Double container

Abstract

The objective is to provide a double-walled container that allows the inner container to be easily removed from the outer container. [Solution] A double container 1 comprising an outer container 10 and an inner container 20, wherein the outer container 10 has an outer opening 11 and an outer storage portion 12, and the inner container 20 has an inner opening 21 and an inner storage portion 22, the inner lower cylindrical portion 21a protrudes downward from the outer lower cylindrical portion 11a, and a gap 30 with a radial width W of 3 to 12 mm is provided between the outer container 10 and the inner container 20 at a height H1 where the lower end 21a2 of the inner lower cylindrical portion 21a is located.

Description

Technical Field

[0001] The present invention relates to a double container made of synthetic resin including an outer container and an inner container.

Background Art

[0002] Conventionally, as a double container made of synthetic resin formed by blow molding, there has been known one configured such that it includes an outer container having an outer mouth portion and an outer storage portion, and an inner container having an inner mouth portion disposed inside the outer mouth portion and an inner storage portion formed thinner than the outer storage portion and peelably laminated inside the outer storage portion, and the inner container can be pulled out from the outer container while collapsing the inner storage portion after use (see, for example, Patent Document 1).

[0003] According to such a double container, pulling out the inner container from the outer container after use allows easy separation of the outer container and the inner container, so that the recyclability of the double container can be improved, for example, when the outer container and the inner container are made of different materials, or when the inner container is so contaminated by the contents that it cannot be recycled.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, in the conventional double-walled container described above, the boundary between the inner opening and the shoulder portion which widens downward from the lower end of the inner opening is difficult to stretch by blow molding. As a result, this boundary portion is not sufficiently thinned during blow molding and is formed as a thicker portion. Furthermore, in a double-walled container formed by blow molding, this boundary portion of the inner container comes into contact with or is in close proximity to the outer container. Therefore, when removing the inner container from the outer container, the frictional resistance between the boundary portion of the inner container and the outer container increases, making it difficult to remove the inner container from the outer container.

[0006] This invention has been made in view of these problems, and its purpose is to provide a double-walled container that allows the inner container to be easily removed from the outer container. [Means for solving the problem]

[0007] The double-walled container of the present invention is a double-walled container made of synthetic resin comprising an outer container and an inner container, wherein the outer container has an outer opening with a cylindrical outer lower cylindrical portion, an outer shoulder portion integrally connected to the lower end of the outer lower cylindrical portion and widening downwards, a cylindrical outer body portion integrally connected to the lower end of the outer shoulder portion, and an outer bottom portion that closes the lower end of the outer body portion, and the inner container has an inner opening with a cylindrical inner lower cylindrical portion disposed inside the outer lower cylindrical portion, and integrally connected to the lower end of the inner lower cylindrical portion The container comprises an inner shoulder portion that widens in diameter downward, a cylindrical inner body portion integrally connected to the lower end of the inner shoulder portion, and an inner bottom portion that closes the lower end of the inner body portion, and is formed to be thinner than the outer container portion and is detachably laminated to the inner surface of the outer container portion, wherein the inner lower cylindrical portion protrudes downward from the outer lower cylindrical portion, and a gap of 3 to 12 mm in diameter is provided between the outer container and the inner container at the height where the lower end of the inner lower cylindrical portion is located.

[0008] In the double-walled container of the present invention, it is preferable that the maximum wall thickness of the portion of the inner lower cylinder that protrudes below the outer lower cylinder is greater than the maximum wall thickness of the outer lower cylinder.

[0009] In the double-walled container of the present invention, it is preferable that the outer opening further comprises an outer stepped portion extending radially outward from the upper end of the outer lower cylindrical portion and a cylindrical outer upper cylindrical portion extending upward from the outer peripheral end of the outer stepped portion, and the inner opening further comprises an inner stepped portion extending radially outward from the upper end of the inner lower cylindrical portion and placed on the outer stepped portion, and a cylindrical inner upper cylindrical portion extending upward from the inner stepped portion.

[0010] In the double-walled container of the present invention, it is preferable that the inner upper cylindrical portion extends above the outer upper cylindrical portion and integrally has an engaging projection on its outer surface that engages with a cap. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a double-walled container that allows the inner container to be easily removed from the outer container. [Brief explanation of the drawing]

[0012] [Figure 1] This is a front view cross-sectional view of a double container according to one embodiment of the present invention. [Figure 2] Figure 1 is an enlarged cross-sectional view of the main part of the double-walled container shown. [Figure 3] This is an enlarged cross-sectional view of area A in Figure 1. [Modes for carrying out the invention]

[0013] The following describes in detail an example of a double-walled container 1 according to one embodiment of the present invention, with reference to the drawings.

