JP2024049090A - Packaging - Google Patents

Abstract

[Problem] To provide a package that is improved so that the conditions for heat sealing can be easily adjusted. [Solution] According to the present invention, there is provided a package for storing contents in a sealed state, the package comprising a lid and a container, the lid being formed by stacking a sealant layer, a base layer and a paper layer in this order, the sealant layer being heat-sealed to the container, the base layer being made of a resin, and the melting point of the base layer being higher than the melting point of the sealant layer. The lower of the Young's modulus in the MD direction and the Young's modulus in the TD direction of the material of the base layer may be 800 MPa or more. [Selected Figure] Figure 1

Description

The present invention relates to a packaging body.

Patent Document 1 discloses a technology for hermetically storing the contents by heat welding a lid to a container. The lid is made of a resin film.

JP 2022-106831 A

The inventors of the present application have been conducting intensive research into using a paper lid instead of a resin film, by heat welding the paper lid to the container via a sealant layer. However, a new problem has arisen in that it is difficult to properly adjust the heat welding conditions when carrying out such heat welding.

The present invention was made in consideration of these circumstances, and provides a package that has been improved to make it easier to adjust the heat sealing conditions.

According to the present invention, the following inventions are provided.
[1] A packaging body for storing contents in a sealed state, the packaging body comprising a lid portion and a container, the lid portion being formed by stacking a sealant layer, a base layer and a paper layer in that order, the sealant layer being heat-welded to the container, the base layer being formed from a resin, and the melting point of the base layer being higher than the melting point of the sealant layer.
[2] A packaging body according to [1], wherein the lower of the Young's modulus in the MD direction and the Young's modulus in the TD direction of the material of the base material layer is 800 MPa or more.
[3] The packaging body according to [1] or [2], wherein the packaging body is a packaging body for microwave heating.
[4] The packaging body according to any one of [1] to [3], wherein the base material layer is formed of a polyester-based resin, a polyamide-based resin, or an olefin-based resin.
[5] A packaging body according to any one of [1] to [3], wherein the container is constructed by laminating a paper material layer and a container resin layer, and the sealant layer is heat-welded to the container resin layer.

After extensive research, the inventors discovered that by sandwiching a base layer with a higher melting point than the sealant layer between the paper layer and the sealant layer, it becomes easier to adjust the conditions for heat welding the lid, which led to the completion of the present invention.

The present invention relates to a packaging body for use in a microwave oven, and more particularly to a packaging material for use in a microwave oven according to an embodiment of the present invention. 2A is a plan view of the package 1 of FIG. 1, FIG. 2B is a cross-sectional view taken along line BB in FIG. 2A, and FIG. 2C is an enlarged cross-sectional view showing the region indicated by the dashed line J in FIG. 2B. FIG. 3 is an enlarged view of an area A in FIG. 2 . FIG. 4A is an explanatory diagram of a method for measuring the peel strength Q between the paper material layer 3a and the container resin layer 3b, and FIG. 4B is an explanatory diagram of a method for measuring the peel strength P between the lid portion 2 and the container 3 at the steam exhaust portion 7. FIG. 5A is an oblique view of a cut-out area near the steam exhaust section 7, and FIG. 5B is a view corresponding to FIG. 5A , showing a state in which the area 7c near the steam exhaust section 7 expands as the internal pressure of the packaging body 1 increases. 2 is a perspective view for explaining a manufacturing method of the packaging body 1. FIG. 7A is a perspective view of the seal bar 9 in FIG. 6, and FIG. 7B is an enlarged view of region B in FIG. 7A.

The following describes the embodiments of the present invention. The various features shown in the embodiments below can be combined with each other. In addition, each feature can be an invention independently.

1. Structure of microwave package 1 As shown in Figures 1 to 7, a microwave package 1 according to one embodiment of the present invention is used for storing contents F in a sealed state. This package 1 comprises a lid 2 and a container 3 sealed by the lid 2. The lid 2 is a thin paper sheet. The contents F may be food that contains moisture and can be heated or cooked in a microwave oven, such as a retort food.

