Photoinitiators for photopolymerization of unsaturated systems

A process for the preparation of an aqueous polymer solution or polymer dispersion comprising photopolymerizing of an ethylenically unsaturated compound present in an aqueous medium, wherein at least one compound of formula I ##STR8## wherein Z is CR.sup.1 R.sup.2 (OR.sup.3),

• R.sup.1 being H, C.sub.1-6 -alkyl or phenyl,
• R.sup.2 being H, C.sub.1-6 -alkyl or C.sub.1-6 -alkoxy and
• R.sup.3 being H, C.sub.1-6 -alkyl or C-.sub.1-6 -alkanoyl and
• Z' is Y-[(CH.sub.2).sub.m --X].sub.n --,
• X being CH.sub.2 or O,
• Y being OH;
• COOH;
• SO.sub.3 H;
• an alkali metal, alkaline earth metal or ammonium salt thereof;
• a salt thereof with an organic nitrogen base;
• NRR' in which R and R' are in each case H, C.sub.1-20 alkyl or C.sub.1-4 -hydroxyalkyl, or quaternized NRR' or NRR' in the form of an acid addition salt, and n and m each being a number 1-4 is added, as a photoinitiator, to the mixture to be polymerized before the photopolymerization is initiated.

A process for the preparation of a water-soluble or hydrophilic polymer comprising photopolymerizing an ethylenically unsaturated compound present in an aqueous medium, wherein the photopolymerization is carried out in the presence of a photoinitiator of ##STR9## wherein Z is CR.sup.1 R.sup.2 (OR.sup.3),

• R.sup.1 being H, C.sub.1-6 -alkyl or phenyl,
• R.sup.2 being H, C.sub.1-6 -alkyl or C.sub.1-6 -alkoxy and
• R.sup.3 being H, C.sub.1-6 -alkyl or C-.sub.1-6 -aklanoyl and
• Z' is Y--[(CH.sub.2).sub.m --X].sub.n --,
• X being CH.sub.2 or O,
• Y being OH;
• COOH;
• SO.sub.3 H;
• an alkali metal, alkaline earth metal or ammonium salt thereof;
• a salt thereof with an organic nitrogen base;
• NRR' in which R and R' are in each case H, C.sub.1-20 -alkyl or C.sub.1-4 -hydroxyalkyl, or quaternized NRR' or NRR' in the form of an acid addition salt, and n and m each being a number 1-4.