Verfahren zur Herstellung von Poly(meth)acrylimiden mit bei thermischer Belastung verbesserter Farbstabilität und daraus erhältliche Formkörper

Production of moulding compositions with reduced yellowing tendency under thermal stress involves producing an imidised methacrylate polymer with units of formula (I) by a conventional imidisation reaction in a reaction extruder. After imidisation, the polymer is treated with 0.005-1 wt.% reducing inorganic phosphorus compound(s) (II) selected from phosphinic and phosphonic acids and their alkali(ne earth) metal, aluminium and ammonium salts, in which the ammonium ion may have upto 4 1-4 carbon (C) alkyl and/or 5-6 C cycloalkyl substituents. R1, R2 = hydrogen (H) or methyl (Me); R3 = H, 1-18 C alkyl, 5-8 C cycloalkyl, 6-10 C aryl or 6-10 C aryl-(1-4 C)-alkyl, optionally mono- to tri-substituted by 1-4 C alkyl, 1-4 C alkoxy and halogen. Also claimed are the mouldings prepared using the claimed process. Preferably, (II) is added in aqueous solution. It is mixed with the particulate polymer or added to a polymer melt freed from volatiles, especially continuously in a degassing extruder following the reaction extruder.