| 摘要 |
1. A process for inhibiting the dimerization of piperidines of the formula I where radicals from R<1> to R<4> are C1- to C6-alkyl, R<1> and R<2> and/or R<3> and R<4> 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, based on the piperidine, of a reducing agent of the formula MXH4-mYm, where M is an alkali metal or 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 CN and m is 0 or 1. 2. A process as claimed in claim 1, wherein R<1>, R<2>, R<3> and R<4> are C1- to C3-alkyl. 3. A process as claimed in claim 2, wherein the compound of the formula MXH4-mYm is sodium borohydride. 4. A mixture comprising A. a piperidine of the formula I where radicals from R<1> to R<4> are C1- to C6-alkyl, R<1> and R<2> and/or R<3> and R<4> together are a CH2 chain having 2 to 5 carbon atoms, B. from 1 to 1000 ppm, based on A, of a compound of the formula II and C. from 0.001 to 0.2 % by weight, based on A, of a reducing agent of the formula MXH4-mYm, where M is an alkali metal or 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 CN and m is 0 or 1. 5. A mixture as claimed in claim 4, where R<1>, R<2>, R<3> and R<4> are C1- to C3-alkyl. 6. A mixture as claimed in claim 4 or 5, where the compound of the formula MXH4-mYm is sodium borohydride. 7. A method of using a mixture as claimed in any of claims 4 to 6 for the preparation of sterically hindered amine light stabilizers therefrom. |
