阅读说明：本技术 一种碱木质素基染料分散剂的制备方法 (Preparation method of alkali lignin-based dye dispersant ) 是由 田中建 吉兴香 姜潇 张凤山 吕高金 马浩 于 2021-07-20 设计创作，主要内容包括：本发明属于制浆造纸工业碱木质素利用领域,涉及一种碱木质素基染料分散剂的制备方法,包括：将碱木质素纯化、在1,6-二溴己烷/二甲基甲酰胺体系中进行分子量调控,超滤,得到高分子量碱木质素；将高分子量碱木质素用1,4-丁磺酸内酯进行磺化处理,得到碱木质素基染料分散剂。本发明以制浆造纸工业碱木质素为原料,首先采用1,6-二溴己烷/二甲基甲酰胺新型烷基化体系调控碱木质素,再用1,4-丁磺酸内酯对调控后碱木质素进行磺化制备碱木质素基染料分散剂。制备的碱木质素基染料分散剂分散等级高、高温稳定性好、对纤维沾污低,各项指标达到或超过HGT 3507-2008中木质素磺酸钠分散剂一等品指标。(The invention belongs to the field of alkali lignin utilization in pulping and papermaking industries, and relates to a preparation method of an alkali lignin-based dye dispersant, which comprises the following steps: purifying alkali lignin, regulating and controlling molecular weight in a 1, 6-dibromohexane/dimethylformamide system, and ultrafiltering to obtain high molecular weight alkali lignin; and (3) sulfonating high molecular weight alkali lignin by using 1, 4-butyl sultone to obtain the alkali lignin-based dye dispersant. The invention takes alkali lignin in pulping and papermaking industry as a raw material, firstly adopts a novel alkylation system of 1, 6-dibromohexane/dimethylformamide to regulate and control the alkali lignin, and then uses 1, 4-butyl sultone to sulfonate the regulated and controlled alkali lignin to prepare the alkali lignin-based dye dispersant. The prepared alkali lignin-based dye dispersant has high dispersion grade, good high-temperature stability and low fiber contamination, and each index reaches or exceeds the first-grade index of sodium lignosulfonate dispersant in HGT 3507-.)

1. A preparation method of an alkali lignin-based dye dispersant is characterized by comprising the following steps:

purifying alkali lignin, regulating and controlling molecular weight in a 1, 6-dibromohexane/dimethylformamide system, and ultrafiltering to obtain high molecular weight alkali lignin;

and (3) sulfonating high molecular weight alkali lignin by using 1, 4-butyl sultone to obtain the alkali lignin-based dye dispersant.

2. The method for preparing the alkali lignin-based dye dispersant according to claim 1, wherein the alkali lignin is crude alkali lignin separated and extracted from the black liquor of the alkaline pulping of the pulping and papermaking enterprises, preferably in powder or block form.

3. The method of claim 1, wherein the molecular weight of the high molecular weight alkali lignin is 3000-13000 g/mol.

4. The method for preparing the alkali lignin-based dye dispersant of claim 1, wherein the mass ratio of the high molecular weight alkali lignin to the 1, 4-butanesultone is 1: 0.05-0.35.

5. The method for preparing the alkali lignin-based dye dispersant of claim 1, wherein the sulfonation comprises the following specific steps: mixing high molecular weight alkali lignin with potassium carbonate, adding DMF (dimethyl formamide), heating to 70-100 ℃ in a water bath, adding 1, 4-butyl sultone, sulfonating for 1-4 h to obtain a mixture, adding the mixture into isopropanol, standing, separating, collecting precipitate, dissolving, dialyzing, evaporating and concentrating under reduced pressure, freezing, freeze-drying, and grinding to obtain the alkali lignin-based dye dispersant.

6. The method of claim 5, wherein the high molecular weight alkali lignin is reacted with K₂CO₃The mass ratio of (A) to (B) is 5: 3-4.

7. The method of claim 5, wherein the mass to volume ratio of the high molecular weight alkali lignin to DMF is from 1:5 to 8.

8. The method for preparing an alkali lignin-based dye dispersant according to claim 5, wherein the specific conditions of dialysis are: dialyzing for 2-3 d in a dialysis bag with 1kDa, and changing water every 10-12 h;

or the temperature of reduced pressure evaporation concentration is 63-65 ℃;

or, the freezing time is 8-10 h;

or the freeze drying time is 24-32 h.

