JP3996619B1 - Food container manufacturing method and food container - Google Patents

Abstract

Even when a plurality of laminated films are subjected to hot press molding at the same time, there is no thermal bonding, and the slipperiness between containers is extremely good, so that each sheet can be taken out quickly. A food container and a method for producing the same are provided.
A method for producing a food container includes a step of bonding a high-density polyethylene film and a biaxially stretched polypropylene film to form a two-layer film; the high-density polyethylene film side and the biaxially stretched polypropylene film side are opposed to each other. A step of laminating a plurality of two-layer films; and a step of hot press-molding the plurality of laminated two-layer films.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a food container and a food container.

  In the past, aluminum containers were used as small food containers such as side dishes for bento boxes. Recently, however, those made of resin films have become mainstream with the spread of microwave ovens.

  This food container made of a resin film is manufactured by laminating a plurality of films and performing hot press molding in order to increase manufacturing efficiency. However, there has been a problem in that the production efficiency of lunch boxes and the like is reduced due to adhesion between the resin films during hot press molding.

  That is, in the manufacture of lunch boxes and frozen foods, a small food container is placed in a lunch container and the food is placed therein. Or the container for foods which put the foodstuff may be put in a lunch box container. Here, when two or more food containers are thermally bonded to each other as described above, when such a production line is automated, two or more food containers are inserted into a lunch container or the like while overlapping. Or the production line itself has to be stopped. Even in the case where the production line is not automated and is manual, the production efficiency is reduced unless the food containers are taken one by one.

  In order to solve the above-described problem of thermal bonding, the technique of Patent Document 1 describes a method for manufacturing a container in which resin films of different materials such as a polyethylene terephthalate film and a biaxially stretched polypropylene film are laminated and formed. Yes.

  In addition, Patent Document 2 discloses a container for a microwave oven formed by molding a laminated sheet in which a biaxially oriented polyester film is laminated on at least one surface of a polypropylene sheet in order to improve heat resistance and the like. In this technique, the coefficient of static friction of the polypropylene sheet is also defined in order to suppress wrinkling during lamination.

Further, Patent Document 3 discloses a container in which a punched sheet made of a biaxially stretched polypropylene film and polyethylene terephthalate is formed in order to improve shape retention during molding.
JP 2003-251689 A (Claims) Japanese Utility Model Laid-Open Publication No. 1-170671 (claim for utility model registration, page 6, bottom line to page 7, line 4) JP 2003-128122 A (Claims)

  As described above, a technique for forming a food container by hot press-molding resin films of different materials is known. Among them, there is a solution to the problem of thermal adhesion between films at the time of hot press molding.

  However, there may be a problem even if the thermal bonding does not occur. That is, when a lunch box or the like is manufactured using a food container, a plurality of food containers into which a side dish or the like is placed are picked up one by one by a machine or by hand from a plurality of stacked containers. At that time, the food containers could not be taken quickly one by one even if they were not thermally bonded, and workability during use sometimes deteriorated.

  Therefore, the problem to be solved by the present invention is that even if a plurality of laminated films are formed by hot press at the same time, there is no thermal bonding and the slipperiness between containers is extremely good one by one. It is in providing the food container which can take out swiftly, and its manufacturing method.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, if it is a two-layer film consisting of a high-density polyethylene film and a biaxially stretched polypropylene film, the slipperiness of both is good, so that multiple containers can be stacked and hot pressed to form containers for food. The present invention was completed by discovering that not only thermal bonding but also quick removal of a single container was possible.

  The method for producing a food container according to the present invention comprises a step of bonding a high-density polyethylene film and a biaxially stretched polypropylene film to form a two-layer film; the high-density polyethylene film side and the biaxially-stretched polypropylene film side are opposed to each other A step of laminating a plurality of two-layer films; and a step of hot press molding the plurality of two-layer films laminated.

  In the said manufacturing method, the aspect which adhere | attaches a high-density polyethylene film and a biaxially-stretched polypropylene film with a solventless adhesive agent is suitable. This is because there is no room for the solvent to be mixed, so that a container suitable for food use can be manufactured.

  The food container of the present invention is characterized by having a two-layer structure comprising a high-density polyethylene film and a biaxially stretched polypropylene film.

