Paper container and its manufacturing method

Abstract

To provide a paper container having a polygonal upper opening with arc-shaped corners, which is formed by folding and pasting together a blank material made of paper, and in which a lid can be securely attached to the upper surface of a flange part without any gap. [Solution] The paper container PC is a paper container with a polygonal top opening with arc-shaped corners, formed by folding and pasting together blank material made of paper with at least the side that will become the inside of the container coated with thermoplastic resin. It has a polygonal bottom plate portion 1, side plate portions 2a, 2b, 3a, 3b that rise upward from the outer peripheral edge of the bottom plate portion 1, and flat flange portions 4 that extend horizontally outward from the tops of the side plate portions 2a, 2b, 3a, 3b, the flange portions 4 having a laminated structure in which the blank material is folded, and the overlapping step G of the edge of the blank material that appears on the top surface of the flange portions 4 is less than 1 / 2 of the thickness of the blank material before it was formed.

Description

[Technical Field]

[0001] The present invention relates to a paper container and a method for manufacturing the same, and more particularly to a paper container having a flange portion and a method for manufacturing the same. [Background technology]

[0002] Until now, paper containers with a rectangular bottom plate and flange, such as Alice Cream containers, have generally been made by folding and pasting together blank material, and the top opening of the paper container has been a rectangle with right-angled corners. Such conventional paper containers have not necessarily been satisfactory in terms of design.

[0003] Therefore, Patent Document 1 proposes a method for manufacturing a paper container in which a blank is folded and bonded together to form a paper container precursor, and then the flange precursor of the paper container precursor is curled (curl bending process) to form a flange. The corners of the top opening of a paper container manufactured in this way are arc-shaped, providing a design that has not been seen before. Patent Document 1 also discloses that force can be applied from above and below the curled flange to make the flange flat. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-82965 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the proposed manufacturing method, when the blank material is folded and bonded together to produce a paper container precursor, an overlapping portion of the edge of the blank material is created in the flange precursor portion, and when such a flange precursor portion is subjected to curl bending processing, a step is created on the surface of the flange portion due to the overlapping portion of the edge of the blank material.

[0006] If such a step exists on the top surface of the flange portion, when a lid body made of film, paper, etc. is attached to the top surface of the flange portion, the lid body and the flange portion cannot be securely attached without any gaps, which may result in leakage or deterioration of the contents of the paper container.

[0007] The present invention was made in consideration of these conventional problems, and its purpose is to provide a paper container that has a polygonal top opening with arc-shaped corners, formed by folding and pasting together a blank piece of paper material, and that can have a lid that can be securely attached to the top surface of the flange portion without any gaps.

[0008] Another object of the present invention is to provide a method for producing the paper container reliably and efficiently. [Means for solving the problem]

[0009] One embodiment of a paper container according to the present invention that achieves the above-mentioned objective is a paper container having a polygonal top opening with arc-shaped corners, formed by folding and pasting together a blank piece made of paper material coated with a thermoplastic resin on at least the side that will become the inner surface of the container, and characterized in that it has a polygonal bottom plate portion, side plate portions that rise upward from the outer peripheral edge of the bottom plate portion, and flat flange portions that extend horizontally outward from the top of the side plate portions, the flange portions having a laminated structure in which the blank piece is folded, and the overlapping step of the edge of the blank piece that appears on the top surface of the flange portion is less than half the thickness of the blank piece before it was formed.

[0010] In the paper container having the above-described structure, the flange portion is preferably formed by compressing the blank in the vertical direction after the blank is subjected to curl bending processing.

[0011] In the paper container having the above-described structure, it is preferable that the paper material is mainly composed of bamboo.

[0012] In addition, one embodiment of a paper container manufacturing method according to the present invention includes the steps of: bending and / or pasting together a blank material made of paper material coated with a thermoplastic resin on at least the side that will become the inner surface of the container, to form a paper container precursor having a polygonal bottom plate portion, a side plate portion rising upward from the outer peripheral edge of the bottom plate portion, and a flange precursor portion extending upward from the top of the side plate portion; curling the flange precursor portion; and pressing the curled flange precursor portion to form a flat flange portion, wherein in the press processing, a lower mold that is pressed against the underside of the flange precursor portion has a groove or recess in the portion facing the overlapping portion of the edge of the blank material in the flange portion.

[0013] In the method for manufacturing a paper container having the above configuration, it is preferable that the paper material contains bamboo as a main component. [Effects of the Invention]

[0014] The paper container according to the present invention has a polygonal top opening with arc-shaped corners, and the lid can be securely attached to the top surface of the flange without any gaps, which prevents leakage and deterioration of the contents of the paper container.

