Sumitomo Rubber Industries Limited

Sri Sports Limited

Dunlop Sports Company Limited

Seiichiro Endo

Keiji Ohama

Masatoshi Yokota

Takahiro Sajima

Kazuhiko Isogawa

Kuniyasu Horiuchi

Koichi Fujisawa

Masaaki Kikuchi

Keiji Moriyama

Yoshikazu Yabuki

Kazuya Kamino

Tsutomu Hirau

Hirotaka Nakamura

Mikio Yamada

Yoshinori Sano

Hiroaki Tanaka

Hyoungchol Kim

Yoshiko Matsuyama

Hideaki Kawamatsu

Yoshiyuki Okido

Yoshiyuki Nakai

Takayuki Tanaka

Yoshiyuki Mimoto

Takamitsu Matsui

Noritake Araki

A golf ballincludes a spherical coreand a coverpositioned outside the core. The coreis obtained by crosslinking a rubber composition including 2-naphthalenethiol. The difference between: a hardness H(5.0) at a point which is located at a distance of 5 mm from the central point of the core; and a hardness Ho at the central point is 6.0 or greater. The difference between: a hardness H(12.5) at a point which is located at a distance of 12.5 mm from the central point; and the hardness H(5.0) is 4.0 or less. The difference between a hardness Hs at the surface of the coreand the hardness H(12.5) is 10.0 or greater. The difference between the hardness Hs and the hardness Ho is 22.0 or greater. There is no zone in which a hardness decreases from the central point to the surface.

Golf ball

Golf ballhas spherical core, coversituated on the external side of the core, and paint layersituated on the external side of the cover. The coverhas a Shore D hardness of no greater than 61. The paint layerhas a Martens hardness of no greater than 2.0 mgf/&#x3bc;m. The base polymer of the paint layeris a polyurethane obtained by a reaction of a polyol with a polyisocyanate. The polyisocyanate contains a buret-modified form of hexamethylene diisocyanate. The coverhas a thickness of 0.3 mm or greater and 1.0 mm or less. The paint layerhas a thickness of 5 &#x3bc;m or greater and 40 &#x3bc;m or less.

A golf ballincludes a spherical coreand a coverpositioned outside the core. The golf ballfurther has dimpleson a surface thereof. The coreis obtained by crosslinking a rubber composition. The difference between a hardness H(5.0) at a point that is located at a distance of 5 mm from the central point of the core, and a hardness Ho at the central point is equal to or greater than 6.0. The difference between a hardness H(12.5) at a point that is located at a distance of 12.5 mm from the central point, and the hardness H(5.0) is equal to or less than 4.0. The difference between a hardness Hs at the surface of the coreand the hardness H(12.5) is equal to or greater than 10.0. The difference between the hardness Hs and the hardness Ho is equal to or greater than 22.0. There is no zone in which a hardness decreases from the central point to the surface. The rubber composition of the coreincludes 2-naphthalenethiol. A cross-sectional shape of each dimpleis a wave-like curve.

Golf ballhas spherical core, surrounding layersituated on the external side of the core, mid layersituated on the external side of the surrounding layer, coversituated on the external side of the mid layer, and paint layersituated on the external side of the cover. The mid layerhas a thickness Tm of 0.1 mm or greater and 1.2 mm or less. The ratio (Tc/Tm) of the thickness Tc of the coverto the thickness Tm of the mid layeris no greater than 0.50. The coverhas a Shore D hardness Hc of no greater than 35. The Shore D hardness Hm of the mid layeris greater than the Shore D hardness Hc of the cover. The base material of the surrounding layeris an ionomer resin. The base material of the mid layeris a polyurethane. The base material of the coveris a polyurethane.

Golf ballhas a spherical core, a mid layercovering this core, a reinforcing layercovering this mid layer, and a covercovering this reinforcing layer. Base polymer of the mid layerincludes an ionomer resin as a principal component. The mid layerhas a hardness Hm as measured with a Shore D type hardness scale of equal to or greater than 55. Base polymer of the reinforcing layeris a thermosetting resin. Base polymer of the coverincludes a thermoplastic polyurethane elastomer as a principal component. The coverhas a thickness Tc of equal to or less than 0.6 mm. The cover has a hardness Hc as measured with a Shore D type hardness scale of equal to or less than 54. Ratio (Tr/Tc) of the thickness Tr of the reinforcing layer to the thickness Tc of the cover is 0.005 or greater and 3.0 or less.

Golf ballhas a spherical center, a mid layercovering this center, a reinforcing layercovering this mid layer, and a covercovering this reinforcing layer. Base polymer of the mid layeris an ionomer resin. Base polymer of the coveris a thermoplastic polyurethane elastomer. The coverhas a thickness Tc of equal to or less than 1.2 mm, and particularly equal to or less than 0.8 mm. The difference (Ho&#x2212;Hc) between the central hardness Ho of the centerand the hardness Hc of the coveris 1 or greater and 30 or less. The coverhas a hardness Hc of 15 or greater and 40 or less. The product (Tc&#xb7;Hc) of the thickness Tc (mm) of the coverand the hardness Hc of the coveris equal to or less than 25.

