Preparation method of high-covering yellow-phase quinacridone pigment

Abstract

The invention provides a preparation method of a high-covering yellow-phase quinacridone pigment. The preparation method comprises the following steps: step 1, using 116-118% of polyphosphoric acid; step 2, adding 2, 5-diphenylamino-3, 6-dihydroterephthalic acid dimethyl ester at the temperature of 90 DEG C to 135 DEG C; step 3, keeping the temperature at 120-135 DEG C for 1-4 hours, cooling to 120 DEG C, and diluting the polyphosphoric acid to 110-112%; step 4, pouring the polyphosphoric acid reactant into water, filtering, and washing with water to obtain 6, 13-dihydroquinacridone; step 5, adding the dried and crushed 6, 13-dihydroquinacridone into a solvent for pulping, and the concentration of the solvent must be greater than 50%; step 6, adding a sodium hydroxide solution, adjusting the pH value to be greater than 11, heating to 80-90 DEG C, and keeping the temperature for 30-60 minutes; step 7, after cooling, adding an oxidizing agent and a catalyst, determining that the pH value is greater than 11, heating to 100-110 DEG C, preserving heat for 2 hours, cooling and filtering to obtain the yellow-phase quinacridone with high coverage; the quinacridone obtained in the invention has excellent weather resistance and covering power, and can be used in printing pigments, water-based paint compositions, varnish, polyurethane varnish, plastic dispersions and spinning solutions; the obtained quinacridone is applied to synthesis and natural polymers, and the quinacridone obtained in the invention can be used in natural, recycled and synthetic fiber materials, and can also be mixed with gas organic and inorganic pigments for use.

Description

Technical Field

[0001] The invention relates to the technical field of pigment production, in particular to a method for preparing a high-hiding yellow-phase quinacridone pigment. Background Art

[0002] Traditionally, the method of synthesizing high-hiding, yellow-phase quinacridone can be divided into two categories according to the solvent used: one is to use an inert solvent such as Dawson oil, which is a mixture of 73% diphenyl ether and 27% biphenyl. It is a good heat-conducting liquid with a boiling point of 257 degrees. The intermediate 2,5-diphenylamino-3,6-dihydroterephthalate is added to Dawson oil and cyclized at high temperature to synthesize 6,13-dihydroquinacridone. The synthesized 6,13-dihydroquinacridone is further oxidized by adding sodium m-nitrobenzene sulfonate in methanol to generate the required quinacridone product. This method needs to be carried out at a high temperature of more than 250 degrees. However, the long-term use of high-temperature reactions, the load on equipment maintenance, and the recovery and reuse of solvents are also difficulties often faced in production. Another method involves cyclizing 2,5-diphenylamino-3,6-terephthalic acid in polyphosphoric acid, and then pouring the cyclized phosphate into water or alcohol for hydrolysis to directly synthesize quinacridone. However, the product obtained by this process has a fine particle size, a blue hue and high transparency compared to the product of the Dawson method, and cannot achieve the required pigment performance. Summary of the invention

[0003] The present invention provides a method for preparing a high hiding yellow phase quinacridone pigment, aiming to solve the problems raised by the above background technology.

[0004] The present invention is achieved by a method for preparing a high hiding yellow phase quinacridone pigment, comprising the following steps:

[0005] Step 1: Use 116%-118% polyphosphoric acid;

[0006] Step 2: Add 2,5-diphenylamino-3,6-dihydroterephthalate at 90-135 degrees;

[0007] Step 3: Keep warm at 120-135 degrees for 1-4 hours, cool to 120 degrees and dilute polyphosphoric acid to 110-112%;

[0008] Step 4: pour the polyphosphoric acid reactant into water, filter, and wash with water to obtain 6,13-dihydroquinacridone;

[0009] Step 5: Add the dried and crushed 6,13-dihydroquinacridone into a solvent for slurrying, and the solvent concentration must be greater than 50%;

[0010] Step 6: Add sodium hydroxide solution, adjust the pH value to greater than 11, heat to 80-90 degrees, and keep warm for 30-60 minutes;

[0011] Step 7: After cooling, add an oxidant and a catalyst, make sure the pH is greater than 11, heat to 100-110 degrees, keep warm for 2 hours, cool and filter to obtain a high-hiding yellow phase quinacridone.

[0012] Preferably, the concentration of the polyphosphoric acid is 116.5-117.5%.

