Biodegradable resin container manufacturing method and manufacturing device

Abstract

The present invention provides a method for manufacturing a container made of a biodegradable resin in which a preform is easily released from an injection molding mold, and the container does not get torn, etc., during blow molding.　A method for manufacturing a container made of a biodegradable resin, the method having at least an injection molding step for injection-molding a preform (1) made of a biodegradable resin in an injection molding mold, a temperature adjustment step for adjusting the temperature of the preform (1) through use of a temperature adjustment mold, and a blow molding step for blow-molding the temperature-adjusted preform (1) in a blow mold to manufacture a container, wherein the temperature of the injection molding mold is set to 40°C or lower.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a biodegradable resin container in a hot parison type blow molding device, specifically to a method and device for producing a biodegradable resin container in which the preform can be easily released from the injection molding mold and the temperature can be adjusted so that the preform does not tear during blow molding. [Background technology]

[0002] Plastics (synthetic resins) are used in large quantities in many fields, such as for resin containers, and their waste is causing serious environmental problems, such as smearing the landscape, adversely affecting marine life, and polluting the global environment, making countermeasures urgently needed. Proposed countermeasures include (1) reducing the amount of non-biodegradable resins (non-biodegradable plastics: polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, etc.) used and discarded, reusing products made from such materials, and promoting the recycling of such discarded materials, or (2) expanding the use of biodegradable resins. Regarding (2) above, expanding the use of biodegradable resins, in the field of resin container manufacturing, one possible solution is to switch from conventional non-biodegradable resins to biodegradable resins. (See, for example, Patent Document 1.) Incidentally, a known conventional hot parison blow molding apparatus for manufacturing containers from non-biodegradable resins (hereinafter simply referred to as normal resins) is a blow molding apparatus equipped with an injection molding section for injection molding preforms, a temperature adjustment section for adjusting the temperature of the preforms molded in the injection molding section, and a blow molding section for blow molding the temperature-adjusted preforms (see, for example, Patent Document 2). The reason for providing the temperature adjustment section is that preforms just molded in the injection molding section do not have a temperature distribution suitable for blow molding, so this temperature adjustment section is used to adjust the temperature of the preforms to a temperature suitable for blow molding.

[0003] In addition, as a temperature adjustment unit for more appropriately and quickly adjusting the temperature to a temperature suitable for blow molding, a blow molding device has been proposed in which the preform is adjusted to have an appropriate temperature distribution between an insertion core (temperature control core or heating core) and a pot member (temperature control pot mold or heating pot mold) before blow molding (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5439692 [Patent Document 2] Japanese Patent Application Publication No. 06-315973 [Patent Document 2] International Publication No. 2013 / 012067 Summary of the Invention [Problem to be solved by the invention]

[0005] However, attempts to produce biodegradable resin containers using conventional blow molding equipment have encountered the following problems. Biodegradable resins generally have poor moldability compared to conventional resins. For this reason, few technologies have been established that enable successful production of medium- to large-sized (500 ml or larger) containers made entirely from biodegradable resins using stretch blow molding (particularly injection stretch blow molding: hot parison blow molding). Furthermore, the cost of biodegradable resins is several times higher than that of resin materials typically used in blow molding (typical resin materials: polyethylene, polypropylene, polyethylene terephthalate, etc.). Therefore, if stable production is not possible, unnecessary material costs can increase, potentially making the process unprofitable. Generally, when molding a container using hot parison blow molding, the preform must be released from the injection mold while retaining the heat required for blow molding (the amount of heat required to blow mold (shape) the preform into a predetermined container shape with the required specifications) in its inner layer (core layer). Furthermore, for preforms molded from certain biodegradable resins, the temperature range with the heat capacity suitable for blow molding is near the melting point of the biodegradable resin, so they must be released from the injection mold at a temperature close to that range. This requires setting the temperature of the injection mold high and releasing the preform at a higher temperature than for standard resins. As a result, the preform cannot be sufficiently cooled during the injection molding process and remains hot. This results in the preform's inner and outer skin layers (surface layers) not fully solidifying, causing them to stick to the injection mold, preventing proper release and resulting in curling deformation. Conversely, if the preform is molded in an injection mold set to a low temperature similar to that used for standard resins (e.g., polyethylene terephthalate), the preform will not retain the heat capacity required for blow molding. Furthermore, in the temperature control process of the hot parison blow molding method, the temperature of the inner and outer skin layers and inner layers of the preform are controlled (cooled) to eliminate temperature variations and achieve the optimal temperature distribution for blow molding.However, it was discovered that if a biodegradable resin preform is adjusted to the same temperature as that for ordinary resin materials, the inner and outer skin layers of the preform will be cooled more than necessary and solidify, and when this preform is blow molded and stretched in the blow molding process, cracks will appear in the preform, or the preform will tear when stretched by the stretching rod before the introduction of blow air, making it impossible to mold a container.

