A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells

Abstract

The present invention relates to the technical field of extraction and dyeing of natural dyes, and discloses a method for microwave-assisted extraction of natural dyes from walnut shells for wool dyeing, comprising the following steps: (1) grinding walnut shells into powder, and then performing microwave-assisted thermal extraction to obtain a dyeing extract; (2) filtering and centrifuging the dyeing extract, and adding a leveling agent to the supernatant to obtain a natural dye; (3) pre-mordanting a wool sample using an aqueous solution of ferrous sulfate to obtain a pre-mordanted wool sample; (4) then, dyeing the pre-mordanted wool sample using a natural dye and tannic acid to obtain a dyed wool sample. The present invention combines a thermal extraction method with a microwave treatment method, and microwave-assisted extraction can achieve better results than traditional extraction, and can better extract the dye components in walnut shells to obtain a natural dye that can be used for dyeing, and the natural dye is applied to the dyeing and finishing of wool fabrics.

Description

Technical Field

[0001] The invention belongs to the technical field of natural dye extraction and dyeing, and more specifically relates to a method for wool dyeing by extracting natural dye from walnut shells with microwave assistance. Background Art

[0002] Wool fabrics are soft, flame retardant, wrinkle-resistant, elastic, hygroscopic, and warm, but they also have disadvantages such as easy felting and poor moth resistance. Therefore, wool fabrics need to be functionally finished before being used in different fields. As consumers' awareness of environmental protection and health increases, ecological technology and natural products are increasingly valued, and the use of natural dyes in the functional finishing of wool fabrics has gradually become a research and development focus.

[0003] Natural dyes have good biodegradability and environmental compatibility, and are becoming more and more popular. However, the extraction and processing of natural dyes currently consumes a lot of energy and time, and the process of dyeing fabrics is complicated, so the process of dyeing fabrics with natural dyes has not been widely used.

[0004] Walnut shells mainly contain chemical components such as phenolic acid, saponin, flavonoids, esters and polysaccharides. Studies have found that good natural dyes can be extracted from walnut shells, which also have antioxidant and antibacterial effects. While dyeing, they can also bring added value to fabrics and can be widely used as functional finishing agents for wool fabrics. In addition, walnut shells are basically all discarded as waste during production and processing. After long-term accumulation, decay and deterioration, the allelopathic substances in them seriously damage the soil structure and plant diversity, causing serious pollution to the environment. Therefore, the industrial development and utilization of walnut shells is of great significance. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for microwave-assisted extraction of natural dyes from walnut shells for wool dyeing. Based on microwave-assisted extraction technology, natural dyes in walnut shells are extracted and wool is dyed. The whole process is safe and environmentally friendly, and the dyeing effect is good.

[0006] To achieve the above object, the present invention provides a method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells, comprising the following steps:

[0007] (1) Grinding walnut shells into powder, and then performing microwave-assisted thermal extraction to obtain a dye extract;

[0008] (2) filtering and centrifuging the dye extract, and adding a leveling agent to the supernatant to obtain a natural dye;

[0009] (3) pre-mordanting the wool sample with an aqueous solution of ferrous sulfate to obtain a pre-mordanted wool sample;

[0010] (4) Then, the pre-mordanted wool sample is dyed using a natural dye and tannic acid to obtain a dyed wool sample.

[0011] Microwave treatment is a safe, fast, low-energy, environmentally friendly natural dye extraction technology, and the technology can also improve color fastness and color uptake. The present invention combines thermal extraction and microwave treatment. Microwave-assisted extraction can achieve better results than traditional extraction. The strong transmission ability of microwaves to biological tissues can cause violent electromagnetic oscillations in the molecules in the dye plant cells. Under the synergistic effect of the solvent, the cell wall structure will be destroyed, which is conducive to the release of the active ingredients in the walnut shell from the cells. The dye components in the walnut shell can be better extracted to obtain a natural dye for dyeing, and it can be applied to the dyeing and finishing of wool fabrics. Microwave extraction can reduce the use of toxic chemicals, solvents and hazardous wastes, and this method can also improve color fastness and color uptake.

