Abstract
Polymeric light stabilizers were synthesized by hydrosilylation of unsaturated 2-hydroxybenzophenone derivatives or pentamethylpiperidine derivatives with different hydridosiloxanes. Investigations of the hydrosilylation reaction by NMR and HPLC show that the stabilizer groups are mainly bound to the siloxane chain by non-hydrolysable SiC bonds. When allyl ethers are used as starting material, side reactions such as ether cleavage, hydrogenation and isomerization take place. To avoid these side reactions, unsaturated ethers or esters with long methylene chains between the double bond and the oxygen were used. The polymeric light stabilizers were tested as stabilizers of polypropylene and compared with TINUVIN 770. The activity of polymeric light stabilizers decrease, with increasing molecular weight. Extraction experiments demonstrate that the polymeric stabilizers are resistant against extraction by organic solvents while TINUVIN 770 is extracted under the same conditions. Thus, our polymeric HALS show a higher effectiveness than TINUVIN 770. The polymeric HALS derivatives with the best activity have molecular weights ( M n) between 2000 and 4000.
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