METHOD OF OBTAINING BUTADIENE-NITRILE RUBBER Russian patent published in 2008 - IPC C08F236/12 C08F220/06 

FIELD: chemistry.

SUBSTANCE: current invention relates to methods of obtaining butadiene-nitrile rubber with carboxyl groups. Described is the method of obtaining butadiene-nitrile rubber with carboxyl groups, including emulsion copolymerisation of monomers, distilling off unpolymerised monomers, separation of the polymer, drying of rubber which is characterised in that before loading the polymeriser is cleared using nitrogen under a pressure of 4 kgf/cm², it's vacuumed till 0.5-0.6 kgf/cm², the water-phase is loaded with ½ part of rongalite, part of the oxidation-reduction system of the polymerisation process, gives in to tertiary dodecyl mercaptan, which is a chain transfer agent and molecular mass distribution of the polymer in the form of a solution in acrylonitrile in the quantity 70% of the calculated one, gives in to methyl-acrylic acid, that is a copolymer in a copolymerisation reaction, at an amount of 100% from the calculated amount, the polymeriser is again cleared using nitrogen under a pressure of 4 kgf/cm², till the oxygen content in the gas-phase is not more than 0.1%, the main monomers are introduced - acrylonitrile and butadiene, emulsification of loaded components is carried out for a period of 1 hour under room temperature, till the achieving in the polymeriser a temperature value in the range of 15-16°C, pine camphor hydro-peroxide is introduced, which is an initiator of the polymerisation process in the quantity of 50% from the calculated, or when achieving conversion of monomers 30% in the polymeriser the second half of pine camphor hydro-peroxide is introduced and 30% of the calculated volume of the tertiary dodecyl mercaptan, while the temperature in the polymeriser must not go beyond 16°C, the second half of rongalite is introduced when the conversion of monomers reaches 40%, interval of values of converting monomers from 40 to 50% the temperature of the reaction mass was kept at not more than 17°C, in relation to the reduction in the speed of polymerisation in the value interval of conversion of monomers from 50 to 60% the temperature in the polymeriser is raised a little and kept at 18-19°C, after bringing the polymerisation process to the set conversion of monomers 60-65%, the pH value of butadiene-nitrile carboxyl containing latex, obtained from 4.0 m.p. methyl-acrylic acid was in the range of 2.5-3.5, carboxyl containing latex is alkalinised til a pH value of 8.5-9.5 with potassium hydroxide solution containing not more than 3% of the mass to rule out viscosity increase in latex, simultaneous alkalinising latex stopping of the polymerisation process is carried out by introducing into the polymeriser a calculated amount of sodium diethyldithiocarbamate, which carries out the role of a stopper to the polymerisation process, separating of the polymer from the latex is conducted with a mixture of ultrafine particles of magnesium hydroxide and magnesium chloride in the form of an aqueous solution containing 1% of the mass with the pH value at 7.5-8.5 in the coagulation zone.

EFFECT: obtaining butadiene-nitrile rubber with the optimal content of carboxyl groups equaling five per cent of the mass.

1 cl