High-temperature stable light-color sulfonated lignin dye dispersant and preparation method thereof

Abstract

The invention provides a method for preparing a high-temperature stable light-color dye dispersant from industrial lignin. The method comprises the following steps: firstly, reacting the industrial lignin, a sulfonating reagent and an aldehyde reagent in an alkaline medium to prepare a first-stage reaction product; reacting the first-stage reaction product with a free radical initiator and a blocking reagent to prepare a second-stage reaction product; and reacting the second-stage reaction product with the introduced ozone / air mixed gas, and performing spray drying on the product to obtain the light-color dye dispersant. The lignin sulfonation degree is improved by adopting two-stage sulfonation, phenolic hydroxyl group sealing and sulfonation are synchronously realized and the molecular weight of the product is increased in the second-stage sulfonation process, and meanwhile, the phenolic hydroxyl group is prevented from being converted into a quinonoid structure by utilizing oxidizing gas, so that the problems of poor high-temperature stability and fiber contamination of a lignin sulfonate dye dispersant are solved; finally, a lignin dye dispersant preparation system with high-temperature stability and light color is constructed, and a green and feasible path is provided for the development of lignin to a high-end printing and dyeing market.

Description

Technical Field

[0001] The invention relates to the technical field of dye dispersants, and in particular to a method for preparing a high-temperature stable light-colored dye dispersant from industrial lignin. Background Art

[0002] Lignin is a globally unique renewable aromatic polymer with enormous potential as a chemical feedstock. According to the latest statistics, global annual industrial lignin production has exceeded 180 million tons. However, the majority of this industrial lignin is currently burned directly for energy, with only a small amount converted into fine chemicals or functional materials through technologies such as catalytic depolymerization and functional modification. This extensive utilization model not only exacerbates environmental pressures but also results in a significant waste of renewable carbon resources. Therefore, promoting the added value of lignin is extremely urgent and necessary.

[0003] In recent years, as typical representatives of biomass-based surfactants, lignin sulfonates and sulfonated lignin have been widely used as dye dispersants in the field of textile printing and dyeing due to their excellent dispersibility and environmental protection properties. However, the above-mentioned dispersants are limited by the inherent defects of the traditional sulfonation process, and there is generally a problem of insufficient sulfonation degree, which leads to poor water solubility of the dispersant after adsorbing the dye, and the electrostatic repulsion it can provide is weak, and the particles are easily agglomerated under high-temperature printing and dyeing conditions. In addition, it contains a large number of chromophores (such as benzene ring conjugated structures and quinone structures), which causes the system to have a dark brown appearance. These defects lead to problems such as poor dispersion performance and fiber contamination during high-temperature printing and dyeing. These problems make it difficult for traditional lignin-based dye dispersants to meet the stringent requirements of high-end textiles for dyeing uniformity and color brightness, seriously restricting its promotion and application in the field of high-end textile printing and dyeing. Summary of the Invention

[0004] The main purpose of the present invention is to overcome the shortcomings of lignin in dye dispersants and provide a method for preparing high-temperature stable light-colored dye dispersants from industrial lignin. The obtained dye dispersant has light fiber contamination and good high-temperature resistance and dispersion properties.

[0005] The purpose of the present invention and the technical problem solved are achieved by adopting the following technical solutions. According to the method proposed in the present invention, a method for preparing a high-temperature stable light-colored dye dispersant from industrial lignin is provided, and the preparation method comprises the following steps:

[0006] Step 1: mixing industrial lignin with the first batch of water, adding a pH regulator to adjust the pH value of the mixture, stirring until fully dissolved, adding a sulfonating reagent and an aldehyde reagent, and reacting the mixture at a first temperature to obtain a first-stage reaction product;

[0007] Step 2: adding a free radical initiator and a blocked monomer to the first-stage reaction product, and reacting the mixture at a second temperature to obtain a second-stage reaction product;

[0008] Step three, adding a second batch of water to the second stage product, introducing ozone / air mixed gas, and reacting the mixture at a third temperature. After the reaction is completed, cooling, spray drying the material to obtain a light-colored dye dispersant.

[0009] Preferably, the first temperature range is 70-95°C; the second temperature range is 70-95°C; and the third temperature range is 70-90°C.

[0010] Preferably, in the step 1, the reaction time of the industrial lignin, the first batch of water, the sulfonation reagent and the aldehyde reagent at the first temperature is 3-6 hours; in the step 2, the reaction time of the first stage product with the free radical initiator and the blocking reagent at the second temperature is 2-4 hours; in the step 3, the reaction time of the second stage product with the ozone / air mixture at the third temperature is 4-8 hours.

