Toluidine red pigment for architectural coatings and preparation method thereof

Abstract

The present application discloses a toluidine red pigment for architectural coatings and a preparation method thereof, and belongs to the field of pigment synthesis technology. The toluidine red pigment is composed of the following raw materials: 75-85 parts by weight of toluidine red pigment matrix, 5-10 parts by weight of nano titanium dioxide, 2-5 parts by weight of nano zinc oxide, 3-8 parts by weight of organosilicon modifier and 1-3 parts by weight of polysiloxane microcapsules. The present application significantly improves the weather resistance, dispersibility and stability of toluidine red pigment for architectural coatings by optimizing the pigment composition and adopting efficient preparation processes such as ultrasonic assistance and microchannel reactors, while reducing the energy consumption of production and improving production efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of pigment synthesis, and more specifically, to a toluidine red pigment for architectural coatings and a preparation method thereof. Background Art

[0002] Toluidine Red, as an important organic pigment, is widely used in architectural coatings and is favored for its bright color and good hiding power. However, the application of existing toluidine red pigment in architectural coatings still faces some challenges. First, traditional toluidine red pigment is prone to fading, discoloration and color change when exposed to environmental factors such as ultraviolet rays, moisture and oxygen, resulting in poor weather resistance of the coating. Secondly, the dispersibility and stability problems of toluidine red pigment also affect the uniform coating effect and service life of the coating. In addition, the production process in the traditional preparation method is complicated and energy-intensive, which limits the efficiency and cost control of large-scale production.

[0003] In order to improve the weather resistance, dispersibility and stability of toluidine red pigment, some modification technologies and preparation methods have been studied, but most technologies still have some limitations. For example, although the performance of the pigment can be improved to a certain extent through conventional surface treatment or the addition of stabilizers, it still has deficiencies in terms of high temperature resistance, UV resistance and environmental adaptability. Modern efficient preparation processes, such as ultrasound-assisted synthesis and microchannel reactors, theoretically have high potential for pigment quality control and production efficiency, but their effectiveness and popularity in practical applications have not yet been fully realized.

[0004] In summary, how to maintain the color stability of the pigment while improving its weather resistance, dispersibility and stability, and to prepare high-quality toluidine red pigment under the premise of ensuring low energy consumption and high efficiency has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In order to overcome a series of defects in the prior art, the purpose of the present application is to provide a toluidine red pigment for architectural coatings in view of the above-mentioned problems, which is composed of the following raw materials: 75-85 parts by weight of toluidine red pigment matrix, 5-10 parts by weight of nano titanium dioxide, 2-5 parts by weight of nano zinc oxide, 3-8 parts by weight of organosilicon modifier and 1-3 parts by weight of polysiloxane microcapsules.

[0006] Furthermore, the organosilicon modifier is CH3Si(OC2H5)3, wherein methyltriethoxysilane accounts for 50-70% of the total amount of the organosilicon modifier.

[0007] Furthermore, the particle size of nano titanium dioxide is 30-50 nanometers, and the specific surface area is 40-80m² / g; the particle size of nano zinc oxide is 20-40 nanometers, and the specific surface area is 30-60m² / g; and the particle size of polysiloxane microcapsules is 1-5μm.

[0008] Furthermore, 80 parts by weight of toluidine red pigment matrix, 7 parts by weight of nano titanium dioxide, 3 parts by weight of nano zinc oxide, 5 parts by weight of organosilicon modifier and 2 parts by weight of polysiloxane microcapsules.

[0009] According to a second aspect of the present application, a method for preparing toluidine red pigment for architectural coatings is provided, comprising the following steps.

[0010] Step 1, dissolving 2-amino-4-methylbenzoic acid in water, adding sodium hydroxide to adjust the pH value to 7.5-8.0, slowly adding sodium nitrite aqueous solution at 0-5°C to carry out diazotization reaction, reacting for 1-2 hours to obtain a diazonium salt solution; at the same time, dissolving β-naphthol in an aqueous solution containing sodium carbonate, controlling the pH value to be between 9.0-10.0, to form a β-naphthol solution.

