An indigo pre-reducing agent, an indigo reduction slurry and application thereof

Abstract

The application belongs to the technical field of textiles, and relates to an indigo pre-reducing agent, an indigo reducing paste and application thereof. The indigo pre-reducing agent is prepared from the following raw materials: isatis indigotica leaf, indigo fermentation liquor, glutinous rice wine and water; the indigo reducing paste is prepared from the following raw materials: the indigo pre-reducing agent, an alkaline compound, a sugar-based reducing agent, water, a penetrating agent and a natural thickening agent. The plant indigo reducing paste provided by the application can be used for printing and dyeing at room temperature, and the process of fixing color by high-temperature steaming in the printing process is omitted, so that energy consumption is saved. Meanwhile, the sugar-based reducing agent is used to replace the chemical reducing agent, so that damage of the traditional chemical reducing agent to protein fibers is avoided, and the printing paste can be applied to various fiber fabrics. The indigo pre-reducing agent and the plant indigo reducing paste provided by the application have wide application prospects in green textiles.

Description

Technical Field

[0001] This invention belongs to the field of textile technology and relates to an indigo pre-reducing agent, an indigo reducing sizing agent, and their applications. Background Technology

[0002] Indigo is a vat dye, insoluble in water, and cannot be directly used for printing and dyeing fabrics. It must be reduced to a soluble leuco form in an alkaline environment using a reducing agent such as sodium hydrosulfite before it can dye the fabric. After dyeing, it is oxidized by air, reforming into insoluble indigo particles that adhere to the yarn, achieving the purpose of dyeing. On the other hand, screen printing using chemical or plant dyes requires high-temperature steaming to fix the pattern. This process is not only complex and energy-intensive but also produces a large amount of waste gas emissions. Furthermore, traditional indigo products are mainly suitable for dyeing cellulose fibers. Due to its high alkalinity, it is not suitable for dyeing protein fibers such as wool and silk, and it has poor leveling properties, resulting in a lighter color on protein fibers.

[0003] Chinese patent application CN110644262A discloses a printing method for plant-based indigo. This method uses a mixture of gum arabic and guar gum as a thickener and a complex of ferrous ions and N-(2-hydroxyethyl)ethylenediaminetriacetic acid trisodium ester as a reducing agent. The plant-based indigo is printed directly. The ferrous salt complex reduction system has a strong reducing potential, which can reduce plant-based indigo, avoiding the use of sodium hydrosulfite. However, the indigo fabric requires high-temperature steaming to fix the color after dyeing.

[0004] Chinese patent application CN109457507A discloses a printing method for indigo-dyed fabrics. This method involves mixing indigo, caustic soda, and sodium dithionite at a specific temperature and ratio, followed by the addition of an acrylate copolymer to prepare an indigo paste. Using this paste for screen printing, the fabric only needs to be air-dried after printing to achieve reduction, followed by washing to remove surface dye and impurities. This eliminates complex processes such as steaming, oxidation, and desizing, shortening the process cycle and reducing wastewater and waste gas emissions. However, the large amount of sodium dithionite used in preparing the paste can significantly damage some fabrics, such as cashmere, and the resulting wastewater causes substantial environmental pollution.

[0005] Therefore, developing a low-temperature green printing technology based on natural indigo has great economic value and social benefits. Summary of the Invention

[0006] In view of this, the present invention provides a plant-based indigo reducing paste that can be printed and dyed at room temperature, eliminating the process of fixing the color by high-temperature steaming in the printing process and saving energy consumption; at the same time, by using a sugar-based reducing agent to replace a chemical reducing agent, the damage to protein fibers caused by traditional chemical reducing agents is avoided, and this printing paste can be applied to a variety of fiber fabrics.

[0007] To achieve the above-mentioned technical objectives, the present invention proposes the following technical solution:

[0008] One objective of this invention is to provide an indigo pre-reducing agent, which is prepared from the following raw materials:

[0009] Ingredients: woad leaves, indigo fermentation liquid, glutinous rice wine, and water.

