A method of dyeing silk fabric

Abstract

The present application relates to the dyeing and finishing technology field of natural dyes on fabrics, and particularly relates to a silk fabric dyeing method. The dyeing method of the present application first dilutes, reduces, and then adjusts the pH and centrifugally processes the observation blue fermentation liquor to obtain an observation blue dye mother liquor, and further dilutes the observation blue dye mother liquor to obtain an observation blue dyeing liquid; then, the pretreated silk fabric is completely immersed below the liquid level of the observation blue dyeing liquid, dyed, taken out, and air-oxidized, and then washed with water, air-dried, finally subjected to soaping treatment and air-drying to obtain the dyed silk fabric. The method provides a dyeing method for silk fabrics aiming at the problem that silk fabrics are difficult to dye at present, selects the observation blue from a microbial source as a dyeing agent, has the advantages of green environmental protection and easy combination with silk fabrics; meanwhile, the dyeing process of the present application reduces the amount of sodium hydrosulfite, thereby reducing the pollution to the environment, and on the other hand, reduces the dyeing temperature and time, reduces the energy consumption, and improves the dyeing efficiency.

Description

Technical Field

[0001] This invention relates to the field of dyeing and finishing technology of fabrics with natural dyes, and more particularly to a dyeing method for silk fabrics. Background Technology

[0002] my country has a long history of using natural dyes for coloring. For example, the ancient Chinese text *Tiangong Kaiwu* mentions using dyes such as phellodendron bark, safflower, sappanwood, and indigo to develop various dyeing techniques. However, with the replacement of natural dyes by synthetic dyes, research and development of natural dyeing processes has significantly decreased. Synthetic dyes often cause substantial pollution; the waste generated during their production and processing, as well as the discharge of dyeing wastewater, pose significant environmental hazards. For instance, synthetic indigo is produced by condensing aniline with chloroacetic acid to form phenylglycine, which is then fused at high temperature with sodium hydroxide to form hydroxyindole. In an alkaline solution, the hydroxyindole is oxidized by air to obtain indigo. Aniline and chloroacetic acid are both harmful pollutants. With the increasing emphasis on green environmental protection, natural dyes are returning to the public eye, and improving natural dyes and dyeing methods has become a key research focus.

[0003] Indigo is a natural blue pigment obtained through microbial fermentation. Belonging to the indole family, it is green, safe, non-toxic, antibacterial, and capable of scavenging free radicals. The molecular formula of indigo is: C 10 H8N4O4 is mainly produced by fermentation using strains such as *Escherichia coli*, *Pseudomonas putida*, *Corynebacterium glutamicum*, and *Rhodotorula flocculationensis*. For example, reportedly, fed-batch fermentation of *Pseudomonas putida* can produce 26 g / L, while fed-batch fermentation of *Rhodotorula flocculationensis* can achieve a yield of 86.3 g / L, demonstrating industrialization potential. With the development of biotechnology and the implementation of green environmental protection policies, the replacement of synthetic indigo with indigo is an inevitable trend.

[0004] Currently, there are no reports on the application of synthetic indigo dyeing processes for silk fabrics. The dyeing process for synthetic indigo requires large amounts of sodium hydrosulfite, caustic soda, and various organic dyeing auxiliaries. This results in dye wastewater containing complex and difficult-to-degrade components such as residual indigo powder, sulfides, large amounts of salt, and organic compounds, increasing the complexity and cost of wastewater treatment. Furthermore, dyeing silk fabrics with synthetic indigo requires prolonged exposure to high temperatures, increasing energy consumption and dyeing costs. Most importantly, the structural differences between synthetic indigo and regular indigo make synthetic indigo unsuitable for dyeing processes. Using synthetic indigo dyeing processes on synthetic indigo can lead to problems such as difficulty in coloring and poor colorfastness.

[0005] The growing awareness of environmental protection has made the use of natural dyes an inevitable choice, and the industrial production of indigo is also an inevitable trend. Therefore, there is an urgent need for a dyeing process for indigo to solve the problems of environmental pollution, energy consumption, and difficulty in coloring synthetic indigo. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a dyeing method for silk fabrics. By utilizing the polyamine properties of indigo dye, the dyeing process of indigo on silk fabrics is simplified. The amount of sodium hydrosulfite used is reduced while selecting a suitable temperature for dyeing indigo, thus saving energy and reducing pollution.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for dyeing silk fabrics, comprising the following steps:

[0009] (1) Pretreatment of silk fabric: Soak the silk fabric in water to moisten it, take it out and absorb the surface liquid to keep the inside of the silk fabric moist.

