Method for manufacturing a resin-made container and manufacturing apparatus

Abstract

A method for manufacturing a resin container includes an injection molding step of injection molding a resin preform having a bottomed cylindrical shape in which a strength in a circumferential direction is different, and a blow molding step of blow molding the preform in a state in which heat is retained at the time of injection molding to manufacture the container. In the injection molding step, an injection mold in which a convex portion is partially formed in the circumferential direction of the bottom is used, at least one of a flow rate and a temperature of resin passing through the convex portion is changed, and thereby a region in which the strength is higher than other portions in the circumferential direction is formed in the preform from a corresponding position of the convex portion as a starting point.

Description

Technical Field

[0001] This invention relates to a method and apparatus for manufacturing resin containers. Background Technology

[0002] Traditionally, resin containers that shrink as their contents are discharged, such as the inner layer of a peelable container with a double-layer structure or a bag-in-a-box (BIB) container inserted into an outer box such as a corrugated cardboard box, are manufactured by blow molding.

[0003] In such containers, it is known that the strength of the main body of the container varies regularly in the circumferential direction, so as to guide the shrinkage deformation in a suitable and regular manner accompanying the discharge of the contents. This structure can be manufactured, for example, by blow molding a preform with regularly varying wall thickness and temperature distribution in the circumferential direction, as in Patent Documents 1 and 2, or by blow molding using a mold with concave and convex grooves on the main body for shrinkage guidance, as in Patent Document 3.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-142186

[0007] Patent Document 2: Japanese Patent No. 3255485

[0008] Patent Document 3: Japanese Patent No. 4588200 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] When using the above method to create a structure in a container that guides shrinkage, the structure for guiding shrinkage can easily become conspicuous. For example, if the container is entirely transparent, a conspicuous shrinkage-guiding structure can negatively impact the container's aesthetics.

[0011] Therefore, the present invention was made in view of such a problem, and its object is to provide a method for manufacturing a resin container in which the structural parts for shrinkage guidance in the container are not conspicuously formed.

[0012] Technical solutions for solving the problem

[0013] A method for manufacturing a resin container according to one aspect of the present invention includes: an injection molding step, in which a bottomed cylindrical resin preform with different circumferential strength distribution is injection molded; and a blow molding step, in which the preform is blow molded while still heated during injection molding to manufacture a container. In the injection molding step, an injection mold having a portion of a protrusion formed in the circumferential direction at the bottom is used, and at least one of the resin flow rate and temperature passing through the protrusion is varied, thereby forming a region in the preform with higher strength than other circumferential regions, starting from the corresponding position of the protrusion.

[0014] Invention Effects

[0015] According to one aspect of the present invention, it is possible to make the structural portion for guiding shrinkage in the container less conspicuous. Attached Figure Description

[0016] Figure 1 (a) is a longitudinal sectional view of the pre-plasticized preform of this embodiment, and (b) is a bottom view of the pre-plasticized preform.

[0017] Figure 2 (a) is a front view of the stripping container of this embodiment, and (b) is a bottom view of the stripping container of this embodiment.

[0018] Figure 3 This is a longitudinal sectional view of the stripping container in this embodiment.

[0019] Figure 4 This is a cross-sectional view near the bottom of an example of a peeling container showing the state after the inner layer has shrunk.

[0020] Figure 5 This is a schematic diagram illustrating the structure of the blow molding apparatus of this embodiment.

[0021] Figure 6 This is a diagram illustrating the manufacturing process of the preform in this embodiment.

[0022] Figure 7 This is a diagram showing the area near the bottom of the first layer in the first injection molding section.

[0023] Figure 8 This is a diagram showing the area near the bottom of the preform in the second injection molding section.

[0024] Figure 9 This is a flowchart illustrating the process of manufacturing a stripping container.

[0025] Figure 10 This is a diagram showing the area near the bottom of the injection-molded portion in a modified example of this embodiment. Detailed Implementation

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In this embodiment, a peeling container will be described as an example of a resin container (hereinafter also simply referred to as a container) that is capable of shrinking as its contents are discharged.

[0027] In the embodiments, for ease of understanding and explanation, structures and elements other than the main parts of the invention are simplified or omitted in the description. Furthermore, in the accompanying drawings, the same elements are labeled with the same symbols. Additionally, the shapes, dimensions, etc., of the elements shown in the accompanying drawings are only schematic representations and do not represent actual shapes, dimensions, etc.

[0028] <Structural Example of Preform>

[0029] First, refer to Figure 1 Hereinafter, a structural example of the pre-plasticized blank for the peeling container according to this embodiment will be described. Figure 1 (a) is a longitudinal sectional view of the pre-plasticized preform 10 of this embodiment. Figure 1 (b) is a bottom view of the preform 10.

[0030] The preform 10 has an overall shape of a bottomed cylindrical shape with one end open and the other end closed. The preform 10 includes: a main body 14 formed in a cylindrical shape; a bottom 15 that closes the other end of the main body 14; and a neck 13 with an opening formed at one end of the main body 14.

[0031] The preform 10 has a double-layer structure in which a second layer (inner layer) 12 is laminated inside a first layer (outer layer) 11. The first layer 11 and the second layer 12 are formed from different thermoplastic resin materials through a two-stage injection molding process, as described later. For example, the first layer 11 is made of a synthetic resin with excellent moldability and transparency. On the other hand, the second layer 12 is made of a synthetic resin with properties that can stably retain the contents of a container and inhibit deterioration (oxidation) (e.g., moisture barrier, gas barrier, heat resistance, chemical resistance). Furthermore, the resin material of the first layer 11 is selected to have a higher melting point than the resin material of the second layer 12.

