Double container

Abstract

To provide a double container that can reduce a force required to pull out an inner bag from the container body.SOLUTION: According to the present invention, a double container is provided with a container body, where the container body has an inner bag and an outer shell arranged to cover the inner bag, the inner bag is configured to be withdrawable from the container body, the innermost layer of the inner bag comprises a water-absorbing softening resin having a property of softening by water absorption.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a double-walled container. [Background technology]

[0002] Conventionally, double-walled containers comprising a container body having an outer shell and an inner bag are known. For example, Patent Document 1 discloses a double-walled container formed by biaxial stretch blow molding with an outer shell preform and an inner bag preform stacked on top of each other. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-10741 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, when the outer shell and inner bag of such a double-walled container are molded from different materials, or when contents adhere to the inner bag after use, it is desirable to separate the outer shell and inner bag when recycling the double-walled container.

[0005] The outer shell and inner bag are intended to be separated by pulling the inner bag out of the container body, and it is desirable to make it easy to pull the inner bag out of the container body.

[0006] This invention has been made in view of these circumstances, and provides a double-walled container that reduces the force required to pull the inner bag out of the container body. [Means for solving the problem]

[0007] According to the present invention, a double-walled container is provided, comprising a container body, wherein the container body comprises an inner bag and an outer shell disposed to cover the inner bag, the inner bag is configured to be removable from the container body, and the innermost layer of the inner bag is made of a water-absorbing, softening resin having the property of softening by water absorption.

[0008] In the double-walled container of the present invention, the innermost layer of the inner bag is made of a water-absorbing, softening resin. By wetting the innermost layer of the inner bag before pulling it out of the container body, the force required to pull the inner bag out of the container body can be reduced.

[0009] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other. Preferably, the double-walled container is as described above, wherein the water-absorbing and softening resin is EVOH or nylon. Preferably, the double-walled container is an inverted container having a cap with an enlarged top surface. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of a double-walled container 1 according to one embodiment of the present invention. The dashed lines in the figure represent boundary lines where the curvature of the surfaces constituting the surface shape changes. The same applies to the other figures. [Figure 2] Figure 1 is an exploded perspective view. [Figure 3] This is a magnified view of region A in Figure 2. [Figure 4] Figure 3 is an exploded perspective view. Only a portion of the inner bag 4 near the opening end 5c is shown. [Figure 5] This is a perspective view of the vicinity of the open end of the outer shell 3. [Figure 6] Figure 6A is a perspective view of the stopper 26 seen from above, and Figure 6B is a perspective view of the stopper 26 seen from below. [Figure 7] This is a longitudinal cross-section passing through the center of the inner stopper 26. [Figure 8]It is a perspective view showing a state where an inner preform 14 and an outer preform 13 are separated. [Figure 9] A preform 15 formed by covering the inner preform 14 with the outer preform 13 MODE FOR CARRYING OUT THE INVENTION

[0011] Embodiments of the present invention will be described below. Various characteristic matters shown in the embodiments described below can be combined with each other. Further, an invention can be claimed independently for each characteristic.

[0012] 1. Configuration of double container 1 <Basic Configuration> As shown in Fig. 1, a double container 1 according to an embodiment of the present invention includes a container body 2 and a mouth attachment member 8.

[0013] As shown in Figs. 2 to 3, the container body 2 includes a mouth portion 5, a body portion 6, and a bottom portion 7. The mouth portion 5 is a cylindrical (preferably circular cylindrical) portion having an open end 5c. The mouth portion 5 includes an engaging portion 5a to which a mouth attachment member 8 such as a cap or a pump can be attached. In the present embodiment, since the mouth attachment member 8 is of a plug-in type, the engaging portion 5a is an annular convex portion 5a2 protruding in the circumferential direction. When the mouth attachment member 8 is of a screw type, the engaging portion 5a serves as a male screw portion. A flange 5b is provided on the mouth portion 5. The flange 5b can be used to support the mouth portion 5 when attaching the mouth attachment member 8 to the mouth portion 5.

[0014] As shown in Fig. 4, the container body 2 includes an inner bag 4 and an outer shell 3 disposed so as to cover the inner bag 4. The inner bag 4 is accommodated in the outer shell 3 at portions other than a protruding portion 4c. In the following description, among the inner bag 4, portions corresponding to the mouth portion 5, the body portion 6, and the bottom portion 7 of the container body 2 are referred to as the mouth portion 5, the body portion 6, and the bottom portion 7 of the inner bag 4, respectively. The same applies to the outer shell 3.

