Method for recycling waste polyester

Abstract

According to the present invention, provided is a method for recycling a waste polyester raw material comprising 40 wt% or less of a heterogeneous component, the method comprising the steps of: depolymerizing a waste polyester raw material through solvolysis; and filtering a depolymerized product of the waste polyester raw material to separate at least a portion of the heterogeneous component from the depolymerized product, wherein the heterogeneous component comprises a compound which is not decomposed in the depolymerizing step.

Description

Recycling methods for waste polyester

[0001] The present invention relates to a method for recycling waste polyester. More specifically, it relates to a method for recycling waste polyester raw materials containing heterogeneous components.

[0002]

[0003] With the recent increase in plastic usage, the disposal of waste plastic has become a significant issue. While waste plastic disposal has traditionally been carried out through methods such as landfilling, ocean dumping, or incineration, these processes have resulted in environmental pollution, toxic gas emissions, and global warming. Consequently, the recycling of waste plastic has become an important research topic.

[0004] Polyester is one of the most widely used plastics and is used in various forms such as bottles, containers, fibers, and films in diverse technical fields, including magnetic recording media, electronic components, process films, packaging materials, medical materials, and industrial materials. For example, when polyester is used as a film, various functional layers such as a pressure-sensitive adhesive layer, a hard coating layer, a polarizing layer, and a UV blocking layer may be formed on one side of the polyester film, or it may be used in a form mixed with other components.

[0005] Therefore, if waste polyester is melted and reused as is, the material constituting the functional layer may be incorporated into the molten polymer, which may reduce the film-forming properties of the molten polymer or degrade the quality of the recycled polyester formed therefrom. Furthermore, even when waste polyester is manufactured into flakes or pellets for reuse, problems may arise where the recycled polyester contains contaminants or foreign substances, leading to discoloration or a deterioration in thermal and mechanical properties.

[0006] Meanwhile, recycled components such as monomers or oligomers can be obtained by depolymerizing waste polyester through chemical recycling methods such as solvent decomposition. However, as mentioned above, the purity and quality of the recycled components may deteriorate as the polyester is mixed with other components; therefore, in order to obtain high-quality and high-purity recycled components, it is required to remove or separate the aforementioned heterogeneous components from the polyester.

[0007] To remove the aforementioned heterogeneous components, the polyester may be mechanically peeled or crushed, physically washed with high-pressure air or high-pressure water, or chemically washed by dissolving or decomposing the heterogeneous components present in the waste polyester film. Additionally, the depolymerization product of the polyester may be filtered using a filtration device to separate and remove unreacted materials that did not participate in the decomposition reaction during the depolymerization stage.

[0008] However, cleaning performance and efficiency may decrease depending on the size, amount, and type of heterogeneous components present in the waste polyester raw material, and filter clogging may occur during the filtration process, or defects may occur in the polyester during the separation and removal of heterogeneous components.

[0009] [Prior Art Literature]

[0010] [Patent Literature]

[0011] (Patent Document 1) Republic of Korea Published Patent No. 10-1997-0042468

[0012]

[0013] The technical problem to be solved by the present invention is to provide a method for recycling waste polyester that can efficiently remove heterogeneous components other than polyester from waste polyester raw materials, thereby improving the purity and quality of the recycled component formed by the depolymerization of polyester, and improving the economic feasibility and efficiency of the recycling process.

[0014] According to one embodiment of the present invention, a method for recycling waste polyester raw material containing 40% by weight or less of a heterogeneous component is provided, comprising: a step of depolymerizing the waste polyester raw material through solvent decomposition; and a step of filtering the depolymerization product of the waste polyester raw material to separate at least a portion of the heterogeneous component from the depolymerization product, wherein the heterogeneous component comprises a compound that is not decomposed in the step of depolymerization.

[0015] According to the recycling method for waste polyester of the present invention, the content of heterogeneous components contained in the waste polyester raw material is controlled to a predetermined range, and after depolymerizing the waste polyester raw material, the depolymerization product of the waste polyester raw material is filtered using a specific filtration device, thereby efficiently removing the heterogeneous components from the depolymerization product while improving the speed, economic efficiency, and productivity of the recycling process and shortening the process time.

[0016] In addition, heterogeneous components recovered from the recycling process can be purified, molded, or converted into energy and used as new raw materials; accordingly, the cost and energy consumption of the recycling process can be reduced, and a more eco-friendly recycling process can be provided.

[0017] FIG. 1 is a schematic process flow diagram illustrating a recycling method according to exemplary embodiments.

[0018] FIG. 2 is a schematic process flow diagram illustrating a recycling method according to exemplary embodiments.

[0019] The present invention will be described in detail below through various embodiments and implementations. The embodiments are not limited to those disclosed below and may be modified in various forms as long as the essence of the invention is not altered.

[0020] In this specification, terms referring to each component are used to distinguish them from other components and are not intended to limit the embodiments. Additionally, in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0021] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0022] In this specification, the description that one component is formed above or below another component, or is connected or coupled to one another, includes both direct formation, connection, or coupling between these components and indirect formation, connection, or coupling through the interposition of another component. Furthermore, it should be understood that the criteria for the "above" and "below" of each component may vary depending on the direction in which the object is observed.

[0023] All numerical ranges representing the amounts, reaction conditions, physical property values, dimensions, etc. of the components described in this specification should be understood to be modified by the term "approximately" in all cases unless otherwise specified.

[0024] In numerical ranges defining the size, physical properties, etc., of components described in this specification, if a numerical range in which only the upper limit is defined and a numerical range in which only the lower limit is defined are separately exemplified, it should be understood that a numerical range combining these upper and lower limits is also included in the exemplary range.

[0025] As used herein, the term "heterogeneous component" may refer to the components contained in waste polyester raw materials or scrap, excluding polyester. As used herein, the term "unreactive substance" may refer to a compound among the heterogeneous components that does not decompose during the depolymerization process of polyester.

[0026] As used in this specification, the term "recycled component" may refer to a component derived from polyester, such as a monomer, oligomer, or polymer, obtained by decomposing, depolymerizing, reprocessing, or repolymerizing polyester by physical or chemical methods.

[0027] In this specification, when it is stated that certain processes are performed continuously, this means that the flow of raw materials between said processes continues without interruption, and other processes or steps may be further included between said processes as long as the flow of raw materials is not interrupted.

[0028]

[0029] Recycling methods for waste polyester

[0030] According to the present invention, a method for recycling waste plastic, specifically waste polyester raw material containing 40% by weight or less of heterogeneous components, is provided. The waste polyester can be chemically recycled, and through a recycling process, the waste polyester polymer can be converted into regenerated components such as low molecular weight polymers, oligomers, and monomers.

[0031] The recycling method described above includes a depolymerization step of depolymerizing waste polyester raw materials through solvent decomposition; and a heterogeneous component removal step of removing or separating at least a portion of the heterogeneous components contained in the waste polyester. The heterogeneous component removal step may be performed after the depolymerization step.

[0032] FIGS. 1 and FIGS. 2 are schematic process flow diagrams illustrating recycling methods according to exemplary embodiments.

[0033] Referring to FIGS. 1 and 2, the recycling method of the present invention includes the step of preparing waste polyester raw material (e.g., step S100).

