Toluidine red pigment for architectural coatings and preparation method thereof

Abstract

The invention discloses a toluidine red pigment for architectural coatings and a preparation method thereof, belonging to the technical field of pigment synthesis. Adamantane is introduced into toluidine red, and the adamantane has a stable cage structure, thereby increasing the water resistance and acid and alkali resistance of the pigment; in addition, the weather resistance and thermal stability of the pigment can be improved, thereby increasing the durability of the toluidine red pigment for architectural coatings in outdoor environments; a cyclodextrin-modified resin can form a stable host-guest complex with the adamantane-modified pigment through self-assembly, thereby increasing the dispersibility and hiding power of the pigment, thereby increasing the stability and construction performance of the pigment; and the invention has good application prospects in the field of architecture.

Description

Technical Field

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

[0002] Toluidine red, also known as Pigment Red 3, is an organic compound mainly used for the coloring of ink pads, ink pencils, crayons, watercolors and oil paints, as well as rubber products. It is also suitable for the coloring of varnished cloth, coatings, plastics and natural lacquers, as well as sand pipes, arts and crafts, and cosmetics. It is also widely used in the field of architectural coatings.

[0003] However, toluidine red is sensitive to environmental factors such as light, heat, and water, has poor acid and alkali resistance, and is prone to fading and discoloration, which reduces the decorative effect and service life of the paint. Compared with inorganic pigments, toluidine red has weaker hiding power and tinting power, so a higher dosage is required to achieve the ideal coating effect. In addition, toluidine red has poor dispersibility in the coating system and is prone to flocculation and precipitation, which affects the construction performance and storage stability of the coating. Therefore, it is of great significance to improve the performance of toluidine red as a building coating by modifying it. Summary of the invention

[0004] To solve the above problems, the object of the present invention is to provide a toluidine red pigment for architectural coatings and a preparation method thereof.

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

[0006] A toluidine red pigment for architectural coatings, comprising the following raw materials, in parts by weight: 1 part of modified toluidine red pigment and 0.3-0.5 parts of cyclodextrin-modified resin;

[0007] The modified toluidine red pigment is prepared by diazotizing o-nitro-p-toluidine and then coupling it with a 2-naphthol derivative modified with adamantane;

[0008] The adamantane-modified 2-naphthol derivative is prepared according to the following method:

[0009] 8-amino-2-naphthol and adamantane ketone are added to an alcohol solvent, stirred and mixed evenly, reacted at 25-40°C for 3-5 hours, and then a reducing agent is added thereto, and the reaction is continued for 5-10 hours. After the reaction is completed, the solvent is removed by distillation under reduced pressure, water is added to the obtained residue, and then dichloromethane is added for extraction 2-3 times, and the obtained organic phase is distilled under reduced pressure to remove the solvent to obtain an adamantane-modified 2-naphthol derivative.

[0010] The alcohol solvent is methanol, ethanol or isopropanol.

[0011] The reducing agent is sodium borohydride or sodium cyanoborohydride.

[0012] The mass ratio of the 8-amino-2-naphthol, adamantane ketone, alcohol solvent, reducing agent, water and dichloromethane is 1:1-1.5:5-10:0.4-0.8:5-10:5-10.

[0013] The preparation method of the modified toluidine red pigment comprises the following steps:

[0014] 1) In parts by weight, add 60-100 parts of water and 5 parts of o-nitro-p-toluidine into a diazotization reaction kettle, stir for 0.5-1h, then add 10-12.5 parts of 30% hydrochloric acid, stir for 1-2h, cool to 0-5°C, dropwise add 20-23 parts of 30% sodium nitrite solution, stir for 1-3h, until Congo red test paper turns blue and potassium iodide starch test paper turns blue, stop the reaction, and obtain diazo solution;

[0015] 2) Add 10-12 parts of adamantane-modified 2-naphthol derivatives and 15-20 parts of ethanol into a coupling reactor, stir and mix evenly, then add the diazo solution obtained in step 1), adjust the pH of the system to 8-8.5 with a 20-30% mass concentration of sodium hydroxide aqueous solution, stir and react for 1-2 hours, heat to 70-80° C. and continue to react for 1-2 hours, filter, wash and dry to obtain a modified toluidine red pigment.

