Method for preparing reactive colored polymer dye and dyed fabric from waste dyed cotton fabric

Abstract

The present invention belongs to the field of light textile industry, and discloses a method for preparing reactive colored polymer dyes and colored fabrics therefrom using waste dyed pure cotton fabrics. The method comprises the following steps: adding the waste dyed pure cotton fabric into an aqueous solution of molten salt, heating and stirring with microwave under the protection of inert gas until dissolved to obtain a cotton fabric molten salt solution without residual solid particles, cooling, washing and drying; under the protection of light avoidance and inert atmosphere, adding the dried colored cellulose into an oxidant solution for treatment to introduce reactive groups, and then washing with water and drying to obtain reactive colored polymer dyes. Periodate is used to oxidize the waste colored cellulose, and the oxidant does not damage the chromophore of the reactive dye, thereby introducing reactive groups, aldehyde groups, into the molecular structure of the waste colored cellulose. It can react with polar groups in protein-based fabrics to greatly ensure the color fastness of the dyed protein-based fabrics.

Description

Technical Field

[0001] The present invention belongs to the field of light textile industry, and particularly relates to a method for preparing reactive colored polymer dyes and colored fabrics therefrom from waste dyed pure cotton fabrics. Background Art

[0002] With the improvement of consumers' consumption ability of textile products, the production volume of waste textiles in China reaches 20 million tons. In 2022, the National Development and Reform Commission, the Ministry of Commerce, and the Ministry of Industry and Information Technology jointly issued the "Implementation Opinions on Accelerating the Recycling of Waste Textiles", proposing that by 2025, the recycling rate of waste textiles reaches 25%, and the output of recycled fibers from waste textiles reaches 2 million tons. By 2030, the recycling rate of waste textiles reaches 30%, and the output of recycled fibers from waste textiles reaches 3 million tons. It can be seen that developing an efficient recycling process for waste textiles will be of great significance for the recycling of waste textiles.

[0003] Cellulose fibers represented by cotton are the most widely used natural fibers currently. Their commercial products are mainly dyed with reactive dyes at present, and the reactive dyes and cellulose fibers are combined in the form of covalent bonds. Therefore, when the textiles made of cotton fibers dyed with reactive dyes are discarded, it is very difficult to replace the reactive dyes from the cotton fibers without causing pollution. At present, the recycling treatment of textiles made of cotton fibers dyed with reactive dyes mainly includes decolorization treatment with strong acids, strong alkalis, oxidants, etc. The above methods will all produce wastewater to a certain extent, and there have also been reports on processing colored cellulose textiles into colorants in recent years. The Chinese invention patent authorization text CN10981155B reports a method for producing dyes from textile waste to dye fabrics. The specific process is to grind the colored textile waste into powders with a size of 5-25 μm by mechanical grinding, and then dye the fabrics treated with cationic treatment agents to finally obtain dyed textiles. However, as is well known, it is very difficult to grind solids very small by mechanical crushing methods, and the particle size distribution of the crushed particles is also very wide. Similarly, the Chinese invention patent publication text CN115233471A also reports a method for preparing colored dyes from waste cotton fabrics. The specific process is to mechanically crush the waste colorless pure cotton fabrics to obtain ultrafine powders, then treat the above powders with polyethyleneimine and crosslinking agent glutaraldehyde to introduce imino groups, and then adsorb anionic dyes such as reactive dyes in the wastewater to obtain colored dyes, and then apply them to textiles by pigment printing. However, as is well known, the molecular structure of reactive dyes is relatively small, and they are mainly combined with imino groups in the form of salt bonds, and the fastness of the colored textiles will be lower than that of normal dyeing. Similarly, the Chinese invention patent publication text CN108504056A reports a method for preparing colored nanocellulose / polylactic acid composite films. The specific process is to use dyed nanocellulose as the aqueous phase and polylactic acid dissolved in organic solvents as the organic phase, combine the two into a Pickering emulsion, and then volatilize the organic solution and water to prepare a colored film by hot pressing. However, as is well known, the specific surface area of nanocellulose is greatly increased, and a large amount of colored wastewater will be generated during the water washing for removing floating color after dyeing, and the volatilization of organic solvents will pose a certain risk to the working environment. The Chinese invention patent publication text CN111793223A reports a method for preparing nanoscale regenerated cellulose using a molten salt system. The specific process is that this method uses colorless cellulose or cellulose containing lignin as the raw material, and uses Li + , Mg 2+ , Zn 2+ , Ag +Using hydrates of chlorides, bromides, iodates, perchlorates, and nitrates of etc. as solvents to prepare nanospheres, nanofibrils, etc. of cellulose. However, as is well known, cellulose fibers dyed with reactive dyes contain structural elements such as aromatic rings, water-soluble groups, and secondary amine bridge bonds in their macromolecular structures, making many molten salts unsuitable.

