An object of the present invention is to provide a golf ball having an excellent initial velocity when being hit at a head speed of 50 m/sec and an improved initial velocity when being hit at a head speed of 40 m/sec. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the golf ball has a rebound equivalence energy ratio (R.sub.40) ranging from 65.50% to 99.0% at a deformation amount of 7%, and a rebound equivalence energy ratio (R.sub.50) ranging from 20.0% to 70.0% at a deformation amount of 19%, in a compression test (measurement temperature: 70 C., compression speed: 30 mm/min) applying a load to the golf ball along a radial direction of the golf ball.

An object of the present invention is to provide a golf ball having an excellent spin performance on approach shots under a wet condition. The present invention provides a golf ball comprising a spherical core and a cover covering the spherical core, wherein the cover is formed from a cover composition containing (A) a polyurethane and (B) a polyrotaxane as a resin component, and wherein (B) the polyrotaxane has a cyclodextrin, a linear molecule piercing through the cyclic structure of the cyclodextrin, and blocking groups 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 OC.sub.3H.sub.6O group.

Provided is a golf ball comprising a spherical core including an inner layer and an outer layer, an intermediate layer and a cover, wherein a difference (H.sub.X+1H.sub.X1) 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 of a hardness gradient of the inner layer is 0 or more, a difference () between the angle and an angle of a hardness gradient of the outer layer is 0 or more, the intermediate layer has a material hardness (Hm) ranging from 65 to 80 in Shore D hardness, and the intermediate layer has a highest hardness among the constituent members of the golf ball.

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 material for obtaining a golf ball having excellent shot feeling and flight distance. The present invention provides a golf ball resin composition 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 containing, as a resin component, (A) a polyamide resin, (B) at least one selected from the group consisting of (b-1) a binary copolymer, (b-2) a metal ion-neutralized product of a binary copolymer, (b-3) a ternary copolymer and (b-4) a metal ion-neutralized product of a ternary copolymer, and (C) a thermoplastic elastomer.

A golf ball 2 includes a core 4, a mid layer 6, a cover 8 and a paint layer 10. The core 4 includes a center 12 and an envelope layer 14. The golf ball 2 satisfies the following mathematical formulas. In the mathematical formulas, Tm represents a thickness of the mid layer, Tcmin represents a minimum thickness of the cover, Tcmax represents a maximum thickness of the cover, and Tp represents a thickness of the paint layer. The golf ball 2 has a large number of dimples 16 on a surface thereof. The number of planes that can divide a pattern of the dimples so that divided patterns are mirror symmetry to each other is one.
Tm>TcmaxTcmin>Tp
(TcmaxTcmin)0.15 mm
0.15(Tp/Tcmin)0.04

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.

A multi-layer golf ball includes a core, an intermediate layer surrounding the core, and a cover layer surrounding the intermediate layer. The core defines an outer surface that includes a plurality of polygonal land portions substantially aligned on a common sphere, which has a diameter of between 22 mm and 32 mm. The intermediate layer has a radially inward-facing surface that is flush with the outer surface of the core, and has a radial thickness of between 4 mm and 9 mm. The outer surface of the core defines a first set of annular grooves disposed about a first axis, and a second set of annular grooves disposed about a second axis. Each of the first and second set of annular grooves extend radially inward from the common sphere, and the first axis and the second axis are orthogonal.

Multi-piece golf balls having a solid core of at least one layer and cover of at least one layer are provided. Thermoplastic ethylene acid copolymer ionomer compositions are used to form the core layers. Preferably, the ball contains a dual-core having an inner core and surrounding outer core layer. Low modulus and high modulus ionomer compositions may be used in the core structure. In one embodiment, a first ionomer composition is used to form the inner core and a second ionomer composition is used to form the outer core, and the flex modulus of the first composition is greater than the flex modulus of the second composition. The ionomer compositions have varying levels of hardness. The resulting ball has high resiliency and rebounding properties.

The present invention relates to a golf ball and a method for manufacturing same. The golf ball may include a first pole, a second pole, and a seam located between the first pole and the second pole, and a section structure including an outer surface having a plurality of dimples, a core, and a cover surrounding the core. In certain embodiments, the core includes 100 parts by weight of a butadiene rubber and 0.5 to 10 parts by weight of a polymer resin. The cover may include 100 parts by weight of an ionomer resin and 1 to 10 parts by weight of a butadiene rubber having a 1,2-bond content of 90% or more.