Container with flange

Abstract

To provide a container with a flange that is provided with an annular joint part shaped accurately according to a shape of a forming mold and is excellent in safety of a heat seal.SOLUTION: A container with a flange has a flange part at a peripheral edge of an opening part thereof and also has an annular joint part as a position that is jointed to a lid material on an upper surface of the flange part. The upper surface of the annular joint part is positioned upper in a direction of an axis of the container with respect to the upper surface of the flange part positioned closer to an inner periphery side and / or an outer periphery side with respect to the annular joint part. An outward protruding part protruding outward in a radial direction of the container is formed in at least a portion of the annular joint part. An outermost position in the radial direction of the container of the outward protruding part is positioned at the same position as the outermost position in the radial direction of the container on a lower surface of the flange part or outside in the radial direction of the container.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a container having a flange portion, and more specifically to a flanged container having an annular joint portion that can exhibit reliable internal pressure release function, stable burst strength, and stable opening performance, and also has excellent heat sealing stability. [Background technology]

[0002] Resin containers, which are sealed by heat-sealing a flexible lid to a flange, combine high sealing performance with easy opening, and are widely used as simple packaging for food and beverages. Even in such easily openable packages, it is desirable to heat the contents in a microwave oven before eating. In order to prevent the package from bursting due to an increase in internal pressure during microwave heating, it has been common practice to partially peel off the lid or to make a hole in the package to form a steam release port before microwave heating. However, since such methods are cumbersome for consumers, it is desirable to be able to heat in a microwave oven without peeling off the lid, etc. Furthermore, during microwave cooking, a steaming effect can be achieved by maintaining the internal pressure of the package in an elevated state for a certain period of time, but if a steam release port is formed in advance, this steaming effect cannot be fully achieved.

[0003] As a packaging container that solves these problems, for example, Patent Document 1 listed below proposes a packaging for microwave cooking in which a lid is heat-sealed to a flange portion to seal the packaging, and in which a protrusion that protrudes toward the inside of the container is formed in the heat-sealed portion and an opening portion that protrudes toward the outside of the container at a position opposite the protrusion, and a resin reservoir is provided around the entire inner edge of the heat-sealed portion excluding the vicinity of the tip of the protrusion and the opening portion, and the seal strength of the resin reservoir is set to 15 to 70 N / 15 mm.

[0004] In a package such as that described in Patent Document 1, in which a protrusion is formed on the upper surface of the flange and an opening portion facing outward and inward is formed on this protrusion, the protrusion on the upper surface of the flange is formed by pressing from the upper surface of the flange with a mold generally called a locator. However, since the part of the mold corresponding to the protrusion is recessed relative to the part that abuts against the upper surface of the flange, if this recess does not have a vent function when the mold is pressed, air will accumulate, and the protrusion will not be able to be shaped according to the shape of the mold.

[0005] An example of a flanged container that can form a protrusion on the upper surface of the flange without causing such problems is the following Patent Document 2. That is, the container described in the following Patent Document 2 has a heat-sealed portion that is formed in a rib shape around the entire periphery of the upper surface of the flange and is heat-sealed to the back surface of the lid, but as is clear from Figure 3(b) of Patent Document 2, this heat-sealed portion is formed from below the flange by a lower mold, so the above-mentioned problems do not occur.

[0006] Furthermore, Patent Document 3 listed below describes a flange molding method for flanged containers, which uses an upper mold having a gripping surface on which grooves are formed continuously or intermittently in the circumferential direction and equipped with a ventilation structure that allows atmospheric gas within the grooves to be discharged from the grooves, and which comprises thermoforming the molding material into a predetermined container shape while gripping a portion of a molding material made of thermoplastic resin that corresponds to the flange with the gripping surface of the upper mold and the gripping surface of a lower mold that is paired with the upper mold, thereby forming a flange around the periphery of the container opening and molding a protrusion that corresponds to the grooves on the top surface of the flange. It also describes that the ventilation structure can be formed by providing an air vent, or by forming the portion where the grooves are formed from a porous material. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4539266 [Patent Document 2] Japanese Patent Application Publication No. 2019-85178 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-88669 Summary of the Invention [Problem to be solved by the invention]

