Preparation method of quinacridone pigment water-based paste

Abstract

The present invention belongs to the field of organic pigments and specifically discloses a method for preparing a water-based pigment paste of quinacridone pigments. In an anhydrous solvent, a portion of the quinacridone pigment is first ionized using a hydrogen extraction agent to promote a certain dispersion of the pigment; a dispersant is then added to promote further dispersion of the pigment; the pigment that has achieved a certain dispersion effect undergoes a modification reaction with a substance containing a hydrophilic group, and the modification reaction and pigment dispersion promote each other, thereby improving the degree of the modification reaction and the dispersion effect. The organic solvent is then removed by suction filtration, and the pigment is dispersed with water to obtain a water-based self-dispersing pigment paste. The method of the present invention utilizes a hydrogen extraction agent to first ionize the pigment, thereby facilitating dispersion; pigment dispersion and modification reaction are effectively combined, and the modification reaction and pigment dispersion promote each other. The paste has high stability, a simple process, and high production capacity, which is conducive to industrial production.

Description

Technical Field

[0001] The invention belongs to the field of organic pigments and specifically discloses a method for preparing a quinacridone pigment water-based paste. Background Art

[0002] Compared to inorganic pigments, organic pigments offer advantages such as bright colors, a wide variety of color spectra, simple production processes, and low toxicity. In recent years, organic pigments have not only been widely used in a variety of industries, including coatings, inks, plastics, textiles, and rubber, but have also found wider application as functional materials due to their unique properties, such as photoconductivity and catalytic performance.

[0003] Organic pigments can be divided into azo pigments, phthalocyanine pigments, and condensed ring ketone pigments according to their chemical structures. Quinacridone organic pigments, which are among the condensed ring ketone pigments, have excellent lightfastness, weather resistance, migration resistance, and thermal stability. As a high-end organic pigment, quinacridone pigments are widely used in automotive coatings, advertising paintings, and the preparation of high-end paints due to their excellent performance. Common quinacridone pigments include Pigment Violet 19, Pigment Red 122, and Pigment Red 202. Their structures are shown in Formula 1:

[0004]

[0005] Here, R represents one of a hydrogen atom, a methyl group, and a chlorine atom.

[0006] At present, with the development of modern economy and society and the improvement of people's environmental awareness, water-based pigment pastes have great development and application value because of their very low harm to human body and environment and excellent performance in all aspects. Therefore, they have become a research hotspot in the field of pigments in recent years. When dispersing organic pigments in aqueous systems, the dispersion effect and stability are generally explained by electrostatic theory and steric hindrance effect. However, in actual applications, since most organic pigments are crystals accumulated by non-polar molecules with benzene rings as the skeleton, they are not active to external forces and have low affinity to the application medium. Therefore, it is difficult for organic pigments to be dispersed uniformly and stably in water. In order to solve this problem, researchers have adopted various methods for surface treatment and modification to enhance the surface activity of organic pigments in order to obtain uniformly and stably dispersed water-based pigment pastes.

[0007] Existing research methods for modifying the hydrophilicity of organic pigments primarily include dispersant addition, polymer surface coating, and pigment derivatives. The basic principle of the pigment derivative method is to introduce characteristic groups into the parent pigment to generate a pigment derivative. The derivative parent and the underivatized pigment adsorb to each other, and because the characteristic groups contained in the derivative have similar polarity to the solvent, the pigment is easily dispersed in the solvent.

[0008] Compared to the dispersant addition method, the pigment derivative method does not attach hydrophilic substances to pigment molecules through simple surface adsorption, but instead directly introduces hydrophilic groups into the pigment structure through specific reactions to obtain hydrophilic pigment particles. This method effectively overcomes the problems of easy dispersant detachment and poor stability of the resulting pigment paste in the dispersant addition method. Regarding the polymer surface coating method, although the surface coating technology can produce a dispersed and stable pigment paste, due to its complex operation and process sensitivity, the produced paste often has disadvantages such as uneven coating, low color, and excessive viscosity. The pigment derivative method does not change the traditional pigment production process and can effectively change the surface properties of the pigment. It is a method worthy of promotion and has broad application prospects in the field of high-end pigment preparation technology.

