A method for recycling waste polyester-ammonia blended fabrics

Abstract

The present invention belongs to the technical field of recycled polyester, and particularly relates to a method for recycling waste polyester-ammonia blended fabrics. The method comprises the following steps: treating and decolorizing the colored waste polyester-ammonia blended fabrics with a treating agent and depolymerizing them; depolymerizing the decolorized polyester fabrics with a depolymerizing agent to obtain terephthalate esters. Among them, the treating agent is one or more of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; the depolymerizing agent is the same as the treating agent; the depolymerization rate of spandex in the waste polyester-ammonia blended fabrics is 98-100%, and the decolorization rate of the waste polyester-ammonia blended fabrics calculated according to the K / S value is more than 98%. The present invention breaks through the bottleneck of high pollution and high energy consumption in the traditional process, and solves the contradiction that it is difficult to balance the component separation and decolorization in the recycling process of blended fabrics.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycled polyester, and particularly relates to a method for recycling waste polyester-ammonia blended fabrics. Background Art

[0002] With the booming development of the textile industry, the quantity of waste textiles has increased sharply, and the problem of recycling polyester-ammonia blended fabrics has become increasingly prominent. Spandex and polyester have significant differences in chemical structure and physical properties, which makes it difficult to efficiently separate and reuse the two by traditional physical and chemical recycling methods. Spandex has poor thermal stability and will depolymerize at relatively low temperatures, while polyester requires high temperatures for depolymerization. The mismatch in temperature requirements not only easily damages polyester during the recycling process but also significantly increases energy consumption.

[0003] Currently, the recycling of polyester-ammonia blended fabrics mainly relies on physical methods and chemical methods. The physical method uses mechanical crushing, melt extrusion granulation, etc. to process, but this method is only applicable to single-component or low-mixed fabrics. For polyester-ammonia blended fabrics, due to the melting point of polyester being about 260°C and the melting point of spandex being about 180°C, the huge difference in melting points will lead to uneven melting, severely deteriorating the properties of the product. Moreover, the physical method cannot effectively remove dyes and impurities in the fabric, resulting in poor quality of recycled products and limited application scope. The chemical method depolymerizes polymers into monomers through hydrolysis, alcoholysis and other reactions. However, this method has problems such as low separation efficiency and complex process flow, with relatively large practical operation difficulties, and often requires the use of a large amount of chemical reagents during the depolymerization process, further increasing the recycling cost and environmental risk.

[0004] Patent CN116871305A discloses a method for stepwise separation and recycling of each component of blended fabrics. This method mainly aims at blended fabrics containing components such as nylon, spandex, polyester fiber, cotton fiber, polypropylene fiber, and other fibers (lyocell fiber, cuprammonium fiber, modal fiber), and uses a combination of chemical and physical methods to selectively stepwise separate and recycle various fibers and polyester fiber degradation products. Its advantage is that there is no need to perform complex sorting on waste clothes, or only simple sorting is required to directly carry out separation and recycling work. However, this method highly depends on various chemical reagents such as tetrahydrofuran (THF), hydrochloric acid, and sulfuric acid. In the actual use process, if these chemical reagents are used improperly, a large amount of waste liquid is likely to be generated. If the waste liquid is not properly treated, it will cause serious pollution to the environment, which greatly restricts the wide application of this method.

[0005] In summary, it is urgent to develop an efficient, environmentally friendly, and economical recycling technology for polyester-ammonia blended fabrics, which can not only relieve the environmental pressure brought by waste textiles but also achieve sustainable utilization of resources. Summary of the Invention

[0006] The object of the present invention is to solve the problems existing in the prior art and provide a method for recycling waste polyester-ammonia blended fabrics.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for recycling waste polyester-ammonia blended fabrics, comprising the step of treating colored waste polyester-ammonia blended fabrics with a treating agent, wherein the treating agent is one or more of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, and the treatment is carried out simultaneously for decolorization and depolymerization. The object of decolorization is polyester in the waste polyester-ammonia blended fabrics, and the object of depolymerization is spandex in the waste polyester-ammonia blended fabrics.

[0009] As a preferred technical solution:

[0010] For the method for recycling waste polyester-ammonia blended fabrics as described above, the specific process of treating colored waste polyester-ammonia blended fabrics with a treating agent is as follows: under the protection of nitrogen or inert gas, the waste polyester-ammonia blended fabrics, a first catalyst and the treating agent are mixed and then treated, followed by solid-liquid separation to obtain a treating solution and decolorized polyester fabrics. Then, the treating solution is subjected to recovery treatment to obtain the recovered treating agent, dyes and spandex depolymerization products.

