Water-based colored aluminum-based pigment and preparation method thereof

Abstract

The invention relates to the technical field of pigments, and particularly discloses a water-based colored aluminum-based pigment and a preparation method thereof. The water-based colored aluminum-based pigment comprises aluminum powder, the surface of the aluminum powder is coated with a silicon dioxide layer, and the surface of the silicon dioxide layer is grafted with amino silanol; the preparation method comprises the following steps: stirring and mixing aluminum powder and absolute ethyl alcohol to obtain an aluminum powder dispersed phase; adding the aluminum powder dispersed phase into the silica sol, then adding ammonia water, and stirring for reaction to obtain aluminum powder coated with a silicon dioxide layer; and adding amino silanol into the aluminum powder coated with the silicon dioxide layer, and carrying out condensation reaction to obtain the water-based colored aluminum-based pigment. According to the water-based colored aluminum-based pigment, the silicon dioxide layer is adopted to reduce corrosion of water to the aluminum powder, the amino silanol and the anionic dye are adopted to generate electrostatic interaction force, and different anionic dyes can be compounded, so that the obtained water-based colored aluminum-based pigment has the advantages of being rich in color, high in stability and good in dispersity in a water-based system.

Description

Technical Field

[0001] The present application relates to the field of pigment technology, and more specifically, to a water-based colored aluminum-based pigment and a preparation method thereof. Background Art

[0002] Aluminum pigment has a scaly structure and a silvery-white metallic luster on its surface. In a transparent medium, its luster and color change with the angle and viewing angle of the incident light. This effect is called the "dual-color effect" and is widely used in daily chemical industries such as textiles, coatings, inks, printing and cosmetics.

[0003] Although aluminum pigments show relatively ideal effects in solvent-based inks and coatings, in water-based systems, due to their high surface activity and easy reaction with water molecules, the surface corrodes and loses its original metallic luster, and the generated hydrogen can easily cause explosions, thus limiting the scope of application of aluminum pigments. Summary of the invention

[0004] In order to improve the stability of aluminum pigments in water-based systems and expand the application scope of aluminum pigments, the present application provides a water-based colored aluminum-based pigment and a preparation method and application thereof.

[0005] In the first aspect, the present application provides a water-based colored aluminum-based pigment, which adopts the following technical solution: A water-based colored aluminum-based pigment comprises aluminum powder, the surface of which is coated with a silicon dioxide layer, and the surface of the silicon dioxide layer is grafted with aminosilanol through a silanol condensation reaction.

[0006] By adopting the above technical solution, the surface of aluminum powder is coated with an inert silica layer with good light transmittance, which can reduce the reaction between aluminum powder and water molecules, thereby improving the stability of aluminum-based pigments in water-based systems. However, because the isoelectric point of silica is as low as 1.7-3.5, the surface of aluminum powder coated with silica layer in the water-based system has negative charge, and there is a large electrostatic repulsion with most water-soluble anionic dyes. It is not easy to stably form a colorful composite pigment after mixing, which cannot meet people's demand for bright colors and exquisite appearance of products.

[0007] Therefore, the present application can improve the isoelectric point of the surface of the obtained water-based colored aluminum-based pigment by grafting aminosilanol on the surface of the silica layer to give the surface of the silica layer positively charged amino groups, so that the surface has a positive charge in the water-based system, thereby improving the electrostatic interaction between the water-based colored aluminum-based pigment and the anionic dye, which is beneficial to enhancing the dispersion stability of the composite pigment in the water-based system, and obtaining a water-based colored aluminum-based pigment with brighter colors and richer hues. At the same time, the amino activity on the surface of the obtained water-based colored aluminum-based pigment is relatively high, which is convenient for further modification and increasing its efficacy.

[0008] Preferably, the surface of the silicon dioxide layer is also grafted with dichloro-s-triazine type reactive dyes and methacrylate block copolymers; The dichloro-s-triazine type reactive dye is grafted by amidation reaction between aminosilanol and dichloro-s-triazine type reactive dye; the methacrylate block copolymer is first grafted by nucleophilic substitution reaction between 2-bromoisobutyryl bromide and aminosilanol, and then atom transfer radical polymerization is carried out by initiating monomer with grafted 2-bromoisobutyryl bromide; The methacrylate block copolymer is prepared by atom transfer free radical polymerization of 2-bromoisobutyryl bromide, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate.

