WO2024143102A1 - Method for manufacturing preform - Google Patents

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

The present invention is a method for manufacturing preforms.

　Traditionally, synthetic resin containers are made by making a cylindrical preform with a bottom using a polyester resin such as polyethylene terephthalate, and then molding this preform into a bottle by biaxial stretch blow molding or the like, and these containers are used in a wide range of fields as containers for various beverages, seasonings, and other contents. This type of container is generally known as a PET bottle, and in recent years, in response to societal 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.

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

Japanese Patent Publication No. 2021-98350

In light of the above background technology, the inventors conducted extensive research to find a way to more efficiently manufacture preforms with the desired characteristics using resin flakes made by crushing recovered polyester resin molded products into flakes, and as a result, they were able to complete the present invention.

The method for manufacturing a preform according to the present invention involves heat-treating resin flakes obtained by crushing recovered polyester 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 resin, biomass material, chemically recycled material, or mechanically recycled material in a predetermined ratio to prepare a raw material resin, and supplying the molten resin to an injection molding device to injection-mold a preform while removing foreign matter from the molten resin obtained by plasticizing the raw material resin.

The preform manufacturing method according to the present invention can be a method of preparing a raw material resin by mixing resin flakes obtained by crushing recovered polyester resin molded products into flakes 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, heat-treating the raw material resin under reduced pressure conditions and then plasticizing the raw material resin, and supplying the molten resin to an injection molding device to injection-mold a preform while removing foreign matter from the molten resin obtained by plasticizing the raw material resin.

According to the present invention, preforms with desired characteristics can be produced more efficiently using resin flakes made by crushing recovered polyester resin molded products into flakes.

1 is an explanatory diagram conceptually illustrating an entire apparatus in which a first embodiment of the present invention can be suitably carried out; FIG. 11 is an explanatory diagram conceptually showing an entire apparatus in which a second embodiment of the present invention can be suitably carried out; FIG. 2 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.

The following describes a preferred embodiment of the present invention.

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

In this embodiment, first, resin flakes are prepared by crushing the recovered polyester resin molded products into flakes.

When preparing such resin flakes, it is preferable to wash them by any washing method such as alkaline washing or hot water washing in order to remove dirt such as residue of contents remaining on the surface and foreign matter that has been mixed in. "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 resource waste, as well as scrap materials (pre-consumer materials) generated during the manufacturing process of polyester resin molded products.

When polyester resin molded products such as used PET bottles are collected and reused as recycled materials through so-called mechanical recycling to manufacture recycled products, the decrease in intrinsic viscosity due to deterioration of the resin caused by the heat history during the manufacture of the collected products 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) generated by thermal decomposition of polyester resin, oligomers such as bishydroxyethyl terephthalate (BHET), monohydroxyethyl terephthalate (MHET), and cyclic trimer (CT) generated by depolymerization of polyester resin, and limonene derived from the contents remain in the recycled materials, they not only affect the quality of the recycled products manufactured, but also cause productivity to decrease by fouling the manufacturing equipment.

In this embodiment, to avoid such problems, the prepared resin flakes are subjected to a heat treatment, preferably in an atmosphere with a reduced pressure of 1000 Pa or less and a temperature of preferably 160 to 240°C, to advance the solid-state polymerization reaction of the polyester resin that forms the resin flakes and promote crystallization while keeping the flakes in their flake form, without melting the resin flakes.

By allowing the solid-phase polymerization reaction to proceed, the end groups of the polyester resin, whose degree of polymerization has decreased due to the cutting of the molecular chains caused by deterioration, re-condense, and as the degree of polymerization is restored, the intrinsic viscosity corresponding to the molecular weight can be restored. Furthermore, by subjecting the resin flakes to heat treatment under reduced pressure conditions, particularly by exposing them to a temperature atmosphere of 160 to 240°C under reduced pressure conditions, it is possible to suppress hydrolysis of the polyester resin 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 impurity components (organic impurity components) as mentioned above that were included in the free volume portion of the resin flakes and the moisture sorbed by the resin flakes to the surface layer of the resin flakes, where they can be volatilized or evaporated, or washed with hot water, steam, organic solvents, etc. as necessary, and efficiently removed.