[0014] In the present specification and claims, the vertical direction (which may also be referred to as the "height direction") refers to the vertical direction (the direction in which the axis O extends) when the double container is in an upright posture as shown in Figure 1, the radial direction refers to the direction passing through the axis O of the double container 1 and perpendicular to the axis O, and the circumferential direction refers to the direction revolving around the axis O of the double container 1.

[0015] The double container 1 shown in Figure 1 is a blow-molded container made of synthetic resin that can be used for storing various contents, for example, food such as food seasonings or beverages like soy sauce, cosmetics such as lotion, and toiletries such as shampoo, conditioner, or liquid soap.

[0016] The double container 1 has a double structure including an outer container 10 and an inner container 20, both made of synthetic resin.

[0017] The outer container 10, also referred to as an outer layer body, is formed into a bottle shape that constitutes the outer shell of the double container 1. In the present embodiment, the outer container 10 is made of polyethylene terephthalate (PET). As the polyethylene terephthalate constituting the outer container 10, for example, homo-PET can be used, but other PETs such as IPA (isophthalic acid) modified PET or CHDM modified PET can also be used.

[0018] The outer container 10 is not limited to being made of polyethylene terephthalate, and may be formed of other synthetic resin materials such as polypropylene (PP) or polyethylene (PE), for example. In addition, the outer container 10 is not limited to a single-layer structure, and may have a multi-layer structure for improving barrier properties and the like.

[0019] The outer container 10 includes an outer mouth portion 11 and an outer accommodating portion 12.

[0020] The outer mouth portion 11 is a portion that is not substantially stretched when the double container 1 is molded by blow molding, and has a predetermined wall thickness.

[0021] As shown in Figure 2, the outer mouth portion 11 includes an outer lower cylinder portion 11a.

[0022] The outer lower cylinder portion 11a has a cylindrical shape. In the present embodiment, the outer lower cylinder portion 11a is cylindrical with the axis O as the center. Note that the outer lower cylinder portion 11a is not limited to a cylindrical shape centered on the axis O, and may have another cylindrical shape such as an elliptical cylinder centered on the axis O or a prismatic cylinder centered on the axis O. The inner peripheral surface of the outer lower cylinder portion 11a is parallel to the axis O, but may have a tapered shape slightly inclined with respect to the axis O, for example, to correspond to the draft of the core mold forming the outer mouth portion 11.

[0023] In the present embodiment, the outer mouth portion 11 further includes an outer stepped portion 11b and an outer upper cylinder portion 11c.

[0024] The outer stepped portion 11b extends radially outward from the upper end 11a1 of the outer lower cylinder portion 11a. More specifically, the outer stepped portion 11b is formed in an annular (flange-like) shape that is integrally connected to the upper end 11a1 of the outer lower cylinder portion 11a and extends radially outward from the entire circumference of the upper end 11a1 of the outer lower cylinder portion 11a. The upward-facing surface of the outer stepped portion 11b may be perpendicular to the axis O, or may be an inclined surface slightly inclined with respect to the axis O.

[0025] The outer upper cylinder portion 11c is a cylindrical portion extending upward from the outer peripheral end of the outer stepped portion 11b. In the present embodiment, the outer upper cylinder portion 11c is cylindrical with a larger diameter than the outer lower cylinder portion 11a centered on the axis O. The outer upper cylinder portion 11c may be provided with a locking protrusion 11d protruding radially inward at the upper end of the inner peripheral surface. Note that the outer upper cylinder portion 11c is not limited to a cylindrical shape centered on the axis O, and may have another cylindrical shape such as an elliptical cylinder centered on the axis O or a prismatic cylinder centered on the axis O.

[0026] As shown in Figure 1 and Figure 2, the outer housing portion 12 includes an outer shoulder portion 12a, an outer body portion 12b, and an outer bottom portion 12c. The outer housing portion 12 is a portion that is stretched when the double container 1 is molded by blow molding.

