Method for recovering polyester component and method for producing recycled polyester using recovered component

Abstract

Provided is a method for recovering a polyester component, the method comprising: bringing a textile product including polyester fibers and an acrylic resin into contact with a polar solvent having a temperature of 90-185°C; and recovering a polyester component. The polyester fibers preferably comprise an alkylene benzenedicarboxylate as a main repeating unit. It is preferable that the acrylic resin be an (un)crosslinked acrylic resin and that the polar solvent be a lower alcohol or an aprotic polar solvent. Also provided is a method for producing a recycled polyester, the method comprising repolymerizing a polyester component obtained by this recovery method. According to the present invention, although a recovered polyester is used, a recycled polyester that has less coloration can be produced.

Description

Method for recovering polyester components and method for producing recycled polyester using recovered components

[0001] The present invention relates to a method for recovering a polyester component from a textile product containing polyester fibers and an acrylic resin, and a method for producing recycled polyester using the recovered polyester.

[0002] Polyester is widely used in textile products due to its excellent properties, but the effective utilization of polyester textile products after use has become a major challenge, including environmental issues. In particular, textile products containing both polyester fiber and acrylic resin have been used in large quantities in recent years, but it has been difficult to separate them and recover the active ingredients.

[0003] For example, textile products in which the surface of a sheet made of polyester fiber is printed with acrylic resin are widely used due to the variety of colors available, but there is a problem in that it is extremely difficult to separate the polyester fiber from the acrylic resin that is strongly bonded to it.

[0004] Furthermore, textile products in which polyester fiber sheets are backed with acrylic resin are used in large quantities as materials for automobile interiors, etc. However, the amount of waste generated during the production process is large, and there is a strong demand for efficient technology for recovering active ingredients.

[0005] Typically, material recycling, thermal recycling, and chemical recycling are considered as the main methods for treating such post-consumer polyester fiber products, and among these, chemical recycling, in which polyester polymers are depolymerized to raw materials and then repolymerized, is superior as a closed-loop recycling method from the viewpoint of minimizing the deterioration in quality associated with recycling. Among these, chemical recycling, which is characterized by depolymerizing polyester to an intermediate from which recycled polyester can be produced by direct polycondensation reaction, is also an excellent method from the viewpoint of energy consumption in chemical recycling.

[0006] However, the recycled polyester polymer obtained in this manner has the problem that discoloration cannot be sufficiently suppressed. In particular, when a polyester fiber product contains other components such as an acrylic resin, it has been difficult to recover the polyester component efficiently and with suppressed discoloration.

[0007] Furthermore, there have been problems with recycled polyester polymers obtained from polyester fiber products that have been printed with acrylic resin, such as extremely poor yields and inability to prevent discoloration of the recovered components.

[0008] In order to suppress discoloration of the recovered polymer, for example, Patent Document 1 has attempted, as a step of removing discoloration-causing substances, an adsorption treatment in which the discoloration-causing substances are brought into contact with an adsorbent after the depolymerized intermediate, a decomposition treatment in which the discoloration-causing substances are decomposed with a decomposing agent, or a reduction treatment in which the discoloration-causing substances are reduced with a reducing agent. However, although these methods remove discoloration-causing substances such as dyes to a certain extent, there is a problem in that it is not possible to obtain a polyester polymer with reduced discoloration to the same extent as a polyester polymer obtained by a conventional production method that does not use recycled raw materials.

[0009] JP 2008-88096 A

[0010] The present invention provides a method for recovering polyester components from textile products containing polyester fibers and acrylic resin, and a method for producing recycled polyester with little coloration using the recovered polyester.

[0011] In order to solve the above problems, the following inventions are provided. 1. A method for recovering a polyester component, comprising contacting a textile product containing polyester fibers and an acrylic resin with a polar solvent at 90°C or higher and 185°C or lower to recover the polyester component. 2. A method for recovering a polyester component according to the above item 1, wherein the polyester fibers are made of a polyester having alkylenebenzene dicarboxylate as the main repeating unit. 3. A method for recovering a polyester component according to the above item 1 or 2, wherein the acrylic resin is a crosslinked acrylic resin. 4. A method for recovering a polyester component according to any one of the above items 1 to 3, wherein the polar solvent is a lower alcohol or an aprotic polar solvent. 5. A method for recovering a polyester component according to any one of the above items 1 to 4, wherein the polar solvent contains a catalyst. 6. A method for recovering a polyester component according to the above item 5, wherein the catalyst is a zinc-based catalyst. 7. A method for recovering a polyester component according to the above item 5, wherein the catalyst is sodium methoxide or titanium tetraoxide. 8. A method for recovering a polyester component according to the above item 4, wherein the lower alcohol is an alkylene glycol. 9. The method for recovering a polyester component according to the above 4, wherein the aprotic polar solvent is at least one selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide. 10. The method for recovering a polyester component according to any one of the above 1 to 8, wherein the acrylic resin is a crosslinked acrylic resin, the polar solvent is a lower alcohol containing a catalyst, and treatment is carried out at a temperature of 100°C to 185°C during solvent contact. 11. The method for recovering a polyester component according to the above 1 or 9, wherein the polar solvent is an aprotic polar solvent, and treatment is carried out at a temperature of 90°C to 160°C during solvent contact. 12. The method for recovering a polyester component according to any one of the above 1 to 11, wherein treatment is carried out with an adsorbent after contact with the polar solvent. 13. The method for recovering a polyester component according to any one of the above 1 to 12, wherein the recovered polyester component is bis(hydroxyalkyl) benzenedicarboxylate. 14. The method for recovering a polyester component according to any one of the above 1 to 13, wherein, after contact with a polar solvent, the polyester component is further depolymerized to bis(hydroxyalkyl) aromatic dicarboxylate in alkylene glycol containing a depolymerization catalyst.15. A method for producing recycled polyester, which comprises repolymerizing the polyester component obtained by the recovery method according to any one of 1 to 14 above.

[0012] According to the present invention, there are provided a method for recovering polyester components from textile products containing polyester fibers and acrylic resin, and a method for producing recycled polyester with little coloration using the recovered polyester.

[0013] The present invention will be described in detail below. The method for recovering a polyester component of the present invention is a method for recovering a polyester component from a textile product containing polyester fibers and an acrylic resin, and essentially comprises contacting the textile product with a polar solvent at a temperature of 90°C or higher and 185°C or lower.

