Blue staining solution as well as preparation method and application thereof

Abstract

The invention discloses an ornamental blue dyeing solution as well as a preparation method and application thereof, and relates to the technical field of textile printing and dyeing. According to the ornamental blue staining solution provided by the invention, the slightly hydrothermal carbonized reducing sugar is added as a reduction retaining agent, and after the reducing sugar is combined with the sodium hydrosulfite for use, the staining solution can keep excellent long-acting stability, and the staining solution can slowly release reducing substances in a staining process as long as 4 hours, so that stable reduction and staining of ornamental blue are realized. According to the staining solution provided by the invention, the maximum reduction potential is only reduced by 30.73% within 4 hours; when the dyeing liquid is used for dyeing, the excellent dyeing effect stability can be obtained without continuously supplementing a reducing agent in the dyeing process, and the K / S value of the obtained dyed cloth is only reduced from 9.3 to 6.2 within 4 hours.

Description

Technical Field

[0001] The invention relates to the technical field of textile printing and dyeing, and in particular to a blue dyeing liquid and a preparation method and application thereof. Background Art

[0002] Indigoidine is a natural blue pigment extracted from microorganisms. It has similar color and properties to indigo and is a type of blue reducing dye. With the development of biotechnology, indigoidine has initially achieved industrial production and application. At the same time, due to its bright coloring, green and environmentally friendly products, and gentle dyeing process, indigoidine has shown its potential to replace indigo in the dyeing field.

[0003] At present, the dyeing process of Guanlan is carried out with reference to the reduction dyeing process of indigo, using insurance powder (sodium dithionite) and caustic soda as dye additives, but the usage is greatly reduced (Guanlan only needs to use 1 times the mass of insurance powder, while indigo needs to use 15 times the mass), so compared with the dyeing of indigo, the dyeing process of Guanlan is more environmentally friendly and the conditions are mild. However, insurance powder is a strong reducing agent that reacts quickly with oxygen in aqueous solution, which leads to the rapid consumption of insurance powder during the dyeing process. When the insurance powder is consumed to a certain extent, the dyeing effect of the dye molecules will be greatly affected, so in the actual dyeing of indigo, it is necessary to continuously replenish insurance powder to maintain the reducing power of the dyeing solution, thereby extending the working time of the dyeing solution. Guanlan will encounter the same problem as indigo during reduction dyeing, that is, the rapid consumption of insurance powder leads to a reduction in the working time of the dyeing solution, but there is currently no good mitigation measure. Since the dyeing conditions of indigo blue are milder and the reduction potential is lower (the reduction potential of indigo blue is above 600mV, while the reduction potential of indigo blue is below 600mV), the required reduction strength is lower. Therefore, adding insurance powder like in the dyeing process of indigo blue can easily make the reduction strength of the dyeing solution too high, affecting the dyeing effect of indigo blue. Therefore, it is urgent to develop a reagent or method that can make the indigo blue dyeing solution have long-term dyeing stability. Summary of the invention

[0004] In order to address the deficiencies of the prior art, the present invention provides an indigo dyeing liquid, wherein a reducing sugar that has undergone hydrothermal treatment is used as a reducing retaining agent. Due to the hydrothermal treatment, the reducing sugar is slightly carbonized, and when used in combination with sodium hydrosulfite, the indigo dyeing liquid can slowly release its reducing properties and maintain the reduction potential within a range suitable for indigo dyeing, thereby enabling the obtained indigo dyeing liquid to maintain long-term dyeing stability.

[0005] Another object of the present invention is to provide a method for preparing a blue dyeing solution.

[0006] Another object of the present invention is to provide a dyeing method.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A blue dyeing solution comprising the following components calculated by mass:

[0009] 1 part of blue, 0.1-1.5 parts of sodium dithionite, 0.5-5 parts of blue reduction retaining agent;

[0010] The blue-viewing reduction retaining agent comprises reducing sugar that has been subjected to hydrothermal treatment, wherein the hydrothermal treatment is carried out under the condition of pH 7.5 to 10.5 and the temperature of the hydrothermal treatment is 85 to 95°C.

