Double container manufacturing method

Abstract

To provide a double container which can extend the expiration date of contents before opening.SOLUTION: A double container 1 is provided with an outside air introduction hole 11 for introducing outside air between an inner container 20 shrinkable according to decrease in contents and an outer container 10 enclosing the inner container 20, and has a double structure in which the inner container 20 and the outer container 10 are laminated to be peelable, wherein the contents are filled in the inner container 20. A low oxygen gas G is sealed between the outer container 10 and the inner container 20.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a double container filled with a content. Vessel It relates to a manufacturing method. [Background technology]

[0002] Double-layered containers, known as delaminated bottles, airless bottles, peelable laminated containers, or the like, are known as containers for storing contents such as liquid seasonings or liquid cosmetics and preserving their freshness (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-147295 A Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes a discharge container in which the gas contained in the gas space formed in the inner container is low in reactivity, such as nitrogen gas, which oxidizes the contents. However, the discharge container described in Patent Document 1 is filled with air between the inner container and the outer container not only after it is opened for use, but also before it is opened. Therefore, even before it is opened, oxygen existing between the inner container and the outer container permeates into the inner container, oxidizing the contents. Therefore, the discharge container described in Patent Document 1 has room for improvement in terms of extending the expiration date of the contents.

[0005] The present invention has been made in consideration of the above circumstances, and an example of an object of the present invention is to solve the above problems. That is, an example of an object of the present invention is to provide a double container that can extend the expiration date of the contents before opening. [Means for solving the problem]

[0011] The present invention The manufacturing method of the double container is as follows: A method for manufacturing a double container in which an outside air inlet hole for introducing outside air is provided between an inner container which can shrink as the contents decrease and an outer container which contains the inner container, the inner container and the outer container have a double structure in which they are peelably laminated, and the contents are filled into the inner container, the method comprising the steps of: a molding step of blow-molding the outer container and the inner container; a blowing step of blowing nitrogen gas, which is a low-oxygen gas, through the outside air inlet hole between the inner container molded in the molding step and the outer container; a restoring step of expanding the inner container which has contracted in the blowing step and restoring it to a shape that matches the outer container; and a filling step of filling the inner container restored in the restoring step with the contents and sealing it; The method further includes a peeling step of shrinking the inner container formed in the molding step and peeling it off from the outer container, and the blowing step is performed as a part of the peeling step.

[0012] The present invention The manufacturing method of the double container is as follows: A method for manufacturing a double container in which an outside air inlet hole for introducing outside air is provided between an inner container which can shrink as the contents decrease and an outer container which contains the inner container, the inner container and the outer container have a double structure in which they are peelably laminated, and the contents are filled into the inner container, the method comprising the steps of: a molding step of blow-molding the outer container and the inner container; a blowing step of blowing nitrogen gas, which is a low-oxygen gas, through the outside air inlet hole between the inner container molded in the molding step and the outer container; a restoring step of expanding the inner container which has contracted in the blowing step and restoring it to a shape that matches the outer container; and a filling step of filling the inner container restored in the restoring step with the contents and sealing it; The method further includes an inspection process for inspecting the inner container molded in the molding process for leaks by blowing in nitrogen gas from the outside air inlet and measuring the flow rate of the nitrogen gas flowing inside the inner container, and the blowing process is performed as part of the inspection process. Effect of the Invention

[0013] The double container according to the present invention Vessel The manufacturing method can provide a double container that can extend the shelf life of the contents before opening. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a schematic diagram showing a vertical cross section of a container body of the double container according to the first embodiment. [Diagram 2] FIG. 2 is a diagram for explaining a method for manufacturing the double container shown in FIG. [Diagram 3] 3A to 3C are diagrams showing the state of the container body in each step shown in FIG. 2. [Figure 4] FIG. 11 is a view for explaining a restoration step in the double container manufacturing method according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] In this embodiment, the direction along the central axis Z of the double container 1 having a bottle shape and filled with the contents is also referred to as the "axial direction", the direction rotating around the central axis Z of the double container 1 as the axis of rotation is also referred to as the "circumferential direction", and the direction perpendicular to the central axis Z of the double container 1 is also referred to as the "radial direction". In this embodiment, the axial direction from the mouth 3 to the bottom 6 of the double container 1 is also referred to as the "downward direction", and the axial direction from the bottom 6 to the mouth 3 of the double container 1 is also referred to as the "upward direction". In this embodiment, the cross section of the double container 1 containing the contents cut along a plane along the central axis Z of the double container 1 is also referred to as the "longitudinal cross section", and the cross section of the double container 1 cut along a plane perpendicular to the central axis Z of the double container 1 is also referred to as the "transverse cross section".

