Laminated container, and method for manufacturing a laminated container

Abstract

The present invention provides a laminated container with improved moldability while including a barrier layer, and a method for manufacturing a laminated container. [Solution] The laminated container 100 of the present disclosure has a body portion 20 for containing contents and a bottom portion 30 that closes the lower end of the body portion 20, and is equipped with a laminated structure, characterized in that the laminated structure comprises a barrier layer 23 made by blending 5% to 20% by weight of high-density polyethylene resin with an ethylene-vinyl alcohol copolymer resin, an outer layer portion 22 provided on the outside of the barrier layer 23 and containing polyethylene resin, and an inner layer portion 24 provided on the inside of the barrier layer 23 and containing polyethylene resin.

Description

Technical Field

[0001] The present disclosure relates to a laminated container and a method for manufacturing a laminated container.

Background Art

[0002] Conventionally, synthetic resin containers excellent in mass productivity have been known as containers for storing content liquids such as food seasonings and beverages like soy sauce, cosmetics like lotions, and toiletries like shampoos, conditioners and liquid soaps (see, for example, Patent Document 1).

[0003] The synthetic resin container described in Patent Document 1 includes a container body having an outer shell and an inner bag. The container body is configured such that the inner bag contracts as the content decreases, and is configured as a rigid container in which the innermost layer of the outer shell is an EVOH layer. When the content in the inner bag is discharged, the volume of the inner bag decreases and deforms, effectively suppressing the inflow of air into the inner bag from the outside. Further, by forming the innermost layer of the outer shell as an EVOH layer, the gas barrier property of the container body can be improved.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] By the way, in the synthetic resin container including the EVOH layer as described above, when an attempt is made to form the container by, for example, thermoforming a laminated sheet, a load is applied to the EVOH layer during the container forming process, which may cause the EVOH layer to break. Therefore, there is still room for improvement in this regard.

[0006] This disclosure has been made in view of these issues, and its purpose is to provide a laminated container that includes a barrier layer while improving moldability, and a method for manufacturing a laminated container. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the laminated container of this disclosure is [1] A stacked container having a body for containing contents and a bottom that closes the lower end of the body, and having a stacked structure, The aforementioned laminated structure is A barrier layer comprising an ethylene-vinyl alcohol copolymer resin blended with a high-density polyethylene resin in an amount of 5% to 20% by weight, An outer layer portion containing polyethylene resin is provided on the outside of the barrier layer, An inner layer portion containing polyethylene resin is provided inside the barrier layer. It is characterized by having the following features.

[0008] Furthermore, the laminated container of this disclosure is [2] In the configuration described in [1] above, it is preferable that at least one of the outer layer and the inner layer includes a bio-resin layer in which a bio-polyethylene resin is compounded with a high-density polyethylene resin.

[0009] Furthermore, the laminated container of this disclosure is [3] In the configuration described in [2] above, the bio-resin layer preferably contains 10% by weight or more of a bio-polyethylene resin.

[0010] Furthermore, the laminated container of this disclosure is [4] In the configuration described in [2] or [3] above, it is preferable that the outer layer has an outer cover layer on the outside of the bio-resin layer, which is made by compounding a bio-polyethylene resin with a high-density polyethylene resin, and the inner layer has an inner cover layer on the inside of the bio-resin layer, which is made by compounding a bio-polyethylene resin with a high-density polyethylene resin.

[0011] Furthermore, the laminated container of this disclosure is [5] In any of the configurations described in [1] to [4] above, it is preferable that the laminated sheet having the laminated structure is formed by thermoforming.

[0012] Furthermore, in order to solve the above-mentioned problems, the manufacturing method of the laminated container of this disclosure is [6] A method for manufacturing a laminated container having a body for containing contents and a bottom for closing the lower end of the body, the laminated container having a laminated structure, The aforementioned laminated structure is A barrier layer comprising an ethylene-vinyl alcohol copolymer resin blended with a high-density polyethylene resin in an amount of 5% to 20% by weight, An outer layer portion containing polyethylene resin is provided on the outside of the barrier layer, An inner layer portion containing polyethylene resin is provided inside the barrier layer. Equipped with, The invention is characterized by forming an outer cover layer, which is the outermost layer of the outer layer, and an inner cover layer, which is the innermost layer of the inner layer, using a molten resin containing polyethylene resin and having a melt flow rate of 1.5 [g / 10min] or more and less than 2.0 [g / 10min].

[0013] Furthermore, the manufacturing method of the laminated container described herein is [7] In the configuration according to the above [6], it is preferable that the resin layer inside the outer cover layer in the outer layer portion and the resin layer outside the inner cover layer in the inner layer portion are formed from a molten resin containing a polyethylene-based resin and having a melt flow rate of 0.5 [g / 10min] or more and 1.1 [g / 10min] or less.

[0014] Further, the method for manufacturing a laminated container of the present disclosure comprises: [8] In the configuration according to the above [6] or [7], it is preferable that an average melt flow rate at the time of melting between the outer cover layer and the resin layer inside the outer cover layer in the outer layer portion, and an average melt flow rate at the time of melting between the inner cover layer and the resin layer outside the inner cover layer in the inner layer portion are 1.0 [g / 10min] or more and less than 1.5 [g / 10min].

