A high-hardness, scratch-resistant two-component polyurethane flat black one-coat paint, a preparation method and applications thereof

Abstract

This invention provides a high-hardness, scratch-resistant, water-based two-component polyurethane matte black base coat, its preparation method, and its application. The two-component matte black base coat comprises component A and component B. Component A includes a water-based hydroxyl polyurethane acrylic dispersion, a water-based hydroxyl acrylic dispersion, hydroxyl microspheres, a high-pigment carbon black paste, water-based additives, a film-forming aid, and water. Component B includes a curing agent and a diluent. The matte black base coat of this invention exhibits high hardness, scratch resistance, and chemical resistance. It also demonstrates excellent workability, activation period, and surface finish, making it suitable for water-based two-component matte black base coat systems. It is particularly suitable for decorative and protective applications in the plastic paint industry, such as 3C consumer electronics, where extremely stringent requirements for abrasion resistance, scratch resistance, and chemical resistance are necessary.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint, its preparation method, and its application. Background Technology

[0002] With the demands of end-user brands, the implementation of the "3060" plan, and the proposal of a low-energy, circular economy, water-based coatings have become synonymous with environmental protection. Due to the environmental requirements of consumers using 3C electronic products, the coatings on these products are generally designed to be thin-film with excellent adhesion and physical properties. Matte black coatings are widely used on 3C product casings and are very popular with consumers. However, the complex and varied usage scenarios of 3C electronic products place high demands on the scratch resistance and hardness of matte black paint. Currently, most commercially available products use oil-based coatings, which not only fail to meet the environmental trend but also negatively impact the user experience and overall impression of product quality. While some water-based matte black paint products have appeared on the market, they cannot replace similar oil-based products in terms of hardness and scratch resistance.

[0003] In addition, traditional 3C plastic coatings are mainly multi-layer systems, usually including a three-layer system of primer, intermediate coat and topcoat, or a two-layer system of primer and topcoat. This type of traditional coating requires the primer to be applied first, and after the primer dries, the next coating can be applied. The construction method is complicated, time-consuming and labor-intensive, and has high VOC.

[0004] Currently, in the plastic coatings industry, the performance requirements for coating films in 3C consumer electronics (laptops) are the highest, and the industry regulations are the most stringent. According to industry practice, the performance indicators and regulatory requirements for water-based two-component polyurethane matte black base and topcoat coatings largely adopt the performance indicators of a representative computer brand's multi-coating system within the laptop industry, as detailed in Table 1.

[0005] Table 1 Performance Requirements of Matte Black Paint on a Representative Laptop Brand in the Laptop Industry

[0006]

[0007]

[0008] Currently, in the plastic paint industry, most water-based two-component acrylic polyurethane matte black paints require a large amount of matting powder and wax emulsion for matting. Although the final paint film has low gloss, its blackness is insufficient (the L value is not low enough), its scratch resistance is very poor, and its adhesion is also poor. This prevents the widespread application of water-based two-component acrylic polyurethane matte black base and topcoat paints.

[0009] For example, CN 114672209 B discloses "a high-performance matte black paint and its preparation method". The matte black paint obtained has excellent workability, a delicate and smooth paint film appearance, and can withstand more than 70 alcohol wipes. It has a grade 0 adhesion after aging and good adhesion and water resistance to the substrate. However, it has problems such as insufficient hardness and scratch resistance, and insufficient blackness.

[0010] CN 112409900 A discloses "a scratch-resistant matte black PU coating and its preparation method". The resulting matte black PU coating has good scratch resistance, excellent cosmetic resistance, and good recoatability. However, the formula mainly uses a mixture of water-soluble resin KN9160A and water-based resin PU356, which has significant deficiencies in VOCs and stability. Furthermore, the formula uses various functional additives such as adhesion promoters, matting agents, and abrasion-resistant agents, which leads to problems such as difficult application, low stability, and low formula tolerance.

[0011] In conclusion, with the rapid pace of economic development, the intensification of the greenhouse effect, and the increasing awareness of environmental protection, it is imperative to develop a water-based two-component polyurethane matte black base and topcoat paint that is highly hard, scratch-resistant, and has excellent durability. Summary of the Invention

[0012] In view of this, and addressing the industry problems encountered during the transition from matte black plastic paint systems to water-based coatings (hardness, matte but not black), the purpose of this invention is to provide a high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint. This coating is easy to use and simple to apply, and the coating has excellent appearance, blackness and matteness, hardness, adhesion, and other properties. It also meets the current RoHS directive and future restrictions on high-potential substances (BCS, benzene compounds, etc.), effectively accelerating the transition to water-based coatings and conforming to the industry's requirements for "low-carbon" green development.

[0013] Another object of the present invention is to provide a method for preparing this high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base coat.

[0014] Another object of the present invention is to provide the application of this high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base coat.

[0015] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0016] A high-hardness, scratch-resistant, water-based two-component polyurethane matte black base and top coat comprises component A and component B in a mass ratio of 6 to 10:1; wherein, based on the total mass of component A, component A comprises the following components by mass percentage:

[0017]

[0018] Based on the total mass of component B, component B comprises the following components by mass percentage:

[0019] Hardener 65-85%, preferably 70-80%,

[0020] Use a diluent of 15-35%; preferably 20-30%.

[0021] The aqueous hydroxyl polyurethane acrylic dispersion is a core-shell structured aqueous hydroxyl polyurethane acrylic dispersion with a hydroxyl content of 1.0-2.2%, preferably from Wanhua Chemical. 4288、

[0022] 4233、 At least one of 6510.

