A kind of easily dispersible toluidine red pigment and preparation method thereof

Abstract

The invention discloses an easily dispersible toluidine red pigment and a preparation method thereof, belonging to the technical field of pigment synthesis. The pigment comprises the following raw materials, measured in parts by weight: 1-2 parts of toluidine red and 0.3-0.5 parts of a polyamide polymer grafted with cyclodextrin; the polyamide polymer grafted with cyclodextrin is prepared by grafting cyclodextrin onto a tri-terminal carboxyl compound, performing a quaternization reaction, and finally reacting with hexamethylenediamine. The easily dispersible toluidine red pigment prepared by the invention has stable dispersibility, high tinting strength and weather resistance, and effectively improves its application effect in the fields of coatings and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of pigment synthesis, and in particular is an easily dispersible toluidine red pigment and a preparation method thereof. Background Art

[0002] Toluidine red is an azo organic pigment with a bright red hue, high tinting strength and good chemical resistance. It is widely used in coatings, inks, plastics and textiles.

[0003] However, the small particles of toluidine red easily generate strong polar attraction between particles, which can cause pigment particles to agglomerate and lead to sedimentation, affecting the performance of the product. The polar groups in the molecular structure of toluidine red pigment give its surface a strong polarity, which in turn affects the pigment's dispersion properties. In addition, toluidine red pigment has poor weather resistance and is easily affected by ultraviolet rays or high temperatures in outdoor applications, causing fading or powdering, which greatly reduces the pigment's service life. Therefore, modifying toluidine red pigment to develop a toluidine red pigment with good dispersion stability and strong weather resistance is of great significance to improving the pigment's performance. Summary of the Invention

[0004] To solve the above problems, the present invention aims to provide an easily dispersible toluidine red pigment and a preparation method thereof.

[0005] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions:

[0006] An easily dispersible toluidine red pigment is composed of the following raw materials, calculated in parts by weight: 1-2 parts of toluidine red and 0.3-0.5 parts of a polyamide polymer grafted with cyclodextrin;

[0007] The polyamide polymer grafted with cyclodextrin is prepared by grafting cyclodextrin onto a tri-terminal carboxyl compound, performing a quaternization reaction, and finally reacting with hexamethylenediamine;

[0008] The three-terminal carboxyl compound is prepared according to the following method:

[0009] Add methyl 3-aminopropionate and methyl 3-bromopropionate to organic solvent 1, then add base 1, stir and mix evenly, heat to 40-80°C and react for 12-24 hours. After the reaction is completed, filter and distill the filtrate under reduced pressure to remove the solvent. Wash the filter cake with water and dry it, then add it to organic solvent 2, stir and dissolve it, add base 2, react at 25-40°C for 12-24 hours, and filter to obtain a three-terminal carboxyl compound.

[0010] The organic solvent 1 is acetonitrile, acetone, tetrahydrofuran, dimethyl sulfoxide or dimethylformamide.

[0011] The base 1 is potassium carbonate or sodium carbonate.

[0012] The organic solvent 2 is methanol, ethanol or isopropanol.

[0013] The base 2 is sodium hydroxide or potassium hydroxide.

[0014] The mass ratio of the methyl 3-aminopropionate, methyl 3-bromopropionate, organic solvent 1, base 1, organic solvent 2 and base 2 is 1:3.5~5:10~20:2.5~4:10~20:1.2~2.4.

[0015] The polyamide polymer grafted with cyclodextrin is prepared according to the following steps:

[0016] 1) Add the tricarboxyl-terminated compound and α-cyclodextrin to a mixed solution of organic solvent 1 and water, then add 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix thoroughly, and react at 25-40°C for 24-48 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin;

[0017] 2) adding the terminal carboxyl compound grafted with α-cyclodextrin prepared in step 1) to organic solvent 4, then adding iodomethane, heating to 40-100° C. and reacting for 8-12 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a terminal carboxyl compound grafted with α-cyclodextrin;

[0018] 3) adding the terminal carboxyl compound of the quaternized grafted α-cyclodextrin and hexamethylenediamine prepared in step 2) to a mixed solution of organic solvent 1 and water, and then adding 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide. After stirring and mixing, the mixture is reacted at 25-40° C. for 24-48 hours, and the solvent is removed by distillation under reduced pressure. The resulting filter cake is washed 2-3 times with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

[0019] In step 1), the volume ratio of the organic solvent 1 to water in the mixed solution of the organic solvent 1 and water is 1:1-3.

