Manufacturing method for double-walled containers

Abstract

The present invention provides a double-walled container that can enhance the gas barrier properties of the inner bag while suppressing deterioration of the inner bag's pullability. [Solution] According to the present invention, a double-walled container is provided, comprising a container body having an inner bag and an outer shell, wherein the container body is a biaxially oriented blow-molded body, and the inner bag comprises an EVOH layer, the EVOH contained in the EVOH layer having an ethylene content of 32 to 46 mol%.

Description

Technical Field

[0001] The present invention relates to a double container.

Background Art

[0002] Conventionally, a double container including a container body having an outer shell and an inner bag is known. For example, Patent Document 1 discloses a double container formed by performing biaxial stretch blow molding in a state where an outer shell preform and an inner bag preform are stacked.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the outer shell and the inner bag of such a double container are formed of different materials, or when the contents adhere to the inner bag after use, etc., when recycling the double container, it is desirable to separate the outer shell and the inner bag.

[0005] The outer shell and the inner bag can be separated by the user pulling out the inner bag from the outer shell, and it is desirable to reduce the force required to pull out the inner bag.

[0006] In addition, in order to suppress deterioration of the contents, it is desirable to enhance the gas barrier property of the inner bag. If an EVOH layer having excellent gas barrier properties is provided in the inner bag, it is possible to enhance the gas barrier property, but the inner bag becomes hard, and the drawability of the inner bag deteriorates.

[0007] The present invention has been made in view of such circumstances, and provides a double container capable of enhancing the gas barrier property of the inner bag while suppressing deterioration of the drawability of the inner bag. [Means for solving the problem]

[0008] According to the present invention, a double-walled container is provided, comprising a container body having an inner bag and an outer shell, wherein the container body is a biaxially oriented blow-molded body, and the inner bag comprises an EVOH layer, the EVOH contained in the EVOH layer having an ethylene content of 32 to 46 mol%.

[0009] The present invention is characterized by providing an EVOH layer in the inner bag of a container body made of a biaxially oriented blow-molded body, and by the fact that the EVOH contained in this EVOH layer has a high ethylene content of 32 to 46 mol%. Generally, the flexibility of EVOH increases as the ethylene content increases. Therefore, according to the present invention, it is possible to improve the gas barrier properties of the inner bag while suppressing deterioration of the pullability of the inner bag.

[0010] 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, comprising a mouth attachment member attached to the mouth of the container body, the inner bag having a protrusion that extends from the open end of the outer shell, and the mouth attachment member engaging with the protrusion. Preferably, the double container is as described above, wherein the inner bag has a single-layer structure of the EVOH layer. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1A is a perspective view of a double-walled container 1 according to the first embodiment of the present invention, showing the mouth attachment member 8 separated from the container body 2. Figure 1B is an enlarged view of region B in Figure 1A. The dashed lines in the figures represent boundary lines where the curvature of the surfaces constituting the surface shape changes. The same applies to the other figures. [Figure 2] This is a cross-sectional view of the container body 2, passing through the central axis C of the mouth 5 and the center of the two recesses 3f. [Figure 3]Figure 3A is a magnified view of region A in Figure 2, and Figure 3B is a magnified view of region B in Figure 2. [Figure 4] Figures 4A to 4C are end views of surfaces A to C in Figure 3A, respectively. [Figure 5] Figures 5A to 5F are the front view, top view, bottom view, right side view, left side view, and rear view of the container body 2, respectively. [Figure 6] Figure 6A is a perspective view with a portion of the mouth attachment member 8 cut out, and Figure 6B is a perspective view of the mouth attachment member 8 viewed from a diagonal downward side. [Figure 7] This is a front view showing the mouth attachment member 8 attached to the container body 2. [Figure 8] Figures 8A and 8B are end views of surfaces A and B in Figure 7, respectively. [Figure 9] This is a perspective view showing the inner preform 14 and outer preform 13 separated. [Figure 10] This is a perspective view of the internal preform 14, seen from diagonally above. [Figure 11] This is a perspective view of a preform 15 constructed by covering an inner preform 14 with an outer preform 13. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature constitutes an independent invention.

[0013] 1. First Embodiment 1-1. Composition of Double Container 1 <Basic configuration> As shown in Figure 1, the double-walled container 1 of the first embodiment of the present invention comprises a container body 2 and a mouth attachment member 8.

[0014] As shown in FIG. 1, the container body 2 includes a mouth portion 5, a body portion 6, and a bottom portion 7. The mouth portion 5 is a tubular (preferably cylindrical) portion having an open end 5c. The mouth portion 5 includes an engaging portion 5a to which a mouth-attached member 8 such as a cap or a pump can be attached. When the mouth-attached member 8 is screw-type, the engaging portion 5a is a male screw portion 5a1, and when the mouth-attached member 8 is a plug-type, it is an annular protrusion protruding in the circumferential direction. The mouth-attached member 8 may or may not have a check valve (not shown). 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-attached member 8 to the mouth portion 5.

