Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J11/00—Recovery or working-up of waste materials
  • C08J11/04—Recovery or working-up of waste materials of polymers
  • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
  • C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
  • C08J11/22—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds
  • C08J11/24—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds containing hydroxyl groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J11/00—Recovery or working-up of waste materials
  • C08J11/04—Recovery or working-up of waste materials of polymers
  • C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
  • C08J11/08—Recovery or working-up of waste materials of polymers without chemical reactions using selective solvents for polymer components
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/16—Dicarboxylic acids and dihydroxy compounds
  • C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
  • C08G63/181—Acids containing aromatic rings
  • C08G63/183—Terephthalic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/88—Post-polymerisation treatment
  • C08G63/89—Recovery of the polymer
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/91—Polymers modified by chemical after-treatment
  • C08G63/914—Polymers modified by chemical after-treatment derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/916—Dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J11/00—Recovery or working-up of waste materials
  • C08J11/04—Recovery or working-up of waste materials of polymers
  • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
  • C08J11/16—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with inorganic material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J11/00—Recovery or working-up of waste materials
  • C08J11/04—Recovery or working-up of waste materials of polymers
  • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
  • C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
  • C08J11/22—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds
  • C08J11/26—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic oxygen-containing compounds containing carboxylic acid groups, their anhydrides or esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
  • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2475/00—Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
  • C08J2475/04—Polyurethanes
  • C08J2475/08—Polyurethanes from polyethers
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P5/00—Other features in dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form
  • D06P5/13—Fugitive dyeing or stripping dyes
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
  • D06P5/00—Other features in dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form
  • D06P5/13—Fugitive dyeing or stripping dyes
  • D06P5/137—Fugitive dyeing or stripping dyes with other compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies
  • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

• the present invention relates to a method for recovering polyester from a textile product containing polyester fibers and urethane fibers, and a method for producing polyester by depolymerizing the polyester and then repolymerizing it to produce polyester.
• polyester Due to its excellent properties, polyester is widely used in textile products, but the effective use of polyester textile products after use is a major issue, including environmental concerns.
• the main disposal methods being considered are material recycling, thermal recycling, and chemical recycling.
• chemical recycling which involves depolymerizing polyester polymers down to raw materials consisting of dicarboxylic acids and diols and then repolymerizing them, is superior as a closed-loop recycling method in terms of minimizing the loss of quality that accompanies recycling.
• the method of using intermediates that can be used to directly carry out a polycondensation reaction to produce recycled polyester is also an excellent method in terms of energy consumption.
• polyester fiber products contain different polymers such as polyurethane or are dyed products, it has been difficult to recover them efficiently and with minimal discoloration.
• Patent Document 1 as a process for removing coloring substances, an adsorption process in which the coloring substances are brought into contact with an adsorbent after the intermediate product is produced after depolymerization, a decomposition process in which the coloring substances are decomposed with a decomposing agent, and a reduction process in which the coloring substances are reduced with a reducing agent are attempted.
• coloring substances such as dyes that are clearly mixed into the polymer are removed to a certain extent
• a manufacturing method for obtaining polyester polymers with reduced coloring to the same extent as polyester polymers produced by normal manufacturing methods that do not use recycled raw materials has not yet been obtained.
• the object of the present invention is to provide a method for recovering less colored polyester from textile products containing polyester fibers and polyurethane fibers.
• the polyester recovery method of the present invention is characterized in that a textile product that is mainly composed of polyester fibers and contains fibers made of a polymer whose constituent component is a urethane group is treated with a solution of aromatic alcohol or a derivative thereof at a temperature in the range of not less than the glass transition temperature of the polyester and not more than the glass transition temperature of the polyester + 100°C.
• the present invention includes preferred embodiments in which the textile product is dyed with a disperse dye, the polyester is polyethylene terephthalate, the polymer containing urethane groups as a constituent component is a polyether polyurethane, and the aromatic alcohol is benzyl alcohol.
• the other invention of the present invention is a method for producing recycled polyester, which comprises depolymerizing the polyester obtained by the above-mentioned recovery method into aromatic bis(hydroxyalkyl) dicarboxylate, and then repolymerizing the aromatic bis(hydroxyalkyl) dicarboxylate to produce recycled polyester.
• the present invention provides a method for recovering less colored polyester from textile products containing polyester fibers and polyurethane fibers.
• the method for recovering polyester of the present invention is a method for recovering polyester from a textile product that is mainly composed of polyester fibers and contains fibers made of a polymer having a urethane group as a constituent component.