[0013] Preferably, the ratio of the polyphosphoric acid to dimethyl 2,5-dianilino-3,6-dihydroterephthalate is 3:1 to 7:1.

[0014] Preferably, the solvent used for the oxidation reaction of dihydroquinacridone is an alcohol, including one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, and ethylene glycol.

[0015] Preferably, the concentration of the alcohol solvent must be greater than 50%.

[0016] Preferably, the oxidation reaction is heated twice. After adding sodium hydroxide for the first time, heating helps the product to be converted into β-type dihydroquinacridone. The oxidant and catalyst are added for the second time to promote the oxidation of the product.

[0017] Preferably, the oxidant required is air, oxygen or hydrogen peroxide, and the molar amount thereof added must be more than twice the molar amount of the dihydroquinacridone.

[0018] Preferably, the required oxidant gas is finely distributed using a gas-liquid mixer.

[0019] Preferably, the catalyst is one of anthraquinone, monochloroanthraquinone, dichloroanthraquinone, 2-anthraquinone sulfonic acid sodium salt, 2,6-anthraquinone disulfonic acid disodium salt, 2-ethylanthraquinone, and 2-bromoanthraquinone.

[0020] Preferably, during the oxidation reaction, the acid value of the reaction solution must be maintained at greater than 11.

[0021] Due to the adoption of the above scheme, the beneficial effects of the present invention are: using 2,5-diphenylamino-3,6-dihydroterephthalic acid dimethyl ester intermediate, it is first closed in a high concentration of polyphosphoric acid, and the closed-ring reactant is diluted with water to separate the crude 6,12-dihydroquinacridone. Then the crude product is re-slurried in an alcohol solvent in an alcohol-containing solvent, a large amount of sodium hydroxide is added, and the slurry is heated to reflux in the solvent. Then the sample is cooled and an oxidant, a catalyst and a sufficient amount of alkali are added to carry out an oxidation reaction, and finally a high hiding power (gamma type) yellow phase quinacridone pigment is produced; the quinacridone obtained in the present invention is very excellent in weather resistance and hiding, and can be used in printing colorants, water-based coating compositions, varnishes, polyurethane varnishes, plastic dispersions, and spinning solutions. The quinacridone obtained in the present invention can be applied to synthetic and natural polymers. These polymers include thermoplastic resins such as polyvinyl chloride, polystyrene, polyethylene, polyesters, phenolic plastics, amino plastics and rubbers. Furthermore, the quinacridone obtained in the present invention can be used in natural, recycled and synthetic fiber materials, and can also be mixed with gaseous organic and inorganic pigments. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] A method for preparing a high hiding yellow phase quinacridone pigment comprises the following steps:

[0024] Step 1: Use 116%-118% polyphosphoric acid;

[0025] Step 2: Add 2,5-diphenylamino-3,6-dihydroterephthalate at 90-135 degrees;

[0026] Step 3: Keep warm at 120-135 degrees for 1-4 hours, cool to 120 degrees and dilute polyphosphoric acid to 110-112%;

[0027] Step 4: pour the polyphosphoric acid reactant into water, filter, and wash with water to obtain 6,13-dihydroquinacridone;

[0028] Step 5: Add the dried and crushed 6,13-dihydroquinacridone into a solvent for slurrying, and the solvent concentration must be greater than 50%;

[0029] Step 6: Add sodium hydroxide solution, adjust the pH value to greater than 11, heat to 80-90 degrees, and keep warm for 30-60 minutes;

[0030] Step 7: After cooling, add an oxidant and a catalyst, make sure the pH is greater than 11, heat to 100-110 degrees, keep warm for 2 hours, cool and filter to obtain a high-hiding yellow phase quinacridone.

[0031] The concentration of the polyphosphoric acid is selected to be 116.5-117.5%; the ratio of the polyphosphoric acid to 2,5-diphenylamino-3,6-dihydroterephthalate is 3:1 to 7:1; the solvent used for the oxidation reaction of dihydroquinacridone is an alcohol, including one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, and ethylene glycol; the concentration of the alcohol solvent must be greater than 50%; the oxidation reaction is heated twice, and after the first addition of sodium hydroxide, the heating helps the product to be converted into β-type dihydroquinacridone Ketone, adding an oxidant and a catalyst for the second time to promote product oxidation; the required oxidant is air, oxygen or hydrogen peroxide, and the molar amount thereof added must be more than twice the molar amount of dihydroquinacridone; the required oxidant gas is finely distributed using a gas-liquid mixer; the catalyst is one of anthraquinone, monochloroanthraquinone, dichloroanthraquinone, 2-anthraquinone sulfonic acid sodium salt, 2,6-anthraquinone disulfonic acid disodium salt, 2-ethylanthraquinone, and 2-bromoanthraquinone; during the oxidation reaction, the acid value of the reaction solution must be maintained at greater than 11.

