METHOD FOR PRODUCTION OF SELF-EXTINGUISHING FOAMING POLYSTYRENE Russian patent published in 2000 - IPC

FIELD: polymer production. SUBSTANCE: self-extinguishing foaming polystyrene applicable as heat- and sound-insulating material in a variety of areas is prepared in two-step water-suspension polymerization of styrene in presence of fire retardant and suspension stabilizer selected from group including freshly prepared tricalcium phosphate plus sec- alkyl sulfate and polyvinyl alcohol solution with 10-14% of residual acetate group. In the first step, suspension polymerization is carried out at mechanical stirring in presence of benzoyl peroxide and optionally tert-butyl perbenzoate. After that, foaming agent is added and polymerization completed. Method is distinguished by that (i) polymerization is conducted in presence of molecular weight regulator and value of p = M*J*K*Q*L is maintained within a range between 3.0-6.3, where M is molecular weight regulator concentration, 0.01-0.04 wt.%, J benzoyl peroxide concentration, 0.25-0.30 wt.%, K first-step polymerization, wt. %, Q styrene prepolymer viscosity in the first polymerization step, s, L coefficient taking account of stirrer type (equal to 1 for blade stirrer and 5.33 for impeller stirrer) and (ii) foaming agent is added before the beginning of the second polymerization step. EFFECT: improved workability of polymer. 1 tbl, 10 ex