JPH0756173Y2 - Reaction injection molding equipment - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reaction injection molding apparatus having a vacuum defoaming function and a pressure defoaming function.

[0002]

2. Description of the Related Art Recently, molding of parts by a casting method in which a two-component reactive liquid synthetic resin composed of a main agent such as epoxy, polyester, polyurethane and a curing agent (crosslinking agent) is injected into a cavity of a mold and cured. Has become popular. The problem with this molding method is the deterioration of appearance and physical properties due to the inclusion of air bubbles in the molded product. For molding parts using the casting method, first, the main agent and the curing agent are stirred and mixed at a predetermined ratio to form a synthetic resin solution for casting, which is poured into the cavity of the mold and then the predetermined It is done by leaving it to stand for a period of time to cure. In this case, molding is performed due to the influence of air and moisture that have entered the synthetic resin liquid during storage of the main agent and curing agent or during this stirring and mixing, the air contained in the cavity of the mold, and the gas generated during the curing reaction. Air bubbles are easily mixed in the product.

Therefore, a reaction injection molding method described in JP-A-60-120023 has been proposed as a means for preventing bubbles from being mixed into a molded product. According to this method, a switching valve is provided in the raw material passage between the mixing head and the cavity, and the raw material passage is communicated with the initial flow fractionation provided separately from the cavity by the switching valve prior to the injection of the liquid raw material, 1 to 1 of the volume of the collision mixing chamber with the mixing head
Thirty times as much liquid raw material is discharged to the initial flow fractionation, and then the raw material passage is communicated with the cavity by the switching valve, and the liquid raw material is injected into the cavity.

Besides, a vacuum defoaming method has been conventionally known. This heats the main agent (synthetic resin liquid) and curing agent,
After removing moisture and air by mixing by vacuum defoaming, etc., the synthetic resin liquid prepared by stirring and mixing both in a sealed state that prevents the inclusion of air is vacuumed in the cavity of the mold installed in the closed chamber. It is a method of injecting while performing vacuum degassing in an exhausted state. Further, this method cannot prevent the inclusion of bubbles in the molded product when the synthetic resin liquid has a property of being difficult to remove by vacuum defoaming.
A casting device described in Japanese Patent Laid-Open No. 3-222817 has been proposed. According to this device, the casting lid that houses the mold for injecting and curing the liquid synthetic resin into the cavity is connected to the resin supply mechanism that stirs and mixes the main agent and the curing agent in a sealed state, and also switches. It is a closed lid that is connected to a vacuum exhaust mechanism (vacuum pump) and a compressed air supply mechanism (compressor and pressurizing chamber connected to this) via a valve. Since the casting lid is closed and connected to the resin supply mechanism that stirs and mixes the main agent and the curing agent, the synthetic resin liquid is supplied to the mold while preventing bubbles from being mixed. Further, the mold is arranged in a closed lid, and the inside of the closed lid is first evacuated, the synthetic resin liquid is vacuum degassed and injected into the cavity, and after a lapse of a predetermined time, a vacuum is passed through a switching valve. It switches from the exhaust to the supply of compressed air and becomes pressurized. Thereby, the bubbles in the molded product are compressed and removed to prevent the inclusion of the bubbles in the molded product.

[0005]

However, the reaction injection molding method described in Japanese Patent Laid-Open No. 60-120023 mentioned above is a method of completely removing the initial flow fraction of the liquid raw material into the initial flow fractionation. , The liquid material of the first flow becomes a loss. In addition, since the initial flow fraction hardens in the initial flow fractionation, it is necessary to replace the auxiliary mold that forms the initial flow fractionation each time the injection work is performed, which is very uneconomical and difficult to prepare. It takes time and effort.

Further, the above-mentioned JP-A-63-222817.
The casting device described in Japanese Patent Publication requires a large-scale compressor and pressurizing chamber, which makes the device system complicated and large.
Therefore, a large installation space is required. Besides,
Since it is pressurized with compressed air, there is a problem that air is easily mixed in the synthetic resin liquid.

The present invention has been made in view of the above-mentioned point. By connecting a hydraulic cylinder device connected to a mixing head to a mold, the hydraulic cylinder device pressurizes the inside of the mold to push bubbles. The purpose is to enhance the defoaming treatment effect in cooperation with crushing and vacuum defoaming and to simplify the entire pressurizing mechanism.