[0010] In some embodiments, the weight ratio of the raw materials, namely, the indigo leaves, indigo fermented liquid, glutinous rice wine and water, is 4-6:0.5-1.5:1-3:8-12.

[0011] In some preferred embodiments, the weight ratio of the woad leaves, indigo fermentation liquid, glutinous rice wine and water is 5:1:2:10.

[0012] The second objective of this invention is to provide the application of any of the aforementioned indigo pre-reducing agents in the preparation of indigo reducing slurry.

[0013] In some embodiments, the indigo reducing paste is used for printing.

[0014] The third objective of this invention is to provide an indigo reducing slurry, which is prepared from the following raw materials:

[0015] The aforementioned indigo pre-reducing agent, alkaline compound, glycosyl reducing agent, water, penetrant, and natural thickener.

[0016] The alkaline compounds are used to adjust the pH of the indigo reducing paste, and the content of the alkaline compounds depends on the specific choice.

[0017] In some embodiments, the indigo reducing slurry is prepared from the following raw materials:

[0018] The ingredients are: 40-70 parts indigo pre-reducing agent, 2-5 parts sugar-based reducing agent, 10-20 parts natural thickener, 0.3-0.6 parts alkaline compound, 5-20 parts water, and 0-1 parts penetrant.

[0019] In some embodiments, the pH of the indigo reducing slurry is 8-13.

[0020] Different geographical locations and climates have different requirements for pH. Those skilled in the art can adjust the pH according to the specific environment and coloring results.

[0021] In some embodiments, the glycosyl reducing agent is selected from at least one of glucose, galactose, fructose, lactose, or maltose.

[0022] In some preferred embodiments, the glycosyl reducing agent is glucose.

[0023] In some embodiments, the natural thickener is selected from at least one of gelatin, guar gum, xanthan gum, carrageenan, locust bean gum, guar gum, gum arabic, pectin, fenugreek gum, and sodium alginate.

[0024] In some preferred embodiments, the natural thickener is guar gum and / or sodium alginate.

[0025] In some embodiments, the alkaline compound is selected from at least one of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3·H2O), sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3), and disodium hydrogen phosphate (NaHPO).

[0026] In some preferred embodiments, the alkaline compound is sodium hydroxide.

[0027] In some embodiments, the penetrant is fatty alcohol polyoxyethylene ether (JFC).

[0028] The fourth objective of this invention is to provide the application of any of the aforementioned indigo reducing pastes in fabric printing.

[0029] In some embodiments, the printing is low-temperature printing.

[0030] In some embodiments, the fabric includes, but is not limited to, cellulose fabrics, regenerated cellulose fabrics, protein fiber fabrics, synthetic fiber fabrics, etc.

[0031] In some embodiments, the fabric is a cellulose fabric.

[0032] In some preferred embodiments, the raw materials of the cellulose fabric include, but are not limited to: cotton, such as upland cotton, island cotton, Asian cotton, African cotton, kapok, etc.; hemp, such as flax, ramie, jute, hemp, abaca, sisal, etc.; bamboo, such as yellow bamboo, moso bamboo, mian bamboo, nan bamboo, etc.

[0033] In some embodiments, the fabric is a regenerated cellulose fabric.

[0034] In some preferred embodiments, the raw materials of the regenerated cellulose fabric include, but are not limited to: viscose, modal, lyocell, triacetate, cupro, seacell, Tencel, chitosan, etc.

[0035] In some embodiments, the fabric is a protein fiber fabric.

[0036] In some preferred embodiments, the raw materials for the protein fiber fabric include natural protein fibers and regenerated protein fibers.

[0037] In some embodiments, the natural protein fibers include, but are not limited to: wool fibers, rabbit hair fibers, horse hair fibers, cow hair fibers, camel hair fibers, silk fibers, etc.

