Process for making self-extinguishing, by means of red phosphorus, synthetic thermoplastic materials and products so obtained

Claim 1

A process for making self-extinguishing thermoplastic materials based on synthetic polymeric substances by incorporation of red phosphorus into said materials, which process comprises the steps of: (a) preparing an in water diluted melamine precondensate by first reacting 21.62 to 25.27% melamine, 30.85 to 36.04% formaldehyde, 25.57 to 29.87% triethanolamine and 8.82 to 21.96% of monohydroxyl alcohol having less than 5 carbon atoms, and then cationizing and diluting with a mineral acid and water until a pH of 7-7.6 and a viscosity of 40-50 centipoise are reached; (b) dispersing a micronized red phosphorus powder in the cationized solution of melamine precondensate obtained in step (a), then heating under stirring at about 100° C. to precipitate said precondensate in the form of a partially cross-linked resin around the red phosphorus particles and finally drying and completing the resin's cross-linking at approx. 100° C. in an inert atmosphere; (c) forming, by mixing and extruding, a concentrate comprising 30 to 70% by weight of a mother polymeric substance and 70 to 30% by weight of the encapsulated red phosphorus obtained in step (b), said mother polymeric substance being a synthetic thermoplastic polymer selected from the group consisting of polyamides, polyolefins, copolymers from acrylonitrile-butadiene-styrene polystyrenes, vinylchloride homo- and co-polymers, vinylacetate copolymers, polycarbonates and linear polyesters; and (d) incorporating said concentrate into a thermoplastic material to be made self-extinguishing, consisting of at least 50% by weight of any synthetic thermoplastic polymer defined in step (c), the amount of the abovesaid concentrate being quantitatively proportioned in such manner, that the final self-extinguishing thermoplastic material contains 1 to 15% by weight of said encapsulated red phosphorus powder.