JPH07318B2 - Injection compression molding method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding method and apparatus.

[0002]

2. Description of the Related Art A conventional injection compression molding apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-283520. In the injection compression molding apparatus shown in the figure, a fixed mold and a movable mold are attached to a fixed plate and a movable plate of a mold clamping device, and when the mold is closed, the convex and concave portions of the fixed mold and the movable mold fit together. However, when the molds are not completely in close contact with each other, that is, when there is a gap between the parting surfaces of the two dies, the molds are temporarily closed, injection is performed in this stopped state, and then The movable platen is moved forward and the mold is clamped to compress the molded product. This makes it possible to obtain a molded product with less distortion and high shape accuracy.

[0003]

However, in the conventional injection compression molding apparatus as described above, a porous molded article having a large number of bubble-like gas inside is molded using a foamable resin. In this case, there is a problem that it is difficult to give the surface of the molded article gloss. That is, the expandable molten resin is injected into the cavity which is not closed to foam inside the cavity, and the surface of the resin in contact with the cavity is made porous, and then the volume of the cavity is reduced and the molded product is compression molded. Therefore, the surface of the molded product cannot be made a glossy and dense surface. In addition, JP-A-62-246
There is a method for molding a foamed resin as disclosed in Japanese Patent No. 710. The molding method shown in this figure allows expansion and contraction of the cavity volume by advancing and retracting the movable die, and when the foam material is injected into the cavity in the contracted state, the movable die is moved in the cavity volume expansion direction almost at the same time, and the cavity volume is set to a predetermined value. I am trying to expand to the size of. By doing so, the cavity can be filled with the foam material even at a relatively low injection pressure, and the foam molded article can be molded by injection molding. However, in the conventional foamed resin injection molding method as described above, although the injection pressure is relatively low, it requires the injection pressure necessary to fill the foam material to the end of the cavity. The value of pressure is considerably larger than that in the case of the injection compression molding method. Further, since a relatively large pressure difference is generated between the vicinity of the gate and the end of the cavity, there is a problem that it is difficult to form a uniform foam inside. Further, it is difficult to make the surface of the molded product a glossy and dense surface. The present invention aims to solve such problems.

[0004]

According to the present invention, a resin is injected in a state where the foaming pressure of the resin is suppressed, and then a compression process is performed to cool the resin and foam the surface in contact with the cavity. The above problem is solved by solidifying the resin in the state where it is not kept, then expanding the cavity volume and foaming the resin inside. . That is, in the injection compression molding method according to the first aspect of the present invention, the molds that are fitted to each other and are relatively movable in the direction of expanding or contracting the cavity volume are positioned at a predetermined cavity volume reduction position, and foamed in the cavity. The capacity of the resin is expanded while injecting it with the resin pressure not to foam the resin, and then the mold is moved in the direction of decreasing the capacity of the resin to compress the resin, and the surface of the resin is cooled and solidified. Then, by moving the mold in the direction of increasing the cavity volume, the pressure of the resin at which foaming starts is lowered to foam the resin inside, and after cooling, the molded product is taken out. Further, in the injection compression molding method according to the second aspect of the present invention, the molds which are fitted to each other and are relatively movable in the direction of expanding or contracting the cavity volume are positioned at a predetermined cavity volume position, and the foamable melt is formed in the cavity. After supplying a gas pressure that does not cause the resin to foam, the expandable molten resin is injected, and then the mold is moved in the direction to reduce the cavity volume, thereby compressing the resin and discharging the gas. After cooling and solidifying, the mold is moved in the direction of increasing the cavity volume to reduce the resin pressure to the point at which foaming starts to foam the resin inside, and after cooling, the molded product is taken out. The second compression step may be performed between the step of foaming the resin and the step of cooling the molded product. Further, an apparatus for carrying out the above method includes a mold clamping device having a fixed plate (10) and a movable plate (12), and a fixed mold (1) attached to the fixed plate (10).
4) and a movable mold (1) attached to the movable plate (12).
6), and the movable mold (16) can be fitted to the fixed mold (14) to expand and contract the volume of the cavity (C).
The volume when the volume is most reduced can be set to be smaller than the volume at the time of molding, and the injection device capable of injecting the foamable molten resin (30a) into the cavity (C). (28) and a detector for detecting the injection state of the foamable molten resin (30a) in the cavity (C),
A controller for injecting the foaming molten resin (30a) into the cavity (C) of the mold (14, 16) before completion of mold closing, while outputting a signal for performing mold clamping based on a signal from the detector. (44) and The above detector is
A position detector (32) that detects the injection stroke of the injection device (28) may be used, and a position detector (34) that detects the stroke position of the movable plate (12) or the movable mold (16) in the mold opening / closing direction. ) May be sufficient. The apparatus of claim 7 of the present invention is a mold clamping device having a fixed plate (10) and a movable plate (12), a fixed mold (14) attached to the fixed plate (10), and a movable plate (12). A movable mold (16) attached to the movable mold (16), and the movable mold (16) is fitted to the fixed mold (14) to expand and contract the volume of the cavity (C). The volume when the volume of the cavity (C) is most reduced can be set to be smaller than the volume at the time of molding, and the foamable molten resin (30a) is injected into the cavity (C). And a movable platen (12) capable of controlling the time and starting the timing when the foamable molten resin (30a) begins to be injected into the cavity (C) and outputting a signal after a lapse of a predetermined time. When the foam is in the foaming position, it starts timing A timer (TX) for outputting a signal after the elapse while, while outputting a signal to the injection cavity (C) in the foaming molten resin (30a) of the mold closing completion before the mold (14, 16),
A controller (4) that outputs a signal for controlling the mold opening / closing direction position of the movable platen (12) based on a signal from the timer (TX).
4) and. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