[0004] In summary, the problems existing in the preparation of colorants from cotton fabrics dyed with reactive dyes currently are as follows:

[0005] (1) According to the second law of thermodynamics, when preparing colored particles by mechanically pulverizing fabrics, the particle size of the colored particles will be very large and the particle size distribution range is also relatively wide.

[0006] (2) Anionic dyes are adsorbed onto cationic cotton fabric particles and are bound in the form of salt bonds. This binding force is relatively weak compared to chemical bonds. Therefore, the color fastness of the finally processed dyed fabrics is lower than that of traditional dyed textiles.

[0007] (3) Conventional metal molten salts, such as Mg 2+ , Ca 2+ , Zn 2+ , Fe 2+ , Fe 3+ etc., will form complexes with strong polar groups, such as sulfonate groups, on cotton fabrics dyed with reactive dyes, resulting in the inability of conventional metal molten salts to dissolve cotton fabrics dyed with reactive dyes. At the same time, due to the presence of water-soluble groups such as sulfonate groups in the macromolecular structure of cotton fabrics dyed with reactive dyes, there will be a competitive relationship with the chlorides, bromides, and perchlorates of Li + for water molecules, ultimately making the conventional process inappropriate. Summary of the Invention

[0008] In order to overcome the above-mentioned disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a method for preparing reactive colored polymer dyes from waste dyed pure cotton fabrics.

[0009] Another object of the present invention is to provide the reactive colored polymer dyes prepared by the above method.

[0010] A further object of the present invention is to provide the application of the above reactive colored polymer dyes in fabric dyeing.

[0011] The object of the present invention is achieved by the following solutions:

[0012] A method for preparing reactive colored polymer dyes from waste dyed pure cotton fabrics, comprising the following steps:

[0013] (1) Add the waste dyed pure cotton fabric into an aqueous solution of molten salt, introduce an inert gas as the protective gas, place it in a microwave reactor, heat and stir until it dissolves to obtain a cotton fabric molten salt solution without residual solid particles;

[0014] (2) After cooling the above-mentioned cotton fabric molten salt solution without residual solid particles, wash it with water until the washing solution contains no molten salt, and then dry the washed colored cellulose for standby;

[0015] (3) Under the protection of light avoidance and inert atmosphere, add the dried colored cellulose into an oxidant solution for treatment to introduce reactive groups, and then wash and dry it with water to obtain a reactive colored polymer dye derived from waste dyed pure cotton fabric.

[0016] In step (1), the color depth (K / S value) of the waste dyed pure cotton fabric is between 5 and 30; the structure of the reactive dye of the waste dyed pure cotton fabric is one or more of anthraquinone dyes (such as reactive blue 5 (the reactive group is monochloro-s-triazine), reactive blue 19 (the reactive group is vinyl sulfone), and reactive blue 261 (the reactive group is monofluoro-s-triazine), etc.), polyazo reactive dyes (such as the primary color dyes reactive red 195, reactive yellow 145, and reactive blue 194, etc.), and violanthrone reactive dyes (such as reactive black 2 (the reactive group is vinyl sulfone + vinyl sulfone)).

[0017] In step (1), the molten salt is a lithium halide (such as lithium chloride, lithium bromide, lithium iodide), and the mass fraction of the molten salt in the aqueous solution of the molten salt is 30% - 60%.

