Highly color-fast fabric dye and method of making same

Abstract

This invention discloses a high-colorfastness fabric dye and its preparation method, relating to the field of novel functional dye technology. The method includes: ultrasonically extracting turmeric powder and distilling under reduced pressure to obtain a concentrated dye pigment solution; reacting it with β-cyclodextrin to form an inclusion complex, followed by γ-aminopropyltriethoxysilane graft modification to obtain a silanized coated modified powder; subjecting the powder to multiple alternating deposition self-assemblies in tannic acid aqueous solution and chitosan acetate solution to construct a multilayer composite shell; finally, mixing anhydrous citric acid and polyethylene glycol 400 with the above multilayer composite powder, drying, and grinding to obtain the final product. This invention significantly improves the structural stability of the dye and its anchoring bond with fibers through the synergistic effects of cyclodextrin molecular coating, silanized cross-linked shells, tannic acid / chitosan layer-by-layer self-assembly, and citric acid chemical cross-linking and polyethylene glycol physical compatibilization. The resulting product exhibits excellent lightfastness, washfastness, and rubbing fastness.

Description

Technical Field

[0001] This invention relates to the field of novel functional dyes, specifically to a high color fastness fabric dye and its preparation method. Background Technology

[0002] Natural plant dyes have gained increasing attention in the textile dyeing field due to their advantages such as being environmentally friendly, renewable, and biocompatible. Compared with synthetic dyes, natural dyes are non-toxic and harmless to the human body, and can be naturally degraded, aligning with current trends in sustainable development and green manufacturing. However, in practical applications, natural dyes suffer from prominent problems such as low colorfastness, poor wash resistance, and severe fading under sunlight, which greatly limits their widespread application. Currently, methods to improve the colorfastness of natural dyes mainly include metal mordant dyeing and chemical fixing agent dyeing. While metal mordant dyeing is effective, the heavy metal salts such as chromium and copper used can pollute the environment, contradicting the concept of green printing and dyeing. Although chemical fixing agent dyeing is simple to operate, it often suffers from short-lasting colorfastness and a significant decrease in colorfastness after repeated washing. Summary of the Invention

[0003] The purpose of this invention is to provide a high color fastness fabric dye and its preparation method to solve the technical problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for preparing a fabric dye with high color fastness includes the following steps:

[0006] 1) The dried turmeric was crushed into turmeric powder, added to an ethanol aqueous solution for ultrasonic extraction, filtered and the filtrate was collected, and the filtrate was concentrated by vacuum distillation to obtain a dye pigment concentrate.

[0007] 2) Dissolve β-cyclodextrin in deionized water to obtain an aqueous solution, then add the dye pigment concentrate, react to form an inclusion complex suspension, and after standing crystallization, filtration and washing, obtain the wet inclusion complex product;

[0008] 3) The wet product of the inclusion compound was dispersed in anhydrous ethanol, and glacial acetic acid was added to adjust the system to acidity. Then, γ-aminopropyltriethoxysilane was added to carry out the grafting reaction. After the reaction was completed, the product was separated by centrifugation, washed, dried and ground to obtain silanized coated modified dye powder.

[0009] 4) The silanized coated modified dye powder is added to a tannic acid aqueous solution for adsorption and deposition. After separation and washing, it is added to a chitosan acetic acid solution for deposition, and then separated and washed again. The above tannic acid deposition and chitosan deposition are regarded as a complete self-assembly cycle. This cycle is repeated many times to construct an alternating composite shell. Finally, after separation, drying and grinding, a multilayer composite coated modified dye powder is obtained.

[0010] 5) Dissolve anhydrous citric acid and polyethylene glycol 400 in deionized water to obtain an auxiliary aqueous solution. Add multilayer composite coated modified dye powder, stir and mix to form a uniform paste mixture. Finally, after drying, grinding and sieving, the high color fastness fabric dye product is obtained.

