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

Abstract

The present disclosure aims to provide a technology that has high mold reproducibility and can improve the productivity of paper containers. The paper base material for a draw-formed paper container has a basis weight of 150 to 400 [g / m 2 ] or less, and the longitudinal and transverse geometric mean value of the tensile energy absorption (TEA) of the paper base material is 900 to 2000 [J / m 2 ] is a paper base material.

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

[0003] 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] JP 2007-16380 A Summary of the Invention [Problem to be solved by the invention]

[0006] Paper containers obtained by drawing may have some tears or cracks during forming, 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> About <1> A paper substrate for a drawn paper container, comprising: The basis weight of the paper base material is 150 to 400 [g / m 2 ] or less, The longitudinal and transverse geometric mean value of the tensile energy absorption (TEA) of the paper base material is 900 to 2000 [J / m 2 ] is a paper base material. <2> The basis weight of the paper base material is 175 [g / m 2 ] or more, <1> The paper base material according to claim 1. <3> The longitudinal and transverse geometric mean value of the breaking elongation of the paper base material is 12.0% or more; <1> or <2> The paper base material 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 claims 1 to 5. <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 claims 1 to 5. <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 corners 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 claims 1 to 5. <10> A bottom portion and 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 bottom-raised portion that is partially raised so that the surface is curved. <6> ~ <9> The paper container according to any one of claims 1 to 5. <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

[0033] preparing a paper base material for a drawn paper container; Drawing the paper substrate; A method for manufacturing a paper container comprising the steps of: Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a technology that has high mold reproducibility and can improve the productivity of paper containers. [Brief description of the drawings]

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

[0010] In this specification, the description "X or more and Y or less" or "X to Y" representing a numerical range means a numerical range including the lower limit and the upper limit, which are the endpoints, unless otherwise specified. In addition, the description "less than X to Y" means a numerical range that is greater than or equal to X and less than Y, including the lower limit, which is the endpoint, but not including 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 arbitrarily.

[0011] In this specification, the machine direction is 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 is the direction perpendicular to the machine direction (CD).

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

[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 cut along line AA in FIG. 1(A). FIG. 1(C) is a cross-sectional view of the paper container 1 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. The paper container 1 is manufactured by forming a single sheet of paper base material, and therefore is integrally formed as a whole. As shown in FIG. 1(A), the paper container 1 has a rectangular shape having a longitudinal direction and a transverse direction perpendicular to the longitudinal direction when viewed from above. The paper container 1 is used, for example, as a container for foods containing moisture, such as chilled foods.

[0014] 1(A) to 1(C) also show an X-axis, a Y-axis, and a Z-axis that are perpendicular to each other. The X-axis direction and the Y-axis direction correspond to a horizontal direction, and the Z-axis direction indicates a vertical direction perpendicular to the horizontal direction. In the following, the directions X, Y, and Z (or the horizontal direction and the vertical direction) will be used for explanation. 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 (C), the paper container 1 has a bottom portion 2 on which food or the like is placed, and a side portion 3 rising from the periphery of the bottom portion 2. The bottom portion 2 and the side portion 3 form an opening 4 corresponding to the inner volume of the paper container 1. The bottom portion 2 has paper container corner portions 5 which are rectangular in shape with four chamfered corners. The side portion 3 rises from the bottom portion 2 to form a space for accommodating food or the like together with the bottom portion 2. A peripheral portion 6 which is the outer periphery of the side portion 3 has opening corner portions 7 which are rectangular in shape with four chamfered corners.

[0016] The angle of the opening corner 7 corresponds to the angle θ between the side surface 3 and an imaginary plane extending vertically at the peripheral portion 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 surface including the peripheral portion 6 of the side surface.

[0017] The paper container 1 also has a flange portion 8 extending outward from the peripheral edge portion 6 of the side portion 3. The flange portion 8 is provided so as to surround the entire circumference of the side portion 3. For this reason, 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 extending approximately parallel to the flat portion with the bottom portion 2, and a step is formed on the outermost periphery that descends toward the bottom portion 2.

