Water-based metal finish paint and preparation method thereof

Abstract

The invention belongs to the technical field of water-based paint, and particularly relates to water-based metal finish paint and a preparation method thereof.The preparation method comprises the steps that a water-based acrylate dispersion, amino resin, a solvent a, a solvent b, a wetting agent, a defoaming agent, a thickening agent, an anti-settling agent, a flatting agent, a pH regulator and deionized water are mixed to obtain a component A; mixing a solvent c, a dispersing agent and deionized water to obtain a component B; cleaning the cylinder wall for preparing the component B with a solvent c to obtain a cleaning solution; and mixing the component A, the component B, a cleaning solution, N-allyl maleimide and nano-modified fluorine-containing polysiloxane, and removing impurities to obtain the water-based metallic paint. The water-based metallic paint disclosed by the invention not only can meet the requirements of high light and high flicker degree, but also has excellent water resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of water-based paints, and in particular relates to a water-based metal topcoat and a preparation method thereof. Background Art

[0002] With the continuous tightening of environmental regulations and the improvement of coating performance requirements in the automotive, construction and other industries, water-based metallic paints have become the mainstream trend due to their low VOC and low pollution characteristics. However, in order to achieve high gloss, weather resistance and water resistance, traditional water-based metallic paints require additional spraying of clear varnish (such as two-component polyurethane or acrylic varnish), which leads to complex processes, increased costs and increased VOC emissions.

[0003] In response to this industry pain point, the development of a non-glazing water-based metallic paint (i.e. a single coating with both metallic effect and long-term protective performance) has become a key technical research focus, but the existing technology still has the following key bottlenecks: The directional arrangement of metallic pigments (such as aluminum powder and pearlescent powder) depends on high shear construction or solvent evaporation gradient control, but the water-based system has high surface tension, which can easily lead to disordered pigment arrangement, low gloss, and weak metallic flash effect.

[0004] However, in order to improve the gloss of existing non-glazing paint, excessive leveling agent needs to be added, which reduces the water resistance. For example, a rust-proof water-based metallic paint with publication number CN104830194A provides a water-based metallic paint with high gloss and good fullness. Although the paint surface obtained has good gloss, the water resistance is reduced. Summary of the invention

[0005] The object of the present invention is to provide a water-based metal topcoat and a preparation method thereof to solve the problems raised in the above background technology.

[0006] In order to achieve the above technical objectives, the technical solution of the present invention is: A method for preparing a water-based metallic topcoat comprises the following steps: S1. Under stirring in a disperser at a speed of 600-800 r / min, slowly add, by weight, 50-60 parts of aqueous acrylate dispersion, 10-12 parts of amino resin, 1-2 parts of solvent a, 1-2 parts of solvent b, 0.05-0.5 parts of wetting agent, 0.5-1.0 parts of defoaming agent, 0.5-2 parts of thickener, 0.5-1 parts of anti-settling agent, 0.1-1.5 parts of leveling agent, 0.5-1.5 parts of pH regulator, and 5-10 parts of deionized water, and stir for 30 minutes to obtain component A; S2. Under stirring in a disperser at a speed of 300-500 r / min, slowly add 2.7-3.6 parts of solvent C, 0.2-0.5 parts of dispersant, and 6-8 parts of deionized water in order by weight, stir for 10-15 minutes, then slowly add 3-5 parts of aluminum powder thereto, and then stir at a speed of 600-800 r / min for 30 minutes to obtain component B; S3, using 0.3-0.4 parts of solvent c to clean the cylinder wall for preparing component B to obtain a cleaning solution; S4. While stirring in a disperser at a speed of 600-800 r / min, add component A and component B in sequence, stir for 10 minutes, then add the cleaning solution, stir for 30 minutes, add 14-15 parts of N-allylmaleimide and 10-12 parts of nano-modified fluorinated polysiloxane, stir for 30 minutes, filter with a 200-mesh copper mesh to remove solid impurities to obtain a water-based metallic paint.