[0010] (2) After diluting the fermentation broth of indigo, add sodium hydrosulfite, reduce it, adjust the pH to 10.0-11.5 with alkali, collect the supernatant after centrifugation, and then adjust the pH to 3.5-4.5 with acid to obtain the mother liquor of indigo dye.

[0011] (3) Dilute the blue dye mother liquor obtained in step (2) to obtain blue dyeing solution, then immerse the pretreated silk fabric completely below the surface of the blue dyeing solution, dye, take out, dry and oxidize, then wash with water and dry, and finally soap and dry to obtain dyed silk fabric.

[0012] This invention addresses the serious environmental pollution and difficulty in dyeing silk fabrics in current fabric dyeing processes. By selecting indigo fermentation broth derived from microorganisms as the dye, a dyeing method with high dyeing rate and good color fastness has been developed for silk fabrics. Furthermore, the amount of sodium hydrosulfite and alkali used in this dyeing method is significantly reduced, effectively reducing pollution and saving energy. The inventors of this application discovered that pretreatment of the silk by soaking and wetting it facilitates subsequent dyeing. After wetting the silk fabric, the surface liquid is absorbed, maintaining the internal moisture of the silk fabric, which allows the indigo dye to penetrate more easily, thereby improving the dyeing rate and color fastness in the subsequent dyeing process. If the liquid on the surface of the silk fabric is not absorbed after wetting, the dye will not adhere well to the fabric during subsequent dyeing, resulting in dye loss.

[0013] The dyeing method of this invention, when used to dye silk fabrics, shows a significant improvement in fabric color depth (K / S) and color fastness compared to commercial indigo. The dyeing method for silk using indigo provided by this invention can increase the K / S value by nearly 100%, and also improves dry rubbing fastness by one grade, wet rubbing fastness by one grade, and soap washing fastness by one grade. This effectively solves the problems of complex processes, difficult dyeing, poor color fastness, and difficult wastewater degradation and treatment in the indigo dyeing and finishing industry. The preparation of the indigo fermentation broth described in this invention is based on patent CN116064363B.

[0014] In the preparation method of the indigo dyeing solution, after adding sodium hydrosulfite for reduction, it is necessary to adjust the environment to alkaline with alkali. This allows the indigo to become a large amount of leuco form and dissolve in the liquid. During the process of adjusting the alkalinity, the inventors found that the final pH should not exceed 11.5, otherwise the indigo will be destroyed, resulting in the inability to dye the fabric subsequently. Then, centrifugation is required. During centrifugation, bacteria can be effectively removed. The indigo remaining in the supernatant needs to be acidified before it can be used to dye silk fabrics, because silk fabrics are not alkali-resistant. Based on this characteristic of silk fabrics, the inventors of this application discovered through experiments the optimal acidic pH range for dyeing. They found that adjusting the pH to the range of 3.5-4.5 with acid can effectively overcome the problem of silk fabrics' inability to withstand alkali. At the same time, silk fabrics have a better dyeing effect under the acidic environment.

[0015] The dyeing method described in this invention is applicable to various specifications of silk fabrics, including but not limited to silk fabrics with a specification of 12 momme.

[0016] Preferably, in step (2), the lanthanum fermentation broth is diluted to a lanthanum concentration of 10-50 g / L.

[0017] Preferably, in step (2), the solvent for diluting the blue violet fermentation broth is a 10 mM phosphate buffer (pH 8.0).

[0018] Preferably, the mass of sodium hydrosulfite added is 0.5-3 times the mass of the blue agarwood.

[0019] The inventors of this application have discovered that adding a small amount of sodium hydrosulfite to the indigo fermentation broth can reduce indigo to water-soluble sodium salt, which is beneficial for subsequent indigo coloring. Too little sodium hydrosulfite will lead to incomplete reduction and affect the subsequent dyeing effect, while too much will lead to pollution of the dyeing wastewater, increasing the process and cost of wastewater treatment.

[0020] Preferably, the reduction conditions are: reaction at room temperature for 15-60 minutes.

[0021] More preferably, the reduction conditions are: reaction at room temperature for 20-40 minutes.

