Method for manufacturing food container and food container

Abstract

To provide a method for manufacturing a food container having a nonwoven fabric layer on the outer surface side, capable of suppressing the loss of a member in a manufacturing process and forming a clear printed image on the surface of the nonwoven fabric, and the food container.SOLUTION: The method for manufacturing the food container 1 includes a step of printing the printed layer 60 by flexographic printing on the 46a of one surface of the outer layer sheet 45 composed of a nonwoven fabric formed of polypropylene, a step of laminate-bonding the other surface of the outer layer sheet 45 opposite to the 46a of the one surface on which the printed layer is printed to the inner layer sheet 35 formed of polypropylene to obtain the raw material sheet 70 in which the outer layer sheet 45 is laminated on the inner layer sheet 35, and a step of molding the raw material sheet 70 into a container-like shape in which the inner layer sheet 35 is disposed inside and the outer layer sheet 45 is disposed outside.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a food container for storing food such as cooked rice, noodles, side dishes, and boxed lunches, and to the food container. [Background technology]

[0002] Conventionally, food containers made of synthetic resin are known that can hold and transport a relatively small amount of the above-mentioned food, such as a single serving, and that can furthermore be used to heat the food in a microwave oven. For example, Patent Document 1 discloses a method for manufacturing an article container capable of holding food, which includes the steps of bonding a polyethylene film with an adhesive to a base sheet made of either a polypropylene sheet or a polyethylene terephthalate sheet, bonding a nonwoven fabric onto the polyethylene film on the base sheet, and offset printing on the surface of the nonwoven fabric that will be the outer surface of the container, of the laminate of the base sheet, polyethylene film, and nonwoven fabric, and curing the print with UV radiation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-87960 Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that offset printing, when forming a printed layer displaying patterns or letters on the surface of a nonwoven fabric that is elastic and has minute irregularities, is difficult to obtain a clear, sharp printed image. Patent Document 1, therefore, claims that a clear printed image can be obtained by curing the printed image with UV radiation after offset printing. However, with this manufacturing method, it is uncertain to what extent UV radiation can sharpen a blurred printed image produced by offset printing. Furthermore, in Patent Document 1, a thin film is bonded to a substrate sheet, and then a nonwoven fabric is bonded to form a laminate. Then, offset printing is performed on the top surface of this laminate. Therefore, loss of components due to printing defects during printing, etc., results in loss of the laminate, including the substrate sheet, resulting in significant loss of components.

[0005] Therefore, the main object of the present invention is to provide a food container manufacturing method and a food container that have a nonwoven fabric layer on the outer surface, which reduces material loss during the manufacturing process and allows for the formation of a clear printed image on the surface of the nonwoven fabric. [Means for solving the problem]

[0006] The method for manufacturing a food container of the present invention includes the steps of printing a printing layer by flexographic printing on one side of an outer layer sheet made of nonwoven fabric formed from polypropylene, laminating the other side of the outer layer sheet opposite to the one side to an inner layer sheet made from polypropylene to obtain a material sheet in which the outer layer sheet is laminated to the inner layer sheet, and molding the material sheet into a container shape in which the inner layer sheet is arranged on the inside and the outer layer sheet is arranged on the outside.

[0007] The food container of the present invention is a food container for storing food, and comprises an inner layer made of polypropylene, an outer layer made of a nonwoven fabric formed from polypropylene and laminated on the outside of the inner layer, a laminate layer that joins the inner layer and the outer layer, and a printed layer formed on the surface of the outer layer using water-based ink. [Effects of the Invention]

