JPS63276530A - Foaming method for thermoplastic synthetic resin block - Google Patents

Abstract

PURPOSE:To contrive a shorter cooling time and a reduction in the irregularity of density distribution of a molded product, by applying vacuum heating and vacuum cooling to block molding, and incorporating automatic instrumentation and control into a system for block forming, thereby performing heating and cooling operations. CONSTITUTION:After pre-expanded beads are charged into a molded product chamber 1, the entire cavity in a metallic mold is evacuated to a vacuum, whereby resistance to passage of a heating vapor is reduced, and fusibility of the beads is enhanced. Next, the vapor is supplied into a vapor chamber for the metallic mold on the fixed side or the movable side while continuing evacuation of a vapor chamber for the mold on the other side, whereby flushing of residual air with the vapor is conducted for the vapor chambers and the molded product chamber 1, to enhance the fusibility of the pre-expanded beads charged in the chamber 1. Then, evacuation is stopped, and the atmospheric pressure is provided on the discharging side. In this condition, heating on one side, heating on the other side and heating at side surfaces are conducted. Next, total heating is conducted to effect foaming, following by cooling and taking out of a molded product.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a foam molding method for thermoplastic synthetic resin blocks, and more specifically, it relates to a foam molding method for thermoplastic synthetic resin blocks. Regarding the foam molding method in which particles (abbreviated as "particles") are filled into a block mold, heated, molded, and then cooled and taken out, more specifically, by combining the molding method with a vacuum device, the density distribution of the block molded product can be reduced. In addition, the present invention relates to a molding method that can significantly shorten the cooling time and the molding cycle.

"Prior Art and Problems" The molding cycle using conventional expanded polystyrene (hereinafter referred to as EPS) block molding technology is approximately 30 minutes long for a lightweight block molded product commonly known as an 8 kg product. Most of the molding cycle of this molded product is the cooling time, so the cooling time of the block is significantly longer than that of other general molded products. For example, the cooling time for a general molded product is about 1 to 4 minutes. The main reason why the cooling time is longer than that of general molded products is due to the thick walls. The wall thickness of general molded products is usually 10
~50mm, whereas the block molded product has a thick wall thickness of 420~500m1, and at the same time, expanded styrene is used as a heat insulating material as shown in J I 5-A9511. Conductivity is 0.034
(kcal/m, H, 'C), so it is thought that the cooling efficiency cannot be improved only by normal conductive heat transfer.

Another problem with the quality of the block is the uneven density distribution between the inside and outside of the professionally molded product.

To show an example of a normal block, the external dimensions (1 block) are 1
B40 (length) x 925 (width) x 425 (thickness),
It is often used by dividing the thickness into 20 equal parts, but when examining the density distribution on the inside and outside, it is found that the center part is the lightest and the outermost part is the heaviest, forming a so-called V-shape. The density ratio of the innermost and outermost areas is approximately 20%. The reason for this difference in density distribution is that during heating during the molding operation, the outside is more easily affected by the heat from steam heating than the inside, and as a result, the foaming agent between the foamed particles dissipates, weakening the foaming power. During cooling, the outside of the molded product is cooled, but because the inside is thick, it is difficult to remove heat sufficiently, and the foaming pressure is high.
It is thought that due to the combination of internal foaming pressure and shrinkage caused by cooling from the outside, the outside of the molded body is compressed and its density increases, and the inside expands and its density decreases. Therefore, if the cooling is performed gradually instead of rapidly, the variation in the density distribution will be reduced, but on the other hand, the cooling time will be extended and the molding time will be extended, which is a contradictory relationship.

"Means for Solving the Problems" In view of the above circumstances, the present inventor has completed the present invention as a result of intensive research to solve the above problems.

