Golf ball having CoR of at least 0.810, specific gravity SG.sub.B of less than 1.00 g/cc, and initial velocity of at least 250 ft/s and comprising a first layer L.sub.1, a second layer L.sub.2 surrounding L.sub.1, and a third layer L.sub.3 surrounding L.sub.2. L.sub.1 is formed from at least one highly neutralized polymer and has first specific gravity SG.sub.1; L.sub.2 is formed from at least one partially neutralized polymer and has second specific gravity SG.sub.2; and L.sub.3 is formed from at least one of a thermoset or thermoplastic composition and has third specific gravity SG.sub.3. At least two of SG.sub.1, SG.sub.2, and SG.sub.3 is less than 1.13 g/cc. SG.sub.1 may be less than 1.13 g/cc, or less than 1.0 g/cc. The thermoset or thermoplastic composition may comprise polyurethane(s), polyurea(s), polyurethane(s)/polyurea(s) hybrids, and/or ionomers such as at least partially neutralized polymers and/or HNPs.

Golf balls having a multi-layered 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 is used to form the foam center. The foam inner core preferably includes a fully-foamed center region and a partially or completely-collapsed foam outer region. The hardness of the fully-foamed region is different than the hardness of the collapsed foam region. Non-foamed thermoset or thermoplastic materials such as polybutadiene rubbers or ethylene acid copolymer ionomer may be used to form the outer core layer. The ball further includes a cover that may be multi-layered. The foam cores have good resiliency.

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

A golf ball with a core comprising polybutadiene and graphene is disclosed herein. The golf ball has a single core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an inner core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an outer core comprising polybutadiene and graphene.

An object of the present invention is to provide a golf ball showing low spin rate on driver shots and high spin rate on approach shots. The present invention provides a multi-piece golf ball comprising a spherical center, at least two envelope layers covering the spherical center, and a cover covering the envelope layers, wherein the envelope layers comprise at least a first envelope layer covering the spherical center, and a second envelope layer covering the first envelope layer, a material hardness (H0) of the spherical center, a material hardness (H1) of the first envelope layer, and a material hardness (H2) of the second envelope layer satisfy an equation of H0>H1>H2, and the material hardness (H2) of the second envelope layer is lowest among the material hardness of the center constituent material and material hardness of envelope layer constituent materials.

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-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 ball comprising layer(s) comprised of a mixture of: (a) low molecular weight acid-containing wax(es); (b) non-acid-polymer(s) including at least one low molecular weight non-acid wax such as high density oxidized polyethylene homopolymers; ethylene maleic anhydride copolymers; polypropylene maleic anhydride copolymers; polypropylene homopolymers; ethylene-vinyl acetate copolymers; high density oxidized homopolymers; oxidized copolymers; polyethylene micronized waxes; polytetrafluoroethylene micronized waxes; emulsifiable low molecular weight non-acid waxes; non-emulsifiable low molecular weight non-acid waxes; and/or chemically modified low molecular weight non-acid waxes; and (c) organic acid(s) or salt thereof. Molecular weight of each low molecular weight acid-containing wax is about 500 to 7000, or up to 30,000. Interactions between components (a), (b), and (c) advantageously produce layer of ionomeric material having heat stability, processability, and well-retained durability, adhesion, CoR, compression and targeted feel without need for blending high and low molecular weight acid-containing polymer(s).

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.