Paper base material, paper container, and method for producing paper container

Abstract

To provide a technology that achieves high mold reproducibility and enables improvement of productivity in paper containers.SOLUTION: A paper base material for a drawn molded paper container, wherein the basis weight of the paper base material is 150 to less than 400 [g / m2], and the geometric mean of tensile energy absorption (TEA) in the machine direction and cross direction of the paper base material is 900 to 2000 [J / m2].SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a paper substrate, a paper container, and a method for manufacturing a paper container. [Background technology]

[0002] Traditionally, plastic containers have been used in large quantities as packaging materials for food containers and various industrial products because they are easy to mold, can be mass-produced, and can be manufactured inexpensively. However, plastic containers have the problem of placing a heavy burden on the environment when disposed of. When plastic containers are landfilled, they remain in the ground semi-permanently without decomposing. In addition, when plastic containers are incinerated, they have problems such as damaging incinerators due to their high combustion calories, being difficult to burn completely, and containers made of polyvinyl chloride potentially generating highly corrosive hydrogen chloride gas.

[0003] Therefore, in recent years, in consideration of environmental issues, recycling issues, and resource conservation, containers made of paper instead of plastic containers have been considered. For example, pulp molded containers are known as paper containers. However, the production of pulp molded containers takes time, which causes a problem in productivity.

[0004] Furthermore, for example, Patent Document 1 discloses a forming base paper for forming a formed container by drawing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-16380 Summary of the Invention [Problem to be solved by the invention]

[0006] Paper containers obtained by drawing may have some ruptures or cracks during the forming process, which may reduce productivity. Patent Document 1 does not disclose a forming base paper that has high mold reproducibility and improves the productivity of paper containers. The present disclosure aims to provide a technology that has high mold reproducibility and can improve the productivity of paper containers. [Means for solving the problem]

[0007] That is, the present disclosure provides the following: <1> ~ <11> Regarding <1> A paper substrate for a draw-formed paper container, The basis weight of the paper base material is 150 to 400 [g / m 2 ] is less than The geometric mean value of the tensile energy absorption (TEA) of the paper base material is 900 to 2000 [J / m 2 ], a paper substrate. <2> The basis weight of the paper base material is 175 [g / m 2 ] is more than <1> The paper substrate according to claim 1. <3> The geometric mean value of the longitudinal and transverse breaking elongation of the paper base material is 12.0% or more. <1> or <2> The paper substrate according to claim 1. <4> The thickness of the paper base material is 0.12 to 0.44 mm. <1> ~ <3> The paper substrate according to any one of the preceding claims. <5> The paper base material has a thermoplastic resin layer, an adhesive resin layer, and a paper layer laminated in this order. <1> ~ <4> The paper substrate according to any one of the preceding claims. <6> <1> ~ <5> A paper container obtained by drawing the paper base material according to any one of claims 1 to 4. <7> The curvature of the corner of the opening formed by drawing is 0.02 to 0.18 [1 / mm]. <6> A paper container as described in <8> The expansion ratio of the opening formed by drawing is 1.01 to 1.35 times. <6> or <7> A paper container as described in <9> The depth of the opening formed by drawing is 5 to 60 mm. <6> ~ <8> The paper container according to any one of the preceding claims. <10> A bottom portion; a side surface portion rising from the periphery of the bottom surface portion; a flange portion extending outward from the side surface portion; Equipped with The bottom surface portion has a raised portion that is partially raised so that the surface is curved. <6> ~ <9> The paper container according to any one of the preceding claims. <11> Basis weight: 150-400 [g / m 2 ] and the geometric mean value of the tensile energy absorption (TEA) is 900 to 2000 [J / m 2 and preparing a paper substrate for a drawn paper container, drawing the paper substrate; A method for manufacturing a paper container, comprising: [Effects of the Invention]

[0008] According to the present disclosure, a technology can be provided that has high mold reproducibility and can improve the productivity of paper containers. [Brief explanation of the drawings]

[0009] [Figure 1] Figure 1(A) is a plan view of a paper container according to the embodiment, Figure 1(B) is a cross-sectional view of the paper container according to the embodiment cut along the short direction, and Figure 1(C) is a cross-sectional view of the paper container according to the embodiment cut along the long direction. [Figure 2] Figure 2(A) is a plan view of a paper container according to a modified example, Figure 2(B) is a cross-sectional view of the paper container according to the modified example when cut along the short side, and Figure 2(C) is a cross-sectional view of the paper container according to the modified example when cut along the long side. [Figure 3] FIG. 3 is a cross-sectional view of the paper substrate according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing the method for manufacturing a paper container according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this specification, unless otherwise specified, the expressions "X or more and Y or less" or "X to Y" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. Furthermore, the expression "less than X to Y" means a numerical range that is greater than X and less than Y, including the lower limit, which is the endpoint, but excluding the upper limit, which is the endpoint. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way.

[0011] In this specification, the machine direction refers to the machine direction (MD) of the paper layer, which is the same as the direction in which the fibers are oriented, and the cross direction refers to the direction perpendicular to the machine direction (CD).

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the configurations of the following embodiments are merely examples, and the present invention is not limited to these configurations.

[0013] [Paper container] 1(A) to 1(C) are diagrams showing a paper container according to an embodiment. FIG. 1(A) is a plan view of the paper container 1 seen from above, and FIG. 1(B) is a cross-sectional view of the paper container 1 when cut along line AA in FIG. 1(A). FIG. 1(C) is a cross-sectional view of the paper container 1 when cut along line BB in FIG. 1(A). The paper container 1 according to this embodiment is obtained by drawing (deep drawing) a single sheet of paper base material. Since the paper container 1 is manufactured by forming a single sheet of paper base material, the entire paper container is formed as a single unit. As shown in FIG. 1(A), the paper container 1 has a rectangular shape with a longitudinal direction and a lateral direction perpendicular to the longitudinal direction when viewed from above. The paper container 1 is used, for example, as a container for moist foods such as chilled foods.

[0014] 1(A) to 1(C) also show X-axis, Y-axis, and Z-axis, which are perpendicular to each other. The X-axis direction and Y-axis direction correspond to a horizontal direction, and the Z-axis direction indicates a vertical direction perpendicular to the horizontal direction. The following explanation will be made using the directions X, Y, and Z (or horizontal and vertical directions). The paper container 1 has a short side direction in the X-axis direction, a long side direction in the Y-axis direction, and a depth formed by deep drawing in the Z-axis direction.

[0015] As shown in Figures 1(A) to 1(C), paper container 1 has a bottom surface 2 on which food or the like is placed, and side surfaces 3 that rise from the periphery of bottom surface 2. The bottom surface 2 and side surfaces 3 form an opening 4 that corresponds to the inner volume of paper container 1. Bottom surface 2 has paper container corners 5 that are rectangular in shape with four chamfered corners. Side surfaces 3 rise from bottom surface 2 to form a space for accommodating food or the like together with bottom surface 2. Peripheral edge 6, which is the outer periphery of side surfaces 3, has opening corners 7 that are rectangular in shape with four chamfered corners.