[0011] For the method for recycling waste polyester-ammonia blended fabrics as described above, during the treatment, the mass ratio of the waste polyester-ammonia blended fabrics to the treating agent is 1:10 - 70, the mass addition amount of the first catalyst is 0.1 - 5 wt.% of the mass of the waste polyester-ammonia blended fabrics, the treatment temperature is 110 - 140 °C, and the treatment time is 10 - 150 min; after the treatment, the depolymerization rate of spandex (= the mass reduction value of spandex after depolymerization / the mass of spandex before depolymerization × 100%) is 98.3 - 100%, and the decolorization rate of the waste polyester-ammonia blended fabrics calculated according to the K / S value is above 98.2%;

[0012] The spandex molecular chain contains urethane bonds, and its thermal stability is relatively low. At a treatment temperature of 110 - 140 °C, the treating agent penetrates the spandex molecular chain and catalyzes the cleavage of its urethane bonds for depolymerization. During the depolymerization of spandex, the dyes are released synchronously with the cleavage of the molecular chain; at the same temperature, the treating agent only has a physical swelling effect on polyester, expanding the micropores of polyester. Through the interaction between the treating agent and the dye molecules, the dyes can be detached from the surface and inside of polyester. In this way, synchronous decolorization and precise separation of the two components of spandex and polyester can be achieved.

[0013] In colored waste polyester-ammonia blended textiles, the short-range interaction between dyes and polyester mainly relies on van der Waals forces and hydrogen bonds. Under high-temperature conditions of 130 - 140 °C (the dyeing temperature of polyester), the dyes will enter the amorphous region of polyester. This also means that if physical methods are to be used to decolorize such dyeing systems, the interactions between the decolorizing agent and the dyes and polyester need to be considered. During the physical decolorization process, when polyester swells in the decolorizing agent, the internal pores will expand. However, for decolorization to occur, the dye molecules must have an effective interaction with the decolorizing agent. If the decolorizing agent cannot dissolve the dyes and simultaneously break the binding force between the dyes and polyester, even if the polyester has swollen, the dyes will still remain on the polyester. Therefore, during the physical decolorization process, swelling is a necessary prerequisite for decolorization, but not a sufficient condition. Taking toluene as an example, toluene can cause slight swelling of polyester, but due to its low solubility for dyes and its inability to break the binding force between dyes and polyester, it is difficult to decolorize colored waste polyester textiles.

[0014] The inventor of the present invention has carried out a large number of experiments and theoretical calculations. After numerous attempts and analyses, the decolorizing agent used in the present invention has been determined. The solubility parameter of this decolorizing agent is extremely close to that of polyester. This characteristic enables the decolorizing agent to smoothly penetrate into the interior of polyester fibers without dissolving the polyester, causing the polyester fibers to swell. The decolorizing agent can also dissolve the dyes and simultaneously break the binding force between the dyes and polyester, thus enabling the dyes to detach from the surface of the polyester fibers.

[0015] For the recycling method of waste polyester-ammonia blended textiles as described above, the first catalyst is a mixture of zinc acetate and a basic catalyst. The content of zinc acetate in the first catalyst is 50 - 100 wt.%, and the basic catalyst is one or more of potassium carbonate, sodium carbonate, sodium hydroxide, and potassium hydroxide. Designing the first catalyst in this way can prevent the treatment agent from decomposing.

[0016] The solid-liquid separation methods include one or more of normal pressure filtration, vacuum filtration (suction filtration), and centrifugal filtration.

[0017] The recycling treatment is divided into two steps. In the first step, the treatment agent is separated from the dyes and the depolymerization products of spandex. The methods used include one or more of distillation, vacuum distillation, rotary evaporation, and rectification. The purity of the recovered treatment agent is 98 - 99.9%. In the second step, the dyes are separated from the depolymerization products of spandex.

[0018] A method for recycling waste polyester-ammonia blended fabrics as described above further includes a step of depolymerizing the decolorized polyester fabric with a depolymerizing agent to obtain terephthalate; terephthalate refers to the ester formed by terephthalic acid, and its type depends on the type of the depolymerizing agent. For example, when the depolymerizing agent is dimethyl carbonate, the terephthalate is dimethyl terephthalate (DMT); when the depolymerizing agent is diethyl carbonate, the terephthalate is diethyl terephthalate; when the depolymerizing agent is diethyl carbonate, the terephthalate is methyl ethyl terephthalate.

