Anti-sinking water-based acrylic resin coating and preparation method thereof

Abstract

The invention belongs to the technical field of coatings, and discloses an anti-sinking water-based acrylic resin coating and a preparation method thereof.The anti-sinking water-based acrylic resin coating is prepared from, by weight, 110-130 parts of modified water-based acrylic resin, 10-25 parts of modified cellulose nanocrystals, 3-5 parts of a composite additive, 4-6 parts of a dispersing agent, 0.5-2 parts of a defoaming agent, 0.5-2 parts of a flatting agent and 10-20 parts of water; the acrylic resin is modified by using the organic silicon oligomer and the epoxy resin, the film hardness is high, the adhesive force is strong, and the film hardness, the impact resistance, the ultraviolet aging resistance and the flame retardant property of the material are improved by adding the modified cellulose nanocrystals and the composite additive.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to an anti-sag water-based acrylic resin coating and a preparation method thereof. Background Art

[0002] In order to avoid metal corrosion, we usually protect the metal by changing the structure of the metal itself, adding a surface protective layer, and utilizing electrochemical principles. The most common method in industry is to apply anti-corrosion and anti-mildew coatings on the surface of steel. Anti-corrosion and anti-mildew coatings have undergone a development process from solvent-based to water-based. Solvent-based coatings have excellent coating performance, but the use of thinners leads to a high content of organic volatiles, which is harmful to the environment and difficult to clean. Water-based coatings use water as a diluent, are environmentally friendly and energy-saving, have a high market price, and will gradually replace solvent-based coatings in the future. "Oil retreats and water advances" will be the development trend of the coatings industry. Water-based acrylic anti-corrosion and anti-mildew coatings have attracted widespread attention from researchers due to their good high temperature resistance, water resistance, weather resistance, stretchability, color retention and outstanding low cost.

[0003] Water-based acrylic paint is an acrylic resin paint based on an acrylic polymer synthesized from three monomers: methyl methacrylate (MMA), butyl acrylate (BA), and acrylic acid (AA), with water as a dispersant. It can be used as a topcoat for metal corrosion protection or a finishing coat for various metal surfaces. It has low viscosity, good stability, and excellent weather resistance. However, water-based acrylic paint itself also has many performance drawbacks, such as slow film drying, low hardness, and poor adhesion, which can lead to the paint film easily sinking after drying. Furthermore, it is prone to cracking and falling off after long periods of outdoor exposure, exposing the internal metal and causing metal corrosion. Exposure to fire is also a major cause of paint film damage, so the weather resistance and flame retardancy of existing water-based acrylic paints need to be improved. Summary of the Invention

[0004] In order to address the deficiencies mentioned in the above-mentioned background technology, the purpose of the present invention is to provide a subsidence-resistant water-based acrylic resin coating and a preparation method thereof. The acrylic resin is modified by silicone oligomers and epoxy resin, and the coating film has high hardness and strong adhesion. By adding modified cellulose nanocrystals and composite additives, the paint film hardness, impact resistance, UV aging resistance and flame retardancy of the material are improved.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] An anti-sag water-based acrylic resin coating comprises the following raw materials in parts by weight: 110-130 parts of modified water-based acrylic resin, 10-25 parts of modified cellulose nanocrystals, 3-5 parts of composite additives, 4-6 parts of dispersant, 0.5-2 parts of defoaming agent, 0.5-2 parts of leveling agent, and 10-20 parts of water;

[0007] The modified waterborne acrylic resin is a silicone / epoxy composite modified acrylic resin;

[0008] The modified cellulose nanocrystals are obtained by coating cellulose nanocrystals with polydopamine and then loading nano-titanium dioxide on the surface through a silane coupling agent;

[0009] The composite additive is a triazine derivative containing a DOPO group and a benzotriazole group.

[0010] Preferably, the dispersant is a polyurethane oligomer or a phosphate ester active agent, the defoamer is a polyether defoamer, an organosilicon defoamer or a polyether siloxane copolymer, and the leveling agent is carboxymethyl cellulose.

