Manufacturing method and manufacturing device for resin container

Abstract

This method for producing a resin container has: an injection molding step for injection molding a preform that is made of resin and that has a body part and a bottom part; a temperature adjustment step for adjusting the temperature of the preform produced in the injection molding step; and a blow molding step for blow molding the preform, the temperature of which has been adjusted, to produce a resin container. In the injection molding step, the preform is injection molded using an injection mold having a bottom-part wall thickness that is 0.7-0.85 relative to the body-part wall thickness. Also, in the temperature adjustment step, a cooling medium is introduced into the preform to cool the bottom part of the preform.

Description

[Technical field]

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

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

[0003] In the hot parison type blow molding method, the body portion of the preform is required to have a heat sufficient to be stretchable, while the bottom central region of the preform is required to be hard enough not to be broken by the stretch rod.

[0004] Conventionally, the above requirement has sometimes been met by increasing the injection cooling efficiency of the bottom by using a preform whose bottom thickness is set to about half the thickness of the body. Patent Document 1 discloses that in a cylindrical thin-walled preform, the bottom surface is formed as an inclined surface at a uniform angle of 20° to 45°, and the connection portion with the body is formed in an arc shape, thereby causing a gradual transition in the thickness from the bottom to the body and suppressing whitening of the bottom surface.

[0005] Recently, a method for manufacturing a container has been proposed in which the cooling time during injection molding is shortened and the preform released from the mold at a high temperature is blow molded at a high stretch ratio (see, for example, Patent Document 2). According to the above-mentioned method for manufacturing a container, a resin container with good physical properties and appearance can be manufactured in a high-speed molding cycle. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-90425 A [Patent Document 2] Patent No. 6505344 Summary of the Invention [Problem to be solved by the invention]

[0007] In the hot parison blow molding method, there are preform shapes suitable for each container depending on the specifications such as the physical properties and stretch ratio of the container. For example, when manufacturing a wide-mouthed thin-walled resin container such as a cup, a flat bowl-shaped preform is used. Since the body thickness of this type of preform is set relatively thin, setting the bottom thickness to about 1 / 2 of the body thickness makes the bottom thickness of the preform even thinner.

[0008] In the injection molding of the above preform, the space at the bottom of the preform in the injection mold becomes very narrow, and the flow resistance of the molten resin near the gate becomes large. This increases the shear heat of the molten resin during injection molding, and the temperature of the bottom center area of ​​the preform becomes high. This makes it difficult to sufficiently cool the bottom center area of ​​the preform, and crystallization (whitening) due to slow cooling is likely to occur in the bottom center area of ​​the preform or container. In particular, when the cooling time during injection molding is shortened and the preform released from the mold at a high temperature is blow molded at a high stretch ratio, it becomes more important to suppress whitening in the central bottom region.

[0009] Therefore, the present invention has been made in consideration of such problems, and aims to provide a manufacturing method that can produce resin containers in a high-speed molding cycle while suppressing whitening in the central bottom region of the preform or container. [Means for solving the problem]

[0010] The method for producing a resin container according to one embodiment of the present invention includes an injection molding step of injection molding a resin preform having a body and a bottom, a temperature adjustment step of adjusting the temperature of the preform produced in the injection molding step, and a blow molding step of blow molding the temperature-adjusted preform to produce a resin container. The preform is bowl-shaped with a neck having a diameter longer than the length from the top end of the neck to the bottom. In the injection molding step, the preform is injection molded using an injection mold in which the thickness of the bottom is 0.7 to 0.85 times the thickness of the body. In the temperature adjustment step, a refrigerant is introduced into the preform to cool the bottom of the preform. The stretch ratio in the longitudinal direction of the preform in the blow molding step is 3.0 to 7.0. The injection mold has a gate area for introducing a resin material from the outside of the bottom, and the gate area of ​​the injection mold is formed in a tapered shape expanding in diameter toward 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 0.90 with respect to the diameter dimension of the tip side of the gate area, and the radius of the round corners is 2.0 mm to 4.0 mm. Effect of the Invention