[0019] For the method for recycling waste polyester-ammonia blended fabrics as described above, the specific process of depolymerizing the decolorized polyester fabric with a depolymerizing agent to obtain terephthalate is as follows: under the protection of nitrogen or inert gas, the decolorized polyester fabric, the depolymerizing agent and the second catalyst are mixed and then subjected to a depolymerization reaction, and then the depolymerization solution is separated and purified to obtain terephthalate.

[0020] For the method for recycling waste polyester-ammonia blended fabrics as described above, the depolymerizing agent is the same as the treating agent.

[0021] For the method for recycling waste polyester-ammonia blended fabrics as described above, during depolymerization, the molar ratio of the depolymerizing agent to the decolorized polyester fabric is 3 - 30:1, the mass addition amount of the second catalyst is 0.1 - 5 wt.% of the mass of the decolorized polyester fabric, the temperature of the depolymerization reaction is 160 - 200 °C, and the time of the depolymerization reaction is 30 - 200 min;

[0022] At this depolymerization temperature, under the action of the catalyst, the depolymerizing agent attacks the ester group in the polyester molecular chain through a nucleophilic reaction, resulting in the breakage of the polyester molecular chain. At the same time, the depolymerizing agent and ethylene glycol generated due to the breakage of the polyester molecular chain spontaneously form a ring to generate ethylene carbonate, thereby promoting the positive shift of the depolymerization reaction equilibrium and finally efficiently depolymerizing to obtain terephthalate;

[0023] The depolymerization solution is separated and purified to obtain terephthalate, that is, first, the depolymerization solution is subjected to reduced-pressure devolatilization at 140 - 190 °C, the removed volatile components are collected, then centrifugal separation is carried out at 70 - 100 °C to obtain a solid product, and then the solid product is processed to obtain terephthalate;

[0024] After depolymerization, the depolymerization rate of the decolorized polyester fabric (= the mass reduction value of the decolorized polyester fabric after depolymerization / the mass of the decolorized polyester fabric before depolymerization × 100%) is 90 - 100%.

[0025] A method for recycling waste polyester-urethane blended fabric as described above, where 10 - 50 wt.% of the depolymerizing agent is the recycled treatment agent, and the second catalyst is a mixture of zinc acetate and a basic catalyst. The content of zinc acetate in the second catalyst is 50 - 100 wt.%, and the basic catalyst is one or more of potassium carbonate, sodium carbonate, sodium hydroxide, and potassium hydroxide. Designing the second catalyst in this way can prevent the depolymerizing agent from decomposing.

[0026] A method for recycling waste polyester-urethane blended fabric as described above. When the terephthalate is DMT, DMT, ethylene glycol, a third catalyst (such as tetrabutyl titanate, antimony glycolate, antimony acetate, antimony trioxide, etc.), and a functional additive (such as triphenyl phosphate, trimethyl phosphite, antioxidant 1010, titanium dioxide, etc.) can be subjected to a repolymerization reaction to obtain regenerated polyethylene terephthalate.

[0027] When the terephthalate is not DMT, the terephthalate can be first converted into DMT, and then DMT, ethylene glycol, a third catalyst (such as tetrabutyl titanate, antimony glycolate, antimony acetate, antimony trioxide, etc.), and a functional additive (such as triphenyl phosphate, trimethyl phosphite, antioxidant 1010, titanium dioxide, etc.) are subjected to a repolymerization reaction to obtain regenerated polyethylene terephthalate. Among them, the conversion method is: mix the terephthalate, methanol, and sodium hydroxide (catalyst), heat to 60°C under nitrogen protection and react for 3 hours, then stop heating, cool to room temperature, and wash with methanol.

[0028] A method for recycling waste polyester-urethane blended fabric as described above, where the content of spandex in the waste polyester-urethane blended fabric does not exceed 20 wt.%.

[0029] Beneficial effects:

[0030] In the present invention, by selecting specific treatment agents and depolymerizing agents and combining with temperature control, selective depolymerization of spandex and polyester is carried out at different stages (i.e., the treatment stage and the depolymerization stage). In particular, in the treatment stage, not only the depolymerization of spandex is completed, but also the decolorization of polyester and spandex is achieved. This operation realizes gradient depolymerization and synchronous decolorization of the two components. Compared with the traditional step-by-step treatment method, the present invention avoids the problems of fiber damage caused by temperature mismatch and energy consumption superposition, and can also remove dyes on the two types of fibers synchronously and efficiently. The synergistic effect of this "one-step method" of decolorization and depolymerization greatly simplifies the process flow and successfully solves the core contradiction that it is difficult to balance component separation and decolorization in the recycling process of blended fabrics.

