Method for separating, recycling and synchronously decolorizing colored waste polyester cotton blended textiles

Abstract

The invention belongs to the technical field of recycling of waste polyester-cotton blended textiles, and particularly relates to a method for separating, recycling and synchronously decolorizing colored waste polyester-cotton blended textiles. The combined synergistic effect of the decolorizing agent and the low-cost green good solvent organic acid is utilized, so that the decolorizing and separating processes of the cotton-polyester blended fabric are mutually promoted, and the decolorizing and separating efficiencies are synchronously improved. The unique solvent combination greatly improves the decolorization efficiency, selectively depolymerizes the cotton fibers and releases the polyester fibers, and realizes effective separation of two components in the polyester-cotton blended textile. By means of the technology, the possible problems in secondary utilization of recycled polyester are avoided, the weak acidity of the organic acid is utilized, the recycling rate of the cotton fibers is guaranteed to the maximum degree, more possibilities are provided for high-value utilization of the cotton fibers, recycling of waste polyester-cotton blended textiles is greatly promoted, and maximum utilization of resources is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling waste polyester-cotton blended textiles, and more specifically relates to a method for separating, recycling and synchronously decolorizing colored waste polyester-cotton blended textiles. Background Art

[0002] Among waste textiles, polyester-cotton blended textiles are the most recyclable textile resources with the highest content of polyester and cotton fibers and the greatest recycling significance. However, during the recycling and reuse process, the doping between the two components often leads to the degradation of the performance of the main body. In addition, since various dyes are added to most waste textiles during production and use, the performance of the recycled products is greatly affected. Therefore, how to efficiently separate the polyester and cotton fiber components in waste polyester-cotton fabrics is the key to achieving high-value recycling and reuse of waste polyester-cotton fabrics.

[0003] Traditional recycling of waste polyester-cotton blended textile resources often involves multiple processing steps to achieve decolorization and separation. It is difficult to simultaneously recover decolorized and separated polyester and cotton fibers. These complex process flows not only increase production costs, but also extend production cycles. Although a variety of methods have been proposed, such as using subcritical water conditions, NMMO aqueous solutions, etc., these methods still face the problem of low separation efficiency in practical applications. In the process of decolorization and stripping, a large amount of chemical reagents, such as antioxidants and 4-methylmorpholine-N-oxide, are usually required. These chemical reagents are not only expensive, but also have a greater impact on the environment. In the process of decolorization and separation, some fibers may be damaged by chemical reactions, resulting in material loss, which not only reduces the quality of the recycled materials, but also increases the processing cost. Therefore, it is urgent to solve the above problems through further technological innovation and optimization to improve the recycling rate and economic benefits of waste polyester-cotton blended textiles. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a method for separating, recovering and simultaneously decolorizing colored waste polyester-cotton blended textiles, in order to use a low-cost decolorizing separator as a mixed solvent, to degrade the cotton fibers in the waste polyester-cotton blended textiles while performing efficient decolorization, and to separately recover the high-purity polyester fibers and cotton fibers after decolorization.

[0005] To achieve the above-mentioned object, in a first aspect, the present invention provides a method for separating, recovering and simultaneously decolorizing colored waste polyester-cotton blended textiles, comprising the following steps:

[0006] The pre-treated waste polyester-cotton blended textiles are mixed with a decolorizing separator solution of a certain concentration, placed in a normal pressure container for heating and degradation, and after the reaction is completed, hot water is added to terminate the reaction;

[0007] The reaction mixture is ultrasonically vibrated and vacuum filtered to obtain preliminarily recovered polyester fibers and a preliminarily filtrate. The preliminarily recovered polyester fibers are washed several times, the washing liquid and the preliminarily filtrate are mixed, and vacuum filtered again to obtain preliminarily recovered cotton fibers, which are then dried to obtain recovered polyester fibers and recovered cotton fibers.

[0008] The waste polyester-cotton blended textiles suitable for the separation, recovery and simultaneous decolorization method have a cotton fiber content of 1-99wt%.

[0009] In some embodiments, the decolorizing separation agent comprises a decolorizing agent and an organic acid, wherein the decolorizing agent is one or a mixture of two or more of hypochlorous acid, hydrogen peroxide, dimethylformamide, and thiourea dioxide, and the organic acid is one of oxalic acid, p-toluenesulfonic acid, malic acid, acetic acid, and citric acid. Low-cost oxalic acid can be produced industrially from plant resources. It is a naturally abundant, biodegradable, non-volatile, and easy to recycle agent, so oxalic acid is preferred as the organic acid.

[0010] In some more preferred embodiments, the decolorizing separation agent is composed of 6% to 14% effective chlorine content in hypochlorous acid, 60-80% oxalic acid and the balance deionized water.

[0011] In some embodiments, the pretreatment includes: subjecting waste polyester-cotton blended textiles to swelling treatment, washing, and drying to obtain pre-treated waste polyester-cotton blended textiles; wherein the swelling treatment uses a high-polarity swelling agent, preferably, the high-polarity swelling agent is dimethyl sulfoxide or cyclohexanone, and more preferably, the high-polarity swelling agent is dimethyl sulfoxide.

