A POLYMERIC COMPOSITE MATERIAL WITH IMPROVED FLAME RESISTANCE

摘要

A polymeric composite material with improved flame resistance contains 25 to 75 parts by weight, preferably 35 to 60 parts by weight of a thermoplastic substance (based on 100 parts by weight of the polymeric composite material), and 75 to 25 parts by weight, preferably 65 to 40 parts by weight of magnesium hydroxide (based on 100 parts by weight of the polymeric composite material) the surface of which is treated by a surface active agent and/or which is uniformly intermixed with a surface active agent. The magnesium hydroxide consists of agglomerates of crystals having all particles with diameters less than 4.0 mu m, 50 % of particles with diameters less than 1.4 mu m, and a specific surface, determined by the BET-method, less than 25 m<2>/g. The magnesium hydroxide is a powdered crystalline product with the crystal size, as determined by Xray powder diffraction method, in the <004> direction greater than 150 ANGSTROM and less than 500 ANGSTROM , the aspect ratio having a value in the range of 2 to 5, strain in the <004> direction being not more than 4.2 x 10<-3>, and strain in the <110> direction being not more than 3.0 x 10<-3>. A method of preparation of a surface treated magnesium hydroxide is characterized in that, the surface active agent or a part of it in the form of a solution or suspension is added to an aqueous suspension of magnesium hydroxide, the mixture is mixed and water separated, providing the surface treated magnesium hydroxide. A mixture of magnesium hydroxide and a surface active agent or a part of it is mixed in a mixer at such elevated temperature, at which the surface active agent is uniformly deposited on the surface of magnesium hydroxide particles, and the product is cooled down.