Aurora color-protecting finishing varnish and preparation method thereof

Abstract

The invention discloses aurora color-protecting finishing varnish and a preparation method thereof. The aurora color-protecting finishing varnish is mainly prepared from the following raw materials: high-solid-content composite resin emulsion, nano TiO2 / SiO2 composite powder, a core-shell ultraviolet light absorber, nano ITO powder, HALS grafted cellulose, a microcapsule repairing agent, a wetting dispersant, an organic silicon defoaming agent, a coalescing agent and deionized water. The nano TiO2 / SiO2 composite powder is preferably selected as the raw material, a multi-layer light interference interface is constructed, the high-gloss aurora effect is achieved, the synergistic effect of four-color maintenance mechanisms of ultraviolet blocking, infrared heat reflection, free radical capture and self-repairing is combined, after artificial weather aging is resisted for 5000 h, the gloss retention rate of a coating is larger than or equal to 90%, the color change degree delta E is smaller than or equal to 1.5, and the coating is free of paint film defects such as cracking. The invention has artistic decoration and long-acting protection functions, can prolong the decoration life of the outer wall of a building to 15 years or more, reduces the comprehensive cost by 40%, and is suitable for high-end stone-like coating systems such as granite-like multicolor paint and stone-like paint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of architectural coatings, in particular to a polar light color protection finish varnish and a preparation method thereof. BACKGROUND

[0002] As the mainstream material for building exterior wall decoration, the texture and color durability of stone-like paint highly depend on the protection of finish varnish. However, traditional finish varnish can provide basic protection, but has significant defects in practical application: first, single gloss system cannot restore the three-dimensional optical effect of natural stone, resulting in lack of dynamic level of stone-like coating; second, the ultraviolet blocking rate is generally lower than 80%, and obvious discoloration occurs after 2-3 years of use in hot and humid, strong ultraviolet areas; third, the anti-pollution performance is insufficient, and nano-level pollutants can easily penetrate into the micropores of the paint film, forming irreversible stains and greatly reducing the decoration life. In addition, existing products are prone to yellowing and cracking under extreme temperature difference, which cannot meet the demand of modern buildings for long-term aesthetics and functionality.

[0003] To solve the above problems, the existing technology attempts to improve by introducing nano materials or ultraviolet absorbers, such as Chinese patent CN118772749B discloses a thick paste type composite stone-like paint and a preparation method, which modifies graphene and titanium dioxide by using light stable coupling monomers and / or new light stabilizers to obtain a graphene-titanium dioxide composite material, which is introduced into the finish varnish to obtain a finish varnish with excellent weather resistance. The introduction of light stabilizers and nanoparticles improves weather resistance, but the single protection mechanism cannot cope with the synergistic aging of light-heat-mechanical in complex environment, and the scattering effect leads to a decrease in light transmittance, covering the natural texture of stone-like coating.

[0004] Therefore, it is urgent to develop a polar light color protection finish varnish with high bright light effect, multi-dimensional protection network and precise repair function to break through the technical barriers of stone-like coating "color protection not durable, protection not coordinated", and meet the comprehensive demand of high-end building market for decoration, durability and environmental protection. SUMMARY

[0005] The present application overcomes the above shortcomings and provides a polar light color protection finish varnish and a preparation method thereof. The polar light color protection finish varnish constructs mirror reflection high light effect and multi-level light interference interface through directional arrangement technology and nano particle refractive index difference, and combines four-dimensional color protection mechanisms of "ultraviolet blocking + infrared heat reflection + free radical capture + self-repairing", thereby comprehensively improving the color protection ability and weather resistance of the finish varnish, such as yellowing resistance, powdering resistance, light loss resistance and cracking resistance.

[0006] To achieve the above purpose, the technical scheme of the present application is as follows: A polar light color protection finish varnish, characterized by mainly consisting of the following raw materials in the following mass fraction ratio: High solid composite resin emulsion 63-77 parts Nano TiO2 / SiO2 composite powder 6-10 parts Core-shell ultraviolet absorber 2-4 parts Nano indium tin oxide 0.5-1.5 parts Hindered amine light stabilizer grafted cellulose 0.5-1.5 parts Light triggered acrylic resin based microcapsule repair agent 1-3 parts Wetting dispersant 1.5-2.5 parts Silicone defoaming agent 0.5-1.5 parts Film forming aid 1-3 parts Deionized water 7-13 parts The high solid composite resin emulsion is prepared by mixing the following raw materials in the following mass fraction ratio: High solid silicone fluorocarbon resin 5-7 parts Hydroxy acrylate emulsion 1 part The nano TiO2 / SiO2 composite powder is prepared by mixing the following raw materials in the following mass fraction ratio: Nano titanium dioxide 1-3 parts Nano silicon dioxide 1 part

[0007] Further, the preparation method of the hindered amine light stabilizer grafted cellulose is as follows: (1) Dissolve cellulose in chlorinated 1-allyl-3-methyl imidazole ionic liquid, then add 2-bromoisobutyryl bromide, and react at 20-30°C for 23-25 h to generate a macromolecular initiator; wherein the mass ratio of cellulose, chlorinated 1-allyl-3-methyl imidazole ionic liquid and 2-bromoisobutyryl bromide is 1:10-30:4-10; (2) Disperse the initiator prepared in step (1) in N,N-dimethylformamide, then sequentially add hindered amine light stabilizer monomer, copper bromide catalyst and N,N-methylene bisacrylamide, wherein the mass ratio of initiator and N,N-dimethylformamide is 1:30-50, the mass ratio of initiator and hindered amine light stabilizer monomer is 1:10-15, the amount of N,N-methylene bisacrylamide is 0.3-0.5% of the mass of the hindered amine light stabilizer monomer, and the amount of copper bromide catalyst is 0.2-0.3% of the mass of the hindered amine light stabilizer monomer; react under the conditions of inert atmosphere, temperature of 60-70°C and stirring speed of 300-400 rpm for 15-17 h, then wash with deionized water until the filtrate is clear, vacuum dry, and crush to obtain the hindered amine light stabilizer grafted cellulose.

