Container with flange

Abstract

To provide a container with a flange that is provided with an annular joint part shaped precisely 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 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 than the upper surface of the flange part positioned closer to an inner periphery side and / or an outer periphery side than the annular joint part. A protruding part connected to the annular joint part is formed in the flange part. The upper surface of the protruding part is positioned lower in a direction of the axis of the container than the upper surface of the annular joint part.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 that is capable of providing 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 portion combine high sealing performance with ease of 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 when eating, and in order to prevent the package from bursting due to an increase in the internal pressure of the container during microwave heating, a method has been widely used in the past in which a steam release hole is formed in advance by partially peeling off the lid or by drilling a hole in the package before microwave heating. However, since such a method is cumbersome for consumers, it is desirable to be able to heat in a microwave oven without peeling off the lid. In addition, during microwave cooking, a steaming effect can be obtained by maintaining the internal pressure of the package in an increased state for a certain period of time, but if a steam release hole is formed in advance, such a steaming effect cannot be obtained sufficiently.

[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, the heat-sealed portion having a protrusion that protrudes toward the inside of the container 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 above, in which a protrusion is formed on the upper surface of the flange portion and an opening portion facing outward and inward is formed on this protrusion, the protrusion on the upper surface of the flange portion is formed by pressing from the upper surface of the flange portion with a mold generally called a locator. However, since the portion of the mold corresponding to the protrusion is recessed relative to the portion that abuts against the upper surface of the flange portion, if this recess does not have a vent function when the mold is pressed, air will accumulate, and there is a problem that the protrusion cannot be shaped according to the shape of the mold.

[0005] An example of a flanged container in which a protrusion can be formed on the upper surface of the flange without causing such problems is the one described in Patent Document 2 below. That is, the container described in Patent Document 2 below has a heat-sealed portion formed in a rib shape around the entire periphery of the upper surface of the flange and 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 by the lower mold from below the flange, so the above-mentioned problems do not occur.

[0006] Furthermore, the following Patent Document 3 describes a flange molding method for a flanged container, which comprises using an upper mold having a gripping surface on which grooves are formed continuously or intermittently along the circumferential direction and equipped with a ventilation structure capable of discharging atmospheric gas within the grooves from the grooves, and gripping a portion of a molding material made of thermoplastic resin corresponding to the flange with the gripping surface of the upper mold and a gripping surface of a lower mold that is paired with the upper mold, and thermoforming the molding material into a predetermined container shape, thereby forming a flange around the periphery of the container opening and molding a protrusion corresponding to the grooves on the top surface of the flange. It is described that the ventilation structure is provided by providing an air hole, 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] JP 2019-85178 A [Patent Document 3] JP 2006-88669 A 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, an outward protrusion, and an inward protrusion for forming an internal pressure release passage with high dimensional accuracy compared to when the protrusion is formed from above the flange portion. Furthermore, according to the molding method of Patent Document 3, since the upper mold has a ventilation structure capable of discharging the atmospheric gas within the groove, it is possible to form a protrusion corresponding to this groove on the upper surface of the flange with good shape reproducibility. However, since the projections are formed by applying pressure to the molten resin, if ventilation is achieved through vent holes formed in the grooves of the mold, the molten resin may enter the vent holes, making it difficult to use the mold continuously for a long period of time. In addition, 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 made of a porous material, the mold becomes very expensive, and there is a problem that clogging occurs easily, as in the case of vent holes.

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

[0010] According to the present invention, a container is provided which has a flange portion on the periphery of an opening and an annular joint on the upper surface of the flange portion which serves as a joining position with a lid material, the upper surface of the annular joint being 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, and the flange portion is formed with a protrusion portion which connects to the annular joint, and the upper surface of the protrusion portion being located lower in the axial direction of the container than the upper surface of the annular joint.

