A method for preparing a pigment for low oil absorption pigment red 57:1 ink

Abstract

The invention discloses a method for preparing a low oil absorption pigment red 57:1 ink pigment, which belongs to the technical field of pigment synthesis. After 4-aminotoluene-3-sulfonic acid is diazotized, it is coupled with 3-hydroxy-2-naphthoic acid, and a carboxyl-terminated hyperbranched polymer and an ionic liquid are added to the crude pigment compound obtained by the coupling reaction, and finally a calcium chloride aqueous solution is added for color lake formation. The low oil absorption pigment red 57:1 ink pigment prepared by the invention not only has a low oil absorption, but also has the advantages of strong tinting power, easy dispersion and high stability, and has good processing and application performance.

Description

Technical Field

[0001] The invention belongs to the technical field of pigment synthesis, and in particular is a method for preparing a pigment for low oil absorption pigment red 57:1 ink. Background Art

[0002] Pigment Red 57:1 is a monoazo lake organic pigment with high tinting strength, good light resistance and solvent resistance. It is widely used in printing inks, coatings, masterbatches, plastics, rubber, wires, daily chemicals, and coloring of oil and watercolor pigments.

[0003] The oil absorption of Pigment Red 57:1 is too high, which leads to high viscosity and poor dispersion stability of the ink, affecting the fluidity and printing effect of the ink. In addition, to prepare high-concentration ink, more oily binders are needed to achieve the desired ink state, which will increase the cost of the ink and limit the content of pigments in the ink to a certain extent, making it difficult to increase the concentration of the ink. During storage, excessive oil absorption can easily cause the ink to deteriorate and form a crust, thereby reducing the storage life and performance of the ink. Therefore, reducing the oil absorption of Pigment Red 57:1 by modifying it is of great significance to improving the quality and performance of the ink. Summary of the invention

[0004] To solve the above problems, the object of the present invention is to provide a method for preparing a pigment for low oil absorption pigment red 57:1 ink.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A method for preparing a pigment for low oil absorption pigment red 57:1 ink, comprising the steps of: diazotizing 4-aminotoluene-3-sulfonic acid, coupling with 3-hydroxy-2-naphthoic acid, adding a carboxyl-terminated hyperbranched polymer and an ionic liquid to a crude pigment compound obtained after the coupling reaction, and finally adding a calcium chloride aqueous solution for lake formation;

[0007] The carboxyl-terminated hyperbranched polymer is prepared according to the following method:

[0008] Add trimesic acid and diethylenetriamine to a non-protonic polar solvent, stir and dissolve, then add diethyl azodicarboxylate and 1-hydroxybenzotriazole, react at 25-40°C for 5-12 hours, and remove the solvent by reduced pressure distillation after the reaction. Wash the residue with acetone for 3-5 times and dry to obtain a carboxyl-terminated hyperbranched polymer.

[0009] The aprotic polar solvent is dimethyl sulfoxide or dimethylformamide.

[0010] The mass ratio of trimesic acid, diethylenetriamine, aprotic polar solvent, diethyl azodicarboxylate and 1-hydroxybenzotriazole is 3.5-4.5:1:20-30:5.5-8:4.5-6.5.

[0011] The ionic liquid is 1-butyl-3-methylimidazolium octyl sulfonate or 1-butyl-3-methylimidazolium methane sulfonate.

[0012] The method for preparing the pigment for low oil absorption pigment red 57:1 ink comprises the following steps:

[0013] 1) Add 4-aminotoluene-3-sulfonic acid to water, stir and cool to 0-10°C, then add 30-36% hydrochloric acid and 30% sodium nitrite aqueous solution to carry out diazotization reaction for 0.5-1h, until Congo red test paper turns blue and potassium iodide starch test paper turns blue, stop the reaction and obtain diazo solution;

[0014] 2) Add water and 3-hydroxy-2-naphthoic acid to a coupling reactor, then add sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution to the diazo solution obtained in step 1) at 25-30° C., and perform coupling reaction for 1-2 hours. Meanwhile, adjust the pH value of the system to 8-9 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound;

[0015] 3) Add the crude pigment compound obtained in step 2) into water, stir and disperse evenly, then add the terminal carboxyl hyperbranched polymer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine, heat to 50-70°C for reaction for 5-8h, cool to 25-30°C, add ionic liquid, stir and react for 1-2h, and after the reaction is completed, add a 20-30% calcium chloride aqueous solution dropwise thereto, stir and react for 1-3h after the addition is completed, heat to 80-90°C and continue stirring for 0.5-1h, filter, wash and dry to obtain low oil absorption pigment red 57:1 ink pigment.