[0011] According to one aspect of the present invention, a resin container can be manufactured in a high-speed molding cycle while suppressing whitening in the central bottom region of the preform or container. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing an example of a preform according to the present embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a resin container according to the present embodiment. [Diagram 3] 1 is a diagram showing a schematic configuration of a blow molding device according to an embodiment of the present invention; [Figure 4] FIG. 2 is a diagram illustrating a configuration example of an injection molding unit. [Diagram 5] FIG. 4 is a diagram illustrating an example of the configuration of a temperature adjustment unit. [Figure 6] 4 is a flow chart showing steps of a method for manufacturing a container. [Figure 7] 4 is a graph showing an example of temperature changes of preforms in the blow molding methods of this embodiment and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiments, in order to make the description easier to understand, structures and elements other than the main parts of the present invention will be described in a simplified or omitted manner. In addition, in the drawings, the same elements are given the same reference numerals. Note that the shapes, dimensions, etc. of each element shown in the drawings are shown only for illustrative purposes, and do not represent the actual shapes, dimensions, etc.

[0014] <Explanation of preform> First, a configuration example of a preform 10 applied to the manufacture of a resin container (hereinafter also simply referred to as a container) of this embodiment will be described with reference to Fig. 1. Fig. 1(a) shows the overall shape of the preform 10, and Fig. 1(b) is a partially enlarged view of the vicinity of a gate portion 14 in Fig. 1(a). Note that the preform 10 in Fig. 1 is applied to the manufacture of a wide-mouthed, thin-walled container such as a cup (see Fig. 2).

[0015] As shown in Fig. 1(a), the overall shape of the preform 10 is a flat bowl shape with a bottom that is convex downward. 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 over the entire circumferential area. The above-mentioned shape of the preform 10 is merely an example, and the preform 10 may be, for example, a cylindrical shape with a bottom that extends in the longitudinal direction.

[0016] In the preform 10 of this embodiment, the thickness th of the bottom portion 12 is 1 However, the thickness of the body 13 2 is set to a value of 0.7 to 0.85 compared to. In other words, the preform 10 of this embodiment has a relatively thick bottom wall thickness compared to a conventional preform in which the bottom wall thickness is set to about 1 / 2 the body wall thickness. In the hot parison type blow molding method, the bottom wall thickness is set to about 1 / 2 the body wall thickness so that the bottom wall is not broken by the stretch rod during the blow molding process, and the bottom wall is sufficiently cooled and solidified during the injection molding process.

[0017] A gate portion 14 is formed in the center of the bottom portion 12 of the preform 10, with its tip protruding toward the outside of the bottom portion 12. The gate portion 14 is a trace of resin introduction from a hot runner mold 33, which will be described later, and is formed in a tapered shape that expands in diameter from the tip side of the gate portion 14 toward the base end side facing the bottom portion 12. Therefore, as shown in FIG. 1(b), the gate portion 14 has a diameter dimension d 1 The diameter dimension d on the base end side 2 In addition, at the base end side of the gate portion 14, a corner portion 15 where the gate portion 14 and the outer surface of the bottom portion are connected is provided with a radius (roundness, circular arc). For example, the radius of the radius is set to a value of 2.0 mm to 4.0 mm (preferably 2.1 mm to 3.0 mm).

[0018] The thickness of the bottom 12 is the diameter dimension d of the gate part. 1 It is set thinner, for example, the diameter dimension d 1 is set to a value of 0.70 to 0.9 (preferably 0.75 to 0.85) when is set to 1. In the preform 10, for example, the maximum diameter D1 (diameter of the neck portion 11) is set to be longer than the length L1 (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 D1 is set to, for example, 1.5 to 3.0 times (preferably 1.5 to 2.5 times, more preferably 1.7 to 2.3 times) the length L1.

