Polymerization discharge

The deposition of organic films by plasma polymerization is an important application of non-thennal plasmas 1301. Plasma polymers are fonned at the electrodes and the walls of electrical discharges containing organic vapours. Oily products, soft soluble films as well as hard brittle deposits and powders are fonned. The properties of plasma... 

Poll Fl-U, Arzt M and Wickleder K-FI 1976 Reaction kinetics in the polymerization of thin films on the electrodes of a glow-discharge gap Eur. Polym. J 12 505-12... 

Photopolymerization and Plasma Polymerization. The use of ultraviolet light alone (14) as well as the use of electrically excited plasmas or glow discharges to generate monomers capable of undergoing VDP have been explored. The products of these two processes, called plasma polymers, continue to receive considerable scientific attention. Interest in these approaches is enhanced by the fact that the feedstock material from which the monomer capable of VDP is generated is often inexpensive and readily available. In spite of these widespread scientific efforts, however, commercial use of the technologies is quite limited. 

The monomer recovery process may vary ia commercial practice. A less desirable sequence is to filter or centrifuge the slurry to recover the polymer and then pass the filtrate through a conventional distillation tower to recover the unreacted monomer. The need for monomer recovery may be minimized by usiag two-stage filtration with filtrate recycle after the first stage. Nonvolatile monomers, such as sodium styrene sulfonate, can be partially recovered ia this manner. This often makes process control more difficult because some reaction by-products can affect the rate of polymerization and often the composition may vary. When recycle is used it is often done to control discharges iato the environment rather than to reduce monomer losses. 

Fig. 12. Unipol PP process where A is the polymerization reactor B, recycle gas compressor C, recycle gas cooler D, product discharge tank E, impact copolymer reactor F, recycle gas compressor G, recycle gas cooler and H, product discharge tank (134).

As the polymer molecular weight increases, so does the melt viscosity, and the power to the stirrer drive is monitored so that an end point can be determined for each batch. When the desired melt viscosity is reached, the molten polymer is discharged through a bottom valve, often under positive pressure of the blanketing gas, and extmded as a ribbon or as thick strands which are water-quenched and chopped continuously by a set of mechanical knives. Large amounts of PET are also made by continuous polymerization processes. PBT is made both by batch and continuous polymerization processes (79—81). 

Other Polymerization Methods. Although none has achieved commercial success, there are a number of experimental alternatives to clay-catalyzed or thermal oligomeriza tion of dimer acids. These iaclude the use of peroxides (69), hydrogen fluoride (70), a sulfonic acid ion-exchange resia (71), and corona discharge (72) (see Initiators). 

Install automatic or manual activation of bottom discharge valve to drop batch into a dump tank with diluent, poison, or inhibitor, or to an emergency containment area (May not be effective for systems such as polymerization reactions where there is a significant increase in viscosity.)... 

Vinyl chloride monomer (VCM) In manufacture, production, reclamation, storage, discharge, transport, use or polymerization... 

There is some question as to whether the total reactor contents will be discharged as assumed. If the reaction is in progress, then material already will have polymerized and will most probably not vent to the atmosphere, thus resulting in a significantly smaller emission. 

The reaction of gaseous SO2 or SO3 with O2 in a silent electric discharge gives colourless polymeric condensates of composition S03+ t (0 < jc < 1). These materials are derived from yS-SO3 by random substitution of oxo-bridges by peroxo-bridges ... 

Hoffman, A. S. Ioninzing Radiation and Gas Plasma (or Glow) Discharge Treatments for Preparation of Novel Polymeric Biomaterials. Vol. 57, pp. 141 — 157. 

The solid-liquid separation of shinies containing particles below 10 pm is difficult by conventional filtration techniques. A conventional approach would be to use a slurry thickener in which the formation of a filter cake is restricted and the product is discharged continuously as concentrated slurry. Such filters use filter cloths as the filtration medium and are limited to concentrating particles above 5 xm in size. Dead end membrane microfiltration, in which the particle-containing fluid is pumped directly through a polymeric membrane, is used for the industrial clarification and sterilisation of liquids. Such process allows the removal of particles down to 0.1 xm or less, but is only suitable for feeds containing very low concentrations of particles as otherwise the membrane becomes too rapidly clogged.2,4,8... 

A typical polymerization process as carried out on an industrial scale is given in Fig. 3.20.5 An autoclave (about 4 m3) is charged widi a concentrated PA salt solution in water (50% at 50°C). The autoclave is flushed with nitrogen and heated to 210°C while the pressure is allowed to increase to 18 bar. In this heating step, the salt concentration is increased to 75%. At 210°C, the reaction is carried out for 60 min. In die second step, the temperature is slowly increased to 280°C while maintaining the pressure at 18 bar. Subsequently, the reaction mass is warmed to 290°C and, at the same time, the pressure is lowered to atmospheric. At 290° C and at a slight pressure, the polymerization is continued for 1 h before the polymer is discharged. 

On an industrial scale, PA-6 is synthesized from e-caprolactam with water as the initiator. The process is very simple if the reaction is earned out at atmospheric pressure. The polymerization is earned out in a VK-reactor (Fig. 3.23), which is a continuous reactor without a stirrer, with a residence time of 12-24 h at temperatures of 260-280°C.5,28 Molten lactam, initiator (water), and chain terminator (acetic acid) are added at the top and the polymer is discharged at the bottom to an extruder. In this extruder, other ingredients such as stabilizers, whiteners, pigments, and reinforcing fillers are added. The extruded thread is cooled in a water bath and granulated. The resultant PA-6 still contains 9-12%... 

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