Manufacturing method and device for plastic containers

Abstract

To provide a manufacturing method that can suppress molding defects in which the resin material of the inner layer unintentionally wraps around to the outer circumference when the hot parison type blow molding method is applied to manufacture peeled containers.SOLUTION: In the second injection molding process for manufacturing a peeled container, a second layer is stacked on the inner side of the first layer of a bottomed cylindrical preform. The first layer is contained in the mold space of the first mold, a second mold is inserted inside the first layer, and a second resin material is injected between the first and second molds. The depth of the mold space of the first mold is shorter than the axial length of the first layer obtained in the first injection molding process.SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] Conventionally, peelable containers made of resin have been known that have a two-layer structure of an inner layer and an outer layer, in which the inner layer peels off from the outer layer as the contents are discharged. This type of peelable container is also called a delaminated bottle or an airless bottle, and is used, for example, as a container for seasoning liquid such as soy sauce or cosmetic liquid. At present, in the manufacture of this type of peelable container, the extrusion blow method is generally used, and the stretch blow method is rarely used (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5267901 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, from the perspective of improving the appearance, dimensional accuracy, and physical strength of peelable containers, as well as reducing the environmental impact by reducing waste of materials, the use of a one-stage hot parison blow molding method that performs the injection molding process and the blow molding process continuously in the manufacture of peelable containers is being considered.

[0005] However, in the case of peelable containers, the melting point of the resin material for the outer layer is often set higher than that of the resin material for the inner layer. In the injection molding process for molding a two-layer preform, if the high-temperature resin material for the outer layer is filled after the inner layer is formed, the surface of the inner layer that comes into contact with the resin material for the outer layer melts and is thermally deformed. For this reason, it is extremely difficult to manufacture peelable containers by applying the hot parison blow molding method.

[0006] In addition, if the adhesion between the outer layer and the inner layer is low in the preform of the peeled container, the outer layer and the inner layer may be unintentionally separated or displaced. For example, when the core mold inserted in the two-layered preform is pulled out, the inner layer may be fixed to the core mold and rolled up, which may cause unintentional separation or displacement from the outer layer. In addition, for example, when the two-layered preform is blow molded, the inner layer may slide against the outer layer, and the peeled container may be molded in a state where the outer layer and the inner layer are displaced.

[0007] Therefore, the present invention has been made in consideration of such problems, and aims to provide a manufacturing method that can suppress unintended separation or misalignment of the outer layer and inner layer when manufacturing a peelable container using a hot parison blow molding method. [Means for solving the problem]

[0008] A method for producing a peelable container according to one aspect of the present invention includes a first injection molding step of injection molding a first layer of a bottomed cylindrical preform with a first resin material, a second injection molding step of injecting a second resin material different from the first resin material to laminate the second layer on the inner periphery side of the first layer, and a blow molding step of blow molding the preform obtained in the second injection molding step while it has the heat retained during injection molding to produce a peelable container. In the second injection molding step, the second resin material is introduced from an opening formed in the first layer to the inner periphery side of the first layer, and a locking portion protruding from the opening on the outer periphery side of the first layer is integrally formed with the second layer. Effect of the Invention

[0009] According to one aspect of the present invention, when a peelable container is manufactured by applying a hot parison type blow molding method, unintended separation or misalignment of an outer layer and an inner layer can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a longitudinal sectional view of the preform of the first embodiment. [Diagram 2] FIG. 2 is a vertical cross-sectional view of the peeling container of the first embodiment. [Diagram 3] FIG. 1 is a diagram illustrating a schematic configuration of a blow molding device according to a first embodiment. [Figure 4] 3A to 3C are diagrams illustrating a manufacturing process of the preform according to the first embodiment. [Diagram 5] FIG. 2A is a diagram showing the vicinity of the bottom of the first layer in the first injection molding section of the first embodiment, and FIG. 2B is a diagram showing the vicinity of the bottom of the preform in the second injection molding section of the first embodiment. [Figure 6] FIG. 2 is a perspective view showing an example of the configuration of a second cavity mold of the first injection molding unit. [Figure 7] 1 is a flowchart showing steps of a method for manufacturing a peeled container. [Figure 8] FIG. 11 is a longitudinal sectional view of a preform according to a second embodiment. [Figure 9] 10A to 10C are diagrams illustrating a manufacturing process of the preform according to the second embodiment. [Figure 10] FIG. 10(a) is a diagram showing the vicinity of the bottom of the first layer in the first injection molding section of the second embodiment, and FIG. 10(b) is a diagram showing the vicinity of the bottom of the preform in the second injection molding section of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiments, in order to make the description easier to understand, structures and elements other than the main parts of the present invention will be described in a simplified or omitted manner. In addition, in the drawings, the same elements are given the same reference numerals. Note that the shapes, dimensions, etc. of each element shown in the drawings are shown only for illustrative purposes, and do not represent the actual shapes, dimensions, etc.

[0012] (First embodiment) <Example of preform configuration> First, referring to Fig. 1, a configuration example of a preform for a peeling container according to the first embodiment will be described. Fig. 1 is a vertical cross-sectional view of a preform 10 according to the first embodiment. The overall shape of the preform 10 is a bottomed cylindrical shape with one end open and the other end closed. The preform 10 includes a body 14 formed in a cylindrical shape, a bottom 15 closing the other end of the body 14, and a neck 13 formed at the opening on one end side of the body 14.

