A method for preparing polyester fabric by recycling waste polyester textiles

Abstract

The invention discloses a method for preparing polyester fabric by recycling waste polyester textiles, belongs to the technical field of polyester recycling, and is used to solve the technical problem that the mechanical properties and antibacterial ability of the regenerated polyester fabric in the prior art need to be further improved. The invention comprises the following steps: adding waste polyester textiles and modified multilayer graphene into a high-pressure reactor, and performing supercritical depolymerization of carbon dioxide to obtain a depolymerization mixed liquid. The modified multilayer graphene is prepared, and its rich void structure enables the supercritical fluid to be slowly released, and the depolymerization effect is improved. At the same time, the rich active functional groups on its surface provide in-situ polymerization sites for the depolymerized monomers, so that the depolymerized monomers can be used as a polymerization hub structure to provide support for organic chain segments, and the spatial structure is hybridized by a chain extender. Finally, a flame-retardant and antibacterial liquid is prepared, and its effective components are cross-linked with the modified multilayer graphene, and the carbonization of the chain extender is promoted during the combustion process, so as to obtain a regenerated polyester fabric with excellent flame-retardant, antibacterial and mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polyester recycling, and in particular to a method for preparing polyester fabrics by recycling waste polyester textiles. Background Art

[0002] The recycling technology of discarded polyester textiles has gradually developed from the initial physical crushing method to the advanced chemical recycling method, which has significantly improved the quality and application scope of the recycled fibers. Chemical recycling not only enables the fibers to achieve performance close to that of the original materials, but also promotes their reuse in high-end markets such as clothing and fine textiles, which helps protect the environment, promotes the efficient recycling of resources, and provides important support for the sustainable development of the textile industry.

[0003] Prior art CN118109920B discloses a method for preparing cool and high-elastic fabrics from regenerated polyester fiber filaments, comprising the following steps: adding a modifier to dolomite, shell powder, boron nitride and expanded perlite, grinding to obtain a nano-scale modified inorganic powder mixture, crushing and depolymerizing the polyester bottle, adding the nano-scale modified inorganic powder mixture and Artemisia annua powder, and then polycondensing to obtain regenerated polyester, melt-spinning the regenerated polyester to obtain regenerated polyester fiber fabrics, spraying a finishing agent on the regenerated polyester fiber fabrics to prepare a cool and high-elastic fabric, wherein the finishing agent is an addition product of intermediate A and 1-dodecene, and intermediate A is obtained by reacting a hydroxy-terminated polydimethylsiloxane aqueous solution, methacrylic acid and triglycidyl isocyanurate.

[0004] However, the above patent content is to add a nano-scale modified inorganic powder mixture to the system of preparing polyester materials by condensation polymerization to achieve the purpose of improving the mechanical properties of polyester fabrics. However, in the process of condensation polymerization, the polyester segments formed by the continuous polymerization of organic monomers are not subjected to hybridization treatment. The polarity of the long-chain polyester segments is extremely low compared to the polarity of inorganic fillers, which makes the interface bonding force between the materials weak, resulting in poor bonding between the two. After the polymerization is completed, an organic system and an inorganic system with a boundary are formed, which ultimately leads to the mechanical properties of the prepared polyester fabric to be further improved.

[0005] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing polyester fabric by recycling waste polyester textiles, so as to solve the technical problem in the prior art that the mechanical properties and antibacterial ability of recycled polyester fabric need to be further improved.

[0007] The purpose of the present invention can be achieved by the following technical solution: A method for preparing polyester fabric by recycling waste polyester textiles, comprising the following steps:

[0008] S1. Adding waste polyester textiles and modified multilayer graphene into a high-pressure reactor to perform supercritical depolymerization of carbon dioxide to obtain a depolymerization mixed solution;

[0009] S2, adding the depolymerization mixture, terephthalic acid, titanium tetrabutyrate and dimethyl sulfoxide into a high-pressure reactor, reacting at high temperature and high pressure for 2-4 hours, continuing to add a chain extender into the high-pressure reactor, reacting at high temperature and high pressure for 1-2 hours, and post-treating to obtain a modified polyester;

[0010] S3, adding the modified polyester into the reactor, raising the temperature of the reactor to 260-280°C, and after the modified polyester is melted, extruding it through a spinneret and transferring it to a side-blowing chamber, and obtaining the regenerated polyester fiber after air cooling and curing;

[0011] S4, using recycled polyester fibers for weaving to obtain polyester fabrics;

[0012] S5. The polyester fabric is modified by impregnation with a flame retardant and antibacterial liquid, and then post-processed to obtain a recycled polyester fabric.

[0013] Reaction principle: During the immersion process, the phosphate groups in the effective components of the flame retardant and bactericidal liquid react with the epoxy groups on the modified graphene and other components in the structure and with the active functional groups to form a stable structure connected by chemical bonds.

[0014] Furthermore, in step S1, the usage ratio of waste polyester textiles and modified multilayer graphene is 8-10g:1-2g, and the waste polyester textiles include industrial waste polyester textiles and post-consumer waste polyester textiles.

[0015] Furthermore, the preparation method of the modified multilayer graphene comprises the following steps:

[0016] A1, adding 98.0wt% concentrated sulfuric acid to a reactor and stirring, adding potassium permanganate powder to the reactor during stirring, stirring at room temperature for 5-10min, raising the temperature of the reactor to 30-45°C and adding multilayer graphene to the reactor, keeping the temperature and stirring for 2-3h, and post-treating to obtain oxidized multilayer graphene;

[0017] Reaction principle for preparing oxidized multilayer graphene: Sulfuric acid is a highly acidic environment that helps to open up the space between graphene layers and increase chemical activity. When potassium permanganate is added to 98.0wt% concentrated sulfuric acid, sulfuric acid acts as a solvent while also promoting the decomposition of potassium permanganate, releasing manganese oxides and free oxygen with strong oxidizing properties. These oxidants attack the carbon atoms in the graphene layers to form active functional groups such as epoxy groups, hydroxyl groups, and carboxyl groups. After the reaction is completed, hydrogen peroxide is added to cool the mixture, which reacts with the residual potassium permanganate to form manganese ions and water, thus terminating the reaction.