[0011] Preferably, the preparation method of the modified waterborne acrylic resin comprises the following steps:

[0012] A1. Mix methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid, and n-dodecyl mercaptan, then add vinyl triethoxysilane and stir evenly to obtain a mixed monomer solution;

[0013] A2. Add epoxy resin E44 and azobisisobutyl cyanide to isopropanol, stir and dissolve, heat to reflux, then slowly add the mixed monomer solution under nitrogen protection, and keep the temperature to react for 1 to 3 hours;

[0014] A3. Raise the temperature to 85-87°C, continue adding azobisisobutyl cyanide and isopropyl alcohol to the reaction system, keep the temperature for 2-4 hours, and remove the isopropyl alcohol by filtration under reduced pressure;

[0015] A4. When the system temperature drops to 55-65°C, add water and diethanolamine, adjust the pH to neutral, and stir and disperse with a high-speed disperser for 30 minutes to obtain a modified water-based acrylic resin.

[0016] Preferably, vinyltriethoxysilane accounts for 3% of the total weight of the monomers, and epoxy resin E44 accounts for 5% of the total weight of the monomers.

[0017] Preferably, the method for preparing modified cellulose nanocrystals comprises the following steps:

[0018] B1. Prepare a Tris buffer solution, then add cellulose nanocrystals to the Tris buffer solution and disperse them by ultrasonication. Then add dopamine hydrochloride to the cellulose nanocrystal dispersion, stir and react for 10 to 12 hours, centrifuge, wash, and dry to obtain cellulose nanocrystals coated with polydopamine.

[0019] B2. Add 3-aminopropyltrimethoxysilane to distilled water and stir for 10-15 minutes. Add nano-titanium dioxide and heat to 80°C. Stir and react for 3-5 hours. Centrifuge, wash, filter and dry to obtain silane-modified nano-titanium dioxide.

[0020] B3. Add cellulose nanocrystals coated with polydopamine to N,N-dimethylformamide for ultrasonic dispersion, then add silane-modified nano-titanium dioxide, heat to 110°C, stir and react for 4 to 6 hours, centrifuge, wash, filter and dry the product to obtain modified cellulose nanocrystals.

[0021] Preferably, the mass ratio of cellulose nanocrystals to dopamine hydrochloride is 1:2-3, and the mass of 3-aminopropyltrimethoxysilane is 3-5% of the mass of nano-titanium dioxide.

[0022] Preferably, the mass ratio of the cellulose nanocrystals coated with polydopamine to the modified nano-titanium dioxide is 3 to 5:1.

[0023] Preferably, the preparation method of the composite modifier comprises the following steps:

[0024] C1. Dissolve p-hydroxybenzaldehyde and 1H-benzotriazole-6-methylamine separately in N,N-dimethylformamide, slowly add the 1H-benzotriazole-6-methylamine solution dropwise to p-hydroxybenzaldehyde, raise the temperature to 55°C, and keep the temperature to react for 1 hour. After the reaction is complete, transfer the product to ice water and let it stand to cool, filter, wash, and dry to obtain intermediate A;

[0025] C2. Add cyanuric chloride and triethylamine to 1,4-dioxane and stir until cyanuric chloride is completely dissolved. Then add intermediate A and heat to 45°C. Stir and react for 3-5 hours. After the reaction, transfer the product to ice water and let it stand to cool. Filter, wash and dry to obtain intermediate B.

[0026] C3. Add DOPO to 1,4-dioxane and stir until DOPO is completely dissolved. Then add intermediate B to the above system, heat to 60°C, and stir to react for 6-8 hours. After the reaction is completed, transfer the product to ice water and let it stand to cool. Filter, wash, and dry to obtain a composite additive.

[0027] Preferably, the molar ratio of p-hydroxybenzaldehyde to 1H-benzotriazole-6-methylamine is 1:1, the molar ratio of cyanuric chloride to intermediate A is 1:3, and the molar ratio of DOPO to intermediate B is 3:1.

