GB580524A - Treatment of polymeric materials - Google Patents

Abstract

Organic diisocyanate modified polyesters or polyester-amides are cured or heated in the presence of formaldehyde or of a formaldehyde-liberating substance, and their physical properties, especially their rubber-like properties are thereby improved. The products are particularly suitable for the construction of petrol-resistant articles. Specified formaldehyde-liberating substances are paraformaldehyde, trioxane, dimethylolurea, trimethylolmelamine, hexamethylolmelamine, diphenylolpropane tetra-alcohol, methylolchloracetamide, methylolstearamide, N-methylol-p-toluenesulphonamide, dimethylolurea dimethyl ether, dimethylolurea dibutyl ether, 1 : 2 - glycol methylene ether, di-(b -hydroxyethyl) formal, N : N1-dimethyloluron dimethyl ether, hexamethylene tetramine-zinc chloride complexes and certain thermo-hardening phenol-formaldehyde condensation products. Curing is preferably effected in the presence of an acidic material, and specified acidic materials are formic, glycollic, oxalic, succinic, maleic, adipic, tartaric, salicylic, anthranilic, phthalic, citric, tannic, boric and phosphoric acids, phthalic and maleic anhydrides, phthalimide and potassium or sodium dihydrogen phosphate. Stabilizers or anti-oxidants customarily used in rubber technology may be present in the mix, and other optional additions are carbon black, clay, asbestos, blanc fixe, whiting, lithopone, mica, natural or synthetic rubbers, vulcanized vegetable oils, dark substitute, white substitute, "Cumar" (Registered Trade Mark) resin, wood rosin, pitch, stearic acid, paraffin wax, oleic acid, lauric acid, dibutyl oleate, tricresyl phosphate, dibutyl phthalate, butylphthalyl butyl glycollate, N-alkyl-toluene-sulphonamides and pigments. Solvents or swelling agents, such as methyl ethyl ketone, benzene - ethanol mixtures and chloroform-methanol mixtures may be added. The various ingredients may be mixed in a rubber mill and then formed into shapes or spread on to a substrate, and finally cured by heating, e.g. in a press or mould or in hot air. Temperatures of 100-150 DEG C. are suitable for curing. Alternatively, the incorporation of the formaldehyde with the polymers may be carried out by soaking shaped articles, e.g. sheets, in solutions containing formaldehyde or the formaldehydeliberating substance, or thin sheets, films, fibres or coatings of the polymer, alone or in admixture with one or more of the compounding ingredients already mentioned, may be heated whilst exposed to formaldehyde vapour, or whilst surrounded by a formaldehyde-liberating substance in powder form. The organic diisocyanate modified polyesters or polyester-amides, improved by curing in accordance with this invention, may be used in the construction of petrol and/or oil resistant gaskets, packings, hose, pump diaphragms, flexible containers, printing rollers, sheathings for insulated electric cables, balls, tyres, elastic threads, belting, engine bearings, coated or impregnated fabrics and floor coverings, and generally in the construction of articles requiring the use of a material having physical properties resembling those of rubber, but also having an outstanding resistance to the action of organic fluids and a very low permeability to gases and vapours. Examples are given. Specifications 534,698, 553,733 and 580,525, [Group VIII], are referred to.