Method and apparatus for manufacturing resin containers

Abstract

To provide a manufacturing method capable of manufacturing a resin container in a fast molding cycle while suppressing occurrence of sink marks of a preform.SOLUTION: A method of manufacturing a resin container has: an injection molding step of injection-molding a resin preform; a temperature adjustment step of adjusting temperature of the preform manufactured in the injection molding step; and a blow molding step of blow molding the temperature-adjusted preform to manufacture the resin container. In the injection molding step, after filling of a resin material and completion of pressure keeping, an injection mold is opened, and the preform is conveyed out without being cooled in the injection mold. Also, in the temperature adjustment step, a coolant is introduced into the preform to cool the preform.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] The hot parison blow molding method has been known as one of the conventional methods for manufacturing resin containers. The hot parison blow molding method utilizes the heat retained during injection molding of the preform to blow-molde the resin container, and is advantageous compared to the cold parison method in that it can produce a variety of resin containers with superior aesthetic appearance.

[0003] Regarding hot parison blow molding methods, various proposals have been made to shorten the molding cycle. To shorten the molding cycle, it is important to shorten the injection molding time of the preform (cooling time of the preform), which is the rate-limiting step, as described in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2017-098673 [Patent Document 2] Japanese Patent Application Publication No. 5-185493 [Overview of the project] [Problems that the invention aims to solve]

[0005] Generally, one cycle in the injection molding process of a preform includes the steps of metering, filling, holding pressure, and cooling. During the cooling time of the injection molding process, the preform cools in the injection mold without holding pressure, which accelerates shrinkage of the preform and makes it prone to sink marks. As a countermeasure, extending the filling and holding pressure times can improve the sink marks of the preform, but this may not lead to a reduction in the injection molding time. In addition, in hot parison blow molding methods, the injection molding process is usually the rate-limiting step and determines the molding cycle time of the blow molding machine.

[0006] Therefore, the present invention has been made in view of these problems, and aims to provide a manufacturing method that can produce resin containers in a high-speed molding cycle while suppressing the occurrence of sink marks in the preform. [Means for solving the problem]

[0007] A method for manufacturing a resin container according to one aspect of the present invention comprises an injection molding step for injection molding a resin preform, a temperature adjustment step for adjusting the temperature of the preform manufactured in the injection molding step, and a blow molding step for blow molding the temperature-adjusted preform to manufacture a resin container. In the injection molding step, after the completion of filling and holding pressure of the resin material, the mold opening of the injection mold and the start of metering of the resin material are performed simultaneously, and after the completion of filling and holding pressure, the preform is removed from the injection mold without cooling, and the next injection molding is started in the injection mold at the later of the completion of the dry cycle from mold opening to mold closing of the injection mold or the completion of metering of the resin material. In the temperature adjustment step, a refrigerant is introduced into the preform to cool it. In addition, in the input screen for setting the conditions of the injection molding step, the cooling time of the preform in the injection mold after the completion of filling and holding pressure is set. but Set to zero The system further includes a parameter setting step that accepts an operation to change at least one of the following values: a first setting value corresponding to the pressure during resin material filling or the screw speed of the injection device, and a second setting value corresponding to the pressure during resin material holding pressure or the screw speed. The input screen includes an injection time display area for setting the injection time consisting of filling and holding pressure, a cooling time display area indicating the cooling time as zero, a screw position display area for displaying the screw position of the injection device, a first display area for displaying the first setting value, and a second display area for displaying the second setting value. [Effects of the Invention]

[0008] According to one aspect of the present invention, a resin container can be manufactured with a high-speed molding cycle while suppressing the occurrence of sink marks on the preform.

Brief Description of the Drawings

[0009] [Figure 1] It is a diagram schematically showing the configuration of the blow molding apparatus of this embodiment. [Figure 2] It is a diagram showing a configuration example of the injection molding section. [Figure 3] It is a diagram showing a configuration example of the temperature adjustment section. [Figure 4] It is a diagram showing an example of an input screen for set values. [Figure 5] It is a flowchart showing the steps of the method for manufacturing a container. [Figure 6] It is a chart showing an operation example of the injection molding process in this embodiment and a comparative example. [Figure 7] It is a graph showing an example of temperature change of the preform in the blow molding methods of this embodiment and a comparative example.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, for easy understanding of the description, structures and elements other than the main part of the present invention will be described in a simplified or omitted manner. Also, in the drawings, the same elements are denoted by the same reference numerals. Note that the shapes, dimensions, etc. of each element shown in the drawings are schematically shown and do not represent actual shapes, dimensions, etc.