[0015] The mouth attachment member 8 may or may not have a check valve (not shown). If the mouth attachment member 8 is not provided with a check valve, the inner bag 4 will not shrink after the contents of the inner bag 4 are discharged, making it difficult to pull out the inner bag 4 through the mouth 5 of the outer shell 3. Since the present invention makes it easy to pull out the inner bag 4 through the mouth 5 of the outer shell 3, the significance of applying the present invention is particularly evident when the mouth attachment member 8 is not provided with a check valve. Furthermore, the container body 2 may or may not have an outside air introduction section for introducing outside air into the intermediate space between the inner bag 4 and the outer shell 3. Examples of outside air introduction sections include an outside air introduction hole formed by perforating the outer shell 3, or a section at the bottom or mouth of the container body 2 where the interface between the outer shell 3 and the inner bag 4 is separated to enable outside air introduction. In the double-walled container 1 of this embodiment, it is not necessary to shrink the inner bag 4, so it is not essential to provide an outside air introduction section.

[0016] The inner diameter of the opening 5 of the outer shell 3 is, for example, 20 to 50 mm, and preferably 25 to 40 mm. Specifically, the inner diameter of the opening 5 of the outer shell 3 is, for example, 20, 25, 30, 35, 40, 45, or 50 mm, and may be within the range of any two of the values ​​exemplified here. The length of the opening 5 is, for example, 15 to 35 mm, specifically, for example, 15, 20, 25, 30, or 35 mm, and may be within the range of any two of the values ​​exemplified here.

[0017] The body portion 6 is positioned adjacent to the mouth portion 5 on the side further away from the opening end 5c than the mouth portion 5. The body portion 6 has a larger outer diameter than the mouth portion 5 (in this specification, "outer diameter" means the circumscribed circle diameter if the cross-section is not circular). The body portion 6 is cylindrical, and the bottom portion 7 is provided at the lower end of the body portion 6, closing the lower end of the body portion 6. The body portion 6 has a shoulder portion 6b whose outer diameter increases as it moves away from the mouth portion 5. The body portion 6 also has a body body 6c on the bottom 7 side of the shoulder portion 6b. The body body 6c has a shape in which the outer diameter is substantially constant toward the bottom 7, or a shape in which the diameter decreases toward the bottom 7.

[0018] <Materials and Layer Composition> The inner bag 4 is configured to be removable from the container body 2. After the contents of the inner bag 4 have been used up, the inner bag 4 can be removed from the container body 2, thereby separating the inner bag 4 from the outer shell 3. The peak torque value (hereinafter simply referred to as "peak torque value") when the inner bag 4 is rotated 45 degrees relative to the outer shell 3 is preferably 200 cN·m or less, more preferably 140 cN·m or less, and even more preferably 100 cN·m or less. This peak torque value is an indicator of the strength of the fit between the inner bag 4 and the outer shell 3 at the mouth 5 of the container body 2. The larger the value, the stronger the fit between the inner bag 4 and the outer shell 3, and the more difficult it is to remove the inner bag 4 from the container body 2. In the container body 2 of this embodiment, the peak torque value is a small value of 200 cN·m or less, making it easy to remove the inner bag 4 from the container body 2. This peak torque value is, for example, 10 to 200 cN·m, specifically, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200 cN·m, and may be within the range between any two of the values ​​exemplified here, or less than or equal to either of them. The peak torque value is the peak torque value measured during rotation when the inner bag 4 is rotated 45 degrees clockwise (counterclockwise when viewed from above with the container body 2 upright) while the outer shell 3 is fixed and the inner bag 4 is gripped, with no contents inside the inner bag 4. The peak torque value can be measured using a torque meter (model: 2TME500CN2, manufactured by Tohnichi Manufacturing Co., Ltd.).

[0019] The innermost layer of the inner bag 4 is made of a water-absorbing, softening resin that softens upon water absorption. Therefore, by wetting the innermost layer of the inner bag 4 before pulling it out of the container body 2, the force required to pull the inner bag 4 out of the container body can be reduced.

[0020] A water-absorbing, softening resin refers to a resin in which the rate of decrease in flexural modulus due to water absorption is 10% or more. This rate of decrease is, for example, 10 to 80%, specifically 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, and 80%, and may be within the range of any two of the values ​​exemplified here, or greater than or equal to either of them.

[0021] The rate of decrease in flexural modulus due to water absorption can be determined by the following procedure. Flexural modulus can be measured at 25°C in accordance with JIS K7171. First, a test specimen measuring 80 mm x 10 mm x 4 mm is prepared using the resin under test by injection molding, and the flexural modulus is measured. The measured value is defined as P1. Next, the test specimen is immersed in water for 96 hours to allow it to absorb water, and then the flexural modulus is measured. The measured value is defined as P2. The rate of decrease in the flexural modulus due to water absorption is calculated based on the following formula (1). The percentage decrease in flexural modulus due to water absorption = 100 × (P1 - P2) / P1 ... (1)

[0022] The flexural modulus of the water-absorbing, softening resin before water absorption is 1000 N / mm². 2 The above is preferable, and 2000 N / mm 2 The above is even more preferable. When the flexural modulus of the water-absorbing and softening resin has such a high value before water absorption, the technical significance of applying the present invention to reduce the pull-out force of the inner bag 4 is remarkable. This flexural modulus is, for example, 1000 to 10000 N / mm 2 Specifically, for example, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 6000, 7000, 8000, 9000, 10000 N / mm 2 The value may be within the range between any two of the numerical values ​​exemplified here, or greater than or equal to any two of them.

