Method for manufacturing preform

Abstract

A preform having desired characteristics is efficiently manufactured using resin flakes obtained by pulverizing a collected polyester resin molded article into flakes. Resin flakes obtained by pulverizing a collected polyester resin molded article into flakes are subjected to heating treatment under a depressurization condition, the resin flakes subjected to the heating treatment and a resin pellet made up of at least one type among a virgin material of a polyester resin, a biomass material, a chemical recycled material, and a mechanical recycled material are mixed together at a prescribed ratio to prepare a raw material resin, and a molten resin is supplied to an injection molding device while removing foreign matter from the molten resin obtained by plasticizing the raw material resin to injection-mold a preform.

Description

Preform manufacturing method

[0001] The present invention relates to a method for manufacturing a preform.

[0002] Conventionally, synthetic resin containers have been used in a wide range of fields as containers for various beverages, seasonings, etc., by producing a bottomed cylindrical preform from a polyester resin such as polyethylene terephthalate and then molding this preform into a bottle by biaxial stretch blow molding or the like. This type of container is generally known as a PET bottle, and in recent years, in response to social demand, a recycling technology known as "bottle-to-bottle" has been considered, in which used PET bottles are collected and reused as recycled material to manufacture PET bottles.

[0003] For example, Patent Document 1 discloses a technology in which recovered polyester resin molded articles are crushed into flakes to produce resin flakes, which are decontaminated, melted to produce resin pellets, and then solid-state polymerized and transported to an injection molding device to produce preforms.

[0004] Japanese Patent Application Publication No. 2021-98350

[0005] In view of the above background art, the present inventors have conducted extensive research to find a method for more efficiently producing preforms with desired properties using resin flakes obtained by crushing recovered polyester resin molded articles into flakes, and as a result, have completed the present invention.

[0006] The method for manufacturing a preform according to the present invention involves heat-treating resin flakes obtained by crushing recovered polyester-based resin molded products into flakes under reduced pressure conditions, mixing the heat-treated resin flakes with resin pellets made of at least one of virgin polyester-based resin material, biomass material, chemically recycled material, or mechanically recycled material in a predetermined ratio to prepare raw material resin, and then supplying the molten resin obtained by plasticizing the raw material resin to an injection molding device to injection-mold a preform while removing foreign matter from the molten resin.

[0007] In addition, the method for manufacturing a preform according to the present invention can be a method of preparing a raw material resin by mixing resin flakes obtained by crushing recovered polyester-based resin molded products into flakes with resin pellets made of at least one of virgin polyester-based resin material, biomass material, chemically recycled material, mechanically recycled material, or post-consumer recycled material in a predetermined ratio, heat-treating the raw material resin under reduced pressure conditions and then plasticizing it, and supplying the molten resin obtained by plasticizing the raw material resin to an injection molding device while removing foreign matter from the molten resin, and injection-molding a preform.

[0008] According to the present invention, preforms having desired properties can be produced more efficiently even when using resin flakes obtained by pulverizing recovered polyester resin molded articles into flakes.

[0009] 1 is an explanatory diagram conceptually showing the entire apparatus in which a first embodiment of the present invention is preferably carried out. FIG. 2 is an explanatory diagram conceptually showing the entire apparatus in which a second embodiment of the present invention is preferably carried out. FIG. 3 is an explanatory diagram showing an example of an apparatus for subjecting resin flakes to a heat treatment in an embodiment of the present invention.

[0010] Preferred embodiments of the present invention will now be described.

[0011] First Embodiment First, a first embodiment of the present invention will be described.

[0012] In this embodiment, first, resin flakes are prepared by crushing recovered polyester resin molded articles into flakes.

[0013] When preparing such resin flakes, it is preferable to wash them by any washing means such as alkaline washing or hot water washing in order to remove stains such as residues of contents remaining on the surface and contaminated foreign matter, etc. "Recovered polyester resin molded products" can include polyester resin molded products (post-consumer materials) such as used PET bottles that have been collected separately as recyclable waste, as well as scrap materials (pre-consumer materials) generated in the process of manufacturing polyester resin molded products.

[0014] When polyester resin molded articles such as used PET bottles are collected and reused as recycled materials by so-called mechanical recycling to manufacture recycled products, a decrease in intrinsic viscosity due to deterioration of the resin caused by the thermal history of the collected articles during production can cause problems in the manufacturing process of the recycled products. Furthermore, if a large amount of low-molecular-weight impurities such as acetaldehyde (AA) produced by thermal decomposition of polyester resins, oligomers such as bishydroxyethyl terephthalate (BHET), monohydroxyethyl terephthalate (MHET), and cyclic trimer (CT) produced by depolymerization of polyester resins, and limonene derived from the contents remain in the recycled materials, they not only affect the quality of the recycled products but also cause productivity reduction by fouling the manufacturing equipment.