[0034] The above waste polyester raw material can be obtained from polyester material products that are discarded after use. For example, the waste polyester raw material may be obtained from waste such as beverage bottles, fabrics, films, cases, boxes, partitions, shelves, protective panels, packaging, building materials, interior and exterior materials, electronic components, optical media, etc., made of various polyester materials (e.g., polyethylene terephthalate (PET) materials) that are discarded by users after use. Additionally, the above waste polyester raw material may be obtained from films, substrates, or sheets used in manufacturing processes for ceramic electronic components such as MLCCs, display components such as polarizers and optical filters, or semiconductor devices.

[0035] In addition, the waste polyester raw material may be obtained from defective products that may be generated during the manufacturing process of the aforementioned products, or from waste such as scraps after the process.

[0036] As described above, depending on the application of the polyester material, the waste polyester raw material may contain various heterogeneous components. Specifically, the heterogeneous components contained in the waste polyester raw material may refer to all components other than polyester contained in products, objects, devices, etc., containing the waste polyester material.

[0037] For example, when waste polyester raw material is obtained from various films such as thermal insulation films, stretched films, and release films, the waste polyester raw material may include components included in various functional layers contained in the polyester film, such as an adhesive layer, adhesive layer, anti-reflective layer, anti-glare layer, hard coating layer, release layer, UV blocking layer, polarizing layer, conductive layer, decorative layer, anti-fouling layer, decorative layer, and paper substrate. For example, the heterogeneous components may include adhesives, antistatic agents, UV absorbers, stabilizers, catalysts, defoaming agents, surfactants, thickeners, antioxidants, foaming agents, conductive materials, fillers, leveling agents, dyes, pigments, or various other additives.

[0038] For example, the waste polyester raw material may be obtained from waste plastics contained in bottles, cases, packaging, films, packaging materials, electronic components, etc. The waste polyester raw material may include colorants such as pigments and dyes contained in cases, packaging, etc., adhesives, reinforcing agents, compatibilizers, waxes, elastomers, conductive additives contained in electronic components, insulators, etc. The waste plastic may include synthetic resins and may further include non-plastic components such as ceramics or metals.

[0039] In addition, the waste polyester raw material may be obtained from fabric. The fabric may include natural fibers such as cotton components or synthetic fibers containing synthetic resins. The fabric may be obtained from clothing, furniture, interior and exterior materials, industrial fibers, etc. For example, the waste polyester raw material may be obtained from clothing such as shirts, socks, dresses, coats, trousers, suits, underwear, sweaters, gloves, hats, bags, etc., or from furniture such as bedding, pillows, mattresses, covers, carpets, curtains, rugs, tablecloths, towels, blankets, etc., or from sanitary products such as diapers, sanitary pads, tissues, etc., or from wallpaper, flooring, tents, ropes, seats of transportation vehicles, mats, etc., but is not limited thereto.

[0040] The above heterogeneous components may include synthetic resin components. The above synthetic resin components may include urethane resin, acrylic resin, silicone resin, epoxy resin, acrylonitrile, polyolefin, polyacrylate, polycarbonate, polyvinyl chloride, polyvinyl alcohol, ethylene vinyl alcohol, polysulfate, polysulfone, polystyrene, polyamide, nylon, styrene butadiene rubber, acryl butadiene styrene, or a combination thereof, but are not limited thereto.

[0041] The above heterogeneous component may include a cotton component. For example, the cotton component may be a natural fiber derived from plants or animals and may include cellulose, lignin, etc., and may include wool, silk, mohair, cashmere, wool, feathers, etc., but is not limited thereto.

[0042] The above heterogeneous component may include ceramic or metal components. For example, the waste polyester raw material may be obtained from a film, sheet, etc. to which ceramic or metal is attached.

[0043] The ceramic may include oxides, nitrides, carbides, borides, etc. of metals or metalloids. Specifically, examples of the ceramic may include oxides such as silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, cerium oxide, zinc oxide, boron oxide; nitrides such as silicon nitride, aluminum nitride, titanium nitride, boron nitride; carbides such as titanium carbide, silicon carbide, aluminum carbide, tungsten carbide; or borides such as magnesium boride, titanium boride, zirconium boride, etc., but are not limited thereto.

[0044] The above metal components may include aluminum, copper, lead, palladium, nickel, cobalt, magnesium, tin, zinc, titanium, barium, manganese, lithium, sodium, silver, manganese, chromium, or iron, and may include an alloy of at least one of these, but are not limited thereto.

[0045]

[0046] The above waste polyester raw material contains the above heterogeneous component in an amount of 40% by weight or less of the total weight of the polyester raw material. If the content of the heterogeneous component contained in the waste polyester raw material exceeds 40% by weight, even if a process to remove the heterogeneous component is performed using a filtration device described later, a large amount of the heterogeneous component may remain in the recycled component or the filtration device may become clogged due to the heterogeneous component. Consequently, the filtration efficiency may decrease, or additional purification and separation processes may be required, which may degrade the economic feasibility, efficiency, and productivity of the process. Furthermore, the yield and purity of the recycled component obtained from the waste polyester raw material may decrease, making the recycled component obtained therefrom unsuitable for reuse.

[0047] In some embodiments, the method may include a step of selecting and recovering waste polyester raw materials in which the content of heterogeneous components among the recovered waste polyester raw materials is 40% by weight or less. Unless otherwise stated, the content of heterogeneous components and the content of polyester components are based on the total weight of the waste polyester raw materials.

[0048] For example, waste polyester raw materials recovered from waste can be transferred to a sorting device, and the waste polyester raw materials can be separated according to the content of polyester components and heterogeneous components contained within the waste polyester raw materials. As the sorting device, any device capable of sorting waste polyester raw materials according to the content of heterogeneous components, such as a density sorting device, a specific gravity sorting device, an electric current sorting device, a magnetic sorting device, or an optical sorting device, may be used without limitation.

[0049] The content of heterogeneous components included in the above waste polyester raw material may be 39 wt% or less, 38 wt% or less, 37 wt% or less, 36 wt% or less, or 35 wt% or less, based on the total weight of the waste polyester raw material; or 30 wt% or less, 29 wt% or less, 28 wt% or less, 27 wt% or less, 26 wt% or less, or 25 wt% or less; or 20 wt% or less, 19 wt% or less, 18 wt% or less, 17 wt% or less, 16 wt% or less, or 15 wt% or less. In one embodiment, the content of heterogeneous components included in the above waste polyester raw material may be 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, or 5 wt% or less.

[0050] The content of heterogeneous components contained in the above waste polyester raw material may be 0.5 weight% or more. As the content of heterogeneous components in the above waste polyester raw material increases, the purity of the recycled component obtained from the waste polyester raw material decreases, which may require additional purification and concentration processes for the recycled component. Furthermore, most of the above heterogeneous components are compounds that do not participate in the solvent decomposition reaction of polyester and may remain in a solid form within the depolymerization product; in this case, the process equipment may be clogged or damaged by the solid heterogeneous components. Therefore, conventionally, only waste polyester raw materials containing heterogeneous components in an amount of 0.3 weight% or less, preferably 0.1 weight% or less, could be fed into the depolymerization process. Consequently, the processing cost of the waste polyester raw material increased, or due to the high content of heterogeneous components, the waste polyester raw material could not be fed into the recycling process and was disposed of as is.