[0038] In some embodiments, the regenerated protein fiber includes, but is not limited to, milk fiber, casein fiber, peanut fiber, soybean fiber, etc.

[0039] In some embodiments, the fabric is a synthetic fiber fabric.

[0040] In some preferred embodiments, the raw materials of the synthetic fiber fabric include, but are not limited to: nylon, polyester, acrylic, vinylon, polypropylene, chlorofiber, spandex, aramid, fluoropolymer, etc.

[0041] The fifth objective of this invention is to provide a method for preparing any of the aforementioned indigo pre-reducing agents, the method comprising the following steps:

[0042] (1) Place the woad leaves, water and indigo fermentation liquid in a container, mix them evenly, seal and carry out the first fermentation;

[0043] (2) After the first fermentation is completed, glutinous rice wine is added, sealed and fermented a second time to obtain indigo pre-reducing agent.

[0044] In some implementations, step (2) further includes the following steps:

[0045] After the second fermentation is completed, the mixture is filtered.

[0046] In some embodiments, the weight ratio of the raw materials, namely, the indigo leaves, indigo fermented liquid, glutinous rice wine and water, is 4-6:0.5-1.5:1-3:8-12.

[0047] In some preferred embodiments, the weight ratio of the woad leaves, indigo fermentation liquid, glutinous rice wine and water is 5:1:2:10.

[0048] In some implementations, the first fermentation time is 24-72 hours.

[0049] In some preferred embodiments, the first fermentation time is 48 hours.

[0050] In some embodiments, the temperature of the first fermentation is room temperature.

[0051] In some implementations, the second fermentation time is 48-96 hours.

[0052] In some preferred embodiments, the second fermentation time is 72 hours.

[0053] The sixth objective of this invention is to provide a method for preparing indigo reducing slurry, the method comprising the following steps:

[0054] Mix indigo pre-reducing agent, alkaline compound, sugar-based reducing agent, water, penetrant and natural thickener evenly, seal and let stand at room temperature for 30-60 minutes to obtain indigo reduced slurry.

[0055] In some embodiments, the preparation method further includes the following steps:

[0056] The indigo pre-reducing agent is filtered before being mixed with other raw materials.

[0057] In this invention, filtering the indigo pre-reducing agent can remove large pigment particles that condense upon reaction with air.

[0058] In some embodiments, the raw materials have the following parts by weight:

[0059] The ingredients are: 40-70 parts indigo pre-reducing agent, 2-5 parts sugar-based reducing agent, 10-20 parts natural thickener, 0.3-0.6 parts alkaline compound, 5-20 parts water, and 0-1 parts penetrant.

[0060] In some embodiments, the glycosyl reducing agent is selected from at least one of glucose, galactose, fructose, lactose, or maltose.

[0061] In some preferred embodiments, the glycosyl reducing agent is glucose.

[0062] In some embodiments, the natural thickener is selected from at least one of gelatin, guar gum, xanthan gum, carrageenan, locust bean gum, guar gum, gum arabic, pectin, fenugreek gum, and sodium alginate.

[0063] In some preferred embodiments, the natural thickener is guar gum and / or sodium alginate.

[0064] In some embodiments, the alkaline compound is selected from at least one of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonia (NH3·H2O), sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3), and disodium hydrogen phosphate (NaHPO).

[0065] In some preferred embodiments, the alkaline compound is sodium hydroxide.

[0066] In some embodiments, the penetrant is fatty alcohol polyoxyethylene ether (JFC).

[0067] The seventh objective of this invention is to provide a method for low-temperature printing of fabrics, the method comprising the following steps:

[0068] 1) Place the screen on the fabric, cover the patterned part of the screen with any of the aforementioned indigo reducing pastes, and let the indigo reducing pastes soak into the fabric to obtain a patterned fabric.

[0069] 2) The patterned fabric is dried for the first time, washed, and then dried a second time to obtain indigo printed fabric.

[0070] In some embodiments, the first drying and the second drying can be natural air drying.

