Method for producing granulated material for chemical cycle, and granulated material for chemical cycle

Abstract

Provided are: a method for forming polyester waste into a granulated material suitable for a depolymerization step in a chemical cycle of polyester waste; and a granulated material for such a chemical cycle. The present invention provides a method for producing a granulated material for a chemical cycle, the method comprising pulverizing polyester waste, melt-extruding the pulverized polyester waste, cooling the melt-extruded polyester waste by air and solidifying the polyester waste, and pulverizing the solidified polyester waste to form a granulated material.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing granules for chemical recycling and to granules for chemical recycling. Background Technology

[0002] Polyesters such as polyethylene terephthalate (PET) are widely produced and used in the food industry due to their excellent chemical stability, serving as materials for everyday life, including fibers, films, and containers, as well as bottles for drinking water and carbonated beverages. Various studies have been conducted to date on the recycling of waste generated during the production and use of polyesters.

[0003] The recycling of polyester waste can be broadly categorized into three types: material recycling, thermal recycling, and chemical recycling.

[0004] Material recycling involves transforming polyester waste into low-quality materials through melt molding. If this process is repeated multiple times, the quality further deteriorates, ultimately making waste unavoidable.

[0005] Thermal cycling involves reusing the heat of combustion generated during the incineration of polyester waste. However, thermal cycling cannot recycle polyester or its raw materials and also produces carbon dioxide from incineration. Therefore, from the perspective of resource conservation and environmental protection, it cannot always be considered the preferred option.

[0006] Chemical recycling involves depolymerizing polyester waste into monomers, which are the building blocks of polyester, and then reusing these monomers in polyester synthesis. One example of chemical recycling methods for polyester waste is the glycolysis-transesterification process, which involves depolymerizing (alcoholysis) polyester waste in the presence of ethylene glycol (EG) to produce bis-2-hydroxyethyl terephthalate (BHET), followed by transesterification with methanol to convert it into dimethyl terephthalate (DMT) and ethylene glycol. Chemical recycling allows for the resynthesis of polyester without compromising quality, thus enabling true resource reuse.

[0007] Patent document 1 (Japanese Patent Application Publication No. 2003-128626) describes "a method for recovering terephthalic acid from polyester waste, characterized in that, when recovering terephthalic acid from polyester fiber waste which is substantially composed of poly(alkyl terephthalate) fibers, natural fibers, and / or chemical fibers other than poly(alkyl terephthalate) fibers, a pretreatment step and a reaction step are combined. In the pretreatment step, the polyester fiber waste is analyzed using a discrimination device, and the substances identified as polyester are crushed and granulated to form crude polyester, and the crude polyester is conveyed to the reaction step." The reaction step includes the following steps (a) to (j): (a) depolymerization step, (b) foreign matter removal step, (c) filtration and screening step, (d) concentration step, (e) transesterification reaction step, (f) purification step, (g) hydrolysis reaction step, (h) separation step, (i) displacement step, and (j) slurry adjustment step.

[0008] Patent document 2 (Japanese Patent Publication No. 2021-533211) describes "a method for recycling waste polyester material, characterized in that it includes: a material pretreatment step, in which the waste polyester material is subjected to dehydration and deoxidation treatment to obtain waste polyester raw material; a melt feeding step, in which the waste polyester raw material is melted to obtain molten waste polyester, which is continuously fed into an alcoholysis reactor, and ethylene glycol as an alcoholysis agent is added during the melting process of the waste polyester raw material for pre-alcoholization; an alcoholysis step, in which the molten waste polyester, alcoholysis agent and alcoholysis catalyst are subjected to a depolymerization reaction in an alcoholysis reactor to obtain alcoholysis product; and an ester exchange step, in which the ester exchange agent, ester exchange catalyst and the alcoholysis product are subjected to an ester exchange reaction in an ester exchange reactor."

