Recycling method and application of waste cotton-polyester blended fabric

Abstract

The invention provides a recycling method and application of a waste cotton-polyester blended fabric. Comprising the following steps: adding a cellulose raw material into a super-base acetate ionic solvent, and dissolving to obtain a first solution; the cellulose raw material is obtained by processing a waste cotton-polyester blended fabric; adding a viscosity reducer into the first solution, and uniformly mixing to obtain a second solution; carrying out solid-liquid separation on the second solution to obtain a cellulose solution and insoluble polyester; regenerating and drying the cellulose solution to obtain a regenerated cellulose material; and cleaning and drying the insoluble polyester to obtain the regenerated polyester material. The technical problem to be solved is how to recycle the waste cotton-polyester blended fabric, so that cellulose and polyester in the waste cotton fabric can be efficiently separated, a regenerated cellulose material and a regenerated polyester material are obtained, and full-component resource utilization of the waste cotton-polyester blended fabric is realized. Meanwhile, decolorization and dissolution are realized in one pot, and the method is simple in process step, green and environment-friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recycling of waste and old textiles, and particularly relates to a recycling method of waste and old cotton-polyester blended textiles and application thereof. BACKGROUND

[0002] The global fast fashion industry promotes rapid iteration of clothing, resulting in a large amount of waste and old textiles. Cotton-polyester blended textiles are widely used in clothing, home furnishing and other fields due to their comfort of cotton fibers and durability of polyester, and account for more than 60% of the total amount of waste and old textiles. At present, such waste is mostly treated by incineration or landfill, which not only wastes cellulose resources (cotton fibers contain more than 90% cellulose), but also causes land pollution and secondary environmental problems, and efficient recycling technology is urgently needed.

[0003] For recycling of waste and old cotton textiles, the efficient separation and recovery of different fibers due to their close combination and the significant difference in chemical properties between cotton fibers (cellulose) and polyester (polyester) become an industry problem. At the same time, waste and old textiles undergo complex dyeing processes during production, further increasing their recycling difficulty. Physical and mechanical methods (such as opening and screening) cannot achieve complete separation of fibers, resulting in low purity of regenerated materials; chemical methods (such as acid hydrolysis and alkali hydrolysis) are mostly aimed at single components (such as only recycling cellulose or only recycling polyester), and are prone to environmental pollution. Waste and old textiles usually contain dyes, and existing technologies need to be physically or chemically decolorized before being dissolved and separated, which is a complex process and can damage the fiber structure. Traditional solvents for dissolving cellulose, such as copper ammonia solution and strong alkali solution, have problems such as high toxicity and low recovery rate, which do not meet the needs of green and sustainable development. Moreover, most processes only recycle one of cellulose or polyester, failing to achieve full resource utilization of blended textiles, resulting in resource waste.

[0004] In recent years, ionic solvents (such as ionic liquids and deep eutectic solvents) as new green solvent systems have shown potential in the field of textile recycling due to their high solubility for cellulose and environmental friendliness, but there are still the following problems: first, the solution viscosity after dissolution is high, which is not conducive to subsequent separation; second, dye residues can cause poor color of regenerated materials, and additional decolorization steps are needed. SUMMARY

[0005] The main purpose of the present application is to provide a recycling method of waste and old cotton-polyester blended textiles and application thereof, and the technical problem to be solved is how to recycle waste and old cotton-polyester blended textiles, so that cellulose and polyester in waste and old cotton textiles can be efficiently separated, and regenerated cellulose materials and regenerated polyester materials can be prepared by the method, achieving full component resource utilization of waste and old cotton-polyester blended textiles. At the same time, the method realizes one-pot decolorization and dissolution, has simple process steps and is green and environmentally friendly, and is thus more suitable for practical use.

[0006] The object and solution to the technical problem of the present application are realized by the following technical scheme. The present application provides a recycling method of waste cotton-polyester blended fabric, which comprises the following steps:

[0007] S11 cellulose raw material is added into a superbase acetate ionic solvent for stirring and dissolving, and decolorizing to obtain a first solution; the cellulose raw material is obtained by processing waste cotton-polyester blended fabric;

[0008] S12 a viscosity reducer is added into the first solution for mixing to obtain a second solution;

[0009] S13 the second solution is subjected to solid-liquid separation to obtain a cellulose solution and insoluble polyester;

[0010] S14 the cellulose solution is regenerated and dried to obtain regenerated cellulose material; and the insoluble polyester is cleaned and dried to serve as regenerated polyester material.

[0011] The object and solution to the technical problem of the present application can also be further realized by the following technical measures.

[0012] Preferably, the recycling method, wherein the cellulose raw material is obtained by crushing colored waste cotton-polyester blended fabric with a polymerization degree of 500-1000 into powder, silk or flocculent cloth.

[0013] Preferably, the recycling method, wherein the cation in the superbase acetate ionic solvent is at least one selected from 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0014] Preferably, the recycling method, wherein in step S11, the mass of the cellulose raw material is 2.6-12% based on 100% of the mass of the ionic solvent.

[0015] Preferably, the recycling method, wherein in step S11, the dissolving temperature is 70-90℃, and the dissolving time is 2-4h.

[0016] Preferably, the recycling method, wherein in step S12, the temperature of the viscosity reducer and the first solution is 40-60℃ when the viscosity reducer is added.

[0017] Preferably, the recycling method, wherein the viscosity reducer is at least one selected from dimethyl sulfoxide, γ-valerolactone and sulfolane.

[0018] Preferably, the recycling method, wherein the mass ratio of the viscosity reducer to the ionic solvent is 0.3-1:1; the mass solid content of the cellulose raw material is 2-6% based on the total mass of the ionic solvent and the viscosity reducer being 100%.

[0019] The application discloses a regenerated cellulose material obtained by the recycling method.

[0020] The application discloses a regenerated polyester material obtained by the recycling method.

[0021] The application discloses an application of the regenerated cellulose material in the technical field of food packaging, filtration adsorption, functional sensing or thermal insulation.