[0032] Furthermore, the above-mentioned relationship does not necessarily need to be satisfied as long as the melting point of the resin material in the first layer 11 is higher than that of the resin material in the second layer 12. For example, the resin material in the first layer 11 can also be a resin material with higher moisture barrier properties, gas barrier properties, heat resistance, and chemical resistance than the resin material in the second layer 12.

[0033] Hereinafter, the resin material of the first layer 11 will also be referred to as the first resin material, and the resin material of the second layer 12 will also be referred to as the second resin material.

[0034] The combination of the first and second resin materials can be appropriately selected according to the specifications of the peeling container. Specific types of materials include, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexanediol terephthalate), Tritan (TRITAN: a copolyester manufactured by Eastman Chemical Company), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic acid), PLA (polylactic acid), etc.

[0035] As an example, the first resin material is PET (polyethylene terephthalate), and the second resin material is PP (polypropylene). The melting point of PP is about 160-170℃, while the melting point of PET is higher than that of PP, at about 245-260℃.

[0036] Furthermore, in the main body 14 of the preform 10, the ratio (t1 / t2) of the thickness t1 of the first layer 11 to the thickness t2 of the second layer 12 is preferably 1.5 or more. From the viewpoint of ensuring the transparency of the formed release container, this thickness ratio is preferably 3.0 or less.

[0037] Additionally, an opening 16 is formed at the bottom 15 of the preform 10, penetrating the center of the bottom of the first layer 11. The opening 16 of the first layer 11 is blocked from the inside by the second layer 12.

[0038] Furthermore, a plurality of recesses 17 for forming air inlet holes on the peeling container are formed radially from the center of the bottom 15 of the preform 10. The recesses 17 are generally circular in shape and are formed at radial intervals from the opening 16. For example, two or more recesses 17 are formed with rotational symmetry about the center of the bottom 15 of the preform 10, preferably four. In this embodiment, an example with four recesses 17 is shown.

[0039] The depth of the recess 17 in the thickness direction of the preform 10 is set to a size such that the recess 17 penetrates the first layer 11 and exposes the surface of the second layer 12 within the recess 17. Furthermore, the recess 17 formed in the preform 10 with a double-layer structure is an example of a second recess.

[0040] Furthermore, a plurality of rib-like first regions 19 extending radially outward from the recesses 17 are formed in the second layer 12. Two or more first regions 19 are formed circumferentially with respect to the center of the bottom 15 of the preform 10, preferably four. Compared to other circumferential regions of the preform 10 (also referred to as second regions), the first regions 19 have different resin density and / or resin orientation, exhibiting characteristics of being difficult to deform in the circumferential and inner diameter directions. For example, the resin density in the first regions 19 is higher than that in the second regions. Additionally, in the first regions 19, the resin orientation is directional in the length direction from the bottom 15 towards the neck 13, whereas in the second regions, the resin orientation deviates from that of the first regions 19 in a direction intersecting the aforementioned length direction.

[0041] Furthermore, the first region 19 in the second layer 12 is difficult to distinguish from the second region visually, but it can be identified by methods such as strain measurement based on photoelasticity.

[0042] <Example of a peeling container structure>

[0043] Next, refer to Figure 2 , Figure 3 , Figure 4 Hereinafter, an example of the structure of the resin-made peeling container 20 according to this embodiment will be described. Figure 2 (a) and (b) are the front view and bottom view of the stripping container 20 in this embodiment. Figure 3 This is a longitudinal sectional view of the stripping container 20 according to this embodiment. Additionally, Figure 4 This is a cross-sectional view near the bottom of an example of a peeling container 20, showing the state after the inner layer has shrunk.

[0044] The release container 20 is a bottle-shaped resin container obtained by stretch blow molding a preform 10, for example, for holding condiments such as soy sauce. Furthermore, the release container 20 can also be used to hold other contents such as cosmetic liquids.

[0045] like Figure 3 As shown, the stripping container 20, like the preform 10, has a double-layer structure in which a bag-shaped second layer 12 is stacked inside the first layer 11. In the main body 22 of the stripping container 20, the ratio of the thickness t11 of the first layer 11 to the thickness t12 of the second layer 12 (t11 / t12) is approximately the same as the thickness ratio (t1 / t2) in the main body 14 of the preform 10.

[0046] like Figure 2As shown in (a), the peeling container 20 has: a neck 21 with an opening at its upper end; a cylindrical main body 22 continuous from the neck 21; and a bottom 23 continuous from the main body 22. Furthermore, the main body 22 may also have the following shape: a shoulder 22a connected at one end to the neck 21 and extending radially toward the other end; a main body 22c connected at the other end to the bottom 23; and a constricted neck 22b connected to the other end of the shoulder 22a and one end of the main body 22c, respectively, connecting the shoulder 22a and the main body 22c. Furthermore, the cross-section of the peeling container 20 is approximately circular at any position in the axial direction.

[0047] In the manufacturing of the release container 20, the main body 14 and bottom 15 of the preform 10 are expanded by stretch blow molding, shaping the main body 22 and bottom 23 of the release container 20. Additionally, during stretch blow molding, the recesses 17 of the preform 10 are stretched, such as... Figure 2 As shown in (b), four air inlet holes 24 penetrating the first layer 11 are formed at the bottom 23 of the stripping container 20.

