Provided is a golf ball is excellent in flight distance performance, approach performance, and feel at impact. A ball 2 includes a core 4, a mid layer 6, and a cover 8. The core 4 includes an inner core 10 and an outer core 12. The cover 8 includes an inner layer cover 10 and an outer layer cover 12. An inner core volume Vc, a mid layer volume Vm, a mid layer hardness Hm, an inner layer cover volume Vinc, an inner layer cover hardness Hinc, an outer layer cover volume Vouc, an outer layer cover hardness Houc, and a ball volume V meet the following relational expressions (a) to (g): (a) Vc/V<0.07, (b) Hm>Hinc>Houc, (c) Hm−Houc>25, (d) Vm>Vinc>Vouc, (e) (Vm+Vinc+Vouc)/V<0.30, (f) Vm/Vouc>1.50, and (g) (Vm*Hm)/(Vouc*Houc)>3.0.

An object of the present invention is to provide a golf ball traveling a great distance on driver shots. The present invention provides a golf ball comprising a spherical core including an inner layer and an outer layer, wherein a difference (H.sub.X+1−H.sub.X−1) between a hardness (H.sub.X+1) at a point outwardly away in a radial direction from a boundary between the inner layer and the outer layer of the spherical core by 1 mm and a hardness (H.sub.X−1) at a point inwardly away in the radial direction from the boundary between the inner layer and the outer layer of the spherical core by 1 mm is 0 or more in Shore C hardness, a surface hardness (H.sub.X+Y) of the spherical core is more than 70 in Shore C hardness, an angle α of a hardness gradient of the inner layer is 0° or more, a difference (α−β) between the angle α and an angle β of a hardness gradient of the outer layer is 0° or more, and the intermediate layer has a highest hardness among the constituent members of the golf ball.

Buoyant dimpled golf ball having CoR ≥0.810, specific gravity <1.00 g/cc, initial velocity ≥250 ft/s, first aerodynamic coefficient magnitude between about 0.25 and about 0.30 and first aerodynamic force angle between about 29 degrees and 34 degrees at Reynolds Number of 230000 and spin ratio of 0.085; and second aerodynamic coefficient magnitude between about 0.26 and about 0.31 and second aerodynamic force angle between about 31 degrees and 36 degrees at Reynolds Number of 180000 and spin ratio of 0.101. Golf ball may additionally have third aerodynamic coefficient magnitude between about 0.27 and about 0.32 and third aerodynamic force angle between about 34 degrees and 39 degrees at Reynolds Number of 133000 and spin ratio of 0.133; and fourth aerodynamic coefficient magnitude between about 0.33 and about 0.38 and fourth aerodynamic force angle between about 38 degrees and 43 degrees at Reynolds Number of 89000 and spin ratio of 0.183.

The invention provides a golf ball that is a one-piece golf ball or a golf ball having a core and a cover of one layer or a plurality of layers, wherein the one-piece golf ball or core is formed of a material molded under heat from a rubber composition containing: (A) a base rubber, (B) an organic peroxide, (C) water, (D) a metal methacrylate and (E) zinc oxide.

The content of component (D) per 100 parts by weight of component (A) is from 30 to 45 parts by weight. The molar ratio (C)/(D) between components (C) and (D) satisfies the formula

0.9<(C)/(D)<1.1.

The core has an initial velocity V.sub.0 of at least 72.0 m/s and up to 75.0 m/s.

In a golf ball having a core and a cover of one or more layer, the core is formed of a material molded under heat from a rubber composition containing (a) a base rubber, (b) water and/or a lower alcohol having a specific molecular weight, (c) an α,β-unsaturated carboxylic acid and/or a metal salt thereof, and (d) an organic peroxide.

The base rubber (a) is a rubber obtained by mixing together (a-1) a polybutadiene and (a-2) an unneutralized ethylene-unsaturated carboxylic acid copolymer, and subsequently neutralizing the copolymer with (a-3) a metal oxide. Component (a-2) has a specific acid content and accounts for a specific portion of the combined amount of components (a-1) and (a-2). The core surface and center have a specific JIS-C hardness difference therebetween.

This ball achieves both a lower spin rate and excellent durability while maintaining a high rebound.

Multi-layer golf balls comprising a single- or dual-layer core, an intermediate layer, and an outer cover layer are disclosed. The intermediate layer is formed from a thermoplastic elastomer composition and has a surface hardness which is greater than the center hardness of the core and less than the outer surface hardness of the core. The outer surface hardness of the outer cover layer is greater than the outer surface hardness of the core.

Golf balls having a single or dual-layered solid core are provided. In one embodiment, the golf ball has dimensions and properties that do not conform to the rules of the United States Golf Association (USGA). For example, the ball weight; ball size; ball spherical symmetry; ball initial velocity; and/or ball overall distance may fall outside of the USGA standards. The dual-layered core can have an inner core comprising a thermoplastic composition and surrounding outer core comprising a thermoset composition. In another embodiment, the dual-layered core has an inner core comprising a thermoplastic composition and outer core comprising a thermoset composition. The thermoplastic composition preferably comprises an ethylene acid copolymer ionomer and plasticizer. The thermoset composition preferably comprises polybutadiene rubber. The ball further includes a cover of at least one layer.

An object of the present invention is to provide a golf ball having excellent durability and good shot feeling. The present invention provides a golf ball comprising a core, wherein a difference (crosslinking density at surface of core-crosslinking density at center of core) between a crosslinking density at a surface of the core and a crosslinking density at a center of the core is more than 1.0×10.sup.2 mol/m.sup.3 and less than 9.0×10.sup.2 mol/m.sup.3, and a hardness difference (Hs−Ho) between Hs and Ho is 13.0 or more and 30.0 or less, and the core satisfies H50-Ho>Hs-H50, wherein Hs (Shore C hardness) is a hardness at the surface of the core, Ho (Shore C hardness) is a hardness at the center of the core, and H50 (Shore C hardness) is a hardness at a midpoint between the center of the core and the surface of the core.

An object of the present invention is to provide a golf ball having excellent resilience performance. The present invention provides a golf ball having a spherical core and at least one cover layer, wherein the spherical core is formed from a rubber composition containing (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, and (c) a crosslinking initiator, provided that the rubber composition further contains (d) a metal compound in the case of containing only (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as the co-crosslinking agent, wherein (c) the crosslinking initiator includes a peroxy ketal represented by the formula (1), and substituents represented by R.sup.1 and R.sup.2 have a bond dissociation energy of 435 KJ/mol or more.

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An object of the present invention is to provide a golf ball having excellent abrasion resistance and spin performance on driver shots. The present invention provides a golf ball having a spherical core and a cover covering the spherical core, wherein the cover contains a polyurethane, wherein the polyurethane comprises, as a constituent component, (A) a polyisocyanate component and (B) a polyol component containing (b1) a polyrotaxane, and wherein (b1) the polyrotaxane has a cyclodextrin, a linear molecule piercing through the cyclic structure of the cyclodextrin, and a blocking group located at both terminals of the linear molecule to prevent disassociation of the cyclodextrin, and at least a part of hydroxyl groups of the cyclodextrin is modified with a caprolactone chain via —O—C.sub.3H.sub.6—O— group.