Functional Modification Methods for the Color Development Properties of Silk by Natural Polyphenols

Abstract

This invention relates to the field of functional modification of silk, specifically to a method for color-modifying silk with natural polyphenols. The method includes: aromatic amination modification of silk using indigo anhydride to generate aromatic primary amine groups on the silk surface, resulting in aromatic amination silk; diazotization of the aromatic amination silk to obtain diazotized silk; and immersion of the diazotized silk in a natural polyphenol coupling solution, followed by a coupling color-modifying reaction under stirring at room temperature to obtain naturally polyphenol-modified silk. The diazo salt coupling color-modifying functional modification method used in this invention can be carried out at room temperature, has a low modification temperature, does not require the addition of mordants or other auxiliaries, and can impart color to silk while retaining the functionality of natural polyphenols. This method also results in cleaner waste liquid, lower energy consumption, and higher environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of functional modification of silk, specifically to a method for functional modification of the color development properties of silk by natural polyphenols. Background Technology

[0002] In recent years, with increasing emphasis on sustainable development and a healthy society, the demand for healthy and environmentally friendly textiles and their manufacturing processes has been rising, driving the textile industry to explore sustainable dyes, biodegradable substrates, and clean production technologies. Bio-extracts, especially those with added functions, such as natural polyphenols obtained from plants, have attracted significant attention in the medical, cosmetic, and food fields due to their excellent antioxidant and antibacterial properties, as well as their environmentally friendly, non-toxic, or low-toxicity characteristics. Furthermore, natural polyphenols can be used for functional finishing of textiles through a one-bath process, with minimal environmental pollution from residual liquids, aligning with the concept of green and environmentally friendly development.

[0003] Silk is a natural protein material with a long history, renowned for its beautiful appearance and comfortable feel. Its high strength, good biocompatibility, and biodegradability make it a cutting-edge material for the preparation of medical textiles, surgical sutures, and wound dressings. However, the functionalization of silk still faces several challenges, including: First, traditional silk functionalization requires high temperatures to diffuse and adsorb functional agents into the fiber, which may lead to fiber degradation and strength loss. Second, the addition of synthetic finishing agents during silk processing reduces the safety and environmental friendliness of silk products. Third, silk's functionality is insufficient; for example, its UV protection, antibacterial, and antioxidant properties are relatively poor, limiting its application beyond clothing as a protective garment and medical material.

[0004] To date, numerous studies have applied bio-extractants to the functionalization of silk materials. Natural polyphenols and other substances extracted from plant roots, stems, leaves, and fruits possess excellent antibacterial, antioxidant, and UV-protective properties, and can be used to treat silk through adsorption or mordant methods to impart functionalities to it.

[0005] For example, the invention CN109736082A, entitled "A Superhydrophobic Anti-UV Flame Retardant Silk Fabric and Its Preparation Method", discloses that: the silk fabric is soaked in a buffer solution, the pH value is controlled at 4-5, and it is reacted with natural polyphenols at 25-45°C under the catalysis of laccase. The natural polyphenols are one or more of tannic acid, ferulic acid, tea polyphenols, dopamine, chlorogenic acid, caffeic acid, gallic acid and guaiacol.

[0006] The invention CN107904935A, entitled "Hydrophobic Silk Fabrics and Their Preparation Methods and Applications," discloses that: silk fabrics are soaked in a mixed solution of water and organic solvents, plant polyphenols, enzyme catalysts, and copper salt co-catalysts are added, the pH is adjusted to 2-6, and then an alkyl-containing hydrophobic compound is added. The mixture is reacted at 25-65°C for 0.5-6 hours to obtain hydrophobic silk fabrics.

[0007] The current method for modifying silk with natural polyphenols is the adsorption method, which involves directly soaking the silk in natural polyphenols, followed by washing and drying. This method has drawbacks such as the silk not having a vibrant color. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for functionalizing the color development of silk with natural polyphenols.

[0009] To address the aforementioned technical problems, this invention provides a method for functionalizing the color development of silk with natural polyphenols, comprising three steps: aromatic amination modification of silk, in-situ diazotization, and coupling modification with natural polyphenols.

