Method and device for producing resin container

Abstract

Provided is a method for producing a resin container by which a resin container with a grip part having sufficient strength can be produced through an injection stretch blow-molding process using a crystalline resin as a material. In this method for producing a resin container, a resin container made of a crystalline resin has a hollow grip part connected to a body part, and a through-hole is formed by the body part and the grip part. The production method comprises an injection molding step in which a preform is injection-molded, and a blow-molding step in which the preform is blow-molded to produce a resin container. The blow-molding step comprises: a pre-blow-molding step in which a pressurized gas is introduced into the preform having a temperature adjusted to 160°C or higher to thereby blow-mold the preform into an intermediate molded object; a step for forming a portion to be cut out, in which the intermediate molded object is accommodated in a pair of split-mold halves having protrusions that, when the split-mold halves are closed, face each other so as to form a gap therebetween, and the split-mold halves are closed to thereby form, in the intermediate molded object, a portion to be cut out which later becomes a through-hole; and a final blow-molding step in which a highly pressurized gas is introduced into the intermediate molded object, thereby blow-molding the intermediate molded object into a resin container.

Description

Method and apparatus for manufacturing resin containers

[0001] The present invention relates to a method and apparatus for manufacturing a resin container, and more particularly to a method and apparatus for manufacturing a resin container made of crystalline resin that has a hollow gripping portion.

[0002] Conventionally, a technique is known for manufacturing resin containers in which a hollow gripping portion (handle) is integrally formed with the body of the container by injection stretch blow molding. When manufacturing a resin container with a hollow gripping portion by injection stretch blow molding, for example, a preform that has been inflated to a certain size by pre-blowing is formed by sandwiching it between a pair of blow-cut molds having projections for forming through holes for the gripping portion. As a result, a container is obtained in which the sandwiched resin is welded at the through-hole forming portion. Next, a container with a gripping portion is obtained by hollowing out the welded portion.

[0003] In resin containers with hollow gripping sections, high transparency and resistance to breakage from drops are required, just like in other containers. When amorphous resins such as polycarbonate or TRITAN (registered trademark) are used as the container material, transparency is easily ensured, and the resin sandwiched in the through-hole formation section is easily welded, allowing sufficient strength to be provided around the gripping section. On the other hand, when crystalline resins are used as the container material, especially crystalline PET (polyethylene terephthalate), which is often used as a material for beverage containers, the molding method using injection stretch blow molding results in differences in the degree of crystallinity from part to part, making it difficult to achieve high transparency and strength. Furthermore, it was also difficult to weld the crystalline resin sandwiched in the through-hole formation section.

[0004] For example, in the method for manufacturing a PET container having a hollow gripping portion described in Patent Document 1, during stretch blow molding, a gripping recess having a pair of opposing concave surfaces is formed by pressing the portion that will become the gripping recess from both sides within the blow cavity mold. Then, after cutting away the pair of opposing concave surfaces, leaving the peripheral edges, to form a through hole, a separately molded resin ring member is placed on the peripheral edges of the remaining concave surfaces, and the peripheral edges are welded and fixed together by this ring member.

[0005] Japanese Patent No. 3816555

[0006] In the manufacturing method of Patent Document 1, by welding a separately formed unoriented ring member and the peripheral edge of the concave portion, the wall thickness of the through-hole forming portion is increased and a reliable welded and fixed state is obtained, making it possible to prevent leakage of the contents. However, since it is necessary to separately manufacture the ring member and weld the ring member after blow molding, there is room for improvement in terms of productivity and cost.

[0007] The present invention has been made in view of such problems, and an object thereof is to provide a method and an apparatus for manufacturing a resin container with a gripping portion having sufficient strength without requiring an additional member by an injection stretch blow molding method using a crystalline resin as a material.

[0008] One aspect of the present invention is a method for manufacturing a resin container made of a crystalline resin, the resin container including a hollow gripping portion connected and communicating with the body portion of the resin container, and a through-hole penetrating in a direction intersecting the central axis of the resin container being formed by the body portion and the gripping portion. The manufacturing method includes an injection molding step of manufacturing a bottomed preform by injection molding, and a blow molding step of blow molding the injection-molded preform to manufacture the resin container. The blow molding step includes a preliminary blow molding step of blow molding the preform adjusted to 160° C. or higher into an intermediate molded body by introducing a pressurized gas and stretching it, and a pair of split molds defining the outer shape of the resin container, each split mold having a protruding portion configured to have a gap and face each other when the pair of split molds are closed. An intermediate molded body is accommodated in the pair of split molds, and by closing the pair of split molds, a cut-out planned portion that will later be cut out to form a through-hole is formed in the intermediate molded body, and a cut-out planned portion forming step; and a final blow molding step of blow molding the resin container before the through-hole is formed by introducing a pressurized gas at a higher pressure than the pressurized gas in the preliminary blow molding step into the intermediate molded body in which the cut-out planned portion is formed.