[0008] According to the present invention, a food container manufacturing method and a food container can be provided that have a nonwoven fabric layer on the outer surface, which reduces the loss of parts during the manufacturing process and allows for the formation of a clear printed image on the surface of the nonwoven fabric. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a food container according to an embodiment. [Figure 2] 1 is a vertical cross-sectional view of a food container according to an embodiment. [Figure 3] 1 is a cross-sectional view schematically showing the layer structure of a food container according to an embodiment. [Figure 4] FIG. 3 is an enlarged view of a portion indicated by IV in FIG. 2. [Figure 5] FIG. 1 is a flow chart showing steps in a method for manufacturing a food container according to an embodiment. [Figure 6] FIG. 2 is a diagram illustrating one embodiment of step 1 of the above-mentioned manufacturing method, and is a plan view illustrating a state in which a printed layer has been formed on one surface of the outer layer sheet by flexographic printing. [Figure 7] FIG. 2 is a cross-sectional view showing a state in which a printed layer has been formed on an outer layer sheet in step 1. [Figure 8] FIG. 2 is a diagram schematically illustrating the structure of flexographic printing performed in step 1 of the above-mentioned manufacturing method. [Figure 9A] FIG. 2 is a cross-sectional view showing step 2 of the manufacturing method, before dry lamination. [Figure 9B] FIG. 10 is a cross-sectional view showing step 2 above, after dry lamination. [Figure 10] FIG. 3 is a cross-sectional view showing step 3 of the manufacturing method. [Figure 11] FIG. 4 is a cross-sectional view showing step 4 of the manufacturing method. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a perspective view of a resin food container 1 according to an embodiment containing food F. Fig. 2 is a vertical cross-sectional view of the food container 1. The food container 1 has an opening 1a that opens upward. The opening 1a is closed by a lid (not shown).

[0011] The food container 1 comprises a bowl-shaped main body 10 and a flange 20. The main body 10 has a circular bottom 11, a sidewall 12 rising from the outer periphery of the bottom 11, and a food storage section 13 surrounded by the bottom 11 and the sidewall 12 and serving as a storage space for food F. The sidewall 12 has an upper edge 12a that is circular in plan view. A flange 20 extends from this upper edge 12a to the outside of the main body 10. The flange 20 is an annular protrusion that follows the upper edge 12a and extends from the upper edge 12a approximately parallel to the bottom 11. The outer surface of the sidewall 12 has a display section 19. Examples of the display section 19 include, but are not limited to, characters indicating the product name or manufacturer name of the food F, patterns or characters indicating the manufacturer's brand or logo, and photographs of the food F.

[0012] As shown in Fig. 2, food container 1 has an inner layer 30 facing food storage section 13, an outer layer 40 outer than inner layer 30, a laminate layer 50 joining inner layer 30 and outer layer 40, and a printed layer 60 formed on surface 40a of outer layer 40. The above-mentioned display section 19 is formed by the printed layer 60. Fig. 3 is a cross-sectional view schematically showing the layer structure of inner layer 30, outer layer 40, laminate layer 50, and printed layer 60.

[0013] The inner layer 30 is a base layer that maintains the shape of the food container 1 and is made of polypropylene (PP). There are no limitations on the thickness of the inner layer 30, but it is preferably, for example, between 30 μm and 1200 μm. This is because a thickness below 30 μm makes it difficult to maintain the shape after molding, and a thickness above 1200 μm requires the application of a large amount of heat during manufacturing, which reduces production efficiency.

[0014] The outer layer 40 is made of a nonwoven fabric formed from polypropylene. That is, both the outer layer 40 and the inner layer 30 are made of the same material, polypropylene. The nonwoven fabric that makes up the outer layer 40 is made of polypropylene fibers molded into a sheet. The thickness of the outer layer 40 is not limited, but is preferably, for example, about 40 μm to 500 μm. This is because if the thickness is less than 40 μm, it may be difficult to obtain sufficient thermal insulation, and if it exceeds 500 μm, moldability deteriorates. The thickness of the outer layer 40 is preferably thinner than the thickness of the inner layer 30. This improves shape stability during molding. When food container 1 is viewed as a whole, bottom 11 and side wall 12 of main body 10 and flange 20 may have approximately the same thickness, or may have different thicknesses.

