Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1997-10-27
2001-07-03
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C525S454000, C473S351000, C473S356000, C473S376000, C473S378000
Reexamination Certificate
active
06255382
ABSTRACT:
DEFINITION OF TERMS
The term “coated golf ball” means a golf ball body which is coated with paint. Accordingly, one which is generally called “golf ball” by consumers and commercially available belongs to the “coated golf ball”. In the present specification, the term “golf ball” may sometimes Indicate the “coated golf ball” according to the common usage.
The term “golf ball body” means a golf ball before coating with paint.
FIELD OF THE INVENTION
The present invention relates to a coated golf ball comprising a golf ball body and a paint layer formed thereon. More particularly, it relates to a coated golf ball having excellent adhesion between the paint and the cover and improved paint durability.
BACKGROUND OF THE INVENTION
Golf balls are generally coated with paint In order to look beautiful or to prevent damage to the ball surface. The paint layer is composed of an enamel paint containing pigments such as titanium oxide, etc., and a clear paint containing no pigments, formed on the enamel paint, or a clear paint only.
Hitherto, an organic solvent based two-package reaction type urethane paint has been used for the paint for golf balls. Also, an epoxy paint is often used as primer. The use of the conventional paint has problems in safety and working environment, because an organic solvent is used.
On the other hand, in recent years, so-called non-enamel golf balls, coated only with clear paint, tend to gain popularity for the reason of good luster and tone. However, they have a defect to deteriorate the golf ball cover surface and to reduce adhesion between the cover and the paint, because sun light penetrates through the paint layer and directly irradiates the cover when non-enamel golf ball is exposed outdoors. Consequently, it is required more than ever to improve the adhesion between the paint and the cover.
To solve the above two problems, that is, to eliminate the use of organic solvents and to improve the adhesion between the paint and the golf ball cover, a water dispersed urethane paint has been proposed in Japanese Patent Kokoku Publication Hei-2(1990)-11095. The paint proposed in the Utility Model Publication solves problems associated with the use of organic solvents and improves the adhesion between the golf ball cover and the paint layer, to some extent. It is, however, desired to further improve adhesion, durability and strength of the paint layer. Also, the paint of the Utility Model Publication employs polyfunctional ethyleneimine (aziridine) compounds as crosslinking agents, which, however, are effective for solving the problems to some extent but not satisfactorily. Further the ethyleneimine is a substance having mutagenicity and is limited in use.
SUMMARY OF THE INVENTION
In order to solve the above mentioned problems and to obtain golf balls which have a coating layer having further Improved adhesion between the golf ball cover and the paint layer, having good toughness and good durability, the present inventors have been actively involved in the investigation, and finally, found that golf balls which use carboxyl group-containing water dispersed polyurethane paint for at least the primer layer of the paint layer which is crosslinked with carbodiimide compounds can provide excellent adhesion and durability superior to the conventional golf balls.
Accordingly, the present invention provides a coated golf ball which comprises a golf ball body and a paint layer formed thereon, wherein the paint layer is formed from a carboxyl group-containing water dispersed polyurethane paint which is crosslinked by a carbodiimide compound.
DETAILED DESCRIPTION OF THE INVENTION
The carboxyl group-containing water dispersed polyurethane paint to be used in the present invention can be manufactured by the known techniques disclosed, for example, in Japanese Kokoku Publication Sho 43-9076, Japanese Kokai Publication Sho 61-36314 and the like. That Is, a linear polyurethane is primarily synthesized from a polyhydroxyl compound, a polyisocyanate, a chain extender having active hydrogen by art known methods. In order to introduce carboxyl group in the polyurethane, If the polyurethane has an isocyanate group (—N═C═O), a compound having both active hydrogen having reactivity with isocyanate carboxyl group are allowed to react in a solution of an organic solvent, for example, acetone, etc. to introduce a carboxyl group. If the polyurethane has a hydroxyl group, a compound having both an isocyanate group and carboxyl group are allowed to react in a solution of an organic solvent, for example, acetone, etc. to introduce a carboxyl group. The carboxyl group is neutralized with ammonia or amines, and after adding water to it, the organic solvent is removed to obtain the desired carboxyl group-containing water dispersed polyurethane paint. In the above case, the preferred polyisocyanate Is a non-yellowing aliphatic or alicyclic polyisocyanate In view of weatherability.
The carboxyl group-containing water dispersed polyurethane paint is commercially available as SUNCURE 776, SUNCURE 895, SUNCURE 11447, SUNCURE 847, SUNCURE 898, etc. from Sanker Company in U.S.A., as U-COAT UWS-140 from Sanyo Chemical Industries, Ltd., as SPENSOL-L53, SPENSOL L-54, SPENSOL L-55, SPENSOL L-56, etc. from Dainippon Ink & Chemicals, Inc., which can be suitably used independently or in combination. All of the commercially available paint are transparent paints containing 25 to 35% by weight of a polyurethane resin colloidally dispersed in water, % by weight being based on the solid content of the paint.
The carbodiimide compounds which are used for the crosslinking agent of the water dispersed polyurethane paint have the following chemical formula.
R—N═C═N—R′
(R and R′ independently show an alkyl group)
The carbodiimide compound exhibits extremely strong reactivity with free carboxyl groups and reacts with carboxyl groups to form N-acylurea. This reaction is conducted as low as about 30-60° C. to crosslink polyurethane. However, since carboxyl groups form salts and are ionized in the water-based paint, the crosslinking reaction scarcely takes place and the carbodiimide compound ensures a long pot life and is stable. Examples of the carbodiimide compounds used in the present invention are N,N′-dicyclohexylcarbodiimide, 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide, and the like. The carbodiimide compound is also commercially available from Union Carbide Corp., USA as UCARLNK XL-25SE and UCARLNK XL-29SE, which can also be suitably used.
An amount of the carbodiimide compound of the present invention to be added to the water dispersed polyurethane paint is preferably 0.5-10 parts by weight, more suitably 1.0-8 parts by weight to 100 parts by weight of the paint. If it is less than 0.5 parts by weight, the effects of addition are poor and if it Is more than 10 parts by weight, crosslinking excessively takes place and durability (crack resistance) lowers.
The carboxyl group-containing water dispersed polyurethane paint according to the present invention may contain a leveling agent such as Zonyl FSO available from du Pont, Aerosol OTS available from American Cyanamide Company and the like, an antifoamer such as Foamaster VL available from Henkel Diamond Shamrock and the like, a thixotropy provider RM825 available from Rohm & Haas and the like, and other surface modifying agents, etc. And an aqueous dispersion of a colorant, particularly, a white pigment such as titanium oxide, etc. is added to be used as an enamel paint. An amount of the pigment may be suitably added by 40-60% by weight, preferably 50 to 55 by weight, based on the solid content of the paint. If the pigment Is less than 40% by weight, film shielding effects Is poor. If it exceeds 60% by weight, film physical properties is poor. In the case of a clear paint, the colorant is not basically contained.
The paint may further contain various additives or diluents, etc. in addition to the above-mentioned components. Examples of additives include a ultraviolet inhibitor, photostabilizer, filler pigment, and fluor
Hamada Akihiko
Horiuchi Kuniyasu
Birch & Stewart Kolasch & Birch, LLP
Buttner David J.
Sumitomo Rubber Industries Ltd.
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