[0006] The present invention aims to provide a method and an apparatus for manufacturing a biodegradable resin container in a hot parison type blow molding apparatus, which allows the preform to be reliably and easily released from the injection molding mold and can adjust the temperature so that the preform does not tear during blow molding. [Means for solving the problem]

[0007] The method for producing a biodegradable resin container of the present invention includes at least an injection molding step of injection-molding a biodegradable resin preform (1) using an injection mold, a temperature control step of controlling the temperature of the preform (1) using a temperature control mold, and a blow molding step of blow-molding the temperature-controlled preform (1) using a blow mold to produce a container, in which the temperature of the injection mold is set to 40°C or less. Preferably, the temperature of the injection mold is set to 15°C to 20°C. Preferably, in the temperature adjusting step, the temperature of the inner and outer skin layers of the preform is heated to a temperature at or near the melting point of the biodegradable resin. Preferably, the heating temperature is 100°C to 180°C. Preferably, in the temperature adjusting step, the temperature of the inner and outer skin layers of the preform is heated to a temperature equal to or higher than the melting point of the biodegradable resin. More preferably, the temperature in the injection molding step is 15°C to 20°C. More preferably, the heating temperature is 100°C to 230°C. More preferably, the biodegradable resin is a synthetic resin containing polybutylene succinate as a component. More preferably, in the injection molding step, the inner and outer skin layers of the preform are solidified until they become opaque, and in the temperature adjustment step, the inner and outer skin layers of the preform are heated until they become transparent. More preferably, the temperature adjustment process comprises an internal heating process for heating at least the body portion of the preform from the inside, and an external heating process for heating at least the body portion of the preform from the outside, and the processing time of the external heating process is longer than the processing time of the internal heating process. Still another apparatus for manufacturing a biodegradable resin container according to the present invention is an apparatus to which any of the above-mentioned manufacturing methods is applied. [Effects of the Invention]

[0008] According to the method and apparatus for producing a biodegradable resin container of the present invention, by setting the temperature of the injection mold to 40°C or less, preferably 15 to 20°C, the preform made of a biodegradable resin material can be easily released from the injection mold and curling deformation can be suppressed. Moreover, by heating the temperature of the inner and outer skin layers of the preform in the temperature control step to the same melting temperature as the inner layer of the preform or a temperature close to that temperature, it is possible to prevent the preform from cracking or tearing in the subsequent blow molding step. Note that in this specification, with reference to Figure 2, for example, the inner circumferential surface 2a and its vicinity of the hollow body 2 of the preform 1 will be referred to as the inner skin layer, the outer circumferential surface 2b and its vicinity will be referred to as the outer skin layer, and the intermediate portion sandwiched between the inner and outer skin layers will be referred to as the inner layer (or core layer). [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a blow molding device to which one embodiment of the method for producing a biodegradable resin container of the present invention is applied. [Figure 2] FIG. 2 is a perspective view of an example of a preform being injection molded in an injection molding process of the apparatus. [Figure 3] 1 shows a cross-sectional view of the injection molding section of the device. [Figure 4]4(A) and 4(B) are a longitudinal sectional view and a transverse sectional view, respectively, of the core pin portion of the injection molding part of FIG. [Figure 5] FIG. 2 is a longitudinal sectional view of a temperature adjusting section of the device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a blow molding apparatus to which one embodiment of the method for manufacturing a biodegradable resin container of the present invention is applied, and FIG. 2 is a perspective view of an example of a preform being injection molded in the injection molding process of the above apparatus.