[0048] Furthermore, at the bottom 23 of the peeling container 20, at the center of the bottom of the first layer 11, an opening 25 penetrating the first layer 11 is formed, similar to that of the preform 10. Material of the second layer 12 is filled into the opening 25 in a way that blocks the opening, resulting in the second layer 12 being exposed on the outside of the first layer 11 near the opening 25 of the bottom 23 of the peeling container 20. With the second layer 12 exposed on the outside of the first layer 11 in the opening 25 of the peeling container 20, the second layer 12 is partially fixed to the first layer 11, and positional displacement of the second layer 12 relative to the first layer 11 is suppressed.

[0049] Furthermore, in the second layer 12 of the peeling container 20, a rib-like high-strength portion 26 is formed, which extends the first region 19 of the preform 10. The high-strength portion 26 extends radially outward from the position of the air inlet hole 24, and four of them are formed in a rotationally symmetrical manner in the circumferential direction with reference to the opening 25 of the bottom 23.

[0050] Similar to the case of the preform 10, the high-strength portion 26 of the peel container 20 differs from other circumferential regions of the second layer 12 (also referred to as the deformable portion 27) in terms of resin density and / or resin orientation, exhibiting characteristics of being difficult to deform in the circumferential direction. Furthermore, while the high-strength portion 26 is visually difficult to distinguish from the deformable portion 27, it can be identified by methods such as strain measurement based on photoelasticity.

[0051] In the peeling container 20, the space inside the second layer 12 is filled with contents. When the contents are discharged from the second layer 12 in the peeling container 20, air slowly flows into the space between the first layer 11 and the second layer 12 through the air inlet 24, causing the first layer 11 and the second layer 12 to gradually peel apart. This allows the volume occupied by the contents of the second layer 12 to be replaced with air without contact with air, enabling the contents filled in the second layer 12 to be discharged outside the container.

[0052] In the stripping container 20, as the contents filled in the second layer 12 are discharged, the second layer 12 gradually contracts inward. Since the high-strength portion 26 of the second layer 12 is less prone to circumferential deformation compared to the easily deformable portion 27, therefore, as... Figure 4 As shown, when the second layer 12 contracts, the deformable portion 27 contracts inward before the high-strength portion 26. Thus, the deformable portion 27 folds tightly along the radially extending high-strength portion 26, and the high-strength portion 26 guides the contraction deformation of the second layer 12 to a proper and regular contraction deformation.

[0053] Furthermore, during the contraction accompanying the drainage from the container, the second layer 12 deforms first from the deformable portion 27 near the upper side of the neck, and the bottom side of the second layer 12 easily becomes attached to the bottom of the first layer 11 due to the load of the contents. Moreover, when the second layer 12 contracts, as... Figure 4 As shown, the bottom of the second layer 12 is folded at the position of the ridge line 28 connecting these angles, with the end or bottom center of the rib-like high-strength portion 26 and a portion of the extension line of the air inlet hole 24 forming an angle. As a result, the bottom of the second layer 12 is deformed from a circular shape to a near-polygonal shape. For example, as Figure 4 Thus, with four air inlet holes 24, the bottom shape of the second layer 12 becomes rectangular. In this way, the bottom-side ridge 28 and the ribbed high-strength portion 26 of the second layer 12 become columnar (beam-like), making the other parts easier to fold. Furthermore, during the contraction accompanying the drainage from the container, air supply from the air inlet holes 24 can cause deformation in the second layer 12, starting from the deformable portion 27 near the bottom or the main body side. Additionally, in the initial stage of the contraction accompanying the drainage, at least the deformable portion 27 on the bottom side of the second layer 12 can peel off from the bottom of the first layer 11.

[0054] <Description of the manufacturing apparatus for the stripping container>

[0055] Figure 5This is a schematic diagram showing the structure of the blow molding apparatus 30 of this embodiment. The blow molding apparatus 30 of this embodiment is an example of a manufacturing apparatus for a release container 20, and adopts a hot preform method (also known as a one-stage method) to blow mold the release container 20 without cooling the preform 10 to room temperature and effectively utilizing the heat retained during injection molding (internal heat).

[0056] The blow molding apparatus 30 includes a first injection molding section 31, a second injection molding section 32, a temperature adjustment section 33, a blow molding section 34, a take-out section 35, and a conveying mechanism 36. The first injection molding section 31, the second injection molding section 32, the temperature adjustment section 33, the blow molding section 34, and the take-out section 35 are positioned at positions that rotate by a given angle (e.g., 72 degrees) around the conveying mechanism 36 each time. Furthermore, a temperature adjustment section may be added between the first injection molding section 31 and the second injection molding section 32 to assist in heating or cooling the first layer 11 of the preform 10. Additionally, a core mold lifting mechanism (not shown) is provided above the conveying mechanism 36 in both the first and second injection molding sections 31 and 32.

[0057] (Conveying mechanism 36)

[0058] Conveying mechanism 36 is equipped with Figure 5 A transfer plate (not shown) moves by rotating around an axis perpendicular to the paper surface. On the transfer plate, a neck mold 36a holds the neck 13 (or the neck 21 of the peeling container 20) of the preform 10. Figure 5 (Not shown in the figure) One or more are arranged at a given angle. The conveying mechanism 36 moves the transfer platen at a given angle each time, conveying the preform 10 (or release container 20) held by the neck mold 36a in the sequence of the first injection molding section 31, the second injection molding section 32, the temperature adjustment section 33, the blow molding section 34, and the take-out section 35. In addition, the conveying mechanism 36 can also raise and lower the transfer platen, and also perform actions related to mold closing and mold opening (demolding) in the first injection molding section 31 and the second injection molding section 32.