[0011] In the technical solution of this invention, the color fastness of fabric dyes is improved synergistically from the following aspects: (1) Modification of dye molecules by cyclodextrin-silane coupling: β-cyclodextrin is a truncated cone-shaped cavity molecule composed of 7 glucose units cyclically linked. Its cavity interior is hydrophobic and its exterior is hydrophilic. The cavity size matches the molecular size of most natural dye pigment molecules. During the inclusion process, the hydrophobic aromatic ring structure in the dye pigment molecule enters the cavity of β-cyclodextrin by means of hydrophobic driving force and van der Waals force, forming a stable host-guest supramolecular inclusion complex. This molecular-level encapsulation structure wraps the dye pigment molecule inside the cage-like cavity, making it less susceptible to direct erosion from external light, heat and washing liquid, thereby greatly improving the lightfastness and wash fastness of the dye. Building upon this, the inclusion complex surface was silanized and grafted with γ-aminopropyltriethoxysilane. Under the acidic environment provided by glacial acetic acid, the ethoxy groups of the silane coupling agent underwent hydrolysis to generate active silanol groups. These silanol groups, on the one hand, underwent dehydration condensation with the hydroxyl groups on the inclusion complex surface to form covalent bonds and were grafted onto the surface; on the other hand, the silanol groups formed a Si-O-Si crosslinking network through intermolecular dehydration condensation, ultimately constructing a dense organosilicon crosslinked shell on the outer surface of the inclusion complex. This shell further enhanced the physical barrier protection for the internal pigment molecules. Simultaneously, the large number of free amino groups retained in the shell provided abundant active reaction sites for subsequent layer-by-layer self-assembly modification and binding with fibers during dyeing, fundamentally improving the structural stability and fixation potential of the dye molecules. (2) Surface modification of dye powder through layer-by-layer self-assembly of tannic acid and chitosan: The amino groups on the surface of the silanized and modified dye powder are positively charged in solution. Tannic acid, as a natural polyphenol compound, contains a large number of phenolic hydroxyl groups, exhibiting significant negative charge and strong hydrogen bond donor capacity. When the dye powder is dispersed in a tannic acid solution, the tannic acid spontaneously adsorbs and deposits on the powder surface through electrostatic attraction and hydrogen bonding with the amino groups, forming a dense phenolic hydroxyl enrichment layer. Chitosan, as a natural cationic polysaccharide, has protonated amino groups that impart positive charge, and it self-assembles and deposits with the tannic acid coating again through electrostatic attraction and hydrogen bonding. Through multiple alternating depositions, a multilayer polyelectrolyte composite shell of tannic acid / chitosan is constructed layer by layer on the surface of the dye powder. This shell layer enriches the surface of dye particles with a large number of active functional groups such as amino and phenolic hydroxyl groups. During the dyeing process, these groups can establish strong hydrogen bonds and ionic bonds with the hydroxyl groups on the surface of cellulose fibers, achieving efficient anchoring between dye particles and fibers. This is equivalent to pre-applying an adhesive functional coating to the surface of dye particles. At the same time, the multi-layer shell structure itself also provides an additional physical barrier protection for the pigment molecules in the core, further enhancing the dye's wash resistance and abrasion resistance.

[0012] Preferably, in step 1), the ratio of turmeric powder to ethanol aqueous solution is (0.5-1.0) g / 10 mL.

[0013] Preferably, in step 1), the water bath temperature is controlled at 55-58°C and the ultrasonic extraction time is 1.5-2 hours.

[0014] Preferably, in step 2), the mass ratio of the dye pigment concentrate to β-cyclodextrin is 1:(2-3).

[0015] Preferably, in step 2), the reaction temperature is 55–60°C and the reaction time is 2–3 hours.

[0016] Preferably, in step 3), the amount of γ-aminopropyltriethoxysilane added is 10-12% of the wet weight of the inclusion compound.

[0017] Preferably, in step 3), the grafting reaction temperature is 65–70°C and the reaction time is 3–5 h.

[0018] Preferably, in step 4), the mass concentration of the tannic acid aqueous solution is 2-4%; and the mass concentration of chitosan in the chitosan acetate solution is 1-2%.

[0019] Preferably, in step 5), the amount of anhydrous citric acid added is 6-8% of the mass of the multilayer composite coated modified dye powder, and the amount of polyethylene glycol 400 added is 4-6% of the mass of the multilayer composite coated modified dye powder.

[0020] While the synergistic effect of the two aspects mentioned above can improve the color fastness of dyes to a certain extent, it was found in the actual preparation process that the silanized shell layer (inner layer) has low surface energy and certain rigidity, while the tannic acid / chitosan polyelectrolyte shell layer (outer layer) has swelling characteristics under wet conditions. The interfacial adhesion between the two layers is not ideal, which leads to the risk of interlayer peeling in the multilayer composite shell structure during dyeing and washing, resulting in the inability to fully exert the synergistic effect of the two aspects. To address this technical problem, this invention introduces citric acid and polyethylene glycol 400 into the dye powder in the final stage. Specifically, the citric acid molecule contains three carboxyl groups and one hydroxyl group. During the composite process, its carboxyl groups can form ammonium salt ionic bonds with the amino groups in the outer chitosan coating through acid-base neutralization. Simultaneously, in the subsequent drying stage, it undergoes partial esterification and amidation crosslinking reactions with the amino and hydroxyl groups in the chitosan and tannic acid coatings, chemically strengthening the layers and significantly enhancing the integrity and stability of the multilayer shell structure. Furthermore, during dyeing applications, the pre-loaded citric acid can further bridge the chemical bonds between the coating and the fiber during the heat curing process on the fiber surface. Polyethylene glycol 400 is a low molecular weight flexible segment polymer that can penetrate into the interfacial gap between the silane shell and the polyelectrolyte shell, reducing interlayer interfacial tension, enhancing interlayer flexibility and adhesion, and simultaneously imparting good water dispersibility to the dye powder, enabling it to disperse quickly and uniformly when preparing dye solutions. The chemical cross-linking reinforcement of citric acid and the physical interface compatibilization of polyethylene glycol 400 work synergistically to enhance the structural stability and interfacial compatibility of the multilayer composite shell from both chemical bonding and physical interface dimensions. This allows the synergistic effect of the two modifications to be fully released, and the resulting dye product exhibits excellent color fastness when applied to fabric dyeing.

