WO1997033738A1

WO1997033738A1 - Hot plate molding method for molded resin foam

Info

Publication number: WO1997033738A1
Application number: PCT/JP1996/000713
Authority: WO
Inventors: Toshiaki Shimono
Original assignee: Athena Kogyo Co., Ltd.
Priority date: 1996-03-15
Filing date: 1996-03-15
Publication date: 1997-09-18
Also published as: JP2879375B2

Abstract

A method of producing a molded resin foam, such as a cover (20) for an instant food container finely and sharply with a high precision by a hot plate molding method, wherein a sheet (1) of resin foam is preheated from one surface (12) thereof in a preheating zone (A), and the preheated sheet (1) of resin foam is fed to a molding zone (B), in which the same sheet (1) is positioned between a hot plate (3) and a mold (4) and heated at the other surface (11) thereof with the hot plate (3) with the sheet (1) of resin foam placed along a molding surface (41) of the mold (4) by an air pressure, whereby the sheet (1) of resin foam is molded. When this method is employed, a molded body of resin foam, such as a cover for an instant Chinese noodle container which requires a high precision at its fine parts can be molded finely and sharply with a high precision, and the mass production of such a product can be carried out easily by shortening the molding cycle.

Description

Description Hot plate molding method for foamed resin molded articles

The present invention relates to a hot plate molding method for a foamed resin molded article, and more specifically, a hot sheet molding of a laminated sheet obtained by laminating a foamed resin sheet and a foamed resin sheet and a synthetic resin film. Accordingly, the present invention relates to a method of molding into a synthetic resin molded article such as a container for instant food or the like and a lid thereof, or a synthetic resin molded article having a shape similar to those containers and lids. Background art

Conventionally, when a relatively shallow bottom container or lid used for storing instant lunches and the like is made of a non-foamed resin molded body, a method of vacuum-pressure forming a non-foamed synthetic resin sheet has been used. It was generally adopted.

In the vacuum pressure molding method, a non-foamed synthetic resin sheet heated to a moldable temperature by passing through a heating zone is sent to the molding zone, and a non-foamed synthetic resin sheet is desired in the molding zone. The step of forming into the shape of is performed. The non-foamed synthetic resin sheet has good thermal conductivity between the front and back surfaces because it has no air bubbles in the inner layer. Therefore, non-foaming synthetic tree If the target is a grease sheet, the above-mentioned vacuum / pressure forming method can achieve high-precision molding with a certain degree of sharpness.

However, such containers and lids often require heat insulation such that the temperature of the hot water poured into the container is not easily transmitted to the hand holding the container or lid. . In order to meet this demand, it is effective to make containers and lids with foamed resin moldings

Therefore, it was conceived to apply the above-mentioned vacuum pressure forming method to a foamed resin sheet that exhibits excellent heat insulating properties due to bubbles in the inner layer.

However, when the foamed resin sheet was molded into a container or a lid by applying the vacuum pressure molding method, the following problems were found. In other words, when the entire thickness of the foamed resin sheet is heated to the moldable temperature by the softening zone, the softened foamed resin sheet may hang down or bend. When the foamed resin sheet is fed into the molding zone, the intended portion of the foamed resin sheet is displaced from the molding die, and the foamed resin molded article can be molded at an appropriate location on the foamed resin sheet. It disappears. In many cases, such as instant containers and lids, the surface of the container is printed and printed.Synthetic resin film with the printed display is usually laminated on the foamed resin sheet. As described above, when it becomes impossible to mold the foamed resin molded article at an appropriate location on the foamed resin sheet, the container or lid, which is the final molded article, is formed. The print display part of is shifted from the normal position.

Under such circumstances, the inventors of the present invention have conducted various studies and found that a foamed resin sheet or a laminated sheet composed of a foamed resin sheet and a synthetic resin film is formed by a hot plate forming method. In other words, if the foamed resin sheet heated by the hot plate and the laminated sheet are formed using a hot plate forming method that can be formed immediately at the heating position, there will be irregularities such as containers and lids. Even when a synthetic resin molded article was molded, the position of the sheet to be molded did not deviate from the molding die, and the fact that the synthetic resin molded article was molded at an appropriate position on the sheet was ascertained. .