[0018] A2. Add oxidized multilayer graphene, γ-glycidyloxypropyltrimethoxysilane, triethylamine and N,N-dimethylformamide into a reaction kettle, stir at room temperature for 30-40 minutes, and post-treat to obtain modified multilayer graphene.

[0019] Reaction principle for preparing modified multilayer graphene: Under alkaline conditions, the epoxy groups on γ-glycidyloxypropyltrimethoxysilane undergo a ring-opening reaction, and the generated free radicals react with the active functional groups on the surface of graphene oxide, ultimately preparing modified multilayer graphene whose surface is modified by a silane coupling agent.

[0020] Further, in step A1, the stirring rate of the reactor is 80-120 rpm, the amount ratio of 98.0 wt% concentrated sulfuric acid, potassium permanganate powder and multilayer graphene is 45-50 mL: 6-8 g: 1-2 g, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is lowered to room temperature, 30 wt% hydrogen peroxide solution is added to the reactor until the solution becomes transparent, the reaction liquid is filtered, the filter cake is collected, and after washing with ethanol and deionized water for 3-5 times, the filter cake is placed at a temperature of 6 The method comprises the following steps: vacuum drying in a drying oven at 0°C to obtain oxidized multilayer graphene; in step A2, the amount ratio of oxidized multilayer graphene, γ-glycidyloxypropyltrimethoxysilane, triethylamine and N,N-dimethylformamide is 8-10g:2-3g:0.3-0.5g:40-60mL, and post-treatment comprises: filtering the reaction solution, collecting the filter cake, washing the filter cake with ethanol and deionized water for 3-5 times, and then placing the filter cake in a drying oven at a temperature of 60°C and vacuum drying to obtain modified multilayer graphene.

[0021] Furthermore, in step S1, the operation process of supercritical depolymerization is as follows: placing the high-pressure reactor in a salt bath furnace, exhausting the air in the high-pressure reactor with carbon dioxide gas, introducing 200-250 Bar of carbon dioxide gas into the high-pressure reactor using a pressurizing device, and raising the temperature of the salt bath furnace to 120-160° C., observing the internal pressure of the high-pressure reactor during heating, using valves on both sides to vent and release the pressure, controlling the pressure in the reactor to be less than 250 Bar, and keeping the reaction warm for 4-6 hours. After the reaction is completed, reducing the pressure in the high-pressure reactor to room temperature and then exhausting the carbon dioxide gas to obtain a depolymerization mixed liquid.

[0022] The reaction equation for preparing the depolymerization mixture is:

[0023] The reaction principle for preparing the depolymerization mixture is to use carbon dioxide gas under high temperature conditions to reach a supercritical fluid state, and to use the supercritical fluid's strong solubility and dispersion capabilities to continuously dissolve small molecules in the process of destroying the ester bonds in the polyester, ultimately completely depolymerizing the polyester to obtain a depolymerization product.

[0024] Furthermore, in step S2, the temperature of the high-pressure reactor is 260-280°C, the pressure is 300-500kPa, the amount ratio of the depolymerization mixed liquid, terephthalic acid, titanium tetrabutyrate, dimethyl sulfoxide and chain extender is 12-16mL:1-2g:0.6-0.8g:40-60mL:3-5g, and the post-treatment includes: after the reaction is completed, the reactor is cooled to room temperature, the reaction liquid is added to a rotary evaporator with a water bath temperature of 80-100°C, and the reduced pressure distillation is carried out until no liquid is produced to obtain a modified polyester.

[0025] The reaction equation for preparing modified polyester is:

[0026] Where: .

[0027] The reaction principle for preparing modified polyester is as follows: under high temperature, high pressure and the promotion of catalysts, a polymerization reaction occurs in the system. After an excess of terephthalic acid is introduced, it reacts in situ with ethylene glycol on the surface of oxidized multilayer graphene to form a polyester structure terminated with a carboxyl group, and further reacts with a chain extender to react with the carboxyl group at the end of the chain segment while hybridizing the spatial structure, ultimately preparing the modified polyester.

[0028] Furthermore, in step S2, the preparation method of the chain extender is: add N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane, 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octoxyphenol, triethylamine and N,N-dimethylformamide into a reactor, stir at room temperature for 30-40 minutes, and post-treat to obtain the chain extender.

[0029] The reaction equation for preparing the chain extender is:

[0030] Where: .

[0031] The reaction principle for preparing the chain extender is as follows: under alkaline conditions, the epoxy group on N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane undergoes a ring-opening reaction, and the generated free radicals react with 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octyloxyphenol and triethylamine to finally prepare the chain extender.

[0032] Furthermore, the amount ratio of N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane, 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octyloxyphenol, triethylamine and N,N-dimethylformamide is 8-10g:6-8g:0.3-0.5g:60-80mL, and the post-treatment includes: after the reaction is completed, the reactor is cooled to room temperature, the reaction solution is added to a rotary evaporator with a water bath temperature of 80-100°C, and the reduced pressure distillation is carried out until no liquid is extracted to obtain a chain extender.

[0033] Furthermore, in step S3, the holes of the spinneret are circular, the mesh number is 32-48, the pore size is 0.1-0.3 mm, and the spinning pressure is 80-150 bar; the cold wind is air, the relative humidity is 30-50%, the temperature is 20-30°C, and the flow rate is maintained at 5-10 m / s.