[0012] In addition, wool dyeing adopts the pre-mordant dyeing method. Wool fabrics have an affinity for natural dyes and mordants, and can form coordination complexes with dye molecules. The hydroxyl groups in the unsaturated part of natural dyes and ionizable carboxyl groups can provide additional dye sites, which increases the color strength of the fabric. Compared with cotton fabrics, which have poor affinity with dyes, they are more dyeable. Using ferrous sulfate as a mordant for pre-mordant dyeing can improve color fastness and make the fabric show better dyeing characteristics. The coordination number of iron ions is 6, and they can form a ternary complex with the fiber at one site and a ternary complex with the dye at another site. Such a strong coordination tendency can enhance the interaction between the fiber and the dye, thereby enhancing the dyeing effect.

[0013] Tannic acid, as a color fixing agent, contains a variety of polar groups and hydrophobic sites in its structure, which can produce good affinity and prevent natural dyes from being parsed from the inside of the fiber. Tannic acid can also act as an adhesive on the fabric. The -OH on the tannic acid molecule forms a hydrogen bond with the -OH on the natural dye molecule. Between the tannic acid and the wool fiber, the tannic acid can form multiple hydrogen bonds with the protein, and also have an ion dipole effect with the -NH3 in the lysine structure, causing cross-linking between the fiber, tannic acid and the dye. The affinity of the dye to the fabric can also be enhanced to a certain extent by opening the structure of the fabric. The dye molecules diffuse into the fiber matrix and are further fixed in the fabric, improving the dyeing effect.

[0014] The invention extracts the natural dye in the walnut shell, which is environmentally friendly, biodegradable, low-toxic and not easy to cause allergic reactions compared with synthetic dyes. The flavonoids in the walnut can remove free radicals generated by ultraviolet rays to achieve an anti-ultraviolet effect, and thus can also give wool fabrics the functional characteristics of increasing ultraviolet protection.

[0015] Further preferably, after the walnut shells are dried in a dark environment, they are fully ground to obtain a smooth powder.

[0016] The purpose of drying the walnut shell is to destroy the cell membrane and cell wall, which is conducive to the smooth leaching. Drying in a dark environment is to prevent light from causing changes in the chemical structure of the components in the walnut shell, and to ensure the integrity of the components as much as possible. The purpose of grinding and crushing is to increase the surface area of ​​the raw materials and increase the leaching speed.

[0017] Further preferably, in step (1), the microwave-assisted thermal extraction is: grinding the walnut shell to obtain a powder and placing it in an ethanol solution, adjusting the pH to 10-11 and the temperature to 60-70° C., and simultaneously subjecting the solution to microwave treatment with a microwave power of 600-750 W for 10-20 min.

[0018] In an alkaline environment, ethanol solvent is used to extract the dye components in the walnut shell. The temperature is set to 60-70℃. Heating will affect the scale layer of wool fibers. When the temperature exceeds 60℃, the disulfide bonds of wool begin to open, which is convenient for dye diffusion. However, too high a dyeing temperature will cause the pigment to degrade and affect the dyeing effect. Considering comprehensively, it is more reasonable to choose a dyeing temperature of 60-70℃. When the microwave power is increased to 600-750W, the heat provided by the microwave will be evenly distributed throughout the fabric, while in traditional heating, only the surface of the material is heated. Microwave-assisted heating makes the extraction and dyeing performance of natural dyes better.

[0019] The crude yield is higher under alkaline conditions because the flavonoids in the walnut shell extract contain a large number of phenolic hydroxyl groups, are weakly acidic, and are easily soluble in alkali. Adding alkali to the extract can promote the dissolution of weakly acidic phenolic hydroxyl groups in the walnut shell extract. High temperature will reduce the viscosity of the solvent, which is conducive to penetrating into the matrix and extracting more colorants.

[0020] Further preferably, in step (1), the mass ratio of the powder to the ethanol solution is 1:10-11, and the mass concentration of the ethanol solution is 40%.

[0021] The ethanol solvent has a low surface tension, which has better dispersing ability and facilitates the transfer of more colorants from the solid surface to the liquid surface.

[0022] Further preferably, in step (2), the leveling agent is a quaternary ammonium salt leveling agent, specifically octadecyl dimethyl benzyl ammonium chloride; the amount of the leveling agent added is.