[0011] Step 2, under the assistance of ultrasound, slowly drop the diazonium salt solution into the β-naphthol solution for coupling reaction, control the temperature at 5-10° C., react for 2-3 hours to form a reaction solution; during this period, a microchannel reactor is used to improve mixing efficiency and reaction uniformity.

[0012] Step 3, separating the reaction solution by centrifugation to obtain a crude toluidine red pigment, washing it with deionized water for 3-5 times, then washing it with ethanol for 1-2 times, and finally drying it under low temperature vacuum for 8-12 hours to obtain a toluidine red pigment matrix.

[0013] Step 4, dispersing nano titanium dioxide and nano zinc oxide in ethanol, and ultrasonically treating for 15-30 minutes to form a uniform dispersion 1; dissolving the organosilicon modifier in ethanol, and stirring evenly to form a uniform dispersion 2; mixing the uniform dispersion 1 with the uniform dispersion 2, stirring and reacting at 50-60° C. for 1-2 hours to form a mixed solution.

[0014] Step 5, adding the toluidine red pigment matrix into the mixed solution, treating it for 0.5-1 hour under the synergistic effect of mechanical stirring and ultrasonic wave, so that the nano oxide and the organosilicon modifier are evenly coated on the surface of the pigment to form a mixture.

[0015] Step 6, adding the prefabricated polysiloxane microcapsules into the mixture, and continuing the reaction at 60-70° C. for 1-2 hours to form a reaction product.

[0016] Step 7, separating the reaction product by centrifugation, vacuum drying at 40-50° C. for 12-16 hours, grinding it in a ball mill for 20-30 minutes, and passing it through a 200-mesh sieve to obtain the final toluidine red pigment for architectural coatings.

[0017] Furthermore, in step 2, the ultrasonic frequency is 20-25 kHz.

[0018] Furthermore, in step 3, the low-temperature vacuum drying temperature is 40-50° C. and the pressure is 5-10 kPa.

[0019] Furthermore, in step 5, the ultrasonic power is 200-300W.

[0020] Furthermore, the preparation steps of polysiloxane microcapsules are: polydimethylsiloxane and tetraethoxysilane are mixed in a mass ratio of 3:1, and microcapsules are prepared by microemulsion polymerization in the presence of an emulsifier.

[0021] Compared with the prior art, the present application has the following beneficial effects.

[0022] This application significantly improves the weather resistance, dispersibility and stability of toluidine red pigment for architectural coatings by optimizing the pigment composition and adopting efficient preparation processes such as ultrasonic assistance and microchannel reactors, while reducing the energy consumption of production and improving production efficiency. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application, but the description of these embodiments should not be construed as limiting the scope of protection of the present application.

[0024] 1. Raw material selection.

[0025] Toluidine red pigment matrix: In different embodiments, the amount of toluidine red pigment matrix is ​​75-85 parts by weight, preferably 80 parts by weight. The pigment matrix is ​​the main component of toluidine red pigment for architectural coatings, and its performance directly affects key indicators such as color and hiding power of the final product.

[0026] Nano titanium dioxide: The particle size of nano titanium dioxide is 30-50 nanometers and the specific surface area is 40-80m² / g. In this application, the dosage is 5-10 parts by weight, preferably 7 parts by weight. With its special particle size and specific surface area, nano titanium dioxide can effectively improve the weather resistance and UV resistance of the pigment, which helps to solve the problem of poor durability in extreme outdoor environments.

[0027] Nano zinc oxide: The particle size of nano zinc oxide is 20-40 nanometers, and the specific surface area is 30-60m² / g. The dosage is 2-5 parts by weight, preferably 3 parts by weight. Nano zinc oxide has antibacterial and mildew-proof properties. It can improve the comprehensive performance of the product in toluidine red pigment for architectural coatings and enhance the stability in harsh outdoor environments.

[0028] Organosilicon modifier: The organosilicon modifier is CH3Si(OC2H5)3, in which methyltriethoxysilane accounts for 50-70% of the total amount of the organosilicon modifier. Its dosage is 3-8 parts by weight, preferably 5 parts by weight. The organosilicon modifier can improve the compatibility of the pigment and the coating system, enhance the dispersibility and stability of the pigment, and improve the durability of the pigment in the outdoor environment.

