Recyclable blue colorant monomer, method for preparing same, blue polyester, method for preparing same, method for recycling same, and method for recycling colored monomer

Abstract

The present application relates to the technical field of high molecular dyes, in particular to a recyclable blue chromophoric monomer, a preparation method thereof, a blue polyester, a preparation method and recycling method thereof, and a recycling method of the recycled coloring monomer. The blue chromophoric monomer comprises a 1,4-diarylamino anthraquinone chromophore and at least one hydroxyalkyl segment, the 1,4-diarylamino anthraquinone chromophore and the at least one hydroxyalkyl segment are bonded through a heteroatom, and the hydroxyalkyl segment can react with a polyester-forming monomer. The blue polyester formed by the blue chromophoric monomer has uniform color and excellent color fastness, and can be subjected to alkaline alcoholysis to obtain a blue chromophoric monomer with high purity and a polyester-forming polyacid, thereby realizing simultaneous closed-loop recycling of the polyester monomer and the colorant. The industry problem that the traditional colored polyester colorant is difficult to recycle at high value is fundamentally solved, and key technical support is provided for the circular economy development of textile materials.

Description

Technical Field

[0001] This invention relates to the field of polymer dye technology, and more specifically, to recyclable blue chromophores and their preparation methods, blue polyesters, their preparation methods and recycling methods, and methods for reusing the recycled chromophores. Background Technology

[0002] Polyester fiber, especially polyethylene terephthalate (PET) fiber, is the world's largest-produced synthetic fiber. Traditional dyeing processes for polyester fibers after textile production suffer from high water consumption, high energy consumption, and serious wastewater pollution, facing severe environmental pressure. Solution dyeing technology, which involves adding colorants before or during the polymerization of polyester fibers, can eliminate dyeing wastewater at the source and is considered an important direction for green manufacturing.

[0003] Currently, solution dyeing mainly uses pigments or copolymer colorants. However, pigment dyeing suffers from problems such as uneven dispersion, affecting fiber mechanical properties, and difficulty in spinning fine denier fibers. While copolymer colorants, especially reactive monomers, can achieve molecular-level dispersion and excellent color fastness through covalent bonding, they bring a new challenge: the obstacle of chemical recycling of dyed polyesters.

[0004] During the chemical recycling of polyester (such as alcoholysis and hydrolysis), these colorants, which are firmly covalently embedded in the molecular backbone, cannot be effectively separated. This results in the recycled PET monomers being contaminated with colorants, leading to a dark color and high impurity content. These monomers can only be used for downgrading or producing dark-colored products, severely limiting their high-value recycling pathways. This contradicts the global strategy of promoting a circular economy and building "zero-waste cities." Furthermore, the inability to recycle the colorants further restricts the use of copolymer colorants.

[0005] Therefore, there is an urgent need in this field for an innovative coloring technology that can retain the advantages of copolymer coloring, such as long-lasting color and excellent performance, while overcoming its fatal defects in the recycling process. This technology would achieve efficient and high-value separation and recycling of colorants and polyester monomers, truly completing a closed loop from "green manufacturing" to "manufacturing green." In view of this, the present invention is proposed.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide recyclable blue chromophore monomers and their preparation methods, blue polyesters, their preparation methods and recycling methods, and methods for reusing the recycled chromophore monomers. Embodiments of this invention provide a novel blue chromophore monomer that enables blue polyesters to maintain high color fastness while achieving depolymerization under alkaline conditions. This allows for the efficient separation and recycling of the blue chromophore monomer and polyester monomers, thus providing a key technical solution for the green recycling of polyester materials throughout their entire lifecycle.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a recyclable blue chromophore comprising a 1,4-diarylaminoanthraquinone chromophore matrix and at least one hydroxyalkyl fragment, wherein the 1,4-diarylaminoanthraquinone chromophore matrix and at least one hydroxyalkyl fragment are bonded by heteroatoms, and the hydroxyalkyl fragment is capable of reacting with monomers that form polyesters.