[0011] Reducing sugars such as glucose are commonly used reducing agents, but their reduction potential is low and their reducing effect in the reduction dyeing system is poor. In the actual dyeing process, it is usually necessary to use high temperature and strong alkaline conditions to obtain a reducing effect similar to that of strong reducing agents such as insurance powder. The inventors of this application have found through a large number of experimental studies that sodium dithionite (insurance powder) and hydrothermally treated reducing sugars are used as reducing agents in the reduction dyeing system of indigo. The hydrothermally treated reducing sugar can be used as an indigo reduction retainer, which slowly and steadily releases reducing power, so that the reduction potential of the indigo dyeing solution is maintained in the range of -600 to -400 mV, thereby increasing the working time of the indigo dyeing solution.

[0012] Specifically, in the indigo dyeing solution provided by the present invention, after the reducing sugar is hydrothermally treated, a slight carbonization reaction will occur, which not only has stronger reducing properties, but also the carbonized reducing sugar has a more stable structure, which can avoid ineffective decomposition. Although the reducing performance of the reducing sugar after carbonization is still weak, it can be used in conjunction with strong reducing agents such as insurance powder to reduce the indigo, which can stably and slowly reduce the indigo. Its principle is similar to that of a buffer solution. In order to release the reducing power, the reducing sugar and insurance powder both need to compete for OH-. Under a certain ratio, the ability of the two to compete for OH- is balanced, so it has a buffering effect, thereby maintaining the potential of the dyeing solution at a relatively stable level, and finally prolonging the duration of the reduction state of the indigo dyeing solution when working. The inventors of this application have found through a large number of experimental attempts that only when the hydrothermal treatment temperature is 85-95°C and the hydrothermal treatment is carried out under the condition of pH 7.5-10.5, the resulting reducing sugar can form a reaction system more suitable for reducing indigo with insurance powder sodium dithionite. Inappropriate temperature and pH of the hydrothermal treatment will lead to inappropriate carbonization structure of the reducing sugar formed, which makes it difficult to fully exert synergistic effects with insurance powder.

[0013] Preferably, the hydrothermal treatment is carried out at a pH of 8.5-10.

[0014] In a specific embodiment of the present invention, the hydrothermal treatment time is 30 minutes.

[0015] Preferably, the blue reduction retaining agent comprises the following components calculated by mass percentage:

[0016] Reducing sugar 50-60%, inorganic salt 1-5%, alcohol 3-8%, and the balance is water.

[0017] The purpose of adding inorganic salts and alcohol to the above-mentioned reducing retainer is to improve the dyeing rate and the solubility of reducing sugar. At the same time, controlling the proportion of each component within the above range can obtain a better reducing effect.

[0018] More preferably, the reducing sugar includes at least one of glucose, fructose and galactose.

[0019] More preferably, the inorganic salt includes at least two of sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, and disodium hydrogen phosphate.

[0020] In a specific embodiment of the present invention, the inorganic salt is an equimolar mixture of sodium carbonate and sodium bicarbonate, or an equimolar mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate. The above two inorganic salts can form a buffer system with a specific pH after combination.

[0021] More preferably, the alcohol includes at least one of ethanol, ethylene glycol and methanol.

[0022] Preferably, the preparation method of the blue-viewing reduction preserving agent comprises the following steps:

[0023] Mix reducing sugar, inorganic salt and water, add the remaining components at 40-60°C, and mix well to obtain the blue reduction retaining agent.

[0024] In a specific embodiment of the present invention, the reducing sugar is mixed with inorganic salt and water and then subjected to hydrothermal treatment.

[0025] In a specific embodiment of the present invention, the pH of the solution after the inorganic salt is dissolved in water is 8.5 to 10. More specifically, when the pH of the solution after the inorganic salt is dissolved in water is not within the above range, a small amount of sodium hydroxide or acetic acid can be added to adjust it.

[0026] Preferably, the pH of the blue dyeing solution is 6.5-11.0.

[0027] In a specific embodiment of the present invention, sodium hydroxide or acetic acid is used to adjust the pH of the dyeing solution to 6.5-11.0.

[0028] More preferably, the reduction potential of the blue dye solution is -600 to -400 mV.

[0029] When the reduction potential of the dye solution is within the above range, it is more suitable for blue dyeing.

[0030] The present invention also protects a method for preparing a blue dyeing solution, comprising the following steps:

[0031] Mix all the components to obtain the blue dye solution.