[0011] <Description of the Blow Molding Apparatus> First, a blow molding apparatus 20 for manufacturing a container will be described with reference to FIG. 1. FIG. 1 is a block diagram schematically showing the configuration of the blow molding apparatus 20. The blow molding apparatus 20 of the present embodiment is a hot parison method (also referred to as a one-stage method) apparatus that performs blow molding by utilizing the retained heat (internal heat quantity) during injection molding without cooling the preform 10 to room temperature.

[0012] The blow molding apparatus 20 includes an injection molding section 21, a temperature adjustment section 22, a blow molding section 23, a take-out section 24, a transfer mechanism 26, and a control device 28. The injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the take-out section 24 are arranged at positions rotated by a predetermined angle (for example, 90 degrees) around the transfer mechanism 26.

[0013] (Transfer mechanism 26) The transfer mechanism 26 includes a transfer plate (not shown) that moves so as to rotate around an axis perpendicular to the plane of FIG. 1. On the transfer plate, one or more neck molds 27 (not shown in FIG. 1) for holding the neck of the preform 10 or a resin container (hereinafter simply referred to as a container) are arranged at each predetermined angle. The transfer mechanism 26 conveys the preform 10 (or container) whose neck is held by the neck mold 27 in the order of the injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the take-out section 24 by moving the transfer plate by 90 degrees at a time. The transfer mechanism 26 further includes a lifting mechanism (a vertical mold opening and closing mechanism) and a mold opening mechanism for the neck mold 27, and also performs operations such as raising and lowering the transfer plate and operations related to mold closing and mold opening (ejection) in the injection molding section 21 and the like.

[0014] (Injection molding section 21) As shown in FIG. 2, the injection molding section 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 state. On the other hand, the injection core mold 32 is fixed to a core mold lifting mechanism (not shown). An injection device 25 for supplying a resin material, which is a raw material of the preform, is connected to the injection molding section 21.

[0015] The injection cavity mold 31 is a mold that defines the outer peripheral shape of the preform 10. The hot runner mold 33 has a resin supply portion 33a for introducing the resin material from the injection device 25 into the mold. The injection core mold 32 is a mold that defines the inner peripheral shape of the preform 10, and is inserted from above into the inner peripheral sides of the neck mold 27 and the injection cavity mold 31.

[0016] In the injection molding section 21, the injection cavity mold 31, the injection core mold 32, and the neck mold 27 of the transport mechanism 26 are closed to form a mold space in the shape of a preform. Then, resin material is poured from the injection device 25 into this preform-shaped mold space via the hot runner mold 33, thereby manufacturing the preform 10 in the injection molding section 21.

[0017] On the other hand, the injection device 25 is a device in which a screw is rotatably and retractably installed inside the cylinder of the barrel, and is responsible for heating and melting the resin material and injecting it into the mold. The injection device 25 sequentially performs injection, holding pressure, and metering through the action of the screw.

[0018] The injection device 25 supplies resin material from a hopper to a cylinder where a screw is located, and performs plasticization, mixing, and metering of the resin material by rotating and retracting the screw (metering step). Then, the injection device 25 injects and fills the mold with molten resin by advancing the screw at high speed (filling step). Next, the injection device 25 injects and fills the mold with additional molten resin by advancing the screw at a low speed at a predetermined pressure to compensate for the shrinkage of the molten resin in the mold, and then holds the pressure in that state (holding pressure step). The injection device 25 controls the movement speed of the screw (injection speed) when the resin material is being filled into the mold at high speed, and controls the pressure (holding pressure) after the resin material has been filled into the mold at high speed. The switch from speed control to pressure control is performed using the screw position or injection pressure as a threshold. Note that the screw described above may be a plunger.

[0019] Furthermore, the overall shape of the preform 10 in this embodiment is a bottomed cylindrical shape extending in the longitudinal direction, as shown in Figure 2. A cylindrical neck portion 11 that opens upward is formed on the upper side of the preform 10, and a bottom portion 12 faces the lower side of the preform 10. The neck portion 11 and the bottom portion 12 are connected by a body portion 13. Although not particularly limited, the thickness of the body portion 13 of the preform 10 is set to, for example, 2.5 mm to 7.0 mm (preferably 3.0 mm to 5.5 mm). The above-described shape of the preform 10 is merely an example; for example, the preform 10 may be a bottomed bowl shape that is convex downwards.