[0027] The outer shoulder portion 12a is integrally connected to the lower end 11a2 of the outer lower cylindrical portion 11a and has a shape that widens downwards. In this embodiment, the outer shoulder portion 12a is a frustoconical shape centered on axis O. However, the outer shoulder portion 12a is not limited to a frustoconical shape centered on axis O; it may be any shape that widens downwards, such as a frustopyrotic shape or a dome shape.

[0028] The wall thickness of the outer container 10 gradually decreases from the outer lower cylindrical portion 11a side toward the outer shoulder portion 12a side at the boundary portion 13 between the lower end 11a2 of the outer lower cylindrical portion 11a and the outer shoulder portion 12a. The lower end 11a2 of the outer lower cylindrical portion 11a is the portion located at the lower end of the outer circumferential surface of the outer lower cylindrical portion 11a parallel to the axis O.

[0029] As shown in Figure 1, the outer body portion 12b is cylindrical and integrally connected to the lower end of the outer shoulder portion 12a. In this embodiment, the outer body portion 12b is cylindrical around axis O. However, the outer body portion 12b is not limited to a cylindrical shape around axis O; it may also be an elliptical cylinder around axis O, a rectangular cylinder around axis O, or other cylindrical shapes. The outer body portion 12b is formed with a thinner wall thickness than the outer opening portion 11, making it squeezeable. However, the outer body portion 12b may be formed with a thicker wall thickness and configured for applications where squeezing is not required.

[0030] The outer bottom portion 12c closes the lower end of the outer body portion 12b. More specifically, the outer bottom portion 12c is integrally connected to the lower end of the outer body portion 12b and closes the lower end of the outer body portion 12b. The shape of the outer bottom portion 12c can be changed as appropriate.

[0031] The inner container 20, also called the inner layer, is located inside the outer container 10, as shown in Figures 1 and 2. In this embodiment, the inner container 20 is made of polypropylene (whether PP, homopolymer, random copolymer, or block copolymer).

[0032] Furthermore, the inner container 20 is not limited to being made of polypropylene, but can also be made of other synthetic resin materials such as polyethylene terephthalate (PET) or polyethylene (PE). In addition, the inner container 20 is not limited to a single-layer structure, but may have a multi-layer structure to improve barrier properties, etc.

[0033] The inner container 20 has an inner opening 21 and an inner storage section 22.

[0034] The inner opening portion 21 is a part that is difficult to stretch when forming the double-walled container 1 by blow molding, and has a predetermined wall thickness so as not to deform easily. As shown in Figure 2, the inner opening portion 21 is provided with an inner lower cylindrical portion 21a.

[0035] The inner lower cylindrical portion 21a is cylindrical and is located inside the outer lower cylindrical portion 11a. In this embodiment, the inner lower cylindrical portion 21a is cylindrical with respect to axis O. More specifically, most of the outer circumferential surface of the inner lower cylindrical portion 21a, except for a part on the side of the lower end 21a2 between the upper end 21a1 and the lower end 21a2, is parallel to axis O, and the inner circumferential surface of the inner lower cylindrical portion 21a has a curved shape that protrudes radially inward between the upper end 21a1 and the lower end 21a2. That is, the wall thickness of the inner lower cylindrical portion 21a gradually increases from the upper end 21a1 to the lower end 21a2, and after passing the point of maximum thickness, it gradually decreases towards the lower end 21a2. Note that the inner lower cylindrical portion 21a is not limited to a cylindrical shape with respect to axis O, but may also be other cylindrical shapes such as an elliptical cylindrical shape or a rectangular cylindrical shape with respect to axis O, corresponding to the outer lower cylindrical portion 11a. Furthermore, the wall thickness of the inner lower cylindrical portion 21a may be uniform between the upper end 21a1 and the lower end 21a2.

[0036] In this embodiment, the inner opening portion 21 further comprises an inner stepped portion 21b and an inner upper cylindrical portion 21c.

[0037] The inner stepped portion 21b extends radially outward from the upper end 21a1 of the inner lower cylindrical portion 21a and rests on the outer stepped portion 11b. More specifically, the inner stepped portion 21b is integrally connected to the upper end 21a1 of the inner lower cylindrical portion 21a and is formed in an annular (flange-like) shape that extends radially outward from the entire circumference of the upper end 21a1 of the inner lower cylindrical portion 21a. The outer diameter of the inner stepped portion 21b is larger than the inner diameter of the outer lower cylindrical portion 11a and equal to the inner diameter of the outer upper cylindrical portion 11c. The inner stepped portion 21b rests on the outer stepped portion 11b and is held in place by the outer opening 11 by an undercut engagement of its outer peripheral end with the locking projection 11d from below.

