CN116041984A - A kind of flaky alumina with self-weathering function and preparation method thereof - Google Patents

Abstract

The invention discloses a flaky alumina with self-weathering function and a preparation method thereof. The method is characterized in that a certain amount of cerium chloride heptahydrate is added in the process of preparing flaky alumina to construct a unique alumina-ceria composite structure. The method makes the prepared flaky alumina itself have good self-weathering function, and has the advantages of good particle dispersibility and large diameter-thickness ratio. The pearlescent pigment prepared from the flaky alumina can meet the requirements of automotive-grade weather resistance without secondary hydrolysis and other complicated treatment processes, and is well used in automotive paint, coatings, ink printing, cosmetics, plastics and other industries.

Description

A kind of flaky alumina with self-weathering function and preparation method thereof

technical field

The invention relates to the technical field of preparation methods of flaky alumina, in particular to a flaky alumina with a self-weathering function and a preparation method thereof.

Background technique

Pearlescent pigments are widely used in ink printing, cosmetics, leather, plastics and other industries due to their unique optical effects and physical and chemical properties. Pearlescent pigments are transparent or translucent flakes as the core, and are coated with a layer or alternate layers of metal/non-metal oxides on the surface by a special chemical process to form a flat sandwich body. When light hits the surface of the pearlescent pigment, while most of the incident light is reflected, the rest of the light is transmitted to the next layer of pigment wafers, and after multiple reflections and transmissions, a three-dimensional pearlescent effect is produced.

The main factors affecting the pearlescent effect are the substrate and the coating process. Among them, the factors of the base material are the refractive index, particle size, shape, surface flatness, cleanliness and so on. Alumina crystals have low refractive index, good light transmission, good chemical stability, and high temperature resistance, and are the best raw materials for preparing pearlescent pigments.

Especially in areas with high weather resistance requirements such as automotive paints and exterior wall coatings, pearlescent pigments will change in adhesion, color and gloss under the combined effects of water vapor, ultraviolet rays and oxygen, which will affect the appearance and performance, and restrict pearlescent pigments. Pigment lifetime. Therefore, it is necessary to cover the surface of the pearlescent pigment with a protective coating in order to achieve the purpose of having a weather resistance function.

For flaky alumina, domestic and foreign scholars have carried out a series of research work and some research results have been transformed into commercial products. The current preparation methods of flake alumina (αAl2O3) include high-temperature sintering method, hydrothermal method, sol-gel method, mechanical method and molten salt method.

Among them, Patent No. 111239/1982 discloses α-alumina in the form of hexagonal flakes having a particle diameter greater than 10 μm and an aspect ratio (particle diameter/thickness) of 5-10. Patent CN101541681 produces flaky alumina with an average particle thickness of ≤0.5 μm and an average particle size of ≥30 μm by hydrolyzing an aqueous solution of aluminum, zinc and tin precursors containing water-soluble fluxes, aging, drying and crystallization. Alumina flakes having an average particle diameter of about 5-60 μm, a thickness of less than 1 μm and an aspect ratio >20 are disclosed in US5702519A. Patent CN1150165A discloses a flake-shaped alumina with an average particle size of 5-60 μm and a thickness of less than 1 μm. The molten salt method is used to mix the aqueous solution of water-soluble aluminum salt and titanium salt with an aqueous solution of alkali metal carbonate, evaporate The gel is dried and calcined at high temperature to obtain the flaky alumina. Patent CN110436501A adopts the molten salt method, mixes aluminum sources such as aluminum hydroxide, aluminum sulfate, and aluminum chloride with water, adds magnesium sulfate, stirs, and calcines at high temperature to obtain flaky alumina. Patent CN103359764A mixes nano-alumina powder with sodium sulfate and potassium sulfate, distills, calcines, filters and dries to obtain flaky α-alumina. Patent CN101941728A discloses a preparation method of flaky alumina, which is characterized in that aluminum hydroxide is used as raw material, sodium sulfate is used as synthesis medium, ethanol is activated and dispersed, and flaky alumina is prepared by high-temperature calcination. Patent CN114920272A discloses a method for rapidly preparing flaky alumina, which adds a mineralizer to the aluminum source, and adds additives, water, etc. to form a mixed solution, which is heated, calcined at high temperature, filtered and dried to obtain flaky alumina. Patent CN113173590A uses aluminum-containing liquid metal as the medium, and the molten salt on the liquid metal medium reacts with alumina to form flaky alumina. Patent CN114958035 A discloses a method of using molten salt as the reaction medium, adding aluminum fluoride to form an aluminum fluoride molten salt system, and preparing flaky α-alumina with a particle size of 15 28 μm and a thickness of about 0.2 μm. aluminum. Patent CN105347377A discloses a preparation method of high-purity flaky alumina with a thickness of ≤1.0 μm and a radial size of 5-20, using high-purity aluminum isopropoxide and isopropanol as main raw materials, controlled by ammonium bifluoride or ammonium fluoride Crystal morphology, forming hydrated alumina, followed by filtration, drying, and calcination to obtain flaky alumina. Patent CN110182834A uses pseudo-boehmite as the aluminum source, adds a crystal production regulator, dries and calcines to obtain flaky α-alumina with a D50 of 18 μm-28 μm and a thickness of 0.3 μm-0.5 μm. Patent CN114590827A provides a method for preparing flaky α-alumina with large particle size and high diameter-thickness ratio. The flaky alumina seed crystals are mixed with the precursor and calcined under specific conditions to obtain an average particle size of about 38 μm and a thickness of about 0.5 μm flake alumina. Patent CN112479241A mixes aluminum hydroxide with a strong alkali solution, ages to obtain flaky aluminum hydroxide, mixes it with molten salt and calcines it under specific conditions to obtain flaky aluminum oxide with an average particle size of about 10 μm and a thickness of 0.5 μm .

