Method for manufacturing a resin-made container and manufacturing apparatus

Abstract

A method of manufacturing a resin container includes an injection molding step of injection molding a pre-mold of resin, a temperature adjustment step of adjusting the temperature of the pre-mold manufactured by the injection molding step, and a blow molding step of blow molding the pre-mold after the temperature adjustment to manufacture the resin container. In the injection molding step, the injection mold is opened after filling and pressure maintaining of the resin material are completed, and the pre-mold is carried out of the injection mold without being cooled after the filling and pressure maintaining are completed. In the temperature adjustment step, a refrigerant is introduced into the pre-mold to cool the pre-mold.

Description

Technical Field

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

[0002] Previously, hot preform blow molding was known as one of the manufacturing methods for resin containers. Hot preform blow molding utilizes the heat retained during the injection molding of a preform to blow mold the resin container. Compared with cold preform blow molding, it is advantageous in terms of being able to manufacture a wide variety of resin containers with excellent appearance.

[0003] Various solutions have been proposed for hot preform blow molding methods with the aim of shortening the molding cycle. To shorten the molding cycle, for example, as in Patent Documents 1 and 2, it is important to shorten the injection molding time of the preform (cooling time of the preform), which is the speed-limiting stage.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2017-098673

[0007] Patent Document 2: Japanese Patent Application Publication No. 5-185493 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Generally, one cycle of injection molding of a preform includes metering, filling, holding pressure, and cooling. During the cooling time of the injection molding process, the preform is cooled within the mold without holding pressure, which promotes shrinkage and easily leads to shrinkage marks. While extending the filling and holding times can improve shrinkage, it sometimes does not shorten the injection molding time. Furthermore, in hot preform blow molding, the injection molding time is typically a speed-limiting stage, defining the cycle time of the blow molding machine.

[0010] Therefore, the present invention was made in view of such problems, and its object is to provide a manufacturing method that can suppress the generation of shrinkage marks in preforms and can manufacture resin containers with high-speed molding cycles.

[0011] Technical solutions for solving the problem

[0012] A method for manufacturing a resin container according to one aspect of the present invention includes: an injection molding step for injection molding a resin preform; a temperature conditioning step for conditioning the temperature of the preform manufactured by the injection molding step; and a blow molding step for blow molding the temperature-conditioned preform to manufacture a resin container. In the injection molding step, after the resin material is filled and pressurized, the injection mold is opened, and the preform is removed from the injection mold without cooling after filling and pressurizing. Furthermore, in the temperature conditioning step, a refrigerant is introduced into the preform to cool it.

[0013] Invention Effects

[0014] According to one aspect of the present invention, the formation of shrinkage marks in the preform can be suppressed, and resin containers can be manufactured with a high-speed molding cycle. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the structure of the blow molding apparatus of this embodiment.

[0016] Figure 2 This is a diagram showing an example of the structure of an injection-molded part.

[0017] Figure 3 This is a diagram showing an example of the structure of the temperature adjustment unit.

[0018] Figure 4 This is an example of an input screen showing the set value.

[0019] Figure 5 It is a flowchart illustrating the process of manufacturing a container.

[0020] Figure 6 This is a flowchart illustrating the operation of the injection molding process in this embodiment and the comparative example.

[0021] Figure 7 This is a graph showing the temperature change of the preform in the blow molding method of this embodiment and the comparative example. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0023] In the embodiments, to facilitate understanding, 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 symbols are used to denote the same elements. Additionally, the shapes, dimensions, etc., of the elements shown in the drawings are schematic representations and do not represent actual shapes, dimensions, etc.

[0024] <Description of Blow Molding Equipment>

[0025] First, refer to Figure 1 The blow molding apparatus 20 used for manufacturing containers will be described. Figure 1 This is a block diagram schematically showing the structure of the blow molding apparatus 20. The blow molding apparatus 20 of this embodiment is a hot preform method (also known as a one-stage method) that effectively utilizes the heat retained during injection molding (internal heat) to perform blow molding without cooling the preform 10 to room temperature.

[0026] The blow molding apparatus 20 includes an injection molding unit 21, a temperature adjustment unit 22, a blow molding unit 23, a take-out unit 24, a conveying mechanism 26, and a control device 28. The injection molding unit 21, the temperature adjustment unit 22, the blow molding unit 23, and the take-out unit 24 are arranged at positions that rotate by a given angle (e.g., 90 degrees) around the conveying mechanism 26 each time.

