A chrome-free anti-fingerprint color coating special for zinc-aluminum-magnesium alloy with acid and alkali resistance

Abstract

The present application relates to a kind of acid and alkali resistant type chrome-free anti-fingerprint color coating special for zinc-aluminum-magnesium, comprising water-based acrylic resin, silicone modified polyurethane resin, nano titanium dioxide sol, acid and alkali resistant pigment, silane coupling agent, dispersant, defoaming agent, leveling agent and deionized water balance.The coating of the present application does not contain harmful chromium element, meets the environmental protection requirements, reduces the harm to environment and human health, can be widely applied in the field with higher environmental protection requirements, by reasonably selecting water-based acrylic resin, silicone modified polyurethane resin, nano titanium dioxide sol and other components, and optimizing its ratio, the coating film formed by coating has excellent acid and alkali resistance, can effectively protect zinc-aluminum-magnesium substrate from erosion in acid and alkali environment, the low surface energy characteristics of silicone modified polyurethane resin and the synergistic effect of coating formula make the coating film surface have good anti-fingerprint performance, reduce fingerprint residue, keep surface beautiful.

Description

Technical Field

[0001] This invention relates to a chromium-free fingerprint-resistant colored coating for use in the home appliance industry, specifically a chromium-free fingerprint-resistant colored coating for use with zinc, aluminum, and magnesium alloys. Background Technology

[0002] Zn-Al-Mg (ZAM) is a novel steel coil coating technology that offers superior corrosion resistance, processability, edge rust prevention, and lower cost compared to hot-dip galvanizing (Zn) and hot-dip aluminized zinc (Zn-Al). Zhonglv ZAM coated steel sheets, with their excellent corrosion resistance (extended lifespan), successfully resolved key process compatibility issues (processability), unique self-healing edge capability (enhanced reliability), and mature mass production assurance (stable supply), have been widely used in the manufacture of key components such as back panels, brackets, and condenser pipes for home appliances like air conditioners and washing machines. This provides strong material support for improving the durability, safety, and overall quality of these products.

[0003] When applying aluminum zinc-aluminum-magnesium alloys to the home appliance industry, two important issues need to be addressed: firstly, they must be available in various colors to meet the color requirements of different scenarios; secondly, they must be resistant to acids and alkalis to meet the practical needs of home use, since home appliances, especially kitchen appliances, are highly likely to come into contact with edible acetic acid and alkaline cleaning agents.

[0004] Current techniques for coloring and functionalizing aluminum-zinc-aluminum-magnesium alloys (AMA) with acid and alkali resistance involve pre-treating the steel coil with a chromium-free, fingerprint-resistant coating, followed by a traditional primer + topcoat coating process using powder coating or roller coating. The main problem with this process is:

[0005] 1. High application cost: The paint film is usually tens of micrometers in size, so a large amount of primer and topcoat paint is required;

[0006] 2. The process is relatively complex: it involves two processes, resulting in a higher failure rate.

[0007] 3. Heavy pollution: Both powder coating and roller coating processes generate serious environmental pollution (dust pollution and solvent pollution) and health hazards to personnel (inhalation of dust hazards and inhalation of solvent hazards).

[0008] Currently, some fingerprint-resistant coatings on the market have several shortcomings. While some chromium-containing fingerprint-resistant coatings offer a degree of corrosion resistance, chromium is toxic and poses a threat to the environment and human health. Some chromium-free fingerprint-resistant coatings perform poorly in terms of acid and alkali resistance and fingerprint resistance, failing to meet the protection requirements for zinc-aluminum-magnesium materials in complex environments. Furthermore, existing colored fingerprint-resistant coatings need improvement in terms of color stability, adhesion to zinc-aluminum-magnesium substrates, and overall protective performance.

[0009] Based on the above background, the present invention provides a novel high-performance color fingerprint-resistant technology that simultaneously meets the requirements of color and acid and alkali resistance, eliminating the need for subsequent coating processes and can be directly applied to home appliances. Summary of the Invention

[0010] To address the shortcomings of existing technologies, this invention provides a chromium-free, fingerprint-resistant colored coating specifically designed for zinc, aluminum, and magnesium alloys. This coating exhibits excellent acid and alkali resistance, fingerprint resistance, good color stability, and adhesion to zinc, aluminum, and magnesium substrates. It is free of harmful chromium elements, meets environmental protection requirements, and boasts extremely low cost. The colored fingerprint-resistant film is only 5-10 micrometers thick. The process is simpler and more efficient, eliminating two subsequent coating steps, resulting in minimal pollution and no dust or solvent hazards.