[0016] The cyclodextrin-modified resin is prepared according to the following method:

[0017] Allyl-β-cyclodextrin, acrylamide and acrylic acid are added to dimethyl sulfoxide, stirred and mixed evenly, and then azobisisobutyronitrile is added thereto, and the mixture is reacted at 80-100°C for 10-15h. After the reaction is completed, the solvent is removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

[0018] The mass ratio of allyl-β-cyclodextrin, acrylamide, acrylic acid, dimethyl sulfoxide and azobisisobutyronitrile is 0.5-1: 0.5-0.8: 0.5-0.8: 3-5: 0.002-0.05.

[0019] The method for preparing the toluidine red pigment for architectural coatings comprises the following steps:

[0020] In parts by weight, 1 part of modified toluidine red pigment and 0.3-0.5 parts of cyclodextrin-modified resin are added to 5-10 parts of water, stirred and mixed for 0.5-1 hour, filtered, and the obtained filter cake is dried and crushed to obtain toluidine red pigment for architectural coatings.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The toluidine red pigment for architectural coatings of the present invention introduces adamantane into toluidine red, and the adamantane has a stable cage structure, thereby increasing the water resistance and acid and alkali resistance of the pigment; in addition, the weather resistance and thermal stability of the pigment can be improved, thereby increasing the durability of the toluidine red pigment for architectural coatings in outdoor environments.

[0023] The toluidine red pigment for architectural coatings of the present invention can form a stable host-guest complex with the adamantane-modified pigment through self-assembly, thereby improving the dispersibility and hiding power of the pigment and thus improving the stability and construction performance of the pigment.

[0024] The toluidine red pigment for architectural coatings prepared by the present invention has strong acid and alkali resistance and weather resistance, and also has good dispersibility and hiding power, thereby improving the durability of the pigment in outdoor use and having good application prospects in the field of construction. 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 adamantane-modified 2-naphthol derivatives:

[0027] 0.1 kg of 8-amino-2-naphthol and 0.1 kg of adamantane ketone were added to 0.5 kg of methanol, stirred and mixed evenly, and reacted at 25°C for 5 hours. Then, 0.04 kg of sodium borohydride was added thereto, and the reaction was continued for 10 hours. After the reaction was completed, the solvent was distilled off under reduced pressure, 0.5 kg of water was added to the obtained residue, and then 0.5 kg of dichloromethane was added and extracted twice. The obtained organic phase was distilled off under reduced pressure to remove the solvent, and an adamantane-modified 2-naphthol derivative was obtained. 1 H NMR (300 MHz, DMSO- d 6 , 298 K) δ 9.18 (s, 1H), 7.78 (d, 1H), 7.33-7.54 (m, 3H), 6.92 (d, 1H), 6.91 (d, 1H), 5.15 (s, 1H), 2.83 (m, 1H), 1.62-1.89 (m, 14H).

[0028] Preparation of modified toluidine red pigment:

[0029] 6 kg of water and 0.5 kg of o-nitro-p-toluidine were added to a diazotization reactor, stirred for 0.5 h, and then 1 kg of 30% hydrochloric acid was added thereto. After stirring for 1 h, the temperature was lowered to 0°C, and 2 kg of 30% sodium nitrite solution was added dropwise thereto. The reaction was stirred for 1 h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. The reaction was stopped to obtain a diazo solution.

[0030] 1 kg of adamantane-modified 2-naphthol derivative and 1.5 kg of ethanol were added into a coupling reactor, stirred and mixed evenly, and then diazo liquid was added thereto. The pH of the system was adjusted to 8 with a 20% mass concentration of sodium hydroxide aqueous solution. The reaction was stirred for 1 hour, the temperature was raised to 70° C. and the reaction was continued for 2 hours. The reaction was filtered, washed, and dried to obtain a modified toluidine red pigment.

[0031] Preparation of cyclodextrin modified resin:

[0032] 0.5 kg of allyl-β-cyclodextrin, 0.5 kg of acrylamide and 0.5 kg of acrylic acid were added to 3 kg of dimethyl sulfoxide, stirred and mixed evenly, and then 0.002 kg of azobisisobutyronitrile was added thereto, and the mixture was reacted at 80° C. for 15 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

[0033] Preparation of Toluidine Red Pigment for Architectural Coatings:

[0034] 1 kg of modified toluidine red pigment and 0.3 kg of cyclodextrin-modified resin were added into 5 kg of water, stirred and mixed for 0.5 h, filtered, and the obtained filter cake was dried and crushed to obtain toluidine red pigment for architectural coatings.

