Protein fiber dyeing method, protein fiber and fabric

Abstract

The invention discloses a protein fiber dyeing method, a protein fiber and a fabric, according to the protein fiber dyeing method, reducing sugar DHA is reacted with indigo blue, and low-temperature green dyeing and functional modification of the protein fiber are synchronously realized by utilizing the dual functions of a reducing agent and a color developing agent of DHA. Specifically, ketose-dihydroxy acetone (DHA) is used for reducing indigo into a leuco body, meanwhile, the ketose-dihydroxy acetone (DHA) and amino in protein fibers are subjected to a Maillard reaction to generate yellowish-brown pigment, and a unique yellow-green system is formed by combining a blue system of traditional indigo, so that the dyeing chromatography is widened, meanwhile, the dyeing process is green and environmentally friendly, and the dyeing efficiency is improved. The dyed protein fiber is endowed with excellent anti-ultraviolet performance (UPFgt; 1800) and oxidation resistance (the free radical scavenging rate can reach 70%), and the strength of the dyed protein fiber is almost not lost after dyeing.

Description

Technical Field

[0001] The invention belongs to the technical field of natural fiber dyeing, relates to green printing and dyeing of natural fibers and functionalization of textile materials, and particularly relates to a protein fiber dyeing method, protein fibers and fabrics. Background Art

[0002] In the modern textile industry, plant-derived indigo dyes, thanks to their excellent biodegradability and unique indigo color, have become the dominant dyeing process for denim apparel. This system involves reducing water-insoluble indigo to a soluble sodium leuco salt under alkaline conditions, which then fixes the dye onto protein fibers through oxidation. While this dyeing mechanism is well-established, the reducing agents commonly used in current processes pose numerous ecological safety risks. For example, Chinese patent CN 105178061A discloses a method for dyeing wool strips with plant-derived indigo. The method involves dissolving plant-derived indigo powder in soft water, sequentially adding caustic soda and sodium hydrosulfite (chemical formula: Na₂S₂O₄), and then dyeing the wool strips at a specific temperature. This process requires highly alkaline conditions, which severely damages the wool and produces harmful substances such as sulfates, making it unsuitable for environmental protection. Chinese patent CN 113981714 B discloses a process for dyeing wool garments with plant indigo. This process involves weighing wool garments, water, plant indigo, caustic soda, and sodium hydrosulfite, preparing the dye liquor in stages, dyeing in a nitrogen atmosphere, and adding hydrogen peroxide three times. Dyeing is completed at 60-70°C. This process is complex and inefficient. The use of sodium hydrosulfite as a reducing agent poses safety risks, and the resulting wastewater is difficult to treat.

[0003] Traditional indigo dyeing systems, due to the electronic stability of their chromophores, exhibit a pronounced monochromatic color spectrum. This phenomenon manifests itself in the hue of the finished dyed product being permanently fixed within the indigo blue domain, preventing cross-color reconstruction. Conventional physicochemical manipulation techniques (such as pH adjustment and temperature gradient control) can alter the aggregation state of dye molecules, but they have not been able to break through the color rendering boundaries of traditional indigo dyeing processes. This inherent limitation in color rendering is increasingly in conflict with the contemporary textile market's demand for diverse and functional colors. Therefore, the development of new dyeing systems is urgently needed to expand the application of indigo dyeing systems in diverse color expression.

[0004] To address the above problems, no effective solutions have been proposed yet. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned prior art, the object of the present invention is to provide a protein fiber dyeing method, protein fiber and fabric.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A first aspect of the present invention provides a protein fiber dyeing method, comprising the following steps: dyeing the protein fiber with a composite system of indigo dye and DHA, and obtaining dyed protein fiber after the dyeing process.

[0007] Preferably, the dyeing process comprises: immersing the protein fiber in a composite system of indigo dye and DHA, reacting at a bath ratio of 1:20-1:50 and 60-85° C. for 60-90 minutes.

[0008] Preferably, the indigo dye is indigo mud, and the composite system of the indigo dye and DHA comprises the following components in mass fractions: 2-3 wt.% of indigo mud and 3.6-5.4 wt.% of DHA.

[0009] Preferably, the indigo dye is synthetic indigo, and the composite system of the indigo dye and DHA comprises the following components by mass fraction: 0.02-0.06 wt.% of synthetic indigo, and 3.6-5.4 wt.% of DHA.