[0010] Specifically as follows:

[0011] 1) Aromatic modification of silk:

[0012] Aromatic modification of silk was carried out by indomethacin anhydride, which produced aromatic primary amine groups on the surface of the silk, thus obtaining aromatic-amined silk.

[0013] 2) Diazotization of aromatic amined silk:

[0014] The aromatic amino-amined silk obtained in step 1) is diazotized to obtain diazotized silk.

[0015] 3) Natural polyphenol coupling and color modification:

[0016] Natural polyphenols are dissolved in water, and then a buffer solution with a pH of 4±0.2 is added to obtain a natural polyphenol coupling solution; the concentration of natural polyphenols in the natural polyphenol coupling solution is 0.1~1g / L.

[0017] The diazotized silk obtained in step 2) was soaked in a natural polyphenol coupling solution and subjected to a coupling color development reaction at room temperature with stirring for 1 ± 0.1 h to obtain natural polyphenol-modified silk.

[0018] Explanation: Diazotized silk undergoes a coupling reaction with a solution containing natural polyphenols, which bind the natural polyphenols to the surface of the silk fibers through nitrogen-nitrogen double bonds, forming a colored substance with an azo structure, thereby endowing the silk with excellent functionality.

[0019] As an improvement of the present invention: in step 3), the volume ratio of buffer solution to water is 1:3.5 to 4.5; the coupling color development bath ratio is 1:80 to 120 (preferably 1:100).

[0020] As a further improvement of the present invention: the natural polyphenol is any one of the following:

[0021] Resveratrol, its structural formula is:

[0022] Caffeic acid, its structural formula is:

[0023] Tannic acid, its structural formula is:

[0024] Rutin, its structural formula is:

[0025] Gallic acid, its structural formula is:

[0026] Curcumin, its structural formula is:

[0027] Scutellarin, its structural formula is:

[0028] All of the above-mentioned natural polyphenols can be purchased commercially.

[0029] As a further improvement of the present invention: the buffer solution is an acetate-sodium acetate buffer solution with pH 4 (acetic acid 16.0 g / L, sodium acetate 3.0 g / L).

[0030] As a further improvement of the present invention, the concentration of natural polyphenols in the natural polyphenol coupling solution is 0.5-1 g / L (more preferably 0.8-1 g / L).

[0031] In this invention:

[0032] Steps 1) and 2) can both refer to the patent "In-situ Diazotization-Coupling Staining Method for Indorubicin Modified Protein Materials" (Application No.: CN202310812659.6);

[0033] Specifically:

[0034] Step 1)

[0035] 5g of silk was soaked in 250±30mL of deionized water. Under the heating of a water bath at 30±5℃, an aqueous solution containing 0.5±0.05g of indomethacin anhydride (20mL in total) was added dropwise with stirring. The pH of the system was controlled at 7-8 during the dropwise addition. After the dropwise addition was completed (the dropwise addition time was about 1.5-2.5 minutes), the reaction was stirred for 1±0.2h to complete the modification.

[0036] Then rinse with hot water at 40±10℃ (rinsing time 0.5~1h), then rinse with clean water, and then air dry naturally to constant weight; thus obtaining aromatic ammonia-treated silk.

[0037] Step 2): Add 1.0 ± 0.02 g of the aromatic amination silk obtained in Step 1) to 45–55 mL of water, then add 0.9–1.1 mL of hydrochloric acid; add dropwise (dropwise for about 1.5–2.5 min) an aqueous solution of NaNO2 consisting of 0.09–0.11 g of NaNO2 and 2.5–3.5 mL of water, and stir the reaction at room temperature for 10–30 min (preferably 20 min); then remove excess nitrous acid.

[0038] The reacted silk fabric is removed, rinsed with water (until the pH of the washing solution is neutral), and then dried to constant weight to obtain diazotized silk fabric.

[0039] This invention advocates using bio-extracts to treat silk, thereby combining the bio-extracts with a bio-based substrate to create bio-based products. To this end, this invention includes the following steps: silk undergoes indigo anhydride aromatication modification and diazotization to produce diazotized silk. Natural polyphenols undergo a coupling reaction with the diazotized silk to achieve functional color modification of the silk.