[0015] Further, the method for manufacturing a laminated container of the present disclosure comprises: [9] In the configuration according to any one of the above [6] to [8], it is preferable that the barrier layer is formed by blending a high-density polyethylene-based resin having a melt flow rate at the time of melting of 0.45 [g / 10min] or more and 1.5 [g / 10min] or less into an ethylene-vinyl alcohol copolymer resin. Effects of the Invention

[0016] According to the present disclosure, it is possible to provide a laminated container that includes a barrier layer and has improved moldability, and a method for manufacturing the laminated container. Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a front view of a laminated container according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a bottom view of a laminated container according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a left side view of a laminated container according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a detailed view of portion A in FIG. 1. [Figure 5] This flowchart shows the procedure for manufacturing a stacked container, which is one embodiment of the present disclosure. [Modes for carrying out the invention]

[0018] The present disclosure will be explained more specifically with reference to the drawings below.

[0019] The stacked container 100, which is one embodiment of the present disclosure shown in Figures 1 to 3, comprises a cylindrical opening 10 for putting in and taking out contents, a cylindrical body 20 connected below the opening 10, and a bottom 30 that closes the lower end of the body 20.

[0020] In this specification, claims, and drawings, the vertical direction refers to the upward and downward directions when the stacked container 100 is in an upright position as shown in Figure 1. The front-to-back direction refers to the direction perpendicular to the plane of the paper in Figure 1 and the left-to-right direction in Figure 3. The left-to-right direction refers to the left-to-right direction in Figure 1 and the direction perpendicular to the plane of the paper in Figure 3. The radially outward direction refers to the direction away from the central axis O of the stacked container 100 in Figure 1, along a straight line passing through and perpendicular to the central axis O, while the radially inward direction refers to the direction approaching the central axis O along the same straight line. The circumferential direction refers to the direction of rotation around the central axis O.

[0021] The accompanying drawings of this disclosure are drawn to an equal scale in the vertical, front-to-back, and left-to-right directions, except for the thicknesses of the outer layer 22, barrier layer 23, and inner layer 24 in Figure 1A and Figure 4. The aspect ratio of the laminated container 100 in the drawings represents the aspect ratio of the laminated container 100 of this disclosure. However, the configuration, shape, dimensional ratio, etc. of the laminated container 100 in the accompanying drawings are merely one embodiment of this disclosure. This disclosure should be interpreted based on the wording of the claims and is not limited to the configuration, shape, dimensional ratio, etc. shown in the drawings.

[0022] As shown in Figures 1 and 2, the opening 10 has an outer peripheral wall 11 that is roughly rectangular in shape (more precisely, the long and short sides bulge slightly radially outward in a plan view) with rounded corners in a plan view, and a flange portion 12 extending radially outward is provided at the upper end of the outer peripheral wall 11. As shown in Figures 1 and 3, the width of the outer peripheral wall 11 of the opening 10 gradually increases slightly downward in a front view and a left side view. The lid may also be attached to the opening 10 by fitting the radial outer edge of the flange portion 12 to the inner surface of the peripheral wall of a lid (not shown). The outer edge of the flange portion 12 has a roughly rectangular shape corresponding to the shape of the outer peripheral wall 11 of the opening 10.

[0023] Below the opening 10, a cylindrical body 20 is provided. The body 20 is integrally formed with the opening 10 and is connected to the lower end of the opening 10 via a stepped portion 15. As shown in Figures 1 and 3, the body 20 is formed to be slightly narrower than the opening 10 in front view and left side view at its upper end. In plan view, the body 20 has a substantially rectangular shape with rounded corners, similar to the opening 10, and is configured so that its width gradually decreases downwards in front view and left side view, as shown in Figures 1 and 3.

[0024] As shown in Figures 1 to 3, the bottom portion 30 is attached to the lower end of the body portion 20. The bottom portion 30 has a contact portion 31 that abuts against the mounting surface when the stacked container 100 is in an upright position, and a bottom recess 32 that is recessed upward at the radial center of the bottom portion 30. As shown in Figures 1 and 3, the corners that form the boundary between the body portion 20 and the bottom portion 30 are rounded off.

[0025] Next, the layer configuration of the stacked container 100 will be explained using Figure 4 and other figures. The body portion 20 comprises an outer layer portion 22, a barrier layer 23, and an inner layer portion 24, arranged in order from the radially outer (outside) to the radially inner (inside). In this embodiment, the outer layer portion 22 and the barrier layer 23 are bonded together by an outer adhesive layer 25a. Similarly, the barrier layer 23 and the inner layer portion 24 are bonded together by an inner adhesive layer 25b. In the bottom portion 30, the outer layer portion 22, the barrier layer 23, and the inner layer portion 24 are stacked in order from the bottom (outside) to the top (inside). That is, in this specification and claims, "inside" means the side of the containment space S in the stacked structure, and "outside" means the opposite side of "inside".

[0026] The outer layer portion 22 has an outer cover layer 22a located on the radially outermost side of the body portion 20 and forming the outermost layer of the laminated container 100, and an outer bio-resin layer 22b located radially inward of the outer cover layer 22a and adjacent to the outer cover layer 22a.

[0027] In this embodiment, the outer cover layer 22a is formed from high-density polyethylene resin (HDPE). More specifically, the outer cover layer 22a is composed of a resin in which 50% by weight each of HDPE manufactured by Nippon Polyethylene Co., Ltd., model number: Novatec® HJ340, and HDPE (biopolyethylene) manufactured by Braskem, model number: SGE7252, are blended. In the state of the laminated sheet before thermoforming, the thickness of the outer cover layer 22a can be, for example, 88 μm.