[0016] The mass ratio of 4-aminotoluene-3-sulfonic acid, water, hydrochloric acid and sodium nitrite aqueous solution in step 1) is 1:8~15:3.5~5:3~5.

[0017] The mass ratio of the 3-hydroxy-2-naphthoic acid in step 2) to the 4-aminotoluene-3-sulfonic acid in step 1) is 1.1-1.5:1.

[0018] The mass ratio of 3-hydroxy-2-naphthoic acid, water and sodium hydroxide in step 2) is 1:8-15:0.25-0.35.

[0019] The mass ratio of the crude pigment compound, water, terminal carboxyl hyperbranched polymer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, 4-dimethylaminopyridine, ionic liquid and calcium chloride aqueous solution in step 3) is 100:800~1000:5~10:3~8:2~5.5:2~5:150~200.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The low oil absorption pigment red 57:1 ink pigment of the present invention uses a hyperbranched polymer to modify the pigment. The highly branched structure of the hyperbranched polymer can provide a better steric hindrance effect, reduce the agglomeration between particles, and reduce the penetration of oily media; it can also reduce the aggregation of the pigment in the ink, thereby further reducing the demand for oily media; the polymer with a polyamide structure can also improve the chemical stability and environmental tolerance of the pigment, and increase the light resistance of the pigment.

[0022] The low oil absorption pigment red 57:1 ink pigment of the present invention uses an amphiphilic ionic liquid to adsorb and adjust the crystal of the pigment. The ionic liquid is adsorbed on the surface of the pigment, and the pigment particles can be regulated to change from a rod-like structure to a spherical structure. The spherical particles have better fluidity and dispersibility, and can effectively reduce the contact area between the pigment and the carrier, thereby reducing the oil absorption of the pigment; and the formed spherical particles are more densely stacked, reducing the gaps between the particles; on the other hand, the ionic liquid surface contains a large number of sulfonic acid groups, which can be laked together with the lake pigment when metal ions are introduced, and deposited and coated on the surface of the pigment, so that the pigment is agglomerated and separated, thereby improving the dispersibility and migration resistance of the pigment.

[0023] The low oil absorption pigment red 57:1 ink pigment prepared by the present invention not only has a lower oil absorption, but also has the advantages of strong tinting power, easy dispersion and high stability, and has good processing and application performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a SEM image of the pigment for low oil absorption Pigment Red 57:1 ink prepared in Example 3 of the present invention, with a scale of 500 nm. DETAILED DESCRIPTION

[0025] In order to better understand the technical solution of the present invention, the above content of the present invention is further described in detail below through specific implementation methods in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples. All technologies realized based on the above content of the present invention belong to the scope of the present invention.

[0026] Example 1 Preparation of carboxyl-terminated hyperbranched polymer

[0027] 0.35 kg of trimesic acid and 0.1 kg of diethylenetriamine were added to 2 kg of dimethyl sulfoxide, and after stirring to dissolve, 0.55 kg of diethyl azodicarboxylate and 0.45 kg of 1-hydroxybenzotriazole were added, and the mixture was reacted at 25°C for 12 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the residue was washed with acetone for 3 times and dried to obtain a carboxyl-terminated hyperbranched polymer.

[0028] Preparation of Pigment Red 57:1 with Low Oil Absorption for Ink

[0029] 1) Add 0.1 kg of 4-aminotoluene-3-sulfonic acid to 0.8 kg of water, stir and cool to 0°C, then add 0.5 kg of 30% hydrochloric acid and 0.3 kg of 30% sodium nitrite aqueous solution to carry out diazotization reaction for 0.5 h, until the Congo red test paper turns blue and the potassium iodide starch test paper turns blue, stop the reaction and obtain diazo solution;

[0030] 2) Add 0.88 kg of water and 0.11 kg of 3-hydroxy-2-naphthoic acid into a coupling reactor, then add 0.028 kg of sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution into the diazo solution obtained in step 1) at 25° C., and perform coupling reaction for 1 hour. Meanwhile, adjust the pH value of the system to 8 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound;

[0031] 3) Add 0.1 kg of the crude pigment compound obtained in step 2) into 0.8 kg of water, stir and disperse evenly, then add 0.005 kg of terminal carboxyl hyperbranched polymer, 0.003 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.002 kg of 4-dimethylaminopyridine, heat to 50 ° C for reaction for 8 hours, cool to 25 ° C, add 0.002 kg of 1-butyl-3-methylimidazolium octane sulfonate, stir and react for 1 hour, and after the reaction is completed, add 0.15 kg of 30% calcium chloride aqueous solution dropwise thereto, stir and react for 1 hour after the addition is completed, heat to 80 ° C and continue stirring for 1 hour, filter, wash and dry to obtain low oil absorption pigment red 57:1 ink pigment.