[0015] In this embodiment, in order to avoid such problems, the prepared resin flakes are subjected to a heat treatment, preferably in a reduced pressure atmosphere of 1000 Pa or less and at a temperature of preferably 160 to 240°C, so that the solid-state polymerization reaction of the polyester resin that forms the resin flakes proceeds and crystallization is promoted while the resin flakes remain in their flake form without melting the resin flakes.

[0016] By allowing the solid-state polymerization reaction to proceed, the end groups of the polyester resin, whose degree of polymerization has decreased due to scission of molecular chains caused by degradation, recondense, thereby restoring the degree of polymerization and restoring the intrinsic viscosity corresponding to the molecular weight. Furthermore, by subjecting the resin flakes to heat treatment under reduced pressure, particularly by exposing them to a temperature atmosphere of 160 to 240°C under reduced pressure, hydrolysis of the polyester resin can be suppressed while effectively promoting crystallization by utilizing the melting point lowering effect. This reduces the free volume between the molecular chains of the polyester resin (reducing the amorphous phase), and selectively bleeds out the low-molecular-weight impurities (organic impurities) that were included in the free volume of the resin flakes and the moisture sorbed by the resin flakes to the surface layer of the resin flakes, where they can be efficiently removed by volatilization or evaporation, or by washing with hot water, steam, organic solvents, or the like, as needed.

[0017] In this embodiment, the specific method for subjecting the resin flakes to the heat treatment is not particularly limited. For example, it is preferable to subject the resin flakes to the heat treatment using a treatment device 100 as shown in Figure 3, which includes at least one preheating chamber 102 and a treatment chamber 103 that can adjust the internal atmosphere to a temperature and pressure suitable for the heat treatment.

[0018] Here, the outline of the processing device 100 shown in FIG. 3 will be explained. The processing device 100 is preferably 7 to 18 m ３ The system includes a sealed container 101 constructed to have an internal volume of 100 psi. A processing chamber 103 is provided within the sealed container 101, and two preheating chambers 102 are provided above the sealed container 101. The preheating chambers 102 are connected to the sealed container 101 via opening / closing mechanisms such as sliding shutters (not shown) so as to be able to communicate with the processing chamber 103 while maintaining airtightness from the outside of the system. Note that Fig. 3 does not show incidental equipment such as a heating device, a decompression device, and associated piping for adjusting the internal atmosphere of the processing chamber 103.

[0019] In order to heat-treat resin flakes using such a treatment device 100, it is preferable to first put the resin flakes into the preheating chamber 102, seal the preheating chamber 102, heat the resin flakes to a predetermined temperature, and reduce the pressure in the preheating chamber 102 to a predetermined level. At this time, for example, a jet hole is provided on the inner wall surface of the preheating chamber 102 to blow in a heated gas (e.g., N ２ It is preferable to spray an inert gas (such as a gas) into the preheating chamber 102, and appropriately adjust the direction and amount of spray to generate an air flow within the preheating chamber 102, stirring and heating the resin flakes, and also to apply a reduced pressure and suction to the preheating chamber 102 to disperse at least some of the impurity components contained in the resin flakes and remove them from the system.

[0020] In this way, when raising the temperature of the resin flakes, it is preferable to appropriately adjust the final temperature and pressure in the preheating chamber 102 taking into consideration the internal atmosphere of the processing chamber 103. Then, it is preferable to open the opening and closing device, maintain airtightness from the outside of the system, and allow the resin flakes in the preheating chamber 102 to fall by their own weight, so that the resin flakes are supplied into the processing chamber 103 without damaging the internal atmosphere of the processing chamber 103, which has been adjusted to a temperature and pressure suitable for the heat treatment.

[0021] In the processing apparatus 100 shown in FIG. 3 , resin flakes are sequentially introduced into two preheating chambers 102, and preheating treatments for raising the temperature of the resin flakes are alternately performed. The resin flakes are then dropped into the processing chamber 103 in the order from the preheating chamber 102 in which the introduced resin flakes have been heated to a predetermined temperature. However, this is not limited to this configuration. Depending on the processing capacity of the processing apparatus 100, i.e., the total amount of resin flakes that can be subjected to heat treatment per unit time, the number of preheating chambers 102 can be one, or three or more. In either case, it is preferable to repeat the operation of dropping the resin flakes from the preheating chamber 102 into the processing chamber 103 so that the resin flakes are evenly dispersed and stacked in layers in each dropped group. It is then preferable to expose the resin flakes, once they have been deposited in the processing chamber 103, to the internal atmosphere of the processing chamber 103, so that the resin flakes can be subjected to heat treatment.

