Double container manufacturing method

Abstract

To provide a double container capable of improving the gas barrier properties of an inner bag while suppressing the deterioration of the drawability of the inner bag.SOLUTION: A double container includes a container body having an inner bag and an outer shell. The container body is a biaxially stretched blow-molded article. The inner bag includes an EVOH layer. An EVOH included in the EVOH layer has an ethylene content of 32-46 mol%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, double-layered containers having a container body with an outer shell and an inner bag have been known. For example, Patent Document 1 discloses a double-layered container formed by biaxially stretching blow molding an outer shell preform and an inner bag preform in a stacked state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-10741 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the outer shell and inner bag of such a double container are formed from different materials, or when contents remain inside the inner bag after use, it is desirable to separate the outer shell and inner bag when recycling the double container.

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

[0006] Furthermore, to prevent deterioration of the contents, it is desirable to improve the gas barrier properties of the inner bag. Although it is possible to improve the gas barrier properties by providing the inner bag with an EVOH layer with excellent gas barrier properties, this makes the inner bag hard, making it difficult to pull out.

[0007] The present invention has been made in consideration of these circumstances, and provides a double-layered container that can improve the gas barrier properties of the inner bag while suppressing deterioration in the pull-out ability of the inner bag. [Means for solving the problem]

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

[0009] The present invention is characterized in that an EVOH layer is provided on the inner bag of a container body made of a biaxially stretched blow-molded article, and the EVOH contained in this EVOH layer has a high ethylene content of 32 to 46 mol%. EVOH generally has a higher ethylene content, which increases its flexibility. Therefore, according to the present invention, it is possible to improve the gas barrier properties of the inner bag while suppressing deterioration in the drawability of the inner bag.

[0010] Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other. Preferably, the double container described above is provided with a mouth attachment member that is attached to the mouth of the container body, the inner bag has a protrusion that protrudes from the opening end of the outer shell, and the mouth attachment member engages with the protrusion. Preferably, the double container described above is a double container in which the inner bag is a single layer of the EVOH layer. [Brief explanation of the drawings]

[0011] [Figure 1] Fig. 1A is a perspective view of a double container 1 according to a first embodiment of the present invention, showing the state in which the spout-mounted member 8 is separated from the container body 2. Fig. 1B is an enlarged view of region B in Fig. 1A. The dashed-dotted line in the figure indicates the boundary line where the curvature of the faces that make up the surface shape changes. The same applies to the other figures. [Figure 2] 1 is a cross-sectional view taken along a line passing through the central axis C of the mouth 5 of the container body 2 and the centers of the two recesses 3f. [Figure 3]3A is an enlarged view of region A in FIG. 2, and FIG. 3B is an enlarged view of region B in FIG. [Figure 4] 4A to 4C are end views taken along planes A to C in FIG. 3A, respectively. [Figure 5] 5A to 5F are a front view, a plan view, a bottom view, a right side view, a left side view, and a rear view of the container body 2, respectively. [Figure 6] FIG. 6A is a perspective view of the mouth-mounted member 8 with a portion cut away, and FIG. 6B is a perspective view of the mouth-mounted member 8 as seen obliquely from below. [Figure 7] FIG. 2 is a front view of the spout-mounted member 8 mounted on the container body 2. [Figure 8] 8A and 8B are end views taken along planes A and B in FIG. 7, respectively. [Figure 9] FIG. 2 is a perspective view showing a state in which the inner preform 14 and the outer preform 13 are separated. [Figure 10] FIG. 2 is a perspective view of the inner preform 14 as seen obliquely from above. [Figure 11] FIG. 1 is a perspective view of a preform 15 formed by covering an outer preform 13 on an inner preform 14. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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 independent invention.

[0013] 1. First embodiment 1-1. Structure of double container 1 <Basic configuration> As shown in FIG. 1, the double container 1 of the first embodiment of the present invention comprises a container body 2 and a spout attachment member 8.

[0014] As shown in FIG. 1, the container body 2 has a mouth 5, a body 6, and a bottom 7. The mouth 5 is a tubular (preferably cylindrical) portion having an open end 5c. The mouth 5 has an engagement portion 5a to which a mouth attachment member 8 such as a cap or a pump can be attached. The engagement portion 5a is a male thread portion 5a1 if the mouth attachment member 8 is a screw type, or is an annular protrusion protruding in the circumferential direction if the mouth attachment member 8 is a stopper type. The mouth attachment member 8 may or may not have a check valve (not shown). The mouth 5 is provided with a flange 5b. The flange 5b can be used to support the mouth 5 when the mouth attachment member 8 is attached to the mouth 5.