[0016] The angle of the opening corner 7 corresponds to the angle θ formed between the side surface 3 and an imaginary plane extending vertically at the peripheral edge 6 of the side surface 3. The depth of the opening 4 corresponds to the distance H between the bottom surface 2 and the opening plane including the peripheral edge 6 of the side surface.

[0017] The paper container 1 also has a flange portion 8 that extends outward from the peripheral edge portion 6 of the side portion 3. The flange portion 8 is provided so as to surround the entire periphery of the side portion 3. Therefore, the flange portion 8 is provided on the outer periphery side of the opening 4. The outermost periphery of the flange portion 8 forms the outer periphery of the paper container 1 in a plan view. The flange portion 8 has a flat surface that extends approximately parallel to the flat portion with the bottom portion 2, and a step that descends toward the bottom portion 2 is formed on the outermost periphery.

[0018] The paper container 1 has a structure in which the bottom portion 2, side portion 3, and flange portion 8 are integrally molded, and each portion is connected to each other.

[0019] The paper container 1 is obtained by drawing a paper base material. The paper container 1 obtained by drawing a paper base material containing pulp has a reduced environmental impact compared to conventional plastic containers. Next, the paper base material according to the embodiment will be described.

[0020] <Paper base material> The basis weight of the paper base material is 150 to 400 [g / m 2 ] is less than. The basis weight of a paper substrate is the mass per unit area of ​​all layers constituting the paper substrate. For example, when a paper substrate has a paper layer, an adhesive resin layer, and a thermoplastic resin layer, the basis weight includes not only the paper layer but also the adhesive resin layer and the thermoplastic resin layer. The mass of the adhesive resin layer and the thermoplastic resin layer is also included in the basis weight of the paper base material.

[0021] If the basis weight of the paper base material is increased, cracks are more likely to occur due to drawing and the mold reproducibility of the paper container is reduced, but conversely, if the basis weight is reduced, tears are more likely to occur due to drawing. Therefore, by controlling the basis weight of the paper container 1 within the above range, tears and cracks due to drawing are less likely to occur, and the productivity of the paper container 1 is improved. In addition, when the basis weight of the paper container 1 is 150 to 400 [g / m 2 ] or less, mold reproducibility can be improved.

[0022] The basis weight of the paper base material is preferably 175 g / m 2 ] or more, and more preferably 200 [g / m 2 In addition, the basis weight of the paper substrate is preferably 375 [g / m 2 ] or more from the viewpoint of improving mold reproducibility and further suppressing cracking. 2 ] or less, and more preferably 350 [g / m 2 ] is as follows. Therefore, the basis weight of the paper substrate is preferably 175 to 375 [g / m 2 ], and more preferably 200 to 350 [g / m 2 The paper base has a basis weight of 175 to 375 [g / m 2], it is easier to prevent breakage or cracking due to drawing, and the productivity of the paper container 1 is further improved. In addition, the basis weight of the paper base material is 175 to 375 [g / m 2 ], the mold reproducibility can be further improved.

[0023] The geometric mean value of the tensile energy absorption (TEA) in the machine direction and the TEA in the cross direction of the paper substrate, i.e., the geometric mean value of the TEA in the machine direction and the cross direction of the paper substrate (hereinafter simply referred to as "TEA of the paper substrate"), is 900 to 2000 [J / m 2 ]. The TEA is measured in accordance with JIS P 8113:2006. The TEA is the amount of energy per unit area required to stretch and break a paper substrate, and is an index related to the elongation and strength of the paper substrate. The TEA of the paper substrate used to form the paper container 1 can also be measured by measuring a portion of the paper container 1 that has not been stretched by drawing (for example, the flange portion 8 shown in Figure 1).

[0024] Increasing the TEA of the paper substrate makes it more likely that cracks will occur during drawing, but conversely, lowering the TEA makes it more likely that tears will occur during drawing. Also, lowering the TEA reduces mold reproducibility. Therefore, it is recommended to set the TEA of the paper substrate to 900-2000 [J / m 2 By controlling the TEA of the paper base material to 900 to 2000 [J / m], breakage or cracking due to drawing is less likely to occur, improving the productivity of the paper container 1. 2 By controlling the temperature to ], it is possible to obtain paper containers with high mold reproducibility. To increase the TEA of the paper base material, methods include increasing the basis weight of the paper base material, adding a resin layer to the paper layer, subjecting the pulp that makes up the paper layer to high-concentration beating, and performing Clupak treatment during paper layer papermaking.To decrease the TEA of the paper base material, methods include decreasing the basis weight of the paper base material and using a single sheet of paper as the paper base material.The TEA of the paper base material should be 900 to 2000 [J / m 2 From the viewpoint of controlling the speed difference between before and after Clupak processing, it is effective to set the speed difference between before and after Clupak processing to, for example, -10 to -35[%].

[0025] The TEA of the paper substrate is preferably 1000 to 1900 [J / m 2 ], and more preferably 1200 to 1700 [J / m 2 The TEA of the paper substrate is 1000 to 1900 [J / m 2 ] or 1200-1700 [J / m 2 By setting the TEA of the paper base material to 1000 to 1900 [J / m], it becomes easier to prevent breakage or cracking due to drawing, and the productivity of the paper container 1 is further improved. 2 ], the mold reproducibility can be further improved.

[0026] The TEA in the machine direction of the paper substrate is preferably 1300 to 2700 [J / m 2 ], and more preferably 1400 to 2600 [J / m 2 ]. The TEA in the cross direction of the paper substrate is preferably 700 to 1500 [J / m 2 ] and is more preferable Preferably 800 to 1400 [J / m 2 ].

[0027] The geometric mean value of the longitudinal and transverse breaking elongations of the paper substrate, i.e., the longitudinal and transverse geometric mean value of the breaking elongation of the paper substrate (hereinafter simply referred to as "breaking elongation of the paper substrate"), is preferably 12.0% or more, more preferably 15.0% or more. There is no particular upper limit to the breaking elongation of the paper substrate, but from a manufacturing standpoint, it is usually 20.0% or less. The breaking elongation is measured in accordance with JIS P 8113: 2006. The breaking elongation of the paper base material can also be measured by using, for example, a portion of the paper container 1 that has not been stretched by drawing (for example, the flange portion 8 shown in FIG. 1 ), thereby measuring the breaking elongation of the paper base material used in forming the paper container 1.

[0028] By making the breaking elongation of the paper base material 12.0 to 20.0%, the formability of the paper container 1 can be further improved, making it easier to prevent breakage and cracking due to drawing, and further improving the productivity of the paper container 1. Methods for increasing the breaking elongation of a paper base material include adding a resin layer to the paper layer, subjecting the pulp that makes up the paper layer to high-concentration beating, and performing Clupak treatment during papermaking of the paper layer.