[0032] Example 2 Preparation of carboxyl-terminated hyperbranched polymer

[0033] 0.39 kg of trimesic acid and 0.1 kg of diethylenetriamine were added to 2.2 kg of dimethylformamide, and after stirring to dissolve, 0.62 kg of diethyl azodicarboxylate and 0.5 kg of 1-hydroxybenzotriazole were added, and the mixture was reacted at 30°C for 10 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the residue was washed with acetone for 4 times and dried to obtain a carboxyl-terminated hyperbranched polymer.

[0034] Preparation of Pigment Red 57:1 with Low Oil Absorption for Ink

[0035] 1) Add 0.1kg of 4-aminotoluene-3-sulfonic acid to 1kg of water, stir and cool to 3°C, then add 0.4kg of 33% hydrochloric acid and 0.35kg of 30% sodium nitrite aqueous solution to carry out diazotization reaction for 0.6h until Congo red test paper turns blue and potassium iodide starch test paper turns blue, then stop the reaction and obtain diazo solution;

[0036] 2) Add 1.2 kg of water and 0.12 kg of 3-hydroxy-2-naphthoic acid into a coupling reactor, then add 0.035 kg of sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution into the diazo solution obtained in step 1) at 26° C., and perform coupling reaction for 1.2 h. Meanwhile, adjust the pH value of the system to 8.2 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound;

[0037] 3) 0.1 kg of the crude pigment compound obtained in step 2) was added to 0.85 kg of water, and after being stirred and dispersed evenly, 0.006 kg of terminal carboxyl hyperbranched polymer, 0.004 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.003 kg of 4-dimethylaminopyridine were added, and the mixture was heated to 55°C for reaction for 7.5 h, and then cooled to 26°C, and 0.003 kg of 1-butyl-3-methylimidazole methanesulfonate was added, and the mixture was stirred for reaction for 1.5 h. After the reaction was completed, 0.16 kg of a 28% calcium chloride aqueous solution was added dropwise, and the mixture was stirred for reaction for 1.5 h after the addition was completed. The mixture was heated to 85°C and stirred for 0.75 h, filtered, washed, and dried to obtain a low oil absorption pigment red 57:1 ink pigment.

[0038] Example 3 Preparation of carboxyl-terminated hyperbranched polymer

[0039] 0.4 kg of trimesic acid and 0.1 kg of diethylenetriamine were added to 2.5 kg of dimethylformamide, and after stirring to dissolve, 0.7 kg of diethyl azodicarboxylate and 0.55 kg of 1-hydroxybenzotriazole were added, and the mixture was reacted at 35°C for 8 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the residue was washed with acetone for 5 times and dried to obtain a carboxyl-terminated hyperbranched polymer.

[0040] Preparation of Pigment Red 57:1 with Low Oil Absorption for Ink

[0041] 1) Add 0.1 kg of 4-aminotoluene-3-sulfonic acid to 1.2 kg of water, stir and cool to 5°C, then add 0.4 kg of 35% hydrochloric acid and 0.4 kg of 30% sodium nitrite aqueous solution for diazotization reaction for 0.75 h until Congo red test paper turns blue and potassium iodide starch test paper turns blue, then stop the reaction and obtain diazo solution;

[0042] 2) Add 1.5 kg of water and 0.13 kg of 3-hydroxy-2-naphthoic acid into a coupling reactor, then add 0.038 kg of sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution into the diazo solution obtained in step 1) at 28° C., and perform coupling reaction for 1.5 hours. Meanwhile, adjust the pH value of the system to 8.5 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound;