[0022] The inventors of this application discovered in experiments that the reduction time should not be too long; more than 60 minutes would cause the blue staining solution to be oxidized prematurely.

[0023] Preferably, in step (2), the alkali is any one of NaOH, ammonia, and sodium carbonate; and the acid is any one of citric acid, sulfuric acid, acetic acid, and phosphoric acid.

[0024] Preferably, the present invention can also use methods such as vacuum filtration instead of centrifugation to obtain the supernatant blue dye mother liquor.

[0025] Preferably, in step (3), the weight of the indigo dye in the indigo dyeing solution is 1-3% of the weight of the silk fabric. It can also be referred to as the indigo dye concentration being 1-3% owf, where owf stands for on weight of fabric, and is used to indicate the percentage content of dye when dyeing, referring to the ratio of the amount of dye used to the weight of the fabric.

[0026] Preferably, in step (3), the ratio of the weight of the silk fabric to the volume of the indigo dyeing solution is 1g:(20-100)mL, which can also be referred to as a liquor ratio of 1:(20-100). Liquor ratio is a term used in textile dyeing and finishing, referring to the ratio of the weight of the fabric to the volume of the dye solution in the dyeing process.

[0027] Preferably, the dyeing conditions are dyeing at 4-30℃ for 5-30 minutes; the drying and oxidation time is 3-5 minutes.

[0028] More preferably, the staining conditions are staining at 15°C for 10-15 minutes.

[0029] Preferably, the washing should be done after re-oxidation while the silk fabric is not completely dry, to prevent blemishes from adhering to the silk surface.

[0030] Preferably, the soaping treatment method is as follows: mix 1-5g / L of neutral soap and 1-5g / L of sodium carbonate to prepare a soap solution, and add the soap solution to the dyed silk fabric for soaping.

[0031] Preferably, the ratio of the weight of the silk fabric to the volume of the soap solution is 1g:(20-100)mL, which can also be referred to as a soap bath ratio of 1:(20-100).

[0032] Preferably, the conditions for the soaping treatment are: soaping temperature 20-60℃, soaping time 5-15min.

[0033] The beneficial effects of this invention are as follows:

[0034] This invention addresses the serious environmental pollution and difficulties in dyeing silk fabrics encountered in current fabric dyeing processes by providing a dyeing method with high dyeing rate and good color fastness. This invention selects indigo dyeing solution derived from microorganisms as the dye, fully utilizing the characteristic of indigo's structure to easily bind with silk. Indigo is a natural blue pigment, a novel biocompatible and environmentally friendly dye. Compared to using indigo as a dye, indigo has a higher dyeing rate and better color fastness. Moreover, the amount of sodium hydrosulfite and alkali used in the dyeing method is significantly reduced, effectively reducing pollution and saving energy. Furthermore, the dyeing method of this invention is simple, does not require high-temperature dyeing (room temperature is sufficient; excessively high temperatures will damage the indigo structure and hinder dyeing), and has a short dyeing time, which is beneficial for energy saving and improving dyeing efficiency. Attached Figure Description

[0035] Figure 1 This is a comparison image of the staining results.

[0036] Figure 2 This is a schematic diagram of the structure of indigo and woad; the area within the dashed line represents the luminescent body. Detailed Implementation

[0037] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0038] The indigo dyed in this embodiment was obtained through our company's self-developed fermentation process and can be purchased from the company's official website. The K / S value was used to characterize the depth of color in the dyed silk fabric. The color fastness to rubbing and to washing of the silk fabric was tested according to GB / T 3920—2008 "Textiles - Tests for Color Fastness to Rubbing" and GB / T 3921—2008 "Textiles - Tests for Color Fastness to Rubbing".

[0039] Example 1

[0040] An embodiment of the dyeing method for silk fabrics according to the present invention includes the following steps:

[0041] (1) Silk pretreatment: Cut 12 momme silk fabric into a certain size, soak it in distilled water at room temperature, remove the air bubbles, take it out after it is completely wetted, place it on a paper towel to absorb the surface liquid, keep the inside of the silk fabric moist, and obtain the pretreated silk fabric.