[0034] Further, in step S4, the weaving operation includes: selecting 100-150D regenerated polyester fiber, the number of monofilaments is 36-48F, setting the twist of the yarn to 400-600 twists / m, the twist direction is Z twist, and after the twisting is completed, heat setting is performed at a temperature of 180-200°C, and winding is performed at a speed of 600-700m / min to obtain the yarn, and the yarns are used as warp yarns and weft yarns respectively, and the polyester fabric is woven; the imperial count of the warp yarn is 40-50s, the imperial count of the weft yarn is 35-45s, and the density of the polyester fabric is 160-180 warp yarns and 100-120 weft yarns per square inch.

[0035] Furthermore, in step S5, the flame retardant antibacterial liquid is prepared by:

[0036] B1. Add N,N,N,N-tetramethyl-2-butene-1,4-diamine, sodium hydroxide powder and dimethyl sulfoxide into a reactor and stir. The temperature of the reactor is raised to 30-50°C, and the stirring rate is 200-240rpm. Benzyl chloride is added dropwise during stirring. The dropping operation is maintained for 2-3h. After the dropwise addition is completed, the stirring rate is reduced to 80-100rpm, and the reaction is kept warm for 1-2h. The modified quaternary ammonium salt is obtained by post-treatment.

[0037] The formula for preparing modified quaternary ammonium salt is:

[0038] The principle of preparing modified quaternary ammonium salt is as follows: the tertiary amine group on N,N,N,N-tetramethyl-2-butene-1,4-diamine acts as a strong nucleophile, and the lone pair of electrons on its nitrogen atom attacks the carbon atom on benzyl chloride. The chlorine group on benzyl chloride acts as a leaving group and falls off under the nucleophilic attack to form a chloride ion. After the reaction, a positively charged tetrasubstituted nitrogen cation is finally formed, and finally a modified quaternary ammonium salt is obtained.

[0039] B2. Add modified quaternary ammonium salt, 2-(hydroxyphosphoryl)hydrazine acid, chloroplatinic acid and dimethyl sulfoxide into a reactor, increase the temperature of the reactor to 40-50° C., and keep the reaction warm for 1-2 hours to obtain a flame retardant antibacterial liquid.

[0040] The formula for preparing flame retardant antibacterial liquid is:

[0041] Where: .

[0042] The principle of preparing the flame retardant antibacterial liquid is as follows: under the catalytic conditions of chloroplatinic acid, the phosphorus-hydrogen bond in 2-(hydroxyphosphoric acid)hydrazine acid undergoes a phosphorus-hydrogen addition reaction and reacts with the carbon-carbon double bond of the modified quaternary ammonium salt to finally obtain the flame retardant antibacterial liquid.

[0043] Furthermore, in step B1, the amount ratio of N,N,N,N-tetramethyl-2-butene-1,4-diamine, sodium hydroxide powder, dimethyl sulfoxide and benzyl chloride is 8-10g:1-2g:40-50mL:3-5g, and the post-treatment includes: after the reaction is completed, the reactor is cooled to room temperature, the reaction solution is added to a rotary evaporator with a water bath temperature of 80-100°C, and the reduced pressure distillation is performed until no liquid is extracted to obtain a modified quaternary ammonium salt; in step B2, the amount ratio of the modified quaternary ammonium salt, 2-(hydroxyphosphoryl)hydrazine acid, chloroplatinic acid and dimethyl sulfoxide is 8-10g:4-6g:1.2-1.6g:40-50mL.

[0044] Furthermore, in step S5, the padding modification operation is a two-dip and two-pad process, the bath ratio is 1:20-25, and the padding rate is 90-110%.

[0045] Furthermore, in step S5, post-processing includes: placing the material in a drying oven at a temperature of 60° C. and vacuum drying the material until the material has a constant weight, thereby obtaining a recycled polyester fabric.

[0046] The present invention has the following beneficial effects:

[0047] 1. The present invention prepares modified multilayer graphene, and in the process of depolymerizing polyester by supercritical carbon dioxide fluid, its abundant voids provide a slow-release effect for the supercritical carbon dioxide fluid. At the same time, the abundant active functional groups on its surface enable the monomers obtained by depolymerization to be polymerized in situ on its surface. A chain extender with a grafted anti-ultraviolet group is prepared, and the organic chain segment is hybridized to enrich its spatial structure. The modified multilayer graphene and the chain extender cooperate with each other, so that the mechanical properties of the modified polyester are significantly enhanced and the modified polyester is endowed with excellent anti-ultraviolet ability. The silane coupling agent on the surface of the modified multilayer graphene enhances the compatibility of the modified polyester with auxiliary materials, so that the breaking strength and breaking elongation of the polyester fiber obtained by template spinning are significantly improved.

[0048] 2. The present invention obtains a quaternary ammonium salt with antibacterial properties by modifying the tertiary amine group in the organic chain segment, and introduces a phosphate group on its surface by reacting with its carbon-carbon double bond through phosphine-hydrogen addition, and cross-links by reacting with the active groups on the surface of the modified multilayer graphene. During the combustion process, the phosphate group decomposes to produce an organic acid, which promotes the carbonization of the triazine structure on the chain extender and cooperates with the modified multilayer graphene to form a flame retardant layer, so that the modified polyester fabric has excellent flame retardancy.