[0009] According to one aspect of the present invention, a resin container with a gripping portion having sufficient strength can be manufactured by injection stretch blow molding using a crystalline resin as the material, without requiring any additional components.

[0010] This is a front view showing an example of a resin container manufactured by a resin container manufacturing method according to one embodiment of the present invention. This is a schematic diagram showing an example of the configuration of a resin container manufacturing apparatus according to one embodiment. This is a flowchart showing the steps of a resin container manufacturing method according to one embodiment. This is a diagram illustrating a preliminary blow molding section. This is a diagram illustrating a final blow molding section. This is a diagram illustrating a flat plate section formed by a projection of a blow molding die. This is a diagram illustrating the final blow in the final blow molding section.

[0011] Embodiments of the present invention will be described below with reference to the drawings. In the embodiments, for the sake of clarity, structures and elements other than the main parts of the present invention will be simplified or omitted in the description. Also, the same elements will be denoted by the same reference numerals in the drawings. Note that the shapes and dimensions of each element shown in the drawings are schematic representations and do not represent the actual shapes and dimensions.

[0012] Furthermore, in the attached drawings, the XYZ coordinate system is shown as a three-dimensional Cartesian coordinate system where appropriate. In the XYZ coordinate system, the X direction is the left-right direction (width direction) in Figures 1, 4 to 7, and the Y direction is the up-down direction (height direction) in Figures 1, 4 to 7, and is perpendicular to the X direction. The Z direction is the vertical direction (depth direction) of the paper in Figures 1, 4 to 7, and is perpendicular to both the X and Y directions.

[0013] <Overview of Resin Containers> First, an example of a resin container 1 manufactured by the resin container manufacturing method according to this embodiment will be described. Figure 1 is a front view of the resin container 1 according to this embodiment. In this embodiment, the resin forming the resin container 1 is a crystalline resin, preferably crystalline polyethylene terephthalate (PET).

[0014] As illustrated in Figure 1, the resin container 1 comprises a neck portion 3, a body portion 5, a bottom portion 6, and a grip portion 7. It may also include a shoulder portion 4 that connects the neck portion 3 and the body portion 5 and widens in diameter towards the body portion 5.

[0015] The neck portion 3 is formed in a substantially cylindrical shape with an opening 2 at its upper end, and the opening 2 serves as an inlet and outlet for the liquid contained in the resin container 1. A threaded portion 8 may be formed on the outer surface of the neck portion 3 to allow the attachment of a lid portion (not shown).

[0016] The body portion 5 is a roughly cylindrical part that connects to the neck portion 3. The body portion 5 extends in a circular motion around the central axis A of the resin container 1 and forms the side surface of the resin container 1.

[0017] The bottom portion 6 is connected to the body portion 5 and is configured to close the lower end of the body portion 5. The body portion 5 and the bottom portion 6 define the storage space for the contents of the resin container 1.

[0018] The gripping portion 7 is provided to connect to the body portion 5 and is formed in a hollow shape that communicates with the inside of the body portion 5. As shown in Figure 1, the body portion 5 and the gripping portion 7 form a through hole H that penetrates in the Z direction, intersecting the central axis A of the resin container 1. The formation of the through hole H makes it easy for the user of the resin container 1 to grasp the gripping portion 7 with their palm and fingers, improving the convenience of transporting or handling the resin container 1.

[0019] In this embodiment, the resin container 1 is formed by first creating a bottomed preform 20 by injection molding, and then stretch blow molding the preform 20. That is, the resin container 1 of this embodiment is formed by injection stretch blow molding (ISBM). The manufacturing method and manufacturing apparatus for the resin container 1 will be described below. Similar to the resin container 1, the resin used to form the preform 20 is a crystalline resin, preferably crystalline polyethylene terephthalate (PET).

[0020] <Overview of Blow Molding Apparatus 10> Figure 2 is a schematic plan view showing the configuration of the blow molding apparatus 10, which is a manufacturing apparatus for the resin container 1 according to this embodiment. The blow molding apparatus 10 is an example of a manufacturing apparatus for the resin container 1 and employs a hot parison method (also called a one-stage method) in which the resin container 1 is blow molded by utilizing the heat retained during injection molding (internal heat quantity) without cooling the resin preform 20 to room temperature.

[0021] The blow molding apparatus 10 comprises an injection molding unit 11, a temperature control unit 12, a blow molding unit 13, a removal unit 14, an injection device 15, and a transport mechanism 16. The injection molding unit 11, the temperature control unit 12, the blow molding unit 13, and the removal unit 14 are positioned at predetermined angles (for example, 90 degrees) around the transport mechanism 16.

