Method for manufacturing container

Abstract

To provide a technique capable of suppressing air leakage from a gap between a preform and a blow core when a container body having a reduced diameter part at an opening end is manufactured by biaxial stretch blow molding.SOLUTION: According to the present invention, there is provided a method for producing a container, comprising a biaxial stretch blow molding step and a removal step, wherein, in the biaxial stretch blow molding step, a preform is subjected to biaxial stretch blow molding in a state in which the preform is attached to a blow core such that an insertion portion of the blow core is disposed inside the preform, the preform includes a tubular extension portion extending from a portion corresponding to an opening end of a container body of the container, the insertion portion is inserted into the extension portion, and in the cutting step, the extension portion is cut off after the biaxial stretch blow molding step. Since the container produced by the method of the present invention is excellent in recyclability, it can be suitably used for producing a recycled material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a container by biaxially stretched blow molding. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a container by biaxially stretching and blow molding a preform. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-130735 Summary of the Invention [Problem to be solved by the invention]

[0004] In one example, biaxial stretch blow molding is performed by placing a blow core inside a preform and blowing air through through holes in the blow core. Generally, the blow core abuts on the inner peripheral surface of the preform or has a shape that makes the gap between the blow core and the inner peripheral surface of the preform very small, thereby suppressing air leakage from the gap between the preform and the blow core.

[0005] In some cases, a sealing member is welded to the open end of a container to close the open end. In this case, a tapered portion is sometimes provided at the open end of the container by bending the outer circumferential surface of the container adjacent to the open end radially inward to ensure an area for welding the sealing member.

[0006] When a container having such a reduced diameter portion is formed by biaxial stretch blow molding, the preform and the blow core come into contact or are close to each other only at the inner peripheral surface of the reduced diameter portion. However, since the area of ​​this inner peripheral surface is very small, there is a problem in that air is likely to leak from the gap between the preform and the blow core.

[0007] The present invention has been made in consideration of these circumstances, and provides a technology that can suppress air leakage from the gap between the preform and the blow core when manufacturing a container body having a reduced diameter portion at the opening end by biaxial stretch blow molding. [Means for solving the problem]

[0008] According to the present invention, the following inventions are provided. [1] A method for manufacturing a container, comprising a biaxially stretched blow molding step and a cutting step, wherein in the biaxially stretched blow molding step, the preform is biaxially stretched blow molded while being attached to a blow core so that an insert portion of the blow core is positioned within the preform, the preform has a cylindrical extension portion extending from a portion corresponding to an open end of a container body of the container, the insert portion being inserted into the extension portion, and in the cutting step, the extension portion is cut off after the biaxially stretched blow molding step. [2] A method as described in [1], wherein the opening end after the cutting step is provided with a reduced diameter portion formed by bending the outer circumferential surface at a position adjacent to the opening end radially inward, and the method includes a contents filling step and a sealing step in this order after the cutting step, wherein the contents filling step fills the container body with contents, and the sealing step welds a sealing member to the upper surface of the reduced diameter portion to close the opening at the opening end. [3] The method according to [1] or [2], wherein the inner circumferential surface of the extension portion and the outer circumferential surface of the insertion portion are brought into contact with or close to each other. [4] A method according to any one of [1] to [3], wherein the preform is formed by covering an outer preform on an inner preform, the inner preform has a protruding portion protruding from an open end of the outer preform, and the extension portion is provided on the protruding portion. [Effects of the Invention]