[0008] Further, the hindered amine light stabilizer monomer is one or a combination of both of a low molecular weight hindered amine light stabilizer HALS-770 and a high molecular weight hindered amine light stabilizer HALS-622 in any ratio, the low molecular weight meaning a molecular weight less than 1000 g / mol, and the high molecular weight meaning a molecular weight more than 1000 g / mol.

[0009] Further, the cellulose is hydroxyethyl cellulose.

[0010] Further, the preparation method of the light-triggered acrylic resin-based microcapsule repair agent is as follows: (1) 60-80 parts of epoxy resin and 5-10 parts of nano indium tin oxide are mixed and dissolved in 200 parts of deionized water, and emulsified at room temperature at a speed of 1000-1500 rpm for 5-10 min to obtain an inner water phase; (2) The inner water phase prepared in step (1) is added to a xylene solution containing methyl methacrylate and butyl acrylate monomers, and reacted at a temperature of 40-50°C and a speed of 2000-3000 rpm for 10-15 min to form a preliminary emulsion; the mass ratio of methyl methacrylate to butyl acrylate is 3-5:1; the mass ratio of the total amount of methyl methacrylate and butyl acrylate to xylene is 1:30-50; and the mixing mass ratio of the inner water phase to the xylene solution containing methyl methacrylate and butyl acrylate monomers is 1:3-6; (3) The polyurethane prepolymer is dissolved in a 1-3 wt% polyvinyl alcohol solution, and then injected into the preliminary emulsion prepared in step (2) and stirred at a speed of 500-800 rpm for 20-30 min to form a double emulsion, wherein the mass ratio of the polyurethane prepolymer to the epoxy resin of step (1) is 20-40:60-80, and the mixing mass ratio of the polyurethane prepolymer to the polyvinyl alcohol solution is 1:20-30; (4) The initiator azobisisobutyronitrile is added to the double emulsion prepared in step (3), and heated to 70-80°C, and reacted for 4-6 h to form an acrylic resin wall material; the amount of initiator azobisisobutyronitrile added is 0.5-1% of the total amount of methyl methacrylate and butyl acrylate monomers in step (2); then the pH is adjusted to 8.0-9.0 by adding ammonia water, and then the ethylenediamine is added and cured for 2-3 h, and then washed and centrifuged 2-3 times with ethanol, and then vacuum dried at a temperature of 50-60°C for 8-12 h to obtain a double-chamber acrylic resin-based microcapsule repair agent; wherein the amount of ethylenediamine added is 10-15% of the amount of polyurethane prepolymer added in step (3).

[0011] Further, the high solid content silicone fluorocarbon resin has a solid content of 40-60%, a Tg of 20-50℃, and a MFFT of 0-10℃, preferably Dow (LS-2840); the hydroxyl acrylic emulsion has a solid content of 39-41%, a Tg of 10-30℃, and a MFFT of 5-15℃, preferably BASF (8300).

[0012] Further, the nano indium tin oxide is a flaky indium tin oxide with a thickness of 200-300 nm, preferably Milan New Material (1173); the nano titanium dioxide is a rutile nano titanium dioxide with a particle size of 30-50 nm; the silica is a nano silica hollow microsphere with a particle size of 40-60 nm; and the core-shell ultraviolet absorber is an ultraviolet absorber with a core-shell structure, wherein the core layer is a benzotriazole ultraviolet absorbing active ingredient, and the shell layer is an organic silicon inorganic material.

[0013] Further, the silicone defoaming agent is one or a combination of polydimethylsiloxane defoaming agent, methyl silicone oil defoaming agent, or condensed silicone defoaming agent.

[0014] Further, the film-forming aid is one or a combination of dodecanol ester and carboxylic acid ester.

[0015] Further, the preparation method of the aurora color protection topcoat varnish comprises the following steps in sequence: (1) Powder dispersion stage: add deionized water to the dispersion cylinder, add nano TiO2 / SiO2 composite powder, nano indium tin oxide, and wetting dispersant at a rotation speed of 300-500 rpm, then increase the rotation speed to 2000-3000 rpm, and continue to disperse for 25-35 min until the pre-dispersed slurry fineness is ≤20 μm; (2) Emulsion modification stage: add core-shell ultraviolet absorber and hindered amine light stabilizer grafted cellulose to the high solid content composite resin emulsion in sequence, and modify at 40-50℃ and a rotation speed of 800-1000 rpm for 1-3 h to obtain a modified emulsion. (3) Gradient blending stage: the pre-dispersed slurry obtained in step (1) is slowly added to the modified emulsion obtained in step (2) in three times, wherein the rotation speed of the dispersion cylinder is adjusted to 1500-2000 rpm in the first time, the rotation speed of the dispersion cylinder is adjusted to 1000-1500 rpm in the second time, the rotation speed of the dispersion cylinder is adjusted to 800-1000 rpm in the third time, and after each time of adding the pre-dispersed slurry, about 1 / 3 of the photo-triggered acrylic resin-based microcapsule repair agent is added for continuous dispersion for 8-10 min; then the silicone defoaming agent and the film-forming aid are added for dispersion for 10-20 min, and after filtering through a 100-300 mesh filter, the polar light color protection topcoat varnish is obtained.

[0016] The advantages of the present application are: The raw materials of the present application are compounded by using hydroxyl acrylic emulsion and combined with gradient blending process, which realizes the ordered arrangement of nanoparticles in the horizontal direction during the film-forming process, enhances the high gloss effect of mirror reflection, and improves the uniform and effective contact of TiO2 / SiO2 by adding the nano TiO2 / SiO2 composite powder into the system after compounding, and the nano SiO2 is a hollow microsphere structure, which forms a multi-level light reflection interface in the coating by using the difference in refractive index between the two under the synergistic effect of nano TiO2, thereby producing a polar light effect. The use of hydroxyl acrylic emulsion with stronger polarity and better compatibility can form an interpenetrating network with silicone fluorocarbon resin, optimize the adhesion between the coating layers, and the polar groups (hydroxyl groups) on the hydroxyl acrylic molecular chain can produce strong hydrogen bonding with the surface of the nano powder, improve the dispersion uniformity and storage stability of the functional components in the system, and avoid the problems of agglomeration or sedimentation caused by the poor compatibility of the added nano powder and microcapsules with fluorocarbon resin.

