THE TECHNOLOGIES OF HALOBUTYL RUBBER PRODUCTION. PART 2. ALTERNATIVE TECHNOLOGIES OF BUTYL RUBBER HALOGENATION
The review is aimed at the consideration of possibilities to improve current technology of the large-scale halobutyl rubbers production, to increase economic efficiency and to mitigate the environmental risks when implementing it on a commercial scale. The review presents the scientific-technical results of the development of halogenating butyl rubber alternative technologies. The author considered the directions for the development of the technology of halobutyl rubber production through the butyl rubber solid phase halogenation, butyl rubber bromination using the oxidizing agents and electrophilic solvents, and the application of electrochemically produced halogen aqueous solutions as the halogenating agents. The paper shows the possibilities of increasing the process efficiency during the solid-phase halogenation of butyl rubber by eliminating the solvent treatment cycle from the process chain. The author mentioned the disadvantages peculiar for this butyl rubber halogenation technology associated with temperature increase when mixing a polymer with a halogenating agent: a considerable drop in the Mooney viscosity index and the isomerization of units with the exo-methylene group, which results in the accelerated rubber vulcanization and time decrease before the vulcanization starts (scorching). The author discusses the application of oxidizing agents and electrophilic solvents for the bromination of butyl rubber that allows achieving almost complete conversion of bromine at the significant reduction of the process duration and ensuring high homogeneity of the reaction product structure. Special attention is paid to the process of butyl rubber bromination in a rotor-film reactor. However, the combination of halogen formation steps and the evolved halogen hydride utilization possible when using the electrochemical production of halogens in the form of their aqueous solutions is considered the most optimal.