Preparation method of red cuprous oxide pigment with core-shell structure

Abstract

The invention belongs to the technical field of inorganic pigments, and particularly discloses a preparation method of a red cuprous oxide pigment with a core-shell structure, which comprises the following steps: modifying cuprous oxide, introducing a silicon source, carrying out precipitation reaction, centrifuging, washing and drying to obtain a pigment-coated precursor, and finally carrying out high-temperature calcination treatment in a hydrogen-argon mixed atmosphere to obtain the red cuprous oxide pigment with the core-shell structure. The silicon dioxide-coated cuprous oxide red pigment is obtained. The silicon dioxide-coated cuprous oxide red pigment with a compact coating layer is obtained through a simple and controllable preparation process, so that the high-temperature stability of cuprous oxide is greatly improved, and the application field of the cuprous oxide is widened.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic pigments, and particularly relates to a method for preparing a cuprous oxide red pigment with a core-shell structure. Background Art

[0002] Currently, the main red pigments used in plastics, coatings, inks, and paper products are molybdenum chromate red, cadmium selenide red, and cadmium mercury red. Their use is subject to increasingly stringent controls due to the presence of toxic heavy metals such as lead, chromium, cadmium, and mercury, which pose health risks and environmental risks. While γ-Ce2S3 red pigments are free of toxic heavy metals, they exhibit poor heat resistance and oxidize at temperatures above 350°C, losing their red color. While their oxidation resistance can be increased through silica coating, the acid-washing step in the preparation process produces toxic H2S gas, which reacts with the acid, resulting in significant environmental pollution. Cuprous oxide (CuO), with its vibrant red color and safe, non-toxic properties, is a promising alternative to toxic red pigments and has become a research hotspot.

[0003] Cuprous oxide (CPO) is a p-type semiconductor material that exhibits unique optical and electrical properties due to quantum size effects. When exposed to visible light, CPO can generate electron-hole pairs. This material exhibits a large surface area, good adsorption capacity, and the ability to suppress the recombination of photogenerated electron-hole pairs. It is used in catalysts, marine antifouling coatings, solar cells, and other fields. Furthermore, CPO exhibits a vibrant red color at room temperature and possesses strong tinting power. However, CPO is highly unstable, easily oxidized, and exhibits poor acid and alkali resistance. In air, CPO oxidizes upon heating to 200°C, resulting in its limited application in inorganic pigments. Summary of the Invention

[0004] In order to solve the problem of cuprous oxide being easily oxidized at high temperatures and prevent red cuprous oxide from being oxidized to black cupric oxide, the present invention provides a method for preparing a core-shell structured cuprous oxide red pigment. The present invention is achieved by the following technical solutions: The present invention provides a method for preparing a core-shell structured cuprous oxide red pigment, characterized by comprising the following steps: Step 1: Dispersing Cu2O powder and a modifying agent in a solvent to obtain a suspension A, and subjecting the suspension A to ultrasonic treatment to obtain a surface-modified Cu2O powder; The modification reagent is at least one of cetyltrimethylammonium bromide (CTAB), polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB), DTAB (dodecyltrimethylammonium bromide), PEG (polyethylene glycol), and SDS (sodium dodecyl sulfonate); Step 2: Dispersing the surface-modified Cu2O powder, organosiloxane, and a pH adjuster in a polar organic solvent to obtain a suspension B, stirring the suspension B for reaction, and adding water dropwise during the reaction to obtain a pigment precursor; the pH adjuster comprises at least one of aqueous ammonia, sodium hydroxide solution, and potassium hydroxide solution; Step 3: calcining the pigment precursor to obtain a cuprous oxide red pigment with a core-shell structure.

[0005] The present invention first modifies the surface of cuprous oxide, then forms a silica coating on the surface of the cuprous oxide, and finally calcines the cuprous oxide under the protection of a hydrogen-argon mixed atmosphere to increase the density of the silica coating, thereby improving the high-temperature oxidation resistance of the cuprous oxide. The advantage of silica as a shell material is that it is highly stable in aqueous solution, and the silica surface is easy to modify to prepare a nano-aqueous solution colloid. The silica shell is used to control the particle spacing and improve the dispersibility of the colorant. The present invention uses a coating modification technology to coat the surface of the cuprous oxide colorant with one or more layers of a transparent, high-temperature stable substance to improve the colorant's high-temperature stability and acid corrosion resistance. The present invention uses silica to coat cuprous oxide, and through the modification treatment, improves the high-temperature oxidation resistance, stability, and high-temperature resistance of the cuprous oxide, thereby expanding the application of its related products in the fields of plastics, rubber, high-temperature coatings, etc.