[0032] The present invention also protects a dyeing method, which uses the above-mentioned indigo dyeing solution for dyeing.

[0033] Preferably, the dyeing time is 0.5 to 4 hours.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The dyeing solution provided by the present invention has a maximum reduction potential of only 30.73% within 4 hours, indicating that the combination of the reducing agent and the hydrosulfite can make the dyeing solution have excellent basic stability, so that the dyeing result can be kept long-term stable during the actual dyeing process. The dyeing solution obtained by the present invention is used for dyeing, and no reducing agent needs to be added during the dyeing process, and excellent dyeing effect stability can also be obtained. The K / S value of the obtained dyed cloth only drops from 9.3 to 6.2 within 4 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a comparison chart of the dyeing results in Effect Examples 1 to 3 of the present invention.

[0037] Figure 2 It is a comparison chart of the reducing retaining agent in Example 1 of the present invention and in Comparative Example 6. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0039] Example 1

[0040] A blue dyeing solution comprising the following components calculated by mass:

[0041] 1 part of indigo plant oil, 0.8 part of hydrosulfite, 1 part of reducing agent;

[0042] Adding sodium hydroxide to the blue dyeing solution to adjust its pH to 10;

[0043] The reduction retaining agent comprises the following components calculated by mass percentage:

[0044] Glucose 50%, inorganic salt 1%, ethylene glycol 3%, and the balance is water.

[0045] The inorganic salt is an equimolar mixture of sodium carbonate and sodium bicarbonate;

[0046] The preparation method of the reduction retaining agent comprises the following steps:

[0047] Add inorganic salt to water and adjust the solution pH to 10; add glucose, raise the temperature to 85°C, and perform hydrothermal treatment for 30 minutes; then lower the solution temperature to 40°C, add ethylene glycol, and mix well to obtain a reduction retaining agent.

[0048] The preparation method of the blue dyeing solution in this embodiment comprises the following steps:

[0049] Mix all the components to obtain the blue dye solution.

[0050] After testing, the reduction potential of the blue dyeing solution described in this example is -581mV.

[0051] Example 2

[0052] A blue dyeing solution comprising the following components calculated by mass:

[0053] 1 part of blue, 0.8 part of sodium dithionite, 0.5 part of reduction retaining agent;

[0054] Adding sodium hydroxide to the blue dyeing solution to adjust its pH to 9;

[0055] The reduction retaining agent comprises the following components calculated by mass percentage:

[0056] Glucose 60%, inorganic salt 5%, ethylene glycol 8%, and the balance is water.

[0057] The inorganic salt is an equimolar mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate;

[0058] The preparation method of the reduction retaining agent comprises the following steps:

[0059] Add inorganic salt to water and adjust the solution pH to 8.5; add glucose, raise the temperature to 95°C, and perform hydrothermal treatment for 30 minutes; then lower the solution temperature to 60°C, add ethylene glycol, and mix well to obtain a reduction retaining agent.

[0060] The preparation method of the blue dyeing solution in this embodiment is consistent with that in embodiment 1.

[0061] After testing, the reduction potential of the blue dyeing solution described in this example is -583mV.

[0062] Example 3

[0063] A blue dyeing solution comprising the following components calculated by mass:

[0064] 1 part of blue, 0.8 part of sodium dithionite, 2 parts of reduction retaining agent;

[0065] Adding sodium hydroxide to the blue dye solution to adjust its pH to 9.6;

[0066] The reduction retaining agent comprises the following components calculated by mass percentage:

[0067] Glucose 50%, inorganic salt 3%, ethylene glycol 5%, and the balance is water.

[0068] The inorganic salt is an equimolar mixture of sodium carbonate and sodium bicarbonate;

[0069] The preparation method of the reduction retaining agent comprises the following steps:

[0070] Add inorganic salt to water and adjust the solution pH to 9.5; add glucose, raise the temperature to 90°C, and perform hydrothermal treatment for 30 minutes; then lower the solution temperature to 50°C, add ethylene glycol, and mix well to obtain a reduction retaining agent.

[0071] The preparation method of the blue dyeing solution in this embodiment is consistent with that in embodiment 1.

[0072] After testing, the reduction potential of the blue dyeing solution described in this example is -581mV.