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2003-128626

[0012] Patent Document 2: Japanese Patent Publication No. 2021-533211 Summary of the Invention

[0013] From the viewpoints of operability and filling efficiency of the reaction unit, polyester waste is preferably crushed and granulated before the depolymerization process. On the other hand, the depolymerization reaction is a solid-liquid heterogeneous reaction between solid polyester and liquid ethylene glycol, therefore the shape and properties of the granulated polyester waste have a significant impact on the reaction efficiency of the depolymerization reaction.

[0014] This disclosure provides a method for forming polyester waste into granules suitable for a depolymerization process in a chemical cycle of polyester waste, and granules for such a chemical cycle.

[0015] The inventors discovered that by melting and extruding pulverized polyester waste and then solidifying it through air cooling, granules with high reactivity in the depolymerization reaction and excellent operability and filling efficiency into the reaction device can be obtained, thus completing the present invention.

[0016] This disclosure includes the following methods.

[0017] [Method 1]

[0018] A method for manufacturing granules for chemical recycling includes:

[0019] Shred the polyester waste.

[0020] The pulverized polyester waste is melt-extruded.

[0021] The above-mentioned polyester waste, after melt extrusion, is solidified by air cooling, and

[0022] The solidified polyester waste is crushed to form granules.

[0023] [Method 2]

[0024] According to the method of method 1, the above-mentioned melt extrusion and curing are performed using a plastic compactor.

[0025] [Method 3]

[0026] The method according to method 1 or 2 further includes grading the granules.

[0027] [Method 4]

[0028] According to the method of method 3, the method further includes reusing the residue generated by the above-mentioned grading in the above-mentioned melt extrusion.

[0029] [Method 5]

[0030] According to the method of any one of methods 1 to 4, the ratio of the apparent density to the bulk density of the granules (apparent density / bulk density) is 1.80 to 2.40.

[0031] [Method 6]

[0032] According to the method described in any of methods 1 to 5, the apparent density of the granules is 1.23 g / cm³. 3 ~1.33g / cm 3 Its bulk density is 0.60 g / cm³. 3 ~0.67g / cm 3 .

[0033] [Method 7]

[0034] The method according to any one of methods 1 to 6, wherein the granules have a closed cavity inside.

[0035] [Method 8]

[0036] A chemically recycled granule is a chemically recycled granule containing a compressed and cured polyester waste.

[0037] The ratio of apparent density to bulk density (apparent density / bulk density) of the above granules is 1.80 to 2.40.

[0038] [Method 9]

[0039] According to method 8, the granules for chemical recycling have an apparent density of 1.23 g / cm³. 3 ~1.33g / cm 3 Its bulk density is 0.60 g / cm³. 3 ~0.67g / cm 3 .

[0040] [Method 10]

[0041] The granules for chemical recycling as described in method 8 or 9, wherein the content of granules with a particle size of 10 mm or less and a particle size of 900 μm or less is 0.2% by mass or less.

[0042] [Method 11]

[0043] The chemical recycling granules according to any one of methods 8 to 10, wherein the granules have a closed cavity inside.

[0044] According to the present invention, a chemically recycled granule for polyester waste can be provided, which has high reactivity in depolymerization reactions and excellent operability and filling efficiency into the reaction apparatus.

[0045] It should be noted that the above description should not be construed as disclosing all embodiments of the present invention or all advantages related to the present invention. Attached Figure Description

[0046] Figure 1 The curves represent the depolymerization reactivity of the samples from Example 1, Comparative Example 1, and Comparative Example 2.

[0047] Figure 2 This is a photograph of the granules from Example 1.

[0048] Figure 3 This is a photograph of the granules from Comparative Example 1. Detailed Implementation

[0049] The present invention will now be described in more detail for the purpose of illustrating representative embodiments of the invention, but the invention is not limited to these embodiments.

[0050] In this disclosure, true density, apparent density, and bulk density are defined according to the definitions in JIS R 1634:1998 by the following formulas. External volume refers to the total volume including closed and open pores, excluding the solid portion of the sample. Apparent volume refers to the volume after removing open pores from the external volume of the sample. If there are closed cavities (closed pores) inside the particles, the apparent density is less than the true density. If there are no closed cavities (closed pores) inside the particles, the apparent density is approximately equal to the true density regardless of whether there are cavities (open pores) communicating with the outside on the particle surface.