[0006] Optionally, the solvent in step 1 is a mixture of a polar organic solvent and water; the ratio of the polar organic solvent to deionized water is 1-4:1.

[0007] Optionally, the solvent of the suspension A and the polar organic solvent in the suspension B are independently at least one of ethanol, propanol and butanol.

[0008] Optionally, the weight ratio of Cu2O powder to modifying agent in step 1 is 1:0.05~0.2.

[0009] Optionally, the water dropping rate in step 2 is controlled at 0.3-0.5 mL / min; Preferably, the dripping rate of water in step 2 is controlled at 0.3 mL / min.

[0010] Preferably, the volume ratio of the amount of water added in step 2 to the suspension B is 1-2:1.

[0011] Optionally, the temperature of the stirring reaction in step 2 should be controlled at 40-60° C., and the stirring time should be 1-2 h; Optionally, in step 1, the frequency of ultrasonic treatment is 10-30 kHz, the power is 1000-1800 W, and the duration is 10-30 min.

[0012] Optionally, OH in suspension B- The content is 0.54~1.32mol / L.

[0013] At low pH concentrations, the hydrolysis and condensation rates of TEOS are very slow, resulting in insufficient hydrolysis of silica oligomers to form SiO2 nuclei. However, at higher pH values, TEOS hydrolysis and condensation rates increase dramatically, leading to higher supersaturation and a faster nucleation rate, resulting in a rapid deposition process. Only when the pH adjuster is adequate can both homogeneous and heterogeneous nucleation occur simultaneously, resulting in a colloidal mixture.

[0014] Preferably, the pH regulator is ammonia water, and the mass fraction of ammonia water in the organic solvent is 0.97% to 3.76%; Preferably, the mass fraction of aqueous ammonia in the alkaline polar organic solvent is 1.92%.

[0015] Optionally, the organosiloxane includes at least one of ethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, and butyl orthosilicate; The content of organosiloxane in suspension B is 1.52~4.46 mol / L.

[0016] Optionally, the calcination process in step 3 includes calcining the pigment precursor in a hydrogen-argon mixed atmosphere, first raising the temperature to 500°C at 0.5-1°C / min, then raising the temperature to 700°C at 1.5-3°C / min, and then raising the temperature to 800-1000°C at 4-5°C / min, with a holding time of 1-2.5 hours. During this process, the flow rate of the hydrogen-argon mixed atmosphere is maintained at 100-300 mL / min. By using a step-by-step heating method, it is possible to ensure that the silica shell is not easily broken during the heat treatment process, thereby improving the density of the silica shell.

[0017] Optionally, the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 0.1% to 0.5%; Preferably, the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 0.2%. Densification of the silicon dioxide coating is performed in a hydrogen-argon mixed atmosphere. Since cuprous oxide is easily oxidized at high temperatures, introducing an appropriate amount of hydrogen into the argon gas can consume the small amount of oxygen remaining in the furnace, preventing oxidation of cuprous oxide at high temperatures. This not only improves coating quality, but also reduces process control difficulty and increases production efficiency.