[0020] Furthermore, the materials for the container and preform 10 are thermoplastic synthetic resins, which can be appropriately selected depending on the application of the container. Specific examples of materials include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexanedimethylene terephthalate), Tritan (Tritan®: a copolyester manufactured by Eastman Chemical Corporation), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic), and PLA (polylactic acid).

[0021] Furthermore, even when the mold of the injection molding unit 21 is opened, the neck mold 27 of the transport mechanism 26 remains closed and continues to hold and transport the preform 10. The number of preforms 10 that are simultaneously molded in the injection molding unit 21 (i.e., the number of containers that can be simultaneously molded in the blow molding apparatus 20) can be set as appropriate.

[0022] (Temperature adjustment section 22) The temperature control unit 22 equalizes the temperature of the preform 10 manufactured in the injection molding unit 21 and removes uneven heating, adjusting the temperature of the preform 10 to a temperature suitable for blow molding (for example, approximately 90°C to 105°C) and to have a temperature distribution suitable for the container shape to be formed. The temperature control unit 22 also has the function of cooling the preform 10, which is in a high-temperature state after injection molding.

[0023] Figure 3 shows an example of the configuration of the temperature control unit 22. The temperature control unit 22 has a cavity type (temperature control pot) 41 capable of housing a preform and an air introduction member 42 as a mold unit for temperature control.

[0024] The cavity mold 41 is a mold having a temperature-controlled space that is approximately the same shape as the preform 10 manufactured in the injection molding section 21. A flow path (not shown) for a temperature-controlled medium (refrigerant) is formed inside the cavity mold 41. Therefore, the temperature of the cavity mold 41 is maintained at a predetermined temperature by the temperature-controlled medium. The temperature of the temperature control medium in the cavity type 41 is not particularly limited, but can be appropriately selected within a range of, for example, 5°C to 80°C, preferably between 30°C and 60°C.

[0025] The air introduction member 42 has an air introduction rod 43 connected to an air supply unit (not shown) and a fitting core 44, and is inserted inside the neck mold 27 and the preform 10. When inserted into the neck mold 27, the air introduction member 42 is in airtight contact with the neck portion 11 of the preform 10. Both the air introduction rod 43 and the fitting core 44 are hollow cylindrical bodies, and the air introduction rod 43 is concentrically arranged inside the fitting core 44.

[0026] The inside of the air introduction rod 43 forms a passage for guiding compressed air (air, gaseous refrigerant) from the air supply unit, and the tip of the air introduction rod 43 is inserted near the bottom surface of the preform 10. In addition, an opening 43a is formed at the tip of the air introduction rod 43 facing the bottom of the preform 10 for supplying or exhausting compressed air into the preform 10.

[0027] The mating core 44 makes close contact with the inner circumference or upper end surface of the neck portion 11 when the air introduction rod 43 is inserted into the neck shape 27, maintaining airtightness between the preform 10 and the air introduction member 42. The tip of the mating core 44 is inserted into or abuts against the neck portion 11 of the preform 10. An opening 45 is also formed at the tip of the mating core 44 for exhausting or supplying air from inside the preform 10. The space between the air introduction rod 43 and the mating core 44 constitutes an exhaust / supply air passage connected to an air exhaust / supply section (not shown).

[0028] (Blow-molded section 23) The blow molding unit 23 manufactures a container by performing stretch blow molding on the preform 10 whose temperature has been controlled by the temperature control unit 22. The blow molding unit 23 includes a blow cavity mold, which is a pair of split molds corresponding to the shape of the container, a bottom mold, a stretching rod, and an air introduction member (none of which are shown). The blow molding unit 23 blow-moldes the preform 10 while stretching it. This allows the preform 10 to be shaped into the shape of the blow cavity mold, thereby manufacturing the container.

[0029] (Removal section 24) The removal section 24 is configured to release the neck portion of the container manufactured in the blow molding section 23 from the neck mold 27 and remove the container to the outside of the blow molding apparatus 20.

[0030] (Control device 28) 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. 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, for example, by controlling the movement of the transfer plate of the transport mechanism 26 and the opening and closing of the molds in each part.

[0031] Furthermore, the control device 28 includes a display device and an input device (neither of which are shown) 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 entered, the control device 28 controls the display device to show a setting value input screen.

[0032] Figure 4 shows an example of a screen for entering setting values. The input screen 50 shown in Figure 4 is a screen that accepts input of conditions related to injection 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.

