Dimer [...] three-dimensional [...] 4-amino-piperidin, manufacturing method and use thereof

PURPOSE : A process for reducing the dimerization of piperidine is provided which gives a simple method for preparing 4-amino-piperidine at a low cost of production and can manufacture HALS compounds having a low content of a by-product. CONSTITUTION : A process for reducing the dimerization of piperidine of formula (I) in which R1 to R4 are C1 to C6 alkyl, R1 and R2 and/or R3 and R4 together are a CH2 chain with 2 to 5 C atoms is described. The process is characterized in that to the piperidine is added 0.001 to 0.2 wt % of a reducing agent of the formula MXH4-mYm, in which M is an alkaline metal, NR4, where R is the same or different C1-4 alkyl groups, or an equivalent of an alkaline earth metal or an equivalent zinc, X is boron or aluminium, Y is H or CN and m is 0 or 1. Also described is a mixture of piperidine (I), 0.001 to 0.2 wt % of a reducing agent and 1 to 1000 ppm of the dimer of the piperidine (I), and the production of HALS stabilizers therefrom.