[0019] The material of the preform 10 is a thermoplastic synthetic resin, and can be appropriately selected according to the application of the container. Specific types of materials include, for example, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCTA (polycyclohexane dimethylene terephthalate), Tritan (Tritan (registered trademark): copolyester manufactured by Eastman Chemical Co.), PP (polypropylene), PE (polyethylene), PC (polycarbonate), PES (polyethersulfone), PPSU (polyphenylsulfone), PS (polystyrene), COP / COC (cyclic olefin polymer), PMMA (polymethyl methacrylate: acrylic), and PLA (polylactic acid). The present invention is particularly effective when a material that is a thermoplastic synthetic resin and a crystalline resin that is prone to whitening due to spherulite crystallization during injection molding (for example, PET or PEN) is selected as the material of the preform 10.

[0020] <Container description> Next, referring to FIG. 2, an example of the configuration of the container of this embodiment will be described. FIG. 2(a) is a plan view of the container, and FIG. 2(b) is a front view of the container. As shown in FIG. 2(a) and (b), the container 1 is a wide-mouthed cup-shaped container with an open top and a closed bottom. The container 1 has a neck 2 facing the opening on the top side, a bottom 3 closing the bottom side, and a body 4 connecting the neck 2 and the bottom 3. The body 4 of the container 1 has a tapered shape (inverted truncated cone shape) that reduces in diameter from the top side to the bottom side. In addition, the container 1 has a length (depth L) in the axial direction of the container that is sufficiently longer than the inner diameter D of the container, and is formed with a deep bottom. The stretch ratio in the longitudinal direction of the preform 10 relative to the container 1 is set to be high, from 3.0 to 7.0 (preferably from 3.5 to 6.0, more preferably from 4.0 to 5.5).

[0021] <Explanation of blow molding equipment> Next, a blow molding apparatus 20 for manufacturing a container will be described with reference to Fig. 3. Fig. 3 is a block diagram that shows a schematic configuration of the blow molding apparatus 20. The blow molding apparatus 20 of this embodiment is an apparatus of a hot parison type (also called a one-stage type) that performs blow molding by utilizing the heat retained during injection molding (internal heat amount) without cooling the preform 10 to room temperature.

[0022] The blow molding apparatus 20 includes an injection molding section 21, a temperature adjustment section 22, a blow molding section 23, a removal section 24, and a conveying mechanism 26. The injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the removal section 24 are disposed at positions rotated a predetermined angle (e.g., 90 degrees) around the conveying mechanism 26.

[0023] (Transport mechanism 26) The transport mechanism 26 includes a transport plate (not shown) that moves so as to rotate around an axis perpendicular to the plane of the drawing in Fig. 3. At least one neck mold 27 (not shown in Fig. 1) that holds the neck of the preform 10 or a resin container (hereinafter simply referred to as a container) is arranged at each predetermined angle on the transport plate. The transport mechanism 26 transports the preform 10 (or the container) whose neck is held by the neck mold 27 to the injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the removal section 24 in this order by moving the transport plate by 90 degrees at a time. The transport mechanism 26 further includes a lifting mechanism (vertical mold opening / closing mechanism) and a mold opening mechanism for the neck mold 27, and performs the operation of lifting and lowering the transport plate and the operation of mold closing and mold opening (mold release) in the injection molding section 21, etc.

[0024] (Injection molding section 21) As shown in Fig. 4(a), 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 device 20 in an integrated state. Meanwhile, the injection core mold 32 is fixed to a core mold lifting mechanism (not shown). Also, an injection device 25 that supplies a resin material, which is a raw material of the preform, is connected to the injection molding section 21.

[0025] The injection cavity mold 31 is a mold that determines the outer periphery shape of the preform 10. The hot runner mold 33 has a resin supply section 33a that introduces the resin material from the injection device 25 into the mold. The injection core mold 32 is a mold that determines the inner periphery shape of the preform 10, and is inserted into the inner periphery side of the neck mold 27 and the injection cavity mold 31 from above.

