Golf ball having at least three layers comprising ionomeric and/or HNP compositions, wherein for each two adjacent layers, a relationship is established between a ratio of the volumes of the two adjacent layers and a ratio of the percent neutralizations of those two layers such that the volumes and % neutralizations of all layers are interrelated and interdependent to produce unique and desirable playing characteristics. In one embodiment, a golf ball of the invention has T layers, wherein T3 and each of T layers has a different volume V and comprises an ionomeric and/or HNP composition having a different % neutralization N. Furthermore, each of n inner layers of the T layers (n<T) has an adjacent surrounding layer n+1 such that a volume V.sub.n and a % neutralization N.sub.n of each inner layer and a volume V.sub.(n+1) and % neutralization N.sub.(n+1) of each adjacent surrounding layer n+1 satisfy the relationship (V.sub.nV.sub.(n+1))/V.sub.n(N.sub.nN.sub.(n+1))/N.sub.(n+1).

Golf ball having at least three layers comprising ionomeric and/or HNP compositions, wherein for each two adjacent layers, a relationship is established between a ratio of the volumes of the two adjacent layers and a ratio of the percent neutralizations of those two layers such that the volumes and % neutralizations of all layers are interrelated and interdependent to produce unique and desirable playing characteristics. In one embodiment, a golf ball of the invention has T layers, wherein T3 and each of T layers has a different volume V and comprises an ionomeric and/or HNP composition having a different % neutralization N; and wherein each of n inner layers of the T layers (n<T) has an adjacent surrounding layer n+1 such that a volume V.sub.n and a % neutralization N.sub.n of each inner layer and a volume V.sub.(n+1) and % neutralization N.sub.(n+1) of each adjacent surrounding layer n+1 satisfy the relationship (V.sub.(n+1)V.sub.n)/V.sub.(n+1)(N.sub.nN.sub.(n+1))/N.sub.(n+1).

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

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.

A foam composition that includes a polymer material such as polyurethane or polyurea and a leachable water-soluble fine powder is provided. This composition can be used in a relatively simple process to obtain a foam body (porous body) that is uniform only at the surface or uniform throughout. The foam body can be suitably used as a golf ball member in golf balls required to have good controllability on approach shots. Also provided is a method for producing a foam member, which method includes the steps of molding the foam composition to obtain a solid molded body, and then leaching out and removing the water-soluble fine powder so as to obtain a foam-molded body.

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.

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

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.

A golf ball has arranged thereon one or more dimples having a cross-sectional shape specified by a particular sequence of steps, and the total number of dimples on the ball surface is from 250 to 380. This ball has a reduced air resistance during flight, enhancing the aerodynamic performance and enabling an increased distance to be achieved.

Multi-layered golf balls having a core made of a foamed composition, preferably polyurethane foam, are provided. The ball includes a dual-layered core having a foam inner core (center) and surrounding outer core layer. The outer core layer may be made from a non-foamed thermoset material such as polybutadiene rubber. The ball further includes an inner cover, preferably made from an ionomer composition comprising an O/X-type acid copolymer, wherein O is -olefin, and X is a C.sub.3-C.sub.8 ,-ethylenically unsaturated carboxylic acid. The outer cover may be made from a non-foamed thermoset or thermoplastic material such as polyurethane. Preferably, the specific gravity of the inner cover is greater than the specific gravity of the outer core, which is greater than the specific gravity of the inner core. The finished ball has good distance and low-spin properties.