[0017] The raw materials of the present application are preferably silicone-modified fluorocarbon resins, which are compounded with hydroxyl acrylic emulsion to form an interpenetrating network structure, which not only improves the stability of nanoparticles in the topcoat varnish, but also improves the adhesion of the topcoat layer to the stone-like coating.

[0018] The polar light color protection topcoat varnish prepared by the present application has a protective effect on the stone-like coating through a four-dimensional color protection mechanism of "ultraviolet blocking + infrared heat reflection + free radical capture + self-repairing", wherein the core-shell ultraviolet absorber is used to achieve full coverage absorption of ultraviolet rays; the hindered amine light stabilizer grafted with hydroxyethyl cellulose is uniformly distributed in the coating to continuously capture and neutralize the free radicals generated by photoaging; the introduction of sheet-shaped nano indium tin oxide can provide a high-transparency and more transparent paint film, which can reflect heat and reduce the surface temperature of the coating, thereby delaying thermal aging; the embedded microcapsule repair agent releases repair substances when the coating appears microcracks to restore the barrier function. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The schematic diagram of aurora effect mechanism and color protection principle of the aurora color protection varnish of the present application. Specific implementation method

[0020] The exemplary embodiments disclosed herein will be described in greater detail below, in order to more completely understand the present application and to enable the present application to be fully conveyed to those skilled in the art. Although exemplary embodiments of the present application are shown, it should be understood that the present application should not be limited by the embodiments set forth herein.

[0021] The raw materials involved in the following examples and comparative examples of the present application and their brands are as follows: Silicone fluorocarbon resin: Dow (LS-2840) Hydroxy acrylate emulsion: BASF (8300) Rutile type nano titanium dioxide: Conada (KND-TH100) Nano silica hollow microspheres: Xingbeike (COOH-HMSNs) Hindered amine light stabilizer HALS-770: Jade (JADEWIN LS 770, molecular weight about 480 g / mol) Hindered amine light stabilizer HALS-622: Jade (JADEWIN LS 662, molecular weight about 3000 g / mol) Cellulose: Australia Run (TH100K) Chlorinated 1-allyl-3-methyl imidazole ionic liquid: Smack 2-bromoisobutyryl bromide: Macklin N,N-dimethylformamide: Nanjing Reagent Copper bromide catalyst: Xijiecheng N,N-methylene bisacrylamide: Xijiecheng Epoxy resin: Sylva (CSR-303) Nano indium tin oxide: Milan New Material (1173) Methyl methacrylate (MMA): Macklin Butyl acrylate (BA): Macklin Polyurethane prepolymer: Covestro (DESMODUR E1660) Polyvinyl alcohol (PVA, powdered polyvinyl alcohol): Jianchao Fort (1788) Initiator AIBN (azobisisobutyronitrile): Taihexi Chemical Ammonia: Wanshengchuantong Chemical Ethylene diamine: New Chemical Ethanol: Dongneng Chemical Core-shell UV absorber: Dongjin Kangtai Chemical (UV-P) Indium tin oxide with flaky structure: Bolaibio (Nano ITO powder) Polydimethylsiloxane defoaming agent: Afcona (AFCONA-2507) Methyl silicone oil defoaming agent: Ningxia Dongke (T931) Condensed silicone defoaming agent: Ningxia Dongke (T932) Dodecanol ester: Huachang Zhilian New Material (C12) Carboxylic acid ester mixture: Shengxinghang (LOCA A+) Example 1

[0022] The aurora color protection finish varnish in this example is composed of the following raw materials by weight: High solid content composite resin emulsion 63 parts, Nano TiO2 / SiO2 composite powder 10 parts, Core-shell UV absorber 4 parts, Nano indium tin oxide 1.5 parts, Hindered amine light stabilizer grafted cellulose 0.5 parts, Light triggered acrylic resin based microcapsule repair agent 3 parts, Wetting dispersant 2.5 parts, Silicone defoaming agent 1.5 parts, Film forming aid 1 part, Deionized water 13 parts.

[0023] The high solid content composite resin emulsion is composed of the following mass fraction ratio: High solid content silicone fluorocarbon resin 5 parts Hydroxy acrylic emulsion 1 part The nano TiO2 / SiO2 composite powder is composed of the following mass fraction ratio: Rutile type nano titanium dioxide 1 part Nano silica hollow microspheres 1 part.

[0024] The performance parameters of each material in this example are as follows: The nano indium tin oxide powder is indium tin oxide with flaky structure, with an average thickness of 200 nm.

[0025] The average particle size of the nano TiO2 is 30 nm.

[0026] The average particle size of the nano SiO2 is 40 nm.

[0027] The silicone defoaming agent is a polydimethylsiloxane defoaming agent.

[0028] The film forming aid is dodecanol ester.

[0029] The cellulose is hydroxyethyl cellulose.

[0030] The hindered amine light stabilizer monomer is low molecular weight hindered amine light stabilizer HALS-770.

[0031] The preparation method of the hindered amine light stabilizer grafted cellulose in this embodiment is as follows: (1) The cellulose is dissolved in 1-allyl-3-methylimidazolium chloride ionic liquid and reacted with 2-bromoisobutyryl bromide at 20°C for 23 h to form a macromolecular initiator, wherein the mass ratio of cellulose, 1-allyl-3-methylimidazolium chloride ionic liquid and 2-bromoisobutyryl bromide is 1:10:4.

[0032] (2) The initiator prepared in step (1) is dispersed in N,N-dimethylformamide, and then hindered amine light stabilizer monomer, copper bromide catalyst and N,N-methylenebisacrylamide are added in sequence, wherein the mass ratio of initiator and N,N-dimethylformamide is 1:30, the mass ratio of initiator and hindered amine light stabilizer monomer is 1:10, N,N-methylenebisacrylamide is 0.3% of the mass of the hindered amine light stabilizer monomer, the amount of copper bromide catalyst is 0.2% of the mass of the hindered amine light stabilizer monomer, and the reaction is carried out under the conditions of inert atmosphere, temperature of 60°C and stirring speed of 300 rpm for 15 h. Finally, after washing with deionized water until the filtrate is clear, vacuum drying and crushing, the hindered amine light stabilizer grafted cellulose is obtained.