In this embodiment, the specific method for subjecting the resin flakes to a heat treatment is not particularly limited. For example, it is preferable to perform the heat treatment using a treatment device 100 as shown in FIG. 3, which includes at least one preheating chamber 102 and a treatment chamber 103 capable of adjusting the internal atmosphere to a temperature and pressure suitable for the heat treatment.

3, the processing apparatus 100 is provided with a sealed container 101 constructed to have an internal volume of preferably 7 to 18 ^m3 . A processing chamber 103 is provided inside the sealed container 101, and above the sealed container 101, two preheating chambers 102 are provided which are connected to the sealed container 101 via an opening/closing mechanism such as a sliding shutter (not shown) so as to be able to communicate with the processing chamber 103 while maintaining airtightness from the outside of the system.
In FIG. 3, illustration of incidental equipment such as a heating device for adjusting the internal atmosphere of the processing chamber 103, a pressure reducing device, and associated piping is omitted.

In order to subject resin flakes to a heat treatment using such a treatment device 100, it is preferable to, prior to the heat treatment, 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 pressure. At that time, for example, a heated gas (e.g., an inert gas such as _N2 gas) is sprayed into the preheating chamber 102 by providing a spray hole opening on the inner wall surface of the preheating chamber 102, and the spray direction and spray amount are appropriately adjusted to generate an air flow in the preheating chamber 102, and the resin flakes are heated while being stirred, and the preheating chamber 102 is decompressed and sucked, so that at least a part of the impurity components contained in the resin flakes are dispersed and removed outside the system.

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 and, while maintaining airtightness from the outside of the system, 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 heat treatment.

In the processing apparatus 100 shown in FIG. 3, resin flakes are sequentially fed into two preheating chambers 102 so that preheating treatments for raising the temperature of the resin flakes are alternately performed, and the resin flakes are dropped into the processing chamber 103 in the order of the preheating chamber 102 in which the fed resin flakes have been heated to a predetermined temperature, but this is not limited to this. The number of preheating chambers 102 may be one or three or more 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. In any 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 scattered and stacked in layers for each group that is dropped. Then, it is preferable to expose the resin flakes to the internal atmosphere of the processing chamber 103 while the resin flakes are piled up in the processing chamber 103, so that the resin flakes can be subjected to heat treatment.

The processing time for heat-treating the resin flakes is usually 30 minutes or more, and is preferably adjusted appropriately within the range of 1 to 8 hours in order to suppress deterioration of the resin's hue while allowing the solid-state polymerization reaction to proceed. It is preferable to manage the processing time by removing the resin flakes accumulated in the processing chamber 103 from the processing chamber 103 in equal amounts to the amount dropped from the preheating chamber 102, starting from the lower layer of the layered deposit as described above, after the processing time has elapsed. In this case, the time required for the preheating process in the preheating chamber 102 depends on the water content and shape of the resin flakes, and there may be variation in the intervals at which the resin flakes are dropped. Therefore, it is preferable to manage the processing time for each set of dropped resin flakes.

In this way, in order to suitably manage the processing time when heat-treating the resin flakes, the processing apparatus 100 shown in FIG. 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, and although there will be some mixing, it is possible to remove each group of resin flakes dropped from the preheating chamber 102.

As described above, impurity components can be efficiently removed by performing heat treatment under reduced pressure conditions, but it is not preferable for the volatilized or evaporated impurity components to remain in the treatment chamber 103. For this reason, the treatment apparatus 100 shown in FIG. 3 is configured to circulate the gas phase components in the treatment chamber 103, and to include a circulation flow path 106 including a catalyst tank 107 in the path for decomposing low molecular weight impurity components derived from polyester resin, and to connect the circulation flow path 106 to the treatment chamber 103. By configuring the treatment apparatus 100 in this way, it is preferable to reduce the impurity components remaining in the treatment chamber 103 by guiding the gas phase components in the treatment chamber 103 to the circulation flow path 106 and circulating them without damaging the internal atmosphere of the treatment chamber 103, for example, by using an _inert gas such as N 2 gas as a carrier gas.