However, none of the flaky alumina prepared in the above-mentioned patents mentions that it has a weather resistance function.

In addition, in the prior art, the surface of the traditional pearlescent powder is used to coat the oxide or hydroxide (alumina, cerium oxide, aluminum hydroxide, cerium hydroxide, etc.) on the surface of the pearlescent pigment by liquid deposition method. , two or more types of silica), and then further coat the surface with a silane coupling agent or an active silicone polymer, so that the pearlescent pigment has a weather resistance function, while the flaky alumina itself does not have a weather resistance function.

Contents of the invention

In view of the deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a self-weather-resistant flake alumina and its preparation method, so that the pearlescent pigment made of the flake alumina does not need surface coating On the premise of coating oxide or hydroxide, it has good weather resistance. In addition, it also has the advantages of good sheet dispersion, smooth surface, good light transmission, uniform particle size distribution, large diameter-thickness ratio and high temperature resistance. .

The technical solution adopted by the present invention to solve its technical problems is:

A flaky aluminum oxide with self-weathering function, which contains aluminum oxide and cerium oxide as main components, wherein the content of cerium oxide is 1-4 wt%.

In a further preferred technical solution, the average particle size of the flaky alumina is 5-65 μm, and the thickness is 0.2-0.8 μm.

A preparation method of flaky alumina with self-weathering function, comprising the steps of:

S1. Preparation of solution A: weigh in parts by mass: 90-110 parts of aluminum sulfate hydrate, 10-30 parts of cerium chloride heptahydrate, 30-40 parts of anhydrous potassium sulfate and 40-50 parts of sodium sulfate , dissolve it in 60-80°C deionized water to obtain A solution;

S2. Preparation of solution B: weigh in parts by mass: 1-2 parts of sodium phosphate dodecahydrate and 50-60 parts of anhydrous sodium carbonate, and dissolve them in deionized water at room temperature to obtain solution B;

S3. Slowly add the B solution to the A solution under constant stirring to prepare a white gel;

S4. Place the white gel in a water bath for evaporation treatment, and then put it in a vacuum drying oven for drying treatment, thereby obtaining a white solid;

S5. Calcining the white solid at a high temperature in an atmosphere muffle furnace, and then cooling it naturally;

S6. Washing, suction filtering and drying the cooled white solid in sequence to finally obtain flaky alumina with self-weathering function.

In a further preferred technical solution, the temperature of the water bath is set at 80-90°C.

In a further preferred technical solution, the temperature of the vacuum drying oven is set at 110-120°C.

In a further preferred technical solution, the white solid is continuously calcined for 3 to 4 hours at a calcination temperature range of 1100-1300° C. during the high-temperature calcination process.

In a further preferred technical solution, during the preparation of the A solution, the aluminum sulfate octadecahydrate can be replaced by aluminum chloride, and the amount remains unchanged.

Further preferred technical solutions, in the preparation process of A solution, the potassium sulfate can be replaced by potassium chloride, and the amount remains unchanged.

Further preferred technical solution, in the preparation process of A solution, the sodium sulfate can be replaced by sodium chloride, and the amount remains unchanged.

Further preferred technical scheme, in the preparation process of B solution, described sodium carbonate can be replaced with sodium hydroxide, and consumption is constant.

