Acid-resistant and alkali-resistant chromium-free fingerprint-resistant colored coating special for zinc, aluminum and magnesium

Abstract

The invention relates to an acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating special for zinc, aluminum and magnesium. The color coating is prepared from waterborne acrylic resin, organic silicon modified polyurethane resin, nano titanium dioxide sol, acid-resistant and alkali-resistant pigment, a silane coupling agent, a dispersing agent, a defoaming agent, a flatting agent and the balance of deionized water. The coating does not contain harmful chromium element, meets the environmental protection requirement, reduces the harm to the environment and human health, can be widely applied to the field with higher environmental protection requirement, and can be used for preparing the coating by reasonably selecting the components such as the water-based acrylic resin, the organic silicon modified polyurethane resin and the nano titanium dioxide sol and optimizing the ratio of the components. The organic silicon modified polyurethane resin is added, so that a film formed by the coating has excellent acid and alkali resistance, a zinc-aluminum-magnesium base material can be effectively protected from being eroded in an acid and alkali environment, the surface of the film has good fingerprint resistance due to the low surface energy characteristic of the organic silicon modified polyurethane resin and the synergistic effect of the coating formula, fingerprint residues are reduced, and the surface attractiveness is kept.

Description

Technical Field

[0001] The present invention relates to a chrome-free fingerprint-resistant color coating for the field of household appliances, specifically an acid-resistant and alkali-resistant chrome-free fingerprint-resistant color coating specially used for zinc, aluminum and magnesium. Background Art

[0002] Galvanized aluminum-magnesium (ZAM) is a new type of steel coil coating technology that offers improved corrosion resistance, workability, edge rust resistance, and low cost compared to hot-dip galvanized (Zn) and hot-dip aluminum-zinc (Zn-Al) coatings. Chalco's ZAM-coated steel sheet, with its superior corrosion resistance (extending service life), successful resolution of key process compatibility issues (machinability), unique cut self-healing capabilities (enhancing reliability), and mature mass production (stable supply), has been adopted in the manufacture of key components such as back panels, brackets, and condenser tubes in home appliances such as air conditioners and washing machines, providing strong material support for improving the durability, safety, and overall quality of these appliances.

[0003] When Chalco Zinc Aluminum Magnesium is applied in the field of home appliances, two important issues need to be resolved. One is that it must have color to meet the color requirements of different scenarios, and the other is that it must be acid and alkali resistant to meet the practical requirements of home scenarios, because home appliances, especially kitchen appliances, are very likely to come into contact with edible acetic acid and alkaline cleaning agents.

[0004] The existing technology for coloring and functionalizing aluminum-zinc-aluminum-magnesium steel is to use a traditional primer + topcoat coating technology, such as powder spraying or roller coating, after the steel coil has undergone a chrome-free fingerprint-resistant pre-treatment. The main problems faced by this process are:

[0005] 1. High application cost: the paint film usually reaches tens of microns, so a large amount of primer and topcoat is required;

[0006] 2. The process is relatively complex: it contains two processes and the process failure rate is high;

[0007] 3. Heavy pollution: Both the powder spraying process and the roller coating process will cause serious environmental pollution (dust pollution and solvent pollution) and personnel health hazards (inhalation dust hazards and inhalation solvent hazards).

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

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

[0010] In response to the deficiencies in the prior art, the present invention provides an acid- and alkali-resistant, chromium-free, fingerprint-resistant color coating specifically for zinc, aluminum, and magnesium. The coating has excellent acid and alkali resistance and fingerprint resistance, as well as good color stability and adhesion to zinc, aluminum, and magnesium substrates. It does not contain harmful chromium elements, meets environmental protection requirements, and has extremely low cost. The color fingerprint-resistant film is only 5-10 microns, and the process is simpler and more efficient, eliminating two subsequent coating processes, resulting in less pollution and no dust or solvent hazards.

[0011] To achieve the above object, 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 and protective properties for coatings.

[0013] Silicone-modified polyurethane resin: 10%-30%. Silicone-modified polyurethane resin combines the weather resistance and low surface energy of silicone with the high wear resistance and flexibility of polyurethane. It can improve the coating's fingerprint resistance and chemical resistance, while also improving the coating's flexibility and impact resistance.