[0029] The longitudinal breaking elongation of the paper substrate is preferably 14.0% or more, more preferably 17.5% or more, and although there is no particular upper limit, it is usually 23.0% or less. The breaking elongation in the transverse direction of the paper substrate is preferably 10.0% or more, more preferably 13.0% or more, and although there is no particular upper limit, it is usually 17.0% or less.

[0030] The geometric mean value of the longitudinal and transverse tensile strengths of the paper substrate, i.e., the longitudinal and transverse geometric mean value of the tensile strength of the paper substrate (hereinafter simply referred to as "tensile strength of the paper substrate"), is preferably 7.8 kN / m or more, more preferably 8.1 kN / m or more. There is no particular upper limit to the tensile strength of the paper substrate, but from a manufacturing standpoint, it is usually 24.0 kN / m or less. The tensile strength is measured in accordance with JIS P 8113: 2006. The tensile strength of the paper base material can also be measured by using, for example, a portion of the paper container 1 that has not been stretched by drawing (for example, flange portion 8), thereby measuring the tensile strength of the paper base material used to form the paper container 1.

[0031] By making the tensile strength of the paper base material 7.8 to 24.0 [kN / m], it becomes easier to prevent breakage or cracking due to drawing, and the productivity of the paper container 1 improves. Methods for increasing the tensile strength of paper substrates include increasing the amount of paper strength agent, increasing the basis weight of the paper substrate, adding a resin layer to the paper layer, reducing the Canadian Standard Freeness (CSF) of the pulp that makes up the paper layer, and increasing the amount of paper strength agent.

[0032] The longitudinal tensile strength of the paper substrate is preferably 9.5 kN / m or more, more preferably 10.5 kN / m or more, and although there is no particular upper limit, it is usually 34.0 kN / m or less. The tensile strength of the paper substrate in the transverse direction is preferably 6.0 kN / m or more, more preferably 6.3 kN / m or more, and although there is no particular upper limit, it is usually 17.0 kN / m or less.

[0033] The thickness of the paper substrate is preferably 0.17 mm or more, more preferably 0.19 mm or more. The thickness of the paper substrate is preferably 0.44 mm or less, more preferably 0.41 mm or less. The thickness of the paper substrate refers to the thickness of all layers constituting the paper substrate. For example, when the paper substrate has a paper layer, an adhesive resin layer, and a thermoplastic resin layer, the thickness of the paper substrate is The thickness of the paper substrate includes not only the thickness of the adhesive resin layer but also the thickness of the thermoplastic resin layer.

[0034] By making the thickness of the paper base material 0.17 to 0.44 mm, it becomes easier to prevent breakage or cracking due to drawing, improving the productivity of the paper container 1. In addition, by making the thickness of the paper base material 0.17 to 0.44 mm, it is possible to further improve the mold reproducibility of the paper container 1.

[0035] The density of the paper substrate is not particularly limited, but is usually 0.75 to 0.95 g / cm 3 ], and preferably 0.80 to 0.90 [g / cm 3 The density is calculated from the basis weight and thickness.

[0036] The expansion ratio of the opening 4 of the paper container 1 shown in FIG. 1 is 1.01 to 1.35 times. The opening 4 of the paper container 1 is a portion formed by drawing, consisting of the bottom portion 2 and side portion 3 of the paper container, and refers to the portion corresponding to the inner volume portion of the paper container 1. The expansion ratio of the opening 4 is an index that indicates how much the surface area has increased as a result of the opening 4 being elongated by drawing.

[0037] When the expansion ratio of the opening 4 of the paper container 1 becomes high, the paper container 1 is more likely to tear. Therefore, by setting the expansion ratio of the opening 4 to 1.35 times or less, the paper container 1 is less likely to tear, improving the productivity of the paper container 1. From a manufacturing standpoint, the expansion ratio of the opening 4 is 1.01 times or more. Methods for lowering the expansion ratio of the opening 4 of the paper container include decreasing the depth of the opening 4 of the paper container, increasing the angle of the opening corner 7, and decreasing the curvature of the paper container corner 5, which will be described later.

[0038] The expansion ratio of the opening 4 of the paper container is preferably 1.01 to 1.30 times, and more preferably 1.01 to 1.20 times. When the expansion ratio of the opening 4 of the paper container is 1.01 to 1.30 times, tearing of the paper container 1 is more easily prevented, and the productivity of the paper container 1 is further improved.

[0039] The curvature of the corner 7 of the opening of the paper container 1 is 0.02 to 0.18 [1 / mm]. The opening corners 7 of the paper container 1 are corners of the peripheral edge 6 of the side surface of the paper container. The peripheral edge is rectangular in shape and has four opening corners 7. The curvature of a corner is the reciprocal of the radius of the circle that touches the corner. A large curvature indicates that the corner is sharp, and a small curvature indicates that the corner is gentle.

[0040] If the curvature of the opening corner 7 of the paper container 1 is large, the paper container 1 is more likely to tear. Therefore, by setting the curvature of the opening corner 7 to 0.18 [1 / mm] or less, the paper container 1 is less likely to tear, improving the productivity of the paper container 1. From a manufacturing standpoint, the curvature of the opening corner 7 is 0.02 [1 / mm] or more. To reduce the curvature of the opening corner 7 of a paper container, methods such as appropriately selecting the conditions for drawing can be used, for example, by appropriately selecting the shape of the mold used for forming.

[0041] The curvature of the opening corner 7 of the paper container is preferably 0.02 to 0.15 [1 / mm], and more preferably 0.02 to 0.10 [1 / mm]. By setting the curvature of the opening corner 7 of the paper container to 0.02 to 0.15 [1 / mm], tearing of the paper container 1 is more easily prevented, and the productivity of the paper container 1 is further improved.

[0042] The depth of the opening 4 of the paper container is preferably 60 mm or less, more preferably 53 mm or less, even more preferably 46 mm or less, and even more preferably 40 mm or less. There is no particular lower limit to the depth of the opening 4 of the paper container, but from a manufacturing standpoint, it is usually 5 mm or more. The depth of the opening 4 of the paper container corresponds to the distance H between the bottom portion 2 of the paper container and the opening surface including the peripheral portion 6 of the side portion.

[0043] By making the depth of the opening 4 of the paper container 5 to 60 mm, mold reproducibility improves, tearing of the paper container 1 is more easily prevented, and productivity of the paper container 1 is further improved. In order to reduce the depth of the opening 4 of the paper container, methods such as appropriately selecting the conditions for drawing can be used, for example, by appropriately selecting the shape of the mold used for forming.

[0044] The angle of the opening corner 7 is preferably 15.00° or more, more preferably 20.00° or more, even more preferably 25.00° or more, and even more preferably 30.00° or more. There is no particular upper limit to the angle of the opening corner 7, but from a manufacturing standpoint, it is usually 85.00° or less. The angle of the opening corner 7 corresponds to the angle θ formed between the side surface 3 and an imaginary plane extending vertically at the peripheral edge 6 of the side surface.