[0015] The body portion 6 is disposed adjacent to the mouth portion 5 on the side farther from the open end 5c than the mouth portion 5. The body portion 6 has a larger outer diameter (in this specification, "outer diameter" means the circumscribed circle diameter when the cross-section is not circular) than the mouth portion 5. The body portion 6 is tubular, and the bottom portion 7 is provided at the lower end of the body portion 6 and closes the lower end of the body portion 6. The body portion 6 includes a shoulder portion 6b whose outer diameter increases as it moves away from the mouth portion 5. Also, the body portion 6 includes a body portion main body 6c having a substantially constant outer diameter on the bottom portion 7 side of the shoulder portion 6b.

[0016] As shown in FIG. 3A, the container body 2 includes an inner bag 4 and an outer shell 3 disposed so as to cover the inner bag 4. Except for the protruding portion 4c, the portion of the inner bag 4 is housed inside the outer shell 3. In the following description, the portions of the inner bag 4 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.

[0017] The container body 2 is a biaxially stretched blow molded body formed by biaxial stretch blow molding, and the inner bag 4 and the outer shell 3 are formed by biaxial stretch blow molding. Details of the biaxial stretch blow molding will be described later. In the biaxially stretched blow molded body, since the adhesion between the inner bag 4 and the outer shell 3 is difficult to increase, the force required to pull out the inner bag 4 from the outer shell 3 is reduced compared to a direct blow molded body which is a blow molded body of a molten parison.

[0018] 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, 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. 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 may be, for example, 0.05, 0.08, 0.10, 0.15, 0.20, or 0.25 mm, and may be within the range of any two of the values ​​exemplified here.

[0019] If the mouth attachment member 8 is not equipped with a check valve, the inner bag 4 will not contract after the contents of the inner bag 4 have been discharged, making it difficult to pull out the inner bag 4 through the mouth 5 of the outer shell 3. The present invention makes it easy to pull out the inner bag 4 through the mouth 5 of the outer shell, so the significance of applying the present invention is particularly pronounced when the mouth attachment member 8 is not equipped with a check valve.

[0020] The inner diameter D2 of the mouth 5 of the outer shell 3 is, for example, 20 to 50 mm, and preferably 25 to 40 mm. The outer diameter D4 of the mouth 5 of the outer shell 3 is, for example, 25 to 55 mm, and preferably 30 to 45 mm. Specifically, the inner diameter D2 is, for example, 20, 25, 30, 35, 40, 45, 50 mm, and the outer diameter D4 is, for example, 25, 30, 35, 40, 45, 50, 55 mm, and each may be within the range of any two of the values ​​exemplified here. The length of the mouth 5 is, for example, 15 to 35 mm, and specifically, for example, 15, 20, 25, 30, 35 mm, and may be within the range of any two of the values ​​exemplified here.

[0021] As shown in Figure 3A, it is preferable that the body portion 6 is provided with a curved portion 6d that curves outward. The curved portion 6d is provided at or near the boundary between the shoulder portion 6b and the body portion 6c. If D is the diameter of the container body 2 at the point 6d1 where the radius of curvature at the curved portion 6d is smallest, and R is the radius of curvature at point 6d1, then it is preferable that R / D is 0.5 or more (0.73 in this embodiment). The larger this value, the larger the radius of curvature R is relative to the diameter D, the more smoothly the curved portion 6d curves, the less the inner bag 4 is pressed against the outer shell 3 near the curved portion 6d, and the force required to pull out the inner bag 4 is reduced. R / D is, for example, between 0.5 and 2, specifically, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0, and may be within the range of any two of the values ​​exemplified here, or greater than or equal to any two of them.

[0022] Furthermore, D / D2 is preferably 1.8 or less (1.4 in this embodiment). The smaller this value, the easier it is for the curved portion 6d to pass through the opening 5, thus reducing the force required to pull out the inner bag 4. D / D2 is, for example, 1.1 to 1.8, specifically, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and may be within the range of any two of the values ​​exemplified here.

[0023] Preferably, the inclination angle α of the shoulder portion 6b with respect to the central axis of the opening portion is 25 degrees or less (19 degrees in this embodiment). The smaller this inclination angle α, the less the inner bag 4 is pressed against the outer shell 3 near the curved portion 6d, and the force required to pull out the inner bag 4 is reduced. The inclination angle α is, for example, 5 to 25 degrees, specifically, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 degrees, and may be within the range between any two of the values ​​exemplified here or less than or equal to any two of them.

[0024] As shown in Figure 1, the body portion 6 has a tapered portion 6e that tapers toward the bottom 7, located on the bottom 7 side of the curved portion 6d. The tapered portion 6e functions as a so-called "pull-out taper," and by providing the tapered portion 6e, the force required to pull out the inner bag 4 is reduced. In this embodiment, since the body portion 6c has a shape that tapers toward the bottom 7, the entire body portion 6c is the tapered portion 6e. On the other hand, for example, a part of the body portion 6c may not taper, while the remaining part of the body portion 6c tapers. Preferably, the part that does not taper is a part whose outer diameter does not change.