That is, the first aspect of the present invention is to fill a mold cavity defined by a stationary side mold, a movable side mold, and a side side mold with pre-expanded thermoplastic synthetic resin particles, and then heat and foam-mold the particles. In a foam molding method for blocks in which a molded body is taken out by cooling,
After filling the mold cavities with pre-expanded particles, the entire mold is evacuated, and then either the stationary side or the movable side supplies steam into the steam chamber of one mold, while the steam of the other mold is supplied. After evacuating the room, the evacuation is stopped and the exhaust side is brought to atmospheric pressure. After heating on one side, heating on the opposite side, and heating on the side, the entire surface is heated and foamed, and then cooled and molded. A second aspect of the present invention is a foam molding method for a thermoplastic synthetic resin block characterized by taking out the body. In the foam molding method for blocks in which pre-expanded particles of plastic synthetic resin are filled, heated and foam-molded, and then cooled and the molded product is taken out, after heating and foam-molding, the entire mold steam chamber is evacuated. The third aspect of the present invention provides a foam molding method for a thermoplastic synthetic resin block, which is characterized in that the molded body is taken out after being returned to atmospheric pressure, water-cooled, drained, and vacuum-exhausted. , a foam molding method for blocks in which pre-expanded thermoplastic synthetic resin particles are filled into a mold cavity defined by a moving side mold and a side mold, heated and foam molded, and then cooled to take out the molded body. After filling the mold cavities with pre-expanded particles, the entire mold is evacuated, and then either the stationary side or the movable side supplies steam into the steam chamber of one mold while filling the other mold. The steam chamber of the mold is evacuated, then the vacuum is stopped and the exhaust side is brought to atmospheric pressure, and one side is heated, the other side is heated, and the side is heated to perform foam molding, and then the entire mold steam chamber is evacuated. The content of each method is a foam molding method for a thermoplastic synthetic resin block, which is characterized in that the molded product is removed after being returned to atmospheric pressure, water-cooled, drained, and vacuum-exhausted.

The present inventor investigated the following two points as possible means for solving the above-mentioned phenomenon of block molding, which contradicts the variation in density distribution and the molding time.

The first point is to create conditions that improve fusion bonding and to minimize the amount of heating.

The second point is to use cooling methods other than conduction cooling.

Vacuum equipment and automatic measurement and control equipment are adopted as a means to effectively utilize the above two points. Vacuum equipment and automatic measurement and control equipment are still in use in some areas, but they are not suitable for block molding. The present invention was completed through intensive research by combining the above two devices.

The present invention will be explained in detail based on FIG.

Block molding uses particles made of pre-expanded thermoplastic foam resin.
That is, the general method is to fill a block mold with preformed grains, heat and fuse them, and then take them out after cooling.The molded product chamber (1) for molding the molded product is a fixed side steam chamber (2). It is surrounded by a movable side steam room (3) and a side side steam room (4).

The side steam chamber (4) is in the shape of a mouth that continuously surrounds the four peripheries of the molded product chamber (1). The structure of the above mold, ie, the steam chamber, is similar to conventional block molding. Regarding the filling device, there is a filling device for filling the preliminary grains and a hopper for storing them, but these are not shown. Further, a mold opening/closing device for opening and closing the moving side steam chamber is also not shown.

Next, a description will be given of a utility device that heats and cools the filled precipitated grains. The fixed side steam chamber (2) has a fixed side steam valve (5), a fixed side cooling water valve (6), and a fixed side vacuum valve (7).
) and a fixed side drain valve (8), both of which are configured to operate automatically. Similarly, the moving side steam chamber (3) includes a moving side steam chamber (9), a moving side cooling water valve (1), and a moving side cooling water valve (1).
0), moving side vacuum valve (11), moving side drain valve (12)
), all of which are configured to operate automatically. Similarly, the side steam chamber (4) is provided with a side steam valve (13), a side cooling water valve (14), a side vacuum valve (15), and a side drain valve (16). is also configured to operate automatically.

In conventional block molding machines, the fixed side steam chamber (2)
The steam valve and the cooling water valve provided in the moving side plate air chamber (3) are shared, and one each is provided, and no vacuum valve is provided in any of the steam chambers.

Next, the measurement control device will be explained.