[0009] At present, there are two methods for pigment derivatives, depending on the different ways of introducing characteristic groups:

[0010] One method is to directly react aldehydes, ketones, esters, etc. with the amino and hydroxyl groups of the pigment molecules, thereby introducing hydrophilic groups such as carboxyl and sulfonic acid groups into the pigment molecules. For example, Yeonkyu Jeong et al. used 1,4-butane sultone as a hydrophilic group to directly react with Pigment Yellow 150, resulting in a Pigment Yellow 150 molecule with sulfonic acid groups grafted onto the surface. The results showed that after the addition of the hydrophilic group, the hydrophilicity of Pigment Yellow 150 was significantly improved, and the dispersion effect and dispersion stability were also significantly improved. The research shows that this method has the characteristics of simple operation and good modification effect. However, at the same time, because organic pigments are non-polar molecular polymers, they are inherently difficult to dissolve in any solvent. Therefore, the modification method has the disadvantages of slow reaction and low pigment modification rate.

[0011] Another approach involves grafting hydrophilic groups onto pigment molecules using a diazo co-coupling process. For example, Lü Tong's research group diazotized 2-amino-5-methylbenzenesulfonic acid to obtain a diazonium salt. Simultaneously, 3-hydroxy-2-naphthoic acid was reacted with polyethylene glycol to produce a 3-hydroxy-2-naphthoic acid-terminated hydroxyl polyether ester derivative. The resulting diazonium salt was then coupled with the 3-hydroxy-2-naphthoic acid-terminated hydroxyl polyether ester derivative to produce water-based Pigment Red 57:1. The results showed that the water-based pigment paste formulated with the modified pigment exhibited better dispersion stability than the unmodified pigment. Furthermore, when the derivative content was maintained between 3% and 7% and the derivative chain length was maintained between 400 and 4000 nm, Water-based Pigment Red 57:1 exhibited excellent dispersion stability. Wen Mingchu et al. first subjected components such as p-aminobenzenesulfonic acid and p-aminobenzoic acid to a diazotization reaction to obtain a diazonium salt, and then directly reacted the prepared diazonium salt with the Pigment Red 122 molecule, thereby introducing hydrophilic groups such as sulfonic acid groups and carboxylates onto the Pigment Red 122 group, giving the pigment dispersion liquid electrostatic stability, thereby improving the dispersion performance of the pigment particles in aqueous solution. The diazo coupling technology is used to graft hydrophilic groups on the pigment surface, and its reaction time is effectively reduced compared to the one-step reaction. However, the use of the diazotization method to modify organic pigments requires the preparation of diazonium salts or derivative components first, and the reaction steps are relatively more, which increases the difficulty of the reaction operation. Secondly, a large amount of wastewater is inevitably produced during the diazotization coupling reaction, which pollutes the environment to a certain extent. In addition, sulfuric acid and hydrochloric acid solutions are used during the diazotization reaction, which can corrode the reaction equipment, and the low reaction concentration during the diazotization reaction is not conducive to industrial production.

[0012] The above-mentioned methods for modifying organic pigments using pigment derivatives demonstrate that existing methods suffer from issues such as slow derivatization reactions due to the difficulty of dispersing pigments in solvents, low modification rates, high wastewater production, and equipment corrosion, making them unsuitable for industrial production. This is also why, despite theoretical analysis demonstrating excellent dispersion and stable colorants, the lack of breakthroughs in dispersion during modification has prevented the pigment derivative method from replacing the dispersant-adding grinding method for preparing organic pigment colorants, preventing large-scale production. Summary of the Invention

[0013] The purpose of the present invention is to overcome the shortcomings of the existing modification methods of quinacridone pigment derivatives pointed out in the background art and to provide a new modification method with simple process, high production capacity and conducive to industrial production.

[0014] The purpose of the present invention is achieved by using quinacridone pigments and chloroacetic acid as raw materials and reacting them using the following formula:

[0015]

[0016] Where A represents Na + , K + , Li + R represents one of hydrogen, methyl and chlorine atoms, and R1 represents one of hydrogen anion, methanol anion, ethanol anion, tert-butanol anion and n-butyl anion.

[0017] The specific steps include:

[0018] (1) Add quinacridone pigment and hydrogenation reagent to an anhydrous solvent and stir to carry out hydrogenation reaction. The reaction liquid gradually changes from purple-red to blue, and negative charges are generated on the surface of the pigment, which promotes the dispersion of the pigment.

[0019] The hydrogen extraction reagent is one or a mixture of sodium hydride, potassium hydride, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, potassium tert-butoxide, sodium tert-butoxide, and n-butyl lithium.

[0020] The molar ratio of the quinacridone pigment to the hydrogen extraction agent is 1:2 to 1:5.

[0021] The solvent is one or a mixture of benzene, toluene, xylene and N,N-dimethylformamide.

