JP2602447B2 - Method for foaming thermoplastic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for foaming a thermoplastic synthetic resin such as a plastic foam, particularly a block, in a mold by heating steam control operation in a mold. The present invention relates to a foam molding method for producing a molded article.

[Conventional technology]

In the production of a foamed molded product, foaming thermoplastic resin particles (beads) are pre-foamed using a mold, or without being pre-foamed, filled in a mold, heated, and then cooled. It is common to dry after release. In this conventional foam molding, the mold is closed, the beads are filled in a mold, blow-backed, foam-formed by steam heating, pre-cooled, then cooled with tap water or other low-temperature cooling water and allowed to cool naturally. A steam chest method of releasing after cooling is often used.

However, in the foam molding method produced by this method, since the volume of the heated steam chamber is constant, the steam temperature in the chamber is directly proportional to the steam pressure, so that the steam pressure is adjusted to adjust the steam temperature. I have.

[Problems to be solved by the invention]

However, in the conventional steam heating method, molding is performed at a relatively high pressure (0.6 to 0.8 kg / cm ² G), and the cycle varies slightly depending on the block weight of the foam molded product.
It took a long time, about 20 minutes, to improve productivity. In addition, since the pressure regulating mechanism is kept constant, only constant steam supply is possible at all times, and considerable time is required for heat molding cycle time, including degassing of raw material beads, and there is a limit for each molding cycle, increasing productivity. In addition to the inability to perform such operations, the operation of adjusting the steam supply was inconvenient due to the inconvenient positional relationship.

The present invention is intended to eliminate these conventional disadvantages, and it is possible to individually and partially adjust the steam pressure of the male mold and the female mold, thereby shortening the steam supply time and degassing the beads. It facilitates, greatly improves productivity, makes molding work easier and quicker, improves production efficiency, and eliminates the need for frequent adjustments, allows automatic adjustments, and requires complicated facilities. It is an object of the present invention to provide a method capable of performing a safe and stable foam molding operation with an inexpensive configuration without any trouble.

[Means for solving the problem]

In the present invention, in order to achieve the above object, expandable thermoplastic resin particles are formed in a cavity formed with a male mold and a female mold provided with a steam chamber, or a female mold is formed so as to be able to approach and separate from each other. In the method of foaming and fusing by heating, the steam chamber in at least one of the male mold and the female mold is divided into a plurality of independent steam chambers, and an on-off valve is provided for each steam chamber. A steam supply path with a valve, a drain discharge path with an on-off valve, and a suction flow path connected to a vacuum pump further with an on-off valve are provided, and the on-off valve of the steam supply path is operated to reduce the steam pressure to low pressure and high pressure. Heat treatment by two-stage switching of
The steam in each steam chamber and the exhaust fluid are extracted.

The on-off valve of the steam supply passage is controlled by a regulator interposed in the operation fluid supply passage, and the operation of the regulator is performed by a voltage command from a computer using an electropneumatic regulator. Preferably, there is.

Further, the female mold is one in which a concave-shaped cavity is formed by separately dividing a ring-shaped steam chamber of a peripheral part and a steam chamber in which one end of the peripheral part is closed, and the other end face is formed. It is preferable that a male mold to be fitted to the portion is provided with another steam chamber.

Further, it is desirable that the steam supply step can be performed by setting with a regulator for adjusting the pressure of the valve opening / closing air of the on / off valve and a pressure reducing valve.

When heating and cooling each mold, it is preferable that the fluid in the steam chamber is sucked using a vacuum pump and heated and cooled under vacuum.

(Operation)

According to the present invention, first, the molding die is closed and the cavity in the die is evacuated. After the supplemental filling, the mold is heated after flowing back, and then the inside of the mold is evacuated by utilizing the vacuum action.

Next, a steam pressure of, for example, 0.2 kg / cm ² G was applied to the independent steam chamber of one mold and the steam chamber of the other mold.
Supply and heat at the following low pressure, steam pressure 0.4k to the independent steam chamber of one mold and the steam chamber of the other mold
g / cm ² G or less, and supply and heat at a high pressure of not more than 0.2 kg, and supply and heat, for example, a steam pressure of 0.2 kg or less to the independent steam chamber of one mold, and steam pressure to the remaining steam chamber of one mold. For example, supply heating at 0.4 kg or less,
After the main heating, the inside of the mold is evacuated at a stretch to 400 mHg or less using a vacuum tank, thereby evacuating the primary gas, and then evacuating the secondary gas by using only a vacuum pump.

Then, after water cooling, through the cooling step of the drainage air, one stage or two or more stages of cooling to be opened and released by performing a cooling to about -700 mmHg with a vacuum pump, can be molded in less than 10 minutes in a cycle In addition, the amount of steam used can be reduced to 1/2 to 1/3 of the conventional amount, for example, 20 kg / shot or less.

