JPS6127175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a thermoplastic resin foam molded article.

Conventionally, in order to produce a thermoplastic resin foam molded article, expandable thermoplastic resin particles are filled into the cavities of a pair of foam molds through a filling device, and water vapor is introduced into the mold cavities to produce the above-mentioned. A method is used in which resin particles are heated and expanded and fused together to form a foamed molded product having a shape corresponding to the shape of a mold cavity, and after cooling this with water, it is taken out from the mold.
A pair of foam molds used at this time generally consists of a core mold and a cavity mold, each of which has a steam chamber formed between the double walls of an inner wall and an outer wall. A steam pipe, a cooling water pipe, and a drain pipe are connected to each other, and the inner wall has many steam holes whose size allows air and water vapor to pass through, but does not allow the foamable thermoplastic resin particles to pass through. It is provided. By the way, in the conventional method, after the foamed molded product is cooled with water, the cooling water remaining in the steam chamber is forcibly discharged with air and then taken out. The water used in However, there was a drawback that the cooling water remaining in the steam holes infiltrated into the mold and adhered to the surface of the foam molded product.

If the accumulated water in the steam hole intrudes into the mold, the inner surface of the mold leaks and filling of the raw material is inhibited, so it is necessary to take extra cracking and blow out the water before filling. However, when the cracking is increased, the weight of the foamed molded product obtained is increased due to overfilling of raw materials, and both the heating time and the cooling time are increased, which causes an increase in product cost. In addition, residual water in the steam holes that enters the mold when the foam molded product is taken out of the mold adheres to the surface of the foam molded product, so as a result, the drying process of the foam molded product is carried out to remove this water. There was also the disadvantage that it took a long time to complete the process.

In view of these circumstances, the present inventor has conducted extensive research into preventing water remaining in the steam holes from penetrating into the mold to eliminate water leakage on the inner surface of the mold and water adhesion on the surface of the foam molded product. , which led to the completion of the present invention.

That is, in the present invention, foamable thermoplastic resin particles are heated and expanded into the cavities of a pair of foam molding molds consisting of a core mold and a cavity mold to form a foam molded body using water vapor, and then cooled with water. The above-mentioned foam molding mold is opened slightly, and pressurized air is applied to the mold cavity surface of the foam molded body and the core mold inner wall from the pressure air pipe introduced into the inner wall of the core mold and the pressure air pipe introduced into the inner wall of the cavity mold. and the mold cavity surface of the cavity mold inner wall alternately or simultaneously,
The present invention relates to a method for producing a thermoplastic resin foam molded article, characterized in that the foam mold is completely opened to completely open the foam molded article and the foamed article is released from the mold.

The expandable thermoplastic resin particles used in the method of the present invention include polystyrene resin,
Unfoamed particles of thermoplastic resin such as polymethyl methacrylate resin, polyethylene resin, etc., added with a blowing agent such as propane, butane, pentane, dichlorofluoromethane, etc. Alternatively, a pre-foamed material may be mentioned.

Next, the method of the present invention will be further explained with reference to the drawings.

In the figure, 1 is a pair of foam molds,
It is composed of a core mold 2 and a cavity mold 3, and is usually made of a material with good thermal conductivity such as aluminum or aluminum alloy casting. When the core mold 2 and the cavity 3 are clamped together, a mold cavity 4 is formed there. The mold cavity 4 is a molding space corresponding to the shape of the foam molded product to be obtained. The core mold 2 and cavity mold 3 have inner walls 21 and 31, respectively.
and outer walls 22, 32, steam chambers 23, 33 are formed between the inner and outer double walls, and the inner wall 2
1 and 31 are provided with a large number of steam holes 24 and 34 having a size that allows the passage of air, steam, and water, but does not allow the passage of expandable thermoplastic resin particles. The steam chambers 23, 33 have steam supply holes 25, 35.
and cooling water pipes 26, 36 are provided. 2
7 and 37 are pressurized air pipes, and the core type inner wall 2
1 and the cavity mold inner wall 31, respectively. 5 is a filler for filling the mold cavity 4 with thermoplastic resin particles, and 6 is an eject pin for taking out the foamed molded product 7 from the mold 1.

