Multi-piece golf balls containing a dual-core structure are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity and a surrounding outer core layer having a relatively low specific gravity. The core structure may have different hardness gradients. In one preferred embodiment, the inner core and outer core each 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 outer core layer preferably is formed from a thermoset composition such as polybutadiene rubber. The resulting ball has high resiliency and good spin control.

Multi-piece golf balls containing a dual-layered core structure are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, and a surrounding outer core layer. The layers of the core structure may have different hardness gradients. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and alloys thereof preferably dispersed in a thermoplastic polymeric matrix. Different plasticizer such as fatty acid esters may be used. The outer core layer is preferably formed from a thermoset composition such as polybutadiene. The resulting ball has high resiliency and good spin.

A golf ball with a center core comprising polybutadiene and a carbon nanotube material in an amount ranging from 0.4 to 2.5 weight percent of the center core is disclosed herein. Alternatively, the golf ball has a mantle layer with a blend of ionomer materials and a carbon nanotube material in an amount ranging from 0.2 to 2.5 weight percent of the mantle layer.

A method for forming a golf ball with a graphene core disclosed herein. The method includes mixing a graphene masterbatch material with a polybutadiene material to form a core mixture, wherein the graphene masterbatch material comprises graphene in an amount from 0.1 to 80.0 weight percent of the graphene masterbatch material mixed with a carrier polymer in an amount from 99.9 to 20 weight percent of the graphene masterbatch material.

An ultra-low compression golf ball is disclosed herein. The core preferably has a PGA compression less than 30. The mantle layer and cover have approximately the same thickness. The cover comprises a thermoplastic polyurethane material and has a specific gravity greater than the core and mantle layer. The golf ball has a PGA compression less than 75 and a COR of at least 0.780.

Golf balls comprising a multi-layer core and a cover are disclosed. The multi-layer core comprises a center, an intermediate core layer, and an outer core layer. At least one layer of the multi-layer core is a high specific gravity layer.

To provide a golf ball that ensures both an improved durability and an extended flight distance, in which cracks or breakage of a core can be prevented while making the hardness of the core surface greater so as to obtain the greater difference in hardness between the core surface and the core center. The golf ball of the present invention includes a core and a cover that surrounds the core, in which the core includes a base rubber and an unsaturated carboxylic acid or its salt as a co-crosslinking agent, the core has a surface hardness of 80 or more in terms of JIS-C hardness, and the unsaturated carboxylic acid or its salt contained in a region ranging from a surface of the core toward its center by less than 2 mm has an average particle diameter of less than 90 m.

Multi-piece golf balls containing a dual-layered core structure are provided. The core structure includes a small, heavy inner core (center) having a relatively high specific gravity, and a surrounding outer core layer. The layers of the core structure may have different hardness gradients. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and alloys thereof dispersed in a thermoset polymeric matrix. The outer core layer is preferably formed from a thermoplastic composition such as an ethylene acid copolymer ionomer resin. The resulting ball has high resiliency and good spin.

A golf ball contains, as a structural element therein, a molded and crosslinked material obtained from a rubber composition which includes: (a) a base rubber (b) an ,-unsaturated carboxylic acid and/or a metal salt thereof, (c) a crosslinking initiator, and (d) a metal carboxylate in which the carboxylic acid bonded to metal is of two or more different types and at least one of the carboxylic acids has 8 or more carbon atoms. The rubber composition has an improved processability in kneading and other operations, and the decrease in the initial velocity of the ball core resulting from the inclusion of additives can be held to a minimum.

Multi-layered golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The outer core layer is preferably formed from a non-foamed composition selected from thermoset compositions and thermoplastic compositions. The core layers have different hardness and specific gravity levels. The specific gravity (density) of the foam inner core is preferably less than the density of the outer core layer.