JPS585769B2 - Seikeihin no seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a molded article, and more particularly to a method for manufacturing a molded article by a contact heating type vacuum or pressure forming method.

The use of contact heating as a heating method for thermoplastic synthetic resin sheets when producing molded products by vacuum forming or pressure forming is a method for forming thermoplastic synthetic resin sheets, especially biaxially oriented polystyrene sheets. This is a very effective method in some cases.

In the forming method using this contact heating method, the straight forming method is generally used.
will be carried out.

Straight molding is an elementary and easy molding method, but it has the drawback that the thickness distribution of the molded product is extremely non-uniform.

A plug assist molding method is sometimes used to improve this drawback.

However, when a contact heating type is used in the plug assist molding method, a part of the heating plate becomes the head of the plug and acts on the molded sheet, making the device extremely complicated in structure.
The dog will also be involved.

In comparison, the heating plate lacks versatility and has the disadvantage that a heating plate is dedicated to each molded product.

The present invention improves the above-mentioned conventional drawbacks, and uses a relatively simple device in a molding method that uses a contact heating method to heat a synthetic resin sheet.
The present invention provides a method for manufacturing a molded article that can obtain a molded article with a suitable wall thickness distribution.

Furthermore, the present invention provides a method by which the thickness distribution of a molded article can be arbitrarily controlled.

The gist of this is that when a thermoplastic synthetic resin sheet is heated using a contact heating method to produce a molded product using a vacuum or pressure forming method, the synthetic resin sheet that has been contact heated with a heating plate is placed in a mold during molding. constitutes part of
And, by bringing a contact plate whose surface temperature can be adjusted into contact with or close to it, the desired thickness of the molded product is created between the part of the synthetic resin sheet where the contact plate contacts or comes close to it and the part where it does not come into contact with or comes close to it. The present invention relates to a method for manufacturing a molded article, which is characterized in that after creating a temperature difference that gives the result, vacuum or pressure forming is carried out.

The present invention will be described in detail below with reference to the drawings, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

FIGS. 1 to 3 of the accompanying drawings are schematic longitudinal cross-sectional views showing an example of an apparatus used in carrying out the method of the present invention for ease of understanding, and FIGS. It shows the movement according to the process order.

In the figure, 1 is an outer frame, 2 is a mold, and 3 is a cavity of the mold 2.

4 is a contact plate, and 10 is a heater built into the contact plate.

The contact plate 4 constitutes a part of the mold 2, and is used in places where the wall thickness of the molded product would naturally become especially thin if conventional methods were followed, or where it is desired to make the wall thickness particularly thick in the molded product. be installed in a location corresponding to

In molding a container, the bottom of the container generally becomes thinner, particularly at some corners, so in this example, the bottom of the mold serves as a contact plate.

Reference numeral 5 denotes a pore that communicates the cavity 3 with a compressed air device (not shown).

6 is a heating plate, 7 is a heater built into the heating plate 6, and 8 is a pressure hole provided in the heating plate 6.

9 is a thermoplastic synthetic resin sheet.

In the method of the present invention, first, as shown in FIG. 1, a synthetic resin sheet 9 is sandwiched between a heating plate 6 and a mold 2, and compressed air is sent through the pores 5 to pressurize the cavity 3. The synthetic resin sheet 9 is brought into close contact with the heating plate 6.

After the synthetic resin sheet 9 reaches the molding temperature, as shown in FIG. 2, the contact plate 4 is driven to bring the contact plate 4 into close contact with the synthetic resin sheet 9 (FIG. 2a).

The contact plate 4 is heated by a heater 10 to a temperature that is lower than the temperature of the heating plate 6, but is still at a temperature that does not interfere with molding.

Although the illustrated example shows an example in which the contact plate 4 has a built-in heater, it is of course possible to provide a through hole through which a refrigerant can pass, or to provide a combination of a heater and a through hole. It is.

The temperature of the part of the synthetic resin sheet 9 that the contact plate 4 is in close contact with decreases due to the transfer of heat to the contact plate 4, resulting in a temperature difference between the part of the synthetic resin sheet 9 that the contact plate 4 is in close contact with and the part that is not. occurs.

Alternatively, at this time, the contact plate 4 is kept close to the synthetic resin sheet 9 without being brought into close contact with it (see Fig. 2b), and compressed air is blown onto the synthetic resin sheet 9 from the air pressure hole 8 to move the synthetic resin sheet 9 onto the contact plate. 4 for a short time to create a temperature difference in the synthetic resin sheet as in the case above.

