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
1999-12-13
2001-05-08
Szekely, Peter (Department: 1714)
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...
C524S275000, C524S276000, C524S487000, C524S489000, C524S501000, C524S507000, C428S423100, C427S385500
Reexamination Certificate
active
06228926
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a non-toxic, water-based coating composition which, when applied to the surface of a substrate, particularly leather and vinyl materials, dries rapidly to provide a tough, protective film bonded firmly to the surface. This invention also relates to the method of using this coating composition.
2. Background Discussion
It is desirable to apply protective coatings to a wide variety of materials. For example, vinyl or leather upholstery for furniture and automobiles, articles of clothing like shoes and jackets, and objects such as purses, wallets, etc. all have an enhanced appearance if coated with a liquid which forms a durable film after evaporation of the carrying agent for the film forming material. U.S. Pat. No. 3,597,373 illustrates a typical coating composition which uses hydrocarbon solvents for the film forming material. These solvents are irritating to skin and mucus membranes, or even toxic upon prolonged exposure. Another disadvantage of hydrocarbon solvent based resin coatings is that the film formed tends to be inflexible. To overcome this, plasticizers are blended in the coating. These plasticizers migrate from the film over a period of time and may leave on the surface of the film a sticky, oily residue. Expensive blocking agents are used to inhibit the migration of the plasticizers from the film'surface. Eventually, the film becomes brittle when the plasticizers have volatized or have been transferred due to contact with other substrates and are no longer present in a sufficient amount to maintain the desired flexibility. Antioxidants are used in hydrocarbon solvent based resin coatings to speed drying and prevent decomposition of the film by air oxidation. Stabilizers are also used in hydrocarbon solvent based resin coatings to impart ultraviolet light resistance to both the coating and the resulting film. These are expensive and sometimes toxic ingredients.
SUMMARY OF THE INVENTION
This invention provides a coating composition which uses water as the carrying agent for the film forming material, and thereby avoids the problems associated with hydrocarbon based coatings. Moreover, a resin, or mixture of resins, is used as the film forming material which has the proper flexibility and abrasion resistance for the application without the need for inclusion of plasticizers into the coating. It has been found that a mixture of resins is desirable in some circumstances to tailor the coating composition to the particular application. For example, a coating applied to vinyl automobile upholstery must be more durable and tougher than a coating for hand bags and gloves.
The coating composition of this invention has several features, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims which follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled, “DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS,” one will understand how the features of this invention provide its advantages, which include high impact and abrasion resistance, excellent elongation and flexibility, outstanding stain and chemical resistance, early film integrity, fast dry-to-handle properties, air drying, outstanding toughness, excellent adhesion to heat and solvent sensitive substrates, compatible with anionic pigments and dispersing agents, water thinnable, suitable for white and light pastel shades, usable as primer and topcoat, stable to repeated freeze/thaw cycles, low solvent content, non-flammable, water clean-up, non-toxic, creates a high heat resistance barrier, high gloss, if desired, and is safe to use.
Briefly, this invention is a non-toxic, water-based, colloidal composition including a thermoplastic, elastomeric polyurethane and wax dispersed in water. After evaporation of the water carrying agent, the polyurethane and wax combine to form a tough film bonded to the surface of the substrate to which the coating composition is applied. The coating, in some instances, is absorbed by leather substrates, and this tends to improved the bond between the film and the substrate.
The composition may clear or pigmented, that is transparent or translucent or opaque. A major portion of solids present in the composition are polyurethane and a minor portion of solids present in the composition are wax. The polyurethane is the principal film forming ingredient, and the wax adds mar resistance to the film. It is believed that the polyurethane and wax interact synergistically to provide a barrier for a substrate which unexpectedly has a high heat and abrasion resistance and, high gloss, when desired. The film formed on, for example, vinyl or leather, creates a high heat resistant barrier. The film without flattening agents has a high gloss. This combination of polyurethane and wax is mainly responsible for the desirable attributes of this invention.
The composition is applied as a coating to the surface of a substrate, and dries rapidly in air at ambient temperatures and pressures, filling any cracks in the surface, to form a tough, durable film that is bonded firmly to the surface. At cold ambient temperatures or high humidity conditions, hot air may be used to speed the rate of drying. It may be used to coat such materials as, for example, leather, vinyl polymers, flexible and semi-rigid plastics, rubber, polycarbonate, reaction-injection molding compound, thermoplastic polyurethane, acrylonitrile-butadient-styrene, wood, aluminum, and galvanized metal.
A dispersing agent, a water soluble leveling agent, and a defoaming agent may also be present in the composition. The dispersing agent is present in the composition in an amount ranging between about I and about 30 weight percent. The dispersing agent insures that the polyurethane is uniformly distributed as tiny, solid particles which remain in suspension. The preferred dispersing agent is N-methylpyrrolidone. The ratio of water to dispersing agent in the composition is from 20/80 to 10/90 by volume. The leveling agent is a surfactant which insures that the film formed upon drying is integral, uniform, and substantially free of discontinuities such as picture framing, edgepull, pin holes, cratering, and fish eyes. The leveling agent is present in an amount ranging from about 0.05 to about 6 weight percent. One suitable leveling agent is a mixture of polyfunctional complex organic compounds in 2-butoxy ethanol. The defoaming agent stops the formation of bubbles during blending of ingredients that would hamper the formation of the desired uniform, integral film. The defoaming agent is present in an amount sufficient to suppress foaming, typically in an amount ranging from 0.05 to 6 weight percent.
A polyurethane colloid is used as the principal ingredient of the composition of this invention. One of the desirable features of the polyurethane used in this invention is that it forms a flexible film. This imparts pliability to the substrate, tending to restore its original hand. Hand is the aesthetic feel of the surface of the substrate. The coating of this invention produces a treated substrate that has a hand which approaches the original, untreated substrate. A characteristic of the polyurethane film is that its has a percent elongation in the range between about 150 and about 700.
The polyurethane used is a fully reacted polyurethane elastomer with no free isocynate, is hydrolytically stable, and when completely dry, does not redissolve in water. The polyurethane is preferably present in the composition in an amount ranging from 20 to 55 weight percent. Preferably, it is an aliphatic polymer having a average molecular weight, calculated on the basis of the gel permeation chromatographic method, ranging from 50,000 to 100,000. Although an aromatic polymer may be used, the film tends to yellow or darken over time, and consequently, an aromatic polymer is unsuitable when a clear, transparent
Connors John J.
Connors & Associates
Szekely Peter
LandOfFree
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