[0022] The reaction temperature is 70-120°C, and the reaction time is 2-8 hours.

[0023] Preferably, the hydrogen removal agent is one of potassium ethoxide, sodium ethoxide, potassium tert-butoxide, and sodium tert-butoxide.

[0024] The molar ratio of the quinacridone pigment to the hydrogen extraction reagent is 1:2.5 to 1:3.5.

[0025] The solvent is preferably N,N-dimethylformamide.

[0026] The reaction temperature is preferably 95-115° C., and the reaction time is 4-6 h.

[0027] (2) After the reaction liquid in step (1) has reacted sufficiently, an anionic surfactant is added to further promote the dispersion of the pigment.

[0028] The added anionic surfactant is a mixture of one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate and dispersant NNO; the added amount of the dispersant is 1 / 15 to 1 / 35 of the pigment mass.

[0029] Preferably, the anionic surfactant is sodium lauryl sulfate, and the amount of the dispersant added is 1 / 25 to 1 / 30 of the pigment mass.

[0030] (3) dissolving halogenated acetic acid in N,N-dimethylformamide and slowly adding the mixture in step (2) to react to obtain quinacridone pigment molecules with hydrophilic groups.

[0031] The molar ratio of the added halogenated acetic acid to the quinacridone pigment is 1:2 to 1:6, the reaction temperature is 70 to 130° C., and the reaction time is 5 to 15 hours.

[0032] Preferably, the halogenated acetic acid includes chloroacetic acid and bromoacetic acid; the molar ratio of the quinacridone pigment to the halogenated acetic acid is 1:3 to 1:5, the reaction temperature is 100 to 120° C., and the reaction time is 10 to 13 hours.

[0033] (4) The reaction solution of step (3) is filtered to remove the solvent, and washed with water to remove inorganic and organic residual substances (inorganic substances refer to potassium chloride, sodium chloride or potassium bromide, sodium bromide produced during the reaction, and organic substances are the residual hydrogen extraction agent and halogenated acetic acid and the organic solvent required for the reaction).

[0034] (5) dissolving the solid obtained in step (4) in water, adding alkali to neutralize and adjust the pH to 7-9;

[0035] The alkaline substance is one of sodium hydroxide, potassium hydroxide, and ammonia water, or a mixture of several of them.

[0036] (6) fully dispersing the color paste obtained in step (5) to obtain a uniformly dispersed water-based pigment color paste;

[0037] Full dispersion is achieved by using one or a combination of rapid stirring, pump circulation, high-speed dispersing homogenizer, ultrasonic dispersion, high-pressure micro-jet method, and sand mill.

[0038] Beneficial effects: The method of the present invention overcomes the shortcomings of the existing process of preparing water-based color paste by modifying derivatives of organic pigments, which is difficult to disperse the pigment in the solvent and the modification reaction is difficult to carry out. First, the pigment is ionized by a hydrogen extraction agent, which effectively promotes pigment dispersion, increases the speed and degree of the modification reaction, shortens the reaction time, improves the modification effect, and thus improves the stability of the water-based color paste; the halogenated acetic acid has a fast reaction activity with the nitrogen atom on the pigment, and the halogenated acetic acid is easy to remove, and the inorganic waste generated is also easy to remove. The halogenated acetic acid is relatively low in price, reducing costs. The method of the present invention is conducive to industrial production. DETAILED DESCRIPTION

[0039] The present application is illustrated below with reference to specific embodiments. However, the embodiments are provided for illustrative purposes only and are not intended to be the entire technical solution of the present invention, nor are they intended to limit the overall technical solution of the present invention. Any modifications or substitutions with the same or similar technical features fall within the scope of protection of the present invention.

[0040] Example 1

[0041] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 6.24g (0.02mol) of Pigment Violet 19, 3.36g (0.04mol) of potassium ethoxide, and 120mL of N,N-dimethylformamide. After 2 hours of reaction at 70-80°C, the reaction solution completely turns blue. Then, add 0.34g (0.00098mol) of sodium dodecylbenzenesulfonate and stir for 2 hours to promote pigment particle dispersion. Then, slowly add 3.78g (0.04mol) of chloroacetic acid and continue the reaction at 70-80°C for 6 hours. After the reaction is complete, add 60mL of deionized water to wash the mixture to remove impurities and residual solvent, then filter to obtain a filter cake. The resulting filter cake is dispersed in 110mL of deionized water and adjusted to a pH of 7-9 with 1.5g of sodium hydroxide. The obtained color paste was stirred and dispersed by a high-speed homogenizer, and 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 48 mm, and the color paste static stability was 52%.