9. An alkali lignin-based dye dispersant prepared by the method of any one of claims 1 to 8.

10. Use of the alkali lignin-based dye dispersant of claim 9 in the dye, textile, printing and dyeing industries.

Technical Field

The invention belongs to the field of alkali lignin utilization in the pulping and papermaking industry, and particularly relates to a preparation method of an alkali lignin-based dye dispersant.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

Lignin is the largest natural source of aromatic compounds, accounts for 15-40 wt% of wood, and is the second largest biomass resource with reserves second to cellulose in the plant world. Currently only about 2% of lignin is used for the production of high value added products, most of which are used only as cheap fuels. The lignin is mainly from the pulping and papermaking industry, and the annual production amount of the lignin as a pulping byproduct is about 5000 ten thousand tons, wherein about 1500 ten thousand tons in China are not separated or utilized, and 95 percent of the lignin is treated in a direct discharge or combustion mode, so that a serious environmental problem is caused. Today, most pulp and paper mills in the world use alkaline pulping, and the lignin produced is mainly alkali lignin. Dispersants are one of the important applications for lignosulfonates and sulfonated alkali lignins. Dispersants (also known as dispersants) are indispensable ingredients in dispersant dyes. The dye dispersant can improve the suspension rate of the dye which is not easy to dissolve and is insoluble in water, thereby improving the dyeing effect. Besides, the dispersant also has the functions of diluting, leveling and balancing the dye strength, and is an essential component in commercial dyes. More than 50 varieties of lignin-based dye dispersants exist abroad, and the market share accounts for more than 90%. Representative of the sulfonated alkali lignin dispersants are mainly Lignosol series produced by Borregaard, Reax series developed by U.S. company, and the like. Currently, the best globally recognized high temperature stability product is Reax-85A developed by Westvaco, USA. Compared with the foreign countries, the lignin-based dye dispersant in China has slower development and smaller market share, is behind the foreign countries in both variety and product quality, and is mainly focused on the middle and low end. The defects of low dispersion grade, poor high-temperature stability, strong fiber contamination and the like are that the domestic lignin dispersant is mostly used as a filling type dispersant.

Disclosure of Invention

In order to solve the problems, the alkali lignin in the pulping and papermaking industry is used as a raw material, the alkali lignin is firstly regulated and controlled by adopting a novel alkylation system of 1, 6-dibromohexane/dimethylformamide, and then the regulated and controlled alkali lignin is sulfonated by using 1, 4-butyl sultone to prepare the alkali lignin-based dye dispersant. The prepared alkali lignin-based dye dispersant has high dispersion grade, good high-temperature stability and low fiber contamination, and each index reaches or exceeds the first-grade index of sodium lignosulfonate dispersant in HGT 3507-2008.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

in a first aspect of the present invention, there is provided a method for preparing an alkali lignin-based dye dispersant, comprising:

purifying alkali lignin, regulating and controlling molecular weight in a 1, 6-dibromohexane/dimethylformamide system, and ultrafiltering to obtain high molecular weight alkali lignin;

and (3) sulfonating high molecular weight alkali lignin by using 1, 4-butyl sultone to obtain the alkali lignin-based dye dispersant.

According to the novel technology developed by the application, the prepared alkali lignin-based dye dispersant has the advantages of high dispersion grade, good high-temperature stability, low fiber contamination and the like, and each index reaches or exceeds the first-grade index of sodium lignosulfonate dispersant in HGT 3507-.

In a second aspect of the invention, there is provided an alkali lignin-based dye dispersant prepared by any of the above-described methods.

In a third aspect of the invention, the application of the alkali lignin-based dye dispersant in the dye, textile and printing and dyeing industries is provided.

The invention has the beneficial effects that:

(1) in the whole preparation process of the alkali lignin-based dye dispersant, organic solvent and acid precipitation methods are adopted to purify alkali lignin, and then a novel 1, 6-dibromohexane/dimethylformamide system is used for regulating and controlling alkylation of the purified alkali lignin. The alkylated alkali lignin has high molecular weight, light color, proper polydispersity and proper content of phenolic hydroxyl functional group.

