Preparation method of quinacridone pigment

Abstract

The invention belongs to the technical field of pigment preparation, and particularly relates to a preparation method of quinacridone series pigments. The preparation method comprises the following steps: firstly, adding polyphosphoric acid into a screw extrusion kneading machine, heating to 130-180 DEG C under the protection of nitrogen, then adding a dispersing agent and a pigment intermediate, immediately cyclizing after the intermediate is in contact with the polyphosphoric acid, and finally, carrying out screw extrusion discharging and treatment to obtain the quinacridone series pigment. The kneading machine with efficient stirring capacity is adopted, and a small amount of dispersing agent is added in the early stage of kneading and before the intermediate is added, so that the fluidity of a cyclization product in polyphosphoric acid is improved, the cyclization condensation efficiency is improved, the cyclization condensation reaction can be completed by using a small amount of polyphosphoric acid, and the production cost is reduced. And when the synthesized pigment is used in paint or plastic, the pigment has excellent tinting strength and good dispersion performance.

Description

Technical Field

[0001] The invention belongs to the technical field of pigment preparation, and particularly relates to a method for preparing a quinacridone pigment. Background Art

[0002] The industrial preparation of quinacridone can be divided into two categories according to the dehydration solvent used: the Dowson oil method and the polyphosphoric acid method (see Chemical Review Chem. Rev. 1967, 67, 1, 1–18). The Dowson oil method is a method in which DuPont uses Dowson oil as a solvent and heats the intermediate 2,5-diphenylaminodihydroterephthalic acid to 250-260°C at high temperature to dehydrate and cyclize to form dihydroquinacridone, which can be further oxidized to form quinacridone. Since the Dowson method can only synthesize unsubstituted quinacridone, it cannot cyclize to prepare dimethylquinacridone and other substituted quinacridones. Therefore, the polyphosphoric acid method has become the main method for preparing quinacridone in China.

[0003] U.S. Patents US3342823 and US6241814 both use a method for preparing quinacridone using polyphosphoric acid. The intermediate 2,5-diphenylamino terephthalic acid or 2,5-di(4-methylanilino)terephthalic acid is directly added to polyphosphoric acid, dehydrated at high temperature, and cyclized to generate quinacridone (Pigment Violet 19) or 2.9-dimethylquinacridone (Pigment Red 122), respectively. The use of polyphosphoric acid has a dual purpose. One is that polyphosphoric acid serves as a solvent to help stir and disperse the reactants; the other is to utilize the dehydration ability of polyphosphoric acid to dehydrate and cyclize the intermediate. Therefore, the weight of polyphosphoric acid used and its concentration are very important. The concentration of polyphosphoric acid must be high enough to fully absorb the water released from the cyclization of 2,5-diphenylamino terephthalic acid or 2,5-di(4-methylanilino)terephthalic acid. In addition, the released water will immediately dilute the polyphosphoric acid. If the polyphosphoric acid is diluted to a concentration close to 100%, the ability of dehydration cyclization will quickly disappear. In addition, polyphosphoric acid is a very viscous substance, and its fluidity is inversely proportional to the concentration. Therefore, high-concentration polyphosphoric acid can hardly be stirred at room temperature and must be heated to above 80-90°C to provide appropriate fluidity and thus act as a solvent. The more polyphosphoric acid there is, the smoother the flow of the intermediate in the polyphosphoric acid, which can make the reactants more fully stirred and more evenly dispersed. The synthesized quinacridone pigment will be dissolved in the polyphosphoric acid in the form of phosphate. If the concentration of polyphosphoric acid is too low or the mass is too small, the water precipitated by cyclization will not only cause the polyphosphoric acid concentration to be lower than 100%, but also cause the quinacridone phosphate to hydrolyze, the pigment particles to precipitate prematurely, and the product particle size to be different. After the cyclization is completed, the resulting quinacridone or 2,9-dimethylquinacridone pigment is still dissolved in the polyphosphoric acid and can be poured into water or a solvent to separate the pigment by precipitation. This is the crude product.

