Double container manufacturing method and double container

Abstract

To provide a method for manufacturing a double container, and a double container, which are capable of reducing a possibility of rupturing a pinch-off part.SOLUTION: There is provided a method for manufacturing a double container, comprising a blow molding process. The blow molding process is carried out by heating and softening an inner preform and an outer preform in a state of covering the outer preform on the inner preform, and then blowing air into the inner preform; the inner preform is a blow molded body; and the blow molding process is carried out in a state of preventing stretching of a bottom part of the outer preform.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a method for producing a double container by blow molding an inner preform and an outer preform in a stacked state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2004 / 071887 Summary of the Invention [Problem to be solved by the invention]

[0004] When the inner preform is a blow-molded article, a pinch-off portion is formed at the bottom of the inner preform where the parison is closed. Since the pinch-off portion has a relatively low strength, if the area near the pinch-off portion is stretched forcefully during blow molding, the pinch-off portion may rupture.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a double container and a double container that can reduce the possibility of the pinch-off portion tearing. [Means for solving the problem]

[0006] [1] A method for manufacturing a double-walled container, comprising a blow molding step, wherein the blow molding step is carried out by heating and softening an outer preform while the inner preform is placed over the outer preform, and then blowing air into the inner preform in that state, wherein the inner preform is a blow molded body, and the blow molding step is carried out while suppressing extension of the bottom of the outer preform. [2] The method according to [1], wherein the outer preform has a reinforcing structure that suppresses elongation of a bottom portion of the outer preform. [3] The method according to [2], wherein the reinforcing structure is an annular protrusion provided on the bottom of the outer preform. [4] The method according to any one of [1] to [3], wherein the blow molding step is carried out in a state in which the bottom of the outer preform is supported by a bottom support mold, thereby suppressing the stretching of the bottom. [5] A method for manufacturing a double container having an inner bag and an outer shell, comprising a blow molding process, in which a preform having a portion that will become the inner bag and a portion that will become the outer shell is heated and softened, and air is blown into the preform in that state, and the blow molding process is performed in a state in which stretching of the bottom of the portion that will become the outer shell is suppressed. [6] The method according to [5], wherein the portion that will become the outer shell has a reinforcing structure that suppresses extension of the bottom of the portion that will become the outer shell. [7] The method according to [6], wherein the reinforcing structure is an annular convex portion provided at the bottom of the portion that will become the outer shell. [8] The method according to [7], wherein an outside air inlet hole is arranged in the outer shell in the area inside the annular convex portion. [9] A method according to any one of [5] to [8], wherein the blow molding step is carried out in a state in which the bottom of the portion that will become the outer shell is supported by a bottom support mold, thereby suppressing the stretching of the bottom.

[10] A double container having an outer shell and an inner bag, the inner bag comprising a container body that is shrinkable, wherein the container body is formed by blow molding a preform having a portion that will become the inner bag and a portion that will become the outer shell, and the blow molding is performed in a state where stretching of the bottom of the portion that will become the outer shell is suppressed.

[11] A double container according to

[10] , wherein the portion that becomes the outer shell has a reinforcing structure that suppresses the extension of the bottom portion of the portion that becomes the outer shell.

[12] A double container having an outer shell and an inner bag, the inner bag being a contractible container body, the container body having a cylindrical body and a bottom provided at the lower end of the body, the outer shell having an annular convex portion at the bottom, and an outside air inlet hole arranged in the outer shell in the area inside the annular convex portion.

[0007] According to the present invention, there is provided a method for manufacturing a double container, which includes a blow molding step, in which the blow molding step is carried out by heating and softening the inner preform and outer preform while the inner preform is covered with the outer preform, and then blowing air into the inner preform in that state, the inner preform being a blow molded body, and the blow molding step is carried out in a state in which stretching of the bottom of the outer preform is suppressed.

[0008] As a result of extensive research, the inventors have found that the above-mentioned problem can be solved by expanding the preform while suppressing the stretching of the bottom of the outer preform. Since the pinch-off portion is located opposite the bottom of the outer preform, suppressing the stretching of the bottom also suppresses the stretching of the portion near the pinch-off portion, thereby solving the above-mentioned problem.