[0023] Octadecyl dimethyl benzyl ammonium chloride can give fabrics good softness and make the dye solution antibacterial.

[0024] Further preferably, in step (3), the pre-mordanting is: soaking the wool sample in an aqueous solution of ferrous sulfate at a temperature of 40-45° C. and a pH of 4-5 for 50-70 min, then irradiating it with ultrasonic wave, and then taking it out and washing and drying it.

[0025] Ultrasonic pretreatment of wool causes certain damage to the epidermal scale structure, and ferrous sulfate is used as a mordant to complex with natural dyes and wool fibers to a certain extent. The synergistic effect of the two further improves the dye uptake and color fastness.

[0026] Further preferably, the mass concentration of the ferrous sulfate aqueous solution is 4-6%; the mass ratio of the wool sample to the ferrous sulfate aqueous solution is 1:10-11.

[0027] The higher the mordant concentration, the darker the color of the fabric sample. When the mordant reaches a certain concentration, the pigment and the mordant effectively react with each other. Continuing to increase the mass concentration of the mordant has little significance for increasing the color strength of the dyed fabric. After comprehensive consideration, the concentration range is set at 4-6%.

[0028] Further preferably, the frequency of the ultrasonic irradiation is 70-85 kHz, and the duration is 20-40 min.

[0029] Further preferably, in step (3), the wool sample is pre-treated before pre-mordanting, and the pre-treatment is: washing the wool sample in a mixed solution of detergent and sodium carbonate aqueous solution at 50-60°C for 20-25 minutes, then rinsing with water and drying.

[0030] After wool is washed with detergent, the grease and impurities on its surface are removed, and the fiber surface structure is modified in the form of cracking of the fiber cuticle and peeling of scales, providing more migration paths for subsequent dye diffusion into the fiber.

[0031] Further preferably, the concentration of the sodium carbonate aqueous solution is 0.1-0.2 g / L; the volume ratio of the detergent to the sodium carbonate aqueous solution is 1:20; and the bath ratio of the wool sample to the mixed solution is 1:40-50.

[0032] Further preferably, in step (4), the dyeing is: adding a natural dye and tannic acid to a dye bath, adjusting the pH to 4.5-4.8 and the temperature to 40-50°C, then adding pre-mordanted wool fabric and soaking for 5-10 minutes, then heating to 70°C at a rate of 0.4-0.7°C / min, and keeping warm for 60-90 minutes.

[0033] Further preferably, the dye bath contains 4% omf of natural dye and 4-6% omf of tannic acid, and the bath ratio is 1:30-35.

[0034] Compared with the prior art, the present invention has the following advantages: a thermal extraction method and a microwave treatment method are combined, and microwave-assisted extraction can achieve better results than traditional extraction, and the dye components in the walnut shell can be better extracted to obtain a natural dye that can be used for dyeing, and the natural dye is applied to the dyeing and finishing of wool fabrics; in addition, wool dyeing adopts a pre-mordant dyeing method, ferrous sulfate is used as a mordant, and tannic acid is used as a fixing agent. Tannic acid can also act as an adhesive on the fabric and can also improve the dyeing effect; the dyed wool fabric has a good coloring effect and is endowed with anti-ultraviolet and antibacterial functional properties. DETAILED DESCRIPTION

[0035] The technical content and effects of the present invention are further described in detail below in conjunction with the embodiments, but the present invention is not limited thereto.

[0036] Example 1

[0037] A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells comprises the following steps:

[0038] (1) After the walnut shell is dried, it is fully ground to obtain a powder. 100 g of the powder is added to 1000 g of a 40% ethanol solution, NaOH is added to adjust the pH to 11, the temperature is adjusted to 65°C, and a 700 W microwave is used for 20 min to obtain a dyeing extract;

[0039] (2) The dye extract was transferred to a rotary vacuum evaporator and concentrated to one-fourth of the volume at 65° C., then filtered, and centrifuged at 10,000 rpm for 10 min. The supernatant was taken and leveling agent 1827 (octadecyl dimethyl benzyl ammonium chloride) was added to obtain a natural dye;

