Paper containers

Abstract

To provide a paper container for food having a three-dimensional shape, which can be efficiently produced, and yet can be heated, by a simple steam circulating mechanism, in a microwave while remaining untouched.SOLUTION: A tray-type paper container 1, which is produced by three dimensionally molding a laminate 2 formed of a paper base material 3 whose basis weight is 30 g / m2 or more and 700 g / m2 or less and a liner material 4, comprises: a horizontal bottom part 5; a side wall part 6 erected from the bottom part; and a horizontal flange part 7 extended from an upper end of the side wall part. The flange part is provided with one or more notches 9 penetrating through the liner material and reaching the paper base material. An easy peel lid material 8 is closely attached to the flange part, so that an opening part is sealed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a paper container, in particular a tray-type paper container formed by three-dimensionally molding a laminate of a paper base material and a liner material, and the packaging body that contains food and has a tightly sealed lid can be heated directly in a microwave oven. [Background technology]

[0002] Plastic containers made from fossil resources are widely used, but from the perspective of protecting the global environment, such as the problem of marine pollution caused by waste plastic, containers made from paper made from wood, which is a renewable resource and has biodegradability, are attracting attention. The paper container described in Patent Document 1 is a paper container in which a paper base punched into a predetermined shape in advance is placed in a vacuum and pressure forming mold, and a plastic sheet is placed on top as a liner, and the two are integrated by vacuum and pressure forming. This method produces a three-dimensional paper container, but it cannot be produced cheaply due to its poor productivity. Although it is a three-dimensional shape, it is a polyhedral shape that is a collection of flat surfaces, and is not a three-dimensional shape with curved surfaces.

[0003] The skin pack package described in Patent Document 2 is a skin pack package consisting of a mount, an article placed on the mount, and a film attached to the top surface of the mount while covering the article. The film needs to be vacuum-formed in advance into a required shape according to the shape of the article, but like the paper container described in Patent Document 1, not only does this pose a problem in terms of productivity, but it is not even considered to be used to store food.

[0004] One method for efficiently giving three-dimensional shapes to paper is embossing with a press. Although it is not possible to create very deep shapes, this method can efficiently produce three-dimensional paper containers.

[0005] Food containers that use plastic trays and lids, such as containers for packed rice, have been known for some time. However, in order to allow the generated water vapor to escape safely, it was necessary to partially open the lid before heating, or to install a complex steam-passing mechanism. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 177652 [Patent Document 2] JP 2019-51944 A Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to propose a three-dimensional paper container for food that can be produced efficiently and that can be heated directly in a microwave oven using a simple steam-passing mechanism. [Means for solving the problem]

[0008] As a means for solving the above problems, the invention described in claim 1 provides a 30 g / m2 sheet having a basis weight of 30 g / m2. 2 More than 700g / m 2 The tray-type paper container is three-dimensionally formed from a laminate of a paper base material and a liner material, and has a horizontal bottom, a side wall rising from the bottom, and a horizontal flange extending from the upper end of the side wall. The flange has one or more cuts that penetrate the liner material and reach the paper base material, and an easy-peel lid is attached to the flange. This paper container is characterized in that the opening is sealed by sealing the opening.

[0009] The paper container according to the present invention ensures three-dimensional formability by using an appropriate paper base material, and by providing a cut in the flange portion, it is possible to allow water vapor generated when heating in a microwave oven to escape.

[0010] The paper base material may have a tensile breaking elongation of 2% to 12% in the MD direction (machine direction, papermaking direction) and 0.5% to 15% in the TD direction (vertical direction, width direction), and a tensile strength of 50 N / 15 mm to 500 N / 15 mm in the MD direction and 30 N / 15 mm to 400 N / 15 mm in the TD direction.

