JPH08281773A - Different direction rotary twin-extrusion screw - Google Patents

Abstract

PURPOSE: To provide a different direction rotary twin-extrusion screw capable of preventing the generation of contamaination and prevented from damage. CONSTITUTION: In a different direction rotary twin-extrusion screw, a solid pressure reducing part 16a where a screw flight is cut off is provided to a screw 10 between the feed part 14a and mixing part 14b of the screw 10. A plurality (four) of notch parts 30a-30d are formed to a plurality (four) of screw flights 12a from the solid pressure reducing part toward the feed part 14a (and/ or the mixing part 14b) so as to continue toward the center axis spiral direction 32 crossing the surfaces of the flights 12a almost at a right angle (notch depth is gradually increased toward the solid pressure reducing part 16a).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to kneading and plasticizing (melting) a resin raw material obtained by mixing a powder for extrusion molding, particularly a resin powder (main ingredient) such as vinyl chloride with a stabilizer (additive). The invention relates to a counter-rotating twin-screw extruding screw.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 5 (a), a counter-rotating twin-screw extruding screw is composed of two screws 10 and 10 rotating in different directions (opposite directions) from a supply section 20. The resin raw material to be supplied is the feed portion 14
a, intermediate part (mixing part 14b, compression part 14c, vent part 1)
4d) and the metering section 14e, and then the extrusion section 22.
Is extruded as a molten resin from the molding machine to produce a molding product such as a vinyl chloride pipe through a molding machine (not shown).

Incidentally, between the respective parts 14a to 14e,
Boundary portion 16 in which the screw flights 12a to 12e are cut off
a to 16d are provided, and particularly, the feed unit 14 is provided.
The boundary portion 16a between the a and the mixing portion 14b is referred to as a solid pressure reducing portion. Further, the screws may be configured in parallel (parallel axis type) without being obliquely crossed (oblique axis type) as shown in the drawing.

Explaining in more detail, screw parts 1
The carrying capacity V (groove volume) of 4a to 14e is shown in FIG.
By adjusting the pitch and / or the depth of each screw flight 12a-12e, as shown in FIG.
Between the feed section 14a and the mixing section 14b, the pressure is gradually reduced through the solid pressure reducing section 14a, and the vent section 14
In d, it is configured to rapidly increase through an exhaust unit 24 (which usually has a vacuum pump (not shown)).

That is, as for the conveying pressure p and the specific gravity 迿, as shown in Fig. 5 (c), the former (between the feed section 14a and the mixing section 14b) gradually increases and the latter (vent section 14d). Has dropped sharply.

As a result, in the former case, particularly in the area of the solid depressurization section 16a, the resin raw material is supplied from the supply section 20. As described above, this is the resin powder (main ingredient), the stabilizer, etc. Although the (additive) is mixed, it does not generate contamination (carbonization product generated by staying of the main agent for a long time), and the transport pressure p is gradually increased to damage the screw flight 12. In the latter case, the resin raw material is so constructed that the powder and gas components therein are sufficiently removed and the resin raw material is stably melted.

Therefore, this type of extrusion screw is widely adopted as a general extrusion screw because its performance is stable, and at the same time, its structure can be made relatively small and inexpensive.

[0008]

However, the conventional counter-rotating twin-screw extruding screw described above still has drawbacks to be improved as described below.

That is, in the extrusion screw of this type, particularly in the region of the solid pressure reducing portion 16a (the region including the feed portion 14a and the mixing portion 14b in the solid pressure reducing portion and the vicinity thereof), the conveying pressure p must be gradually increased. As described above, there is a risk that the screw may be damaged and the screw may be damaged as a result of the abnormal rise (p ′ or descent from the reference line p). It was not possible to reliably prevent (prevention of abnormal increase or decrease in the transfer pressure) The rapid decrease of the transfer pressure p at the vent portion 14d can be easily achieved by appropriately providing a vacuum pump. can do.