[0042] Example 2

[0043] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 7.6g (0.02mol) of Pigment Red 202, 6.72g (0.06mol) of potassium tert-butoxide, and 120mL of N,N-dimethylformamide. Keep the temperature at 80-90°C and allow to react for 3 hours, until the reaction solution turns completely blue. Then, add 0.23g (0.00049mol) of dispersant NNO and stir for 2 hours to promote dispersion of the pigment particles. Then, slowly add 5.67g (0.06mol) of chloroacetic acid and continue the reaction at 80-90°C for 8 hours. After the reaction is complete, add 60mL of deionized water to wash the mixture to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the resulting filter cake in 110mL of deionized water and adjust the pH to 7-9 with 1.5g of sodium hydroxide. The obtained color paste was stirred and dispersed by a high-speed homogenizer, and 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 30 mm, and the color paste static stability was 70%.

[0044] Example 3

[0045] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 13.6g (0.04mol) of Pigment Red 122, 8.96g (0.08mol) of potassium tert-butoxide, and 180mL of N,N-dimethylformamide. Keep the temperature at 90-100°C and allow to react for 5 hours, until the reaction solution turns completely blue. Then, add 0.54g (0.0019mol) of sodium lauryl sulfate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 11.34g (0.12mol) of chloroacetic acid and continue the reaction at 90-100°C for 10 hours. After the reaction is complete, wash with 100mL of deionized water to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the resulting filter cake in 220mL of deionized water and adjust the pH to 7-9 with 3g of sodium hydroxide. The obtained color paste was stirred and dispersed by a high-speed homogenizer, and 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 16 mm, the color paste static stability was 84%, and the absolute value of the color paste Zeta potential was measured to be 30.6 mv.

[0046] Example 4

[0047] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 13.6g (0.04mol) of Pigment Red 122, 13.46g (0.12mol) of potassium tert-butoxide, and 180mL of N,N-dimethylformamide. Keep the temperature at 90-100°C and allow to react for 5 hours until the reaction solution turns completely blue. Then, add 0.54g (0.0019mol) of sodium lauryl sulfate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 11.34g (0.12mol) of chloroacetic acid and allow the reaction to continue at 90-100°C for 10 hours. After the reaction is complete, wash with 100mL of deionized water to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the filter cake in 220mL of deionized water and adjust the pH to 7-9 with 3g of sodium hydroxide. Circulate the resulting pigment paste through a pump to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 12 mm, the color paste static stability was 88%, and the absolute value of the color paste Zeta potential was measured to be 32.7 mv.

[0048] Example 5

[0049] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 13.6g (0.04mol) of Pigment Red 122, 13.46g (0.12mol) of potassium tert-butoxide, and 180mL of N,N-dimethylformamide. Keep the temperature at 90-100°C and allow to react for 5 hours until the reaction solution turns completely blue. Then, add 0.54g (0.0019mol) of sodium lauryl sulfate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 15.12g (0.16mol) of chloroacetic acid and continue the reaction at 90-100°C for 10 hours. After the reaction is complete, wash with 100mL of deionized water to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the filter cake in 220mL of deionized water and adjust the pH to 7-9 with 3g of sodium hydroxide. The resulting color paste is dispersed in a high-speed homogenizer to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 9 mm, the color paste static stability was 91%, and the absolute value of the color paste Zeta potential was measured to be 34.8 mv.

[0050] Example 6

[0051] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 7.6g (0.02mol) of Pigment Red 202, 4.08g (0.06mol) of sodium ethoxide, and 120mL of N,N-dimethylformamide. Keep the temperature at 100-110°C and allow to react for 6 hours until the reaction solution turns completely blue. Then, add 0.19g (0.00055mol) of sodium dodecylbenzenesulfonate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 7.56g (0.08mol) of chloroacetic acid and continue the reaction at 100-110°C for 12 hours. After the reaction is complete, add 60mL of deionized water to wash the mixture to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the resulting filter cake in 110mL of deionized water and adjust the pH to 7-9 with 1.5g of sodium hydroxide. The resulting color paste is dispersed in a high-speed homogenizer to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 36 mm, and the color paste static stability was 64%.

