JP7683322B2 - Paper container and its manufacturing method - Google Patents

Description

The present invention relates to a tray-shaped paper container, and in particular to a tray-shaped paper container with excellent sealing properties for the lid material and suitable for small-lot production, as well as a method for manufacturing the same.

Tray- or box-shaped paper containers with waterproofed interior are widely used. The simplest type is a laminated body with waterproofing treatment such as laminating a resin film on the interior of cardboard, assembled simply into a box shape, and used as a container for storing lunch boxes with little liquid or snacks. These containers do not require significant water resistance and are intended to be used horizontally, so there are also examples where a simple lid is used for the lid.

When using a tray-shaped paper container as a sealed container, it is necessary to consider not only the sealability of the container itself, but also the sealability with the lid. To achieve this, a method is used in which a horizontal flange is provided on the upper edge of the paper container and the lid is tightly sealed to this flange.

The tray container blank described in Patent Document 1 has side panels raised from the four sides of a rectangular bottom panel, with edge pieces extending from the tip of each side panel, so that the four edge pieces form a flange portion. A tray-shaped paper container with a flange portion formed thereon can be used as an airtight container by sealing it with a lid material.

This invention solves the problem of tiny holes that can leak out at the intersections of the side panels and the edge pieces, which previously existed, by providing a small protrusion on the edge of the tongue piece at the tip of the flange.

However, in containers assembled from the tray container blanks described in Patent Document 1, it was unavoidable that a step would occur in the laminate at the flange due to its structure. If there was a step on the top surface of the flange, there was a risk of pinholes occurring at the step when the lid was sealed.

Patent No. 3687396

To solve this problem, we developed a new tray-shaped paper container in which the laminate does not overlap at the flange, and therefore there is no step at the flange. (Patent Application No. 2020-059941)

This paper container is a paper tray made of a paper blank, and the paper blank is made of a backing paper and a thermoplastic resin layer formed on both the front and back sides or on the inner surface of the tray. The paper tray is composed of a bottom surface, side panels, and edge pieces. The side panels rise around the bottom surface to form the tray. The edge pieces are continuous with the upper ends of the side panels and form flanges around the periphery of the tray parallel to the bottom surface. The backing paper that constitutes the blank is arranged so that the side panels do not overlap with the adjacent side panels at the corners of the tray when the side panels are raised. The edge pieces are cut out, and the gap between adjacent edge pieces is also cut out so that they do not overlap when the entire edge piece is formed, the thermoplastic resin layer is laminated from both the front and back sides of the backing paper or the surface that will become the inside of the tray, including the part where the backing paper has been cut out, and the side panels that rise up around the bottom are sealed and connected between the side panels and adjacent side panels by the thermoplastic resin layer of the part where the backing paper has been cut out, and similarly, the edge pieces and adjacent edge pieces are sealed and connected by the thermoplastic resin layer of the part where the backing paper has been cut out to form the tray, which is a paper tray.

In this paper tray, adjacent edge pieces are cut out in advance so that they do not overlap, and then a thermoplastic resin layer is formed, resulting in a flat flange without any steps. As a means of efficiently and inexpensively manufacturing such paper trays, a method is adopted in which a window is cut out in the cup base paper, and then thermoplastic resin is extruded and laminated on the front and back surfaces, as described in the examples.

However, with this method, the three processes of window cutting, extrusion lamination, and blank punching all need to be carried out by winding. For this reason, while this method allows for inexpensive and efficient production for large-scale production, it is completely unsuitable for small-scale production.

The problem that this invention aims to solve is to propose a method for manufacturing tray-type paper containers that can also be used for small-lot production, and a tray-type paper container with a layer structure suitable for this.