[0049] 3. In the process of preparing recycled polyester fabrics, the multilayer graphene is firstly oxidized and cross-linked with a silane coupling agent. During the depolymerization of supercritical fluid carbon dioxide, the density of the fluid is close to that of a liquid, but the viscosity and diffusion properties are closer to those of a gas. The rich void structure of the modified graphene is conducive to the rapid transfer and mixing of substances. Through the sustained release effect, it helps to maintain the uniform distribution of the components in the reaction mixture, thereby accelerating the reaction rate and improving the uniformity of the reaction, so that the polyester can be depolymerized more fully. DETAILED DESCRIPTION

[0050] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Example 1

[0052] The present embodiment provides a method for recycling waste polyester textiles to prepare polyester fabrics, comprising the following steps:

[0053] S1. Depolymerization of waste polyester fibers

[0054] Weigh: 45.0 mL of 98.0 wt% concentrated sulfuric acid is added to a reactor and stirred at a stirring rate of 80 rpm. During the stirring process, 6.0 g of potassium permanganate powder is added to the reactor. After stirring at room temperature for 5 min, the temperature of the reactor is increased to 30° C., and 1.2 g of multilayer graphene is added to the reactor. The reaction is kept warm and stirred for 2 h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and 30 wt% hydrogen peroxide solution is added to the reactor until the solution becomes transparent. The reaction liquid is filtered, and the filter cake is collected. After washing with ethanol and deionized water for 3 times, the filter cake is placed in a drying oven at a temperature of 60° C. and vacuum dried to obtain oxidized multilayer graphene.

[0055] Weigh: 8.4 g of oxidized multilayer graphene, 2.4 g of γ-glycidyloxypropyltrimethoxysilane, 0.3 g of triethylamine and 40.0 mL of N,N-dimethylformamide, add them into a reactor, stir at room temperature for 30 min, filter the reaction liquid, collect the filter cake, wash it with ethanol and deionized water for 4 times, and then place the filter cake in a drying oven at a temperature of 60° C. and vacuum dry it to obtain modified multilayer graphene;

[0056] Weigh: 8.4g of industrial waste polyester textiles and 1.6g of modified multilayer graphene are added to a high-pressure reactor, the high-pressure reactor is placed in a salt bath furnace, and the air in the high-pressure reactor is exhausted with carbon dioxide gas. Then, 200Bar of carbon dioxide gas is introduced into the high-pressure reactor using a booster device, and the temperature of the salt bath furnace is raised to 120°C. During the heating process, the internal pressure of the high-pressure reactor is observed, and the valves on both sides are used to vent and release the pressure. The pressure in the reactor is controlled to be less than 250Bar, and the reaction is kept warm for 4h. After the reaction is completed, the pressure in the high-pressure reactor is reduced to room temperature and the carbon dioxide gas is discharged to obtain a depolymerization mixed liquid.

[0057] S2. Preparation of polyester fabric

[0058] Weigh: 8.4 g of N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane, 6.4 g of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octoxyphenol, 0.3 g of triethylamine and 60.0 mL of N,N-dimethylformamide, add them into a reactor, stir at room temperature for 30 min, after the reaction is completed, cool the reactor to room temperature, add the reaction solution into a rotary evaporator with a water bath temperature of 80°C, and distill under reduced pressure until no liquid is produced to obtain a chain extender;

[0059] Weigh: 12.0 mL of the depolymerization mixed solution, 1.2 g of terephthalic acid, 0.6 g of titanium tetrabutyrate and 40 mL of dimethyl sulfoxide are added to a high-pressure reactor, the temperature of the high-pressure reactor is 260° C., the pressure is 300 kPa, and the high-temperature and high-pressure reaction is carried out for 2 h. 3.6 g of a chain extender is further added to the high-pressure reactor, and the high-temperature and high-pressure reaction is carried out for 1 h. After the reaction is completed, the reactor is cooled to room temperature, and the reaction liquid is added to a rotary evaporator with a water bath temperature of 80° C., and the modified polyester is obtained by vacuum distillation until no liquid is produced;

[0060] The modified polyester is added into a reactor, the temperature of the reactor is raised to 280°C, and after the modified polyester is melted, it is extruded through a spinneret, the hole of the spinneret is circular, the mesh number is 32, the aperture is 0.1mm, and the spinning pressure is 80bar. After extrusion, it is transferred to a side-blowing air chamber, the cold air is air, the relative humidity is 30%, the temperature is 20°C, and the flow rate is maintained at 5m / s, and the regenerated polyester fiber is obtained after air cooling and curing;

[0061] 100D recycled polyester fiber is selected, the number of monofilaments is 36F, the twist of the yarn is set to 400 twists / m, the twist direction is Z twist, and after the twisting is completed, it is heat-set at a temperature of 180°C and wound at a speed of 600m / min to obtain the yarn. The yarns are used as warp yarns and weft yarns, respectively, and the polyester fabric is woven; the imperial count of the warp yarn is 40s, the imperial count of the weft yarn is 35s, and the density of the polyester fabric is 160 warp yarns and 100 weft yarns per square inch.

[0062] S3, flame retardant and antibacterial treatment of fabrics

[0063] Weigh: 8.4g N,N,N,N-tetramethyl-2-butene-1,4-diamine, 1.6g sodium hydroxide powder and 42.0mL dimethyl sulfoxide are added to a reactor and stirred. The temperature of the reactor is raised to 30°C and the stirring rate is 200rpm. During the stirring process, 3.6g benzyl chloride is added dropwise. The dropping operation is maintained for 2h. After the dropwise addition is completed, the stirring rate is reduced to 80rpm. The heat preservation reaction is continued for 1h. After the reaction is completed, the reactor is cooled to room temperature, and the reaction solution is added to a rotary evaporator with a water bath temperature of 80°C, and the reaction solution is distilled under reduced pressure until no liquid is produced to obtain a modified quaternary ammonium salt;

[0064] Weigh: 8.4 g of modified quaternary ammonium salt solution, 4.8 g of 2-(hydroxyphosphoryl)hydrazine acid, 1.2 g of chloroplatinic acid, and 40.0 mL of dimethyl sulfoxide, add them into a reactor, raise the temperature of the reactor to 40° C., and keep the temperature for 1 hour to obtain a flame retardant antibacterial liquid;

[0065] The polyester fabric was immersed in a flame retardant and antibacterial liquid with a bath ratio of 1:20. A two-immersion and two-rolling process was adopted with a immersion and rolling rate of 90%. After the immersion and rolling, the material was placed in a drying oven at a temperature of 60°C and vacuum dried until the material had a constant weight to obtain the recycled polyester fabric.