[0018] The paper container 1 has a structure in which the bottom portion 2, the side portion 3, and the flange portion 8 are integrally formed, 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 reduces the 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, not only the paper layer but also the The mass of the adhesive resin layer and the thermoplastic resin layer are also included in the basis weight of the paper base material.

[0021] Increasing the basis weight of the paper base material makes it more likely that cracks will occur due to drawing and reduces the mold reproducibility of the paper container, but conversely, decreasing the basis weight makes it more likely that tears will 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, the 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 base material is preferably 375 [g / m2 or more] from the viewpoint of improving mold reproducibility and further suppressing the occurrence of cracks. 2 ] or less, and more preferably 350 [g / m 2 ]below. Therefore, the basis weight of the paper base material is preferably 175 to 375 [g / m 2 ], and more preferably 200 to 350 [g / m 2 The basis weight of the paper base material is 175 to 375 [g / m 2By making the paper base material have a basis weight of 175 to 375 [g / m], it is possible to more easily 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.

[0023] The geometric mean value of the tensile energy absorption (TEA) in the longitudinal direction of the paper base material and the TEA in the transverse direction, i.e., the geometric mean value of the TEA in the longitudinal direction and the transverse direction of the paper base material (hereinafter, simply referred to as "TEA of the paper base material"), 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 pull 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 in forming the paper container 1 can also be measured by measuring a portion of the paper container 1 that is not elongated by drawing (for example, the flange portion 8 shown in FIG. 1).

[0024] If the TEA of the paper base material is increased, cracks due to drawing tend to occur, but conversely, if the TEA is decreased, tears due to drawing tend to occur. Also, if the TEA is decreased, mold reproducibility decreases. Therefore, the TEA of the paper base material is set to 900 to 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, and the productivity of the paper container 1 is improved. 2 By controlling the temperature within this range, it is possible to obtain paper containers with high mold reproducibility. In order to increase the TEA of the paper base material, there are several methods, such as increasing the basis weight of the paper base material, adding a resin layer to the paper layer, subjecting the pulp that constitutes the paper layer to high concentration beating, and performing Clupak treatment during papermaking of the paper layer. In order to decrease the TEA of the paper base material, there are several methods, such as decreasing the basis weight of the paper base material and using a single sheet of paper as the paper base material. In order to increase the TEA of the paper base material to 900-2000 [J / m 2 From the viewpoint of controlling the speed difference before and after Clupac processing to, for example, -10 to -35% is effective.

[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 base material 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 improved. 2 ], the mold reproducibility can be further improved.

[0026] The TEA in the longitudinal 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 lateral direction of the paper substrate is preferably 700 to 1500 [J / m 2 ] and is more preferable. Preferably 800-1400 [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 the viewpoint of manufacturing, 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 is not elongated by drawing (for example, the flange portion 8 shown in FIG. 1 ) to measure the breaking elongation of the paper base material used in forming the paper container 1.

[0028] By making the paper base material have a breaking elongation of 12.0 to 20.0%, the formability of the paper container 1 can be further improved, making it easier to prevent breakage or cracking due to drawing, and the productivity of the paper container 1 can be further improved. Methods for increasing the breaking elongation of a paper base material include providing a resin layer on the paper layer, subjecting the pulp constituting the paper layer to high concentration beating, and carrying out Clupak treatment during papermaking of the paper layer.

[0029] The longitudinal breaking elongation of the paper base material 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 base material 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 tensile strength and the transverse tensile strength 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 the viewpoint of manufacturing, 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 is not stretched by drawing (e.g., flange portion 8), thereby measuring the tensile strength of the paper base material used in forming the paper container 1.

