GB717680A - Improvements in and relating to the stabilisation of alkylated phenylene diamines - Google Patents

Abstract

Alkylated phenylene diamines having reduced tendency to discolour are obtained by treating the diamine or crude diamine with an alkaline or basic substance of which preferably some, but not more than 1 per cent by weight, is left in the diamine as stabilizer. Phenylene diamines which can be treated in this way are, for example, NN1-di(sec. butyl)-p-phenylene diamine, the corresponding m- and o-diallyl compounds, the N-mono-alkyl p-compounds; the N-mono-alkyl-m- and o-compounds, the p-trialkyl compounds, the m- and o-trialkyl compounds, and especially these compounds in which the alkyl groups contain from 1 to 5 carbon atoms. Examples of such compounds, which are particularly valuable as antioxidants for petroleum products, are NN1-di(sec. butyl)-p - phenylene diamine; NN1 - di - isopropyl p - phenylene diamine, NN - dimethyl - N1-sec. butyl-p-phenylene diamine, and NN-dimethyl - N1 - isopropyl - p - phenylene diamine. Other diamines which may be treated according to the invention are N-sec. butyl-p-phenylene diamine, NN1-di-isopropyl-2,3,5,6-tetramethyl-p-phenylene diamine, and NN1-di(sec. butyl)-n-phenylene diamine. Suitable alkaline or basic substances are, for example, the alkali metal hydroxides such as caustic soda, the alkoxides especially those containing up to 6 carbon atoms, the trialkylamines, especially those containing up to 6 carbon atoms in the alkyl group, and the tetra alkyl ammonium hydroxides, especially those containing up to 5 carbon atoms in the alkyl group. The treatment with the alkaline or basic substance may be carried out before or after distilling the crude mixture. In the examples (a) NN1-di(sec. butyl)-p-phenylene diamine (obtained by reacting p-nitroaniline and methyl ethyl ketone in the presence of hydrogen at superatmospheric pressure) is heated with a solution of caustic soda in a mixture of methanol and water; the mixture is distilled to give the pure diamine with reduced tendency to discolour; (b) freshly distilled NN1-di-sec. butyl p-phenylene diamine which has been distilled in the absence of caustic soda is stored under nitrogen over 1 per cent of its weight of solid sodium methoxide; and (c) freshly distilled NN1-di-sec.-butyl p-phenylene diamine is mixed with about 1 per cent of its weight of a saturated solution of sodium methoxide in methanol and stored under nitrogen.