[0032] The present invention relates to a method for preparing a high hiding (gamma type) yellow phase quinacridone pigment, which comprises: (1) using 116.0% to 118.0% polyphosphoric acid, preferably 116.5% to 117.5%, (2) adding 2,5-diphenylamino-3,6-dihydroterephthalic acid dimethyl ester at 90 to 135 degrees, (3) keeping the temperature at 120 to 135 degrees for 1 to 4 hours, (4) cooling to 120 degrees, diluting the polyphosphoric acid concentration with water or dilute phosphoric acid to 110 to 112%, (5) pouring the polyphosphoric acid reactant into water for hydrolysis, filtering, and washing with water to obtain 6 , 13-dihydroquinacridone (6) Add the dried and crushed 6,13-dihydroquinacridone to a solvent for slurrying. The solvent concentration must be greater than 50%, preferably 50-65% (7) First neutralize with sodium hydroxide, then add a certain amount of sodium hydroxide to determine that the pH value is greater than 11, (8) Heat to reflux temperature and keep warm for 30-60 minutes (9) After cooling, add an oxidant and a catalyst to determine that the pH value is greater than 11 (10) Heat to 90-110 degrees, preferably 95-105 degrees, and keep warm for 2 hours (11) Cool and filter to obtain a high-covering yellow phase quinacridone.

[0033] The 2,5-diphenylamino-3,6-dihydroterephthalate intermediate used in the present invention can be prepared by dehydration condensation of 1 gram molecule of dimethyl succinylsuccinate and 2 gram molecules of aniline in methanol in the presence of a small amount of acetic acid through a conventional condensation reaction. The reaction is fast and simple. After the reaction, the slurry is filtered, the filter cake is washed with clean water, and then dried and crushed. In addition to using 2,5-diphenylamino-3,6-dihydroterephthalate, 2,5-diphenylamino-3,6-dihydroterephthalate diethyl can also be used as an intermediate. When performing a closed-loop reaction, if the intermediate is not completely dried and the moisture content exceeds 2.0%, not only will the concentration of polyphosphoric acid be changed when added, but it will also cause an exothermic reaction, causing the temperature to rise and cannot be controlled. The resulting pigment is very transparent, the hue is bluish, and the color strength is weak. Analysis proves that part of the dihydroquinacridone is not completely oxidized. Therefore, the moisture content of the intermediate must be strictly controlled below 2.0% in order to produce a product with the correct yellow phase and high hiding power.

[0034] The ring-closing reaction of 2,5-diphenylamino-3,6-dihydroterephthalate can be carried out in polyphosphoric acid or concentrated sulfuric acid, and polyphosphoric acid is commonly used. The temperature of the ring closure is between 90-135 degrees. Due to the high density of 2,5-diphenylamino-3,6-dihydroterephthalate, the dry powder is very loose. When added, it is often suspended on the surface of polyphosphoric acid and cannot be wetted and mixed into the acid. Once dissolved, a large amount of methanol released by the ring closure reacts with polyphosphoric acid, causing rapid heat release, which can easily cause the production temperature to get out of control. Therefore, the feeding temperature can be controlled between 90-130 degrees. After the feeding is completed, the ring closure reaction is basically completed. It is necessary to stir for another 1-4 hours, and then dilute the polyphosphoric acid with water or 75% phosphoric acid solution to 110-112%, and then pour it into water for hydrolysis. The purpose of dilution is to increase the fluidity of the reactants and facilitate the transfer of materials. After the slurry is filtered, 6,13-dihydroquinacridone is obtained. The obtained filter cake must be thoroughly washed with clean water until the pH is greater than 4. The initial concentration of polyphosphoric acid must be between 116-118%, preferably between 116.5% and 117.5%. If the concentration is too low, the oxidized product is transparent and bluish; if the concentration is too high, it will increase the cost without much change in quality. The ratio of polyphosphoric acid to 2,5-diphenylamino-3,6-dihydroterephthalate can be from 3:1 to 7:1. Using a large amount of polyphosphoric acid makes it easy to control the stirring during the reaction, but it is not cost-effective. Therefore, it is a common method to use 3 to 4 times the polyphosphoric acid for closed loop and use high temperature to feed.

