UV absorbers, their preparation and the use thereof

A compound of formula ##STR46## wherein B.sub.1 and B.sub.2 are each independently of the other an aliphatic linking group,

• U is the radical of formula ##STR47## wherein (L.sub.1).sub.1-3 is 1 to 3 radicals L.sub.1 selected from the group consisting of sulfo, hydroxy, C.sub.1 -C.sub.4 alkyl and C.sub.1 -C.sub.12 alkoxy and (L.sub.2).sub.0-1 is 0 to 1 substituents L.sub.2 selected from the group consisting of sulfo, C.sub.1 -C.sub.4 alkyl and C.sub.1 -C.sub.12 alkoxy,
• W is a group --NR.sub.2 --, --O-- or --S--,
• R.sub.2 is hydrogen or unsubstituted or substituted C.sub.1 -C.sub.4 alkyl,
• W.sub.1 is a radical --C(O)O--, --O(O)C--, --C(O)NH-- or --HN(O)C--,
• .dbd.E-- is a group .dbd.N-- or .dbd.C(T.sub.1)--, and T.sub.1 is halogen, C.sub.1 -C.sub.4 alkylsulfonyl, formyl, C.sub.2 -C.sub.4 alkoxycarbonyl or cyano,
• X.sub.1 is halogen, hydroxy, sulfo, C.sub.1 -C.sub.4 alkylsulfonyl, phenylsulfonyl, unsubstituted or substituted amino, 3-carboxypyridin-1-yl or 3-carbamoylpyridin-1-yl,
• T independently has one of the meanings given for X.sub.1 or is an alkoxy, aryloxy, alkylthio or arylthio radical, or is a nitrogen-containing heterocyclic radical or is a reactive radical of formula ##STR48## R.sub.1 is hydrogen, C.sub.1 -C.sub.4 alkyl which is unsubstituted or substituted by hydroxy, sulfo, sulfato, carboxy or cyano, or is a radical ##STR49## R.sub.3 is hydrogen or C.sub.1 -C.sub.4 alkyl, R.sub.4 is hydrogen, hydroxy, sulfo, sulfato, carboxy, cyano, halogen, C.sub.1 -C.sub.4 alkoxycarbonyl, C.sub.1 -C.sub.4 alkanoyloxy, carbamoyl or the group --SO.sub.2 --Y,
• alk and alk' are each independently of the other C.sub.1 -C.sub.6 alkylene,
• arylene is a phenylene or naphthylene radical which is unsubstituted or substituted by sulfo, carboxy, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy or halogen,
• Y is vinyl or a radical --CH.sub.2 --CH.sub.2 --Z and Z is a leaving group,
• W.sub.2 is --O-- or --NR.sub.3 --,
• W.sub.3 is a group --SO.sub.2 --NR.sub.1 --, --CONR.sub.1 -- or --NR.sub.1 CO--, and
• r, s, t and u are each independently of one another 0 or 1, s being 0 when t is 0,
• with the proviso that the compound of formula (1) carry at least one sulfo or sulfato group and at least one group which is removable under alkaline conditions.