[0009] In the method of the present invention, the preform has a cylindrical extension extending from a portion corresponding to the open end of the container body, and the insert portion of the blow core is inserted into the extension. Since the extension can be formed into any shape, by adopting a configuration in which the insert portion of the blow core is inserted into the extension, it is possible to suppress air leakage during biaxial stretch blow molding. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view of a container 10 according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an exploded view of the container 10 in FIG. [Figure 3] 2 is a cross-sectional view of the vicinity of the mouth 5 of the container 10 of FIG. 1. [Figure 4] 4 is a cross-sectional view showing a state in which a discharge member 43 is separated from the state shown in FIG. 3. FIG. [Figure 5] 5 is a cross-sectional view showing a state in which the main body member 41 is separated from the state shown in FIG. 4. FIG. [Figure 6] FIG. 2 is a cross-sectional view showing a state in which the inner preform 14 and the outer preform 13 are separated. [Figure 7] 1 is a cross-sectional view of a preform 15 and a blow core 21. FIG. [Figure 8] 1 is a cross-sectional view showing a state in which a preform 15 is attached to a blow core 21 and brought close to a heater 32. FIG. [Figure 9] FIG. 2 is a cross-sectional view illustrating biaxial stretch blow molding of a preform 15. [Figure 10] FIG. 2 is a cross-sectional view of a molded body 2a obtained by biaxial stretch blow molding. [Figure 11] FIG. 10 is a cross-sectional view showing a comparative preform 15X and a blow core 21. 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 invention independently. Furthermore, in the following embodiments, elements not specified in the claims are optional elements and can be omitted. Any number of "0"s (for example, one or two) may be added to the end of numerical values ​​disclosed in the following description. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400."

[0012] 1. First embodiment A first embodiment of the present invention will be described with reference to FIGS.

[0013] 1-1. Configuration of the container 10 <Basic configuration> As shown in FIGS. 1 and 2, a container 10 according to a first embodiment of the present invention includes a container body 2 and a spout attachment member 8. The container 10 is a bottle-shaped container capable of holding beverages, seasonings, and the like. The container 10 may be a single-walled container or a double-walled container. The following description will be given using the container 10 as a double-walled container 1 as an example. In the following description, terms related to directions, such as "upper" and "lower," refer to directions when the bottom 7 is in contact with the ground. In addition, in the following description, the "axial direction" refers to the direction in which the central axis C (shown in FIG. 2) of the spout 5 extends, e.g., the direction in which the inner bag 4 is pulled out of the container body 2. The "circumferential direction" refers to the rotational direction about the central axis C of the spout 5, e.g., the direction in which the inner bag 4 is rotated relative to the outer shell 3 at the spout 5. Unless otherwise specified, "clockwise" and "counterclockwise" refer to directions as viewed from above the double-walled container 1.

[0014] 2, 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 open end 5c is the open end of the container body 2 and also the open end of the inner bag 4.

[0015] The body 6 is disposed adjacent to the mouth 5 on a 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 equivalent circular diameter when 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 on the bottom 7 side of the shoulder 6b. The body main body 6c has a shape in which the outer diameter is approximately constant toward the bottom 7, or a shape in which the diameter decreases toward the bottom 7, for example.

[0016] As shown in Figures 3 to 6, 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 has an inner bag body 4d other than the protruding portion 4c housed within the outer shell 3. 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] <Detailed structure of outer shell 3 and inner bag 4> 4 and 5, engaging portions 4c6 and 4c3 are provided in this order from the opening end 5c side on the protruding portion 4c of the inner bag 4. First and second flange portions 3f1 and 3f2 are provided in this order from the opening end 3a side on the outer shell 3.

[0018] As shown in Fig. 5, the inner bag 4 includes a first tube 4a and a second tube 4b. The first tube 4a is disposed within the outer shell 3. The second tube 4b has a larger outer diameter than the first tube 4a and is disposed closer to the open end 5c of the inner bag 4 than the first tube 4a. The entire second tube 4b may be disposed outside the outer shell 3, or part or all of the second tube 4b may be disposed within the outer shell 3, with the remainder disposed outside the outer shell 3.

