Description: Coverage of production capacity in Europe: 68%
Types:
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text_type: Report,
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Comment: The dataset represents the production mix of commercial HDPE production technologies: slurry suspension polymerisation, gas phase polymerisation and solution polymerisation using Ziegler-Natta, Philips, and Metallocene catalysts. HDPE is mainly produced with the slurry suspension, solution or the gas phase process, which belong to the low-pressure technologies. As catalysts, usually Ziegler-Natta or Phillips-type catalysts are applied, but metallocene-type catalysts can also be used. Due to this wide range of choice of process technology, reactor type, or catalyst type, a typical process for HDPE production cannot be defined. The suspension polymerisation can be described as precipitation process. The formation of the polymer takes place in a hydrocarbon diluent and under conditions, where the monomer is soluble in the solution. The precipitated polymer, however, is insoluble and forms a fine suspension. The polymer is then separated by centrifugation. The suspension process can be combined with a stirred tank reactor or a loop reactor. Different diluents can be chosen, like C5 to C9 hydrocarbons, hexane, or isobutane. For solution polymerisation, the hydrocarbon solvent (C9-C6) is kept at high temperature (>130 °C) to ensure that the formed polymer stays dissolved after production. In a subsequent step, the solvent is evaporated and recycled, and the liquid polymer can directly be sent to the extruder. In the gas phase processes a fluidised bed of polymer particles and catalyst is maintained by a steady gaseous monomer feed from the bottom of the reactor. Polymer powder is continuously extracted at the bottom of the fluidised bed reactor. Unreacted monomer gas from the top is compressed and recycled to the reactor inlet. Catalyst, and co-catalyst if necessary, is also continuously fed to the reactor. Typically Ziegler-Natta catalysts are used for gas phase polymerisation where the catalyst is supported on inert silica particles so that the reaction takes place at the catalyst surface. After the reaction phase, most of the residual (unreacted) monomers (which are mostly present as gases) are separated from the polymer and are either recycled back into the process or flared of. Depending on the purity of the separated monomers, the gas can either be fed directly back into the production line or the monomers are returned to a purification unit. To limit the accumulation of impurities in the process, usually a small side-stream (purge) of the unreacted gas is sent back to the cracker or to a dedicated purification unit. After polymerisation, the polymer is usually fed di-rectly into a hot melt extruder, where additives can be added to the melted polymer if required. The polymer is then pelletised in an underwater pelletiser. The pelletised product is dried, blended where required and degassed.
Origin: /Bund/UBA/ProBas
Tags: Polyethylen ? Granulat ? Europa ? Manufacture of basic chemicals, fertilizers and nitrogen compounds, plastics and synthetic rubber in primary forms ? Manufacture of chemicals and chemical products ? Manufacture of plastics and synthetic rubber in primary forms ? Manufacturing ?
License: unbekannt
Language: Deutsch
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