| 摘要 |
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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