At this point, the foamed resin sheet has excellent heat insulating properties due to the bubbles existing in the inner layer. For this reason, in hot plate forming, if the foamed resin sheet is simply heated from one side along the hot plate in the molding zone, the heat of the hot plate depends on the thickness of the foamed resin sheet. It may happen that the information is not sufficiently transmitted to the other side. If the foamed resin sheet placed between the hot plate and the molding die in such a state is formed by hot plate forming, it will be difficult to form fine and sharp details with high precision. To improve this point, it is conceivable to increase the heating temperature by the hot plate or lengthen the heating time.However, when the heating temperature is increased, the secondary foaming of the foamed resin sheet occurs remarkably. As a result, the surface of the synthetic resin molded article becomes rough, and if the heating time is prolonged, the time required for molding one cycle becomes longer, which hinders mass production. You. The same can be said for the laminated sheet described above. Therefore, the hot plate molding of the details of a foamed resin molded body such as a container or a lid formed from a foamed resin sheet or a laminated sheet is required to be as fine and precise as required. As a result of diligent research on a method that makes it possible to easily produce a mass-produced product without causing surface roughness due to secondary foaming, the present invention has been completed.

That is, the present invention is based on the fact that a foamed resin sheet such as a foamed polystyrene resin sheet is hot-plated to form a foamed resin molded article such as a container or a lid. In such a case, a hot plate molding method for a foamed resin molded article that enables fine, sharp, high-precision molding of the details of the foamed resin molded article and that can be easily mass-produced without surface roughness. The purpose is to provide. Disclosure of the invention

In the hot plate molding method for a foamed resin molded article according to the present invention, a foamed resin sheet fed into a molding zone is arranged between a hot plate installed in the molding zone and a molding die, and the foaming is performed. One side of the resin sheet is placed along the hot plate to heat the foamed resin sheet from one side, and a differential pressure is generated between one side and the other side of the foamed resin sheet. Hot foaming of a foamed resin molded article to be molded by moving the foamed resin sheet along the molding surface of the mold In the molding method, the foamed resin sheet is heated from the other side by a preheating zone provided in front of the molding zone to preheat the foamed resin sheet, and the foamed resin sheet after the preheating is described above. It is sent to the molding zone.

According to this hot plate forming method, the foamed resin sheet fed into the forming zone is preheated by being heated from the other side by the preheating zone, and such preheating is performed. The foamed resin sheet is heated from one side by a hot plate in a molding zone. Therefore, at the stage of molding by generating a pressure difference between one surface side and the other surface side of the foamed resin sheet and causing the foamed resin sheet to be along the molding surface of the mold, heat is applied to the entire thickness portion. The foamed resin sheet that has been sufficiently transmitted faithfully follows the molding surface of the mold. As a result, the foamed resin molded article can be molded with high precision in a sharp and detailed manner. When the final molded article is used for pouring hot water, the molded article is not easily deformed even when hot water is added.

By adopting the above method, it is not necessary to increase the heating temperature of the foamed resin sheet, so that the surface of the foamed resin molded article does not become rough, and the heating time of the foamed resin sheet is reduced. Since it is not necessary to increase the length, mass production becomes easy.

In performing the above method, if the preheating by heating the foamed resin sheet in the preheating zone is performed by the radiant heat of the far-infrared heater, the effect of the heating is not only on the other surface of the foamed resin sheet but also on the other side. Since it reaches the inner layer in a short time, the preheating of the foamed resin sheet can be sufficiently performed in a short time.

Further, when the preheating temperature of the foamed resin sheet is set to a temperature lower than the glass transition point of the foamed resin sheet, the foamed resin sheet is not softened so that there is no danger of sagging or bending.

In the present invention, a foamed polystyrene resin sheet can be suitably used as the foamed resin sheet. Foamed polystyrene resin sheets have excellent heat insulation properties, and are suitable for molding synthetic resin molded articles such as containers for instant foods and lids, which are prepared by pouring hot water into them.

A foamed polystyrene resin sheet can be used as the foamed resin sheet. It is desirable that the thickness of the foamed synthetic resin sheet be set to 0.3 to 0.95 mm. The preferred thickness of the foam synthetic resin sheet for molding containers and lids for ready-to-eat food is 0.5 to 0.9 mm, and the most preferred thickness is 0.65 to 0.85 mm. It is. If the foamed synthetic resin sheet is too thick, preheating and molding may take time, and the molding cycle time may not be able to be shortened to the level of mass production. Conversely, if the foamed polystyrene resin sheet is too thin, it will not be possible to satisfactorily insulate the container or lid as a foamed synthetic resin molded article.

The hot plate molding method for a foamed resin molded article as described above can be applied to a laminated sheet made of a foamed resin sheet and a synthetic resin film as it is. Has the same effect Brief description of the drawings

FIG. 1 is an explanatory view showing a preheating zone and a molding zone for performing the hot plate molding method for a foamed resin molded article according to the present invention.

FIG. 2A is an explanatory view showing a state in which a foamed resin sheet is provided between a hot plate and a mold.

FIG. 2B is an explanatory view of the step of heating the foamed resin sheet with a hot plate.

