process for producing biureto poliisocianati blocked by dialchil malonati and varnishes obtained from them

摘要

1442024 Polyurethanes from blocked biuret polyisocyanates BAYER AG 22 Aug 1974 [23 Aug 1973] 36919/74 Heading C3R [Also in Division C2] Polyurethane resins are obtained from polyols and aliphatic, cycloaliphatic or araliphatic biuret polyisocyanates which have an -NCO functionality of more than 2 and which are blocked with diallyl malonates and which are obtained by reacting the corresponding buiret polyisocyanates with malonic acid dialkyl esters, at 20‹ to 120‹ C., the reaction being carried out in a solvent which contains ester groups, and the reaction mixture always containing excess of the dialkyl malonate.