[0042] (2) Preparation of blue dye mother liquor: Dilute the blue fermentation broth with 10mM phosphate buffer to a blue concentration of 10g / L, add 5g / L sodium hydrosulfite, reduce at room temperature for 15min, adjust the pH to 11.0 with NaOH, centrifuge at 9000rpm for 10min, collect the supernatant, adjust the pH to 3.5 with 500g / L citric acid to obtain blue dye mother liquor;

[0043] (3) Dyeing process: Dilute the blue dye mother liquor obtained in step (2) to a blue dye concentration of 1% owf to obtain blue dyeing solution. Add the pretreated silk fabric in step (1) with a liquor ratio of 1:20 so that the silk is completely immersed below the surface of the dyeing solution. Dye at room temperature for 10 minutes, take it out, dry and oxidize for 3 minutes, wash with water for 1 minute, and dry to obtain dyed silk fabric.

[0044] (4) Soap washing process: The dyed silk fabric obtained in step (3) is subjected to soap washing treatment. 2g / L neutral soap and 2g / L sodium carbonate are mixed to prepare soap solution. The soap washing bath ratio is 1:20. Soap wash at room temperature for 5 minutes, and then take it out and air dry.

[0045] Example 2

[0046] An embodiment of the dyeing method for silk fabrics according to the present invention includes the following steps:

[0047] (1) Silk pretreatment: Cut 12 momme silk fabric into a certain size, soak it in distilled water at room temperature, remove the air bubbles, take it out after it is completely wetted, place it on a paper towel to absorb the surface liquid, keep the inside of the silk fabric moist, and obtain the pretreated silk fabric.

[0048] (2) Preparation of blue dye mother liquor: Dilute the blue fermentation broth with 10mM phosphate buffer to a blue concentration of 15g / L, then add 15g / L sodium hydrosulfite, reduce at room temperature for 15min, adjust the pH to 10.5 with NaOH, centrifuge at 9000rpm for 10min, collect the supernatant, adjust the pH to 4.5 with 500g / L citric acid to obtain blue dye mother liquor;

[0049] (3) Dyeing process: Dilute the blue dye mother liquor obtained in step (2) to a blue dye concentration of 1.5% owf to obtain blue dyeing solution. Add the pretreated silk fabric in step (1) with a liquor ratio of 1:50 so that the silk is completely immersed below the surface of the dyeing solution. Dye at room temperature for 10 minutes, take it out, dry and oxidize for 3 minutes, wash with water for 1 minute, and dry to obtain the dyed silk fabric.

[0050] (4) Soap washing process: The dyed silk fabric obtained in step (3) is subjected to soap washing treatment. 2g / L neutral soap and 2g / L sodium carbonate are mixed to prepare soap solution. The soap washing bath ratio is 1:20. Soap wash at room temperature for 5 minutes, and then take it out and air dry.

[0051] Example 3

[0052] An embodiment of the dyeing method for silk fabrics according to the present invention includes the following steps:

[0053] (1) Silk pretreatment: Cut 12 momme silk fabric into a certain size, soak it in distilled water at room temperature, remove the air bubbles, take it out after it is completely wetted, place it on a paper towel to absorb the surface liquid, keep the inside of the silk fabric moist, and obtain the pretreated silk fabric.

[0054] (2) Blue dye mother liquor: Dilute the blue fermentation broth with 10mM phosphate buffer to a blue concentration of 30g / L, add 20g / L sodium hydrosulfite, reduce at room temperature for 30min, adjust the pH to 11.5 with NaOH, centrifuge at 9000rpm for 10min, collect the supernatant, adjust the pH to 3.5 with 40% sulfuric acid to obtain blue dye mother liquor;

[0055] (3) Dyeing process: Dilute the blue dye mother liquor obtained in step (2) to a blue dye concentration of 3% owf to obtain blue dyeing solution. Add the pretreated silk fabric in step (1) with a liquor ratio of 1:50 so that the silk is completely immersed below the surface of the dyeing solution. Dye at room temperature for 30 minutes, take it out, dry and oxidize for 5 minutes, wash with water for 1 minute, and dry to obtain dyed silk fabric.

[0056] (4) Soap washing process: The dyed silk fabric obtained in step (3) is subjected to soap washing treatment. 2g / L neutral soap and 2g / L sodium carbonate are mixed to prepare soap solution. The soap washing bath ratio is 1:20. Soap wash at room temperature for 5 minutes, and then take it out and air dry.

[0057] Example 4

[0058] An embodiment of the dyeing method for silk fabrics according to the present invention includes the following steps:

[0059] (1) Silk pretreatment: Cut 12 momme silk fabric into a certain size, soak it in distilled water at room temperature, remove the air bubbles, take it out after it is completely wetted, place it on a paper towel to absorb the surface liquid, keep the inside of the silk fabric moist, and obtain the pretreated silk fabric.