The tips of the pressure air pipes 27, 37 are formed with slits 271, 371 as shown in FIG. 2, or check valves 272, 371 as shown in FIG.
372 or by punching holes directly in the inner walls 21 and 31 (not shown), the structure is designed to allow air and water vapor to pass through, but not to allow thermoplastic resin particles to pass through. There is. In the check valves 272, 372, cylinders 273, 373 are fitted into the inner walls 21, 31, and the cylinders 273, 37
3, movers 274, 374 are inserted. The movers 274, 374 have heads 2 in the shape of an inverted truncated cone.
75, 375, and when the mover 274, 374 retreats, the head 275, 375 moves into the cylinder 273,
It is designed to close the tip of 373. Mover 2
Through holes 276, 376 are bored in the holes 74, 374, and when the mover 274, 374 protrudes, pressurized air passes through the holes 276, 376 into the mold cavity 4.
It is now being supplied to the inside. Conversely, mover 2
When 74,374 retreats, the head is 275,375
It is becoming more and more closed. A check valve 272 having this inverted truncated conical head 275, 375,
372 is preferable because the introduced pressure air can be easily diffused. In addition, the pressure air pipes 27, 3
7 may be branched in the middle, and the above-mentioned slits 271, 371 or check valves 272, 372, etc. may be provided at the tips of the branches.

In the method of the present invention, first, the core mold 2 and the cavity mold 3 are clamped, and the mold cavity 4 is completely filled with the expandable thermoplastic resin particles from the filling device 5. Next, heated steam is blown into the steam chambers 23, 33 of the core mold 2 and cavity mold 3 from the steam supply ports 25, 35 to heat the resin particles filled in the mold cavities 4 to a temperature higher than the softening point of the resin. The heat-softened expandable thermoplastic resin particles are foamed and fused together to form a foamed molded body 7 corresponding to the shape of the mold cavity 4 . Next, the drain valves 28 and 38 are opened, and cooling water is introduced into the steam chambers 23 and 33 from the cooling water pipes 26 and 36 to cool the foam molded body 7, and then the air valve 2
9 and 39 are opened and the cooling water remaining in the steam chambers 23 and 33 is forcibly discharged with air.

Next, the foam mold 1 is slightly heated, e.g.
At the same time as opening the mm mold, open the pressure air valve 210,
Pressure air pipe 2 introduced into the inner wall 21 of the core mold 2
7 to about 0.2 to 1.2 kg/cm ² of pressurized air is supplied between the foam molded body 7 and the cavity surface of the core mold inner wall 21 (see FIG. 4). Then, the supplied pressurized air pushes out the foamed molded product 7 toward the cavity mold 3 side to form a space 211, and this space 2
11, passes through a large number of steam holes 24 provided in the core mold 2 to a steam chamber 23, and is discharged to the outside. As a result, the remaining cooling water accumulated in the steam hole 24 of the core mold 2 is removed from the steam chamber 24 along with the pressurized air.
3 is completely excluded from the outside. Subsequently, the pressure air valve 210 is closed, the pressure air valve 310 is opened, and the same pressure air as described above is supplied from the pressure air pipe 37 supplied to the inner wall 31 of the cavity mold 3 to the mold cavity surface of the foamed molded body 7 and the cavity mold inner wall 31. (See Figure 5). The introduced pressurized air then pushes out the foamed molded product 7 toward the core mold 2 side to form a space 311, and this space 31
1, passes through a large number of steam holes 34 provided in the cavity mold 3 to a steam chamber 33, and is discharged to the outside. At this time, the remaining cooling water accumulated in the steam holes 34 of the cavity mold 3 is completely removed from the steam chamber 33 to the outside together with the pressurized air.

In the above explanation, the foaming mold 1 is opened slightly, and pressurized air is first supplied from the pressure air pipe 27 introduced into the inner wall 21 of the core mold 2, and then introduced into the inner wall 31 of the cavity mold 3. However, the foaming mold 1 was slightly opened and the compressed air was first supplied from the pressure air pipe 37 introduced into the inner wall 31 of the cavity mold 3 to the foamed molded product 7. Pressurized air is supplied between the mold surface of the inner wall 31 of the cavity mold 3 and discharged from the steam hole 34 of the cavity mold 3, and then from the pressure air pipe 27 introduced into the inner wall 21 of the core mold 2. and the mold cavity surface of the core mold inner wall 21 and discharged from the steam hole 24 of the core mold 2, or the foaming mold 1 is slightly opened and introduced into the inner wall 21 of the core mold 2. Pressure air is simultaneously applied from the pressure air pipe 27 and the pressure air pipe 37 introduced into the inner wall 31 of the cavity mold 3 to the mold cavity surface of the foamed molded body 7, the mold cavity surface of the core mold inner wall 21, and the mold cavity surface of the cavity mold inner wall 31. The same effect can be achieved by supplying the gas between the two and discharging from the steam holes 24 of the core mold 2 and the steam holes 34 of the cavity mold 3, respectively.