[0025] <Materials and Layer Composition> The inner bag 4 preferably includes an EVOH layer. The EVOH layer is a layer composed of an EVOH-based resin containing 50% by mass or more of EVOH (ethylene-vinyl alcohol copolymer). 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 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 the 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.

[0026] The EVOH in the EVOH layer preferably has an ethylene content of 32 to 46 mol%. The presence of an EVOH layer in the inner bag 4 enhances its gas barrier properties. If the ethylene content of the EVOH is too low, the flexibility of the inner bag 4 decreases significantly, and the pull-out properties of the inner bag 4 tend to deteriorate significantly. Furthermore, as will be described later, if the ethylene content of the EVOH is too low, the inner bag 4 becomes too brittle, and as shown in Figure 1, there is a risk of cracking 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 the EVOH is too high, the improvement in the gas barrier properties of the inner bag 4 tends to be insufficient. By setting the ethylene content within the above range, the occurrence of the above problems can be suppressed. The ethylene content is specifically, for example, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, or 46 mol%, and may be within the range of any two of the values ​​exemplified here.

[0027] The inner bag 4 may be a single-layer structure of the EVOH layer, or it may be a multi-layer structure including the EVOH layer. If the inner bag 4 is a single-layer structure of the EVOH layer, 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 on one or both of the inner and outer sides of the EVOH layer. An example of another layer is an olefin resin layer made of an olefin resin. The olefin resin is described above. Specifically, the layer structure of the inner bag 4 can be, from the outer side, an outer layer / EVOH layer, an EVOH layer / inner layer, or an outer layer / EVOH layer / inner layer. The outer layer and the inner layer are each the other layers described above, and these layers may be a single-layer structure or a multi-layer structure. It is particularly preferable that the outer layer and the inner layer are each polypropylene layers.

[0028] If the adhesion between the EVOH layer and the other layer is not good, an adhesive resin layer may be provided between the EVOH layer and the other layer, or / or an adhesive resin may be incorporated into one or both of the EVOH layer and the other layer. The adhesive resin is a resin that has good adhesion to both the EVOH layer and the other layer, and examples include acid-modified polyolefin resins (e.g., maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene).

[0029] The EVOH layer may or may not be exposed to the inner surface of the inner bag 4. When the EVOH layer is exposed to the inner surface of the inner bag 4, it has the advantage of becoming more flexible by absorbing moisture from the contents, making it easier to remove the inner bag 4. Also, since EVOH does not readily adsorb citrus fragrance components, if the contents contain citrus fragrance components, making the EVOH layer the innermost layer of the inner bag 4 can suppress deterioration of the contents' flavor. When the EVOH layer is exposed to the inner surface of the inner bag 4, the gas barrier properties of the EVOH layer are slightly reduced due to moisture absorption, but the higher the ethylene content of the EVOH, the less the gas barrier properties are reduced due to moisture absorption, so the advantage of improved flexibility outweighs the disadvantage of reduced gas barrier properties. On the other hand, when the EVOH layer is not exposed to the inner surface of the inner bag 4, the absorption of moisture from the contents by the EVOH layer is suppressed, thus suppressing the reduction in the gas barrier properties of the EVOH layer.

[0030] 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.

[0031] <Inner surface of opening 5 has an uneven shape 9> As shown in Figure 4C, it is preferable that the inner surface of the mouth 5 and at least one of the inner surfaces of the body 6 adjacent to the mouth 5 is provided with an uneven surface 9 in which recessed ridges 9a and raised ridges 9b alternately appear in the circumferential direction of the mouth 5. The uneven surface 9 is provided on the inner surface of the inner bag 4. The number of recessed ridges 9a is, for example, 4 to 30, and preferably 10 to 20. It is preferable that the recessed ridges 9a and raised ridges 9b extend non-parallel to the circumferential direction of the mouth 5. The direction in which the recessed ridges 9a and raised ridges 9b extend is preferably 0 to 60 degrees, and preferably 0 to 30 degrees, with respect to the axial direction of the mouth 5. Specifically, this angle is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 degrees, and may be within the range of any two of the values ​​exemplified here. The uneven shape 9 may be provided only in the opening 5, or in a position adjacent to the opening 5 on the body 6, but it is preferable that it spans both the opening 5 and the body 6. The uneven shape 9 may be formed with a smaller thickness for the recessed ridges 9a, a larger thickness for the raised ridges 9b, or a smaller thickness for the recessed ridges 9a and a larger thickness for the raised ridges 9b compared to other parts of the opening 5 of the inner bag 4.

[0032] Since the thickness of the convex ridge 9b is greater than the thickness of the concave ridge 9a, when the twist applied by the opening 5 is transmitted to the body 6, the force is transmitted more easily to the convex ridge 9b than to the concave ridge 9a. As a result, the convex ridge 9b rotates faster than the concave ridge 9a, and as a result, folds are formed in the inner bag 4 along the concave ridge 9a and its extension, making it easier for the inner bag 4 to fold into a pleated shape. Therefore, by providing the uneven shape 9, the body 6 folds into a pleated shape, and as a result, the diameter of the body 6 is quickly reduced. It is preferable not to provide an uneven shape on the outer surface of the inner bag 4. This is because if an uneven shape is provided on the outer surface of the inner bag 4, the inner bag 4 and the outer shell 3 will engage in the direction of rotation of the inner bag 4, making it difficult for the inner bag 4 to rotate relative to the outer shell 3.