That is, in the conventional extruding screw, generally, the feedability V of the resin raw material in the feed section 14a and the mixing section 14b is increased by decreasing the pitch of the screw flight 12a and decreased by increasing it. Is configured. In other words, the conveying pressure in the region of the solid pressure reducing portion 16a is set to be higher than the reference pressure line p in the former case and lower in the latter case.

Therefore, in the former extrusion screw, in the former case, the high-pressure transport stress excessively filled with the resin raw material is applied between the flights of the small pitch width, and the screw is damaged. At the same time, it has a drawback that the transport capacity V is also lowered. On the other hand, in the latter case, there is a problem that the resin material (particularly its main component) stays and is contaminated because the resin material is not filled and has voids, especially in the solid decompression section 16a. . It is apparent that this contamination deteriorates the physical properties of the molten resin and deteriorates the quality of the molded product. In addition, the solid decompression unit 1
6a must smoothly convey the resin raw material (mixture of unmixed plasticized main agent and additive) from the feed section 14a to the mixing section 14b.

In order to overcome the above-mentioned difficulties,
It is proposed to adjust the pitch and the depth of the screw flight corresponding to each resin material, but such a method is absolutely impossible for an unspecified number of resin materials.

Therefore, an object of the present invention is to provide a counter-rotating twin-screw extruding screw capable of reliably preventing the occurrence of contamination and the screw damage.

[0014]

In order to achieve the above-mentioned object, a counter-rotating twin-screw extruding screw according to the present invention comprises a solid depressurization section in which a screw flight is cut off between a screw feed section and a mixing section. In the counter-rotating twin-screw extrusion screw having, one or a plurality of notches are provided for one or a plurality of screw flights from the solid pressure reducing section toward the feed section and / or the mixing section.

In this case, the cutout portion can be formed so as to be continuous with respect to the plurality of screw flights in the spiral direction of the central axis which is substantially orthogonal to the flight planes. Further, the notch depth can be configured so as to gradually increase toward the solid pressure reducing portion.

[0016]

In the present invention, when the conveying pressure at the specific portion in the area of the solid depressurizing portion rises abnormally, a part of the resin raw material at this portion flows back to the upstream side through the notch. That is, since the reverse flow is uniformly remixed and conveyed, the abnormally elevated conveyance pressure is also eliminated. Therefore, according to the present invention, since the resin raw material uniformly fills the screw and is smoothly conveyed, it is apparent that it is possible to prevent the damage of the screw due to the high-pressure conveying stress and the contamination due to the retention of the resin material. is there.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a counter-rotating twin-screw extrusion screw according to the present invention will be described in detail below with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional structure shown in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

First, the different-direction rotating twin-screw extruding screw of the present invention is basically the same as the conventional structure [(a) of FIG. 5]. Therefore, in the present embodiment, the extrusion screw includes the feed portion 14a and the mixing portion 14b of the screw 10.
Solid decompression section 16 with screw flight 12 cut off between
Clarify that it has a.

In the present invention, however, first, in FIG. 1, one or a plurality (four in the illustrated example) of screw flights 12a are directed from the solid pressure reducing section 16a toward the feed section 14a. One or more (four in the illustrated example, see FIG. 2) notches 30 a to 30 d are continuously formed in the central axis spiral direction 32 that is substantially orthogonal to the plane of each flight 12 a.

Further, in FIG. 3, the solid pressure reducing portion 16a
To the mixing section 14b from each of the one or more (two in the illustrated example) screw flights 12b, four notches 34a (only two are shown),
34b are formed so as to continue toward the central axis spiral direction 36 substantially orthogonal to the planes of the respective flights 12b, and to gradually increase the notch depth h toward the solid pressure reducing portion 16a (see FIG. 4). There is.

Incidentally, these methods for the notch are selected according to the resin material to be applied, and the latter method (FIG. 3) can be set for both the feed section 14a and the mixing section 14b, for example.