[0012] In some embodiments, the swelling treatment temperature is 110-130° C., and the swelling treatment time is 20-40 min.

[0013] In some embodiments, the temperature of the thermal degradation is 100-110° C., and the time of the thermal degradation treatment is 1-3 hours.

[0014] In some embodiments, the solid-to-liquid mass ratio of the pre-treated waste polyester-cotton blended textile to the decolorizing separator solution is 1:10-100.

[0015] In some embodiments, the temperature of the ultrasonic oscillation is set to 60° C., and the time is set to 20 min.

[0016] In some embodiments, after respectively recovering the polyester and cotton fibers, the filtrate is recovered, cooled in an environment of 2-4°C for 16-24 hours, filtered to obtain crude oxalic acid crystals, and dried in a vacuum environment to obtain high-purity oxalic acid crystals.

[0017] In a second aspect, the present invention provides a polyester and / or cotton fiber textile produced by using recycled polyester fiber and / or recycled cotton fiber obtained by the separation, recovery and simultaneous decolorization method described in the first aspect of the present invention.

[0018] Different from the prior art, the above technical scheme utilizes the synergistic effect of the combination of decolorizing agent and low-cost green excellent solvent organic acid, so that the decolorization and separation process of polyester-cotton blended fabric promote each other. Through the strong oxidizing effect of decolorizing agent such as sodium hypochlorite, decomposition products with strong activity are released in the decolorization process, which act on some polar groups in the dye, ionize the dye molecules, and destroy the electron-donating ability of the electron-donating group. At this time, the dye will produce a light color effect, thereby lightening the color. At the same time, the reaction sites of hydrogen ions in cotton fibers are gradually exposed, which promotes the hydrogen ions ionized by organic acid oxalic acid and carboxylic acid groups to attack the glycosidic bonds or hydroxyl groups of cotton fibers, so that the molecular chains of cotton fibers are broken and peeled off from the polyester surface. In this process, the dyeing sites in cotton fibers also increase, and the decolorization and separation efficiency are simultaneously improved. This unique solvent combination not only greatly improves the decolorization efficiency, but also selectively depolymerizes cotton fibers and releases polyester fibers, thereby realizing the effective separation of the two components in polyester-cotton blended textiles. This technology not only avoids the problems that recycled polyester may encounter in secondary use, but also maximizes the recovery rate of cotton fibers by utilizing the weak acidity of organic acids, providing more possibilities for the high-value utilization of recycled cotton fibers. It greatly promotes the recycling of waste polyester-cotton blended textiles and maximizes the utilization of resources.

[0019] The implementation process of the present invention pays special attention to the formulation and implementation of environmental protection strategies. By preventing excessive hydrolysis, the present invention ensures that cotton fibers can maintain a high yield during the recycling process. At the same time, the present invention also effectively avoids equipment damage and the problem of difficult solvent recovery by optimizing process design and equipment selection, and significantly reduces potential risks to the environment. The implementation of this environmentally friendly recycling strategy not only reduces the risk of secondary pollution, but also improves the efficiency and sustainability of the entire recycling process, providing strong support for the recycling of waste polyester-cotton blended textiles. The present invention makes the recycling of waste polyester-cotton blended textiles more efficient and environmentally friendly through the innovative application of a combination of a decolorizer and a green organic acid solvent, selective depolymerization, efficient component separation technology, and the implementation of an environmentally friendly recycling strategy, bringing progress to the recycling field of waste polyester-cotton blended textiles and making positive contributions to environmental protection and resource conservation.

[0020] The above-mentioned records related to the invention content are only an overview of the technical solution of the present application. In order to enable ordinary technicians in the field to more clearly understand the technical solution of the present application, and then implement it according to the text of the specification and the contents recorded in the drawings, and to make the above-mentioned purpose and other purposes, features and advantages of the present application easier to understand, the following is an explanation in combination with the specific implementation mode and drawings of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings are only used to illustrate the principles, implementation methods, applications, characteristics and effects of the specific embodiments of the present application and other related contents, and shall not be considered as limitations of the present application.

[0022] In the drawings of the specification:

[0023] Figure 1 The scanning electron microscope (SEM) images of waste polyester-cotton textiles before and after separation;

[0024] Figure 2 Fourier transform infrared spectra (FTIR) of waste polyester-cotton textiles before and after separation;

[0025] Figure 3 Comparison chart of waste polyester-cotton textiles of different colors before and after separation and bleaching. DETAILED DESCRIPTION

[0026] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0027] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0028] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0029] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0030] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0031] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0032] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0033] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0034] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0035] The traditional recycling process of waste polyester-cotton blended textiles is complicated, and it is difficult to balance decolorization and separation, which increases costs and cycles. Although existing methods such as subcritical water and NMMO aqueous solution have been proposed, the separation efficiency needs to be improved, and the amount of chemical reagents used is large, the cost is high and it pollutes the environment. The fibers are easily damaged during the separation process, resulting in low quality of the recycled products and increased costs. There is an urgent need for technical innovation and optimization to improve recycling efficiency and economic benefits and reduce environmental burdens, and the present invention was created based on this.

