JPH09141726A - Method and apparatus for extrusion molding of vinyl chloride molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable molding at low temp. while degassing a volatile component and a gas component by a method wherein a material of a vinyl chloride molded product is kneaded and melted by a screw type twin-screw kneader to be raised in pressure by a gear pump and this material is subjected to extrusion molding through a molding die. SOLUTION: A powdery or pellet like vinyl chloride material being a main raw material is supplied to a screw type twin-screw kneader 1 from a hopper 2b and uniformly mixed in the feed parts 3a of screws 3 by two meshed screws 3 and preheated by a cylinder 2 heated by a heater to be sent to a kneading part 3b. The preheated material receives shearing action in the kneading part 3b to be easily melted and the material from which gas is removed is allowed to flow to the through-passage 5a of a gear pump 4 by the transport action of the screws 3. In the gear pump 4, the material flowing through the through-passage 5a in a molten state is successively raised in pressure by two sets of gears 6 to be extruded from a leading end opening under high pressure to flow in the nozzle 7a of a die 7 and this material is continuously extruded while molded into a predetermined shape during the flowing through the nozzle 7a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the addition of an additive to a material of hard vinyl chloride or soft vinyl chloride, kneading and melting, and continuously forming a pipe or a long product having a complicated cross section through a molding die. The present invention relates to a method and an apparatus for direct extrusion molding.

[0002]

2. Description of the Related Art When molding a hard vinyl chloride or a soft vinyl chloride molded product such as a pipe or a long product (profile) having a complicated cross-section, powder or pellet vinyl chloride as the main raw material is used. , A material to which a stabilizer, a lubricant, a colorant and other additives are added is kneaded and melted by a kneading extruder, and a material in a molten state is extruded through a die provided at the tip of the kneading extruder, and continuously. The extruded molded product is cooled and cut into a predetermined length. In order to directly extrude such a vinyl chloride molded product, the main raw material and various kinds of additives are uniformly mixed, and the mixture is kneaded at a low temperature for easy thermal decomposition of the main raw material.
It is required to knead and melt to give a high extrusion pressure for the low flowability of the material. For extrusion molding of vinyl chloride molded products, as an extrusion molding machine that satisfies the above conditions, a perfect meshing counter-rotating oblique shaft extruder (conical machine) with good kneading dispersibility and high extrusion pressure can be constantly obtained. A shaft extruder) is conventionally used. This conical twin-screw extruder typically has a minimum screw tip diameter of about 8
0 mm, and the ratio of the length to the diameter (L / D) is 15 to 16.

[0003]

Since the conventional extrusion molding method and apparatus for a vinyl chloride molded product are configured as described above, the following problems exist. That is, the extrusion molding capacity of the extrusion molding apparatus is limited, and the production capacity cannot be increased. To increase the production capacity, increase the screw diameter to increase the throughput per revolution, or increase the screw rotation speed to increase the throughput per unit time.
Alternatively, it is possible to increase both the screw diameter and the screw rotation speed. However, in the conical twin-screw extruder, when the screw diameter is increased, the diameter of the rear end becomes larger, and not only the extruder itself but also auxiliary equipment such as a driving device is compared with a normal parallel twin-screw extruder. It will be very large. Therefore, the current screw tip diameter of 80 mm is the maximum. Further, when the rotation speed of the screw is increased, the tendency that the material is forcibly concentrated in the meshing portion due to the different-direction rotation meshing is strengthened. Therefore, the pressure of the material concentrated in the meshing portion of the two screws spreads the screw, and the outer diameter of the screw is strongly pressed against the inner wall surface of the cylinder and slides at a high speed, causing a galling phenomenon. It may damage the cylinder. Furthermore, by increasing the number of rotations, a greater shearing action is continuously applied to the material, but the main raw material vinyl chloride is heated to a high temperature due to the large shearing action and generates heat to decompose and generate chlorine gas. become. In the conventional conical twin-screw extruder, the screw rotation speed is about 100 rpm.
Is the limit. Further, in the conical twin-screw extruder, in order to extrude the molten material from the tip of the extruder to the die, the cylinder near the tip is filled with the molten material under high pressure. Therefore, the volatile components, gas components and slight decomposition gases contained in the molten material are not degassed by the extruder, and the material is extruded together with the gas components, which may cause defective products or chlorine gas It diverges into the inside.

The present invention has been made in order to solve the problems as described above, and increases the production capacity, and also kneads and melts at a low temperature while degassing volatile components and gas components to provide stable kneading extrusion molding. The present invention provides an extrusion molding method and an extrusion molding device for a vinyl chloride molded article that enables the above.

[0005]

The extrusion molding method of a vinyl chloride molded product according to the present invention comprises kneading and melting the material of a vinyl chloride molded product with a screw type twin-screw kneader, and pressurizing the molten material with a gear pump and molding it. It is a method of extrusion molding through a die.

More specifically, the temperature of the molten material is controlled by detecting the pressure of the molten material at the tip of the screw type twin-screw kneader and controlling the rotation speed of the gear pump using the pressure as an index. Is the way.

