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

A golf ball includes a thermoplastic HNP inner core layer having a center hardness less than the surface hardness to define a positive hardness gradient. An outer core layer is formed from a thermoset rubber composition. The core layer has an inner surface hardness less than the outer surface hardness to define a positive hardness gradient of 3 to 30 Shore D. Inner and outer cover layers are disposed about the outer core layer. The HNP composition includes an acid copolymer of ethylene and an ,-unsaturated carboxylic acid; a non-acid polymer comprising polyolefins, polyamides, polyesters, polyethers, polyurethanes, metallocene-catalyzed polymers, single-site catalyst polymerized polymers, ethylene propylene rubber, ethylene propylene diene rubber, styrenic block copolymer rubbers, alkyl acrylate rubbers, or functionalized derivatives thereof; an organic acid or salt thereof; and a cation source in an amount sufficient to neutralize at least about 80% of the acid groups.

Multi-layered golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) comprising a thermoplastic composition, preferably including: a) ethylene acid copolymer, b) plasticizer, and c) cation source. Preferably, a fatty acid ester such as ethyl oleate is used as the plasticizer. The outer core layer is preferably formed from a thermoset composition such as polybutadiene rubber. The core layers have different hardness levels. For example, the inner core can have a positive, zero, or negative hardness gradient. 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.

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.

A golf ball has an inner core layer including a thermoplastic highly-neutralized ionomer and having a geometric center hardness less than a surface hardness to define a first positive hardness gradient. An outer core layer is formed about the inner core and includes a homogenous thermoset composition. The outer core has an interior hardness less than an outer surface hardness to define a second positive hardness gradient. An inner and outer cover layers are disposed about outer core layer. The first and second hardness gradients each have a slope and the slope of the second hardness gradient is less than the slope of the first hardness gradient such that a ratio of the first and second slopes is 0.8 to 0.85.

Golf ball having at least three layers comprising an ionomeric and/or HNP composition, 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, each of T layers, wherein T3, has a different volume V and comprises an ionomeric/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.(n+1)N.sub.n)/N.sub.n.

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

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

A golf ball includes an inner core layer including a thermoplastic highly-neutralized ionomer formed from a copolymer of ethylene and an ,-unsaturated carboxylic acid, an organic acid or salt thereof, and sufficient cation source to neutralize the acid groups of the copolymer by 80% or greater. The inner core has a geometric center hardness and a surface hardness to define a first positive hardness gradient having a first slope, S.sub.1. An outer core layer is disposed about the inner core and is formed from a second thermoplastic highly-neutralized ionomer. The outer core layer has an interior hardness and an outer surface hardness greater than the interior hardness to define a second positive hardness gradient having a second slope, S.sub.2. The golf ball also includes a cover layer.

The present invention relates to the use of a mono (meth)acrylate ester in a golf ball layer. The mono (meth)acrylate ester may be added to one or more portions of a golf ball including a core, intermediate, or cover layer. For example, in one embodiment, the mono (meth)acrylate ester may be blended with a polybutadiene rubber material. In another embodiment, the mono (meth)acrylate ester of the present invention may be blended with an ionomer. In some embodiments, the mono (meth)acrylate ester may be blended with a formulation including both a polybutadiene rubber component and an ionomer.