[0008]

In order to achieve the above-mentioned object, the reaction injection molding apparatus of the present invention comprises two or more kinds of liquid raw materials which are collided and mixed in a mixing head and then injected into a cavity of a closed mold. And a reaction-molding device, wherein a vacuum pump is connected to the mold through a switching valve, and a hydraulic cylinder device is continuously connected so that its piston rod can be pushed into the mixing head. The apparatus pressurizes the inside of the mold through the mixing head.

[0009]

According to the reaction injection molding apparatus having the above structure,
When the cavity of the mold is decompressed with a vacuum pump and then sealed and kept in a decompressed state, two or more kinds of liquid raw materials are collided and mixed in the mixing head and then injected, and then mixed into the liquid raw material. The bubbles are vacuum degassed in the cavity. Then, after the liquid raw material is injected into the mold (cavity), the piston rod of the hydraulic cylinder device is pushed out and held in the mixing head (collision mixing chamber) to increase the pressure in the mold (cavity). It is then held at that elevated pressure. As a result, the bubbles remaining in the liquid raw material after vacuum defoaming are crushed (crushed), and the bubbles are surely extinguished in cooperation with the vacuum defoaming action.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional front view showing a main part of a reaction injection molding apparatus according to an embodiment of the present invention.

A cavity 2 corresponding to the shape of a molded product is formed in a mold 1 for injection molding. A vacuum pump 3 for reducing the pressure inside the cavity 2 is connected to the upper part of the mold 1 via a ball valve 4 which is a switching valve. On the other hand, the hydraulic cylinder device 5 is replaced by the mixing head 6
It is connected to the lower part of the mold 1 via. A piston rod 8 is reciprocally mounted in the cylinder 7 of the hydraulic cylinder device 5, and a hydraulic chamber 9 is formed between the inner surface of the cylinder 7 and the piston rod 8.

An expanded pressure receiving portion 10 is formed at the base of the piston rod 8, and trapezoidal protrusions 10a are connected to the front and rear of the pressure receiving portion 10. As a result, when the piston rod 8 is pulled into the cylinder 7 (FIG. 1) or pushed out (FIG. 2), the pressure receiving portion is secured even when the piston rod 8 is in contact with the base end surface or the tip end surface of the cylinder 7. There is.

The hydraulic pipes 11 and 12 are connected to hydraulic ports a and b provided at both ends of the cylinder 7, and pressure oil is injected from the hydraulic port a at the retracted position of the piston rod 8 in FIG. And the piston rod 8 is
Moves right while sliding on the inner surface of the cylinder 7.

On the other hand, in the mixing head 6, there is provided a long hollow portion in which the piston rod 8 can slide, and this hollow portion forms the collision mixing chamber 6a. When the piston rod 8 is pushed rightward in this manner, the liquid raw material that has been collision-mixed in the collision-mixing chamber 6a is pushed into the mold 1 and pressurizes the cavity 2. The mixing head 6 is connected to the mold 1 via a pipe joint 6b so that it can be attached to and detached from the mold 1.

Incidentally, as shown in the drawing, the mixing head 6
Is connected to one end of two injection pipes, that is, an injection pipe 13 for the main agent and an injection pipe 14 for the curing agent, and a throttle valve is attached to each injection pipe 13, 14.
13a and 14a are interposed. The other end of the injection pipe 13 is connected to a main agent storage tank 18 via a pressure pump 19, and the other end of the injection pipe 14 is connected to a curing agent storage tank 20 via a pressure pump 21. Each injection tube 13, 14 (one end),
A three-way switching valve 22 embedded in the wall of the mixing head 6,
23 through the injection nozzles 13b and 14b and the impingement mixing chamber 6a
It communicates with the inside. On the other hand, each three-way switching valve 22, 23 is a return pipe
The return pipes 15 and 16 are connected to one ends of the storage tanks 18 and 20, respectively. Therefore, by switching the three-way switching valves 22 and 23,
The injection pipes 13 and 14-the return pipes 15 and 16 form a circulation path via the storage tanks 18 and 20. With this configuration, the main agent and the curing agent can be circulated except when ejected into the mixing head 6. Further, a pressure gauge 17 for detecting the discharge pressure of each liquid is connected to each of the injection pipes 13 and 14.