[0033] If T is the wall thickness of the inner bag 4 at the protruding ridge 9b of the opening 5 (radius of the circumscribed circle of the inner bag 4 - radius of the inscribed circle passing through the vertex of the protruding ridge 9b), and D is the depth of the recessed ridge 9a (radius of the inscribed circle passing through the bottom of the recessed ridge 9a - radius of the inscribed circle passing through the vertex of the protruding ridge 9b), then the maximum value of D / T is, for example, 0.2 to 0.8, and preferably 0.3 to 0.5. Specifically, this value is, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and may be within the range of any two of the values ​​exemplified here. The wall thickness of the inner bag 4 in the part of the opening 5 other than the uneven shape 9 is, for example, 1 to 2 mm, specifically, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0 mm, and may be within the range of any two of the values ​​exemplified here. The depth of the groove 9a in the part where the depth of the groove 9a is maximum is, for example, 0.3 to 1.0 mm, specifically, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 mm, and may be within the range of any two of the values ​​exemplified here.

[0034] The distance from the opening end 5c of the mouth portion 5 to the upper end of the uneven shape 9 is, for example, 0 to 30 mm, specifically, for example, 0, 5, 10, 15, 20, 25, 30 mm, and may be within the range of any two of the values ​​exemplified here. The distance from the upper end to the lower end of the uneven shape 9 is, for example, 10 to 40 mm, specifically, for example, 10, 15, 20, 25, 30, 35, 40 mm, and may be within the range of any two of the values ​​exemplified here.

[0035] <Structure of the bottom 7> As shown in Figure 3B, a projection 4e is provided on the bottom 7 of the inner bag 4. An annular projection 3b is provided on the bottom 7 of the outer shell 3, and a through hole 3c is provided in the region inside the annular projection 3b. The inner bag 4 is positioned relative to the outer shell 3 by the insertion of the projection 4e into the through hole 3c. The annular projection 3b and the region inside it are hardly stretched during biaxial stretch blow molding, so the wall thickness is large in both the outer shell 3 and the inner bag 4. The annular projection 3b is optional.

[0036] If the outer diameter of the annular projection 3b is D1 and the inner diameter of the mouth 5 of the outer shell 3 is D2, then D1 / D2 is preferably 0.9 or less, and more preferably 0.6 or less. The annular projection 3b and the region inside it have a larger wall thickness in the inner bag 4, so the smaller D1 / D2 is, the easier it is for the bottom 7 of the inner bag 4 to be reduced in diameter. D1 / D2 is, for example, 0.1 to 0.9, specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and may be within the range between any two of the values ​​exemplified here, or less than or equal to any two of them.

[0037] The bottom 7 of the container body 2 (that is, the bottom 7 of both the inner bag 4 and the outer shell 3) is provided with a bottom recess region 7a and a peripheral region 7b surrounding the bottom recess region 7a. The bottom recess region 7a is the area where the bottom 7 is recessed toward the interior of the container body 2. The peripheral region 7b is the contact surface of the container body 2. As shown in Figure 3B, on the peripheral surface 7a1 of the bottom recess region 7a, the wall thickness of the inner bag 4 and the outer shell 3 gradually decreases as it approaches the peripheral region 7b. The peripheral surface 7a1 is an inclined surface that slopes away from the center of the bottom 7 toward the peripheral region 7b. In other words, the peripheral surface 7a1 constitutes part of a cone that tapers toward the bottom surface 7a2 of the bottom recess region 7a. The bottom surface 7a2 of the bottom recess region 7a is approximately flat. Therefore, the bottom recess region 7a is approximately frustoconical in shape.

[0038] The bottom surface 7a2 of the bottom recess region 7a is difficult to stretch during biaxial stretch blow molding and tends to have a large wall thickness. Therefore, a smaller diameter D3 of the bottom surface 7a2 (in other words, the diameter of the region enclosed by the boundary line between the bottom surface 7a2 and the circumferential surface 7a1) makes it easier for the bottom 7 of the inner bag 4 to be reduced in diameter. D3 / D2 is preferably 0.9 or less, and more preferably 0.6 or less. D3 / D2 is, for example, 0.1 to 0.9, specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and may be within the range between any two of the values ​​exemplified here, or less than or equal to either of them.

[0039] <Design> The container body 2 has a novel aesthetic appearance. The design of the container body 2 shown in Figure 5 can be understood as an overall design, and the area A can be understood as the "part for which design registration is sought as a partial design," the area B can be understood as the "part for which design registration is sought as a partial design," and the other parts can be understood as the "part for which design registration is sought as a partial design." For convenience, areas A and B are shown only in the front view, but the intention is to consider the entire circumference of the container body 2 as the "part for which design registration is sought as a partial design."