[0019] A lower surface 4b4 of the second tube 4b abuts against the outer shell 3. The lower surface 4b4 abuts against an inner bag support surface 3a3 provided on the outer shell 3. The lower surface 4b4 is supported by the inner bag support surface 3a3, thereby preventing the inner bag 4 from falling off into the outer shell 3. The inner bag support surface 3a3 may be flush with the opening edge 3a, or may be provided at a lower position than the opening edge 3a. In this embodiment, the inner bag support surface 3a3 is provided at a lower position than the opening edge 3a. Therefore, a portion of the second tube 4b is disposed inside the outer shell 3, and the remainder is disposed outside the outer shell 3.

[0020] A cam mechanism is preferably provided between the inner bag 4 and the outer shell 3. The cam mechanism functions to displace the inner bag 4 in a direction that allows it to be removed from the container body 2 by rotating the inner bag 4 clockwise or counterclockwise relative to the outer shell 3. This cam mechanism can be configured, for example, by a ridge provided on the outer peripheral surface of the inner bag 4 and a cam rail provided on the inner peripheral surface of the outer shell 3. When the inner bag 4 is rotated relative to the outer shell 3 at the opening 5, the inner bag 4 is twisted and its diameter is reduced, making it even easier to pull out.

[0021] <Mouth attachment part 8> The spout-mounted member 8 is a member that is attached to the spout 5 of the container body 2. As shown in Fig. 3, the spout-mounted member 8 includes a main body member 41 and a discharge member 43. The discharge member 43 has a discharge opening 43a that communicates with the interior of the inner bag 4.

[0022] 5, an insertion hole 41h through which the protrusion 4c is inserted is provided in the main body member 41. The protrusion 4c is inserted into the insertion hole 41h.

[0023] The main body member 41 includes an inner tube 41b and a main body member seal tube 41d. The inner tube 41b has a smaller outer diameter than the main body member seal tube 41d. The main body member seal tube 41d is provided with an engaging protrusion 41d4 that axially engages with the protrusion 4c. The engaging protrusion 41d4 axially engages with the protrusion 4c (more specifically, with the engaging portion 4c3), thereby axially engaging the main body member 41 with the protrusion 4c. It is also preferable that the main body member seal tube 41d circumferentially engages with the protrusion 4c. In this case, the protrusion 4c can be rotated in conjunction with the rotation of the main body member 41. The inner tube 41b and the main body member seal tube 41d are connected to each other at a top surface 41g. An insertion hole 41h is provided in the top surface 41g.

[0024] As shown in Fig. 4, the inner peripheral surface 41d2 of the main body member sealing tube 41d and the outer peripheral surface 3g4 of the outer shell 3 at a position adjacent to the open end 3a thereof are in close contact with each other at a contact surface 51. The contact surface 51 is preferably inclined with respect to the axial direction. This inclination angle is, for example, 0.5 to 15 degrees (7.5 degrees in this embodiment), and preferably 3 to 10 degrees. Specific examples of this inclination angle include 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 11, 12, 13, 14, and 15 degrees, and may be in a range between any two of the values ​​exemplified here.

[0025] The main body member sealing tube 41d does not engage with the outer shell 3 in a convex-concave manner. Because the main body member sealing tube 41d and the outer shell 3 are in close contact with each other, they are frictionally engaged, but the convex portions of one do not fit into the concave portions of the other. This allows the main body member sealing tube 41d to be quickly detached from the outer shell, preventing an increase in the force required to pull out the inner bag 4. Furthermore, because the contact surface 51 is inclined to prevent undercuts, the contact at the contact surface 51 can be broken by slightly moving the main body member 41 away from the outer shell 3. This prevents an increase in the force required to pull out the inner bag 4 due to friction at the contact surface 51.

[0026] The inner peripheral surface 41b1 of the inner cylinder 41b is in close contact with the outer peripheral surface 4c7 of the protruding portion 4c. A contact surface 52 between the inner peripheral surface 41b1 of the inner cylinder 41b and the outer peripheral surface 4c7 of the protruding portion 4c is preferably inclined with respect to the axial direction. The inclination angle is, for example, 0.5 to 15 degrees (6.7 degrees in this embodiment), and preferably 3 to 10 degrees. Specific examples of the inclination angle are 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 11, 12, 13, 14, and 15 degrees, and may be within a range between any two of the values ​​exemplified here.