[0073] Example 4

[0074] A blue dyeing solution, which is different from Example 3 only in that:

[0075] The glucose in the reducing agent was replaced with fructose.

[0076] The preparation method of the blue dyeing solution in this embodiment is consistent with that in embodiment 1.

[0077] After testing, the reduction potential of the blue dyeing solution described in this example is -585mV.

[0078] Example 5

[0079] A blue dyeing solution, which is different from Example 1 only in that:

[0080] The reducing retaining agent only includes reducing sugars.

[0081] The preparation method of the blue dyeing solution in this embodiment is consistent with that in embodiment 1.

[0082] After testing, the reduction potential of the blue dyeing solution described in this embodiment is -576mV.

[0083] Example 6

[0084] A blue dyeing solution, which is different from Example 1 only in that:

[0085] The reduction retaining agent comprises the following components calculated by mass percentage:

[0086] Glucose 70%, inorganic salt 1%, ethylene glycol 3%, and the balance is water.

[0087] The preparation method of the blue dyeing solution in this embodiment is consistent with that in embodiment 1.

[0088] After testing, the reduction potential of the blue dyeing solution described in this example is -589mV.

[0089] Example 7

[0090] A blue dyeing solution, which is different from Example 1 only in that:

[0091] The reduction retaining agent comprises the following components calculated by mass percentage:

[0092] Glucose 40%, inorganic salt 1%, ethylene glycol 3%, and the balance is water.

[0093] The preparation method of the blue dyeing solution in this embodiment is consistent with that in embodiment 1.

[0094] After testing, the reduction potential of the blue dyeing solution described in this example is -582mV.

[0095] Example 8

[0096] A blue dyeing solution, which is different from Example 1 only in that it includes the following components calculated by mass:

[0097] 1 part of blue, 0.8 part of sodium dithionite, 5 parts of reduction retaining agent;

[0098] The preparation method of the blue dyeing solution in this embodiment is consistent with that in embodiment 1.

[0099] After testing, the reduction potential of the blue dyeing solution described in this embodiment is -588mV.

[0100] Comparative Example 1

[0101] A blue dyeing solution, which is different from Example 1 only in that:

[0102] No reducing agent was added.

[0103] The preparation method of the indigo dyeing solution in this comparative example is consistent with that in Example 1.

[0104] After testing, the reduction potential of the blue dyeing solution in this comparative example is -592mV.

[0105] Comparative Example 2

[0106] A blue dyeing solution, which is different from Example 1 only in that:

[0107] No sodium dithionite was added.

[0108] The preparation method of the indigo dyeing solution in this comparative example is consistent with that in Example 1.

[0109] After testing, the reduction potential of the blue dyeing solution in this comparative example is -364mV.

[0110] Comparative Example 3

[0111] A blue dyeing solution, which is different from Example 1 only in that it includes the following components calculated by mass:

[0112] 1 part of blue, 0.8 part of sodium dithionite, 0.2 part of reduction retaining agent;

[0113] The preparation method of the indigo dyeing solution in this comparative example is consistent with that in Example 1.

[0114] After testing, the reduction potential of the blue dyeing solution in this comparative example is -581mV.

[0115] Comparative Example 4

[0116] A blue dyeing solution, which is different from Example 1 only in that:

[0117] In the preparation method of the reduction retaining agent, an inorganic salt is added into water, a small amount of sodium hydroxide is added to adjust the pH of the solution to 11, and then glucose is added to perform hydrothermal treatment.

[0118] The preparation method of the indigo dyeing solution in this comparative example is consistent with that in Example 1.

[0119] After testing, the reduction potential of the blue dyeing solution in this comparative example is -625mV.

[0120] Comparative Example 5

[0121] A blue dyeing solution, which is different from Example 1 only in that:

[0122] In the preparation method of the reduction retaining agent, an inorganic salt is added into water, a small amount of acetic acid is added to adjust the pH of the solution to 7, and then glucose is added to perform hydrothermal treatment.

[0123] The preparation method of the indigo dyeing solution in this comparative example is consistent with that in Example 1.

[0124] After testing, the reduction potential of the blue dyeing solution in this comparative example is -573mV.

