Patent GB-981342-A (GB)
Title: Flame retardant resins
Inventor: STEPHENSON ROBERT JAMES
IPC: C08J9/35
Filed: 1962-01-26
Abstract: An aqueous dispersion of an organic bromine containing flame retardant is treated with a precipitating agent in the presence of particles of a synthetic resin such that the flame retardant is deposited on to the resin particles. Specified resins are homo- or co-polymers of:-olefines, e.g. ethylene, propylene, butylene, styrene or a -methylstyrene; acrylates, e.g. methyl methacrylate; vinyl esters, e.g. vinyl acetate, and copolymers or mixtures of the above with acrylonitrile, butadiene or isoprene.  The polystyrene may contain natural or synthetic rubber and/or a chemical or physical blowing agent. Particles of the resin may be formed by chopping up an extruded resin filament; or by direct coagulation after a suspension polymerization process.  Specified flame retardants are tris-(2,3 - dibromopropyl) phosphate, a brominated natural rubber latex or a bromine containing homo- or co-polymer of a diene such as butadiene, isoprene or chloroprene. A flame-retardant precursor may first be dispersed in water and then brominated.  An adhesive, e.g. natural or synthetic rubber or a styrene/butadiene copolymer, and a buffer, e.g. tetrasodium pyrophosphate, may be added prior to halogenation. Precipitation may be effected by a decrease of pH, e.g. by adding H2SO4 or HCl, or by adding an electrolyte, e.g. potash, alum or NaC1. Precipitation and bromination may be effected simultaneously, the HBr formed during bromination effecting precipitation.  The treated particles should contain 1-5% Br.  In the examples, latices of styrene/butadiene copolymers (60 and 23% styrene respectively) were brominated using a tetrasodium pyrophosphate as buffer and precipitated on to polystyrene beads containing pentane with dilute H2SO4, the treated beads being foamed with steam and moulded into blocks; and natural rubber latex was added to polystyrene beads, containing pentane, suspended in bromine water, the treated beads being foamed and moulded.ALSO:An aqueous dispersion of an organic bromine-containing flame retardant is treated with a precipitating agent in the presence of particles of a synthetic resin such that the flame retardant is deposited on the resin particles.  Specified resins are homo- or copolymers of: olfines, e.g. ethylene, propylene, butylene, styrene or a -methylstyrene; acrylates, e.g. methyl methacrylate; vinyl esters, e.g. vinyl acetate and mixtures thereof. The polystyrene may contain natural or synthetic rubber.  Flame retardants specified are: tris-(2,3-dibromo-propyl)-phosphate, brominated natural rubber and bromine-containing homo- or copolymers of dienes, e.g. butadiene, isoprene or chloroprene. An adhesive, e.g. a natural or synthetic rubber or a styrene/butadiene copolymer and a buffer, e.g. tetrasodium pyrophosphate, may be added.  Precipitation may be effected by a decrease in pH, e.g. by adding H2SO4 or HCl or by adding an electrolyte such as potash, alum or NaCl.  The treated particles may contain 1-5% Br.  In Examples (1 and 2) a latex of a styrene/butadiene copolymer was brominated and precipitated on to polystyrene beads.  In Example (3) a natural rubber latex was added to polystyrene beads in bromine water.