[0033] The preparation method of the acrylic resin-based microcapsule in this embodiment is as follows: (1) 60 parts of epoxy resin and 5 parts of nano indium tin oxide are mixed and dissolved in 200 parts of deionized water to obtain an inner aqueous phase by emulsification at room temperature and a stirring speed of 1000 rpm for 5 min.

[0034] (2) The inner aqueous phase prepared in step (1) is added to a xylene solution containing methyl methacrylate (MMA) and butyl acrylate (BA) monomers, and the reaction is carried out at a temperature of 40°C and a stirring speed of 2000 rpm for 10 min to form a preliminary emulsion, wherein the mass ratio of methyl methacrylate to butyl acrylate is 3:1, the mass ratio of the total amount of methyl methacrylate and butyl acrylate to xylene is 1:30; and the mixing mass ratio of the inner aqueous phase to the xylene solution containing methyl methacrylate and butyl acrylate monomers is 1:3.

[0035] (3) 20 parts of polyurethane prepolymer was dissolved in 1 wt% polyvinyl alcohol solution, and then was injected into the primary emulsion prepared in step (2) and stirred at a speed of 500 rpm for 20 min to form a double emulsion, wherein the mass ratio of polyurethane prepolymer to epoxy resin in step (1) was 20:60, and the mixed mass ratio of polyurethane prepolymer to polyvinyl alcohol solution was 1:20.

[0036] (4) 0.5% of initiator AIBN (azobisisobutyronitrile) based on the total mass of methyl methacrylate and butyl acrylate monomers in step (2) was added to the double emulsion prepared in step (3), and the temperature was raised to 70°C, and the reaction was continued for 4 h to form an acrylic resin wall material; the pH was adjusted to 8.0 by adding ammonia water, and then ethylenediamine was added and cured for 2 h, and then washed with ethanol and centrifuged twice, and then vacuum dried at a temperature of 50°C for 8 h to obtain a double-chamber acrylic resin-based microcapsule repair agent, wherein the amount of ethylenediamine added was 10% of the amount of polyurethane prepolymer added.

[0037] The preparation method of the aurora color protection finish varnish in this example is as follows: (1) Powder dispersion stage: deionized water was added to a dispersion cylinder, and nano TiO2 / SiO2 composite powder, nano indium tin oxide powder, and wetting dispersant were added at a speed of 500 rpm, and then the speed was increased to 3000 rpm, and the dispersion was continued for 35 min until the pre-dispersion slurry fineness was ≤20 μm.

[0038] (2) Emulsion modification stage: core-shell ultraviolet absorber and hindered amine light stabilizer (HALS) grafted cellulose were sequentially added to the high-solid composite resin emulsion, and a modification reaction was carried out at 40°C and a speed of 1000 rpm for 1 h to obtain a modified emulsion.

[0039] (3) Gradient blending stage: the pre-dispersion slurry obtained in step (1) was slowly added to the modified emulsion obtained in step (2) in three times, wherein the first time was at a speed of 2000 rpm, the second time was at a speed of 1500 rpm, and the third time was at a speed of 1000 rpm, and after each addition of the pre-dispersion slurry, about 1 / 3 of the light-triggered acrylic resin-based microcapsule repair agent was added and dispersed for 20 min; then silicone defoaming agent and film-forming aid were added and dispersed for another 20 min, and then filtered through a 100-mesh filter to obtain the aurora color protection finish varnish. Example 2

[0040] The aurora color protection finish varnish in this example is composed of the following raw materials by weight: high-solid composite resin emulsion 70 parts, nano TiO2 / SiO2 composite powder 8 parts, core-shell ultraviolet absorber 3 parts, Nano indium tin oxide 1 part, Hindered amine light stabilizer grafted cellulose 1 part, Light triggered acrylic resin based microcapsule repair agent 2 parts, Wetting dispersant 2 parts, Silicone defoaming agent 1 part, Film forming aid 2 parts, Deionized water 10 parts.

[0041] The high solid content composite resin emulsion is composed of the following mass fraction ratio: High solid content silicone fluorocarbon resin 6 parts Hydroxy acrylic emulsion 1 part The nano TiO2 / SiO2 composite powder is composed of the following mass fraction ratio: Rutile type nano titanium dioxide 2 parts Nano silica hollow microspheres 1 part.

[0042] The performance parameters of each material in this embodiment are as follows: The nano indium tin oxide powder is a flaky indium tin oxide with an average thickness of 250 nm.

[0043] The average particle size of the nano TiO2 is 40 nm.

[0044] The average particle size of the nano SiO2 is 50 nm.

[0045] The silicone defoaming agent is a methyl silicone oil type defoaming agent.

[0046] The film forming aid is a mixture of dodecanol ester and carboxylic acid ester combined in a 1:1 ratio.

[0047] The cellulose is hydroxyethyl cellulose.

[0048] The hindered amine light stabilizer monomer is a combination of low molecular weight hindered amine light stabilizer HALS-770 with a molecular weight below 1000 g / mol and high molecular weight hindered amine light stabilizer HALS-622 with a molecular weight above 1000 g / mol in a 1:1 ratio.

[0049] The preparation method of hindered amine light stabilizer grafted cellulose in this embodiment is: Dissolve the cellulose in chlorinated 1-allyl-3-methyl imidazole ionic liquid, and react with 2-bromoisobutyryl bromide at 25°C for 24h to form a macromolecular initiator, wherein the mass ratio of cellulose, chlorinated 1-allyl-3-methyl imidazole ionic liquid and 2-bromoisobutyryl bromide is 1:20:7.

