Games using tangible projectile – Golf – Ball
Reexamination Certificate
2000-12-28
2002-10-15
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S377000, C473S365000
Reexamination Certificate
active
06464600
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a golf ball having high rebound characteristics and exceptional controllability at approach shot from the rough, which accomplished by controlling its cover material morphology.
BACKGROUND OF THE INVENTION
There have been various requirements for physical properties of golf balls, such as flight distance, controllability, shot feel, click sound and the like. Among these, the controllability is rated by top-rank golfers as one of the most important properties for scoring; especially when approach shots are made from the rough. As such, a technique used to improve controllability involves making the cover softer, which increases the amount of spin, even when approach shots are made from the rough. However, golf balls obtained using such a technique suffer from the drawbacks of diminished rebound characteristics and reduced flight distance.
OBJECTS OF THE INVENTION
A main object of the present invention is to provide a golf ball which has high rebound characteristics and exceptional controllability at approach shot from the rough.
According to the present invention, the object described above has been accomplished by forming a base resin of a cover from a material having at least two phases, and setting the phase angle difference of these phases, as measured by an atomic force microscope to within a specific range to control the morphology in such a way that the phase that is contained in the base resin of the cover, which has the maximum phase angle, is present in the form of a continuous matrix, and the phase with the minimum phase angle is present in discrete locations within the matrix, thereby providing a golf ball having high rebound characteristics and exceptional controllability at approach shot from the rough, even when hit through grass or when wet conditions tend to limit the amount of spin when approach shots are made from the rough.
SUMMARY OF THE INVENTION
The present invention relates to a golf ball comprising a core and a cover covering the core, wherein the base resin of the cover is formed from a material having at least two phases whose phase angle difference is at least 2 degrees as measured by using an atomic force microscope; a maximum phase angle phase, which is contained in the base resin of the cover and has an absolute value of a maximum phase angle, is present in the form of a continuous matrix; and a minimum phase angle phase, which has an absolute value of a minimum phase angle, is present in discrete locations within the matrix.
In order to put the present invention into a more suitable practical application, it is desired that the minimum phase angle phase have a mean dispersion particle size of no more than 700 nm.
It is universally accepted that the less hardness a golf ball cover material has, the more spin will result; however, it goes without saying that low hardness also causes a decrease in rebound characteristics and durability. Using a hard material, accordingly, in order to obtain an increase in the rebound characteristics and durability, translates into diminished spin performance. Upon conducting diligent research on the cover material, the inventors of the present invention discovered that by fabricating the cover from a specific material, and also by using such materials in combination, will result in an increase in both the rebound characteristics and the durability. The inventors predicted that the appearance of these properties was related to the phase structure (morphology) of the material, and by using an atomic force microscope to analyze the morphology, which is not observable using common electronic microscopes, it was discovered that the cover contains a so-called “sea-island” structure, wherein the maximum phase angle phase, which contains the largest phase angle in the material used in the base resin of the cover, is present in a continuous matrix (“sea”), and the minimum phase angle phase, which contains the smallest phase angle, is present in discrete locations (“islands”) within the “sea”, and in the cover there exists a very strong correlation between the phase angle difference of the minimum phase angle phase and the maximum phase angle phase in the material used in the base resin of the cover, the amount of spin and the rebounding performance. Moreover, it is preferable for the mean dispersion particle size in the minimum phase angle phase (“islands”) to be no greater than 700 nm.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the detailed description of the present invention which follows, the golf ball of the present invention comprises a core and a cover formed on said core. The core used in the golf ball of the present invention may be e.g. a solid core (of a single layer structure or one comprising two or more layers) or a thread-wound core. Examples of materials which can be used as a solid core include thermoplastic elastomers, thermoplastic resins or rubber compositions which comprise a base rubber, an organic peroxide, a co-crosslinking agent and the like. Of these, the rubber compositions are preferable.
In solid cores as described above, the base rubber may be natural and/or synthetic rubber, which has been conventionally used for solid golf balls. Preferred is so-called high-cis polybutadiene rubber containing a cis-1,4-structure of not less than 40%, preferably not less than 80% and even more preferably not less than 90%. According to need, the high-cis polybutadiene rubber can be mixed with natural rubber, polyisoprene rubber, styrene butadiene rubber or ethylene-propylene-diene rubber (EPDM) and the like in amount of 0 to 50 parts by weight, based on 100 parts by weight of the base rubber.
Examples of co-crosslinking agents include &agr;,&bgr;-unsaturated carboxylic acids with 3 to 8 carbon atoms (e.g. acrylic acid, methacrylic acid, etc.), a mono- or bivalent metal salt such as the zinc or magnesium salt thereof, functional monomers such as triethanolpropane trimethacrylate and mixtures thereof. The preferred co-crosslinking agent is zinc acrylate because it imparts high rebound characteristics to the resulting golf ball. The amount of the co-crosslinking agent is 5 to 50 parts by weight, and preferably 10 to 40 parts by weight, based on 100 parts by weight of the base rubber. When the amount is larger than 50 parts by weight, the core is too hard, and the shot feel is poor. On the other hand, when the amount is smaller than 5 parts by weight, an appropriate level of hardness is not obtained, and the rebound characteristics are severely degraded, which reduces the flight distance.
Examples of organic peroxides include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide and the like. The preferred organic peroxide is dicumyl peroxide because it imparts high rebound characteristics to the resulting golf ball. The amount of the organic peroxide is 0.1 to 5.0 parts by weight, and preferably 0.2 to 3.0 parts by weight, based on 100 parts by weight of the base rubber. When the amount is smaller than 0.1 parts by weight, the core becomes too soft, the rebound characteristics are degraded, which reduces the flight distance. On the other hand, the amount is larger than 5.0 parts by weight, the core becomes too hard, which causes cracks to form.
Where appropriate, it is possible to compound a component which is typically used in the manufacture of solid golf ball cores together with the rubber composition; e.g., fillers such as zinc oxide, barium sulfate and the like as a specific gravity regulator, and other additives such as antioxidants, peptizing agents and organic sulfide compounds. Preferably the amount of the filler is 5 to 50 parts by weight, the amount of the antioxidant is 0.1 to 5 parts by weight, the amount of the peptizing agent is 0.1 to 5 and the amount of the organic sulfide compound is 0.1 to 2 parts by weight, based on 100 parts by weight of the base rubber.
A method for manufacturing the core when a rubber composition is used involves the rubber compo
Kishimoto Hiroyuki
Sakagami Seigou
Takemura Kohei
Birch & Stewart Kolasch & Birch, LLP
Hunter Alvin A.
Sewell Paul T.
Sumitomo Rubber Industries Inc.
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