[0018] In step (1), the relative dosage of the waste dyed pure cotton fabric and the molten salt satisfies that the mass of the waste dyed pure cotton fabric accounts for 0.1% - 4% of the total mass of the waste dyed pure cotton fabric and the aqueous solution of the molten salt;

[0019] In step (1), the inert gas is at least one of nitrogen, carbon dioxide, and argon;

[0020] In step (1), the output power of the microwave reactor is 500 - 800W, the microwave time is 5 min - 120 min, the microwave temperature is 80 - 150 °C, the stirring method is mechanical stirring, and the stirring speed is 100 - 200 rpm.

[0021] The hydrogen bonds formed between numerous hydroxyl groups between cellulose macromolecular chains will be affected by Li in the molten salt +is opened, so that the cellulose has a certain degree of dispersion in a suitable solution. In the macromolecular structure of the cotton fabric dyed with reactive dyes, in addition to the hydrogen bonds formed between numerous hydroxyl groups in the cellulose macromolecular chain, strong polar groups also include water-soluble groups such as sulfonate groups. The sulfonate groups will form hydrated ions with water molecules in the molten salt. Therefore, the hydrogen bonds between hydroxyl groups in the macromolecular structure of the cellulose modified by reactive dyes are broken by Li + with increased difficulty and slower opening speed. By introducing microwaves, the molecular heat is generated due to the intense oscillation of Li + , and at the same time, the induction force and dispersion between the halogen anions and Li + are also enhanced in the microwave, thereby accelerating the dissolution of the cellulose fiber dyed with reactive dyes.

[0022] In step (2), the washing liquid after washing with water can also be collected, and the lithium metal molten salt can be recovered by distillation and freeze-drying.

[0023] The drying described in step (2) is preferably freeze-drying, and the freeze-drying time is 1 - 24 h.

[0024] The inert atmosphere described in step (3) is at least one of nitrogen, carbon dioxide, and argon;

[0025] The oxidant described in step (3) is at least one of sodium periodate and potassium periodate.

[0026] In the oxidant solution described in step (3), the solvent is water; the concentration of the oxidant in the oxidant solution is 1 - 10 g / L; the pH of the oxidant solution is 5 - 7;

[0027] The dosage of the colored cellulose described in step (3) satisfies that the bath ratio of the oxidant solution to the dried colored cellulose is 10 - 30:1.

[0028] The temperature of the treatment described in step (3) is 10 - 30 °C, and the treatment time is 10 min - 360 min.

[0029] The number of times of washing described in step (3) is 5 - 10 times; the drying is freeze-drying, the freeze-drying temperature is -50 to -80 °C, and the freeze-drying time is 1 - 24 h.

[0030] A reactive colored polymer dye derived from waste dyed pure cotton fabric prepared by the above method.

[0031] Application of the above reactive colored polymer dye derived from waste dyed pure cotton fabric in protein fabric dyeing.

[0032] The application of the reactive colored polymer dye in the dyeing of protein fabrics specifically includes the following steps: dyeing the protein fabric with the obtained reactive colored polymer dye by padding, pad dyeing or printing, and then performing a fixation treatment on the dyed fabric.

[0033] The dyeing bath ratio is (1 - 20):1, the dosage of the reactive colored polymer dye is 5 - 10% owf, the dyeing pH value is 4 - 6, the dyeing temperature is 80 - 95 °C, and the dyeing time is 10 - 30 min.

[0034] The fixing agent is a water-soluble polyurethane-based cationic fixing agent, the bath ratio of the fixing bath is (1 - 20):1, the dosage of the fixing agent is 1 - 10 g / L, the fixing temperature is 40 - 80 °C, and the fixing time is 10 - 30 min.