[0011] As shown in FIG. 1, the blow molding apparatus 70 includes an injection molding section 10 that performs the injection molding process of the preform 1, a temperature adjustment section 20 that performs the temperature adjustment process (temperature control process) of the preform 1, a blow molding section 30 that performs the blow molding process of manufacturing a container 111 from the preform 1, and an extraction section 40 that performs the extraction process of transporting the container out of the machine.

[0012] The injection molding section 10, the temperature adjustment section 20, the blow molding section 30, and the removal section 40 are arranged in an array that forms the four sides of a square when viewed from above. Above these, a turntable 60 (not shown) is provided with neck dies 50 (see FIG. 3) that hold the neck sections 3 (see FIG. 2) of the preforms 1 molded in the injection molding section 10. This turntable 60 has four sets of neck dies 50 arranged in an array that forms the four sides of a square when viewed from above. As a result, the turntable rotates counterclockwise by 90 degrees around a vertical axis above the injection molding section 10, the temperature adjustment section 20, the blow molding section 30, and the removal section 40, so that each process is performed on the preforms 1 held in the neck dies 50.

[0013] The injection molding section 10 includes an injection core mold 11, an injection cavity mold 12, and an injection device (not shown), and is provided to injection mold the preform 1. As shown in FIG. 2, the preform 1 has an open neck portion 3, a hollow body portion 2, and a closed bottom portion 4, and is formed in the shape of a bottomed test tube. The average thickness of the body portion 2 is preferably set to be at least twice the average thickness of the neck portion 3 (formed thick). The average thickness of the bottom portion 4 is preferably set to be not more than half (more preferably one-third) the average thickness of the body portion 2 (formed thin). For example, the average thickness of the body portion 3 may be set to be 2.0 mm to 7.0 mm (preferably 2.5 mm to 5.0 mm), and the average thickness of the bottom portion 4 may be set to be 0.5 mm to 2.5 mm (preferably 0.8 mm to 1.5 mm). The preform 1 is blow molded to become a finished container 111 (see FIG. 1). As mentioned above, in the following, the inner surface 2a of the hollow body 2 of the preform 1 and its surrounding area will be referred to as the inner skin layer (or surface layer), the outer surface 2b and its surrounding area will be referred to as the outer skin layer, and the intermediate area sandwiched between the inner and outer skin layers will be referred to as the inner layer (or core layer).

[0014] Next, FIG. 3 shows an injection-molded part 10 used in the manufacturing method of the biodegradable resin container of the present invention. Examples of biodegradable resin materials include biodegradable plastics containing polybutylene succinate (PBS), polyhydroxyalkanoate (PHA, e.g., polyhydroxybutyrate), polylactic acid (PLA), and the like. BioPBS (e.g., BiOPBS® manufactured by Mitsubishi Chemical Corporation) contains polybutylene succinate (PBS) and is naturally decomposed into water and carbon dioxide by microorganisms in soil. It also has high heat resistance compared to other common biodegradable resins and is highly compatible with fibers and other materials. Of course, various other biodegradable resin materials may be used in addition to the above materials. The mold structure of the injection molding section 10 includes an injection core mold 100 and an injection cavity mold body 112 and a lip mold 115 of the injection cavity mold 12 .