[0011] To achieve the above objectives, the present invention provides the following technical solution, comprising the following components:

[0012] Waterborne acrylic resin: 30%-60%. Waterborne acrylic resin has good weather resistance, chemical resistance and adhesion, and can provide basic film-forming properties and protective properties for coatings.

[0013] Organosilicon-modified polyurethane resin: 10%-30%. Organosilicon-modified polyurethane resin combines the weather resistance and low surface energy of organosilicon with the high abrasion resistance and flexibility of polyurethane. It can improve the fingerprint resistance and chemical resistance of coatings, while also improving the flexibility and impact resistance of the coating.

[0014] Nano titanium dioxide sol: 5%-15%. Nano titanium dioxide sol has good photocatalytic properties and chemical stability, and can form a dense protective film on the coating surface, improving the coating's acid and alkali resistance and self-cleaning properties.

[0015] Acid and alkali resistant pigments: 5%-15%. Pigments with excellent acid and alkali resistance are selected, such as certain organic pigments and inorganic pigments with special surface treatment, to give the coatings a rich range of colors while ensuring color stability in acidic and alkaline environments.

[0016] Silane coupling agent: 1%-5%. Silane coupling agents can enhance the bonding force between organic and inorganic components in coatings, improve the adhesion of the coating to zinc-aluminum-magnesium substrates, and improve the water resistance and chemical resistance of the coating.

[0017] Dispersant: 0.5%-2%. Dispersants are used to uniformly disperse pigments in the coating system, prevent pigment agglomeration, and improve the stability and gloss of the coating film.

[0018] Defoamer: 0.1%-1%. Defoamers are used to eliminate air bubbles generated during the preparation and application of coatings, ensuring the quality of the coating film.

[0019] Leveling agent: 0.1%-1%. Leveling agents can improve the flowability of coatings, making the coating surface smoother and more even, and improving the decorative properties of the coating.

[0020] Deionized water: Balance. Used as a solvent in the coating to ensure uniform dispersion of all components and form a stable coating system.

[0021] Preparation method:

[0022] Step 1: Add deionized water to the reactor, turn on the stirrer, and control the speed at 200-400 r / min.

[0023] Step 2: Slowly add the dispersant into the reactor and stir until homogeneous. The stirring time is 15-30 minutes.

[0024] Step 3: Add acid and alkali resistant pigments and continue stirring for 30-60 minutes to fully disperse the pigments in the deionized water and form a uniform pigment slurry.

[0025] Step 4: Add the water-based acrylic resin and the silicone-modified polyurethane resin to the reactor in sequence, increase the stirring speed to 400-600 r / min, and stir for 30-60 min to ensure that the resin and pigment paste are fully mixed.

[0026] Step 5: Add nano titanium dioxide sol and stir until homogeneous. Stirring time is 15-30 minutes.

[0027] Step 6: Slowly add the silane coupling agent dropwise into the reactor while reducing the stirring speed to 200-300 r / min. The dropwise addition time is 15-30 min. After the dropwise addition is complete, continue stirring for 30-60 min to allow the silane coupling agent to fully react with the other components.

[0028] Step 7: Add the defoamer and leveling agent in sequence, and stir evenly for 15-30 minutes.

[0029] Step 8: Filter the prepared coating through a 100-200 mesh filter to remove any impurities and obtain the finished coating.

[0030] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0031] 1. The coating of this invention does not contain harmful chromium elements, meets environmental protection requirements, reduces harm to the environment and human health, and can be widely used in fields with high environmental protection requirements. By rationally selecting components such as water-based acrylic resin, organosilicon-modified polyurethane resin, and nano titanium dioxide sol, and optimizing their ratio, the coating film formed by the coating has excellent acid and alkali resistance, which can effectively protect zinc-aluminum-magnesium substrates from corrosion in acid and alkali environments and extend their service life.

[0032] 2. The low surface energy characteristics of the silicone-modified polyurethane resin of this invention and the synergistic effect of the coating formulation give the coating surface good fingerprint resistance, reduce fingerprint residue, maintain the surface appearance, and make it easy to clean.

