Method for carrying out functional modification on color rendering property of silk by using natural polyphenol

Abstract

The invention relates to the field of functional modification of silk, in particular to a color-rendering functional modification method of natural polyphenols on silk, which comprises the following steps: carrying out aromatic amination modification on the silk by utilizing isatoic anhydride to generate aromatic primary amino on the surface of the silk to obtain aromatic aminated silk; diazotizing the arylated silk to obtain diazotized silk; and soaking the diazotized silk in a natural polyphenol coupling solution, and carrying out coupling chromogenic reaction under the condition of stirring at room temperature to obtain the natural polyphenol chromogenic modified silk. The diazonium salt coupling color-developing functional modification method used in the invention can be carried out at room temperature, the modification temperature is low, assistants such as mordant do not need to be added, the silk can be endowed with color on the premise of retaining the functionality of natural polyphenol, and the method has the advantages of cleaner waste liquid, lower energy consumption and high environmental protection property.

Description

Technical Field

[0001] The invention relates to the field of functional modification of silk, and in particular to a method for functional modification of the color development of silk by using natural polyphenols. Background Art

[0002] In recent years, as people pay more and more attention to the social themes of sustainable development and life and health, the demand for healthy and environmentally friendly textiles and their manufacturing processes has continued to rise, driving the textile industry to explore sustainable dyes, biodegradable substrates and clean production technologies. Biological extracts, especially biological extracts with additional functions, such as natural polyphenols obtained from plants, have attracted much attention in the fields of medicine, cosmetics, food, etc. due to their excellent antioxidant and antibacterial properties, as well as their environmental friendliness, non-toxicity or low toxicity. In addition, natural polyphenols can achieve functional finishing of textiles through a one-bath method, and the residual liquid has little pollution to the environment, which is in line with the concept of green and environmentally friendly development.

[0003] Silk is a natural protein material with a long history, known for its gorgeous appearance and comfortable touch. Its high strength, good biocompatibility and biodegradability make it a cutting-edge material for the preparation of medical textiles, surgical sutures, wound dressings, etc. However, the functionalization of silk still faces many challenges, as follows: First, the functional finishing of traditional silk requires the use of high temperatures to diffuse and adsorb the functional finishing agent into the fiber, but this may cause degradation of the silk fiber and loss of strength. Secondly, the addition of synthetic finishing agents during silk finishing reduces the safety and environmental friendliness of silk products. Third, the lack of functionality of silk, such as poor UV protection, antibacterial and antioxidant properties, limits its application as protective clothing, medical materials, etc. outside of clothing.

[0004] So far, a large number of studies have applied biological extracts to the functionalization of silk materials. Natural polyphenols extracted from plant roots, stems, leaves, and fruits have good antibacterial, antioxidant, and UV protection properties. They can be treated with silk by adsorption or mordanting to give silk functionality.

[0005] For example, the invention of CN109736082A "A super-hydrophobic, anti-ultraviolet and flame-retardant silk fabric and its preparation method" states: the silk fabric is immersed in a buffer solution, the pH value is controlled to be 4-5, and reacted with natural polyphenols at 25-45°C under the catalysis of laccase, and 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 of CN107904935A "Hydrophobic silk fabric, preparation method and application thereof" states: soak the silk fabric in a mixed solution of water and an organic solvent, add plant polyphenols, an enzyme catalyst and a copper salt co-catalyst thereto, adjust the pH to 2-6, then add an alkyl-containing hydrophobic compound, react at 25-65°C for 0.5-6h, and obtain a hydrophobic silk fabric.

[0007] The current existing method for modifying silk using natural polyphenols is an adsorption method, that is, the silk is directly immersed in natural polyphenols; then washed and dried; this method has the disadvantages of the silk not having bright 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 using natural polyphenols.

[0009] In order to solve the above technical problems, the present invention provides a method for functionalizing the color development of silk with natural polyphenols, comprising three steps of aromatic amination modification of silk, in-situ diazotization, and coupling modification with natural polyphenols.

[0010] The details are as follows:

[0011] 1) Aromatic modification of silk:

[0012] The silk is modified by aromatic amination using isatoic anhydride to produce aromatic primary amine groups on the surface of the silk, thereby obtaining aromatic amination silk.

