Water-reduced urethane coating compositions
First Claim
1. A stable aqueous dispersion which is emulsifiable in the absence of added emulsifier of a non-gelled polyurethane formed by reacting in the presence of water:
- A. a partially reacted NCO-containing polymer containing salt groups and highly active hydrogens selected from the group consisting of hydroxyl, thiol, primary and secondary amine, said partially reacted NCO-containing polymer having a reactive hydrogen equivalent weight of 150 to 10,000,B. an active hydrogen-containing compound having at least one hydrogen more reactive with NCO groups than water to form a polyurethane having an intrinsic viscosity of less than 4.0 deciliters per gram.
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Abstract
A water-diluted, ungelled, non-sedimenting polyurethane and a process for preparing such a polyurethane in the presence of water is disclosed. The polyurethanes are prepared so that they contain a high percentage of highly active hydrogens which enable the polyurethanes to be further reacted with a curing agent to form thermoset products. The polyurethanes of the present invention are prepared by first dispersing a partially reacted NCO-containing polymer in water, which is then chain extended with a material such as an organic diamine. Thermosetting compositions are made by adding curing agent to the chain extended material. Curing agents can also be incorporated into the polymer molecule either in the making of the partially reacted NCO-containing prepolymer or by further reaction with the partially reacted NCO-containing prepolymer. The water-dispersed polyurethanes of the present invention are excellent film formers, capable of making coatings with a wide spectrum of desirable properties. In addition, they can be added to other water-compatible compositions to improve flexibility, hardness, drying and other coating properties.
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Citations
35 Claims
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1. A stable aqueous dispersion which is emulsifiable in the absence of added emulsifier of a non-gelled polyurethane formed by reacting in the presence of water:
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A. a partially reacted NCO-containing polymer containing salt groups and highly active hydrogens selected from the group consisting of hydroxyl, thiol, primary and secondary amine, said partially reacted NCO-containing polymer having a reactive hydrogen equivalent weight of 150 to 10,000, B. an active hydrogen-containing compound having at least one hydrogen more reactive with NCO groups than water to form a polyurethane having an intrinsic viscosity of less than 4.0 deciliters per gram. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. An aqueous coating composition comprising:
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A. stable aqueous dispersion which is emulsifiable in the absence of added emulsifier of an ungelled NCO-free polyurethane formed by reacting in the presence of water; 1. a partially reacted NCO-containing polymer containing salt groups and reactive active hydrogens selected from the group consisting of hydroxyl, thiol, primary and secondary amine, said polymer having a reactive active hydrogen equivalent weight of 150 to 10,000, 2. an active hydrogen-containing compound having at least one hydrogen more reactive with NCO groups than water to form a polyurethane having an intrinsic viscosity of 2.0 deciliters per gram or less; B. a curing agent. - View Dependent Claims (29, 30, 31, 32, 33, 34)
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35. A method of forming a stable aqueous dispersion which is emulsifiable in the absence of added emulsifier of an ungelled polyurethane comprising:
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A. preparing a partially reacted NCO-containing polymer containing ionic salt groups or groups which are capable of forming ionic salt groups and highly active hydrogens selected from the group consisting of hydroxyl, thiol, primary and secondary amine, said partially reacted NCO-containing polymer having a highly active hydrogen equivalent weight of 150 to 10,000, B. dispersing said partially reacted NCO-containing polymer in aqueous medium in which water is the principal ingredient, C. chain extending the NCO-containing polymer with an active hydrogen-containing compound having at least one hydrogen more reactive with the NCO groups than water to form a polyurethane having an intrinsic viscosity of 4.0 deciliters per gram or less.
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Specification