[0028] A method for preparing an anti-sag water-based acrylic resin coating comprises the following steps: mixing a modified water-based acrylic resin, a composite additive, a dispersant, a defoamer, a leveling agent, and water to obtain a mixed liquid; and then adding modified cellulose nanocrystals to the mixed liquid and dispersing them at high speed to obtain the water-based acrylic resin coating.

[0029] Beneficial effects of the present invention:

[0030] The present invention utilizes organosilicon oligomers and epoxy resin to modify acrylic resin, resulting in a coating with high hardness and strong adhesion. By adding modified cellulose nanocrystals and composite additives, the material's film hardness, impact resistance, UV aging resistance and flame retardancy are improved.

[0031] The addition of epoxy resin increases crosslinking between acrylic resin molecular chains, creating an internal network structure that significantly enhances the adhesion and hardness of the coating. Silicone has extremely low surface energy, its Si-O bond energy is far greater than that of CC and CO bonds, and the bonds are easily rotatable. These properties give the material excellent water resistance, high and low temperature resistance, gloss retention, flexibility, and impact resistance.

[0032] The present invention incorporates modified cellulose nanocrystals, which are surface-modified with polydopamine and then loaded with nano-titanium dioxide. Cellulose nanocrystals are a green material that combines nanoscale and renewable properties. They exhibit excellent mechanical properties and demonstrate a strong reinforcing effect when added to a wide range of polymers. Nano-titanium dioxide also has a strong UV shielding capability, with an equivalent attenuation rate exceeding 90%. This material has promising application prospects in enhancing the UV resistance of coatings. Application to coatings effectively shields the paint film from UV damage, improving the coating's weather resistance.

[0033] The composite additive of the present invention is prepared by synthesizing a hydroxyl-containing Schiff base compound from p-hydroxybenzaldehyde and 1H-benzotriazole-6-methylamine, reacting the compound with cyanuric chloride to synthesize a Schiff base compound containing a triazine structure, and finally reacting the compound with DOPO. The molecular structure of the composite additive comprises a triazine ring, a DOPO group, and a benzotriazole group. The triazine ring binds a large amount of N and P elements in the DOPO group, which can decompose under high temperature conditions to produce phosphate esters and gas, promote polymer dehydration and carbonization, and simultaneously form a carbonaceous protective layer. The non-combustible gas produced by the decomposition also has a good gas-phase flame retardant effect. When the benzotriazole group is exposed to ultraviolet radiation, the hydrogen bonds in the molecule are broken or phototautomers are formed, thereby converting harmful ultraviolet light energy into harmless heat energy for release, protecting the material from ultraviolet damage, thereby improving the material's ultraviolet resistance, and synergizing with nano-titanium dioxide in the modified cellulose nanocrystals to further improve the material's ultraviolet aging resistance. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 any creative efforts shall fall within the scope of protection of the present invention.

[0035] Example 1

[0036] A modified waterborne acrylic resin is prepared by composite modification of organic silicon and epoxy resin, and the preparation method comprises the following steps:

[0037] A1. Methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid, and n-dodecyl mercaptan were mixed, and then 3% by weight of vinyltriethoxysilane was added and stirred to obtain a mixed monomer solution.

[0038] A2. Add 5% of the total weight of epoxy resin E44 and 3% of the total weight of azobisisobutyl cyanide to isopropanol, stir and dissolve, heat to reflux, then slowly add the mixed monomer solution under nitrogen protection, and keep the reaction warm for 5 hours;

[0039] A3. Raise the temperature to 86°C, continue to add azobisisobutyl cyanide and isopropyl alcohol to the reaction system, keep the temperature for 3 hours, and remove the isopropyl alcohol by filtration under reduced pressure;

[0040] A4. When the system temperature drops to 60°C, add water and diethanolamine, adjust the pH to neutral, and stir and disperse with a high-speed disperser for 30 minutes to obtain a modified water-based acrylic resin.

