Embedded type short-screw-flight same-direction asymmetric multi-screw extruder and machining method thereof

Abstract

The invention discloses an embedded type short-screw-flight same-direction asymmetric multi-screw extruder and a machining method thereof. A screw mechanism in the extruder comprises a first screw and a second screw which are engaged with each other. The first screw is of a single-start thread structure, and the second screw is of a four-start thread structure. Embedded type short screw flights used as auxiliary screw flights are arranged in screw channel passageways each formed between two adjacent main screw flights in the first screw. The height of the auxiliary screw flights is smaller than or equal to the height of the main screw flights. According to the machining method of the embedded type short-screw-flight same-direction asymmetric multi-screw extruder, material conveying is achieved under the common effect of the axial positive displacement conveying force of the screw mechanism and the friction force between the first screw and the second screw. By means of the homoclinic orbit flow disturbance which is introduced through the embedded type short screw flights and shaped like the Arabic number '8', the whole-journey chaotic mixing in the screw channel passageways, the one-to-two topological chaotic effect formed by a passageway composed of the first screw and the second screw, the periodic compression and expansion effect generated by the passageways of the screw mechanism and the differential-speed rotation effect of the two screws are triggered, and the materials are sufficiently mixed, molten, mixed and plastified.

Description

technical field [0001] The invention relates to the technical field of multi-screw extruders, in particular to an embedded short-flight co-rotating asymmetric multi-screw extruder and a processing method thereof. Background technique [0002] The co-rotating twin-screw extruder with self-cleaning function is a widely used mixing processing equipment at present. This type of equipment mainly includes a barrel and two twin-screws installed in parallel in the inner cavity of the barrel. In order to generate high shear, the multi-thread structure is often used, which leads to different topological routes of material flow. When the processed material enters the inner cavity of the barrel from the feed port, the material will enter different topological flow channels, such as double The head thread will divide the flow channel in the barrel into three disconnected flow channels. The materials will not mix with each other during the forward conveying process. The unevenness of the...

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Problems solved by technology

In order to generate high shear, the multi-thread structure is often used, which leads to different topological routes of material flow. When the processed material enters the inner cavity of the barrel from the feed port, the material will enter different topological flow channels, such as double The head thread will divide the flow channel in the barrel into three disconnected flow channels. The materials will not mix with each other during the forward conveying process. The unevenness of the feed composition may lead to uneven composition of the materials entering different flow channels. , this unevenness will not be improved by mixing with each other as the materials move forward, which often leads to unstable product quality

Only in the area where the kneading block is installed can it be mixed with each other, but the kneading block will cause many problems such as high shear, material accumulation, dead space and reduced self-cleaning performance

On the other hand, due to the geometric meshing relationship, the use of multi-start threads will also lead to shallower grooves and lower output

The traditional co-rotating twin-screw extruder only provides disturbance in the meshing area to improve the mixing quality, and lacks a chaotic mixing trigger mechanism away from the meshing area. Moreover, the volume of the material in the left and right screw grooves is the same, and the mechanism of the tensile force field cannot be introduced. , the main part of the screw channel volume lacks an effective structure for promoting mixing, which will lead to the inability to further improve the distribution mixing effect, and the lack of tensile force field effect will lead to unsatisfactory dispersion mixing

In addition, most of the processing process of the twin-screw extruder is in a non-full state, and the almost unchanged flow path leads to a great reduction in the plasticization and mixing of materials. In order to improve the mixing effect and increase the output, high speed is often used to achieve high shear in engineering practice. Cutting, the large length-to-diameter ratio screw prolongs the processing process, but this method brings many problems such as high energy consumption, low efficiency and material degradation.

In recent years, differential twin-screw extrusion technology has emerged. Although chaotic mixing and tensile force field effects have been successfully introduced, it still lacks the topological chaos effect of runner segmentation, melt blending and exhaust during twin-screw extrusion. There is still a lot of room for improvement

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