[0045] By setting the angle of the opening corner 7 to 15.00 to 85.00°, it becomes easier to prevent the paper container 1 from breaking, and the productivity of the paper container 1 is further improved. In order to increase the angle of opening corner 7, methods such as appropriately selecting the conditions for drawing can be used, for example, by appropriately selecting the shape of the mold used for forming.

[0046] The curvature of the paper container corners 5 is preferably 0.10 [1 / mm] or less, and more preferably 0.08 [1 / mm] or less. There is no particular lower limit to the curvature of the paper container corners 5, but from a manufacturing standpoint, it is 0.03 [1 / mm] or more. The paper container corners 5 are corners that the bottom surface 2 has. The bottom surface 2 is rectangular in shape and has four paper container corners 5.

[0047] By setting the curvature of the corners 5 of the paper container to 0.03 to 0.10 [1 / mm], tearing of the paper container 1 can be more easily prevented, and the productivity of the paper container 1 can be further improved. In order to reduce the curvature of the corners 5 of the paper container, methods such as appropriately selecting the conditions for drawing can be used, for example, by appropriately selecting the shape of the mold used for forming.

[0048] Next, a paper container according to a modified example of the embodiment will be described. Figures 2(A) to 2(C) are diagrams showing a paper container according to a modified example. Figure 2(A) is a plan view of the paper container 1 seen from above, and Figure 2(B) is a cross-sectional view of the paper container 1 taken along line CC in Figure 2(A). Figure 2(C) is a cross-sectional view of the paper container 1 taken along line DD in Figure 2(A).

[0049] The bottom surface 2 of the paper container 1 according to this modification has a raised bottom portion 2A, which is partially raised so that the surface is curved. The raised bottom portion 2A has a rectangular shape with chamfered corners, similar to the entire bottom surface 2, so that its center coincides with the center of the raised bottom portion 2A. As shown in Figures 2(B) and (C), the raised bottom portion 2A is formed into a curved surface that is convex vertically upward. The depth of the paper container 1 corresponds to the vertical distance H between the bottom surface 2 excluding the raised bottom portion 2A and the peripheral edge 6 of the side surface portion 3.

[0050] The surface of the raised bottom portion 2A is a smooth curved surface with no corners formed by the intersection of two straight lines. The bottom portion 2 on the outside of the raised bottom portion 2A is also a smooth curved surface. Similarly, the surface of the side portion 3 is a smooth curved surface. By forming the bottom portion 2 and the side portion 3 into smooth curved surfaces, the paper container 1 can eliminate wrinkles and cracks, improving its aesthetic appeal. The container 1 has smoothly curved bottom 2 and side 3, which allows oil and moisture from the contents to flow around the raised bottom 2A and collect therein. For example, when food drips, the paper container 1 allows the drips to flow around the raised bottom 2A and collect therein. Furthermore, by providing the raised bottom 2A, the paper container 1 can reduce the contact area between the user's hand and the bottom 2 when lifting the bottom 2, which makes it less likely for heat to be transferred to the hand even when the contents are hot. In this way, the paper container 1 is more convenient.

[0051] Furthermore, by providing the raised bottom portion 2A, the paper container 1 has a large moment of inertia in the longitudinal direction, and the strength against bending in the longitudinal direction is improved. The strength of the paper container 1 can be improved.

[0052] 2(B), when the bottom surface portion 2 including the raised bottom portion 2A is cut in the direction of extension of the short side (X-axis direction), the cross section of the raised bottom portion 2A is an arc-shaped portion that is convex vertically upward. By making the raised bottom portion 2A an arc-shaped portion that is convex vertically upward, the paper container 1 is able to more easily disperse impact when dropped.

[0053] The bottom surface portion 2, the side surface portion 3, and the flange portion 8 each have a long side extending in the Y-axis direction and a short side perpendicular to the X-axis direction. In this modification, the bottom surface portion 2, excluding the raised bottom portion 2A, forms the lowest portion, which is formed parallel to the XY plane. Therefore, as shown in FIG. 2, when the paper container 1 is viewed from the long side of the side surface portion 3, the lowest portion of the bottom surface portion 2 is linear extending along the Y-axis. When the paper container 1 is placed with its lowest portion on a horizontal surface, the lowest portion evenly abuts on the horizontal surface, preventing it from wobbling and ensuring stability. Note that, as shown in FIG. 2, the angle of the opening corner portion 7 corresponds to the angle θ formed between the side surface portion 3 and an imaginary plane extending vertically at the peripheral portion 6 of the side surface portion 3.

[0054] <Paper layer> The paper base material for a draw-formed paper container has a paper layer. The paper layer may be a single-layer paper obtained by the single-layer papermaking method described later, or a multi-layer paper obtained by the multi-layer papermaking method described later.

[0055] The paper substrate may be obtained using a single sheet of paper having only one paper layer, but is preferably obtained using a slip sheet in which two or more paper layers are bonded together. The slip sheet further includes an adhesive resin layer between the two or more paper layers. That is, for example, a slip sheet in which two paper layers are bonded together is used as the paper substrate, and the paper substrate is formed by laminating a paper layer, an adhesive resin layer, and another paper layer in this order. For example, as shown in FIG. 3, when the paper substrate 10 is a slip sheet in which a thermoplastic resin layer 11, an adhesive resin layer 12, and a paper layer 13 are laminated in this order, tearing and cracking due to drawing can be more easily suppressed, and the productivity of the paper container 1 can be improved.

[0056] The paper layer is not particularly limited as long as it is a commonly used paper, but is preferably a paper containing plant-derived pulp as a main component, and more preferably a paper containing wood pulp as a main component. Furthermore, the raw material pulp contained in the paper layer is preferably wood pulp, and more preferably kraft pulp. Kraft pulp, depending on the raw material, includes hardwood kraft pulp (LKP) and softwood kraft pulp (NKP). Depending on the processing state, bleached kraft pulp (BKP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP) are examples, with bleached kraft pulp (BKP) being preferred from the viewpoint of printability. Recycled paper pulp may also be used.

[0057] Among these, the raw material pulp is preferably at least one selected from the group consisting of hardwood kraft pulp (LKP), softwood kraft pulp (NKP), and recycled paper pulp, and more preferably softwood kraft pulp (NKP).

[0058] The average fiber width of the pulp constituting the paper layer is preferably 28.0 μm or less, more preferably 27.0 μm or less, even more preferably 26.0 μm or less, and even more preferably 21.0 μm or less. There is no particular lower limit, but it is preferably 12.0 μm or more, more preferably 15.0 μm or more.

[0059] The length-weighted average fiber length of the pulp constituting the paper layer is preferably 0.5 to 2.5 mm, more preferably 0.6 to 2.4 mm, and even more preferably 0.6 to 1.2 mm.

