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

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.degree. 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.degree. 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.