[0015] The body 6 is disposed adjacent to the mouth 5 on the side farther from the open end 5c than the mouth 5. The body 6 has a larger outer diameter (in this specification, "outer diameter" means the circumscribed circle diameter if the cross section is not circular) than the mouth 5. The body 6 is cylindrical, and the bottom 7 is provided at the lower end of the body 6 and closes the lower end of the body 6. The body 6 has a shoulder 6b whose outer diameter increases with increasing distance from the mouth 5. The body 6 also has a body main body 6c with a substantially constant outer diameter, located closer to the bottom 7 than the shoulder 6b.

[0016] As shown in Fig. 3A, the container body 2 includes an inner bag 4 and an outer shell 3 arranged to cover the inner bag 4. The inner bag 4 is housed within the outer shell 3 except for the protruding portion 4c. In the following description, the portions of the inner bag 4 that correspond to the mouth 5, body 6, and bottom 7 of the container body 2 will be referred to as the mouth 5, body 6, and bottom 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 product formed by biaxial stretch blow molding, and the inner bag 4 and outer shell 3 are also formed by biaxial stretch blow molding. Details of biaxial stretch blow molding will be described later. In a biaxially stretched blow-molded product, it is difficult to achieve a high degree of adhesion between the inner bag 4 and the outer shell 3, so less force is required to pull the inner bag 4 out of the outer shell 3 than in a direct blow-molded product, which is a blow-molded product from a molten parison.

[0018] The thickness of the outer shell 3 at the center in the height direction of the container body 2 is, for example, 0.2 to 0.8 mm, preferably 0.25 to 0.5 mm. Specific examples of this thickness include 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 mm, and may be within a range between any two of the values ​​exemplified here. The thickness of the inner bag 4 at the center in the height direction of the container body 2 is, for example, 0.05 to 0.25 mm, preferably 0.08 to 0.20 mm. Specific examples of this thickness include 0.05, 0.08, 0.10, 0.15, 0.20, and 0.25 mm, and may be within a range between any two of the values ​​exemplified here.

[0019] If the mouth-attached member 8 is not provided with a check valve, the inner bag 4 does not shrink even after the contents of the inner bag 4 are expelled, 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, the significance of applying the present invention is particularly evident when the mouth-attached member 8 is not provided 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. The inner diameter D2 is specifically, for example, 20, 25, 30, 35, 40, 45, or 50 mm, and the outer diameter D4 is specifically, for example, 25, 30, 35, 40, 45, 50, or 55 mm, and each may be within a range between any two of the numerical values ​​exemplified here. The length of the mouth 5 is, for example, 15 to 35 mm, and specifically, for example, 15, 20, 25, 30, or 35 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0021] As shown in Fig. 3A, the body 6 preferably has 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 main body 6c. If the diameter of the container body 2 at a portion 6d1 where the radius of curvature of the curved portion 6d is smallest is D and the radius of curvature at the portion 6d1 is R, then it is preferable that R / D is 0.5 or greater (0.73 in this embodiment). The larger this value, the larger the ratio of the radius of curvature R to the diameter D, and the more gently the curved portion 6d curves. This prevents the inner bag 4 from being pressed against the outer shell 3 near the curved portion 6d, reducing the force required to pull out the inner bag 4. R / D is, for example, 0.5 to 2, and 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, or 2.0, and may be within a range between any two of the numerical values ​​exemplified here or equal to or greater than any one 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 curved portion 6d to pass through opening 5, thereby reducing the force required to pull out inner bag 4. D / D2 is, for example, 1.1 to 1.8, and specifically, for example, 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 numerical values ​​exemplified here.

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

[0024] As shown in FIG. 1 , the body 6 is provided with a tapered portion 6e, which is closer to the bottom 7 than the curved portion 6d and which tapers in diameter toward the bottom 7. The tapered portion 6e has a shape that functions as a so-called "pull-out taper," and providing the tapered portion 6e reduces the force required to pull out the inner bag 4. In this embodiment, the body main body 6c has a shape that tapers in diameter toward the bottom 7, so the entire body main body 6c forms the tapered portion 6e. Alternatively, for example, a portion of the body main body 6c may not be tapered in diameter, and the remaining portion of the body main body 6c may be tapered in diameter. The portion that does not be tapered is preferably a portion where the outer diameter does not change.