[0011] Preferably, the mass ratio of the industrial lignin in the step 1 to the first batch of water added is 3:6.7-11.7, the mass ratio of the sulfonated reagent to the industrial lignin added is 5-6:10, and the molar ratio of the aldehyde reagent to the sulfonated reagent added is 1.2-1.5:1; the mass ratio of the free radical initiator and the blocking reagent in the step 2 to the industrial lignin added in the step 1 is 0.5-1:25-50:50; the mass ratio of the second batch of water in the step 3 to the industrial lignin added in the step 1 is 140-300:3.

[0012] Preferably, the industrial lignin in step 1 is one of the wood raw material kraft lignin or grass raw material alkali lignin produced in the pulping and papermaking process, the pH regulator is sodium hydroxide, the sulfonating agent is one of sodium sulfite or sodium bisulfite, and the aldehyde reagent is a formaldehyde aqueous solution or an acetaldehyde aqueous solution; the free radical initiator in step 2 is one of potassium persulfate or ammonium persulfate, and the blocking agent is one of sodium allyl sulfonate or sodium methacrylate sulfonate; the ozone / air mixed gas in step 3 has a volume ratio of ozone to air of 1:99-5:95, and the mixed gas is introduced at a rate of 2-3 L / min

[0013] Preferably, the pH value of the mixture is adjusted by the pH adjuster in step 1 to 10.5-12.5; and the mass concentration of the formaldehyde or acetaldehyde solution in step 2 is 30%-37%.

[0014] The present invention also provides a light-colored dye dispersant prepared from industrial lignin, wherein the light-colored dye dispersant is prepared by the method according to any one of claims 1 to 6.

[0015] By means of the above technical solution, the present invention has at least the following advantages:

[0016] (1) The present invention adopts a two-stage sulfonation technology to improve the sulfonation degree of lignin, and uses a free radical graft polymerization reaction to simultaneously achieve chemical blocking of phenolic hydroxyl groups and introduction of sulfonic acid groups in the second stage of sulfonation, thereby avoiding the deterioration of its dispersion performance due to oxidation in high-temperature dye solution. At the same time, after monomer polymerization, the molecular weight of the sulfonated lignin is effectively increased, which significantly improves the high-temperature stability of the dispersant and solves the problems of low sulfonate content, low molecular weight and high phenolic hydroxyl content of single sulfomethylated lignin.

[0017] (2) The present invention uses ozone as an oxidant. The gas is prepared by air corona discharge technology, which can be used immediately after production without the need for gas source storage and transportation. The gas by-products after the reaction can be completely degraded into environmentally friendly oxygen molecules. There is no secondary pollution in the whole process. Compared with the traditional chemical reagent oxidation technology, it is safer and provides a highly feasible clean production solution for the preparation of light-colored sulfonated lignin dye dispersants. By setting an appropriate amount of ozone, the remaining free phenolic hydroxyl groups in the sulfonated lignin can be completely oxidized to carboxyl groups, effectively blocking the conversion path of phenolic hydroxyl groups to quinone-type dark groups, and preventing excessive oxidation damage to the lignin structure, which affects the performance of the dispersant. This technology fundamentally inhibits the deepening of lignin color, reduces the contamination of fibers by sulfonated lignin during high-temperature printing and dyeing, and promotes the promotion and application of lignin dye dispersants to the high-end market. DETAILED DESCRIPTION

[0018] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a detailed description is given below in conjunction with preferred embodiments.

[0019] Preparation method

[0020] This preparation method mainly comprises the following steps:

[0021] Step 1: mixing industrial lignin with the first batch of water, adding a pH regulator to adjust the pH value of the mixture, stirring until fully dissolved, adding a sulfonating reagent and an aldehyde reagent, and reacting the mixture at a first temperature to obtain a first-stage reaction product.