[0009] Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other. Preferably, in the double container described above, the spacer is a protrusion provided on the outer shell or the inner bag. Preferably, in the double container described above, the spacers are arranged radially. Preferably, in the double container described above, the spacer is arranged to form an intermittent circle. Preferably, in the double container described above, the container body is a double container formed by heating and blow molding an inner preform that becomes the inner bag and an outer preform that becomes the outer shell, with the inner preform that becomes the inner bag being covered with an outer preform that becomes the outer shell. Preferably, the double container described above is a double container in which the inner preform has a positioning pin at the bottom of the inner preform, the outer preform has a positioning hole at the bottom of the outer preform, and the blow molding is performed with the positioning pin inserted into the positioning hole. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B show a container body 2 of a double container 1 according to a first embodiment of the present invention, with FIG. 1A being a front view and FIG. 1B being a bottom view. [Figure 2] 2A is a perspective view of the container body 2 of FIG. 1 as seen from the bottom 7 side, and FIG. 2B is a cross-sectional perspective view of the vicinity of the bottom 7 of the outer shell 3 as seen from inside the container. [Figure 3] 3A is a cross-sectional view taken along line AA in FIG. 1B, and FIG. 3B is a cross-sectional view taken along line BB in FIG. 3A. [Figure 4] FIG. 2 is a perspective view showing a state in which the inner preform 14 and the outer preform 13 are separated. [Figure 5] 5 is a cross-sectional perspective view of the vicinity of the bottom 13c of the outer preform 13 of FIG. 4, as viewed from the inside of the outer preform 13. FIG. [Figure 6] FIG. 6A is a perspective view of an assembly 15 formed by covering an outer preform 13 over an inner preform 14, and FIG. 6B is a perspective view of FIG. 6A seen from a different angle. [Figure 7] 1 is a cross-sectional view showing the biaxially stretched blow molding process, illustrating a state in which an assembly 15 is attached to a mouth support mold 21. FIG. [Figure 8] 8 is a cross-sectional view showing the state after the forming dies 23 and 24 are closed and the bottom support die 22 supports the bottom 13c of the outer preform 13 from the state of FIG. 7. FIG. [Figure 9] 9 is a cross-sectional view showing the state after the support rods 25 are extended and the bottom support mold 22 is retracted from the state of FIG. 8 to longitudinally stretch the assembly 15. FIG. [Figure 10] 6 is a cross-sectional perspective view corresponding to FIG. 5, showing an outer preform 13 having intermittent circular projections 13c1. FIG. [Figure 11] FIG. 10 is a perspective view showing an inner preform 14 having a configuration in which radial projections 14c2 are provided on a bottom portion 14c. [Figure 12] FIG. 10 is a perspective view showing an inner preform 14 having a bottom portion 14c provided with intermittent circular protrusions 14c2. [Figure 13] 10 is an enlarged view of the vicinity of a bottom portion 14g of an inner preform 14 of a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] 1. First embodiment As shown in Fig. 1, the double container 1 of the first embodiment of the present invention includes a container body 2. As shown in Fig. 3A, the container body 2 has an outer shell 3 and an inner bag 4, and is configured so that the inner bag 4 shrinks as the contents decrease.

[0013] As shown in FIG. 1, the container body 2 has a mouth 5, a body 6, and a bottom 7. The mouth 5 has an engagement portion 5a to which a pump (not shown) can be attached. The engagement portion 5a is a male thread in the case of a screw-type pump, and is an annular projection that protrudes in the circumferential direction in the case of a cap-type pump. The mouth 5 is provided to extend from the upper end 6a of the body 6. The mouth 5 is cylindrical. 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.

[0014] 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 bottom 7 has a central recess 7a provided in the center of the bottom 7 and a peripheral edge 7b surrounding the central recess 7a.

[0015] As shown in FIG. 2A, the central recess 7a is provided with a locking portion 7a1, an outside air introduction hole 7a2, an annular protrusion 7a3, and a positioning recess 7a4. As shown in FIG. 3A, the locking portion 7a1 is formed by inserting a locking protrusion 4a provided on the inner bag 4 into an insertion hole 3a provided in the outer shell 3. The locking portion 7a1 prevents the inner bag 4 from coming off the outer shell 3. The outside air introduction hole 7a2 is a through-hole that penetrates the outer shell 3. As the inner bag 4 contracts, outside air is introduced into the intermediate space between the outer shell 3 and the inner bag 4 through the outside air introduction hole 7a2. The locking portion 7a1 and the outside air introduction hole 7a2 are located within the annular protrusion 7a3. The positioning recess 7a4 is used to position the container body 2 circumferentially when performing printing or the like on the container body 2.