[0011] In the container of the present invention, (1) An outward protrusion protruding outward in the container radial direction is formed on at least a part of the annular joint, and the protrusion is connected to the outward protrusion; (2) The upper surface of the annular joint is formed so that the axial height of the upper surface of the annular joint is greater on the outer side than on the inner side in the radial direction of the container at least at a portion where the upper surface is connected to the protruding portion; (3) 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) The outermost position of the protrusion in the container radial direction is located outward in the container radial direction from the inner surface of the outer wall. (5) It is for microwave heating. is preferred. Effect of the Invention

[0012] In the flanged container of the present invention, a protrusion, the upper surface of which is located lower in the axial direction of the container than the upper surface of the annular joint, is formed on the outer or inner side of the annular joint formed on the upper surface of the flange portion, in the inner and / or outer radial direction of the container.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, etc., this protrusion makes it easier for air in the recess for forming the annular joint (hereinafter sometimes referred to as the ``recess'') formed in the locator to flow toward the outer or inner side of the flange portion, and the air can be efficiently released from within the recess, making it possible to form an annular joint with excellent dimensional stability that conforms to the shape of the recess. Furthermore, in a container in which an outward protrusion that protrudes radially outward from the container is formed on at least a portion of the annular joint, the above-mentioned protrusion is formed on the outer peripheral end of such outward protrusion, making it possible to more effectively release air from within the above-mentioned recess.

[0013] 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 at the connection portion with the protrusion. 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 protrusion, makes it possible to more efficiently escape the air within the recess. This air discharge action transfers the annular joint forming recess formed on the locator to the flange, and the annular joint can be formed with good 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 description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an example of a flanged container of the present invention. [Diagram 2] 2 is an enlarged partial plan view showing a flange portion of the container shown in FIG. [Diagram 3] 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 for explaining a method for forming the protrusions shown in FIG. 2. FIG. [Diagram 5] 4 is an enlarged plan view showing a flange portion of another example of a flanged container of the present invention. FIG. [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 for explaining a method for forming the protrusions shown in FIG. 6. [Figure 8] 4 is an enlarged plan view showing a flange portion of another example of a flanged container of the present invention. FIG. [Figure 9] 4 is an enlarged plan view showing a flange portion of another example of a flanged container of the present invention. FIG. [Figure 10] FIG. 13 is a diagram for explaining a method for measuring opening force. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The container and packaging body 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 roughly 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. As a result, 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.

[0016] 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 shows an enlarged YY cross section of Fig. 2, the upper surface of the flange portion 4 has an annular joint 41, which is the joining position (heat seal position) of the lid material, in the center, and an inner step portion 42 on the inside of the annular joint 41. In addition, in the specific example shown in Fig. 2, an outer step portion 43 is formed on the outside of the annular joint 41. Note that grooves 41c and 41d, in which the surface seal layer 7 is thin or missing, are formed between the container radial inner edge (hereinafter referred to as the "inner peripheral edge") 41a and the container radial outer edge 41b (hereinafter referred to as the "outer peripheral edge") of the annular joint 41 and the inner step portion 42 and the outer step portion 43, respectively. By having these inner step portion 42 and outer step portion 43, as described below, when the lid material is joined to the annular joint portion 41 by heat sealing, 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.

[0017] 2, the container of the present invention may have a plurality of inwardly protruding portions formed at the annular joint 41, which protrude inward in the radial direction of the container, and when the internal pressure rises due to microwave heating, stress is concentrated at these inwardly protruding portions, causing the base material layer 6 and surface seal layer 7 in these portions to peel off in preference to other portions, forming a passage for releasing the internal pressure. Also, as long as the container has an internal pressure release function that forms an internal pressure release passage, it is not limited to the inwardly protruding portions described above, but hereinafter the portion at the annular joint 41 where the inwardly protruding portions are formed will be referred to as the "internal pressure release portion."

