Preparation method of high light resistance composite pigment

Abstract

The application belongs to the technical field of functional pigments, and particularly relates to a preparation method of high-light-resistance composite pigments. The preparation method of the application is that: after pretreatment and cleaning, hexagonal boron nitride is obtained to be modified boron nitride nanosheet, and then the modified boron nitride nanosheet is compounded with organic pigments to obtain ideal high-light-resistance composite pigments. The modified boron nitride nanosheet used in the application can be better combined with the organic pigments by using the principle of entropy increase, the rich electron boron-nitrogen plane of the hexagonal boron nitride and the aromatic conjugated system of the lithol red molecules produce pi-pi stacking interaction, and then the two are driven to self-assemble to form high-light-resistance composite pigments, and the high-light-resistance composite pigments form a structure that is compact. The high-light-resistance composite pigments obtained by the application still maintain the chemical structure and gloss of the original organic pigments, and have excellent stability and good light resistance, and the problem of poor light resistance of the organic pigments is solved.

Description

Technical Field

[0001] This invention belongs to the field of functional pigment technology, specifically relating to a method for preparing a high lightfastness composite pigment. Background Technology

[0002] With the rapid development of the low-altitude economy, equipment coatings are placing increasingly stringent demands on the weather resistance of organic pigments. Studies have shown that the ultraviolet radiation intensity at an altitude of 3000 m can be 1.8 times that at the Earth's surface, and the drastic temperature changes and particle erosion in the low-altitude environment can also accelerate the photochemical degradation of pigments. Currently, Lithol Rubin (CIPigment Red 57:1), a commercially available organic pigment, is a classic azo pigment. Although it has bright colors and high tinting strength, the quinone groups, sulfonic acid groups, and conjugated double bonds in its molecular structure are prone to degradation under environmental conditions, resulting in significant defects in weather resistance. To adapt to the rapid development of the market, the modification of Lithol Rubin has become a key research direction in the pigment industry.

[0003] In existing technologies, the modification of Lithol Ruby Red includes the following methods: Inorganic coating is used, coating the pigment particles with nanoparticles such as silica and alumina. While this coating layer blocks ultraviolet radiation from eroding the pigment particles, it leads to a decrease in color saturation and a deterioration in thermal conductivity. Another method involves rare-earth ion doping, such as Ce. 3+ La 3 + While rare earth ions can improve the shielding of the composite system against ultraviolet rays, their use not only increases production costs but also creates an environmental burden. In particular, the disposal of rare earth waste must comply with environmental regulations, which will further increase the economic burden.

[0004] Improving the lightfastness of Lithol Ruby requires comprehensive consideration of its product performance, environmental impact, and cost. Currently, there is no method for preparing highly stable and lightfast composite pigments that can achieve good lightfastness in practical applications. Summary of the Invention

[0005] To address the problems of Litholbert pigment red's tendency to agglomerate and poor lightfastness, this invention provides a method for preparing a composite pigment with high lightfastness.

[0006] The technical solution of this invention is summarized as follows:

[0007] (1) Boron nitride pretreatment: Hexagonal boron nitride raw material is pretreated to obtain boron nitride slurry;

[0008] (2) Cleaning of boron nitride nanosheets: The pH of the boron nitride slurry obtained in step (1) was adjusted with hydrochloric acid, the product was filtered and then freeze-dried to obtain modified boron nitride nanosheets with defects on the surface.

[0009] (3) Composite: Modified boron nitride nanosheets are mixed with organic pigments, and the mixture is uniformly dispersed in a solvent to obtain a mixed solution. The obtained mixed solution is ultrasonically treated and then subjected to oscillation reaction to obtain a high lightfastness composite pigment. The electron-rich boron-nitrogen plane of hexagonal boron nitride and the aromatic conjugated system of Lithol Rubin molecule generate π-π stacking interaction, which drives the two to self-assemble into a high lightfastness composite pigment.

[0010] Further, the specific steps of the pretreatment in step (1) are as follows: the hexagonal boron nitride raw material is mixed with a strong alkaline solution and ball-milled in a planetary ball mill for a certain period of time to obtain boron nitride slurry.