[0060] The basis weight of the paper layer is preferably 80 to 340 g / m 2 ], and more preferably 90 to 320 [g / m 2 ], and more preferably 100 to 300 [g / m 2 ]. The basis weight of the paper layer is the total basis weight of all paper layers included in the paper container 1 when the paper container 1 is obtained using interleaving paper in which two or more paper layers are bonded together.

[0061] The thickness of the paper layer is preferably 0.12 to 0.44 mm, more preferably 0.13 to 0.42 mm, and even more preferably 0.14 to 0.40 mm. The thickness of the paper layer is the total thickness of all the paper layers included in the paper container 1 when the paper container 1 is obtained using interleaving paper in which two or more paper layers are bonded together.

[0062] The Canadian Standard Freeness (CSF) of the pulp that constitutes the paper layer is not particularly limited, but is preferably 400 to 750 [mL], and more preferably 500 to 700 [mL]. CSF is the freeness value measured using a Canadian standard freeness tester in accordance with JIS-P8121 after a sample is disintegrated using a standard disintegrator in accordance with JIS-P8220.

[0063] When preparing the paper layer, internal additives may be added, such as sizing agents, fillers, paper strength agents, polymer flocculants (retention aids), pH adjusters, drainage improvers, water-resistant agents, softeners, antistatic agents, antifoaming agents, slime control agents, dyes, and pigments.

[0064] Paper strength agents include dry strength agents and wet strength agents. Dry strength agents include cationized starch, polyacrylamide, carboxymethyl cellulose, etc., and wet strength agents include polyamide polyamine epichlorohydrin, urea formaldehyde resin, melamine formaldehyde resin, etc.

[0065] In making the paper layer, a known wet paper machine can be appropriately selected and used. Examples of the paper machine include a Fourdrinier paper machine, a gap former type paper machine, a cylinder paper machine, a short wire paper machine, etc. The Clupak treatment may be carried out by providing a Clupak device capable of carrying out the Clupak treatment in these paper machines.

[0066] In making a paper layer, for example, a method can be used in which a paper stock is cast onto a wire or the like, dewatered to obtain a wet paper, and if necessary, multiple wet papers are stacked, and this single-layer or multi-layer wet paper is pressed and dried. In this case, if multiple wet papers are not stacked, a single-layer paper layer is obtained, and if multiple wet papers are stacked, a multi-layer paper layer is obtained. When a multi-layer paper layer is obtained, starch, polyacrylamide, etc., which strengthens interlayer adhesion, can be applied between the layers during the papermaking process, and then the layers can be stacked together.

[0067] When applying starch, the amount of starch (e.g., the amount of coating after drying) is 0.1 to 5.0 [g / m 2 ], and 0.5 to 2.0 [g / m 2 It is more preferable that the paper layer formed by the paper machine is conveyed by, for example, a felt and dried in a dryer. A hairdryer may also be used.

[0068] The paper layer obtained as described above may be subjected to a surface treatment using a calendar to make the thickness and profile uniform. For the calendar treatment, a known calendaring machine can be appropriately selected and used.

[0069] Known Clupak devices can be used. For example, a Clupak device equipped with nip rolls and an endless thick elastic rubber blanket can be used. As described above, in the Clupak process, a paper web is fed between the nip rolls and the blanket, and when the paper web is compressed by the nip rolls and the blanket, the pre-stretched blanket is contracted to shrink the paper web and impart creping. The Clupak device is usually installed as part of the dryer unit of a paper machine, and after creping, the paper is dried and fixed. A paper layer can be obtained in this manner.

[0070] The Oken smoothness (JIS P 8155:2010) of the paper layer is not particularly limited, but is preferably 5 seconds or more, more preferably 10 to 1000 seconds. The 75° gloss of the paper layer is also not particularly limited, but is preferably 5% or more, more preferably 10 to 70%.

[0071] <Adhesive resin layer> When the paper substrate is an interleaving paper in which two or more paper layers are bonded together, an adhesive resin layer is included between the two or more paper layers. When the paper substrate has not only a paper layer but also a thermoplastic resin layer, an adhesive resin layer may also be included between the paper layer and the thermoplastic resin layer.

[0072] The adhesive resin layer may be a layer containing a thermoplastic resin. By using a thermoplastic resin, a laminated interleaf paper can be easily obtained by coating a paper layer with a heat-molten resin and laminating another paper layer.

[0073] Specific examples of thermoplastic resins include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; polyolefin resins such as polyvinyl chloride, polyvinylidene chloride, polybutene, polybutadiene, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, ethylene-propylene copolymer, and polymethylpentene; polycarbonate; polyurethane; polyamide; polyacrylonitrile; and poly(meth)acrylate.

[0074] Among these, polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers, and polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate are preferred, polyethylene, polypropylene, polyethylene terephthalate, polylactic acid, and polybutylene succinate are more preferred, polyethylene and polypropylene are even more preferred, and polypropylene is even more preferred. In addition to the above materials, biomass resins and biodegradable resins may also be used as the resin. These resins may be used alone or in combination of two or more.

[0075] The adhesive resin layer may be a resin-based adhesive suitable for dry lamination or wet lamination. The adhesive is not particularly limited, but water-based, solvent-based, UV-based, and other types can be used, with water-based adhesives being preferred. That is, the adhesive layer is preferably a water-based adhesive layer formed from a water-based adhesive. Furthermore, among the water-based adhesives, at least one selected from the group consisting of vinyl acetate adhesives, acrylic adhesives, polyurethane adhesives, and isocyanate adhesives is preferred.

[0076] The thickness of each adhesive resin layer is preferably 5 to 100 μm, and more preferably 10 to 50 μm.

[0077] <Thermoplastic resin layer> From the viewpoint of improving waterproofness and stain resistance, the paper substrate for the draw-formed paper container may have a thermoplastic resin layer on at least one surface, or the paper substrate may have a thermoplastic resin layer on one surface or on both surfaces. The thermoplastic resin used in the thermoplastic resin layer is not particularly limited and may be appropriately selected from known thermoplastic resins, and may also be appropriately selected from the thermoplastic resins described above as the thermoplastic resin contained in the adhesive resin layer.

[0078] The thickness of each thermoplastic resin layer is preferably 8 to 150 μm, and more preferably 15 to 80 μm.

[0079] <Manufacturing method of paper containers> There are no particular limitations on the method for manufacturing the paper container 1, and any known method can be used. First, an example of a method for manufacturing the paper base material that constitutes the paper container 1 will be described below.

[0080] When the paper substrate is a laminated paper made of two or more paper layers bonded together, an adhesive resin layer can be coated on one side of the paper layer, for example by melt lamination, and another paper layer can be bonded to this coated surface to obtain the laminated paper. As described above, the slip sheet includes two or more paper layers, but it may also include three or more paper layers. When the slip sheet includes three or more paper layers, the multiple adhesive resin layers that bond these paper layers together may be different from each other or the same.

