Method for manufacturing a resin-made container and manufacturing apparatus

Abstract

A method for manufacturing a resin container includes: an injection molding step of injection molding a resin pre-form having a main body portion and a bottom portion; a temperature adjustment step of adjusting the temperature of the pre-form manufactured by the injection molding step; and a blow molding step of blow molding the pre-form after the temperature adjustment to manufacture the resin container. In the injection molding step, the pre-form is injection molded using an injection mold in which the wall thickness of the bottom portion is 0.7 to 0.85 relative to the wall thickness of the main body portion. In the temperature adjustment step, a refrigerant is introduced into the pre-form to cool the bottom portion of the pre-form.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a resin-made container and a manufacturing apparatus. BACKGROUND

[0002] In the past, as one of the manufacturing methods of a resin-made container, a hot parison type blow molding method has been known. The hot parison type blow molding method is a method of blow molding a resin-made container using the retained heat at the time of injection molding of a pre-molded parison, and is advantageous in that various resin-made containers having excellent appearance can be manufactured, as compared with a cold parison type.

[0003] In the hot parison type blow molding method, it is required that the main body portion and the like of the pre-molded parison retain heat capable of stretching, and on the other hand, it is required that the bottom central region of the pre-molded parison maintain a degree of hardness that does not break due to a stretching rod.

[0004] In the past, for example, there has been a case where a pre-molded parison in which the bottom thickness is set to about 1 / 2 of the main body portion thickness is used, and the above requirement is addressed by improving the injection cooling efficiency of the bottom portion. Patent Document 1 discloses that, in a cylindrical thin-walled pre-molded parison, the bottom surface is formed into an inclined surface of the same angle of 20° to 45°, and the connecting portion with the main body portion is formed into a circular arc shape, thereby making the wall thickness of the main body portion smoothly transition from the bottom portion to suppress whitening of the bottom surface.

[0005] In addition, in recent years, a manufacturing method of a container has been proposed in which a pre-molded parison that is demolded at a high temperature by shortening the cooling time at the time of injection molding is blow molded at a high stretching ratio (for example, refer to Patent Document 2). According to the above manufacturing method of a container, a resin-made container having excellent physical properties and appearance can be manufactured at a high molding cycle.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Publication No. 2004-90425

[0009] Patent Document 2: Japanese Patent No. 6505344 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] In the hot parison type blow molding method, depending on the specifications of the container such as physical properties and stretching ratio, the shape of the pre-molded parison suitable for each container exists. For example, in the case of manufacturing a resin-made container such as a cup that is wide-mouthed and thin-walled, for example, a flat bowl-shaped pre-molded parison is applied. In such a pre-molded parison, since the main body portion thickness is set to be relatively thin, if the bottom thickness is set to about 1 / 2 of the main body portion thickness, the bottom thickness of the pre-molded parison further thins.

[0012] In the above-described injection molding of the preform, the space of the bottom portion of the preform in the injection mold is very narrow, and the flow resistance of the molten resin near the gate portion becomes large. Thus, the shear heat generation of the molten resin at the time of injection molding increases, and the bottom central portion of the preform is subjected to high-temperature treatment. Due to this, it is difficult to sufficiently cool the bottom central portion of the preform, and crystallization (whitening) due to slow cooling is likely to occur in the bottom central portion of the preform, the container.

[0013] In particular, in the case where the preform, which is ejected at a high temperature by shortening the cooling time at the time of injection molding and at a high stretching ratio, is subjected to blow molding, the suppression of whitening of the bottom central portion becomes more important.

[0014] Therefore, the present application has been made in view of such circumstances, and it is an object of the present application to provide a production method of a resin container, which can suppress whitening of a bottom central portion of a preform, a container, and can produce the resin container at a high molding cycle.

[0015] Technical Solution for Solving the Problem

[0016] The production method of a resin container of one embodiment of the present application includes an injection molding step of injection molding a preform made of resin, which has a main body portion and a bottom portion; a temperature adjustment step of performing temperature adjustment of the preform produced by the injection molding step; and a blow molding step of blow molding the preform after the temperature adjustment to produce a resin container. In the injection molding step, the preform is injection molded using an injection mold in which the wall thickness of the bottom portion is 0.7 to 0.85 times the wall thickness of the main body portion. In addition, in the temperature adjustment step, a refrigerant is introduced into the preform to cool the bottom portion of the preform.