[0035] The isolated 6,13-dihydroquinacridone filter cake has weak acidity and can be used directly without drying and crushing. However, the filter cake needs to be pulped with a solvent in an autoclave, and then a sodium hydroxide solution is added to adjust the pH value to above 11, and heated to reflux temperature, kept warm for 30-60 minutes, and then the temperature is lowered, an oxidant and a catalyst are added, and then heated to 90-120 degrees to ensure the synthesis of yellow phase gamma quinacridone. This is a two-step heating process, in which the acidic crude product is made into a slurry in a solvent, and then a small amount of sodium hydroxide is added to neutralize the slurry. Then a quantitative amount of sodium hydroxide is added, and the amount of sodium hydroxide used is about 0.45-0.66 times the amount of 6,13-dihydroquinacridone dry powder. Heat to reflux and keep warm for 30-60 minutes, which is to ensure that the synthesized 6,13-dihydroquinacridone can be converted into β-type in alkali, because only pure β-type dihydroquinacridone can be oxidized into the required gamma-type quinacridone. Stir and cool. The second step is to add oxidant and catalyst to the cooled slurry, and then reheat the sample to high temperature for final oxidation and crystallization. The solvent used in this method must be miscible with water, mainly alcohols, such as methanol, isopropanol, butanol, isobutanol, tert-butanol, ethylene glycol can be used, and the concentration of the solvent must be greater than 50%, preferably 55-65%. The amount of solvent used should be 6-10 times the amount of 6,13-dihydroquinacridone dry powder. The added alkaline solution, in addition to sodium hydroxide, can also use potassium hydroxide, lithium hydroxide, etc., the purpose of which is to adjust the pH value of the reaction solution to pH>11. When performing the second step of heating, it must also be confirmed that the pH value is greater than 11, which is conducive to the crystallization growth of the pigment under alkalinity. The oxidants are mainly air, oxygen, and hydrogen peroxide. When using gas, a common gas-liquid mixer can be used to help distribute the oxygen. In addition, the addition of a catalyst is necessary for complete oxidation. Commonly used catalysts include anthraquinone, monochloroanthraquinone, dichloroanthraquinone, 2-anthraquinone sulfonic acid sodium salt, 2,6-anthraquinone disulfonic acid disodium salt, 2-ethylanthraquinone, and 2-bromoanthraquinone. Sometimes inorganic molybdenum oxide, vanadium oxide, ferrous sulfate, nickel sulfate, etc. can also be added in moderation to assist the oxidation reaction. Anthraquinone catalysts and their derivatives are well known for their excellent redox ability in the chemical industry. Anthraquinone is widely used in the chemical industry, peroxide production, and pharmaceutical companies such as anti-cancer and anti-inflammatory. In addition, anthraquinone is the most abundant dye other than azo dyes. As one of the cheapest organic dyes, anthraquinone has developed very rapidly in the past few decades. Their addition amount is about 0.5-5% of the dry powder of 6,13-dihydroquinacridone. In particular, the presence of anthraquinone catalyst provides a more effective and complete oxidation reaction. The prepared samples also tend to turn yellow. When using anthraquinone derivative catalysts, the purity of the solvent alcohol must be maintained between 55-65% to ensure a more opaque, cleaner and less yellow final product.If sodium hydroxide and an oxidant are added at the same time and a one-step heating and pressurizing method is used, the synthesized quinacridone has high transparency and poor bright color, and cannot achieve the desired pigment properties. The oxidation reaction can be carried out simultaneously with the heating crystallization, or after the oxidation is completed, the crystallization can be heated to a higher temperature. It can be changed according to the characteristics of the solvent used.

