An object of the present invention is to provide a golf ball traveling a great flight distance. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the golf ball has a ratio (t2/t1) of a time (t2) to a time (t1) of 1.05 or more in a hitting test using a driver (at a head speed of 40 m/sec), wherein the time (t1) is a time taken from a moment that the driver begins to contact with the golf ball to a moment that the golf ball reaches a maximum deformation amount, and the time (t2) is a time taken from the moment that the golf ball reaches the maximum deformation amount to a moment that the golf ball leaves the driver.

An object of the present invention is to provide a cured product of a golf ball rubber composition capable of imparting excellent durability to a golf ball. The present invention provides a cured product of a golf ball rubber composition, wherein the golf ball rubber composition contains (a) a base rubber, (b) an ,-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, and wherein an effective crosslinking density DC (mmol/cm.sup.3) of the cured product of the golf ball rubber composition and a tensile elastic modulus TM (MPa) between 0.05% strain and 0.25% strain of the cured product of the golf ball rubber composition satisfy a relation of TM3.33In(DC)>(0.10).

A golf ball includes a core and a cover. The core is formed of a material molded under heat from a rubber composition. The rubber composition includes components (A) through (C). The components (A) through (C) are (A) a base rubber, (B) an organic peroxide, and (C) a water providing agent. The water providing agent releases water at a vulcanization temperature at which the rubber composition is vulcanized. The dissociation rate of water of the water providing agent in the case of heating the water providing agent up to the vulcanization temperature of the rubber composition is 60% by mass or more.

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.

A golf ball includes a main body and a paint layer positioned outside the main body. The paint layer includes an inner layer and an outer layer positioned outside the inner layer. When an indentation depth (nm) is measured on a cross-section along a plane passing through a central point of the golf ball when a force of 30 mgf is applied to the cross-section in a direction perpendicular to the cross-section, an indentation depth Di on a cross-section of the inner layer is smaller than an indentation depth Do on a cross-section of the outer layer. A thickness To of the outer layer is larger than a thickness Ti of the inner layer.

An object of the present invention is to provide a cured product of a golf ball rubber composition imparting excellent durability. The present invention provides a cured product of a golf ball rubber composition cured from a golf ball rubber composition containing (a) a base rubber, (b) an ,-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, wherein the cured product of the golf ball rubber composition satisfies the following mathematical formula (1):

Y<0.1X1.30(1) in the formula (1), Y represents an effective crosslinking density of the cured product of the rubber composition (mmol/cc), and X represents an amount of the component (b) with respect to 100 parts by mass of (a) the base rubber (parts by mass).

A golf ball with a cover or mantle layer that comprises a polyurethane and ionomer hybrid made by compounding or dry blending acid functional polyurethane and an ionomer is disclosed herein. The golf ball comprises a core (single core or dual core), a mantle layer (single layer or dual layer) and a cover layer.

A golf ball with a core comprising polybutadiene and graphene with an embedded IC is disclosed herein. The golf ball preferably has a single core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an inner core comprising polybutadiene and graphene. Alternatively, the golf ball has a dual core with an outer core comprising polybutadiene and graphene.

Golf ball incorporating polyurethane mixture having wt. % NCO content of 4-20 and including a prepolymer polyol portion comprised of trans--Farnesene diol(s) in an amount of about 3-70 wt. % of total weight of prepolymer. Trans--Farnesene diol may be 15 carbon, long chain, branched, unsaturated 3,4-vinyl-containing bio-hydrocarbon having the formula: ##STR00001## Prepolymer can include a 1:99 to 99:1 blend (wt. % ratio) of Trans--Farnesene diol(s) and polybutadiene-based polyol(s) in an amount of about 35-85 wt. %, along with about 15 wt. %-65 wt. % of diisocyanate(s). Curative may be combined with prepolymer in amount of about 3-25 wt. % of total weight of curative and prepolymer combined, and may be mixture of aromatic diamine(s) and white dispersion in a wt. % ratio of about 90:10 to 50:50, plus catalyst. Hardness of polyurethane mixture can be from 75. Shore A to 75 Shore D or a material hardness can be from about 40 Shore D to about 65 Shore D.

In a multi-piece solid golf ball having a core, an intermediate layer and a cover, the cover is formed primarily of a polyurethane material, the ball has a higher surface hardness on the Shore C hardness scale than the sphere obtained by encasing the core with the intermediate layer (intermediate layer-encased sphere), and the ball has a deflection of at least 3.6 mm when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf). The golf ball has an excellent flight performance when hit by golfers whose head speeds are not very fast and moreover has a good, soft feel at impact, making it suitable for use by amateur golfers.