[0018] In the specific example shown in Fig. 2 and Fig. 3, a plurality of protrusions 44 are formed, connected to the outer end of the outer protrusion 45 in the container radial direction, and the protrusions 44 are lower in height than the container axial height of the annular joint 41. The upper surface of the annular joint 41 on which the outer protrusion 45 is formed is formed as an inclined surface whose height increases from the inside of the container to the outside. As a result, as described later, air in the recess of the locator can be efficiently released during container molding, and the annular joint can be molded with high dimensional accuracy. The upper surface of 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 outside than on the inside of the container radial direction. Furthermore, if the upper surface of the annular joint is formed as an inclined surface, when it is pressed from above with a locator, it is believed that the air in the recess flows from the shallow inner part of the recess which first comes into contact with the resin sheet to the deep outer part, thereby discharging the air in the recess to the outside of 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. In addition, when the annular joint, whose upper surface is an inclined surface as described above, is pressed and heated from above by a heat seal head, the outer part, which is taller, is pressed and heated more than the inner part, so that the outer peripheral end of the surface seal layer of the annular joint melts and protrudes more than the inner peripheral end, and the outer side of the seal layer of the lid material 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 material, which are not easily peelable from each other, are integrated, so that when opening, they are integrated and follow the movement of the lid material, so that it is possible to easily proceed with interlayer peeling with the base layer of the container, and the lid material can be easily peeled off from the container, improving the ease of opening.

[0019] Fig. 4 is a schematic diagram for explaining a method for forming the protrusion 44 connected to the outer tip in the radial direction of the container of the outward protrusion 45 shown in Fig. 2 and Fig. 3. Note that in Fig. 4, a part of the mold other than the part for forming the flange portion is omitted. Although the container of the present invention is not limited to this method, it can be suitably molded by thermoforming such as vacuum molding or plug-assisted pressure molding, in which case molding of the container and formation of the annular joint on the upper surface of the flange can be performed simultaneously. That is, as shown in Fig. 4, in a state where the part of the resin sheet that will become the flange is sandwiched from above and below by a mold 100 capable of forming the container shape and a locator 101 capable of forming the annular joint, pressure is applied from above to bring the resin sheet into contact with the mold 100 to form the container shape, and an annular joint 41 is formed on the upper surface of the flange 4 by a recess for forming the annular joint (hereinafter, sometimes simply referred to as a "recess") 102 formed on the lower surface of the locator 101.

[0020] In the flanged container of the first embodiment having an outer wall (annular skirt portion 5) hanging down from the outer peripheral end of the flange portion, a protrusion 44 lower than the height of the annular joint 41 is formed outside the outer peripheral edge of the annular joint 41, so that the container radially outermost position A (hereinafter sometimes referred to as "position A") of the protrusion 44 is located radially outward of the container radially outermost position B (hereinafter sometimes referred to as "position B") of the lower surface of the flange portion 4. Therefore, as is clear from Fig. 4, when the flange portion 4 is pressed with the locator 101 to form the annular joint 41, the vertical distance between the upper surface of the mold 100 that sandwiches the flange portion and the lower surface of the locator 101 is different between positions A and B on the flange portion 4 (position B: t0<position A: t1). For this reason, at the flange portion radially inward of the container than position B, the pressing force from the locator 101 is firmly supported over a short distance by the upper surface of the mold 100, whereas at the flange portion radially outward of the container than position B, 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, so that almost no reaction force from the mold 100 acts on position A of the flange portion, and position A is more likely to bend due to the pressing force of the locator 101 than position B. 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 to be connected to the protrusion 44, is efficiently discharged from position A, which is likely to bend downward due to the pressing force of the locator 101, combined with the fact that the height of the protrusion 44 is lower than that of the annular joint 41, and therefore the air from the recess 102 can easily escape through the protrusion 44.This makes it possible to form an annular joint having a shape that matches the shape of the recess 102 formed in the locator 101.

[0021] Figures 5 and 6 are figures showing another example of a flanged container of the present invention. This flanged container of the second embodiment has a container shape that is almost the same as the flanged container of the first embodiment 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. That is, as is clear from Fig. 5, which is a partially enlarged plan view showing the flange portion of the container enlarged from the top, and Fig. 6, which is an enlarged view of the ZZ cross section of Fig. 5 as a schematic diagram for explaining the flanged container of Fig. 5, a plurality of pairs of two continuous outward protrusions 45, 45 are formed in the annular joint 41. Furthermore, protrusions 44 whose height is lower than the height of the upper surface of the annular joint are formed and connected to the ends of the outward protrusions 45 in the container radial direction.