[0014] [Textile Products] The textile products used in the present invention contain polyester fibers and acrylic resin. Furthermore, it is preferable that the textile product be primarily composed of polyester fibers. Here, "primarily composed of polyester fibers" means that polyester fibers constitute the majority of the fibers constituting the textile product. The polyester fibers preferably account for 50% by weight or more of the textile product, more preferably 60% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, and particularly preferably 90% by weight or more. Furthermore, various fibers such as polyamide fibers, acrylic fibers (polyacrylonitrile), and cotton can be used as other fibers within the scope of the present invention, provided that the object of the present invention is not impaired.

[0015] Such textile products made of polyester fibers and acrylic resin are textile products in which crosslinked or non-crosslinked acrylic resin is attached to woven or knitted fabrics or the like mainly made of polyester fibers.

[0016] More specifically, examples of textile products containing acrylic resin crosslinked with polyester fibers include T-shirts with acrylic prints on the surface, clothing with acrylic prints as logos, and flags and banners with acrylic resin printed all over. Since such textile products are produced and consumed in large quantities and a large amount is discarded, there is also a great demand for recycling. The amount of crosslinked acrylic resin attached to the textile product is preferably less than 50% by weight, particularly in the range of 10 to 25% by weight.

[0017] Examples of products in which acrylic resins are used in textiles without crosslinking include those used to maintain the shape of textiles, such as backings, and specific examples include automobile interior materials, such as acrylic resin-backed polyester textiles for car seats, which are mass-produced and tend to produce waste material during the manufacturing process. In these cases, the amount of acrylic resin, based on the weight of the textile, is preferably 30% by weight or less, more preferably 20% by weight or less and 2% by weight or more, and particularly 10% by weight or less and 1% by weight or more.

[0018] [Polyester Fiber] Here, polyester fiber refers to a fiber made of a polycondensate synthesized by dehydration condensation of a polycarboxylic acid and a polyalcohol to form an ester bond. The polyester forming the fiber is a polymer having an ester bond and is generally classified into aliphatic polyester, semi-aromatic polyester, and wholly aromatic polyester.

[0019] The polycarboxylic acid constituting this polyester is preferably a dicarboxylic acid or an ester-forming derivative thereof, and more preferably an aromatic dicarboxylic acid such as terephthalic acid or 2,6-naphthalenedicarboxylic acid.

[0020] The polyalcohol, the other component constituting the polyester, is preferably a diol or an ester-forming derivative thereof. As the diol, an aliphatic glycol having 2 to 20 carbon atoms is preferably used. Examples of this aliphatic glycol include ethylene glycol (hereinafter sometimes abbreviated as EG), 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. The aliphatic glycol may be an alicyclic glycol having 3 to 30 carbon atoms, and a specific example is 1,4-cyclohexanedimethanol.

[0021] In the present invention, a polyester combining such a polycarboxylic acid and a polyalcohol is used as one of the starting materials for constituting a textile product. Among these, it is preferable that the polyester is an aromatic polyester, more specifically, a polyester having alkylenebenzene dicarboxylate as the main repeating unit. Furthermore, it is preferable that the polyester is a polyester having polyalkylene terephthalate, particularly polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, or the like, as the main component.

[0022] Furthermore, when the aromatic polyester is polyalkylene terephthalate (terephthalic acid: para position), it is also preferable that the polymer contains this as the main polymer component and other minor polymer components. Here, the main polyester component means 60 mass% or more of the weight of the polymer. The minor polymer component is preferably, for example, polyalkylene isophthalate (isophthalic acid: meta position).

[0023] In particular, when the polyester is a polyalkylene terephthalate, which is an aromatic polyester, a polyester obtained by copolymerizing terephthalic acid as the dicarboxylic acid component with isophthalic acid or a sulfoisophthalic acid cation salt such as 5-sodium sulfoisophthalic acid as the copolymerization component is one preferred embodiment in terms of its high dyeability and the resulting physical properties. Additionally, depending on the purpose of imparting functionality, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, hydroxycarboxylic acids, organic phosphate esters, ethers (diethylene glycol, polyethylene glycol, polytetramethylene glycol, etc.), etc. may also be copolymerized. Furthermore, the polyester fiber may be colored with a pigment or the like.

[0024] [Acrylic Resin] The textile products used in the present invention contain acrylic resin in addition to the polyester fibers described above. Here, the acrylic resin is a combination of acrylic acid esters and / or methacrylic acid esters, and a representative example is polymethyl methacrylate (PMMA) resin. In the present invention, textile products to be recovered include woven or knitted fabrics mainly made of polyester fibers to which crosslinked or non-crosslinked acrylic resin has been attached.

[0025] The non-crosslinked acrylic resin is preferably a non-crosslinked acrylic resin used as a backing material for sheet-like objects, such as a backing material for car seats. Here, the non-crosslinked acrylic resin is an acrylic resin that has adhesive properties by utilizing a physical change rather than a chemical reaction (polymerization reaction) to solidify. The acrylic resin may contain a flame retardant such as an organic phosphorus flame retardant, a halogen-based flame retardant such as chlorine or bromine, a metal hydroxide, or an antimony oxide to impart flame retardancy.

[0026] The crosslinking agent for the crosslinked acrylic resin may be an epoxy or isocyanate-based agent, or a fixer that is commonly used to improve the fastness and washing durability of resin prints. The degree of crosslinking is preferably 0.1% to 10%, and more preferably 1% to 5%.

[0027] Such crosslinked acrylic resins include those used as acrylic prints on the surface of clothing such as T-shirts, acrylic prints as logos on the surface of clothing, acrylic resins printed all over flags, banners, etc. Such textile products are produced and consumed in large quantities, and a large amount is also discarded, so there is a great demand for recycling them.

[0028] [Polar solvent treatment (1) for recovering polyester components] In the present invention, a textile product containing polyester fibers and an acrylic resin as described above is used as a starting material to recover the polyester components. The textile product is then treated by contacting it with a polar solvent at a temperature of 90°C or higher and 185°C or lower to recover the polyester components.

[0029] In the case of a crosslinked acrylic resin, the polar solvent is preferably a lower alcohol having a linear hydrocarbon group with a small number of carbon atoms, and in the case of a non-crosslinked acrylic resin, an aprotic polar solvent such as dimethyl sulfoxide (DMSO) is preferred. Next, the optimal conditions for the crosslinked acrylic resin and the non-crosslinked acrylic resin will be described separately.