[0040] In this invention, the modification of silk with indigo anhydride and the preparation of diazotized silk are both mature technologies and will not be described in detail. Considering that natural polyphenols contain abundant phenolic hydroxyl groups, and their ortho positions can serve as sites for coupling reactions, this invention provides a method for the color-developing functional modification of silk fibers by natural polyphenols based on the mechanism of the reaction between diazotized silk and coupling components. This method does not require mordants, can occur at room temperature, and the polyphenol coupling solution is acidic, causing minimal damage to the silk fibers. Compared with the traditional adsorption method and metal salt mordant method used to modify silk fibers with natural polyphenols, the diazo salt coupling color-developing functional modification method used in this invention can be carried out at room temperature, has a low modification temperature, does not require the addition of mordants or other auxiliaries, and can impart color to silk while retaining the functionality of natural polyphenols. This method also results in cleaner waste liquid, lower energy consumption, and higher environmental friendliness.

[0041] This invention involves a coupling reaction between natural polyphenols and diazotized silk, employing a colorimetric functionalization modification method to form nitrogen-nitrogen double bonds. The reaction mechanism is as follows: Figure 1 As shown.

[0042] The method for functionalizing the color development of diazotized silk using natural polyphenols provided in this invention has the following advantages:

[0043] (1) The modification conditions are room temperature acidity, which causes little damage to silk and has low energy consumption;

[0044] (2) To make colorless natural polyphenols appear on silk;

[0045] (3) As a reactive modification, natural polyphenols are firmly bound to silk. Attached Figure Description

[0046] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] Figure 1 This is a diagram of the reaction mechanism;

[0048] Figure 2 The results obtained by modifying silk with the natural polyphenol coupling method described in Examples 1 and 2 series;

[0049] Figure 3 The results obtained by modifying silk with natural polyphenols as described in Comparative Example 1;

[0050] Figure 4 This is a comparison chart of the UV protection performance of silk modified by coupling method and silk modified by adsorption method as described in Examples 1, 2 series and Comparative Example 1;

[0051] Figure 5 This is a comparison chart of the antioxidant activities of silk modified by coupling method and silk modified by adsorption method as described in Examples 1, 2 series and Comparative Example 1;

[0052] Figure 6 The changes in the antioxidant activity of silk fabrics before and after DMF stripping as described in Examples 1, 2 series and Comparative Example 1, (a) coupling method modification, (b) adsorption method modification;

[0053] Figure 7 The antibacterial activity of silk modified by coupling method as described in Example 1 and Comparative Example 1 is shown in the figure above, which is a picture of the culture medium for antibacterial activity test results. The figure below is a bar chart of the inhibition rate of different polyphenols against two bacteria.

[0054] Figure 8 The result is obtained by modifying silkworm silk using the coupling method described in Example 3-1;

[0055] Figure 9 The UV protection performance diagram of the silk modified by coupling method as described in Example 3-1 is shown.

[0056] Figure 10 The diagram shows the antioxidant activity of the silk modified by the coupling method described in Example 3-1.

[0057] Figure 11 The result is obtained by modifying silkworm silk using the coupling method described in Examples 3-2;

[0058] Figure 12The UV protection performance of the silk modified by the coupling method described in Examples 3-2 is shown in the figure.

[0059] Figure 13 The antioxidant activity diagram of the silk modified by coupling method as described in Examples 3-2 is shown.

[0060] Figure 14 The results obtained from the modified silkworm silk in Comparative Example 2;

[0061] Figure 15 The UV protection performance of the modified silk obtained in Comparative Example 2 is shown in the figure.

[0062] Figure 16 This is a graph showing the antioxidant activity of the modified silk obtained in Comparative Example 2. Detailed Implementation

[0063] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0064] The room temperature in this invention refers to 22–28°C.

[0065] The silk is regular white silk.