[0015] The nonwoven fabric constituting the outer layer 40 may be either short fiber or long fiber, but long fiber is preferred because it is cheaper and has better strength than short fiber. The nonwoven fabric constituting the outer layer 40 is preferably a spunbonded nonwoven fabric formed by a spunbonding method that forms continuous long fibers.

[0016] The basis weight of the nonwoven fabric constituting the outer layer 40 is not limited, but is, for example, 12 g / m 2 More than 130g / m 2 This is preferably 12 g / m or less. 2 If the density is less than 130 g / m, the nonwoven fabric may break during printing or molding. 2 If the temperature exceeds this range, moldability will be deteriorated.

[0017] The laminate layer 50 is an adhesive layer and is formed, for example, by dry lamination. In dry lamination, an adhesive is applied to one surface 30a of the inner layer 30, dried, and then heated. The outer layer 40 is pressed against the inner layer 30 via the adhesive to bond them together. The adhesive may be applied to the outer layer 40 instead of the inner layer 30, or to both the inner layer 30 and the outer layer 40. The type of adhesive used in dry lamination is not limited, but a polyester urethane adhesive is preferred. The thickness of the laminate layer 50 is not limited, but is preferably between 1.5 μm and 15 μm to ensure adhesion while remaining as thin as possible. The laminate layer 50 is significantly thinner than the inner layer 30 and the outer layer 40, and its thickness is one-third or less of the thicknesses of the inner layer 30 and the outer layer 40. The bonding of the inner layer 30 and the outer layer 40 by lamination is not limited to dry lamination, and other lamination methods such as thermal lamination, extrusion lamination, and wet lamination may also be used.

[0018] The printed layer 60 is formed by printing an aqueous ink, whose solvent is primarily water, onto a resin base material. Examples of resin base materials for aqueous ink include, but are not limited to, acrylic and urethane. The thickness of the printed layer 60 is not limited, but it is preferably approximately 3 μm, for example, in order to ensure that it is as thin as possible and clearly displayed. Flexographic printing, which will be described later, is a suitable printing method for forming the printed layer 60 using aqueous ink. The printed layer 60 is significantly thinner than the inner layer 30 and the outer layer 40, and the thickness of the printed layer 60 is one-tenth or less of the thickness of the inner layer 30 and the outer layer 40.

[0019] FIG. 4 is an enlarged view of a portion indicated by IV in FIG. 2, and is a cross-sectional view of a portion rising from the bottom portion 11 of the main body portion 10 to the side wall portion 12.

[0020] As shown in FIG. 4, the portion of the main body 10 rising from the bottom 11 to the side wall 12 includes a bottom corner 14. This bottom corner 14 is formed in an R-shaped, i.e., curved, shape. The radius of curvature R1 of the outer periphery of the bottom corner 14 is preferably 1 mm or more. It is more preferable that the radius of curvature R1 of the outer periphery of the bottom corner 14 is, for example, 3 mm or more. This is because if the value of the radius of curvature R1 of the outer periphery of the bottom corner 14 is less than 3 mm, stress will be concentrated at the bottom corner 14 during molding, making the nonwoven fabric more likely to tear.

[0021] As shown in Figure 4, the inclination angle θ1 of the side wall 12 relative to the bottom 11 on the inside (food storage section 13 side) of the bottom side corner 14 is formed arbitrarily within the range of 91° to 179°. This is set depending on the type of food F to be stored and the designed shape of the food container 1, etc.

[0022] The above is the configuration of the food container 1 according to the embodiment. Next, a method for manufacturing the food container 1 according to the embodiment will be described.

[0023] 5 is a flow chart showing the steps of the manufacturing method according to the embodiment. As shown in FIG. 5, the manufacturing method includes the following steps 1 to 4.