An extrusion molding apparatus for a vinyl chloride molded article according to the present invention is a screw type twin screw kneader, a gear pump connected to the tip of the screw type twin screw kneader, and a discharge port of the gear pump. It is composed of a molding die.

More specifically, the screw type twin-screw kneader is of the same rotational mesh type.

More specifically, the screw type twin-screw kneader has a vent device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the extrusion molding method and apparatus for a vinyl chloride molded article according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram showing a main part of an extrusion molding apparatus for a vinyl chloride molded product according to the present invention. In the figure, reference numeral 1 is a screw type twin-screw kneader, and a gear pump 4 and a die 7 are sequentially connected in series to the tip of the screw type twin-screw kneader 1 to form a molding device. . In the screw type twin-screw kneader 1, two screws 3 are rotatably inserted into an inner hole 2a of a cylinder 2. The outer diameters of the two screws 3 are substantially constant in the lengthwise direction, the flights having the same shape are formed in the two screws 3, the flights are arranged in parallel with each other so that the flights rotate in the same direction. ing. Further, the screw 3 is formed with a feed portion 3a from the rear end portion to the middle portion and a kneading portion 3b from the middle portion to the front end. The cylinder 2 has a hopper opening 2 at the rear end.
b, a vent port 2 is provided in the upstream part of the kneading part 3b of the screw 3.
c is formed. The gear pump 4 is rotatably arranged such that two sets of gears 6 mesh with each other along a through-flow passage 5a formed inside the housing 5. Further, the gear pump 4 is connected to the screw type twin-screw kneader 1 such that the upstream side opening of the through-flow passage 5a communicates with the tip end opening of the cylinder 2. The die 7 is formed with a nozzle 7a penetrating therethrough, and the shape of the tip opening is formed in a cross-sectional shape of a pipe or a profile to be extruded. The die 7 is connected to the gear pump 4 so that the upstream opening of the nozzle 7 a communicates with the tip opening of the housing 5.

A case of molding a vinyl chloride molded product in the molding apparatus configured as described above will be described. In a screw type twin-screw kneading machine 1 in which two screws 3 are connected to the rear end portion thereof and are driven to rotate in the same direction by a driving device (not shown), a chlorinated powder or pellets as a main raw material is fed from a hopper port 2b. Stabilizer on vinyl,
When the material to which the lubricant, the colorant, and other additives are added is supplied, the material is fed in the feed portion 3a of the screw 3,
The materials that are evenly mixed by the two meshed screws 3 and are preheated by the cylinder 2 that is heated by a heating device (not shown), uniformly mixed and preheated to a predetermined temperature are sent to the kneading section 3b. In the kneading section 3b,
The preheated material undergoes shearing action and melts easily. 2
If the screw 3 of the book rotates in the same direction while meshing,
Due to the self-cleaning action, the mixing action is further large, and the material is transported in the downstream direction without being retained.
The upstream portion of the kneading section 3b is in an unfilled state, and the gas generated by kneading, that is, the gas component contained in the material, the volatile component, and the decomposition gas generated when the material is decomposed are vented from the vent port 2c. It is forcibly sucked and easily exhausted by the device 8.

The material which is uniformly melted by the screw type twin-screw kneader 1 and whose gas is exhausted from the opening of the tip of the cylinder 2, that is, the upstream opening of the gear pump 4 to the gear pump 4
To the through-flow passage 5a by the transport action of the screw 3. In the gear pump 4, the molten material flowing in the through flow path 5a is sequentially pressurized by two sets of gears 6 which are rotationally driven by a driving device (not shown), and is extruded at high pressure from the tip opening. The molten material extruded at a high pressure by the gear pump 4 flows into the nozzle 7a from the upstream opening of the die 7, is formed into a predetermined shape while flowing in the nozzle 7a, and continuously has a predetermined cross-sectional shape from the tip opening. Is extruded into.

That is, in the screw type twin-screw kneader 1,
The materials are uniformly kneaded and melted, and in the gear pump 4, a high extrusion pressure necessary for flowing the molten material through the nozzle 7a of the die 7 is applied. Therefore, in the screw type twin-screw kneading machine 1, only the energy necessary for kneading and melting is added, and in the gear pump 4, only the energy necessary for pressurizing is added, so that the temperature of the material rises due to the kneading and melting. Extruded in the low temperature melt with minimal energy applied. The quality of vinyl chloride moldings is sensitively affected by the melting temperature during extrusion. Therefore, in order to extrude a molded product of good quality, the operation of each device is controlled so that the temperature T1 of the molten material at the tip of the screw type twin-screw kneader 1 becomes a predetermined temperature. When the screw type twin-screw kneader 1 is operated at a constant speed rotation and the material supply ratio is constant, the gear pump 4
When the number of rotations is decreased, the extrusion rate of the material is decreased, so that the material stays in the kneading section 3b (the filling rate is increased), and the molten material at the upstream of the gear pump 4, that is, the tip of the screw type twin-screw kneader 1 is The pressure P1 increases. At this time, the material stays in the kneading section for a long time and is subjected to a large shearing action, so that the temperature T1 rises. Conversely, when the rotation speed of the gear pump 4 is increased, the pressure P1 decreases and the temperature T1 also decreases. Therefore, regarding the temperature of the material to be extruded, the temperature T1 of the material can be easily controlled by controlling the rotation speed of the gear pump 4 so that the pressure P1 becomes a predetermined value. Further, the molten material needs a pressure to be extruded from the nozzle 7, and the pressure P2 downstream of the gear pump 4 and the temperature T2 increased by the boosting energy of the gear pump 4 are monitored.