[0011] The paper base material has a basis weight of 100 g / m 2 More than 400g / m 2 It is more preferable that the tensile elongation at break of the paper base material is 3% to 11% in the MD direction and 1% to 14% in the TD direction. It is more preferable that the tensile strength of the paper base material is 100N / 15mm to 400N / 15mm in the MD direction and 80N / 15mm to 300N / 15mm in the TD direction. Effect of the Invention

[0012] The paper container according to the present invention is a tray-type paper container made by three-dimensionally forming a laminate consisting of a paper base material and a liner material with good formability, and has a tray shape with a horizontal bottom, side walls rising from the bottom, and horizontal flanges extending from the upper ends of the side walls, so it can be produced by drawing using a press machine. This makes production efficient and therefore inexpensive.

[0013] Higher formability can be ensured by appropriately selecting the basis weight, tensile breaking elongation in the MD and TD directions, and tensile strength of the paper base material.

[0014] By providing a notch in the flange, even if the container is heated in a microwave oven without peeling off the easy-peel lid, the generated steam is released outside the container through the notch, so the container will not burst. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic plan view showing one embodiment of a paper container according to the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing the AA′ cross section of FIG. [Diagram 3] FIG. 3 is an explanatory cross-sectional view showing the state of cuts in a paper container according to the present invention. [Figure 4] FIG. 4 is a cross-sectional explanatory view showing how water vapor escapes when the paper container according to the present invention is heated in a microwave oven. [Diagram 5] FIG. 5 is a schematic plan view showing another example of the arrangement of cuts in a paper container according to the present invention. [Figure 6] FIG. 6 is a schematic plan view showing another example of the arrangement of cuts in a paper container according to the present invention. [Figure 7] FIG. 7 is a schematic plan view showing another example of the arrangement of cuts in a paper container according to the present invention. [Figure 8] FIG. 8 is a schematic plan view showing another example of the arrangement of cuts in a paper container according to the present invention. [Figure 9] FIG. 9 is a schematic plan view showing another example of the arrangement of cuts in a paper container according to the present invention. [Figure 10] FIG. 10 is a schematic plan view showing another example of the arrangement of cuts in a paper container according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The paper container according to the present invention will be described in detail below with reference to the drawings. Fig. 1 is a schematic plan view showing one embodiment of a paper container 1 according to the present invention. Fig. 2 is a schematic cross-sectional view showing the AA' cross section of Fig. 1. Fig. 3 is an explanatory cross-sectional view showing the state of the incision 9 in the paper container 1 according to the present invention. Fig. 4 is an explanatory cross-sectional view showing the state of water vapor escaping when the paper container 1 according to the present invention is heated in a microwave oven.

[0017] The paper container 1 according to the present invention is a tray-type paper container obtained by three-dimensionally forming a laminate 2 made of a paper base material 3 and a liner material 4. It has a horizontal bottom 5, a side wall 6 rising from the bottom 5, and a horizontal flange 7 extending from the upper end of the side wall 6.

[0018] The flange portion 7 has one or more slits 9 that penetrate the liner material 4 and reach the paper base material 3, and the opening is sealed by tightly contacting an easy-peel lid material 8 with the flange portion 7. When contents are stored in the paper container 1 of the present invention and the package with the opening sealed with the easy-peel lid material 8 is heated in a microwave oven, the generated water vapor 11 passes through the paper layer of the paper base material 3 from the slits 9 and is discharged outside the container, as shown in Figure 4.

[0019] The basis weight of the paper base material 3 is 30 g / m 2 More than 700g / m 2 It is necessary that the thickness is less than 100 g / m 2 More than 400g / m 2 Less than 30g / m 2 If it is less than 700 g / m, it becomes difficult to bond it to the liner material. 2 Above this, the paper becomes too strong and difficult to form into a tray shape.

[0020] The tensile breaking elongation of the paper base material is desirably 2% to 12% in the MD (machine direction) and 0.5% to 15% in the TD (perpendicular direction), and the tensile strength is desirably 50N / 15mm to 500N / 15mm in the MD and 30N / 15mm to 400N / 15mm in the TD.

