Blank sheet, and paper container

Abstract

[Problem] To provide a blank sheet for use in a paper container, the blank sheet having suppressed curling, which in turn reduces the risk of causing jamming between various rollers and the like in a production line. [Solution] A heat insulating outer sleeve 2 as a blank sheet which is a heat insulating sheet used for a paper cup 1 as a paper container, the heat insulating outer sleeve 2 being characterized by comprising a coating layer 3 formed by applying a water-based coating agent onto at least one of a front face and a back face of a sheet body 2A of the heat insulating outer sleeve 2 and drying the water-based coating agent, wherein the coating layer 3 on the front face or the back face of the sheet body 2A is formed with non-coated faces 4 as spaces provided at a plurality of locations.

Description

Blank sheets and paper containers

[0001] The present invention relates to a blank sheet used for a paper container, and a paper container provided with this blank sheet.

[0002] Conventionally, many paper containers, including paper cups, have been manufactured using blank sheets made primarily of paper.

[0003] For example, Patent Document 1 discloses a paper cup as a paper container in which an insulating outer sleeve made of a blank sheet is wrapped around the outer periphery of the barrel of the paper container body.

[0004] In this type of paper container, for the purpose of heat-sealing type adhesion or the like, either the front or back of the blank sheet used in the paper container is often subjected to lamination processing in which a film made of, for example, a resin is covered.

[0005] However, when lamination processing is performed to cover either the front or back of a blank sheet with a film made of resin or the like, the covered film shrinks when the blank sheet is cooled from a heated state to a room temperature state, causing the blank sheet to warp toward the covered film side.

[0006] On the other hand, blank sheets used for paper containers pass between various rollers on a production line during mass production.

[0007] In this case, we independently discovered that if the blank sheet is significantly warped, there is a high risk of problems such as jamming occurring when the blank is transported on the production line.

[0008] JP 2016-000623 A

[0009] The present invention was devised in consideration of the above-mentioned problems, and its purpose is to provide a blank sheet for use in paper containers that can suppress curling of the blank sheet and thereby reduce the risk of clogging between various rollers on the production line during mass production, and a paper container equipped with this blank sheet.

[0010] In order to solve the above-mentioned problems, the inventor invented a blank sheet to be used for paper containers, in which an aqueous coating agent is applied to at least one of the front and back surfaces of the sheet body of the blank sheet, and a coating layer is formed by drying the aqueous coating agent, and the coating layer on the front or back surface of the sheet body is formed at intervals in multiple locations.

[0011] The blank sheet according to the first invention is a blank sheet used for paper containers, characterized in that an aqueous coating agent is applied to at least one of the front and back surfaces of the sheet body of the blank sheet, and a coating layer is formed by drying the aqueous coating agent, and the coating layer on the front or back surface of the sheet body is formed at intervals in multiple locations.

[0012] The blank sheet according to the second invention is the blank sheet according to the first invention, characterized in that the coating layers at a plurality of locations are formed symmetrically on the front or back surface of the sheet body.

[0013] A blank sheet according to a third aspect of the present invention is the blank sheet according to the first or second aspect of the present invention, characterized in that the coating layer is provided on only one of the front and back surfaces of the sheet body.

[0014] A blank sheet according to a fourth aspect of the present invention is the blank sheet according to any one of the first to third aspects of the present invention, characterized in that the coating layer has a thickness of 5 to 20 μm.

[0015] The blank sheet according to the fifth invention is characterized in that, in any of the first to fourth inventions, the ratio of the coating area occupied by the coating layer on the front or back surface of the sheet body is 80% or less.

[0016] The blank sheet according to the sixth invention is characterized in that, in any of the first to fifth inventions, the ratio of the coating area occupied by the coating layer on the front or back surface of the sheet body is 17% or more.

[0017] A blank sheet according to a seventh aspect of the present invention is any one of the first to sixth aspects of the present invention, wherein the Cobb water absorbency difference between the front and back surfaces of the sheet body on which the coating layers are formed in a plurality of locations is 15.5 g / m ２The present invention is characterized by the following:

[0018] The blank sheet according to an eighth aspect of the present invention is characterized in that, in any one of the first to seventh aspects of the present invention, it is a heat insulating sheet that covers the outer surface of the paper container body of the paper container.

[0019] The blank sheet of the ninth invention is characterized in that, in the eighth invention, the paper container body is a paper cup body, and the insulating sheet is an insulating outer sleeve that is wrapped around the outer periphery of the body of the paper cup body.