[0017] Effects of the Invention

[0018] According to one embodiment of the present application, whitening of a bottom central portion of a preform, a container can be suppressed, and a resin container can be produced at a high molding cycle. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a view that shows one example of a preform of the present embodiment.

[0020] Figure 2 is a view that shows one example of a resin container of the present embodiment.

[0021] Figure 3 is a view that schematically shows the structure of a blow molding device of the present embodiment.

[0022] Figure 4 is a view that shows a structure example of an injection molding portion.

[0023] Figure 5 This is a diagram showing an example of the structure of the temperature adjustment unit.

[0024] Figure 6 It is a flowchart illustrating the process of manufacturing a container.

[0025] 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

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0027] 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 and dimensions of the elements shown in the drawings are schematic representations and do not represent actual shapes and dimensions.

[0028] <Description of Preform>

[0029] First, refer to Figure 1 A structural example of the preform 10 used in the manufacture of the resin container (hereinafter also simply referred to as the container) of this embodiment will be described. Figure 1 (a) represents the overall shape of the preform 10. Figure 1 (b) is Figure 1 A magnified view of a portion near the gate 14 in (a). Additionally, Figure 1 The preform 10 is used for manufacturing wide-mouthed and thin-walled containers, such as cups (see reference). Figure 2 (The situation is as follows.)

[0030] like Figure 1 As shown in (a), the preform 10 has an overall shape of a flat, bottomed bowl that bulges downwards. 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 over the entire circumferential region. However, the above-described shape of the preform 10 is only one example; for instance, the preform 10 could also be a bottomed cylindrical shape extending along its length.

[0031] Further, in the preform 10 of the present embodiment, the wall thickness thl of the bottom portion 12 is set to a value of 0.7 to 0.85 as compared to the wall thickness th2 of the main body portion 13. That is, the preform 10 of the present embodiment has a relatively thick wall thickness of the bottom portion as compared to the conventional preform in which the bottom portion thickness is set to about 1 / 2 of the main body portion thickness. In the heat-type blow molding method, in order to prevent the bottom portion from being broken by the stretch rod at the time of the blow molding step, the bottom portion thickness is set to about 1 / 2 of the main body portion thickness, and the bottom portion is sufficiently cooled and solidified in the injection molding step.

[0032] In the center of the bottom portion 12 of the preform 10, a gate portion 14 protruding toward the outside of the bottom portion 12 from the front end thereof is formed. The gate portion 14 is a resin introduction mark from a later-described hot runner mold 33, and is formed in a tapered shape expanding in diameter from the front end side of the gate portion 14 toward the base end side facing the bottom portion 12. Therefore, as shown in (b) of FIG. 1, the diameter size d2 of the base end side of the gate portion 14 is wider than the diameter size dl of the front end side. Further, in the base end side of the gate portion 14, a round corner (chamfer, arc) is provided in the corner portion 15 connecting the gate portion 14 and the outer surface of the bottom portion. The round corner is set to a value of, for example, 2.0 mm to 4.0 mm (preferably 2.1 mm to 3.0 mm) in radius. Figure 1

[0033] The thickness of the bottom portion 12 is set to be thinner than the diameter size dl of the gate portion, for example, to a value of 0.70 to 0.9 (preferably 0.75 to 0.85) when the diameter size dl is set to 1. Further, in the preform 10, for example, the largest diameter Dl (diameter of the neck portion 11) is set to be longer than the length LI (length of the bottom portion 12 from the upper end of the neck portion 11 to the upper end of the gate portion 14). The diameter Dl is set to, for example, 1.5 times to 3.0 times (preferably 1.5 times to 2.5 times, more preferably 1.7 times to 2.3 times) the length LI.

[0034] ​The material of the preform 10 is a thermoplastic synthetic resin, which can be appropriately selected depending on the use of the container. As a specific kind of the material, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexane dimethanol terephthalate), Tritan (TRITAN (registered trademark): copolyester manufactured by Eastman Chemical Company), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyether sulfone), PPSU (polysulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic acid), PLA (polylactic acid), and the like can be mentioned. In addition, the present application is particularly effective in a case where a material that is a thermoplastic synthetic resin and a crystalline resin and is likely to cause whitening due to spherulitic crystallization at the time of injection molding (for example, PET or PEN) is selected as the material of the preform 10.