[0009] The feed ratio of 2-bromoisobutyryl bromide, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate is (0.1-2) mL: (1-5) mL: (5-15) mL: (1-5) mL.

[0010] The coating of silica cannot completely isolate the aluminum powder from the external solvent system, and the dyes bonded by electrostatic interaction are difficult to maintain stability under some high-intensity shearing. By adopting the above technical scheme, the methacrylate block copolymer grafted on the surface of the silica layer has a further coating effect on the aluminum powder, which can improve the coating of the aluminum powder, thereby improving the stability of the obtained water-based colored aluminum-based pigment. At the same time, by the amidation reaction of aminosilanol and dichloro-s-triazine type active dyes, dichloro-s-triazine type active dyes can be grafted on the surface of the silica layer, which can not only enrich the color of the water-based colored aluminum-based pigment, but also improve the color stability of the water-based colored aluminum-based pigment.

[0011] Preferably, the dichloro-s-triazine type reactive dye is reactive blue X-BR or reactive red X-3B or reactive yellow XR.

[0012] By adopting the above technical scheme, reactive blue X-BR or reactive red X-3B or reactive yellow XR is not only bright in color, but also has high reactivity with aminosilanol, which is conducive to obtaining water-based colored aluminum-based pigments with high grafting rate, good stability and bright color.

[0013] In a second aspect, the present application provides a method for preparing a water-based colored aluminum-based pigment, using the following technical solution: A method for preparing a water-based colored aluminum-based pigment, comprising the following steps: S1: Aluminum powder and anhydrous ethanol are stirred and mixed to obtain an aluminum powder dispersed phase; tetraethyl orthosilicate, hydrochloric acid and anhydrous ethanol are stirred and mixed to obtain a silica sol; the aluminum powder dispersed phase is first added to the silica sol, and then ammonia water is added, stirred and reacted to obtain aluminum powder coated with a silicon dioxide layer; S2: After stirring and mixing the aminosilane coupling agent and anhydrous ethanol, aminosilanol is obtained; the aminosilanol is added to aluminum powder coated with a silicon dioxide layer to carry out a condensation reaction to obtain a water-based colored aluminum-based pigment.

[0014] By adopting the above technical scheme, the present application uses an aluminum-based pigment with excellent performance as the core, and through a multi-layer coating design concept, a stable core-shell structured colored aluminum-based pigment is prepared. Due to the metallic luster of the aluminum pigment itself, and a variety of active dyes are combined with the pigment through chemical bonding, and finally through polymer coating, the effect of bright color, rich hue, and stable structural performance is obtained.

[0015] Preferably, S2 comprises the following steps: S21: stirring and mixing an aminosilane coupling agent and anhydrous ethanol to obtain aminosilanol; adding the aminosilanol to aluminum powder coated with a silicon dioxide layer to carry out a condensation reaction to obtain an aluminum-based pigment grafted with aminosilanol; S22: After stirring and mixing the aluminum-based pigment grafted with aminosilanol, triethanolamine and an organic solvent, 2-bromoisobutyryl bromide is added to carry out a nucleophilic substitution reaction to obtain an aluminum-based pigment grafted with 2-bromoisobutyryl bromide; S23: After the aluminum-based pigment grafted with 2-bromoisobutyryl bromide and the organic solvent are stirred and mixed, the pH value is adjusted to 8-9, and then a dichloro-s-triazine type active dye is added to carry out an amidation reaction to obtain an aluminum-based pigment grafted with a dichloro-s-triazine type active dye and 2-bromoisobutyryl bromide; S24: After the aluminum-based pigment grafted with dichloroisotriazine-type reactive dye and 2-bromoisobutyryl bromide and an organic solvent are stirred and mixed, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate are added to carry out atom transfer radical polymerization reaction to obtain a water-based colored aluminum-based pigment.

[0016] By adopting the above technical solution, since the present application adopts a chemical bonding method to combine the active dye with the pigment base and finally coats it with a polymer, the obtained aluminum-based pigment has the effects of bright color, rich hue and stable structure.

[0017] Preferably, in S1, the feed ratio of aluminum powder, tetraethyl orthosilicate and anhydrous ethanol is (2-10) g: (5-20) mL: (10-60) mL.

[0018] By adopting the above technical solution, the encapsulation of aluminum powder with poor stability was completed. The feed ratio of tetraethyl orthosilicate and anhydrous ethanol regulated the encapsulation degree of aluminum powder and the number of active sites for subsequent chemical modification, which is beneficial to increasing the application range of aluminum-based pigments.

