A waterborne acrylic resin coating resistant to sagging and a method of preparing the same

Abstract

The application belongs to the technical field of paint, and discloses an anti-sagging water-based acrylic resin paint and a preparation method thereof. The anti-sagging water-based acrylic resin paint comprises the following raw materials in parts by weight: modified water-based acrylic resin 110-130 parts, modified cellulose nanocrystal 10-25 parts, composite additive 3-5 parts, dispersing agent 4-6 parts, defoaming agent 0.5-2 parts, leveling agent 0.5-2 parts, and water 10-20 parts. The acrylic resin is modified by using an organic silicon oligomer and an epoxy resin, so that the coating film has high hardness and strong adhesion. By adding the modified cellulose nanocrystal and the composite additive, the paint film hardness, impact resistance, ultraviolet aging resistance and flame retardant performance of the material are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and particularly relates to an anti-sagging water-based acrylic resin coating and a preparation method thereof. BACKGROUND

[0002] In order to avoid metal corrosion, we usually change the structure of the metal itself, increase the surface protective layer, use the principle of electrochemistry, etc. to protect the metal, and the most common method in industry is to coat the surface of steel with anticorrosive and antifungal coating. Anticorrosive and antifungal coating has experienced a development process from solvent type to water type. The coating layer of solvent type coating has excellent performance, but the use of thin material leads to high content of organic volatile matter, which is harmful to the environment and is not easy to clean. Water-based coating uses water as a diluent, is environmentally friendly and energy-saving, has a high market price, and will gradually replace solvent type coating. Water-based acrylic anticorrosive and antifungal coating has been widely concerned by researchers due to its good high temperature resistance, water resistance, weather resistance, tensile property, color retention and outstanding low cost.

[0003] Water-based acrylic coating is an acrylic resin coating with methyl methacrylate (MMA), butyl acrylate (BA) and acrylic acid (AA) as the base material, and water as the dispersant. It can be used as a topcoat for metal corrosion protection or a topcoat for various metal surfaces. It has low viscosity, good stability and weather resistance. However, water-based acrylic coating also has many performance defects, such as slow drying of the paint film, low hardness, and poor adhesion, which leads to sagging of the paint film after drying. At the same time, it is easy to crack and fall off after long-term outdoor exposure, which exposes the internal metal and causes metal corrosion. Fire contact is also one of the important reasons for damage to the paint film, so the weather resistance and flame retardance of existing water-based acrylic coating need to be improved. SUMMARY

[0004] To solve the problems mentioned in the background, the present application provides an anti-sagging water-based acrylic resin coating and a preparation method thereof. The acrylic resin is modified by using organic silicon oligomers and epoxy resin, which has high coating film hardness and strong adhesion. The addition of modified cellulose nanocrystals and composite additives improves the paint film hardness, impact resistance, ultraviolet aging resistance and flame retardance of the material.

[0005] The object of the present application can be achieved by the following technical solutions:

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

[0007] The modified water-based acrylic resin is an organic silicon / epoxy composite modified acrylic resin;

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

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

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

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

[0012] A1, mixing methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid and n-dodecyl mercaptan, then adding vinyl triethoxysilane and stirring uniformly to obtain a mixed monomer solution;

[0013] A2, adding epoxy resin E44 and azobis isobutyronitrile into isopropyl alcohol and stirring to dissolve, heating to reflux, then slowly adding the mixed monomer solution under nitrogen protection, and incubating for 1-3 h;

[0014] A3, heating to 85-87°C, continuing to add azobis isobutyronitrile and isopropyl alcohol into the reaction system, incubating for 2-4 h, and removing isopropyl alcohol by vacuum filtration;

[0015] A4, when the system temperature drops to 55-65°C, adding water and diethanolamine to adjust the pH to neutral, and stirring and dispersing with a high-speed dispersion machine for 30 min to obtain the modified water-based acrylic resin.

