JPH0657432B2 - Foam molding method for thermoplastic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention produces a foamed molded product in a mold by a heating steam adjusting operation when molding a foam of a thermoplastic synthetic resin such as a plastic foam. The present invention relates to a foam molding method.

[Conventional technology]

For the production of foamed molded products, a mold is used to pre-expand the expandable thermoplastic resin particles (beads), or it is filled into the mold without pre-expanding, heat-molded, and then cooled and released. Generally, it is dried.

In this conventional foam molding, a steam chest method in which beads are filled in a mold, steam-heated to perform foam molding, cooled with cooling water such as tap water, and then released from the mold is often used.

However, in the foam molding apparatus produced by this method, as shown in JP-A-58-14724 proposed by the present applicant, since the volume of the heating steam chamber is constant, the steam temperature in the room is directly proportional to the steam pressure. Therefore, the steam pressure is adjusted to adjust the steam temperature. That is, in the conventional device, as shown in FIG. 3, the opening / closing valve device V ₁ and the pressure reducing valve device V ₁ are provided in the steam supply passage A.
_Two valves of No. 2 are arranged adjacent to each other, and the adjustment nut B for adjusting the opening degree of the pressure reducing valve body of the pressure reducing valve device V ₂ is performed accordingly.

[Problems to be solved by the invention]

However, when the steam pressure is adjusted by the valve device, the pressure adjusting mechanism is kept constant, so that only a constant steam supply is possible, and the heat molding cycle time including degassing of the raw material beads takes about 10 to 25 seconds and molding is performed. -There was a problem that there was a limit for each cycle and it was not possible to improve productivity, and the steam supply adjustment was difficult due to the inconvenient positional relationship.

The present invention is intended to eliminate these conventional drawbacks, and facilitates the degassing of beads, greatly improves the shortening of the steam supply time, speeds up the molding work, improves the production efficiency, and frequently adjusts the work. It is an object of the present invention to provide a method capable of performing a stable and stable foam molding operation, which does not need to be performed in advance, can be automatically adjusted, has no complicated restrictions in terms of equipment, can have an inexpensive structure, and can be stably and stably formed.

[Means for solving problems]

The present invention relates to a foam molding method in which expandable thermoplastic resin particles are heated and foamed and fused in a mold formed by a male mold and a female mold, and a chamber portion in the male mold and the female mold is provided. Is a method of foaming a thermoplastic resin, characterized in that heating steam is supplied by pulsating the steam supplied by an on-off valve which is interposed in a steam supply path to and operated by decompression.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.
Inner plate with ventilation holes and chambers 1 ₁ , 2 ₁
A molding die is formed by a pair of a male die 1 and a female die 2 each having a frame, and the molds are arranged so as to come into contact with and separate from each other so that a cavity is formed between the molds 1 and 2. A steam supply pipe 3 for supplying heating steam from the heating steam source S to each of the chamber parts 1 ₁ and 2 ₁ attached to the body is provided so as to be connected thereto, and an air source P is provided in the steam supply pipe 3. An on-off valve 5 having a pressure adjusting unit 4 communicating with is provided. Further, the pressure adjusting portion 4 is connected by a pipe 6 using a diaphragm so that the secondary steam from the male mold 1 and the female mold 2 is introduced, and a pressure adjusting air pipe 7 is connected to the air source P. A solenoid valve 9 and a pipe 8 having a pressure reducing valve 10 are provided for supplying valve opening / closing air, and the heating steam supply pipe 3 is adjusted over a range from fully open to fully closed. When the steam is aged, the chamber portion 1 is pulsated.
It is adapted to supply to ₁ and 2 ₁ . In this case, it is preferable that the mold chamber section is operated by discharging pressurized air from the pneumatic device corresponding to the vapor pressure, and in any case, the operation of the on-off valve 5 is performed by pressure-controlled air. Diaphragm 1
In the pressure regulator 4 of No. 3, the valve opening / closing air adjusted from the pressure reducing valve 10 and the solenoid valve 9 for opening / closing, the secondary side steam communicated with the mold, and the fluctuation of the air pressure balance with the pressure adjusting air are performed. However, this pulsation is not limited to one period such as ripening, but may be divided into a start period and a final period, or continuous pulsation may be given.