[0030] [When a lower alcohol is used] In the case of a textile product containing a crosslinked acrylic resin, the polar solvent is preferably a lower alcohol, and more preferably a lower alcohol containing a catalyst.

[0031] [Lower Alcohols] Examples of lower alcohols used in the recovery method of the present invention include monohydric alcohols having a linear hydrocarbon group with 5 or less carbon atoms, dihydric alcohols (also called diols or glycols), trihydric alcohols, and benzyl alcohol having an aromatic ring. These have a relatively low viscosity even at room temperature and easily penetrate into the resin, making them ideal for the present invention.

[0032] More specific examples include methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, diethylene glycol, glycerin, and benzyl alcohol. Among these, ethylene glycol, diethylene glycol, propanediol, and benzyl alcohol are more preferred, and ethylene glycol (EG) is particularly preferred. By using such lower alcohols, boiling, evaporation, decomposition, and side reactions are less likely to occur in the treatment temperature range described below, and the moderate viscosity provides good permeability into the resin, allowing for more efficient recovery.

[0033] In addition, it is preferable to select alkylene glycol as the lower alcohol used in the recovery method of the present invention, and this makes it possible to simultaneously obtain bis(hydroxyalkyl) benzenedicarboxylate, which is an intermediate for polyester polymer, in the above recovery step.

[0034] [Step of recovering polyester component using lower alcohol] In the present invention, when a textile product containing polyester fiber and crosslinked acrylic resin is used as a starting material to recover a polyester component, it is preferable to use a lower alcohol as described above as a polar solvent. Furthermore, it is preferable to treat such a textile product in a lower alcohol containing a catalyst at a temperature of 100°C to 185°C to recover the polyester component.

[0035] The treatment conditions are preferably a temperature range of 125° C. to 185° C., particularly 130° C. to 180° C. The treatment time is preferably 6 hours or less, more preferably 0.5 to 4 hours. The treatment pressure is preferably normal pressure, but when a solvent with a low boiling point is used, it is preferably under pressure.

[0036] The amount of lower alcohol solution used during treatment is preferably 2 to 20 times the weight of the textile product, which is the structure to be treated. A liquid volume of 3 to 10 times is more preferable. During treatment with the solution, in addition to immersion and standing, it is preferable to agitate the solution with a liquid circulation system or a rotating blade or the like.

[0037] In the recovery method of the present invention, the textile product is treated in a lower alcohol containing a high temperature catalyst, whereby the polyester fiber is depolymerized to form bis(hydroxyalkyl) benzenedicarboxylate, which is then dissolved in the lower alcohol, while the crosslinked acrylic resin remains mostly in a solid state. Therefore, it is possible to separate the polyester component in the solution from the solid crosslinked acrylic resin by solid-liquid separation.

[0038] The polyester component recovered in this manner can be used as is after purification and drying, or can be further depolymerized to a bis(hydroxyalkyl) benzenedicarboxylate to form an intermediate for a polyester polymer, which can then be used for repolymerization of the polyester polymer.

[0039] Furthermore, in the recovery method of the present invention, it is more preferable to select alkylene glycol as the lower alcohol and use a polyester depolymerization catalyst as the catalyst. In this case, in the recovery process, the polyester component is depolymerized to bis(hydroxyalkyl) benzenedicarboxylate, and at the same time, the acrylic resin having a crosslinked structure is partially dissolved but remains mostly in a solid state. Therefore, it is possible to separate the bis(hydroxyalkyl) benzenedicarboxylate, which is the polyester component in solution, from the solid crosslinked acrylic resin by solid-liquid separation. Furthermore, trace amounts of acrylic resin contained in the recovered polyester component can be easily removed by subsequent crystallization or adsorption processes.

[0040] [Catalyst] The catalyst preferably used when using this lower alcohol is one containing a first transition metal, and specific examples of the first transition metal include titanium, chromium, manganese, iron, cobalt, nickel, copper, and zinc. Of these, zinc and titanium are preferred, and zinc-based catalysts that can be used at low temperatures are particularly preferred. Furthermore, these catalysts are preferably those used in depolymerization and transesterification of polyesters.

[0041] In addition to utilizing the recovered polyester component as is, one of the purposes of the present invention is to further depolymerize and repolymerize it to produce chemically recycled polyester. Even if manganese or zinc remains in the process of separating and recovering the acrylic resin and polyester, it is unlikely to have a negative effect on the quality (particularly the hue) of the chemically recycled polyester in the subsequent depolymerization and repolymerization processes.

[0042] In the present invention, the catalyst is preferably an acetate of a first transition metal, sodium methoxide, or titanium tetraoxide. Zinc acetate is particularly preferred. Although the mechanism behind this is unclear, it is thought that this is because it is active at relatively low temperatures and can selectively depolymerize only polyester.

[0043] The amount of catalyst used during depolymerization varies depending on the catalyst used. In the case of zinc acetate or titanium tetraoxide, the amount is preferably 20 to 1000 mmol%, more preferably 30 to 750 mmol%, and particularly preferably 50 to 500 mmol% relative to the polyester. In the case of sodium methoxide, the amount is preferably 25 to 300 mol%, more preferably 50 to 200 mol%, and particularly preferably 100 to 150 mol%. Here, "mol%" refers to the ratio of the number of catalyst molecules to the structural units of the polyester. In the case of "mmol%", the ratio is 1 / 1000 of that "mol%". If the amount of catalyst used is less than the above range, the catalytic activity will be insufficient, and if it is greater, the effect of suppressing discoloration will be reduced, which is undesirable.

[0044] [When an aprotic polar solvent is used] In the case of textile products containing non-crosslinked acrylic resin, it is preferable to use an aprotic polar solvent such as DMSO as the polar solvent. In the present invention, a textile product containing polyester fiber and acrylic resin is used as the starting material to recover the polyester component. If the acrylic resin is not crosslinked, a preferred method is to contact the textile product with an aprotic polar solvent at a temperature of 90 to 160°C. Then, by removing the polar solvent from the textile product, it is possible to simultaneously remove the solvent and the acrylic resin, pigment, flame retardant, and other additives dissolved therein.

