Method for manufacturing a resin-made container and manufacturing apparatus

Abstract

This invention provides a method and apparatus for manufacturing a resin container. The method for manufacturing a resin container having a translucent area and a non-translucent area extending axially includes: a first injection molding step, in which a first layer of a preform having an axially extending protrusion is injection molded using a first resin material having translucent properties; a second injection molding step, in which a colored second resin material is injected into the forming surface side of the protrusion of the first layer, and while exposing the protrusion axially, a colored second layer is laminated in the area other than the protrusion of the first layer; and a blow molding step, in which the preform is blow molded in a state of heat retention as in injection molding.

Description

Technical Field

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

[0002] Previously, a type of resin container was known where the main body was colored to make it opaque in order to improve the light-blocking effect on the contents and the container's aesthetics. However, with the main body of the container opaque, it was difficult to ascertain the remaining amount of contents. Therefore, in this type of resin container, a window consisting of a longitudinally elongated transparent area was formed in the main body of the container.

[0003] So-called windowed resin containers, which have windows formed in the main body of the container, are mainly manufactured by extrusion blow molding, but manufacturing methods using three-layer molding or insert molding have also been proposed.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6061250

[0007] Patent Document 2: Japanese Utility Model Publication No. 1-33291

[0008] Patent Document 3: Japanese Utility Model Publication No. 60-75009 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, if extrusion blow molding is used to manufacture resin containers with windows, the aesthetics and dimensional accuracy of the containers are generally reduced. Moreover, in extrusion blow molding, subsequent processes are necessary, and a large amount of waste is generated.

[0011] Furthermore, manufacturing a windowed resin container using a three-layer molding process requires a special hot runner mold. Also, while the three-layer molding process involves simultaneously injecting transparent and colored materials to achieve the desired shape, injection control is very difficult, increasing manufacturing costs.

[0012] Furthermore, when manufacturing windowed resin containers using insert molding, it is necessary to pre-accumulate the molded parts for inserting into the preform. Moreover, when inserting into the molded parts, the preform must be fully cooled, and a process of reheating the cooled preform before blow molding is required, thus increasing the manufacturing cost accordingly.

[0013] Therefore, the present invention was made in view of such a problem, and its object is to provide a method for manufacturing a windowed resin container that can produce an aesthetically pleasing and dimensionally accurate product at a lower cost than before.

[0014] Technical solutions for solving the problem

[0015] A method for manufacturing a resin container according to one aspect of the present invention includes: a first injection molding step, wherein a first layer of a preform is injection molded using a first resin material having translucency, the preform being formed into a bottomed cylindrical shape and having an axially extending protrusion on an inner or outer circumferential surface; a second injection molding step, wherein a colored second resin material is injected into the forming surface side of the protrusion of the first layer, and while exposing the protrusion axially, a colored second layer is laminated in areas other than the protrusion of the first layer; and a blow molding step, wherein the preform obtained in the second injection molding step is blow molded in a state where it is kept hot during injection molding to manufacture the resin container. The resin container has an axially extending translucent area formed by shaping the protrusion, and a non-translucent area formed by shaping the second layer.

[0016] Invention Effects

[0017] According to one aspect of the present invention, it is possible to manufacture aesthetically pleasing and dimensionally accurate resin containers with windows at a lower cost than ever before. Attached Figure Description

[0018] Figure 1 This is a diagram illustrating an example of the container used in this embodiment.

[0019] Figure 2 This is a diagram showing an example of the preform of this embodiment.

[0020] Figure 3 This is a diagram schematically illustrating the structure of the blow molding apparatus of this embodiment.

[0021] Figure 4 This is a diagram showing the manufacturing process of the preform in the first example of this embodiment.

[0022] Figure 5 This is a diagram showing the manufacturing process of the preform in the second example of this embodiment.

[0023] Figure 6 It is a cross-sectional view showing the manufacturing process of the preform.

[0024] Figure 7 This is a diagram showing an example of the structure of the second temperature adjustment unit.

[0025] Figure 8 It is a flowchart illustrating the process of manufacturing a container.

[0026] Figure 9 This is a diagram showing a modified example of the second temperature adjustment section. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0028] 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 reference numerals. Also, the shapes and dimensions of the elements shown in the drawings are schematic and do not represent actual shapes and dimensions.

[0029] <Example of the structure of a resin container>

[0030] First, refer to Figure 1 Hereinafter, a structural example of the resin container (hereinafter also referred to as container) 10 of this embodiment will be described.

[0031] Figure 1 This is a diagram showing an example of the container 10 in this embodiment.

[0032] Figure 1 The container 10 shown is formed, for example, from a resin material such as PET (polyethylene terephthalate). The container 10 has: a neck 12 with an opening 11 at the upper end; a cylindrical body 13 continuous from the neck 12; and a bottom 14 continuous from the body 13.

