Method for recovering polyester component and method for producing recycled polyester

Abstract

To provide a method for recovering a polyester component from a fiber product mainly containing a polyester fiber and an acrylic resin, and a method for producing recycled polyester which uses the recovered polyester component and shows little coloration.SOLUTION: A method for recovering a polyester component brings a fiber product containing a polyester fiber and an acrylic resin into contact with an aprotic polar solvent at a temperature of 90 to 160°C. The polyester fiber is composed of polyester containing alkylene benzene dicarboxylate as a main repeating unit, the acrylic resin is a non-crosslinked acrylic resin, and the aprotic polar solvent is preferably any one of dimethylsulfoxide, dimethylacetamide and dimethylformamide. A method for producing recycled polyester repolymerizes the polyester component obtained by the recovery method.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for recovering polyester components from textile products that mainly contain polyester fibers and acrylic resins, and a method for producing recycled polyester using the recovered polyester. [Background technology]

[0002] Polyester is widely used in textile products due to its excellent properties, but the effective utilization of polyester textile products after use is a major issue, including environmental concerns. In particular, textile products in which polyester fiber sheets are backed with acrylic resins are used in large quantities as materials for automobile interiors, and there is a problem in that a large amount of waste is generated during the production process.

[0003] Typically, material recycling, thermal recycling, and chemical recycling are considered as the main methods for treating used polyester fiber products. 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 of quality associated with recycling. Among these, chemical recycling, which is characterized by depolymerizing polyester to an intermediate that can be directly subjected to a polycondensation reaction to produce recycled polyester, is also an excellent method from the viewpoint of energy consumption.

[0004] 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.

[0005] For example, in Patent Document 1, as a step of removing discoloration-causing substances, attempts have been made to produce an intermediate product after depolymerization, such as an adsorption treatment in which the discoloration-causing substances are brought into contact with an adsorbent, 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, while these methods can remove to some extent discoloration-causing substances such as dyes that are clearly mixed into the polymer, there is a problem in that it is not possible to obtain a polyester polymer with reduced discoloration at the same level as that obtained by a polyester polymer produced by a normal production method that does not use recycled raw materials. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-88096 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for recovering polyester components from textile products that mainly contain polyester fibers and acrylic resin, and a method for producing recycled polyester with little coloration using the recovered polyester. [Means for solving the problem]

[0008] The method for recovering a polyester component of the present invention includes the following inventions. (1) A method for recovering a polyester component, comprising contacting a textile product containing polyester fibers and an acrylic resin with an aprotic polar solvent at a temperature of 90 to 160°C, and recovering the polyester component. (2) The method for recovering a polyester component according to (1) above, wherein the polyester fiber is made of a polyester having alkylenebenzene dicarboxylate as the main repeating unit. (3) The method for recovering a polyester component according to (1) or (2) above, wherein the acrylic resin is a non-crosslinked acrylic resin. (4) The method for recovering a polyester component according to any one of (1) to (3) above, wherein the aprotic polar solvent is at least one selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide. (5) A method for recovering a polyester component according to any one of (1) to (4) above, which comprises contacting the polyester component with an aprotic polar solvent, recovering the polyester component, and then depolymerizing the polyester component into a bis(hydroxyalkyl) aromatic dicarboxylate in an alkylene glycol containing a depolymerization catalyst. (6) The method for recovering a polyester component according to (5) above, wherein the depolymerization conditions are a temperature of 180°C to 250°C for 2 to 8 hours. (7) A method for producing recycled polyester, which comprises repolymerizing the polyester component obtained by the recovery method according to any one of (1) to (6) above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for recovering polyester components from textile products that mainly contain polyester fibers and acrylic resin, and a method for producing recycled polyester with little coloration using the recovered polyester. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 it is essential that the textile product is brought into contact with an aprotic polar solvent at a temperature of 90 to 160°C.

[0011] [Textile products] The textile product used in the present invention contains polyester fibers and acrylic resin. Furthermore, it is preferable that the textile product is primarily composed of polyester fibers, and here, "primarily composed of polyester fibers" means that polyester fibers make up the largest proportion of the fibers that make up the textile product. The polyester fibers preferably account for 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more, based on the weight of the textile product.

[0012] The acrylic resin used simultaneously with the textile product is preferably used to maintain the shape of the textile product, such as a backing, and is preferably 30% by weight or less, more preferably 20% by weight to 2% by weight, and particularly preferably 10% by weight to 1% by weight, based on the weight of the textile product.

[0013] More specifically, it is particularly effective for automobile interior materials, such as acrylic resin-backed polyester fiber products for car seats, which are mass-produced and tend to produce scraps during the manufacturing process.