[0013] The preform 10 has a two-layer structure in which a second layer (inner layer) 12 is laminated on the inside of a first layer (outer layer) 11. The first layer 11 and the second layer 12 are formed from different thermoplastic resin materials by two-stage injection molding as described below. The first layer 11 is made of a synthetic resin having excellent moldability and transparency. On the other hand, the second layer 12 is made of a synthetic resin having properties (e.g., moisture barrier properties, gas barrier properties, heat resistance, chemical resistance) that can stably store the contents of the container and suppress deterioration (oxidation). In addition, a resin material having a higher melting point than that of the second layer 12 is selected for the first layer 11.

[0014] Hereinafter, the resin material of the first layer 11 will also be referred to as a first resin material, and the resin material of the second layer 12 will also be referred to as a second resin material. The combination of the first resin material and the second resin material 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 (polycyclohexane dimethylene terephthalate), Tritan (Tritan (registered trademark): copolyester manufactured by Eastman Chemical Co.), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic), and PLA (polylactic acid).

[0015] 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 to 170°C, and the melting point of PET is higher than that of PP, about 245 to 260°C.

[0016] In addition, in the 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 peelable container to be molded, the thickness ratio is preferably 3.0 or less.

[0017] In addition, in the bottom 15 of the preform 10, an opening 16 is formed at the center of the bottom of the first layer 11, penetrating the first layer 11. The opening 16 of the first layer 11 is blocked from the inside by the second layer 12. Outside the first layer 11, the second layer 12 has a locking portion 19 that protrudes radially outward from the opening 16. The locking portion 19 may be formed in an annular shape along the edge of the opening 16, or a plurality of locking portions 19 may be formed at intervals in the circumferential direction.

[0018] In addition, a recess 17 for forming an air introduction hole in the peeling container is formed in the bottom 15 of the preform 10. The recess 17 has, for example, a circular cross section, and is formed at least in one place at a radial interval from the center of the bottom 15 of the preform 10, but a plurality of recesses 17 may be formed along the circumferential direction of the bottom 15. The depth of the recess 17 in the thickness direction of the container is set to a dimension such that the recess 17 penetrates at least the first layer 11 and the surface of the second layer 12 is exposed in the recess 17. The recess 17 formed in the two-layered preform 10 may be called a second recess, distinguished from a recess (described later) formed only in the first layer 11. In addition, the cross section of the recess 17 may be a circle, an ellipse, a polygon, a slit, or a combination of these.

[0019] <Example of peeling container configuration> Next, a configuration example of the resin stripping container 20 according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a vertical cross-sectional view of the stripping container 20 according to the first embodiment.

[0020] The peelable container 20 is a bottle-shaped resin container obtained by stretch-blow molding the preform 10, and contains, for example, seasoning liquid such as soy sauce. The peelable container 20 may also be used to contain other contents such as cosmetic liquid.

[0021] The peeling container 20 has a two-layer structure in which a second layer 12 is laminated inside a first layer 11, similar to the preform 10. In the body portion 22 of the peeling container 20, the ratio (t11 / t12) of the thickness t11 of the first layer 11 to the thickness t12 of the second layer 12 is approximately the same as the thickness ratio (t1 / t2) in the body portion 14 of the preform 10.

[0022] The peeling container 20 has a neck 21 having an opening at the top, a cylindrical body 22 continuing from the neck 21, and a bottom 23 continuing from the body 22. In manufacturing the peeling container 20, the body 14 and bottom 15 of the preform 10 are expanded by stretch blowing, thereby forming the body 22 and bottom 23 of the peeling container 20. In addition, during the stretch blowing, the recess 17 of the preform 10 is stretched, thereby forming an air introduction hole 24 penetrating the first layer 11 in the bottom 23 of the peeling container 20.

[0023] In the peeling container 20, the contents are filled in the space inside the second layer 12. In the peeling container 20, when the contents are discharged from the second layer 12, air gradually flows between the first layer 11 and the second layer 12 from the air introduction hole 24, and the first layer 11 and the second layer 12 are peeled off. This allows the volume occupied by the contents in the container to be replaced with air without exposing the contents of the second layer 12 to air, and allows the contents filled in the second layer 12 to be discharged outside the container.

[0024] In addition, an opening 25 (non-laminated portion, single layer portion) penetrating the first layer 11 is formed in the center of the bottom 23 of the peeling container 20, similar to the preform 10. The material of the second layer 12 is filled in the opening 25 to close the opening 25, and the second layer 12 is exposed outside the first layer 11 in the vicinity of the opening 25 of the bottom 23 of the peeling container 20. In addition, in the bottom 23 of the peeling container 20, a locking portion 26 (bulging portion 26) of the second layer 12 is formed, which protrudes radially outward from the opening 25 of the first layer 11. The locking portion 26 is formed by extending the locking portion 19 of the preform 10. By exposing the second layer 12 to the outside of the first layer 11 at the opening 25 of the peeling container 20, the second layer 12 is partially fixed to the first layer 11, and the positional deviation of the second layer 12 with respect to the first layer 11 is suppressed.

[0025] <Description of the peeling container manufacturing equipment> 3 is a diagram showing a schematic configuration of a blow molding apparatus 30 according to the first embodiment. The blow molding apparatus 30 according to the first embodiment is an example of an apparatus for manufacturing the peelable container 20, and employs a hot parison method (also called a one-stage method) for blow molding the peelable container 20 by utilizing the heat (internal heat) retained during injection molding without cooling the preform 10 to room temperature.