(2) The alkali lignin is regulated and controlled by alkylation, and is sulfonated by using 1, 4-butanesultone, so that the prepared alkali lignin-based dye dispersant has high dispersion grade, good high-temperature stability and low fiber contamination, and each index reaches or exceeds the first-grade index of sodium lignosulfonate dispersant in HGT 3507-.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

A preparation method of alkali lignin-based dye dispersant takes alkali lignin in pulping and papermaking industry as raw material, and comprises the following steps:

the alkali lignin in the pulping and papermaking industry is used as a raw material, the alkali lignin is purified by an organic solvent and an acid precipitation method, and a novel alkylation system 1, 6-dibromohexane/dimethylformamide is adopted to regulate and control alkali lignin molecules, so that the alkali lignin (CAL) regulated and controlled by the molecules is obtained. Separating out alkali lignin (CAL) with medium and high molecular weight (3000-_h). At CAL_hAccording to CAL_h：K₂CO₃Add solid potassium carbonate to 5:3(w/w) in three-necked flask according to CAL_h: DMF ═ 1:5(w: v), heating in water bath at 70-100 deg.C_h:1, 4-butane sultone is added into 1, 4-butane sultone at a ratio of 1: 0.05-0.35, and the mixture is sulfonated for 1-4 h under stirring. The mixture was poured into a beaker and 4 volumes of isopropanol were added. After standing for a period of time, the mixture was centrifuged. The precipitate was dissolved with water and the solution was poured into a 1kDa dialysis bag and dialyzed for 2d, with water change every 12 h. Evaporating the dialyzed mixture at 63 deg.C under reduced pressure for concentration, freezing in refrigerator for 8 hr, freeze drying for 24 hr, and grinding to obtain alkali lignin-based dye dispersant.

The detailed steps for preparing the alkali lignin-based dye dispersant comprise the following steps:

(1) alkali lignin in pulping and papermaking industry is used as a raw material, and the alkali lignin is purified by an organic solvent and an acid precipitation method.

(2) The purified alkali lignin reacts in a 1, 6-dibromohexane/dimethylformamide system to obtain alkali lignin (CAL) regulated by molecules.

(3) Grading of CAL: separating out alkali lignin (CAL) with medium and high molecular weight (3000-_h)。

(4) Sulfonation of alkali lignin: at CAL_hAccording to CAL_h：K₂CO₃Add solid potassium carbonate to 5:3(w/w) in three-necked flask according to CAL_h: DMF ═ 1:5(w: v), heating in water bath at 70-100 deg.C_h:1, 4-butane sultone is added into 1, 4-butane sultone at a ratio of 1: 0.05-0.35, and the mixture is sulfonated for 1-4 h under stirring.

(5) Separating, purifying and drying the alkali lignin-based dye dispersant: the mixture was poured into a beaker and 4 volumes of isopropanol were added. After standing for a period of time, the mixture was centrifuged. The precipitate was dissolved with water and the solution was poured into a 1kDa dialysis bag and dialyzed for 2d, with water change every 12 h. Evaporating the dialyzed mixture at 63 deg.C under reduced pressure for concentration, freezing in refrigerator for 8 hr, freeze drying for 24 hr, and grinding to obtain alkali lignin-based dye dispersant.

The method specifically comprises the following steps:

(1) alkali lignin in pulping and papermaking industry is used as a raw material, and the alkali lignin is purified by an organic solvent and an acid precipitation method.

(2) The purified alkali lignin reacts in a 1, 6-dibromohexane/dimethylformamide system to obtain alkali lignin (CAL) regulated by molecules.

(3) Separating out alkali lignin (CAL) with medium and high molecular weight (3000-_h)。

(4) In (3) at CAL_hAccording to CAL_h：K₂CO₃Add solid potassium carbonate to 5:3(w/w) in three-necked flask according to CAL_h: DMF ═ 1:5(w: v), heating in water bath at 70-100 deg.C_h:1, 4-butane sultone is added into 1, 4-butane sultone at a ratio of 1: 0.05-0.35, and the mixture is sulfonated for 1-4 h under stirring.

(5) Pouring the mixture in (4) into a beaker, and adding 4 times of isopropanol by volume. After standing for a period of time, the mixture was centrifuged. The precipitate was dissolved with water and the solution was poured into a 1kDa dialysis bag and dialyzed for 2d, with water change every 12 h. Evaporating the dialyzed mixture at 63 deg.C under reduced pressure for concentration, freezing in refrigerator for 8 hr, freeze drying for 24 hr, and grinding to obtain alkali lignin-based dye dispersant.