[0022] The treatment time for heat-treating the resin flakes is typically 30 minutes or more, and is preferably adjusted appropriately within the range of 1 to 8 hours to promote the solid-state polymerization reaction while suppressing deterioration of the resin's color. It is preferable to manage the treatment time by sequentially removing the resin flakes deposited in the treatment chamber 103 from the treatment chamber 103 after the treatment time has elapsed, starting from the lower layer of the deposited layers as described above, in amounts equal to the amount dropped from the preheating chamber 102. Since the time required for the preheating treatment in the preheating chamber 102 depends on the water content and shape of the resin flakes, and variations may occur in the intervals between repeated dropping operations of the resin flakes, it is preferable to manage the treatment time for each group of dropped resin flakes.

[0023] In this way, in order to suitably manage the processing time when heat-treating resin flakes, the processing apparatus 100 shown in Figure 3 is provided with an opening / closing mechanism 104 on the bottom side of the sealed container 101. The opening / closing mechanism 104 forms the bottom surface of the processing chamber 103 and is configured to serve as a partition between the processing chamber 103 and the removal section 105 provided at the bottom of the sealed container 101. This allows the resin flakes to spill into the removal section 105 when the opening / closing mechanism 104 is opened, and by appropriately adjusting the timing of opening and closing the opening / closing mechanism 104, it is possible to remove an amount of resin flakes equal to the amount dropped from the preheating chamber 102. Although there will be some mixing, the resin flakes can be removed in groups dropped from the preheating chamber 102.

[0024] As mentioned above, impurity components can be efficiently removed by performing heat treatment under reduced pressure conditions, but it is not desirable for volatilized or evaporated impurity components to remain in the treatment chamber 103. For this reason, the treatment apparatus 100 shown in Figure 3 is configured to circulate the gas phase components in the treatment chamber 103, and is equipped with a circulation flow path 106 including a catalyst tank 107 in the path that decomposes low-molecular-weight impurity components derived from polyester-based resins, and the circulation flow path 106 is connected to the treatment chamber 103. By configuring the treatment apparatus 100 in this way, for example, N ２ It is preferable to reduce impurity components remaining in the processing chamber 103 by using an inert gas such as a gas as a carrier gas and circulating the gas phase components in the processing chamber 103 through the circulation flow path 106 without damaging the internal atmosphere of the processing chamber 103.

[0025] Furthermore, when cleaning the impurity components selectively bled out from the surface layer of the resin flakes, the resin flakes removed from the treatment chamber 103 can be liquid washed using a rotary or convection liquid washer, or steam washed using a pressurized steam convection washer, although not shown. When liquid washing is applied, the resin flakes after washing must be dried. For this drying process, the resin flakes may be subjected to a heat treatment again in an atmosphere equivalent to the internal atmosphere of the treatment chamber 103, or may be dried using a hot air circulation dryer. Furthermore, the resin flakes can be dried using two jacketed rolls with spiral grooves on their surfaces, utilizing the shear heat generated by the roll rotation to semi-weld and press-bond the surface layer of the resin flakes, and then further removing organic impurities and moisture from the resin flakes using a rotary forward drying device (open roll twin-screw extruder). In this case, the resin flakes dried in the open-roll twin-screw extruder are easily separated and dispersed into flakes by the pressure of the pressure rolls in the cooling section downstream of the rolls.

[0026] In this embodiment, the resin flakes are heat-treated under reduced pressure conditions to remove (decontaminate) low-molecular-weight impurities, and then the heat-treated resin flakes are mixed in a predetermined ratio with resin pellets made of at least one of virgin polyester resin, biomass material, chemically recycled material, and mechanically recycled material to prepare a raw material resin. In the example shown in Figure 1, the resin flakes stored in the first tank 1 are supplied to the processing device 100, and the resin pellets stored in the second tank 2 are mixed with the heat-treated resin flakes in the mixer 3.