As a means for solving the above problems, the invention described in claim 1 comprises the steps of: punching out the necessary parts of a paperboard cut into a predetermined shape; applying adhesive to the surface of the paperboard other than the punched parts; and drying the adhesive.
A synthetic resin film with dimensions larger than that of the paperboard is placed on the adhesive surface.
The whole is pressed with a flat press to bond the paperboard and the synthetic resin film together.
After preparing a laminate having a paperboard layer and an inner synthetic resin film layer,
A method for manufacturing a tray-type paper container, comprising punching out a predetermined blank sheet shape,
The blank sheet has a bottom plate having a shape of a regular octagon stretched in the vertical and horizontal directions, and rectangular corner plates are connected to the four unstretched sides of the bottom plate via mountain fold lines,
The other sides of the bottom panel are connected to inverted trapezoidal side panels via mountain folds, and edge pieces are connected to each side panel via valley folds.
Between each corner plate and the side plate, and between each corner plate and the edge piece, there are portions where the paperboard layer is punched out and only the inner synthetic resin film layer is present;
When forming the panel, the tip and edge of each side panel are folded inside each corner panel so that the tips do not overlap.
The edge piece is continuous with the upper end of the side panel, and forms a horizontal, stepless, flat flange portion that is parallel to the bottom surface and surrounds the periphery of the opening of the paper container;
The method for producing a tray-type paper container is characterized in that the paperboard layer and the inner synthetic resin film layer are laminated via an adhesive layer having a thickness of 1 μm or more and 10 μm or less.

The method for manufacturing tray-type paper containers according to the present invention can accommodate small-lot production because the paperboard layer and the inner synthetic resin film layer can be bonded together using a flat press machine commonly known as a PP bonding machine.

Similarly, the invention described in claim 2 is a method for cutting a paperboard into a predetermined shape, and then punching the paperboard as necessary.
A synthetic resin film with a larger size than the paperboard is placed on the board, and adhesive is applied to the entire surface of the film.
The whole is pressed with a flat press to bond the paperboard and the synthetic resin film together.
Then, the sheet is punched into a predetermined blank sheet shape,
The blank sheet has a bottom plate having a shape of a regular octagon stretched in the vertical and horizontal directions, and rectangular corner plates are connected to the four unstretched sides of the bottom plate via mountain fold lines,
The other sides of the bottom panel are connected to inverted trapezoidal side panels via mountain folds, and edge pieces are connected to each side panel via valley folds.
Between each corner board and the side board, and between each corner board and the edge piece, there are portions where the paperboard layer is punched out and only the inner synthetic resin film layer and the adhesive layer are present;
When forming the panel, the tip and edge of each side panel are folded inside each corner panel so that the tips do not overlap.
The edge piece is continuous with the upper end of the side panel, and forms a horizontal, stepless, flat flange portion that is parallel to the bottom surface and surrounds the periphery of the opening of the paper container;
The method for producing a tray-type paper container is characterized in that the paperboard layer and the inner synthetic resin film layer are laminated via an adhesive layer having a thickness of 1 μm or more and 10 μm or less.

The invention described in claim 3 is a tray-type paper container obtained by punching out a laminate having a paperboard layer and an inner synthetic resin film layer into a predetermined shape to form a blank sheet,
The blank sheet has a bottom plate having a shape of a regular octagon stretched in the vertical and horizontal directions, and rectangular corner plates are connected to the four unstretched sides of the bottom plate via mountain fold lines,
The other sides of the bottom panel are connected to inverted trapezoidal side panels via mountain folds, and edge pieces are connected to each side panel via valley folds.
Between each corner plate and the side plate, and between each corner plate and the edge piece, there are portions where the paperboard layer is punched out and an inner synthetic resin film layer is present;
When forming the panel, the tip and edge of each side panel are folded inside each corner panel so that the tips do not overlap.
The edge piece is continuous with the upper end of the side panel, and forms a horizontal, stepless, flat flange portion that is parallel to the bottom surface and surrounds the periphery of the opening of the paper container;
The tray-type paper container is characterized in that the paperboard layer and the inner synthetic resin film layer are laminated via an adhesive layer having a thickness of 1 μm or more and 10 μm or less.

The invention described in claim 4 is the tray-type paper container described in claim 3, characterized in that the thickness of the adhesive layer is 2 μm or more and 6 μm or less.

The invention described in claim 5 is the tray-type paper container described in claim 3 or 4, characterized in that the adhesive forming the adhesive layer is an aqueous dispersion having the same composition as the inner synthetic resin film layer.

The method for manufacturing tray-type paper containers described in claim 1 or 2 allows for production in much smaller lots than the conventional manufacturing method using a winding method that involves three steps, making it a manufacturing method suitable for small-lot, multi-item production, which has been increasing in recent years.

Whether the adhesive is applied to the paperboard side, as in the manufacturing method described in claim 1, or to the inner synthetic resin film side, as in the manufacturing method described in claim 2, can be selected according to existing manufacturing equipment, so the introduction of new production equipment can be kept to a minimum.