The present invention is described in further detail below with reference to specific examples, which are intended to be illustrative of the invention and not limiting.

In the following examples, all chemical grades used are chemically pure.

Example 1: the preparation of the alkali lignin-based dye dispersant is realized by the following steps.

(1) Organic solvent purification of crude alkali lignin: to the dried crude alkali lignin was added an aqueous acidic dioxane solution at a ratio of 1:10(w: v) (dioxane/water 9: 1, v: v, pH 2). The mixture was stirred at 87 ℃ for 2 hours and then centrifuged to remove the precipitate. The supernatant solution of sodium bicarbonate was added and kept stirring for 3 hours to neutralize the acid in the solution. After centrifugation again to remove the precipitate, the supernatant was subjected to vacuum rotary evaporation at 55 ℃ to remove and recover dioxane.

(2) Acid precipitation, separation and purification of alkali lignin: the supernatant after rotary evaporation in vacuo was added to 2000mL of hydrochloric acid solution (pH 2), and then centrifuged to obtain a precipitate. Freeze drying the precipitate to obtain solid powder of Purified Alkali Lignin (PAL).

(3) Alkylation of PAL: PAL was dissolved in Dimethylformamide (DMF) in a ratio of 1: 20. Adding K with the mass 0.6 times of that of the purified alkali lignin into the mixed solution₂CO₃As an acid binder to absorb the acid generated in the reaction, and a trace amount of KI was added as an activator of 1, 6-dibromohexane. Under the protection of nitrogen, the mixture is heated to a specified temperature of 90 ℃, 1, 6-dibromohexane is added, the temperature is kept for reaction for 2 hours, and then 2mol/L hydrochloric acid aqueous solution is added to complete the reaction.

(4)CALAcid precipitation and fractionation: the mixture was precipitated with aqueous hydrochloric acid (pH 2). Centrifuging to obtain precipitate, washing with hydrochloric acid water solution (pH 2), and freeze drying to obtain solid powder substance, i.e. alkali lignin (CAL) regulated by molecule. Separating out alkali lignin (CAL) with medium and high molecular weight (3000-_h)。

(5) Sulfonation of alkali lignin: according to CAL in a three-neck flask_h: adding solid potassium carbonate in a ratio of 5:3, and adding the mixture according to CAL_hDMF 1:5(w: v) is mixed and heated in a water bath until reaching 70 ℃, and then is treated according to CAL_h:1, 4-Butanesulfonactone ═ 1:0.15(w: w) 1, 4-butanesultone was added and the mixture was sulfonated for 4h with stirring.

(6) Separating, purifying and drying the alkali lignin-based dye dispersant: the mixture was poured into a beaker and 4 volumes of isopropanol were added. After standing for a period of time, the mixture was centrifuged. The precipitate was dissolved with water and the solution was poured into a 1kDa dialysis bag and dialyzed for 2d, with water change every 12 h. Evaporating the dialyzed mixture at 63 deg.C under reduced pressure for concentration, freezing in refrigerator for 8 hr, freeze drying for 24 hr, and grinding to obtain alkali lignin-based dye dispersant. The main indexes of the obtained dispersant are compared with the main indexes in HGT3507-2008, and the indexes are shown in Table 1.

TABLE 1 comparison of alkali lignin-based dye dispersants with current standard indices

Example 2: the preparation of the alkali lignin-based dye dispersant is realized by the following steps.

(1) Organic solvent purification of crude alkali lignin: to the dried crude alkali lignin was added an aqueous acidic dioxane solution at a ratio of 1:10(w: v) (dioxane/water 9: 1, v: v, pH 2). The mixture was stirred at 87 ℃ for 2 hours and then centrifuged to remove the precipitate. The supernatant solution of sodium bicarbonate was added and kept stirring for 3 hours to neutralize the acid in the solution. After centrifugation again to remove the precipitate, the supernatant was subjected to vacuum rotary evaporation at 55 ℃ to remove and recover dioxane.

(2) Acid precipitation, separation and purification of alkali lignin: the supernatant after rotary evaporation in vacuo was added to 2000mL of hydrochloric acid solution (pH 2), and then centrifuged to obtain a precipitate. Freeze drying the precipitate to obtain solid powder of Purified Alkali Lignin (PAL).

