Patent ID: 7038003
Filing Date: 2006-05-02
Classification: C08G

Abstract:
1. A process for preparing polyisocyanate prepolymers containing allophanate structural units comprising reacting a) one or more polyisocyanates with b) one or more polyetherpolyols containing less than or equal to 0.02 milliequivalent of unsaturated end groups per gram of polyol (method of determination: ASTM D2849-69) and having a polydispersity (PD=M  to provide an NCO-functional polyurethane prepolymer comprising urethane groups that are partly or fully allophanatized by further reaction with c) polyisocyanates, which may be different from those from a), and d) catalysts and optionally adding e) acidic additives before, during and/or after the allophanatization.