JPH07100902A - Extruder screw - Google Patents

Abstract

(57) [Summary] [Purpose] Eliminates factors that hinder the transport of material resin in the screw flight-free areas that exist at the boundaries of the feed section, compression section, vent section, metering section, etc. of multi-screw screws. Prevent stagnation and thermal decomposition of the material resin. [Structure] At the boundary of the screw flight zone, the rear end of the screw flight in the front end side zone is extended to the boundary to give the propulsive force of the material resin and to increase the transport speed of the material resin around it. None, thus preventing stagnation and thermal decomposition of the material resin at the boundary portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a multiple screw for an extruder.

[0002]

2. Description of the Related Art Generally, an extruder screw has a plurality of parts having different roles, that is, as shown in FIG.
It is composed of a supply part A, a compression part B, a vent part C, a measuring part D, etc., and at the boundary of these parts, a part E with no screw flight of 15 to 20 mm for processing convenience.
Are formed (Japanese Patent Laid-Open No. 4-37506).

For example, in the vent portion C and the measuring portion D, as shown in FIG. 4, the screw flight d of the measuring portion D on the tip side is four, while the screw flight c of the vent portion C is four. Is defined as Article 2. The boundary E between the two is formed as a portion 3 having no screw flight.

In the boundary portion E where there is no such screw flight, there is no driving force for transporting the material resin. Therefore,
The material resin of this part is the screw flight c on the root side.
Is pushed by the driving force of the
Then it will be sent to the left). By the way, the size of the groove formed by the screw flight c of the vent portion C is
It is considerably larger than the groove of the measuring section D. Therefore, the transport speed of the material resin in this groove is slowed down. Due to such a reason, the transport of the material resin is hindered at the boundary portion E, and as a result, the stagnation of the resin is very likely to occur. In particular, in the case of a resin having poor fluidity and thermal stability such as a vinyl chloride resin, troubles such as thermal decomposition often occur at this portion. After extruding the vinyl chloride resin composition, the barrel was removed, and the state of resin stagnation and thermal decomposition at the boundary E of the screw was observed. As a result, traces e of the resin thermally decomposing and the resin flow stagnation were found.

[0005]

For the reasons described above, the resin stagnation at the screw flight-free portion existing at the boundary of the feed section, compression section, vent section, metering section, etc. of the multi-thread screw, The advent of measures to prevent the occurrence of thermal decomposition based on the above has been earnestly desired.

[0006]

As a result of various studies to solve the above problems, the following means were found to be effective and the present invention was reached. That is, the extruder screw of the present invention is a multi-screw extruder for which there is no screw flight at the boundary portion of the feeding portion, the compression portion, the vent portion, the measuring portion, etc., in the boundary portion, the screw flight on the tip side of the screw It is characterized in that the rear end portion is extended.

The extruder equipped with the screw of the present invention may be a single-screw extruder or a multi-screw extruder having two or more screws. In the case of a twin-screw extruder, the two screws may be a meshing type or a non-meshing type, and the two screws may rotate in the same direction or in different directions.

[0008]

According to the screw of the present invention, the rear end of the tip side screw flight is extended and a new screw flight is created at the boundary. As a result, the propulsive force of the material resin is applied to the boundary, and the material resin stays. The time is shortened and the stagnation of the resin is prevented.

[0009]

【Example】

(Embodiment 1) FIG. 1 is a partial front view showing an example of an extruder screw according to the present invention. In the drawing, 1 is a tip side zone (measuring section) of adjacent flight zones, and has four flights 11, and 2 is a root side zone (vent section) of adjacent flight zones, It has a flight 21 of. 3 is a boundary between the measuring unit 1 and the vent unit 2. The boundary portion 3 has a tip end side weighing unit 1
The rear ends of the screw flights 11 are alternately extended to form extension flights 4.

Although not shown in the drawing, the flight rear end portion on the front end side is also extended to each boundary portion between the supply portion, the compression portion, the vent portion, etc., but the extension of this flight is It may be only the boundary where the problems such as retention and decomposition of the material resin occur at the boundary.

