Preparation method and dyeing application of lignin-based reactive dye

Abstract

The invention relates to the field of lignin processing, in particular to a preparation method and dyeing application of a lignin-based reactive dye. The preparation method of the lignin-based reactive dye comprises the following steps: adding lignin into a reaction liquid a (cyanuric chloride aqueous solution), and reacting after adjusting the pH value; performing acid precipitation to obtain an intermediate product; and adding the intermediate product into the reaction solution b (a mixed solution of sodium sulfite and sodium hydroxide), stirring for reaction, and carrying out post-treatment such as standing, acid precipitation, washing and drying on a product obtained after the reaction to obtain the lignin-based reactive dye. The invention also provides a dyeing application method of the lignin-based reactive dye. The high-water-solubility brown reactive dye has the advantages of being high in fabric dye-uptake rate, deep in dyeing depth, high in dyeing fastness and the like, and a new way is provided for high value-added utilization of lignin.

Description

Technical Field

[0001] The present invention relates to the field of lignin processing, in particular to a preparation method and dyeing application of lignin-based reactive dyes. Background Art

[0002] Lignin is one of the most abundant aromatic polymers in nature, widely present in plant cell walls and the second largest renewable biomass resource after cellulose. However, lignin's high molecular weight, complex three-dimensional network structure, and low solubility limit its application in high-value-added applications. Currently, lignin is primarily incinerated as a byproduct of the papermaking industry to generate power or used as fertilizer, resulting in low added value and negative environmental impacts. Therefore, developing efficient technologies for the conversion and utilization of lignin has important economic and environmental implications.

[0003] Lignin, as a brown material, can be used to dye textiles. However, the resulting fabrics fail to meet the color fastness requirements of commercial textiles. The reason is that the lignin molecules lack reactive groups that can covalently bond to the fabric, making it difficult to achieve good color fastness. Traditional metal salt mordant dyeing can improve the color fastness of dyed fabrics, but excessive use of metal salts can be harmful to human health and the environment. Therefore, how to modify lignin through chemical or biological methods to prepare a reactive lignin dye has become a key to its application in textile dyeing. Currently, there are few methods for modifying lignin. Patent CN103703082A discloses a method for preparing sulfur dyes using lignin. However, methods for modifying lignin into reactive dyes have not been reported. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method and dyeing application of a lignin-based reactive dye.

[0005] To solve the above technical problems, the present invention provides a method for preparing a lignin-based reactive dye, comprising the following steps:

[0006] 1) Add lignin (lignin powder) to the reaction solution a at a solid-liquid ratio of 1 g / 20 mL to 1 g / 150 mL (preferably 1 g / 50 to 1 g / 100 mL), stir evenly, adjust the pH to 8 to 11 (preferably 8 to 10), and stir the mixture in an ice bath for 3 to 8 hours (preferably 4 to 6 hours);

[0007] After the reaction is completed, the pH of the reaction product is adjusted to 2-3 for acid precipitation, and the solid obtained by the acid precipitation is washed (pH is about neutral) and then dried to obtain an intermediate product;

[0008] The reaction solution a is a cyanuric chloride aqueous solution with a mass fraction of 5% to 15% (preferably 6 to 12%);

[0009] 2) Add the intermediate product obtained in step 1) to the reaction solution b at a solid-liquid ratio of 1g / 20-1g / 150mL (preferably 1g / 50-1g / 100mL), stir evenly, and react at 55±10°C with stirring for 1-6h (preferably 3-5h);

[0010] The reaction solution b is composed of 3% to 15% (preferably 5% to 10%) of sodium sulfite by mass, 2% to 15% (preferably 4% to 12%) of sodium hydroxide by mass, and pure water as the balance;

[0011] Note: The stirring reaction speed in step 1) and step 2) is 500±100 rpm;

[0012] 3) The pH of the reaction product obtained in step 2) is adjusted to neutral and then allowed to stand (standing for 5±1h), then filtered and the supernatant is collected; the pH of the supernatant is adjusted to 2-3 for acid precipitation, and the solid obtained by the acid precipitation is washed (pH is approximately neutral) and then dried to obtain a lignin-based reactive dye.

