JPH09323338A - Injection molding method and apparatus for foam molded article - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a manufacturing method and an apparatus for continuously molding a foam-molded article by achieving accurate weighing and improving gas solubility in a molten resin. SOLUTION: A gas and a molten resin are agitated by repeating the rotation and extrusion of a screw 2. To stir the gas and the molten resin, first, the gas and the molten resin are transferred to the front of the heating cylinder containing the sleeve 7 with the outer peripheral groove by the rotation of the screw, and then the groove 18 of the sleeve 7 with the outer peripheral groove is extruded by the screw extrusion. The gas and the molten resin are transferred to the rear of the heating cylinder via the same, and the rotation by the screw and the extrusion operation are repeated. The injection into the mold cavity 6 is performed by inserting the resin flow passage holes connected to the plurality of grooves of the sleeve with the outer peripheral groove into the needle valve 10.
After closing with, the screw 2 is pushed out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for continuously producing foam.

[0002]

2. Description of the Related Art As a conventional method for producing a fine foam by dissolving a gas in a molten resin and injecting it into a mold to form a fine foam, gas is supplied to a heating cylinder as described in US Pat. No. 5,160,674. Then, the gas and the molten resin are stirred and measured by rotating a screw built in the heating cylinder. Further, the injection of the molten resin in which the gas is melted into the mold cavity is also performed by the screw extruding operation. This method is the same as the general injection molding that has been widely used in the past, except for the gas supply step. That is, the method of stirring and measuring the gas and the molten resin by rotating the screw is not described in detail.

[0003]

FIG. 10 shows an injection mechanism section of a conventional injection molding machine. The structure is heating cylinder 1, screw 2, hopper 13, shut-off nozzle 5, motor.
20, a gas supply unit 24, and a gas pipe 16. The pelletized resin 12 in the hopper 13 is transferred to the high temperature heating cylinder 1 by the rotation of the screw 2 and melted, and is mixed and stirred with the gas injected from the gas supply port, and the gas is dissolved in the molten resin. Thereafter, the molten resin is injected into the mold cavity 6 through the shutoff nozzle 5 as the screw 2 advances. The amount of resin injected into the mold cavity 6, that is, the measurement on the molding machine side is controlled by the screw rotation speed and time, and a pressure value called back pressure that opposes the screw retreat. However, when the gas is dissolved in the molten resin as in the prior art, the molten resin in which the high-pressure gas is dissolved remains inside the heating cylinder 1 and the shutoff nozzle 5 in the first injection stage. For this reason, the pressure at the front of the heating cylinder remains high due to the pressure of the residual molten resin. And
Just before the rotation of the screw for measuring, the screw retracts at the stage where the back pressure is still ineffective, and there arises a problem that predetermined measuring becomes impossible. In order to solve this problem, it is necessary to eliminate the residual resin in order to remove the residual pressure after each injection. However, it is difficult to eliminate the residual molten resin due to the structure of the injection molding machine. In addition, performing several shots without gas supply to prevent residual pressure leads to increased costs in continuous production.

Further, in the prior art, since the gas and the molten resin are stirred during the measurement, there are cases where the gas is insufficiently dissolved in the molten resin and the foaming is insufficient.

An object of the present invention is to solve these problems of the prior art.

[0006]

In order to solve the problems of the prior art and to provide a manufacturing method for continuously molding various foam molded articles by injecting a molten resin in which a gas is melted into a mold cavity, The following method and structure were adopted.

The gas and the molten resin are agitated by repeating the rotation and extrusion of the screw. The gas and the molten resin are agitated by first transferring the gas and the molten resin to the front of the heating cylinder having the sleeve with the outer circumferential groove by the rotation of the screw, and then through the groove of the sleeve with the outer circumferential groove by the extrusion of the screw. The gas and the molten resin were transferred to the rear of the heating cylinder, and the rotation and the extrusion operation by this screw were repeated. The injection into the mold cavity is performed by closing the resin flow passage holes connected to the plurality of grooves of the sleeve with outer peripheral groove with a needle valve and then pushing out the screw.

In another method, even when the screw is continuously rotated, the gas and the molten resin are repeatedly transferred to the front and the rear of the heating cylinder through the groove of the sleeve having the outer peripheral groove to stir the gas and the molten resin. Thus, the gas can be dissolved in the molten resin.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The method and apparatus for producing a foam-molded article of the present invention will be described in detail below.