[0020] The mass ratio of the three-terminal carboxyl compound, α-cyclodextrin, mixed solution, 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step 1) is 1:0.75~1:5~10:0.3~0.6:0.33~0.66.

[0021] The organic solvent 4 in step 2) is dimethyl sulfoxide or dimethylformamide.

[0022] In step 2), the mass ratio of the carboxyl-terminated compound grafted with α-cyclodextrin, the organic solvent 4, and iodomethane is 1:5-10:0.3-0.6.

[0023] In step 3), the volume ratio of the organic solvent 1 to water in the mixed solution of the organic solvent 1 and water is 1:1-3.

[0024] The mass ratio of the quaternized ammonium grafted α-cyclodextrin terminal carboxyl compound, hexamethylenediamine, mixed solution, 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step 3) is 1:0.25-0.35:5-10:0.27-0.54:0.35-0.7.

[0025] The preparation method of the easily dispersible toluidine red pigment comprises the following steps:

[0026] In parts by weight, 0.3-0.5 parts of a cyclodextrin grafted polyamide polymer and 1-2 parts of toluidine red are added to a mixed solvent of 10-20 parts of an organic solvent 1 and water in a volume ratio of 1:2-3, and the mixture is stirred for 24-48 hours. The solvent is removed by distillation under reduced pressure, and the mixture is dried to obtain an easily dispersible toluidine red pigment.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] The easily dispersible toluidine red pigment of the present invention is prepared by synthesizing a polyamide polymer grafted with cyclodextrin. Firstly, the polyamide main chain has good film-forming properties. Secondly, the unique annular cavity of cyclodextrin is utilized to encapsulate the toluidine red molecules, thereby avoiding aggregation between the toluidine red molecules, reducing the contact of the dye molecules with unstable factors such as oxygen, acidic and alkaline substances, and ultraviolet rays in the air, and enhancing the stability and weather resistance of the dye molecules. Thirdly, the synthesized polymer main chain carries positive charges, thereby avoiding aggregation between toluidine red dye molecule particles. The positive charges on the polymer main chain generate electrostatic attraction with the toluidine red pigment, causing the polymer to be firmly adsorbed on the surface of the toluidine red pigment, thereby further enhancing the dispersion stability of the pigment.

[0029] The easily dispersible toluidine red pigment of the present invention has a synthesized polyamide polymer grafted with cyclodextrin without unsaturated functional groups, such as olefins and aromatic ring groups, thereby reducing the light absorption effect of the polymer. Furthermore, the polymer does not participate in the synthesis and crystallization process of the pigment and does not affect the color of the pigment. The longer polymer main chain can provide sufficient steric hindrance, which, combined with the host-guest inclusion complex and the rigid steric hindrance group of cyclodextrin, achieves a synergistic enhancement effect and more effectively prevents the pigment particles from approaching and agglomerating.

[0030] The easily dispersible toluidine red pigment prepared by the present invention has stable dispersibility, high tinting strength and weather resistance, and effectively improves its application effect in the fields of coatings and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1This is a graph showing the dispersion performance of the easily dispersible toluidine red pigment prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] In order to better understand the technical solutions of the present invention, the following is a further detailed description of the above content of the present invention through specific implementation methods in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0033] Example 1 Preparation of a three-terminal carboxyl compound

[0034] 0.1 kg of methyl 3-aminopropionate and 0.35 kg of methyl 3-bromopropionate were added to 1 kg of acetonitrile, and then 0.25 kg of potassium carbonate was added, stirred and mixed evenly, heated to 40 ° C and reacted for 12 hours. After the reaction was completed, the filtrate was filtered, and the solvent was distilled off under reduced pressure. The filter cake was washed with water and dried, and then added to 1 kg of methanol, stirred and dissolved, and 0.12 kg of sodium hydroxide was added. The mixture was reacted at 25 ° C for 12 hours and filtered to obtain a three-terminal carboxyl compound. 1 H NMR (300 MHz, DMSO- d 6 , 298 K) δ 12.25 (s, 3H), 3.70 (t, 6H), 2.53 (t, 6H).

