Twin-screw extrusion counter rotating

T. Sakai and N. Hashimoto, Application of Novel Counter-rotating Intermeshed Twin Extruder for Degassing Operation, SPE ANTEC Tech. Papers, 32, 860-863 (1986) also T. Sakai, N. Hashimoto, and N. Kobayashi, Experimental Comparison between Counterrotation and Co-rotation on the Twin Screw Extrusion Performance, SPE ANTEC Tech. Papers, 33, 146-151 (1987). 

Tangential Counter-Rotating Twin-Screw Extrusion... 

Sakai, T., Hashimoto, N., Kobayashi, N. Experimentai Comparison Between Counter-Rotation and Co-Rotation on the Twin Screw Extrusion Performance, Proceedings of SPE Antec, Los Angeies, 1987, p. 146- 151... 

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. 

The industrial use of twin-screw extruders for this purpose revolves extensively, but not exclusively, around intermeshing co-rotating variants. Closely in-termeshing counter-rotating designs are widely used for profile extrusion of UPVC dry-blends since they permit close temperature control and exhibit a high conveying efficiency due to the positive displacement of material where the screws intermesh [150]. 

Co-Rotating Twin Screw Extruder (CTSE). This system is commonly used for compounding and profile extrusion in high output applications. CTSE with its high shear is, however, harder to control than the counter rotating system (see below). 

Woodtruder. The woodtruder is a dual extrusion system for wood composite materials made by Davis-Standard Ltd. [276]. It comprises a primary parallel, 28 1 I/D, counter-rotating twin-screw... 

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. 

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-... 

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