[0021] A high color fastness fabric dye is prepared by the method described above.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. By encapsulating the dye with cyclodextrin to form a molecular-level cage-like protective structure, and combining it with a silane coupling agent to construct a dense organosilicon cross-linked shell, the dye effectively blocks external light, heat and detergent erosion, thus significantly improving the structural stability of the dye.

[0024] 2. By utilizing the layer-by-layer self-assembly of tannic acid and chitosan, a large number of amino and phenolic hydroxyl active groups are enriched on the dye surface. During dyeing, strong hydrogen bonds and ionic bonds are formed with cellulose fibers to achieve efficient color fixation.

[0025] 3. Citric acid is introduced for chemical cross-linking reinforcement, and polyethylene glycol 400 is used for physical compatibilization. This synergistic effect of chemical bonding and interfacial flexibility prevents interlayer peeling and fully releases the synergistic effect of dual modification, resulting in excellent color fastness of the final product. Attached Figure Description

[0026] Figure 1 This is a low-magnification SEM image of the high color fastness fabric dye prepared in Example 4 of the present invention.

[0027] Figure 2 This is a medium-magnification SEM image of the high color fastness fabric dye prepared in Example 4 of the present invention.

[0028] Figure 3 This is a high-magnification SEM image of the high color fastness fabric dye prepared in Example 4 of the present invention.

[0029] Figure 4 The XRD pattern of the high color fastness fabric dye prepared in Example 4 of this invention is shown. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing a fabric dye with high color fastness includes the following steps:

[0033] 1) Weigh 85g of dried turmeric, pulverize it, and pass it through an 80-mesh sieve to obtain turmeric powder. Add the turmeric powder to 1000mL of a 70% (v / v) ethanol aqueous solution, and extract using ultrasound at 400W power and 40kHz frequency, controlling the water bath temperature at 56℃ for 2 hours. After extraction, filter and collect the filtrate. Concentrate the filtrate by vacuum distillation at 55℃ and a vacuum degree of 0.085MPa to obtain a concentrated dye pigment solution.

[0034] 2) Add 45g of β-cyclodextrin to 800mL of deionized water and stir at 400r / min in a 58℃ constant temperature water bath until completely dissolved. Add 16g of dye / pigment concentrate while continuously stirring, and react at 58℃ and 400r / min for 2.5h to form an inclusion complex suspension. Cool the suspension to 2℃ and allow it to crystallize for 16h. Filter under vacuum and wash the filter cake twice with a small amount of ice water to obtain the wet inclusion complex.

[0035] 3) Disperse 48g of the wet inclusion compound in 720mL of anhydrous ethanol, stir well, and then add glacial acetic acid to adjust the pH of the system to 3-4. Then slowly add 5.5g of γ-aminopropyltriethoxysilane. Install a condenser in a 68℃ constant temperature water bath to prevent ethanol evaporation, and stir the mixture at 400r / min for 4h. After the reaction is complete, cool to room temperature, centrifuge at 4000r / min for 10min, wash three times each with anhydrous ethanol and deionized water, dry at 55℃ for 8h, and grind through a 100-mesh sieve to obtain the silanized coated modified dye powder.

[0036] 4) 36g of silanized coated modified dye powder was dispersed in 540mL of 3.5% tannic acid aqueous solution. Adsorption deposition was carried out at 40℃ with stirring at 400r / min for 30min, followed by centrifugation at 4000r / min for 10min and washing twice with deionized water. The resulting powder was then redispersed in 540mL of chitosan-acetic acid solution (chitosan mass concentration 1.8%, acetic acid volume fraction 1.5%), and deposition was carried out at 40℃ with stirring at 400r / min for 30min. After centrifugation, the powder was washed twice with deionized water. The above tannic acid deposition and chitosan deposition were considered a complete self-assembly cycle, and this cycle was repeated four times. Finally, the resulting powder was dried at 55℃ for 8h, ground, and passed through a 100-mesh sieve to obtain multilayer composite coated modified dye powder.

[0037] 5) Dissolve 2.8g of anhydrous citric acid and 2.2g of polyethylene glycol 400 in 100mL of deionized water and stir until completely dissolved. Add 38g of multilayer composite coated modified dye powder and stir at 400r / min for 45min at a constant temperature of 45℃ to form a moist paste mixture. Dry the mixture at 55℃ for 8h, grind it, and pass it through a 100-mesh sieve to obtain the high color fastness fabric dye product.