[0027] (Conveying mechanism 26)

[0028] Conveying mechanism 26 is equipped with Figure 1 A transfer plate (not shown) moves by rotating around an axis perpendicular to the paper surface. On the transfer plate, a neck mold 27 holds the neck of the preform 10 or resin container (hereinafter referred to as the container). Figure 1 (Not shown in the diagram) One or more are arranged at each given angle. The conveying mechanism 26 moves the transfer platen 10 (or container) with its neck held by the neck mold 27 in the order of injection molding section 21, temperature adjustment section 22, blow molding section 23, and take-out section 24 by moving the transfer platen 90 degrees each time. In addition, the conveying mechanism 26 also has a lifting mechanism (a longitudinal mold opening and closing mechanism), a mold opening mechanism for the neck mold 27, and performs actions involving lifting the transfer platen, mold closing, and mold opening (demolding) in the injection molding section 21, etc.

[0029] (Injection Molding Section 21)

[0030] like Figure 2 As shown, the injection molding unit 21 includes an injection cavity mold 31, an injection core mold 32, and a hot runner mold 33, and manufactures the preform 10 by injection molding. The injection cavity mold 31 and the hot runner mold 33 are fixed to the machine base of the blow molding apparatus 20 in an integrated manner. On the other hand, the injection core mold 32 is fixed to a core mold lifting mechanism (not shown). In addition, an injection device 25 for supplying resin material, which serves as the raw material for the preform, is connected to the injection molding unit 21.

[0031] The injection cavity mold 31 is a mold that defines the shape of the outer periphery of the preform 10. The hot runner mold 33 has a resin supply section 33a that introduces resin material from the injection device 25 into the mold. In addition, the injection core mold 32 is a mold that defines the shape of the inner periphery of the preform 10, and is inserted from above into the inner periphery of the neck mold 27 and the injection cavity mold 31.

[0032] In the injection molding section 21, the injection cavity mold 31, the injection core mold 32, and the neck mold 27 of the delivery mechanism 26 are closed to form a mold space in the shape of a preform. Then, resin material is flowed from the injection device 25 into such a preform-shaped mold space via the hot runner mold 33, thereby manufacturing a preform 10 in the injection molding section 21.

[0033] On the other hand, the injection unit 25 is a device in which a screw is rotatably and retractably installed within the cylinder of the barrel, and it is responsible for heating and melting the resin material and injecting it into the mold. The injection unit 25 performs injection, pressure holding, and metering sequentially through the action of the screw.

[0034] The injection unit 25 supplies resin material from the hopper to the cylinder equipped with the screw, and performs plasticizing, mixing, and metering of the resin material by rotating and retracting the screw (metering step). Then, the injection unit 25 injects molten resin into the mold by advancing the screw at high speed (filling step). Next, the injection unit 25 injects additional molten resin into the mold by advancing the screw at a low speed under a given pressure to compensate for the shrinkage of the molten resin in the mold, and holds pressure in this state (holding pressure step). While filling the mold with resin material at high speed, the injection unit 25 controls the screw's movement speed (injection speed), and after filling the mold with resin material at high speed, it controls the pressure (holding pressure). The switching from speed control to pressure control is performed based on a screw position or injection pressure threshold. Alternatively, the screw described above can also be a plunger.

[0035] In addition, such as Figure 2 As shown, the preform 10 of this embodiment has an overall shape of a bottomed cylindrical shape extending in the length direction. A cylindrical neck 11 with an upward opening is formed on the upper side of the preform 10, and the lower side of the preform 10 faces the bottom 12. Furthermore, the neck 11 and the bottom 12 are connected by a main body 13. Although not particularly limited, the thickness of the main body 13 of the preform 10 is, for example, set to 2.5 mm to 7.0 mm (preferably 3.0 mm to 5.5 mm).

[0036] Furthermore, the shape of the preform 10 described above is just one example. For instance, the preform 10 may also be a bottomed bowl shape that protrudes downwards.

[0037] Furthermore, the materials for the container and the preform 10 are thermoplastic synthetic resins, which can be appropriately selected according to the intended use of the container. Specific types of materials include, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexanediol terephthalate), Tritan (TRITAN: a copolyester manufactured by Eastman Chemical Company), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic acid), PLA (polylactic acid), etc.

[0038] Furthermore, when the injection molding section 21 is opened, the neck mold 27 of the conveying mechanism 26 remains closed and is used to hold and convey the preform 10 unchanged. The number of preforms 10 simultaneously molded by the injection molding section 21 (i.e., the number of containers that can be simultaneously molded by the blow molding device 20) can be appropriately set.