[0026] The blow molding device 30 includes a first injection molding section 31, a first temperature adjustment section 32, a second injection molding section 33, a second temperature adjustment section 34, a blow molding section 35, a take-out section 36, and a conveying mechanism 37. The first injection molding section 31, the first temperature adjustment section 32, the second injection molding section 33, the second temperature adjustment section 34, the blow molding section 35, and the take-out section 36 are disposed at positions rotated by the same predetermined angle (for example, 60 degrees) around the conveying mechanism 37. The blow molding device 30 may be configured without the first temperature adjustment section 32 (in this case, each molding station is disposed at a position rotated by 72 degrees around the conveying mechanism 37). In addition, the first injection molding section 31 and the second injection molding section 33 are provided with a core mold lifting mechanism (not shown) above the conveying mechanism 37.

[0027] (Transport mechanism 37) The transport mechanism 37 includes a rotating plate (transport plate) 37a that rotates around an axis perpendicular to the plane of the drawing in FIG. 3. At least one neck mold 37b (not shown in FIG. 3) that holds the neck portion 13 of the preform 10 (or the neck portion 21 of the peeling container 20) is arranged at each predetermined angle on the rotating plate 37a. The transport mechanism 37 rotates the rotating plate 37a to transport the preform 10 (or the peeling container 20) held by the neck mold 37b to the first injection molding section 31, the first temperature adjustment section 32, the second injection molding section 33, the second temperature adjustment section 34, the blow molding section 35, and the removal section 36 in that order. The transport mechanism 37 can also raise and lower the rotating plate 37a, and also performs operations related to mold closing and mold opening (mold release) in the first injection molding section 31 and the second injection molding section 33.

[0028] (First injection molding section 31) The first injection molding section 31 includes a cavity mold 40, a core mold 41, and a hot runner mold 42, and cooperates with a neck mold 37b that is transported during molding to manufacture 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 38 that supplies a first resin material to the hot runner mold 42 is connected to the first injection molding section 31. The cavity mold 40 and the hot runner mold 42 are fixed to the machine base of the blow molding device 30 in an integrated state. The core mold 41 is fixed to a core mold lifting mechanism.

[0029] 4(a) and (b) show the first injection molding section 31 for molding the first layer 11 of the preform 10 of the first embodiment. Fig. 5(a) is a diagram showing the vicinity of the bottom of the first layer 11 in the first injection molding section 31 of the first embodiment. Fig. 6(a) is a perspective view showing an example of the configuration of the cavity mold 40 (second cavity mold 40B) of the first injection molding section 31.

[0030] The cavity mold 40 defines (determines) the shape of the outer periphery of the first layer 11. The first cavity mold 40A is a mold facing the opening side (the side that abuts against the neck mold 37b when the mold is closed) of the cavity mold 40, and defines the shape of the outer periphery of the body of the first layer 11. The second cavity mold 40B is a mold facing the bottom side (the side that abuts against the hot runner mold 42) of the cavity mold 40, and defines the shape of the outer periphery of the bottom of the first layer 11. The second cavity mold 40B further includes a gate portion 40Ba that introduces the resin material from the hot runner mold 42 to the cavity surface. In addition, the hot runner mold 42 has a resin supply portion 42a (resin flow passage 42a) that introduces the first resin material plasticized (melted) by the first injection device 38 into the second cavity mold 40B. The core mold 41 is a metal mold that determines the shape of the inner periphery of the first layer 11, and is inserted from above into the inner periphery of the cavity mold 40. The neck mold 37b determines the outer shape of the neck portion 13 of the preform 10 (first layer 11).

[0031] 4(a) and (b), in the first injection molding section 31, the cavity mold 40, the core mold 41, and the neck mold 37b of the transport mechanism 37 are closed to form a mold space for the first layer 11. Then, the first resin material is poured from the bottom of the mold space through the hot runner mold 42, whereby the first layer 11 of the preform 10 is manufactured in the first injection molding section 31.

[0032] A first protrusion 44 having a cylindrical, tapered cylindrical or rectangular column shape is provided at a predetermined position on the upper surface (cavity surface side) of the second cavity mold 40B facing the bottom outer periphery of the first layer 11. As shown in FIG. 6(a), at least one first protrusion 44 is disposed at a radial interval from the center of the bottom where the resin supply unit 42a is located. As shown in FIG. 5(a), the protrusion amount h1 of the first protrusion 44 from the cavity reference surface (cavity surface that defines the lower end shape of the bottom outer periphery of the first layer 11) of the second cavity mold 40B is approximately the same dimension as the thickness of the first layer 11. Therefore, when the first injection molding unit 31 is closed, the tip of the first protrusion 44 faces the surface of the core mold 41 (is disposed near the surface of the core mold 41). As a result, in the injection molding of the first injection molding section 31, the first protrusion 44 forms a recess 11a, such as a circular recess, in the first layer 11 at a position corresponding to the recess 17 of the preform 10. The recess 11a in the first layer 11 may penetrate the first layer 11, or may have a thin film formed by being sandwiched between the core mold 41 and the first protrusion 44. The recess 11a in the first layer 11 formed by the first injection molding section 31 is also referred to as a first recess.