[0031] By making the paper base material have a tensile strength of 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 a paper base material include increasing the amount of paper strength agents, increasing the basis weight of the paper base material, adding a resin layer to the paper layer, lowering the Canadian Standard Freeness (CSF) of the pulp that makes up the paper layer, and increasing the amount of paper strength agents.

[0032] The longitudinal tensile strength of the paper base material 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 lateral tensile strength of the paper substrate 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 is 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 0.17 mm or more. The thickness of the paper base material includes the thickness of the adhesive resin layer and the thermoplastic resin layer as well as the thickness of the paper base material.

[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 base material is not particularly limited, but is usually 0.75 to 0.95 [g / cm 3 ], 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 the side portion 3 of the paper container, and corresponds 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 break. Therefore, by setting the expansion ratio of the opening 4 to 1.35 times or less, the paper container 1 is less likely to break and the productivity of the paper container 1 is improved. 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, as described below, increasing the angle of the opening corner 7, as described below, and decreasing the curvature of the paper container corner 5, as described below.

[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. By expanding the opening 4 of the paper container to a ratio of 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 opening corner 7 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 a 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] When the curvature of the opening corner 7 of the paper container 1 becomes large, the paper container 1 becomes more likely to tear. Therefore, by making the curvature of the opening corner 7 0.18 [1 / mm] or less, the paper container 1 becomes 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. In order to reduce the curvature of the opening corner 7 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 molding.

[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 making the curvature of the opening corner 7 of the paper container 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 part 2 of the paper container and the opening surface including the peripheral part 6 of the side part.

[0043] By setting the depth of the opening 4 of the paper container to 5 to 60 mm, mold reproducibility is improved, tearing of the paper container 1 is more easily prevented, and the 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. The upper limit of the angle of the opening corner 7 is not particularly limited, but is usually 85.00° or less from the viewpoint of manufacturing. The angle of the opening corner 7 corresponds to the angle θ between the side portion 3 and a virtual plane extending vertically at the peripheral portion 6 of the side portion.

[0045] By setting the angle of the opening corner 7 to 15.00 to 85.00°, 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 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 of the bottom surface 2. 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 (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 cut along line CC in Figure 2(A). Figure 2(C) is a cross-sectional view of the paper container 1 cut along line DD in Figure 2(A).

[0049] The bottom portion 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 its corners chamfered like the bottom portion 2 as a whole so that its center coincides with the center of the bottom portion 2. 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 portion 2 other than the raised bottom portion 2A and the peripheral portion 6 of the side 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 a smooth curved surface, the paper container 1 can be made to be free of wrinkles and cracks, improving its aesthetic appeal. The container 1 has a bottom portion 2 and side portions 3 formed into smooth curved shapes, which allows oil and moisture from the contents to flow around the raised bottom portion 2A and collect therein. For example, when food drips, the paper container 1 allows the drips to flow around the raised bottom portion 2A and collect therein. Furthermore, by providing the raised bottom portion 2A, the paper container 1 can reduce the contact area between the hand and the bottom portion 2 when the user lifts the bottom portion 2 with their hand, which makes it difficult for heat to be transferred to the hand even if the contents are hot. In this way, the paper container 1 has improved convenience.

[0051] Furthermore, by providing the raised bottom portion 2A, the paper container 1 has a large moment of area 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 extension direction of the short side (X-axis direction), the cross section of the raised bottom portion 2A has an arc shape that is convex vertically upward. By making the raised bottom portion 2A have an arc shape that is convex vertically upward, the paper container 1 is more likely to disperse impact when dropped.

[0053] In addition, 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 is formed so that the portion excluding the bottom-raised portion 2A forms the lowest portion, and the lowest portion is 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 a straight line extending along the Y-axis. When the lowest portion of the paper container 1 is placed on a horizontal surface, the lowest portion is uniformly abutted on the horizontal surface, so that the paper container 1 is stable and does not wobble. 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 the draw-formed paper container has a paper layer. The paper layer may be a single-layer paper obtained by the single-layer papermaking process described later, or a multi-layer paper obtained by the multi-layer papermaking process described later.