[0033] Although the illustration is omitted, the main body 13 and bottom 14 of container 10 have a structure consisting of an inner layer facing the inner surface of the container and an outer layer facing the outer surface of the container. This structure is formed by blow molding the preform 20, which will be described later.

[0034] Furthermore, the main body 13 of the container 10 has a non-transparent region 15 with low light transmittance due to coloring, and a translucent region 16 with higher light transmittance than the non-transparent region 15. The non-transparent region 15 occupies most of the main body 13 of the container 10 and is colored to improve light-blocking properties for the contents and the aesthetics of the container. The non-transparent region 15 can be formed using a resin material that colors either the outer or inner layer of the preform 20 of the laminated structure.

[0035] The light-transmitting area 16 is a strip-shaped area partially formed in the circumferential direction of the main body 13 and extending along the axial direction of the container 10. The light-transmitting area 16 functions as a window for confirming the remaining amount of contents from the outside of the container 10. The light-transmitting area 16 can be formed by using a transparent resin material in one of the outer or inner layers of the preform 20 of the laminated structure, and partially providing areas where the colored resin material and the transparent resin material do not overlap radially.

[0036] <Structural Example of Preform>

[0037] Figure 2 This section shows an example of a preform 20 used in the manufacture of the container 10 in this embodiment.

[0038] Figure 2 (a) is a longitudinal sectional view of the pre-plasticized preform 20 of the first example of this embodiment. Figure 2 (b) is Figure 2 (a) Sectional view along line IIb-IIb. Figure 2 (c) is a longitudinal sectional view of the preform in the second example of this embodiment. Figure 2 (d) is Figure 2 (c) Sectional view of line IId-IId.

[0039] Figure 2 The preforms 20 shown in (a) and (c) are both bottomed cylindrical shapes with one open end and the other closed. The preforms 20 in the first and second examples include: a cylindrical main body 23; a bottom 24 closing the other end of the main body 23; and a neck 22 with an opening at one end of the main body 23. Furthermore, the preforms 20 in the first and second examples have a multi-layered structure consisting of a transparent first layer 25 and a colored second layer 26. The first layer 25 and the second layer 26 are formed by a two-stage injection molding process, as described later.

[0040] exist Figure 2 In the first example of the preform 20 shown in (a) and (b), a transparent first layer 25 is formed on the outer peripheral side, and a colored second layer 26 is formed on the inner peripheral side. In the first example of the preform 20, a neck is formed on the first layer 25 located on the outer peripheral side, and the second layer 26 is stacked on the inner peripheral side from the neck 22 to the bottom 24 of the first layer 25. In addition, in the first example of the preform 20, a hole 27 is formed at the center of the bottom of the first layer 25, and the hole 27 of the first layer 25 is blocked from the inside by the second layer 26.

[0041] Furthermore, in the first layer of the preform 20 in the first example, a protrusion 28a protruding inward is formed in a portion of the circumferential direction. The protrusion 28a extends axially from the neck 22 to the bottom 24 of the preform 20. The front end of the radially protruding protrusion 28a faces the inner circumferential surface of the preform 20, as shown below. Figure 2 As shown in (b), on the inner circumferential surface of the preform 20, the second layer 26 and the front end of the protrusion 28a are on the same plane.

[0042] In the area outside the protrusion 28a of the first layer 25, the colored second layer 26 is located on the inner periphery of the transparent first layer 25. Therefore, the color of the second layer 26 is visible on the outside through the transparent first layer 25. Thus, the area outside the protrusion 28a of the first layer 25 corresponds to the opaque area 15 of the blow-molded container 10.

[0043] On the other hand, in the region of the protrusion 28a of the first layer 25, only the first layer 25 exists radially, and the colored second layer 26 is not formed. Therefore, light is well transmitted in the region of the protrusion 28a of the first layer 25. Thus, the region of the protrusion 28a of the first layer 25 corresponds to the light-transmitting region 16 of the blow-molded container 10.

[0044] On the other hand, Figure 2 In the preform 20 of the second example shown in (c) and (d), a transparent first layer 25 is formed on the inner peripheral side, and a colored second layer 26 is formed on the outer peripheral side. In the preform 20 of the second example, a neck 22 is formed on the first layer 25 located on the inner peripheral side, and the second layer 26 is stacked on the outer peripheral side from the main body 23 of the first layer 25 to the bottom 24.

[0045] Furthermore, in the first layer 25 of the preform 20 in the second example, a protrusion 28b protruding outward is formed in a portion of the circumferential direction. The protrusion 28b extends axially from the main body 23 to the bottom 24 of the preform 20. The front end of the radially protruding protrusion 28b faces the outer peripheral surface of the preform 20, as shown below. Figure 2 As shown in (d), on the outer peripheral surface of the preform 20, the second layer 26 and the front end of the protrusion 28b are on the same plane.

[0046] In the area outside the protrusion 28b of the first layer 25, the second layer 26 faces the outer peripheral surface, so the color of the second layer 26 is directly visible on the outside. Therefore, the area outside the protrusion 28b of the first layer 25 corresponds to the opaque area 15 of the blow-molded container 10.

