Polyurethane-urea coatings - made from prepolymer of a poly:hydroxy cpd., a di:isocyanate and a tri:isocyanate and a curing agent contg. amino gps.

摘要

In a process for coating substrates with polyurethaneureas, a temporary carrier is coated with a reaction mixt. comprising (a) an NCO-contg. prepolymer made by reacting (A) a polyhydroxy cpd. with a mol. wt. of 400-7000, (B) a diisocyanate and (C) a triisocyanate using an NCO/OH ratio of 1.5:1 to 3:1 and a mol. ratio (B):(C) of 80:20 to 98:2, esp. 90:10 to 97:3, and (b) an NH2 g.-contg. hardener. While the coating compsn. is still tacky, the coated carrier is laminated to the substrate to be coated and the coating is cured by heating, with evapn. of any solvent used. The carrier is then sepd. from the coated substrate. Process is esp. useful for the prodn. of synthetic leather. The process is less critical than known processes for coating substrates with polyurethanes, and allows wider variations in temp., humidity, belt speed and hand lay up procedures.