[0039] (Temperature adjustment unit 22)

[0040] The temperature adjustment unit 22 homogenizes and eliminates temperature deviations in the preform 10 manufactured by the injection molding unit 21, adjusting the temperature of the preform 10 to a temperature suitable for blow molding (e.g., approximately 90°C to 105°C) and providing a temperature distribution suitable for the container shape to be shaped. Furthermore, the temperature adjustment unit 22 also functions to cool the preform 10 at its high temperature after injection molding.

[0041] Figure 3 This is a diagram showing a structural example of the temperature adjustment unit 22. The temperature adjustment unit 22, as a mold unit for temperature adjustment, has a cavity mold (temperature regulating tank) 41 capable of accommodating a pre-plasticized preform and an air inlet component 42.

[0042] The cavity mold 41 is a mold having a temperature-regulating space with a shape substantially the same as that of the preform 10 manufactured by the injection molding section 21. Inside the cavity mold 41, a flow path (not shown) is formed for the flow of a temperature-regulating medium (refrigerant). Therefore, the temperature of the cavity mold 41 is maintained at a given temperature by the temperature-regulating medium.

[0043] In addition, the temperature of the temperature adjustment medium of the cavity mold 41 is not particularly limited. For example, it can be appropriately selected in the range of 5°C to 80°C, preferably in the range of 30°C to 60°C.

[0044] The air inlet component 42 has an air inlet rod 43 connected to the air supply unit (not shown) and a fitting core 44, and is inserted into the neck mold 27 and the inner side of the preform 10. When inserted into the neck mold 27, the air inlet component 42 can airtightly abut against the neck 11 of the preform 10. Both the air inlet rod 43 and the fitting core 44 are hollow cylindrical bodies, and the air inlet rod 43 is concentrically arranged inside the fitting core 44.

[0045] The internal structure of the air guide rod 43 is configured to guide the flow path of compressed air (air or gaseous refrigerant) from the air supply section, and the front end of the air guide rod 43 is inserted near the bottom surface of the pre-plasticized blank 10. In addition, an opening 43a for supplying or discharging compressed air into or out of the pre-plasticized blank 10 is formed at the front end of the air guide rod 43 facing the bottom of the pre-plasticized blank 10.

[0046] When the air guide rod 43 is inserted into the neck mold 27, the fitting core 44 is in close contact with the inner circumference or upper end face of the neck 11, maintaining the airtightness between the pre-plasticized blank 10 and the air guide component 42.

[0047] The front end of the fitting core 44 is inserted into or abuts against the neck 11 of the preform 10. Additionally, an opening 45 is formed at the front end of the fitting core 44 for discharging or supplying air from or to the preform 10. Furthermore, the space between the air guide rod 43 and the fitting core 44 forms a flow path for discharging / supplying air, which connects to an air exhaust / supply section (not shown).

[0048] (Blow Molding Section 23)

[0049] The blow molding section 23 stretches and blow molds the pre-plasticized preform 10, which has been temperature-adjusted by the temperature adjustment section 22, to manufacture a container.

[0050] The blow molding section 23 includes a pair of parting dies corresponding to the shape of the container, namely a blow molding cavity mold, a bottom mold, a stretching rod, and an air inlet component (all not shown). The blow molding section 23 performs blow molding while stretching the pre-plasticized preform 10. Thus, the pre-plasticized preform 10 can be shaped into the shape of the blow molding cavity mold to manufacture a container.

[0051] (Removal section 24)

[0052] The removal section 24 is configured to open the neck of the container manufactured by the blow molding section 23 from the neck mold 27 and remove the container to the outside of the blow molding apparatus 20.

[0053] (Control device 28)

[0054] The control device 28 is composed of a computer such as a PLC (Programmable Logic Controller) and comprehensively controls the operation of each part of the blow molding apparatus 20. For example, the control device 28 controls the injection molding operation in the injection molding section 21, the temperature adjustment operation in the temperature adjustment section 22, and the blow molding operation in the blow molding section 23 by controlling the movement of the transfer plate of the conveying mechanism 26 and the opening and closing of the molds in each part.

[0055] In addition, the control device 28 includes a display device and an input device (neither shown) that serve as a user interface. The control device 28 receives various setting values ​​from the user via the input device and controls the operation of each part based on the input setting values. When setting values ​​are input, the input screen of the setting values ​​is displayed on the display device under the control of the control device 28.

[0056] Figure 4 This is an example of an input screen showing the set value.

[0057] Figure 4 The input screen 50 shown is a screen for accepting inputs related to injection conditions of the injection molding unit 21. The input screen 50 includes at least an injection time display area 51, a cooling time display area 52, and a screw position display area 53 as display items.