[0023] The aqueous hydroxyacrylic acid dispersion is a core-shell structured aqueous hydroxyacrylic acid dispersion with a hydroxyl content of 2.5-4.2%, preferably from Wanhua Chemical. 2032 2706

[0024] 2042, Covestro One or more of A2770.

[0025] The hydroxyl microspheres are aqueous hydroxyl microspheres with a core-shell structure, wherein the core is made of a component including hard monomers, hydrophilic monomers, and functional monomers, and the shell is made of a component including hard monomers, hydroxyl monomers, and hydrophilic monomers; preferably, the hydroxyl microspheres are prepared by free radical emulsion polymerization; more preferably, the preparation method of the hydroxyl microspheres includes:

[0026] 1) Preparation of the core layer of hydroxyl microspheres:

[0027] Under a nitrogen atmosphere, weigh 40-60% water by mass and place it in a polymerization container, then heat it to 80-85°C. Mix 10-20% water, 0.5-2% emulsifier I, 5-10% hydrophilic monomer I, 15-35% hard monomer I, and 1-3% functional monomer to obtain a pre-emulsion. Weigh 2-5% initiator and add it to the pre-emulsion. Add the pre-emulsion to the polymerization container and keep it at 80-85°C for 0.5-1 h. Cool it to room temperature and filter to obtain the hydroxyl microsphere core layer.

[0028] 2) Preparation of hydroxyl microspheres:

[0029] Under a nitrogen atmosphere, weigh out 55-75% water, 0.1-1% initiator, 10-18% hydroxyl microsphere core layer, 8-12% hard monomer II, 1-5% hydrophilic monomer II, 1.5-3% hydroxyl monomer, and 0.2-0.6% emulsifier II by mass fraction and add them to a polymerization container. React at 80-85℃ for 0.5-2 hours. Then add 2-5% neutralizer and 0.1-0.5% initiator and keep at this temperature for 0.5-1 hours to obtain hydroxyl microspheres.

[0030] Emulsifier I and Emulsifier II are ionic emulsifiers, preferably each independently selected from sodium dodecyl sulfate, sodium p-styrene sulfonate, and stearate; and / or

[0031] The hydrophilic monomer I and hydrophilic monomer II are each independently selected from methacrylic acid and acrylic acid; and / or

[0032] Hard monomer I and hard monomer II are each independently selected from styrene, methyl methacrylate, ethyl methacrylate, and acrylonitrile; and / or

[0033] The functional monomer is selected from acrylamide and methacrylamide; and / or

[0034] The hydroxyl monomer is selected from any one of hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate; and / or

[0035] The neutralizing agent is selected from ammonia, triethanolamine, or...

[0036] The initiator is a redox system, selected from either ammonium persulfate-tert-butyl hydroperoxide or sodium persulfate-tert-butyl hydroperoxide.

[0037] The water-based additives include at least one of wetting agents, leveling agents, defoamers, neutralizing agents, and thickeners; preferably, the wetting agent is selected from any one of Tego 270, Tego KL 245, and Tego 346, the leveling agent is selected from any one of BYK333, BYK381, and Tego Glide100, the defoamer is selected from any one of Tego 902W, TEGO Foamex825, and Tego 1488, the thickener is selected from any one of Wanhua U505, U905, and U605, and the neutralizing agent is selected from any one of DEMA and AMP95.

[0038] The film-forming aid is one or more of dipropylene glycol methyl ether, dipropylene glycol butyl ether, and dipropylene glycol dimethyl ether.

[0039] The curing agent is a water-based isocyanate curing agent, preferably a sulfonate-modified isocyanate curing agent, such as a sulfonate-modified HDI trimer, like that from Wanhua Chemical. 268.

[0040] 270. One or more of 278.

[0041] The diluent is one or more of ethylene glycol butyl ether acetate (BGA), propylene glycol diacetate (PGDA), and propylene glycol methyl ether acetate (PMA).

[0042] In another aspect, the present invention provides a method for preparing the above-mentioned high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base coat, comprising the following steps:

[0043] (1) Mix the waterborne hydroxyl polyurethane acrylic dispersion, waterborne hydroxyl acrylic dispersion, hydroxyl microspheres, water, high pigment carbon black paste, waterborne additives, and film-forming aids in proportion, and filter to obtain component A;

[0044] (2) Mix the curing agent and diluent evenly to obtain component B;

[0045] (3) Mix components A and B according to the metering ratio, add water, adjust the viscosity, preferably adjust the viscosity of Zein-3 cup to 15-20s, and filter to obtain the high hardness scratch-resistant water-based two-component polyurethane matte black base and top coat.

[0046] In another aspect of the present invention, the aforementioned high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base coat is used in the decorative and protective fields of the plastic paint industry, preferably in the 3C consumer electronics field.

[0047] The water-based two-component polyurethane matte black base and topcoat paint with high hardness, scratch resistance, and excellent durability provided by this invention has the following advantages compared with the prior art:

[0048] (1) The water-based hydroxy acrylic dispersion added to the matte black base and top coat of the present invention has extremely high hardness and toughness, excellent chemical resistance and other characteristics, which can improve the hardness, scratch resistance and chemical resistance of the paint film.