[0016] Preferably, the vinyl triethoxysilane accounts for 3% of the total mass of the monomers, and the epoxy resin E44 accounts for 5% of the total mass of the monomers.

[0017] Preferably, the preparation method of the modified cellulose nanocrystal comprises the following steps:

[0018] B1, preparing a Tris buffer solution, then adding cellulose nanocrystal into the Tris buffer solution and ultrasonically dispersing, then adding hydrochloric acid dopamine into the cellulose nanocrystal dispersion, stirring and reacting for 10-12 h, centrifuging, washing and drying to obtain cellulose nanocrystal coated with polydopamine on the surface;

[0019] B2, adding 3-aminopropyltrimethoxysilane into distilled water and stirring for 10-15 min, then adding nano titanium dioxide, heating to 80°C, stirring and reacting for 3-5 h, centrifuging, washing and filtering, and then drying to obtain silane modified nano titanium dioxide.

[0020] B3, the cellulose nanocrystals coated with polydopamine are added into N,N-dimethylformamide and ultrasonically dispersed, then nano-titanium dioxide modified with silane is added, heated to 110 DEG C, and stirred for 4-6 h, and the product is centrifuged, washed, filtered and dried to obtain modified cellulose nanocrystals.

[0021] Preferably, the mass ratio of cellulose nanocrystals and 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 cellulose nanocrystals coated with polydopamine and modified nano-titanium dioxide is 3-5:1.

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

[0024] C1, p-hydroxybenzaldehyde and 1H-benzotriazole-6-methylamine are respectively dissolved in N,N-dimethylformamide, the 1H-benzotriazole-6-methylamine solution is slowly added to the p-hydroxybenzaldehyde, heated to 55 DEG C, and incubated for 1 h, and after the reaction is completed, the product is transferred to ice water and cooled, filtered, washed and dried to obtain intermediate A;

[0025] C2, cyanuric chloride and triethylamine are added to 1,4-dioxane, stirred until cyanuric chloride is completely dissolved, then intermediate A is added, heated to 45 DEG C, and stirred for 3-5 h, and after the reaction is completed, the product is transferred to ice water and cooled, filtered, washed and dried to obtain intermediate B;

[0026] C3, DOPO is added to 1,4-dioxane, stirred until DOPO is completely dissolved, then intermediate B is added to the above system, heated to 60 DEG C, and stirred for 6-8 h, and after the reaction is completed, the product is transferred to ice water and cooled, filtered, washed and dried to obtain the composite additive.

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

[0028] A preparation method of an anti-sagging water-based acrylic resin paint, comprising the following steps: mixing modified water-based acrylic resin, composite additive, dispersing agent, defoaming agent, leveling agent and water to obtain a mixed solution; then adding modified cellulose nanocrystals into the mixed solution and high-speed dispersing to obtain a water-based acrylic resin paint.

[0029] The beneficial effects of the present application are:

[0030] The present application modifies the acrylic resin by using organic silicon oligomer and epoxy resin, the coating film has high hardness and strong adhesion, by adding modified cellulose nanocrystals and composite additives, the film hardness, impact resistance, UV aging resistance and flame retardant performance of the material are improved.

[0031] The addition of epoxy resin increases the crosslinking between the molecular chains of the acrylic resin, and the network structure formed inside significantly improves the adhesion and hardness of the coating film. The organic silicon has extremely low surface energy, the bond energy of Si-O is much greater than that of C-C and C-O, and the bond is easy to rotate, which endows the material with excellent water resistance, high and low temperature resistance, gloss retention, softness, impact resistance and other properties.

[0032] The present application adds modified cellulose nanocrystals, which are loaded with nano titanium dioxide after polydopamine surface modification, cellulose nanocrystals are green materials with nanometer and renewable properties, and have excellent mechanical properties, when added to various polymers, they show good reinforcing effect, and nano titanium dioxide has very strong UV shielding ability, with an equivalent attenuation rate of >90%. Especially in improving the anti-ultraviolet ability of the coating film, it has good application prospect, and when applied to coatings, it can effectively shield the damage of ultraviolet rays to the paint film and improve the weather resistance of the coating.