[0047] On the other hand, in the region of the protrusion 28b of the first layer 25, only the first layer 25 exists radially, and the colored second layer 26 is not formed. Therefore, light is well transmitted in the region of the protrusion 28b of the first layer 25. Thus, the region of the protrusion 28b of the first layer 25 corresponds to the light-transmitting region 16 of the blow-molded container 10.

[0048] In addition, the shape, size and other specifications of the first layer 25 and the second layer 26 can be appropriately adjusted according to the shape of the manufactured container 10.

[0049] Hereinafter, the resin material forming the first layer 25 will be referred to as the first resin material, and the resin material forming the second layer 26 will be referred to as the second resin material. For example, the first resin material is transparent, and the second resin material is internally colored by adding a colorant. Here, a colorant may be added to the first resin material within a range that ensures relatively high light transmittance relative to the second resin material. On the other hand, the second resin material may also have some light transmittance within a range where its light transmittance is lower than that of the first resin material.

[0050] Both the first and second resin materials are thermoplastic synthetic resins, which can be appropriately selected according to the specifications of container 10. Specific types of materials include, for example, PET, PEN (polyethylene naphthalate), PCTA (polycyclohexanedimethyl terephthalate), and Tritan (Tritan... TM (Registered Trademarks): Copolyesters, 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., manufactured by Eastman Chemical Company.

[0051] The first resin material and the second resin material can be appropriately combined according to the specifications of the container 10, but it is preferable to combine materials with high weldability. As an example, the first resin material and the second resin material can also be the same resin material with different colorant compositions (e.g., PET to each other). Alternatively, one resin material can be PP and the other resin material can be PET.

[0052] <Description of the container manufacturing apparatus>

[0053] Figure 3 This is a schematic diagram illustrating the structure of the blow molding apparatus of this embodiment. The blow molding apparatus 30 of this embodiment is an example of a container manufacturing apparatus, which employs a hot preform method (also known as a one-stage method) to blow mold the container 10 without cooling the preform 20 to room temperature and effectively utilizing the heat retained during injection molding (internal heat).

[0054] The blow molding apparatus 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 arranged at positions that rotate by a given angle (e.g., 60 degrees) around the conveying mechanism 37 each time.

[0055] (Conveying mechanism 37)

[0056] Conveying mechanism 37 is equipped with Figure 3 A rotating plate 37a rotates around an axis perpendicular to the paper surface. On the rotating plate 37a, at each given angle, one or more neck molds 37b are respectively arranged to hold the neck 22 (or the neck 12 of the container 10) of the preform 20. Figure 3 (Not shown in the figure). The conveying mechanism 37, by rotating the rotating plate 37a, conveys the preform 20 (or container 10) held by the neck mold 37b in the following sequence: first injection molding section 31, first temperature adjustment section 32, second injection molding section 33, second temperature adjustment section 34, blow molding section 35, and take-out section 36. In addition, the conveying mechanism 37 can also raise and lower the rotating plate 37a, and also perform the actions involved in mold closing and mold opening (demolding) in the first injection molding section 31 and the second injection molding section 33.

[0057] (First Injection Molding Section 31)

[0058] The first injection molding section 31 includes a cavity mold 40, a core mold 41, and a hot runner mold 42, and manufactures the first layer 25 of the preform 20. For example... Figure 3 As shown, a first injection device 38 is connected to the first injection molding section 31 to supply the first resin material to the hot runner mold 42.

[0059] Figure 4 (a) and (b) represent the preform 20 of the first example. Figure 2 The first injection molding section 31a is formed by molding the first layer 25 of (a) and (b). Figure 5 (a) indicates the pre-plasticized preform of the second example. Figure 2 The first injection molding portion 31b is formed by molding the first layer 25 of (c) and (d). In addition, in this specification, when it is not necessary to distinguish between the first injection molding portions 31a and 31b, they are collectively referred to as the first injection molding portion 31.

[0060] like Figure 4 of (a), Figure 5 As shown in (a), in the first injection molding section 31, the cavity mold 40, the core mold 41, and the neck mold 37b of the conveying mechanism 37 are closed to form a mold space for the first layer 25. Then, the first resin material is fed from the first injection device 38 into the mold space via the hot runner mold 42, thereby manufacturing the first layer 25 of the preform 20 in the first injection molding section 31.

[0061] like Figure 4As shown in (a), a groove 41a for forming a protrusion 28a of the first layer 25 is formed in the core mold 41 of the first injection molding part 31a. Thus, the first injection molding part 31a can form the protrusion 28a on the inner periphery of the first layer 25.

[0062] On the other hand, such as Figure 5 As shown in (a), a groove 40a for forming a protrusion 28b of the first layer 25 is formed in the cavity mold 40 of the first injection molding part 31b. Thus, the first injection molding part 31b can form the protrusion 28b on the outer periphery of the first layer 25.