[0035] <Explanation of the container>

[0036] Next, with reference to Figure 2 , the structure example of the container of the present embodiment will be described. Figure 2 (a) of FIG. 1 is a plan view of the container, Figure 2 (b) of FIG. 1 is a front view of the container. As Figure 2 indicated in (a), (b) of FIG. 1, the container 1 is a wide-mouthed cup-shaped container that is open at the upper surface side and is closed at the bottom surface side. The container 1 has a neck portion 2 that faces the opening portion of the upper surface side, a bottom portion 3 that closes the bottom surface side, and a main body portion 4 that connects the neck portion 2 and the bottom portion 3. The main body portion 4 of the container 1 is in a tapered shape (inverted circular truncated cone shape) that is reduced in diameter from the upper surface side to the bottom surface side. In addition, with respect to the container 1, the length (depth L) in the axial direction of the container is sufficiently long compared to the inner diameter D of the container, and is formed as a deep bottom. The stretch ratio in the longitudinal axis direction of the preform 10 of the container 1 is set to be as high as 3.0 to 7.0 (preferably 3.5 to 6.0, and more preferably 4.0 to 5.5).

[0037] <Explanation of the blow molding device>

[0038] Next, with reference to Figure 3 , the blow molding device 20 for manufacturing the container will be described. Figure 3 is a block diagram that schematically represents the structure of the blow molding device 20. The blow molding device 20 of the present embodiment is a hot parison method (also referred to as a one-stage method) device that effectively utilizes the retained heat (internal heat) at the time of injection molding without cooling the preform 10 to room temperature to perform blow molding.

[0039] 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, and a conveying mechanism 26. 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.

[0040] (Conveying mechanism 26)

[0041] Conveying mechanism 26 is equipped with Figure 3 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) 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, closing the mold on the injection molding section 21, and opening the mold (demolding).

[0042] (Injection Molding Section 21)

[0043] like Figure 4 As shown in (a), 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 as raw material for the preform is connected to the injection molding unit 21.

[0044] 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 the top into the inner periphery of the neck mold 27 and the injection cavity mold 31.

[0045] The mold space S formed by the injection cavity mold 31 and the injection core mold 32 is shaped similarly to the preform 10 described above. Within the mold space S, the spacing th of the mold space corresponds to the thickness of the bottom 12. 1’ Compared to the thickness of the main body 13, the spacing th of the mold space is... 2’ The value is set to 0.7 to 0.85.

[0046] likeFigure 4 As shown in (b), in the injection cavity mold 31, the gate region S1 connected to the resin supply portion 33a is formed in a tapered shape that expands in diameter toward the injection core mold 32. In addition, the outlet of the gate region S1 facing the injection core mold 32 is rounded at the corner portion 34 connecting the gate region S1 and the bottom outer surface. In addition, the radius of curvature of the corner portion 34 is, for example, 1 mm or more.

[0047] In the injection molding section 21, the injection cavity mold 31, the injection core mold 32, and the neck mold 27 of the transfer mechanism 26 are closed to form a mold space S in the shape of a preform. Then, by flowing the resin material from the injection device 25 into such a mold space S in the shape of a preform via the hot runner mold 33, a preform 10 is manufactured in the injection molding section 21.

[0048] On the other hand, the injection device 25 is a device in which a screw is rotatably and retractably provided in a cylinder of a barrel, and functions to heat and melt the resin material and inject it into the mold. The injection device 25 sequentially performs injection, pressure holding, and metering by the action of the screw.

[0049] The injection device 25 supplies the resin material from a hopper to the cylinder in which the screw is provided, and performs plasticizing kneading and metering of the resin material by rotation and retraction of the screw. Then, the injection device 25 injects and fills the molten resin into the mold by advancing the screw at high speed. Next, the injection device 25 advances the screw at low speed at a given pressure to additionally inject and fill the molten resin into the mold to compensate for the shrinkage amount of the molten resin in the mold, and pressure holding is performed in this state. The injection device 25 controls the moving speed (injection speed) of the screw when filling the resin material into the mold at high speed, and controls the pressure (pressure holding pressure) after filling the resin material into the mold at high speed. The switching from speed control to pressure control is performed with the screw position or the injection pressure as a threshold value.

