Container and production method thereof

Abstract

To prepare a foamed heat insulating container excellent in recyclability for replacement of a foam heat insulating paper container using synthetic resin belonging to a single category or a same category.SOLUTION: A container comprises foamed label sheet 12 and a container body 11, wherein the foamed label sheet 12 is configured by only olefin-based resin and has a print layer on one surface thereof, and the container body 11 is configured by only olefin-based resin, and an outer side surface thereof is integrated with a surface of an opposite side of the print layer of the foamed label sheet 12. Further, the container body 11 is formed through injection molding.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a container, and more particularly to a container in which a label sheet made of polyolefin and a container body are integrated. [Background technology]

[0002] Products made from synthetic resins made from raw materials such as petroleum (hereinafter referred to simply as "plastic products") are used in a variety of situations due to their characteristics of being inexpensive, lightweight, easy to process, durable, and resistant to corrosion.

[0003] On the other hand, plastic products are difficult to decompose, and if they are not disposed of properly, some can remain for hundreds of years. In recent years, the issue of microplastics caused by plastic products has been attracting attention. Microplastics are plastics smaller than 5mm in size. Microplastics have the ability to absorb marine pollution and harmful substances. When marine life mistakes microplastics that have absorbed harmful substances for food and ingests them, they are taken up by fish, birds, and marine life through the food chain, and further accumulate in their bodies through "bioaccumulation." It is said that humans who eat these fish may also be affected by marine pollution.

[0004] In addition to microplastics, illegal dumping of plastic products on land is also a problem. One possible reason for the illegal dumping of plastic products is that they are easily available, leading to a lack of awareness of recycling and resulting dumping. Another reason is that plastic products are generally synthesized by combining multiple materials to give them various functions. In order to recycle them, these materials must be separated one by one, but because separation is costly and time-consuming, it is thought that this hinders recycling and leads to illegal dumping. Therefore, it is necessary to develop products that are easy to recycle by constructing them using materials that belong to a single group or the same category as much as possible (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-064753

[0006] However, for example, in the case of a foam insulated container, if the foam insulated container uses a paper base material, the moisture contained in the paper base material can be used to foam the polyethylene provided on one side of the paper base material, but in the case of a synthetic resin, it cannot be made using the same principle as a foam insulated container using a paper base material. Therefore, when making a foam insulated container using a single synthetic resin or synthetic resins belonging to the same classification, a new structure must be considered. Summary of the Invention [Problem to be solved by the invention]

[0007] The inventors of the present invention investigated whether it was possible to produce a foamed heat-insulating container using a single synthetic resin or synthetic resins belonging to the same category, and discovered that the above-mentioned problems could be solved by integrating a polyolefin label sheet with a polyolefin container body, which led to the completion of the present invention. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a container comprising a foam label sheet and a container body, wherein the foam label sheet is made only of an olefin-based resin and has a printed layer on one side, while the container body is made only of an olefin-based resin, and the surface of the foam label sheet opposite the printed layer is integrated with the outer surface of the container body.

[0009] According to this configuration, both the foam label sheet and the container body can be made of only olefin-based resin, so that a foamed heat-insulating container can be manufactured using only synthetic resins belonging to a single or the same category.

[0010] In the above configuration, it is preferable that the container body is formed by injection molding.

[0011] This structure allows the container to be formed into any desired shape by injection molding, and also allows the foam label sheet and the container body to be integrated without the need for a separate adhesive layer.

[0012] In order to solve the above problems, the present invention provides a method for manufacturing a container made only of an olefin-based resin, using a mold having a resin injection port in either the concave or convex mold, the method including: an arrangement step of arranging a foam label sheet made of an olefin-based resin molded into an inverted frustum or cylindrical shape inside the concave mold; and a filling step of filling the cavity formed between the concave and convex molds with an olefin-based resin through the resin injection port.