[0025] <Materials and layer structure> The inner bag 4 preferably includes an EVOH layer. The EVOH layer is a layer made 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 may be a mixed resin of EVOH and other resins. Examples of other resins include olefin-based resins. The olefin-based resin is a resin containing 50% by mass or more of olefin units. 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, or 100% by mass, and may be within a range between any two of the numerical values ​​exemplified here or any value greater than or equal to any one 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 (such as ethylene). 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 a range between any two of the numerical values ​​exemplified here or equal to or greater than any one of them.

[0026] The EVOH contained in the EVOH layer preferably has an ethylene content of 32 to 46 mol %. By providing the inner bag 4 with an EVOH layer, the gas barrier properties of the inner bag 4 are improved. If the ethylene content of the EVOH is too low, the flexibility of the inner bag 4 will be significantly reduced, and the pullability of the inner bag 4 will likely be significantly impaired. Furthermore, as will be described later, if the ethylene content of the EVOH is too low, the inner bag 4 will be too brittle, and as shown in Figure 1, there is a risk that cracks will occur in the protruding portion 4c of the inner bag 4 when the spout attachment member 8 is engaged with the protruding portion 4c. On the other hand, if the ethylene content of the EVOH is too high, the gas barrier properties of the inner bag 4 will likely not be sufficiently improved. 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 a range between any two of the values ​​exemplified here.

[0027] The inner bag 4 may have a single layer structure of an EVOH layer, or a multi-layer structure including an EVOH layer. When the inner bag 4 has a single layer structure of an EVOH layer, the inner preform 14 (shown in FIG. 9) used to form the inner bag 4 can also have a single layer structure. The single-layer inner preform 14 can be formed by general injection molding, thereby reducing manufacturing costs. When the inner bag 4 has a multi-layer structure, an additional layer is provided on one or both of the inner and outer sides of the EVOH layer. An example of the additional layer is an olefin-based resin layer made of an olefin-based resin. The olefin-based resin has been described above. Specific examples of the layer structure of the inner bag 4 include, from the outer side, an outer layer / EVOH layer, an EVOH layer / inner layer, and an outer layer / EVOH layer / inner layer. The outer layer and the inner layer are each the aforementioned additional layers, and these layers may have a single layer structure or a multi-layer structure. It is particularly preferable that the outer layer and the inner layer are each a polypropylene layer.

[0028] If the adhesion between the EVOH layer and the other layer is poor, an adhesive resin layer may be provided between the EVOH layer and the other layer, and / or an adhesive resin may be blended 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 thereof 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 on the inner surface of the inner bag 4. When the EVOH layer is exposed on the inner surface of the inner bag 4, it absorbs moisture from the contents and becomes flexible, making it easier to remove the inner bag 4. Furthermore, since EVOH does not readily adsorb citrus-like fragrance components, placing the EVOH layer as the innermost layer of the inner bag 4 can prevent deterioration of the flavor of the contents when the contents contain citrus-like fragrance components. When the EVOH layer is exposed on the inner surface of the inner bag 4, the gas barrier properties of the EVOH layer are slightly reduced due to moisture absorption. However, the degree of deterioration in gas barrier properties due to moisture absorption is smaller for EVOH with a higher ethylene content, so the benefit of improved flexibility outweighs the disadvantage of reduced gas barrier properties. On the other hand, when the EVOH layer is not exposed on the inner surface of the inner bag 4, the EVOH layer is prevented from absorbing moisture from the contents, thereby preventing deterioration in the gas barrier properties of the EVOH layer.

[0030] The material and layer structure of the outer shell 3 are not particularly limited, and the outer shell 3 can be formed from a thermoplastic resin such as polyester (e.g., PET) or polyolefin (e.g., polypropylene, polyethylene), with PET being preferred from the standpoint of recyclability. Furthermore, from the standpoint of reducing environmental impact, the outer shell 3 is preferably formed from biomass plastic.

[0031] <Uneven shape 9 on the inner surface of the mouth 5> As shown in FIG. 4C , the inner surface of at least one of the mouth 5 and a position of the body 6 adjacent to the mouth 5 is preferably provided with an uneven pattern 9 in which grooves 9a and protrusions 9b alternate in the circumferential direction of the mouth 5. The uneven pattern 9 is provided on the inner surface of the inner bag 4. The number of grooves 9a is, for example, 4 to 30, and preferably 10 to 20. The grooves 9a and protrusions 9b preferably extend non-parallel to the circumferential direction of the mouth 5. The extending direction of the grooves 9a and protrusions 9b is preferably 0 to 60 degrees, and preferably 0 to 30 degrees, relative to the axial direction of the mouth 5. Specific examples of this angle are 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 degrees, and may be within a range between any two of the values ​​exemplified here. The uneven shape 9 may be provided only in the mouth 5 or may be provided in a position on the body 6 adjacent to the mouth 5, but is preferably provided across the mouth 5 and body 6. The uneven shape 9 may be formed by reducing the thickness of the recesses 9a or by increasing the thickness of the protrusions 9b compared to other parts of the mouth 5 of the inner bag 4, or by reducing the thickness of the recesses 9a and increasing the thickness of the protrusions 9b.