[0008] When forming a protrusion from below the flange portion as in Patent Document 2, it is difficult to form an annular joint with high dimensional accuracy or an inward protruding portion for forming an internal pressure release passage for the outward protrusion, compared to when forming the protrusion from above the flange portion. Furthermore, according to the molding method of Patent Document 3, the upper mold has a ventilation structure that can exhaust atmospheric gas from the groove portion, so that it is possible to form a protrusion portion corresponding to this groove portion on the upper surface of the flange with good shape reproducibility. However, since the protrusions are formed by pressurizing the molten resin, if ventilation is achieved through vent holes formed in the grooves of the mold, there is a risk that the molten resin will enter the vent holes, making it difficult to use the mold continuously for a long period of time. Furthermore, if the resin that has entered the vent holes falls out, it may end up in the product. Furthermore, if the grooves of the mold are formed from a porous material, the mold becomes very expensive and, like the case of vent holes, there are problems with clogging.

[0009] Therefore, the object of the present invention is to provide a flanged container having an annular joint, which is the heat-sealed point with the lid material, that has a shape that can be precisely formed to match the shape of the molding die, and which can provide reliable internal pressure release function, stable burst strength, and stable opening performance, as well as excellent heat-sealing stability. [Means for solving the problem]

[0010] According to the present invention, there is provided a flanged container having a flange portion on the periphery of an opening and an annular joint portion on the upper surface of the flange portion that serves as a joint position with a lid material, characterized in that the upper surface of the annular joint portion is located higher in the axial direction of the container than the upper surface of the flange portion, which is located on the inner and / or outer side of the annular joint portion, and at least a part of the annular joint portion is formed with an outward protrusion portion that protrudes radially outward in the container direction, and the outermost position of the outward protrusion in the container radial direction is located at the same position as or radially outward from the outermost position of the lower surface of the flange portion in the container radial direction.

[0011] In the flanged container of the present invention, (1) The upper surface of the annular joint is formed so that the axial height on the outer side is higher than the axial height on the inner side in the container radial direction at least in the portion where the outward protrusion is formed. (2) The flange portion has an outer wall that hangs down from the outer peripheral end of the flange portion in the container axial direction, (3) A plurality of the outward protrusions are formed. (4) It is for microwave heating. is preferred. [Effects of the Invention]

[0012] In the flanged container of the present invention, the outermost position in the container radial direction of the outward protrusion formed on at least a part of the annular joint formed on the upper surface of the flange portion is located at the same position as the outermost position in the container radial direction of the lower surface of the flange portion or is located outward in the container radial direction.Therefore, when the flange portion is pressed with a mold (hereinafter referred to as a "locator") for forming the upper surface of the flange portion including the annular joint, air in the recess formed in the locator is more likely to flow toward the outer periphery of the flange portion, making it possible to efficiently release air from the outward protrusion. Furthermore, the upper surface of the annular joint is formed so that the axial height is higher on the outside than on the inside in the radial direction of the container, at least in the part where the outward protrusion is formed.This causes air within the recess to flow from the outer periphery to the inner periphery when the locator is pressed, and this, combined with the presence of the above-mentioned outward protrusion, makes it possible to more efficiently release air within the recess. This air release action effectively transfers the recessed portion formed in the locator for forming the annular joint to the flange, allowing the annular joint to be formed with high dimensional accuracy. This allows containers with an internal pressure release function to exhibit stable internal pressure release function and stable opening performance. Even containers without an internal pressure release function can exhibit stable burst strength and stable opening performance. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing an example of a flanged container of the present invention. [Figure 2] 2 is an enlarged partial plan view showing a flange portion of the container shown in FIG. 1. FIG. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing the YY cross section of FIG. 2. [Figure 4] 3 is a partially enlarged cross-sectional view illustrating a method for forming the outward protrusions shown in FIG. 2. FIG. [Figure 5] FIG. 2 is an enlarged plan view showing a portion of the flange portion of another example of a flanged container of the present invention. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing a ZZ cross section of FIG. 5. [Figure 7] 7 is a partially enlarged cross-sectional view illustrating a method for forming the outward protrusions shown in FIG. 6. FIG. [Figure 8] FIG. 10 is a diagram for explaining a method for measuring opening force. DETAILED DESCRIPTION OF THE INVENTION