[0066] Example 2

[0067] The present embodiment provides a method for recycling waste polyester textiles to prepare polyester fabrics, comprising the following steps:

[0068] S1. Depolymerization of waste polyester fibers

[0069] Weigh: 48.0 mL of 98.0 wt% concentrated sulfuric acid is added to a reactor and stirred at a stirring rate of 120 rpm. During the stirring process, 6.0 g of potassium permanganate powder is added to the reactor. After stirring at room temperature for 10 min, the temperature of the reactor is increased to 45° C., and 2.0 g of multilayer graphene is added to the reactor. The reaction is kept warm and stirred for 3 h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and 30 wt% hydrogen peroxide solution is added to the reactor until the solution becomes transparent. The reaction solution is filtered, and the filter cake is collected. After washing with ethanol and deionized water for 5 times, the filter cake is placed in a drying oven at a temperature of 60° C. and vacuum dried to obtain oxidized multilayer graphene.

[0070] Weigh: 10.0 g of oxidized multilayer graphene, 3.0 g of γ-glycidyloxypropyltrimethoxysilane, 0.5 g of triethylamine and 60.0 mL of N,N-dimethylformamide, add them into a reactor, stir at room temperature for 40 min, filter the reaction liquid, collect the filter cake, wash it with ethanol and deionized water for 4 times, and then place the filter cake in a drying oven at a temperature of 60° C. and vacuum dry it to obtain modified multilayer graphene;

[0071] Weigh: 10.0g of industrial waste polyester textiles and 2.0g of modified multilayer graphene are added to a high-pressure reactor, the high-pressure reactor is placed in a salt bath furnace, and the air in the high-pressure reactor is exhausted with carbon dioxide gas. Then, 250Bar of carbon dioxide gas is introduced into the high-pressure reactor using a booster device, and the temperature of the salt bath furnace is raised to 160°C. During the heating process, the internal pressure of the high-pressure reactor is observed, and the valves on both sides are used to vent and release the pressure, and the pressure in the reactor is controlled to be less than 250Bar. The reaction is kept warm for 6h. After the reaction is completed, the pressure in the high-pressure reactor is reduced to room temperature and the carbon dioxide gas is discharged to obtain a depolymerization mixed liquid.

[0072] S2. Preparation of polyester fabric

[0073] Weigh: 10.0 g of N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane, 8.0 g of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octoxyphenol, 0.5 g of triethylamine and 80.0 mL of N,N-dimethylformamide, add them into a reactor, stir at room temperature for 40 min, after the reaction is completed, cool the reactor to room temperature, add the reaction solution into a rotary evaporator with a water bath temperature of 100° C., and distill under reduced pressure until no liquid is produced to obtain a chain extender;

[0074] Weigh: 16.0 mL of the depolymerization mixed solution, 2.0 g of terephthalic acid, 0.8 g of titanium tetrabutyrate and 60.0 mL of dimethyl sulfoxide are added to a high-pressure reactor, the temperature of the high-pressure reactor is 280° C., the pressure is 500 kPa, and the high-temperature and high-pressure reaction is carried out for 4 hours. 5.0 g of a chain extender is continuously added to the high-pressure reactor, and the high-temperature and high-pressure reaction is carried out for 2 hours. After the reaction is completed, the reactor is cooled to room temperature, and the reaction liquid is added to a rotary evaporator with a water bath temperature of 100° C., and the modified polyester is obtained by vacuum distillation until no liquid is produced;

[0075] The modified polyester is added into a reactor, the temperature of the reactor is raised to 280°C, and after the modified polyester is melted, it is extruded through a spinneret, the hole of the spinneret is circular, the mesh number is 32, the aperture is 0.1mm, and the spinning pressure is 80bar. After extrusion, it is transferred to a side-blowing air chamber, the cold air is air, the relative humidity is 30%, the temperature is 20°C, and the flow rate is maintained at 5m / s, and the regenerated polyester fiber is obtained after air cooling and curing;

[0076] 150D recycled polyester fiber is selected, the number of monofilaments is 48F, the twist of the yarn is set to 600 twists / m, the twist direction is Z twist, and after the twisting is completed, it is heat-set at a temperature of 200°C and wound at a speed of 700m / min to obtain the yarn. The yarns are used as warp yarn and weft yarn respectively. The British count of the warp yarn is 50s and the British count of the weft yarn is 45s. The density of the polyester fabric is 180 warp yarns and 120 weft yarns per square inch, and the polyester fabric is woven.