[0051] True density (g / cm³) 3 = Mass of the sample (g) / Volume occupied by the sample only (cm³) 3 )

[0052] Apparent density (g / cm³) 3 = Mass of sample (g) / Apparent volume of sample (cm³) 3 )

[0053] Bulk density (g / cm³) 3 = Mass of sample (g) / External volume of sample (cm²) 3 )

[0054] [Method for manufacturing granules for chemical recycling]

[0055] One embodiment of the method for manufacturing granules for chemical recycling includes:

[0056] Shred the polyester waste.

[0057] The pulverized polyester waste is melt-extruded.

[0058] The above-mentioned polyester waste, after melt extrusion, is solidified by air cooling, and

[0059] The solidified polyester waste is crushed to form granules.

[0060] <Pulverizing process>

[0061] There are no particular limitations on the form of polyester waste. Examples include carpets, carpet fibers, yarns, woven fabrics, knitted fabrics, ropes, cords, twists, fillings, filter media, bottles, and membranes, which are discharged as industrial waste or used materials or products. Polyester waste can also include waste and residues generated during product manufacturing.

[0062] Examples of polyesters included in polyester waste include polyethylene terephthalate (PET), polypropylene terephthalate (PTT), and polybutylene terephthalate (PBT). PET is preferred as the polyester included in the polyester waste.

[0063] Polyester waste may contain other materials besides polyester, such as nylon, polyethylene, polypropylene, and cotton, but these materials do not participate in chemical recycling. The polyester content in polyester waste is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more. Polyester waste with low polyester content can be excluded at the raw material receiving stage. For example, the composition of polyester waste can be analyzed using absorption spectra obtained by near-infrared spectroscopy, and polyester waste that does not have the desired composition can be excluded from the next process.

[0064] Polyester waste is pulverized to a size suitable for feeding into the extruder during the melt extrusion process. The size of the pulverized material can be appropriately set depending on the type of extruder, typically ranging from 2 mm to 15 mm. Pulverization can be performed, for example, using a single-shaft pulverizer. A two-stage pulverizer can also be used to improve pulverization efficiency. In the case of using a two-stage pulverizer, for example, the polyester waste is coarsely pulverized to a size of 30 mm to 150 mm using a primary pulverizer, and then pulverized to a size of 2 mm to 15 mm using a secondary pulverizer. In this disclosure, the size of the pulverized material is defined by the smallest mesh size of the mesh through which the pulverized material can pass when it falls freely onto the metal mesh. For example, the size of the pulverized material passing through a 15 mm square metal mesh is less than 15 mm, while the size of the pulverized material not passing through a 2 mm square metal mesh exceeds 2 mm.

[0065] <Melted Extrusion Process>

[0066] Next, the pulverized polyester waste is melt-extruded. The polyester waste is compressed through melt extrusion into a state suitable for granulation. Melt extrusion can be performed using a standard single-screw or twin-screw extruder (extruder). In melt extrusion, as the polyester waste moves within the extruder barrel under pressure, at least the surface of the polyester waste melts due to frictional heat generated on its surface. The molten polyester acts as a binder, compressing the polyester waste. The extruder's barrel inner diameter, screw shape, motor output, die shape, etc., are appropriately designed to at least melt the surface of the polyester waste.

[0067] The diameter of the melt extrudate is preferably 2 mm to 20 mm, more preferably 3 mm to 15 mm, and even more preferably 4 mm to 10 mm. The diameter of the melt extrudate is determined by the shape and size of the die opening.

