JP2012200966A - Method of manufacturing paper container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a paper container for stabilizing an integrated state and improving quality of the paper container.SOLUTION: In the method of manufacturing the paper container comprising side plate base paper 11 and bottom plate base paper, a first film 21 is formed on the inner surface side of the container and a second film 22 is formed on the outer surface side of the container, and sectorial side plate base paper 11 having opposed side edges 14a and 14b is prepared first. Then, a first step part and a second step part 18 having double thickness of the first step part are formed at one side edge 14a, and a folded part 19 for which a part on the side of the end of the first step part is folded to the outer surface side of the paper container, piled up on the remaining part of the first step part and integrated is formed. Finally, the side plate base paper 11 is rounded into a cylindrical shape, heat is applied to a part where the side edge 14b is superimposed onto the folded part 19 and the second stage part 18, in a pressurized state, the first film 21 of the side edge 14b, the first film 21 of the folded part 19 and the second step part 18 comprising the paper are thermally welded respectively, and the side edge 14a and the side edge 14b are integrated.

Description

  The present invention relates to a method for manufacturing a paper container, and more particularly to a method for manufacturing a paper container that contains a liquid or food.

  FIG. 8 is a perspective view showing an external shape of a conventional paper container, FIG. 9 is a plan view of a paper material for manufacturing the paper container shown in FIG. 8, and FIG. FIG. 11 is an enlarged cross-sectional view of the XX line shown, FIG. 11 is a plan view showing an external shape of a side plate base paper rolled into a cylindrical shape, and FIG. 12 is a view showing a welding process of the side plate base paper FIG. 12 is an enlarged schematic view of the “X” portion shown in FIG. 11.

  Referring to these drawings, a paper container 70 is obtained by laminating a water-resistant and heat-meltable first film 81 and second film 82 made of polyethylene terephthalate (PET) on both surfaces of a paper sheet body 84. The base paper 71 is formed by punching out the base paper into a fan shape and the bottom base paper 72 punched out in a circle. The side plate base paper 71 has opposing side edges 74a and 74b.

  In forming the paper container 70, first, the side plate base paper 71 is rolled into a cylindrical shape with the first film 81 side inward so that the side edge 74a is on the inner surface side of the cylinder and the side edge 74b is on the outer surface side of the cylinder. The side edge 74a and the side edge 74b are overlapped with each other. Next, heat is applied in a pressed state to the overlapped portion with a pair of hot plates 90a and 90b, and the second film 82 of the side edge 74a and the first film 81 of the side edge 74b are thermally welded to the side, The edge 74a and the side edge 74b are integrated to form the side plate base paper 71 in a cylindrical shape. Finally, one of the openings of the cylindrical side board base paper 71 is closed with a bottom board base paper 72 whose outer edge is bent, and the process of forming the paper container 70 is completed.

  However, in the paper container 70 formed in this way, the end 75 of the side edge 74a exposed to the inner surface side is not covered with the first film 81 or the second film 82. In addition, there is a problem in quality that moisture, oil, and the like generated from food enter the sheet body 84 from the end portion 75 as indicated by the two-dot chain arrows in the figure.

  Therefore, the following method has been proposed as a method for treating the end portion 75 exposed on the inner surface side of the paper container 70.

  FIG. 13 is an enlarged schematic view showing a state in which a step portion is formed on one of the side edges in a conventional paper container manufacturing method, and FIG. 14 shows a state in which the step portion shown in FIG. 13 is folded. FIG. 15 is an enlarged schematic view showing a welding process of the side plate base paper including one of the side edges shown in FIG.

  In these drawings, first, referring to FIG. 13, the outer surface side of the paper container of one side edge 74a is removed along the end portion 75, and the thickness H / 2 that is half the thickness H of the side board base paper is removed. And a step 77 having a width L is formed. An adhesive 80 that can be used for food containers is applied to a part of the stepped portion 77.

  Next, referring to FIG. 13 and FIG. 14, a part of the end portion 75 side of the stepped portion 77 is folded back to the outer surface side of the paper container and overlapped with the remaining portion of the stepped portion 77 through the adhesive 80. Integrate.

  Finally, referring to FIG. 15, first, the side edge 74a including the folded portion 79 and the side edge 74b are overlapped. Next, heat is applied to the overlapping portion in a pressed state with a pair of hot plates 90a and 90b, and the first film 81 of the folded portion 79, the second film 82 of the side edge 74a, and the first film 81 of the side edge 74b. The side edges 74a and 74b are integrated by heat welding.