[0019] Preferably, in S21, the feed ratio of aminosilane coupling agent to anhydrous ethanol is (10-50) mL:(5-10) mL.

[0020] By adopting the above technical scheme, the surface modification of silicon-coated aluminum pigment is completed. The amount of silane coupling agent can not only adjust the isoelectric point of aluminum-based pigment, but also adjust the number of surface active groups of aluminum-based pigment, which is beneficial to subsequent modification.

[0021] Preferably, in S21 and S22, the feed ratio of aminosilane coupling agent, anhydrous ethanol and 2-bromoisobutyryl bromide is (10-50) mL: (10-50) mL: (0.1-2) mL.

[0022] By adopting the above technical scheme, the initiator 2-bromoisobutyryl bromide is introduced into the surface of the aluminum-based pigment grafted with aminosilanol, and the polymerization degree of the final methacrylate block copolymer is regulated by optimizing the dosage of 2-bromoisobutyryl bromide, thereby controlling the thickness of the methacrylate block copolymer coated on the surface of the aluminum-based pigment grafted with aminosilanol, which is beneficial to improve the stability of the obtained aluminum-based pigment.

[0023] Preferably, in S22 and S24, the feed ratio of 2-bromoisobutyryl bromide, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate is (0.1-2) mL: (1-5) mL: (5-15) mL: (1-5) mL.

[0024] By adopting the above technical solution, the cross-linking of the active dye on the pigment surface and the polymer layer is achieved. By optimizing the dosage of the monomer and the initiator, the thickness of the final cross-linked layer is regulated, which is beneficial to improving the stability of the obtained aluminum-based pigment.

[0025] Preferably, in S21 and S23, the feed ratio of aminosilane coupling agent, anhydrous ethanol and dichloro-s-triazine type reactive dye is (10-50) mL: (10-50) mL: (0.5-2.5) g.

[0026] Preferably, in S23, the dichloro-s-triazine type reactive dye is reactive blue X-BR, reactive red X-3B or reactive yellow XR.

[0027] By adopting the above technical scheme, the three basic colors of active dyes are introduced into the aluminum-based pigment grafted with aminosiliconol according to the above-mentioned feed ratio. Finally, the color of the pigment can be regulated by compounding the three colors, which greatly enriches the selectivity of the pigment color.

[0028] In summary, this application has the following beneficial effects: 1. The silicon dioxide layer coated on the surface of aluminum powder in the present application can reduce the reaction between water and aluminum powder and improve the stability of aluminum powder. The aminosilanol grafted on the surface of the silicon dioxide layer can generate a large electrostatic interaction force with the anionic dye, which is beneficial to enhance the dispersion stability of the composite pigment in the water-based system. 2. The dichlorotriazine type active dye and methacrylate block copolymer grafted on the surface of the silica layer through chemical bonds have high stability, which can not only enrich the color of aluminum-based pigments and improve the color stability of aluminum-based pigments, but also further coat aluminum powder to improve the stability of aluminum-based pigments in water-based systems; 3. The method of the present application successively adopts silica deposition coating, silane coupling agent modification and polymer encapsulation, thereby obtaining the composite pigment with bright color, rich hue and stable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a mechanism diagram of grafting aminosilanol in water-based colored aluminum-based pigment in Example 1; Figure 2 This is a mechanism diagram of grafting 2-bromoisobutyl bromide in the water-based colored aluminum-based pigment in Example 2; Figure 3 This is a mechanism diagram of grafting dichloro-s-triazine type reactive dye and methacrylate block copolymer in water-based colored aluminum-based pigment in Example 2. DETAILED DESCRIPTION

[0030] The present application is further described in detail below in conjunction with embodiments and drawings. Example

[0031] Example 1 A water-based colored aluminum-based pigment comprises aluminum powder, the surface of which is coated with a silicon dioxide layer, and the surface of the silicon dioxide layer is grafted with aminosilanol.

[0032] The raw materials used in the preparation process of the above-mentioned water-based colored aluminum-based pigment and their corresponding amounts are shown in the following table.

