JPH0475807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an injection molding apparatus for foam molded articles, and particularly to an injection molding apparatus improved so that silver stripes do not appear on the surface of the molded article.

<Prior Art> A conventional injection molding apparatus for foam molded products is shown in FIG. 7, for example. This injection molding apparatus includes a main cylinder 2, a hopper 1 for supplying thermoplastic resin A into the main cylinder 2, and a main screw 3 that rotates and moves forward and backward by a transmission connected to a screw rotation motor. A mixing nozzle 6 having a static mixer 5 is interposed between the head portion of the cylinder 2 and a mold 7 for resin molding, and the screw 3 is used to mold thermoplastic resin A.
is injected into the mold 7. Also,
A sub cylinder 8 having an injection capacity of 5 to 10% of the injection capacity of the cylinder 2 is connected to the cylinder head 4, and a thermoplastic synthetic resin and a blowing agent supplied by a hopper (not shown) or the like are supplied to the sub cylinder 8. The mixture D is injected into the cylinder head 4 by a screw provided in the sub-cylinder 8. Also, the rear part of the mixing nozzle 6, that is, the cylinder head 4
The connecting portion of the sub-cylinder 8 including the cylinder 2 is equipped with a control mechanism for injecting or stopping the mixture from the sub-cylinder 8 at any time during the process of injecting the thermoplastic resin by the cylinder 2. As a result of molding foam molded products of various sizes with this configuration, molded products with smooth and beautiful surfaces and substantially uniformly foamed insides are obtained. That is, in order to configure the gate portion of the molded product with a skin layer, injection from the sub-cylinder 8 is stopped immediately before the completion of one shot injection, and the injection is again switched to only the resin from the main cylinder 2. By this process, while the sprue and runner parts are finally filled, the foamable resin in the mixing nozzle 6 is replaced with the non-foamable resin in the main cylinder 2, so that foaming does not occur at the beginning of the next shot. It disappears.

<Problems to be solved by the invention> However, in such conventional injection molding equipment, depending on the shape of the molded product and the way the gate is formed, the capacity of the sprue and runner is small, and the mixing nozzle The foamable resin in the molded product may not be completely replaced, and as a result, a small amount of air bubbles may be partially exposed on the surface of the molded product at the beginning of the next shot, and silver stripes may appear on the surface of the molded product. Taking this situation into consideration, a resin reservoir with a capacity of about 20 to 80 c.c. is provided in the middle of the sprue or runner of the mold, and the resin that is likely to cause silver streaks at the initial stage of the injection process is introduced into this resin reservoir. There is a method to prevent silver streaks from forming on the surface of the molded product. In this case, the resin introduced into the resin reservoir is released from the mold together with the molded product.
Since it is collected and reused, the loss of the resin itself is minimal, but there is a problem in that additional man-hours are required for collection and crushing, which reduces workability.

The present invention was made in view of these points, and its purpose is to provide injection molding of foam molded products that can obtain foam molded products with beautiful surfaces without silver streaks without creating resin pools by improving the mixing unit. The purpose is to provide equipment.

<Means for Solving the Problems> In order to achieve the above object, the present invention includes a main cylinder and a sub cylinder, and while different resin materials are injected from both, one of these resin materials can be injected singly or is a molding apparatus equipped with a mixing unit that mixes and injects the resin, and the mixing unit is provided with a passage for one type of resin and a passage for the other type of resin, and a cylinder connection of these passages. The gist is that valve members are provided at the side end and the nozzle connection end, respectively, and injection control is performed by operating these valve members.

<Function> First, in the first stage of injection operation, the passage hole for thermoplastic resin conduction is opened by the operation of the valve member, while the passage hole for mixed resin conduction is closed, and the thermoplastic resin flows from the main cylinder to the mixing unit. It is sent to the mold through the Next, in the second stage of injection operation, the sub-cylinder is also turned on and the passage hole for the thermoplastic resin is closed by the operation of the valve member, while the passage hole for the mixed resin is opened. Therefore, the two types of resins are kneaded in the mixing unit to form a mixed resin, which is sent to a mold to form a mixed resin layer inside the thermoplastic resin. Then, in a third injection operation, the injection operation state of the first step is returned, and the runner and sprue portion are filled with thermoplastic resin to form a resin molded article. Since switching of the passage holes in each stage is performed by valve members provided at the inlet and outlet portions of the mixing unit, residual resin from the previous injection operation in the second stage only accumulates in the narrow space of the nozzle hole. As a result of the injection operation in the third stage, silver streaks hardly appear on the surface of the molded product.