[0058] In the injection time display area 51, the set value 51b for the injection time (filling + holding pressure) in the injection molding section 21 is entered, and the actual measured value 51a and the set value 51b of the injection time are displayed respectively. In the cooling time display area 52, the set value 52b for the cooling time in the mold after filling and holding pressure are entered, and the actual measured value 52a and the set value 52b of the cooling time are displayed respectively. In the screw position display area 53, the actual measured value of the current screw position is displayed. In this embodiment, the set value 52b for the cooling time is set to zero. Similarly, the actual measured value 52a for the cooling time is also usually represented as zero.

[0059] The input screen 50 also includes an indicator 54 showing the position of the screw of the injection device 25, and a setting display area 55 for setting the position of the screw in each of the filling and holding pressure processes. The setting display area 55 includes: a setting display area 55a for setting the positional conditions for changing the moving speed of the screw of the injection device 25 during the filling process; a setting display area 55b for setting the time for the screw of the injection device 25 to advance at a certain pressure and low speed during the holding pressure process; and a setting display area 55c for setting the position for switching the screw's motion control from speed control to pressure control.

[0060] Here, in setting display area 55a, during the filling process where the screw's movement is controlled based on speed, the position for changing its speed is set. In setting display area 55b, during the pressure holding process where the screw's movement is controlled based on pressure, the elapsed time is set.

[0061] In addition, the input screen 50 also includes: a first display area 56 for setting the operating conditions of the drive mechanism (hydraulic pump, etc.) that operates the screw of the injection device 25 during the filling process; and a second display area 57 for setting the operating conditions of the drive mechanism (hydraulic pump, etc.) that operates the screw of the injection device 25 during the pressure holding process.

[0062] The upper sections of the first display area 56 and the second display area 57 respectively display the pressure setting value 58 of the drive mechanism (hydraulic pump, etc.) side corresponding to the pressure of the screw of the injection device 25. The pressure setting value 58 mentioned above is, for example, the discharge pressure of the working oil flowing from the hydraulic pump, or the pressure detected by a force sensor, etc., in an electric motor driven type. Furthermore, the lower sections of the first display area 56 and the second display area 57 respectively display the parameter setting value 59 of the drive mechanism (hydraulic pump, etc.) side corresponding to the speed of the screw of the injection device 25. The parameter setting value 59 mentioned above is, for example, the flow rate of the working oil flowing from the hydraulic pump, or the distance detected by an encoder, etc., in an electric motor driven type.

[0063] exist Figure 4 In the input screen 50, the first display area 56 displays the input and display of pressure settings 58 and flow rate (or screw speed) settings 59 for the first to third stages corresponding to the filling process. Additionally, the second display area 57 displays the input and display of pressure settings 58 and speed settings 59 for the fourth and fifth stages corresponding to the holding pressure process. Furthermore, the setting display area 55 displays the input and display of settings for changing the flow rate (or screw speed) positions for the first and second stages, and the second and third stages corresponding to the filling process.

[0064] That is, starting from the right side of the input screen 50, the first section indicates the setting for the filling process where the injection device 25 is operated at a pressure of 12.0 MPa and a flow rate of 40.0% of the rated flow rate (relative to the rated flow rate of the working oil) (when the hydraulic pump's working oil discharge is at its maximum). The second section indicates the setting for the filling process where the injection device 25 is operated at a pressure of 12.0 MPa and a flow rate of 99.0% of the rated flow rate. The third section indicates the setting for the filling process where the injection device 25 is operated at a pressure of 12.0 MPa and a flow rate of 99.0% of the rated flow rate. The fourth section indicates the setting for the pressure holding process where the injection device 25 is operated at a pressure of 2.5 MPa and a flow rate of 25.0% of the rated flow rate. The fifth section indicates the setting for the pressure holding process where the injection device 25 is operated at a pressure of 2.0 MPa and a flow rate of 25.0% of the rated flow rate.

[0065] <Explanation of Blow Molding Method>

[0066] Next, the blow molding method of the blow molding apparatus 20 based on this embodiment will be described.

[0067] Figure 5 This is a flowchart illustrating the steps involved in the blow molding process.

[0068] (Step S101: Injection Molding Process)

[0069] like Figure 2 As shown, in the injection molding section 21, resin is injected from the injection device 25 into the mold space of the preform shape formed by the injection cavity mold 31, the injection core mold 32 and the neck mold 27 of the conveying mechanism 26 to manufacture the preform 10.

