Dowlex Solution Process

Figure 2.39 Dowlex solution process for polyethylene production.

Dowlex A low-pressure, solution process for making linear polyethylene using 1-octene as the comonomer. Developed by Dow Chemical Company and used by that company to make products having the same name, but not offered for license. 

Continuous stirred-tank reactors (CSTRs) are used for large productions of a reduced number of polymer grades. Coordination catalysts are used in the production of LLDPE by solution polymerization (Dowlex, DSM Compact process [29]), of HDPE in slurry (Mitsui CX-process [30]) and of polypropylene in stirred bed gas phase reactors (BP process [22], Novolen process [31]). LDPE and ethylene-vinyl acetate copolymers (EVA) are produced by free-radical polymerization in bulk in a continuous autoclave reactor [30]. A substantial fraction of the SBR used for tires is produced by coagulating the SBR latex produced by emulsion polymerization in a battery of about 10 CSTRs in series [32]. The CSTRs are characterized by a broad residence time distribution, which affects to product properties. For example, latexes with narrow particle size distribution cannot be produced in CSTRs. 

The Dowlex process by Dow Chemicals is the dominant process in solution polymerization, but Dow does not license this technology to other companies (Figure 2.39). The Dowlex process uses two CSTRs in series with a high boiling hydrocarbon solvent. Other competing processes include the DSM process and the Sclairtech process by Nova Chemicals. In some configurations, these processes may also have tubular reactors operated in series with the CSTR to complete monomer conversion. 

The Dow Chemical Company developed the solution polymerization process with the Dowlex tradename in the 1970s to manufacture ethylene/1-octene linear low-density polyethylene (LLDPE) copolymers. The process is proprietary and not available for license. The ethylene/1-octene copolymers exhibit many superior physical properties relative to other ethylene copolymers based on 1-butene or 1-hexene. 

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