JPH04113822A - Injection compression molding and device thereof - Google Patents

Abstract

PURPOSE:To manufacture a molded article, the foamed state of which is uniform and the dimensional stability of which is favorable, by a method wherein molten foamable resin is injected in the cavity of a mold before the completion of mold closing and, after that, mold clamping is carried out by detecting the foamed state of the resin so as to compress the molten foamable resin in order to form the molded article. CONSTITUTION:By means of command signal emitted from a controller 34, molten foamable resin 30 is injected from an injection device through a resin passage 14a in a cavity C. After that, the pressure in the cavity C is detected with a pressure sensor 20 so as to compare the detection pressure outputted from the pressure sensor 20 with the reference pressure by a comparator 24. When the measured output coincides with the reference pressure, signal is outputted from the comparator 24 to the controller so as to drive a movable platen 12 on the basis of the command signal emitted from the controller 34 in order to clamp the mold. Thus, compression forming is performed under the state that the pressure in the cavity C is held at atomspheric pressure so as to turn a molten foamable resin 30a into a foamed article 30b having a U-shape in crosssection.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an injection compression molding method and apparatus.

(b) Conventional technology As a conventional injection compression molding apparatus, for example,
There is one shown in Japanese Patent No. 283520. In the injection compression molding apparatus shown in this figure, a fixed mold and a movable mold are attached to the fixed plate and the movable plate of the mold clamping device, respectively, and when the mold is closed, the convex portions and concave portions of the fixed mold and the movable mold fit into each other. However, in a state where the molds are not completely in contact with each other, that is, in a state where there is a gap between the parting surfaces of both molds, mold closing is temporarily stopped, injection is performed in this stopped state, and then further injection is performed. The molded product is compressed by moving the movable platen forward and clamping the mold. As a result, a molded product with less distortion and high shape accuracy can be obtained.

(c) Problems to be Solved by the Invention However, in the conventional injection compression molding apparatus as described above, a porous molded product containing a large number of bubbles of gas inside is molded using a foamable resin. In some cases, there is a problem in that it is difficult to determine the timing of mold clamping after resin injection. That is, if the timing of this mold clamping is too early, compression molding will not substantially be performed, making it impossible to obtain a molded product in a uniformly foamed state. Furthermore, if the mold clamping timing is too late, it will be the same as simply compressing the molded product after foaming is completed, and the dimensions of the molded product after being removed from the mold will be larger than the predetermined size.

The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention solves the above problems by injecting a foamable molten resin into the cavity before closing the mold and clamping the mold according to the foaming state of the foamable molten resin. Solve. That is, the injection compression molding method corresponding to claim 1 of the present invention injects the foamable molten resin (30) into the cavity (C) of the mold (14, 16) before the mold closure is completed, and expands the resin. By detecting the state and performing mold clamping, the foamable molten resin (30) is compressed to form a molded product (30b).

Moreover, the injection compression molding method corresponding to claim 2 of the present invention is as follows:
The foamable molten resin (30) is injected into the cavity (C) of the mold (14, 16) before the mold is closed, and after a preset time has elapsed, the foamable molten resin is (30) is compressed to form a molded product (30b).

Further, an apparatus for carrying out the injection compression molding method according to claim 1 of the present invention includes a mold clamping device having a fixed platen (10) and a movable platen (12), and a fixed mold (10) attached to the fixed platen (10). 14), a movable mold (16) attached to the movable platen (12), and a foamable molten resin (
The sensor (20) detects the foaming state of the mold (30), and the sensor (20) injects the foamable molten resin (30) into the cavity (C) of the mold (14, 16) before completion of mold closing.
0), and a controller (34) that causes the mold to be clamped in response to a signal from the controller (34).

The sensor may be a pressure sensor (20) that measures the pressure in the cavity (C), or a temperature sensor (28) that measures the temperature of the foamable molten resin (30). It may also be a proximity sensor that detects passage of the molten resin (30). Note that the symbols in parentheses indicate corresponding members in the embodiment.

[e) Inject foamable molten resin into the cavity before closing the working mold. In the injection compression molding method according to claim 1 of the present invention, the foaming state of the foamable molten resin is detected by detecting any one of the pressure inside the cavity, the temperature of the foamable molten resin, etc. , the mold is clamped at a predetermined timing, and the foamable molten resin is compression molded. Further, in the injection compression pot-shaped blade method corresponding to claim 2 of the present invention, the mold is clamped after a preset time has elapsed after injection is completed, and the foamable molten resin is compression-molded.

After cooling the mold, the mold is opened. By doing so, it is possible to produce a molded article that is uniformly foamed and has good dimensional stability.