[0059] (First Injection Molding Section 31)

[0060] The first injection molding unit 31 includes a cavity mold 40, a core mold 41, and a hot runner mold 42, and manufactures the first layer 11 of the preform 10. The cavity mold 40 is composed of a first cavity mold 40A on the opening side (upper side) and a second cavity mold 40B on the bottom side (lower side). A first injection device 37 for supplying first resin material to the hot runner mold 42 is connected to the first injection molding unit 31. The cavity mold 40 and the hot runner mold 42 are fixed to the machine base of the blow molding apparatus 30 in an integrated manner. The core mold 41 is fixed to a core mold lifting mechanism.

[0061] Figure 6 (a) and (b) represent the first injection molding section 31 that forms the first layer 11 of the preform 10 in this embodiment. Figure 7 This is a diagram showing the area near the bottom of the first layer 11 in the first injection molding section 31.

[0062] The cavity mold 40 defines the shape of the outer periphery of the first layer 11. The first cavity mold 40A is a mold facing the opening side of the cavity mold 40, defining the shape of the outer periphery of the main body of the first layer 11. The second cavity mold 40B is a mold facing the bottom side of the cavity mold 40, defining the shape of the outer periphery of the bottom of the first layer 11. In addition, the hot runner mold 42 has a resin supply section 42a for introducing the first resin material from the first injection device 37. The core mold 41 is a mold defining the shape of the inner periphery of the first layer 11, and is inserted into the inner periphery of the cavity mold 40 from above. Furthermore, the first cavity mold 40A and the second cavity mold 40B may also be integrally formed.

[0063] like Figure 6 As shown in (a) and (b), in the first injection molding section 31, the cavity mold 40, the core mold 41, and the neck mold 36a of the conveying mechanism 36 are closed to form a mold space for the first layer 11. Then, by flowing the first resin material from the bottom of the mold space through the hot runner mold 42, the first layer 11 of the preform 10 is manufactured in the first injection molding section 31.

[0064] On the upper surface of the second cavity mold 40B facing the bottom outer periphery of the first layer 11, a plurality of rib-shaped first protrusions 44 are arranged radially. The first protrusions 44 are arranged radially spaced apart from the bottom center where the resin supply section 42a is located, and are formed in a rotationally symmetrical manner with respect to the bottom center, preferably four. Figure 7 As shown in (a), the protrusion h1 of the first protrusion 44 from the bottom outer peripheral surface of the first layer 11 is approximately the same size as the thickness of the first layer 11. Therefore, when the first injection molding part 31 is closed, the front end of the first protrusion 44 faces the surface of the core mold 41. Thus, during the injection molding of the first injection molding part 31, a circular recess 11a is formed in the first layer 11 at a position corresponding to the recess 17 of the preform 10 via the first protrusion 44. The recess 11a of the first layer 11 can penetrate the first layer 11 or have a thin film formed by being held between the core mold 41 and the first protrusion 44. Furthermore, the recess 11a of the first layer 11 formed by the first injection molding part 31 is also referred to as the first recess.

[0065] In addition, such as Figure 6As shown in (b), a valve pin 43 is provided in the resin supply section 42a of the hot runner mold 42, which can move axially to a position close to the core mold 41. The valve pin 43 is housed inside the hot runner mold 42 before the first resin material is filled into the mold space, and protrudes to a position close to the core mold 41 after the first resin material is filled into the mold space. By moving the valve pin 43 during injection molding in this way, a thin film portion 18 of resin material with a wall thickness thinner than the periphery can be formed at the center of the bottom of the first layer 11.

[0066] Furthermore, when the first injection molding section 31 is opened, the neck mold 36a of the conveying mechanism 36 remains closed and the first layer 11 of the preform 10 is conveyed as is. The number of preforms 10 simultaneously molded by the first injection molding section 31 (i.e., the number of release containers 20 that can be simultaneously molded by the blow molding device 30) can be appropriately set.

[0067] (Second Injection Molding Section 32)

[0068] The second injection molding section 32 includes a cavity mold 50, a core mold 51, and a hot runner mold 52, and injects and molds the second layer 12 on the inner circumferential side of the first layer 11. The cavity mold 50 is composed of a first cavity mold 50A on the opening side (upper side) and a second cavity mold 50B on the bottom side (lower side). A second injection device 38 for supplying a second resin material to the hot runner mold 52 is connected to the second injection molding section 32. Alternatively, the first cavity mold 50A and the second cavity mold 50B can be integrally formed.

[0069] Figure 6 (c) indicates the second injection molding part 32 that shapes the second layer 12 of the preform 10. Figure 8 (a) and (b) are diagrams showing the area near the bottom of the preform 10 in the second injection molding section 32.

[0070] Cavity mold 50 is a mold that houses the first layer 11. First cavity mold 50A is a mold facing the opening side of cavity mold 50, housing the main body of the first layer 11. Second cavity mold 50B is a mold facing the bottom side of cavity mold 50, housing the bottom of the first layer 11. Additionally, hot runner mold 52 has a resin supply section 52a that introduces the second resin material from the second injection device 38. Core mold 51 is a mold that defines the shape of the inner circumferential side of the second layer 12, inserted from above into the inner circumferential side of cavity mold 50.