[0014] [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.

[0015] The polycarboxylic acid constituting the 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.

[0016] The polyalcohol, the other component constituting the polyester, is preferably a diol or an ester-forming derivative thereof. The diol is preferably an aliphatic glycol having 2 to 20 carbon atoms. Examples of the 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.

[0017] In the present invention, a polyester obtained by combining such a polycarboxylic acid and a polyalcohol is used as one of the starting materials for forming 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, and 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.

[0018] 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).

[0019] In particular, when the polyester is a polyalkylene terephthalate, which is an aromatic polyester, a polyester obtained by copolymerizing terephthalic acid as a dicarboxylic acid component with isophthalic acid or a sulfoisophthalic acid cation salt such as 5-sodium sulfoisophthalic acid as a copolymerization component is one preferred embodiment in terms of 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. The polyester fibers may be colored with a pigment or the like.

[0020] [Acrylic resin] The textile product used in the present invention contains, in addition to the polyester fibers described above, an acrylic resin, which is a resin made from a combination of acrylic acid esters and / or methacrylic acid esters, such as polymethyl methacrylate (PMMA) resin.

[0021] Furthermore, the acrylic resin used in the present invention 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 physical changes rather than a chemical reaction (polymerization reaction) to solidify. The acrylic resin may contain flame retardants such as organophosphorus flame retardants, halogen-based flame retardants such as chlorine and bromine, metal hydroxides, and antimony oxides to impart flame retardancy.

[0022] [Polar solvent treatment (1) Polyester component recovery process] In the present invention, a textile product containing the above-described polyester fiber and acrylic resin is used as a starting material to recover the polyester component. The textile product is then contacted with an aprotic polar solvent at a temperature of 90 to 160°C. The aprotic solvent is then removed from the textile product, thereby removing the solvent and additives such as the acrylic resin, pigment, and flame retardant dissolved therein.

[0023] 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 fiber 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.

[0024] The temperature of the aprotic polar solvent during treatment is 90° C. to 160° C., 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.

[0025] In the solvent contacting step, the textile product is preferably brought into contact with the aprotic polar solvent by immersing the textile product in the aprotic polar solvent. This immersion treatment may be carried out by leaving the textile product stationary in the aprotic polar solvent, or is preferably carried out by immersing the textile product in the aprotic polar solvent and then stirring the resulting mixture with a liquid circulation system or a rotary blade.

[0026] This polyester component recovery process (1) is useful for removing coloring substances such as pigments from the fibers as well as removing 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. Dewatering can be performed by squeezing, centrifugal separation, or Soxhlet extraction.

[0027] 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 the "polyester component recovery step (1) polar solvent treatment," the solvent contact step and the removal step may be performed once, but are preferably performed five or fewer times, and more preferably three or fewer times.

[0028] The draining step is carried out 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.

[0029] According to the above-described method, the acrylic resin, dye components, and pigment components are dissolved in an aprotic polar solvent from a textile product containing polyester fibers and an acrylic resin, and the solution is then removed, thereby recovering the polyester itself as the polyester component. This method has made it possible to effectively remove foreign matter from the polyester components recovered, including acrylic resins and additives such as dyes, pigments, and flame retardants.

[0030] [Polyester component recovery process (2) Depolymerization treatment] Furthermore, it is preferable that the polyester obtained in the polyester component recovery step (1) is further depolymerized.

[0031] More specifically, it is preferable to depolymerize the polyester component obtained in the polyester component recovery step (1) into a bis(hydroxyalkyl) aromatic dicarboxylate in alkylene glycol containing a depolymerization catalyst, and recover the bis(hydroxyalkyl) aromatic dicarboxylate as the polyester component in the polyester component recovery step (2). The present inventors have discovered that if the depolymerization treatment in the polyester component recovery step (2) is carried out without the polar solvent treatment in the polyester component recovery step (1) and without removing the acrylic resin, the depolymerization reaction does not proceed, and therefore it is particularly preferable to combine the recovery steps (1) and (2).

[0032] 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.

[0033] [catalyst] The catalyst used in the depolymerization reaction of the depolymerization step is preferably a first transition metal catalyst. Specific examples include first transition metal fatty acid salts, carbonates, sulfates, phosphates, oxides, hydroxides, halides, and alcoholates. Manganese and zinc are preferably used as the first transition metal.

[0034] As the catalyst, manganese oxide, manganese acetate, zinc oxide, or zinc acetate is preferably used, with manganese acetate being particularly preferred. 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 process. The catalyst is preferably dissolved or suspended in alkylene glycol before use.