[0010] Preferably, the mass ratio of the protein fiber to the composite system of indigo dye and DHA is 1:25-55. Preferably, the dyeing process specifically includes the following steps: S1. Immerse the protein fiber in an aqueous solution of DHA and react at a bath ratio of 1:20-1:50 and 60-85°C for 40-60 minutes; S2. Add indigo dye to the reaction system, continue to react at a bath ratio of 1:20-1:50 and 60-85° C. for 20-30 min, and after the reaction is completed, wash with water and dry to obtain dyed protein fibers.

[0011] Preferably, the indigo dye is indigo mud, and the mass ratio of DHA, indigo mud and water is 3.6-5.4:2-3:100.

[0012] Preferably, the indigo dye is synthetic indigo, and the mass ratio of DHA, synthetic indigo and water is 3.6-5.4:0.02-0.06:100. Preferably, the protein fiber is wool.

[0013] A second aspect of the present invention provides a dyed protein fiber obtained by dyeing using the above protein fiber dyeing method.

[0014] The third aspect of the present invention provides a fabric obtained by weaving the above-mentioned dyed protein fiber or blending it with other fibers. (1) The present invention achieves low-temperature green dyeing of protein fibers by reacting a reducing sugar DHA with an indigo dye. Specifically, ketose-dihydroxyacetone (DHA) is used, which has the dual functions of a reducing agent and a dye: while reducing indigo to a leuco form, it undergoes a Maillard reaction with the amino groups in the protein fiber to produce a tan pigment, which combines with the blue color of traditional indigo dye to form a unique yellow-green color. This not only broadens the dyeing color spectrum, but also realizes a green and environmentally friendly dyeing process. At the same time, it gives the dyed protein fiber excellent anti-ultraviolet and antioxidant properties, and there is almost no loss of fiber strength after dyeing.

[0015] (2) The present invention uses a composite system of indigo dye and DHA for dyeing, which greatly improves the antioxidant properties of protein fibers compared to other dyeing systems, especially when indigo mud and wool are used.

[0016] (3) In the dyeing method of the present invention, dihydroxyacetone is used as the indigo reducing agent. It is the simplest ketose DHA. The entire dyeing process is green and environmentally friendly, and no insurance powder is needed.

[0017] (4) In the dyeing method of the present invention, the required dyeing temperature is relatively low, and the protein fiber can be dyed as low as 60°C; the required dyeing time is short, and the dark dyeing of the protein fiber can be completed as low as 60 minutes.

[0018] The present invention utilizes the dual functions of DHA as a reducing agent and a color developer for the first time to achieve simultaneous dyeing and functional modification; through the kinetic matching of the indigo dye reduction / oxidation reaction and the Maillard reaction process, a composite color development system with controllable hue is established; not only an ecological dyeing system suitable for natural protein fibers is developed to solve the problems of narrow color gamut and high pollution in traditional indigo dye dyeing processes, but also with the help of the molecular-level synergistic effect of indigo dye and DHA, the antioxidant and UV resistance of the dyed fibers are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 Figures 1 and 2 are: (A) Electron transfer pathway diagram for DHA reduction of indigo; (B) Maillard reaction equation for wool; Figure 2 The a* and b* values ​​and color chart comparison of dyed wool fibers of Example 1, Comparative Examples 1 and 2, and the control group are shown; Figure 3The actual pictures of dyed wool fibers and the comparison of color depth K / S values ​​of Example 1, Comparative Examples 1 and 2, and the control group are shown; Figure 4 This is a comparison chart of UPF values ​​of dyed wool fibers of Example 1 and 2, Comparative Example 1 and 2, and the control group; Figure 5 This is a comparison chart of the free radical scavenging rate values ​​of dyed wool fibers over time for Example 1 and 2, Comparative Example 1-4, and the control group; Figure 6 This is a comparison chart of free radical scavenging rates of wool fibers 2 hours after dyeing in Example 1 and 2, Comparative Example 1-4 and the control group; Figure 7 This is a comparison chart of the tensile strength of dyed wool fibers of Examples 1 and 2, Comparative Examples 1 and 2, and the control group. DETAILED DESCRIPTION

[0021] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may also be implemented in other embodiments without these specific details.