[0033] 3. The acid and alkali resistant pigments and the stability of the coating system selected in this invention ensure the stability of the coating color under different environmental conditions, thus meeting the long-term aesthetic requirements of the product appearance.

[0034] 4. The use of silane coupling agent in this invention enhances the adhesion between the coating and the zinc-aluminum-magnesium substrate, enabling the coating to adhere firmly to the substrate surface, making it less prone to peeling off and improving the protective effect. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation process of an acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys according to the present invention.

[0036] Figure 2 These are comparative diagrams of embodiments of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] Please see Figure 1 and Figure 2 The acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys in this embodiment comprises the following components by weight percentage:

[0040] The water-based acrylic resin contains 40% water-based acrylic resin. The glass transition temperature of the water-based acrylic resin is 20℃, and the number average molecular weight is 50,000.

[0041] The resin contains 20% silicone-modified polyurethane resin, with a silicone mass fraction of 5%, and the resin has a tensile strength of 10 MPa and an elongation at break of 200%.

[0042] The nano-titanium dioxide sol contains 10% titanium dioxide particles, with an average particle size of 10 nm and a solid content of 20%.

[0043] The acid and alkali resistant pigments account for 10% of the total content. These pigments are inorganic pigments that have undergone surface silanization treatment, and the oil absorption of the pigments is 30g / 100g.

[0044] 3% silane coupling agent; the silane coupling agent is an amino-containing silane coupling agent.

[0045] 1% dispersant, which is a polymeric dispersant with an HLB value of 10;

[0046] The defoamer is 0.5%, and it is a polyether-modified silicone defoamer with an effective ingredient content of 95%.

[0047] 0.5% leveling agent, which is an acrylic leveling agent, has a minimum film-forming temperature of 10°C in the coating;

[0048] 15% deionized water.

[0049] A method for preparing an acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys includes the following steps:

[0050] S1. Add deionized water to the reactor, turn on the stirrer, and control the speed at 200 r / min;

[0051] S2. Slowly add the dispersant into the reactor and stir until homogeneous. The stirring time is 15 minutes.

[0052] S3. Add acid and alkali resistant pigments and continue stirring for 30 minutes to form a uniform pigment slurry;

[0053] S4. Add water-based acrylic resin and organosilicon-modified polyurethane resin to the reactor in sequence, increase the stirring speed to 400 r / min, and stir for 30 min.

[0054] S5. Add nano titanium dioxide sol and stir until homogeneous for 15 minutes.

[0055] S6. Slowly add the silane coupling agent dropwise into the reactor while reducing the stirring speed to 200 r / min. The dropwise addition time is 15 min. After the dropwise addition is complete, continue stirring for 30 min.

[0056] S7. Add the defoamer and leveling agent in sequence, and stir evenly for 15 minutes.

[0057] S8. Filter the prepared coating through a 100-mesh filter to obtain the finished coating.

[0058] After the coating is applied to the zinc-aluminum-magnesium substrate, the resulting film thickness is 18μm. The surface drying time of the coating is 45min and the complete drying time is 20h at an ambient temperature of 50℃.

[0059] Coating performance:

[0060] Acid and alkali resistance: Zinc-aluminum-magnesium samples coated with the coating of this invention were immersed in 5% hydrochloric acid solution and 5% sodium hydroxide solution respectively. After immersion at room temperature for 72 hours, there were no obvious corrosion, discoloration, blistering or other phenomena on the sample surface, and the coating adhesion still reached level 0 (tested according to GB / T9286-1998 standard "Cross-cut test of paint and varnish film").

[0061] Fingerprint resistance: Press your finger on the surface of a zinc-aluminum-magnesium sample coated with the coating of this invention, and then gently wipe it with a clean soft cloth. The fingerprint marks on the sample surface are not obvious, and the surface gloss is well restored after wiping. The gloss difference with the unpressed area is less than 5% (gloss test according to relevant industry standards).

[0062] Color stability: After the zinc-aluminum-magnesium sample coated with the coating of this invention is exposed to the outdoor natural environment for 6 months, or tested in an artificial accelerated aging test chamber according to the standard GB / T1865-2009 "Artificial climate aging and artificial radiation exposure (filtered xenon arc radiation)" for 1000 hours, the color change of the sample surface ΔE*ab≤3 (the color difference is calculated according to the CIELAB color space).