[0009] In an optional embodiment, the blue chromophore is selected from compounds shown in the following structural formula: , where R 1 R 2 R 3 R 4 Alkyl groups independently selected from C1-C8, where X is a C1-C8 alkylene group and A is oxygen or sulfur.

[0010] In an optional implementation, R 1 R 2 R 3 R 4 Alkyl groups independently selected from C1-C5, where X is a C1-C4 alkylene group and A is oxygen or sulfur.

[0011] In an optional embodiment, it is selected from any of the compounds shown in the following structural formulas: , , ,

[0012] and . , .

[0013] In a second aspect, the present invention provides a method for preparing the recyclable blue chromophore described in the foregoing embodiments, comprising: reacting a 1,4-diarylaminoanthraquinone blue dye with a halogenating reagent to form a halogenated intermediate; Under the action of a catalyst, the halogenated intermediate is reacted with a hydroxyalkyl-substituted phenolic derivative to introduce a hydroxyalkyl fragment into a 1,4-diarylaminoanthraquinone blue dye.

[0014] In an optional embodiment, the halogenated reagent includes a bromide; Preferably, the molar amount of the halogenated reagent is 1-3 times the molar amount of the 1,4-diarylaminoanthraquinone blue dye; Preferably, the temperature at which the halogenated intermediate is formed is 10-40°C; Preferably, the catalyst comprises a palladium catalyst; Preferably, the molar ratio of the halogenated intermediate to the hydroxyalkyl-substituted phenolic derivative is 1:(1-3); the molar ratio of the halogenated intermediate to the catalyst is 1:(0.005-0.015). Preferably, the temperature with the hydroxyalkyl-substituted phenolic derivative is 100-150°C.

[0015] Thirdly, the present invention provides a method for preparing blue polyester, comprising: mixing polyol, polyacid, esterification catalyst and the recyclable blue chromophore of the foregoing embodiments for a co-condensation reaction; Preferably, the amount of the blue chromophore added is 0.1-5.0% of the molar amount of the polybasic acid, more preferably 0.5-2.0%; The amount of the polyol used is 1.05-2.50 times the molar amount of the polyacid, preferably 1.10-2.20 times; The amount of the esterification catalyst is 0.00001-0.005 times the molar amount of the polybasic acid, preferably 0.00005-0.001 times; Preferably, the temperature of the polycondensation reaction is 200-280℃.

[0016] Fourthly, the present invention provides a blue polyester, which is prepared by the blue polyester preparation method described in the foregoing embodiments.

[0017] Fifthly, the present invention provides a method for recycling blue polyester, comprising: subjecting the blue polyester described in the foregoing embodiments to alcoholysis under alkaline conditions to form recycled coloring monomers; Preferably, the reaction includes: reacting the blue polyester, an alkaline catalyst, and an alcohol solvent at 160-220°C, followed by cooling and filtration to form a recovered coloring monomer and an aqueous phase; and acid precipitation of the aqueous phase to form a recovered polybasic acid.

[0018] In a sixth aspect, the present invention provides a method for reusing recycled coloring monomers, comprising: applying the recycled coloring monomers formed by the recycling method of the blue polyester described in the foregoing embodiments to the preparation method of the blue polyester described in the foregoing embodiments.

[0019] The present invention has the following beneficial effects: (1) Excellent coloring performance: the blue chromophore is covalently attached to the blue polyester chain, which fundamentally solves the problems of migration and color fastness. The resulting blue polyester has a uniform color, is washable and wear-resistant.

[0020] (2) Recyclability: The blue chromophore provided in this embodiment adopts the design of "anthraquinone chromophore + dihydroxy active site + specific heteroatom connection", which makes the blue chromophore stable during polyester synthesis. Under specific alkaline alcoholysis conditions, the chemical bonds at the heteroatom or active site are selectively broken or deactivated, resulting in a change in the polarity of the entire molecule. Subsequently, the blue chromophore can be precipitated from the depolymerization liquid, realizing its efficient separation and recycling.

