Polychloroprene Production from Butadiene and Chlorine

The process under analysis comprises two major sections: (1) Butadiene Chlorination; and (2) Chloroprene Polymerization.

Butadiene Chlorination. In the first step, butadiene, chlorine and recycled butadiene and hydrochloric acid are mixed and fed to the chlorination reactor, where butadiene is chlorinated in the vapor phase. A large excess of butadiene is used to prevent the formation of super chlorinated species during this reaction. The two main products of the chlorination are 1,4-dichloro-2-butene and 3,4-dichloro-1-butene. An isomerization step is used to convert 1,4-dichloro-2-butene into 3,4-dichloro-1-butene (precursor to chloroprene), conducted in the reboiler of a distillation column. Caustic soda is diluted in process water, mixed with the 3,4-dichloro-1-butene stream and fed to a series of continuously stirred vessels. The gaseous chloroprene-rich stream is separated from heavy ends by means of stripping, evaporation and distillation steps.

Chloroprene Polymerization. The Polymerization is comprised of continuously stirred jacketed tank reactors connected in series, cooled by a brine solution. Chloroprene is first mixed with emulsifier, demineralized water and initiators (hydroperoxides/ferrous sulfates). The polymer molecular weight is controlled by means of a chain-transfer agent (tertiary dodecyl mercaptan). The reaction termination is accomplished with the addition of shortstop agents.The latex produced is steam-stripped for the removal of residual chloroprene, recycled. The hot latex is mixed with antioxidant and fed to a freeze roll to be coagulated into a polymer sheet, which is fed to a wash belt for removing polymerization reaction medium. The washed Polychloroprene film is dried in squeeze rolls and continuous-belt dryers. After drying, the film is formed into a rope and cut into polychloroprene chips, packed in bags.