[0081] When the paper substrate has not only a paper layer but also a thermoplastic resin layer, an adhesive resin layer can be coated on one side of the paper layer by, for example, melt lamination, and then a thermoplastic resin layer can be laminated to this coated surface to obtain a paper substrate having a thermoplastic resin layer. The thermoplastic resin layer may also be coated by melt extrusion coating.

[0082] The obtained paper base material may be cut to an appropriate size taking into consideration the size and shape of the contained items, and suitability for transportation and display. From the viewpoint of efficiently obtaining interleaf sheets of the same shape, cutting is preferably performed by punching. The punching process is preferably carried out using a high-speed automatic punching machine, a flat-bed punching machine, or a rotary punching machine, and more preferably a high-speed automatic punching machine, which can easily and efficiently obtain paper substrates in shapes such as rectangular, rounded rectangular, oval, etc.

[0083] An example of a method for producing the paper container 1 obtained from the above-mentioned paper base material will be described below. Examples of methods for manufacturing paper containers include a manufacturing method called press molding, in which a paper base material for a drawn paper container is punched into a container blank sheet, and the blank sheet is sandwiched between a press mold consisting of a male mold and a female mold and heated and pressurized to form it.Other examples include vacuum forming, in which a male mold or a female mold alone is used under heating to create a vacuum between the mold and the blank sheet and mold the blank sheet in close contact with the mold, and pressure forming, in which a male mold or a female mold is used under heating to sandwich the blank sheet between one mold and the other air pressure device and mold the blank sheet by the pressure from the pressure device.

[0084] In this case, the paper substrate may be humidified in advance to adjust the moisture content. Methods for adjusting the moisture content of the paper substrate include adding moisture to the paper layer immediately before forming, or humidifying the paper layer after it leaves the dryer during papermaking, and transporting and storing it in a state where the moisture is maintained.

[0085] Next, the steps for manufacturing a paper container 1 from a paper base material will be described. Figure 4 is a flowchart relating to the method for manufacturing a paper container. In the method for manufacturing a paper container according to this embodiment, a paper base material for a draw-formed paper container is prepared (step S101). In step S102, which follows step S101, the paper base material is draw-formed (step S102). This results in the paper container 1. When the draw-formation is performed by press processing, it is performed using a pair of press dies. The pair of press dies consists of a convex die that is shaped to correspond to the inner volume portion of the paper container 1, and a concave die that is shaped to correspond to the outer shape of the paper container 1. The pair of press dies can press the blank sheet by moving at least one die back and forth or up and down.

[0086] When drawing is performed by vacuum forming, the blank sheet is formed into a shape that matches the mold using only one of the female or male molds. Preferably, the gap between the blank sheet and the mold is reduced in pressure under heating, and the blank sheet is pressed tightly against the mold to form it. If necessary, after cooling, air is blown in to remove the paper container 1.

[0087] When drawing is performed by compressed air molding, either a male or female mold and a compressed air device (also called a compressed air box) are used to form the paper into a shape that matches the mold. A blank sheet is sandwiched between the mold and the compressed air device, and the blank sheet is pressed tightly against the mold by pressure from the pressure device, preferably under heating, to form the paper container 1. After cooling as necessary, the paper container 1 is removed. The pressure from the pressure device is preferably 0.01 to 0.30 [bar], and more preferably 0.05 to 0.20 [bar].

[0088] Examples of methods for heating the blank sheet include high-frequency heating, hot air heating, and infrared heating. The blank sheet may be preheated before drawing. The blank sheet is preferably preheated to 40 to 80°C, and more preferably to 50 to 70°C.

[0089] Alternatively, the entire mold may be heated. In this case, a means for heating the mold is required. A common mold heating method is to provide an electric heating device to heat the mold, but there is also a method for drying by connecting a high-frequency oscillator to the mold and applying high-frequency waves. Electric heating and high-frequency heating can also be used in combination. The mold is preferably heated to 90 to 130°C, more preferably 100 to 120°C.

[0090] Once the drawing process is complete, the paper container 1 can be removed from the mold and air-cooled. However, to improve dimensional stability, it is also preferable to fix the hot paper container 1 in the cooling mold for a certain period of time to cool it.

[0091] The mold may be made of known materials such as aluminum, aluminum alloys, brass, iron, stainless steel, and ceramics.

[0092] The mold can be operated using any of a hydraulic press, an air cylinder, or a cam mechanism. In the present invention, the specific method for controlling the clearance between the upper and lower molds is to use hydraulic or air pressure, and to control the pressure by computer control according to the thickness of the molded product, or to control the position of a stopper. When using a cam mechanism, control is possible by a pre-designed cam shape and the lowering speed of the mold. The pressing time during press molding is preferably 1 second or more and 30 seconds or less from the viewpoint of moldability and workability.

[0093] The methods for measuring each physical property are described below. The physical properties of the paper substrate are measured before drawing. In this case, a portion of the paper container after drawing may be cut out and measured. When cutting out a portion of the paper container after drawing and measuring, the sample may be cut out from a flat portion of the paper container, which is the unprocessed portion, and if the paper container 1 has a flange portion 8, the sample may be cut out from the flange portion 8.

[0094] <Basis weight of paper base material> The basis weight of the paper base material is measured in accordance with JIS P 8124:2011 after humidity conditioning in a humidity-conditioning environment specified in JIS P 8111:1998. Specifically, the mass of a paper substrate cut to a predetermined size is measured and the basis weight is calculated.

[0095] <TEA, breaking elongation, and tensile strength of paper substrate> The TEA, breaking elongation, and tensile strength of the paper base material are measured in accordance with JIS P 8113:2006 after humidity conditioning in a humidity-controlled environment specified in JIS P 8111:1998. Specifically, a paper substrate was cut to a width of 15 mm and a length of 150 mm. The sample was attached to a tensile testing machine (Model RTC-1210A, manufactured by A&D Co., Ltd.) with a chuck distance of 100 mm. A tensile test was performed at a speed of 10 mm / min to measure the TEA, breaking elongation, and tensile strength in both the MD (machine direction) and CD (cross direction). Ten measurements were taken for each of the machine direction and cross direction, and the arithmetic mean values ​​were used. The geometric mean values ​​of the machine direction and cross direction arithmetic mean values ​​were then calculated.

[0096] <Paper base thickness> The thickness of the paper base material is measured in accordance with JIS P 8118:2014 after humidity conditioning in a humidity-controlled environment specified in JIS P 8111:1998. Specifically, a paper thickness meter (model number: No. 132 digital thickness measuring instrument, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used to measure 10 points on the sample, and the arithmetic mean value was used. In addition, the thickness of the paper substrate and the paper layer, adhesive resin layer, and thermoplastic resin layer that make up the paper substrate can be measured from an observation image of the cross section of the paper substrate using a scanning electron microscope (SEM).

[0097] <Paper base density> The density of the paper substrate is calculated from the basis weight and thickness obtained by the above-mentioned measurement method.