[0038] Example 2

[0039] A method for preparing a fabric dye with high color fastness includes the following steps:

[0040] 1) Weigh 60g of dried turmeric, pulverize it, and pass it through an 80-mesh sieve to obtain turmeric powder. Add the turmeric powder to 1000mL of a 70% (v / v) ethanol aqueous solution, and extract using ultrasound at 400W power and 40kHz frequency, controlling the water bath temperature at 56℃ for 2 hours. After extraction, filter and collect the filtrate. Concentrate the filtrate by vacuum distillation at 55℃ and a vacuum degree of 0.085MPa to obtain a concentrated dye pigment solution.

[0041] 2) Add 35g of β-cyclodextrin to 800mL of deionized water and stir at 400r / min in a 58℃ constant temperature water bath until completely dissolved. Add 16g of dye / pigment concentrate while continuously stirring, and react at 58℃ and 400r / min for 2.5h to form an inclusion complex suspension. Cool the suspension to 2℃ and allow it to crystallize for 16h. Filter under vacuum and wash the filter cake twice with a small amount of ice water to obtain the wet inclusion complex.

[0042] 3) Disperse 48g of the wet inclusion compound in 720mL of anhydrous ethanol, stir well, add glacial acetic acid to adjust the pH of the system to 3-4, and then slowly add 5.0g of γ-aminopropyltriethoxysilane. Install a condenser in a 68℃ constant temperature water bath to prevent ethanol evaporation, and stir the reaction at 400r / min for 4h. After the reaction is complete, cool to room temperature, centrifuge at 4000r / min for 10min, wash three times each with anhydrous ethanol and deionized water, dry at 55℃ for 8h, grind through a 100-mesh sieve to obtain the silanized coated modified dye powder.

[0043] 4) 36g of silanized coated modified dye powder was dispersed in 540mL of 2.5% tannic acid aqueous solution. Adsorption deposition was carried out at 40℃ with stirring at 400r / min for 30min, followed by centrifugation at 4000r / min for 10min and washing twice with deionized water. The resulting powder was then redispersed in 540mL of chitosan-acetic acid solution (chitosan mass concentration 1.2%, acetic acid volume fraction 1.5%), and deposition was carried out at 40℃ with stirring at 400r / min for 30min. After centrifugation, the powder was washed twice with deionized water. The above tannic acid deposition and chitosan deposition were considered a complete self-assembly cycle, and this cycle was repeated four times. Finally, the resulting powder was dried at 55℃ for 8h, ground, and passed through a 100-mesh sieve to obtain multilayer composite coated modified dye powder.

[0044] 5) Dissolve 2.5g of anhydrous citric acid and 1.8g of polyethylene glycol 400 in 100mL of deionized water and stir until completely dissolved. Add 38g of multilayer composite coated modified dye powder and stir at 400r / min for 45min at a constant temperature of 45℃ to form a moist paste mixture. Dry the mixture at 55℃ for 8h, grind it, and pass it through a 100-mesh sieve to obtain the high color fastness fabric dye product.

[0045] Example 3

[0046] A method for preparing a fabric dye with high color fastness includes the following steps:

[0047] 1) Weigh 70g of dried turmeric, pulverize it, and pass it through an 80-mesh sieve to obtain turmeric powder. Add the turmeric powder to 1000mL of a 70% (v / v) ethanol aqueous solution, and extract using ultrasound at 400W power and 40kHz frequency, controlling the water bath temperature at 56℃ for 2 hours. After extraction, filter and collect the filtrate. Concentrate the filtrate by vacuum distillation at 55℃ and a vacuum degree of 0.085MPa to obtain a concentrated dye pigment solution.

[0048] 2) Add 40g of β-cyclodextrin to 800mL of deionized water and stir at 400r / min in a 58℃ constant temperature water bath until completely dissolved. Add 16g of dye / pigment concentrate while continuously stirring, and react at 58℃ and 400r / min for 2.5h to form an inclusion complex suspension. Cool the suspension to 2℃ and allow it to crystallize for 16h. Filter under vacuum and wash the filter cake twice with a small amount of ice water to obtain the wet inclusion complex.

[0049] 3) Disperse 48g of the wet inclusion compound in 720mL of anhydrous ethanol, stir well, add glacial acetic acid to adjust the pH of the system to 3-4, and then slowly add 5.2g of γ-aminopropyltriethoxysilane. Install a condenser in a 68℃ constant temperature water bath to prevent ethanol evaporation, and stir the reaction at 400r / min for 4h. After the reaction is complete, cool to room temperature, centrifuge at 4000r / min for 10min, wash three times each with anhydrous ethanol and deionized water, dry at 55℃ for 8h, grind through a 100-mesh sieve to obtain the silanized coated modified dye powder.

