JP6719347B2 - Twin screw extruder - Google Patents

Description

The present invention relates to a twin-screw extruder in which a gate facing a screw is provided and the degree of kneading is adjusted by controlling the width and width of a flow path through which the kneaded material is fed by opening and closing the gate.

There are various kinds of thermoplastic resins to be kneaded in the extruder, and the melt viscosity thereof ranges from high viscosity to low viscosity. Then, various additives are added to these thermoplastic resins. In order to knead such an object with good dispersibility, it is necessary to select appropriate kneading conditions and screw elements, but this alone is not sufficient. Therefore, the flow rate of the kneaded material is reduced and the filling rate of the kneaded material is reduced. Various methods have been proposed for adjusting the kneading degree by controlling the residence time and the residence time.

For example, in Patent Document 1, two screws are rotatably inserted in a through hole of a cylinder, and a supply unit, a first transport unit, a first kneading unit, a gate unit, and a first screw unit are provided in a longitudinal direction of the screw. A second transporting part and a second kneading part/discharging part are formed, and the kneading degree is adjusted in the gate part, and the first kneading part located at the most upstream is moved to the wall surface of the through-hole of the cylinder. A screw-type twin-screw kneading extruder that adjusts plasticization by changing the distance between the wall surface of the through-hole of the cylinder and the outer circumference of the screw by moving a freely provided wall body in the direction perpendicular to the screw axis. A kneading degree adjusting device has been proposed. It is said that this kneading degree adjusting device can satisfactorily knead a resin having a high melt viscosity to a resin having a low melt viscosity, which has been difficult in the past.

Further, in Patent Document 2, a kneading device provided in a processing device for continuously kneading a material to be kneaded by a kneading screw having a kneading portion rotatably inserted in a barrel and feeding the material from upstream to downstream. A degree adjusting mechanism, which is provided on the downstream side of the kneading section of the kneading screw and which pushes back the material to the upstream side to promote retention in the kneading section, and an outer peripheral surface of the pushing back section. A kneading degree adjusting mechanism has been proposed that has a facing surface facing each other and has a kneading degree adjusting member that adjusts the kneading degree of the material by moving the facing surface closer to and away from the push-back portion. In this kneading degree adjusting mechanism, since the staying action of the kneading degree adjusting member and the pushing-back action of the push-back portion to the upstream side interact, the kneading degree does not change rapidly even when the kneading degree adjusting member is opened and closed. It is said to change linearly. Further, it is said that the kneading degree adjusting mechanism can reduce the thrust force acting on the kneading screw because the kneading degree adjusting member does not project from the inner peripheral surface of the barrel when fully closed.

Japanese Patent Laid-Open No. 2008-168459 JP 2009-113246 A

The kneading degree adjusting device of the twin-screw kneading extruder described in Patent Document 1 can satisfactorily knead a resin having a high melt viscosity to a resin having a low viscosity, which has been difficult in the past. From the state where the inner surface of the wall surface body provided in the kneading part coincides with the wall surface of the through hole of the cylinder (plasticization position M), the inner surface of the wall surface body is largely separated from the wall surface of the through hole of the cylinder vertically (non-plasticizing). The kneading degree adjusting device that adjusts the plasticization of the synthetic resin raw material by moving to the liquefying position N), the cylindrical screw with no flight formed in the gate part, and the separating part along the outer periphery of this screw. There is a problem that it is necessary to provide a rotary slot bar type kneading degree adjusting device composed of a rotary slot bar that is possible and two kneading degree adjusting devices.

The kneading degree adjusting mechanism described in Patent Document 2 has a problem that it is difficult to adjust the kneading degree of a resin having a low melt viscosity, which has been difficult in the past. In addition, since the kneading degree adjusting device described in Patent Document 1 or the kneading degree adjusting mechanism described in Patent Document 2 is used in a form in which the inner wall of the cylinder or barrel has a recess, the mixed flow adheres to or separates from the recess. As a result, the desired kneading becomes difficult, and further, the product is contaminated. Further, in the cylindrical screw provided in the gate portion described in Patent Document 1, similarly, there is a problem that the mixed flow material is fixed or released to cause contamination of the product.

In view of such conventional problems, the present invention can prevent contamination due to a gate for adjusting the degree of kneading, and kneads well from a resin having a high melt viscosity to a resin having a low viscosity, which has been difficult in the past. An object of the present invention is to provide a twin-screw extruder whose degree can be adjusted.

The twin-screw extruder according to the present invention is a twin-screw extruder provided with a gate for adjusting the degree of kneading by opening and closing a screw in the cylinder cross section of the twin-screw extruder, and squeezing the transfer passage to the downstream of the kneaded material. In the extruder, a gate screw element of a portion facing the gate of the screw has a length of 1 pitch or more and is engaged with each other so as to be self-cleaning, and the gate is formed from an inner peripheral surface of the cylinder. The gate screw element is provided with a protrusion amount adjusting means capable of protruding to a position substantially equal to the mountain diameter of the gate screw element to narrow the transfer passage.

In the above invention, the gate screw element preferably has a mountain diameter that is 5% to 20% smaller than the mountain diameter of the screw element provided in the conveying section or the kneading section. Also, the gate screw element can be a reverse flight or reverse offset kneading disc.