[0043] 3) Add 0.1 kg of the crude pigment compound obtained in step 2) into 0.9 kg of water, stir and disperse evenly, then add 0.0075 kg of terminal carboxyl hyperbranched polymer, 0.005 kg of 1-ethyl-(3-dimethylaminopropyl) carbodiimide and 0.004 kg of 4-dimethylaminopyridine, heat to 60 ° C for 7 hours, cool to 28 ° C, add 0.004 kg of 1-butyl-3-methylimidazole methanesulfonate, stir and react for 2 hours, and then add 0.18 kg of 25% calcium chloride aqueous solution after the reaction is completed. After the addition is completed, stir and react for 2 hours, heat to 85 ° C and continue stirring for 0.7 hours, filter, wash, and dry to obtain low oil absorption pigment red 57:1 ink pigment. Its SEM scanning picture is as follows Figure 1 As shown by Figure 1 It can be seen that the appearance of the pigment for low oil absorption pigment red 57:1 ink is spherical or quasi-spherical particles, the particles are closely arranged and have a small porosity, indicating that the hyperbranched polymer and the ionic liquid form a uniform coating layer on the pigment surface.

[0044] Example 4 Preparation of carboxyl-terminated hyperbranched polymer

[0045] 0.42 kg of trimesic acid and 0.1 kg of diethylenetriamine were added to 2.8 kg of dimethyl sulfoxide, and after stirring to dissolve, 0.75 kg of diethyl azodicarboxylate and 0.6 kg of 1-hydroxybenzotriazole were added, and the mixture was reacted at 38°C for 6 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the residue was washed with acetone for 4 times and dried to obtain a carboxyl-terminated hyperbranched polymer.

[0046] Preparation of Pigment Red 57:1 with Low Oil Absorption for Ink

[0047] 1) Add 0.1 kg of 4-aminotoluene-3-sulfonic acid to 1.4 kg of water, stir and cool to 8°C, then add 0.45 kg of 35% hydrochloric acid and 0.45 kg of 30% sodium nitrite aqueous solution to carry out diazotization reaction for 1 hour until Congo red test paper turns blue and potassium iodide starch test paper turns blue, then stop the reaction and obtain diazo solution;

[0048] 2) Add 1.9 kg of water and 0.14 kg of 3-hydroxy-2-naphthoic acid into a coupling reactor, then add 0.042 kg of sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution into the diazo solution obtained in step 1) at 29° C., and perform coupling reaction for 1.8 h. Meanwhile, adjust the pH value of the system to 8.8 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound;

[0049] 3) 0.1 kg of the crude pigment compound obtained in step 2) was added to 0.95 kg of water, and after being stirred and dispersed evenly, 0.009 kg of terminal carboxyl hyperbranched polymer, 0.006 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.005 kg of 4-dimethylaminopyridine were added, and the mixture was heated to 65 ° C for reaction for 6 h, then cooled to 29 ° C, 0.004 kg of 1-butyl-3-methylimidazolium octane sulfonate was added, and the mixture was stirred for reaction for 1.9 h. After the reaction was completed, 0.19 kg of a 22% calcium chloride aqueous solution was added dropwise thereto. After the addition was completed, the mixture was stirred for reaction for 2.5 h, and the mixture was heated to 88 ° C and stirred for 0.55 h. The mixture was filtered, washed and dried to obtain a low oil absorption pigment red 57:1 ink pigment.

[0050] Example 5 Preparation of carboxyl-terminated hyperbranched polymer

[0051] 0.45 kg of trimesic acid and 0.1 kg of diethylenetriamine were added to 3 kg of dimethyl sulfoxide, and after stirring to dissolve, 0.8 kg of diethyl azodicarboxylate and 0.65 kg of 1-hydroxybenzotriazole were added, and the mixture was reacted at 40°C for 5 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the residue was washed with acetone for 3 times and dried to obtain a carboxyl-terminated hyperbranched polymer.

[0052] Preparation of Pigment Red 57:1 with Low Oil Absorption for Ink

[0053] 1) Add 0.1 kg of 4-aminotoluene-3-sulfonic acid to 1.5 kg of water, stir and cool to 10°C, then add 0.35 kg of 36% hydrochloric acid and 0.5 kg of 30% sodium nitrite aqueous solution to carry out diazotization reaction for 1 hour until Congo red test paper turns blue and potassium iodide starch test paper turns blue, then stop the reaction and obtain diazo solution;

[0054] 2) Add 2.25 kg of water and 0.15 kg of 3-hydroxy-2-naphthoic acid into a coupling reactor, then add 0.052 kg of sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution into the diazo solution obtained in step 1) at 30° C., and perform coupling reaction for 2 h. Meanwhile, adjust the pH value of the system to 9 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound;

[0055] 3) Add 0.1 kg of the crude pigment compound obtained in step 2) into 1 kg of water, stir and disperse evenly, then add 0.01 kg of terminal carboxyl hyperbranched polymer, 0.008 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.0055 kg of 4-dimethylaminopyridine, heat to 70°C for reaction for 5 hours, cool to 30°C, add 0.005 kg of 1-butyl-3-methylimidazole methanesulfonate, stir and react for 2 hours, and after the reaction is completed, add 0.2 kg of 20% calcium chloride aqueous solution dropwise thereto, stir and react for 3 hours after the addition is completed, heat to 90°C and continue stirring for 0.5 hours, filter, wash and dry to obtain low oil absorption pigment red 57:1 ink pigment.

