Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1996-03-01
2002-05-28
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S048000, C528S052000, C528S053000, C528S055000, C528S056000, C528S057000, C528S058000, C528S067000, C528S073000, C528S075000, C528S081000, C528S083000, C473S378000, C473S600000, C473S607000
Reexamination Certificate
active
06395861
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to game balls, and more particularly to a quick-cure coating for game balls.
For decades, golf balls were finished by applying one or more coats of paint or the like to the outer surface of a 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, the concept of incorporating pigment into the cover material prior to molding the cover of the golf ball was introduced, 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 outer coatings are applied to the ball. Typically, such clear coatings consist of a clear solvent based primer or water borne primer followed by a clear urethane top coat. The logo or other indicia typically is stamped on the primed ball before application of the top coat. The urethane top coat is usually a two-part polyurethane, consisting of a polyol and a polyisocyanate mixed together and reacted to form the urethane coating.
In golf ball manufacturing, the period of time required to apply and cure the final glossy top coat encompasses a large percentage of the total time required for golf ball manufacture. Known golf ball finish coatings typically require 6-8 hours of curing at an elevated temperature. Curing is generally conducted in a batch-type manner in large ovens.
One advantage of the conventional method for finishing golf balls is that the long cure time of the final top coat ensures that adhesion of the finish coating to the golf ball is strong, and as a result, the golf ball has a long, useful life. Another advantage is that the pot life of the mixed coating is relatively long. However, known methods are disadvantageous in that the 6-8 hour curing time prevents same day delivery of golf balls, particularly customized logo balls. Furthermore, one or more very large ovens are required if a sizable number of golf balls are to be manufactured daily.
In a conventional polyurethane finish coating system for coating golf balls, a polyol and a polyisocyanate are mixed in a pressure pot without a catalyst. The mixture in the pressure pot is then sprayed on the outer surface of the golf balls. Most of the mixture remains in the pot for some period of time before spraying. Thus, it is important to include enough solvent in the coating mixture to prevent the coating mixture from curing while it is still in the pressure pot and to provide for acceptable flowout of the coating mixture. However, it would be environmentally beneficial to be able to reduce the quantity of solvents in the coating system.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fast curing coating system for game balls, such as golf balls, softballs, baseballs, cricket balls and the like.
Another object of the invention is to provide a game ball having a fast curing coating that demonstrates adhesion and abrasion resistance which is comparable or superior to prior known urethane coatings.
Yet another object of the invention is to provide a game ball coating system having a high solids concentration.
Yet another object of the invention is to provide a low V.O.C. coating system for a game ball.
Further objects of the invention will become apparent from the following description.
The invention in a preferred form is a game ball coating system comprising a mixture of a polyol, a polyisocyanate is present in a quantity appropriate to provide of —N═C═O equivalents to —OH, in the range of 0.90 to or more preferably 0.90 to 1.5%, up to 65 wt % of a solvent, and a compatible catalyst. The catalyst is present in a quantity such that the coating composition will be cured to a Sward rocker hardness of at least 10 in less than about 1.5 hours at an elevated temperature. The quantity of catalyst is preferably sufficient to provide for an at least 100% increase in viscosity of the coating system within 30 minutes at 25° C., 1 atm and 60% relative humidity.
When applied to a game ball, the polyurethane finish coating preferably has an average initial wet thickness of no more than about 3.5 mils. In a particularly preferred form of the invention, the coating system is a two-part system including a first part containing the polyol, the catalyst and at least a portion of any solvent which is used, and a second part containing the polyisocyanate and/or polyisocyanurate.
The polyol preferably comprises at least one of a polyester, polyether or acrylic, and has a hydroxyl equivalent weight of 50-1500, and more preferably 100-1000. Blends of different polyols can be used. More preferably, the polyol is a saturated polyester polyol, and most preferably is the reaction product of an organic acid which includes at least one member selected from the group consisting of adipic acid, phthalic acid and isophthalic acid, an anhydride, and a glycol which includes at least one member selected from the group consisting of ethylene glycol and trimethylol propane.
The polyisocyanate or preferably includes at least one member selected from the group consisting of biurets and isocyanurate trimers of hexamethylene diisocyanate. Blends of polyisocyanates can be used. The solvent preferably includes one or more members selected from the group consisting of ketones, esters and acetates.
The catalyst preferably comprises at least one member selected from the group consisting of dibutyl tin dilaurate, dibutyl acetylacetonate, dibutyl tin dibutoxide, dibutyl tin sulphide, dibutyl tin di-2-ethylhexanoate, dibutyl tin (IV) diacetate, dialkyltin (IV) oxide, tributyl tin laurylmercaptate, dibutyl tin dichloride, organo lead, tetrabutyl titanate, tertiary amines, mercaptides, stannous octoate, potassium octoate, zinc octoate, diaza compounds, and potassium acetate. The catalyst preferably is present in a quantity of 0.01-10 weight % active catalyst (not including any carrier) based on total resin solids (polyol plus polyisocyanate, excluding solvents). The quantity of catalyst will depend upon the type of catalyst, polyol, polyisocyanate or polyisocyanurate, and solvents which are used, as well as the curing temperature and desired curing time. When dibutyl tin dilaurate is used as the catalyst, it preferably is present in an amount of about 0.05-0.35 weight % active catalyst based upon total resin solids, and more preferably 0.08-0.15 weight % based upon total resin solids. Excellent results have been achieved using about 0.1 weight % dibutyl tin dilaurate based upon total resin solids. Other catalysts preferably are used at levels which will produce the same state of cure as 0.05-0.35 weight % or more preferably 0.08-0.15 weight % active dibutyl tin dilaurate. The catalyst preferably is present in an amount sufficient to reduce the curing time of the coating by at least about 75% as compared to a coating system which does not contain the catalyst but is otherwise identical.
The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The invention is a coating system which will form a highly durable polyurethane coating on a game ball. The coating system contains an amount of catalyst which far exceeds the quantity of catalyst recommended by polyurethane coating manufacturers. When the high level of catalyst is used in conjunction with the mixing parameters of the invention, an excellent game ball coating can be formed at
Sergent Rabon
Spalding Sports Worldside, Inc.
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