[0013] 2) Diazotization of aromatic amination silk:

[0014] Diazotizing the aromatic aminated silk obtained in step 1) to obtain diazotized silk;

[0015] 3) Natural polyphenol coupling color modification:

[0016] Dissolving natural polyphenols in water, and then adding a buffer solution with a pH of 4±0.2 to obtain a natural polyphenol coupling solution; the concentration of natural polyphenols in the natural polyphenol coupling solution is 0.1-1 g / L;

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

[0018] Description: Diazotized silk undergoes a coupling reaction with a solution containing natural polyphenols, and the natural polyphenols are bonded to the surface of silk fibers through nitrogen-nitrogen double bonds to form colored substances with an azo structure, thereby giving silk excellent functionality.

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

[0020] As a further improvement of the present invention: the natural polyphenol is any 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 has the structural formula:

[0026] Curcumin, its structural formula is:

[0027] Huangling glycoside, its structural formula is:

[0028] The above-mentioned natural polyphenols can all be purchased commercially.

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

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

[0031] In the present invention:

[0032] Step 1) and step 2) can refer to the patent "In situ diazotization-coupling dyeing method for indigo anhydride modified protein materials" (application number: CN202310812659.6);

[0033] Specifically:

[0034] Step 1)

[0035] 5 g of silk was immersed in 250±30 mL of deionized water, and an aqueous solution containing 0.5±0.05 g of isatoic anhydride (20 mL in total) was added dropwise under stirring under heating in a water bath at 30±5°C, and the pH of the system was controlled to be 7-8 during the addition process; after the addition was completed (the addition time was about 1.5-2.5 minutes), the reaction was continued to stir for 1±0.2 h, thereby completing the modification;

[0036] Then, rinse with hot water at 40±10°C (rinsing time 0.5-1h), then rinse with clean water, and then dry naturally to constant weight; thus, aromatic aminated silk is obtained.

[0037] Step 2), put 1.0±0.02g of the aromatic aminated silk obtained in step 1) into 45-55mL of water, then add 0.9-1.1mL of hydrochloric acid; dropwise add (dropwise addition time is about 1.5-2.5min) a NaNO2 aqueous solution consisting of 0.09-0.11g of NaNO2 and 2.5-3.5mL of water, and stir the reaction at room temperature for 10-30min (preferably 20min); then remove excess nitrous acid;

[0038] The silk fabric after the reaction is taken out, rinsed with water (until the pH of the washing liquid is neutral), and then blown dry to constant weight to obtain a diazotized silk fabric.

[0039] The present invention advocates the use of biological extracts to finish silk, thereby combining the biological extracts with biological substrates to produce bio-based products. To this end, the present invention sets the following steps: the silk is modified by aromatic amination of isatinic anhydride and diazotized to produce diazotized silk. Natural polyphenols react with diazotized silk to achieve functional color modification of silk.

[0040] In the present invention, the modification of silk by isocyanic 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, its ortho position can become the action site of coupling reaction. According to the mechanism of reaction between diazotized silk and coupling component, the present invention provides a method for functional modification of the color development of silk fiber by natural polyphenols. The method does not require a mordant and can occur at room temperature. The polyphenol coupling solution is acidic and has little damage to the silk fiber. Compared with the adsorption method and metal salt mordant method used for traditional natural polyphenol modification of silk fiber, the diazonium salt coupling color development functional modification method used in the present invention can be carried out at room temperature, the modification temperature is low, no auxiliaries such as mordants are required, and the silk color can be given under the premise of retaining the functionality of natural polyphenols. The method has cleaner waste liquid, lower energy consumption, and higher environmental protection.

[0041] The present invention couples natural polyphenols with diazotized silk to form a nitrogen-nitrogen double bond to form a color-developing functional modification method. Figure 1 shown.

[0042] The method for functionalizing the color development of diazotized silk with natural polyphenols provided by the present invention has the following advantages:

[0043] (1) The modification conditions are room temperature acidic, which causes little damage to the silk and consumes less energy;

[0044] (2) causing colorless natural polyphenols to produce color on silk;

[0045] (3) It is a reactive modification, and natural polyphenols are firmly bound to silk. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0047] Figure 1 is the reaction mechanism diagram;

[0048] Figure 2 These are the results obtained by modifying silk using the natural polyphenol coupling method described in Example 1 and Example 2;

[0049] Figure 3 The results obtained by modifying silk using the natural polyphenol adsorption method described in Comparative Example 1;

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

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

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

[0053] Figure 7 The antibacterial activity of silk modified by the coupling method described in Example 1 and Comparative Example 1; the upper figure is a picture of the culture medium of the antibacterial activity test results, and the lower figure is a bar graph of the antibacterial rate of different polyphenols against two bacteria.