[0051] However, according to embodiments of the present invention, since a filtration step using a specific filtration device is performed after the depolymerization step, even if the waste polyester raw material contains 0.5 weight% or more of heterogeneous components, high-purity and high-quality recycled components can be obtained at a high yield and production speed.

[0052] The content of heterogeneous components included in the above waste polyester raw material may be 1 wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, 6 wt% or more, 7 wt% or more, 8 wt% or more, 9 wt% or more, 10 wt% or more, 11 wt% or more, 12 wt% or more, 13 wt% or more, 14 wt% or more, or 15 wt% or more, or may be 20 wt% or more, 25 wt% or more, or 30 wt% or more.

[0053] For example, the content of heterogeneous components included in the waste polyester raw material may be 0.5% to 40% by weight based on the total weight of the waste polyester raw material, 1% to 40% by weight, 1% to 35% by weight, or 1% to 30% by weight, or 5% to 40% by weight, 5% to 35% by weight, or 5% to 30% by weight, or 10% to 40% by weight, 15% to 40% by weight, or 15% to 35% by weight.

[0054] In one embodiment, the content of the polyester component included in the waste polyester raw material may be 60 wt% or more, 61 wt% or more, 62 wt% or more, 63 wt% or more, 64 wt% or more, 65 wt% or more, 70 wt% or more, 71 wt% or more, 72 wt% or more, 73 wt% or more, 74 wt% or more, 75 wt% or more, 80 wt% or more, 81 wt% or more, 82 wt% or more, 83 wt% or more, 84 wt% or more, 85 wt% or more, 90 wt% or more, 91 wt% or more, 92 wt% or more, 93 wt% or more, 94 wt% or more, or 95 wt% or more, based on the total weight of the waste polyester raw material. In addition, the content of the polyester component included in the waste polyester raw material may be 99.5% by weight or less, 99% by weight or less, 98% by weight or less, 97% by weight or less, 96% by weight or less, or 95% by weight or less, and may also be 90% by weight or less, 89% by weight or less, 88% by weight or less, 87% by weight or less, 86% by weight or less, 85% by weight or less, or 80% by weight or less.

[0055] In one embodiment, the waste polyester raw material may include a raw material obtained from a transparent polyester material (hereinafter abbreviated as transparent polyester raw material). The transparent polyester material refers to a material that appears colorless when observed with the naked eye, and, for example, refers to a plastic having high transparency in the visible light region.

[0056] In one embodiment, the waste polyester raw material may include a raw material obtained from a colored polyester material (hereinafter abbreviated as colored polyester raw material). The colored polyester material may refer to any plastic other than the transparent polyester material described above. For example, the colored polyester material may include a non-transparent polyester resin or other colored plastics.

[0057] The above-mentioned transparent polyester raw material and colored polyester raw material differ from one another in the types or content of heterogeneous components contained within the raw material, and accordingly, they can generally be classified as different types of plastics. Therefore, in order to efficiently separate and recover similar types of heterogeneous components and to easily remove them from the polyester, the transparent polyester and colored polyester can be sorted and separated separately before being fed into the recycling process.

[0058] In one embodiment, the transparent polyester raw material and the colored polyester raw material may be separated and fed into separate recycling processes. The transparent polyester raw material and the colored polyester raw material may be classified by visual inspection or by using various classification devices, such as an optical classification device or a density classification device.

[0059] For example, transparent polyester raw material can be separated and recovered from waste polyester raw material. The transparent polyester raw material can be fed into a recycling process and depolymerized.

[0060] For example, colored polyester raw materials can be separated and recovered from waste polyester raw materials. The colored polyester raw materials can be fed into a recycling process and depolymerized.

[0061] The above waste polyester raw material may be crushed to a predetermined size. For example, the above waste polyester raw material may have the form of flakes or chips.

[0062] Wet grinding or dry grinding may be used as the grinding method for the above waste polyester raw material.

[0063] According to some embodiments, the crushing step may be performed under wet conditions, for example, by feeding the waste polyester raw material into a wet crusher to crush it. A known device may be used as the wet crusher, for example, a grind mill, ball mill, rod mill, rolling mill, rotate mill, bead mill, turbo mill, etc.

[0064] In the case of wet grinding, since heat generation and friction are controlled by water, damage to polyester components and the occurrence of defects caused by high temperature or friction can be suppressed compared to when other grinding methods such as dry grinding are used. Additionally, the phenomenon of the ground material adhering to the inner wall or blade of the grinder due to high temperature can be prevented, thereby further increasing process efficiency and the lifespan of the equipment. Furthermore, during the wet grinding process, at least some of the impurities and heterogeneous components contained in the waste polyester raw material can be removed by dissolving in water or reacting with water.

[0065] In addition, in the case of wet grinding, the flow of the ground raw material can continue continuously through the depolymerization stage, filtration stage, and / or recovery stage after the grinding stage, which can increase the speed of the process and further enhance the efficiency of the process.

[0066] In some embodiments, the size of the crushed material may be 50 mm or less, specifically 1 mm to 50 mm. Within this range, the reaction surface area and impregnation rate of the waste polyester raw material can be sufficiently secured, allowing heterogeneous components to be easily removed by pretreatment or washing, thereby enabling the recovery of high-purity and high-quality recycled components. If the size of the crushed material is controlled to be less than 1 mm, the crushing process must be performed under relatively harsh conditions, which may result in damage to the polyester components. The size of the crushed material may be 1 mm to 40 mm, 1 mm to 35 mm, 3 mm to 35 mm, 3 mm to 30 mm, 5 mm to 30 mm, or 5 mm to 25 mm. The size of the crushed material may be the length of the longest diameter of the crushed particles.

[0067] In some embodiments, the thickness of the pulverized material may be 0.5 mm or less. Specifically, the thickness of the pulverized material may be 0.5 mm or less, 0.3 mm or less, or 0.2 mm or less, and preferably 0.1 mm or less. For example, the thickness of the pulverized material may be greater than 0 mm and 0.1 mm or less. In one embodiment, the thickness of the pulverized material may be 0.1 mm to 0.5 mm. The thickness of the pulverized material may be the length of the shortest diameter of the pulverized particles.

[0068] The above crushed material can be passed through a filter screen having a mesh to obtain waste polyester raw material having a desired size. For example, the filter screen may have a mesh of 50 mm, 40 mm, 35 mm, 30 mm, or 25 mm.

[0069] In some embodiments, prior to the crushing step, a cutting process may be further performed to obtain waste polyester raw material by cutting the waste polyester material into a predetermined size. The waste polyester material may have various shapes depending on the purpose or application of use; for example, waste polyester material having different shapes may be collected and recovered from containers such as PET bottles, packaging materials, molded parts for transportation means such as automobiles, or electronic devices and parts such as PCs and portable communication devices, optical recording media, etc. By cutting the collected waste polyester material into a certain size through the cutting process, the crushing efficiency, cleaning efficiency, and filtration efficiency may be further improved. For example, through the cutting process, the waste polyester material may be cut to a size of 100 cm or less.

[0070] The above cutting process can be performed using known cutting machines such as hammer crushers, impact crushers, hydraulic cutters, and rotary crushers. Specifically, the above cutting process can be performed using a hydraulic cutter.