<Example> FIGS. 1 to 6 are diagrams showing the structure of an injection molding apparatus and the injection molding operation process according to an example of the present invention. This injection molding device has a main cylinder 12
, a screw 13 that rotates and moves back and forth in the axial direction within the main cylinder 12 , and a mixing unit 16 connected to the cylinder head 14 of the main cylinder 12 .
and the mixing unit 16 via the connecting pipe 20.
and an auxiliary cylinder 18 connected to the auxiliary cylinder 18. The main cylinder 12 is configured to inject the non-foaming thermoplastic resin A supplied into the main cylinder 12 from an opening 14a of a cylinder head 14 by means of a screw 13.

The mixing unit 16 includes a unit main body 15 having a cylindrical structure and having a nozzle 21 at the tip and a flange portion 22 at the rear end.
The flange portion 22 is connected to the main cylinder with the flange portion 22 in contact with the cylinder head 14. The unit main body 15 has a chamber 24 formed at the center of the base end thereof, which communicates with the opening 14a of the cylinder head 14 and receives the resin sent from the main cylinder 12. A central hole 25 extending along the central hole 2
Passage holes 26 and 27 are provided at the top and bottom (or left and right) of the chamber 5 and communicate with the chamber 24, respectively. The tips of the center hole 25 and the passage holes 26 and 27 are the nozzle 2.
It is connected to 1. Inside the center hole 25, screw members 28 of right-handed and left-handed twists are loaded to constitute a static mixer. In addition, a communication pipe 20 is provided at the rear end portion of the central hole 25.
An injection hole 29 connected to is provided. The control mechanism 23 includes a valve member, ie, a first socket 30, which is fitted vertically into the rear end of the unit body 15 of the mixing unit 16, and a valve member, ie, a first socket 30, which is fitted in the vertical direction at the tip of the unit body 15. a second pot 31; an operating cylinder 32 that is connected to the second pot 31 and rotates the second pot 31; and a first pot 30 that rotates in response to the movement of the second pot 31. It consists of a link mechanism 33 that transmits power for movement. 1st
A through hole 34 is formed at a position corresponding to the central hole 25 and a through hole 34 for communicating the central hole 25 and the chamber 24, and a through hole 34 is formed at a position corresponding to the passage holes 26 and 27 in the pot 30. , 27 are formed to communicate with the chamber 24.
A through hole 37 is formed in the second pot 31 at a position corresponding to the central hole 25 to communicate the central hole 25 and the noise hole 21a.
Communication holes 38 and 39 are formed at positions corresponding to the passage holes 26 and 27 to communicate with the nozzle hole 21a. The relationship between the through hole 34 and the communicating holes 35, 36, or the relationship between the through hole 37 and the communicating holes 38, 39, is such that, for example, the relationship between the through hole 34 and the communicating holes 38, 39 is 90 degrees apart from each other in a plane perpendicular to the central axis of each pot 30, 31 They are formed with an angular relationship of degrees, so that when one is in a communicating state, the other is in a closed state.

However, the communication hole 34 or 37 formed in each pot 30, 31 and the communication hole 35, 36 or 38, 39
intersect with each other at an angle of 90 degrees, but as illustrated for the first pot 30 in FIG. The through holes 34, 37 and the communicating holes 35, 36,
The dimensions of 38 and 39 are set.

Furthermore, when the through hole 34 is in communication between the first kettle 30 and the second kettle 31, the through hole 37
The control mechanism 23 is set so that when the communication holes 35 and 36 are in communication, the communication holes 38 and 39 are also in communication.

The sub-cylinder 18 has a built-in sub-screw 19, in which foamable resin D is produced by mixing thermoplastic resin B and foaming agent C, and is passed through the connecting pipe 20 and injection hole 29 to the center hole 2 of the mixing unit 16.
Send to 5.

