Double-walled container and method for producing the same

Abstract

To provide a double container capable of improving discharge performance.SOLUTION: According to the present invention, there is provided a double-walled container including a container body, wherein the container body includes an inner bag and an outer shell disposed to cover the inner bag, a seal portion is formed at a bottom of the container body, the seal portion is provided with a slit-shaped fresh air inlet communicating with an internal space between the outer shell and the inner bag, and the bottom is provided with an airflow regulating member configured to regulate a flow of air through the fresh air inlet.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a double container and a method for manufacturing the same. [Background technology]

[0002] Patent Document 1 discloses a double container having a structure capable of suppressing peeling of the inner layer at the bottom of the double container. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-90282 Summary of the Invention [Problem to be solved by the invention]

[0004] In the double container of Patent Document 1, outside air is introduced between the outer layer and the inner layer through an outside air inlet hole formed at the bottom of the container, so that the outer layer maintains its shape while only the inner layer reduces in volume.

[0005] However, when squeezing the container to dispense the contents, air escapes from the bottom, which increases the squeezing pressure and makes dispensing difficult.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a double container that can improve the discharge performance. [Means for solving the problem]

[0007] According to the present invention, the following inventions are provided. [1] A double container comprising a container body, the container body comprising an inner bag and an outer shell arranged to cover the inner bag, a seal portion formed at the bottom of the container body, a slit-shaped outside air introduction hole that communicates with the internal space between the outer shell and the inner bag, and an air flow regulating member that regulates the flow of air through the outside air introduction hole, at the bottom. [2] A double container as described in [1], wherein the bottom portion has a pair of resin reservoir portions arranged to intersect with the sealing portion, and the outside air inlet hole extends to the pair of resin reservoir portions. [3] A double container as described in [1] or [2], wherein the bottom has a pair of legs protruding from the bottom, and the air flow regulating member is positioned between the pair of legs. [4] A double container according to [3], wherein the bottom of the container body is flat and the pair of legs are arranged at both ends of the flat shape in the longitudinal direction. [5] The double container according to any one of [1] to [4], wherein the air flow regulating member is a breathable membrane welded at a joint surrounding the outside air introduction hole. [6] A double container as described in [5], wherein a recess is provided in the bottom, the outside air inlet is positioned within the recess, and the joint is positioned to surround the recess. [7] A method for manufacturing a double container described in [5] or [6], wherein the joint is formed by ultrasonically welding the breathable membrane to an annular convex portion arranged to surround the outside air inlet hole. [8] A method for manufacturing a double container described in any one of [1] to [5], wherein the outside air introduction hole is located in a recess provided in the bottom, and the outside air introduction hole is formed by opening a pair of split molds in a state where they are hooked onto the recesses during direct blow molding. [Effects of the Invention]

[0008] According to the present invention, the bottom of the container body is provided with a seal portion, a slit-shaped outside air inlet hole that communicates with the internal space between the outer shell of the container body and the inner bag at the seal portion, and an air flow regulating member that regulates the flow of air through the outside air inlet hole, thereby making it possible to improve discharge performance. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1A is a side view of a double container 1 with the container body 2, dispensing cap 12 and lid 13 shown separated, and FIG. 1B is a cross-sectional view of the container body 2 along section BB in FIG. 1A. [Figure 2] FIG. 2A is a perspective view showing the bottom 5 of the container body 2, FIG. 2B is a perspective view of the bottom 5 with the air flow restriction member 25 separated from the bottom 5, and FIG. 2C is a plan view of the bottom 5 without the air flow restriction member 25. [Figure 3] 3A is a cross-sectional view of the container body 2 taken along the cross section AA in FIG. 2C, and FIG. 3B is an enlarged view showing a region B in FIG. 3A. [Figure 4] FIG. 4 is a cross-sectional view of the container body 2 taken along the cross section AA in FIG. 2C, showing the internal space 26 formed when the inner bag 15 and the outer shell 14 are separated by the discharge of the contents. [Figure 5] FIG. 5A is a schematic diagram showing the process of manufacturing the container body 2 by extrusion blow molding, and FIG. 5B is a plan view showing the bottom of a pair of split molds 32 clamped together in the manufacturing process. [Figure 6] FIG. 6 is a cross-sectional view showing a part of the process in which the gas-permeable membrane 25a (air flow restriction member 25) is welded to the annular protrusion 23a (welding margin) on the bottom 5 of the container body 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently. Furthermore, in the following embodiments, elements not specified in the claims are optional elements and can be omitted. Any number of "0"s (for example, one or two) may be added to the end of numerical values ​​disclosed in the following description. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400."