[0066] Example 1: A method for functionalizing the color development of diazotized silk with natural polyphenols, comprising the following steps:

[0067] 1) Aromatic modification of silk:

[0068] Aromatic modification of silk is achieved by using indocyanine anhydride to generate aromatic primary amino groups on the silk surface, resulting in aromatic-amined silk. This can be referenced in the patent "In-situ Diazotization-Coupling Staining Method for Indocyanine Anhydride-Modified Protein Materials" (Application No.: CN202310812659.6).

[0069] Specifically:

[0070] Five grams of silk were soaked in 250 mL of deionized water. Under heating and stirring conditions in a 30°C water bath, an aqueous solution containing 0.5 g (0.0025 mol) of indomethacin (20 mL) was added dropwise to the silk soaking solution. During the process, the pH of the reaction bath was controlled between 7 and 8 using a sodium carbonate aqueous solution (40 g / L). After the addition was complete (addition time was 2 min), the reaction was stirred for another 1 h to complete the modification. The silk was then washed in hot water at 40 ± 10°C for 0.5 h, rinsed with clean water, and air-dried to constant weight to obtain aromatic-amined silk.

[0071] 2) Diazotization of aromatic amined silk

[0072] Add 50 mL of water to a beaker, then add 1.0 g ± 0.02 g of the aromatic amination silk obtained in step 1) to the water, and then add 1 mL of hydrochloric acid to the beaker; separately dissolve 0.1 g of NaNO2 in 3 mL of water and slowly add it dropwise to the beaker, completing the addition in about 2 minutes. After stirring the reaction at room temperature for 20 minutes, add urea to remove excess nitrite. Dip the solution into starch-potassium iodide test paper and test it. If there is no color change, it means that the nitrite has been removed.

[0073] The reacted silk fabric is removed, rinsed with water (until the pH of the washing solution is neutral), and then dried to constant weight to obtain diazotized silk fabric.

[0074] 3) Coupling and color development of natural polyphenols

[0075] Resveratrol was chosen as the coupling component, and its structure is as follows:

[0076]

[0077] First, resveratrol was dissolved in a mixture of water and a pH 4 acetate-sodium acetate buffer solution to prepare a coupling component solution; in the coupling solution, the concentration of resveratrol was 0.8 g / L, and the volume ratio of buffer solution to water was 1:4.

[0078] 0.5 g of the diazotized silk obtained in step 2) was immersed in 50 mL of the above coupling component solution (i.e., the coupling color development bath ratio is 1:100), and stirred at room temperature for 1 h to achieve the color development functional modification of the diazotized silk by natural polyphenols. After that, the silk was taken out, washed with water (until the pH of the washing solution was neutral), and dried to constant weight to obtain the color development functionalized silk modified with natural polyphenols.

[0079] Example 2 series:

[0080] The natural polyphenols in Example 1, which were originally "resveratrol", were replaced with tannic acid, caffeic acid, rutin, gallic acid, curcumin, and baicalin, respectively, while the amounts remained the same. The rest of the ingredients were the same as in Example 1.

[0081] Comparative Example 1: Diazotized silk was replaced with unmodified silk, and natural polyphenols were modified into the silk using an adsorption method.

[0082] Natural polyphenol adsorption process: Using 0.5g (±0.02g) of silk as in Example 1, the natural polyphenols were first dissolved in a mixed system consisting of water and an acetic acid-sodium acetate buffer solution (acetic acid 5.0g / L, sodium acetate 9.5g / L, pH 5), with a volume ratio of buffer solution to water of 1:4; the concentration of natural polyphenols was 0.8g / L.

[0083] Add 0.5g (±0.02g) of silk to 50mL of the above solution (i.e., the modification bath ratio is 1:100). The initial modification temperature is 30℃, then the temperature is increased to 90℃ at a rate of approximately 2℃ / min. Maintain this temperature at 90℃ for 1 hour, then cool to 30℃. After the modification is complete, remove the modified silk fabric sample, wash, and dry. The natural polyphenols are resveratrol, tannic acid, caffeic acid, rutin, gallic acid, curcumin, and baicalin.

[0084] The following experiment compares the differences between the natural polyphenol coupling method modification of this invention and the adsorption method modification of Comparative Example 1 on silk fabrics.

