The present invention is directed to multi-layer golf balls including a layer formed from a composition comprising a relatively soft or low modulus HNP, a layer formed from a composition comprising a relatively hard or high modulus HNP, an inner cover layer formed from a thermoplastic composition, and an outer cover layer.

The present invention is directed to multi-layer golf balls including a layer formed from a relatively soft or low modulus HNP composition and a layer formed from a relatively hard or high modulus HNP composition. Optionally, the soft (or low modulus) HNP composition and/or the hard (or high modulus) HNP composition is plasticized or is replaced with a different plasticized acid copolymer composition.

In a multi-piece solid golf ball having a core, a cover and an intermediate layer therebetween, the core, an intermediate layer-encased sphere and the ball have surface hardnesses which satisfy a specific relationship, and the intermediate layer and the cover have thicknesses which satisfy a specific relationship. Also, the core has a hardness profile in which the hardnesses at the core surface, core center, a position 5 mm from the core center, and a position midway between the surface and center of the core satisfy specific relationships. This golf ball, when used by mid- and high-level amateurs, enables the golfer to maintain an adequate distance on shots with a driver and achieve a good distance on iron shots, has a good spin performance on approach shots and has a good feel on impact. In addition, the ball has an excellent scuff resistance when struck with a grooved wedge.

In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer, and a cover with a plurality of dimples thereon, the core is a two-layer core consisting of an inner core layer and an outer core layer each formed primarily of a base rubber, the envelope layer, the intermediate layer and the cover layer are each composed of at least one layer and formed primarily of a synthetic resin material, and the initial velocities and surface hardnesses of the core, the envelope layer-encased sphere and the intermediate layer-encased sphere are designed within specific ranges. This golf ball satisfies at a very high level the flight and control performances expected for use by professional golfers and skilled amateurs, has the ability to move forward on a straight path particularly on full shots, and also has an excellent scuff resistance.

A golf ball 2 includes a core 4, a first mid layer 10, a second mid layer 12, a third mid layer 14, and a cover 8. A volume Vinm and a Shore D hardness Hinm of the first mid layer, a volume Vm and a Shore D hardness Hm of the second mid layer, a volume Voum and a Shore D hardness Houm of the third mid layer, a volume Vc and a Shore D hardness Hc of the cover, and a volume V of an entirety of the ball meet: (a) Hinm<Hm>Houm>Hc, (b) Vinm<Vm>Voum>Vc, (c) HmHc>25, (d) (Vinm+Vm+Voum+Vc)/V<0.40, (e) Vm/Vc>1.50, and (f) (Vm*Hm)/(Vc*Hc)>3.0.

In a multi-piece solid golf ball having a two-layer core consisting of an inner layer and an outer layer, a cover, at least one intermediate layer between the core and the cover, and a paint film layer formed on the cover surface, each layer of the two-layer core is formed primarily of a rubber composition, the intermediate layer and the cover are each formed primarily of a resin material, the core has a hardness profile which satisfies specific conditions, and the sphere consisting of the core encased by the intermediate layer has a higher surface hardness than the ball. When used by mid- to high-level golfers, this ball achieves sufficient reduction in the spin rate on full shots with a driver, enabling the distance to be increased, and the spin performance on approach shots is excellent, enhancing the enjoyability of the game.

Multi-layered golf balls containing a three-layered core assembly are provided. Preferably, at least one of the core layers is formed from a thermoplastic composition that comprises: a) thermoplastic non-acid polymer, and b) plasticizer. In one preferred embodiment, the inner core is made of a first thermoset composition, for example, polybutadiene rubber; and the intermediate core layer is made of a thermoplastic composition; and the outer core is made of a second thermoset composition. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. Suitable non-acid polymers include, for example, polyesters, polyamides, polyolefins, and polyurethanes. The core assembly has a relatively high resiliency at given compressions.

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 having at least three layers comprising an ionomeric and/or HNP composition, wherein for each two adjacent layers there is a relationship 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 the T layers has a different volume V and comprises an ionomeric and/or HNP composition having a different % neutralization N. Furthermore, each inner layer n 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.(n+1)N.sub.n)/N.sub.n.

In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer, and a cover with a plurality of dimples thereon, the core is a two-layer core consisting of an inner core layer and an outer core layer each formed primarily of a base rubber, the envelope layer, the intermediate layer and the cover layer are each composed of at least one layer and formed primarily of a synthetic resin material, and the initial velocities and surface hardnesses of the core, the envelope layer-encased sphere and the intermediate layer-encased sphere are designed within specific ranges. This golf ball satisfies at a very high level the flight and control performances expected for use by professional golfers and skilled amateurs, has the ability to move forward on a straight path particularly on full shots, and also has an excellent scuff resistance.