[0013] According to this configuration, it is possible to manufacture a foamed heat-insulating container in which a foamed label sheet made of a single synthetic resin or of the same type is integrated with a container body without providing a separate adhesive layer. [Effects of the Invention]

[0014] According to the present invention, a foamed insulated container made of a single or identical synthetic resin can be produced. In addition, since the container can be produced from a single or identical synthetic resin, it is possible to provide a container that is highly recyclable. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a container for explaining the structure of a container 1 according to the present invention. [Figure 2] FIG. 1 is a cross-sectional view of an injection mold for manufacturing a container according to the present invention. [Figure 3] 1A to 1C are explanatory views for explaining a method for manufacturing a container according to the present invention. [Figure 4] FIG. 10 is a diagram summarizing the results of each test example in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, preferred embodiments for carrying out the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is an example of a typical embodiment of the present invention, and the scope of the present invention should not be construed as being narrow.

[0017] As shown in Fig. 1, the container 1 according to this embodiment is composed of a bottomed container body 11 with a flange at the top end, and a foam label sheet 12 attached to the side of the container body 11. The foam label sheet 12 and the container body 11 are integrated together. In this embodiment, a truncated cone shape will be described as an example.

[0018] The shape of the container body 11 according to this embodiment is not particularly limited, but is preferably a truncated cone shape with a bottom and a flange at the top. From the viewpoint of stacking, a plurality of ribs may be provided on the outer periphery of the side surface of the container body.

[0019] The material that can be used for the container body 11 is preferably a thermoplastic resin, and preferably a synthetic resin that is the same as or belongs to the same classification as the foam label sheet 12 described below. The names of the synthetic resin materials listed below conform to JIS K6899-1 (2015) or ISO472 (2013). Specific examples of synthetic resins include polyester resin, polyolefin resin, polystyrene resin, polyamide resin, polycarbonate resin, polyacrylonitrile resin, polyimide resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, ethylene vinyl alcohol resin, and polyurethane resin. A container made of only one of the above materials falls under the "single" category defined in the claims.

[0020] In this embodiment, a single synthetic resin may be used, or a combination of synthetic resins belonging to the same category may be used. Here, synthetic resins belonging to the same category refer to different materials classified as having common properties. For example, synthetic resins can be classified into thermoplastic resins and thermosetting resins. Thermoplastic resins can be further classified into general-purpose plastics and engineering plastics. General-purpose plastics can be further classified into crystalline resins and amorphous resins. Meanwhile, engineering plastics can be classified into general-purpose engineering plastics and super engineering plastics, which can be further classified into crystalline resins and amorphous resins, respectively. In this embodiment, olefin-based resins, which include polyethylene resins and polypropylene resins classified as crystalline resins of general-purpose plastics, are preferred. Furthermore, in this embodiment, different materials may be used in a laminated structure or blended together. Furthermore, the label sheet and the container body may each be made of a different olefin-based resin.

[0021] The container body 11 according to this embodiment can be formed by a conventional forming method such as injection molding, vacuum forming, pressure forming, vacuum pressure forming, hot plate forming, etc. In this embodiment, injection molding is particularly preferred.

[0022] The foam label sheet 12 according to this embodiment is not particularly limited in shape as long as it can provide heat insulation during use, but a shape that can cover the entire side of the container body is preferred. Furthermore, from the viewpoint of processing, a sheet shape is preferred. From the viewpoint of heat insulation, the thickness of the foam label sheet 12 is preferably 0.2 mm or more, more preferably 0.3 mm or more. If it is less than 0.2 mm, the sheet will lack stiffness and will have poor formability. On the other hand, there is no particular upper limit to the thickness of the foam label sheet 12, but it is preferably a thickness equivalent to 50 to 85% of the total thickness of the side wall of the container body 11 and the foam label sheet 12. If the thickness of the foam label sheet 12 exceeds 85% of the total thickness, formability will be poor.

[0023] The foam label sheet 12 used in this embodiment preferably has a compression set of 6% or less (based on JIS K6767, 2013). If the set exceeds 6%, the deformation due to heat and pressure during molding will be significant, resulting in poor appearance of the molded product.

[0024] The expansion ratio of the foamed label sheet 12 used in this embodiment is preferably 7 times or more, more preferably 8 times or more, and even more preferably 10 times or more. On the other hand, an expansion ratio of more than 20 times causes surface roughness and a poor feel. Here, the expansion ratio is calculated as the reciprocal of the density. In other words, it is calculated by dividing the volume after expansion by the volume of the raw material.