[0041] Example 2

[0042] A modified cellulose nanocrystal is obtained by coating the cellulose nanocrystal with polydopamine and then loading nano-titanium dioxide on the surface through a silane coupling agent. The preparation method comprises the following steps:

[0043] B1. Prepare a Tris buffer solution, then add 3.5 g of cellulose nanocrystals to 50 ml of Tris buffer solution and disperse them by ultrasonication. Then add 8.1 g of dopamine hydrochloride to the cellulose nanocrystal dispersion, stir and react for 12 hours, centrifuge, wash, and dry to obtain cellulose nanocrystals coated with polydopamine.

[0044] B2. Add 0.2 g of 3-aminopropyltrimethoxysilane to 20 ml of distilled water and stir for 10-15 min. Add 5.1 g of nano-titanium dioxide and heat to 80°C. Stir and react for 4 h. Centrifuge, wash, filter and dry to obtain silane-modified nano-titanium dioxide.

[0045] B3. Add 10.4 g of cellulose nanocrystals coated with polydopamine to 50 ml of N,N-dimethylformamide for ultrasonic dispersion, then add 2.6 g of silane-modified nano-titanium dioxide, heat to 110°C, stir and react for 5 h, centrifuge, wash, filter and dry the product to obtain modified cellulose nanocrystals.

[0046] Example 3

[0047] A composite modifier is prepared by synthesizing a hydroxyl-containing Schiff base compound by reacting p-hydroxybenzaldehyde and 1H-benzotriazole-6-methylamine, which is then reacted with cyanuric chloride to synthesize a Schiff base compound containing a triazine structure, which is finally reacted with DOPO. The preparation method comprises the following steps:

[0048] C1. Dissolve 0.05 mol of p-hydroxybenzaldehyde and 0.05 mol of 1H-benzotriazole-6-methylamine in 30 ml of N,N-dimethylformamide, then slowly dropwise add the 1H-benzotriazole-6-methylamine solution to p-hydroxybenzaldehyde. Heat to 55°C and keep the temperature to react for 1 hour. After the reaction is complete, transfer the product to ice water and allow it to cool. Filter, wash, and dry to obtain intermediate A, which has the following structural formula:

[0049]

[0050] C2. Add 0.02 mol of cyanuric chloride and 10 ml of triethylamine to 20 ml of 1,4-dioxane, stir until the cyanuric chloride is completely dissolved, then add 0.06 mol of intermediate A, heat to 45°C, stir and react for 4 hours. After the reaction is completed, transfer the product to ice water and let it stand to cool, filter, wash and dry to obtain intermediate B, whose structural formula is as follows:

[0051]

[0052] C3. Add 0.05 mol of DOPO to 50 ml of 1,4-dioxane and stir until DOPO is completely dissolved. Then add 0.02 mol of intermediate B to the above system, heat to 60°C, and stir to react for 8 hours. After the reaction is completed, transfer the product to ice water and let it stand to cool. Filter, wash, and dry to obtain a composite additive with the following structural formula:

[0053]

[0054] Example 4

[0055] A subsidence-resistant water-based acrylic resin coating comprises the following raw materials in parts by weight: 120 parts of a modified water-based acrylic resin, 18 parts of modified cellulose nanocrystals, 4 parts of a composite additive, 5 parts of a dispersant BYK-190, 1.2 parts of a defoamer BYK-020, 1.5 parts of carboxymethyl cellulose, and 15 parts of water; the modified water-based acrylic resin is the organosilicon / epoxy composite modified acrylic resin prepared in Example 1; the modified cellulose nanocrystals are nano-titanium dioxide-loaded polydopamine-coated cellulose nanocrystals prepared in Example 2; and the composite additive is the triazine derivative containing a DOPO group and a benzotriazole group prepared in Example 3.

