JPH0655451B2 - Synthetic resin food container and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a food container made of synthetic resin capable of sterilizing a boil and a retort. In particular, the present invention relates to a synthetic resin food container which is thermoplastic and transparent, has heat resistance, is strong and has impact resistance, and has low gas and water vapor permeability.

(Prior Art) A film obtained by laminating various thermoplastic resin films into an integrated body is already known as a laminated film. The laminated film has the characteristics of the individual thermoplastic resin films that are stuck together, and as a result, has the characteristics that cannot be obtained by a single resin film. Therefore, an attempt was made to make a container using a laminated film.

Japanese Patent Laid-Open No. 53-39377 discloses forming a container by thermoforming using a sheet-like material composed of an inner resin layer and an outer resin layer, in which the inner resin layer is covered by the outer resin layer, as a molding material. Is taught. In this publication, in addition to ethylene / vinyl alcohol copolymer resin as the inner resin, 3
Since it has been described that three kinds of resins are suitable as the outer resin and three kinds of resins are suitable as the outer resin, various combinations of the resins are possible. However, this publication is completely unaware of the difference in the properties of the laminated film depending on the combination.

Further, in JP-A-47-20275, a high-density polyethylene film is placed outside and a film made of low-density polyethylene, vinyl acetate / ethylene copolymer or ethylene / ethyl acrylate is placed inside as a packaging container for a fish mill. The use of multilayer bags is disclosed.

Further, JP-A-55-59929 has a drawback that the surface of the polycarbonate plate is easily scratched by scratches. Therefore, in order to improve scratch resistance, polyacrylate, polymethacrylate, silicone resin, or methylamine is used. It teaches surface coating with cross-linked hydroxylated fluorine containing polymers.

However, these disclosures have failed to provide a container suitable for containing and storing foods that are easily altered and sold.
That is, it has low permeability to gas and water vapor, is easy to mold, has appropriate heat resistance, is transparent and non-toxic, and has a strong elasticity and impact resistance so that its shape does not collapse. It was not possible to obtain a container having the above properties and capable of being sterilized by boiling and retorting.

Further, JP-A-60-179255 discloses a laminated body in which an intermediate layer made of a thermoplastic resin having a gas barrier property is interposed between an inner layer made of a polycarbonate resin and an outer layer and a hollow like a bottle. It describes making a container. There, it is said that various resins such as polyacrylonitrile, polyester, nylon, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol and a copolymer of ethylene and vinyl alcohol can be used as the resin constituting the intermediate layer, Some of them do not adhere to the polycarbonate resin, and some cannot be used as food containers. Furthermore, a hollow container such as a bottle is inconvenient for containing solid foods due to its widening, is not suitable for boil and retort sterilization, and requires blow molding to make this. However, there is a drawback that the manufacturing efficiency is poor and the molding is not easy.

(Problems to be Solved by the Invention) This invention has a low gas and water vapor permeability, and has a shape that narrows from the opening to the bottom, so that it is easy to mold and has a heat resistance of about 130 ° C. An object of the present invention is to provide a synthetic resin food container which is transparent, non-toxic, tough, has high impact resistance and shape stability, and can be sterilized by boiling and retort. As a result, the present invention aims to provide a container that can preserve easily-altered food items for a long time. Further, the present invention is intended to provide a method for easily manufacturing the above-mentioned synthetic resin food container.

Here, the boil sterilization means that the food is sterilized at a temperature of 100 ° C. or lower. That is, put a container in which food is sealed in hot water boiling under normal pressure,
Means heating for ~ 30 minutes. The retort sterilization means sterilizing food at a temperature exceeding 100 ° C. Usually, the container in which the food is sealed is immersed in the solution, the temperature of the solution is increased to 120 ° C or higher under pressure and maintained at this temperature for 20 to 30 minutes, and the central portion of the food is heated to 120 ° C or higher for 4 minutes. To be retained.
For this reason, it is required that the container for retort sterilization should not be destroyed by heating under pressure.