[0035] The present invention has the following advantages and beneficial effects compared with the prior art:

[0036] (1) Treating the colored waste cotton fabric with a metal molten salt based on lithium halides (such as lithium chloride, lithium bromide, lithium iodide), the extremely polar Li + attacks the macromolecular chain of cellulose bound by hydrogen bonds, causing the macromolecular chains to lose the force between each other and disperse in the molten salt. The crystallinity of the colored waste cotton fabric drops significantly. At the same time, the molten salt does not destroy the covalent bond between the reactive dye and the cellulose fiber, so no colored wastewater is produced, meeting the requirements of clean production in the textile industry.

[0037] (2) Oxidizing the waste colored cellulose with periodate to prepare a reactive colored polymer dye. The oxidant does not destroy the chromophore of the reactive dye, thus introducing a reactive group aldehyde group into the molecular structure of the waste colored cellulose.

[0038] (3) The protein-based fabric contains abundant polar groups such as amino, hydroxyl, and mercapto groups, which can form imino, amino, acetal, hemiacetal, thioacetal, etc. with the above reactive colored polymer dye. Combining with the fixation reaction of the cationic fixing agent can greatly ensure the dyeing fastness of the dyed protein-based fabric, thereby realizing the recycling and reuse of the waste reactive dyed cellulose-based fabric and reducing the environmental pollution caused by the waste dyed cellulose fabric. Description of the Drawings

[0039] Figure 1 It is the decolorization principle of the present invention.

[0040] Figure 2 It is the absorbance curve of Reactive Red 195, the washing liquid after LiBr dissolution, and the washing liquid after sodium periodate oxidation in Example 1.

[0041] Figure 3 FT-IR spectra of the waste solid-color cotton fabric, the solid-color cellulose after LiBr dissolution, and the solid-color cellulose after sodium periodate oxidation in Example 1.

[0042] Figure 4 X-ray diffraction patterns of the waste solid-color cotton fabric, the solid-color cellulose after LiBr dissolution, and the solid-color cellulose after sodium periodate oxidation in Example 1.

[0043] Figure 5 SEM images of the reactive polymer dye particles prepared from the waste solid-color cotton fabric in Example 1.

[0044] Figure 6 K / S curves of the silk fabric dyed with the reactive polymer dye prepared from the waste solid-color cotton fabric in Example 1.

[0045] Figure 7 Silk fabric printed with the reactive polymer dye prepared from the waste solid-color cotton fabric in Example 2. Detailed implementation manners

[0046] The present invention will be further described in detail below with reference to the examples and the accompanying drawings, but the implementation manners of the present invention are not limited thereto. For those conditions not specified in the examples, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0047] Unless otherwise specified, the reagents used in the examples can be conventionally purchased from the market.

[0048] Example 1

[0049] (1) LiBr dissolution: Prepare a molten salt solution of 200 g of LiBr with a mass fraction of 58% using distilled water. Accurately weigh 6 g of the waste solid-color cotton fabric, which is dyed with reactive red 195 and has a color depth (K / S) of 23. Cut the above cotton fabric into small pieces of 5×5 mm in advance with scissors, and then add them to the above molten salt solution. Then start mechanical stirring at a speed of 100 rpm, heat to 120 °C, then turn on the microwave (output power: 500 watts) and continue for 60 min. It is observed that there is no solid particle residue in the cotton fabric molten salt solution. After the above solution is cooled to room temperature, add distilled water to extract LiBr 5 times, collect the above extraction solution, and recover the lithium molten salt by distillation and freeze-drying. Transfer the above colored cellulose to a freeze dryer for drying treatment, and the drying time is 3 h.

[0050] (2) Oxidization by oxidant: Take 4 g from the above-mentioned dried colored cellulose, place it in a 5 g / L sodium periodate solution, process it in the dark and introduce nitrogen. The bath ratio is 20:1, the pH value of the treatment solution is maintained at 6 ± 0.5, the treatment temperature is 25 °C, and the treatment time is 120 min. Then wash the above-mentioned oxidized and recovered colored cellulose with distilled water 5 times, and perform freeze-drying treatment. The drying time is 6 h, and finally a reactive colored polymer dye derived from waste colored cotton fabrics is obtained.