[0031] In the whole process of the present invention, the treatment agent and the depolymerizing agent used are the same substance, avoiding the steps of solvent replacement and multiple treatments in the traditional process, and greatly simplifying the process flow; the treatment agent is efficiently recovered and used as a depolymerizing agent in the depolymerization reaction, significantly reducing its loss and environmental pollution, and providing a more economical and efficient solution for the industrial closed-loop recycling of waste polyester-ammonia blended fabrics.

[0032] The treatment agent used in the present invention has the characteristic of low boiling point, all lower than 130 °C. In particular, the boiling point of dimethyl carbonate is only 90 °C. Compared with traditional high-boiling treatment agents, such as dimethyl sulfoxide with a boiling point of 189 °C, the distillation recovery temperature of the treatment agent of the present invention is reduced by more than 40%, and the energy consumption is reduced by about 35%. At the same time, the treatment agent of the present invention also has low toxicity and high volatility, greatly reducing its residue in the recycled polyester material, reducing both environmental and health risks, and improving the quality and application performance of the recycled polyester material, which is in line with the development direction of green chemistry.

[0033] The present invention realizes a technical system of gradient depolymerization - solvent reuse - closed-loop regeneration in one, breaking through the bottleneck of high pollution and high energy consumption in the traditional process. Description of the Drawings

[0034] Figure 1 It is the infrared spectrum of the decolorized polyester fabric in Example 1 of the present invention;

[0035] Figure 2 It is the nuclear magnetic resonance hydrogen spectrum of DMT in Example 1 of the present invention;

[0036] Figure 3 It is the infrared spectrum of DMT in Example 1 of the present invention;

[0037] Figure 4 It is the color contrast diagram of the waste polyester-ammonia blended fabric (corresponding to a) in Figure 4 and the decolorized polyester fabric (corresponding to b) in Example 1 Figure 4 ; Detailed Embodiments

[0038] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0039] The following are the test methods for relevant performance indicators in each embodiment and comparative example:

[0040] Decolorization rate: Use the S81 desktop spectrophotometer produced by Tianjin Trus Technology Co., Ltd. which has been calibrated. Under the conditions of D65 light source, 10° viewing angle, reflection mode with UV400 cut-off, and φ18, measure the K / S values of the fabric before and after decolorization. Fold the fabric to be tested twice to ensure that the sample is opaque during color measurement. Each group of samples is measured 5 times, and the average value is taken. Calculate the decolorization rate of the fabric according to the following formula:

[0041] ;

[0042] In the formula: is the K / S value of the fabric before decolorization, is the K / S value of the fabric after decolorization.

[0043] Purity: Use the GC-2010 Pro gas chromatograph produced by Shimadzu Corporation of Japan, equipped with a flame ionization detector (FID) and a chromatographic data processing workstation to quantitatively analyze the purity of the collected DMT, and perform purity fitting by the internal standard method;

[0044] Select dipropyl phthalate as the internal standard substance, use chloroform as the solvent, and perform quantitative calculation through the peak area ratio; the test conditions are set as follows: the carrier gas uses high-purity nitrogen with a purity ≥ 99.95%, the split ratio is 15:1, the chromatographic injection port temperature is 280 °C, the column temperature is 60 °C, the total flow rate is 3.7 mL / min, and the chromatographic column flow rate is 0.7 mL / min.

[0045] Oligomer content: Use the Shimadzu LC 16 high-performance liquid chromatograph (HPLC), equipped with a WondaSil C18-WR (200 mm, packing particle size 5 μm) chromatographic column and an ultraviolet detector, to qualitatively and quantitatively analyze the oligomer content in DMT; the detection conditions are set as follows: the detection wavelength is 254 nm, the column temperature is 40 °C, a binary gradient elution program is used, the mobile phase is methanol-water (volume ratio 3:1), the flow rate is 0.8 mL / min, and quantitative calculation is performed by the external standard method.

[0046] Fourier transform infrared spectroscopy FTIR characterization: Use a Nicolet 6700 Fourier transform infrared spectrometer to perform structural characterization on the sample. Dry the sample before testing, and use an attenuated total reflection (ATR) accessory for total reflection testing. The scanning range is set to 4000~600 cm -1 .

[0047] 1H nuclear magnetic resonance spectrum test: Weigh 5-10 mg of the dry sample and place it in a 5 mm nuclear magnetic tube. After adding 0.5 mL of deuterated trifluoroacetic acid (CF3COOD) reagent to dissolve it, use an Avance-400 nuclear magnetic resonance spectrometer produced by Bruker Corporation of Germany for testing. Use tetramethylsilane (TMS) as the internal standard substance, and set the test frequency to 600 MHz.

