Games using tangible projectile – Golf – Ball
Reexamination Certificate
2001-03-15
2002-12-03
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S377000
Reexamination Certificate
active
06488597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf ball that exhibits great flight distance with favorable shot feeling and that easily comes to a halt even though exhibiting high spin rate when shot from the rough or when shot in a raining condition.
2. Description of the Background Art
Conventional golf balls formed with a thread-wound layer around a liquid center and surrounded by a balata cover are widely used by low-handicapped golfers and professional golfers by virtue of its superior shot feeling and controllability. However, the structure of such golf balls has the disadvantage that the fabrication process is difficult and the cut resistance is inferior. Various soft cover materials are now proposed as a substitute for balata covers.
For example, U.S. Pat. No. 4,884,814 discloses the technique of using soft ionomer resins for the basic resin of the cover. However, the golf ball according to such technique was not satisfactory from the standpoint of spin maintenance since the spin rate in a wet condition was inferior to the spin rate in a dry condition.
Also, the basic resin of a cover disclosed in GB2311530 is formed having as the main component a heated mixture of two components, i.e. ionomer resin, and a styrene-butadiene-styrene block copolymer including a polybutadiene block containing an epoxy group or a styrene-isoprene-styrene block copolymer including a polyisoprene block containing an epoxy group. This publication proposes a golf ball characterized in that the cover composition forming the cover has a flexural modulus of 50-300 MPa and a Shore D hardness of 40-60. The technology provides superior shot feeling and controllability and also favorable flight performance and cut resistance. However, it was not directed to improve the spin maintenance.
U.S. Pat. No. 5,716,293 proposes a golf ball directed to improve the shot feeling and the spin rate when shot with a short iron by virtue of the usage of a solid rubber center including oily substance and a soft cover material.
However, the impact resilience and the shot feeling are not completely satisfactory since oil-resistant rubber or ionomer resin of high hardness is employed for the outer side of the solid rubber center.
The inventor has already proposed a golf ball with a core and a cover surrounding the core, wherein the cover is formed of a mixture including an ionomer resin, a thermoplastic elastomer and a tackifier with a Shore D hardness of 40-65 to improve the spin performance when shot in a wet condition (U.S. Ser. No. 09/662,800). However, the impact resilience was not of a satisfactory level at low temperature.
SUMMARY OF THE INVENTION
In view of the foregoing problems of conventional golf balls, the object of the present invention is to provide a golf ball exhibiting soft feeling with a superior impact resilience even at low temperature, and that can easily come to a halt though the spin rate is great when shot from the rough or when shot in a raining condition.
According to an aspect of a golf ball including a core and a cover surrounding the core of the present invention, the cover is constituted by a mixture of an ionomer resin, a thermoplastic elastomer with a rubber segment, and a tackifier having a softening point of not more than 100° C. The cover exhibits a peak temperature of not more than 5° C. for the loss tangent, and a Shore D hardness of at least 35 and not more than 60.
According to another aspect of the golf ball of the present invention, the tackifier is blended 5-30 parts by weight with respect to the total 100 parts by weight of the ionomer resin and thermoplastic elastomer with a rubber segment constituting the cover.
According to a further aspect of the golf ball of the present invention, the thermoplastic elastomer with a rubber segment includes a styrene-isoprene-butadiene-styrene block copolymer (SIBS structure), a styrene-butadiene-styrene block copolymer (SBS structure), a styrene-ethylene-butylene-styrene block copolymer (SEBS structure) corresponding to the hydrogenated double bonded portion of the butadiene of the SBS structure, a styrene-isoprene-styrene block copolymer (SIS structure), a styrene-ethylene-propylene-styrene block copolymer (SEPS structure) corresponding to the hydrogenated double bonded portion of that isoprene of the SIS structure, a styrene- ethylene- ethylene-propylene-styrene block copolymer (SEEPS structure), and a modified product thereof.