[0014] The container and package of the present invention will be described with reference to the specific examples shown in the accompanying drawings. As shown in Fig. 1, the container of the first embodiment, generally designated by 1, is generally composed of a bottom 2, a body 3, a flange 4 extending radially outward from the upper end of the body 3, and an annular skirt (outer wall) 5 hanging down from the outer periphery of the flange 4. As is clear from Fig. 1, the container 1 is integrally formed from a laminate consisting of a base layer 6 and a surface seal layer 7, with the surface seal layer 7 forming the upper surface of the flange 4 that faces a lid (not shown). The base material layer 6 and the surface seal layer 7 are formed from resins that are easily peelable from each other, so that when heated in a microwave oven and the internal pressure increases, the base material layer 6 and the surface seal layer 7 easily peel away from each other, reliably forming an internal pressure release passage and improving the ease of opening when removing the lid material.

[0015] As is clear from Fig. 2, which is a partially enlarged plan view showing the flange portion of the container shown in Fig. 1 enlarged from the top, and Fig. 3, which is an enlarged view of the YY cross section of Fig. 2, the upper surface of the flange portion 4 has an annular joint 41 in the center, which is the joining position (heat sealing position) of the lid material, and an inner step 42 located inside the annular joint 41. In the specific example shown in Fig. 2, an outer step 43 is formed outside the annular joint 41. Note that grooves 41c and 41d, where the surface seal layer is thin or missing, are formed between the inner step 42 and the outer step 43 and between the inner edge 41a (hereinafter referred to as the "inner peripheral edge") and the outer edge 41b (hereinafter referred to as the "outer peripheral edge") of the annular joint 41 in the container radial direction and the outer step 43, respectively. By having these inner step portion 42 and outer step portion 43, when the lid material is joined to the annular joint portion 41 by heat sealing, as described below, the molten resin of the surface seal layer 7 is prevented from joining to the inner step portion 42 or the outer step portion 43, effectively preventing a decrease in the openability or internal pressure release function. 2, in the container of the present invention, a plurality of inwardly protruding portions that protrude radially inward of the container may be formed at the annular joint 41, and when the internal pressure increases due to microwave heating, stress concentrates at these inwardly protruding portions, causing the base material layer 6 and surface seal layer 7 in this area to peel off, forming a passage for releasing the internal pressure. Furthermore, as long as the container has an internal pressure release function that allows the internal pressure release passage to be formed, it is not limited to the inwardly protruding portions described above, but hereinafter the portion of the annular joint 41 where the inwardly protruding portions are formed will be referred to as the "internal pressure release portion."

[0016] 2 and 3, the upper surface of the outward protrusion 45 or the annular joint 41 is formed as an inclined surface whose height increases from the inner side to the outer side in the radial direction of the container. Furthermore, a plurality of outward protrusions 45 are formed. As described below, this allows air to efficiently escape from the recessed portion of the locator for forming the annular joint during container molding, enabling the annular joint to be molded with high dimensional accuracy and improving the ease of opening the container. Furthermore, the upper surface of the outward protrusion 45 or the annular joint 41 is not limited to an inclined surface, and may be arch-shaped as long as it is formed so that its height is higher on the outer side than on the inner side in the radial direction of the container. In other words, when forming an outward protrusion 45 or annular joint 41 whose upper surface is formed as such an inclined surface, when it is pressed from above with a locator, the air in the recess flows from the shallow inner part of the recess which first comes into contact with the resin sheet to gradually move towards the deeper outer part, which is thought to expel the air in the recess from the recess, making it possible to form an annular joint that matches the shape of the recess for forming the annular joint with high dimensional accuracy.