The present invention provides a golf ball having excellent rebound characteristics and flight performance, while maintaining good durability and appearance. The present invention relates to a golf ball comprising a center, an intermediate layer and a cover, the intermediate layer comprises an outermost layer and a second layer adjacent to the underside of the outermost layer, and the cover has many dimples on the surface thereof, wherein the second layer is formed from thermoplastic resin and has a thickness of 0.5 to 2.0 mm, the outermost layer is formed from thermosetting or thermoplastic resin and has a thickness of 1 to 100 &#x3bc;m, the intermediate layer has depressions on the surface thereof at the position and shape corresponding to the dimples through the cover, and the cover is formed from thermoplastic resin and has a thickness of 0.1 to 0.8 mm in land portion having no dimple.

The present invention provides a golf ball having excellent rebound characteristics and excellent flight performance, while maintaining good durability and good appearance. The present invention relates to a golf ball comprising a core composed of a center and at least one intermediate layer formed on the center, and a cover covering the core, and having many dimples on the surface thereof, wherein the outermost layer of the intermediate layer is formed from thermoplastic resin, has a thickness of 0.5 to 3.0 mm, and has depressions on the surface thereof at the position and shape corresponding to the dimples through the cover, and the cover is formed from thermoplastic resin and has a thickness of 0.1 to 0.8 mm in land portion having no dimple.

Golf ballhas a spherical core, a mid layercovering this core, a reinforcing layercovering this mid layer, and a covercovering this reinforcing layer. Base polymer of this mid layerincludes an ionomer resin as a principal component. Base polymer of this coverincludes a thermoplastic polyurethane elastomer as a principal component. The coverhas a thickness Tc of equal to or less than 0.6 mm. The coverhas a hardness Hc as measured with a Shore D type hardness scale of equal to or less than 54. The coverhas a volume V of equal to or less than 3.0 cm. A product obtained by multiplying the thickness Tc, the hardness Hc and the volume V is equal to or less than 90. The reinforcing layerincludes a thermosetting resin as a base polymer. The reinforcing layer has a thickness of 3 &#x3bc;m or greater and 50 &#x3bc;m or less.

A core having a center, and a mantle layer comprising a thermoplastic resin composition is provided. Next, a reinforcing layer including a thermosetting resin composition is formed on the surface of this core to obtain a spherical body. Next, this spherical bodyis covered by two pieces of half shell. Next, the spherical bodyand the half shellsare placed into a mold. Next, the moldis clamped at a velocity of 0.01 mm/sec or greater and 1.0 mm/sec or less. The thermoplastic resin composition of the half shellis heated while being compressed in the spherical cavity to result in flow. This thermoplastic resin composition is hardened to give a cover having a thickness of 0.1 mm or greater and less than 0.7 mm. The difference (T&#x2212;Fc) between the molding temperature T and the incipient fluidization temperature Fc of the thermoplastic resin composition of the cover is 0&#xb0; C. or greater and 30&#xb0; C. or less.

Method for the production of golf ball

A mold () includes an upper mold half (U) and a lower mold half (L). The mold () includes a gate (G), a pole vent pin (P), a support pin (S) and an intermediate vent pin (M). The support pin (S) has a latitude (&#x3b8;s) of 45 degrees to 85 degrees. Each of the upper mold half (U) and the lower mold half (L) has at least three support pins (S). The intermediate vent pin (M) has a latitude (&#x3b8;m) of 45 degrees to 85 degrees. Each of the upper mold half (U) and the lower mold half (L) has at least three intermediate vent pins (M). A difference between the latitude (&#x3b8;m) of the intermediate vent pin (M) and the latitude (&#x3b8;s) of the support pin (S) is equal to or smaller than 15 degrees. A clearance between the intermediate vent pin (M) and a pin hole () is 5 &#x3bc;m to 50 &#x3bc;m. By the mold (), a cover having a thickness of 1.4 mm or less is formed.

Mold for golf ball

A mold comprises a spherical cavity, a support pin capable of being moved forward and backward with respect to the cavity, and a vent pin (). The vent pin () includes two slits (S), an annular groove () and a vertical groove (). An upper end () of the slit (S) is opened toward the cavity. A lower end () of the slit (S) is opened toward the annular groove (). The annular groove () is coupled to the vertical groove (). The lower end of the vertical groove () is opened toward air. A width (W) of the slit (S) is preferably equal to or greater than 1 &#x3bc;m, is more preferably equal to or greater than 3 &#x3bc;m, and is particularly preferably equal to or greater than 5 &#x3bc;m. A depth (D) of the slit (S) is preferably equal to or greater than 10% of a diameter (&#x3c6;), is more preferably equal to or greater than 15% of the diameter (&#x3c6;), and is particularly preferably equal to or greater than 20% of the diameter (&#x3c6;). It is preferable that the same slit () should be formed on the support pin.

A golf ballhas a core, a mid layer and a cover. This mid layer comprises 10 parts by weight or greater and 70 parts by weight or less of a thermoplastic elastomer containing a styrene block having a material hardness of less than 10, and 30 parts by weight or greater and 90 parts by weight or less of an ethylene-(meth)acrylic acid copolymer based ionomer resin having a material hardness of 50 or greater and 70 or less. Hardness of this mid layer is less than 40, and the thickness is equal to or less than 1.2 mm. This golf ballhas seven kinds of dimples (A to G), each having a different diameter. When all the dimples are arranged in decreasing order of the diameter Di, ratio (Dx/Dn) of the mean diameter Dx of the dimples ranking in the top 10% to the mean diameter Dn of the dimples ranking in the bottom 10% is equal to or greater than 1.30. Standard deviation &#x3b7; of diameters of all the dimples is equal to or less than 0.52.

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Kobe, Japan

Seiichiro Endo