[0063] Adhesion: Tested according to GB / T9286-1998 "Cross-cut test of paint and varnish film", the film adhesion reaches level 0, the coating is tightly bonded to the zinc-aluminum-magnesium substrate and is not easy to fall off.

[0064] Tests showed that the coating exhibited good acid and alkali resistance when applied to zinc-aluminum-magnesium alloy samples. After immersion in 5% hydrochloric acid and 5% sodium hydroxide solutions for 72 hours, the sample surface showed no significant changes, and the coating adhesion was rated at level 0. It also demonstrated excellent fingerprint resistance, with minimal fingerprint marks and good gloss recovery after wiping. Furthermore, it exhibited high color stability, with a color change of ΔE*ab=2 after 6 months of outdoor exposure, and achieved a level 0 adhesion.

[0065] Example 2

[0066] Please see Figure 1 and Figure 2 The acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys in this embodiment comprises the following components by weight percentage:

[0067] The water-based acrylic resin contains 35% water, and its glass transition temperature is 30℃, with a number average molecular weight of 100,000.

[0068] The resin contains 25% silicone-modified polyurethane resin, with a silicone mass fraction of 10%, and a tensile strength of 15 MPa and an elongation at break of 240%.

[0069] The nano-titanium dioxide sol contains 12% titanium dioxide particles, with an average particle size of 50 nm and a solid content of 40%.

[0070] The acid and alkali resistant pigments account for 12% of the total content. These pigments are inorganic pigments that have undergone surface silanization treatment, and the oil absorption of the pigments is 25g / 100g.

[0071] 4% silane coupling agent; the silane coupling agent is an epoxy-containing silane coupling agent.

[0072] Dispersant 1.5%, the dispersant is a polymeric dispersant with an HLB value of 15;

[0073] The defoamer is 0.8%, and it is a polyether-modified silicone defoamer with an effective ingredient content of 97%.

[0074] The leveling agent is 0.7%, and it is an acrylic leveling agent with a minimum film-forming temperature of 20°C in the coating.

[0075] 9% deionized water.

[0076] A method for preparing an acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys includes the following steps:

[0077] S1. Add deionized water to the reactor, turn on the stirrer, and control the speed at 400 r / min;

[0078] S2. Slowly add the dispersant into the reactor and stir until homogeneous. Stirring time is 30 minutes.

[0079] S3. Add acid and alkali resistant pigments and continue stirring for 60 minutes to form a uniform pigment slurry;

[0080] S4. Add water-based acrylic resin and organosilicon-modified polyurethane resin to the reactor in sequence, increase the stirring speed to 600 r / min, and stir for 60 min.

[0081] S5. Add nano titanium dioxide sol and stir until homogeneous for 30 minutes.

[0082] S6. Slowly add the silane coupling agent dropwise into the reactor while reducing the stirring speed to 300 r / min. The dropwise addition time is 30 min. After the dropwise addition is complete, continue stirring for 60 min.

[0083] S7. Add the defoamer and leveling agent in sequence, stir evenly, and stir for 30 minutes.

[0084] S8. Filter the prepared coating through a 200-mesh filter to obtain the finished coating.

[0085] After the coating is applied to the zinc-aluminum-magnesium substrate, the resulting film thickness is 22μm. The surface drying time of the coating is 50min and the complete drying time is 22h at an ambient temperature of 50℃-60℃.

[0086] The coating performance testing method is the same as in Example 1. The test results show that the coating performs well in terms of acid and alkali resistance. After soaking in the corresponding acid and alkali solutions for 72 hours, the surface condition of the sample is good and the coating adhesion is grade 0. The fingerprint resistance is good and meets the relevant requirements. The color stability is good. After 1000 hours of artificial accelerated aging test, the color change ΔE*ab=2.5. The adhesion is grade 0.

[0087] Example 3

[0088] Please see Figure 1 and Figure 2 The acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys in this embodiment comprises the following components by weight percentage:

[0089] The waterborne acrylic resin contains 45% waterborne acrylic resin, with a glass transition temperature of 50°C and a number-average molecular weight of 150,000.

[0090] The silicone-modified polyurethane resin contains 15% silicone by mass, and the resin has a tensile strength of 20 MPa and an elongation at break of 280%.

[0091] The nano-titanium dioxide sol contains 8% titanium dioxide particles, with an average particle size of 30 nm and a solid content of 32%.

