JPH06328449A - Raw material supplying apparatus - Google Patents

Abstract

PURPOSE:To improve the general purpose properties with respect to the discharge quantity, particle size, and pressure reduction degree of the raw material by a method wherein in an apparatus wherein a raw material is transferred to a vacuum chamber side with a screw, deaerated and supplied to an extruder, a volume of a raw material- transferring space which is enclosed with a flight of a screw and an inner peripheral surface of a cylinder is decreased gradually toward a discharge opening side. CONSTITUTION:In the raw material supplier, a raw material in a hopper part 7 is transferred to a vacuum chamber side connected to a kneading part of an extruder with a screw 12, and deaerated by reducing pressure of a discharge opening 11a side of a cylinder. Further, a sealing valve 10 adjusting airtightness of the discharge opening 11a is provided. A volume of a raw material-transferring space enclosed with a screw shaft of the screw 12, the flight 16, and an inner peripheral surface of the cylinder 11 is decreased gradually to the less toward the discharge opening 11a, and a function wherein the raw material is compressed is provided thereto. Pulsation of the raw material near the discharge opening 11a is restrained, and stable deaeration can be performed. Further, the sealing valve 10 can be stopped at a specific position, the general purpose properties with respect to the discharge quantity, a particle size, and a pressure reduction degree of the raw material is improved thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a raw material supply device for supplying a raw material under reduced pressure to an extruder.

[0002]

2. Description of the Related Art There is a so-called extrusion molding machine for molding various kinds of plastic materials made of polymers.

This extrusion molding machine pressurizes raw materials in the machine,
The raw material is melted and kneaded while being heated, and a molded product having a desired cross-sectional shape is continuously extruded.

By the way, as one type of molded article, there is a so-called plastic foam obtained by foaming an olefin polymer such as polyethylene or polypropylene. This plastic foam is also often molded by the above-mentioned extrusion molding machine, but from the viewpoint of ensuring shapeability,
It is required that the raw material of the powder supplied to the extruder be sufficiently deaerated in advance.

Therefore, conventionally, a hopper portion into which a raw material is fed into a raw material feeding port of an extruder and a feed for transferring the raw material from the hopper portion to the vacuum chamber side by rotation of a screw built in a cylinder. Part, a vacuum pump for reducing the air pressure on the discharge port side of the cylinder, and a raw material supply device equipped with a seal valve for adjusting the airtightness of the discharge port of the cylinder. I often go to. According to this, the pressure in the cylinder can be reduced by suction of the vacuum pump, and this reduced pressure state can be maintained to some extent by the seal valve, so that the raw material can be compressed and deaerated.

However, as the number of revolutions of the screw increases, pulsation occurs in the discharge of the raw material, and this pulsation may cause the seal valve to move slightly. For this reason, there is a problem that the decompression in the cylinder fluctuates, and as a result, uneven deaeration occurs in a part of the raw material.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 3-243305, there has been proposed one in which the gap between the discharge port of the cylinder and the vacuum pump side is regulated to a certain size. According to this, since the seal valve does not move, stable degassing can be performed.

[0008]

However, in the case of such a vacuum hopper, since the gap between the discharge port of the cylinder and the vacuum pump side is constant, it is a general-purpose material for the discharge amount of the raw material and the degree of pressure reduction. It has the disadvantage of lacking sex.

The present invention was created in view of such circumstances, and an object of the present invention is to provide a raw material supply device capable of improving versatility with respect to the discharge amount of the raw material and the degree of pressure reduction. Is.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention removes the raw material from the hopper portion by the rotation of a hopper portion into which the raw material is fed, a vacuum chamber, and a screw built in a cylinder. In a raw material supply device having a feed section for transferring to the vacuum chamber side and connecting the vacuum chamber to an extruder body kneading section, a screw shaft outer peripheral surface of the screw and a spiral around the outer periphery of the screw shaft. It is characterized in that the volume of the raw material transfer space surrounded by the flights arranged in a circle and the inner peripheral surface of the cylinder is reduced from the root side of the screw toward the discharge port side of the cylinder. .

[0011]

According to the raw material supply apparatus of the present invention, the raw material transfer space surrounded by the screw shaft outer peripheral surface, the flight spirally arranged around the outer periphery of the screw shaft, and the inner peripheral surface of the cylinder. Since the volume of the screw is reduced from the root side of the screw to the discharge port side of the cylinder, the screw itself also has a function of compressing the raw material, the occurrence of pulsation is suppressed, and the resistance to the seal valve is reduced. be able to. Therefore, stable deaeration of the raw material can be performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a raw material supply apparatus according to the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 is a single-screw extruder. This single screw extruder 1 has a barrel 2 and a screw 3
It has and. A raw material inlet 4 is provided on the upper portion of the barrel 2.