[0055] The paper base material may be obtained using a single 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 base material, and the paper base material is formed by laminating a paper layer, an adhesive resin layer, and a paper layer in this order. For example, as shown in FIG. 3, by using 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 as the paper base material 10, it becomes easier to suppress breakage and cracking due to drawing, and the productivity of the paper container 1 is improved.

[0056] The paper layer is not particularly limited as long as it is a commonly used paper, and is preferably a paper containing plant-derived pulp as a main component, and more preferably a paper containing wood pulp as a main component. The raw material pulp contained in the paper layer is preferably wood pulp, and more preferably kraft pulp. The kraft pulp includes hardwood kraft pulp (LKP) and softwood kraft pulp (NKP) based on the difference in raw material. The kraft pulp includes bleached kraft pulp (BKP), unbleached kraft pulp (UKP) and oxygen bleached kraft pulp (OKP) based on the difference in processing state, and bleached kraft pulp (BKP) is preferred from the viewpoint of printability. Waste 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, and 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 refers to the total basis weight of all paper layers included in the paper container 1 when the paper container 1 is obtained using an 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 refers to the total thickness of all the paper layers included in the paper container 1 when the paper container 1 is obtained using an interleaving paper in which two or more paper layers are bonded together.

[0062] The Canadian Standard Freeness (CSF) of the pulp constituting 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 by disintegrating a sample using a standard disintegrator in accordance with JIS-P8220 and then measuring the freeness using a Canadian standard freeness tester in accordance with JIS-P8121.

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

[0064] Paper strength agents include dry strength agents and wet strength agents. Dry strength agents include cationic starch, polyacrylamide, carboxymethyl cellulose, etc., while 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. These paper machines may be equipped with a Clupak device capable of carrying out the Clupak treatment, and the Clupak treatment may be carried out.

[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, dehydrated to obtain a wet paper, and multiple wet papers are stacked as necessary, 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. that strengthens interlayer adhesion may be applied between the layers during the papermaking process, and the layers may be stacked together.

[0067] When applying starch, the amount of starch (e.g., the amount of starch applied 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 papermaking machine is conveyed, for example, by a felt and dried by a dryer. A dryer may also be used.

[0068] The paper layer obtained as described above may be surface-treated with a calendar to make the thickness and profile uniform. A known calendaring machine can be appropriately selected and used for the calendaring.

[0069] A Clupak device may be any known device. For example, a Clupak device equipped with a nip roll and an endless thick elastic rubber blanket may be used. As described above, in the Clupak process, the paper web is fed between the nip roll and the blanket, and when the paper web is compressed by the nip roll and the blanket, the blanket, which has been stretched in advance, is contracted to shrink the paper web and impart creping. The Clupak device is usually provided as part of the dryer of a papermaking machine, and after creping, the paper is dried and fixed. In this manner, a paper layer can be obtained.

[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 base material is an interleaving paper in which two or more paper layers are laminated together, an adhesive resin layer is included between the two or more paper layers. When the paper base material 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, it is possible to easily obtain an interleaving paper as a laminate by coating a paper layer with a heat-molten resin and laminating another paper layer.

[0073] Specific examples of thermoplastic resins include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; polyolefin-based 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 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 may be used, and among them, water-based adhesives are 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 antifouling properties, the paper substrate for the draw-formed paper container may have a thermoplastic resin layer on at least one surface. 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 be appropriately selected from the thermoplastic resins mentioned 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 is no particular limitation on the method for producing the paper container 1, and any known method can be used. First, an example of a method for producing the paper base material that constitutes the paper container 1 will be described below.

