JPH09314629A - Gas assisted high cycle molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To settle problems such as the floating of filler, the development of weldlines, jetting or the like and eliminate or reduce surface treatment by a method wherein the temperature of a mold at the injection of a thermoplastic resin in the mold is set to be lower than the thermal deformation temperature of the thermoplastic resin to be injected by a specified value of temperature. SOLUTION: During one cycle of the temperature of a mold, at the injection of a molten resin, the temperature of the mold is set to be lower than the thermal deformation temperature of the resin to be molded by 0-40 deg.C. This mold temperature controlling system has a temperature controller 1 for hot water and a chiller 2 for cold water connecting with a changing-over and controlling unit 3. On the changing-over and controlling unit 3, an outlet 5, through which cold water and hot water are respectively supplied to the mold 4, and a return port 6 for recovering the cold water and hot water are provided. In order to realize the desired temperature of the mold, the respective changing- over vales VIN and VR of this device are properly controlled. Thus, by setting the temperature of the mold to be near as much as possible to the thermal deformation temperature of the resin at the injection of the molten resin, the molten resin can be charged without being cooled abruptly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method in a field in which a high quality surface is required for a molded product such as an exterior part or an outer plate in a gas assist molding of a thermoplastic resin and a high cycle is required. In particular, the present invention relates to a high cycle molding method in which a mold temperature is raised in order to eliminate or reduce appearance defects such as weld lines and jetting and appearance defects in an inorganic filler-filled material.

[0002]

2. Description of the Related Art Conventionally, in gas-assisted molding, when a resin filled with an inorganic filler is used, the resin pressure in the mold is lower than that in general injection molding, and the mold transferability is poor, or the product is thick and thus shrinks. Due to the high rate, the inorganic filler floated on the surface of the molded product, impairing the appearance of the molded product.

When injecting an inert gas into a molded product in gas-assisted molding, a thick portion called a gas channel is formed in order to form a hollow portion as a target, and the thickness of the product differs from that of a general surface. Is provided so that the inert gas selectively enters the thick portion. However, since there is a difference in product thickness and the flowing speed of the molten resin in the general surface is different from that in the gas channel portion, a weld line is generated, impairing the appearance of the molded product.

Further, in one of the features of gas assisted molding, which is one of the features of super-thickness molding such that the product thickness exceeds 10 mm, when the molten resin flows through the gate in the mold into the product part, Due to the volume expansion, the resin temperature was lowered and jetting occurred, impairing the appearance of the molded product.

It is a well-known fact that the molding resin temperature and the mold temperature are set high in order to solve these problems. However, when the molding resin temperature and the mold temperature are increased, it takes a long time for the molten resin to cool and solidify, and the molding cycle is prolonged.

[0006]

DISCLOSURE OF THE INVENTION The present invention is capable of eliminating or reducing the defect of poor appearance in conventional gas-assisted molding without prolonging the molding cycle, and forming a desired molded product appearance quality. An object is to provide a high cycle molding method for a molded product.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a roof rail, a door handle, an automobile part such as a grip, an FA.
In gas-assisted molding having a hollow molding part used as a housing for X, copy and other office equipment, household electric appliances, etc., when the molten resin is injected within one cycle of the temperature of the mold forming the product shape. Is a mold temperature control system that can be controlled to 0 to 40 ° C lower than the heat deformation temperature of the resin to be molded, and can be controlled 0 to 100 ° C lower than the temperature in the cooling step, and a high cycle molding method for hollow molded products using the mold. it can.

The mold temperature control system used in the high cycle molding method according to the present invention means that cooling water, cooling oil is stopped when the temperature is raised and hot water, heating oil or a heater is used alone or in combination, and when the temperature is lowered. The hot water, the heating oil, or the heater is stopped, and the cooling water and the cooling water are turned to the same mold temperature control pipe or separate mold temperature control pipes.

At this time, the higher the temperature of the hot water and the heating oil used to raise the temperature, the lower the temperature of the cooling water and the cooling oil used to lower the temperature, and the higher the flow rate, the shorter the molding cycle can be made. become. For electric heaters, the higher the watt density, the better.

As many mold temperature control pipes are provided within a range that does not cause a problem in mold strength, the efficiency is improved and the molding cycle can be shortened.

[0011]

According to the present invention, by setting the mold temperature closer to the heat distortion temperature during injection of the molten resin, the molten resin can be filled without being rapidly cooled, and jetting or weld line In addition, the molding cycle can be shortened by quenching after filling the molten resin.

