Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-07-06
2003-08-19
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C525S09200D, C525S093000, C525S143000, C525S149000, C525S221000, C473S378000, C473S385000
Reexamination Certificate
active
06608127
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to golf balls, particularly a golf ball that exhibits high spinning and that easily comes to a halt even when shot from the rough or when shot in a raining condition such as a balata covered golf ball.
2. Description of the Background Art
Golf balls with a balata cover are generally widely used by low handicap and professional golfers by virtue of its superior hit feeling and controllability. Recently, various soft covers have been proposed to replace balata covers due to their complicated fabrication process and poor cut resistance.
For example, the basic resin of a cover disclosed in Japanese Patent Laying-Open No. 10-179802 is formed having as the main component a heated mixture of 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. A golf ball is proposed 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 basic resin of a cover disclosed in Japanese Patent Laying-Open No. 10-179801 is formed having as the main component a heated mixture of ionomer resin, acid modified thermoplastic elastomer or thermoplastic elastomer with an OH group added at the terminal, and a styrene-butadiene-styrene block copolymer including a polybutadiene block containing epoxy or a styrene-isoprene-styrene block copolymer including a polyisoprene block containing epoxy. A golf ball is proposed 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.
Although the golf balls of these inventions are improved in the hit feeling (feeling imparted to the golfer when the ball is hit), controllability, and cut resistance, the spin rate in a wet condition is inferior to the spin rate in a dry condition. These golf balls were not satisfactory from the aspect of spin maintenance.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a golf ball having a high ratio of the spin rate in a wet condition to the spin rate in a dry condition, i.e., having a high spin maintenance.
According to an aspect of the present invention, a golf ball formed of a core and a cover is characterized in that the cover composition is blended with basic resin and a tackifier.
Particularly, the basic resin of the cover is preferably ionomer resin alone, or ionomer resin blended with one or at least two types of polystyrene type elastomer, polyolefin type elastomer, polyurethane type elastomer and polyester type elastomer. A tackifier such as terpene resins and rosin ester resin is added 5-50 parts by weight to the basic 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 EMBODIMENTS
In the present invention, the ionomer resin employed as the basic resin of the cover is, for example, a copolymer of &agr;-olefin and &agr;, &bgr;-unsaturated carboxylic acid of carbon number 3-8, obtained by neutralizing at least a portion of the carboxyl group thereof with metallic ion. Alternatively, a ternary copolymer of &agr;-olefin, &agr;, &bgr;-unsaturated carboxylic acid of carbon number 3-8, and &agr;, &bgr;-unsaturated carboxylic acid ester of carbon number 2-22, obtained by neutralizing at least a portion of the carboxyl group thereof can be used. 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 copolymer of &agr;-olefin and &agr;, &bgr;-unsaturated carboxylic acid of carbon number 3-8. When the base polymer is a ternary copolymer of &agr;-olefin, &agr;, &bgr;-unsaturated carboxylic acid of carbon number 3-8, and &agr;, &bgr;-unsaturated carboxylic acid ester of carbon number 2-22, 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 are preferable. It is also preferable that the melt index (MI) of these ionomer resins is 0.1-20, preferably 0.2-20, 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 of carbon number 3-8, 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 copolymer of &agr;-olefin and &agr;, &bgr;-unsaturated carboxylic acid or the 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, or the like, 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 1605 (Na), 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-Du Pont Polychemical Co., Ltd. are available. As the ternary copolymer ionomer resin, Hi-milan 1856 (Na), Hi-milan 1855 (Zn), Hi-milan AM7316 (Zn), and the like are available from Mitsui-Du Pont Polychemical Co., Ltd. From Du Pont Co. are available Surlyn 8920 (Na), Surlyn 8940 (Na), Surlyn 8945 (Na), Surlyn 9910 (Zn), Surlyn 9945 (Zn), Surlyn 7930 (Li) and Surlyn 7940 (Li) as the ionomer resin, and Surlyn AD8265 (Na), Surlyn AD8269 (Na) and the like as the ternary copolymer type ionomer resin.
As the ionomer resin available from Exxon Chemical Japan Ltd., Iotek 7010 (Zn), Iotek 8000 (Na) and the like can be enumerated. Na, Zn, K, Li, Mg and the like in the above parenthesis following respective trade names of the ionomer resin indicate the metal type of these neutralize metallic ions. In the present invention, the ionomer resin used for the basic resin of the cover may have at least two of those enumerated above mixed. Alternatively, at least two types of the ionomer resin neutralized with monovalent metallic ions enumerated above and ionomer resin neutralized with divalent metallic ions can be mixed to be used.
As the tackifier employed in the present invention, coumarone-indene type resins, polyterpene type resins, rosin derivatives, phenol-formaldehyde type resins, alkyl phenol-formaldehyde type resins, petroleum type resins, xylene-formaldehyde type resins, oligomers of polybutene, liquid rubber such as liquid polyisoprene and the like can be enumerated. Particularly, the terpene type resins and rosin ester type resins are preferably applicable.
Furthermore, hydrogenated terpene resins are favorable. Particularly, hydrogenated terpene resins having a softening point that is not higher than 130° C., measured according to JIS-K 6863, are preferable.
Specific trade names of the tackifier are set forth in the following. As the coumarone resins, Process Resin A81, Process Resin AC5, Process Resin TX from Kobe Petrochemical Industry Co., Ltd., Coumarone CL from Ouchishinko Chemical Industrial Co., Ltd., and Coumarone resin NG4 from Nippon Steel Chemical Industries, Co., L
Hiraoka Hidenori
Iwami Satoshi
Kato Akira
Yokota Masatoshi
Buttner David J.
Sumitomo Rubber Industries Ltd.
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