[0033] 4(b), the resin supply section 42a of the hot runner mold 42 is provided with a valve pin (a rod-shaped member for opening and closing the resin supply section 42a) 43 that is axially movable to a position close to the core mold 41. The valve pin 43 is housed inside the hot runner mold 42 until the mold space is filled with the first resin material, and after the mold space is filled with the first resin material, it protrudes beyond the opening end of the gate portion 40Ba on the cavity side to a position close to the core mold 41. By such movement of the valve pin 43 during injection molding, a thin film portion 18 in which the thickness of the resin material is thinner than that of the peripheral portion can be formed in the center of the bottom of the first layer 11.

[0034] Furthermore, even when the first injection molding section 31 is opened, the neck mold 37b of the transport mechanism 37 is not opened, but continues to hold and transport the first layer 11 of the preform 10. The number of preforms 10 simultaneously molded in the first injection molding section 31 (i.e., the number of peeling containers 20 that can be simultaneously molded by the blow molding device 30) can be set appropriately.

[0035] (First temperature adjustment section 32) The first temperature adjustment unit 32 is equipped with a temperature adjustment mold (not shown) (a heating pot or temperature adjustment pot (temperature adjustment pot) that adjusts the temperature of the first layer 11 from the outside, and a heating rod, temperature adjustment rod (temperature adjustment rod) or air introduction rod that adjusts the temperature of the first layer 11 from the inside)). The first temperature adjustment unit 32 cools (or heats) the first layer 11, which is in a high temperature state after injection molding, by placing it in a temperature adjustment mold that is kept at a predetermined temperature. The first temperature adjustment unit 32 also has the function of adjusting the temperature distribution of the first layer 11 to a predetermined state before it is transported to the second injection molding unit 33.

[0036] (Second injection molding section 33) The second injection molding section 33 includes a cavity mold 50, a core mold 51, and a hot runner mold 52, and cooperates with a neck mold 37b that is transported during molding to injection mold the second layer 12 onto the inner periphery 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 39 that supplies a second resin material to the hot runner mold 52 is connected to the second injection molding section 33.

[0037] Fig. 4(c) shows the second injection molding section 33 for molding the second layer 12 of the preform 10. Fig. 5(b) is a diagram showing the vicinity of the bottom of the preform 10 in the second injection molding section 33.

[0038] The cavity mold 50 is a mold that houses the first layer 11. The first cavity mold 50A is a mold facing the opening side of the cavity mold 50 and houses the body part of the first layer 11. The second cavity mold 50B is a mold facing the bottom side of the cavity mold 50 and houses the bottom part of the first layer 11. The second cavity mold 50B further includes a gate part 50Ba that guides the resin material from the hot runner mold 52 to the cavity surface. The hot runner mold 52 also has a resin supply part 52a (resin flow passage 52a) at the center of the bottom that introduces the second resin material plasticized (melted) by the second injection device 39. The core mold 51 is a mold that determines the shape of the inner circumference side of the second layer 12 and is inserted from above into the inner circumference side of the cavity mold 50. The neck mold 37b defines the upper end surface (top surface) of the neck portion 13 of the preform 10 (second layer 12). The hot runner mold 52 may have a structure having a valve pin like the hot runner mold 42. However, the position of the valve pin when closing the second resin material is set to a position that does not protrude from the opening end of the gate portion 50Ba on the cavity side.

[0039] As shown in Fig. 4(c), the second injection molding section 33 accommodates the first layer 11 of the preform 10 injection molded in the first injection molding section 31. When the second injection molding section 33 is in a closed state, a mold space is formed between the inner periphery of the first layer 11 and the surface of the core mold 51. In the second injection molding section 33, a second resin material is poured from the bottom of the mold space through a hot runner mold 52 to form the preform 10 in which the second layer 12 is laminated on the inner periphery of the first layer 11.

[0040] Further, on the upper surface side (cavity surface side) of the second cavity mold 50B facing the bottom outer periphery of the first layer 11, a second protrusion 54 having a shape such as a columnar shape corresponding to the shape of the recess 17 of the preform 10 is provided at a predetermined position corresponding to the first protrusion 44 of the first injection molding section 31. The second protrusion 54 is inserted into the recess 11a of the first layer 11 when the first layer 11 is accommodated in the second injection molding section 33. In this way, the basic configuration of the protrusions etc. in the second cavity mold 50B is almost the same as that of the second cavity mold 40B of the first injection molding section 31.

[0041] Here, as shown in FIG. 5(b), the protrusion amount h2 of the second protrusion 54 from the cavity reference surface (cavity surface abutting against the lower end region of the bottom outer peripheral surface of the first layer 11) of the second cavity mold 50B is a dimension larger than the thickness of the first layer 11. In other words, the protrusion amount h2 of the second protrusion 54 is larger than the protrusion amount h1 of the first protrusion 44 (h2>h1). Therefore, when the second injection molding section 33 is closed, the tip of the second protrusion 54 penetrates the recess 11a of the first layer 11 and protrudes to the inner peripheral side of the first layer 11. By providing the second protrusion 54 on the second cavity mold 50B of the second injection molding section 33, the recess 17 can be formed in the bottom 15 of the preform 10.

[0042] Moreover, the protrusion amount h2 of the second protrusion 54 is set to be smaller than the thickness of the preform 10. That is, in the injection molding in the second injection molding section 33, the second resin material flows between the core mold 51 and the second protrusion 54, so that the second protrusion 54 does not form a hole penetrating the second layer 12.