  As the food container, a container printed on the inside of a high-density polyethylene film and / or a biaxially stretched polypropylene film is suitable. This is because the printed surface does not come into contact with food and is hygienic.

  The printing is preferably performed with water-based ink. Unlike oil-based inks, water-based inks are preferable from the viewpoint of food hygiene.

  The food container according to the present invention is not only hard to be thermally bonded to each other, but also has a very good slipping property between containers even when a plurality of material films are laminated and hot press molded. Each container can be quickly removed from the container, and the workability during use is remarkably improved. Therefore, the food container of the present invention is extremely useful industrially as being able to achieve automation and efficiency in production when used for lunch boxes, frozen foods, and the like.

The method for producing a food container according to the present invention comprises:
Adhering a high density polyethylene film and a biaxially oriented polypropylene film to form a two-layer film;
A step of laminating a plurality of two-layer films so that the high-density polyethylene film side and the biaxially oriented polypropylene film side face each other; and a step of hot press-molding the plurality of laminated two-layer films;
It is characterized by including.

  The food container of the present invention has a two-layer structure composed of a high-density polyethylene film and a biaxially stretched polypropylene film. The high-density polyethylene film and the biaxially stretched polypropylene film are difficult to thermocompress even if they are opposed to each other by hot press molding, and the sliding property is good between these films. However, it is possible to take out one by one quickly and is extremely excellent in workability during use.

High density polyethylene (hereinafter sometimes referred to as “HDPE”) refers to polyethylene having a density of 0.942 g / cm ³ or more in accordance with JIS K6748. In addition, although it is said that 5 mol% or less of α-olefin monomer and 1 mol% or less of non-olefin monomer may be copolymerized in polyethylene, the density tends to decrease when these monomers are present. Therefore, the HDPE of the present invention preferably reduces the proportion of monomers other than ethylene as much as possible, and more preferably is a homopolymer of ethylene.

  The thickness of the HDPE film is not particularly limited and may be appropriately adjusted. For example, the thickness can be about 10 to 30 μm, and more preferably about 15 to 25 μm.

  As the HDPE film, a commercially available film can be selected and used according to the purpose, but a desired film can be produced and used. A known method may be used as a method for producing the HDPE film. Specifically, in the presence of a Ziegler catalyst or a Philips catalyst, the monomer is polymerized at an intermediate pressure or low pressure to obtain an ethylene polymer molecule with few branches.

  Biaxially stretched polypropylene (hereinafter sometimes referred to as “OPP”) can be used without particular limitation as long as it is biaxially stretched to improve strength and the like. For example, the draw ratio in the MD direction or TD direction and the isotacticity of the raw material polypropylene are not particularly limited, and may be appropriately selected in consideration of necessary strength and the like. However, if the amount of the ethylene component to be copolymerized is large, there is a risk that it will be thermally bonded to HDPE during hot press molding. Therefore, the ethylene monomer to be copolymerized is preferably suppressed to such an extent that polyethylene exhibits crystallinity. It is more preferable to use a homopolymer of

  The thickness of the OPP film is not particularly limited and may be adjusted as appropriate. For example, the thickness can be about 10 to 30 μm, and more preferably about 15 to 25 μm.

  As the OPP film, a commercially available film can be selected and used according to the purpose, but a desired film can be produced and used. A known method may be used for the production method and stretching method of the OPP film.

  In the method for producing a food container according to the present invention, first, an HDPE film and an OPP film are bonded to form a two-layer film.

  The HDPE film and the OPP film may be bonded by a conventional method, but it is preferably bonded by a solventless adhesive. Since the container of the present invention is for food, it is not preferable to mix a solvent, and if an adhesive containing a solvent is used, a drying step is required. Therefore, in the present invention, the solventless adhesive is heated and the viscosity is appropriately adjusted, which is applied to one film by a conventional method, and the other film is bonded. If necessary, the adhesive is cured by aging.

  The solvent-free adhesive is not particularly limited as long as it can adhere an HDPE film and an OPP film satisfactorily and does not require the use of a solvent. For example, a urethane-based adhesive is used. be able to.

  The obtained laminated film is cut according to the size and shape of the intended food container. For example, the film wound on a roll may be cut into an appropriate size and then punched into an appropriate shape.