[0016] The peripheral portion 7b is provided with a ground contact portion 7b1 and a peripheral recess 7b2. The ground contact portion 7b1 is a portion that comes into contact with the support surface on which the container body 2 is placed when the container body 2 is placed upright. If the entire peripheral portion 7b were to be the ground contact portion 7b1, the central recess 7a would form an airtight space between the container body 2 and the support surface when the container body 2 is placed upright, which could hinder the introduction of outside air through the outside air inlet hole 7a2. Therefore, the peripheral recess 7b2 is provided as an air passage to prevent the inside of the central recess 7a from becoming an airtight space.

[0017] When the contents of the inner bag 4 are discharged by a pump attached to the opening 5, the inner bag 4 contracts and attempts to separate from the outer shell 3. At this time, outside air is introduced into the space between the inner bag 4 and the outer shell 3 through the outside air inlet hole 7a2. On the other hand, as shown in FIG. 3A , the peripheral edge 7b has a small radius of curvature, making it difficult for the inner bag 4 to separate from the outer shell 3 at the peripheral edge 7b, and thus making it difficult to form an air passage through which the outside air introduced through the outside air inlet hole 7a2 can pass. Therefore, it is difficult for outside air to be introduced into the body 6. In this case, there is a problem in that the outer shell 3 contracts together with the inner bag 4 as the contents decrease. To address this problem, in this embodiment, a spacer 9 is disposed between the outer shell 3 and the inner bag 4. In this embodiment, the spacer 9 is a protrusion 3b that protrudes from the outer shell 3 toward the inner bag 4. When the spacer 9 is provided, a gap 8 is formed between the outer shell 3 and the inner bag 4 at a position adjacent to the spacer 9, and the gap 8 forms an air passage connecting the body 6 and the bottom 7, making it easier for outside air introduced through the outside air inlet holes 7a2 to be introduced into the body 6 through the peripheral edge 7b. The spacers 9 are provided radially so as to straddle the bottom 7 and the body 6, making it easier to form an air passage spanning the bottom 7 and the body 6.

[0018] As shown in Figures 4 to 6, the container body 2 can be formed by heating and biaxially stretching blow molding an inner preform 14 that will become the inner bag 4 and an outer preform 13 that will become the outer shell 3, with the inner preform 14 and the outer preform 13 being placed over each other.

[0019] 4, the inner preform 14 is cylindrical with a bottom and includes a mouth portion 14a, a body portion 14b, and a bottom portion 14c. A flange 14a1 is provided at the open end of the mouth portion 14a. A positioning pin 14c1 is provided at the bottom portion 14c.

[0020] As shown in Fig. 4, the outer preform 13 is cylindrical with a bottom and includes a mouth portion 13a, a body portion 13b, and a bottom portion 13c. As shown in Fig. 5, the inner surface of the bottom portion 13c of the outer preform 13 is provided with radially arranged protrusions 13c1. The bottom portion 13c is provided with positioning holes 13c2 and outside air introduction holes 13c3. As shown in Fig. 6B, an annular protrusion 13c4 is provided on the outer surface of the bottom portion 13c. The positioning holes 13c2 and outside air introduction holes 13c3 are located in the area inside the annular protrusion 13c4. The outer preform 13 is sized to allow the inner preform 14 to be inserted therein.

[0021] The inner preform 14 and the outer preform 13 can be formed by blow molding, injection molding, or the like using thermoplastic resins such as polyester (e.g., PET) or polyolefin (e.g., polypropylene or polyethylene). In one example, the inner preform 14 is formed by blow molding polypropylene, and the outer preform 13 is formed by injection molding PET. By making the inner preform 14 and the outer preform 13 from different materials, welding to each other during blow molding is suppressed. Furthermore, when the outer preform 13 is formed by injection molding, the outside air introduction hole 13c3 can be formed during injection molding, thereby eliminating the need for post-processing.