(3) Alkylation of PAL: PAL was dissolved in Dimethylformamide (DMF) in a ratio of 1: 20. Adding K with the mass 0.6 times of that of the purified alkali lignin into the mixed solution₂CO₃As an acid binder to absorb the acid generated in the reaction, and a trace amount of KI was added as an activator of 1, 6-dibromohexane. Under the protection of nitrogen, the mixture is heated to a specified temperature of 90 ℃, 1, 6-dibromohexane is added, the temperature is kept for reaction for 2 hours, and then 2mol/L hydrochloric acid aqueous solution is added to complete the reaction.

(4) Acid out and fractionation of CAL: the mixture was precipitated with aqueous hydrochloric acid (pH 2). Centrifuging to obtain precipitate, washing with hydrochloric acid water solution (pH 2), and freeze drying to obtain solid powder substance, i.e. alkali lignin (CAL) regulated by molecule. Separating out alkali lignin (CAL) with medium and high molecular weight (3000-_h)。

(5) Sulfonation of alkali lignin: according to CAL in a three-neck flask_h: adding solid potassium carbonate in a ratio of 5:3, and adding the mixture according to CAL_hDMF is mixed at a ratio of 1:5(w: v), and then heated in a water bath until the temperature reaches 90 ℃, and then the mixture is subjected to CAL treatment_h:1, 4-Butanesulfonactone ═ 1:0.35(w: w) 1, 4-butanesultone was added and the mixture was sulfonated for 2h each with stirring.

(6) Separating, purifying and drying the alkali lignin-based dye dispersant: the mixture was poured into a beaker and 4 volumes of isopropanol were added. After standing for a period of time, the mixture was centrifuged. The precipitate was dissolved with water and the solution was poured into a 1kDa dialysis bag and dialyzed for 2d, with water change every 12 h. Evaporating the dialyzed mixture at 63 deg.C under reduced pressure for concentration, freezing in refrigerator for 8 hr, freeze drying for 24 hr, and grinding to obtain alkali lignin-based dye dispersant. The main indexes of the obtained dispersant are compared with the main indexes in HGT3507-2008, and the indexes are shown in Table 2.

TABLE 2 comparison of alkali lignin-based dye dispersants with current standard indicators

Example 3: the preparation of the alkali lignin-based dye dispersant is realized by the following steps.

(1) Organic solvent purification of crude alkali lignin: to the dried crude alkali lignin was added an aqueous acidic dioxane solution at a ratio of 1:10(w: v) (dioxane/water 9: 1, v: v, pH 2). The mixture was stirred at 87 ℃ for 2 hours and then centrifuged to remove the precipitate. The supernatant solution of sodium bicarbonate was added and kept stirring for 3 hours to neutralize the acid in the solution. After centrifugation again to remove the precipitate, the supernatant was subjected to vacuum rotary evaporation at 55 ℃ to remove and recover dioxane.

(2) Acid precipitation, separation and purification of alkali lignin: the supernatant after rotary evaporation in vacuo was added to 2000mL of hydrochloric acid solution (pH 2), and then centrifuged to obtain a precipitate. Freeze drying the precipitate to obtain solid powder of Purified Alkali Lignin (PAL).

(3) Alkylation of PAL: PAL was dissolved in Dimethylformamide (DMF) in a ratio of 1: 20. Adding K with the mass 0.6 times of that of the purified alkali lignin into the mixed solution₂CO₃As an acid binder to absorb the acid generated in the reaction, and a trace amount of KI was added as an activator of 1, 6-dibromohexane. Under the protection of nitrogen, the mixture is heated to a specified temperature of 90 ℃, 1, 6-dibromohexane is added, the temperature is kept for reaction for 2 hours, and then 2mol/L hydrochloric acid aqueous solution is added to complete the reaction.

(4) Acid out and fractionation of CAL: the mixture was precipitated with aqueous hydrochloric acid (pH 2). Centrifuging to obtain precipitate, washing with hydrochloric acid water solution (pH 2), and freeze drying to obtain solid powderIs alkali lignin (CAL) regulated by molecules. Separating out alkali lignin (CAL) with medium and high molecular weight (3000-_h)。

(5) Sulfonation of alkali lignin: according to CAL in a three-neck flask_h: adding solid potassium carbonate in a ratio of 5:3, and adding the mixture according to CAL_hDMF 1:5(w: v) is mixed and heated in a water bath until reaching 70 ℃, and then is treated according to CAL_h:1, 4-Butanesulfonactone ═ 1:0.35(w: w) 1, 4-butanesultone was added and the mixture was sulfonated for 4h with stirring.

