airtight container

Abstract

The lid material, which is heat-sealed to the container body having a flange portion, provides a sealed container that combines both excellent ease of opening and airtightness without causing the edges to peel off. [Solution] A sealed container comprising a container body having a flange portion and a lid material welded to the flange portion by heat sealing, wherein the container flange portion and the lid material are welded at the inner circumferential welding portion and the outer circumferential welding portion of the flange portion, a non-adhered portion is formed between the outer circumferential edge of the inner circumferential welding portion and the inner circumferential edge of the outer circumferential welding portion, and the outer circumferential welding portion is formed by a distributed region consisting of a sealed portion and an unsealed portion.

Description

Technical Field

[0001] The present invention relates to a sealed container comprising a container having a flange portion and a lid material welded to the flange portion by heat sealing. More specifically, the present invention relates to a sealed container that is excellent in sealing performance and easy opening property, and effectively prevents the end of the lid material from curling.

Background Art

[0002] A sealed container formed by heat-sealing a flexible lid material to a flange portion is widely used for foods and drinks, etc. as a container with excellent storage properties for the contents due to its high sealing performance. In such a sealed container, when opening the container, it is necessary to have an easy opening property that allows the lid material to be easily peeled off and removed, and also to have a sealing performance that is not impaired even when subjected to heat sterilization treatment such as retort sterilization, when the internal pressure increases, or when subjected to a dropping impact, etc. It is required to have contradictory performances of an easy opening property that allows easy start of opening from the outside of the container and a high sealing performance that does not easily peel off from the inside of the container.

[0003] As such a sealed container, for example, in Patent Document 1 below, an easy-opening container is formed by heat-sealing a lid body provided with a heat-sealing layer on its inner surface, with the heat-sealing layer facing the peripheral edge of the opening of the container body. A sealing material is adhered to the upper surface of the peripheral edge of the opening so that an unadhered portion or a weakly adhered portion is formed on the inner side of the container, and the heat-sealing layer of the lid body and the sealing material are adhered with an adhesion strength weaker than the adhesion strength of the portion excluding the unadhered portion or the weakly adhered portion between the sealing material and the peripheral edge of the opening. An easy-opening container characterized by heat-sealing the lid body to the peripheral edge of the opening is described.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, as described in Patent Document 1 above, if an unbonded or weakly bonded portion is provided on the outer edge of the flange portion, the lid material made of flexible film may peel from the outer edge of the lid material, causing the end of the lid material to break or curl, which may impair the appearance of the product. Furthermore, if such peeling occurs, there is a risk of unintended opening from a point other than the opening point, or opening by misidentifying the opening point, which may prevent proper opening. In recent years, containers that can be heated in a microwave oven while remaining sealed have also been put into practical use. However, with the aforementioned easy-open containers, it is difficult to properly release the internal pressure that rises due to microwave heating.

[0006] Therefore, the object of the present invention is to provide a sealed container in which a lid material, which is heat-sealed to a container body having a flange portion, does not peel off at the edges and possesses both excellent ease of opening and sealing properties. [Means for solving the problem]

[0007] According to the present invention, a sealed container is provided comprising a container body having a flange portion and a lid material welded to the flange portion by heat sealing, wherein the container flange portion and the lid material are welded at an inner circumferential welding portion and an outer circumferential welding portion of the flange portion, a non-adherent portion is formed between the outer circumferential edge of the inner circumferential welding portion and the inner circumferential edge of the outer circumferential welding portion, and the outer circumferential welding portion is formed by a distributed region consisting of a sealed portion and an unsealed portion.

[0008] In the sealed container of the present invention, (1) The distribution region is a distribution region in which unsealed portions are distributed within a continuous seal portion, or a distribution region in which sealed portions are distributed within a continuous unsealed portion. (2) The inner and outer edges of the inner circumferential welded portion are formed with an inner circumferential resin mass and an outer circumferential resin mass, respectively. (3) The inner circumferential resin mass is larger than the outer circumferential resin mass. (4) At least the uppermost surface of the flange portion of the container body is made of an easily peelable heat-sealable resin layer. This is preferable. [Effects of the Invention]