[0026] The mold space S formed by the injection cavity mold 31 and the injection core mold 32 has a shape following the shape of the preform 10. In the mold space S, the mold space interval th corresponding to the thickness of the bottom portion 12 is 1’ is the mold space interval th corresponding to the thickness of the body 13 2’ It is set to a value of 0.7 to 0.85 compared to

[0027] As shown in FIG. 4(b), in the injection cavity mold 31, a gate region S connected to the resin supply portion 33a is 1 The gate region S facing the injection core mold 32 is formed in a tapered shape that expands in diameter toward the injection core mold 32. 1 At the exit of the gate region S 1 The corner portion 34 where the outer surface of the bottom portion is connected is rounded. The radius of curvature of the corner portion 34 is, for example, 1 mm or more.

[0028] 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 S having a preform shape. Then, a resin material is poured from the injection device 25 through the hot runner mold 33 into the mold space S having the preform shape, whereby the preform 10 is manufactured in the injection molding section 21.

[0029] On the other hand, the injection device 25 is a device in which a screw is provided inside the cylinder of a barrel so as to be rotatable and movable forward and backward, and has the function of heating and melting the resin material and injecting it into a mold. The injection device 25 performs injection, pressure holding, and metering in that order by the action of the screw.

[0030] The injection device 25 supplies resin material from a hopper to a cylinder in which a screw is arranged, and plasticizes, kneads, and measures the resin material by rotating and retreating the screw. The injection device 25 then advances the screw at high speed to inject and fill the molten resin into the mold. Next, the injection device 25 advances the screw at low speed at a predetermined pressure to additionally inject and fill the molten resin into the mold to compensate for the amount of shrinkage of the molten resin in the mold, and holds the pressure in that state. 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. Switching from speed control to pressure control is performed using the screw position or injection pressure as a threshold value.

[0031] Incidentally, even when the injection molding section 21 is opened, the neck mold 27 of the transport mechanism 26 is not opened, but continues to hold and transport the preforms 10. The number of preforms 10 simultaneously molded in the injection molding section 21 (i.e., the number of containers that can be simultaneously molded by the blow molding device 20) can be set appropriately.

[0032] (Temperature adjustment section 22) Temperature adjustment section 22 equalizes the temperature of preform 10 manufactured in injection molding section 21 and removes temperature deviations, and adjusts the temperature of preform 10 to a temperature suitable for blow molding (for example, about 90°C to 105°C) and to provide a temperature distribution suitable for the container shape to be molded. Temperature adjustment section 22 also has the function of cooling preform 10 in a high-temperature state after injection molding.

[0033] 5 is a diagram showing an example of the configuration of the temperature adjustment unit 22. The temperature adjustment unit 22 has a cavity mold (temperature adjustment pot) 41 capable of accommodating a preform, and an air introduction member 42, as a mold unit for temperature adjustment.

[0034] The cavity mold 41 is a mold having a temperature control space having approximately the same shape as the preform 10 manufactured in the injection molding section 21. A flow path (not shown) through which a temperature control medium (coolant) flows is formed inside the cavity mold 41. Therefore, the temperature of the cavity mold 41 is maintained at a predetermined temperature by the temperature control medium. The temperature of the temperature adjustment medium of the cavity mold 41 is not particularly limited, but can be appropriately selected within the range of, for example, 5°C to 80°C, preferably 30°C to 60°C.

[0035] The air introducing member 42 has an air introducing 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 introducing member 42 abuts airtightly against the neck portion 11 of the preform 10. The air introducing rod 43 and the fitting core 44 are both hollow cylindrical bodies, and the air introducing rod 43 is arranged concentrically inside the fitting core 44.

[0036] The inside of the air introduction rod 43 constitutes a flow path for guiding compressed air (air, gaseous refrigerant) from the air supply unit, and the tip of the air introduction rod 43 is inserted up to the vicinity of the bottom surface of the preform 10. In addition, at the tip 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.