[0063] In addition, the radial depth of the groove 41a of the first injection molding part 31a and the groove 40a of the first injection molding part 31b (i.e., the radial protrusion of the protrusions 28a and 28b) is set to be longer than the thickness of the second layer 26.

[0064] In addition, such as Figure 4 As shown in (b), in the first injection molding section 31a, a valve pin 43 capable of moving axially to a position close to the core mold 41 is disposed inside the hot runner mold 42. 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. Through such movement of the valve pin 43 during injection molding, a thin film portion 27a of resin material with a wall thickness thinner than the peripheral portion can be formed at the center of the bottom of the first layer 25.

[0065] Furthermore, when the first injection molding section 31 opens, the neck mold 37b of the conveying mechanism 37 remains closed and directly holds the first layer 25 of the preform 20 for conveying. The number of preforms 20 simultaneously molded by the first injection molding section 31 (i.e., the number of containers 10 that can be simultaneously molded by the blow molding device 30) can be appropriately set. Additionally, in Figure 3 The diagram shows a structure that simultaneously transports four pre-plasticized blanks.

[0066] (First temperature adjustment unit 32)

[0067] The first temperature adjustment unit 32 includes a temperature adjustment mold unit (temperature regulating tank and temperature regulating core) for temperature adjustment (not shown). The first temperature adjustment unit 32 cools the first layer 25 of the preform 20, which is in a high-temperature state after injection molding, by placing it in the mold unit and maintaining it at a given temperature. In addition, the first temperature adjustment unit 32 also functions to adjust the temperature distribution of the first layer 25 of the preform 20 to a given state before it is conveyed to the second injection molding unit 33.

[0068] (Second Injection Molding Section 33)

[0069] The second injection molding section 33 includes a cavity mold 50, a core mold 51, and a hot runner mold 52, and injects and molds the second layer 26 into the outer or inner periphery of the first layer 25. For example... Figure 3 As shown, a second injection device 39 for supplying the second resin material to the hot runner mold 52 is connected to the second injection molding section 33.

[0070] Figure 4 (c) indicates the second injection molding section 33a that forms the second layer 26 of the preform 20 in the first example. Figure 5 (b) indicates the second injection molding portion 33b that forms the second layer 26 of the preform 20 in the second example. Furthermore, in this specification, when it is not necessary to distinguish between the second injection molding portions 33a and 33b, they are collectively referred to as the second injection molding portion 33.

[0071] The second injection molding section 33a houses the first layer 25 of the preform 20, which is injection molded by the first injection molding section 31a. For example... Figure 4 As shown in (c), with the second injection molding section 33a closed, a mold space is formed between the neck and the surface of the core mold 51 from the inner circumferential side of the first layer 25 to the bottom. By filling the mold space with a second resin material from the second injection device 39 via the hot runner mold 52, a second layer 26 is formed on the inner circumferential side of the first layer 25. Thus, the preform 20 of the first example is manufactured.

[0072] Furthermore, a curved recess 51a is formed at the front end of the core mold 51 of the second injection molding section 33a. When the mold is closed, the recess 51a is opposite to the outlet of the second resin material located at the center of the cavity mold, forming a space for resin accumulation between it and the hole 27 of the first layer 25.

[0073] Furthermore, in the second injection molding section 33a, the axial depth of the mold space of the cavity mold 50 that houses the first layer 25 can be shorter than the axial length of the first layer 25. As a result, when the first layer 25 is housed in the cavity mold 50, the bottom of the first layer 25 presses against the bottom surface of the cavity mold 50 and the two come into contact, which can suppress the generation of gaps between the bottom of the first layer 25 and the cavity mold 50.

[0074] On the other hand, the second injection molding section 33b houses the first layer 25 of the preform 20 injected by the first injection molding section 31b. For example... Figure 5 As shown in (b), with the second injection molding section 33b closed, a mold space is formed between the main body portion on the outer periphery of the first layer 25 and the inner surface of the cavity mold 50. By filling the mold space with second resin material from the second injection device 39 via the hot runner mold 52, a second layer 26 is formed on the outer periphery of the first layer 25. Thus, a preform 20 of the second example is manufactured.

[0075] (Second temperature adjustment unit 34)

[0076] The second temperature adjustment unit 34 homogenizes and removes temperature deviations in the preform 20 manufactured by the second injection molding unit 33, adjusting the temperature of the preform 20 to a temperature suitable for final blow molding (e.g., approximately 90°C to 105°C). In addition, the second temperature adjustment unit 34 also cools the preform 20 at its high temperature after injection molding.

[0077] like Figure 7 As shown, the second temperature adjustment unit 34 includes a cavity mold (can mold) 60 and a heating rod 61.

[0078] The cavity mold 60 is a mold with a temperature-regulating space capable of accommodating the preform 20 manufactured by the second injection molding section 33. The cavity mold 60 is a structure divided into three sections along the axial direction of the preform 20, namely, upper section mold 60a, middle section mold 60b, and lower section mold 60c, from top to bottom.