[0040] (3) Weigh 2 g of wool sample and wash it in 80 g of an aqueous solution containing 2 wt% of Lebolin (nonionic soap) detergent and 0.2 g / L of sodium carbonate, heat it at 50° C. for 20 min, wash the wool sample twice with tap water, and then dry it in an oven at 105° C. for 1 h to obtain a pretreated wool sample;

[0041] (4) Using ferrous sulfate as a mordant, the pretreated wool sample is placed in 20 g of a ferrous sulfate solution with a pH of 4-5 and a mass concentration of 6%, the temperature is set at 40°C, and the wool sample is soaked for 60 minutes; then 80kHz ultrasonic radiation is used for 30 minutes; finally, the wool sample is washed with water, squeezed and dried, and air-dried in an oven at 35°C for 2 hours to obtain a pre-mordanted wool sample;

[0042] (5) Add natural dye and tannic acid to the dye bath (the dye bath contains 4% natural dye omf and 5% tannic acid omf), adjust the pH to 4.5-4.8 and the temperature to 45°C, add the pre-mordanted wool sample and soak it (bath ratio is 1:30), keep it warm for 5 minutes, then increase the temperature to 70°C at 0.5°C / min and keep it warm for 90 minutes; after dyeing is completed, take it out and soak it in cold water for washing, squeeze it, and dry it at 105°C for 1 hour, and the dyeing is completed.

[0043] Example 2

[0044] A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells comprises the following steps:

[0045] (1) After the walnut shell is dried, it is fully ground to obtain a powder. 100 g of the powder is added to 1000 g of a 40% ethanol solution, NaOH is added to adjust the pH to 11, the temperature is adjusted to 65°C, and a 700 W microwave is used for 20 min to obtain a dyeing extract;

[0046] (2) The dye extract was transferred to a rotary vacuum evaporator and concentrated to one-fourth of the volume at 65° C., then filtered, and centrifuged at 10,000 rpm for 10 min. The supernatant was taken and leveling agent 1827 (octadecyl dimethyl benzyl ammonium chloride) was added to obtain a natural dye;

[0047] (3) Weigh 5 g of wool sample and wash it in 200 g of an aqueous solution containing 2 wt% of Lebolin (nonionic soap) detergent and 0.2 g / L of sodium carbonate, heat it at 50° C. for 20 min, wash the wool sample twice with tap water, and then dry it in an oven at 105° C. for 1 h to obtain a pretreated wool sample;

[0048] (4) Using ferrous sulfate as a mordant, the pretreated wool sample is placed in 50 g of a ferrous sulfate aqueous solution with a pH of 4-5 and a mass concentration of 5%, the temperature is set at 40° C., and the sample is immersed for 60 minutes; then 80 kHz ultrasonic radiation is used for 30 minutes; finally, the sample is washed with water, squeezed and dried, and air-dried in an oven at 35° C. for 2 hours to obtain a pre-mordanted wool sample;

[0049] (5) Add natural dye and tannic acid to the dye bath (the dye bath contains 4% natural dye omf and 6% tannic acid omf), adjust the pH to 4.5-4.8 and the temperature to 45°C, add the pre-mordanted wool sample and soak it (bath ratio is 1:30), keep it warm for 5 minutes, then increase the temperature to 70°C at 0.5°C / min and keep it warm for 90 minutes; after dyeing is completed, take it out and soak it in cold water, wash it, squeeze it, and dry it at 105°C for 1 hour, and the dyeing is completed.

[0050] Example 3

[0051] A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells comprises the following steps:

[0052] (1) After the walnut shell is dried, it is fully ground to obtain a powder. 100 g of the powder is added to 1000 g of a 40% ethanol solution, NaOH is added to adjust the pH to 11, the temperature is adjusted to 65°C, and a 700 W microwave is used for 20 min to obtain a dyeing extract;

[0053] (2) The dye extract was transferred to a rotary vacuum evaporator and concentrated to one-fourth of the volume at 65° C., then filtered, and centrifuged at 10,000 rpm for 10 min. The supernatant was taken and leveling agent 1827 (octadecyl dimethyl benzyl ammonium chloride) was added to obtain a natural dye;