[0022] Indigo mud is the primary dye used in traditional natural indigo dyeing. It is a paste-like dye complex prepared from indigo-containing plants (such as Polygonum tinctorium and Indigofera tinctoria) through a process of maceration, fermentation, and lime precipitation. Its core dyeing component is indigo. Synthetic indigo is an organic dye produced through chemical synthesis, also primarily composed of indigo. The two indole rings in the indigo molecule are bridged by conjugated double bonds to form a rigid planar structure, giving it a strong blue color and photostability.

[0023] As a green reducing agent and natural dye with a unique chemical structure, DHA's hydroxyl and carbonyl groups exhibit excellent reducing properties, effectively reducing indigo molecules. Its oxidation products (such as glyceric acid) are also water-soluble and ecologically safe. Furthermore, DHA covalently bonds with wool keratin through the Maillard reaction, enabling a low-temperature, rapid, and sustainable dyeing process, imparting a yellow hue to wool fibers.

[0024] See Figure 1 The dual action mechanism is as follows: Indigo reduction mechanism: The active groups (C=O and -OH) in the DHA molecule have strong reducing ability, and each molecule can provide 8 electrons to reduce indigo (C 16 H 10 N2O2) is reduced to a soluble leuco compound (C 16 H 12 N2O2), enhance the affinity of dye to protein fiber; Maillard color development mechanism: The free amino groups in wool nucleophilically attack the carbonyl group of DHA to form a Schiff base, which undergoes Amadori rearrangement to generate the Heins product; at the same time, DHA is converted into highly active methylglyoxal (MGO), which reacts with the Heins product through aldol condensation, tautomerism and cyclization to finally form a chromophore with a conjugated double bond (compound 8), giving the fiber a brown-yellow color.

[0025] The indigo dye and DHA complex system creates a molecular-level synergistic effect among the active ingredients, promoting improved fiber performance. The melanoidins (containing pyridine and furan heterocycles) generated by the Maillard reaction form an extended π-conjugated system with the indole ring of the indigo molecule, significantly enhancing electron transfer. Furthermore, the NH bonds of indigo form a hydrogen bond network with the phenolic hydroxyl groups of the Maillard product, synergistically capturing various active free radicals and further improving free radical scavenging rates. Furthermore, the indigo dyeing environment overlaps with the optimal pH range for the Maillard reaction. At this point, the reduction potential of the indigo leucomorph is elevated, forming a continuous electron transport chain with the reduction potential of the Maillard intermediate compound, thereby prolonging the antioxidant effect.

[0026] Example 1 Weigh 1g of indigo mud and 2.7g of DHA into an Erlenmeyer flask, add 50mL of water, and stir thoroughly to obtain a solution containing 2wt% indigo mud and 5.4wt% DHA. Then, add 1g of wool fiber to the solution and press with a glass rod until completely soaked. After sealing, the solution was reacted in a water bath at 85°C at a bath ratio of 1:50 for 90 minutes. Gently shake the Erlenmeyer flask every 15 minutes to ensure uniform dyeing (to avoid damaging the wool through direct stirring). After the reaction, remove the wool fiber, wash it, and dry it to obtain the dyed wool fiber. The experimental results showed an a* value of -3.57, a b* value of 11.39, a K / S ratio of 4.72, a UPF value of 1879.8, and a free radical scavenging rate of 70.2%.

[0027] Example 2 0.02g of synthetic indigo and 2.7g of DHA were weighed and placed in an Erlenmeyer flask. 50mL of water was added and stirred to form a uniform solution, resulting in a solution containing 0.04wt.% synthetic indigo and 5.4wt.% DHA. One gram of wool fiber was then added to the solution and pressed with a glass rod until completely soaked. The solution was sealed and allowed to react in a water bath at 85°C at a bath ratio of 1:50 for 90 minutes. The flask was gently shaken every 15 minutes to ensure uniform dyeing (to avoid direct agitation and damage to the wool). After the reaction, the wool fiber was removed, washed, and dried to obtain the dyed wool fiber. The experimental results showed an a* value of -3.63, a b* value of 11.22, a K / S ratio of 4.62, a UPF value of 1802.8, and a free radical scavenging rate of 53.1%.