[0043] 5(b), in the cavity mold 50, the cavity end 53 connected to the gate portion 50Ba has a curved expanded diameter portion (bulging portion) that expands toward the mold space. Therefore, near the center of the bottom of the second injection molding portion 33, a gap is generated between the curved surface of the cavity end 53 of the cavity mold 50 and the outer peripheral surface of the first layer 11. The second resin material flows into the gap during injection molding. This allows the locking portion 19, which protrudes radially outward from the opening 16, to be formed integrally with the second layer 12 on the outside of the first layer 11.

[0044] (Second temperature adjustment section 34) The second temperature adjustment section 34 includes a mold unit for temperature adjustment (a heating pot or a temperature adjustment pot (temperature adjustment pot) for adjusting the temperature of the preform 20 from the outside, and a heating rod, a temperature adjustment rod (temperature adjustment rod) or an air introduction rod for adjusting the temperature of the preform 20 from the inside) not shown. The second temperature adjustment section 34 accommodates the preform 10 transferred from the second injection molding section 33 in a mold unit maintained at a predetermined temperature, thereby equalizing the temperature and removing temperature deviation, and adjusting the temperature of the preform 10 to a temperature suitable for the final blow (for example, about 90°C to 105°C). The second temperature adjustment section 34 also has the function of cooling the preform 10 in a high-temperature state after injection molding.

[0045] (Blow molding section 35) The blow molding section 35 performs blow molding on the preform 10 whose temperature has been adjusted in the second temperature adjustment section 34 , and produces the peeled container 20 . The blow molding section 35 includes a blow cavity mold, which is a pair of split molds corresponding to the shape of the peeling container 20, a bottom mold, a stretching rod, and an air introduction member (none of which are shown). The blow molding section 35 blow molds the preform 10 while stretching it. This allows the preform 10 to be shaped into the shape of the blow cavity mold, thereby manufacturing the peeling container 20.

[0046] (Removal part 36) The removal section 36 is configured to release the neck section 21 of the peeled container 20 manufactured in the blow molding section 35 from the neck mold 37 b , and remove the peeled container 20 to the outside of the blow molding apparatus 30 .

[0047] <Explanation of container manufacturing method> Next, a method for manufacturing the peelable container 20 by the blow molding apparatus 30 of the first embodiment will be described. Fig. 7 is a flow chart showing steps of the method for manufacturing the peelable container 20.

[0048] (Step S101: First injection molding process) 4(a), in the first injection molding section 31, a first resin material is injected from a first injection device 38 into a mold space formed by a cavity mold 40, a core mold 41, and a neck mold 37b to mold a first layer 11 of a preform 10. At this time, a recess 11a is formed in the bottom of the first layer 11 by a first protrusion 44.

[0049] 4(b), after the first layer 11 of the preform 10 is molded in the first injection molding section 31, a step of protruding the valve pin 43 to a position close to the core mold 41 is carried out. As a result, a thin film portion 18 having a thickness thinner than that of the peripheral portion is formed in the center of the bottom of the first layer 11.

[0050] Thereafter, the first injection molding section 31 is opened, and the first layer is released. When the first injection molding section 31 is opened, the rotating plate 37a of the transport mechanism 37 rotates a predetermined angle, and the first layer 11 of the preform 10 held in the neck mold 37b is transported to the first temperature adjustment section 32 while retaining the heat retained during the injection molding.

[0051] (Step S102: First temperature adjustment process) Next, in the first temperature adjustment section 32, the first layer 11 of the preform 10 is placed in a temperature adjustment mold, and cooling and temperature distribution adjustment (uniform temperature and removal of temperature deviation) of the first layer 11 are performed. Note that the first temperature adjustment step may be omitted.

[0052] After the first temperature adjustment step (or the first injection molding step), the rotating plate 37a of the transport mechanism 37 rotates a predetermined angle, and the temperature-adjusted first layer 11 held in the neck mold 37b is transported to the second injection molding section 33.

[0053] (Step S103: Second injection molding process) Next, the first layer 11 of the preform 10 is placed in the second injection molding section 33, and the second layer 12 is injection molded.

[0054] 4(c), in the second injection molding section 33, a mold space is formed between the inner periphery of the first layer 11 and the surface of the core mold 51 facing the inner periphery of the first layer 11, and the above mold space is filled with the second resin material from the hot runner mold 52. Note that a thin film portion 18 is formed at the bottom of the first layer 11, but the thin film portion 18 is broken by the injection pressure of the second resin material to form an opening 16 at the bottom, and the second resin material is introduced from the above opening 16 to the inner periphery of the first layer 11.

[0055] Here, the temperature of the second resin material filled in the second injection molding section 33 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 when the second resin material is filled in the second injection molding section 33 is cooled to a temperature equal to or lower than the melting point of the second resin material.

[0056] In the second injection molding section 33, the cavity mold 50 faces the outer periphery of the first layer 11, and the shape of the first layer 11 is maintained from the outer periphery 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.

[0057] In the second injection molding section 33, the second protrusions 54 penetrate and close the recesses 11a of the first layer 11, so that the recesses 17 of the preform 10 are not closed with the second resin material. In addition, the tip of the second protrusions 54 in the second injection molding section 33 protrudes to the inner periphery side of the first layer, so that the recesses 17 of the preform 10 formed by the second protrusions 54 penetrate the first layer 11 and have a shape in which the surface of the second layer 12 is exposed in the recesses 17.