[0027] According to this configuration, the main body member 41 is in close contact with both the outer shell 3 and the inner bag 4, so that an airtight space can be formed between the outer shell 3 and the inner bag 4.

[0028] As shown in FIG. 4, the discharge member 43 is attached to a tip portion 4c5 that protrudes from the main body member 41 through an insertion hole 41h of the protrusion 4c. More specifically, an engagement portion 4c6 is provided in the tip portion 4c5, and the discharge member 43 is attached to the tip portion 4c5 by engaging with the engagement portion 4c6. In this embodiment, the engagement portion 4c6 is a male thread portion 4c12 provided on the outer surface of the tip portion 4c5, and this male thread portion is threadedly engaged with a female thread portion 43b provided on the inner circumferential surface of the discharge member 43. The discharge member 43 may be attached to the tip portion 4c5 in a plug-type manner.

[0029] As shown in FIG. 4, the discharge member 43 includes a discharge member main body 45 and an overcap 46. The discharge member main body 45 includes a nozzle 45a and an engaging tube 45b. The nozzle 45a and the engaging tube 45b are connected to each other at a top surface 45c. The nozzle 45a is provided with a discharge port 45d that communicates with the interior of the inner bag 4, allowing the contents of the inner bag 4 to be discharged through the nozzle 45a and the discharge port 45d. The nozzle 45a is provided with a discharge valve 42. The discharge valve 42 is configured to allow the contents to be discharged while preventing outside air from entering the inner bag 4. The discharge port 45d can be closed using the overcap 46. When in use, the overcap 46 can be removed to open the discharge port 45d and discharge the contents.

[0030] 5, the open end 5c of the protrusion 4c has a reduced diameter portion 4c9 formed by bending the outer peripheral surface of the protrusion 4c adjacent to the open end 5c radially inward. If the inner diameter of the reduced diameter portion 4c9 is Di and the outer diameter is Do, Di / Do is, for example, 0.50 to 0.95 (0.70 in this embodiment), and preferably 0.76 to 0.90. Specific examples of this value include 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, and 0.95, and may be within a range between any two of the values ​​exemplified here.

[0031] If the thickness of the reduced diameter portion 4c9 at the inner circumferential surface 4c13 is T, the value of {(Do - Di) / T} is, for example, 2.5 or more (7.2 in this embodiment), and preferably 4 or more. This value is, for example, 2.5 to 15, and preferably 4 to 10, and specifically, for example, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0, 11, 12, 13, 14, or 15, and may be in a range between any two of the values ​​exemplified here. The thickness T is, for example, 0.40 to 1.20 mm, and preferably 0.50 to 1.00 mm. Specific examples of this thickness include 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, and 1.20 mm, and may be in a range between any two of the values ​​exemplified here.

[0032] A sealing member 44 is welded to an upper surface 4c10 of the reduced diameter portion 4c9. In one example, the sealing member 44 is configured by laminating a sealant layer and a gas barrier layer, and the sealant layer is welded to the upper surface 4c10. In one example, the gas barrier layer is an aluminum layer. By welding the sealing member 44 configured in this way to the upper surface 4c10 and closing the opening 4c11 of the open end 5c, deterioration of the contents within the inner bag 4 is suppressed. At the start of use, the discharge member 43 can be temporarily removed, the sealing member 44 can be peeled off, and then the discharge member 43 can be reattached to the tip portion 4c5.

[0033] The upper surface 4c10 of the reduced diameter portion 4c9 is preferably inclined so as to rise toward the radial center of the protruding portion 4c (i.e., toward the outside of the protruding portion 4c in the axial direction). The inclination angle of the upper surface 4c10 with respect to the horizontal plane (i.e., a plane perpendicular to the axial direction) is, for example, 1 to 25 degrees (12 degrees in this embodiment), and preferably 5 to 20 degrees. When this inclination angle is within the above range, welding defects of the seal member 44 are unlikely to occur. Specifically, this inclination angle may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25 degrees, or may be within a range between any two of the values ​​exemplified here.