[0052] Example 7

[0053] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 12.5g (0.04mol) of Pigment Violet 19, 13.44g (0.12mol) of potassium tert-butoxide, and 180mL of N,N-dimethylformamide. Keep the temperature at 95-105°C and allow to react for 6 hours, until the reaction solution turns completely blue. Then, add 0.4g (0.00081mol) of dispersant NNO and stir for 2 hours to promote pigment particle dispersion. Then, slowly add 15.12g (0.16mol) of chloroacetic acid and allow the reaction to continue at 110-120°C for 12 hours. After the reaction is complete, wash with 120mL of deionized water to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the filter cake in 220mL of deionized water and adjust the pH to 7-9 with 3g of sodium hydroxide. The resulting color paste is dispersed in a high-speed homogenizer to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 12 mm, the color paste static stability was 88%, and the absolute value of the color paste Zeta potential was measured to be 32.8 mv.

[0054] Example 8

[0055] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 6.8g (0.02mol) of Pigment Red 122, 5.61g (0.05mol) of potassium tert-butoxide, and 120mL of N,N-dimethylformamide. Keep the temperature at 100-110°C and allow to react for 6 hours until the reaction solution turns completely blue. Then, add 0.22g (0.00076mol) of sodium lauryl sulfate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 7.56g (0.08mol) of chloroacetic acid and continue the reaction at 110-120°C for 12 hours. After the reaction is complete, wash with 60mL of deionized water to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the filter cake in 110mL of deionized water and adjust the pH to 7-9 with 1.5g of sodium hydroxide. The resulting color paste is dispersed in a high-speed homogenizer to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 6 mm, the color paste static stability was 94%, and the absolute value of the color paste Zeta potential was measured to be 35.6 mv.

[0056] Example 9

[0057] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 6.8g (0.02mol) of Pigment Red 122, 6.72g (0.06mol) of potassium tert-butoxide, and 120mL of N,N-dimethylformamide. Keep the temperature at 100-110°C and allow to react for 6 hours until the reaction solution turns completely blue. Then, add 0.22g (0.00076mol) of sodium lauryl sulfate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 7.56g (0.08mol) of chloroacetic acid and continue the reaction at 110-120°C for 12 hours. After the reaction is complete, add 60mL of deionized water to wash the mixture to remove impurities and residual solvent, then filter the mixture to obtain a filter cake. Disperse the filter cake in 110mL of deionized water and adjust the pH to 7-9 with 1.5g of sodium hydroxide. The resulting color paste is dispersed in a high-speed homogenizer to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 4 mm, the color paste static stability was 96%, and the absolute value of the color paste zeta potential was measured to be 36.2 mv.

[0058] Example 10

[0059] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 6.8g (0.02mol) of Pigment Red 122, 6.72g (0.06mol) of potassium tert-butoxide, and 120mL of N,N-dimethylformamide. Keep the temperature at 100-110°C and allow to react for 6 hours until the reaction solution turns completely blue. Then, add 0.22g (0.00076mol) of sodium lauryl sulfate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 9.45g (0.10mol) of chloroacetic acid and continue the reaction at 110-120°C for 12 hours. After the reaction is complete, add 60mL of deionized water to wash the mixture to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the filter cake in 110mL of deionized water and adjust the pH to 7-9 with 1.5g of sodium hydroxide. Circulate the resulting pigment paste through a pump to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 3 mm, the color paste static stability was 97%, and the absolute value of the color paste Zeta potential was measured to be 36.6 mv.

[0060] Example 11

[0061] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, 6.8g (0.02mol) of Pigment Red 122, 0.22g (0.00076mol) of sodium lauryl sulfate, and 120mL of N,N-dimethylformamide were added sequentially and stirred for dispersion. Due to the lack of a hydrogen stripping agent, the dispersion was found to be uneven. 7.56g (0.08mol) of chloroacetic acid was then slowly added, and the reaction was maintained at 110-120°C for 12 hours. After the reaction, 60mL of deionized water was added for washing to remove impurities and residual solvent, and the filter cake was filtered. The resulting filter cake was added to 110mL of deionized water and stirred for dispersion, but the dispersion was poor. After adjusting the pH to 7-9 with 1.5g of sodium hydroxide, the mixture was dispersed in a high-speed homogenizer to obtain a uniformly dispersed pigment paste. A 15mL sample of the prepared paste was placed in a test tube and allowed to stand for 24 hours. The sedimentation height of the paste was 34mm, and the static stability of the paste was 66%.

