In Basell's Spheripol process, homopolymerization is carried out in the liquid phase using a high activity/high stereospecificity catalyst system, which includes a MgCl2 supported titanium catalyst in spherical form. Liquid propylene and the catalyst system are fed continuously into a loop reactor together with hydrogen (for controlling molecular weight); ethylene is added to produce random copolymers. Polymerization occurs at temperatures of 60 to 80oC and at pressures of 3,500 to 4,000 kPa. The reaction vessel is cooled by using a water jacket. Spheres of polymer form as a slurry; the granules can then be fed to a gas phase copolymerization reactor, and unreacted monomer is condensed and recycled. Gaseous ethylene and propylene are copolymerized on a fluid bed of polymer particles; the composition of the spherical impact copolymer can be controlled by changing the amount of gases that are recycled. Solid products are finally treated on a fluid bed to deactivate the residual catalyst and to remove volatiles. The Spheripol process was developed by Himont/Montedison using technology devised under a cooperative research and development agreement with Mitsui Petrochemical of Japan. In 2002, Basell commercialized the Spherizone process. This new process uses a multizone-circulating reactor with bulk and gas phase zones separated by a barrier fluid.
Borealis
Borealis offers for license Borstar PP, a multiple reactor polymerization technology based upon an extension of their Borstar polyethylene process. Borstar PP consists of a slurry loop reactor, followed by a number of gas phase reactors in series. Two, three or four reactor configurations are available depending on the type of polypropylene required. Borealis has demonstrated the feasibility of this new technology by constructing their first 200 thousand tonnes line at Schwechat, Austria.
Ineos (formerly BP Chemicals)
In 1999, BP Chemicals acquired Amoco Chemicals and has since restructured its polypropylene and polyethylene businesses. As part of this restructuring, Amoco's and BP Chemicals'ÂÂ licensing businesses were combined. The polypropylene technology originally developed by Amoco is now offered under the brand Innovene PP. This gas phase polymerization technology uses a horizontal stirred bed process operating at 2,200 kPa. Only one reactor is used to produce homopolymers and random copolymers; two gas phase reactors in series are used to produce impact copolymers. The unique reactor reportedly allows near plug flow (a linear flow of the propylene/polypropylene through the reactor, versus a random removal with recycling). The near plug flow, in turn, provides a much narrower molecular weight distribution than a back mixed reactor, as the residence time of each molecule is very nearly the same.
Chisso
Chisso co-developed the horizontal gas phase polymerization process with Amoco, and they co-licensed this technology for a number of years. This cooperative arrangement has since ended, and Chisso under JPP now offers its own version for license.
Grace
Dow entered the polypropylene licensing business in 2001 through its acquisition of Union Carbide. The Unipol PP process is based upon an extension of Union Carbide's gas phase polymerization technology which was originally developed to produce polyethylene. The SHAC Catalyst technology, which Union Carbide acquired from Shell, involves a high activity titanium chloride/triethyl aluminum-based catalyst. The dual reactor configuration can produce a complete range of commercial polypropylene grades. Dow then developed Advanced Donor Technology (ADT) and produced non-phthalate PP catalysts. Grace purchased Dow's PP catalyst/licensing business on October 11, 2013. All Dow's PP technologies now belong to Grace.
Mitsui Petrochemical
The Hypol polymerization process utilizes a high activity, high stereospecificity catalyst which was developed jointly by Himont/Montedison and Mitsui. First-generation Hypol technology is based upon a hybrid process, which uses a bulk stirred tank reactor for the first stage and a gas phase reactor for the second stage. In second-generation Hypol II units, a bulk loop reactor is used for the first stage. In either case, homopolymers and random copolymers are made in an auto-refrigerated adiabatic vessel using the bulk polymerization process. Impact copolymers are then made in the second stage gas phase reactor. Line configurations with more than two reactors have been used in order to manufacture polymers with specific characteristics or properties.
Novolen Technologies
As a consequence of the merger between Montell Polyolefins and Targor to form Basell, licensing rights to the Novolen process were divested to a separate company called Novolen Technologies Holdings, an 80/20 percent joint venture between ABB Lummus and Equistar. Originally developed by BASF, the Novolen process is based upon gas phase polymerization technology using a vertical stirred powder bed at 50 to 105ÂoC. and 2,500 to 4,000 kPa. A modified Ziegler-Natta catalyst is used for high polymerization yield. Only one reactor is necessary to produce homopolymers and random copolymers, while a cascade of two gas phase reactors is used to produce impact copolymers.
A two-reactor system can manufacture strictly homopolymer at up to 130 percent of the designed plant capacity as both reactors are utilized to manufacture homopolymer. Cooling is provided by vaporizing liquid propylene, which is injected into the reactor, condensed, re-injected and recycled continuously. Polypropylene powder is discharged periodically from the reactor into a vessel for downstream cleansing, finishing, and pelletizing.
Rexene
In the Rexene or El Paso process, polypropylene homopolymers and copolymers can be produced in a single-train plant (up to 150,000 tonnes/year). Homopolymers and random copolymers are produced via a liquid pool process in a single stirred tank reactor. Impact copolymers are made by on-line transfer of the polymers to a gas phase copolymer reactor system. The process uses high-yield catalysts, and the removal of catalyst residues and atactic polymer is not required.
Sumitomo Chemical
Sumitomo offers gas phase polymerization technology using a fluidized bed reactor. Only one reactor is necessary to produce homopolymers and random copolymers; a cascade of two gas phase reactors is used to produce impact copolymers. Proprietary fourth generation catalyst technology has also been developed. The combination of the catalyst and process technology has enabled Sumitomo to manufacture very high MFR grades, highly crystalline PP, and high ethylene-propylene rubber content copolymers.
The long-term outlook for polypropylene is positive as the promise of abundant, low-priced propylene supports continued PP growth and attractive margins.
For an in-depth review of the players, developments, markets and outlook for polypropylene please Contact Us.