[0022] (Transport mechanism 16) The transport mechanism 16 includes a transport plate (not shown) that moves in a rotational direction about an axis perpendicular to the plane of the paper in Figure 2. The transport plate is composed of a single disc-shaped flat plate member or a plurality of substantially fan-shaped flat plate members divided for each molding station. One or more neck-shaped members 161 (see Figure 4, etc.) for holding the neck portion of the preform 20 (or intermediate molded body 30, resin container 1) are arranged on the transport plate at predetermined angles.

[0023] The transport mechanism 16 includes a rotating mechanism (not shown) that intermittently rotates the transport plate, for example, counterclockwise when viewed from above. This allows the transport mechanism 16 to transport the preform 20 (or intermediate molded body 30, resin container 1), whose neck is held by the neck mold 161, to the injection molding section 11, the temperature control section 12, the blow molding section 13, and the removal section 14 in that order. In the transport mechanism 16, the preform 20 is transported to each section with its neck facing upwards and its longitudinal direction aligned vertically in an upright position. The transport mechanism 16 also includes a lifting mechanism (vertical mold opening / closing mechanism) and a mold opening mechanism for the neck mold 161, which perform operations such as raising and lowering the transport plate, and mold closing and mold opening (release) in the injection molding section 11, etc.

[0024] (Injection Molding Section 11) The injection molding section 11 manufactures the preform 20 using an injection molding die. As shown in Figure 2, an injection device 15 is connected to the injection molding section 11 to supply the resin material, which is the raw material for the preform 20.

[0025] The overall shape of the preform 20 is a bottomed cylindrical shape with one end open and the other end closed (see Figure 4). The preform 20 has a neck portion formed at one end with an opening, a cylindrical body portion connected to the neck portion, and a bottom portion connected to the body portion that closes the other end.

[0026] The injection molding unit 11 includes an injection cavity mold, an injection core mold, and a hot runner mold that guides the molten resin supplied from the injection device 15 into the mold space (none of which are shown). The injection cavity mold and the injection core mold are examples of injection molding dies. In the injection molding unit 11, the molten resin injected from the injection device 15 is introduced into the mold space defined by the injection molding die (the space that defines the outer shape of the preform 20), thereby molding the preform 20 having the shape described above.

[0027] (Temperature Control Unit 12) After the injection-molded preform 20 is released from the injection molding die, it is transported to the temperature control unit 12 by the transport mechanism 16. The temperature control unit 12 is equipped with a temperature control mold (not shown) and controls the temperature (heats) of the preform 20, which is in a high-temperature state after injection molding, by placing it in the temperature control mold which is maintained at a predetermined temperature. The temperature control unit 12 also has the function of adjusting the temperature distribution of the preform 20 to a predetermined state before transport to the blow molding unit 13.

[0028] The temperature control mold of the temperature control unit 12 is configured to accommodate the preform 20 inside and includes a temperature control pot (or heating pot) that controls the temperature of the body and bottom of the preform 20 from the outside, and a temperature control rod (or heating rod) that is inserted inside the preform 20 and controls the temperature of the preform 20 from the inside.

[0029] As will be described later, in this embodiment, the temperature control unit 12 adjusts the temperature of the blow-molded portion of the preform 20 at the time it is transported to the blow molding unit 13 (immediately before blow molding or pre-blow) to a temperature significantly higher than the optimal stretching temperature of the crystalline PET material (usually around 100°C) (160°C to 250°C, preferably 170°C to 230°C). Alternatively, the temperature of the blow-molded portion of the preform 20 at the time it is brought into the blow molding unit 13 may be adjusted to 160°C to 200°C. For this reason, the temperature control unit 12 adjusts the temperature of the blow-molded portion of the preform 20 transported from the injection molding unit 11 to a temperature of 170°C or higher (for example, 170°C to 300°C, preferably 170°C to 260°C). The temperature control unit 12 may also adjust the temperature of at least a part of the preform 20 (such as the bottom) to a temperature higher than the melting point of the crystalline PET material. The temperature control unit 12 of this embodiment is configured to prevent the preform 20 from coming into contact with the temperature control pod even if the preform 20 stretches downward (drawdown) due to its own weight. For example, it includes a temperature control pod whose position can be changed vertically to adjust the position of the pod member facing the bottom of the preform 20, and a rod member that sucks the inner surface of the bottom of the preform 20 to suppress drawdown.