[0017] [Embodiment 1: Configuration of the container body of the double container] FIG. 1 is a schematic diagram showing a vertical cross section of a container body 2 of a double container 1 according to the first embodiment.

[0018] The double container 1 is a container containing the contents, which is formed by filling the contents into a bottle-shaped container body 2 and sealing it with a cap. As shown in Fig. 1, the container body 2 includes a mouth 3 which is one end of the container body 2 and through which the contents are poured out, a bottom 6 which is the other end of the container body 2 and is in contact with the ground, a shoulder 4 which extends downward from the mouth 3 while spreading outward in the radial direction, and a body 5 which extends downward from the shoulder 4 and is connected to the bottom 6.

[0019] The container body 2 comprises an outer container 10 that forms the outer shell of the container body 2 and contains an inner container 20, and the inner container 20 that is filled with contents and can contract as the contents decrease. The container body 2 is a container having a double structure in which the inner surface of the outer container 10 and the outer surface of the inner container 20 are laminated in a peelable manner.

[0020] The outer container 10 and the inner container 20 are containers made of synthetic resin and are manufactured by blow molding. Preferably, the outer container 10 and the inner container 20 are manufactured by biaxial stretch blow molding using a test tube-shaped preform. Specifically, the outer container 10 and the inner container 20 are manufactured by simultaneously stretch blow molding the preform of the outer container 10 and the preform of the inner container 20 in a state where the preform of the inner container 20 is inserted into the preform of the outer container 10 and stacked. Alternatively, the outer container 10 and the inner container 20 may be manufactured by stretch blow molding the preform of the outer container 10 and then stretch blow molding the preform of the inner container 20 inside the outer container 10.

[0021] The outer container 10 and the inner container 20 are manufactured using polyolefin resin, ethylene-vinyl copolymer, styrene resin, vinyl resin, polyamide resin, polyester resin, polycarbonate resin, polyphenylene oxide resin, or biodegradable resin. Preferably, the outer container 10 and the inner container 20 are manufactured using polyolefin resin or polyester resin. More preferably, the outer container 10 and the inner container 20 are manufactured using polyester resin. Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolymer polyesters thereof. Particularly preferably, the outer container 10 and the inner container 20 are manufactured using polyethylene terephthalate resin. Moreover, the inner container 20 is manufactured using a resin containing an oxygen absorbent in order to ensure the oxygen barrier property of the inner container 20 against the contents. The content of the oxygen absorbent may be 0.1% or more and 5% or less.

[0022] The outer container 10 is formed so as to be self-supporting with the bottom 6 in contact with the ground. The outer container 10 is formed so as to maintain the shapes of the mouth 3, shoulder 4, body 5 and bottom 6 in the self-supporting state. The shoulder 4 and body 5 of the outer container 10 are formed so as to bend and deform inward when pressed by a squeeze operation, and to restore to their original shapes before pressing when the pressure is released.

[0023] The inner container 20 has a filling space S into which the contents are filled, and is formed to have a shape that fits the outer container 10. The shoulder portion 4 and body portion 5 of the inner container 20 are formed to have a thickness thinner than the outer container 10 so that they will shrink as the contents decrease. The mouth portion 3 of the inner container 20 is formed to have a rigidity higher than that of the shoulder portion 4 and body portion 5, and will not shrink as the contents decrease.

[0024] The mouth 3 of the outer container 10 is provided with an outside air introduction hole 11. The outside air introduction hole 11 is a hole for introducing outside air into the space A between the outer container 10 and the inner container 20 as the contents are poured out by the squeezing operation. The space A includes a first space A1 and a second space A2. The first space A1 is a space located between the mouth 3 of the outer container 10 and the mouth 3 of the inner container 20. The second space A2 is a space A formed between the shoulder 4 and the bottom 6 of the outer container 10 and between the shoulder 4 and the bottom 6 of the inner container 20 by peeling the outer container 10 and the inner container 20. The outside air introduction hole 11, the first space A1, and the second space A2 are mutually connected. The outside air introduction hole 11 may be provided as a slit in a portion where the mouth 3 of the outer container 10 and the mouth 3 of the inner container 20 are fixed.