[0007] As a further improvement, the preparation method of the nano-modified fluorinated polysiloxane is: at room temperature, adding hydrogen-terminated fluorinated polysiloxane to 1,3-bis(trifluoromethyl)benzene solvent, adding nano-silica thereto, stirring, and ultrasonically treating for 30 minutes to obtain the nano-modified fluorinated polysiloxane.

[0008] As a further improvement, the preparation method of the terminal hydrogen-containing fluorine-containing polysiloxane is as follows: trifluoropropyl cyclotrisiloxane, hydroxyl-containing cyclotetrasiloxane and tetramethyldihydrodisiloxane are mixed, the temperature is raised to 75° C. in an oil bath under nitrogen protection, stirred for 30 minutes to keep the system temperature constant, and then the catalyst trifluoromethanesulfonic acid is added, and the reaction is continued for 8 hours. After the reaction is completed, it is cooled to room temperature, and then n-heptane is added to neutralize the trifluoromethanesulfonic acid in the system, and then filtered and distilled to remove the solvent, and the pressure is reduced at 180° C. for 30 minutes to obtain the terminal hydrogen-containing fluorine-containing polysiloxane.

[0009] As a further improvement, the hydroxyl-containing cyclotetrasiloxane is prepared by using allyl hydroxyethyl ether and tetramethyltetrahydrocyclotetrasiloxane as raw materials, reacting at 80° C. for 12 hours under the catalysis of a platinum catalyst.

[0010] As a further improvement, the molar ratio of the trifluoropropyl cyclotrisiloxane to the hydroxyl-containing cyclotetrasiloxane is 1:1, the added amount of the tetramethyldihydrogendisiloxane is 3% of the molar amount of the trifluoropropyl cyclotrisiloxane, and the added amount of the trifluoromethanesulfonic acid is 5% of the total molar amount of the trifluoropropyl cyclotrisiloxane, the hydroxyl-containing cyclotetrasiloxane and the tetramethyldihydrogendisiloxane.

[0011] As a further improvement, the molar ratio of allyl hydroxyethyl ether to tetramethyltetrahydrocyclotetrasiloxane is 4.5:1.

[0012] As a further improvement, the mass of the nano-silica is 0.1% of the mass of the hydrogen-terminated fluorine-containing polysiloxane.

[0013] As a further improvement, the solvent a is any one or more of ethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol methyl ether, diethylene glycol monobutyl ether, and dipropylene glycol butyl ether; the solvent b is a mixture of isopropanol and ethanol, the mass ratio of isopropanol to ethanol is 1:1; and the solvent c is one or more of ethylene glycol butyl ether, isooctyl alcohol, and ethylene glycol isooctyl ether.

[0014] As a further improvement, the aqueous acrylate dispersion is AQUAPAC 8256 of Fuqisen, the amino resin is Cymel 325, the wetting agent is any one or more of Surfynol 440, TEGO WET 510 or TEGO Twin 4100, the defoamer is any one or more of BYK-024, Tego airex 902W, Tego foamex 810, Foamstar 2400 or Surfynol 104E, the thickener is any one or more of BYK-8421, THIXATROL 5020W, RHEOLATE299, and the anti-settling agent is LAPONITE of BYK. RD, the leveling agent is any one or more of BYK-381, BYK-347, PW-336 or BYK-345, the pH adjuster is AMP-95 or DMEA, the aluminum powder is water-based aluminum powder ZW-6130B or solvent-based aluminum powder 37C of Silver Arrow Company, and the dispersant is BYK-192.

[0015] The invention also provides a water-based metal topcoat.

[0016] The reaction equation for the preparation process of hydroxyl epoxy polysiloxane is as follows: ; The reaction equation for the preparation process of hydrogen-terminated fluorinated polysiloxane is as follows: ; Among them, R 1 The structural formula is .

[0017] Due to the adoption of the above technical solution, the beneficial effects of the present invention are: The water-based metal topcoat obtained by the preparation method of the water-based metal topcoat provided by the present invention has no soft sedimentation or hard sedimentation phenomenon after adding the anti-settling agent LAPONITE RD at 50° C. for 30 days, and has good thermal stability.