[0058] In the second injection molding section 33, a second resin material is injected into the gap between the curved surface of the cavity end section 53 adjacent to the gate section 50Ba of the cavity mold 50B and the outer circumferential surface of the first layer 11, thereby forming a locking section 19 integrally with the second layer 12 on the outside of the first layer 11. The locking section 19 is caught on the outside of the first layer 11, thereby preventing the second layer 12 from slipping off from the first layer 11.

[0059] In this manner, the preform 10 in which the second layer 12 is laminated on the inner peripheral side of the first layer 11 is manufactured by the first injection molding step and the second injection molding step. Thereafter, when the second injection molding section 33 is opened, the rotating plate 37a of the conveying mechanism 37 rotates a predetermined angle, and the preform 10 held in the neck mold 37b is conveyed to the second temperature adjustment section 34 while retaining the heat retained during injection molding.

[0060] (Step S104: Second temperature adjustment process) Next, in the second temperature adjustment section 34, the preform 10 is accommodated in a mold unit for temperature adjustment, and temperature adjustment is performed to bring the temperature of the preform 10 close to a temperature suitable for the final blow. After that, the rotating plate 37a of the conveying mechanism 37 rotates by a predetermined angle, and the preform 10 after temperature adjustment held in the neck mold 37b is conveyed to the blow molding section 35.

[0061] (Step S105: Blow molding process) Next, in the blow molding section 35, the peeling container 20 is blow molded. First, the blow cavity mold is closed to accommodate the preform 10 in the mold space, and an air introduction member (blow core) is lowered to bring the air introduction member into contact with the neck 13 of the preform 10. Then, a stretching rod is lowered to hold down the bottom 15 of the preform 10 from the inside, and while vertical axis stretching is performed as necessary, blow air is supplied from the air introduction member to horizontally stretch the preform 10. As a result, the preform 10 is bulged and shaped so as to fit closely into the mold space of the blow cavity mold, and is blow molded into the peeling container 20.

[0062] (Step S106: container removal process) When the blow molding is completed, the blow cavity mold is opened, which allows the peeling container 20 to be removed from the blow molding section 35. Next, the rotating plate 37a of the conveying mechanism 37 rotates a predetermined angle, and the peeled container 20 is conveyed to the removal section 36. In the removal section 36, the neck section 21 of the peeled container 20 is released from the neck mold 37b, and the peeled container 20 is removed to the outside of the blow molding apparatus 30.

[0063] This completes one cycle in the method for manufacturing peeled containers. After that, the rotating plate 37a of the conveying mechanism 37 is rotated by a predetermined angle to repeat the above steps S101 to S106. During operation of the blow molding device 30, six sets of peeled containers 20 are manufactured in parallel, with a time difference between each step.

[0064] In addition, due to the structure of the blow molding device 30, the waiting times for the first injection molding process, the first temperature adjustment process, the second injection molding process, the second temperature adjustment process, the blow molding process, and the container removal process are all the same. Similarly, the transport times between each process are also the same.

[0065] The effects of the blow molding apparatus and the blow molding method according to the first embodiment will be described below. In the first embodiment, the first layer 11 (outer layer) of the preform 10 is molded in the first injection molding process, and the second layer 12 (inner layer) is injection molded inside the first layer 11 from the opening 16 of the first layer 11 in the second injection molding process to manufacture the two-layered preform 10. According to the first embodiment, the outer layer is formed first with a resin material having a high melting point, and then the inner layer can be formed with a resin material having a lower melting point than the outer layer. In other words, the inner layer is continuously injection molded while the outer layer has the heat retained during injection molding, and the two-layered preform 10 suitable for the specifications of the peeling container 20 can be manufactured. In the first embodiment, the two-layered preform 10 is released while both the outer layer and the inner layer have the heat retained during injection molding, so that the preform 10 suitable for manufacturing the peeling container 20 by the hot parison type blow molding method can be obtained.

[0066] In the first embodiment, the preform 10 having the above-mentioned two-layer structure is stretch-blow molded while retaining the heat from the injection molding to manufacture the peelable container 20. Therefore, in the first embodiment, the hot parison type blow molding method can manufacture the peelable container 20 having excellent aesthetic appearance and physical strength. Compared to the cold parison type blow molding, in the first embodiment, the manufactured preform 10 does not need to be cooled to near room temperature, and the process of reheating the preform 10 is also unnecessary. Therefore, according to the first embodiment, a series of processes from the injection molding of the preform 10 to the blow molding of the peelable container 20 can be completed in a relatively short time, and the peelable container 20 can be manufactured in a shorter cycle.

[0067] In addition, in the first embodiment, in the second injection molding process, a locking portion 19 is integrally formed on the outside of the first layer 11 using the second resin material that forms the second layer 12, thereby preventing the second layer 12 from slipping out of the first layer 11. As a result, when a force acts on the second layer 12 in the pulling direction toward the neck, the locking portion 19 comes into contact with the first layer 11 to resist the force in the pulling direction, making it difficult for the outer layer and the inner layer of the preform 10 to shift out of place. Therefore, in the first embodiment, it is possible to suppress unintended separation or shifting of the outer layer and the inner layer, for example, when the core mold is pulled out in the second injection molding process or in the blow molding process, and the manufacturing yield of the peelable container 20 can be improved.

[0068] Second embodiment Next, a second embodiment will be described. In the following description, the same elements as those in the first embodiment are given the same reference numerals, and the duplicated description will be omitted.