[0049] (2) The water-based hydroxyl polyurethane acrylic dispersion added to the matte black base coat of the present invention contains more internal crosslinking and self-crosslinking, and there is an interpenetrating network structure between the chain segments. It has a large molecular weight and high acid value, which can balance the rigidity and flexibility of the final paint film. At the same time, it can also reduce the gloss of the final paint film and the compatibility of the black paste, which is beneficial to the adhesion, hardness and matte / blackness of the paint film.

[0050] (3) The hydroxyl microspheres added to the matte black base and top paint of the present invention can replace traditional matting powder and other fillers, and can undergo cross-linking reaction, which can reduce the gloss of the paint film and improve the density of the paint film, which is conducive to gloss stability, hardness, scratch resistance and durability. Detailed Implementation

[0051] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention. All other embodiments obtained based on the overall concept of the embodiments of the present invention without inventive step are within the protection scope of the present invention.

[0052] A high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and top coat comprises component A and component B; wherein, based on the total mass of component A, component A comprises the following components by mass percentage:

[0053] The aqueous hydroxyl polyurethane acrylic dispersion comprises 40% to 80%, including but not limited to 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80%, preferably 45% to 70%.

[0054] The aqueous hydroxyacrylic acid dispersion is 5% to 35%, for example, including but not limited to 5%, 10%, 15%, 20%, 25%, 30%, and 35%, preferably 10% to 30%;

[0055] Hydroxyl microspheres: 1% to 6%, including but not limited to 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, preferably 1% to 4%;

[0056] The deionized water content is 0.1% to 6%, including but not limited to 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, and 6%, preferably 0.5% to 5%.

[0057] The high-pigment carbon black paste is 6% to 18%, for example, including but not limited to 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, preferably 8% to 14%;

[0058] The aqueous additive is 0.5% to 2.5%, for example, including but not limited to 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, and 2.5%, preferably 0.7% to 2%.

[0059] The film-forming aid is 0.2% to 2%, for example, including but not limited to 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, and 2%, preferably 0.5% to 1.5%.

[0060] Based on the total mass of component B, component B comprises the following components by mass percentage:

[0061] The curing agent is 65% to 85%, for example, including but not limited to 65%, 70%, 75%, 80%, and 85%, preferably 70% to 80%;

[0062] The dilution solvent is 15% to 35%, for example, including but not limited to 15%, 20%, 25%, 30%, and 35%, preferably 20% to 30%;

[0063] The mass ratio of component A to component B is 6 to 10:1, for example, including but not limited to 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, and 10:1.

[0064] The aqueous hydroxyl polyurethane acrylic dispersion of the present invention is an aqueous hydroxyl polyurethane acrylic dispersion with a core-shell structure, such as that from Wanhua Chemical. 4288、 4233、 6510, etc., have a hydroxyl content of 1.0 to 2.2% (mass content), such as 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, etc.

[0065] The waterborne hydroxyl polyurethane acrylic dispersion of this invention, compared with conventional hydroxyl acrylic / hydroxyl polyurethane or polyurethane, exhibits superior properties. Conventional low-gloss matte PU has poor scratch resistance and is prone to fingernail scratches, especially when paired with a black base, making scratch resistance even more challenging. Conventional hydroxyl acrylic resins have fast reaction speeds and high crosslinking densities, offering good chemical resistance, weather resistance, and recoatability, but require the addition of large amounts of matting agents, resulting in poor scratch resistance and irreversible scratches on the paint film. PU / OH-PUD resin paint films have a porous structure and low crosslinking density, exhibiting excellent fingernail scratch resistance, but suffer from numerous drawbacks in application, such as insufficient hardness and poor chemical resistance. In contrast, the waterborne hydroxyl polyurethane acrylic dispersion polymer used in this invention contains more internal crosslinks and self-crosslinks, with an interpenetrating network structure between PU and PA, eliminating compatibility issues. Its large molecular weight and high acid value balance the rigidity and flexibility of the paint film, while also reducing the final gloss and compatibility with the black pigment, thus benefiting paint film adhesion and the matte / blackness of the paint film appearance.

[0066] The aqueous hydroxyacrylic acid dispersion of the present invention is an aqueous hydroxyacrylic acid dispersion with a core-shell structure, such as that from Wanhua Chemical. 2032 2706 2042, Covestro A2770 and others have a hydroxyl content of 2.5% to 4.2% (mass content), such as 2.5%, 2.8%, 3%, 3.3%, 3.6%, 4%, 4.2%, etc.

[0067] The aqueous hydroxyl acrylic dispersion of the present invention has a moderate hydroxyl content. After cross-linking with the curing agent, it has a high cross-linking density, but the internal stress is released slowly, which is beneficial to the adhesion and the final paint film is hard and tough.

[0068] The hydroxyl microspheres of the present invention are aqueous hydroxyl microspheres with a core-shell structure. For example, the core layer of the hydroxyl microsphere is formed by emulsion polymerization of components including hard monomers, hydrophilic monomers, and functional monomers, and the shell layer is formed by emulsion polymerization of components including hard monomers, hydroxyl monomers, and hydrophilic monomers. This free radical emulsion polymerization method is a conventional method in the art and is not particularly limited. For example, an exemplary preparation method includes:

[0069] 1) Preparation of the core layer of hydroxyl microspheres:

[0070] Under a nitrogen atmosphere, weigh 40–60% deionized water (e.g., 40%, 45%, 50%, 55%, 60%, etc.) by mass fraction and place it in a polymerization container, then heat to 80–85°C (e.g., 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, etc.); take 10–20% water (e.g., 10%, 15%, 20%, etc.), 0.5–2% emulsifier I (e.g., 0.5%, 1%, 1.5%, 2%, etc.), 5–10% hydrophilic monomer I (e.g., 5%, 6%, 7%, 8%, 9%, 10%, etc.), and 15–35% hard monomer I (e.g., 15%, 20%, 25%, 30%, 35%). Mix 1% to 3% of functional monomers (e.g., 1%, 1.5%, 2%, 2.5%, 3%, etc.) to obtain a pre-emulsion; weigh 2% to 5% of initiator (e.g., 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.) and ammonium persulfate (NH4)2S2O8 and add them to the pre-emulsion. Add the pre-emulsion to a polymerization container and keep it at 80 to 85°C (e.g., 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, etc.) for 0.5 to 1 hour (e.g., 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, 1 hour, etc.) until it cools to room temperature. Filter to obtain the hydroxyl microsphere core layer.