[0021] In this way, three-dimensional formability is ensured by specifying the range of values ​​for the basis weight, tensile breaking elongation, and tensile strength of the paper base material 3 in the MD direction (machine direction, flow direction, papermaking direction) and TD direction (transverse direction, vertical direction, width direction).

[0022] The tensile breaking elongation of the paper base material 3 is preferably 2% to 12% in the MD (machine direction) and 0.5% to 15% in the TD (perpendicular direction), more preferably 3% to 11% in the MD and 1% to 14% in the TD. If the MD is less than 2% and the TD is less than 0.5%, the elongation may be insufficient during molding and the paper may break. It is difficult to manufacture paper that exceeds 12% in the MD and 15% in the TD, and is not practical.

[0023] The tensile strength of the paper base material 3 is preferably 50N / 15mm to 500N / 15mm in the MD direction and 30N / 15mm to 400N / 15mm in the TD direction, and more preferably 100N / 15mm to 400N / 15mm in the MD direction and 100N / 15mm to 400N / 15mm in the TD direction. The strength is between 80N / 15mm and 300N / 15mm. If it is less than 50N / 15mm in the MD direction or 30N / 15mm in the TD direction, the strength is insufficient and it may break during molding. Also, paper that exceeds 500N / 15mm in the MD direction or 400N / 15mm in the TD direction is too hard to be molded, and is not practical.

[0024] The shape of the paper container is not limited to the example in Fig. 1, and may be any shape that can be formed, such as a circle, oval, square, rectangle, star, etc. It is necessary that the shape does not have wrinkles in the flanges, bottom, side walls, etc.

[0025] 5 to 10 are plan schematic diagrams showing examples of the shape and arrangement of the notches 9 in the paper container 1 according to the present invention. In the example shown in Fig. 1, one linear notch 9 is provided in the center of the flange portion 7 on the long side of the paper container 1, parallel to the longitudinal direction of the flange portion 7. In the example shown in Fig. 5, one linear notch 9 is provided in the center of the flange portion 7 on the long side of the paper container 1, perpendicular to the longitudinal direction of the flange portion 7.

[0026] In the example shown in FIG. 6, one circular cut 9 is provided in the center of the flange portion 7 on the long side of the paper container 1. In the example shown in FIG. 7, three linear cuts 9 are provided in the flange portion 7 on the long side of the paper container 1, parallel to the longitudinal direction of the flange portion 7. In the example shown in FIG. 8, three linear cuts 9 are provided in the flange portion 7 on the long side of the paper container 1, perpendicular to the longitudinal direction of the flange portion 7. In the example shown in FIG. 9, three circular cuts 9 are provided in the flange portion 7 on the long side of the paper container 1. In the example shown in FIG. 10, one linear cut 9 is provided in the center of the flange portion 7 on the long side of the paper container 1, parallel to the longitudinal direction of the flange portion 7, and one linear cut 9 is provided in the center of the flange portion 7 on the short side, parallel to the longitudinal direction of the flange portion 7.

[0027] As described above, there are no particular restrictions on the shape, number, and arrangement of the cuts 9, and they may be determined in accordance with the amount of water vapor generated, which differs depending on the type and amount of the contents 10. It is preferable to provide the cuts 9 in a location where the greatest force is applied to the lid material when water vapor is generated, depending on the shape of the paper container 1.

[0028] An important point about the incision 9 is that it must be deep enough to penetrate the liner material 4 and reach the paper base material 3, and an incision that ends halfway through the liner material 4 is ineffective. Also, the incision 9 may reach the middle of the paper base material 3.

[0029] There are no particular restrictions on the material of the paper base material 3 constituting the laminate 2, and it is sufficient if it can be molded into the desired shape. Examples include white paperboard such as manila cardboard and white cardboard, yellow chipboard, colored paperboard, cardboard base paper, art paper, coated paper, card base paper, kraft paper, etc.