[0015] In the figure, lip mold 115 has a pair of split molds 115a and 115b that can be opened in the left-right direction in the figure, and has a cavity surface 115c that defines the outer wall of lip portion 3 of preform 2. Also, injection cavity mold body 112 has cavity surface 112a that defines outer peripheral surface 2b (see FIG. 2) of body portion 2 of preform 1, molten resin filling gate 112b at the lower end, and internal cooling passage 112c. As a result, the biodegradable resin injected into the space formed by the outer surface 101a of the core pin 101 of the injection core mold 100, the cavity surface 112a of the cavity mold 112, and the cavity surface 115c of the lip mold in a molten state (at or above its melting point (melting temperature), for example, 115°C or above (e.g., approximately 115°C to 180°C) in the case of BioPBS, and 100°C or above (e.g., 100 to 230°C) in the case of other biodegradable resin materials) cools the inner and outer skin layers of the body 2 and bottom 4 to the desired temperature described below by the cooling mechanism of the injection core mold 100 and the injection cavity mold 12 (or the injection cavity mold main body 112), and the preform 1 is molded.

[0016] The mold structure of the injection molding section 10 described above is itself known, but in the present invention, as will be described later, the temperature of each of the injection molding molds 100, 112, and 115 is kept at 40°C or below, which is lower than the usual set temperature when articles made of biodegradable resin (cup-shaped or bottle-shaped containers) are extrusion blow molded, injection molded, or injection blow molded.

[0017] 4(A) and (B) show an example of a cooling structure on the injection core mold 100 side. In the figure, a hollow portion 102 is formed in the axial direction inside the core pin 101 of the injection core mold 100, and a cooling pipe 110 having an outer diameter smaller than the inner diameter of the hollow portion 102 is inserted. Thus, an inner water passage 110a is formed inside the cooling pipe 110, and an outer water passage 110b is formed outside the pipe. By flowing cold water from the inner water passage 110a to the outer water passage 110b in the direction of the arrow in the figure, the core pin 101 is cooled to 40°C or less, preferably 15 to 20°C, as described above. Also on the injection cavity mold main body 112 side, cold water is flowed through a cooling passage 112c, and the core pin 101 is cooled to 40°C or less, preferably 15 to 20°C.

[0018] In the conventional injection-molded section 10, when a typical resin material other than biodegradable resin, such as polyethylene terephthalate, is used, the temperature of the injection mold is set to a low temperature of approximately 10°C. Therefore, the inner and outer skin layers in the thickness direction of the body section 2 of the preform at the end of the injection molding process can be sufficiently cooled and solidified, and the inner layer of the body section 2 can be set to a temperature below a predetermined melting temperature (e.g., 270°C) and above or near the optimum blowing temperature (e.g., 140°C). This ensures the required heat for blow molding while allowing the preform to be easily released from the injection mold. Furthermore, since the preform temperature suitable for blow molding with this resin is approximately 100 to 120°C, the temperature is slightly lowered (the amount of heat is reduced) during the temperature control process while performing the necessary steps to eliminate temperature variations and maintain a uniform temperature.