After removing the residual water in the steam holes 24 of the core mold 2 and the steam holes 34 of the cavity mold 3 as described above, the foam mold 1 is clamped and left to cool naturally. The mold is completely opened, the eject pin 6 is pushed out, and the foamed molded product 7 is released from the mold. Note that the step of removing residual water in the steam holes 24, 34 using pressurized air may be performed at the end of the cooling step. In this case, there is no need to clamp the foaming mold 1 again after the step of eliminating residual water in the steam holes 24, 34, and the mold can be opened and released immediately.

According to the method of the present invention, the pressurized air pipe 27 introduced into the inner wall 21 of the core mold 2 and the pressure air pipe 37 introduced into the inner wall 31 of the cavity mold 3 as described above.
Pressure air is supplied to the foamed molded body 7 and the core mold inner wall 2.
The pressurized air is supplied between the mold cavity surface of the core mold 2 and the mold cavity surface of the cavity mold inner wall 31 alternately or simultaneously.
By discharging the steam chambers 23 and 33 to the outside through the steam holes 34 of the core mold 2 and the cavity mold 3, the cooling water remaining in the steam holes 24 of the core mold 2 and the steam holes 34 of the cavity mold 3 is discharged to the steam chamber 23 together with the pressurized air. ,3
3 to the outside, so the steam holes 24, 34
The cooling water remaining inside is prevented from infiltrating into the mold cavity 4, and water leakage from the mold cavity surfaces of the core mold inner wall 21 and cavity mold inner wall 31 and water adhesion on the surface of the foam molded body 7 are eliminated. As a result, the filling of raw materials can be carried out smoothly, and the foamed molded body 7 can be dried in a short time, which is a remarkable effect.

Next, a specific example of the method of the present invention will be explained.

(Example 1) As the expandable thermoplastic resin particles, pre-expanded particles were used which were made by steam heating polystyrene resin particles containing a blowing agent propane and foaming them to a bulk ratio of 55 times. The foaming mold 1 can be divided into a core mold 2 and a cavity mold 3 as shown in Fig. 1, and is box-shaped with external dimensions of 243 x 330 x 390 mm and a thickness of 25 mm. A mold having 4 mold holes was used. First, the mold cavity 4 is filled with the pre-expanded particles, and then 115°C water vapor is introduced into the mold cavity 4 to heat and expand the pre-expanded particles and fuse them together. A foamed molded article 7 corresponding to the shape of was formed. Next, the drain valves 28 and 38 are opened, and cooling water is introduced into the steam chambers 23 and 33 from the cooling water pipes 26 and 36 to cool the foam molded body 7, and then the air valve 2
9 and 39 were opened, and the cooling water remaining in the steam chambers 23 and 33 was forcibly discharged with air. Next, the foam mold 1 is opened by 7 mm, and at the same time the pressure air valve 210 is opened, and 0.5 kg/cm ² of pressurized air is applied from the pressure air pipe 27 of the core mold 2 to the foam mold 7 and the mold cavity of the core mold inner wall 21. A space 211 is formed between the foam molding 7 and the mold cavity surface of the core mold inner wall 21, and the supplied pressurized air is passed from the space 211 through the steam holes 24 of the core mold 2. The remaining water in the steam holes 24 of the core mold 2 was discharged to the outside by draining into the steam chamber 23 and exhausting to the outside. Next, close the pressure air valve 210 and open the pressure air valve 310.
Pressure air of 0.7 Kg/cm ² is supplied from the pressure air pipe 37 to the inner wall 31 of the cavity mold 3 between the foamed molded product 7 and the mold cavity surface of the inner wall 31 of the cavity mold 3.
the foamed molded body 7 and the cavity mold inner wall 3.
A space 311 is formed between the space 311 and the cavity surface of the cavity mold 3, and the supplied pressurized air is discharged from the space 311 to the steam chamber 33 through the steam hole 34 of the cavity mold 3 to the outside. Steam vent 3
The residual water in 4 was expelled to the outside. Next, the pressure air valve 310 was closed, the foam mold 1 was clamped, and the mold 1 was left to cool naturally for 45 seconds, and then the mold 1 was opened, and the eject pin 6 was pushed out to release the foam mold 7. .

The adhesion moisture of the obtained foamed molded product 7 was quite low at 7%, and almost no water leakage was observed on the mold cavity surfaces of the core mold inner wall 21 and the cavity mold inner wall 31, and the filling of pre-expanded particles in the next cycle was smooth. I was able to do it.

