MONOFUNCTIONAL ALCOHOLS TO PREVENT GELATION IN TWO COMPONENTISOCYANATE COATINGS

摘要

An improved process for applying a two component polyurethane coating composition to a substrate; a stream of a polyol having reactive hydroxyl groups is mixed with a stream of an organic polyisocyanate crosslinking agent to form a blend that is applied to the substrate; the improvement used in this process is as follows: adding to the stream of polyol a monohydric primary or secondary alcohol in a ratio of about 0.5 - 2.0 equivalents of alcohol hydroxyl to polyol hydroxyl before mixing with the stream of organic polyisocyanate and before application to the substrate to prevent or substantially reduce the formation of gel particles; wherein the monohydric primary or secondary alcohol has a 90% evaporation rate at 25.degree.C of less than 10,000 seconds as determined by ASTM D3539 using an Automatic Shell Thin Film Evaporator.