Paper containers

Abstract

To provide a paper container that serves as a sheet for high-frequency cooking, with little risk of a heat-resistant film falling off after microwave cooking, and that eliminates the need to prepare another tray to catch oil or juices.SOLUTION: A paper container 1 includes a bottom surface portion 3, and side surface portions 5 connected from the bottom surface portion 3. The side surface portion 5 includes a directional change portion 11 that curves or bends in a direction surrounding the bottom surface portion 3, and the directional change portion 11 retains its shape by thermal compression molding of the high-frequency cooking sheet. The directional change portion 11 has a relatively rigid structure, and the shape thereof is stable before and after microwave cooking. Even if the heat-resistant film on a surface of the sheet for high-frequency cooking shrinks and peels off from a paper substrate during the microwave cooking, it is difficult to apply tension to the area afterward.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a paper container. [Background technology]

[0002] Conventionally, plate-shaped high-frequency cooking sheets have been known that heat and brown food using high-frequency waves (microwaves) emitted by a microwave oven. For example, the high-frequency cooking sheet described in Patent Document 1 has a paper base and a heat-resistant film laminated with an extremely thin layer of aluminum vapor-deposited on it. When food is placed on this sheet and heated in a microwave oven, the aluminum vapor-deposited layer absorbs the microwaves, generating Joule heat that contributes to heating the food. In particular, the contact surface between the sheet and the food quickly browns the food and gives it a crispy texture. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-62990 Summary of the Invention [Problem to be solved by the invention]

[0004] The heat-resistant film constituting the high-frequency cooking sheet is prone to shrinkage due to the heat generated by the aluminum vapor deposition layer during microwave cooking. The inventors' investigations revealed that when the sheet is removed from the microwave oven after cooking, some of the heat-resistant film shrinks and peels off (is raised) from the paper substrate, and applying tension with the fingers to this area can cause the heat-resistant film to tear. This tendency is particularly pronounced when microwave cooking is attempted while the sheet is curved or bent. The heat-resistant film that peels off from the paper substrate may then tear further, breaking into pieces that fall off and become contaminated with food.

[0005] Furthermore, because conventional high-frequency cooking sheets are plate-shaped, when cooking foods that contain a lot of oil or that tend to spill, a separate tray must be provided to catch the spilled oil or juice.

[0006] Therefore, the present invention aims to provide a paper container that functions as a high-frequency cooking sheet, has little risk of the heat-resistant film falling off after microwave cooking, and does not require a separate tray to catch oil or juice. [Means for solving the problem]

[0007] The present invention provides a paper container formed from a high-frequency cooking sheet having a heat-resistant film layer, an aluminum vapor deposition layer, an adhesive layer, and a paper layer in this order, and comprising a bottom portion and a side portion that surrounds the bottom portion and is connected to the bottom portion so as to have a recess on the heat-resistant film layer side, the side portion having a direction change portion that curves or bends in a direction surrounding the bottom portion, and the shape of the direction change portion is maintained by heat-pressing molding of the high-frequency cooking sheet.

[0008] In this paper container, the shape of the direction change section is maintained by thermocompression molding, so it has a relatively rigid structure and its shape remains stable before and after microwave cooking. Therefore, even if the heat-resistant film shrinks and peels off from the paper base during microwave cooking, tension is not easily applied to that section afterwards, so there is little risk of the shrunken heat-resistant film tearing and falling off. In addition, because this paper container has side sections, it can also function as a tray to catch oil and juices that leak out from heated food.

[0009] In this paper container, the direction change portion has a crease extending from the bottom portion toward the peripheral edge of the side portion, and the crease portion may have wrinkles or creases due to thermocompression molding. When the high-frequency cooking sheet is molded into a container shape, wrinkles or creases are inevitably generated. If the turning portion has a crease, wrinkles or creases can be induced in the creased portion, making it easier to achieve the shape of the direction change portion as expected.

[0010] The peripheral edge of the side surface may form a flange portion that is bent outward when viewed from the inside of the container. The presence of the flange portion increases the strength of the side surface.