Detecting steam pressure in each heating operation of each steam chamber,
The pressure gauges with contacts that signal the closing of each valve when the set value is reached are the fixed side pressure gauge with contacts (17), the moving side pressure gauge with contacts (2o), and the side pressure gauge with contacts ( 23) respectively. This control system using a pressure gauge with contacts is widely used in general molding, but conventional block molding machines employ a timer control system instead of this pressure gauge with contacts.

The pressure reducing valve controls the steam pressure so that the steam pressure in each steam chamber does not exceed the set value, and the spring tightening of the pressure reducing valve is remotely regulated by air pressure instead of formula adjustment. On the secondary side of each steam valve, there are a fixed pressure reducing valve (18), a fixed remote controlled valve (19), a moving pressure reducing valve (21), a moving remote controlled valve (22), and a side pressure reducing valve on the secondary side of each steam valve. It is provided as a valve (24) and a side remote control valve (25). The method of steam pressure reducing valve with remote control valve is -e
Although it is widely used for molding, there are few examples of it being used for conventional block molding, and like the steam valve above, there is one shared on the fixed side and moving side, and one on the side side. ing.

A surface pressure gauge (26) for detecting the foaming pressure caused by steam heating of the preformed particles filled in the mold is provided in the center of the stationary side steam chamber (2). This surface pressure gauge transmits the foaming pressure that determines the final operation of steam heating, which is full-surface heating, vacuum cooling immediately after heating, and demolding.The control device (27) receives this and transmits a control signal to control the heating and This is to control the cooling operation. This pressure gauge control system is not used in general molding, and is used only as a signal to start mold release in conventional block molding. As an effect of foaming pressure control, for example, in a 3 kg block, the foaming pressure when the entire surface is heated is normally 0.8 kg/antG, but if it becomes 0.9 kg/c+dG, the cooling time may be extended by about 10 minutes. It has been observed. In addition, the foaming pressure decreases rapidly during vacuum cooling immediately after heating, but the
/cMG or less, the molded body shrinks and does not recover even after curing.

In block molding, the preliminary particles are filled into a completely closed mold. As a filling method, there is a method of using a normal filling device alone, but a method of using a vacuum device in conjunction with the method of suctioning and reducing the pressure inside the mold for filling is effective in improving the filling properties of the pre-precipitated grains, and is therefore preferable.

Hereinafter, methods related to heating and cooling will be explained.

The operation method will be explained for each operation based on Tables 1 to 4 and the device shown in FIG.

The first operation of the heating method is evacuation. The purpose of this operation is to reduce the resistance of the heating steam passing through the mold by exhausting the air within the mold, thereby improving the fusion properties of the filled pre-formed grains. Specifically, after sealing the mold, only the fixed side vacuum valve (7), moving side vacuum valve (11), and side side vacuum valve (15) are opened, and the vacuum pressure is automatically controlled by setting a timer (not shown). do.

The second operation is vacuum heating. The purpose of this operation is to supply steam from one side of the mold and continue evacuation from the other side to replace the remaining air in the steam chamber and molded product chamber (1) with steam, and to remove the filled precipitate particles. This improves fusion properties. Specific operations include, for example, the fixed side steam valve (5
) is opened, the moving side vacuum valve (11) is opened, and automatic control is performed by setting a timer.

Unless the vacuum evacuation method in the first operation and the vacuum heating method in the second operation are used, it is difficult to maintain the internal and external heating balance and infiltrate the inside of the pre-formed particles with a thickness of approximately 4211 mm. The weight of internal fusion by this method is extremely large.

The third heating operation does not involve evacuation, that is, it is one-sided heating with evacuation stopped. The purpose of this operation is to pressurize and heat the tea spirit that has circulated and permeated into the filled preliminary grains to fuse them internally. The operation is automatically controlled by setting the steam pressure, which is an indicator of fusion. This operation is a technique widely used in general molding. On the other hand, in conventional block molding, one-sided heating is performed by simultaneously supplying steam from the stationary side and moving side steam chambers, as shown in Table 2.
This method excludes internal air and drain from the side chamber. Although this conventional method has the advantage of being simple, there is little steam penetration in the center of the block, and a so-called picture frame phenomenon occurs due to an imbalance in heat fusion between the outside and the inside.