[0034] <Use of double container 1> In this embodiment, the discharge valve 42 is provided in the opening-mounted member 8, so that the inner bag 4 contracts as the contents of the inner bag 4 are discharged. Furthermore, by providing an air inlet hole that can introduce outside air into the intermediate space between the outer shell 3 and the inner bag 4, a peelable container can be created in which the inner bag 4 separates from the outer shell 3 and contracts as the contents are discharged. The air inlet hole may be provided in either the outer shell 3 or the opening-mounted member 8. Furthermore, an air inlet valve may be provided in the air inlet hole to allow outside air to be introduced into the intermediate space while suppressing the discharge of outside air from the intermediate space. In this case, compressing the outer shell 3 increases the pressure in the intermediate space, allowing the contents to be discharged from the inner bag 4. When the compressive force on the outer shell 3 is removed and the outer shell 3 returns to its original shape, the introduction of outside air into the intermediate space allows the outer shell 3 to quickly restore its original shape. This configuration makes it possible to realize a squeeze-type peelable container. The double-walled container 1 of this embodiment is characterized by its ability to easily form an airtight space between the outer shell 3 and the inner bag 4, so it is preferable to use it as a squeeze-type peelable container.

[0035] <Pull out inner bag 4> Because the main body member 41 is engaged with the protruding portion 4c in the axial direction, the inner bag 4 can be pulled out of the container body 2 by pulling the main body member 41. Furthermore, if the main body member 41 is also engaged with the protruding portion 4c in the circumferential direction, the inner bag 4 can be twisted and reduced in diameter by rotating the main body member 41. This reduces the force required to pull out the inner bag 4.

[0036] Furthermore, if a cam mechanism is provided between the inner bag 4 and the outer shell 3, the inner bag 4 is configured to move in a direction to be removed from the container body 2 as the inner bag 4 rotates. With this configuration, by rotating the main body member 41, the inner bag 4 can be moved in a direction to be removed from the container body 2 while twisting, and then the inner bag 4 can be pulled out of the container body 2 by pulling the main body member 41.

[0037] 1-2. Manufacturing method of container 10 The container body 2 can be manufactured by a method including a biaxially stretched blow molding process and a cutting process. The container 10 can be manufactured by attaching the mouth attachment member 8 to the container body 2.

[0038] 1-2-1. Preform 15 The preform 15 includes an inner preform 14 that will become the inner bag 4 and an outer preform 13 that will become the outer shell 3.

[0039] As shown in Fig. 6, the inner preform 14 is cylindrical with a bottom and includes a mouth portion 14a, a body portion 14b, and a bottom portion 14c. The bottom portion 14c is provided so as to close the lower end of the body portion 14b. The mouth portion 14a is provided with a protruding portion 14d. As shown in Fig. 7, the protruding portion 14d is a portion of the preform 15 that protrudes from the open end 13f of the outer preform 13. The protruding portion 14d does not deform during molding and remains in its original shape to become the protruding portion 4c.

[0040] As shown in Figures 6 and 7, the inner preform 14 has a cylindrical extension 14f extending from a portion 14e corresponding to the open end 5c of the container body 2. The extension 14f is provided on the protruding portion 14d. The extension 14f has, in order from the open end 14g side of the inner preform 14, an expanded diameter portion 14h and a reduced diameter portion 14i. The reduced diameter portion 14i has an inner diameter smaller than that of the expanded diameter portion 14h. The expanded diameter portion 14h and the reduced diameter portion 14i are connected by an inclined portion 14j.

[0041] 6, 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.