[0037] When the air introducing rod 43 is inserted into the neck mold 27 , the fitting core 44 comes into close contact with the inner circumference or upper end face of the neck portion 11 , and maintains an airtight seal between the preform 10 and the air introducing member 42 . The tip of the fitting core 44 is inserted or abutted up to the position of the neck portion 11 of the preform 10. An opening 45 for exhausting air from inside the preform 10 is formed at the tip of the fitting core 44. The space between the air introduction rod 43 and the fitting core 44 constitutes an exhaust flow path connected to an air exhaust section (not shown).

[0038] (Blow molding section 23) The blow molding section 23 performs stretch blow molding on the preform 10 whose temperature has been adjusted in the temperature adjustment section 22, to manufacture a container. The blow molding section 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 section 23 blow molds the preform 10 while stretching it. This allows the preform 10 to be shaped into the shape of the blow cavity mold to manufacture a container.

[0039] (Removal part 24) The removal section 24 is configured to release the neck 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.

[0040] <Explanation of the blow molding method> Next, a blow molding method using the blow molding apparatus 20 of this embodiment will be described. FIG. 6 is a flow chart showing the steps of the blow molding method.

[0041] (Step S101: Injection molding process) In step S101, in the injection molding section 21, resin is injected from the injection device 25 into a preform-shaped mold space 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 .

[0042] The resin injected from the injection device 25 is delivered from the resin supply section 33a of the hot runner mold 33 to the gate region S of the injection cavity mold 31. 1 3, and is filled into the mold space S between the injection cavity mold 31 and the injection core mold 32.

[0043] Gate area S of injection cavity mold 31 1 Since the gate area S has a tapered shape that expands toward the injection core mold 32, 1 The flow rate of the resin flowing through the gate area S 1 The flow resistance of the resin also decreases toward the outlet. Also, the gate region S 1 At the exit of the gate region S, the corner portion 34 is rounded, so that vortexes are unlikely to occur in the resin flow at the corner portion 34. 1 The resin flow at the outlet tends to be a laminar flow that flows along the curved surface into the bottom region, and an increase in flow resistance due to vortices is also suppressed.

[0044] Furthermore, the mold space interval th corresponding to the thickness of the bottom 12 1’ is the mold space interval th corresponding to the thickness of the body 13 2’ The value is 0.7 to 0.85 compared to the conventional mold, which has a bottom thickness that is about half the thickness of the body, and the bottom distance is wider. Therefore, in the bottom region of the mold space S, the resin flows more easily toward the body than in the conventional mold, and the flow resistance of the resin is also smaller.

[0045] Then, after the injection (filling and pressure holding) of the resin material is completed, or after a minimum cooling time has elapsed after the completion of the injection, the injection mold of the injection molding portion 21 is opened.

[0046] From the viewpoint of manufacturing a container with a high-speed molding cycle, it is preferable to open the mold in step S101 after the injection (filling and pressure holding) of the resin material is completed without providing a cooling time for the preform 10 in the injection mold. In the above case, the preform 10 is not cooled in the injection mold without pressure holding, so that the preform 10 shrinks during the cooling time, which can prevent sink marks from occurring.

[0047] On the other hand, when the preform 10 is cooled to a minimum extent in the injection mold, the time to cool the resin material after the injection of the resin material is completed in the injection molding section 21 (cooling time) is preferably 1 / 2 or less of the time to inject the resin material (injection time). The cooling time can be made shorter than the time to inject the resin material depending on the weight of the resin material. For example, the cooling time is more preferably 2 / 5 or less of the injection time of the resin material, even more preferably 1 / 4 or less, and particularly preferably 1 / 5 or less.

[0048] When the injection mold is opened in step S101, the preform 10 is released from the injection cavity mold 31 and the injection core mold 32 at a high temperature that allows the outer shape to be maintained. Next, the transfer plate of the transport mechanism 26 moves so as to rotate by a predetermined angle, and the preform 10 in a high temperature state held in the neck mold 27 is transported to the temperature adjustment unit 22.

