Termooxidaition destruction of butadiene-nitrile rubbers and industrial waste

Abstract

The process of thermooxidation destruction of industrial butadiene-nitrile copolymers of the grades SKN-18, SKN-26 and substandard products is investigated. The process is carried out in aromatic solvents (toluene in the xylene) under the influence of air oxygen in the presence of an adduct of the radical initiator azodiisobutyronitrile with N-metilpirrolidone. The mass-average molecular weights of the resulting products were determined by gel permeation chromatography, and molecular weight distribution calculations were performed. The influence of the temperature and the content of the initiator on the change in the intrinsic viscosity of solutions of the resulting degradation products, depending on the time of the process, is considered. Based on a comparative analysis of the destruction parameters using toluene and xylene at 80 °C and an initiator concentration of 0.8% by weight. It was found that the type of solvent and the time of destruction practically do not affect the process of thermooxidative destruction with the production of low molecular weight polymers with a molecular weight of 40 ? 103. It is shown that in the course of the destruction of industrial rubbers differing in the content of acrylonitrile, the process proceeds with the formation of higher molecular weight compounds in rubbers with a higher content of acrylonitrile units. When carrying out the destruction of substandard rubber SKN-26SNT with high Defoe hardness, it is necessary to increase the concentration of the initiator to 1.1% of the mass. and temperature. The mechanism of thermooxidative destruction of the studied polymers is considered. According to the data of IR spectroscopy and chemical analysis, it was found that the products of thermooxidative destruction of nitrile butadiene rubbers contain oxygen-containing functional groups. Thus, a simple commercially method for producing low-molecular-weight butadiene-nitrile polymers based on special-purpose rubbers and substandard product with functional hydroxyl, carboxyl and epoxy groups has been developed.