[0018] The present invention has the following beneficial effects: The present invention provides a method for preparing a core-shell structured, silica-coated cuprous oxide red colorant. The method utilizes silica to coat cuprous oxide. Through modification, the resulting silica coating is uniform and dense, effectively addressing the issue of cuprous oxide's susceptibility to oxidation. The resulting cuprous oxide red colorant exhibits significantly improved stability and high-temperature resistance, broadening the application of related products in fields such as plastics, rubber, and high-temperature coatings. By controlling the amount of organosiloxane added, the silica coating thickness can be controlled, providing a method for the precise control and preparation of core-shell structures. The method is simple to operate, requires no complex synthetic steps, uses a limited number of reagents, is pollution-free, and offers excellent product stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The performance comparison between the packaged pigment prepared by the present invention and the comparative pigment is shown; Figure 2 This is the TEM image of pure cuprous oxide pigment in Comparative Example 1; Figure 3 This is the TEM image of the cuprous oxide pigment coated with silica in Comparative Example 2; Figure 4 This is the TEM image of the cuprous oxide pigment coated with silica in comparative example 3; Figure 5 This is the TEM image of the cuprous oxide pigment coated with silica in Comparative Example 4; Figure 6 This is the TEM image of the cuprous oxide pigment coated with silica in Comparative Example 5; Figure 7 This is a TEM image of the cuprous oxide pigment coated with silica in Example 1; Figure 8 This is a TEM image of the cuprous oxide pigment coated with silicon dioxide in Example 2; Figure 9 This is a TEM image of the cuprous oxide pigment coated with silica in Example 3; Figure 10 This is the TEM image of the cuprous oxide pigment coated with silica in Example 4. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0022] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0024] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0025] The Cu2O in the present invention comes from nano Cu2O produced by Jinan Wuba Research Metals, and the other raw materials used are all commercially available products.

[0026] Example 1 Step 1: 1 g of Cu2O powder and 0.1 g of cetyltrimethylammonium bromide (CTAB) were added to 50 ml of ethanol and 50 ml of deionized water to obtain suspension A. The suspension was ultrasonically dispersed for 10 min at a frequency of 30 kHz and a power of 1800 W. The suspension was magnetically stirred for 1 h. The product was washed with ethanol and then with deionized water, and dried to obtain surface-modified Cu2O powder.

[0027] Step 2: Then carry out the encapsulation process, disperse the modified Cu2O in anhydrous ethanol, add ammonia water, 1.52mol / L ethyl orthosilicate, water bath at 40℃, magnetic stirring for 1h, and obtain 30mL of OH - To the suspension B having a content of 0.54 mol / L, 30 mL of deionized water was slowly added at a rate of 0.5 mL / min, and the mixture was stirred for reaction for 1 h. After washing with alcohol and water, the mixture was placed in an oven and dried at 100°C for 3 h to obtain a pigment precursor.

[0028] Step 3: After grinding the pigment precursor, place it in an atmosphere furnace and maintain a gas flow rate of 100 mL / min in a hydrogen-argon mixed atmosphere. In a hydrogen-argon mixed atmosphere with a hydrogen content of 0.1%, the temperature is increased to 500°C at 0.5°C / min, increased to 700°C at 1.5°C / min, and increased to 800°C at 4°C / min for calcination. Keep warm for 1 hour, cool to room temperature with the furnace, and obtain a silicon dioxide-coated cuprous oxide red pigment after acid washing, water washing, and drying.

[0029] Example 2 Step 1: 1 g of Cu2O powder and 0.05 g of cetyltrimethylammonium bromide (CTAB) were added to 67 ml of propanol and 33 ml of deionized water to obtain suspension A. The suspension was ultrasonically dispersed for 15 min at a frequency of 20 kHz and a power of 1400 W. The suspension was magnetically stirred for 1.5 h. The product was washed with ethanol and then with deionized water, and dried to obtain surface-modified Cu2O powder.

[0030] Step 2: Then carry out the encapsulation process, disperse the modified Cu2O in propanol, add sodium hydroxide and 2.47mol / L methyl orthosilicate in sequence, place in a 45℃ water bath, stir magnetically for 1h, and obtain 30mL of OH - To the suspension B having a content of 0.76 mol / L, 50 mL of deionized water was slowly added at a rate of 0.4 mL / min, and the mixture was stirred for reaction for 2 h. After washing with alcohol and water, the mixture was placed in an oven and dried at 100°C for 3 h to obtain a pigment precursor.

[0031] Step 3: After grinding the pigment precursor, place it in an atmosphere furnace and maintain a gas flow rate of 200 mL / min in a hydrogen-argon mixed atmosphere with a hydrogen content of 0.1%. Raise the temperature to 500°C at 0.7°C / min, raise it to 700°C at 2°C / mi, and raise it to 850°C at 4.5°C / min for calcination. Keep it warm for 1.5 hours, cool it to room temperature with the furnace, and obtain a silicon dioxide-coated cuprous oxide red pigment after acid washing, water washing, and drying.