[0036] In the separation, recovery and simultaneous decolorization method of the present invention, if the specific requirements for raw materials and reagents are not described in detail, it is deemed that conventional commercially available raw materials and reagents that meet industrial or laboratory standards are used. The physical and chemical properties of these raw materials and reagents, such as purity, particle size, shape, etc., should meet the basic requirements of the preparation method to ensure the quality and performance of the final product. For special raw materials or reagents used in certain key steps, their selection basis and standards will be described in detail in the relevant steps.

[0037] The instruments and equipment involved in the separation and recovery and synchronous decolorization method of the present invention, if no specific model or brand is particularly indicated, means that these equipment are universal in the field, can perform corresponding operations and meet the requirements of the preparation process. In actual operation, appropriate instruments and equipment can be selected for preparation based on comprehensive consideration of factors such as laboratory conditions, production scale and cost-effectiveness. At the same time, it should be ensured that all instruments and equipment are properly calibrated and inspected before use to ensure the accuracy and reliability of the experiment or production.

[0038] The raw materials used in the following examples are waste fabrics recycled from factories, and the operations used in the following examples are common operating methods in the art unless otherwise specified. The proportions, ratios, contents, etc. described in the following examples are weight ratios unless otherwise specified, and the recovery rate refers to the ratio of the polyester (or cotton fiber) collected after separation to the polyester (or cotton fiber) content in the untreated waste polyester-cotton textiles.

[0039] Example 1

[0040] A method for efficiently separating and recovering components of colored waste polyester-cotton blended textiles and for simultaneously decolorizing them

[0041] Take a certain amount of blue waste polyester-cotton blended fabric raw material with a cotton content of 32% and wash it with water, cut or crush it into a block size of about 1.0000±0.0002g, put it into an oven to dry it, put it into a dryer to dry it to constant weight, take it out, weigh it with a weighing bottle and record the mass, add 16ml of dimethyl sulfoxide to a three-necked flask and stir it with the dried fabric at 110℃ for 20min, collect the fabric, wash it, and dry it to obtain the pre-treated waste polyester-cotton blended fabric. Put the above pre-treated waste polyester-cotton blended fabric into a decolorization separation system solution composed of 15ml sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 60% oxalic acid, and the balance is deionized water, and the mass ratio of the pre-treated waste polyester-cotton blended fabric to the decolorization separation system solution is 1:10, set the temperature of the digital display constant temperature oil bath pot to 105℃, and the reaction time is 3h, in which the degradation reaction of cotton fibers in the waste polyester-cotton blended fabric is completed. After the reaction is completed, add enough 100°C hot water to stop the reaction. Place the mixed solution after the reaction is stopped in an ultrasonic cleaning device and perform ultrasonic deep cleaning at 60°C for 20 minutes. Then perform preliminary filtration to obtain preliminary recovered polyester fibers, wash the preliminary recovered polyester fibers with cold water several times to obtain washing liquid. Then mix the preliminary filtrate and washing liquid and drain through the filter membrane under vacuum suction conditions, and filter and recover again to obtain preliminary recovered cotton fibers. Finally, dry the recovered preliminary recovered polyester fibers and preliminary recovered cotton fibers in an oven for 4-16 hours, then put them in a dryer to cool and dry to constant weight, take them out and weigh them within 2 minutes, which are the recovered polyester fibers and recovered cotton fibers.

[0042] Example 2

[0043] The difference from Example 1 is that the added decolorizing separation agent system solution contains 15 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 50% of oxalic acid, and the balance is deionized water. The other operating steps and parameters are the same as those in Example 1.

[0044] Example 3

[0045] The difference from Example 1 is that the added decolorizing separation agent system solution contains 15 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The other operating steps and parameters are the same as those in Example 1.

[0046] Example 4

[0047] The difference from Example 1 is that the added decolorizing separation agent system solution contains 15 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 80% of oxalic acid, and the balance is deionized water. The other operating steps and parameters are the same as those in Example 1.