[0013] As an improvement to the preparation method of the lignin-based reactive dye of the present invention:

[0014] Step 1):

[0015] The solid obtained by acid precipitation is washed with pure water and ethanol in sequence (until the pH of the eluent is close to neutral), and finally dried at 50±10°C (to constant weight) to obtain an intermediate product;

[0016] Step 3):

[0017] The solid obtained by acid precipitation is washed with pure water (until the pH of the eluent is neutral), and finally dried at 50±10° C. (to constant weight) to obtain a lignin-based reactive dye.

[0018] As a further improvement of the preparation method of the lignin-based reactive dye of the present invention:

[0019] 0.5-1M sodium hydroxide solution and 0.5-1M hydrochloric acid are used to adjust the pH.

[0020] As a further improvement of the preparation method of the lignin-based reactive dye of the present invention:

[0021] In the step 1), the reaction solution a is a 12% by mass cyanuric chloride aqueous solution, the solid-liquid ratio of lignin to the reaction solution a is 1 g / 50 mL, the pH is 10, and the reaction time is 6 h;

[0022] In the step 2), in the reaction solution b, the mass fraction of sodium sulfite is 10%, the mass fraction of sodium hydroxide is 12%, the material-liquid ratio of the intermediate product to the reaction solution b is 1 g:50 mL, and the reaction time is 5 h.

[0023] The present invention also provides a dyeing application method of a lignin-based reactive dye: the lignin-based reactive dye prepared by any of the above methods comprises the following steps:

[0024] ①, setting the lignin-based reactive dye: fabric mass ratio = 1% to 5% (preferably 2% to 4%), dissolving the lignin-based reactive dye in pure water, adjusting the pH to 8 to 11 (preferably 8.5 to 10.5), and obtaining a dye solution;

[0025] ②, setting the dyeing bath ratio to 1:(50±5), immersing the fabric in the dye liquor, heating the temperature to 70°C to 95°C (preferably 75°C to 90°C) at a set heating rate and keeping warm for 60±5 minutes; adding NaCl to the dye liquor during the 15th to 30th minute (preferably 20th minute) of the holding period to promote dyeing; the amount ratio of NaCl to dye liquor is 1g / 100ml to 4g / 100ml (preferably 2-3g / 100ml);

[0026] ③. Wash the fabric obtained after step ② and then dry it (conventional drying) to obtain the dyed fabric (final dyed product).

[0027] As an improvement of the dyeing application method of the lignin-based reactive dye of the present invention:

[0028] In step ①, 1±0.2 M sodium carbonate is used to adjust the pH.

[0029] As a further improvement of the dyeing application method of the lignin-based reactive dye of the present invention:

[0030] In step ②, the heating rate is 2±0.5°C / min.

[0031] As a further improvement of the dyeing application method of the lignin-based reactive dye of the present invention:

[0032] In the step ③, the fabric obtained after the step ② is rinsed with pure water until the washed water becomes colorless, and then the washed fabric is dried at 80±10°C.

[0033] This invention uses a two-step chemical process to prepare a highly water-soluble lignin-based reactive dye (brown). First, chlorotriazine is grafted onto the lignin raw material at low temperature (ice bath) and alkaline conditions to obtain an intermediate product. Subsequently, the temperature is further increased and, under alkaline conditions, sulfonic acid groups are further grafted onto the chlorotriazine rings of the intermediate product to improve water solubility. Finally, the modified lignin is purified (acid precipitation followed by washing) and dried to obtain the highly water-soluble lignin-based reactive dye. This dye can be used for efficient dyeing of textiles. This invention provides a green and sustainable method for preparing reactive dyes with significant environmental and economic benefits.