[0054] Figure 8 The results of modifying silk by the coupling method described in Example 3-1;

[0055] Fig. 9 This is a graph showing the UV protection performance of the silk modified by the coupling method described in Example 3-1;

[0056] Fig.10 This is a graph showing the antioxidant activity of the silk modified by the coupling method described in Example 3-1;

[0057] Fig.11 This is the result obtained by modifying silk using the coupling method described in Example 3-2;

[0058] Fig.12This is a graph showing the UV protection performance of the silk modified by the coupling method described in Example 3-2;

[0059] Fig.13 This is a graph showing the antioxidant activity of the silk modified by the coupling method described in Example 3-2;

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

[0061] Fig.15 This is a graph showing the UV protection performance of the modified silk obtained in Comparative Example 2;

[0062] Fig.16 This is the antioxidant activity diagram of the modified silk obtained in Comparative Example 2. DETAILED DESCRIPTION

[0063] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0064] The room temperature in the present invention refers to 22 to 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] The silk is modified by aromatic amination using isatoic anhydride to produce aromatic primary amino groups on the surface of the silk to obtain aromatic amination silk; please refer to the patent "In situ diazotization-coupling dyeing method for protein materials modified by isatoic anhydride" (application number: CN202310812659.6)

[0069] Specifically:

[0070] 5g of silk was immersed in 250mL of deionized water, heated in a water bath at 30℃ and stirred, and an aqueous solution containing 0.5g (0.0025mol) of isocyanic anhydride (20ml in total) was added to the silk soaking solution. During the process, the pH of the reaction bath was controlled between 7 and 8 with an aqueous sodium carbonate solution (40g / L). After the addition was completed (the addition time was 2min), the reaction was continued to stir for 1h to complete the modification. Then, the mixture was washed in hot water at 40±10℃ for 0.5h, then rinsed with clean water and dried naturally to constant weight; aromatic amination silk was obtained.

[0071] 2) Diazotization of aromatic amination silk

[0072] Add 50 mL of water to a beaker, add 1.0 g ± 0.02 g of the aromatic aminated silk obtained in step 1) into the water, and then add 1 mL of hydrochloric acid to the beaker; dissolve 0.1 g of NaNO2 in 3 mL of water and slowly drip it into the beaker. The addition takes about 2 minutes. After stirring and reacting at room temperature for 20 minutes, urea is added to remove excess nitrous acid. Dip the solution into starch potassium iodide test paper for detection. No color change indicates that the nitrous acid has been removed.

[0073] The silk fabric after the reaction is taken out, rinsed with water (until the pH of the washing liquid is neutral), and then blown dry to constant weight to obtain a diazotized silk fabric.

[0074] 3) Coupling color development of natural polyphenols

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

[0076]

[0077] First, resveratrol is dissolved in a mixed system consisting of water and acetic acid-sodium acetate buffer solution of pH 4 to prepare a coupling component solution; in the coupling solution, the concentration of resveratrol is 0.8 g / L, and the volume ratio of buffer solution: water is 1:4;

[0078] Immerse 0.5 g of the diazotized silk obtained in step 2) in 50 mL of the above-mentioned coupling component solution (i.e., the coupling color development bath ratio is 1:100), and stir the reaction at room temperature for 1 hour to achieve the color development functional modification of the diazotized silk by natural polyphenols. Then, take out the silk, wash it with clean water (until the pH of the washing liquid is neutral), and blow dry it to constant weight to obtain natural polyphenol color development functional modified silk.

[0079] Example 2 series:

[0080] The natural polyphenols in Example 1 were changed from "resveratrol" to: tannic acid, caffeic acid, rutin, gallic acid, curcumin, and scutellaria baicalensis respectively, with the dosage remaining unchanged, and the rest were the same as in Example 1.

[0081] Comparative Example 1: The diazotized silk was replaced with unmodified silk, and the natural polyphenols were modified into silk by adsorption method.

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

[0083] 0.5g (±0.02g) of silk was added to 50mL of the above solution (i.e., the modification bath ratio was 1:100), the modification starting temperature was 30℃, the temperature was raised to 90℃, the heating rate was about 2℃ / min, and the temperature was kept at 90℃ for 1h, and finally cooled to 30℃. After the end, the modified silk cloth sample was taken out, washed, and dried. The natural polyphenols were resveratrol, tannic acid, caffeic acid, rutin, gallic acid, curcumin, and scutellaria baicalensis.

[0084] The following experiments are conducted to compare the differences between the modification by the coupling method of natural polyphenols of the present invention and the modification by the adsorption method of Comparative Example 1 in the application on silk fabrics.

[0085] Experiment 1: Test the K / S values ​​of the modified silk obtained in 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 shown.