[0048] The recovery rates of the polyester fibers and cotton fibers recovered in Examples 1 to 4 were calculated according to the ratio of recovery rate = polyester (or cotton fiber) collected after separation / polyester (or cotton fiber) content in untreated waste polyester-cotton textiles, and the recovery rates of polyester and cotton fibers were used as evaluation indicators. It was found that the recovery rate of polyester in Example 1 (oxalic acid concentration was 60%) was 99.70%, and the recovery rate of cotton fiber was 92.69%; the recovery rate of polyester in Example 2 (oxalic acid concentration was 50%) was 107.67% ( A recovery rate greater than 100% indicates that there are residual cotton fibers that have not been completely separated), and the recovery rate of cotton fibers is 82.98%; Example 3 (oxalic acid concentration is 70%) and Example 4 (oxalic acid concentration is 80%) polyester and cotton fibers are completely separated, and the separated polyester recovery rates are 99.73% and 99.07%, respectively, and the cotton fiber recovery rates are 94.63% and 88.32%, respectively. This shows that the separation and decolorization effect of the mixed solution system containing 70wt% oxalic acid in the decolorizing separator system solution is the best. The polyester fiber recovered in Example 3 was calculated by the ratio of the mass of the polyester fiber obtained by the reaction to the mass of the polyester fiber before the reaction according to GB / T 2910.11-2009 "Quantitative Chemical Analysis of Textiles Part 11: Mixtures of Cellulose Fibers and Polyester Fibers (Sulfuric Acid Method)", and the polyester fiber purity was 100%. The loss rate of the recovered polyester fiber and cotton fiber was calculated according to the loss rate = the ratio of the difference between the polyester (or cotton fiber) content collected after separation and the polyester (or cotton fiber) content in the untreated waste polyester-cotton textile to the polyester (or cotton fiber) content in the untreated waste polyester-cotton textile. The mass loss rate of the polyester recovered from the completely separated polyester-cotton blended fabric in Example 1, Example 3, and Example 4 was less than 1%, and the mass loss rate of the cotton fiber was less than 10%. The fabric decolorization rate was calculated according to the ratio of the absorbance difference of the waste polyester-cotton textile before and after treatment / the absorbance of the waste polyester-cotton textile before treatment, and the fabric decolorization rate could reach up to 79.66%.

[0049] Example 5

[0050] The difference from Example 1 is that the added decolorizing separation agent system solution contains 10 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The other operating steps and parameters are the same as those in Example 1.

[0051] Example 6

[0052] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The other operating steps and parameters are the same as those in Example 1.

[0053] Example 7

[0054] The difference from Example 1 is that the added decolorizing separation agent system solution contains 30 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The other operating steps and parameters are the same as those in Example 1.

[0055] The results showed that separation was completed in Examples 5 to 7, and the recovery rate of separated polyester was over 99%, and the recovery rate of cotton fiber was as high as 94.37%. The purity of polyester completely separated and recovered from polyester-cotton blended fabrics in Examples 5 to 7 was 100%, the mass loss rate of polyester was less than 1%, and the mass loss rate of cotton fiber was less than 10%. The decolorization results are as follows: compared with Example 3, the decolorization rate is 79.66% when 15ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%) is added; the decolorization rate is 70.01% when 10ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%) is added in Example 5; the decolorization rate is 82.15% when 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%) is added in Example 6; the decolorization rate is 81.69% when 30ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%) is added in Example 7. It is found that 20ml of sodium hypochlorite aqueous solution in the decolorizing separation agent system solution can achieve an ideal decolorization effect in the mixed solution system, and the decolorization effect of continuing to increase the volume does not change significantly.

[0056] Example 8

[0057] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath is set to 90° C., and the other operating steps and parameters are carried out according to Example 1.

[0058] Example 9

[0059] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath is set to 100° C., and the other operating steps and parameters are carried out according to Example 1.

[0060] Example 10

[0061] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath is set to 110° C., and the other operating steps and parameters are carried out according to Example 1.

[0062] The results show that when the temperature is 90°C in Example 8, the polyester recovery rate is 110.16%, and the recovery rate is greater than 100%, indicating that the cotton fiber is not completely separated, and the cotton fiber recovery rate is 77.75%; when the temperature is 100°C in Example 9, the polyester recovery rate is 99.44%, and the cotton fiber recovery rate is 92.42%; when the temperature is 110°C in Example 10, the polyester recovery rate is 99.26%, and the cotton fiber recovery rate is 87.12%. It shows that the separation and decolorization effect is best when the decolorization and degradation temperature is 100°C. In Examples 9 and 10, the polyester purity of the polyester-cotton blended fabric completely separated and recovered is 100%, the polyester mass loss rate is less than 1%, and the cotton fiber mass loss rate is less than 10%. Decolorization and separation have been completed in Examples 8-10, and the fabric decolorization rate can reach up to 82.54%.

[0063] Embodiment 11

[0064] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97° C., the reaction time is 1 hour, and the other operating steps and parameters are carried out according to Example 1.

[0065] Example 12

[0066] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath is set to 97° C., the reaction time is 2 hours, and the other operating steps and parameters are carried out according to Example 1.

[0067] Example 13

[0068] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97° C., the reaction time is 3 hours, and the other operating steps and parameters are carried out according to Example 1.

[0069] Embodiment 14

[0070] The difference from Example 1 is that the added decolorizing separation agent system solution contains 20 ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% of oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97° C., the reaction time is 4 hours, and the other operating steps and parameters are carried out according to Example 1.