[0050] (2) The initiator prepared in step (1) is dispersed in N,N-dimethylformamide, and then a hindered amine light stabilizer monomer, a copper bromide catalyst and N,N-methylene bisacrylamide are sequentially added, wherein the mass ratio of the initiator to N,N-dimethylformamide is 1:40, the mass ratio of the initiator to the hindered amine light stabilizer monomer is 1:12, N,N-methylene bisacrylamide is 0.4% of the mass of the hindered amine light stabilizer monomer, and the amount of the copper bromide catalyst is 0.25% of the mass of the hindered amine light stabilizer monomer, and the reaction is carried out under the conditions of an inert atmosphere, a temperature of 65°C and a stirring speed of 350 rpm for 16 h, and finally the product is washed with deionized water until the filtrate is clear, vacuum dried and crushed to obtain the hindered amine light stabilizer grafted cellulose.

[0051] The preparation method of the acrylic resin-based microcapsule in this example is as follows: (1) 70 parts of epoxy resin and 7 parts of nano indium tin oxide are mixed and dissolved in 200 parts of deionized water to obtain an inner water phase by emulsification at room temperature and a rotation speed of 1200 rpm for 7 min.

[0052] (2) The inner water phase prepared in step (1) is added to a xylene solution containing methyl methacrylate (MMA) and butyl acrylate (BA) monomers, and the reaction is carried out at a temperature of 45°C and a rotation speed of 2500 rpm for 13 min to form a preliminary emulsion, wherein the mass ratio of methyl methacrylate to butyl acrylate is 4:1, the mass ratio of the total amount of methyl methacrylate and butyl acrylate to xylene is 1:40, and the mixing mass ratio of the inner water phase to the xylene solution containing methyl methacrylate and butyl acrylate monomers is 1:4.

[0053] (3) The polyurethane prepolymer is dissolved in a 2wt% polyvinyl alcohol solution, and then injected into the preliminary emulsion prepared in step (2) and stirred at a rotation speed of 700 rpm for 25 min to form a double emulsion, wherein the mass ratio of the polyurethane prepolymer to the epoxy resin of step (1) is 30:70, and the mixing mass ratio of the polyurethane prepolymer to the polyvinyl alcohol solution is 1:25.

[0054] (4) 0.7% of initiator AIBN (azobisisobutyronitrile) based on the total mass of methyl methacrylate and butyl acrylate monomers in step (2) is added to the double emulsion prepared in step (3), and the temperature is raised to 75°C, and the reaction is continued for 5 h to form an acrylic resin wall material; the pH is adjusted to 8.5 by adding ammonia water, and then 2.5 h of curing is carried out by adding ethylenediamine, and then the product is washed and centrifuged three times with ethanol, and then vacuum dried at a temperature of 55°C for 10 h to obtain a double-chamber acrylic resin-based microcapsule repair agent, wherein the amount of ethylenediamine added is 12% of the amount of polyurethane prepolymer added.

[0055] The preparation method of the aurora color protection varnish in this example is as follows: (1) Powder dispersion stage: Add deionized water to the dispersion cylinder, add nano TiO2 / SiO2 composite powder, nano indium tin oxide powder and wet dispersant at a rotation speed of 400 rpm, then increase the rotation speed to 2500 rpm, and continue to disperse for 30 min until the pre-dispersed slurry fineness is ≤20 μm.

[0056] (2) Emulsion modification stage: Add core-shell ultraviolet absorber and hindered amine light stabilizer (HALS) grafted cellulose in the high solid content composite resin emulsion in sequence, and modify at 45°C and a rotation speed of 900 rpm for 2 h to obtain a modified emulsion.

[0057] (3) Gradient blending stage: The pre-dispersed slurry obtained in step (1) is slowly added to the modified emulsion obtained in step (2) in three times, wherein the first rotation speed is 1800 rpm, the second rotation speed is 1200 rpm, and the third rotation speed is 900 rpm, and after each addition of the pre-dispersed slurry, about 1 / 3 of the light-triggered acrylic resin-based microcapsule repair agent is added and dispersed for 15 min; then add silicone defoaming agent and film-forming aid and disperse for another 15 min, and filter through a 200 mesh screen to obtain the polar light color protection topcoat varnish. Example 3

[0058] The polar light color protection topcoat varnish in this example is composed of the following raw materials by weight: high solid content composite resin emulsion 77 parts, nano TiO2 / SiO2 composite powder 6 parts, core-shell ultraviolet absorber 2 parts, nano indium tin oxide 0.5 parts, hindered amine light stabilizer grafted cellulose 1.5 parts, light-triggered acrylic resin-based microcapsule repair agent 1 part, wetting dispersant 1.5 parts, silicone defoaming agent 0.5 parts, film-forming aid 3 parts deionized water 7 parts.

[0059] The high solid content composite resin emulsion is composed of the following mass fraction ratio: hydroxy acrylate emulsion 1 part high solid content silicone fluorocarbon resin 7 parts The nano TiO2 / SiO2 composite powder is composed of the following mass fraction ratio: rutile nano titanium dioxide 3 parts nano silica hollow microspheres 1 part.

[0060] The performance parameters of each material in this example are as follows: The nano indium tin oxide powder is a flaky indium tin oxide with an average thickness of 300 nm.

[0061] The average particle size of the nano TiO2 is 50 nm.

[0062] The average particle size of the nano SiO2 is 60 nm.

[0063] The organic silicon defoaming agent is a condensation type organic silicon defoaming agent.

[0064] The film-forming aid is a carboxylic acid ester mixture.

[0065] The cellulose is hydroxyethyl cellulose.

[0066] The hindered amine light stabilizer monomer is a high molecular weight hindered amine light stabilizer HALS-622.

[0067] The preparation method of the hindered amine light stabilizer grafted cellulose in this embodiment is as follows: (1) The cellulose is dissolved in chlorinated 1-allyl-3-methyl imidazole ionic liquid, and reacted with 2-bromoisobutyryl bromide at 30°C for 25 h to form a macromolecular initiator, wherein the mass ratio of cellulose, chlorinated 1-allyl-3-methyl imidazole ionic liquid and 2-bromoisobutyryl bromide is 1:30:10.