  In this way, since the sheet body 84 is completely covered by the first film 81 or the second film 82 including the end portion 75, as shown by the two-dot chain line arrow in the figure, the liquid contained in the paper container, Moisture, oil, etc. generated from food do not enter the sheet body 84, and the quality of the paper container is improved.

  By the way, in recent years, in order to have different properties such as water resistance and gas resistance, paper containers in which films having different properties are formed on the inner surface side and the outer surface side have been proposed. When the edge processing described above is performed, the following problems occur.

  FIG. 16 is an enlarged schematic view showing a welding process by a conventional method for manufacturing a paper container of a side plate base paper on which a different material film is formed, corresponding to FIG. 15, and FIG. It is the expansion schematic diagram which showed the peeling state of the folding | turning part of the side-plate base paper shown by.

  Among these drawings, first, referring to FIG. 16, the second film 82 is replaced with a material made of polyethylene (PE) having gas resistance, which is a material different from that of the first film 81. Since other components are the same as those shown in FIG. 15, the description thereof will not be repeated here.

  In this state, when heat is applied to a portion where the side edge 74a and the side edge 74b including the folded portion 79 are overlapped, the first films 81 of the same material are thermally welded to each other, but the first films 81 of different materials are used. And the second film 82 are not sufficiently heat-welded in the “A” portion. Accordingly, there is a portion where the side edge 74a and the side edge 74b are not sufficiently integrated.

  Then, as shown by the arrow in FIG. 17, when an external force is applied to the side edge 74 b toward the outer surface side of the paper container, the “A” portion and the folded portion 79 cannot be maintained in the bonded state and are peeled off. As described above, the adhesive that bonds the folded portion 79 must be usable for food containers for the purpose of paper containers. Can not.

  As described above, in the conventional method for manufacturing a paper container, the side edges centering on the adhesive are integrated, so that it cannot be said that the strength is sufficient. In particular, when films of different materials are formed on the inner surface side and the outer surface side of the paper container, the integrated state of one side edge and the other side edge is unstable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a paper container manufacturing method in which the integrated state is stable and the quality of the paper container is improved.

  In order to achieve the above object, the invention according to claim 1 is a method for manufacturing a paper container, wherein a first film having water resistance and heat melting property is formed on at least one surface and opposing side edges. A sheet-like base paper having a first side and a first step and a first step having a first thickness and a first width by removing one of the side edges from the other side of the base paper along the edge. A step of forming a second step portion having a second thickness and a second width twice as large as the adjacent first thickness, a part of the end portion side of the first step portion is folded back to the other surface side, Overlaying and integrating the remaining part of the step part, and rounding the base paper to one side, overlapping the other side edge to the second step part, heat-welding the first film and integrating it with one of the side edges And a step of making it.

  If comprised in this way, while the other film of a side edge will be heat-welded to one 2nd step part of a side edge, the level | step difference of the junction part of side edges will become small.

  According to a second aspect of the invention, in the configuration of the first aspect of the invention, the first width is set to be twice the second width.

  If comprised in this way, the length which the 1st film heat-welds to the 1st film will become substantially equal to the length which heat-welds to paper.

  According to a third aspect of the present invention, in the configuration of the first or second aspect of the present invention, a second film different from the first film is formed on the other side of the base paper.

  If comprised in this way, a 1st film and a 2nd film will not contact | connect.

  Invention of Claim 4 is a manufacturing method of a paper container, Comprising: The 1st film which has water resistance and a heat-melting property is formed in at least one surface, and it prepares the sheet-like base paper which has a side edge which opposes A step of removing one of the side edges from the other side of the base paper along the edge to form a step having a half thickness of the base paper and a predetermined width, and at least a part of the step The step of installing a heat-meltable film and a part of the end portion side of the step portion are folded back to the other side, and the step portion is heat-meltable by overlapping with the remaining portion of the step portion sandwiching the heat-meltable film. The process of heat-welding and integrating the film, the base paper is rolled to one side, the other side edge is overlaid on the outer surface of the folded portion of the stepped portion, and the first film is heat-welded and integrated to one of the side edges And a step of making it.