At the time of the above-mentioned heating, high-pressure, low-pressure two-stage steam is used for heating, so it is better to foam at a low pressure than to foam at a relatively high pressure. The outside is fused by heating on both sides to form a good quality block product.In the degassing process, the inside foaming gas is evacuated to a vacuum and degassed forcibly and a vacuum tank is used. The best way to degas the inside of the steam chamber to a high vacuum is -400 mmHg or less. This is because, when the bottom vacuum is applied at once, the styrene is pulled outward by the vacuum force, the frame phenomenon occurs, the specific gravity of the outside and the inside differ, and therefore the outside becomes large (the density is large) and the gas This is because the street becomes worse and the cycle becomes longer, so that a good block product cannot be produced.

In any case, as a steam supply process for heating the mold. The heat treatment is preferably performed by switching the vapor pressure between a bottom pressure and a high pressure in two stages.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2. Referring to FIGS.
The molds 1 and 3 on which the molds 2 and 13 are formed constitute a mold as a pair of a female mold and a male mold, and the male and female are opposed to each other so as to freely contact and separate so that a cavity 5 is formed between the molds. Steam supply pipes 21, which are attached to the respective frame bodies and supply heating steam from the heating steam source S to the steam chambers 11, 12, and 13, respectively.
On / off valves 31, 32, 33 having a pressure regulating unit 4 communicating with an air source P are interposed and provided in the steam supply pipes 21, 22, 23, respectively.

That is, at least one of a female mold and a male mold,
Alternatively, the steam chambers in both molds are divided into a plurality of independent steam chambers, and the on-off valves 31 and 3 are provided for each steam chamber.
Steam supply path with 2, 33 and on-off valves 34, 3 for drain valves
Drain discharge paths 24, 25, 26 with 5, 36, and suction paths 27, 28, 29 connected to a vacuum pump 40 with open / close valves 37, 38, 39 of vacuum valves are further provided. By sequentially operating the male and female molds, the supplied steam and the discharged fluid are adjusted and extracted while adjusting the pressure individually.

The on-off valve is controlled by a regulator 20 interposed in the steam supply pipes 21, 22, and 23.
It is preferable to use an electropneumatic regulator and an operation that is performed by a voltage command from a computer.However, if necessary, the operation of the on-off valve is performed using pressure-adjusted air. It is performed by the fluctuation of the air pressure balance between the valve opening / closing air adjusted from the pressure reducing valve and the solenoid valve for opening and closing to the pressure part, the secondary steam connected to the mold, and the regulated air regulated by the regulator. Or a regulator that regulates the pressure of the valve opening / closing air of the on / off valve.
What can be set and performed by 20 and the pressure reducing valve 19 may be used.

In the present embodiment, the female mold is constituted by a mold in which a steam chamber 12 of a ring-shaped peripheral part and a steam chamber 11 in which one end of the peripheral part is closed are individually partitioned, and a concave cavity is formed therein. 5 which is provided with a male mold 3 fitted to the other end face portion and having another steam chamber 13, the male and female molds may be reversed. The mold may be a female mold.

When the molds 1 and 3 are heated and cooled, the fluid in the steam chambers 11, 12 and 13 is sucked using the vacuum pump 40 and heated and cooled under vacuum.

Further, the pressure regulating unit 4 is connected by a pipe 16 using a diaphragm so that secondary steam from the molds 1 and 3 is introduced, is connected to an air source P, and is connected to a pressure regulating pipe having a regulator 20. 17 and solenoid valve for supplying valve opening / closing air
18 and a pipe 15 having a source pressure valve 19, respectively, so that the heating steam supply pipes 21, 22, and 23 are adjusted over a range from fully open to fully closed, and supplied by the on-off valves 31, 32, and 33. The steam is supplied to the steam chambers 11, 12, and 13. In this case, the pressurized air is preferably discharged from the pneumatic device in accordance with the steam pressure of each mold steam chamber section. It is.

The regulator 20 uses an electropneumatic regulator so that the male mold and the female mold can individually adjust the steam pressure, is arranged in each pipe 17, and automatically adjusts according to a voltage command or a current command of the computer Q. Remote control or manual hand control can be selected, and the supply of steam is preferably pulsated by opening and closing control by the on-off valves 31, 32, and 33 by adjusting the regulator 20. Further, a flow control valve or a pressure reducing valve may be used as necessary.

In the steam chambers 11, 12, and 13, it is effective that the steam chambers 11 and 13 are controlled in the same manner and are controlled in a different system from the steam chamber 12, so that the amount of steam used can be reduced and effective machining operations can be performed. Becomes In addition, it is effective that a steam pipe is built in the steam chamber of each of the molds so that the molds are uniformly heated and processed with a uniform distribution of steam.

When the molding method in the example of FIG. 1 is followed over time, a vacuum step (45 seconds) is performed after closing the male and female molds and before filling the raw materials.
Raw material filling (15 seconds), supplementary filling process (15 seconds), flow back (5 seconds), mold heating (5 seconds), vacuum before heating (5 seconds),
Low pressure one-side heating (19 seconds): steam pressure 0.1 kg / cm ² G, high pressure one-side heating (10 seconds): steam pressure 0.35 kg / cm ² G, low pressure other heating (15 seconds): steam pressure 0.1 kg / cm ² G After the main heating (8
Second): Steam pressure was 0.35 kg / cm ² G.