[0069] For example, when molding a two-layer preform, if the outer layer is molded first and the inner layer is molded later, the resin material of the inner layer that is filled later may unintentionally wrap around to the outer periphery and cover the outside of the preform, significantly impairing the aesthetic appearance of the container after blow molding. In the second embodiment, a configuration will be described that suppresses molding defects caused by the resin material of the inner layer unintentionally flowing around to the outer periphery when a peelable container is manufactured by applying a hot parison type blow molding method.

[0070] Fig. 8 is a longitudinal sectional view of the preform 10 of the second embodiment. The differences between the preform 10 of the first embodiment shown in Fig. 1 and the second embodiment will be described below. A protuberance 12a protruding in a curved shape toward the inner periphery of the second layer 12 is formed on the bottom 15 of the preform 10 of the second embodiment shown in Fig. 8. The protuberance 12a is a resin pool formed during injection molding of the second resin material, and is formed at a position facing the opening 16 of the first layer 11. The configuration of the peeling container 20 in the second embodiment is similar to that in the first embodiment, so a duplicated description will be omitted.

[0071] Moreover, the basic configuration of the blow molding apparatus 30 of the second embodiment is similar to that of the blow molding apparatus 30 of the first embodiment shown in Fig. 3. Differences in the second embodiment will be described below.

[0072] Fig. 9 is a diagram showing a manufacturing process of a preform of the second embodiment. Fig. 10(a) is a diagram showing the vicinity of the bottom of the first layer in the first injection molding part of the second embodiment, and Fig. 10(b) is a diagram showing the vicinity of the bottom of the preform in the second injection molding part of the second embodiment. Fig. 9 corresponds to Fig. 4 of the first embodiment, and Fig. 10 corresponds to Fig. 5 of the first embodiment.

[0073] In the first injection molded part 31 of the second embodiment, as shown in FIG. 9(a), the axial length of the inner periphery of the cavity mold 40 corresponding to the bottom surface from the top end of the body of the first layer 11 is set to L1.

[0074] 9(c), in the second injection molding section 33 of the second embodiment, the axial length (depth) of the inner peripheral portion of the cavity mold 50 that accommodates the first layer 11 from the top end to the bottom surface of the body is set to L2, which is shorter than L1 (L1>L2). For example, L2 is set shorter than L1 by the deformation allowance of the first layer 11 (the amount of compression of the first layer 11 due to the upward pushing of the cavity mold 50 or the amount of contraction of the first layer 11 due to heat dissipation or the like before the second injection molding step). In other words, the depth of the mold space of the cavity mold 50 that accommodates the first layer 11 is shorter than the axial length of the first layer 11.

[0075] 9(c) and 10(b), a curved recess 51a is formed at the tip of the core mold 51 in the second embodiment. When the mold is closed, the recess 51a faces the outlet of the second resin material located at the center of the second cavity mold 50B, and forms a resin pool space between the recess 51a and the opening 16 of the first layer 11. This resin pool forms a protrusion 12a on the inner peripheral side of the second layer 12.

[0076] 10(b), for example, in the second injection molding section 33 of the second embodiment, the aperture d2 (diameter of the valve pin) of the tip of the hot runner die 52 is set smaller than the aperture (diameter of the valve pin 43) of the tip of the hot runner die 42 of the first injection molding section 31 and the diameter d1 of the opening 16 of the first layer 11. By narrowing the aperture d2 of the tip of the hot runner die 52 smaller than the diameter d1 of the opening 16, the flow rate of the second resin material injected into the mold space of the second injection molding section 33 can be increased.

[0077] The steps of the method for manufacturing the peelable container 20 in the second embodiment include a first injection molding step (S101), a first temperature adjustment step (S102), a second injection molding step (S103), a second temperature adjustment step (S104), a blow molding step (S105), and a container removal step (S106), as shown in Fig. 7. The first injection molding step (S101) and the first temperature adjustment step (S102) in the second embodiment are the same as those in the first embodiment.

[0078] In the second injection molding step (S103) of the second embodiment, the first layer 11 of the preform 10 is accommodated in the second injection molding section 33, and the second layer 12 is injection molded.

[0079] 9(c), in the second injection molding section 33, a mold space is formed between the inner periphery of the first layer 11 and the surface of the core mold 51 facing the inner periphery of the first layer 11, and the above mold space is filled with the second resin material from the hot runner mold 52. Note that a thin film portion 18 is formed at the bottom of the first layer 11, but the thin film portion 18 is broken by the injection pressure of the second resin material to form an opening 16 at the bottom, and the second resin material is introduced from the above opening 16 to the inner periphery of the first layer 11.

[0080] As described above, the depth of the mold space of the cavity mold 50 that accommodates the first layer 11 is shorter than the axial length of the first layer 11. Therefore, when the first layer 11 is accommodated in the cavity mold 50, the bottom of the first layer 11 is pressed against the bottom surface of the cavity mold 50 to bring them into contact with each other, thereby preventing a gap from being generated between the bottom of the first layer 11 and the cavity mold 50.

[0081] Furthermore, a resin pool space is formed between the opening 16 of the first layer 11 and the recessed portion 51a of the core mold 51. The second resin material that has passed through the opening 16 hits the recessed portion 51a of the core mold 51 and is stirred in the resin pool space, and then flows into the mold space between the inner circumference of the first layer 11 and the surface of the core mold 51. As the second resin material is stirred in the resin pool space, the fragments of the thin film portion 18 of the first layer 11 are mixed with the high-temperature second resin material and melt. This allows the fragments of the thin film portion 18 to dissipate to an extent that they cannot be visually recognized.