When an aqueous dispersion with the same composition as the inner synthetic resin film layer is used as the adhesive as in the invention described in claim 5, unlike solvent-type adhesives, it does not adversely affect the indoor environment, and it is also economically advantageous because a general-purpose synthetic resin film such as a polyethylene resin film can be used as the inner synthetic resin film layer.

FIG. 1 is a perspective view showing an example of a tray-type paper container according to the present invention. FIG. 2 is a schematic plan view of a blank sheet for the tray-type paper container shown in FIG. FIG. 3 is a schematic cross-sectional view showing the layer structure of a blank sheet manufactured by the manufacturing method according to claim 1, and corresponds to the A-A' cross section of FIG. FIG. 4 is a schematic cross-sectional view showing a state in which the blank sheet of FIG. 3 has been molded, and corresponds to cross section B of FIG. FIG. 5 is a schematic cross-sectional view showing the layer structure of a blank sheet manufactured by the manufacturing method according to the second aspect of the invention, and corresponds to the cross section taken along the line AA' in FIG. FIG. 6 is a schematic cross-sectional view showing a state in which the blank sheet of FIG. 5 has been molded, and corresponds to cross section B of FIG. FIG. 7 is an explanatory cross-sectional view showing a state in which an inner synthetic resin film is placed on a paperboard on which an adhesive layer has already been formed, with the hot platens of a flat press machine in an open state, in the manufacturing method described in claim 1. FIG. 8 is an explanatory cross-sectional view showing a state where the hot platen is pressed from the state shown in FIG. FIG. 9 is an explanatory plan view showing a state in which the necessary punching has been performed on the paperboard layer in the method for producing a tray-type paper container according to the first aspect of the present invention. FIG. 10 is an explanatory plan view showing the inner synthetic resin film cut to a predetermined size. FIG. 11 is an explanatory plan view showing a laminate obtained by laminating the punched paperboard shown in FIG. 9 and the inner synthetic resin film shown in FIG. FIG. 12 is an explanatory plan view showing a state in which the laminate shown in FIG. 11 is punched out to form a blank sheet.

Hereinafter, the tray type paper container 10 according to the present invention and the manufacturing method thereof will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing an example of the tray type paper container 10 according to the present invention. FIG. 2 is a schematic plan view of the blank sheet BL of the tray type paper container 10 shown in FIG. 1. FIG. 3 is a schematic cross-sectional view showing the layer structure of the blank sheet BL manufactured by the manufacturing method described in claim 1, and corresponds to the A-A' cross section in FIG. 2. FIG. 4 is a schematic cross-sectional view showing the state in which the blank sheet in FIG. 3 has been molded, and corresponds to the B cross section in FIG. 1. Hereinafter, the manufacturing method of the tray type paper container according to the present invention and the tray type paper container manufactured thereby will be described with reference to these drawings.

As an embodiment of the method for manufacturing the tray-type paper container 10 according to the present invention, as described in claim 1,
This method for manufacturing a tray-type paper container 10 is characterized in that a paperboard 2 cut to a prescribed shape is subjected to the necessary punching 11, an adhesive 3 is applied to the surface of the paperboard other than the punched portions and dried, a synthetic resin film having dimensions larger than those of the paperboard is placed on the adhesive surface, and the whole is pressed with a flat press to bond the paperboard and the synthetic resin film to create a laminate 1 in which the paperboard layer 2 and the inner synthetic resin film layer 4 are laminated via an adhesive layer 3 having a thickness of 1 μm or more and 10 μm or less, and then the laminate is punched out into the prescribed blank sheet BL shape.

As shown in FIG. 2, the blank sheet BL has a bottom panel 5 in the shape of a regular octagon stretched vertically and horizontally, and rectangular corner panels 6, 6, 6, 6 are connected to the four unstretched sides of the bottom panel 5 via mountain fold lines e, f, g, h, respectively, and inverted trapezoidal side panels 7, 7, 7, 7 are connected to the other sides of the bottom panel 5 via mountain fold lines a, b, c, d, respectively, and edge pieces 8 are connected to each side panel 7 via valley fold lines i, j, k, l. Between each corner panel 6 and side panel 7, and between each corner panel 6 and edge piece 8, there are portions where the paperboard layer 2 has been punched out and only the inner synthetic resin film layer 4 is present, i.e., punched sections 11.

