FIELD: rubbers.
SUBSTANCE: present invention relates to heat-resistant nitrile butadiene rubber and a method for its production. A halogenated polymer based on nitrile rubber is a heat-resistant halogenated diene-containing copolymer, which contains from 20 wt.% to 75 wt.% of halogenated groups based on the total weight of the copolymer, is characterized by a temperature of 5% weight loss from 230°C to 265°C, weight average molecular weight 50-200 thousand amu, content of residual double bonds of at least 0.5 wt.% based on the total weight of the copolymer, softening point of at least 120°C, an average granule size of 20 mcm. A method is also described for producing the above halogenated polymer based on nitrile butadiene rubber, which includes the following steps: a) dissolving the original copolymer in a hydrocarbon solvent by stirring at a temperature of 10 to 50°C, whereas the mass ratio of the hydrocarbon solvent to the original copolymer can be from 5:1 to 30:1, the dissolution process time is from 10 to 60 minutes; b) halogenation is carried out by adding the solution of the initial copolymer obtained in step a) in a hydrocarbon solvent to the halogenating agent, the molar ratio of the initial copolymer and the halogenating agent is from 1:1.5 to 1:5, the ratio is chosen in such a way as to ensure the achievement of the pH no more than 5.5; halogenation is carried out at a temperature from 0 to 50° C, the process time is from 15 to 120 minutes, whereas the resulting mass comprises a halogenated copolymer and a solvent; c) neutralizing the reaction mass obtained in step b) containing the halogenated copolymer solution by adding an aqueous solution of a neutralizing agent, followed by washing the neutralized reaction mass with water and separating the aqueous layer and the organic layer containing the halogenated copolymer, whereas the molar ratio of the neutralizing agent and the halogen added at stage b) in the modifying system is from 1:1 to 3:1, whereas the ratio is chosen in such a way as to ensure the achievement of a pH of at least 7.5; the neutralization process is carried out at a temperature of 15 to 50°C, wherein the neutralization is carried out using at least a one-time excess of water relative to the volume of the reaction mass subjected to neutralization, resulting in the separation of the reaction mass into two layers: an organic layer containing a halogenated copolymer and an aqueous layer; d) separating the halogenated copolymer by precipitation, to precipitate the halogenated copolymer, an alcohol-precipitant is added to the organic layer obtained in step c) in a mass ratio of alcohol-precipitant: halogenated copolymer from 1 to 10; f) the halogenated copolymer is filtered at a temperature of 20 to 40°C inclusively and the copolymer is dried at a temperature of 50 to 105°C and pressure from 1 to 20 kPa.
EFFECT: obtaining a halogenated polymer based on nitrile-butadiene rubber with improved properties of its distribution in the polystyrene mass, as well as providing high fire-retardant properties to expandable polystyrene.
12 cl, 1 dwg, 1 tbl, 7 ex