In addition, when cleaning the impurity components selectively bled out on the surface layer of the resin flakes, the resin flakes taken out of the processing chamber 103 can be liquid cleaned using a rotary or convection type liquid cleaner, or steam cleaned using a pressurized steam convection cleaner, although not shown in the figure. When applying liquid cleaning, the resin flakes after cleaning must be dried, and 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 processing 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 the surface, using the shear heat generated by the roll rotation to semi-weld and press the surface layer of the resin flakes, and further removing organic impurities and moisture from the resin flakes using a rotary forward drying device (open roll type 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 compression rolls in the cooling section downstream of the rolls.

In this embodiment, as described above, the resin flakes are heat-treated under reduced pressure conditions to remove (decontaminate) low molecular weight impurity components, 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 material, biomass material, chemically recycled material, or mechanically recycled material to prepare 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 resin flakes that have been subjected to heat treatment in the mixer 3.

Here, 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 chemically synthesized diol and dicarboxylic acid components 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. In recent recycling technologies, recycling technologies that reuse resin materials for molding include material recycling and chemical recycling. Among recycled materials using material recycling, those that have been washed to make them reusable from recovered polyester resin molded products are referred to as post-consumer recycled materials, and those that have had their intrinsic viscosity adjusted and low molecular weight impurities decontaminated are referred to as mechanical recycled materials. In chemical recycling, the polyester resin contained in the recovered polyester resin molded products is depolymerized and broken down to at least the oligomer components, and the repolymerized polyester resin is called the chemically recycled material.

When preparing raw material resin by mixing the 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 the desired characteristics. For example, the amount of acetaldehyde remaining is 1 to 15 ppm, preferably 1 to 10 ppm, more preferably 1 to 5 ppm, the amount of bishydroxyethyl terephthalate remaining is 1 to 35 ppm, preferably 1 to 30 ppm, more preferably 1 to 20 ppm, the amount of monohydroxyethyl terephthalate remaining is 1 to 35 ppm, preferably 1 to 30 ppm, more preferably 1 to 20 ppm, the amount of cyclic trimer remaining is 6000 ppm or less, preferably 4000 ppm or less, more preferably 3000 ppm or less, and when the mass of the preform is 14 to 50 g, it is possible to adjust so that a preform having an L ^* value of 70 to 90 and a b ^* value of 2 to 18 in the L ^* a ^* b ^* color system can be produced. For this purpose, it is preferable to mix 11 to 400 parts by weight of resin pellets with respect to 100 parts by weight of resin flakes.

Here, the remaining amount and intrinsic viscosity of acetaldehyde, bishydroxyethyl terephthalate (BHET), monohydroxyethyl terephthalate (MHET), and cyclic trimer (CT) can be determined, for example, as follows.

<Residual amount of acetaldehyde>
A piece cut from the preform is used as a sample, and 1.0 g of the sample is weighed out and placed in a glass bottle, and 5.0 mL of pure water is added and sealed. This suspension is heated for 60 minutes in an oven adjusted to 120°C, and then cooled in ice water. 1.0 mL of the supernatant of the suspension is taken, and 0.2 mL of a 0.1% concentration 2,4-dinitrophenylhydrazine-phosphate solution is added to this, and the mixture is left for 30 minutes and measured by high performance liquid chromatography. At the same time, the standard solution is also measured, and the acetaldehyde content is calculated based on the obtained calibration curve.

<Remaining Amounts of BHET, MHET, and CT>
A piece cut from the preform is used as a sample, and 0.2 g of the sample is weighed out and 1 mL of a mixed solvent of hexafluoroisopropanol and chloroform (weight ratio 1/1) is added to it to completely dissolve it. After adding 4 mL of chloroform to the solution, 5 mL of acetonitrile is gradually added and left for 3 hours to precipitate the PET polymer. 1 mL is taken from this suspension and filtered through a membrane filter with a pore size of 0.45 μm, and the filtrate is measured by high performance liquid chromatography. At the same time, the standard solution is also measured, and the contents of MHET, BHET and CT in the pellet are calculated based on the obtained calibration curve.