[0017] Furthermore, when heat-sealing the lid, the annular joint, which has an inclined upper surface as described above, is pressed and heated from above by a heat-sealing head, and the higher outer portion is pressed and heated more than the inner portion, so that the outer side of the surface seal layer of the annular joint melts and protrudes more than the inner side, and similarly, the outer side of the seal layer of the lid melts more. As a result, on the outside of the annular joint, the molten resin that protrudes from the surface seal layer of the container and the seal layer of the lid, which are not easily separable from each other, become integrated, and when opened, these become integrated and follow the movement of the lid, allowing easy interlayer delamination with the base layer of the container to proceed, and the lid can be easily peeled off from the container, improving openability.

[0018] Fig. 4 is a schematic diagram for explaining a method for forming the outward protrusion 45 shown in Fig. 2 and Fig. 3. Note that in Fig. 4, parts of the mold other than the part where the flange portion is formed are partially omitted. The container of the present invention can be suitably formed by thermoforming such as vacuum forming or plug-assisted pressure forming, although this method is not limited to this. In this case, the formation of the container and the formation of the annular joint on the upper surface of the flange can be performed simultaneously. That is, as shown in Fig. 4, the portion of the resin sheet that will become the flange is sandwiched from above and below between a mold 100 capable of forming the container shape and a locator 101 capable of forming the flange including the annular joint. Pressure is applied from above to bring the resin sheet into contact with the mold 100, thereby forming the container shape, and annular joint 41 is formed on the upper surface of the flange 4 by an annular joint-forming recess (hereinafter sometimes simply referred to as "recess") 102 formed on the lower surface of the locator 101.

[0019] As described above, an important feature of the container of the present invention is that, at the location where the outward protrusion 45 of the annular joint 41 is formed, the outermost position A (hereinafter sometimes referred to as "position A") of the outward protrusion 45 in the container radial direction is located at the same position as or radially outward from the outermost position B (hereinafter sometimes referred to as "position B") of the underside of the flange portion 4 in the container radial direction. In the specific example shown in Figures 2 to 4, the flange portion 4 has an annular skirt portion 5 hanging down from its outer peripheral edge, and the outermost position A of the outward protrusion 45 of the annular joint 41 is located radially outward from the outermost position B of the underside of the flange portion 4 in the container radial direction.

[0020] In molding a container having such a flange shape, when the flange portion 4 is pressed by the locator 101 to form the annular joint portion 41, the vertical distance between the upper surface of the mold 100 and the lower surface of the locator 101, which sandwich the flange portion, is different at positions A and B in the flange portion 4 (position B: t0 < position A: t1). Therefore, at the flange portion radially inward of position B of the flange portion, the pressing force from the locator 101 is supported by the upper surface of the mold 100 at a shorter distance, and the reaction force from the mold 100 acts immediately on the flange portion, whereas at the flange portion radially outward of position B of the flange portion, the pressing force from the locator 101 reaches the upper surface of the mold 100 from the flange portion 4 through the annular skirt portion 5, and therefore almost no reaction force from the mold 100 acts on position A of the flange portion. As a result, the air that was present in the recess 102 of the locator 101, which corresponds to the shape of the annular joint 41, is efficiently discharged from a position radially inward of the container, farther than position B, where the pressing force of the locator is more likely to be applied, toward position A, where the pressing force of the locator is less likely to be applied, making it possible to form an annular joint having a shape that matches the shape of the recess 102 formed in the locator.