During the forming process, the tip and edge piece 8 of each side panel 7 are folded inside each corner panel 6 so that the tips do not overlap, and the edge piece 8 is continuous with the upper end of the side panel 7, forming a horizontal, stepless, flat flange portion 9 that is parallel to the bottom surface 5 and surrounds the periphery of the opening of the paper container 10.

As another embodiment of the method for manufacturing the tray-type paper container 10 according to the present invention, as described in claim 2,
This method for manufacturing a tray-type paper container 10 is characterized in that a synthetic resin film 4 having dimensions larger than those of a paperboard 2, which has previously been coated with adhesive 3 all over, is placed on top of the paperboard 2, and the whole is pressed with a flat press to create a laminate 1 in which the paperboard 2 and the synthetic resin film 4 are laminated together via an adhesive layer 3 having a thickness of 1 μm or more and 10 μm or less, and then the laminate is punched out into a predetermined blank sheet BL shape.

The blank sheet BL obtained by this method has a plan view similar to that shown in Figure 2. However, it differs in that in the areas 11 where the paperboard layer 2 is punched out between each corner plate 6 and side plate 7, and between each corner plate 6 and edge piece 8, not only is there an inner synthetic resin film layer 4, but also an adhesive layer 3.

The paperboard layer 2, which is usually the outside of the container, is printed and forms the front surface of the laminate 1. Therefore, fold lines that form a mountain on the paperboard layer 2 side are mountain fold lines, and fold lines that form a valley on the paperboard layer 2 side are valley fold lines. In Figure 2, mountain fold lines are shown with dotted lines, and valley fold lines are shown with dashed lines. Note that Figure 2 shows the blank sheet BL as viewed from the front surface side.

The other sides of the bottom panel 5 are connected to inverted trapezoidal side panels 7 via mountain fold lines a, b, c, and d, and edge pieces 8 are connected to each side panel via valley fold lines i, j, k, and l.

Between each corner plate 6 and each side plate 7 and edge piece 8, the paperboard layer 2 is punched out to leave only the inner synthetic resin film layer 4. In forming the panel, the tip and flange 8 of each side plate 7 are folded inwardly of each corner plate 6 so that the tips do not overlap.

By preventing the edge pieces 8 on all four sides from overlapping, the flange portion 9 after molding has a flat finish and is step-free, which prevents pinholes from occurring when sealing the lid and improves sealing performance.

In addition, after the necessary punching is performed on the paperboard layer 2, the inner synthetic resin film layer 4 is formed on the entire surface, and then a blank sheet is used that is punched into the specified shape. Therefore, in the molded tray-type paper container, the inner synthetic resin film layer 4 is continuous from the bottom surface to the flange, so there is no need to worry about water leakage.

Figure 3 is a schematic cross-sectional view showing the layer structure of the blank sheet BL manufactured by the manufacturing method described in claim 1, and corresponds to the A-A' cross section in Figure 2. Since the adhesive layer 3 is applied onto the paperboard layer 2, no adhesive layer is present on the inner synthetic resin film layer 4 of the punched portion 11. Figure 4 is a schematic cross-sectional view showing the blank sheet of Figure 3 in a molded state, and corresponds to the B cross section in Figure 1.

Figure 5 is a schematic cross-sectional view showing the layer structure of the blank sheet BL manufactured by the manufacturing method described in claim 2, and corresponds to the A-A' cross section in Figure 2. Figure 6 is a schematic cross-sectional view showing the blank sheet of Figure 5 in a molded state, and corresponds to the B cross section in Figure 1.

In either case of FIG. 4 or FIG. 6, heat and pressure are applied during molding, so that the inner synthetic resin film layers 4 are thermally fused together to become one body.

The adhesive that bonds the paperboard layer 2 and the inner synthetic resin film layer 4 must have a thickness of 1 μm or more and 10 μm or less. If the thickness is less than 1 μm, the amount of adhesive may be insufficient and the adhesive strength may be insufficient. If the thickness is more than 10 μm, not only is it uneconomical because the amount of adhesive is too large, but there is also the possibility of problems due to poor drying, etc. A more desirable thickness for the adhesive layer 3 is 2 μm or more and 6 μm or less.