[0042] As shown in FIG. 7, the preform 15 can be formed by covering the inner preform 14 with the outer preform 13. The mouth portions 13a, 14a become the mouth portion 15a of the preform 15, the body portions 13b, 14b become the body portion 15b of the preform 15, and the bottom portions 13c, 14c become the bottom portion 15c of the preform 15. During biaxial stretch blow molding, the portion closer to the bottom portion 15c than the flange 13d (the body portion 15b and the bottom portion 15c) is mainly stretched. The mouth portion 15a is hardly deformed during molding and becomes the mouth portion 5 of the container body 2. The above-described configuration included in the mouth portion 5 can also be applied to the configuration included in the mouth portion 15a, as long as it is not contrary to the spirit thereof.

[0043] The inner preform 14 and the outer preform 13 can be formed by direct blow molding or injection molding using a thermoplastic resin such as polyester (e.g., PET) or polyolefin (e.g., polypropylene, polyethylene). The outer preform 13 is preferably formed by injection molding. The inner preform 14 is preferably formed by direct blow molding using a molten cylindrical parison. Direct blow molding has the advantage that it is easier to make thinner and multi-layered parts than injection molding.

[0044] 1-2-2. Biaxial stretch blow molding process The biaxial stretch blow molding process will be described with reference to Figures 7 to 9. In the biaxial stretch blow molding process, the preform 15 is attached to the blow core 21 so that the insertion portion 21b of the blow core 21 is positioned within the preform 15, and the preform 15 is then biaxially stretch blow molded.

[0045] In one example, the biaxial stretch blow molding process includes a mounting step, a heating step, and a stretching step. Each step will be described below.

[0046] <Installation process> In the mounting step, as shown in FIGS. 7 and 8, the preform 15 is mounted to the blow core 21 so that the insertion portion 21b of the blow core 21 is positioned within the preform 15 (more specifically, the extension portion 14f). The blow core 21 includes a base portion 21a, an insertion portion 21b, and a through-hole 21c. The insertion portion 21b is provided so as to protrude from the base portion 21a. The insertion portion 21b is tapered, making it easier to insert the insertion portion 21b into the extension portion 14f of the preform 15.

[0047] The insertion portion 21b has, in order from the distal end 21g side, a reduced diameter portion 21h, an inclined portion 21i, and an expanded diameter portion 21j. The reduced diameter portion 21h has a smaller outer diameter than the expanded diameter portion 21j. The expanded diameter portion 21j and the reduced diameter portion 21h are connected by the inclined portion 21i. The reduced diameter portion 21h, the inclined portion 21i, and the expanded diameter portion 21j have shapes corresponding to the reduced diameter portion 14i, the inclined portion 14j, and the expanded diameter portion 14h, respectively, and preferably have complementary shapes. As shown in FIG. 8, when the insertion portion 21b is inserted into the extension portion 14f, it is preferable that at least one (preferably two or three) of the reduced diameter portion 21h, the inclined portion 21i, and the expanded diameter portion 21j abut or come into close proximity to the reduced diameter portion 14i, the inclined portion 14j, and the expanded diameter portion 14h, respectively. For example, the inclined portion 21i can be in contact with the inclined portion 14j, the reduced diameter portion 21h can be in contact with or close to the reduced diameter portion 14i, and the expanded diameter portion 21j can be in contact with or close to the expanded diameter portion 14h. By providing the extension portion 14f as in this embodiment, it is possible to make the inner circumferential surface of the inner preform 14 and the outer circumferential surface of the insertion portion 21b face each other over a wide area, and by making the inner circumferential surface of the extension portion 14f in contact with or close to the outer circumferential surface of the insertion portion 21b, leakage of air from a gap between the inner preform 14 and the blow core 21 during biaxial stretch blow molding is suppressed.

[0048] For example, in a comparative preform 15X in which the inner preform 14 does not have an extension 14f, as shown in Figure 11, the inner preform 14 and the blow core 21 come into contact or are close to each other only at the inner surface 14e1 of the portion 14e corresponding to the opening end 5c of the container body 2. However, since the area of ​​the inner surface 14e1 is very small, air leakage is likely to occur from the gap between the inner preform 14 and the blow core 21.