[0071] In some embodiments, the washing is performed using water at 30-40°C.

[0072] In some preferred embodiments, the water used for washing contains an anti-sticking agent, preferably an acidic anti-sticking agent, and more preferably TY-CKG8070 anti-sticking agent.

[0073] In some embodiments, the printing is low-temperature printing.

[0074] In some embodiments, the fabric includes, but is not limited to, cellulose fabrics, regenerated cellulose fabrics, protein fiber fabrics, synthetic fiber fabrics, etc.

[0075] In some embodiments, the fabric is a cellulose fabric.

[0076] In some preferred embodiments, the raw materials of the cellulose fabric include, but are not limited to: cotton, such as upland cotton, island cotton, Asian cotton, African cotton, kapok, etc.; hemp, such as flax, ramie, jute, hemp, abaca, sisal, etc.; bamboo, such as yellow bamboo, moso bamboo, mian bamboo, nan bamboo, etc.

[0077] In some embodiments, the fabric is a regenerated cellulose fabric.

[0078] In some preferred embodiments, the raw materials of the regenerated cellulose fabric include, but are not limited to: viscose, modal, lyocell, triacetate, cupro, seacell, Tencel, chitosan, etc.

[0079] In some embodiments, the fabric is a protein fiber fabric.

[0080] In some preferred embodiments, the raw materials for the protein fiber fabric include natural protein fibers and regenerated protein fibers.

[0081] In some embodiments, the natural protein fibers include, but are not limited to: wool fibers, rabbit hair fibers, horse hair fibers, cow hair fibers, camel hair fibers, silk fibers, etc.

[0082] In some embodiments, the regenerated protein fiber includes, but is not limited to, milk fiber, casein fiber, peanut fiber, soybean fiber, etc.

[0083] In some embodiments, the fabric is a synthetic fiber fabric.

[0084] In some preferred embodiments, the raw materials of the synthetic fiber fabric include, but are not limited to: nylon, polyester, acrylic, vinylon, polypropylene, chlorofiber, spandex, aramid, fluoropolymer, etc.

[0085] The plant-based indigo reducing paste provided by this invention, which can be printed and dyed at room temperature, eliminates the process of fixing the color through high-temperature steaming in the printing process, thus saving energy consumption. At the same time, by using a sugar-based reducing agent instead of a chemical reducing agent, the damage to protein fibers caused by traditional chemical reducing agents is avoided, and this printing paste can be applied to a variety of fiber fabrics.

[0086] The indigo pre-reducing agent containing natural glycosides provided by this invention is prepared based on a low-temperature bio-fermentation method. By adding a glycosyl reducing agent and sodium hydroxide for low-temperature reduction, an indigo printing paste with a pH range of 8-12 can be obtained. This paste exhibits natural permeability, high dye uptake, and maintains a good reduced state in a sealed container protected from light at room temperature. It can be directly used for printing patterns in environments with air humidity above 40%. After printing, it can be air-dried naturally for 2-6 hours without the need for steaming, chemical oxidation, or desizing processes; it can be directly washed and dried. Therefore, the indigo pre-reducing agent and plant-based indigo reducing paste provided by this invention have broad application prospects in green textiles. Detailed Implementation

[0087] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly used in the field to which this invention pertains. For the purposes of interpreting this specification, the following definitions will apply, and where appropriate, terms used in the singular will also include the plural forms, and vice versa.

[0088] Unless the context clearly indicates otherwise, the terms “a” and “an” as used herein include plural references. For example, reference to “a cell” includes multiple such cells and equivalents known to those skilled in the art, etc.

[0089] As described in this disclosure, the term "water" should be understood in the broadest sense and has no specific meaning or limitation in this invention. Those skilled in the art will recognize that the choice of water depends on specific production specifications. Generally, there are no special requirements, but in some production or preparation processes requiring sterility, the water must not contain microorganisms that could interfere with the production or preparation. In such cases, water confirmed to be clean and sterile by conventional testing methods can be used, such as commercially available purified water, filtered water, distilled water, sterile water, double-distilled water, etc.