[0028] The melt flow rates (MFRs) of HJ340 and SGE7252 during melting are 1.5 [g / 10min] and 2.0 [g / 10min], respectively. Other HDPEs (petroleum-derived) and biopolyethylenes with similar melt flow rates may be used instead of HJ340 and SGE7252.

[0029] The outer bio-resin layer 22b is formed from high-density polyethylene resin (HDPE). More specifically, the outer bio-resin layer 22b is composed of a resin blend of 65% by weight and 35% by weight of HDPE (model no. Novatec® HB439R) manufactured by Nippon Polyethylene Co., Ltd., and HDPE (bio-polyethylene) manufactured by Braskem, Ltd., respectively. In the laminated sheet state before thermoforming, the thickness of the outer bio-resin layer 22b can be, for example, 782 μm.

[0030] The melt flow rates (MFRs) of HB439R and SGE7252 are 0.55 [g / 10min] and 2.0 [g / 10min], respectively. Other HDPEs (petroleum-derived) and biopolyethylenes with similar melt flow rates may be used instead of HB439R and SGE7252.

[0031] The outer layer 22 may have a petroleum-derived high-density polyethylene resin layer that does not contain biopolyethylene instead of the outer bio-resin layer 22b. Similarly, the inner layer 24 may have a petroleum-derived high-density polyethylene resin layer that does not contain bio-polyethylene instead of the inner bio-resin layer 24b. Either the outer layer 22 or the inner layer 24 may have a bio-resin layer containing biopolyethylene, or neither the outer layer 22 nor the inner layer 24 may have a bio-resin layer.

[0032] The outer cover layer 22a of the outer layer 22 may be made of petroleum-derived polyethylene resin that does not contain biopolyethylene. Similarly, the inner cover layer 24a of the inner layer 24 may be made of petroleum-derived polyethylene resin that does not contain biopolyethylene. Either the outer cover layer 22a or the inner cover layer 24a may contain biopolyethylene, or neither the outer cover layer 22a nor the inner cover layer 24a may contain biopolyethylene.

[0033] The outer layer 22 is bonded to the inner barrier layer 23 by an outer adhesive layer 25a. For the outer adhesive layer 25a, for example, an acid-modified polyolefin resin (manufactured by Mitsui Chemicals, Inc., model number: Admer® NF518) can be used. Admer NF518 is a maleic acid-modified polyolefin, a suitable material for food containers, and offers excellent safety when containing food. In the laminated sheet state before thermoforming, the thickness of the outer adhesive layer 25a can be, for example, 37 μm. When containing contents other than food, various adhesive resins other than Admer NF518 may be used.

[0034] The barrier layer 23 is provided between the outer layer 22 and the inner layer 24 to suppress the permeation of moisture and gases such as oxygen through the body 20. In this embodiment, the barrier layer 23 is composed of a resin in which EVOH resin with an ethylene content of approximately 44 mol% and HDPE manufactured by Nippon Polyethylene Co., Ltd., model number: Novatec® HB439R, are blended in amounts of 82% by weight and 18% by weight, respectively.

[0035] The mixing ratio of the EVOH resin and HB439R described above can be such that the proportion of HB439R is 5% by weight or more and 20% by weight or less (i.e., the proportion of EVOH resin is less than 95% by weight but greater than 80% by weight). By setting the proportion of HB439R, which is HDPE, to 5% by weight or more and 20% by weight or less, when the laminated container 100 is formed by thermoforming a laminated sheet having the configuration shown in Figure 4, as described later, it is possible to effectively suppress the occurrence of defects in the barrier layer 23 while ensuring the barrier properties of the barrier layer 23 against oxygen and the like.

[0036] In other words, by including 5% by weight or more of HDPE such as HB439R in the barrier layer 23 containing EVOH resin, the ductility of the barrier layer 23 is increased, effectively suppressing the tearing of the barrier layer 23 when the laminated container 100 is manufactured by thermoforming or the like. Furthermore, by keeping the proportion of HDPE such as HB439R at 20% by weight or less, the oxygen permeability of the laminated container 100 can be reduced to 0.03 [cc / day / pack] or less.

[0037] In addition, other polyethylenes (petroleum-derived) with a similar melt flow rate (for example, within ±50% or ±0.1 [g / 10min] of the melt flow rate of HB439R) may be used instead of HB439R that constitutes the barrier layer 23.

[0038] The inner layer portion 24 has an inner cover layer 24a located radially inward of the body portion 20 and forming the innermost layer of the laminated container 100, and an inner bio-resin layer 24b located radially outward of the inner cover layer 24a and adjacent to the inner cover layer 24a.

[0039] In this embodiment, the inner cover layer 24a is formed from high-density polyethylene resin (HDPE). More specifically, the inner cover layer 24a is composed of a resin in which 50% by weight each of Novatec HJ340, an HDPE manufactured by Nippon Polyethylene Co., Ltd., and SGE7252, an HDPE (biopolyethylene) manufactured by Braskem, are blended. In the state of the laminated sheet before thermoforming, the thickness of the inner cover layer 24a can be, for example, 84 μm.