[0071] like Figure 6As shown in (c), the second injection molding section 32 houses the first layer 11 of the preform 10 injected by the first injection molding section 31. With the second injection molding section 32 closed, a mold space is formed between the inner circumferential side of the first layer 11 and the surface of the core mold 51. In the second injection molding section 32, a second resin material flows in from the bottom of the mold space through the hot runner mold 52, thereby forming a preform 10 with a second layer 12 stacked on the inner circumferential side of the first layer 11.

[0072] Furthermore, on the upper surface of the second cavity mold 50B facing the bottom outer periphery of the first layer 11, at a given position corresponding to the first protrusion 44 of the first injection molding part 31, a second protrusion 54 in a circular shape corresponding to the shape of the recess 17 of the preform 10 is provided. When the first layer 11 is received by the second injection molding part 32, the second protrusion 54 is inserted through the recess 11a of the first layer 11.

[0073] Here, Figure 8 (a) represents the longitudinal section at the position of the second protrusion 54 in the circumferential direction. Figure 8 (b) represents the longitudinal section at the location where there is no second protrusion in the circumferential direction.

[0074] like Figure 8 As shown in (a), the amount h2 of the second protrusion 54 protruding from the bottom outer peripheral surface of the first layer 11 is greater than the thickness of the first layer 11. That is, the amount h2 of the second protrusion 54 protruding is greater than the amount h1 of the first protrusion 44 (h2 > h1). Therefore, when the second injection molding part 32 is closed, the front end of the second protrusion 54 protrudes through the recess 11a of the first layer 11 and extends to the inner peripheral side of the first layer 11. By providing the second protrusion 54 in the second cavity mold 50B of the second injection molding part 32, a recess 17 can be formed at the bottom 15 of the preform 10.

[0075] Furthermore, although not specifically limited, the difference between the protrusion amount h1 of the first protrusion 44 and the protrusion amount h2 of the second protrusion 54 (the protrusion amount of the second protrusion 54 from the first layer) is preferably set to less than 1 / 4 to less than 1 / 5 of the bottom thickness of the preform 10.

[0076] The protrusion h2 of the second protrusion 54 is set to be smaller than the thickness of the preform 10. That is, during injection molding in the second injection molding section 32, since the second resin material flows between the core mold 51 and the second protrusion 54, a hole penetrating the second layer 12 will not be formed due to the second protrusion 54.

[0077] In the second injection molding section 32, the second resin material is filled between the first layer 11 and the core mold 51, but... Figure 8As shown in (a), the second protrusion 54 is located in contact with the second resin material, which also contacts the second protrusion 54 penetrating the recess 11a of the first layer 11. Additionally, in the second injection molding section 32, Figure 8 The distance L1 between the second protrusion 54 shown in (a) and the surface of the core mold 51 is greater than that between the second protrusion 54 and the core mold 51. Figure 8 The distance L2 between the inner circumferential surface of the first layer 11 and the surface of the core mold 51 shown in (b) is small.

[0078] (Temperature adjustment unit 33)

[0079] The temperature adjustment unit 33 includes a temperature adjustment mold unit (temperature regulating tank, temperature regulating core) for temperature adjustment (not shown). The temperature adjustment unit 33 homogenizes and eliminates temperature deviations by housing the preform 10 conveyed from the second injection molding unit 32 within the mold unit, which maintains the preform at a given temperature, thereby adjusting the temperature of the preform 10 to a temperature suitable for final blow molding (e.g., approximately 90°C to 105°C). Furthermore, the temperature adjustment unit 33 also functions to cool the preform 10 at its high temperature after injection molding.

[0080] (Blow molding section 34)

[0081] The blow molding section 34 blow molds the pre-plasticized preform 10, which has been temperature-adjusted by the temperature adjustment section 33, to manufacture the release container 20.

[0082] The blow molding section 34 includes a pair of parting dies corresponding to the shape of the release container 20, namely a blow molding cavity mold, a bottom mold, a stretching rod, and an air inlet component (all not shown). The blow molding section 34 performs blow molding while stretching the pre-plasticized preform 10. Thus, the pre-plasticized preform 10 can be shaped into the shape of the blow molding cavity mold to manufacture the release container 20.

[0083] (Removal section 35)

[0084] The removal section 35 is configured to open the neck 21 of the release container 20 manufactured by the blow molding section 34 from the neck mold 36a and remove the release container 20 to the outside of the blow molding apparatus 30.

[0085] <Description of the manufacturing method of the container>

[0086] Next, the manufacturing method of the stripping container 20 using the blow molding apparatus 30 of this embodiment will be described. Figure 9 This is a flowchart illustrating the process of manufacturing the stripping container 20.

[0087] (Step S101: First Injection Molding Process)

[0088] First, such as Figure 6As shown in (a), in the first injection molding section 31, a first resin material is injected from the first injection device 37 into the mold space formed by the cavity mold 40, the core mold 41, and the neck mold 36a, forming the first layer 11 of the preform 10. At this time, as Figure 7 As shown, a recess 11a is formed at the bottom of the first layer 11 through the first protrusion 44.