[0051] (3) Dyeing + Fixing: Take the above-mentioned reactive colored polymer dye derived from waste colored cotton fabrics to impregnate silk fabrics. The bath ratio is 10:1, the dosage of the polymer dye is 8% owf, and the pH value is 5.5. The specific dyeing process curve is: dye at room temperature for 20 min, then slowly heat up to 90 °C at a rate of 1 °C / min, and keep it at this temperature for 30 min. Then drain the water in the dye bath, add a fixing bath, the bath ratio is 10:1, the fixing agent is water-soluble cationic polyurethane, and its dosage is 1 g / L. The treatment temperature is 60 °C, and the treatment time is 20 min. Finally, a silk fabric dyed with a reactive colored polymer dye recovered from waste colored cellulose is obtained.

[0052] The K / S value of the waste plain-colored pure cotton fabric reaches about 23. Take the washing liquid after LiBr dissolution and water washing in step (1) and the washing liquid after oxidation with sodium periodate as the oxidant and washing with distilled water in step (2) respectively, and test the maximum absorption wavelength in the visible light region (400 - 800 nm). The dye Reactive Red 195 has the maximum absorbance at 525 nm, while the maximum absorption wavelength is hardly detected in the two washing liquids. See the appendix Figure 2 for details, indicating that there is no color in the washing solution. This is because the chemical bond between the reactive dye and the cellulose fiber is not damaged, so there is no absorbance when testing the washing liquid, which shows that the present invention will not produce colored wastewater.

[0053] The infrared spectra of the waste plain-colored pure cotton fabric, the plain-colored cellulose after LiBr dissolution in step (1), and the plain-colored cellulose after oxidation with sodium periodate in step (2) are shown in the appendix Figure 3 . It can be found from the figure that the main change in the three curves is that there will be an additional stretching vibration peak of the carbonyl group (C=O) in the aldehyde group at 1722 cm -1 for the plain-colored cellulose after oxidation with sodium periodate.

[0054] The X-ray diffraction results of the waste plain-colored pure cotton fabric, the plain-colored cellulose after LiBr dissolution in step (1), and the plain-colored cellulose after oxidation with sodium periodate in step (2) are shown in the appendix Figure 4The peaks of the discarded solid-color pure cotton fabric appear at 14.8°, 16.6°, 22.8°, and 34.5°, and the crystallinity is 83.5%; the peaks of the solid-color cellulose after LiBr dissolution appear at 12.2°, 20.1°, and 22.3°, and the crystallinity drops to 54.2%; the peaks of the solid-color cellulose after sodium periodate oxidation appear at 15.5°, 20.6°, and 22.4°, and the crystallinity further drops to 43.1%. A lower crystallinity means an increase in the amorphous region of the prepared cellulose-based reactive polymer dye, and its contact area with the subsequent treated protein-based fabric will increase, which helps the dyeing and fixation of the reactive polymer dye.

[0055] The size of the reactive polymer dye prepared from the discarded solid-color pure cotton fabric is within 0 - 0.5 μm. The specific results are shown in the appendix Figure 5 A smaller diameter is more conducive to the combination of the dye and the protein fabric.

[0056] The K / S curve of the silk fabric dyed with the reactive polymer dye prepared from the discarded solid-color pure cotton fabric is shown in the appendix Figure 6 As can be seen from the figure, the color depth of the dyed silk fabric is 11.8, indicating that the dyed silk fabric with this reactive polymer dye has obtained a relatively high color depth, meeting the requirements of current commercial dyed fabrics.

[0057] Example 2

[0058] The method of Example 2 is basically the same as that of Example 1.

[0059] The difference between Example 2 and Example 1 is that the color of the discarded solid-color pure cotton fabric described in step (1) is green, and the color depth (K / S value) is 18. The coloring method for the silk fabric in step (3) is printing, specifically: preparing printing paste - printing - drying - baking. The composition of the printing paste is: 10 g / L reactive colored polymer dye, 7 g / L thickener TH5000 (Rudolf), 40 g / L binder BO6000 (Rudolf), and the solvent is distilled water. The preparation sequence is to add water first, then add the thickener and binder under high-speed shearing conditions, and finally add the reactive colored polymer dye. The shearing speed is 7000 rpm / min, and the shearing time is 10 min. Printing process: The mesh number of the screen is 150, and the liquor pickup is 80%. The drying temperature is 90 °C, and the drying time is 1 min. The baking temperature is 140 °C, and the baking time is 3 min. The silk fabric printed with the reactive polymer dye prepared from the discarded solid-color pure cotton fabric is shown in Figure 7 .