(Means for Solving the Problem) The present inventor has found that among a large number of thermoplastic resins, polycarbonate (hereinafter, referred to as PC) and polyethylene terephthalate-based polyester resin (hereinafter, referred to as PE).
(T). PC has the characteristics of being transparent, heat-resistant, strong and tough, but has the drawback of having a large water absorption and therefore a poor barrier property. On the other hand, PET is transparent and becomes stiff and tough when stretched, but PET that is not stretched is flexible and has poor heat resistance, so a stretched film was used exclusively. The stretched film could not be laminated without the use of an adhesive. But PET
Has better barrier and chemical resistance than PC.

Therefore, this inventor has not stretched the PET film 30
Using a film with a thickness of -600 microns,
It was confirmed that when sandwiched between PC films having a thickness of -300 microns to form a laminated film, boil and retort sterilization can be performed, and a barrier property which is practically satisfactory appears. Further, the present inventor has found that when PC and PET are brought into contact with each other in a molten state when they are formed into a film by an extrusion method, the two films strongly adhere to each other without using an adhesive, so that it can be easily formed here. It has been found that a laminated film can be obtained. The present invention has been completed based on such confirmations and findings.

According to the present invention, a PET film having a thickness of 30-600 μm is sandwiched between PC films having a thickness of 30-300 μm, and a laminated film which is heat-welded and integrated is bent to have a shape that narrows toward the bottom. The present invention relates to a synthetic resin food container capable of sterilizing boil and retort.

Further, according to the present invention, PC and PET are heated and melted in separate extruders, and these heat-melted resins are formed into a film in a single die, and a PET film having a thickness of 30 to 600 microns is placed inside. 30- on both sides of the sandwich
Characteristic is that a PC film having a thickness of 300 microns is positioned, these films are welded to each other and integrally formed into a laminated film, and the laminated film is pressed against a molding die to be bent and formed into a shape that narrows toward the bottom to form a container. The present invention relates to a method for producing a synthetic resin food container capable of sterilizing a boil and a retort.

(Example) Hereinafter, this invention is demonstrated about an Example. Figure 1 shows
FIG. 3 is a partially cutaway perspective view of the synthetic resin food container according to the present invention. FIG. 2 is an enlarged view of a portion II in FIG.
FIG. 3 is a partially cutaway sectional view showing an embodiment of a laminated film manufacturing step in the method of the present invention. FIG. 4 is a partially cutaway sectional view showing another embodiment of the laminated film manufacturing step in the method of the present invention. FIG. 5 is a sectional view showing one embodiment of the step of bending the laminated film in the method of the present invention.

(Example of Product Invention) First, a food container according to the present invention will be described with reference to FIGS. 1 and 2. The container A in FIG. 1 is made of a laminated film as shown in an enlarged view in FIG. The laminated film is formed by sandwiching a PET, that is, a thermoplastic polyester film 2 between a PC, that is, a polycarbonate film 1, and integrating them. That is, the PC1 and the PET2 are not bonded to each other by using an adhesive, but are fused by heat to be integrated. The container A is formed by bending such a laminated film into a shape having a bottom and a side wall.

PET is a resin having many ester bonds in the main chain of the molecule. PET is made from a dibasic acid and a dihydric alcohol as raw materials. Usually, terephthalic acid is used as the dibasic acid, and ethylene glycol is used as the dihydric alcohol. The PET film is made by melting this. There are two types of films, stretched and non-stretched. In the present invention, the unstretched film is used.

PC has many carbonate bonds in the backbone of the molecule, namely It is a resin with the structure of. PC is made from bisphenol A and phosgene or diphenyl carbonate. In this invention, a film obtained by melting PC is used.

A suitable thickness for the PC film is 30-300 microns, and a suitable thickness for the PET film is 30-600.
Micron is suitable. Also, the PC film is PET
Generally, it is preferable to make the thickness thinner than the film.
The C film is preferably provided on both sides of the PET film so as to have the same thickness.

The laminated film may have an additional interposition of a mixed film layer made of a mixture of PC and PET between the PC film and the PET film. Since the mixed film is colorless and transparent, the interposition of the mixed film does not impair the transparency,
Further, it does not hinder the direct welding of the PC film and the PET film.