[0071] The results showed that when the separation was not completed at 1h and 2h in Example 11 and Example 12, the polyester recovery rates were 120.46% and 111.84%, respectively, and the cotton fiber recovery rates were 56.09% and 74.21%, respectively; when the time was 3h in Example 13, the polyester recovery rate was 99.64%, and the cotton fiber recovery rate was 95.26%; when the time was 4h in Example 14, the polyester recovery rate was 99.32%, and the cotton fiber recovery rate was 80.88%. It shows that the separation and decolorization effect is best when the decolorization degradation temperature is 3h. In Example 13 and Example 14, the polyester purity of the polyester-cotton blended fabric completely separated and recovered is 100%, the polyester mass loss rate is less than 1%, and the cotton fiber mass loss rate is less than 10%. Decolorization and separation have been completed in Example 13 and Example 14, and the fabric decolorization rate can reach up to 81.61%.

[0072] Embodiment 15

[0073] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material is 1wt%, and the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97°C, the reaction time is 3h, and the other operating steps and parameters are carried out according to Example 1.

[0074] Example 16

[0075] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material is 20wt%, the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97°C, the reaction time is 3h, and the other operating steps and parameters are carried out according to Example 1.

[0076] Embodiment 17

[0077] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material is 50wt%, the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath is set to 97°C, the reaction time is 3h, and the other operating steps and parameters are carried out according to Example 1.

[0078] Embodiment 18

[0079] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material is 80wt%, the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97°C, the reaction time is 3h, and the other operating steps and parameters are carried out according to Example 1.

[0080] Embodiment 19

[0081] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material is 99wt%, the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97°C, the reaction time is 3h, and the other operating steps and parameters are carried out according to Example 1.

[0082] As a result, the polyester-cotton blended textile with a cotton content of 1wt% in Example 15 had a polyester recovery rate of 99.41% and a cotton fiber recovery rate of 93.22%; the polyester-cotton blended textile with a cotton content of 20wt% in Example 16 had a polyester recovery rate of 99.28% and a cotton fiber recovery rate of 95.97%; the polyester-cotton blended textile with a cotton content of 50wt% in Example 17 had a polyester recovery rate of 99.31% and a cotton fiber recovery rate of 94.31%; the polyester-cotton blended textile with a cotton content of 80wt% in Example 18 had a polyester recovery rate of 99.6% and a cotton fiber recovery rate of 92.42%; the polyester-cotton blended textile with a cotton content of 99wt% in Example 19 had a polyester recovery rate of 99.26% and a cotton fiber recovery rate of 92.12%. For blended textiles with a higher cotton content, hydrolysis is more likely to occur, resulting in more cotton fiber dissolution. It is shown that for polyester-cotton blended textiles with a cotton fiber content of 1-99wt%, the method of the present invention achieves decolorization and complete separation of polyester and cotton fibers, the recovery rate of separated polyester is above 99%, and the recovery rate of cotton fibers can reach up to 95.97%. The polyester purity is 100%, the polyester mass loss rate is less than 1%, the cotton fiber mass loss rate is less than 10%, and the fabric decolorization rate can reach up to 83.21%.

[0083] Embodiment 20

[0084] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material is 32wt%, the fabric color is black, and the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97°C, the reaction time is 4h, and the other operating steps and parameters are carried out according to Example 1.

[0085] Embodiment 21

[0086] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material used is 32wt%, the fabric color is gray, and the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97°C, the reaction time is 4h, and the other operating steps and parameters are carried out according to Example 1.

[0087] Embodiment 22

[0088] The difference from Example 1 is that the cotton fiber content in the waste polyester-cotton blended textile raw material used is 32wt%, the fabric color is rose red, and the added decolorizing separation agent system solution contains 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6% to 14%), 70% oxalic acid, and the balance is deionized water. The temperature of the digital display constant temperature oil bath pot is set to 97°C, the reaction time is 4h, and the other operating steps and parameters are carried out according to Example 1.

[0089] As a result, the black fabric in Example 20 has a polyester recovery rate of 99.33%, a cotton fiber recovery rate of 95.70%, and a decolorization rate of 75.27%; the gray fabric in Example 21 has a polyester recovery rate of 99.28%, a cotton fiber recovery rate of 95.31%, and a decolorization rate of 79.68%; the rose red fabric in Example 22 has a polyester recovery rate of 99.11%, a cotton fiber recovery rate of 95.62%, and a decolorization rate of 82.15%. The effect of the sodium hypochlorite aqueous solution on light-colored fabrics in the decolorization separation system is stronger than that on dark-colored fabrics, but both can achieve an ideal decolorization effect. It shows that for fabrics of different colors of polyester-cotton blended textiles, the method of the present invention achieves decolorization and complete separation of polyester and cotton fibers, and the polyester recovery rate obtained by separation is above 99%, and the cotton fiber recovery rate can reach up to 95.70%. The polyester purity is 100%, the polyester mass loss rate is less than 1%, and the cotton fiber mass loss rate is less than 10%.