[0060] Example 3

[0061] The method of Example 3 is basically the same as that of Example 1.

[0062] Example 3 is different from Example 1. In the waste solid-color pure cotton fabric described in step (1), the solid-color fabric is dyed with Reactive Blue 19, and the color depth (K / S value) is 9.

[0063] Example 4

[0064] The method of Example 4 is basically the same as that of Example 1.

[0065] Example 4 is different from Example 1. In the waste solid-color pure cotton fabric described in step (1), the solid-color fabric is dyed with Reactive Black 2, and the color depth (K / S value) is 14.

[0066] Example 5

[0067] The method of Example 5 is basically the same as that of Example 1.

[0068] Example 5 is different from Example 1. In the waste solid-color pure cotton fabric described in step (1), the solid-color fabric is dyed with Reactive Red 195, Reactive Yellow 145 and Reactive Blue 194 in a mass ratio of 1:1:1, and the dyed fabric is black, and the color depth (K / S value) is 19.

[0069] Example 6

[0070] The method of Example 6 is basically the same as that of Example 2.

[0071] Example 6 is different from Example 2. In the waste solid-color pure cotton fabric described in step (1), the used solid-color fabric is dyed with Reactive Black 2, the color depth (K / S value) is 14, and it is used for subsequent printing treatment.

[0072] Comparative Example 1

[0073] The dyeing method of Comparative Example 1 is basically the same as that of Example 1, except that the reactive colored polymer dye used is not treated with sodium periodate oxidation, that is, there is no step (2).

[0074] Comparative Example 2

[0075] The method of Comparative Example 2 is basically the same as that of Example 1.

[0076] The dyeing method of Comparative Example 2 is basically the same as that of Example 1, except that the dye used in step (3) is not the reactive colored polymer dye derived from waste colored cotton fabric, but Acid Red 97, and the dye dosage is 2.2% owf.

[0077] Comparative Example 3

[0078] The method of Comparative Example 3 is basically the same as that of Example 1.

[0079] The oxidation method of Comparative Example 3 is basically the same as that of Example 1, except for the oxidation process conditions. The sodium periodate solution is not treated in the dark, the treatment temperature is 80 °C, and the treatment time is 30 min. After oxidation with sodium periodate, the cellulose after being washed with distilled water is dried. Due to the peroxidation of sodium periodate, the structure of the chromophore in the reactive dye changes, and the color of the polymer dye changes from red to light yellow similar to that of raw cotton fibers.

[0080] Comparative Example 4

[0081] The method of Comparative Example 4 is basically the same as that of Example 1.

[0082] The LiBr method of Comparative Example 4 is basically the same as that of Example 1, except that the mass fraction of LiBr in the aqueous LiBr solution is 25%. As a result, due to the relatively large content of water molecules, LiBr cannot form an effective hydrate, so the dissolution of the red pure cotton fabric was not observed finally.

[0083] A method for preparing reactive colored polymer dyes and their colored fabrics from waste dyed pure cotton fabrics according to the present invention, the color fastness of the treated silk fabrics is shown in Table 1 below:

[0084] Table 1 Color fastness of silk fabrics treated in Examples 1-6 and Comparative Examples 1-2

[0085]

[0086]

[0087] It can be found from the table that Comparative Example 1 is a cellulose-based polymer dye without introducing reactive groups, and its washing fastness and rubbing fastness are about 1 level lower than those of Example 1. Except for the light fastness, the washing fastness and rubbing fastness of Comparative Example 1 do not meet the requirements of commercial products for color fastness. In Examples 1, 2, 3, 4, 5 and 6, due to the introduction of reactive groups in the polymer dye and the post-treatment of fixing the color after dyeing, the color fastness of the treated silk fabrics basically reaches the color fastness of commercial colored silk products.

