Extruder reactors

Reactive extruders and extrusion dies of different designs can be easily included in standard technological scheme of polymer production plants, such as those for polycaproamide synthesis, as shown in Fig. 4.39. In this case, a reactive material premixed in a tank 1 is fed into a static device 2 for prepolymerization, where part of the polymerization process takes place. Then the reactive mixture enters the extruder-reactor 3. The necessary temperature distribution is maintained along the extruder. Transfer of the reactive mass proceeds by a system of two coaxial screws mounted in series in a common barrel. Controlling the relative rotation speed of both screws provides the necessary residence time for the reactive mass in the extrader, so that the material reaching the outlet section of the die is a finished polymer. 

Fig. 11.15 RTD cumulative functions of a single screw tangential counter-rotating twin-screw extruder (TCTSE) under matched and staggered conditions, and the back-mixed extruder reactor. [Reprinted by permission from Y. Lu, Ph.D Dissertation, Department of Chemical Engineering, Stevens Institute of Technology, Hoboken, NJ, 1993.]...

D. B. Todd, Features of Extruder Reactors, in Reactive Extrusion, M. Xanthos, Ed., Hanser, New York, 1992, Chapter 5. 

J. Grenci and D. B. Todd, Effect of Conversion on Chain Addition Copolymerizations Performed in a Backmixed Drag Flow Extruder Reactor, Int. Polym. Process., 15, 147-156 (2000). 

The nature of the polymerization reactor also depends upon the desired form of the product (pellet, powder, bead, etc.). For example, extruder reactors (Stuber and Tirrell, 1985) are best suited to producing pellets, sheets, and coatings. The beads that may be directly useful in processing are best produced by the suspension polymerization process. The round beads, however, may not have suitable bulk-flow properties and are dangerous if spilled. Alternate shapes and the appropriate methods of production are, therefore, often employed. 

An advantage of an extrusion device as a reactor is the combination of several chemical process operations into one piece of equipment with accompanying high space-time yields of product. An extruder reactor is ideally suited for continuous production of material after equilibrium is established in the extruder barrel for the desired chemical processes. 

Brauer, F. Continuous production of polyurethanes on a twin-screw extruder reactor. In PPS Summer Meeting Conference Abstracts, Amherst, MA, August 16-17, 1989 7D. 

Table 5.4. Copolymer formation processes in extruder reactors [adapted from Brown, 1992]...

Diels-AIder system, which includes MAH and dicyclopentadiene, showed increased grafting efficiency only in a mixer of intermittent action. No special advantages have been detected in this system in comparison with neat MAH when extruder reactors were used (24). 

The effect of PP and PE ratios has been studied earlier (45 7) when itaconic acid (lA) was grafted to their blends containing L-101 peroxide as the initiator. Grafting was done in the extruder reactor assembled on the base of Brabender plastograph (Duisburg, Germany) equipped with the dynamic mixer (48,49). 

Giudici, R. Nascimento, C.A. O. Scherbakoff, N. Modeling of industrial nylon-6,6 polymerization process in a twin screw extruder reactor. I. Phenomenological and parameter adjusting, J. Appl Polym. Sci., 1998, 67, 1583-1587. 

Robust equipment has been developed for the various processing steps, including stirred-tank and tubular reactors, flash devolatilizers, extruder reactors, and extruder devolatilizers. Equipment costs are high based on working volume, but the volumetric efficiency of bulk polymerization is also high. If a polymer can be made in bulk, manufacturing economics will most likely favor this approach. 

Davis, W.M. (1992) Heat Transfer in Extruder Reactors, in Reactive, Extrusion Principles and Practice (ed, M. Xanthos), ch. 7, Hanser, Munich, pp, 257-282. 

In the third plant design we consider the influence of parallel scale-up on the economy of the process. Instead of one large extruder reactor with a screw diameter of 200 mm, eight kneaders with a diameter of 100 mm are used in parallel to improve the heat transfer. 

The monomers are fed continuously into the extruder reactor from a preheated vessel equal to the one used for the solution polymerization. The initiator is fed continuously from a cooled vessel (V2) (10°C) through a cooled tube system into the extruder. 

If produced in a classical solution batch process the integral cost price of the terpolymer considered amounts to 2700/ton. The most favored production method with reactive extrusion utilizes one extruder reactor of 200 mm diameter and leads to an integral cost prize of 2559/ton. Finally, a rather unfavorable reactive extrusion method needs eight 100-mm extruders in parallel. In this case the cost prize will be 2769/ton. 

An alternative process is bulk-phase halogenation (74-76). Dry butyl rubber is fed into a specially designed extruder reactor and contacted in the melt phase with chlorine or bromine vapor. By-product halogen acids are vented directly, avoiding the need for a separate neutralization step. Halogenated rubbers comparable in composition and properties to commercial products can be obtained. 

Often, a monomer or prepolymer is fed in liquid form to the extruder reactor. Due to this liquid feed, two zones can be distinguished ... 

Prut, E.V., Zelenetskii, A.N. (2001) Chemical modification and blending of polymers in an extruder reactor. Russian Chemical Reviews, 70 (1) 65-80. 

NJ Ward, HGM Edwards, AF Johnson, DJ Fleming, PD Coates. Application of Raman spectroscopy for determining residence time distribution in extruder reactors. Appl Spectrosc 50 812-815,... 

PureVision Technology Inc. has developed a continuous countercurrent extruder reactor that can be used to fractionate agricultural waste into its various components such as xylose. 

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