[0040] In the bottom portion 7, the area C including the bottom recessed area 7a may or may not be included in the "part for which design registration is sought as a partial design."

[0041] <Engagement structure between the mouth attachment member 8 and the inner bag 4, and engagement structure between the inner bag 4 and the mouth 5 of the outer shell 3> Preferably, the mouth attachment member 8 is configured to be attachable to the mouth 5, and the inner bag 4 rotates in conjunction with the rotation of the mouth attachment member 8 (in this case, rotation relative to the outer shell 3). With such a configuration, it is possible to twist the inner bag 4 by rotating the mouth attachment member 8. Since the body portion 6 of the container body 2 has a larger outer diameter than the mouth 5, it is not easy to pull the inner bag 4 through the mouth 5 of the outer shell 3 simply by pulling the inner bag 4. However, by twisting the inner bag 4 and reducing the diameter of the body portion 6 of the inner bag 4, the body portion 6 of the inner bag 4 becomes easier to pass through the mouth 5 of the outer shell 3, and the inner bag 4 can be easily pulled out of the outer shell 3.

[0042] The engagement structure between the mouth attachment member 8 and the inner bag 4 will be described in more detail below.

[0043] As shown in Figure 1, 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, an engaging flange 4c3, and a contact flange 4c4.

[0044] The engaging projection 4c2 protrudes radially outward from the circumferential surface of the protruding cylinder 4c1. The engaging flange 4c3 is an annular portion positioned further from the opening end 3a than the engaging projection 4c2 and having a larger diameter than the protruding cylinder 4c1. The abutment flange 4c4 is an annular portion positioned to abut against the opening end 3a and having a larger diameter than the protruding cylinder 4c1. The abutment flange 4c4 abutting against the opening end 3a prevents the inner bag 4 from falling into the outer shell 3. Alternatively, the abutment flange 4c4 may be omitted, and the engaging projection 4c2 may be brought into contact with the opening end 3a to prevent the inner bag 4 from falling into the outer shell 3.

[0045] As shown in Figure 6, the mouth attachment member 8 comprises an outer cylinder 8a, an inner cylinder 8c, an engaging portion 8d, a claw portion 8e, a top plate 8f, and a discharge port 8g.

[0046] The outer surface of the outer cylinder 8a is provided with an uneven surface pattern in which the bumps and grooves are alternately repeated in the circumferential direction. This makes it easy to rotate the mouth mounting member 8. An engaging portion 8d is provided on the inner surface of the outer cylinder 8a. The engaging portion 8d is an engaging portion that engages with the engaging portion 5a of the mouth 5, and by engaging the engaging portion 8d with the engaging portion 5a, the mouth mounting member 8 is attached to the mouth 5.

[0047] The top surface of the outer cylinder 8a is covered by a top plate 8f. The top plate 8f is provided with a discharge port 8g. A nozzle may be provided at the discharge port 8g. The inner cylinder 8c has a smaller diameter than the outer cylinder 8a and is a so-called inner ring positioned inside the outer cylinder 8a.

[0048] The inner surface of the outer cylinder 8a is provided with claw portions 8e. Multiple claw portions 8e (8 in this embodiment) are provided, spaced apart in the circumferential direction. The number of claw portions 8e is, for example, 1 to 20, and preferably 4 to 12. The top plate 8f is provided with through holes 8h at positions opposite to the claw portions 8e.

[0049] A mouth attachment member 8 of this shape can be manufactured using a split mold that opens and closes vertically. Since the through hole 8h and the upper surface 8e1 of the claw portion 8e can be formed using a projection provided on the upper mold, the claw portion 8e can be formed without forcibly removing the lower mold. Therefore, the amount of protrusion of the claw portion 8e does not need to be such that it can be forcibly removed, and it can be set to an amount suitable for engagement with the inner bag 4 (e.g., 1 mm or more).

[0050] In this embodiment, the engaging portion 5a is a male threaded portion 5a1, and the engaging portion 8d is a female threaded portion 8d1 that can be screwed into the male threaded portion 5a1. Therefore, the mouth attachment member 8 can be attached to the mouth 5 by rotating it relative to the mouth 5 in the tightening direction (usually clockwise when viewed from above) (hereinafter, the relative rotation with respect to the mouth 5 will also be simply referred to as "rotation"). When the mouth attachment member 8 is rotated in the tightening direction, the female threaded portion 8d1 is screwed into the male threaded portion 5a1 while the outer circumferential surface of the inner cylinder 8c shown in Figure 8A is in close contact with the inner circumferential surface of the inner bag 4. At this time, if the mouth 5 of the inner bag 4 rotates together with the mouth attachment member 8 due to friction between the outer circumferential surface of the inner cylinder 8c and the inner circumferential surface of the inner bag 4, the inner bag 4 will twist. Before the mouth attachment member 8 is attached, the inner bag 4 is filled with contents, and if the inner bag 4 twists, the contents inside the inner bag 4 will spill out. To prevent this problem, the inner bag 4 and the outer shell 3 should be tightly fitted together at the mouth 5 so that the inner bag 4 does not rotate relative to the outer shell 3. However, simply tightly fitting them together creates a new problem: it becomes difficult to pull the inner bag 4 out of the outer shell 3.

