KR100246928B1 - Plastic forming method offering high quality appearance of product - Google Patents

Abstract

The present invention provides a molding method for obtaining a plastic molded article having a desired high quality appearance, and in the gas assist molding method of a thermoplastic resin, when a molten thermoplastic resin is injected into a mold, a mold temperature of the mold is injected. It is a molding method to obtain a plastic molded article having a high-quality appearance that is controlled to be a temperature 10-100 ℃ higher than the heat deformation temperature.

Description

Plastic molding method with high quality appearance

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for obtaining a plastic molded article applicable to a field requiring high quality surface appearance in molded parts such as exterior parts and outer plates of various products, in particular, weld lines and jetting. The present invention relates to a molding method for obtaining a plastic molded article having a high-quality appearance for eliminating appearance defects caused by poor appearance and inorganic filler filler.

Conventionally, when inert gas is injected into a molded article in the gas assist molding method, a thick portion called a gas channel is formed in order to mold the hollow portion as a target. This thick part is designed to give a difference in product thickness from the general surface of the molded part and to selectively enter the inert gas into the thick part. However, due to the difference in product thickness, weld lines occurred because the flow rates of the molten resin in the general surface and the gas channel part were different, which damaged the appearance of the molded product.

In addition, in the case of extremely thick molding having a product thickness of more than 10 mm, which is a characteristic of gas assist molding, jetting occurs due to the strong resin temperature because molten resin causes extreme volume expansion when it flows through the gate in the mold to the product part. And damaged molding appearance.

In addition, in the gas assist molding, when the resin filled with the inorganic filler is used, the mold transfer property is poor because the resin pressure in the mold is lower than that of the general injection molding, and the inorganic filler floats on the molded article surface to damage the appearance of the molded article.

In order to solve these problems, it is well known to set the molding resin temperature and the mold temperature high. However, there is a drawback that the molding cycle becomes long because the time required for the cooling and solidification of the molten resin is required. In addition, when the mold temperature is set above the heat deflection temperature of the resin, there is a problem that the molten resin is not hardened and cannot be released.

An object of the present invention is to provide a method for molding a hollow molded article that can eliminate the drawbacks of conventional gas assist molding and obtain a plastic molded article having a desired high quality appearance.

SUMMARY OF THE INVENTION An object of the present invention is to form a product shape in a gas assist molding method having a hollow molded part used as an automobile part such as a roof rail, a door handle, a grip, an office device such as a fax machine, a copier, a housing of a household electrical appliance, and the like. When injecting molten resin in one cycle, the mold temperature is set to 10-100 ° C higher than the thermal deformation temperature of the resin to be molded, and the mold temperature that can be controlled 0-100 ° C lower than the thermal deformation temperature of the resin in the cooling process. This can be solved by the molding method of the hollow molded article using the control system and the mold structure thereof.

The mold temperature control system used in the present invention is used to stop cold water and cooling oil at elevated temperature and to use hot water, heating oil or electrothermal heater alone or in combination, and to supply hot water, heating oil or electrothermal heater during temperature drop. Stop the cold water and coolant to the same mold temperature control pipe or to each mold temperature control pipe.

At this time, the higher the temperature of the hot water and heating oil used for the elevated temperature, the lower the temperature of the cold water and cooling oil used for the temperature drop, and the larger the flow rate, the shorter the molding cycle becomes possible. For electric heaters, the higher the power density, the better.

The more it is installed in the range where there is no problem in mold strength with respect to the mold temperature control pipeline, the better the efficiency and the shorter the cycle becomes possible.

According to the present invention, when the mold temperature is higher than the heat deformation temperature at the time of injection of the molten resin, the molten resin can be filled in a sufficient molten state without being rapidly cooled.

By filling in the molten state in this manner, jetting and weld lines can be eliminated. In addition, the transfer rate of the mold is dramatically improved, the gloss of the molded article is improved, and the filler is completely lifted off for the inorganic filler filling material, and a molded article having excellent appearance quality equivalent to that of the non-filling material can be obtained.

1 is a block diagram showing a schematic configuration example of a mold temperature control system suitable for carrying out the molding method according to the present invention.

2 is a cross-sectional view showing a configuration example of an embodiment of a mold suitable for carrying out the molding method according to the present invention.

3 is a perspective view showing an embodiment of a molded article molded by the molding method according to the present invention.