[0025] The mouth 3 of the inner container 20 is disposed so as to be exposed upward from the upper end of the mouth 3 of the outer container 10, and is fixed to the mouth 3 of the outer container 10. An opening 21 for pouring out the contents is provided at the upper end of the mouth 3 of the inner container 20. Caps with check valves are attached to the outer surfaces of the mouths 3 of the outer container 10 and the inner container 20. The caps are attached so as to cover the opening 21 from above, and to cover the outside air introduction hole 11 from the radially outward direction.

[0026] When the double container 1 is unopened, i.e., before the double container 1 is opened for use by a user, low oxygen gas G is sealed in the space A between the outer container 10 and the inner container 20. The low oxygen gas G is a gas having an oxygen concentration of 1% or less. The low oxygen gas G may be, for example, an inert gas such as nitrogen gas.

[0027] In a normal double container, the space between the outer container and the inner container is filled with air when the container is unopened. The inner container is exposed to the air that fills the space between the outer container and the inner container. When the inner container contains an oxygen absorbent, the oxygen absorbent absorbs the oxygen present in the space between the outer container and the inner container. That is, in a normal double container, the oxygen absorbent contained in the inner container is consumed even when the container is unopened. For this reason, in a normal double container, the expiration date of the contents filled in the double container is relatively short even when the double container is unopened.

[0028] For example, the weight of one inner container is 8g. The content of oxygen absorbent in one inner container is 4%. The oxygen absorption performance of the oxygen absorbent is 40ml / g. Then, the amount of oxygen that one inner container can absorb is about 12.8ml. Meanwhile, the amount of air that fills the space between the outer container and the inner container when unopened is 10ml. The oxygen concentration in the air is 20%. Then, the amount of oxygen that exists in the space between the outer container and the inner container when unopened is about 2ml. As a result, in a normal double container, about 15% of the oxygen absorbent contained in the inner container is consumed even when it is unopened. Therefore, the air that fills the space between the outer container and the inner container has a significant effect on the expiration date of the contents filled in the double container.

[0029] In the double container 1 according to the first embodiment, a low oxygen gas G is sealed in the space A between the outer container 10 and the inner container 20. Therefore, in the double container 1 according to the first embodiment, consumption of the oxygen absorbent contained in the inner container 20 when the container is unopened can be suppressed, and the amount of oxygen permeating from the space A into the inside of the inner container 20 can be suppressed.

[0030] [Embodiment 1: Method for manufacturing a double container] FIG. 2 is a diagram for explaining a manufacturing method of the double container 1 shown in FIG. 1. FIG. 3 is a diagram showing the state of the container body 2 in each step shown in FIG. 2. FIG. 3(a) shows the state of the container body 2 in the molding step shown in FIG. 2. FIG. 3(b) shows the state of the container body 2 in the peeling step shown in FIG. 2. FIG. 3(c) shows the state of the container body 2 in the inspection step shown in FIG. 2. FIG. 3(d) shows the state of the container body 2 in the restoration step shown in FIG. 2.

[0031] In the manufacturing method of the double container 1, first, a molding process of the container body 2 is performed (step 201). In the molding process, first, preforms of the outer container 10 and the inner container 20 are molded by injection molding or the like. Next, the preforms of the outer container 10 and the preforms of the inner container 20 are molded into the outer container 10 and the inner container 20, respectively, by biaxial stretch blow molding, thereby forming the container body 2 (see FIG. 3(a)).

[0032] Thereafter, in the manufacturing method of the double container 1, a peeling step is performed in which the inner container 20 formed in the molding step is shrunk and peeled off from the outer container 10 (step 202). In a normal peeling step, the inner container is peeled off from the outer container by sucking air from the mouth of the molded inner container or by blowing air between the outer container and the inner container from an outside air introduction hole. In contrast, in the peeling step according to the first embodiment, as shown in FIG. 3(b), the inner container 20 is peeled off from the outer container 10 by blowing low oxygen gas G between the outer container 10 and the inner container 20 from the outside air introduction hole 11. That is, in the manufacturing method of the double container 1 according to the first embodiment, a blowing step 202a in which low oxygen gas G is blown from the outside air introduction hole 11 of the outer container 10 formed in the molding step is performed as a part of the peeling step.

