| abstract |
Compounds of the formula I, <IMAGE> wherein Ar is phenyl or phenyl which is substituted by halogen, C1-C4alkyl or C1-C4alkoxy, R<1> is hydrogen, C1-C4alkyl, benzyl or allyl, R<2> is one of the groups -CO-R<3>, -CO-O-R<3>, -CO-NH-R<3>, -CO-N(R<4>)2 or -SO-R<3>, while <3> is C1-C12alkyl, C2-C12alkenyl, C7-C6phenylalkyl or C5-C7cycloalkyl, or has one of the meanings assigned to Ar, and R<4> is C1-C4alkyl, are suitable for use as sensitizers for the photopolymerisation of unsaturated compounds and for the photochemical crosslinking of polyolefins. They are distinguished in particular by an excellent resistance to yellowing of the polymers. These compounds are obtained by reaction of the corresponding benzoins with formaldehyde and subsequent acylation of the benzoin- hydroxymethyl ethers by conventional methods. |