[0011] As shown in FIG. 1A, a double-walled container 1 according to one embodiment of the present invention is primarily comprised of a container body 2. The container body 2 includes a storage section 3 for storing contents and a spout 4 for discharging the contents from the storage section 3. The storage section 3 includes a bottom 5, a cylindrical body 6 formed to rise from the periphery of the bottom 5, a shoulder 7 formed on the body 6 and tapered so that the circumferential size of the cylindrical body 6 decreases toward the spout 4, and a neck 8 disposed between the shoulder 7 and the spout 4. The spout 4 includes a base end 9 and a cylindrical cap 10 formed to rise from the base end 9, and the cap 10 may have a helical protrusion 10a formed as a male screw.

[0012] The double container 1 includes a cap 11 attached to the cap portion 10. The cap 11 may include a discharge cap 12 and a lid 13, as shown in FIG. 1A. The discharge cap 12 is held in place by abutting against the inner circumferential surface of the mouth portion 4. The contents of the inner bag 15 are discharged through the discharge cap 12 when the outer shell 14 is pressed from the outside of the container body 2. The lid 13 is attached to the container body 2 before and after discharge to prevent dirt from adhering to the discharge cap 12. The lid 13 may include a spiral recess 13a as a female screw corresponding to the spiral protrusion 10a of the cap portion 10 for attachment to the container body 2. The discharge cap 12 is configured to allow the contents of the inner bag 15 to be discharged but prevent air from being drawn into the inner bag 15. For example, the discharge cap 12 may include a check valve (not shown). Furthermore, as shown in FIG. 1B, the container body 2 includes an outer shell 14 and an inner bag 15.

[0013] 1B, the storage section 3 of the container body 2 has a flattened shape (e.g., an elliptical cross-section) from the bottom 5 to the shoulder 7 in a cross section perpendicular to the central axis 16 of the container body 2. The longitudinal length of the ellipse (flattened cross-section) is, for example, 17 mm to 27 mm (22 mm in this embodiment), specifically, for example, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, or 27 mm, and may be within a range between any two of the numerical values ​​exemplified here. The lateral length of the ellipse (flattened cross-section) is, for example, 11 mm to 21 mm (16 mm in this embodiment), specifically, for example, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21 mm, and may be within a range between any two of the numerical values ​​exemplified here. Furthermore, the value of the ratio of the longitudinal length to the lateral length of the ellipse (flat cross section), [longitudinal length / lateral length], is, for example, 1.0 to 1.8 (1.375 in this embodiment), and specifically, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or 1.8, and may be within a range between any two of the values ​​exemplified here. The central axis 16 of the container body 2 is defined as a line that passes through the center of gravity of the container body 2 and extends in a direction perpendicular to the horizontal surface when the container body 2 is placed on a horizontal surface with the bottom 5 as the ground surface.

[0014] The length from the bottom 5 to the mouth 4 of the container body 2 in the direction along the central axis 16 (i.e., the height of the container body 2) is, for example, 33 mm to 53 mm (42.8 mm in this embodiment), specifically, for example, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0015] The cross section of the neck portion 8 and the mouth portion 4 in a direction perpendicular to the central axis 16 is formed into a circle, and the outer diameter of the base end portion 9 of the mouth portion 4 in this cross section is larger than the outer diameters of the neck portion 8 and the cap portion 10 (excluding the spiral convex portion 10a). In other words, the base end portion 9 forms an annular convex portion that protrudes in the radial direction of the circular cross section perpendicular to the central axis 16. The inner diameter of the mouth portion 4 is, for example, 4 mm to 14 mm (8.7 mm in this embodiment), and specifically, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0016] Container body 2 is configured such that outer shell 14 encases inner bag 15. Outer shell 14 and inner bag 15 are configured to be peelable, and in storage section 3, inner bag 15 separates from outer shell 14 and shrinks as the contents in inner bag 15 decrease. The capacity of inner bag 15 is, for example, 3 ml to 25 ml, and more specifically, for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 ml, and may be within a range between any two of the numerical values ​​exemplified here.