[0023] Table 1 shows the results of measuring the flexural modulus and its reduction rate for several types of resins by the method described above. As shown in Table 1, EVOH and nylon are water-absorbent softening resins because their reduction rate of flexural modulus due to water absorption is 10% or more, whereas polypropylene and PET are not water-absorbent softening resins because the aforementioned reduction rate is less than 10%.

Table 1

[0024] The inner bag 4 preferably has a flexural rigidity per unit width of 100 mN·mm or less. Flexural rigidity is a parameter that serves as an index of flexibility, and if the flexural rigidity is too high, it may become difficult to pull the inner bag 4 out of the container body 2. The flexural rigidity per unit width of the inner bag 4 is preferably 10 mN·mm or more. This is because reducing the flexural rigidity requires reducing the wall thickness of the inner bag 4, and reducing the wall thickness of the inner bag 4 tends to cause pinholes in the inner bag 4. Specific examples of the flexural rigidity per unit width of the inner bag 4 include 10, 15, 20, 23, 25, 30, 35, 40, 45, 50, 51, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 100 mN·mm, and it may be within a range between any two of the numerical values exemplified herein or be equal to or less than any of the numerical values exemplified herein.

[0025] Flexural rigidity can be calculated based on the following formulas (2) to (3). Flexural rigidity [N·mm 2 = Flexural modulus E [N / mm 2 × Second moment of area I [mm 4 ···(2) Second moment of area I [mm 4 = Width b [mm] × Thickness h 3 [mm 3 / 12 ···(3)

[0026] Flexural rigidity per unit width is defined by the following formula (4), and can be calculated based on formula (5) with reference to formulas (2) to (3). Flexural rigidity per unit width [N·mm] = Flexural rigidity [N·mm2 ] / Width b[mm] ···(4) Bending stiffness per unit width [N·mm] = Bending modulus E [N / mm] 2 ] × thickness h 3 [mm 3 ] / 12 ···(5)

[0027] If the resin constituting the inner bag 4 is polypropylene and the wall thickness of the inner bag 4 is 0.1 mm, the bending stiffness per unit width is 51 mN·mm. Therefore, when the bending stiffness per unit width is within the above numerical range, the inner bag 4 has a flexibility almost equivalent to that of an inner bag 4 made of polypropylene. Furthermore, if the resin constituting the inner bag 4 is the above-mentioned EVOH and the wall thickness of the inner bag 4 is 0.05 mm, the bending stiffness per unit width is 23 mN·mm.

[0028] Examples of water-absorbing and softening resins include EVOH (ethylene-vinyl alcohol copolymer), nylon, and paper-mixed plastics. Preferably, the water-absorbing and softening resin is an EVOH-based resin containing 50% by mass or more of EVOH. The EVOH-based resin may contain only EVOH, or it may be a mixed resin of EVOH and other resins. Examples of other resins include nylon and olefin-based resins. An olefin-based resin is a resin in which the olefin units in the resin are 50% by mass or more. Examples of olefins include ethylene and propylene. The proportion of olefin units contained in an olefin-based resin is, for example, 50 to 100% by mass, specifically, for example, 50, 60, 70, 80, 90, and 100% by mass, and may be within the range between any two of the values ​​exemplified here, or greater than or equal to either of them. Examples of olefin-based resins include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, and copolymers (random copolymers or block copolymers) of propylene and other olefins (ethylene, etc.). The proportion of EVOH in the EVOH-based resin is, for example, 50 to 100% by mass, specifically, for example, 50, 60, 70, 80, 90, or 100% by mass, and may be within the range of any two of the values ​​exemplified here, or greater than or equal to either of them.

[0029] Preferably, the ethylene content of EVOH is 25 to 46 mol%. If the ethylene content of EVOH is too low, the flexibility of the inner bag 4 will decrease significantly, and the pullability of the inner bag 4 will deteriorate significantly. Also, if the ethylene content of EVOH is too low, the inner bag 4 will become too brittle, and as shown in Figure 1, there is a risk that cracks will occur in the protrusion 4c when engaging the mouth attachment member 8 with the protrusion 4c of the inner bag 4. On the other hand, if the ethylene content of EVOH is too high, the improvement of the gas barrier properties of the inner bag 4 will be insufficient. By setting the ethylene content within the above range, the occurrence of the above problems can be suppressed. Specifically, the ethylene content is, for example, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, and 46 mol%, and may also be within the range of any two of the values ​​exemplified here.