[0088] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing reactive colored polymer dyes from waste dyed cotton fabrics, characterized in that It includes the following steps: (1) Add the waste dyed pure cotton fabric into an aqueous solution of molten salt, introduce an inert gas as a protective gas, put it into a microwave reactor, heat and stir until it dissolves to obtain a cotton fabric molten salt solution without solid particle residues; (2) After cooling the above-mentioned cotton fabric molten salt solution without solid particle residues, wash it with water until the washed solution does not contain molten salt, and then dry the washed colored cellulose for standby; (3) Under the protection of light avoidance and inert atmosphere, add the dried colored cellulose into an oxidant solution for treatment to introduce reactive groups, and then wash and dry it with water to obtain a reactive colored polymer dye derived from waste dyed pure cotton fabric.

2. The method for preparing a reactive colored polymer dye from waste dyed pure cotton fabric according to claim 1, wherein: In step (1), the color depth of the waste dyed pure cotton fabric is between 5 and 30; the structure of the reactive dye of the waste dyed pure cotton fabric is one or a compound dye composed of at least two of anthraquinone type, polyazo type reactive dyes, and violanthrone type reactive dyes.

3. The method for preparing a reactive colored polymer dye from waste dyed pure cotton fabric according to claim 2, wherein: In step (1), the reactive dye of the waste dyed pure cotton fabric is one or a compound dye composed of at least two of reactive blue 5, reactive blue 19, reactive blue 261, reactive red 195, reactive yellow 145, reactive blue 194, and reactive black 2.

4. The method for preparing a reactive colored polymer dye from waste dyed pure cotton fabric according to claim 1, wherein: In step (1), the molten salt is a lithium halide, and the mass fraction of the molten salt in the aqueous solution of the molten salt is 30% - 60%; The relative dosage of the waste dyed pure cotton fabric and the molten salt in step (1) satisfies that the mass of the waste dyed pure cotton fabric accounts for 0.1% - 4% of the total mass of the waste dyed pure cotton fabric and the aqueous solution of the molten salt.

5. The method for preparing a reactive colored polymer dye from waste dyed pure cotton fabric according to claim 4, wherein: In step (1), the molten salt is at least one of lithium chloride, lithium bromide, and lithium iodide.

6. The method for preparing a reactive colored polymer dye from waste dyed pure cotton fabric according to claim 1, wherein: In step (1), the output power of the microwave reactor is 500 - 800W, the microwave time is 5 min - 120 min, the microwave temperature is 80 - 150 °C, the stirring method is mechanical stirring, and the stirring speed is 100 - 200 rpm.

7. The method for preparing a reactive colored polymer dye from waste dyed pure cotton fabric according to claim 1, wherein: In step (3), the oxidant is at least one of sodium periodate and potassium periodate.

8. The method for preparing a reactive colored polymer dye from waste dyed pure cotton fabric according to claim 1, wherein: In step (3), the solvent in the oxidant solution is water; the concentration of the oxidant in the oxidant solution is 1-10 g / L; the pH of the oxidant solution is 5-7; In step (3), the dosage of the colored cellulose satisfies that the bath ratio of the oxidant solution to the dried colored cellulose is 10-30:

1.

9. The method for preparing the reactive colored polymer dye from waste dyed cotton fabric according to claim 1, characterized in that: In step (3), the temperature of the treatment is 10-30 °C, and the time of the treatment is 10 min-360 min.

10. A reactive colored polymer dye prepared by the method according to any one of claims 1-9.

11. Use of the reactive colored polymer dye according to claim 10 in the dyeing of protein fabrics.

12. Use of the reactive colored polymer dye according to claim 11 in dyeing protein fabrics, characterized in that It includes the following steps: dyeing the protein fabric with the obtained reactive colored polymer dye by padding, pad dyeing or printing, and then performing a fixing treatment on the dyed fabric.

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