[0029] Polysiloxane microcapsules: The particle size of polysiloxane microcapsules is 1-5 μm, and the dosage is 1-3 parts by weight, preferably 2 parts by weight. Polysiloxane microcapsules can protect the pigment, improve the storage stability of the pigment, and improve the film-forming properties of the coating to a certain extent, further improving the durability of the pigment outdoors.

[0030] 2. Preparation of polysiloxane microcapsules.

[0031] Polydimethylsiloxane and tetraethoxysilane are mixed in a mass ratio of 3:1, and microcapsules are prepared by microemulsion polymerization in the presence of an emulsifier. The specific process is as follows: first, the emulsifier is added to an appropriate amount of water and stirred evenly to form an emulsifier solution; then, polydimethylsiloxane and tetraethoxysilane weighed in proportion are slowly added to the emulsifier solution to form a microemulsion system under high-speed stirring; then, at a certain temperature and reaction time, the system is polymerized to finally form polysiloxane microcapsules. Compared with the traditional method, this preparation method reduces energy consumption to a certain extent and improves preparation efficiency.

[0032] 3. Preparation of toluidine red pigment for architectural coatings.

[0033] Dissolve 2-amino-4-methylbenzoic acid in water, add sodium hydroxide to adjust the pH value to 7.5-8.0, slowly add sodium nitrite aqueous solution at 0-5°C for diazotization reaction, and react for 1-2 hours to obtain a diazonium salt solution. At the same time, dissolve β-naphthol in an aqueous solution containing sodium carbonate, control the pH value between 9.0-10.0, and form a β-naphthol solution. In this step, optimized reaction conditions and precise pH control help improve reaction efficiency and reduce unnecessary energy consumption.

[0034] Coupling reaction: With the assistance of ultrasound, the diazonium salt solution is slowly added to the β-naphthol solution for coupling reaction. The temperature is controlled at 5-10°C and the reaction is carried out for 2-3 hours to form a reaction solution. The ultrasonic frequency is 20-25kHz, and a microchannel reactor is used during the reaction to improve mixing efficiency and reaction uniformity. The use of a microchannel reactor can enhance mass and heat transfer, shorten reaction time, reduce energy consumption, and improve preparation efficiency.

[0035] Separation and drying of toluidine red pigment matrix: The reaction solution is separated by centrifugation to obtain crude toluidine red pigment, which is then washed with deionized water for 3-5 times, then washed with ethanol for 1-2 times, and finally dried under low temperature vacuum for 8-12 hours to obtain toluidine red pigment matrix. The low temperature vacuum drying temperature is 40-50°C and the pressure is 5-10kPa. This drying method can achieve effective drying at a lower temperature, avoid the influence of high temperature on the performance of the pigment, and reduce energy consumption.

[0036] Preparation of mixed solution: Disperse nano titanium dioxide and nano zinc oxide in ethanol, and perform ultrasonic treatment for 15-30 minutes to form uniform dispersion 1; dissolve the organosilicon modifier in ethanol, and stir evenly to form uniform dispersion 2; mix uniform dispersion 1 with uniform dispersion 2, and stir and react at 50-60°C for 1-2 hours to form a mixed solution. Reasonable reaction temperature and time settings ensure that the components are fully mixed and reacted, thereby improving production efficiency.

[0037] Coating treatment: Add the toluidine red pigment matrix to the mixed solution and treat it for 0.5-1 hour under the synergistic effect of mechanical stirring and ultrasonic waves, so that the nano oxide and the organosilicon modifier are evenly coated on the surface of the pigment to form a mixture. The ultrasonic power is 200-300W. This step uses mechanical stirring and ultrasonic waves to accelerate the coating process and improve production efficiency.

[0038] Add polysiloxane microcapsules and react: Add the prefabricated polysiloxane microcapsules to the mixture and continue to react at 60-70°C for 1-2 hours to form a reaction product. The appropriate reaction temperature and time ensure that the polysiloxane microcapsules react fully with the mixture to improve the performance of the pigment.