The adhesive can be selected appropriately depending on the material of the inner synthetic resin film, but desirable results can be obtained by using an aqueous dispersion with the same composition as the inner synthetic resin film. For example, if a polyethylene resin film is used as the inner synthetic resin film, a polyethylene resin dispersion is the optimal adhesive, and if a polypropylene resin film is used as the inner synthetic resin film, a polypropylene resin dispersion is the optimal adhesive.

Figure 7 is a cross-sectional explanatory diagram showing the state in which the hot platen 21 of the flat press 20 is open and the inner synthetic resin film 4 is placed on the paperboard 2 on which the adhesive layer 3 has already been formed, in the manufacturing method described in claim 1. Also, Figure 8 is a cross-sectional explanatory diagram showing the state in which the hot platen 21 is pressed from the state shown in Figure 7, in the manufacturing method described in claim 1.

In Figures 7 and 8, only one set is pressed, but in some cases multiple sets are stacked with release film between them and then pressed together for adhesion. Also, cushions and release films are omitted from the figures.

Figures 9 to 12 explain the method for manufacturing a tray-type paper container according to the present invention in the order of steps. Figure 9 is an explanatory plan view showing the state in which the necessary punching 11 has been applied to the paperboard layer 2 in the method for manufacturing a tray-type paper container according to claim 1. Figure 10 is an explanatory plan view showing the inner synthetic resin film 4 cut to a predetermined size. Figure 11 is an explanatory plan view showing the state in which the punched paperboard shown in Figure 9 and the inner synthetic resin film shown in Figure 10 are bonded together to form a laminate 1. Figure 12 is an explanatory plan view showing the state in which the laminate 1 shown in Figure 11 has been punched out to form a blank sheet BL.

According to the method for manufacturing tray-type paper containers of the present invention, all processes for manufacturing blank sheets BL can be completed using a sheet-by-sheet method, making it possible to produce small lots, and it can be said to be a method suitable for small-lot production of a wide variety of products. The tray-type paper containers of the present invention will be specifically described below based on the examples.

Example 1
After punching out a paperboard (Pearl Card manufactured by Mitsubishi Paper Mills, basis weight 260 g/m ² ), a polypropylene resin dispersion (Baron manufactured by Daiichi Toryo Co., Ltd.) was applied as an adhesive so that the thickness after drying would be 1.0 μm, and then a polypropylene resin film (thickness 40 μm) was placed on the adhesive surface as an inner synthetic resin film, and the film was bonded by pressing with a flat press at a thermocompression temperature of 140 to 150° C. The obtained laminate was punched out into a predetermined blank shape and then molded into a tray-type paper container having the shape shown in FIG.

The moldability during molding, odor after molding, and heat resistance in a microwave oven were evaluated.

Example 2
A blank sheet was prepared in the same manner as in Example 1, except that the adhesive was applied to the PP film surface instead of the paperboard surface, and similarly molded into a tray-type paper container. Evaluation was performed in the same manner as in Example 1.

Example 3
A laminate was prepared in the same manner as in Example 1, except that a polyethylene resin dispersion (Arrowbase PE, manufactured by Unitika Ltd.) was used as the adhesive, a polyethylene resin film was used as the inner synthetic resin film, and the heat compression bonding temperature was 90 to 100°C. The laminate was then molded into a tray-type paper container in the same manner and evaluated in the same manner.

Example 4
A laminate was prepared in the same manner as in Example 2, except that a polyethylene resin dispersion (Arrowbase PE, manufactured by Unitika Ltd.) was used as the adhesive, a polyethylene resin film was used as the inner synthetic resin film, and the heat compression bonding temperature was 90 to 100°C. The laminate was then molded into a tray-type paper container in the same manner and evaluated in the same manner.

<Comparative Example 1>
A laminate was prepared in the same manner as in Example 2, except that a maleic acid-modified polypropylene resin adhesive (solvent-based) (Arrowbase PP DB5010, manufactured by Unitika Ltd.) was used as the adhesive and the heat-compression bonding temperature was set to 60 to 70°C. The laminate was then molded into a tray-type paper container in the same manner and evaluated in the same manner.