[0090] From the above embodiments, it can be seen that the preferred process of the present invention for simultaneously decolorizing and separating the two components of waste polyester-cotton blended textiles based on the decolorizing separator is as follows: the waste polyester-cotton blended textiles are subjected to heating degradation with a mixed solution composed of 20 ml of sodium hypochlorite aqueous solution (with an effective chlorine content of 6% to 14%) and 70% oxalic acid, the reaction temperature for heating degradation is preferably 97° C., and the reaction time is preferably 3 hours. The cotton fiber content of the waste polyester-cotton textiles treated by the present invention is 1%-99%, that is, it is suitable for polyester-cotton blended textiles of most colors.

[0091] The polyester and cotton fibers recovered from decolorization and separation in Example 17 were analyzed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy. Figure 1 Scanning electron microscope images of waste polyester-cotton textiles before and after separation. Figure 2 Fourier transform infrared spectra of waste polyester-cotton textiles before and after separation Figure 3 Comparison of different colored waste polyester-cotton textiles before and after separation and decolorization. It can be seen that the polyester component and cotton fiber component in the treated waste polyester-cotton textiles have been effectively separated, and no cotton fiber can be observed in the separated polyester ( Figure 1 ), the polyester and cotton fibers on the surface have been completely separated, and the surface of the polyester fibers is still smooth and undamaged; the cotton fibers are completely peeled off from the state of being intertwined and entangled with the polyester, and the separated cotton fibers are broken into curved fiber bodies of different sizes.

[0092] See also Figure 2 The Fourier transform infrared spectroscopy (FTIR) analysis comparison of polyester fiber and cotton fiber before and after the reaction shows that the FTIR spectrum of the polyester fiber treated with the decolorizing agent is consistent with that of the pure polyester fiber, and no new peaks appear, indicating that the polyester fiber maintains its original chemical structure after being treated with the decolorizing agent. Compared with the untreated pure cotton fabric, the cotton fiber product treated with the decolorizing agent solution has a peak at 1611cm -1 There is an obvious carboxyl absorption peak at , indicating that the separated product contains carboxyl groups, proving that the cotton fiber is hydrolyzed and oxidized to oxidized cellulose containing carboxyl groups. Pure polyester fiber is 100% polyester fabric, and pure cotton fabric is 100% cotton fabric, both of which are provided by Fujian Huafeng New Materials Co., Ltd.

[0093] See also Figure 3 As shown in the figures before and after separation and decolorization of waste polyester-cotton textiles of different colors, it can be seen that while the polyester-cotton blended fabric is stripped of its color and restored to its state before dyeing in the decolorization separator system, the separation of the two components in the waste polyester-cotton blended textiles is completed.

[0094] Therefore, the chemical structure of the polyester separated from the waste polyester-cotton blended fabric is consistent with that of the pure polyester fiber (reference), and the chemical structure of the separated cotton fiber is basically consistent with that of the pure cotton fabric.

[0095] The specific reagent dosages and conditions used in the separation, recovery and simultaneous decolorization methods of Examples 1 to 22, as well as the specific conditions of the colored waste polyester-cotton blended textiles and the test results of various indicators are shown in Table 1.

[0096] Table 1 Example 1-Example 22 Separation and recovery and synchronous decolorization method and its test data

[0097]

[0098]

[0099] Embodiment 23

[0100] The solution obtained by filtering after the reaction in Example 6 is recovered, and after the reaction system completes filtering and separating the polyester fiber and the cotton fiber, a filtrate containing oxalic acid crystals is obtained, and the filtrate is placed in an environment of 2-4°C and cooled for 16-24h to ensure that the oxalic acid can be fully crystallized; after the oxalic acid crystals are completed, filter paper or a filter is used to leave the oxalic acid crystals on the filter, and the aqueous solution flows out through the filter. The oxalic acid crystals obtained by filtration also contain a certain amount of moisture or other impurities. They are placed in a vacuum environment and heated to evaporate the moisture and other volatile substances in the oxalic acid crystals to obtain 29.70g of dry, high-purity oxalic acid crystals. The oxalic acid obtained is not much different from the oxalic acid that does not participate in the reaction, and still presents a white crystalline state. The oxalic acid is recovered and circulated 5 times. A total of 31.27g of fresh oxalic acid was initially used. The recovery rate was calculated to show that the total amount of oxalic acid gradually decreased with the increase in the number of cycles. However, after 5 cycles, the total amount of oxalic acid recovered was still 25.9g, and the total recovery rate of 5 cycles was as high as 82.8%. The oxalic acid recovery rate of a single cycle was higher than 95%.

[0101] Comparative Example 1

[0102] Take a certain amount of polyester-cotton blended raw material with a cotton content of 32%, cut it into a block size of about 1.0000±0.0002g, put it in an oven for 4-16h, take it out, and put it in a dryer to dry to constant weight. Add 16ml of dimethyl sulfoxide to a three-necked flask and stir the dried fabric at 110℃ for 20min, collect the fabric and wash it. Put the washed fabric and 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6%~14%) into a digital display constant temperature oil bath pot at 60℃ for 1min, take it out and wash it, and then obtain a light-colored fabric and reaction liquid. Put the above decolorized fabric and 70% oxalic acid aqueous solution into a digital display constant temperature oil bath pot at 97℃ for 2h to complete the degradation of cotton fiber. After the reaction is completed, add hot water to stop the reaction. Place the mixed solution in an ultrasonic cleaning device, and perform ultrasonic deep cleaning of the polyester fiber and cotton fiber in the solution at 60℃ for 20min. The reaction mixture is then initially filtered to obtain polyester fibers, which are then washed with cold water several times, and the remaining mixed solution and washing solution are then filtered through a filter membrane, vacuum-sucked and drained, and filtered to obtain cotton fibers. Finally, the polyester fibers and cotton fibers are dried in an oven for 4-16 hours, and then placed in a dryer to cool and dry to a constant weight, and taken out and weighed within 2 minutes.