[0077] S3, flame retardant and antibacterial treatment of fabrics

[0078] Weigh: 9.6 g N, N, N, N-tetramethyl-2-butene-1, 4-diamine, 1.6 g sodium hydroxide powder and 50.0 mL dimethyl sulfoxide are added to a reactor and stirred. The temperature of the reactor is raised to 50° C. and the stirring rate is 240 rpm. During the stirring process, 4.8 g benzyl chloride is added dropwise. The dropping operation is maintained for 3 hours. After the dropwise addition is completed, the stirring rate is reduced to 100 rpm. The heat preservation reaction is continued for 2 hours. After the reaction is completed, the reactor is cooled to room temperature, and the reaction solution is added to a rotary evaporator with a water bath temperature of 100° C., and the reaction solution is distilled under reduced pressure until no liquid is produced to obtain a modified quaternary ammonium salt;

[0079] Weigh: 9.6 g of modified quaternary ammonium salt solution, 4.8 g of 2-(hydroxyphosphoryl)hydrazine acid, 1.6 g of chloroplatinic acid and 50.0 mL of dimethyl sulfoxide and add them into a reactor, raise the temperature of the reactor to 50° C., and keep the temperature for 2 hours to obtain a flame retardant antibacterial liquid;

[0080] The polyester fabric was immersed in a flame retardant and antibacterial liquid with a bath ratio of 1:25. A two-immersion and two-rolling process was adopted with a immersion and rolling rate of 110%. After the immersion and rolling, the material was placed in a drying oven at a temperature of 60°C and vacuum dried until the material had a constant weight to obtain the recycled polyester fabric.

[0081] Example 3

[0082] The present embodiment provides a method for recycling waste polyester textiles to prepare polyester fabrics, comprising the following steps:

[0083] S1. Depolymerization of waste polyester fibers

[0084] Weigh: 48.0 mL of 98.0 wt% concentrated sulfuric acid is added to a reactor and stirred at a stirring rate of 100 rpm. During the stirring process, 7.2 g of potassium permanganate powder is added to the reactor. After stirring at room temperature for 8 min, the temperature of the reactor is increased to 40° C., and 2.0 g of multilayer graphene is added to the reactor. The reaction is kept warm and stirred for 3 h. After the reaction is completed, the temperature of the reactor is lowered to room temperature, and 30 wt% hydrogen peroxide solution is added to the reactor until the solution becomes transparent. The reaction liquid is filtered, and the filter cake is collected. After washing with ethanol and deionized water for 4 times, the filter cake is placed in a drying oven at a temperature of 60° C. and vacuum dried to obtain oxidized multilayer graphene.

[0085] Weigh: 9.6 g of oxidized multilayer graphene, 2.4 g of γ-glycidyloxypropyltrimethoxysilane, 0.4 g of triethylamine and 50.0 mL of N,N-dimethylformamide, add them into a reactor, stir at room temperature for 35 min, filter the reaction liquid, collect the filter cake, wash it with ethanol and deionized water for 4 times, and then place the filter cake in a drying oven at a temperature of 60° C. and vacuum dry it to obtain modified multilayer graphene;

[0086] Weigh: 8.4g of industrial waste polyester textiles and 1.6g of modified multilayer graphene are added to a high-pressure reactor, the high-pressure reactor is placed in a salt bath furnace, and the air in the high-pressure reactor is exhausted with carbon dioxide gas. Then, 225Bar of carbon dioxide gas is introduced into the high-pressure reactor using a booster device, and the temperature of the salt bath furnace is raised to 140°C. During the heating process, the internal pressure of the high-pressure reactor is observed, and the valves on both sides are used to vent and release the pressure. The pressure in the reactor is controlled to be less than 250Bar, and the reaction is kept warm for 5h. After the reaction is completed, the pressure in the high-pressure reactor is reduced to room temperature and the carbon dioxide gas is discharged to obtain a depolymerization mixed liquid.

[0087] S2. Preparation of polyester fabric

[0088] Weigh: 9.6 g N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane, 7.2 g 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octoxyphenol, 0.4 g triethylamine and 72.0 mL N,N-dimethylformamide, add to a reactor, stir at room temperature for 35 min, after the reaction is completed, cool the reactor to room temperature, add the reaction solution to a rotary evaporator with a water bath temperature of 90° C., and distill under reduced pressure until no liquid is produced to obtain a chain extender;

[0089] Weigh: 14.4 mL of depolymerization mixed solution, 1.6 g of terephthalic acid, 0.7 g of titanium tetrabutyrate and 48.0 mL of dimethyl sulfoxide are added to a high-pressure reactor, the temperature of the high-pressure reactor is 270° C., the pressure is 400 kPa, and the high-temperature and high-pressure reaction is carried out for 3 hours. 4.8 g of chain extender is further added to the high-pressure reactor, and the high-temperature and high-pressure reaction is carried out for 2 hours. After the reaction is completed, the reactor is cooled to room temperature, and the reaction liquid is added to a rotary evaporator with a water bath temperature of 100° C., and the modified polyester is obtained by reduced pressure distillation until no liquid is produced;

[0090] The modified polyester is added into a reactor, the temperature of the reactor is raised to 280°C, and after the modified polyester is melted, it is extruded through a spinneret, the hole of the spinneret is circular, the mesh number is 32, the aperture is 0.1mm, and the spinning pressure is 80bar. After extrusion, it is transferred to a side-blowing air chamber, the cold air is air, the relative humidity is 30%, the temperature is 20°C, and the flow rate is maintained at 5m / s, and the regenerated polyester fiber is obtained after air cooling and curing;

[0091] 125D recycled polyester fiber is selected, the number of monofilaments is 42F, the twist of the yarn is set to 500 twists / m, the twist direction is Z twist, and after the twisting is completed, it is heat-set at a temperature of 190°C and wound at a speed of 650m / min to obtain the yarn. The yarns are used as warp yarn and weft yarn respectively. The imperial count of the warp yarn is 45s and the imperial count of the weft yarn is 40s. The density of the polyester fabric is 170 warp yarns and 110 weft yarns per square inch, and the polyester fabric is woven.