[0048] The conversion rate of DMT (%) can be calculated by the following formula:

[0049] Conversion rate of DMT = ;

[0050] In the formula, is the mass of DMT collected (unit: g), is the molar mass of the collected DMT (unit: g / mol), is the added mass of the decolorized polyester fabric (unit: g), is the molar mass of the repeating unit of the decolorized polyester fabric (for waste polyethylene terephthalate fabric, the value is 192 g / mol).

[0051] The color fastness to washing of the colored waste polyester-ammonia blended fabric used in the present invention is at least 4-5 levels, and it is prepared by high-temperature high-pressure dyeing method, carrier dyeing method, thermosol dyeing method or atmospheric pressure high-temperature dyeing method with disperse dyes (azo disperse dyes, anthraquinone disperse dyes, heterocyclic disperse dyes, etc.), or by cationic dyes through processes such as dipping and fixing, or by acid dyes through processes such as acid bath dyeing and fixing treatment, or by vat dyes through processes such as reduction, oxidation and soaping. In view of the fact that disperse dyes are common dyes for dyeing polyester textiles, the following examples of the present invention are only described by taking the colored waste polyester-ammonia blended fabric dyed with disperse dyes as an example.

[0052] Example 1

[0053] A method for recycling waste polyester-ammonia blended fabric, the specific steps are as follows:

[0054] (1) Preparation of raw materials;

[0055] Colored waste polyester-ammonia blended fabric: brand is Jingyilai Embroidery, product number is J25215-12, color is XC-8860 green (as Figure 4 shown in a below);

[0056] The first catalyst and the second catalyst: both are zinc acetate;

[0057] The treatment agent and the depolymerizing agent: both are dimethyl carbonate;

[0058] (2) Treat the colored waste polyester-ammonia blended fabric with the treatment agent;

[0059] Under the protection of nitrogen or inert gas, after mixing waste polyester-ammonia blended fabric, the first catalyst and the treatment agent, first treat at 140 °C for 150 min, and then perform solid-liquid separation (using the atmospheric pressure method) to obtain a treatment solution and decolorized polyester fabric (the infrared spectrum of the decolorized polyester fabric is as shown in Figure 1 shown, and the color is as shown in Figure 4 b in

[0060] ), then sequentially separate the treatment agent from the dye and the depolymerization product of spandex (using the rotary evaporation method), and separate the dye from the depolymerization product of spandex to obtain the recovered treatment agent, dye and depolymerization product of spandex; wherein, the mass ratio of waste polyester-ammonia blended fabric to the treatment agent is 1:70, and the mass addition amount of the first catalyst is 3 wt.% of the mass of the waste polyester-ammonia blended fabric;

[0061] (3) Depolymerize the decolorized polyester fabric using a depolymerizing agent;

[0062] Under the protection of nitrogen or inert gas, after mixing the decolorized polyester fabric, the depolymerizing agent, the recovered treatment agent and the second catalyst, carry out a depolymerization reaction at 200 °C for 180 min, first carry out vacuum devolatilization on the depolymerization solution at 170 °C, collect the removed volatile components, then carry out centrifugal separation at 100 °C to obtain a solid product, and then mix the solid product with methanol at a mass ratio of 1:15, stir at a constant temperature of 60 °C for 50 min, selectively remove impurities through the dissolution-recrystallization process, and finally obtain DMT through solid-liquid separation; wherein, the mass of the recovered treatment agent is 10 wt.% of the total mass of the depolymerizing agent and the recovered treatment agent, the total molar amount of the depolymerizing agent and the recovered treatment agent is in a ratio of 20:1 to the molar amount of the decolorized polyester fabric, and the mass addition amount of the second catalyst is 3 wt.% of the mass of the decolorized polyester fabric;

[0063] After depolymerization, the depolymerization rate of the decolorized polyester fabric is 100%, the conversion rate of DMT is 100%, the purity of DMT is 99.9%, and the oligomer content of DMT is 0.01 wt.%.

