Counter-rotating twin screw extruder

Comparison of single-screw, co-rotating and counter-rotating twin-screw extruders... 

Most of the compounds were extrusion compounded in a conical, partially intermeshing, counter rotating twin screw extruder (Haake Reomix TW-lOO). The extruder speed was set at 50 rpm and the barrel temperature profile was set to produce a melt temperature of 260°C at the die. Samples were injection molded in a 31.8 MT Battenfeld press with a 59 cc shot size. Where noted, samples were compounded in a 60 cc Brabender internal mixer and compression molded. 

There seems to be considerable disagreement about co-versus counter-rotating twin screw extruders between different groups in the polymer processing industry and academic community. 

Figure 3.36 Number and weight average of polyamide 6 domain sizes along the screws for a counter-rotating twin screw extruder.

J. W. Cho and J. L. White, Melting and Blending in a Modular Corotating/Counter-rotating Twin Screw Extruder, Int. Polym. Process., 11, 21-28 (1996). 

T. Li and I. Manas-Zloczower, A Study of Distributive Mixing in Counter-rotating Twin Screw Extruders, Int. Polym. Process., 10, 314—320 (1995). 

A. Kiani and H. J. Samann, The Influence of Curvature on the Simulation of Flow in a Tangential Counter-rotating Twin Screw Extruder, SPE ANTEC Tech. Papers, 39, 2758 (1993). 

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.]...

Counter-rotating twin screw extruders are used almost exclusively for the production of uPVC pipes, profiles and sheet because they treat material more gently than single screws. Parallel screw and conical twin screw extruders are compared. Cincinnati Milacron Austria introduced its Argos parallel twin screw extruders last year. These machines are intended to complement the company s Titan conical screw range. Coextrusion of foamed core pipes is also described. 

A silicone semi-IPN modified thermoplastic urethane illustrates this technology. The following composition is mixed in the melt state by pumping a preblend of the silicones into a counter-rotating twin-screw extruder with... 

White, J.L. Modular counter-rotating twin screw extruders intermeshing and tangential. In Polymer Mixing Technology and Engineering White, J.L., Coran, A.Y., Moet, A., Eds. Hanser Munich, 2001 167. 

The first patent on the precursor of the TSE dates from 1869. However, the first commercial CORI for handling polymers was marketed 70 years later. Several intermeshing counter-rotating twin screw extruders (ICRR) were developed in the 1920-30 s. After the 2nd World War, the corotating, fully intermeshing TSE (CORI) started... 

Waste ground rubber tire powder was devulcanized and mixed with 30 per hundred rubber (phr) natural rubber to give satisfactory vulcanizate properties. An intermeshing counter-rotating twin-screw extruder with constant root and flight diameters of the screw was designed and installed for waste rubber recycling [31]. 

By far most of the PVC produced is then further processed by extrusion to make products such as pipes, plates, and profiles for the construction industry. Processing of PVC dryblends to make plasticizer-free hard PVC is done almost exclusively on counter-rotating twin-screw extruders, whereby the process engineering is geared to the specific material requirements. The chamber feed resulting from the screw geometry of the counter-rotating twin-screw extruder facilitates efficient plastifica-tion at precisely controlled temperatures — an important aspect for PVC [29]. 

The extrusion of PVC is a field well adapted to use of microwave technology. Use of the chemically polar basic polymer means that microwave absorption within the polymer is possible. Nonpolar polyolefins, on the other hand, cannot be heated directly by microwaves. Since, however, the counter-rotating twin-screw extruders used in PVC extrusion process practically nothing besides PVC, use of the micro-wave does not amount to a loss of flexibility as far as the range of materials an aggregate is designed to handle. 

Initial tests of microwave-supported plastification run in a test kneader, the kneading chamber of which has the same geometry as the counter-rotating twin-screw extruder, showed very good microwave transmission to the PVC to be plasticized. These tests also demonstrated that plastification is possible even at a clearly reduced kneading chamber temperature and that this clearly reduces the plastification time. 

Figure 8.34 Counter-rotating twin-screw extruder...

Figure 1.20 Leistritz modular intermeshing counter-rotating twin-screw extruders [120-124] (a) Tenner CC machine (b) Thiele counter flight machine.

Tangential (Non-intermeshing) Counter-rotating Twin-Screw Extruder This extruder is used more for latex coagulation, recovery, devolatilization of polymer solutions, and for reactive extmsion. 

The counter-rotating twin screw extruder has a milling type of intermeshing as shown in Fig. 10.29. 

Since twin screw extruders have become an important segment of the field of extrusion it is reasonable to discuss important aspects of commercial twin screw machinery. A good reference on capabilities of twin screw extruders is the book edited by David Todd [43]. In this book, some of the main suppliers of twin screw extruders describe their machinery and capabilities the companies are Leistritz, Werner Pfleiderer, Berstorff, APV (Baker Perkins), Japan Steel Works, Welding Engineers, Parrel, and Buss. The book describes both co- and counter-rotating twin screw extruders and internal mixers. Another good reference on twin screw extruders is the book by James White [44]. This book gives an excellent historical over-... 

Table 10.8 Comparison of Co- to Counter-Rotating Twin Screw Extruders...

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