[0071] The recycling method of the present invention includes a step of depolymerizing waste polyester raw materials (e.g., step S200).

[0072] The above waste polyester raw material can be depolymerized through solvolysis. Solvolysis refers to a reaction in which polyester is chemically decomposed in the presence of a solvent to form low-polymers such as monomers and oligomers (e.g., dimers, trimers, etc.).

[0073] A regenerated component can be obtained from the polyester component contained in the waste polyester raw material through the above depolymerization step. For example, a solid regenerated component can be obtained by washing and drying the reaction product obtained by solvent decomposition of the waste polyester raw material.

[0074] The above recycled components may include recycled bis-2-hydroxyethyl terephthalate (r-BHET), recycled dimethyl terephthalate (r-DMT), recycled dibutyl terephthalate (r-DBTP), recycled diisooctyl terephthalate (r-DOTP), recycled terephthalic acid (r-TPA), recycled ethylene glycol (r-EG), etc., or may include oligomers such as dimers and trimers thereof.

[0075] Examples of solvent decomposition used in the above depolymerization step include glycolysis, alcoholylysis, hydrolysis, methanolysis, ammonolysis, and aminolysis.

[0076] In some embodiments, the depolymerization step may be performed using a glycolysis reaction that decomposes the polyester component using a glycol such as ethylene glycol or diethylene glycol. Accordingly, a regenerated component including regenerated bis(2-hydroxyethyl)terephthalate (r-BHET), etc., may be obtained.

[0077] In one embodiment, the depolymerization step may further include a step of hydrolyzing regenerated bis(2-hydroxyethyl)terephthalate (r-BHET) produced by a glycolysis reaction. Regenerated bis(2-hydroxyethyl)terephthalate (r-BHET) may be hydrolyzed to obtain solid terephthalic acid (TPA), and ethylene glycol may be generated as a byproduct of hydrolysis.

[0078] The glycolysis reaction above can be performed at a temperature of 140 ℃ or higher, 150 ℃ or higher, 160 ℃ or higher, 170 ℃ or higher, or 180 ℃ or higher, and can be performed at a temperature of 280 ℃ or lower, 240 ℃ or lower, 220 ℃ or lower, or 200 ℃ or lower.

[0079] In another embodiment, the depolymerization step may be performed through a methanolosis reaction using methanol. By decomposing waste polyester raw materials with methanol, a regenerated component including regenerated dimethyl terephthalate (r-DMT), etc., may be obtained from the polyester component contained in the waste polyester raw materials.

[0080] In one embodiment, the depolymerization step may further include a step of hydrolyzing regenerated dimethyl terephthalate (r-DMT) produced by a methanolysis reaction. The regenerated dimethyl terephthalate (r-DMT) may be hydrolyzed to obtain solid terephthalic acid (TPA), and methanol may be generated as a byproduct of the hydrolysis.

[0081] The above methanolysis reaction can be carried out at a temperature of 140 ℃ or higher, 150 ℃ or higher, 160 ℃ or higher, 170 ℃ or higher, or 180 ℃ or higher, and can be carried out at a temperature of 300 ℃ or lower, 280 ℃ or lower, 240 ℃ or lower, or 220 ℃ or lower.

[0082] In another embodiment, the depolymerization step may be performed through an alcoholysis reaction using an alcohol having 4 or more carbon atoms. By alcoholizing waste polyester raw materials, a regenerated component including regenerated terephthalic acid (r-TPA) or regenerated ethylene glycol (r-EG), etc., may be obtained from the polyester component.

[0083] When waste polyester raw materials are depolymerized through an alcoholysis reaction, solid terephthalic acid can be produced directly; therefore, if the processability is excellent, additional hydrolysis or neutralization steps are not required, making it environmentally friendly.

[0084] The number of carbon atoms in the alcohol used in the above alcoholysis reaction may be 4 or more, 6 or more, 8 or more, 10 or more, or 12 or more, or 4 to 14, 4 to 13, 4 to 10, 4 to 8, 6 to 12, 8 to 14, or 8 to 13.

[0085] The above alcoholysis reaction can be performed at a temperature of 150 ℃ or higher, 160 ℃ or higher, 170 ℃ or higher, 180 ℃ or higher, or 190 ℃ or higher, and can be performed at a temperature of 280 ℃ or lower, 270 ℃ or lower, 260 ℃ or lower, or 250 ℃ or lower.

[0086] In the above depolymerization step, the amount of solvent (e.g., glycol, methanol, alcohol, etc.) added may be 1 or more, 2 or more, or 3 or more times the weight of the waste polyester raw material, and may also be 10 or less, 8 or less, 6 or less, or 5 or less.

[0087] In another embodiment, the depolymerization step may be performed through a hydrolysis reaction using water. As the polyester component reacts with water and the ester bond is broken, a regenerated component including regenerated terephthalic acid (r-TPA) or regenerated ethylene glycol (r-EG), etc., may be obtained from the polyester component.

[0088] In one embodiment, the hydrolysis reaction may include acidic hydrolysis using an aqueous solution of an inorganic acid such as sulfuric acid, alkaline hydrolysis using an aqueous solution of an alkaline acid such as an aqueous solution of sodium hydroxide, or neutral hydrolysis using water or steam.

[0089] In the depolymerization step using the above hydrolysis reaction, the amount of water or aqueous solution added may be 1 or more, 2 or more, or 3 or more times the weight of the waste polyester raw material, and may also be 500 or less, 400 or less, 250 or less, 100 or less, or 20 or less.

[0090] The above hydrolysis reaction can be performed at a temperature of 100 ℃ or higher, 150 ℃ or higher, 180 ℃ or higher, or 200 ℃ or higher, and can be performed at a temperature of 300 ℃ or lower, 280 ℃ or lower, 260 ℃ or lower, or 250 ℃ or lower.

[0091] A catalyst may be further used in the above depolymerization process. The catalyst may include a metal catalyst, a metal salt catalyst, or a metallic organic catalyst. The catalyst may be an acetate, carbonate, oxide, or hydroxide of a metal, and the metal may be an alkali metal such as Li, Na, K, or Cs, an alkaline earth metal such as Be, Mg, Ca, or Ba, or a transition metal such as Ti, Zn, Co, or Mn. Specifically, the catalyst may be at least one of zinc acetate, sodium acetate, cobalt acetate, and manganese acetate, or in the form of a hydrate or anhydrous form thereof.

[0092] The above depolymerization process may also be carried out as a catalyst-free reaction. Additionally, metal components present in the waste polyester raw material may function as catalysts for the depolymerization process. Meanwhile, if the content of metal components in the waste polyester raw material is high, a catalyst-free reaction may be more advantageous for efficiently treating and removing heterogeneous components after the depolymerization step.

[0093] In one embodiment, the depolymerization process may be performed using a glycolysis reaction, a hydrolysis reaction, or a methanolis reaction, and the depolymerization process may be performed at a temperature of 150°C to 280°C. Accordingly, high-purity and high-quality regenerated components such as r-BHET, r-TPA, and r-DMT can be obtained in a high yield.