[0125] Comparative Example 6

[0126] A blue dyeing solution, which is different from Example 1 only in that:

[0127] In the preparation method of the reduction retaining agent, glucose, inorganic salt and water are uniformly mixed without hydrothermal reaction, and the temperature is directly raised to 50° C. and ethylene glycol is added.

[0128] Performance Testing

[0129] 1. Basic performance test of dyeing solution

[0130] Next, the basic stability of the dyeing solution was explored by characterizing the reduction potential changes of the dyeing solution obtained in the embodiment and the comparative example within 4 hours. The good basic stability indicates that the dyeing solution has a certain long-term stability.

[0131] Reduction potential test: Connect the Leix 501-ORP electrode to the Leix PHS-25 detector as a reduction potential detection machine. Insert the ORP electrode below the liquid surface to be tested, let it stand for 30 seconds, read the reading on the detector, and record it as the reduction potential reading.

[0132] The specific performance is shown in Table 1. Figure 2 As shown:

[0133] Table 1. Reduction potential of the dyeing solution obtained in the examples and comparative examples within 4 hours

[0134]

[0135] According to Table 1 above and Figure 2 It can be seen from the results that the reduction potential of the dyeing solution provided by the present invention only decreases by 30.73% at most within 4 hours (Example 5, from the initial -576mV to -399mV), indicating that the combination of the reducing retaining agent and the insurance powder can make the blue dyeing solution have excellent basic stability, so that the dyeing result can maintain long-term stability in the actual dyeing process.

[0136] According to the results of Examples 1 to 4 and Comparative Examples 4 to 5, it can be seen that in the process of preparing the blue reduction retaining agent by hydrothermal treatment of reducing sugar, the hydrothermal treatment is carried out under the condition of pH 8.5 to 10 (Examples 1 to 4), and the obtained blue reduction dyeing liquid has better long-term dyeing stability, which is presumably due to the more stable carbonized structure of the reducing sugar formed. When the hydrothermal treatment is carried out under the condition of higher or lower pH (Comparative Examples 4 to 5), the dyeing stability of the obtained dyeing liquid decreases.

[0137] According to the results of Examples 1 and 5, adding an auxiliary dyeing medium such as alcohol to the reducing agent can improve the stability of the blue dyeing solution (Example 1), but the reducing agent is still the main component of the reducing agent. According to the results of Examples 1, 6 to 7, when the proportion of glucose in the reducing agent is increased from 50% (Example 1) to 70% (Example 6), the dyeing stability of the obtained dyeing solution is almost the same, and 70% is close to the solubility limit of reducing sugar, which will lead to easy precipitation, but it is easy to reduce the long-term stability of the dyeing solution. When the proportion of reducing sugar in the reducing agent is reduced to 40% (Example 7), the stability of the dyeing solution is insufficient. According to the results of Examples 1 and 8, the increase in the amount of reducing agent added to the dyeing solution will not bring greater improvement to the stability of the dyeing solution, but it is easy to cause the precipitation of reducing sugar and thus reduce the stability of the dyeing solution.

[0138] According to the results of Comparative Examples 1 to 2, when the reducing dyeing solution of the indigo plant only includes insurance powder and there is no synergistic effect, the long-term dyeing stability of the obtained dyeing solution is greatly reduced; and when the reducing dyeing solution of the indigo plant only includes reducing sugar, the reducing sugar itself can release a certain reducing power, but the resulting reducing dyeing solution system is also not suitable for dyeing indigo plant due to its too low potential (lower than -400 mV).

[0139] According to Comparative Example 3, the amount of reducing retainer added to the reducing dye solution is too small, and the reducing sugar and the hydrosulfite are difficult to fully exert the synergistic effect, resulting in decreased stability of the reducing dye solution.

[0140] According to Comparative Example 6, reducing sugar was not subjected to hydrothermal carbonization treatment, and reducing sugar and other substances were directly added at 50°C to prepare the reducing retaining agent. The glucose that was not subjected to carbonization treatment was not soluble in the system at a temperature of 50°C, resulting in a large amount of precipitation (see Figure 2 ), which is difficult to apply in practice.

[0141] 2. Dyeing effect test of dyeing solution

[0142] Next, dyeing was performed using the dyeing solution obtained in Example 1 and Comparative Example 1, and also using a conventional long-term dyeing process (adding insurance powder during the dyeing process), as shown in Effect Examples 1 to 3. The long-term dyeing stability of the dyeing solution was explored by changing the K / S value of the dyed cloth under different dyeing times.