(Embodiment 1) FIG. 1 is a sectional view showing an injection mechanism portion of an injection molding apparatus of the present invention. FIG. 2 is a perspective view of a sleeve with an outer peripheral groove incorporated in the heating cylinder of FIG.
3 to 5 are enlarged cross-sectional views of the vicinity of the needle valve mounting portion, FIG. 3 shows a state in which gas and molten resin are supplied into the heating cylinder, and FIG. 4 shows a state in which only molten resin is supplied to the heating cylinder. And FIG. 5 shows a state in which neither gas nor molten resin is supplied. FIG. 6 is a perspective view of a molded product manufactured according to the present invention. FIG. 7 is a partially enlarged view of FIG.

The manufacturing method and apparatus will be described below along with the process. In FIG. 1, the pellet resin 12 is put into a hopper 13. The resin moves in front of the heating cylinder by rotating the screw back with the motor 20 to start molding.
Transferred to 59. At that time, the needle valve 10 is tightened with the needle 11 downward so that neither the resin nor the gas is supplied, as shown in FIG. Next, after closing the hopper valve 14 provided in the hopper 13, the valve of the gas pipe 16 is closed.
Open 15 and supply about 20 MPa of carbon dioxide gas. As shown in FIG. 3, the needle valve 10 is left completely open. Then, the screw is advanced. Then, the molten resin is transferred to the trough portion 9 of the screw through the groove portion 18 of the grooved sleeve 7 shown in FIG. Next, the molten resin and gas are transferred to the front part of the heating cylinder by retreating while rotating the screw again. By repeating this while supplying the gas, the gas is gradually dissolved in the molten resin. The number of repetitions needs to be set according to the type of resin used, the amount of resin to be injected, and the gas supply pressure. In this embodiment, an acrylonitrile-butadiene-styrene copolymer is used, and the amount of resin injected is 70 g,
Repeated 3 times. After this repeated operation, the valve 15 for supplying the gas is closed, the needle valve 10 is completely closed as shown in FIG. 5, and the screw is pushed out to inject and fill the mold cavity 6. In addition, the injection nozzle 51 adopts a hydraulic sealing nozzle,
It is designed so that it can be opened and injected only when high pressure is applied during injection. Furthermore, the screw 2 is provided with a check ring 8 that is generally used, and a gap is formed when the molten resin is transferred forward, and the gap is closed so that the molten resin does not flow backward when injected. It is supposed to be.

After the second shot, the needle valve 10 after injection
By opening the nozzle halfway as shown in Fig. 4,
Residual pressure due to residual resin around 59 is made uniform over the entire heating cylinder. Therefore, at the time of measurement for the next injection, it is possible to prevent the screw from moving backward without measuring.

In the present invention, the valve 15 and the needle valve 1 are controlled by the control unit 100 of the molding machine body as shown in FIG.
By controlling 0, the hopper valve 14 and the screw 2, a series of operations can be performed fully automatically.

A foamed molded product 21 manufactured according to the present invention is shown in FIG. Further, although a partially enlarged view thereof is shown in FIG. 7, it was possible to obtain a molded product in which the central portion 22 in the thickness direction was finely foamed and the surface 23 was non-foamed.

(Embodiment 2) FIG. 8 shows the overall structure of an injection molding apparatus according to a second embodiment of the present invention. The manufacturing method and apparatus will be described below along with processes. Pellet resin
12 is thrown into the hopper 13. The screw 2 is rotated to start molding. By doing so, the resin is transferred to the front part 59 of the heating cylinder, but the resin is transferred to the front part of the heating cylinder until the resin is filled up to the tip 91 of the valley of the screw, that is, the screw 2 is not retracted. Let At that time, the needle valve 90 tightens the needle 11 and keeps it closed. Next, after closing the hopper valve 14 provided in the hopper 13, open the valve 95 of the gas pipe 96 to
Carbon dioxide gas of 20 MPa is supplied and the needle valve 90 is also completely opened. Then, rotate the screw. Then, the molten resin is transferred to the valley portion of the screw through the groove portion 18 of the grooved sleeve 7 shown in FIG. 2 and the needle valve 90 built in the heating cylinder 101, and is melted by the screw 2 which is continuously rotating. The resin and gas are transferred to the front part of the heating cylinder. By continuously performing this while supplying gas, the gas gradually dissolves in the molten resin. It is necessary to set the circulation time of the molten resin in the heating cylinder according to the type of resin used, the amount of resin to be injected, and the gas supply pressure. In the present embodiment, the acrylonitrile-butadiene-styrene copolymer was used, and the amount of the resin to be injected was 70 g, and circulation was performed for about 30 seconds. After this circulation, the valve 95 for supplying gas is closed, and the needle valve 10 is completely closed as shown in FIG. After that, the mold cavity 6 is injected and filled by being extruded. The injection nozzle 51 and the check nozzle 8 used were the same as those described in the first embodiment of the invention.