[0050] 4) 36g of silanized coated modified dye powder was dispersed in 540mL of 3% (w / w) tannic acid aqueous solution. Adsorption deposition was carried out at 40℃ with stirring at 400r / min for 30min, followed by centrifugation at 4000r / min for 10min and washing twice with deionized water. The resulting powder was then redispersed in 540mL of chitosan-acetic acid solution (chitosan mass concentration 1.5%, acetic acid volume fraction 1.5%), and deposition was carried out at 40℃ with stirring at 400r / min for 30min. After centrifugation, the powder was washed twice with deionized water. The above tannic acid deposition and chitosan deposition were considered a complete self-assembly cycle, and this cycle was repeated four times. Finally, the resulting powder was dried at 55℃ for 8h, ground, and passed through a 100-mesh sieve to obtain multilayer composite coated modified dye powder.

[0051] 5) Dissolve 2.7g of anhydrous citric acid and 2.0g of polyethylene glycol 400 in 100mL of deionized water and stir until completely dissolved. Add 38g of multilayer composite coated modified dye powder and stir at 400r / min for 45min at a constant temperature of 45℃ to form a moist paste mixture. Dry the mixture at 55℃ for 8h, grind it, and pass it through a 100-mesh sieve to obtain the high color fastness fabric dye product.

[0052] Example 4

[0053] A method for preparing a fabric dye with high color fastness includes the following steps:

[0054] 1) Weigh 100g of dried turmeric, pulverize it, and pass it through an 80-mesh sieve to obtain turmeric powder. Add the turmeric powder to 1000mL of a 70% (v / v) ethanol aqueous solution, and extract using ultrasound at 400W power and 40kHz frequency, controlling the water bath temperature at 58℃ for 2 hours. After extraction, filter and collect the filtrate. Concentrate the filtrate by vacuum distillation at 55℃ and a vacuum degree of 0.085MPa to obtain a concentrated dye pigment solution.

[0055] 2) Add 48g of β-cyclodextrin to 800mL of deionized water and stir at 400r / min in a 58℃ constant temperature water bath until completely dissolved. Add 16g of dye pigment concentrate under continuous stirring, and react at 60℃ and 400r / min for 3h to form an inclusion complex suspension. Cool the suspension to 2℃ and allow it to crystallize for 16h. Filter under vacuum and wash the filter cake twice with a small amount of ice water to obtain the wet inclusion complex.

[0056] 3) Disperse 48g of the wet inclusion compound in 720mL of anhydrous ethanol, stir well, add glacial acetic acid to adjust the pH of the system to 3-4, and then slowly add 5.8g of γ-aminopropyltriethoxysilane. Install a condenser in a 70℃ constant temperature water bath to prevent ethanol evaporation, and stir the reaction at 400r / min for 5h. After the reaction is complete, cool to room temperature, centrifuge at 4000r / min for 10min, wash three times each with anhydrous ethanol and deionized water, dry at 55℃ for 8h, grind through a 100-mesh sieve to obtain the silanized coated modified dye powder.

[0057] 4) 36g of silanized coated modified dye powder was dispersed in 540mL of 4% (w / w) tannic acid aqueous solution. Adsorption deposition was carried out at 40℃ with stirring at 400r / min for 30min, followed by centrifugation at 4000r / min for 10min and washing twice with deionized water. The resulting powder was then redispersed in 540mL of chitosan-acetic acid solution (chitosan mass concentration 2%, acetic acid volume fraction 1.5%), and deposition was carried out at 40℃ with stirring at 400r / min for 30min. After centrifugation, the powder was washed twice with deionized water. The above tannic acid deposition and chitosan deposition were considered a complete self-assembly cycle, and this cycle was repeated four times. Finally, the resulting powder was dried at 55℃ for 8h, ground, and passed through a 100-mesh sieve to obtain multilayer composite coated modified dye powder.

[0058] 5) Dissolve 3.0g of anhydrous citric acid and 2.3g of polyethylene glycol 400 in 100mL of deionized water and stir until completely dissolved. Add 38g of multilayer composite coated modified dye powder and stir at 400r / min for 45min at a constant temperature of 45℃ to form a moist paste mixture. Dry the mixture at 55℃ for 8h, grind it, and pass it through a 100-mesh sieve to obtain the high color fastness fabric dye product.

[0059] Example 5

[0060] A method for preparing a fabric dye with high color fastness includes the following steps:

[0061] 1) Weigh 50g of dried turmeric, pulverize it, and pass it through an 80-mesh sieve to obtain turmeric powder. Add the turmeric powder to 1000mL of a 70% (v / v) ethanol aqueous solution, and extract using ultrasound at 400W power and 40kHz frequency, controlling the water bath temperature at 55℃ for 1.5h. After extraction, filter and collect the filtrate. Concentrate the filtrate by vacuum distillation at 55℃ and a vacuum degree of 0.085MPa to obtain a concentrated dye pigment solution.

[0062] 2) Add 32g of β-cyclodextrin to 800mL of deionized water and stir at 400r / min in a 58℃ constant temperature water bath until completely dissolved. Add 16g of dye / pigment concentrate while continuously stirring, and react at 55℃ and 400r / min for 2h to form an inclusion complex suspension. Cool the suspension to 2℃ and allow it to crystallize for 16h. Filter under vacuum and wash the filter cake twice with a small amount of ice water to obtain the wet inclusion complex.