[0039] The final product is obtained by post-processing: the reaction product is separated by centrifugation, vacuum dried at 40-50°C for 12-16 hours, ground by a ball mill for 20-30 minutes, and passed through a 200-mesh screen to obtain the final toluidine red pigment for architectural coatings. The entire post-processing process not only ensures the quality of the product, but also reduces unnecessary energy consumption.

[0040] 4. Embodiment

[0041] Example 1.

[0042] Raw material ratio: 80 parts by weight of toluidine red pigment matrix, 7 parts by weight of nano titanium dioxide, 3 parts by weight of nano zinc oxide, 5 parts by weight of organosilicon modifier and 2 parts by weight of polysiloxane microcapsules.

[0043] Preparation method: In the diazotization reaction of preparing toluidine red pigment matrix, the reaction temperature is controlled at 3°C ​​and the reaction time is 1.5 hours; in the coupling reaction, the ultrasonic frequency is set to 22kHz, the reaction temperature is maintained at 7°C, and the reaction time is 2.5 hours; when preparing the mixed solution, the nano oxide is ultrasonically treated for 20 minutes, the stirring reaction temperature is 55°C, and the time is 1.5 hours; during the coating treatment, the ultrasonic power is 250W, and the treatment time is 0.8 hours; when adding polysiloxane microcapsules, the temperature is 65°C and the reaction time is 1.5 hours; the vacuum drying temperature is 45°C and the time is 14 hours; and the ball mill is ground for 25 minutes.

[0044] Example 2.

[0045] Raw material ratio: 75 parts by weight of toluidine red pigment matrix, 5 parts by weight of nano titanium dioxide, 2 parts by weight of nano zinc oxide, 3 parts by weight of organic silicon modifier and 1 part by weight of polysiloxane microcapsule.

[0046] Preparation method: diazotization reaction temperature is 4°C, reaction time is 1.2 hours; coupling reaction ultrasonic frequency is 20kHz, temperature is 5°C, reaction time is 2 hours; nano-oxide ultrasonic treatment is 15 minutes, the mixed solution is stirred, reaction temperature is 50°C, time is 1 hour; coating treatment ultrasonic power is 200W, treatment time is 0.5 hour; polysiloxane microcapsule reaction temperature is 60°C, time is 1 hour; vacuum drying temperature is 40°C, time is 12 hours; ball mill grinding is 20 minutes.

[0047] Example 3.

[0048] Raw material ratio: 85 parts by weight of toluidine red pigment matrix, 10 parts by weight of nano titanium dioxide, 5 parts by weight of nano zinc oxide, 8 parts by weight of organosilicon modifier and 3 parts by weight of polysiloxane microcapsules.

[0049] Preparation method: diazotization reaction is carried out at 0°C and the reaction time is 2 hours; coupling reaction ultrasonic frequency is 25kHz, temperature is 10°C, and reaction time is 3 hours; nano-oxide is ultrasonically treated for 30 minutes, the mixed solution is stirred and the reaction temperature is 60°C, and the time is 2 hours; coating treatment ultrasonic power is 300W, and the treatment time is 1 hour; polysiloxane microcapsule reaction temperature is 70°C, and the time is 2 hours; vacuum drying temperature is 50°C, and the time is 16 hours; ball mill grinding is 30 minutes.

[0050] Example 4.

[0051] Raw material ratio: 82 parts by weight of toluidine red pigment matrix, 8 parts by weight of nano titanium dioxide, 4 parts by weight of nano zinc oxide, 6 parts by weight of organic silicon modifier and 2.5 parts by weight of polysiloxane microcapsules.

[0052] Preparation method: diazotization reaction temperature is 1°C, reaction time is 1.8 hours; coupling reaction ultrasonic frequency is 23kHz, temperature is 8°C, reaction time is 2.8 hours; nano-oxide ultrasonic treatment is 25 minutes, the mixed solution is stirred, the reaction temperature is 58°C, and the time is 1.8 hours; coating treatment ultrasonic power is 280W, and the treatment time is 0.9 hours; polysiloxane microcapsule reaction temperature is 68°C, and the time is 1.8 hours; vacuum drying temperature is 48°C, and the time is 15 hours; ball mill grinding is 28 minutes.