[0034] In the present invention, the role of sodium sulfite in the reaction solution b is to introduce sulfonic acid groups into the cyanuric chloride grafted lignin molecules (which are poorly soluble in water), thereby improving the water solubility of the modified lignin and obtaining a water-soluble lignin-based reactive dye; the role of sodium hydroxide is to provide an alkaline environment and promote the reaction.

[0035] The beneficial effects of the present invention are mainly reflected in:

[0036] The present invention develops a method for converting lignin into a reactive dye, and prepares a highly water-soluble brown reactive dye with the advantages of high dye uptake on fabrics, deep dyeing depth, high dye fastness, etc., providing a new way for high value-added utilization of lignin. DETAILED DESCRIPTION

[0037] The performance parameters of the lignin powder of the present invention are:

[0038] Lignin (powdered) was purchased from Guangdong Yunxing Biotechnology Co., Ltd., with a molecular weight of approximately 871 g / mol and a solubility in water of 0.12 mg / mL.

[0039] The following dyeing examples and comparative examples all use conventional silk fabrics (silk fabrics), but the application of the present invention is not limited to fabrics.

[0040] Example 1: Preparation of a lignin-based reactive dye and its dyeing application:

[0041] 1. Preparation method of lignin-based reactive dyes, the following steps are carried out in sequence

[0042] Step 1): In a three-necked flask, reaction solution a is first added, wherein the reaction solution a is a 6% mass fraction of cyanuric chloride aqueous solution, and then lignin is added at a material-liquid ratio of 1:50 (g / mL). After uniform stirring, the pH is adjusted to 10 with 0.5M sodium hydroxide solution, and then the three-necked flask is placed in an ice bath and stirred at a speed of 500 rpm for 6 hours.

[0043] After the reaction is completed, the pH of the reaction product is adjusted to 2-3 with 1M hydrochloric acid for acid precipitation, and then filtered to collect the solid. The filtered solid is washed with pure water and ethanol solution in sequence (until the pH of the eluent is close to neutral), and finally dried at 50°C to constant weight to obtain an intermediate product.

[0044] Step 2): In a three-necked flask, reaction solution b (an aqueous solution containing 10% by mass of sodium sulfite and 4% by mass of sodium hydroxide) was first added, and then the intermediate product obtained in step 1) was added at a solid-liquid ratio of 1:50 (g / mL). After uniform stirring, the mixture was stirred at 50°C and 500 rpm for 5 hours;

[0045] Step 3): The pH of the product obtained after the reaction in step 2) was adjusted to 7 with 1M hydrochloric acid, allowed to stand for 5 hours, and then filtered to collect the supernatant. The pH of the filtered supernatant was then adjusted to 2-3 with 1M hydrochloric acid to perform acid precipitation. The filtered solid was then washed with pure water until the eluate had a neutral pH, and finally dried at 50°C to constant weight to obtain a lignin-based reactive dye.

[0046] 2. The dyeing application method of lignin-based reactive dyes is carried out in the following steps:

[0047] ①, according to the mass ratio of lignin-based reactive dye to silk fabric = 4%, weigh the lignin-based reactive dye, dissolve the lignin-based reactive dye in pure water, and adjust the pH value to 9 with 1M sodium carbonate to obtain a dye solution;

[0048] ② Immerse the fabric in a dye bath at a dye bath ratio of 1:50. Raise the temperature of the dye bath from room temperature to 90°C at a rate of 2°C / min and maintain for 60 minutes. At the 20th minute mark of the dye bath, add NaCl to accelerate dyeing, using a ratio of 3g / 100ml of NaCl per 100ml of dye bath.

[0049] ③ After dyeing is completed (after keeping warm for 60 minutes), the fabric is rinsed with pure water until the washing water is colorless, and then the fabric is dried at 80°C to obtain the dyed fabric (final dyed product).