[0018] By adding isopropyl alcohol and ethanol to form a gradient volatile solvent with ethylene glycol monobutyl ether, it is beneficial to improve the anti-sagging performance of the metallic paint and ensure the good appearance and construction window of the paint film.

[0019] Through the cross-linking reaction of the fast-crosslinking amino resin Cymel 325 and the hydrophobic AQUAPAC 8256 resin, a dense paint film is formed with excellent drainage. At the same time, the addition of aluminum powder further enhances the hydrophobicity and ensures water resistance.

[0020] The aluminum powder is dispersed by wrapping it with a dispersant, and the aluminum powder is dispersed more evenly with solvent c and deionized water. The solvent-based aluminum powder is dispersed by the dispersant, hydrophilic solvent and deionized water and then added to the resin base material. The resin itself is hydrophobic, which further coats the solvent-based aluminum powder and avoids the occurrence of shrinkage holes during construction.

[0021] The water-based metallic paint of the present invention can achieve the requirements of high gloss and high sparkle.

[0022] By adding nano-modified fluorinated polysiloxane and adding allyl hydroxyethyl ether to tetramethyltetrahydrocyclotetrasiloxane, hydroxyl groups are grafted onto the side chains of the nano-modified fluorinated polysiloxane. The hydroxyl groups can form hydrogen bonds with the polar groups on the water-based acrylic ester dispersion, so that the nano-modified fluorinated polysiloxane is filled in the cross-linking gaps between the water-based acrylic ester dispersion and the amino resin, thereby improving the adhesion between the topcoat formed with the water-based acrylic ester dispersion and the amino resin.

[0023] Through the modification of nano-silica, the strength of nano-modified fluorinated polysiloxane is improved, and the hardness and scratch resistance of the paint film are improved. At the same time, the side chains of nano-modified fluorinated polysiloxane contain long fluorinated chains. During the curing process, the long fluorinated chains wrap around the paint film to form a waterproof and anti-fouling layer, protecting the car paint with a hydrophobic lotus leaf effect. It has super hydrophobicity and is easy to clean and maintain.

[0024] The thickener and LAPONITE RD in the present invention play a role in the orientation of the aluminum powder, thereby preventing the aluminum powder from blooming during construction.

[0025] The present invention is a non-glazing process, avoids the use of solvent-based varnish, and is beneficial to reducing VOC emissions. DETAILED DESCRIPTION

[0026] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0027] Embodiments 1-3 respectively provide a water-based metallic topcoat.

[0028] The difference between the water-based metallic topcoat in the above embodiments is that the weight proportions of the raw material components in the base material are different, as shown in Table 1.

[0029] The method for preparing the water-based metallic topcoat in the above embodiment comprises the following steps: S1. Under stirring in a disperser at a speed of 600 r / min, slowly add water-based acrylic ester dispersion, amino resin, solvent a, solvent b, wetting agent, defoamer, thickener, anti-settling agent, leveling agent, pH adjuster, and deionized water in sequence, and stir for 30 minutes to obtain component A; S2. While stirring in a disperser at a speed of 300 r / min, slowly add solvent C, dispersant, and deionized water in sequence, stir for 10 min, slowly add aluminum powder thereto, and then stir at a speed of 600 r / min for 30 min to obtain component B; S3, using solvent c to clean the cylinder wall for preparing component B to obtain a cleaning solution; S4. While stirring in a disperser at a speed of 600 r / min, add component A and component B in sequence, stir for 10 minutes, then add the cleaning solution, stir for 30 minutes, add N-allylmaleimide and nano-modified fluorinated polysiloxane, stir for 30 minutes, filter with a 200-mesh copper mesh to remove solid impurities to obtain a water-based metallic paint.