[0056] Example 6 Preparation of carboxyl-terminated hyperbranched polymer

[0057] 0.4 kg of trimesic acid and 0.1 kg of diethylenetriamine were added to 2.8 kg of dimethylformamide, and after stirring to dissolve, 0.7 kg of diethyl azodicarboxylate and 0.6 kg of 1-hydroxybenzotriazole were added, and the mixture was reacted at 35°C for 10 hours. After the reaction was completed, the solvent was removed by distillation under reduced pressure, and the residue was washed with acetone for 4 times and dried to obtain a carboxyl-terminated hyperbranched polymer.

[0058] Preparation of Pigment Red 57:1 with Low Oil Absorption for Ink

[0059] 1) Add 0.1 kg of 4-aminotoluene-3-sulfonic acid to 1.5 kg of water, stir and cool to 0°C, then add 0.35 kg of 30% hydrochloric acid and 0.5 kg of 30% sodium nitrite aqueous solution to carry out diazotization reaction for 1 hour until Congo red test paper turns blue and potassium iodide starch test paper turns blue, then stop the reaction and obtain diazo solution;

[0060] 2) Add 1.5 kg of water and 0.13 kg of 3-hydroxy-2-naphthoic acid into a coupling reactor, then add 0.04 kg of sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution into the diazo solution obtained in step 1) at 25° C., and perform coupling reaction for 2 h. Meanwhile, adjust the pH value of the system to 8 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound;

[0061] 3) Add 0.1 kg of the crude pigment compound obtained in step 2) into 0.9 kg of water, stir and disperse evenly, then add 0.005 kg of terminal carboxyl hyperbranched polymer, 0.007 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 0.005 kg of 4-dimethylaminopyridine, heat to 70 ° C for reaction for 8 h, cool to 30 ° C, add 0.002 kg of 1-butyl-3-methylimidazole methanesulfonate, stir and react for 1.5 h, and then add 0.2 kg of 30% calcium chloride aqueous solution dropwise thereto after the reaction is completed. After the addition is completed, stir and react for 2.5 h, heat to 90 ° C and continue stirring for 1 h, filter, wash and dry to obtain low oil absorption pigment red 57:1 ink pigment.

[0062] The low oil absorption pigment red 57:1 ink prepared in Examples 1 to 6 was tested for pigments, wherein the tinting strength was tested according to the method in GB1708-79; the fluidity was tested according to the method in GB1719-79; the bulk density was tested according to the method in GB / T 21877-2015, and the determination method was: accurately weigh 50 g of the pigment compound, put it into a measuring cylinder, seal it, shake it up and down 10 times, and record the sample scale in the measuring cylinder; the transparency was tested according to the method in DIN 53163:1988, and the oil absorption was tested according to the method in GB / T 5211.15-2014; the light resistance was tested according to the method in GB1710-79, and Comparative Example 1 was commercially available Pigment Red 57:1, and its test results are shown in Table 1.

[0063] Table 1 Pigment performance test results of examples and comparative examples

[0064]

[0065] It can be seen from the results in Table 1 that the low oil absorption pigment red 57:1 ink pigment prepared by the present invention has strong tinting power, high fluidity, low bulk density, good transparency, low oil absorption and good light resistance. In the process of preparing the low oil absorption pigment red 57:1 ink pigment, the present invention introduces a hyperbranched polymer and an ionic liquid to control the transformation of the pigment particles from rods to spheres, reduce the bulk density, reduce the voids, and have lower oil absorption and better dispersibility.