[0011] Further, in step (2), the pH of the boron nitride slurry obtained in step (1) is adjusted to 7.0-7.5 using hydrochloric acid.

[0012] Furthermore, in step (3), the mass ratio of modified boron nitride nanosheets to organic pigments in the mixture is 1:100-1:20, and the mass ratio of the mixture to solvent is 1:100-1:5. This ensures that the mixture of modified boron nitride nanosheets and organic pigments can be uniformly dispersed, and also ensures that the organic pigments retain their bright colors and high color intensity.

[0013] Furthermore, the organic pigment mentioned in step (3) is Lithol Rubber Red, and the solvent mentioned in step (3) is one or more of water, ethanol, and acetone that are completely miscible.

[0014] Furthermore, the duration of ultrasonic treatment in step (3) is 2-4 hours, and the duration of oscillation reaction in step (3) is 4-8 hours.

[0015] Furthermore, the strong base is sodium hydroxide or potassium hydroxide, and the concentration of the strong base solution is 8-12 mol / L.

[0016] Furthermore, the hexagonal boron nitride is mixed with the strong alkaline solution at a mass ratio of 1:20 to 1:50.

[0017] Furthermore, the planetary ball mill has a rotational speed of 300-500 rpm and a grinding time of 12-24 hours.

[0018] Furthermore, the grinding balls used in the planetary ball mill are made of zirconium oxide, and the ball-to-material ratio is controlled to be 15:1-30:1.

[0019] The present invention has the following beneficial effects:

[0020] 1. The method for preparing high lightfastness composite pigments provided by this invention uses boron nitride as raw material, and utilizes ball milling to create defects on the surface of boron nitride, while simultaneously causing OH...- It allows for easier insertion into the middle of boron nitride sheets, and can more effectively improve the corrosion effect of strong alkalis on boron nitride nanosheets; after etching, the boron nitride can better bond with organic pigments through the principle of entropy increase, forming a tightly structured, highly lightfast composite pigment; the modified boron nitride nanosheets exhibit strong absorption in the ultraviolet region, which can effectively block ultraviolet damage to organic pigments, producing an ultraviolet shielding effect. At the same time, the unique two-dimensional lattice structure of boron nitride nanosheets can form a better stacking structure with Lithol Rubin, promoting the structural stability of Lithol Rubin; the highly lightfast nanosheets prepared by this invention... The lightfastness of the composite pigment meets the requirement that after 50 hours of xenon lamp aging, the intensity of the ultraviolet-visible absorption spectrum decreases by ≤1.15%, which significantly improves the lightfastness of organic pigments. At the same time, the electron-rich boron-nitrogen plane of hexagonal boron nitride and the aromatic conjugated system of Lithol Ruby Red molecules generate π-π stacking interactions, which drive the two to self-assemble into a high-lightfastness composite pigment. This can effectively construct electron transport and heat transfer channels, improve the photostability and thermal stability of the system, and enable the high-lightfastness composite pigment obtained by this invention to maintain its original vividness and high coloring strength.

[0021] 2. The raw materials used in the high lightfastness composite pigments provided by this invention are relatively inexpensive and rare, and the requirements for reaction conditions are low and easy to achieve. The equipment required in the preparation process is simple and readily available. The reagents used in the reaction process are easy to process and do not cause environmental pollution. This invention can adjust the structure and performance of high lightfastness composite pigments by adjusting the parameters in the preparation process, providing a basis for further optimization of the structure of high lightfastness composite pigments. Attached Figure Description

[0022] Figure 1 These are scanning electron microscope (SEM) images of hexagonal boron nitride and modified boron nitride nanosheets;

[0023] Figure 2 It is the diffuse reflectance absorption spectrum of modified boron nitride nanosheets;

[0024] Figure 3 These are scanning electron microscope images of Litholite and the high lightfastness composite pigment obtained in Example 1;

[0025] Figure 4 The infrared spectra of Litholite Red, Boron Nitride, and the high lightfastness composite pigment obtained in Example 1 are shown.

[0026] Figure 5 The xenon lamp aging UV-Vis absorption spectra of Litholite and the high lightfastness composite pigment obtained in Example 1 are shown.