[0080] When the paper base material is a laminated paper in which two or more paper layers are laminated together, an adhesive resin layer can be coated on one side of the paper layer, for example by melt lamination, and then a further paper layer can be laminated to this coated surface to obtain the laminated paper. As described above, the slip sheet includes two or more paper layers, but may include three or more paper layers. When the slip sheet includes three or more paper layers, the multiple adhesive resin layers that bond the paper layers together may be different from each other or may be 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 applied to one side of the paper layer, for example, by melt lamination, and a thermoplastic resin layer can be laminated to the applied surface to obtain a paper substrate having a thermoplastic resin layer. The thermoplastic resin layer may be applied 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 stored items, and suitability for transportation and display. Cutting is preferably performed by punching in order to efficiently obtain interleaf sheets of the same shape. 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. The high-speed automatic punching machine and the flat-bed punching machine can easily and efficiently obtain paper base materials in shapes such as a rectangle, a rounded rectangle, an ellipse, 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, the blank sheet is sandwiched between a press mold consisting of a male mold and a female mold, and heated and pressurized to form the blank sheet. Examples of methods include vacuum molding, 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 the blank sheet is molded by adhering to the mold, and pressure molding, in which a male mold or a female mold is used under heating to sandwich the blank sheet between one mold and a pressure device on the other, and the blank sheet is molded by adhering to the mold by the pressure from the pressure device.

[0084] In this case, the paper base material may be previously humidified to adjust the moisture content. Examples of methods for adjusting the moisture content of the paper base material include a method of adding moisture to the paper layer immediately before forming, and a method of 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 process of manufacturing the paper container 1 from the paper base material will be described. FIG. 4 is a flow chart relating to the method of manufacturing a paper container. In the method of 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 following 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 is a convex die that is convex and has a shape corresponding to the inner volume portion of the paper container 1, and a concave die that is concave and has a shape corresponding 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 in the front-back or up-down direction.

[0086] When the drawing process is performed by vacuum forming, the blank sheet is formed into a shape that matches the mold using only one of the female and male molds. Preferably, the blank sheet is molded by closely contacting the mold by reducing the pressure in the gap between the blank sheet and the mold under heating, and if necessary, after cooling, air is blown in to remove the paper container 1.

[0087] When drawing is performed by compressed air molding, a shape is formed to fit the mold using either a male or female mold and a compressed air device (also called a compressed air box). A blank sheet is sandwiched between the mold and the compressed air device, and the blank sheet is pressed against the mold by pressure from the pressure device, preferably under heating, and molded. 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 preheated to 50 to 70°C.

[0089] The entire mold may be heated. In this case, a means for heating the mold is required. As a mold heating means, an electric heating device is generally provided on the mold to heat it, but there is also a means 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 to 100 to 120°C.

[0090] Once the drawing process is complete, the paper container 1 may 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 a cooling mold for a certain period of time to cool it.

[0091] The material of the mold may be any known material, such as aluminum, aluminum alloys, brass, iron, stainless steel, or ceramics.

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

[0093] The measurement methods for each physical property are described below. The physical properties of the paper base material are measured before the paper base material is drawn. In this case, a part of the paper container after drawing may be cut out and measured. When cutting out a part of the paper container after drawing to measure, a sample may be cut out from a flat part of the paper container, which is an unprocessed part, and when 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 base material 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-conditioning environment specified in JIS P 8111:1998. Specifically, a paper substrate cut to a width of 15 mm and a length of 150 mm is prepared. A sample is attached to a tensile tester (model RTC-1210A, manufactured by A&D Co., Ltd.) so that the chuck distance is 100 mm, and a tensile test is performed at a speed of 10 mm / min to measure the TEA, breaking elongation, and tensile strength in each of the MD (machine direction) and CD (cross direction). Ten values ​​in the machine direction and the cross direction are measured, and the arithmetic mean value of these values ​​is adopted. Furthermore, the geometric mean value of the machine direction arithmetic mean value and the cross direction arithmetic mean value is calculated.

