JPH0752185A - Molding method and molding apparatus for long-fiber composite material - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a molding method and a molding apparatus for a long fiber composite material, which can suppress the cutting of reinforcing fibers as much as possible even in the injection molding of the long fiber composite material using a screw extruder. . [Structure] A long fiber composite material 15, which is a composite material of long fibers for reinforcement and a thermoplastic resin, is plasticized under a small shearing action by using a screw type extrusion device 2 with bi-directionally rotating biaxial meshing. The plastic material 43 is supplied to the plunger type extrusion device 4 having no screw, and the plastic material is injected into the injection compression molding die 5 slightly opened from the plunger type extrusion device 4 to perform compression molding, or It is a method and apparatus for extrusion molding from a type extrusion device 4 to an extrusion die.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for molding a long fiber composite material in which a resin and a reinforcing fiber such as a glass fiber having a length of about 10 mm are compounded, and particularly, the reinforcing fiber can be cut as much as possible. Regarding what you can reduce.

[0002]

2. Description of the Related Art In injection molding of long fiber composite materials,
Usually, a single screw inserted in a cylindrical cylinder is used for plasticizing and pressing. The rotary transfer action of the screw flight sends the long fiber composite material forward along the groove of the screw. In this process, the long fiber composite material is heated by a heater wound around the outer circumference of the cylinder, and is plasticized mainly by the heat generated by the shearing action between the screw groove and the cylinder, and becomes a plastic and is sent to the tip of the screw. Pressurized.

When plasticizing a long fiber composite material using a single screw in this way, since the heat generated by the shearing action occupies a considerable specific gravity, the reinforcing fibers such as glass fibers are cut and various strengths are reduced. To do. Fiber length 6
In the case of glass fiber reinforced polypropylene containing mm, the glass fiber is cut to about 0.2 to 0.5 mm, and various strengths are reduced to 50%.

Such cutting of the glass fiber occurs not only in the screw but also in the bent portion of the sprue or runner or in the mold. 16,
In 1990, p29-41, "Study on evaluation of formability and physical properties of long fiber reinforced composite materials", most of the cutting occurs during the plasticizing process in the screw, and especially the shear rate of the screw is large. Depends on.
Therefore, the cutting of the glass fiber in the long fiber composite material occurs not only in the injection molding but also in the plasticizing step of the extrusion molding using the T die.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and its object is to mold a long fiber composite material using a screw extruder. Even so, it is an object of the present invention to provide a method and an apparatus for molding a long-fiber composite material, which can suppress cutting of reinforcing fibers as much as possible.

[0006]

A method for molding a long-fiber composite material that solves the above-described object is a long-fiber composite material, which is a composite material of long-fibers and a thermoplastic resin for reinforcement, meshed in different directions by biaxial rotation. Plasticize using a screw type extruder, supply this plastic to a plunger type extruder, and inject the plastic into the injection compression molding die from this plunger type extruder, or the extruder from this plunger type extruder. It is a method of extruding a plastic material into a mold, and preferably, the number of revolutions of the screw type extruder is set to a low speed such that the shearing speed between the screw and the cylinder is 20 sec ^-1 or less, and the shearing force of the screw engaging portion is made small. Yes, and more preferably, the long fiber composite material supplied to the twin-screw type extruder is heated to a softened state by passing a high temperature inert gas. It is the law.

A molding device for a long fiber composite material which solves the above-mentioned object is a screw type extruding screw of different directions rotating for plasticizing a long fiber composite material which is a composite material of long fibers for reinforcement and a thermoplastic resin. A device, a storage device for storing the plastic material from the screw type extrusion device, a plunger type extrusion device for pressurizing the plastic substance from the storage device, and a compression molding of the plastic substance injected from the extrusion device. An apparatus comprising an injection compression molding die or an extrusion die for extruding a plastic material extruded from this extrusion apparatus, preferably supplying a long fiber composite material to the screw type extrusion apparatus. A supply device is provided, and the supply device is connected to a circulating device of high temperature inert gas with respect to the supplied long fiber composite material, and more preferably, the screw type extruder. The feed portion of the crus, a device circulating apparatus of the hot inert gas for a long fiber composite material to be sent are connected.