[0024] First, a printed layer 60 is formed by flexographic printing on one surface 46a of an outer layer sheet 45, which is made of a sheet-like polypropylene nonwoven fabric and which will become the outer layer 40 and has multiple container-forming regions 45a (described below) (Step 1). Next, the outer layer sheet 45 and a polypropylene inner layer sheet 35 are laminated together by dry lamination to obtain a material sheet 70 (Step 2). Next, the multiple container-forming regions 45a of the material sheet 70 are formed into container shapes (Step 3). Next, each container-forming region 45a of the material sheet 70 is cut to obtain multiple food containers 1 (Step 4). Note that cutting is a means for cutting out the container-forming regions 45a, and the cutting means is not limited to cutting, and other means, such as punching, may also be used.

[0025] Figure 6 schematically shows step 1. In this case, the outer layer sheet 45 made of polypropylene nonwoven fabric has the above-mentioned circular container-forming areas 45a for obtaining multiple food containers 1. On one surface 46a of each container-forming area 45a in the outer layer sheet 45, a printing layer 60 is formed by flexographic printing in a shape that will obtain a display section 19 of a predetermined shape. Figure 7 schematically shows a cross section of the outer layer sheet 45 after the printing layer 60 has been formed on the outer layer sheet 45 in step 1.

[0026] Fig. 8 shows a schematic diagram of the structure of flexographic printing. As shown in Fig. 8, in flexographic printing, aqueous ink P in an ink tank 100 is transferred to an ink roll 101, and the aqueous ink P, whose layer thickness has been adjusted by a doctor blade 102, is then applied to a plurality of relief plates 103a on a printing roll 103. Next, the aqueous ink P is transferred from the relief plates 103a on the printing roll 103 to one surface 46a of an outer layer sheet 45, which is transported between the printing roll 103 and an impression roll 104, to form a printed layer 60. The flexographic printing in this process is preferably aqueous flexographic printing, using a water-soluble acrylic resin or a water-soluble urethane resin as the main component resin of the aqueous ink P.

[0027] In step 2, as shown in Fig. 9A, the outer layer sheet 45 is dry-laminated to one surface 35a of the inner layer sheet 35 via a dried adhesive 51. The other surface 46b of the outer layer sheet 45, opposite the surface 46a on which the printing layer 60 printed with the water-based ink P is printed, is laminated to the one surface 35a of the inner layer sheet 35. This results in a material sheet 70 in which the outer layer sheet 45 and the inner layer sheet 35 are bonded via the laminate layer 50 made of the adhesive 51, as shown in Fig. 9B.

[0028] In step 3, as shown in FIG. 10, the plurality of container-forming regions 45a in the material sheet 70 are press-molded together to form a plurality of food containers 1 from the material sheet 70. Here, the inner layer sheet 35 is positioned on the inside and the outer layer sheet 45 is positioned on the outside. A suitable press-molding method is, for example, vacuum / pressure molding, which is a common method for drawing resin sheets, or a pressure molding method. Then, as shown in FIG. 11, the container-forming regions 45a of the material sheet 70 are cut. This results in a plurality of food containers 1 as shown in FIGS. 1 and 2.

[0029] The above is a food container 1 and its manufacturing method according to the embodiment. In the food container 1 according to the embodiment, the display section 19 is formed on the surface 40a of the outer layer 40 made of nonwoven fabric by a printing layer 60 printed by flexographic printing using water-based ink. Flexographic printing easily produces clear printed images even on printing surfaces with minute irregularities, such as the surface of nonwoven fabric. Therefore, the display section 19 printed by flexographic printing produces a printed image with clear and sharp outlines, even if it contains complex patterns or fine characters.