[0094] Meanwhile, unreacted materials contained in the waste polyester raw materials may remain intact within the depolymerization product as they are not decomposed by the solvent during the depolymerization step. Therefore, to increase the purity of the regenerated component within the depolymerization product, it is necessary to selectively separate and recover the unreacted materials from the depolymerization product.

[0095] The step of separating the heterogeneous components can be performed continuously after the depolymerization step. For example, at least a portion of the heterogeneous components can be separated and recovered from the depolymerization product obtained by depolymerizing the waste polyester raw material.

[0096] After the depolymerization step of the waste polyester raw material (e.g., step S200), a step of filtering the depolymerization product (e.g., step S300) may be included.

[0097] If the aforementioned waste polyester raw material is fed directly into the depolymerization step without pretreatment, the depolymerization product may contain the heterogeneous components contained in the polyester raw material. Since these heterogeneous components mainly consist of unreacted substances that are not decomposed during the polyester depolymerization process, solid impurities may remain in the depolymerization product. Therefore, in order to obtain a high-purity regenerated component from the depolymerization product, it is required to separate the unreacted solid substances contained in the depolymerization product.

[0098] The above filtration step may include passing the depolymerization product through a filtration device. The filtration device may include a filter having a mesh size of 2,000 μm or less.

[0099] If the mesh size of the filter provided in the filtration device exceeds 2,000 μm, the filtration characteristics for the heterogeneous component may be degraded, and a significant amount of the heterogeneous component may remain in the depolymerization product that has passed through the filter. Specifically, the mesh size of the filter included in the filtration device may be 1,950 μm or less, 1,900 μm or less, 1,800 μm or less, 1,500 μm or less, 1,200 μm or less, 1,000 μm or less, 800 μm or less, 600 μm or less, or 500 μm or less.

[0100] The mesh size of the filter included in the above filtration device may be 40 µm or larger, 75 µm or larger, 100 µm or larger, 150 µm or larger, 200 µm or larger, or 300 µm or larger. If the mesh size of the above filter is less than 45 µm, productivity and efficiency may decrease as the filtration speed slows down, and the yield of the regenerated component may decrease.

[0101] Specifically, the mesh size of the filter included in the filtration device may be 40 µm to 2,000 µm, 75 µm to 2,000 µm, 75 µm to 1,950 µm, 100 µm to 1,900 µm, 100 µm to 1,800 µm, 100 µm to 1,500 µm, 100 µm to 1,200 µm, 100 µm to 1,000 µm, 100 µm to 800 µm, 100 µm to 600 µm, 100 µm to 500 µm, 150 µm to 500 µm, 200 µm to 500 µm, or 300 µm to 500 µm. Within the above range, the separation efficiency of heterogeneous components can be improved while the filtration speed can be further increased, thereby improving the productivity of the regenerated component.

[0102] The above filtration device may include at least one of a rotary filter, a vibrating screen filter, and a self-cleaning filter. By including the filters described above in the filtration device, the filtration efficiency for the heterogeneous components can be further enhanced through solid-liquid separation, and the yield and purity of the regenerated component in the depolymerization product can be further improved.

[0103] For example, in the case of filtration devices conventionally used in the depolymerization process of waste polyester, clogging of the filter can be caused by unreacted materials contained in the waste polyester. Furthermore, when the depolymerization process is performed as a continuous process, clogging of the filter can easily occur even if the waste polyester contains a small amount of unreacted materials. Therefore, in the past, to prevent clogging of the filtration device, only raw materials with an unreacted material content of less than 0.3 weight% could be fed into the depolymerization process, which resulted in increased processing costs for the raw materials or difficulties in management.

[0104] According to embodiments of the present invention, by using a rotary filter, a screen vibrating filter, or a self-cleaning filter as the filtration device, clogging of the filter can be prevented even if unreacted material is contained in the waste polyester raw material at a rate of 0.3 weight% or more. Therefore, the raw material can be fed directly into the depolymerization process without processing, and the regenerated component obtained by depolymerization and the recovery of heterogeneous components can be carried out within a single continuous process, thereby further improving economic efficiency, processability, and productivity.

[0105] The rotary filter comprises a rotating body that receives a depolymerization product and a filter membrane located around the rotating body, wherein the filter membrane may be at least partially submerged in the depolymerization product. The pressure inside the rotating body of the rotary filter may be lower than the pressure outside the rotating body, so that when the rotating body rotates, the depolymerization product passes through the filter membrane and solid heterogeneous components (i.e., unreacted material) may accumulate on the surface of the filter membrane.

[0106] In addition, as the rotating body rotates, it continuously draws liquid from the heterogeneous components accumulated on the surface of the filter membrane, causing dehydration of the heterogeneous components, and consequently, the amount of the heterogeneous components finally recovered can be further reduced.

[0107] The heterogeneous components accumulated on the surface of the filter membrane can be released and recovered from the rotary filter. For example, a filter cake impregnated with heterogeneous components can be recovered from the rotary filter, and the solid heterogeneous components can be separated from the filter by physically or mechanically peeling off the filter cake, or the heterogeneous components can be separated by washing the filter cake.

[0108] In one embodiment, the rotary filter may include a rotary drum filter. For example, the rotating body may include a drum, and the filter membrane may have a cylindrical structure.

[0109] The screen vibration filter described above may include a vibration motor and a vibration screen connected to the vibration motor. For example, as the depolymerization product passes through the vibration screen, solid heterogeneous components contained within the depolymerization product are caught on the vibration screen, and the residual liquid passes through the vibration screen to obtain a regenerated component of high purity.

[0110] In addition, since the vibrating screen is periodically vibrated by a vibrating motor within the screen vibrating filter, solid heterogeneous components accumulated on the vibrating screen can be moved and collected by the vibration of the screen. For example, when the three-dimensional motion of the vibrating motor is transmitted to the surface of the screen, the heterogeneous components on the screen surface move in a direction, thereby removing the heterogeneous components from the screen surface. Therefore, since solid heterogeneous components can be continuously recovered from the vibrating screen even during the filtration process, a continuous filtration process can be performed without clogging of the filter, even if the waste polyester raw material contains 0.5 weight% or more of heterogeneous components.

[0111] The self-cleaning filter described above is a filtration device having a self-cleaning function and includes a filter, a sensing sensor that detects the degree of attachment of foreign substances to the filter, and a cleaning unit that cleans the filter. For example, as the depolymerization product passes through the filter, solid heterogeneous components may adhere to the surface of the filter. The amount of heterogeneous components attached to the surface of the filter can be detected by the sensing sensor, and if the heterogeneous components are excessively attached to the surface of the filter beyond a set value, the filtration of the depolymerization product is stopped, and a cleaning solution, etc., is sprayed from the cleaning unit to clean the filter.

[0112] Since heterogeneous components attached to the filter can be periodically removed from the filter by the above washing, even if the content of heterogeneous components contained in the waste polyester raw material increases, the filter can be prevented from clogging, thereby maintaining excellent filtering efficiency, and the depolymerization step of the waste polyester raw material and the recovery step of the regenerated component can be performed continuously.

[0113] The washing solution obtained after washing the filter can be dehydrated and dried to recover solid heterogeneous components. Depending on the type, the recovered heterogeneous components can be converted into energy or reused as recycled pulp, etc.