[0017] The outer shell 14 is formed to be thicker than, for example, the inner bag 15 so as to increase the restorability of the container body 2. The thickness of the outer shell 14 is, for example, 0.5 mm to 1.0 mm, specifically, for example, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0018] Examples of materials that can be used for the shell 14 include synthetic resins such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene copolymers, and mixtures thereof. Furthermore, the shell 14 may be formed containing a random copolymer of propylene and another monomer. This improves the shape recovery, transparency, and heat resistance of the shell 14. The shell 14 may also have a multi-layer structure.

[0019] The tensile modulus (also referred to as Young's modulus) of the outer shell 14 is, for example, 400 to 2000 MPa, preferably 1000 to 1600 MPa. When the tensile modulus is within this range, the shape recovery property can be particularly good. Specific examples of the tensile modulus are 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, and 2000 MPa, and may be within a range between any two of the values ​​exemplified here.

[0020] The inner bag 15 may be made of polyolefins such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, cycloolefin polymer (COP), ethylene-propylene copolymer, and mixtures thereof. Furthermore, the inner bag 15 is preferably made of an ethylene-vinyl alcohol copolymer (EVOH) resin or polyamide, which may contain an oxygen absorber to improve oxygen barrier properties. The inner bag 15 preferably has a multi-layer structure, for example, an EVOH layer in contact with the outer shell 14 and a COP layer in contact with the contents. An adhesive layer is preferably used between the EVOH layer and the COP layer. By using an EVOH layer (or polyamide layer) in the layer of the inner bag 15 that contacts the outer shell 14 (i.e., the outermost layer of the inner bag 15), the outer shell 14 and the inner bag 15 can be separated from each other. In other embodiments, instead of the layer in inner bag 15 that contacts outer shell 14, an EVOH layer (or polyamide layer) may be used in the layer in outer shell 14 that contacts inner bag 15 (i.e., the innermost layer in outer shell 14).

[0021] The tensile modulus of inner bag 15 is, for example, 50 to 300 MPa, and preferably 70 to 200 MPa. When the tensile modulus is within this range, inner bag 15 can be particularly flexible. Specific examples of the tensile modulus value are 50, 70, 100, 150, 200, 250, and 300 MPa, and it may be within a range between any two of the values ​​exemplified here.

[0022] <Details of the container bottom> As shown in FIG. 2A , the bottom 5 is provided with an air flow restriction member 25. Here, the structure of the portion of the bottom 5 covered with the air flow restriction member 25 will be described. As shown in FIG. 2B , the bottom 5 is provided with a recess 20 recessed toward the container body 2. The recess 20 includes a seal portion 21 and an outside air introduction hole 21a extending radially from the recess 20 in a plan view, as shown in FIG. 2C . The recess 20 may further include a resin reservoir 22 and / or a step 22a protruding toward the outside of the container body 2 along the central axis 16. The recess 20 is formed, for example, in a circular shape in a plan view. For example, a joint 23 and / or a leg 24 may be provided in the outer region of the recess 20. The joint 23 may be formed in a ring shape surrounding the recess 20. The joint 23 is a region formed by joining the air flow restriction member 25 to the bottom 5. When the outer shell 14 is pressed from the outside of the container body 2 to discharge the contents of the inner bag 15, the air flow restriction member 25 is configured to either allow air to flow out of the inner space 26 between the outer shell 14 and the inner bag 15 to an extent that the pressure in the inner space 26 increases to facilitate the discharge of the contents, or to prevent air from flowing out. When the pressure is stopped, the air flow restriction member 25 is configured to allow air to flow into the inner space 26 from the outside of the container body 2 so that the shape of the outer shell 14 is restored.