[0011] The direction change portion may have a wrinkle or crease extending from the bottom portion toward the peripheral edge of the side portion on the surface opposite the recessed portion. The direction change portion may have a plurality of wrinkles or creases. The presence of these wrinkles or creases increases the strength of the direction change portion.

[0012] The direction change portion may be a curved portion in which the side portion is curved in a direction surrounding the bottom portion. In this case, the side portion may be entirely curved in the direction surrounding the bottom portion.

[0013] The basis weight of the paper that makes up the paper layer is 100 g / m 2 ~500g / m 2 If the basis weight is within this range, the shape of the container is less likely to be distorted, and the shape of the direction change portion is more likely to be firmly maintained by thermocompression molding.

[0014] The heat-resistant film layer may be a polyethylene terephthalate film, which has a relatively high glass transition point and melting point and is therefore suitable for thermocompression molding within a normal temperature range.

[0015] The thickness of the aluminum vapor deposition layer may be 60 ű20 Å.

[0016] The adhesive layer may be a polyurethane-based dry laminating adhesive or an acrylic emulsion adhesive. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a paper container that functions as a high-frequency cooking sheet, has little risk of the heat-resistant film falling off after microwave cooking, and does not require a separate tray to catch oil or juice. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a plan view of a paper container according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 2 is a partially enlarged view of FIG. [Figure 4] FIG. 4 is a diagram showing the part shown in FIG. 3 as viewed from the back. [Figure 5] FIG. 2 is a cross-sectional view of a high-frequency cooking sheet that constitutes a paper container. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted.

[0020] (Paper containers) As shown in Figures 1 and 2, the paper container 1 of this embodiment is formed from a sheet for high-frequency cooking (reference numeral 100 in Figure 5), which will be described later, and is used to place food inside it for cooking in a microwave oven. The paper container 1 has a bottom surface 3, on which food is placed, and side surfaces 5 that surround the periphery of the bottom surface 3. The side surfaces 5 are connected to the periphery of the bottom surface 3 and extend upward at a predetermined angle, forming a recess that serves as a storage area for the container. The angle formed by the bottom surface 3 and the side surfaces 5, as viewed from the recess side (the interior side of the container), may be 90° to 150°, or may be 100° to 130°. The periphery of the side surfaces 5 forms a flange 7 that is bent outward when viewed from the interior of the paper container 1.

[0021] The paper container 1 has a rounded rectangular shape in a plan view. The side surface portion 5 is continuous around the entire circumference of the paper container 1 (in the direction surrounding the bottom surface portion 3), and as shown in Figure 3, the rounded corners have curved portions (direction change portions) 11 that are curved in the circumferential direction. The curved portions 11 refer to the portions of the side surface portion 5 that extend continuously around the circumference of the paper container 1 and do not extend linearly. In other words, they refer to the portions where linearly extending portions of the side surface portion 5 are connected by a curved structure.

[0022] The curved portion 11 has multiple lines extending from the bottom portion 3 toward the peripheral edge of the side portion 5 (the lines are not shown), and the lines have wrinkles 9a that were created during the molding process described below. These multiple wrinkles 9a are observed as linear depressions from the front side of the paper container 1, which is the side on which food is placed. There are seven wrinkles 9a per rounded corner, and they are lined up at equal intervals in the circumferential direction of the side portion 5. Of the seven lined up wrinkles 9a, the central wrinkle 9a has the deepest depression, and the further away from the center the wrinkles 9a, the shallower the depressions become.

[0023] In this embodiment, the curved portion 11 is formed when the surface layer (heat-resistant film layer 101 described below) of the paper container 1 is softened by heat and compressed in the in-plane direction when the paper container 1 is formed by heat-pressure molding, and the surface layer is fused in the compressed state, thereby fixing and maintaining the curved shape. Alternatively, the curved portion 11 is formed when the surface layers come into contact with each other in the softened and compressed state and are fused in that state. Furthermore, the overall shape of the paper container 1 is maintained by the paper layer 107 described below, and the curved portion 11 exhibits hardness according to the basis weight of the paper layer 107. Note that "softening" here means that the resin becomes fluid when its temperature reaches or exceeds the glass transition point.