[0021] (3) Achieving dual closed-loop recycling: This invention not only efficiently recovers high-value chromophores, but also simultaneously recovers high-purity polyacids (such as terephthalic acid) and polyols (such as ethylene glycol), truly realizing the dual circulation of chromophores and polyester monomers, and solving the industry pain point of "recycling is pollution" in traditional copolymer coloring technology.

[0022] (4) Strong process adaptability: The use of blue chromophores is fully compatible with the existing polyester esterification / polymerization production lines, and the recycling process is also compatible with the mainstream ethylene glycol alcoholysis process, making it easy to promote industrialization.

[0023] (5) Promoting the circular economy: This invention provides a feasible path for high-value chemical recycling of waste colored polyester products in textiles, packaging and other fields, which has significant environmental and economic value. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is an image of the blue polyester fiber product provided in Embodiment 1 of the present invention; Figure 2 This is an image of the blue polyester powder provided in Example 1 of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0027] This invention provides a recyclable blue chromophore comprising a 1,4-diarylaminoanthraquinone chromophore matrix and at least one hydroxyalkyl fragment, wherein the 1,4-diarylaminoanthraquinone chromophore matrix and at least one hydroxyalkyl fragment are bonded by heteroatoms, and the hydroxyalkyl fragment is capable of reacting with monomers that form polyesters.

[0028] Specifically, the recyclable blue chromophore provided in this embodiment of the invention uses a 1,4-diarylaminoanthraquinone derivative as the chromophore matrix and contains at least one (e.g., two) hydroxyalkyl segments that match the activity of polyester polymerization. These hydroxyalkyl segments are connected to the chromophore matrix via heteroatoms (e.g., oxygen or sulfur atoms). This blue chromophore exhibits good hydrophobicity, facilitating its precipitation in an aqueous phase.

[0029] Furthermore, the hydroxyalkyl fragment is compatible with the polyester polymerization activity, meaning the hydroxyl groups in the hydroxyalkyl fragment can react with the polyester monomer, thereby bonding the blue chromophore to the polyester chain. Preferably, the blue chromophore contains two hydroxyalkyl fragments, which further facilitates the formation of blue polyester and the subsequent recovery of the blue chromophore.

[0030] Furthermore, the blue chromophore is selected from compounds with the following structural formulas: , where R 1 R 2 R 3 R 4 Alkyl groups are independently selected from C1-C8, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, etc., preferably C1-C5 alkyl groups. X is a C1-C8 alkylene group, such as methylene, ethylene, n-propylene, n-butylene, etc., preferably C1-C4 alkylene groups. A is a heteroatom, such as an oxygen atom or a sulfur atom.

[0031] Furthermore, the recyclable blue chromophore is selected from any one of the compounds shown in the following structural formulas: , , ,

[0032] and . , .

[0033] Secondly, embodiments of the present invention provide a method for preparing the above-mentioned recyclable blue chromophore, comprising: S1, forming a halogenated intermediate; A 1,4-diarylaminoanthraquinone blue dye is reacted with a halogenating reagent to form a halogenated intermediate. The structural formula of the halogenated intermediate is shown below: Where X represents a halogen, such as bromine or iodine; R 1 R 2 R 3 R 4 For the limitations, please refer to the limitations of the recyclable blue chromophores mentioned above.

[0034] Specifically, a halogenated solvent, a halogenated reagent, and a 1,4-diarylaminoanthraquinone blue dye are mixed and reacted at 10-40°C for 10-20 hours. The halogenated solvent includes, but is not limited to, halogen-substituted C1-C3 alkane solvents such as dichloromethane. The halogenated reagent includes bromides; for example, but not limited to, N-bromosuccinimide, N-iodosuccinimide, and dibromohydantoin. The molar amount of the halogenated reagent is 1-3 times the molar amount of the 1,4-diarylaminoanthraquinone blue dye.

[0035] After the reaction is complete, the reaction system undergoes post-treatment, which is a conventional process, including but not limited to distillation, washing, and recrystallization. Details are not further elaborated in the embodiments of this invention.