[0023] The outside air introduction hole 21a is provided along the seal portion 21 so as to communicate with the internal space 26 between the outer shell 14 and the inner bag 15. That is, as shown in FIGS. 3A and 3B , the outside air introduction hole 21a is formed as a slit-like hole penetrating the outer shell 14 at the seal portion 21. The air flow restriction member 25 is arranged to cover the outside air introduction hole 21a, and air passing through the outside air introduction hole 21a flows in and out through the air flow restriction member 25, so that the flow of air through the outside air introduction hole 21a is restricted by the air flow restriction member 25. The outside air introduction hole 21a preferably extends to the resin reservoir 22 and is arranged inside the area surrounded by the recess 20 or the joint portion 23. The outside air introduction hole 21a may be formed over the entire length of the seal portion 21, or may be formed in a portion or multiple locations of the seal portion 21.

[0024] The resin reservoir 22 can be formed to be thickest in the recess 20. The thickness here refers to the thickness of the resin reservoir 22 in the outer shell 14 in the direction along the central axis 16. Furthermore, in a plan view of the bottom 5 as shown in FIG. 2C , the length of the resin reservoir 22 in a direction perpendicular to the longitudinal direction of the seal portion 21 (i.e., the distance between a pair of straight lines parallel to the longitudinal direction of the seal portion 21 when the resin reservoir 22 is sandwiched between the pair of straight lines so as to be in contact with the resin reservoir periphery 22b) is longer than the length of the resin reservoir 22 in the longitudinal direction of the seal portion 21 (i.e., the distance between a pair of straight lines perpendicular to the longitudinal direction of the seal portion 21 when the resin reservoir 22 is sandwiched between the pair of straight lines so as to be in contact with the resin reservoir periphery 22b).

[0025] The bottom 5 may include a pair of legs 24, and the recess 20 and the joint 23 may be disposed between the pair of legs 24. The pair of legs 24 are disposed, for example, at both ends of the bottom 5 along the longitudinal direction of the seal portion 21, thereby allowing a larger area in the bottom 5 for disposing the recess 20. Furthermore, in a plan view of the bottom 5 as shown in FIG. 2C , the length of each of the pair of legs 24 in a direction perpendicular to the longitudinal direction of the seal portion 21 (defined in the same manner as the length of the resin reservoir 22 in that direction) is longer than the length of the leg 24 in the longitudinal direction of the seal portion 21 (defined in the same manner as the length of the resin reservoir 22 in that direction). The legs 24 are formed to protrude in a direction from the mouth 4 toward the bottom 5 along the central axis 16 of the container body 2.

[0026] In a plan view of the bottom 5 as shown in FIG. 2C , the ratio of the total area of ​​the resin reservoirs 22 (the total area of ​​the regions surrounded by the resin reservoir peripheries 22b) to the area of ​​the recesses 20 (the area of ​​the regions surrounded by the recess peripheries 20a) is, for example, 10 to 40% (20% in this embodiment), and preferably 15 to 25%. Specifically, this value may be, for example, 10, 15, 20, 25, 30, 35, or 40%, and may be within a range between any two of the values ​​exemplified here. Furthermore, the distance between the lowest point of the recesses 20 other than the resin reservoirs 22 and the highest point of the resin reservoirs 22 in the direction from the mouth 4 toward the bottom 5 along the central axis 16 (i.e., the height of the resin reservoirs 22) is, for example, 0.1 to 1.5 mm, and preferably 0.6 to 1.0 mm. This value is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5 mm, and may be within a range between any two of the values ​​exemplified here. The length of resin reservoir 22 in the longitudinal direction of seal portion 21 is, for example, 1 to 5 mm, and for example, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 mm, and may be within a range between any two of the values ​​exemplified here. The length of resin reservoir 22 in a direction perpendicular to the longitudinal direction of seal portion 21 is, for example, 6 to 10 mm, specifically, for example, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10 mm, and may be within a range between any two of the numerical values ​​exemplified herein. Furthermore, the value of [length of resin reservoir 22 in a direction perpendicular to the longitudinal direction of seal portion 21 / length of resin reservoir 22 in the longitudinal direction of seal portion 21] is, for example, 1.5 to 2.5, specifically, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5, and may be within a range between any two of the numerical values ​​exemplified herein.

