Special extrusion screw for polyethylene of raised temperature resistance and extrusion method of special extrusion screw

Abstract

The invention discloses a special extrusion screw for polyethylene of raised temperature resistance (PE-RT) and an extrusion method of the special extrusion screw. The special extrusion screw comprises a feeding segment, a compression segment, a first metering segment, a pressure reducing segment, a second metering segment, a mixing segment and a screw head which are connected in sequence, wherein the feeding segment, the pressure reducing segment, the first metering segment and the second metering segment all adopt single-start thread structures; the compression segment adopts a double-start thread structure consisting of a main thread and an auxiliary thread; the auxiliary thread and the main thread intersect at one side of the feeding segment and do not intersect at one side of the first metering segment; and the mixing segment adopts a trapezoidal structure. The special extrusion screw for PE-RT is simple in structure, convenient to use, high in fusing efficiency, uniform in plasticization, high in conveying capability and high and stable in yield at a high rotational speed.

Description

technical field [0001] The invention relates to a plastic extrusion screw, in particular to a special extrusion screw for heat-resistant polyethylene and an extrusion method thereof, belonging to the production field of heat-resistant polyethylene pipes. Background technique [0002] Such as figure 1 As shown, it is a structural schematic diagram of a common polyolefin extrusion screw. The screw is a single-flight structure, generally including a feeding section 1, a compression section 2, a metering section 3 and a screw head 4. When the plastic enters the barrel from the hopper, Therefore, the material enters the feeding section 1, and under the action of the screw rotation, it is gradually transported forward to the compression section 2 through the friction between the inner wall of the barrel and the surface of the screw. The depth of the screw groove in the compression section 2 becomes shallower, and the solid material is further compacted. Heated outside the barrel,...

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Problems solved by technology

[0007] At present, the disadvantages of the extruding screw in the prior art are: 1) the pressure of the entire screw is established by the pressure of the feeding section. When the head pressure is high, this will reduce the feeding capacity of the screw; 2) the output of the screw is affected by the machine The impact of the head pressure is obvious, and the plastic extrusion fluctuates greatly; 3) The plasticizing effect of the material is not good, the melting efficiency is low, the mixing is not uniform enough, and the output is not high; 4) When the output is high, the plasticization is relatively poor and the melt temperature difference is relatively large , production fluctuations are relatively large

[0008] Polyethylene of raised temperature resistance (PE-RT) raw material, as a polyethylene material, has a lower degree of shear thinning than polypropylene (PP) during shearing, so it is used in high-speed production A better shearing effect is needed to meet the plasticizing requirements of the raw material; however, due to the narrow molecular weight distribution of the heat-resistant polyethylene raw material and the small processing temperature range, oxidative degradation will occur in a short time at a temperature higher than the decomposition temperature, so it must be Avoid the situation of strong shear, but it must be fully plasticized during processing

Therefore, the current polyolefin extrusion screw is not suitable for the production of heat-resistant polyethylene pipes

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