[0035] Example 2 Preparation of adamantane-modified 2-naphthol derivatives:

[0036] 0.1 kg of 8-amino-2-naphthol and 0.11 kg of adamantane ketone were added to 0.6 kg of ethanol, stirred and mixed evenly, and reacted at 30°C for 4.5 hours. Then, 0.05 kg of sodium cyanoborohydride was added thereto, and the reaction was continued for 9 hours. After the reaction was completed, the solvent was distilled off under reduced pressure, 0.6 kg of water was added to the obtained residue, and then 0.6 kg of dichloromethane was added and extracted 3 times. The obtained organic phase was distilled off under reduced pressure to remove the solvent, and an adamantane-modified 2-naphthol derivative was obtained.

[0037] Preparation of modified toluidine red pigment:

[0038] 7 kg of water and 0.5 kg of o-nitro-p-toluidine were added to a diazotization reactor, stirred for 0.6 h, and then 1.1 kg of 30% hydrochloric acid was added thereto. After stirring for 1.2 h, the temperature was lowered to 2°C, and 2.1 kg of 30% sodium nitrite solution was added dropwise thereto. The reaction was stirred for 1.5 h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. The reaction was stopped to obtain a diazo solution.

[0039] 1.1 kg of adamantane-modified 2-naphthol derivative and 1.6 kg of ethanol were added to a coupling reactor, stirred and mixed evenly, and then diazo liquid was added thereto. The pH of the system was adjusted to 8.1 with a 25% mass concentration of sodium hydroxide aqueous solution. The reaction was stirred for 1.5 hours, the temperature was raised to 75°C and the reaction was continued for 1.8 hours. The reaction was filtered, washed, and dried to obtain a modified toluidine red pigment.

[0040] Preparation of cyclodextrin modified resin:

[0041] 0.6 kg of allyl-β-cyclodextrin, 0.6 kg of acrylamide and 0.6 kg of acrylic acid were added to 3.5 kg of dimethyl sulfoxide, stirred and mixed evenly, and then 0.01 kg of azobisisobutyronitrile was added thereto, and the mixture was reacted at 85° C. for 14 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

[0042] Preparation of Toluidine Red Pigment for Architectural Coatings:

[0043] 1 kg of modified toluidine red pigment and 0.35 kg of cyclodextrin-modified resin were added into 6 kg of water, stirred and mixed for 0.6 h, filtered, and the obtained filter cake was dried and crushed to obtain toluidine red pigment for architectural coatings.

[0044] Example 3 Preparation of adamantane-modified 2-naphthol derivatives:

[0045] 0.1 kg of 8-amino-2-naphthol and 0.12 kg of adamantane ketone were added to 0.7 kg of isopropanol, stirred and mixed evenly, and reacted at 35°C for 4 hours. Then, 0.06 kg of sodium borohydride was added thereto, and the reaction was continued for 8 hours. After the reaction was completed, the solvent was distilled off under reduced pressure, 0.7 kg of water was added to the obtained residue, and then 0.7 kg of dichloromethane was added and extracted 3 times. The obtained organic phase was distilled off under reduced pressure to remove the solvent, and an adamantane-modified 2-naphthol derivative was obtained.

[0046] Preparation of modified toluidine red pigment:

[0047] 8 kg of water and 0.5 kg of o-nitro-p-toluidine were added to a diazotization reactor, stirred for 0.7 h, and then 1.2 kg of 30% hydrochloric acid was added thereto. After stirring for 1.5 h, the temperature was lowered to 3°C, and 2.2 kg of 30% sodium nitrite solution was added dropwise thereto. The reaction was stirred for 2 h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. The reaction was stopped to obtain a diazo solution.

[0048] 1.15 kg of adamantane-modified 2-naphthol derivative and 1.7 kg of ethanol were added to a coupling reactor, stirred and mixed evenly, and then diazo liquid was added thereto. The pH of the system was adjusted to 8.2 with a 25% mass concentration of sodium hydroxide aqueous solution. The reaction was stirred for 1.6 hours, the temperature was raised to 75°C and the reaction was continued for 1.5 hours. The reaction was filtered, washed, and dried to obtain a modified toluidine red pigment.