[0008]

In the screw-type extruding device with the bi-directionally rotating two-shaft meshing mechanism, the screw flights are meshed with each other, so that the long fiber composite material is positively extruded. There is little kneading due to shearing of the fiber composite material, and it is mainly sent to the front, and the shearing action is reduced and it is plasticized by heating with a heater or the like. This plastic is pressed by a plunger type extruder without shearing, and is further injected into an injection compression molding mold in a slightly opened state at a low shear rate to mold by compression by closing the mold, or extrusion. Extrude through a mold. When the rotation speed of the screw type extruder is set to a low ^{value such} that the shear speed between the screw and the cylinder is 20 sec ^-1 or less, and the shear force at the screw meshing portion is made small, the reinforced fiber is cut less. If a high temperature inert gas is passed through the long fiber composite material in advance to soften it, the screw length is shortened and the shearing action is reduced accordingly.

Since plasticization in the screw-type extruder with different-direction rotating twin-shaft meshing is carried out in continuous operation, while injection in the plunger-type extruder is carried out in intermittent operation, they are connected via a storage device. However, the plastic material from the screw type extruder during the injection of the plunger type extruder is stored in the storage device. In addition, as a circulating place of the high temperature inert gas for the long fiber composite material, if a feeding device for the screw type extruder or a screw feed part of the screw type extruder is used, the continuous flow of the long fiber composite material can be achieved. You can preheat.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. First, a molding apparatus when injection molding is applied will be described based on FIGS. 1 and 2, and then a molding method thereof will be described. 1 is a sectional view of the entire injection molding apparatus, and FIG. 2 is a plan view showing a screw of a screw type extrusion apparatus.

In FIG. 1, reference numeral 1 is a constant amount supply device, 2 is a screw-type extrusion device of bi-rotating biaxial mesh, 3 is a storage device, 4 is a plunger-type extrusion device, and 5 is an injection compression molding die.

The constant quantity supply device 1 is of a screw conveyor type, and the long fiber pellets or bulky long fiber composite material 15 in the hopper 14 is sent forward by the flight 13 of the screw 12 which is rotationally driven by the motor 11. A predetermined amount of long fiber composite material 1 determined by the number of rotations and the space between the flights 13
5 is cut out to the chute 16 at the tip. Screw 12
Has a central hole 12a, and a large number of blowing holes 12b communicating with the central hole 12a are opened at the groove bottom in front of the middle of the screw. A discharge hole 17a is opened on the hopper 14 side of the cylinder 17 into which the screw 12 is inserted.
A pipe 19 from the high temperature inert gas circulation device 18 is connected to the center hole 12a via a rotary joint (not shown), and a pipe 20 reaching the high temperature inert gas circulation device 18 is connected to the discharge hole 17a.

The high temperature inert gas circulation device 18 is composed of an exhaust gas treatment device 21, a blower 22 and a heater 23 connected in series, and a nitrogen gas cylinder 24 connected upstream of the blower 22. As the medium, long fiber pellets or bulk long fiber composite material 15 is heated to be in a softened state.

A screw-type push-out device 2 with two-rotating biaxially meshing different directions is provided with two screws 3 in a cylinder 31 having a spectacle-shaped cross section.
2 and 33 are inserted in parallel. The cylinder 31 is provided with an opening 31a to which the chute 16 is connected and a discharge hole 31b to which the pipe 20 of the high temperature inert gas circulating device 18 is connected, and a heater 34 is arranged on the outer periphery thereof. A large number of blowing holes 32a are provided in the groove bottom of the feed portion near the openings 31a of the screws 32, 33, and a central hole 32b communicating with the blowing holes 32a has a high temperature inert gas circulating device 18 through a rotary joint (not shown). The pipe 20 is connected to the pipe 19. Therefore, the long fiber composite material 15 sent from the constant quantity supply device 1 in a softened state becomes a semi-molten state by heating the high temperature gas, and is further plasticized by the external heating of the heater 34 while being sent by the screws 32 and 33.