[0033] The composite additive of the present application synthesizes a Schiff base compound containing a hydroxyl group by synthesizing hydroxybenzaldehyde and 1H-benzotriazole-6-methylamine, then reacts with cyanuric chloride to synthesize a Schiff base compound containing a triazine structure, and finally reacts with DOPO to obtain it. The molecular structure contains triazine ring, DOPO group and benzene propyl triazole group, among which the triazine ring and DOPO group contain a large number of N and P elements, which can decompose to produce phosphate and gas under high temperature conditions, promoting the dehydration and carbonization of the polymer, and forming a carbon protective layer. The non-combustible gas produced by decomposition also has good gas phase flame retardant effect. When the benzene propyl triazole group is subjected to ultraviolet irradiation, the hydrogen bonds in the molecule will be broken or form photoisomers, thereby converting harmful ultraviolet light energy into harmless heat energy, protecting the material from ultraviolet damage, thereby improving the anti-ultraviolet ability of the material. In combination with the nano titanium dioxide in the modified cellulose nanocrystals, the UV aging resistance of the material is further improved. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0035] Example 1

[0036] A modified water-based acrylic resin modified by composite modification of organic silicon and epoxy resin, a preparation method thereof comprising the following steps:

[0037] A1, methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid and n-dodecyl mercaptan are mixed, then 3% of the total mass of the monomers of vinyl triethoxysilane is added and stirred uniformly to obtain a mixed monomer solution;

[0038] A2, 5% of the total mass of the monomers of epoxy resin E44 and 3% of the total mass of the monomers of azobis isobutyronitrile are added into isopropyl alcohol and stirred to dissolve, heated to reflux, then the mixed monomer solution is slowly added under nitrogen protection, and incubated for 5h;

[0039] A3, heated to 86℃, continue to add azobis isobutyronitrile and isopropyl alcohol to the reaction system, incubate for 3h, and remove isopropyl alcohol by vacuum filtration;

[0040] A4, when the system temperature drops to 60℃, add water and diethanolamine, adjust the pH to neutral, and stir and disperse with a high-speed dispersion machine for 30min to obtain the modified water-based acrylic resin.

[0041] Example 2

[0042] A modified cellulose nanocrystal, which is obtained by coating cellulose nanocrystal with polydopamine and then loading nano titanium dioxide on the surface of the cellulose nanocrystal coated with polydopamine, a preparation method thereof comprising the following steps:

[0043] B1, prepare a Tris buffer solution, then add 3.5g of cellulose nanocrystal into 50ml of Tris buffer solution and ultrasonically disperse, then add 8.1g of dopamine hydrochloride into the cellulose nanocrystal dispersion, stir and react for 12h, centrifugal wash and dry to obtain cellulose nanocrystal coated with polydopamine on the surface;

[0044] B2, 0.2g of 3-aminopropyltrimethoxysilane is added into 20ml of distilled water and stirred for 10-15min, then 5.1g of nano titanium dioxide is added and heated to 80℃, stirred and reacted for 4h, centrifugal washed, filtered and dried to obtain silane modified nano titanium dioxide;

[0045] B3, 10.4g of cellulose nanocrystal coated with polydopamine on the surface is added into 50ml of N,N-dimethylformamide and ultrasonically dispersed, then 2.6g of silane modified nano titanium dioxide is added and heated to 110℃, stirred and reacted for 5h, the product is centrifugal washed, filtered and dried to obtain the modified cellulose nanocrystal.

