GB715364A - Heat stabilization of synthetic linear polyamides - Google Patents

Abstract

Synthetic linear polyamides are stabilized against the degradative effects of heat and oxygen by the addition of 0.1-1 per cent. by weight of a phosphorous acid or alkali metal salt thereof and of .25-2.5 per cent. by weight of an alkali metal halide, other than a fluoride. The stabilizing ingredients are preferably added to the amine salt prior to condensation to form the polyamide. They may also be added during the condensation, to the molten polymer followed by homogenization by extrusion, or may be tumbled with solid polyamide particles followed by extrusion. Sodium or potassium bromide or iodide are the preferred alkali metal halides. The phosphorous compound catalyses the condensation reaction so that to produce a polyamide of given viscosity it will be necessary either to shorten the usual reaction period or to add acetic acid as a viscosity stabilizer. Conventional additives, e.g. plasticizers, resin, waxes, fillers or pigments, may be blended with the stabilized polyamides. By reason of their properties the polyamides are especially suitable for such uses as textile fabrics, electrical insulation, kinematograph film, or sausage casings. Examples describe the addition to polyhexamethylenediammonium adipate before polyamide formation of mixtures of (1) phosphorous acid and potassium bromide, (2) phosphorous acid and potassium iodide, (3) sodium dihydrogen phosphate and potassium bromide, and (4) sodium dihydrogen phosphate and potassium iodide. Specifications 461,236, 461,237, 557,544, 619,707 and U.S.A. Specification 2,493,597 are referred to.