[0035] Generally, depolymerized polyester products often gradually become discolored due to long-term storage, etc. However, the products obtained by the recovery method and production method of the present invention clearly show little discoloration. In particular, when a manganese-based catalyst is used during depolymerization, a polyester polymer with little discoloration can be obtained.

[0036] The amount of catalyst used during depolymerization is preferably 20 to 500 mmol%, more preferably 30 to 300 mmol%, and particularly preferably 50 to 150 mmol% relative to the polyester. Here, "mol%" refers to the ratio of the number of catalyst molecules to the constituent units of the polyester. "mmol%" is 1 / 1000 of that. 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 inhibiting discoloration will decrease, which is not preferable. If a manganese-based catalyst is used as the catalyst, depolymerization can be carried out with a small amount used.

[0037] [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.

[0038] 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.

[0039] 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 amount of contaminating depolymerization catalyst and other foreign matter can be reduced.

[0040] [Refining process] The method for recovering a polyester component of the present invention preferably further comprises a purification step of purifying the depolymerization reaction product after the depolymerization step. The purification step may be crystallization or adsorption treatment, and it is more preferable to perform both of them.

[0041] [Crystallization] The purification step is carried out by lowering the temperature of the depolymerization reaction product in alkylene glycol to cause crystallization. The temperature lowering conditions for crystallization are preferably from a temperature of 60°C or higher to 25°C or lower, and more preferably to 15°C or lower.

[0042] After the crystallization, solid-liquid separation is preferably carried out. The alkylene glycol content in the cake after the solid-liquid separation is preferably 100% by weight or less, more preferably 55% by weight or less, still more preferably 1 to 30% by weight, and particularly preferably 5 to 25% by weight.

[0043] 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 substances that cause coloration can be washed away, and a more highly purified bis(hydroxyalkyl) aromatic dicarboxylate can be obtained.

[0044] 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. If the liquid temperature is higher than this, the cake itself will be more likely to dissolve, resulting in a lower yield, which is not preferred.

[0045] After washing, the product is dried in a vacuum dryer or the like to obtain the aromatic dicarboxylic acid bis(hydroxyalkyl). 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.

[0046] [Adsorption treatment] It is also preferable to further subject the obtained aromatic dicarboxylate bis(hydroxyalkyl) to adsorption treatment for foreign matter using an adsorbent such as activated carbon. Other adsorbents include those made of styrene or acrylic cross-linked copolymers, and more preferably, synthetic adsorbents made of styrene or acrylic cross-linked copolymers having a macroporous structure without functional groups.

[0047] This adsorption treatment is a process in which a bis(hydroxyalkyl) aromatic dicarboxylate composition is brought into contact with an adsorbent, and organic matter derived from decomposition products of fibers and resins other than polyester contained in the bis(hydroxyalkyl) aromatic dicarboxylate composition, as well as additives such as dyes, pigments, and flame retardants, is adsorbed onto the adsorbent, thereby obtaining a more purified bis(hydroxyalkyl) aromatic dicarboxylate.

[0048] This adsorption step can be carried out by dissolving the aromatic dicarboxylate bis(hydroxyalkyl) composition in water or an organic solvent to form a solution, and then adding the adsorbent to the solution, thereby bringing the two into contact in water or an organic solvent.

[0049] [Polyester component: bis(hydroxyalkyl) benzenedicarboxylate] The polyester components contained in textile products can be recovered as bis(hydroxyalkyl) aromatic dicarboxylates as polyester intermediates through the depolymerization process. These bis(hydroxyalkyl) aromatic dicarboxylates, which are also polyester components, can be used as intermediates in the production of recycled polyester polymers.

[0050] The bis(hydroxyalkyl) aromatic dicarboxylate obtained by the recovery method of the present invention varies depending on the polyester and alkylene glycol subjected to depolymerization. When the polyester is a polyester (polyalkylene terephthalate) using terephthalic acid as the polycarboxylic acid as the raw material, bis(hydroxyalkyl) benzenedicarboxylate (hereinafter sometimes referred to as BHAT; bishydroxyalkyl terephthalate) is obtained.

[0051] 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.

[0052] As described above, the method for recovering a polyester component of the present invention is preferably a method for recovering a polyester component, which comprises contacting a textile product containing polyester fibers and an acrylic resin with an aprotic polar solvent at a temperature of 90 to 160°C to recover the polyester component, wherein the polyester fibers are made of a polyester having alkylenebenzene dicarboxylate as a main repeating unit, the acrylic resin is a non-crosslinked acrylic resin, the aprotic polar solvent is at least one selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide, and further comprising depolymerizing the resulting product into a bis(hydroxyalkyl) aromatic dicarboxylate in alkylene glycol after removing the acrylic resin.