[0070] Here, refer to Figure 6 An example of the operation of the injection molding unit 21 in this embodiment will be described. Figure 6 (A) indicates the operation of the injection molding unit 21 in this embodiment. Figure 6 (B) indicates the operation of the injection molding unit in the comparative example (existing method) described later. Additionally, Figure 6 The horizontal axis represents time.

[0071] like Figure 6 As shown in (A), in the injection molding section 21 of this embodiment, resin material is injected (filled and held under pressure) into the mold after it is closed during the period from time point t0 to time point t1. When the injection (filling and holding under pressure) of the resin material is completed at time point t1, the cooling step of the preform 10 in the mold of the injection molding section 21 is not performed, and the mold of the injection molding section 21 is opened.

[0072] When the mold of the injection molding section 21 opens, the pre-plasticized preform 10, which is in a high-temperature state, is demolded from the injection cavity mold 31 and the injection core mold 32. Next, the transfer plate of the conveying mechanism 26 is moved by rotating a given angle, and the pre-plasticized preform 10, which is in a high-temperature state and held in the neck mold 27, is conveyed to the temperature adjustment section 22. Afterwards, for the next injection molding, the mold of the injection molding section 21 closes after molding. The above-described actions... Figure 6 The process is carried out during the period from time point t1 to time point t2 of (A).

[0073] On the other hand, when the injection unit 25 finishes injecting resin material at time t1, it performs plasticizing, mixing, and metering of the resin material for the next injection molding. Figure 6 In example (A), the metering of the injection device 25 is assumed to end at time point t3.

[0074] exist Figure 6 In example (A), at time t2, when the mold closing of the injection molding unit 21 is completed, the metering of the injection device 25 has not yet ended, so the next injection molding cannot begin. At a later time t3, since both mold closing and metering of the injection device 25 have ended, the next injection molding can begin. Therefore, in the injection molding unit 21, the cycle of the next injection molding begins from time t3.

[0075] Furthermore, if the time required for metering by the injection unit 25 (t1 to t3) is shorter than the time required for the drying cycle consisting of mold opening, rotation, and mold closing (t1 to t2), metering will end before mold closing. Therefore, in the above case, the next injection molding cycle will begin from the completion time t2 of mold closing.

[0076] Thus, in this embodiment, after the injection (filling and holding) of the resin material is completed, the next injection molding begins at the later of the timing, either the end of the drying cycle or the end of the metering of the injection device 25.

[0077] Additionally, refer to Figure 7 The temperature change of the preform 10 in the blow molding method of this embodiment will be explained. Figure 7 The vertical axis represents the temperature of the preform 10. Figure 7 The horizontal axis represents time. Figure 7 In this embodiment, the temperature change example of the pre-plasticized preform 10 is as follows: Figure 7 It is shown in (A) of the comparative examples. Additionally, the temperature change example of the preform in the comparative examples described later is shown in... Figure 7 As shown in (B). In addition, the time required for each process, such as the transfer of the preform 10 or the container, is the same length.

[0078] In this embodiment, when the resin material is injection molded at a temperature above its melting point, the mold is opened immediately after filling and holding pressure in the injection molding unit 21. After filling and holding pressure, the preform 10 is transported to the temperature adjustment unit 22 without cooling. Furthermore, in the screen for setting the injection molding conditions of the preform 10, the cooling time is set to zero. Then, the preform 10 is cooled and its temperature is adjusted in the temperature adjustment unit 22.

[0079] In this embodiment, since the preform 10 is not cooled in the mold without holding pressure in the injection molding section 21, shrinkage marks of the preform 10 will not be generated in the injection molding section 21.

[0080] Furthermore, in this embodiment, since the cooling time of the preform 10 is not set, the skin layer (the surface layer in a solidified state) of the preform is formed thinner than before, and the core layer (the inner layer in a softened or molten state) is formed thicker than before. That is, compared with the comparative example, the preform 10 with a large thermal gradient between the skin layer and the core layer, high temperature, and high heat retention is formed.

[0081] In this embodiment, the preform 10 is demolded from the injection molding section 21 at a higher demolding temperature than that of the comparative example and is conveyed to the temperature adjustment section 22. As it moves to the temperature adjustment section 22, the preform 10 undergoes temperature homogenization based on heat exchange (heat conduction) between the skin layer and the core layer. Additionally, the preform 10 is slightly cooled from its outer surface through contact with external air. However, the temperature of the preform 10 in this embodiment remains very high compared to the comparative example before it is conveyed to the temperature adjustment section 22 (e.g., a surface temperature of 130°C or higher when the material is PET).