[0046] Example 3

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

[0048] C1, 0.05 mol of p-hydroxybenzaldehyde and 0.05 mol of 1H-benzotriazole-6-methylamine are dissolved in 30 ml of N,N-dimethylformamide respectively, the 1H-benzotriazole-6-methylamine solution is slowly added to the p-hydroxybenzaldehyde, and the temperature is raised to 55°C, and the reaction is kept for 1h, after the reaction is completed, the product is transferred to ice water for standing and cooling, and then filtered, washed and dried to obtain an intermediate A, whose structural formula is as follows:

[0049]

[0050] C2, 0.02 mol of cyanuric chloride and 10 ml of triethylamine are added to 20 ml of 1,4-dioxane, and stirred until the cyanuric chloride is completely dissolved, then 0.06 mol of intermediate A is added, the temperature is raised to 45°C, and the reaction is stirred for 4h, after the reaction is completed, the product is transferred to ice water for standing and cooling, and then filtered, washed and dried to obtain an intermediate B, whose structural formula is as follows:

[0051]

[0052] C3, 0.05 mol of DOPO is added to 50 ml of 1,4-dioxane, and stirred until the DOPO is completely dissolved, then 0.02 mol of intermediate B is added to the above system, the temperature is raised to 60°C, and the reaction is stirred for 8h, after the reaction is completed, the product is transferred to ice water for standing and cooling, and then filtered, washed and dried to obtain a composite additive, whose structural formula is as follows:

[0053]

[0054] Example 4

[0055] An anti-sagging water-based acrylic resin coating, comprising the following raw materials by weight: modified water-based acrylic resin 120 parts, modified cellulose nanocrystal 18 parts, composite additive 4 parts, dispersant BYK-190 5 parts, defoamer BYK-020 1.2 parts, carboxymethyl cellulose 1.5 parts, and water 15 parts; the modified water-based acrylic resin is the organic silicon / epoxy composite modified acrylic resin prepared in Example 1; the modified cellulose nanocrystal is the nanometer titanium dioxide loaded polydopamine coated cellulose nanocrystal prepared in Example 2; and the composite additive is the triazine derivative containing DOPO groups and benzotriazole groups prepared in Example 3.

[0056] The preparation method of the anti-sagging water-based acrylic resin paint comprises the following steps: mixing modified water-based acrylic resin, composite additive, dispersant BYK-190, defoaming agent BYK-02, carboxymethyl cellulose and water to obtain a mixed solution; and then adding modified cellulose nanocrystals into the mixed solution for high-speed dispersion to obtain the water-based acrylic resin paint.

[0057] Example 5

[0058] The anti-sagging water-based acrylic resin paint comprises the following raw materials in parts by weight: modified water-based acrylic resin 110 parts, modified cellulose nanocrystals 25 parts, composite additive 3 parts, dispersant BYK-111 6 parts, defoaming agent BYK-019 0.5 parts, carboxymethyl cellulose 2 parts and water 10 parts; the modified water-based acrylic resin is the organic silicon / epoxy composite modified acrylic resin prepared in Example 1; the modified cellulose nanocrystals are the nanometer 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.

[0059] The preparation method of the anti-sagging water-based acrylic resin paint comprises the following steps: mixing modified water-based acrylic resin, composite additive, dispersant, defoaming agent, leveling agent and water to obtain a mixed solution; and then adding modified cellulose nanocrystals into the mixed solution for high-speed dispersion to obtain the water-based acrylic resin paint.

[0060] Example 6

[0061] The anti-sagging water-based acrylic resin paint comprises the following raw materials in parts by weight: modified water-based acrylic resin 130 parts, modified cellulose nanocrystals 10 parts, composite additive 5 parts, dispersant BYK-190 4 parts, defoaming agent BYK-028 2 parts, carboxymethyl cellulose 0.5 parts and water 20 parts; the modified water-based acrylic resin is the organic silicon / epoxy composite modified acrylic resin prepared in Example 1; the modified cellulose nanocrystals are the nanometer 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.

[0062] The preparation method of the anti-sagging water-based acrylic resin paint comprises the following steps: mixing modified water-based acrylic resin, composite additive, dispersant, defoaming agent, leveling agent and water to obtain a mixed solution; and then adding modified cellulose nanocrystals into the mixed solution for high-speed dispersion to obtain the water-based acrylic resin paint.