[0098] <Expansion ratio of the opening of the paper container> The expansion ratio of the opening of the paper container is calculated using the following formula. Opening expansion ratio = surface area after expansion / surface area before expansion The surface area before and after unfolding can be measured by capturing three-dimensional data of the paper container before and after unfolding (before and after drawing) using a 3D scanner-type coordinate measuring machine (VL-700 series, manufactured by Keyence Corporation). The expansion ratio is an indicator of how much the drawn-formed area has been stretched. By checking the paper container 1 from the opening side, the formed area can be identified and the surface area before expansion can also be derived, so the expansion ratio can be measured from the paper container after drawing.

[0099] <Curvature of the corners of the opening of the paper container, depth of the opening, angle of the corners of the opening, and curvature of the corners of the paper container> The curvature of the corners of the opening of a paper container, the depth of the opening, the angle of the corners of the opening, and the curvature of the corners of the paper container can be measured by capturing three-dimensional data of the paper container using a 3D scanner-type coordinate measuring machine (VL-700 series, manufactured by Keyence Corporation).

[0100] [Example] The present invention will be specifically described below using examples, but the scope of the invention is not limited to the description of the examples. Furthermore, unless otherwise specified, "parts" means "parts by mass."

[0101] [Manufacturing of paper layers 1 to 8] Softwood bleached kraft pulp (NBKP) was subjected to high-concentration beating using a double-disc refiner until the disintegrated freeness (CSF: Canadian standard freeness) reached 700 mL, to prepare a pulp slurry with a pulp solids concentration of 0.5% by mass. To 100 parts by mass of this pulp slurry, 0.2 parts by mass of a synthetic sizing agent (SPS400, manufactured by Arakawa Chemical Industries, Ltd.), 1.0 part by mass of aluminum sulfate, 0.2 parts by mass of a polyacrylamide (CK-311, manufactured by Misawa Ceramic Co., Ltd.) as a paper strength agent, and 0.0025 parts by mass of a nonionic acrylamide (Percoll 47, manufactured by Allied Colloid Co., Ltd.) as a polymer flocculant were added to prepare a paper stock. Using this paper stock, a wet paper machine (Bellform III type, manufactured by Mitsubishi Heavy Industries, Ltd.) equipped with an expansion device (manufactured by Clupak) was used to measure the speed before and after Clupak treatment. The difference is set to -20.0 m / min and the basis weight is 150 g / m 2 The paper was made so that the paper layer 1 was obtained.

[0102] Basis weight: 50g / m 2 Paper layer 2 was obtained in the same manner as paper layer 1, except that paper was made so that:

[0103] Paper layer 3 was obtained in the same manner as paper layer 1, except that high-concentration beating was carried out until the disintegrated freeness reached 600 mL.

[0104] Basis weight: 250 g / m 2 Paper layer 4 was obtained in the same manner as paper layer 1, except that paper was made so that:

[0105] Basis weight: 200g / m 2 Paper layer 5 was obtained in the same manner as paper layer 1, except that paper was made so that:

[0106] Basis weight: 100g / m 2 Paper layer 6 was obtained in the same manner as paper layer 1, except that paper was made so that:

[0107] Beating was carried out until the disintegration freeness reached 600 mL, and the basis weight was 350 g / m 2 Paper layer 7 was obtained in the same manner as paper layer 1, except that paper was made using a Fourdrinier Yankee paper machine so that the paper layer 7 had the following properties.

[0108] Basis weight: 75g / m 2 Paper layer 8 was obtained in the same manner as paper layer 1, except that paper was made so that:

[0109] [Production of interleaving papers 1 to 4 and single sheets 1 to 4] PP adhesive resin was fed into a single-screw extruder (D2025, manufactured by Toyo Seiki) and melt-laminated on top of the paper layer 1 at 330°C so that the resin thickness was 25 μm. A 40 μm thick PP film was then laminated onto the adhesive resin layer, and the film was quickly quenched while being sandwiched between cooling rolls adjusted to 20°C, to obtain a single sheet of paper with a thermoplastic resin layer, adhesive resin layer, and paper layer 1 laminated in that order. Furthermore, in the same manner as above, a single-screw extruder was used to melt-laminated PP adhesive resin at 330°C onto the paper layer 1 of the obtained interleaf paper so that the resin thickness was 25 μm, and the paper layer 1 was then laminated onto the adhesive resin layer, and the interleaf paper 1 was quickly quenched while being sandwiched between cooling rolls adjusted to a temperature of 20°C, thereby obtaining an interleaf paper 1 in which a thermoplastic resin layer, adhesive resin layer, paper layer 1, adhesive resin layer, and paper layer 1 were laminated in this order.

[0110] Interleaf paper 2 was obtained in the same manner as interleaf paper 1, except that paper layer 2 was used instead of paper layer 1.

[0111] PE resin (LC522, manufactured by Japan Polyethylene Corporation) was fed into a single-screw extruder and melt-laminated at 320°C onto the paper layer 3 so that the resin was 30 μm thick. The paper layer 3 was then bonded onto the adhesive resin layer, and the laminate was quickly cooled by sandwiching it between cooling rolls adjusted to 20°C, to obtain an interleaving paper in which the paper layer 3, adhesive resin layer, and paper layer 3 were laminated in that order. Furthermore, in the same manner as above, a single-screw extruder was used to melt-laminated PE resin at 320°C onto the paper layer 3 of the obtained interleaf paper so that the resin thickness was 18 μm, and then the interleaf paper was rapidly cooled while being sandwiched between cooling rolls whose temperature was adjusted to 20°C, thereby obtaining an interleaf paper 3 in which a thermoplastic resin layer, a paper layer 3, an adhesive resin layer, and a paper layer 3 were laminated in this order.

[0112] Interleaf paper 4 was obtained in the same manner as interleaf paper 1, except that paper layer 4 was used instead of paper layer 1.

[0113] Single paper 1 was obtained in the same manner as interleaf paper 1, except that paper layer 5 was used instead of paper layer 1, and a single paper was obtained in which a thermoplastic resin layer, an adhesive resin layer, and paper layer 5 were laminated in that order.

[0114] A paper sheet 2 was obtained in the same manner as the paper sheet 1, except that paper layer 6 was used instead of paper layer 5.

[0115] PE resin was fed into a single-screw extruder and melt-laminated on top of the paper layer 7 at 320°C so that the resin thickness was 18 μm. It was then quickly quenched while being clamped between cooling rolls adjusted to 20°C, to obtain a single paper 3 in which a thermoplastic resin layer and a paper layer 7 were laminated in that order.

[0116] A paper sheet 4 was obtained in the same manner as the paper sheet 1, except that paper layer 8 was used instead of paper layer 5.

[0117] The configurations of the interleaf sheets 1 to 4 and the single sheets 1 to 4 are shown in Table 1, and the thickness of each layer is shown in Table 2.