[0082] (Step S102: Temperature Adjustment Process)

[0083] Next, in the temperature adjustment unit 22, cooling and temperature adjustment are performed to bring the temperature of the preform 10 close to the temperature suitable for final blow molding (blow molding temperature). The blow molding temperature is set, for example, to 90°C to 105°C in the case of PET resin. Furthermore, the lower the blow molding temperature, the better the tensile orientation of the preform 10 becomes, and sometimes it can even improve the strength (physical properties) of the container. Therefore, the blow molding temperature is set, for example, to 90°C to 95°C in the case of PET resin.

[0084] like Figure 7As shown, in the temperature adjustment unit 22, the temperature of the preform 10 is reduced to the blow molding temperature, and then the temperature of the preform 10 is maintained at the blow molding temperature before blow molding. Since the preform at a high temperature is rapidly cooled in the temperature adjustment unit 22, whitening (clouding) caused by spherulite crystallization that may occur during slow cooling can also be suppressed.

[0085] In the temperature adjustment process, such as Figure 3 As shown, firstly, the preform 10 is housed in the cavity mold 41. Next, the air inlet component 42 is inserted into the neck of the preform 10 housed in the cavity mold 41. At this time, the neck 11 of the preform 10 is in close contact with the fitting core 44, maintaining an airtight state between the two.

[0086] Next, cooling blow molding of the preform 10 is performed. In the cooling blow molding of the preform 10 in this embodiment, for example, compressed air is introduced from the air inlet rod 43 to the bottom side of the preform 10 and the compressed air is discharged from the neck side of the preform 10.

[0087] In cooling blow molding, compressed air is ejected from the opening 43a of the air guide rod 43, causing the low-temperature compressed air to contact the bottom 12 of the preform 10 facing the opening 43a of the air guide rod 43. The preform 10 is cooled from the inside by the compressed air flowing inside, but the temperature of the compressed air gradually increases towards the body portion 13 and the neck portion 11 through heat exchange with the preform 10. Therefore, in cooling blow molding, the bottom 12 of the preform 10 is locally cooled more strongly than the neck portion 11 and the body portion 13. Alternatively, cooling blow molding can also be performed by ejecting compressed air from the opening 45 at the front end of the insert core 44 and venting air from the opening 43a of the air guide rod 43.

[0088] Furthermore, the preform 10 in the temperature adjustment section 22 is continuously in contact with the cavity mold 41, which is maintained at a given temperature, under the pressure of compressed air from the inside. Therefore, during the temperature adjustment process, the preform 10 is temperature-adjusted from the outside in a manner that prevents it from falling below a temperature suitable for blow molding, thereby reducing the temperature deviation that occurs during injection molding. In addition, during the temperature adjustment process, the shape of the preform 10 is maintained by the cavity mold 41 without significant changes.

[0089] After the temperature adjustment process, the transfer plate of the conveying mechanism 26 moves by rotating a given angle, and the pre-plasticized preform 10, which has been temperature adjusted and is held in the neck mold 27, is conveyed to the blow molding section 23.

[0090] (Step S103: Blow molding process)

[0091] Next, the container is blow-molded in the blow molding section 23.

[0092] First, the blow molding cavity is closed, housing the preform 10 within the mold space. The air inlet component (blow molding core) is lowered, bringing it into contact with the neck of the preform 10. Then, the tension rod (longitudinal tension component) is lowered, pressing the bottom of the preform 10 from its inner surface. Simultaneously, longitudinal tension is performed as needed, while blow molding air is supplied from the air inlet component, thereby stretching the preform 10 laterally. As a result, the preform 10 expands and is shaped in close contact with the mold space of the blow molding cavity, blow molding it into a container. Furthermore, the bottom mold remains in a position below the preform 10, not in contact with its bottom, before the blow molding cavity is closed, and rapidly rises to the molding position before or after mold closure.

[0093] (Step S104: Container Removal Process)

[0094] When blow molding is complete, the blow molding cavity mold and bottom mold are opened. As a result, the container can be moved from the blow molding section 23.

[0095] Next, the transfer plate of the conveying mechanism 26 moves by rotating a given angle, and the container is conveyed to the take-out section 24. In the take-out section 24, the neck of the container opens from the neck mold 27, and the container is taken out of the blow molding apparatus 20.

[0096] The above completes the series of steps in the blow molding method. Then, by moving the transfer plate of the conveying mechanism 26 by a given rotation angle, the steps S101 to S104 described above are repeated. During the operation of the blow molding apparatus 20, the manufacturing of four sets of containers, each with a time difference of one step, is performed in parallel.

[0097] Furthermore, in the structure of the blow molding apparatus 20, the transfer plate stops for the same amount of time in the injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the take-out section 24. Similarly, the transport time of the transfer plate between each section is also the same.