[0027] The resin reservoir 22 may have a step 22a that protrudes further in the direction from the mouth 4 toward the bottom 5 along the central axis 16. As shown in Fig. 2C, the step 22a has a rectangular shape in a plan view of the bottom 5, the length in a direction perpendicular to the longitudinal direction of the seal portion 21 being greater than the longitudinal length of the seal portion 21, and is located inside the region of the resin reservoir 22 in plan view. The presence of the step 22a increases the surface area of ​​the resin reservoir 22, increasing the area where the bottom 5 comes into contact with the mold during the production of the double container 1, thereby improving cooling efficiency.

[0028] 3B, the ratio of the sum of lengths L1, L2 of resin reservoirs 22 in the longitudinal direction of seal portion 21 to the length L3 of recess 20 in the same direction [total length of resin reservoirs 22 (L1+L2) / length of recess 20 (L3)] is, for example, 25 to 65% (45% in this embodiment), and preferably 35 to 55%. Within this range, seal portion 21 and outside air introduction hole 21a can be well formed within the area surrounded by recess 20 or joint portion 23. This value is specifically, for example, 25, 30, 35, 40, 45, 50, 55, 60, or 65%, and may be within a range between any two of the values ​​exemplified here.

[0029] The air flow restriction member 25 may be joined by welding or bonding at the joint 23, for example. Furthermore, the air flow restriction member 25 may be, for example, a gas-permeable membrane 25a. From the viewpoint of the restorability and ejection properties of the container body 2, the gas-permeable membrane 25a preferably has appropriate gas permeability. The gas permeability of the gas-permeable membrane 25a can be determined by its Gurley seconds. The Gurley seconds are a measure based on the "Gurley air permeability" in accordance with JIS-L1096, and represent the number of seconds required for a certain volume of air (here, 100 ml) to pass through a certain area of ​​a gas-permeable membrane under a certain pressure difference. The smaller this value, the easier it is for air to pass through. The Gurley seconds of the gas-permeable membrane 25a are, for example, 2.5 to 20 seconds, and preferably 2.5 to 10 seconds. This is because when the Gurley seconds are within this range, the ejection properties and restorability of the double-walled container 1 are improved. Specifically, the Gurley seconds may be, for example, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 seconds, and may be within a range between any two of the values ​​exemplified here.

[0030] The breathable membrane 25a may be a microporous membrane made primarily of, for example, polytetrafluoroethylene (PTFE), or the like, or the microporous membrane may be a composite of a nonwoven fabric or a polyethylene terephthalate (PET) mesh. Furthermore, the breathable membrane 25a may be a surgical tape made primarily of, for example, a nonwoven fabric or a resin. The surgical tape may have an adhesive layer for adhesion.

[0031] <Operation principle when using double container 1> The double container 1 of this embodiment can be used, for example, as an eye drop container. Before use by a user, with the contents filled in the inner bag 15, it is preferable that the inner bag 15 contacts the outer shell 14, as shown in Fig. 3A.

[0032] When using the double container 1, the user grasps the double container 1 by, for example, the body 6 of the double container 1 and squeezes (presses) it to dispense the contents through the dispensing cap 12. As the contents decrease, the inner bag 15 contracts. When the pressure is eased after the contents are dispensed, air flows into the internal space 26 through the air flow restricting member 25 and the outside air introduction hole 21a, and as shown in FIG. 4, the shape of the outer shell 14 returns to its original shape while the inner bag 15 remains contracted. If the air inflow is slow (if the Gurley seconds of the inflow are large), the restoration of the outer shell 14 is delayed, reducing the restoration ability of the double container 1.

[0033] Depending on the speed at which the double container 1 is restored, a pressure (negative pressure) smaller than atmospheric pressure may act on the contents in the inner bag 15. In order to prevent air from flowing into the inner bag 15 through the discharge cap 12 at that time, the discharge cap 12 is provided with, for example, a check valve (not shown), which allows the contents in the inner bag 15 to be discharged but prevents air from being taken into the inner bag 15.