[0030] The inner bag 4 may be a single-layer or multi-layer structure. If the inner bag 4 is a single-layer structure, the entire inner bag 4 becomes the innermost layer. Also, if the inner bag 4 is a single-layer structure, the inner preform 14 (shown in Figure 9) for forming the inner bag 4 can also be a single-layer structure. Since a single-layer inner preform 14 can be formed by general injection molding, manufacturing costs can be reduced. If the inner bag 4 is a multi-layer structure, another layer is provided outside the innermost layer made of water-absorbing and softening resin. An example of such another layer is an olefin resin layer made of olefin resin. The explanation of olefin resin is as described above.

[0031] The wall thickness of the inner bag 4 at the center of the height direction of the container body 2 is, for example, 0.05 to 0.25 mm, preferably 0.08 to 0.20 mm. Specifically, this wall thickness is, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.15, 0.20, 0.25 mm, and may be within the range of any two of the values ​​exemplified here. The ratio of the wall thickness of the innermost layer to the total wall thickness of the inner bag 4 is preferably 30% or more. The larger this value, the more pronounced the softening effect of the inner bag 4 due to water absorption by the innermost layer. This ratio is, for example, 30 to 100%, specifically, for example 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100%, and may be within the range of any two of the values ​​exemplified here.

[0032] The material and layer structure of the outer shell 3 are not particularly limited. The outer shell 3 can be formed from thermoplastic resins such as polyester (e.g., PET) or polyolefins (e.g., polypropylene, polyethylene). From the viewpoint of recyclability, it is preferable to form it from PET. Furthermore, from the viewpoint of reducing environmental impact, it is preferable to form the outer shell 3 from biomass plastic.

[0033] The wall thickness of the outer shell 3 at the center of the height direction of the container body 2 is, for example, 0.2 to 0.8 mm, and preferably 0.25 to 0.5 mm. Specifically, this wall thickness may be, for example, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8 mm, and may be within the range of any two of the values ​​exemplified here.

[0034] <Structure of the mouth attachment member 8 and the engagement structure between the mouth attachment member 8 and the container body 2> The mouth attachment member 8 is attached to the mouth 5 of the container body 2. As shown in Figure 2, the mouth attachment member 8 is, for example, a cap and comprises an inner stopper 26 and an overcap 27. The overcap 27 is optional. The inner stopper 26 is engaged with the inner bag 4 in the axial direction and may or may not be engaged in the circumferential direction. The overcap 27 is engaged with the inner stopper 26. This engagement may be a screw engagement or a snap engagement. In this specification, "axial direction" refers to the direction in which the central axis C of the mouth 5 extends, or in other words, the direction in which the inner bag 4 is pulled out of the container body 2. "Circumferential direction" refers to the direction of rotation around the central axis C of the mouth 5, or in other words, the direction in which the inner bag 4 rotates relative to the outer shell 3 at the mouth 5.

[0035] By the way, it is preferable that the double-walled container 1 is an inverted container having a cap with an enlarged top surface. In this case, the double-walled container 1 can be stably placed by setting the top surface in an inverted state. In this embodiment, in order to enable the double-walled container 1 to be stably placed in an inverted state, the overcap 27 is provided with an enlarged portion 27e that includes the top surface 27d of the overcap 27. In the inverted state, the top surface 27d is the contact surface, and by providing the enlarged portion 27e, the area of ​​the top surface 27d is increased, and the stability of the double-walled container 1 in the inverted state is improved.

[0036] Incidentally, when the double container 1 is placed in an inverted position, the contents are more likely to come into contact with the shoulder portion 6b even after the amount of contents has decreased. Since the contents contain moisture, contacting the contents with the shoulder portion 6b softens the water-absorbing, softening resin that makes up the innermost layer of the inner bag 4. When the inner bag 4 is pulled out of the container body 2, the resistance force that is likely to be greater when the shoulder portion 6b passes through the opening 5 is likely to be greater, so softening the shoulder portion 6b of the inner bag 4 particularly reduces the force required to pull the inner bag 4 out of the container body 2.

[0037] The mouth attachment member 8 is preferably configured such that the inner bag 4 rotates at the mouth 5 as the mouth attachment member 8 rotates (in this case, rotation relative to the outer shell 3) (i.e., the mouth attachment member 8 is preferably engaged with the inner bag 4 in the circumferential direction). With such a configuration, it is possible to rotate the inner bag 4 at the mouth 5 by rotating the mouth attachment member 8. In this embodiment, as the inner bag 4 rotates relative to the outer shell 3, the inner bag 4 moves in a direction away from the container body 2, so the inner bag 4 can be raised from the container body 2 by rotating the mouth attachment member 8. Then, using the raised portion of the inner bag 4 from the container body 2 as a starting point, the inner bag 4 can be easily pulled out of the container body 2.