[0033] The injection time display area 51 is where the set value 51b for the injection time (filling + holding pressure) in the injection molding unit 21 is entered, and the measured value 51a and the set value 51b of the injection time are displayed, respectively. The cooling time display area 52 is where the set value 52b for the cooling time in the mold after the completion of filling and holding pressure is entered, and the measured value 52a and the set value 52b of the cooling time are displayed, respectively. The screw position display area 53 displays the measured value of the current screw position. In this embodiment, the set value 52b for the cooling time is set to zero. Similarly, the measured value 52a for the cooling time is also normally zero, just like the set value 52b.

[0034] The input screen 50 further 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 position conditions that change the movement speed of the screw of the injection device 25 during the filling process, a setting display area 55b for setting the time for advancing the screw of the injection device 25 at a constant pressure and low speed during the holding pressure process, and a setting display area 55c for setting the position for switching the screw operation control from speed control to pressure control. In the setting display area 55a, the position at which the screw speed is changed is set during the filling process, in which the screw's operation is controlled on a speed basis. In the setting display area 55b, the elapsed time is set during the holding pressure process, in which the screw's operation is controlled on a pressure basis.

[0035] Furthermore, the input screen 50 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 holding pressure process.

[0036] The upper sections of the first display area 56 and the second display area 57 show the set values ​​58 of the pressure on the drive mechanism (hydraulic pump, etc.) side, corresponding to the pressure of the screw of the injection device 25. The set values ​​58 of the pressure mentioned above are, for example, the discharge pressure of the hydraulic fluid flowing from the hydraulic pump, or the pressure detected by a load cell, etc., in the case of an electric motor drive system. The lower sections of the first display area 56 and the second display area 57 show the set values ​​59 of the parameters on the drive mechanism (hydraulic pump, etc.) side, corresponding to the speed of the screw of the injection device 25. The set values ​​59 of the parameters mentioned above are, for example, the flow rate of the hydraulic fluid flowing from the hydraulic pump, or the distance detected by an encoder, etc., in the case of an electric motor drive system.

[0037] In the input screen 50 of Figure 4, the first display area 56 displays the pressure setting value 58 and the flow rate (or screw speed) setting value 59 for the first to third stages, which correspond to the filling process. The second display area 57 displays the pressure setting value 58 and the speed setting value 59 for the fourth and fifth stages, which correspond to the holding pressure process. The setting display area 55 displays the setting value for the position where the flow rate (or screw speed) is changed for the first and second stages, and the second and third stages, which correspond to the filling process.

[0038] Specifically, from right to left on the input screen 50, the first stage shows the settings 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 value (when the discharge amount of hydraulic fluid by the hydraulic pump is at its maximum) (the ratio of the hydraulic fluid flow rate to the rated value). The second stage shows the settings 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 value. The third stage shows the settings 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 value. The fourth stage shows the settings for the holding pressure 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 value. The fifth stage shows the settings for the holding pressure 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 value.

[0039] <Explanation of blow molding method> Next, a blow molding method using the blow molding apparatus 20 of this embodiment will be described. Figure 5 is a flowchart showing the steps of the blow molding method.

[0040] (Step S101: Injection molding process) As shown in Figure 2, in the injection molding section 21, resin is injected from the injection device 25 into the mold space, which is shaped like a preform and formed by the injection cavity mold 31, the injection core mold 32, and the neck mold 27 of the transport mechanism 26, thereby manufacturing a preform 10.

[0041] Here, with reference to Figure 6, an example of the operation of the injection molding unit 21 in this embodiment will be described. Figure 6(A) shows the operation of the injection molding unit 21 in this embodiment, and Figure 6(B) shows the operation of the injection molding unit in a comparative example (conventional method) described later. The horizontal axis in Figure 6 represents time.

[0042] As shown in Figure 6(A), in the injection molding unit 21 of this embodiment, resin material is injected (filled and held) into the clamped mold during the period from time t0 to time t1. When the injection (filled and held) of the resin material is completed at time t1, the mold of the injection molding unit 21 is opened without performing a cooling step for the preform 10 inside the mold of the injection molding unit 21.

[0043] When the mold of the injection molding unit 21 is opened, the high-temperature preform 10 is released from the injection cavity mold 31 and the injection core mold 32. Next, the transfer plate of the transport mechanism 26 moves to rotate by a predetermined angle, and the high-temperature preform 10 held in the neck mold 27 is transported to the temperature control unit 22. After that, the mold of the injection molding unit 21 is closed and then clamped for the next injection molding. The above operations are performed during the period from time t1 to time t2 in Figure 6(A).