[0027] Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene furanoate, and copolymers thereof. Among these polyester resins, polyester resins obtained by polymerizing a chemically synthesized diol component and a dicarboxylic acid component are referred to as virgin materials. Polyester resins with increased biomass content, such as those using ethylene glycol or its derivatives derived from plant-derived bioethanol as the diol component, terephthalic acid or its derivatives derived from plant-derived bioparaxylene as the dicarboxylic acid component, or furandicarboxylic acid or its derivatives derived from plant-derived fructose as the dicarboxylic acid component, are referred to as biomass materials. Recent recycling technologies for reusing resin materials for molding include material recycling and chemical recycling. Among recycled materials obtained through material recycling, recovered polyester resin molded articles that have been cleaned and made reusable are referred to as post-consumer recycled materials, and those that have undergone further adjustment of the intrinsic viscosity and decontamination of low-molecular-weight impurities are referred to as mechanically recycled materials. In chemical recycling, the polyester resin contained in the recovered polyester resin molded product is depolymerized to at least the oligomer component, and the repolymerized polyester resin is called chemically recycled material.

[0028] When preparing a raw material resin by mixing heat-treated resin flakes with resin pellets made of at least one of virgin polyester resin, biomass material, chemically recycled material, or mechanically recycled material, the ratio of the two can be appropriately adjusted so as to produce a preform with desired properties. For example, when the residual amount of acetaldehyde is 1 to 15 ppm, preferably 1 to 10 ppm, more preferably 1 to 5 ppm, the residual amount of bishydroxyethyl terephthalate is 1 to 35 ppm, preferably 1 to 30 ppm, more preferably 1 to 20 ppm, the residual amount of monohydroxyethyl terephthalate is 1 to 35 ppm, preferably 1 to 30 ppm, more preferably 1 to 20 ppm, the residual amount of cyclic trimer is 6000 ppm or less, preferably 4000 ppm or less, more preferably 3000 ppm or less, and the mass of the preform is 14 to 50 g, L ＊ a ＊ b ＊ L in color system ＊ Value 70-90, b ＊ It can be adjusted so as to produce a preform having a value of 2 to 18. For this purpose, it is preferable to mix 100 parts by weight of resin flakes with 11 to 400 parts by weight of resin pellets.

[0029] Here, the residual amounts of acetaldehyde, bishydroxyethyl terephthalate (BHET), monohydroxyethyl terephthalate (MHET), and cyclic trimer (CT), and the intrinsic viscosity can be determined, for example, as follows.

[0030] <Residual Amount of Acetaldehyde> A piece cut from a preform is used as a sample. 1.0 g of the sample is weighed into a glass bottle, and 5.0 mL of pure water is added and sealed. This suspension is heated for 60 minutes in an oven controlled at 120°C, and then cooled in ice water. 1.0 mL of the supernatant of the suspension is sampled, to which 0.2 mL of a 0.1% 2,4-dinitrophenylhydrazine / phosphate solution is added. The mixture is left to stand for 30 minutes and then measured by high-performance liquid chromatography. A standard solution is also measured at the same time, and the acetaldehyde content is calculated based on the obtained calibration curve.

[0031] <Residual Amounts of BHET, MHET, and CT> A piece cut from a preform was used as a sample. 0.2 g of the sample was weighed, and 1 mL of a mixed solvent of hexafluoroisopropanol and chloroform (weight ratio 1 / 1) was added to completely dissolve the sample. 4 mL of chloroform was added to the solution, and then 5 mL of acetonitrile was gradually added. The solution was left for 3 hours to precipitate the PET polymer. 1 mL of the suspension was sampled and filtered through a membrane filter with a pore size of 0.45 μm, and the filtrate was measured by high-performance liquid chromatography. Measurements of standard solutions were also performed at the same time, and the contents of MHET, BHET, and CT in the pellets were calculated based on the obtained calibration curve.

[0032] <Intrinsic Viscosity> A piece cut out from the preform is used as a sample, and this sample is vacuum dried at 150°C for 1 hour and weighed out at 0.2 g. A mixed solvent of 1,1,2,2-tetrachloroethane and phenol (weight ratio 1:1) is added to this to adjust the concentration to 1.00 g / dL, and the mixture is stirred at 120°C for 20 minutes to completely dissolve it. The dissolved solution is cooled to room temperature, and the relative viscosity is measured using a relative viscometer temperature-controlled at 30°C to determine the intrinsic viscosity.

[0033] Also, L ＊ a ＊ b ＊ L in color system ＊ value, b ＊ The value is measured at the body of the preform using a spectrophotometer under the measurement conditions of a D65 light source and a 2° field of view.