The beneficial effects of the present invention are: the flaky alumina prepared by this scheme adopts the molten salt method to construct a unique alumina-cerium oxide composite structure by adding cerium chloride heptahydrate, and the pearlescent Pigments, without the need for a coating, can meet the requirements of automotive-grade weather resistance.

In addition, the flaky alumina prepared by this scheme has excellent parameters in all aspects, for example: particle size is 5-65 μm, thickness is 0.2-0.8 μm, and the dispersibility of the flakes is good, the surface is smooth, the light transmittance is good, the particles The advantages of uniform diameter distribution, large diameter-to-thickness ratio, and high temperature resistance.

Description of drawings

Fig. 1 is the preparation flow chart of flaky alumina in this scheme.

Fig. 2 is the XRD diffractogram of the substrate product of Example 1.

Fig. 3 is the particle size distribution diagram of the substrate product of Example 1.

FIG. 4 is a scanning electron micrograph of the substrate product of Example 1.

Detailed ways

In order to better illustrate the present invention, the following clearly and completely describes the technical solutions in the embodiments of the present invention.

Example 1:

The implementation process of this program is shown in Figure 1:

Step 1: Prepare Solution A

Weigh respectively: 90g of aluminum sulfate hydrate, 10g of cerium chloride heptahydrate, 30g of anhydrous potassium sulfate and 40g of sodium sulfate, and dissolve them in 400-500ml of deionized water at 60-80°C to obtain solution A .

Step Two: Prepare Solution B

Weigh respectively in parts by mass: 1 g of sodium phosphate dodecahydrate and 50 g of anhydrous sodium carbonate, and dissolve them in 200-300 ml of normal temperature deionized water to obtain solution B.

Step 3: Obtain a White Gel

S3. Slowly add solution B to solution A at 60-80° C. under constant stirring, so as to prepare a white gel.

Step 4: Obtain a white solid

The white gel is placed in a water bath at 80-90° C. for evaporation treatment, and then placed in a vacuum drying oven at 110-120° C. for drying treatment, thereby obtaining a white solid.

The fifth step: high temperature calcination treatment

The white solid is calcined at a high temperature in an atmosphere muffle furnace, and then cooled naturally; during the high-temperature calcination process, ensure that the calcination temperature is within the range of 1100-1300°C for 3-4 hours.

Step 6: Wash and dry

The cooled white solid is washed with water, suction filtered and dried in sequence to finally obtain flaky alumina with self-weathering function.

Detect the flaky alumina produced by this scheme:

Detection of alumina-ceria composite structure: as shown in Figure 2, the flake alumina was measured by XRD analysis, and the characteristic peaks of alumina and ceria were found in the diffraction pattern, and the flake alumina contained 4.0 % of cerium oxide.

Detection of the size of the flake alumina: as shown in Figure 3, the size of the flake alumina was measured with the Euro-American LS-609 laser particle size analyzer, and the D50 was 27.05 μm, and the D90 was 68.15 μm. (Evaluate the size of flaky alumina with the European and American LS-609 laser particle size analyzer, and the size parameters are represented by D10, D50, and D90. Among them, D10 refers to the corresponding particle size when the cumulative particle size distribution number of a sample reaches 10%. The physical meaning is that the particles with a particle size smaller than it account for 10%; D50 refers to the particle size corresponding to the cumulative particle size distribution percentage of a sample reaching 50%, also called the median or median particle size, usually used to represent powder The average particle size of the body; D90 refers to the corresponding particle size when the cumulative particle size distribution number of a sample reaches 90%.)

Inspection of the longitudinal dimension of the flake alumina: as shown in Figure 4, the thickness of the flake alumina is 0.2-0.8 μm observed with a field emission scanning electron microscope, and no cross-linking or stacked flakes are observed. (Use a field emission scanning electron microscope (SEM) to observe the longitudinal dimension of the flake aluminum oxide, the test conditions are acceleration voltage 5.0KV, probe current 20nA, magnification 10-1000000x.)

Test the gloss, dispersibility, and flatness of flake alumina: put the flake alumina in water and stir, and a silky streamlined pearlescent effect can be observed; add 10% to polyurethane, scrape and dry Finally, the surface is flat and free of graininess, which proves that the flaky alumina has good dispersion and no cross-linking of the flakes.

Testing of the weather resistance of pearlescent pigments made of this flaky alumina:

The following is an example of the preparation process of the most conventional silver-white pearlescent pigment:

(1) Weigh 50g of flaky alumina dry powder, pour it into a beaker, and add deionized water to 800ml.

