Games using tangible projectile – Golf – Ball
Reexamination Certificate
1999-10-07
2001-01-30
Chapman, Jeanette (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S372000
Reexamination Certificate
active
06179728
ABSTRACT:
This invention relates to one-piece golf balls, solid golf balls and wound golf balls having a high resilience and improved flight performance, feel and control.
BACKGROUND OF THE INVENTION
Known golf balls include solid golf balls comprising a solid core, an optional intermediate layer and a cover, wound golf balls comprising a wound core (having a solid center and thread rubber) and a cover, and one-piece golf balls formed from a rubber composition into a single piece. Attempts have been made on these golf balls to improve their flight distance and performance by tailoring the materials of their components.
Thermoplastic polyether ester elastomers, because of their flexibility and resilience, are often used in golf balls as the intermediate layer between the core and the cover. These elastomers are also used as various core materials, for example, solid core material, solid center material and one-piece golf ball material.
However, when thermoplastic polyether ester elastomers are used as the core material, their potential compression set raises the problem that the ball undergoes plastic deformation upon hitting.
Partially because the demand on golf balls is diversified in recent years, it is desired to develop a more flexible and resilient material as a multilayer structure material and for the solid core, solid center or one-piece golf ball.
SUMMARY OF THE INVENTION
An object of the invention is to provide solid golf balls, wound golf balls, and one-piece golf balls which are unsusceptible to compression set and have a high resilience, improved flight performance and pleasant feel.
The invention provides a solid golf ball comprising a solid core and a cover, a wound golf ball comprising a solid center, thread rubber and a cover, or a one-piece golf ball. The solid core, the solid center or the one-piece golf ball is formed mainly of a heated mixture of (A) a thermoplastic polyether ester elastomer having a Shore D hardness of 25 to 60, a tan &dgr; value of up to 0.15 in the temperature range of −10° C. to 20° C. as determined by viscoelasticity measurement, and a glass transition temperature of not higher than −20° C. and (B) an olefin elastomer, modified olefin elastomer, styrene-conjugated diene block copolymer or hydrogenated or modified styrene-conjugated diene block copolymer having a JIS A hardness of up to 80. Then the balls leave little compression set, are restrained from plastic deformation upon hitting, and have a high resilience or restitution, improved flight performance and pleasant feel.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The golf balls contemplated herein include solid golf balls, wound golf balls, and one-piece golf balls. The solid core in the case of a solid golf ball, the solid center in the case of a wound golf ball, or the one-piece golf ball itself, which are comprehensively referred to as a “core sphere” hereinafter, is formed mainly of a heated mixture of components (A) and (B).
Component (A) is a thermoplastic polyether ester elastomer having a Shore D hardness of 25 to 60, preferably 30 to 50, more preferably 30 to 47. A Shore D hardness of higher than 60 leads to an unpleasant feel. A Shore D hardness of less than 25 leads to a lower resilience.
Using a viscoelasticity measurement, the thermoplastic polyether ester elastomer should have a tan &dgr; value of up to 0.15 in the temperature range of −10° C. to 20° C. The tan &dgr; value in the temperature range of −10° C. to 20° C. as determined by viscoelasticity measurement is one index representing viscoelastic properties of a resin. The tan &dgr; value is determined as follows. The elastomer is formed into a specimen having a thickness of 10 mm, a width of 12 mm, and a length of about 35 mm. By means of a viscoelasticity spectrometer Rhios V4.3.2 (Rheometrics Co.), the specimen is measured for loss elastic modulus and storage elastic modulus at a frequency of 62.8 rad/s and a heating rate of 2° C./min in the temperature range of −10° C. to 20° C. The tan &dgr; value is an average determined by dividing the loss elastic modulus by the storage elastic modulus.