[0015] Furthermore, according to the paper container of the present invention, the paper container of the present invention can be manufactured reliably and efficiently. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a perspective view showing one embodiment of a paper container according to the present invention. [Figure 2] FIG. 2 is a front view of the paper container of FIG. [Figure 3] FIG. 2 is a right side view of the paper container of FIG. [Figure 4] FIG. 2 is a plan view of the paper container of FIG. [Figure 5] FIG. 2 is a bottom view of the paper container of FIG. 1. [Figure 6] FIG. 2 is a plan view of a blank material for producing the paper container of FIG. 1. [Figure 7]FIG. 7 is a partially enlarged view of the blank piece of FIG. 6. [Figure 8] FIG. 8 is a partial perspective view of a precursor of a paper container formed by folding and pasting the blank material of FIG. 7. [Figure 9] FIG. 10 is a process diagram showing how a flange precursor is curled and bent into a cylindrical shape. [Figure 10] FIG. 10 is a process diagram showing a process in which a cylindrical flange precursor is compressed between upper and lower dies of a press machine to form a flat flange portion. DETAILED DESCRIPTION OF THE INVENTION

[0017] The paper container and its manufacturing method according to the present invention will be described in more detail below with reference to the drawings, but the present invention is not limited to these embodiments.

[0018] Fig. 1 shows a perspective view of one embodiment of a paper container according to the present invention, Fig. 2 shows a front view of the paper container in Fig. 1, Fig. 3 shows a right side view, Fig. 4 shows a plan view, and Fig. 5 shows a bottom view.

[0019] The paper container PC shown in Figures 1 to 5 has a rectangular bottom plate 1, side plate portions 2a, 2b, 3a, and 3b that rise upward from the outer peripheral edge of the bottom plate 1 at an angle away from the bottom plate 1, and flange portions 4 that extend horizontally outward from the upper ends of the side plate portions 2a, 2b, 3a, and 3b. As will be described later, the flange portions 4 are formed by bending a blank material BL (shown in Figure 6) into a curled shape and then compressing it in the vertical direction to form a flat plate. An overlapping step G at the edge of the blank material BL that appears on the upper surface of the flange portions 4 is set to be equal to or less than half the thickness of the blank material BL.

[0020] The paper container PC shown in these figures is manufactured by folding and pasting together a blank material BL made of the paper material shown in Figure 6. The blank material BL in Figure 6 has, in the center, a rectangular bottom plate portion 1, a pair of side plate portions 2a, 2b connected to opposing long sides of the bottom plate portion 1 via valley fold lines 91a, 91b, a pair of side plate portions 3a, 3b connected to short sides of the bottom plate portion 1 via valley fold lines 92a, 92b, edge portions 41a, 41b that become flange portions 4 (shown in Figure 1) connected to the circumferential center of the outer peripheral edges of the pair of side plate portions 2a, 2b via mountain fold lines 93a, 93b, four tongue portions 5 connected to both circumferential sides of the outer peripheral edges of the pair of side plate portions 2a, 2b via mountain fold lines 93a, 93b, and flange portions 4 connected to the outer peripheral edges of the pair of side plate portions 3a, 3b via mountain fold lines 94a, 94b. The paper container PC has edge portions 42a, 42b that form the paper container PC (shown in FIG. 1), protrusions 43a, 44a and protrusions 43b, 44b provided on both circumferential sides of edge portions 42a, 42b, and four fan-shaped fold-in joints 61-64 provided between side plate portions 2a, 2b and side plate portions 3a, 3b via mountain fold lines 95a, 95b, 95c, 95d and valley fold lines 96a, 96b, 96c, 96d. Note that the mountain fold lines and valley fold lines are those when viewed from the inside of the paper container PC.

[0021] There are no particular limitations on the type of paper material that constitutes the blank material BL used in the present invention, and it may be made of wood pulp or non-wood pulp. From the standpoint of its ability to conform to the mold shape during press molding and its shape retention after molding, a paper material primarily composed of bamboo, which has longer fibers than wood pulp, is preferably used. Note that a paper material primarily composed of bamboo means one in which the bamboo content is 50% or more by volume of the paper material.

[0022] The paper material is coated with a thermoplastic resin (not shown) on the side that will become the inner surface of the paper container PC. This improves water resistance and prevents liquid leakage from the paper container PC and a decrease in strength. It also improves the overlapping of the blank material BL and the heat sealing properties between the flange portion 4 and the lid (not shown). Of course, the side that will become the outer surface of the paper container PC may also be coated with a thermoplastic resin. Examples of thermoplastic resins that can be used include polyethylene resins, polypropylene resins, and polyethylene terephthalate resins.

[0023] To form a paper container PC from a blank material BL having such a configuration, the side plate portions 2a, 2b and the side plate portions 3a, 3b are valley-folded relative to the bottom plate portion 1 along valley fold lines 91a, 91b, 92a, 92b to erect them, and the fold-in joint portions 61 to 64 are mountain-folded relative to the side plate portions 3a, 3b along mountain fold lines 95a to 95d and valley-folded relative to the side plate portions 2a, 2b along valley fold lines 96a to 96d.

