Games using tangible projectile – Golf – Ball
Reexamination Certificate
2000-03-23
2001-11-06
Woodward, Ana (Department: 1711)
Games using tangible projectile
Golf
Ball
C273SDIG008, C427S322000, C427S407100, C427S412100, C427S412300, C427S426000, C473S374000, C473S377000, C473S378000
Reexamination Certificate
active
06312347
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
The present invention relates to golf balls having a clear finish or top coating and, in particular, to an improved polyurethane top coating composition for golf balls.
For decades, golf balls were finished by applying an opaque coating to the outer surface to the golf ball cover. To achieve a desirable white appearance, a multicoat paint system typically comprising a primer coat followed by one or more opaque coatings was applied to the golf ball. Such golf balls are typically referred to as “painted balls”.
In the 1980's, a pigment was incorporated into the cover material prior to molding the cover of the golf ball, thereby eliminating the step of painting the golf ball. Such golf balls are typically referred to as “pigmented balls”.
Whether the golf balls are painted or pigmented, identifying indicia such as the manufacturer's trademark or logo, or a model or identification number are stamped on the ball. In order to prevent the stamped indicia from being rubbed off, and also to impart a desirable glossiness to the ball, one or two clear finishes or top coatings are applied to the ball. Typically, such clear coatings consist of a clear epoxy primer, followed by a clear urethane top coat. The urethane top coat is usually a two part polyurethane, including a polyol part and a diisocyanate part. The two parts are mixed together and reacted to form the urethane coating.
While early urethane top coatings imparted a desirable glossiness to the ball, they suffered from certain disadvantages. For example, the urethane coatings made from aromatic diisocyanates tended to yellow very quickly upon exposure to ultraviolet light, thus detracting from the appearance of the painted or pigmented ball. Also, the early urethane coatings typically suffered from adhesion and abrasion resistance problems. Good adhesion is required to protect the indicia stamped on the ball, while good abrasion resistance is needed to maintain the glossiness of the ball.
To avoid the problems associated with the early urethane top coatings, urethane top coatings have been prepared using biurets and isocyanurate trimers of hexamethylene diisocyanate as crosslinking agents. Coatings made with such crosslinking agents exhibit superior adhesion and abrasion resistance, and superior color retention upon exposure to ultraviolet radiation. Top coatings using these crosslinking agents are disclosed in U.S. Pat. No. 5,459,220, which is incorporated herein by reference in its entirety.
Although the top coatings disclosed in U.S. Pat. No. 5,459,220 are qualitatively superior to earlier top coatings, application of these and other similar coatings to golf balls requires a drying or curing period. To describe the typical application process in more detail, the polyol and diisocyanate parts of the top coat are premixed in a pressure pot. Dry air is used to push the coating to an air atomizing spray gun where it is forced out of a small diameter fluid nozzle onto the surface of the golf balls. The sprayed golf balls are then placed into an oven for a predetermined length of time, and at a predetermined temperature, such that the solvent evaporates and the polyol and the diisocyanate polymerize to form the desired top coat. The oven times necessary to cure existing top coats can range anywhere from five minutes to six hours or more, while oven temperatures typically range from 140° F. to 200° F.
Regardless of whether the manufacturer uses a fast cure top coat (with cure times measured in minutes) or a slow cure top coat (with cure times measured in hours), the balls must spend some time in an oven to effect the cure. As the time necessary to cure a particular top coat increases, the golf balls must either spend more time in the ovens or be subjected to higher oven temperatures. Either way, greater amounts of energy must be applied to the golf balls to complete the manufacturing process, thus increasing the cost of manufacture. In addition, as a golf ball is exposed to greater amounts of heat, the possibility of damage to the surface of the ball itself is increased. For example, the surface of a modem golf ball is covered with spaced “dimples” to improve the aerodynamics of the ball when it travels through the air. Excessive heat exposure may cause the dimples to deform. Even a slight aberration in the shape of the dimples can adversely affect the ball's aerodynamic properties.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a urethane top coating that demonstrates an increased rate of curing compared to at least some other top coatings.
Another object of the present invention is to provide a urethane top coating that can be applied to a golf ball with less risk of damaging the surface of the golf ball.
An additional object of the present invention is to provide a urethane top coating that demonstrates superior adhesion and abrasion resistance and yet still demonstrates an increased rate of curing compared to at least some other top coatings.
Still another object of the present invention is to provide a urethane top coating that demonstrates good color retention (non-yellowing) properties and yet still demonstrates an increased rate of curing compared to at least some other top coatings.
Other objects of the invention will become apparent to one skilled in the art who has the benefit of the specification and the prior art.
One aspect of the invention, which satisfies one or more of the foregoing objects, in whole or in part, is a method of coating a golf ball by applying a urethane top coat to the surface of the golf ball, where the top coat is made from the reaction of a polyol portion with an isocyanate blend comprised of an aliphatic diisocyanate and an aliphatic/aromatic polyisocyanate copolymer, where the aliphatic/aromatic copolymer is in the blend in a sufficient amount to accelerate curing of the top coat but at less than 50 parts by weight per 50 parts by weight of the purely aliphatic diisocyanate.
Another aspect of the invention is a method as previously defined, where the aliphatic diisocyanate in the top coat is a biuret of hexamethylene diisocyanate, an isocyanurate trimer of hexamethylene diisocyanate, or a mixture of the two.
Still another aspect of the invention is a method as previously defined, where the polyol portion of the top coat includes a catalyst that is present at greater than about 0.17 percent by weight solids in the entire top coat. As used herein, the phrase “weight solids” means the weight of the substance or composition in question minus the weight of any solvents present (such as methyl isobutyl ketone, methyl amyl ketone, or n-butyl acetate).
Yet another aspect of the invention is a golf ball having a cover that is coated with a urethane top coat as previously defined.
DETAILED DESCRIPTION OF THE INVENTION
The polyurethane top coat of the present invention is a two-part solvent borne polyurethane system. The first part comprises a hydroxyl functional polyol having an hydroxyl equivalent weight in the range of 50 to 1500, with the preferred equivalent weight being 200 to 500. Compounds containing the hydroxyl functional polyol contemplated herein include polyesters, polyethers, or acrylics. Alternately, the hydroxyl functional polyol is ethylenically saturated. Suitable saturated polyesters for use herein include poly (oxydiethylene adipates) that are condensation products of diethylene glycol and adipic acid, branched with trimethylolpropane or pentaerythritol, and polycaprolactone (hydroxycaproic acid) polyesters. Suitable saturated polyethers include polymers of propylene oxide or propylene oxide/ethylene oxide. Such materials are usually triols or diols with molecular weights between 1000 and 7000. Suitable saturated acrylics include derivatives of acrylic acid, such as methyl methacrylate, co-polymerized with hydroxyl functional monomers, such as 2-hydroxy-ethyl methacrylate. Polyols marketed by Miles Corporation, Pittsbu
Spalding Sports Worldwide Inc.
Woodward Ana
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