(Effect of Invention of Product) The laminated film in the present invention is formed by sandwiching a PET film between PC films and melting and adhering these films without using an adhesive to form an integrated body. Therefore, this laminated film is firmly integrated without peeling and has good transparency. In addition, since the PCs are located on both sides of the PET, the laminated film does not warp during processing and use, and the PC is heat-resistant, elastic and tough, so that the morphology is stable. Is good. Further, although the barrier property is inferior only with PC, the PET is sandwiched therein, so that the barrier property is improved as a whole. In addition, both PC and PET are thermoplastic and stable. PC has a thickness of 30-300 microns and PET has a thickness of 30-600 microns, so the laminated film should be molded by heating. Is easy. Therefore, the container made by bending the laminated film is suitable as a container for easy-to-manufacture and easy-to-alter food products. The container also has impact resistance and heat resistance up to 130 ° C. Especially, P
Since both C and PET are harmless resins, they can be brought into direct contact with food products. Further, even if it is sterilized by heating by contacting with steam, the container is not deformed, so that it can be used as a retort or boil container for food products.

The container according to the present invention is used by putting food or the like therein and then attaching a lid from above. As a lid,
Similarly, a thin film obtained by laminating a PC film and a PET film is generally used. The lid is provided so that the PC film side is the outside and an adhesive resin that can be easily peeled off is also extrusion-molded on the PET film to close the opening of the container. When it is necessary to take out the contents of the container, pick a part of the lid, remove the lid and take out the contents. The lid is a PC
The film surface may be subjected to metal vapor deposition or printing.

The synthetic resin food container according to the present invention can be sterilized by boiling and retort, and can also be microwaved. The contents include curry, stew, butter, cheese, pudding, jellies, mutton, hamburg, rice, miso,
A container that can be filled with jam, marmalade, prepared food, juice, liquor, raw meat, processed marine products, pickles, boiled vegetables, processed agricultural products, instant products, etc. and can be distributed at room temperature or chilled.

(Example of Invention of Manufacturing Method) Next, the method of the present invention will be described. The method of the present invention comprises the steps of producing a laminated film and molding the laminated film into a container. Each of these steps can be performed separately or in succession. Hereinafter, a case where each step is performed separately will be described with reference to the drawings. Third
FIGS. 4 and 5 show the steps of producing a laminated film by means of a section of the equipment used therein.

FIG. 3 shows an embodiment of producing a laminated film by the feed block method. In FIG. 3, the PC 1 is heated and melted in the extruder 3 and extruded into the die 5. On the other hand, the PET 2 is heated and melted in the extruder 4 and extruded into the die 5. The extruded molten PET2 has a base 5
The film is molded into a film with a thickness of 30-300 microns inside, but the PET film 7 goes straight through the die 5 and
Proceed through the central part of the resin passage inside. On the other hand, the extruded molten PC1 is divided into two in the die 5, is positioned on both sides of the PET film 7 by changing the traveling direction, is formed into a film along with the PET film 7, and is formed on both sides of the PET film 7. The PC film 6 is formed. In this way, the PC film 6 and the PET 7 are welded to each other while being in contact with each other in a molten state to proceed to form a laminated film 8. At this time, the PC film 6 has a thickness of 30-300.
Micron, PET film 7 has a thickness of 30-60
It is assumed to be 0 micron. Thus, the laminated film 8 is immediately pulled out from the base 5.

FIG. 4 shows a mode of producing a laminated film by the multi-manifold method. In FIG. 4, the PC is heated and melted in the extruders 11 and 13 and extruded into the die 14. On the other hand, PET is heated and melted in the extruder 12 and extruded into the die 14. The extruded PC and PET are formed into a film shape in the respective separated passages 15 to 17, and the formed films are brought into contact with each other at the confluence point 18 with the PET film interposed therebetween and welded to each other. To form an integral laminated film 19. Thus, the laminated film 1 is immediately obtained from the base 15.
9 is withdrawn. In FIG. 4, numeral 20 indicates a thickness adjusting tool for adjusting the thickness of the film, whereby the PC film has a thickness of 30-30.
0 micron, PET film thickness is 30-60
It is assumed to be 0 micron.