[0051] Therefore, in this embodiment, a configuration is adopted in which the first resistance of relative rotation of the inner bag 4 with respect to the outer shell 3 in one direction at the mouth portion 5 is greater than the second resistance of relative rotation in the other direction. For example, if the male screw portion 5a1 is a right-hand thread, the one direction and the other direction are the clockwise and counterclockwise directions when viewed from the top of the container body 2, respectively. In other words, one direction is the tightening direction of the mouth portion attachment member 8, and the other direction is the loosening direction of the mouth portion attachment member 8. With this configuration, when attaching the mouth portion attachment member 8, the inner bag 4 is less likely to rotate relative to the outer shell 3, so the problem of the inner bag 4 twisting when attaching the mouth portion attachment member 8 is suppressed. Also, since the second resistance of relative rotation in the other direction is relatively small, when separating the inner bag 4 from the outer shell 3 after use, the inner bag 4 can be easily twisted and reduced in diameter by rotating the mouth portion 5 of the inner bag 4 relative to the outer shell 3 in the other direction, so the inner bag 4 can be easily pulled out from the outer shell 3.

[0052] Specifically, the inner bag 4 and the outer shell 3 are engaged in a convex-convex engagement at the opening 5, and this engagement is configured such that the first resistance is greater than the second resistance. More specifically, as shown in Figure 4B, the convex-convex engagement is the engagement between a convex portion 4f provided on the outer circumferential surface of the inner bag 4 and a concave portion 3f provided on the inner circumferential surface of the outer shell 3. As shown in Figure 4B, on the clockwise side (tightening direction side) of the convex portion 4f, the outer shell 3 is provided with a projection 3g that protrudes inward, whereas on the counterclockwise side (loosening direction side) of the convex portion 4f, no such projection is provided. Therefore, at the opening 5, the resistance to rotating the inner bag 4 relative to the outer shell 3 in the tightening direction (first resistance) is greater than the resistance to rotating it relative to the outer shell 3 in the loosening direction (second resistance). In this embodiment, two sets of convex portion 4f and concave portion 3f are provided at 180-degree intervals, but the number of sets of convex portion 4f and concave portion 3f may be one or three or more.

[0053] Furthermore, the engagement between the recessed and convex parts may be an engagement between a recess provided on the outer circumferential surface of the inner bag 4 and a convex part provided on the inner circumferential surface of the outer shell 3. In addition, although the recessed part 3f is formed by a through hole that penetrates the outer shell 3, the recessed part 3f only needs to be capable of engaging with the convex part 4f and does not need to penetrate the outer shell 3.

[0054] As the mouth mounting member 8 is further rotated in the tightening direction, the female thread portion 8d1 is screwed into the male thread portion 5a1, and the claw portion 8e gradually approaches the protruding portion 4c. At a certain point, the inclined surface on the underside of the claw portion 8e comes into contact with the engagement flange 4c3 shown in Figure 1B. In this state, as the mouth mounting member 8 is further rotated in the tightening direction, the claw portion 8e moves over the engagement flange 4c3, resulting in the state shown in Figure 8A. In this state, the claw portion 8e is positioned between the engagement flange 4c3 and the contact flange 4c4. The engagement flange 4c3 is housed in the gap between the claw portion 8e and the top plate 8f. As shown in Figure 8A, the protruding cylinder 4c1 is positioned between the claw portion 8e and the inner cylinder 8c. At this point, if the male thread portion 5a1 and the female thread portion 8d1 are not fully tightened, the claw portion 8e is guided by the circumferentially inclined surface 4c5 provided on the engaging projection 4c2 and overcomes the engaging projection 4c2, allowing the mouth mounting member 8 to rotate further in the tightening direction. After the male thread portion 5a1 and the female thread portion 8d1 are fully tightened, the mouth mounting member 8 becomes unable to rotate in the tightening direction and is unable to move in the axial direction of the mouth portion 5.

[0055] In this state, the engaging projection 4c2 engages with the claw portion 8e of the mouth mounting member 8 in the rotational direction of the mouth mounting member 8, and the engaging flange 4c3 engages with the claw portion 8e of the mouth mounting member 8 in the axial direction of the mouth 5. In other words, the claw portion 8e is engaged with the engaging projection 4c2 and the engaging flange 4c3.

[0056] Therefore, after the contents of the inner bag 4 have been used up, if the mouth attachment member 8 is rotated in the loosening direction (usually counterclockwise when viewed from above), the inner bag 4 will rotate along with the rotation of the mouth attachment member 8. As a result, the inner bag 4 is twisted and its diameter is reduced.