[0054] (3) Weigh 3 g of wool sample and wash it in 135 g of an aqueous solution containing 2 wt% of Lebolin (nonionic soap) detergent and 0.2 g / L of sodium carbonate, heat it at 50° C. for 20 min, wash the wool sample twice with tap water, and then dry it in an oven at 105° C. for 1 h to obtain a pretreated wool sample;

[0055] (4) Using ferrous sulfate as a mordant, the pretreated wool sample is placed in 33 g of a ferrous sulfate aqueous solution with a pH of 4-5 and a mass concentration of 6%, the temperature is set to 40° C., and the wool sample is soaked for 60 minutes; then 80 kHz ultrasonic radiation is used for 30 minutes; finally, the wool sample is washed with water, squeezed and dried, and air-dried in an oven at 35° C. for 2 hours to obtain a pre-mordanted wool sample;

[0056] (5) Add natural dye and tannic acid to the dye bath (the dye bath contains 4% natural dye omf and 4% tannic acid omf), adjust the pH to 4.5-4.8 and the temperature to 45°C, add the pre-mordanted wool sample and soak it (bath ratio is 1:35), keep it warm for 5 minutes, then increase the temperature to 70°C at 0.5°C / min and keep it warm for 90 minutes; after dyeing is completed, take it out and soak it in cold water for washing, squeeze it, and dry it at 105°C for 1 hour, and the dyeing is completed.

[0057] Comparative Example 1 (the difference from Example 1 is that the microwave power is 350W)

[0058] A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells comprises the following steps:

[0059] (1) After the walnut shell is dried, it is fully ground to obtain a powder. 100 g of the powder is added to 1000 g of a 40% ethanol solution, NaOH is added to adjust the pH to 11, the temperature is adjusted to 65°C, and a 350W microwave is used for 20 minutes to obtain a dyeing extract;

[0060] (2) The dye extract was transferred to a rotary vacuum evaporator and concentrated to one-fourth of the volume at 65° C., then filtered, and centrifuged at 10,000 rpm for 10 min. The supernatant was taken and leveling agent 1827 (octadecyl dimethyl benzyl ammonium chloride) was added to obtain a natural dye;

[0061] (3) Weigh 2 g of wool sample and wash it in 80 g of an aqueous solution containing 2 wt% of Lebolin (nonionic soap) detergent and 0.2 g / L of sodium carbonate, heat it at 50° C. for 20 min, wash the wool sample twice with tap water, and then dry it in an oven at 105° C. for 1 h to obtain a pretreated wool sample;

[0062] (4) Using ferrous sulfate as a mordant, the pretreated wool sample is placed in 20 g of a ferrous sulfate solution with a pH of 4-5 and a mass concentration of 6%, the temperature is set at 40°C, and the wool sample is soaked for 60 minutes; then 80kHz ultrasonic radiation is used for 30 minutes; finally, the wool sample is washed with water, squeezed and dried, and air-dried in an oven at 35°C for 2 hours to obtain a pre-mordanted wool sample;

[0063] (5) Add natural dye and tannic acid to the dye bath (the dye bath contains 4% natural dye omf and 5% tannic acid omf), adjust the pH to 4.5-4.8 and the temperature to 45°C, add the pre-mordanted wool sample and soak it (bath ratio is 1:30), keep it warm for 5 minutes, then increase the temperature to 70°C at 0.5°C / min and keep it warm for 90 minutes; after dyeing is completed, take it out and soak it in cold water for washing, squeeze it, and dry it at 105°C for 1 hour, and the dyeing is completed.