[0030] As the material of the liner material 4, moldable synthetic resin films can be used alone or in combination. For example, polyethylene resin (PE), polypropylene resin (PP), non-oriented polypropylene resin (CPP), heat sealable polyethylene terephthalate resin (HS-PET), polyvinylidene chloride resin (PVDC), ethylene vinyl alcohol copolymer (EVOH), polyacrylonitrile resin (PAN), and various biodegradable resins can be used. Examples of biodegradable resins include polybutylene succinate resin (PBS), polylactic acid resin (PLA), polyhydroxyalkanoic acid resin (PHA), poly(butylene adipate / terephthalate) resin (PBAT), polycaprolactone resin (PCL), and poly(hydroxybutyrate / hydroxyhexanoate) resin (PHBH (registered trademark)).

[0031] A sealant with barrier properties may be used as the innermost layer, such as paper base material / adhesive resin / barrier sealant, as the liner material 4. Examples of the barrier sealant include Diamilon MF (manufactured by Mitsubishi Chemical Corporation) and Multitron ZEX (manufactured by Tamapoly Corporation).

[0032] The liner material 4 may also be a multi-layer film produced by co-extrusion of two or more layers, such as PE / EVOH / PE.

[0033] The lid material 8 is preferably an easy-peel film that can be peeled by cohesion, interface, or interlayer. An easy-peel layer may also be present on the tray side. Examples of easy-peel films include CF Film (manufactured by Toray Industries, Inc.) 9501A and 9501F, and SMX (manufactured by J-Film, Inc.). The paper container 1 according to the present invention will be specifically described below based on examples and comparative examples. EXAMPLES

[0034] <Example 1> Basis weight 300g / m 2The paper was used as the paper substrate, and a 90μm-thick multi-layer barrier film (Multitron ZEX101, manufactured by Tamapoly) was used as the liner material. The layer structure of the liner material was PE / EVOH / PE. The two were bonded together to form a laminate. This laminate was then molded to produce a paper container (tray) with the shape shown in Figure 1. The tray size was 127mm x 200mm, and the depth was 25mm. The flange was flat, and no wrinkles or creases were observed on the side walls or bottom.

[0035] A linear cut was made on the flange (long side) similar to that shown in Figure 1. The depth of the cut was such that it penetrated through the liner material and into the paper base material.

[0036] An easy-peel film (Diamiron V441, manufactured by Mitsubishi Chemical Corporation) with a thickness of 60 μm was used as the easy-peel lid material. The layer structure of the easy-peel lid material is PE / EVOH / NY / PE. (NY is an abbreviation for nylon.)

[0037] The resulting paper containers were evaluated for liquid leakage, impact resistance, and steam release, which are basic quality requirements for containers. <Leakage>: After storing the penetrant in the container for one month (temperature: 40°C, humidity: 75%), if no leakage occurred, the container was rated as good. <Impact resistance>: In accordance with JIS Z0200, after sealing 200g of contents, a drop and vibration test was carried out. If the liner material and the paper base material did not separate, it was rated as "good". <Steam release>: Heat in a microwave oven at 500W for 120 seconds, and if the steam passed through the slits and escaped from the paper layer or from the interface between the liner material and the paper base material, it was rated as ◯. If the steam escaped from the interface between the liner material and the lid material, it was rated as △. If the steam did not escape and the container burst, it was rated as ×.

[0038] <Example 2> A paper container was produced in the same manner as in Example 1, except that a 50 μm-thick polyethylene film was used as the liner material and the shape of the cut was circular as shown in FIG. 6, and was evaluated in the same manner.

[0039] <Example 3> A paper container was produced in the same manner as in Example 1, except that HS-PET with a thickness of 100 μm was used as the liner material, and was evaluated in the same manner.

[0040] <Example 4> A paper container was produced in the same manner as in Example 1, except that a 100 μm-thick PBS film was used as the liner material, and was evaluated in the same manner.

[0041] <Example 5> Paper containers were produced in the same manner as in Example 1, except that the incision depth was set to a depth that penetrated the liner material but did not penetrate into the paper base material, and were evaluated in the same manner.