  Next, a plurality of the obtained two-layer films are laminated so that the HDPE film side and the OPP film side face each other. Here, when the hot press molding is performed after the HDPE films or the OPP films are laminated so as to face each other, it becomes difficult to perform thermocompression bonding or to quickly take out the obtained food containers one by one.

  In addition, after laminating | stacking a some laminated | multilayer film, you may cut | disconnect to an appropriate magnitude | size and shape, or you may punch. The laminate thus obtained can be directly subjected to the next hot pressing step.

  Next, a plurality of laminated two-layer films are formed by hot press forming into a food container. The general hot press molding conditions can be used. For example, at least one of the male mold or female mold of the hot press molding machine may be heated to about 100 to 140 ° C. and hot pressed for about 2 to 10 seconds.

  Hereinafter, the food container of the present invention will be described. The food container of the present invention is characterized by having a two-layer structure comprising an HDPE film and an OPP film.

  The shape of the food container of the present invention is not particularly limited as long as it is determined according to the type and amount of food contained therein or a container such as a lunch container into which the container is further added. For example, the shape shown in FIG.

The food container shown in FIG. 1 has a circular bottom surface and pleats on the side surface. Such a shape is merely an example. For example, the bottom surface is not limited to a circle, but may be a polygon such as a triangle or a rectangle, an ellipse, or the like. In addition, it is not always necessary that the side also put the fold. Furthermore, although the side surface is tapered in the food container of FIG. 1, it may be perpendicular to the bottom surface.

  The food container of the present invention has a two-layer structure comprising an HDPE film and an OPP film, but the HDPE film is on the inside and the OPP film is on the outside, or the HDPE film is on the outside and the OPP film is on the inside. There can be any one. However, since the OPP film is relatively superior in transparency to the HDPE film, when printing is provided inside, it is preferable that the side on which the printing is to be shown is constituted by the OPP film.

  The HDPE film and the OPP film are bonded via an adhesive. The kind of adhesive is as described above, and a solventless adhesive is preferred.

  In a food container, a pattern or the like may be printed in order to improve the type of food, the name of the food manufacturer, or the design. However, when printing ink comes into contact with food, there is a risk of sanitary problems. Therefore, printing is preferably performed on the inside of the HDPE film and / or the OPP film, that is, on the inside of the two-layer structure film constituting the food container. It is preferable to apply.

  As the printing ink, it is preferable to use water-based ink in consideration of hygiene. Examples of such water-based inks include those in which a resin component such as a styrene-acrylic acid resin and an inorganic or organic pigment are dissolved or dispersed in water and a mixed solvent of water and alcohol such as ethanol. .

  In the food container of the present invention described above, even when a plurality of two-layer films are laminated and hot-pressed, the opposing HDPE film and OPP film are difficult to thermally bond. In addition, since the slipperiness between the HDPE film and the OPP film is good, it can be quickly taken out one by one from the stacked food containers. Therefore, it is extremely excellent in workability at the time of use, and the production efficiency of lunch boxes, frozen foods, cakes and the like using the food container of the present invention can be increased.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

Example 1
A high-density polyethylene film (density: 0.952 kg / m ³ , width: 620 mm, thickness: 21.5 μm) manufactured by Asahi Kasei Chemicals Co., Ltd. was installed in the first feeding portion of the non-solvent laminator. In addition, a biaxially stretched polypropylene film (width: 600 mm, average thickness: 20 μm) was placed in the second feeding portion. Separately, as an adhesive, an OH-terminated urethane prepolymer (main agent) manufactured by Mitsui Chemicals, a mixture of an NCO-terminated propolymer and 4,4′-diphenylmethane diisocyanate (MDI) (curing agent, containing 18% of MDI) The mixture was mixed at a ratio of 10: 9 (mass ratio) and melt-mixed at 70 ° C. This adhesive is supplied between the non-solvent laminator application roll and the metering roll and indirectly to the single side of the high density polyethylene film transported through the coating roll and impression cylinder in an amount of 1.8 g / m ^2. It was applied to. Both films were transported to a nip roll, and a biaxially stretched polypropylene film was bonded to the adhesive-coated surface of the high-density polyethylene film, pressure-bonded at a pressure of 18000 N / m ² and wound up. The wound laminated film was held at room temperature for 96 hours to accelerate the curing of the adhesive.