FIG. 2C is an explanatory diagram of a step of molding a foamed resin molded article. FIG. 2D is an explanatory view of the molded foamed resin article.

FIG. 3 is a schematic perspective view showing a lid as a foamed resin molded body and a container to which the lid is attached.

Figure 4 is an enlarged cross-sectional view of the lid and part of the container.

FIG. 5 is an enlarged sectional view of a part of a lid as a foamed resin molded article molded from a laminated sheet. BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows a preheating zone A for performing a hot plate molding method for a foamed resin molded article according to the present invention, and a molding zone B provided adjacent thereto. The preheating zone A is located in front of the molding zone B, and the foamed resin sheet fed into the preheating zone A 1 is fed into forming zone B after being preheated in its preheating zone A.

Preheating zone A is provided with heating unit 2 consisting of a far infrared heater. In the molding zone B, a hot plate 3 and a molding die 4 are provided. The hot plate 3 and the mold 4 have ventilation holes (not shown) connected to an air supply device or a suction device, so that air can be supplied or sucked through the ventilation holes. As a result, a pressure difference is generated between one side 11 and the other side 12 of the foamed resin sheet 1 disposed between the hot plate 3 and the molding die 4, and the pressure difference causes the foamed resin sheet 1 to move. 1 can be made to follow the molding surface 41 of the molding die 4.

In the thermoforming method according to the present invention, the foamed resin sheet 1 is first fed into the preheating zone A. The foamed resin sheet 1 sent into the preheating zone A is heated from the other side 12 by the radiant heat of the heating unit 2. Since the heating unit 2 uses far-infrared rays, the effect of heating is short, not only on the other surface 12 of the foamed resin sheet 1 but also on its inner layer, Therefore, the preheating of the foamed resin sheet 1 is sufficiently performed in a short time.

The foamed resin sheet 1 preheated in the preheating zone A is sent to the molding zone B, and is disposed between the hot plate 3 and the molding die 4. 2A to 2D illustrate the process of molding the lid of the instant container with the molding bon A. The mold 4 in Fig. 1 Although the shape of the molding surface 4 1 is different from that of the molding die 4 of FIGS. 2A to 2D, this is illustrated in FIGS. 1 and 2A to 2D. This is because it is merely an accurate representation of the molding surface 1 of the actual mold 4.

As the foamed resin sheet 1 for forming the lid, a foamed polystyrene resin sheet having a thickness of 0.3 to 0.95 mm and an expansion ratio of 1.5 to 8 times is used. I have. As described in FIG. 1, the foamed resin sheet 1 preheated in the preheating zone A is fed into the molding zone B. Then, the foamed resin sheet 1 sent into the molding zone B is disposed between the hot plate 3 and the molding die 4 as shown in FIG. 2A. Next, as shown in Fig. 2B, the foamed resin sheet 1 is sandwiched between the hot plate 3 and the molding die 4, and the foamed resin sheet 1 is blown out from the molding die 4 'side as indicated by an arrow. By heating the foamed resin sheet 1 from the one side 11 side with the one side 11 along the heat pipe 3, the foamed resin sheet 1 is heated to a moldable temperature. After such heating, air is blown out from the hot plate 3 side as shown in FIG. 2C, so that one side 11 side of the foamed resin sheet 1 and the other side 12 side are formed. The foamed resin sheet 1 softened by the action of the pressure difference is brought into close contact with the molding surface 41 of the molding die 4, and a plurality of lids 20 are formed at a plurality of locations on the foamed resin sheet 1. Simultaneous molding to After releasing the mold as shown in FIG. 2D, the individual lids 2 are punched out of the foamed resin sheet 1.

In this method, foaming resin sheet 1 in preheating zone A is used. The preheating temperature is set to a temperature lower than the glass transition point of the foamed resin sheet 1, specifically, about 50. The heating temperature of the foamed resin sheet 1 by the hot plate 3 in the molding zone B is about 100 to 140 ° C., and the time from the start of heating to the end of molding is 6 seconds. The differential pressure between one side 11 and the other side 12 of the foamed resin sheet 1 described in FIG. 2C is 3 to 5 kg / cm ² .

In the method described above, although the foamed resin sheet 1 is used, a laminated sheet in which the synthetic resin film is laminated on the foamed resin sheet 1 can also be used. The laminated sheet preferably has a thickness of the foamed resin sheet of 0.3 to 0.95 mm and a thickness of the synthetic resin film of 15 to 80 m. The synthetic resin film is useful not only for printing on the lid 20 but also for suppressing the cracking etc. by supplementing the strength of the foamed resin sheet 1 forming the lid 20. Useful.