[0060] (2) Preparation of blue dye mother liquor: Dilute the blue fermentation broth with 10mM phosphate buffer to a blue concentration of 10g / L, then add 10g / L sodium hydrosulfite, reduce at room temperature for 15min, adjust the pH to 11.0 with NaOH, centrifuge at 9000rpm for 10min, collect the supernatant, adjust the pH to 4.5 with acetic acid to obtain blue dye mother liquor;

[0061] (3) Dyeing process: Dilute the blue dye mother liquor obtained in step (2) to a blue dye concentration of 1% owf to obtain blue dyeing solution. Add the pretreated silk fabric in step (1) with a liquor ratio of 1:40 so that the silk is completely immersed below the surface of the dyeing solution. Dye at room temperature for 15 minutes, take it out, dry and oxidize for 3 minutes, wash with water for 1 minute, and dry to obtain dyed silk fabric.

[0062] (4) Soap washing process: The dyed silk fabric obtained in step (3) is subjected to soap washing treatment. 2g / L neutral soap and 2g / L sodium carbonate are mixed to prepare soap solution. The soap washing bath ratio is 1:20. Soap wash at room temperature for 5 minutes, and then take it out and air dry.

[0063] Example 5

[0064] An embodiment of the dyeing method for silk fabrics according to the present invention includes the following steps:

[0065] (1) Silk pretreatment: Cut 12 momme silk fabric into a certain size, soak it in distilled water at room temperature, remove the air bubbles, take it out after it is completely wetted, place it on a paper towel to absorb the surface liquid, keep the inside of the silk fabric moist, and obtain the pretreated silk fabric.

[0066] (2) Preparation of blue dye mother liquor: Dilute the blue fermentation broth with 10mM phosphate buffer to a blue concentration of 50g / L, then add 25g / L sodium hydrosulfite, reduce at room temperature for 60min, adjust the pH to 10.0 with NaOH, centrifuge at 9000rpm for 10min, collect the supernatant, adjust the pH to 3.5 with 500g / L citric acid to obtain blue dye mother liquor;

[0067] (3) Dyeing process: Dilute the blue dye mother liquor obtained in step (2) to a blue dye concentration of 1% owf to obtain blue dyeing solution. Add the pretreated silk fabric in step (1) with a liquor ratio of 1:100 so that the silk is completely immersed below the surface of the dyeing solution. Dye at room temperature for 5 minutes, take it out, dry and oxidize for 3 minutes, wash with water for 1 minute, and dry to obtain dyed silk fabric.

[0068] (4) Soap washing process: The dyed silk fabric obtained in step (3) is subjected to soap washing treatment. 5g / L neutral soap and 5g / L sodium carbonate are mixed to prepare soap solution. The soap washing bath ratio is 1:100. Soap washing is carried out at 20℃ for 15 minutes. After taking it out, it is dried.

[0069] Example 6

[0070] An embodiment of the dyeing method for silk fabrics according to the present invention includes the following steps:

[0071] (1) Silk pretreatment: Cut 12 momme silk fabric into a certain size, soak it in distilled water at room temperature, remove the air bubbles, take it out after it is completely wetted, place it on a paper towel to absorb the surface liquid, keep the inside of the silk fabric moist, and obtain the pretreated silk fabric.

[0072] (2) Preparation of blue dye mother liquor: Dilute the blue fermentation broth with 10mM phosphate buffer to a blue concentration of 10g / L, add 30g / L sodium hydrosulfite, reduce at room temperature for 15min, adjust the pH to 11.0 with NaOH, centrifuge at 9000rpm for 10min, collect the supernatant, adjust the pH to 3.5 with 500g / L citric acid to obtain blue dye mother liquor;

[0073] (3) Dyeing process: Dilute the blue dye mother liquor obtained in step (2) to a blue dye concentration of 1% owf to obtain blue dyeing solution. Add the pretreated silk fabric in step (1) with a liquor ratio of 1:20 so that the silk is completely immersed below the surface of the dyeing solution. Dye at room temperature for 10 minutes, take it out, dry and oxidize for 3 minutes, wash with water for 1 minute, and dry to obtain dyed silk fabric.