[0049] Furthermore, the preform 15 is preferably transported while being supported by the blow core 21, and by providing the extension 14f, the preform 15 can be stably supported by the blow core 21. On the other hand, as shown in Fig. 11, if the inner preform 14 does not have the extension 14f, the preform 15 is supported by the blow core 21 at the inner peripheral surface 14e1, which has a small area, and the supporting state is likely to become unstable.

[0050] <Heating process> The heating step can be performed using a heating device 35 shown in FIG. 8. In the heating step, the preform 15 is heated and softened to a softened state. In one example, the heating step can be performed by placing the preform 15 near a heater 32 while the preform 15 is attached to a blow core 21, as shown in FIG. 8. The heating step is performed by heating the body portion 15b and bottom portion 15c while the flange 13d provided on the preform 15 is covered with a heat shield 33. This softens the body portion 15b and bottom portion 15c. On the other hand, the flange 13d and the mouth portion 15a covered with the heat shield 33 receive little or no heat from the heater 32 and are not softened. In one example, the preform 15 can be heated while being rotated. In one example, the heater 32 is composed of multiple rod-shaped heaters arranged along the side of the preform 15, but other configurations are also possible.

[0051] <Stretching process> The stretching step can be performed using a blow molding apparatus 36 shown in Fig. 9. In the stretching step, the softened preform 15 is stretched. In one example, the stretching step includes a first stretching step and a second stretching step.

[0052] ·First stretching process In the first stretching step, the preform 15 is stretched along a first axial direction (i.e., the vertical direction). The first axis is, for example, a direction parallel to the central axis C of the mouth portion 5, which is the vertical direction in FIG. 9. In one example, as shown in FIG. 9, this step can be performed by setting the heated preform 15 in a molding die 23, supporting the bottom 15c of the preform 15 with a bottom support die 22, and then pressing a stretch rod 25 inserted through a through hole 21c provided in a blow core 21 against the inner bottom surface of the inner preform 14 to stretch it. At this time, it is preferable to retract the bottom support die 22 in synchronization with the stretching of the stretch rod 25. This allows the preform 15 to be stably stretched.

[0053] The preform 15 can be transferred from the heating device 35 to the blow molding device 36 while supported by the blow core 21. The molding die 23 is composed of a split mold that can be opened and closed, and includes a cavity surface 23a that corresponds to the outer surface shape of the container body 2, and a flange accommodating portion 23b that can accommodate the flange 13d. The preform 15 is set in the molding die 23 so that the flange 13d is disposed within the flange accommodating portion 23b. The first stretching step can be performed in a state where the flange 13d is pressed against the opposing surface 23c that faces the flange 13d in the first axial direction.

[0054] ·Second stretching process In the second stretching step, after the first stretching step, air is blown into the inner preform 14 to stretch (i.e., expand) the preform 15 in the second axial direction (i.e., the lateral direction) and shape it into the shape of the cavity surface 23a. Air can be blown in through the through holes 21c provided in the blow core 21. In this embodiment, the provision of the extensions 14f prevents air from leaking from the gap between the inner preform 14 and the blow core 21, thereby suppressing the occurrence of molding defects.

[0055] Through the above steps, a molded body 2a having a structure in which the extension portion 14f is connected to the container body 2 as shown in FIG. 10 is obtained.

[0056] 1-2-3. Excision process In the cutting step, after the biaxially stretched blow molding step, the extension 14f is cut off along the dotted line 47. This results in the container body 2 having the structure shown in Fig. 5. After the cutting step, the open end 5c has a reduced diameter portion 4c9 formed by bending the outer circumferential surface at a position adjacent to the open end 5c radially inward.

