JPS58110224A - Heat-molding method for synthetic resin foaming sheet - Google Patents

Abstract

PURPOSE:To produce a synthetic resin foam-molded product being excellent in quality, by a method wherein, after a resin foaming sheet is brought into direct contact with a pair of heating plates for heating and softening, a molding is conducted. CONSTITUTION:A synthetic resin foaming sheet 1, wound around a winding roll 2, is unrolled, the sheet is positiond by the nip formed by heating plates 3 in a manner to bring it into direct contact with the plates 3, and it is usually heated to about 100-170 deg.C for softening. At a heating time, the synthetic resin foaming sheet 1 is softened and simultaneously is secondarily foamed to hold it in a thickness within a size range to allow the molding of the sheet. A molding is then conducted by a mold 4 consisting of a male force 4a and a female force 4b to produce a molded product 13. As above, a secondary foaming thickness of a foaming sheet 1' covers a size range which is sufficiently thick to allow the molding of it, and there occurs no damage such as scrub flaws due to friction with the force 4 at a molding time, whereby a molded product having an excellent quality can be produced.

Description

[Detailed description of the invention] The present invention relates to a method for thermoforming synthetic resin foam sheets.

Conventionally, when manufacturing food containers, cups, etc. by thermoforming a synthetic resin foam sheet, the foam sheet is taken out from a winding roll, heated and softened in a heating furnace, and then molded using a mold. Heat molded into the specified shape.

The product was obtained by punching out this molded body. However, 2
Foamed sheets undergo secondary foaming when heated, increasing the thickness of the sheet, but since it is difficult to control the thickness of the sheet with radiant heating or convection heating in a heating furnace, when this sheet is thermoformed, There were problems such as scratches, etc., and the molding itself became impossible. Furthermore, since this heating method uses radiation or convection for heating, it has a problem of poor thermal efficiency and large energy loss.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for thermoforming a synthetic resin foam sheet, which eliminates the drawbacks of the above-mentioned conventional techniques and allows a synthetic resin foam molded product of good quality to be obtained.

That is, the gist of the present invention is a thermoforming method for a synthetic resin foam sheet, which is characterized in that the synthetic resin foam sheet is heated and softened by bringing it into direct contact with a pair of heating plates, and then molded.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic diagram of each step of a thermoforming method which is an embodiment of the present invention. Here, 1 is the winding roll 2
Synthetic resin foam sheet wrapped around.

Reference numeral 3 designates a pair of heating plates for heating and softening the synthetic resin foam sheet 1. The heating plate 3 has a built-in heater within the space between the upper and lower sides, and the opposing surfaces are coated with Teflon or the like to prevent sheet adhesion. 4 is a mold 4 consisting of a male mold 4a and a female mold 4b.

Examples of the synthetic resin foam sheet 1 that can be used in the present invention include sheets of polystyrene foam, polyethylene foam, polypropylene foam, etc., and the thickness thereof is usually 0.5 to 7 mm. It is OR.

In order to thermoform the synthetic resin foam sheet 1 with the above configuration, the synthetic resin foam sheet 1 wound around the two-roll roll 2 is taken out and held between the heating plates 3 in direct contact with each other. 2. Usually softened by heating to about 100°C to 170°C. When heated, the synthetic resin foam sheet 1 softens and is maintained at a thickness within a size range that can be formed by secondary foaming. Next, it is molded in a mold 4 consisting of a male mold 4a and a female mold 4b,
A molded body 13 is obtained. The molded product 13 obtained in this way has a secondary foaming thickness of the two-foamed sheet 1' within the moldable size range, and has no damage such as scratches due to friction with the mold 4 during molding. It is of good quality as it has not received a rating of 9. In addition, by controlling the clearance between the heating plates and utilizing the suppressing effect of the heating plates, it is possible to set a finer range of moldable dimensions, and the resulting molded product 13 has even higher quality. It will be good. The final product is then obtained by punching out the molded body 13.

2 to 8 show a heating plate 3 used in another embodiment of the present invention. These embodiments perform so-called non-uniform heating in which the heating temperature is partially different.

In FIGS. 2 and 3, recesses 5 are provided at appropriate positions on opposing surfaces of two upper and lower heating plates 3. By using such a heating plate 3, a high temperature area and a low temperature area can be provided on the sheet 1, thereby making it possible to make the thickness of the molded body uniform. The recesses 5 in FIGS. 2 and 3 have low thermal conductivity, so the heating temperature is lower than that of the protruding parts of the heating plate 3 other than the recesses 5. The fluidity of the resin is also reduced compared to the other parts. That is, when forming the deep-drawn container molded body 13' shown in FIG. 9, in the conventional forming method, the upper part A of the side wall near the opening and the part C near the bottom part are forcibly stretched, and the upper part A of the side wall Moreover, the thickness near the bottom C is not thinner than the thickness of the bottom B, resulting in a problem that the thickness of the container molded body becomes uneven. Also.

The A part and the C part had a disadvantage in that they were easily damaged by friction with the mold. However, the heating plate 3 as described above
If the sheet 1 is heated using a heat exchanger, the portion E which will be finally trimmed and does not form the container molded body will be made into a high temperature part, and the other parts will be made into a low temperature part.

During molding, resin is supplied from part E where the resin has high fluidity to other parts, allowing smooth molding.
It is possible to obtain a good molded product with uniform wall thickness for B, C, and D.