Function: The foamable molten resin is injected into the cavity before the mold is closed. In the injection compression molding apparatus corresponding to claim 4 of the present invention, the injection state of the foamable molten resin is detected by the detector that detects the injection state of the foamable molten resin in the cavity, and the resin does not start foaming. ) At a predetermined timing, mold clamping is performed to a position where the volume is smaller than the molding position, the expandable molten resin is compression molded, and the resin in contact with the cavity solidifies in the unfoamed state, then expands the cavity volume and foams. Form. Further, in the injection compression molding apparatus according to claim 7 of the present invention, when the foamable molten resin starts to be injected into the cavity, timing is started and after a predetermined time elapses, the mold is clamped to a position having a smaller volume than the molding position. On the other hand, after the mold clamping, when the movable plate is again driven in the mold opening direction and positioned at the foaming position, timing is started, and after a lapse of a predetermined time, the mold clamping is performed to compression-mold the foamable molten resin. After cooling the mold, the mold is opened. By doing so, it is possible to manufacture a foam-molded article having a glossy surface and foamed inside.

[0006]

FIG. 1 shows the first embodiment of the present invention. The fixed platen 10 and the movable platen 12 of the mold clamping device are provided so as to face each other. The movable platen 12 can be moved by a mold clamping cylinder (not shown) in a direction toward and away from the fixed platen 10. A fixed die 14 is attached to the fixed platen 10, and a movable die 16 is attached to the movable platen 12. The fixed mold 14 is formed in a columnar shape having two stepped protrusions. The movable mold 16 has a "concave" cross section. The middle outer diameter portion of the fixed mold 14 can be fitted into the hole of the movable mold 16. With the movable mold 16 and the fixed mold 14 fitted together, the space C between the molds 14 and 16 forms a cavity C having a U-shaped cross section. The volume of the cavity C becomes maximum at the injection start position (the position where both molds 14 and 16 are closed but the molds are not clamped) which will be described later and which is shown in FIG. The size is such that it is minimized at the later-described compression position (mold clamping position) shown in FIG. Note that FIG.
The foaming position described later in (1) can be a volume position between the molding position shown in FIG. 7 and the maximum volume position shown in FIG. The fitting portion of the fixed mold 14 and the movable mold 16 is selected to have a size capable of discharging the air in the cavity C. A resin passage 18 that opens into the cavity C is formed in the fixed mold 14. Cavity C
It is possible to inject the foamable molten resin 30a from the injection device 28 through the resin passage 18. Injection device 2
A position detector 32 for detecting the position of the injection plunger 28a of No. 8 is attached. Position detector 32
A comparator 36 that receives the signal of (1) is provided, and the comparator 36 is provided with a setting device 38 that sets the reference position of the injection plunger 28a. The comparator 36 includes a controller 4
4 is connected. The controller 44 outputs a command signal to inject the foamable molten resin 30a into the cavities C of the molds 14 and 16 before the mold closing is completed, and the comparator 3
It is possible to control the operation of a mold clamping cylinder (not shown) by a signal from 6.