[0143] Effect Example 1

[0144] A dyeing method, using the dyeing solution obtained in Comparative Example 1, during the dyeing process, 1 g / L of sodium hypochlorite is added to the dyeing solution at 0.5 h, 1 h, 1.5 h and 2 h; the dyeing method comprises the following steps:

[0145] Cut the pure cotton woven fabric into a size of 5cm*5cm, soak it in the penetrant, and use a padder to dry it after 30s for later use. Take 200mL of 5g / L dyeing solution, soak a piece of woven fabric in the dyeing for 1min, take it out and use a padder to dry it, oxidize it for 30s, soak it in clean water for 30s, then use a padder to dry it, and finally air dry it in the sun as the dyeing sample at 0h; then dye a piece of it after the dyeing solution is placed for 0.5h, 1h, 2h, and 4h, and the dyeing method is consistent with the operation at 0h.

[0146] Effect Example 2

[0147] A dyeing method is carried out using the dyeing solution obtained in Example 1, and no substance is added during the dyeing process; the dyeing method described in this effect example is consistent with that in effect example 1.

[0148] Effect Example 3

[0149] A dyeing method is carried out using the dyeing solution obtained in comparative example 1, and no substance is added during the dyeing process; the dyeing method described in this effect example is consistent with that in effect example 1.

[0150] The dyed fabric obtained by dyeing the above effect example was tested for K / S value, and the specific data are shown in Table 2 and Figure 1 As shown:

[0151] Table 2. Data on the K / S value of the dyed fabrics obtained in Effect Examples 1 to 3 as a function of time

[0152]

[0153]

[0154] According to the data in Table 2 above and Figure 1 It is obvious that when dyeing is carried out using the dyeing solution obtained in Example 1 of the present invention (Effect Example 2), there is no need to continue to add a reducing agent during the dyeing process, and an excellent dyeing effect stability can also be obtained. The K / S value of the obtained dyed cloth only decreases from 9.3 to 6.2 within 4 hours.

[0155] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A blue dyeing solution, characterized in that It includes the following components calculated by mass: 1 part of blue, 0.1-1.5 parts of sodium dithionite, 0.5-5 parts of blue reduction retaining agent; The blue-viewing reduction retaining agent comprises reducing sugar that has been subjected to hydrothermal treatment, wherein the hydrothermal treatment is carried out under the condition of pH 7.5 to 10.5 and the temperature of the hydrothermal treatment is 85 to 95°C.

2. The blue dyeing solution according to claim 1, characterized in that The hydrothermal treatment is carried out at a pH of 8.5-10.

3. The blue dyeing solution according to claim 1, characterized in that The blue-viewing reduction retaining agent comprises the following components calculated by mass percentage: Reducing sugar 50-60%, inorganic salt 1-5%, alcohol 3-8%, and the balance is water.

4. The blue dyeing solution according to claim 3, characterized in that Include at least one of the following (a) to (c): (a) the reducing sugar in the blue reducing agent comprises at least one of glucose, fructose and galactose; (b) the inorganic salt in the blue reduction retaining agent comprises at least two of sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, and disodium hydrogen phosphate; (c) The alcohol in the blue reduction preserving agent includes at least one of ethanol, ethylene glycol and methanol.

5. The blue dyeing solution according to claim 3 or 4, characterized in that: The preparation method of the blue-viewing reduction retaining agent comprises the following steps: Mix reducing sugar, inorganic salt and water, add the remaining components at 40-60°C, and mix well to obtain the blue reduction retaining agent.

6. The blue dyeing solution according to claim 1, characterized in that The pH of the blue dyeing solution is 6.5-11.

0.

7. The blue dyeing solution according to claim 6, characterized in that The reduction potential of the blue dye solution is -600 to -400 mV.

8. The method for preparing the indigo dyeing solution according to any one of claims 1 to 7, characterized in that: The steps include: Mix all the components to obtain the blue dye solution.

9. A dyeing method, comprising dyeing with the indigo dye solution according to any one of claims 1 to 7.

10. The dyeing method according to claim 9, characterized in that: The dyeing time is 0.5 to 4 hours.

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