New style Single Screw Extruder with improved Plastification and Output Power

New style Single Screw Extruder with improved Plastification and Output Power

A single-screw-extruder is presented, existing in a barrel with a grooved feed zone (helical grooves), a grooved melting zone (axial or helical grooves) and a barrier-screw with mixing and shearing elements.

Compared with extruders with a smooth melting zone, significant processing improvements are achieved regarding mass throughput, pressure build-up, mass temperature, melt homogenity, feed-zone cooling, processing wall-slipping polymers, abrasiv wear, residence time, total degree of efficiency and economy. The processing principles of the new extruder are explained. Experimental results confirm the theoretical predictions.

The Right Mixer for Every Application:
The Mixing Technology Division of Thyssen Henschel Industrietechnik will be dividing its exhibition stand into five thematic islands corresponding to the various branch-specific applications of its mixers. The company's entire range comprises six series of mixers, each series being available in various sizes, and a universal laboratory mixer. Under the motto Everything from a single source , the company also supplies turnkey installations for plastics compounding - for the PVC industry, for example, or for innovative compounding technologies involving the blending of natural materials with plastics.

The most widely used system for the compounding of PVC still consists of a combination of a FM Fluid Mixer and a vertical KM Cooling Mixer or - for high throughput rates - a HM Horizontal Mixer. By virtue of their large-diameter vessels, Henschel mixers are capable of a particularly high mixing performance and can, thanks to the adjustable height and angle of their guide blades, be readily adapted to specific mixing requirements. The self-cleaning mixing rotors permit fast and easy change-over from one material and/or colour to another. A still recent development is the application of Type CTM Continuous Turbo Mixers, this being particularly suitable for the energy-saving, material-friendly in-line compounding of PVC, especially at pelletizing processes with high throughput rates.
The blending of natural materials, such as wood flour or natural fibres, with plastics is a particularly innovative and future-oriented application.

On account of the natural moisture of these materials, Thyssen Henschel has equipped its FM Fluid Mixers, which are used for this application, with a vacuum drying system. With this system, the processor can proceed with the downstream extrusion or injection moulding of the agglomerates immediately they are discharged from the mixer. For the coating of expandable polystyrene (EPS), the Mixing Technology Division has developed the CTM Continuous Turbo Mixer, which has meanwhile
proved itself in countless other applications, too. It is equipped with two counterrotating mixing rotors which rotate slowly at speeds of between 5 and 20 m/s, ensuring both an optimum mixing effect and a gentle treatment of the material, without causing damage or abrasion. These mixers are distinguished by three special features: firstly, thanks to their continuous operation, they are ideal for immediate downstream processing in in-line installations; secondly, they are capable of extremely high throughput rates of up to 10 tonnes/hour; and, thirdly, they require an extraordinarily low input of energy.

The premixing of masterbatches is a particularly exacting task. The mixers specially developed for this application - MB Masterbatch Mixers - are equipped with water-cooled mixing rotors. These rotors permit the use of a special cooling process which ensures that, after a thorough dispersion of the pigments and waxes in the base material and homogenization of the mixture, the finished product can be discharged as a dust-free, free-flowing agglomerate.

When manufacturing powder coatings, the first step is to premix all the components, whereby the mixer must homogenize them gently but thoroughly, and at as low a temperature as possible. The most suitable mixer for this application is the CM Container Mixer which combines two mixing principles: while the inclined position of the container during the mixing process
permits a gentle, gravimetric compounding of the material, a high-speed mixing element generates a centrifugal mixing action which thoroughly swirls and disperses the material. The result is a product which has been gently
compounded in a minimum of time and with only a minimum rise in temperature.

A further advantage of the CM is the extremely short time which is needed for cleaning it between batches. The sixth thematic island will be devoted to a presentation of the Mixing Technology Centre which is located at the company's headquarters in Kassel.
Here customers can perform systematic trials on different mixers in order to ascertain the optimum solution to their own specific, often complex mixing problems.