[0053] Comparative Examples.

[0054] Raw material ratio: 95 parts by weight of toluidine red pigment base, 3 parts by weight of dispersant (sodium dodecylbenzene sulfonate), 2 parts by weight of wetting agent (fatty alcohol polyoxyethylene ether), and 1 part by weight of deflocculant.

[0055] Preparation method: In the diazotization reaction of preparing the toluidine red pigment matrix, the reaction temperature is controlled at 8°C, the reaction time is 2.5 hours, and the pH value is adjusted to 1.8; during the coupling reaction, conventional mechanical stirring (350rpm) is used without ultrasonic assistance, the reaction temperature is maintained at 12°C, the reaction time is 3.5 hours, and the pH value is 11.0; the separated pigment is washed with tap water 3 times; the drying is carried out by the traditional oven method at a temperature of 85°C for 22 hours; the dried pigment matrix is ​​mixed with the additive, water is added, and wet-grinded in a ball mill for 3.5 hours (ball-to-material ratio 5:1); after filtering, it is dried in an oven at 80°C for 14 hours; after crushing, it passes through a 100-mesh screen to obtain the final comparative sample. The comprehensive energy consumption is 7.8kWh / kg, the total preparation cycle is 36.2 hours, and the product yield is 85.3%.

[0056] 5. Performance testing

[0057] 1. Weather resistance test.

[0058] The prepared architectural coating was made into a sample with toluidine red pigment and tested in a xenon lamp artificial climate aging test chamber according to the GB / T1865-2009 standard method. The test conditions were: irradiance: 60±2W / m² (300-400nm band); blackboard temperature: 63±3°C; relative humidity: 50±5%; spray cycle: 102 minutes drying, 18 minutes spraying; test period: 2000 hours.

[0059] The test results are as follows.

[0060] Example 1: The color change (ΔE) was 1.8, the gloss retention (%) was 92.5, the chalking grade was 0, and the comprehensive weather resistance score was 9.2.

[0061] Example 2: The color change (ΔE) was 2.9, the gloss retention (%) was 87.3, the chalking grade was 1, and the comprehensive weather resistance score was 8.5.

[0062] Example 3: Color change (ΔE) was 1.5, gloss retention (%) was 94.2, chalking grade was 0, and the comprehensive weather resistance score was 9.5.

[0063] Example 4: Color change (ΔE) was 2.0, gloss retention (%) was 91.8, chalking grade was 0, and comprehensive weather resistance score was 9.0.

[0064] Comparative Example: Color change (ΔE) was 5.7, gloss retention (%) was 72.6, chalking grade was 2, and comprehensive weather resistance score was 6.4.

[0065] 2. Dispersion test.

[0066] The pigment was dispersed in an acrylic latex coating system at a dosage of 5%. The dispersion fineness of the pigment was measured using a scraper fineness meter, and the D50 and D90 values ​​were determined using a laser particle size analyzer.

[0067] The test results are as follows.

[0068] Example 1: fineness (μm) is 5.2, D50 (μm) is 0.68, D90 (μm) is 1.75, and dispersion stability index is 0.92.

[0069] Example 2: fineness (μm) is 6.8, D50 (μm) is 0.72, D90 (μm) is 2.10, and dispersion stability index is 0.85.

[0070] Example 3: fineness (μm) is 4.9, D50 (μm) is 0.61, D90 (μm) is 1.62, and dispersion stability index is 0.94.

[0071] Example 4: fineness (μm) is 5.5, D50 (μm) is 0.70, D90 (μm) is 1.82, and dispersion stability index is 0.90.

[0072] Comparative Example: fineness (μm) is 12.3, D50 (μm) is 1.28, D90 (μm) is 3.85, and dispersion stability index is 0.68.

[0073] The dispersion stability index is the ratio of the D50 value measured again after 30 days to the initial D50 value.

[0074] 3. Storage stability test.