[0089] In the first injection molding section 31, such as Figure 6 As shown in (b), after the first layer 11 of the preform 10 is formed, a process is performed to make the valve pin 43 protrude to a position close to the core mold 41. Thus, as... Figure 7 As shown, a thin film portion 18 with a wall thickness thinner than the periphery is formed at the bottom center of the first layer 11.

[0090] Then, the first injection molding section 31 is opened, and the first layer 11 is demolded. When the first injection molding section 31 is opened, the transfer plate of the conveying mechanism 36 moves by rotating a given angle, and the first layer 11 of the preform 10 held in the neck mold 36a is conveyed to the second injection molding section 32 while still heated during injection molding.

[0091] (Step S102: Second Injection Molding Process)

[0092] Next, the first layer 11 of the preform 10 is housed in the second injection molding section 32, and the second layer 12 is injection molded.

[0093] In the second injection molding section 32, such as Figure 6 As shown in (c), a mold space is formed between the inner circumferential side of the first layer 11 and the surface of the core mold 51 facing the inner circumference of the first layer 11, and a second resin material is filled into the mold space from the hot runner mold 52. In addition, a thin film portion 18 is formed at the bottom of the first layer 11, but the thin film portion 18 breaks due to the injection pressure of the second resin material, forming an opening 16 at the bottom, and the second resin material is guided to the inner circumferential side of the first layer 11 from the opening 16.

[0094] Here, the temperature of the second resin material filled in the second injection molding section 32 is set to a temperature lower than the melting point of the first resin material. In addition, the surface temperature of the first layer 11 is cooled to a temperature below the melting point of the second resin material when the second resin material is filled in the second injection molding section 32.

[0095] In the second injection molding section 32, the cavity mold 50 faces the outer peripheral side of the first layer 11, and the shape of the first layer 11 is maintained from the outer peripheral side by the cavity mold 50. Therefore, even if the second resin material comes into contact with the first layer 11, thermal deformation of the first layer 11 can be suppressed.

[0096] Furthermore, in the second injection molding section 32, since the second protrusion 54 penetrates and blocks the recess 11a of the first layer 11, the recess 17 of the preform 10 will not be blocked by the second resin material. Additionally, since the front end of the second protrusion 54 in the second injection molding section 32 protrudes to the inner circumference of the first layer, the recess 17 of the preform 10 formed by the second protrusion 54 becomes a shape that penetrates the first layer 11, exposing the surface of the second layer 12 within the recess 17.

[0097] In addition, in the second injection molding section 32, the second resin material flows radially outward between the core mold 51 and the second protrusion 54, thereby forming a rib-like first region 19 in the second layer 12.

[0098] First, in the second injection molding section 32, such as Figure 8 As shown in (b), a second resin material is filled between the surface of the first layer 11 and the core mold 51, and the second resin material undergoes cooling based on contact with the core mold 51. In contrast, in Figure 8 At the location of the second protrusion 54 shown in (a), the second resin material flows between the core mold 51 and the second protrusion 54, undergoing cooling based on the contact between the core mold 51 and the second protrusion 54. Therefore, at the location of the second protrusion 54, the second resin material is cooled more strongly than at other locations due to the second protrusion 54, thus increasing the viscosity of the second resin material and increasing the density of the resin in the first region 19.

[0099] Additionally, in the second injection molding section 32, Figure 8 The distance L1 between the second protrusion 54 shown in (a) and the surface of the core mold 51 is greater than that between the second protrusion 54 and the core mold 51. Figure 8 The distance L2 between the first layer 11 and the surface of the core mold 51 shown in (b) is small. Therefore, the flow rate of resin between the second protrusion 54 and the core mold 51 is faster than the flow rate of resin between the first layer 11 and the core mold 51. As a result, in the circumferential direction of the second injection molding section 32, the second resin material is filled from the position of the second protrusion 54, and the flow of resin in the first region 19 becomes a flow along the length direction from the bottom 15 toward the neck 13. Therefore, the orientation of the resin in the first region 19 has a directional orientation along the aforementioned length direction.

[0100] In contrast, in the second region of the second layer 12, the resin flows in later than in the first region 19, thus the flow of resin in the second region is supplemented by the circumferential diffusion of resin from the first region 19. Therefore, the orientation of the resin in the second region deviates from that in the first region 19.

[0101] Thus, the first region 19 of the second layer 12 has a higher resin density than the second region, and is directional in that the resin orientation is along the length of the preform 10, thus having the characteristic of being difficult to deform in the circumferential direction.

[0102] As described above, a preform 10 with a second layer 12 stacked on the inner circumferential side of the first layer 11 is manufactured through a first injection molding process and a second injection molding process.

[0103] Subsequently, when the second injection molding section 32 opens, the transfer plate of the conveying mechanism 36 moves by rotating a given angle, and the preform 10 held in the neck mold 36a is conveyed to the temperature adjustment section 33 while still heated during injection molding.

[0104] (Step S103: Temperature adjustment process)

[0105] Next, in the temperature adjustment unit 33, the preform 10 is housed in the temperature adjustment mold unit, and temperature adjustment is performed to bring the temperature of the preform 10 close to the temperature suitable for final blow molding. Afterward, the transfer plate of the conveying mechanism 36 moves by rotating a given angle, and the preform 10, which has been temperature adjusted and held in the neck mold 36a, is conveyed to the blow molding unit 34.

[0106] (Step S104: Blow molding process)

[0107] Next, in the blow molding section 34, the release container 20 is blow molded.