[0114] The filtration rate for the above depolymerization product may be 20 kg / min or higher. Accordingly, the throughput of waste polyester raw materials and the recovery amount of recycled components can be increased, while the filtration efficiency can be improved, allowing only heterogeneous components to be effectively separated and collected. In addition, a high filtration rate of 20 kg / min or higher can be provided as the content of heterogeneous components in the waste polyester raw materials is controlled to 40 weight% or less, and the residual amount of solid unreacted material in the depolymerization product is appropriately controlled.

[0115] In one embodiment, the filtration rate may be 600 kg / min or less. If the filtration rate for the depolymerization product exceeds 600 kg / min, the heterogeneous components may not be sufficiently filtered due to the high filtration pressure and may pass through the filter, remaining in the depolymerization product after filtration, which may lower the purity of the regenerated components obtained therefrom.

[0116] For example, the filtration rate for the depolymerization product may be 30 kg / min or more, 50 kg / min or more, 70 kg / min or more, 100 kg / min or more, 150 kg / min or more, 180 kg / min or more, or 200 kg / min or more, and may be 500 kg / min or less, 450 kg / min or less, 400 kg / min or less, 350 kg / min or less, or 300 kg / min or less. Within the above range, while maintaining excellent processability and productivity, the filtration efficiency of heterogeneous components is further increased and regenerated components of high purity and yield can be recovered.

[0117] In the above filtration step, the filtration time for the depolymerization product may be 1 minute or more, 2 minutes or more, 3 minutes or more, 5 minutes or more, 10 minutes or more, or 15 minutes or more, or 60 minutes or less, 50 minutes or less, 40 minutes or less, 35 minutes or less, 30 minutes or less, or 20 minutes or less, but is not limited thereto.

[0118] In one embodiment, the moisture content (content amount) of the heterogeneous component recovered through the filtration step can be controlled to 20% or less. For example, the moisture content of the heterogeneous component may be 15% or less, 10% or less, or 5% or less. By using the filters described above as a filtration device, solid-liquid separation can occur efficiently, thereby further reducing the moisture content of the heterogeneous component. Additionally, since the heterogeneous component has a low moisture content, it can be reused as a solid energy raw material or recycled pulp, as described later, and additional dehydration, drying, and purification processes are not required, thereby improving processability, processability, and productivity.

[0119] In one embodiment, the moisture content of the heterogeneous component recovered through the filtration process may be greater than 0%, and may be, for example, 0.5% or more, 1% or more, or 2% or more.

[0120]

[0121] Referring to FIG. 2, the polyester component contained in the waste polyester raw material or the recycled component obtained therefrom can be moved through path R1, path R2, path R3 and path R4.

[0122] Specifically, waste polyester raw material can be prepared by recovering discarded polyester material (e.g., step S100). The waste polyester raw material can be transferred to a depolymerization step (e.g., step S200) and depolymerized. The depolymerization product of the waste polyester raw material can be transferred to a filtration step (e.g., step S300), and a regenerated component can be recovered in the filtration step (e.g., step S400). The recovered regenerated component can be fed directly into a repolymerization process to obtain recycled polyester (e.g., step S500).

[0123] The heterogeneous components contained in the above waste polyester raw material can move through path R1, path R2, path R3', and path R4'.

[0124] Specifically, heterogeneous components can be separated from the depolymerization product in the filtration step. The separated heterogeneous components can be recovered and collected through path R3'. The heterogeneous components can be fed into a sorting step through path R4' as needed, through which combustible raw materials can be sorted and fed into an energy conversion process, or cellulose fibers can be sorted and fed into a regenerative pulping process to be reused as recycled raw materials.

[0125] As heterogeneous components contained in the above waste polyester raw material are separated and recovered during the filtration step and reused, the purity of the recycled component can be increased, and as the recovery rate of the heterogeneous component is relatively increased and can be used as a recycled raw material, the environmental friendliness of the process can be further enhanced.

[0126]

[0127] The recycling method of the present invention may further include the step of forming a solid refuse fuel (SRF) using heterogeneous components separated from waste polyester raw materials.

[0128] After separating heterogeneous components from the above waste polyester raw material, combustible raw materials among the heterogeneous components can be selected, and the combustible raw materials can be transferred to an SRF device to be converted into solid fuel products. For example, the combustible raw materials may include combustible synthetic resins such as urethane resin, acrylic resin, and silicone resin, and may also include natural resins such as paper products.

[0129] Through the above separation process, non-combustible materials such as ceramics and metals can be removed from heterogeneous components, and combustible materials can be selectively recovered. Specific gravity separation, wind separation, magnetic separation, vibration separation, optical separation, etc., may be used as separation methods for the heterogeneous components, but are not limited thereto. For example, magnetic ceramic or metal components with magnetic properties may be separated and recovered through magnetic separation, and ceramic or metal components with relatively high specific gravity may be separated and recovered through specific gravity separation.

[0130] The selected combustible raw material can be crushed to form a solid fuel product. The solid fuel product may be crushed and used in the form of fluff, or the crushed combustible fuel may be molded and used in the form of pellets.

[0131] A drying process may be further performed on the crushed combustible raw material, and the moisture of the combustible raw material may be evaporated by heating it with a high-temperature heat source, such as hot air, for example. For example, the amount of the combustible raw material after the drying process may be 20% or less, 15% or less, or 10% or less. Accordingly, the combustibility of the solid fuel product may be further increased, and the calorific value and energy conversion rate may be further improved.

[0132] The above solid fuel product may further include carbon-based additive materials. For example, a solid fuel product can be formed by adding a carbon-based material to the crushed combustible fuel. Accordingly, the calorific value of the solid fuel product can be further enhanced, and energy efficiency can be improved.

[0133] The above solid fuel product can be reused as an energy source for the recycling method of the waste polyester raw material. For example, the above solid fuel product can be appropriately supplied and used in stages requiring external energy, such as crushing, conveying, pretreatment, and washing processes. By reusing impurities, such as heterogeneous components disposed of from waste polyester raw material, as a solid fuel product, the energy consumption of the recycling process can be reduced, and environmentally friendly recycling can be achieved at a low cost.

[0134]

[0135] The recycling method of the present invention may further include the step of manufacturing recycled pulp using heterogeneous components recovered from waste polyester raw materials.

[0136] After separating heterogeneous components from the above waste polyester raw material, cotton components among the heterogeneous components can be selected, and the cotton components can be transferred to a pulp manufacturing device to be converted into recycled pulp. In one embodiment, the cotton components may include paper-derived components such as cellulose fibers.

[0137] Through the above separation process, foreign substances such as plastics, synthetic resins, ceramics, and metals can be removed from the cotton components. As the separation method, filtration, specific gravity separation, wind separation, magnetic separation, vibration separation, and optical separation may be used. For example, cellulose fibers with high particle size can be separated from synthetic resins with low particle size through filtration, and since cellulose fibers have a low density, they can be separated from ceramics, metals, etc. through specific gravity separation or through magnetic separation.

[0138] Meanwhile, cotton components such as paper may contain various ink components depending on the purpose of use or printing application. The ink components may include coloring agents such as pigments and dyes, binders such as acrylic resins and epoxy resins, or additives such as reinforcing agents, waxes, and inorganic particles. Therefore, in order to manufacture recycled pulp, it is necessary to remove ink components from the recovered cotton components.