[0020] A paper container according to a tenth aspect of the present invention is characterized in that the blank sheet according to any one of the first to ninth aspects of the present invention is directly or indirectly provided on a paper container body.

[0021] The paper cup of the eleventh invention is characterized in that it comprises the blank sheet of the ninth invention as the insulating outer sleeve that is wrapped around the outer periphery of the body of the paper cup body.

[0022] According to the present invention having the above-described configuration, an aqueous coating agent is applied to at least one of the front and back surfaces of the sheet body of a blank sheet used for paper containers, and the coating layer formed by drying the aqueous coating agent is formed at multiple intervals. Experimental verification has shown that this can suppress warping of the blank sheet. This reduces the risk of clogging between various rollers on the production line during mass production.

[0023] Fig. 1(a) is a side view showing a paper cup as a paper container according to an embodiment of the present invention, with a portion cut away, and Fig. 1(b) is a plan view showing the back surface of an insulating outer sleeve as a blank sheet that is an insulating sheet for the paper cup of Fig. 1(a). Fig. 2 is a partially enlarged view showing the back surface of an insulating outer sleeve as a blank sheet that is an insulating sheet for the paper cup of Fig. 1(b). Fig. 3 is a table showing the results of Experimental Verification 1. Fig. 4 is a table showing the results of Experimental Verification 2. Fig. 5 is a table showing the results of Experimental Verification 3. Fig. 6 is a table showing the results of Experimental Verification 4.

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

[0025] [Embodiment] First, a paper cup 1 as a paper container according to an embodiment of the present invention will be described using Figures 1 and 2. Figure 1(a) is a side view showing a paper cup 1 as a paper container according to an embodiment of the present invention, with a portion cut away, and Figure 1(b) is a plan view showing the back surface of an insulating outer sleeve 2 as a blank sheet that is an insulating sheet for the paper cup 1 in Figure 1(a). Figure 2 is a partially enlarged view showing the back surface of an insulating outer sleeve 2 as a blank sheet that is an insulating sheet for the paper cup 1 in Figure 1(b).

[0026] As shown in Figure 1(a) , a paper cup 1 as a paper container according to an embodiment of the present invention comprises a paper cup body 11 as the paper container body, and an insulating outer sleeve 2 as a blank sheet that is an insulating sheet wrapped around the outer periphery of the body 11a of the paper cup body 11.

[0027] The paper cup body 11 is made up of a cylindrical body portion 11a with a bottom and a curled portion 11b at its upper edge.

[0028] As shown in Figure 1(b), the insulating outer sleeve 2 comprises a sheet body 2A made primarily of paper, and a coating layer 3 formed by applying an aqueous coating agent to the back surface of the sheet body 2A and drying the aqueous coating agent.

[0029] The sheet body 2A is fan-shaped and, when wrapped around the outer periphery of the body 11a of the paper cup body 11, covers the outer surface of the body 11a.

[0030] The coating layer 3 is formed at a plurality of locations on the rear surface of the sheet body 2A, with non-coated surfaces 4 provided as intervals.

[0031] The coating layers 3 at the plurality of locations have substantially the same area, and the spacing between the non-coated surfaces 4 is substantially the same. The coating layers 3 at the plurality of locations are symmetrical on the back surface of the sheet main body 2A.

[0032] The coating layers 3 at the multiple locations are not limited to the vertical stripe pattern shown in FIG. 1(b), but may be formed in other patterns such as horizontal stripes or a grid pattern.

[0033] Furthermore, the coating layer 3 at these multiple locations has multiple cracks 5 as shown in FIG.

[0034] The coating layer 3 at these multiple locations may be formed so as not to have multiple cracks 5 .

[0035] The insulating outer sleeve 2 is wrapped around the outer periphery of the body 11a of the paper cup body 11 and is attached by heating the coating layer 3 as a heat seal.

[0036] Here, for the purpose of heat-seal type adhesion using these coating layers 3 at multiple locations, a minimum thickness of 5 μm is required in consideration of heat-sealability, and since a thickness exceeding 20 μm is wasted, it has been found that a thickness of 5 to 20 μm is preferable, but other ranges may also be used.

[0037] Furthermore, as will be shown in the results of Experimental Verification 1 described later, the ratio of the coating area occupied by the coating layer 3 to the back surface of the sheet body 2A is preferably 80% or less, and more preferably 60% or less.