[0090] As described in this disclosure, the terms "room temperature" and "normal temperature" refer to indoor temperature under natural conditions without the aid of any equipment to provide additional heat. These temperatures vary depending on the altitude or latitude of the location, and the specific temperature range depends on the actual conditions of the location where this invention is implemented. In some preferred embodiments, the room temperature is 25-30°C.

[0091] As described in this disclosure, the terms “glutinous rice wine,” “glutinous rice wine,” “sweet wine,” “fermented rice,” or “fermented glutinous rice” all refer to wines made from glutinous rice.

[0092] As described in this disclosure, the term "indigo fermentation broth" refers to the liquid obtained from the fermentation of indigo, where the fermentation has been completed. In some instances, the indigo fermentation broth can be taken from conventional indigo fermentation tanks.

[0093] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments without a specified manufacturer are commercially available conventional products. Numerous specific details are provided in the following detailed embodiments to better illustrate the invention. The specific embodiments described herein are for illustrative purposes only and are not intended to constitute any limitation on the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0094] Example 1: Indigo Printing on Cashmere Fabric

[0095] 1.1 Preparation of Indigo Reduction Slurry

[0096] Mix 70 parts of plant indigo pre-reducing agent, 2.6 parts of glycosyl reducing agent (glucose), and 10 parts of water together. Slowly add about 0.4 parts of NaOH and stir until the paste turns yellow or green and the pH is 10. Then add 10 parts of guar gum and 7 parts of sodium alginate. After stirring thoroughly and letting it stand at room temperature for 45 minutes, it is ready for cashmere printing.

[0097] 1.2 Fabric Printing

[0098] First, rinse a 100% cashmere knitted fabric sheet in 40℃ warm water for 20 minutes. After rinsing and wringing, dry it at 60℃. Iron it flat and lay it flat on a printing table. Cover it with a pattern screen, apply the prepared printing paste to the patterned area of ​​the screen, and print using standard printing procedures. After printing, leave it at room temperature (30℃) for 2.5 hours. You will see the printed area on the cashmere fabric change from green to blue, at which point it is ready for the washing stage.

[0099] Add 1% acidic anti-sticking agent (TY-CKG8070 anti-sticking agent, Dongguan Dayang Textile Products Co., Ltd.) to 40℃ water, and wash the cashmere printed fabric twice, 4 minutes each time. After washing and drying, you will get a high-fixed-color indigo printed fabric.

[0100] Example 2: Indigo Printing on a Blended Fabric (Linen:Cashmere = 50:50)

[0101] Compared with Example 1, this embodiment adds more water and penetrant - fatty alcohol polyoxyethylene ether (JFC), which gives the dye better penetration on the fabric and a longer reduction time.

[0102] 2.1 Preparation of Indigo Reduction Slurry

[0103] Mix 70 parts of indigo pre-reducing agent, 2.6 parts of glycosyl reducing agent (glucose), 15 parts of water, and 1 part of penetrant together. Slowly add about 0.4 parts of NaOH and stir until the paste turns yellow or green and the pH is 10. Then add 10 parts of guar gum and 7 parts of sodium alginate. After stirring thoroughly and letting it stand at room temperature for 45 minutes, it can be used for printing on blended fabrics.

[0104] 2.2 Fabric Printing

[0105] First, wash the blended fabric at 40℃, dry it, iron it, and then lay it flat on the printing table. Use indigo paste to cover the patterned part of the screen. You can see that the dye on the fabric changes from green to blue. After more than 3 hours of natural drying, it can enter the washing stage.

[0106] Add 1% acidic anti-sticking agent (TY-CKG8070 anti-sticking agent, Dongguan Dayang Textile Products Co., Ltd.) to 30℃ water, wash 3 times, 4 minutes each time. After washing and drying, you will get a blended indigo printed fabric with high color fastness.