[0035] Preparation of polyamide polymer grafted with cyclodextrin

[0036] 1) Add 0.1 kg of a three-terminal carboxyl compound and 0.075 kg of α-cyclodextrin to 0.5 kg of a mixed solution of acetonitrile and water in a volume ratio of 1:1, then add 0.03 kg of 4-dimethylaminopyridine and 0.033 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix until uniform, and react at 25°C for 24 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin;

[0037] 2) adding 0.1 kg of the carboxyl-terminated grafted α-cyclodextrin compound prepared in step 1) to 0.5 kg of dimethyl sulfoxide, and then adding 0.03 kg of iodomethane, heating to 40° C. for 8 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a quaternized ammonium grafted α-cyclodextrin carboxyl-terminated compound;

[0038] 3) 0.1 kg of the quaternized grafted α-cyclodextrin terminal carboxyl compound prepared in step 2) and 0.025 kg of hexamethylenediamine were added to 0.5 kg of a mixed solution of acetonitrile and water in a volume ratio of 1:1, followed by the addition of 0.027 kg of 1-hydroxybenzotriazole and 0.035 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. The mixture was stirred and mixed thoroughly, and the mixture was reacted at 25°C for 24 h. The solvent was then removed by distillation under reduced pressure. The resulting filter cake was washed twice with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

[0039] Preparation of easily dispersible toluidine red pigment

[0040] 0.3 kg of cyclodextrin grafted polyamide polymer and 1 kg of toluidine red were added to a mixed solvent of 10 kg of acetonitrile and water in a volume ratio of 1:2, stirred and mixed for 24 hours, and the solvent was removed by reduced pressure distillation and dried to obtain an easily dispersible toluidine red pigment.

[0041] Example 2 Preparation of a three-terminal carboxyl compound

[0042] 0.1 kg of methyl 3-aminopropionate and 0.4 kg of methyl 3-bromopropionate were added to 1.2 kg of acetone, and then 0.28 kg of sodium carbonate was added, stirred and mixed evenly, heated to 45 ° C and reacted for 15 hours. After the reaction was completed, the filtrate was filtered, and the solvent was distilled off under reduced pressure. The filter cake was washed with water and dried, and then added to 1.1 kg of ethanol, stirred and dissolved, and 0.15 kg of potassium hydroxide was added. The mixture was reacted at 28 ° C for 14 hours and filtered to obtain a three-terminal carboxyl compound.

[0043] Preparation of polyamide polymer grafted with cyclodextrin

[0044] 1) Add 0.1 kg of a three-terminal carboxyl compound and 0.08 kg of α-cyclodextrin to 0.6 kg of a mixed solution of acetone and water in a volume ratio of 1:1.5, then add 0.035 kg of 4-dimethylaminopyridine and 0.04 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix thoroughly, and react at 30°C for 30 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin;

[0045] 2) adding 0.1 kg of the carboxyl-terminated grafted α-cyclodextrin compound prepared in step 1) to 0.6 kg of dimethylformamide, and then adding 0.035 kg of iodomethane, heating to 50° C. for 9 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a quaternized carboxyl-terminated grafted α-cyclodextrin compound;

[0046] 3) 0.1 kg of the quaternized grafted α-cyclodextrin terminal carboxyl compound prepared in step 2) and 0.028 kg of hexamethylenediamine were added to 0.6 kg of a mixed solution of acetone and water in a volume ratio of 1:1.2, followed by the addition of 0.032 kg of 1-hydroxybenzotriazole and 0.04 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. The mixture was stirred and mixed thoroughly, and the mixture was reacted at 30° C. for 30 h. The solvent was then removed by distillation under reduced pressure. The resulting filter cake was washed three times with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

[0047] Preparation of easily dispersible toluidine red pigment

[0048] 0.35 kg of cyclodextrin grafted polyamide polymer and 1.4 kg of toluidine red were added to a mixed solvent of 12 kg of acetone and water in a volume ratio of 1:2.2, stirred and mixed for 30 hours, and the solvent was removed by vacuum distillation and dried to obtain an easily dispersible toluidine red pigment.