[0044] Meanwhile, once the injection molding device 25 has finished injecting the resin material at time t1, it performs plasticization, kneading, and weighing of the resin material for the next injection molding. In the example shown in Figure 6(A), the weighing of the injection molding device 25 is assumed to be completed at time t3.

[0045] In the example shown in Figure 6(A), at time t2, when the mold clamping of the injection molding unit 21 is completed, the injection device 25 has not yet finished metering, so the next injection molding cycle cannot be started. At time t3, both the mold clamping and the injection device 25 have finished metering, so the next injection molding cycle can be started. Therefore, the next injection molding cycle in the injection molding unit 21 starts at time t3.

[0046] Furthermore, if the time required for metering in the injection device 25 (t1-t3) is shorter than the time required for the dry cycle consisting of mold opening, rotation, and mold clamping (t1-t2), metering will be completed before mold clamping. In this case, the next injection molding cycle will start from the time t2 when mold clamping is completed. Thus, in this embodiment, the next injection molding is started after the injection (filling and holding pressure) of the resin material is completed, in accordance with the later of the end of the dry cycle or the end of metering in the injection device 25.

[0047] Furthermore, the temperature change of the preform 10 in the blow molding method of this embodiment will be explained with reference to Figure 7. The vertical axis of Figure 7 represents the temperature of the preform 10, and the horizontal axis represents time. In Figure 7, an example of the temperature change of the preform 10 in this embodiment is shown in Figure 7(A). An example of the temperature change of the preform of the comparative example described later is shown in Figure 7(B). The gaps between each process represent the time required for transporting the preform 10 or the container, etc., and are all of the same length.

[0048] In this embodiment, when the resin material is injection molded at a temperature above its melting point, the injection molding unit 21 opens the mold immediately after filling and holding pressure is completed, and after filling and holding pressure is completed, the preform 10 is transported to the temperature control unit 22 without cooling the preform 10 inside the mold. Note that the cooling time is set to zero on the screen for setting the injection molding conditions of the preform 10. Then, the temperature control unit 22 cools and adjusts the temperature of the preform 10.

[0049] In this embodiment, since the preform 10 is not cooled in the mold of the injection molding section 21 without holding pressure, no sink marks occur in the preform 10 in the injection molding section 21. Furthermore, in this embodiment, since no cooling time is set for the preform 10, the skin layer (the solidified surface layer) of the preform is thinner than in the conventional method, and the core layer (the softened or molten inner layer) is thicker than in the conventional method. In other words, compared to the comparative example, the thermal gradient between the skin layer and the core layer is larger, and a preform 10 with high heat retention at high temperatures is molded.

[0050] In this embodiment, the preform 10 is demolded from the injection molding unit 21 at a higher demolding temperature than the comparative example and transported to the temperature control unit 22. As it moves to the temperature control unit 22, the preform 10 undergoes temperature equalization through heat exchange (heat conduction) between the skin layer and the core layer. In addition, the preform 10 is slightly cooled from the outer surface by contact with the outside air. However, the temperature of the preform 10 in this embodiment remains at a very high level compared to the comparative example (for example, a surface temperature of 130°C or higher if the material is PET) until it is transported to the temperature control unit 22.

[0051] (Step S102: Temperature adjustment process) Next, the temperature control unit 22 performs cooling and temperature adjustment to bring the temperature of the preform 10 closer to a temperature suitable for the final blowing (blow temperature). The blow temperature is set to 90°C to 105°C, for example, for PET resin. However, a lower blow temperature may result in better stretch orientation of the preform 10, which can increase the strength (physical properties) of the container. For this reason, the blow temperature may be set to 90°C to 95°C, for example, for PET resin.

[0052] As shown in Figure 7, in the temperature control unit 22, the temperature of the preform 10 is lowered to the blow temperature, and then the temperature of the preform 10 is maintained at the blow temperature until blow molding is performed. Since the temperature control unit 22 rapidly cools the preform when it is at a high temperature, whitening (clouding) due to spherulite formation and crystallization that may occur when it is cooled slowly is also suppressed.

[0053] In the temperature control process, as shown in Figure 3, first the preform 10 is placed in the cavity mold 41. Next, the air introduction member 42 is inserted into the neck of the preform 10 placed in the cavity mold 41. At this time, the neck 11 of the preform 10 and the fitting core 44 are in close contact, maintaining airtightness between them.