[0033] The preparation method of the above-mentioned water-based colored aluminum-based pigment comprises the following steps: S1: After mixing aluminum powder and anhydrous ethanol, ultrasonic dispersion was performed for 0.33 h to obtain an aluminum powder dispersed phase; after mixing ethyl orthosilicate, hydrochloric acid (concentration of 12 mol / L), water, ether and anhydrous ethanol, stirring and mixing at 40° C. for 1 h to obtain a silica sol; First, slowly add the aluminum powder dispersed phase into the silica sol, then add ammonia water (concentration of 13.38 mol / L), stir and react for 5 hours to obtain a reaction solution; filter the reaction solution, collect the precipitate and wash it with anhydrous ethanol for 3 to 5 times (3 times in the embodiment of the present application), and then dry it at 50°C for 12 hours to obtain aluminum powder coated with a silicon dioxide layer (denoted as Al / SiO2).

[0034] S2: After stirring and mixing an aminosilane coupling agent (aminopropyltriethoxysilane) and anhydrous ethanol, add dropwise to aluminum powder coated with a silica layer, stir and react for 5 hours to obtain a reaction liquid; filter the reaction liquid, collect the precipitate and wash it with anhydrous ethanol for 3 to 5 times (5 times in the embodiment of the present application), and then dry it at 50°C for 12 hours to obtain a water-based colored aluminum-based pigment (denoted as Al / SiO2 / KH-550).

[0035] Example 2 A water-based colored aluminum-based pigment comprises aluminum powder, the surface of which is coated with a silicon dioxide layer, and the surface of the silicon dioxide layer is grafted with aminosilanol, dichloro-s-triazine type active dye and methacrylate block copolymer.

[0036] The raw materials used in the preparation process of the above-mentioned water-based colored aluminum-based pigment and their corresponding amounts are shown in the following table.

[0037] The preparation method of the above-mentioned water-based colored aluminum-based pigment comprises the following steps: S1: After mixing aluminum powder and anhydrous ethanol, ultrasonic dispersion is performed for 0.33 h to obtain an aluminum powder dispersed phase; after mixing tetraethyl orthosilicate, hydrochloric acid (concentration of 12 mol / L), water, ether and anhydrous ethanol, stirring and mixing at 40°C for 1 h to obtain a silica sol.

[0038] First, slowly add the aluminum powder dispersed phase into the silica sol, then add ammonia water (concentration of 13.38 mol / L), stir and react for 5 hours to obtain a reaction solution; filter the reaction solution, collect the precipitate and wash it with anhydrous ethanol for 3 to 5 times (3 times in the embodiment of the present application), and then dry it at 50°C for 12 hours to obtain aluminum powder coated with a silicon dioxide layer (denoted as Al / SiO2).

[0039] S2: S21: After stirring and mixing an aminosilane coupling agent (aminopropyltriethoxysilane) and anhydrous ethanol, add dropwise to aluminum powder coated with a silica layer, stir and react for 5 hours to obtain a reaction solution; filter the reaction solution, collect the precipitate and wash it with anhydrous ethanol for 3 to 5 times (5 times in the embodiment of the present application), and then dry it at 50°C for 12 hours to obtain an aluminum-based pigment grafted with aminosilanol (denoted as Al / SiO2 / KH-550).

[0040] S22: An aluminum-based pigment grafted with aminosilanol, triethanolamine and toluene are stirred and mixed for 0.33 hours to obtain a mixture; 2-bromoisobutyryl bromide is added to the mixture at 0-5°C, stirred and reacted for 2 hours to obtain a reaction liquid; the reaction liquid is filtered, the precipitate is collected and washed with anhydrous ethanol for 3 times, and then dried at 50°C for 12 hours to obtain an aluminum-based pigment grafted with 2-bromoisobutyryl bromide (denoted as Al / SiO2 / KH-550 / Br).

[0041] S23: After stirring and mixing the aluminum-based pigment grafted with 2-bromoisobutyryl bromide and anhydrous ethanol for 0.33 h, the pH value was adjusted to 8, and then a dichlorotriazine-type reactive dye (reactive red X-3B) was added, and the reaction was stirred at 45°C for 4 h to obtain a reaction solution; the reaction solution was centrifuged, the precipitate was collected and washed with diformamide for 3 times, and then dried at 50°C for 12 h to obtain an aluminum-based pigment grafted with dichlorotriazine-type reactive dye and 2-bromoisobutyryl bromide (recorded as Al / SiO2 / KH-550 / Br / dye).