[0063] 3) Disperse 48g of the wet inclusion compound in 720mL of anhydrous ethanol, stir well, add glacial acetic acid to adjust the pH of the system to 3-4, and then slowly add 4.8g of γ-aminopropyltriethoxysilane. Install a condenser in a 65℃ constant temperature water bath to prevent ethanol evaporation, and stir the reaction at 400r / min for 3h. After the reaction is complete, cool to room temperature, centrifuge at 4000r / min for 10min, wash three times each with anhydrous ethanol and deionized water, dry at 55℃ for 8h, grind through a 100-mesh sieve to obtain the silanized coated modified dye powder.

[0064] 4) 36g of silanized coated modified dye powder was dispersed in 540mL of 2% (w / w) tannic acid aqueous solution. Adsorption deposition was carried out at 40℃ with stirring at 400r / min for 30min, followed by centrifugation at 4000r / min for 10min and washing twice with deionized water. The resulting powder was then redispersed in 540mL of chitosan-acetic acid solution (chitosan mass concentration 1%, acetic acid volume fraction 1.5%), and deposition was carried out at 40℃ with stirring at 400r / min for 30min. After centrifugation, the powder was washed twice with deionized water. The above tannic acid deposition and chitosan deposition were considered a complete self-assembly cycle, and this cycle was repeated four times. Finally, the resulting powder was dried at 55℃ for 8h, ground, and passed through a 100-mesh sieve to obtain multilayer composite coated modified dye powder.

[0065] 5) Dissolve 2.3g of anhydrous citric acid and 1.5g of polyethylene glycol 400 in 100mL of deionized water and stir until completely dissolved. Add 38g of multilayer composite coated modified dye powder and stir at 400r / min for 45min at a constant temperature of 45℃ to form a moist paste mixture. Dry the mixture at 55℃ for 8h, grind it, and pass it through a 100-mesh sieve to obtain the high color fastness fabric dye product.

[0066] Comparative Example 1: The difference from Example 4 is that steps 2) and 3) are omitted, i.e., β-cyclodextrin inclusion and silanization grafting treatment are not performed. Specifically, the dye pigment concentrate obtained in step 1) is directly dried to constant weight at 55°C, ground through a 100-mesh sieve to obtain unmodified dye powder, and then this unmodified dye powder is used to replace the silanized coated modified dye powder and directly enters step 4) for tannic acid-chitosan layer-by-layer self-assembly surface modification. The remaining operating conditions are exactly the same as in Example 4.

[0067] Comparative Example 2: The difference from Example 4 is that γ-aminopropyltriethoxysilane was not added for silanization grafting in step 3). Specifically, 48g of the wet inclusion compound was directly dried at 55°C for 8 hours, ground through a 100-mesh sieve to obtain cyclodextrin inclusion dye powder. This powder was then used to replace the silanized coating modified dye powder and directly entered step 4) for tannic acid-chitosan layer-by-layer self-assembly surface modification. The remaining operating conditions were exactly the same as in Example 4.

[0068] Comparative Example 3: The difference from Example 4 is that step 4) is not performed, that is, the tannic acid-chitosan layer-by-layer self-assembly surface modification is not performed. Specifically, the silanized coated modified dye powder obtained in step 3) is directly fed into step 5) for synergistic compounding, and the remaining operating conditions are exactly the same as in Example 4.

[0069] Comparative Example 4: The difference from Example 4 is that step 5) is omitted, i.e., the synergistic compounding of citric acid and polyethylene glycol 400 is not performed. Specifically, the multilayer composite coated modified dye powder obtained in step 4) is used directly as the finished dye product, and the remaining operating conditions are exactly the same as in Example 4.

[0070] Comparative Example 5: The difference from Example 4 is that only 3.0 g of anhydrous citric acid was added in step 5), and polyethylene glycol 400 was not added. The remaining operating conditions were exactly the same as in Example 4.

[0071] Comparative Example 6: The difference from Example 4 is that only 2.3g of polyethylene glycol 400 was added in step 5), and anhydrous citric acid was not added. The remaining operating conditions were exactly the same as in Example 4.

[0072] Performance testing:

[0073] 1. Wash fastness test: The dyed fabric sample and the lining fabric were sewn together to form a composite sample, which was then placed in a soap solution containing 5 g / L soap flakes and treated at 40±2℃ for 30 min (liquor ratio 1:50). After treatment, the composite sample was removed, rinsed twice with deionized water and dehydrated, and dried at a temperature not exceeding 60℃. The color change grade of the sample and the staining grade of the lining fabric were assessed using a gray scale, expressed as grades 1 to 5, with higher grades indicating better color fastness. The test results are shown in Table 1.