[0036] In this embodiment, the control of rigorous reaction condition parameters can provide product stability and production repeatability. The polyphosphoric acid used is the main reagent for closed loop. Polyphosphoric acid is formed by heating and dehydrating condensation of phosphoric acid. It can also be obtained by adding phosphorus pentoxide to pure water and then heating and condensing. It is similar to concentrated sulfuric acid and is a good dehydrating agent. It is a colorless and transparent syrupy substance at room temperature. It is a solid glassy substance at low temperature, and it starts to melt when heated to 70°C and becomes fluid. It is easy to deliquesce, miscible with water and hydrolyzed into phosphoric acid. The intermediate of 2,5-diphenylamino 3,6-dihydroterephthalate is added to the molten polyphosphoric acid, and the intermediate can quickly close the ring to synthesize 6,13-dihydroquinacridone. It was found in the reaction that the concentration and temperature of polyphosphoric acid can affect the hiding power of the final product quinacridone. Generally, the higher the concentration, the greater the hiding power. The purpose of polyphosphoric acid is not only to help closed loop condensation, but also has the ability of solvent, dissolving intermediates and providing smooth stirring. Its concentration must be large enough to absorb the released water or alcohol, and its quantity must be large enough to provide suitable stirring capacity.

[0037] The temperature of cyclization is usually preferably controlled at 90-100 degrees. However, in large-scale production, due to the high density of 2,5-diphenylamino 3,6-dihydroterephthalate dimethyl ester, it often floats on the surface of polyphosphoric acid, is not easy to wet, and is difficult to evenly enter the acid. In case of fusion, the intermediate condensation reaction is fast or slow, the amount of alcohol released is different, and the temperature is not easy to control, resulting in the inability to repeat the product quality. The present invention aims at this phenomenon and increases the feeding temperature to 90-125 degrees, which can not only improve the stirring conditions of the reactants, but also enhance the hiding power of the final pigment and provide uniform product quality. Of course, the density of the intermediate can also be improved by controlling the conditions of pulverization. The synthesis of the intermediate is easy, but its quality and moisture content can also affect the quality of the product and must be strictly controlled. The 6,13-dihydroquinacridone synthesized by closed loop needs to be further oxidized to yellow quinacridone by adding an oxidant. This reaction must be carried out in water-soluble alcohol and can be divided into two parts. First, add 6,13-dihydroquinacridone filter cake to alcohol for pulping, add alkali, heat and crystallize, cool, add oxidant and catalyst, and heat again to complete the oxidation reaction. Commonly used oxidants include air or oxygen, and hydrogen peroxide can also be used. During the oxidation process, it is also necessary to add an appropriate amount of catalyst to provide a rapid reaction and synthesize stronger, yellower, and more colorful quinacridone pigments.

[0038] Example 1

[0039] Add 120 grams of 117.2% polyphosphoric acid to a reaction kettle, heat it to 105 degrees, start feeding, control the temperature below 125 degrees during feeding, add 30 grams of 2,5-diphenylamino-3,6-dihydroterephthalate dry powder over three hours, heat the temperature to 125 degrees after feeding, keep warm for 1 hour, cool to 90 degrees, slowly add 7 grams of water, control the temperature between 90-120 degrees, pour the reactants into a dilution kettle containing 300 grams of water, the water temperature is controlled at 10-15 degrees, stir for 30 minutes, make sure that the temperature of the dilution kettle is not higher than 25 degrees during the whole process; filter, wash with water until the acid value is greater than 4.

[0040] The obtained 6,13-dihydroquinacridone filter cake is added to an autoclave, 210 grams of n-butanol is added, and the mixture is beaten for 1 hour. Then the concentration of n-butanol is adjusted to 60%, the pH is adjusted to 7.0, 22 grams of 50% sodium hydroxide solution is added, and the mixture is heated to reflux temperature, about 93 degrees, and kept warm for 45 minutes. The mixture is cooled to 60 degrees, 0.45 kilograms of 2-anthraquinone sulfonic acid is added, and the mixture is stirred evenly. Air is introduced, and the mixture is refined using a gas-liquid mixer. The acid value is tested and must be greater than 11. The temperature is controlled at reflux temperature and kept warm for 2 hours. After sampling and testing for complete oxidation, the oxidation is stopped. The reaction slurry is heated to 110 degrees and kept warm for 2 hours. The mixture is cooled to 60 degrees, filtered, and washed with water until neutral. The product is spray-dried to obtain 20.5 grams of yellow-phase gamma-type quinacridone.

