JPH06270185A - Degassing method of reaction injection molding and device therefor - Google Patents

Abstract

PURPOSE:To contrive to prevent product defect due to bubbles from developing by a method wherein the bubbles during molding are escaped from a cavity by vibrating a mold through he movement of the center of gravity the load of a mold clamping device during the reaction injection molding of two-pack molding material. CONSTITUTION:Vibration is generated by rotating a motor 18, which is mounted to the side portion of a movable platen 14 and to which a circular disc weight 20 having an off-set center of gravity. The vibration is transmitted to the whole mold clamping device and molds 10 and 12 for vibrating them. Accordingly, even if the bubbles developing in a cavity formed by the molds 10 and 12 are caught, the bubbles ascend stably and escape. The closing of the movable mold 10 and the fixed mold 12 is detected with a sensor and the influx amount of resin in the cavity is detected with the flow meter of resin. On the basis of these detection signals, the vibration is outputted by a controlling device. Accordingly, the vibration continues over the period of time ranging from the start of the pouring of the resin to the end of its curing, resulting in preventing a defective product due to residual bubbles from developing.

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 degassing reaction injection molding, and more particularly to a method and apparatus for removing gas that causes generation of product defects due to air or gas entrainment. Regarding

[0002]

2. Description of the Related Art Reaction injection molding (hereinafter referred to as RIM molding (Reac
(tion injection molding) is used as a molding method for urethane, nylon, and dicyclopentadiene (DCPD). This is because the pressure at the time of molding is low, so that the die manufacturing cost can be made low (the die rigidity is not required to be so high). for that reason,
It has the advantage of being able to produce a small amount of plastic products at low cost (the die amortization cost is low). Therefore, it is often used for parts such as construction machines and boards whose monthly production is less than 5000 pieces.

The viscosity of the liquid of the molding material used for RIM molding is 500 to 1,500 cps for urethane and 5 to 300 for DCPD.
Very low as cps (100,000 for thermoplastics for injection molding)
~ 1,000,000 cps: Plastic Age August 1989),
Generally, two or more liquids are poured into a mold cavity, and a polymerization or polycondensation reaction is performed in the cavity to cure the liquid.

In such RIM molding, for example, as shown in FIG. 4, when the product having the window 1 is injected from the gate port 2, air is easily entrained in the reaction side of the window. However, in the RIM molding, since the molding pressure is very low, unlike the injection molding, when bubbles are mixed, it is not possible to crush the bubbles by pressure or to push them to the vent port by pressure. In addition, since the resin used for injection molding has a high viscosity, this air will not escape, but R
Before the hardening of the IM material, it goes up in the liquid in the direction opposite to gravity. Then, the bubbles are expelled to the vent port for venting. At this time, since the pressure is low, the method of expelling the bubbles by the pressure from the vent port cannot be adopted.

Therefore, conventionally, a method of expelling bubbles together with the resin from a large gap, that is, a method of ejecting bubbles to a portion where burr is generated has been used. This burr is shaved off after molding. Thus, in actual RIM molding,
When bubbles are mixed in, a method of escaping the bubbles by gravity is used. At this time, as one means for directing the gas venting vent in the direction opposite to gravity, the mold clamping device itself is tilted so that the gas venting vent of the mold is directed upward, which is the opposite direction of gravity. I am trying to do it.

[0006]

However, in the conventional method, the gas or air in the mold cavity rises due to the buoyancy, so that a slight damage to the cavity,
If there are burrs remaining in the previous shot molding, air bubbles are caught in the burrs, and curing proceeds while stopping at that portion, and the air bubbles are trapped in the product.

Further, as shown in FIG. 5, when the air bubbles stop in the middle of the mold cavity and do not come out to the burr portion, the air bubbles remain at the end of the product. Shot).

Naturally, if the air bubbles come out on the surface of the product, they will become defective in surface defects, and even if they enter between the meat of the product, if they are strong parts, those parts will become stress concentration points and the strength will be increased. It is an undesired defect because it lowers it. Naturally, the short shot is defective because it lacks meat.