[0064] The nuclear magnetic resonance hydrogen spectrum of DMT prepared in this example is as shown in Figure 2 shown, and the infrared spectrum is as shown in Figure 3 shown; as can be seen from Figure 2 , the chemical shifts and integral areas of each peak are consistent with the theoretical values of DMT. Among them, the hydrogen proton peak on the benzene ring corresponds to the chemical shift of 8.09 ppm, and the methyl hydrogen proton peak directly connected to the ester group corresponds to the chemical shift of 3.98 ppm. After calculation, the ratio of the peak areas at the two places (benzene ring hydrogen to methyl hydrogen) is about 0.66 (4 / 6.02≈0.66), indicating that the depolymerization reaction product is DMT and has a high purity; fromFigure 3 It can be seen that the absorption peak at 2961 cm -1 corresponds to the C—H stretching vibration characteristics of methyl, and the absorption peak at 1718 cm -1 matches the stretching vibration mode of C=O in the ester group. The absorption peak at 1433 cm -1 corresponds to the stretching vibration of C=C in the benzene ring skeleton, while the absorption peaks at 1279 cm -1 and 1115 cm -1 correspond to the stretching vibrations of C—O in the ester group respectively. These characteristic absorption peaks are in complete agreement with the functional group vibration modes in the DMT molecular structure, further verifying that the product of the depolymerization reaction is DMT.

[0065] After depolymerizing the decolorized polyester fabric with a depolymerizing agent, DMT, ethylene glycol, a third catalyst, and a functional additive can also be subjected to a repolymerization reaction to obtain regenerated polyethylene terephthalate.

[0066] Example 2

[0067] A method for recycling waste polyester-ammonia blended fabrics, the specific steps are as follows:

[0068] (1) Preparation of raw materials;

[0069] Colored waste polyester-ammonia blended fabric: brand is Jingyilai Embroidery, product number is J25215-8, color is XC-8831 light blue;

[0070] The first catalyst and the second catalyst: both are mixtures of zinc acetate and sodium carbonate, and the content of zinc acetate in the first catalyst and the second catalyst is 65 wt.%;

[0071] The treatment agent and the depolymerizing agent: both are mixtures of dimethyl carbonate and diethyl carbonate with a molar ratio of 2:1;

[0072] (2) Treat the colored waste polyester-ammonia blended fabric with a treatment agent;

[0073] Under the protection of nitrogen or inert gas, the waste polyester-ammonia blended fabric, the first catalyst, and the treatment agent are mixed, first treated at 130 °C for 80 min, and then solid-liquid separation (by centrifugation) is carried out to obtain a treatment solution and a decolorized polyester fabric. Then, the treatment agent is separated from the dye and the polyurethane depolymerization product (by rectification) in turn, and the dye is separated from the polyurethane depolymerization product to obtain the recovered treatment agent, dye, and polyurethane depolymerization product; among them, the mass ratio of the waste polyester-ammonia blended fabric to the treatment agent is 1:50, and the mass addition amount of the first catalyst is 5 wt.% of the mass of the waste polyester-ammonia blended fabric;

[0074] After treatment, the depolymerization rate of spandex is 99.7%, and the decolorization rate of waste polyester-spandex blended fabric is 99.3%; the purity of the recovered treatment agent is 99.7%;

[0075] (3) Depolymerize the decolorized polyester fabric with a depolymerizing agent;

[0076] Under the protection of nitrogen or inert gas, after mixing the decolorized polyester fabric, the depolymerizing agent, the recovered treatment agent and the second catalyst, carry out a depolymerization reaction at 175 °C for 200 min. First, carry out vacuum devolatilization on the depolymerization solution at 190 °C, collect the removed volatile components, then carry out centrifugal separation at 80 °C to obtain a solid product. Then mix the solid product with methanol at a mass ratio of 1:10, stir at a constant temperature of 70 °C for 60 min, selectively remove impurities through the dissolution-recrystallization process, and finally obtain terephthalate through solid-liquid separation; among them, the mass of the recovered treatment agent is 25 wt.% of the total mass of the depolymerizing agent and the recovered treatment agent, the total molar amount of the depolymerizing agent and the recovered treatment agent is in a ratio of 30:1 to the molar amount of the decolorized polyester fabric, and the mass addition amount of the second catalyst is 1 wt.% of the mass of the decolorized polyester fabric;

[0077] After depolymerization, the depolymerization rate of the decolorized polyester fabric is 99%.

[0078] After depolymerizing the decolorized polyester fabric with a depolymerizing agent, it is also possible to first convert terephthalate into DMT, and then carry out a repolymerization reaction on DMT, ethylene glycol, the third catalyst and the functional additive to obtain recycled polyethylene terephthalate.