After the second shot, the needle valve 90 after injection
Is opened, the residual pressure due to the residual resin in the vicinity of the nozzle front part 5 is made uniform over the entire heating cylinder. Therefore, when transferring the molten resin forward for the next injection,
It is possible to prevent the screw from moving backward.

As described in the first embodiment, the valve 100, the needle valve 90, the hopper valve 14 and the screw 2 are controlled by the control unit 100 of the molding machine body shown in FIG. I decided to do it.

According to the present invention, a foam molded article similar to that of the first embodiment of the invention can be obtained.

[0019]

EFFECTS OF THE INVENTION According to the present invention, in a method for injection molding of a foamed molded product in which a molten resin in which a gas is melted is injected into a mold for molding, a stable injection amount is ensured and molding of sufficient foaming is performed. It is possible to provide a method and an apparatus for continuously manufacturing products.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an injection mechanism portion of an injection molding device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a sleeve with an outer peripheral groove built in the heating cylinder of FIG.

FIG. 3 is a sectional view of the vicinity of a needle valve mounting portion.

FIG. 4 is a sectional view of the vicinity of a needle valve mounting portion.

FIG. 5 is a cross-sectional view near a needle valve mounting portion.

FIG. 6 is a perspective view of a molded product manufactured according to the present invention.

7 is an explanatory diagram of a portion A in FIG.

FIG. 8 is a cross-sectional view showing an injection mechanism portion of the injection molding device according to the second embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a state in which operations of various valves and screws are controlled by the control unit of the molding machine main body of the present invention.

FIG. 10 is a cross-sectional view showing a conventional injection mechanism section.

[Explanation of symbols]

1 ... Heating cylinder, 2 ... Screw, 6 ... Mold cavity, 7 ...
Grooved sleeve, 8 ... Check ring, 9 ... Screw trough, 10 ... Needle valve, 15 ... Valve, 59 ... Heating cylinder front part, 100 ... Control part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Iida 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock Engineering Co., Ltd.

Claims (5)

[Claims] 1. An injection molding method for a foamed molded article, wherein a molten resin in which gas is dissolved is injected into a mold for molding, and the screw and the molten resin are retracted by rotating a screw built into a heating cylinder. It is sent to the front of the heating cylinder, the screw is moved forward, and the gas and the molten resin are sent to the rear of the heating cylinder through the groove of the grooved sleeve incorporated in the heating cylinder, and this operation is repeated to make the gas A method for injection-molding a foam-molded article, comprising: 2. An injection mechanism section of an injection molding apparatus comprising a resin supply section, a heating cylinder having a built-in screw, and a shut-off nozzle, and a plurality of grooves for circulating molten resin around the outer periphery of the heating cylinder. An injection molding apparatus comprising a grooved sleeve having a rib and a resin flow path, wherein gas supply and stop are performed by opening and closing a needle valve provided at the center of the heating cylinder. 3. Injection of molten resin in which gas is dissolved into a mold cavity, residual pressure release in a heating cylinder and shutoff nozzle immediately after injection, supply and measurement of resin, supply of high pressure gas and supply of gas and molten resin The injection molding apparatus according to claim 2, further comprising a controller for performing continuous stirring operation. 4. An injection molding method for a foamed molded article, wherein a molten resin having gas dissolved therein is injected into a mold for molding, wherein stirring of the gas and molten resin is carried out by rotating a screw to form a grooved sleeve built into a heating cylinder. An injection molding method for a foam-molded article, which comprises repeatedly transferring the gas and the molten resin to the front and the rear of the heating cylinder through a groove, and then injecting the molten resin having the gas dissolved into a mold. 5. The injection molding apparatus according to claim 4, further comprising a gas supply unit with a check valve at a front portion of the heating cylinder and a plurality of needle valves at a rear portion of the heating cylinder for opening and closing resin flow passage holes.