In an injection device having such a configuration, when performing resin molding, the sub cylinder 18 is supplied with the same or different but compatible resin as that supplied to the main cylinder 12, and 2 to 5% of a chemical blowing agent. The mixture is fed and kneaded by the sub-screw 19. Next, when injecting the resin material, first set the barrels 30 and 31 in the state shown in FIG.
4 to the passage holes 26, 2 of the mixing unit 16.
7 and is shot in a predetermined amount from the nozzle 21 into the mold 7 (FIG. 4). At any time during this injection,
At the same time as the foamable resin D is injected from the sub-cylinder 18 through the communication pipe 20, the actuating cylinder 32 rotates the tips 30 and 31 by 90 degrees. As a result, the mixing unit 16 enters the state shown in FIG. 2, and the resin injected from the main cylinder 12 is introduced into the central hole 25 and is kneaded with the foamable resin by the static mixer to become the mixed resin E. It is supplied to the nozzle 21 through the hole 37 and injected into the mold 7 through the nozzle hole 21a. By this injection, the kneaded mixed resin flows inside the previously shot thermoplastic resin A and is shot into the mold 7 according to the principle of molten resin flow, and is shot inside the thermoplastic resin A. A foam layer is formed in the form of fine closed cells (Fig. 5). Before completing the injection of a predetermined amount of the mixed resin material, stop the operation of the sub-screw 19 to stop the injection from the sub-cylinder 18, and at the same time operate the operating cylinder 32 to rotate the screws 30 and 31 by 90 degrees. When the state shown in FIG. 1 is restored, the thermoplastic resin injected from the main cylinder 12 passes through the passage holes 26 and 27 again, and is injected into the mold 7 through the nozzle hole 21a. As a result, the sprue and gate portion are formed of thermoplastic resin (FIG. 6), and the injection process is completed. The volume of the nozzle hole 21a is usually a small value of 3 to 5 c.c., and the through holes 34, 37 and communication holes 35, 36, 38,
39 is such that when the tips 30 and 31 are rotated 90 degrees, one opens before the other closes, so the nozzle hole is closed while the resin at the end of injection fills the sprue and runner. Inside 21a, the resin containing the foaming agent is replaced with the resin not containing the foaming agent. Therefore, there is no possibility that silver stripes will appear on the surface of the formed product at the beginning of the next shot.

<Effects of the Invention> As explained above, according to the present invention, a mixing unit connected to a plurality of cylinders for injecting different types of resin materials is provided with a flow path through which different resins pass through, thereby improving the efficiency of injection work. Since the communication to the nozzle is switched, the previously shot resin will not be mixed in when switching shots, and silver streaks will not appear on the surface of the molded product, making it possible to obtain a foamed molded product with a smooth and beautiful surface. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main parts of an injection molding apparatus according to an embodiment of the present invention, viewed from the front side, FIG. 2 is a sectional view taken along the line - - in FIG. The figure is a sectional view showing the configuration of the kettle in the above embodiment, Figures 4, 5 and 6 are diagrams showing the resin flow in the mold due to the operation of the above embodiment, and Figure 4 is a diagram showing the flow of resin in the mold due to the operation of the first stage injection operation. Figure 5 is a diagram showing the flow of thermoplastic resin. Figure 5 is a diagram showing the flow of foamable resin due to the second stage injection operation. Figure 6 is a diagram showing the flow of thermoplastic resin due to the third stage injection operation. 7
The figure is a sectional view showing the main parts of a conventional injection molding device. 1...Hopper, 2,12...Main cylinder, 3,
13... Main screw, 4, 14... Cylinder head, 6... Mixing nozzle, 7... Mold,
8, 18... sub cylinder, 9, 20... connecting pipe,
16... Mixing unit, 23... Control mechanism, 25... Center hole (mixed resin passage), 26,
27... Passage hole (thermoplastic resin passage), 30...
...First pot (valve member), 31...Second pot (valve member).

Claims (1)

[Claims] 1 Equipped with a main cylinder and a sub-cylinder, one injects thermoplastic resin and the other injects foaming resin material, while a mixing unit with a nozzle attached to the tip is connected to these cylinders to inject both types of resin. In an injection molding apparatus that mixes or non-mixes, the mixing unit is provided with a passage for the thermoplastic resin and a passage for the mixed resin, and a passage is provided at the end of the cylinder connection side of these passages. is provided with a valve member that controls the mixing of the different types of resins, and a valve member that switches and controls the injection of mixed resin and non-mixed resin is provided at the nozzle installation end of the passage, and the valve member is operated to control the injection of mixed resin and non-mixed resin. An injection molding device for foam molded products, characterized in that injection is controlled using a foam molding device.