Reduction dyeing method using vat dye in salt-free low-water environment and application thereof

Abstract

The invention belongs to the technical field of textile dyeing, and particularly relates to a reduction dyeing method in a salt-free low-water environment by utilizing a vat dye and application of the reduction dyeing method. The dyeing method comprises the following steps: S1, dispersing vat dye in an alcohol reagent to form a dyeing liquor mother solution; s2, a reducing agent and a coupling agent are added into the dyeing mother liquor for reduction, the pH value is adjusted to 7.5-10, and reduced dyeing mother liquor is obtained; and S3, diluting the reduction dyeing mother solution to obtain a reduction dyeing solution, putting the to-be-dyed fiber pretreated by the alcohol reagent into the reduction dyeing solution for dyeing, and cleaning and drying the fiber after dyeing is finished, the vat dye comprises an ornamental blue derivative dye. The invention provides an innovative salt-free low-water reduction dyeing method, the environmental protection and high efficiency of the dyeing process are realized by reducing the use of chemical substances and the consumption of water resources, and the salt-free low-water reduction dyeing method has important significance for promoting the green transformation of the textile industry.

Description

Technical Field

[0001] This invention belongs to the field of textile dyeing technology, specifically relating to a method for vat dyeing using vat dyes in a salt-free and low-water environment and its application. Background Technology

[0002] The derivatives of 5,5'-dihydroxy-blue and N-butylamino-N'-acetyl blue dyes, as novel chemically synthesized pigments, are obtained by chemically modifying blue as a substrate. Using the dye identification scheme mentioned in ISO 16373-1:2015 (General principles of testing colored textiles for dyestuff identification), the derivatives of 5,5'-dihydroxy-blue and N-butylamino-N'-acetyl blue dyes were identified as vat dyes.

[0003] In traditional textile dyeing processes, the dyeing of vat dyes typically requires the use of large amounts of sodium sulfate (Na₂SO₄) as a dyeing accelerator to improve dye uptake and uniformity. This is especially true for traditional vat dyes like indigo, where the concentration of sodium sulfate used in industrial production is typically 60-100 g / L. However, the use of sodium sulfate not only increases dyeing costs but also leads to the discharge of high-salinity wastewater, increasing the complexity and cost of wastewater treatment and imposing a serious burden on the environment.

[0004] In recent years, with the increasing awareness of environmental protection and the promotion of the concept of sustainable development, the development of environmentally friendly dyeing processes has become a research hotspot in the textile industry. Salt-free dyeing technology has emerged, the core of which lies in reducing or completely avoiding the use of sodium sulfate by replacing traditional sodium sulfate dyeing accelerators.

[0005] While the possibilities of salt-free and low-water dyeing have been explored with reactive dyes, no salt-free or low-water dyeing technologies have been reported for vat dyes. Currently, a comprehensive solution is lacking that can achieve the goals of salt-free, low-water, and efficient recovery. Furthermore, although salt-free dyeing with reactive dyes can be achieved by modifying fabrics with quaternary ammonium salt surfactants, this undoubtedly increases the dyeing process and makes it more complex. Simultaneously, quaternary ammonium salts have poor chemical stability; the modified fibers readily elute the quaternary ammonium salts, and the eluted quaternary ammonium salts react with the leuco groups in the vat dye bath, causing flocculation and resulting in uneven dyeing in subsequent processes. Quaternary ammonium salts also have poor heat resistance and are prone to thermal decomposition at high temperatures, greatly limiting their application in high-temperature processing environments. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a reduction dyeing method in a salt-free and low-water environment, thus broadening the application range of blue derivative dyes. This method does not use sodium sulfate as a dyeing accelerator, but uses alcohol reagents to replace part or all of the water to promote the dissolution and diffusion of the dye, avoid the aggregation of leuco pigments, and increase the affinity between the fiber and the dye, thereby significantly improving the dyeing effect and the dye uptake rate. Furthermore, the alcohol reagents can be repeatedly recycled and reused, thus achieving the effects of environmental protection and energy saving.