According to still another aspect of the golf ball of the present invention, the tackifier is a terpene resin and/or rosin ester resin.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is directed to a golf ball including a core and a cover surrounding the core.
In the present invention, the ionomer resin employed as the basic resin of the cover is, for example, a binary copolymer of &agr;-olefin and &agr;, &bgr;-unsaturated carboxylic acid having 3-8 carbon atoms, obtained by neutralizing at least a portion of the carboxyl group thereof with metallic ions. Alternatively, a ternary copolymer of &agr;-olefin, &agr;, &bgr;-unsaturated carboxylic acid having 3-8 carbon atoms, and &agr;, &bgr;-unsaturated carboxylic acid ester having 2-22 carbon atoms, obtained by neutralizing at least a portion of the carboxyl group thereof with metallic ions can be employed. As to the composition ratio, 80-90% by weight of &agr;-olefin and 10-20% by weight of &agr;, &bgr;-unsaturated carboxylic acid are preferable when the base polymer of the ionomer resin is a binary copolymer of &agr;-olefin and &agr;, &bgr;-unsaturated carboxylic acid having 3-8 carbon atoms. When the base polymer is a ternary copolymer of &agr;-olefin, &agr;, &bgr;-unsaturated carboxylic acid having 3-8 carbon atoms and &agr;, &bgr;-unsaturated carboxylic acid ester having 2-22 carbon atoms, 70-85% by weight of &agr;-olefin, 5-20% by weight of &agr;, &bgr;-unsaturated carboxylic acid, and 10-25% by weight of &agr;, &bgr;-unsaturated carboxylic acid ester are preferable. It is also preferable that the melt index (MI) of these ionomer resins is 0.1-20, particularly 0.5-15.
As the &agr;-olefin, ethylene, propylene, 1-butene, 1-pentene, for example, are employed, wherein ethylene is particularly preferable. As the &agr;, &bgr;-unsaturated carboxylic acid having 3-8 carbon atoms, acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid, for example, are employed, wherein acrylic acid and methacrylic acid are particularly preferable. As the unsaturated carboxylic acid ester, methyl, ethyl, propyl, n-butyl, isobutyl ester or the like of acrylic acid, methacrylic acid, fumaric acid, maleic acid or the like, for example, are employed, wherein acrylic acid ester and methacrylic acid ester are particularly preferable. As the metallic ion neutralizing at least a portion of the carboxyl group in the foregoing copolymer of &agr;-olefin and &agr;, &bgr;-unsaturated carboxylic acid or the foregoing ternary copolymer of &agr;-olefin, &agr;, &bgr;-unsaturated carboxylic acid and &agr;, &bgr;-unsaturated carboxylic acid ester, sodium ion, lithium ion, zinc ion, magnesium ion, potassium ion, for example, can be enumerated. When the ionomer resin has at least a portion of the carboxyl group in the copolymer of ethylene and acrylic acid or methacrylic acid neutralized with metallic ions, the highly rigid and high flow type having a melt index of 3-7 and a flexural modulus of 200-400 MPa is preferable.
Specific trade names of the ionomer resin are enumerated in the following. Hi-milan 1555 (Na), Hi-milan 1557 (Zn), Hi-milan 1605 (Na), Hi-milan 1706 (Zn), Hi-milan 1707 (Na), Hi-milan AM7318 (Na), Hi-milan 1706 (Zn), Hi-milan AM7315 (Zn), Hi-milan AM7317 (Zn), Hi-milan AM7311 (Mg), and Hi-milan MK7320 (K) sold by Mitsui-DuPont Polychemical Co., Ltd. are available as the binary copolymer ionomer resin. As the ternary copolymer ionomer r
Iwami Satoshi
Kato Akira
Moriyama Keiji
Birch & Stewart Kolasch & Birch, LLP
Hunter Alvin A.
Sewell Paul T.
Sumitomo Rubber Industries Ltd.
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