[0139] In one embodiment, the process of separating the cotton component from the heterogeneous component may include a deinking process. Ink may be separated from the cotton component through the deinking process. For example, the deinking process may include a process of peeling ink from the cotton component and a process of removing the peeled ink. The peeling process may include peeling and micronizing the ink by fluidic shear force or frictional force between the cotton components. Additives such as surfactants, bleaching agents, and deinking agents may be further added during the peeling process. Impurities such as ink components may be removed from the cotton component by washing or filtering the peeled and micronized ink.

[0140] In addition, according to embodiments of the present invention, in the depolymerization step (S300) and / or filtration step (S400), the waste polyester raw material can be depolymerized or filtered, and at the same time, the ink contained in the cotton component can be peeled off and removed. Accordingly, the recovered heterogeneous component can be fed directly into the recycled pulp manufacturing process, and since no additional deinking process is required, it can be advantageous in terms of cost, energy, and environment.

[0141] The above recycled pulp manufacturing step may further include a process of washing and dewatering the processed and refined cotton components.

[0142] The recovered cotton component can be molded into a lump of a certain size and used as a raw material for recycled pulp. For example, the cotton component can be concentrated using a disc filter, a screw press, etc. Recycled pulp can be manufactured by molding the concentrated cotton component into a lump of a certain size.

[0143] In one embodiment, the step of forming a coating layer or a printing layer on the manufactured paper may be further included. The recycled pulp can be used for recycled paper, recycled tissue paper, recycled cardboard, etc.

[0144]

[0145] The recycling method of the present invention may further include a step of repolymerizing the depolymerization product (e.g., step S500). For example, the regenerated component contained in the depolymerization product may be used as a polymerization raw material for the repolymerization reaction of a polyester resin.

[0146] By the filtration step (S300) described above, the residual amount of heterogeneous components in the depolymerization product can be minimized, and a high-purity regenerated component can be obtained. Therefore, a high-quality polyester resin can be obtained even if the recovered regenerated component is used directly in the repolymerization step without undergoing additional purification and processing steps. The polyester resin obtained in the repolymerization step is a regenerated polyester resin produced through the chemical recycling of waste polyester.

[0147] Since the above polyester resin is polymerized using regenerative components such as r-BHET, r-TPA, and r-DMT, it contains repeating units derived from said regenerative components within the polymerization chain. Additionally, in the repolymerization step of the above polyester resin, other monomers, dimers, or trimers, etc., may be used in addition to said regenerative components.

[0148] In one embodiment, a polyester resin can be produced by condensing the regenerated component. In another embodiment, a low molecular weight oligomer can be produced by condensing the regenerated component (first condensation reaction), and a polyester resin can be produced by condensing the oligomer (second condensation reaction). The condensation reaction can be performed under reduced pressure conditions.

[0149] In one embodiment, the content of the recycled component in the polyester resin may be 1 wt% or more, 5 wt% or more, 10 wt% or more, 30 wt% or more, 50 wt% or more, 70 wt% or more, or 90 wt% or more, based on the total weight of the polyester resin. Additionally, the content of the recycled component may be 100 wt% or less, 99 wt% or less, 80 wt% or less, 60 wt% or less, 40 wt% or less, or 20 wt% or less, based on the total weight of the polyester resin.

[0150] The above repolymerization step may further include a process of molding the polyester resin to form pellets.

[0151] Since the recycled component obtained through the recycling method described above has high purity and high quality, the physical properties of the polyester resin manufactured using it, such as mechanical strength, processability, transparency, heat resistance, and stretchability, can be excellent.

[0152]

[0153] The present invention will be explained in more detail below through the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited thereto.

[0154]

[0155] [Example 1]

[0156] 350 kg of polyethylene terephthalate (PET) scrap containing 27 wt% adhesive components was used as a waste polyester raw material. The 350 kg of PET scrap, 850 kg of ethylene glycol, and 1.23 kg of anhydrous zinc acetate were fed into a stainless steel (SUS) reactor. The adhesive components contained in the PET scrap included silicone-based adhesives, acrylic-based adhesives, urethane-based adhesives, and / or epoxy-based adhesives. The internal temperature of the reactor was raised to 195 ℃, and depolymerization was carried out for 4 hours.

[0157]

[0158] The reaction product obtained after the depolymerization reaction was continuously fed into a rotary filter with a mesh size of 100 μm and filtered to separate the heterogeneous component (adhesive component) from the reaction product, and then washed and dried. The total filtration time was 6.5 minutes, and filtration was carried out smoothly at a filtration speed of 182 kg / min. The amount of the heterogeneous component obtained was 94.5 kg, and the content of the heterogeneous component was 3%.

[0159] After filtration, the reactants were distilled, adsorbed, and crystallized through a separation and purification process to obtain 304 kg of r-BHET as the final regenerated monomer.

[0160]

[0161] [Example 2]

[0162] 350 kg of polyethylene terephthalate (PET) scrap containing 35 wt% cotton components, 850 kg of ethylene glycol, and 1.23 kg of anhydrous zinc acetate were fed into a stainless steel (SUS) reactor. The cotton components contained in the PET scrap included natural fibers such as cellulose. The internal temperature of the reactor was raised to 195 ℃, and depolymerization was carried out for 5 hours.

[0163] The reaction product obtained after the depolymerization reaction was continuously fed into a rotary filter with a mesh size of 500 μm and filtered to separate the heterogeneous component (cotton component) from the reaction product, and then washed and dried. The total filtration time was 16.5 minutes, and filtration was carried out smoothly at a filtration speed of 72 kg / min. The amount of the heterogeneous component obtained was 122.5 kg, and the content of the heterogeneous component was 9%.

[0164] After filtration, the reactants were distilled, adsorbed, and crystallized through a separation and purification process to obtain 265 kg of r-BHET as the final regenerated monomer.

[0165]

[0166] [Example 3]

[0167] 350 kg of polyethylene terephthalate (PET) scrap containing 35 wt% cotton components, 600 kg of water, and 210 kg of sodium chloride were introduced into a stainless steel (SUS) reactor. The cotton components contained in the PET scrap included natural fibers such as cellulose. The internal temperature of the reactor was raised to 250 ℃, and depolymerization was carried out for 4 hours.

[0168] The reaction product obtained after the depolymerization reaction was continuously fed into a self-cleaning filter with a mesh size of 100 μm and filtered to separate the heterogeneous component (cotton component) from the reaction product, and then washed and dried. The total filtration time was 32.3 minutes, and filtration was carried out smoothly at a filtration speed of 37 kg / min. The amount of the heterogeneous component obtained was 120.1 kg, and the liquid content of the heterogeneous component was 12%.

[0169] After filtration, the reactants were acidified, adsorbed, and crystallized through a separation and purification process to obtain 148 kg of r-TPA as the final regenerated monomer.

[0170]

[0171] [Example 4]

[0172] 350 kg of polyethylene terephthalate (PET) scrap containing 18 wt% heteroplastics, 300 kg of methanol, and 1.23 kg of zinc anhydride were fed into a stainless steel (SUS) reactor. The heteroplastics contained in the PET scraps included polyolefin (PO) and / or polystyrene (PS). The internal temperature of the reactor was raised to 280 °C, and depolymerization was carried out for 4 hours.