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

[0008] In a first aspect, the present invention provides a reduction staining solution for salt-free staining, the reduction staining solution comprising a vat dye, an alcohol reagent, a reducing agent, and a coupling agent, wherein the vat dye is dispersed in the alcohol reagent; the concentration of the vat dye is 50-100 g / L; the mass ratio of the vat dye to the reducing agent is 1:(0.5-10), and the mass ratio of the vat dye to the coupling agent is 1:(0.01-1); the vat dye includes a blue derivative dye.

[0009] Preferably, the reducing agent is at least one selected from thiourea dioxide, sodium borohydride, hydrazine hydrate, and glucose.

[0010] Preferably, the blue derivative dye includes 5,5'-dihydroxy-blue or N-butylamino-N'-acetylblue.

[0011] Preferably, the coupling agent comprises 3-aminopropyltriethoxysilane (APTES); the alcohol reagent comprises at least one selected from ethanol, propylene glycol, 1,2-hexanediol and butanediol.

[0012] Traditional indigo dyeing typically requires the use of 60-100 g / L sodium sulfate as a dyeing accelerator during the dyeing process. However, the reductive dyeing solution described in this invention does not use sodium sulfate as a dyeing accelerator, effectively avoiding the generation of high-salinity wastewater compared to indigo dyeing. Wastewater from reductive dyes such as indigo usually contains high levels of salt (e.g., sodium chloride, sodium sulfate), along with extremely high chemical oxygen demand (COD), deep color, and complex composition. High-salinity wastewater is highly corrosive to treatment equipment and pipelines, especially wastewater containing sodium chloride and sodium sulfate, which shortens equipment lifespan. High-salinity wastewater is prone to scaling during treatment, affecting equipment operating efficiency. Furthermore, high salinity inhibits microbial activity, rendering traditional biological treatment methods ineffective.

[0013] Experimental studies have revealed that alcohol-based reagents (such as ethanol and butanediol) promote the dyeing of 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue dyes. In vat dyeing systems, alcohol-based reagents facilitate dye dissolution and diffusion, prevent leuco aggregate aggregation, and increase the affinity between fibers and dyes, thereby significantly improving dyeing effects and dye uptake. The use of coupling agents increases the adsorption force between fabric and dye through covalent bonding, exhibiting stability far exceeding that of quaternary ammonium salt surface modifiers. Simultaneously, the use of alcohol-based reagents aids in the diffusion of coupling agents, improving their utilization rate. It is precisely through the combined effects of alcohol-based reagents and coupling agents that 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue dyes can achieve the dyeing effects of traditional vat dyes without the need for salt-based dyeing or modification of fabrics with quaternary ammonium salt surfactants.

[0014] Secondly, the present invention provides a reduction dyeing method for salt-free dyeing, wherein the reduction dyeing solution is used to dye the fibers, specifically including the following steps:

[0015] S1. Disperse the vat dye in an alcoholic reagent to form a mother liquor for the dyeing solution;

[0016] S2. Add reducing agent and coupling agent to the staining solution mother liquor for reduction, and adjust the pH value to 7.5-10 to obtain reduced staining mother liquor;

[0017] S3. Dilute the reduction dyeing mother liquor to obtain the reduction dyeing solution. Place the fibers to be dyed, which have been pretreated with alcohol reagents, into the reduction dyeing solution for dyeing. After dyeing, wash and dry the fibers.

[0018] Preferably, the vat dye includes a blue derivative dye; the reducing agent is at least one selected from thiourea dioxide, sodium borohydride, hydrazine hydrate, and glucose.

[0019] Preferably, the blue derivative dye is 5,5'-dihydroxy-blue or N-butylamino-N'-acetylblue.