Further, since the product defect due to the bubbles is caused by a fine resistance, it does not occur every shot, and the next shot in which a fine residue remains in the cavity or the mold surface is not sufficiently cleaned. It will occur in the next shot. Therefore, even if the molding conditions are constant, the production quality is not stable, leading to poor yield.

It is an object of the present invention to provide a method and an apparatus for letting air bubbles during molding escape without staying in the middle of a mold cavity, as opposed to the conventional molding method which is apt to cause such product defects. To do.

[0011]

In order to achieve the above object, the method of degassing a reaction injection molding according to the present invention is to inject two or more molding materials into a mold cavity and During molding in reaction injection molding, which cures by polymerization or polycondensation reaction,
It is configured to vibrate the mold. In this case, the vibration is performed after the injection of the reactive solution into the mold cavity is completed and before the reaction curing of the polymer is completed.

Further, the vibration may be generated by performing a minute tilt and a tilt return of the mold clamping device once or a plurality of times, or by attaching a vibration device that generates vibration by moving the load center of gravity of the mold clamping device. You can do this.

In a degassing apparatus for reaction injection molding according to the present invention for realizing the above method, a fixed mold and a movable mold forming a cavity are attached, and the fixed mold and the movable mold are opened and closed. In a reaction injection molding apparatus having a mold opening / closing cylinder, a sensor for detecting closing of a movable mold and a fixed mold, a flow meter for measuring resin flowing into a cavity, a fixed mold and a movable mold. And a control device that outputs vibration to the vibration device in response to signals from the flow meter and the contact sensor.

[0014]

According to the above construction, it is possible to prevent the bubbles from stopping and staying in the fine resistance portion by vibrating the mold during molding, and to prevent the bubbles from being caught.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of a gas injection method for reaction injection molding according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an apparatus configuration for realizing the degassing method for RIM molding according to the first embodiment. RI
In the M molding machine, the upper and lower molds 10 and 12 are respectively moved to the movable platen 14,
The fixed mold 12 mounted on the fixed plate 16 is driven by the mold clamping cylinder to drive the movable plate 14
On the other hand, the movable mold 10 is joined to perform mold clamping, and a molding material is supplied to perform molding in the cavity.

In such a molding machine, the movable plate 1 is
The motor 18 is attached to the side surface of No. 4, and the motor 18
A disc weight 20 having a decentered center of gravity is attached to the motor, and the motor 18 is rotated to generate vibration. Vibration caused by a so-called vibrator attached to the movable plate 14 not only vibrates the mold clamping device as a whole, but also vibrates the molds 10 and 12. Therefore, even when air bubbles are caught in the cavity, the vibration is caught. Bubbles can also be stably raised.

This vibration may be performed throughout the mold clamping, but it may be performed until the air bubbles are actually generated and the rising is completed. Therefore, the vibration is generated from the start of the resin injection to the end of the injection and the completion of curing. Just let me.

FIG. 2 shows an apparatus configuration for realizing the gas venting method according to the second embodiment. In this example, the whole mold clamping device is configured to largely oscillate and vibrate. That is, the mold clamping device connects the fixed platen 16 and the end plate 22 with the rod 24, and the movable platen 14 is driven by using the rod 24 as a guide. A mold clamping cylinder 26 is attached to the end plate 22 so that the movable platen 14 can be driven. A supporting shaft 28 serving as a swinging fulcrum is attached to the stationary platen 16 in such a mold clamping device, and the entire mold clamping device can be swung about this supporting shaft 28. Then, a tilt cylinder 32 connected between the side end of the upper end plate 22 and the fixed frame 30 is connected, and the expansion and contraction action of the tilt cylinder 32 allows the mold clamping device to be oscillated around the support shaft 28. ing. A flow path switching valve 34 is connected to the tilt cylinder 32, and the hydraulic pressure supplied from a pressure oil supply source 36 is shorted to the rod side or the bottom side during or after resin injection into the tilt cylinder 32. If it is introduced in time and then the pressure oil injection is stopped, vibration can be generated by the inclination and its stop.

