JPH0477221A - Molding process of multiplex molded object - Google Patents

Abstract

PURPOSE:To fill a cavity uniformly with the resin containing inorganic filler even if the flow path of the cavity is short by a method in which before the molding cavity for injection-molding the synthetic resin with which inorganic filler is mixed, is opposed to a common core, it is preliminarily heated, and then said molding cavity is moved and opposed to the common core, and further injection molding is carried out. CONSTITUTION:The necessary molding cavity of a plurality of molding cavities 6a, 6b is selectively opposed to a common core 6c, and after mold-clamping, synthetic resin is injection-molded in the cavity. After mold-opening, next molding cavity is moved and is opposed to the common core holding an injection- molded object and then injection molding is achieved similarly, whereby the multiplex molded object in which inorganic filler is mixed with at least one layer, is molded. Then, before at least the cavity 6a of a plurality of molding cavities for injection-molding the synthetic resin with which inorganic filler is mixed, is opposed to the common core 6c, the cavity is preliminarily heated by a heating device 7a, and said heated molding cavity 6a is moved and then is opposed to the common core 6c, and injection molding is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for molding a multi-layer molded product in which at least one layer contains an inorganic filler such as a conductive filler.

(Conventional technology) Conductive resin has traditionally been used for the cases and internal parts of OA equipment and home appliances as electromagnetic shielding measures and static electricity countermeasures, but in recent years, there has been a need for partial insulation, and innovative As designs become more popular, there is a demand for thin, double-walled molded products with conductive filler mixed in at least one layer.

Traditional methods for forming double molded products include injection molding each layer individually and then bonding the injection molded products together, or placing two injection devices facing each other on both sides of an injection molding device and placing a A molding cavity is reversibly provided to face the injection device, and, for example, a synthetic resin is injected between the first movable core provided on the first injection device side and the molding cavity by the first injection device. After molding the first molded product, while holding the first molded product, the molding cavity is turned over so as to face the second injection device, and the molding cavity provided on the second injection device side is A method has been adopted in which synthetic resin is injected between the second movable core and the molding cap using a second injection device, and the second molded product is integrally molded into the first molded product. In the method described above, the adhesive on the joint surface oozes out and adheres to the surface, resulting in poor appearance, and in the latter method, it is difficult to mold large molded products because a high mold clamping force cannot be obtained. For this purpose, a mold having multiple molding cavities that can be moved vertically or horizontally by a sliding mechanism is prepared, and the first molding cavity among the plurality of molding cavities is selectively opposed to the common core. After opening the mold, a second molding cavity is moved to face the common core that holds the injection molded product, and a second molding cavity is similarly injection molded to the first molded product. A method of integrally molding a molded product has been considered, but it is difficult to uniformly fill the cavity with resin mixed with a conductive filler, especially when the cavity flow path is 0.7 to 1.9 degrees. Since this is particularly difficult, attempts have been made to increase the injection pressure until a bubble appears during molding, or to heat the entire mold to fill it uniformly.

(Problem to be solved by the invention) As mentioned above, increasing the injection pressure or heating the entire mold improves filling performance, but the cooling time increases, warping and deformation occur, and productivity decreases. There was a problem.

The present invention was made to solve these problems, and an object of the present invention is to provide a method for molding a multi-layer molded product with excellent conductivity and light weight without impairing productivity.

[Structure of the Invention] (Means for Solving the Problems) The present invention selectively opposes a desired molding cavity to a common core among a plurality of molding cavities that can be moved up and down or left and right by a slide mechanism, and after mold clamping. , a synthetic resin was injection molded into the cavity, and after the mold was opened, the next molding cavity was moved to face the common core holding the injection molded product, and injection molded in the same manner, and at least one layer of the inorganic filler was mixed. When molding a multi-molded product, one of the plurality of molding molds for injection molding a synthetic resin mixed with at least an inorganic filler is heated in advance before facing the common core, and the heating The molded core is moved to face the common core, and injection molding is performed.

The molding cavity is heated to 80° C. or higher using a high-frequency induction heating device, a far-infrared irradiation device, a halogen lamp, a general-purpose heater, etc., but in any case, it is preferable to use a device with high temperature raising efficiency. It is also possible to create a special heating attachment that matches the shape of the product.

(Function) In this way, instead of heating the entire mold, the molding cavity for injection molding the inorganic filler-containing synthetic resin is heated before the molding cavity is opposed to the common core, that is, during the injection molding process in the previous process, the next molding cavity is heated. Since it is heated, there is no need to increase the injection pressure, and there is no longer cooling time that will impair productivity.Even if the cavity channel is short and thin, it can be uniformly filled with inorganic filler-containing resin, and it is highly conductive and lightweight. It is possible to obtain a multilayer molded product with excellent properties, adhesion of each layer, and good appearance.

(Example) Next, one embodiment of the present invention will be described using the drawings.

Fig. 1 is a cross-sectional view schematically showing an apparatus implementing the molding method according to the present invention, and Figs. 2 (a) and (b) show the direction in which the molding machine moves relative to the mounting position of the injection unit. The perspective view and FIG. 3 are block diagrams schematically showing the steps of the molding method according to the present invention.