[0108] First, the blow molding cavity is closed, housing the preform 10 within the mold space. The air inlet component (blow molding core) is lowered, bringing it into contact with the neck 13 of the preform 10. Then, the tension rod is lowered, pressing the bottom 15 of the preform 10 from its inner surface. Longitudinal stretching is performed as needed, and blow molding air is supplied from the air inlet component, thereby transverse stretching of the preform 10. As a result, the preform 10 bulges out and is shaped to fit tightly against the mold space of the blow molding cavity, and is blow-molded into a release container 20.

[0109] Furthermore, during blow molding, by stretching the first region 19 of the preform 10, a ribbed high-strength portion 26 is formed in the second layer 12 of the peel container 20.

[0110] (Step S105: Container Removal Process)

[0111] When the blow molding process is complete, the blow molding cavity mold is opened. As a result, the release container 20 can be moved from the blow molding section 34.

[0112] Next, the transfer plate of the conveying mechanism 36 moves by a given rotation angle, and the peeling container 20 is conveyed to the take-out section 35. In the take-out section 35, the neck 21 of the peeling container 20 opens from the neck mold 36a, and the peeling container 20 is taken out of the blow molding apparatus 30.

[0113] This concludes one cycle of the method for manufacturing the release container. Afterwards, by moving the transfer plate of the conveying mechanism 36 by a given rotation angle, the aforementioned steps S101 to S105 are repeated. Furthermore, while the blow molding apparatus 30 is operating, the manufacturing of five sets of release containers 20, each with a time difference of one step, is performed in parallel.

[0114] Furthermore, in the structure of the blow molding apparatus 30, the standby time for the first injection molding process, the second injection molding process, the temperature adjustment process, the blow molding process, and the container removal process is the same length. Similarly, the conveying time between each process is also the same length.

[0115] The effects of the container manufacturing method of this embodiment will be explained below.

[0116] In this embodiment, in the first injection molding step, the first layer 11 (outer layer) of the preform 10 is formed, and in the second injection molding step, the second layer 12 (inner layer) is injection molded from the opening 16 of the first layer 11 inside the first layer 11 to manufacture a preform 10 with a double-layer structure. According to this embodiment, the outer layer can be formed first with a resin material with a high melting point, and then the inner layer can be formed with a resin material with a lower melting point than the outer layer. That is, by continuously performing injection molding of the inner layer while the outer layer is still heated during injection molding, a preform 10 with a double-layer structure suitable for the specifications of the release container 20 can be manufactured. In this embodiment, since the preform 10 with a double-layer structure is demolded while both the outer and inner layers are still heated during injection molding, a preform 10 suitable for manufacturing the release container 20 using a hot preform blow molding method can be obtained.

[0117] In this embodiment, a recess 11a is formed in the first layer 11 using the first protrusion 44 in the first injection molding process. Then, in the second injection molding process, a second protrusion 54, which has a larger protrusion than the first protrusion 44, penetrates the recess 11a in the first layer 11, forming a recess 17 at the bottom 15 of the preform 10. As a result, an air inlet hole 24 that penetrates the first layer 11 and reaches the surface of the second layer 12 can be reliably formed in the release container 20.

[0118] Furthermore, in the second injection molding process, an injection mold with a second protrusion 54 partially formed in the circumferential direction at the bottom is used to change the flow rate and temperature of the resin passing through the second protrusion 54. As a result, in the second layer 12 of the preform 10, a first region 19 with higher strength than other circumferential regions is formed, starting from the recess 17 formed through the second protrusion 54.

[0119] Then, in this embodiment, the preform 10 with the double-layer structure described above is stretched and blow-molded to manufacture the release container 20 while still heated as during injection molding. At this time, the first region 19 of the preform 10 is stretched, forming a rib-like high-strength portion 26 in the second layer 12 of the release container 20. During the shrinkage of the second layer 12 of the release container 20, the deformable portion 27 folds tightly along the radially extending high-strength portion 26, guiding the shrinkage deformation of the second layer 12 to a suitable and regular shrinkage deformation through the high-strength portion 26.

[0120] Furthermore, the first region 19 of the preform 10 is formed by changing the resin flow rate and temperature through the second protrusion 54, and therefore has almost no difference in appearance from the second region. The same applies to the high-strength portion 26 in the second layer 12 of the release container 20. Therefore, in this embodiment, the shrinkage guiding structure can be formed inconspicuously, improving the aesthetics and functionality of the release container 20.

[0121] Furthermore, in this embodiment, a first region 19, which forms the basis of a structural portion for guiding the contraction of the container, is formed in the second layer 12 using the second protrusion 54 for forming the air inlet hole 24. This allows the inner surface of the second layer 12 filled with contents to remain flat, and the structural portion for guiding the contraction is formed in the second layer 12, thus improving drainage performance when the remaining volume is low in the blow-molded release container 20.

[0122] This invention is not limited to the above-described embodiments. Various improvements and design changes can be made without departing from the spirit of this invention.

[0123] In the above embodiment, an example of forming a circular recess 17 at the bottom 15 of the preform 10 by forming rib-shaped protrusions at the bottom of the cavity mold has been described. However, the shape of the protrusions formed at the bottom of the cavity mold is not limited to the above and can be any shape. In addition, the number of protrusions formed at the bottom of the cavity mold can be, for example, one or more than four.