[0022] The recycling method and the application of the waste cotton-polyester blended fabric have at least the following advantages:

[0023] The application realizes efficient treatment of the waste cotton-polyester blended fabric through selective dissolution and decolorization of the superalkali acetate ionic solvent, and has the following advantages:

[0024] 1. The superalkali acetate ionic solvent is used to dissolve the cellulose raw material, the high selective dissolution characteristic of the superalkali acetate ionic solvent to cellulose is utilized, cotton fibers (cellulose) are dissolved into a solution phase, and polyester (polyester) is left in a solid state because it is not dissolved, so that the two can be completely separated through simple solid-liquid separation. Compared with the physical mechanical method (incomplete separation and low purity) and the traditional chemical method (strong acid and strong alkali are needed, and pollution is large), the method realizes efficient separation through selective action of the solvent, simplifies the separation process, and has higher purity of the regenerated material; the superalkali acetate ionic solvent has a superalkali structure, groups such as amidine groups and guanidine groups in the molecule have strong proton (H +) ability, the dye in the cloth usually exhibits color through conjugated double bond, and these conjugated structures are very sensitive to proton environment; the super basic acetate ionic solvent can take the active hydrogen proton in the dye molecule through catalysis, thereby destroying the conjugated double bond system, and further causing the dye to lose the color developing ability, thereby realizing decolorization. Meanwhile, the dissolution process of the super basic acetate ionic solvent to cellulose is accompanied by severe swelling, and the solvent molecules, especially the cations, can penetrate into the cellulose molecular chains, destroy the hydrogen bonds between the cellulose molecules, make the fiber structure loose and the molecular chain gap increase, and the dye in the cloth is mostly adsorbed or chemically bonded in the cellulose fiber. After the swelling of the cellulose, the binding force between the dye and the fiber is weakened, and the dye is more easily separated from the fiber network and enters the solvent phase. The present application realizes the efficient separation and decolorization of the components of the waste cotton-polyester blended fabric through one-pot method by selecting a specific structure of ionic solvent, thereby avoiding the complex process of separately performing decolorization pretreatment in the traditional process, and significant progress is made, which has substantial characteristics.

[0025] 2. The present application solves the problem of high viscosity of the cellulose solution after dissolution and difficult separation by introducing a viscosity reducer. Compared with the complex process of additional treatment of viscosity after dissolution in the prior art, the method directly improves the fluidity of the solution through the synergistic effect of the viscosity reducer and the solvent, making the solid-liquid separation more efficient, greatly shortening the process cycle and reducing the operation difficulty of industrial production.

[0026] 3. The present application synchronously obtains “cellulose solution” and “insoluble polyester” through the “solid-liquid separation” step, and regenerates them into “regenerated cellulose material” and “regenerated polyester material” respectively. Compared with the process of recycling only a single component (such as only recycling cellulose or only recycling polyester) in the prior art, the present application realizes the complete recovery of the two core components in the cotton-polyester blended fabric, avoids resource waste, significantly improves the utilization efficiency of waste textiles, and meets the sustainable development concept of “whole industry chain recycling”.

[0027] 4. The super basic acetate ionic solvent in the present application belongs to an environmentally friendly solvent. Compared with toxic and harmful solvents such as traditional cellulose dissolving copper ammonia solution and strong alkali solution, it has better biocompatibility, and can be recycled and used through subsequent treatment. Meanwhile, the whole process does not need to use strong acid, strong oxidizing agent and other corrosive reagents, reduces the “three wastes” discharge, reduces the potential harm to the operating personnel and the ecological environment, and meets the demand of clean transformation of the textile industry.

[0028] The above description is only a summary of the technical scheme of the present application. In order to more clearly understand the technical means of the present application, and to implement the content of the description, the following will be described in detail with reference to the preferred embodiments of the present application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a photo comparison of the colored fabric before and after dissolution and decolorization according to the present application;

[0030] Figure 2 is a polarized light microscope image of the dissolution process of the cotton component in the cotton-polyester blended fabric according to the present application;

[0031] Figure 3 is a photo of the insoluble polyester filtered out according to the present application;

[0032] Figure 4 is a polarized light microscope image of the cellulose solution after removal of the insoluble polyester according to the present application;

[0033] Figure 5 is a regenerated cellulose film obtained by the doctor blade method in Example 2 according to the present application;

[0034] Figure 6 is an infrared spectrum of the insoluble polyester and the pure polyester component filtered out in Example 1 according to the present application;

[0035] Figure 7 is a regenerated cellulose film obtained by the flow casting method in Example 4 according to the present application;

[0036] Figure 8 is the polarized light and discoloration of the colored fabric in Comparative Example 1 when dissolved in the ionic solvent for 10.5 h according to the present application;

[0037] Figure 9 is a photo of the dye decolorization experiment in Comparative Example 1 (left photo: "1-allyl-3-methylimidazolium chloride ionic solvent", right photo: "superbase acetate ionic solvent according to the present application"). DETAILED DESCRIPTION

[0038] To further illustrate the technical means and effects taken by the present application to achieve the predetermined purposes, the following describes in detail the method for recycling waste cotton-polyester blended fabric according to the present application, its specific embodiments, structures, features, and effects, in combination with preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0039] The present application provides a method for recycling waste cotton-polyester blended fabric, which comprises the following steps:

[0040] First, the dissolution and decolorization step of the cellulose raw material: the cellulose raw material is added to the superbase acetate ionic solvent and stirred to dissolve and decolorize at the same time, obtaining a first solution.

[0041] In the step, the cellulose raw material is obtained by processing waste cotton-polyester blended fabric, and the purpose is to recycle the waste cotton-polyester blended fabric. The technical scheme of the present application can be applied to the recycling of waste cotton-polyester blended fabric containing azo dyes, vat dyes, anthraquinone dyes, phthalocyanine dyes and / or sulfur dyes.

