Preparation method of light sodium lignin sulfonate dispersing agent

Abstract

The invention discloses a preparation method of a light sodium lignin sulfonate dispersing agent, which comprises the following steps: (a) precipitating and filtering papermaking black liquor to remove impurities, performing membrane concentration treatment on filtrate, intercepting crude lignin with the relative molecular weight of 10 * 10 < 3 >-30 * 10 < 3 >, and performing acid precipitation and filter pressing treatment to obtain high-purity lignin; (b) mixing the lignin prepared in the step (a) with a sulfonating agent and water to carry out sulfonation reaction, then adding formaldehyde to carry out condensation reaction, and then adding sodium peroxide to carry out oxidation reaction; and (c) after the reaction is finished, carrying out spray drying on the reaction liquid, and uniformly mixing the obtained sodium lignin sulfonate powder with a low-foam wetting agent DP-225 and an acrylic acid-maleic acid copolymer sodium salt according to a mass ratio of 1: (0-0.25): (0-0.2) to obtain the light sodium lignin sulfonate dispersing agent. The dispersing agent prepared by the preparation method disclosed by the invention has the advantages of reduction of fiber contamination, better dispersity and heat-resistant stability, and suitableness for being used as a dye dispersing agent and the like.

Description

Technical Field

[0001] The invention relates to the technical field of dispersants, and more specifically to a method for preparing a light sodium lignin sulfonate dispersant. Background Art

[0002] In the dye-water system, the lipophilic end of lignin sulfonate tends to the dye, and the hydrophilic end tends to the water, preventing the dye particles from agglomerating through electrostatic repulsion and steric hindrance, thereby playing a role in dispersion and stabilization. However, lignin dye dispersants also have some limitations. For example, their catechol structure is easily oxidized to a quinone structure, which not only deepens the color of lignin, but also destroys the azo bond of azo dyes, making the dye reduction ineffective. During the dyeing process, lignin dye dispersants will also adsorb on the fiber surface through hydrogen bonding, causing contamination. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a method for preparing a light sodium lignin sulfonate dispersant. The obtained dispersant reduces fiber contamination, has good dispersibility and heat stability, and is suitable for use as a dye dispersant, etc.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A method for preparing a light sodium lignin sulfonate dispersant comprises the following steps:

[0006] (a) The papermaking black liquor is filtered and precipitated to remove impurities, and the filtrate is concentrated by membrane and the cut-off molecular weight is 10×10 3 -30×10 3 The crude lignin is then treated with acid precipitation and filter pressing to obtain high-purity lignin;

[0007] (b) mixing the lignin obtained in step (a) with a sulfonating agent and water to carry out a sulfonation reaction, then adding formaldehyde to carry out a condensation reaction, and then adding sodium peroxide to carry out an oxidation reaction;

[0008] (c) After the reaction is completed, the reaction solution is spray-dried, and the obtained sodium lignin sulfonate powder is mixed with a low-foam wetting agent DP-225 and sodium salt of acrylic acid-maleic acid copolymer in a mass ratio of 1:0-0.25:0-0.2 to obtain a light sodium lignin sulfonate dispersant.

[0009] Furthermore, in step (a), the solid content of the concentrated liquid after membrane concentration is 25-30%.

[0010] Furthermore, in step (b), the mass ratio of lignin to sulfonating agent and water is 1:0.5-0.8:4.

[0011] Furthermore, in step (b), the sulfonating agent is sodium sulfite.

[0012] Furthermore, in step (b), the sulfonation reaction temperature is 90-100° C., and the sulfonation reaction time is 3-5 h.

[0013] Furthermore, in step (b), the amount of formaldehyde added is 20-30% of the mass of the lignin.

[0014] Furthermore, in step (b), the condensation reaction temperature is 70-90° C., and the reaction time is 2-3 h.

[0015] Furthermore, in step (b), the amount of sodium peroxide added is 5-8% of the mass of the reaction system.

[0016] Furthermore, in step (c), the mass ratio of sodium lignin sulfonate powder to low foam wetting agent DP-225 and sodium salt of acrylic acid-maleic acid copolymer is 1:0.13:0.1.