[0038] The inner upper cylindrical portion 21c is a cylindrical part that extends upward from the inner stepped portion 21b. In this embodiment, the inner upper cylindrical portion 21c is a cylindrical shape with a larger diameter than the inner lower cylindrical portion 21a centered on axis O. Note that the inner upper cylindrical portion 21c is not limited to a cylindrical shape centered on axis O, but may also be an elliptical cylindrical shape or a rectangular cylindrical shape centered on axis O, corresponding to the outer upper cylindrical portion 11c.

[0039] In this embodiment, the inner upper cylindrical portion 21c extends above the outer upper cylindrical portion 11c and is integrally provided with an annular engaging projection 21d on its outer surface with which a cap (not shown) engages. That is, after the contents are placed inside the double container 1, the inner opening 21 is closed by the cap when the cap is pressed into the inner upper cylindrical portion 21c so as to engage with the engaging projection 21d in an undercut manner.

[0040] Alternatively, instead of the annular engaging projection 21d, a male screw may be integrally provided as an engaging projection on the inner upper cylinder portion 21c, and the cap may be attached to the inner upper cylinder portion 21c by screw connection. Furthermore, the cap attached to the inner upper cylinder portion 21c may be of various types, such as a closure cap, a dispensing cap, or a mounting cap for holding a pump-type dispensing device.

[0041] As shown in Figures 1 and 2, the inner housing portion 22 comprises an inner shoulder portion 22a, an inner body portion 22b, and an inner bottom portion 22c. The inner housing portion 22 is the part that is stretched when the double container 1 is formed by blow molding. As shown in Figure 3, the inner housing portion 22 is a bag-like shape with a thinner wall thickness than the inner opening portion 21, and is peelably laminated to the inner surface of the outer housing portion 12. The peeling of the inner housing portion 22 from the inner surface of the outer housing portion 12 may be peeling from an adhesive state, peeling from a pseudo-adhered state in the case of incompatible resin laminates, or separation from an adhering state.

[0042] As shown in Figure 2, the inner shoulder portion 22a is integrally connected to the lower end 21a2 of the inner lower cylindrical portion 21a and has a shape that expands in diameter downwards. In this embodiment, the inner shoulder portion 22a is a frustoconical shape centered on axis O corresponding to the outer shoulder portion 12a. However, the inner shoulder portion 22a is not limited to a frustoconical shape centered on axis O, but may be any shape that expands in diameter downwards to correspond to the outer shoulder portion 12a, such as a frustopyrotic shape or a dome shape. The inner shoulder portion 22a is laminated to the inner surface of the outer shoulder portion 12a in a peelable manner.

[0043] The thickness of the inner container 20 gradually decreases from the inner lower cylindrical portion 21a side towards the inner shoulder portion 22a side at the boundary portion 23 between the lower end 21a2 of the inner lower cylindrical portion 21a and the inner shoulder portion 22a.

[0044] As shown in Figure 1, the inner body portion 22b is cylindrical and integrally connected to the lower end of the inner shoulder portion 22a. In this embodiment, the inner body portion 22b is cylindrical around the axis O corresponding to the outer body portion 12b. However, the inner body portion 22b is not limited to a cylindrical shape around the axis O, but may also be an elliptical cylinder or a rectangular cylinder around the axis O corresponding to the outer body portion 12b. The inner body portion 22b is peelably laminated to the inner surface of the outer body portion 12b.

[0045] The inner bottom portion 22c closes the lower end of the inner body portion 22b. More specifically, the inner bottom portion 22c is integrally connected to the lower end of the inner body portion 22b and closes the lower end of the inner body portion 22b. The shape of the inner bottom portion 22c corresponds to the shape of the outer bottom portion 12c. The inner bottom portion 22c is laminated on the inner surface of the outer bottom portion 12c in a peelable manner.

[0046] The interior of the inner storage compartment 22 is a storage space 24 for contents, and contents can be stored in the storage space 24.