[0022] Among them, the industrial lignin is preferably one of the wood raw material kraft lignin produced in the pulping and papermaking process or the alkali lignin of the grass raw material, more preferably the wood raw material kraft lignin; the pH adjuster is preferably solid sodium hydroxide; the sulfonation reagent is preferably one of sodium sulfite or sodium bisulfite, more preferably sodium sulfite; the aldehyde reagent is preferably formaldehyde solution or acetaldehyde solution, more preferably formaldehyde solution; the formaldehyde or acetaldehyde aqueous solution is preferably used at a mass concentration of 30%-37%, more preferably 34%-37%; the pH value of the mixture is preferably 11-12.5, more preferably 11. 5-12; the first temperature range is preferably 70-95°C, more preferably 85-90°C; the reaction time of industrial lignin, sulfonated reagent and aldehyde reagent at the first temperature is preferably 3-6h, more preferably 4-5h; the mass ratio of industrial lignin to the first batch of water added is preferably 3:6.7-11.70, more preferably 3:7.7-9.7; the mass ratio of sulfonated reagent to lignin added is 5-6:10, preferably 5-5.5:10; the molar ratio of aldehyde reagent to sulfonated reagent added is preferably 1.1-1.6:1.0, more preferably 1.1-1.3:1.0.

[0023] Step 2: adding a free radical initiator and a blocked monomer to the first-stage reaction product, and reacting the mixture at a second temperature to obtain a second-stage reaction product;

[0024] Among them, the free radical initiator is preferably one of potassium persulfate or ammonium persulfate, more preferably potassium persulfate; the blocking reagent is preferably one of sodium allyl sulfonate or sodium methacrylate sulfonate, more preferably sodium allyl sulfonate; the second reaction temperature is preferably 70-95°C, more preferably 85-90°C; the reaction time of the first stage product and the blocking reagent at the second temperature is preferably 2-4h, more preferably 3-4h; the mass ratio of the free radical initiator, the blocking reagent and the industrial lignin added in the step one is preferably 0.5-1:25-50:50, more preferably 0.8-1:35-50:50.

[0025] Step three, adding a second batch of water to the second stage product, introducing ozone / air mixed gas, and reacting the mixture at a third temperature. After the reaction is completed, cooling, spray drying the material to obtain a light-colored dye dispersant.

[0026] The ozone / air mixture preferably has a volume ratio of ozone to air of 1-5:95-99, more preferably 2-4:97-99; the gas mixture introduction rate is preferably 2-3 L / min, more preferably 2.5-3 L / min; the third temperature is preferably 70-90°C, more preferably 75-85°C; the reaction time of the second stage product and the ozone / oxygen mixture at the third temperature is preferably 4-8 hours, more preferably 5-7 hours. The mass ratio of the second batch of water to the lignin added in step 1 is preferably 140-300:3, more preferably 240-290:3.

[0027] The present invention constructs a high-temperature stable light-colored sulfonated lignin dye dispersant preparation system with two-stage sulfonation and synergistic ozone oxidation. On the basis of the first-stage sulfonation, free radical graft polymerization is used to simultaneously achieve the goals of blocking phenolic hydroxyl groups, introducing sulfonic acid groups, and increasing the molecular weight of sulfonated lignin. At the same time, air corona in-situ activation technology is introduced to generate ozone / peroxy radicals of controllable concentrations, which blocks the conversion path of the remaining free phenolic hydroxyl groups in the sulfonated lignin to quinone structures through selective oxidation, effectively inhibiting the generation of lignin chromophores. This dual-effect synergistic mechanism not only enables the product to maintain colloidal stability in the high-temperature dye bath, but also achieves a reduction in the chromaticity of the dispersant itself, successfully breaking through the technical barrier that lignin-based materials are difficult to meet the requirements of light-colored textile processing. The entire process completes the high-value conversion of lignin without the intervention of heavy metal catalysts, providing an industrial solution for replacing petroleum-based dispersants with biomass resources that combines performance advantages with environmental friendliness.

[0028] The present invention will be further described below with examples.

[0029] Example 1

[0030] (1) 300 g of industrial lignin and the first batch of 870 g of water were added to a reaction vessel to form a reaction system. Solid sodium hydroxide was added to adjust the pH of the system to 12 and stirred until fully dissolved. 151.02 g of sodium sulfite and 116.73 g of formaldehyde solution (37% concentration) were added, and the reaction system was heated to 90° C. and kept at this temperature for 4 hours to obtain the first-stage reaction product.

[0031] (2) Add 5.4 g of potassium persulfate and 240 g of sodium allyl sulfonate to the first-stage reaction product in step (1), and continue the reaction at 90° C. for 3 h to obtain a second-stage reaction product.

[0032] (3) Adding a second batch of water (28,800 g) to the second-stage product in step (2), introducing an ozone / air mixed gas (ozone to air volume ratio of 4:96) at a rate of 3 L / min, cooling the reaction system to 80° C., keeping the temperature for 6 h, cooling, and spray drying the material to obtain a light-colored sulfonated lignin dye dispersant.

