Process for producing a golf ball

Details Process for producing a golf ball Process for producing a golf ball

1996-07-05

2001-02-27

Silbaugh, Jan H. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

To produce composite, plural part or multilayered article

C264S255000, C264S275000, C264S278000, C264S279100, C264S308000

Reexamination Certificate

active

06193920

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for producing a golf ball comprising a core and a cover formed on the core, wherein the cover has a thickness of 3.0 to 5.0 mm.
BACKGROUND OF THE INVENTION
Golf balls are generally composed of a core and a cover covering the core, and the cover is generally formed from ionomer resin and has a thickness of 2.4 mm or less. The cover thickness of less than 2.4 mm has been required in view of the producing process.
However, it has been recently proposed that the cover be made thicker than the conventional thickness to add another function. For example, the cover is made having a thickness of 3.0 to 5.0 mm and the core is made softer, which attains a higher hit angle and lower spin amount and results in enhancement of flight performance. As mentioned above, however, a thick covering on the core gives rise to some problems in the producing process. The covering process is generally conducted by injection molding or press molding, but the following three problems would occur:
(1) The cover thickness is non-uniform and the sphericity of the resulting golf ball is deteriorated in comparison with the conventional golf ball having a cover thickness of up to 2.4 mm.
(2) When injection molding, the cores are held by holding pins in a mold and the traces of the holding pin remain in the produced golf balls. The holding pin traces produce bad effects in the durability of the golf balls.
(3) When injection molding, the cover resin contracts a little. The thicker the cover, the larger the contraction, and the resulting golf balls often have a smaller diameter than required by he PGA rules.
SUMMARY OF THE INVENTION
The present invention provides a solution of the above mentioned problems in the production process of a golf ball having a cover thickness of 3.0 to 5.0 mm. The process of the present invention comprises:
providing a core,
covering the core with a cover composition to form a first cover layer having a thickness of 30 to 70% of a total cover thickness, and
further covering the first cover layer with the same cover composition to form a second cover layer having a thickness sufficient to form the total cover thickness.
The core preferably has a JIS-C hardness of not less than 50 and the cover preferably has a melt index (MI) of not less than 0.5.
The second covering process is preferably conducted at least 10° C. higher than the first covering process.


REFERENCES:
patent: 696866 (1902-04-01), Kempshall
patent: 3317646 (1967-05-01), Dames, Jr.
patent: 4919434 (1990-04-01), Saito
patent: 5556098 (1996-09-01), Higuchi et al.
patent: 2278609 (1994-07-01), None

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