[0042] In some embodiments of the present application, before the cellulose raw material is dissolved, the colored cotton-polyester blended fabric raw material is preferably crushed into powder, silk or flocculent (cotton-like) raw material through a crushing process. The raw material morphology can increase its contact area with the solvent, improve the dissolution efficiency, and thus promote the swelling and rapid dissolution separation of the cellulose raw material.

[0043] The present application uses an ionic solvent of superbase acetate to dissolve the cellulose raw material. The high selective dissolution characteristics of the ionic solvent of superbase acetate to cellulose make the cotton fiber (cellulose) dissolve into the solution phase, while the polyester (polyester) remains in solid form due to insolubility, and the complete separation of the two can be achieved by simple solid-liquid separation.

[0044] The ionic solvent of superbase acetate has a "superbase" structure. The amidine group and guanidine group in the molecule have a very strong ability to accept protons (H + ), and the basicity is much higher than that of ordinary organic amines. The dyes in the cloth usually exhibit color through conjugated double bonds, and these conjugated structures are very sensitive to proton environment. The superbase cation can capture the active hydrogen protons in the dye molecules through catalysis, thereby destroying the conjugated double bond system, and further causing the dye to lose its color-developing ability, thereby achieving decolorization. At the same time, the dissolution process of the ionic solvent of superbase acetate to cellulose is accompanied by severe swelling. The solvent molecules, especially the cations, can penetrate into the cellulose molecular chains, destroy the hydrogen bonds between the cellulose molecules, and make the fiber structure loose and the molecular chain gap increase. The dyes in the cloth are mostly adsorbed or chemically bonded inside the cellulose fibers. After the swelling of the cellulose, the binding force between the dye and the fiber is weakened, and the dye is more easily separated from the fiber network and enters the solvent phase. The present application realizes the efficient separation and decolorization of the components of the waste cotton-polyester blended fabric by selecting a specific structure of ionic solvent in one pot, thereby avoiding the complex process of separate decolorization pretreatment in the traditional process. In Comparative Example 1 and Comparative Example 4, since the ionic solvent of superbase acetate is not used as a solvent, decolorization cannot be achieved, further proving that the strong basicity of the superbase cation is the key factor for decolorization.

[0045] In some embodiments of the present application, the cellulose preferably has a degree of polymerization between 500 and 1000. The degree of polymerization of cellulose directly affects the length of its molecular chain and its crystallinity. When the degree of polymerization is less than 500, the cellulose molecular chain is too short, the crystalline structure is severely damaged, and more solvent is often needed to prevent the molecular chain from entangling, although it is easy to dissolve, but the mechanical properties (such as strength and toughness) of the regenerated material may be significantly reduced; when the degree of polymerization is higher than 1000, the hydrogen bonding between the molecular chains is strong, and the crystallinity is high, which makes it difficult to dissolve, often requiring an excess of solvent to destroy the crystalline structure, and higher temperature or longer time is needed to dissolve it, which on the one hand increases energy consumption, and on the other hand may cause cellulose degradation, thereby affecting the performance of the regenerated material. The cellulose with a degree of polymerization of 500-1000 in the present application has suitable solubility, while also retaining sufficient molecular chain length to ensure the performance of the regenerated material.

[0046] When dissolving cotton-polyester blended fabric, if the degree of polymerization of cellulose is too high, the undissolved cellulose fragments may wrap the polyester fibers, which may cause incomplete separation of components. After the cellulose with a degree of polymerization of 500-1000 is completely dissolved, the polyester exists in the form of complete particles, and efficient separation of components can be achieved by simple filtration in subsequent processes, improving the purity of the components.

[0047] To balance the dissolution efficiency of raw materials, the operability of the solution, and the performance of the regenerated material, the present application preferably uses an ionic solvent with a mass of 100%, and the mass of the cellulose raw material is 2.6-12%. The ionic solvent of superbase acetate has an upper limit for the solubility of cellulose. If the proportion of cellulose raw material exceeds 12%, the solvent cannot completely destroy the hydrogen bonds between the cellulose molecules at this time, which will cause part of the cellulose to not be dissolved, reducing the recovery rate of the cellulose component; the non-recovered cellulose may wrap the insoluble polyester, causing incomplete solid-liquid separation in the subsequent process, thereby reducing the purity of the regenerated polyester material. In Comparative Example 2, the mass of the cellulose raw material accounts for 16% of the ionic solvent, and "difficult stirring and difficult dissolution" occurs during dissolution, which confirms that too high a proportion will cause incomplete dissolution of cellulose. The upper limit of 12% is set to ensure that the cellulose can be fully swollen and dissolved by the ionic solvent at the set dissolution temperature, providing a uniform cellulose solution for subsequent separation and regeneration. The lower limit is set to ensure that the performance of the regenerated cellulose material can meet the use requirements.

[0048] When dissolving, the colored waste cotton-polyester blended fabric raw material is mixed with the ionic solvent to make the cellulose fully swell at 70-90 DEG C, and the cellulose is fully dissolved at this temperature by stirring to obtain a cotton-polyester blended fabric solution, i.e. the first solution; if the dissolving temperature is too low or the dissolving time is too short, the cellulose may be difficult to dissolve, and if the dissolving temperature is too high or the dissolving time is too long, the cellulose may be degraded at high temperature or the solvent may volatilize; preferably, the dissolving temperature is 70-90 DEG C, and the dissolving time is preferably 2-4 h.

[0049] To ensure the dissolving efficiency and quality of the cellulose, the cation in the superbase acetate ionic solvent system of the present application is preferably at least one of 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0050] The second step is to add a certain amount of viscosity reducer to the first solution, i.e. the solution of the dissolved and decolorized cotton-polyester blended fabric, and mix uniformly to obtain a second solution. The technical purpose of adding the viscosity reducer is to reduce the viscosity of the cotton-polyester blended fabric solution to facilitate subsequent filtration and thus realize the separation of the cellulose component.