• "mainly composed of polyester fibers” means that the polyester fibers make up the largest proportion of the fibers that make up the textile product.
• the polyester fibers account for preferably 50 wt % or more, more preferably 80 wt % or more of the textile product.
• polyester is a polycondensation product synthesized by dehydrating and condensing polycarboxylic acids and polyalcohols to form ester bonds.
• Polyesters are polymers that have ester bonds, and are generally classified into aliphatic polyesters, semi-aromatic polyesters, and fully aromatic polyesters.
• the polycarboxylic acid constituting this polyester is preferably a dicarboxylic acid or an ester-forming derivative thereof.
• dicarboxylic acid an aromatic dicarboxylic acid such as terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferably used.
• the polyalcohol, the other component constituting the polyester, is preferably a diol or an ester-forming derivative thereof.
• the diol an aliphatic glycol having 2 to 20 carbon atoms is preferably used.
• 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.
• a polyester obtained by combining the above-mentioned polyvalent carboxylic acid and polyalcohol is used as the starting material.
• the preferred polyester is polyalkylene terephthalate, and among these, polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate are particularly preferred.
• the textile product used in the present invention contains, in addition to the fibers mainly made of polyester described above, fibers made of a polymer containing urethane groups as a constituent component.
• fibers made of polymers containing urethane groups include polyurethane fibers and polyurethane urea fibers. These often have the properties of elastic fibers.
• the preferred fiber made of a polymer containing urethane groups is polyurethane fiber, which has urethane bonds (-NHCOO-) in the molecular chain.
• Polyurethane fibers are made up of a flexible soft segment with a low melting point and a hard segment with a high melting point, and have excellent elasticity. These polyurethane fibers are classified into polyether polyurethane fibers and polyester polyurethane fibers according to the soft segment.
• the polyurethane fiber is preferably a polyether polyurethane fiber, and particularly preferably a polyether polyurethane fiber obtained from a polyether diol such as polytetramethylene glycol as the diol component, an aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate as the diisocyanate component, and ethylenediamine as the diamine component.
• a polyether diol such as polytetramethylene glycol as the diol component
• aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate
• ethylenediamine as the diamine component
• polyether-based polyurethane fiber is "ROICA” (registered trademark) manufactured by Asahi Kasei Fibers Corporation.
• the polyurethane fiber is preferably one with a high elongation modulus.
• Polyurethane fibers may be used as a single component yarn, or may be in the form of blended fibers, blended yarns, covered yarns (with a urethane fiber core), composite yarns, etc. with polyester fibers.
• the content of polyurethane fibers in textile products is preferably 50 wt% or less, more preferably less than 50 wt%, even more preferably 30 wt% or less, and particularly preferably 5 to 20 wt%.
• the textile products may be in the form of, for example, sportswear, uniforms, socks, etc.
• the textile product is a dyed textile product. It is also a preferred embodiment that the dyeing is performed with a disperse dye. Furthermore, it is also a preferred embodiment that the disperse dye is a dye containing nitrogen atoms.
• the recovery method of the present invention involves treating the above-mentioned textile product with a solution of aromatic alcohol or its derivatives at a temperature in the range of not less than the glass transition temperature of the polyester and not more than 100°C above the glass transition temperature of the polyester, and recovering the polyester.
• aromatic alcohol examples include benzyl alcohol, benzaldehyde, and benzoic acid, and preferably benzyl alcohol (hereinafter sometimes referred to as "BA") is used.
• BA benzyl alcohol
• the aromatic alcohol or its derivative is used in a heated solution state.
• the aromatic alcohol or its derivative may be used by mixing it with another solvent.
• the boiling point of each of them is preferably 100°C or higher, more preferably 150 to 250°C.
• the recovery method of the present invention involves treating a textile product with a solution of such an aromatic alcohol or its derivative at a temperature range above the glass transition temperature of the polyester and below the glass transition temperature of the polyester + 100°C, and recovering the polyester.
• the temperature for treating the textile product is preferably in the range of +10°C to +80°C above the glass transition temperature of the polyester, and more preferably in the range of +15°C to +60°C above the glass transition temperature of the polyester.
• the amount of solution used during treatment is preferably 3 to 1000 times, more preferably 5 to 500 times, and particularly preferably 8 to 50 times, the weight of the textile product to be treated.
• the treatment is carried out by immersing the textile product in the solution.
