Polyolefins production technologies

Polyolefins are a major class of commodity synthetic polymers. The technology for the production of these important polymers is well estabUshed, from catalyst synthesis to polymerization reactor technology. Despite constant advancements in polyolefin production technology, applications of polyolefins are stiU mainly limited to commodity products. The recent interest in the production of polyolefin-clay nanocomposites extends the use of polyolefins to specialty and engineering plastic appHcations. Polyolefin-clay nanocomposites are lighter than conventional composites, but have thermal stability, barrier, and mechanical properties that are comparable to those of engineering plastics. 

Sittig, M., Polyolefin Production Processes, Chemical Technology Review No. 79, New Jersey, Noyes Data Corp., 1976, p. 9. 

Polyolefin industry, catalysts in, 26 503 Polyolefin (PO) resins, 17 699-700 technologies and uses for, 17 707-708 Polyolefin products, Ziegler-Natta catalysts for, 26 533-544 Polyolefins, 10 518... 

Section 7.2 Reviews on industrial polyolefin production K. S. Whiteley, G. T. Heggs, H. Koch, R. L. Mawer, W. Immel, Polyolefins, in Ullmann s Encyclopedia of Industrial Chemistry, sixth edition, VCH Weinheim, 2003, vol. 28, p. 393 G. Cecchin, G. Morini, F. Piemontesi, Ziegler-Natta Catalysts, in Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley Sons, Inc, 2003 L. L. Bohm, Angew. Chem. Int. Ed. Engl. 2003, 42, 5010. 

Baron, N. 1990. A new polyolefin product family based on Exxpol catalyst technology. 

The combination of transition metal halides and aluminium alkyls has remained at the heart of the Ziegler catalyst, and is today the world s most widely employed technology for polyolefin production [16]. 

How many of these polyolefin production plants have been installed since the beginning of this industry One way to develop the answer to this question, which we do not pursue in depth here, is to follow the technology licensors. For example, we know that ICI were active in licensing LDPE and that by 1977, they had 23 licensees, and a total installed capacity of 812,000 tons. However, their founding technology was based on the stirred tank reactor (autoclave), and this could not be scaled up in the same way that tubular reactors, developed by others, could. By 1980, ICI had lost the first producer advantage , had not led the way in technology development, and in 1982, exited the PE business. 

Two of the most interesting aspects of the catalysts used in this work are their ability to copolymerize ethylene and a-olefins with polar monomers and their inertness toward impurities, allowing for a relatively straightforward production of these types of polymers in SCCO2. Although the activity of these catalysts is still rather low for commercial use, it may be expected that this will improve significantly in the near future. This would enable the development of clean polyolefin production based on C02-technology, for which future applications may be expected in the production of EPDM and other elastomers. 

Union Carbide, now part of Dow Chemical, was the first company to commercialize the technology for polyolefin production using fluidized-bed gas-phase reactors. Since polymerization occurs in the gas phase, separation of the unreacted monomer from the polymer product is achieved simply by flashing off the monomer. Any low molecular weight polymer formed remains in the polymer particles and no further separation is necessary. The process only requires a fluidized-bed gas-phase reactor, a product discharge system to get... 

Galli, P. (2001) Contribution of the Reactor Granule Technology (RGT) to the Expansion of the Polyolefin Product Property Envelope. FlexPo 2001, Galveston, USA, 22-24 August. 

Metallocene catalysts which are to be used as drop-in catalysts in existing plants for polyolefin production have to be heterogenized due to the fact that current technology is based on gas phase and slurry processes. Thus the metallocenes are to be fixed on a carrier. Carriers may be divided into three groups (1) metals have been used as fillers (2) inorganics like silica, aluminia, zeoliths or MgCl2 [470,476] and (3) organic materials like cyclodextrins [477], starch (as a filler) [478] and polymers (polystyrenes, polyamides) have been used to support either the metallocene or the cocatalyst. 

The introduction of metallocene and other single-site technologies (Fig. 31) made possible new process/ comonomer combinations, use of novel comonomers such as styrene, norbornene, and carbon monoxide, and seemingly impossible property combinations. Potential adaptation of polyolefin manufacturing technologies to the production of engineering thermoplastics is possible. 

Compared to other polymer production processes and even among polyolefin processes, the high-pressure LDPE production technology is highly suitable for... 

Molecular management of polyolefin properties requires advanced analytical technology that can provide detailed compositional and microstructural information of the polyolefin product. In principle, structural information can be obtained by breaking the polymer into short sequences, which are then analysed. Indeed, Py-MS has been used for many years to characterise polymers in this manner [4-7]. However, chemical information can be lost if the pyrolysates undergo additional fragmentation when they are ionised, which is often the case with polyolefins. 

Gas Phase Fluid Bed Processes. These processes are of particular commercial importance with polyolefin production. A prominent example of this technology is the Unipol process, first commercialized in 1975. A flow sheet is shown in Fig. 19.16. A gaseous monomer, such as ethylene or propylene, along with comonomers and chain transfer... 

The synthesis of new polymeric materials having complex properties has recently become of great practical importance to polymer chemistry and technology. The synthesis of new materials can be prepared by either their monomers or modification of used polymers in industry. Today, polystyrene (PS), which is widely used in industrial applications as polyolefins and polyvinylchlorides, is also used for the production of plastic materials, which are used instead of metals in technology. For this reason, it is important to synthesize different PS plastic materials. Among the modification of PS, two methods can be considered, viz. physical and chemical modifications. These methods are extensively used to increase physico-mechanical properties, such as resistance to strike, air, or temperature for the synthesizing of new PS plastic materials. 

In addition to the two-phase TPEs, two new technologies have emerged. They are the metallocene-catalyzed polyolefin plastomers (POPs, the name given to Exxon s EXACT product line) and polyolefin elastomers (POEs, DuPont Dow Elastomer s ENGAGE), and reactor-made thermoplastic polyolefin elastomers (R-TPOs). These new types of TPEs are often called metallocene elastomers-TPEs (MEs-TPEs) [87]. The new POPs and POEs are essentially very low-molecular-weight-Unear low-density PEs (VLMW-LLDPE). These new-generation TPEs exhibit mbber-like properties and can be processed on... 

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