[0030] In the manufacturing method of the food container 1 according to the embodiment, a printed layer 60 is formed on one surface 46a of the single-layer outer layer sheet 45 by flexographic printing before laminating the outer layer sheet 45 made of nonwoven fabric to the inner layer sheet 35. The outer layer sheet 45 is then laminated to the inner layer sheet 35 on the printed layer 60. Therefore, material loss due to printing defects during printing is limited to the nonwoven fabric of the outer layer sheet. This reduces material loss. Furthermore, flexographic printing on the one surface 46a of the single-layer outer layer sheet 45 facilitates direct transmission of printing pressure from the printing roll 103 to the outer layer sheet 45, which in turn facilitates the printing of the indicia 19 with clear, sharply displayed print images. Furthermore, flexographic printing on the one surface 46a of the single-layer outer layer sheet 45 offers the following additional advantages: Because nonwoven fabric has an air layer, the printed layer 60 of the outer layer sheet 45 dries easily, allowing for faster printing. When an outer layer sheet 45 and an inner layer sheet 35 with different thermal shrinkage rates are laminated and then printed, the difference in the degree of shrinkage after printing causes curling, but this problem does not occur. Because the single outer layer sheet 45 that is not laminated is thinner than a two-layer laminate of the outer layer sheet 45 and the inner layer sheet 35, the diameter of the raw roll that can be installed in the printing machine during printing is generally fixed, so the raw roll can be made longer. As a result, the work of switching raw rolls can be reduced and work efficiency improved.

[0031] Flexographic printing using aqueous inks leaves less residual solvent than other printing methods such as gravure printing that use inks containing solvents such as organic solvents, making it safer and avoiding the risk of environmental pollution.

[0032] Nonwoven fabrics have an air layer inside and are resistant to deformation even at high temperatures, making them less susceptible to conductive heat transfer and providing excellent thermal insulation, or in other words, heat retention. Therefore, when food F is heated in a microwave oven together with a food container 1 having an outer layer 40 made of nonwoven fabric, the warmth of the food F is more easily maintained than when the outer layer 40 is made of a solid resin rather than nonwoven fabric. This allows the delicious flavor of hot food F to be enjoyed for a long time. Furthermore, the excellent thermal insulation properties make it easy to hold the food container 1 containing heated food F with bare hands.

[0033] In the food container 1 according to the embodiment, both the inner layer 30 and the outer layer 40 are made of polypropylene. In other words, the inner layer 30 and the outer layer 40 are made of the same material, making the food container 1 a mono-material. For example, if the inner layer 30 and the outer layer 40 were made of different materials, they would be difficult to separate or separate, and would often have to be incinerated after disposal. However, the food container 1, being a mono-material, is easy to recycle. As a result, this leads to a reduction in emissions of carbon dioxide, a greenhouse gas.

[0034] According to the embodiment described above, the following effects are achieved.

[0035] (1) A manufacturing method of the food container 1 according to the embodiment includes the steps of printing a printing layer 60 by flexographic printing on one side 46a of an outer layer sheet 45 made of a nonwoven fabric formed from polypropylene, laminating the other side 46b of the outer layer sheet 45 opposite the side 46a on which the printing layer 60 is printed to an inner layer sheet 35 made from polypropylene to obtain a material sheet 70 in which the outer layer sheet 45 is laminated to the inner layer sheet 35, and molding the material sheet 70 into a container shape in which the inner layer sheet 35 is arranged on the inside and the outer layer sheet 45 is arranged on the outside.

[0036] This reduces material loss during the manufacturing process for food containers 1 that have a nonwoven outer layer 40 on the exterior side, and allows for the production of food containers 1 with a clear printed layer 60 formed on the surface of the nonwoven fabric. Furthermore, because food containers 1 are made into a monomaterial, they are easy to recycle, which helps reduce emissions of carbon dioxide, a greenhouse gas.

[0037] (2) In the manufacturing method (1) according to the embodiment, the ink used in the flexographic printing is a water-based ink.

[0038] This allows the formation of the printed layer 60 on the one surface 46a of the outer layer sheet 45 with less residual solvent, making it safe and avoiding the risk of environmental pollution.

[0039] (3) In the manufacturing methods (1) and (2) according to the embodiment, the fibers of the nonwoven fabric constituting the outer layer sheet 45 are preferably long fibers.

[0040] This makes it cheaper and stronger than short fibers.