[0038] Furthermore, since the body 6 of the container body 2 has a larger outer diameter than the opening 5, simply pulling the inner bag 4 will not easily allow it to pass through the opening 5 of the outer shell 3. However, by rotating the opening 5 of the inner bag 4 and twisting the inner bag 4, the body 6 of the inner bag 4 will be able to pass through the opening 5 of the outer shell 3 more easily, allowing the inner bag 4 to be easily pulled out of the container body 2.

[0039] The engagement structure between the mouth attachment member 8 and the container body 2 will be described in more detail below.

[0040] As shown in Figures 3 and 4, the inner bag 4 is provided with a protruding portion 4c that extends from the open end 3a of the outer shell 3. The protruding portion 4c comprises a protruding cylinder 4c1, an engaging projection 4c2, and a contact flange 4c4.

[0041] The engaging projection 4c2 protrudes radially outward from the circumferential surface of the protruding cylinder 4c1. Multiple engaging projections 4c2 are provided at circumferentially spaced intervals (eight in this embodiment). The engaging projection 4c2 has a tapered surface 4c3 on its upper surface. This makes it easier for the annular projection 28c of the mouth mounting member 8 (shown in Figures 6B and 7) to overcome the engaging projection 4c2, as will be described later.

[0042] The contact flange 4c4 is positioned to abut against the open end 3a and is an annular portion with a larger diameter than the protruding cylinder 4c1. The contact flange 4c4 abuts against the open end 3a, preventing the inner bag 4 from falling into the outer shell 3. Alternatively, the contact flange 4c4 may be omitted, and the inner bag 4 may be prevented from falling into the outer shell 3 by abutting the engaging projection 4c2 against the open end 3a.

[0043] The outer circumferential surface of the mouth portion 5 of the outer shell 3 is provided with an annular projection 5a2 and intermittently arranged protrusions 3k on the annular projection 5a2. The protrusions 3k are provided at multiple locations (eight locations in this embodiment) on the annular projection 5a2, spaced apart in the circumferential direction.

[0044] As shown in Figures 2, 6, and 7, in this embodiment, the mouth mounting member 8 is of the plug type, and it is possible to attach the mouth mounting member 8 to the mouth 5 by applying axial force to the mouth mounting member 8.

[0045] As shown in Figure 7, the stopper 26 comprises a main body portion 28 and a band portion 29. The main body portion 28 and the band portion 29 are connected to each other via an easily tearable connecting portion 30.

[0046] The band portion 29 engages axially with the opening 5 of the outer shell 3. Therefore, the axial movement of the band portion 29 relative to the opening 5 of the outer shell 3 is restricted. The band portion 29 may or may not be engaged circumferentially with the opening 5 of the outer shell 3. If the band portion 29 is engaged circumferentially with the opening 5 of the outer shell 3, the circumferential movement of the band portion 29 relative to the opening 5 of the outer shell 3 is restricted.

[0047] The main body portion 28 engages axially with the opening portion 5 of the inner bag 4. Therefore, the axial movement of the main body portion 28 relative to the opening portion 5 of the inner bag 4 is restricted. The main body portion 28 may or may not be engaged circumferentially with the opening portion 5 of the inner bag 4. If the main body portion 28 is engaged circumferentially with the opening portion 5 of the inner bag 4, the circumferential movement of the main body portion 28 relative to the opening portion 5 of the inner bag 4 is restricted.

[0048] The connecting portion 30 is configured to be torn apart by applying force (shear force, rotational force, etc.) between the main body portion 28 and the band portion 29. Preferably, the connecting portion 30 is thinner than the main body portion 28 and the band portion 29.

[0049] The band portion 29 comprises an outer cylinder 29a and an inner cylinder 29b. The inner cylinder 29b is positioned inside the outer cylinder 29a. The outer cylinder 29a and the inner cylinder 29b are connected at the lower end of the band portion 29, and the inner cylinder 29b is connected to the main body portion 28 via a connecting portion 30. The inner cylinder 29b is positioned to surround the annular projection 5a2. The inner circumferential surface of the inner cylinder 29b is provided with an engaging projection 29c that extends in the circumferential direction. The band portion 29 engages axially with the mouth portion 5 of the outer shell 3 by the axial engagement of the engaging projection 29c with the annular projection 5a2. A tapered surface is provided on the lower side of the engaging projection 29c, reducing the force required for the engaging projection 29c to overcome the annular projection 5a2.

[0050] Furthermore, the projection 3k provided on the annular protrusion 5a2 is pressed against the inner stopper 26, causing the inner stopper 26 to frictionally engage with the mouth 5 of the outer shell 3 in the circumferential direction. As will be described later, the double container 1 of this embodiment is configured such that the mouth attachment member 8 and the inner bag 4 rotate together, causing the inner bag 4 to move in a direction that causes it to detach from the container body 2. If the mouth attachment member 8 rotates unintentionally relative to the outer shell 3, there is a risk that the inner bag 4 may detach unintentionally from the container body 2. To prevent such a problem from occurring, the inner stopper 26 is engaged with the mouth 5 of the outer shell 3 in the circumferential direction to suppress the rotation of the mouth attachment member 8 relative to the mouth 5 of the outer shell 3.