Next, the operation of the first embodiment will be described.
The position of the injection plunger 28a when the injection device 28 injects a predetermined amount of molten resin is set as the reference position by the setting device 38 in advance. This reference position signal is input to the comparator 36. When a mold clamping cylinder (not shown) is operated by a command signal from the controller 44, the movable platen 12 is temporarily stopped in a state where it moves to a mold closing midway position (injection start position) shown in FIG. . Next, in response to a command signal from the controller 44, the foamable molten resin 30a is injected from the injection device 28 into the cavity C through the resin passage 18. Injection plunger 28
When a moves forward to the right in FIG. 1 and reaches the reference position, a signal is output from the comparator 36 to the controller 44, which causes the controller 44 to output a control signal to a mold clamping cylinder (not shown). Move the movable platen 12 to the mold clamping position. The timing of the movement of the movable platen 12 is set so as to be performed before the foamable molten resin 30a in the cavity C starts foaming. As a result, the expandable molten resin 30a is spread to the corners of the cavity C as shown in FIG. That is, the surface portion of the resin which is in contact with the cavity C has gloss and is solidified as a dense surface (resin 30
b). Next, the movable platen 12 is moved in the mold opening direction by a command signal from the controller 44 at a predetermined timing.
As shown in (4), it is stopped at a foaming position of a volume larger than the molding volume. As a result, the molten resin inside starts to foam, and sufficient foaming is performed under reduced pressure (resin 30
c). Next, at a predetermined timing, the movable platen 12 is moved in the mold closing direction by a command signal from the controller 44.
It is stopped at the molding position shown in. As a result, the foamed molded product 30d having a predetermined size is molded. 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 30d is taken out. By repeating the above operation, it is possible to repeatedly manufacture the foamed molded product 30d having a glossy surface and a porous inside.

FIG. 2 shows a second embodiment of the present invention. The difference from the first embodiment of the second embodiment is that the injection device 28
Position detector 3 for detecting the position of the injection plunger 28a of
Instead of 2, the position detector 34 for detecting the position of the movable plate 12 in the mold opening / closing direction is provided. The position detector 34 may be provided on the movable mold 16 without any problem. Next, the operation of the second embodiment will be described. The reference position (movable plate reference position) of the movable plate 12 when a predetermined amount of the foamable molten resin 30a is injected into the cavity C is set in advance in the setting device 42, and the signal of this reference position is the comparator. 40 has been entered. With the movable platen 12 positioned at the injection start position shown in FIG.
The foamable molten resin 30a is injected into the cavity C from 8. With the increase in the injection amount of the foamable molten resin 30a,
The movable platen 12 is pushed upward in the figure, but the amount of movement of the movable platen 12 is detected by the position detector 34, and when the movable platen 12 reaches the movable platen reference position described above, control is performed from the comparator 40. The signal is output to the container 44. Based on this signal, the controller 44 outputs a control signal to a mold clamping cylinder (not shown), whereby the movable platen 12 moves to the compression position shown in FIG. The timing of the movement of the movable platen 12 is set so as to be performed before the foamable molten resin 30a in the cavity C starts foaming. As a result, the expandable molten resin 30a is spread to the corners of the cavity C as shown in FIG. That is, the surface portion of the resin which is in contact with the cavity C has gloss and is solidified as a dense surface (resin 30b). Next, at a predetermined timing, the movable platen 1 is sent by a command signal from the controller 44.
2 is moved in the mold opening direction and stopped at a foaming position larger than the molding volume as shown in FIG. As a result, the molten resin inside starts to foam, and sufficient foaming is performed in the depressurized state (resin 30c). Next, the movable platen 12 is moved in the mold closing direction by a command signal from the controller 44 at a predetermined timing and stopped at the molding position shown in FIG. As a result, the foamed molded product 30d having a predetermined size is molded. 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 foam molded product 3
Take out 0d.