[0045] Examples of the aprotic polar solvent used in the recovery of the polyester component of the present invention include dimethyl sulfoxide, dimethylacetamide, dimethylformamide, acetone, acetonitrile, and diethyl ether. The boiling point of the aprotic polar solvent and the solubility of the acrylic resin in the aprotic polar solvent should be high, and from this viewpoint, dimethyl sulfoxide, dimethylacetamide, and dimethylformamide are preferably used as the aprotic polar solvent, and dimethyl sulfoxide (DMSO) is particularly preferably used.

[0046] The temperature of the aprotic polar solvent during the treatment is preferably in the range of 90° C. to 160° C., more preferably 100° C. to 150° C., and particularly preferably 120° C. to 130° C. The amount of the aprotic polar solvent used in the solvent contact step is preferably 10 to 500 times, more preferably 50 to 300 times, and particularly preferably 60 to 100 times the weight of the textile product to be treated by solvent contact.

[0047] In the solvent contact step, the solvent contact treatment in which the textile product is brought into contact with the polar solvent is preferably carried out by immersing the textile product in the polar solvent. This immersion treatment may be carried out by leaving the textile product stationary in the polar solvent, or is preferably carried out by immersing the textile product in the polar solvent and then stirring it with a liquid circulation system or a rotary blade.

[0048] This polyester component recovery process using an aprotic polar solvent is useful for removing coloring substances such as pigments from the fibers as well as the acrylic resin. This solvent contact treatment process is carried out by removing the aprotic polar solvent from between the fibers of the textile product or from the textile product in which the aprotic polar solvent has been absorbed between the fibers and the resin. The removal of the liquid can be carried out by squeezing, centrifugal separation, or Soxhlet extraction.

[0049] The solvent contact step and the removal step may be performed once, but are preferably repeated multiple times. Incidentally, when the "polyester component recovery step (2) depolymerization treatment" is additionally performed following this "polyester component recovery step," the solvent contact step and the removal step may be performed once, but are preferably performed five times or less, and more preferably three times or less. The draining step is performed so that the weight of the textile product containing the aprotic polar solvent after the removal step is preferably 300% by weight or less, more preferably 150 to 250% by weight, and particularly preferably 180 to 220% by weight, based on 100% by weight of the dry weight of the textile product.

[0050] By using the above-described method, the acrylic resin and dye and pigment components can be dissolved in an aprotic polar solvent from a textile product containing polyester fibers and an acrylic resin, and the resulting solution can be removed to recover the polyester itself as a polyester component. This method makes it possible to effectively remove foreign matter from the polyester component recovered, such as the acrylic resin and additives such as dyes, pigments, and flame retardants.

[0051] [Polyester Component Recovery Step (2): Depolymerization Treatment] The polyester component obtained in the above-mentioned "Polar Solvent Treatment for Polyester Component Recovery Step (1)" is preferably further depolymerized. More specifically, the polyester component obtained in the above-mentioned polyester component recovery step (1) is preferably depolymerized into a bis(hydroxyalkyl) aromatic dicarboxylate in an alkylene glycol containing a depolymerization catalyst, and the bis(hydroxyalkyl) aromatic dicarboxylate is recovered as the polyester component in the polyester component recovery step (2). The present inventors have discovered that if the polar solvent treatment in the polyester component recovery step (1) is not performed and the depolymerization treatment in the polyester component recovery step (2) is performed without removing the acrylic resin, the depolymerization reaction does not proceed. Therefore, it is particularly preferable to combine the recovery steps (1) and (2).

[0052] The treatment conditions for depolymerization are preferably normal pressure, at a temperature in the range of 180°C to 250°C, for 2 to 8 hours, or more preferably at a temperature in the range of 200°C to 240°C, for 3 to 6 hours, while stirring.

[0053] [Catalyst] As the catalyst for depolymerization, a catalyst based on a first transition metal is preferably used. Specific examples include fatty acid salts, carbonates, sulfates, phosphates, oxides, hydroxides, halides, and alcoholates of first transition metals. As the first transition metal, manganese and zinc are preferably used.

[0054] As the catalyst, manganese oxide, manganese acetate, zinc oxide, or zinc acetate is preferably used, and manganese acetate is particularly preferably used. One or more types of catalyst may be used in combination. In particular, when manganese acetate is used as the catalyst, it has high solubility in alkylene glycol, making it possible to reduce the amount of catalyst remaining in the subsequent step. The catalyst is preferably dissolved or suspended in alkylene glycol before use.

[0055] As for the catalyst used in the depolymerization reaction in this depolymerization step, when the crosslinked acrylic resin is treated with a lower alcohol as described above, it is preferable to use the same catalyst as that used with the lower alcohol.

[0056] Generally, depolymerized polyester products often gradually discolor over time due to long-term storage, but the products obtained by the recovery method and production method of the present invention show significantly less discoloration. In particular, the use of a manganese catalyst during depolymerization makes it possible to obtain polyester polymers with less discoloration. The amount of catalyst used during depolymerization is generally preferably 20 to 500 mmol%, more preferably 30 to 300 mmol%, and particularly preferably 50 to 150 mmol%, based on the polyester.

[0057] When zinc acetate or titanium tetraoxide is used as a catalyst for depolymerization, the amount is preferably 20 to 1000 mmol%, more preferably 30 to 750 mmol%, and particularly preferably 50 to 500 mmol%, based on the polyester, and when sodium methoxide is used, the amount is preferably 25 to 300 mol%, more preferably 50 to 200 mol%, and particularly preferably 100 to 150 mol%, based on the polyester.

[0058] Here, "mol %" indicates the ratio of the number of catalyst molecules to the constituent units of the polyester. In the case of "mmol %", it is 1 / 1000 of that "mol %". If the amount of catalyst used is less than the above range, the catalytic activity will be insufficient, and if it is more, the effect of suppressing discoloration will decrease, which is not preferable. If a manganese catalyst is used as the catalyst, depolymerization can be performed with a small amount used.

[0059] [Alkylene Glycol] The alkylene glycol (AG) used in the depolymerization reaction in the depolymerization step is the same as the polyalcohol forming the skeletal structure of the polyester used in the textile product, or the same as the polyalcohol constituting the polyester obtained by repolymerizing the intermediate bis(hydroxyalkyl) aromatic dicarboxylate.

[0060] Examples of alkylene glycols that are the same as the polyalcohols that form the backbone structure of the polyester include ethylene glycol (EG) when the polyester is polyethylene terephthalate (PET), 1,3-propanediol (trimethylene glycol, C3G) when the polyester is polytrimethylene terephthalate, and 1,4-butanediol (C4G) when the polyester is polybutylene terephthalate. The alkylene glycol may be a mixture of the alkylene glycols.