[0017] Furthermore, in step (b), the oxidation reaction temperature is 50-60° C., and the oxidation reaction time is 0.5-1 h.

[0018] The beneficial effects of the present invention are:

[0019] The invention discloses a sodium lignin sulfonate dye dispersant with low phenolic hydroxyl and carboxyl content and good heat stability, by modifying lignin with a specific molecular weight through sulfonation reaction and condensation reaction, and then oxidizing it through sodium oxide, thereby weakening the hydrogen bonding between sodium lignin sulfonate and fiber and reducing staining. When the sodium lignin sulfonate dye is compounded with low-foam wetting agent DP-225 and surfactant sodium salt of acrylic acid-maleic acid copolymer to form a dispersant, the synergistic effect between the substances can be brought into play, further reducing staining and improving dispersion performance. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The preparation method of the light sodium lignin sulfonate dispersant of the present invention comprises the following steps:

[0022] (a) The papermaking black liquor is filtered and precipitated to remove impurities, and the filtrate is concentrated by membrane and the cut-off molecular weight is 10×10 3 -30×10 3 The crude lignin (the solid content of the concentrated liquid after membrane concentration is 25-30%) is then treated by acid precipitation and filter pressing to obtain high-purity lignin;

[0023] (b) mixing the lignin obtained in step (a) with a sulfonating agent and water for sulfonation reaction (the mass ratio of lignin to sulfonating agent and water is 1:0.5-0.8:4, the sulfonation reaction temperature is 90-100°C, and the sulfonation reaction time is 3-5h), then adding formaldehyde for condensation reaction (the amount of formaldehyde added is 20-30% of the mass of lignin, the condensation reaction temperature is 70-90°C, and the sulfonation reaction time is 2-3h), and then adding sodium peroxide (the amount of sodium peroxide added is 5-8% of the mass of the reaction system) for oxidation reaction at 50-60°C, and the oxidation reaction time is 0.5-1h;

[0024] (c) After the reaction is completed, the reaction solution is spray-dried, and the obtained sodium lignin sulfonate powder is mixed with a low-foaming wetting agent DP-225 (purchased from Wuhan Aoke Special Chemical Co., Ltd., which has excellent hard surface cleaning ability and wetting performance, and extremely low foam), and sodium salt of acrylic acid-maleic acid copolymer (which has good surface activity and emulsifying properties) in a mass ratio of 1:0-0.25:0-0.2 to obtain a light sodium lignin sulfonate dispersant.

[0025] Example 1

[0026] (a) The papermaking black liquor is placed in a sedimentation tank and allowed to stand for 24 hours, filtered, and then polyacrylamide is added for flocculation and precipitation, and then filtered. The filtrate is concentrated by membrane and the relative molecular weight cutoff is 10×10 3 -30×10 3 The solid content of the concentrated solution is controlled to be 28.2%, the temperature of the concentrated solution is adjusted to 80°C by a heat exchanger, 20% sulfuric acid is added, acid precipitation is performed to pH = 5, and filter pressing is performed to obtain high-purity lignin;

[0027] (b) adding the lignin prepared in step (a) and water into a reaction kettle, adding sodium hydroxide solid to adjust the pH to 9, then adding a sulfonating agent to carry out a sulfonation reaction (the mass ratio of lignin to the sulfonating agent and water is 1:0.7:4, the sulfonation reaction temperature is 95°C, and the sulfonation reaction time is 5h), then adding formaldehyde to carry out a condensation reaction (the amount of formaldehyde added is 25.6% of the mass of the lignin, the condensation reaction temperature is 85°C, and the reaction time is 3h), and then adding sodium peroxide (the amount of sodium peroxide added is 5.7% of the mass of the reaction system) for oxidation reaction at 60°C for 40min;

[0028] (c) After the reaction is completed, the reaction solution is spray-dried to obtain a light sodium lignin sulfonate dispersant.

[0029] Example 2

[0030] A light sodium lignin sulfonate dispersant is prepared according to the method of Example 1, except that step (c) is as follows: after the reaction is completed, the reaction solution is spray dried, and the obtained sodium lignin sulfonate powder is mixed with a low-foam wetting agent DP-225 and sodium salt of acrylic acid-maleic acid copolymer in a mass ratio of 1:0.13:0.1 to obtain a light sodium lignin sulfonate dispersant.