Next, the operation of the third embodiment of the present invention will be described based on the molding process shown in FIG. When the movable platen 12 is stopped at the injection start position shown in FIG. 4 (mold closed), the injection device 28 starts injecting the foamable molten resin 30a into the cavity C (injection), and at the same time, the timer TX1 is set. Start time measurement. The timer TX1 outputs a signal to the controller 44 when the set time has elapsed. Controller 4
4 outputs a control signal to a mold clamping cylinder (not shown), whereby the movable platen 12 is moved to the compression position shown in FIG. That is, the foamable molten resin 30a is spread to every corner of the cavity C without being expanded (first compression). As a result, the resin solidifies as a dense surface having a glossy surface portion in contact with the cavity C (resin 30
b). Next, the movable platen 12 is moved in the mold opening direction by a command signal from the controller 44 at a predetermined timing.
As shown in (4), it is stopped at the foaming position where the volume is larger than the molding volume (at the same time, the timer TX2 starts measuring time). As a result, the resin in a molten state inside starts to foam (foaming), and sufficient foaming is performed under a reduced pressure (resin 30
c). When the set time of the timer TX2 elapses,
The signal is output to the controller 44. The controller 44 again outputs a control signal to the mold clamping cylinder, whereby the movable platen 12 is
It is moved in the mold closing direction and stopped at the molding position shown in FIG. 7 (second compression). As a result, the foamed molded product 30d having a predetermined size is molded. Both molds 14 and 16 are cooled (cooling), the movable platen 12 is moved in the mold opening direction to open the movable mold 16, and the foamed molded product 30d is taken out.

Next, the operation of the fourth embodiment of the present invention will be described with reference to FIG. First, the movable platen 12 is moved to the injection start position below the mold closing midway position shown in FIG. 4 (“mold closing” in FIG. 8, hereinafter the parentheses indicate the process in FIG. 8). At this time, the movable mold 16 is located at a lower position in the drawing than the molding position shown in FIG. 7, and the cavity volume is reduced. From the nozzle of the injection device 28, the foamable molten resin starts to be injected into the cavity C through the resin passage 18 (injection). When the resin injection is started, the movable platen 12 is moved in the mold opening direction. That is, the resin 30a in the cavity C
Is injected in a predetermined amount as shown in FIG. 4 while maintaining the pressure at which foaming does not start. Next, the movable platen 12 is pushed in the mold closing direction to enter the compression step shown in FIG. 5, and the resin 30a is spread to every corner of the cavity C (compression).
During the compression, the surface of the resin 30a that is in contact with the cavity C is cooled. As a result, the resin surface is solidified without being foamed. Next, the movable platen 12 is moved from the compression position shown in FIG. 5 to the foaming position shown in FIG. As a result, the resin pressure in the cavity C is reduced to the pressure at which foaming starts, so that foaming inside the resin is started, and the foamed material 30d is molded (foaming) as shown in FIG. Both molds 14 ・ 16
Is cooled (cooling), the mold is opened, and the foamed product 30d is taken out as a molded product. By repeating the above steps, a molded product having a smooth surface and a porous inside can be repeatedly manufactured.

