An object of the present invention is to provide a golf ball resin composition having improved rebound resilience performance. The present invention provides a golf ball resin composition containing: (A) a thermoplastic resin having an infrared absorption peak in a region from 3200 cm.sup.1 to 3600 cm.sup.1, and (B) at least one resin component selected from the group consisting of (b-1) a binary copolymer composed of an olefin and an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms, (b-2) a metal ion-neutralized product of a binary copolymer composed of an olefin and an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms, (b-3) a ternary copolymer composed of an olefin, an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms and an ,-unsaturated carboxylic acid ester, and (b-4) a metal ion-neutralized product of a ternary copolymer composed of an olefin, an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms and an ,-unsaturated carboxylic acid ester, wherein when a relaxation modulus Er (20 C., 9%) of the golf ball resin composition is measured under conditions of 20 C. and a strain of 9%, a relaxation curve is plotted with the relaxation modulus (MPa) as the vertical axis and a logarithm (ln(t)) of time (sec) as the horizontal axis, and the relaxation curve is linearly approximated to obtain a linear approximation curve, the linear approximation curve has a slope in an absolute value of 7 or more.

In a golf ball having a core, an outermost layer and an intermediate layer therebetween, the intermediate layer is formed of a thermoplastic resin composition that includes (A) an ionic olefin-methacrylic acid-unsaturated carboxylic acid ester copolymer, (B) a nonionic olefin-acrylic acid copolymer, (C) an organic acid or a metal salt thereof, and (D) a basic inorganic metal compound, and the outermost layer is formed of a thermoplastic resin composition that includes (a) a specific ionic olefin-unsaturated to carboxylic acid copolymer and (h) a specific ionic olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer. The ratio (tan ) between the tensile storage modulus (E) and the tensile loss modulus (E) in a dynamic viscoelasticity test on the outermost layer-forming resin composition conducted under specific conditions is not more than 0.150. This combination of intermediate layer and outermost layer materials has is a large spin rate-lowering effect on the ball, enabling the ball to travel further.

An object of the present invention is to provide a golf ball travelling a great flight distance on driver shots, exhibiting an excellent spin performance on approach shots under a dry condition and a wet condition, and showing an excellent shot feeling and durability. The present invention provides a golf ball comprising a golf ball body having a spherical core, an intermediate layer and a cover, and a paint film composed of two or more layers, wherein a 10% elastic modulus difference (M.sub.inM.sub.out) between an innermost layer and an outermost layer of the paint film is 25 kgf/cm.sup.2 or more.

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

A method for forming a golf ball provides a core member comprising a core of a golf ball into a cavity of a mold so that the core member is supported by a movable holding pin disposed in the mold; forming a layer outside the core member by injecting a material of the layer into the cavity; and retracting the pin from the cavity into the mold during the material injection so that a portion projecting from a surface of the layer is formed by a tip of the pin, the projecting portion having a site area of at least 0.2% in relation to an entire area of the tip of the pin and having a height of at least 0.2 mm. This method can be implemented by controlling the retraction of the pin, or alternatively by using the pin having a predetermined indentation portion on the tip.

The invention provides a golf ball having a core and a cover of one or more layer encasing the core, wherein the cover has an outermost layer molded of a thermoplastic material selected from the group consisting of polyurethane, polyurea and mixtures thereof and, letting the absorbance peak heights near a wave number of 1512 cm.sup.1 measured by the attenuated total reflectance method in Fourier transform infrared absorption spectroscopy (FT-IR/ATR spectroscopy) at an outside portion and an inside portion of the outermost cover layer be respectively P.sub.1 and P.sub.2, the value P.sub.1-P.sub.2 is at least 0.02.

A golf ball has a large number of dimples 10 on a surface thereof. The dimples 10 include a plurality of small dimples 10S each having an area of less than 8.0 mm.sup.2, and a plurality of large dimples 10L each having an area of equal to or greater than 8.0 mm.sup.2. A ratio PS of a sum of areas of all the small dimples 10S to a surface area of a phantom sphere of the golf ball is less than 2.0%. A ratio PL of a sum of areas of all the large dimples 10L to the surface area of the phantom sphere is equal to or greater than 79.0%. A degree G of uniformity of areas of the large dimples 10L is equal to or less than 1.15.

The invention provides a golf ball having a core and a cover of one or more layer encasing the core, wherein the cover has an outermost layer molded of a thermoplastic material selected from the group consisting of polyurethane, polyurea and mixtures thereof and, letting the absorbance peak heights near a wave number of 1512 cm.sup.1 measured by the attenuated total reflectance method in Fourier transform infrared absorption spectroscopy (FT-IR/ATR spectroscopy) at an outside portion and an inside portion of the outermost cover layer be respectively P.sub.1 and P.sub.2, the value P.sub.1P.sub.2 is at least 0.02.

An object of the present invention is to provide a golf ball travelling a great flight distance on driver shots, exhibiting an excellent spin performance on approach shots under a dry condition and a wet condition, and showing an excellent shot feeling and durability. The present invention provides a golf ball comprising a golf ball body having a spherical core, an intermediate layer and a cover, and a paint film composed of two or more layers, wherein a 10% elastic modulus difference (M.sub.inM.sub.out) between an innermost layer and an outermost layer of the paint film is 25 kgf/cm.sup.2 or more.

An object of the present invention is to provide a golf ball showing an increased spin rate on approach shots under a wet condition while maintaining a spin rate on approach shots under a dry condition. The present invention provides a golf ball comprising a golf ball body and a paint film formed on a surface of the golf ball body, wherein the paint film has a multi-layered construction composed of two or more layers, and a difference (M.sub.outM.sub.in) between a 10% elastic modulus (M.sub.out) of an outermost layer of the paint film and a 10% elastic modulus (M.sub.in) of an innermost layer of the paint film is 25 kgf/cm.sup.2 or more.