[0050] In Examples 2 to 10, relative to Example 1, corresponding process parameters are changed, as described in Table 1 below; the rest are the same as in Example 1.

[0051] Table 1

[0052]

[0053]

[0054] Test method:

[0055] The water solubility of the modified lignin was tested using GB 21845-2008 (at a water temperature of 25°C);

[0056] The yields of intermediate products and final dyes (lignin-based reactive dyes) were obtained by weighing calculation method.

[0057] The UV spectrophotometer was used to measure the lignin dye solution before and after dyeing at wavelength λ max The absorbance at is measured and the dye uptake (%) of the dye on the silk fabric is calculated according to the following formula.

[0058]

[0059] A0 and A1 represent the absorbance of the dye solution before and after staining, respectively.

[0060] Test the color depth (K / S value) of dyed products using a conventional spectrophotometer.

[0061] AATCC 61-2003 "Color Fastness to Home and Commercial Laundry: Rapid Method" was used to test the color fastness of dyed products to washing.

[0062] GB / T 3920-2008 “Textiles—Tests for colour fastness—Colour fastness to rubbing” was used to test the colour fastness of dyed fabrics to dry and wet rubbing.

[0063] Implementation effect: The test results are shown in Table 2.

[0064] Taking Example 1 as an example, the water solubility of gained lignin-based reactive dye is 40.4mg / mL, which is much higher than the water solubility (water solubility is 0.12mg / mL) of unmodified lignin. It has good water solubility, fully meets the textile dyeing demand. The final yield of lignin-based reactive dye under these conditions is 40.3%, with good economy. The dyeing rate of silk fabric dyeing is 85.4%, and the K / S value of dyed fabric is 8.7, and dyeing color performance is better. The color fastness to washing of dyed fabric is 4-5 level, and the color fastness to dry rubbing is 4 level, and the color fastness to wet rubbing is 3 level, all meet the requirement of national standard (not less than 3 levels). As can be seen, the lignin-based reactive dye prepared by the inventive method has good performance.

[0065] Table 2

[0066]

[0067] Comparative Example 1: The mass fraction of cyanuric chloride in the reaction solution a of Example 3 was changed to 1%, and the rest was the same as Example 3. The obtained effects are shown in Table 3.

[0068] This solution leads to a decrease in the effect of grafting chlorotricyandiamide groups onto lignin, which will significantly affect the solubility and reactivity of the dye, resulting in a worse fabric dyeing effect and a lower color depth value of the final dyed fabric.

[0069] Comparative Example 2: The material-liquid ratio of lignin powder to reaction solution a in step 1) of Example 3 was changed to 1:250 (g / mL), and the rest was the same as Example 3. The obtained effects are shown in Table 3.

[0070] This solution results in a worse effect of grafting chlorotricyandiamide groups onto lignin, which will significantly affect the water solubility and reactivity of the dye and result in a lower color depth value of the dye.

[0071] Comparative Example 3: The reaction time in step 1) of Example 3 was changed to 1 h, and the rest was the same as Example 3. The obtained results are shown in Table 3.

[0072] This solution leads to a decrease in the effect of grafting chlorotricyandiamide groups onto lignin, which will significantly affect the solubility and reactivity of the dye, resulting in a worse fabric dyeing effect and a lower color depth value of the final dyed fabric.

[0073] Comparative Example 4-1: The mass fraction of sodium sulfite in the reaction solution b of Example 3 was changed to 1%, and the rest was the same as Example 3. The obtained effects are shown in Table 3.

[0074] This solution results in a poor effect of grafting sulfonic acid groups onto the intermediate product, which will significantly affect the water solubility of the dye and result in a lower color depth value of the dye.

[0075] Comparative Example 4-2: The mass fraction of sodium sulfite in the reaction solution b of Example 3 was changed to 18%, and the rest was the same as Example 3. The obtained effects are shown in Table 3.