[0034] Furthermore, when preparing the raw material resin, the resin flakes removed from the processing chamber 103 as described above may be mixed directly with the resin pellets. Alternatively, the resin flakes may be stored in the buffer tank 300 and then mixed with the resin pellets to prepare the raw material resin. When managing the processing time for the heat treatment of the resin flakes as described above, the removal of the resin flakes from the processing chamber 103 is performed intermittently depending on the interval between repetitions of the operation of dropping the resin flakes from the preheating chamber 102 into the processing chamber 103. The amount of resin flakes removed each time also depends on the amount of resin processed in the preheating chamber 102. In such a case, particularly if there is variation in the interval between repetitions of the operation of dropping the resin flakes, the amount of resin flakes removed per unit time will not be constant. For this reason, if the resin flakes are stored in the buffer tank 300 and can be removed from the buffer tank 300 in fixed amounts at any interval, it becomes easy to adjust the mixing ratio with the resin pellets. Furthermore, in the plasticization process described below, the amount of raw material resin fed can be easily adjusted according to the processing capacity of the extruder 200 so that the amount of resin plasticized in the extruder 200 can always be kept constant.

[0035] When installing the buffer tank 300, it is preferable to appropriately adjust the internal volume of the buffer tank 300 so that a larger amount of resin flakes can be stored. By doing so, even if a problem occurs in a subsequent process after the process of preparing the raw material resin, causing the subsequent process to be stopped, the heating treatment of the resin flakes can be continued without interruption, and the amount that cannot be sent to the subsequent process can be stored in the buffer tank 300.

[0036] Furthermore, in anticipation of such trouble occurring or changes in circumstances such as an increase or decrease in the processing speed of the subsequent process, a relief tank 400 can be installed midway along the transport path that transports the resin flakes removed from the processing chamber 103 to the buffer tank 300. It is preferable to transport the resin flakes to the buffer tank 300 while allowing them to be evacuated to the relief tank 400 during transport.

[0037] By doing so, for example, when the subsequent process is stopped, the resin flakes removed from the process chamber 103 can be evacuated to the relief tank 400, and their transport to the buffer tank 300 can be limited. When the processing speed of the subsequent process increases, the resin flakes evacuated to the relief tank 400 can be transported to the buffer tank 300 together with the resin flakes removed from the process chamber 103. When the processing speed of the subsequent process decreases, some of the resin flakes removed from the process chamber 103 can be evacuated to the relief tank 400, and the amount of resin flakes transported to the buffer tank 300 can be adjusted appropriately. In this way, when evacuating the resin flakes to the relief tank 400 as needed, the internal atmosphere of the relief tank 400 is preferably set to 100°C or higher to prevent the resin flakes from absorbing moisture.

[0038] Next, the prepared raw material resin is plasticized. At this time, the raw material resin may be fed into the extruder 200 and plasticized while being melted and kneaded by the heat from the heating cylinder and the shear heat of the screw, but it is preferable to use a twin-screw extruder for plasticization. A twin-screw extruder has a high kneading effect, can plasticize the resin flakes more uniformly, and can also shorten the time required for plasticization, so it is also preferable in terms of suppressing resin deterioration, thermal decomposition, and depolymerization.

[0039] When plasticizing raw material resins using a twin-screw extruder, it is preferable to configure the twin-screw extruder with a vent port. For example, it is preferable to vacuum-suction and discharge gaseous components containing low-molecular-weight impurities derived from the polyester resin that remain in the twin-screw extruder through a vent port provided through the heating cylinder. This can further reduce the impurities remaining in the plasticized polyester resin. In particular, cyclic oligomers are generated during equilibrium reactions during thermal melting, so cyclic oligomers are generated when polyethylene terephthalate is melted. Therefore, it is important to perform vacuum absorption and removal at the vent port of the twin-screw extruder. The optimal conditions (temperature and pressure) for gas-liquid separation of cyclic oligomers are estimated. The melting point of cyclic oligomers is 319°C and they are sublimable. Assuming that the resin melt temperature at the vent port of a twin-screw extruder for polyethylene terephthalate is 300°C, the reduced vacuum pressure at which cyclic oligomers can sublimate (transform into gas) is generally 0.1 KPa (100 Pa) or less, so it is necessary to adjust the pressure to a relatively high vacuum. This increases the possibility of the molten resin venting up at the vent port. To avoid venting up, it is preferable to use a twin-screw extruder with counter-rotating (counter-rotating) screws rather than one with the same (co-rotating) screw rotation direction.

[0040] In this embodiment, after the above steps, foreign matter is removed from the molten resin obtained by plasticizing the raw material resin, and the molten resin is then supplied to the injection molding apparatus 500 to injection mold a preform. Removal of foreign matter from the molten resin obtained by plasticizing the raw material resin can be achieved, for example, by providing a filter 600 for removing foreign matter on the discharge port side of the extruder 200. Furthermore, the specific configuration of the injection molding apparatus 500 is not particularly limited. For example, a preform can be injection molded using an injection molding apparatus 500 including at least one injection pot configured to measure the supplied molten resin and then inject a predetermined amount of molten resin.