[0053] [Production of recycled polymers (repolymerization)] The polyester component obtained by the recovery method of the present invention can be further repolymerized to produce recycled polyester. In particular, when the obtained polyester component is a bis(hydroxyalkyl) aromatic dicarboxylate, 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, is less colored, and has excellent hue.

[0054] As a catalyst for repolymerization to obtain a recycled polyester polymer, for example, a known antimony-based, germanium-based or titanium-based catalyst can be used, and for example, diantimony trioxide can be used.

[0055] It is preferable to carry out the polycondensation reaction while discharging alkylene glycol and the like generated in the repolymerization reaction outside the reactor. The amount of catalyst used is in the range of 10 to 1000 ppm based on the weight of the aromatic dicarboxylic acid bis(hydroxyalkyl).

[0056] 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.

[0057] [Physical properties of recycled polymers] The recycled polyester polymer obtained in this manner is a polymer with little yellowness, which is considered to be of inferior quality. The polyester recovery method of the present invention allows for sufficient removal of acrylic resin, which was previously impossible to remove and hindered depolymerization, thereby reducing the generation of colored by-products when intermediates are produced by depolymerization, etc. Furthermore, the addition of a subsequent crystallization step or other process is thought to facilitate dissociation of the catalyst from the intermediate, such as aromatic dicarboxylate bis(hydroxyalkyl), and therefore reduces the likelihood of impurities remaining in the system. This effect is particularly pronounced when depolymerization is performed using a low concentration of manganese-based catalyst.

[0058] In the recycled polyester polymer obtained by the present invention, the acrylic resin has been removed, and if the polyester fiber in the textile product is dyed, the dye has also been removed.

[0059] The resulting recycled polyester polymer preferably exhibits the following properties: The resulting recycled polyester polymer meets the L certification of the International Commission on Illumination (CIE). * , a * , b * As the hue in the color space colorimeter, b * The value is preferably 8 or less. The resulting recycled polyester polymer preferably has a yellowness index (YI) of 15 or less. The resulting recycled polyester polymer preferably has a whiteness (W) of 75 or more. The resulting 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. [Example]

[0060] The present invention will be described in more detail below with reference to examples, in which the values ​​were determined by the following methods.

[0061] 1) Hue (L * a * b * , YI, W) A sample (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 measurement device (NW-12 manufactured by Nippon Denshoku Industries Co., Ltd.). * , a * , b * The values ​​were measured. The yellowness index (YI) was calculated by the following formula (1), and the whiteness index (W) was calculated by the following formula (2). Yellowness (YI): 0.34-71.7×a * / L * +178.78×b * / L * (1) Whiteness (W):100-√{(100-L * ) 2 +a *2 +b *2} (2) The higher the yellowness index (YI) number, the more yellowish the color, and the higher the whiteness index (W) number, the whiter the color.

[0062] 2) Intrinsic viscosity (IV) The fiber (polymer) sample 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.

[0063] [Example 1] (Textile products) 400g of discarded fabric sheet material for vehicle interiors generated during the manufacturing process was prepared. This textile product contained 94wt% polyethylene terephthalate fiber (PET fiber, IV 0.6dl / g, Tg = 70°C, Tm = 256°C, single fiber fineness 5.0dtex, strength 1.2cN / dtex, elongation 35%) and 6wt% acrylic resin (PMMA resin) used as a backing agent. The fiber was also colored with pigment.

[0064] (Polar solvent treatment) 400 g of this textile product was placed in a 5-liter separable flask, and 4000 g of dimethyl sulfoxide (DMSO) that had been heated in a separate beaker until the internal temperature reached 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).

[0065] The textile was then removed from the separable flask and squeezed to remove excess treatment liquid (a liquid in which dye and acrylic resin were dissolved in dimethyl sulfoxide). Coloration was observed in the treatment liquid, and the weight of the lightly decolorized textile 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.

[0066] (Polyester component recovery process (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, 1500 parts by weight of ethylene glycol (EG), and 0.38 parts by weight of manganese acetate (Mn acetate) as a depolymerization catalyst (100 mmol% relative to polyester) were placed in a 2 L separable flask and then sealed with nitrogen. At this time, Mn acetate was dissolved in EG before being added. Thereafter, the separable flask containing the polyester was heated using a mantle heater with the internal temperature set to 220°C, and depolymerization treatment was carried out for 4 hours at normal pressure while stirring, to obtain a BHET (bis(hydroxyethyl) benzenedicarboxylate) solution.