Next, a case where injection molding is performed while defoaming bubbles using the apparatus having the above-mentioned structure will be described with reference to FIGS. 1 and 2.

First, the vacuum pump 3 is turned on to reduce the pressure inside the cavity 2 of the mold 1, and then the ball valve 4 is closed to seal the inside of the mold 1 (cavity 2). At this time, the piston rod 8 of the hydraulic cylinder device 5 is in the retracted position in FIG. The main agent and the curing agent are in a circulating state.

Here, the flow rate is adjusted by the throttle valves 13a and 14a, and then the three-way switching valves 22 and 23 are switched so that the main agent and the curing agent are injected into the collision mixing chamber 6a of the mixing head 6 from the injection nozzles 13b and 14b. Discharge. And collision mixing chamber 6
The two liquids that have been collision-mixed in a are further injected into (the cavity 2 of) the mold 1 that is vacuum-sealed. In this way, the cavity 2 is completely filled with the mixed liquid and is in a full state.
At this time, the bubbles mixed in each liquid are degassed in vacuum.
After this, as shown in FIG. 2, pressure oil is sent from the hydraulic pipe 11 to the hydraulic port a to press the pressure receiving portion 10 of the piston rod 8 and push the piston rod 8 into the collision mixing chamber 6a while sliding it. Further, the piston rod 8 is held in a state of being projected into the collision mixing chamber 6a (while the casting is completed).

Then, the pressure in the cavity 2 rises, the mixed air bubbles are crushed, and the air bubbles disappearing work is performed together with the vacuum degassing. After a certain time (curing time) has elapsed, the mixing head 6 and the mold 1 are removed at the pipe joint 6b, the mold 1 is opened, and the molded product is taken out, whereby the injection molding work is completed. After the injection of the two liquids into the mold 1, the three-way switching valves 22 and 23 are switched to return to the circulating state.

After that, the mold 1 is closed and connected to the mixing head 6 via the pipe joint 6b, and the injection molding operation may be repeated in the same manner as above.

[0021]

[Effect of the Invention] As is clear from the above explanation,
The reaction injection molding apparatus of the present invention has the following effects. (1) Vacuum defoaming is performed by injecting two or more kinds of liquid raw materials through a mixing head into a mold which is hermetically sealed after being depressurized by a vacuum pump and then kept in a depressurized state. Also, by operating the hydraulic cylinder device and pushing the piston rod into the mixing head to keep it in the pushed state until it is hardened, the pressure inside the mold is raised, so that the bubbles mixed in the liquid raw material It is effectively crushed and complements the vacuum defoaming, resulting in a high quality product without bubbles. (2) Since the hydraulic cylinder device is connected to the mixing head and the piston rod of the hydraulic cylinder device is pushed out into the mixing head to pressurize the inside of the mold, the pressure defoaming mechanism is simplified. In addition to being compact, the pressurization inside the mold can be achieved efficiently.

[Brief description of drawings]

FIG. 1 is a front view, partly in cross section, showing a main part of a reaction injection molding apparatus according to an embodiment of the present invention, showing a state when a piston rod of a hydraulic cylinder device is retracted.

2 is a front view showing a state in which a part of the reaction injection molding apparatus of FIG. 1 is defoamed under pressure by a hydraulic cylinder device in a sectional view, showing a state where a piston rod is pushed out into a mixing head.

[Explanation of symbols]

 1 Mold 2 Cavity 3 Vacuum Pump 4 Ball Valve (Switching Valve) 5 Hydraulic Cylinder Device 6 Mixing Head 6a Collision Mixing Chamber 7 Hydraulic Cylinder 8 Piston Rod 13, 14 Injection Pipe 22, 23 3-way Switching Valve

Claims (1)

[Scope of utility model registration request] 1. An apparatus for molding by mixing two or more kinds of liquid raw materials by collision and mixing in a mixing head, and then injecting them into a cavity of a closed mold to cause a reaction, wherein a vacuum is applied to the mold through a switching valve. In addition to connecting the pump, a hydraulic cylinder device is connected so that its piston rod can be pushed out into the mixing head, and the hydraulic cylinder device pressurizes the inside of the mold via the mixing head. Reaction injection molding equipment.