[0024] As shown in Figure 4, these wrinkles 9a are wrinkles 9b that are observed as linear protrusions on the back surface of the paper container 1. Here, the depth of the depressions of the wrinkles 9a on the front surface is reflected in the height of the protrusions on the back surface. The wrinkles 9b may be linear with ridges at the tops of the protrusions, or may be flattened at the tops.

[0025] The depth of the paper container 1 need only be deep enough to prevent oil and juices from the food to be heated from spilling out, and may be 0.5 cm to 8 cm, 1 cm to 7 cm, or 2 cm to 6 cm. Here, "depth" refers to the vertical distance from the inner surface of the bottom portion 3 to the edge of the side portion 5 (including the flange portion 7) when the paper container 1 is placed on a horizontal surface.

[0026] (High frequency cooking sheet) The paper container 1 is formed from a sheet 100 for high-frequency cooking shown in Fig. 5. The sheet 100 for high-frequency cooking comprises, in this order, a heat-resistant film layer 101, an aluminum vapor-deposited layer 103, an adhesive layer 105, and a paper layer 107. The sheet 100 for high-frequency cooking can be produced by dry-laminating the heat-resistant film layer 101, on which the aluminum vapor-deposited layer 103 has been formed, to the paper layer 107 using an adhesive.

[0027] The heat-resistant film layer 101 is made of a film that is heat-resistant to the heat generated by the aluminum vapor deposition layer 103 due to high-frequency heating during microwave cooking. The heat resistance is preferably such that the film has a glass transition point and melting point that are partially fluid but not completely fluid at temperatures typically set for thermocompression molding. Resins are preferred as such materials, and polyethylene terephthalate, a type of polyester resin, is preferred. From the viewpoint of strength and heat resistance, stretched films are also preferred. Stretched films may be uniaxially stretched or biaxially stretched. Biaxially stretched films provide greater strength as paper containers. The thickness of the heat-resistant film layer 101 may be 5 μm to 30 μm, or 10 μm to 20 μm.

[0028] The aluminum deposition layer 103 is deposited on the entire surface of the heat-resistant film layer 101, and its thickness is preferably 60 ű20 Å. When aluminum atoms are deposited to this thickness, they follow the contraction and expansion of the heat-resistant film layer 101.

[0029] The adhesive layer 105 is preferably a polyurethane-based dry laminating adhesive or an acrylic emulsion adhesive. The adhesive preferably has a glass transition temperature Tg that is high enough to prevent transition even when cooked in a microwave oven.

[0030] The paper material constituting the paper layer 107 is preferably paperboard, and more preferably Manila cardboard. The basis weight of the paper is 100 g / m 2 ~500g / m 2 150 g / m 2 ~490g / m 2 200 g / m 2 ~480g / m 2 The thickness of the paper layer 107 may be 110 μm to 630 μm, or 230 μm to 600 μm. When the basis weight or thickness of the paper layer 107 is within this range, the shape of the paper container 1 is less likely to be distorted, and the curved shape due to thermocompression molding is more likely to be firmly maintained.

[0031] (Manufacturing method of paper containers) The paper container 1 can be formed by thermocompression molding the blank sheet. Here, "thermocompression molding" refers to a processing method in which heat and pressure are applied to at least a portion of the object to be processed, causing the portions to adhere to each other and deforming the object into a predetermined shape. In this embodiment, a mode using a female mold (die) and a male mold (punch) is described. In this mode, the blank sheet is sandwiched between the two molds from above and below, and pressure is applied simultaneously with molding.

[0032] First, the sheet 100 for high-frequency cooking shown in Fig. 5 is punched out into a rounded rectangle using all cutting blades. The size of the punched rectangle should be at least the area of ​​the bottom surface 3 and side surface 5 of the paper container 1 to be manufactured. It is preferable to make ruled lines in the areas that are to become the curved portions 11. In this embodiment, seven ruled lines are made radially from the area that will become the bottom surface 3 toward the edge of the blank sheet at each of the rounded corners.