[0020] This invention optimizes the dyeing process by utilizing the properties of vat dyes 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue, combining specific reducing agents and alcohol reagents to replace part or all of the water as the dyeing medium. This substitution effectively improves dyeing efficiency and dye uptake, accelerates the dyeing process, and shortens the dyeing time. Alcohol reagents have a certain dyeing-promoting effect, effectively opening fiber channels and facilitating dye penetration into the fiber interior, thus increasing the dye uptake rate. This means more dye can be effectively adsorbed onto the fiber, reducing dye waste and lowering production costs. Furthermore, the use of alcohol reagents helps to accelerate the dyeing process, further reducing energy consumption. Compared with traditional indigo dyeing methods, the dyeing time is significantly reduced, the dye uptake rate is significantly increased, the fabric color depth (K / S) is significantly improved, and the color fastness is only slightly different when using the dyeing method of this invention with 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue dyes. Therefore, the innovative salt-free, low-water reduction dyeing method provided by this invention achieves environmental protection and high efficiency in the dyeing process by reducing the use of chemical substances and the consumption of water resources, which is of great significance for promoting the green transformation of the textile industry.

[0021] Preferably, the concentration of the reducing staining solution is 50-100 g / L; more preferably, the concentration of the reducing staining solution is 60 g / L.

[0022] Preferably, in step S2, the coupling agent comprises 3-aminopropyltriethoxysilane.

[0023] Preferably, in step S1, the alcohol reagent includes at least one of ethanol, propylene glycol, 1,2-hexanediol and butanediol; more preferably, the alcohol reagent is ethanol.

[0024] Preferably, in step S2, the mass ratio of the vat dye to the reducing agent is 1:(0.5-10), and the mass ratio of the vat dye to the coupling agent is 1:(0.01-1).

[0025] This invention, by introducing the aforementioned specific coupling agent and alcohol reagent, can significantly improve the dyeing effect and uptake rate of vat dyes 5,5'-dihydroxy-vitamin blue and N-butylamino-N'-acetylvitamin blue. Furthermore, experimental investigations have revealed that the mass ratio of the coupling agent and alcohol reagent to the vat dye has a significant impact on the dyeing effect; using the above-mentioned optimized ratio can further optimize the dye performance and improve the dye adhesion rate and uniformity during the dyeing process.

[0026] More preferably, in step S2, the mass ratio of the vat dye to the reducing agent is 1:1, and the mass ratio of the vat dye to the coupling agent is 1:0.1.

[0027] Preferably, in step S2, the reduction time is 20-60 min; more preferably, the reduction time is 30 min.

[0028] Preferably, in step S2, the pH value of the dyeing solution mother liquor is adjusted to alkaline 7.5-10.0, which can be done using sodium hydroxide or potassium hydroxide to improve the reduction effect of the dye; more preferably, the concentration of the sodium hydroxide or potassium hydroxide is 200 g / L.

[0029] Preferably, in step S3, the concentration of the diluted reduction dyeing solution is 1-5% owf, and the mass ratio of the fiber to be dyed to the reduction dyeing solution is 1:(5-50); more preferably, the dye concentration of the reduction dyeing solution is 4% owf, and the mass ratio of the fiber to be dyed to the reduction dyeing solution is 1:10. In this invention, owf (on weight of fabric) refers to the percentage content of dye used during dyeing, which is the ratio of the amount of dye used to the weight of the fabric.

[0030] Preferably, in step S3, the specific dyeing conditions are: dyeing at 15-60℃ for 30-120 minutes; more preferably, the specific dyeing conditions are: dyeing at 20℃ for 60 minutes. By precisely controlling the dyeing temperature and time, sufficient dye uptake is ensured. During the dyeing process, the dyeing solution is continuously stirred to ensure uniform dye distribution.

[0031] Preferably, in step S1, the mass concentration of the alcohol reagent is 10-100%, more preferably, the mass concentration of the alcohol reagent is 40-80%.

[0032] Preferably, in step S3, the fibers to be dyed include cotton, linen, or Tencel. An alcohol-based reagent is used to pretreat the fibers to remove impurities and grease from the fiber surface, facilitating subsequent dyeing.

[0033] Preferably, in step S3, the pretreatment time of the fiber to be dyed is 10-30 minutes to ensure that the inside of the fiber is fully wetted; after the fiber is taken out, it needs to be removed by a roller to remove excess moisture from the surface.