[0032] Because the thickness of the ridges 9b is greater than the thickness of the recesses 9a, when the twist applied by the mouth 5 is transmitted to the body 6, the force is transmitted more easily to the ridges 9b than to the recesses 9a, and the ridges 9b rotate faster than the recesses 9a, resulting in the formation of creases in the inner bag 4 along the recesses 9a and their extensions, making it easier for the inner bag 4 to fold into pleats. For this reason, providing the uneven surface 9 causes the body 6 to fold into pleats, thereby quickly reducing the diameter of the body 6. It is preferable not to provide an uneven surface on the outer surface of the inner bag 4. This is because if an uneven surface is provided on the outer surface of the inner bag 4, the inner bag 4 and the outer shell 3 will engage with each other in the rotational direction of the inner bag 4, making it more difficult for the inner bag 4 to rotate relative to the outer shell 3.

[0033] If the thickness of the inner bag 4 at the ridges 9b of the mouth 5 (the radius of the circumscribing circle of the inner bag 4 minus the radius of the inscribed circle passing through the apexes of the ridges 9b) is T and the depth of the recesses 9a (the radius of the inscribed circle passing through the bottoms of the recesses 9a minus the radius of the inscribed circle passing through the apexes of the ridges 9b) is D, the maximum value of D / T is, for example, 0.2 to 0.8, and preferably 0.3 to 0.5. Specific examples of this value are 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8, and may be within a range between any two of the values ​​exemplified here. The thickness of the inner bag 4 at the mouth 5 other than the concave-convex 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, or 2.0 mm, or may be within a range between any two of the numerical values ​​exemplified here. The depth of the concave streaks 9a at the portion where the depth is greatest 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, or 1.0 mm, or may be within a range between any two of the numerical values ​​exemplified here.

[0034] The distance from the opening edge 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, or 30 mm, and may be within a range between any two of the numerical 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, or 40 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0035] <Structure of bottom 7> As shown in Figure 3B, a protrusion 4e is provided on the bottom 7 of the inner bag 4. An annular protrusion 3b is provided on the bottom 7 of the outer shell 3, and a through-hole 3c is provided in the area inside the annular protrusion 3b. The protrusion 4e is inserted into the through-hole 3c, thereby positioning the inner bag 4 relative to the outer shell 3. The annular protrusion 3b and its inner area are hardly stretched during biaxial stretch blow molding, so the wall thickness of both the outer shell 3 and the inner bag 4 is large. The annular protrusion 3b can be omitted.

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

[0037] The bottom 7 of the container body 2 (i.e., the bottoms 7 of the inner bag 4 and the outer shell 3) is provided with a bottom recessed region 7a and a peripheral region 7b surrounding the bottom recessed region 7a. The bottom recessed region 7a is a region of the bottom 7 recessed toward the inside of the container body 2. The peripheral region 7b serves as the contact surface of the container body 2. As shown in FIG. 3B, the thickness of the inner bag 4 and the outer shell 3 gradually decreases along the peripheral surface 7a1 of the bottom recessed region 7a 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 forms part of a cone that tapers toward the bottom surface 7a2 of the bottom recessed region 7a. The bottom surface 7a2 of the bottom recessed region 7a is generally flat. Therefore, the bottom recessed region 7a has a generally truncated cone shape.

[0038] The bottom surface 7a2 of the bottom recessed region 7a is difficult to stretch during biaxial stretch blow molding and is therefore likely to have a large wall thickness. Therefore, the smaller the diameter D3 of the bottom surface 7a2 (in other words, the diameter of the region surrounded by the boundary between the bottom surface 7a2 and the peripheral surface 7a1), the easier it is 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, and specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, and may be within a range between any two of the values ​​exemplified here or less than any one 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 portion can also be understood as the "portion for which a design registration is sought as a partial design," the area B portion can also be understood as the "portion for which a design registration is sought as a partial design," and the other portions can also be understood as the "portion for which a design registration is sought as a partial design." For convenience, areas A and B are shown only in the front view, but it is intended that the entire periphery of the container body 2 be the "portion for which a design registration is sought as a partial design."