[0049] Example 3 Preparation of a three-terminal carboxyl compound

[0050] 0.1 kg of methyl 3-aminopropionate and 0.42 kg of methyl 3-bromopropionate were added to 1.5 kg of dimethyl sulfoxide, and then 0.33 kg of potassium carbonate was added, stirred and mixed evenly, heated to 50 ° C and reacted for 18 hours. After the reaction was completed, the filtrate was filtered, and the solvent was distilled off under reduced pressure. The filter cake was washed with water and dried, and then added to 1.4 kg of ethanol, stirred and dissolved, and 0.18 kg of sodium hydroxide was added. The mixture was reacted at 30 ° C for 16 hours and filtered to obtain a three-terminal carboxyl compound.

[0051] Preparation of polyamide polymer grafted with cyclodextrin

[0052] 1) Add 0.1 kg of a tricarboxyl-terminated compound and 0.085 kg of α-cyclodextrin to 0.7 kg of a mixed solution of tetrahydrofuran and water in a volume ratio of 1:2, then add 0.04 kg of 4-dimethylaminopyridine and 0.045 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix until uniform, and react at 33°C for 35 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin;

[0053] 2) adding 0.1 kg of the carboxyl-terminated grafted α-cyclodextrin compound prepared in step 1) to 0.7 kg of dimethylformamide, and then adding 0.04 kg of iodomethane, heating to 70° C. for 10 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a quaternized carboxyl-terminated grafted α-cyclodextrin compound;

[0054] 3) 0.1 kg of the quaternized grafted α-cyclodextrin terminal carboxyl compound prepared in step 2) and 0.03 kg of hexamethylenediamine were added to 0.7 kg of a mixed solution of tetrahydrofuran and water in a volume ratio of 1:1.5, followed by the addition of 0.04 kg of 1-hydroxybenzotriazole and 0.05 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. The mixture was stirred and mixed thoroughly, and the mixture was reacted at 35° C. for 35 h. The solvent was then removed by distillation under reduced pressure. The resulting filter cake was washed three times with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

[0055] Preparation of easily dispersible toluidine red pigment

[0056] 0.4 kg of cyclodextrin grafted polyamide polymer and 1.5 kg of toluidine red were added to a mixed solvent of 14 kg of tetrahydrofuran and water in a volume ratio of 1:2.5, stirred and mixed for 35 hours, and the solvent was removed by vacuum distillation and dried to obtain an easily dispersible toluidine red pigment.

[0057] Example 4 Preparation of a three-terminal carboxyl compound

[0058] 0.1 kg of methyl 3-aminopropionate and 0.45 kg of methyl 3-bromopropionate were added to 1.6 kg of dimethylformamide, and then 0.35 kg of sodium carbonate was added, stirred and mixed evenly, heated to 60 ° C and reacted for 20 hours. After the reaction was completed, the filtrate was filtered, and the solvent was distilled off under reduced pressure. The filter cake was washed with water and dried, and then added to 1.6 kg of methanol, stirred and dissolved, and 0.2 kg of sodium hydroxide was added. The mixture was reacted at 35 ° C for 20 hours and filtered to obtain a three-terminal carboxyl compound.

[0059] Preparation of polyamide polymer grafted with cyclodextrin

[0060] 1) Add 0.1 kg of a three-terminal carboxyl compound and 0.09 kg of α-cyclodextrin to 0.8 kg of a mixed solution of dimethyl sulfoxide and water in a volume ratio of 1:2.5, then add 0.05 kg of 4-dimethylaminopyridine and 0.055 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix until uniform, and react at 35°C for 40 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin;

[0061] 2) adding 0.1 kg of the terminal carboxyl compound of grafted α-cyclodextrin prepared in step 1) to 0.8 kg of dimethyl sulfoxide, and then adding 0.05 kg of iodomethane, heating to 80° C. for 11 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a terminal carboxyl compound of grafted α-cyclodextrin;