[0075] The pigments were sealed and stored at 45°C for 28 days, and their viscosity changes, sedimentation rates, and color parameter changes were measured.

[0076] The test results are as follows.

[0077] Example 1: The viscosity change rate (%) was 4.2, the sedimentation rate (%) was 2.1, the color parameter change (ΔE) was 0.8, and the storage stability score was 9.3.

[0078] Example 2: The viscosity change rate (%) was 6.8, the sedimentation rate (%) was 3.5, the color parameter change (ΔE) was 1.3, and the storage stability score was 8.6.

[0079] Example 3: The viscosity change rate (%) was 3.7, the sedimentation rate (%) was 1.8, the color parameter change (ΔE) was 0.6, and the storage stability score was 9.5.

[0080] Example 4: The viscosity change rate (%) was 4.8, the sedimentation rate (%) was 2.4, the color parameter change (ΔE) was 0.9, and the storage stability score was 9.1.

[0081] Comparative Example: The viscosity change rate (%) was 15.3, the sedimentation rate (%) was 8.7, the color parameter change (ΔE) was 2.6, and the storage stability score was 6.2.

[0082] 4.Energy consumption and efficiency assessment.

[0083] The energy consumption and production efficiency indicators during the preparation process of each embodiment were recorded.

[0084] The test results are as follows.

[0085] Example 1: The total energy consumption (kWh / kg) is 3.8, the product yield (%) is 92.5, and the energy efficiency ratio is 92.1.

[0086] Example 2: The total energy consumption (kWh / kg) is 3.0, the product yield (%) is 89.2, and the energy efficiency ratio is 88.5.

[0087] Example 3: The total energy consumption (kWh / kg) is 5.2, the product yield (%) is 95.3, and the energy efficiency ratio is 88.7.

[0088] Example 4: The total energy consumption (kWh / kg) is 4.5, the product yield (%) is 93.6, and the energy efficiency ratio is 90.2.

[0089] Comparative Example: The total energy consumption (kWh / kg) is 7.8, the product yield (%) is 85.3, and the energy efficiency ratio is 71.3.

[0090] Among them, energy efficiency ratio = (product yield × comprehensive weather resistance score) / (total energy consumption × standardization factor).

[0091] 5. Comprehensive performance evaluation.

[0092] The pigment products of different embodiments were comprehensively evaluated, including key indicators such as tinting strength, hiding power, light fastness, acid and alkali resistance, etc.

[0093] The test results are as follows.

[0094] Example 1: Tinting power (%) is 122, hiding power (g / m²) is 18.5, light fastness (grade) is 7, acid and alkali resistance (pH3-11) is excellent, and the comprehensive performance index is 9.3.

[0095] Example 2: Tinting strength (%) is 115, hiding power (g / m²) is 20.3, light fastness (grade) is 6, acid and alkali resistance (pH3-11) is good, and the comprehensive performance index is 8.5.

[0096] Example 3: Tinting strength (%) is 128, hiding power (g / m²) is 17.2, light fastness (grade) is 8, acid and alkali resistance (pH3-11) is excellent, and the comprehensive performance index is 9.6.

[0097] Example 4: Tinting strength (%) is 125, hiding power (g / m²) is 18.0, light fastness (grade) is 7, acid and alkali resistance (pH3-11) is excellent, and the comprehensive performance index is 9.4.

[0098] Comparative Example: tinting strength (%) is 100, hiding power (g / m²) is 25.6, light fastness (grade) is 5, acid and alkali resistance (pH3-11) is medium, and the comprehensive performance index is 6.7.

[0099] Based on all the test data, the toluidine red pigment for architectural coatings provided by this application shows excellent durability and stability in artificial accelerated aging tests, and also has excellent dispersibility and storage stability. In the artificial climate aging test, the color change of Example 3 after 2000 hours is only 1.5ΔE, the dispersion stability index of Example 1 is 0.92, and the storage stability score is 9.3, which is much better than the corresponding indicators of the comparative example (color change 5.7ΔE, dispersion stability index 0.68, storage stability score 6.2). This technical solution successfully achieves the dual goals of high performance and green and efficient production.

