A golf ball comprising a cover composed of a PPDI-based thermoplastic polyurethane material. The phase morphology of the PPDI-based thermoplastic polyurethane material coupled with high levels of hard segment domain cohesion imparts excellent low temperature flexibility, rubber like elasticity, and mechanical properties to the final elastomer.

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.

A golf ball 2 includes a core 4 and a cover 6. A value V calculated by the following mathematical formula is equal to or less than 1080 Hz.

V=NF(2)22/3*NF(2)1

In the mathematical formula, NF(2)1 represents a secondary natural frequency of the core 4, and NF(2)2 represents a secondary natural frequency of the golf ball 2. A difference (H1sH1o) between a Shore C hardness H1s at a surface of the core 4 and a Shore C hardness H1o at a central point of the core 4 is equal to or greater than 10. An amount of compressive deformation Df1 of the core 4 is equal to or greater than 4.1 mm.

Golf ball having a core and a cover of one or more layers, the core being formed of a material molded under heat from a rubber composition including a base rubber, an organic peroxide, and water and/or a metal monocarboxylate. Defining the tan slope as (tan .sub.10tan .sub.1)/(10%1%), where tan .sub.1 and tan .sub.10 are the loss tangents at dynamic strains of, respectively, 1% and 10% when the loss tangents of the core center and the core surface are measured at 12 C. and 15 Hz, the difference between the tan slopes at the core surface and the core center is larger than 0.002. Because a core material which undergoes little decrease in resilience over time and experiences little energy loss can be obtained, the golf ball maintains a good rebound, has a reduced spin rate and thus is able to achieve an increased distance.

Golf ball comprising at least one layer having a Shore D material hardness of from about 10 to about 55 and consisting of a millable polyurethane rubber composition comprising rubber consisting of: at least one polyether-based millable polyurethane rubber; at least one polyester-based millable polyurethane rubber; at least one polycaprolactone-based millable polyurethane rubber; or combinations thereof; wherein the millable polyurethane rubber composition is vulcanized. The rubber may be mixed/compounded with additional non-rubber ingredients such as at least one cross linking agent, peroxide initiator, filler, antioxidant, processing agent, light stabilizer, colorant, adhesion promotor, isocyanate and/or polyol, or combinations thereof. The at least one layer may be a cover layer, with a second layer, formed from at least one of a thermoset urethane or a thermoplastic material, being adjacent to an inner surface of the cover layer and meanwhile disposed about a polybutadiene-containing core. The rubber may be peroxide and/or sulfur cured.

Multi-layered golf ball core sub-assemblies and the resulting golf balls are provided. The core structure includes an inner core (center) comprising a foam composition, preferably foamed polyurethane. The intermediate and outer core layers are preferably formed from foamed and non-foamed thermoset compositions. For example, the intermediate core can be formed from a thermoset rubber so there are adjoining foam core layers (inner and intermediate) and the outer core layer can be formed from a non-foamed thermoset rubber. The core layers have different hardness and specific gravity levels. The core assembly preferably has a positive hardness gradient extending across the entire assembly. The core structure and resulting ball have relatively good resiliency.

An object of the present invention is to provide a golf ball excellent in flying performance, in particular, to provide a golf ball traveling a great flight distance. The present invention provides a golf ball having a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a rubber composition containing (a) a base rubber, (b) an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, and (d1) an aromatic carboxylic acid or (d2) an aromatic carboxylic acid salt, provided that the rubber composition further contains (e) a metal compound in the case of containing only (b) the ,-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent.