GB591382A - Process for the preparation of n-alkoxymethyl polyamides in granular form - Google Patents

Abstract

N-alkoxy methyl polyamides are obtained in granular form by adding water to a stirred alcoholic solution of the polyamide, thereby causing the precipitation of a viscous resin-containing fluid, which is then agitated in the presence of water either after separation from the mother liquor or admixed with it, and the resulting hard finely divided granules are then separated from the aqueous phase. The N-alkoxy methyl polyamides, e.g. polyhexamethylene adipamide, polyhexamethylene sebamide and polyamides derived from e -amino caproic acid, are prepared by condensing a synthetic linear polyamide with formaldehyde and an alcohol in the presence of an oxygen-containing acid catalyst, preferably phosphoric acid. The reaction is stopped by pouring the reaction mixture into a quenching bath containing chiefly methanol, water and an alkali, preferably ammonia. In the granulation process, the quenched solution is stirred with water, and the resulting viscous resin containing fluid, which separates out, is mechanically worked, in a dough mixer, with further quantities of water, the small granules into which the doughy, resinous mass breaks up after prolonged working being then separated. On the addition of further water and after continued stirring the granules harden and are separated by filtration or centrifugation. To obtain the preferred methylol content (i.e. below 0.4 per cent) the quenched solution is treated with an aqueous or alcoholic solution of a methylol-removing agent such as a water-soluble sulphite, hydroxide or carbonate of an alkali metal or alkaline earth metal before granulation, or on prolonged storage in alcoholic ammonia the methylol content is reduced. Specifications 461,236, 461,237, 544,715, 573,482, and U.S.A. Specification 2,130,948 are referred to.