[0021] Figures 5 and 6 show another example of a flanged container of the present invention. This second embodiment of the flanged container has a container shape that is almost the same as the first embodiment of the flanged container shown in Figures 2 and 3, except that the flange portion 4 does not have the annular skirt portion 5 shown in Figure 1 and the shape of the annular joint is different. As can be seen from FIG. 5, a partially enlarged plan view showing the flange portion of the container enlarged from above, and FIG. 6, an enlarged view of the ZZ cross section of FIG. 5, the annular joint 41 has a plurality of pairs of two consecutive outward protrusions 45, 45. Furthermore, between each pair of outward protrusions 45, 45, there is an inward protrusion 46 that protrudes radially inward in the container as a planned internal pressure release portion. When internal pressure increases due to microwave heating, stress is concentrated on the inward protrusion 46, causing delamination to initiate at the inward protrusion 46 prior to other portions, thereby enabling efficient release of internal pressure. Furthermore, by forming such a pair of protrusions, the width of the internal pressure release passage is prevented from unnecessarily widening. As can be seen from FIG. 6, the outermost position (position A) of the outward protrusion 45 in the container's radial direction reaches the outermost position (position B) of the flange portion 4 in the container's radial direction, and positions A and B are at the same position in the container's axial direction.

[0022] 7, in molding a container having such a flange shape, as in the container of the first embodiment, the portion of the resin sheet that will become the flange is sandwiched between a mold 100 capable of shaping the container shape and a locator 101 capable of forming an annular joint, and pressure is applied to the resin sheet from above to shape the container and form an annular joint 41 on the upper surface of the flange 4, but the outer side of the annular joint-forming recess 102 in the container radial direction penetrates to the side surface of the locator (the outermost position in the container radial direction), and the outermost position in the container radial direction of the annular joint 41 is restricted by a protrusion 103 formed on the mold 100. In this way, since the recess 102 penetrates to the side surface of the locator, air within the recess 102 of the locator 101 can be efficiently discharged. In this embodiment, which does not have an annular skirt portion, after the annular joint is formed, the flange portion located radially outward of the container at the outermost position (position A) of the outward protrusion 45 is trimmed at the portion indicated by the dotted line in Figure 7, so that positions A and B are at the same position in the container axial direction.

[0023] As described above, the flanged container of the present invention has the outermost position A in the container radial direction of the outward protrusion of the flange located at the same position as or radially outward from the outermost position B in the container radial direction of the underside of the flange, which allows air to be efficiently discharged from the recess for forming the annular joint on the underside of the locator during molding, and the molten resin that forms the surface seal layer fills the recess without any gaps, making it possible to form the annular joint as designed. In other words, as long as the above-mentioned positions A and B are in the above-mentioned positional relationship, the container is not limited to the specific example described above. For example, in the specific example shown in the figure, the height of the upper surface of the outward protrusion 45 increases from the inside to the outside in the radial direction of the container, but this is not limited thereto, and for example, the height of the upper surface of a portion of the annular joint, or particularly the inward protrusion, may be higher on the inside side than on the central portion of the annular joint. When a container having an internal pressure release function is heat-sealed to a lid, by locally raising the inside side of the internal pressure release portion, more of the surface seal layer on the inside side of the container in the radial direction melts and protrudes, and similarly, more of the seal layer of the lid melts on its inside side. As a result, the molten resin that protrudes from the surface seal layer of the container and the seal layer of the lid, which are not easily separable from each other, become integrated inside the internal pressure release portion. When the internal pressure increases due to microwave heating, these integrate and follow the movement of the lid, allowing for easy interlayer delamination with the base layer of the container, thereby enabling smooth internal pressure release. In addition, by positioning the tip of the inward protruding portion of the portion intended to release internal pressure radially inward of the surrounding annular joint, stress is more likely to be concentrated, and delamination begins preferentially at the surrounding annular joint, making it possible to efficiently release internal pressure. Furthermore, in containers that do not have an internal pressure release function, by forming the annular joint so that it becomes higher as it goes from the inside to the outside in the radial direction of the container, the overflow of molten resin on the inside side of the annular joint in the radial direction of the container is suppressed, and stable burst strength (pressure resistance strength) can be achieved.

[0024] The height difference between the highest inner or outer circumferential edge and the lowest point of the annular joint formed on the upper surface is, but not limited to, 0.5 mm or less, preferably in the range of 0.010 to 0.3 mm, and more preferably in the range of 0.025 to 0.2 mm. This, in combination with the positional relationship between Position A and Position B described above, allows air to efficiently escape from the recess of the locator for forming the annular joint.