[0050] In addition, when the mold opening of the injection molding section 21 is performed, the neck mold 27 of the transfer mechanism 26 is not opened but remains as it is to hold and transfer the preform 10. 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.

[0051] (Temperature adjustment section 22)

[0052] The temperature adjustment section 22 performs temperature equalization and temperature bias elimination of the preform 10 manufactured by the injection molding section 21, adjusts the temperature of the preform 10 to a temperature (for example, about 90°C to 105°C) suitable for blow molding and having a temperature distribution suitable for the container shape to be molded. In addition, the temperature adjustment section 22 also functions to cool the preform 10 in a high-temperature state after injection molding.

[0053] Figure 5 FIG. 2 is a diagram showing a structure example of the temperature adjustment section 22. The temperature adjustment section 22, as a mold unit for temperature adjustment, has a cavity mold (temperature adjustment tank) 41 capable of housing a preform and an air introduction member 42.

[0054] The cavity mold 41 is a mold having a temperature adjustment space having substantially the same shape as the preform 10 manufactured by the injection molding section 21. In the inside of the cavity mold 41, a flow path (not shown) for a temperature adjustment medium (refrigerant) to flow is formed. Therefore, the temperature of the cavity mold 41 is maintained at a given temperature by the temperature adjustment medium.

[0055] In addition, the temperature of the temperature adjustment medium of the cavity mold 41 is not particularly limited, and for example, can be appropriately selected within a range of 5°C to 80°C, preferably within a range of 30°C to 60°C.

[0056] The air introduction member 42 has an air introduction rod 43 connected to an air supply section (not shown) and a fitting core 44 inserted into the inside of the neck mold 27 and the preform 10. The air introduction member 42 is capable of air-tightly abutting against the neck portion 11 of the preform 10 in a state of being inserted into the neck mold 27. The air introduction rod 43 and the fitting core 44 are each a hollow cylindrical body, and the air introduction rod 43 is concentrically disposed inside the fitting core 44.

[0057] The inside of the air introduction rod 43 constitutes a flow path for guiding compressed air (air, gas-like refrigerant) from the air supply section, and the front end of the air introduction rod 43 is inserted into the vicinity of the bottom surface of the preform 10. In addition, at the front end of the air introduction rod 43 facing the bottom of the preform 10, an opening 43a for supplying compressed air into the preform 10 is formed.

[0058] When the air introduction rod 43 is inserted into the inside of the neck mold 27, the fitting core 44 is in close contact with the inner periphery or the upper end surface of the neck portion 11, and the air-tightness of the preform 10 and the air introduction member 42 is maintained.

[0059] The front end of the fitting core 44 is inserted into or abuts against the position of the neck portion 11 of the preform 10. In addition, at the front end of the fitting core 44, an opening 45 for discharging air from the inside of the preform 10 is formed. In addition, the space between the air introduction rod 43 and the fitting core 44 constitutes a flow path for air discharge connected to an air discharge section (not shown).

[0060] (Blow Molding Section 23)

[0061] The blow molding section 23 performs stretch blow molding of the preform 10 whose temperature has been adjusted by the temperature adjustment section 22, and manufactures a container.

[0062] The blow molding section 23 has a pair of split molds, i.e., a blow cavity mold, a bottom mold, a stretch rod, and an air introduction member (none of which is shown) corresponding to the shape of the container. The blow molding section 23 performs blow molding while stretching the preform 10. Thus, the preform 10 can be shaped into the shape of the blow cavity mold to produce the container.

[0063] (Taking-out section 24)

[0064] The taking-out section 24 is configured to open the neck portion of the container produced by the blow molding section 23 from the neck mold 27 and take the container out to the outside of the blow molding apparatus 20.

[0065] <Blow molding method>

[0066] Next, a blow molding method performed by the blow molding apparatus 20 of the present embodiment will be described.

[0067] Figure 6 is a flowchart showing the steps of the blow molding method.