[0088] according to Figure 2 and Figure 3 It can be seen that the modified silk obtained by the existing adsorption method has a bright yellow color and a deeper color depth, except for the fabric modified by curcumin, the modified silk obtained by the other natural polyphenols is mostly grayish yellow, dull in color and shallow in color depth, and the K / S value is mostly only about 1; while the modified silk obtained by the coupling method of the present invention has a relatively bright color, mainly orange-yellow, and the obtained modified silk has a deeper color depth, and the K / S value is above 13. This is because most natural polyphenols do not have bright colors themselves, so when they are adsorbed on silk, they can only show their own colors, so that the modified silk does not have bright colors; and the coupling method modification is through the coupling reaction between diazotized silk and natural polyphenols, so that the silk and natural polyphenols are connected by nitrogen-nitrogen double bonds to form an azo color-producing structure, giving the modified silk a bright color.

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

[0090] The UPF value of the modified silk was measured in a textile UV transmission tester (HD902C UV Transmission Performance Tester from Nantong Hongda Experimental Instrument Co., Ltd.). A single layer of 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 shown.

[0092] according to Figure 4It can be seen that the ultraviolet protection performance of the modified silk obtained by the coupling method of the present invention is much stronger than that of the modified silk obtained by the existing adsorption method; the UPF value of the modified silk obtained by the adsorption method can only reach about 35 at most; while the UPF value of the modified silk obtained by the coupling method can reach more than 60. The main reason is that the modified silk obtained by the coupling method not only combines natural polyphenols to the surface of the fabric, but also gives the fabric color. Its ultraviolet protection performance is partly provided by the natural polyphenols on the surface of the fabric, and the other part is provided by the dark color of the fabric; while the modified silk obtained by the adsorption method does not have a dark color, and only provides ultraviolet protection performance through the natural polyphenols on the surface of the fabric, so the performance is poor.

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

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

[0095] Experimental group: ABTS (7 mM) solution and potassium persulfate (2.45 mM) solution were mixed in a volume ratio of 1:1, and the mixture was stirred at room temperature in the dark for 12-16 hours to obtain ABTS· + Before use, dilute ABTS with phosphate buffer solution (0.1 M, pH 7.4). + Stock solution, so that the absorbance at 734nm reaches 0.700±0.020. Take 20mg sample and immerse it in 20mL of diluted ABTS· + After sealing and shaking for 1 min, place in a dark environment. After 30 min, measure ABTS· + The absorbance at 734 nm. A blank control group without fabric was set up and the above operation was repeated.

[0096] The antioxidant activity was calculated by formula (1). ctrl The blank control group was ABTS· + The absorbance, A spl For the sample group ABTS + The absorbance.

[0097]

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

[0099] according to Figure 5It can be seen that the antioxidant activity of the modified silk obtained by the coupling method and the adsorption method is not significantly different. The antioxidant activity of the silk fabric modified by the coupling method with a few natural polyphenols is much stronger than that obtained by the adsorption method. It is speculated that the reason may be that the adsorption method adsorbs the natural polyphenols on the surface of the fabric. + The natural polyphenols in the solution will be resolved from the fabric and enter the solution, thus showing good antioxidant activity; the coupling method fixes the natural polyphenols on the surface of the fabric, and after shaking, the fabric and ABTS· + The solution is fully in contact, thereby playing an antioxidant role.

[0100] Experiment 4: Testing the firmness of the modified silk obtained in Example 1, Example 2 series and Comparative Example 1;

[0101] The modified silk fabrics obtained by the two methods were treated by 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 DMF and extracted at 95 °C for 30 min. After 30 min, the fabric was taken out, washed with water and dried. The antioxidant activity of the silk fabric after stripping was then tested and compared with that before stripping.

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

[0104] according to Figure 6 It can be seen that after DMF stripping, the antioxidant activity of the modified silk obtained by the coupling method decreased less, while the antioxidant activity of the modified silk obtained by the adsorption method decreased significantly. The reason is that DMF has good solubility for small organic molecules. The adsorption method only adsorbs natural polyphenols on the surface of silk fabrics, which will be stripped off by DMF, resulting in a large reduction in the content of natural polyphenols on the surface of the fabric and a decrease in performance; while the coupling method connects natural polyphenols to silk fabrics through nitrogen-nitrogen double bonds, and DMF cannot strip these natural polyphenols bound by covalent bonds. Only a small amount of natural polyphenols attached to the surface are stripped off, so the antioxidant activity of the modified silk does not decrease significantly.

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

[0106] The antibacterial activity of modified silk was tested using Escherichia coli (E.coil) and Staphylococcus aureus (S.aureus).