[0004] Taking 2,9-dimethylquinacridone as an example, the traditional synthesis process is to slowly add 1 part of the intermediate 2,5-di(4-methylanilino)terephthalic acid to 3 to 7 parts of 110% to 118% polyphosphoric acid at a high temperature of 90-120° C. through a high-pressure reaction device. After the mixture is heated at 100-140° C. for 1 to 4 hours, the viscous reactant is cooled to about 100° C., and then the polyphosphoric acid is diluted as needed to reduce the viscosity, and finally the diluted reactant is poured into 8-20 parts of a solvent (such as water or methanol), heated to boiling point, and kept warm for 1-3 hours before filtering and separating. Because when the ratio of polyphosphoric acid to the intermediate is reduced to less than 2, the viscosity of the reactant after dehydration reaches the extreme, which cannot be handled by general stirring, so the general reactor must add 3 times or more than 3 times the polyphosphoric acid of the intermediate, but this not only increases the cost of raw materials, but also increases the cost of environmental protection treatment (neutralization of phosphoric acid and recovery). Summary of the invention

[0005] The invention provides a method for preparing a quinacridone pigment. By utilizing the efficient stirring capacity of a kneader, a cyclization condensation reaction can be completed using a small amount of polyphosphoric acid, thereby greatly reducing the production cost. The pigment synthesized by the invention is used in coatings or plastics and has good dispersibility and high tinting strength.

[0006] The preparation method of the quinacridone pigment of the present invention comprises the following steps: adding polyphosphoric acid, a dispersant and a pigment intermediate into a screw extruder kneader for stirring and reaction.

[0007] The specific steps are:

[0008] (1) Add polyphosphoric acid into a kneader and heat to 130-180° C.;

[0009] (2) adding a small amount of dispersant and pigment intermediate to a kneader, stirring and reacting at 130-180° C. for 1-3 hours, with a mass ratio of polyphosphoric acid to pigment intermediate = 1-2.5:1;

[0010] (3) The reaction product is discharged through a screw extruder and added into rapidly stirred water or low-boiling alcohol, and treated at 90-130° C. for 1-3 hours to obtain a quinacridone pigment.

[0011] The quinacridone pigment is quinacridone or 2,9-dimethylquinacridone.

[0012] The intermediate is 2,5-diphenylamino terephthalic acid or 2,5-di(4-methylanilino)terephthalic acid.

[0013] The kneader is a sigma kneader with screw extrusion.

[0014] The concentration of the polyphosphoric acid is 108-120%.

[0015] The low boiling point alcohol is at least one of methanol, ethanol, propanol, butanol, isopropanol and isobutanol.

[0016] Preferably, nitrogen protection is used in steps (1) and (2) of the present invention to prevent the polyphosphoric acid from absorbing moisture, thereby preventing the concentration of the polyphosphoric acid from decreasing due to moisture absorption, leading to hydrolysis of quinacridone phosphate, premature precipitation of pigment particles, and uneven product particle sizes.

[0017] Polyphosphoric acid is a very viscous substance, and its fluidity is inversely proportional to its concentration. Therefore, high-concentration polyphosphoric acid can hardly be stirred at room temperature and must be heated to above 80-90°C to provide appropriate fluidity and thus act as a solvent. If the temperature is raised after adding polyphosphoric acid and the intermediate, it is not conducive to the mixing of the intermediate.

[0018] The dispersant has a certain dispersing effect, which can reduce the fluidity of the cyclized product in polyphosphoric acid, and is conducive to improving the efficiency of cyclization condensation. In step (2), before adding the pigment intermediate, the dispersant is first added to the kneader, and the mass ratio of the dispersant to the pigment intermediate is 0.01-0.1:1; because the dispersant helps to reduce the fluidity of the cyclized product in polyphosphoric acid and improve the efficiency of cyclization condensation, the technical indicators such as the coloring strength and weather resistance of the product can be improved in this way. The dispersant is quinacridone sulfonic acid or quinacridone sulfonate. For example, the quinacridone sulfonate can be quinacridone aluminum sulfonate.