[0063] Comparative Example 1

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

[0065] The water-based acrylic resin is not modified by organic silicon and epoxy resin, and the preparation method comprises the following steps:

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

[0067] A2, azobis isobutyronitrile is added to isopropyl alcohol and stirred to dissolve, heated to reflux, then slowly add the mixed monomer solution under nitrogen protection, incubate for 2-4h, remove isopropyl alcohol by vacuum filtration;

[0068] A3, when the system temperature drops to 55-65℃, add water and diethanolamine, adjust the pH to neutral, and stir and disperse with a high-speed dispersing machine for 30min to obtain the water-based acrylic resin.

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

[0070] The preparation method of the anti-sagging water-based acrylic resin paint comprises the following steps: mixing the water-based acrylic resin, the composite additive, the dispersant BYK-190, the defoamer BYK-02, the carboxymethyl cellulose and the water to obtain a mixed solution; then adding the modified cellulose nanocrystals into the mixed solution and high-speed dispersing to obtain the water-based acrylic resin paint.

[0071] Comparative Example 2

[0072] An anti-sagging water-based acrylic resin paint comprises the following raw materials by weight: modified water-based acrylic resin 120 parts, composite additive 4 parts, dispersant BYK-190 5 parts, defoamer BYK-020 1.2 parts, carboxymethyl cellulose 1.5 parts, and water 15 parts; the modified water-based acrylic resin is the organic silicon / epoxy composite modified acrylic resin prepared in Example 1; the composite additive is the triazine derivative containing DOPO groups and benzotriazole groups prepared in Example 3.

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

[0074] Comparative Example 3

[0075] An anti-sagging waterborne acrylic resin paint comprising the following raw materials by weight: modified waterborne acrylic resin 120 parts, modified cellulose nanocrystal 18 parts, dispersant BYK-190 5 parts, defoamer BYK-02 1.2 parts, carboxymethyl cellulose 1.5 parts, water 15 parts; the modified waterborne acrylic resin is the organic silicon / epoxy composite modified acrylic resin prepared in Example 1; the modified cellulose nanocrystal is the nanometer titanium dioxide loaded polydopamine coated cellulose nanocrystal prepared in Example 2.

[0076] The preparation method of the anti-sagging waterborne acrylic resin paint described above, comprising the following steps: mixing the modified waterborne acrylic resin, the dispersant BYK-190, the defoamer BYK-02, the carboxymethyl cellulose, and the water to obtain a mixed solution; then adding the modified cellulose nanocrystal into the mixed solution and dispersing at high speed to obtain the waterborne acrylic resin paint.

[0077] Performance detection

[0078] I. The anti-sagging waterborne acrylic resin paints prepared in Examples 4-6 and Comparative Examples 1-3 were determined for pencil hardness according to GBT 6739-2022, for impact resistance of paint film according to GB / T 1732-2020, for adhesion of paint film according to GB / T 9286-2021, and for wear resistance of paint film according to GB / T 1768-2006, and the data are shown in Table 1 below.

[0079] Table 1 Chemical properties of anti-sagging waterborne acrylic resin paint

[0080]

[0081]

[0082] As can be seen from the data in Table 1, the anti-sagging waterborne acrylic resin paints prepared in Examples 3-5 and Comparative Example 1 have good pencil hardness, impact resistance, and wear resistance after curing. The paint film adhesion in Comparative Example 1 is slightly decreased because the waterborne acrylic resin is not modified by organic silicon and epoxy resin. The pencil hardness and wear resistance of the paint film in Comparative Example 2 are significantly decreased because the modified cellulose nanocrystal is not added.