[0027] Figure 6 These are scanning electron microscope images of the comparative sample obtained in Comparative Example 1;

[0028] Figure 7 These are scanning electron microscope images of the high lightfastness composite pigment obtained in Example 2;

[0029] Figure 8 These are scanning electron microscope images of the high lightfastness composite pigment obtained in Example 3. Detailed Implementation

[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0033] Example 1

[0034] (1) Boron nitride pretreatment: Weigh 2 g of hexagonal boron nitride powder and measure 50 mL of sodium hydroxide solution with a concentration of 10 mol / L. Mix the two and put them into the ball mill jar of a planetary ball mill. Add the grinding balls and control the ball-to-material ratio to be 20:1. After sealing the ball mill jar, ball mill at 400 rpm for 16 hours to obtain boron nitride slurry.

[0035] (2) Cleaning of boron nitride nanosheets: The obtained boron nitride slurry was neutralized to pH=7.0 with 0.1 mol / L hydrochloric acid, and after filtration to remove ionic impurities, it was freeze-dried to obtain modified boron nitride nanosheet solids with defects on the surface;

[0036] (3) Composite: Weigh 40g of acetone and 1000g of water and mix them evenly as a solvent. Weigh 1g of modified boron nitride nanosheets and 50g of Lithol Rubber Red. Disperse the two evenly in the solvent to obtain a mixed solution. Sonicate at 50℃ for 3 hours. Adjust the shaking speed to 80 rpm and the amplitude to 25mm. Shake the mixed solution for 6 hours to obtain a high lightfastness composite pigment.

[0037] The morphology of the hexagonal boron nitride raw material observed by scanning electron microscopy is as follows: Figure 1 As shown in (a), hexagonal boron nitride exhibits a typical irregular plate-like structure with clear edges. Its lateral size (particle size) is mainly distributed between 2 and 5 μm, and some thin plates show slight wrinkles and stacking. Figure 1(b) shows the microstructure of the modified boron nitride nanosheets. The nanosheets have an uneven surface with obvious wrinkles and curling features, which is a typical characteristic of ultrathin two-dimensional nanomaterials. The surface is rich in defects, and the thickness distribution of the sheets is relatively narrow, about 0.5-2 micrometers. This uniform sheet structure indicates that the modification process can effectively exfoliate while controlling the size of the nanosheets. Figure 2 The diffuse reflectance absorption spectrum of the modified boron nitride nanosheets shows that the modified boron nitride nanosheets have a significant and strong absorption peak in the ultraviolet region.

[0038] The morphology of the raw material Litholite Red observed using a scanning electron microscope is as follows: Figure 3 As shown in (a), the pigment particles are randomly stacked together and easily aggregate, with particle sizes ranging from 0.05 to 3 μm; the scanning electron microscope morphology of the experimentally obtained high lightfastness composite pigment is as follows. Figure 3 As shown in (b), the pigment particles still retain the original particle size and structure of Lithol Rubin, but the pigment particles are tightly bound together with boron nitride nanosheets, and the pigment particles are no longer prone to agglomeration, thus improving the stability of the organic pigment. Figure 4 The infrared spectra of lissol bromide, boron nitride, and a high-lightfastness composite pigment are shown. Compared to the infrared characteristic curve of lissol bromide, the infrared characteristic curve of the high-lightfastness composite pigment did not show any new characteristic peaks. This indicates that the functional groups, chemical bonds, and molecular structure of the high-lightfastness composite pigment are consistent with those of lissol bromide, meaning that the chemical properties of the high-lightfastness composite pigment are consistent with those of lissol bromide. The high-lightfastness composite pigment still maintains the brightness and chemical properties of lissol bromide pigment. Furthermore, the characteristic absorption peak of lissol bromide in the infrared spectrum of the high-lightfastness composite pigment shows a red shift. This indicates that the layered structure of the modified boron nitride nanosheets and the conjugated π system of the lissol bromide molecules produce π-π stacking interactions. The π-π stacking expands the conjugated system and reduces the π-π* transition energy.