[0085] Experiment 1: Test the K / S values ​​of modified silk obtained from Example 1, Example 2 series and Comparative Example 1.

[0086] The K / S value and maximum absorption wavelength of the modified silk fabric were measured using a Datacolor colorimeter.

[0087] The results are as follows Figure 2 and Figure 3 As shown.

[0088] according to Figure 2 and Figure 3 It is known that existing adsorption methods for modified silk, except for curcumin-modified silk which exhibits a vibrant yellow and a relatively deep color, generally result in grayish-yellow modified silk with a dull and light color, and K / S values ​​mostly around 1. In contrast, the modified silk obtained through the coupling method of this invention has a more vibrant color, primarily orange-yellow, and a relatively deep color, with K / S values ​​all above 13. This is because most natural polyphenols themselves do not possess vibrant colors; therefore, when adsorbed onto silk, they can only display their own colors, resulting in modified silk that lacks vibrancy. The coupling method, however, involves diazotizing the silk and natural polyphenols to induce a coupling reaction, linking the silk and polyphenols through nitrogen-nitrogen double bonds to form an azo color-developing structure, thus endowing the modified silk with a vibrant color.

[0089] Experiment 2: Testing the UV protection performance of the modified silk obtained in Examples 1, 2, and Comparative Example 1;

[0090] The UPF value of modified silk was measured using a textile ultraviolet transmittance tester (HD902C type ultraviolet transmittance performance tester from Nantong Hongda Experimental Instrument Co., Ltd.). A single-layer modified silk fabric was used for the measurement. Each sample was tested three times at different locations, and the average value was reported.

[0091] The results are as follows Figure 4 As shown.

[0092] according to Figure 4It is evident that the UV protection performance of modified silk obtained by the coupling method of this invention is far superior to that of modified silk obtained by the existing adsorption method. The UPF value of modified silk obtained by the adsorption method can only reach a maximum of about 35, while the UPF value of modified silk obtained by the coupling method can reach over 60. The main reason for this is that the modified silk obtained by the coupling method not only binds natural polyphenols to the fabric surface but also imparts color to the fabric. Its UV protection performance is partly provided by the natural polyphenols on the fabric surface and partly by the dark color of the fabric. In contrast, the modified silk obtained by the adsorption method does not have a dark color and only provides UV protection performance through the natural polyphenols on the fabric surface, thus its performance is inferior.

[0093] Experiment 3: Test the antioxidant activity of the modified silk obtained in Examples 1 and 2 and Comparative Example 1;

[0094] The antioxidant activity of fabrics was evaluated using the ABTS free radical decolorization test.

[0095] Experimental group: ABTS (7mM) solution and potassium persulfate (2.45mM) solution were mixed at a 1:1 volume ratio, and the mixture was stirred and reacted in the dark at room temperature for 12-16 hours to obtain ABTS· + Stock solution. Dilute ABTS with phosphate buffer (0.1M, pH 7.4) before use. + The stock solution was prepared to achieve an absorbance of 0.700 ± 0.020 at 734 nm. 20 mg of sample was immersed in 20 mL of diluted ABTS· + In the solution, after sealing and shaking for 1 min, place in the dark. After 30 min, measure ABTS using a UV-Vis spectrophotometer. + The absorbance at 734 nm was measured. A blank control group without fabric was also set up, and the above operation was repeated.

[0096] Antioxidant activity was calculated using formula (1). Where A... ctrl ABTS is the blank control group. + absorbance, A spl For sample group ABTS· + Absorbance.

[0097]

[0098] The results are as follows Figure 5 As shown.

[0099] according to Figure 5It can be seen that the antioxidant activity of modified silk obtained by coupling and adsorption methods is not significantly different. However, the antioxidant activity of silk fabrics modified by coupling with a few natural polyphenols is much stronger than that obtained by adsorption. It is speculated that this is because the adsorption method adsorbs the natural polyphenols onto the fabric surface, and then... (The sentence is incomplete and requires further context to translate accurately.) + Natural polyphenols in solution can leach from the fabric into the solution, thus exhibiting good antioxidant activity; while the coupling method fixes natural polyphenols on the fabric surface, and after shaking, the fabric is exposed to ABTS· + The solution is in full contact, thus achieving its antioxidant function.