[0040] The inner bio-resin layer 24b is formed from high-density polyethylene resin (HDPE). More specifically, the inner bio-resin layer 24b is composed of a resin blend of 65% by weight and 35% by weight of HDPE (model no. Novatec® HB439R) manufactured by Nippon Polyethylene Co., Ltd., and HDPE (bio-polyethylene) manufactured by Braskem, Ltd., respectively. In the state of the laminated sheet before thermoforming, the thickness of the inner bio-resin layer 24b can be, for example, 781 μm.

[0041] The inner layer 24 is bonded to the outer barrier layer 23 by an inner adhesive layer 25b. For the inner adhesive layer 25b, for example, an acid-modified polyolefin resin (manufactured by Mitsui Chemicals, Inc., model number: Admer® NF518), which is an adhesive resin, can be used. In the state of the laminated sheet before thermoforming, the thickness of the inner adhesive layer 25b can be, for example, 40 μm. When containing contents other than food, various adhesive resins other than Admer NF518 may be used.

[0042] In this embodiment, the outer bio-resin layer 22b of the outer layer 22 and the inner bio-resin layer 24b of the inner layer 24 contain bio-polyethylene (manufactured by Braskem, model number: SGE7252) with a plant-derived carbon content of 96% or more. Bio-polyethylene is a biomass plastic made from plant-derived (biomass) raw materials and can be obtained by dehydration and polymerization of bioethanol produced from sugarcane through a fermentation process. Since sugarcane absorbs carbon dioxide through photosynthesis during its growth stage, bio-polyethylene can offset the carbon dioxide emitted when it is incinerated as waste with the carbon dioxide absorbed during the sugarcane's growth stage.

[0043] In this embodiment, the outer bio-resin layer 22b and the inner bio-resin layer 24b are composed of HDPE (model number: Novatec HB439R) manufactured by Nippon Polyethylene Co., Ltd. and bio-polyethylene (model number: SGE7252) manufactured by Braskem, in amounts of 65% by weight and 35% by weight, respectively. By forming the outer bio-resin layer 22b and the inner bio-resin layer 24b by blending bio-polyethylene with petroleum-derived HDPE in this way, the ductility of these resin layers can be improved. Therefore, when molding the laminated container 100, the occurrence of molding defects can be effectively suppressed while improving load-bearing capacity, and by further increasing the proportion of bio-polyethylene, carbon dioxide emissions from the manufacture to the disposal of the laminated container 100 can be reduced.

[0044] In this embodiment, in addition to the outer bio-resin layer 22b and the inner bio-resin layer 24b, the outer cover layer 22a and the inner cover layer 24a are also blended with bio-polyethylene to petroleum-derived HDPE. More specifically, the outer cover layer 22a and the inner cover layer 24a are composed of a resin blended with 50% by weight each of Novatec HJ340, an HDPE manufactured by Nippon Polyethylene Co., Ltd., and SGE7252, a bio-polyethylene manufactured by Braskem. By blending bio-polyethylene with petroleum-derived HDPE in this way to form the outer cover layer 22a and the inner cover layer 24a, the ductility of these resin layers can be improved. Therefore, when molding the laminated container 100, the occurrence of molding defects can be effectively suppressed while improving load-bearing capacity, and the proportion of bio-polyethylene can be increased to reduce carbon dioxide emissions from the manufacture to the disposal of the laminated container 100.

[0045] Next, the manufacturing method of the stacked container 100 will be explained in detail using the flowchart in Figure 5 and other diagrams.

[0046] When manufacturing the laminated container 100, the resins that make up each resin layer of the laminated structure shown in Figure 4 are prepared (step S101 in Figure 5). The resin layers are, from the outside in, the outer cover layer 22a, the outer bio-resin layer 22b, the outer adhesive layer 25a, the barrier layer 23, the inner adhesive layer 25b, the inner bio-resin layer 24b, and the inner cover layer 24a. For example, to form the outer cover layer 22a and the inner cover layer 24a, a molten resin is prepared by blending Novatec HJ340 manufactured by Nippon Polyethylene Co., Ltd. and Braskem's model no. SGE7252 in 50% by weight each. Also, to form the outer bio-resin layer 22b and the inner bio-resin layer 24b, a molten resin is prepared by blending Novatec HB439R manufactured by Nippon Polyethylene Co., Ltd. and Braskem's model no. SGE7252 in 65% by weight and 35% by weight each, respectively. Furthermore, to form the outer adhesive layer 25a and the inner adhesive layer 25b, a molten resin containing Admer NF518, manufactured by Mitsui Chemicals, Inc., is prepared. In addition, to form the barrier layer 23, a molten resin is prepared by blending EVOH resin with an ethylene content of approximately 44 mol% and Novatec HB439R, manufactured by Nippon Polyethylene Co., Ltd., with a melt flow rate (MFR) of 0.55 [g / 10min] in the molten state, in amounts of 82% and 18% respectively. Note that the HDPE blended with the EVOH resin is not limited to Novatec HB439R; it has been confirmed that Novatec HJ340 (MFR 1.5 [g / 10min]) is also acceptable, and other polyethylene-based resins with a melt flow rate (MFR) of 0.45 [g / 10min] or more and 1.5 [g / 10min] or less may also be used.

[0047] Next, a laminated sheet is created including an outer cover layer 22a, an outer bio-resin layer 22b, an outer adhesive layer 25a, a barrier layer 23, an inner adhesive layer 25b, an inner bio-resin layer 24b, and an inner cover layer 24a (step S102 in Figure 5). The laminated sheet can be formed, for example, by co-extrusion, in which the above-mentioned multiple molten resins are simultaneously extruded, thereby forming a laminated sheet having the laminated structure shown in Figure 4. Alternatively, the laminated sheet may be formed by a method other than co-extrusion, such as a lamination method.