[0062] Example 12

[0063] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 6.8g (0.02mol) of Pigment Red 122, 6.72g (0.06mol) of potassium tert-butoxide, and 120mL of N,N-dimethylformamide. Keep the temperature at 100-110°C and allow to react for 6 hours until the reaction solution turns completely blue. Then, add 0.20g (0.00058mol) of dispersant NNO and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 9.45g (0.10mol) of chloroacetic acid and continue the reaction at 110-120°C for 12 hours. After the reaction is complete, add 60mL of deionized water to wash the mixture to remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the filter cake in 110mL of deionized water and adjust the pH to 7-9 with 1.5g of sodium hydroxide. Circulate the resulting pigment paste through a pump to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 11 mm, the color paste static stability was 89%, and the absolute value of the color paste Zeta potential was measured to be 33.2 mv.

[0064] Example 13

[0065] To a 250mL four-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel, add 6.8g (0.02mol) of Pigment Red 122, 6.72g (0.06mol) of potassium tert-butoxide, and 120mL of N,N-dimethylformamide. Keep the temperature at 100-110°C and allow to react for 6 hours until the reaction solution turns completely blue. Then, add 0.22g (0.00076mol) of sodium lauryl sulfate and stir for 3 hours to promote pigment particle dispersion. Then, slowly add 11.12g (0.08mol) of bromoacetic acid and continue the reaction at 110-120°C for 12 hours. After the reaction is complete, add 60mL of deionized water to wash and remove impurities and residual solvent, then filter to obtain a filter cake. Disperse the filter cake in 110mL of deionized water and adjust the pH to 7-9 with 1.5g of sodium hydroxide. Circulate the resulting pigment paste through a pump to obtain a uniformly dispersed pigment paste. 15 mL of the prepared color paste sample was placed in a test tube. After standing for 24 hours, the color paste sedimentation height was 4 mm, the color paste static stability was 96%, and the absolute value of the color paste Zeta potential was measured to be 36.4 mv.

Claims

1. A method for preparing a quinacridone pigment water-based paste, characterized in that: The preparation method comprises the following steps: (1) In anhydrous solvents, quinacridone pigments react with hydrogen extraction reagents to generate negative charges on the pigment surface, promoting pigment dispersion; The structure of quinacridone pigments is shown in Formula 1: ， Formula 1 Wherein, R represents one of a hydrogen atom, a methyl group, and a chlorine atom; (2) Add anionic surfactant to promote pigment dispersion and further extract hydrogen; (3) Add haloacetic acid to react and obtain pigment molecules with hydrophilic groups: ， Wherein, R represents one of a hydrogen atom, a methyl group, and a chlorine atom; (4) The reaction solution from step (3) is filtered to remove the solvent and washed with water to remove inorganic and organic residual substances; (5) Add water to the solid obtained in step (4), stir evenly, and add alkaline substances to adjust the pH of the pigment paste to 7-9; (6) The color paste obtained in step (5) is fully dispersed to obtain a uniformly dispersed water-based pigment color paste.

2. The method for preparing the aqueous quinacridone pigment paste according to claim 1, wherein: In step (1), the hydrogenation reagent is one or a mixture of sodium ethoxide, potassium ethoxide, potassium tert-butoxide, and sodium tert-butoxide; and the molar ratio of the quinacridone pigment to the hydrogenation reagent is 1:2.5 to 1:3.

5.

3. The method for preparing the aqueous quinacridone pigment paste according to claim 1, wherein: In step (1), the solvent is one or a mixture of benzene, toluene, xylene, and N,N-dimethylformamide; the reaction temperature is 70-120° C., and the reaction time is 2-8 h.

4. The method for preparing a quinacridone pigment aqueous paste according to claim 1, wherein: The anionic surfactant added in step (2) is a mixture of one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and dispersant NNO; the amount of the anionic surfactant added is 1 / 15-1 / 35 of the pigment mass.

5. The method for preparing the aqueous quinacridone pigment paste according to claim 1, wherein: In step (3), the halogenated acetic acid includes chloroacetic acid and bromoacetic acid; the molar ratio of the quinacridone pigment to the halogenated acetic acid is 1:2 to 1:6, the reaction temperature is 70 to 130° C., and the reaction time is 5 to 15 h.

6. The method for preparing a quinacridone pigment aqueous paste according to claim 1, wherein: In step (5), the alkaline substance is one of sodium hydroxide, potassium hydroxide and ammonia water.

7. The method for preparing a quinacridone pigment aqueous paste according to claim 1, characterized in that: In step (6), the dispersion is carried out by one or a combination of rapid stirring, pump circulation, high-speed homogenizer, ultrasonic dispersion, high-pressure microfluidization, and sand mill.

8. A quinacridone pigment aqueous paste prepared according to the method according to any one of claims 1 to 7.

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