[0079] Heaters are provided in the upper mold 60a, middle mold 60b, and lower mold 60c, or flow paths (not shown) are formed inside for the flow of temperature regulating medium (cooling medium). Therefore, the temperature of the cavity mold 60 is maintained at a given temperature by the heaters or temperature regulating medium. Alternatively, the temperature distribution of the preform 20 can be varied axially by changing the temperatures of the heaters and temperature regulating medium in the upper mold 60a, middle mold 60b, and lower mold 60c.

[0080] A heating rod 61 is inserted into the interior of the preform 20 and configured to move forward and backward relative to the neck mold 37b that holds the preform 20. Figure 7 In (a), the state in which the heating rod 61 is inserted into the neck mold 37b is shown.

[0081] A heating element 62 extending axially is mounted on the heating rod 61. For example... Figure 7 As shown in (b), the heating element 62 is partially disposed in the circumferential direction at a position corresponding to the protrusion 28a (28b) of the pre-plasticized blank 20, and performs the function of locally heating the protrusion 28a (28b) of the pre-plasticized blank 20.

[0082] (Blow molding section 35)

[0083] The blow molding section 35 blow molds the pre-plasticized preform 20, whose temperature has been adjusted by the second temperature adjustment section 34, to manufacture the container 10.

[0084] The blow molding section 35 includes a blow molding cavity mold, a bottom mold, a stretching rod, and an air inlet member (all not shown) that serve as a pair of parting molds corresponding to the shape of the container 10. The blow molding section 35 performs blow molding while stretching the preform 20. As a result, the preform 20 is shaped into the shape of the blow molding cavity mold, enabling the manufacture of the container 10.

[0085] (Removal section 36)

[0086] The removal section 36 is configured to open the neck 12 of the container 10 manufactured by the blow molding section 35 from the neck mold 37b and remove the container 10 to the outside of the blow molding apparatus 30.

[0087] <Description of the manufacturing method of the container>

[0088] Next, the manufacturing method of the container 10 of the blow molding apparatus 30 based on this embodiment will be described. Figure 8 This is a flowchart illustrating the process of manufacturing container 10.

[0089] (Step S101: First Injection Molding Process)

[0090] First, such as Figure 4 of (a), Figure 5 As shown in (a), in the first injection molding section 31, the first resin material is injected from the first injection device 38 into the mold space formed by the cavity mold 40, the core mold 41 and the neck mold 37b of the conveying mechanism 37 to form the first layer 25 of the preform 20.

[0091] In the case of molding the preform 20 in the first example, the first injection molding part 31a is used, such as Figure 6 As shown in (a), a first layer 25 with a protrusion 28a is formed on the inner circumferential side. The radial protrusion ra of the protrusion 28a is set to be longer than the thickness t2 of the second layer 26, mimicking the radial dimension of the groove 41a of the core mold 41.

[0092] In the first injection molding section 31a, such as Figure 4 As shown in (b), after the first layer 25 of the preform 20 is formed, a process is performed to make the valve pin 43 protrude to a position close to the core mold 41. As a result, a thin film portion 27a with a wall thickness thinner than the periphery is formed at the center of the bottom of the first layer 25.

[0093] On the other hand, when molding the preform 20 in the second example, the first injection molding part 31b is used, such as... Figure 6 As shown in (b), a first layer 25 with a protrusion 28b is formed on the outer peripheral side. The radial protrusion rb of the protrusion 28b is set to be longer than the thickness t2 of the second layer 26, mimicking the radial dimension of the groove 40a of the cavity mold 40.

[0094] Subsequently, if the first injection molding section 31 opens, the rotating plate 37a of the conveying mechanism 37 rotates by a given angle, and the first layer 25 of the preform 20 held in the neck mold 37b is conveyed to the first temperature adjustment section 32 while retaining heat during injection molding.

[0095] (Step S102: First temperature adjustment process)

[0096] Next, in the first temperature adjustment unit 32, the first layer 25 of the preform 20 is housed in the temperature adjustment mold unit, and the first layer 25 is cooled and its temperature distribution is adjusted (homogenization and removal of temperature deviation). Afterward, the rotating plate 37a of the conveying mechanism 37 rotates by a given angle, and the first layer 25 of the preform 20 held in the neck mold 37b is conveyed to the second injection molding unit 33.

[0097] (Step S103: Second Injection Molding Process)

[0098] Next, the first layer 25 of the preform 20 is housed in the second injection molding section 33, and the second layer 26 is injection molded. The second injection molding section 33a is used when molding the preform 20 of the first example, and the second injection molding section 33b is used when molding the preform 20 of the second example.

