A multi-piece solid golf ball for professional golfers and skilled amateurs in particular is endowed with an excellent distance, a soft yet good feel at impact and a good durability. In the ball, which includes a core, an envelope layer, an intermediate layer and a cover, the core has a hardness profile which satisfies specific conditions, the envelope layer has a thickness of from 0.3 to 1.2 mm, the intermediate layer has a thickness of from 0.3 to 1.2 mm, and the envelope and intermediate layers have a combined thickness from of 0.8 to 1.7 mm.

In a resin composition for golf balls that includes, as a primary ingredient, a polyurethane or polyurea, letting P1 be the absorbance peak height near a wave number of 697 cm.sup.1 and P2 be the absorbance peak height near a wave number of 1512 cm.sup.1 in the infrared absorption spectrum of the composition measured by ATR/FT-IR spectroscopy, the ratio P1/P2 is from 0.03 to 2.10. When used as a cover material in golf balls having a core and a cover of one or more layer, the resin composition keeps the ball from flying too far on approach shots and also gives the ball a good controllability without sacrificing distance on shots with a driver.

In a multi-piece solid golf ball made up of, successively, a core, an intermediate layer and a cover having numerous dimples on the surface thereof, the intermediate layer is formed of a resin material and the cover is formed of a urethane resin material, each having a specific respective Shore D hardness. The ball has a specific (intermediate layer thickness)/(core diameter) value and a specific (cover thickness)/(core diameter) value, and the core has a specific deflection. The sphere consisting of the core encased by the intermediate layer has an initial velocity A and the core has an initial velocity B which together satisfy the condition AB0 m/s. This golf ball provides an increased distance and has both a soft feel when played and a high durability to repeated impact.

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.

In a multi-piece solid golf ball having a core, an intermediate layer encasing the core and a cover which encases the intermediate layer and has numerous dimples on an outside surface thereof, the intermediate layer is formed of a resin material comprising an ionomer resin as a base resin and an inorganic granular filler, the cover is formed of a urethane resin material, the core has a diameter of at least 38.0 mm, the core has specific deflection, the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere) has a surface hardness on the Shore D hardness scale of at least 69, the ball has a surface hardness on the Shore D hardness scale of 62 or less, and the (intermediate layer thickness)/(core diameter) value is from 0.025 to 0.043, the (cover thickness)/(core diameter) value is from 0.014 to 0.027.

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.

Golf ball comprising layer(s) consisting of a mixture consisting of: i) ethylene acid copolymer(s) and/or ionomer(s); ii) polyethylene(s); iii) polymeric epoxy crosslinker(s); and iv) compatibilizing polymer(s). The ethylene acid copolymer(s)/ionomer(s) and the polyethylene(s) may be included in a blend in a wt % ratio of from about 85:15 to 55:45; the at least one polymeric epoxy crosslinker and compatibilizing polymer may be included in amounts, based on 100 parts of the blend, of from about 2.0 to about 10.0 parts; and from about 1.0 to about 10.0 parts, respectively. The polyethylene may be polyethylene butene; polyethylene hexene; polyethylene octene; and combinations thereof. Each ethylene acid copolymer, polyethylene, polymeric epoxy crosslinker, and compatibilizing polymer has a density less than 1.0 g/cm.sup.3. The mixture is moldable and meanwhile possesses similar desirable CoR, DCM compression, Shore D hardness, and Shore C hardness as a mixture consisting of ingredients i), ii) and iv).

Golf ball having CoR of at least 0.700 and compression of at least 50 and comprising a layer of a mixture of thermoset or thermoplastic composition and a plurality of conductive nanoshelled structures such as conductive hollow nanoshells and/or nanorice particles. Conductive nanoshelled structures may be included in amount of from about 2 wt % to greater than 50 wt. % of total weight of mixture. Diameter of each conductive nano shelled structure at widest cross-section may be up to 1000 nm. Each conductive hollow nanoshell may have shell thickness to longitudinal diameter ratio of from about 1:3 to about 1:100. Each nanorice particle may have longitudinal diameter of up to 1000 nm. Shell thickness can be from 1 nm to 100 nm and may be controlled. A layer consisting of mixture may have specific gravity that differs from specific gravity of a layer consisting of the thermoset or thermoplastic composition portion of mixture.

Golf ball constructions incorporating at least one layer comprising a polycyclopentene rubber having advantageously modified end groups.