[0030] The preparation method of nano-modified fluorinated polysiloxane is as follows: S41, take allyl hydroxyethyl ether, add tetramethyltetrahydrocyclotetrasiloxane thereto, the molar ratio of allyl hydroxyethyl ether to tetramethyltetrahydrocyclotetrasiloxane is 4.5:1, then add solvent 1,3-bis(trifluoromethyl)benzene and 1 mL of platinum catalyst thereto, place the system in an oil bath, heat to 80°C and react for 12 hours, after the reaction is completed, distill and remove the solvent to obtain hydroxy-containing cyclotetrasiloxane, the amount of solvent 1,3-bis(trifluoromethyl)benzene added is equal to the total molar amount of the raw materials allyl hydroxyethyl ether and tetramethyltetrahydrocyclotetrasiloxane; S42, trifluoropropyl cyclotrisiloxane, hydroxyl-containing cyclotetrasiloxane and tetramethyldihydrodisiloxane are mixed, the temperature is raised to 75°C in an oil bath under nitrogen protection, stirred for 30 minutes to make the system temperature constant, and then trifluoromethanesulfonic acid is added as a catalyst, and the reaction is continued for 8 hours. After the reaction is completed, it is cooled to room temperature, and then n-heptane is added to neutralize the trifluoromethanesulfonic acid in the system, and then filtered and distilled to remove the solvent, and the pressure is reduced at 180°C for 30 minutes to obtain a terminal hydrogen-containing fluorine-containing polysiloxane, wherein the molar ratio of trifluoropropyl cyclotrisiloxane to hydroxyl-containing cyclotetrasiloxane is 1:1, the amount of tetramethyldihydrodisiloxane added is 3% of the molar amount of trifluoropropyl cyclotrisiloxane, and the amount of trifluoromethanesulfonic acid added is 5% of the total molar amount of trifluoropropyl cyclotrisiloxane, hydroxyl-containing cyclotetrasiloxane and tetramethyldihydrodisiloxane; S43. At room temperature, add the terminal hydrogen-containing fluorinated polysiloxane to 1,3-bis(trifluoromethyl)benzene solvent, add nano-silica thereto, stir, and ultrasonically treat for 30 minutes to obtain nano-modified fluorinated polysiloxane, wherein the mass of nano-silica is 0.1% of the mass of the terminal hydrogen-containing fluorinated polysiloxane, and the mass ratio of the added amount of the solvent 1,3-bis(trifluoromethyl)benzene to the terminal hydrogen-containing fluorinated polysiloxane is 1:1.

[0031] In this embodiment, solvent a is ethylene glycol monobutyl ether, solvent b is a mixture of isopropanol and ethanol, solvent c is ethylene glycol monobutyl ether, and the mass ratio of isopropanol to ethanol is 1:1.

[0032] In this embodiment, the water-based acrylic ester dispersion is AQUAPAC 8256 produced by Fuqisen, the amino resin is Cymel 325, the wetting agent is Surfynol 440, the defoamer is BYK-024, the thickener is BYK-8421, the anti-settling agent is LAPONITE RD produced by BYK, the leveling agent is BYK-345, the pH adjuster is DMEA, the aluminum powder is water-based aluminum powder ZW-6130B produced by Silver Arrow, and the dispersant is BYK-192.

[0033]

[0034] Embodiments 4-8 each provide a water-based metallic topcoat.

[0035] The difference between the above embodiment and embodiment 1 is that the materials used for the components in component A and component B are different, as shown in Table 2.

[0036]

[0037] Comparative Examples 1-3 each provide a water-based metallic topcoat.

[0038] The difference between the above embodiment and embodiment 1 is that the amount of each raw material component in the base material is different, as shown in Table 3.

[0039]

[0040] The water-based metal topcoats in Example 1 and Comparative Examples 1-3 were subjected to performance tests, and the test results are shown in Table 4, wherein the storage stability was tested according to GB / T 6753.3-1986, the adhesion was tested according to GB / T 9286-2021, the water resistance was tested according to GB / T 5209-1985, the salt spray resistance was tested according to GB / T 1771-2007, the paint film hardness was tested according to GB / T 6739-2022, the anti-sagging was tested according to GB / T 9264-2012, the gloss test was tested by Elcometer 480 gloss meter, the acid resistance and alkali resistance were tested according to GB / T 9274-1988, and the aging resistance was tested according to GB / T 1865-2009.