[0061] The amount of alkylene glycol is preferably 2 to 20 times, and more preferably 3 to 10 times, the weight of the recovered polyester. By using a large amount of alkylene glycol during depolymerization in this manner and subsequently carrying out crystallization and solid-liquid separation, the amounts of contaminating depolymerization catalysts and other foreign substances can be reduced.

[0062] [Purification step] The method for recovering a polyester component of the present invention preferably includes a purification step of further purifying the obtained polyester component after the above-described steps. The purification step includes crystallization or adsorption treatment, and it is more preferable to perform both of them.

[0063] [Crystallization] When the recovered polyester component is a depolymerization reaction product, the purification step is carried out by lowering the temperature in alkylene glycol to crystallize it. The temperature lowering conditions for crystallization are preferably lowering the temperature from a temperature of 60°C or higher to 25°C or lower, and more preferably cooling to 15°C or lower. After crystallization, solid-liquid separation is preferably performed. The alkylene glycol content in the cake after solid-liquid separation is preferably 100% by weight or less, more preferably 55% by weight or less, even more preferably 1 to 30% by weight, and particularly preferably 5 to 25% by weight.

[0064] When solid-liquid separation is performed after crystallization, it is preferable to wash the crystallized product with water or alkylene glycol. The washing is preferably performed by treating the product in a Nutsche filter while spraying a washing liquid. By performing these treatments, the depolymerization catalyst dissolved in the alkylene glycol and other color-causing substances can be washed away, and a more highly purified bis(hydroxyalkyl) aromatic dicarboxylate can be obtained.

[0065] The solution used for washing is preferably one with low viscosity, and from this viewpoint, water is preferably used. The amount of washing liquid is preferably 1 to 100 times, more preferably 1.5 to 10 times, the weight of the cake. The liquid temperature during washing is 0 to 40°C. A liquid temperature higher than this is undesirable because the cake itself tends to dissolve and the yield decreases. After washing, the resulting mixture can be dried in a vacuum dryer or the like to obtain a bis(hydroxyalkyl) aromatic dicarboxylate. Note that when the alkylene glycol used in the production method of the present invention is the same as the diol component of the polyester after repolymerization, it is also preferable to repolymerize it without drying.

[0066] [Adsorption Treatment] It is also preferable to further subject the obtained polyester component to adsorption treatment of foreign matter, etc., using an adsorbent such as activated carbon. Other adsorbents include adsorbents made of styrene-based or acrylic-based crosslinked copolymers. Furthermore, synthetic adsorbents made of styrene-based or acrylic-based crosslinked copolymers having a macroporous structure without functional groups are preferred.

[0067] This adsorption treatment is a process in which the polyester component is brought into contact with an adsorbent to adsorb, for example, organic substances derived from decomposition products of fibers and resins other than polyester contained in the aromatic dicarboxylate bis(hydroxyalkyl) composition, and additives such as dyes and pigments, thereby obtaining a more purified polyester component. This adsorption process can be carried out by dissolving the polyester component in water or an organic solvent to prepare an aqueous solution or solution, and then adding the adsorbent thereto, thereby bringing the two into contact in water or an organic solvent.

[0068] [Polyester component: bis(hydroxyalkyl) benzenedicarboxylate] When the polyester component contained in a textile product is recovered as a bis(hydroxyalkyl) aromatic dicarboxylate as a polyester intermediate by the above-mentioned recovery step (depolymerization), it can be used as an intermediate in the production of recycled polyester polymers.

[0069] The aromatic bis(hydroxyalkyl) dicarboxylate varies depending on the polyester contained in the starting textile product and the type of alkylene glycol used. When the polyester is a polyester (polyalkylene terephthalate) that mainly uses terephthalic acid as a polycarboxylic acid, bis(hydroxyalkyl) benzenedicarboxylate (hereinafter sometimes referred to as BHAT; bishydroxyalkyl terephthalate) is obtained.

[0070] Specifically, when C3G (1,3-propanediol (trimethylene glycol)) is used as the alkylene glycol for depolymerization, BHPT (bishydroxypropyl terephthalate) is obtained. When C4G (1,4-butanediol) is used as the alkylene glycol for depolymerization, BHBT (bishydroxybutyl terephthalate) is obtained. When ethylene glycol is used as the alkylene glycol for depolymerization, BHET (bishydroxyethyl terephthalate) is obtained.

[0071] [Production of Recycled Polymer (Repolymerization)] The polyester component obtained by the recovery method of the present invention can be further repolymerized to produce a recycled polyester. In particular, when the obtained polyester component is an aromatic dicarboxylate bis(hydroxyalkyl), a recycled polyester polymer can be more efficiently produced by polycondensation reaction. The recycled polyester polymer obtained by the present invention has a low content of foreign matter, little coloration, and excellent hue.

[0072] As a catalyst for repolymerization to obtain a recycled polyester polymer, known catalysts such as antimony, germanium or titanium catalysts can be used, specifically diantimony trioxide.

[0073] It is preferable to carry out the polycondensation reaction while flushing out alkylene glycol and other compounds generated during the repolymerization reaction outside the reactor. The amount of catalyst used is in the range of 10 to 1,000 ppm based on the weight of the aromatic bis(hydroxyalkyl) dicarboxylate. After polycondensation, it is preferable to add a conventionally known phosphorus-based stabilizer such as orthophosphoric acid or phosphorous acid. The amount of the phosphorus-based stabilizer used is preferably in the range of 1 to 100 ppm based on the weight of the aromatic bis(hydroxyalkyl) dicarboxylate.

[0074] [Physical Properties of Recycled Polymer] The recycled polyester polymer obtained in this manner is a polymer with little yellowness, which is considered to be of inferior quality. According to the polyester recovery method of the present invention, colored by-products caused by components other than polyester are less likely to be produced. In the recycled polyester polymer obtained by the present invention, the acrylic resin has been removed. Furthermore, if the acrylic resin is colored with a pigment, the pigment has also been removed.