[0051] The outer cylinder 29a of the band portion 29 is provided with a thin-walled portion 29a1. By starting to tear at the thin-walled portion 29a1 and then tearing the connecting portion 30, the band portion 29 can be removed.

[0052] The main body 28 comprises an outer cylinder 28a, an inner cylinder 28b, an annular projection 28c, an engaging projection 28d, a top plate 28e, a discharge cylinder 28f, and a mounting cylinder 28g.

[0053] The top plate 28e is provided on the upper surface of the outer cylinder 28a. An inner cylinder 28b is provided on the lower surface of the top plate 28e. The inner cylinder 28b has a smaller diameter than the outer cylinder 28a and is a so-called inner ring located inside the outer cylinder 28a. A discharge cylinder 28f and a mounting cylinder 28g are provided on the upper surface of the top plate 28e. The contents of the inner bag 4 are discharged through the discharge cylinder 28f. As shown in Figure 2, a male screw portion 28g1 is provided on the outer circumference of the mounting cylinder 28g, and the male screw portion 28g1 engages with a female screw portion provided on the inner circumference of the cylindrical portion 27c of the overcap 27, thereby screw-engaging the overcap 27 with the inner plug 26. In this case, the overcap 27 can be attached to and detached from the inner plug 26 by rotating the overcap 27 relative to the inner plug 26. Alternatively, the overcap 27 may be attached to and detached from the inner plug 26 by snap-fitting and releasing.

[0054] The annular projection 28c is an annular projection provided on the inner circumferential surface of the outer cylinder 28a so as to extend in the circumferential direction. The annular projection 28c engages with the engaging projection 4c2 in the axial direction, thereby causing the main body 28 to engage with the opening 5 of the inner bag 4 in the axial direction. Multiple engaging projections 28d are provided at intervals in the circumferential direction (eight in this embodiment). The engaging projections 28d are positioned between adjacent engaging projections 4c2, thereby causing the main body 28 to engage with the opening 5 of the inner bag 4 in the circumferential direction.

[0055] <Engagement structure between outer shell 3 and inner bag 4> As shown in Figure 4, the outer circumferential surface of the inner bag 4 is provided with a cam projection 4g and an engaging projection 4h. The cam projection 4g and the engaging projection 4h are connected to each other. The lower surfaces of the cam projection 4g and the engaging projection 4h are inclined such that, when viewed from the opening end 5c side of the mouth 5, they approach the opening end 5c as you move clockwise.

[0056] As shown in Figure 5, the inner circumferential surface of the outer shell 3 is provided with a cam rail 3l and an engagement recess 3m. The engagement recess 3m is provided such that its lower surface is continuous with the upper surface of the cam rail 3l. The upper surface of the cam rail 3l and the lower surface of the engagement recess 3m are inclined so that, when viewed from the opening end 3a side, they approach the opening end 3a as one moves clockwise. In the state before the inner bag 4 is pulled out of the container body 2, the engagement projection 4h is positioned within the engagement recess 3m, and the lower surface of the cam projection 4g is in contact with the upper surface of the cam rail 3l. The cam projection 4g and the cam rail 3l constitute the cam mechanism 31. In this embodiment, the engagement recess 3m is a through hole, but it may also be a non-through hole.

[0057] <How to remove inner bag 4> First, before starting to pull out the inner bag 4, the innermost layer of the inner bag 4 is moistened and softened. The innermost layer of the inner bag 4 may be moistened with the moisture from the contents, or it may be moistened with water supplied from the outside after the contents have been used up. Also, if the double container 1 is an inverted container, the contents will remain in contact with the shoulder portion 6b until just before the contents are used up, so the shoulder portion 6b will be moistened without any additional work being done after the contents have been used up. Furthermore, even if the double container 1 is not an inverted container, the shoulder portion 6b can be moistened with the contents by inverting the double container 1 before the contents are used up.

[0058] Next, the inner bag 4 is removed from the container body 2. This can be done in the following way, for example.

[0059] Before attempting to remove the inner bag 4, the main body 28 and band 29 of the mouth attachment member 8 are connected, and the band 29 is axially engaged with the mouth 5 of the outer shell 3. In this state, the inner bag 4 cannot be removed from the container body 2. Therefore, first, the connecting part 30 is torn to remove the band 29. This releases the engagement between the mouth attachment member 8 and the mouth 5 of the outer shell 3, making it possible to remove the inner bag 4.