[0036] S2, forms blue chromophore monomers; In the presence of a catalyst, the halogenated intermediate is reacted with a hydroxyalkyl-substituted phenolic derivative to introduce a hydroxyalkyl fragment into a 1,4-diarylaminoanthraquinone blue dye. Specifically, the halogenated intermediate, the hydroxyalkyl-substituted phenolic derivative, a basic substance, and the catalyst are mixed and reacted at 100-150°C.

[0037] Furthermore, the catalyst includes palladium catalysts, such as, but not limited to, palladium chloride diphenylphosphine and palladium tetraphenylphosphine, and the basic substance includes potassium or sodium salts, such as, but not limited to, potassium phosphate, potassium carbonate, and sodium carbonate, and hydroxyalkyl-substituted phenolic derivatives such as p-hydroxyethylphenol and p-mercaptobenzyl alcohol.

[0038] Further, the molar ratio of the halogenated intermediate to the hydroxyalkyl-substituted phenolic derivative is 1:(1-3); the molar ratio of the halogenated intermediate to the catalyst is 1:(0.005-0.015); and the molar ratio of the halogenated intermediate to the basic substance is 1:(1-3).

[0039] At the same time, the system is post-processed after the reaction is completed, such as including but not limited to crystallization.

[0040] Thirdly, embodiments of the present invention provide a method for preparing blue polyester, comprising: A polyol, a polyacid, an esterification catalyst, and a recyclable blue chromophore are mixed and subjected to a co-condensation reaction. The condensation reaction temperature is 200-280℃. The amount of blue chromophore added is 0.1-5.0% of the molar amount of the polyacid, preferably 0.5-2.0%. The amount of polyol used is 1.05-2.50 times the molar amount of the polyacid, preferably 1.10-2.20 times; the amount of the esterification catalyst used is 0.00001-0.005 times the molar amount of the polyacid, preferably 0.00005-0.001 times. The polyol includes, but is not limited to, ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and diethylene glycol; the polyacid includes, but is not limited to, terephthalic acid, phthalic acid, isophthalic acid, adipic acid, azelaic acid, and sebacic acid.

[0041] Fourthly, embodiments of the present invention provide a blue polyester, which is prepared by the above-described method for preparing blue polyester. In this blue polyester, the chromophores are uniformly linked to the polymer chain via covalent bonds, resulting in uniform color and excellent colorfastness.

[0042] Fifthly, embodiments of the present invention provide a method for recycling blue polyester, comprising: subjecting the blue polyester to alcoholysis under alkaline conditions to form recycled coloring monomers.

[0043] Specifically, blue polyester, an alkaline catalyst, and an alcohol solvent are mixed and reacted at 160-220°C to completely depolymerize the polyester, yielding a mixed system containing polyacid salts, polyols, and blue chromophores. The amount of alkaline catalyst used is 2-2.5 times the molar amount of the polyacids forming the blue polyester.

[0044] The alkaline catalysts include carbonates, bicarbonates, acetates, or hydroxides, such as, but not limited to, sodium acetate, sodium carbonate, and sodium hydroxide. The alcohol solvents include polyols, such as ethylene glycol.

[0045] After depolymerization, the reaction system is cooled to below 80°C, such as room temperature. At this temperature, the blue chromophore, due to its specific molecular structure (hydrophobic anthraquinone core and deactivated dihydroxyl groups), is almost insoluble in the cooled alcohol-water system (e.g., an ethylene glycol-water mixture). Therefore, the blue chromophore precipitates in solid form. The recovered chromophore can then be efficiently recovered through simple filtration, washing, and drying.

[0046] Further, filtration forms the desired recycled coloring monomers and aqueous phase. The aqueous phase contains the desired polybasic acid (which exists in the form of a polybasic acid salt).

[0047] Furthermore, although the coloring monomers are recovered and precipitated, the aqueous phase still contains colored impurities. Therefore, the aqueous phase is decolorized with activated carbon and then subjected to solid-liquid separation.

[0048] The aqueous phase is then subjected to acid precipitation, causing the polybasic acid to precipitate. After filtration, washing, and drying, a high-purity polybasic acid is obtained; this polybasic acid can be reused in the synthesis of polyesters. The acids used for acid precipitation include, but are not limited to, hydrochloric acid or sulfuric acid.