[0041] Example 2

[0042] Add 120 grams of 116.3% polyphosphoric acid to a reactor, heat to 105 degrees, start feeding, control the temperature below 125 degrees, add 30 grams of 2,5-diphenylamino 3,6-dihydroterephthalate dry powder over three hours, heat to 125 degrees after feeding, keep warm for 1 hour, cool to 90 degrees, slowly add 6.8 grams of water, control the temperature between 90-120 degrees, pour the reactants into a dilution kettle, the dilution kettle contains 300 grams of water, the water temperature is controlled at 10-15 degrees, stir for 30 minutes, and make sure that the dilution kettle temperature is not higher than 25 degrees during the whole process. Filter and wash with water until the acid value is greater than 4.

[0043] The obtained 6,13-dihydroquinacridone filter cake is added to an autoclave, 210 grams of n-butanol are added, and the mixture is beaten for 1 hour. Then the concentration of n-butanol is adjusted to 60%, the pH is adjusted to 7.0, 22 grams of 50% sodium hydroxide solution are added, and the mixture is heated to reflux temperature, about 93 degrees, kept warm for 45 minutes, cooled to 60 degrees, 0.45 kilograms of 2-anthraquinone sulfonic acid are added, stirred evenly, air is introduced, and the mixture is refined using a gas-liquid mixer. The acid value is detected and must be greater than 11. The temperature is controlled at reflux temperature and kept warm for 2 hours. Samples are taken to detect complete oxidation, heated to 110 degrees, and kept warm for 2 hours. Cooled to 60 degrees, filtered, and washed with water until neutral. The product is spray dried to obtain 21.2 grams of yellow gamma quinacridone. Compared with Example 1, this product is bluer and has a slightly higher transparency.

[0044] Example 3

[0045] Add 120 grams of 117.2% polyphosphoric acid to a reactor, heat to 105 degrees, start feeding, control the temperature below 125 degrees, add 30 grams of 2,5-diphenylamino 3,6-dihydroterephthalate dry powder over three hours, heat to 125 degrees after feeding, keep warm for 1 hour, cool to 90 degrees, slowly add 7 grams of water, control the temperature between 90-120 degrees, pour the reactants into a dilution kettle, the dilution kettle contains 300 grams of water, the water temperature is controlled at 10-15 degrees, stir for 30 minutes, and make sure that the temperature of the dilution kettle is not higher than 25 degrees during the whole process. Filter and wash with water until the acid value is greater than 4.

[0046] The obtained 6,13-dihydroquinacridone filter cake is added to an autoclave, 210 grams of n-butanol are added, and the mixture is beaten for 1 hour. Then the concentration of n-butanol is adjusted to 60%, the pH is adjusted to 7.0, 25 grams of 50% sodium hydroxide solution are added, and the mixture is heated to reflux temperature, about 93 degrees, kept warm for 45 minutes, cooled to 60 degrees, 0.35 kilograms of 2-anthraquinone sulfonic acid and 0.1 kilograms of ferrous oxide are added, stirred evenly, air is introduced, and the mixture is refined using a gas-liquid mixer. The acid value is detected, which must be greater than 11. The temperature is controlled at reflux temperature and kept warm for 2 hours. Samples are taken to detect complete oxidation, heated to 110 degrees, and kept warm for 2 hours. Cooled to 60 degrees, filtered, and washed with water until neutral. The product is spray dried to obtain 21.5 grams of yellow-phase gamma-type quinacridone.

[0047] Example 4

[0048] Add 120 grams of 117.2% polyphosphoric acid to a reactor, heat to 105 degrees, start feeding, control the temperature below 125 degrees, add 30 grams of 2,5-diphenylamino 3,6-dihydroterephthalate dry powder over three hours, heat to 125 degrees after feeding, keep warm for 1 hour, cool to 90 degrees, slowly add 7 grams of water, control the temperature between 90-120 degrees, pour the reactants into a dilution kettle, the dilution kettle contains 300 grams of water, the water temperature is controlled at 10-15 degrees, stir for 30 minutes, and make sure that the temperature of the dilution kettle is not higher than 25 degrees during the whole process. Filter and wash with water until the acid value is greater than 4.

[0049] The obtained 6,13-dihydroquinacridone filter cake is added to an autoclave, 220 grams of ethylene glycol are added, and the mixture is beaten for 1 hour. Then the concentration of n-butanol is adjusted to 55%, the pH is adjusted to 7.0, 24 grams of 50% sodium hydroxide solution are added, the mixture is heated to 90 degrees, kept warm for 45 minutes, cooled to 60 degrees, 0.45 kilograms of 2-anthraquinone sulfonic acid are added, stirred evenly, air is introduced, and the mixture is refined using a gas-liquid mixer. The acid value is tested and must be greater than 11. The temperature is controlled at reflux temperature and kept warm for 2 hours. After sampling and testing for complete oxidation, the oxidation is stopped. The reaction slurry is heated to 120 degrees and kept warm for 2 hours. Cool to 60 degrees, filter, and wash with water until neutral. The product is spray dried to obtain 19.7 grams of yellow-phase gamma-type quinacridone.