<Comparative Example 2>
A laminate was prepared in the same manner as in Example 2, except that a urethane resin-based adhesive (solvent-based) (Takelac A969V, manufactured by Mitsui Chemicals, Inc.) was used as the adhesive and the heat-compression temperature was set to 60 to 70°C. The laminate was then molded into a tray-type paper container in the same manner and evaluated in the same manner.

<Comparative Example 3>
A laminate was prepared in the same manner as in Example 4, except that a urethane resin-based adhesive (solvent-based) (Takelac A969V, manufactured by Mitsui Chemicals, Inc.) was used as the adhesive and the heat-compression temperature was set to 60 to 70°C. The laminate was then molded into a tray-type paper container in the same manner and evaluated in the same manner.

<Comparative Example 4>
A laminate was prepared in the same manner as in Example 4, except that a polyethylene terephthalate resin film (thickness 20 μm) was used as the inner synthetic resin film, a urethane resin-based adhesive (solvent-based) (Takelac A969V, manufactured by Mitsui Chemicals, Inc.) was used as the adhesive, and the heat-compression bonding temperature was 60 to 70° C., and then the laminate was molded into a tray-type paper container in the same manner and evaluated in the same manner.

<Comparative Example 5>
A laminate was prepared in the same manner as in Example 4, except that a polybutylene terephthalate resin film (thickness 20 μm) was used as the inner synthetic resin film, a urethane resin-based adhesive (solvent-based) (Takelac A969V, manufactured by Mitsui Chemicals, Inc.) was used as the adhesive, and the heat-compression bonding temperature was 60 to 70° C., and then the laminate was molded into a tray-type paper container in the same manner and evaluated in the same manner.

<Comparative Example 6>
A laminate was prepared in the same manner as in Example 4, except that a polymethylpentene resin film (thickness 20 μm) was used as the inner synthetic resin film, a urethane resin-based adhesive (solvent-based) (Takelac A969V, manufactured by Mitsui Chemicals, Inc.) was used as the adhesive, and the heat-compression bonding temperature was 60 to 70° C., and then molded into a tray-type paper container in the same manner and evaluated in the same manner.

The above results are summarized in Table 1.

The results in Table 1 show that the tray-type paper container manufactured by the method for manufacturing tray-type paper containers according to the present invention has performance that is in no way inferior to that of tray-type paper containers manufactured by the conventional continuous winding method.

1: Laminate 2: Paperboard layer 3: Adhesive layer 4: Inner synthetic resin film layer BL: Blank sheet 5: Bottom plate 6: Corner plate 7: Side plate 8: Edge piece 9: Flange portion 10: Tray-type paper container 11: Punched-out portions a to l: Fold line 20: Flat press machine 21: Hot plate

Claims (9)