[0038] Furthermore, as will be shown in the results of Experimental Verification 2 described later, it is preferable that the ratio of the coating area occupied by the coating layer 3 on the rear surface of the sheet body 2A is 17% or more.

[0039] In addition, as shown in the results of Experimental Verification 3 described later, the difference in Cobb water absorbency between the front and back surfaces of the sheet body 2A on which the coating layer 3 is formed in multiple locations is 15.5 g / m ２ It is preferable that:

[0040] Furthermore, as shown in the results of Experimental Verification 4 described later, when the coating layer 3 has a plurality of cracks 5 at a plurality of locations, the area ratio of the plurality of cracks 5 to the coating layer 3 is 11.8% or less per unit area (here, the unit area is 1 mm ２ ) is preferable.

[0041] The surface of the sheet body 2A may also be provided with a coating layer 3 for the purpose of further improving the heat insulating properties, giving it a high-quality appearance, and increasing its commercial value.

[0042] Examples of resins that are the main component of the aqueous coating agent used to form the coating layer 3 include polyolefin resins, polypropylene resins, polyethylene resins, modified polypropylene resins, modified polyethylene resins, polyethyleneimine resins, ethylene-vinyl acetate copolymer resins, polyolefin ionomer resins, ethylene-acrylic acid copolymer resins, ethylene-methacrylic acid copolymer resins, ethylene-methyl methacrylate copolymer resins, ethylene-vinyl chloride copolymer resins, ethylene-methyl acrylate copolymer resins, polyvinyl alcohol resins, acrylic acid resins, acrylic acid copolymer resins, styrene-acrylic acid copolymer resins, methacrylic acid resins, polymethyl methacrylate resins, methacrylic acid copolymer resins, vinyl chloride resins, polyvinylidene chloride resins, vinyl acetate resins, polyurethane resins, polyester resins, polyethylene terephthalate resins, polylactic acid resins, polyhydroxyalkanoic acid resins, polybutylene succinate resins, polyamide resins, copolymer nylon resins, polystyrene resins, styrene-maleic acid copolymer resins, phenolic resins, and rosin-modified phenolic resins.

[0043] Alternatively, for example, in consideration of the environment, a biodegradable resin or the like may be used as the resin that forms the main component of the aqueous coating agent used to form the coating layer 3 .

[0044] According to the embodiment of the present invention described above, the coating layer 3 is formed by drying an aqueous coating agent applied to the back surface of the sheet body 2A of the insulating outer sleeve 2 serving as a blank sheet for use in a paper cup 1 serving as a paper container. The coating layer 3 is formed at multiple locations on the back surface of the sheet body 2A, with uncoated surfaces 4 provided as gaps. Experimental verification, which will be described later, has shown that warping of the insulating outer sleeve 2 serving as a blank sheet can be suppressed. This reduces the risk of problems such as blank clogging on the production line during mass production.

[0045] Furthermore, in the embodiment of the present invention, the coating layer 3 is used for heat-sealing type bonding, which is superior to cold-sealing type bonding, and therefore, in the embodiment of the present invention, there are also advantages such as improved operation rate and reduced defect rate in mass production of paper cups 1.

[0046] In this embodiment of the present invention, the coating layers 3 at multiple locations have approximately the same area, and the spacing between the non-coated surfaces 4 is approximately the same. Furthermore, these coating layers 3 at multiple locations are symmetrical on the back surface of the sheet body 2A. Therefore, in this embodiment of the present invention, uniformity in the adhesive strength of the insulating outer sleeve 2 to the outer periphery of the body 11a of the paper cup body 11 can be ensured.

[0047] Furthermore, in the embodiment of the present invention, the coating layer 3 at a plurality of locations has a plurality of cracks 5. Therefore, in the embodiment of the present invention, the coating layer 3 can be formed, for example, by applying a next coating layer over the previous coating layer before the previous coating layer dries, and therefore the coating layer 3 can be formed in a short time, resulting in good manufacturing efficiency.

[0048] Example 1 The results of Experimental Verification 1, which was conducted to confirm the effects of the present invention, will be described below.

[0049] In this experimental verification 1, the samples of Comparative Example 1, Inventive Example 1, Inventive Example 2, and Inventive Example 3 all had a thickness of 0.239 mm and a basis weight of 200 g / m ２ A fan-shaped blank sheet was used.