[0042] S24: After stirring and mixing an aluminum-based pigment grafted with a dichloro-s-triazine type reactive dye and 2-bromoisobutyryl bromide and anhydrous methanol, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate are slowly added, and the mixture is stirred and mixed for 0.33 h to obtain a mixture; First, nitrogen was charged into the mixture for 0.5 h to remove the air in the mixture, and then cuprous bromide was added and nitrogen was continuously charged for 0.17 h. Finally, the mixture was stirred and reacted at 50° C. for 12 h to obtain a reaction solution. The reaction solution was filtered, and the precipitate was collected and washed twice with methanol and once with acetone to obtain a water-based colored aluminum-based pigment (denoted as Al / SiO2 / KH-550 / Br / dye / polymer).

[0043] Example 3 A water-based colored aluminum-based pigment, which is different from Example 2 in that, in the preparation process of S1 silica sol, the amount of ethyl orthosilicate used is 20 mL, and the amount of anhydrous ethanol used is 60 mL.

[0044] Example 4 A water-based colored aluminum-based pigment, which is different from Example 2 in that, during the preparation of S21, the amount of aminosilane coupling agent used is 50 mL, and the amount of anhydrous ethanol used is 50 mL.

[0045] Example 5 A water-based colored aluminum-based pigment, which is different from Example 2 in that, in the preparation process of S24, the amount of pentamethyldiethylenetriamine used is 5 mL, the amount of dimethylaminoethyl methacrylate used is 15 mL, and the amount of diethylene glycol dimethacrylate used is 5 mL.

[0046] Example 6 A water-based colored aluminum-based pigment, which is different from Example 2 in that, during the preparation of S22, the amount of 2-bromoisobutyl bromide used is 2 mL.

[0047] Example 7 A water-based colored aluminum-based pigment, which is different from Example 2 in that, during the preparation of S23, the amount of dichloro-s-triazine type reactive dye used is 2.5 g.

[0048] Example 8 A water-based colored aluminum-based pigment, which is different from Example 2 in that, in the preparation process of S23, the dichloro-s-triazine type reactive dye is reactive blue X-BR.

[0049] Example 9 A water-based colored aluminum-based pigment, which is different from Example 2 in that, in the preparation process of S23, the dichloro-s-triazine type reactive dye is Reactive Yellow XR.

[0050] Embodiments 10 to 11 A water-based colored aluminum-based pigment, which is different from Example 2 in that the raw materials used in the preparation process and their corresponding amounts are shown in the following table.

[0051] Comparative Example Comparative Example 1 An aluminum-based pigment comprises aluminum powder, the surface of which is coated with a silicon dioxide layer.

[0052] The raw materials used in the preparation process of the above aluminum-based pigments and their corresponding amounts are shown in the following table.

[0053] The preparation method of the above-mentioned water-based aluminum-based pigment comprises the following steps: A1: After aluminum powder and anhydrous ethanol were stirred and mixed, ultrasonic dispersion was performed for 0.33 h to obtain an aluminum powder dispersed phase; after ethyl orthosilicate, hydrochloric acid, water, ether and anhydrous ethanol were stirred and mixed, the mixture was stirred and mixed at 40° C. for 1 h to obtain a silica sol; A2: First, slowly add the aluminum powder dispersion into the silica sol, then add ammonia water, stir and react for 5 hours to obtain a reaction solution; filter the reaction solution, collect the precipitate and wash it with anhydrous ethanol for 3 times, and then dry it at 50°C for 12 hours to obtain a water-based aluminum-based pigment.

[0054] Performance Testing The water-based colored aluminum-based pigment prepared in Example 1 of the present application and the water-based aluminum-based pigment prepared in Comparative Example 1 were subjected to adsorption and isoelectric point tests, and the water-based colored aluminum-based pigments prepared in Examples 1 to 11 of the present application were subjected to stability tests. The specific test methods are as follows: 1. Adsorption test 5g of water-based colored aluminum-based pigment or water-based aluminum-based pigment is added to 5000mg / kg of dye aqueous solution (reactive blue X-BR, reactive red X-3B, reactive yellow XR), and then stirred at 600r / min for 6h at room temperature to obtain a suspension. The suspension is separated into solid and liquid by suction filtration, the filter cake is washed with pure water for 3 times, and then the filtrate is combined and the absorbance of the filtrate is measured by ultraviolet spectrophotometer, which is recorded as A1; First, prepare standard solutions of different reactive dye series with gradient concentrations (50 mg / kg, 200 mg / kg, 800 mg / kg, 2000 mg / kg, 4000 mg / kg), then measure their absorbance by ultraviolet spectrophotometer, and calculate the standard curve within the concentration range. Then, calculate the reactive dye concentration C1 in the filtrate by the standard curve.