[0049] In a sixth aspect, embodiments of the present invention also provide a method for reusing recycled coloring monomers, comprising: applying the recycled coloring monomers formed by the above-described recycling method of the recycled blue polyester to a method for preparing blue polyester.

[0050] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0051] Example 1 This invention provides a method for preparing a recyclable blue chromophore (denoted as monomer 1), comprising: synthesizing according to the following synthetic route:

[0052] (1) Under an ice-water bath, dichloromethane (halogenated solvent) was added to the reaction vessel, the volume of which was 50% of the total volume of the container; then Blue 1 was dissolved in it (the weight of dichloromethane was 4 times that of Blue 1), and N-bromosuccinimide (halogenated reagent) was added in batches (the molar amount of which was 2 times that of Blue 1), and the reaction was stirred at 20°C for 15 h.

[0053] After the reaction is complete, the product is concentrated by distillation, filtered, and washed successively with saturated sodium sulfite solution (reducing agent solution) and water. Recrystallization with dimethylformamide (organic solvent) yields the corresponding halogenated intermediate (denoted as intermediate 1).

[0054] (2) Intermediate 1, p-hydroxyethylphenol, potassium carbonate (alkaline substance), and tetrakis(triphenylphosphine) palladium (palladium catalyst) were added to a reaction vessel in a molar ratio of 1:2.2:2.0:0.01. Then, 1,4-dioxane (coupling solvent) was added, with the weight of the coupling solvent being 5 times that of intermediate 1. Under nitrogen protection, the reaction was carried out at 120°C for 15 hours. The insoluble matter was removed by filtration, and water was added to precipitate the product. The product was then crystallized with dimethylformamide to obtain a blue chromophore (denoted as monomer 1).

[0055] The characterization data of the blue chromophore are as follows: 1H NMR (500 MHz, CDCl3) δ 11.71 (s, 2H),8.06 (dd, J = 6.1, 3.4 Hz, 2H), 7.82 (dd, J = 6.0, 3.4 Hz, 2H), 7.49 (s, 2H),7.11 – 7.05 (m, 4H), 6.97 (d, J = 8.5 Hz, 4H), 6.63 (s, 4H), 3.76 (q, J = 5.7Hz, 4H), 2.82 – 2.76 (m, 4H), 2.66 – 2.58 (m, 10H), 1.21 (t, J = 7.1 Hz, 12H).

[0056] This embodiment also provides a method for preparing blue polyester 1, including: In a 5L polymerization reactor, 3.0 kg of terephthalic acid (PTA), 1.8 kg of ethylene glycol (EG), 45 g of monomer 1, and 2.0 g of antimony trioxide as an esterification catalyst were added. Under nitrogen protection, the temperature was gradually increased to 250℃ for esterification. Esterification ended after approximately 600 mL of water was discharged. Subsequently, 1.5 g of triphenyl phosphate as a polycondensation catalyst was added, and polycondensation was carried out for 2 hours at a vacuum of <100 Pa and a temperature of 275-280℃. The material was discharged, pelletized, and dark blue polyester chips with an intrinsic viscosity of 0.65 dL / g were obtained. These chips were then spun into fibers. See the image of the spun fibers for further details. Figure 1 The fiber achieves a dry / wet rubbing fastness and a soap washing fastness of grade 4-5 (GB / T3921-2008).

[0057] This embodiment also provides a method for recycling blue polyester 1, including: The prepared blue polyester 1 was pulverized into powder. 3.5 kg of the blue polyester 1 powder was added to a reactor containing 2.5 L of ethylene glycol and 800 g of sodium hydroxide. Under nitrogen protection, the mixture was heated to 190°C and stirred for 2 hours until the polyester completely depolymerized, resulting in a deep blue, transparent solution. Heating was stopped, and the reaction solution was allowed to cool naturally to room temperature. During this process, a deep blue solid gradually precipitated, which was then filtered. The filter cake was washed with a small amount of water and dried to obtain 47.1 g of recovered blue solid with a purity of 98.8%. NMR analysis showed that the structure of the blue solid was consistent with monomer 1. Therefore, this embodiment yielded a high-purity, recyclable blue chromophore, denoted as the recovered coloring monomer.