[0071] 2) Preparation of hydroxyl microspheres:

[0072] Under a nitrogen atmosphere, weigh out 55–75% deionized water (e.g., 55%, 60%, 65%, 70%, 75%, etc.), 0.1–1% initiator (e.g., 0.1%, 0.2%, 0.5%, 1%, etc.), sodium persulfate (Na)₂S₂O₈, and 10–18% hydroxyl microsphere core layer (e.g., 10%, 11%, 12%, 13%) by mass fraction.

[0073] 14%, 15%, 16%, 17%, 18%, etc.), 8-12% hard monomer II (e.g., 8%, 9%, 10%)

[0074] 11%, 12%, etc.), 1-5% hydrophilic monomer II (e.g., 1.5%, 2%, 2.5%, 3%, 3.5%, 4%),

[0075] 4.5%, 5%, etc.), 1.5-3% hydroxyl monomers (e.g., 1.5%, 2%, 2.5%, 3%, etc.), and 0.2-0.6% emulsifier II (e.g., 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, etc.) are added to a polymerization container and reacted at 80-85℃ (e.g., 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, etc.) for 0.5-2 hours (e.g., 0.5 hours, 2.5%).

[0076] After 0.8h, 1h, 1.8h, 2h, etc., add 2-5% neutralizing agent (e.g., 2%, 2.5%, 3%).

[0077] 3.5%, 4%, 4.5%, 5%, etc.), and 0.1%–0.5% initiators (e.g., 0.1%, 0.2%, 0.3%).

[0078] 0.4%, 0.5%, etc.) tert-butyl hydroperoxide (TBHP) reaction, kept at temperature for 0.5–1 h (e.g., 0.5 h, 0.6 h, etc.).

[0079] Hydroxyl microspheres were obtained by incubation periods of 0.7h, 0.8h, 0.9h, 1h, etc.

[0080] Wherein, emulsifier I and emulsifier II are ionic emulsifiers, preferably any one of sodium dodecyl sulfate (SDS), sodium p-styrene sulfonate (SSS), and stearate; hydrophilic monomer I and hydrophilic monomer II are selected from any one of methacrylic acid (MAA) and acrylic acid (AA); hard monomer I and hard monomer II are selected from any one of styrene (St), methyl methacrylate (MMA), ethyl methacrylate (EMA), and acrylonitrile (AN); functional monomer is selected from any one of acrylamide (AM) and methacrylamide (MAM); hydroxyl monomer is selected from any one of hydroxyethyl methacrylate (HEMA), hydroxypropyl acrylate (HPA), and hydroxypropyl methacrylate (HPMA); neutralizing agent is selected from any one of ammonia and triethanolamine; and initiator is a redox initiator, selected from any one of ammonium persulfate (NH4)2S2O8-tert-butyl hydroperoxide (TBHP) and sodium persulfate (Na)2S2O8-tert-butyl hydroperoxide (TBHP).

[0081] The aqueous hydroxyl microspheres of this invention not only possess excellent hydrophilicity and stable dispersion in water, but also, when added to aqueous emulsions as a substitute for traditional matting agents and other fillers, can undergo cross-linking reactions with film-forming substances to form a three-dimensional network structure. This reduces the gloss of the paint film while improving its density, ensuring a smooth and delicate surface with stable gloss, and enhanced hardness and scratch resistance. The use of aqueous hydroxyl microspheres instead of matting agents in the composition of this invention achieves better results than matting agents and avoids the problem of poor scratch resistance.

[0082] The high-pigment carbon black paste of the present invention, also known as high-pigment carbon black water-based color paste, high-pigment carbon black paste, high-pigment black paste, etc., is a black paste used for coloring.

[0083] The water-based additives of this invention include at least one of wetting agents, leveling agents, defoamers, neutralizing agents, and thickeners, but are not limited thereto. Those skilled in the art can select appropriate additives according to the performance requirements of matte black paint, as is well known to them. For example, the wetting agent is selected from Tego 270, Tego KL 245, BYK346, etc.; the leveling agent is selected from BYK333, BYK381, Tego Glide 100, etc.; the defoamer is selected from Tego 902W, TEGO Foamex 825, Tego1488, etc.; the thickener is selected from Wanhua U505, U905, U605, etc.; and the neutralizing agent is selected from DEMA, AMP95, etc. There are no particular limitations on the amount of each additive added; for example, refer to the conventional addition amounts in the art, such as 0.10% to 1.00%.