[0075] In particular, when aprotic polar solvents are used for treatment, the acrylic resin, which is difficult to remove and hinders depolymerization, can be sufficiently removed, and colored by-products are less likely to be produced when intermediates are produced by depolymerization, etc. Furthermore, by adding a subsequent step such as crystallization, the catalyst is more likely to dissociate from the intermediate, such as bis(hydroxyalkyl) aromatic dicarboxylate, and impurities are less likely to remain in the system. This effect is particularly pronounced when depolymerization is performed using a low concentration of manganese-based catalyst. Furthermore, in addition to removing the acrylic resin, if the polyester fibers in the textile product are dyed, the dye is also removed.

[0076] The resulting recycled polyester polymer preferably exhibits the following properties: ＊ , a ＊ , b＊ As the hue in the color space colorimeter, b ＊ The value is preferably 8 or less. The yellowness index (YI) is preferably 15 or less. The whiteness index (W) is preferably 75 or more. The obtained recycled polyester polymer has an intrinsic viscosity (IV) of the polymer of preferably 0.30 to 1.50 dL / g, more preferably 0.40 to 1.30 dL / g, and particularly preferably 0.50 to 1.20 dL / g.

[0077] The present invention will be described in more detail below with reference to the following examples. The values ​​in the examples were determined by the following methods. 1) Intrinsic Viscosity (IV): The recovered polyester was dissolved in 10 mL of a tetrachloroethane / phenol mixed solvent (volume ratio 1 / 1), and the intrinsic viscosity (dL / g) at 35°C was measured.

[0078] 2) Glass transition point (Tg), crystallization temperature (Tc), melting point (Tm) 10 mg of the sample was cut and placed in an aluminum pan, and the melting point was measured using a differential scanning calorimeter "DSC Q10" manufactured by TA Instruments-Waters LLC. The measurement conditions were as follows: first, the sample was heated from 25°C to 300°C at a heating rate of 20°C / min, and then rapidly cooled and quenched. The quenched sample was then heated from 25°C to 300°C at a heating rate of 20°C / min, and the crystalline melting point was determined.

[0079] 3) Polymer Hue The dissolved recovered material (5 g) was pressed between two metal plates to form a plate, which was then heated at 140°C for 2 hours to crystallize the sample to prepare a measurement sample. The measurement sample was measured for hue L according to JIS Z8781-4:2013 using a measuring device ("SE7700" manufactured by Nippon Denshoku Industries Co., Ltd.). ＊ , a ＊ , b ＊ The yellowness index (YI) was calculated using the following formula (1), and the whiteness index (W) was calculated using the following formula (2). Yellowness index (YI): 0.34-71.7×a ＊ / L ＊ +178.78 x b ＊ / L ＊ (1) Whiteness (W): 100-√{(100-L ＊ ) ２+a ＊２ +b ＊２} (2) The higher the yellowness index (YI) value, the stronger the yellowness, and the higher the whiteness index (W) value, the stronger the whiteness.

[0080] [Example 1] (Polyester component recovery process) As a textile product made of polyester fiber and acrylic resin, an acrylic-printed polyester fabric (hereinafter referred to as "fabric") was prepared as a sample by printing an acrylic rubber containing a pigment ink onto a fabric made of polyester fiber (2 / 2 twill weave, 100% polyethylene terephthalate (PET) fiber). The acrylic resin was crosslinked.

[0081] 300 g of this fabric was placed in a 2-L separable flask along with 1500 g of ethylene glycol (EG, a polar solvent) (1501.13 g total) in which 1.13 g of zinc acetate (a depolymerization catalyst) had been dissolved, and the flask was then sealed with nitrogen. The separable flask containing the sample was then heated to an internal temperature of 175°C using a mantle heater, and depolymerization treatment was carried out at atmospheric pressure for 1 hour while stirring. Insoluble matter, likely a printed portion, was identified in the depolymerized BHET (bis(hydroxyethyl) benzenedicarboxylate) solution. The depolymerized solution was then filtered through a 200 μm mesh, and the remaining printed portion was removed by solid-liquid separation. The recovered printed portion retained its original shape and had not been decomposed during the above process.

[0082] Meanwhile, the 175°C BHET solution obtained by solid-liquid separation was cooled to 90°C and filtered through a cartridge filter with a mesh size of 0.20 μm to remove impurities. After further slow cooling to 70°C, the temperature was lowered to 15°C while stirring and cooling, and then stirring was carried out for 60 minutes while maintaining the internal temperature at 15°C. The internal temperature was lowered to precipitate BHET crystals, yielding a BHET / EG slurry. This 15°C BHET / EG slurry was subjected to a compression treatment using a filter press manufactured by Nippon Filter Equipment Co., Ltd., to perform solid-liquid separation of BHET and EG. The separated BHET contained 35% by mass of EG based on the weight of the cake recovered after the filter press.

[0083] After the solid-liquid separation was completed, the BHET was dissolved in 20 times its mass of hot water (90°C), and then 0.25 times its mass of activated carbon was added and stirred for 1 hour. Nutsche filtration was then performed, and the aqueous solution from which the activated carbon had been removed was cooled to 5°C to precipitate BHET. Nutsche filtration was then performed again to recover the BHET, which is a polyester component. The recovered BHET was dried in a vacuum dryer at 50°C for 8 hours, yielding 254 g of dried BHET. The resulting BHET was white and free of any visible foreign matter.

[0084] (Repolymerization of Polyester) Then, 254 g of the obtained dried BHET was placed in a reaction vessel under normal pressure in a nitrogen atmosphere, together with 0.007 g of a phosphorus-based stabilizer and 0.07 g of diantimony trioxide as a repolymerization catalyst. Next, the temperature inside the reactor was set to 285°C, and the pressure was gradually reduced under the following conditions: normal pressure for 10 minutes, a pressure of 4 kPa for 10 minutes, and a pressure of 0.4 kPa for 40 minutes. A polycondensation reaction was carried out while distilling off ethylene glycol and other substances generated during the reaction outside the reactor, to obtain a recycled polyester polymer.

[0085] The resulting recycled polyester polymer was continuously extruded in the form of strands from the discharge port, cooled, and cut into pellets of approximately 3 mm in size. The whiteness was high and no foreign matter was found to be present. The color of the recycled polyester after repolymerization was L. ＊ a ＊ b ＊ The physical properties such as the values ​​are shown in Table 1.

[0086] [Example 2] The depolymerization catalyst used in Example 1 was changed from 1.13 g of zinc acetate to 120 g of sodium methoxide per 300 g of fabric, and the internal temperature was changed from 175°C to 130°C. The polyester component as an intermediate substance was recovered by vacuum drying in the same manner as in Example 1, and further repolymerized to obtain recycled polyester.