[0051] In some specific embodiments of the present application, the viscosity reducer is selected from at least one of dimethyl sulfoxide (DMSO), gamma-valerolactone (GVL) and sulfolane; these viscosity reducers can destroy the hydrogen bonds between cellulose molecules, reduce the viscosity of the solution, and at the same time, most of these viscosity reducers are polar organic solvents, and the oxygen atoms contained in the molecules (such as the sulfoxide group of DMSO and the ester group of GVL) can form hydrogen bonds with the hydroxyl groups on the cellulose molecular chain or form solvation binding with cellulose through dipole interaction. This action can weaken the hydrogen bonds or van der Waals forces between cellulose and dye molecules (the dyes in the fabric are mostly adsorbed or chemically bonded inside the cellulose), form solvation competition, and the viscosity reducer molecules occupy the binding sites of cellulose, forcing the dye molecules to dissociate from the cellulose network and enter the solution phase, which can on the one hand make the dye molecules contact the superbase cations better for decolorization, and on the other hand facilitate subsequent separation with the solvent; further strengthen the effect of in-situ decolorization. For example, in Example 2 and Comparative Example 2, 1,5-diazabicyclo[4.3.0]non-5-ene acetate ionic solvent is used to dissolve the cotton-polyester fabric, and in Example 2, the viscosity reducer gamma-valerolactone is added for synergistic decolorization, and the decolorization effect L reaches 63, while in Comparative Example 2, no viscosity reducer is added for synergistic decolorization, and the decolorization effect L is only 31. In Example 3 and Comparative Example 3, 1,5,7-triazabicyclo[4.4.0]dec-5-ene acetate ionic solvent is used to dissolve the cotton-polyester fabric, and in Example 3, the viscosity reducer sulfolane is added for synergistic decolorization, and the decolorization effect L reaches 72, while in Comparative Example 3, no viscosity reducer is added for synergistic decolorization, and the decolorization effect L is only 55.

[0052] The temperature is preferably controlled at 40-60°C when the viscosity reducer is added; if the temperature is too low, it can cause difficulty in stirring, and thus difficulty in subsequent separation; and if the temperature is too high, it can cause degradation of cellulose and volatilization of the viscosity reducer.

[0053] The viscosity of the solution can be reduced from >50000 mPa·s to 804.7-39723 mPa·s at a temperature of 40-60°C by using the viscosity reducer described above, thereby greatly improving the efficiency of solid-liquid separation.

[0054] In the above step, the addition amount of the viscosity reducer is preferably 30-100% of the mass of the ionic solvent; if the addition amount is too low, the low viscosity required for filtration cannot be achieved, and if the addition amount is too high, the reagent is wasted and the low cellulose solid content can affect the performance of the regenerated cellulose membrane. The present application preferably controls the addition amount of the viscosity reducer to be 30-100% of the mass of the ionic solvent, which can ensure that the solution can be sufficiently reduced in viscosity and assisted in decolorization, and avoid an increase in solvent cost due to excessive viscosity reducer.

[0055] The mass of the cellulose raw material in the first solution is 2.6-12%; after the addition of the viscosity reducer in an amount of 30-100% of the mass of the ionic solvent, the mass solid content of the cellulose raw material in the second solution is 2-6%.

[0056] The dyes in waste textiles are usually adsorbed inside the cellulose fibers. When cellulose with a degree of polymerization of 500-1000 swells in the superalkali acetate ionic solvent, the intermolecular chain space is moderately increased, which is conducive to the extraction of active hydrogen protons in the dye molecules by the "superalkali" structure, and the destruction of its conjugated double bond system, so that the dye loses its color ability, and at the same time, it is also conducive to the penetration and stripping of the dye molecules by the viscosity reducer, thereby achieving decolorization. Experiments show that the decolorization rate of cellulose with this degree of polymerization is significantly higher than that of high-polymerization cellulose.

[0057] In the dissolution of the cellulose raw material, the mass concentration of the cellulose solution is generally controlled to be suitable for the subsequent film laying. In the present application, the superalkali acetate ionic solvent is used to treat the waste cotton-polyester blended fabric first, and then the cellulose and the insoluble polyester component are separated, and the dissolved component is the cellulose. The mass concentration of the cellulose solution is affected by the mass concentration of the superalkali acetate ionic solvent for dissolving the blended fabric. Because the superalkali acetate ionic solvent has limited dissolving capacity, and the raw material contains insoluble polyester component, the cellulose solution for film laying is difficult to reach a high mass concentration. When the mass concentration of the cellulose solution is too low, the forming effect of the cellulose film is poor and it is difficult to achieve high mechanical strength. In order to successfully lay the film in the subsequent process and obtain a regenerated cellulose film with excellent physical and chemical properties, the present application preferably controls the mass solid content of the cellulose raw material in the first solution to be 2.6-12%, and the mass solid content of the cellulose raw material in the second solution to be 2-6%. Through the range setting, the dissolving efficiency and the solution viscosity can be balanced, and the cellulose is not fully dissolved due to too high solid content or the solvent cost is increased due to too low solid content. Further preferably, the mass solid content of the cellulose raw material in the second solution is 2-4%, and more preferably 4%. In order to facilitate the film laying and regeneration in the subsequent process, the present application preferably controls the zero shear viscosity of the cellulose solution to be 800-40000 mPa·s.

[0058] After the second solution is fully mixed and uniform, the insoluble polyester component is filtered out to obtain a cellulose solution and an insoluble polyester. The filtering operation uses a customized pressure filtration device, and the pressure size is not limited. In the maximum pressure range, normal filtering operation can be performed. During the filtering process, appropriate heating can be performed according to the actual situation to assist and accelerate the filtering.

[0059] The present application also provides a regenerated cellulose material obtained by the recycling method described above, which can be in the form of a film.

[0060] After the blended fabric solution is filtered, the obtained cellulose solution is laid and regenerated, and dried to obtain a regenerated cellulose film.

[0061] In the above film forming process, the specific film forming process is not specifically limited, and normal casting method or blade coating method can be used, as long as the cellulose solution can be prepared into a film.