[0079] Example 3

[0080] A method for recycling waste polyester-spandex blended fabric, the specific steps are as follows:

[0081] (1) Preparation of raw materials;

[0082] Colored waste polyester-spandex blended fabric: Manufacturer is Dongguan Liangdiandian Textile Co., Ltd., product number is 025;

[0083] The first catalyst and the second catalyst: both are mixtures of zinc acetate and potassium hydroxide, and the content of zinc acetate in the first catalyst and the second catalyst is 80 wt.%;

[0084] The treatment agent and the depolymerizing agent: both are ethyl methyl carbonate;

[0085] (2) Treat the colored waste polyester-spandex blended fabric with a treatment agent;

[0086] Under the protection of nitrogen or inert gas, the waste polyester-ammonia blended fabric, the first catalyst and the treating agent are mixed, and then treated at 120 °C for 120 min, followed by solid-liquid separation (using vacuum filtration method, the pressure is 0.03 MPa) to obtain the treating solution and the decolorized polyester fabric. Then, the treating agent is separated from the dye and the polyurethane depolymerization product in turn (using vacuum distillation method), and the dye is separated from the polyurethane depolymerization product to obtain the recovered treating agent, dye and polyurethane depolymerization product; wherein, the mass ratio of the waste polyester-ammonia blended fabric to the treating agent is 1:30, and the mass addition amount of the first catalyst is 1 wt.% of the mass of the waste polyester-ammonia blended fabric.

[0087] After treatment, the depolymerization rate of polyurethane is 99.4%, and the decolorization rate of the waste polyester-ammonia blended fabric is 99.1%; the purity of the recovered treating agent is 99.4%.

[0088] (3)Depolymerize the decolorized polyester fabric with a depolymerizing agent;

[0089] Under the protection of nitrogen or inert gas, the decolorized polyester fabric, the depolymerizing agent, the recovered treating agent and the second catalyst are mixed, and after depolymerization reaction at 190 °C for 90 min, first carry out vacuum devolatilization on the depolymerization solution at 140 °C, collect the removed volatile components, then carry out centrifugal separation at 70 °C to obtain a solid product, and then mix the solid product with methanol according to a mass ratio of 1:20, stir at a constant temperature of 60 °C for 40 min, selectively remove impurities through the dissolution-recrystallization process, and finally obtain terephthalate through solid-liquid separation; wherein, the mass of the recovered treating agent is 40 wt.% of the total mass of the depolymerizing agent and the recovered treating agent, the molar ratio of the total amount of the depolymerizing agent and the recovered treating agent to the molar amount of the decolorized polyester fabric is 10:1, and the mass addition amount of the second catalyst is 5 wt.% of the mass of the decolorized polyester fabric.

[0090] After depolymerization, the depolymerization rate of the decolorized polyester fabric is 96%.

[0091] After depolymerizing the decolorized polyester fabric with a depolymerizing agent, it is also possible to first convert terephthalate into DMT, and then carry out a repolymerization reaction on DMT, ethylene glycol, the third catalyst and the functional additive to obtain recycled polyethylene terephthalate.

[0092] Example 4

[0093] A method for recycling waste polyester-ammonia blended fabric, the specific steps are as follows:

[0094] (1)Preparation of raw materials;

[0095] Colored waste polyester-ammonia blended fabric: brand is Jingyilai Embroidery, product number is J25215-8, color is XC-8815 light green;

[0096] The first catalyst and the second catalyst: Both are mixtures of zinc acetate and sodium hydroxide, and the content of zinc acetate in the first catalyst and the second catalyst is 50 wt.%;

[0097] The treating agent and the depolymerizing agent: Both are mixtures of dimethyl carbonate and ethyl methyl carbonate with a molar ratio of 1:1;

[0098] (2) Treat the colored waste polyester-ammonia blended fabric with the treating agent;

[0099] Under the protection of nitrogen or inert gas, mix the waste polyester-ammonia blended fabric, the first catalyst and the treating agent, first treat at 110 °C for 10 min, then carry out solid-liquid separation (using vacuum filtration method, the pressure is 0.03 MPa) to obtain the treating solution and the decolorized polyester fabric, and then separate the treating agent from the dye and the depolymerization product of spandex in turn (using distillation method), and separate the dye from the depolymerization product of spandex to obtain the recovered treating agent, dye and depolymerization product of spandex; among them, the mass ratio of the waste polyester-ammonia blended fabric to the treating agent is 1:10, and the mass addition amount of the first catalyst is 0.1 wt.% of the mass of the waste polyester-ammonia blended fabric;

[0100] After treatment, the depolymerization rate of spandex is 98.3%, and the decolorization rate of the waste polyester-ammonia blended fabric is 98.2%; the purity of the recovered treating agent is 98%;

[0101] (3) Depolymerize the decolorized polyester fabric with the depolymerizing agent;