[0087] In the BHET solution immediately after depolymerization at 130°C, insoluble matter that appeared to be the printed part was confirmed, as in Example 1. The printed part recovered by filtering the solution through a 200 μm mesh retained its original shape and was not decomposed during the above process. The finally obtained recycled polyester polymer also had a high whiteness and was free of any foreign matter. The color L of the recycled polyester after repolymerization was ＊ a ＊ b ＊ The physical properties such as the values ​​are also shown in Table 1.

[0088] [Example 3] In the same manner as in Example 1, except that the depolymerization catalyst used in Example 1 was changed from 1.13 g of zinc acetate to 1.57 g of titanium tetraoxide and the internal temperature was changed from 175°C to 130°C, BHET, a polyester component, was recovered and further repolymerized to obtain a recycled polyester.

[0089] In the BHET solution immediately after depolymerization at 130°C, insoluble matter that appeared to be the printed part was confirmed, as in Example 1. The printed part recovered by filtering the solution through a 200 μm mesh retained its original shape and was not decomposed during the above process. The finally obtained recycled polyester polymer also had a high whiteness and was free of any foreign matter. The color L of the recycled polyester after repolymerization was ＊ a ＊ b ＊ The physical properties such as the values ​​are shown in Table 1.

[0090] Comparative Example 1 An attempt was made to recover BHET, a polyester component, in the same manner as in Example 1, except that the internal temperature of the EG containing the depolymerization catalyst in Example 1 was changed from 175°C to 220°C. However, the insoluble matter in the BHET solution immediately after the depolymerization treatment no longer maintained its original shape and was partially decomposed, and not only BHET but also the acrylic print and the black pigment contained in the print were mixed into the EG solution, making separation impossible. When the depolymerization treatment time was changed from 1 hour to 4 hours, the dissolution of the acrylic print further progressed.

[0091] Comparative Example 2 An attempt was made to recover BHET, a polyester component, in the same manner as in Example 1, except that the internal temperature of the EG containing the depolymerization catalyst in Example 1 was changed from 175°C to 70°C and the depolymerization treatment time was changed from 1 hour to 4 hours. However, it was confirmed that neither the printed portion nor the woven portion changed, and separation was not possible.

[0092] Comparative Example 3 The polyester component BHET was recovered and further repolymerized to obtain a recycled polyester in the same manner as in Example 1, except that the depolymerization catalyst in Example 1 was changed from 1.13 g of zinc acetate to 0.38 g of manganese acetate, the internal temperature was changed from 175°C to 220°C, and the depolymerization treatment time was changed from 1 hour to 4 hours.

[0093] However, in the BHET solution immediately after depolymerization at 220°C, insoluble matter that appeared to be the printed part was confirmed, as in Example 1. However, unlike Example 1, the acrylic printed part did not maintain its original shape and was partially decomposed, and a small amount of the acrylic printed part was mixed into the EG solution. In addition, coloration was observed in the recycled polyester recovered in the same manner as in Example 1. The color L of the recycled polyester after repolymerization was ＊ a ＊ b ＊ The physical properties such as the values ​​are shown in Table 1.

[0094]

[0095] Example 4 (Textile Product) 400 g of discarded fabric sheet material for vehicle interiors generated during the manufacturing process was prepared. This textile product contained 94 wt% polyethylene terephthalate fiber (PET fiber, IV 0.6 dl / g, Tg = 70°C, Tm = 256°C, single fiber fineness 5.0 dtex, strength 1.2 cN / dtex, elongation 35%) and 6 wt% acrylic resin (PMMA resin) used as a backing agent. The acrylic resin was not crosslinked, and the fibers were colored with a pigment.

[0096] (Polar Solvent Treatment (1) Polyester Component Recovery Step) 400 g of this textile product was placed in a 5-liter separable flask, and 4,000 g of dimethyl sulfoxide (DMSO, a polar solvent) that had been heated in a separate beaker to an internal temperature of 105°C was added to the separable flask. With the textile product immersed in dimethyl sulfoxide, the mixture was stirred for 180 minutes while the internal temperature was adjusted to 105°C (immersion treatment). The textile product was then removed from the separable flask and squeezed to remove excess treatment liquid (a liquid in which a dye and an acrylic resin were dissolved in dimethyl sulfoxide). Coloration was observed in the treatment liquid, and the weight of the lightly decolorized textile product after squeezing was 970 g. The textile product after the above treatment was dried in a vacuum dryer at 80°C for 8 hours to remove the DMSO, and 320 g of a textile product made of polyester was recovered as a polyester component.

[0097] (Polyester Component Recovery Step (2): Depolymerization Treatment) The polyester component in the textile product recovered by the above method was further depolymerized. First, 300 parts by weight of polyester, 1,500 parts by weight of ethylene glycol (EG), and 0.38 parts by weight (100 mmol% relative to the polyester) of manganese acetate (Mn acetate) as a depolymerization catalyst were placed in a 2-L separable flask and nitrogen was sealed inside. At this time, the Mn acetate was dissolved in EG before being added. Thereafter, the separable flask containing the polyester was heated using a mantle heater to an internal temperature of 220°C, and depolymerization treatment was carried out at normal pressure for 4 hours while stirring, yielding a BHET (bis(hydroxyethyl) benzenedicarboxylate) solution.

[0098] The BHET solution after depolymerization was brown. Therefore, this depolymerized solution was further filtered through a 200 μm mesh to remove the solid content remaining inside, and then slowly cooled to 70° C. After that, while stirring and cooling, a temperature-lowering treatment (1) from 70° C. to 40° C. was carried out for 10 minutes from 0 to 10 minutes, a temperature-lowering treatment (2) from 40° C. to 30° C. was carried out for 50 minutes from 10 to 60 minutes, and a temperature-lowering treatment (3) from 30° C. to 15° C. was carried out for 120 minutes from 60 to 180 minutes, and then stirring was carried out for 60 minutes while maintaining the internal temperature at 15° C. The internal temperature was lowered over a total of 4 hours, causing BHET crystals to precipitate, thereby obtaining a BHET / EG slurry.

