Reactor Polyvinyl chloride

Two patents (41,42) discuss the design of special agitators to maintain adequate heat transfer in bulk polyvinyl chloride reactors. 

Figure 12-4. The European Vinyls Corp. process for producing polyvinyl chloride using suspension polymerization (1) reactor, (2) blow-down vessels (to separate unreacted monomer), (3) stripping column, (4) reacted monomer recovery, (5) slurry centrifuge, (6) slurry drier.

The properties of a polymer depend not only on its gross chemical composition but also on its molecular weight distribution, copolymer composition distribution, branch length distribution, and so on. The same monomer(s) can be converted to widely differing polymers depending on the polymerization mechanism and reactor type. This is an example of product by process, and no single product is best for all applications. Thus, there are several commercial varieties each of polyethylene, polystyrene, and polyvinyl chloride that are made by distinctly different processes. 

This comprehensive article supplies details of a new catalytic process for the degradation of municipal waste plastics in a glass reactor. The degradation of plastics was carried out at atmospheric pressure and 410 degrees C in batch and continuous feed operation. The waste plastics and simulated mixed plastics are composed of polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene, and polyethylene terephthalate. In the study, the degradation rate and yield of fuel oil recovery promoted by the use of silica alumina catalysts are compared with the non-catalytic thermal degradation. 9 refs. lAPAN... 

Cadmium is found in low concentrations in most soils and waters. It is produced as a by-product of zinc and lead mining and smeltering. Industrial use of cadmium has led to a dramatic increase in environmental problems caused by this element. Cadmium is used in semiconductors, nickel-cadmium batteries, electroplating, polyvinyl chloride (PVC) manufacturing, and control rods for nuclear reactors. The most important sources for aquatic contamination are active and inactive lead-zinc mines, land application of sewage sludge, zinc-cadmium smelters, effluents from plastic and steel production, and wastewaters from the production of nickel-cadmium batteries and electroplating (Zuiderveen, 1994). 

Mitsui Chemicals, Inc. Polyvinyl chloride Vinyl chloride monomer Clean, large reactor technology, high productivity and high-quality product 19 1997... 

Vin Tec GmbH/Degassa A197AG Polyvinyl chloride Vinyl chloride monomer Up to 200 m3 reactor technology yields suspension, hijji-impact and emulsion PVC 10 1992... 

Vin Tec GmbH/Krupp Uhde Polyvinyl chloride (emulsion) Vinyl chloride monomer Batch process uses 2 or more reactors special coating/buildup suppressant allows many batch operations before cleaning NA NA... 

ABB Lummus Global/Sohray SA Polyvinyl chloride (suspension) Vinyl chloride monomer On-site initiator synthesis and high reactor productivity minimize operating costs wide range of high quality products NA NA... 

Pyrolysis and reforming of several types of common plastics (polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyurethane, and polycarbonate) were studied qualitatively, using a micro-reactor interfaced with a MBMS. Each type of plastic pyrolyzed at 550-750°C. This was followed by steam reforming of vapors in a fixed bed of C-11 NK catalyst at 750-800°C. The composition of the product gas (mass spectrum) was observed for different values of the steam-to-carbon mtio and space velocity that changed depending on the size of plastic samples. Preliminary tests showed that at process conditions similar to those used for reforming natural gas, polymers were almost completely converted to hydrogen and carbon oxides. 

There are also specific content requirements for labels. Containers of polyvinyl chloride resin waste from reactors, or any other wastes contaminated with vinyl chloride, shall be legibly labeled ... 

Plastomer modification of PP continues to progress. Current work in many development laboratories focuses on modification of reactor TPOs to make soft flexible compounds for extruded or calendared sheet. In many such applications flexible PP sheets would replace plasticized polyvinyl chloride (PVC) or PVC blends, chlorinated polyethylene, or EPDM. 

Experimental studies have shown that irradiation and heating of polyvinyl chloride insulation found on electrical cables in many reactor containment will yield both hydrochloric acid (HCl), sulfiirous acid (H2SO3), and sulfuric acid (H2SO4). Some investigators believe that acids formed by the combination of radiolysis and pyrolysis of electrical cable insulation can be of dominant importance to the pH of solutions in the reactor containment. Others feel that acid formation by this process is over-emphasized because acids generated within the pol5mer are not able to escape to the atmosphere except when they are formed near the polymer surface. 

Labels, (i) In addition to the other requirements in this paragraph (I), the employer shall ensure that labels for containers of polyvinyl chloride resin waste from reactors or other waste contaminated with vinyl chloride are legible and include the following information ... 

Atia et al 2003 Goto et al., 1992), polyvinyl chloride (Rucka and Turkiewicz, 1990 Shaw et al., 1990), poly(vinylidene difluoride) (Tsai and Shaw, 1998), or polyetherim-ide (Merton et al., 1997), where the lipase can be immobilized on the aqueous side of the membrane. Conversely, in hydrophilic membrane reactors, lipase is immobilized on the organic side of the membrane, which is made of cellulose (Guit et al 1991 ... 

VC manufacturing Polyvinyl chloride (PVC) manufacturing Equipment Reactor opening loss Reactor manual vent valve Sources after stripper... 

Polyvinyl chloride is one of the cheapest plastics in use today. It is prepared by the polymerization of vinyl chloride (VCM) (CH2=CHC1, B.P.—14°C) as a suspension or emulsion in a pressure reactor. The polymer is unstable at high temperamres and liberates HCl at T > 200°C. It can be injection molded or formed into a hard and brittle material. It can be readily softened by the addition of plasticizers such as diethylhexylphthalate to the extent of 30%. Plasticized PVC is used as an upholstery substitute for leather. Since the plasticizer is volatile to a small extent, it slowly leaves the vinyl which eventually becomes hard, brittle, and then cracks. This can be restored by replacing the plasticizer by repeated conditioning of the vinyl surface. 

There are compositional differences between polymers, especially between polyvinyl chloride and chlorinated polyvinyl chloride, which are more susceptible to degradation in processing and require higher levels of processing stabilizers, and polyolefins, which must be stabilized for processing stability as well as for protection into the service environments. There are also differences in material handling as PVC is converted from reactor flake product, whereas CPVC, PE, PP, and other materials are converted from pelletized compounds. 

In the polymerization of polyvinyl chloride, unwanted gas is generated by side reactions, and some small amounts of air leak into the reactors. These inerts must be vented from the process. Because vinyl chloride monomer (VCM) is extremely volatile, the purge gas, although it is typically at 4-5 bars pressure, can contain as much as 50vol% monomer. As a consequence, the vented gas stream, although small, may contain several hundred thousand dollars worth of monomer values. A typical process flow scheme to recover VCM is shown in Figure 21.10 (Lahierc et al., 1993). 

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