[0092] The acid and alkali resistant pigments are 8%, and they are inorganic pigments that have undergone surface silanization treatment. The oil absorption of the pigments is 28g / 100g.

[0093] 2% silane coupling agent, the silane coupling agent is a methacryloyloxy silane coupling agent;

[0094] The dispersant is 0.8%, and it is a polymeric dispersant with an HLB value of 13.

[0095] The defoamer is 0.6%, and it is a polyether-modified silicone defoamer with an effective ingredient content of 98%.

[0096] The leveling agent is 0.6%, and it is an acrylic leveling agent with a minimum film-forming temperature of 18°C ​​in the coating.

[0097] 20% deionized water.

[0098] A method for preparing an acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys includes the following steps:

[0099] S1. Add deionized water to the reactor, turn on the stirrer, and control the speed at 350 r / min;

[0100] S2. Slowly add the dispersant into the reactor and stir until homogeneous. The stirring time is 28 minutes.

[0101] S3. Add acid and alkali resistant pigments and continue stirring for 56 minutes to form a uniform pigment slurry;

[0102] S4. Add water-based acrylic resin and silicone-modified polyurethane resin to the reactor in sequence, increase the stirring speed to 550 r / min, and stir for 55 min.

[0103] S5. Add nano titanium dioxide sol and stir until homogeneous for 28 minutes.

[0104] S6. Slowly add the silane coupling agent dropwise into the reactor while reducing the stirring speed to 275 r / min. The dropwise addition time is 25 min. After the dropwise addition is complete, continue stirring for 58 min.

[0105] S7. Add the defoamer and leveling agent in sequence, and stir evenly for 26 minutes.

[0106] S8. Filter the prepared coating through a 180-mesh filter to obtain the finished coating.

[0107] After the coating is applied to the zinc-aluminum-magnesium substrate, the resulting film thickness is 15μm. The surface drying time of the coating is 40min and the complete drying time is 18h at an ambient temperature of 55℃.

[0108] The coating performance testing method is the same as in Example 1. The coating film formed by the coating has reliable acid and alkali resistance. After soaking in 5% hydrochloric acid and 5% sodium hydroxide solution for 72 hours, the sample showed no abnormalities and the coating film adhesion was grade 0. The fingerprint resistance performance met expectations. The color stability was high. After outdoor exposure and artificial accelerated aging tests, the color change was within the standard range. The adhesion reached grade 0.

[0109] Example 4

[0110] This embodiment describes a chromium-free, fingerprint-resistant, acid- and alkali-resistant colored coating specifically for zinc, aluminum, and magnesium alloys, comprising the following components by weight percentage:

[0111] Waterborne acrylic resin: 30%. The glass transition temperature of the waterborne acrylic resin is 50℃, and the number average molecular weight is 150,000.

[0112] Organosilicon-modified polyurethane resin: 30%. The organosilicon-modified polyurethane resin contains 5% organosilicon by mass, and the resin has a tensile strength of 20 MPa and an elongation at break of 280%.

[0113] Nano-titanium dioxide sol: 15%. The average particle size of the titanium dioxide particles in the nano-titanium dioxide sol is 10 nm, and the solid content of the sol is 20%.

[0114] Acid and alkali resistant pigments: 15%. The acid and alkali resistant pigments are inorganic pigments that have undergone surface silanization treatment, and the oil absorption of the pigments is 30g / 100g.

[0115] Silane coupling agent: 5%. The silane coupling agent is a methacryloyloxy silane coupling agent.

[0116] Dispersant: 2%. The dispersant is a polymeric dispersant with an HLB value of 10.

[0117] Defoamer: 1%. The defoamer is a polyether-modified silicone defoamer with an effective ingredient content of 98%.

[0118] Leveling agent: 1%. The leveling agent is an acrylic leveling agent, and its minimum film-forming temperature in the coating is 10℃.

[0119] Deionized water: 1%.

[0120] A method for preparing an acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys includes the following steps:

[0121] Step 1: Add deionized water to the reactor, turn on the stirrer, and control the speed at 400 r / min.

[0122] Step 2: Slowly add the dispersant into the reactor and stir until homogeneous. Stirring time is 30 minutes.

[0123] Step 3: Add acid and alkali resistant pigments and continue stirring for 60 minutes to fully disperse the pigments in the deionized water and form a uniform pigment slurry.