[0041]

[0042] It can be seen from Table 4 that, compared with Example 1 and Comparative Examples 1 and 3, Comparative Example 2 did not add LAPONITE RD, resulting in reduced storage stability and sedimentation and stratification.

[0043] Compared with Example 1 and Comparative Examples 2-3, Comparative Example 1 does not add solvent b, resulting in a decrease in the anti-sagging performance of Comparative Example 1. This is because in Example 1, by adding isopropanol and ethanol, a gradient volatile solvent is formed with ethylene glycol monobutyl ether, which is beneficial to improving the anti-sagging performance of the metallic paint and ensuring a good appearance and construction window of the paint film.

[0044] Comparative Example 3 Compared with Example 1 and Comparative Examples 1-2, no N-allylmaleimide and nano-modified fluorinated polysiloxane were added, resulting in a certain degree of decrease in the water resistance, adhesion and hardness of the paint film of Comparative Example 3. This is because in Example 1, by adding nano-modified fluorinated polysiloxane, allyl hydroxyethyl ether was added to tetramethyltetrahydrocyclotetrasiloxane, so that hydroxyl groups were grafted on the side chains of the nano-modified fluorinated polysiloxane. The hydroxyl groups were able to form hydrogen bonds with the polar groups on the aqueous acrylate dispersion, making the nano-modified fluorinated polysiloxane The oxane is filled in the cross-linked gaps between the water-based acrylic dispersion and the amino resin, which improves the adhesion between the topcoat formed with the water-based acrylic dispersion and the amino resin. The strength of the nano-modified fluorinated polysiloxane is improved through the modification of nano-silica, and the hardness and scratch resistance of the paint film are improved. At the same time, the side chains of the nano-modified fluorinated polysiloxane contain long fluorinated chains. During the curing process, the long fluorinated chains wrap around the paint film to form a waterproof and anti-fouling layer, protecting the car paint with a hydrophobic lotus leaf effect. It has super hydrophobicity and is easy to clean and maintain.

[0045] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a water-based metallic topcoat, characterized in that: The following steps are involved: S1. Under stirring in a disperser at a speed of 600-800 r / min, slowly add, by weight, 50-60 parts of aqueous acrylate dispersion, 10-12 parts of amino resin, 1-2 parts of solvent a, 1-2 parts of solvent b, 0.05-0.5 parts of wetting agent, 0.5-1.0 parts of defoaming agent, 0.5-2 parts of thickener, 0.5-1 parts of anti-settling agent, 0.1-1.5 parts of leveling agent, 0.5-1.5 parts of pH adjuster and 5-10 parts of deionized water, and stir for 30 minutes to obtain component A; S2. Under stirring in a disperser at a speed of 300-500 r / min, slowly add 2.7-3.6 parts of solvent C, 0.2-0.5 parts of dispersant and 6-8 parts of deionized water in sequence by weight, stir for 10-15 minutes, slowly add 3-5 parts of aluminum powder thereto, and then stir at a speed of 600-800 r / min for 30 minutes to obtain component B; S3, using 0.3-0.4 parts of solvent c to clean the cylinder wall for preparing component B to obtain a cleaning solution; S4. While stirring in a disperser at a speed of 600-800 r / min, add component A and component B in sequence, stir for 10 minutes, then add the cleaning solution, stir for 30 minutes, add 14-15 parts of N-allylmaleimide and 10-12 parts of nano-modified fluorinated polysiloxane, stir for 30 minutes, filter with a 200-mesh copper mesh to remove solid impurities to obtain a water-based metallic paint.