[0118] [Table 1]

[0119] [Table 2]

[0120] [Examples 1 to 8 and Comparative Examples 1 to 6] Drawing was carried out using the interleaf paper or single paper shown in Table 4 as the paper substrate. The paper substrate was preheated to 60°C with a heater, and then fed to a lower mold heated to 120°C. The upper mold was pressed into the paper substrate at a compressed air pressure of 0.50 bar for a molding time of 5 seconds to obtain a paper container.

[0121] In Examples 1 to 4 and Comparative Examples 1 to 4, molds of the same shape were used so that the expansion ratio of the opening of the paper container, the curvature of the corners of the opening, the depth of the opening, the angle of the corners of the opening, and the curvature of the corners of the paper container were the same values ​​(values ​​listed in Table 4). In Examples 5 to 8 and Comparative Examples 5 to 6, molds of different shapes were used from those in Examples 1 to 4 and Comparative Examples 1 to 4 so that the expansion ratio of the opening of the paper container, the curvature of the corners of the opening, the depth of the opening, the angle of the corners of the opening, and the curvature of the corners of the paper container were the values ​​listed in Table 4.

[0122] <Evaluation of formability> The paper containers after drawing were visually inspected and evaluated for the presence or absence of breaks and cracks according to the following criteria. The results are shown in Table 3. The results are shown in Table 3. Here, "break" refers to a state in which the paper was unable to withstand the tensile stress acting on the entire paper during forming, and was broken across the entire thickness direction. Furthermore, "crack" refers to a state in which the paper was unable to withstand the tensile stress acting on the outermost layer side of the paper (outside the container) due to bending deformation during forming, and only the outermost layer was broken (cracked state). (Evaluation criteria) A: Three paper containers were produced, and none of them showed any tears or cracks. B: Three paper containers were produced, and one or more had tears and / or cracks.

[0123] <Evaluation of mold reproducibility> Three or more paper piping containers were produced, and three of them were free of any breaks or cracks. A 3D scanner-type coordinate measuring machine (VL-700 series, Keyence Corporation) captured the three-dimensional data of the paper piping containers, and the arithmetic mean value of the depth of the three paper piping containers was calculated. The difference between the mean depth of the paper piping containers and the depth of the mold used for piping was evaluated according to the following criteria. The results are shown in Table 4. (Evaluation criteria) A: The difference between the average depth of the paper squeeze container and the depth of the mold is less than 1 mm. B: The difference between the average depth of the paper squeeze container and the depth of the mold is 1 mm or more but less than 3 mm. C: The difference between the average depth of the paper squeeze container and the depth of the mold is 3 mm or more.

[0124] [Table 3]

[0125] From the results of the Examples and Comparative Examples, it can be seen that the paper container of the present disclosure does not break or crack due to drawing. It is clear that the paper container of the present disclosure has high mold reproducibility.

[0126] [Examples 1' to 8': Paper containers with raised bottoms] Squeeze molding was carried out using the interleaf paper or single paper shown in Table 5 as the paper substrate. The paper substrate was preheated to 60°C with a heater, and then fed to a lower mold heated to 120°C. The upper mold was pressed into the paper substrate at a compressed air pressure of 0.50 bar for a molding time of 5 seconds to obtain a paper container.

[0127] In Examples 1' to 4', molds of the same shape were used so that the expansion ratio of the opening of the paper container, the curvature of the corners of the opening, the depth of the opening, the angle of the corners of the opening, and the curvature of the corners of the paper container were the same values ​​(values ​​listed in Table 5). In Examples 5' to 8', molds of different shapes were used than in Examples 1' to 4' so that the expansion ratio of the opening of the paper container, the curvature of the corners of the opening, the depth of the opening, the angle of the corners of the opening, and the curvature of the corners of the paper container would be the values ​​listed in Table 5.

[0128] In Examples 1' to 8', the resulting paper containers each had a bottom, a side, and a flange, and the bottom had a raised portion where part of the bottom was raised so that the surface was curved, and molds were used such that the bottom and side had smooth curved surfaces. The paper containers obtained in Examples 1' to 8' have the same characteristics as the paper containers obtained in Examples 1 to 8, except that they have a bottom portion with a partially raised bottom, a flange portion, and the bottom portion and side portion have smoothly curved surfaces.

[0129] [Table 4]

[0130] The paper containers obtained in Examples 1' to 8' were less likely to break or crack during drawing, similar to the paper containers obtained in Examples 1 to 8, and had high productivity. Furthermore, similar to the paper containers obtained in Examples 1 to 8, they also had high mold reproducibility.

[0131] In addition, the paper containers obtained in Examples 1' to 8' were more aesthetically pleasing than the paper containers obtained in Examples 1 to 8, and were able to channel and collect oil and moisture from the contents around the raised bottom, making them less likely to transfer heat to the hands even when the contents were hot. They also had improved strength against bending in the longitudinal direction, and were more likely to disperse impacts when dropped. [Explanation of symbols]

[0132] 1. Paper containers 2 Bottom part 3 Side part 4 Openings 5 Corner of paper container 6. Periphery of the side 7 Opening corner 8 Flange 10 Paper base material 11 Thermoplastic resin layer 12 Adhesive resin layer 13 Paper layer

Claims

1. A paper substrate for a draw-formed paper container, The basis weight of the paper base material is 150 to 400 [g / m ２ ] and The geometric mean value of the tensile energy absorption (TEA) of the paper substrate is 900 to 2000 [J / m ２ ], a paper substrate.

2. The basis weight of the paper base material is 175 [g / m ２ ] or more, The paper substrate of claim 1.

3. The geometric mean value of the longitudinal and transverse breaking elongation of the paper base material is 12.0% or more. The paper substrate of claim 1.

4. The thickness of the paper base material is 0.12 to 0.44 mm. The paper substrate of claim 1.

5. The paper base material has a thermoplastic resin layer, an adhesive resin layer, and a paper layer laminated in this order. The paper substrate of claim 1.

6. A paper container obtained by drawing the paper base material according to any one of claims 1 to 5.

7. The curvature of the corner of the opening formed by drawing is 0.02 to 0.18 [1 / mm]. The paper container according to claim 6.

8. The expansion ratio of the opening formed by drawing is 1.01 to 1.35 times. The paper container according to claim 6.

9. The depth of the opening formed by drawing is 5 to 60 mm. The paper container according to claim 6.

10. A bottom portion; a side surface portion rising from the periphery of the bottom surface portion; a flange portion extending outward from the side surface portion; Equipped with The bottom surface portion has a raised portion that is partially raised so that the surface is curved. The paper container according to claim 6.

11. Basis weight: 150 to 400 [g / m ２ ] and the geometric mean value of the tensile energy absorption (TEA) in the vertical and horizontal directions is 900 to 2000 [J / m ２ and preparing a paper substrate for a drawn paper container, drawing the paper substrate; A method for manufacturing a paper container, comprising:

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