[0058] Keep the filtrate at 70-90℃, add 25 g of activated carbon (about 0.5 wt% of the filtrate mass), stir and decolorize for 30 min, then filter while hot to remove the activated carbon, and obtain a light-colored transparent filtrate.

[0059] 20% hydrochloric acid was slowly added to the filtered liquid with stirring until pH=2, at which point a large amount of white precipitate was formed. After filtration, washing with water, and drying, approximately 2.8 kg of white terephthalic acid (TPA) powder with a purity of 99.7% was obtained.

[0060] Further testing of the terephthalic acid yielded the following results: the acid value was 675 mg KOH / g, the ash content was <0.001%, and the color (APHA) was 15, meeting the superior grade standard of GB / T 30921-2014 "Purified Terephthalic Acid for Industrial Use". The recovered ethylene glycol, after distillation, had a purity of 99.9% and a water content of <0.05%, and can be directly reused in polyester polymerization.

[0061] As can be seen, this embodiment can recover recyclable blue chromophore monomers and polyester monomers.

[0062] Example 2 This invention provides a method for preparing a recyclable blue chromophore (denoted as monomer 2), comprising: synthesizing according to the following synthetic route:

[0063] (1) Under an ice-water bath, dichloroethane (halogenated solvent) was added to the reaction vessel, the volume of which was 50% of the total volume of the container; then Blue 2 was dissolved in it (the weight of dichloroethane was 4 times the weight of Blue 2), and dibromohydantoin (halogenated reagent) was added in batches (the amount of which was 1.1 times the molar amount of Blue 2), and the reaction was stirred at 20°C for 15 h.

[0064] After the reaction is complete, the product is concentrated by distillation and filtered, and then washed successively with saturated sodium sulfite solution (reducing agent solution) and water. Recrystallization with dimethylformamide (organic solvent) yields the corresponding halogenated intermediate (denoted as intermediate 2).

[0065] (2) Intermediate 2, p-mercaptobenzyl alcohol, potassium phosphate (alkaline substance), and di-triphenylphosphine palladium chloride (palladium catalyst) were added to a reaction vessel in a molar ratio of 1:2.2:2.5:0.01. Subsequently, 1,4-dioxane (coupling solvent) was added, with a weight of 6 times that of intermediate 2. Under nitrogen protection, the reaction was carried out at 120°C for 15 h. The insoluble matter was removed by filtration, water was added to precipitate the product, and crystallization with dimethylformamide yielded a blue chromophore (denoted as monomer 2).

[0066] The characterization data for the blue chromophore are as follows: 1 H NMR (500 MHz, CDCl3) δ 11.75 (s, 1H), 8.06 (dd, J = 6.0, 3.4 Hz, 1H), 7.82 (dd,J = 6.0, 3.4 Hz, 1H), 7.49 (s, 1H), 7.34 (d, J = 7.9 Hz, 2H), 7.26 – 7.19 (m, 2H), 7.06 (s, 2H), 5.69 (dt, J = 5.7, 1.0 Hz, 2H), 3.69 (t, J = 5.7 Hz, 1H), 2.22 (s, 6H).

[0067] This embodiment also provides a method for preparing blue polyester 2, including: In a 5L polymerization reactor, 3.0 kg of terephthalic acid (PTA), 1.8 kg of ethylene glycol (EG), 42 g of monomer 2, and 2.0 g of tetrabutyl titanate as an esterification catalyst were added. Under nitrogen protection, the temperature was gradually increased to 250℃ for esterification. Esterification ended after approximately 610 mL of water was discharged. Subsequently, 1.5 g of triphenyl phosphate as a polycondensation catalyst was added, and polycondensation was carried out for 2 hours under a vacuum of <100 Pa and a temperature of 275-280℃. The product was discharged, granulated, and dark blue polyester chips with an intrinsic viscosity of 0.64 dL / g were obtained. An image of the obtained blue polyester powder is shown below. Figure 2 The fibers produced by spinning achieve a dry / wet rubbing fastness and a soaping fastness of grade 4-5 (GB / T 3921-2008).