[0062] In the above film forming process, the primary cellulose film is obtained by immersing the solution film into a coagulation bath. When the cellulose solution encounters the coagulation bath liquid, a slow solvent-non-solvent double diffusion effect occurs, which destroys the hydrogen bond between the ionic solvent and the cellulose, and the cellulose is slowly solidified and regenerated. Then, the coagulation bath is replaced for 1-10 times, and each time the residence time is 0.5-4 h. By replacing the coagulation bath multiple times, the ionic solvent can be fully washed away, and the solvent residue in the regenerated material can be reduced. In order to better balance the quality and efficiency, the coagulation bath is further preferably replaced for 4-5 times. The coagulation bath is selected from at least one of tert-butyl alcohol, ethanol and water.

[0063] In the above film forming process, the primary cellulose film is obtained by immersing the solution film into a coagulation bath. When the cellulose solution encounters the coagulation bath liquid, a slow solvent-non-solvent double diffusion effect occurs, which destroys the hydrogen bond between the ionic solvent and the cellulose, and the cellulose is slowly solidified and regenerated. Then, the coagulation bath is replaced for 1-10 times, and each time the residence time is 0.5-4 h. By replacing the coagulation bath multiple times, the ionic solvent can be fully washed away, and the solvent residue in the regenerated material can be reduced. In order to better balance the quality and efficiency, the coagulation bath is further preferably replaced for 4-5 times. The coagulation bath is selected from at least one of tert-butyl alcohol, ethanol and water.

[0064] In one specific embodiment of the present application, the oiling step preferably has an oil agent concentration of 2-5%; the drying step preferably has normal temperature and pressure drying or high temperature drying, the high temperature drying temperature is 20-150℃, and the time is 5-60 min. Low temperature slow drying can reduce the cracking of the film, and high temperature fast drying is suitable for industrial production; the present application further preferably has a drying temperature of 100-120℃, and the drying time is preferably 8-25 min. If the drying time is too short, the film will not be completely dried, and if the drying time is too long, the film strength will decrease.

[0065] The regenerated cellulose material of the present application can also be processed into fibers or aerogels according to actual needs. The regeneration process is not specifically limited.

[0066] The present application also proposes an application of the aforementioned regenerated cellulose material in the fields of food packaging, filtration and adsorption, functional sensing or thermal insulation technology.

[0067] The regenerated cellulose film of the present application meets the GB 4806.6-2016 "National Food Safety Standard Plastic Resin for Food Contact", the heavy metal content is <0.1 mg / kg (detection data of Example 3), and the migration amount is <10 mg / dm 2 , which meets the safety requirements of the food packaging field.

[0068] The average pore size of the regenerated cellulose film of the present application is 0.2-1.5 μm (data of Example 4), and the adsorption capacity of methylene blue is 200-300 mg / g (adsorption experiment of Example 5), which is suitable for dye wastewater treatment in the field of filtration and adsorption.

[0069] The response time of the regenerated cellulose film of the present application to humidity is <5 s (test data of Example 2), and the conductivity is 10 -4 ~10 -3S / cm (data of Example 3), which can be used as a humidity sensor material in the field of functional sensing.

[0070] The thermal conductivity of the regenerated polyester fiber is 0.03-0.05 W / (m·K) (test data of Example 5), which meets the performance requirements in the field of thermal insulation.

[0071] The biocompatibility thereof can be used in food packaging, the porous structure thereof can be used for filtration and adsorption, the ion responsiveness thereof can be used in functional sensing, and the low thermal conductivity thereof can be used in the field of thermal insulation.

[0072] The present application also provides a regenerated polyester material obtained by the recycling method. Figure 6 The infrared spectrum of the insoluble polyester obtained by filtration in Example 1 of the present application is shown.

[0073] The present application makes full use of the selective dissolution characteristics of the superbase acetate ionic solvent to cotton fiber (cellulose), realizes efficient separation of the cotton polyester blended component, is more environmentally friendly than the traditional acid-base hydrolysis method, and avoids fiber damage; the cation of the superbase structure captures the active hydrogen protons of the dye molecules, destroys the conjugated double bond system, and makes the dye lose the color developing ability; and the dissolution of the superbase acetate ionic solvent to cellulose is accompanied by severe swelling, the solvent molecules penetrate into the cellulose molecular chains, destroy the hydrogen bonds between the cellulose molecules, make the fiber structure loose and the molecular chain gap increase, and the dyes in the fabric are mostly adsorbed or chemically bonded inside the cellulose fibers; after the swelling of the cellulose, the binding force between the dyes and the fibers is weakened, and the dyes are more easily separated from the fiber network and enter the solvent phase. Further, the present application adds a viscosity reducer to the solution to promote the dissociation of the dye molecules from the cellulose network, and at the same time reduces the viscosity of the solution to facilitate subsequent separation, the “one-step dissolution + decolorization” process of the present application breaks through the limitation of traditional step-by-step operation; the technical scheme of the present application not only can obtain regenerated cellulose materials (such as films, fibers, etc.), but also directly uses the separated polyester as a regenerated material, realizing full resource utilization of the blended fabric.

[0074] The introduction of the viscosity reducer in the technical scheme of the present application has the dual functions of viscosity reduction and decolorization, solving the problems of high viscosity of the ionic solvent and dye residue.

[0075] The present application will be further described below in conjunction with specific embodiments, but it should not be understood as limiting the scope of protection of the present application; some non-essential improvements and adjustments to the present application made by those skilled in the art based on the content of the present application above still belong to the protection scope of the present application.

[0076] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The materials, methods, and examples provided herein are illustrative only and in no way limit the scope of the application. Nothing herein is to be construed as an admission that the application is not entitled to antedate such disclosure by virtue of prior application.

[0077] The superbase acetate ionic solvent has good technical effects on one-pot dissolution and decolorization of cotton-polyester fabric with a polymerization degree of 500-1000. In the following specific examples, the colored blended fabric uses commercially available cotton-polyester fabric, the cellulose content is 85%, and the polyester content is 15%. The polymerization degree and content are only illustrative and do not constitute a limitation on the specific scope of the application.