[0068] (Step S101: injection molding step)

[0069] In step S101, in the injection molding section 21, resin is injected from the injection device 25 to 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 transport mechanism 26 to produce the preform 10.

[0070] The resin injected from the injection device 25 passes through the gate region S1 of the injection cavity mold 31 from the resin supply portion 33a of the hot runner mold 33 to fill the mold space S between the injection cavity mold 31 and the injection core mold 32.

[0071] Since the gate region S1 of the injection cavity mold 31 is tapered toward the injection core mold 32, the flow rate of the resin flowing through the gate region S1 decreases toward the outlet of the gate region S1, and the flow resistance of the resin also decreases.

[0072] In addition, at the outlet of the gate region S1, since the corner portion 34 has a rounded corner, the flow of the resin at the corner portion 34 is less likely to generate a vortex. Thus, the flow of the resin at the outlet of the gate region S1 is more likely to become laminar flow into the region of the bottom portion, and the increase in flow resistance caused by the vortex is also suppressed.

[0073] Furthermore, the interval th 1’ In contrast, the interval th 2’The value is 0.7 to 0.85, which is a wider gap at the bottom compared to conventional molds where the bottom thickness is set to about half the thickness of the main body. Therefore, in the bottom region of the mold space S, the resin flows more easily to the main body, and the flow resistance of the resin is also reduced compared to the past.

[0074] Then, after the injection (filling and holding) of the resin material is completed, or after the minimum cooling time set after injection, the injection mold of the injection molding section 21 is opened.

[0075] From the viewpoint of manufacturing containers with a high-speed molding cycle, in step S101, it is preferable to open the mold without setting a cooling time for the preform 10 in the injection mold after the injection (filling and holding pressure) of the resin material is completed. In this case, since the preform 10 is not cooled in the injection mold without holding pressure, the phenomenon of shrinkage and shrinkage marks caused by the preform 10 shrinking during the cooling time can also be suppressed.

[0076] On the other hand, when the preform 10 is cooled to a minimum within the injection mold, the time for cooling the resin material after injection in the injection molding section 21 (cooling time) is preferably less than 1 / 2 of the time for injecting the resin material (injection time). Furthermore, the cooling time can be set even shorter relative to the injection time, depending on the weight of the resin material. For example, the cooling time relative to the injection time is more preferably less than 2 / 5, further preferably less than 1 / 4, and particularly preferably less than 1 / 5.

[0077] When the injection mold is opened in step S101, the preform 10 is demolded from the injection cavity mold 31 and the injection core mold 32 at a high temperature that can maintain its shape. Then, the transfer plate of the conveying mechanism 26 moves by rotating a given angle, and the preform 10, which is kept at a high temperature in the neck mold 27, is conveyed to the temperature adjustment unit 22.

[0078] 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 (A) indicates the case. Additionally, the temperature change examples of the preforms in the comparative examples described later are... Figure 7 (B) indicates this. Furthermore, the time required between each process, such as the transfer of the preform 10 or the container, is the same length.

[0079] In the comparative example (existing method), such asFigure 7 As shown in (B), in the mold of the injection molding section, the preform is cooled to a temperature that is lower than or approximately the same as the blow molding temperature.

[0080] In contrast, in this embodiment, as described above, since there is no cooling time (or a very short cooling time) for the preform 10 in the injection mold, 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 is formed, and has a high temperature and retains high heat.

[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. Furthermore, through contact with external air, the preform 10 is slightly cooled from its outer surface. 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.

[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 can also be set to 90°C to 95°C, for example, in the case of PET resin.

[0084] like Figure 5 As 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 ​ 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] Subsequently, cooling blow of the preform 10 is performed. In the cooling blow of the preform 10 in the present embodiment, compressed air is introduced from the air introduction 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 the cooling blow, since the compressed air is ejected from the opening 43a of the air introduction rod 43, the low-temperature compressed air comes into contact with the bottom 12 of the preform 10 facing the opening 43a of the air introduction 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 toward the main body portion 13 and the neck portion 11 by heat exchange with the preform 10. Therefore, in the cooling blow, the bottom 12 of the preform 10 is locally more strongly cooled than the neck portion 11 and the main body portion 13 of the preform 10.

