Abstract: A two step method of preparing fire retardant thermoplastic polymer granules from fire retarding agents and thermoplastic polymers in a stationary granulating cylinder containing mixing elements mounted to a central rotating shaft which fluidizes and throws contained materials toward the center of the cylinder, forcing axial and radial flows simultaneously on the materials thereby forming granules. In the first step, a fire retarding agent is mixed with a fluid thermoplastic polymer at a temperature exceeding the solidification point of the polymer until a homogeneous mixture is formed. In the second stage, the mixture is solidified by cooling while the granulating cylinder continues to operate until the fire retardant agent is bound together in homogeneous granular form by a matrix of solid thermoplastic polymer. Suitable fire retarding agents include alumina, phosphates, borates, melamine, melamine cyanurate, metal cyanurates, and halogenated phenols.

Abstract: A method of preparing fire retardant concentrates wherein a base soluble cyanurate is dissolved in base and mixed with a fluid thermoplastic polymer. An amino-s-triazine is then reacted in-situ with the solubulized cyanurate to precipitate very fine insoluble cyanurate-amino-s-triazine adduct evenly distributed in the polymer. The mixture is cooled below its solidification point, binding the film particles of the insoluble adduct together by a matrix of solid thermoplastic polymer. The solidified matrix bound adduct is comminuted to form particulate thermoplastic fire retardant concentrate. The fluid thermplastic polymer may be a melt or an aqueous dispersion of a stable polymer such as nylon, polyolefin, polycarbonate, polyester, polystyrene, and polybutadiene. The particulate granules may contain concentrations as high as 65 to 95 percent of the adducts produced from soluble cyanurates such as sodium isocyanurate, and base solubulized isocyanuric acid and chlorocyanuric acid.