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

[0108]

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

[0110] according to Figure 7 It can be seen that the modified silk obtained by the coupling method has excellent antibacterial activity. For both bacteria, most of the silk modified with natural polyphenols can achieve an antibacterial rate of more than 80%, and the inhibitory effect on Staphylococcus aureus is better than that on Escherichia coli. It can be seen that the covalent bonding of natural polyphenols to silk fabrics does not affect the display of their antibacterial activity.

[0111] In summary, the coupling color development functional modification method of natural polyphenols on diazotized silk described in the present invention connects natural polyphenols to silk fabrics through nitrogen-nitrogen double bonds. Compared with the traditional adsorption method, the modification method can be carried out at room temperature, which is more energy-saving and environmentally friendly. In addition, natural polyphenols and silk are firmly combined through covalent bonds, which can have better durability. The above advantages not only enable natural polyphenols to successfully show their excellent performance on the surface of silk fabrics, but also reduce the energy consumption required for the modification process, save resources, and meet the needs of industrial production.

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

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

[0114] Then, the above experiments 1 to 3 were followed to test, and the results were as follows: Figure 8 to Figure 10 shown.

[0115] according to Figure 8 to Figure 10What is known: When the concentration of natural polyphenols is reduced, the K / S value of modified silk decreases. This is because the content of natural polyphenols in the modification bath is reduced, and the amount of reaction with diazotized silk is less, resulting in a decrease in the color depth of the modified silk. Due to the reduction in the amount of natural polyphenols modified on diazotized silk, the UPF value of the modified silk decreases, and the UV protection performance decreases. The reduction in the concentration of natural polyphenols is also reflected in the antioxidant activity. The ability of modified silk to scavenge free radicals has decreased, among which resveratrol, gallic acid, curcumin and berberine have decreased more significantly.

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

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

[0118] Then, the above experiments 1 to 3 were followed to test, and the results were as follows: Figure 11 to Figure 13 shown.

[0119] according to Figure 11 to Figure 13 It is known that increasing the concentration of natural polyphenols will increase the K / S value of modified silk. This is because the amount of natural polyphenols that react with diazotized silk increases, resulting in an increase in the color depth of the modified silk. Correspondingly, the UV protection of modified silk also increases with the increase in the amount of natural polyphenol modification. From the performance in antioxidant activity, it can be seen that the ability of modified silk to scavenge free radicals is significantly improved, and the antioxidant activity of most natural polyphenol-modified silk can reach more than 90%.

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

[0121] Cancel step 1) and step 2);

[0122] That is, the original silk is used instead of the diazotized silk to directly carry out step 3); the rest is the same as Example 1 and Example 2.

[0123] Then, the above experiments 1 to 3 were followed to test, and the results were as follows: Figure 14 to Figure 16 shown.

[0124] according to Figure 14 to Figure 16As is known, the modified silk obtained by treating silk in a natural polyphenol modification bath at room temperature and pH 4 is off-white, except for the light yellow modified with curcumin. This is because under this condition, natural polyphenols can only be adsorbed on the surface of silk in small amounts, and natural polyphenols are almost colorless, making the modified silk extremely light in color. Since natural polyphenols are only adsorbed on the surface of silk, the binding force is weak, and most of them are washed away in the cleaning stage after the modification, and only a very small part remains on the surface of the fabric. Therefore, the modified silk obtained in the end has poor performance, the UPF value can only reach about 10, the ultraviolet protection performance is poor, and the antioxidant activity is less than 50%, which is far less than the modified silk obtained by the combined modification of the present invention.

[0125] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for functionalizing the color development of silk using natural polyphenols, characterized in that Follow these steps in order: 1) Aromatic modification of silk: The silk was modified by aromatic amination using isatoic anhydride to produce aromatic primary amine groups on the surface of the silk to obtain aromatic amination silk. 2) In-situ diazotization: Diazotizing the aromatic aminated silk obtained in step 1) to obtain diazotized silk; 3) Coupling modification of natural polyphenols: Dissolving natural polyphenols in water, and then adding a buffer solution with a pH of 4±0.2 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) is immersed in a natural polyphenol coupling solution, and a coupling color development reaction is carried out at room temperature with stirring for 1±0.1h to obtain natural polyphenol color-modified silk.

2. The method for functionalizing the color development of silk using 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 bath ratio is 1:80-120.

3. The method for functionalizing the color development of silk using 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 gallate, curcumin, and scutellaria baicalensis.

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

5. The method for functionalizing the color development of silk using 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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