In the method of the present invention, the laminated film obtained as described above is pressed against a molding die to form a container. Two molds, an outer mold and an inner mold, may be used to press the molding mold, but it is also possible to use one mold and press it by air pressure. In any case, it is necessary to heat the laminated film to soften it in advance. When using air pressure, it is possible to send pressurized air to the laminated film surface from the side opposite to the molding die, to press the laminated film against the molding die, and also to reduce the pressure between the laminated film surface and the molding die, It is also possible to press the laminated film against the mold.

FIG. 5 shows a mode in which the pressure is reduced from the molding die side for molding. The molding die 20 has an inner wall surface formed into a desired container shape. An air passage 21 for reducing pressure is provided at the bottom, and the air inside can be sucked from a pipe 22. The frame 23 fixes the periphery of the laminated film 24 and covers the opening of the molding die 20.

To mold, first, as shown in (a) of FIG.
The laminated film 24 is fixed to the frame 23, placed on the mold 20, and heated by a heating tool (not shown),
Softened. Air is then sucked from the tube 22. Then, the laminated film 24 is pressed against the inner wall surface of the molding die 20 by the atmospheric pressure on the side opposite to the decompression side, is bent, and is deformed into a container shape as shown in (b) of FIG. The container 25 is formed. After cooling the container 25, pressurized air is sent from the pipe 22 into the molding die 20, and the container 25 is separated from the inner wall surface by the air pressure. Then, the fifth
The state shown in FIG. Then, the frame 23 is removed to obtain the container 25.

FIG. 5 shows a mode in which after obtaining the laminated film, it is once cooled and then heated and molded again. However, the laminated film obtained by the extrusion method may be immediately molded without cooling. it can. Although FIG. 5 shows a mode in which air pressure is used during molding, it is also possible to mold by using an outer mold and an inner mold that mesh with each other without using air pressure.

(Effect of Inventive Method) According to the invented method, since PC and PET are integrated in one die by using a plurality of extruders, a laminated film can be continuously manufactured. Therefore, the laminated film can be easily and efficiently manufactured. Also,
The laminated film thus obtained has a thickness of 30-300 microns for the PC film and a thickness of 30-600 microns for the PET film, so that it can be easily used as a container. Moreover, in the container obtained there, since the PET is sandwiched in between and the PCs are located on both sides, as described above, it is transparent and can be colored,
Since it has heat resistance up to ℃, is firm and strong, and has barrier properties, it can be sterilized by boil and retort, and is suitable for containing foods that are easily altered.
Therefore, it can withstand the normal temperature distribution of foods that are easily altered. In this respect, the method of the present invention has a great advantage.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a container according to the present invention. FIG. 2 is an enlarged view of a portion II in FIG. 3 to 5 are sectional views showing some steps of the method of the present invention. In the figure, 1 is a polycarbonate, 2 is a thermoplastic polyester resin, 3 and 4 are extruders, 5 is a die, 6 is a polycarbonate film, 7 is a thermoplastic polyester resin film, 8 is a laminated film, 11 to 13 are extruders, 14 is a base, 15 and 17 are polycarbonate films, 16 is a thermoplastic polyester resin film, 18
Is a confluence point, 19 is a laminated film, 20 is a mold, 21 is an air passage, 22 is a tube, 23 is a frame, 24 is a laminated film,
25 is a food container.

Claims (2)

[Claims] 1. A shape in which a thermoplastic polyester film having a thickness of 30-600 μm is sandwiched between polycarbonate films having a thickness of 30-300 μm and heat-welded to form a laminated film which is bent and narrowed toward the bottom. Food container made of synthetic resin that can be sterilized by boiling and retort. 2. A polycarbonate and a thermoplastic polyester resin are heated and melted in separate extruders, and these heat-melted resins are formed into a film in a single die, and a thermoplastic polyester having a thickness of 30 to 600 μm. A polycarbonate film with a thickness of 30-300 microns is positioned on both sides of the film sandwiched between them, and these films are welded together to form a laminated film, which is pressed into a mold and bent to the bottom. A method for producing a food container made of synthetic resin capable of sterilizing a boil and a retort, characterized by forming the container into a constricted shape.