[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%. Select pigments with excellent acid and alkali resistance, such as certain organic pigments and inorganic pigments with special surface treatment, to give the paint rich colors while ensuring color stability in acid and alkali environments.

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

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

[0018] Defoamer: 0.1%-1%. Defoamer is used to eliminate bubbles generated during the preparation and application of coatings to ensure the quality of the coating film.

[0019] Leveling agent: 0.1%-1%. Leveling agent can improve the fluidity of the coating, make the coating surface smoother and flatter, and enhance the decorative effect of the coating.

[0020] Deionized water: the balance. As the solvent of the coating, it allows the various components to be evenly dispersed to form a stable coating system.

[0021] Preparation method:

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

[0023] Step 2: Slowly add the dispersant into the reactor and stir evenly for 15-30 minutes.

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

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

[0026] Step 5: Add nano-titanium dioxide sol and stir evenly for 15-30 minutes.

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

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

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

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

[0031] 1. The coating of the present 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, silicone-modified polyurethane resin, and nano-titanium dioxide sol, and optimizing their ratios, the coating film formed by the coating has excellent acid and alkali resistance, can effectively protect zinc, aluminum, and magnesium substrates from corrosion in acidic and alkaline environments, and extend their service life.

[0032] 2. The low surface energy characteristics of the silicone-modified polyurethane resin of the present invention and the synergistic effect of the coating formula make the coating surface have good fingerprint resistance, reduce fingerprint residue, maintain surface beauty, and be easy to clean.

[0033] 3. The stability of the acid and alkali resistant pigments and the coating system selected in the present invention ensures the stability of the coating color under different environmental conditions and meets the demand for long-term beautiful product appearance.

[0034] 4. The use of the silane coupling agent of the present invention enhances the adhesion between the coating and the zinc-aluminum-magnesium substrate, so that the coating can be firmly attached to the surface of the substrate and is not easy to fall off, thereby improving the protective effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart for preparing an acid-resistant and alkali-resistant chromium-free and fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to the present invention;

[0036] Figure 2 This is a comparison diagram of the embodiments of the present invention. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Example 1

[0039] See also Figure 1 and Figure 2 In this embodiment, an acid-resistant, alkali-resistant, chromium-free, fingerprint-resistant color coating specifically for zinc, aluminum, and magnesium includes the following components by weight percentage:

[0040] 40% water-based acrylic resin, the glass transition temperature of the water-based acrylic resin is 20°C, and the number average molecular weight is 50,000;

[0041] 20% organosilicon-modified polyurethane resin, the mass fraction of organosilicon in the organosilicon-modified polyurethane resin is 5%, and the tensile strength of the resin is 10 MPa and the elongation at break is 200%;

[0042] 10% nano-titanium dioxide sol, wherein the average particle size of titanium dioxide particles in the nano-titanium dioxide sol is 10 nm, and the solid content of the sol is 20%;

[0043] 10% acid and alkali resistant pigment, which is an inorganic pigment with surface silanization treatment and an oil absorption of 30g / 100g;

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

[0045] Dispersant 1%, the dispersant is a high molecular weight dispersant with an HLB value of 10;

[0046] Defoamer 0.5%, the defoamer is a polyether modified silicone defoamer with an active ingredient content of 95%;

[0047] Leveling agent 0.5%, the leveling agent is an acrylic leveling agent, and its minimum film-forming temperature in the coating is 10°C;

[0048] Deionized water 15%.

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

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

[0051] S2. Slowly add the dispersant into the reactor and stir evenly for 15 minutes;

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

[0053] S4, adding water-based acrylic resin and silicone-modified polyurethane resin into the reactor in sequence, increasing the stirring speed to 400 r / min, and stirring for 30 min;

[0054] S5, add nano titanium dioxide sol, stir evenly, stirring time is 15min;

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

[0056] S7, add defoamer and leveling agent in sequence, stir evenly, stirring for 15 minutes;

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

[0058] After the paint is applied on the zinc-aluminum-magnesium substrate, the coating film thickness is 18 μm. At an ambient temperature of 50°C, the paint has a surface drying time of 45 minutes and a thorough drying time of 20 hours.