[0028] Example 3 Weigh 2.7 g of DHA and place it in a conical flask. Add 50 mL of water and stir evenly to obtain a DHA solution with a mass concentration of 5.4 wt.%. Add 1 g of wool to the DHA solution and press with a glass rod until it is completely soaked. After sealing, react in a constant temperature water bath at a bath ratio of 1:50 and 60°C for 60 minutes. During this period, gently shake the conical flask every 15 minutes to ensure uniform dyeing (avoid direct stirring and damaging the wool). Then add 1.5 g of indigo mud and continue to react in a constant temperature water bath at a bath ratio of 1:50 and 85°C for 0.5 hour. After the reaction is completed, remove the wool, wash it with water, and dry it to obtain dyed wool fiber.

[0029] Experimental results: a* is -3.98, b* is 12.74, K / S value is 5.14, and UPF value is 1978.3.

[0030] Example 4 Weigh 1.8g of DHA into an Erlenmeyer flask, add 45mL of water, and stir thoroughly to obtain a DHA solution with a mass concentration of 3.6wt%. Add 1g of wool to the solution and press with a glass rod until completely soaked. Seal the flask and allow the solution to react for 60 minutes in a water bath at a bath ratio of 1:45 and a constant temperature of 75°C. Gently shake the flask every 15 minutes to ensure uniform dyeing (to avoid damaging the wool by direct stirring). Add 0.01g of synthetic indigo and continue the reaction in a water bath at a bath ratio of 1:45 and a constant temperature of 75°C for 20 minutes. After the reaction, remove the wool, wash it, and dry it to obtain the dyed wool fiber. The experimental results showed a* of -3.34, b* of 10.72, a K / S ratio of 4.23, and a UPF of 1813.2.

[0031] Example 5 Weigh 1.8g of DHA into an Erlenmeyer flask, add 35mL of water, and stir thoroughly to obtain a DHA solution with a mass concentration of 3.6wt%. Add 1g of wool to the solution and press with a glass rod until completely soaked. Seal the flask and allow the solution to react in a water bath at a bath ratio of 1:35 and a constant temperature of 75°C for 60 minutes. Gently shake the flask every 15 minutes to ensure uniform dyeing (to avoid damaging the wool by direct stirring). Add 1g of indigo mud and continue the reaction in a water bath at a bath ratio of 1:35 and a constant temperature of 75°C for 20 minutes. After the reaction, remove the wool, wash it, and dry it to obtain the dyed wool fiber. Experimental results: a* is -3.23, b* is 10.72, K / S ratio is 4.10, and UPF is 1873.2.

[0032] Example 6 Weigh 1.2g of indigo mud and 2.2g of DHA into an Erlenmeyer flask, add 45mL of water, and stir thoroughly to obtain a solution containing 2.4wt% indigo mud and 4.4wt% DHA. Add 1g of wool to the solution and press with a glass rod until completely soaked. Seal the flask and allow the mixture to react in a water bath at 85°C at a bath ratio of 1:45 for 90 minutes. Gently shake the Erlenmeyer flask every 15 minutes to ensure uniform dyeing (to avoid damaging the wool through direct stirring). After the reaction, remove the wool fiber, wash it with water, and dry it to obtain the dyed wool fiber. Experimental results: a* was -3.72, b* was 10.98, the K / S ratio was 4.24, and the UPF was 1888.5.

[0033] Comparative Example 1 Weigh 1g of indigo mud and 6g of glucose into an Erlenmeyer flask, add 50mL of water, and stir to form a uniform solution. Add 1g of wool fiber to the solution and press with a glass rod until completely soaked. Seal the flask and heat in an 85°C water bath for 90 minutes. Gently shake the Erlenmeyer flask every 15 minutes to ensure uniform dyeing (to avoid damaging the wool by direct stirring). Remove the wool, wash it, and dry it to obtain the dyed wool fiber. Experimental results: a* was -3.54, b* was 2.04, the K / S ratio was 1.73, the UPF was 2000.0, and the free radical scavenging rate was 28.7%. Comparative Example 2 Weigh 2.7g of DHA into a conical flask, add 50ml of water, and stir to form a uniform solution. Add 1g of wool fiber to the solution and press with a glass rod until completely soaked. Seal the flask and heat in an 85°C water bath for 90 minutes. Gently shake the conical flask every 15 minutes to ensure uniform dyeing (to avoid damaging the wool by direct stirring). Remove the wool, wash it, and dry it to obtain the dyed wool fiber. Experimental results: a* was 11.19, b* was 31.99, the K / S ratio was 5.47, the UPF was 1788.5, and the free radical scavenging rate was 13.1%.