  If comprised in this way, the folding | turning part of a step part will be integrated by the heat welding of a heat-meltable film.

  According to a fifth aspect of the present invention, in the configuration of the fourth aspect of the invention, the heat-meltable film is disposed so as to cover the end portion of the folded portion of the stepped portion.

  If comprised in this way, the whole folding | turning part of a step part will be integrated.

  According to a sixth aspect of the present invention, in the configuration of the fourth or fifth aspect of the present invention, a second film different from the first film is formed on the other side of the base paper, and the other end of the side edge is It aligns with the front-end | tip part of the folding | turning part of a step part.

  If comprised in this way, a 1st film will not contact | connect a 2nd film.

  As described above, the invention according to claim 1 integrates because the other film of the side edge is thermally welded to one second step part of the side edge and the step of the joint part between the side edges is reduced. The state is stabilized and the quality of the paper container is improved.

  In the invention according to claim 2, in addition to the effect of the invention according to claim 1, the length of the first film thermally welded to the first film is substantially equal to the length thermally welded to the paper. Stabilize.

  In addition to the effect of the invention of claim 1 or 2, the invention according to claim 3 does not contact the first film and the second film, so that the quality of the product is improved and the second film is integrated. Does not affect the state.

  In the invention according to claim 4, since the folded portion of the step portion is integrated by heat welding of the heat-meltable film, the integrated state of the folded portion is stabilized and the quality of the paper container is improved.

  In the invention according to claim 5, in addition to the effect of the invention according to claim 4, since the entire folded portion of the step portion is integrated, the integrated state of the folded portion is more stable.

  According to the sixth aspect of the invention, in addition to the effect of the fourth or fifth aspect of the invention, the first film does not contact the second film, so that the bonding failure between the side edges does not occur.

In the manufacturing method of the paper container by 1st Embodiment of this invention, it is the expansion schematic diagram which showed the state in which the step formation part was formed in one of the side edges. FIG. 2 is an enlarged schematic view showing a state where a first step portion and a second step portion are formed on one of the side edges shown in FIG. 1. FIG. 3 is an enlarged schematic diagram illustrating a state where the first step portion illustrated in FIG. 2 is folded. It is the expansion schematic diagram which showed the welding process of the side board base paper containing one of the side edges shown in FIG. In the manufacturing method of the paper container by the 2nd Embodiment of this invention, the step part is formed in one of the side edges, and it is the expansion schematic diagram which showed the state in which a heat-meltable film is installed. FIG. 6 is an enlarged schematic diagram showing a state where the stepped portion shown in FIG. 5 is folded and welded. It is the expansion schematic diagram which showed the welding process of the side board base paper including one of the side edges shown in FIG. It is the perspective view which showed the external appearance shape of the conventional paper container. It is a top view of the paper material for manufacturing the paper container shown in FIG. It is an expanded sectional view of the XX line shown in FIG. It is the top view which showed the external appearance shape of the state which rolled the side board base paper into the cylinder shape. It is the figure which showed the welding process of the side board base paper, Comprising: It is an enlarged schematic diagram of the "X" part shown in FIG. In the manufacturing method of the conventional paper container, it is the expansion schematic diagram which showed the state in which the step part was formed in one of the side edges. It is the expansion schematic diagram which showed the state which turned the step part shown in FIG. It is the expansion schematic diagram which showed the welding process of the side board base paper including one of the side edges shown in FIG. FIG. 16 is an enlarged schematic diagram illustrating a welding process of a side plate base paper on which a different material film is formed by a conventional paper container manufacturing method, corresponding to FIG. 15. It is the expansion schematic diagram which showed the peeling state of the folding | turning part of the side board base paper shown in FIG.

  1 is an enlarged schematic view showing a state in which a step forming portion is formed on one of the side edges in the paper container manufacturing method according to the first embodiment of the present invention. FIG. FIG. 3 is an enlarged schematic view showing a state where the first step portion and the second step portion are formed on one of the shown side edges, and FIG. 3 is an enlarged schematic view showing a state where the end portion shown in FIG. 2 is folded. FIG. 4 is an enlarged schematic diagram showing a welding process of the side plate base paper including one of the side edges shown in FIG.