[0009] In the sealed container of the present invention, the welded portion, which is the joint portion with the lid material formed on the upper surface of the container flange portion, is welded at two locations: an inner circumference welded portion and an outer circumference welded portion of the flange portion. As a result, airtightness is ensured at the inner circumference welded portion, and the outer circumference welded portion, which has a distributed area consisting of a sealed portion and an unsealed portion, effectively prevents the edges of the lid material from peeling, while also providing easy opening. Furthermore, by having a non-adhesive portion between the inner and outer welded portions, and in conjunction with the outer welded portion having an unsealed portion, it becomes possible to slowly release steam generated during microwave heating to the outside of the container. This effectively prevents the container from bursting, not only when partially opened, but also when microwave heating is performed while the container is completely sealed, even if the internal pressure rises excessively. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of an example of a sealed container of the present invention. [Figure 2] This diagram illustrates the welded portion in section X of the sealed container shown in Figure 1. [Figure 3] This is a schematic cross-sectional view showing the YY section in Figure 2. [Figure 4] This diagram illustrates an example of a heat seal head used for forming an inner circumferential weld. [Modes for carrying out the invention]

[0011] The sealed container of the present invention will be described with reference to the attached drawings. Figure 1 is a perspective view showing an example of a sealed container of the present invention, Figure 2 is a diagram illustrating the welded portion in part X of Figure 1, and Figure 3 is a schematic cross-sectional view showing the YY section of Figure 2. As is clear from Figure 1, the sealed container of the present invention consists of a container and a lid material 10, which are represented as a whole by 1. The container 1 consists of a bottom portion 2 and a side wall 3, and a flange portion 4 extending horizontally from the upper end of the side wall 3. At least the uppermost surface of the flange portion 4 has a heat-sealable heat-seal layer 5a that can be heat-sealed with the heat-seal layer of the lid material 10, which will be described later. In the specific example shown in the figure, as is clear from Figure 3, it is equipped with at least an easily peelable heat-seal layer 5a and a base resin layer 5b. As a result, when opening the sealed container, cohesive failure occurs in the easily peelable heat-seal layer 5a or interfacial delamination occurs between it and the base resin layer 5b, making it easy to open. The lid material 10 consists of a laminate having at least a heat-seal layer 11a on the side facing the flange portion of the container 1. In the specific example shown in the figure, the laminate 10 constituting the lid material has a two-layer structure with a flexible base film 11b, but is of course not limited to this.

[0012] As is clear from Figures 2 and 3, a key feature of the sealed container of the present invention is that the welded portion between the flange portion 4 and the lid material 10 consists of two welded portions: an inner circumferential welded portion 20 located on the inner circumference side of the flange portion 4, and an outer circumferential welded portion 21 located at a certain distance from the outer edge of the inner circumferential welded portion 20, with the area between the inner circumferential welded portion 20 and the outer circumferential welded portion 21 being formed as an unwelded, non-adhesive portion 22. In other words, in the present invention, in addition to the inner circumferential welding portion 20 which securely welds the lid material to the container flange portion to ensure the airtightness of the sealed container, an outer circumferential welding portion 21 is formed on the outer circumferential side of the flange portion, extending to near the outer edge of the flange portion, thereby effectively preventing the edges of the lid material from peeling off.

[0013] Furthermore, since the outer peripheral welded portion 21 is formed by a distributed region consisting of a sealed portion 21a and an unsealed portion 21b, it is more firmly welded than when the entire outer peripheral welded portion is welded as a weakly adhesive sealed portion. However, because it has an unsealed portion, the adhesive strength is weaker than that of the inner peripheral welded portion, and peeling from the edges mentioned above can be effectively prevented without compromising ease of opening. Moreover, even when the internal pressure increases due to microwave heating, the sealed portion easily peels off towards the outer peripheral end of the flange, making it possible to easily release the internal pressure. Furthermore, in areas where the outer peripheral welding portion 21 is not formed up to the outer peripheral edge of the flange portion 4, the flange portion 4 and the lid material 10 are not adhered to each other, making it easy to grasp only the lid material 10, thus forming the opening start portion 23. Furthermore, because a non-adhesive portion 22 is formed between the inner circumferential welded portion 20 and the outer circumferential welded portion 21, even if steam generated by rising internal pressure leaks from the inner circumferential welded portion 20, this steam can be temporarily contained in the non-adhesive portion 22, and the seal portion of the outer circumferential welded portion 21 can easily peel off to form an internal pressure release path, thereby effectively preventing the container from rupturing.