[0033] Thereafter, in the manufacturing method of the double container 1, an inspection step is performed to inspect the inner container 20 molded in the molding step (step 203). In the inspection step, first, as shown in FIG. 3(c), a flowmeter F is installed at the opening 21 of the mouth 3 of the inner container 20. Next, in the inspection step, as shown in FIG. 3(c), low oxygen gas G is blown in from the outside air introduction hole 11, and the flow rate of the low oxygen gas G flowing inside the inner container 20 is measured by the flowmeter F. For example, if the measurement value of the flowmeter F is a significant value indicating leakage of the low oxygen gas G, it can be determined that the low oxygen gas G is leaking from the outside to the inside of the inner container 20, and that a pinhole or the like is present in the inner container 20. On the other hand, if the measurement value of the flowmeter F is not a significant value, it can be determined that a pinhole or the like is not present in the inner container 20.

[0034] Thereafter, in the manufacturing method of the double container 1, a restoration process is carried out in which the inner container 20 is expanded and restored to a shape conforming to the outer container 10 (step 204). In the restoration process, as shown in Fig. 3(d), gas is blown into the inner container 20 from the mouth portion 3 of the inner container 20 to restore the inner container 20. The gas blown into the inner container 20 in the restoration process may be low-oxygen gas G or air.

[0035] Thereafter, in the manufacturing method of the double container 1, a filling step is performed in which the inner container 20 restored in the restoration step is filled with the contents and sealed (step 205). In the filling step, first, the inner container 20 is filled with the contents. Next, in the filling step, a cap is attached to the container body 2 so as to cover the opening 21 from above and to cover the outside air introduction hole 11 from the radially outward side, thereby sealing the inside of the inner container 20 and sealing the space A between the inner container 20 and the outer container 10. Thereafter, in the manufacturing method of the double container 1, a packaging material such as a label or film is wrapped around the outer surfaces of the container body 2 and the cap.

[0036] In the above-mentioned inspection step, the low oxygen gas G is blown in through the outside air introduction hole 11. For this reason, in the manufacturing method of the double container 1 according to the first embodiment, the blowing step 202a of blowing the low oxygen gas G through the outside air introduction hole 11 of the outer container 10 formed in the molding step may be performed as part of the inspection step. Also, in the manufacturing method of the double container 1 according to the first embodiment, the peeling step and the inspection step may be performed integrally as one step. That is, in the manufacturing method of the double container 1 according to the first embodiment, the low oxygen gas G may be blown in through the outside air introduction hole 11 to peel the inner container 20 from the outer container 10, and the flow rate of the low oxygen gas G flowing inside the inner container 20 may be measured.

[0037] [Embodiment 1: Action and effect] As described above, in the double container 1 according to the first embodiment, the low oxygen gas G is enclosed between the outer container 10 and the inner container 20. That is, in the double container 1 according to the first embodiment, the inner container 20 is less likely to be directly exposed to oxygen in the air when the container is unopened. Therefore, in the double container 1 according to the first embodiment, the amount of oxygen that permeates from between the outer container 10 and the inner container 20 to the inside of the inner container 20 when the container is unopened can be suppressed. As a result, in the double container 1 according to the first embodiment, the time when oxygen actually starts to permeate from between the outer container 10 and the inner container 20 to the inside of the inner container 20 can be delayed after the double container 1 is opened. Therefore, in the double container 1 according to the first embodiment, the time when the freshness of the contents starts to decrease can be delayed even during the period of use of the double container 1 after opening, and the best-before date of the contents when the container is used can be extended. Therefore, in the double container 1 according to the first embodiment, the best-before date of the contents can be extended both before and after opening.

[0038] Furthermore, in the double container 1 according to the first embodiment, the low-oxygen gas G sealed between the outer container 10 and the inner container 20 is nitrogen gas. Therefore, in the double container 1 according to the first embodiment, the amount of oxygen passing through the inner container 20 when unopened and during use can be suppressed simply by sealing in nitrogen gas, which is inexpensive and easily available. Therefore, in the double container 1 according to the first embodiment, the expiration date of the contents can be easily extended both before and after opening.