[0088] By quenching the bottom 12 of the preform 10 in the above-described cooling blow, whitening of the central region of the bottom of the preform 10 can be effectively suppressed.

[0089] In addition, the preform 10 of the present embodiment, as compared with the conventional preform in which the bottom thickness is set to about 1 / 2 of the main body portion thickness, the wall thickness of the bottom 12 is relatively thick, and thus the retained heat of the bottom 12 is large. However, as described above, the bottom 12 is locally cooled in the temperature adjustment portion 22, and thus the retained heat of the bottom 12 is reduced, and thus excessive stretching of the bottom 12 (for example, breakage of the bottom 12) at the time of blow molding of the container can be suppressed.

[0090] In addition, the preform 10 in the temperature adjustment portion 22 is continuously in contact with the cavity mold 41 maintained at a given temperature from the inside by the pressure of the compressed air. Therefore, in the temperature adjustment process, the preform 10 is temperature-adjusted from the outside in such a manner that the temperature does not become lower than the temperature suitable for blow molding, and further, the temperature deviation generated at the time of injection molding is reduced. In addition, in the temperature adjustment process, the shape of the preform 10 is maintained by the cavity mold 41 and does not greatly change.

[0091] After the temperature adjustment process, the transfer plate of the transfer mechanism 26 is moved by rotating by a given angle, and the preform 10 after the temperature adjustment, which is held by the neck mold 27, is transferred to the blow molding portion 23.

[0092] (Step S103: Blow Molding Process)

[0093] Subsequently, in the blow molding portion 23, blow molding of the container 1 is performed.

[0094] 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 to abut against the neck of the preform 10. Then, the stretch rod (longitudinal axis stretching member) is lowered to press the bottom of the preform 10 from the inner surface, and the preform 10 is stretched in the longitudinal axis direction as needed while blow air is supplied from the air introduction member, whereby the preform 10 is inflated in close contact with the mold space of the blow cavity mold and is shaped into the container 1. In addition, the bottom mold is kept at a position below the bottom of the preform 10 without contacting the bottom before the blow cavity mold is closed, and is quickly raised to the molding position before or after the blow cavity mold is closed.

[0095] (Step S104: container taking-out process)

[0096] When the blow molding is completed, the blow cavity mold and the bottom mold are opened. Thus, the container 1 can be moved from the blow molding section 23.

[0097] Next, the transfer plate of the conveyance mechanism 26 is moved by a given angle of rotation, and the container 1 is conveyed to the taking-out section 24. In the taking-out section 24, the neck of the container 1 is opened from the neck mold 27, and the container 1 is taken out to the outside of the blow molding device 20.

[0098] Thus, the series of processes of the blow molding method is completed. Thereafter, the processes of S101 to S104 described above are repeated by moving the transfer plate of the conveyance mechanism 26 by a given angle of rotation. During the operation of the blow molding device 20, four sets of containers 1 each having a time difference of one process are manufactured in parallel.

[0099] In addition, in the structure of the blow molding device 20, the time during which the transfer plate is stopped in the injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the taking-out section 24 is the same length. Also, the conveyance time of the transfer plate between the sections is the same length.

[0100] Hereinafter, the effects of the present embodiment will be described.

[0101] In the injection molding process (S101) of the present embodiment, the preform 10 made of resin having the main body portion 13 and the bottom portion 12 is injection molded, and the preform 10 is demolded in a high-temperature state in which the outer shape of the preform can be maintained. In the injection molding process (S101), an injection mold in which the wall thickness of the bottom portion 12 is 0.7 to 0.85 times the wall thickness of the main body portion 13 is used. The injection mold of the present embodiment has a wider interval of the bottom portion 12 than a conventional mold, and the flow resistance of the resin at the bottom portion of the preform is reduced. Therefore, the shear heat generation at the bottom portion of the preform during injection molding is reduced, and the excessive accumulation of heat in the central region of the bottom portion of the preform can be suppressed.

[0102] Further, in the temperature adjustment step (S102) of the present embodiment, cooling blow in which compressed air is introduced into the preform 10 to cool the bottom 12 of the preform 10 is performed. By quenching the bottom of the preform together with reduction of shear heat generation at the bottom of the preform, whitening of the central region of the bottom of the preform 10 is suppressed. Thus, even in a high-speed molding cycle in which the preform 10 is demolded in a high-temperature state, a container with high transparency and high quality can be produced.