[0084] The curing agent of this invention is an aqueous isocyanate curing agent, such as a sulfonate-modified isocyanate curing agent, which can be a sulfonate-modified HDI trimer, but is not limited to this. For example, Wanhua Chemical's... 268. 270. 278, etc.; it has good hand-stirring properties, low viscosity, good transparency, excellent water dispersibility, excellent early resistance and hardness establishment, and excellent compatibility and resistance, which can ensure the controllable reaction rate of the paint film hardness, resistance and hydroxy acrylic dispersion and avoid the occurrence of side reactions.

[0085] The present invention will be further explained and illustrated below through more specific embodiments, but these do not constitute any limitation.

[0086] <Testing Methods>

[0087] Adhesion: Use an adhesion cross-cutting tool to form approximately 100 grids of 1mm × 1mm size on the paint film. Adhere adhesion tape to the grid coating, then peel off the tape and observe the paint film peeling. ≥4B.

[0088] Dry film thickness (DFT): Push the dial of the Mikrotest thickness gauge forward to the maximum range, press the button, and the instrument will automatically perform the test.

[0089] Whiteness L: The whiteness of the paint film is measured by placing a colorimeter on the surface of the paint film.

[0090] Pencil hardness: Install pencils of different hardness on a pencil hardness tester, gently place them on the surface of the object to be tested, and advance them at a speed of 5-10 cm / s. Observe whether the sample surface is scratched.

[0091] Drying speed: At a dry film thickness of 15±3µm, level at room temperature for 3 minutes, then remove from the oven at 50℃ for 20 minutes. After cooling to room temperature, press firmly with your finger; no fingerprints should be left on the surface of the film.

[0092] Water resistance: When the paint film is immersed in water at 85℃ for 30 minutes / 2 hours, the paint film does not bubble, change color, or lose gloss, △E≤1.0, and the adhesion does not decrease, ≥4B.

[0093] High temperature and high humidity resistance: When the paint film is placed at 50℃ and RH 95% for 10 days, the paint film will not bubble or wrinkle, slight loss of gloss and discoloration are allowed, △E≤1.0, adhesion will not decrease, ≥4B.

[0094] RCA resistance test: Place the paint film on an RCA instrument and test it under a force of 175g. Count the number of times the paint film does not wear through. ≥80 times.

[0095] Chemical resistance test: Use a cotton gauze soaked in the specified solvent to wipe the substrate back and forth with a 500g weight and observe the number of times the substrate's paint film is damaged.

[0096] Artificial aging resistance: The substrate to be tested is placed in a QUV aging instrument (UVA, 1000h) and the color difference value ΔE and gloss loss rate are measured before and after. The gloss loss rate is ≤30% and ΔE is ≤3.0.

[0097] Activation period: Mix components A and B and add them to water. Adjust the viscosity of the Zein-3 cup to 15-20s and place it in a 35℃ oven. Test the viscosity every 0.5h. The viscosity fluctuation should be ≤2s within 2h.

[0098] Preparation Example 1: Preparation of hydroxyl microspheres a:

[0099] 1) Preparation of the core layer of hydroxyl microspheres:

[0100] The required mass percentage of substances in this reaction step is calculated based on 100%. Under a nitrogen atmosphere, weigh 40% deionized water according to the formula, place it in a container, and heat it to 85°C. Weigh 16.8%...

[0101] Water, 1% sodium dodecyl sulfate, 8% methacrylic acid, 30% methyl methacrylate, and 1.2% acrylamide were mixed evenly to obtain a pre-emulsion. 3% ammonium persulfate initiator was weighed and added to the pre-emulsion. The pre-emulsion was then added dropwise to a container and kept at 80°C for 1 hour. After cooling to room temperature, the mixture was filtered to obtain the hydroxyl microsphere core layer.

[0102] 2) Preparation of hydroxyl microspheres a:

[0103] The required mass percentages of substances in this reaction step are calculated based on 100%. Under a nitrogen atmosphere, weigh out the following components according to the formula: 66.6% deionized water, 0.6% sodium persulfate, 10% hydroxyl microsphere core layer, 11% methyl methacrylate, 4% methacrylic acid, and 2% methacrylic acid. Hydroxyethyl ester and 0.5% sodium p-styrene sulfonate (SSS) were reacted at 80°C for 2 hours. Then, 5% ammonia (25% by mass) and 0.3% tert-butyl hydrogen peroxide (10% by mass) were added sequentially and kept at this temperature for 30 minutes to obtain hydroxyl microspheres a.

[0104] Preparation Example 2: Preparation of hydroxyl microspheres b:

[0105] 1) Preparation of the core layer of hydroxyl microspheres:

[0106] The required mass percentages of substances in this reaction step are calculated based on 100%. Under a nitrogen atmosphere, 60% deionized water was weighed according to the formula and placed in a container, then heated to 80°C. 14.6% water, 0.7% sodium p-styrene sulfonate (SSS), 6% acrylic acid, 15% styrene, and 1.7% acrylamide were weighed and mixed thoroughly to obtain a pre-emulsion. 2% ammonium persulfate initiator was weighed and added to the pre-emulsion. The pre-emulsion was then added dropwise to a container and kept at 85°C for 1 hour. After cooling to room temperature, the mixture was filtered to obtain the hydroxyl microsphere core layer.

[0107] 2) Preparation of hydroxyl microspheres b:

[0108] The required mass percentages of the substances in this reaction step are calculated based on 100%. Under a nitrogen atmosphere, 70.7% deionized water, 0.3% sodium persulfate, 14% hydroxyl hollow microsphere core layer, 8% methyl methacrylate, 2% methacrylic acid, 1.5% hydroxypropyl acrylate, and 0.3% sodium dodecyl sulfate were weighed according to the formula. After reacting at 85°C for 1 hour, 3% ammonia (25% mass concentration) and 0.2% tert-butyl hydrogen peroxide (10% mass concentration) were added sequentially, and the mixture was kept at this temperature for 60 minutes to obtain hydroxyl microspheres b.