Further, in the above invention, the gate is preferably provided downstream of the kneading section.

The twin-screw extruder according to the present invention can prevent contamination due to a gate that adjusts the kneading degree, and adjusts the kneading degree satisfactorily from a resin having a high melt viscosity to a resin having a low viscosity, which was conventionally difficult. be able to.

It is a schematic diagram of the part in which the gate of the twin-screw extruder which concerns on this invention was provided, FIG.1(a) is a longitudinal cross-sectional view, FIG.1(b) is a cross-sectional view. It is a schematic diagram of the gate screw element (FIG. 2(a)) facing the gate of the screw of FIG. 1, and the screw element (FIG. 2(b)) of a conveyance part or a kneading part.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 shows a cross section of a portion where a gate is provided in a twin-screw extruder according to the present invention. As shown in FIG. 1A, the twin-screw extruder 10 includes a gate 15 that opens and closes with a screw 12 sandwiched in a cross section of a cylinder 11, that is, a gate 15 that includes a vertically moving gate door 150A and a gate door 150B. The screw 12 has a gate screw element 125 at a portion facing the gate 15. The gate screw element 125 has a length of 1 pitch or more, and as shown in FIG. 1B, the gate screw elements 125 are engaged with each other for self-cleaning. The gate 15 has projection amount adjusting means (not shown) capable of projecting (closing) the transfer passage from the inner peripheral surface of the cylinder 11 to a position approximately equal to the peak diameter of the gate screw element 125 (closed). There is.

As described above, the projection amount of the gate 15 is adjusted by the projection amount adjusting means. As shown in FIG. 1(b), the gate door 15A and the gate door 15B move up and down by the protrusion amount adjusting means, and when reaching the maximum protrusion amount (when fully closed), they are almost in contact with the gate screw element 125 and their mountain diameters. To a position approximately equal to. When the protruding amount of the gate doors 150A and 150B is minimum (when fully opened), the gate doors 150A and 150B are substantially flush with the cylinder inner surface C. Adjustment of the projection amount of the gate door 150A, the gate door 150B, that is, the transfer passage of the kneaded material can be narrowed by opening and closing the gate 15, and the filling rate of the kneaded material in the kneading section and the residence time of the kneaded material can be adjusted. The kneading degree can be adjusted. In this twin-screw extruder, since the gate 15 (150A, 150B) is always used in a state of protruding from the cylinder inner surface C, a recess is formed on the cylinder inner surface as in the maintenance state shown in FIG. 1(b). Never. For this reason, it is possible to prevent problems caused by the kneaded material sticking to or leaving the depressions on the inner surface of the cylinder. The gate 15 is designed such that the gate door 150A and the gate door 150B can be retracted from the cylinder inner surface C during maintenance, as shown in FIG. 1(b). By moving the gate door 150B up and down, cleaning and maintenance around the gate can be performed.

A gate screw element 125 is provided opposite to the gate 15. The gate screw element 125 has a length of 1 pitch or more, and can be engaged with each other and self-cleaning. Therefore, the gate screw element 125 can maintain a fresh surface.

Further, the gate screw element 125 is smaller than a normal screw element provided in the transport section or the confusion section. The crest diameter of the gate screw element 125 is (0.95 to 0.80)*D of the crest diameter D of the normal screw element 120 shown in FIG. 2(b), that is, 5 to 20%, as shown in FIG. 2(a). It is better to make it smaller. With this, it is possible to adjust the required kneading degree by narrowing the transfer flow path, and it is possible to give required pressure fluctuations to the kneaded material and the gate portion, and the kneaded material is fixed to the gate 15 protruding from the cylinder inner surface C. Can be prevented. In FIG. 2, the A dimension is the distance between the screw centers.

The gate screw element 125 can use a kneading disc whose shape is reverse flight or reverse shift. This makes it possible to further expand the adjustment range of the filling rate and the residence time of the kneaded material in the kneading section. The reverse shifting kneading disc is
It is a screw element which has self-cleaning and can generate a high kneading pressure with a low carrying capacity.

10 twin screw extruder
11 cylinders
12 screws
120 Normal screw element
125 gate screw element
15 gates
150A, 150B gate door
125 gate screw element

Claims (4)

A twin-screw extruder provided with a gate for adjusting the degree of kneading by opening and closing a screw in the cylinder cross section of the twin-screw extruder, and squeezing the transfer passage to the downstream of the kneaded material,
The gate screw element of the portion facing the gate of the screw has a length of 1 pitch or more and is engaged with each other so as to be self-cleaning,
The gate is a twin-screw extruder having projection amount adjusting means that can project from the inner peripheral surface of the cylinder to a position approximately equal to the mountain diameter of the gate screw element to narrow the transfer passage. The twin screw extruder according to claim 1, wherein the gate screw element has a mountain diameter that is 5% to 20% smaller than the mountain diameter of the screw element provided in the conveying unit or the kneading unit. The twin screw extruder according to claim 1 or 2, wherein the gate screw element is a reverse flight or reverse offset kneading disc. The twin-screw extruder according to claim 1, wherein the gate is provided downstream of the kneading section.

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