[0034] Preferably, in step S3, the fibers are cleaned with an alcohol-based reagent for 5-20 minutes to remove residual dyes and reducing agents from the surface. Preferably, the concentration of the alcohol-based reagent is 40%-80%, and the cleaned fibers are then air-dried or subjected to low-temperature drying.

[0035] Thirdly, the present invention provides the application of the described reduction dyeing solution and / or the described reduction dyeing method in the dyeing of fiber fabrics.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] (1) Salt-free dyeing: This invention does not use sodium sulfate as a dyeing accelerator, nor does it use quaternary ammonium salt surface modifiers to modify cotton fibers. This avoids the generation of high-salinity wastewater and does not complicate the dyeing process. It also avoids the disadvantages of poor stability and poor heat resistance of quaternary ammonium salts. This invention optimizes the dyeing process and utilizes the characteristics of vat dyes 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue, combined with specific reducing agents, alcohol reagents and coupling agents, to effectively achieve salt-free dyeing.

[0038] (2) The invention focuses on the dyeing-promoting effect of specific alcohol reagents and coupling agents on 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue dyes. The invention has found that alcohol reagents can promote the dissolution and diffusion of dyes in a vat dyeing system, prevent the aggregation of leuco pigments, and increase the affinity between fibers and dyes, thereby significantly improving the dyeing effect and dye uptake rate. The use of coupling agents can increase the adsorption force between fabric and dye through covalent bonding, and the stability is much higher than that of quaternary ammonium salt surface modifiers. At the same time, the use of alcohol reagents helps the coupling agent diffuse and improves its utilization rate. Under the action of specific alcohol reagents and coupling agents, 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue dyes can achieve or even surpass the dyeing effect of traditional vat dyes without the need for salt to promote dyeing or the use of quaternary ammonium salt surfactants on the fabric. Attached Figure Description

[0039] Figure 1 These are images showing the staining results after staining using the staining methods described in Examples 1-7;

[0040] Figure 2 These are images showing the staining results after staining using the staining methods described in Comparative Examples 1-4;

[0041] Figure 3 The structural formula of the vat dye N-butylamino-N'-acetyl blue is shown below;

[0042] Figure 4 The structural formula of the vat dye 5,5'-dihydroxy-blue is given. Detailed Implementation

[0043] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0044] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available and commonly used raw materials.

[0045] The 5,5'-dihydroxy-blue and N-butylamino-N'-acetylblue vat dyes used in this embodiment were developed in-house by our company (Nanjing Hegu Life Biotechnology Co., Ltd.) and can be purchased from the company's official website.

[0046] The K / S value is used to characterize the lightness or darkness of dyed fiber clothing fabrics. The color fastness to rubbing and color fastness to washing of fiber clothing fabrics are tested in accordance with GB / T 3920—2008 "Textiles - Tests for Color Fastness to Rubbing" and GB / T 3921—2008 "Textiles - Tests for Color Fastness to Rubbing".

[0047] In this invention, owf (on weight of fabric) refers to the percentage content of dye used in dyeing, which is the ratio of the amount of dye used to the weight of the fabric; the liquor ratio is a term used in textile dyeing and finishing, which refers to the ratio of the weight of the fabric to the volume of the dye liquor in the dyeing process.

[0048] Example 1

[0049] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The fiber to be dyed is pure cotton fabric, and the alcohol reagent used is ethanol. The method includes the following steps:

[0050] (1) Fabric pretreatment: Cut pure cotton fabric into 5cm*5cm pieces, soak them in 50% ethanol, remove air bubbles and remove surface impurities and grease. After 20 minutes, take them out and pass them through a rolling mill to remove excess alcohol reagents on the surface to obtain pretreated pure cotton fabric.