In this embodiment, the fixed mold 12 and the movable mold 10 are closed by the mold clamping cylinder 26 before the liquid injection is started. Next, the entire mold clamping device is tilted at an angle that facilitates the removal of bubbles during molding. This tilt is performed by the tilt cylinder 32.

When the pressure change oil is introduced into the chilled cylinder 32 by operating the tilt switching valve 34, if the rod side and the bottom side are repeated, the mold clamping device oscillates reciprocally, and forced vibration can be repeatedly applied. is there. The vibration by the tilt cylinder 32 may be one vibration, but may be during the same vibration time as that by the motor 18 in the first embodiment.

FIG. 3 shows an apparatus configuration for realizing the degassing method according to the third embodiment. In this example, a fixed mold 52 and a movable mold 53 forming a cavity 51 are attached to a mold clamping device (not shown), and the movable mold 53 is moved to the movable mold 53 toward the fixed mold 52. A mold opening / closing cylinder 54 is provided. The fixed mold 52 is provided with a contact sensor 55 that detects that the movable mold 53 has come into contact with the fixed mold 52. Further, the mold clamping device includes a vibrating cylinder 56 of a vibration device that vibrates the fixed mold 52 and the movable mold 53 while the resin flows into the cavity 51 after the fixed mold 52 and the movable mold 53 come into contact with each other. It is installed. The vibration cylinder 56 may be hydraulic, pneumatic, or electric. The fixed mold 52 has a flow meter 5
7 and DCPD are mixed with a mixing head 58 for mixing two liquids (A, B), and two mixing machines 60, 61 are connected to the mixing head 58.
Reference numerals 0 and 61 are connected to two-liquid (A, B) compounded liquid tanks 62 and 63 for accommodating DCPD.

Signals from the contact sensor 55 and the flow meter 57 are input to the control device 70 including a controller, the mold opening / closing cylinder 54, the vibration cylinder 56, and the like.
A command is output to the mixing head 58 and the injectors 60 and 61.

The operation of the above configuration is as follows. After the previous product is taken out, the mold opening / closing cylinder 54 is operated to move the movable mold 53 toward the fixed mold 52, and the molds 52 and 53 are brought into contact with each other to be closed. At this time, the contact sensor 55 detects the contact between the two molds 52 and 53 and detects the contact with the control device 7.
It outputs to 0 that both molds 52 and 53 are closed. The controller 70 outputs a command to the mixing head 58 and the injectors 60, 61 in response to the closing of the molds 52, 53 to operate the mixing head 58 and the injectors 60, 61. As a result, the DC from the mixed liquid tanks 62 and 63
The two liquids (A, B) of PD are injected into the mixing head 58. The flow meter 57 measures the flow rate that passes through and outputs a measurement signal to the control device 70.

The controller 70 determines the volume of the two liquids (A, B) that have passed through the flow rate signal from the flow meter 57 and the time.
When the control device 70 determines that the predetermined amount has passed, a command is output to the vibrating cylinder 56. The vibration cylinder 56 gives a vibration to the fixed mold 52 and the movable mold 53 according to a command,
Bubbles are discharged from the mixed solution of the two liquids (A and B) in the cavity 51 to a reservoir through a film gate (not shown).

In the above construction, the flow meter 57 attached to the fixed mold 52 was used, but a lightweight pump was used as an injection machine to measure the discharge amount and the resin amount injected into the cavity from the time. Is also good. Further, although the contact of the mold is detected by the contact sensor, the position of the mold may be detected.

Further, in the above description, the term fixed mold is used, but it is a term for a movable mold, and as mentioned above, the fixed mold does not vibrate or swing. Further, the example in which the fixed mold is stopped and the movable mold approaches is shown, but both molds may move and come into contact with each other to form a cavity.

