DuPont Sclair Process

DuPont introduced a commercial solution process in the 1960s with the tradename of Sclair that reportedly used a Ziegler-type catalyst based on both a vanadium compound (VCl or VOCI3) and a titanium compormd (TiCl ) in the presence of an aluminum alkyl cocatalyst. Operating conditions were above 200°C and 1,000 psi [42]. 

DuPont s Sclair process was extremely important technology which was introduced in the 1960s, as it offered commercial ethylene copolymers at densities as low as 0.916 g/cc with improved physical properties over comparable polyethylene resins produced with the high-pressure process. In addition, DuPont scientists also developed improved catalysts for the Sclair process based on vanadium compounds that produced homogeneous branching distribution of the short-chain branches introduced along the polymer backbone by incorporation of a comonomer such as 1-butene into the polymer structure. 

Although some catalyst aspects of the Sclair technology were presented in Chapter 4 of this book, additional details are presented below. 

Copolymers with the structural features outlined above produce polyethylene films with reduced haze, higher gloss, higher dart impact strength, lower heat seal temperature, lower solvent extractables, and less film orientation, as characterized by less change between machine direction (MD) properties and transverse direction (TD) properties. 

Some typical polymerization data provided by Elston is summarized in Table 5.28. 

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At the time, DuPont operated a 275 million pound/year solution-polymerization process in Canada (Sclair Process) that was commercialized in the 1960s for the manufacture of LLDPE. However, DuPont sold the business to Canadian-based Nova Corporation in the mid 1970s. 

Because licensees of the Ziegler catalyst developed their own proprietary process technology, DuPont Sclair provides an excellent example how a Ziegler licensee developed and expanded both the process, catalyst and product technology, developing new markets and applications for low-pressure polyethylene. 

Sclair A process for polymerizing ethylene. Depending on the co-monomer used, the product can be linear low-density polyethylene (LLDPE) or high-density polyethylene (HDPE). Developed by DuPont in 1960 and widely licensed. Engineered by Uhde under the name Sclairtech. Nova Chemicals (Alberta) acquired the technology in 1994. 

The first ELDPE (Sclaire resins) was produced by DuPont Canada Ltd. in a solution process using Z-N vanadium (V) catalyst 0 0-n butyl)2 Cl, and A1 (Et)i li.5. The comonomer was C4-20. with the Al/V ratio increasing with comonomer MW from 5 1 to 12 1... 

Nova Chemicals presently operates more than a 1.5 billion Ib/yr solution phase polymerization process in Alberta, Canada and a second plant in Ontario. Nova obtained the Sclair technology from DuPont in 1994. 

AST [Advanced Sclair Technology] The latest version of an ethylene polymerization process developed by DuPont and acquired by NOVA Chemicals. See also Sclair, Sclairtech. 

The first commercial process for making LLDPE was the Sclair technology developed by Dupont Canada and now implemented by NOVA Chemicals. This process involves high-temperature solution polymerization. Much LLDPE is now made in gas-phase reactors with butene or hexene as the co-monomer. The constrained-geometry catalyst (CGC) is a metallocene catalyst developed by Dow Chemical for the manufacture of linear, very-low density polyethylene resins by solution polymerization with octene as the comonomer. For a given co-monomer content, the solid-state density is lower for octene than for lower a-olefins. 

The first reactors used to make HOPE were based on a solution process. This had the advante es of small reactor size, short residence time, and the possibility of removing catalyst particles from the product by filtration or centrifugation. Dupont Canada later took advantage of the high operating temperature, 150 °C, for the incorporation of octene comonomer to make Sclair LLDPE. 

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