[0022] 2. Biaxially stretched blow molding The biaxially stretched blow molding can be carried out by the following method.

[0023] First, as shown in Fig. 6, the outer preform 13 is placed over the inner preform 14 (in other words, the inner preform 14 is inserted into the outer preform 13) to form an assembly 15. At this time, the flange 14a1 is brought into contact with the open end of the mouth portion 13a, and the positioning pin 14c1 is inserted into the positioning hole 13c2. 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.

[0024] The assembly 15 is then heated to soften it.

[0025] Next, the assembly 15 is placed in a mold for blow molding, and with the mouth portion 13a and the annular protrusion 13c4 supported by a jig, air is blown into the inner preform 14 to expand the assembly 15 and make it adhere to the inner surface of the cavity of the mold. At this time, a support rod (not shown) may be pressed against the inner bottom surface of the inner preform 14 to prevent the assembly 15 from shaking within the mold. Also, a recess into which the support rod fits may be provided on the inner bottom surface of the inner preform 14 to make it easier to fix the support rod to the inner preform 14.

[0026] The assembly 15 expands through blow molding to produce the container body 2 shown in FIGS. 1 to 3. The mouths 13a and 14a become the mouth 5, the body 13b and 14b become the body 6, and the bottoms 13c and 14c become the bottom 7. The protrusions 13c1, the annular protrusion 13c4, and the air inlet hole 13c3 become the protrusion 3b, the annular protrusion 7a3, and the air inlet hole 7a2, respectively. During blow molding, the mouths 13a and 14a and the annular protrusion 13c4 and its inner region are hardly deformed, while other regions are primarily deformed. The air inlet hole 13c3 is located in the inner region of the annular protrusion 13c4, so it is less likely to be deformed and blocked during blow molding. The flange 14a1 becomes the flange 4b ​​that covers the open end of the mouth 5 of the container body 2, as shown in FIG. 1A.

[0027] After blow molding, the positioning hole 13c2 becomes the insertion hole 3a shown in Fig. 3A, and the positioning pin 14c1 is inserted into the insertion hole 3a. Thereafter, the positioning pin 14c1 is deformed (i.e., crushed or bent) to become the locking protrusion 4a shown in Fig. 3A. This forms the locking portion 7a1 of the container body 2.

[0028] 3. Details of biaxial stretch blow molding The biaxial stretch blow molding described above can be performed, for example, using a mold unit 20 shown in Figures 7 to 9. The mold unit 20 includes a mouth support mold 21, a bottom support mold 22, and molding molds 23 and 24.

[0029] The mouth support mold 21 is configured to be able to support the mouth 13a of the outer preform 13. An insertion hole 21a is provided in the mouth support mold 21, and a support rod 25 is inserted into the insertion hole 21a. The support rod 25 can be extended and retracted by a drive mechanism (not shown). The bottom support mold 22 is driven by a drive mechanism 22c and is configured to be able to move in the vertical extension direction (up and down direction in Figure 7). The forming molds 23 and 24 are openable and closable, and each have a cavity surface 23a and 24a. The cavity surfaces 23a and 24a come together to form a cavity having a shape corresponding to the outer shape of the container body 2.

[0030] The method includes a preform heating step, a bottom supporting step, a stretching step, and a blow molding step.

[0031] <Preform heating process> In the preform heating step, the assembly 15, which is formed by covering the inner preform 14 with the outer preform 13, is attached to the mouth support mold 21 as shown in Figure 7, and in this state the assembly 15 is heated and softened. The assembly 15 may be heated while it is placed between the molding dies 23 and 24, or may be heated outside the space between the molding dies 23 and 24. Furthermore, before the preform heating step, the tip of the support rod 25 may be brought into contact with the inner bottom surface of the inner preform 14. This prevents the softened assembly 15 from shaking.

[0032] <Bottom support process> In the bottom support step, as shown in FIG. 8 , the bottom support mold 22 moves toward the bottom 13c of the outer preform 13 and supports the bottom 13c of the outer preform 13. The bottom support mold 22 preferably has a recess 22a capable of accommodating the annular protrusion 13c4, and supports the bottom 13c so that the annular protrusion 13c4 is accommodated within the recess 22a. This prevents the annular protrusion 13c4 and its inner region from being stretched during the blow molding step. The recess 22a is preferably annular. The bottom support mold 22 preferably has a recess 22b capable of accommodating the positioning pin 14c1, and supports the bottom 13c so that the positioning pin 14c1 is accommodated within the recess 22b. This prevents the positioning pin 14c1 from interfering with the bottom support mold 22. Although FIG. 8 shows a state in which the molding dies 23 and 24 are closed, the molding dies 23 and 24 may be closed at any time before the blow molding step, and may be closed after the longitudinal stretching step.