[0059] Coating properties:

[0060] Acid and alkali resistance: The zinc-aluminum-magnesium sample panels coated with the coating of the present invention were immersed in a 5% hydrochloric acid solution and a 5% sodium hydroxide solution, respectively. After immersion at room temperature for 72 hours, there was no obvious corrosion, discoloration, blistering, etc. on the surface of the sample panels, and the coating film adhesion still reached level 0 (tested in accordance with GB / T9286-1998 "Scratch test for paint and varnish films" standard).

[0061] Fingerprint resistance: Press the surface of the zinc-aluminum-magnesium sample coated with the coating of the present invention with your finger, and then gently wipe it with a clean soft cloth. No obvious fingerprint marks are found on the sample surface, and the surface gloss is well restored after wiping, with the gloss difference from the unpressed area being less than 5% (gloss test is performed in accordance with relevant industry standards).

[0062] Color stability: After the zinc-aluminum-magnesium sample coated with the coating of the present invention is exposed to the sun outdoors for 6 months, or tested in an artificial accelerated aging test chamber for 1000 hours in accordance with the standard GB / T1865-2009 "Artificial Weathering and Artificial Radiation Exposure of Paints and Varnishes (Filtered Xenon Arc Radiation)", the surface color change of the sample is ΔE*ab≤3 (color difference calculated according to the CIELAB color space).

[0063] Adhesion: tested in accordance with GB / T9286-1998 "Scratch test for paint and varnish films", the coating adhesion reaches level 0, the coating is tightly bonded to the zinc-aluminum-magnesium substrate and is not easy to fall off.

[0064] After testing, the coating has good acid and alkali resistance after being applied to the zinc-aluminum-magnesium sample. After immersion in 5% hydrochloric acid solution and 5% sodium hydroxide solution for 72 hours, there is no obvious change on the surface of the sample, and the coating adhesion is level 0; the fingerprint resistance is excellent, the fingerprint marks are not obvious, and the gloss is well restored after wiping; the color stability is high, and after 6 months of outdoor exposure, the color change ΔE*ab=2; the adhesion reaches level 0.

[0065] Example 2

[0066] See also Figure 1 and Figure 2 In this embodiment, an acid-resistant, alkali-resistant, chromium-free, fingerprint-resistant color coating specifically for zinc, aluminum, and magnesium includes the following components by weight percentage:

[0067] 35% water-based acrylic resin, the glass transition temperature of the water-based acrylic resin is 30°C, and the number average molecular weight is 100,000;

[0068] 25% of silicone-modified polyurethane resin, the mass fraction of silicone in the silicone-modified polyurethane resin is 10%, and the tensile strength of the resin is 15 MPa and the elongation at break is 240%;

[0069] Nano-titanium dioxide sol 12%, the average particle size of titanium dioxide particles in the nano-titanium dioxide sol is 50nm, and the solid content of the sol is 40%;

[0070] 12% of acid and alkali resistant pigments, which are inorganic pigments with surface silanization treatment and an oil absorption of 25g / 100g;

[0071] Silane coupling agent 4%, the silane coupling agent is a silane coupling agent containing epoxy group;

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

[0073] Defoamer 0.8%, the defoamer is a polyether modified silicone defoamer with an active ingredient content of 97%;

[0074] Leveling agent 0.7%, the leveling agent is an acrylic leveling agent, and its minimum film-forming temperature in the coating is 20°C;

[0075] Deionized water 9%.

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

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

[0078] S2. Slowly add the dispersant into the reactor and stir evenly for 30 min;

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

[0080] S4, adding water-based acrylic resin and silicone-modified polyurethane resin into the reactor in sequence, increasing the stirring speed to 600 r / min, and stirring for 60 min;

[0081] S5, add nano titanium dioxide sol, stir evenly, stirring time is 30min;

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

[0083] S7, add defoamer and leveling agent in sequence, stir evenly, stirring for 30 minutes;

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

[0085] After the paint is coated on the zinc-aluminum-magnesium substrate, the coating film thickness is 22μm. At an ambient temperature of 50℃-60℃, the surface drying time of the paint is 50min and the actual drying time is 22h.

