A golf ball includes a core and a cover. The core is formed of a material molded under heat from a rubber composition. The rubber composition includes components (A) through (C). The components (A) through (C) are (A) a base rubber, (B) an organic peroxide, and (C) a water providing agent. The water providing agent releases water at a vulcanization temperature at which the rubber composition is vulcanized. The dissociation rate of water of the water providing agent in the case of heating the water providing agent up to the vulcanization temperature of the rubber composition is 60% by mass or more.

A multi-piece solid golf ball for professional golfers and skilled amateurs in particular is endowed with an excellent distance, a soft yet good feel at impact and a good durability. In the ball, which includes a core, an envelope layer, an intermediate layer and a cover, the core has a hardness profile which satisfies specific conditions, the envelope layer has a thickness of from 0.3 to 1.2 mm, the intermediate layer has a thickness of from 0.3 to 1.2 mm, and the envelope and intermediate layers have a combined thickness from of 0.8 to 1.7 mm.

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. 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 intermediate core layer is preferably formed from a first thermoplastic composition such as an ethylene acid copolymer ionomer resin; and the outer core layer is preferably formed from a second thermoplastic composition. The resulting ball has high resiliency and good spin control.

Multi-layered golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) made from a foam or metal-containing composition, or it has a hollow shell construction, and the outer core layer is made of a thermoplastic composition. 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. The core assembly preferably has a positive hardness gradient extending across the entire assembly. The core structure and resulting ball have relatively good resiliency at given compressions.

Golf balls having cores with increased hardness gradients are provided. The cores have an increased positive hardness gradient (or a hard-to-soft hardness) where the outer surface of the core is harder than the center. The increased positive hardness gradient can be achieved by introducing a water-releasing agent into the core rubber formulation during the curing process. The resulting golf balls have reduced spin and sufficient impact durability.

Golf balls having cores with increased hardness gradients are provided. The cores have an increased positive hardness gradient (or a hard-to-soft hardness) where the outer surface of the core is harder than the center. The increased positive hardness gradient can be achieved by introducing a water-releasing agent into the core rubber formulation during the curing process. The resulting golf balls have reduced spin and sufficient impact durability.

Method of making a golf ball, the golf ball comprising a core, an outer layer and at least one adhesion promoting coating disposed between each of the core and the outer layer; the core comprising a rubber composition comprising at least one zinc-containing and/or magnesium-containing component; the outer layer comprising at least one ionomer; and the adhesion promoting coating comprising a waterborne dispersion comprised of at least one ethylene acid copolymer having an acid content of at least 15% by weight wherein the copolymer is at least partially neutralized with one or more neutralizing agent; wherein at least one neutralizing agent is selected from ammonia compounds and/or amine compounds. In a specific embodiment, the at least one neutralizing agent comprises i) mono and/or divalent metal compounds and ii) ammonia compounds and/or amine compounds.

Multi-layered golf balls having a core, intermediate layer, and cover are provided. The ball includes a non-foamed inner core (center) made of a thermoplastic or thermoset composition such as polybutadiene rubber. An intermediate layer comprising a foamed composition, such as polyurethane foam, is disposed about the inner core. The foamed intermediate layer may have a specific gravity gradient within the layer, wherein the outer surface specific gravity is greater than the midpoint specific gravity. Ball constructions having two intermediate layers, wherein at least one layer is a foamed layer can be made. A cover having at least one layer is disposed about the intermediate layer.

Multi-piece golf balls having a multi-layered solid core and multi-layered cover are provided.

A golf ball for amateur golfers is endowed with both an excellent flight when hit by golfers whose head speed is not very high and a soft yet good feel at impact. The ball has a core, an envelope layer, an intermediate layer and a cover. The core is formed primarily of a base rubber and the intermediate layer is formed so as to be thicker than the envelope layer and the cover. The respective surface hardnesses of the core, envelope layer-encased sphere, intermediate layer-encased sphere and ball satisfy a specific relationship. The core hardness profile is designed such that the surface areas A to F calculated from hardness differences between positions located at specific distances in the core and differences between the specific distances satisfy a specific formula.