[0124] Furthermore, the blow molding apparatus 30 and blow molding method of the present invention can also be implemented as a 6-station blow molding apparatus and blow molding method. That is, a temperature adjustment unit (temperature adjustment process) can be further added between the first injection molding section 31 and the second injection molding section 32 (between the first injection molding process and the second injection molding process).

[0125] Furthermore, in the above embodiment, the case where a high-strength portion for shrinkage guidance is formed in the inner layer of the double-layered peelable container was described. However, the present invention can also be applied to the manufacture of single-layered containers (such as BIB containers) that can shrink as the contents are discharged. In this case, the blow molding apparatus has one injection molding unit (a so-called 4-station type).

[0126] The preform 10A corresponding to the single-layer container is manufactured in the following manner.

[0127] For example, such as Figure 10 As shown, at the bottom of the second cavity mold 40B of the injection molding section, a protrusion 44 of a height that does not contact the core mold 41 is partially formed in the circumferential direction. Figure 10 In this case, the resin contacts the core mold 41 and the second cavity mold 40B over the entire circumferential area, but the resin flow rate increases in the portion passing through the protrusion 44. Therefore, at the position corresponding to the protrusion 44 of the preform 10A, as described above, the resin orientation can be made directional.

[0128] As described above, even in a single-layer preform 10A, a rib-like first region 19 extending from the corresponding position of the protrusion 44 can be formed, similar to the embodiment described above. By blow molding this preform 10A, even in a single-layer container, a high-strength portion 26, the same as the second layer 12 of the peelable container 20 described above, can be formed.

[0129] Furthermore, the high-strength portion 26 of the peelable container 20 described in the above embodiment may also be partially formed on the bottom 23 of the container (or the lower region from the bottom 23 of the container to the main body 22). For example, the high-strength portion 26 may not be formed on the upper region of the main body 22 of the container (such as the shoulder 22a of the container). In the case described above, on the bottom side of the container, the deformable portion 27 is divided circumferentially by the high-strength portion 26, while on the other hand, in the upper region of the main body 22 of the container where the high-strength portion 26 is not present, the second layer 12 becomes the deformable portion 27 throughout the entire circumference. Furthermore, in the case described above, the first region 19 formed on the second layer 12 of the preform 10 is also partially formed from the bottom side toward the main body, but not formed on the neck side.

[0130] Furthermore, the embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the invention is defined not by the foregoing description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0131] Symbol Explanation

[0132] 10, 10A…Pre-plastic preform; 11…First layer; 11a…Recess; 12…Second layer; 16…Opening; 17…Recess; 19…First region; 20…Peeling container; 24…Air inlet hole; 26…High-strength section; 27…Deformable section; 30…Blow molding device; 31…First injection molding section; 32…Second injection molding section; 34…Blow molding section; 37…First injection device; 38…Second injection device; 40B, 50B…Cavity mold; 44…First protrusion; 54…Second protrusion.

Claims

1. A method for manufacturing a peeling container, comprising: In the first injection molding process, the first injection mold is used to inject the outer layer of the bottomed cylindrical preform into the first resin material. In the second injection molding process, a second injection mold is used to inject a second resin material, different from the first resin material, into the inner circumference of the outer layer to create a multi-layered preform with an inner layer stacked on the inner side of the outer layer; and The blow molding process involves blow molding multiple layers of the pre-plasticized preform while maintaining the heat of the injection molding process to manufacture a release container in which the inner layer, for filling contents, is stacked on the inner periphery of the outer layer, and the inner layer shrinks as the contents of the inner layer are discharged. In the first injection molding process, a first recess is formed in at least a portion of the outer layer by means of a first protrusion provided on the first injection mold. In the second injection molding process, by inserting the second protrusion provided in the second injection mold through the first recess, a second recess is formed on the preform that penetrates the outer layer and exposes the surface of the inner layer. By contacting the second protrusion with the second resin material, at least one of the flow rate and temperature of the second resin material passing through the second protrusion changes, and a region with higher strength than other circumferential parts is formed in the inner layer, starting from the corresponding position of the second recess.

2. The method for manufacturing the stripping container according to claim 1, wherein, The region extends radially outward from the corresponding position of the second recess toward the inner layer.

3. The method for manufacturing the stripping container according to claim 1 or 2, wherein, In the blow molding process, an air inlet hole is formed in the outer layer at the corresponding position of the second recess.

4. An apparatus for manufacturing a peeling container, comprising: The first injection molding section uses a first injection mold to injection mold the outer layer of a bottomed cylindrical preform using a first resin material. The second injection molding section uses a second injection mold to inject a second resin material, different from the first resin material, into the inner circumference of the outer layer to manufacture a multi-layered preform with an inner layer stacked on the inner side of the outer layer; and A blow molding section blow molds multiple layers of the pre-plasticized preform while retaining heat as in injection molding, to manufacture a release container in which the inner layer, for filling contents, is stacked on the inner periphery of the outer layer, and the inner layer shrinks as the contents of the inner layer are discharged. In the first injection molding section, a first recess is formed in at least a portion of the outer layer by means of a first protrusion provided in the first injection mold. In the second injection molding section, by inserting a second protrusion provided in the second injection mold through the first recess, a second recess is formed in the preform that penetrates the outer layer and exposes the surface of the inner layer. By contacting the second protrusion with the second resin material, at least one of the flow rate and temperature of the second resin material passing through the second protrusion changes, and a region with higher strength than other circumferential parts is formed in the inner layer, starting from the corresponding position of the second recess.

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