A screw type twin-screw kneader 1 for kneading and melting materials has been put to practical use with a screw 3 having a diameter of about 500 mm. A gear pump 4 compatible with such a large screw-type twin-screw kneader 1 is also available. Existence and increased throughput is easily realized. Further, since the screw type twin-screw kneader 1 is almost solely responsible for the kneading and melting action, the length of the screw 3 is 8 to 10 in diameter ratio (L / D), which is much shorter than the conventional diameter ratio. Becomes Further, although the gear pump 4 is provided with two sets of gears 6 in the present embodiment, one set of gears 6 may be used. However, when a high extrusion pressure of the material is required, such as in the case of extrusion molding of a profile having a complicated shape, by providing a plurality of sets of the gears 6 in series, each of the gears 6 is allowed to share the boosting action and smooth. It is possible to increase the voltage.

[0015]

Since the extrusion molding method and the extrusion molding apparatus for a vinyl chloride molded article according to the present invention are configured as described above, the following effects can be obtained. (1) The molding equipment consisting of a screw type twin-screw kneader, a gear pump and a molding die has been enlarged in size, and it is easy to realize a large capacity molding by combining these large equipment. it can. (2) Kneading and melting the materials with a screw type twin-screw kneader
By sharing the extruding of the molten material by the gear pump, the material is kneaded at a low pressure in the screw type twin-screw kneader and the pressure is efficiently raised in the gear pump, so the temperature rise is low and thermal decomposition and generation of chlorine gas are generated. There is almost no, and efficient molding (low power consumption) is performed. (3) By controlling the rotation speed of the gear pump based on the pressure of the molten material at the tip of the screw type twin-screw kneader, the pressure of the molten material is easily controlled to a predetermined value of low pressure,
Therefore, the temperature is maintained below the thermal decomposition temperature. (4) In the screw type twin-screw kneading machine, since the materials are kneaded and melted at a low pressure, the force to spread the two screws is hardly generated, and the galling phenomenon of the screw and the cylinder is hardly generated. It will not occur. (5) The screw type twin-screw kneader is a co-rotating mesh type, so that the screw has self-cleaning characteristics, the material is uniformly kneaded, and the material does not stay in the kneader for a long time. Deterioration does not occur due to the retention of (6) Since the screw type twin-screw kneader is equipped with a vent device, the volatile components and gas components contained in the material to be kneaded and melted at a low pressure are easily degassed and the material is thermally decomposed. Therefore, even if chlorine gas is generated, it can be safely exhausted.

[Brief description of the drawings]

FIG. 1 is a structural cross-sectional view showing a main part of an extrusion molding device for a vinyl chloride molded article according to the present invention.

[Explanation of symbols]

 1 Screw type twin-screw kneader 2 Cylinder 3 Screw 3a Feed part 3b Kneading part 4 Gear pump 6 Gear 7 Die 8 Vent device

Front page continuation (72) Inventor Shoji Ishida 1-6-1, Funakoshi Minami, Aki-ku, Hiroshima City, Hiroshima Prefecture Japan Steel Works, Ltd.

Claims (5)

[Claims] 1. A material for a vinyl chloride molded product is kneaded and melted by a screw type twin-screw kneader (1), and the molten material is pressurized by a gear pump (4) and extruded through a molding die (7). A method for extrusion-molding a vinyl chloride molded product characterized by: 2. The pressure (P1) of the molten material at the tip of the screw type twin-screw kneader (1) is detected, and the rotation speed of the gear pump (4) is controlled by using the pressure (P1) as an index. The extrusion molding method of a vinyl chloride molded article according to claim 1, wherein the temperature (T1) of the molten material is controlled by: 3. A screw type twin-screw kneader (1), and a gear pump (4) connected to the tip of the screw type twin-screw kneader (1).
And a molding die connected to the discharge port of the gear pump (4)
(7) An extrusion molding device for a vinyl chloride molded article, which is characterized by comprising: 4. The extrusion molding apparatus for a vinyl chloride molded article according to claim 3, wherein the screw type twin-screw kneader (1) is a rotary meshing type in the same direction. 5. The screw type twin-screw kneader (1) is provided with a vent device (8).
Alternatively, the extrusion molding device of the vinyl chloride molded article according to 4 above.