[0074] 2. Color fastness to rubbing test: A color fastness to rubbing tester was used to conduct dry and wet rubbing tests on the dyed fabric samples. The rubbing head was covered with standard white cotton cloth, and the fabric was rubbed back and forth 10 times along the warp direction under a pressure of 9N, with a stroke of 100mm and a frequency of 1 rub / s. In the wet rubbing test, the moisture content of the white cotton cloth was controlled between 95% and 105%. After the test, the white cotton cloth was dried at room temperature, and the staining grade was evaluated using a gray scale, expressed as grade 1 to 5. The test results are shown in Table 1.

[0075] 3. Lightfastness Test: The dyed fabric sample and the blue wool standard were mounted on an exposure rack and exposed to a xenon arc lamp. The blackboard temperature was 47±3℃, the relative humidity was 40±10%, and the irradiance was 0.35W / m² (wavelength 420nm). The test was terminated when the blue wool standard reached a level 6 color change. The color change grade of the sample was evaluated using a gray scale, expressed as grades 1 to 8, with higher grades indicating better lightfastness. The test results are shown in Table 1.

[0076] 4. K / S value determination: Using a Datacolor 650 computer colorimeter, the dyed fabric sample was folded to be opaque (four layers), and its K / S value was measured at the maximum absorption wavelength. The average value was taken at four different locations for each sample. The K / S value was calculated using the Kubelka-Munk equation, i.e., K / S = (1-R). 2 / 2R, where R is the reflectance of the fabric. A higher K / S value indicates a higher dye uptake and a darker color. The test results are shown in Table 1.

[0077] 5. Dyeing rate determination: The dyeing rate was determined by spectrophotometry. At the maximum absorption wavelength, the absorbance A0 of the dye solution before dyeing and the absorbance A1 of the residual solution after dyeing were measured (the residual solution was brought to the same volume as the dye solution before measurement). The dyeing rate was calculated using the formula E(%) = (A0 - A1) / A0 × 100%. Each sample was measured in triplicate, and the average value was taken. The test results are shown in Table 1.

[0078] 6. Water Dispersion Stability Test: Weigh 1g of each dye product and disperse it in 100mL of deionized water. After ultrasonic dispersion for 5min, allow it to stand. After standing for 0h and 2h, take the supernatant and measure the absorbance at the maximum absorption wavelength using a UV-Vis spectrophotometer. The ratio of the absorbance after 2h to the absorbance after 0h is taken as the Dispersion Stability Index (DSI). The closer the DSI value is to 1.00, the better the dispersion stability. The test results are shown in Table 1.

[0079] Table 1:

[0080] sample Wash fastness (color change) / grade Wash fastness (staining) / grade Color fastness to dry rubbing / grade Color fastness to wet rubbing / grade Lightfastness / Grade K / S value Dyeing rate / % Dispersion Stability Index (DSI) Example 1 4 4 4～5 3～4 5～6 9.8 72.5 0.91 Example 2 4 3～4 4 3～4 5 9.2 68.3 0.89 Example 3 4～5 4 4～5 4 5～6 10.5 75.1 0.92 Example 4 4～5 4～5 5 4～5 6 11.8 79.6 0.94 Example 5 4 3～4 4 3～4 5 8.5 65.7 0.87 Comparative Example 1 2～3 2 3 2 3 5.1 41.2 0.82 Comparative Example 2 3 2～3 3～4 2～3 4 6.3 49.5 0.78 Comparative Example 3 3～4 3 3～4 3 5 7.8 55.8 0.90 Comparative Example 4 3～4 3 4 3 5～6 8.9 62.4 0.71 Comparative Example 5 4 3～4 4～5 3～4 5～6 10.6 73.8 0.76 Comparative Example 6 3～4 3 4 3 5～6 9.3 66.1 0.88

[0081] From the table above, we can obtain:

[0082] Comparative Example 1 (without cyclodextrin inclusion and silanization grafting) showed the most significant decrease in various color fastness indicators. The wash fastness dropped to grade 2-3, the light fastness dropped to grade 3, the K / S value was only 5.1, and the dyeing rate was only 41.2%. This indicates that the cyclodextrin-silane coupling coating modification is the fundamental key step in this invention to improve the color fastness and coloring performance of the dye. Its absence leads to the dye pigment molecules lacking effective structural protection and surface functionalization, and thus cannot form a stable bond with the fiber.

[0083] Comparative Example 2 (only cyclodextrin inclusion without silanization grafting) showed some improvement compared to Comparative Example 1, but still lagged significantly behind Example 4. Its wash fastness was only grade 3, its K / S value was only 6.3, and its dispersion stability index dropped to 0.78. This indicates that relying solely on cyclodextrin inclusion is insufficient to achieve high color fastness. The silanization cross-linked shell plays an irreplaceable role in enhancing pigment protection and providing a stable reaction surface for subsequent layer-by-layer self-assembly. At the same time, the lack of a positively charged surface in the silane shell makes it difficult for tannic acid to be deposited effectively, resulting in an unstable layer-by-layer self-assembled coating structure and decreased particle dispersibility.