[0051] (2) Preparation of staining mother liquor: Take 60g of N-butylamino-N'-acetylglucosamine blue dye and prepare the dye concentration to 60g / L with 100% ethanol. Then add 60g of thiourea dioxide, adjust the pH to 8.0 with 200g / L sodium hydroxide, and add 0.6g of coupling agent APTES, that is, the mass ratio of vat dye: reducing agent: coupling agent is 1:1:0.01. Reduce at room temperature for 30min to obtain the staining mother liquor of N-butylamino-N'-acetylglucosamine blue biological dye.

[0052] (3) Dyeing process: Dilute the dye mother liquor obtained in step (2) to a dye concentration of 4% owf to obtain N-butylamino-N'-acetyl blue dyeing solution. Add the pure cotton fabric pretreated in step (1). The mass ratio of the fiber to be dyed to the reducing dyeing solution is 1:10. So that the pure cotton fabric is completely immersed below the surface of the dyeing solution. Dye at 20°C for 60 min.

[0053] (4) Post-treatment: The dyed pure cotton fabric obtained in step (3) is cleaned by washing the fibers with 50% ethanol reagent for 10 minutes to remove residual dye and reducing agent on the surface. The cleaned pure cotton fabric is then air-dried or dried at low temperature.

[0054] Example 2

[0055] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The fiber to be dyed is Tencel fabric, and the alcohol reagent used is 1,2-hexanediol. The method includes the following steps:

[0056] (1) Fabric pretreatment: cut Tencel fabric into fibers of size 4cm*15cm, soak them in 80% 1,2-hexanediol, remove the bubbles and remove surface impurities and grease, take them out after 10 minutes, and pass them through a rolling mill to remove excess alcohol reagents on the surface to obtain pretreated Tencel fabric.

[0057] (2) Preparation of staining mother liquor: Take 50g of N-butylamino-N'-acetylglucosamine blue dye and prepare the dye concentration to 50g / L with 1,2-hexanediol, then add 25g of hydrazine hydrate, adjust the pH to 7.5 with 200g / L potassium hydroxide, add 50g of coupling agent APTES, that is, the mass ratio of vat dye: reducing agent: coupling agent is 1:0.5:1, reduce at room temperature for 60min to obtain the staining mother liquor of N-butylamino-N'-acetylglucosamine blue biological dye;

[0058] (3) Dyeing process: Dilute the dye mother liquor obtained in step (2) to a dye concentration of 1% owf to obtain N-butylamino-N'-acetyl blue dyeing solution. Add the Tencel fabric pretreated in step (1). The mass ratio of the fiber to be dyed to the reducing dyeing solution is 1:20, so that the Tencel fabric is completely immersed below the surface of the dyeing solution. Dye at 15°C for 120 min.

[0059] (4) Post-treatment: The dyed Tencel fabric obtained in step (3) is cleaned by washing the fibers with 80% ethanol reagent for 5 minutes to remove residual dye and reducing agent on the surface. The cleaned Tencel fabric is then air-dried or dried at low temperature.

[0060] Example 3

[0061] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The fiber to be dyed is pure cotton fabric, and the alcohol reagent used is butanediol. The method includes the following steps:

[0062] (1) Fabric pretreatment: Cut pure cotton fabric into 5cm*5cm pieces, soak them in 50% butanediol, remove the bubbles and remove surface impurities and grease. After 30 minutes, take them out and pass them through a rolling mill to remove excess alcohol reagents on the surface to obtain pretreated pure cotton fabric.

[0063] (2) Preparation of staining mother liquor: Take 70g of N-butylamino-N'-acetylglucosamine blue dye and prepare the dye concentration to 70g / L with 40% butanediol. Then add 700g of glucose, adjust the pH to 9 with 200g / L potassium hydroxide, and add 35g of coupling agent APTES, i.e., the mass ratio of vat dye: reducing agent: coupling agent is 1:10:0.5. Reduce at room temperature for 40min to obtain the staining mother liquor of N-butylamino-N'-acetylglucosamine blue biological dye.