[0014] In the sealed container of the present invention, the heat sealing of the lid material to the container flange is performed with the inner circumferential welding portion 20 being fully welded and the outer circumferential welding portion 21 being welded in a distributed area, resulting in different welding patterns. Therefore, it is desirable to form these in separate processes under different heat sealing conditions. Generally, heat sealing is performed by pressing and heating the lid material from the lid material side with a heat sealing head (not shown) while the lid material is placed on the flange. As shown in Figure 3, the upper surface of the inner circumferential welding portion 20 is recessed downwards, and inner circumferential resin lumps 20a and outer circumferential resin lumps 20b are formed at the inner and outer ends of the inner circumferential welding portion 20, respectively, due to the pressure applied to the flowing resin. That is, the inner peripheral resin mass 20a has the container-side heat seal layer 5a and the lid material-side heat seal layer 11a integrally adhered thereto. When the internal pressure rises, the lid material 10 moves in the vertical direction, and cohesive failure of the easily peelable heat seal layer 5a is suppressed, thus improving the pressure resistance. On the other hand, the outer peripheral resin mass 20b has the container-side heat seal layer 5a and the lid material-side heat seal layer 11a integrally adhered thereto. At the time of opening, the lid material 10 moves and follows in the flange direction integrally, so that it becomes possible to promote the cohesive failure of the easily peelable heat seal layer 5a, improving the easy opening property.

[0015] Also, in the outer peripheral welding portion 21, a distribution region having a sealed portion 21a and an unsealed portion 21b is formed. Since the outer peripheral welding portion has an unsealed portion, the sealing force is reduced, and as a whole, the sealing force of the welding portion is weaker than that of the inner peripheral welding portion 20. As described above, the easy opening property is not impaired. Further, the sealed portion 21a in the outer peripheral welding portion 21 does not have a weak adhesive force as in the prior art. By forming the sealed portion 21a up to the edge of the flange portion 4, it is possible to effectively prevent the lid material 10 from being turned up from the end portion. Furthermore, in the pattern shown in FIG. 2, when the unsealed portion 21b forms a continuous phase and the sealed portion 21a is formed in this continuous phase, an internal pressure release path is formed in the outer peripheral welding portion, so that the internal pressure can be easily released. Also, in addition to the patterns shown in the figure, for example, when the sealed portion 21a forms a continuous phase and has a distribution in which the unsealed portion 21b is formed in this continuous phase, when the internal pressure rises and pressure is applied to the boundary portion between the non-adhesive portion 22 and the outer peripheral welding portion, the pressure propagates to the unsealed portion 21b and an internal pressure release path is easily formed in the outer peripheral welding portion. As a result, the vapor generated in the container can be slowly released from the edge of the flange portion, and the rupture of the container can be effectively prevented.

[0016] In the sealed container of the present invention, the inner peripheral side welding part, non-sealing part, and outer peripheral side welding part formed on the flange part depend on the sealing strength of the inner peripheral side welding part and the outer peripheral side welding part. When the shape of the opening part of the container is rectangular, based on the width of the flange part other than the corner part, it is preferable that the inner peripheral side welding part is in the range of 5 to 40%, the non-sealing part is in the range of 5 to 90%, and the outer peripheral side welding part is in the range of 10 to 90%. Thereby, it becomes possible to obtain both the reliable sealing property (pressure resistance) and the easy-opening property of the sealed container. The width of each of the inner peripheral side welding part, non-sealing part, and outer peripheral side welding part is not particularly limited. However, in order to slowly release the steam to the outside of the container, it is preferable that the width of the outer peripheral side welding part is larger than the width of the inner peripheral side welding part, and the width of the non-sealing part is larger than the width of the inner peripheral side welding part. The relationship between the width of the outer peripheral side welding part and the width of the non-sealing part is not particularly limited. Preferably, at the corner part of the flange, the width of the outer peripheral side welding part is larger than the width of the non-sealing part. By adopting such a form, even when the internal pressure is locally concentrated at the corner part due to deformation of the container or the like, the occurrence of rupture or the like of the sealed container can be effectively prevented.