Next, after 40 seconds for primary gas release (-400 mmHg) and 20 seconds for secondary gas release, water cooling (5 seconds) drain air (5 seconds),
The mold is opened and released with cooling -1 (5 seconds) and cooling 2 (surface pressure 0.1 kg / cm ² G), and a block-shaped foamed resin molded product with a product weight of 8.1 kg is obtained. Cycle shortening (cycle 5:22). The amount of steam used was about 20 kg.

In the figure, reference numeral 6 denotes a driving unit for moving the mold, for example, a hydraulic cylinder is used, which is a movable mold for the fixed mold. Reference numeral 10 denotes a vacuum tank, which is provided as required by a pipe 9 having an on-off valve 8 and is bypassed to the vacuum pump 40.

Further, in the mold, before the mold closing is completed, the mold 3 in the movable steam chamber 13 including the moving frame with respect to the fixed mold is switched from a high-speed mold closing to a low-speed mold closing, and Completion position, this is the signal to shift to the raw material filling process, and the eject position of the position that controls the timing of pushing down the product in the female mold with the eject pin, etc.
Before the mold opening is completed, the operation is performed by setting a change position for switching from a low speed mold opening to a high speed mold opening, a mold opening completion position, a position for controlling a mold opening interval when performing mold release, and the like.

In any case, in the computer Q, when the male mold and the female mold are arranged opposite to each other in an openable and closable manner to perform in-mold molding,
The data of the mold closing, cracking, eject, and mold opening completion are detected by an analog sensor, input as an analog signal, converted to a digital signal by an A / D converter, and internally processed by a data processing unit. The opening / closing operation of the mold and the forming process are adjusted by controlling a driving unit such as a cylinder or a motor for moving and moving the mold by comparing the fixed data with the fixed data, or by performing cycle control in each process.

〔The invention's effect〕

As described above, according to the present invention, the steam chamber in at least one of the male mold and the female mold is divided into a plurality of independent steam chambers, and each steam chamber has an open / close valve. A steam supply path, a drain discharge path with an on-off valve, and a suction flow path connected to a vacuum pump with an on-off valve are further provided, and the on-off valve of the steam supply path is operated to reduce the steam pressure to two stages, low pressure and high pressure. The heat treatment is performed by switching, and the steam and exhaust fluid in each steam chamber are extracted, so that the foam molding cycle can be significantly shortened, and the amount of steam used is small, and high-quality product processing is performed smoothly and reliably. In addition, the bead degassing action is facilitated, the fusion molding cycle can be greatly shortened, productivity can be significantly improved, and the temperature and adjustment of the heated steam are easy, and maintenance and security are simple. There, there is an effect that can be made handling of simple and inexpensive simplified type.

[Brief description of the drawings]

FIG. 1 is a system explanatory diagram of an embodiment of the present invention, and FIG. 2 is a system explanatory diagram of one embodiment of an on-off valve. S: steam source, P: air source, Q: computer,
1, 3 ... mold, 4 ... pressure regulating section, 5 ... cavity section,
11, 12, 13 ... steam chamber, 21, 22, 23 ... steam supply pipe, 24, 25, 26 ... drain discharge path, 27, 28, 29 ... suction flow path, 31, 32, 33 ... On-off valve, 34, 35, 36 ... On-off valve,
40 ... Vacuum pump.

Claims (5)

(57) [Claims] A male and female mold with a steam chamber;
Alternatively, in a method of foaming and molding a thermoplastic resin in which a foamable thermoplastic resin particle is heated and foamed and fused in a cavity formed by facing the female molds so as to be able to approach and separate from each other, the method comprises the steps of: A steam chamber in at least one of the molds is divided into a plurality of independent steam chambers, and a steam supply path having an on-off valve for each steam chamber;
A drain discharge path having an on-off valve and a suction flow path connected to a vacuum pump further having an on-off valve are provided, and the on-off valve of the steam supply path is operated to perform a heat treatment by switching the vapor pressure between low pressure and high pressure in two stages. And extracting steam and exhaust fluid from each of the steam chambers. 2. An on-off valve for a steam supply path is controlled by a regulator interposed in an operation fluid supply path. The regulator is operated by an electropneumatic regulator in response to a voltage command from a computer. The method for foaming and molding a thermoplastic resin according to claim 1, wherein 3. A female mold wherein a concave cavity is formed therein by separately dividing a steam chamber having a ring-shaped peripheral portion and a steam chamber having a closed one end portion of the peripheral portion. 3. The method of foaming thermoplastic resin according to claim 1, further comprising a male mold fitted to the other end face portion with another steam chamber. 4. The foaming of a thermoplastic resin according to claim 1, wherein the steam supply step can be performed by setting a regulator and a pressure reducing valve for adjusting the pressure of the valve opening and closing air of the opening and closing valve. Molding method. 5. When heating and cooling each mold, the fluid in the steam chamber is sucked using a vacuum pump to heat and cool the mold under vacuum.
5. The foam molding method for a thermoplastic resin according to claim 2, wherein the thermoplastic resin is allowed to cool.