Dowlex process

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. 

Chemical Market Resources [45] has reported that the Dowlex process consists of two stirred tank reactors in series with an isoparaffin (mixture of Cg and C ) solvent operating at 160°C and approximately 320... 

Fig. 10.64 The temperature dependent tensile yield stress for LLDPE (Dow, Dowlex 2045) obtained at Instron crosshead speed of 20 in/min. [Reprinted by permission from H. Jung and J. L White, Investigation of Melting Phenomena in Modular Co-TSEs, Int. Polym. Process., 18, 127 (2003).]...

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. 

Dowlex DSM Compact process Mitsui CX-process Novolen process Innovene process (horizontal stirred bed reactor)... 

Figure 2.39 Dowlex solution process for polyethylene production.

In 1992 the 3 M disclosed blends that comprised 100 parts VLDPE [Flexomer or Attane 80-95 mol% ethylene and 5 mol% C4 g comonomer(s)] and 15-600 parts m-LLDPE [DOWLEX ethylene copolymer with 2-8 mol% Cg]. The blends showed excellent processability. Formed into 10-300 pm thick films, they were used for transdermal drug delivery devices as single-layer backings. The films were clear, colorless, transparent to visible light, and sealable at relatively low temperature. They were permeable to O2, stable to various common components of transdermal delivery devices, strong, and comfortable and did not absorb significant amounts of common elements of transdermal carriers (Godbey and Martin 1993, 1994). 

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. 

HDPE resins offer both strength and processability - the two properties every injection moulding processor wants, but rarely obtains at the same time. This advantage is available across the wide spectrum of end-use applications. The range includes homopolymers and copolymers, with a variety of melt indices and densities. Dowlex improved processing resins bring to fabricators better flow characteristics compared to other HDPE with similar melt indices. 

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