[0042] <Example 6> Paper containers were produced in the same manner as in Example 2, except that the incision depth was set to a depth that penetrated the liner material but did not penetrate into the paper base material, and were evaluated in the same manner.

[0043] <Example 7> Paper containers were prepared and evaluated in the same manner as in Example 1, except that the cuts were arranged as shown in Figure 10, with one linear cut on each of the short and long sides of the flange portion, and the depth of the cuts was set so that they penetrated the liner material but did not penetrate into the paper base material.

[0044] <Comparative Example 1> Paper containers were produced in the same manner as in Example 1, except that the position and shape of the cuts were as shown in FIG. 6 and the depth of the cuts was set to halfway through the liner material, and were similarly evaluated.

[0045] <Comparative Example 2> Paper containers were produced in the same manner as in Example 2, except that the incision depth was set to halfway through the liner material, and were evaluated in the same manner.

[0046] <Comparative Example 3> Paper containers were produced in the same manner as in Example 2, except that the position and shape of the cuts were only on the short side of Figure 10 and the depth of the cuts was limited to halfway through the liner material, and similar evaluations were performed.

[0047] <Comparative Example 4> Paper containers were produced in the same manner as in Example 1, except that the position and shape of the cuts were the same as in FIG. 10 and the depth of the cuts was set to halfway through the liner material, and were evaluated in the same manner.

[0048] <Comparative Example 5> A paper container was produced in the same manner as in Example 1, except that no cuts were made, and was evaluated in the same manner.

[0049] <Comparative Example 6> A paper container was produced in the same manner as in Example 2, except that no cuts were made, and was evaluated in the same manner.

[0050] <Comparative Example 7> Except for not providing the cuts, paper containers were produced and evaluated in the same manner as in Example 4. The evaluation results for Examples 1 to 7 and Comparative Examples 1 to 7 are summarized in Table 1.

[0051] [Table 1]

[0052] In Examples 1 to 7, where the incision is deep enough to penetrate the liner material, steam is safely released. In Comparative Examples 1 to 4, where the incision does not penetrate the liner material, or Comparative Examples 5 to 7, where no incision exists, the lid material tends to burst or steam tends to escape from a position other than the intended target position. [Explanation of symbols]

[0053] 1. Paper container 2. Laminate 3...Paper base material 4. Liner material 5...Bottom 6. Side wall 7. Flange section 8. Easy-peel lid material 9. Cutting 10...Contents 11. Water vapor

Claims

1. Basis weight 30g / m ２ More than 700g / m ２ A tray-type paper container formed by three-dimensionally molding a laminate consisting of a paper base material and a liner material as described below, characterized in that the paper container has a horizontal bottom, a side wall portion rising from the bottom, and a horizontal flange portion extending from the upper end of the side wall portion, the flange portion having one or more notches that penetrate the liner material, reach the middle of the paper base material but do not penetrate the paper base material, and are arranged perpendicular to the longitudinal direction of the flange portion, and the opening is sealed by tightly adhering an easy-peel lid material to the flange portion.

2. The paper container according to claim 1, characterized in that the paper base material has a tensile breaking elongation of 2% to 12% in the MD direction (machine direction) and 0.5% to 15% in the TD direction (vertical direction), and a tensile strength of 50 N / 15 mm to 500 N / 15 mm in the MD direction and 30 N / 15 mm to 400 N / 15 mm in the TD direction.

3. The basis weight of the paper base material is 100 g / m ２ More than 400g / m ２ 3. The paper container according to claim 1, wherein the paper container is:

4. The paper container according to any one of claims 1 to 3, characterized in that the tensile breaking elongation of the paper base material is 3% to 11% in the MD direction and 1% to 14% in the TD direction.

5. The paper container according to any one of claims 1 to 4, characterized in that the tensile strength of the paper base material is 100 N / 15 mm or more and 400 N / 15 mm or less in the MD direction and 80 N / 15 mm or more and 300 N / 15 mm or less in the TD direction.

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