[0098] Next, refer to Figure 6 (B) Figure 7 The actions of the injection molding process and the temperature change of the preform in the comparative example (existing method) will be explained.

[0099] like Figure 6 As shown in (B), in the injection molding section of the comparative example, from time point t0 to time point t... 11 During this period, resin material is injected (filling and holding pressure) into the mold after it is closed. Then, at time point t... 11 up to time point t 12During this period, the preform inside the mold is cooled without holding pressure. For example... Figure 7 As shown, in the comparative example, the preform is cooled to a temperature lower than or approximately the same as the blow molding temperature within the mold of the injection molding section.

[0100] At time t 12 When the preform has finished cooling, the injection molding mold opens, releasing the cooled preform from the injection cavity and core mold. Next, the conveyor platen moves by a given rotation angle, transporting the preform held in the neck mold to the temperature adjustment section. Afterwards, for the next injection molding, the injection molding mold closes. The above actions are performed in... Figure 6 (B) time point t 12 up to time point t 14 It will be carried out during this period.

[0101] On the other hand, the injection device at time point t 11 After the resin injection is completed, the resin material is plasticized, mixed, and metered in preparation for the next injection molding process. Figure 6 In (B), the metering of the injection device during the drying cycle (t) 12 ~t 14 That is, time point t 13 The end. Therefore, in Figure 6 In the comparative example shown in (B), the cycle of the next injection molding is from time point t. 14 start.

[0102] In the comparative example, the preform is cooled inside the mold of the injection molding section. Therefore, in the comparative example, one cycle of the injection molding process is longer than that of this embodiment by an amount corresponding to the cooling time (t11 to t12).

[0103] Furthermore, in the comparative example, since the preform is cooled without holding pressure within the injection molding mold, shrinkage of the preform is promoted during cooling, making it prone to shrinkage marks. In the comparative example, to suppress shrinkage marks in the preform, the injection (filling and holding pressure) time must be ensured for a longer period compared to this embodiment, resulting in a longer cycle time for the injection molding process. Figure 6 In (B), the extended time of the indentation inhibition during the injection time is represented by the symbol α.

[0104] As an example, the time required for one cycle of the injection molding process in this embodiment and the comparative example are respectively shown. Here, the thickness of the main body of the preform is set to 4.0 mm, the injection (filling and holding) time is set to 8 seconds, the cooling time is set to 6.5 seconds, the metering time is set to 8 seconds, and the drying cycle time is set to 4 seconds.

[0105] Under the conditions described above, one cycle of the injection molding process in this embodiment is 16 seconds (8+8). Since the mechanical action in this embodiment is performed within the metering time, the drying cycle time in this embodiment can be assumed to be zero. On the other hand, one cycle of the injection molding process in the comparative example is 18.5 seconds (8+6.5+4). However, in the case of the comparative example described above, shrinkage marks caused by cooling within the mold occur. Therefore, if the injection time is extended to suppress shrinkage marks, the required time for the injection molding process in the comparative example is further extended, actually longer than 18.5 seconds (for example, more than 20 seconds).

[0106] Furthermore, the required time for each step of the hot preform blow molding process is set in conjunction with the injection molding process, which is a speed-limiting stage. In the continuous cycle of the hot preform blow molding, the time difference with the comparative example is accumulated according to the number of steps. Therefore, it can be seen that, according to this embodiment, compared with the comparative example, one blow molding cycle can be significantly shortened.

[0107] Furthermore, according to this embodiment, when the injection time and metering time are approximately equal, and the injection time and metering time are shorter than the drying cycle time (injection time ≈ metering time < drying cycle), the molding cycle time can be significantly shortened compared to the comparative example (conventional method). For example, when the injection time and metering time are 3.5 seconds and the drying cycle is 4 seconds, the molding cycle (including one blow molding cycle) is 7.5 seconds. Additionally, when the metering time is less than or equal to the drying cycle time (metering time < drying cycle), the molding cycle time can be shortened compared to the comparative example (conventional method). For example, when the injection time is 5 seconds, the metering time is 4 seconds, and the drying cycle is 4 seconds, the molding cycle is 9 seconds. Moreover, since the pressure holding process is not performed, material consumption can be reduced, and the preform 10 and the container can be made lighter. As an example, in this embodiment, compared to a preform of the same size with pressure holding, a weight reduction of approximately 2 to 5% can be achieved.

[0108] The effects of this embodiment will be explained below.