[0067] The BHET solution after depolymerization was brown. Therefore, the depolymerized solution was further filtered through a 200 μm mesh to remove the remaining solids. After gradual cooling to 70°C, the solution was stirred and cooled, with temperature reduction treatment (1) from 70°C to 40°C for 10 minutes from 0 to 10 minutes, temperature reduction treatment (2) from 40°C to 30°C for 50 minutes from 10 to 60 minutes, and temperature reduction treatment (3) from 30°C to 15°C for 120 minutes from 60 to 180 minutes. Subsequently, the internal temperature was maintained at 15°C and stirring was continued for 60 minutes. The internal temperature was reduced over a total of 4 hours, allowing BHET crystals to precipitate, yielding a BHET / EG slurry.

[0068] Furthermore, this BHET / EG slurry was subjected to solid-liquid separation of BHET and EG by pressing using a filter press manufactured by Nippon Filter Equipment Co., Ltd. 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.

[0069] (repolymerization of polyester) Thereafter, 254 parts by weight of the obtained dry BHET was charged into a reaction vessel under normal pressure in a nitrogen atmosphere together with 0.007 part by weight of a phosphorus-based stabilizer and 0.07 part by weight of diantimony trioxide as a repolymerization catalyst.

[0070] The temperature inside the reactor was then raised to 285°C, and the pressure was gradually reduced under the following conditions: atmospheric pressure for 10 minutes, a pressure of 4 kPa for 10 minutes, and a pressure of 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 produce recycled polyester. Before recovery and treatment, dried product after treatment, L of recycled polyester after repolymerization * a * b * The physical properties such as the values ​​are shown in Table 1.

[0071] [Example 2] The polyester component (BHET) was recovered in the same manner as in Example 1, except that the treatment temperature when immersing the textile product 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 process was darker than in Example 1, and precipitates thought to be dissolved PET were 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.

[0072] This depolymerized polyester component (BHET) was subjected to a polycondensation reaction in the same manner as in Example 1 to obtain a recycled polyester. Before recovery and treatment, dried product after treatment, L of recycled polyester after repolymerization * a * b * The physical properties such as the values ​​are also shown in Table 1.

[0073] [Example 3] 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 the vacuum dryer was a polyester fabric with a high degree of whiteness. Furthermore, the polyester component (BHET) after depolymerization of the polyester was also white.

[0074] This depolymerized polyester component (BHET) was subjected to a polycondensation reaction in the same manner as in Example 1 to obtain a recycled polyester. Before recovery and treatment, dried product after treatment, L of recycled polyester after repolymerization * a * b * The physical properties such as the values ​​are also shown in Table 1.

[0075] [Comparative Example 1] The depolymerization treatment of the polyester component was carried out in the same manner as in Example 1, except that the textile product was not immersed in dimethyl sulfoxide (DMSO). Specifically, 1500 parts by weight of ethylene glycol (EG) and 0.38 parts by weight of manganese acetate (100 mmol% relative to polyester) as a depolymerization catalyst were placed in a 2-L separable flask for 400 g of textile product, and the flask was then filled with nitrogen. Note that the manganese acetate was dissolved in EG before use.

[0076] The separable flask containing the fiber 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 or dissolution occurred, and depolymerization did not proceed.

[0077] [Table 1] [Industrial Applicability]

[0078] The present invention relates to a method for recovering polyester components from textile products containing polyester fibers and acrylic resins. The method involves depolymerizing the polyester, separating and adsorbing non-polyester organic matter, and then repolymerizing the depolymerized polyester. The resulting recycled polyester polymer has the same color and physical properties as virgin polyester polymer obtained by polymerization of petroleum-derived raw materials, and can therefore be used as a raw material for textile products. This 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 a polyester component, comprising contacting a textile product containing polyester fibers and an acrylic resin with an aprotic polar solvent at a temperature of 90 to 160°C, and recovering the polyester component.

2. 2. The method for recovering a polyester component according to claim 1, wherein the polyester fiber is made of a polyester having alkylenebenzene dicarboxylate as a main repeating unit.

3. 2. The method for recovering a polyester component according to claim 1, wherein the acrylic resin is a non-crosslinked acrylic resin.

4. 2. The method for recovering a polyester component according to claim 1, wherein the aprotic polar solvent is at least one selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide.

5. 2. The method for recovering a polyester component according to claim 1, wherein after the polyester component is recovered by contacting the polyester with an aprotic polar solvent, the polyester component is depolymerized into a bis(hydroxyalkyl) aromatic dicarboxylate in an alkylene glycol containing a depolymerization catalyst.

6. 6. The method for recovering a polyester component according to claim 5, wherein the depolymerization conditions are a temperature of 180 to 250° C. for 2 to 8 hours.

7. 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 6.

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