[0034] Comparative Example 3 Weigh 0.02g of Vat Pink R (referring to the amount of 0.02g of synthetic indigo dye needed to achieve the same dyeing effect as 1g of indigo mud) and 2.7g of DHA into a conical flask. Add 50mL of water and stir to form a homogeneous solution. Add 1g of wool fiber to the solution and press with a glass rod until completely soaked. Seal the flask and heat in an 85°C waterbath for 90 minutes. Gently shake the conical flask every 15 minutes to ensure uniform dyeing (to avoid damaging the wool through direct stirring). Remove the wool, wash it with water, and dry it to obtain the dyed wool fiber. Experimental results: UPF value of 435.2, free radical scavenging rate of 3.5%.

[0035] Comparative Example 4 Weigh 0.02g of vat orange 3 (referring to the amount of 0.02g of synthetic indigo dye needed to achieve the same dyeing effect as 1g of indigo mud) and 2.7g of DHA into a conical flask. Add 50mL of water and stir to form a homogeneous solution. Add 1g of wool fiber to the solution and press with a glass rod until completely soaked. Seal the flask and heat in an 85°C water bath for 90 minutes. Gently shake the conical flask every 15 minutes to ensure uniform dyeing (to avoid direct agitation and damage to the wool). Remove the wool fiber, wash it with water, and dry it to obtain the dyed wool fiber. Experimental results: UPF value is 546.7, and free radical scavenging rate is 6.1%.

[0036] Comparative Example 5 Weigh 1g of indigo mud and 2.7g of DHA into an Erlenmeyer flask, add 50mL of water, and stir thoroughly to obtain a solution containing 2wt% indigo mud and 5.4wt% DHA. Add 1g of silk fiber to the solution and press with a glass rod until completely soaked. Seal the flask and allow the solution to react in a water bath at 85°C at a bath ratio of 1:50 for 90 minutes. Gently shake the Erlenmeyer flask every 15 minutes to ensure uniform dyeing. After the reaction, remove the silk fiber, wash it with water, and dry it to obtain the dyed silk fiber. Experimental results: a* was -0.17, b* was 2.63, the K / S ratio was 1.21, and the UPF value was 876.4.

[0037] Comparative Example 6 Weigh 1g of indigo mud and 2.7g of DHA into an Erlenmeyer flask, add 10mL of water, and stir thoroughly. Add 1g of wool fiber to the solution and press with a glass rod until completely soaked. Seal the flask and allow the mixture to react in a constant-temperature water bath at 85°C at a bath ratio of 1:10 for 90 minutes. Gently shake the Erlenmeyer flask every 15 minutes to ensure uniform dyeing. After the reaction, remove the wool fiber, wash it, and dry it to obtain the dyed wool fiber. Experimental results: a* was -2.07, b* was 1.63, the K / S ratio was 0.61, the UPF was 576.4, and the free radical scavenging rate was 21%.

[0038] Comparative Example 7 Untreated wool fibers served as the blank control group.

[0039] The dyed wool fibers obtained in Examples 1-2 and Comparative Examples 1-2 and Comparative Example 7 (untreated fibers) were tested, and the results are shown in Table 1. The dyed wool fibers and silk fibers obtained in Examples 1-2 and Comparative Examples 1-6 are respectively designated as Group 1-2 and Group 1-6, and the blank untreated wool fibers in Comparative Example 7 serve as a control group.

[0040] Table 1. Performance results comparison

[0041] 1. CIE color space and K / S test The Datacolor 850 colorimeter was used to measure the a*, b* and K / S values ​​of wool and silk fibers before and after treatment using an ultra-small aperture (USAV, 6.6mm) mode that includes specular gloss. 1g of each sample was evenly and neatly clamped on a glass slide. Five different positions were randomly selected for testing, and the average value was taken. Among them, +a* is the red axis, -a* is the green axis, +b* is the yellow axis, and -b* is the blue axis. The larger the K / S value, the darker the color of the fiber surface and the better the dyeing effect. The results are as follows Figure 2 and Figure 3 shown.