(2) Heat the water bath to 75°C, adjust the pH to 2.0 with 2M hydrochloric acid, and stir at a constant speed for 10 minutes.

(3) Use a peristaltic pump to slowly add 70 ml of 2M titanium solution dropwise, and at the same time add dropwise 4M liquid caustic soda to maintain a stable pH value. After the reaction is complete, continue stirring for 10 minutes.

(4) The obtained solid was repeatedly washed with deionization until the pH value was about 7, vacuum filtered, and dried at 110°C.

(5) The dried solid was calcined in an atmosphere muffle furnace at a calcination temperature of 700° C., kept at a constant temperature for 1 hour, and cooled naturally to obtain a silver-white pearlescent pigment.

The weather resistance of the prepared pearlescent pigments was tested in a ZN-G ultraviolet light box.

The test conditions are 40W UVB-313el lamp, light intensity 0.71W/m ² , 4h light, 4h condensation, blackboard temperature 60±3℃, condensation temperature 50±3℃. The CM-M6 portable colorimeter tests data every 200 hours to record changes in weather resistance.

Among them, △E*ab refers to the size of the color difference change, the smaller the value, the smaller the color change, that is, the better the weather resistance; △L indicates the brightness, and the larger the L value, the whiter (brighter); a refers to the red and green of the color , +a means reddish, -a means greenish; b means yellow-blue color, +b means yellowish, -b means bluish.

The following is Merck's pearlescent pigment product with weather resistance (Merck 9103 pearlescent pigment) as a control program, and the experimental comparison data obtained from the test

From the comparative data in the above table, it can be seen that after the flaky alumina in this scheme has undergone a 500h weather resistance test, in the same test temperature environment, the color difference value of the flaky alumina prepared in this scheme is △E*ab The smallest, that is, its weather resistance is better than that of conventional weather resistance pearlescent pigments.

Example 2:

Step 1: Prepare Solution A

Weigh respectively: 100g of aluminum sulfate hydrate, 28g of cerium chloride heptahydrate, 35g of anhydrous potassium sulfate and 44g of sodium sulfate, and dissolve them in deionized water at 60-80°C to obtain solution A.

Step Two: Prepare Solution B

Weigh respectively: 1.3g of sodium phosphate dodecahydrate and 56g of anhydrous sodium carbonate, and dissolve them in 200-300ml of normal temperature deionized water to obtain solution B.

Step 3: Obtain a White Gel

S3. Slowly add solution B to solution A under constant stirring to prepare a white gel.

Step 4: Obtain a white solid

The white gel is placed in a water bath at 80-90° C. for evaporation treatment, and then placed in a vacuum drying oven at 110-120° C. for drying treatment, thereby obtaining a white solid.

The fifth step: high temperature calcination treatment

The white solid is calcined at a high temperature in an atmosphere muffle furnace, and then cooled naturally; during the high-temperature calcination process, ensure that the calcination temperature is within the range of 1100-1300°C for 3-4 hours.

Step 6: Wash and dry

The cooled white solid is washed with water, suction filtered and dried in sequence to finally obtain flaky alumina with self-weathering function.

The size of the flaky alumina was measured by the European and American LS-609 laser particle size analyzer, and the D50 was 25.34 μm, and the D90 was 49.83 μm. The thickness of the flake aluminum oxide observed by a field emission scanning electron microscope is 0.4-0.7 μm, and there is basically no stacking phenomenon. The flaky alumina was measured by XRD analysis, and the characteristic peaks of aluminum oxide and cerium oxide were found in the diffraction pattern, and the flaky alumina contained 2.1% cerium oxide through chemical analysis. It can be observed that the flaky alumina has good dispersibility when stirred in water.

Example 3:

Step 1: Prepare Solution A

Weigh respectively: 110g of aluminum sulfate hydrate, 30g of cerium chloride heptahydrate, 40g of anhydrous potassium sulfate and 50g of sodium sulfate, and dissolve them in deionized water at 60-80°C to obtain solution A.

Step Two: Prepare Solution B

Weigh respectively: 2g of sodium phosphate dodecahydrate and 60g of anhydrous sodium carbonate, and dissolve them in 200-300ml of normal temperature deionized water to obtain solution B.

Step 3: Obtain a White Gel

S3. Slowly add solution B to solution A under constant stirring to prepare a white gel.

Step 4: Obtain a white solid

The white gel is placed in a water bath at 80-90° C. for evaporation treatment, and then placed in a vacuum drying oven at 110-120° C. for drying treatment, thereby obtaining a white solid.

