Paper containers

Abstract

To provide a technology of suppressing oozing of a content in a paper container.SOLUTION: A paper container is formed of a body part and a bottom part. The body part is formed by rounding a fan-shaped blank and by bonding both end parts. A base paper 1 inside is subjected to oil resistant treatment and an oil resistant layer 2 is formed. The base paper 1 inside (a side coming into contact with a content) is coated with a high-melting point polyethylene layer 3. Inside of the high-melting point polyethylene layer 3 is coated with a low-melting point polyethylene layer 4. At one end part of the blank, the low-melting point polyethylene layer 4 is folded back so as to coat an end face 5. At a bonding part, the low-melting point polyethylene layers 4 are heat welded with each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a paper container that is required to be oil-resistant. [Background technology]

[0002] Paper containers for storing foodstuffs that contain a large amount of oil are required to be oil-resistant (Patent Document 1 and Patent Document 2).

[0003] In particular, food ingredients are now often heated in microwave ovens, making oil resistance more important. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-056127 A [Patent Document 2] JP 2009-030192 A Summary of the Invention [Problem to be solved by the invention]

[0005] An example of a paper container is a paper cup. A paper cup has a circular bottom and a body part that stands upright from the bottom in an inverted truncated cone shape or a cylindrical shape. If necessary, the body part may have a flange or a lid on the upper edge.

[0006] The body of the paper cup is made by rolling a sector-shaped blank, placing one end underneath and the other end on top of it, and then overlapping and joining the two ends (for example, by heat welding).

[0007] Pinholes may occur when the blank is deformed during container molding, and also when the joints are thermally welded.

[0008] When heating in a microwave oven, the temperature inside the container can exceed 100°C, which may cause pinholes to form due to moisture foaming or softening of the coating layer.

[0009] These pinholes can cause oil seepage, and generally speaking, joints are particularly prone to problems.

[0010] Generally, various designs are printed on the outer surface of commercially available paper containers for packaging food, and oil bleeding can seriously mar the aesthetic appearance.

[0011] The present invention is devised to solve the above-mentioned problems, and aims to provide a technique for preventing bleeding of contents in paper containers such as paper cups. [Means for solving the problem]

[0012] The paper container of the present invention, which achieves the above object, comprises a body formed by rolling a blank and joining the ends of the blank together, and a bottom joined to the lower end of the body. The paper container is formed from a base paper that has been treated to be oil-resistant on the inside, and a high-melting-point polyethylene layer that covers the inside of the base paper. The melting point of the high-melting-point polyethylene layer is 115°C or higher.

[0013] The use of a high melting point polyethylene layer can prevent pinholes from occurring during heating in a microwave oven, and the oil-resistant treatment can prevent bleeding through pinholes even if they do occur.

[0014] Preferably, the laminate is formed from a low melting point polyethylene layer coated on the inside of the high melting point polyethylene layer, and the melting point of the low melting point polyethylene layer is lower than the melting point of the high melting point polyethylene layer.

[0015] Preferably, the melting point of the low melting point polyethylene layer is at least 10° C. lower than the melting point of the high melting point polyethylene layer.

[0016] This ensures good jointability, which in turn improves leakage from the joint.

[0017] Preferably, at one end of the blank, the low melting point polyethylene layer is folded back to cover the end face.

[0018] This can prevent the contents from seeping through the blank end faces. Also, the low melting point polyethylene layers are heat welded together, further improving the bondability.

[0019] Preferably, the container contains contents that include oil.

[0020] According to the paper container of the present invention, bleeding of contents containing oil can be suppressed. Effect of the Invention

[0021] According to the present invention, bleeding of the contents can be suppressed. [Brief description of the drawings]

[0022] [Figure 1] General method for forming paper containers [Diagram 2] Cross-section of joint (comparison with general example) [Diagram 3] Summary of verification results DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] ~Basic configuration~ Fig. 1 is a diagram showing an outline of a method for forming a paper cup. The paper container of this embodiment includes a paper cup. The body of the paper cup is formed from a sector-shaped blank.

[0024] The blank is rolled, one end is placed on the bottom and the other end is placed on top of it so that the joining surfaces face each other, and both ends are overlapped and joined at a predetermined joining width to form the body of a paper cup.

[0025] The paper cup bottom is circular. The paper cup is formed by joining the paper cup body and the paper cup bottom.

[0026] ~Characteristic composition~ This embodiment suitably has the following characteristic configurations (see FIG. 2).

[0027] The inside of the base paper 1 (the side in contact with the contents) is treated for oil resistance, forming an oil-resistant layer 2. In detail, the base paper 1 is made of multiple pulp layers (e.g., five layers), and only the innermost pulp layer is treated for oil resistance. It is preferable that the outside is not treated for oil resistance because it is used for design printing. If printing is not required on the bottom, both sides may be treated for oil resistance.