[0064] (3) Dyeing process: Dilute the dye mother liquor obtained in step (2) to a dye concentration of 2% owf to obtain N-butylamino-N'-acetyl blue dyeing solution. Add the pure cotton fabric pretreated in step (1). The mass ratio of the fiber to be dyed to the reducing dyeing solution is 1:5. So that the pure cotton fabric is completely immersed below the surface of the dyeing solution. Dye at 60°C for 30 minutes.

[0065] (4) Post-treatment: The dyed pure cotton fabric obtained in step (3) is washed with 40% butanediol reagent for 20 minutes to remove residual dye and reducing agent from the surface. The washed pure cotton fabric is then air-dried or dried at low temperature.

[0066] Example 4

[0067] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The fiber to be dyed is linen fabric, and the alcohol reagent used is propylene glycol. The method includes the following steps:

[0068] (1) Fabric pretreatment: Cut the linen fabric into 5cm*5cm pieces, soak them in 70% propylene glycol, remove the air bubbles and remove surface impurities and grease, take them out after 15 minutes, and pass them through a rolling mill to remove excess alcohol reagents on the surface to obtain pretreated linen fabric.

[0069] (2) Preparation of staining mother liquor: Take 100g of N-butylamino-N'-acetylglucosamine blue dye and prepare the dye concentration to 100g / L with 10% propylene glycol. Then add 500g of sodium borohydride, adjust the pH to 10 with 200g / L sodium hydroxide, and add 10g of coupling agent APTES, i.e., the mass ratio of vat dye: reducing agent: coupling agent is 1:5:0.1. Reduce at room temperature for 20min to obtain the staining mother liquor of N-butylamino-N'-acetylglucosamine blue biological dye.

[0070] (3) Dyeing process: Dilute the dye mother liquor obtained in step (2) to a dye concentration of 5% owf to obtain N-butylamino-N'-acetyl blue dyeing solution. Add the pure cotton fabric pretreated in step (1). The mass ratio of the fiber to be dyed to the reducing dyeing solution is 1:50. So that the fabric is completely immersed below the surface of the dyeing solution. Dye at 30°C for 90 minutes.

[0071] (4) Post-treatment: The dyed fabric obtained in step (3) is washed with 50% propylene glycol reagent for 10 minutes to remove residual dye and reducing agent from the surface. The washed pure cotton fabric is then air-dried or dried at low temperature.

[0072] Example 5

[0073] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The fiber to be dyed is pure cotton fabric, and the alcohol reagent used is ethanol. The method includes the following steps:

[0074] (1) Fabric pretreatment: Cut the fabric into yarns of 4cm*15cm size, soak them in 80% ethanol, remove the bubbles and remove surface impurities and grease, take them out after 15 minutes, and pass them through a rolling mill to remove excess alcohol reagents on the surface to obtain pretreated linen fabric.

[0075] (2) Preparation of staining mother liquor: Take 60g of N-butylamino-N'-acetylglucosamine blue dye and prepare the dye concentration to 60g / L with 80% ethanol. Then add 60g of thiourea dioxide, adjust the pH to 9.5 with 200g / L sodium hydroxide, add 6g of coupling agent APTES, that is, the mass ratio of vat dye: reducing agent: coupling agent is 1:1:0.1, reduce at room temperature for 25min to obtain the staining mother liquor of N-butylamino-N'-acetylglucosamine blue biological dye;

[0076] (3) Dyeing process: Dilute the dye mother liquor obtained in step (2) to a dye concentration of 3% owf to obtain N-butylamino-N'-acetyl blue dyeing solution. Add the pure cotton fabric pretreated in step (1). The mass ratio of the fiber to be dyed to the reducing dyeing solution is 1:10. So that the pure cotton fabric is completely immersed below the surface of the dyeing solution. Dye at 25°C for 10 min.

[0077] (4) Post-treatment: The dyed pure cotton fabric obtained in step (3) is washed by cleaning the fibers with 80% ethanol reagent for 10 minutes to remove residual dye and reducing agent on the surface. The washed pure cotton fabric is then air-dried or dried at low temperature.

[0078] Example 6

[0079] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment, the only difference from Embodiment 1 being that the dye used in this embodiment is 5,5'-dihydroxy-blue.