[0056] The method for preparing the anti-sag water-based acrylic resin coating comprises the following steps: mixing a modified water-based acrylic resin, a composite additive, a dispersant BYK-190, a defoamer BYK-02, carboxymethyl cellulose, and water to obtain a mixed liquid; and then adding modified cellulose nanocrystals to the mixed liquid and dispersing them at high speed to obtain a water-based acrylic resin coating.

[0057] Example 5

[0058] A subsidence-resistant water-based acrylic resin coating comprises the following raw materials in parts by weight: 110 parts of a modified water-based acrylic resin, 25 parts of modified cellulose nanocrystals, 3 parts of a composite additive, 6 parts of a dispersant BYK-111, 0.5 parts of a defoamer BYK-019, 2 parts of carboxymethyl cellulose, and 10 parts of water; the modified water-based acrylic resin is the organosilicon / epoxy composite modified acrylic resin prepared in Example 1; the modified cellulose nanocrystals are nano-titanium dioxide-loaded polydopamine-coated cellulose nanocrystals prepared in Example 2; and the composite additive is the triazine derivative containing a DOPO group and a benzotriazole group prepared in Example 3.

[0059] The preparation method of the above-mentioned anti-sag water-based acrylic resin coating comprises the following steps: mixing modified water-based acrylic resin, composite additives, dispersant, defoamer, leveling agent and water to obtain a mixed liquid; then adding modified cellulose nanocrystals to the mixed liquid and dispersing them at high speed to obtain a water-based acrylic resin coating.

[0060] Example 6

[0061] A subsidence-resistant water-based acrylic resin coating comprises the following raw materials in parts by weight: 130 parts of a modified water-based acrylic resin, 10 parts of modified cellulose nanocrystals, 5 parts of a composite additive, 4 parts of a dispersant BYK-190, 2 parts of a defoamer BYK-028, 0.5 parts of carboxymethyl cellulose, and 20 parts of water; the modified water-based acrylic resin is the organosilicon / epoxy composite modified acrylic resin prepared in Example 1; the modified cellulose nanocrystals are the nano-titanium dioxide-loaded polydopamine-coated cellulose nanocrystals prepared in Example 2; and the composite additive is the triazine derivative containing a DOPO group and a benzotriazole group prepared in Example 3.

[0062] The preparation method of the above-mentioned anti-sag water-based acrylic resin coating comprises the following steps: mixing modified water-based acrylic resin, composite additives, dispersant, defoamer, leveling agent and water to obtain a mixed liquid; then adding modified cellulose nanocrystals to the mixed liquid and dispersing them at high speed to obtain a water-based acrylic resin coating.

[0063] Comparative Example 1

[0064] An anti-sag water-based acrylic resin coating comprises the following raw materials in parts by weight: 120 parts of water-based acrylic resin, 18 parts of modified cellulose nanocrystals, 4 parts of composite additives, 5 parts of dispersant BYK-190, 1.2 parts of defoamer BYK-020, 1.5 parts of carboxymethyl cellulose, and 15 parts of water;

[0065] The water-based acrylic resin is not modified by silicone and epoxy resin, and its preparation method includes the following steps:

[0066] A1. Mix methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid, and n-dodecyl mercaptan and stir to obtain a mixed monomer solution;

[0067] A2. Add azobisisobutyl cyanide to isopropanol, stir and dissolve, heat to reflux, then slowly add the mixed monomer solution under nitrogen protection, keep the temperature to react for 2-4 hours, and remove the isopropanol by filtration under reduced pressure;

[0068] A3. When the system temperature drops to 55-65°C, add water and diethanolamine, adjust the pH to neutral, and stir and disperse with a high-speed disperser for 30 minutes to obtain a water-based acrylic resin.

[0069] The modified cellulose nanocrystals are the nano-titanium dioxide-loaded polydopamine-coated cellulose nanocrystals prepared in Example 2; and the composite additive is the triazine derivative containing DOPO groups and benzotriazole groups prepared in Example 3.