[0042] Depend on Figure 2 The results show that both Example 1 and Comparative Example 1 used an indigo mud dyeing system. The a* values ​​for the wool fibers from both dyeing groups were negative, with a small difference, indicating that the hue of the wool from both dyeing groups leaned towards green. Regarding the b* coordinate, the wool fibers from Example 1 had a b* value of 11.39, exhibiting a yellow-green hue (broadening the color gamut). This value was higher than the 2.04 b* value for the wool fibers from Comparative Example 1, which had undergone glucose reduction of indigo mud. This is due to the role of DHA as a reducing agent. In contrast, the wool fibers from Comparative Example 1, which had undergone glucose reduction of indigo mud, exhibited a more bluish-green hue. In addition, Example 2 used synthetic indigo dyeing, and its green value (a*=-3.63 and yellow value (b*=11.22) were similar to those of Example 1 (a*=-3.57) and yellow value (b*=11.39). Comparative Example 5 used silk fiber as the dyeing object, and its green value (a*=-0.17) and yellow value (b*=2.63) were significantly lower than those of Example 1, and the dyeing effect was significantly inferior to that of wool fiber.

[0043] Depend on Figure 3 The results show that the K / S value of wool fibers dyed in Example 1 was superior to that of Comparative Example 1 and the control group, and slightly lower than that of Comparative Example 2. This indicates that, under the same conditions, DHA-reduced indigo mud produces a darker color than glucose, and the green color is visually more distinct. Furthermore, Example 2, dyed with synthetic indigo, achieved a K / S value (4.62) similar to that of Example 1 (4.72), demonstrating that natural indigo mud, after DHA reduction, can achieve dyeing results comparable to those of synthetic indigo. Comparative Example 5, dyed with silk fibers, achieved a K / S value (1.52) significantly lower than that of Example 1, indicating significantly inferior dyeing results to wool fibers.

[0044] 2. Anti-ultraviolet effect test Using the UV2000-F textile sun protection factor analyzer, referring to GB / T 18830-2009 "Evaluation of UV Protection Performance of Textiles", the UV protection factor (UPF) value of the sample was tested within the UV wavelength range of 290-400nm to determine the protection ability of the sample. The wool fiber was uniformly sampled, and 5 different positions were randomly selected for testing, and the average value was taken. The results are as follows Figure 4 shown.

[0045] Depend on Figure 4 The results show that the UPF values ​​of Examples 1 and 2 exceeded 1800, more than five times that of the wool fiber in the control group (UPF = 327). This shows that the wool fiber dyed with the indigo dye and DHA composite system has excellent UV resistance.

[0046] 3. Antioxidant performance test A TV-1901 UV-Vis spectrophotometer was used to measure changes in the absorbance of the solution, and the scavenging rate of ABTS+ free radicals by the wool fiber was calculated to characterize the antioxidant properties of the sample. The ABTS+ free radical solution was prepared using the ABTS method described in the "Determination of the Antioxidant Properties of Chemical Fibers Using DPPH and ABTS Methods": 40 mg of ABTS and 6.88 mg of potassium persulfate were mixed with 10 mL of deionized water and allowed to react in the dark for 16 hours. Before use, the solution was diluted with anhydrous ethanol solution to an absorbance of 0.70 ± 0.02 at 734 nm. Each wool fiber powder sample was added to the solution and allowed to react for 30 minutes before the absorbance was measured.

[0047] The scavenging ability of ABTS+ is calculated as follows:

[0048] Where, is the initial absorbance of ABTS+, is the residual absorbance of ABTS+. Figure 5 and Figure 6 shown.

[0049] Depend on Figure 5 and Figure 6The results show that, in the indigo dye and DHA composite dyeing system, the antioxidant properties of Example 1 (indigo mud and DHA) were slightly better than those of Example 2 (synthetic indigo and DHA). This is likely due to the presence of other natural substances with excellent antioxidant properties in natural indigo mud. The free radical scavenging rates of wool fibers in both dyeing groups exceeded 50%, significantly exceeding those of the other comparative examples and the control group. Comparative experiments revealed that dyeing with glucose-reduced indigo mud, dyeing with DHA alone, and treating wool fibers with other vat dyes (such as indigo-based Vat Pink R and anthraquinone-based Vat Orange 3) did not significantly improve their antioxidant properties. This further demonstrates the synergistic effect of the indigo dye and DHA composite system, effectively imparting excellent antioxidant properties to wool fibers.