[0049] Preparation of cyclodextrin modified resin:

[0050] 0.7 kg of allyl-β-cyclodextrin, 0.7 kg of acrylamide and 0.7 kg of acrylic acid were added to 4 kg of dimethyl sulfoxide, stirred and mixed evenly, and then 0.02 kg of azobisisobutyronitrile was added thereto, and the mixture was reacted at 90° C. for 13 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

[0051] Preparation of Toluidine Red Pigment for Architectural Coatings:

[0052] 1 kg of modified toluidine red pigment and 0.4 kg of cyclodextrin-modified resin were added into 7 kg of water, stirred and mixed for 0.8 h, filtered, and the obtained filter cake was dried and crushed to obtain toluidine red pigment for architectural coatings.

[0053] Example 4 Preparation of adamantane-modified 2-naphthol derivatives:

[0054] 0.1 kg of 8-amino-2-naphthol and 0.14 kg of adamantane ketone were added to 0.8 kg of ethanol, stirred and mixed evenly, and reacted at 37°C for 3.5 hours. Then, 0.07 kg of sodium cyanoborohydride was added thereto, and the reaction was continued for 6 hours. After the reaction was completed, the solvent was distilled off under reduced pressure, 0.8 kg of water was added to the obtained residue, and then 0.9 kg of dichloromethane was added and extracted 3 times. The obtained organic phase was distilled off under reduced pressure to remove the solvent, and an adamantane-modified 2-naphthol derivative was obtained.

[0055] Preparation of modified toluidine red pigment:

[0056] 8 kg of water and 0.5 kg of o-nitro-p-toluidine were added to a diazotization reaction kettle, stirred for 0.8 h, and then 1.2 kg of 30% hydrochloric acid was added thereto. After stirring for 1.8 h, the temperature was lowered to 4°C, and 2.25 kg of 30% sodium nitrite solution was added dropwise thereto. The reaction was stirred for 2.5 h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. The reaction was stopped to obtain a diazo solution.

[0057] 1.1 kg of adamantane-modified 2-naphthol derivative and 1.8 kg of ethanol were added to a coupling reactor, stirred and mixed evenly, and then diazo liquid was added thereto. The pH of the system was adjusted to 8.4 with a 28% mass concentration of sodium hydroxide aqueous solution. The reaction was stirred for 1.8 hours, the temperature was raised to 78°C and the reaction was continued for 1.2 hours. The reaction was filtered, washed, and dried to obtain a modified toluidine red pigment.

[0058] Preparation of cyclodextrin modified resin:

[0059] 0.9 kg of allyl-β-cyclodextrin, 0.6 kg of acrylamide and 0.7 kg of acrylic acid were added to 4.5 kg of dimethyl sulfoxide, stirred and mixed evenly, and then 0.04 kg of azobisisobutyronitrile was added thereto, and the mixture was reacted at 95° C. for 12 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

[0060] Preparation of Toluidine Red Pigment for Architectural Coatings:

[0061] 1 kg of modified toluidine red pigment and 0.45 kg of cyclodextrin-modified resin were added into 9 kg of water, stirred and mixed for 0.9 h, filtered, and the obtained filter cake was dried and crushed to obtain toluidine red pigment for architectural coatings.

[0062] Example 5 Preparation of adamantane-modified 2-naphthol derivatives:

[0063] 0.1 kg of 8-amino-2-naphthol and 0.15 kg of adamantane ketone were added to 1 kg of methanol, stirred and mixed evenly, and reacted at 40°C for 3 hours. Then, 0.08 kg of sodium cyanoborohydride was added thereto, and the reaction was continued for 5 hours. After the reaction was completed, the solvent was distilled off under reduced pressure, 1 kg of water was added to the obtained residue, and then 1 kg of dichloromethane was added and extracted 3 times. The obtained organic phase was distilled off under reduced pressure to remove the solvent, and an adamantane-modified 2-naphthol derivative was obtained.

[0064] Preparation of modified toluidine red pigment:

[0065] 10 kg of water and 0.5 kg of o-nitro-p-toluidine were added to a diazotization reaction kettle, stirred for 1 hour, and then 1.25 kg of 30% hydrochloric acid was added thereto. After stirring for 2 hours, the temperature was lowered to 5°C, and 2.3 kg of 30% sodium nitrite solution was added thereto dropwise. The reaction was stirred for 3 hours until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. The reaction was stopped to obtain a diazo solution.