[0107] Example 3: 100% Cotton Knitted Fabric

[0108] Compared with Example 2, this embodiment increases the proportion of water and penetrant in the sizing agent to take into account the dyeing characteristics of cotton, so that the dye has high penetration on the fabric and a longer reduction dyeing time.

[0109] 3.1 Preparation of Indigo Reduction Slurry

[0110] Mix 70 parts of indigo pre-reducing agent, 2.6 parts of glycosyl reducing agent (glucose), 20 parts of water, and 2 parts of penetrant together. Slowly add about 0.4 parts of NaOH and stir until the paste turns yellow or green and the pH is 10. Then add 17 parts of sodium alginate. After stirring thoroughly and letting it stand at room temperature for 45 minutes, it can be used for printing on blended fabrics.

[0111] 3.2 Fabric Printing

[0112] First, wash the 100% cotton knitted fabric at 50 degrees Celsius, dry it, iron it, and lay it flat on the printing table. Use indigo paste to cover the patterned part of the screen. You can see that the dye on the fabric changes from green to blue. After more than 3 hours of natural drying, it can enter the washing stage.

[0113] Add 1% acidic anti-sticking agent (TY-CKG8070 anti-sticking agent, Dongguan Dayang Textile Products Co., Ltd.) to 30℃ water, wash 3 times, 4 minutes each time. After washing and drying, you will get a blended indigo printed fabric with high color fastness.

[0114] Example 4: 100% Rayon Knitted Fabric

[0115] The difference between this embodiment and Embodiment 1 is that, based on the lightweight nature of the fabric, the moisture content in the formula is halved to avoid pattern diffusion.

[0116] 4.1 Preparation of Indigo Reduction Slurry

[0117] Mix 70 parts of plant indigo pre-preparation, 2.6 parts of glycosyl reducing agent (glucose), and 5 parts of water together. Slowly add about 0.4 parts of NaOH and stir until the slurry turns yellow or green and the pH is 10. Then add 10 parts of guar gum and 7 parts of sodium alginate. After stirring thoroughly and letting it stand at room temperature for 45 minutes, it can be used for printing on rayon knitted fabrics.

[0118] 4.2 Fabric Printing

[0119] Wash the 100% rayon knitted fabric in 50℃ water, dry it, iron it, and lay it flat on the printing table. Use a paste mixture to cover the patterned part of the screen. You can see that the dye on the fabric changes from green to blue. After natural drying for more than 2 hours, it can enter the washing stage.

[0120] Add 1% acidic anti-sticking agent (TY-CKG8070 anti-sticking agent, Dongguan Dayang Textile Products Co., Ltd.) to 40℃ water, and wash the cashmere printed fabric twice, 4 minutes each time. After washing and drying, you will get a high-fixed-color indigo printed fabric.

[0121] Test Example 1: Lightfastness Test

[0122] The light fastness of the indigo printed fabrics with high color fastness obtained in Examples 1-4 was tested according to ISO 105-B02:2014.

[0123] Test Example 2: Colorfastness to Washing

[0124] The wash fastness of the indigo printed fabrics with high color fastness obtained in Examples 1-4 was tested, and the test method was in accordance with ISO 105-C06:2010.

[0125] Test Example 3: Color fastness to rubbing

[0126] The color fastness to rubbing of the indigo printed fabrics with high color fastness obtained in Examples 1-4 was tested according to ISO 105-X12:2016.

[0127] Test Example 4: Color fastness test against non-chlorine bleaching

[0128] The indigo printed fabrics with high color fastness obtained in Examples 1-4 were tested for their resistance to non-chlorine bleaching, and the test method was in accordance with AATCC TS-001.

[0129] The test results for test examples 1-4 are shown in Table 1.

[0130] Table 1

[0131]

[0132] The results showed that the four fabrics printed with plant-based indigo at low temperature met the color fastness requirements for textiles.