[0032] Example 3 Step 1: 1 g of Cu2O powder, 0.1 g of polyvinylpyrrolidone (PVP) and 0.05 g of dodecyltrimethylammonium bromide were added to 75 ml of butanol and 25 ml of deionized water to obtain suspension A. The suspension was ultrasonically dispersed for 20 min at a frequency of 20 kHz and a power of 1400 W. The suspension was magnetically stirred for 2 h. The product was washed with ethanol and then with deionized water, and dried to obtain surface-modified Cu2O powder.

[0033] Step 2: Then carry out the encapsulation process, disperse the modified Cu2O in butanol, add potassium hydroxide, 3.69mol / L propyl orthosilicate in sequence, place in a 50℃ water bath, stir magnetically for 1h, and obtain 30mL of OH - To the suspension B having a content of 0.98 mol / L, 60 mL of deionized water was slowly added at a rate of 0.4 mL / min, and the mixture was stirred for 2 h. After washing with alcohol and water, the precursor was dried in an oven at 100°C for 3 h to obtain the precursor.

[0034] Step 3: After grinding the precursor, place it in an atmosphere furnace and maintain a gas flow rate of 250 mL / min in a hydrogen-argon mixed atmosphere. In a hydrogen-argon mixed atmosphere with a hydrogen content of 0.2%, the temperature is raised to 500°C at 1°C / min, raised to 700°C at 3°C / min, and raised to 900°C at 5°C / min for calcination. Keep warm for 2 hours, cool to room temperature with the furnace, and obtain silica-coated cuprous oxide red pigment after acid washing, water washing, and drying.

[0035] Example 4 Step 1: 1 g of Cu2O powder, 0.1 g of polyvinyl butyral (PVB), 0.05 g of polyethylene glycol, and 0.05 g of sodium dodecyl sulfate were added to 80 ml of ethanol and 20 ml of deionized water to obtain suspension A. The suspension was ultrasonically dispersed for 30 min at a frequency of 10 kHz and a power of 1000 W. The suspension was magnetically stirred for 2 h. The product was washed with ethanol and then with deionized water, and dried to obtain surface-modified Cu2O powder.

[0036] Step 2: Then carry out the encapsulation process, disperse the modified Cu2O in ethanol, add potassium hydroxide and 4.46mol / L butyl orthosilicate in sequence, place in a 60℃ water bath, stir magnetically for 1h, and obtain 30mL of OH - To the suspension B having a content of 1.32 mol / L, 60 ml of deionized water was slowly added at a rate of 0.3 mL / min, and the mixture was stirred for reaction for 2 h. After washing with alcohol and water, the mixture was placed in an oven and dried at 100 ° C for 3 h to obtain a pigment precursor.

[0037] Step 3: After grinding the pigment precursor, place it in an atmosphere furnace and maintain a gas flow rate of 300 mL / min in a hydrogen-argon mixed atmosphere. In a hydrogen-argon mixed atmosphere with a hydrogen content of 0.5%, increase the temperature to 500°C at 1°C / min, increase it to 700°C at 3°C / min, and increase it to 1000°C at 5°C / min for calcination. Keep it warm for 2.5 hours, cool it to room temperature with the furnace, and obtain a silicon dioxide-coated cuprous oxide red pigment after acid washing, water washing, and drying.

[0038] Comparative Example 1 It is pure cuprous oxide without packaging treatment.

[0039] Comparative Example 2 (1) Cu2O was dispersed in 30 mL of butanol, and 0.98 mol / L potassium hydroxide and 3.69 mol / L propyl orthosilicate were added in sequence. The mixture was placed in a 50°C water bath and magnetically stirred for 1 h. Then, 60 mL of deionized water was slowly added and stirred for 0.5 h. The product was washed with ethanol and then with deionized water, and dried in an oven at 100°C for 3 h to obtain a pigment precursor.

[0040] (2) After the pigment precursor is ground, it is placed in an atmosphere furnace and the gas flow rate in the hydrogen-argon mixed atmosphere is maintained at 250 mL / min. The temperature is raised to 500°C at 1°C / min, to 700°C at 3°C / min, and to 900°C at 5°C / min in a hydrogen-argon mixed atmosphere with a hydrogen content of 0.2%, and calcined. The temperature is kept for 2 hours, and the pigment is cooled to room temperature in the furnace. After acid washing, water washing, and drying, a silicon dioxide-coated cuprous oxide red pigment is obtained.