[0068] (2) The initiator prepared in step (1) is dispersed in N,N-dimethylformamide, and then hindered amine light stabilizer monomer, copper bromide catalyst and N,N-methylene bisacrylamide are added in sequence, wherein the mass ratio of initiator and N,N-dimethylformamide is 1:50, the mass ratio of initiator and hindered amine light stabilizer monomer is 1:15, N,N-methylene bisacrylamide is 0.5% of the mass of the hindered amine light stabilizer monomer, the amount of copper bromide catalyst is 0.3% of the mass of the hindered amine light stabilizer monomer, and the reaction is carried out under the conditions of inert atmosphere, temperature of 70°C and stirring speed of 400 rpm for 17 h. Finally, after washing with deionized water until the filtrate is clear, vacuum drying and crushing, the hindered amine light stabilizer grafted cellulose is obtained.

[0069] The preparation method of the acrylic resin-based microcapsule in this embodiment is as follows: (1) 80 parts of epoxy resin and 10 parts of nano indium tin oxide are mixed and dissolved in 200 parts of deionized water to obtain an inner aqueous phase, which is emulsified at room temperature at a speed of 1500 rpm for 10 min.

[0070] (2) The internal water phase prepared in step (1) is added to a xylene solution containing methyl methacrylate (MMA) and butyl acrylate (BA) monomers, and reacted at a temperature of 50°C and a rotation speed of 3000 rpm for 15 min to form a preliminary emulsion, wherein the mass ratio of methyl methacrylate to butyl acrylate is 5:1, the mass ratio of the total amount of methyl methacrylate and butyl acrylate to xylene is 1:50, and the mixing mass ratio of the internal water phase to the xylene solution containing methyl methacrylate and butyl acrylate monomers is 1:6.

[0071] (3) The polyurethane prepolymer is dissolved in a 3wt% polyvinyl alcohol solution, and then injected into the preliminary emulsion prepared in step (2) and stirred at a rotation speed of 800 rpm for 30 min to form a double emulsion, wherein the mass ratio of the polyurethane prepolymer to the epoxy resin of step (1) is 40:80, and the mixing mass ratio of the polyurethane prepolymer to the polyvinyl alcohol solution is 1:30.

[0072] (4) 1% of the total amount of monomers of methyl methacrylate and butyl acrylate monomers in step (2) is added to the double emulsion prepared in step (3) as initiator AIBN (azobisisobutyronitrile), and heated to 80°C for continuous reaction for 6 h to form an acrylic resin wall material; the pH is adjusted to 9.0 by adding ammonia water, and then ethylenediamine is added for curing for 3 h, followed by ethanol washing and centrifugal separation for 3 times, and vacuum drying at a temperature of 60°C for 12 h to obtain a double-chamber acrylic resin-based microcapsule repair agent, wherein the addition amount of ethylenediamine is 15% of the addition amount of the polyurethane prepolymer.

[0073] The preparation method of the aurora color protection varnish in this embodiment is as follows: (1) Powder dispersion stage: Deionized water is added to a dispersion cylinder, and nano TiO2 / SiO2 composite powder, nano indium tin oxide powder, and wetting dispersant are added at a rotation speed of 300 rpm, and then the rotation speed is increased to 2000 rpm, and the pre-dispersed slurry is dispersed for 25 min until the fineness is ≤20μm.

[0074] (2) Emulsion modification stage: core-shell ultraviolet absorber and hindered amine light stabilizer (HALS) grafted cellulose are sequentially added to the high-solid composite resin emulsion, and modified at a temperature of 50°C and a rotation speed of 800 rpm for 3 h to obtain a modified emulsion.

[0075] (3) Gradient blending stage: the pre-dispersed slurry obtained in step (1) is slowly added to the modified emulsion obtained in step (2) in three times, wherein the first time rotation speed is 1500 rpm, the second time rotation speed is 1000 rpm, and the third time rotation speed is 800 rpm, and after each addition of the pre-dispersed slurry, about 1 / 3 of the light-triggered acrylic resin-based microcapsule restorer is added for continuous dispersion for 10 min; then silicone defoaming agent and film-forming aid are added for dispersion for 10 min again, and after filtration through a 300-mesh filter screen, the polar light color-protection topcoat varnish is obtained.

[0076] In order to embody the beneficial effects of the present application, the following comparative examples are set based on the above-mentioned examples: Comparative Example 1:

[0077] The difference between this comparative example and Example 2 is that no nano-TiO2 / SiO2 composite powder is added. Comparative Example 2:

[0078] The difference between this comparative example and Example 2 is that ordinary glass beads are used instead of nano-indium tin oxide powder. Comparative Example 3:

[0079] The difference between this comparative example and Example 2 is that no microcapsule restorer is added. Comparative Example 4:

[0080] The difference between this comparative example and Example 2 is that the gradient blending process is not used, but one-time mixing is performed. Comparative Example 5:

[0081] Commercial high-gloss topcoat varnish. Comparative Example 6:

[0082] The difference between this comparative example and Example 2 is that pure acrylic emulsion is used instead of hydroxyl acrylic emulsion. Comparative Example 7:

[0083] The difference between this comparative example and Example 2 is that hydroxyethyl cellulose is used instead of hindered amine light stabilizer grafted cellulose.

[0084] The samples obtained in the above-mentioned examples and comparative examples are detected. The detection method is as follows: 1) The above samples are tested according to HG / T 5065-2016 "Architectural Coatings Overcoat Varnish" standard; a UV-visible spectrophotometer (PerkinElmer Lambda 950) is used to measure the UV blocking rate; the weather resistance related test indexes are tested according to GB / T 1865-2009 "Paint and Varnish Artificial Weathering and Artificial Radiation Exposure Filtered Xenon Arc Radiation", a Ci5000 xenon lamp artificial weathering tester of American ATLAS Company is used to conduct xenon lamp aging test, the test conditions are: irradiance (340 nm) 0.51 W / m2; relative humidity (40-60) %; black label temperature (65±2) ℃; rainfall cycle 18 min / 102 min (water spraying time / non-water spraying time). The xenon lamp artificial accelerated aging test is conducted for 5000 h, and the weather resistance of the sample is investigated.

[0085] 2) The above samples are tested according to GB / T 9754-2007 "Paint and Varnish Determination of 20°, 60° and 85° Specular Gloss of Paint Film without Metal Pigment", a BYK 4520 multi-angle gloss meter of Germany BYK-Gardner is used to measure the 60° specular gloss of the coating film. 3) The above samples are tested according to GB / T 1766-2008 "Paint and Varnish Rating Method for Coating Film Aging" to calculate the gloss retention rate of the coating film after aging.