[0060] Next, the mouth attachment member 8 is rotated clockwise when viewed from the opening end 5c. Since the inner bag 4 is engaged with the mouth attachment member 8 in the circumferential direction, the inner bag 4 rotates in the same direction as the mouth attachment member 8 rotates, and the cam projection 4g moves along the cam rail 3l, causing the inner bag 4 to move in a direction away from the container body 2. At this time, the inner bag 4 is twisted, and the diameter of the body portion 6 of the inner bag 4 is reduced. Note that if you try to rotate the inner bag 4 counterclockwise when viewed from the opening end 5c, the cam projection 4g of the inner bag 4 interferes with the projection that makes up the cam rail 3l, making it impossible to rotate the inner bag 4. This prevents you from rotating the inner bag 4 in the wrong direction.

[0061] Next, the mouth attachment member 8 is moved axially to pull the inner bag 4 out of the container body 2. Since the mouth attachment member 8 is engaged with the inner bag 4 in the axial direction, the axial force applied to the mouth attachment member 8 is transmitted to the inner bag 4, and the inner bag 4 is pulled out of the container body 2. This pulling is performed with the inner bag 4 raised above the container body 2, so the force required to pull out the inner bag 4 is reduced.

[0062] In the example above, the inner bag 4 is removed using the mouth attachment member 8, but the inner bag 4 may also be removed by grasping it by hand and pulling it out. In either case, since the innermost layer of the inner bag 4 is softened by water absorption, the force required to remove the inner bag 4 is reduced.

[0063] 2. Manufacturing method of double-walled container 1 As shown in Figures 8 and 9, the container body 2 can be formed by blow molding a parison. The blow molding may be direct blow molding or injection blow molding. In direct blow molding, the container body 2 is manufactured by sandwiching a molten cylindrical (preferably cylindrical) parison extruded from an extruder between a pair of split molds and blowing air into the parison. In injection blow molding, a test tube-shaped bottomed parison called a preform is formed by injection molding, and blow molding is performed using this parison. In injection blow molding, the inner bag 4 does not adhere easily to the outer shell 3, and the inner bag 4 is easy to pull out, so the container body 2 can be formed by injection blow molding.

[0064] The manufacturing method for the container body 2 by injection blow molding will be described in detail below. In injection blow molding, the container body 2 can be formed by heating the preform 15 and performing biaxial stretch blow molding.

[0065] <Composition: Inner preform 14, outer preform 13, preform 15> In one example, the preform 15 can be constructed by covering an inner preform 14, which will become the inner bag 4, with an outer preform 13, which will become the outer shell 3.

[0066] As shown in Figure 8, the inner preform 14 is a bottomed cylindrical shape and comprises a mouth portion 14a, a body portion 14b, and a bottom portion 14c. A projection 14d is provided at the open end of the mouth portion 14a. The projection 14d remains unchanged in shape during molding and becomes the projection 4c. Therefore, the matters described for the projection 4c also apply to the projection 14d. The bottom portion 14c is provided to close the lower end of the body portion 14b. A positioning pin 14c1 is provided on the bottom portion 14c. The outer circumferential surface of the mouth portion 14a of the inner preform 14 is provided with cam projections 14g and 14h, which become cam projections 4g and 4h, respectively.

[0067] As shown in Figure 8, the outer preform 13 is a bottomed cylindrical shape and comprises a mouth portion 13a, a body portion 13b, and a bottom portion 13c. The bottom portion 13c is provided to close the lower end of the body portion 13b. The bottom portion 13c is provided with an annular projection 13d and a positioning hole (not shown). The mouth portion 13a of the outer preform 13 is provided with a cam rail 13l which becomes a cam rail 3l and an engagement recess 13m which becomes an engagement recess 3m.

[0068] As shown in Figure 9, when forming the preform 15, the protrusion 14d is brought into contact with the opening end of the mouth portion 13a, and the positioning pin 14c1 is inserted into the positioning hole. This positions the inner preform 14 and the outer preform 13 relative to each other. In this state, the mouth portions 14a and 13a face each other, and the body portions 14b and 13b face each other.

[0069] The openings 13a and 14a become the opening 15a of the preform 15, the body portions 13b and 14b become the body portion 15b of the preform 15, and the bottom portions 13c and 14c become the bottom portion 15c of the preform 15. The body portion 15b and the bottom portion 15c are mainly stretched in biaxial stretch blow molding.

[0070] <Interaction of the inner preform 14 and the outer preform 13 at the opening 15a> Incidentally, when heating the preform 15 and performing biaxial stretch blow molding, the inner circumferential surface side of the preform 15 (i.e., the inner circumferential surface side of the inner preform 14) is usually supported. There are two methods for transporting the preform 15: upright transport with the bottom 15c facing downwards, and inverted transport with the bottom 15c facing upwards. Upright transport is common and preferred. On the other hand, if the preform 15 is transported upright, there is a risk that the outer preform 13 may detach from the inner preform 14 and fall off. If the outer preform 13 and the inner preform 14 are tightly fitted together at the opening 15a, it is possible to suppress the detachment of the outer preform 13, but in that case, a new problem arises in the container body 2 obtained by molding, where the inner bag 4 becomes difficult to detach from the container body 2.