[0099] In the second injection molding section 33a, such as Figure 4 (c) Figure 6 As shown in (a), a mold space is formed between the neck 22 on the inner circumferential side of the first layer 25 and the core mold 51 facing the inner circumference of the first layer 25, extending from the neck 22 to the bottom 24. The radial protrusion ra of the protrusion 28a is longer than the thickness t2 of the second layer 26, so when the first layer 25 is housed in the second injection molding section 33a and the mold is closed, the protrusion 28a of the first layer presses against the core mold 51 and forms a tight seal (see reference). Figure 6 (a) Therefore, it is possible to suppress the formation of a gap between the protrusion 28a of the first layer 25 and the core mold 51, and to prevent the second resin material from flowing into the inner surface side of the protrusion 28a. As a result, an area for exposing the first layer 25 can be formed on the inner circumferential side of the preform 20 in the first example.

[0100] The second resin material is filled from the hot runner mold 52 into the mold space described above. A thin film portion 27a is formed at the bottom of the first layer 25, but the thin film portion 27a breaks under the injection pressure of the second resin material, forming a hole 27 at the bottom. The second resin material is guided to the inner peripheral side of the first layer 25 through the hole 27.

[0101] like Figure 4As shown in (c), the cavity mold 50 faces the outer peripheral side of the first layer 25, and the shape of the first layer 25 is maintained by the cavity mold 50 from the outer peripheral side. Therefore, even if the second resin material comes into contact with the first layer 25, thermal deformation of the first layer 25 can be suppressed.

[0102] Furthermore, a resin accumulation space is formed between the hole 27 of the first layer 25 and the recess 51a of the core mold 51. The second resin material, passing through the hole 27, comes into contact with the recess 51a of the core mold 51 and is stirred in the resin accumulation space before flowing into the mold space between the inner periphery of the first layer 25 and the surface of the core mold 51. By stirring the second resin material in the resin accumulation space, the fragments of the film portion 27a of the first layer 25 are mixed with the high-temperature second resin material and melted. As a result, the fragments of the film portion 27a can be dissipated to a degree that is not visually perceptible.

[0103] Furthermore, in the second injection molding section 33a, the axial depth of the mold space of the cavity mold 50 housing the first layer 25 is shorter than the axial length of the first layer 25. Therefore, the bottom 24 of the first layer 25 presses against the bottom surface of the cavity mold 50, thereby suppressing the formation of a gap between the bottom 24 of the first layer 25 and the cavity mold 50. Consequently, the second resin material is less likely to flow between the first layer 25 and the cavity mold 50, thus suppressing the occurrence of molding defects where the second resin material covers the outer periphery of the first layer 25.

[0104] As described above, when forming the preform 20 of the first example, a second layer 26 can be formed on the inner circumferential side of the first layer 25.

[0105] On the other hand, in the second injection molding section 33b, such as Figure 5 (b) Figure 6 As shown in (b), a mold space is formed between the main body portion 23 on the outer periphery side of the first layer 25 and the cavity mold 50 facing the outer periphery of the first layer 25, extending from the bottom 24. The radial protrusion rb of the protrusion 28b is longer than the thickness t2 of the second layer 26, so when the first layer 25 is housed in the second injection molding portion 33b and the mold is closed, the protrusion 28b of the first layer 25 presses against the cavity mold 50 and forms a tight seal (see reference). Figure 6 (b)). Thus, it is possible to suppress the formation of a gap between the protrusion 28b of the first layer 25 and the cavity mold 50, and to prevent the second resin material from flowing into the outer surface side of the protrusion 28b. Thus, it is possible to form an area on the outer periphery of the preform 20 in the second example for exposing the first layer 25.

[0106] The second resin material is filled into the aforementioned mold space from the hot runner mold 52. For example... Figure 5As shown in (b), a core mold 51 is inserted into the inner circumferential side of the first layer 25, and the shape of the first layer 25 is maintained from the inner circumferential side by the core mold 51. Therefore, even if the second resin material comes into contact with the first layer 25, thermal deformation of the first layer 25 can be suppressed. As described above, in the case of molding the preform of the second example, a second layer 26 can be formed on the outer circumferential side of the first layer 25.

[0107] As described above, the preform 20 of the first or second example is manufactured through the first injection molding process and the second injection molding process.

[0108] Subsequently, if the second injection molding section 33 opens, the rotating plate 37a of the conveying mechanism 37 rotates by a given angle, and the preform 20 held in the neck mold 37b is conveyed to the second temperature adjustment section 34 while retaining heat during injection molding.

[0109] (Step S104: Second temperature adjustment process)

[0110] Next, the pre-plasticized preform 20 is housed in the second temperature adjustment section 34, and temperature adjustment is performed to bring the temperature of the pre-plasticized preform 20 close to the temperature suitable for final blow molding.

[0111] like Figure 7 As shown, in the second temperature adjustment section 34, the position of the protrusion 28a (28b) of the preform 20 is locally heated from the inner circumferential side by the heating plate 62 of the heating rod 61.