[0066] 1.2 kg of adamantane-modified 2-naphthol derivative and 2 kg of ethanol were added to a coupling reactor, stirred and mixed evenly, and then diazo liquid was added thereto. The pH of the system was adjusted to 8.5 with a 30% mass concentration of sodium hydroxide aqueous solution. The reaction was stirred for 2 hours, the temperature was raised to 80° C. and the reaction was continued for 1 hour. The reaction was filtered, washed, and dried to obtain a modified toluidine red pigment.

[0067] Preparation of cyclodextrin modified resin:

[0068] 1 kg of allyl-β-cyclodextrin, 0.8 kg of acrylamide and 0.8 kg of acrylic acid were added to 5 kg of dimethyl sulfoxide, stirred and mixed evenly, and then 0.05 kg of azobisisobutyronitrile was added thereto, and the mixture was reacted at 100° C. for 10 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

[0069] Preparation of Toluidine Red Pigment for Architectural Coatings:

[0070] 1 kg of modified toluidine red pigment and 0.5 kg of cyclodextrin-modified resin were added into 10 kg of water, stirred and mixed for 1 hour, filtered, and the obtained filter cake was dried and crushed to obtain toluidine red pigment for architectural coatings.

[0071] Example 6 Preparation of adamantane-modified 2-naphthol derivatives:

[0072] 0.1 kg of 8-amino-2-naphthol and 0.12 kg of adamantane ketone were added to 1 kg of ethanol, stirred and mixed evenly, and reacted at 40°C for 5 hours. Then, 0.06 kg of sodium borohydride was added thereto, and the reaction was continued for 10 hours. After the reaction was completed, the solvent was distilled off under reduced pressure, 0.5 kg of water was added to the obtained residue, and then 1 kg of dichloromethane was added and extracted 3 times. The obtained organic phase was distilled off under reduced pressure to remove the solvent, and an adamantane-modified 2-naphthol derivative was obtained.

[0073] Preparation of modified toluidine red pigment:

[0074] 10 kg of water and 0.5 kg of o-nitro-p-toluidine were added to a diazotization reactor, stirred for 0.5 h, and then 1.15 kg of 30% hydrochloric acid was added thereto. After stirring for 1.5 h, the temperature was lowered to 5°C, and 2 kg of 30% sodium nitrite solution was added dropwise thereto. The reaction was stirred for 1 h until the Congo red test paper turned blue and the potassium iodide starch test paper turned blue. The reaction was stopped to obtain a diazo solution.

[0075] 1.2 kg of adamantane-modified 2-naphthol derivative and 1.5 kg of ethanol were added into a coupling reactor, stirred and mixed evenly, and then diazo liquid was added thereto. The pH of the system was adjusted to 8.5 with a 30% mass concentration of sodium hydroxide aqueous solution. The reaction was stirred for 2 hours, and the temperature was raised to 70° C. to continue the reaction for 1 hour. The reaction was filtered, washed, and dried to obtain a modified toluidine red pigment.

[0076] Preparation of cyclodextrin modified resin:

[0077] 0.5 kg of allyl-β-cyclodextrin, 0.8 kg of acrylamide and 0.5 kg of acrylic acid were added to 4 kg of dimethyl sulfoxide, stirred and mixed evenly, and then 0.03 kg of azobisisobutyronitrile was added thereto, and the mixture was reacted at 90° C. for 15 hours. After the reaction was completed, the solvent was removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

[0078] Preparation of Toluidine Red Pigment for Architectural Coatings:

[0079] 1 kg of modified toluidine red pigment and 0.4 kg of cyclodextrin-modified resin were added into 10 kg of water, stirred and mixed for 0.5 h, filtered, and the obtained filter cake was dried and crushed to obtain toluidine red pigment for architectural coatings.

[0080] The toluidine red pigment for architectural coatings prepared in Examples 1 to 6 were tested respectively, wherein the tinting strength was tested according to the method in GB1708-79; the bulk density was tested according to the method in GB / T 21877-2015, 50 g of toluidine red pigment for architectural coatings was accurately weighed, put into a measuring cylinder, sealed, oscillated up and down 10 times, and the sample scale in the measuring cylinder was recorded; the light fastness was tested according to the standard GB1710-79; the water resistance, acid resistance and alkali resistance were tested according to GB 5211.5-2008-T, and the comparative example used the toluidine red YS (PR3) product of our company, and the test results are shown in Table 1. It can be seen from the results in Table 1 that the toluidine red pigment for architectural coatings prepared by the present invention has strong acid and alkali resistance and weather resistance, and has good dispersibility and hiding power, improves the durability of the pigment in outdoor use, and has good application prospects in the field of construction.

