Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-05-19
2003-04-01
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S332600, C473S365000, C473S374000, C473S377000, C473S378000
Reexamination Certificate
active
06541574
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a golf ball with a core and a cover surrounding the core, particularly to a golf ball superior in spinning performance and impact resilience. In more detail, the present invention relates to a golf ball having high impact resilience and one which is relatively resistant to exhibiting a flier shot even when played from the rough. The present invention also relates to a method of manufacturing such a golf ball.
Conventionally, solid golf balls having a core with polybutadiene rubber as the base material surrounded by a cover resin and thread-wound golf balls having rubber thread wound around a core and enveloped by a cover resin such as ionomer are widely used in tournament matches.
During play, the golf ball often sinks deeply into the grass or rough of the fairway. A shot from the rough will often produce a flier type shot, i.e., the phenomenon whereby the ball is lifted very high due to a decrease of the backspin caused by the presence of grass between the club and the ball when the ball is struck. This flier yields unsatisfactory control, particularly at the time of an approach shot.
This phenomenon is encountered in both solid golf balls and thread-wound golf balls. Particularly, the aforementioned golf ball which has the ionomer resin cover experiences the disadvantage that a spin cannot be easily applied to the golf ball, leading to a degradation in controllability, although it still maintains good impact resilience due to the high elastic modulus.
It is said that a golf ball with a balata cover, i.e., a trans 1,4-polyisoprene cover is relatively resistant to a flier shot and superior in spin control. This is due to its appropriate hardness and high spinning performance due to the crystalline polymer portion and the crosslinking rubber portion of the golf ball.
In the case where crosslinking is effected at a temperature higher than the melting point of trans 1,4-polyisoprene (50° C.-60° C.), the crystalline portion will not be formed, even if cooling is effected after crosslinking. As a result, appropriate hardness cannot be obtained.
Therefore, it was conventionally necessary to carry out vulcanization over a long period of time under special ambience.
Japanese Patent Laying-Open No. 54-99177, for example, discloses the art of effecting a crosslinking reaction by immersing a golf ball in a xanthate type super vulcanization accelerator solution. However, there are many problems in the manufacturing step since immersion in the solution renders the post-process difficult.
Also, Japanese Patent Laying-Open No. 6-54928 discloses a method of crosslinking balata with a metal salt of an unsaturated fatty acid and a crosslinking initiator. This method has the disadvantage that the core enveloped by the cover is degraded due to the heat generated during the reaction. Also, an appropriate hardness could not be obtained since the crystal growth is not effected. Furthermore, if an accelerator for vulcanization such as the generally-used sulfur is employed, a vulcanization temperature of at least 120° C. is required. In this case, the desired hardness cannot be obtained since crystal growth is not achieved.
SUMMARY OF THE INVENTION
The present invention is directed to solving the above problems, and accordingly it is an object of the present invention to provide a golf ball improved in spinning performance and impact resilience, and a method of manufacturing such a golf ball.
According to one aspect of the present invention, a golf ball is provided having a core enveloped by a cover with trans 1,4-polyisoprene as the main component, including a super accelerator formed of dithiocarbamate and/or xanthate. The golf ball is vulcanized at a temperature lower than the melting point of trans 1,4-polyisoprene.
According to another aspect of the present invention, a golf ball is provided having a core enveloped by an inner layer cover and an outer layer cover. The inner layer cover, which envelopes the core, has trans 1,4-polyisoprene as the main component, and includes a super accelerator formed of dithiocarbamate and/or xanthate. The outer layer cover, which envelopes the inner layer cover, has trans 1,4-polyisoprene as the main component and includes a super accelerator of an amount larger than the amount in the inner layer cover.
According to a further aspect of the present invention, a golf ball is provided having a super accelerator formed of dithiocarbamate and/or xanthate.
According to still another aspect of the present invention, a golf ball is provided including an inner layer cover and an outer layer cover vulcanized at a temperature lower than the melting point of trans 1,4-polyisoprene.
According to a still further aspect of the present invention, a golf ball is provided including an outer layer cover and an inner layer cover having the ratio (W0/W1) of the thickness of the outer layer cover (W0) to the thickness of the inner layer cover (W1) in the range of 0.1-10.
According to yet a further aspect of the present invention, a golf ball is provided having a core which is a thread-wound core.
According to yet another aspect of the present invention, a method of manufacturing a golf ball including a core having a solid or thread-wound structure and a cover enveloping the core is provided, including the steps of blending a super accelerator for low temperature vulcanization in a polymer component with trans 1,4-polyisoprene as the main component to prepare a composition for the cover, molding the cover composition into a half shell, disposing a core enveloped by the half shell in a mold and forming dimple patterns at the surface of the cover composition, and vulcanizing the cover composition at a temperature lower than the melting point of trans 1,4-polyisoprene.
According to yet a still further aspect of the present invention, a method of manufacturing a golf ball is provided having a super accelerator formed of dithiocarbamate and/or xanthate.
According to still another aspect of the present invention, a method of manufacturing a golf ball is provided having a vulcanization temperature of 30° C.-50° C.
According to still another aspect of the present invention, a method of manufacturing a golf ball is provided including the steps of blending a super accelerator for low temperature vulcanization in a polymer component mainly composed of trans 1,4-polyisoprene to prepare a composition for an inner layer cover, blending a super accelerator of an amount larger than the amount in the inner layer cover in a polymer component mainly composed of trans 1,4-polyisoprene to prepare a composition for an outer layer cover, molding the inner layer cover composition into an inner half shell, molding the outer layer cover composition into an outer half shell, disposing a core enveloped by the outer layer half shell and the inner layer half shell in a mold, forming dimple patterns at the surface of the outer layer cover composition, and vulcanizing the inner layer cover composition and outer layer cover composition at a temperature lower than the melting point of trans 1,4-polyisoprene.
According to an additional aspect of the present invention, a method of manufacturing a golf ball is provided utilizing a super accelerator formed of dithiocarbamate and/or xanthate.
According to yet another aspect of the present invention, a method of manufacturing a golf ball is provided having a vulcanization temperature of 20° C.-50° C.
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 composition for the cover is mainly composed of trans 1,4-polyisoprene. Here, trans 1,4-polyisoprene refers to a component having at least 60 trans structures in the polymer molecule. If the number of trans structures is less than 60, the crystalline portion is so small that the melting point becomes too low to be able to satisfy the basic prope
Fushihara Kazuhisa
Sakagami Seigou
Takemura Kohei
Yamada Kaname
Birch & Stewart Kolasch & Birch, LLP
Buttner David J.
Sumitomo Rubber Industries Ltd.
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