Games using tangible projectile – Golf – Ball
Reexamination Certificate
2001-06-20
2003-07-01
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S351000
Reexamination Certificate
active
06585607
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to processes for improving the adhesion between adjacent layers of material.
BACKGROUND OF THE INVENTION
Golf balls traditionally have been categorized in different groups, namely as one-piece, two-piece and three-piece balls. One-piece balls comprise a solid molded mass of the same material and do not have a core. Two-piece golf balls comprise a solid resilient core and an outer cover comprised of a different type of material molded thereon. Three-piece golf balls traditionally include a liquid or solid core, an elastomeric winding around the core and an outer cover molded thereon.
The outer cover of either two or three-piece golf balls may comprise single or multiple layers of molded material. The cover material may be balata (transpolyisoprene, natural or synthetic rubbers), although synthetic covers comprising non-ionomeric materials, for example polyurethane, or ionomeric polymers (polymers containing interchain ionic bonding) have become increasingly prevalent.
Additionally, despite their two and three-piece names, golf balls of either type may also comprise additional layers intermediate the cover and core or windings. The intermediate layers may be comprised of a wide range of materials, including polymers such as polyurethane, non-ionomeric and ionomeric materials.
Typically, the layers of multilayer golf balls are formed by applying them around the golf ball core or a preceding intermediate layer. Conventional techniques for applying such layers include injection molding, compression molding and casting the layer material around the underlying structure. A crucial aspect of the manufacture of multilayer balls is obtaining good adhesion strength between the various layers. If the adhesion strength between the layers does not meet desired levels, the performance of the golf ball will be adversely affected. For example, poor adhesion can cause air pockets between the layers, which can result in separation of the layers when the golf ball is struck with a club.
Further, as can be seen from the above, the possible combinations of core layers and materials, intermediate layers and materials and cover layers and materials are very large. As would be expected, the materials of one layer are often dissimilar in physical and chemical properties from those of an adjacent layer. This can make achieving a desired adhesion strength between the dissimilar layers difficult. In any configuration however, the material of each of the golf ball layers must be securely joined to the adjacent underlying and overlying layers to provide acceptable adhesion strength, performance and durability.
SUMMARY OF THE INVENTION
An object of the invention is to provide a process for improving interlayer adhesion strength of joined adjacent materials.
Another object of the invention is to provide a process for enhancing interlayer adhesion strength of molded parts.
A further object of the invention is to provide a process to improve adhesion strength between adjacent layers in a golf ball.
One aspect of the present invention comprises a process for enhancing adhesion between adjacent layers. The process comprises roughening the surface of one of the layers; chlorination of the roughened layer and joining of the roughened and chlorinated layer to an untreated layer. Advantageously, the process comprises roughening the surface of one of the layers, followed by chlorination of the roughened layer, after which the layers are joined and subjected to a post-treatment involving holding the joined layers at a temperature well above their normal cure temperature for a predetermined time. Further advantageously the surfaces of both layers may be roughened and/or chlorinated. The process provides a bond of enhanced strength between adjacent layers. The enhanced interlayer adhesion strength minimizes undesirable early or premature separation between the joined layers.
Another aspect of the present invention comprises a process for enhancing adhesion between adjacent layers. The process comprises application of a silicone-based adhesion promoter to a layer of a golf ball, then application of an additional layer to the treated layer. Optionally, the process comprises roughening the surface of one of the layers prior to application of the silicone-based adhesion promoter. The layers may optionally be subjected to a post-treatment involving holding the joined layers at a temperature well above their normal cure temperature for a predetermined time, or other types of post treatment known in the art, such as gamma radiation, infrared treatment (IR), ultraviolet treatment (UV), corona treatment, plasma treatment, interlocking mechanical features, other chemical adhesion promoters, e-beam treatment, and the like. Further advantageously the surfaces of both layers may be roughened and/or treated with the adhesion promoter. The process provides a bond of enhanced strength between adjacent layers. The enhanced interlayer adhesion strength minimizes undesirable early or premature separation between the joined layers.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others and the article possessing the features, properties, and the relation of elements exemplified in the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
For ease of understanding and clarity of description, the inventive adhesion process is below described in its application to golf balls. It should be understood that this description is nonlimiting and the process has applications beyond such description.
Golf balls comprise a core over which a cover is molded. The golf ball may have at least one intermediate or mantle layer disposed between the core and the cover. Conventional solid cores can be compression molded from a slug of uncured or lightly cured elastomer composition comprising a high cis content polybutadiene and a metal salt of an unsaturated carboxylic acid such as zinc mono or diacrylate or methacrylate. To achieve higher coefficients of restitution in the core, the manufacturer may include fillers such as small amounts of a metal oxide, for example zinc oxide. In addition, larger amounts of metal oxide than those that are needed to achieve the desired coefficient are often included in conventional cores in order to increase the core weight. Other materials may be used in the core composition including, for example, a compatible rubber, ionomer or low molecular weight fatty acids such as stearic acid. Free radical initiators such as peroxides are admixed with the core composition so that on the application of heat and pressure, a complex curing cross-linking reaction takes place. The core materials are mixed, milled, preformed into a slug, molded into a core and optionally ground to size. Wound cores are generally produced by winding under tension an elastic thread around a solid or liquid filled balloon center. Wound cores are also suitable for use with the invention.
At least one intermediate or mantle layer can be formed around the core using known techniques. For example the mantle layer can be formed by injection molding techniques wherein the core is placed into the center of a mold and the molten intermediate layer composition is injected into the mold. The injected composition is retained within the mold to solidify and/or cure for a suitable period of time at a suitable mold temperature. The exact mold temperature and retention time is dependent on the composition used for the intermediate layer, although it is generally desired to use as low a temperature and as short a time as possible. Alternatively, the intermediate layer material can be formed into hemispherical shells such as by injection molding molten material into a mold and cooling. The molded half shells are then positioned around the core in a mold and subjected to compression molding at e.g. about 200 to 300° F. for about 2 to 10 minutes, followed by cooling at about 50 to 70° F. for about 2 to 10 minutes. Compression mol
Kennedy, III Thomas J.
Melanson David M.
Risen, Jr. William M.
Tzivanis Michael John
Weiss Robert A.
Hunter Alvin A.
Sewell Paul T.
Spalding Sports Worldwide Inc.
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