[0109] Preparation Example 3: Preparation of hydroxyl microspheres c:

[0110] 1) Preparation of the core layer of hydroxyl microspheres:

[0111] The required mass percentages of substances in this reaction step are calculated based on 100%. Under a nitrogen atmosphere, 50% deionized water was weighed according to the formula and placed in a container, then heated to 85°C. 10.8% water, 1.7% sodium p-styrene sulfonate (SSS), 10% methacrylic acid, 20% methyl methacrylate, and 3% methacrylamide were weighed and mixed thoroughly to obtain a pre-emulsion. 4.5% ammonium persulfate initiator was weighed and added to the pre-emulsion. The pre-emulsion was then added dropwise to a container and kept at 85°C for 1 hour. After cooling to room temperature, the mixture was filtered to obtain the hydroxyl microsphere core layer.

[0112] 2) Preparation of hydroxyl microspheres c:

[0113] The required mass percentages of the substances in this reaction step are calculated based on 100%. Under a nitrogen atmosphere, 57% deionized water, 0.8% sodium persulfate, 18% hydroxyl hollow microsphere core layer, 12% acrylonitrile, 3% methacrylic acid, 1.5% acrylic acid, 3% hydroxypropyl methacrylate (HPMA), and 0.4% sodium dodecyl sulfate were weighed according to the formula. After reacting at 80°C for 1.5 h, 4% triethanolamine (25% mass concentration) and 0.3% tert-butyl hydroperoxide (10% mass concentration) were added sequentially, and the mixture was kept at this temperature for 30 min to obtain hydroxyl microspheres c.

[0114] Example 1

[0115] Prepare paint component A according to the following formula. All the proportions below are by weight percentage.

[0116]

[0117]

[0118] Component B, by weight percentage of each raw material, includes: 80% water-based isocyanate curing agent. 278, 20% diluted propylene glycol methyl ether acetate (PMA).

[0119] Component A:Component B = 100:10.

[0120] The preparation method of a two-component polyurethane matte black base coat includes the following steps: First, add hydroxyl acrylic emulsion / hydroxyl acrylic polyurethane to a container, adjust the dispersion speed to 800 r / min, add hydroxyl microspheres a and stir for 20 min. Then add film-forming aid, defoamer, substrate wetting agent, neutralizer, leveling agent, thickener, water-based colorant and deionized water. After adding, maintain the dispersion speed and continue dispersion for 20 min. Filter through a 325 mesh screen to obtain component A. Dilute the curing agent in component B with a diluent. Mix the measured quantities of components A and B according to the designed ratio, add deionized water, and adjust the Zein-2 cup viscosity to approximately 17 s to obtain a water-based two-component polyurethane matte black base coat, which is ready for spraying.

[0121] Example 2

[0122] Prepare paint component A according to the following formula. All the proportions below are by weight percentage.

[0123]

[0124]

[0125] Component B, by weight percentage of each raw material, includes: water-based isocyanate curing agent. 270 accounts for 80%, and the diluent propylene glycol methyl ether acetate (PMA) accounts for 20%.

[0126] Component A:Component B = 100:16.5.

[0127] The preparation method of a two-component polyurethane matte black base and top coat includes the following steps: First, add hydroxyl acrylic emulsion / hydroxyl acrylic polyurethane to a container, adjust the dispersion speed to 800 r / min, add hydroxyl microspheres b and stir for 20 min. Then add film-forming aid, defoamer, substrate wetting agent, neutralizer, leveling agent, thickener, water-based colorant and deionized water. After adding all the ingredients, maintain the dispersion speed and continue dispersing for 20 min. Filter through a 325 mesh screen to obtain component A. Dilute the curing agent in component B with a diluent. Mix the measured quantities of components A and B according to the designed ratio, add deionized water, and adjust the Zein-2 cup viscosity to approximately 17 s to obtain a water-based two-component polyurethane matte black base and top coat, which is ready for spraying.

[0128] Example 3

[0129] Prepare paint component A according to the following formula. All the proportions below are by weight percentage.

[0130]

[0131]

[0132] Component B, by weight percentage of each raw material, includes: water-based isocyanate curing agent. 270% is 70%, and the diluent propylene glycol methyl ether acetate (PMA) accounts for 30%.

[0133] Component A:Component B = 100:14.

[0134] The preparation method of a two-component polyurethane matte black base and top coat includes the following steps: First, add hydroxyl acrylic emulsion / hydroxyl acrylic polyurethane to a container, adjust the dispersion speed to 800 r / min, add hydroxyl microspheres C and stir for 20 min. Then add film-forming aid, defoamer, substrate wetting agent, neutralizer, leveling agent, thickener, water-based colorant and deionized water. After adding, maintain the dispersion speed and continue dispersion for 20 min. Filter through a 325 mesh screen to obtain component A. Dilute the curing agent in component B with a diluent. Mix the measured quantities of components A and B according to the designed ratio, add deionized water, and adjust the Zein-2 cup viscosity to approximately 17 s to obtain a water-based two-component polyurethane matte black base and top coat, which is ready for spraying.

[0135] Example 4

[0136] Prepare paint component A according to the following formula. All the proportions below are by weight percentage.