[0048] Next, the laminated sheet created in step S102 is heated and softened, then placed in close contact with the cavity of the thermoforming mold and cooled to form the mouth portion 10, body portion 20, and bottom portion 30 shown in Figures 1 to 3, thereby forming the laminated container 100 (step S103 in Figure 5). Thermoforming may be performed by vacuum forming, in which the space between the heated and softened sheet and the mold is made into a vacuum (by removing air through tiny holes in the mold to create a vacuum), causing the laminated sheet to adhere to the mold and be deformed; or it may be performed by pressure forming, in which the heated and softened sheet is pressed against the mold with compressed air to transfer the shape of the mold.

[0049] In step 103, the manufacturing of the laminated container 100 is completed by releasing the laminated container 100, which was formed by thermoforming, from the thermoforming mold.

[0050] As described above, this embodiment is a laminated container 100 having a laminated structure, having a body portion 20 for containing contents and a bottom portion 30 that closes the lower end of the body portion 20. The laminated structure is configured to include a barrier layer 23 made by blending 5% to 20% by weight of high-density polyethylene resin with an ethylene-vinyl alcohol copolymer resin, an outer layer portion 22 provided outside the barrier layer 23 and containing polyethylene resin, and an inner layer portion 24 provided inside the barrier layer 23 and containing polyethylene resin. By adopting this configuration, the ductility of the barrier layer 23 can be increased, effectively suppressing the tearing of the barrier layer 23 when manufacturing the laminated container 100 by thermoforming or the like. Furthermore, load-bearing suitability can be increased while effectively suppressing the occurrence of molding defects. In addition, the oxygen permeability of the laminated container 100 can be kept below a predetermined amount.

[0051] Furthermore, in this embodiment, at least one of the outer layer 22 and the inner layer 24 is configured to include a bio-resin layer (outer bio-resin layer 22b and / or inner bio-resin layer 24b) which is a high-density polyethylene resin blended with a bio-polyethylene resin. By adopting such a configuration, bio-polyethylene can be incorporated into the resin constituting the laminated container 100, thereby reducing carbon dioxide emissions from the manufacture to the disposal of the laminated container 100.

[0052] Furthermore, in this embodiment, the bio-resin layer (outer bio-resin layer 22b and / or inner bio-resin layer 24b) is configured to contain 10% by weight or more of bio-polyethylene resin. By adopting such a configuration, the proportion of bio-polyethylene in the resin constituting the laminated container 100 can be increased, further reducing carbon dioxide emissions from the manufacture to the disposal of the laminated container 100.

[0053] Furthermore, in this embodiment, the outer layer 22 has an outer cover layer 22a made of a high-density polyethylene resin blended with a biopolyethylene resin on the outside of the bio-resin layer (outer bio-resin layer 22b), and the inner layer 24 has an inner cover layer 24a made of a high-density polyethylene resin blended with a biopolyethylene resin on the inside of the bio-resin layer (inner bio-resin layer 24b). By adopting such a configuration, biopolyethylene can be included in the cover layer constituting the laminated container 100, thereby further effectively reducing carbon dioxide emissions from the manufacture to the disposal of the laminated container 100.

[0054] Furthermore, in this embodiment, the laminated sheet having a laminated structure is formed by thermoforming. By adopting this configuration, the barrier layer 23, which is made by blending 5% to 20% by weight of a high-density polyethylene resin with an ethylene-vinyl alcohol copolymer resin, is combined with thermoforming, thereby effectively suppressing the occurrence of molding defects in the laminated container 100 while improving its load-bearing capacity.

[0055] Furthermore, this embodiment is a method for manufacturing a laminated container 100 having a laminated structure, having a body portion 20 for containing contents and a bottom portion 30 that closes the lower end of the body portion 20. The laminated structure comprises a barrier layer 23 made by blending 5% to 20% by weight of high-density polyethylene resin with an ethylene-vinyl alcohol copolymer resin, an outer layer portion 22 provided outside the barrier layer 23 and containing polyethylene resin, and an inner layer portion 24 provided inside the barrier layer 23 and containing polyethylene resin. The configuration includes forming an outer cover layer 22a, which is the outermost layer of the outer layer portion 22, and an inner cover layer 24a, which is the innermost layer of the inner layer portion 24, using a molten resin containing polyethylene resin with a melt flow rate of 1.5 [g / 10min] or more and less than 2.0 [g / 10min]. By adopting such a configuration, the ductility of the barrier layer 23 can be increased, effectively suppressing the tearing of the barrier layer 23 when manufacturing the laminated container 100 by thermoforming or the like. Furthermore, it is possible to improve load-bearing capacity while effectively suppressing the occurrence of molding defects. In addition, the oxygen permeability of the laminated container 100 can be kept below a predetermined amount. Moreover, by using a highly fluid resin material for the outer cover layer 22a and the inner cover layer 24a, the extrusion moldability of the laminated sheet can be improved.