The control drive for vibrating the mold clamping device using the above-described device configuration is performed as follows. The RIM material is supplied as a mixture of two or more liquids, and the motor is detected by detecting the time when the pumping of the material is started from the mixing part of the material to the mold cavity closed by the pump or the time when the mold clamping is completed. 18 or the tilt cylinder 32 is driven to apply vibration to the mold clamping device. This vibration is for preventing the bubbles from staying in the cavity, and it is not necessary to give a high frequency, and it may be set to have a frequency of about 1 to 10 Hz. Then, when the cooling time in the cavity elapses, or when the time when the polymerization or polycondensation reaction starts to start, the stop signal is output to the vibration applying means. By controlling in this way,
The bubbles generated in the cavity are smoothly guided to the vent port even if they are stagnating inside due to a minute scratch or the like, and it is possible to prevent the generation of defective products due to this.

[0029]

As described above, the present invention is applicable to reaction injection molding in which two or more molding materials are injected into a mold cavity and a curing or polymerization reaction is carried out in the cavity to effect curing. During molding, the mold is configured to vibrate, and the vibration is set to be performed after the injection of the reactive solution into the mold cavity until the reaction curing of the polymer is completed. The mold clamping device is configured to generate a slight tilt and return to one or more times, or to be generated by moving the load center of gravity of the mold clamping device, and is controlled by the mold clamping sensor and the flow rate detection of the molding material. Since it is possible to escape bubbles during molding without staying in the middle of the mold cavity, it is possible to reliably prevent residual bubbles in reaction injection molding and improve the problem of product defects. Effect that can Rukoto is obtained.

[Brief description of drawings]

FIG. 1 is a side view showing an apparatus configuration for realizing a degassing method of reaction injection molding according to a first embodiment.

FIG. 2 is a side view showing an apparatus configuration for realizing a gas injection method for reaction injection molding in a second embodiment.

FIG. 3 is a configuration diagram of an apparatus for realizing a reaction injection molding degassing method in a third embodiment.

FIG. 4 is an explanatory diagram of a gas entrainment occurrence state during conventional reaction injection molding.

FIG. 5 is an explanatory diagram of a product defect.

[Explanation of symbols]

 10 movable mold 12 fixed mold 14 movable plate 16 fixed plate 18 motor 20 disk weight 22 end plate 24 rod 26 mold clamping cylinder 28 swing support shaft 30 fixed frame 32 tilt cylinder 34 flow path switching valve 36 pressure oil supply source

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29C 45/34 7158-4F 45/76 7365-4F

Claims (5)

[Claims] 1. Vibrating a mold during molding in reaction injection molding in which two or more molding materials are injected into a mold cavity and a polymerization or polycondensation reaction is carried out in the cavity to effect curing. A degassing method for reaction injection molding, which is characterized by: 2. The degassing for reaction injection molding according to claim 1, wherein the vibration is performed after the injection of the reactive solution into the mold cavity is completed and before the reaction curing of the polymer is completed. Method. 3. The vibration is characterized in that a slight tilt and a tilt return of the mold clamping device are performed once or a plurality of times.
Alternatively, the method of degassing the reaction injection molding according to the item 2. 4. The degassing method for reaction injection molding according to claim 1, wherein the vibration is generated by mounting a vibration device that generates vibration by moving a load center of gravity of the mold clamping device. 5. A reaction injection molding apparatus in which a fixed mold and a movable mold which form a cavity are attached, and which has a fixed mold and a mold opening / closing cylinder for opening and closing the movable mold, and the movable mold and the fixed mold. A sensor that detects when the mold is closed, a flow meter that measures the resin that flows into the cavity, a vibration device that vibrates the fixed mold and the movable mold, and a vibration from the signals from the flow meter and the contact sensor. A reaction injection molding apparatus comprising: a control device that outputs vibration to the device.