[0040] In the bottom 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 Mouth-Attachment Member 8 and Inner Bag 4, and Engagement Structure Between Inner Bag 4 and Mouth 5 of Outer Shell 3> The mouth attachment member 8 is preferably configured to be attachable to the mouth 5, and configured so that the inner bag 4 rotates as the mouth attachment member 8 rotates (here, relative rotation with respect to the outer shell 3). With this configuration, it is possible to twist the inner bag 4 by rotating the mouth attachment member 8. Because the body 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 6 of the inner bag 4, the body 6 of the inner bag 4 can more easily 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-attached member 8 and the inner bag 4 will now be described in more detail.

[0043] 1, inner bag 4 has a protruding portion 4c that protrudes from open end 3a of outer shell 3. Protruding portion 4c has a protruding tube 4c1, an engaging protrusion 4c2, an engaging flange 4c3, and an abutting flange 4c4.

[0044] The engaging protrusion 4c2 protrudes radially outward from the circumferential surface of the protruding tube 4c1. The engaging flange 4c3 is an annular portion located farther from the open end 3a than the engaging protrusion 4c2 and having a larger diameter than the protruding tube 4c1. The abutting flange 4c4 is an annular portion located at a position abutting the open end 3a and having a larger diameter than the protruding tube 4c1. The abutting flange 4c4 abuts against the open end 3a, thereby preventing the inner bag 4 from falling into the outer shell 3. Alternatively, the abutting flange 4c4 may be omitted and the engaging protrusion 4c2 may be abutted against the open end 3a to prevent the inner bag 4 from falling into the outer shell 3.

[0045] As shown in FIG. 6, the mouth-mounted member 8 includes an outer tube 8a, an inner tube 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 tube 8a is provided with an uneven pattern in which protrusions and recesses alternate in the circumferential direction. This makes it easy to rotate the mouth-attached member 8. An engagement portion 8d is provided on the inner surface of the outer tube 8a. The engagement portion 8d is an engagement portion that engages with the engagement portion 5a of the mouth 5, and the mouth-attached member 8 is attached to the mouth 5 by engaging the engagement portion 8d with the engagement portion 5a.

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

[0048] Claws 8e are provided on the inner surface of the outer cylinder 8a. A plurality of claws 8e (eight in this embodiment) are provided and spaced apart in the circumferential direction. The number of claws 8e is, for example, 1 to 20, and preferably 4 to 12. Through holes 8h are provided in the top plate 8f at positions facing the claws 8e.

[0049] The mouth attachment member 8 having such a shape can be manufactured using a split mold that opens and closes in the vertical direction. The through-hole 8h and the upper surface 8e1 of the claw portion 8e can be formed using a protrusion on the upper mold, so the claw portion 8e can be formed without forcibly removing the lower mold. Therefore, it is not necessary to set the protrusion amount of the claw portion 8e to an amount that allows for forcible removal, and it can be set to an amount that is 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 threaded onto the male threaded portion 5a1. Therefore, the mouth attachment member 8 can be attached to the mouth 5 by rotating the mouth attachment member 8 relative to the mouth 5 in the tightening direction (usually clockwise when viewed from above) (hereinafter, 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 threaded onto the male threaded portion 5a1 while the outer peripheral surface of the inner tube 8c shown in FIG. 8A is in close contact with the inner peripheral surface of the inner bag 4. At this time, friction between the outer peripheral surface of the inner tube 8c and the inner peripheral surface of the inner bag 4 causes the mouth 5 of the inner bag 4 to rotate together with the mouth attachment member 8, resulting in a twisting of the inner bag 4. Before the mouth-attaching member 8 is attached, the inner bag 4 is filled with contents, and if the inner bag 4 is twisted, the contents inside the inner bag 4 will spill out. To prevent this problem from occurring, the inner bag 4 and the outer shell 3 can be tightly fitted together at the mouth 5 to prevent the inner bag 4 from rotating relative to the outer shell 3. However, simply fitting them tightly together creates a new problem in that 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 to relative rotation of the inner bag 4 in one direction relative to the outer shell 3 at the mouth 5 is greater than the second resistance to relative rotation in the other direction. For example, if the male thread portion 5a1 is a right-handed thread, the one direction and the other direction are the clockwise and counterclockwise directions, respectively, when viewed from above the container body 2. In other words, the one direction is the direction in which the mouth attachment member 8 is tightened, and the other direction is the direction in which the mouth attachment member 8 is loosened. With this configuration, the inner bag 4 is less likely to rotate relative to the outer shell 3 when attaching the mouth attachment member 8, thereby preventing the inner bag 4 from twisting when attaching the mouth attachment member 8. Furthermore, because the second resistance to 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 5 of the inner bag 4 relative to the outer shell 3 in the other direction, making it easy to pull the inner bag 4 out of the outer shell 3.