[0039] According to GB / T 12967.4-2022, the lightfast composite pigment obtained in Example 1 and Lithol Rubin with the same concentration were coated with a 50 μm thick pigment layer on a stainless steel substrate using an automatic coating machine. The substrate was placed in a xenon lamp weathering tester and irradiated with a xenon lamp source with a wavelength of 340 nm and an intensity of 0.65 W / m². The high lightfast composite pigment and Lithol Rubin obtained after xenon lamp aging experiments for 0, 10, 20, 30, 40, and 50 hours were tested using a UV-Vis absorption spectrometer, and the experiment was repeated three times.

[0040] Figure 5(a) is the ultraviolet-visible absorption spectrum of Lithol Ruby Red obtained in the xenon lamp aging experiment. After the xenon lamp aging experiment, the absorbance ratio of Lithol Ruby Red before and after 50 hours of xenon lamp irradiation in three parallel experiments was calculated. The average light absorption loss was 5.61% (standard deviation was 0.32), and the light absorption characteristics of the pigment were significantly reduced. Figure 5 (b) The UV-Vis absorption spectrum of the high lightfastness composite pigment obtained from the xenon lamp aging experiment was calculated. The absorbance ratio of the high lightfastness composite pigment before and after 50 hours of xenon lamp irradiation in the three parallel experiments was calculated, and the average light absorption loss rate was only 1.07% (standard deviation was 0.18). Compared with untreated Lithol Ruby Red, the high lightfastness composite pigment showed good lightfastness and stability, and the photoaging rate decreased significantly.

[0041] Comparative Example 1

[0042] 40g of acetone and 1000g of water were weighed and mixed evenly as a solvent. 1g of hexagonal boron nitride raw material and 50g of Rissol red were weighed and dispersed in the solvent to obtain a mixed solution. The solution was ultrasonically treated at 50℃ for 3 hours. The shaking speed was adjusted to 80 rpm and the amplitude to 25 mm. The mixed solution was shaken for 6 hours to obtain a comparison sample.

[0043] Figure 6 To compare the electron microscopy images obtained from the scanning of the samples, the pigment particles in the comparison samples spontaneously agglomerated together, while only a small number of pigment particles were attached to the surface of hexagonal boron nitride. The direct dispersion of hexagonal boron nitride raw material and organic pigment in solvent cannot enable the pigment particles to tightly bind with hexagonal boron nitride on the surface of hexagonal boron nitride to form a dense complex, which cannot play a role in the stability of the pigment.

[0044] Example 2

[0045] (1) Boron nitride pretreatment: Weigh 2 g of hexagonal boron nitride powder and measure 40 mL of 8 mol / L sodium hydroxide solution. Mix the two and put them into the ball mill jar of a planetary ball mill. Add grinding balls and control the ball-to-powder ratio to 20:1. After sealing the ball mill jar, ball mill at 400 rpm for 16 hours to obtain boron nitride slurry;

[0046] (2) Cleaning of boron nitride nanosheets: The boron nitride slurry was neutralized to pH=7.0 with 0.1 mol / L hydrochloric acid, and after filtration to remove ionic impurities, it was freeze-dried to obtain modified boron nitride nanosheet solids with defects on the surface;

[0047] (3) Composite: Weigh 20g of ethanol and 1000g of water and mix them evenly as solvent. Weigh 1g of modified boron nitride nanosheets and 50g of Lithol Rubber Red. Disperse the two evenly in the solvent to obtain a mixed solution. Sonicate at 70℃ for 3 hours. Adjust the shaking speed to 80 rpm and the amplitude to 25mm. Shake the mixed solution for 6 hours to obtain a high lightfastness composite pigment.

[0048] The obtained high lightfastness composite pigment was observed using a scanning electron microscope. Figure 7 The morphology of the obtained high lightfastness composite pigment is consistent with that of the electron microscope image obtained in Example 1. The pigment particles are tightly bonded to the modified boron nitride nanosheets on the surface of the modified boron nitride nanosheets, indicating that the obtained high lightfastness composite pigment has good stability.