[0054] Subsequently, the preform 10 is subjected to a cooling blow. In the cooling blow of the preform 10 in this embodiment, for example, compressed air is introduced from the air introduction rod 43 to the bottom side of the preform 10, and the compressed air is exhausted from the neck side of the preform 10.

[0055] In the cooling blow, compressed air is ejected from the opening 43a of the air introduction rod 43, so the bottom 12 of the preform 10 facing the opening 43a of the air introduction rod 43 comes into contact with the low-temperature compressed air. The preform 10 is cooled from the inside by the compressed air flowing through it, but the temperature of the compressed air gradually increases as it moves towards the body 13 and neck 11 due to heat exchange with the preform 10. Therefore, in the cooling blow, the bottom 12 of the preform 10 is cooled locally more strongly than the neck 11 and body 13 of the preform 10. Alternatively, the cooling blow may be performed by ejecting compressed air from the opening 45 at the tip of the fitting core 44 and exhausting it from the opening 43a of the air introduction rod 43.

[0056] Furthermore, in the temperature control section 22, the preform 10 remains in contact with the cavity mold 41, which is maintained at a predetermined temperature by compressed air pressure from the inside. Therefore, during the temperature control process, the temperature of the preform 10 is adjusted from the outside so that it does not fall below a temperature suitable for blow molding, and uneven heating that occurred during injection molding is also reduced. In addition, during the temperature control process, the shape of the preform 10 is maintained by the cavity mold 41 and does not change significantly.

[0057] After the temperature adjustment process, the transfer plate of the transport mechanism 26 moves to rotate by a predetermined angle, and the temperature-adjusted preform 10 held in the neck mold 27 is transported to the blow molding section 23.

[0058] (Step S103: Blow molding process) Next, the container is blow-molded in the blow molding section 23. First, the blow cavity mold is closed to house the preform 10 in the mold space, and the air introduction member (blow core) is lowered so that it contacts the neck of the preform 10. Then, the stretching rod (longitudinal stretching member) is lowered to press the bottom of the preform 10 from the inside, and while stretching along the longitudinal axis as needed, blow air is supplied from the air introduction member to stretch the preform 10 along the lateral axis. As a result, the preform 10 expands and is shaped to fit tightly into the mold space of the blow cavity mold, and is blow-molded into a container. The bottom mold waits in a lower position that does not contact the bottom of the preform 10 before the blow cavity mold is closed, and quickly rises to the molding position before or after the mold is closed.

[0059] (Step S104: Container removal process) Once the blow molding is complete, the blow cavity mold and bottom mold are opened. This allows the container to be moved out of the blow molding section 23. Next, the transport plate of the transport mechanism 26 moves to rotate by a predetermined angle, and the container is transported to the removal section 24. In the removal section 24, the neck of the container is released from the neck mold 27, and the container is removed to the outside of the blow molding apparatus 20.

[0060] This completes the series of steps in the blow molding method. Subsequently, the transfer plate of the transport mechanism 26 is moved to rotate by a predetermined angle, thereby repeating each of the steps S101 to S104 described above. When the blow molding apparatus 20 is in operation, the manufacture of four sets of containers, each with a time difference between each step, is carried out in parallel.

[0061] Note that, due to the structure of the blow molding apparatus 20, the time during which the transfer plate stops in the injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the take-out section 24 is the same length. Similarly, the conveyance time of the transfer plate between each section is also the same length.

[0062] Next, referring to FIGS. 6(B) and 7, the operation of the injection molding process in the comparative example (conventional method) and an example of the temperature change of the preform will be described.

[0063] As shown in FIG. 6(B), in the injection molding section of the comparative example, from time t0 to time t 14 , 11 , 12 , 12 , 14 , 12 , 13 , 14 ,

[0065] , , during this period, injection (filling and holding pressure) of the resin material is performed into the clamped mold. After that, from time t 11 to time t 12 during this period, cooling of the preform in the mold is performed without holding pressure. As shown in FIG. 7, in the comparative example, the preform in the mold of the injection molding section is cooled to a temperature lower than or approximately the same as the blow temperature.

[0064] When the cooling of the preform ends at time t 12 , the mold of the injection molding section is opened, and the preform cooled in the mold is released from the injection cavity mold and the injection core mold. Next, the transfer plate of the transfer mechanism moves so as to rotate by a predetermined angle, and the preform held by the neck mold is conveyed to the temperature adjustment section. After that, for the next injection molding, after the mold of the injection molding section is closed, it is clamped. The above operations are performed from time t 12 to time t 14 in FIG. 6(B).