[0092] S3, flame retardant and antibacterial treatment of fabrics

[0093] Weigh: 9.6 g N, N, N, N-tetramethyl-2-butene-1, 4-diamine, 1.6 g sodium hydroxide powder and 48.0 mL dimethyl sulfoxide are added to a reactor and stirred. The temperature of the reactor is raised to 40° C. and the stirring rate is 210 rpm. During the stirring process, 4.8 g benzyl chloride is added dropwise. The dropping operation is maintained for 2 hours. After the dropwise addition is completed, the stirring rate is reduced to 90 rpm. The heat preservation reaction is continued for 2 hours. After the reaction is completed, the reactor is cooled to room temperature, and the reaction solution is added to a rotary evaporator with a water bath temperature of 90° C., and the reaction solution is distilled under reduced pressure until no liquid is produced to obtain a modified quaternary ammonium salt;

[0094] Weigh: 9.6 g of modified quaternary ammonium salt solution, 5.4 g of 2-(hydroxyphosphoryl)hydrazine acid, 1.6 g of chloroplatinic acid and 48.0 mL of dimethyl sulfoxide and add them into a reactor. The temperature of the reactor is raised to 45° C. and the reaction is kept warm for 2 hours to obtain a flame retardant antibacterial liquid.

[0095] The polyester fabric was immersed in a flame retardant and antibacterial liquid with a bath ratio of 1:24. A two-immersion and two-rolling process was adopted with a immersion and rolling rate of 100%. After the immersion and rolling, the material was placed in a drying oven at a temperature of 60°C and vacuum dried until the material had a constant weight to obtain the recycled polyester fabric.

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 3 is that the step of preparing modified graphene in step S1 is eliminated, and an equal amount of multilayer graphene is used to replace the modified multilayer graphene.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 3 is that the step of preparing the chain extender in step S2 is eliminated, and an equal amount of glycerol is used to replace the chain extender.

[0100] Comparative Example 3

[0101] The difference between this comparative example and Example 3 is that the step of preparing the flame retardant antibacterial liquid in step S3 is eliminated, and an equal amount of 0.01 wt % silver ion solution is used to replace the flame retardant antibacterial liquid.

[0102] Performance Test:

[0103] The regenerated polyester fibers prepared in Examples 1-3 and Comparative Examples 1-3 were tested for breaking strength and breaking elongation in accordance with the standard GB / T 14337-2008 “Test Method for Tensile Properties of Chemical Staple Fibers”;

[0104] Referring to the standard GB / T 20944.3-2008 "Evaluation of antibacterial properties of textiles Part 3: Oscillation method", the antibacterial rate of the polyester fabrics prepared in Examples 1-3 and Comparative Examples 1-3 was tested, wherein the selected bacterial species were Gram-positive bacteria Staphylococcus aureus, Gram-negative bacteria Escherichia coli, and fungi Candida albicans;

[0105] The limiting oxygen index of the polyester fabrics prepared in Examples 1-3 and Comparative Examples 1-3 was tested with reference to the standard GB / T 2406.2-2009 "Determination of Combustion Behavior of Plastics by Oxygen Index Method Part 2: Room Temperature Test";

[0106] See Table 1 for specific data;

[0107] With reference to the standard HG / T 4735-2014 "Determination of anti-ultraviolet properties of textile dyeing and finishing auxiliaries and anti-ultraviolet finishing agents", the ultraviolet protection factor and ultraviolet transmittance of the polyester fabric prepared in Example 3 were measured, and after circulating water washing, the ultraviolet protection factor and ultraviolet transmittance of the polyester fabric prepared in Example 3 were further measured. The specific data are shown in Table 2.

[0108] Table 1-Performance test data of each sample

[0109] Table 2-UV protection performance test data of each sample

[0110] Data Analysis:

[0111] According to the data in Table 1 above, the regenerated polyester fabric prepared by the present invention has a breaking strength of 7.2 MPa, a breaking elongation of 146.5%, an antibacterial rate of 97.5%, 98.2% and 98.3% against Staphylococcus aureus, Escherichia coli and Candida albicans, respectively, and a limiting oxygen index of 30.1%.

[0112] Referring to the data in Table 2 above, the UV protection factor of the recycled polyester fabric prepared by the present invention is 51, and the UV protection factor is still 44 after 100 washes; the UV transmittance is 1.9%, and the UV transmittance is still only 2.0% after 100 washes;

[0113] The invention prepares modified multilayer graphene, and in the process of depolymerizing polyester by supercritical carbon dioxide fluid, the abundant voids of the modified multilayer graphene provide a slow-release effect for the supercritical carbon dioxide fluid, and at the same time, the abundant active functional groups on the surface of the modified multilayer graphene enable the monomer obtained by depolymerization to be polymerized in situ on the surface of the modified multilayer graphene. A chain extender with a grafted anti-ultraviolet group is prepared, and the organic chain segment is hybridized to enrich the spatial structure of the modified multilayer graphene. The modified multilayer graphene and the chain extender cooperate with each other, so that the mechanical properties of the modified polyester are significantly enhanced and the modified polyester is endowed with excellent anti-ultraviolet ability. The silane coupling agent on the surface of the modified multilayer graphene enhances the compatibility of the modified polyester with auxiliary materials, so that the breaking strength and breaking elongation of the polyester fiber obtained by template spinning are significantly improved.

[0114] The invention obtains a quaternary ammonium salt with antibacterial properties by modifying the tertiary amine group in the organic chain segment, introduces a phosphoric acid group on the surface of the quaternary ammonium salt by reacting the carbon-carbon double bond with the phosphine-hydrogen addition, and crosslinks the quaternary ammonium salt with the active group on the surface of the modified multilayer graphene. During the combustion process, the phosphoric acid group decomposes to generate an organic acid, promotes the carbonization of the triazine structure on the chain extender, and forms a flame retardant layer in combination with the modified multilayer graphene, so that the modified polyester fabric has excellent flame retardancy.