[0068] <Air-cooled curing process>

[0069] Polyester waste after melt extrusion is solidified by air cooling. While not bound by any theory, surface solidification is slower when solidifying melt-extruded polyester waste by air cooling compared to water cooling. During the melt extrusion process, the polyester waste, under pressure, is released into atmospheric pressure after melt extrusion. Therefore, the evaporation of moisture and other substances that may be present inside the melt extrudate competes with surface solidification. Thus, it is believed that cavities formed inside the compressed solidified material due to moisture remaining inside the melt extrudate are formed. Furthermore, during the melt extrusion process, air enters the interior of the polyester waste, and the melt extrudate is solidified by air cooling while enclosed in air, sometimes resulting in cavities inside the compressed solidified material. Such internal cavities are advantageous in improving the contact efficiency between the granules and ethylene glycol during the depolymerization reaction. Additionally, because surface solidification is slow, although there may be fine irregularities or depressions on the surface of the compressed solidified material, the surface is macroscopically smooth. Therefore, despite the presence of internal cavities and thus a lower apparent density, the bulk density of the granules can be increased, resulting in improved operability and filling efficiency into the reaction apparatus. Furthermore, air-cooled curing reduces the amount of moisture remaining inside or adhering to the surface of the granules, thereby simplifying or eliminating the need for subsequent drying processes.

[0070] Air cooling can be achieved by directly placing the molten extrudate, or by forcing it while simultaneously bringing air or other gases into contact with the molten extrudate.

[0071] Plastic Compactor

[0072] Melt extrusion and air-cooled curing are preferably performed using a plastic compactor. By using a plastic compactor, the apparent density, bulk density, particle size and particle size distribution, moisture content and other physical properties of the granules can be stabilized regardless of the type of polyester waste input.

[0073] The plastic compactor has a rotating compression disc and a fixed compression disc, with a compression zone defined between them. The fixed compression disc is connected to a mixing guide with interchangeable threaded fittings. Crushed polyester waste is fed from a feed hopper to the mixing guide and continuously fed into the compression zone of the plastic compactor through the center of the fixed compression disc. The polyester waste is rapidly heated within the compression zone by friction generated from contact with these compression discs and by friction within the polyester waste itself. The heated polyester waste melts at least on its surface, extending towards the outer periphery of the compression disc, forming an elongated, worm-like shape. Heating within the compression zone further reduces the moisture content of the polyester waste. The elongated molten extrusion, ejected from the outer periphery of the compression disc of the plastic compactor, falls while being cooled by air and is collected in a collection device. Plastic compactors are commercially available, for example, from Herbold Meckesheim GmbH (Meckesheim, Baden-Württemberg, Germany) in the form of the Plastcompactor HV series.

[0074] In melt extrusion and air-cooled curing using a plastic compactor, the diameter of the elongated melt extrudate is approximately determined by the width of the grooves formed on the surface of the fixed compression disc. Furthermore, the heated polyester waste extends towards the outer periphery of the compression disc while in contact with the grooves, resulting in a relatively smooth surface for the melt extrudate. Therefore, by using a plastic compactor, granules with uniform particle size and a relatively smooth surface can be obtained. Such granules have a small angle of repose, thus offering excellent operability.

[0075] <Pellet Formation Process>

[0076] The cured polyester waste (compressed cured material) is transported to a pulverizer using compressed air or similar means to be pulverized into granules of the desired size. A single-shaft pulverizer can be used, for example. Pulverization is preferably carried out with the granules having a particle size of 10 mm or less.

[0077] <Grading Process>

[0078] The resulting granules can be graded to obtain granules with a narrower particle size distribution. Granules with a narrow particle size distribution exhibit excellent operability and filling efficiency into the reaction apparatus.

[0079] Grading can be performed by sieving. Sieving can separate and remove granules that exceed the desired size, while granules that are smaller than the desired size are sent to the next process. Granules that exceed the desired size can be recycled as residue and returned to the crushing process.

[0080] After grading by sieving, air classifiers such as sawtooth classifiers can be used to separate and remove granules smaller than the desired size, while granules larger than the desired size are sent to the next process. Alternatively, granules smaller than the desired size can be recycled as residue and reused in the melt extrusion process.