[0025] The foam label sheet 12 according to this embodiment is preferably made of the same synthetic resin as the container body 11 or of the same class. By using the same synthetic resin as the container body 11 or of the same class, recyclability can be improved. Specifically, olefin resins including polyethylene resin and polypropylene resin are preferred.

[0026] The foamed label sheet 12 according to this embodiment may have a printed layer on the outer periphery. The printed layer can be formed by printing on the foamed label sheet R. There are no particular restrictions on the printing method, and any existing printing method can be used. In this embodiment, flexographic printing is preferred.

[0027] A method for manufacturing the container 1 according to this embodiment will be described with reference to FIGS. 2 and 3. Here, injection molding will be used as an example. First, a foam label sheet 12 is prepared. The foam label sheet 12 may be prepared by kneading a foaming agent into molten polyethylene, or a commercially available foam label sheet 12 may be used. A printing layer may be provided on one side of the foam label sheet 12 by flexographic printing.

[0028] Next, the foam label sheet 12 is punched into a predetermined shape. Specifically, the laminate is punched with the printed surface facing outward so that when the edges are bonded together, a truncated cone shape is formed. The punched foam label sheet 12 is then curved into a truncated cone shape, and the edges are then heat-sealed together. Heat-sealing the edges in advance improves operability in the following steps. Of course, it is also possible to use the foam label sheet 12 without heat-sealing the edges together.

[0029] The mold 60 used in this embodiment is composed of a convex mold 60A, a concave mold 60B, and a plate mold 60C. Note that the mold 60 is merely an example and can be modified as appropriate to match the shape of the container 1. After the convex mold 60A and the concave mold 60B are fitted together, the plate mold 60C is placed on top to form a cavity in the shape of the container. Thermoplastic resin is then injected into the cavity through an injection port 60D provided on the bottom surface of the concave mold 60B. Note that the cavity thickness may be approximately 0.5 to 2 mm. If it is less than 0.5 mm, the resin is likely to clog, and if it is more than 2 mm, not only will the amount of resin required to form the container increase, but the weight of the container 1 will also increase. Furthermore, the thickness of the cavity may vary from place to place.

[0030] First, the heat-sealed foam label sheet 12 is placed in the recessed mold 60B (see FIG. 3). At this time, if the foam label sheet 12 is to be applied to the entire wall surface of the container body 11, the foam label sheet 12 is placed by fitting it into the recessed mold 60B so that the printed surface of the foam label sheet 12 faces outward. Care must be taken to ensure that the foam label sheet 12 does not overlap the recessed portion for forming the flange provided on the top of the recessed mold 60B.

[0031] After placing the foaming label sheet 12 in the recessed mold 60B, molds 60A and 60B are fitted together. Then, after placing 60C, molten olefin resin such as polypropylene is injected through injection port 60D. The injected olefin resin such as polypropylene fills the cavity. The injected resin flows through the gap between the surface opposite the printed surface of foaming label sheet 12 and convex metal fitting 60A. The injected resin cools and hardens to become container body 11. This results in container 1, in which foaming label sheet 12 and container body 11 are integrated. [Example]

[0032] The present invention will be described in more detail below, but is not limited thereto. Here, the present invention will be described taking as an example a case where a foam label sheet is provided on the entire side surface of a container body.

[0033] (Test Example 1) Molten polypropylene resin was filled into the mold shown in Figure 1 to create a truncated cone-shaped container with a bottom (inner diameter of the opening: 95 mm, inner diameter of the bottom: 75 mm, height from the bottom to the opening: 80 mm, volume: 390 mL). The cavity thickness was 0.6 mm.

[0034] (Test Example 2) A foam label sheet formed into a truncated cone shape so as to cover the entire side surface of the container body was set on the inner surface of the concave mold used in Test Example 1. An olefin resin foam label sheet with a thickness of 0.3 mm, an expansion ratio of 7, and a compression set of 6% (manufactured by Sekisui Chemical Co., Ltd.) was used. Then, molten polypropylene resin was filled in the same manner as in Test Example 1.