[0030] (Blow molding section 13) The blow molding section 13 performs stretch blow molding on a preform 20 that is at a high temperature of 160°C or higher (160°C to 250°C, preferably 170°C to 230°C), which has been temperature-controlled by the temperature control section 12, to manufacture a resin container 1 before the through-hole H is formed. As will be described later, the blow molding section 13 of this embodiment includes a preliminary blow molding section 40 (see Figure 4) that performs preliminary blow molding on the preform 20 to form an intermediate molded body 30, and a final blow molding section 50 (see Figures 5 to 7) that performs final blow molding on the intermediate molded body 30 to form a resin container 1 before the through-hole H is formed. Details of the configuration and operation of each molding section will be described later. In the blow molding section 13 of this embodiment, the preliminary blow molding section 40 and the final blow molding section 50 are configured to be in the same position. However, the blow molding section 13 may be configured such that the preliminary blow molding section 40 and the final blow molding section 50 are located in different positions, and the intermediate molded body 30 is transported from the preliminary blow molding section 40 to the final blow molding section 50. In the above case, for example, the blow molding apparatus disclosed in Japanese Patent No. 6952022 may be used.

[0031] (Removal section 14) The removal section 14 is configured to release the neck portion 3 of the resin container 1 manufactured in the blow molding section 13 from the neck mold 161 and remove the resin container 1 to the outside of the blow molding apparatus 10.

[0032] <Explanation of the method for manufacturing the container> Next, the method for manufacturing the resin container 1 using the blow molding apparatus 10 of this embodiment will be explained. Figure 3 is a flowchart showing the steps for manufacturing the resin container 1.

[0033] (Step S101: Injection Molding Process) First, in the injection molding section, molten resin is injected from the injection device 15 into the mold space, which is shaped like a preform and formed by the injection cavity mold, the injection core mold, and the neck mold 161 of the transport mechanism 16, to form a preform 20. Then, after the injection (filling and holding pressure) of the resin material is completed, or after a minimum cooling time has elapsed after the completion of injection, the mold of the injection molding section 11 is opened.

[0034] While not particularly limited, from the viewpoint of manufacturing containers in a high-speed molding cycle, it is preferable to perform mold opening in step S101 without allowing a cooling time for the preform 20 in the injection molding die after the completion of resin material injection (filling and holding pressure). On the other hand, if minimal cooling of the preform 20 is performed in the injection molding die, it is preferable that the time for cooling the resin material after the completion of resin material injection in the injection molding section 11 (cooling time) is 1 / 2 or less of the time for injecting the resin material (injection time). This allows the surface layer (skin layer) of the body and bottom of the preform 20 to solidify, and the preform 20 can be released from the injection molding die without deformation. In addition, the internal layer (core layer) sandwiched between the surface layers of the body and bottom of the preform 20 retains a high amount of heat, which can shorten the heating time of the preform 20 in the temperature adjustment process.

[0035] Once the injection molding of the preform 20 is complete, the mold in the injection molding section 11 is opened, and the preform 20 is released from the injection cavity mold and the injection core mold. Next, the transfer plate of the transport mechanism 16 moves to rotate by a predetermined angle, and the preform 20, held in the neck mold 161, is transported to the temperature control section 12 while still retaining the heat from the injection molding process.

[0036] (Step S102: Temperature adjustment step) Next, in the temperature adjustment section 12, the preform 20 is placed in a temperature adjustment mold, and the temperature of the preform 20 is adjusted to bring it closer to a temperature suitable for stretch blowing in the blow molding process. In this embodiment, immediately before the blow molding process or immediately before the pre-blow process, the temperature is adjusted so that the surface temperature of at least the body and bottom of the preform 20, which is formed using crystalline PET, is 160°C or higher. Preferably, immediately before the blow molding process or immediately before the pre-blow process, the surface temperature of the blown portion (body and bottom) of the preform 20 is adjusted to a temperature between 160°C and 250°C, preferably between 170°C and 230°C (10°C to 90°C, preferably 20°C to 80°C lower than the melting point of crystalline PET). Therefore, in the temperature adjustment step, for example, the temperature of the blow-molded portion of the preform 20 transported from the injection molding section 11 is adjusted to a temperature of 170°C or higher (for example, 170°C to 300°C, preferably 170°C to 260°C). In the temperature adjustment step, at least a portion of the preform 20 (such as the bottom) may be heated to a temperature higher than the melting point of the crystalline PET material.

[0037] In this way, the preform 20 is adjusted to a temperature significantly higher than the normal optimal temperature for stretching crystalline PET. This allows the resin film portions (flat portions P) that are pressed against each other to be well welded together when the resin film portion corresponding to the gripping portion 7 of the intermediate molded body 30 is pressed with the projection portion 53 during the subsequent blow molding process (blow mold closing process S104 to final blow molding process S105). As a result, when the flat portions P are later removed from the resin container 1 to form a through hole H, the periphery of the through hole H can be given sufficient strength, thereby improving resistance to cracking when dropped.

[0038] After the temperature adjustment process, the transfer plate of the transport mechanism 16 moves to rotate by a predetermined angle, and the temperature-adjusted preform 20 held in the neck mold 161 is transported to the blow molding section 13.