[0112] The protrusions 28a (28b) of the preform 20 are formed from the first resin material over the entire radial area. Therefore, the protrusions 28a (28b) of the preform 20 retain less heat compared to the area where the high-temperature second resin material is laminated in the second injection molding section 33, making them less prone to deformation during blow molding. By locally heating the protrusions 28a (28b) using the second temperature adjustment section 34, the circumferential temperature deviation of the preform 20 is reduced, which in particular improves the shapeability of the light-transmitting area 16 of the container 10.

[0113] Subsequently, the rotating plate 37a of the conveying mechanism 37 rotates by a given angle, and the pre-plasticized preform 20, which is kept at the temperature adjusted by the neck mold 37b, is conveyed to the blow molding section 35.

[0114] (Step S105: Blow molding process)

[0115] Next, the container 10 is blow-molded in the blow molding section 35.

[0116] First, the blow molding cavity mold is closed, housing the preform 20 within the mold space. The air inlet component (blow molding core) is lowered, bringing it into contact with the neck 22 of the preform 20. Then, the tension rod is lowered, restraining the bottom 24 of the preform 20 from its inner surface. Simultaneously, longitudinal stretching is performed as needed, while blow molding air is supplied from the air inlet component, thereby stretching the preform 20 laterally. As a result, the preform 20 bulges out and is shaped within the mold space of the blow molding cavity mold, blow-molded into the container 10. Furthermore, if the preform 20 is longer than the container 10, the bottom mold remains in a position below the bottom 24 of the preform 20 before the blow molding cavity mold is closed, and rapidly rises to the molding position after mold closing.

[0117] In this embodiment, by blow molding the preform 20 of the first or second example, the opaque area 15 of the container 10 is formed by stretching the second layer 26, and the translucent area 16 of the container 10 is formed by extending the protrusion of the first layer 25. Thus, a container 10 with a strip-shaped window formed in the main body 13 is manufactured.

[0118] (Step S106: Container Removal Process)

[0119] When the blow molding process is complete, the blow molding cavity mold opens. As a result, the container 10 can move from the blow molding section 35.

[0120] Next, the rotating plate 37a of the conveying mechanism 37 rotates by a given angle, and the container 10 is conveyed to the take-out section 36. In the take-out section 36, the neck 12 of the container 10 is opened from the neck mold 37b, and the container 10 is taken out of the blow molding apparatus 30.

[0121] This concludes one cycle of the manufacturing method for container 10. Afterwards, by rotating the rotating plate 37a of the conveying mechanism 37 by a given angle, the processes S101 to S106 described above are repeated. Furthermore, while the blow molding apparatus 30 is operating, the manufacturing of six sets of containers, each with a time difference of one process, is performed concurrently.

[0122] Furthermore, in the structure of the blow molding apparatus 30, the time for each of 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 is the same length. Similarly, the conveying time between each process is also the same length.

[0123] As described above, in this embodiment, a first layer 25 having longitudinal strip-shaped protrusions 28a and 28b is injection molded in the first injection molding step, and a second layer 26 is injection molded in the area outside the protrusions, either on the inner or outer periphery of the first layer 25, thereby manufacturing a preform 20 with a multi-layer structure suitable for a windowed container. In this embodiment, since the transparent material and the colored material are injection molded in two stages, it is not necessary to simultaneously inject the transparent material and the colored material during injection molding, thus reducing the manufacturing cost of the preform 20 compared to the three-layer molding method.

[0124] Furthermore, in this embodiment, a hot preform method is employed, where blow molding is performed while the preform is still hot, similar to injection molding. For example, compared to the method of creating a multi-layered preform by assembling cooled preforms and then reheating them for blow molding (cold preform method), in this embodiment, the preform is not cooled to near room temperature, and there is no need for preform assembly or reheating. Therefore, according to this embodiment, a series of processes from injection molding of the preform 20 to blow molding of the container 10 can be completed in a relatively short time. Consequently, the container 10 with a strip-shaped window on the main body 13 can be manufactured in a shorter cycle, significantly reducing the manufacturing cost of the container 10 compared to conventional methods.

[0125] Furthermore, in this embodiment, the container is manufactured by stretch blow molding, a process known as stretch blow molding, which involves stretching the preform 20 while simultaneously performing blow molding. Therefore, in this embodiment, the appearance and dimensional accuracy of the container 10 are improved compared to containers manufactured by extrusion blow molding. Additionally, in this embodiment, waste generation is suppressed compared to extrusion blow molding, thus reducing the manufacturing cost of the container 10.

[0126] <Modifications of the Implementation>

[0127] 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.

[0128] The structure of the second temperature adjustment unit 34 is not limited to a structure in which a heating rod 61 equipped with heating elements 62 is used to locally heat the pre-plasticized blank 20, as in the embodiment described above. For example, as Figure 9 As shown in (a) and (b), the heating rod 61 can also be positioned closer to the protrusion 28a (28b) of the preform 20, with the heating rod 61 eccentrically arranged relative to the central axis. Figure 9 The structure also allows for localized heating of the protrusions 28a (28b) of the preform from the inner circumference, achieving the same effect as the above-described embodiment.