[0041] Comparative Example 3 (1) 1 g of Cu2O powder and 0.1 g of polyvinylpyrrolidone (PVP) were added to 75 ml of butanol and 25 ml of deionized water to obtain suspension A. The suspension was ultrasonically dispersed for 20 min at a frequency of 10-30 kHz and a power of 1000-1800 W. The suspension was magnetically stirred for 2 h. The product was washed with ethanol and then with deionized water, and dried to obtain surface-modified Cu2O powder.

[0042] (2) Then, the encapsulation process was carried out. The modified Cu2O was dispersed in butanol, 3.69 mol / L propyl orthosilicate was added, and magnetic stirring was performed for 1 h in a 50°C water bath to obtain 30 mL of suspension B. 60 mL of deionized water was slowly added to the suspension B, and the suspension was stirred for 2 h. After washing with alcohol and water, the suspension was placed in an oven at 100°C for 3 h to obtain a pigment precursor.

[0043] (3) After the pigment precursor is ground, it is placed in an atmosphere furnace and the gas flow rate in the hydrogen-argon mixed atmosphere is maintained at 250 mL / min. The temperature is raised to 500°C at 1°C / min, to 700°C at 3°C / min, and to 900°C at 5°C / min in a hydrogen-argon mixed atmosphere with a hydrogen content of 0.2%, and calcined. The temperature is kept for 2 hours, and the pigment is cooled to room temperature in the furnace. After acid washing, water washing, and drying, a silicon dioxide-coated cuprous oxide red pigment is obtained.

[0044] Comparative Example 4 (1) 1 g of Cu2O powder and 0.1 g of polyvinylpyrrolidone (PVP) were added to a suspension of 75 ml of butanol and 25 ml of deionized water, ultrasonically dispersed for 20 min, and magnetically stirred for 2 h. 30 mL of ethanol, 0.98 mol / L potassium hydroxide, and 3.69 mol / L propyl orthosilicate were added in sequence. The mixture was placed in a 50 °C water bath and magnetically stirred for 1 h. The mixture was then stirred for 0.5 h. The product was washed with ethanol and then with deionized water, and dried in an oven at 100 °C for 3 h to obtain a pigment precursor.

[0045] (2) After the pigment precursor is ground, it is placed in an atmosphere furnace and the gas flow rate in the hydrogen-argon mixed atmosphere is maintained at 250 mL / min. The temperature is raised to 500°C at 1°C / min, to 700°C at 3°C / min, and to 900°C at 5°C / min in a hydrogen-argon mixed atmosphere with a hydrogen content of 0.2%, and calcined. The temperature is kept for 2 hours, and the pigment is cooled to room temperature in the furnace. After acid washing, water washing, and drying, a silicon dioxide-coated cuprous oxide red pigment is obtained.

[0046] Comparative Example 5 (1) 1 g of Cu2O powder and 0.1 g of polyvinylpyrrolidone (PVP) were added to 75 ml of butanol and 25 ml of deionized water to obtain suspension A. The suspension was ultrasonically dispersed for 20 min at a frequency of 10-30 kHz and a power of 1000-1800 W. The suspension was magnetically stirred for 2 h, washed with alcohol, washed with water, and dried to obtain surface-modified Cu2O powder.

[0047] (2) Then, the encapsulation process was carried out. The modified Cu2O was dispersed in butanol, and 0.98 mol / L potassium hydroxide and 3.69 mol / L propyl orthosilicate were added in sequence. The mixture was placed in a 50°C water bath and magnetically stirred for 1 h to obtain 30 mL of suspension B. 60 mL of deionized water was slowly added to the suspension B and stirred for 2 h. The product was washed with ethanol and then with deionized water. It was placed in an oven and dried at 100°C for 3 h to obtain a pigment precursor.

[0048] (3) After the pigment precursor is ground, it is placed in an atmosphere furnace and the gas flow rate in the hydrogen-argon mixed atmosphere is maintained at 250 mL / min. It is calcined at a temperature of 10°C / min to 900°C in a hydrogen-argon mixed atmosphere with a hydrogen content of 0.2%. The mixture is kept warm for 2 hours and cooled to room temperature in the furnace. After acid washing, water washing, and drying, a silicon dioxide-coated cuprous oxide red pigment is obtained.