[0039] (Blow molding process) Next, the resin container 1 is blow molded in the blow molding section 13. The blow molding process in the present invention is configured to include a preliminary blow molding process in step S103, a blow mold closing process in step S104, a final blow molding process in step S105, a cooling blow process in step S106, and a blow mold opening process in step S107.

[0040] (Step S103: Pre-blow molding process) The pre-blow molding process is a process in which the pre-blow molded body 30 is manufactured by pre-blowing the preform 20, which has been transported to the blow molding section 13 at a temperature adjusted to 160°C or higher. Figure 4 is a schematic diagram showing an example of the configuration of the pre-blow molding section 40. In the figure, the shape of the preform 20 is shown by a dashed line. The pre-blow molding section 40 is equipped with a pre-blow core mold 41 and a stretching rod 42. The pre-blow core mold 41 is inserted into the neck of the preform 20 and is configured to introduce pre-blow air into the preform 20. The stretching rod 42 is inserted through the pre-blow core mold 41 so as to be movable in the vertical direction. When the pre-blow molding section 40 and the final blow molding section 50 are in the same position, the pre-blow core mold 41 is the same as the final blow core mold 54 described later, and the stretching rod 42 is the same as the stretching rod 55 described later.

[0041] In the pre-blow molding process, a stretching rod 42 is inserted into the preform 20, which is held by the neck mold 161 and the pre-blow core mold 41. The tip of the stretching rod 42 is brought into contact with the bottom of the preform 20, and the stretching rod 42 is further displaced downward, thereby stretching the preform 20 in the vertical axis direction (Y direction). As a result, the height (length in the Y direction) of the preform 20 and the intermediate molded body 30 becomes equal to the height of the final molded product, the resin container 1.

[0042] After or in parallel with the stretching in the longitudinal direction by the stretching rod 42, pressurized gas, called blow air (preliminary blow air), is introduced into the preform 20 from the preliminary blow core mold 41, and the preform 20 is stretched radially. This yields an intermediate molded body 30.

[0043] The intermediate molded body 30 is conveyed to the final blow molding section 50 by the conveying mechanism 16 while being held by the neck mold 161. In this embodiment, as described above, since the preliminary blow molding section 40 and the final blow molding section 50 are configured to be in the same position, this conveying process becomes unnecessary.

[0044] In the blow mold closing process described later, the intermediate molded body 30 is molded to a size such that the gripping portion 7 can be formed by sandwiching a part of the body portion of the intermediate molded body with the protrusion 53 of the blow cavity mold 51. That is, the intermediate molded body 30 is molded to be larger than the preform 20 and to be equal to or slightly smaller than the resin container 1. For example, the intermediate molded body 30 is molded such that the body diameter is 70% to 90% of the body diameter of the resin container 1 and the length is 80% to 100% of the length of the resin container 1. In this embodiment, since the temperature of the preform conveyed to the preliminary blow molding section 40 is adjusted to a high temperature of 160°C or higher, the preform 20 can be stretched in the radial direction stably and well. Therefore, the moldability of the gripping portion 7 and the flat plate portion P in the subsequent process can be improved.

[0045] The pressure of the preliminary blow air supplied to the preform 20 in the preliminary blow molding process is set lower than the pressure of the blow air in the final blow molding process described later in order to prevent the preform 20 from bursting. Also, the flow rate of the preliminary blow air is set to a relatively low speed. For example, the flow rate (or flow rate) of the preliminary blow air may be set to a flow rate that causes the volume of the intermediate molded body 30 to expand by 10% to 50%, preferably 20% to 40% per second. Alternatively, the flow rate (or flow rate) of the preliminary blow air may be set to a flow rate that causes the volume of the resin container 1 to expand by 10% to 40%, preferably 15% to 35% per second. Also, the pressure of the preliminary blow air can be set to 0.05 MPa to 0.30 MPa, preferably 0.10 MPa to 0.20 MPa.

[0046] (Step S104: Blow mold closing process (planned cut-off part forming process)) Subsequently, in the final blow molding part 50, with the intermediate molded body 30 accommodated therein, the blow molding die is closed. As will be described later, this blow mold closing process is also a planned cut-off part forming process for forming a planned cut-off part on the intermediate molded body 30 that will later be cut off to form the through hole H. Further, the final blow molding part 50 is also a planned cut-off part forming part.

[0047] The blow molding die includes, for example, a blow cavity die 51 and a blow bottom die 52 as shown in FIG. 5. The blow cavity die 51, together with the neck die 161 and the blow bottom die 52, forms a blow molding space that defines the outer shape of the resin container 1. Further, the final blow molding part 50 includes a final blow core die 54 and an extension rod 55. The final blow core die 54 is configured to introduce final blow air into the intermediate molded body 30 while being inserted into the neck portion of the intermediate molded body 30. Further, the extension rod 55 is inserted into the final blow core die 54 so as to be movable in the vertical direction. Note that the final blow core die 54 and the extension rod 55 may be the same as the preliminary blow core die 41 and the extension rod 42 of the preliminary blow molding part 40.