[0070] The method for preparing the anti-sag water-based acrylic resin coating comprises the following steps: mixing a water-based acrylic resin, a composite additive, a dispersant BYK-190, a defoamer BYK-02, carboxymethyl cellulose, and water to obtain a mixed liquid; and then adding modified cellulose nanocrystals to the mixed liquid and dispersing them at high speed to obtain a water-based acrylic resin coating.

[0071] Comparative Example 2

[0072] A sag-resistant water-based acrylic resin coating comprises the following raw materials in parts by weight: 120 parts of a modified water-based acrylic resin, 4 parts of a composite additive, 5 parts of a dispersant BYK-190, 1.2 parts of a defoamer BYK-020, 1.5 parts of carboxymethyl cellulose, and 15 parts of water; the modified water-based acrylic resin is the organosilicon / epoxy composite modified acrylic resin prepared in Example 1; and the composite additive is the triazine derivative containing a DOPO group and a benzotriazole group prepared in Example 3.

[0073] The preparation method of the anti-sag water-based acrylic resin coating comprises the following steps: mixing a modified water-based acrylic resin, a composite additive, a dispersant BYK-190, a defoamer BYK-02, carboxymethyl cellulose, and water to obtain a mixed liquid, and dispersing the mixture at high speed to obtain a water-based acrylic resin coating.

[0074] Comparative Example 3

[0075] A subsidence-resistant water-based acrylic resin coating comprises the following raw materials in parts by weight: 120 parts of a modified water-based acrylic resin, 18 parts of modified cellulose nanocrystals, 5 parts of a dispersant BYK-190, 1.2 parts of a defoamer BYK-020, 1.5 parts of carboxymethyl cellulose, and 15 parts of water; the modified water-based acrylic resin is the organosilicon / epoxy composite modified acrylic resin prepared in Example 1; and the modified cellulose nanocrystals are the nano-titanium dioxide-loaded polydopamine-coated cellulose nanocrystals prepared in Example 2.

[0076] The preparation method of the above-mentioned anti-sag water-based acrylic resin coating includes the following steps: mixing a modified water-based acrylic resin, a dispersant BYK-190, a defoamer BYK-02, carboxymethyl cellulose, and water to obtain a mixed liquid; then adding modified cellulose nanocrystals to the mixed liquid and dispersing them at high speed to obtain a water-based acrylic resin coating.

[0077] Performance testing

[0078] 1. The anti-sag water-based acrylic resin coatings prepared in Examples 4 to 6 and Comparative Examples 1 to 3 were tested for the pencil hardness of the paint film according to GBT6739-2022, the impact resistance of the paint film was measured according to GB / T 1732-2020, the adhesion of the paint film was measured according to GB / T 9286-2021, and the abrasion resistance of the paint film was tested according to GB / T 1768-2006. The data are shown in Table 1 below.

[0079] Table 1 Physical and chemical properties of anti-sag water-based acrylic resin coatings

[0080]

[0081] As can be seen from the data in Table 1, the anti-sag water-based acrylic resin coatings prepared in Examples 3 to 5 and Comparative Example 1 have good pencil hardness, impact resistance, and abrasion resistance after curing. In Comparative Example 1, the water-based acrylic resin was not modified by silicone and epoxy resin, and the adhesion of the paint film was slightly reduced. In Comparative Example 2, no modified cellulose nanocrystals were added, and the pencil hardness and abrasion resistance of the paint film decreased significantly.

[0082] 2. UV aging resistance test

[0083] The anti-sag water-based acrylic resin coatings prepared in Examples 4-6 and Comparative Examples 1-3 were applied to the surface of a 20 mm × 50 mm × 2 mm aluminum alloy plate (the aluminum alloy plate was first degreased and dehydrated in acetone and ethanol, followed by drying). After the paint film solidified, the sample was placed flat in an artificial ultraviolet accelerated aging test chamber. The test conditions were: the power of the ultraviolet lamp used was 50 W, the wavelength peaks were 254 μm and 365 μm, the distance between the paint film and the ultraviolet lamp was 20 cm, and the test was set for 2400 hours. The gloss change of the paint film before and after aging was visually observed and the gloss before and after aging was measured according to GB / T 9754. The gloss loss (%) was calculated as gloss loss = A0 - A1 / A0 × 100%, where A0 is the gloss value before aging and A1 is the gloss value after aging. The data are shown in Table 2 below.