[0039] Furthermore, in the double container 1 according to the first embodiment, the oxygen concentration contained in the low oxygen gas G sealed between the outer container 10 and the inner container 20 is 1% or less. Therefore, in the double container 1 according to the first embodiment, the amount of oxygen passing through the inner container 20 when unopened and during use can be further suppressed. Therefore, in the double container 1 according to the first embodiment, the expiration date of the contents can be further extended both before and after opening.

[0040] Furthermore, in the double container 1 according to the first embodiment, the outer container 10 and the inner container 20 are made of polyethylene terephthalate resin, and the inner container 20 contains an oxygen absorbent. Therefore, in the double container 1 according to the first embodiment, the outer container 10 and the inner container 20 are made of a resin that has high oxygen barrier properties, is inexpensive, and is easily available, and the amount of oxygen that passes through the inner container 20 can be significantly reduced. Therefore, in the double container 1 according to the first embodiment, the expiration date of the contents can be further extended both before and after opening.

[0041] In particular, when low-oxygen gas G is enclosed between the inner container 20 containing an oxygen absorbent and the outer container 10, the double container 1 according to the first embodiment can suppress consumption of the oxygen absorbent contained in the inner container 20 when the container is unopened. In addition, in this case, the time when consumption of the oxygen absorbent actually starts can be delayed after the double container 1 is opened, so that the oxygen absorbent can absorb a large amount of oxygen during the period when the double container 1 is used after opening. Therefore, in this case, the double container 1 according to the first embodiment can significantly suppress the amount of oxygen permeation through the inner container 20 when the container is unopened and during the period of use, and can significantly extend the expiration date of the contents both before and after opening.

[0042] The manufacturing method of the double container 1 according to the first embodiment includes a molding step of blow molding the outer container 10 and the inner container 20, and a blowing step of blowing low oxygen gas G from the outside air introduction hole 11 between the outer container 10 and the inner container 20 molded by the molding step. In addition, the manufacturing method of the double container 1 according to the first embodiment includes a restoration step of expanding the inner container 20 contracted by the blowing step and restoring it to a shape that conforms to the outer container 10, and a filling step of filling the inner container 20 restored by the restoration step with the contents and sealing it. That is, in the manufacturing method of the double container 1 according to the first embodiment, the double container 1 in which the low oxygen gas G is sealed between the outer container 10 and the inner container 20 can be manufactured by simply adding a blowing step of blowing low oxygen gas G after the existing molding step of blow molding. Therefore, in the manufacturing method of the double container 1 according to the first embodiment, the double container 1 that can extend the shelf life of the contents both before and after opening can be easily manufactured.

[0043] Furthermore, the manufacturing method of the double container 1 according to the first embodiment further includes a peeling step in which the inner container 20 formed in the molding step is contracted and peeled off from the outer container 10, and the blowing step is performed as part of the peeling step. Therefore, the manufacturing method of the double container 1 according to the first embodiment can blow the low oxygen gas G between the outer container 10 and the inner container 20 as part of the existing peeling step without providing a special step. Therefore, the manufacturing method of the double container 1 according to the first embodiment can more easily manufacture the double container 1 that can extend the expiration date of the contents both before and after opening.

[0044] Furthermore, the manufacturing method of the double container 1 according to the first embodiment further includes an inspection step of inspecting the inner container 20 for leaks by blowing in the low oxygen gas G from the outside air inlet 11 and measuring the flow rate of the low oxygen gas G flowing inside the inner container 20, and the blowing step is performed as part of the inspection step. Therefore, the manufacturing method of the double container 1 according to the first embodiment can blow in the low oxygen gas G between the outer container 10 and the inner container 20 as part of the existing inspection step without providing a special step. Therefore, the manufacturing method of the double container 1 according to the first embodiment can more easily manufacture the double container 1 that can extend the expiration date of the contents both before and after opening.

[0045] [Other embodiments] A description will be given of a method for manufacturing the double container 1 according to embodiment 2. In the description of the method for manufacturing the double container 1 according to embodiment 2, the description of the same configuration and operation as in embodiment 1 will be omitted to avoid duplication.

[0046] FIG. 4 is a diagram for explaining the restoration step in the manufacturing method of the double container 1 according to the second embodiment.