[0049] Example 3

[0050] (1) Boron nitride pretreatment: Weigh 2 g of hexagonal boron nitride powder and measure 50 mL of 12 mol / L sodium hydroxide solution. Mix the two and put them into the ball mill jar of a planetary ball mill. Add grinding balls and control the ball-to-powder ratio to 30:1. After sealing the ball mill jar, ball mill at 500 rpm for 16 hours to obtain boron nitride slurry;

[0051] (2) Cleaning of boron nitride nanosheets: The boron nitride slurry was neutralized to pH=7.5 with 0.1 mol / L hydrochloric acid, and after filtration to remove ionic impurities, it was freeze-dried to obtain modified boron nitride nanosheet solids with defects on the surface;

[0052] (3) Composite: Weigh 20g of ethanol and 1000g of water and mix them evenly as solvent. Weigh 1g of modified boron nitride nanosheets and 100g of Lithol Rubber Red. Disperse the two evenly in the solvent to obtain a mixed solution. Sonicate at 80℃ for 4 hours. Adjust the shaking speed to 80 rpm and the amplitude to 25mm. Shake the mixed solution for 8 hours to obtain a high lightfastness composite pigment.

[0053] The morphology of the obtained high lightfastness composite pigment was observed under a scanning electron microscope as follows: Figure 8 As shown, its morphology is consistent with the electron microscope image of Example 1. The pigment particles are tightly bonded to the modified boron nitride nanosheets on the surface of the modified boron nitride nanosheets, indicating that the prepared high lightfastness composite pigment also has good stability.

[0054] In the description of this specification, the terms "one embodiment", "some embodiments", "specific embodiment", etc., refer to a specific feature, structure, material or characteristic described in connection with that embodiment or example that is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0055] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a high lightfastness composite pigment, characterized in that, Includes the following steps: (1) Boron nitride pretreatment: Hexagonal boron nitride raw material is pretreated to obtain boron nitride slurry; (2) Cleaning of boron nitride nanosheets: The pH of the boron nitride slurry obtained in step (1) was adjusted with hydrochloric acid, the product was filtered and then freeze-dried to obtain modified boron nitride nanosheets with defects on the surface. (3) Composite: Modified boron nitride nanosheets are mixed with organic pigments, and the mixture is uniformly dispersed in a solvent to obtain a mixed solution. The obtained mixed solution is then subjected to ultrasonic treatment and oscillation reaction to obtain a high lightfastness composite pigment. The specific steps of the pretreatment in step (1) are as follows: hexagonal boron nitride raw material is mixed with a strong alkaline solution and ball-milled in a planetary ball mill to obtain boron nitride slurry; The organic pigment mentioned in step (3) is Lithol Rubin, and the solvent mentioned in step (3) is one or more of water, ethanol, and acetone.

2. The method for preparing a high lightfastness composite pigment according to claim 1, characterized in that: In step (2), the pH of the boron nitride slurry obtained in step (1) is adjusted to 7.0-7.5 using hydrochloric acid.

3. The method for preparing a high lightfastness composite pigment according to claim 1, characterized in that: In step (3), the mass ratio of modified boron nitride nanosheets to organic pigments in the mixture is 1:100-1:20, and the mass ratio of the mixture to solvent is 1:100-1:

5.

4. The method for preparing a high lightfastness composite pigment according to claim 1, characterized in that: The duration of ultrasonic treatment in step (3) is 2-4 hours, and the duration of oscillation reaction in step (3) is 4-8 hours.

5. The method for preparing a high lightfastness composite pigment according to claim 1, characterized in that: The strong base is sodium hydroxide or potassium hydroxide, and the concentration of the strong base solution is 8-12 mol / L.

6. The method for preparing a high lightfastness composite pigment according to claim 1, characterized in that: The hexagonal boron nitride is mixed with the strong alkaline solution at a mass ratio of 1:20 to 1:

50.

7. The method for preparing a high lightfastness composite pigment according to claim 1, characterized in that: The planetary ball mill has a rotational speed of 300-500 rpm and a milling time of 12-24 hours.

8. The method for preparing a high lightfastness composite pigment according to claim 1, characterized in that: The planetary ball mill uses zirconium oxide grinding balls, and the ball-to-material ratio is controlled at 15:1-30:1.

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