[0033] Next, thermocompression molding is performed using a female mold and a male mold. The female mold and the male mold are heated in advance, and the blank sheet for high-frequency cooking 100 at room temperature is placed on the female mold with the heat-resistant film layer 101 facing the male mold. The blank sheet is then pressed with the male mold at a predetermined temperature and pressure. The temperature at this time is preferably equal to or higher than the glass transition point and lower than the melting point of the resin constituting the heat-resistant film layer 101. For example, the temperature may be 70°C to 150°C, 80°C to 130°C, or 90°C to 100°C. Heating and pressurization may be performed on the entire blank sheet, or only on the portion that will become the curved portion 11.

[0034] By the thermocompression molding, the portions near the edges of the blank sheet rise up to form the side surface portion 5. At the same time, the rounded corners of the side surface portion 5 are compressed in-plane, and wrinkles 9a are formed in the lined portion, absorbing the compression and forming the curved portion 11. Because the heat-resistant film layer 101 on the surface is softened by heating and compressed in-plane, the resin is fused together around the wrinkles 9a. The paper container 1 is manufactured by the above process.

[0035] (Effect of paper containers) The inventors have found that with conventional high-frequency cooking sheets, after food is placed on the sheet and cooked in a microwave oven, the heat-resistant film shrinks and leaves (floats) some of the paper substrate, and applying tension with a finger to this area can cause the heat-resistant film to tear. This tendency is particularly pronounced when microwave cooking is attempted while the high-frequency cooking sheet is curved or bent. The heat-resistant film that has peeled off from the paper substrate then tears further and breaks into pieces that fall off and may become contaminated with the food.

[0036] In contrast, the paper container 1 of this embodiment is formed by molding a high-frequency cooking sheet into a container shape. When frozen or refrigerated food such as fried rice or yakitori is placed inside the paper container 1 and cooked in a microwave oven, the food is heated and quickly browned at the contact surface between the paper container 1 and the food, resulting in a crispy texture. Here, the heat-resistant film layer 101 of the paper container 1 is compressed in a softened state during thermocompression molding, and the curved shape of the rounded corners is fixed and maintained by fusion bonding in the compressed state. Therefore, the curved portion 11 has a relatively rigid structure, and its shape is stable before and after microwave cooking. Therefore, even if the heat-resistant film layer 101 shrinks and peels off from the paper layer 107 during microwave cooking, tension is unlikely to be applied to that portion afterwards. In other words, the paper container 1 is unlikely to be stretched, so there is little risk of the shrunken heat-resistant film layer 101 tearing and falling off.

[0037] Furthermore, the paper container 1 of this embodiment has side portions 5, which also function as a tray, and can catch oil and juices that flow out from heated food.

[0038] Furthermore, in the paper container 1, the curved portion 11 has a crease extending in a direction from the bottom portion 3 toward the peripheral edge of the side portion 5, and wrinkles 9a are generated in the crease portion due to thermocompression molding. If the crease is added at the blank sheet stage, the crease 9a that inevitably occurs during thermocompression molding can be guided to the crease portion, making it easier to achieve the shape of the curved portion 11 that was previously expected. Furthermore, the crease 9a on the front surface side and the crease 9b on the back surface side increase the strength of the curved portion 11.

[0039] Furthermore, in the thermocompression molding, all layers from the heat-resistant film layer 101 to the paper layer 107 are deformed simultaneously, so that the heat-resistant film layer 101 can follow the deformation of the paper layer 107, and the shape of the part where the wrinkles 9a have occurred is firmly maintained.

[0040] Furthermore, the paper container 1 has a flange 7 formed at the periphery of the side surface 5, which is bent outward when viewed from the inside of the paper container 1, increasing the strength of the side surface 5. As a result, the shape of the upper end (opening) of the recess in the paper container 1 is stable, making it easier to handle as a container. Also, when cooked food is hot, the flange can be held.