[0019] The kneader is a special stirring and mixing equipment. It can be divided into four types according to the different stirring paddles: fishtail kneader, simple kneader, cutting kneader, and sigma type machine. Among them, the sigma type kneader has two Σ-shaped blades and adopts a parallel tangential differential arrangement, that is, one agitator has a fast speed and the other has a slow speed, which produces high shear force. The material passes repeatedly between the two rollers to complete the mixing. The inventor found that in the preparation process of quinacridone pigments, the viscosity of polyphosphoric acid is relatively high. If a particularly strong kneading force can be provided for the mixing of the intermediate and polyphosphoric acid and the cyclization condensation, it is very helpful for the cyclization condensation reaction. Based on this, the inventor used a sigma type kneader to replace the traditional reactor and achieved excellent results.

[0020] The material obtained by the reaction (quinacridone phosphate or 2,9-dimethylquinacridone phosphate) is discharged by screw extrusion, added to water or low-boiling alcohol with a stirring device, and the obtained slurry is fully stirred and subjected to high temperature treatment. At this time, the material is hydrolyzed or alcoholyzed, and then filtered and washed to obtain an excellent pigment product. The amount of water or alcohol used is about 8 to 20 times that of the material. Since the hydrolysis or alcoholysis of quinacridone phosphate or 2,9-dimethylquinacridone phosphate is an exothermic reaction, the speed needs to be controlled during the discharge process to control the temperature during the reaction process to be constant and ensure uniform distribution of the pigment particle size. The hydrolysis or alcoholysis of the material can be quickly completed through high temperature and high pressure. Sometimes a preheated solvent can also be used to accelerate the decomposition of phosphates and promote the growth of pigment particle size.

[0021] The present invention uses a kneading machine with high-efficiency stirring capacity for the first time in the cyclization condensation reaction preparation process of the pigment. Combined with the reaction conditions of the process, the cyclization condensation reaction can be completed by using a small amount of polyphosphoric acid, which greatly reduces the production cost. In addition, a small amount of dispersant is added in the early stage of kneading, which helps to reduce the fluidity of the cyclization product in the polyphosphoric acid and improve the efficiency of the cyclization condensation. The pigment synthesized by the present invention is used in coatings or plastics and has good dispersibility and high coloring strength. DETAILED DESCRIPTION

[0022] Example 1

[0023] (1) 190.4 kg of polyphosphoric acid (concentration 117.7%) was added to a sigma screw extruder kneader and heated to 130° C. under nitrogen protection;

[0024] (2) adding 95.6 kg of 2,5-di(4-methylanilino)terephthalic acid to a kneader and stirring the mixture at 135-145° C. for 1 hour;

[0025] (3) The reaction material was discharged into 4500 kg of rapidly stirred water (room temperature) through screw extrusion, fully stirred, heated to 90-95° C., kept warm for 1 hour, cooled, filtered, washed with water, and dried to obtain 2,9-dimethylquinacridone pigment with a yield of 98% and a purity of 97.3%.

[0026] Example 2

[0027] (1) 167.4 kg of polyphosphoric acid (concentration 117.7%) was added to a sigma screw extruder kneader and heated to 130° C. under nitrogen protection;

[0028] (2) adding 126.6 kg of 2,5-diphenylamino terephthalic acid to a kneader and stirring the mixture at 135-145° C. for 1 hour;

[0029] (3) The reaction material was discharged into 4500 kg of rapidly stirred water (room temperature) by screw extrusion, fully stirred, heated to 90-95° C., kept warm for 1 hour, cooled, filtered, washed with water, and dried to obtain quinacridone with a yield of 97.8% and a purity of 96.2%.