[0035] (Test Example 3) The test was the same as Test Example 2, except that an olefin-based resin foam label sheet (manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.5 mm, an expansion ratio of 10, and a compression set of 4% was used.

[0036] (Test Example 4) The test was the same as Test Example 2, except that an olefin-based resin foam label sheet (manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.1 mm, an expansion ratio of 4, and a compression set of 12% was used.

[0037] (Test Example 5) The test was the same as Test Example 2, except that an olefin-based resin foam label sheet (manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.7 mm, an expansion ratio of 10, and a compression set of 4% was used.

[0038] (Test Example 6) The test was the same as Test Example 1 except that linear polyethylene was used instead of polypropylene.

[0039] (Test Example 7) An olefin resin foam label sheet with a thickness of 0.3 mm, an expansion ratio of 7 times, and a compression set of 6% was set on the inner surface of the concave mold used in Test Example 1, and molten linear polyethylene resin was filled in the same manner as in Test Example 1.

[0040] (Test Example 8) The same as Test Example 7 was used except that a foam label sheet made of an olefin resin with a thickness of 0.5 mm, an expansion ratio of 10 times, and a compression set of 4% was used.

[0041] (Reference example) A heat insulating foam paper container was prepared by removing the contents from a commercially available cup noodle (registered trademark: manufactured by Nissin Food Products).

[0042] Test Examples 1 to 8 and the Reference Example were judged based on the following criteria.

[0043] <Moldability> 〇: The molten resin does not get around to the printed side of the label sheet, and the container can be produced as designed. △: The molten resin has partially leaked onto the printed surface of the label sheet, or the resin has not reached the flange. ×: The molten resin has spread all around the printed surface of the label sheet, or the resin is not completely filled in, making it impossible to use as a container.

[0044] <Thermal insulation> 230 mL of boiling water at approximately 100°C was poured into Test Examples 1 to 8 and the Reference Example, and the opening was covered with a plastic lid. The temperature of the side of the container was measured from the outside after 60, 120, 180, and 240 seconds. The results are shown in Figure 4.

[0045] When the container body is made of polypropylene, Test Examples 2 to 4, which are provided with a foam label sheet, show better insulation than Test Example 1, which does not have a foam label sheet. In particular, Test Examples 3 and 4 show insulation properties comparable to that of the Reference Example. In contrast, Test Example 5, which also has a foam label sheet, showed results similar to Test Example 1, with no insulation effect observed. This suggests that a foam label sheet thickness of 0.2 mm or more is preferable. Furthermore, while the thicker the foam label sheet, the better the insulation, and it was clear that moldability deteriorated when the foam label sheet thickness exceeded the cavity thickness, as in Test Example 4.

[0046] Next, when we look at the case where the container body is made of linear polyethylene, it can be seen that Test Examples 7 and 8, which have a foam label sheet, have a better insulating effect than Test Example 6, which does not have a foam label sheet. In particular, it can be seen that Test Example 8 has the same level of insulating properties as the Reference Example.

[0047] As explained above, the container according to the present invention is a container that provides heat insulation based on a different principle from conventional foam insulating paper containers. Furthermore, since the foam label sheet and the container body are made only of olefin-based resin and are integrally molded without the use of adhesive, the container has excellent recyclability. [Explanation of symbols]

[0048] 1 container 11 Container body 12 Foam Label Sheets 60 molds 60A convex mold 60B concave mold 60C Plate Type Die 60D injection port

Claims

1. A container consisting of a foam label sheet and a container body, The foam label sheet is made of only an olefin resin and has a printing layer on one side. The container body is made entirely of olefin-based resin. A container in which the surface opposite the printed layer of the foam label sheet is integrated with the outer surface of the container body.

2. 2. The container of claim 1, wherein the container body is formed by injection molding.

3. A method for manufacturing a container using a mold having a resin injection port in either a concave mold or a convex mold, a placement step of placing a foam label sheet made of an olefin resin formed into an inverted frustum or a cylindrical shape inside the recessed mold; a filling step of filling an olefin-based resin through a resin injection port into a cavity formed between the concave mold and the convex mold; A method for producing a container made only of an olefin-based resin, comprising:

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