Conventional synthetic rubbers are generally produced by liquid phase polymerization (including homopolymerization and copolymerization) by dissolving or dispersing a monomer in a solvent or water for polymerization. The olefin plastic can be a gas phase polymerization method. Since the 1990s, U.S. Union Carbide Corporation has transplanted this technology into EPDM rubber with olefinic monomers as raw materials, and has achieved success. It is unique in its ability to integrate rubber and plastics. Open up new avenues for elastomer production technology.
According to the traditional synthesis method, the synthesis process of EPDM rubber consists of three parts: polymerization, degassing and post-drying treatment. Among them, the degassing part has the most links, including monomer recovery, solvent/diluent recovery, extrusion dewatering and drying. The process in the degassing phase is the longest, and the energy consumption and labor occupation are also the most, and the waste gas and waste water pollute the environment.
Now that the gas phase polymerization method is used, the production appearance changes greatly. It is only necessary to separately add ethylene, propylene and the third monomer to a fluid bed. The particulate rubber is formed in a gas phase environment, and the heat of reaction is carried away by the circulating gas. The recycle gas fluidizes the polymer to function as a feedstock in conventional polymerization and is then continuously coated with carbon black.
Carbon black acts here as a fluidization aid (FA). The thus obtained product (EPDM granule) contains a part of carbon black. 100% of the gas phase polymerization is EPDM rubber, and the yield in the traditional liquid polymerization is only 8%~25%, and the solvent, diluent and unreacted monomer are separated after multiple post-treatments. Recycling. The use of a gas phase polymerization process also eliminates a large amount of water (for solvent separation and as a polymeric carrier). This gas phase polymerization process, which does not use solvents, makes the product cleaner and less polluting.
Although gas phase polymerization has many of the above advantages, the monomers involved must be gaseous, so it is currently only applicable to the binary ethylene propylene rubber or ethylene propylene diene monomer in the rubber synthesis field.