[0103] Further, the gate region S1 of the injection cavity mold 31 is tapered toward the bottom, and the flow rate and flow resistance of the resin are reduced more toward the outlet of the gate region S1. Therefore, even if the gate region S1 is provided in a tapered shape, shear heat generation at the bottom of the preform can be further reduced.

[0104] Further, since the corner 34 connecting the gate region S1 and the outer surface of the bottom is provided with a rounded corner, flow resistance caused by vortex is less likely to occur at the outlet of the gate region S1. Therefore, by imparting a rounded corner to the corner 34 of the injection cavity mold 31, shear heat generation at the bottom of the preform can be further reduced.

[0105] The present application is not limited to the above-described embodiments, and various modifications and design changes can be made within the scope of the present application without departing from the spirit of the present application.

[0106] In the above-described embodiments, a 4-station type device configuration of a hot parison type has been described as an example of a blow molding device. However, the blow molding device of the present application is not limited to the above-described embodiments, and as long as it has an injection molding section, a temperature adjustment section, and a blow molding section, it can be applied to other blow molding devices other than the 4-station type.

[0107] Further, it should be considered that the embodiments disclosed this time are illustrative in all respects, not restrictive. The scope of the present application is shown by the claims rather than the above description, and is intended to include all modifications equivalent within the meaning and scope of the claims.

[0108] Explanation of symbols

[0109] 1... container, 10... preform, 12... bottom, 14... gate portion, 15... corner, 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, 34... corner, 41... cavity mold, 42... air introduction member, S... mold space, S1... corner region.

Claims

1. A method for manufacturing a resin container, comprising: The injection molding process involves injection molding a resin preform with a main body and a bottom. 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. The preform is bowl-shaped with a neck diameter longer than its length from the top of the neck to the bottom. In the injection molding process, the preform is injection molded using an injection mold whose bottom wall thickness is 0.7 to 0.85 times that of the main body. In the temperature adjustment process, refrigerant is introduced into the pre-plasticized preform to cool its bottom. The longitudinal stretching ratio of the preform in the blow molding process is 3.0 to 7.

0. The injection mold has a gate area for introducing resin material from the outside of the bottom. The gate area of ​​the injection mold is formed in a cone shape that expands towards the bottom. The corners connecting the gate area and the outer surface of the bottom are rounded. The thickness of the bottom is 0.70 to 0.9 mm relative to the diameter of the front end of the gate area. The radius of curvature of the corner is 1.0 mm or more.

2. The method for manufacturing a resin container according to claim 1, wherein, In the injection molding process, after the resin material is filled and pressure is maintained, the injection mold is opened, and the preform is removed from the injection mold without cooling.

3. The method for manufacturing a resin container according to claim 1, wherein, In the injection molding process, the preform is demolded at a high temperature that is sufficient to maintain the shape of the preform.

4. The method for manufacturing a resin container according to claim 1, wherein, In the injection molding process, the time for cooling the resin material in the injection mold after the resin material injection is completed is less than 1 / 2 of the time for injecting the resin material into the injection mold.

5. An apparatus for manufacturing a resin container, comprising: The injection molding unit performs injection molding on a resin preform having a main body and a bottom. 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. The preform is bowl-shaped with a neck diameter longer than its length from the top of the neck to the bottom. The injection molding section uses an injection mold with a bottom wall thickness of 0.7 to 0.85 relative to the wall thickness of the main body to injection mold the preform. The temperature adjustment unit introduces refrigerant into the pre-plasticized preform to cool the bottom of the pre-plasticized preform. The longitudinal stretch ratio of the preform in the blow molding section is 3.0 to 7.

0. The injection mold has a gate area for introducing resin material from the outside of the bottom. The gate area of ​​the injection mold is formed in a cone shape that expands towards the bottom. The corners connecting the gate area and the outer surface of the bottom are rounded. The thickness of the bottom is 0.70 to 0.9 mm relative to the diameter of the front end of the gate area. The radius of curvature of the corner is 1.0 mm or more.

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