[0100] Experiment 4: Test the strength of the modified silk obtained from Examples 1 and 2 and Comparative Example 1;

[0101] The modified silk fabrics obtained by the two methods were treated using the DMF stripping method, and the changes in the antioxidant properties of the fabrics before and after stripping were compared.

[0102] DMF stripping method: The modified silk fabric was immersed in 50 mL of DMF and extracted at 95 °C for 30 min. After 30 min, the fabric was removed, washed with water, and dried. The antioxidant activity of the stripped silk fabric was then tested and compared with that before stripping.

[0103] The results are as follows Figure 6 As shown.

[0104] according to Figure 6 It can be seen that after DMF stripping, the antioxidant activity of modified silk obtained by the coupling method decreased less, while the antioxidant activity of modified silk obtained by the adsorption method decreased significantly. This is because DMF has good solubility for small organic molecules. The adsorption method merely adsorbs natural polyphenols onto the surface of the silk fabric, which are then stripped off by DMF, resulting in a significant reduction in the natural polyphenol content on the fabric surface and a decline in performance. In contrast, the coupling method links natural polyphenols to the silk fabric through nitrogen-nitrogen double bonds. DMF cannot strip these covalently bonded natural polyphenols; only a small amount of surface-attached natural polyphenols are stripped off, thus the decrease in antioxidant activity of the modified silk is not significant.

[0105] Experiment 5: Test the antibacterial activity of the modified silk obtained in Example 1 and Comparative Example 1;

[0106] The antibacterial activity of two bacteria, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), on modified silk was tested.

[0107] Place 0.5g of the pulverized sample (size < 0.5*0.5cm) into 10mL of the prepared bacterial solution (10 5In CFU, the bacterial culture was shaken in a shaker at an appropriate temperature (30℃ for E. coli, 24℃ for S. aureus) for 24 h. Then, the bacterial culture was diluted 1000 times and inoculated onto agar medium, and cultured at 37℃ for a certain period (24 h for E. coli, 48 h for S. aureus). Finally, the number of colonies on the medium was counted, and the antibacterial rate of the fabric was calculated using formula (2). Where N... ctrl N is the colony count of the blank control group without fabric. spl It represents the number of colonies in the sample group.

[0108]

[0109] The results are as follows Figure 7 As shown.

[0110] according to Figure 7 It is evident that the modified silk obtained by the coupling method possesses excellent antibacterial activity. For both types of bacteria, most naturally polyphenol-modified silk achieved an inhibition rate of over 80%, and its inhibitory effect on Staphylococcus aureus was superior to that on Escherichia coli. This demonstrates that the covalent bonding between natural polyphenols and silk fabrics did not affect their antibacterial activity.

[0111] In summary, the coupling and color-developing functional modification method for diazotized silk using natural polyphenols described in this invention links natural polyphenols to silk fabrics via nitrogen-nitrogen double bonds. Compared to traditional adsorption methods, this modification method can be carried out at room temperature, making it more energy-efficient and environmentally friendly. Furthermore, the strong covalent bond between natural polyphenols and silk provides better durability. These advantages not only enable natural polyphenols to successfully exhibit their excellent properties on the surface of silk fabrics but also reduce the energy consumption required for the modification process, conserving resources and meeting the needs of industrial production.

[0112] Example 3-1: Adjust the concentration of "natural polyphenols in the coupling component solution" in step 3) of Example 1, that is, change the concentration of natural polyphenols from "0.8 g / L" to "0.5 g / L".

[0113] The rest is the same as in Examples 1 and 2.

[0114] Then, the tests were conducted according to Experiments 1 through 3 above, and the results are as follows: Figures 8-10 As shown.

[0115] according to Figures 8-10It is known that reducing the concentration of natural polyphenols decreases the K / S value of modified silk. This is because the reduced content of natural polyphenols in the modification bath results in a smaller amount reacting with the diazotized silk, leading to a lower color depth in the modified silk. The reduced amount of natural polyphenols modifying the diazotized silk also lowers the UPF value, thus reducing its UV protection performance. The decrease in natural polyphenol concentration is also reflected in antioxidant activity; the ability of modified silk to scavenge free radicals is reduced across the board, with resveratrol, gallic acid, curcumin, and baicalin showing the most significant decreases.