[0065] On the other hand, when the injection of the resin material ends at time t [[ID=​​​​​​​​​

[0066] In the comparative example, the preform is cooled within the mold of the injection molding section. Therefore, in the comparative example, the cooling time (t 11 ~t 12 Because it includes ), one cycle of the injection molding process becomes longer than in this embodiment.

[0067] Furthermore, in the comparative example, the preform is cooled in the mold of the injection molding section without holding pressure, so shrinkage of the preform is accelerated during cooling, making it prone to sink marks. In order to suppress sink marks in the comparative example, the injection (filling and holding pressure) time must be longer than in this embodiment, making one cycle of the injection molding process even longer than in this embodiment. In Figure 6(B), the time extended for sink mark suppression within the injection time is indicated by the symbol α.

[0068] As an example, the time required for one cycle of the injection molding process in this embodiment and comparative example is shown below. Here, the body thickness of the preform is 4.0 mm, the injection (filling and holding pressure) time is 8 seconds, the cooling time is 6.5 seconds, the metering time is 8 seconds, and the dry cycle time is 4 seconds.

[0069] Under the above conditions, one cycle of the injection molding process in this embodiment is 16 seconds (8 + 8). Since the machine operation in this embodiment is performed during the metering time, the dry 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 above, shrinkage occurs due to cooling in the mold. Therefore, if the injection time is extended to suppress shrinkage, the required time for the injection molding process in the comparative example will be further extended, and will actually be longer than 18.5 seconds (for example, 20 seconds or more).

[0070] Furthermore, the time required for each step of the hot parison blow molding process is set to coincide with the injection molding step, which is the rate-limiting step. In a continuous cycle of hot parison blow molding, the time difference compared to the comparative example is accumulated for each step. Therefore, it can be seen that, according to this embodiment, one cycle of blow molding can be significantly shortened compared to the comparative example.

[0071] Furthermore, according to this embodiment, when the injection time and metering time are approximately equal, and the injection time or metering time is shorter than the dry cycle time (injection time ≈ metering time < dry cycle), the molding cycle time can be significantly shortened compared to the comparative example (conventional method). For example, if the injection time and metering time are 3.5 seconds and the dry cycle is 4 seconds, the molding cycle (one cycle including blow molding) will be 7.5 seconds. Also, when the metering time is less than or equal to the dry cycle time (metering time < dry cycle), the molding cycle time can be shortened compared to the comparative example (conventional method). For example, if the injection time is 5 seconds, the metering time is 4 seconds and the dry cycle is 4 seconds, the molding cycle will be 9 seconds. In addition, since the holding pressure process is not performed, the amount of material consumed can be reduced, and the weight of the preform 10 and container can be reduced. As an example, in this embodiment, a weight reduction of about 2 to 5 percent can be achieved compared to a preform of the same size when holding pressure is performed.

[0072] The effects and advantages of this embodiment will be described below. In the injection molding process (S101) of this embodiment, after the completion of filling and holding pressure of the resin material, the injection cavity mold 31 and the injection core mold 32 are opened, and after the completion of filling and holding pressure, the preform 10 is removed from the mold without cooling.

[0073] In this embodiment, since the preform 10 is not cooled in the mold of the injection molding section 21 without holding pressure, the phenomenon of shrinkage of the preform 10 in the injection molding section 21 causing sink marks can be suppressed. Furthermore, in this embodiment, there is no cooling time required to cool the preform 10 in the mold without holding pressure during the injection molding process, and the injection molding time, which is the rate-limiting step, can be shortened, so that the container can be manufactured in a high-speed molding cycle.

[0074] Furthermore, in this embodiment, the temperature control step (S102) involves introducing compressed air into the preform 10 to perform a cooling blow to cool the preform 10. Since the cooling of the preform 10 can be handled by the cooling blow of the temperature control unit 22, the preform 10 will not suffer from insufficient cooling. The preform 10, which is transported to the temperature control unit 22 without being cooled in the mold, is at a very high temperature, and if cooled slowly, crystallization can cause whitening or changes in the shape of the preform 10 (drawdown). However, in this embodiment, the preform 10 is rapidly cooled in the temperature control unit 22 by cooling blow using compressed air, so blow molding with a preform 10 that does not whiten becomes possible.

[0075] Furthermore, in this embodiment, unlike in the comparative example, it is not necessary to reheat the preform in the temperature control unit 22 to a temperature below the blow molding temperature. Therefore, the temperature control of the preform becomes more efficient, and the blow molding process can be simplified.