[0030] Example 3

[0031] (1) 156.9 kg of polyphosphoric acid (concentration 117.7%) was added to a sigma screw extruder kneader and heated to 130° C. under nitrogen protection;

[0032] (2) adding 1.5 kg of aluminum quinacridone sulfonate to a kneader, mixing for 10 minutes, adding 130 kg of 2,5-di(p-toluidine)terephthalic acid, stirring and reacting at 135-145° C. for 1 hour;

[0033] (3) The reaction material was discharged into 4500 kg of rapidly stirred water (room temperature) by screw extrusion, fully stirred, heated to 90-95° C., kept warm for 1 hour, cooled, filtered, washed with water, and dried to obtain 2,9-dimethylquinacridone pigment with a yield of 96.4% and a purity of 97.8%.

[0034] Example 4

[0035] (1) 145 kg of polyphosphoric acid (concentration 117.7%) was added to a sigma screw extruder kneader and heated to 140° C. under nitrogen protection;

[0036] (2) adding 7 kg of quinacridone sulfonic acid to a kneader, mixing for 10 minutes, adding 145 kg of 2,5-di(4-methylanilino)terephthalic acid, stirring and reacting at 140-145° C. for 1 hour;

[0037] (3) The reaction material is discharged into an autoclave through screw extrusion, and the autoclave contains 3500 kg of 70% methanol preheated to 30° C. After high-speed stirring for 1 hour, the temperature is raised to 130° C. and kept warm for 3 hours. The product is cooled, filtered, and washed with water to obtain 2,9-dimethylquinacridone pigment with a yield of 96% and a purity of 95.9%.

[0038] Example 5

[0039] (1) 145 kg of polyphosphoric acid (concentration 117.7%) was added to a sigma screw extruder kneader and heated to 140° C. under nitrogen protection;

[0040] (2) adding 2 kg of quinacridone aluminum sulfonate to a kneader, mixing for 10 minutes, adding 145 kg of 2,5-di(4-methylanilino)terephthalic acid, stirring and reacting at 140-145° C. for 1 hour;

[0041] (3) The reaction material is discharged into an autoclave through screw extrusion, and the autoclave contains 3500 kg of 70% methanol preheated to 30° C. After high-speed stirring for 1 hour, the temperature is raised to 130° C. and kept warm for 3 hours. The product is cooled, filtered, and washed with water to obtain 2,9-dimethylquinacridone pigment with a yield of 98% and a purity of 98.9%.

[0042] Example 6

[0043] (1) 190.4 kg of polyphosphoric acid (concentration 117.7%) was added to a sigma screw extruder kneader and heated to 130° C. under nitrogen protection;

[0044] (2) adding 4.5 kg of quinacridone aluminum sulfonate to a kneader, mixing for 10 minutes, adding 95.6 kg of 2,5-diphenylamino terephthalic acid, stirring and reacting at 135-145° C. for 1 hour;

[0045] (3) The reaction product was discharged into an autoclave through screw extrusion. The autoclave contained 6000 kg of 70% methanol. After high-speed stirring for 1 hour, the temperature was raised to 130° C. and kept warm for 3 hours. The product was cooled, filtered, and washed with water to obtain 2,9-dimethylquinacridone pigment with a yield of 97% and a purity of 98.9%.

[0046] Example 7

[0047] (1) 190.4 kg of polyphosphoric acid (concentration 117.7%) was added to a sigma screw extruder kneader and heated to 130° C.;

[0048] (2) adding 4.5 kg of quinacridone aluminum sulfonate to a kneader, mixing for 10 minutes, adding 95.6 kg of 2,5-diphenylamino terephthalic acid, stirring and reacting at 135-145° C. for 1 hour;

[0049] (3) The reaction product was discharged into an autoclave through screw extrusion. The autoclave contained 6000 kg of 70% methanol. After high-speed stirring for 1 hour, the temperature was raised to 130° C. and kept warm for 3 hours. The product was cooled, filtered, and washed with water to obtain 2,9-dimethylquinacridone pigment with a yield of 97% and a purity of 98.9%.