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

[0053] The recessed / convex engagement may be an engagement between a recessed portion provided on the outer peripheral surface of the inner bag 4 and a protruding portion provided on the inner peripheral surface of the outer shell 3. Furthermore, the recessed portion 3f is configured as a through-hole that penetrates the outer shell 3, but the recessed portion 3f does not have to penetrate the outer shell 3 as long as it can engage with the protruding portion 4f.

[0054] As the mouth-mounting member 8 is further rotated in the tightening direction, the female thread 8d1 threads into the male thread 5a1, and the claw 8e gradually approaches the protruding portion 4c. At some point, the inclined surface on the underside of the claw 8e abuts the engaging flange 4c3 shown in FIG. 1B. In this state, as the mouth-mounting member 8 is further rotated in the tightening direction, the claw 8e overcomes the engaging flange 4c3, resulting in the state shown in FIG. 8A. In this state, the claw 8e is positioned between the engaging flange 4c3 and the abutting flange 4c4. The engaging flange 4c3 is accommodated in the gap between the claw 8e and the top plate 8f. As shown in FIG. 8A, the protruding tube 4c1 is positioned between the claw 8e and the inner tube 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 circumferential inclined surface 4c5 provided on the engaging projection 4c2 and passes over the engaging projection 4c2, thereby allowing the mouth attachment member 8 to further rotate in the tightening direction. After the male thread portion 5a1 and the female thread portion 8d1 are fully tightened, the mouth attachment member 8 cannot rotate in the tightening direction and cannot move in the axial direction of the mouth portion 5.

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

[0056] Therefore, when the mouth-attaching member 8 is rotated in the loosening direction (usually counterclockwise when viewed from above) after the contents inside the inner bag 4 have been used up, the inner bag 4 rotates in conjunction with the rotation of the mouth-attaching member 8. This causes the inner bag 4 to twist and reduce in diameter.

[0057] When the mouth attachment member 8 is further rotated in the loosening direction to release the engagement between the female thread portion 8d1 and the male thread portion 5a1, the mouth attachment member 8 becomes movable in a direction away from the open end 3a (i.e., in the axial direction of the mouth 5). Because the engagement flange 4c3 is engaged with the mouth attachment member 8 in the axial direction of the mouth 5, when the mouth attachment member 8 is moved in the axial direction of the mouth 5, the inner bag 4 also moves together with the mouth attachment member 8, and the inner bag 4 is pulled out of the outer shell 3.

[0058] As described above, according to 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, and then pulled out from the outer shell 3, making it possible to smoothly separate the inner bag 4 and the outer shell 3 with a simple operation.

[0059] <Loosening prevention structure of the mouth attachment member 8> In the container body 2 of this embodiment, the male thread portion 5a1 and the female thread portion 8d1 are multiple-start threads (more specifically, triple-start threads), which makes them prone to loosening even after tightening. Therefore, as shown in FIG. 8B , a locking structure 24 is provided to prevent loosening of the threaded engagement between the spout 5 and the spout mounting member 8. In this embodiment, the locking structure 24 is composed of a protrusion 3i protruding from the outer peripheral surface of the outer shell 3 and a protrusion 8i protruding from the inner peripheral surface of the outer tube 8a of the spout mounting member 8. The protrusions 3i and the protrusions 8i are each provided in multiple positions (three in this embodiment), preferably evenly spaced apart in the circumferential direction. The locking structure 24 may also be configured to engage the spout 5 and the spout mounting member 8 in a different circumferential direction. For example, the protrusions 3i may be engaged with a recess provided on the inner peripheral surface of the outer tube 8a of the spout mounting member 8.

[0060] <Protrusion 3h on the inner surface of the mouth 5 of the outer shell 3> As shown in FIG. 4A , a protrusion 3h is provided on the inner surface of the mouth portion 5 of the outer shell 3, closer to the opening end 3a than the protrusion 3g. The protrusion 3h is preferably provided so as to connect to the protrusion 3g. The mouth portion 5 of the outer shell 3 is thinned at the locations where the protrusions 3g and 3h are provided, so that the outer shell 3 abuts the inner bag 4 only at the protrusions 3g and 3h. This reduces the contact area between the outer shell 3 and the inner bag 4, thereby reducing the force required to pull out the inner bag 4. The protrusions 3g and 3h are also provided at multiple locations (two locations in this embodiment) circumferentially, preferably spaced apart at equal intervals. This allows the mouth portion 5 of the outer shell 3 and the mouth portion 5 of the inner bag 4 to be maintained concentric.