[0115] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for recycling waste polyester textiles to prepare polyester fabrics, characterized in that: The following steps are involved: S1. Adding waste polyester textiles and modified multilayer graphene into a high-pressure reactor to perform supercritical depolymerization of carbon dioxide to obtain a depolymerization mixed solution; S2, adding the depolymerization mixture, terephthalic acid, titanium tetrabutyrate and dimethyl sulfoxide into a high-pressure reactor, reacting at high temperature and high pressure for 2-4 hours, continuing to add a chain extender into the high-pressure reactor, reacting at high temperature and high pressure for 1-2 hours, and post-treating to obtain a modified polyester; S3, adding the modified polyester into the reactor, raising the temperature of the reactor to 260-280°C, and after the modified polyester is melted, extruding it through a spinneret and transferring it to a side-blowing chamber, and obtaining the regenerated polyester fiber after air cooling and curing; S4, using recycled polyester fibers for weaving to obtain polyester fabrics; S5, using a flame retardant and antibacterial liquid to perform padding modification on the polyester fabric, and then post-processing to obtain a recycled polyester fabric; The preparation method of the modified multilayer graphene comprises the following steps: A1, adding 98.0wt% concentrated sulfuric acid to a reactor and stirring, adding potassium permanganate powder to the reactor during stirring, stirring at room temperature for 5-10min, raising the temperature of the reactor to 30-45°C and adding multilayer graphene to the reactor, keeping the temperature and stirring for 2-3h, and post-treating to obtain oxidized multilayer graphene; A2. Add oxidized multilayer graphene, γ-glycidyloxypropyltrimethoxysilane, triethylamine and N,N-dimethylformamide into a reaction kettle, stir at room temperature for 30-40 minutes, and post-treat to obtain modified multilayer graphene.

2. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step S1, the usage ratio of waste polyester textiles and modified multilayer graphene is 8-10g:1-2g, and the waste polyester textiles include industrial waste polyester textiles and post-consumer waste polyester textiles.

3. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step A1, the stirring rate of the reactor is 80-120rpm, and the amount ratio of 98.0wt% concentrated sulfuric acid, potassium permanganate powder and multilayer graphene is 45-50mL:6-8g:1-2g; in step A2, the amount ratio of oxidized multilayer graphene, γ-glycidyloxypropyltrimethoxysilane, triethylamine and N,N-dimethylformamide is 8-10g:2-3g:0.3-0.5g:40-60mL.

4. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step S1, the operation process of supercritical depolymerization is as follows: placing the high-pressure reactor in a salt bath furnace, exhausting the air in the high-pressure reactor with carbon dioxide gas, introducing 200-250 Bar of carbon dioxide gas into the high-pressure reactor using a pressurizing device, and raising the temperature of the salt bath furnace to 120-160° C., observing the internal pressure of the high-pressure reactor during heating, using valves on both sides to vent and release the pressure, controlling the pressure in the reactor to be less than 250 Bar, and keeping the reaction warm for 4-6 hours. After the reaction is completed, reducing the pressure in the high-pressure reactor to room temperature and then exhausting the carbon dioxide gas to obtain a depolymerization mixed liquid.

5. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step S2, the temperature of the high-pressure reactor is 260-280° C., the pressure is 300-500 KPa, and the dosage ratio of the depolymerization mixed liquid, terephthalic acid, titanium tetrabutyrate, dimethyl sulfoxide and chain extender is 12-16 mL: 1-2 g: 0.6-0.8 g: 40-60 mL: 3-5 g.

6. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step S2, the preparation method of the chain extender is: add N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane, 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-octyloxyphenol, triethylamine and N,N-dimethylformamide into a reaction kettle, stir at room temperature for 30-40 minutes, and post-treat to obtain the chain extender.

7. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step S3, the holes of the spinneret are circular, the mesh number is 32-48, the pore size is 0.1-0.3 mm, and the spinning pressure is 80-150 bar; the cold wind is air, the relative humidity is 30-50%, the temperature is 20-30°C, and the flow rate is maintained at 5-10 m / s.

8. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step S4, the weaving operation includes: selecting 100-150D regenerated polyester fiber, the number of monofilaments is 36-48F, setting the twist of the yarn to 400-600 twists / m, the twist direction is Z twist, and after the twisting is completed, heat setting is performed at a temperature of 180-200°C, and winding is performed at a speed of 600-700m / min to obtain the yarn, and the yarns are used as warp yarns and weft yarns respectively, and the polyester fabric is woven; the imperial count of the warp yarn is 40-50s, the imperial count of the weft yarn is 35-45s, and the density of the polyester fabric is 160-180 warp yarns and 100-120 weft yarns per square inch.

9. The method for preparing polyester fabric by recycling waste polyester textiles according to claim 1, characterized in that: In step S5, the method for preparing the flame retardant antibacterial liquid is: B1. Add N,N,N,N-tetramethyl-2-butene-1,4-diamine, sodium hydroxide powder and dimethyl sulfoxide into a reaction kettle and stir. The temperature of the reaction kettle is raised to 30-50° C. and the stirring rate is 200-240 rpm. Benzyl chloride is added dropwise during stirring. The dropping operation is maintained for 2-3 hours. After the dropwise addition is completed, the stirring rate is reduced to 80-100 rpm. The reaction is kept warm for 1-2 hours to obtain a modified quaternary ammonium salt solution. B2. Add the modified quaternary ammonium salt solution, 2-(hydroxyphosphoryl)hydrazine acid, chloroplatinic acid and dimethyl sulfoxide into the reactor, increase the temperature of the reactor to 40-50° C., and keep the reaction temperature for 1-2 hours to obtain a flame retardant antibacterial liquid.

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