The paperboard is cut into a specified shape, the necessary punching is performed, and adhesive is applied to the surface of the paperboard other than the punched parts and dried.
A synthetic resin film with dimensions larger than that of the paperboard is placed on the adhesive surface.
The whole is pressed with a flat press to bond the paperboard and the synthetic resin film together.
After preparing a laminate having a paperboard layer and an inner synthetic resin film layer,
A method for manufacturing a tray-type paper container, comprising punching out a predetermined blank sheet shape,
The blank sheet has a bottom plate having a shape of a regular octagon stretched in the vertical and horizontal directions, and rectangular corner plates are connected to the four unstretched sides of the bottom plate via mountain fold lines,
The other sides of the bottom panel are connected to inverted trapezoidal side panels via mountain folds, and edge pieces are connected to each side panel via valley folds.
Between each corner plate and the side plate, and between each corner plate and the edge piece, there are portions where the paperboard layer is punched out and only the inner synthetic resin film layer is present;
When forming the panel, the tip and edge of each side panel are folded inside each corner panel so that the tips do not overlap.
The edge piece is continuous with the upper end of the side panel, and forms a horizontal, stepless, flat flange portion that is parallel to the bottom surface and surrounds the periphery of the opening of the paper container;
A method for producing a tray-type paper container, characterized in that the paperboard layer and the inner synthetic resin film layer are laminated via an adhesive layer having a thickness of 1 μm or more and 10 μm or less. After cutting the paperboard into the required shape,
A synthetic resin film with a larger size than the paperboard is placed on the board, and adhesive is applied to the entire surface of the film.
The whole is pressed with a flat press to bond the paperboard and the synthetic resin film together.
Then, the sheet is punched into a predetermined blank sheet shape,
The blank sheet has a bottom plate having a shape of a regular octagon stretched in the vertical and horizontal directions, and rectangular corner plates are connected to the four unstretched sides of the bottom plate via mountain fold lines,
The other sides of the bottom panel are connected to inverted trapezoidal side panels via mountain folds, and edge pieces are connected to each side panel via valley folds.
Between each corner board and the side board, and between each corner board and the edge piece, there are portions where the paperboard layer is punched out and only the inner synthetic resin film layer and the adhesive layer are present;
When forming the panel, the tip and edge of each side panel are folded inside the corner panel so that the tips do not overlap.
The edge piece is continuous with the upper end of the side panel, and forms a horizontal, stepless, flat flange portion that is parallel to the bottom surface and surrounds the periphery of the opening of the paper container;
A method for producing a tray-type paper container, characterized in that the paperboard layer and the inner synthetic resin film layer are laminated via an adhesive layer having a thickness of 1 μm or more and 10 μm or less. A tray-type paper container formed by punching out a laminate having a paperboard layer and an inner synthetic resin film layer into a predetermined shape to form a blank sheet,
The blank sheet has a bottom plate having a shape of a regular octagon stretched in the vertical and horizontal directions, and rectangular corner plates are connected to the four unstretched sides of the bottom plate via mountain fold lines,
The other sides of the bottom panel are connected to inverted trapezoidal side panels via mountain folds, and edge pieces are connected to each side panel via valley folds.
Between each corner plate and the side plate, and between each corner plate and the edge piece, there are portions where the paperboard layer is punched out and an inner synthetic resin film layer is present;
When forming the panel, the tip and edge of each side panel are folded inside each corner panel so that the tips do not overlap.
The edge piece is continuous with the upper end of the side panel, and forms a horizontal, stepless, flat flange portion that is parallel to the bottom surface and surrounds the periphery of the opening of the paper container;
The paperboard layer and the inner synthetic resin film layer are laminated via an adhesive layer having a thickness of 1 μm or more and 10 μm or less,
1. A tray-type paper container, comprising: a paperboard layer in contact with one side of the adhesive layer; and an inner synthetic resin film layer in contact with the other side of the adhesive layer . A tray-type paper container formed by punching out a laminate having a paperboard layer and an inner synthetic resin film layer into a predetermined shape to form a blank sheet,
The blank sheet has a bottom plate having a shape of a regular octagon stretched in the vertical and horizontal directions, and rectangular corner plates are connected to the four unstretched sides of the bottom plate via mountain fold lines,
The other sides of the bottom panel are connected to inverted trapezoidal side panels via mountain folds, and edge pieces are connected to each side panel via valley folds.
Between each corner plate and the side plate, and between each corner plate and the edge piece, there are portions where the paperboard layer is punched out and an inner synthetic resin film layer is present;
When forming the panel, the tip and edge of each side panel are folded inside the corner panel so that the tips do not overlap.
The edge piece is continuous with the upper end of the side panel, and forms a horizontal, stepless, flat flange portion that is parallel to the bottom surface and surrounds the periphery of the opening of the paper container;
The paperboard layer and the inner synthetic resin film layer are laminated via an adhesive layer having a thickness of 1 μm or more and 10 μm or less,
A tray -type paper container, wherein the adhesive forming the adhesive layer is a dried aqueous dispersion having the same composition as that of the inner synthetic resin film layer. 5. The tray-type paper container according to claim 3 , wherein the adhesive layer has a thickness of 2 μm or more and 6 μm or less. A tray-type paper container as described in any one of claims 3 to 5, characterized in that at each corner of the blank sheet, there are two portions where the paperboard layer is punched out and the inner synthetic resin film layer is present, and the two portions are separated by the corner plate. The tray-type paper container according to any one of claims 3 to 6, characterized in that in the portion where the paperboard layer is punched out and the inner surface synthetic resin film layer is present, only the inner surface synthetic resin film layer is present. The inner synthetic resin film layer is a polyethylene resin film,
8. The tray-type paper container according to claim 3, wherein the adhesive forming the adhesive layer is a dried polyethylene resin dispersion. The inner synthetic resin film layer is a polypropylene resin film,
8. The tray-type paper container according to claim 3, wherein the adhesive forming the adhesive layer is a dried polypropylene resin dispersion.

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