GB1016904A - Process for imparting flame-retarding properties - Google Patents

Abstract

A thermoplastic synthetic resin is rendered flame retardant by depositing a polymer containing ethylenic unsaturation from an aqueous latex on to the particles of resin and treating it with a halogenating agent. Specified resins are homo- or co-polymers of ethylenically unsaturated monomers, e.g. ethylene, propylene, butylene, styrene, a -methylstyrene, methyl methacrylate or vinyl acetate and copolymers or mixtures of these with acrylonitrile, butadiene or isoprene. The resins may contain a chemical or physical blowing agent, e.g. pentane, and polystyrene may also contain synthetic or natural rubber. Particles of the resin may be prepared by chopping up an extruded resin filament or as the direct result of suspension polymerization. Specified polymers containing 0.5-2.0 ethylenic double bonds per 100 monomer units are natural rubber latex or homo- and co-polymers of dienes, e.g. butadiene, isoprene or chloroprene, with or without other monomers, e.g. styrene. They may be rigid or resilient and may be formed as an aqueous dispersion by emulsion polymerization. Deposition may be brought about by freezing or heating the latex, e.g. to 70-100 DEG C., and/or altering its pH, e.g. by adding H2SO4 or HCl whilst agitating it. The treated resin should contain 1-5% polymer for subsequent bromination or 5-15% polymer for chlorination. Specified halogenating agents are free Cl2 or Br2 used as gas, mist or vapour, bromotri-chloromethane in the presence of a redox catalyst, a sulphuryl halide or phosphorus pentahalide. Halogenation can be effected immediately after deposition or the particles can be filtered off and re-suspended in water. The treated resin should contain 1-5% Br or 2-20% Cl. In Example (1) a rubbery styrene/butadiene copolymer was deposited from aqueous dispersion on to beads of polystyrene containing pentane, the coated beads being centrifuged off, brominated with bromine water, dried, foamed with steam and moulded into a block. The process of Example (2) was similar to 1 but was carried out under N2.ALSO:A thermoplastic synthetic resin is rendered flame retardant by depositing a polymer containing ethylenic unsaturation from an aqueous latex on to particles of the resin and treating it with a halogenating agent. Specified resins are homo- or co-polymers of ethylenically unsaturated monomers, e.g. ethylene, propylene, butylene, styrene, a -methyl styrene, methyl methacrylate or vinyl acetate, and copolymers or mixtures of these with acrylonitrile, butadiene or isoprene. They may contain synthetic or natural rubbers. Specified coating polymers containing 0,5-2,0 ethylenic double bonds per 100 monomer units are natural rubber latex or homo- or co-polymers of dienes, e.g. butadiene, isoprene or chloroprene, with or without other monomers, e.g. styrene. They may be rigid or resilient and may be formed as an aqueous latex by emulsion polymerization. Deposition may be brought about by freezing or heating the dispersion, e.g. to 70 - 100 DEG C., and/or altering its pH, e.g. by adding HCl or H2SO4 whilst agitating it. The coating should represent 1-15% of the particles. Specified halogenating agents are free Cl2 or Br2, CBrCl3 with a redox catalyst and sulphuryl halides or phosphorus pentahalides.