Technology

Historical Background

The SCLAIRTECH™ process was invented by Dupont^[1], which built the first commercial plant in 1960^[2].

NOVA Chemicals acquired the rights to SCLAIRTECH™ technology, the SCLAIR^® trademark, and the worldwide SCLAIRTECH licensing business when it acquired DuPont Canada's polyethylene business in 1994^[3].

Process Details

SCLAIRTECH™ is a solution process for producing HDPE and LLDPE from ethylene and comonomers such as 1-butene, or 1-octene^[1,3]. The feed material is ethylene and comonomer dissolved in cyclohexane together with a catalyst. Only a small amount of comonomer is used to create short chain branches in the polyethylene chain. By varying the amount of comonomer, one can control the polymer density (i.e. crystallinity)^[1].

The reactor system operates adiabatically at temperatures up to 300°C in cyclohexane solution.Polymerization is very rapid, requiring less than 2 minutes, so small reactors can turn out relatively large volumes of polymer.^[3]. The hydrocarbon solvent is used to keep the contents of the reactor in solution and also aids in heat removal. High conversions maximize production and eliminate any potential for runaway reactions^[2].

The extrusion and stripping sections of a SCLAIRTECH™ plant are also designed to facilitate very quick transitions between products, on the order of 30 minutes^[3]. The solvent together with and unreacted monomers are flashed and recovered, along with the energy captured from the heat of reaction, and circulated back to the reactor^[1,2]. The molten polymer is sent to a simple extruder and pelletizer assembly where the polymer is chopped into pellets for shipment^[1].

Products

Advanced SCLAIRTECH technology can deliver both wide Density ranges (0.905 to 0.967 g/cm³) and wide Melt Index ranges (0.40 to 150 g/10 min). Additionnally the dual reactor process allows for tailored molecular weight distributions - from very narrow to very broad.

Wth this dual-reactor solution technology both proprietary single-site (SSC) or Ziegler-Natta (ZN) catalysts are used in combination with octene-1 comonomer, producing products branded as SURPASS^® (SSC resins) and SCLAIR^® (ZN resins)^[4]. 

References

1.  W. Harmon Ray, Jun 2013, Some Engineering Opportunities and Challenges when Producing Polymer.
2. Hydrocarbon Processing, SCLAIRTECH, via Big Chemical Encyclopedia.
3. Dr. Faisal H. Syed, Dr. William D. Vernon, Chemical Market Resources, Inc., NEW GENERATION POLYOLEFINS, Jun-Jul 2002, Volume 7, Issue n° 6.
4. NOVA Chemicals, Technology, Advanced SCLAIRTECH™ Technology, retrieve from the Web Archive, 24^th Apr 2013.