[0173] The reaction product obtained after the depolymerization reaction was continuously fed into a screen vibrating filter with a mesh size of 500 μm and filtered to separate the heterogeneous component (heterogeneous plastic) from the reaction product, and then washed and dried. The total filtration time was 3.7 minutes, and filtration was carried out smoothly at a filtration speed of 324 kg / min. The amount of the heterogeneous component obtained was 63 kg, and the content of the heterogeneous component was 3%.

[0174] After filtration, the reactants were distilled, adsorbed, and crystallized through a separation and purification process to obtain 203 kg of r-DMT as the final regenerated monomer.

[0175]

[0176] [Example 5]

[0177] 350 kg of polyethylene terephthalate (PET) scrap containing 5 wt% of a low-heat-resistant resin, 850 kg of ethylene glycol, and 1.23 kg of anhydrous zinc acetate were fed into a stainless steel (SUS) reactor. The low-heat-resistant resin contained in the PET scrap included polyvinyl chloride (PVC) and / or polyvinyl alcohol (PVA), etc. The internal temperature of the reactor was raised to 195 ℃, and depolymerization was carried out for 4 hours.

[0178] The reaction product obtained after the depolymerization reaction was continuously fed into a screen vibrating filter with a mesh size of 500 μm and filtered to separate the heterogeneous component (low heat-resistant resin) from the reaction product, and then washed and dried. The total filtration time was 3.2 minutes, and filtration was carried out smoothly at a filtration speed of 368 kg / min. The amount of the heterogeneous component obtained was 17.5 kg, and the content of the heterogeneous component was 3%.

[0179] After filtration, the reactants were distilled, adsorbed, and crystallized through a separation and purification process to obtain 409 kg of r-BHET as the final regenerated monomer.

[0180]

[0181] [Comparative Example 1]

[0182] 350 kg of polyethylene terephthalate (PET) scrap containing 60 wt% cotton components, 850 kg of ethylene glycol, and 1.23 kg of anhydrous zinc acetate were introduced into a stainless steel (SUS) reactor. The internal temperature of the reactor was raised to 195 ℃, and depolymerization was carried out for 4 hours.

[0183] The reaction product obtained after the depolymerization reaction was continuously fed into a screen vibrating filter with a mesh size of 50 μm and filtered to separate the heterogeneous component (cotton component) from the reaction product, and then washed and dried. The total filtration time was 81 minutes, and filtration was performed at a filtration rate of 15 kg / min. The amount of the heterogeneous component obtained was 210 kg, and the liquid content of the heterogeneous component was 21%.

[0184] After filtration, the reactants were distilled, adsorbed, and crystallized through a separation and purification process to obtain 148 kg of r-BHET as the final regenerated monomer.

[0185]

[0186] [Comparative Example 2]

[0187] 350 kg of polyethylene terephthalate (PET) scrap containing 45 wt% adhesive components, 850 kg of ethylene glycol, and 1.23 kg of anhydrous zinc acetate were introduced into a stainless steel (SUS) reactor. The adhesive components contained in the PET scrap included silicone-based adhesives, acrylic-based adhesives, urethane-based adhesives, and / or epoxy-based adhesives. The internal temperature of the reactor was raised to 195 ℃, and depolymerization was carried out for 4 hours.

[0188] The reaction product obtained after the depolymerization reaction was continuously fed into a rotary filter with a mesh size of 100 μm and filtered to separate the heterogeneous component (adhesive component) from the reaction product, and then washed and dried. The total filtration time was 66.1 minutes, and filtration was performed at a filtration rate of 18 kg / min. The amount of the heterogeneous component obtained was 175 kg, and the liquid content was 22%.

[0189] After filtration, the reactants were distilled, adsorbed, and crystallized through a separation and purification process to obtain 197 kg of r-BHET as the final regenerated monomer.

[0190]

[0191] The process conditions and results of the examples and comparative examples are shown in Table 1 below.

[0192]

[0193]

[0194]

[0195] Referring to Table 1, in the case of Examples 1 to 5, the content of heterogeneous components included in the PET scrap was controlled to a predetermined range, so the filtration speed increased, and the filtration time was significantly reduced compared to the comparative examples.

[0196] However, in the case of the comparative examples, the content of the heterogeneous component exceeded 40% by weight, which significantly reduced the filtration rate and consequently greatly increased the filtration time. In addition, the heterogeneous component obtained after filtration had a high moisture content (content amount), and in this case, it may be difficult to feed the heterogeneous component into the regeneration process in its obtained state.

Claims

1. A method for recycling waste polyester raw materials containing 40% by weight or less of heterogeneous components, A step of depolymerizing waste polyester raw materials through solvent decomposition; and The method includes the step of filtering the depolymerization product of the waste polyester raw material to separate and recover at least a portion of the heterogeneous component from the depolymerization product. A method for recycling waste polyester, wherein the above heterogeneous component comprises a compound that is not decomposed in the above depolymerization step.

2. In Paragraph 1, A method for recycling waste polyester, wherein the filtration step comprises passing the depolymerization product through a filtration device having a mesh size of 2,000 μm or less.

3. In Paragraph 2, A method for recycling waste polyester, wherein the mesh size of the filter included in the above filtration device is 40 μm to 2,000 μm.

4. In Paragraph 2, A method for recycling waste polyester, wherein the filtration device comprises at least one of a rotary filter, a vibrating screen filter, and a self-cleaning filter.

5. In Paragraph 1, A method for recycling waste polyester, wherein the filtration rate of the above depolymerization product is 20 kg / min or more.

6. In Paragraph 1, A method for recycling waste polyester, wherein the depolymerization step is performed at a temperature of 150 ℃ to 280 ℃.

7. In Paragraph 1, A method for recycling waste polyester, wherein the waste polyester raw material comprises 0.5% by weight to 40% by weight of heterogeneous components.

8. In Paragraph 1, A method for recycling waste polyester, wherein the waste polyester raw material comprises at least 60% by weight of polyester based on the total weight of the waste polyester raw material.

9. In Paragraph 1, A method for recycling waste polyester, wherein the above heterogeneous component includes a synthetic resin component.

10. In Paragraph 9, A method for recycling waste polyester, further comprising the step of manufacturing a solid refuse fuel (SRF) from the recovered heterogeneous components.

11. In Paragraph 10, A method for recycling waste polyester, wherein the above synthetic resin component comprises urethane resin, acrylic resin, silicone resin, epoxy resin, acrylonitrile, polyolefin, polyacrylate, polycarbonate, polyvinyl chloride, polyvinyl alcohol, ethylene vinyl alcohol, polysulfate, polysulfone, polystyrene, polyamide, nylon, styrene butadiene rubber, acrylobutadiene styrene, or a combination thereof.

12. In Paragraph 1, A method for recycling waste polyester, wherein the above heterogeneous component includes a cotton component.

13. In Paragraph 12, A method for recycling waste polyester, further comprising the step of manufacturing recycled pulp from the recovered heterogeneous components.

14. In Paragraph 1, A method for recycling waste polyester, wherein the above heterogeneous component includes ceramic or metal.

15. In Paragraph 1, A method for recycling waste polyester, further comprising the step of repolymerizing the above depolymerization product to produce polyester.

Images