[0103] The recovery rate of polyester fiber and cotton fiber recovered in Comparative Example 1 was calculated according to the ratio of recovery rate = polyester (or cotton fiber) collected after separation / polyester (or cotton fiber) content in untreated waste polyester-cotton textiles, and the recovery rate of polyester and cotton fiber was used as an evaluation index. It was found that polyester and cotton fiber were not completely separated, the recovery rate of cotton fiber was 27.37%, the decolorization rate of fabric was 60.66%, and the recovery rate of separated polyester was above 99%. It can be seen from the test results of this comparative example that compared with the decolorization of polyester-cotton fabrics in Example 1 using a decolorizing separation agent to act simultaneously, the decolorization separation agent used in the present invention has a higher efficiency in the one-step method using a sodium hypochlorite aqueous solution and oxalic acid to act step by step on polyester-cotton fabrics within the same reaction time.

[0104] Comparative Example 2

[0105] Take a certain amount of polyester-cotton blended raw material with a cotton content of 32%, cut it into a block size of about 1.0000±0.0002g, put it in an oven for 4-16h, take it out, and put it in a dryer to dry to constant weight. Add 16ml of dimethyl sulfoxide to a three-necked flask and stir the dried fabric at 110℃ for 20min, collect the fabric and wash it. Put the washed fabric and 20ml of sodium hypochlorite aqueous solution (effective chlorine content is 6%~14%) into a digital display constant temperature oil bath pot at 60℃ for reaction for 3h, take it out and wash it, and then obtain a light-colored fabric and reaction liquid. Put the above decolorized fabric and 70% oxalic acid aqueous solution into a digital display constant temperature oil bath pot at 97℃ for reaction for 3h to complete the degradation of cotton fiber. After the reaction is completed, add hot water to stop the reaction. Place the mixed solution in an ultrasonic cleaning device, and perform ultrasonic deep cleaning of the polyester fiber and cotton fiber in the solution at 60℃ for 20min. The reaction mixture is then initially filtered to obtain polyester fibers, which are then washed with cold water several times, and the remaining mixed solution and washing solution are then filtered through a filter membrane, vacuum-sucked and drained, and filtered to obtain cotton fibers. Finally, the polyester fibers and cotton fibers are dried in an oven for 4-16 hours, and then placed in a dryer to cool and dry to a constant weight, and taken out and weighed within 2 minutes.

[0106] Taking the recovery rates of polyester and cotton fibers as evaluation indicators, it was found that the recovery rate of polyester separated in Comparative Example 2 was above 99%, the recovery rate of cotton fibers was 81.15%, the decolorization rate of fabric was 70.61%, the polyester purity was 100%, the polyester mass loss rate was less than 1%, and the cotton fiber mass loss rate was greater than 5%. The test results of this comparative example show that compared with Comparative Example 2, which uses a sodium hypochlorite aqueous solution and oxalic acid to act on the polyester-cotton fabric in steps with sufficient reaction time, the decolorization separation agent used in Example 1 of the present invention is used to act on the polyester-cotton fabric simultaneously, and the one-step method of the decolorization separation agent used is more efficient.

[0107] Comparative Example 3

[0108] Take a certain amount of blue polyester-cotton blended raw material, cut it into a block size of about 1.0000±0.0002g, put it in an oven for 4-16h, take it out, and put it in a dryer to dry to constant weight. Add 16ml of dimethyl sulfoxide to a three-necked flask and stir the dried fabric at 110℃ for 20min, collect the fabric for washing. Prepare 20ml of a mixed solvent of 5% sulfuric acid, 10g / L hydrosulfite, and 25g / L sodium hydroxide solution, and put the swollen fabric and the mixed solvent into a digital constant temperature oil bath to complete the degradation reaction of the cotton fiber. After the reaction is completed, add hot water to stop the reaction. Place the mixed solution in an ultrasonic cleaning device, and perform ultrasonic deep cleaning of the polyester fiber and cotton fiber in the solution at 60℃ for 20min. Then filter the reaction mixture preliminarily to obtain polyester fiber, wash the polyester fiber with cold water several times, and then pass the remaining mixed solution and washing liquid through a filter membrane, vacuum suction and drainage, and filter to obtain cotton fiber. Finally, the polyester fiber and cotton fiber were dried in an oven for 4-16 hours respectively, and then placed in a dryer to cool and dry to constant weight, and then taken out and weighed within 2 minutes.