<Intrinsic Viscosity>
A piece cut from the preform is used as a sample, and the 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. The dissolved solution is cooled to room temperature, and the relative viscosity is measured using a relative viscometer adjusted to 30°C, to determine the intrinsic viscosity.

The L ^* value and b ^* value in the L ^* a ^* b ^* color system are measured at the body of the preform as the measurement site using a spectrocolorimeter under the measurement conditions of a D65 light source and a 2° visual field.

In addition, when preparing the raw material resin, the resin flakes taken out from the processing chamber 103 as described above may be mixed with the resin pellets as they are, or 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 when the resin flakes are heat-treated as described above, the resin flakes are taken out from the processing chamber 103 intermittently according to the interval at which the operation of dropping the resin flakes from the preheating chamber 102 into the processing chamber 103 is repeated, and the amount of resin flakes taken out each time also depends on the processing amount in the preheating chamber 102. In such a case, especially if there is variation in the interval at which the operation of dropping the resin flakes is repeated, the amount of resin flakes taken out per unit time will not be constant. For this reason, if the resin flakes are stored in the buffer tank 300 and can be taken out of the buffer tank 300 in fixed amounts at any interval, it becomes easy to adjust the ratio at which they are mixed with the resin pellets. Furthermore, in the plasticization process described below, the amount of raw 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 kept constant.

When installing the buffer tank 300, it is preferable to adjust the internal volume of the buffer tank 300 as appropriate so that more resin flakes can be stored. By doing this, even if a problem occurs in a subsequent process after the process of preparing the raw material resin, causing the subsequent process to stop, the heating process of the resin flakes can continue without being stopped, and the amount that cannot be sent to the subsequent process can be stored in the buffer tank 300.

In addition, in anticipation of such trouble occurring or changes in circumstances such as the processing speed of the subsequent process speeding up or slowing down, 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.

By doing this, for example, when the subsequent process is stopped, the resin flakes taken out of the processing 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 is increased, the resin flakes evacuated to the relief tank 400 can be transported to the buffer tank 300 together with the resin flakes taken out of the processing chamber 103. When the processing speed of the subsequent process is decreased, a portion of the resin flakes taken out of the processing chamber 103 can be evacuated to the relief tank 400, and the amount of resin flakes transported to the buffer tank 300 can be appropriately adjusted. In this way, when evacuating the resin flakes to the relief tank 400 as necessary, it is preferable that the internal atmosphere of the relief tank 400 be 100°C or higher so that the resin flakes do not become hydrated.

Then, the prepared raw material resin is plasticized. At that 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 from 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 deterioration, thermal decomposition, and depolymerization of the resin.

When plasticizing raw material resin using a twin-screw extruder, it is preferable to configure the twin-screw extruder with a vent port, and to decompress and suck out the gaseous phase components containing low molecular weight impurities derived from polyester resin that remain in the twin-screw extruder through a vent port provided through the heating cylinder, for example, and discharge them from the system. This makes it possible to 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 the operation of decompression 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 polyethylene terephthalate twin-screw extruder is 300°C, the reduced vacuum pressure at which cyclic oligomers can sublime (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 a counter-rotating (different) type of screw rotation rather than one with the same (same) type of screw rotation.

In this embodiment, after going through the above steps, the molten resin obtained by plasticizing the raw material resin is supplied to the injection molding device 500 to injection mold a preform while removing foreign matter from the molten resin obtained by plasticizing the raw material resin. 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. Furthermore, the specific configuration of the injection molding device 500 is not particularly limited, and for example, the preform can be injection molded using an injection molding device 500 equipped with at least one injection pot and a preform mold configured to measure the supplied molten resin and then inject a fixed amount of molten resin.