[0081] Table 1 Performance test results of the pigments prepared in Examples 1 to 6 and the comparative examples

[0082]

[0083] 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 toluidine red pigment for architectural coatings, characterized in that: The composition is composed of the following raw materials in parts by weight: 1 part of modified toluidine red pigment and 0.3-0.5 part of cyclodextrin-modified resin; The modified toluidine red pigment is prepared by diazotizing o-nitro-p-toluidine and then coupling it with a 2-naphthol derivative modified with adamantane; The adamantane-modified 2-naphthol derivative is prepared according to the following method: 8-amino-2-naphthol and adamantane ketone are added to an alcohol solvent, stirred and mixed evenly, reacted at 25-40°C for 3-5 hours, and then a reducing agent is added thereto, and the reaction is continued for 5-10 hours. After the reaction is completed, the solvent is removed by distillation under reduced pressure, water is added to the obtained residue, and then dichloromethane is added for extraction 2-3 times, and the obtained organic phase is distilled under reduced pressure to remove the solvent, thereby obtaining an adamantane-modified 2-naphthol derivative; The cyclodextrin-modified resin is prepared according to the following method: Allyl-β-cyclodextrin, acrylamide and acrylic acid are added to dimethyl sulfoxide, stirred and mixed evenly, and then azobisisobutyronitrile is added thereto, and the mixture is reacted at 80-100°C for 10-15h. After the reaction is completed, the solvent is removed by reduced pressure distillation to obtain a cyclodextrin-modified resin.

2. The toluidine red pigment for architectural coatings according to claim 1, characterized in that: The alcohol solvent is methanol, ethanol or isopropanol.

3. The toluidine red pigment for architectural coatings according to claim 1, characterized in that: The reducing agent is sodium borohydride or sodium cyanoborohydride.

4. The toluidine red pigment for architectural coatings according to claim 1, characterized in that: The mass ratio of the 8-amino-2-naphthol, adamantane ketone, alcohol solvent, reducing agent, water and dichloromethane is 1:1-1.5:5-10:0.4-0.8:5-10:5-10.

5. The toluidine red pigment for architectural coatings according to claim 1, characterized in that: The preparation method of the modified toluidine red pigment comprises the following steps: 1) In parts by weight, add 60-100 parts of water and 5 parts of o-nitro-p-toluidine into a diazotization reaction kettle, stir for 0.5-1h, then add 10-12.5 parts of 30% hydrochloric acid, stir for 1-2h, cool to 0-5°C, dropwise add 20-23 parts of 30% sodium nitrite solution, stir for 1-3h, until Congo red test paper turns blue and potassium iodide starch test paper turns blue, stop the reaction, and obtain diazo solution; 2) Add 10-12 parts of adamantane-modified 2-naphthol derivatives and 15-20 parts of ethanol into a coupling reactor, stir and mix evenly, then add the diazo solution obtained in step 1), adjust the pH of the system to 8-8.5 with a 20-30% mass concentration of sodium hydroxide aqueous solution, stir and react for 1-2 hours, heat to 70-80° C. and continue to react for 1-2 hours, filter, wash and dry to obtain a modified toluidine red pigment.

6. The toluidine red pigment for architectural coatings according to claim 1, characterized in that: The mass ratio of allyl-β-cyclodextrin, acrylamide, acrylic acid, dimethyl sulfoxide and azobisisobutyronitrile is 0.5-1: 0.5-0.8: 0.5-0.8: 3-5: 0.002-0.

05.

7. The method for preparing the toluidine red pigment for architectural coatings according to claim 1, characterized in that: The following steps are involved: In parts by weight, 1 part of modified toluidine red pigment and 0.3-0.5 parts of cyclodextrin-modified resin are added to 5-10 parts of water, stirred and mixed for 0.5-1 hour, filtered, and the obtained filter cake is dried and crushed to obtain toluidine red pigment for architectural coatings.

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