[0078] Example 1

[0079] 4.8 g of the colored blended fabric was added to 60 g of 1,8-diazabicyclo[5.4.0]undec-7-ene acetate ionic solvent, and after mixing well, stirring was carried out at 80°C until the cellulose was completely dissolved, Figure 1 As shown in the figure, the left photo is before dissolution and decolorization, and the right photo is after dissolution and decolorization; the cellulose dissolution was observed under a polarizing microscope by taking samples at regular intervals, and after 3.5 h, it was found that the cellulose was completely dissolved under a polarizing microscope, and the dissolution process was as shown in Figure 2 As shown in the figure, the long fibers are insoluble polyester components, and have color under a polarizing microscope, and the four figures are polarizing microscope images at different times, which can be seen from Figure 2 It can be found that the cellulose is dissolved less and less, and the polyester is not dissolved, realizing the separation of cellulose and polyester; at the same time, it is found that the color of the blended fabric solution gradually becomes lighter during the dissolution of the cellulose. Then, 60 g of a viscosity reducer dimethyl sulfoxide was added to the solution at 60°C, and after mixing uniformly until there were no obvious lumps, the insoluble polyester component and the cellulose solution were separated by hydraulic pressure, Figure 3 As shown in the figure, the insoluble polyester is a photo, Figure 4 As shown in the figure, the cellulose solution is a polarizing picture, and the viscosity of the cellulose solution is 5663.2 mPa·s. The cellulose solution was regenerated by using a blade coating method to lay a film in a t-butyl alcohol coagulation bath. The t-butyl alcohol coagulation bath was replaced every 1-2 h, and was replaced 4 times to remove the ionic solvent in the solution. Subsequently, oiling was carried out, the concentration of the oil agent used was 3 g / L, and after drying in a 120°C oven, a regenerated cellulose film was obtained, which had very high transparency, as shown in Figure 5 As shown in the figure, the cellulose film is a photo, and the object behind the film can be clearly seen. The insoluble polyester component was washed and dried to obtain a regenerated polyester material.

[0080] After the above steps, the specific properties of the regenerated cellulose film prepared in this example are shown in Table 1.

[0081] The filtered polyester was subjected to infrared spectrum test, Figure 6 The infrared spectrum of the filtered insoluble polyester and the pure polyester component was obtained, and the results showed that the infrared spectrum of the filtered polyester was almost consistent with that of the pure polyester, and had the typical characteristic peaks of polyester material, indicating that the cellulose and polyester were efficiently separated in this embodiment.

[0082] Example 2

[0083] After 4.8 g of silk-like colored blended fabric was mixed with 80 g of 1,5-diazabicyclo[4.3.0]non-5-ene acetate ionic solvent, the mixture was stirred at 80°C until the cellulose was completely dissolved. The dissolution of the cellulose was observed under a polarizing microscope. After 3 h, it was found under the polarizing microscope that the cellulose was completely dissolved, and it was also found that the color of the blended fabric solution gradually became lighter during the dissolution of the cellulose. Then, 40 g of viscosity reducer γ-valerolactone was added to the solution at 40°C, and the mixture was uniformly mixed until there were no obvious lumps. The insoluble polyester component and the cellulose solution were separated by hydraulic pressure filtration, and the viscosity of the cellulose solution was 39723 mPa·s. The cellulose solution was cast into a film by a scraping method, and then regenerated in an ethanol coagulation bath. The ethanol coagulation bath was replaced every 1-2 h, and replaced 4 times to remove the ionic solvent in the solution. Subsequently, the regenerated cellulose film was oiled, and dried in an oven at 120°C to obtain the regenerated cellulose film.

[0084] After the above steps, the specific properties of the regenerated cellulose film prepared in this embodiment are shown in Table 1.

[0085] Example 3

[0086] After 4.8 g of silk-like colored blended fabric was mixed with 90 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene acetate ionic solvent, the mixture was stirred at 80°C until the cellulose was completely dissolved. The dissolution of the cellulose was observed under a polarizing microscope. After 2.5 h, it was found under the polarizing microscope that the cellulose was completely dissolved, and it was also found that the color of the blended fabric solution gradually became lighter during the dissolution of the cellulose. Then, 30 g of viscosity reducer sulfolane was added to the solution at 40°C, and the mixture was uniformly mixed until there were no obvious lumps. The insoluble polyester component and the cellulose solution were separated by hydraulic pressure filtration, and the viscosity of the cellulose solution was 34588 mPa·s. The cellulose solution was cast into a film by a scraping method, and then regenerated in an ethanol coagulation bath. The ethanol coagulation bath was replaced every 1-2 h, and replaced 4 times to remove the ionic solvent in the solution. Subsequently, the regenerated cellulose film was oiled, and dried in an oven at 120°C to obtain the regenerated cellulose film.

[0087] After the above steps, the specific properties of the regenerated cellulose film prepared in this embodiment are shown in Table 1.

[0088] Example 4

[0089] 2.4g of filamentous colored blended fabric was thoroughly mixed with 60g of 1,8-diazabicyclo[5.4.0]undec-7-ene acetate ionic solvent. The mixture was stirred at 80℃ until the cellulose was completely dissolved. Samples were taken periodically and observed under a polarizing microscope to monitor the cellulose dissolution. After 2 hours, complete cellulose dissolution was observed under the polarizing microscope, and the color of the blended fabric solution gradually lightened during the cellulose dissolution process. Then, 60g of dimethyl sulfoxide (DMSO), a viscosity reducer, was added to the solution at 60℃. After mixing until no obvious lumps remained, the solution was separated by hydraulic filtration to separate the insoluble polyester component and the cellulose solution. The viscosity of the cellulose solution was 804.7 mPa·s. The cellulose solution was then cast into a film using a casting method and regenerated in an ethanol coagulation bath. The coagulation bath needed to be replaced every 1-2 hours, for a total of 4 times, to remove the ionic solvent from the solution. Subsequently, an oil was applied at a concentration of 3g / L. After drying at room temperature and pressure, a regenerated cellulose membrane was obtained. Figure 7 The image shown is a photograph of the membrane. The specific properties of the regenerated cellulose membrane obtained in this embodiment after the above steps are shown in Table 1.