[0133] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. An indigo reducing slurry, characterized in that, The indigo reducing slurry is prepared from the following raw materials: The ingredients are: 40-70 parts indigo pre-reducing agent, 2-5 parts sugar-based reducing agent, 10-20 parts natural thickener, 0.3-0.6 parts alkaline compound, 5-20 parts water, and 0-1 parts penetrant. The pH of the indigo reducing slurry is 8-13; The preparation method of the indigo reducing slurry includes the following steps: mixing indigo pre-reducing agent, alkaline compound, sugar-based reducing agent, water, penetrant and natural thickener evenly, sealing and letting stand at room temperature for 30-60 min to obtain indigo reducing slurry; The indigo pre-reducing agent is prepared from the following raw materials: woad leaves, indigo fermentation liquid, glutinous rice wine and water, wherein the weight ratio of woad leaves, indigo fermentation liquid, glutinous rice wine and water is 4-6:0.5-1.5:1-3:8-12. The preparation method of the indigo pre-reducing agent includes the following steps: (1) Place the woad leaves, water and indigo fermentation liquid in a container, mix them evenly, seal and carry out the first fermentation; (2) After the first fermentation is completed, glutinous rice wine is added, sealed and fermented a second time to obtain indigo pre-reducing agent.

2. The indigo reducing slurry according to claim 1, characterized in that, The weight ratio of the woad leaves, indigo fermented liquid, glutinous rice wine, and water is 5:1:2:

10.

3. The indigo reducing slurry according to claim 1, characterized in that, The glycosyl reducing agent is selected from at least one of glucose, galactose, fructose, lactose, or maltose.

4. The indigo reducing slurry according to claim 1, characterized in that, The natural thickener is selected from at least one of gelatin, guar gum, xanthan gum, carrageenan, locust bean gum, guar gum, gum arabic, pectin, fenugreek gum, and sodium alginate.

5. The indigo reducing slurry according to claim 1, characterized in that, The alkaline compound is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia, sodium bicarbonate, sodium carbonate, and disodium hydrogen phosphate.

6. The indigo reducing slurry according to claim 1, characterized in that, The penetrant is fatty alcohol polyoxyethylene ether.

7. The application of the indigo reducing paste according to any one of claims 1-6 in fabric printing.

8. The method for preparing indigo reducing slurry according to any one of claims 1-2, characterized in that, The preparation method of the indigo pre-reducing agent includes the following steps: (1) Place the woad leaves, water and indigo fermentation liquid in a container, mix them evenly, seal and carry out the first fermentation; (2) After the first fermentation is completed, glutinous rice wine is added, sealed and fermented a second time to obtain indigo pre-reducing agent.

9. The preparation method according to claim 8, characterized in that, Step (2) also includes the following steps: filtration is performed after the second fermentation is completed.

10. The preparation method according to claim 8, characterized in that, The first fermentation time is 24-72 hours.

11. The preparation method according to claim 10, characterized in that, The first fermentation time was 48 hours.

12. The preparation method according to claim 8, characterized in that, The second fermentation time is 48-96 hours.

13. The preparation method according to claim 12, characterized in that, The second fermentation time was 72 hours.

14. The method for preparing indigo reducing slurry according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: Mix indigo pre-reducing agent, alkaline compound, sugar-based reducing agent, water, penetrant and natural thickener evenly, seal and let stand at room temperature for 30-60 minutes to obtain indigo reduced slurry.

15. The preparation method according to claim 14, characterized in that, The preparation method further includes the following step: filtering the indigo pre-reducing agent before mixing it with other raw materials.

16. A method for room temperature printing on fabrics, characterized in that, The method includes the following steps: 1) Place the screen on the fabric, cover the patterned portion of the screen with the indigo reducing paste as described in any of claims 1-6, and allow the indigo reducing paste to penetrate the fabric to obtain a patterned fabric. 2) The patterned fabric is dried for the first time, washed, and then dried a second time to obtain indigo printed fabric; The first and second drying processes were carried out by natural air drying.

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