[0041] Furthermore, when supplying the molten resin obtained by plasticizing raw material resin to injection molding apparatus 500, it is undesirable for the resin to deteriorate (particularly, its color) during transportation. To this end, in order to shorten the time the molten resin remains in the transportation path, it is preferable to set the transportation distance from the time the molten resin is supplied to injection molding apparatus 500 after removing foreign matter to 1 to 7 m, more specifically, the distance from the outlet of gear pump 700 installed downstream of filter 600 to the inlet of the injection pot provided in injection molding apparatus 500. In this case, the transportation rate of the molten resin is preferably 900 to 1500 kg / h.

[0042] According to the present embodiment as described above, preforms with desired properties can be produced more efficiently even when using resin flakes obtained by pulverizing recovered polyester resin molded articles into flakes.

[0043] Second Embodiment Next, a second embodiment of the present invention will be described.

[0044] In this embodiment, similarly to the first embodiment, resin flakes are prepared by crushing recovered polyester resin molded articles into flakes.

[0045] In the first embodiment, the resin flakes prepared in this manner are subjected to a heat treatment, but in the present embodiment, prior to the heat treatment, the prepared resin flakes are mixed with resin pellets made of at least one of virgin polyester resin, biomass material, chemically recycled material, mechanically recycled material, or post-consumer recycled material in a predetermined ratio to prepare a raw material resin. In the example shown in Figure 2, the resin flakes stored in the first tank 1 are mixed with the resin pellets stored in the second tank 2 in a mixer 3.

[0046] Hereinafter, the present embodiment will be described, focusing on the differences from the first embodiment, while omitting the overlapping explanations with the first embodiment as appropriate.

[0047] In this embodiment, the prepared raw material resin is subjected to a heat treatment in the same manner as the resin flakes were subjected to a heat treatment in the first embodiment, and the resin flakes and resin pellets contained in the raw material resin are not melted, but rather the solid-state polymerization reaction of the polyester-based resin in the raw material resin, particularly the polyester-based resin that forms the resin flakes, is promoted and crystallization is promoted in their original form.

[0048] Furthermore, when the raw resin is heat-treated, a solid-state polymerization reaction also occurs in the polyester resin that forms the resin pellets contained in the raw resin. This increases the degree of polymerization of the polyester resin, making it easier to adjust the intrinsic viscosity of the raw resin as a whole, especially when the resin pellets contain post-consumer recycled material. Furthermore, by subjecting the raw resin and resin flakes to heat treatment under reduced pressure, the moisture sorbed in the resin pellets can be efficiently removed, reducing the water content of the entire raw resin. As a result, a drying step can be omitted when plasticizing the raw resin.

[0049] Here, prior to the heat treatment, resin flakes are mixed with resin pellets made of at least one of virgin polyester resin, biomass material, chemical recycled material, mechanical recycled material, or post-consumer recycled material to prepare a raw material resin. The ratio of the two can be appropriately adjusted in the same manner as in the first embodiment so that a preform with desired properties can be produced.

[0050] In this embodiment, the specific method for subjecting the raw material resin to heat treatment is not particularly limited. For example, it is preferable to subject the raw material resin to heat treatment using a processing device 100 as shown in Figure 3, in the same manner as the heat treatment of the resin flakes in the first embodiment. Note that the description of subjecting the raw material resin to heat treatment in this embodiment can be applied by appropriately replacing "resin flakes" with "raw material resin" in the description of subjecting the resin flakes to heat treatment in the first embodiment.

[0051] In this embodiment, the raw material resin is heat-treated under reduced pressure conditions to remove (decontaminate) low-molecular-weight impurities, and then plasticized, in the same manner as in the first embodiment, in which the resin flakes are heat-treated. In this case, the heat-treated raw material resin is fed into the extruder 200, and plasticized while being melted and kneaded by the heat from the heating cylinder and the shear heat of the screw, in the same manner as in the first embodiment.

[0052] The raw material resin that has been subjected to heat treatment using the processing apparatus 100 shown in FIG. 3 and removed from the processing chamber 103 may be directly fed into the extruder 200 for plasticization, or may be stored in a buffer tank 300 and then fed into the extruder 200 for plasticization. In the same manner as the processing time for heat-treating the resin flakes was managed in the first embodiment, the processing time for heat-treating the raw material resin can also be managed in this embodiment. In this case, the raw material resin is intermittently removed from the processing chamber 103 according to the interval between repeated operations of dropping the raw material resin from the preheating chamber 102 into the processing chamber 103, and the amount of raw material resin removed each time also depends on the amount of material processed in the preheating chamber 102. In such a case, particularly if there is variation in the interval between repeated operations of dropping the raw material resin, the amount of raw material resin removed per unit time will not be constant. Therefore, if the raw material resin is stored in the buffer tank 300 and can be removed from the buffer tank 300 in fixed amounts at any interval, the amount of raw material resin input can be easily adjusted according to the processing capacity of the extruder 200 so that the amount of resin plasticized in the extruder 200 can always be maintained constant.