[0084] Comparative Example 3 (without tannic acid-chitosan layer-by-layer self-assembly) showed a significant decrease in wash fastness and rubbing fastness, with the K / S value dropping to 7.8 and the dye uptake rate decreasing to 55.8%. However, the light fastness remained at grade 5, reflecting that the photoprotective effect of the cyclodextrin-silane coupling shell on the internal pigment was preserved. The lack of a multilayer polyelectrolyte shell resulted in insufficient active adsorption sites between the dye particles and the fiber, which significantly affected the color fixation ability and color depth.

[0085] Comparative Example 4 (without citric acid and polyethylene glycol 400 additives) showed little change in light fastness (grades 5-6), but both wash fastness and rubbing fastness decreased, with the K / S value dropping to 8.9. In particular, the dispersion stability index dropped significantly to 0.71, indicating that the interlayer adhesion between the multiple shell layers was not strong enough after the additives were not added, making it easy for some interlayer peeling to occur during the dyeing process. At the same time, the water dispersibility of the dye powder deteriorated, making it unable to be fully and evenly dispersed in the dye liquor, which seriously affected the dyeing efficiency and dyeing uniformity.

[0086] Comparative Example 5 (with only citric acid and no polyethylene glycol 400) showed similar color fastness indices to Example 4, but its dispersion stability index dropped to 0.76. This indicates that the water dispersion stability of the dye powder decreased significantly after the absence of polyethylene glycol 400, which may lead to uneven dyeing in practical applications. This further confirms the auxiliary synergistic effect of polyethylene glycol 400 in improving interlayer interface compatibility and enhancing dye water dispersibility.

[0087] Comparative Example 6 (with only polyethylene glycol 400 added and no citric acid) showed a more significant decrease in wash fastness and rubbing fastness compared to Comparative Example 5, with the K / S value dropping to 9.3 and the dyeing rate decreasing to 66.1%. This indicates that the chemical cross-linking and strengthening effect of citric acid is the main contributing factor in the auxiliary compounding step, and the ionic bonds and cross-linking network formed between its carboxyl groups and chitosan amino groups are the core mechanisms for maintaining the stability of the multilayer shell structure and promoting dyeing fixation.

[0088] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the essence and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high color fastness fabric dye, characterized in that, Includes the following steps: 1) The dried turmeric was crushed into turmeric powder, added to an ethanol aqueous solution for ultrasonic extraction, filtered and the filtrate was collected, and the filtrate was concentrated by vacuum distillation to obtain a dye pigment concentrate. 2) Dissolve β-cyclodextrin in deionized water to obtain an aqueous solution, then add the dye pigment concentrate, react to form an inclusion complex suspension, and after standing crystallization, filtration and washing, obtain the wet inclusion complex product; 3) The wet product of the inclusion compound was dispersed in anhydrous ethanol, and glacial acetic acid was added to adjust the system to acidity. Then, γ-aminopropyltriethoxysilane was added to carry out the grafting reaction. After the reaction was completed, the product was separated by centrifugation, washed, dried and ground to obtain silanized coated modified dye powder. 4) The silanized coated modified dye powder is added to a tannic acid aqueous solution for adsorption and deposition. After separation and washing, it is added to a chitosan acetate solution for deposition, and then separated and washed again. The above-mentioned tannic acid deposition and chitosan deposition are regarded as a complete self-assembly cycle. This cycle is repeated many times to construct alternating composite shells. Finally, after separation, drying and grinding, multi-layer composite coated modified dye powder is obtained. 5) Dissolve anhydrous citric acid and polyethylene glycol 400 in deionized water to obtain an auxiliary aqueous solution. Add multilayer composite coated modified dye powder, stir and mix to form a uniform paste mixture. Finally, after drying, grinding and sieving, the high color fastness fabric dye product is obtained.

2. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 1), the ratio of turmeric powder to ethanol aqueous solution is (0.5-1.0) g / 10 mL.

3. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 1), the water bath temperature is controlled at 55-58℃ during ultrasonic extraction, and the ultrasonic extraction time is 1.5-2 hours.

4. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 2), the mass ratio of the dye pigment concentrate to β-cyclodextrin is 1:(2-3).

5. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 2), the reaction temperature is 55-60℃ and the reaction time is 2-3h.

6. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 3), the amount of γ-aminopropyltriethoxysilane added is 10-12% of the wet weight of the inclusion compound.

7. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 3), the grafting reaction temperature is 65-70℃ and the reaction time is 3-5h.

8. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 4), the mass concentration of the tannic acid aqueous solution is 2-4%; the mass concentration of chitosan in the chitosan acetate solution is 1-2%.

9. The method for preparing a high color fastness fabric dye according to claim 1, characterized in that, In step 5), the amount of anhydrous citric acid added is 6-8% of the mass of the multilayer composite coated modified dye powder, and the amount of polyethylene glycol 400 added is 4-6% of the mass of the multilayer composite coated modified dye powder.

10. A high color fastness fabric dye, characterized in that, It is prepared by the method described in any one of claims 1 to 9 above.

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