As shown in FIG. 2, the screws 32 and 33 are double screws whose inclination directions are opposite to each other and mesh with each other. The degree of meshing of the screws 32 and 33 has a sufficient clearance at the root, and the meshing ratio is gradually ensured to attain a compression ratio as the screw 32, 33 moves toward the tip. In addition,
The root is a double screw, the middle is a triple screw, and the tip has a compression ratio by changing the lead like a quadruple screw. Such bidirectionally rotating two-shaft meshing screw 32,
The flights 32c and 33c of 33 mesh with each other so as to sandwich each other, and when the screws 32 and 33 rotate in different directions as indicated by arrows a and b, the meshing portion A moves as if to move forward, and the flights 32c and 33c. The long fiber composite material 15 in the notched ring-shaped space defined by 33c is fed forward. Therefore, unlike the single screw, it is not necessary to make the groove depth shallow for feeding, the grooves of the screws 32 and 33 are deep, and the shearing action with a cylinder (not shown) is small. Then, the long fiber composite material 15 is plasticized by the energy mainly of the external heating of the heater 34 of FIG.

The storage device 3 is one in which the tip of the cylinder 31 of the screw type extrusion device 2 is connected to the side surface of the vertical container 40, and a pushing cylinder 41 is provided on the vertical container 40, and The lower end is connected to the plunger pushing device 4 via a diverter valve 42. When the diverter valve 42 is closed, the plastic material 43 from the screw type extruder 2 pushes the piston 41 of the pushing cylinder 41.
A is pushed up and stored in the vertical container 40. When the diverter valve 42 is opened and the piston 41a of the pushing cylinder 41 is pushed down, a predetermined amount of the plastic material 43 in the vertical container 40 is supplied to the plunger pushing device 4.

The plunger pushing-out device 4 allows a plunger 52 inserted in a cylinder 51 to move forward and backward by a hydraulic cylinder 53. A rotary valve 54 is provided at the tip of the cylinder 51, and the plastic material 43 is pressurized with the rotary valve 54 closed, and the rotary valve 54 is opened to open the injection nozzle 5.
The plastic material 43 is injected from 5 at a stretch.

The injection compression molding die 5 has a cavity 63 as a molding space formed between a fixed die 61 and a movable die 62. The dies 61 and 62 before injection are opened by a slight gap ε from the fully closed state, and the cavity 63 is wider than the actual molding space. Since the plastic material 43 corresponding to the actual molding space is injected therein, low-pressure low-speed injection with less shearing action can be performed. Then, the mold 6 after injection
1, 62 are closed, and the plastic material in the cavity 63 is compressed to form a molded product having a predetermined shape.

Next, the injection molding method using the above-mentioned injection molding apparatus will be described with reference to FIG. The long fiber composite material 15 in the hopper 14 of the constant quantity supply device 1 is sent forward by the flight 13 of the screw 12, and a predetermined amount of the long fiber composite material 15 is fed.
Is supplied to the screw type extruder 2 through the chute 16 which rotates in different directions and meshes with the two shafts. Then, the long fiber composite material 15 is in a softened state due to the high-pressure inert gas blown out from the screw 12, and the screws 32 and 33 are further added.
The blown high-pressure inert gas from the state changes the softened state to the anti-melted state.

The long-fiber composite material 15 in the softened state or the anti-melted state is fed forward by the screws 32 and 33 in the screw-type extrusion device 2 in the different rotation direction biaxially meshing, with a small shearing action, and outside the heater 34. It is plasticized by heating. Since the grooves of the screws 32 and 33 are deep and there is no backflow, the reinforcing fibers are less cut during the plasticizing process. Further, in order to further reduce the shearing force of the meshing portion of the screw type extrusion device 2, the screw 32,
33 is preferably low-speed rotation, and the number of rotation is selected so that the shearing speed between the screw and the cylinder is 20 sec ^-1 or less.

The screw type extruder 2 is continuously operated for stable operation, and the plastic material 43 is contained in the vertical container 40 of the storage device 3 for matching with the intermittently operating plunger extruder 4. Stored in. Before injection, the diverting valve 42 is opened and the piston 41a is pushed down to push a predetermined amount of the plastic material into the plunger pushing device 4. Then, the divert valve 42 is closed, the plastic 43 is pressurized to a predetermined pressure by the hydraulic cylinder 53, the rotary valve 54 is opened, and the plastic 43 is injected into the injection compression molding die 5 through the injection nozzle 55. The molds 61 and 62 are open, the plastic is injected into the wide cavity at low pressure and low speed, and the molds 61 and 62 are closed and compression molded. Since the plunger extrusion device 4 does not use a screw, the shearing action in the injection step is small, and the injection compression molding die 5 which injects with the molds 61 and 62 slightly opened, is used in the molding process. The shearing action is also small, and the cutting of the reinforcing fiber is prevented as much as possible in combination with the small shearing action in the plasticizing step described above.