[0083] II. Test of UV aging resistance

[0084] The anti-sagging waterborne acrylic resin coatings prepared in Examples 4-6 and Comparative Examples 1-3 were coated on the surface of an aluminum alloy plate material (20 mm x 50 mm x 2 mm) which was degreased and dehydrated by acetone and ethanol in sequence and then dried, and after the paint film was cured, the sample plate was placed horizontally in an artificial ultraviolet accelerated aging test chamber, and the test conditions were as follows: the power of the ultraviolet lamp used was 50 W, the wavelength peak values were 254 μm and 365 μm, respectively, the distance between the paint film and the ultraviolet lamp was 20 cm, and the test setting time was 2400 h. The gloss change degree of the paint film before and after aging was observed by eye, and the gloss before and after aging was determined according to GB / T 9754, and the gloss loss rate (%) was calculated (gloss loss rate = (A0-A1) / A0 x 100%, A0 is the gloss determination value before aging, and A1 is the gloss determination value after aging), and the data are shown in Table 2.

[0085] Table 2 Test results of the anti-sagging waterborne acrylic resin coatings for ultraviolet aging resistance

[0086]

[0087]

[0088] As can be seen from the data in Table 2, the anti-sagging waterborne acrylic resin coatings in Examples 4-6 and Comparative Example 1 all have good ultraviolet aging resistance, and the anti-sagging waterborne acrylic resin coatings in Comparative Examples 2 and 3 have general ultraviolet aging resistance, indicating that the modified cellulose nanocrystals and the composite additives in the present application can both improve the ultraviolet aging resistance of the paint film.

[0089] III. Test of flame retardant performance

[0090] The anti-sagging waterborne acrylic resin coatings prepared in Examples 4-6 and Comparative Examples 1-3 were poured into a polytetrafluoroethylene mold, and after the paint film was cured, the vertical burning (UL94) grade was tested according to ASTM3801 standard, and the data are shown in Table 3.

[0091] Table 3 Test results of the anti-sagging waterborne acrylic resin coatings for flame retardant performance

[0092] 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

[0093] As can be seen from the data in Table 3, the anti-sagging waterborne acrylic resin coatings in Examples 4-6 and Comparative Example 2 all have good flame retardant performance, and the anti-sagging waterborne acrylic resin coatings in Comparative Example 1, which is not modified by silicone and epoxy resin, have slightly decreased flame retardant performance, because the addition of silicone promotes the dehydration and carbonization of the polymer during thermal cracking, and at the same time forms a carbon protective layer of Si-O and Si-C, which can improve the flame retardant performance of the material. The anti-sagging waterborne acrylic resin coatings in Comparative Example 3, which is not added with a composite additive, have a more obvious decrease in flame retardant performance.