1.1. Structure of the container 3 The container 3 is a paper material container formed by laminating a paper material layer 3a and a container resin layer 3b bonded thereto. The paper material layer 3a can be made of a paper material such as pulp. The paper material layer 3a is preferably a pulp mold. A pulp mold is a molded product made of pulp (wood fiber) and can be formed by drawing up pulp dispersed in water in a mold and then drying it. When the container 3 is formed by deep drawing, wrinkles are likely to be formed in the flange portion 5, but with the pulp mold, a container 3 without wrinkles in the flange portion 5 can be formed, so that the welding accuracy of the lid portion 2 to the flange portion 5 is improved. The container resin layer 3b can be made of any resin that can be heat-sealed to the lid portion 2, and can be made of, for example, a polyolefin resin such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or ethylene-propylene block copolymer. The melting point of the container resin layer 3b is determined by the resin material used, but as an example, if low-melting point polypropylene is used, the melting point will be about 143° C. The container resin layer 3b can be bonded to the paper material layer 3a with an adhesive.

The thickness of the paper material layer 3a is, for example, 300 to 1000 μm, and preferably 500 to 800 μm. Specifically, the thickness may be, for example, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, or 1000 μm, or may be within a range between any two of the numerical values exemplified here. The thickness of the container resin layer 3b is, for example, 40 to 160 μm, and preferably 60 to 120 μm. Specifically, the thickness may be, for example, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, or 160 μm, or may be within a range between any two of the numerical values exemplified here.

As shown in Figure 4A, the peel strength Q of the paper material layer 3a and the container resin layer 3b can be obtained by cutting out a flat part of the container 3 with a size of width W (mm) x 100 mm, peeling the paper material layer 3a and the container resin layer 3b at a part 50 mm long from the end to create a test piece 12, gripping the parts 12a and 12b corresponding to the paper material layer 3a and the container resin layer 3b, respectively, with jigs 11a and 11b, and moving the jig 11b upward at 300 mm/min with the jig 11a fixed, dividing the maximum value of the load measured by the width W of the test piece. W is, for example, 5 to 15 mm, specifically, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 mm, and may be within a range between any two of the numerical values exemplified here. The peel strength Q is, for example, 5 to 20 gf/mm, specifically, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 gf/mm, and may be within a range between any two of the values exemplified here.

The container 3 has a container body 4 formed in a concave shape capable of containing the contents F, and an annular flange portion 5 extending outward from the upper end 4a of the container body 4. The flange portion 5 has a heat-sealed portion 6 at which the flange portion 5 and the lid portion 2 are heat-sealed. The heat-sealed portion 6 is annular and is provided around the entire circumference of the flange portion 5. Therefore, the flange portion 5 and the lid portion 2 are heat-sealed at the heat-sealed portion 6, whereby the contents F are sealed within the package 1.

The heat-sealed portion 6 includes a steam exhaust portion 7 for exhausting steam generated by heating the contents F in a microwave oven. The steam exhaust portion 7 is a portion that is more easily peeled off than the other portion 6a of the heat-sealed portion 6, and when the internal pressure of the package 1 increases with heating of the contents F, the lid portion 2 and the flange portion 5 are preferentially peeled off at the steam exhaust portion 7, making it possible to exhaust steam through the steam exhaust portion 7. This configuration prevents steam from leaking from unintended areas and prevents the package 1 from bursting due to failure to exhaust steam.

The steam exhaust section 7 is preferably configured by curving a portion of the heat-sealed section 6 toward the inner edge 5a of the flange section 5. In this case, the steam exhaust section 7 has a substantially V-shape. With such a shape, the peeling force generated as the internal pressure of the package 1 increases tends to be concentrated at the tip A of the steam exhaust section 7, making peeling at the steam exhaust section 7 even easier.