[0033] <Longitudinal stretching process> In the longitudinal stretching step, as shown in Figures 8 and 9, the support rods 25 are pressed against the inner bottom surface of the inner preform 14 and extended, thereby extending the assembly 15 in the longitudinal direction (the vertical direction in Figure 9). At this time, it is preferable to retract the bottom support mold 22 in synchronization with the extension of the support rods 25. This allows the assembly 15 to be stably extended. Note that the longitudinal stretching step can also be performed in a state where the bottom 13c is not supported by the bottom support mold 22, and therefore the bottom support step may be performed after the longitudinal stretching step.

[0034] <Blow molding process> In the blow molding process, air is blown into the inner preform 14 from the state shown in Figure 9, thereby stretching (i.e., expanding) the assembly 15 in the lateral direction and forming it into the shape of the cavity surfaces 23a, 24a. The air can be blown in through the air passage 26 between the mouth support mold 21 and the support rod 25, but it is also possible, for example, to provide an air passage in the support rod 25 and blow air out from the side of the support rod 25.

[0035] In this embodiment, air is blown into the outer preform 13 while the bottom 13c of the outer preform 13 is supported by the bottom support mold 22, so that the stretching of the bottom 13c of the outer preform 13 is suppressed.

[0036] The blow molding step can be performed simultaneously with the longitudinal stretching step. That is, air can be blown into the inner preform 14 while stretching the assembly 15 in the longitudinal direction. Alternatively, the longitudinal stretching step can be omitted, and air can be blown into the inner preform 14 after the bottom support step without stretching the assembly 15 in the longitudinal direction.

[0037] 4. Other embodiments In the above embodiment, the spacers 9 are arranged radially, but the spacers 9 may have other shapes. For example, the spacers 9 may be arranged to form a segmented circle. In this case, an air passage is formed in the missing portion of the circle. It is preferable that a plurality of segmented circles are arranged concentrically. For example, as shown in FIG. 10, such a spacer 9 can be formed by using an outer preform 13 having segmented circular protrusions 13c1. In the above embodiment, the protrusions 3b protruding from the outer shell 3 toward the inner bag 4 are formed by providing the protrusions 13c1 on the outer preform 13. However, as shown in Figures 11 and 12, protrusions (spacers) protruding from the inner bag 4 toward the outer shell 3 may be formed by providing protrusions 14c2 (e.g., radial protrusions as shown in Figure 11 or intermittent circular protrusions as shown in Figure 12) on the bottom 14c of the inner preform 14. The spacer 9 may be formed of a separate member. The spacer 9 can be disposed between the outer shell 3 and the inner bag 4 by performing blow molding with a spacer member disposed between the inner preform 14 and the outer preform 13.

[0038] 5. Inventions from a different perspective When the inner preform 14 is a blow-molded article (more specifically, a direct blow-molded article), a pinch-off portion 14h is formed at the position where the parison is closed in the bottom portion 14g of the inner preform 14, as shown in Fig. 13. Since the pinch-off portion 14h has a relatively low strength, there is a risk that the pinch-off portion 14h will rupture if the area near the pinch-off portion 14h is stretched forcefully during biaxial stretch blow molding.

[0039] 13, the inner preform 14 has a multilayer structure, including, from the inside out, an innermost layer 14d, a gas barrier layer (e.g., an EVOH layer) 14e, and an outermost layer 14f. The innermost layer 14d and the outermost layer 14f are made of polyolefin (e.g., polyethylene, polypropylene), PET, or the like. At the pinch-off portion 14h, the opposing gas barrier layers 14e1 and 14e2 are connected to each other, or if they are separated, the gap G between them is very small. If the area near the pinch-off portion 14h is stretched too forcefully during biaxial stretch blow molding, the gas barrier layer 14e may tear or the gap G may become larger, resulting in problems such as a decrease in gas barrier properties.