The fourth heating operation is reverse heating. The purpose of this operation is to fuse the surface and corners on the moving side opposite to the third heating operation. Although this technique is also widely used in general molding, it has not been used in conventional block molding.

The fifth heating operation is side heating. The purpose of operation is the third above.
And opposite to the fourth heating operation, the steam supply is from the side steam valve (
13) from the side steam chamber (4) to the fixed side steam chamber (2).
) and the movable side steam chamber (3), and the settings are automatically controlled by steam pressure. Although this heating method is not used in general molding, it is used in conventional block molding, but it is controlled by timer settings.

The fifth heating operation is full-surface heating. The purpose of this heating operation is to perform surface fusion. This operation is also used in conventional block molding.

However, the final method is controlled using a surface pressure gauge (26) that indicates the foaming pressure.
In contrast, the conventional method involves setting a timer.

The surface pressure gauge (26) is a more effective method for absorbing and responding to fluctuations in the volatile content of the precipitated grains and changes in the heating conditions before the entire surface is heated.

The sixth heating operation is auxiliary heating. The purpose of this heating operation is to reheat each mold surface that has been insufficiently heated, and can be omitted. Control is a timer setting. This is a widely used operation in general molding.

The seventh heating operation is heat retention. The purpose of this heating operation is
The purpose is to promote fusion by leaving each drain valve closed without supplying steam.

At the same time, in the final cooling process, vacuum depressurization is performed in the first operation of the next cooling process, so it is undesirable to start the cooling process with high-pressure steam remaining, so leave it until the pressure in the steam chamber drops. . Control is a timer setting.

The first operation of the cooling method is evacuation. The purpose of this operation is to remove residual steam, drainage, and volatile matter inside the molded body by vacuum suction, and it is characterized in that it is performed before water cooling. The reason for this is that when water cooling is performed, a membrane-like skin layer is formed on the surface of the molded product due to the expansion pressure inside the molded product and the cooling contraction of the surface.
This is because this becomes an obstacle to vacuum suction of residual vapor drain inside the molded body.

The second operation is water cooling in a state where the pressure is returned to atmospheric pressure.

The purpose of this operation is to cool the mold temperature with cooling water and reduce the foaming pressure of the block molded body. This is a method commonly used in foam molding. Control is a timer setting.

The third operation is drainage. The purpose is to drain the cooling water remaining in the mold. Excess residual cooling water from the mold will reduce the cooling efficiency of the next vacuum cooling, so
Thoroughly drain the water. Further, as in the second operation, the reduced pressure inside the molded body in the first operation is restored to atmospheric pressure until the inside of the mold reaches atmospheric pressure, which is effective in preventing shrinkage of the molded body. If vacuum cooling is performed continuously, the molded product will shrink, so a feature of the final cooling method is that it is performed continuously.

Control is done by timer settings.

The fourth operation is vacuum exhaust cooling. The purpose of this operation is to lower the temperature of the mold due to the residual cooling water adhering to the mold and to reduce the foaming pressure by suctioning and removing the residual steam inside the molded body. This control is performed by setting a timer. The above water cooling,
It is preferable to repeat drainage and vacuum exhaust cooling two or more times.
In some cases, this may be done three or more times. In this case, it is used when the foaming ratio is low and the foaming pressure decreases slowly.

In the fifth operation, the foaming pressure is allowed to rise from near the set value until it reaches the set value, and the block molded body is taken out by a mold release operation. Control is performed by surface pressure gauge settings.

"Function/Effect" As explained above, the cooling time can be shortened by applying vacuum heating and vacuum cooling to block molding, incorporating automatic measurement control into this, and performing heating and cooling operations as described above. At the same time, it is possible to reduce variations in density distribution of the molded body. In addition, because the moisture content of the molded product is low, conventionally it was impossible to cut nichrome without drying it, but
When using the method of the present invention, cutting can be performed even immediately after molding. As mentioned above, the present invention not only shortens the molding cycle, improves product quality, and shortens the processing cycle after molding, but also saves energy, and has great industrial significance.

