Sensitizers for photopolymerization

In a method for the photopolymerisation of unsaturated compounds or for the photochemical crosslinking of polyolefins employing a sensitizer, the improvement according to which the sensitizer is a compound of the formula ##STR58## wherein Ar is a tetrahydronaphthyl or indanyl radical,

• X represents one of the groups --NR.sup.4 R.sup.5, --OR.sup.6, O--Si(R.sup.7)(R.sup.8).sub.2, hydroxymethoxy, (C.sub.1 -C.sub.4 alkoxy)methoxy, (C.sub.2 -C.sub.8 acyloxy)methoxy or together with R.sup.1 represents --OCH(C.sub.1 -C.sub.8 alkyl)--O(CH.sub.2).sub.1-2 --, --OCH(C.sub.6 -C.sub.14 aryl)--O--, --OCH(C.sub.1 -C.sub.8 alkyl)-- or --OCH(C.sub.6 -C.sub.14 aryl)--,
• R.sup.1, if X is --OR.sup.6, represents (a) C.sub.1 -C.sub.8 alkyl, (b) C.sub.1 -C.sub.8 alkyl substituted by C.sub.2 -C.sub.8 acyloxy, --COO--(C.sub.1 -C.sub.4)alkyl or --CN, (c) C.sub.5 -C.sub.6 cycloalkyl or (d) C.sub.7 -C.sub.9 phenylalkyl, and, in all other cases, represents (a) alkyl of 1 to 8 carbon atoms, (b) alkyl of 1 to 8 carbon atoms substituted by OH, C.sub.1 -C.sub.4 alkoxy, C.sub.2 -C.sub.8 acyloxy, --COO--(C.sub.1 -C.sub.4)alkyl or --CN, (c) cycloalkyl of 5 to 6 carbon atoms or (d) phenylalkyl of 7 to 9 carbon atoms,
• R.sup.2 has one of the meanings assigned to R.sup.1 or represents allyl, methallyl, 2-carbamoylethyl, 2-(N-C.sub.1 -C.sub.4 alkylcarbamoyl)ethyl, 2-(N,N-di-C.sub.1 -C.sub.4 alkylcarbamoyl)ethyl, 2-(2-pyridyl)ethyl, 2-(2-oxo-1-pyrrolidinyl)ethyl or 2-(di-O-C.sub.1 -C.sub.4 alkylphosphono)ethyl, or R.sup.1 and R.sup.2 together represent alkylene of 4 to 6 carbon atoms, oxaalkylene of 3 to 4 carbons or azaalkylene of 3 to 4 carbon atoms, or R.sup.1 and R.sup.2 are both hydroxymethyl,
• R.sup.4 represents (a) alkyl of 1 to 12 carbon atoms, (b) alkyl of 2 to 4 carbon atoms which is substituted by --OH or --Oalk, (c) allyl, (d) cyclohexyl, (e) phenylalkyl of 7 to 9 carbon atoms, (f) phenyl or (g) phenyl which is substituted by Cl, alk, OH, --Oalk or --COOalk,
• R.sup.5 represents (a) alkyl of 1 to 12 carbon atoms, (b) alkyl of 2 to 4 carbon atoms which is substituted by --OH or --Oalk, (c) allyl, (d) cyclohexyl or (e) phenylalkyl of 7 to 9 carbon atoms, or R.sup.4 and R.sup.5 together represent alkylene of 4 to 5 carbon atoms which can be interrupted by --O--, --NH-- or --Nalk--, or, together with R.sup.2 represents alkylene or phenylalkylene of 1 to 9 carbon atoms, oxaalkylene of 2 to 3 carbon atoms or azaalkylene of 2 to 3 carbon atoms,
• R.sup.6 represents (a) hydrogen, (b) alkyl of 1 to 12 carbon atoms, (c) alkyl of 2 to 4 carbon atoms which is substituted by --OH or --Oalk, (d) allyl, (e) cyclohexyl, (f) phenylalkyl of 7 to 9 carbon atoms, (g) phenyl or (h) phenyl which is substituted by Cl or alk,
• R.sup.7 and R.sup.8 are the same or different and represent alkyl of 1 to 4 carbon atoms or phenyl.