The peel strength P between the lid 2 and the container 3 at the steam exhaust section 7 is preferably 100 to 250 kgf, and more preferably 120 to 220 kgf. If the peel strength P is too low, the timing at which peeling occurs at the steam exhaust section 7 when heated in a microwave oven may be too early, making it difficult to increase the heating effect of the contents, i.e., the heating properties may be poor. If the peel strength P is too high, the internal pressure of the package 1 may be too high before peeling occurs at the steam exhaust section 7, causing the container 3 to deform, or when opening the lid 2 after peeling occurs at the steam exhaust section 7, the paper material layer 3a and the container resin layer 3b may peel off, making it difficult to open. The peel strength P is preferably 120 to 220 kgf. Specifically, the peel strength P is, for example, 100, 105, 110, 115, 120, 125, 130, 133, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 207, 210, 215, 220, 225, 230, 235, 240, 242, 245, or 250 kgf, and may be within a range between any two of the numerical values exemplified here.

The peel strength P can be determined from the maximum load measured when the test piece 10 is cut out to a size of 10 mm x 100 mm from a 10 mm wide section 7h centered on the bisector 7g of the corner on the side of the steam exhaust section 7, which is defined by a pair of line segments S1 connecting the tip A of the steam exhaust section 7 and a pair of bases 7a on the inner edge side of the steam exhaust section 7, so as to include the section between the inner edge 5a and the outer edge 5c of the flange section 5. As shown in FIG. 4B, the test piece 10 is gripped by jigs 11a and 11b at the sections 10a and 10b corresponding to the inside of the container 3 and the lid section 2, respectively, and the jig 11b is moved upward at 300 mm/min with the jig 11a fixed. At this time, peeling of the steam exhaust section 7 progresses from the tip A side.

As shown in FIG. 3, the portion on the tip A side of the first line segment 7e connecting the pair of bases 7a is the steam exhaust section 7. The distance between the tip A and the intersection C of the bisector 7g and the first line segment 7e is, for example, 4 to 10 mm (6.4 mm in this embodiment), specifically, for example, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 mm, and may be within a range between any two of the numerical values exemplified here.

The average line width of the steam exhaust section 7 is preferably smaller than the average line width of the other portions 6a of the heat-sealed portion 6. The average line width of the steam exhaust section 7 is calculated by dividing the area of the portion on the tip A side of the first line segment 7e by the longitudinal length of the steam exhaust section 7. The average line width of the other portions 6a is calculated by dividing the area of the portion on the side farther from the tip A than the base 7a by the longitudinal length of the other portions 6a. In other words, the longitudinal length is the length of the center line in the line width direction. The value of {average line width of the steam exhaust section 7/average line width of the other portions 6a} is, for example, 0.01 to 0.9 (0.20 in this embodiment), preferably 0.05 to 0.5, and more preferably 0.1 to 0.4. Specifically, this value may be, for example, 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, or 0.90, and may be within a range between any two of the numerical values exemplified here, or equal to or less than any of the values.

The average line width of the steam exhaust portion 7 is, for example, 0.5 to 2.0 mm (1 mm in this embodiment), specifically, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 mm, and may be within a range between any two of the numerical values exemplified here.

3, the length of the first line segment 7e connecting the pair of bases 7a is L1, the point where a straight line passing through the tip A and parallel to the first line segment 7e reaches the inner edge of the heat-sealed portion 6 is B, and the length of the second line segment 7f connecting the tip A and point B is L2, then L2/L1 ≧ 1.0 (1.3 in this embodiment). The larger the value of L2/L1 ≧ 1.0, the easier it is for the region 7c adjacent to the steam exhaust portion 7 to expand due to the internal pressure caused by the steam from the contents F, as shown in Figures 5A to 5B, and as a result, the peeling force generated by the increase in the internal pressure of the package 1 is more likely to be concentrated at the tip A of the steam exhaust portion 7, making peeling at the steam exhaust portion 7 even easier. L2/L1 is, for example, 1.0 to 3.0, preferably 1.1 to 1.8, and more preferably 1.2 to 1.6. Specifically, this value may be, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.5, or 3.0, and may be within a range between any two of the numerical values exemplified here, or may be equal to or greater than any of them.

As shown in FIG. 3, the angle between the line segment S1 connecting the tip A and the base 7a and the line segment S2 connecting the base 7a and point B is preferably 91 to 120 degrees (102 degrees in this embodiment). In this case, the peeling force generated with an increase in the internal pressure of the package 1 is more likely to be concentrated at the tip A of the steam exhaust section 7, making peeling at the steam exhaust section 7 even easier. Specifically, this angle is, for example, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, or 120 degrees, and may be within a range between any two of the numerical values exemplified here.