[0033] (4) The various properties of the light-colored sulfonated lignin dye dispersant of this embodiment were tested, and the results are listed in Table 1.

[0034] Example 2

[0035] (1) 300 g of industrial lignin and 1170 g of the first batch of water were added to a reaction vessel to form a reaction system. Solid sodium hydroxide was added to adjust the pH of the system to 11.5 and stirred until fully dissolved. 170.1 g of sodium sulfite and 153.24 g of formaldehyde solution (37% concentration) were added, and the reaction system was heated to 85° C. and kept at this temperature for 5 hours to obtain the first-stage reaction product.

[0036] (2) Add 4.8 g of potassium persulfate and 260 g of sodium allyl sulfonate to the first-stage reaction product in step (1), and continue the reaction at 90° C. for 4 h to obtain a second-stage reaction product.

[0037] (3) adding a second batch of water (24,000 g) to the second-stage product in step (2), introducing an ozone / air mixed gas (ozone to air volume ratio of 2:98) at a rate of 2.5 L / min, cooling the reaction system to 75° C., keeping the temperature for 8 h, cooling, and spray drying the material to obtain a light-colored sulfonated lignin dye dispersant.

[0038] (4) The various properties of the light-colored sulfonated lignin dye dispersant of this embodiment were tested, and the results are listed in Table 1.

[0039] Example 3

[0040] (1) Add 300 g of industrial lignin and the first batch of 970 g of water to a reaction vessel to form a reaction system. Add solid sodium hydroxide to adjust the pH of the system to 12 and stir until fully dissolved. Add 156.09 g of sodium sulfite and 188 g of acetaldehyde solution. Heat the reaction system to 70°C and keep it warm for 6 hours to obtain the first-stage reaction product.

[0041] (2) Add 5.4 g of ammonium persulfate and 270 g of sodium methyl propylene sulfonate to the first-stage reaction product in step (1), and continue the reaction at 90° C. for 3 h to obtain a second-stage reaction product.

[0042] (3) Adding a second batch of water (28,800 g) to the second-stage product in step (2), introducing an ozone / air mixture (ozone to air volume ratio of 5:95) at a rate of 3 L / min, heating the reaction system to 85° C., keeping the temperature for 7 h, cooling, and spray drying the material to obtain a light-colored sulfonated lignin dye dispersant.

[0043] (4) The various properties of the light-colored sulfonated lignin dye dispersant of this embodiment were tested, and the results are listed in Table 1.

[0044] Comparative Example 1

[0045] A sulfonated lignin dye dispersant was prepared according to the traditional method, and the properties of the prepared dye dispersant were tested.

[0046] Comparative Example 2

[0047] Commonly used lignin sulfonate was used as a dye dispersant, and its various properties as a dye dispersant were tested.

[0048] Table 1 Test of the dispersion performance of dyes in the examples and comparative examples

[0049] Note: The disperse dye used is disperse dark blue S-3bg dye filter cake;

[0050] The test dye dispersion was prepared as follows: dispersant: filter cake: water in a mass ratio of 1.5:1.0:6.0. The mixture was then thoroughly ground in a planetary ball mill at 400 rpm for 4 hours. After grinding, the mixture was diluted to 0.5% to obtain the dye dispersion.

[0051] The average particle size of the above dyes was tested using an OMEC laser particle size analyzer;

[0052] The high-temperature dye treatment method described above involves adjusting the pH of a 0.5% dye dispersion to 5.0 using an acetic acid / sodium acetate mixture. The dye dispersion is placed in a dyeing machine and heated to 130°C at a rate of 2°C / min. The temperature is then maintained at this temperature for 45 minutes. The temperature is then lowered to 80°C at a rate of 4°C / min before removal.

[0053] The above D 450 Testing Principle: The quinone structure is the primary factor contributing to the darkening of lignin's color. This structure's primary absorption range in the UV spectrum is near 450nm, so the absorbance of sulfonated lignin at 450nm can roughly reflect its inherent color depth. Prepare a 0.5g / L dispersant solution at a pH of 5.0, and measure its absorbance at 450nm to characterize the color of the dispersant solution.