[0050] In the sample of Comparative Example 1, the ratio of the coating area occupied by the coating layer 3 having a thickness of 10 μm on one side of the blank sheet was set to 100%.

[0051] In the sample of Inventive Example 1, the ratio of the coating area occupied by the coating layer 3 having a thickness of 10 μm on one side of the blank sheet was set to 80%.

[0052] In the sample of Inventive Example 2, the ratio of the coating area occupied by the coating layer 3 having a thickness of 10 μm on one side of the blank sheet was set to 60%.

[0053] In the sample of Inventive Example 3, the ratio of the coating area occupied by the coating layer 3 having a thickness of 10 μm on one side of the blank sheet was set to 40%.

[0054] The samples of Comparative Example 1, Inventive Example 1, Inventive Example 2, and Inventive Example 3 thus constructed were checked for the presence or absence of warping, and the test results shown in FIG. 3 were obtained.

[0055] The aqueous coating agent used to form the coating layer 3 of the samples of Comparative Example 1, Inventive Example 1, Inventive Example 2, and Inventive Example 3 was an aqueous coating agent (product name: Chemipearl S300) manufactured by Mitsui Chemicals, Inc., with a solids concentration of 35%, containing ionomer (ethylene methacrylic acid copolymer) as the main resin component, to which 5% dilution solvent (isopropyl alcohol) was added. This was then applied to one side of each sample so that the coating area occupied by the coating layer 3 was the desired ratio, and the sample was dried in an oven at 140°C for 50 seconds to produce the sample.

[0056] 3, the sample of Comparative Example 1 had warpage (warpage height: 20 mm) on the coating layer 3 side. In contrast, the samples of Inventive Examples 1, 2, and 3 had no warpage.

[0057] This confirmed that it is preferable that the ratio of the coating area occupied by the coating layer 3 on the front or back surface of the sheet body 2A be 80% or less.

[0058] Example 2 The results of Experimental Verification 2, which was conducted to confirm the effects of the present invention, will be described below.

[0059] In this Experimental Verification 2, samples of Comparative Example 2 and Inventive Example 4 were prepared in the same manner as in Experimental Verification 1.

[0060] In the sample of Comparative Example 2, the ratio of the coating area occupied by the 10 μm thick coating layer 3 on one side of the blank sheet was set to 10.7%.

[0061] In the sample of Inventive Example 4, the ratio of the coating area occupied by the 10 μm thick coating layer 3 on one side of the blank sheet was set to 16.8%.

[0062] The samples of Comparative Example 2 and Inventive Example 4 constructed in this manner were subjected to a peel test from the adherend, and it was confirmed that the samples were rated as good if they had the required adhesive strength, and as poor if they did not. The test results are shown in FIG. 4.

[0063] 4, the sample of Comparative Example 2 was found to be poor, whereas the sample of Inventive Example 4 was found to be good.

[0064] This confirmed that the ratio of the coating area occupied by the coating layer 3 on the front or back surface of the sheet body 2A is preferably 17% or more, particularly for adhesive purposes.

[0065] Example 3 The results of Experimental Verification 3, which was conducted to confirm the effects of the present invention, will be described below.

[0066] In this experimental verification 3, in addition to the samples of Comparative Example 1 and Inventive Example 1 used in Experimental Verification 1, a sample of Inventive Example 5 was used, in which the coating area ratio of the 10 μm thick coating layer 3 on one side of the blank sheet was 30%.

[0067] Then, the Cobb water absorbency of the front and back surfaces of the sheet body 2A of each sample was measured, and the difference between the Cobb water absorbencies was calculated.

[0068] The Cobb water absorbency was measured over a 2-minute measurement area of ​​20 cm ２ (JIS P 8140).

[0069] As shown in FIG. 5, in the sample of Comparative Example 1, the difference in Cobb water absorbency between the front and back surfaces of the sheet body 2A was 17.5 g / m ２ In contrast, in the samples of Inventive Examples 1 and 5, the Cobb water absorbency difference between the front and back surfaces of the sheet body 2A was 15.5 g / m ２ The following was confirmed.

[0070] This confirms that if the ratio of the coating area occupied by the coating layer 3 on the front or back surface of the sheet body 2A is set to 80% or less, the difference in moisture absorption between the front and back surface of the sheet body 2A will be reduced, and by reducing the difference in moisture absorption between the front and back surface of the sheet body 2A, warping can be suppressed.