[0041] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiments, the side surface portion 5 has the curved portion 11 that curves in a direction surrounding the bottom surface portion 3, but the curved portion 11 may be bent (folded) instead of curved. Furthermore, in the above embodiments, the curved portion 11 has the wrinkles 9a and 9b, but the curved portion 11 may have creases instead of wrinkles.

[0042] Furthermore, in the above embodiment, the container has a rounded rectangular shape in plan view, but the container may have a circular shape in plan view. In this case, the side surface portion 5 has a curved portion 11 all along the direction surrounding the bottom surface portion 3. In addition, the side surface portion 5 may have a polygonal shape such as a triangle, hexagon, or octagon in plan view. In this case, it is preferable that the corners of the polygon have a rounded shape with curved portions as in this embodiment. Furthermore, in the above embodiment, the side surface portion 5 rises diagonally upward in a straight line (FIG. 2), but it may also rise while forming a curved surface.

[0043] In the above embodiment, the thermocompression molding is performed using a female mold and a male mold, but the thermocompression molding may be performed using other processing methods. A method called drawing may also be adopted.

[0044] Furthermore, in the above embodiment, the high-frequency cooking sheet 100 having four layers as shown in FIG. 5 is used, but the high-frequency cooking sheet may also have other functional layers. [Example]

[0045] The present invention will be described in more detail below with reference to experimental examples, but the present invention is not limited to the following experimental examples.

[0046] (Materials used) Heat-resistant film: Biaxially stretched polyethylene terephthalate film (Toyobo Co., Ltd., "E5100", thickness 12 μm) Adhesive: Modified acrylic copolymer resin emulsion (Nichiei Kako Co., Ltd., "Life Bond RAN-026A") is the main ingredient, and epoxy resin (Nichiei Kako Co., Ltd., "Life Bond RAN-026B") is the hardener, with a weight ratio of 100 parts main ingredient to 1 part hardener. ·Paperboard...N Pearl Card (Mitsubishi Paper Mills Co., Ltd.)

[0047] (Production of high frequency cooking sheets) A biaxially stretched polyethylene terephthalate film was vapor-deposited with aluminum to a thickness of 60 Å. The vapor-deposited layer side was then coated with the above adhesive to a basis weight of 260 g / m. 2 The paperboard was dry laminated to prepare a sheet for high-frequency cooking. 2 A high-frequency cooking sheet was similarly prepared using the paperboard.

[0048] (Experimental Example 1) Basis weight 260g / m 2 A microwave cooking sheet made from paperboard was punched into a rounded rectangle (9 cm x 15 cm) using a full-cutting blade, and seven radial lines were applied to each of the four rounded corners that would become the side surfaces after molding. Using a male and female mold, the sheet was molded by heat and pressure at 100°C with the male mold in contact with the polyethylene terephthalate film side, and formed into a tray shape with flanges as shown in Figures 1 to 4. Wrinkles were formed in the four corners of the score lines. These wrinkles appeared as grooves when viewed from the front side and protruding streaks when viewed from the back side. Frozen dumplings were placed on this paper tray and cooked in a microwave oven at 600W for 3 minutes. The tray was then removed from the microwave. Peeling (lifting) of the polyethylene terephthalate film was observed in the curved portions of the side surfaces, but the film was not torn. Attempts to stretch the area with fingers were made, but the curved portions were hard, just as before microwave cooking, and could not be stretched. Therefore, no tearing of the film occurred.

[0049] (Experimental Example 2) Basis weight 450g / m 2 A test was conducted in the same manner as in Experimental Example 1, except that a high-frequency cooking sheet made from the paperboard of Example 1 was used. When the paper tray was removed from the microwave oven, peeling (lifting) of the polyethylene terephthalate film was observed at the curved part of the side, but the film was not torn. An attempt was made to stretch this part with the fingers, but the curved part was hard, just as before microwave cooking, and could not be stretched. Therefore, no tearing of the film occurred.