4 and 5 show that recesses 5 are provided at appropriate opposing positions of the heating plate 3, and a heat insulating material 6 is loaded into the recesses 5. In this heating plate 3, the portion 3a where the heat insulating material 6 is not loaded becomes high temperature, and the portion where the heat insulating material 6 is loaded becomes low temperature.
It is possible to add high-temperature and low-temperature areas to the
A molded body 13' having a uniform thickness can be obtained as in the case where the heating plate 3 shown in FIG. 2 is used.

FIG. 6 and FIG. 7 show a heating plate 3 made of a heat insulating material.
The opposing surfaces of the main body are partially protruded 3b.

A heater 8 is shown in the non-protruding portion (recess 7). In this heating plate 3.

The loading part of the heater 8 becomes high l, and the heater non-loading part 3
b is the low temperature section, similar to the heating plate 3 in FIG.

The foamed sheet 1 can be provided with a high-temperature region and a low-temperature region, and during molding, a molded product 13' having a uniform thickness can be obtained as in the case of using the heating plate 3 shown in FIG. 2.

The heating plate 3 shown in FIG. 8 is constructed by attaching a heating aid 11 made of a thermal conductor having a recess 10 on the surface to a heating main body 9 containing a heater 8, and filling the recess 10 with a heat insulating material 12. It is something. In this heating plate 3, the part loaded with the heat insulating material 12 is the low temperature part, and the part 3a not loaded with the heat material is the high temperature part, and when the heated sheet 1 is molded using this heating plate, it is the same as described above.

A molded body 13' having a uniform thickness is obtained. When the heating auxiliary tool 11 is attached in this manner, there is no need to perform complicated processing on the heating plate main body, and the heating plate is highly versatile. Similarly, in this embodiment, the recess 10 of the heating aid 11
Although the description has been made regarding the case where the heat insulating material 12 is loaded, it can be used without the heat insulating material 12 being loaded. 9 In the present invention, the high temperature section.

It is also possible to form a temperature distribution in the heating plate not only in two stages in the low temperature section but also in three or more stages.

The molded body 2 obtained by the method of the present invention is, for example, 2.

It can be used for food containers, etc.

As explained above, according to the present invention, molding can be performed by suppressing the increase in thickness of a synthetic resin foam sheet due to secondary foaming by using a heating plate to maintain a moldable thickness. In addition, especially during pressure molding, the molded product will not be damaged due to friction with the mold because the secondary foaming thickness of the sheet is too thick, and molding can be performed reliably. In addition, since the heating plate directly contacts and heats the foam sheet, even if there is variation in the thickness of the material sheet, it will be pressed by the heating plate, making it possible to obtain a molded product with uniform thickness and good quality. Direct contact heating provides high thermal efficiency. Furthermore, if the heating plate is configured so that the temperature differs partially,
If the part that is finally trimmed and does not form the container is used as the high temperature part, resin will be supplied from this part to the parts that will form the container, allowing smooth molding and a molded product of good quality with no variation in thickness. It has various advantages such as being able to obtain

Next, the present invention will be explained in more detail by referring to specific examples.

Specific Example 1 A polystyrene foam sheet with a thickness of 30 m was sandwiched between a pair of heating plates having a uniform surface temperature, and heated at 155° C. for 12 seconds. After heating, the two foamed sheets were pressure-formed in a thermoforming mold having a clearance of 2 Omm to obtain a tonburi-shaped container. No damage such as scratches occurred on the surface of the obtained tonpuri-shaped container.

Specific Example 2 (7) A polystyrene foam sheet with a thickness of 300 mm is placed between a pair of heating plates that are movable up to a vertical distance of 5 m and are made by providing a BOwxl recess on the surface of the foam sheet side and filling the recess with a heat insulating material. The parts were sandwiched together and heated for 12 seconds at a temperature of 120°C in the part with the insulation material and 155°C in the part without the insulation material. The heating plates were moved so that the interval between the heating plates became 5 m as the sheet underwent secondary foaming due to heating. After heating, the foamed sheet was molded using a mold to obtain a cup-shaped container. The resulting cup-shaped container was uniform with no variation in thickness.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the aging process of a synthetic resin foam sheet according to one embodiment of the present invention, and Figs. 2 to 8 are longitudinal sectional views showing heating plates used in other embodiments of the present invention. and a plan view, and FIG. 9 is a longitudinal sectional view showing a state in which the container is molded. 1--1 synthetic resin foam sheet 3-1 heating plate 4 =-
-------1 Molding mold (8) Figure 4 Figure 7 Figure 5 Noa Figure 6 - Figure 9 1 Procedural amendment (voluntary) December 29, 1981 Patent jII of 1982 No. 211860 2, Title of the invention: Aging method for synthetic resin foam sheets 3, Relationship to the case of the person making the amendment Patent applicant address: 2-6-7 Konan, Minato-ku, Tokyo Name: Nippon Zanbac Co., Ltd. Company Representative Honma Goshi Part 4, Agent Address: 101-5, Date of Amendment Order Voluntary '4JE8, Contents of Amendment Figure 8 is amended as shown in the attached sheet. Figure 8 141-

Claims (1)

[Claims] A thermoforming method for a synthetic resin foam sheet, which comprises heating and softening the synthetic resin foam sheet by bringing it into direct contact with a pair of heating plates, and then molding the sheet.