[0064] Comparative Example 2 (the difference from Example 2 is that the wool sample is not pretreated and pre-mordanted)

[0065] A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells comprises the following steps:

[0066] (1) After the walnut shell is dried, it is fully ground to obtain a powder. 100 g of the powder is added to 1000 g of a 40% ethanol solution, NaOH is added to adjust the pH to 11, the temperature is adjusted to 65°C, and a 700 W microwave is used for 20 min to obtain a dyeing extract;

[0067] (2) The dye extract was transferred to a rotary vacuum evaporator and concentrated to one-fourth of the volume at 65° C., then filtered, and centrifuged at 10,000 rpm for 10 min. The supernatant was taken and leveling agent 1827 (octadecyl dimethyl benzyl ammonium chloride) was added to obtain a natural dye;

[0068] (3) Add natural dye and tannic acid to the dye bath (the dye bath contains 4% natural dye omf and 6% tannic acid omf), adjust the pH to 4.5-4.8 and the temperature to 45°C, add the wool sample to soak (bath ratio is 1:30), keep warm for 5 minutes, then increase the temperature to 70°C at 0.5°C / min and keep warm for 90 minutes; after dyeing is completed, take out and soak and wash with cold water, squeeze, and dry at 105°C for 1 hour, and dyeing is completed.

[0069] Comparative Example 3 (the difference from Example 1 is that the mordant is directly added for dyeing)

[0070] A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells comprises the following steps:

[0071] (1) After the walnut shell is dried, it is fully ground to obtain a powder. 100 g of the powder is added to 1000 g of a 40% ethanol solution, NaOH is added to adjust the pH to 11, the temperature is adjusted to 65°C, and a 700 W microwave is used for 20 min to obtain a dyeing extract;

[0072] (2) The dye extract was transferred to a rotary vacuum evaporator and concentrated to one-fourth of the volume at 65° C., then filtered, and centrifuged at 10,000 rpm for 10 min. The supernatant was taken and leveling agent 1827 (octadecyl dimethyl benzyl ammonium chloride) was added to obtain a natural dye;

[0073] (3) Weigh 2 g of wool sample and wash it in 80 g of an aqueous solution containing 2 wt% of Lebolin (nonionic soap) detergent and 0.2 g / L of sodium carbonate, heat it at 50° C. for 20 min, wash the wool sample twice with tap water, and then dry it in an oven at 105° C. for 1 h to obtain a pretreated wool sample;

[0074] (4) Add natural dye, tannic acid and ferrous sulfate to the dye bath (the dye bath contains 4% omf natural dye, 5% omf tannic acid and 6% omf ferrous sulfate), adjust the pH to 4.5-4.8 and the temperature to 45°C, add the pretreated wool sample and soak (bath ratio is 1:30), keep warm for 5 minutes, then increase the temperature to 70°C at 0.5°C / min and keep warm for 90 minutes; after dyeing, take out, soak and wash with cold water, squeeze, and dry at 105°C for 1 hour, and dyeing is completed.

[0075] Comparative Example 4 (the difference from Example 1 is that only microwave extraction is performed)

[0076] A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells comprises the following steps:

[0077] (1) After the walnut shell is dried, it is fully ground to obtain a powder. 100 g of the powder is added to 1000 g of a 40% ethanol solution, and NaOH is added to adjust the pH to 11. Under room temperature, a 700 W microwave is used for 20 min to obtain a dyeing extract;

[0078] (2) The dye extract was transferred to a rotary vacuum evaporator and concentrated to one-fourth of the volume at 65° C., then filtered, and centrifuged at 10,000 rpm for 10 min. The supernatant was taken and leveling agent 1827 (octadecyl dimethyl benzyl ammonium chloride) was added to obtain a natural dye;

[0079] (3) Weigh 2 g of wool sample and wash it in 80 g of an aqueous solution containing 2 wt% of Lebolin (nonionic soap) detergent and 0.2 g / L of sodium carbonate, heat it at 50° C. for 20 min, wash the wool sample twice with tap water, and then dry it in an oven at 105° C. for 1 h to obtain a pretreated wool sample;

[0080] (4) Using ferrous sulfate as a mordant, the pretreated wool sample is placed in 20 g of a ferrous sulfate solution with a pH of 4-5 and a mass concentration of 6%, the temperature is set at 40°C, and the wool sample is soaked for 60 minutes; then 80kHz ultrasonic radiation is used for 30 minutes; finally, the wool sample is washed with water, squeezed and dried, and air-dried in an oven at 35°C for 2 hours to obtain a pre-mordanted wool sample;

[0081] (5) Add natural dye and tannic acid to the dye bath (the dye bath contains 4% natural dye omf and 5% tannic acid omf), adjust the pH to 4.5-4.8 and the temperature to 45°C, add the pre-mordanted wool sample and soak it (bath ratio is 1:30), keep it warm for 5 minutes, then increase the temperature to 70°C at 0.5°C / min and keep it warm for 90 minutes; after dyeing is completed, take it out and soak it in cold water for washing, squeeze it, and dry it at 105°C for 1 hour, and the dyeing is completed.