[0049] Also, referring to Fig. 7, the temperature change of the preform 10 in the blow molding method of this embodiment will be described. The vertical axis of Fig. 7 indicates the temperature of the preform 10, and the horizontal axis of Fig. 7 indicates time. In Fig. 7, an example of the temperature change of the preform 10 of this embodiment is shown in Fig. 7(A). Also, an example of the temperature change of the preform of a comparative example described later is shown in Fig. 7(B). Note that the gaps between each process are the time required for transporting the preform 10 or the container, and are all the same length.

[0050] In a comparative example (conventional method), as shown in FIG. 7(B), the preform is cooled in the mold of the injection molding section to a temperature lower than or approximately the same as the blow temperature.

[0051] In contrast, in this embodiment, as described above, there is no cooling time for the preform 10 in the injection mold (or the cooling time is very short), so the skin layer (surface layer in a solidified state) of the preform is formed thinner than in the past, and the core layer (internal layer in a softened or molten state) is formed thicker than in the past. In other words, compared to the comparative example, the thermal gradient between the skin layer and the core layer is large, and a preform 10 with high retained heat at high temperatures is molded.

[0052] The preform 10 of this embodiment is demolded from the injection molding section 21 at a higher demolding temperature than the comparative example, and is transported to the temperature adjustment section 22. As the preform 10 moves to the temperature adjustment section 22, the temperature of the preform 10 is uniformized by heat exchange (thermal 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 of this embodiment is maintained at a much higher temperature than that of the comparative example until it is transported to the temperature adjustment section 22.

[0053] (Step S102: Temperature adjustment process) Next, in the temperature adjusting section 22, cooling and temperature adjustment are performed to bring the temperature of the preform 10 close to a temperature (blow temperature) suitable for the final blow. The blow temperature is set to 90°C to 105°C for PET resin, for example. Note that a lower blow temperature may improve the stretch orientation of the preform 10 and increase the strength (physical properties) of the container. Therefore, the blow temperature may be set to 90°C to 95°C for PET resin, for example.

[0054] 7, in the temperature adjustment section 22, the temperature of the preform 10 is lowered to the blow temperature, and thereafter, the temperature of the preform 10 is maintained at the blow temperature until blow molding is performed. In the temperature adjustment section 22, the preform in a high temperature state is rapidly cooled, so that whitening (opacity) due to spherulite generation crystallization that may occur in the case of slow cooling is suppressed.

[0055] 5, in the temperature adjustment step, first, the preform 10 is accommodated in a cavity mold 41. Next, an air introduction member 42 is inserted into the neck portion of the preform 10 accommodated in the cavity mold 41. At this time, the neck portion 11 of the preform 10 and a fitting core 44 are in close contact with each other, maintaining an airtight state between them.

[0056] Thereafter, a cooling blow is performed on the preform 10. In the cooling blow on the preform 10 of this embodiment, 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.

[0057] In the cooling blow, compressed air is ejected from the opening 43a of the air inlet rod 43, so that the low-temperature compressed air comes into contact with the bottom 12 of the preform 10 facing the opening 43a of the air inlet rod 43. The preform 10 is cooled from the inside by the compressed air flowing inside, but the temperature of the compressed air gradually rises as it moves toward 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 locally cooled more strongly than the neck 11 and body 13 of the preform 10. The bottom 12 of the preform 10 is quenched by the above-mentioned cooling blow, so that whitening of the central area of ​​the bottom of the preform 10 is effectively suppressed.

[0058] Furthermore, in the preform 10 of this embodiment, compared to a conventional preform in which the bottom thickness is about half the body thickness, the thickness of the bottom 12 is relatively thicker, and so the heat held by the bottom 12 is greater. However, as described above, the heat held by the bottom 12 is reduced by locally cooling the bottom 12 in the temperature adjustment section 22, and therefore excessive stretching of the bottom 12 (e.g., breakage of the bottom 12) is suppressed during blow molding of the container.