[0040] As explained in "2. Biaxially stretched blow molding" and "3. Details of biaxially stretched blow molding," the above problem can be solved by expanding the assembly 15 while suppressing the stretching of the bottom portion 13c of the outer preform 13. Since the pinch-off portion 14h is disposed at a position facing the bottom portion 13c of the outer preform 13, suppressing the stretching of the bottom portion 13c also suppresses the stretching of the region near the pinch-off portion 14h, thereby solving the above problem.

[0041] In "2. Biaxially stretched blow molding," the rigidity of the bottom 13c is increased and stretching of the bottom 13c is suppressed by providing an annular protrusion 13c4 on the bottom 13c of the outer preform 13. The structure provided to increase the rigidity of the bottom 13c may be a reinforcing structure other than the annular protrusion 13c4.

[0042] In "3. Details of Biaxial Stretch Blow Molding," stretching of the bottom 13c is suppressed by performing the blow molding process while the bottom 13c of the outer preform 13 is supported by the bottom support mold 22. In the above explanation, the annular convex portion 13c4 is accommodated in the recess 22a, but even if the bottom 13c does not have the annular convex portion 13c4, supporting the bottom 13c with the bottom support mold 22 suppresses stretching of the bottom 13c due to friction between the bottom 13c and the bottom support mold 22.

[0043] Considering the above points, according to the present invention, A method for manufacturing a double container, comprising: A blow molding process is provided. The blow molding step is carried out by heating and softening the inner preform and the outer preform in a state where the inner preform is covered with the outer preform, and then blowing air into the inner preform in that state; the inner preform is a blow molded body, A method is provided wherein the blow molding step is performed with restrained stretching of the bottom of the outer preform.

[0044] Preferably, the outer preform has a reinforcing structure that inhibits expansion of the bottom portion of the outer preform. Preferably, the reinforcing structure is an annular protrusion provided on the bottom of the outer preform. Preferably, the blow molding step is carried out in a state in which the bottom of the outer preform is supported by a bottom support mold to suppress stretching of the bottom.

[0045] Also, from another perspective, A method for manufacturing a double container, comprising: A blow molding process is provided. The blow molding step is carried out by covering the inner preform with the outer preform, heating the inner preform and the outer preform to soften them, and then blowing air into the inner preform, the inner preform is a blow molded body, A method is provided wherein the outer preform has an annular protrusion at its bottom.

[0046] In another aspect of the invention, the position of the outside air introduction hole is not limited, and it may be provided in any of the mouth 5, body 6, or bottom 7 of the container body 2. Furthermore, the spacer 9 for forming a gap between the outer shell 3 and the inner bag 4 is not essential. [Explanation of symbols]

[0047] 1:Double container 2: Container body 3: Outer shell 3a: Insertion hole 3b: Protrusion 4: Inner bag 4a: Locking protrusion 4b: Flange 5: Mouth 5a: Engagement part 6: Body 6a: Upper end 7: Bottom 7a: Central recess 7a1: Locking part 7a2: Outside air intake 7a3: Annular convex part 7a4: Positioning recess 7b: Periphery 7b1: Grounding part 7b2: Peripheral recess 8: Gap 9: Spacer 13: Outer preform 13a: Mouth 13b: Torso 13c: Bottom 13c1 :Protrusion 13c2: Positioning hole 13c3: Outside air intake 13c4: Annular convex part 14: Inner preform 14a: Mouth 14a1: Flange 14b: Torso 14c: Bottom 14c1: Locating pin 14c2 :Protrusion 14d: innermost layer 14e: Gas barrier layer 14e1: Gas barrier layer 14e2: Gas barrier layer 14f: Outermost layer 14g: Bottom 14h: Pinch-off section 15: Assembly 20: Mold unit 21: Mouth support type 21a: Insertion hole 22: Bottom support type 22a: recess 22b: recess 22c: Drive mechanism 23: Molding mold 23a: Cavity surface 24: Molding mold 24a: Cavity surface 25: Support rod 26: Air passage G: Gap

Claims

1. A method for manufacturing a double container, comprising: A blow molding process is provided. The blow molding step is carried out by heating and softening the inner preform and the outer preform in a state where the inner preform is covered with the outer preform, and then blowing air into the inner preform in that state; the inner preform is a blow molded body, the blow molding step is carried out in a state where stretching of a bottom portion of the outer preform is suppressed, The method wherein the outer preform comprises a reinforcing structure that inhibits stretching of a bottom portion of the outer preform.