Next, the operation of the fifth embodiment of the present invention will be described with reference to FIG. The steps of FIGS. 4 to 7 are performed in the same manner as in the first embodiment. That is, the movable mold 16 is pushed down to a predetermined injection start position where the volume of the cavity C is smaller than the molding position (“mold closing” in FIG. 9, hereinafter the parentheses indicate the process in FIG. 9), and in this state From the injection device 28 through the resin passage 18 to the cavity C, the foamable molten resin 30a
Is injected (injection). The movable mold 16 is moved upward in the drawing so as to increase the volume of the cavity C in synchronization with the injection of the resin. After the injection of the resin is completed, the movable mold 16 is moved downward in the drawing to compress the resin in the cavity C (first compression). Cavity C during compression
The surface of the resin 30aa that is in contact with is cooled. As a result, the resin surface is solidified without being foamed. Next, the movable platen 12 is moved from the compression position shown in FIG. 5 to the foaming position shown in FIG. This foaming position is a position with a larger cavity volume than the molding position shown in FIG. As a result, the resin pressure in the cavity C is reduced to a pressure at which foaming starts, so that foaming inside the resin is started and the foamed material 30c is molded (foaming) as shown in FIG. Next, the movable mold 16 is moved to the molding position shown in FIG. 7, and the foamed material 30c is compressed into a molded product 30d (second compression).
Both molds 14 and 16 are cooled (cooling), the mold is opened, and the molded product 30d is taken out. By repeating the above steps,
A molded product having a smooth surface and a porous inside can be repeatedly manufactured. In the fifth embodiment, a sufficient foaming volume is ensured during the foaming process, so that a molded product with stable dimensional accuracy can be obtained without causing insufficient foaming.

Next, a sixth embodiment of the present invention will be described. Figure 1
0, the other configuration is the same as that shown in FIG. 4 except that the movable mold 16 is provided with the gas supply / discharge passage 22. Next, the operation of the sixth embodiment will be described. First, the movable platen 12 is lowered from the mold open state to a predetermined cavity volume position shown in the figure and stopped. Next, the gas supply / discharge channel 2
Cavity C is a pressurized gas adjusted to a predetermined pressure from 2
Supplied within. The gas pressure is set to a level such that the expandable molten resin can be injected into the cavity C, and does not start foaming when the resin is supplied. Next, from the injection device 28 to the foamable molten resin 30a
Is injected into the cavity C (the amount of gas corresponding to the amount of resin injected is discharged from the gas supply / discharge channel 22). Resin 3
After the injection of 0a, the movable platen 12 moves to a compression position below the position shown in FIG. 10 and spreads the resin to every corner of the cavity C (all the gas in the cavity C is discharged from the gas supply / discharge passage 22). Discharged). In this state, the gas pressure applied to the gas supply / discharge channel 22 is released to atmospheric pressure. During the compression, the surface of the resin 30a that is in contact with the cavity C is cooled. As a result, the resin surface is solidified without being foamed. Next, the movable platen 12 is moved to a molding position above the compression position to expand the capacity of the cavity C and foam the resin inside. After the molding is completed, the mold is opened and the molded product is taken out.

In the above description, the movable platen 16 is stopped at the position shown in FIG. 4, for example. However, it may be moved at a slight speed without being stopped. Also the third
Although the two timers TX-1 and TX-2 are provided in the embodiment, one timer may be used as long as it can perform a plurality of operations. In the description of the sixth embodiment described above, after cooling the surface of the resin 30a in the cavity C, the cavity volume is expanded to the molding position. However, similar to that described in the fifth embodiment, Alternatively, the cavity volume may be once expanded to a state larger than the molding position to sufficiently foam the resin inside, and then reduced to the molding position. In this way, it is possible to manufacture a molded product with good dimensional accuracy without causing insufficient foaming.

[0014]

As described above, according to the present invention,
It is possible to produce a foam-molded article having a glossy surface and a porous inside. Even if the molded product has a thin portion or a rib portion, these portions can be surely made porous. Since the molten resin is injected into the cavity before the mold is closed, the injection pressure may be low and the mechanical device can be inexpensive. The expansion ratio of the resin can be controlled arbitrarily. Therefore, it is possible to obtain a foamed state according to the weight, strength, etc. required of the molded product.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a process of a third embodiment of the present invention.

FIG. 4 is a diagram showing a state in which a foamable molten resin is injected into a cavity.

FIG. 5 is a diagram showing a state in which the expandable molten resin in the cavity is compressed without being expanded.

FIG. 6 is a view showing a state in which a foamable molten resin in a cavity is foamed.

FIG. 7 is a view showing a state where foamed resin in a cavity is compression molded.

FIG. 8 is a diagram showing a process of a fourth embodiment of the present invention.