[0059] Furthermore, the preform 10 in the temperature adjustment section 22 continues to be in contact with the cavity mold 41, which is maintained at a predetermined temperature by compressed air pressure from the inside. Therefore, in the temperature adjustment 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 temperature deviations that occur during injection molding are also reduced. In the temperature adjustment process, the shape of the preform 10 is maintained in the cavity mold 41 and does not change significantly.

[0060] After the temperature adjustment step, the transfer plate of the transport mechanism 26 moves so as to rotate by a predetermined angle, and the preform 10 after temperature adjustment held by the neck mold 27 is transported to the blow molding section 23.

[0061] (Step S103: Blow molding process) Next, in the blow molding section 23, the container 1 is blow molded. First, the blow cavity mold is closed to accommodate the preform 10 in the mold space, and the air introduction member (blow core) is lowered to bring the air introduction member into contact with the neck of the preform 10. Then, the stretch rod (vertical axis stretching member) is lowered to hold the bottom of the preform 10 from the inside, and while performing vertical axis stretching as necessary, blow air is supplied from the air introduction member to horizontally stretch the preform 10. As a result, the preform 10 is shaped by expanding so as to fit closely into the mold space of the blow cavity mold, and is blow molded into the container 1. Note that the bottom mold waits at a lower position where it does not come into contact with 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.

[0062] (Step S104: container removal process) When the blow molding is completed, the blow cavity mold and the bottom mold are opened, which makes it possible to remove the container 1 from the blow molding section 23. Next, the transfer plate of the conveying mechanism 26 moves so as to rotate a predetermined angle, and the container 1 is conveyed to the removal section 24. In the removal section 24, the neck portion of the container 1 is released from the neck mold 27, and the container 1 is removed to the outside of the blow molding apparatus 20.

[0063] This completes the series of steps in the blow molding method. Thereafter, the transfer plate of the conveying mechanism 26 is moved so as to rotate by a predetermined angle, and the above steps S101 to S104 are repeated. When the blow molding apparatus 20 is in operation, four sets of containers 1 are produced in parallel, with a time difference between each step.

[0064] Due to the structure of the blow molding apparatus 20, the time during which the transfer plate is stopped is the same in the injection molding section 21, the temperature adjustment section 22, the blow molding section 23, and the removal section 24. Similarly, the transport time of the transfer plate between each section is also the same.

[0065] The effects of this embodiment will be described below. In the injection molding step (S101) of this embodiment, a resin preform 10 having a body 13 and a bottom 12 is injection molded, and the preform 10 is released from the mold at a high temperature that allows the outer shape of the preform to be maintained. In this injection molding step (S101), an injection mold is used in which the thickness of the bottom 12 is 0.7 to 0.85 times the thickness of the body 13. In the injection mold of this embodiment, the distance between the bottoms 12 is wider than in conventional molds, and the flow resistance of the resin at the bottom of the preform is reduced. Therefore, shear heat generation at the bottom of the preform during injection molding is reduced, and excessive heat accumulation in the central area of ​​the bottom of the preform can be suppressed.

[0066] Furthermore, in the temperature adjustment step (S102) of this embodiment, a cooling blow is performed by introducing compressed air into the preform 10 to cool the bottom 12 of the preform 10. The rapid cooling of the preform bottom along with the reduction in shear heat at the preform bottom suppresses whitening of the central area of ​​the bottom of the preform 10. This makes it possible to manufacture a high-quality container with high transparency even in a high-speed molding cycle in which the preform 10 is demolded at a high temperature.

[0067] Also, the gate area S of the injection cavity mold 31 1 The flow rate and flow resistance of the resin are controlled by the gate area S. 1 Therefore, the gate area S 1 The shear heat at the bottom of the preform can also be further reduced by making the shape of the preform tapered.