[0062] 3) 0.1 kg of the quaternized grafted α-cyclodextrin terminal carboxyl compound prepared in step 2) and 0.032 kg of hexamethylenediamine were added to 0.8 kg of a mixed solution of dimethylformamide and water in a volume ratio of 1:2, followed by the addition of 0.045 kg of 1-hydroxybenzotriazole and 0.06 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. The mixture was stirred and mixed thoroughly, and the mixture was reacted at 38°C for 40 h. The solvent was then removed by distillation under reduced pressure. The resulting filter cake was washed three times with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

[0063] Preparation of easily dispersible toluidine red pigment

[0064] 0.45 kg of cyclodextrin grafted polyamide polymer and 1.7 kg of toluidine red were added to a mixed solvent of 16 kg of dimethyl sulfoxide and water in a volume ratio of 1:2.8, stirred and mixed for 40 hours, and the solvent was removed by vacuum distillation and dried to obtain an easily dispersible toluidine red pigment.

[0065] Example 5 Preparation of a three-terminal carboxyl compound

[0066] 0.1 kg of methyl 3-aminopropionate and 0.48 kg of methyl 3-bromopropionate were added to 1.8 kg of tetrahydrofuran, and then 0.38 kg of potassium carbonate was added, stirred and mixed evenly, heated to 70 ° C and reacted for 22 hours. After the reaction was completed, the filtrate was filtered, and the solvent was removed by distillation under reduced pressure. The filter cake was washed with water and dried, and then added to 1.8 kg of methanol, stirred and dissolved, and 0.22 kg of potassium hydroxide was added. The mixture was reacted at 40 ° C for 24 hours and filtered to obtain a three-terminal carboxyl compound.

[0067] Preparation of polyamide polymer grafted with cyclodextrin

[0068] 1) Add 0.1 kg of a three-terminal carboxyl compound and 0.095 kg of α-cyclodextrin to 0.9 kg of a mixed solution of dimethyl sulfoxide and water in a volume ratio of 1:2.8, then add 0.055 kg of 4-dimethylaminopyridine and 0.06 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix until uniform, and react at 38°C for 45 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin;

[0069] 2) adding 0.1 kg of the carboxyl-terminated grafted α-cyclodextrin compound prepared in step 1) to 0.9 kg of dimethyl sulfoxide, followed by 0.055 kg of iodomethane, and heating to 90° C. for 11 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a quaternized carboxyl-terminated grafted α-cyclodextrin compound;

[0070] 3) 0.1 kg of the quaternized grafted α-cyclodextrin terminal carboxyl compound prepared in step 2) and 0.034 kg of hexamethylenediamine were added to 0.9 kg of a mixed solution of dimethyl sulfoxide and water in a volume ratio of 1:2.5, followed by the addition of 0.05 kg of 1-hydroxybenzotriazole and 0.065 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. The mixture was stirred and mixed thoroughly, and the mixture was reacted at 38°C for 45 h. The solvent was then removed by distillation under reduced pressure. The resulting filter cake was washed three times with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

[0071] Preparation of easily dispersible toluidine red pigment

[0072] 0.5 kg of cyclodextrin grafted polyamide polymer and 2 kg of toluidine red were added to a mixed solvent of 19 kg of dimethylformamide and water in a volume ratio of 1:3, stirred and mixed for 45 hours, and the solvent was removed by vacuum distillation and dried to obtain an easily dispersible toluidine red pigment.

[0073] Example 6 Preparation of a three-terminal carboxyl compound

[0074] 0.1 kg of methyl 3-aminopropionate and 0.5 kg of methyl 3-bromopropionate were added to 2 kg of tetrahydrofuran, and then 0.4 kg of sodium carbonate was added, stirred and mixed evenly, heated to 80 ° C and reacted for 24 hours. After the reaction was completed, the filtrate was filtered, and the solvent was distilled off under reduced pressure. The filter cake was washed with water and dried, and then added to 2 kg of ethanol, stirred and dissolved, and 0.24 kg of sodium hydroxide was added. The mixture was reacted at 40 ° C for 12 hours and filtered to obtain a three-terminal carboxyl compound.