[0017] In addition, the inner peripheral side resin mass and the outer peripheral side resin mass formed on the inner peripheral side welding part described above can be formed by pressing a heat seal head from above at the location where the inner peripheral side welding part is formed. However, as shown in FIG. 4, by using a heat seal head 30 having a curved surface at the inner peripheral side corner part 31 and a pressing surface 32 that slopes upward in the outer peripheral direction, it becomes possible to form an inner peripheral side resin mass larger than the outer peripheral side resin mass. Since a larger resin mass is formed on the inner peripheral side, the heat seal layer 5a is less likely to be cohesively broken, so the pressure resistance is improved. In addition, the formation of resin masses on the outer peripheral side also improves the easy-opening property. Furthermore, due to the presence of the non-adhesive part 22, the heat seal layer 5a easily flows toward the non-adhesive part side. Therefore, combined with the presence of the above-mentioned upwardly inclined pressing surface, the formation of resin masses on the outer peripheral side resin mass becomes easy, and the easy-opening property is improved.

[0018] In the specific example shown in the figure, the sealed and unsealed portions formed in the outer peripheral welding area had a knurled pattern in which the unsealed portion was a continuous phase and the sealed portion was a dispersed phase, but of course, it is not limited to this pattern. As mentioned above, the sealed portion may be a continuous phase and the unsealed portion a dispersed phase, or various distribution areas can be formed, such as a pattern in which the sealed and unsealed portions are formed alternately radially, or a checkerboard pattern. The area ratio of the sealed portion to the unsealed portion in the outer peripheral welded portion varies depending on the seal strength obtained by the sealed portion and cannot be specified in general terms. However, it is preferable that the area ratio of the sealed portion to the outer peripheral welded portion (seal area ratio) is in the range of 0.5 to 95%, and particularly 1 to 50%. In the sealed container of the present invention, it is preferable that the seal strength of the inner circumferential welded portion is in the range of 5 to 40 N / 15 mm, and the seal strength of the outer circumferential welded portion is in the range of 2 to 30 N / 15 mm. This makes it possible to achieve both airtightness (pressure resistance) and ease of opening of the sealed container.

[0019] (container) In the sealed container of the present invention, the container is a flanged container in which a flange is formed around the entire circumference of the opening, and its shape is not limited to that of a tray with a rectangular opening as shown in the figure, but can also be a cup with a circular opening or various other shapes of containers. Furthermore, the method of molding the container is not particularly limited. While a flanged container can be easily integrally molded by thermoforming such as plug-assisted pressure forming using a resin sheet, the method is not limited to this. Conventional known flanged containers, such as a cup-shaped container with a flange attached separately, can also be used. Furthermore, while there are no material limitations for the container as long as a heat-seal layer is formed on at least the uppermost surface of the flange, it is preferable that the container be made of a laminate comprising a heat-seal layer, a base resin layer, a gas barrier layer, and an oxygen-absorbing layer, in order to particularly improve the preservation of the contents.

[0020] The base resin layer can be made from resins that have been conventionally used as packaging materials, such as olefin resins and polyester resins. Examples include, but are not limited to, polyethylenes such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and linear ultra-low-density polyethylene (LVLDPE); olefin resins such as polypropylene, ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer, and ion-crosslinked olefin copolymer (ionomer); and polyester resins such as polyethylene terephthalate and polybutylene terephthalate. In particular, since it is desirable to have heat resistance that can withstand heat and pressure sterilization treatments such as retort sterilization, polypropylene and polyethylene terephthalate can be suitably used.

[0021] The gas barrier layer can be made of a conventionally known gas barrier resin. Suitable gas barrier resins include ethylene vinyl alcohol copolymer (EVOH) and polyamide resins. Examples of polyamide resins include xylylene group-containing polyamides such as nylon 6, nylon 6,6, nylon 6 / 6,6 copolymer, nylon 6,10, nylon 11, nylon 12, nylon 13, metaxylylene adipamide, and metaxylylene sevacamide, with ethylene vinyl alcohol copolymer being particularly suitable.