(6) Separating, purifying and drying the alkali lignin-based dye dispersant: the mixture was poured into a beaker and 4 volumes of isopropanol were added. After standing for a period of time, the mixture was centrifuged. The precipitate was dissolved with water and the solution was poured into a 1kDa dialysis bag and dialyzed for 2d, with water change every 12 h. Evaporating the dialyzed mixture at 63 deg.C under reduced pressure for concentration, freezing in refrigerator for 8 hr, freeze drying for 24 hr, and grinding to obtain alkali lignin-based dye dispersant. The main indexes of the obtained dispersant are compared with the main indexes in HGT3507-2008, and the indexes are shown in Table 3.

TABLE 3 comparison of alkali lignin-based dye dispersants with current standard indicators

Example 4: the preparation of the alkali lignin-based dye dispersant is realized by the following steps.

(1) Organic solvent purification of crude alkali lignin: to the dried crude alkali lignin was added an aqueous acidic dioxane solution at a ratio of 1:10(w: v) (dioxane/water 9: 1, v: v, pH 2). The mixture was stirred at 87 ℃ for 2 hours and then centrifuged to remove the precipitate. The supernatant solution of sodium bicarbonate was added and kept stirring for 3 hours to neutralize the acid in the solution. After centrifugation again to remove the precipitate, the supernatant was subjected to vacuum rotary evaporation at 55 ℃ to remove and recover dioxane.

(2) Acid precipitation, separation and purification of alkali lignin: the supernatant after rotary evaporation in vacuo was added to 2000mL of hydrochloric acid solution (pH 2), and then centrifuged to obtain a precipitate. Freeze drying the precipitate to obtain solid powder of Purified Alkali Lignin (PAL).

(3) Alkylation of PAL: PAL was dissolved in Dimethylformamide (DMF) in a ratio of 1: 20. Adding K with the mass 0.6 times of that of the purified alkali lignin into the mixed solution₂CO₃As an acid binder to absorb the acid generated in the reaction, and a trace amount of KI was added as an activator of 1, 6-dibromohexane. Under the protection of nitrogen, the mixture is heated to a specified temperature of 90 ℃, 1, 6-dibromohexane is added, the temperature is kept for reaction for 2 hours, and then 2mol/L hydrochloric acid aqueous solution is added to complete the reaction.

(4) Acid out and fractionation of CAL: the mixture was precipitated with aqueous hydrochloric acid (pH 2). Centrifuging to obtain precipitate, washing with hydrochloric acid water solution (pH 2), and freeze drying to obtain solid powder substance, i.e. alkali lignin (CAL) regulated by molecule. Separating out alkali lignin (CAL) with medium and high molecular weight (3000-_h)。

(5) Sulfonation of alkali lignin: according to CAL in a three-neck flask_h: adding solid potassium carbonate in a ratio of 5:3, and adding the mixture according to CAL_hDMF 1:5(w: v) is mixed and heated in a water bath until reaching 70 ℃, and then is treated according to CAL_h:1, 4-Butanesulfonactone ═ 1:0.05(w: w) 1, 4-butanesultone was added and the mixture was sulfonated for 4h with stirring.

(6) Separating, purifying and drying the alkali lignin-based dye dispersant: the mixture was poured into a beaker and 4 volumes of isopropanol were added. After standing for a period of time, the mixture was centrifuged. The precipitate was dissolved with water and the solution was poured into a 1kDa dialysis bag and dialyzed for 2d, with water change every 12 h. Evaporating the dialyzed mixture at 63 deg.C under reduced pressure for concentration, freezing in refrigerator for 8 hr, freeze drying for 24 hr, and grinding to obtain alkali lignin-based dye dispersant. The main indexes of the obtained dispersant are compared with the main indexes in HGT3507-2008, and the indexes are shown in Table 4.

TABLE 4 comparison of alkali lignin-based dye dispersants with current standard indicators

It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and the present invention is not limited thereto, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications and equivalents can be made in the technical solutions described in the foregoing embodiments, or equivalents thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.