[0028] Furthermore, the inside of the base paper 1 is covered with a high melting point polyethylene layer 3 .

[0029] The inside of the high melting point polyethylene layer 3 is covered with a low melting point polyethylene layer 4 .

[0030] At one end of the blank, the low melting point polyethylene layer 4 is folded back (edge ​​protect (EP) treatment) so as to cover the end surface 5. As a result, the low melting point polyethylene layer at one end and the low melting point polyethylene layer at the other end are joined together.

[0031] For comparison, a cross-sectional view of a typical paper cup joint is added to Figure 2.

[0032] ~Verification Test~ Several sample examples created for the verification test of the above characteristic configuration will be described (see FIG. 3).

[0033] General example: Neither the body nor the base are treated for oil resistance. There is no high melting point polyethylene layer. The low melting point polyethylene layer is 15μm thick. No EP treatment has been applied (see Figure 2).

[0034] Sample A: Only the bottom part is oil-resistant. The high melting point polyethylene layer is 20 μm. The low melting point polyethylene layer is 20 μm. It is EP treated.

[0035] Sample B: Only the bottom part is oil-resistant. The high melting point polyethylene layer is 20 μm. There is no low melting point polyethylene layer. It is EP treated.

[0036] Sample C: Only the bottom part is oil-resistant. The high melting point polyethylene layer is 40 μm. There is no low melting point polyethylene layer. It is EP treated.

[0037] Sample D: The body and bottom are oil-resistant. The high melting point polyethylene layer is 20 μm thick. There is no low melting point polyethylene layer. Not EP treated.

[0038] Sample E: The body and bottom are oil-resistant. The high melting point polyethylene layer is 20 μm thick. The low melting point polyethylene layer is 20 μm thick. It is EP-treated (see Figure 2).

[0039] It should be noted that the above samples are merely examples, and the present invention is not limited to the above samples.

[0040] Two verification tests were carried out on the above sample example.

[0041] Mapo tofu microwave heating: Mapo tofu was placed in a paper cup and heated in a microwave at 1520W for 20 seconds, and the oil seepage was observed.

[0042] Shrimp chili left for 10 hours: Shrimp chili was placed in a paper cup and left for 10 hours, after which oil seepage was observed.

[0043] It should be noted that the above tests are merely examples of problems that may arise when a paper container is used to store foodstuffs that contain a large amount of oil, and the present invention is not limited to these problems.

[0044] The base paper for the above samples has a basis weight of 250 to 260 g / m 2 , and the bottom has a basis weight of 200~220g / m 2 The paper used was:

[0045] Below, we will explain each point by comparing the verification test results.

[0046] Point 1 When oily contents are heated in a microwave oven, the contents can exceed 100°C, causing pinholes due to moisture foaming and softening of the polyethylene layer, which can lead to oil seepage. To address this issue, a high melting point polyethylene layer is used.

[0047] The verification results of the general example are compared with those of samples A and B. None of them have oil-resistant treatment on the body. The general example has a low-melting point polyethylene layer, while samples A and B have a high-melting point polyethylene layer on the inside.

[0048] Comparing the test results of heating mapo tofu in a microwave oven, in the general example, bleeding occurred around the entire outer surface of the container, whereas in sample A and sample B, no bleeding was observed.

[0049] By replacing the low-melting polyethylene layer with a high-melting polyethylene layer, the occurrence of pinholes during microwave heating can be suppressed regardless of whether or not the product is oil-resistant. Also, the results for sample B show that the occurrence of pinholes during microwave heating can be suppressed even without a low-melting polyethylene layer.

[0050] For the low melting point polyethylene, low density polyethylene (LDPE) is used. The melting point of low density polyethylene is about 100 to 115°C. The melting point of the low melting point polyethylene in the above sample was 108°C.

[0051] High-melting-point polyethylene includes high-density polyethylene (HDPE) and low-density polyethylene with a higher melting point by incorporating high-density polyethylene or ethylene-propylene copolymers. The melting point of high-density polyethylene is around 120-140°C. The melting point of the high-melting-point polyethylene in the above sample was 128°C. The melting point of high-melting-point polyethylene is increased by incorporating ethylene-propylene copolymers into low-melting-point polyethylene.

[0052] In the present application, polyethylene with a melting point of less than 115° C. is referred to as low melting point polyethylene, and polyethylene with a melting point of 115° C. or higher is referred to as high melting point polyethylene.

[0053] The melting point of the low melting point polyethylene layer is preferably at least 10° C. lower than the melting point of the high melting point polyethylene layer. In the above sample, the difference is 20° C.

[0054] Point 2 By covering the inside of the base paper with a high melting point polyethylene layer, there is a risk that the heat welding of the joints during container molding will be insufficient. As a result, there is a risk that the contents will leak from the unsealed parts of the bottom. By increasing the heating temperature, the heat welding can be achieved reliably, but there is a risk that the base paper will be damaged, such as by burning. To address this issue, a low melting point polyethylene layer is used.