[0099] This BHET / EG slurry was then compressed using a filter press manufactured by Nippon Filter Equipment Co., Ltd., to separate the BHET and EG into solid and liquid forms. The BHET after this solid-liquid separation contained 35 wt % EG. The BHET was then dried in a vacuum dryer at 50°C for 8 hours, and the dried BHET was recovered as a polyester component. The resulting BHET was white and free of any visible foreign matter.

[0100] (Repolymerization of Polyester) Then, 254 parts by weight of the obtained dried BHET was charged into a reaction vessel under normal pressure and nitrogen atmosphere, together with 0.007 parts by weight of a phosphorus-based stabilizer, and 0.07 parts by weight of diantimony trioxide as a repolymerization catalyst. The temperature inside the reactor was then set to 285°C, and the pressure was gradually reduced under the following conditions: normal pressure for 10 minutes, 4 kPa for 10 minutes, and then 0.4 kPa for 40 minutes. While products such as ethylene glycol generated in the reaction were distilled out of the reactor, a polycondensation reaction was carried out to obtain recycled polyester. The L of the dried product before and after the recovery treatment and the recycled polyester after repolymerization were shown in Fig. 1. ＊ a ＊ b ＊ The physical properties such as the values ​​are shown in Table 2.

[0101] [Example 5] The polyester component (BHET) was recovered in the same manner as in Example 1, except that the treatment temperature when the textile product was immersed in dimethyl sulfoxide (DMSO) was changed from 105°C to 130°C. The color of the treatment liquid after squeezing in the acrylic resin removal step was darker than in Example 1, and a precipitate thought to be a dissolved PET was also confirmed in the treatment liquid. However, the textile product itself dried in a vacuum dryer was a polyester fabric with high whiteness. The polyester component (BHET) after depolymerization of the polyester was also white. This depolymerized polyester component (BHET) was subjected to a polycondensation reaction in the same manner as in Example 1 to obtain recycled polyester. The L values ​​of the dried product before the recovery treatment, the product after the treatment, and the recycled polyester after repolymerization were shown in Table 1. ＊ a ＊ b ＊ The physical properties such as the values ​​are also shown in Table 2.

[0102] [Example 6] The polyester component (BHET) was recovered in the same manner as in Example 1, except that the treatment temperature when the textile product was immersed in dimethyl sulfoxide (DMSO) was changed from 105°C to 160°C. The weight of the recovered polyester was reduced, and the color of the treatment liquid after squeezing in the acrylic resin removal step was darker than in Examples 1 and 2. However, the textile product itself dried in a vacuum dryer was a polyester fabric with a high degree of whiteness. The polyester component (BHET) after depolymerization of the polyester was also white. This depolymerized polyester component (BHET) was subjected to a polycondensation reaction in the same manner as in Example 1 to obtain recycled polyester. The L values ​​of the dried product before the recovery treatment, after the treatment, and the recycled polyester after repolymerization were shown in Table 1. ＊ a ＊ b ＊ The physical properties such as the values ​​are also shown in Table 2.

[0103] Comparative Example 4 The procedure for depolymerization of the polyester component was the same as in Example 1, except that the textile product was not immersed in dimethyl sulfoxide (DMSO). Specifically, 400 g of textile product, 1500 parts by weight of ethylene glycol (EG), and 0.38 parts by weight (100 mmol% relative to the polyester) of manganese acetate as a depolymerization catalyst were added to a 2-L separable flask and nitrogen was sealed inside. Note that the manganese acetate was dissolved in EG before use. The separable flask containing the textile product was then heated to an internal temperature of 220°C using a mantle heater, and treated at normal pressure while stirring. However, the fiber shape was maintained, and only slight decomposition, dissolution, etc. occurred, and depolymerization did not proceed.

[0104]

[0105] The present invention provides a method for recovering polyester components from textile products containing polyester fibers and acrylic resin. The recovered polyester components are then depolymerized, and organic matter other than polyester is separated and adsorbed and removed. The resulting recycled polyester polymer is then repolymerized. Because it has the same color and physical properties as virgin polyester polymer obtained by polymerization of petroleum-derived raw materials, it can be used as a raw material for textile products. This method promotes the reuse of discarded textile products that would otherwise not be recycled into fibers, thereby contributing to reducing environmental impact.

Claims

1. A method for recovering polyester components, comprising contacting a textile product containing polyester fibers and acrylic resin with a polar solvent at a temperature of 90°C or higher and 185°C or lower, and recovering the polyester components.

2. The method for recovering polyester components according to claim 1, wherein the polyester fibers are made of polyesters having alkylenebenzene dicarboxylate as the main repeating unit.

3. The method for recovering polyester components according to claim 1, wherein the acrylic resin is a crosslinked acrylic resin.

4. The method for recovering a polyester component according to claim 1, wherein the polar solvent is a lower alcohol or an aprotic polar solvent.

5. The method for recovering a polyester component according to claim 4, wherein the polar solvent contains a catalyst.

6. The method for recovering a polyester component according to claim 5, wherein the catalyst is a zinc-based catalyst.

7. The method for recovering a polyester component according to claim 5, wherein the catalyst is sodium methoxide or titanium tetraoxide.

8. The method for recovering a polyester component according to claim 4, wherein the lower alcohol is an alkylene glycol.

9. The method for recovering a polyester component according to claim 4, wherein the aprotic polar solvent is at least one selected from the group consisting of dimethyl sulfoxide, dimethylacetamide and dimethylformamide.

10. A method for recovering a polyester component according to claim 1, wherein the acrylic resin is a crosslinked acrylic resin, the polar solvent is a lower alcohol containing a catalyst, and the solvent is contacted at a temperature of 100°C to 185°C.

11. The method for recovering a polyester component according to claim 1, wherein the polar solvent is an aprotic polar solvent and the treatment is carried out at a temperature of 90°C or higher and 160°C or lower when the solvent is brought into contact.

12. The method for recovering a polyester component according to claim 1, wherein after contact with the polar solvent, the polyester component is treated with an adsorbent.

13. The method for recovering a polyester component according to claim 1, wherein the recovered polyester component is a bis(hydroxyalkyl) benzenedicarboxylate.

14. The method for recovering a polyester component according to claim 13, wherein after contact with the polar solvent, the polyester is further depolymerized into a bis(hydroxyalkyl) aromatic dicarboxylate in an alkylene glycol containing a depolymerization catalyst.

15. A method for producing recycled polyester, which comprises repolymerizing the polyester component obtained by the recovery method according to any one of claims 1 to 14.

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