[0048] As will be described later, the blow cavity die 51 and the blow bottom die 52 are set to a temperature significantly lower than that of the preform 20 and the intermediate molded body 30 so that the manufactured resin container 1 can be rapidly cooled. For example, a refrigerant flow path can be provided inside the blow cavity die 51 and the blow bottom die 52, and the refrigerant such as chiller water can be configured to circulate through this refrigerant flow path. For example, the temperature of the blow cavity die 51 and the blow bottom die 52 is set to 5°C to 20°C.

[0049] The blow cavity mold 51 is a pair of split molds configured to open towards the front and back of the paper in the Z direction of Figure 5. Each split mold of the blow cavity mold 51 has a projection (nesting mold member) 53 that protrudes in the Z direction and has a flat surface at its tip. Each projection 53 is formed to protrude inward from the blow cavity mold 51, and when the blow cavity mold 51 is closed, the flat surfaces of the projections face each other with a small gap in between.

[0050] Figure 6 illustrates the flat plate portion P formed in the intermediate molded body 30 when the blow molding die (blow cavity mold 51) is closed. When the blow cavity mold 51 is closed, the protrusions 53 formed on each split mold move closer to each other. The flat tip of each protrusion 53 comes into contact with the resin film on the body of the intermediate molded body 30 housed inside, pressing and deforming the contact area. This forms a flat plate portion P made of resin film sandwiched between the flat portions of each protrusion 53. The flat plate portion P is a portion to be cut later to form a through hole H.

[0051] The formation of the flat plate portion P creates a portion in the intermediate molded body 30 that will later become the gripping portion 7. In this invention, the preform 20, which has been adjusted to 160°C or higher, is molded into the intermediate molded body 30, and the flat plate portion P is formed on the intermediate molded body 30 while it is still at a high temperature, thereby improving the weldability of the resin film in the flat plate portion P. With the flat plate portion P formed by closing the blow molding die in this manner, the process proceeds to the next final blow molding step.

[0052] (Step S105: Final blow molding process) In the final blow molding process, pressurized blow air (final blow air), which is a gas, is supplied from the final blow core mold 54 to the intermediate molded body 30 on which the flat plate portion P has been formed. This stretches each part and shapes it into the form of the resin container 1 (see Figure 7). The pressure of the final blow air supplied to the intermediate molded body 30 in the final blow molding process is set higher than the pressure of the preliminary blow air. Furthermore, in order to successfully mold the resin container 1, which has a relatively complex three-dimensional shape due to the presence of the gripping portion 7, the final blow molding process may have multiple stretching processes. For example, the final blow molding process may consist of a primary blowing process in which stretching blow is performed at a lower pressure and a secondary blowing process in which stretching blow is performed at a higher pressure. For example, the pressure of the blow air in the primary blowing process may be set to 0.3 MPa to 0.5 MPa, and the pressure of the blow air in the secondary blowing process may be set to 1.5 MPa to 3.5 MPa.

[0053] In the final blow molding process, the final blow air is introduced into the intermediate molded body 30 from the final blow core mold 54, and the intermediate molded body 30 is shaped into the final molded product, the resin container 1. At this stage, the flat plate portion P, which is to be cut off, has not been removed, so the through hole H has not been formed yet. However, the shapes of the body portion 5 and the grip portion 7 surrounding the through hole H are completely formed.

[0054] (Step S106: Cooling blow process) After the intermediate molded body 30 is shaped into the resin container 1 in the final blow molding process, a cooling blow process is performed to rapidly lower the temperature of the resin container 1. As described above, the resin container 1 is molded using a preform 20 adjusted to a high temperature of 160°C or higher, while maintaining the high temperature. Due to its shape, the gripping portion 7 and bottom portion 6 of the resin container 1 tend to be formed with relatively thick walls, so the resin container 1 is molded with high heat retention in the gripping portion 7 and bottom portion 6. Here, if the molded resin container 1 remains at the crystallization promotion temperature of crystalline PET (120 to 140°C) for a long time, crystallization of the crystalline PET will progress, and the transparency of the container will be impaired due to whitening. In order to suppress this whitening caused by slow cooling, the resin container 1 is rapidly cooled by the cooling blow process.

[0055] In the cooling blow process, the pressure inside the blow molding die, which had been maintained at a high pressure by the final blow air, is released, and the final blow air is exhausted. In conjunction with this exhaust process, atmospheric pressure cooling air is introduced into the resin container 1 from air holes (not shown) provided in the final blow core mold 54 or the stretching rod 55 and circulated to cool the resin container 1. As described above, the blow cavity mold 51 and the blow bottom mold 52 are configured to maintain a low temperature of, for example, 5°C to 20°C. Therefore, the resin container 1 is cooled from the outside by contact with the blow cavity mold 51 and the blow bottom mold 52, and at the same time cooled from the inside by the circulation of cooling air. In this way, the resin container 1 can be cooled in a short time, whitening of the container can be suppressed, and high transparency can be achieved.