[0071] Example 4 The results of Experimental Verification 4, which was conducted to confirm the effects of the present invention, will be described below.

[0072] In this experimental verification 4, samples of comparative example 3 and invention example 6 were created using a method similar to that used in experimental verification 1 above, in which the coating area on one side of the blank sheet was occupied by a 10 μm thick coating layer 3, accounting for 80% of the coating area.However, unlike the sample of invention example 1, the coating layer 3 had multiple cracks 5.

[0073] In the sample of Comparative Example 3, the area ratio of the plurality of cracks 5 to the coating layer 3 is 11.84% per unit area (where the unit area is 1 mm ２ Let's say.)

[0074] In the sample of Inventive Example 6, the area ratio of the plurality of cracks 5 to the coating layer 3 is 11.8% per unit area (where the unit area is 1 mm ２ Let's say.)

[0075] Five samples each of Comparative Example 3 and Inventive Example 6 thus constructed were prepared, and it was confirmed whether or not there were cases in which the surface of the coating layer 3 was lifted.

[0076] The test results are shown in FIG. 6. In Comparative Example 3, the surface of the coating layer 3 of two out of five samples was lifted.

[0077] In contrast, in the case of the samples of Inventive Example 6, none of the five samples had the surface of the coating layer 3 lifted.

[0078] From the test results, it was found that the area ratio of the multiple cracks 5 in the coating layer 3 exceeded 11.8% per unit area (where the unit area is 1 mm ２), the surface of the coating layer 3 will float, resulting in a slight deterioration in quality. For this reason, when the coating layer 3 has a plurality of cracks 5 at a plurality of locations, the manufacturing efficiency is good, but the area ratio of the plurality of cracks 5 to the coating layer 3 is 11.8% or less per unit area (here, the unit area is 1 mm ２ It was confirmed that the following is preferable.

[0079] Furthermore, taking into account the results of experimental verifications 1 to 4 conducted to confirm the effects of the present invention, it is believed that the present invention is particularly effective when the coating layer 3 is provided on only one side of the sheet body 2A.

[0080] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims.

[0081] In the above-described embodiment, the present invention is applied only to the paper cup 1, but is not limited to this and may be applied to other paper containers, such as paper containers for food or medicine, for example.

[0082] REFERENCE SIGNS LIST 1 Paper cup (paper container) 11 Paper cup body (paper container body) 11a Body 11b Curled portion 2 Heat insulating outer sleeve (blank sheet) 2A Sheet body 3 Coating layer 4 Uncoated surface (gap) 5 Crack

Claims

1. A blank sheet used for paper containers, characterized in that an aqueous coating agent is applied to at least one of the front and back surfaces of the sheet body of the blank sheet, and a coating layer is formed by drying the aqueous coating agent, and the coating layer on the front or back surface of the sheet body is formed at multiple locations with intervals between them.

2. A blank sheet according to claim 1, characterized in that the coating layers are formed in multiple locations symmetrically on the front or back of the sheet body.

3. A blank sheet according to claim 1 or 2, characterized in that the coating layer is provided on only one of the front and back surfaces of the sheet body.

4. A blank sheet according to any one of claims 1 to 3, characterized in that the thickness of the coating layer is 5 to 20 μm.

5. A blank sheet according to any one of claims 1 to 4, characterized in that the ratio of the coating area of ​​the surface or back surface of the sheet body occupied by the coating layer is 80% or less.

6. A blank sheet according to any one of claims 1 to 5, characterized in that the ratio of the coating area of ​​the coating layer on the front or back surface of the sheet body is 17% or more.

7. The difference in Cobb water absorbency between the front and back surfaces of the sheet body on which the coating layers are formed in multiple locations is 15.5 g / m ２ The blank sheet according to any one of claims 1 to 6, characterized in that:

8. A blank sheet according to any one of claims 1 to 7, characterized in that it is a heat insulating sheet that covers the outer surface of the paper container body of the paper container.

9. The blank sheet according to claim 8, wherein the paper container body is a paper cup body, and the heat insulating sheet is an outer heat insulating sleeve that is wrapped around the outer periphery of the body of the paper cup body.

10. A paper container characterized in that the blank sheet according to any one of claims 1 to 9 is directly or indirectly provided on the paper container body.

11. A paper cup characterized in that the blank sheet according to claim 9 is provided as the insulating outer sleeve wrapped around the outer periphery of the body of the paper cup body.

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