2. The method for preparing a water-based metallic topcoat according to claim 1, characterized in that: The preparation method of the nano-modified fluorinated polysiloxane is as follows: at room temperature, hydrogen-terminated fluorinated polysiloxane is added to a 1,3-bis(trifluoromethyl)benzene solvent, nano-silicon dioxide is added thereto, and the mixture is stirred and ultrasonically treated for 30 minutes to obtain the nano-modified fluorinated polysiloxane.

3. The method for preparing a water-based metallic topcoat according to claim 2, characterized in that: The preparation method of the terminal hydrogen-containing fluorine-containing polysiloxane is as follows: trifluoropropyl cyclotrisiloxane, hydroxyl-containing cyclotetrasiloxane and tetramethyldihydrodisiloxane are mixed, the temperature is raised to 75° C. in an oil bath under nitrogen protection, stirred for 30 minutes to keep the system temperature constant, then trifluoromethanesulfonic acid as a catalyst is added, the reaction is continued for 8 hours, after the reaction is completed, the system is cooled to room temperature, and then n-heptane is added to neutralize the trifluoromethanesulfonic acid in the system, and then the system is filtered and distilled to remove the solvent, and the pressure is reduced at 180° C. for 30 minutes to obtain the terminal hydrogen-containing fluorine-containing polysiloxane.

4. The method for preparing a water-based metallic topcoat according to claim 3, characterized in that: The hydroxyl-containing cyclotetrasiloxane is prepared by using allyl hydroxyethyl ether and tetramethyltetrahydrocyclotetrasiloxane as raw materials, and reacting at 80° C. for 12 hours under the catalysis of a platinum catalyst.

5. The method for preparing a water-based metallic topcoat according to claim 3, characterized in that: The molar ratio of the trifluoropropyl cyclotrisiloxane to the hydroxyl-containing cyclotetrasiloxane is 1:1, the added amount of the tetramethyldihydrogendisiloxane is 3% of the molar amount of the trifluoropropyl cyclotrisiloxane, and the added amount of the trifluoromethanesulfonic acid is 5% of the total molar amount of the trifluoropropyl cyclotrisiloxane, the hydroxyl-containing cyclotetrasiloxane and the tetramethyldihydrogendisiloxane.

6. The method for preparing a water-based metallic topcoat according to claim 4, characterized in that: The molar ratio of the allyl hydroxyethyl ether to the tetramethyltetrahydrocyclotetrasiloxane is 4.5:

1.

7. The method for preparing a water-based metallic topcoat according to claim 2, characterized in that: The mass of the nano-silicon dioxide is 0.1% of the mass of the hydrogen-terminated fluorine-containing polysiloxane.

8. The method for preparing a water-based metallic topcoat according to claim 1, characterized in that: The solvent a is any one or more of ethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol methyl ether, diethylene glycol monobutyl ether, and dipropylene glycol butyl ether; the solvent b is a mixture of isopropanol and ethanol, the mass ratio of isopropanol to ethanol is 1:1; and the solvent c is one or more of ethylene glycol butyl ether, isooctyl alcohol, and ethylene glycol isooctyl ether.

9. The method for preparing a water-based metallic topcoat according to claim 1, characterized in that: The water-based acrylic ester dispersion is AQUAPAC 8256 from Fuchisen, the amino resin is Cymel 325, the wetting agent is any one or more of Surfynol 440, TEGO WET510 or TEGO Twin 4100, the defoamer is any one or more of BYK-024, Tego airex 902W, Tego foamex 810, Foamstar 2400 or Surfynol 104E, the thickener is any one or more of BYK-8421, THIXATROL 5020W, RHEOLATE 299, and the anti-settling agent is LAPONITE from BYK. RD, the leveling agent is any one or more of BYK-381, BYK-347, PW-336 or BYK-345, the pH adjuster is AMP-95 or DMEA, the aluminum powder is water-based aluminum powder ZW-6130B or solvent-based aluminum powder 37C of Silver Arrow Company, and the dispersant is BYK-192.

10. The water-based metallic topcoat obtained by the preparation method of the water-based metallic topcoat according to claim 1.

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