Referring to these drawings, a side base paper 11 of a paper material for producing a paper container is one side of a paper sheet 24 having a basis weight of 170 to 500 g / m ² and a thickness of 0.2 to 0.5 mm. A base paper in which a first film 21 of 30 μm thick made of PET and a second film 22 of 30 μm thick PE made of PE are formed by extrusion lamination on the other side, as shown in the conventional example of FIG. It is made from what is punched. In addition, the side board base paper 11 has the side edges 14a and 14b which oppose. At the time of forming the paper container, the side plate base paper 11 is rolled into a cylindrical shape with the first film 21 side inward, and the side edges 14a and the side edges 14b are integrated into a cylindrical shape.

  In making the side board base paper into a cylindrical shape, first, referring to FIG. 1, a part of the outer surface side of the paper container of the side edge 14a is cut and removed along the end 15 to obtain the thickness H of the side board base paper. The step forming portion 16 having a thickness 2H / 3 and a width L of 2/3 is formed. Here, the width L is 12 mm.

  Next, referring to FIG. 1 and FIG. 2, the outer surface side of the paper container of the step forming portion 16 is further cut and removed along the end portion 15 to have a thickness H / 3 and a width 2L / 3. The first step portion 17 is formed, and the adhesive 20 is applied to a part of the first step portion 17. The remaining portion of the step forming portion 16 becomes the second step portion 18. Thus, the effect by having set the dimension of the 1st step part 17 and the 2nd step part 18 is mentioned later. For convenience, the thickness H / 3 of the first step portion 17 is the first thickness, the thickness 2H / 3 of the second step portion 18 is the second thickness, and the width 2L / 3 of the first step portion 17 is the second thickness. One width and the width L / 3 of the second step portion 18 are defined as a second width.

  Next, referring to FIG. 2 and FIG. 3, a part of the end portion 15 side of the first step portion 17 is folded back to the outer surface side of the paper container, and overlapped with the remaining portion of the first step portion 17. Integrate via 20.

  As shown in FIG. 2, since the first width is set to be twice the second width, the width W of the folded portion 19 is substantially equal to the second width. The effect of having such a configuration will be described later. Further, since the first thickness is set to ½ of the second thickness, the thickness of the folded portion 19 is substantially equal to the second thickness. The effect by being comprised in this way is also mentioned later. The folded portion 19 has a width of about 4 mm and a second width of 4 mm, and the total of these widths is about 8 mm.

  Finally, referring to FIG. 4, in integrating the side edge 14a and the side edge 14b, first, the side edge 14b is overlapped with the folded portion 19 and the second step portion 18 of the side edge 14a. Then, as described above, since the thickness of the folded portion 19 and the second thickness are substantially equal, the side edges 14b are substantially flush with the surfaces of the first film 21 and the second stepped portion 18 of the folded portion 19. The first film 21 is contacted. In this state, when the folded portion 19 and the second step portion 18 and the portion where the side edge 14b overlaps are heated while being pressed by the pair of hot plates 90a and 90b, the first film 21 on the side edge 14b is made of the same material. Since both the first film 21 of the folded portion 19 that is a film and the second step portion 18 made of paper are thermally welded, the side edge 14a and the side edge 14b are completely integrated.

  In this way, the first film 21 of the side edge 14b is thermally welded to the second step portion 18 of the side edge 14a, and the “B” portion, which is the step of the joint portion between the side edge 14a and the side edge 14b, is shown in FIG. Therefore, the integrated state is stabilized and the quality of the paper container is improved. Also, as shown in FIG. 3, the width W of the folded portion 19 is substantially equal to the second width, so that the first film 21 on the side edge 14b is thermally welded to the first film 21 on the side edge 14a, The length of heat welding to the two-step portion 18 becomes substantially equal, and the integrated state is stabilized. Furthermore, since the 1st film 21 and the 2nd film 22 do not contact, the quality of goods improves and the presence of the 2nd film 22 does not affect an integrated state.

  FIG. 5 is an enlarged schematic diagram showing a state where a step is formed on one of the side edges and a heat-meltable film is installed in the method for manufacturing a paper container according to the second embodiment of the present invention, 6 is an enlarged schematic view showing a state where the stepped portion shown in FIG. 5 is folded and welded, and FIG. 7 is an enlarged view showing a welding process of the side plate base paper including one of the side edges shown in FIG. It is a schematic diagram.