[0053] When installing the buffer tank 300, it is preferable to appropriately adjust the internal volume of the buffer tank 300 so that it can store a larger amount of raw material resin. By doing so, even if a problem occurs in a subsequent process after the process of plasticizing the raw material resin and causes the subsequent process to be stopped, the heating treatment of the raw material resin can be continued without interruption, and the amount that cannot be sent to the subsequent process can be stored in the buffer tank 300.

[0054] Furthermore, in anticipation of such trouble occurring or changes in circumstances such as an increase or decrease in the processing speed of the subsequent process, a relief tank 400 can be installed midway along the transport path that transports the raw material resin removed from the processing chamber 103 to the buffer tank 300. It is preferable to transport the raw material resin to the buffer tank 300 while allowing it to be evacuated to the relief tank 400 during transport.

[0055] In this way, for example, when the subsequent process is stopped, the raw material resin removed from the process chamber 103 can be evacuated to the relief tank 400, and the transport to the buffer tank 300 can be limited. When the processing speed of the subsequent process increases, the raw material resin evacuated to the relief tank 400 can be transported to the buffer tank 300 together with the raw material resin removed from the process chamber 103. When the processing speed of the subsequent process decreases, a portion of the raw material resin removed from the process chamber 103 can be evacuated to the relief tank 400, and the amount of raw material resin transported to the buffer tank 300 can be adjusted appropriately. When evacuating the raw material resin to the relief tank 400 as needed in this way, the internal atmosphere of the relief tank 400 is preferably set to 100°C or higher to prevent the raw material resin from absorbing moisture.

[0056] In this embodiment, after the above-described steps are performed, foreign matter is removed from the molten resin obtained by plasticizing the raw material resin, and the molten resin is then supplied to the injection molding apparatus 500 to injection mold a preform. To remove foreign matter from the molten resin obtained by plasticizing the raw material resin, for example, a filter 600 for removing foreign matter may be provided on the discharge port side of the extruder 200, as in the first embodiment. Furthermore, the specific configuration of the injection molding apparatus 500 is not particularly limited. For example, as in the first embodiment, a preform can be injection molded using an injection molding apparatus 500 including at least one injection pot configured to measure the supplied molten resin and then inject a predetermined amount of molten resin.

[0057] According to the present embodiment as described above, preforms with desired properties can be produced more efficiently even when using resin flakes obtained by pulverizing recovered polyester resin molded articles into flakes.

[0058] The present invention has been described above by showing preferred embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

[0059] REFERENCE SIGNS LIST 100 Processing device 101 Processing chamber 102 Preheating chamber 107 Catalyst tank 200 Extruder (twin-screw extruder) 300 Buffer tank 400 Relief tank 500 Injection molding device 600 Filter 700 Gear pump

Claims

1. The recovered polyester resin molded articles are pulverized into flakes, and the resulting resin flakes are heat-treated under reduced pressure conditions; The heat-treated resin flakes are mixed with resin pellets made of at least one of virgin polyester resin, biomass resin, chemically recycled material, and mechanically recycled material in a predetermined ratio to prepare a raw material resin; A method for manufacturing a preform, comprising the steps of: removing foreign matter from a molten resin obtained by plasticizing the raw material resin; supplying the molten resin to an injection molding machine; and injection molding the preform.

2. The method for producing a preform according to claim 1, wherein the resin flakes are heat-treated in an atmosphere reduced in pressure to 1000 Pa or less and at a temperature of 160 to 240°C.

3. Resin flakes obtained by crushing the recovered polyester-based resin molded articles into flakes are mixed with resin pellets made of at least one of virgin polyester-based resin material, biomass material, chemically recycled material, mechanically recycled material, and post-consumer recycled material in a predetermined ratio to prepare a raw material resin; The raw material resin is heat-treated under reduced pressure and then plasticized; A method for manufacturing a preform, comprising the steps of: removing foreign matter from a molten resin obtained by plasticizing the raw material resin; supplying the molten resin to an injection molding machine; and injection molding the preform.

