Games using tangible projectile – Golf – Ball
Reexamination Certificate
2001-08-24
2004-02-10
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S365000, C473S385000
Reexamination Certificate
active
06688992
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to golf balls, and more particularly, to a golf ball exhibiting good spin performance with its easiness to control spin rate when hit with an iron club, and excellent in cut resistance, while maintaining good resilience performance.
2. Description of the Background Art
Conventionally, a golf ball obtained by forming a thread-wound layer around a liquid center and enveloping it with a balata cover has been widely used by skilled golfers and professional golfers, because of its superiority in hit feeling and controllability. The structure of the golf ball, however, requires a complicated manufacturing process and the golf ball itself is inferior in cut resistance. Thus, various kinds of soft covers have recently been proposed to replace the balata cover.
For example, Japanese Patent Laying-Open No. 10-179802 discloses a golf ball wherein resin as a base material of the cover is chiefly composed of a heated mixture of ionomer resin and styrene-butadiene-styrene block copolymer having a polybutadiene block containing epoxy group or styrene-isoprene-styrene block copolymer having a polyisoprene block containing epoxy group. Flexural rigidity of the composition constituting the cover is from 50 MPa to 300 MPa, and Shore D hardness is from 40 to 60. With this technique, improvement in hit feeling, spin performance and flying performance is expected. However, there still is room for improvement in cut resistance.
U.S. Pat. No. 5,716,293 discloses a golf ball that is formed of a solid rubber center containing an oily material and a soft cover material to improve the hit feeling and increase the spin rate when hit with a short iron club.
This however uses oil-resistant rubber and ionomer resin of great hardness around the solid rubber center. Therefore, resilience performance and the hit feeling have yet to be improved.
U.S. Pat. No. 5,935,021 discloses a golf ball wherein fibrous aluminum borate whisker is blended into a cover material mainly composed of thermoplastic resin or thermoplastic elastomer to improve resilience performance, durability and cut resistance. With this technique, however, the whisker blended into the cover material deteriorates the resilience performance thereof.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a golf ball superior in resilience performance, cut resistance and spin performance.
The golf ball of the present invention is composed of a core and a cover surrounding the core, and the cover is formed of a cover composition having organic short fiber blended in a polymer component including thermoplastic elastomer as its main component.
Preferably, the thermoplastic elastomer is one of styrene type thermoplastic elastomer and urethane type thermoplastic elastomer.
Thermoplastic resin such as ionomer resin may be blended in the polymer component of the cover composition, in a blended amount of less than 50 parts by weight with respect to 100 parts by weight of the polymer component.
Preferably, the blended amount of the organic short fiber is 0.5-20 parts by weight with respect to 100 parts by weight of the polymer component including the thermoplastic elastomer and possibly the thermoplastic resin or the like.
Still preferably, the cover composition of the present invention is set to have a flexural rigidity of 80-300 MPa and a Shore D hardness at the cover surface of 41-56.
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
The golf ball of the present invention is composed of a core and a cover enveloping the core. The cover is formed of a composition including thermoplastic elastomer as a polymer component.
The thermoplastic elastomer for use in the present invention may be any of styrene type thermoplastic elastomer, urethane type thermoplastic elastomer, ester type thermoplastic elastomer, olefin type thermoplastic elastomer, and amide type thermoplastic elastomer.
The styrene type thermoplastic elastomer is a block copolymer having a soft segment and a hard segment within a molecule. The soft segment is a unit of, e.g., butadiene block or isoprene block that is obtained from conjugated diene compound. Here, as the conjugated diene compound, one or at least two of butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene and others can be selected. Among them, butadiene, isoprene and a combination thereof are preferable. The component constituting the hard segment is a unit of styrene block, for example, that is obtained from a compound having one or at least two types selected from styrene and its derivatives, e.g., &agr;-methyl styrene, vinyl toluene, p-tertiary butyl styrene, 1,1-diphenyl ethylene and others. The styrene block unit is suitable in particular.
Specific examples of the styrene type thermoplastic elastomer includes: styrene-isoprene-butadiene-styrene block copolymer (SIBS structure); styrene-butadiene-styrene block copolymer (SBS structure); styrene-ethylene-butylene-styrene block copolymer (SEBS structure) obtained by hydrogenation of the double bonding of the butadiene of the SBS structure; styrene-isoprene-styrene block copolymer (SIS structure); styrene-ethylene-propylene-styrene block copolymer (SEPS structure) obtained by hydrogenation of the double bonding of the isoprene of the SIS structure; styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS structure); and modified block copolymers thereof.
The content of styrene (or its derivatives) in each of the SIBS, SBS, SEBS, SIS, SEPS and SEEPS structures is preferably in a range of 10-50 wt. %, and more preferably in a range of 15-45 wt. % within the copolymer. If the content is less than 10 wt. %, the cover becomes too soft, degrading the cut resistance. If it exceeds 50 wt. %, sufficient levels of hit feeling and controllability cannot be maintained.
In the present invention, it is possible to use the copolymer of the SIBS, SBS, SEBS, SIS, SEPS or SEEPS structure having its portion modified by a functional group selected from epoxy group, hydroxyl group, acid anhydride and carboxyl group.
For example, the styrene-butadiene-styrene block copolymer (SBS structure) having a polybutadiene block containing epoxy group is a block copolymer that has a polymer chain with polystyrene at both ends and polybutadiene containing the epoxy group at the intermediate portion. It may include a part or all of the double bonding of the polybutadiene portion subjected to hydrogenation. The styrene-isoprene-styrene block copolymer (SIS structure) is a block copolymer having a polymer chain with polystyrene at both ends and polyisoprene containing the epoxy group at the intermediate portion, and a part or all of the double bonding of the polyisoprene portion may have been subjected to hydrogenation.
The epoxidized styrene type thermoplastic elastomer with an epoxy equivalent in a range from 200 to 3000 may be used. When the epoxidized thermoplastic elastomer is mixed with ionomer resin or the like, it comes to react with free carboxyl group of the ionomer resin. This increases the strength of the cover composition and improves the cut resistance still further. If the epoxy equivalent is less than 200, a sufficient level of improvement in the cut resistance cannot be expected. If it exceeds 3000, too much reaction will occur between the epoxy group and the free carboxyl group of the ionomer resin. In this case, the fluidity is degraded, making it difficult to mold the ball.
Each of the hydroxyl group, acid anhydride and carboxyl group may also be introduced into the intermediate or end portion of the polymer chain of the block copolymer.
In the cover composition of the present invention, thermoplastic resin may be blended as the polymer component in addition to the thermoplastic elastomer. Here, the thermoplastic resin may include general purpose resins such as ionomer resin, polyethylene, polypropylene
Sakagami Seigo
Takemura Kohei
Duong Tom P
Sewell Paul T.
Sumitomo Rubber Industries Ltd.
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