The angle between the pair of line segments S1 connecting the tip A and the base 7a (90 degrees in this embodiment) is preferably 60 to 120 degrees, and more preferably 80 to 110 degrees. Specifically, this angle may be, for example, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 degrees, or may be within a range between any two of the numerical values exemplified here.

It is preferable that the steam exhaust section 7 be curved so that the portion 7b between the tip A and the base 7a is convex toward the outer edge 7d of the steam exhaust section 7. In this case, the distance between the pair of portions 7b narrows near the tip A and the distance between the pair of bases 7a widens, making it easier to peel off the steam exhaust section 7 near the tip A and widening the steam exhaust path after peeling.

It is preferable that the tip A of the steam exhaust part 7 is sharp. In this case, peeling at the tip A becomes even easier.

The heat-sealed portion 6 preferably has a transition portion 8 adjacent to the steam exhaust portion 7, the line width of which gradually narrows toward the steam exhaust portion 7. The transition portion 8 is preferably formed by bringing the inner edge of the transition portion 8 closer to the outer edge of the flange portion 5. In this case, the area 7c adjacent to the steam exhaust portion 7 becomes wider, making peeling at the steam exhaust portion 7 even easier. The transition portion 8 is part of the other portion 6a.

The maximum angle between the outer edge and the inner edge of the transition portion 8 is, for example, 5 to 30 degrees (12 degrees in this embodiment), and preferably 8 to 15 degrees. This maximum value is specifically, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 degrees, and may be within a range between any two of the values exemplified here.

The heat-sealed portion 6 is preferably provided on the flat surface of the flange portion 5. The container 3 is formed from a material that contains paper material such as pulp, but such materials have poor moldability compared to resin, and it may be difficult to form ribs accurately on the flange portion 5. For this reason, by providing the heat-sealed portion 6 on the flat surface of the flange portion 5, it becomes possible to form the heat-sealed portion 6 accurately regardless of the material that constitutes the container 3.

It is preferable that the flange portion 5 has a wide portion 5b. The wide portion 5b is a portion whose width (the distance between the inner edge and the outer edge of the flange portion 5) is wider than the average width of the entire flange portion 5. It is preferable that the steam exhaust portion 7 is provided in the wide portion 5b. This makes it possible to provide the steam exhaust portion 7 without widening the width of the entire flange portion 5 to match the steam exhaust portion 7 or protruding the inner edge 5a of the flange portion 5 toward the inside of the container 3. It is also preferable that the outer edge 5c of the flange portion 5 has a rectangular shape in plan view, the corners of which may be chamfered, and it is preferable that the wide portion 5b is provided at a corner of the rectangle. Note that a plan view means that the microwave oven package 1 is viewed vertically from above.

The flange portion 5 is preferably provided with an inclined portion 5e that slopes downward along the outer edge 5c of the flange portion 5. By providing the inclined portion 5e, the rigidity of the flange portion 5 is increased and the container resin layer 3b of the container 3 is prevented from peeling off from the paper material layer 3a.

1.2. Configuration of the lid 2 The lid 2 is preferably composed of a thin paper sheet having an outer edge of approximately the same size as the outer edge of the flange 5. The lid 2 includes a paper layer 2a, a base layer 2b, and a sealant layer 2c, which are stacked in this order. If the lid 2 and the flange 5 come into close contact at the steam exhaust section 7 after steam is released from the steam exhaust section 7, the inside of the package 1 may become depressurized when the package 1 cools down, causing the package 1 to deform. However, if the lid 2 has heat shrinkability, the lid 2 shrinks, making it difficult for the lid 2 and the flange 5 to come into close contact, and the shrinkage force of the lid 2 warps the flange 5, making it possible to suppress the close contact between the lid 2 and the flange 5.

By making the lid 2 out of paper, it is possible to meet the needs of reducing the environmental impact. There are no limitations on the type of paper material that constitutes the paper layer 2a and its manufacturing method, and various types of packaging paper materials can be used. The paper layer 2a may be a thin paper sheet, for example, with a thickness of about 55 μm. An outer layer such as a printed layer may be laminated on the outer surface of the paper layer 2a.

The base layer 2b is made of a resin. Specifically, the material of the base layer 2b may be a polyester resin such as polyethylene terephthalate, a polyamide resin such as nylon 6, or an olefin resin such as polyethylene or polypropylene. The melting point of the base layer 2b is determined by the type of resin material, and if a mixed resin is used, the melting point is determined by the ratio of the resins.

The sealant layer 2c can be formed of a polyolefin resin such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or ethylene-propylene block copolymer, and more specifically, unstretched polypropylene or linear low-density polyethylene can be used. More preferably, an easy-peel sealant made by mixing polyethylene and polypropylene in a specified ratio can be used. This makes it easier to peel the lid portion 2 from the flange portion 5.

Here, it is also possible to adjust the peel strength by changing the ratio of the resins to be mixed. For example, if the container body 4 is polypropylene, increasing the ratio of polypropylene in the mixed resin can increase the adhesive strength, and decreasing it can increase the peelability. As an example, the ratio may be PP:PE = 3:1, but is not limited to this. When PE is expressed as 1 time and PP is expressed as M times (PP:PE = M:1), this M is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5 or 10, and this M may be a value within the range between any two of the numerical values exemplified here. The melting point of the sealant layer 2c is determined according to the type of resin material and its mixing ratio.

The melting point of the base layer 2b is higher than that of the sealant layer 2c. In this way, it was found that by sandwiching the base layer 2b, which has a higher melting point than the sealant layer 2c, between the paper layer 2a and the sealant layer 2c, it becomes easier to adjust the conditions when heat welding the lid portion 2. The base layer 2b prevents the paper layer 2a from participating in the welding, and prevents the paper layer 2a from tearing.

If the difference between the melting point of the base layer 2b and the melting point of the sealant layer 2c is ΔT _MP , this ΔT _MP is, for example, 10 to 150° C., preferably 20 to 140° C., and more preferably 40 to 110° C. Specifically, ΔT _MP is, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150° C., and may be within a range between any two of the numerical values exemplified here.

For example, when nylon is used, the melting point of the base material layer 2b is about 221° C. When the sealant layer 2c is a mixed resin layer of PE and PP with a mixing ratio of PP:PE=3:1, for example, the melting point of the sealant layer 2c is about 154° C. In this case, ΔT _MP is about 67° C.

There is no limit to the thickness of the lid portion 2, and there is no limit to the thickness of each layer constituting the lid portion 2. If half of the total weight of the lid portion 2 is made up of paper, the lid portion 2 as a whole is treated as a paper material. As an example, if the entire lid portion 2 has a weight of 100 g/ ^m2 , it is preferable to use a paper material of 50 to 80 g/ ^m2 for the paper layer 2a. For example, the thickness of the paper layer 2a may account for 50% or more of the thickness of the lid portion 2.

The thickness of the paper layer 2a is, for example, 10 to 100 μm, and preferably 40 to 60 μm. Specifically, the thickness may be, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 μm, or may be within a range between any two of the values exemplified here.

The thickness of the base layer 2b is, for example, 5 to 80 μm, and preferably 10 to 40 μm. Specific examples of the thickness of the base layer 2b are 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 μm, and may be within a range between any two of the numerical values exemplified here.

The thickness of the sealant layer 2c is, for example, 5 to 80 μm, and preferably 10 to 40 μm. Specifically, the thickness of the sealant layer 2c may be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80 μm, or may be within a range between any two of the values exemplified here.

To prevent tearing of the lid portion 2, it is preferable that the Young's modulus of the base material layer 2b is relatively high. Specifically, as an example, the lower of the Young's modulus in the MD direction and the Young's modulus in the TD direction of the base material layer 2b is preferably 800 MPa or more. This lower Young's modulus is, for example, 400 to 5000 MPa, and preferably 600 to 3000 MPa. Specifically, this lower Young's modulus may be, for example, 400, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 3000, 3200, 3400, 3600, 3800, 4000, 4200, 4400, 4600, 4800, or 5000 MPa, or may be within a range between any two of the values exemplified here.

2. Manufacturing Method of Microwave Oven Package 1 As shown in Figure 6, microwave oven package 1 can be manufactured by placing lid 2 on flange 5 with container 3 filled with content F, and then pressing seal bar 9 against lid 2 to form heat-sealed portion 6. Lid 2 may be prepared in advance by any manufacturing method, and may be prepared, for example, by adhering sheets or films constituting each layer by dry lamination or the like and cutting them to the specified dimensions.

As shown in FIG. 7, the seal bar 9 is provided with a protrusion 9a that is shaped to correspond to the shape of the heat-sealed portion 6. The heated protrusion 9a is pressed against the lid 2. This allows the sealant layer 2c of the lid 2 and the flange 5 to be heat-sealed. Various conditions such as the temperature and time for pressing during this welding process are set in advance so as to obtain a good seal. The presence of the base layer 2b has the effect of preventing the lid 2 and the container 3 from being overly welded even if the sealing temperature is high or the sealing time is long, which has the advantage of making it easier to adjust the conditions during welding.

As a modified example, the container 3 may be made of resin instead of paper. As another modified example, the steam exhaust section 7 may not be provided. In that case, as one example, the lid section 2 may be partially peeled off to allow the inside of the container 3 to be exposed to the outside air, and then the package 1 may be heated in a microwave oven. Note that the package 1 and its modified examples may be provided for purposes other than microwave heating.

1. Manufacturing of Example Sample and Comparative Example Sample The Example Sample and Comparative Example Sample were manufactured with the same structure and manufacturing method, except that the lid portion 2 has a base layer 2b. For both samples, 1.5 g of paper sheet and 8.5 g of water were placed in a container 3 (dimensions: 110 mm x 180 mm x 30 mm) made of a paper material having a shape shown in Figure 6, and then the lid portion 2 was welded to the flange portion 5 of the container 3 under multiple sealing conditions (temperature and time) shown in Table 1 to obtain a package 1 having a shape shown in Figures 1 to 5. The lid portion 2 was welded using a seal bar 9 shown in Figures 6 and 7.

In the example sample, the layer structure of the container 3 and the lid portion 2 is as follows.
Container 3: Paper material layer 3a (pulp: 650 μm) / container resin layer 3b (PP: 80 μm)
Lid 2: Paper layer 55 μm/DL/Base material layer (Ny: 15 μm)/DL/Sealant layer (PE and PP mixed resin: 30 μm)

In the example sample, the three-layer structure of the lid portion 2 is bonded with a dry laminate (DL), and the thickness of the DL layer is negligible. The material of the base material layer 2b is nylon (manufactured by Mitsubishi Chemical Corporation, grade ST), and its melting point is 220.7°C. The sealant layer 2c is CMPS (registered trademark) manufactured by Mitsui Chemicals Tohcello Co., Ltd., and is a mixed resin of PE and PP. The melting point of the sealant layer 2c is 153.95°C. This value is calculated based on the melting point of PP of 162.4°C and the melting point of PE of 125.0°C, assuming a mixture ratio of PP:PE = 3:1. The difference ΔT _MP between the melting point of the base material layer 2b and the melting point of the sealant layer 2c is 66.75°C. The base material layer 2b has a melting point 60°C or more higher than the sealant layer 2c.

In the comparative sample, the container 3 and the lid portion 2 have the following layer configurations: The comparative sample is the same as the example sample, except that the base layer is removed from the lid portion 2.
Container 3: Paper material layer 3a (pulp: 650 μm) / container resin layer 3b (PP: 80 μm)
Lid 2: Paper layer 55 μm / sealant layer (PE and PP mixed resin: 30 μm)

Explaining the sealing conditions shown in Table 1, the conditions for samples No. 1 to 6 were such that the sealing time was constant (1.5 seconds) and the sealing temperature was varied. Conversely, the conditions for samples No. 7 to 12 were such that the sealing temperature was constant (150°C) and the sealing time was varied. In Table 1, the example samples are No. 1 to 3 and No. 7 to 9, and the comparative example samples are No. 4 to 6 and No. 10 to 12.

2. Opening test After the heating test, the sample was removed from the microwave oven and left at room temperature for 1 minute, and then the lid 2 was grasped at the wide portion 5b where the steam exhaust portion 7 is provided, and the lid 2 was slowly peeled off. A test was then performed to visually observe the state of the lid. The same test was performed on 12 samples, and based on the results, each sample was scored according to the following criteria to evaluate the ease of opening in three stages.

The scoring criteria are as follows:
1: Not sealed at all.
2: There was a small amount of stickering.
3: The seal was excellent.
4: The adhesive surface turned white.
5: The lid was torn.

Each score corresponds to the following three-level rating:
◯: Good seal (score 3).
△: Weak but sealed (score 2).
x: The seal was too strong or there was no seal at all (scores 1, 4, and 5).

First, looking at samples No. 1 to 6, in the examples, sample No. 3, which had a high sealing temperature, was rated as ○. However, in the comparative examples, sample No. 6, which had a high sealing temperature (160°C), was rated as ×. Next, looking at samples No. 7 to 12, in the examples, sample No. 9, which had a long sealing time, was rated as ○. However, in the comparative examples, sample No. 12, which had a long sealing time (2.0 seconds), was rated ×. Thus, in the examples, even if the sealing temperature was high or the sealing time was long, the lid 2 and the container 3 were not excessively welded together, and whitening of the adhesive surface or tearing of the lid material did not occur when the product was opened.

Looking at example samples No. 1 and No. 7, even samples with a lower sealing time (140°C) or a shorter sealing time (1.0) received a rating of △ equivalent to the comparative example. It was found that with the configuration of the example, even though the layer configuration is increased due to the presence of base layer 2b, welding equivalent to the comparative example can be performed even if the sealing temperature is lower or the sealing time is shorter.

As described above, the embodiment has the advantage of making it easier to adjust the conditions during heat welding.

3. Burst Strength Test The seal strength was measured when the lid 2, which had been opened halfway, was pulled toward the unopened side. The seal width was 3 mm. The higher the sealing temperature and the longer the sealing time, the higher the seal strength. In order to avoid the seal strength being too weak in the case of microwave heating, the seal strength is preferably 2.0 N or more.

1: Microwave oven package 2: Lid 2a: Paper layer 2b: Base layer 2c: Sealant layer 3: Container 3a: Paper material layer 3b: Container resin layer 4: Container body 4a: Top end 5: Flange 5a: Inner edge 5b: Wide portion 5c: Outer edge 5e: Inclined portion 6: Heat-sealed portion 6a: Region 7: Steam exhaust portion 7a: Base 7b: Region 7c: Region 7d: Outer edge 7e: First line segment 7f: Second line segment 7g: Bisector 7h: Region 8: Transition portion 9: Seal bar 9a: Protruding portion 10: Test piece 10a: Region 10b: Region 11a: Jig 11b: Jig 12: Test piece 12a: Region 12b: Region A: Tip C: Intersection F: Contents S1: Line segment S2: Line segment

Claims (5)

A package for storing contents in a sealed state, comprising:
The packaging body includes a lid and a container,
The lid portion is formed by stacking a sealant layer, a base layer, and a paper layer in this order,
the sealant layer is heat welded to the container;
The base layer is formed of a resin,
A packaging body, wherein the base layer has a melting point higher than the melting point of the sealant layer. 2. The packaging of claim 1,
The packaging body, wherein the lower of the Young's modulus in the MD direction and the Young's modulus in the TD direction of the base material layer is 800 MPa or more. The packaging body according to claim 1 or 2,
The package is a package for microwave heating. The packaging body according to claim 1 or 2,
The packaging body, wherein the base layer is formed from a polyester-based resin, a polyamide-based resin, or an olefin-based resin. The packaging body according to claim 1 or 2,
The container is constructed by laminating a paper material layer and a container resin layer,
The sealant layer is heat-sealed to the container resin layer.