[0061] Incidentally, when the mouth attachment member 8 is rotated in the loosening direction, the threaded engagement between the mouth attachment member 8 and the mouth 5 is released after approximately half a turn. This release of the threaded engagement allows the inner bag 4 to be pulled out of the outer shell 3. However, this can cause a problem in that the user may not immediately notice that the threaded engagement has been released, causing the mouth attachment member 8 to continue to spin freely. In contrast, in this embodiment, when the convex portion 4f is rotated in the loosening direction (counterclockwise in FIGS. 4A and 4B), the convex portion 4f reaches the protrusion 3h after approximately half a turn (e.g., the convex portion 4f on the right side in FIG. 4B reaches the protrusion 3h on the left side in FIG. 4A), preventing further rotation of the inner bag 4. This configuration allows the inner bag 4 to be pulled out at the point when the inner bag 4 stops turning when the mouth attachment member 8 is rotated in the loosening direction. This allows the inner bag 4 to be pulled out at the appropriate time, improving usability.

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

[0063] <Configuration of inner preform 14, outer preform 13, and preform 15> For example, the preform 15 can be constructed by covering an inner preform 14 that will become the inner bag 4 with an outer preform 13 that will become the outer shell 3 .

[0064] As shown in Figure 9, the inner preform 14 is cylindrical and has a bottom, a mouth portion 14a, a body portion 14b, and a bottom portion 14c. A protrusion 14d is provided at the open end of the mouth portion 14a. The protrusion 14d does not deform during molding and remains in its original shape to become the protrusion 4c. Therefore, the matters described for the protrusion 4c also apply to the protrusion 14d. The bottom portion 14c is provided so as to close the lower end of the body portion 14b. A positioning pin 14c1 is provided on the bottom portion 14c.

[0065] 10, an uneven shape 19 is provided on the inner surface of the inner preform 14. The uneven shape 19 remains as it is or is stretched during molding to become the uneven shape 9 of the container body 2. The explanation regarding the uneven shape 9 also applies to the uneven shape 19 as long as it is not contrary to the spirit thereof.

[0066] As shown in Fig. 9, the outer preform 13 is cylindrical with a bottom and includes a mouth portion 13a, a body portion 13b, and a bottom portion 13c. The bottom portion 13c is provided so as to close the lower end of the body portion 13b. The bottom portion 13c is provided with an annular protrusion 13d and a positioning hole (not shown). The mouth portion 13a of the outer preform 13 is provided with a protrusion 13h that will become the protrusion 3h, a protrusion (not shown) that will become the protrusion 3g, and a protrusion 13i that will become the protrusion 3i.

[0067] 11, when forming the preform 15, the protrusion 14d is brought into contact with the open 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 portion 14a faces the mouth portion 13a, and the body portion 14b faces the body portion 13b.

[0068] The mouth portions 13a and 14a become the mouth portion 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 primarily stretched in the biaxial stretch blow molding. However, since the biaxial stretch blow molding is performed with the annular convex portion 13d supported, the annular convex portion 13d and its inner region are hardly stretched during the biaxial stretch blow molding. The annular convex portion 13d becomes the annular convex portion 3b after molding.

[0069] <Engagement of the Concave and Convex Parts at the Mouth Portion 15a of the Inner Preform 14 and the Outer Preform 13> When the preform 15 is heated and biaxially stretched and blow-molded, the inner surface of the preform 15 (i.e., the inner surface of the inner preform 14) is usually supported. The preform 15 can be conveyed upright, with the bottom 15c facing downward, or inverted, with the bottom 15c facing upward. Upright conveyance is common and preferred. However, conveying the preform 15 upright can cause a problem in that the outer preform 13 becomes detached from the inner preform 14 and falls off. While tightly fitting the outer preform 13 and the inner preform 14 together at the mouth 15a can prevent the outer preform 13 from falling off, this creates a new problem in that the inner bag 4 is difficult to detach from the outer shell 3 in the container body 2 obtained by molding.