[0056] (Step S107: Blow mold opening process) After the cooling blow process, the blow cavity mold 51 is opened, and the final blow core mold 54 is removed from the neck of the resin container 1. This makes the resin container 1 movable from the blow molding section 13.

[0057] (Step S108: Container Removal Process) The resin container 1, released from the blow molding die, is carried to the removal section 14 by the transport mechanism 16 while still held in the neck mold 161. In the removal section 14, the neck portion 2 of the resin container 1 is released from the neck mold 161, and the resin container 1 is removed to the outside of the blow molding apparatus 10. The neck mold from which the resin container 1 has been released is then transported again to the injection molding section 11 by the transport mechanism 16 and used in a new manufacturing cycle.

[0058] Furthermore, the flat plate portion P of the resin container 1 needs to be prevented from falling off the resin container 1 until the resin container 1 is removed from the blow molding apparatus 10 at the removal section 14. After the resin container 1 is removed from the blow molding apparatus 10, the flat plate portion P is cut off from the resin container 1, thereby forming a through hole H.

[0059] As described above, one container manufacturing cycle in the manufacturing method of the resin container 1 is completed. Thereafter, by moving the transfer plate of the transport mechanism 16 by a predetermined angle, each of the steps S101 to S108 described above is repeated. When the blow molding apparatus 10 is in operation, the manufacturing of four sets of containers, each with a time difference between each step, is carried out in parallel. Furthermore, in the configuration in this embodiment, where the preliminary blow molding step and the final blow molding step are performed in the same location, the time for each of the injection molding step, temperature adjustment step, blow molding step, and container removal step is the same length. Similarly, the transport time between each step is also the same length.

[0060] The effects of this embodiment will be described below. According to this embodiment, the resin container 1 made of crystalline resin is provided with a hollow gripping portion 7 that is connected to and communicates with the body portion 5, and a through hole H is formed by the body portion 5 and the gripping portion 7 in a direction intersecting the central axis A of the resin container 1. The manufacturing method of the resin container 1 includes a blow molding process consisting of a pre-blow molding process, a cut-off portion formation process (blow mold closing process), and a final blow molding process. In the pre-blow molding process, pressurized pre-blow air is introduced into a preform 20 adjusted to 160°C or higher and stretched to blow-molde an intermediate molded body 30. In the cut-off portion formation process, the intermediate molded body 30 is housed in a pair of split molds (blow cavity molds 51) that define the outer shape of the resin container 1, each split mold having a projection 53 configured to face the pair of split molds with a gap between them when the molds are closed. Then, by closing the pair of split molds, a portion to be cut out (flat plate portion P), which will later be cut out to become a through hole H, is formed in the intermediate molded body 30. In the final blow molding process, the resin container 1 is blow molded before the through hole H is formed by introducing a final blow air at a higher pressure than the preliminary blow air into the intermediate molded body 30 in which the portion to be cut out has been formed.

[0061] In the manufacturing method of the resin container of this embodiment, a preliminary blow molding process is performed on a preform 20 adjusted to 160°C or higher to form an intermediate molded body 30, which allows for stable and good radial stretching of the preform 20. This improves the moldability of the gripping portion 7 and the flat plate portion P in subsequent processes. Furthermore, since a blow mold closing process, which is a process for forming a portion to be cut, is performed on the intermediate molded body 30 while it is still at a high temperature after the preliminary blow molding process to form the flat plate portion P, which is the portion to be cut, the weldability of the resin film on the flat plate portion P can be improved. Therefore, in the resin container 1 formed through the final blow molding process, sufficient strength can be provided to the periphery of the through hole H.

[0062] Therefore, according to the manufacturing method of the resin container 1 of this embodiment, a resin container 1 with a gripping portion having sufficient strength can be manufactured by injection stretch blow molding using crystalline PET, which is a crystalline resin, as the material, without requiring any additional components.

[0063] Furthermore, in this embodiment, the temperature of the blow cavity mold 51 is set to 5°C to 20°C, and after the final blow molding process, atmospheric pressure cooling air is introduced into the resin container 1 and circulated while the final blow air is exhausted. As a result, the resin container 1 is cooled on its outer surface by contact with the blow cavity mold 51, and its inner surface is cooled by the circulation of the cooling air. Therefore, the resin container 1 can be cooled rapidly after molding, which suppresses whitening (crystallization) of the container and allows it to have high transparency.