As shown in FIG. 1, the injection molding apparatus has a fixed platen 1 erected on the right side and a movable platen 2 erected on the left side connected to a mold clamping device (not shown). 4 guide rods 3
is horizontally suspended, and the movable platen 2 is supported so as to be slidable in the axial direction of the rod. The fixed plate 1 has a through hole (not shown)
is formed and the injection unit 4 is attached. The injection unit has a built-in injection screw that is rotationally driven by a drive motor, and is moved in the axial direction by an operating member so that the nozzle portion is inserted into the through hole of the fixed plate. In addition, a slide guide 5a is provided on the movable platen side of the fixed platen.
A slide plate 5b is attached to this slide guide 5a, as shown in FIG.
As shown in FIG. 2(b), it is supported so as to be movable left and right. In this case, the primary injection unit 4a and the secondary injection unit 4b must be mounted in the directions shown in the drawings. A hydraulic actuator 5c is connected to the slide plate 5b, and the slide plate 5b is moved vertically or horizontally by a required distance by the operation of the hydraulic actuator 5C. This slide plate has bolt holes for mounting the mold, grooves for clamping, and a clamping device, and the molds formed at a required interval between the first molding cavity 6a and the second molding cavity 6b are attached. There is. Further, a mold in which a common core 6C is formed is attached to the movable platen 2 so as to face the primary molding cavity or the secondary molding cavity in sequence. Heating devices 7a and 7b are installed in positions that do not face the common core in either the primary molding cavity or the secondary molding cavity, facing the respective molding cavities or either one of them. It can be installed by fixing it to a part of a movable platen, by fixing it to a tie bar of a molding machine, or by providing a stand and fixing it there. Note that the reference numeral 8 in the figure is an ejector pin for releasing the molded product.

Next, a double injection molding method using the apparatus configured as described above will be explained with reference to the process diagram of FIG. 3.

First, the primary forming cap is preheated using a heating device.
process), when the surface temperature reaches 80°C or higher, the primary molding cavity is moved by the slide mechanism to face the common core (second process), and after the mold is clamped (third process), a conductive filler is placed inside the cavity. The synthetic resin is filled with the primary injection unit and injection molding is performed on the primary side, and the secondary molding cavity is preheated with a heating device (
4th step). When the molding on the primary side is completed, the mold is opened (step 5), and the slide mechanism moves it from the primary molding cavity to the secondary molding cavity whose surface temperature is 80°C or higher, facing the common core ( After the mold is clamped (seventh process), injection molding is performed on the secondary side, and during that time, the primary molding cavity is preheated (eighth process). When the injection molding on the secondary side is completed, open the mold (
9th step), the molded product is released from the mold using an ejector pin (10th step), and the slide plate is moved and replaced with the primary molding cavity. By repeating this process, the double molded product of the present invention can be continuously molded.

By the way, ABS containing conductive filler can be produced by the method of the present invention.
The system resin was heated at a resin temperature of 240°C and a mold temperature of 80°C.
It was preheated to 00°C and 120°C and injection molded.

Regarding the example and the comparative example where the mold temperature is 50°C, the product wall thickness is in order of 2.0, 1.5 dragon, 1. The minimum injection pressure required for complete filling was measured in the order of 0mm and 01. The results were as shown in Table 1. The mold uses a multi-point pin gate mold, and the injection speed is 90%.
I kept it constant. Also, the dimensions of the product are 200m+sX 3
It was set to 00.

Table 1 As is clear from Table 1, when the mold temperature is set to 80°C or higher, even if the product wall thickness is thin, it can be filled uniformly, and the injection pressure can be lower than when no heating is performed.

Furthermore, the tensile failure load was measured for double molded products obtained by injection molding the two types of materials shown in Table 2 using the method of the present invention at mold temperatures of 80°C, 100°C, and 50°C. . The results were as shown in Table 2. The tensile breaking load is based on the product dimensions: width I2.7 x 127
This is the breaking load measured by conducting a tensile test using a test piece mold with a width of I2.7 mm x 3 mm on the joint surface using MRA.

(Left below) Table 2 *PS: Polystyrene *ABS: Acrylonitrile butadiene styrene *P
PE: Polyphenylene ether As is clear from Table 2, when the mold is preheated to 80° C. or higher, the adhesion between the two layers is improved.

[Effects of the Invention] As explained above, according to the method of the present invention, the molding chamber for injection molding the inorganic filler-containing resin is preheated, so even if the cavity flow path is short, the inorganic filler can be removed without increasing the injection pressure. It is possible to obtain a multi-layer molded product that can be uniformly and completely filled with resin, has excellent conductivity, light weight, and adhesion between each layer, and has a good appearance without warping or deformation.

In addition, instead of heating the entire mold, only the necessary molding cavities are efficiently heated during the waiting time when the other molding cavity is clamping and molding, which lengthens the cooling time and impairs productivity. Not at all.

[Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing an apparatus implementing the molding method according to the present invention, FIGS. 2a and 2b are perspective views showing the mounting position of the injection unit and the direction in which the molding cavity moves, and
The figure is a block diagram schematically showing the steps of the molding method according to the present invention. 1...Fixed plate 2...Movable plate 3...Guide rod 4...Injection unit 4a... ...Primary injection unit 4b...Secondary injection unit 5a...Slide guide 5b...Slide plate 5C...Hydraulic actuator 6a... ...Primary forming cavity 6b...Second forming cavity 6C...Common core 7a...Primary side heating device 7b...Secondary side heating device 8...Protruding bottle

Claims (1)

[Claims] Of the multiple molding cavities that can be moved vertically or horizontally by a slide mechanism, the required molding cavity is selectively opposed to the common core, and after the mold is closed, synthetic resin is injected into the cavity, and after the mold is opened, the next When the molding cavities are moved to face the common core holding the injection molded product and are similarly injection molded to mold a multi-layer molded product in which at least one layer contains an inorganic filler, at least one of the plurality of molding cavities is A molding cavity for injection molding a synthetic resin mixed with an inorganic filler is heated in advance before facing the common core, and the heated molding cavity is moved to face the common core and injection molding is performed. A method for forming a multi-layered product characterized by: