Container and laminated sheet

Abstract

To provide a container and a laminated sheet that can compatibly have preferable opening and sealing properties while decreasing joining strength between a sealant and a container body covering a resin reservoir.SOLUTION: A container comprises a lid body which is joined to a container body in a joining region to form an internal space, the container body consists of a laminate at least including a first layer and a second layer joined to the first layer to face a joint region, and the lid body consists of a laminate at least including a third layer facing the joint region and a fourth layer joined to the third layer, wherein the second layer is a cohesion failure layer and the third layer is a layer formed of a resin composition consisting principally of polypropylene resin. Here, the cohesion strength of the cohesion failure layer is lower than the inter-layer joint strength between the first layer and second layer and between the third layer and fourth layer, and the resin composition forming the second layer includes 10 mass% or more and 69 mass% or less of polypropylene resin.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a container and a laminated sheet. [Background technology]

[0002] In recent years, refrigerated or frozen foods packaged in containers have been cooked by heating them directly in a microwave oven. In such containers for food or the like that are made up of a container body and a lid, it is not easy to achieve both the hermeticity of the container and the ease of opening, i.e., the ease of peeling the lid from the container body when opening. This is because increasing the bonding strength between the container body and the lid improves the hermeticity but decreases the ease of opening, and conversely, decreasing the bonding strength improves the ease of opening but decreases the hermeticity. Various techniques have been proposed to solve this problem.

[0003] For example, Patent Document 1 describes a technique for forming a lump-shaped resin pool in the surface layer of the container body and the seal layer of the lid near the inner periphery of the joining area when the flange of the container body and the lid are heat-sealed. By forming such a resin pool and making the surface layer of the container body a cohesive failure layer, a container that is both sealable and easy to open can be manufactured. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-102081 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, for containers to be used for microwave heating or for retort sterilization, the contents become hot when heated, so it is preferable to use a film using a polypropylene resin such as non-oriented polypropylene (CPP), which has better heat resistance than polyethylene (PE) resin, as a sealant as a lid. However, when a polypropylene resin is used to form the lump-shaped resin pool described in Patent Document 1, the sealant completely covers the resin pool, inhibiting the progress of peeling, and thus a deterioration in the feeling of opening is confirmed.

[0006] Therefore, an object of the present invention is to provide a container and a laminated sheet that can achieve both suitable openability and sealability while reducing the bonding strength between the sealant covering the resin reservoir and the container body. [Means for solving the problem]

[0007] [1] A container comprising a container body including a recess and a flange portion formed along the periphery of the recess and extending outward from the periphery, and a lid body joined to the container body at a joining region formed on the flange portion to form an internal space between the container body and the recess, wherein the container body is made of a laminate including at least a first layer and a second layer joined to the first layer and facing the joining region, the lid body is made of a laminate including at least a third layer facing the joining region and a fourth layer joined to the third layer, the second layer is a cohesive failure layer and the third layer is a layer formed of a resin composition mainly composed of a polypropylene-based resin, the cohesive strength of the cohesive failure layer is weaker than the interlayer bonding strength between the first layer and the second layer and between the third layer and the fourth layer, and the resin composition forming the second layer has a polypropylene-based resin ratio of 10% by mass or more and 69% by mass or less. [2] The container described in [1], wherein at least a portion of the inner periphery of the bonding region is formed with a first resin reservoir portion made of resin forming the first layer and the second layer and having a hump-shaped cross-section inclined toward the recess, and a second resin reservoir portion made of resin of the third layer and located closer to the recess than the first resin reservoir portion and covering the first resin reservoir. [3] The container described in [1] or [2], wherein at least a portion of the outer periphery of the bonding region is formed with a third resin reservoir portion having a hump-shaped cross-section made of resin forming the first layer and the second layer and inclined toward the outer periphery of the bonding region, and a fourth resin reservoir portion having a hump-shaped cross-section made of resin of the third layer and positioned closer to the outer periphery of the bonding region than the third resin reservoir portion. [4] The container according to [3], wherein the third resin reservoir portion and the fourth resin reservoir portion are formed in a portion excluding a portion of the circumferential direction of the bonding region. [5] The container according to any one of [1] to [4], wherein the crystallization temperature of the polypropylene-based resin forming the third layer is 90°C or higher and 140°C or lower. [6] The container according to any one of [1] to [5], wherein the melting point of the polypropylene-based resin forming the third layer is 130°C or higher and 175°C or lower. [7] The container according to any one of [1] to [6], wherein the polypropylene-based resin forming the third layer is a block polypropylene. [8] The container described in any one of [1] to [7], wherein the thickness of the cohesive failure layer is 5 μm or more and 300 μm or less. [9] The container described in any one of [3] to [8], wherein in a portion where the third resin reservoir portion and the fourth resin reservoir portion are not formed on the outer periphery of the bonding region, the radius of curvature R of the concave curved surface formed from the position where the second layer is most compressed toward the internal space is 0.10H or more and 1.00H or less, where H is the width at which the second layer and the third layer contact, and in a portion where the third resin reservoir portion and the fourth resin reservoir portion are formed on the outer periphery of the bonding region, the radius of curvature R is 0.15H or more and 1.50H or less.

[10] A laminate sheet comprising: a surface layer which is a cohesive failure layer and has a resin composition containing a polypropylene-based resin and a polyethylene-based resin, the resin composition having a ratio of the polypropylene-based resin of 10% by mass or more and 69% by mass or less; and a first base layer adjacent to the surface layer and containing a polypropylene-based resin and a polyethylene-based resin.

[11] The laminate sheet according to

[10] , wherein the surface layer contains a polyethylene resin.

[12] The laminate sheet according to

[10] or

[11] , further comprising a second base material layer containing a polypropylene-based resin in addition to the surface layer and the first base material layer.

[13] The laminated sheet includes a recess and a flange portion formed along a periphery of the recess and extending outward from the periphery, and is joined to the lid body at a joining region formed on the flange portion. A laminate sheet used to form a container body, wherein the surface layer becomes a cohesive failure layer when joined to the lid body, as described in any one of

[10] to

[12] .

[14] The laminate of the container body is a laminate sheet described in any one of

[10] to

[13] , and is provided with a degassing mechanism formed in the non-bonded area of ​​the lid body, the degassing mechanism including an opening formed in the lid body and a sealing film covering the opening. The container described in any one of [1] to [9].

[15] The container described in

[14] , wherein the degassing mechanism includes a non-penetrating notch formed in the lid body.

[16] The container described in

[14] or

[15] , wherein the degassing mechanism includes a heating element arranged in contact with the lid.

[17] A container described in any one of

[14] to

[16] , wherein the lid body includes at least two parts, and the degassing mechanism includes an unjoined portion or a notch formed in a seal portion that joins the two parts to each other.

[18] A container as described in any one of [2] to [9] or any one of

[14] to

[17] , wherein a vapor passage portion is formed in the joining region, which can connect the internal space to an external space when the internal pressure of the internal space increases, and the vapor passage portion does not have the first resin reservoir portion and the second resin reservoir portion formed on the inner peripheral side of the joining region, and does not have the third resin reservoir portion and the fourth resin reservoir portion formed on the outer peripheral side of the joining region. Effect of the Invention

[0008] According to the container and laminate sheet of the present invention, the resin composition forming the surface layer has a polypropylene-based resin ratio of 10% by mass or more and 69% by mass or less, which makes it possible to achieve both suitable openability and sealability while reducing the bonding strength between the sealant covering the resin reservoir and the container body. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a container according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the container shown in FIG. [Diagram 3] FIG. 2 is a partial cross-sectional view of the container shown in FIG. [Figure 4] FIG. 11 is a partial cross-sectional view of a container according to a conventional example. [Diagram 5] 2 is a diagram showing a method of forming a resin reservoir portion in a partial cross section of the container shown in FIG. 1. [Figure 6] FIG. 2 is a partial cross-sectional view of the container shown in FIG. [Figure 7] 2 is a diagram showing a method of forming a resin reservoir portion in a partial cross section of the container shown in FIG. 1. [Figure 8] 4 is a graph showing the results of DSC measurement of a resin composition forming a polypropylene-based resin layer of a third layer. [Figure 9] 4 is a graph showing the results of DSC measurement of a resin composition forming a polypropylene-based resin layer of a third layer. [Figure 10A] FIG. 2 is a diagram showing a first example of a degassing mechanism provided on a lid of a container in one embodiment of the present invention. [Figure 10B] FIG. 2 is a diagram showing a first example of a degassing mechanism provided on a lid of a container in one embodiment of the present invention. [Figure 11A] 6A and 6B are diagrams showing a second example of a degassing mechanism provided on the lid of the container in one embodiment of the present invention. [Figure 11B] 6A and 6B are diagrams showing a second example of a degassing mechanism provided on the lid of the container in one embodiment of the present invention. [Figure 12] 6A and 6B are diagrams showing a second example of a degassing mechanism provided on the lid of the container in one embodiment of the present invention. [Figure 13] 11 is a diagram showing a third example of a degassing mechanism provided on the lid of the container in one embodiment of the present invention. FIG. [Figure 14A] 11 is a diagram showing a third example of a degassing mechanism provided on the lid of the container in one embodiment of the present invention. FIG. [Figure 14B] 11 is a diagram showing a third example of a degassing mechanism provided on the lid of the container in one embodiment of the present invention. FIG. [Figure 15] FIG. 2 is a schematic cross-sectional view showing a first configuration example of a laminate. [Figure 16] FIG. 4 is a schematic cross-sectional view showing a second configuration example of a laminate. [Figure 17] FIG. 11 is a schematic cross-sectional view showing a third configuration example of the laminate. [Figure 18] FIG. 11 is a schematic cross-sectional view showing another example of the third configuration example of the laminate. [Figure 19] 10A to 10C are diagrams illustrating a manufacturing process of a laminate according to a third configuration example. [Figure 20] FIG. 2 is a plan view of a container used for measuring the seal strength and puncture pressure strength according to an embodiment of the present invention. [Figure 21] 1 is a graph showing the relationship between puncture pressure strength and sealing temperature. [Figure 22] 1 is a graph showing the measurement results of the initial opening strength when heat-sealed at a sealing pressure of 240 kgf. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and duplicated explanations will be omitted.

[0011] In this specification, the main component of the resin composition forming each layer of the laminate means the resin component with the highest content among the resin compositions forming that layer. Therefore, the resin composition may contain other components in addition to the main component. The main component can be confirmed, for example, by an IR method. In this specification, the content of the component of the resin composition forming each layer of the laminate is expressed in mass% relative to the entire resin composition forming that layer, unless otherwise specified.

[0012] (Overall configuration of container and manufacturing method) FIG. 1 is a perspective view of a container 100 according to an embodiment of the present invention. As shown in FIG. 1(A), the container 100 includes a container body 110 and a lid 130. The container body 110 has a substantially circular planar shape, and includes a cup-shaped recess 111 and a flange portion 112 formed along the periphery of the recess 111 and extending outward from the periphery. The lid 130 is a film-like member that covers the opening of the recess 111, and is joined to the container body 110 at an annular joining region 140 formed on the flange portion 112 using heat sealing, ultrasonic sealing, or the like to form an internal space SP between the lid 130 and the recess 111. The lid 130 includes a tab 130A formed by extending from the periphery of the flange portion 112 of the container body 110.

[0013] FIG. 2 is a plan view of the container 100 shown in FIG. 1. As shown in the figure, an inner resin reservoir 120 is formed on the inner periphery side of the annular joining region 140, and an outer resin reservoir 125 is formed on the outer periphery side of the joining region 140. Here, the outer resin reservoir 125 is not formed in a part of the circumferential direction of the joining region 140, specifically, in the unsealable portion 141, and is generally C-shaped. In this way, the inner resin reservoir 120 is formed on the inner periphery side, but the outer resin reservoir 125 is not formed in at least a part of the circumferential direction on the outer periphery side, thereby improving the sealing property of the container 100 and, as shown in FIG. 2(B), when opening, the lid material in the joining region 140 can be easily opened at the unsealable portion 141. In addition, the joining region 140 may be formed with a vapor passage portion (not shown) that can communicate the internal space SP with the external space when the internal pressure of the internal space SP increases. In the vapor passage portion, the inner resin reservoir 120 is not formed on the inner circumferential side of the bonding region 140, and the outer resin reservoir 125 is not formed on the outer circumferential side of the bonding region 140 either.

[0014] FIG. 3 is a partial cross-sectional view of the container 100 shown in FIG. 1. FIG. 3 is a cross-sectional view of the opening portion 141 along the line III-III shown in FIG. 2, where (A) shows the state before the opening portion 141 is broken, and (B) shows the state after the opening portion 141 is broken. In the illustrated example, the container body 110 is formed by forming a laminate 114 including a base layer 114A, a subsurface layer 114B, and a surface layer 114C into a shape including a recess 111 and a flange portion 112 by vacuum forming or pressure forming. The base layer 114A is located on the outside of the container body 110 and exerts rigidity required to maintain the shape of the container body 110. The subsurface layer 114B is located between the base layer 114A and the surface layer 114C and is bonded to each layer. The surface layer 114C is located on the inside of the container body 110, i.e., on the side facing the internal space SP, and faces the bonding area 140 formed in the flange portion 112.

[0015] Here, the base material layer 114A and the undersurface layer 114B of the laminate 114 are formed of a resin including at least one of the group consisting of, for example, an olefin-based resin, a polystyrene-based resin, and a polyester-based resin. Examples of the olefin-based resin include polypropylene and polyethylene. Examples of the polyester-based resin include polyethylene terephthalate (PET). For example, the rigidity is different between the base material layer 114A and the undersurface layer 114B. An inorganic filler such as talc may be added to the base material layer 114A to improve the rigidity.

[0016] On the other hand, the surface layer 114C of the laminate 114 preferably contains homopolypropylene (HPP) from the viewpoint of improving the appearance after heating, but may contain polypropylene such as metallocene catalyst-based random polypropylene, polyethylene such as low-density polyethylene, etc., other than HPP. The ratio of polypropylene-based resin contained in the surface layer 114C is preferably 10% by mass to 69% by mass, more preferably 40% by mass to 68% by mass, and even more preferably 55% by mass to 65% by mass. The thickness of the surface layer 114C is preferably 5 μm to 300 μm, and more preferably 10 μm to 50 μm, in order to form a resin pool.

[0017] In the illustrated example, the laminate 114 includes three layers, a base layer 114A, a subsurface layer 114B, and a surface layer 114C, but in other examples, the laminate 114 may include additional layers. For example, the laminate 114 may include a plurality of base layers and an adhesive layer (not shown) that bonds the base layers when high rigidity is required. The adhesive layer is formed of, for example, a urethane-based elastomer, a styrene-based elastomer, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, or ethylene vinyl acetate (EVA). The laminate 114 may also include a gas barrier layer that blocks oxygen and the like. The gas barrier layer may be an oxygen barrier layer. The oxygen barrier layer is a layer that has oxygen barrier properties, and can suppress oxidative deterioration of the contents when used as a container. Examples of materials used for the oxygen barrier layer include ethylene vinyl alcohol copolymer resin (EVOH), MX nylon (MXNy), polyvinylidene chloride resin (PVDC), polyacrylonitrile resin (PAN), etc., and one of these may be used alone or two or more may be used in combination. The oxygen barrier layer can also be formed by a coating method, and examples of materials that can be used in this case include coating materials selected from the group consisting of inorganic materials such as silica, alumina, aluminum, and silicon nitride, organic materials such as polyvinyl alcohol (PVA), and organic-inorganic hybrid materials such as silica / PVA.

[0018] The lid 130 is made of a film-like laminate 131 including an outer layer 131A and a sealing layer 131B. The outer layer 131A is located on the front side of the lid 130, i.e., on the side that does not face the container body 110, and exhibits the flexibility and tensile strength required for the lid 130. The outer layer 131A is formed of, for example, a polyethylene terephthalate (PET) film or a biaxially oriented nylon film (O-Ny). On the other hand, the sealing layer 131B is located on the back side of the lid 130, i.e., on the side facing the container body 110, and faces the joining region 140 formed in the flange portion 112. The sealing layer 131B is a layer formed of a resin composition mainly composed of a polypropylene-based resin. The crystallization temperature of the polypropylene-based resin is 90°C or higher and 140°C or lower, or the melting point of the polypropylene-based resin is 130°C or higher and 175°C or lower. For example, it is preferable to use block polypropylene (BPP), but random polypropylene (RPP) may also be used. In the container 100, the outer layer 131A and the sealing layer 131B are bonded to each other. Note that in other examples, the laminate 131 may also include additional layers.

[0019] The crystallization temperature of polypropylene, which is the main component of the resin composition forming the seal layer 131B of the lid 130, is preferably 90°C or higher and 140°C or lower in order to achieve both easy peeling and resin pool formation, and is more preferably 95°C or higher and 135°C or lower, and even more preferably 104°C or higher and 130°C or lower, in terms of both easy opening and suitable resin pool formation. Furthermore, the melting point of the polypropylene is preferably 130°C or higher and 175°C or lower in order to achieve both easy peeling and resin pool formation, and is more preferably 135°C or higher and 172°C or lower, and even more preferably 144°C or higher and 170°C or lower, in terms of both easy opening and resin pool formation. By using polypropylene with a relatively high crystallization temperature or melting point of the resin composition for the seal layer 131B, the bonding strength between the sealant covering the resin pool and the container body can be suppressed, making it easier to peel the lid 130 from the container body 110.

[0020] Here, in the container 100, the cohesive strength of the surface layer 114C of the laminate 114 is weaker than the bonding strength between the lid 130 and the container body 110 in the bonding region 140, weaker than the cohesive strength of each layer other than the surface layer 114C constituting the laminate 114 and the laminate 131, and weaker than the interlayer bonding strength between each layer of the laminate 114 and the laminate 131. In other words, when the subsurface layer 114B is the first layer, the surface layer 114C is the second layer, the seal layer 131B is the third layer, and the outer layer 131A is the fourth layer, the cohesive strength of the second layer is weaker than the bonding strength between the lid 130 and the container body 110, the cohesive strength of the first layer, the third layer, and the fourth layer, and the interlayer bonding strength between the first layer and the second layer and between the third layer and the fourth layer. Furthermore, the seal layer 131B of the lid 130 may also be a cohesive layer, in which case the cohesive strength of the seal layer 131B may be equal to or weaker than the cohesive strength of the surface layer 114C of the container body 110. In this way, by making the surface layer 114C a cohesive failure layer, the container 100 can be easily opened. Furthermore, by selecting polypropylene for use as the polypropylene-based resin of the surface layer 114C as described above, the container 100 can be easily opened. In this specification, the cohesive strength means the strength exerted by the intermolecular force (cohesive force) that binds the resins constituting each layer of the laminates 114, 131. It can be confirmed that the cohesive strength of the surface layer 114C, which is a cohesive failure layer, is weaker than the interlayer bonding strength between the subsurface layer 114B and the surface layer 114C and between the seal layer 131B and the outer layer 131A, because the container body 110 and the lid 130 can be opened by peeling them off from the outer periphery side due to cohesive failure.

[0021] Further, as shown in FIG. 3, a first resin reservoir 121 and a second resin reservoir 122 are formed at the edge of the bonding region 140 on the recess 111 side. The first resin reservoir 121 has a nodular cross section made of resin forming the surface underlayer 114B and the surface layer 114C of the laminate 114. The second resin reservoir 122 is made of resin forming the seal layer 131B of the lid 130, and is located closer to the recess 111 than the first resin reservoir 121, and covers the first resin reservoir 121. As shown in the figure, the surface layer 114C is formed along the surface of the first resin reservoir 121 and passes through the gap between the first resin reservoir 121 and the second resin reservoir 122. In the following description, the first resin reservoir 121 and the second resin reservoir 122 are also collectively referred to as resin reservoir 120.

[0022] Next, the operation of opening the container 100 will be described. The user can start opening the container 100 by pinching the tab 130A of the lid 130 that extends outward beyond the flange portion 112 and peeling off the lid 130 from this tab as shown in FIG. 3(A). As described above, the cohesive strength of the surface layer 114C is weaker than the bonding strength between the lid 130 and the surface layer 114C in the bonding region 140, the cohesive strength of each layer of the laminate 114 and the laminate 131 other than the surface layer 114C, and the interlayer bonding strength between each layer of the laminate 114 and the laminate 131. Therefore, when the user peels off the lid 130, the surface layer 114C pulled by the lid 130 in the bonding region 140 is cohesively broken. As a result, a part of the surface layer 114C is peeled off together with the lid 130, and the remaining part of the surface layer 114C remains on the surface sublayer 114B side. When the user further peels off the lid body 130, as shown in FIG. 3B, the cohesive failure of the surface layer 114C stops at the resin reservoir 120, and only the lid body 130 is peeled off from there. This is because the cohesive failure of the surface layer 114C progresses along the shape of the first resin reservoir 121 in the resin reservoir 120. The surface layer 114C is pulled from both sides and breaks near the edge 140E of the bonding area 140 where the surface of the first resin reservoir 121 and the surface of the second resin reservoir 122 are separated from each other, and moves away from the lid body 130 together with the second resin reservoir 122. In addition, if the cohesive strength of the seal layer 131B is equal to or weaker than the cohesive strength of the surface layer 114C, the first resin reservoir 121 and the second resin reservoir 122 break, and the lid body 130 is peeled off.

[0023] Here, a container according to a conventional example will be described with reference to FIG. 4. FIG. 4 is a partial cross-sectional view of a container according to a conventional example, in which (A) shows the state before the opening part is broken, and (B) shows the state when the opening part is broken. In the illustrated example, the container body 910 is formed by forming a laminate 914 including a base layer 914A, a surface underlayer 914B, and a surface layer 914C into a shape including a recess and a flange part (not shown) by vacuum forming or pressure forming. The base layer 914A is located on the outside of the container body 910 and exerts the rigidity required to maintain the shape of the container body 910. The surface underlayer 914B is located between the base layer 914A and the surface layer 914C and is bonded to each layer. The surface layer 914C is located on the inside of the container body 910, i.e., on the side facing the internal space SP, and faces the bonding area 940 formed in the flange part 912. The lid 930 is made of a film-like laminate 931 including an outer layer 931A and a seal layer 931B. The outer layer 931A is located on the front side of the lid 930, i.e., on the side not facing the container body 910, and provides the flexibility and tensile strength required for the lid 930. A first resin reservoir 921 and a second resin reservoir 922 are formed on the edge of the bonding region 940 on the recess side, and the second resin reservoir 922 covers the first resin reservoir 921. The first resin reservoir 921 and the second resin reservoir 922 are also collectively referred to as resin reservoir 920.

[0024] In the container according to the conventional example, the surface layer 914C contains a polypropylene-based resin, and the ratio of the polypropylene-based resin contained in the surface layer 914C is 70 mass % or more. As shown in FIG. 4B, when a user peels off the lid 930 of the container according to the conventional example, the surface layer 914C pulled by the lid 930 undergoes cohesive failure in the bonding region 940, but the surface layer 914C and the seal layer 931B cannot be peeled off in the resin reservoir portion 920, which inhibits the progress of peeling. Therefore, the opening feeling when peeling off the lid 930 from the container body 910 is not good.

[0025] In contrast to the container according to the conventional example, the container 100 according to the present embodiment described with reference to FIG. 3 can peel the surface layer 114C and the seal layer 131B at the resin reservoir 120 as described above, and the lid 130 can be peeled off from the container body 110 together with the second resin reservoir 122. When the ratio of polypropylene-based resin contained in the surface layer 114C is high, the bonding strength between the surface layer 114C and the seal layer 131B is high. Therefore, in the present embodiment, the bonding strength between the surface layer 114C and the seal layer 131B is reduced by reducing the ratio of polypropylene-based resin contained in the surface layer 114C. In addition, by using polypropylene having a relatively high crystallization temperature or melting point of the resin composition for the seal layer 131B of the lid 130, the bonding strength between the sealant covering the resin reservoir and the container body can be suppressed, and the lid 130 can be easily peeled off from the container body 110.

[0026] In this way, by weakening the cohesive strength of the surface layer 114C of the laminate 114 and suppressing the bonding strength between the surface layer 114C and the seal layer 131B in the resin reservoir 120, the user can peel off the lid 130 with less force when opening, making it easier to open. On the other hand, before opening, when the container body 110 and the lid 130 are bonded to each other and the internal pressure of the internal space SP increases, stress is concentrated near the base of the first resin reservoir 121 on the recess 111 side in the bonding region 140, so that the peeling is prevented by the resin bump formed by the surface underlayer 114B that does not undergo cohesive failure during the peeling process, and it is possible to resist high internal pressure. In this way, the container 100 according to this embodiment can achieve both ease of opening and resistance to internal pressure.

[0027] 5 is a diagram showing a method for forming the resin reservoir 120 in a partial cross section (cross section along line III-III in FIG. 2) of the container 100 shown in FIG. 1. As shown in FIG. 5, the manufacturing process of the container 100 includes a step of joining the lid 130 and the container body 110 by heat sealing using an annular sealing plate 601. Here, the annular sealing plate 601 includes an inner inclined surface 602 facing the inner peripheral side of the joining region 140 formed in the flange portion 112 of the container body 110, i.e., the edge portion on the recess 111 side, and an outer inclined surface 603 spreading outward from the inner inclined surface 602. The inner inclined surface 602 may be a convex curved surface.

[0028] The radius of curvature of the inner inclined surface 602 of the annular seal plate 601 is preferably 0.5 or more in the portion corresponding to the opening portion 141 in order to form a resin reservoir, more preferably 0.8 or more, and even more preferably 1.05 or more. H shown in FIG. 5 is the width where the surface layer 114C and the seal layer 131B contact each other by heat sealing. At this time, the radius of curvature R of the concave curved surface formed from the most compressed position of the surface layer 114C toward the internal space SP of the container heat-sealed in the section where the resin reservoir is formed only on the inner periphery side of the bonding region 140 is preferably 0.10H or more and 1.00H or less, more preferably 0.12H or more and 0.85H or less, and even more preferably 0.15H or more and 0.70H or less.

[0029] 5 and 7 described later, when the annular sealing disk 601 descends from the upper side in the figure, the portion in contact with the inner inclined surface 602 and the outer inclined surface 603 comes into contact with the lid body 130 before the other portions. The order in which the annular sealing disk 601 comes into contact with the lid body 130 is not limited to the above and may vary depending on the shape of the annular sealing disk 601. At the portion where the inner inclined surface 602 and the outer inclined surface 603 abut, heat is applied from the annular sealing plate 601 to the resin forming the lid 130 and the container body 110, and the lid 130 and the container body 110 are joined by heat sealing. At this time, at the edge portion on the inner periphery side of the joining region 140, the resin forming the undersurface layer 114B and the surface layer 114C of the container body 110, which are melted by the applied heat, and the resin forming the seal layer 131B of the lid 130 are pushed out by the inner inclined surface 602 toward the recess 111 to form the first resin reservoir 121 and the second resin reservoir 122.

[0030] When the sealing layer 131B is mainly composed of a polypropylene component such as block polypropylene (BPP), the resin pool is not formed unless the sealing temperature is relatively high. Therefore, it is important to be able to form the resin pool at a lower temperature by devising the shape of the annular sealing disk 601 as described above. When a PET-based resin is selected as the resin in contact with the annular sealing disk 601, the upper limit of the sealing temperature is about 230°C in order to prevent the lid material from becoming rough. In actual production, there is a possibility that the sealing temperature may become lower than the set temperature due to changes in the outside air temperature or the contents becoming contaminated by the flange. Therefore, if the resin pool is only formed at the upper sealing temperature, there is a high possibility that a container in which the resin pool is not formed will be produced as production continues. By devising the shape of the annular sealing disk so that the resin pool can be formed at a low temperature, even if the sealing conditions fluctuate during actual production, a container that has both suitable openability and sealability can be manufactured.

[0031] FIG. 6 is a partial cross-sectional view taken along line VI-VI of the container 100 shown in FIG. 1. As shown in the figure, the inner resin reservoir 120 described above is formed on the inner periphery side of the annular bonding region 140, and the outer resin reservoir 125 is formed on the outer periphery side of the bonding region 140. The outer resin reservoir 125 includes a third resin reservoir 123 and a fourth resin reservoir 124. The third resin reservoir 123 has a hump-shaped cross section made of the resin forming the surface underlayer 114B and the surface layer 114C of the laminate 114. The fourth resin reservoir 124 is made of the resin forming the seal layer 131B of the lid 130, and has a hump-shaped cross section located on the outer periphery side of the bonding region 140 relative to the third resin reservoir 123. The inner resin reservoir 120 is formed to be able to resist the internal pressure of the internal space SP, and the outer resin reservoir 125 is formed to be able to resist the force of opening the container 100 from the outside. Therefore, while it is difficult to open the container 100 in the areas other than the tearable portion 141 shown in the figure, the outer resin reservoir portion 125 is not formed in the tearable portion 141, making it easy to open.

[0032] FIG. 7 is a diagram showing a method for forming the resin reservoirs 120, 125 in a partial cross section (cross section along line VI-VI in FIG. 2) of the container 100 shown in FIG. 1. As shown in FIG. 7, the manufacturing process of the container 100 includes a step of joining the lid 130 and the container body 110 by heat sealing using an annular sealing plate 701. Here, the annular sealing plate 701 includes an inner inclined surface 702 facing the inner peripheral side of the joining region 140 formed in the flange portion 112 of the container body 110, i.e., the edge portion on the recess 111 side, and an outer inclined surface 703 spreading outward from the inner inclined surface 702. H shown in FIG. 7 is the width where the surface layer 114C and the seal layer 131B come into contact with each other by heat sealing. In this case, the radius of curvature R of the concave curved surface formed from the most compressed position of the surface layer 114C toward the internal space SP is preferably 0.15H or more and 1.50H or less, more preferably 0.20H or more and 1.35H or less, and even more preferably 0.25H or more and 1.20H or less.

[0033] In the above manufacturing process, when the annular sealing disk 701 descends from the upper side in the figure, the pressure of the inner inclined surface 702 and the outer inclined surface 703 that come into contact with the lid body 130 becomes greater than the pressure of the inner inclined surface 602 and the outer inclined surface 603 of the annular sealing disk 601. Therefore, by heat sealing, the resin that forms the molten undersurface layer 114B and surface layer 114C of the container body 110 and the seal layer 131B of the lid body 130 is pushed out to the inner and outer circumferential sides of the bonding region 140, forming the inner resin reservoir 120 and the outer resin reservoir 125.

[0034] 8 and 9 are graphs showing the results of differential scanning calorimetry (DSC) of the resin composition forming the polypropylene-based resin layer. The peak of the DSC curve is defined in JIS K7121 as "the part from when the curve leaves the baseline to when it returns to the baseline again", and the baseline is defined as "the temperature region (omitted) DSC curve where no transition or reaction occurs in the test piece". In other words, the peak is the temperature region from when the transition or reaction begins to occur after the DSC curve reaches the baseline once, until it no longer occurs. Using "Diamond DSC" manufactured by PerkinElmer Japan, a test piece of the resin composition was isothermally held at 0°C for 5 minutes, and then heated to 220°C at 10.00°C / min (1st Run), and the melting temperature at the peak position was measured according to the definition of the peak as described above from the DSC curve. After the first run, the sample was isothermally held at 220°C for 5 minutes, and then cooled from 220°C to 0.00°C in 10.00°C minutes. The crystallization temperature at the peak position was measured from the DSC curve according to the definition of the peak as described above, and the results are shown in Figure 8.

[0035] As described above, when a polypropylene-based resin having a crystallization temperature peak in a DSC curve of 90°C or more and 140°C or a polypropylene-based resin having a 1st run peak of 130°C or more and 175°C or less is used for the layer adhered to the cohesive failure layer, it is possible to achieve both favorable openability and sealability.

[0036] (Configuration of degassing mechanism) 10A and 10B are diagrams showing a first example of a degassing mechanism 150 provided in the lid 130 of the container 100 in one embodiment of the present invention. The degassing mechanism 150 in the container 100 shown in FIG. 1 is a degassing mechanism 150A according to this first example. The degassing mechanism 150A includes an opening 151 formed in the lid 130 and a sealing film 152 covering the opening 151. In the example of FIG. 10A, the sealing film 152 is bonded to the outside of the opening 151 by heat welding or adhesive, and in the example of FIG. 10B, the sealing film 152 is bonded to the internal space SP side of the opening 151 by heat welding or adhesive. For example, by forming the sealing film 152 from a film having a lower strength than the lid 130, when the pressure of the internal space SP increases due to water vapor generated by heating the contents, the sealing film 152 can be broken before other parts of the lid 130 or the joint region 140 are broken, and water vapor can be stably discharged.

[0037] 11A, 11B, and 12 are diagrams showing a second example of a degassing mechanism 150 provided in the lid 130 of the container 100 in one embodiment of the present invention. In the illustrated example, the degassing mechanism 150B includes a non-penetrating cut 153 formed in the lid 130. In the example of FIG. 11A, the cut 153 is formed from the outside, and in the example of FIG. 11B, the cut 153 is formed from the internal space SP side. In this case, when the pressure in the internal space SP increases due to water vapor generated by heating the contents, the part of the lid 130 whose strength is reduced due to the cut 153 is broken before other parts of the lid 130 or the joint region 140 are broken, and water vapor can be stably discharged. Alternatively, as shown in FIG. 12, a notch 153 may be formed from the internal space SP side at a position close to the bonding area 140, and when the pressure in the internal space SP rises, the interlayer adhesion of the laminate 131 forming the lid body 130 (for example, the adhesion between the outer layer 131A and the sealing layer 131B of the laminate 131 in the example of FIG. 3) may be destroyed through the notch 153, allowing water vapor to be discharged from the end of the lid body 130 beyond the bonding area 140.

[0038] 13, 14A and 14B are diagrams showing a third example of a degassing mechanism 150 provided in the lid 130 of the container 100 in one embodiment of the present invention. In the illustrated example, the lid 130 is made up of two parts 130B and 130C. These parts are joined together by a seal part 132 using heat sealing, ultrasonic sealing or an adhesive, but in the part of the degassing mechanism 150C, an unjoined part 154 as shown in FIG. 14A or a cut 155 as shown in FIG. 14B is provided in the seal part 132. In either case, in the degassing mechanism 150C, the unjoined part 154 or the cut 155 narrows the joint width of the seal part 132. Therefore, when the pressure in the internal space SP increases due to water vapor generated by heating the contents, the part of the degassing mechanism 150C where the bonding width of the sealing portion 132 is narrowed due to the unbonded portion 154 or the notch 155 is broken before other parts of the lid body 130 or the bonding area 140 are destroyed, and the water vapor can be discharged stably.

[0039] As another example, the degassing mechanism 150 may include a heating element disposed in contact with the lid 130. The heating element is, for example, an element that generates heat when microwaves from the microwave oven are concentrated, and may be, for example, a member such as a metal foil or a film having a metal-deposited portion bonded to at least a part of the lid 130, or may be, for example, a paint containing metal powder that is applied to the lid 130, or may be a metal-deposited surface of the lid 130. Examples of such heating elements that can be used include aluminum, nickel, and chromium.

[0040] The container 100 according to one embodiment of the present invention has a puncture pressure strength sufficient to withstand the generation of steam inside. By providing the above-mentioned degassing mechanism 150 in such a container 100, high pressure can be maintained with the inside of the container 100 filled with steam, improving cooking efficiency. For example, when the pressure of the container 100 is set to 0.0196 MPa, the temperature inside the container 100 filled with steam rises to 102.5°C instead of 100°C, and the heating time can be shortened by approximately 17%.

[0041] (Example of laminate structure) Next, a configuration example of the laminate forming the container body 110 in one embodiment of the present invention will be described. In the following description, the main component of the resin composition forming each layer of the laminate means the resin component with the highest content among the resin compositions forming that layer. Therefore, the resin composition may contain other components in addition to the main component. The main component can be confirmed by, for example, an IR method. In the following description, the content of the component of the resin composition forming each layer of the laminate is expressed as mass% with respect to the entire resin composition forming that layer, unless otherwise specified.

[0042] FIG. 15 is a schematic cross-sectional view showing the structure of a laminate 10 according to one embodiment of the present invention. As shown in FIG. 15, the laminate 10 has a surface layer 11, subsurface layers 12 and 15, and base layers 13 and 14. When the laminate 10 is associated with the laminate 114 shown in FIG. 3, the surface layer 11 corresponds to the surface layer 114C, the subsurface layers 12 and 15 correspond to the subsurface layer 114B, and the base layers 13 and 14 correspond to the base layer 114A. The configuration of each layer will be described below. The laminate 10 is formed to a thickness suitable for forming a container 100 as described later, specifically, a thickness of 0.3 mm or more and 1.2 mm or less, but is not limited to this example.

[0043] The surface layer 11 is a layer that is joined to the lid 130 by heat sealing or the like when the laminate 10 is molded into the container 100 described later. Specifically, the surface layer 11 is formed of a resin composition mainly composed of polypropylene. The resin composition forming the surface layer 11 (hereinafter also referred to as the first resin composition) preferably contains homopolypropylene (HPP) from the viewpoint of improving the appearance after heating, but may contain polypropylene such as metallocene catalyst-based random polypropylene, polyethylene such as low-density polyethylene, and the like other than HPP. The ratio of polypropylene-based resin contained in the surface layer 114C is preferably 10% by mass or more and 69% by mass or less.

[0044] The base material layers 13 and 14 are laminated on the opposite side of the surface layer 11 to the undersurface layer 12, and are formed of a resin including at least one of the group consisting of an olefin resin, a polystyrene resin, and a polyester resin. Examples of the olefin resin include polypropylene and polyethylene. Examples of the polyester resin include polyethylene terephthalate (PET). The base material layers 13 and 14 may be added with an inorganic filler such as talc to improve rigidity. An oxygen barrier layer including an ethylene vinyl alcohol resin such as ethylene-vinyl alcohol copolymer (EVOH) may be added between the base material layers 13 and 14. The oxygen barrier layer is the same as that included in the laminate 114 shown in FIG. 3, and therefore a detailed description thereof will be omitted.

[0045] At least a part of the polypropylene-based resin may be a biomass-derived polypropylene-based resin (biopolypropylene). Biopolypropylene can be obtained, for example, by fermenting the molasses of sorghum, a non-edible plant, with microorganisms to generate an intermediate material, and then dehydrating the intermediate material. At least a part of the polyethylene-based resin may contain biomass-derived polyethylene. Examples of materials for biomass-derived polyethylene include corn, cassava, sugarcane, sugar beet, palm, soybean, and castor bean. Biomass-derived polyethylene may be produced by any method, such as fermentation, bacterial fermentation, chemical reaction, and culture extraction. Such biomass-derived polyethylene may be, for example, a low-density polyethylene derived from biomass. As the polyethylene-based resin, a fossil fuel-derived polyethylene resin and a biomass-derived polyethylene resin may be used in combination. Such biomass-derived resins are also used in the first base material layers 22, 25 and second base material layers 23, 24 in the second configuration example of the laminate described below, and in the first base material layer 31 and second base material layers 32, 33 in the third configuration example of the laminate.

[0046] In the laminate 10 described above, the layer configuration other than the surface layer 11 and the subsurface layer 12 is optional. For example, depending on the required rigidity and barrier properties, additional layers may be included, or any of the layers may be omitted.

[0047] FIG. 16 is a schematic cross-sectional view showing a second configuration example of the laminate. In the illustrated example, the laminate 20 has a surface layer 21, first base material layers 22, 25, second base material layers 23, 24, a barrier layer 26, and an adhesive layer 27. In the laminate 20, the surface layer 21, the first base material layer 22 (subsurface layer), the second base material layer 23, the adhesive layer 27, the barrier layer 26, the adhesive layer 27, the second base material layer 24, and the first base material layer 25 are laminated in this order. In the laminate 20, additional layers may be included depending on, for example, the required rigidity and barrier properties, or any of the layers may be omitted. For example, in another example, any of the first base material layers 22, 25 or the second base material layers 23, 24 may be omitted, and the surface layer, a single base material layer, an adhesive layer, a barrier layer, an adhesive layer, and a single base material layer may be laminated in this order. In yet another example, the first base material layers 22, 25 and the second base material layers 23, 24 may be formed with the same resin composition. The laminate 20 is formed with a thickness suitable for forming the container 100, specifically, for example, a thickness of 0.2 mm or more and 1.4 mm or less, but is not limited to this example. When the laminate 20 is associated with the laminate 114 shown in FIG. 3, the surface layer 21 corresponds to the surface layer 114C, the first base material layer 22 corresponds to the subsurface layer 114B, and the layers from the second base material layer 23 to the first base material layer 25 correspond to the base material layer 114A. The configuration of each layer will be described below.

[0048] From the viewpoint of improving the appearance after heating, the surface layer 21 preferably contains homopolypropylene (HPP), but may also contain polypropylene such as metallocene catalyst-based random polypropylene, polyethylene such as low-density polyethylene, etc. The ratio of polypropylene-based resin contained in the surface layer 21 is preferably 10% by mass or more and 69% by mass or less.

[0049] Furthermore, the polyolefin resin forming the surface layer 21 may contain a linear ethylene-α-olefin copolymer, etc. As a non-limiting example, if the surface layer 21 is broken when the container 100 is opened, the thickness of the surface layer 21 is preferably 5 μm or more and 300 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0050] The first base layer 22, 25 is formed of a resin composition containing a polypropylene-based resin and a polyethylene-based resin. As the polypropylene-based resin, for example, homopolypropylene (HPP), block polypropylene (BPP), random polypropylene (RPP) can be used, and homopolypropylene (HPP) and block polypropylene (BPP) are preferable, and any one or more of these can be used in combination depending on the application. As the polyethylene-based resin, for example, high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE) can be used, and high density polyethylene or low density polyethylene is preferable, and any one or more of these can be used in combination depending on the application.

[0051] At least a part of the polyethylene resin contained in each of the first base material layers 22, 25 as described above may be a polyethylene resin derived from biomass (biopolyethylene). From the viewpoint of the functionality of the laminate 20, the amount of the biopolyethylene blended is, for example, 70 mass% or less, preferably 40 mass% or less, and more preferably 35 mass% or less, based on the entire laminate 20. On the other hand, from the viewpoint of effectively reducing the environmental load, the amount of the biopolyethylene blended is 0.1 mass% or more, preferably 0.5 mass% or more, and more preferably 2.5 mass% or more, based on the entire laminate 20.

[0052] The second base layers 23, 24 as described above may contain, in addition to polypropylene-based resin and polyethylene-based resin, various polyolefin-based resins, polystyrene-based resins, polyester-based resins, mixtures of these, etc. Inorganic fillers such as talc may be added to the second base layers 23, 24 to improve rigidity.

[0053] The barrier layer 26 is an oxygen barrier layer containing, for example, an ethylene vinyl alcohol resin such as ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride, or polyacrylonitrile. The material of the oxygen barrier layer may be the same as that in the case where the oxygen barrier layer is included in the laminate 114 of the container body 110. The thickness of the barrier layer 26 is, for example, 0.1% to 15% of the entire laminate 20. The adhesive layer 27 is formed of, for example, a urethane-based elastomer, a styrene-based elastomer, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, ethylene vinyl acetate (EVA), or the like. The thickness of the adhesive layer 27 is, for example, 0.1% to 5% of the entire laminate 10.

[0054] Fig. 17 is a schematic cross-sectional view showing a third configuration example of the laminate. In the illustrated example, the laminate 30 includes a first base material layer 31 and second base material layers 32 and 33 laminated on both sides of the first base material layer 31. When the laminate 30 is associated with the laminate 114 shown in Fig. 3, the second base material layer 32 corresponds to the surface layer 114C, and the first base material layer 31 and the second base material layer 33 correspond to the base material layer 114A. The configuration of each layer will be described below.

[0055] The first base layer 31 is mainly composed of a resin composition obtained by mixing a polypropylene-based resin and a polyethylene-based resin. The polypropylene-based resin may be a polymer containing at least propylene. Examples of the polymer containing propylene include homopolypropylene and a copolymer of propylene and an olefin. The copolymer of propylene and an olefin may be a block copolymer or a random copolymer, or a mixture thereof. From the viewpoint of heat resistance and hardness, the polypropylene-based resin is preferably homopolypropylene.

[0056] On the other hand, the polyethylene resin contained in the first base layer 31 may be a polymer containing at least ethylene. Examples of the polyethylene resin include low-density polyethylene resin, particularly linear low-density polyethylene resin.

[0057] The second base layer 32, 33 contains a polypropylene-based resin. At least a part of the polypropylene-based resin may be a biomass-derived polypropylene-based resin (biopolypropylene). The second base layer 32, 33 preferably contains homopolypropylene (HPP) from the viewpoint of improving the appearance after heating, but may contain polypropylene such as metallocene catalyst-based random polypropylene, polyethylene such as low-density polyethylene, and the like, in addition to HPP. The ratio of the polypropylene-based resin contained in the second base layer 32, 33 is preferably 10% by mass or more and 69% by mass or less, more preferably 40% by mass or more and 68% by mass or less, and even more preferably 55% by mass or more and 65% by mass or less.

[0058] Moreover, the laminate 30 is not limited to a three-layer structure consisting of the first base layer 31 and the second base layers 32, 33 as in the above example, but may be a multi-layer structure of four or more layers. A laminate of a multi-layer structure of four or more layers may have other layers in addition to the first base layer and the second base layer. For example, in the laminate 30 of FIG. 17, a laminate 30 having other layers (not shown) between the first base layer 31 and the second base layers 32, 33, etc., may be mentioned. Examples of the other layers include a barrier layer, an adhesive layer, or an anti-fogging layer containing an anti-fogging agent. The laminate 30 may have a second base layer 32 only on one side of the first base layer 31. For example, as shown in FIG. 18, a laminate 30A in which the second base layer 32 is laminated only on one side of the first base layer 31 may be mentioned. In addition, the second base material layers 32, 33 are laminated on at least one side of the first base material layer 31, but other layers such as a barrier layer or an adhesive layer may be interposed between the first base material layer 31 and the second base material layers 32, 33.

[0059] FIG. 19 is a diagram showing a manufacturing process of a laminate according to a third configuration example. In the manufacturing process, the laminate 30 co-extruded from a T-die 501 of an extruder is sandwiched between a first cooling roll 502 and a second cooling roll 503 together with a metallic endless belt 506. The metallic endless belt 506 is continuously transported by each cooling roll and a transport roll 505. Each cooling roll is equipped with a cooling means (not shown), such as a water cooling tube. The laminate 30 immediately after molding is cooled by contact with the circumferential surfaces of the first cooling roll 502 and the second cooling roll 503, and the metallic endless belt 506. In a portion corresponding to the approximately lower half of the second cooling roll 503, the laminate 20 is sandwiched between the metallic endless belt 506 and the second cooling roll 503, and cooling water is sprayed onto the back side of the metallic endless belt 506 using a spray nozzle 507 to further cool the laminate 30. The sprayed cooling water is collected using a water tank 508. The laminate 30 leaves the second cooling roll 503 together with the metallic endless belt 506 and moves onto the third cooling roll 504, where it is cooled in a portion corresponding to approximately the upper half of the third cooling roll 504, and is then guided by the peeling roll 510 to leave the third cooling roll 504 and the metallic endless belt 506, completing the cooling process, and is then transported further. Note that water adhering to the back surface of the metallic endless belt 506 is removed by a water absorbing roll 509 provided midway between the second cooling roll 503 and the third cooling roll 504.

[0060] According to the manufacturing process as described above, the laminate 30 immediately after molding can be rapidly cooled to a required temperature by contact with the multiple cooling rolls 502, 503 and the metallic endless belt 506, and by spraying cooling water onto the laminate 30, thereby enabling the laminate 30 to exhibit, for example, mechanical properties and transparency.

[0061] In the container 100 according to one embodiment of the present invention, the surface layer 114C of the container body 110 is a cohesive failure layer, so that the force required by the user to peel off the lid body 130 when opening the container 100 is small, and the container 100 is easily opened. In addition, by forming the inner resin reservoir 120 on the inner circumferential side of the bonding region 140, the sealing property of the container 100 is improved. Furthermore, by setting the ratio of polypropylene-based resin in the resin composition of the surface layer 114C forming the cohesive failure layer to 10% by mass or more and 69% by mass or less, the bonding strength between the container body 110 and the lid body 130 can be reduced. By setting the peak crystallization temperature of the polypropylene constituting the seal layer 131B to 90° C. or less and the peak melting point of the 1st run to 130° C. or more and 175° C. or less, the interface strength can be suppressed, and the lid body 130 can be easily peeled off from the container body 110.

[0062] As described above, according to the container 100 of one embodiment of the present invention, by using block polypropylene having a high melting point as the resin composition, it is possible to reduce the bonding strength between the sealing layer 131B of the lid body 130 and the surface layer 114C, thereby suppressing the interfacial strength and achieving both favorable openability and sealability. EXAMPLES

[0063] Next, examples and comparative examples of the present invention will be described, but the present invention is not limited to these examples. In each example, the film structure, raw materials, preparation of evaluation samples, measurement of sealing property and opening property, measurement of seal strength and measurement of puncture pressure strength were performed by the following methods.

[0064] [Examples 1-2, Comparative Examples 1-2] Using the following raw materials, a sheet with a total thickness of about 650 μm and a surface layer with a thickness of about 30 to 50 μm and a film with a BPP seal layer with a thickness of 70 μm were heat-sealed using a sealing plate to prepare an evaluation sample. The prepared evaluation sample was used to measure the sealing property and the ease of opening. The sealing time between the surface layer and the seal layer was 1.0 second, and the measurement was performed once. The sealing pressure was 240 kgf, which is a higher pressure than usual and is used to form a resin pool.

[0065] <Raw materials> (Surface layer) Component (1): Homopolypropylene (MFR: 0.5g / 10min, melting point: 150-165℃) Component (2): Metallocene catalyst-based random polypropylene (MFR: 2.0 g / 10 min, melting point: 125°C) Component (3): Low-density polyethylene (MFR: 4.3g / 10min, melting point: 128℃) (Sealing layer: "BPP") Main component: Block polypropylene (BPP): MFR: 3.0g / 10min, melting point 150~165℃ <Seal plate shape> Opening section: The distance from the inner edge to the outer edge of the annular shape is 5.1 mm, the seal width by the inner inclined surface is 1.3 mm, and the curvature radius of the inner inclined surface is 1.6 Joint area: The distance from the inner periphery to the outer periphery of the annular shape is 1.5 mm, the seal width by the inner inclined surface is 1.3 mm, and the curvature radius of the inner inclined surface is 1.6 Sheets A to D, which are surface layer films, were prepared according to the formulations shown in Table 1. The obtained surface layer (one of sheets A to D) was heat-sealed with a sealing plate at temperatures of 210°C to 230°C to prepare evaluation samples.

[0066] [Table 1] Since components (1) and (2) are polypropylene-based resins, sheets A and B contain 60% by mass of polypropylene-based resin, and sheets C and D contain 70% by mass of polypropylene-based resin.

[0067] <Measurement results> The obtained sheet having the surface layer (one of sheets A to D) and the seal layer ("BPP") were heat-sealed at temperatures of 210°C to 230°C using a sealing plate, and the sealing property and the opening property of each were measured. The results are shown in Table 2. The sealing property was evaluated qualitatively based on the sensation when the film was opened from the inside of the container 100 by making a cut in the film in the bonding area 140. In Table 2, the case where the film did not peel off is described as "A", the case where the film peeled off easily is described as "B", and the case where the film peeled off with resistance is described as "C". The opening property was evaluated qualitatively based on the sensation when opening. In Table 2, the opening property is described as "A" when the film peeled off easily, "B" when the film did not peel off, and "C" when the film peeled off with resistance.

[0068] [Table 2]

[0069] As shown in Examples 1 and 2 in Table 2 above, when the surface layer is Sheet A or B and the sealing layer is mainly composed of BPP, if the sealing temperature is 220° C. or 230° C., the sealability and openability were rated as "A." As shown in Table 1, the surface layer, Sheet A, contains 60% by mass of homopolypropylene, and the surface layer, Sheet B, contains 50% by mass of homopolypropylene and 10% by mass of metallocene catalyst-based random polypropylene. In other words, the surface layer, Sheets A and B, contain 60% by mass of polypropylene component. Moreover, under the conditions shown in Comparative Examples 1 and 2, in which the resin composition of the seal layer was random polypropylene, sealing properties and openability were not compatible, or the sheet was broken. Therefore, it can be seen that when the polypropylene ratio in the surface layer is 60 mass %, both the sealability and the openability are achieved.

[0070] [Examples 3 to 4, Comparative Example 3] Next, according to the combinations shown below, a container molded from a sheet having a total thickness of about 650 μm with a surface layer having a thickness of about 30 to 50 μm and a film having a BPP seal layer having a thickness of 70 μm were heat-sealed at temperatures of 210 ° C to 230 ° C using a sealing plate to prepare evaluation samples. The puncture pressure strength, initial opening strength, and seal strength were measured using the evaluation samples prepared. The sealing time between the surface layer and the seal layer was 1.0 second, and the number of measurements was three. The sealing pressure was 240 kgf, which is a higher pressure than usual and is used to form a resin pool. Example 3: Surface layer "Sheet A", sealing layer "BPP" Example 4: Surface layer "Sheet B", sealing layer "BPP" Comparative Example 3: Surface layer "Sheet C", sealing layer "BPP" As explained with reference to Table 1, the surface layer sheets A and B contain 60% by mass of polypropylene resin, and the surface layer sheet C contains 70% by mass of polypropylene resin.

[0071] <Measurement conditions> 20 is a plan view of the container 100 used to measure the puncture pressure strength, initial opening strength, and seal strength. In this embodiment, the seal strength was measured at five measurement points P1 to P5 for the rectangular container 100 in which the joint area 140 is formed on the flange portion 112 in the shape shown in the figure. The measurement point P1 is the opening portion 141, and the resin pool is formed only on the inner periphery side of the joint area 140. The measurement points P2 to P5 are the joint area 140, and are formed on the inner and outer periphery sides of the joint area 140. The initial opening strength was measured at the opening portion 141, and the seal strength was measured at each of the measurement points P1 to P5.

[0072] The puncture pressure strength is the maximum pressure at the time of rupture, and can be measured, for example, by blowing air into the internal space SP between the container body 110 and the lid 130 at a predetermined air flow rate (1.0±0.2 L / min (approximate)). The puncture pressure strength of the container 100 is, for example, 0.001 MPa or more, and preferably 0.04 MPa or more. The upper limit of the puncture pressure strength of the container 100 is, for example, 0.20 MPa or less. The puncture pressure strength can be measured in accordance with JIS Z0238 "8. Burst strength test for containers".

[0073] The initial opening strength is the maximum value of the force that peels off the lid 130 when opening the container until it reaches the internal space SP. For example, it is 3.0 kgf or less, preferably 2.8 kgf or less, and more preferably 2.5 kgf or less. The lower limit of the opening strength is not particularly limited, but is, for example, 0.1 kgf or more from the viewpoint of preventing unintentional opening. The opening strength is measured by attaching a measuring tool to the opening start portion (tab portion) of the lid 130, pulling the opening start side of the lid 130 at an angle of 135 degrees against the flange surface of the container body 110, and measuring the maximum value of the tensile strength. An IMADA push-pull gauge can be used as the opening strength measuring device.

[0074] The seal strength was measured by clamping the side surface of the recess 111 adjacent to the flange 112 and the lid 130 with a jig at the inner peripheral edge side of the bonding area 140 at each of the measurement points P1 to P5, and pulling a 15 mm wide evaluation sample upward from the inside of the container at a pulling speed of 300 mm / min. The seal strength of Examples 3 and 4 and Comparative Example 3 was measured using a push-pull gauge made by IMADA.

[0075] <Measurement results> Fig. 21 is a graph showing the relationship between puncture pressure strength and sealing temperature in the examples and comparative examples. Fig. 22 is a graph showing the measurement results of the initial opening strength when heat sealed at a sealing pressure of 240 kgf. As shown in the graph in Fig. 21, in all of Examples 3 and 4 and Comparative Example 3, the puncture pressure strength increases as the sealing temperature increases, and it can be said that the container 100 is highly sealed, especially when the sealing temperature is 220°C or 230°C.

[0076] Also, as shown in Fig. 22, in the case of Example 3 or 4 in which the resin composition of the surface layer contains 60% by mass of polypropylene resin, the initial opening strength increases as the sealing temperature increases, but in the case of Comparative Example 3 in which the resin composition of the surface layer contains 70% by mass of polypropylene resin, opening was not possible when the sealing temperature was 220°C or 230°C. That is, from Figs. 21 and 22, in the case of Example 3 or 4, even in a high-sealed state in which the puncture pressure strength has increased by increasing the sealing temperature, peeling of the film at the opening portion 141 is possible. However, in Comparative Example 3, it can be said that peeling of the film at the opening portion 141 was not possible in a high-sealed state. The results of measuring the seal strength also show that a high level of sealing is achieved at temperatures of 220° C. or higher. Table 4 below shows the results of measuring the seal strength of Examples 3 and 4 and Comparative Example 3. The units of values ​​are kgf / 15 mm.

[0077] [Table 3] The seal strength when sealed at each sealing temperature was measured three times at five measurement points P1 to P5 for the rectangular container 100. The average value in Table 3 is the average of the seal strength values ​​measured three times, but if peeling was not possible in some of the three measurements, the average value of the seal strength values ​​when peeling was possible is shown.

[0078] As shown in Table 3, for the seal strength of Examples 3 and 4, P1 was the lowest under all conditions. This P1 was a value of about 2.0 kgf / 15 mm when the sealing temperature was 210° C., which means that peeling was relatively easy. However, at 220° C., the average P1 was 3.0 kgf / 15 mm or more, making peeling difficult. At 230° C., peeling was 5.0 kgf / 15 mm in Example 3, and peeling was not possible in Examples 4 and 3 ("-" in the table). This supports the results shown in FIG. 22 as data on peeling from the inside of the container, and shows that high sealing is achieved when the sealing temperature is 220° C. or higher.

[0079] Although the preferred embodiment of the present invention has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an example. It is clear that a person having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or amended examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0080] 100: Container 110: Container body 111: Recess 112: Flange part 114: Laminate 114A: Base material layer 114B: Subsurface layer 114C: Surface layer 120: Inner resin reservoir 121: First resin reservoir 122: Second resin reservoir 130: Lid 130A: Tab 131: Laminate 131A: Outer layer 131B: Sealing layer 140:Joint area 141: Opening section 150: Deaeration mechanism

Claims

1. a container body including a recess and a flange portion formed along a periphery of the recess and extending outward from the periphery; a lid body that is joined to the container body at a joining region formed in the flange portion to form an internal space between the lid body and the recess portion; A container comprising: the container body is made of a laminate including at least a first layer and a second layer joined to the first layer and facing the joining area; the lid body is made of a laminate including at least a third layer facing the bonding area and a fourth layer bonded to the third layer, the second layer is a cohesive failure layer and the third layer is a layer formed of a resin composition containing a polypropylene-based resin as a main component, the cohesive strength of the cohesive failure layer is weaker than the interlayer bond strength between the first layer and the second layer and between the third layer and the fourth layer; The resin composition forming the second layer has a polypropylene resin content of 10% by mass or more and 69% by mass or less. container.

2. a first resin reservoir portion, at least in part of which is formed on an inner circumferential side of the bonding region, and which is made of the resin forming the first layer and the second layer and has a nodular cross section inclined toward the recessed portion; a second resin reservoir made of the third layer of resin, located closer to the recess than the first resin reservoir, and covering the first resin reservoir; The container of claim 1.

3. a third resin reservoir portion, at least in part of which is formed from the resin forming the first layer and the second layer, on the outer periphery side of the bonding region and having a hump-shaped cross section inclined toward the outer periphery of the bonding region; a fourth resin reservoir portion having a hump-shaped cross section, the fourth resin reservoir portion being made of the third layer of resin and positioned closer to the outer periphery of the joining region than the third resin reservoir portion; 3. The container according to claim 1 or claim 2.

4. The third resin reservoir portion and the fourth resin reservoir portion are formed on the outer periphery of the joining area. in the portion where the second layer is not compressed, a radius of curvature R of a concave curved surface formed from the most compressed position of the second layer toward the internal space is 0.10H or more and 1.00H or less, where H is a width where the second layer and the third layer contact each other; In a portion where the third resin reservoir portion and the fourth resin reservoir portion are formed on the outer circumferential side of the joining region, the radius of curvature R is equal to or greater than 0.15H and equal to or less than 1.50H.

4. The container of claim 3.

5. the third resin reservoir portion and the fourth resin reservoir portion are formed in a portion of the joining region excluding a portion in the circumferential direction.

4. The container of claim 3.

6. the crystallization temperature of the polypropylene-based resin forming the third layer is 90°C or higher and 140°C or lower; 3. The container according to claim 1 or claim 2.

7. The melting point of the polypropylene-based resin forming the third layer is 130°C or higher and 175°C or lower.

3. The container according to claim 1 or claim 2.

8. The polypropylene-based resin forming the third layer is a block polypropylene.

3. The container according to claim 1 or claim 2.

9. The thickness of the cohesive failure layer is 5 μm or more and 300 μm or less.

3. The container according to claim 1 or claim 2.

10. A degassing mechanism is provided in the non-bonded region of the lid body, the degassing mechanism including an opening formed in the lid body and a sealing film covering the opening.

3. The container according to claim 1 or claim 2.

11. The degassing mechanism includes a non-through cut formed in the lid.

11. The container of claim 10.

12. The degassing mechanism includes a heating element disposed in contact with the lid.

11. The container of claim 10.

13. The lid includes at least two portions, the degassing mechanism includes an unbonded portion or a notch formed in the seal portion joining the two portions together; Container according to any one of claims 10.

14. At least a portion of the inner periphery of the joining region is made of resin forming the first layer and the second layer, and has a nodular cross section inclined toward the recess; a second resin reservoir portion made of the third layer of resin, located closer to the recess than the first resin reservoir portion, and covering the first resin reservoir portion; a third resin reservoir portion, at least in part of which is formed from the resin forming the first layer and the second layer, on the outer periphery side of the bonding region and having a hump-shaped cross section inclined toward the outer periphery of the bonding region; a fourth resin reservoir portion having a hump-shaped cross section, the fourth resin reservoir portion being made of the third layer of resin and positioned closer to the outer periphery of the joining region than the third resin reservoir portion; a vapor passage portion is formed in the joining region, the vapor passage portion being capable of communicating the internal space with an external space when the internal pressure of the internal space increases; the first resin reservoir portion and the second resin reservoir portion are not formed on the inner circumferential side of the joining region, and the third resin reservoir portion and the fourth resin reservoir portion are not formed on the outer circumferential side of the joining region in the vapor passage portion; The container of claim 1.

15. A surface layer containing a polypropylene resin and having a resin composition in which the ratio of the polypropylene resin is 10% by mass or more and 69% by mass or less; a first base layer adjacent to the surface layer and containing a polypropylene-based resin; A laminated sheet comprising:

16. The surface layer contains a polyethylene-based resin. The laminate sheet according to claim 15.

17. In addition to the surface layer and the first base material layer, the laminate further comprises a second base material layer containing a polypropylene-based resin. The laminate sheet according to claim 15 or 16.

18. The laminated sheet includes a recess and a flange portion formed along the periphery of the recess and extending outward from the periphery, and is used to form a container body that is joined to a lid body at a joining region formed on the flange portion, The surface layer becomes a cohesive failure layer when bonded to the lid. The laminate sheet according to claim 15 or 16.

Images