[0057] When the mouth mounting member 8 is further rotated in the loosening direction, the screw-fitting of the female thread portion 8d1 and the male thread portion 5a1 is released, allowing the mouth mounting member 8 to move away from the opening end 3a (i.e., in the axial direction of the mouth 5). Since the engaging flange 4c3 is engaged with the mouth mounting member 8 in the axial direction of the mouth 5, when the mouth mounting member 8 is moved in the axial direction of the mouth 5, the inner bag 4 also moves together with the mouth mounting member 8, and the inner bag 4 is pulled out from the outer shell 3.

[0058] As described above, with the configuration of this embodiment, by simply rotating the mouth attachment member 8 in the loosening direction, the inner bag 4 is twisted and reduced in diameter before being pulled out from the outer shell 3, making it possible to smoothly separate the inner bag 4 and the outer shell 3 with simple operation.

[0059] <Anti-loosening structure for mouth attachment member 8> In this embodiment, the container body 2 has a multi-start thread (more specifically, a triple-start thread) for the male thread portion 5a1 and the female thread portion 8d1, so the male thread portion 5a1 and the female thread portion 8d1 are prone to loosening even after being tightened. Therefore, as shown in Figure 8B, a loosening prevention structure 24 is provided to suppress the loosening of the screw connection between the mouth portion 5 and the mouth portion mounting member 8. In this embodiment, the loosening prevention structure 24 consists of a projection 3i protruding from the outer peripheral surface of the outer shell 3 and a projection 8i protruding from the inner peripheral surface of the outer cylinder 8a of the mouth portion mounting member 8. Multiple projections 3i and 8i are provided, preferably evenly spaced in the circumferential direction (three in this embodiment). The loosening prevention structure 24 may also have a different configuration that engages the mouth portion 5 and the mouth portion mounting member 8 in the circumferential direction; for example, a recess provided on the inner peripheral surface of the outer cylinder 8a of the mouth portion mounting member 8 may engage with the projection 3i.

[0060] <Protrusion 3h on the inner surface of the mouth 5 of the outer shell 3> As shown in Figure 4A, a projection 3h is provided on the inner surface of the mouth 5 of the outer shell 3, closer to the opening end 3a than projection 3g. Preferably, projection 3h is provided so as to connect to projection 3g. In the areas where projections 3g and 3h are provided, the mouth 5 of the outer shell 3 is thinned, so that the outer shell 3 contacts the inner bag 4 only at projections 3g and 3h. As a result, the contact area between the outer shell 3 and the inner bag 4 is reduced, and the force required to pull out the inner bag 4 is reduced. Furthermore, projections 3g and 3h are provided at multiple locations (two locations in this embodiment), preferably at equal intervals in the circumferential direction. This makes it possible to maintain the mouth 5 of the outer shell 3 and the mouth 5 of the inner bag 4 concentrically.

[0061] By the way, when the mouth attachment member 8 is rotated in the loosening direction, the screw connection between the mouth attachment member 8 and the mouth 5 is released in about half a turn. Once this connection is released, the inner bag 4 can be pulled out from the outer shell 3. However, a problem may arise in that the user may not immediately notice that the connection has been released and may continue to rotate the mouth attachment member 8 freely. On the other hand, in this embodiment, when the protrusion 4f is rotated in the loosening direction (counterclockwise direction in Figures 4A to 4B), the protrusion 4f reaches the projection 3h in about half a turn (for example, the protrusion 4f on the right side of Figure 4B reaches the projection 3h on the left side of Figure 4A), preventing further rotation of the inner bag 4. With this configuration, when the mouth attachment member 8 is rotated in the loosening direction, the inner bag 4 can be pulled out when it stops rotating, so it is possible to pull out the inner bag 4 at the appropriate timing, improving usability.

[0062] 1-2. Manufacturing method of double-walled container 1 As shown in Figures 9 to 11, the container body 2 can be formed by heating the preform 15 and biaxially stretched blow molding it.

[0063] <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.

[0064] As shown in Figure 9, 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.

[0065] As shown in Figure 10, the inner surface of the inner preform 14 is provided with a textured surface 19. The textured surface 19 remains in its original shape or is stretched during molding to become the textured surface 9 of the container body 2. The description of the textured surface 9 also applies to the textured surface 19, unless otherwise stated.

[0066] As shown in Figure 9, 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 projection 13h which becomes projection 3h, a projection (not shown) which becomes projection 3g, and a projection 13i which becomes projection 3i.

[0067] As shown in Figure 11, 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.

[0068] 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 during biaxial stretch blow molding. However, since biaxial stretch blow molding is performed with the annular projection 13d supported, the annular projection 13d and its inner region are hardly stretched during biaxial stretch blow molding. The annular projection 13d becomes the annular projection 3b after molding.

[0069] <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 surface of the preform 15 (i.e., the inner surface 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. However, 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 outer shell 3.

[0070] Therefore, in order to allow the inner bag 4 to be easily pulled out from the outer shell 3 after use, while suppressing the detachment of the outer preform 13, in this embodiment, the inner preform 14 and the outer preform 13 are interlocked at the opening 15a.