[0022] The oxygen-absorbing layer is preferably made of a conventionally known oxygen-absorbing resin composition in which an iron-based oxygen absorbent containing reduced iron is contained in the base resin. The iron-based oxygen absorbent can be one that is known in itself, and one containing reduced iron and metal halides is preferably used. When an iron-based oxygen absorbent is used as the oxygen absorbent layer, it is preferable that the base resin layer contains a white pigment to conceal it.

[0023] The heat seal layer can use any conventionally known heat sealable resin without limitation, as long as it can be heat-sealed with the heat seal layer of the lid material described later. However, as mentioned above, it is preferable that the heat seal layer itself has easy peelability, so a blend made by appropriately combining two or more heat-sealable but mismatched thermoplastic resins can be suitably used. For example, when the base resin layer is made of a propylene polymer, the heat seal layer can be made of a blend of an ethylene polymer and a propylene polymer to ensure airtightness while maintaining easy opening, and the peel strength can be adjusted by appropriately changing the blending ratio of the blended materials.

[0024] Examples of the above-mentioned propylene-based polymers include homopolypropylene, as well as block copolymers and random copolymers of propylene with ethylene or other α-olefins, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Examples of the above-mentioned ethylene-based polymers include homopolymers of ethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and medium- and high-density polyethylene (MDPE, HDPE), or copolymers of ethylene with other α-olefins such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene, or vinyl monomers such as (meth)acrylic acid, ethyl (meth)acrylate, methyl (meth)acrylate, vinyl acetate, and styrene, or ionomers. In addition to combinations of the olefin polymers mentioned above, blends can also be made using thermoplastic polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and copolymers thereof modified with isophthalates, as well as combinations of polycarbonate resins, polyacrylonitrile resins, etc., with the olefin polymers mentioned above.

[0025] To facilitate the layer structure, it is preferable that the heat seal layer itself has easy peelability, but it is not limited to this. Even if the heat seal layer does not have easy peelability, if an easily peelable resin layer capable of exhibiting easy peelability is further formed between the heat seal layer and the base resin layer, the same effects as when the heat seal layer has easy peelability can be achieved.

[0026] (lid material) The lid material can be of any form as long as it is heat-sealed to the container flange. In addition to the sheet-like lid material shown in the figure, conventionally known lid materials such as molded lids with a flange can be used. However, in the sealed container of the present invention, the presence of a welded portion on the outer circumference effectively prevents the edges of the lid material from peeling, so a flexible sheet-like lid material is preferably used as the lid material. The lid material can be made from conventionally known sheets, as long as it has a heat-seal layer on the portion facing the container flange, and can consist of a single layer of heat-sealable resin. However, similar to the container, it is preferable to include a barrier layer or the like from the viewpoint of improving the preservation of the contents. Examples of such a barrier layer include a layer made of the gas barrier resin mentioned above, or a metal foil such as aluminum foil or a vapor-deposited layer.

[0027] (Sealing method) As described above, in the sealing method for the sealed container of the present invention, since the welding pattern and seal strength differ between the inner circumferential welding portion and the outer circumferential welding portion, it is preferable to perform these in separate processes. In other words, it is preferable to place the lid material on the container flange, then form the inner circumferential welding portion, and then form the outer circumferential welding portion. The sealing conditions cannot be defined in general terms, as they depend on the materials of the container and lid used, as well as the thickness and width of the heat seal layer. However, when ethylene propylene copolymer is used as the heat seal layer on the container side and a propylene polymer is used as the heat seal layer on the lid side, the sealing conditions for the inner circumferential weld are preferably 160-240°C with pressure heating for 0.8-3.0 seconds. For the outer circumferential weld, in the knurling pattern shown in Figure 2, the knurling is preferably performed at a peak temperature of 160-240°C for 0.8-3.0 seconds. [Examples]

[0028] (Containers and lids) A multilayer sheet (base resin layer: 470 μm, heat seal layer: 30 μm) was formed by co-extruding polypropylene as the base resin layer and ethylene propylene copolymer as the heat seal layer. A container (flanged tray) of the following dimensions was then formed using a vacuum pressure forming machine with plug assist. Flange outer diameter: Long axis 153mm x Short axis 121mm Caliber: Long axis 137mm x Short axis 105mm Bottom outer diameter: Long axis 90mm x Short axis 57mm Height: 33mm As the lid material, a barrier film (87 μm thick) made by dry laminating silica vapor-deposited film and unoriented polypropylene film was used.