[0109] In the injection molding process (S101) of this embodiment, after the resin material is filled and pressure is maintained, the injection cavity mold 31 and the injection core mold 32 are opened, and the preform 10 is removed from the mold without cooling after the filling and pressure are maintained.

[0110] In this embodiment, since the preform 10 is not cooled when there is no pressure in the mold of the injection molding section 21, the phenomenon of shrinkage marks caused by the preform 10 shrinking in the injection molding section 21 can be suppressed.

[0111] Furthermore, in this embodiment, the cooling time of the preform 10 in the mold without holding pressure during the injection molding process is not used, which can shorten the injection molding time, which is the speed-limiting stage, and thus enable the manufacture of containers with a high-speed molding cycle.

[0112] Furthermore, in this embodiment, during the temperature adjustment process (S102), compressed air is introduced into the preform 10 to cool it using a cooling blow molding process. Since the preform 10 can be cooled by the cooling blow molding of the temperature adjustment unit 22, the preform 10 will not be under-cooled.

[0113] The preform 10, which is moved into the temperature adjustment section 22 without being cooled in the mold, has a very high temperature. If it is slowly cooled, it may cause whitening due to crystallization, shape changes (drooping) of the preform 10, etc. However, in this embodiment, since the preform 10 is rapidly cooled in the temperature adjustment section 22 by using compressed air cooling blow molding, it is possible to blow mold the preform 10 without whitening.

[0114] Furthermore, in this embodiment, it is not necessary to reheat the preform below the blow molding temperature in the temperature adjustment unit 22 as in the comparative example. Therefore, the temperature adjustment of the preform is efficient, which simplifies the blow molding process.

[0115] Furthermore, for example, when using a bowl-shaped preform, the wall thickness ratio of the bottom to the main body is conventionally set to 0.5, resulting in a relatively thin bottom. In this embodiment, through the cooling blow molding effect of the temperature adjustment unit 22, the wall thickness ratio of the bottom to the main body can be increased to 0.85. As a result, the flow resistance of the resin near the bottom gate is reduced, thereby reducing shear heating and thus making it easier to suppress whitening of the preform near the bottom gate.

[0116] 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.

[0117] In the above embodiments, a four-station blow molding apparatus structure of the hot preform type was described as an example. However, the blow molding apparatus of the present invention is not limited to the above embodiments. As long as it includes an injection molding section, a temperature adjustment section, and a blow molding section, it can also be applied to other blow molding apparatuses other than the four-station type.

[0118] Furthermore, the embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the invention is shown by the claims rather than by the foregoing description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0119] Symbol Explanation

[0120] 10…Pre-plastic preform, 20…Blow molding device, 21…First injection molding section, 22…Temperature adjustment section, 23…Blow molding section, 25…Injection device, 26…Conveying mechanism, 31…Injection cavity mold, 32…Injection core mold, 41…Cavity mold, 42…Air inlet component.

Claims

1. A method for manufacturing a resin container, comprising: The injection molding process involves injection molding a resin preform. The temperature adjustment process involves adjusting the temperature of the preform manufactured through the injection molding process; and The blow molding process involves blow molding the pre-plasticized preform after temperature adjustment to manufacture resin containers. In the injection molding process, after the resin material is filled and pressure is maintained, the injection mold is opened and the resin material is metered simultaneously. After the filling and pressure maintenance are completed, the preform is removed from the injection mold without cooling. The next injection molding process begins in the injection mold at either the later of the drying cycle from the opening of the injection mold to the closing of the injection mold or the completion of the resin material metering. In the temperature adjustment process, a refrigerant is introduced into the pre-plasticized preform to cool it.

2. The method for manufacturing a resin container according to claim 1, wherein, During the temperature adjustment process, the bottom of the preform is cooled more intensely than other parts.

3. The method for manufacturing a resin container according to claim 1 or 2, wherein, In the temperature adjustment process, the preform is housed in the cavity mold, and the pressure of the refrigerant is used to make the preform adhere tightly to the cavity mold to cool the preform.

4. An apparatus for manufacturing a resin container, comprising: The injection molding section performs injection molding on a resin preform. A temperature adjustment unit that adjusts the temperature of the preform manufactured by the injection molding unit; and The blow molding section blow molds the pre-plasticized preform after temperature adjustment to manufacture resin containers. After the resin material is filled and held under pressure, the injection molding unit simultaneously opens the injection mold and begins metering the resin material. After filling and holding pressure, the preform is removed from the injection mold without cooling. The next injection molding operation begins in the injection mold at either the later of the drying cycle (from mold opening to mold closing) or the completion of resin material metering. The temperature adjustment unit introduces refrigerant into the pre-plasticized preform to cool it.

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