The thermoplastic polyether ester elastomer (A) should have a tan &dgr; value of up to 0.15, preferably 0.01 to 0.1, upon viscoelasticity measurement in the temperature range of −10° C. to 20° C. A tan &dgr; value in excess of 0.15 can increase the energy loss of the ball when hit and compromise the resilience of the ball.
Additionally, the thermoplastic polyether ester elastomer should have a glass transition temperature (Tg) of not higher than −20° C.
The thermoplastic polyether ester elastomer (A) is commercially available under the trade name of Hytrel 3078, Hytrel 4047 and Hytrel 4767 from Toray-Dupont K.K.
Component (B) is an olefin elastomer, modified olefin elastomer, styrene-conjugated diene block copolymer or hydrogenated or modified styrene-conjugated diene block copolymer, each having a JIS A hardness of up to 80, especially 20 to 75.
The olefin elastomers include copolymers of ethylene with alkenes of at least 3 carbon atoms, preferably copolymers of ethylene with alkenes of 3 to 10 carbon atoms, and copolymers of &agr;-olefins with unsaturated carboxylic acid esters or carboxyl or carboxylic anhydride group-bearing polymerizable monomers. Exemplary olefin elastomers are ethylene-propylene copolymer rubber, ethylene-butene copolymer rubber, ethylene-hexene copolymers, and ethylene-octene copolymers. Also included are ethylene-propylene-non-conjugated diene copolymers, for example, copolymers using 5-ethylidene norbornene, 5-methylnorbornene, 5-vinylnorbornene, dicyclopentadiene or butene. Illustrative examples are ethylene-propylene-butene copolymers, ethylene-propylene-butene copolymer rubber, and ethylene-ethyl acrylate copolymer resins.
Modified products of the above-mentioned olefin elastomers are also useful. Such modified olefin elastomers include ethylene-ethyl acrylate copolymer resins graft modified with maleic anhydride.
The olefin elastomers are commercially available under the trade name of MITSUI EPT and Toughmer from Mitsui Chemical Industry K.K., ENGAGE from Dow Chemical, and Dynaron from Nippon Synthetic Rubber K.K. A commercial product of the modified olefin elastomer is HPR AR201 from Mitsui-Dupont Polychemical K.K.
Component (B) also includes styrene-conjugated diene block copolymers, preferably those copolymers having conjugated diene blocks composed of butadiene alone, isoprene alone or a mixture of isoprene and butadiene. Also useful are hydrogenated products of these styrene block copolymers, for example, hydrogenated styrene-butadiene-styrene block copolymers and hydrogenated styrene-isoprene-styrene block copolymers.
Such hydrogenated styrene-conjugated diene block copolymers are commercially available under the trade name of Dynaron from Nippon Synthetic Rubber K.K., Septon and Hiblur from Kurare K.K., and Toughtec from Asahi Chemicals Industry K.K. A commercial product of the modified styrene-conjugated diene block copolymer is Epoblend from Dicell Chemical K.K.
One or more of the above-described members in component (A) may be mixed with one or more of the above-described members in component (B) and adjusted as appropriate. As the mixture of (A) and (B), a commercially available product such as Primalloy from Mitsubishi Chemical K.K. may also be used.
In the manufacture of the golf ball, the core sphere is formed mainly from a mixture of components (A) and (B). No particular limit is imposed on the mixing ratio of components (A) and (B). The mixing ratio may be determined as appropriate although it is recommended to mix components (A) and (B) in a weight ratio of from 95/5 to 30/70, more preferably from 90/10 to 40/60. A mixture containing more than 95% by weight of the thermoplastic polyether ester elastomer would be less flexible or soft, fail to improve the controllability and feel of the golf ball, and allow a compression set to be left after hitting, which tends to invite plastic deformation. On the other hand, if the content of the thermoplastic
Ichikawa Yasushi
Kashiwagi Shunichi
Takesue Rinya
Bridgestone Sports Co. Ltd.
Chapman Jeanette
Gorden Raeann
Sughrue Mion Zinn Macpeak & Seas, PLLC
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