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

[0097] <Paper base material density> The density of the paper base material is calculated from the basis weight and thickness obtained by the above-mentioned measuring 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 expansion can be measured by capturing three-dimensional data of the paper container before and after expansion (before and after extrusion) using a 3D scanner-type coordinate measuring machine (VL-700 series, manufactured by Keyence Corporation). The expansion ratio is an index that indicates how much the drawn-formed area has been stretched. The formed area can be identified by checking the paper container 1 from the opening side, 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 opening corners of the paper container, depth of the opening, angle of the opening corners, and curvature of the paper container corners> The curvature of the opening corners of a paper container, the depth of the opening, the angle of the opening corners, 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. In addition, unless otherwise specified, "parts" refers to "parts by mass".

[0101] [Manufacture of paper layers 1 to 8] Softwood bleached kraft pulp (NBKP) was subjected to high-concentration beating using a double-disc refiner until the disintegration 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 Co., Ltd.), 1.0 part by mass of aluminum sulfate, 0.2 parts by mass of polyacrylamide (CK-311, manufactured by Misawa Ceramic Co., Ltd.) as a paper strength agent, and 0.0025 parts by mass of nonionic acrylamide (Percol 47, manufactured by Allied Colloids Co., Ltd.) as a polymer flocculant were added to prepare a paper stock. Using this paper stock, the speed before and after Clupac treatment was measured using a wet papermaking machine (Bellform III type, manufactured by Mitsubishi Heavy Industries Co., Ltd.) equipped with an expansion device (manufactured by Clupac). The difference is set to -20.0 m / min and the basis weight is 150 g / m 2 The paper was made so as to obtain paper layer 1.

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

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

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

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

[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 the paper was made using a Fourdrinier Yankee paper machine so that the paper layer 7 had a diameter of 100 mm.

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

[0109] [Manufacture of interleaving papers 1-4 and single sheets 1-4] 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 layer was quickly quenched while being sandwiched between cooling rolls adjusted to 20°C, to obtain a single sheet of paper in which a thermoplastic resin layer, an adhesive resin layer, and a paper layer 1 were laminated in that order. Furthermore, in the same manner as described 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, while the paper layer 1 was 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 on top of the paper layer 3 so that the resin had a thickness of 30 μm. The paper layer 3 was then bonded onto the adhesive resin layer while being quickly clamped between cooling rolls whose temperature was adjusted to 20°C, and quenched 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, using a single-screw extruder, PE resin was melt-laminated at 320°C on the paper layer 3 of the obtained interleaf paper so that the resin thickness was 18 μm, and then the interleaf paper was quickly quenched 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 to obtain a single paper in which a thermoplastic resin layer, an adhesive resin layer, and paper layer 5 were laminated in that order.

[0114] A single sheet 2 was obtained in the same manner as the single sheet 1, except that the paper layer 6 was used instead of the 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 had a thickness of 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 single sheet 4 was obtained in the same manner as the single sheet 1, except that the paper layer 8 was used instead of the paper layer 5.

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

[0118] [Table 1]

[0119] [Table 2]

[0120] [Examples 1 to 8 and Comparative Examples 1 to 6] Squeeze molding was performed using the interleaf paper or monolith paper shown in Table 4 as the paper base material. The paper base material was preheated to 60°C with a heater, and sent to the lower mold heated to 120°C. The upper mold was pressed down with compressed air at 0.50 bar for a molding time of 5 seconds to obtain a paper container.

[0121] In addition, for 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 from those used in Examples 1 to 4 and Comparative Examples 1 to 4 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 values ​​listed in Table 4.

