Process for the production of a lightfast and colorfast composite

Abstract

A first reaction mixture, prepared from (a) aromatic isocyanates with isocyanate contents of from 5 to 50%, and (b) compounds with molecular weights of from 32 to 10,000 which contain at least two isocyanate-reactive hydrogen atoms, in an equivalent ratio of component 'a' to component 'b' of 0.8:1 to 5:1, from 0.1 to 20% of a blowing agent and, optionally, other known additives, is introduced into a closed mold with a rigid cavity. After this mixture has become resistant to permeation, but is still compressible, a second reaction mixture, prepared from (c) aliphatic and/or cycloaliphatic polyisocyanates having isocyanate contents of from 5 to 50% and (d) compounds with molecular weights of from 32 to 10,000 which contain at least two isocyanate-reactive hydrogen atoms, in an equivalent ratio of component 'c' to component 'd' of from 0.8:1 to 5:1, an internal mold release agent and optionally blowing agents and other additives, is introduced into the mold, such that the second mixture surrounds the first mixture and compresses it. A third, optional, reaction mixture, the same as or different from the second mixture, may also be employed in a manner similar to the introduction of the second mixture. The final composite plastic part releases smoothly from the mold and evidences good lightfast and colorfast properties.