[0082] The performance of the embodiments and comparative examples was tested, and the results are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] According to the data analysis in Table 1, through the technical improvement of the present invention, the color intensity of Examples 1-3 is obviously higher than that of the comparative example, indicating that the dyeing effect is better. Compared with Comparative Example 1, after 700W microwave treatment, the dyeing performance of the dye is improved and the dyeing rate of the material is improved. Compared with Comparative Example 2, the dyeing rate and color intensity of the treated wool are higher than those of the untreated wool, and obvious differences can be seen from the color intensity comparison. Compared with Comparative Example 3, the color uptake rate of the wool pre-mordanted in Example 1 is higher than that of the directly dyed sample, indicating that the pre-mordanting is coordinated and combined first, which can improve the color fastness and make the fabric show better dyeing characteristics. Compared with Comparative Example 4, the dyeing efficiency of the natural dye extracted at room temperature in Example 1 is weaker than that of the natural dye extracted at high temperature.

[0087] The above embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells, characterized in that: The following steps are involved: (1) Grinding walnut shells into powder and then performing microwave-assisted thermal extraction to obtain a dye extract; The microwave-assisted thermal extraction comprises: grinding the walnut shell to obtain powder, placing it in an ethanol solution, adjusting the pH to 10-11 and the temperature to 60-70° C., and simultaneously performing microwave heating with a microwave power of 600-750 W for 10-20 min; (2) filtering and centrifuging the dye extract, and adding a leveling agent to the supernatant to obtain a natural dye; (3) washing the wool sample in a mixed solution of detergent and sodium carbonate aqueous solution at 50-60°C for 20-25 minutes, then rinsing with water and drying to obtain a pretreated wool sample; soaking the pretreated wool sample in a ferrous sulfate aqueous solution at a temperature of 40-45°C and a pH of 4-5 for 50-70 minutes, then irradiating with ultrasonic waves, then taking out and washing and drying to obtain a pre-mordanted wool sample; (4) Then, the pre-mordanted wool sample is dyed with a natural dye and tannic acid to obtain a dyed wool sample.

2. The method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells as claimed in claim 1, characterized in that: In step (1), the mass ratio of the powder to the ethanol solution is 1:10-11, and the mass concentration of the ethanol solution is 40%.

3. The method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells as claimed in claim 1, characterized in that: In step (2), the leveling agent is a quaternary ammonium salt leveling agent; the amount of the leveling agent added is 0.2-0.3% of the mass of the supernatant.

4. The method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells as claimed in claim 1, characterized in that: The mass concentration of the ferrous sulfate aqueous solution is 4-6%; the mass ratio of the wool sample to the ferrous sulfate aqueous solution is 1:10-11.

5. The method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells as claimed in claim 1 or 4, characterized in that: The frequency of the ultrasonic irradiation is 70-85kHz, and the duration is 20-40min.

6. The method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells as claimed in claim 1, characterized in that: The concentration of the sodium carbonate aqueous solution is 0.1-0.2 g / L; the volume ratio of the detergent to the sodium carbonate aqueous solution is 1:20; and the bath ratio of the wool sample to the mixed solution is 1:40-50.

7. The method for wool dyeing by microwave-assisted extraction of natural dyes from walnut shells as claimed in claim 1, characterized in that: In step (4), the dyeing is as follows: adding a natural dye and tannic acid into a dye bath, adjusting the pH to 4.5-4.8 and the temperature to 40-50°C, adding pre-mordanted wool fabric and soaking for 5-10 minutes, then heating to 70°C at a rate of 0.4-0.7°C / min, and keeping warm for 60-90 minutes; the dye bath contains 4% omf of natural dye and 4-6% omf of tannic acid, and the bath ratio is 1:30-35.

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