[0076] Under this protocol, the yield of the lignin-based reactive dye dropped significantly to 30.1%. This is due to the high concentration of inorganic salts in the reaction solution. This reduced the solubility of the synthesized lignin-based reactive dye in this highly concentrated inorganic salt solution, resulting in partial product loss during supernatant recovery. Considering the sodium sulfite dosage and product yield, this protocol is not cost-effective. It is not recommended, and further experiments were not performed.

[0077] Comparative Example 5-1: The mass fraction of sodium hydroxide in the reaction solution b of Example 3 was changed to 1%, and the rest was the same as Example 3. The obtained effects are shown in Table 3.

[0078] This solution leads to a worse effect of grafting sulfonic acid groups on the intermediate product, which will significantly affect the water solubility of the dye, resulting in a worse fabric dyeing effect and a lower color depth value of the final dyed fabric.

[0079] Comparative Example 5-2: The mass fraction of sodium hydroxide in the reaction solution b of Example 3 was changed to 18%, and the rest was the same as Example 3. The obtained effects are shown in Table 3.

[0080] Under this scheme, the yield of lignin-based reactive dyes dropped significantly to 32.3%. This is because the alkali concentration in the reaction solution is too high, and a large amount of acid is needed to neutralize it when performing step 3), and a large amount of inorganic salts are produced, which makes the solubility of the lignin-based reactive dye product in this high-concentration inorganic salt solution deteriorate. When the supernatant is recovered, some product is lost. Considering the comprehensive alkali dosage, acid dosage and product yield, this scheme is not recommended. Therefore, no subsequent experiments were performed.

[0081] Comparative Example 6: The solid-liquid ratio of the intermediate product to the reaction solution b in Example 3 was changed to 1:300 (g / mL), and the rest was the same as Example 3. The obtained effects are shown in Table 3.

[0082] This solution results in a poor effect of grafting sulfonic acid groups on the intermediate product, which will significantly affect the water solubility of the dye, resulting in a poor dyeing effect on the fabric and a lower color depth value of the final dyed fabric.

[0083] Comparative Example 7: The reaction time in step 2) in Example 3 was changed to 0.5 h, and the rest was the same as Example 3. The obtained results are shown in Table 3.

[0084] This solution results in a poor effect of grafting sulfonic acid groups on the intermediate product, which will significantly affect the water solubility of the dye and make the color depth of the dyed fabric lower.

[0085] Comparative Example 8: The mass ratio of dye / fabric in Example 3 was changed to 0.5%, and the rest was the same as Example 3. The obtained effects are shown in Table 4.

[0086] It can be seen that the dye / fabric mass ratio is too low, which makes the dyeing effect of the fabric worse and the color depth of the final dyed fabric is low.

[0087] Comparative Example 9: The dyeing temperature in Example 3 was changed to 60° C., and the rest was the same as Example 3. The obtained effects are shown in Table 4 below.

[0088] It can be seen that the dyeing temperature is too low during dyeing application, which leads to reduced reactivity of dye with silk, reduced dyeing rate, and poor dyeing effect and color fastness.

[0089] Comparative Example 10: The NaCl addition ratio in the dyeing process of Example 3 was changed to 1% (ie, NaCl: dye solution = 1 g / 100 ml), and the rest was the same as Example 3. The obtained results are shown in Table 4 below.

[0090] It can be seen that if the amount of NaCl is too low, it will significantly affect the degree of adsorption of dyes by the fabric, reduce the dyeing rate, and make the dyeing effect worse.

[0091] Comparative Example 11: Lignin was directly used instead of the lignin-based reactive dye, and the rest was the same as Example 3. The obtained effects are shown in Table 4 below.

[0092] After dyeing, the fabric's color depth (K / S value) is very low, indicating minimal color uptake. Furthermore, its color fastness to washing and rubbing is also low, far below commercial requirements. This is because the unmodified lignin is essentially a direct dye with low solubility, and lacks the ability to react with the fabric to form a strong covalent bond. Consequently, its dyeing ability and color fastness are poor.