Reference numeral 5 denotes a raw material supply device for transferring the raw material 6 of the polyolefin polymer to the raw material inlet 4.

The raw material supply device 5 is provided with a hopper portion 7 into which the raw material 6 is charged, a feed portion 8, a vacuum chamber 9 as a vacuum pressure reducing means, and a seal valve 10 as a regulating means.

The feed section 8 is composed of a cylinder 11 and a screw 12 built in the cylinder 11,
This is for transferring the raw material 6 supplied from the hopper section 7 to the single screw extruder 1 side by the screw 12 rotated by a motor (not shown).

A vacuum pump (not shown) is connected to the vacuum chamber 9, and the air pressure on the discharge port 11a side of the cylinder 11 is reduced (about 600 mmHg) by suction of this vacuum pump. The vacuum chamber 9 is connected to the kneading section of the extruder body.

The seal valve 10 is attached to one end of the telescopic rod 13, and the other end of the telescopic rod 13 is attached to the piston 15 of the air cylinder 14. With this configuration, the seal valve 10 is stopped in the direction of the arrow in the figure, and the discharge port 11a of the cylinder 11 is stopped.
The airtightness of can be adjusted. The air cylinder 1
The pressure of about 4 to 7 kgf / cm 2 is adopted as No. 4.

The wall thickness of the flight 16 spirally arranged around the outer circumference of the screw shaft of the screw 12 goes from the root side of the screw 12, that is, the right side in the drawing, to the discharge port 11a side of the cylinder 11, that is, the left side in the drawing. It is set to be thicker. Therefore, the volume of the raw material transfer space surrounded by the screw shaft of the screw 12, the flight 16, and the inner peripheral surface of the cylinder 11 is reduced from the right side to the left side in the drawing.

The screw 12 has a function of compressing the raw material 6 by itself.
Therefore, the pulsation of the flow of the raw material 6 near the discharge port 11a of the cylinder 11 is suppressed, and the resistance to the seal valve 10 is reduced. As a result, the raw material 6 in the cylinder 11 and the vacuum chamber 9 can be stably degassed. Further, since the seal valve 10 can be stopped and fixed at a predetermined position in the direction of the arrow in the figure,
It is possible to improve the versatility of the vacuum hopper 5 with respect to the discharge amount and particle size of the raw material 6 and the degree of pressure reduction for obtaining a desired molded product.

FIG. 2 shows a modification of this embodiment. In the case of the screw 21 shown in FIG.
The pitch of 2 is set wider in the order of P1, P2, and P3. Also by this, the volume of the raw material transfer space can be reduced from the base side of the screw 21 toward the discharge port side of the cylinder. Further, in the case of the screw 31 shown in (B), the height H of the flight 32 of the screw 31
(Protrusion amount from the outer peripheral surface of the screw 31) is set to be lower from the root side of the screw 31 toward the discharge port side of the cylinder. Also by this, the volume of the raw material transfer space can be similarly reduced.

The present invention is not limited to the above embodiments, and design changes and the like made by those skilled in the art are also included in the technical scope of the present invention. For example, the reduction of the volume of the raw material transfer space of the screw can also be achieved by adopting a conical twin screw in which two screw shafts are obliquely crossed with each other. Further, in the above-mentioned embodiment, the single-screw extruder is used as the object of application, but it is of course applicable to a twin-screw extruder. Furthermore, in the case of non-foamed molded products, by preventing unnecessary air mixing,
Shape defects such as pinholes and fish eyes can also be prevented.

[0023]

As described above, according to the raw material supply device of the present invention, it is possible to improve the versatility with respect to the discharge amount of the raw material and the degree of depressurization. This also has the effect of preventing the above-mentioned shape defect.

[Brief description of drawings]

FIG. 1 is an explanatory sectional view showing an embodiment of a raw material supply apparatus according to the present invention.

FIG. 2 is a side view of a screw showing a modified example of the same embodiment.

[Explanation of symbols]

 1 single screw extruder, 5 raw material supply device, 6 raw material, 7 hopper part, 8 feed part, 9 vacuum chamber, 10 seal valve, 11 cylinder, 11a discharge port side, 12 screw, 16 flight.

Claims (1)

[Claims] 1. A vacuum chamber, comprising: a hopper portion into which a raw material is charged; a vacuum chamber; and a feed portion that transfers the raw material from the hopper portion to the vacuum chamber side by rotation of a screw built into a cylinder. In a raw material supply device in which a chamber is connected to an extruder body kneading section, a screw shaft outer peripheral surface of the screw, a flight spirally arranged around the outer periphery of the screw shaft, and an inner peripheral surface of the cylinder. The raw material supply device is characterized in that the volume of the raw material transfer space surrounded by is reduced from the root side of the screw toward the discharge port side of the cylinder.