"Examples" The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited by these in any way.

Examples 1 to 3, Comparative Example Blocks were molded using polystyrene beads under the following conditions. Table 3 shows the molding cycle and the density variations of the obtained block molded bodies.
KM 2) Pre-foaming machine; Pressure hatch type pre-expanding machine (manufactured by Oma Kogyo Co., Ltd. B HP1300S-A) 3) Expansion ratio: 85 times 2, molding conditions 1) Molding machine; S manufactured by Toyo Kikai Kinzoku Co., Ltd. -184 2) Mold dimensions (mn); 1845 x 930
X 426

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus used to implement the present invention. 1... Molded product chamber, 2... Stationary side steam chamber, 3... Moving side steam chamber, 4...
...Side side steam chamber 5...Fixed side steam valve, 6
...Fixed side cooling water valve 7...Fixed side vacuum valve, 8...Fixed side drain valve 9...
Moving (!l!) Steam valve, 10...Moving side cooling water valve 11...Moving side vacuum valve, 12...
...Moving side drain valve 13...Side side steam valve,
14... Side cooling water valve 15...
Side side vacuum valve, 16...Side side drain valve 1
7... Pressure gauge with fixed side contact, 18...
Fixed side pressure reducing valve 19...Fixed side remote control valve, 20
......Moving side pressure gauge with contact 21...Moving side pressure reducing valve, 22...Moving side remote control valve 23
......Pressure gauge with side contact, 24......Side pressure reducing valve 25......Side side remote control valve, 26.
... Surface pressure gauge 27 ... Control device

Claims (1)

[Claims] 1. After filling the mold cavity defined by the stationary side mold, the movable side mold, and the side side mold with pre-expanded thermoplastic synthetic resin particles, and performing foam molding by heating, In the foam molding method for blocks in which the molded body is removed by cooling, after filling the mold cavity with pre-foamed particles, the entire mold is evacuated, and then either the fixed side or the movable side of the mold is evacuated. While supplying steam into the steam chamber, the steam chamber of the other mold is evacuated, then the vacuum evacuation is stopped and the exhaust side is brought to atmospheric pressure, and one side heating, reverse one side heating, and side heating are performed. A method for foam molding a thermoplastic synthetic resin block, which is characterized by heating the entire surface to perform foam molding, and then cooling and taking out the molded body. 2. The molding method according to claim 1, in which the steam pressure of each steam chamber is controlled to a set value in one-sided heating, reverse one-sided heating, and side heating, and the foaming pressure of the resin is controlled to a set value in full-surface heating. . 3. Fill the mold cavity defined by the stationary side mold, the movable side mold, and the side side mold with pre-expanded thermoplastic synthetic resin particles, heat and foam mold, and then cool to form a molded body. In the foam molding method for the block to be taken out, after heating and foam molding, the entire mold steam chamber is evacuated, returned to atmospheric pressure, cooled with water, drained, and vacuum-exhausted, and then the molded body is taken out. A foam molding method for thermoplastic synthetic resin blocks characterized by: 4. Fill the mold cavity defined by the stationary side mold, the movable side mold, and the side side mold with pre-expanded thermoplastic synthetic resin particles, heat and foam mold, and then cool to form a molded body. In the foam molding method for blocks to be taken out, after filling the mold cavity with pre-expanded particles, the entire mold is evacuated, and then steam is supplied to the steam chamber of either the stationary side or the movable side mold. At the same time, the steam chamber of the other mold is evacuated, then the vacuum evacuation is stopped and the exhaust side is brought to atmospheric pressure, and heating is performed on one side, heating on the opposite side, and side heating to perform foam molding. A foam molding method for a thermoplastic synthetic resin block, which comprises evacuating a room, returning the pressure to atmospheric pressure, cooling with water, draining water, and evacuation cooling, and then taking out the molded body. 5. A patent claim that controls the set value of the steam pressure in each steam chamber during one-sided heating, reverse one-sided heating, and side heating, and controls the set value of the foaming pressure of the resin during full-face heating and/or vacuum cooling after full-face heating. The molding method according to item 4.