[0041] (4) In the manufacturing method of the food container according to the embodiment (1) to (3), the basis weight of the nonwoven fabric constituting the outer layer sheet 45 is 12 g / m 2 More than 130g / m 2 It is preferable that:

[0042] This makes it possible to obtain sufficient heat insulation properties and good moldability.

[0043] (5) The food container 1 of the embodiment is a food container 1 for containing food F, and comprises an inner layer made of polypropylene, an outer layer made of nonwoven fabric formed from polypropylene and laminated on the outside of the inner layer, a laminate layer 50 that joins the inner layer 30 and the outer layer 40, and a printed layer 60 formed on the surface 40a of the outer layer 40 with aqueous ink P.

[0044] Flexographic printing is a suitable printing method using aqueous ink P, and flexographic printing using aqueous ink P can form a clear printed layer 60 on the surface 40a of the outer layer 40 made of nonwoven fabric, which is difficult to print clearly on. Furthermore, because the food container 1 is made of a single material, it is easy to recycle and avoids the need for combustion as a disposal method, which leads to a reduction in emissions of carbon dioxide, a greenhouse gas.

[0045] (6) In the food container 1 according to the above embodiment (5), the fibers of the nonwoven fabric constituting the outer layer 40 are preferably long fibers.

[0046] This makes it cheaper and stronger than short fibers.

[0047] (7) In the food container 1 according to the above embodiments (5) and (6), the basis weight of the nonwoven fabric constituting the outer layer sheet 45 is 12 g / m 2 More than 130g / m 2 It is preferable that:

[0048] This makes it possible to obtain sufficient heat insulation properties and good moldability.

[0049] The food container 1 and the manufacturing method thereof according to the embodiment have been described above, but the present invention is not limited to this embodiment and can be modified as appropriate.

[0050] For example, the shape of food container 1 is not limited to a circular shape in a plan view, but may be a rectangular shape, a polygonal shape, an elliptical shape, or the like.

[0051] The food container 1 may be provided with a lid that closes the opening 1a. In this case, the lid is preferably made of polypropylene, similar to the inner layer 30 and outer layer 40 of the food container 1, from the viewpoints of recycling and avoiding environmental pollution as described above. [Explanation of symbols]

[0052] 1 food container 30 inner layer 35 Inner layer sheet 40 outer layer 40a Surface of outer layer 45 outer layer sheet 46a One side of the outer layer sheet 46b Other side of outer layer sheet 50 laminate layers 60 printing layer 70 Material Sheet F Food P Water-based ink

Claims

1. a step of printing a printing layer by flexographic printing on one surface of an outer layer sheet made of a nonwoven fabric formed from polypropylene; laminating the other side of the outer layer sheet opposite to the side on which the printed layer is printed to an inner layer sheet made of polypropylene, thereby obtaining a material sheet in which the outer layer sheet is laminated on the inner layer sheet; and forming the material sheet into a container shape in which the inner layer sheet is disposed on the inside and the outer layer sheet is disposed on the outside.

2. 2. The method for manufacturing a food container according to claim 1, wherein the ink used in the flexographic printing is a water-based ink.

3. The method for manufacturing a food container according to claim 1 or 2, wherein the fibers of the nonwoven fabric are long fibers.

4. The weight of the nonwoven fabric is 12 g / m ２ 130g / m or more ２ The method for manufacturing a food container according to claim 1 or 2, wherein the method is as follows:

5. A food container for containing food, an inner layer made of polypropylene; an outer layer made of a nonwoven fabric formed from polypropylene and laminated on the outside of the inner layer; a laminate layer joining the inner layer and the outer layer; A food container comprising: a printed layer formed on the surface of the outer layer using a water-based ink.

6. The food container according to claim 5, wherein the fibers of the nonwoven fabric constituting the outer layer are long fibers.

7. The weight of the nonwoven fabric is 12 g / m ２ 130g / m or more ２ 7. The food container according to claim 5 or 6, wherein:

Images