[0070] Therefore, in this embodiment, in order to make it possible to easily pull out the inner bag 4 from the outer shell 3 after use while preventing the outer preform 13 from falling off, the inner preform 14 and the outer preform 13 are engaged with each other via a concave-convex structure at the mouth portion 15a.

[0071] 9, in this embodiment, the recess-projection engagement is an engagement between a protrusion 14f provided on the outer peripheral surface of the mouth portion 14a of the inner preform 14 and a recess 13f provided on the inner peripheral surface of the mouth portion 13a of the outer preform 13. The protrusion 14f and the recess 13f become the protrusion 4f and the recess 3f, respectively.

[0072] <Materials and manufacturing method of the inner preform 14 and the 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 costs, etc., it is preferable to form it by injection molding. The inner bag 4 having a multi-layer structure can be formed using an inner preform 14 having a multi-layer structure. The inner preform 14 having 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 materials described above for the outer shell 3. The outer preform 13 can be formed by direct blow molding, injection molding, or the like, but is preferably formed by injection molding from the viewpoint of production costs, etc.

[0074] The preform 15 may be formed by combining the inner preform 14 and the outer preform 13 after they have been formed separately, or may be formed by two-color molding. [Example]

[0075] 1. Manufacturing of the container body 2 Example 1 According to the method described above, the container body 2 (capacity 300 mL) shown in FIG. 1 was produced by biaxially stretch-blow molding the preform 15 shown in FIGS. 9 to 11. The inner preform 14 was produced by injection molding EVOH (ethylene content 38 mol%, model: G-Soarnol GH3804B, manufactured by Mitsubishi Chemical Corporation) at 250°C. The outer preform 13 was produced by injection molding PET (model: titanium-based catalyst grade, manufactured by Teijin Limited) at 300°C to form the outer preform shape, followed by rapid cooling to 20°C. The rapid cooling converted the molten PET into an amorphous state.

[0076] Such a preform 15 was heated to 110° C. (the temperature at the center in the longitudinal direction of the preform 15) and then subjected to biaxial stretch blow molding to obtain a container body 2.

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

[0078] 2. Exam A crack resistance test and a pull-out ability test were performed on the container bodies 2 of Example 1 and Comparative Example 1. The container body 2 of Example 1 received a good result in both the crack resistance test and the pull-out ability test. On the other hand, the container body 2 of Comparative Example 1 received a poor result in both the crack resistance test and the pull-out ability test.

[0079] Specifically, the crack resistance test and the pull-out test were carried out in the following manner.

[0080] <Crack resistance test> When the mouth-mounting member 8 shown in Figure 1 was engaged with the mouth 5 of the container body 2, a test was conducted to determine whether or not the claw portion 8e of the mouth-mounting member 8 would cause cracks in the engaging protrusion 4c2, and the test was evaluated according to the following criteria. ○: No cracks occurred ×: Cracks occurred

[0081] <Pull-out test> After water was placed in the inner bag 4 of the container body 2, the mouth attachment member 8 was attached to the mouth 5, and the mouth attachment member 8 was 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 then the mouth attachment member 8 was rotated in the loosening direction to release the engagement with the mouth 5, and then the mouth attachment member 8 was pulled to pull the inner bag 4 out of the container body 2. The pull-out strength at this time was measured and evaluated according to the following criteria. ○: Pull-out strength is less than 3 kgf ×: Pull-out strength is 3kgf 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: Recess 13h: Protrusion 13i: Protrusion 14: Inner preform 14a: Mouth 14b: Torso 14c: Bottom 14c1: Locating pin 14d:Protrusion 14f: Convex part 15: Preform 15a: Mouth 15b: Body 15c: bottom 19: Uneven shape 24: Anti-loosening structure

Claims

1. A method for manufacturing a double container having a container body with an inner bag and an outer shell, The container body is formed by biaxial stretch blow molding, The inner bag comprises an EVOH layer; the EVOH contained in the EVOH layer has an ethylene content of 32 to 46 mol %, The double container is configured so that the inner bag is twisted to reduce its diameter, The double container includes a mouth attachment member that is attached to the mouth of the container body, the inner bag has a protrusion protruding from the open end of the outer shell, The protruding portion includes a protruding tube and an engaging protrusion protruding radially outward from a circumferential surface of the protruding tube, The double container is configured such that the engaging projection engages with the claw portion of the mouth attachment member in the rotation direction of the mouth attachment member, thereby causing the inner bag to rotate in accordance with the rotation of the mouth attachment member, The engagement protrusion abuts against the claw portion in the rotational direction.

2. 10. The method of claim 1, The inner bag is a single layer of the EVOH layer.

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