[0076] For example, when applying a bowl-shaped preform, conventionally the bottom was molded to be considerably thinner, with a wall thickness ratio of 0.5 to the body. In this embodiment, the cooling blow effect of the temperature control unit 22 makes it possible to increase the wall thickness ratio of the bottom to the body to 0.85. This reduces the flow resistance of the resin near the gate at the bottom, resulting in less shear heat generation, and thus makes it easier to suppress whitening of the preform near the gate at the bottom.

[0077] The present invention is not limited to the embodiments described above, and various improvements and design modifications may be made without departing from the spirit of the invention.

[0078] In the above embodiment, a hot parison type 4-station blow molding apparatus was described as an example. However, the blow molding apparatus of the present invention is not limited to the above embodiment, and may be applied to other blow molding apparatuses other than the 4-station type, as long as they include an injection molding section, a temperature control section, and a blow molding section.

[0079] Furthermore, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0080] 10…Preform, 20…Blow molding machine, 21…First injection molding section, 22…Temperature control section, 23…Blow molding section, 25…Injection device, 26…Transport mechanism, 31…Injection cavity mold, 32…Injection core mold, 41…Cavity mold, 42…Air introduction member

Claims

1. The injection molding process involves injection molding a resin preform, A temperature adjustment step for adjusting the temperature of the preform manufactured in the injection molding step, A method for manufacturing a resin container, comprising a blow molding step of blow molding the temperature-controlled preform to manufacture a resin container, In the injection molding process, after the completion of filling and holding pressure of the resin material, the injection mold is opened and the metering of the resin material is started simultaneously, and after the completion of filling and holding pressure, the preform is removed from the injection mold without cooling, and the next injection molding is started in the injection mold at the later of the completion of the dry cycle from opening the injection mold to closing the injection mold or the completion of metering of the resin material. In the temperature adjustment step, a refrigerant is introduced into the preform to cool the preform. In the input screen for setting the conditions of the injection molding process, with the cooling time of the preform in the injection mold after the completion of the filling and holding pressure set to zero, the system further includes a parameter setting step that accepts an operation to change at least one of the values ​​of a first setting value corresponding to the pressure during filling of the resin material or the screw speed of the injection device, and a second setting value corresponding to the pressure during holding pressure of the resin material or the screw speed. The input screen includes an injection time display area for setting the injection time consisting of the filling and holding pressure, a cooling time display area for indicating the cooling time as zero, a screw position display area for displaying the screw position of the injection device, a first display area for displaying the first setting value, and a second display area for displaying the second setting value. A method for manufacturing resin containers.

2. In the temperature adjustment step, the preform is housed in a cavity mold, and the preform is cooled by the pressure of the refrigerant, which causes it to adhere tightly to the cavity mold. A method for manufacturing a resin container according to claim 1.

3. An injection molding section for injection molding resin preforms, A temperature control unit for controlling the temperature of the preform manufactured in the injection molding unit, The system includes a blow molding section that blow-moldes the temperature-controlled preform to manufacture a resin container, The injection molding unit, after the completion of filling and holding pressure of the resin material, simultaneously opens the injection mold and starts metering the resin material, and after the completion of filling and holding pressure, removes the preform from the injection mold without cooling it, and starts the next injection molding in the injection mold at the later of the completion of the dry cycle from opening the injection mold to closing the injection mold or the completion of metering the resin material. The temperature control unit cools the preform by introducing a refrigerant into it. The control device further includes a control device that displays an input screen on a display device that accepts an operation to change at least one of the following values: a first setting value corresponding to the pressure during filling of the resin material or the screw speed of the injection device, and a second setting value corresponding to the pressure during holding pressure of the resin material or the screw speed, while the cooling time of the preform in the injection mold after the completion of filling and holding pressure in the injection molding section is set to zero. The input screen includes an injection time display area for setting the injection time consisting of the filling and holding pressure, a cooling time display area for indicating the cooling time as zero, a screw position display area for displaying the screw position of the injection device, a first display area for displaying the first setting value, and a second display area for displaying the second setting value. Manufacturing equipment for plastic containers.

4. The temperature control unit comprises a cavity mold for housing the preform and an air introduction member for supplying and exhausting refrigerant to the preform housed in the cavity mold, and uses the pressure of the refrigerant to bring the preform into close contact with the cavity mold, and the refrigerant flowing through the preform cools the preform. The apparatus for manufacturing a resin container according to claim 3.

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