[0066] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for preparing a pigment for low oil absorption pigment red 57:1 ink, characterized in that: After diazotization of 4-aminotoluene-3-sulfonic acid, it is coupled with 3-hydroxy-2-naphthoic acid. After the coupling reaction is completed, a crude pigment compound is obtained. The crude pigment compound is added into water, stirred and dispersed uniformly, and then a terminal carboxyl hyperbranched polymer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine are added. After heating to 50-70° C. for reaction for 5-8 hours, the temperature is lowered to 25-30° C., an ionic liquid is added, and the reaction is stirred for 1-2 hours. After the reaction is completed, a calcium chloride aqueous solution with a mass concentration of 20-30% is added dropwise thereto. After the addition is completed, the reaction is stirred for 1-3 hours, the temperature is raised to 80-90° C., and the stirring is continued for 0.5-1 hour. The pigment is filtered, washed, and dried to obtain a low oil absorption pigment red 57:1 ink pigment; The carboxyl-terminated hyperbranched polymer is prepared according to the following method: The method comprises adding trimesic acid and diethylenetriamine to a non-protonic polar solvent, stirring and dissolving, adding diethyl azodicarboxylate and 1-hydroxybenzotriazole, reacting at 25-40° C. for 5-12 hours, and removing the solvent by distillation under reduced pressure after the reaction is completed. The obtained residue is washed with acetone for 3-5 times and dried to obtain a carboxyl-terminated hyperbranched polymer. The mass ratio of trimesic acid, diethylenetriamine, aprotic polar solvent, diethyl azodicarboxylate and 1-hydroxybenzotriazole is 3.5-4.5:1:20-30:5.5-8:4.5-6.5; The ionic liquid is 1-butyl-3-methylimidazolium octyl sulfonate or 1-butyl-3-methylimidazolium methane sulfonate.

2. The method for preparing the low oil absorption pigment red 57:1 ink pigment according to claim 1, characterized in that: The aprotic polar solvent is dimethyl sulfoxide or dimethylformamide.

3. The method for preparing the low oil absorption pigment red 57:1 ink pigment according to claim 1, characterized in that: The following steps are involved: 1) Add 4-aminotoluene-3-sulfonic acid to water, stir and cool to 0-10°C, then add 30-36% hydrochloric acid and 30% sodium nitrite aqueous solution to carry out diazotization reaction for 0.5-1h, until Congo red test paper turns blue and potassium iodide starch test paper turns blue, stop the reaction and obtain diazo solution; 2) Add water and 3-hydroxy-2-naphthoic acid to a coupling reactor, then add sodium hydroxide, stir and dissolve to obtain a mixed solution, add the obtained mixed solution to the diazo solution obtained in step 1) at 25-30° C., and perform coupling reaction for 1-2 hours. Meanwhile, adjust the pH value of the system to 8-9 with sodium carbonate during the reaction. After the reaction is completed, filter and dry to obtain a crude pigment compound; 3) Add the crude pigment compound obtained in step 2) into water, stir and disperse evenly, then add the terminal carboxyl hyperbranched polymer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and 4-dimethylaminopyridine, heat to 50-70°C for reaction for 5-8h, cool to 25-30°C, add ionic liquid, stir and react for 1-2h, and after the reaction is completed, add a 20-30% calcium chloride aqueous solution dropwise thereto, stir and react for 1-3h after the addition is completed, heat to 80-90°C and continue stirring for 0.5-1h, filter, wash and dry to obtain low oil absorption pigment red 57:1 ink pigment.

4. The method for preparing the pigment for ink with low oil absorption pigment red 57:1 as claimed in claim 3, characterized in that: The mass ratio of 4-aminotoluene-3-sulfonic acid, water, hydrochloric acid and sodium nitrite aqueous solution in step 1) is 1:8~15:3.5~5:3~5.

5. The method for preparing the low oil absorption pigment red 57:1 ink pigment according to claim 3, characterized in that: The mass ratio of the 3-hydroxy-2-naphthoic acid in step 2) to the 4-aminotoluene-3-sulfonic acid in step 1) is 1.1-1.5:

1.

6. The method for preparing the pigment for ink with low oil absorption pigment red 57:1 as claimed in claim 3, characterized in that: The mass ratio of 3-hydroxy-2-naphthoic acid, water and sodium hydroxide in step 2) is 1:8-15:0.25-0.

35.

7. The method for preparing the pigment for ink with low oil absorption pigment red 57:1 as claimed in claim 3, characterized in that: The mass ratio of the crude pigment compound, water, terminal carboxyl hyperbranched polymer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide, 4-dimethylaminopyridine, ionic liquid and calcium chloride aqueous solution in step 3) is 100:800~1000:5~10:3~8:2~5.5:2~5:150~200.

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