[0124] Step 4: Add the water-based acrylic resin and the silicone-modified polyurethane resin to the reactor in sequence, increase the stirring speed to 600 r / min, and stir for 60 min to ensure that the resin and pigment paste are fully mixed.

[0125] Step 5: Add nano titanium dioxide sol and stir until homogeneous for 30 minutes.

[0126] Step 6: Slowly add the silane coupling agent dropwise into the reactor while reducing the stirring speed to 300 r / min. The dropwise addition time is 30 min. After the dropwise addition is complete, continue stirring for 60 min to allow the silane coupling agent to fully react with the other components.

[0127] Step 7: Add the defoamer and leveling agent in sequence, stir well, and stir for 30 minutes.

[0128] Step 8: Filter the prepared coating through a 200-mesh filter to remove any impurities and obtain the finished coating.

[0129] After the coating is applied to the zinc-aluminum-magnesium substrate, the resulting film thickness is 30μm. The surface drying time of the coating is 48min and the complete drying time is 20h at an ambient temperature of 50℃.

[0130] The coating performance testing method is the same as in Example 1. The test results show that the coating performs well in terms of acid and alkali resistance. After soaking in the corresponding acid and alkali solutions for 72 hours, the surface condition of the sample is good and the coating adhesion is grade 0. The fingerprint resistance is good and meets the relevant requirements. The color stability is good. After 1000 hours of artificial accelerated aging test, the color change ΔE*ab=2.4. The adhesion is grade 0.

[0131] Example 5

[0132] This embodiment describes a chromium-free, fingerprint-resistant, acid- and alkali-resistant colored coating specifically for zinc, aluminum, and magnesium alloys, comprising the following components by weight percentage:

[0133] Waterborne acrylic resin: 60%. The glass transition temperature of the waterborne acrylic resin is 50℃, and the number average molecular weight is 50,000.

[0134] Organosilicon-modified polyurethane resin: 10%. The organosilicon-modified polyurethane resin contains 20% organosilicon by mass, and the resin has a tensile strength of 15 MPa and an elongation at break of 210%.

[0135] Nano-titanium dioxide sol: 5%. The average particle size of titanium dioxide particles in the nano-titanium dioxide sol is 50 nm, and the solid content of the sol is 40%.

[0136] Acid and alkali resistant pigments: 5%. The acid and alkali resistant pigments are inorganic pigments that have undergone surface silanization treatment, and the oil absorption of the pigments is 25g / 100g.

[0137] Silane coupling agent: 1%. The silane coupling agent is an epoxy-based silane coupling agent.

[0138] Dispersant: 0.5%. The dispersant is a polymeric dispersant with an HLB value of 15.

[0139] Defoamer: 0.1%. The defoamer is a polyether-modified silicone defoamer with an effective ingredient content of 96%.

[0140] Leveling agent: 0.1%. The leveling agent is an acrylic leveling agent, and its minimum film-forming temperature in coatings is 20°C.

[0141] Deionized water: 18.3%.

[0142] A method for preparing an acid- and alkali-resistant, chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys includes the following steps:

[0143] Step 1: Add deionized water to the reactor, turn on the stirrer, and control the speed at 200 r / min.

[0144] Step 2: Slowly add the dispersant into the reactor and stir until homogeneous. Stirring time is 15 minutes.

[0145] Step 3: Add acid and alkali resistant pigments and continue stirring for 30 minutes to fully disperse the pigments in the deionized water and form a uniform pigment slurry.

[0146] Step 4: Add the water-based acrylic resin and the silicone-modified polyurethane resin to the reactor in sequence, increase the stirring speed to 400 r / min, and stir for 30 min to ensure that the resin and pigment paste are fully mixed.

[0147] Step 5: Add nano titanium dioxide sol and stir until homogeneous for 15 minutes.

[0148] Step 6: Slowly add the silane coupling agent dropwise into the reactor while reducing the stirring speed to 200 r / min. The dropwise addition time is 15 min. After the dropwise addition is complete, continue stirring for 30 min to allow the silane coupling agent to fully react with the other components.

[0149] Step 7: Add the defoamer and leveling agent in sequence, and stir well for 15 minutes.

[0150] Step 8: Filter the prepared coating through a 100-mesh filter to remove any impurities and obtain the finished coating.