[0047] As shown in Figure 2, in the double-walled container 1 according to this embodiment, the inner lower cylindrical portion 21a protrudes downward from the outer lower cylindrical portion 11a, and at a height H1 where the lower end 21a2 of the inner lower cylindrical portion 21a is located, a gap 30 with a radial width W of 3 to 12 mm is provided between the outer container 10 and the inner container 20. More specifically, the lower end 21a2 of the inner lower cylindrical portion 21a is located below the lower end 11a2 of the outer lower cylindrical portion 11a, and at a height H1 where the lower end 21a2 of the inner lower cylindrical portion 21a is located, a gap 30 with a radial width W of 4 mm is provided between the boundary portion 13 of the outer container 10 and the lower end 21a2 of the inner lower cylindrical portion 21a of the inner container 20. The gap 30 is a space formed during blow molding where the outer container 10 and the inner container 20 are not in close contact with each other, and the cross-sectional shape perpendicular to the circumferential direction is substantially the same over the entire circumference. The gap 30 extends to predetermined ranges on both the upper and lower sides (ranges where boundary portions 13 are provided) centered on the height H1 where the lower end 21a2 of the inner lower cylindrical portion 21a is located, but the radial width W is maximum at the height H1 where the lower end 21a2 of the inner lower cylindrical portion 21a is located.

[0048] In this embodiment, the maximum wall thickness t1 of the portion of the inner lower cylinder 21a that protrudes downward from the outer lower cylinder 11a is thicker than the maximum wall thickness t2 of the outer lower cylinder 11a. The wall thickness of the inner lower cylinder 21a gradually decreases downward, and the portion where it becomes the same as the maximum wall thickness t2 of the outer lower cylinder 11a is the lower end 21a2 of the inner lower cylinder 21a. In this embodiment, the lower end 21a2 of the inner lower cylinder 21a is located 10 mm below the height H2 where the upper end 21a1 is located.

[0049] In the double-walled container 1 according to this embodiment, after use, i.e., after all the contents have been poured out, the outer container 10 and the inner container 20 can be separated by pulling the inner container 20 out of the outer container 10. That is, after use, the inner upper cylindrical portion 21c of the inner container 20 is pulled upward relative to the outer container 10, thereby separating the inner opening 21 from the outer opening 11, and the inner housing portion 22 of the inner container 20 is crushed while it is pulled out to the outside through the outer opening 11, thereby separating the outer container 10 and the inner container 20.

[0050] Furthermore, in the double-walled container 1 according to this embodiment, the inner lower cylindrical portion 21a protrudes lower than the outer lower cylindrical portion 11a, and a gap 30 with a radial width W of 3 to 12 mm is provided between the outer container 10 and the inner container 20 at a height H1 where the lower end 21a2 of the inner lower cylindrical portion 21a is located. This ensures that a sufficient gap 30 is provided above the boundary portion 23 between the inner opening portion 21 and the inner shoulder portion 22a, thereby reducing the frictional resistance generated between the boundary portion 23 and the outer container 10 when the inner container 20 is pulled out of the outer container 10, and also making it easier to deform the inner shoulder portion 22a to reduce its diameter. As a result, the force required to pull out the inner container 20 from the outer container 10 is reduced, making it easier to pull out the inner container 20 from the outer container 10.

[0051] Furthermore, if the radial width W of the gap 30 at height H1 where the lower end 21a2 of the inner lower cylinder portion 21a is located is less than 3 mm, the state in which the outer container 10 and the inner container 20 are in close contact is not significantly different, and it is not possible to easily remove the inner container 20 from the outer container 10. On the other hand, if the radial width W of the gap 30 at height H1 where the lower end 21a2 of the inner lower cylinder portion 21a is located exceeds 12 mm, the boundary portion 23 of the inner container 20 will bend upward starting from the lower end 21a2 of the inner lower cylinder portion 21a, and there is a risk that the inner container 20 will tear at that starting point.

[0052] Furthermore, in the double-walled container 1 according to this embodiment, the maximum wall thickness t1 of the portion of the inner lower cylinder 21a that protrudes below the outer lower cylinder 11a is made thicker than the maximum wall thickness t2 of the outer lower cylinder 11a. This makes it difficult for the portion of the inner lower cylinder 21a that protrudes below the outer lower cylinder 11a to be stretched by blow molding, making it easier to manufacture a double-walled container 1 with a gap 30. In particular, when the outer container 10 is made of polyethylene terephthalate resin and the inner container 20 is made of polypropylene resin, the portion of the inner lower cylinder 21a that protrudes below the outer lower cylinder 11a is prevented from being stretched by blow molding, making it easier to manufacture a double-walled container 1 with a gap 30.