[0050] Compared with Example 1, the final product of Example 2 is bluer in color and slightly more transparent. This indicates that better pigment quality can be obtained under slightly lower polyphosphoric acid concentration and slight adjustment of water, which may be related to the uniformity and stability of the reaction.

[0051] Compared with Example 2 and Example 3, the final product of Example 3 is 21.5 grams, which increases the yield, concentration and starting point compared with Example 2, indicating that under the optimization of sodium hydroxide and oxidation, the oxidation reaction is more complete and the pigment quality is improved.

[0052] Compared with Example 3 and Example 4, after changing the solvent and concentration, the reaction efficiency decreased, resulting in a decrease in product quality. The nature and concentration of the solvent had a significant impact on the reaction rate and product characteristics. The final product of Example 4 was 19.7 grams, with a slightly darker color and reduced transparency.

[0053] It can be seen from the above embodiments that each embodiment achieves high-quality production of pigments by adjusting the polyphosphoric acid concentration, the amount of water added, the amount of sodium hydroxide and the bleaching agent, and other components to optimize the reaction conditions in a step-by-step manner.

[0054] The improvements in Examples 1 to 3 resulted in an increase in the color, transparency and average yield of the product, while in Example 4, due to improper selection of solvent and concentration, the product quality was reduced, demonstrating the importance of optimization.

[0055] The above description of the embodiments is to facilitate the understanding and use of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the principles of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high hiding yellow phase quinacridone pigment, characterized in that: The steps include: Step 1: Use 116%-118% polyphosphoric acid; Step 2: Add 2,5-diphenylamino-3,6-dihydroterephthalate at 90-135 degrees; Step 3: Keep warm at 120-135 degrees for 1-4 hours, cool to 120 degrees and dilute polyphosphoric acid to 110-112%; Step 4: pour the polyphosphoric acid reactant into water, filter, and wash with water to obtain 6,13-dihydroquinacridone; Step 5: Add the dried and crushed 6,13-dihydroquinacridone into a solvent for slurrying, and the solvent concentration must be greater than 50%; Step 6: Add sodium hydroxide solution, adjust the pH value to greater than 11, heat to 80-90 degrees, and keep warm for 30-60 minutes; Step 7: After cooling, add an oxidant and a catalyst, make sure the pH is greater than 11, heat to 100-110 degrees, keep warm for 2 hours, cool and filter to obtain a high-hiding yellow phase quinacridone.

2. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 1, characterized in that: The concentration of the polyphosphoric acid is selected to be 116.5-117.5%.

3. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 2, characterized in that: The ratio of the polyphosphoric acid to dimethyl 2,5-dianilino-3,6-dihydroterephthalate is 3:1 to 7:

1.

4. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 3, characterized in that: The solvent used for the oxidation reaction of dihydroquinacridone is an alcohol, including one of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and ethylene glycol.

5. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 4, characterized in that: The concentration of the alcohol solvent must be greater than 50%.

6. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 4, characterized in that: The oxidation reaction is heated twice. After adding sodium hydroxide for the first time, heating helps the product to be converted into β-type dihydroquinacridone. The oxidant and catalyst are added for the second time to promote the oxidation of the product.

7. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 4, characterized in that: The required oxidant is air, oxygen or hydrogen peroxide, and the molar amount thereof added must be more than twice the molar amount of the dihydroquinacridone.

8. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 4, characterized in that: The required oxidant gas is finely distributed using a gas-liquid mixer.

9. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 4, characterized in that: The catalyst is one of anthraquinone, monochloroanthraquinone, dichloroanthraquinone, 2-anthraquinone sulfonic acid sodium salt, 2,6-anthraquinone disulfonic acid disodium salt, 2-ethylanthraquinone and 2-bromoanthraquinone.

10. The method for preparing a high hiding yellow phase quinacridone pigment according to claim 8, characterized in that: During the oxidation reaction, the acid value of the reaction solution must be maintained at greater than 11.