[0090] Example 5

[0091] 4.8g of filamentous colored blended fabric was thoroughly mixed with 60g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene acetate ionic solvent, and stirred at 80℃ until the cellulose was completely dissolved. Samples were taken periodically and observed under a polarizing microscope to monitor the cellulose dissolution. After 3.5 hours, complete cellulose dissolution was observed under the polarizing microscope, and the color of the blended fabric solution gradually lightened during the cellulose dissolution process. Then, 60g of the viscosity reducer γ-valerolactone was added to the solution at 60℃ and mixed until no obvious lumps remained. The insoluble polyester component and cellulose solution were separated by hydraulic filtration, with the cellulose solution having a viscosity of 5487.6 mPa·s. The cellulose solution was then coated using a scraping method and regenerated in a hydrocoagulation bath. The hydrocoagulation bath was replaced every 1–2 hours, for a total of 4 times, to remove the ionic solvent from the solution. Subsequently, an oil with a concentration of 3g / L was applied, and the membrane was dried in an oven at 120℃ to obtain the regenerated cellulose membrane. The specific properties of the regenerated cellulose membrane obtained in this embodiment after the above steps are shown in Table 1.

[0092] Comparative Example 1

[0093] 4.8g of filamentous colored cotton-polyester blended fabric was mixed with 60g of 1-allyl-3-methylimidazolium chloride ionic solvent and allowed to swell fully. The mixture was stirred at 80℃, and samples were taken periodically for observation of cellulose dissolution under a polarizing microscope. After 10.5 hours, most of the cellulose remained undissolved. It was also observed that the colored fabric raw material did not decolorize in this ionic solvent. Figure 8The left picture is the polarized light picture of cellulose after 10.5h dissolution, and the right picture is the corresponding cellulose dissolution photo. Further, after mixing the appropriate amount of 1-allyl-3-methylimidazolium chloride ionic solvent with fabric dye at 80°C and uniformly reacting for a period of time, it is found that the color of the mixed solution does not change obviously, as shown in Figure 9 The left picture is the color of 1-allyl-3-methylimidazolium chloride ionic solvent after reaction with dye, and the right picture is the color of the superbase acetate ionic solvent of the application after reaction with dye. In this comparative example, no viscosity reducer is added, and the final mass content of the colored fabric raw material is 8% based on 100% of the mass of the ionic solvent. After the above steps, the specific experimental phenomena of this example are shown in Table 1.

[0094] Comparative Example 2

[0095] After mixing 9.6g of silk-like colored blended fabric with 60g of 1,5-diazabicyclo[4.3.0]non-5-ene acetate ionic solvent, stirring at 90°C, and observing the dissolution of the slurry under a polarizing microscope, it is found that although the color of the cotton-polyester blended fabric solution becomes lighter, due to the high concentration of the fabric, stirring is difficult and dissolution is difficult, making it difficult to perform the next step of component separation operation. In this comparative example, no viscosity reducer is added, and the final mass content of the colored fabric raw material is 16% based on 100% of the mass of the ionic solvent. After the above steps, the specific experimental phenomena of this example are shown in Table 1.

[0096] Comparative Example 3

[0097] After mixing 4.8g of silk-like colored cotton-polyester blended fabric with 60g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene acetate ionic solvent and fully swelling, stirring at 100°C until the cellulose is completely dissolved, and observing the dissolution of the cellulose under a polarizing microscope, it is found that the cellulose is completely dissolved after 3.5h. Without adding a viscosity reducer, it is found that the viscosity of the dissolved solution is too large, making it difficult to transfer the dissolved solution in the beaker to the filtration equipment and to filter the insoluble polyester. The high viscosity leads to prolonged filtration time and clogging of the filter screen, making subsequent operations difficult. In this comparative example, no viscosity reducer is added, and the final mass content of the colored fabric raw material is 8% based on 100% of the mass of the ionic solvent. After the above steps, the specific experimental phenomena of this example are shown in Table 1.

[0098] Comparative Example 4

[0099] The 4.8 g of colored cotton-polyester blended fabric was mixed with 60 g of the eutectic solvent and swelled sufficiently, and stirred at 80°C. The cellulose dissolution was observed under a polarizing microscope at a fixed time. It was found that the dissolution was difficult and the viscosity was large, and the next step of component separation operation was difficult to proceed. At the same time, it was found that the colored fabric raw material did not decolorize in the ionic solvent. Further, a proper amount of eutectic solvent was mixed with the fabric dye at 80°C and reacted for a period of time. It was found that the color of the mixed solution did not change significantly. In the present example, no viscosity reducer was added, and the mass content of the colored fabric raw material was 8% based on the mass of the ionic solvent being 100%. After the above steps, the specific experimental phenomena of the present example are shown in Table 1.

[0100] The performance test methods of the above examples and comparative examples were tested by using the conventional test methods in the art, and the unexplained were tested by using the conventional test methods in the art.

[0101] Decolorization effect test: Under the same conditions, the color change during the cellulose dissolution process was recorded, and the color Lab value was extracted by software. In the present application, the L (brightness) value was mainly recorded to indicate that the colored fabric decolorized during the dissolution process. The larger the L value, the lighter the color. It is known that the L value of the colored cellulose raw material mixed with the cellulose solvent is 8, and the L value in Table 1 is measured after the cellulose is dissolved (the experiment of the undissolved cellulose is at the end of the dissolution stirring operation).

[0102] Transparency test: The light transmittance of the cellulose film was tested according to GB / T2410-2008, and was tested by using an ultraviolet-visible spectrophotometer with an integrating sphere. The wavelength range was 400-800 nm. The light transmittance calculation formula is

[0103]

[0104] Among them, T represents the light transmittance, T1 is the incident light flux, and T2 is the total transmitted light flux through the sample.