As for the on-off valve 5, as shown in FIG. 2, the valve body is a stopper valve / secondary side in which the opening / closing part of the piston 12 by the single-acting spring cylinder 11 and the diaphragm 13 for adjusting the secondary side steam pressure are integrated. constant pressure comprise a pressure regulating valve 14, the determination of the air enters the cylinder 11 ₁ from the valve inlet _81, this air pressure, the piston 12 is spring 15
The on-off valve 5 is separated from the valve seat 20 and the steam on the primary side flows into the mold through the steam supply pipe 3 while being pushed up against. When the steam pressure in the mold rises, the steam pressure from the secondary steam inlet ₆₁ enters the diaphragm 13,
When this secondary side steam pressure is lower than the regulated air pressure, the on-off valve 5 is in the fully open state, but as the secondary side steam pressure approaches the regulated air pressure, the secondary side steam pressure is increased. , The balance of the regulated air pressure and the valve opening / closing air pressure is lost, and the valve opening / closing air flows through the regulating valve 1 in the pressurized air flow passage 17.
逃Ru from the exhaust hole 16 through the spring chamber 11 ₂ to the outside by 4.
As the amount of escaped air increases, the force pushing up the on-off valve 5 weakens, and the force of the spring 15 causes the piston 12 to descend and the on-off valve 5 to fall, limiting the flow of steam on the primary side. The steam pressure of the mold is regulated,
At this time, since the opening degree of the on-off valve 5 is large and a large amount of steam (large amount of heat) is put in, there is a time lag until the pressure in the molds 1 and 2 and the pressure of the diaphragm 13 become the same, so that the pressure is supplied. The steam pulsating is put into the molds 1 and 2 so that the steam easily enters between the beads in the molds 1 and 2, and the beads are crushed to facilitate the degassing of the beads. It is possible to quickly perform pressure feeding into the mold. Further, when heating the molds 1 and 2, the on-off valve 5 is always closed by the spring 15, but the on-off valve solenoid valve 9 is opened and operated, and it is not desired to pulsate the steam pressure depending on the foamed molded product. At times, the pressure of the valve opening / closing air can be set low by the pressure reducing valve 10 in the pipe 8 to prevent pulsation. However, the heating time becomes slightly longer. For example, when it set pressure when pulsing steam source pressure is 3-4 kg / cm ² not pulsation becomes 5~7kg / cm ^2.
Further, when normally molded, the steam pressure is about 0.5 to 0.8 kg / cm ^{2 in} the case of 50 to 60 times, although it depends on the expansion ratio.
It is effective because it gives a pulsation around ± 0.15kg / cm ² to the set value. Moreover, the heating time was conventionally 15 seconds on the fixed side (female die) and 10 seconds on the moving side (male die), but can be shortened to 5 seconds on the fixed side and 4 seconds on the moving side. Has become.

Although the exhaust hole 16 in the spring cylinder 11 is open to the atmosphere, a silencer or a steam recycle mechanism may be selected and connected.

Further, when the steam temperature (steam pressure) in the molds 1 and 2 drops, the diaphragm 13 is pushed down by the pressure-controlled air, and the support shaft 22 of the diaphragm 13 causes the pressurized air flow passage 17 to flow.
The upper regulating valve 14 is pressed to stop the outflow of pressurized air into the atmosphere. As a result, the air pressure below the piston 12 rises, the piston 12 rises against the spring 15, the opening of the on-off valve 5 also expands, and a larger amount of steam from the heating steam source S is transferred to the chambers 1 of the molds 1 and 2. _It can be supplied to ₁ , 2 ₁ .

〔The invention's effect〕

The present invention relates to a valve opening / closing part connected to an air pressure source via an electromagnetic valve, a pressure adjusting part connected to the air pressure source, and a pressure adjusting part operated by the vapor pressure in the mold to the pressure adjusting part when supplying steam. By operating the solenoid valve of the on-off valve with and operating the valve opening and closing part to intermittently control the supply steam, pulsating the heating steam and supplying it to the mold chamber part to perform foam molding The supply steam is pulsated, it is easy for the steam to enter between the expandable thermoplastic resin particles in the mold, and the supply of heating steam into the mold is performed smoothly and reliably in a short time, and the beads The degassing action can be facilitated, the fusion molding cycle can be greatly shortened, the productivity can be significantly improved, the temperature and control of the heating steam can be adjusted easily, maintenance and security can be simplified, and the cost can be reduced even when the equipment is configured. There is an effect that it can be a simple type.

[Brief description of drawings]

FIG. 1 is a system explanatory view of an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of an on-off valve, and FIG. 3 is a system explanatory view of a conventional example. S ... Steam source, P ... Air source, 1 ... Male mold, 2 ...
Female die, 3 ... Steam supply pipe, 4 ... Pressure adjusting part, 5 ... Open / close valve, 6 ... Secondary side steam piping, 7 ... Pressure adjusting air piping, 8 ... Valve opening / closing air piping.

Claims (3)

[Claims] 1. A method of foam-molding by filling a mold with expandable thermoplastic resin particles, and then supplying heated steam to the chamber of the mold by operating an opening / closing valve of a steam supply path,
At the time of steam supply, a valve opening / closing part connected to an air pressure source via a solenoid valve, a pressure adjusting part connected to the air pressure source, and a pressure adjusting part operated by the steam pressure in the mold are provided in the pressure adjusting part. The heat is characterized in that the valve opening / closing part is operated by operating the solenoid valve of the opening / closing valve to intermittently control the supply steam, and the heating steam is pulsated to be supplied to the mold chamber part for foam molding. Foam molding method for plastic resin. 2. The operation of the pressure regulating portion of the on-off valve is performed by changing the balance between the air pressure connected to the air pressure source and the secondary side steam pressure connected to the mold. The foam molding method according to claim 1. 3. The foam molding method according to claim 1, wherein the opening / closing air pressure of the opening / closing valve is adjusted and set by a pressure reducing valve.