FIG. 9 is a diagram showing a process of a fifth embodiment of the present invention.

FIG. 10 is a diagram showing a sixth embodiment of the present invention.

[Explanation of symbols]

 10 Fixed Plate 12 Movable Plate 14 Fixed Mold 16 Movable Mold 18 Resin Passage 22 Gas Supply / Discharge Flow Path 28 Injection Device 30a Foaming Molten Resin 30d Foam Molded Product 32 Position Detector 34 Position Detector 36 Comparator 38 Setter 40 Comparator 42 Setting device 44 Controller TX1 timer TX2 timer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // B29C 45/70 7365-4F B29K 105: 04

Claims (7)

[Claims] 1. A mold which fits into each other and is capable of relative movement in a direction of expanding or contracting the cavity volume is positioned at a predetermined cavity volume reduction position, and is maintained at a resin pressure that does not cause foamable molten resin to foam in the cavity. While moving, the mold is moved in the cavity volume expansion direction, then the mold is moved in the cavity volume contraction direction to compress the resin, the surface of this is cooled and solidified, and then the mold is Is moved again in the direction of increasing the capacity of the cavity to lower the resin pressure at which foaming starts to foam the resin inside, and after cooling, an injection compression molding method in which the molded product is taken out. 2. A mold which is fitted into each other and is capable of relatively moving in a direction of expanding or contracting the cavity volume is located at a predetermined cavity volume position, and a gas pressure of a size that does not cause foamable molten resin to foam in the cavity. With the
Injecting expandable molten resin, then moving the mold in the direction of cavity volume reduction to compress the resin and discharge gas, cool the surface of the resin to solidify it, and then expand the mold volume An injection compression molding method in which the resin pressure inside the resin is reduced to a pressure at which foaming starts by moving the resin in the direction to foam the resin inside, and after cooling, the molded product is taken out. 3. The injection compression molding method according to claim 1, wherein a second compression step is performed between the step of foaming the resin and the step of cooling the molded product. 4. A mold clamping device having a fixed plate (10) and a movable plate (12), a fixed mold (14) attached to the fixed plate (10), and a movable mold attached to the movable plate (12). (16) and, and the movable mold (16) has
The cavity (C) is fitted to the fixed mold (14).
It is possible to increase and decrease the volume of the cavity (C), and the volume when the cavity (C) volume is most reduced can be set to be smaller than the volume at the time of molding. An injection device (28) capable of injecting a foamable molten resin (30a) into the cavity, and a cavity (C)
A detector for detecting the injection state of the foamable molten resin (30a) in the inside and a signal for injecting the foamable molten resin (30a) into the cavity (C) of the mold (14.16) before the mold closing is completed. An injection compression molding apparatus having a controller (34) which outputs a signal for performing mold clamping based on a signal from the detector while outputting the signal. 5. The injection compression molding apparatus according to claim 4, wherein the detector is a position detector (32) for detecting an injection stroke of the injection device (28). 6. The injection compression molding apparatus according to claim 4, wherein the detector is a position detector (34) for detecting the stroke position of the movable plate (12) or the movable mold (16) in the mold opening / closing direction. 7. A mold clamping device having a fixed plate (10) and a movable plate (12), a fixed mold (14) attached to the fixed plate (10), and a movable mold attached to the movable plate (12). (16) and, and the movable mold (16) has
The cavity (C) is fitted to the fixed mold (14).
It is possible to increase and decrease the volume of the cavity (C), and the volume when the cavity (C) volume is most reduced can be set to be smaller than the volume at the time of molding. An injection device (28) capable of injecting a foamable molten resin (30a) into the cavity, and a cavity (C)
When the foamable molten resin (30a) begins to be injected into the inside, the clock is started and a signal is output after a predetermined time has elapsed, while when the movable plate (12) is located at the foaming position, the time is started and the signal is output after the predetermined time has elapsed. And a signal for injecting the foamable molten resin (30a) into the cavity (C) of the mold (14.16) before completion of mold closing, while the timer (TX) outputs The movable plate (1
An injection compression molding apparatus having a controller (44) for outputting a signal for controlling the position of the mold opening / closing direction of 2).