[0129] At this time, the temperature deviation of the protrusions 28a (28b) of the pre-plasticized blank 20 can be further controlled by adjusting the interval of the cavity mold 60 of the second temperature adjustment part 34 on the protrusions 28a (28b) of the pre-plasticized blank 20.

[0130] In addition, in the first temperature adjustment unit 32 of the above embodiment, the protrusions 28a and 28b of the pre-plasticized blank 20 can also be heated locally in the same way as the second temperature adjustment unit 34.

[0131] Furthermore, in the above embodiment, the first temperature adjustment step between the first injection molding step and the second injection molding step can also be omitted. That is, the blow molding apparatus 30 can also be a structure (5-station machine) that does not have a first temperature adjustment unit 32 and arranges the first injection molding unit 31, the second injection molding unit 33, the second temperature adjustment unit 34, the blow molding unit 35, and the take-out unit 36 ​​at a position that rotates 72 degrees each time around the conveying mechanism 37.

[0132] Furthermore, in the above-described embodiments Figure 2 In the preform 20 of the second example shown in (c) and (d), as the resin material of the outer layer (second layer 26) that is not exposed on the inner circumferential side and does not come into contact with the contents, recycled materials (e.g., crushed materials (sheet materials)) may also be used.

[0133] Furthermore, the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the invention is indicated not by the foregoing description but by the scope of the patent claims, and is intended to include equivalents to the scope of the patent claims and all modifications within that scope.

[0134] Symbol Explanation

[0135] 10… Container; 15… Non-transparent area; 16… Transparent area; 20… Preform; 25… First layer; 26… Second layer; 28a, 28b… Protrusions; 30… Blow molding device; 31… First injection molding section; 32… First temperature adjustment section; 33… Second injection molding section; 34… Second temperature adjustment section; 35… Blow molding section; 38… First injection device; 39… Second injection device; 50… Cavity mold; 51… Core mold.

Claims

1. A method for manufacturing a resin container, comprising: In the first injection molding process, a first layer of a preform is injection molded using a first resin material that is translucent. The preform is formed into a bottomed cylindrical shape and has a convex portion that extends axially on the inner or outer circumferential surface. In the second injection molding process, a colored second resin material is injected into the forming surface side of the protrusion of the first layer, and while the protrusion is exposed axially, a colored second layer is laminated in the area other than the protrusion of the first layer. The temperature adjustment process involves adjusting the temperature of the preform obtained in the second injection molding process. as well as The blow molding process involves blow molding the pre-plasticized preform, after temperature adjustment, under the same heat-retaining condition as injection molding, to manufacture resin containers. The resin container has an axially elongated light-transmitting area formed by the shaping of the protrusion, and a light-blocking area formed by the shaping of the second layer. In the temperature adjustment process, at least the portion of the protrusion in the circumferential direction of the preform is locally heated.

2. The method for manufacturing a resin container according to claim 1, wherein, In the first injection molding process, the protrusion is formed on the inner peripheral surface of the first layer. In the second injection molding process, the second resin material is injected between the inner peripheral surface of the first layer and the mold disposed on the inner peripheral side of the first layer, and the second layer is stacked on the inner peripheral side of the first layer while the protrusion is exposed on the inner peripheral surface of the preform.

3. The method for manufacturing a resin container according to claim 1, wherein, In the first injection molding process, the protrusion is formed on the outer peripheral surface of the first layer. In the second injection molding process, the second resin material is injected between the outer peripheral surface of the first layer and the mold disposed on the outer peripheral side of the first layer, and the second layer is stacked on the outer peripheral side of the first layer while the protrusion is exposed on the outer peripheral surface of the preform.

4. The method for manufacturing a resin container according to claim 1, wherein, The radial dimension of the protrusion in the first layer obtained in the first injection molding process is greater than the thickness of the second layer. In the second injection molding process, the front end of the protrusion is pressed against the mold of the second layer which is radially opposed.

5. An apparatus for manufacturing a resin container, comprising: The first injection molding section uses a first resin material with light transmittance to injection mold the first layer of the preform. The preform is formed into a bottomed cylindrical shape and has a protrusion extending axially on the inner or outer circumferential surface. The second injection molding section injects a colored second resin material into the forming surface side of the protrusion of the first layer, and while exposing the protrusion along the axial direction, a colored second layer is laminated in the area other than the protrusion of the first layer. The temperature adjustment unit adjusts the temperature of the preform obtained in the second injection molding unit; as well as The blow molding section blow molds the pre-plasticized preform, after temperature adjustment, under the same heat-retaining condition as injection molding to manufacture resin containers. The resin container has an axially elongated light-transmitting area formed by the shaping of the protrusion, and a light-blocking area formed by the shaping of the second layer. The temperature adjustment unit locally heats at least the convex portion of the preform in the circumferential direction.

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