[0022] In molding a container having such a flange shape, as shown in Figure 7, as in the first embodiment of the container, the portion of the resin sheet that will become the flange portion is clamped 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 and a protrusion 44 on the upper surface of the flange portion 4. However, since the annular joint 41 is connected to the protrusion 44, and the protrusion 44 is lower in height than the annular joint, and the radial outer side of the protrusion 44 extends to the side of the locator 101 (the outermost position in the radial direction of the container), the air in the recess 102 of the locator 101 is efficiently discharged from the side of the locator 101 through the protrusion 44.

[0023] In this embodiment having no annular skirt portion, trimming can be performed along line L-L shown in Fig. 5 at the same time as molding the container with the mold and locator shown in Fig. 7, or trimming can be performed along line MM shown in Fig. 5 after molding the container with the mold and locator shown in Fig. 7. When trimming is performed along line MM, the layer ends of the laminate consisting of the base layer and surface seal layer constituting the container are exposed, facilitating interlayer peeling, improving the ease of opening the container.

[0024] The flanged container of the present invention is not limited to the specific example described above, so long as a protrusion is formed on the outer circumferential side and / or the inner circumferential side of the annular joint in the container radial direction. The shape and number of the protrusions can be appropriately changed, but it is preferable that they are formed in multiple places. For example, in the specific example shown in the figure, the protrusion is formed in connection with the outer peripheral end of the outward protrusion of the annular joint, which makes it possible to efficiently discharge air from within the portion for forming the annular joint. However, as shown in Figure 8, even if a protrusion 44 is formed on the outer peripheral side of the annular joint 41 in the portion that is not the outward protrusion (Figure 8(A)), or even if a protrusion 44 is formed on the inner peripheral side of the annular joint 41 in the portion that is not the outward protrusion (Figure 8(B)), the air from within the recess for forming the annular joint can escape through the protrusion. In addition, when the outer protrusion is shaped to protrude outward at an acute angle, as shown in Fig. 9, corners 41e are formed at both inner roots of the outer protrusion, and if the protrusion 44 is formed so as to connect to the corners 41e, the air in the annular joint can be discharged from the recess to the inside of the container, as in the case where the outer protrusion is connected to the outer circumferential end of the outer protrusion and protrudes through the protrusion. In addition, it is preferable to provide the protrusion 44 on the outer circumferential side of the annular joint, but as shown in Fig. 9, by providing the protrusion 44 on the inner circumferential side in addition to the outer circumferential side, the air in the recess can be efficiently discharged. In the case where the protrusion is provided on the inner circumferential side, the innermost position A' in the container radial direction of the protrusion is provided to be located inward in the container radial direction from the innermost position B' in the container radial direction of the lower surface of the flange, as in the case where the protrusion is on the outer circumferential side.

[0025] In addition, the height of the upper surface of the annular joint is formed so as to increase from the inside to the outside in the container radial direction, but this is not limited thereto, and the height of the upper surface of the annular joint may be higher on the inner side than the central part of the annular joint. In this case, the surface seal layer on the inner side of the container radial direction of the annular joint melts and protrudes in a large amount, and the seal layer of the lid material melts in a large amount on the inner side as well, and the molten resin protruding from the surface seal layer of the container and the seal layer of the lid material, which are not easily peeled from each other, are integrated inside the annular joint. When the internal pressure increases due to microwave heating, these are integrated and follow the movement of the lid material, making it possible to easily proceed with interlayer peeling with the base layer of the container, and an internal pressure release passage is formed, making it possible to smoothly release the internal pressure.

[0026] The height difference formed on the upper surface of the annular joint between the highest inner or outer circumferential end and the lowest part is not limited to this, but is preferably 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. In addition, the higher the height of the protrusion in the axial direction of the container, the greater the effect of removing air, but if it is higher than the height of the annular joint in the axial direction of the container or if the height is close to that of the annular joint, there is a risk of impairing the ease of opening during heat sealing, etc. Therefore, it is preferable that the height of the protrusion is lower than the height of the outer circumferential end or inner circumferential end of the adjacent annular joint, and the difference is in the range of 0.05 mm to 0.4 mm, particularly 0.1 to 0.3 mm. This, coupled with the positional relationship between Position A and Position B described above, allows air to be efficiently released from the annular joint forming recess of the locator.