[0047] In the manufacturing method of the double container 1 according to the first embodiment, the restoration step is carried out by blowing gas into the inside of the inner container 20 from the mouth 3 of the inner container 20 .

[0048] In contrast, in the manufacturing method of the double container 1 according to the second embodiment, the restoration step may be performed by sucking in gas from the outside air inlet 11, as shown in Fig. 4. In this case, unless the space A between the outer container 10 and the inner container 20 is sucked to a significant negative pressure, the volume of the space A will be approximately the same as in the first embodiment, and the same amount of low oxygen gas G as in the first embodiment can be secured.

[0049] For this reason, the method for manufacturing the double container 1 according to the second embodiment, like the first embodiment, can seal low oxygen gas G between the outer container 10 and the inner container 20. Therefore, like the first embodiment, the method for manufacturing the double container 1 according to the second embodiment can easily manufacture the double container 1 that can extend the expiration date of the contents both before and after opening.

[0050] [others] In the above embodiment, the double container 1 corresponds to an example of the "double container" described in the claims. The outer container 10 corresponds to an example of the "outer container" described in the claims. The inner container 20 corresponds to an example of the "inner container" described in the claims. The outside air introduction hole 11 corresponds to an example of the "outside air introduction hole" described in the claims. The molding process of step 201 corresponds to an example of the "molding process" described in the claims. The peeling process of step 202 corresponds to an example of the "peeling process" described in the claims. The blowing process of step 202a corresponds to an example of the "blowing process" described in the claims. The inspection process of step 203 corresponds to an example of the "inspection process" described in the claims. The restoration process of step 204 corresponds to an example of the "restoration process" described in the claims. The filling process of step 205 corresponds to an example of the "filling process" described in the claims.

[0051] The above-described embodiments, including modified examples, can apply the techniques of each other. The above-described embodiments do not limit the content of the present invention, and can be modified to the extent that they do not depart from the scope of the claims.

[0052] The terms used in the above embodiments and claims should be interpreted as open-ended terms. For example, the term "including" should be interpreted as "not limited to what is described as including." The term "containing" should be interpreted as "not limited to what is described as containing." The term "comprises" should be interpreted as "not limited to what is described as comprising." The term "having" should be interpreted as "not limited to what is described as having." [Explanation of symbols]

[0053] 1 double container 2 Container body 3 Mouth 4 Shoulder 5. Torso 6 Bottom 10 Outer container 11. Outside air intake 20 Inner container 21 Opening A Space A1 1st space A2 2nd space F Flowmeter G. Low oxygen gas S filling space Z center axis

Claims

1. A method for manufacturing a double container in which an air inlet hole for introducing air into an inner container that can shrink as the contents decrease and an outer container that contains the inner container is provided, the inner container and the outer container have a double structure in which they are peelably laminated, and the contents are filled in the inner container, a molding step of blow molding the outer container and the inner container; a blowing step of blowing nitrogen gas, which is a low-oxygen gas, through the outside air inlet between the inner container and the outer container formed in the molding step; a restoring step of expanding the inner container contracted by the blowing step and restoring the inner container to a shape conforming to the outer container; a filling step of filling the inner container restored by the restoring step with the content and sealing the same; Equipped with The molding step further comprises a peeling step of shrinking the inner container formed in the molding step and peeling it off from the outer container. The blowing step is carried out as part of the peeling step. A method for manufacturing a double container.

2. A method for manufacturing a double container in which an outside air inlet hole for introducing outside air is provided between an inner container which can shrink as the contents decrease and an outer container which contains the inner container, the inner container and the outer container have a double structure in which they are peelably laminated, and the contents are filled in the inner container, a molding step of blow molding the outer container and the inner container; a blowing step of blowing nitrogen gas, which is a low-oxygen gas, through the outside air inlet between the inner container and the outer container formed in the molding step; a restoring step of expanding the inner container contracted by the blowing step and restoring the inner container to a shape conforming to the outer container; a filling step of filling the inner container restored by the restoring step with the content and sealing the same; Equipped with a test step of testing the inner container for leaks by blowing the nitrogen gas through the outside air inlet and measuring the flow rate of the nitrogen gas flowing into the inner container, The blowing step is carried out as part of the inspection step. A method for manufacturing a double container.

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