[0056] Furthermore, in this embodiment, the structure includes forming the inner resin layer of the outer cover layer 22a in the outer layer portion 22 and the outer resin layer of the inner cover layer 24a in the inner layer portion 24 using a molten resin containing polyethylene resin with a melt flow rate of 0.5 [g / 10min] or more and 1.1 [g / 10min] or less. By adopting such a structure, it is possible to improve the extrusion moldability of the laminated sheet while making it easier to adjust the thickness of the laminated sheet.

[0057] Furthermore, in this embodiment, the average melt flow rate when melting the outer cover layer 22a and the resin layer inside the outer cover layer 22a in the outer layer portion 22, and the average melt flow rate when melting the inner cover layer 24a and the resin layer outside the inner cover layer 24a in the inner layer portion 24, are configured to be 1.0 [g / 10min] or more and less than 1.5 [g / 10min]. By adopting such a configuration, it is possible to improve the extrusion moldability of the laminated sheet while making it easier to adjust the thickness of the laminated sheet.

[0058] Furthermore, in this embodiment, the barrier layer 23 is formed by blending an ethylene-vinyl alcohol copolymer resin with a high-density polyethylene resin having a melt flow rate of 0.45 [g / 10 min] or more and 1.5 [g / 10 min] or less during melting. By adopting this configuration, the ductility of the barrier layer 23 is enhanced, effectively suppressing the tearing of the barrier layer 23 when the laminated container 100 is manufactured by thermoforming or the like. In addition, load-bearing suitability can be improved while effectively suppressing the occurrence of molding defects.

[0059] While this disclosure has been described based on various drawings and embodiments, it should be noted that those skilled in the art will find it easy to make various modifications and alterations based on this disclosure. Therefore, it should be noted that these modifications and alterations are included within the scope of the present invention. For example, the functions included in each component can be rearranged in a logically consistent manner, and multiple components can be combined into one or separated. It should be understood that these are also included within the scope of the present invention.

[0060] For example, in this embodiment, the outer layer 22 and the inner layer 24 are configured to each have two resin layers, but the embodiment is not limited to this. At least one of the outer layer 22 and the inner layer 24 may be configured to have three or more resin layers.

[0061] Furthermore, although this embodiment is configured to form the laminated container 100 by thermoforming a laminated sheet, the embodiment is not limited to this, and the laminated container 100 may be formed by blow molding a laminated parison or the like.

[0062] Furthermore, in this embodiment, the outer layer 22 and the inner layer 24 are configured to be bonded to the barrier layer 23 by an outer adhesive layer 25a and an inner adhesive layer 25b, respectively, but the embodiment is not limited to this. The outer adhesive layer 25a and the inner adhesive layer 25b may be omitted, and the outer layer 22 and the inner layer 24 may be configured to be bonded to the barrier layer 23 by adhesive resins contained in, for example, the outer bio-resin layer 22b and the inner bio-resin layer 24b. [Examples]

[0063] To confirm the effects of the laminated container 100 of this disclosure, the moldability of the laminated sheet, moldability during thermoforming, buckling strength [N], filling suitability (load-bearing suitability), oxygen permeability, and oxygen barrier properties were evaluated for Examples 1 to 5 having the layer configuration of the present invention as shown in Table 1, and Comparative Examples 1 to 8 prepared as comparative subjects as shown in Tables 2-1 and 2-2. In Tables 1, 2-1, and 2-2, "layer thickness" refers to the layer thickness of each resin layer in the state of the laminated sheet before forming the laminated container 100 by thermoforming. The flexural modulus, density, and MFR of each resin material are summarized in Table 3.

[0064] [Table 1]

[0065] [Table 2-1]

[0066] [Table 2-2] [Table 3]

[0067] In Tables 1, 2-1, and 2-2, the resin used for the barrier layer 23 is either EVOH containing approximately 44 mol% ethylene (indicated as EVOH (ethylene 44 mol%)) or EVOH containing approximately 44 mol% ethylene blended with other HDPEs (indicated as EVOH:HB439R=82:18, etc.). For moldability (sheet), moldability (thermoform), fillability (load-bearing capacity), and oxygen barrier properties, those that met the standards were marked "Good," and those that did not met the standards were marked "Poor." The molded laminated container 100 has the shape shown in Figures 1 to 3 (only the layer thickness differs from the actual dimensional ratio and aspect ratio), and the opening cross-sectional area at the upper end of the mouth 10 is 61.26 cm². 2 The total height is 106.1 mm, and the thickness of the flange portion 12 is 1.2 mm. Furthermore, the thickness of the body portion 20 after thermoforming is 0.31 mm at a height of 20 mm below the flange portion 12, 0.33 mm at a height of 60 mm below the flange portion 12, and 0.43 mm at a height of 90 mm below the flange portion 12. Therefore, the thickness of each resin layer in the body portion 20 after thermoforming can be calculated from the ratio of the thickness of each resin layer to the thickness of the laminated sheet layer in Tables 1, 2-1, and 2-2, and the thickness of the body portion 20 after thermoforming. Note that although there are resin layers labeled as the outer bio-resin layer and the inner bio-resin layer in Tables 1, 2-1, and 2-2, there are examples or comparative examples, such as Example 2 and Comparative Examples 1, 2, and 7, that do not include biomass plastics made from plant-derived (biomass) raw materials.

[0068] The moldability (sheet) evaluates the extrusion moldability of the laminated sheet. As in Comparative Example 2, when resin with too low fluidity (average MFR: 0.55 [g / 10min]) is used in the outer layer 22 and inner layer 24, the extrusion moldability of the laminated sheet deteriorates, resulting in a "fail" rating.