With reference to these drawings, a side plate base paper 11 of a paper material for manufacturing a paper container is one side of a paper sheet 24 having a basis weight of 170 to 500 g / m ² and a thickness of 0.3 to 0.4 mm. A base paper in which a first film 21 of 30 μm thick made of PET and a second film 22 of 30 μm thick PE made of PE are formed by extrusion lamination on each side, as shown in the conventional example of FIG. It is made from what is punched. In addition, the side board base paper 11 has the side edges 14a and 14b which oppose. At the time of forming the paper container, the side plate base paper 11 is rolled into a cylindrical shape with the first film 21 side inward, and the side edges 14a and the side edges 14b are integrated into a cylindrical shape.

  In making the side board base paper into a cylindrical shape, first, referring to FIG. 5, a part of the outer side of the paper container of the side edge 14a is cut and removed along the end portion 35, and the thickness H of the side board base paper is removed. The step portion 37 having a thickness H / 2 and a width L of 1/2 of the above is formed. Here, the width L is 16 mm. Next, a heat-meltable film 40 made of PE having a thickness of 20 μm or PET having a thickness of 30 μm is placed on the stepped portion 37. Here, the heat-meltable film 40 is disposed so as to cover the end portion 35 when the stepped portion 37 to be described later is folded back. The effect of such a configuration will be described later.

  Next, referring to FIG. 6, a part of the end portion 35 side of the step portion 37 is folded back to the outer surface side of the paper container, and the heat melt film 40 is sandwiched between the remaining portions of the step portion 37. The step portion 37 is integrated by pressing the pair of hot plates 50a and 50b and applying heat to heat-melt the film 40. Here, since the width L is 16 mm as described above, the width of the folded portion 39 is about half that of about 8 mm.

  If comprised in this way, since the folding | turning part 39 of the paper step part 37 will be integrated by the heat welding of the heat-meltable film 40, the integrated state of the folding | turning part 39 will be stabilized and the quality of a paper container will improve.

  Further, as described above, since the heat-meltable film 40 is disposed so as to cover the end portion 35 of the folded portion 39, all the surfaces of the folded portion 39 of the stepped portion 37 are integrated inside. The integrated state of the folded portion 39 is more stable.

  Finally, referring to FIG. 7, in the integration of the side edges 14a and 14b, first, the side edges 14b are aligned so that the end 45 of the side edge 14b is aligned with the end 35 of the folded portion 39. Is overlapped with the folded portion 39. Next, heat is applied while pressing the overlapping portion with a pair of hot plates 90a and 90b, and the first film 21 of the folded portion 39 and the first film 21 of the side edge 14b, which are the same material, are thermally welded, The side edge 14a and the side edge 14b are integrated.

  If it does in this way, since the 1st film 21 does not touch the 2nd film 22, the part in which side edge 14a and side edge 14b are not fully integrated does not arise. Further, since the folded portion 39 is sufficiently integrated with the heat-meltable film 40 and the side edge 14a and the side edge 14b are sufficiently integrated with each other by the heat welding between the first films 21, the side edge 14a. And the side edge 14b are not defectively bonded.

  In each of the above embodiments, the first film is formed on one side of the side plate base paper and the second film is formed on the other side, but the water-resistant and heat-meltable film is formed on at least one side. Just do it.

  In each of the above embodiments, the first film is a film made of PET having a specific thickness. However, the first film may be a film having a different material and thickness as long as it is a water-resistant and heat-meltable film.

  Furthermore, in each of the above-described embodiments, the second film is a film made of PE having a specific thickness. However, a film having a different material, such as foamed PE, polybutylene terephthalate (PBT), or polypropylene (PP), or a thickness. May be different films.

  Furthermore, in each of the above-described embodiments, the side plate base paper is a single sheet made of paper, but it may be a sheet having a structure of two layers or three or more layers bonded to an aluminum foil. Good.

  Further, in each of the above embodiments, the first film and the second film are formed by extrusion lamination, but may be formed by other methods such as dry lamination.

  Further, in each of the above embodiments, the first film and the second film are different materials, but may be the same material.

  Furthermore, in the first embodiment, the first thickness and the second thickness are set to specific dimensions. However, the second thickness is set to be twice the first thickness. For example, different dimensions may be set.

  Furthermore, in the first embodiment, the first width and the second width are set to specific dimensions, but may be set to different dimensions. The first width is twice the second width. Other dimensions may be set.