[0093] The comparative examples are shown in Tables 3 and 4 below:

[0094] Table 3

[0095]

[0096]

[0097] Table 4

[0098]

[0099] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention are considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a lignin-based reactive dye, characterized in that The steps include: 1) Add lignin to the reaction solution a at a solid-liquid ratio of 1g / 20mL to 1g / 150mL, stir evenly, adjust the pH to 8-11, and stir in an ice bath for 3-8h; After the reaction is completed, the pH of the reaction product is adjusted to 2-3 for acid precipitation, and the solid obtained by the acid precipitation is washed and dried to obtain an intermediate product; The reaction solution a is a 5% to 15% by mass cyanuric chloride aqueous solution; 2) Add the intermediate product obtained in step 1) to the reaction solution b at a solid-liquid ratio of 1g / 20 to 1g / 150mL, stir evenly, and react at 55±10°C with stirring for 1 to 6 hours; The reaction solution b is composed of 3% to 15% by mass of sodium sulfite, 2% to 15% by mass of sodium hydroxide and pure water as the balance; 3) The pH of the reaction product obtained in step 2) is adjusted to neutral, allowed to stand, and then filtered to collect the supernatant; the pH of the supernatant is adjusted to 2-3 for acid precipitation, and the solid obtained by the acid precipitation is washed and dried to obtain a lignin-based reactive dye.

2. The method for preparing a lignin-based reactive dye according to claim 1, wherein: Step 1): The solid obtained by acid precipitation was washed with pure water and ethanol in sequence, and finally dried at 50±10°C to obtain the intermediate product; Step 3): The solid obtained by acid precipitation is washed with pure water and finally dried at 50±10° C. to obtain a lignin-based reactive dye.

3. The preparation method of lignin-based reactive dye according to claim 1 or 2, wherein: 0.5-1M sodium hydroxide solution and 0.5-1M hydrochloric acid are used to adjust the pH.

4. The method for preparing a lignin-based reactive dye according to any one of claims 1 to 3, wherein: In the step 1), the reaction solution a is a 12% by mass cyanuric chloride aqueous solution, the solid-liquid ratio of lignin to the reaction solution a is 1 g / 50 mL, the pH is 10, and the reaction time is 6 h; In the step 2), in the reaction solution b, the mass fraction of sodium sulfite is 10%, the mass fraction of sodium hydroxide is 12%, the material-liquid ratio of the intermediate product to the reaction solution b is 1 g:50 mL, and the reaction time is 5 h.

5. A dyeing application method of lignin-based reactive dyes, characterized in that: The lignin-based reactive dye prepared by the method according to any one of claims 1 to 4 comprises the following steps: ①, set the lignin-based reactive dye: fabric mass ratio = 1% to 5%, dissolve the lignin-based reactive dye in pure water, adjust the pH to 8 to 11, and obtain a dye solution; ②, setting the dyeing bath ratio to 1:(50±5), immersing the fabric in the dye liquor, heating the temperature to 70°C to 95°C at a set heating rate and maintaining the temperature for 60±5 minutes; adding NaCl to the dye liquor during the 15th to 30th minute of the holding period to accelerate dyeing; the NaCl / dye liquor usage ratio is 1g / 100ml to 4g / 100ml; ③. Wash the fabric obtained after step ② and then dry it to obtain a dyed fabric.

6. The dyeing application method of lignin-based reactive dyes according to claim 5, characterized in that: In step ①, 1±0.2 M sodium carbonate is used to adjust the pH.

7. The dyeing application method of lignin-based reactive dyes according to claim 6, characterized in that: In step ②, the heating rate is 2±0.5°C / min.

8. The dyeing application method of lignin-based reactive dyes according to claim 7, characterized in that: In the step ③, the fabric obtained after the step ② is rinsed with pure water until the washed water becomes colorless, and then the washed fabric is dried at 80±10°C.

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