[0081] [Granulated material for chemical recycling]

[0082] One embodiment of the chemical recycling granules comprises a compressed and cured polyester waste. The ratio of apparent density to bulk density (apparent density / bulk density) of the granules is preferably 1.80 to 2.40, more preferably 1.84 to 2.22, and particularly preferably 1.92 to 2.10. By setting the above ratio to 1.84 to 2.22, the granules can exhibit the excellent operability and filling efficiency of the reaction apparatus as described above, while also exhibiting good depolymerization reactivity as described later. If the value of the above ratio deviates significantly from the above range due to either apparent density or bulk density being too large or too small, the granules cannot achieve all the above effects at a high level.

[0083] While not bound by any theoretical constraints, the granules of this embodiment are considered to have closed cavities inside because their apparent density is lower than that of polyester particles. These closed cavities are exposed from the surface of the granules as the depolymerization reaction proceeds, thus improving the contact efficiency between the granules and ethylene glycol. On the other hand, since the granules are heavier than ethylene glycol (the specific gravity of ethylene glycol is 1.116 at 20°C), they settle in the reaction liquid of the depolymerization process. This also contributes to improving the contact efficiency between the granules and ethylene glycol.

[0084] Furthermore, the granules of this embodiment have a high bulk density, thus enabling the transport and storage of larger quantities of granules in less space. They are less prone to bridging in storage devices such as hoppers, resulting in excellent operability and filling efficiency into the reaction apparatus. It is believed that granules with high bulk density have a smooth surface with few bumps, making them less susceptible to the surface tension of the reaction liquid. Therefore, the granules of this embodiment readily and quickly adapt to the reaction liquid in the depolymerization process and disperse within it. Additionally, it reduces the solid-liquid volume ratio (solid volume / liquid volume) in the reaction liquid, lowering the load on stirring power during the depolymerization process.

[0085] In this disclosure, the apparent density of the granules is determined using a helium hydrometer method. Specifically, the granules are placed in a volume V at a temperature of 25°C. C (m) 3In the sample chamber, helium gas is introduced into the sample chamber to purge and displace the pores of the granulated material. After displacement, the sample chamber is pressurized to a pressure P1 (Pa) above atmospheric pressure and then sealed. Once the pressure inside the sample chamber stabilizes, the solenoid valve located downstream of the sample chamber is opened, allowing helium gas to flow into the volume V. A (m) 3 Helium gas is introduced into the comparison chamber of the sample chamber, and the pressure P2 (Pa) in both the sample and comparison chambers is measured. The apparent volume V of the granules is calculated using the following formula based on the ideal gas law. P (m) 3 The apparent density of the granules is calculated from the obtained apparent volume and the mass of the granules.

[0086] P1(V) C -V P )=n1RT

[0087] P2(V) C +V A -V P )=n1RT

[0088] ⇔P1(V C -V P ) = P2(V C +V A -V P )

[0089] ⇔V P =V C -V A / [(P1 / P2)-1]

[0090] The apparent density of the granules is preferably 1.23 g / cm³. 3 ~1.33g / cm 3 More preferably, it is 1.25 g / cm³. 3 ~1.30g / cm 3 .

[0091] In this disclosure, the bulk density of the granules is determined by the mass of the granules placed in a container of a specified volume. Specifically, the granules are filled into a 1L graduated cylinder at room temperature and normal pressure, and the mass of the filled granules is determined by the mass change before and after filling, thereby calculating the bulk density.

[0092] The preferred bulk density of the granules is 0.60 g / cm³. 3 ~0.67g / cm 3 More preferably, it is 0.62 g / cm³. 3 ~0.65g / cm 3 .

[0093] In one embodiment, the granules have a closed cavity inside. The presence of a closed cavity can be confirmed by image analysis of X-ray CT images.

[0094] The ratio of the apparent density of the granules to the true density of the polyester contained in the granules (apparent density of granules / true density of polyester) is preferably 0.90 to 0.99, more preferably 0.91 to 0.96. By setting this ratio to 0.90 or higher, the granules readily sink into the reaction solution of the depolymerization process. As a result, the contact area between the reaction solution and the granules is increased immediately after the granules are added to the reaction solution, promoting the depolymerization reaction. By setting this ratio to 0.99 or lower, the depolymerization reactivity is improved compared to PET resin particles.