[0031] Comparative Example 1

[0032] A light sodium lignin sulfonate dispersant was prepared according to the method of Example 2, except that the order of the sulfonation reaction and the condensation reaction in step (b) was reversed, specifically: the lignin prepared in step (a) and water were added to a reactor, solid sodium hydroxide was added to adjust the pH to 9, and then formaldehyde was added for condensation reaction (the amount of formaldehyde added was 25.6% of the mass of the lignin, the condensation reaction temperature was 85°C, and the reaction time was 3h), and then a sulfonating agent was added for sulfonation reaction (the mass ratio of lignin to the sulfonating agent and water was 1:0.7:4, the sulfonation reaction temperature was 95°C, and the sulfonation reaction time was 5h), and then sodium peroxide was added (the amount of sodium peroxide added was 5.7% of the mass of the reaction system) for oxidation reaction at 60°C for 40min.

[0033] Comparative Example 2

[0034] A light sodium lignin sulfonate dispersant was prepared according to the method of Example 2, except that in step (c), the mass of low foam wetting agent DP-225 was replaced by sodium lignin sulfonate powder.

[0035] Comparative Example 3

[0036] A light sodium lignin sulfonate dispersant was prepared according to the method of Example 2, except that an equal mass of sodium lignin sulfonate and an equal mass of sodium salt of acrylic acid-maleic acid copolymer as in Example 2 were added in step (c).

[0037] Comparative Example 4

[0038] A light sodium lignin sulfonate dispersant was prepared according to the method of Example 2, except that in step (c), an equal amount of sodium salt of acrylic acid-maleic acid copolymer was replaced by sodium lignin sulfonate powder.

[0039] Comparative Example 5

[0040] A light sodium lignin sulfonate dispersant was prepared according to the method of Example 2, except that an equal mass of sodium lignin sulfonate and an equal mass of low foam wetting agent DP-225 as in Example 2 were added in step (c).

[0041] The performance tests were performed on the dispersants prepared in Example 1-Example 2 and Comparative Example 1-Comparative Example 5. The results are shown in Table 1.

[0042] Table 1

[0043]

[0044]

[0045] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a light sodium lignin sulfonate dispersant, characterized in that: The following steps are involved: (a) The papermaking black liquor is filtered and precipitated to remove impurities, and the filtrate is concentrated by membrane and the cut-off molecular weight is 10×10 3 -30×10 3 The crude lignin is then treated with acid precipitation and filter pressing to obtain high-purity lignin; (b) mixing the lignin obtained in step (a) with a sulfonating agent and water to carry out a sulfonation reaction, then adding formaldehyde to carry out a condensation reaction, and then adding sodium peroxide to carry out an oxidation reaction; (c) After the reaction is completed, the reaction solution is spray-dried, and the obtained sodium lignin sulfonate powder is mixed with a low-foam wetting agent DP-225 and sodium salt of acrylic acid-maleic acid copolymer in a mass ratio of 1:0-0.25:0-0.2 to obtain a light sodium lignin sulfonate dispersant.

2. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (a), the solid content of the concentrated liquid after membrane concentration is 25-30%.

3. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (b), the mass ratio of lignin to sulfonating agent and water is 1:0.5-0.8:

4.

4. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (b), the sulfonating agent is sodium sulfite.

5. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (b), the sulfonation reaction temperature is 90-100° C., and the sulfonation reaction time is 3-5 hours.

6. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (b), the amount of formaldehyde added is 20-30% of the mass of the lignin.

7. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (b), the condensation reaction temperature is 70-90° C. and the reaction time is 2-3 h.

8. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (b), the amount of sodium peroxide added is 5-8% of the mass of the reaction system.

9. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (b), the oxidation reaction temperature is 50-60° C., and the oxidation reaction time is 0.5-1 h.

10. The method for preparing a light sodium lignin sulfonate dispersant according to claim 1, characterized in that: In step (c), the mass ratio of sodium lignin sulfonate powder to low foam wetting agent DP-225 and sodium salt of acrylic acid-maleic acid copolymer is 1:0.13:0.1.

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