Further, the transfer rate of the mold is improved, the gloss of the molded product is improved, and the inorganic filler-filled material can be molded while shortening the molding cycle while molding the filler.

[0013]

Examples The invention will now be disclosed with reference to the accompanying figures, which show examples. FIG. 1 is a block diagram showing a structural example of a mold temperature control system suitable for a high cycle molding method of a hollow molded product according to the present invention.

This mold temperature control system has a hot water temperature controller 1 and a cold water chiller 2, and is connected to a switching unit 3. The switching unit 3 has an outlet 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 / control unit 3 is controlled so that the switching valves VIN and VR in the apparatus are in appropriate states with each other.

FIG. 2 is a sectional view of a mold suitable for carrying out the high cycle molding method according to the present invention. This mold has a cavity 9 on the mating surface between the fixed mold 7 and the movable mold 8.
The fixed mold 7 is provided with a sprue 10 and a gate 11 for filling the molten resin into the cavity 9, and the movable mold 8 is provided for injecting gas into the filled resin. There is a gas inlet 12.

In this example, a modified PPE resin Noryl GFN3 (trademark: glass fiber filling amount of 30% by Nippon GE Plastics Co., Ltd.) which is a thermoplastic resin, and an alloy Xenoy 1760 (polycarbonate resin and polybutylene terephthalate resin) were used. Trademark: Nippon GE Plastics Co., Ltd. Glass fiber filling amount 1
0%).

In order to confirm the effects of the examples, molding was performed using the same mold at the mold temperature used during ordinary gas-assisted molding, and comparison was made.

FIG. 3 is a schematic view of a molded product obtained by injection molding using the mold of the embodiment shown in FIG. It has a pad portion 13 that forms a hollow portion by gas injection.

In this example, the molding conditions shown in Table 1 were used.

[0020]

[Table 1]

Table 2 shows the result of the molding cycle for obtaining a molded product having no problem in the product, which was carried out to confirm the effect of this embodiment.

[0022]

[Table 2]

[0023]

EFFECTS OF THE INVENTION According to the present invention, a product having excellent appearance quality in gas assist molding can be stably molded while achieving a high cycle. Especially in the case of inorganic filler-filled materials, it is possible to eliminate or reduce secondary processing similar to surface treatments such as sanding, painting and plating by eliminating problems such as floating of fillers, weld lines and jetting. .

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a mold structure suitable for carrying out the high cycle molding method according to the present invention.

FIG. 3 is a perspective view showing an example of a molded product molded by the high cycle molding method according to the present invention.

[Explanation of symbols]

 1 Hot water temperature controller 2 Cold water chiller 3 Switching / control unit 4 Mold 5 Heat / cold water supply port to mold 6 Heat / cold water return port from mold 7 Fixed mold 8 Movable mold 9 Cavity 10 Sprue 11 Gate 12 Gas inlet

Claims (6)

[Claims] 1. In a gas-assisted molding method of a thermoplastic resin, when a molten thermoplastic resin is injected into a mold, the mold temperature of the mold is 0 than the heat deformation temperature of the thermoplastic resin to be injected. A high cycle molding method, characterized in that the temperature is set to be lower by 40 ° C to 40 ° C. 2. The time for keeping the mold temperature lower than the heat distortion temperature of the thermoplastic resin by 0 ° C. to 40 ° C. is from the start to the completion of injection of the thermoplastic resin into the mold, and during the injection. The high cycle molding method according to claim 1, wherein the temperature is set to be lower than the set temperature. 3. In order to quickly cool and solidify the thermoplastic resin injected into the mold at a mold temperature set to 0 ° C. to 40 ° C. lower than the heat deformation temperature of the thermoplastic resin during one molding cycle, The high cycle molding method according to claim 1, wherein the temperature is lower than the set temperature. 4. The method according to claim 1, wherein the timing of raising and lowering the mold temperature during the molding cycle can be arbitrarily controlled according to the molding material and the molding object. The high cycle molding method according to any one of the above. 5. The temperature of the mold is raised by using hot water, heating oil or an electric heater alone or in combination, and the temperature of the mold is lowered by circulating cold water or cooling oil. The high cycle molding method according to any one of claims 1 to 4, wherein the high cycle molding method is performed by 6. The high cycle molding method according to claim 1, wherein the gas is injected while injecting the molten resin or at any time after the completion of the injection.