[0109] The results show that the polyester and cotton fibers are not completely separated in the comparative example 3, the cotton fiber recovery rate is 32%, the fabric decolorization rate is 55.28%, and the separated polyester recovery rate is above 99%. It can be seen from the experimental results of this comparative example that compared with the weak decolorization effect of the hydrosulfite in comparative example 3, the decolorization efficiency of the decolorization separation agent used on the polyester-cotton fabric in Example 1 of the present invention is higher.

[0110] The specific reagent dosages and conditions used in the separation, recovery and simultaneous decolorization methods of Comparative Examples 1-3, as well as the specific conditions of the colored waste polyester-cotton blended textiles and the test results of various indicators are shown in Table 2.

[0111] Table 2 Comparative Examples 1-3 Separation and Recovery and Synchronous Decolorization Methods and Test Data

[0112]

[0113]

[0114] In summary, the present invention is significantly more advanced than the prior art, can solve the problem of recycling waste polyester-cotton blended textiles, utilizes the combination of decolorizing agent and low-cost green good solvent organic acid to strip the color of polyester-cotton blended textiles and restore them to the state before dyeing, while selectively depolymerizing cotton fibers to release polyester fibers for effective separation, the decolorization rate of polyester-cotton is more than 80%, the recovery rate of polyester in waste polyester-cotton blended textiles is more than 99%, the purity is 100%, and the polyester mass loss rate is less than 1%; the recovery rate of cotton fibers can reach more than 95%, the decolorization and separation process is advanced, does not pollute the environment, has good decolorization effect, and the chemical, physical and mechanical properties of the recycled polyester and cotton fibers are stable, which is a very ideal method for synchronous decolorization and efficient component separation of waste polyester-cotton blended textiles.

[0115] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A method for separating, recovering and simultaneously decolorizing colored waste polyester-cotton blended textiles, characterized in that: The following steps are involved: The pre-treated waste polyester-cotton blended textiles are mixed with a decolorizing and separating agent solution of a certain concentration, placed in a normal pressure container for heating and degradation, and after the reaction is completed, hot water is added to terminate the reaction; The reaction mixture is ultrasonically vibrated and vacuum filtered to obtain preliminarily recovered polyester fibers and a preliminarily filtrate. The preliminarily recovered polyester fibers are washed several times, the washing liquid and the preliminarily filtrate are mixed, and vacuum filtered again to obtain preliminarily recovered cotton fibers, which are then dried to obtain recovered polyester fibers and recovered cotton fibers.

2. The separation, recovery and simultaneous decolorization method according to claim 1, characterized in that: The decolorizing separation agent comprises a decolorizing agent and an organic acid, wherein the decolorizing agent is one of hypochlorous acid, hydrogen peroxide, dimethylformamide, and thiourea dioxide, or a mixture of two or more thereof, and the organic acid is one of oxalic acid, p-toluenesulfonic acid, malic acid, acetic acid, and citric acid.

3. The separation, recovery and simultaneous decolorization method according to claim 2, characterized in that: The decolorizing and separating agent is composed of 6% to 14% effective chlorine content in hypochlorous acid, 60-80% oxalic acid and the balance deionized water.

4. The separation, recovery and simultaneous decolorization method according to claim 1, characterized in that: The pre-treatment includes: The waste polyester-cotton blended textiles are subjected to swelling treatment, then washed and dried to obtain pre-treated waste polyester-cotton blended textiles; The swelling treatment uses a high polarity swelling agent, preferably, the high polarity swelling agent is dimethyl sulfoxide or cyclohexanone, more preferably, the high polarity swelling agent is dimethyl sulfoxide.

5. The separation, recovery and simultaneous decolorization method according to claim 4, characterized in that: The temperature of the swelling treatment is 110-130° C., and the swelling treatment time is 20-40 minutes.

6. The separation, recovery and simultaneous decolorization method according to claim 1, characterized in that: The temperature of the heating degradation is 100-110° C., and the time of the heating degradation is 1-3 hours.

7. The separation, recovery and simultaneous decolorization method according to claim 1, characterized in that: The solid-liquid mass ratio of the pre-treated waste polyester-cotton blended textile to the decolorizing separator solution is 1:10-100.

8. The separation, recovery and simultaneous decolorization method according to claim 1, characterized in that: The temperature of the ultrasonic oscillation was set to 60° C., and the time was set to 20 min.

9. The separation, recovery and simultaneous decolorization method according to claim 1, characterized in that: The method also includes recovering the filtrate after respectively recovering the polyester and cotton fibers, cooling it in an environment of 2-4° C. for 16-24 hours, filtering it to obtain crude oxalic acid crystals, and drying it in a vacuum environment to obtain high-purity oxalic acid crystals.

10. A polyester and / or cotton fiber textile, characterized in that: The recovered polyester fiber and / or recovered cotton fiber is produced by the separation, recovery and simultaneous decolorization method according to any one of claims 1 to 9.

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