[0034] When pressure is applied again, the pressure acts on inner bag 15 via the air in internal space 26, causing the contents to be expelled. At this time, the air in internal space 26 can escape from internal space 26 through outside air introduction hole 21a and air flow restriction member 25. However, if the air escapes slowly (if the Gurley seconds of the escape are large), the rate at which the air escapes is slower than the rate at which the volume of internal space 26 decreases due to the pressure, causing the pressure in internal space 26 to increase and facilitating the expulsion of the contents from internal bag 15. Therefore, such slow air escape is acceptable. On the other hand, if the air escapes quickly (if the Gurley seconds of the escape are small), the rate at which the volume of internal space 26 decreases due to the pressure and the rate at which the air escapes are approximately equal, causing the pressure in internal space 26 to not increase. As a result, the pressure required to expel the contents increases, which may result in poor expulsion performance.

[0035] Before and / or after use, the double container 1 can be placed on a flat surface such as a table, in which case the legs 24 can be placed on the surface to contact the flat surface, allowing the double container 1 to be placed in a stable, stationary state. Furthermore, since the air flow restriction member 25 does not come into contact with the ground, adhesion of dirt to the air flow restriction member 25 can be suppressed.

[0036] <Method of manufacturing double container 1> Below, we will briefly explain the method for manufacturing the container body 2. The cap 11 can be manufactured by, for example, injection molding, but the explanation thereof will be omitted.

[0037] The container body 2 can be manufactured by, for example, extrusion blow molding (also referred to as direct blow molding). As shown in Fig. 5A, a laminated parison 31 extruded and hanging down from an extrusion head 30 is sandwiched between a pair of split dies 32 that open and close in a direction perpendicular to the plane of the drawing and closed. A compressive force is applied by clamping the laminated parison 31 at the lower part of the split dies 32 at a pinch-off section 34, and the laminated parison 31 at the upper part of the split dies 32 is cut off by a cutter 33. At the pinch-off section 34, the laminated parison 31 is crushed along a parting surface 35 of the split dies 32, thereby forming a seal portion 21 at the bottom 5 of the container body 2 that is aligned with the parting surface 35 in a plan view, as shown in Fig. 5B. At this time, a recess in the cavity 36 of the split mold 32, which corresponds to the resin reservoir 22 of the bottom 5, suppresses the extension of the seal portion 21 along the parting surface 35 in the plan view of FIG. 5B during mold clamping, thereby promoting the placement of the seal portion 21 within the region surrounded by the recess 20 or the joint 23. Next, the split mold 32 or the blow nozzle 37 is moved so that the blow nozzle 37 is positioned above the split mold 32, and the blow nozzle 37 is inserted into the laminated parison 31 to introduce pressurized fluid, causing the laminated parison 31 to expand along the cavity 36 of the split mold 32. The pressurized fluid may be introduced, for example, by extending the mouth 4 to form a wasted portion and then inserting an elongated blow nozzle into the wasted portion through a blow hole formed in the split mold 32 (the wasted portion is removed in a subsequent process), or by incorporating the blow nozzle 37 into the extrusion head 30. Next, the split mold 32 is cooled to solidify the laminated parison 31 expanded in the cavity 36, and then the split mold 32 is opened and the product is removed. If necessary, finishing such as removing burrs may be performed.

[0038] When the container body 2 of this embodiment is manufactured by the above-described manufacturing method, the recess 20 of the bottom portion 5 is caught by the pair of split molds 32 when the molds are opened. In other words, these portions become undercuts, and the molds are opened (forced removal) in the direction of arrow Z in FIG. 5B with the bottom portion 5 caught. At this time, tensile stress acts on the seal portion 21 in a direction perpendicular to the longitudinal direction of the seal portion 21. This tensile stress causes the outer shell 14 in the seal portion 21 to rupture along the longitudinal direction of the seal portion 21, forming the outside air introduction hole 21a. To form the outside air introduction hole 21a by such forced removal, for example, the compressive force applied when the molds are clamped may be set small so that the outer shell 14 is not completely welded in the seal portion 21, and a gap that can serve as a starting point for rupture may be formed. Furthermore, as a method other than forceful removal, for example, after release from split mold 32, inner bag 15 may be depressurized to shrink and then pressurized to expand, thereby separating inner bag 15 from outer shell 14 and causing seal portion 21 to tear open from gaps in outer shell 14, thereby forming outside air introduction hole 21a. Alternatively, after release from the mold, bottom portion 5 may be pressed to tear open seal portion 21, thereby forming outside air introduction hole 21a. Outside air introduction hole 21a may be one continuous tear or multiple tears and / or gaps.