[0151] After the coating is applied to the zinc-aluminum-magnesium substrate, the resulting film thickness is 10μm. The surface drying time of the coating is 1 hour and the actual drying time is 24 hours at an ambient temperature of 50℃.

[0152] The coating performance testing method is the same as in Example 1. The test results show that the coating performs well in terms of acid and alkali resistance. After soaking in the corresponding acid and alkali solutions for 72 hours, the surface condition of the sample is good and the coating adhesion is grade 0. The fingerprint resistance is good and meets the relevant requirements. The color stability is good. After 1000 hours of artificial accelerated aging test, the color change ΔE*ab=2.6. The adhesion is grade 0.

[0153] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0154] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A chrome-free anti-fingerprint colored coating material for zinc-aluminum-magnesium, which is acid and alkali resistant, characterized in that, By weight percentage, it includes the following components: Water-based acrylic resin 30-60%; 10-30% silicone-modified polyurethane resin; Nano-titanium dioxide sol 5-15%; Acid and alkali resistant pigments 5-15%; Silane coupling agent 1-5%; Dispersant 0.5-2%; Defoamer 0.1-1%; Leveling agent 0.1-1%; Deionized water balance; The organosilicon-modified polyurethane resin has an organosilicon mass fraction of 5%-20%, and the resin has a tensile strength greater than 10 MPa and an elongation at break greater than 200%. The acid and alkali resistant pigment is an inorganic pigment that has undergone surface silanization treatment, and the oil absorption of the pigment is less than 30g / 100g. The silane coupling agent is one or more of the silane coupling agents containing amino, epoxy, or methacryloxy groups.

2. A chrome-free anti-fingerprint color coating resistant to acid and alkali, which is specific to zinc-aluminum-magnesium according to claim 1, characterized in that, The waterborne acrylic resin has a glass transition temperature of 20℃-50℃ and a number average molecular weight of 50,000-150,000.

3. The acid and alkali resistant chrome-free anti-fingerprint color coating specific to zinc-aluminum-magnesium according to claim 1, characterized in that, The average particle size of the titanium dioxide particles in the nano-titanium dioxide sol is 10nm-50nm, and the solid content of the sol is 20%-40%.

4. The acid and alkali resistant chrome-free anti-fingerprint color coating specific to zinc-aluminum-magnesium according to claim 1, characterized in that, The dispersant is a polymeric dispersant with an HLB value of 10-15.

5. The acid and alkali resistant chrome-free anti-fingerprint color coating specific to zinc-aluminum-magnesium according to claim 1, characterized in that, The defoamer is a polyether-modified silicone defoamer with an effective ingredient content greater than 95%, and the leveling agent is an acrylic leveling agent with a minimum film-forming temperature of 10℃-20℃ in the coating.

6. A chromium-free, fingerprint-resistant colored coating specifically for zinc, aluminum, and magnesium alloys, as described in any one of claims 1-5, characterized in that, It also includes the following preparation steps: S1. Add deionized water to the reactor, turn on the stirrer, and control the speed at 200-400 r / min; S2. Slowly add the dispersant into the reactor and stir until homogeneous. The stirring time is 15-30 minutes. S3. Add acid and alkali resistant pigments and continue stirring for 30-60 minutes to form a uniform pigment slurry; S4. Add the water-based acrylic resin and the organosilicon-modified polyurethane resin to the reactor in sequence, increase the stirring speed to 400-600 r / min, and stir for 30-60 min. S5. Add nano titanium dioxide sol and stir until homogeneous. Stirring time is 15-30 minutes. S6. Slowly add the silane coupling agent dropwise into the reactor while reducing the stirring speed to 200-300 r / min. The dropwise addition time is 15-30 min. After the dropwise addition is complete, continue stirring for 30-60 min. S7. Add the defoamer and leveling agent in sequence, and stir evenly for 15-30 minutes. S8. Filter the prepared coating through a 100-200 mesh filter to obtain the finished coating.

7. A chrome-free anti-fingerprint color coating specific to zinc-aluminum-magnesium, which is resistant to acid and alkali, according to claim 6, characterized in that, After the coating is applied to the zinc-aluminum-magnesium substrate, the resulting film thickness is 10μm-30μm. The surface drying time of the coating is less than 1 hour and the actual drying time is less than 24 hours at an ambient temperature of 50℃-60℃.

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