[0064] Furthermore, this embodiment includes a temperature adjustment step in which the body and bottom of the preform 20 after injection molding are heated to adjust the temperature of at least the body and bottom to 160°C or higher. Since there is a separate temperature adjustment step after the injection molding process, the temperature of the preform 20 can be reliably and stably adjusted to 160°C or higher.

[0065] In particular, in this embodiment, the temperature of the preform 20 immediately before blow molding (pre-blow molding) is adjusted in the temperature control step to be between 160°C and 250°C, so that the blow molding step can be carried out at a high temperature within the range in which the preform 20 can maintain its shape.

[0066] The present invention is not limited to the embodiments described above, and various improvements and design changes may be made without departing from the spirit of the invention. For example, in the above embodiments, an example was described in which the method for manufacturing a resin container of the present invention is carried out using a four-station type blow molding apparatus 10 equipped with an injection molding section 11, a temperature control section 12, a blow molding section 13, and a removal section 14. However, it is also possible to carry out the method for manufacturing a resin container of the present invention using a three-station type blow molding apparatus that does not have a temperature control section. In this case, for example, the temperature of the preform 20 can be adjusted to 160°C or higher by utilizing the heat generated during injection molding in the injection molding section. Furthermore, the resin container 1 may be manufactured using a cold parison type (two-step type) blow molding apparatus, such as U.S. Patent No. 7,727,454.

[0067] 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.

[0068] 1... Resin container, 5... Body of resin container, 7... Gripping part of resin container, 10... Blow molding machine (manufacturing machine for resin containers), 11... Injection molding section, 12... Temperature control section, 13... Blow molding section, 20... Preform, 30... Intermediate molded body, 40... Pre-blow molding section, 50... Final blow molding section, 51... Blow cavity mold (pair of split molds), 53... Protrusion, H... Through hole, P... Flat plate section (part to be cut off)

Claims

1. A method for manufacturing a resin container made of crystalline resin, wherein the resin container is provided with a hollow gripping portion connected to and communicating with the body of the resin container, and a through hole is formed between the body and the gripping portion in a direction intersecting the central axis of the resin container, the manufacturing method comprising: an injection molding step of manufacturing a bottomed preform by injection molding, and a blow molding step of manufacturing the resin container by blow molding the injection-molded preform, the blow molding step comprising: a pre-blow molding step of blow molding an intermediate molded body by introducing pressurized gas into the preform adjusted to 160°C or higher and stretching it; a cut-off portion formation step of forming a cut-off portion in the intermediate molded body by housing the intermediate molded body in a pair of split molds that define the outer shape of the resin container, each split mold having projections configured to face each other with a gap when the pair of split molds are closed, and closing the pair of split molds to form a cut-off portion in the intermediate molded body that will later be cut out to become the through hole, A method for manufacturing a resin container, comprising: a final blow molding step of blow molding the resin container before the formation of the through hole by introducing a pressurized gas at a higher pressure than the pressurized gas used in the pre-blow molding step into the intermediate molded body on which the portion to be cut is formed.

2. The method for manufacturing a resin container according to claim 1, characterized in that the temperature of the pair of split molds is 5 to 20°C, and the blow molding step further includes a cooling blow step after the final blow molding step, in which the pressurized gas is exhausted and atmospheric pressure gas is circulated to cool the resin container.

3. The method for manufacturing a resin container according to claim 1, further comprising a temperature adjustment step of heating the body and bottom of the injection-molded preform and adjusting the temperature of at least the body and bottom to 160°C or higher.

4. The method for manufacturing a resin container according to claim 3, characterized in that the temperature adjustment step adjusts the temperature of the body and bottom of the preform immediately before the blow molding step to be 160°C or more and 250°C or less.

5. The method for manufacturing a resin container according to claim 1, characterized in that the crystalline resin is crystalline polyethylene terephthalate.

6. A manufacturing apparatus for a resin container made of crystalline resin, wherein the resin container is provided with a hollow gripping portion connected to and communicating with the body of the resin container, and a through hole is formed by the body and the gripping portion in a direction intersecting the central axis of the resin container, the manufacturing apparatus comprises an injection molding section for manufacturing a bottomed preform by injection molding, and a blow molding section for manufacturing the resin container by blow molding the injection-molded preform, the blow molding section comprises a pre-blow molding section for blow molding an intermediate molded body by introducing pressurized gas into the preform adjusted to 160°C or higher and stretching it, and a cut-off section forming section for a pair of split molds that define the outer shape of the resin container, each split mold having projections configured to face each other with a gap when the pair of split molds are closed, and by closing the pair of split molds, a cut-off section to be later cut out of the intermediate molded body, which will become the through hole, A manufacturing apparatus for resin containers, comprising: a final blow molding section that blow-moldes the resin container before the through-hole is formed by introducing a pressurized gas at a higher pressure than the pressurized gas in the pre-blow molding section into the intermediate molded body on which the portion to be cut is formed.

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