(F) Embodiment Figures 1 to 3 show a first embodiment of the present invention. A fixed platen 10 and a movable platen 12 of the mold clamping device are provided facing each other. The movable platen 12 is movable in the direction toward and away from the fixed platen 10 by a mold clamping cylinder (not shown).

A fixed mold 14 is attached to the fixed platen 10, and a movable mold 16 is attached to the movable plate 12. The fixed mold 14 is formed into a columnar shape having two stepped protrusions. The movable mold 16 has a "concave" shape in cross section. An intermediate outer diameter portion of the fixed mold 14 can be fitted into a cylindrical hole of the movable mold 16. Movable mold 1
6 and fixed mold 14 are fitted together, both molds 1
The space between 4 and 16 forms a cavity C having a U-shaped cross section. Fixed mold 14
The fitting portion of the movable mold 16 is selected to have dimensions that allow the air in the cavity C to be confined in the position shown in FIG. A resin passage 14a opening into the cavity C is formed in the fixed mold 14. A resin passage 1 is connected to the cavity C from an injection device (not shown).
It is also possible to inject foamable molten resin through 4a. On the left side wall of the movable mold 16 in the figure, there is a cavity C.
A through hole 16a passing through is formed, and a branch pipe 18 is attached to this.

A pressure sensor 20 is attached to one end of the branch pipe 18, and a two-position switching valve 22 is attached to the other end thereof in a normally closed position. The two-position switching valve 22 is capable of communicating the cavity C with the atmosphere when switched to the open position.

The pressure sensor 20 is equipped with a comparator 2 that uses the signal as a human input.
4 is connected, and the comparator 24 is provided with a setting device 26 for setting a reference pressure. A controller 34 is connected to the comparator 24 . The controller 34 instructs to inject the foamable molten resin 30 into the cavities C of the molds 14 and 16 before the mold closing is completed, and also sets the two-position switching valve 22 to the open position based on the signal from the comparator 24. It is possible to give commands to switch and to perform mold clamping.

Next, the operation of this first embodiment will be explained. A reference pressure is set in the comparator 24 in advance by the setter 26. The movable platen 12 is moved to the middle of the mold opening position shown in FIG. 1 and then stopped. Next, in response to a command signal from the controller 34, the foamable molten resin 30 is injected from an injection device (not shown) into the cavity C through the resin passage 14a. Due to the action of the foaming agent contained in the foamable molten resin 30, the foamable molten resin 30
As shown in the figure, the foamable molten resin 30a is expanded. This increases the air pressure within the cavity C, and this pressure is detected by the pressure sensor 20.

The detected pressure output from the pressure sensor 20 is detected by the comparator 24.
compared to the reference pressure. When the measured pressure matches (or becomes higher than) the reference pressure, comparator 2
4 outputs a signal to the controller 34, and in response to the command signal from the controller 34, the two-position switching valve 22 is switched to the open position, and the movable platen 12 is driven again to clamp the mold as shown in FIG. be done. As a result, compression molding is performed with the inside of the cavity C at atmospheric pressure, and the foamable molten resin 3
0a is a foamed molded product 30b having a U-shaped cross section. Both molds 14 and 16 are cooled, the movable platen 12 is moved in the mold opening direction, the movable mold 16 is opened, and the foamed molded product 30 is opened.
Take out b. Next, the two-position switching valve 22 is returned to the normally closed position. By repeating the above operations, the foam molded product 30
b can be produced repeatedly.

Next, FIG. 4 shows a second embodiment of the present invention. Movable mold 16
In the upper surface of the figure, there is a through hole 16b communicating with the cavity C.
is formed, and a temperature sensor 28 is hermetically fixed to this. The temperature sensor 28 is capable of measuring the temperature of the foamable molten resin 30. The installation position of the through hole 16b is selected so that the foamable molten resin 30 foamed in the cavity C comes into contact with the heat sensitive part of the temperature sensor 28 when expanded to a preset volume. The output signal of the temperature sensor 28 is input to a temperature controller 32. The temperature regulator 32 includes a controller 3.
6 is connected. The controller 36 instructs to inject the foamable molten resin 30 into the cavities C of the molds 14 and 16 before the mold closing is completed, and also instructs the mold to be clamped by a signal from the temperature controller 32. Is possible. The fitting portions of the molds 14 and 16 are selected to have dimensions that allow air to be discharged from between them, so that when the movable platen 12 moves downward from the illustrated position, the mold 14
- It is possible to reduce the volume of cavity C by discharging air from between 16 and 16. The rest of the structure is the same as that of the first embodiment, so the same members as those of the first embodiment are given the same reference numerals and the explanation thereof will be omitted.