[0019] However, various experiments have shown that the properties of biodegradable resin materials are significantly different from those of such ordinary resin materials, and that in order to ensure that the preform 1 has the amount of heat required for blow molding, it is necessary to release the preform 1 from the injection molding mold under conditions where the inner layer is at or above the melting point of the biodegradable resin (melting temperature), and the inner and outer skin layers are at or near the melting point of the biodegradable resin material (e.g., 100°C to 180°C, preferably 110°C to 180°C, more preferably 110°C to 140°C), or at or above the melting point (e.g., 100°C to 230°C, preferably 110°C to 230°C, more preferably 110°C to 180°C) in order to melt the surfaces of the inner and outer skin layers and reduce their thickness, taking into account the ease of the subsequent blow molding process. Here, "near the melting point" refers to a temperature below the melting point, for example, a temperature within -15°C of the melting point (preferably within -10°C of the melting point, and more preferably within -7°C of the melting point). Therefore, to summarize, in this specification, the inner layer is heated to a temperature at or above the melting point (melting temperature), and the inner and outer skin layers are heated to a temperature at or near the melting point (e.g., 100°C to 180°C), and in some cases, the inner and outer skin layers are heated to a temperature at or above the melting point (e.g., 100°C to 230°C). Therefore, when the temperature of the injection molding mold was set to a high temperature of about 70°C to mold preform 1, it was confirmed that body portion 2 tended to stick adhesively to the mold (specifically, injection core mold 11 and injection cavity mold 12), making it difficult to release from the mold. For example, when the injection core mold 11 was raised to release the preform 1 from the injection core mold 11, the adhesion between the body portion 2 and the injection core mold 11 was not released, resulting in frequent curling deformation (carrying-up deformation) of the body portion 2 (on the other hand, the neck portion 3 was thinner than the body portion 2 and was therefore more susceptible to the cooling effect from the mold, and solidified even under these conditions).

[0020] However, in the method for producing a biodegradable resin container of the present invention, based on the above experimental results, both the injection core mold 100 and the injection cavity mold body 112 are cooled (set to a low temperature) with temperature-controlled cold water (chiller water) to 40°C or less, preferably 15 to 20°C. Therefore, the biodegradable resin preform 1 in a molten state filled in the space formed by each mold 100, 112, and 115 is rapidly cooled by heat conduction with the molds 100 and 112 from a molten temperature of, for example, about 110 to 180°C to, for example, about 50 to 90°C (more preferably 80 to 90°C), causing the thickness of the inner and outer skin layers of the body 2 to temporarily increase. This confirmed that the preform 1 (more specifically, the body portion 2) was successfully released from the mold of the injection molding section 10, i.e., the injection core mold 100 and the injection cavity mold body 112, without adhesively sticking, and that curling deformation was also suppressed. It is preferable to cool and solidify the preform 1 during the injection molding process until the inner and outer skin layers of the body portion 2 become white (opaque). Furthermore, the average thickness of the bottom portion 4 of the preform 1 may be set to half or less the average thickness of the body portion 2 (to form a thin wall) to enhance the cooling effect of the bottom portion 4 (particularly the central portion of the bottom portion 4 near the molten resin filling gate 112b), and the inner and outer skin layers of the bottom portion 4 may be solidified so that they are thicker than the inner and outer skin layers of the body portion 2. In this case, it is preferable to cool and solidify the inner and outer skin layers of the bottom portion 4 until they also become white.

[0021] Next, the preform 1, which has been injection molded and cooled in the injection molding section 10 and solidified to a certain extent, is lifted upward together with the turntable 60 while still held by the neck mold 50, and is pulled out from the injection cavity mold body 112. As shown in Figure 1, the turntable rotates 90 degrees counterclockwise, and the preform is transported to the temperature adjustment section 20.