[0084] Table 2 Test results of UV aging resistance of anti-sag water-based acrylic resin coating

[0085]

[0086] It can be seen from the data in Table 2 that the anti-sag water-based acrylic resin coatings in Examples 4 to 6 and Comparative Example 1 all have good anti-ultraviolet aging performance, and the anti-sag water-based acrylic resin coatings in Comparative Example 2 and Comparative Example 3 have average anti-ultraviolet aging effects, indicating that the modified cellulose nanocrystals and composite additives of the present invention can improve the anti-ultraviolet aging performance of the paint film.

[0087] 3. Flame retardant performance test

[0088] The anti-sag water-based acrylic resin coatings prepared in Examples 4 to 6 and Comparative Examples 1 to 3 were poured into a polytetrafluoroethylene template. After the paint film was cured, the vertical burning rating (UL94) was tested according to the ASTM3801 standard. The data obtained are shown in Table 3 below.

[0089] Table 3 Flame retardant performance test results of anti-sag water-based acrylic resin coating

[0090] Group Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 UL94 V-0 V-0 V-0 V-1 V-0 V-2

[0091] As can be seen from the data in Table 3, the anti-sag water-based acrylic resin coatings in Examples 4-6 and Comparative Example 2 all have good flame retardant properties. In Comparative Example 1, the water-based acrylic resin was not modified with silicone and epoxy resin, and the flame retardant effect of the paint film was slightly reduced. This is because the addition of silicone promotes dehydration and carbonization of the polymer during thermal cracking, while forming a carbonaceous protective layer of Si-O and Si-C, which can improve the flame retardant properties of the material. In Comparative Example 3, no composite additive was added, and the flame retardant effect of the paint film was significantly reduced.

[0092] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0093] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. An anti-sag water-based acrylic resin coating, characterized in that: The invention comprises the following raw materials in parts by weight: 110-130 parts of modified waterborne acrylic resin, 10-25 parts of modified cellulose nanocrystals, 3-5 parts of composite additives, 4-6 parts of dispersant, 0.5-2 parts of defoaming agent, 0.5-2 parts of leveling agent and 10-20 parts of water; The modified waterborne acrylic resin is a silicone / epoxy composite modified acrylic resin; The modified cellulose nanocrystals are obtained by coating cellulose nanocrystals with polydopamine and then loading nano-titanium dioxide on the surface through a silane coupling agent; The composite additive is a triazine derivative containing a DOPO group and a benzotriazole group.

2. The anti-sag water-based acrylic resin coating according to claim 1, characterized in that: The dispersant is a polyurethane oligomer or a phosphate active agent, the defoamer is a polyether defoamer, an organosilicon defoamer or a polyether siloxane copolymer, and the leveling agent is carboxymethyl cellulose.

3. The anti-sag water-based acrylic resin coating according to claim 1, characterized in that: The preparation method of the modified waterborne acrylic resin comprises the following steps: A1. Mix methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid, and n-dodecyl mercaptan, then add vinyl triethoxysilane and stir evenly to obtain a mixed monomer solution; A2. Add epoxy resin E44 and azobisisobutyl cyanide to isopropanol, stir and dissolve, heat to reflux, then slowly add the mixed monomer solution under nitrogen protection, and keep the temperature to react for 1 to 3 hours; A3. Raise the temperature to 85-87°C, continue adding azobisisobutyl cyanide and isopropyl alcohol to the reaction system, keep the temperature for 2-4 hours, and remove the isopropyl alcohol by filtration under reduced pressure; A4. When the system temperature drops to 55-65°C, add water and diethanolamine, adjust the pH to neutral, and stir and disperse with a high-speed disperser for 30 minutes to obtain a modified water-based acrylic resin.