[0094] In the description of the specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0095] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. An anti-sag waterborne acrylic resin paint, characterized by, The raw materials include the following components by weight: modified water-based acrylic resin 110-130 parts, modified cellulose nanocrystal 10-25 parts, composite additive 3-5 parts, dispersant 4-6 parts, defoaming agent 0.5-2 parts, leveling agent 0.5-2 parts, and water 10-20 parts; The modified water-based acrylic resin is a silicone / epoxy composite modified acrylic resin; The modified cellulose nanocrystal is obtained by coating cellulose nanocrystal with polydopamine and then loading nano-titanium dioxide on the surface of the cellulose nanocrystal through a silane coupling agent; The composite additive is a triazine derivative containing a DOPO group and a phenylpropyl triazole group; The preparation method of the modified cellulose nanocrystal comprises the following steps: B1. A Tris buffer solution is prepared, and then cellulose nanocrystal is added into the Tris buffer solution for ultrasonic dispersion, and then hydrochloric acid dopamine is added into the cellulose nanocrystal dispersion, and the mixture is stirred for 10-12 hours, centrifuged, washed and dried to obtain cellulose nanocrystal coated with polydopamine on the surface; B2. 3-aminopropyltrimethoxysilane is added into distilled water, stirred for 10-15 minutes, and then nano-titanium dioxide is added, and the mixture is heated to 80°C and stirred for 3-5 hours, and then centrifuged, washed, filtered and dried to obtain silane-modified nano-titanium dioxide; B3. The cellulose nanocrystal coated with polydopamine on the surface is added into N,N-dimethylformamide for ultrasonic dispersion, and then the silane-modified nano-titanium dioxide is added, and the mixture is heated to 110°C and stirred for 4-6 hours, and then the product is centrifuged, washed, filtered and dried to obtain the modified cellulose nanocrystal; The preparation method of the composite additive comprises the following steps: C1. p-Hydroxybenzaldehyde and 1H-benzotriazole-6-methylamine are respectively dissolved in N,N-dimethylformamide, and the 1H-benzotriazole-6-methylamine solution is slowly added into the p-hydroxybenzaldehyde, and the mixture is heated to 55°C and kept for 1 hour, and then the product is transferred into ice water for cooling, and then filtered, washed and dried to obtain intermediate A; C2. Cyanuric chloride and triethylamine are added into 1,4-dioxane, and the mixture is stirred until the cyanuric chloride is completely dissolved, and then intermediate A is added, and the mixture is heated to 45°C and stirred for 3-5 hours, and then the product is transferred into ice water for cooling, and then filtered, washed and dried to obtain intermediate B; C3. DOPO is added into 1,4-dioxane, and the mixture is stirred until the DOPO is completely dissolved, and then intermediate B is added into the above system, and the mixture is heated to 60°C and stirred for 6-8 hours, and then the product is transferred into ice water for cooling, and then filtered, washed and dried to obtain the composite additive; The molar ratio of the p-hydroxybenzaldehyde to the 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.

2. The anti-sagging waterborne acrylic resin paint according to claim 1, characterized by, The dispersant is a polyurethane oligomer or a phosphate ester active agent, the defoaming agent is a polyether defoaming agent, a silicone type defoaming agent or a polyether siloxane copolymer, and the leveling agent is carboxymethyl cellulose.

3. The sag-resistant waterborne acrylic resin paint according to claim 1, characterized by, The preparation method of the modified water-based acrylic resin comprises the following steps: A1, methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, acrylic acid and n-dodecyl mercaptan are mixed, then vinyl triethoxysilane is added and stirred uniformly to obtain a mixed monomer solution; A2, the epoxy resin E44 and azobis isobutyronitrile are added into isopropyl alcohol and stirred to dissolve, heated to reflux, then the mixed monomer solution is slowly added under nitrogen protection, and the reaction is kept for 1-3h; A3, the temperature is raised to 85-87℃, azobis isobutyronitrile and isopropyl alcohol are continuously added to the reaction system, and the reaction is kept for 2-4h, and isopropyl alcohol is removed by vacuum filtration; A4, when the system temperature drops to 55-65℃, water and diethanolamine are added, the pH is adjusted to neutral, and the mixture is stirred and dispersed for 30min by a high-speed dispersion machine to obtain a modified water-based acrylic resin.

4. The anti-sagging waterborne acrylic resin paint according to claim 3, characterized by, The vinyl triethoxysilane accounts for 3% of the total mass of the monomers, and the epoxy resin E44 accounts for 5% of the total mass of the monomers.

5. The sag-resistant waterborne acrylic resin paint according to claim 1, characterized by, The mass ratio of the cellulose nanocrystals and dopamine hydrochloride is 1:2-3, and the mass of 3-aminopropyl trimethoxysilane is 3-5% of the mass of the nano-titanium dioxide.

6. The sag-resistant waterborne acrylic resin paint according to claim 1, characterized by, The mass ratio of the cellulose nanocrystals coated with polydopamine and the modified nano-titanium dioxide is 3-5:

1.

7. A process for the preparation of a sag-resistant aqueous acrylic resin paint as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: The modified water-based acrylic resin, the composite additive, the dispersing agent, the defoaming agent, the leveling agent and water are mixed to obtain a mixed solution, and then the modified cellulose nanocrystals are added into the mixed solution and dispersed at high speed to obtain a water-based acrylic resin coating.

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