[0068] This embodiment also provides a method for recycling blue polyester 2, including: The prepared blue polyester 2 was pulverized into powder. 3.5 kg of the blue polyester 2 powder was added to a reactor containing 2.5 L of ethylene glycol and 800 g of sodium hydroxide. Under nitrogen protection, the mixture was heated to 190°C and stirred for 2 hours until the polyester completely depolymerized, resulting in a deep blue, transparent solution. Heating was stopped, and the reaction solution was allowed to cool naturally to room temperature. During this process, a deep blue solid gradually precipitated. The solution was then filtered. The filter cake was washed with a small amount of water and dried to obtain 42.2 g of recovered blue solid. Based on the theoretical content of monomer 2 in this batch of pulverized samples (approximately 46.0 g), the recovery rate was approximately 91.7%. The purity of the recovered blue solid was determined by HPLC (area normalization method), and its ¹H NMR was consistent with that of monomer 2.

[0069] Keep the filtrate at 70-90℃, add 25 g of activated carbon (about 0.5 wt% of the filtrate mass), stir and decolorize for 30 min, then filter while hot to remove the activated carbon, and obtain a light-colored transparent filtrate.

[0070] 20% sulfuric acid was slowly added to the decolorized filtrate with stirring until pH=2, causing terephthalic acid to precipitate. The precipitate was filtered, washed with water, and dried to obtain approximately 2.80 kg of white terephthalic acid (TPA) powder with an HPLC purity of 99.6%.

[0071] Example 3 This embodiment provides a method for recycling and reusing coloring monomers, including: 50 g of the recovered coloring monomer obtained in Example 1 was placed in a flask, and 200 mL of a 1:1 volume ratio ethanol-water mixture at 60°C was added. The mixture was stirred and washed for 30 minutes to remove small amounts of ethylene glycol and inorganic salts adsorbed on the surface. After filtration, the filter cake was washed with a small amount of cold water and dried under vacuum at 80°C for 6 hours to obtain 48.5 g of purified recovered blue monomer 1, with a calculated purification yield of 97%.

[0072] The purified recovered blue monomer 1 was tested. High performance liquid chromatography (HPLC) analysis showed that its purity reached 99.2% (area normalization method). The 1H NMR and Fourier transform infrared (FT-IR) spectra were consistent with the original monomer 1 synthesized in Example 1, indicating that the recovery process did not destroy its core chromophore and functional group structure.

[0073] The recycled blue monomer 1 obtained above was used to resynthesize polyester in accordance with the formula and process provided in "Preparation Method of Blue Polyester 1" in Example 1 (using 45g of the recycled blue monomer 1 obtained above).

[0074] The intrinsic viscosity of the obtained polyester chips was 0.64 dL / g. Its CIELAB colorimetric value was measured using a colorimeter: L =25.3, a = 2.1, b = -35.8, compared to the chromaticity (L) of polyester chips prepared using virgin monomer 1. = 25.5, a = 2.0,b = -36.0) There is almost no difference. When the chips are melt-spun, the dry rubbing fastness, wet rubbing fastness and soaping fastness of the fibers are all maintained at grade 4-5.

[0075] It is evident that the recovered coloring monomers can still be used to prepare blue polyester, and the properties of the resulting blue polyester are consistent with those of the original blue polyester.

[0076] Comparative Example The chromophore monomers were recovered using colored polyester. Specifically, a blue anthraquinone dye containing dicarboxylic acid, as shown in the following structure, was used as the monomer for the colored polyester, and the colored polyester was prepared according to the preparation method of the blue polyester provided in Example 1. Simultaneously, the same alkaline ethylene glycol depolymerization experiment was performed according to the recovery method of blue polyester 1 provided in Example 1. The study found that after depolymerization, when the reaction system was cooled to room temperature, the reaction system remained deep blue, with no solid precipitation, and the chromophore monomers could not be recovered.