The fifth step: high temperature calcination treatment

The white solid is calcined at a high temperature in an atmosphere muffle furnace, and then cooled naturally; during the high-temperature calcination process, ensure that the calcination temperature is within the range of 1100-1300°C for 3-4 hours.

Step 6: Wash and dry

The cooled white solid is washed with water, suction filtered and dried in sequence to finally obtain flaky alumina with self-weathering function.

The size of the flaky alumina was measured by the European and American LS-609 laser particle size analyzer, and the D50 was 26.41 μm, and the D90 was 60.22 μm. The thickness of the flake aluminum oxide observed by a field emission scanning electron microscope is 0.5-0.8 μm, and there is basically no stacking phenomenon. The flaky alumina was measured by XRD analysis, and the characteristic peaks of alumina and cerium oxide were found in the diffraction pattern. According to chemical analysis, the flaky alumina contained 3.6% cerium oxide. It can be observed that the flaky alumina has good dispersibility when stirred in water.

Example 4:

On the basis of Example 1, in the preparation process of solution A, aluminum sulfate octadecahydrate can be replaced by aluminum chloride, and the dosage remains unchanged. Potassium sulfate can be replaced by potassium chloride, and the amount remains unchanged. Sodium sulfate can be replaced by sodium chloride, and the amount remains unchanged.

During the preparation of solution B, sodium carbonate can be replaced by sodium hydroxide, and the amount remains unchanged.

The basic principles and main features of the scheme and the advantages of the scheme have been shown and described above. Those skilled in the industry should understand that this program is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principles of this program. On the premise of not departing from the spirit and scope of this program, this program will also have Variations and improvements all fall within the scope of the claimed solution. The scope of protection required by the program is defined by the appended claims and their equivalents.

Claims (10)

1. A flaky aluminum oxide with self-weathering function, characterized in that it contains aluminum oxide and cerium oxide as main components, wherein the content of cerium oxide is 1-4 wt%. 2. A flaky alumina with self-weathering function according to claim 1, characterized in that the average particle size of the flaky alumina is 5-65 μm, and the thickness is 0.2-0.8 μm. 3. A preparation method of flaky alumina with self-weathering function, is characterized in that, comprises the steps: S1. Preparation of solution A: weigh in parts by mass: 90-110 parts of aluminum sulfate hydrate, 10-30 parts of cerium chloride heptahydrate, 30-40 parts of anhydrous potassium sulfate and 40-50 parts of sodium sulfate , dissolve it in 60-80°C deionized water to obtain A solution; S2. Preparation of solution B: weigh in parts by mass: 1-2 parts of sodium phosphate dodecahydrate and 50-60 parts of anhydrous sodium carbonate, and dissolve them in deionized water at room temperature to obtain solution B; S3. Slowly add the B solution to the A solution under constant stirring, so as to prepare a white gel; S4. Place the white gel in a water bath for evaporation treatment, and then put it in a vacuum drying oven for drying treatment, thereby obtaining a white solid; S5. Calcining the white solid at a high temperature in an atmosphere muffle furnace, and then cooling it naturally; S6. Washing, suction filtering and drying the cooled white solid in sequence to finally obtain flaky alumina with self-weathering function. 4. A method for preparing flaky alumina with self-weathering function as claimed in claim 3, characterized in that the temperature of the water bath is set at 80-90°C. 5. A method for preparing flaky alumina with self-weathering function according to claim 3, characterized in that the temperature of the vacuum drying oven is set at 110-120°C. 6. A method for preparing flaky alumina with self-weathering function as claimed in claim 3, characterized in that, during the high-temperature calcination process, the white solid is guaranteed to be within the range of 1100-1300°C for the calcination temperature , Continuous calcination for 3 to 4 hours. 7. A kind of preparation method of the flaky alumina with self-weathering function as claimed in claim 3, is characterized in that, in the preparation process of A solution, described aluminum sulfate octadecahydrate can adopt aluminum chloride to replace, And the dosage remains unchanged. 8. A kind of preparation method of the flaky alumina with self-weathering function as claimed in claim 3, is characterized in that, in the preparation process of A solution, described potassium sulfate can adopt potassium chloride to replace, and consumption is not Change. 9. A kind of preparation method of the flaky aluminum oxide with self-weathering function as claimed in claim 3, is characterized in that, in the preparation process of A solution, described sodium sulfate can adopt sodium chloride to replace, and consumption is not Change. 10. A kind of preparation method of the flaky alumina with self-weathering function as claimed in claim 3, is characterized in that, in the preparation process of B solution, described sodium carbonate can be replaced with sodium hydroxide, and consumption is not Change.

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