[0055] 2. Isoelectric point detection A series of aqueous colored aluminum-based pigment aqueous solutions or aqueous aluminum-based pigment aqueous solutions with the same mass concentration of pH (2-12) were prepared respectively. The Zeta potential of different dispersions was measured by a nanoparticle size and Zeta potential analyzer, and a pH-Zeta potential diagram was drawn to calculate the isoelectric point of the aqueous colored aluminum-based pigment or aqueous aluminum-based pigment.

[0056] 3. Stability test 0.1 g of water-based colored aluminum-based pigment was added to 20 mL of water, and the mixture was stirred and shaken at 50° C. for 12 h to obtain a suspension. The suspension was separated into solid and liquid by suction filtration, and the filter cake was washed with pure water for 3 times. The filtrates were then combined and the absorbance of the filtrates was measured by an ultraviolet spectrophotometer, which was recorded as A2. First, prepare standard solutions of different reactive dye series with gradient concentrations (1 mg / kg, 10 mg / kg, 50 mg / kg, 200 mg / kg, 500 mg / kg), then measure their absorbance by ultraviolet spectrophotometer, and calculate the standard curve within the concentration range. The reactive dye concentration C2 in the filtrate is calculated by the standard curve.

[0057] Performance test results The adsorption and isoelectric point test results of the water-based colored aluminum-based pigment prepared in Example 1 and the water-based aluminum-based pigment prepared in Comparative Example 1 are shown in the following table.

[0058] Depend on Figure 1 It can be seen that after the hydrolysis of ethyl orthosilicate, silanol is formed and bonds with the hydroxyl groups on the surface of the aluminum powder to form a silicon dioxide layer. Subsequently, the aminosilane is hydrolyzed and grafted on the surface of the silicon dioxide layer through a silanol condensation reaction, thereby obtaining a water-based colored aluminum-based pigment modified by a silane coupling agent in Example 1.

[0059] By analyzing the data in the above table, it can be seen that compared with the water-based aluminum-based pigment prepared by using silicon dioxide-coated aluminum powder in Comparative Example 1, the water-based color aluminum-based pigment prepared by using silane coupling agent modification in Example 1 has a higher isoelectric point, that is, its surface is positively charged in a system with a pH less than 8.6, thereby combining with the active dye through a strong electrostatic interaction, significantly improving the stability of the dye on the surface of the aluminum-based pigment. At the same time, the residual amount of the active dye in Example 1 is lower. This shows that the water-based color aluminum-based pigment prepared by using silane coupling agent modification has higher adsorption.

[0060] The stability test results of the water-based colored aluminum-based pigments prepared in Examples 1 to 11 are shown in the following table.

[0061] Depend on Figure 2 It can be seen that 2-bromoisobutyl bromide undergoes a nucleophilic substitution reaction with the amino group on the surface of the water-based colored aluminum-based pigment modified by a silane coupling agent (denoted as Al / SiO2 / KH-550), thereby being grafted onto the surface of the silica layer to obtain an aluminum-based pigment grafted with 2-bromoisobutyl bromide (denoted as Al / SiO2 / KH-550 / Br).

[0062] Depend on Figure 3 It can be seen that the dichlorotriazine type active dye (R = NH-dye matrix in the figure) undergoes an amidation reaction with the amino group on the surface of the aluminum-based pigment grafted with 2-bromoisobutyryl bromide (denoted as Al / SiO2 / KH-550 / Br), thereby being grafted on the surface of the silica layer to obtain the aluminum-based pigment grafted with dichlorotriazine type active dye and 2-bromoisobutyryl bromide (denoted as Al / SiO2 / KH-550 / Br / dye).

[0063] Subsequently, the aluminum-based pigment grafted with dichlorotriazine-type reactive dyes and 2-bromoisobutyryl bromide (denoted as Al / SiO2 / KH-550 / Br / dye) contains an initiator 2-bromoisobutyryl bromide, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate undergo an atom transfer radical polymerization (ATRP) reaction under the initiation of 2-bromoisobutyryl bromide to form a methacrylate block copolymer grafted on the surface of the silica layer to obtain a water-based colored aluminum-based pigment (denoted as Al / SiO2 / KH-550 / Br / dye / polymer).