4. The method for producing a preform according to claim 3, wherein the raw material resin is heat-treated in an atmosphere reduced in pressure to 1000 Pa or less and at a temperature of 160 to 240°C.

5. A method for manufacturing a preform as described in claim 1, wherein the resin flakes are placed into a preheating chamber, heated to a predetermined temperature, and then the pressure inside the preheating chamber is reduced to a predetermined level, and then the resin flakes are dropped from the preheating chamber into a processing chamber whose internal atmosphere is adjusted to a predetermined temperature and pressure while maintaining airtightness from the outside of the system, and the resin flakes are deposited in the processing chamber and subjected to a heat treatment.

6. A method for manufacturing a preform as described in claim 5, wherein the heat-treated resin flakes are sequentially removed from the treatment chamber in amounts equal to the amount dropped from the preheating chamber, starting from the bottom layer of the resin flakes deposited in the treatment chamber, and then mixed with the resin pellets to prepare the raw material resin.

7. A method for manufacturing a preform as described in claim 5, wherein the heat-treated resin flakes are sequentially removed from the processing chamber in amounts equal to the amount dropped from the preheating chamber, starting from the bottom layer deposited in the processing chamber, and stored in a buffer tank, and then mixed with the resin pellets to prepare the raw material resin.

8. A method for manufacturing a preform as described in claim 7, wherein a relief tank is installed midway along the transport path that transports the resin flakes removed from the processing chamber to the buffer tank, so that the resin flakes can be evacuated to the relief tank during transport while being transported to the buffer tank.

9. The resin flakes are sequentially introduced into a plurality of preheating chambers, and the resin flakes are dropped into the processing chambers in the order of the preheating chambers in which the introduced resin flakes have been heated to a predetermined temperature. A method for manufacturing a preform according to any one of claims 5 to 8.

10. A method for manufacturing a preform according to any one of claims 5 to 8, wherein an airflow of heated gas is generated in the preheating chamber, the resin flakes are heated while being stirred by the airflow, and the pressure inside the preheating chamber is reduced.

11. 4. The method for manufacturing a preform according to claim 3, wherein the raw material resin is charged into a preheating chamber, the raw material resin is heated to a predetermined temperature, the pressure inside the preheating chamber is reduced to a predetermined pressure, and then the raw material resin is dropped from the preheating chamber into a processing chamber whose internal atmosphere is adjusted to a predetermined temperature and a predetermined pressure while maintaining airtightness from the outside of the system, and the raw material resin is deposited in the processing chamber and subjected to a heat treatment.

12. The method for manufacturing a preform according to claim 11, wherein the raw material resin that has been subjected to the heat treatment is sequentially removed from the treatment chamber in amounts equal to the amount dropped from the preheating chamber, starting from the bottom layer deposited in the treatment chamber, and plasticized.

13. 12. A method for manufacturing a preform according to claim 11, wherein the raw material resin that has been subjected to the heat treatment is sequentially removed from the treatment chamber in amounts equal to the amount dropped from the preheating chamber, starting from the bottom layer deposited in the treatment chamber, and stored in a buffer tank, and then plasticized.

14. 14. The method for manufacturing a preform according to claim 13, wherein a relief tank is installed midway along a transport path for transporting the raw material resin removed from the processing chamber to the buffer tank, so that the raw material resin can be evacuated to the relief tank during transport while being transported to the buffer tank.

15. The raw material resin is sequentially charged into a plurality of preheating chambers, and the charged raw material resin is heated to a predetermined temperature in the preheating chamber. The method for manufacturing a preform according to any one of claims 11 to 14, wherein the raw material resin is dropped into the processing chamber in order.

16. 15. The method for producing a preform according to any one of claims 11 to 14, wherein an airflow of heated gas is generated in the preheating chamber, the raw material resin is heated while being stirred by the airflow, and the pressure inside the preheating chamber is reduced.

17. The method for manufacturing a preform according to any one of claims 5 to 8 and 11 to 14, wherein the treatment chamber is connected to a circulation flow path that allows the gas phase components in the treatment chamber to circulate and includes a catalyst layer in the path that decomposes low molecular weight components derived from polyester-based resins, and the gas phase components in the treatment chamber are guided and circulated through the circulation flow path, thereby reducing the low molecular weight components remaining in the treatment chamber.

18. The method for producing a preform according to any one of claims 1 to 8 and 11 to 14, wherein the raw material resin is plasticized by being charged into a twin-screw extruder.

19. The twin-screw extruder is provided with a vent port, and gas phase components containing low molecular weight components derived from the polyester resin remaining in the twin-screw extruder are sucked under reduced pressure through the vent port and discharged outside the system.