition such as polybutadiene rubber, and the outer core layer is preferably formed from a thermoplastic composition such as an ethylene acid copolymer. The resulting ball has high resiliency and good spin control.

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.

Multi-piece golf balls containing a multi-layered core structure are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, an intermediate core layer, and a surrounding outer core layer. The layers of the core structure may have different hardness gradients. In one preferred embodiment, each core layer has a positive hardness gradient. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and alloys thereof. The intermediate core layer is preferably formed from a first thermoset composition such as polybutadiene rubber, and the outer core layer is preferably formed from a second thermoset composition. The resulting ball has high resiliency and good spin control.

Golf balls having a multi-layered core made of a foamed composition are provided. The core assembly preferably includes a foam inner core (center) and surrounding outer core layer. Preferably, a polyurethane foam composition is used to form the foam center. The core layers have different hardness gradients and specific gravity values. The foamed inner core assembly includes a geometric center, outer surface (skin), and thermal barrier layer that helps protect the foamed center region from the negative effects of high temperatures used during the ball-manufacturing process. Non-foamed thermoset materials such as polybutadiene rubber may be used to form the thermal barrier layer. The foam cores have good resiliency, thermal stability, and durability over a wide temperature range. The ball further includes a cover that may be multi-layered.

Multi-layered golf balls having a core made of a foamed composition, preferably polyurethane foam, are provided. The ball includes a dual-layered core having a foam inner core (center) and surrounding outer core layer. The outer core layer may be made from a non-foamed thermoset material such as polybutadiene rubber. The ball further includes an inner cover, preferably made from an ionomer composition comprising an O/X-type acid copolymer, wherein O is -olefin, and X is a C.sub.3-C.sub.8 ,-ethylenically unsaturated carboxylic acid. The outer cover may be made from a non-foamed thermoset or thermoplastic material such as polyurethane. Preferably, the specific gravity of the inner cover is greater than the specific gravity of the outer core, which is greater than the specific gravity of the inner core. The finished ball has good distance and low-spin properties.

Multi-layered golf balls having at least one layer made of a foamed silicone composition are provided. Multi-layered golf balls having at least one layer made of non-foamed silicone elastomer composition also are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core and cover structures can be made. The foamed silicones have good thermal stability and durability without sacrificing resiliency. The non-foamed silicone elastomers have high elongation, tensile strength, chemical/fluid-resistance, and weatherability properties. These compositions can be used to form any layer, for example, core, intermediate, or cover, in the golf ball.

The invention provides a golf ball having a core and a cover of one or more layer encasing the core, wherein the core has a center core and a foamed outer layer that directly, or indirectly through another layer, envelops the center core. The foamed outer layer is made of a rubber composition that includes a base rubber, a co-crosslinking agent and an organic peroxide. The foamed outer layer has an inside portion facing the ball center and an outside portion facing the outside of the ball that are unfoamed regions, and contains a foamed region in an intermediate portion therebetween. A method of manufacturing such a golf ball is also provided.

Multi-layered, golf balls having a core made of a foamed composition are provided. The core preferably has a foam inner core (center) and surrounding thermoset or thermoplastic outer core layer. Preferably, a polyurethane foam composition comprising secondary blowing agents that are activated by heat is used to form the foam center. Non-foamed thermoset materials such as polybutadiene rubber may be used to form the outer core layer. The core layers have different hardness gradients and specific gravity values. The foam cores have good resiliency, thermal stability, and durability over a wide temperature range. The ball further includes a cover that may be multi-layered.