  The obtained laminated film was cut every 0.8 m, and 36 sheets were stacked so that the high-density polyethylene film and the biaxially stretched polypropylene film faced each other, and punched into a circle having a diameter of 9 cm using a mold. This laminate is placed in a hot press machine, the female mold is heated to 120 ° C., and hot-pressed for 5.6 seconds so that the biaxially oriented polypropylene film side is on the inside, thereby having the shape shown in FIG. A food container having a bottom surface of 4 cm in diameter was manufactured.

  The obtained food container has no thermocompression bonding between the containers, and the slipperiness between the outer film made of high-density polyethylene and the inner film made of biaxially stretched polypropylene is very good, and a plurality of films were formed at the same time. The container was able to be quickly acquired one by one. In order to quantitatively express such slipperiness, the static friction coefficient between both films was measured in Test Example 1 below.

Comparative Example 1
Currently, food containers made of biaxially stretched polypropylene films were manufactured as follows as the mainstream food containers made of resin films. That is, a food container was produced in the same manner as in Example 1 except that 36 biaxially stretched polypropylene films (thickness: 40 μm) were stacked and hot-press molded. In the obtained food container, the slipping property between the inner side and the outer side was relatively poor, and it was impossible to say that the container could be quickly obtained one by one from a plurality of films formed at the same time. The static friction coefficient of the film constituting the container was also measured according to Test Example 1 below.

Comparative Example 2
A food cup was produced in the same manner as in Example 1, except that a mat-like biaxially stretched polypropylene film was used instead of the high-density polyethylene film, and the mat-like film was externally heat-press molded. Although the obtained food container has no thermocompression bonding between the containers, the slipperiness between the inner film and the outer film is relatively poor, and the container can be quickly obtained one by one from a plurality of films formed at the same time. It was a result that could not be said. The static friction coefficient of the film constituting the container was also measured according to Test Example 1 below.

Test Example 1 Static friction coefficient measurement The static friction coefficient between films was measured according to JIS K7125. Specifically, the high-density polyethylene film (length 21 cm × width 29.7 cm) used in Example 1 above is fixed on a test table of an inclined friction tester, and a 200 g weight is wrapped with biaxially stretched polypropylene. Then, the weight was pulled on a high-density polyethylene film, and the static friction coefficient when the weight started to move was measured. The static friction coefficients of the biaxially stretched polypropylene films used in Comparative Example 1 and the biaxially stretched polypropylene film and the matte-like biaxially stretched polypropylene film used in Comparative Example 2 were also measured in the same manner. The results are shown in Table 1.

  As described above, the static friction coefficient between the biaxially stretched polypropylene films was high. This is considered to be the reason why the containers cannot be taken out quickly one by one. Even when the outer side was matte, the tendency was the same although the coefficient of static friction was somewhat lower.

  On the other hand, the food cup of the present invention can be quickly taken out one by one even if a plurality of sheets are subjected to hot press molding at the same time. Both films are difficult to be thermocompression bonded and the coefficient of static friction between the two films is low. It was revealed that. Therefore, the food cup according to the present invention is very useful as a product suitable for an automated production line for bento lunch boxes and capable of suppressing a delay in production due to difficulty in taking out the cup even if it is manual.

It is a figure which shows an example of the container for foodstuffs of this invention.

Claims (5)

Adhering a high density polyethylene film and a biaxially oriented polypropylene film to form a two-layer film;
A step of laminating a plurality of two-layer films so that the high-density polyethylene film side and the biaxially oriented polypropylene film side face each other; and a step of hot press-molding the plurality of laminated two-layer films;
The manufacturing method of the container for foodstuffs characterized by including.   The manufacturing method of the container for foodstuffs of Claim 1 which adhere | attaches a high-density polyethylene film and a biaxially-stretched polypropylene film with a solvent-free adhesive. A food container produced by the method of claim 1 or 2 and having a two-layer structure comprising a high-density polyethylene film and a biaxially stretched polypropylene film.   The food container according to claim 3, wherein printing is performed on the inside of the high-density polyethylene film and / or the biaxially oriented polypropylene film.   The food container according to claim 4, wherein the printing is based on water-based ink.

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