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

According to this embodiment, preforms with the desired characteristics can be produced more efficiently while using resin flakes made by crushing recovered polyester resin molded products into flakes.

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

In this embodiment, similar to the first embodiment, resin flakes are prepared by crushing the recovered polyester resin molded products into flakes.

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

The following describes this embodiment, focusing on the differences from the first embodiment, while omitting explanations that overlap with the first embodiment as appropriate.

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 resin in the raw material resin, particularly the polyester resin that forms the resin flakes, is advanced and crystallization is promoted in their original form.

In addition, when the raw material resin is subjected to a heat treatment, a solid-phase polymerization reaction also proceeds in the polyester resin that forms the resin pellets contained in the raw material resin. This increases the degree of polymerization of the polyester resin, making it easier to adjust the intrinsic viscosity of the raw material resin as a whole, particularly when the resin pellets contain post-consumer recycled materials. Furthermore, by subjecting the resin flakes to a heat treatment under reduced pressure conditions together with the resin flakes, the moisture sorbed in the resin pellets can also be efficiently removed, reducing the moisture content of the entire raw material resin. As a result, the drying process can be omitted when plasticizing the raw material resin.

Here, prior to the heat treatment, the 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 to prepare the raw material resin, and the ratio of the two can be appropriately adjusted in the same manner as in the first embodiment so that a preform with the desired characteristics can be manufactured.

In this embodiment, the specific method of subjecting the raw material resin to the heat treatment is not particularly limited. For example, it is preferable to subject the raw material resin to the heat treatment using a treatment device 100 as shown in FIG. 3 in the same manner as the heat treatment of the resin flakes in the first embodiment.
In addition, the explanation of the heat treatment of raw material resin in this embodiment can be applied to the explanation of the heat treatment of resin flakes in the first embodiment by appropriately replacing ``resin flakes'' with ``raw material resin.''

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 the resin flakes were heat-treated in the first embodiment. At that time, the raw material resin that has been heat-treated is fed into the extruder 200, and plasticized while being melted and kneaded by the heat from the heating cylinder and the shear heat from the screw, in the same manner as the raw material resin was plasticized in the first embodiment.

The raw material resin that has been subjected to heat treatment using the processing device 100 shown in FIG. 3 and removed from the treatment 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 treatment chamber 103 according to the interval at which the operation of dropping the raw material resin from the preheating chamber 102 into the treatment chamber 103 is repeated, and the amount of raw material resin removed each time also depends on the amount of processing in the preheating chamber 102. In such a case, particularly if there is variation in the interval at which the operation of dropping the raw material resin is repeated, 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 kept constant.

When installing the buffer tank 300, it is preferable to adjust the internal volume of the buffer tank 300 as necessary so that a larger amount of raw material resin can be stored. By doing this, even if a problem occurs in the process subsequent to the process of plasticizing the raw material resin, causing the subsequent process to stop, the heating process of the raw material resin can continue without being stopped, and the amount that cannot be sent to the subsequent process can be stored in the buffer tank 300.

Also, in anticipation of such trouble occurring or changes in circumstances such as the processing speed of the subsequent process speeding up or slowing down, 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.

By doing this, for example, when the subsequent process is stopped, the raw material resin taken out from the processing 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 is increased, the raw material resin evacuated to the relief tank 400 can be transported to the buffer tank 300 together with the raw material resin taken out from the processing chamber 103. When the processing speed of the subsequent process is decreased, a part of the raw material resin taken out from the processing 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 appropriately adjusted. In this way, when evacuating the raw material resin to the relief tank 400 as necessary, the internal atmosphere of the relief tank 400 is preferably 100°C or higher so that the raw material resin does not become hydrated.

In this embodiment, after going through the above steps, the molten resin obtained by plasticizing the raw material resin is supplied to the injection molding device 500 to injection mold a preform while removing foreign matter from the molten resin obtained by plasticizing the raw material resin. As in the first embodiment, foreign matter can be removed from the molten resin obtained by plasticizing the raw material resin by, for example, 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 device 500 is not particularly limited, and, for example, as in the first embodiment, the preform can be injection molded using the injection molding device 500 equipped with at least one injection pot and a preform mold configured to measure the supplied molten resin and then inject a certain amount of molten resin.