[0054] The staining test method for the above dispersant on polyester fibers is as follows: prepare a 2g / L dispersant solution, adjust the pH to 5.0 with an acetic acid / sodium acetate mixture, add 1% of the dispersant solution by weight to the polyester fibers, pour the solution into the dye cup, and then perform a high-temperature treatment. After the treated polyester fibers are rinsed and dried naturally, the K / S ratio is measured using a colorimeter.450 , K / S 450 The larger the value, the stronger the dispersant stains the polyester fiber.

[0055] From the data in Table 1, we can see

[0056] (1) The average particle size of the lignin light-colored dye dispersants prepared in Examples 1-3 of the present invention at room temperature and high temperature conditions is significantly lower than that of Comparative Examples 1 and 2, and their dispersion performance and high-temperature stability are better than those of the commonly used sulfonated lignin dye dispersants, indicating that they have good high-temperature resistance and dispersion performance.

[0057] (2) The lignin light-colored dye dispersant prepared in Examples 1-3 of the present invention, wherein D 450 With K / S 450 The values are significantly lower than those in Comparative Examples 1 and 2, which proves that the dispersant has a weak staining effect on polyester fibers.

[0058] In summary, the lignin light-colored dye dispersant prepared by the present invention not only has good high temperature resistance and dispersion properties, but also reduces the staining effect of lignin on polyester fibers, and has great economic and social significance.

[0059] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiment in accordance with the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A process for preparing a light-colored dye dispersant from industrial lignin, characterized in that: The preparation method comprises the following steps: Step 1: mixing industrial lignin with the first batch of water, adding a pH regulator to adjust the pH value of the mixture, stirring until fully dissolved, adding a sulfonating reagent and an aldehyde reagent, and reacting the mixture at a first temperature to obtain a first-stage reaction product; Step 2: adding a free radical initiator and a blocked monomer to the first-stage reaction product, and reacting the mixture at a second temperature to obtain a second-stage reaction product; Step three, adding a second batch of water to the second stage product, introducing ozone / air mixed gas, and reacting the mixture at a third temperature. After the reaction is completed, cooling, spray drying the material to obtain a light-colored dye dispersant.

2. The process for preparing a light-colored dye dispersant from industrial lignin according to claim 1, characterized in that: The first temperature range is 70-95°C; the second temperature range is 70-95°C; and the third temperature range is 70-90°C.

3. The process for preparing light-colored dye dispersant from industrial lignin according to claim 1, characterized in that: In the step 1, the reaction time of the industrial lignin, the first batch of water, the sulfonation reagent and the aldehyde reagent at the first temperature is 3-6 hours; in the step 2, the reaction time of the first stage product with the free radical initiator and the blocking reagent at the second temperature is 2-4 hours; in the step 3, the reaction time of the second stage product with the ozone / air mixture at the third temperature is 4-8 hours.

4. The process for preparing a light-colored dye dispersant from industrial lignin according to claim 1, characterized in that: The mass ratio of the industrial lignin in the step one to the first batch of water added is 3:6.7-11.7, the mass ratio of the sulfonated reagent to the industrial lignin added is 5-6:10, and the molar ratio of the aldehyde reagent to the sulfonated reagent added is 1.1-1.6:1; the mass ratio of the free radical initiator and the blocking reagent in the step two to the industrial lignin added in the step one is 0.5-1:25-50:50; the mass ratio of the second batch of water in the step three to the industrial lignin added in the step one is 140-300:

3.

5. The process for preparing light-colored dye dispersant from industrial lignin according to claim 1, characterized in that: In the step 1, the industrial lignin is one of kraft lignin produced as a wood raw material in the pulping and papermaking process or alkali lignin as a grass raw material, the pH adjuster is sodium hydroxide, the sulfonating reagent is one of sodium sulfite or sodium bisulfite, and the aldehyde reagent is a formaldehyde aqueous solution or an acetaldehyde aqueous solution; in the step 2, the free radical initiator is one of potassium persulfate or ammonium persulfate, and the blocking reagent is one of sodium allyl sulfonate or sodium methallyl sulfonate; and in the ozone / air mixed gas in the step 3, the volume ratio of ozone to air is 1:99-5:95, and the mixed gas is introduced at a rate of 2-3 L / min.

6. The process for preparing light-colored dye dispersant from industrial lignin according to claim 1, characterized in that: In the step 1, the pH value of the mixture is adjusted by the pH adjuster to 10.5-12.5; and in the step 2, the mass concentration of the formaldehyde or acetaldehyde solution is 30%-37%.

7. A light-colored dye dispersant prepared from industrial lignin, characterized in that: The light-colored dye dispersant is prepared by the method according to any one of claims 1 to 6.

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