[0074] (4) Soap washing process: The dyed silk fabric obtained in step (3) is subjected to soap washing treatment. 2g / L neutral soap and 2g / L sodium carbonate are mixed to prepare soap solution. The soap washing bath ratio is 1:20. Soap washing is carried out at 60℃ for 5 minutes. After washing, the fabric is taken out and dried.

[0075] Comparative Example 1

[0076] This invention provides a comparative example of the dyeing method for silk fabrics. Commercial indigo was used as a control; the indigo was purchased from Ron Reagents, in powder form, and dissolved in 10 mM phosphate buffer before use.

[0077] The dyeing method includes the following steps: (1) Silk pretreatment: Cut 12 momme silk fabric into a certain size, soak it in distilled water at room temperature, remove the air bubbles, take it out after it is completely wetted, place it on a paper towel to absorb the surface liquid, keep the inside of the silk fabric moist, and obtain the pretreated silk fabric.

[0078] (2) Preparation of indigo dye mother liquor: Dilute the indigo solution with 10mM phosphate buffer to an indigo concentration of 10g / L, add 10g / L sodium hydrosulfite, reduce at room temperature for 15min, adjust the pH to 11.0 with NaOH, centrifuge at 9000rpm for 10min, collect the supernatant, adjust the pH to 3.5 with 500g / L citric acid to obtain indigo dye mother liquor;

[0079] (3) Dyeing process: Dilute the indigo dye mother liquor obtained in step (2) to an indigo dye concentration of 1% owf to obtain indigo dyeing solution. Add the pretreated silk fabric in step (1) at a liquor ratio of 1:20 so that the silk is completely immersed below the surface of the dyeing solution. Dye at room temperature for 30 minutes, take it out, dry and oxidize for 3 minutes, wash with water for 1 minute, and dry to obtain dyed silk fabric.

[0080] (4) Soap washing process: The dyed silk fabric obtained in step (3) is subjected to soap washing treatment. 2g / L neutral soap and 2g / L sodium carbonate are mixed to prepare soap solution. The soap washing bath ratio is 1:20. Soap wash at room temperature for 5 minutes, and then take it out and air dry.

[0081] Experimental Example 1

[0082] The silk fabrics of Examples 1-6 and Comparative Example 1 were dyed multiple times. The color depth (K / S) and color fastness of the silk fabrics were measured. The color fastness was tested according to GB / T 3920-2008 "Textiles - Tests for Color Fastness to Rubbing" and GB / T 3921-2008 "Textiles - Tests for Color Fastness to Washing". At least 3 fabric pieces were taken for each group for testing, and the average result was calculated. The specific test results are shown in Table 1 below. One piece of silk fabric was selected from each of Examples 1-6 and Comparative Example 1 for comparison. The undyed silk fabric served as a blank control. The dyeing results are shown in the figure below. Figure 1 As shown.

[0083] Table 1

[0084]

[0085]

[0086] Table 1 shows that: In Example 1, the average K / S of the dyed silk fabric was 4.5, with a dry rubbing color fastness grade of 5, a wet rubbing color fastness grade of 4, and a washing color fastness grade of 4; in Example 2, the average K / S of the dyed silk fabric was 5.1, with a dry rubbing color fastness grade of 5, a wet rubbing color fastness grade of 4, and a washing color fastness grade of 4; in Example 3, the average K / S of the dyed silk fabric was 6.7, with a dry rubbing color fastness grade of 4, a wet rubbing color fastness grade of 3-4, and a washing color fastness grade of 3-4; in Example 4, the average K / S of the dyed silk fabric was 6.1, with a dry rubbing color fastness grade of 5, a wet rubbing color fastness grade of 4, and a washing color fastness grade of 3-4; and in Example 4, the average K / S of the dyed silk fabric was 6.1, with a dry rubbing color fastness grade of 5.5, a wet rubbing color fastness grade of 4, and a washing color fastness grade of 3-4. The average K / S of the dyed silk fabric in Example 5 was 6.7, with a dry rubbing color fastness of 4, a wet rubbing color fastness of 3-4, and a soap washing color fastness of 3-4. The average K / S of the dyed silk fabric in Example 6 was 4.4, with a dry rubbing color fastness of 4, a wet rubbing color fastness of 4, and a soap washing color fastness of 3-4. In contrast, the average K / S of the dyed silk fabric in Comparative Example 1 was 3.4, with a dry rubbing color fastness of 4, a wet rubbing color fastness of 3, and a soap washing color fastness of 3.