[0025] The shape and number of the inward protruding portions that make up the internal pressure release portion can also be changed as appropriate, but it is preferable to form multiple portions on the flange portion. When the internal pressure inside the container increases due to heating, such as in a microwave oven, an internal pressure release passage for releasing the internal pressure is formed in only one of the multiple internal pressure release portions. When the internal pressure is released, the other internal pressure release portions do not become internal pressure release passages, but because interlayer delamination has progressed by the time the internal pressure release passage is formed, the container can be easily opened after microwave heating. Furthermore, when a container with a flange is molded integrally by thermoforming such as vacuum forming or plug-assisted pressure forming, differences in thickness are likely to occur in the flange. However, by forming multiple outward protrusions 45 and portions intended for releasing internal pressure on the flange, it is possible to absorb any thickness differences that occur and form an annular joint with high dimensional accuracy, making it possible to reliably release internal pressure by heating in a microwave oven, etc.

[0026] The step between the upper surface of the inner peripheral edge of the annular joint in the intended internal pressure release portion and the internal step portion is, but is not limited to, in the range of 0.2 to 2.0 mm, preferably 0.2 to 1.0 mm. By keeping it in this range, molten resin from the surface sealing layer of the container and lid material can be prevented from coming into contact with the internal step portion, and the smooth formation of the internal pressure release passage is not hindered. Furthermore, when there is an outer wall (annular skirt portion) hanging down from the outer peripheral edge of the flange portion, it is preferable to have an outer step portion, and the step between the outer step portion and the upper surface of the outer peripheral edge of the annular joint portion is, but is not limited to, in the range of 0.2 to 2.0 mm, preferably 0.2 to 1.0 mm, and as above, this prevents molten resin from the surface sealing layer of the container and lid material from coming into contact with the outer step portion, and does not impair openability.

[0027] It is preferable for the flange portion to have an outer wall (annular skirt portion) hanging down from the outer peripheral end of the flange portion in order to improve the mechanical strength of the flange portion, but depending on the thickness of the flange portion, it is not necessary for the annular skirt portion to be formed. Furthermore, in the specific example shown in the figure, the container is integrally molded from a laminate having a base layer and a surface seal layer, and the surface seal layer is also formed on the inner surface of the container, but it is of course also possible for the surface seal layer to be formed only on the flange portion. The container of the present invention is preferably cup-shaped, but is not limited to this and may be tray-shaped as long as it has a flange. In addition, although the specific example shown in the figure is a round container, it may also be a rectangular container, or may be a polygonal or oval container. The lid material that can be used with the container of the present invention may be a flexible sheet-like lid material, or may be a formed lid in the shape of a drop lid.

[0028] As described above, the base material layer and the surface seal layer of the container are preferably peeled off by interlayer peeling, but cohesive peeling or interfacial peeling may also be used as long as easy peeling is possible.Furthermore, the base material layer and the heat seal layer on the lid side may be peeled off easily. A suitable peel strength for satisfying both sealing performance and easy-open performance is an opening force (peel strength) measured by attaching a push-pull gauge to the grip of the lid and pulling it up at a 45-degree angle to the lid, as shown in Figure 8, which is preferably in the range of 0.3 to 3.0 kgf, and more preferably in the range of 0.5 to 2.5 kgf.

[0029] As a combination of resins that can exhibit such peel strength, two or more thermoplastic resins that have heat sealability and are incompatible with each other can be appropriately combined. The base layer of the container can be made of a conventionally known thermoplastic resin that has been used in the molding of resin containers, such as an olefin resin or a polyester resin. For example, when the base layer is made of a propylene-based polymer, the heat seal layer can be made of a blend of an ethylene-based polymer and a propylene-based polymer, thereby ensuring hermetic sealing while maintaining easy opening, and the peel strength can be adjusted by appropriately changing the blend ratio of the blend.