[0080] Example 7

[0081] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment, the only difference from Embodiment 2 being that the dye used in this embodiment is 5,5'-dihydroxy-blue.

[0082] Example 8

[0083] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment, the only difference from Embodiment 3 being that the dye used in this embodiment is 5,5'-dihydroxy-blue.

[0084] Example 9

[0085] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment, the only difference from Embodiment 4 being that the dye used in this embodiment is 5,5'-dihydroxy-blue.

[0086] Example 10

[0087] This embodiment provides a reduction dyeing method using vat dyes in a salt-free and low-water environment, the only difference from Example 5 being that the dye used in this embodiment is 5,5'-dihydroxy-blue.

[0088] Comparative Example 1

[0089] This comparative example provides a reduction dyeing method using vat dye in a saline, low-water environment. The only difference between this method and Example 1 is that sodium sulfate is added to the dyeing solution instead of a coupling agent for saline dyeing. The mass ratio of the vat dye, reducing agent, and sodium sulfate is 1:1:1.

[0090] Comparative Example 2

[0091] This comparative example provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The only difference between this method and Example 1 is that indigo dye is used instead of N-butylamino-N'-acetyl blue dye.

[0092] Comparative Example 3

[0093] This comparative example provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The only difference between this method and Example 1 is that no coupling agent is added during the dyeing process.

[0094] Comparative Example 4

[0095] This comparative example provides a reduction dyeing method using vat dyes in a salt-free and low-water environment. The only difference between this method and Example 1 is that water is used instead of alcohol reagents when preparing the dyeing mother liquor.

[0096] Comparative Example 5

[0097] This comparative example provides a conventional method for salt-free dyeing of pure cotton fabrics using quaternary ammonium salt surfactants, comprising the following steps:

[0098] (1) Fabric modification treatment: The pure cotton fabric was placed in a quaternary ammonium salt solution with a concentration of 20 g / L of terminal amino hyperbranched compound and immersed at 20°C for 80 min. The fabric was then removed, washed and set aside.

[0099] (2) The modified cotton fabric was dyed at room temperature in reactive dye Turquoise Blue B-BGFN. The dyeing process was as follows: reactive dye / % (owf) 2.0 g / L, anhydrous Na2CO3 20 g / L, bath ratio 1:50; after dyeing, the fabric was washed with water, 3 g / L soap flakes were added, and the fabric was boiled at 90℃ for 10 min, then dried.

[0100] Example 1

[0101] Examples 1-10 and Comparative Examples 1-5 were dyed multiple times, and the color depth (K / S) and color fastness of the fabrics were measured. The color fastness was tested in accordance with 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 results are shown in Table 1 below.

[0102] Table 1. Fabric dyeing parameters (data from three replicate experiments per group)

[0103]

[0104]

[0105] Tests conducted in Examples 1-10 revealed that N-butylamino-N'-acetyl cobalt blue or 5,5'-dihydroxy-cobalt blue dyes can be used to dye various fiber materials, and various alcohol reagents can be used as solvents for dyeing. Furthermore, N-butylamino-N'-acetyl cobalt blue and 5,5'-dihydroxy-cobalt blue dyes exhibit excellent color fastness to rubbing and washing when dyed using the specific dyeing method described in this invention, and can withstand the tests of friction and washing in daily use. Moreover, from the perspective of environmental protection and sustainable development, dyeing fabrics using the aforementioned N-butylamino-N'-acetyl cobalt blue and 5,5'-dihydroxy-cobalt blue dyes under the specific dyeing method of this invention can effectively reduce environmental pollution and resource consumption. Therefore, N-butylamino-N'-acetyl cobalt blue and 5,5'-dihydroxy-cobalt blue dyes and the dyeing method described in this invention are expected to be widely applied in the field of fabric dyeing in the future, bringing a greener and more efficient development model to the textile industry.