[0071] Therefore, in order to allow the inner bag 4 to be easily removed from the container body 2 after use, while suppressing the outer preform 13 from falling off, in this embodiment, the inner preform 14 and the outer preform 13 are engaged with each other at the opening 15a.

[0072] In this embodiment, the interlocking engagement is the engagement between an engaging projection 14h provided on the outer circumferential surface of the opening 14a of the inner preform 14 and an engaging recess 13m provided on the inner surface of the opening 13a of the outer preform 13, as shown in Figure 8. The engaging projection 14h and the engaging recess 13m become the engaging projection 4h and the engaging recess 3m, respectively.

[0073] <Materials and manufacturing method of inner preform 14 and outer preform 13> The inner preform 14 can be formed from the materials described above for the inner bag 4. The inner preform 14 can be formed by direct blow molding, injection molding, etc., but from the viewpoint of manufacturing cost, it is preferable to form it by injection molding. The inner bag 4 with a multi-layer structure can be formed using the inner preform 14 with a multi-layer structure. The inner preform 14 with a multi-layer structure can be formed by two-color molding or co-injection molding.

[0074] The outer preform 13 can be formed from the material described above for the outer shell 3. The outer preform 13 can be formed by direct blow molding, injection molding, etc., but from the viewpoint of manufacturing cost, it is preferable to form it by injection molding.

[0075] The preform 15 may be formed by separately forming the inner preform 14 and the outer preform 13 and then combining them, or it may be formed by two-color molding.

[0076] 3. Other Embodiments In the above embodiment, the method for removing the inner bag 4 was explained using the case where the mouth attachment member 8 is of the stopper type as an example, but the mouth attachment member 8 may also be of the screw type. If the mouth attachment member 8 is of the screw type, if the mouth attachment member 8 is engaged with the inner bag 4 in the circumferential and axial directions, rotating the mouth attachment member 8 to release the screwing of the mouth attachment member 8 and the mouth 5 will cause the inner bag 4 to rise from the container body 2 as the mouth attachment member 8 moves in the axial direction. In this case, there is no need to provide a mechanism such as a cam mechanism 31 between the outer shell 3 and the inner bag 4. [Explanation of Symbols]

[0077] 1:Double container 2: Container body 3: Outer shell 3a: Open end 3k:Protrusion 3L: Cam Rail 3m: Engaging recess 4: Inner bag 4c:Protrusion 4c1:Protruding tube 4c2: Engagement convex part 4c3: Tapered surface 4c4: Contact flange 4g: Cam protrusion 4h: Engagement protrusion 5: Mouth 5a: Engagement part 5a2: Annular protrusion 5b: Flange 5c: Open end 6: Torso 6b:Shoulder 6c: Torso body 7: Bottom 8: Mouthpiece mounting member 13: External preform 13a: Mouth 13b: Torso 13c: Bottom 13d: Annular protrusion 13L: Cam Rail 13m: Engaging recess 14: Internal preform 14a: Mouth 14b: Torso 14c: Bottom 14c1: Positioning pin 14d:Protrusion 14g: Cam protrusion 14h: Engagement protrusion 15: Preform 15a: Mouth 15b: Torso 15c: bottom 26: Inner stopper 27: Overcap 27c:Cylinder part 27d: Top surface 27e: Expanded diameter part 28: Main body 28a: Outer cylinder 28b: Inner cylinder 28c: Annular protrusion 28d: Engagement convex part 28e: Top plate 28f:Discharge tube 28g: Mounting tube 28g1: Male threaded part 29: Band Club 29a: Outer cylinder 29a1: Thin wall part 29b: Inner cylinder 29c: Engagement convex part 30:Connection part 31: Cam mechanism A :Area C: Central axis

Claims

1. A double-walled container comprising a container body, The container body comprises an inner bag and an outer shell positioned to cover the inner bag. The inner bag is configured to be removable from the container body. The inner bag comprises an innermost layer and an olefin resin layer disposed outside the innermost layer. The innermost layer is made of a water-absorbing, softening resin that has the property of softening upon water absorption. The olefin resin layer is composed of an olefin resin. The olefin resin is low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, or a copolymer of propylene and ethylene, in a double-walled container.

2. A double-walled container according to claim 1, The water-absorbing, softening resin is EVOH or nylon, and the container is double-walled.

3. A double-walled container according to claim 1 or claim 2, The aforementioned double-walled container is an inverted container having a cap with an enlarged top surface. The container body comprises a mouth portion which is a cylindrical part having an open end, and a body portion which is located adjacent to the mouth portion on the side away from the mouth portion. The body of the container is a double-walled container, having a shoulder portion adjacent to the opening, the shoulder portion having an outer diameter that increases as it moves away from the opening.

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