  Further, in the second embodiment, the other side edge is superimposed on the folded portion so as to be aligned with the end portion of the folded portion of the stepped portion. Good.

  Furthermore, in the second embodiment, the heat-meltable film is disposed so as to cover the end portion of the folded portion, but may be disposed so as to be sandwiched at least by the folded portion.

  Furthermore, in said 2nd Embodiment, although the heat-meltable film was a film which consists of PET of specific thickness, or a film which consists of PE, if it has heat-meltability, the film which consists of other raw materials It may be. Moreover, if it is a film of the same material as the second film, the second film and the heat-meltable film are heat-welded, so that the integrated state of the folded portion may be further stabilized.

  Furthermore, in the second embodiment described above, the width of the stepped portion is set to a specific size, but may be set to a different size.

  Further, in the above first embodiment, after the step forming portion is formed, the first step portion and the second step portion are formed. However, the first step portion is formed by another forming method such as forming from the first step portion. May be.

  Further, in each of the above embodiments, each of the first step portion, the second step portion, and the step portion is formed by cutting and removing a part on the outer surface side of the paper container. The end portion may be compressed in a state in which the corresponding portion is removed to obtain a desired stepped portion shape.

  Further, in each of the above embodiments, the outer surface side of the paper container is plain, but a film on which the second film is formed after printing the pattern or the like on the outer surface, or the pattern or the like is printed on the inner surface side May be formed as a second film so that a pattern or the like is added to the outer surface side of the paper container.

  Furthermore, in the first embodiment, the surface of the first step portion is formed so as to be parallel to one surface and the other surface of the side plate base paper, but is tapered toward the end portion. You may form so that it may become an inclined surface.

  Furthermore, in the second embodiment, the surface of the step portion is formed so as to be parallel to the one surface and the other surface of the side plate base paper, but the inclined surface is tapered toward the end portion. It may be formed to be.

  Further, in each of the above-described embodiments, heat welding is performed using a hot plate, but heat welding using ultrasonic waves may be performed.

DESCRIPTION OF SYMBOLS 11 ... Side board base paper 14a, 14b ... Side edge 15 ... End part 17 ... 1st step part 18 ... 2nd step part 21 ... 1st film 22 ... 2nd film 35 ... End part 37 ... Step part 39 ... Folding part 40 ... Heat-meltable film 45... End portion 70... Paper container.

Claims (6)

A method of manufacturing a paper container,
A step of preparing a sheet-like base paper having a side edge opposed to the first film having water resistance and heat-melting property formed on at least one surface;
One of the side edges is removed from the other side of the base paper along the edge, and a first step portion having a first thickness and a first width and a first thickness 2 adjacent to the first step portion. Forming a second step having a doubled second thickness and second width;
A step of folding a part of the first step portion on the side of the end portion toward the other surface and superimposing and integrating with the remaining portion of the first step portion;
Rounding the base paper to the one surface side, overlaying the other of the side edges on the second stepped portion, and heat-welding the first film to be integrated with the one of the side edges, A method of manufacturing a paper container.   The paper container manufacturing method according to claim 1, wherein the first width is set to be twice the second width.   The manufacturing method of the paper container of Claim 1 or Claim 2 with which the 2nd film different from the said 1st film is formed in the other side of the said base paper. A method of manufacturing a paper container,
A step of preparing a sheet-like base paper having a side edge opposed to the first film having water resistance and heat-melting property formed on at least one surface;
Removing one of the side edges along the edge from the other side of the base paper to form a step having a thickness half the thickness of the base paper and a predetermined width;
Installing a heat-meltable film on at least a part of the step;
A part of the step portion on the end side is folded back to the other surface side, and the step portion is overlapped with the remaining portion of the step portion sandwiching the heat-meltable film, and the step portion is heated with the heat-meltable film. A process of welding and integrating,
Rounding the base paper to the one surface side, overlaying the other of the side edges on the outer surface of the folded portion of the stepped portion, and heat-welding the first film so as to be integrated with the one of the side edges. A method for manufacturing a paper container.   The paper container manufacturing method according to claim 4, wherein the heat-meltable film is disposed so as to cover an end portion of the folded portion of the stepped portion.   5. The second film different from the first film is formed on the other surface of the base paper, and the other end of the side edge is aligned with the tip of the folded portion of the stepped portion. 5. A method for producing a paper container according to 5.

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