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

[0087] Example 3

[0088] See also Figure 1 and Figure 2 In this embodiment, an acid-resistant, alkali-resistant, chromium-free, fingerprint-resistant color coating specifically for zinc, aluminum, and magnesium includes the following components by weight percentage:

[0089] 45% water-based acrylic resin, the glass transition temperature of the water-based acrylic resin is 50°C, and the number average molecular weight is 150,000;

[0090] 15% of silicone-modified polyurethane resin, the mass fraction of silicone in the silicone-modified polyurethane resin is 15%, and the tensile strength of the resin is 20 MPa and the elongation at break is 280%;

[0091] Nano-titanium dioxide sol 8%, the average particle size of titanium dioxide particles in the nano-titanium dioxide sol is 30nm, and the solid content of the sol is 32%;

[0092] 8% acid and alkali resistant pigment, which is an inorganic pigment with surface silanization treatment and an oil absorption of 28g / 100g;

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

[0094] Dispersant 0.8%, the dispersant is a high molecular weight dispersant with an HLB value of 13;

[0095] Defoamer 0.6%, the defoamer is a polyether modified silicone defoamer with an active ingredient content of 98%;

[0096] Leveling agent 0.6%, the leveling agent is an acrylic leveling agent, and its minimum film-forming temperature in the coating is 18°C;

[0097] Deionized water 20%.

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

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

[0100] S2. Slowly add the dispersant into the reactor and stir evenly for 28 minutes;

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

[0102] S4, adding water-based acrylic resin and silicone-modified polyurethane resin to the reactor in sequence, increasing the stirring speed to 550 r / min, and stirring for 55 min;

[0103] S5, add nano titanium dioxide sol, stir evenly, stirring time is 28min;

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

[0105] S7, add defoamer and leveling agent in sequence, stir evenly, stirring for 26 minutes;

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

[0107] After the paint is applied on the zinc-aluminum-magnesium substrate, the coating film thickness is 15 μm. At an ambient temperature of 55°C, the surface drying time is 40 minutes and the actual drying time is 18 hours.

[0108] The coating performance testing method is the same as that in Example 1. After testing, the coating film formed by the coating has reliable acid and alkali resistance. After immersion in 5% hydrochloric acid and 5% sodium hydroxide solution for 72 hours, the sample has no abnormality and the coating film adhesion is level 0; the fingerprint resistance performance is in line with expectations; the color stability is high, and after outdoor exposure and artificial accelerated aging tests, the color changes are within the standard range; the adhesion reaches level 0.

[0109] Example 4

[0110] In this embodiment, an acid-resistant, alkali-resistant, chromium-free, fingerprint-resistant color coating specifically for zinc, aluminum, and magnesium includes the following components by weight percentage:

[0111] Water-based acrylic resin: 30%. The glass transition temperature of the water-based acrylic resin is 50°C and the number average molecular weight is 150,000.

[0112] Silicone-modified polyurethane resin: 30%. The mass fraction of silicone in the silicone-modified polyurethane resin is 5%, 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 titanium dioxide particles in the nano-titanium dioxide sol is 10nm, and the solid content of the sol is 20%.

[0114] Acid and alkali resistant pigment: 15%. Acid and alkali resistant pigment is an inorganic pigment that has undergone surface silanization treatment, and the oil absorption of the pigment 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 high molecular weight dispersant with an HLB value of 10.

[0117] Defoamer: 1%. The defoamer is a polyether-modified silicone defoamer with an active 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°C.

[0119] Deionized water: 1%.

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

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

[0122] Step 2: Slowly add the dispersant into the reactor and stir evenly for 30 minutes.

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

[0124] Step 4: Add water-based acrylic resin and silicone-modified polyurethane resin into the reactor in sequence, increase the stirring speed to 600 r / min, and stir for 60 minutes to fully mix the resin and pigment slurry.

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

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

[0127] Step 7: Add defoamer and leveling agent in sequence and stir evenly 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 paint is applied on the zinc-aluminum-magnesium substrate, the coating film thickness is 30 μm. At an ambient temperature of 50°C, the surface drying time is 48 minutes and the actual drying time is 20 hours.