2. 10. The method of claim 1, The method, wherein the reinforcing structure is an annular protrusion provided on the bottom of the outer preform.

3. 3. The method of claim 1 or claim 2, The blow molding step is carried out in a state in which the bottom of the outer preform is supported by a bottom support mold to suppress stretching of the bottom.

4. The method according to claim 3, a bottom portion of the outer preform is provided with an annular convex portion and a positioning hole disposed in an area inside the annular convex portion; a positioning pin to be inserted into the positioning hole is provided at the bottom of the inner preform; The method further comprises: the bottom support mold having a recess capable of accommodating the locating pin; and supporting the bottom of the outer preform so as to accommodate the locating pin within the recess.

5. A method according to claim 3 or claim 4, a bottom portion of the outer preform is provided with an annular convex portion surrounding the center of the bottom portion of the outer preform; the bottom support mold has a recess capable of accommodating the annular protrusion, and supports the bottom of the outer preform so as to accommodate the annular protrusion within the recess; The method wherein the recess is annular.

6. A method for manufacturing a double container having an inner bag and an outer shell, A blow molding process is provided. The blow molding step is performed by heating and softening a preform including a portion that will become the inner bag and a portion that will become the outer shell, and then blowing air into the preform in that state; The blow molding step is carried out in a state where stretching of the bottom portion of the portion that will become the outer shell is suppressed, The shell portion includes a reinforcing structure that inhibits expansion of a bottom portion of the shell portion.

7. 7. The method of claim 6, The reinforcing structure is an annular protrusion provided at the bottom of the portion that will become the outer shell.

8. 8. The method of claim 6 or claim 7, The blow molding step is carried out in a state in which the bottom of the portion that will become the outer shell is supported by a bottom support mold, thereby suppressing stretching of the bottom.

9. The method of claim 8, a bottom portion of the portion that becomes the outer shell is provided with an annular protrusion and a positioning hole that is disposed in an area inside the annular protrusion; A positioning pin to be inserted into the positioning hole is provided at the bottom of the portion that will become the inner bag, The bottom support mold has a recess capable of accommodating the positioning pin, and supports the bottom of the portion that will become the outer shell so as to accommodate the positioning pin within the recess.

10. The method according to claim 8 or claim 9, a bottom portion of the portion that will become the outer shell is provided with an annular convex portion that surrounds the center of the bottom portion of the portion that will become the outer shell; the bottom support mold has a recess capable of accommodating the annular protrusion, and supports a bottom of the portion that becomes the outer shell so as to accommodate the annular protrusion within the recess; The method wherein the recess is annular.

11. A double container having an outer shell and an inner bag, the inner bag comprising a contractible container body, the container body is formed by blow molding a preform having a portion that becomes the inner bag and a portion that becomes the outer shell, The blow molding is performed in a state where stretching of the bottom portion of the portion that will become the outer shell is suppressed, The portion that becomes the outer shell has a reinforcing structure that suppresses the extension of the bottom portion of the portion that becomes the outer shell.

12. A double container having an outer shell and an inner bag, the inner bag comprising a contractible container body, The container body includes a cylindrical body portion and a bottom portion provided at a lower end of the body portion, The outer shell is provided with an annular protrusion at the bottom, A double container, wherein an outside air introduction hole is arranged in the outer shell in the region inside the annular convex portion.

13. A method for manufacturing a double container having an inner bag and an outer shell, comprising: A blow molding process is provided. The blow molding step is performed by heating and softening a preform including a portion that will become the inner bag and a portion that will become the outer shell, and then blowing air into the preform in that state; The blow molding step is carried out in a state where stretching of the bottom portion of the portion that will become the outer shell is suppressed, the portion that will become the outer shell has a reinforcing structure that suppresses extension of a bottom portion of the portion that will become the outer shell, the reinforcing structure is an annular convex portion provided at the bottom of the portion that becomes the outer shell, The method, wherein an outside air introduction hole is arranged in the outer shell in the region inside the annular protrusion.

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