According to this embodiment, preforms with the desired characteristics can be produced more efficiently while using resin flakes made by crushing recovered polyester resin molded products into flakes.

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.

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 (19)

The recovered polyester resin molded products 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 producing 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 device; and injection molding the preform. The method for manufacturing a preform according to claim 1, in which the resin flakes are heat-treated in an atmosphere at a temperature of 160 to 240°C and reduced pressure to 1000 Pa or less. The recovered polyester resin molded products are crushed into flakes to obtain resin flakes, and resin pellets made of at least one of virgin polyester resin, biomass material, chemically recycled material, mechanically recycled material, and post-consumer recycled material are mixed 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 producing 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 device; and injection molding the preform. The method for manufacturing a preform according to claim 3, in which the raw material resin is heat-treated in an atmosphere at a temperature of 160 to 240°C and reduced pressure to 1000 Pa or less. The method for manufacturing a preform according to claim 1 or 2, in which the resin flakes are put into a preheating chamber, the resin flakes are heated to a predetermined temperature, the preheating chamber is depressurized to a predetermined pressure, 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 piled up in the processing chamber and subjected to a heat treatment. The method for manufacturing a preform according to claim 5, in which the resin flakes that have been subjected to the heat treatment 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 that have been piled up in the treatment chamber, and then mixed with the resin pellets to prepare the raw material resin. The method for manufacturing a preform according to claim 5, in which the resin flakes that have been subjected to the heat treatment 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 that have been piled up in the treatment chamber, and stored in a buffer tank, and then mixed with the resin pellets to prepare the raw material resin. The method for manufacturing preforms according to claim 7, in which a relief tank is installed midway along the transport path for transporting the resin flakes removed from the processing chamber to the buffer tank, and the resin flakes are transported to the buffer tank while being able to be evacuated to the relief tank during transport. The method for manufacturing a preform according to any one of claims 5 to 8, in which the resin flakes are sequentially fed into a plurality of preheating chambers, and the resin flakes are dropped into the processing chamber in the order of the preheating chamber in which the fed resin flakes have been heated to a predetermined temperature. The method for manufacturing a preform according to any one of claims 5 to 9, in which 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. The method for manufacturing a preform according to claim 3 or 4, in which the raw material resin is poured 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 the raw material resin is 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 raw material resin is piled up in the processing chamber and subjected to a heat treatment. The method for manufacturing a preform according to claim 11, in which 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. The method for manufacturing a preform according to claim 11, in which 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. The method for manufacturing preforms according to claim 13, in which 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, and the raw material resin is transported to the buffer tank while being able to be evacuated to the relief tank during transport. The method for manufacturing a preform according to any one of claims 11 to 14, in which the raw material resin is sequentially fed into a plurality of preheating chambers, and the raw material resin is dropped into the processing chamber in the order of the preheating chamber in which the fed raw material resin has been heated to a predetermined temperature. The method for manufacturing a preform according to any one of claims 11 to 15, in which 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 inside of the preheating chamber is depressurized. The method for manufacturing a preform according to any one of claims 5 to 16, wherein the treatment chamber is connected to a circulation flow path that allows the gaseous components in the treatment chamber to circulate and includes a catalyst layer in the path that decomposes low molecular weight components derived from polyester resin, and the gaseous components in the treatment chamber are guided to the circulation flow path and circulated, thereby reducing the low molecular weight components remaining in the treatment chamber. The method for manufacturing a preform according to any one of claims 1 to 17, in which the raw material resin is plasticized by feeding it into a twin-screw extruder. The method for producing a preform according to claim 18, wherein the twin-screw extruder is provided with a vent port, and gas phase components containing low molecular weight components derived from the polyester resin that remain in the twin-screw extruder are sucked under reduced pressure through the vent port and discharged outside the system.

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