[0069] The moldability (thermoforming) evaluation assesses the moldability during thermoforming. As seen in Comparative Examples 1, 5, and 6, when resins with excessively high fluidity in the outer layer 22 and inner layer 24 (average MFR: 1.5 [g / 10min] or higher) are used, it becomes difficult to adjust the wall thickness of the laminated container 100, resulting in a "No" rating.

[0070] From the comparison of the examples and comparative examples shown in Tables 1, 2-1, and 2-2, it can be seen that by forming the barrier layer 23 with a resin layer containing 5% to 20% by weight of high-density polyethylene resin (HB439R) in an ethylene-vinyl alcohol copolymer resin, and configuring the outer layer 22 and inner layer 24 to include polyethylene resin (HDPE in Examples 1 to 5), a "good" result was obtained in all evaluation items: moldability (sheet), moldability (thermoform), filling suitability (load-bearing suitability), and oxygen barrier properties. On the other hand, when the barrier layer 23 does not contain high-density polyethylene resin (Comparative Examples 1, 3 to 5) or when the outer layer 22 and inner layer 24 do not contain high-density polyethylene resin (Comparative Examples 5 and 6), a "bad" result was obtained in filling suitability (load-bearing suitability), mainly due to reasons such as the EVOH resin in the barrier layer 23 breaking during thermoforming. Furthermore, even when the barrier layer 23 does not contain high-density polyethylene resin, if the outer layer 22 and inner layer 24 are formed of a low-fluidity high-density polyethylene resin (Comparative Example 2), although the filling suitability (load-bearing suitability) was rated as "good," problems sometimes arose with the extrusion moldability of the laminated sheet, resulting in a "bad" rating in the moldability (sheet) evaluation. In Comparative Examples 7 and 8, the barrier layer 23 is formed of a resin layer in which 25% by weight of high-density polyethylene resin is blended with ethylene-vinyl alcohol copolymer resin, resulting in an oxygen permeability exceeding the standard value (0.03 [cc / day / pack]), and thus the oxygen barrier performance evaluation item is rated as "bad."

[0071] Furthermore, a comparison of the examples and comparative examples shown in Tables 1, 2-1, and 2-2 shows that when the barrier layer 23 is formed from a resin layer containing 5% to 20% by weight of high-density polyethylene resin (HB439R) in an ethylene-vinyl alcohol copolymer resin, and the outer cover layer 22a and inner cover layer 24a are formed from a molten resin containing high-density polyethylene resin (HJ340) with a melt flow rate of 1.5 [g / 10min] or more and less than 2.0 [g / 10min], all evaluation items for moldability (sheet), moldability (thermoform), filling suitability (load-bearing suitability), and oxygen barrier properties are evaluated as "good". On the other hand, when the barrier layer 23 does not contain high-density polyethylene resin (Comparative Examples 1, 3 to 5), the filling suitability (load-bearing suitability) is evaluated as "bad", mainly due to reasons such as the EVOH resin in the barrier layer 23 breaking during thermoforming. Furthermore, in the case where the outer cover layer 22a and inner cover layer 24a are formed from a molten resin (SGE7252) with a melt flow rate of 2.0 [g / 10min] (Comparative Example 6), the high fluidity of the molten resin made it difficult to adjust the wall thickness, resulting in a "fail" rating in the moldability (thermoform) evaluation. Also, in the case where the outer cover layer 22a and inner cover layer 24a are formed from a high-density polyethylene resin (HB439R) with low fluidity (melt flow rate of 0.55 [g / 10min]) (Comparative Example 2), problems with extrusion moldability sometimes occurred, resulting in a "fail" rating in the moldability (sheet) evaluation. In Comparative Examples 7 and 8, the barrier layer 23 is formed from a resin layer in which 25% by weight of high-density polyethylene resin is blended with ethylene-vinyl alcohol copolymer resin, resulting in an oxygen permeability exceeding the standard value (0.03 [cc / day / pack]), resulting in a "fail" rating in the oxygen barrier performance evaluation. Furthermore, as long as the above-mentioned melt flow rate range is met, the polyethylene-based resin included in the outer cover layer 22a and the inner cover layer 24a does not have to be HDPE. The same applies to the polyethylene-based resin included in the outer bio-resin layer 22b and the inner bio-resin layer 24b.

[0072] Furthermore, from the results of Examples 1 to 5, it was found that if the average MFR of the outer layer 22 and the inner layer 24 (for the outer layer 22, the average value of the MFR of the outer cover layer 22a and the outer bio-resin layer 22b; for the inner layer 24, the average value of the MFR of the inner cover layer 24a and the inner bio-resin layer 24b) is 1.0 [g / 10min] or more and less than 1.5 [g / 10min], it is easier to achieve both extrusion moldability and thermoforming moldability of the laminated sheet. In addition, as an example of satisfying the above average MFR, it was found that the MFR range of the outer cover layer 22a and the inner cover layer 24a should be 1.5 [g / 10min] or more and less than 2.0 [g / 10min], and the MFR range of the outer bio-resin layer 22b and the inner bio-resin layer 24b should be 0.5 [g / 10min] or more and 1.1 [g / 10min] or less (in the case of Examples 1 to 5). The MFR range of the outer cover layer 22a and the inner cover layer 24a is most preferably 1.5 [g / 10min] or more and 1.75 [g / 10min] or less.