[0095] The particle size of the granules is preferably 10 mm or less. In this disclosure, the particle size of the granules is the sieve diameter measured using a metal mesh sieve as specified in JIS Z 8801-1:2019. By making the particle size of the granules 10 mm or less, operability and filling efficiency into the reaction apparatus can be improved.

[0096] The content of granules with a particle size of 900 μm or less is preferably 0.2% by mass or less. This prevents the granules from scattering during operation and also suppresses the granules from floating to the surface of the reaction liquid during the depolymerization process.

[0097] One embodiment of the granules substantially does not contain a binder. Here, "substantially does not contain" means that the binder content is less than 1% by mass, preferably less than 0.5% by mass, more preferably less than 0.1% by mass. Examples of binders include thermoplastic resins such as polyethylene, polypropylene, acrylonitrile-butadiene-styrene copolymer (ABS), and wood flour. Granules substantially free of binders can provide monomers with fewer impurities after the depolymerization reaction.

[0098] [Instructions for use of granules for chemical recycling]

[0099] The chemically recycled granules are applicable to the recycling of polyester waste based on the glycolysis-transesterification reaction using ethylene glycol (EG).

[0100] The method for manufacturing granules for chemical recycling disclosed herein, and the granules themselves, are not limited to chemical recycling applications, but can also be applied and used for other purposes.

[0101] Example

[0102] The following embodiments illustrate specific implementations of this disclosure, but the invention is not limited thereto. Unless otherwise specified, all parts and percentages, including those in tables, are by mass. Numerical values ​​inherently include errors caused by the measuring principle and measuring apparatus. All numerical values, including those listed in tables, are expressed as significant figures after conventional rounding.

[0103] [Example 1]

[0104] The chemical recycling granules of Example 1 were prepared according to the following steps: 100% polyester raw fabric and 100% cotton raw fabric were uniformly mixed to prepare a raw material of 95% polyester by mass and 5% cotton by mass, on average. The raw material was pulverized to less than 15 mm, compressed in a plastic compactor, and melted by frictional heat. The molten raw material was extruded between two discs rotating at 425 rpm through a groove with a 5.2 mm gap. The molten extrudate that passed through the groove was cut into appropriate lengths under centrifugal force and rapidly cooled and solidified in air. The resulting compressed and solidified material was pulverized using a pulverizer to obtain granules with a particle size of less than 10 mm. The apparent density of the granules of Example 1 was 1.291 g / cm³. 3 Its bulk density is 0.632 g / cm³. 3 The content of granules with a particle size of less than 10 mm and less than 900 μm is less than 0.2% by mass.

[0105] [Comparative Example 1]

[0106] As Comparative Example 1, granules (foam material, manufactured by ZHANGJIAGANG FIBRE MINGHONG MACHINERY FACTORY) prepared by melt extrusion of polyester waste followed by rapid cooling in water were used. The apparent density of the granules in Comparative Example 1 was 1.335 g / cm³. 3 Its bulk density is 0.450 g / cm³. 3 The particle size is less than 40 mm. The granules of Comparative Example 1 have large irregularities on the surface formed when rapidly cooled in water, and the particle size distribution is also larger than that of the granules of Example 1.

[0107] [Comparative Example 2]

[0108] As Comparative Example 2, PET resin granules (semi-dull, manufactured by Zhejiang Jiaren New Materials Co., Ltd.) were used. The apparent density of the PET resin granules in Comparative Example 2 was 1.345 g / cm³. 3 Its bulk density is 0.80 g / cm³. 3 The particle size is less than 7mm.

[0109] The depolymerization reactivity of the granules of Example 1, the granules of Comparative Example 1, and the PET resin particles of Comparative Example 2 was evaluated according to the following steps. The sample and ethylene glycol were added to a 1L flask in a mass ratio ranging from 1:2 to 1:3. Under the same conditions, a single-stage propeller was used as a stirrer, and the rotation speed was slowly increased to 200 rpm or 300 rpm while stirring the mixture and heating it to 190°C. After maintaining the temperature of the mixture at 190°C and stirring continuously for a period of time, a depolymerization catalyst was added to the flask. The catalyst addition time was set to 0 minutes, and the reaction solution was continuously sampled at 190°C for 4 hours while stirring continuously. The amount of bis(hydroxyethyl) terephthalate (BHET) in the flask was quantified by gas chromatography.