[0087] Indigo is generally unsuitable for dyeing silk fabrics. Indigo is a vat dye, poorly soluble in water, and requires reduction under alkaline conditions to become a soluble leuco sodium salt before it can dye fibers. Traditional indigo dyeing methods use wood ash, lime, etc., which are unsuitable for industrial production. Synthetic indigo uses large amounts of sodium hydrosulfite and caustic soda to prepare the dyeing solution, causing significant pollution. Since silk is a protein fiber with poor alkali resistance, dyeing silk with reduced indigo under alkaline conditions will damage the luster of the silk fabric and reduce its strength. While converting the indigo leuco to leuco acid can change the alkaline environment to an acidic one, the low solubility of indigo leuco acid results in poor dye uptake on silk. While the properties of indigo dye are similar to those of indigo, structurally... Figure 2 Indigo has two more amino groups than indigo, making it more soluble in water and easier to bind with protein fibers, theoretically making it more suitable for dyeing silk.

[0088] This invention addresses the shortcomings of traditional indigo dyeing processes, including high pollution and energy consumption, by providing a method for dyeing silk fabrics at room temperature using a small amount of sodium hydrosulfite. This invention specifically targets indigo dyeing from microorganisms, simplifying the process of dyeing silk fabrics with synthetic indigo, improving dyeing efficiency, and reducing pollution from material selection and the dyeing process, thus emphasizing a green and environmentally friendly approach. Compared to synthetic indigo dyeing, this method better matches the structural characteristics of indigo by reducing the amount of sodium hydrosulfite used and lowering the dyeing temperature and time. The dyeing method of this invention significantly improves the color depth (K / S) and color fastness of silk fabrics compared to commercial indigo: the indigo dyeing method provided by this invention can increase the K / S value by nearly 100%, and also improves the dry rubbing color fastness by one grade, wet rubbing color fastness by one grade, and soap washing color fastness by one grade, effectively solving the problems of complex processes, difficult coloring, poor color fastness, and difficult wastewater degradation and treatment in the indigo dyeing and finishing industry.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for dyeing silk fabrics, characterized in that, Includes the following steps: (1) Pretreatment of silk fabric: Soak the silk fabric in water to moisten it, take it out and absorb the surface liquid to keep the inside of the silk fabric moist. (2) After diluting the fermentation broth of Aglaonema, add sodium hydrosulfite, reduce it, adjust the pH to 10.0-11.5 with alkali, collect the supernatant after centrifugation, and then adjust the pH to 3.5-4.5 with acid to obtain Aglaonema dye mother liquor; the mass of sodium hydrosulfite added is 0.5-3 times the mass of Aglaonema; the reduction conditions are: reaction at room temperature for 15-60 min; (3) Dilute the blue dye mother liquor obtained in step (2) to obtain blue dyeing solution, then immerse the pretreated silk fabric completely below the surface of the blue dyeing solution, dye, take out, sun-dry and oxidize, then wash with water and dry, and finally soap and dry to obtain dyed silk fabric; the dyeing conditions are dyeing at 4-30℃ for 5-30 min; the sun-drying and oxidation time is 3-5 min.

2. The dyeing method for silk fabrics as described in claim 1, characterized in that, In step (2), the lanthanum fermentation broth is diluted to a lanthanum concentration of 10-50 g / L.

3. The dyeing method for silk fabrics as described in claim 1, characterized in that, In step (3), the weight of the blue dye in the blue dye solution is 1-3% of the weight of the silk fabric.

4. The dyeing method for silk fabrics as described in claim 1, characterized in that, In step (3), the ratio of the weight of the silk fabric to the volume of the blue dyeing solution is 1g:(20-100)mL.

5. The dyeing method for silk fabrics as described in claim 1, characterized in that, The soaping treatment method is as follows: mix 1-5 g / L of neutral soap and 1-5 g / L of sodium carbonate to prepare a soap solution, and add the soap solution to the dyed silk fabric for soaping.

6. The dyeing method for silk fabrics as described in claim 5, characterized in that, The ratio of the weight of the silk fabric to the volume of the soap solution is 1g:(20-100)mL.

7. The dyeing method for silk fabrics as described in claim 5, characterized in that, The conditions for the soaping treatment are: soaping temperature 20-60℃, soaping time 5-15 min.

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