* Explanation of symbols for main parts of the drawings

1: temperature controller for hot water 2: chiller for cold water

3: switching and control unit 4: mold

5: Heat and cold water supply path to the mold 6: Heat and cold water return from the mold

7: fixed mold 8: movable mold

9: Cavity 10: Tanggu

11: gate 12: gas inlet

EMBODIMENT OF THE INVENTION Hereinafter, this invention is disclosed, referring an accompanying drawing which shows an Example. 1 is a block diagram showing a schematic configuration of a mold temperature control system suitable for carrying out a molding method of a molded article according to the present invention.

This mold temperature control system arranges the temperature controller 1 for hot water and the chiller 2 for cold water, and is connected to the switching unit 3. The switching / control unit 3 includes a supply port 5 for supplying cold water and hot water to the mold 4 and a return port 6 for recovery. In order to achieve a desired mold temperature, the switching and control unit 3 is controlled so that the respective switching valves VIN and VR in the apparatus are in an appropriate state.

2 is a cross-sectional view of a mold suitable for carrying out the molding method according to the present invention. The mold is formed with a cavity 9 at the mating surface of the stationary mold 7 and the movable mold 8, and the stationary mold 7 has a spout 10 and a gate (10) for filling molten resin in the cavity 9. 11), the movable mold 8 has a gas inlet 12 for injecting gas into the filled resin.

In this embodiment, the modified PPO resin Noryl GFN3 (trademark: made by Japan Plastic Co., Ltd., glass fiber filling amount: 30%), and an alloy of polycarbonate resin and polybutylene terephthalate resin, XENOY 1760 (trademark: Japan Paper Plastics, and a glass fiber filling amount of 10%). In order to confirm the effect of the examples, the same mold was used and the molding was performed at the mold temperature used for ordinary gas assist molding and the like.

3 is a schematic view of a molded article obtained by injection molding using the mold of FIG. It has the thickness part 13 which forms the hollow part by gas injection. Molding of this example was performed according to the molding conditions of Table 1.

In order to confirm the effect of this Example, the result of having measured the surface roughness of a molded article using the universal surface shape measuring instrument (MODEL SE-3H Co., Ltd. product) is shown in Table 2.

Also about the weld line, the comparative example was clearly shown on the surface of the molded article, and the depth was 30 mu. In addition, in the comparative example, the jetting also appears clearly on the surface of the molded article, and it is difficult to eliminate the molding conditions. However, the molding method in the present invention can be molded without any problem.

According to the present invention, a product excellent in appearance quality can be stably molded in gas assist molding. Particularly, in the material filled with the inorganic filler, problems such as the lifting of the filler, the weld line and the jetting can be solved, so that secondary processing for improving the surface appearance such as sanding, painting and plating can be omitted.

Claims (7)

In the gas assist molding method of the thermoplastic resin, when the molten thermoplastic resin is injected into the mold, the mold temperature of the mold is set to be 10-100 ° C. higher than the thermal deformation temperature of the thermoplastic resin to be injected. Molding method to obtain a plastic molded article having a. The method of claim 1, wherein the mold temperature is set at a temperature of 10-100 ° C. higher than the thermal deformation temperature of the thermoplastic resin, which is at least part of a period from the start of the injection of the thermoplastic resin into the mold to completion. Molding method to obtain a plastic molded article having an appearance. 3. The heat deflection temperature of the thermoplastic resin according to claim 1 or 2, wherein the mold temperature set 10-100 DEG C. higher than the heat deflection temperature of the thermoplastic resin during the molding cycle is used to cool the thermoplastic resin injected into the mold. Molding method to obtain a plastic molded article having a high-quality appearance characterized in that the temperature is controlled to be a temperature lower than 0-100 ℃. 4. The molding method according to claim 3, wherein the timing at which the mold temperature starts to rise and fall during the molding cycle can be arbitrarily controlled. The high-quality appearance of claim 4, wherein at least one heating source of hot water, heating oil, or electrothermal heater is used for raising the temperature of the mold, and at least one of cooling or cooling oil is used for raising the temperature of the mold. Molding method to obtain a plastic molded article having. The molding method according to claim 5, wherein the system for controlling the temperature rise or fall of the mold and the mold temperature control system are partially shared. 4. The molding method according to claim 3, wherein the system for controlling the temperature rise or fall of the mold and the mold temperature control system are formed as separate systems.

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