[0022] The temperature adjustment unit 20 is disposed adjacent to the injection molding unit 10, and as shown in FIG. 5, includes an upper heating rod mold 221 and a lower heating pot mold 226. The heating rod mold 221 is inserted into the body portion 2 (hollow portion) of the preform 1 and performs a process of heating at least the body portion 2 of the preform 1 from the inside (internal heating process), while the heating pot mold 226 houses the preform 1 and performs a process of heating at least the body portion 2 of the preform 1 from the outside (external heating process). Note that, if necessary, the inner and outer peripheral surfaces of the bottom portion 4 may be heated in the internal heating process and external heating process (for example, when the inner and outer skin layers of the bottom portion 4 have solidified excessively in the injection molding process, or when it is desired to heat the inner and outer surfaces of the bottom portion 4 that do not substantially come into contact with the stretch rod in consideration of formability, etc.). The heating rod mold 221 includes a rod-shaped first heater 222 located in the center (actually, only the lower half portion in the drawing, facing the heating pot mold 226, is the heater portion), a sleeve 223 into which the first heater 222 is fitted and fixed, and a heating core sleeve 224 fitted into the sleeve 223. The heating rod mold 221 is housed in a core housing 225 and fixed by a locking member (set screw) 234. The heating rod mold 221 is driven to move up and down via the core housing 225. The heating pot mold 226 includes, for example, three pot molds 226a, 226b, and 226c, each having a ring-shaped cross section, stacked with a heat insulating material 227 interposed therebetween, housed in a housing 228, and fastened by a fixing member (such as a bolt) 231 between upper and lower fixing plates 229 and 230. The heating pot mold 226 has a cavity 226d and includes a band-shaped second heater 232 provided around its outer periphery. Reference numeral 233 denotes a second heater fixing member that fastens the second heater 232. The heating pot mold 226 is driven to move up and down via a fixing plate 230.

[0023] Next, the operation of the temperature adjustment unit 20, which handles preforms 1 molded from biodegradable resin material, will be described. As shown in FIG. 5, the preform 1 is transported from the injection molding unit 10 to the temperature adjustment unit 20 and is stationary with its neck portion 3 held by the neck mold 50. The heating pot mold 226 rises to accommodate the preform 1 in the cavity 226d, and the heating rod mold 221 descends to insert the preform 1 into the preform 1. At this time, the neck mold 50 is centered relative to the centering ring 260 attached to the heating pot mold 226. Appropriately sized gaps are formed between the inner circumferential surface 2a (see FIG. 2) of the preform 1 and the outer circumferential surface of the heating core sleeve 25, and between the outer circumferential surface 2b (see FIG. 2) of the preform 1 and the inner circumferential surface of the cavity 26d of the heating pot mold 26. If the preform 1 transferred from the injection molding section 10 were made of a conventional ordinary resin material, the temperature would generally be adjusted in this temperature control step so that the inner and outer skin layers of the body portion 2 of the preform were cooled or maintained at a predetermined temperature. However, various experiments have confirmed that even if the inner and outer skin layers of the body portion 2 of the preform 1 molded from a biodegradable resin are treated in the temperature control step in the same way as for ordinary resins, the cooled and solidified state is not resolved, and the preform is torn off when stretched by a stretch rod in the subsequent blow molding step, making it impossible to mold it into a container.

[0024] Therefore, in the present invention, the biodegradable resin preform 1 transferred to the temperature adjustment unit 20 has a heating rod mold 221 disposed inside the preform 1 and a heating pot mold 226 disposed outside the preform 1, as shown in FIG. 5. At this point, the inner layer in the thickness direction of the body portion 2 of the biodegradable resin preform 1 remains molten and is at a temperature above the melting point (melting temperature), but the inner and outer skin layers in the thickness direction of the body portion 2 have been cooled by the low-temperature molds 11 and 112 of the injection molding unit 10 in the previous process, as described above, to, for example, about 50 to 90°C (more preferably, 80 to 90°C), and are white (opaque). If the biodegradable resin preform 1 with the low-temperature inner and outer skin layers is sent directly to the blow molding process, there is a risk of the preform 1 being torn off, as described above. However, in the present invention, the first heater 222 and second heater 232 in the temperature adjustment process are electrically heated to a high temperature, for example, about 245°C. Therefore, the heat from heaters 222 and 223 is transferred to preform 1 in a short time via heater sleeve 223 and heating pot mold 226, radiating heat through the gap to the inner and outer skin layers of body 2 of preform 1. As a result, the temperature of the inner and outer skin layers of body 2 of preform 1 is heated from the above-mentioned 50 to 90°C (more preferably 80 to 90°C) to a temperature close to the molten inner layer, specifically, to the melting point or a temperature near the melting point of the biodegradable resin material (for example, 110 to 140°C), or to a temperature at or above the melting point (for example, 110 to 180°C). This changes the body 2 of the preform 1 from white (opaque) to a transparent state (a state with higher transparency than at the time of demolding in the injection molding process; the increased transparency may be yellowish), and the temperature of the inner and outer skin layers is raised to reduce the thickness of the inner and outer skin layers formed in the injection molding process, eliminating the highly solidified state (hardened state) and softening it. At the same time, the inner and outer skin layers, in addition to the inner layer, are set to a temperature at or near the melting point of the biodegradable resin material, which is the optimum temperature for blowing, or a temperature at or above the melting point (brought to a high temperature state just before drawdown).