[0110] Figure 1 The depolymerization reactivity of the samples from Example 1, Comparative Example 1, and Comparative Example 2 is shown as a curve. The horizontal axis represents the reaction time (minutes), with the catalyst added at 0 minutes. The vertical axis represents the mass (mol) of BHET in the flask. When the catalyst is added to the flask, the depolymerization of the polyester proceeds slowly, and BHET increases rapidly again (from 0 minutes to 50 minutes). The depolymerization reaction rates (slopes) in the initial stages of the reactions of Example 1 and Comparative Example 1 are the same, while the depolymerization reaction in Comparative Example 2 proceeds slowly in the initial stages. These results indicate that the chemically recycled granules of Example 1 have the same depolymerization reactivity as the granules of Comparative Example 1.

[0111] Furthermore, compared to the granules of Comparative Example 1, the granules for chemical recycling in Example 1, despite having a lower apparent density, have excellent flow characteristics as granules due to their high bulk density, resulting in superior operability and filling efficiency into the reaction apparatus.

[0112] Figure 2 and Figure 3 The images show photographs of the granules from Example 1 and Comparative Example 1, respectively. Figure 2 As shown, the granules used in the chemical recycling process of Example 1 have a uniform particle size and a relatively smooth surface. Furthermore, a hardness that does not deform under certain pressure was confirmed. On the other hand, as... Figure 3 As shown, the granules of Comparative Example 1 have uneven surfaces formed by rapid water cooling, and compared with the granules for chemical recycling of Example 1, they are more prone to deformation or dispersion due to external pressure.

[0113] It will be apparent to those skilled in the art that various modifications can be made to the above-described embodiments and examples without departing from the basic principles of the invention. Furthermore, it will be apparent to those skilled in the art that various improvements and modifications can be implemented without departing from the spirit and scope of the invention.

[0114] Industrial availability

[0115] The methods and granules disclosed herein are applicable to the chemical recycling of polyester waste.

Claims

1. A method for manufacturing granules for chemical recycling, comprising: Shred the polyester waste. The pulverized polyester waste is melt-extruded. The polyester waste after melt extrusion is solidified by air cooling, and The solidified polyester waste is crushed to form granules.

2. The method according to claim 1, wherein, The melt extrusion and the curing are performed using a plastic compactor.

3. The method according to claim 1 or 2, wherein, This further includes classifying the granules.

4. The method according to claim 3, wherein, This further includes reusing the residue generated by the grading process in the melt extrusion.

5. The method according to claim 1 or 2, wherein, The ratio of the apparent density to the bulk density of the granules, i.e., apparent density / bulk density, is 1.80 to 2.

40.

6. The method according to claim 1 or 2, wherein, The apparent density of the granules is 1.23 g / cm³. 3 ~1.33g / cm 3 Its bulk density is 0.60 g / cm³. 3 ~0.67g / cm 3 .

7. The method according to claim 1 or 2, wherein, The granules have a closed cavity inside.

8. A chemically recycled granule, comprising a compressed and cured polyester waste product, The ratio of the apparent density to the bulk density of the granules, i.e., apparent density / bulk density, is 1.80 to 2.

40.

9. The granules for chemical recycling according to claim 8, wherein, The apparent density of the granules is 1.23 g / cm³. 3 ~1.33g / cm 3 Its bulk density is 0.60 g / cm³. 3 ~0.67g / cm 3 .

10. The granules for chemical recycling according to claim 8 or 9, wherein, The content of granules with a particle size of less than 10 mm and less than 900 μm is less than 0.2% by mass.

11. The granules for chemical recycling according to claim 8 or 9, wherein, The granules have a closed cavity inside.

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