[0024] 7 and 8 show the blank BL before and after folding in the circled portion of FIG. 6. When the fold-in joint 61 is mountain-folded along the mountain fold line 95a relative to the side plate 3a and valley-folded along the valley fold line 96a relative to the side plate 2a, the inner surface of the fold-in joint 61 overlaps the side plate 2a and the outer surface of the fold-in joint 61 comes into contact with the outer surface of the side plate 3a, and the blank BL becomes a paper container precursor 10. At this time, as shown in FIG. 8, the circumferential side of the edge 41a and the protruding piece 43a of the edge 42a are connected with an overlapping portion OP, forming a flange precursor 40. The tongue portions 5 located on the outside of the corners of the paper container PC serve to reinforce the corners of the flange 4, where stress is likely to concentrate.

[0025] Next, as shown in Figures 9(a) to 9(d), the paper container precursor 10 is subjected to a curling bending process consisting of multiple press processes to form a cylindrical flange precursor 40. Figure 9 is a partial vertical cross-sectional view of an overlapping portion OP of the flange precursor 40. The cylindrical flange precursor 40 is further pressed into a flat flange portion 4.

[0026] Figure 10 shows a cross-sectional view taken along line AA in Figure 9(d). The cylindrical flange precursor 40 is compressed into a flat plate by the upper mold 7 and lower mold 8 of the press machine. At this time, a groove 81 is formed in the lower mold 8 of the press machine in a portion facing the overlapping portion OP between the edge 41a of the flange precursor 40 and the protruding piece 43a of the edge 42a. On the other hand, the pressing surface of the upper mold 7 of the press machine is flat. Note that the groove 81 of the lower mold 8 may be replaced with a recess.

[0027] When the cylindrical flange precursor 40 is compression molded using such upper mold 7 and lower mold 8, the overlapping portion OP of the blank material BL, which is thicker than the other portions, enters the groove portion 81 of the lower mold 8, as shown in Figure 10(c), and the upper surface of the flange precursor 40 becomes approximately flat.

[0028] As shown in Figure 10(d), the press machine of the above configuration makes the upper surface of the flange portion 4 almost flat, and the overlapping step G between the edge portion 41a of the flange precursor portion 40 and the protrusion 43a of the edge portion 42a can also be reduced to less than half of the initial thickness of the blank material BL.

[0029] By keeping the step G on the upper surface of the flange portion 4 of the paper container PC small in this manner, a lid body made of film, paper, etc. can be reliably attached to the upper surface of the flange portion 4 without any gaps, thereby preventing leakage or deterioration of the contents of the paper container PC.

[0030] During this press working, it is desirable to heat the flange portion 4 while applying pressure. Heating melts the thermoplastic resin coating the inner surface of the blank material BL, welding the overlapping portions OP of the blank material BL, making it easier to maintain the flat shape of the flange portion 4 even after the pressure is released. [Industrial Applicability]

[0031] The paper container of the present invention has a polygonal top opening with arc-shaped corners, and a lid made of film, paper, etc. can be securely attached to the top surface of the flange without any gaps, thereby preventing leakage or deterioration of the contents of the paper container. [Explanation of symbols]

[0032] 1 Bottom plate part 2a,2b Side plate part 3a,3b Side plate part 4 Flange 7 Upper mold 8 Lower mold 10 Paper container precursors 40 Flange precursor 81 Groove G Step BL blank material OP overlapping part PC paper container

Claims

1. A paper container having a polygonal top opening with arc-shaped corners, formed by folding and pasting a blank material made of paper material coated with a thermoplastic resin at least on the side that will become the inner surface of the container, A polygonal bottom plate portion, a side plate portion rising upward from the outer peripheral edge of the bottom plate portion; a flat flange portion extending horizontally outward from an upper portion of the side plate portion; and The flange portion has a laminated structure in which the blank material is folded, The overlapping step at the edge of the blank material that appears on the upper surface of the flange portion is 1 / 2 or less of the thickness of the blank material before molding. A paper container characterized by:

2. 2. The paper container according to claim 1, wherein the flange portion is formed by compressing the blank in the vertical direction after the blank is subjected to curling bending.

3. 3. The paper container according to claim 1, wherein the paper material is mainly composed of bamboo.

4. The method for manufacturing a paper container according to claim 1 or 2, A process of folding and / or pasting a blank material made of paper material coated with a thermoplastic resin on at least the side that will become the inner surface of the container to form a paper container precursor having a polygonal bottom plate portion, side plate portions rising upward from the outer peripheral edge of the bottom plate portion, and flange precursor portions extending upward from the top of the side plate portions; a step of curling the flange precursor portion; a step of pressing the curled flange precursor portion to form a flat flange portion; Equipped with A method for manufacturing a paper container, characterized in that during the press processing, the lower mold that is pressed against the underside of the flange precursor portion has a groove or recess in the portion facing the overlapping portion of the edge of the blank material in the flange portion.

5. 5. The method for manufacturing a paper container according to claim 4, wherein the paper material is mainly composed of bamboo.

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