[0086] 4) The above samples are tested according to ISO 7724-3:1984 "Paint and Varnish Colorimetry Part 3: Color Difference Calculation", a CR10 color difference meter of Japan KONICA MOINLTA Company is used to measure the color difference change of the coating film, and the discoloration degree of the coating film after aging is evaluated according to GB / T 1766-2008 "Paint and Varnish Rating Method for Coating Film Aging".

[0087] The test results are as follows:

[0088] From the above table, after 5000 h artificial climate aging, the aurora color protection finish varnish prepared in the application (Examples 1-3) is superior to the comparative examples and the traditional product in core performance. Relative to Comparative Example 1, it is shown that the nano TiO2 / SiO2 composite powder contributes to the aurora color protection effect. Due to the lack of multi-level light reflection structure, the ultraviolet light directly hits the stone-like coating, resulting in a sharp decrease in gloss retention, a more obvious discoloration degree and a more obvious powdering degree. Relative to Comparative Example 2, it is shown that the surface temperature of the coating increases after the ordinary glass beads replace the nano ITO powder (indium tin oxide), resulting in an accelerated thermal aging rate and a significant powdering degree. Therefore, the infrared reflectivity of the nano ITO powder is significantly higher than that of the glass beads, and the ordinary glass beads have no strong hydrogen bond support in the system, thereby causing thermal storage and dilution precipitation. Relative to Comparative Example 3, it is shown that the self-repairing efficiency of the coating is significantly reduced after the lack of the microcapsule repair agent. Not only is the powdering degree serious, but also the cracks increase significantly and the crack propagation is larger, thereby causing the cracks to gradually lengthen. Relative to Comparative Example 4, it is shown that the one-time mixing affects the ordered distribution and directional arrangement of the nanoparticles to form a film, thereby causing powder agglomeration and other phenomena. Not only does it cause thermal storage and dilution precipitation, but also it affects the gloss and reduces the color protection function. Relative to Comparative Example 5, it is shown that the commercially available high gloss finish varnish can only meet the standard high gloss effect, and the weather resistance is significantly lower than that of the aurora color protection finish varnish prepared in the application. Relative to Comparative Example 6, it is shown that the adhesion of the sample is significantly reduced after the use of ordinary non-hydroxyl emulsion, and serious delamination and precipitation phenomena occur after thermal storage and dilution. The remaining performance is equivalent to that of the example. Relative to Comparative Example 7, it is shown that the gloss loss, discoloration degree and powdering degree are significantly reduced after the use of ordinary cellulose, thereby causing the damage of the paint film and the occurrence of powdering and cracking phenomena. Therefore, the hindered amine light stabilizer is firmly bonded to the cellulose by chemical grafting, which greatly reduces the gloss and color fading of the coating, and ensures the weather resistance of the paint film. In addition, the lack of each key raw material not only affects one performance index, but also collectively reduces the core performance. Therefore, under the four-dimensional synergistic effect of "ultraviolet absorption + infrared heat reflection + free radical capture + microcapsule linear repair", the light aging rate is reduced, the coating service life is longer, and the aurora color protection effect is achieved.

[0089] The above conclusion is also supported by the aurora effect mechanism and color protection function principle diagram of the aurora color protection finish varnish of the application, as shown in Figure 1The left side coating system shows that the "nanoparticles are ordered and oriented → light path regulation → aurora visual effect" can be intuitively conveyed. Specifically, sunlight enters the cover layer and is specularly reflected on the surface of TiO2, part of the light enters the SiO2 hollow sphere and is internally reflected multiple times, and the final emitted light presents an aurora color dispersion effect. The right side cover layer detail micrograph shows a four-dimensional protection system, including a top layer of honeycomb grid to block ultraviolet rays, a middle layer of dendritic structure to capture aging free radicals, a lower layer of horizontal ITO to reflect infrared rays, and a bottom layer of microcapsule to repair cracks. Through the synergistic effect of the four-dimensional color maintenance mechanism, the coating is prevented from being penetrated by ultraviolet rays, leading to the accumulation of free radicals and the formation of color spots, and the coating gradually high-temperature pulverization, resulting in cracking of the coating.

Claims

1. An aurora color protection mask top varnish, characterized by: It is mainly composed of the following raw materials in the following mass ratio: High solid content composite resin emulsion 63-77 parts Nano TiO2 / SiO2 composite powder 6-10 parts Core-shell ultraviolet absorber 2-4 parts Nano indium tin oxide 0.5-1.5 parts Hindered amine light stabilizer grafted cellulose 0.5-1.5 parts Photo-triggered acrylic resin-based microcapsule repair agent 1-3 parts Wetting dispersant 1.5-2.5 parts Silicone defoaming agent 0.5-1.5 parts Film forming aid 1-3 parts Deionized water 7-13 parts; The high solid content composite resin emulsion is mixed by the following raw materials in the following mass ratio: High solid content silicone fluorocarbon resin 5-7 parts Hydroxy acrylic emulsion 1 part; The nano TiO2 / SiO2 composite powder is mixed by the following raw materials in the following mass ratio: Nano titanium dioxide 1-3 parts Nano silicon dioxide 1 part.

2. The polar guard coat varnish according to claim 1, characterized in that: The preparation method of the hindered amine light stabilizer grafted cellulose is: Dissolve the cellulose in chlorinated 1-allyl-3-methyl imidazole ionic liquid, then add 2-bromoisobutyryl bromide, and react at 20-30℃ for 23-25h to generate a macromolecular initiator; wherein the mass ratio of cellulose, chlorinated 1-allyl-3-methyl imidazole ionic liquid and 2-bromoisobutyryl bromide is 1:10-30:4-10; Disperse the initiator prepared in step (1) in N,N-dimethylformamide, then add hindered amine light stabilizer monomer, copper bromide catalyst and N,N-methylene bisacrylamide in sequence, wherein the mass ratio of initiator and N,N-dimethylformamide is 1:30-50, the mass ratio of initiator and hindered amine light stabilizer monomer is 1:10-15, the amount of N,N-methylene bisacrylamide is 0.3-0.5% of the mass of the hindered amine light stabilizer monomer, and the amount of copper bromide catalyst is 0.2-0.3% of the mass of the hindered amine light stabilizer monomer; react under the conditions of inert atmosphere, temperature of 60-70℃ and stirring speed of 300-400 rpm for 15-17h, then wash with deionized water until the filtrate is clear, vacuum dry and crush to obtain the hindered amine light stabilizer grafted cellulose.

