In a golf ball having a core composed of one or more layer, the outermost layer of the core is formed of a rubber composition containing an α,β-unsaturated metal carboxylate, and an envelope layer directly encasing the core is formed of a resin composition containing a thermoplastic resin having a structure that includes α,β-ethylenically unsaturated carboxylic acid copolymerization units. The infrared absorption spectra at surface sites on the outermost layer of the core, as measured by ATR FT-IR spectroscopy, satisfy a specific condition. The ball has an enhanced adhesion between the rubber-based core and the adjacent cover layer that is formed of an ionomer resin or other α,β-ethylenically unsaturated carboxylic acid copolymer-containing resin material.

An object of the present invention is to provide a golf ball having a decreased spin rate on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a rubber composition containing (a) a base rubber, (b) two or more α,β-unsaturated carboxylic acids having 3 to 14 carbon atoms and having no substituent group at a carbon atom bonding to the carboxy group, and/or a metal salt thereof, and (c) a crosslinking initiator.

A golf ball has a core, an inner cover, an outer cover, and dimples. The golf ball satisfies the following mathematical formulas.
Sa=4500+10(A−0.5B−2Cs)≥4000
0.04Sa+160−20≤D≤0.04Sa+160+20 A: a compression (Atti) of the golfball B: a hardness difference (Shore C) between a surface and a center of the core Cs: (Hi×Ti+2Ho×To)/(Ti+2To) D: a total volume (mm.sup.3) of the dimples Hi: a hardness (Shore D) of the inner cover Ho: a hardness (Shore D) of the outer cover Ti: a thickness (mm) of the inner cover To: a thickness (mm) of the outer cover

In a golf ball having a core and a cover, the cover is formed primarily of polyurethane, the ball has a diameter of at least 42.8 mm and a weight of not more than 44.9 g and, in an impact test carried out by hitting the ball with a driver at a head speed of 40 m/s, the sum t1+t2 of the time t1 required from initial contact by the driver with the ball for deformation of the ball to reach a maximum and the time t2 required from the state of maximum ball deformation for the ball and driver to separate is not more than 660 μsec. This golf ball makes it possible for golfers who have a high head speed and ordinary golfers who do not to compete without relying excessively on superiority in terms of distance.

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. In one preferred embodiment, each core layer has a positive hardness gradient. The center of the core comprises a metal material such as copper, steel, brass, tungsten, titanium, aluminum, and alloys thereof. The intermediate core layer is preferably formed from a thermoset composition such as polybutadiene rubber, and the outer core layer is preferably formed from a thermoplastic composition such as an ethylene acid copolymer. The resulting ball has high resiliency and good spin control.

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

An object of the present invention is to provide a golf ball having a decreased spin rate on driver shots. The present invention provides a golf ball comprising a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a rubber composition containing (a) a base rubber, (b) a compound represented by the formula (1) as a co-crosslinking agent, and (c) a crosslinking initiator,
(R.sup.1COO)M(OCOR.sup.2)m  (1) in the formula (1), M represents a metal atom, m represents 1 or 2, R.sup.1 and R.sup.2 are different from each other, represent an alkenyl group having 2 to 30 carbon atoms or an alkynyl group having 2 to 30 carbon atoms and have a carbon-carbon double bond or a carbon-carbon triple bond at an α-position carbon atom bonding to the carbonyl group, and when m is 2, two of R.sup.2 may be identical to or different from each other.

A golf ball includes a core, a mid layer, and a cover. An amount of compressive deformation C3 of the golf ball can be not less than 2.80 mm. The golf ball can satisfy the following mathematical formulas (1) and (2):
C1>(124.8−Hs)/11.5  (1)
C2−C1≥(−1/6*C1+(68−H2)/20+(5−Hd)/100)*T2  (2), where C1 is an amount of compressive deformation (mm) of the core, C2 is an amount of compressive deformation (mm) of a sphere including the core and the mid layer, Hd is Hs−Ho, Ho is a hardness (Shore C) of a center the core, Hs is a hardness (Shore C) of a surface of the core, H2 is a hardness (Shore D) of the mid layer, and T2 is a thickness (mm) of the mid layer.

Golf ball comprising a core, an outer layer and at least one adhesion promoting coating disposed between each of the core and the outer layer; the core comprising a rubber composition comprising at least one zinc-containing and/or magnesium-containing component; the outer layer comprising at least one ionomer; and the adhesion promoting coating comprising a waterborne dispersion comprised of at least one ethylene acid copolymer having an acid content of at least 15% by weight wherein the copolymer is at least partially neutralized with one or more neutralizing agent; wherein at least one neutralizing agent is selected from ammonia compounds and/or amine compounds. In a specific embodiment, the at least one neutralizing agent comprises i) mono and/or divalent metal compounds and ii) ammonia compounds and/or amine compounds.

The present invention provides the rubber composition for a golf ball comprising (a) a base rubber, (b) a co-crosslinking agent which is an α,β-unsaturated carboxylic acid or a metal salt thereof or both, (c) a crosslinking initiator, and (d) an alcohol, wherein the amount of component (d) is from 0.1 to 10 parts by weight per 100 parts by weight of the base rubber (a) and the compounding ratio between component (b) and component (c) is set to at least 60 of E value that is represented by “E=the molar amount of component (b)/the molar amount of the active oxygen of component (c), and a golf ball using the rubber composition, in order to achieve the object that good durability of the golf ball to impact is maintained.