Therefore, in the present invention, the transporting capacity V is set sufficiently so that the solid decompression section 16a has a specific portion in the area (the area including the solid decompression section 16a and the feed section 14a and the mixing section 14b in the vicinity thereof). When the conveying pressure p rises abnormally p ′, a part of the resin raw material in this portion flows back to the upstream side through the notches 30 and 34. That is, at the same time that the resin raw materials are remixed,
The abnormally elevated conveying pressure p'is also eliminated. Therefore, according to the present invention, since the resin raw material uniformly fills the screw 10 and is conveyed smoothly, even when the extrusion screw is operated for a long time, the contamination due to the retention of the resin material is prevented, The physical properties of the molten resin are improved, and damage to the screw 10 due to high-pressure transport stress is reliably prevented.

That is, Table 1 shows the heating before (primary molded product) and heating of a vinyl chloride pipe using a molten resin, which is obtained from the extrusion screw of the present invention having such a constitution and the conventional extrusion screw. Tensile strength (20 ° C. conversion value, kgf / cm ² ) in a tensile test after (150 ° C., 15 minutes) (secondary molded product) and elongation (%) are compared. As can be seen, according to the present invention,
It is clear that the properties of the secondary molded product (after heating) are greatly improved.

[0024]

[Table 1]

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and many design changes can be made without departing from the spirit thereof.

[0026]

INDUSTRIAL APPLICABILITY As described above, the counter-rotating twin-screw extruding screw according to the present invention has the two-direction counter-rotating twin-screw having the solid pressure reducing portion with the screw flight cut between the feed portion and the mixing portion of the screw. In the extrusion screw, from the solid pressure reducing section toward the feed section and / or the mixing section,
By providing one or a plurality of notches for one or a plurality of screw flights, if the conveying pressure at a specific site in the region of the solid decompression section rises abnormally, part of the resin raw material at this site It flows backward through the notch to the upstream side. That is, at the same time that the resin raw materials are remixed, the abnormally elevated conveying pressure is also eliminated.

Therefore, according to the present invention, since the resin raw material can uniformly fill the screw and can be smoothly conveyed, it is possible to reliably prevent the screw from being damaged by the high-pressure conveying stress and from being contaminated due to the retention of the resin material. You can

[Brief description of drawings]

FIG. 1 is a side view showing an example of a notch portion directed from a solid pressure reducing portion to a feed portion in a counter-rotating twin-screw extrusion screw according to the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line II-II of FIG.

FIG. 3 is a side view showing an example of a notch portion directed from the solid pressure reducing portion to the mixing portion in the counter-rotating twin-screw extruding screw according to the present invention.

4 is a schematic cross section taken along line IV-IV of FIG.

FIG. 5A is a schematic side view showing a general configuration of a biaxial extrusion screw with different rotation directions, and FIG. 5B is a waveform diagram showing the characteristics of the carrying capacity V of the biaxial extrusion screw shown in FIG. (C) is a waveform diagram showing the characteristic of the conveying pressure p of the twin screw extruder shown in (a).

[Explanation of symbols]

 10 screw 12a, 12b screw flight 14a feed part 14b mixing part 16a boundary part (solid pressure reducing part) 30a to 30d cutout part 32 center axis spiral direction 34a, 34b cutout part 36 center axis spiral direction

Claims (3)

[Claims] 1. A counter-rotating twin-screw extruding screw having a solid pressure reducing section with a screw flight cut off between a screw feeding section and a mixing section, from the solid pressure reducing section toward the feed section and / or the mixing section. A counter-rotating twin-screw extruding screw, characterized in that one or more notches are provided for one or more screw flights. 2. The counter-rotating twin-screw extruding screw according to claim 1, wherein the notch portion is formed continuously with respect to a plurality of screw flights in a spiral direction of a central axis line substantially orthogonal to the flight planes. 3. The counter-rotating twin-screw extruding screw according to claim 2, wherein the notch has a notch depth that gradually increases toward the solid pressure reducing section.