Polymeric light stabilizers for plastics

A polyurea of the general formula Ia, ##STR61## in which n represents a value from 2 to about 50, A' is alkylene with 2-12 C atoms, arylene with 6-12 C atoms, 4,4'-dicyclohexylenemethane or a radical -phenylene-Z.sup.4 -phenylene- in which Z.sup.4 is --CH.sub.2 --, >C(CH.sub.3).sub.2, --O-- or --SO.sub.2 --, X and X' are NY and Y represents hydrogen, alkyl with 1-18 C atoms, cycloalkyl with 5-12 C atoms or aralkyl with 7-11 C atoms, and B is one of the radicals XXXI to XXXIX, ##STR62## in which R represents hydrogen or alkyl with 1-5 C atoms, R' is hydrogen, alkyl with 1-12 C atoms, allyl, benzyl, acetyl, acryloyl or crotonyl, Z is a direct bond or --CH.sub.2 CH.sub.2 -- or --OCH.sub.2 CH.sub.2 CH.sub.2 --, Z.sup.2 is one of the radicals --N(R")--, --NR.sup.3 --CO--NR.sup.3 --, --NR.sup.3 --CO--CO--NR.sup.3 --, NR.sup.3 --CO--Z.sup.3 --CO--NR.sup.3 --, alkylene with 4-10 C atoms, p-xylylene, ##STR63## --O-alkylene-O-- with 1-10 C atoms, --O-alkenylene-O-- with 4-8 C atoms or --O-xylylene-O--, wherein R" is alkanoyl with 1-8 C atoms or alkenoyl with 3-5 C atoms, R.sup.3 is hydrogen, alkyl with 1-12 C atoms, cyclohexyl, benzyl or aryl with 6-14 C atoms and Z.sup.3 is alkylene with 1-10 C atoms or phenylene, B" is alkylene with 2-12 C atoms, alkenylene with 4-8 C atoms, xylylene or hexahydroxylylene, cyclohexylene or a radical of the formula --CH.sub.2 CH.sub.2 OCH.sub.2 CH.sub.2 -- or --CH.sub.2 CH.sub.2 O-phenylene-OCH.sub.2 CH.sub.2 --, R.sup.5 is hydrogen, methyl or phenyl, Z.sup.5 represents alkylene or alkenylene with 4-8 C atoms, p-xylylene or a group of the formula ##STR64## wherein Z.sup.7 is alkylene with 2-12 C atoms, arylene with 6-12 C atoms, 4,4'-dicyclohexylenemethane or a radical --phenylene-Z.sup.4 -phenylene, Z.sup.7' is alkylene or alkenylene with 4-8 C atoms or p-xylylene, X" is oxygen or NH and Z.sup.8 is alkylene with 1-6 C atoms or phenylene or in formula Ia --X--B--X'-- is one of the groups of the formulae XLI to XLIII ##STR65## in which R.sup.3 is hydrogen, alkyl with 1-12 C atoms, cyclohexyl, benzyl, or aryl with 6-14 C atoms and Z.sup.9 is --CH.sub.2 CH.sub.2 -- or --OCH.sub.2 CH.sub.2 CH.sub.2 --.