GB1121109A - Improvements in or relating to preparation of epsilon-caprolactams - Google Patents

Abstract

Epsilon-caprolam and its derivatives are prepared by reacting an epsilon-hydroxy-caproic acid derivative in aqueous solution with ammonia or a primary amine in an amount from 1 to 10 moles per mol. of monomeric derivative or per ester equivalent of polyester taking into account the nitrogen contained in said derivative at a temperature from 250 DEG to 450 DEG C. under the autogenous pressure of the mixture in the absence of a catalyst and in the presence of a neutral salt soluble in water, and extracting the resultant e -caprolactam with a solvent. Epsilon-hydroxy-caproic acid derivatives are e -caprolactones, alkyl e -hydroxy caproates, e -acetoxycaproic acids, ammonium salts of e -hydroxycaprioc acid or e -hydroxycaproamides or capronitriles or polyesters of e -hydroxycaproic acid with molecular weights between 400 and 4000. The starting material is preferably a solution containing 5 to 25% by weight of the acid derivative. The neutral salt may be an alkali metal or alkaline-earth metal salt of inorganic or organic acids having anions stable under the reaction conditions, e.g. sodium and potassium chlorides, bromides, fluorides, sulphates, orthophosphates, carbonates and acetates; ammonium chloride, bromide, fluoride, sulphate and orthophosphate; and lithium, calcium and barium chlorides, bromides and acetates. Mixtures of these may be used. The neutral salt may also be the alkali metal or alkaline-earth metal salt of e -hydroxycaproic acid prepared in situ by the addition of an alkali metal or alkaline-earth metal compound, e.g. caustic soda or potash. In the case of e.g. a hydroxycaproamide or a capronitrile separate addition of ammonium or primary amine may not be necessary.