[0116] Example 3-2: Adjust the concentration of "natural polyphenols in the coupling component solution" in step 3) of Example 1, that is, change the concentration of natural polyphenols from "0.8 g / L" to "1 g / L".

[0117] The rest is the same as in Examples 1 and 2.

[0118] Then, the tests were conducted according to Experiments 1 through 3 above, and the results are as follows: Figures 11-13 As shown.

[0119] according to Figures 11-13 It is known that increasing the concentration of natural polyphenols improves the K / S value of modified silk. This is because the increased amount of natural polyphenols reacting with diazotized silk leads to a greater color depth in the modified silk. Correspondingly, the UV protection properties of the modified silk also increase with the increase in the amount of natural polyphenols used in the modification. In terms of antioxidant activity, the modified silk demonstrates a significantly enhanced ability to scavenge free radicals, with most natural polyphenol-modified silk exhibiting antioxidant activity exceeding 90%.

[0120] Comparative Example 2, relative to Example 1:

[0121] Cancel steps 1) and 2);

[0122] That is, step 3) is carried out directly by replacing the diazotized silk with the original silk; the rest is the same as in Example 1 and Example 2.

[0123] Then, the tests were conducted according to Experiments 1 through 3 above, and the results are as follows: Figures 14-16 As shown.

[0124] according to Figures 14-16It is known that modified silk obtained by treating silkworm silk in a natural polyphenol modification bath at room temperature and pH 4 is grayish-white, except for the light yellow obtained by curcumin modification. This is because under these conditions, only a small amount of natural polyphenols can be adsorbed onto the silkworm silk surface, and natural polyphenols are almost colorless, resulting in extremely light colors in the modified silkworm silk. Since the natural polyphenols are only adsorbed onto the silkworm silk surface and have weak binding force, most of them are washed away during the washing stage after modification, with only a very small portion remaining on the fabric surface. Therefore, the final modified silkworm silk has poor performance, with a UPF value of only about 10, poor ultraviolet protection performance, and antioxidant activity of less than 50%, far inferior to the modified silkworm silk obtained by the coupling modification method of this invention.

[0125] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for functionalizing the color development properties of silk with natural polyphenols, characterized in that... Perform the following steps in sequence: 1) Aromatic modification of silk: Aromatic modification of silk was carried out by indomethacin anhydride, which produced aromatic primary amine groups on the surface of the silk, thus obtaining aromatic-amined silk. 2) In-situ diazotization: The aromatic amino-amined silk obtained in step 1) is diazotized to obtain diazotized silk; 3) Natural polyphenol coupling modification: Natural polyphenols are dissolved in water, and then a buffer solution with a pH of 4 ± 0.2 is added to obtain a natural polyphenol coupling solution; the concentration of natural polyphenols in the natural polyphenol coupling solution is 0.1~1 g / L. The diazotized silk obtained in step 2) was soaked in a natural polyphenol coupling solution and subjected to a coupling color development reaction at room temperature with stirring for 1 ± 0.1 h to obtain natural polyphenol-modified silk.

2. The method for functionalizing the color development properties of silk with natural polyphenols according to claim 1, characterized in that: In step 3), the volume ratio of buffer solution to water is 1:3.5~4.5; the coupling color development bath ratio is 1:80~120.

3. The method for functionalizing the color development of silk with natural polyphenols according to claim 1 or 2, characterized in that, The natural polyphenols are any of the following: resveratrol, caffeic acid, tannic acid, rutin-gallic acid, curcumin, and baicalin.

4. The method for functionalizing the color development of silk with natural polyphenols according to claim 3, characterized in that: The buffer solution is an acetate-sodium acetate buffer solution with pH=4.

5. The method for functionalizing the color development of silk with natural polyphenols according to claim 3, characterized in that: The concentration of natural polyphenols in the natural polyphenol coupling solution is 0.5 ~ 1 g / L.

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