JP2845987B2 - In-line two-stage extruder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an extruder for melting and mixing plastics, rubber, and the like, and performing granulation or various moldings of films, sheets, pipes, and the like. -It relates to a serial two-stage extruder with excellent mixing performance.

(Prior art) A so-called two-stage extruder, in which two extruders are connected in series, is well known for its improved melting and mixing. In the case of molding a sheet or a sheet, there is no other means other than the use of the in-line two-stage extruder, and recently, it is increasingly used. Prior to the adoption of this in-line two-stage extruder, it was impossible to form directly from raw materials that were difficult to melt and mix as described above, so the raw materials were melted and mixed and granulated (pelletized) once. Films and sheets were manufactured on another molding line using the pellets.

FIG. 2 shows an outline of the above-described two-stage in-line extruder, in which the upper right extruder is the first stage extruder, and the lower left extruder is the second stage extruder. The extruding section of the first-stage extruder and the molten resin introduction section of the second-stage extruder are connected by a connecting pipe 4.

In the figure, reference numeral 1 denotes a raw material supply port of the first-stage extruder, 2 denotes the barrel, and 3 denotes the screw rotation drive unit. The barrel 2 adopts a segment system so that the kneading state and other functions (such as deaeration) can be changed according to the resin material or the application, and has a structure that can be appropriately rearranged as needed.

5 is a barrel of the second-stage extruder, 6 is a screw rotation drive unit, 7 is a die, and 8 is an extruded product.

In the in-line two-stage extruder, the first-stage extruder and the second-stage extruder each use one screw, that is, one screw, and the two-screw, that is, two screws, each of which are arranged so as to mesh with each other. In some cases, one of the first-stage extruder and the second-stage extruder may be single-screw or twin-screw.

The in-line two-stage extruder of the present invention may be any combination of these, but from the viewpoint of enhancing the melting and mixing performance, it is preferable that at least the first-stage extruder is configured as a twin-screw extruder. . Further, a melt pump such as a gear pump may be used in place of the second stage extruder.

By the way, regarding the barrel of the conventional in-line two-stage extruder, all the hole cross sections perpendicular to the axial direction are formed in a perfect circle or an arc.

FIG. 3 shows a cross-sectional shape perpendicular to the axial direction of the twin-screw extruder. As is clear from FIG. 3, the cross-section of the hole of the barrel 2 is two pieces corresponding to the rotation of the two screws 9. Are combined. And this shape is the second
The same applies to any of the zones A, B, and C shown in the figure.

(Problems to be Solved by the Invention) Usually, the first-stage extruder melts and mixes the raw material, and the second-stage extruder homogenizes the raw material, and constantly extrudes the molten raw material against the resistance of the die. Each plays a role, but recently, with the diversification and compounding of products, the number of raw materials that are difficult to mix themselves has increased. In other words, polymer blends, which are a mixture of different types of resins, and extrusion, in which various fillers are mixed with the resin, have been increasing. Depending on the raw materials, insufficient mixing may occur or the mixing performance may be insufficient to provide sufficient mixing performance. In some cases, the screw length of the single-stage extruder must be further increased.

The present invention has been made to solve such a technical problem, and an object of the present invention is to extend the screw length of the first-stage extruder and sufficiently play a role in raw materials that are difficult to mix. It is to develop an in-line two-stage extruder capable of fulfilling the requirements.

(Means for Solving the Problems) Therefore, the present invention relates to an extruder in which a first-stage extruder and a second-stage extruder are connected in series, and the first-stage extruder barrel has a polygonal cross-sectional shape in a barrel. A shaft type extruder is incorporated, and this is used as a means for solving the problem.

(Action) The twin-screw extruder has a better plasticizing function than the single-screw extruder, and a barrel having a polygonal cross section has a better plasticizing function than a barrel having a round cross section. The effect of the serial two-stage extruder is exhibited by separating the functions, such as plasticizing the resin in the first stage and performing volumetric extrusion of the molten resin in the second stage. You. Therefore, the present invention uses a barrel having a biaxial polygonal cross section capable of maximally exhibiting a plasticizing function in the first stage, and performs pressure stabilization and low resin temperature extrusion by a second stage extruder. As a whole, the function of the extruder is sufficiently satisfied.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to the drawings.

FIG. 1 shows a sectional shape of a barrel hole of a first-stage twin-screw extruder, which is a characteristic part of a typical embodiment of the present invention. In the illustrated example, the barrel hole has a hexagonal cross section perpendicular to the axis. Shape. Of course, the shape of the barrel hole is not limited to a hexagon, but may be any combination of squares, for example, an octagon. Here, the screw shape may be changed, but need not be changed.

Further, in this embodiment, a square barrel hole is adopted only in the zone B in FIG. 2, and the other barrels A and C have an arc-shaped barrel hole shape shown in FIG. Of course, the barrel hole shape can be square as shown in FIG. 1 in all of the zones A, B and C.

The position at which the barrel hole is formed in a square shape is not uniformly determined, but is generally most effectively set to a position where the resin is melted and mixed.

The present invention will be described more specifically based on the configuration of the illustrated example.

As the first-stage twin-screw extruder, a 65φ co-rotating meshing twin-screw extruder, L / D = 30, was used. As a first embodiment, a barrel hole having a hexagonal cross section is used for the plasticized portion of the barrel by a length corresponding to 30% of the entire length, and a barrel hole cross section is used for comparison over the entire length of the barrel for comparison. Was.

In order to mix 60-70% of titanium oxide powder with thermoplastic powder in these extruders, screw rotation speed is 100r.
As a result of extruding at 400 pm / h and an extrusion rate of 400 kg / h, the kneading state of the extruded product was unsatisfactory due to the secondary agglomeration of titanium oxide in the case of a comparator having only a circular barrel hole. In the extruder having a hexagonal cross section in the portion, the kneading state was extremely good.

As Example 2, the other conditions were the same as in Example 1, and extrusion was performed under the following conditions.

30% glass fiber (GF) is added to PP pellets,
The screw rotation speed was 200 rpm and the extrusion rate was 300 kg / h. In addition, the GF charging position is on the downstream side of the PP pellet charging position, and the ratio of the length of the hexagonal barrel to the entire barrel length is
25% before the GF injection position and 12.5% after the GF injection position.

The result showed that L / D = 24 was sufficient for a hexagonal barrel extruder to obtain a GF dispersion equivalent to that of a circular barrel extruder with L / D = 30.

(Effects of the Invention) As is clear from the above description, according to the present invention, good kneading performance can be exhibited even with a raw material that is difficult to plasticize and knead, and the screw length in the first-stage extruder can be shortened accordingly. It can save cost, energy and space.

[Brief description of the drawings]

FIG. 1 is a barrel sectional view showing a characteristic portion of a first-stage extruder which is a typical embodiment of the present invention, FIG. 2 is a side view showing an entire in-line two-stage extruder, and FIG. It is a barrel sectional view of a 1st stage extruder. Description of main parts in the drawing 2... (First stage extruder) barrel 5... (Second stage extruder) barrel 9... (First stage extruder) screw

Continuation of the front page (56) References JP-B-55-46307 (JP, B2) Jpn. Microfilm (JP, U)

Claims (1)

(57) [Claims] An extruder in which a first-stage extruder and a second-stage extruder are connected in series, wherein a twin-screw extruder having a polygonal cross-sectional shape is incorporated in the first-stage extruder barrel. A two-stage in-line extruder.