[0064] By analyzing the data in the above table, it can be seen that compared with the water-based colored aluminum-based pigment prepared by modification with a silane coupling agent in Example 1, the water-based colored aluminum-based pigment prepared by grafting dichloro-s-triazine type active dyes and methacrylate block copolymers on the surface of the silica layer in Examples 2 to 11 has a lower residual dye concentration in the filtrate. The reason for this may be that the water-based colored aluminum-based pigment in Example 1, or the aluminum-based pigment prepared by directly using silica-coated aluminum powder in Comparative Example 1, is mainly combined with the active dye through van der Waals force and electrostatic interaction force, which is a non-chemical bond. However, the water-based colored aluminum-based pigments in Examples 2 to 11 firmly fix the active dye on the surface of the aluminum powder through chemical bonding and cross-linking and coating of the polymer layer, thereby greatly improving the stability of the water-based colored aluminum-based pigment. This shows that in the water-based colored aluminum-based pigment of the present application, grafting dichloro-s-triazine type active dyes and methacrylate block copolymers on the surface of the silica layer can improve the stability of the water-based colored aluminum-based pigment. Compared with Example 2, Example 3 increases the amount of tetraethyl orthosilicate and anhydrous ethanol in the preparation process of S1 silica sol, and the residual dye concentration in the filtrate is similar to that of Example 2. This shows that in the total raw materials for preparing the water-based colored aluminum-based pigment of the present application, the feed ratio of aluminum powder, tetraethyl orthosilicate and anhydrous ethanol is controlled in step S1 to be (2-10) g: (5-20) mL: (10-60) mL, and the obtained water-based colored aluminum-based pigment has excellent stability.

[0065] Compared with Example 2, Example 4 increases the amount of aminosilane coupling agent and anhydrous ethanol during the preparation process of S21, and the residual dye concentration in the filtrate decreases. Analysis shows that the reason may be that increasing the amount of aminosilane coupling agent and anhydrous ethanol can regulate the number of active groups on the surface of the aluminum-based pigment, increase the grafting rate of the polymer and the active dye, and thus improve the stability of the obtained water-based colored aluminum-based pigment. This shows that in the total raw materials for the preparation of the water-based colored aluminum-based pigment of the present application, the feed ratio of aminosilane coupling agent and anhydrous ethanol is controlled to be (10-50) mL: (10-50) mL in step S21, and the obtained water-based colored aluminum-based pigment has excellent stability.

[0066] Compared with Example 2, Example 6 increases the amount of 2-bromoisobutyl bromide during the preparation process of S22, and the residual dye concentration in the filtrate decreases. Analysis of the reason may be that increasing the amount of 2-bromoisobutyl bromide can increase the degree of polymerization of the final methacrylate block copolymer, thereby increasing the thickness of the methacrylate block copolymer coated on the surface of the aluminum-based pigment grafted with aminosilanol, thereby improving the stability of the obtained aluminum-based pigment. This shows that in the total raw materials for the preparation of the water-based colored aluminum-based pigment of the present application, the amount of 2-bromoisobutyl bromide is (0.1-2) mL, and the obtained water-based colored aluminum-based pigment has excellent stability.

[0067] Compared with Example 2, Example 7 increases the amount of dichloro-s-triazine type active dye during the preparation process of S23, and the residual dye concentration in the filtrate increases. Analysis of the reason may be that when the amount of aminosilane in step S21 remains unchanged, the amount of dichloro-s-triazine type active dye increases, and the grafting amount of methacrylate block copolymers will decrease, so the stability of the water-based colored aluminum-based pigment is reduced. This shows that in the total raw materials for the preparation of water-based colored aluminum-based pigments in the present application, the feed ratio of aminosilane coupling agent, anhydrous ethanol and dichloro-s-triazine type active dye in steps S21 and S23 is controlled to be (10-50) mL: (10-50) mL: (0.5-2.5) g, and the obtained water-based colored aluminum-based pigments have excellent stability.

[0068] Compared with Example 2, in Examples 8 and 9, the type of dichloro-s-triazine type active dye is changed during the preparation process of S23, and the residual dye concentration in the obtained filtrate is as low as 0.09 to 0.32. This shows that in the total raw materials for preparing the water-based colored aluminum-based pigment of the present application, the dichloro-s-triazine type active dye in step S23 is reactive red X-3B or reactive blue X-BR or reactive yellow XR, and the obtained water-based colored aluminum-based pigment has excellent stability.