Further, specific examples will be described below.
Polypropylene resin and 10mm as long fiber composite material
The compound long fiber pellets having a length of glass fiber (having a glass fiber content of 30% by weight) were used for molding in the apparatus shown in FIG. The high temperature inert gas circulation device 18 blows out nitrogen gas at 200 ° C., and the screw type extrusion device 2 of the bidirectionally rotating twin screw mesh has a screw diameter of 70 mm and a screw rotation number of 5
rpm, cylinder heating temperature 240 ° C. Cylinder heating temperature of plunger extrusion molding machine 240 ° C, injection speed 500cc / sec, passage diameter of injection nozzle 55 6mm
Is. Residual fiber length in molded products is 95 for 6 mm or more
%, The breakage of the reinforcing fibers was significantly improved.

In the case of extrusion molding, instead of the injection nozzle of FIG. 1, an extrusion die such as a T die is connected to form a long extrusion molded article having a desired shape such as a plate or sheet. To get it. In this case, the plunger 4 of the plunger extruder 4 moves at a constant speed. In order to operate continuously, it is possible to switch between the two plunger extruders 4.

[0024]

INDUSTRIAL APPLICABILITY The method and apparatus for molding a long-fiber composite material according to the present invention uses a different-direction rotating biaxial meshing screw type extruder having a small shearing action for plasticizing a reinforcing fiber in a plasticizing step. Less cutting, no screw used in injection process and extrusion process, injection compression molding die by compression or simple extrusion mold used in molding process, less cutting of reinforcing fiber in all processes A molded product having excellent mechanical strength can be obtained.

Further, the injection molding apparatus uses a screw type extrusion apparatus of continuous operation and a plunger type extrusion apparatus of intermittent operation, but since both are connected by a storage device, efficient continuous production is possible. .

[Brief description of drawings]

FIG. 1 is a sectional view of the entire molding apparatus of the present invention.

FIG. 2 is a plan view showing a screw of a screw type extruder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed-quantity supply device 2 Different direction rotation 2 axis meshing screw type extrusion device 3 Reservoir device 4 Plunger extrusion device 5 Injection compression molding die

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[Procedure amendment]

[Submission date] September 30, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (6)

[Claims] 1. A long-fiber composite material, which is a composite material of long-fibers and a thermoplastic resin for reinforcement, is plasticized by using a screw-type extruder with two-direction rotating twin-shaft meshing, and the plastic is extruded with a plunger. And the plastic material is injected from this plunger type extrusion device into the injection compression molding die, or
A method for molding a long fiber composite material in which a plastic material is extruded from this plunger type extrusion device into an extrusion die. 2. The long fiber composite according to claim 1, wherein the number of revolutions of the screw type extruder is set to a low ^{value such} that the shearing speed between the screw and the cylinder is 20 sec ⁻¹ or less, and the shearing force at the screw engaging portion is made small. Forming method of material. 3. The method for molding a long fiber composite material according to claim 1, wherein the long fiber composite material supplied to the twin-screw type extruder is heated in a softened state by passing a high temperature inert gas. . 4. A screw-type extruder with counter-rotating biaxial meshing for plasticizing a long-fiber composite material, which is a composite material of long fibers and a thermoplastic resin for reinforcement, and a plastic material from the screw-type extruder. A storage device for storing the material, a plunger type extrusion device for pressurizing the plastic material from the storage device, an injection compression molding die for compression molding the plastic material injected from the extrusion device, or an extruding device from the extrusion device. And a molding die for extruding a plastic material to be molded. 5. A supply device for supplying the long fiber composite material to the screw type extrusion device is provided, and a circulation device of a high temperature inert gas to the supplied long fiber composite material is connected to the supply device. The apparatus for molding a long fiber composite material according to claim 4. 6. The apparatus for molding a long-fiber composite material according to claim 4, wherein a circulating device for circulating a high temperature inert gas to the long-fiber composite material to be fed is connected to a feed portion of the screw of the screw type extruder.