[0053] The double-walled container 1 described above can be formed, for example, by manufacturing a preform assembly in which a synthetic resin inner preform, having a test tube-shaped outer extension integrally connected to the lower end of an outer opening corresponding to an outer opening 11, is incorporated inside a synthetic resin inner preform, having a test tube-shaped inner extension integrally connected to the lower end of an inner opening corresponding to an inner opening 21, and then blow molding this preform assembly.

[0054] The present invention is not limited to the embodiments described above, and can be modified in various ways without departing from its spirit.

[0055] For example, in the above embodiment, the inner lower cylindrical portion 21a has a cross-sectional shape perpendicular to the circumferential direction that is the same around its entire circumference. However, the configuration is not limited to this, and multiple ribs may be provided on at least one of the inner circumferential surface and the outer circumferential surface in a manner that causes the wall thickness to vary in the circumferential direction. Even with such a configuration, the portion of the inner lower cylindrical portion 21a that protrudes below the outer lower cylindrical portion 11a is less likely to be stretched by blow molding, making it easier to manufacture a double-walled container 1 with a gap 30.

[0056] Furthermore, when both the outer container 10 and the inner container 20 are made of polyethylene terephthalate resin, or when crystalline resin is used for the inner container 20, the inner opening 21 may be subjected to thermal crystallization. [Explanation of symbols]

[0057] 1 double container 10 Outer container 11 Outer mouth 11a Outer lower cylinder part 11a1 Top edge 11a2 bottom edge 11b Outside step 11c Upper outer cylinder part 11d Locking protrusion 12 Outer housing 12a Outside shoulder 12b Outer body 12c outer bottom 13 Boundary part 20 Inner container 21 Inner opening 21a Inner lower cylinder part 21a1 top end 21a2 bottom edge 21b Inner step section 21c Inner upper cylinder part 21d Engagement protrusion 22 Inner housing 22a Medial shoulder 22b Inner body 22c inner bottom 23 Boundary part 24 Storage space 30 gaps O axis H1 Height H2 Height W is the width in the radial direction. t1 maximum wall thickness t2 maximum wall thickness

Claims

1. A double-walled container made of synthetic resin, comprising an outer container and an inner container, The aforementioned outer container An outer opening having a cylindrical outer lower section, It has an outer housing portion comprising an outer shoulder portion that is integrally connected to the lower end of the outer lower cylindrical portion and widens in diameter downward, a cylindrical outer body portion integrally connected to the lower end of the outer shoulder portion, and an outer bottom portion that closes the lower end of the outer body portion, The aforementioned inner container, An inner opening portion having a cylindrical inner lower cylinder portion positioned inside the outer lower cylinder portion, It comprises an inner shoulder portion integrally connected to the lower end of the inner lower cylindrical portion and widening in diameter downward, a cylindrical inner body portion integrally connected to the lower end of the inner shoulder portion, and an inner bottom portion that closes the lower end of the inner body portion, and an inner housing portion formed to be thinner than the outer housing portion and detachably laminated to the inner surface of the outer housing portion, A double-walled container characterized in that the inner lower cylindrical portion protrudes lower than the outer lower cylindrical portion, and a gap of 3 to 12 mm in diameter is provided between the outer container and the inner container at the height where the lower end of the inner lower cylindrical portion is located.

2. The double-walled container according to claim 1, wherein the maximum wall thickness of the portion of the inner lower cylinder that protrudes downward from the outer lower cylinder is greater than the maximum wall thickness of the outer lower cylinder.

3. The outer opening portion further comprises an outer stepped portion extending radially outward from the upper end of the outer lower cylindrical portion, and a cylindrical outer upper cylindrical portion extending upward from the outer peripheral end of the outer stepped portion. The double-walled container according to claim 1 or 2, wherein the inner opening further comprises an inner stepped portion extending radially outward from the upper end of the inner lower cylindrical portion and resting on the outer stepped portion, and a cylindrical inner upper cylindrical portion extending upward from the inner stepped portion.

4. The double-walled container according to claim 3, wherein the inner upper cylindrical portion extends above the outer upper cylindrical portion and is integrally provided with an engaging projection on its outer surface that engages with a cap.

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