[0077] Next, the depolymerized reaction system was subjected to acid precipitation according to the recovery method in Example 1. The terephthalic acid obtained after acid precipitation was a distinct blue solid, indicating that the dye molecules still existed in the system in the form of soluble carboxylate or small molecules after depolymerization, and contaminated the recovered TPA, making separation impossible.

[0078]

[0079] Conclusion: The recyclable blue chromophore provided by this invention successfully achieves the dual goals of high-quality polyester coloring and high-efficiency, high-purity chemical closed-loop recycling, demonstrating significant technical advantages and outstanding industrial application value. Polyesters formed using other chromophores, however, cannot be recycled.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A recyclable blue chromophore, characterized in that, It comprises a 1,4-diarylaminoanthraquinone chromophore matrix and at least one hydroxyalkyl fragment, wherein the 1,4-diarylaminoanthraquinone chromophore matrix and at least one hydroxyalkyl fragment are bonded by heteroatoms, and the hydroxyalkyl fragment is capable of reacting with monomers that form polyesters.

2. The recyclable blue chromophore according to claim 1, characterized in that, The blue chromophore is selected from compounds shown in the following structural formulas: , where R 1 R 2 R 3 R 4 Alkyl groups independently selected from C1-C8, where X is a C1-C8 alkylene group; and A is oxygen or sulfur.

3. The recyclable blue chromophore according to claim 1 or 2, characterized in that, It is selected from any one of the compounds shown in the following structural formulas: 、 、 、 and , .

4. A method for preparing the recyclable blue chromophore according to claim 1, characterized in that, include: 1,4-Diarylaminoanthraquinone blue dyes are reacted with halogenated reagents to form halogenated intermediates; In the presence of a catalyst, the halogenated intermediate is reacted with a hydroxyalkyl-substituted phenolic derivative to introduce a hydroxyalkyl fragment into a 1,4-diarylaminoanthraquinone blue dye.

5. The preparation method according to claim 4, characterized in that, The halogenated reagent includes bromides; Preferably, the molar amount of the halogenated reagent is 1-3 times the molar amount of the 1,4-diarylaminoanthraquinone blue dye; Preferably, the temperature at which the halogenated intermediate is formed is 10-40°C; Preferably, the catalyst comprises a palladium catalyst. Preferably, the molar ratio of the halogenated intermediate to the hydroxyalkyl-substituted phenolic derivative is 1:(1-3); the molar ratio of the halogenated intermediate to the catalyst is 1:(0.005-0.015). Preferably, the temperature with the hydroxyalkyl-substituted phenolic derivative is 100-150°C.

6. A method for preparing blue polyester, characterized in that, include: A co-condensation reaction is carried out by mixing polyols, polyacids, esterification catalysts and the recyclable blue chromophore of claim 1; Preferably, the amount of the blue chromophore added is 0.1-5.0% of the molar amount of the polybasic acid, more preferably 0.5-2.0%; The amount of the polyol used is 1.05-2.50 times the molar amount of the polyacid, preferably 1.10-2.20 times; The amount of the esterification catalyst is 0.00001-0.005 times the molar amount of the polybasic acid, preferably 0.00005-0.001 times; Preferably, the temperature of the polycondensation reaction is 200-280℃.

7. A blue polyester, characterized in that, It is prepared by the method for preparing blue polyester as described in claim 6.

8. A method for recycling blue polyester, characterized in that, include: The blue polyester of claim 7 is subjected to alcoholysis under alkaline conditions to recover the coloring monomer; Preferably, the process includes: mixing the blue polyester, an alkaline catalyst, and an alcohol solvent at 160-220°C for reaction, followed by cooling and filtration to form a recovered coloring monomer and an aqueous phase; and acid precipitation of the aqueous phase to form a recovered polybasic acid.

9. A method for recycling and reusing coloring monomers, characterized in that, include: The recycled coloring monomer formed by the recycling method of the blue polyester according to claim 8 is applied to the preparation method of the blue polyester according to claim 6.

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