[0102] Under the protection of nitrogen or inert gas, mix the decolorized polyester fabric, the depolymerizing agent, the recovered treating agent and the second catalyst, carry out depolymerization reaction at 160 °C for 30 min, then carry out vacuum devolatilization on the depolymerization solution at 165 °C, collect the removed volatile components, then carry out centrifugal separation at 90 °C to obtain the solid product, and then mix the solid product with methanol according to a mass ratio of 1:5, stir at a constant temperature of 50 °C for 30 min, selectively remove impurities through the dissolution-recrystallization process, and finally obtain terephthalate through solid-liquid separation; among them, the mass of the recovered treating agent is 50 wt.% of the total mass of the depolymerizing agent and the recovered treating agent, the total molar amount of the depolymerizing agent and the recovered treating agent is in a ratio of 3:1 to the molar amount of the decolorized polyester fabric, and the mass addition amount of the second catalyst is 0.1 wt.% of the mass of the decolorized polyester fabric;

[0103] After depolymerization, the depolymerization rate of the decolorized polyester fabric is 90%.

[0104] After depolymerizing the decolorized polyester fabric with the depolymerizing agent, it is also possible to first convert terephthalate into DMT, and then carry out a repolymerization reaction on DMT, ethylene glycol, the third catalyst and the functional additive to obtain regenerated polyethylene terephthalate.

Claims

1. A method for recycling waste polyester-ammonia blended fabrics, characterized in that, It includes the steps of treating the colored waste polyester-ammonia blended fabric with a treating agent and depolymerizing the decolorized polyester fabric with a depolymerizing agent; The specific process of treating the colored waste polyester-ammonia blended fabric with a treating agent is as follows: under the protection of nitrogen or inert gas, the waste polyester-ammonia blended fabric, the first catalyst and the treating agent are mixed and then treated, followed by solid-liquid separation to obtain a treating solution and a decolorized polyester fabric. Then, the treating solution is subjected to recovery treatment to obtain the recovered treating agent, dye and spandex depolymerization product; The first catalyst is a mixture of zinc acetate and a basic catalyst. The content of zinc acetate in the first catalyst is 50-100 wt.%, and the basic catalyst is one or more of potassium carbonate, sodium carbonate, sodium hydroxide and potassium hydroxide. The mass addition amount of the first catalyst is 0.1-5 wt.% of the mass of the waste polyester-ammonia blended fabric; The treating agent is one or more of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, and the treating temperature is 110-140 °C; The depolymerizing agent is the same as the treating agent, and the temperature of the depolymerization reaction is 160-200 °C.

2. The recycling method of a waste polyester-ammonia blended fabric according to claim 1, characterized in that, During the treatment, the mass ratio of the waste polyester-ammonia blended fabric to the treating agent is 1:10-70, and the treatment time is 10-150 min. After the treatment, the depolymerization rate of spandex is 98.3-100%, and the decolorization rate of the waste polyester-ammonia blended fabric calculated by the K / S value is above 98.2%.

3. A method for recycling waste polyester-ammonia blended textiles according to claim 1, characterized in that, The recovery treatment is divided into two steps. The first step is to separate the treating agent from the dye and the spandex depolymerization product, and the second step is to separate the dye from the spandex depolymerization product.

4. A method for recycling waste polyester-ammonia blended textiles according to claim 1, characterized in that, The specific process of depolymerizing the decolorized polyester fabric with a depolymerizing agent to obtain terephthalate is as follows: under the protection of nitrogen or inert gas, the decolorized polyester fabric, the depolymerizing agent and the second catalyst are mixed and then subjected to a depolymerization reaction, and then the depolymerization solution is separated and purified to obtain terephthalate.

5. A method for recycling waste polyester-ammonia blended fabric according to claim 4, characterized in that, During the depolymerization, the molar ratio of the depolymerizing agent to the decolorized polyester fabric is 3-30:1, the mass addition amount of the second catalyst is 0.1-5 wt.% of the mass of the decolorized polyester fabric, and the depolymerization reaction time is 30-200 min. After the depolymerization, the depolymerization rate of the decolorized polyester fabric is 90-100%.

6. The recycling method of a waste polyester-ammonia blended fabric according to claim 5, characterized in that, 10-50 wt.% of the depolymerizing agent is the recovered treating agent, and the second catalyst is a mixture of zinc acetate and a basic catalyst. The content of zinc acetate in the second catalyst is 50-100 wt.%, and the basic catalyst is one or more of potassium carbonate, sodium carbonate, sodium hydroxide and potassium hydroxide.

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