• This treatment may be carried out by leaving the textile product in the solution, but is preferably carried out by agitating the solution in which the textile product is immersed, using a liquid circulation system or a rotating blade, etc.
• the textile product After soaking, the textile product is dehydrated.
• Methods that can be used to dehydrate the textile product after soaking include squeezing, centrifugal separation, and Soxhlet extraction.
• the dewatering process is carried out under conditions in which the weight of the textile product containing the solution after dewatering is preferably 300 wt% or less, more preferably 150 to 250 wt%, and particularly preferably 180 to 220 wt%, based on the dry weight of the textile product.
• Another method for producing recycled polyester according to the present invention is a method for producing recycled polyester, which comprises depolymerizing the polyester obtained by the above-mentioned polyester recovery method into a bis(hydroxyalkyl) aromatic dicarboxylate, and then repolymerizing the bis(hydroxyalkyl) aromatic dicarboxylate.
• This method makes it possible to obtain polyester with low yellowness and high whiteness.
• a catalyst it is preferable to use a catalyst during depolymerization.
• a catalyst of the first transition metal is preferably used.
• Specific examples of the catalyst include oxides, fatty acid salts, carbonates, sulfates, phosphates, oxides, hydroxides, halides, and alcoholates of the first transition metals.
• the first transition metal preferably manganese or zinc is used.
• the catalyst preferably manganese oxide, manganese acetate, zinc oxide, zinc acetate, and particularly preferably manganese acetate, is used.
• the catalyst may be one type or a combination of two or more types.
• the catalyst is preferably used as a solution in which it has been dissolved in alkylene glycol beforehand. It is preferable to use, as the alkylene glycol (hereinafter sometimes abbreviated as AG), the same diol as the diol component that forms the backbone structure of the polyester used in the textile product.
• AG alkylene glycol
• alkylene glycol a diol that constitutes the polyester obtained as the final product by repolymerizing an intermediate aromatic dicarboxylate bis(hydroxyalkyl) may be used.
• the diol that is the same as the diol component that forms the polyester backbone structure is 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.
• EG ethylene glycol
• PET polyethylene terephthalate
• C3G 1,3-propanediol
• C4G 1,4-butanediol
• the diols may be a mixture.
• polyester depolymerized products tend to gradually become discolored when stored for long periods of time, but the products obtained using the recovery and production methods of the present invention clearly show less discoloration.
• a manganese catalyst is used during depolymerization, there is less discoloration.
• 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.
• mol % indicates the ratio of the number of catalyst molecules to the constituent units of the polyester.
• mmol % is 1/1000 times that amount. 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-based catalyst is used as the catalyst, depolymerization can be performed with a small amount of catalyst used.
• alkylene glycol is preferably used in an amount 2 to 20 times, and more preferably 3 to 10 times, the weight of the polyester after recovery processing.
• the resulting aromatic dicarboxylate bis(hydroxyalkyl) may be treated to remove foreign matter using an adsorbent such as activated carbon.
• the alkylene glycol used in the manufacturing method of the present invention is the same as the diol component of the polyester after repolymerization, it can be repolymerized without drying. This is a preferred embodiment.
• polyester used in textile products is a polyester (polyalkylene terephthalate) that mainly uses terephthalic acid as the polycarboxylic acid, bis(hydroxyalkyl)benzenedicarboxylate (hereinafter sometimes referred to as BHAT; bishydroxyalkyl terephthalate) is obtained.
• BHAT bis(hydroxyalkyl)benzenedicarboxylate
• BHPT bishydroxypropyl terephthalate
• BHBT bishydroxybutyl terephthalate
• ethylene glycol is used as the alkylene glycol for depolymerization
• BHET bishydroxyethyl terephthalate
• the aromatic dicarboxylate bis(hydroxyalkyl) can be repolymerized by a conventional method to produce a polyester, which is a recycled polyester that is resistant to coloration and has excellent color tone.
• catalysts such as antimony, germanium or titanium catalysts can be used, and diantimony trioxide is preferably used.
• the alkylene glycol generated during the repolymerization reaction is preferably discharged outside the reactor while the polycondensation reaction is carried out.
• the amount of catalyst used is preferably in the range of 10 to 1000 ppm based on the weight of the aromatic dicarboxylate bis(hydroxyalkyl).