[0082] In addition, the diameter d2 of the tip of the hot runner mold 52 is narrowed down to be smaller than the diameter d1 of the opening 16 of the first layer 11. By increasing the flow rate of the second resin material as it passes through the tip of the hot runner mold 52 and hits the recessed portion 51a, the second resin material is sufficiently agitated in the space of the resin pool, making it easier to dissipate the fragments of the thin film portion 18. Furthermore, it makes it easier to break the thin film portion 18. After hitting recess 51a, a portion of the second resin material passes through opening 16 and is guided to the outside of first layer 11, and circulates in the vicinity of opening 16. This flow also agitates the second resin material, accelerating the dissipation of fragments of thin film portion 18.

[0083] Here, the temperature of the second resin material filled in the second injection molding section 33 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 when the second resin material is filled in the second injection molding section 33 is cooled to a temperature equal to or lower than the melting point of the second resin material.

[0084] In the second injection molding section 33, the cavity mold 50 faces the outer periphery of the first layer 11, and the shape of the first layer 11 is maintained from the outer periphery 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.

[0085] In the second injection molding section 33, the second protrusions 54 penetrate and close the recesses 11a of the first layer 11, so that the recesses 17 of the preform 10 are not closed with the second resin material. In addition, the tip of the second protrusions 54 in the second injection molding section 33 protrudes to the inner periphery side of the first layer, so that the recesses 17 of the preform 10 formed by the second protrusions 54 penetrate the first layer 11 and have a shape in which the surface of the second layer 12 is exposed in the recesses 17.

[0086] In this manner, the preform 10 in which the second layer 12 is laminated on the inner peripheral side of the first layer 11 is manufactured by the first injection molding step and the second injection molding step. Thereafter, when the second injection molding section 33 is opened, the rotating plate 37a of the conveying mechanism 37 rotates a predetermined angle, and the preform 10 held in the neck mold 37b is conveyed to the second temperature adjustment section 34 while retaining the heat retained during injection molding. The second temperature adjusting step (S104), the blow molding step (S105), and the container removal step (S106) of the second embodiment are all similar to those of the first embodiment.

[0087] The effects of the blow molding apparatus and the blow molding method according to the second embodiment will be described below. In the second embodiment, in the second injection molding section 33, the depth of the mold space of the cavity mold 50 that accommodates the first layer 11 is shorter than the axial length of the first layer 11. Therefore, the bottom of the first layer 11 is pressed against the bottom surface of the cavity mold 50, and the occurrence of a gap between the bottom of the first layer 11 and the cavity mold 50 is suppressed. Therefore, according to this embodiment, it becomes difficult for the second resin material to flow between the first layer 11 and the cavity mold 50, and the occurrence of molding defects in which the second resin material covers the outer periphery of the first layer 11 is suppressed.

[0088] In the second embodiment, a recess 51a is provided at the tip of the core mold 51, and the fragments of the thin film portion 18 are mixed and melted by stirring them with the high-temperature second resin material during injection molding, making it easier to dissipate the fragments of the thin film portion 18. This reduces the risk of the fragments of the thin film portion 18 remaining in the inner layer of the preform 10 or the peeling container 20, which would spoil the aesthetic appearance.

[0089] The present invention is not limited to the above-described embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.

[0090] In the above embodiment, an example in which one recess 17 is provided on the bottom 15 of the preform 10 has been described, but the number of recesses 17 may be multiple. FIG. 6(b) shows an example in which the first protrusions 44 are provided in two places in the second cavity mold 40B of the first injection molding section 31. In the example of FIG. 6(b), the two first protrusions 44 are arranged at positions that are point symmetric with respect to the central axis at an interval of 180°. The number of the first protrusions 44 may be three or more. In this case, it is preferable that each of the first protrusions 44 is arranged in a positional relationship that is point symmetric with respect to the central axis. According to the above-mentioned configuration, the unevenness in the circumferential direction of the resin flow during injection molding is reduced. In addition, in the case of the above-mentioned configuration, it becomes necessary to dispose the second protrusion 54 at the same position as the first protrusion 44 in the second injection molding part 33 as well.

[0091] In addition, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0092] 10...preform, 11...first layer, 11a...recess, 12...second layer, 16...opening, 17...recess, 18...thin film portion, 19, 26...locking portion, 20...peeling container, 24...air inlet hole, 30...blow molding device, 31...first injection molding section, 33...second injection molding section, 35...blow molding section, 38...first injection device, 39...second injection device, 40B, 50B...cavity mold, 44...first protrusion, 54...second protrusion

Claims

[Claim 1] a first injection molding step of injection molding a first layer of a bottomed cylindrical preform with a first resin material; a second injection molding step of injecting a second resin material different from the first resin material to laminate a second layer on the inner periphery side of the first layer; A blow molding process for producing a peelable container by blow molding the preform obtained in the second injection molding process while maintaining the heat retained during injection molding, In the second injection molding step, the first layer is accommodated in a mold space of a first mold, a second mold is inserted into the inside of the first layer, and the second resin material is injected between the first layer and the second mold; The depth of the mold space of the first mold is shorter than the axial length of the first layer obtained in the first injection molding process. A method for manufacturing a peelable container.

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