Compositions including a hardness agent and a water releasing agent and golf ball cores made from such compositions having a tailored hardness gradient are disclosed. The type and concentration of the components in the composition, including a hardness agent and a water releasing agent, affect the hardness, hardness gradient, and compression of cores made from the composition and, thus, can be used to produce a golf ball having desirable performance characteristics.

In a golf ball having a two-layer core consisting of an inner core layer and an outer core layer and a cover of one or more layer, the inner core layer and outer core layer are each formed of a rubber composition made up primarily of a base rubber, the inner core layer has a diameter of not more than 30 mm; and the core has specific hardness ratios (JIS-C hardness/Shore D hardness) at specific points on the cross-section thereof. This golf ball has a reduced spin rate on full shots with a driver and middle irons, thus imparting to an excellent flight performance, and moreover has a good controllability in the short game on approach shots, making it ideal as a golf ball for professional golfers and mid- and high-level amateur golfers.

A golf ball 2 includes a core 4 and a cover 6 positioned outside the core 4. The cover 6 is molded in a mold having support pins by injection molding. A ratio (K/S) of a surface hardness K of the core 4 to an amount of compressive deformation S of the core 4 satisfies the following mathematical formula.

13.0K/S24.0

The cover 6 has a hardness H of not greater than 62. A product (*V) of a latitude of each support pin and a volume V of the cover 6 is not less than 300.

Compositions including a compression agent and a water-producing agent golf ball cores made from such compositions having an increased compression and Coefficient of Restitution are disclosed. The type and concentration of the components in the composition, including the compression agent and water-producing agent, affects the compression, Coefficient of Restitution, hardness, and hardness gradient of cores made from the composition and, thus, can be used to produce a golf ball having desirable performance characteristics.

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.

A golf ball includes a core and a cover. The cover has a shore D hardness of not less than 50. The cover has a thickness of not less than 1.00 mm. The golf ball has a plurality of dimples 10 on a surface thereof. A standard deviation Su of areas of all the dimples 10 is not greater than 1.7 mm.sup.2. A standard deviation Pd of distances L between dimples of all neighboring dimple pairs is less than 0.500 mm. A dimple pattern of each hemisphere of a phantom sphere of the golf ball includes three units (T1, T2, T3) that are rotationally symmetrical to each other. A dimple pattern of the unit T1 includes two small units (T1a, T1b) that are mirror-symmetrical to each other.

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.

Multi-layered golf balls having at least one layer made from silicone (polysiloxane) elastomers; silicone (polysiloxane) elastomer/polyurethane blends; polycarbonate-polysiloxane blends and copolymers; and polycarbonate-polysiloxane/polyurethane blends are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core and cover structures can be made. The polysiloxane compositions have good thermal stability and durability without sacrificing resiliency. The polysiloxane compositions also 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.

A golf ball with a cover formed by spraying is disclosed herein. In the present invention, a mixture of a low viscous diisocyanate component and a diamine free of organic solvent are sprayed onto a mantle insert to form a cover layer for a golf ball. A rapid reaction occurs and a solid layer forms within ten seconds. The polyurea material is extremely durable so that the cover layer performs with excellent shear cut durability.

Low compression, multi-piece golf balls containing a solid core and two or three-layered cover assemblies are provided. Preferably, the ball has a compression of less than 60 and more preferably less than 50. At least one cover layer is made of a plasticized thermoplastic composition. For example, two-layered and three-layered covers may be made. Preferably, the plasticized thermoplastic composition comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A fatty acid ester such as ethyl oleate or butyl oleate is preferably used as the plasticizer. The cover assembly has good impact durability and helps provide the ball with relatively high resiliency at given compressions.