[0050] (Experimental Example 3) Basis weight 260g / m 2 A microwave cooking sheet made from paperboard was punched into a rectangle (14 cm x 15 cm) using a full-cutting blade, and two parallel lines were scored 2 cm apart along the center from edge to edge. These lines were then folded (bent) at approximately 90° so that the polyethylene terephthalate film was facing inward, and frozen dumplings were sandwiched between the sheets and cooked in a microwave oven at 600 W for 3 minutes. The sheet was then removed from the microwave. When the folded portions were returned to their original state and the entire sheet was flattened (i.e., stretched), it was observed that the film had torn along the scores.

[0051] (Experimental Example 4) Basis weight 260g / m 2 A microwave cooking sheet made from paperboard was punched out into a rectangle (14 cm x 15 cm) using a full-cutting blade, and two parallel lines were scored 2 cm apart in the approximate center from end to end. Without folding, frozen dumplings were placed on the polyethylene terephthalate film side and cooked in a microwave oven at 600 W for 3 minutes. The sheet was then removed from the microwave. Observation of the surface revealed that the film had not been cut along the scoring lines.

[0052] The results are summarized in Table 1. [Table 1]

[0053] The results of Experimental Examples 1 to 4 showed that when processed into a tray shape by thermocompression molding, the curved portion hardens and the shape is fixed. It was also found that the heat-resistant film tears when the bent portion is stretched after microwave cooking. It was also found that the formation of the score lines does not itself induce tearing of the heat-resistant film. Note that tearing of the heat-resistant film here refers to the possibility that the film may further tear and break into pieces that fall off. [Industrial Applicability]

[0054] The present invention can be used for microwave cooking of food. [Explanation of symbols]

[0055] 1...paper container, 3...bottom portion, 5...side portion, 7...flange portion, 9a, 9b...wrinkles, 11...curved portion (direction change portion), 100...high-frequency cooking sheet, 101...heat-resistant film layer, 103...aluminum vapor deposition layer, 105...adhesive layer, 107...paper layer.

Claims

1. The high-frequency cooking sheet is formed from a high-frequency cooking sheet having a heat-resistant film layer, an aluminum vapor deposition layer, an adhesive layer, and a paper layer in this order, a bottom surface portion; and a side surface portion surrounding the bottom surface portion and extending from the bottom surface portion so as to have a recess on the heat-resistant film layer side, The thickness of the aluminum vapor deposition layer is 60 ű20 Å, The side surface portion has a direction change portion that curves or bends in a direction surrounding the bottom surface portion, the direction change portion has a ruled line extending in a direction from the bottom surface portion toward the peripheral edge side of the side surface portion, The portion of the crease has wrinkles or creases, a plurality of the wrinkles or folds are arranged in a circumferential direction in which the side surface portion extends, and among the arranged wrinkles or folds, the central one has the deepest depression, and the depressions of the wrinkles or folds further away from the center become shallower; The paper container has a shape that is maintained at the direction change portion by the heat-resistant film layer being fused around the wrinkles or folds.

2. The paper container according to claim 1, wherein the heat-resistant film layer has a thickness of 10 μm to 20 μm.

3. 3. The paper container according to claim 1, wherein the peripheral edge of the side surface forms a flange portion that is bent outward when viewed from the inside of the container.

4. The direction change portion has a wrinkle or crease extending in a direction from the bottom surface portion toward a peripheral edge side of the side surface portion on a surface opposite to the recessed portion, The paper container according to any one of claims 1 to 3, wherein the number of the wrinkles or folds is the same as the number of the lines.

5. The paper container according to any one of claims 1 to 4, wherein the direction change portion is a curved portion in which the side portion curves in a direction surrounding the bottom portion.

6. The paper container according to claim 5 , wherein the side surface portion is entirely curved in a direction surrounding the bottom surface portion.

7. The basis weight of the paper constituting the paper layer is 100 g / m ２ ~500g / m ２ The paper container according to any one of claims 1 to 6.

8. The paper container according to any one of claims 1 to 7, wherein the heat-resistant film layer is a polyethylene terephthalate film.

9. The paper container according to any one of claims 1 to 8, wherein the adhesive layer is a polyurethane-based dry lamination adhesive or an acrylic emulsion adhesive.

Images