Low compression multi-piece golf balls having a solid core comprising at least one layer made of a plasticized thermoplastic composition are provided. Preferably, the ball has a compression of less than 60 and more preferably less than 50. The ball includes a cover in addition to the core sub-assembly. For example, two-piece and three-piece golf balls may be made. The plasticized thermoplastic composition preferably comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. Preferably, a fatty acid ester such as butyl oleate is used as the plasticizer. In two-layered core constructions, the outer core layer is preferably formed from a thermoset composition such as polybutadiene rubber. The core layers may have different hardness levels. The core structure and resulting ball have relatively good resiliency at given compressions.

An object of the present invention is to provide a golf ball showing a low spin rate on driver shots and a high spin rate on approach shots. The present invention provides a golf ball having a low hardness part having a hardness in a range from 5 to 40 in Shore D hardness or a lowest hardness point in a core hardness distribution in a region located at a distance from 36.0% to 65.0% of a radius of the golf ball from a center point of the golf ball.

A thermoplastic multi-layer golf ball has a core center including a first thermoplastic material, a core layer including a second thermoplastic material, and a cover including a third thermoplastic material. The core center has a diameter of 21-29 mm and a surface Shore D hardness H1 of less than about 50. The core layer is at least about 5 mm thick with an outer surface Shore D hardness H2 of more than about 50. The cover has an outer surface Shore D hardness H3 of more than about 60. H3 is up to about 20 Shore D units higher than H2, and H2 is up to about 10 Shore D units higher than H1. The core layer has a specific gravity that is at least 0.1 g/cm.sup.3 greater than the specific gravity of the core center.

An object of the present invention is to provide a golf ball having excellent shot feeling and flight distance. The present invention provides a golf ball comprising a spherical core, a first resin layer and a second resin layer, wherein the first resin layer is formed from a first resin composition containing (A) a polyamide resin, (B) a copolymer and/or a metal ion-neutralized product thereof, and (C) a thermoplastic elastomer, and having a ratio (flexural elastic modulus/slab hardness) of a flexural elastic modulus (MPa) to a slab hardness (Shore D hardness) in a range from 3 to 5; and the second resin layer is formed from a second resin composition containing (D) a polyamide resin, and (E) a copolymer and/or a metal ion-neutralized product thereof.

Multi-layered golf balls having at least one layer made of a foamed silicone composition are provided. Multi-layered golf balls having at least one layer made of non-foamed silicone elastomer composition also are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core and cover structures can be made. The foamed silicones have good thermal stability and durability without sacrificing resiliency. The non-foamed silicone elastomers have high elongation, tensile strength, chemical/fluid-resistance, and weatherability properties. These compositions can be used to form any layer, for example, core, intermediate, or cover, in the golf ball.

A rubber composition for golf balls includes (A) a base rubber, (B) an acrylate ester or methacrylate ester containing an isocyanate group or a blocked isocyanate group, (C) diacrylic acid, dimethacrylic acid or a metal salt thereof, and (D) an organic peroxide. In a golf ball having a core formed of the rubber composition and a cover of one or more layers which encases the core, the rubber composition exhibits a spin rate-lowering effect on shots and can thus improve the flight performance of the ball.

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, the cover is formed of a urethane resin material, the core has a diameter of at least 38.0 mm, the core has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) of at least 3.9 mm, the core has a center and a surface such that the value obtained by subtracting the JIS-C hardness at the core center from the JIS-C hardness at the core surface is at least 15, 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, an envelope layer, an intermediate layer and a cover, the core, an intermediate layer-encased sphere and the ball have surface hardnesses which satisfy a specific relationship, and the envelope layer, 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.

A constituent member of a golf ball comprising a vulcanized form of a rubber composition includes (a) a base rubber, (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid and/or a metal salt thereof, (c) an organic peroxide, (d) water, (e) an antioxidant which is a benzoimidazole of the following general formula and/or a metal salt thereof, and (g-1) an organosulfur being alkylphenoldisulfide polymers represented by the specific chemical formula or (h) sulfur. When the rubber composition is used in constituent members of a golf ball, especially the core, the golf ball exhibits low spin properties on shots, resulting in an improved flight performance and enabling a good durability to be maintained.

Methods for making multi-piece golf balls comprising at least one component made of ethylene-propylene diene copolymer (EPDM) rubber and the resulting balls are provided. The multi-piece golf ball includes a cover, preferably a dual-cover having inner and outer cover layers. The outer cover is preferably made of a liquid rubber composition based on liquid EPDM rubber. In one version, the ball sub-assembly is dipped in a bath containing liquid EPDM rubber to form the outer cover. In another version, a casting method is used and the liquid EPDM rubber is dispensed into mold cavities to form the outer cover. The inner core of the ball may be made of polybutadiene rubber and the outer core layer may be made of EPDM rubber. The resulting golf ball has high resiliency, a soft feel, and good weatherability.