[0055] The verification results of Sample A and Sample C are compared. Neither of them have been treated to make the body oil-resistant. Sample C has the same structure as Sample B, but the polyethylene layer thickness is the same as Sample A (layer thickness 40 μm). Sample A is coated with a low-melting point polyethylene layer, whereas Sample C is not.

[0056] Comparing the test results of leaving shrimp chili for 10 hours, sample C had a leak at the bottom in one out of ten tests, whereas sample A had no leaks at the bottom in any of the ten tests.

[0057] The low melting point polyethylene layer is securely heat welded, ensuring good adhesion. As a result, leakage from unwelded areas can be prevented.

[0058] For reference, the verification results of the general example and sample D are compared. The general example is not treated for oil resistance, whereas sample D is. The general example is not coated with a high melting point polyethylene layer, whereas sample D is coated with a high melting point polyethylene layer.

[0059] According to the results of a test in which shrimp chili was left for 10 hours, leakage was observed from the bottom, although the degree of leakage varied.

[0060] This suggests that the high melting point polyethylene layer coating and oil resistance treatment alone are insufficient to address the problem of bottom leakage.

[0061] Point 3 When forming a container, the body of the paper cup is made by rolling up a sector-shaped blank. There is a risk of pinholes occurring due to blank deformation. In addition, the joints are heat-welded during container formation, so there is a risk of pinholes occurring at the joints. To address this issue, oil-resistant treatment is applied.

[0062] The verification results of Sample A and Sample E are compared. Sample A does not have an oil-resistant treatment on the body, whereas Sample E has an oil-resistant treatment on the body. The other components are the same.

[0063] Comparing the test results after leaving the specimen in chili shrimp for 10 hours, slight bleeding was observed at the joint edge of sample A, whereas no bleeding was observed at all for sample E.

[0064] Even if pinholes do occur, the oil-resistant treatment can suppress bleeding through the pinholes.

[0065] Oil resistance (= oil repellency) is exhibited when the surface tension of a solid surface (base paper surface) is lower than that of the liquid (oil). When fluorine compounds, etc. are present on the base paper surface, the intermolecular forces that the oil receives from the base paper at the interface between the base paper and the oil are weak, making the oil unstable at the interface and making it easier for the surface tension of the oil to act, resulting in oil repellency. In other words, even if there are pinholes, bleeding through the pinholes can be suppressed.

[0066] Examples of oil-resistant agents include fluorine-based compounds, acrylic compounds, and silicon-based compounds. There are two methods for processing oil-resistant agents: adding them when making paper (internal addition method) and impregnating or coating the surface after making paper (external addition method). Generally, fluorine-based compounds are used in papermaking using the internal addition method.

[0067] In order to improve the adhesion between the oil-resistant treated base paper and the polyethylene layer, an AC agent (anchor coating agent) may be used.

[0068] Point 4 Furthermore, there is a risk of the contents seeping through the blank edge. To address this issue, edge protection (EP) processing is used.

[0069] The verification results of sample D and sample E are compared. Sample D is not EP-processed, whereas sample E is EP-processed.

[0070] Comparing the test results after leaving shrimp chili for 10 hours, sample D showed bleeding to the same extent as the general example, while sample E showed no bleeding at all.

[0071] In particular, in sample E, the low melting point polyethylene layer at one end and the low melting point polyethylene layer at the other end are thermally welded together by the EP treatment, thereby further improving the bondability (see point 2).

[0072] In EP treatment, a part of the edge of the base paper is cut off and folded back together with the low melting point polyethylene layer and the high melting point polyethylene layer. The thickness of the EP treatment part is made the same as the laminate thickness. This allows the edge to be protected by the coating layer. [Explanation of symbols]

[0073] 1 Base paper 2 Oil-resistant layer 3 High melting point polyethylene layer 4 Low melting point polyethylene layer 5 End face

Claims

1. A paper container that is microwaveable and can accommodate contents containing oil, and that includes a body portion formed by rolling a blank and joining the blank end portions together, and a bottom portion joined to the lower end of the body portion, A base paper having an innermost pulp layer which is an oil-resistant layer; A high melting point polyethylene layer coated on the inside of the base paper; a low melting point polyethylene layer coated on the inside of the high melting point polyethylene layer; is formed from The melting point of the high melting point polyethylene layer is 115° C. or higher, The melting point of the low melting point polyethylene layer is lower than the melting point of the high melting point polyethylene layer, At one end of the blank, the low melting point polyethylene layer is folded back to cover the end surface. A paper container characterized by:

2. The melting point of the low melting point polyethylene layer is lower than the melting point of the high melting point polyethylene layer by 10° C. or more.

2. The paper container according to claim 1.

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