3. An auroral color guard mask finish according to claim 2, characterized in that: The hindered amine light stabilizer monomer is one or a combination of low molecular weight hindered amine light stabilizer HALS-770 and high molecular weight hindered amine light stabilizer HALS-622 in any proportion; The cellulose is hydroxyethyl cellulose.

4. The polar guard coat varnish of claim 1, wherein: The photo-triggered acrylic resin-based microcapsule repair agent is an acrylic resin-based microcapsule with a double-chamber structure, which has two chambers in the inner part, respectively wrapping the repair agent and the curing agent, and can realize synergistic repair through photo-thermal response.

5. An auroral color shield finish according to claim 4, characterized in that: The preparation method of the photo-triggered acrylic resin-based microcapsule repair agent is: Mix 60-80 parts of epoxy resin and 5-10 parts of nano indium tin oxide, then dissolve in 200 parts of deionized water, and emulsify at room temperature and a rotation speed of 1000-1500 rpm for 5-10 min to obtain the inner water phase; The inner water phase prepared in step (1) is added into a xylene solution containing methyl methacrylate and butyl acrylate monomers, and reacted for 10-15 min at a temperature of 40-50℃ and a rotation speed of 2000-3000 rpm to form a preliminary emulsion; wherein the mass ratio of methyl methacrylate to butyl acrylate is 3-5:1, the mass ratio of the total amount of methyl methacrylate and butyl acrylate to xylene is 1:30-50; and the mixing mass ratio of the inner water phase to the xylene solution containing methyl methacrylate and butyl acrylate monomers is 1:3-6; The polyurethane prepolymer is dissolved in a 1-3wt% polyvinyl alcohol solution, and then injected into the preliminary emulsion prepared in step (2) and stirred at a rotation speed of 500-800 rpm for 20-30 min to form a double emulsion, wherein the mass ratio of the polyurethane prepolymer to the epoxy resin of step (1) is 20-40:60-80, and the mixing mass ratio of the polyurethane prepolymer to the polyvinyl alcohol solution is 1:20-30; The initiator azobisisobutyronitrile is added to the double emulsion prepared in step (3), and heated to 70-80℃, and the reaction is continued for 4-6 h to form an acrylic resin wall material, wherein the amount of initiator azobisisobutyronitrile added is 0.5-1% of the total mass of the methyl methacrylate and butyl acrylate monomers in step (2); then the pH is adjusted to 8.0-9.0 by adding ammonia water, and then the ethylenediamine is added and cured for 2-3 h, and then washed and centrifuged 2-3 times with ethanol, and then vacuum dried at a temperature of 50-60℃ for 8-12 h to obtain a double-chamber acrylic resin-based microcapsule repair agent; wherein the amount of ethylenediamine added is 10-15% of the amount of polyurethane prepolymer added in step (3).

6. The polar guard coat varnish of claim 1, wherein: The high-solid silicone fluorocarbon resin has a solid content of 40-60%, a Tg of 20-50℃, and a MFFT of 0-10℃; the hydroxyl acrylic emulsion has a solid content of 39-41%, a Tg of 10-30℃, and a MFFT of 5-15℃.

7. The polar guard coat varnish of claim 1, wherein: The nano indium tin oxide is a flaky indium tin oxide with a thickness of 200-300 nm; the nano titanium dioxide is a rutile-type nano titanium dioxide with a particle size of 30-50 nm; the nano silicon dioxide is a nano silicon dioxide hollow microsphere with a particle size of 40-60 nm; and the core-shell ultraviolet absorber is a core-shell ultraviolet absorber with a core-shell structure, wherein the core layer is a benzotriazole ultraviolet absorption active ingredient, and the shell layer is an organic silicon inorganic material.

8. The polar guard coat varnish of claim 1, wherein: The silicone defoaming agent is one or more than two of polydimethylsiloxane defoaming agent, methyl silicone oil defoaming agent, or condensed silicone defoaming agent in any proportion.

9. The polar guard coat varnish of claim 1, wherein: The film-forming aid is one or a combination of the two in any proportion of a dodecanol ester and a carboxylic acid ester mixture.

10. A process for the preparation of a polar aurora color shield top varnish according to any one of claims 1 to 9, characterized in that: The method comprises the following steps in sequence: The method comprises the following steps in sequence: (1) Powder dispersion stage: add deionized water in the dispersion cylinder, add nano TiO2 / SiO2 composite powder, nano indium tin oxide, wetting dispersant under the rotation speed of 300-500 rpm, then increase the rotation speed to 2000-3000 rpm, and continuously disperse for 25-35 min until the pre-dispersed slurry fineness is ≤20 μm; (2) Emulsion modification stage: add core-shell ultraviolet absorber and hindered amine light stabilizer grafted cellulose in the high solid composite resin emulsion in sequence, and modify the reaction at 40-50°C and the rotation speed of 800-1000 rpm for 1-3 h to obtain the modified emulsion; (3) Gradient blending stage: add the pre-dispersed slurry obtained in step (1) into the modified emulsion obtained in step (2) in three times, wherein the rotation speed of the dispersion cylinder is adjusted to 1500-2000 rpm when adding for the first time, the rotation speed of the dispersion cylinder is adjusted to 1000-1500 rpm when adding for the second time, and the rotation speed of the dispersion cylinder is adjusted to 800-1000 rpm when adding for the third time, and about 1 / 3 of the light-triggered acrylic resin-based microcapsule repair agent is added after each addition of the pre-dispersed slurry, and continuously dispersed for 8-10 min; then add silicone defoaming agent and film-forming aid and disperse for 10-20 min again, and filter through a 100-300 mesh filter to obtain the polar light color protection mask varnish.

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