[0071] In this embodiment, the interlocking engagement is the engagement between a protrusion 14f provided on the outer circumferential surface of the opening 14a of the inner preform 14 and a recess 13f provided on the inner circumferential surface of the opening 13a of the outer preform 13, as shown in Figure 9. The protrusion 14f and recess 13f become a protrusion 4f and a recess 3f, respectively.

[0072] <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.

[0073] 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.

[0074] 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. [Examples]

[0075] 1. Manufacturing of container body 2 <Example 1> Following the method described above, the container body 2 (300 mL capacity) shown in Figure 1 was manufactured by biaxial stretch blow molding the preform 15 shown in Figures 9 to 11. The inner preform 14 was manufactured by injection molding EVOH (ethylene content 38 mol%, model: G Soanol GH3804B, manufactured by Mitsubishi Chemical Corporation) at 250°C. The outer preform 13 was manufactured by injection molding PET (model: titanium catalyst grade, manufactured by Teijin Corporation) at 300°C to form the shape of the outer preform, and then rapidly cooling it to 20°C. Rapid cooling converted the molten PET into an amorphous state.

[0076] After heating such a preform 15 to 110°C (temperature at the center of the longitudinal direction of the preform 15), the container body 2 was obtained by biaxial stretch blow molding.

[0077] <Comparative Example 1> The container body 2 was obtained in the same manner as in Example 1, except that the material for the inner preform 14 was formed from EVOH (ethylene content 29 mol%, model: Soanol D2908, manufactured by Mitsubishi Chemical Corporation).

[0078] 2. Exam A crack resistance test and a tensile strength test were performed on the container body 2 of Example 1 and Comparative Example 1. The container body 2 of Example 1 passed both the crack resistance test and the tensile strength test. On the other hand, the container body 2 of Comparative Example 1 failed both the crack resistance test and the tensile strength test.

[0079] The crack resistance test and tensile strength test were specifically conducted using the following methods.

[0080] <Crack resistance test> When the mouth attachment member 8 shown in Figure 1 is engaged with the mouth 5 of the container body 2, a test was conducted to determine whether or not cracks occur in the engaging projection 4c2 due to the claw portion 8e of the mouth attachment member 8, and the results were evaluated according to the following criteria. ○: No cracks occurred. ×: Crack occurred

[0081] <Pulling Test> After filling the inner bag 4 of the container body 2 with water, the mouth attachment member 8 was attached to the mouth 5 and engaged with the inner bag 4, and this was left for one day. After that, all the water was drained from the inner bag 4, and the mouth attachment member 8 was rotated in the loosening direction to release its engagement with the mouth 5. Then, the mouth attachment member 8 was pulled to remove the inner bag 4 from the container body 2. The pull-out strength at that time was measured and evaluated according to the following criteria. ○: Pull-out strength less than 3 kgf ×: Pull-out strength of 3 kgf or more [Explanation of symbols]

[0082] 1:Double container 2: Container body 3: Outer shell 3a: Open end 3b: Annular protrusion 3c: Through hole 3f: concave part 3g: protrusion 3h: Protrusion 3i: protrusion 4:Inner bag 4c: Protrusion 4c1: Protruding cylinder 4c2: Synaptic protrusion 4c3: Combination フランジ 4c4: When picking up Furuno 4c5: Circumferential inclined surface 4e: protrusion 4f: convex part 5: Mouth 5a: System 5a1: Ambrose 5b :フランジ 5c: Open end 6:Torch 6b: Shoulder 6c: Trunk body 6d:wanqubu 6d1: Location 6e: Reduced diameter section 7: Bottom 7a: Bottom concave area 7a1: Peripheral 7a2: Bottom surface 7b: Zhou Yuan's Domain 8: Mouth mounting parts 8a: Outer cylinder 8c: Inner cylinder 8d: System 8d1: Female part 8e: Claw 8e1: Above 8f: top plate 8g: Spout 8h: Through hole 8i: protrusion 9: Concave-convex shape 9a: concave strip 9b: convex strip 13:Outdoor プリフォーム 13a: Mouth 13b: trunk 13c: Bottom 13d: Annular protrusion 13f: recessed 13h: Protrusion 13i: Protrusion 14: Internal preform 14a: Mouth 14b: Torso 14c: Bottom 14c1: Positioning pin 14d:Protrusion 14f: Convex part 15: Preform 15a: Mouth 15b: Torso 15c: bottom 19: Uneven shape 24: Anti-loosening structure

Claims

1. A double-walled container comprising a container body having an inner bag and an outer shell, The container body is a biaxially stretched blow-molded body, The inner bag comprises an EVOH layer, The EVOH contained in the aforementioned EVOH layer is a double-walled container with an ethylene content of 32 to 46 mol%.

2. A double-walled container according to claim 1, The container body is equipped with a mouth attachment member that is attached to the mouth of the container body, The inner bag is provided with a protruding portion that extends from the open end of the outer shell, The mouth attachment member is a double container that engages with the protruding portion.

3. A double-walled container according to claim 1 or claim 2, The inner bag is a double-walled container with a single-layer structure of the EVOH layer.

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