(Example 2) The same procedure as in Example 1 was carried out except that the pressurized air in Example 1 was first supplied from the pressure air pipe 37 on the cavity mold 3 side, and then from the pressure air pipe 27 on the core mold 2 side. Using the same type of pre-expanded particles, foam molded articles 7 of the same size were manufactured.

The moisture content of the obtained foamed molded product 7 was 7%, and almost no water leakage was observed on the mold cavity surfaces of the core mold inner wall 21 and the cavity mold inner wall 31, and filling with pre-expanded particles in the next cycle could be carried out smoothly. Ta.

(Example 3) The pressure air supply in Example 1 was changed to core type 2.
Example 1 except that the air pressure was carried out simultaneously from the pressure air pipe 27 on the side and the pressure air pipe 37 on the side of the cavity mold 3.
A foamed molded article 7 of the same size was produced in the same manner as above using the same type of pre-expanded particles.

The moisture content of the obtained foamed molded product 7 was 8%, and almost no water leakage was observed on the mold cavity surfaces of the core mold inner wall 21 and the cavity mold inner wall 31, and filling with pre-expanded particles in the next cycle could be carried out smoothly. Ta.

(Comparative Example) A foamed molded article of the same size was produced using the same type of pre-expanded particles in the same manner as in Example 1, except that the compressed air was not supplied from the compressed air pipe in Example 1.

The moisture content of the resulting foam molded product was as high as 17%.
In addition, many water droplets adhere to the mold cavity surfaces of the core mold inner wall 21 and the cavity mold inner wall 31, which hinders the filling of pre-expanded particles in the next cycle. I had to fill it up afterwards.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the method for manufacturing a thermoplastic resin foam molded article according to the present invention, in which FIG. 1 is a schematic cross-sectional view of a foam mold showing a clamped state, and FIG. Figure 3 is a cross-sectional view showing an example of how the air tube is attached, Figure 4 is a cross-sectional view showing an example of how the air tube is attached, and Figure 4 is when pressurized air is supplied from the pressure air tube introduced into the inner wall of the core mold. FIG. 5 is a schematic sectional view of the foaming mold showing a state in which pressurized air is supplied from a pressure air pipe introduced into the inner wall of the cavity mold. In the figure, 1 is a foam mold, 2 is a core mold, and 3 is a foam mold.
is a cavity mold, 4 is a mold cavity, 7 is a foamed molded product, 2
4 and 34 are steam holes, and 27 and 37 are pressure air pipes.

Claims (1)

[Claims] 1. Filling the cavities of a pair of foam molds consisting of a core mold and a cavity mold with expandable thermoplastic resin particles, and heating and expanding the resin particles with water vapor to form a foam molded product. After that, the foam mold is cooled with water, and then the foam mold is slightly opened, and pressurized air is applied from the pressure air pipe introduced into the inner wall of the core mold between the foam mold and the mold cavity surface of the inner wall of the core mold. After supplying pressurized air between the foam molded body and the mold cavity surface of the cavity mold inner wall from a pressure air pipe introduced into the inner wall of the cavity mold, the foam mold is completely molded. 1. A method for producing a thermoplastic resin foam molded product, which comprises releasing the foam molded product by opening the mold. 2. Fill the cavities of a pair of foam molds consisting of a core mold and a cavity mold with foamable thermoplastic resin particles, heat and expand the resin particles with water vapor to form a foam molded product, and then cool with water. Next, the foam molding mold is slightly opened, and pressurized air is supplied between the foam molding and the mold cavity surface of the inner wall of the cavity mold from a pressure air pipe introduced into the inner wall of the cavity mold. After supplying pressurized air between the foam molded body and the cavity surface of the core mold inner wall from a pressure air pipe introduced into the inner wall of the core mold, the foam mold is completely opened and the foam molding is performed. A method for producing a thermoplastic resin foam molded article, which comprises releasing the body from the mold. 3 Fill the cavities of a pair of foam molds consisting of a core mold and a cavity mold with foamable thermoplastic resin particles, heat and expand the resin particles with water vapor to form a foam molded product, and then cool with water. Then, the foam molding mold is slightly opened, and pressurized air is simultaneously applied to the foam molded product from the pressure air pipe introduced into the inner wall of the core mold and the pressure air pipe introduced into the inner wall of the cavity mold. The thermoplastic resin is supplied between the mold cavity surface of the core mold inner wall and the mold cavity surface of the cavity mold inner wall, and then the foam mold is completely opened to release the foam molded product. A method for producing a foam molded product.