[0025] Next, this preform 1 is transferred by the neck mold 50 to the blow molding section 30 and placed in a blow mold 31 consisting of a pair of split molds, after which it is blow-molded using a stretch rod and compressed air at a predetermined pressure (e.g., 0.3 MPa to 2.0 MPa). At this time, the inner layer of the body 2 and the inner and outer skin layers of the preform 1 are both in a substantially molten state, so even though the preform 1 is made of a biodegradable resin, the preform 1 is successfully blow-stretch molded without cracking or tearing when stretched by the stretch rod, and a biodegradable resin container can be successfully manufactured. Furthermore, if the average thickness of the bottom 4 of the preform 1 is set to less than half the average thickness of the body 2 and the bottom 4 is sufficiently solidified in the injection molding process, it is possible to reliably prevent the stretch rod from breaking through (perforating) the bottom 4 when the preform 1 is stretched. Furthermore, before the stretch rod comes into contact with the preform 1, low-pressure (e.g., 0.3 MPa to 0.5 MPa) primary air may be introduced into the preform 1 at a slow flow rate (e.g., 200 L / min (ANR) or less) to slowly and slightly inflate the preform 1, and then the preform 1 may be stretched by the stretch rod and high-pressure secondary air (e.g., 0.6 MPa to 3.5 MPa) introduced to blow-mold the preform 1 into the container 111. This can reduce the risk of bursting that can easily occur when the preform 1 is blow-molded.

[0026] In the above embodiment, both the first heater 222 and the second heater 232 are electrically heated. However, this is not limiting and the heater may be one that transmits the temperature of gas combustion heating. When the preform 1 is transferred from the injection molding section 10 to the temperature adjustment section 20, the outer peripheral surface 2b of the body section 2 tends to cool more than the inner peripheral surface 2a due to natural cooling, resulting in the outer skin layer solidifying thicker than the inner skin layer. Therefore, in the temperature adjustment process, it is desirable to make the processing time (heating time) of the outer heating step longer than the processing time of the inner heating step. For example, it is desirable to set the processing time of the outer heating step to 8 to 20 seconds and the processing time of the inner heating step to 4 to 6 seconds, making the outer heating step time at least twice the time of the inner heating step. Alternatively, the processing times of the outer heating step and the inner heating step may be approximately the same, and the heating intensity of the outer heating step (output of the second heater) may be higher than the heating intensity of the inner heating step (output of the first heater).

[0027] Furthermore, the inner and outer skin layers of the preform 1 made of biodegradable plastic, which have been cooled to a low temperature in the injection molding section 10, are heated to a high temperature in the temperature adjustment section 20, thereby enabling the successful production of biodegradable containers. Therefore, the present invention can be suitably carried out only with a hot parison type blow molding apparatus 70 equipped with a temperature adjustment section (a hot parison type blow molding method equipped with a temperature adjustment process).

[0028] 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.