[0050] 4. Tensile performance test The fiber's elastic recovery at a constant elongation was tested using an LLY-06E electronic single fiber strength tester at a test speed of 10 mm / min, a gauge of 10 mm, and a pre-tension of 0.2 cN. Fifty wool fibers were selected for each sample and the average value was taken. The tensile breaking strength of wool before and after dyeing was tested with reference to the "Test Method for Tensile Properties of Chemical Staple Fibers" GB / T 14337-2008. The results are shown in the figure below. Figure 7 shown.

[0051] Depend on Figure 7 As can be seen, the tensile strength of wool fibers from Examples 1 and 2 and Control Examples 1 and 2 after dyeing was slightly lower than that of the control group, but there was no significant difference. The dyeing method of 85°C (higher temperature) and 1.5 hours (longer treatment time) is relatively gentle and will not affect the surface structure of the fiber.

[0052] In summary, the indigo dye and DHA complex used in the present invention improves free radical scavenging efficiency by over 40% compared to the individual components alone. Furthermore, the indigo's NH bonds (bond energy 397 kJ / mol) form a hydrogen bond network with the phenolic hydroxyl groups (OH bond energy 467 kJ / mol) of the Maillard product, synergistically capturing different active free radicals and further enhancing free radical scavenging efficiency. Furthermore, the indigo dyeing environment overlaps with the optimal pH range for the Maillard reaction. At this point, the reduction potential of the indigo leuco-form increases, forming a continuous electron transport chain with that of the Maillard intermediate Amadori compound, thereby extending the antioxidant effect. Finally, the Maillard reaction generates volatile antioxidants such as methylpyrazine, which can embed themselves into the interstitial spaces of the indigo crystalline structure. The simultaneously formed melanoidin polymer network forms an interpenetrating structure with the indigo nanoparticles, reducing the oxygen permeability and contributing to the improved antioxidant properties.

[0053] The present invention is not limited to the above-mentioned specific implementation methods. Various changes made by ordinary technicians in this field based on the above-mentioned concept without creative work are all within the scope of protection of the present invention.

Claims

1. A protein fiber dyeing method, characterized in that, The method comprises the following steps: dyeing the protein fiber with a composite system of indigo dye and DHA, and obtaining the dyed protein fiber after the dyeing process.

2. The protein fiber dyeing method according to claim 1, wherein The dyeing process includes: immersing the protein fiber in a composite system of indigo dye and DHA, and reacting the mixture at a bath ratio of 1:20-1:50 and at 60-85° C. for 60-90 minutes.

3. The protein fiber dyeing method according to claim 2, wherein The indigo dye is indigo mud, and the composite system of the indigo dye and DHA includes the following components in mass fractions: 2-3 wt.% of indigo mud and 3.6-5.4 wt.% of DHA.

4. The protein fiber dyeing method according to claim 2, wherein The indigo dye is synthetic indigo, and the composite system of the indigo dye and DHA comprises the following components by mass fraction: 0.02-0.06 wt.% of synthetic indigo and 3.6-5.4 wt.% of DHA.

5. The protein fiber dyeing method according to claim 2, wherein The mass ratio of the composite system of the protein fiber, indigo dye and DHA is 1:25-55.

6. The protein fiber dyeing method according to claim 1, wherein The dyeing process specifically comprises the following steps: S1. Immerse the protein fiber in an aqueous solution of DHA and react at a bath ratio of 1:20-1:50 and 60-85°C for 40-60 minutes; S2. Add indigo dye to the reaction system, continue to react at a bath ratio of 1:20-1:50 and 60-85° C. for 20-30 min, and after the reaction is completed, wash with water and dry to obtain dyed protein fibers.

7. The protein fiber dyeing method according to claim 6, wherein The indigo dye is indigo mud, and the mass ratio of the DHA, indigo mud and water is 3.6-5.4:2-3:

100.

8. The protein fiber dyeing method according to claim 6, wherein The indigo dye is synthetic indigo, and the mass ratio of the DHA, synthetic indigo and water is 3.6-5.4:0.02-0.06:

100.

9. A dyed protein fiber obtained by dyeing using the protein fiber dyeing method according to any one of claims 1 to 8.

10. A fabric, characterized in that: The fabric is obtained by weaving the dyed protein fiber according to claim 9 or blending it with other fibers.

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