[0137]

[0138] Component B, by weight percentage of each raw material, includes: water-based isocyanate curing agent. 278 accounts for 80%, and the diluent propylene glycol diacetate (PGDA) accounts for 20%.

[0139] Component A:Component B = 100:12.

[0140] The preparation method of a two-component polyurethane matte black base coat includes the following steps: First, add hydroxyl acrylic emulsion / hydroxyl acrylic polyurethane to a container, adjust the dispersion speed to 800 r / min, add hydroxyl microspheres b and c, and stir for 20 min. Then add film-forming aid, defoamer, substrate wetting agent, neutralizer, leveling agent, thickener, water-based colorant, and deionized water. After adding all the ingredients, maintain the dispersion speed and continue dispersing for 20 min. Filter through a 325-mesh filter to obtain component A. Dilute the curing agent in component B with a diluent. Mix the measured quantities of components A and B according to the designed ratio, add deionized water, and adjust the Zein-2 cup viscosity to approximately 17 s to obtain a water-based two-component polyurethane matte black base coat, which is ready for spraying.

[0141] Example 5

[0142] Prepare paint component A according to the following formula. All the proportions below are by weight percentage.

[0143] label substance proportion Classification supplier 1 Lacper 4233 50.00 Hydroxyacrylate polyurethane Wanhua Chemical 2 Antkote 2042 30.00 Hydroxyacrylic acid Wanhua Chemical 3 Hydroxy microspheres b 1.00 / / 4 water 1.30 / / 5 High-pigment carbon black 14.00 Pigment world famous 6 BYK333 0.20 Leveling agent BYK 7 DPM 1.50 Film-forming aids DOW 8 BYK 346 0.50 wetting agent Tego 9 TEGO 1488 0.10 Defoamer Tego 10 U905(50％) 1.20 Thickener Wanhua Chemical 11 DMEA (10%) 0.20 Neutralizing agent Dow

[0144] Component B, by weight percentage of each raw material, includes: water-based isocyanate curing agent. 268 accounts for 70%, and the diluent propylene glycol methyl ether acetate (PMA) accounts for 30%.

[0145] Component A:Component B = 100:13.

[0146] The preparation method of a two-component polyurethane matte black base and top coat includes the following steps: First, add hydroxyl acrylic emulsion / hydroxyl acrylic polyurethane to a container, adjust the dispersion speed to 800 r / min, add hydroxyl microspheres b and stir for 20 min. Then add film-forming aid, defoamer, substrate wetting agent, neutralizer, leveling agent, thickener, water-based colorant and deionized water. After adding all the ingredients, maintain the dispersion speed and continue dispersing for 20 min. Filter through a 325 mesh screen to obtain component A. Dilute the curing agent in component B with a diluent. Mix the measured quantities of components A and B according to the designed ratio, add deionized water, and adjust the Zein-2 cup viscosity to approximately 17 s to obtain a water-based two-component polyurethane matte black base and top coat, which is ready for spraying.

[0147] Comparative Example 1

[0148] Aqueous hydroxyl acrylic dispersions are not used. 2706, replace it with the corresponding amount of water, the rest is the same as in Example 2.

[0149] Comparative Example 2

[0150] Water-based hydroxyl acrylic polyurethane dispersions are not used. 6510, replace it with the corresponding amount of water, the rest is the same as in Example 2.

[0151] Comparative Example 3

[0152] In Example 2, matting agent E1011 was used to replace aqueous hydroxyl microspheres b, while the rest remained unchanged.

[0153] The performance of the water-based two-component polyurethane matte black base coat in each embodiment was tested, and the results are shown in Table 2.

[0154] Table 2 Performance test results of water-based two-component polyurethane matte black base and topcoat paint

[0155]

[0156]

[0157] As can be clearly seen from Table 2, the water-based two-component polyurethane matte black base and top coat of the present invention has significant advantages over comparative examples 1-3 in terms of hardness, scratch resistance, whiteness, adhesion, and chemical resistance.

[0158] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint, characterized in that, It consists of component A and component B in a mass ratio of 6 to 10:1; wherein, based on the total mass of component A, component A consists of the following components in mass percentage: Waterborne hydroxyl polyurethane acrylic dispersion 40-80%, Aqueous hydroxy acrylic acid dispersion 5~35%, Hydroxyl microspheres 0.5~6%, Water 0.1~6%, High-pigment carbon black paste 6~18%, Water-based additives 0.5~2.5%, Film-forming aid 0.2~2%, Based on the total mass of component B, component B is composed of the following components by mass percentage: Hardener 65~85%, Dilute with 15-35% solvent; The aqueous hydroxyl polyurethane acrylic dispersion is an aqueous hydroxyl polyurethane acrylic dispersion with a core-shell structure, and the hydroxyl content is 1.0~2.2%; The aqueous hydroxy acrylic acid dispersion is an aqueous hydroxy acrylic acid dispersion with a core-shell structure, and the hydroxyl content is 2.5-4.2%. The hydroxyl microspheres are aqueous hydroxyl microspheres with a core-shell structure, wherein the core is made of a component including hard monomers, hydrophilic monomers, and functional monomers, and the shell is made of a component including hard monomers, hydroxyl monomers, and hydrophilic monomers. The hydrophilic monomer is selected from either methacrylic acid or acrylic acid; The hard monomer is selected from any one of styrene, methyl methacrylate, ethyl methacrylate, and acrylonitrile; The functional monomer is selected from either acrylamide or methacrylamide; The hydroxyl monomer is selected from any one of hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate; The hydroxyl microspheres were prepared by free radical emulsion polymerization.

2. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 1, characterized in that, Based on the total mass of component A, component A is composed of the following components by mass percentage: Waterborne hydroxyl polyurethane acrylic dispersion 45~70%, 10-30% aqueous hydroxy acrylic acid dispersion Hydroxyl microspheres 1-4%, Water 0.5-5%, High-pigment carbon black paste 8~14%, Water-based additives 0.7-2%, Film-forming aid 0.5~1.5%, Based on the total mass of component B, component B is composed of the following components by mass percentage: Hardener 70-80%, Dilute the solvent to 20-30%.

3. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 1 or 2, characterized in that, The aqueous hydroxyl polyurethane acrylic dispersion is at least one of Wanhua Chemical's Lacper® 4288, Lacper® 4233, and Crysol® 6510.

4. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 1 or 2, characterized in that, The aqueous hydroxy acrylic dispersion is one or more of Wanhua Chemical's Antkote® 2032, Antkote® 2706, Antkote® 2042, and Covestro's Bayhydrol® A2770.

5. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 1, characterized in that, The method for preparing the hydroxyl microspheres includes: 1) Preparation of the core layer of hydroxyl microspheres: Under a nitrogen atmosphere, weigh 40-60% water by mass and place it in a polymerization container, then heat it to 80-85°C. Mix 10-20% water, 0.5-2% emulsifier I, 5-10% hydrophilic monomer I, 15-35% hard monomer I, and 1-3% functional monomer to obtain a pre-emulsion. Weigh 2-5% initiator and add it to the pre-emulsion. Add the pre-emulsion to the polymerization container and keep it at 80-85°C for 0.5-1 h. Cool it to room temperature and filter to obtain the hydroxyl microsphere core layer. 2) Preparation of hydroxyl microspheres: Under a nitrogen atmosphere, weigh out 55-75% deionized water, 0.1-1% initiator, 10-18% hydroxyl microsphere core layer, 8-12% hard monomer II, 1-5% hydrophilic monomer II, 1.5-3% hydroxyl monomer, and 0.2-0.6% emulsifier II by mass fraction and add them to a polymerization container. React at 80-85℃ for 0.5-2 hours. Then add 2-5% neutralizer and 0.1-0.5% initiator and keep at this temperature for 0.5-1 hours to obtain hydroxyl microspheres. The hydrophilic monomer I and hydrophilic monomer II are each independently selected from either methacrylic acid or acrylic acid; The hard monomer I and hard monomer II are each independently selected from styrene, methyl methacrylate, ethyl methacrylate, and acrylonitrile.

6. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 5, characterized in that, The emulsifiers I and II are ionic emulsifiers; and / or The neutralizing agent is selected from ammonia, triethanolamine, or... The initiator is a redox system, selected from either ammonium persulfate-tert-butyl hydroperoxide or sodium persulfate-tert-butyl hydroperoxide.

7. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 6, characterized in that, The emulsifier I and emulsifier II are each independently selected from sodium dodecyl sulfate, sodium p-styrene sulfonate, and stearate.

8. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 1 or 2, characterized in that, The water-based additives include at least one of wetting agents, leveling agents, defoamers, neutralizing agents, and thickeners.

9. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 8, characterized in that, The wetting agent is selected from any one of Tego270, TegoKL245, and Tego346, and / or The leveling agent is selected from any one of BYK333, BYK381, and TegoGlide100, and / or The defoamer is selected from any one of Tego902W, TEGOFoamex825, and Tego1488, and / or The thickener is selected from any one of Wanhua U505, U905, and U605, and / or The neutralizing agent is selected from either DEMA or AMP95.

10. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 1 or 2, characterized in that, The film-forming aid is one or more of dipropylene glycol methyl ether, dipropylene glycol butyl ether, and dipropylene glycol dimethyl ether.

11. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 1 or 2, characterized in that, The curing agent is an aqueous isocyanate curing agent.

12. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 11, characterized in that, The curing agent is a sulfonate-modified HDI trimer.

13. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 12, characterized in that, The curing agent is one or more of Wanhua Chemical's Aquolin® 268, Aquolin® 270, and Aquolin® 278.

14. The high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base and topcoat paint as described in claim 12, characterized in that, The diluent is selected from one or more of ethylene glycol butyl ether acetate, propylene glycol diacetate, and propylene glycol methyl ether acetate.

15. A method for preparing the high-hardness, scratch-resistant, water-based two-component polyurethane matte black base coat according to any one of claims 1-14, comprising the following steps: (1) Mix the waterborne hydroxyl polyurethane acrylic dispersion, waterborne hydroxyl acrylic dispersion, hydroxyl microspheres, water, high pigment carbon black paste, waterborne additives, and film-forming aids in proportion, and filter to obtain component A; (2) Mix the curing agent and diluent evenly to obtain component B; (3) Mix components A and B according to the metering ratio, add water, adjust the viscosity, and filter to obtain the high hardness scratch-resistant water-based two-component polyurethane matte black base and top coat.

16. The preparation method according to claim 15, characterized in that, In step (3), the viscosity is adjusted to 15~20s for the Zein-3 cup.

17. The application of the high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base coat as described in any one of claims 1-14 in the decorative and protective fields of the plastic paint industry.

18. The application of the high-hardness, scratch-resistant, water-resistant two-component polyurethane matte black base coat as described in claim 17 in the decorative and protective fields of the plastic paint industry, characterized in that... Applications in the 3C consumer electronics field.

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