[0050] The products obtained in Examples 1, 3-5 and a standard sample of CI Pigment Red 122 (commercially available), and the products obtained in Examples 2, 6, and 7 and a standard sample of CI Pigment Violet 19 (commercially available) were tested in polyethylene resin, and the results are as follows:

[0051]

[0052]

[0053] The synthesis method of the dispersant in the embodiment is as follows:

[0054] In a 500mL round-bottom beaker, add 645g of 98% concentrated sulfuric acid, heat to 20°C, and stir for 10 minutes. Slowly add 65g of crude quinacridone powder, control the temperature below 35°C, and stir for 15 minutes. Heat to 60°C, keep warm for 5 hours, cool to 30°C, slowly pour into a glass beaker containing 3000mL of water, control the temperature below 50°C, stir for 30 minutes, filter, and wash with 300mL of water to obtain a filter cake of quinacridone sulfonic acid.

[0055] The quinacridone sulfonic acid filter cake was added to 3800 mL of water, stirred at high speed to form a slurry, heated to 50°C, added with 750 g of aluminum sulfate, stirred for 1 hour, heated to 93°C, kept warm for 2 hours, cooled to 60°C, filtered, and washed with 50°C hot water until the conductivity was less than 300 μs·cm -1 , drying the quinacridone aluminum sulfonate filter cake at 80° C. and crushing it to obtain quinacridone aluminum sulfonate.

[0056] As can be seen from the above table, the pigment synthesized by the present invention is used in coatings or plastics, and has good dispersibility and higher tinting strength compared with commercial standard samples. Example 7 also illustrates that adding a dispersant can still synthesize a useful quinacridone pigment under non-nitrogen protection conditions after adding a dispersant compared with the traditional method.

Claims

1. A method for preparing a quinacridone pigment, characterized in that: Adding polyphosphoric acid, dispersant and pigment intermediate into a screw extruder kneader for stirring reaction specifically comprises the following steps: (1) Add polyphosphoric acid into a kneader and heat to 130-180° C.; (2) adding a small amount of dispersant and pigment intermediate to a kneader, stirring and reacting at 130-180° C. for 1-3 hours, with a mass ratio of polyphosphoric acid to pigment intermediate = 1-2.5:1; (3) The reaction product is discharged through a screw extruder and added into rapidly stirred water or low-boiling alcohol, and treated at 90-130° C. for 1-3 hours to obtain a quinacridone pigment.

2. The method for preparing a quinacridone pigment according to claim 1, characterized in that: The quinacridone pigment is quinacridone or 2,9-dimethylquinacridone.

3. The method for preparing a quinacridone pigment according to claim 1, characterized in that: The pigment intermediate is at least one of 2,5-diphenylamino terephthalic acid and 2,5-di(4-methylanilino)terephthalic acid.

4. The method for preparing a quinacridone pigment according to claim 1, characterized in that: In step (2), before adding the pigment intermediate, a dispersant is first added to the kneader, and the mass ratio of dispersant:pigment intermediate is 0.01-0.1:

1.

5. The method for preparing quinacridone series pigments according to claim 4, characterized in that: The dispersant is quinacridone sulfonic acid or quinacridone sulfonate.

6. The method for preparing quinacridone pigments according to claim 1, characterized in that: The concentration of the polyphosphoric acid is 108-120%.

7. The method for preparing a quinacridone pigment according to claim 1, wherein the low-boiling alcohol is at least one of methanol, ethanol, propanol, butanol, isopropanol and isobutanol.

8. The method for preparing a quinacridone pigment according to claim 1, characterized in that: The kneading machine includes but is not limited to an extrusion-type sigma kneading machine having a kneading structure such as a screw.

9. The method for preparing a quinacridone pigment according to claim 1, characterized in that: Step (1) and step (2) are carried out under nitrogen protection.

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