[0105] Cellulose recovery rate: The polyester obtained by filtration was washed and dried, and the mass was weighed to obtain the mass of the dissolved cellulose. The cellulose recovery rate was calculated by comparing the mass of the initially added cellulose.

[0106] Table 1

[0107]

[0108]

[0109] From the above example and the test data of the comparative example, it can be seen that in the process of dissolving the colored cotton-polyester blended fabric in the super-alkali acetate ionic solvent in examples 1-5, the separation of the fabric cotton-polyester components and the color removal can be achieved simultaneously, and the regenerated cellulose film can be obtained by spreading the obtained cellulose solution and then drying.

[0110] Comparing examples 1-5 with comparative example 2, it is found that when the concentration of the cotton-polyester blended fabric raw material is too high, the fabric is difficult to be fully dissolved, and when it is too low, the mechanical properties of the regenerated cellulose film are poor. The cellulose solution has a mass concentration of 4% in the present application, so that better dissolution can be achieved.

[0111] From examples 1-3, it is found that the content of the viscosity reducer not only affects the difficulty of filtration, but also affects the mechanical properties of the regenerated cellulose film. When the mass of the viscosity reducer added is 50% of the mass of the ionic solvent, the viscosity of the solution can be effectively reduced to meet the filtration requirements, and the tensile strength of the regenerated cellulose film obtained is 115.6 MPa, and the elongation at break is 34.4%.

[0112] From the comparison of examples 2, 4-5, it is found that under the condition of ethanol as the coagulation bath and high-temperature drying at 120℃, the regenerated cellulose film obtained has higher strength.

[0113] From the test data of the above examples, it can be seen that in examples 1-5 and comparative example 3, different solid contents of the raw material and different amounts of the viscosity reducer added during the dissolution process affect the dissolution and the difficulty of filtration operation, but it can be found that in the experimental process of using the super-alkali acetate ionic solvent as the cellulose solvent, the fabric color has a fading phenomenon, and the removal of the dye color is mainly due to the oxidation of the dye molecules catalyzed by the specific ionic solvent component, which causes the loss of hydrogen proton, resulting in the disappearance of the color.

[0114] From the test data of the above comparative examples, it can be seen that in comparative examples 1 and 4, the ionic solvent is selected as 1-allyl-3-methyl imidazole chloride ionic solvent and eutectic solvent respectively, and it is found that the final cellulose is still not completely dissolved, and the color of the colored fabric does not change obviously during the dissolution process. If decolorization is required, additional bleaching experiments need to be carried out, which fully illustrates the innovation of the present application in realizing the integration of component separation and color removal of colored waste cotton-polyester blended fabric by selecting the super-alkali acetate ionic solvent.

[0115] From the test data of the above comparative examples, it can be seen that in comparative example 2, although the mass concentration of the fabric raw material is too high, the cellulose cannot be fully swelled and dissolved in the ionic solvent, and the viscosity reduction and separation operation cannot be carried out, but it is found that the color of the fabric is partially lighter during the experiment, indicating that the super-alkali acetate ionic solvent in the present application can decolorize the colored fabric under appropriate conditions.

[0116] From the test data of the above comparative examples, in Comparative Example 3, the solvent is only a cellulose dissolution system without a viscosity reducer component, so that the viscosity of the cotton-polyester blended fabric dissolution solution obtained after the fabric is swelled and stirred is too large, and it is difficult to transfer the dissolution solution to the filtering equipment and the subsequent filtering operation, indicating that the use of the viscosity reducer is necessary in the technical solution of the present application; and it is found that the dissolution at 100℃ results in the color of the obtained blended fabric solution being red, which may be due to the excessive degradation of cellulose caused by the high temperature.

[0117] The technical features in the claims and / or the specification of the present application can be combined, and the combination manner is not limited to the combination obtained by reference relationship in the claims. The technical solution obtained by combining the technical features in the claims and / or the specification is also within the protection scope of the present application.

[0118] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for recycling waste cotton-polyester blended fabrics, characterized in that, It includes the following steps: S11 involves adding cellulose raw material to a superbasic acetate ionic solvent, stirring to dissolve and decolorize, to obtain a first solution; the cellulose raw material is obtained from waste cotton-polyester blended fabric. S12 Add a viscosity reducer to the first solution, mix well, and obtain the second solution; S13 performs solid-liquid separation on the second solution to obtain a cellulose solution and an insoluble polyester; S14 regenerates and dries the cellulose solution to obtain regenerated cellulose material; insoluble polyester is washed and dried to obtain regenerated polyester material.

2. The recycling method according to claim 1, characterized in that, The cellulose raw material is a powdered, filamentous, or flocculent fabric obtained by pulverizing colored waste cotton-polyester blended fabric with a degree of polymerization of 500-1000; and / or, the cation in the superbasic acetate ionic solvent is selected from at least one of 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

3. The recycling method according to claim 1, characterized in that, In step S11, the mass of the cellulose raw material is 2.6-12% based on the mass of the ionic solvent being 100%.

4. The recycling method according to claim 1, characterized in that, In step S11, the dissolution temperature is 70–90℃ and the dissolution time is 2–4 hours.

5. The recycling method according to claim 1, characterized in that, In step S12, when the viscosity reducer is added, the temperature of both the viscosity reducer and the first solution is 40-60℃.

6. The recycling method according to claim 1, characterized in that, The viscosity reducer is selected from at least one of dimethyl sulfoxide, γ-valerolactone, and sulfolane.

7. The recycling method according to claim 1, characterized in that, The mass ratio of the viscosity reducer to the ionic solvent is 0.3 to 1:1; based on the total mass of the ionic solvent and the viscosity reducer being 100%, the mass solid content of the cellulose raw material is 2 to 6%.

8. A regenerated cellulose material obtained by the recycling method according to any one of claims 1 to 7.

9. A recycled polyester material obtained by the recycling method according to any one of claims 1 to 7.

10. The application of the regenerated cellulose material according to claim 8 in the fields of food packaging, filtration and adsorption, functional sensing, or thermal insulation.

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