[0106] A comparison of Comparative Example 1 and Example 1 revealed a significant difference in color depth between low-water, salt-free and low-water, salt-containing dyeing using N-butylamino-N'-acetylglucosamine dye. This indicates that N-butylamino-N'-acetylglucosamine dye itself can achieve good dyeing results without the addition of salt. Therefore, N-butylamino-N'-acetylglucosamine dye can achieve completely salt-free dyeing, effectively avoiding the generation of high-salinity wastewater. A comparison of Comparative Example 2 and Example 1 showed that, under the same dyeing conditions, N-butylamino-N'-acetylglucosamine dye performed better than traditional indigo dyes in low-water, salt-free dyeing. Its dyeing effect reached the depth of traditional indigo dye with better coloring results, producing a rich and uniform blue tone. In Comparative Example 3, where no coupling agent was added, and in Comparative Example 4, where no specific alcohol reagent was added, the dyeing effect was reduced to some extent compared to Example 1. This indicates that in the dyeing method based on N-butylamino-N'-acetyl blue dye described in this invention, the addition of coupling agent and alcohol reagent has a significant impact on the dyeing effect. The absence of both will lead to a decrease in the affinity between the dye and the fiber to be dyed, thereby significantly reducing the dyeing effect and dye uptake rate of N-butylamino-N'-acetyl blue dye.

[0107] 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 reducing staining solution for salt-free staining, characterized in that, The vat dyeing solution comprises vat dye, alcohol reagent, reducing agent, and coupling agent, wherein the vat dye is dispersed in the alcohol reagent; the concentration of the vat dye is 50-100 g / L; the mass ratio of the vat dye to the reducing agent is 1:(0.5-10), and the mass ratio of the vat dye to the coupling agent is 1:(0.01-1); the vat dye includes a blue derivative dye.

2. The reducing staining solution as described in claim 1, characterized in that, The reducing agent is at least one of thiourea dioxide, sodium borohydride, hydrazine hydrate, and glucose; the coupling agent includes 3-aminopropyltriethoxysilane; and the alcohol reagent includes at least one of ethanol, propylene glycol, 1,2-hexanediol, and butanediol.

3. The reducing staining solution as described in claim 1, characterized in that, The blue dye derivatives include 5,5'-dihydroxy-blue dye or N-butylamino-N'-acetylblue dye.

4. A reduction staining method for salt-free staining, characterized in that, The dyeing of fibers using the reducing dyeing solution according to any one of claims 1-3 specifically includes the following steps: S1. Disperse the vat dye in an alcoholic reagent to form a mother liquor for the dyeing solution; S2. Add reducing agent and coupling agent to the staining solution mother liquor for reduction, and adjust the pH value to 7.5-10 to obtain reduced staining mother liquor; S3. Dilute the reduction dyeing mother liquor to obtain the reduction dyeing solution. Place the fibers to be dyed, which have been pretreated with alcohol reagents, into the reduction dyeing solution for dyeing. After dyeing, wash and dry the fibers.

5. The reduction staining method as described in claim 4, characterized in that, In step S2, the reduction time is 20-60 minutes.

6. The reduction staining method as described in claim 4, characterized in that, In step S3, the dye concentration of the diluted reduction dyeing solution is 1-5% owf, and the mass ratio of the fiber to be dyed to the reduction dyeing solution is 1:(5-50).

7. The reduction staining method as described in claim 4, characterized in that, In step S3, the specific conditions for staining are: staining at 15-60℃ for 30-120 minutes.

8. The reduction staining method as described in claim 4, characterized in that, The blue dye derivative is 5,5'-dihydroxy-blue dye or N-butylamino-N'-acetylblue dye.

9. The reduction staining method as described in claim 4, characterized in that, In step S1, the mass concentration of the alcohol reagent is 10-100%; In step S3, the fibers to be dyed include cotton, linen, or Tencel; the pretreatment time for the fibers to be dyed is 10-30 minutes; the fibers are cleaned with an alcohol reagent for 5-20 minutes.

10. The application of the reduction dyeing solution as described in any one of claims 1-3, and / or the reduction dyeing method as described in any one of claims 4-9, in the dyeing of fiber fabrics.

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