[0073] The filling suitability (load-bearing suitability) is determined by filling the laminated container with contents at approximately 40°C, and then lifting the laminated container from below while pressing the lid from above to create an undercut fit. The result is whether or not buckling occurs in the body 20 of the laminated container 100. When the wall thickness of the laminated container 100 cannot be adjusted (Comparative Examples 1, 5, 6), or when the EVOH layer breaks during thermoforming because only EVOH is used in the barrier layer 23 (Comparative Examples 1, 3 to 5), the filling suitability (load-bearing suitability) is determined to be "fail". As a result of diligent research by the inventors of the present invention, it was found that by blending 5% by weight or more of HDPE with EVOH (ethylene 44 mol%) as the resin constituting the barrier layer 23, the occurrence of the problem of the barrier layer 23 breaking during thermoforming can be effectively suppressed.

[0074] The oxygen barrier property (oxygen permeability) [cc / day / pack] is the amount of oxygen [cc] that enters the container from outside to inside per day under the following conditions: external atmosphere: air (O2: 21%), external temperature: 23°C, external relative humidity: 55%, internal atmosphere: N2, internal temperature: 23°C, internal relative humidity: 90%, measured using a MOCON oxygen permeability measuring device (OX-TRAN2 / 20). An oxygen barrier property of 0.03 [cc / day / pack] or less is considered the guideline for the oxygen barrier property required to suppress deterioration of the contents. Therefore, the oxygen barrier property is evaluated as "not good" if the oxygen permeability exceeds 0.03 [cc / day / pack]. In comparative examples 7 and 8, because 25% by weight of HDPE (more than 20% by weight) is blended with EVOH (ethylene 44 mol%) in the barrier layer 23, the oxygen barrier property falls below the above standard (oxygen permeability exceeds the standard).

[0075] Based on the above results, by blending 5% to 20% by weight of HDPE with EVOH (ethylene 44 mol%) as the barrier layer 23, it is possible to achieve both packability (load-bearing capacity) and oxygen barrier properties. [Explanation of Symbols]

[0076] 10 Mouth 11 Peripheral wall 12 Flange section 15 Step section 20 Torso 22 Outer layer 22a Outer cover layer 22b Outer bio-resin layer 23 Barrier layer 24 Inner layer 24a Inner cover layer 24b Inner bio-resin layer 30 bottom 31 Contact part 32 Bottom recess 100 stacked containers O center axis S Containment space

Claims

1. A stacked container having a body for containing contents and a bottom that closes the lower end of the body, and having a stacked structure, The aforementioned laminated structure is A barrier layer comprising an ethylene-vinyl alcohol copolymer resin blended with a high-density polyethylene resin in an amount of 5% to 20% by weight, An outer layer portion containing polyethylene resin is provided on the outside of the barrier layer, An inner layer portion containing polyethylene resin is provided inside the barrier layer. A stacked container equipped with the following features.

2. The laminated container according to claim 1, wherein at least one of the outer layer and the inner layer includes a bio-resin layer obtained by compounding a bio-polyethylene resin with a high-density polyethylene resin.

3. The laminated container according to claim 2, wherein the bio-resin layer contains 10% by weight or more of a bio-polyethylene resin.

4. The outer layer has an outer cover layer outside the bio-resin layer, which is made of a bio-polyethylene resin compounded with a high-density polyethylene resin. The laminated container according to claim 2 or 3, wherein the inner layer has an inner cover layer inside the bio-resin layer, which is made by compounding a bio-polyethylene resin with a high-density polyethylene resin.

5. A laminated container according to any one of claims 1 to 3, formed by thermoforming a laminated sheet having the aforementioned laminated structure.

6. A method for manufacturing a laminated container having a body for containing contents and a bottom for closing the lower end of the body, the laminated container having a laminated structure, The aforementioned laminated structure is A barrier layer comprising an ethylene-vinyl alcohol copolymer resin blended with a high-density polyethylene resin in an amount of 5% to 20% by weight, An outer layer portion containing polyethylene resin is provided on the outside of the barrier layer, An inner layer portion containing polyethylene resin is provided inside the barrier layer. Equipped with, A method for manufacturing a laminated container, comprising forming an outer cover layer, which is the outermost layer of the outer layer, and an inner cover layer, which is the innermost layer of the inner layer, using a molten resin containing polyethylene resin and having a melt flow rate of 1.5 [g / 10 min] or more and less than 2.0 [g / 10 min].

7. A method for manufacturing a laminated container according to claim 6, comprising forming the resin layer inside the outer cover layer in the outer layer and the resin layer outside the inner cover layer in the inner layer using a molten resin containing a polyethylene resin and having a melt flow rate of 0.5 [g / 10 min] or more and 1.1 [g / 10 min] or less.

8. The method for manufacturing a laminated container according to claim 6, wherein the average melt flow rate when the outer cover layer and the resin layer inside the outer cover layer in the outer layer portion melts, and the average melt flow rate when the inner cover layer and the resin layer outside the inner cover layer in the inner layer portion melts, is 1.0 [g / 10 min] or more and less than 1.5 [g / 10 min].

9. A method for manufacturing a laminated container according to any one of claims 6 to 8, comprising forming the barrier layer by blending an ethylene-vinyl alcohol copolymer resin with a high-density polyethylene resin having a melt flow rate of 0.45 [g / 10 min] or more and 1.5 [g / 10 min] or less when melted.

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