The lid 20 molded in this way has excellent heat retention during pouring and not only does not eliminate the danger of burns when draining, but also has a sharp and high-level detail, such as the fitting part. It is molded with high precision and can be mass-produced.

FIG. 3 shows a container 10 used for ready-to-eat foods, specifically “quick fried noodles” or “quick 席”, and a lid 20 formed by the above-described method of the present invention. The container 10 is made of expanded polystyrene resin or expanded polypropylene resin having a high expansion ratio (about 10 times). The lid 20 is mounted on the container 10 by fitting the fitting projection 21 on the peripheral edge thereof to the lid receiving portion 15 on the container 10 side. Then, in order to ensure the mounting state, an engaging ridge 22 is formed inward on the fitting projection 21, and the engaging ridge 22 is formed on the lid receiving portion 15. It is designed to engage with. Further, the lid 20 has a hollow frame portion 23 for accommodating the lid receiving portion 15 in a fitting shape in an outer peripheral portion in a swelling shape, and the hollow frame portion 23 has two hollow frame portions. Diagonal corners are used for pouring and draining water and venting / J ヽ An opening 24 and a cut-and-raised piece 25 for closing it are provided, and the product name of the contents can be displayed in three dimensions. A bulged portion 26 for display and small protrusions 27 are provided at predetermined positions on the inner side of the hollow frame portion 23. The fitting projection 21, the engaging ridge 22, the hollow frame 23, and the small projection 27 described above correspond to the details of the lid 20, and these details are fine, sharp, and precise. It is molded into.

FIG. 5 shows a part of the lid 20 formed by the method of the present invention using the above-described laminated sheet. In the figure, 1 is a foamed resin sheet, and 5 is a synthetic resin film. Also in this lid 20, details such as a fitting projection 21, an engagement ridge 22, a hollow frame 23, and a small projection 27 are formed with high precision and sharpness. Industrial applicability The hot plate molding method for a foamed resin molded article according to the present invention comprises the steps of: preheating a foamed resin sheet by heating the other side of the laminated sheet with a preheating zone; Since one side of the sheet is heated after being heated in the molding zone, the heat is sufficiently transmitted to the entire thickness of the foamed resin sheet during molding. Therefore, not only is it possible to form fine, sharp, and high-precision molding, but also the molding cycle time is short, and mass production can be easily performed.

By using the radiant heat of the far-infrared heater to perform the preheating in the preheating zone, the cycle time for molding can be further reduced.

Claims

The scope of the claims

(1) The foamed resin sheet fed into the molding zone is placed between the hot plate installed in the molding zone and the mold, and one side of the foamed resin sheet is placed along the hot plate. The foamed resin sheet is heated from one side, and a pressure difference is generated between one side and the other side of the foamed resin sheet so that the foamed resin sheet is placed on the molding surface of the above-mentioned mold. In the hot plate molding method for a foamed resin molded article formed by

The foamed resin sheet is heated from the other side by the preheating zone provided in front of the molding zone to preheat the foamed resin sheet, and the foamed resin sheet after the preheating is sent to the molding zone. Hot plate molding method for resin molded body.

(2) The hot plate molding method for a foamed resin molded article according to claim 1, wherein the preheating by heating the foamed resin sheet in the preheating zone is performed by radiant heat of far infrared rays.

(3) The hot plate molding method for a foamed resin molded article according to claim 2, wherein the preheating temperature of the foamed resin sheet is lower than the glass transition point of the foamed resin sheet.

(4) The hot plate molding method for a foamed resin molded article according to claim 1, wherein the foamed resin sheet is a foamed polystyrene resin sheet.

(5) The hot plate molding method for a foamed resin molded article according to claim 2, wherein the foamed resin sheet is a foamed polystyrene resin sheet.

(6) The hot plate molding method for a foamed resin molded article according to claim 4, wherein the thickness force of the foamed resin sheet is 0.3 to 0.95 mm.

(7) The hot plate molding method for a foamed resin molded article according to claim 5, wherein the thickness of the foamed resin sheet is 0.3 to 0.95 mm.

(8) A laminated sheet composed of a foamed resin sheet and a synthetic resin film fed into the molding zone is arranged between the hot plate installed in the molding zone and the molding die, and the laminated sheet is provided. The laminated sheet is heated from one side along one side of the sheet along the hot plate, and a differential pressure is generated between the one side and the other side of the laminated sheet, thereby forming the laminated sheet. In the hot plate molding method for a foamed resin molded article to be molded along the molding surface of the molding die, the laminated sheet is heated from the other side by a preheating zone provided in front of the molding zone. A hot plate molding method for a foamed resin molded article, wherein the laminated sheet is preheated and the preheated laminated sheet is sent to the molding zone.