[0029] (Example 1) After filling the above container with water, the lid material was placed and fixed to the flange portion. Heat sealing was performed for 1.0 second at 200°C using the heat sealing head shown in Figure 4 so that the width of the inner circumference welded portion was 2 mm. Then, heat sealing was performed for 1.0 second at 200°C using a knurling tool with a sealing area ratio of 4% so that the width of the outer circumference welded portion was 2 mm from the flange edge, thereby creating a sealed container with an outer circumference welded portion formed around the entire circumference. Note that one corner was left without an outer circumference welded portion and designated as the opening point.

[0030] (Examples 2-3) A sealed container was prepared in the same manner as in Example 1, except that a knurling tool with a sealing area ratio of the values ​​shown in Table 1 was used.

[0031] (Example 4) A sealed container was created in the same manner as in Example 1, except that the width of the welded portion on the outer circumference of the long and short sides of the flange was 2 mm from the flange edge, the width of the welded portion on the outer circumference of the corner was 8 mm from the flange edge, and the width of the unsealed portion was 2 mm, thus achieving a predetermined seal area ratio. When the sealed container was heated in a microwave oven, steam escaped from the corner of the flange.

[0032] (Comparative Example 1) A sealed container was prepared in the same manner as in Example 1, except that a welded portion was not formed on the outer circumference.

[0033] (Comparative Example 2) A sealed container was prepared in the same manner as in Example 1, except that the outer periphery was heat-sealed at a temperature of 200°C for 1.0 second using a known heat-sealing bar to completely weld the surface (100% of the sealed area).

[0034] (Evaluation of sealing performance) The resulting sealed containers were evaluated for leakage using the JIS Z 0238 drop strength test. The results are shown in Table 1. ○: Items that were not leaked. ×: Items that were missing

[0035] (Evaluation of ease of opening) The resulting sealed containers were opened by lifting the lid from the opening point, and their ease of opening was evaluated. The results are shown in Table 1. ◎: Easy to open ○: Easy to open △: Somewhat difficult to open ×: Difficult to open

[0036] (Evaluation of lid material curl suppression) The edges of the lid material of the obtained sealed containers were visually evaluated. The results are shown in Table 1. ◎: Best ○: Good △: Partially curled ×: Curly

[0037] (Ventilation properties) The resulting sealed containers were heated in a 600W microwave oven for 2 minutes, and the amount of steam generated was visually evaluated to see if it was released outside the container. The results are shown in Table 1. ○: Steam is released slowly. ×: Steam is released rapidly

[0038] [Table 1] [Explanation of Symbols]

[0039] 1 container, 2 bottom, 3 side wall, 4 flange, 5a heat seal layer, 5b base resin layer, 10 lid material, 11a heat seal layer, 11b base film, 20 inner circumference welded part, 20a inner circumference resin mass, 20b outer circumference resin mass, 21 outer circumference welded part, 21a sealed part, 21b unsealed part, 22 non-adhesive part, 23 opening start part.

Claims

1. In a sealed container comprising a container body having a flange portion and a lid material that is heat-sealed to the flange portion, The container flange and the lid material are welded together at the inner and outer circumferential welding portions of the flange, and a non-adhesive portion is formed between the outer edge of the inner circumferential welding portion and the inner edge of the outer circumferential welding portion. A sealed container characterized in that the outer peripheral welded portion is formed by a distributed region consisting of a sealed portion and an unsealed portion.

2. The sealed container according to claim 1, wherein the distribution structure is a distribution region in which unsealed portions are distributed within a continuous sealed portion, or a distribution region in which sealed portions are distributed within a continuous unsealed portion.

3. The sealed container according to claim 1 or 2, wherein an inner circumferential resin mass and an outer circumferential resin mass are formed on the inner circumferential edge and outer circumferential edge of the inner circumferential welding portion, respectively.

4. The sealed container according to claim 3, wherein the inner circumferential resin mass is larger than the outer circumferential resin mass.

5. The sealed container according to claim 1 or 2, wherein at least the uppermost surface of the flange portion of the container body is made of an easily peelable heat-sealable resin layer.

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