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

[0131] Example 5

[0132] In this embodiment, an acid-resistant, alkali-resistant, chromium-free, fingerprint-resistant color coating specifically for zinc, aluminum, and magnesium includes the following components by weight percentage:

[0133] Water-based acrylic resin: 60%. The glass transition temperature of the water-based acrylic resin is 50°C and the number average molecular weight is 50,000.

[0134] Silicone-modified polyurethane resin: 10%. The mass fraction of silicone in the silicone-modified polyurethane resin is 20%, 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 50nm, and the solid content of the sol is 40%.

[0136] Acid and alkali resistant pigment: 5%. Acid and alkali resistant pigment is an inorganic pigment that has undergone surface silanization treatment and has an oil absorption of 25g / 100g.

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

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

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

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

[0141] Deionized water: 18.3%.

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

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

[0144] Step 2: Slowly add the dispersant into the reactor and stir evenly for 15 minutes.

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

[0146] Step 4: Add water-based acrylic resin and silicone-modified polyurethane resin into the reactor in sequence, increase the stirring speed to 400 r / min, and stir for 30 minutes to fully mix the resin and pigment slurry.

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

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

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

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

[0151] After the paint is coated on the zinc-aluminum-magnesium substrate, the coating film thickness is 10 μm. At an ambient temperature of 50°C, the surface drying time of the paint is 1 hour and the actual drying time is 24 hours.

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

[0153] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

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

Claims

1. A chromium-free, fingerprint-resistant color coating specially designed for zinc, aluminum, and magnesium, characterized in that: Calculated by weight percentage, it includes the following components: Water-based acrylic resin 30-60%; Silicone modified polyurethane resin 10-30%; Nano titanium dioxide sol 5-15%; Acid and alkali resistant pigments 5-15%; Silane coupling agent 1-5%; Dispersant 0.5-2%; Defoaming agent 0.1-1%; Leveling agent 0.1-1%; Deionized water balance.

2. The acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to claim 1, characterized in that: The waterborne acrylic resin has a glass transition temperature of 20° C.-50° C. and a number average molecular weight of 50,000-150,000.

3. The acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to claim 1, characterized in that: The mass fraction of silicone in the silicone-modified polyurethane resin is 5%-20%, and the tensile strength of the resin is greater than 10 MPa and the elongation at break is greater than 200%.

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

5. The acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to claim 1, characterized in that: The acid-resistant and alkali-resistant pigment is an inorganic pigment that has been surface-silanized, and the oil absorption of the pigment is less than 30g / 100g. The silane coupling agent is one or more silane coupling agents containing amino, epoxy or methacryloxy groups.

6. The acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to claim 1, characterized in that: The dispersant is a polymer dispersant with an HLB value of 10-15.

7. The acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to claim 1, characterized in that: The defoaming agent is a polyether-modified organic silicon defoaming agent, and the effective component content thereof is greater than 95%. The leveling agent is an acrylic leveling agent, and the minimum film-forming temperature thereof in the coating is 10° C.-20° C.

8. The acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to any one of claims 1 to 7, characterized in that: The following preparation steps are also included: S1. Add deionized water to the reactor, start stirring, and control the speed at 200-400r / min; S2. Slowly add the dispersant into the reactor and stir evenly for 15-30 minutes; S3. Add acid and alkali resistant pigment and continue stirring for 30-60 minutes to form a uniform pigment slurry; S4, adding water-based acrylic resin and silicone-modified polyurethane resin to the reactor in sequence, increasing the stirring speed to 400-600 r / min, and stirring for 30-60 min; S5, add nano titanium dioxide sol, stir evenly, stirring time is 15-30min; S6. Slowly add the silane coupling agent dropwise to the reactor while reducing the stirring speed to 200-300 r / min. The addition time is 15-30 min. After the addition is complete, continue stirring for 30-60 min. S7. Add 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 a finished coating.

9. The acid-resistant and alkali-resistant chromium-free fingerprint-resistant color coating specifically for zinc, aluminum and magnesium according to claim 8, characterized in that: After the coating is coated on a zinc-aluminum-magnesium substrate, the coating film formed has a thickness of 10 μm-30 μm. At an ambient temperature of 50° C.-60° C., the surface drying time of the coating is less than 1 hour, and the actual drying time is less than 24 hours.

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