Next, the operation of this second embodiment will be explained. A resin reference temperature is set in the temperature regulator 32 in advance. The movable platen 12 is moved to the middle of the mold closing position shown in FIG. 4 and then stopped. Next, in response to a command signal from the controller 36, the foamable molten resin 30 is injected from an injection device (not shown) into the cavity C through the resin passage 14a. When the foamable molten resin 30 expands due to the action of the foaming agent contained in the foamable molten resin 30 and comes into contact with the heat-sensitive portion of the temperature sensor 28, the temperature sensor 28 begins to measure the temperature of the resin. The air inside the cavity C is pushed by the expansion of the foamable molten resin 30 and the molds 14 and 16
is discharged to the outside through the fitting gap. When the measured temperature matches (or becomes higher than) the set temperature, the temperature regulator 32 sends a signal to the controller 36, and the movable platen 12 is driven again by the command signal from this point to clamp the mold. Both molds 14 and 16 are cooled, the movable platen 12 is moved in the mold opening direction to open the movable mold 16, and the foamed molded product is taken out.

Next, a method according to a third embodiment of the present invention will be explained along with its operation. Expandable molten resin is injected into the cavity before the mold is closed, and time measurement begins at the same time. After a preset time has elapsed, a compression process by mold clamping is performed. The mold clamping start time is selected to be an appropriate timing before foaming is completed. After the cooling process, the mold is opened and the foam molded product is taken out.

In the above description, the resin passage 14a is provided in the fixed mold 14, but it may be provided in the movable mold 16.

Furthermore, in the above explanation, the movable platen 12 is stopped in the middle of mold closing and the foamable molten resin 30 is injected. It is also possible to inject the foamable molten resin 30.

Furthermore, in the above description, the two-position switching valve 22 is switched at the same time as the mold opening resumes, but it can also be switched at a timing different from the mold opening restart.

Note that although the pressure sensor 20 that measures the pressure in the cavity C or the temperature sensor 28 that measures the resin temperature is used as the sensor, a proximity sensor that senses the passage of the resin or the like may also be used.

(G) As described in detail, according to the present invention, the foamable molten resin being foamed is compressed to fit the cavity, so that a foamed molded product with a uniform foamed state can be manufactured. I can do it. Even if the molded product has thin-walled parts or ribbed parts, these parts can be reliably made porous. Furthermore, since the mold is clamped before foaming is completed, porous compression molded products with good dimensional stability can be produced. Since the molten resin is injected into the cavity before the mold is closed, the injection pressure can be low, and the mechanical device can be made inexpensive. The foaming ratio of the resin can be controlled arbitrarily. Therefore, a foamed state can be obtained that matches the weight, strength, etc. required for the molded product.

[Brief explanation of the drawing]

Fig. 1 is a structural explanatory diagram showing a cross section of an injection compression apparatus according to a first embodiment of the present invention, Fig. 2 is a diagram showing an expanded state of the foamable molten resin, and Fig. 3 shows a state after compression molding is completed. Figure, 4th
The figure is a cross-sectional view for explaining the structure of an injection compression device according to a second embodiment of the present invention. 10 ・Fixed plate, 12. ・Movable plate, 14... Fixed mold, 16. ・Movable mold, 18. ・Branch piping, 20
...Pressure sensor, 28...Temperature sensor, 30...
Expandable molten resin foam molding/control device, ・Cavity. Patent patent applicant Japan Steel Works, Ltd.

Claims (1)

[Claims] 1. Cavity (C) of the mold (14, 16) before completion of mold closing
), the foamable molten resin (30) is injected, the foamed state of the resin is detected, and the mold is clamped, thereby compressing the foamable molten resin (30) and molding the molded product (30b). Molding method. 2. Cavity (C) of mold (14, 16) before mold closing is completed
), and after a preset time has elapsed, the mold is clamped to compress the foamable molten resin (30) and mold the molded product (30b). Compression molding method. 3. A mold clamping device having a fixed platen (10) and a movable platen (12), and a fixed mold (14) attached to the fixed platen (10).
) and a movable mold (16) attached to the movable platen (12).
), a sensor (20) that detects the foaming state of the foamable molten resin (30) in the cavity (C), and a sensor (20) that detects the foaming state of the foamable molten resin (30) in the cavity (C), and a sensor (20) that detects the foaming state of the foamable molten resin (30) in the mold cavity (C) before mold closing is completed An injection compression molding apparatus that includes a controller (34) that injects resin (30) and performs mold clamping based on a signal from a sensor (20). 4. The injection compression molding apparatus according to claim 3, wherein the sensor is a pressure sensor (20) that measures the pressure in the cavity (C). 5. The injection compression molding apparatus according to claim 3, wherein the sensor is a temperature sensor (28) that measures the temperature of the foamable molten resin (30). 6. The injection compression molding apparatus according to claim 3, wherein the sensor is a proximity sensor that detects passage of the foamable molten resin (30).