[0057] 1-2-4. Content filling process and sealing process The cutting step may be followed by a content filling step and a sealing step, in this order. In the content filling step, the container body 2 is filled with content. Examples of the content include mayonnaise and sauce. In the sealing step, a sealing member 44 is welded to the upper surface 4c10 of the reduced diameter portion 4c9 to close the opening 4c11 at the open end 5c. This prevents the content from deteriorating.

[0058] 2. Other embodiments In the above embodiment, the preform 15 is a two-body structure of the inner preform 14 and the outer preform 13, but it may also be a one-body structure. In this case, an extension portion 14f is provided on the preform 15. In this case, the description of the inner preform 14 in the above embodiment can be read as a description of the preform 15, as long as it does not contradict the spirit of the description. [Explanation of symbols]

[0059] 1:Double container 2: Container body 2a: Molded object 3: Outer shell 3a: Open end 3a3: inner bag support surface 3f1: First flange 3f2: Second flange part 3g4: Outer surface 4: Inner bag 4a: 1st tube 4b: 2nd tube 4b4:Bottom surface 4c:Protrusion 4c10:Top surface 4c11: Opening 4c12: Male thread part 4c3: Engagement part 4c5:Tip part 4c6: Engagement part 4c7: Outer surface 4c9: Reduced diameter part 4d: Inner bag body 5: Mouth 5c: Open end 6: Body 6b:Shoulder 6c: Body 7: Bottom 8: Mouth attachment member 10: Container 13: Outer preform 13a: Mouth 13b: Torso 13c: Bottom 13d: Flange 13f: Open end 14: Inner preform 14a: Mouth 14b: Torso 14c: Bottom 14d:Protrusion 14e: Part 14e1: Inner surface 14f: Extension part 14g: Open end 14h: Expanded diameter part 14i: Reduced diameter part 14j: Inclined part 15: Preform 15X: Preform 15a: Mouth 15b: Body 15c: bottom 21: Blow Core 21a: base 21b: Insertion part 21c: Through hole 21g: Tip 21h: Reduced diameter part 21i: Inclined part 21j: Expanded diameter part 22: Bottom support type 23: Molding mold 23a: Cavity surface 23b: flange housing 23c: Opposite surface 25: Stretching rod 32: Heater 33: Heat shielding section 35: Heating device 36: Blow molding equipment 41: Main body member 41b: Inner cylinder 41b1: Inner peripheral surface 41d: Main body member seal tube 41d2: Inner peripheral surface 41d4: Engagement protrusion 41g:Top part 41h: Insertion hole 42: Discharge valve 43: Discharge member 43a:Discharge port 43b: Female thread 44: Sealing material 45: Discharge member body 45a: Nozzle 45b: Engagement tube 45c: Top part 45d:Discharge port 46: Overcap 47:Dotted line 51: Contact surface 52: Contact surface C: Central axis

Claims

1. A method for manufacturing a container, comprising a biaxially stretched blow molding step and a cutting step, In the biaxially stretched blow molding step, the preform is biaxially stretched blow molded in a state in which the preform is attached to the blow core so that an insertion portion of the blow core is disposed within the preform, the preform has a cylindrical extension portion extending from a portion corresponding to an open end of the container body of the container, the insert portion is inserted into the extension portion; The method, wherein the cutting step includes cutting off the extension portion after the biaxially stretch blow molding step.

2. 10. The method of claim 1, The opening end after the cutting step is provided with a reduced diameter portion formed by bending an outer circumferential surface at a position adjacent to the opening end radially inward, a content filling step and a sealing step are provided in this order after the cutting step, The content filling step includes filling the container body with a content, In the sealing step, a seal member is welded to an upper surface of the reduced diameter portion to close the opening at the open end.

3. 10. The method of claim 1, The method wherein an inner circumferential surface of the extension portion and an outer circumferential surface of the insertion portion are brought into contact or proximity.

4. The method according to any one of claims 1 to 3, The preform is configured by covering an outer preform with an inner preform, the inner preform has a protruding portion protruding from an open end of the outer preform, The method wherein the extension is provided on the protrusion.

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