[0068] Also, the gate region S 1 The corner portion 34 connecting the gate region S and the bottom outer surface is rounded. 1 Therefore, by providing a rounded corner 34 of the injection cavity mold 31, the shear heat at the bottom of the preform can be further reduced.

[0069] The present invention is not limited to the above-described embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.

[0070] In the above embodiment, a hot parison type four-station device configuration has been described as an example of a blow molding device. However, the blow molding device of the present invention is not limited to the above embodiment, and may be applied to blow molding devices other than the four-station type as long as they include an injection molding section, a temperature adjustment section, and a blow molding section.

[0071] In addition, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0072] 1...container, 10...preform, 12...bottom, 14...gate portion, 15...corner portion, 20...blow molding device, 21...first injection molding section, 22...temperature adjustment section, 23...blow molding section, 25...injection device, 26...transport mechanism, 31...injection cavity mold, 32...injection core mold, 34...corner portion, 41...cavity mold, 42...air introduction member, S...mold space, S 1 …Corner area

Claims

1. an injection molding step of injection molding a resin preform having a body portion and a bottom portion; A temperature adjustment process for adjusting the temperature of the preform manufactured in the injection molding process; A blow molding step of producing a resin container by blow molding the temperature-controlled preform, The preform is bowl-shaped with a neck having a diameter greater than the length from the top to the bottom of the neck, In the injection molding step, the preform is injection molded using an injection mold in which the thickness of the bottom portion is 0.7 to 0.85 times the thickness of the body portion; In the temperature adjustment step, a refrigerant is introduced into the preform to cool the bottom of the preform, The stretch ratio in the longitudinal direction of the preform in the blow molding step is 3.0 to 7.0; The injection mold has a gate area for introducing a resin material from outside the bottom portion, The gate region of the injection mold is formed in a tapered shape expanding in diameter toward the bottom, A corner portion connecting the gate region and the outer surface of the bottom portion is rounded, the thickness of the bottom portion is 0.70 to 0.90 relative to the diameter of the tip side of the gate region; The radius of the corner is 2.0 mm to 4.0 mm. A method for manufacturing a resin container.

2. In the injection molding process, the injection mold is opened after the filling of the resin material and the pressure holding are completed, and the preform is removed without being cooled in the injection mold. The method for producing the resin container according to claim 1.

3. In the injection molding process, the preform is released from the mold at a high temperature so that the outer shape of the preform can be maintained. The method for producing the resin container according to claim 1.

4. In the injection molding step, the time required to cool the resin material in the injection mold after the injection of the resin material is completed is 1 / 2 or less of the time required to inject the resin material into the injection mold. The method for producing the resin container according to claim 1.

5. The resin container is a wide-mouth container whose axial length is longer than its inner diameter. A method for producing a resin container according to any one of claims 1 to 4.

6. an injection molding unit that injection molds a resin preform having a body portion and a bottom portion; A temperature adjustment unit that adjusts the temperature of the preform manufactured in the injection molding unit; a blow molding section for producing a resin container by blow molding the temperature-controlled preform, The preform is bowl-shaped with a neck having a diameter greater than the length from the top to the bottom of the neck, The injection molding unit injection molds the preform using an injection mold in which the thickness of the bottom portion is 0.7 to 0.85 times the thickness of the body portion; The temperature adjustment unit introduces a refrigerant into the preform to cool the bottom of the preform, The stretch ratio in the longitudinal direction of the preform in the blow molding section is 3.0 to 7.0; The injection mold has a gate area for introducing a resin material from outside the bottom portion, The gate region of the injection mold is formed in a tapered shape expanding in diameter toward the bottom, A corner portion connecting the gate region and the outer surface of the bottom portion is rounded, the thickness of the bottom portion is 0.70 to 0.90 relative to the diameter of the tip side of the gate region; The radius of the corner is 2.0 mm to 4.0 mm. Plastic container manufacturing equipment.

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