[0029] For example, instead of a highly biodegradable synthetic resin (biodegradable plastic), a synthetic resin (biomass plastic) with low biodegradability but low environmental impact (biomass plastic) can be used. Examples of biomass plastics that can be used include biomass-derived polyethylene (biopolyethylene: bioPE, Bio-Polyethylene). The optimum blowing temperature for biopolyethylene preforms is near their melting point (e.g., 120°C to 140°C), so the injection molding and temperature control steps described above are effective. In other words, even if the material used is bioplastic (a general term for biodegradable plastics and biomass plastics), the above-described manufacturing method (injection molding and temperature control steps) can be implemented to smoothly release the bioplastic preform from the injection mold during the injection molding process and prevent tearing of the preform during the blow molding process, thereby enabling successful production (blow molding) of a bioplastic container.

[0030] Furthermore, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0031] 1. Preform 2. Preform body 2a...Inner peripheral surface 2b...Outer surface 3. Neck 4...Bottom 10...Injection molding section 11. Injection core mold 12. Injection cavity mold 20...Temperature adjustment section 30 Blow molding section 31 Blow mold 40 Extraction section 50···Neck type 70 Blow molding equipment 100···Injection core mold 101 Core pin 101a: Core pin outer surface 102...Hollow part 110 Cooling pipe 110a...inland waterway 110b...Outer waterway 111...Completed container 112···Injection cavity mold body 112a···Cavity surface 112b Molten resin filling gate 112c...Cooling passage 115···Lip type 115a, 115b...split mold 115c···Cavity surface 221... Heating rod type 222 First Heater 223 Sleeve 224 Heating core sleeve 225···Core housing 226 (226a, 226b, 226c) Heating pot type 226d···Pot cavity 227···Insulation material 228···Housing 229, 230... Fixed plate 231 Fixing member 232 Second Heater 233 Pot heater fixing member 234...Locking member

Claims

1. A hot parison type method for producing a biodegradable resin container, comprising at least an injection molding step of injection-molding a biodegradable resin preform (1) using an injection mold, a temperature control step of heating at least a body portion of the preform (1) to a predetermined temperature using a temperature control mold, and a blow molding step of blow-molding the heated preform (1) using a blow mold to produce a container, the biodegradable resin is a synthetic resin containing polybutylene succinate as a component, The temperature of the injection mold is set to 15°C to 20°C. Manufacturing method.

2. A hot parison type method for producing a biodegradable resin container, comprising at least an injection molding step of injection-molding a biodegradable resin preform (1) using an injection mold, a temperature control step of heating at least a body portion of the preform (1) to a predetermined temperature using a temperature control mold, and a blow molding step of blow-molding the heated preform (1) using a blow mold to produce a container, the biodegradable resin is a synthetic resin containing polybutylene succinate as a component, Set the temperature of the injection mold to 15°C to 20°C; In the temperature control step, the temperature of the inner and outer skin layers in the thickness direction of the body portion (2) of the preform is heated to a heating temperature at or near the melting point of the biodegradable resin. Manufacturing method.

3. The manufacturing method according to claim 2, The heating temperature is 100°C to 180°C. Manufacturing method.

4. The manufacturing method according to claim 1, In the temperature control step, the temperature of the inner and outer skin layers in the thickness direction of the body portion (2) of the preform is heated to a temperature equal to or higher than the melting point of the biodegradable resin. Manufacturing method.

5. The manufacturing method according to claim 4, The heating temperature is 100°C to 230°C. Manufacturing method.

6. 6. The manufacturing method according to claim 1, In the injection molding process, the inner and outer skin layers in the thickness direction of the body portion (2) of the preform are solidified until they become opaque. In the temperature control step, the preform is heated until the inner and outer skin layers become transparent. Manufacturing method.

7. 6. The manufacturing method according to claim 1, The temperature adjustment step includes: an inward heating step of heating at least the body portion of the preform from the inside; an external heating step of heating at least the body portion of the preform from the outside; Equipped with The processing time of the outer heating step is longer than the processing time of the inner heating step. Manufacturing method.

8. The manufacturing method according to any one of claims 1 to 7 is applied. Manufacturing equipment for biodegradable resin containers.

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