[0075] Preparation of polyamide polymer grafted with cyclodextrin

[0076] 1) Add 0.1 kg of a three-terminal carboxyl compound and 0.1 kg of α-cyclodextrin to 1 kg of a mixed solution of dimethylformamide and water in a volume ratio of 1:3, then add 0.06 kg of 4-dimethylaminopyridine and 0.066 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix until uniform, and react at 40°C for 48 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin;

[0077] 2) adding 0.1 kg of the carboxyl-terminated grafted α-cyclodextrin compound prepared in step 1) to 1 kg of dimethylformamide, and then adding 0.06 kg of iodomethane, heating to 100° C. for 12 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a quaternized carboxyl-terminated grafted α-cyclodextrin compound;

[0078] 3) 0.1 kg of the quaternized grafted α-cyclodextrin terminal carboxyl compound prepared in step 2) and 0.035 kg of hexamethylenediamine were added to 1 kg of a mixed solution of acetone and water in a volume ratio of 1:3, followed by the addition of 0.054 kg of 1-hydroxybenzotriazole and 0.07 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide. The mixture was stirred and mixed thoroughly, and the mixture was reacted at 40°C for 48 h. The solvent was then removed by distillation under reduced pressure. The resulting filter cake was washed three times with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

[0079] Preparation of easily dispersible toluidine red pigment

[0080] 0.5 kg of cyclodextrin grafted polyamide polymer and 1 kg of toluidine red were added to a mixed solvent of 20 kg of dimethylformamide and water in a volume ratio of 1:3, stirred and mixed for 48 hours, and the solvent was removed by vacuum distillation and dried to obtain an easily dispersible toluidine red pigment.

[0081] The easily dispersible toluidine red pigments prepared in Examples 1 to 6 were tested for tinting strength according to the method specified in GB 1708-79, color shade according to the method specified in GB 1864-80, and bulk density according to the method specified in GB / T 21877-2015. 50 g of the easily dispersible toluidine red pigment was accurately weighed and placed in a graduated cylinder, which was sealed and shaken up and down 10 times. The sample graduation on the cylinder was recorded. Lightfastness was tested according to GB 1710-79, and water resistance, acid resistance, and alkali resistance were tested according to GB 5211.5-2008-T. Toluidine Red YS (PR3) for coatings, a product of our company, was used as a comparative example. The test results are shown in Table 1. As can be seen from the results in Table 1, the easily dispersible toluidine red pigment prepared in the present invention exhibits better dispersibility and tinting strength than the comparative example, and also exhibits excellent lightfastness, water resistance, acid resistance, and alkali resistance.

[0082] Table 1 Performance test results of pigments prepared in Examples 1 to 6 and comparative examples

[0083]

[0084] In parts by weight, 10 parts of the easily dispersible toluidine red pigment prepared in Example 3 and 100 parts of acrylic latex paint were added to a high-speed disperser and stirred and ground at 2500 r / min. During the grinding process, the dispersion was taken and the fineness change of the pigment under different grinding times was measured using a scraper fineness meter. The test results are shown as follows: Figure 1 As shown. Figure 1The results show that the easily dispersible toluidine red pigment prepared by the present invention reaches its minimum fineness around 30 minutes compared to the comparative example, and the fineness remains essentially unchanged with further grinding, indicating that the easily dispersible toluidine red pigment prepared by the present invention has excellent dispersibility. The slurries ground for 50 minutes were added to 50 ml centrifuge tubes and allowed to stand at 25°C for 2 weeks. The sedimentation rate and color change were tested, and the test results are shown in Table 2. As can be seen from the results in Table 2, the easily dispersible toluidine red pigment prepared by the present invention has a lower sedimentation rate and smaller color parameter changes, indicating that the easily dispersible toluidine red pigment prepared by the present invention has better dispersibility and is less prone to flocculation and sedimentation.

[0085] Table 2 Pigment sedimentation rate and color change results

[0086]