[0030] Examples of the propylene-based polymer include homopolypropylene, as well as block copolymers and random copolymers of propylene with ethylene or other α-olefins, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. Examples of the ethylene-based polymer include ethylene homopolymers such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and medium- to high-density polyethylenes (MDPE, HDPE), copolymers of ethylene with other α-olefins, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene, or copolymers of ethylene with vinyl monomers, such as (meth)acrylic acid, ethyl (meth)acrylate, methyl (meth)acrylate, vinyl acetate, and styrene, and ionomers.

[0031] In addition to the above-mentioned combinations of olefin-based polymers, the blends may also include combinations of the above-mentioned olefin-based polymers with thermoplastic polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and isophthalate-modified copolymers thereof, or with polycarbonate resins, polyacrylonitrile resins, etc. When a propylene-based polymer and an ethylene-based polymer are used as a blend, in order to ensure good releasability of the flange member made of the blend from the container body made of the propylene-based polymer, it is preferable to use a blend in which the propylene-based polymer and the ethylene-based polymer are blended in a weight ratio ranging from 5:5 to 9.5:0.5.

[0032] The flanged container of the present invention has a structure that efficiently removes air from the recess of the locator for forming the annular joint during container molding, allowing the annular joint to be formed accurately according to the shape of the recess, and by appropriately adjusting the temperature of the locator and the melt flow rate of the surface seal layer so that the resin constituting the surface seal layer can exhibit flowability in response to the pressure of the locator, it is possible to form the annular joint with even greater dimensional accuracy. From this perspective, it is preferable that the melt flow rate of the surface seal layer be 1 g / min or more, preferably 5 g / min or more, more preferably 10 g / min or more, and even more preferably 15 g / min or more, when measured at a temperature of 190°C and a load of 2.16 kg in accordance with JIS K7210-1:2014.

[0033] The container may be an integrally molded two-layer laminate having the above-mentioned base layer and surface seal layer, or may have a multi-layer structure with a gas barrier intermediate layer between the base layers. As mentioned above, the surface seal layer may be formed only on the flange portion of the container. The container of the present invention may be manufactured by any method as long as the flange portion satisfies the above-described configuration, but it is preferable to integrally mold the laminate by thermoforming such as vacuum forming or plug-assisted pressure forming. According to this method, the unevenness corresponding to the annular joint portion and the inner and outer step portions can be easily formed on the upper surface of the flange portion by using a locator (flange holder) during molding. [Industrial Applicability]

[0034] The container of the present invention has an annular joint formed on the upper surface of the flange portion that is dimensionally stable, so it has excellent sealing properties when heat sealed, can be easily opened with less opening force, and can reliably release internal pressure when heated in a microwave oven, making it suitable for use as a container for food and beverages. [Explanation of symbols]

[0035] 1 container, 2 bottom, 3 body, 4 flange, 5 annular skirt, 6 base material layer, 7 surface seal layer, 41 annular joint (joining position), 42 inner step, 43 outer step, 45 outward protrusion, 46 inward protrusion, 100 mold, 101 locator, 102 recess for forming annular joint, 103 protrusion.

Claims

1. A container having a flange portion on the periphery of an opening and an annular joint portion on the upper surface of the flange portion to be joined to a lid material, an upper surface of the annular joint is located higher in the container axial direction than an upper surface of a flange portion located on the inner circumferential side and / or the outer circumferential side of the annular joint; A container characterized in that an outward protrusion that protrudes outward in the container radial direction is formed on at least a portion of the annular joint, and the container radially outermost position of the outward protrusion is located at the same position as or radially outward from the container radially outermost position of the lower surface of the flange portion.

2. 2. The container according to claim 1, wherein the upper surface of the annular joint is formed so that the axial height on the outer side is greater than the axial height on the inner side in the container radial direction at least in the portion where the outward protrusion is formed.

3. 3. The container according to claim 1, wherein the flange portion has an outer wall extending downward from an outer peripheral end of the flange portion in an axial direction of the container.

4. 3. The container according to claim 1, wherein a plurality of said outward protrusions are formed.

5. 3. The package according to claim 1 or 2, which is for use in microwave heating.

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