[0100] The above embodiments are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A toluidine red pigment for architectural coatings, characterized in that: The invention is composed of the following raw materials: 75-85 parts by weight of toluidine red pigment matrix, 5-10 parts by weight of nano titanium dioxide, 2-5 parts by weight of nano zinc oxide, 3-8 parts by weight of organosilicon modifier and 1-3 parts by weight of polysiloxane microcapsule; The organosilicon modifier is CH3Si(OC2H5)3, wherein methyltriethoxysilane accounts for 50-70% of the total amount of the organosilicon modifier; The particle size of the nano titanium dioxide is 30-50 nanometers, and the specific surface area is 40-80m² / g; the particle size of the nano zinc oxide is 20-40 nanometers, and the specific surface area is 30-60m² / g; the particle size of the polysiloxane microcapsule is 1-5μm; The preparation method of the toluidine red pigment for architectural coatings comprises the following steps: Step 1, dissolving 2-amino-4-methylbenzoic acid in water, adding sodium hydroxide to adjust the pH value to 7.5-8.0, slowly adding sodium nitrite aqueous solution at 0-5°C to carry out diazotization reaction, reacting for 1-2 hours to obtain a diazonium salt solution; at the same time, dissolving β-naphthol in an aqueous solution containing sodium carbonate, controlling the pH value to be between 9.0-10.0, to form a β-naphthol solution; Step 2, under the assistance of ultrasound, slowly dropwise add the diazonium salt solution into the β-naphthol solution to carry out coupling reaction, control the temperature at 5-10° C., react for 2-3 hours, and form a reaction solution; during this period, a microchannel reactor is used to improve mixing efficiency and reaction uniformity; Step 3, centrifugally separating the reaction solution to obtain a crude toluidine red pigment, washing it with deionized water for 3-5 times, then washing it with ethanol for 1-2 times, and finally drying it under low temperature vacuum for 8-12 hours to obtain a toluidine red pigment matrix; Step 4, dispersing nano titanium dioxide and nano zinc oxide in ethanol, and ultrasonically treating for 15-30 minutes to form a uniform dispersion 1; dissolving the organosilicon modifier in ethanol, and stirring to form a uniform dispersion 2; mixing the uniform dispersion 1 with the uniform dispersion 2, and stirring and reacting at 50-60° C. for 1-2 hours to form a mixed solution; Step 5, adding the toluidine red pigment matrix to the mixed solution, treating it for 0.5-1 hour under the synergistic effect of mechanical stirring and ultrasonic wave, so that the nano oxide and the organosilicon modifier are evenly coated on the surface of the pigment to form a mixture; Step 6, adding the prefabricated polysiloxane microcapsules to the mixture, and continuing the reaction at 60-70° C. for 1-2 hours to form a reaction product; Step 7, separating the reaction product by centrifugation, vacuum drying at 40-50° C. for 12-16 hours, grinding it in a ball mill for 20-30 minutes, and passing it through a 200-mesh sieve to obtain the final toluidine red pigment for architectural coatings; The preparation steps of polysiloxane microcapsules are as follows: polydimethylsiloxane and tetraethoxysilane are mixed in a mass ratio of 3:1, and the microcapsules are prepared by microemulsion polymerization in the presence of an emulsifier.

2. The toluidine red pigment for architectural coatings according to claim 1, characterized in that: The invention is composed of the following raw materials: 80 parts by weight of toluidine red pigment matrix, 7 parts by weight of nano titanium dioxide, 3 parts by weight of nano zinc oxide, 5 parts by weight of organic silicon modifier and 2 parts by weight of polysiloxane microcapsule.

3. The method for preparing toluidine red pigment for architectural coatings according to claim 1, characterized in that: In step 2, the ultrasonic frequency is 20-25kHz.

4. The method for preparing toluidine red pigment for architectural coatings according to claim 1, characterized in that: In step 3, the low-temperature vacuum drying temperature is 40-50° C. and the pressure is 5-10 kPa.

5. The method for preparing toluidine red pigment for architectural coatings according to claim 1, characterized in that: In step 5, the ultrasonic power is 200-300W.