Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – Composite article making
Reexamination Certificate
2002-05-10
2004-01-13
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
Composite article making
C264S050000, C264S321000
Reexamination Certificate
active
06676866
ABSTRACT:
FIELD OF INVENTION
The present invention is directed to golf balls and golf ball-forming microcellular materials, and to methods for forming such golf balls and of controlling material properties and weight distribution of golf balls formed of such materials.
BACKGROUND OF THE INVENTION
Conventional golf balls can be divided into several general classes: (a) solid golf balls having one or more layers, and (b) wound golf balls. Solid golf balls include one piece balls, which are easy to construct and relatively inexpensive, but have poor playing characteristics and are thus generally limited for use as range balls. Two-piece balls are constructed with a generally solid core and a cover and are generally the most popular with recreational golfers because they are very durable and provide maximum distance. Balls having a two-piece construction are commonly formed of a polymeric core encased by a cover. Typically, the core is formed from polybutadiene that is chemically crosslinked with zinc diacrylate and/or other similar crosslinking agents. These balls are generally easy to manufacture, but are regarded as having limited playing characteristics. Solid golf balls also include multi-layer golf balls that are comprised of a solid core of one or more layers and/or a cover of one or more layers. These balls are regarded as having an extended range of playing characteristics.
Wound golf balls are generally preferred by many players due to their high spin and soft “feel” characteristics. Wound golf balls typically include a solid, hollow, or fluid-filled center, surrounded by a tensioned elastomeric material and a cover. Wound balls generally are more difficult and expensive to manufacture than solid two-piece balls.
Golf ball performance characteristics are typically described in terms of their distance, durability, spin and feel. These characteristics need not be mutually exclusive, and yet golf balls that have a suitable feel, such as those with balata covers, tend not to be extraordinarily durable. This is because materials that have high tensile and compressive strengths often diminish the compressibility of the balls into which they are incorporated, and thus they generally feel hard. There thus exists a need for resilient and durable materials that may be used to form golf ball covers, mantle layers, and centers that retain the soft feel desired by many golfers.
Numerous attempts have been made to provide such materials. For example, U.S. Pat. Nos. 4,274,637 and 4,431,193 disclose covers and mantle layers, respectively, made of cellular, or foamed ionomer materials. These materials, which are lighter than the solid materials from which they are made, are produced with blowing agents, nucleating agents, and other additives that thermally decompose at high temperatures to form bubbles within a polymer melt. Foamed materials made in this manner are hereinafter referred to as “conventional foams.”
U.S. Pat. No. 5,824,746 discloses golf balls covers comprising foamed, metallocene-catalyzed polymers. These polymers were also formed using conventional blowing or foaming agents.
The use of foamed materials can alter the coefficient of restitution of a golf ball, which is generally indicative of its resiliency. Resiliency, which is regulated by the U.S. Golf Association, is measured by the “Initial Velocity Test,” wherein a golf ball is struck by a club face moving at a speed of approximately 146 feet per second. Once struck by the club face, the velocity of the ball is measured. The maximum prescribed limit for a golf ball tested in this manner is 250+2% ft/s at 75° F.
Conventional foams typically include about 10
3
to 10
6
cells/cm
3
, with the cells averaging about 100 &mgr;M or larger in diameter. It is this large average size and an uneven cell size distribution that are believed to account for the relatively poor mechanical properties of conventional foams. See, e.g., Behravesh, A. H., et al.,
Antec '
98
Conference Proceedings,
vol. II, pp. 1958-1967 (Apr. 26-30, 1998). Consequently, golf balls including conventional foams are expected to be inferior compared to those that do not include such conventional foams.
A further limitation of conventional foams is that they cannot be used to form materials thinner than the average cell size of about 100 &mgr;M. This limitation restricts the applications in which foamed materials may be used. In addition, the conventional foams require chemical blowing agents, which may produce some environmental concerns.
A material property of conventional foams can be modified or improved by the use of microcellular materials. These materials are made by exposing a polymer melt to a gas under high pressure, and then quickly removing that pressure. The resulting cells are smaller, more narrowly distributed with regard to size, and occur in higher densities than those of conventional foams. Until recently, however, microcellular materials were made primarily from simple, single component polymer melts, such as polystyrene.
For example, U.S. Pat. No. 4,473,665 discloses microcellular closed cell foams made from polystyrene, polycarbonate, polyester, nylon, or a thermoplastic material, and a method of making such foams. Also disclosed are closed cell sizes on the order of 2 to 25 microns, as well as the addition of fillers such as carbon black to control void size.
U.S. Pat. No. 5,160,674 discloses microcellular foams of amorphous or semi-crystalline polymers, such as polyethylene or polypropylene, having bubbles on the order of 5 to 25 microns in diameter with bubble density of approximately 10
10
bubbles/cm
3
.
Recently, reports have begun to surface in the literature of microcellular materials made from mixtures of polymeric and other compounds such as cellulose fiber. See, e.g., Barlow, C., et al.,
Antec '
98
Conference Proceedings
vol. II, pp. 1944-1948 (Apr. 26-30, 1998); and Matuana, L. M. et al.,
Antec '
98
Conference Proceedings
vol. II, pp. 1968-1975 (Apr. 26-30, 1998).
U.S. Pat. No. 5,181,717 discloses an inflated bladder-type sports or leisure ball, e.g., a football, that includes an external layer of polyurethane or polyurethane-polyurea foam with compact integral skin. The foamed layer is microalveolate or microcellular at its core, with a compact skin and an intermediate zone between the core and skin with progressively smaller cells towards the skin.
WO 99/63019 discloses microcellular thermoplastic elastomeric polymeric structures having an average cell size less than 100 &mgr;m in diameter. These materials may be formed from a thermoplastic elastomeric olefin, preferably metallocene-catalyzed polyethylene, with article densities ranging from less than 0.5 g/cm
3
to less than 0.3 gm/cm
3
.
U.S. Pat. No. 6,037,383 discloses microcellular polyurethane elastomers having improved dynamic properties based on an isocyanate consisting essentially of 4,4′-MDI.
Despite these disclosures of microcellular materials, however, Applicants are not aware of any disclosures that include such microcellular materials in golf balls. Thus, the need still exists to produce components with material properties modified by the use of microcellular materials.
SUMMARY OF THE INVENTION
This invention is directed to microcellular golf ball-forming materials for one-piece, two-piece, and multi-layer (i.e., three or more layers) golf balls, such as golf balls that are fluid-filled, include one or more wound layers, include a multi-layer cover, and the like.
In particular, the invention encompasses a golf ball including at least one core layer and at least one cover layer disposed over the at least one core layer, with the at least one cover layer having a thickness of at least about 0.03 inches, wherein at least one of the core layers or cover layers is formed of a microcellular composition having an average cavity density of about 10
5
cavities/cm
3
to 10
14
cavities/cm
3
, and an average cavity diameter of less than about 100 microns. In one embodiment, the cover has at least one of a dimple coverage of greater than about 60
Cavallaro Christopher
Harris Kevin M.
Rajagopalan Murali
Acushnet Company
Kuhns Allan R.
Swidler Berlin Shereff & Friedman, LLP
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