[0069] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A water-based colored aluminum-based pigment, characterized in that: The invention comprises aluminum powder, the surface of which is coated with a silicon dioxide layer, and the surface of which is grafted with aminosilanol.

2. The water-based colored aluminum-based pigment according to claim 1, characterized in that: The surface of the silicon dioxide layer is also grafted with dichloro-s-triazine type active dyes and methacrylate block copolymers; The methacrylate block copolymer is prepared by atom transfer free radical polymerization of 2-bromoisobutyryl bromide, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate.

3. The water-based colored aluminum-based pigment according to claim 2, characterized in that: The dichloro-s-triazine type reactive dye is reactive blue X-BR, reactive red X-3B or reactive yellow XR.

4. The water-based colored aluminum-based pigment according to claim 2, characterized in that: The feed ratio of 2-bromoisobutyryl bromide, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate is (0.1-2) mL: (1-5) mL: (5-15) mL: (1-5) mL.

5. The method for preparing the water-based colored aluminum-based pigment according to claim 1, characterized in that: The following steps are involved: S1: Aluminum powder and anhydrous ethanol are stirred and mixed to obtain an aluminum powder dispersed phase; tetraethyl orthosilicate, hydrochloric acid and anhydrous ethanol are stirred and mixed to obtain a silica sol; the aluminum powder dispersed phase is first added to the silica sol, and then ammonia water is added, stirred and reacted to obtain aluminum powder coated with a silicon dioxide layer; S2: After stirring and mixing the aminosilane coupling agent and anhydrous ethanol, aminosilanol is obtained; the aminosilanol is added to aluminum powder coated with a silicon dioxide layer to carry out a condensation reaction to obtain a water-based colored aluminum-based pigment.

6. The method for preparing the water-based colored aluminum-based pigment according to claim 5, characterized in that: S2 includes the following steps: S21: stirring and mixing an aminosilane coupling agent and anhydrous ethanol to obtain aminosilanol; adding the aminosilanol to aluminum powder coated with a silicon dioxide layer to carry out a condensation reaction to obtain an aluminum-based pigment grafted with aminosilanol; S22: After stirring and mixing the aluminum-based pigment grafted with aminosilanol, triethanolamine and an organic solvent, 2-bromoisobutyryl bromide is added to carry out a nucleophilic substitution reaction to obtain an aluminum-based pigment grafted with 2-bromoisobutyryl bromide; S23: After the aluminum-based pigment grafted with 2-bromoisobutyryl bromide and the organic solvent are stirred and mixed, the pH value is adjusted to 8-9, and then a dichloro-s-triazine type active dye is added to carry out an amidation reaction to obtain an aluminum-based pigment grafted with a dichloro-s-triazine type active dye and 2-bromoisobutyryl bromide; S24: After the aluminum-based pigment grafted with dichloroisotriazine-type reactive dye and 2-bromoisobutyryl bromide and an organic solvent are stirred and mixed, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate are added to carry out atom transfer radical polymerization reaction to obtain a water-based colored aluminum-based pigment.

7. The method for preparing a water-based colored aluminum-based pigment according to claim 5 or 6, characterized in that: In the S1, the feed ratio of aluminum powder, tetraethyl orthosilicate and anhydrous ethanol is (2-10) g: (5-20) mL: (10-60) mL.

8. The method for preparing the water-based colored aluminum-based pigment according to claim 6, characterized in that: In the S21, the feed ratio of the aminosilane coupling agent to anhydrous ethanol is (10-50) mL:(10-50) mL.

9. The method for preparing the water-based colored aluminum-based pigment according to claim 6, characterized in that: In S21 and S22, the feed ratio of aminosilane coupling agent, anhydrous ethanol and 2-bromoisobutyryl bromide is (10-50) mL: (10-50) mL: (0.1-2) mL.

10. The method for preparing the water-based colored aluminum-based pigment according to claim 9, characterized in that: In S22 and S24, the feed ratio of 2-bromoisobutyryl bromide, pentamethyldiethylenetriamine, dimethylaminoethyl methacrylate and diethylene glycol dimethacrylate is (0.1-2) mL: (1-5) mL: (5-15) mL: (1-5) mL.

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