[0049] The silicon dioxide coated cuprous oxide red pigment prepared in the present invention (each embodiment and comparative example) was placed in an electric furnace, heated to 500°C at a rate of 10°C / min in air atmosphere, and kept at that temperature for 30 minutes for high temperature oxidation calcination. The color parameters before and after calcination were as follows: Figure 1The samples were characterized using the WSD-3C fully automatic whiteness meter produced by Beijing Kangguang Instrument Co., Ltd., and the sample L*, a*, and b* chromaticity values ​​were obtained according to the International Commission on Illumination (CIE) standard (where L* represents lightness, a* represents red and green, and b* represents yellow and blue). Figure 1 It can be seen that after the comparative example is oxidized at 500°C, the a* value is significantly reduced, while the a* value of the silica-coated cuprous oxide red colorant prepared by the present invention does not change significantly before and after the 500°C oxidation treatment, indicating that it has good high-temperature antioxidant performance.

[0050] Figure 2-10 The TEM images of the embodiment and comparative example of the red pigment of cuprous oxide coated with silicon dioxide prepared by the present invention are shown. It can be seen from the figure that the coating layer of the cuprous oxide coated with silicon dioxide prepared by the present invention is uniform and dense.

[0051] In summary, the present invention utilizes a coating modification technique to coat the surface of cuprous oxide pigment with transparent, high-temperature-stable silica to enhance the pigment's high-temperature stability and acid corrosion resistance. This modification enhances the high-temperature oxidation resistance, stability, and heat resistance of cuprous oxide, broadening the application of related products in fields such as plastics, rubber, and high-temperature coatings.

[0052] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a core-shell structured cuprous oxide red pigment, characterized in that: The steps include: Step 1: Dispersing Cu2O powder and a modifying agent in a solvent to obtain a suspension A, and subjecting the suspension A to ultrasonic treatment to obtain a surface-modified Cu2O powder; The modification reagent is at least one of hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone, polyvinyl butyral, dodecyltrimethylammonium bromide, polyethylene glycol, and sodium dodecylsulfonate; Step 2: Dispersing the surface-modified Cu2O powder, organosiloxane, and a pH adjuster in a polar organic solvent to obtain a suspension B; stirring the suspension B to react, and adding water dropwise during the reaction to obtain a pigment precursor; the pH adjuster comprises at least one of aqueous ammonia, sodium hydroxide solution, and potassium hydroxide solution; Step 3: calcining the pigment precursor to obtain a cuprous oxide red pigment with a core-shell structure.

2. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein The solvent in step 1 is a mixture of a polar organic solvent and deionized water; the ratio of the polar organic solvent to the deionized water is 1 to 4:1; The solvent of the suspension A and the polar organic solvent in the suspension B are independently selected from at least one of ethanol, propanol and butanol.

3. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein: The weight ratio of Cu2O powder to the modifying agent in step 1 is 1:0.05-0.

2.

4. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein: The water drop rate in step 2 is controlled at 0.3-0.5 mL / min; The volume ratio of water added in step 2 to suspension B is 1-2:

1.

5. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein: The temperature of the stirring reaction in step 2 should be controlled at 40-60° C., and the stirring time should be 1-2 hours.

6. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein: In the step 1, the frequency of the ultrasonic treatment is 10-30 kHz, the power is 1000-1800 W, and the duration is 10-30 min.

7. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein: OH in suspension B - The content is 0.54~1.32mol / L.

8. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein: The organosiloxane includes at least one of ethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, and butyl orthosilicate; The content of organosiloxane in suspension B is 1.52~4.46 mol / L.

9. The method for preparing the core-shell cuprous oxide red pigment according to claim 1, wherein The calcination process in step 3 includes: calcining the pigment precursor in a hydrogen-argon mixed atmosphere, first raising the temperature to 500°C at 0.5-1°C / min, then raising the temperature to 700°C at 1.5-3°C / min, and then raising the temperature to 800-1000°C at 4-5°C / min, with a holding time of 1-2.5 hours. During this process, the flow rate of the hydrogen-argon mixed atmosphere is maintained at 100-300 mL / min.

10. The method for preparing the core-shell cuprous oxide red pigment according to claim 9, wherein: The volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 0.1% to 0.5%.

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