In this case, the area of the synthetic resin sheet 9 in contact with the contact plate 4 can be made smaller than in the above case, and therefore the area of the part of the synthetic resin sheet where the temperature is low can be made smaller.

Thereafter, the supply of compressed air from the pores 5 is stopped, and as shown in FIG. The molding is completed by bringing the resin sheet 9 into close contact with the cavity 3.

How should the contact plate 4 be brought into close contact or close to the synthetic resin sheet 9, how long should the contact plate 4 be in close contact or close to the synthetic resin sheet 9, and how much should the temperature of the contact plate 4 control the wall thickness distribution of the molded product? Appropriate selection can be made by conducting repeated tests in advance.

In the method of the present invention, specific portions of the heated synthetic resin sheet are brought into contact with a contact plate to suitably change the temperature before being molded, so that portions with lower temperatures are less likely to stretch during molding.

Therefore, by bringing the contact plate into contact with the extremely thin part of the molded product in the conventional molding method and molding at a low temperature, it is possible to avoid the extremely thin part of the molded product, and the overall thickness of the molded product increases. The thickness becomes uniform.

It is also possible to intentionally make the wall thickness distribution of a molded article non-uniform using the method of the present invention.

That is, by bringing the contact plate into contact with the portion where the thickness is desired and molding at a low temperature, the thickness can be controlled as desired.

At this time as well, a desired thickness distribution can be achieved by appropriately selecting the time of close contact or close contact and the temperature of the contact plate.

In addition, the method of the present invention is characterized by a simple device, and has extremely high industrial utility value.

The effects of the present invention will be described below with reference to Examples.

FIG. 4 is a longitudinal cross-sectional view of a container molded using the method of the present invention.

That is, a biaxially stretched polystyrene sheet with a thickness of 0.3 m/m is used as a raw material sheet, and the length of one side is directed to the opening 120,
A truncated pyramid-shaped container with a bottom of 100 m/m and a height of 65 m/m was molded according to the method of the present invention.

At this time, the temperature of the surface of the heating plate (the side in contact with the sheet) is approximately 130°C, the contact time between the raw material sheet and the heating plate is approximately 9 seconds, the surface temperature of the contact plate is approximately 60°C, and the contact time between the raw material sheet and the contact plate is approximately 60°C. The contact time was approximately 8 seconds.

The measurement results of the wall thickness of parts a to g in FIG. 4 of the obtained container are as follows:
It is shown in FIG.

Measurement areas are a: 15m/m and b from the top, respectively.
: 3 5m/m, c: 55m/m position, d is part of the corner, and e: 35m/m from the bottom center point, respectively.
f: 20 m/m, and g is the center point of the bottom.

In Fig. 5, the ○ marks are the measured values of the molded product molded using the method of the present invention, and the Δ marks are the measured values of the wall thickness of the parts corresponding to the above-mentioned parts of the molded product molded by the conventional straight molding method. It is.

As is clear from Fig. 5, the container formed using the conventional method is extremely thin at some corners (approximately 27% of the thickness of the original sheet), whereas the container formed using the method of the present invention is extremely thin (about 27% of the thickness of the original sheet). The resulting container is not that thin (46% of the thickness of the original sheet).

In addition, even if the container made by the method of the present invention uses a raw material sheet of the same thickness, the molded product after molding is generally thicker than the container made by the conventional method, and it can be said that it is superior in terms of strength.

[Brief explanation of the drawing]

Figures 1 to 3 are schematic vertical cross-sectional views of steps showing one embodiment of the method of the present invention, Figure 4 is a vertical cross-sectional view of a container molded using the method of the present invention, and Figure 5 is a schematic view of a molded product. It is a table of wall thickness distribution measurement values. In the figure, 2 is a mold, 4 is a contact plate, 6 is a heating plate, 9 is a thermoplastic synthetic resin sheet, and 10 is a heater built into the contact plate.

Claims (1)

[Claims] 1. When manufacturing a molded product by heating a thermoplastic synthetic resin sheet using a contact heating method and using a vacuum or pressure forming method, the synthetic resin sheet that has been contact heated with a heating plate is used to form a part of a mold during molding. , and a contact plate whose surface temperature can be adjusted is brought into contact with or in close proximity, and the desired thickness of the resulting molded product is created between the part of the synthetic resin sheet in which the contact plate is in contact with or in close proximity to the contact plate and the part of the synthetic resin sheet that is not in contact with or in close proximity to the contact plate. A method for producing a molded article, which comprises creating a temperature difference that yields the following results, and then performing vacuum or pressure forming.