[0122] <Evaluation of moldability> 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 is unable to withstand the tensile stress acting on the entire paper during forming, and is broken across the entire thickness direction. Additionally, "crack" refers to a state in which the paper is unable to withstand the tensile stress acting on the outermost layer side (outside of the container) due to bending deformation during forming, and only the area near the outermost layer is broken (cracked state). (Evaluation Criteria) A: Three paper containers were produced, and none of them had 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 squeezed containers were manufactured, and three of them were manufactured without any breaks or cracks. The three-dimensional data of the paper squeezed containers was captured using a 3D scanner type coordinate measuring machine (VL-700 series, manufactured by Keyence Corporation), and the arithmetic average value of the depth of the three paper squeezed containers was calculated. The difference between the average depth of the paper squeezed containers and the depth of the mold used for squeeze molding 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 is clear 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 performed using the interleaf paper or monolith paper shown in Table 5 as the paper base material. The paper base material was preheated to 60°C with a heater, and sent to the lower mold heated to 120°C. The upper mold was pressed down with compressed air at 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 from those 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 were the values ​​listed in Table 5.

[0128] In each of Examples 1' to 8', a mold was used to produce a paper container having a bottom portion, a side portion, and a flange portion, the bottom portion having a raised portion where a portion of the bottom portion was raised so that the surface was curved, and the bottom portion and the side portion were smoothly curved. The paper containers obtained in Examples 1' to 8' have a bottom portion with a raised bottom portion, a flange portion, and the bottom portion and side portion have smoothly curved shapes, and other than that, the characteristics are the same as those of the paper containers obtained in Examples 1 to 8, respectively.

[0129] [Table 4]

[0130] The paper containers obtained in Examples 1' to 8' were less likely to break or crack due to drawing, and the productivity of the paper containers was high, similar to the paper containers obtained in Examples 1 to 8. In addition, similar to the paper containers obtained in Examples 1 to 8, the mold reproducibility was also high.

[0131] In addition, the paper containers obtained in Examples 1' to 8' were more beautiful than the paper containers obtained in Examples 1 to 8, the oil and water in the contents could flow and accumulate around the raised bottom, and the shape was such that heat was less likely to be transferred to the hands even when the contents were hot. Furthermore, the strength against bending in the longitudinal direction was improved, and the impact of being dropped was easily dispersed. [Explanation of symbols]

[0132] 1 Paper container 2 Bottom part 3 Side part 4 Openings 5 Corner of paper container 6. Periphery of side part 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 drawn paper container, comprising: The basis weight of the paper base material is 150 to 400 [g / m ２ ], The longitudinal and transverse geometric mean value of the tensile energy absorption (TEA) of the paper base material is 900 to 2000 [J / m ２ ], The longitudinal and transverse geometric mean value of the breaking elongation of the paper base material is 12.0 to 20.0%; The longitudinal and transverse geometric mean value of the tensile strength of the paper base material is 7.8 to 24.0 [kN / m]; The paper base material has a thermoplastic resin layer, an adhesive resin layer, and a paper layer laminated in this order; The paper base material is used for drawing to form a paper container such that the curvature of the corners of an opening formed by drawing is 0.02 to 0.18 [1 / mm], the expansion ratio of the opening is 1.01 to 1.35 [times], and the depth of the opening is 5 to 60 [mm].

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

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

4. A paper container obtained by drawing the paper base material according to any one of claims 1 to 3.

5. A bottom portion and 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 bottom-raised portion that is partially raised so that the surface is curved. The paper container according to claim 4.

6. Basis weight: 150 to 400 [g / m ２ ] or less, and the longitudinal and transverse geometric mean value of the tensile energy absorption (TEA) is 900 to 2000 [J / m ２ The geometric mean value of the longitudinal and transverse breaking elongation is 1 2.0 to 20.0 [%], and a longitudinal and transverse geometric mean value of tensile strength is 7.8 to 24.0 [kN / m], and a paper base material for a squeeze-formed paper container is prepared in which a thermoplastic resin layer, an adhesive resin layer, and a paper layer are laminated in this order; The paper base material is drawn so that the curvature of the corners of the opening formed by drawing is 0.02 to 0.18 [1 / mm], the expansion ratio of the opening is 1.01 to 1.35 [times], and the depth of the opening is 5 to 60 [mm]; A method for manufacturing a paper container comprising the steps of:

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