[0027] The shape and number of the outward protruding portion and the inward protruding 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 in a microwave oven or the like, 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 as a single unit 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 and portions intended for releasing internal pressure in the flange, it is possible to absorb the differences in thickness that occur and form an annular joint with high dimensional accuracy, and it becomes possible to reliably release the internal pressure by heating in a microwave oven, etc.

[0028] The step between the upper surface of the container's radially inner end portion of the annular joint in the intended internal pressure release portion and the inner step portion is, although not limited to, in the range of 0.2 to 2.0 mm, preferably 0.2 to 1.0 mm. By having it in this range, molten resin from the surface sealing layer of the container and lid material can be prevented from contacting the inner 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 end 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 end of the annular joint is, although 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.

[0029] 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, etc., 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 a 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 thereto, 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 be a square container, or may be a polygonal container or an elliptical container. As a lid material that can be used with the container of the present invention, in addition to a flexible sheet-like lid material, it may also be a molded lid in the shape of a drop lid.

[0030] As described above, the base material layer and the surface seal layer of the container are preferably peeled off by interlayer peeling, but may be peeled off by cohesive peeling or interfacial peeling as long as they can exhibit easy peeling properties. Also, the base material layer and the heat seal layer on the lid side may be peeled off easily. As a suitable peel strength for satisfying both the sealing performance and the easy-open performance, the opening force (peel strength) measured by attaching a push-pull gauge to the gripping part of the lid and pulling it up in a direction at 45 degrees to the lid, as shown in Figure 10, 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.

[0031] As a combination of resins capable of exhibiting such peel strength, two or more types of 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 such as an olefin resin, polyester resin, or the like that has been conventionally used in molding resin containers. 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.

[0032] Examples of the propylene-based polymer include homopolypropylene, as well as block copolymers and random copolymers of propylene and 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), medium-high density polyethylene (MDPE, HDPE), etc., copolymers of ethylene and other α-olefins, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc., and vinyl monomers, such as (meth)acrylic acid, ethyl (meth)acrylate, methyl (meth)acrylate, vinyl acetate, styrene, etc., and ionomers.

[0033] 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, polycarbonate resins, polyacrylonitrile resins, etc. When a propylene-based polymer and an ethylene-based polymer are used as a blend, in order to ensure that a flange member made of the blend exhibits good peelability from a container body made of a propylene-based polymer, it is preferable to suitably use a blend in which a propylene-based polymer and an ethylene-based polymer are blended in a weight ratio in the range of 5:5 to 9.5:0.5.

[0034] 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, and can form the annular joint with good reproducibility according to the shape of the recess, but 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 express fluidity in response to the pressure of the locator, it is possible to form the annular joint with even better dimensional accuracy. From this viewpoint, it is preferable that the melt flow rate of the surface seal layer is 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.

[0035] The container may be an integrally molded two-layer laminate having the above-mentioned base layer and surface seal layer, or may be a multi-layer structure having a gas barrier intermediate layer as an intermediate layer between the base layers. Also, as described 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-mentioned configuration, but it is preferable to integrally mold the laminate by thermoforming such as vacuum forming, plug-assisted pressure forming, etc. According to this method, the unevenness corresponding to the annular joint portion and the inner and outer steps can be easily formed on the upper surface of the flange portion by a locator (flange holder) during molding. [Industrial Applicability]

[0036] The container of the present invention has an annular joint formed on the upper surface of the flange portion which is dimensionally stable, and therefore 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]

[0037] 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, 44 protrusion, 45 outward protrusion, 100 mold, 101 locator, 102 recess for forming annular joint.

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 a protrusion portion is formed on the flange portion to connect to the annular joint, and an upper surface of the protrusion portion is located lower in the container axial direction than an upper surface of the annular joint.

2. 2. The container according to claim 1, wherein an outward protrusion protruding radially outwardly of the container is formed at at least a portion of the annular joint, and the protrusion is connected to the outward protrusion.

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

4. 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.

5. 5. The container according to claim 4, wherein the outermost positions of the projections in a radial direction of the container are positioned radially outward of the inner surface of the outer wall.

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

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