| 摘要 |
PCT No. PCT/EP97/02763 Sec. 371 Date Nov. 12, 1998 Sec. 102(e) Date Nov. 12, 1998 PCT Filed May 28, 1997 PCT Pub. No. WO97/46528 PCT Pub. Date Dec. 11, 1997The invention relates to a process for reducing the dimerization of piperidines of the formula I where R1 to R4 are C1- to C6-alkyl, R1 and R2 and/or R3 and R4 together are a CH2 chain having 2 to 5 carbon atoms, which comprises adding to the piperidine from 0.001 to 0.2% by weight of a reducing agent of the formula MXH4-mYm, where M is an alkali metal, NR4, where R are identical or different C1-C4-alkyl groups, or an equivalent of an alkaline earth metal or an equivalent of zinc, X is boron or aluminum, Y is H or CN and m is 0 or 1. The invention also relates to a mixture of piperidines of the formula I, from 0.001 to 0.2% by weight of a reducing agent and from 1 to 1000 ppm of dimers of the piperidines of the formula I, and to the preparation of hindered amine light stabilizers therefrom.
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