This screw is mounted in the barrel of the extruder, and the material resin is supplied from the hopper of the extruder and is heated and melted while being transported to the left side in the drawing, and reaches the boundary 3. Since there is originally no flight in this portion, there is no propulsive force of the material resin, and the volume of the resin passage is large. Therefore, the transport speed of the material resin decreases and the material resin is likely to stagnate. However, in the above screw, the boundary portion 3
Since the extended flight 4 is provided, the propulsive force is applied, the transport speed of the material resin is increased, and the stagnation is resolved.

(Embodiment 2) FIG. 2 is a development view showing another portion of the application of the present invention relating to a screw having a multiple flight for a twin-screw extruder, around a portion where there was originally no screw flight. In the drawings, 11a is a screw flight in the tip side flight zone 1a of one screw, 11b is a screw flight in the tip side zone 1a of the other screw, 21a is a screw flight in a flight zone 2a adjacent to the above zone of one screw, 21b is a screw flight in a zone adjacent to the root side of the above-mentioned zone of the other screw. Further, 4a and 4b are extended flights from the screw zone on the tip side.

In setting the extension flight 4a, the screw flight 41 that is not extended is first used as a reference, and the gap between the rear end portion and the flight 21a in the root side zone is set to a dimension f so that the screw can be machined. To set. Next, a line parallel to the root-side screw flight 21a is drawn from the rear end portion of the screw flight that is not extended, and the extension length of the tip-side screw flight is determined so that it is on this parallel line.
In order to avoid contact with the screw flight 21b of the other screw, a straight line connecting the tips of the base side screw flights 21a and 21b is drawn so that the extended end of the screw flight does not exceed this straight line. Screw flight 42 that is likely to cross the above straight line
In regard to the above, as a screw flight that does not extend, a line parallel to the screw flight 21b is drawn from the rear end, and the length of the extended flight 4b of the adjacent screw flights is determined as described above. Similarly, to the boundary part 3a where there was originally no screw flight,
The length of the extended flight is decided. The extension length of the right-sided screw, which is not attached to the drawing number, is determined and formed in the same manner.

As described above, by using the development view, it is possible to easily perform the extension design of the screw flight in which the screw flights of the two screws do not come into contact with each other and the desired effect can be achieved. I can.

[0015]

EFFECTS OF THE INVENTION According to the present invention, in a screw having a multi-flight flight screw, the screw in the tip side zone is provided in a portion where there is no screw flight existing in the boundary portion such as the feeding portion, the compression portion, the vent portion and the measuring portion. By extending the trailing end of the flight, the propulsive force of the material resin is given to the part where there is no screw flight, and at the same time the volume of the resin passage in this part is reduced, and the transport speed of the material resin in this part is reduced. As a result, the stagnation of the material resin, which has been easily generated in the related art, and the thermal decomposition of the material resin due to the stagnation are prevented as a result. As a result, it becomes possible to continuously perform extrusion molding of a material resin such as a vinyl chloride-based resin compound, which has conventionally been often thermally decomposed, without trouble, for a long time.

[Brief description of drawings]

FIG. 1 is a partial front view of a screw for an extruder according to the present invention.

FIG. 2 is a partial development view of a screw for a twin-screw extruder according to the present invention.

FIG. 3 is an explanatory diagram of an extruder screw having different flight zones.

FIG. 4 is a partial front view of a conventional screw corresponding to the screw of FIG.

[Explanation of symbols]

1, 1a Tip side zone (metering section) of adjacent flight zones 11, 11a, 11b Screw flight 2, 2a Root side zone (vent section) of adjacent flight zones 21, 21a, 21b Screw flight 3, 3a Flight zone Boundary 4, 4a, 4b Extended flight

Claims (1)

[Claims] 1. A screw for an extruder having no screw flight at the boundary between the supply section, the compression section, the vent section, the metering section, etc., wherein the rear end of the screw flight on the front end side of the screw is extended to the boundary section. A screw for an extruder, which is characterized in that