• the recycled polyester obtained in this way is less likely to yellow or discolor. This effect is particularly noticeable when a manganese catalyst is used at a low concentration for depolymerization. This is thought to be because colored by-products are less likely to be produced, and the catalyst is more likely to dissociate from the aromatic dicarboxylate bis(hydroxyalkyl) in subsequent crystallization and other processes, making it less likely to remain as an impurity.
• the resulting recycled polyester preferably exhibits the following properties:
• the resulting recycled polyester has a hue b * value of 8 or less, preferably 1 to -20, and more preferably 0.5 to -15, as measured by a colorimeter in the L * , a * , b * color space of the International Commission on Illumination (CIE).
• CIE International Commission on Illumination
• the resulting recycled polyester preferably has a yellowness index (YI) of 15 or less, more preferably 5 to -50, and even more preferably 0 to -20.
• YI yellowness index
• the resulting polyester has a whiteness (W) of 75 or more, and more preferably 80 to 100.
• the nitrogen content derived from polyurethane and dyes contained in the resulting recycled polyester is preferably 15 ppm or less, and more preferably 10 ppm or less.
• the recycled polyester after repolymerization preferably has a polymer IV of 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.
• Yellowness index (YI) was calculated using the following formula (1), and whiteness index (W) was calculated using the following formula (2).
• Yellowness index (YI) 0.34-71.7 ⁇ a/L+178.78 ⁇ b/L
• 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.
• Nitrogen (N) Content The nitrogen content in textile products such as fabrics and fibers was measured using a total nitrogen trace analyzer (TN-110, manufactured by Mitsubishi Kasei Corporation).
• Example 1 Polyurethane As a textile product, a fabric consisting of 360 g of dyed polyethylene terephthalate (hereinafter referred to as "PET”) fiber and 40 g of polyurethane (hereinafter sometimes referred to as "PU”) was prepared.
• PET dyed polyethylene terephthalate
• PU polyurethane
• the PU fiber was a polyether-based polyurethane fiber with high elasticity ("Leuca” manufactured by Asahi Kasei Fibers Corporation, 22 dtex/strand, strength 1.6 cN/dtex, elongation 345%, 300%, elongation modulus 82%, and nitrogen (N) content 1.06 wt%).
• the fabric-like textile product was removed from the separable flask and squeezed to remove excess treatment liquid. 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 squeezing, the textile product was placed back into the separable flask, and the same process of soaking in the solution and squeezing was repeated a total of six times. Visually, the textile product had turned white after the third treatment, but even after the fourth treatment, the squeezed treatment liquid was slightly colored, and it was only after the sixth treatment that the treatment liquid finally became transparent.
• the textile product after the above treatment was dried in a vacuum dryer at 80°C for 8 hours, and white polyester with high whiteness was recovered.
• polyester recycling process 300 parts by weight of the polyester recovered by the above method, 1500 parts by weight of ethylene glycol (EG), and 0.38 parts by weight (100 mmol% based on the polyester) of manganese acetate as a depolymerization catalyst were charged into a 2 L separable flask and nitrogen was sealed in. At this time, the manganese acetate was dissolved in EG before charging.
• EG ethylene glycol
• the separable flask containing the sample was heated to an internal temperature of 220°C using a mantle heater, and depolymerization treatment was carried out at normal pressure for 4 hours while stirring.
• the BHET (bis(hydroxyethyl)benzenedicarboxylate) solution after this depolymerization was colorless and transparent, with no visible coloration.
• the depolymerized solution was then filtered through a 200 ⁇ m mesh to remove any solids remaining inside, and slowly cooled to 70°C.
• the BHET/EG slurry was pressed using a filter press manufactured by Nippon Filter Equipment Co., Ltd., and solid-liquid separation of BHET and EG was carried out.
• the separated BHET contained 35 wt% EG based on the weight of the cake recovered after the filter press.
• the cake was washed with water using a Nutsche filter while being sprayed with 2 times its weight of 25°C pure water.
• the BHET was dried in a vacuum dryer at 50°C for 8 hours to obtain dried BHET.
• the obtained BHET was white and free of any visible foreign matter.
• Example 2 The recovery and recycling processes were carried out in the same manner as in Example 1, except that the treatment temperature of benzyl alcohol (BA) was increased from 105° C. to 130° C.
• the color of the residual liquid after squeezing in the recovery process was darker than that of Example 1, and a precipitate thought to be a PET soluble product was confirmed in the residual liquid, and the textile product itself was a polyester fabric with high whiteness.
• the weight of the textile product after treatment and drying was 302 g, and the yield was slightly inferior.