4. The anti-sag water-based acrylic resin coating according to claim 3, characterized in that: The vinyl triethoxysilane accounts for 3% of the total weight of the monomers, and the epoxy resin E44 accounts for 5% of the total weight of the monomers.

5. The anti-sag water-based acrylic resin coating according to claim 1, characterized in that: The preparation method of the modified cellulose nanocrystals comprises the following steps: B1. Prepare a Tris buffer solution, then add cellulose nanocrystals to the Tris buffer solution and disperse them by ultrasonication. Then add dopamine hydrochloride to the cellulose nanocrystal dispersion, stir and react for 10 to 12 hours, centrifuge, wash, and dry to obtain cellulose nanocrystals coated with polydopamine. B2. Add 3-aminopropyltrimethoxysilane to distilled water and stir for 10-15 minutes. Add nano-titanium dioxide and heat to 80°C. Stir and react for 3-5 hours. Centrifuge, wash, filter and dry to obtain silane-modified nano-titanium dioxide. B3. Add the cellulose nanocrystals coated with polydopamine to N,N-dimethylformamide for ultrasonic dispersion, then add silane-modified nano-titanium dioxide, heat to 110° C., stir and react for 4 to 6 hours, centrifuge, wash, filter and dry the product to obtain the modified cellulose nanocrystals.

6. The anti-sag water-based acrylic resin coating according to claim 5, characterized in that: The mass ratio of the cellulose nanocrystals to dopamine hydrochloride is 1:2-3, and the mass of the 3-aminopropyltrimethoxysilane is 3-5% of the mass of the nano-titanium dioxide.

7. The anti-sag water-based acrylic resin coating according to claim 5, characterized in that: The mass ratio of the cellulose nanocrystals coated with polydopamine to the modified nano-titanium dioxide is 3 to 5:

1.

8. The anti-sag water-based acrylic resin coating according to claim 1, characterized in that: The preparation method of the composite modifier comprises the following steps: C1. Dissolve p-hydroxybenzaldehyde and 1H-benzotriazole-6-methylamine separately in N,N-dimethylformamide, slowly add the 1H-benzotriazole-6-methylamine solution dropwise to p-hydroxybenzaldehyde, raise the temperature to 55°C, and keep the temperature to react for 1 hour. After the reaction is complete, transfer the product to ice water and let it stand to cool, filter, wash, and dry to obtain intermediate A; C2. Add cyanuric chloride and triethylamine to 1,4-dioxane and stir until cyanuric chloride is completely dissolved. Then add intermediate A and heat to 45°C. Stir and react for 3-5 hours. After the reaction, transfer the product to ice water and let it stand to cool. Filter, wash and dry to obtain intermediate B. C3. Add DOPO to 1,4-dioxane and stir until DOPO is completely dissolved. Then add intermediate B to the above system, heat to 60° C., stir and react for 6 to 8 hours. After the reaction is completed, transfer the product to ice water and let it stand to cool. Filter, wash and dry to obtain the composite additive.

9. The anti-sag water-based acrylic resin coating according to claim 1, characterized in that: The molar ratio of the p-hydroxybenzaldehyde to 1H-benzotriazole-6-methylamine is 1:1, the molar ratio of the cyanuric chloride to the intermediate A is 1:3, and the molar ratio of the DOPO to the intermediate B is 3:

1.

10. A method for preparing the anti-sag water-based acrylic resin coating according to any one of claims 1 to 9, characterized in that: The following steps are involved: The modified water-based acrylic resin, composite additives, dispersant, defoamer, leveling agent and water are mixed to obtain a mixed liquid; the modified cellulose nanocrystals are then added to the mixed liquid and dispersed at high speed to obtain a water-based acrylic resin coating.

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