[0087] 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. An easily dispersible toluidine red pigment, characterized in that: The preparation method comprises the following raw materials in parts by weight: 1-2 parts of toluidine red and 0.3-0.5 parts of polyamide polymer grafted with cyclodextrin; The polyamide polymer grafted with cyclodextrin is prepared by grafting cyclodextrin onto a tri-terminal carboxyl compound, performing a quaternization reaction, and finally reacting with hexamethylenediamine; The three-terminal carboxyl compound is prepared according to the following method: Add methyl 3-aminopropionate and methyl 3-bromopropionate to organic solvent 1, then add base 1, stir and mix evenly, heat to 40-80°C and react for 12-24 hours. After the reaction is complete, filter and remove the solvent from the filtrate by vacuum distillation. Wash the filter cake with water and dry it, then add it to organic solvent 2, stir and dissolve it, add base 2, react at 25-40°C for 12-24 hours, and filter to obtain a three-terminal carboxyl compound. The polyamide polymer grafted with cyclodextrin is prepared according to the following steps: 1) Add the tricarboxyl-terminated compound and α-cyclodextrin to a mixed solution of organic solvent 1 and water, then add 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stir and mix thoroughly, and react at 25-40°C for 24-48 hours. After the reaction is completed, filter and remove the solvent from the filtrate under reduced pressure to obtain a carboxyl-terminated compound grafted with α-cyclodextrin; 2) adding the terminal carboxyl compound grafted with α-cyclodextrin prepared in step 1) to organic solvent 4, then adding iodomethane, heating to 40-100° C. and reacting for 8-12 hours. After the reaction is complete, removing the solvent by vacuum distillation to obtain a terminal carboxyl compound grafted with α-cyclodextrin; 3) adding the terminal carboxyl compound of the quaternized grafted α-cyclodextrin and hexamethylenediamine prepared in step 2) to a mixed solution of organic solvent 1 and water, and then adding 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide. After stirring and mixing, the mixture is reacted at 25-40° C. for 24-48 hours, and the solvent is removed by distillation under reduced pressure. The resulting filter cake is washed 2-3 times with ethanol and dried to obtain a polyamide polymer grafted with cyclodextrin.

2. The easily dispersible toluidine red pigment according to claim 1, wherein: The organic solvent 1 is acetonitrile, acetone, tetrahydrofuran, dimethyl sulfoxide or dimethylformamide; the base 1 is potassium carbonate or sodium carbonate; the organic solvent 2 is methanol, ethanol or isopropanol; and the base 2 is sodium hydroxide or potassium hydroxide.

3. The easily dispersible toluidine red pigment according to claim 1, wherein: The mass ratio of the methyl 3-aminopropionate, methyl 3-bromopropionate, organic solvent 1, base 1, organic solvent 2 and base 2 is 1:3.5~5:10~20:2.5~4:10~20:1.2~2.

4.

4. The easily dispersible toluidine red pigment according to claim 1, wherein: The volume ratio of the organic solvent 1 to water in the mixed solution of the organic solvent 1 and water in step 1) is 1:1-3; the mass ratio of the three-terminal carboxyl compound, α-cyclodextrin, mixed solution, 4-dimethylaminopyridine and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step 1) is 1:0.75-1:5-10:0.3-0.6:0.33-0.

66.

5. The easily dispersible toluidine red pigment according to claim 1, wherein: The organic solvent 4 in step 2) is dimethyl sulfoxide or dimethylformamide; the mass ratio of the carboxyl-terminated compound grafted with α-cyclodextrin, the organic solvent 4 and iodomethane in step 2) is 1:5-10:0.3-0.

6.

6. The easily dispersible toluidine red pigment according to claim 1, wherein: In step 3), the volume ratio of the organic solvent 1 to water in the mixed solution of the organic solvent 1 and water is 1:1-3.

7. The easily dispersible toluidine red pigment according to claim 1, wherein: The mass ratio of the quaternized ammonium grafted α-cyclodextrin terminal carboxyl compound, hexamethylenediamine, mixed solution, 1-hydroxybenzotriazole and 1-ethyl-(3-dimethylaminopropyl)carbodiimide in step 3) is 1:0.25-0.35:5-10:0.27-0.54:0.35-0.

7.

8. The method for preparing the easily dispersible toluidine red pigment according to claim 1, wherein: The following steps are involved: In parts by weight, 0.3-0.5 parts of a cyclodextrin grafted polyamide polymer and 1-2 parts of toluidine red are added to a mixed solvent of 10-20 parts of an organic solvent 1 and water in a volume ratio of 1:2-3, and the mixture is stirred for 24-48 hours. The solvent is removed by distillation under reduced pressure, and the mixture is dried to obtain an easily dispersible toluidine red pigment.

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