• Example 3 The recovery process was carried out in the same manner as in Example 1, except that the treatment temperature of benzyl alcohol (BA) was increased from 105° C. to 160° C.
• the color of the residual liquid after squeezing in the recovery process was darker than in Examples 1 and 2, and more precipitates thought to be PET dissolved products were confirmed in the residual liquid than in Example 2, and the textile product itself was a polyester fabric with high whiteness.
• the weight of the textile product after treatment and drying was 178 g, which was a poor yield, so a recycling process was not carried out.
• Example 4 The recovery and recycling processes were carried out in the same manner as in Example 1, except that an undyed white fabric was used.
• Comparative Example 1 The recovery process was carried out in the same manner as in Example 1, except that the treatment temperature of benzyl alcohol (BA) was lowered from 105° C. to 25° C. No coloring was observed in the textile product in the recovery process or in the residual liquid after squeezing. No dissolution of PU occurred, and the textile product remained as a stretchable fabric, and the weight of the textile product after treatment and drying was unchanged at 400 g.
• BA benzyl alcohol
• Comparative Example 2 The recovery process was carried out in the same manner as in Example 1, except that the treatment temperature of benzyl alcohol (BA) was increased from 105° C. to 205° C. During the treatment process at 205° C., the entire amount of the textile product containing PET was dissolved in the BA, and the product after the squeezing process could not be recovered.
• BA benzyl alcohol
• Comparative Example 3 Except for using an undyed white fabric as in Example 4, a textile product containing the same PU fiber as in Example 1 was used, the benzyl alcohol (BA) in Example 1 was changed to ethylene glycol (EG), and the treatment temperature was increased from 105°C to 160°C to perform a recovery process.
• BA benzyl alcohol
• EG ethylene glycol
• Comparative Example 4 A textile product using dyed PET fibers similar to that of Example 1 except that it did not contain PU fibers was used, and the benzyl alcohol (BA) of Example 1 was replaced with ethylene glycol (EG). Since there was no change in the textile product or the squeezed liquid, the treatment temperature was raised from 105°C to 160°C and a recovery process was performed.
• BA benzyl alcohol
• EG ethylene glycol
• Example 1 A textile product using dyed PET fibers similar to that in Example 1 was used, except that it did not contain PU fibers, and the recovery and recycling processes were otherwise similar to those in Example 1. The physical properties of the obtained recycled polyester were similar to those of Example 1.
• Example 2 Except for using an undyed white fabric as in Example 4, the same textile product containing PU fiber as in Example 1 was used, and the same recycling process as in Example 4 was carried out except that the recovery step was omitted.
• Example 3 The same recycling process as in Example 1 was carried out except that a textile product using only undyed PET fibers, without containing PU fibers, was used and the recovery step was omitted.
• the physical properties of the obtained recycled polyester were similar to those of Example 1.
• Example 5 The recovery and recycling processes were carried out in the same manner as in Example 1, except that 1.5 g of manganese acetate was added to 4,000 g of benzyl alcohol (BA). The weight of the fiber product after recovery and drying was 319 g. The yield was slightly inferior.
• BA benzyl alcohol
• Example 6 Dried BHET was obtained in the same manner as in Example 1. The BHET was then dissolved in hot water (90°C) of 20 times its weight, and activated carbon was added to the solution in an amount of 0.25 times the weight of the BHET. The solution was stirred for 1 hour. Nutsche filtration was then performed to remove the activated carbon, and the aqueous solution was cooled to precipitate BHET. Nutsche filtration was performed again to recover the BHET.
• the recovered BHET was dried in a vacuum dryer at 50°C for 8 hours.
• the resulting dried BHET was whiter than that obtained in Example 1, and no foreign matter was found to be present.
• the temperature inside the reactor was then raised to 285°C, and the pressure was gradually reduced under the following conditions: normal pressure for 10 minutes, 4 kPa pressure for 10 minutes, and then 0.4 kPa pressure for 40 minutes.
• the ethylene glycol and other substances generated during the reaction were distilled out of the reactor while the polycondensation reaction was carried out, yielding recycled polyester.
• Example 7 An undyed white fabric was used as the textile product, and in the polyester recovery process, 1.5 g of manganese acetate was added to 4,000 g of benzyl alcohol, and the process of immersion in the solution and squeezing was performed once in total, in the same manner as in Example 1.
• polyester recovered and the recycled polyester produced in the present invention can be suitably used for applications such as fibers, films, and resins.

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• 2023
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