[0039] After the outside air introduction hole 21a is formed, the air flow restriction member 25 is joined to the bottom 5 in a region surrounding the outside air introduction hole 21a, thereby forming the joint 23. For example, as shown in Fig. 6, this joint 23 may be formed by ultrasonically welding the air flow restriction member 25 (e.g., the air permeable membrane 25a) to an annular protrusion 23a that protrudes outward from the container body 2 along the central axis 16 (in the case of welding, the annular protrusion 23a functions as a welding allowance).

[0040] <Modification> Although the embodiments have been described above, the technical ideas of the present disclosure can also be adopted in the following aspects.

[0041] The double container 1 may be used as a container for cosmetics or food other than eye drops. In such cases, the size of the container body 2 and the capacity of the inner bag 15 may be appropriately changed (for example, made larger) from the values ​​described in this specification.

[0042] The shape of the bottom portion 5 and the body portion 6 may be a shape other than an ellipse (for example, a circle, a polygon, or a shape that is a combination thereof).

[0043] The air flow restriction member 25 may be a valve (for example, a flap valve or a ball valve) that allows air to easily flow into the internal space 26 and prevents air from flowing out of the internal space 26. Furthermore, the air flow restriction member 25 may be bonded to the bottom 5 by adhesion using an adhesive or the like.

[0044] There may be more or less than a pair of legs 24. If there is only one leg 24, it may be integrally formed along the periphery of the bottom 5. [Explanation of symbols]

[0045] 1:Double container 2: Container body 3: Storage section 4: Mouth 5: Bottom 6: Body 7:Shoulder 8: Neck 9: Proximal end 10: Cap part 10a: Spiral convex portion 11: Cap 12: Discharge cap 13: Lid 13a: Spiral recess 14: Outer shell 15: Inner bag 16: Central axis 20: Recess 20a: recessed portion periphery 21: Seal part 21a: Outside air intake 22: Resin reservoir 22a: Stepped section 22b: Resin reservoir periphery 23: Joint 23a: Annular convex part 24: Legs 25: Regulating member 25a: Breathable membrane 26: Interior space 30: Extrusion head 31: Laminated parison 32: Split mold 33: Cutter 34: Pinch-off section 35: Parting surface 36: Cavity 37: Blowing nozzle Z: Arrow

Claims

1. A double container comprising a container body, The container body includes an inner bag and an outer shell disposed to cover the inner bag, A seal portion is formed on the bottom of the container body, The sealed portion is provided with a slit-shaped outside air introduction hole communicating with an internal space between the outer shell and the inner bag, The double container has an air flow regulating member provided on the bottom for regulating the flow of air through the outside air introduction hole.

2. The double container according to claim 1, the bottom portion includes a pair of resin reservoir portions arranged to intersect with the seal portion, The outside air introduction hole extends to the pair of resin reservoirs.

3. The double container according to claim 1, The bottom portion is provided with a pair of legs protruding from the bottom portion, The air flow restriction member is disposed between the pair of legs.

4. The double container according to claim 3, The bottom of the container body has a flat shape, The pair of legs are disposed at both ends of the flat shape in the longitudinal direction of the double container.

5. The double container according to claim 1, The air flow regulating member is a breathable membrane welded at a joint surrounding the outside air introduction hole.

6. The double container according to claim 5, The bottom portion is provided with a recess, the outside air introduction hole is disposed within the recess, The joint is disposed so as to surround the recess.

7. A method for manufacturing a double container according to claim 5 or claim 6, The joining portion is formed by ultrasonically welding the ventilation membrane to an annular protrusion disposed so as to surround the outside air introduction hole.

8. A method for manufacturing a double container according to any one of claims 1 to 5, the outside air introduction hole is disposed in a recess provided in the bottom portion, The outside air introduction hole is formed by opening a pair of split molds in a state where the split molds are hooked onto the recesses during direct blow molding.

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