A water-based mirror back coating for glass and its preparation method and application

Abstract

The application discloses a kind of water-based glass mirror back coating and its preparation method and application, belong to the field of coating.The coating comprises the following raw materials: water-based acrylic acid epoxy modified alkyd resin, adhesion promoter, defoaming agent, anti-sedimentation thixotropic agent, dispersing agent, thickening agent, flash rust inhibitor, pigment and filler, deionized water, substrate wetting agent, cosolvent, drier and n-butylated urea formaldehyde resin.The application obtains water-based acrylic acid epoxy modified alkyd resin with excellent corrosion resistance, thermal stability, weather resistance, impact resistance and film-forming property by modifying alkyd with epoxy resin and acrylic resin, and makes water-based glass mirror back coating with water-based acrylic acid epoxy modified alkyd resin as main raw material, which can well solve the problems of poor solvent resistance, short neutral salt spray resistance time and poor hardness of existing water-based glass mirror coating.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a water-based glass mirror back coating, its preparation method, and its application. Background Technology

[0002] The main raw materials for producing silver-plated glass mirrors include: flat glass, plating solution, and silver-plated glass mirror back coating. The annual demand for silver-plated glass mirror back coating exceeds 20,000 tons. With increasingly stringent environmental regulations, the currently used solvent-based silver-plated glass mirror back coatings can no longer meet these requirements. The replacement of solvent-based silver-plated glass mirror back coatings with water-based, copper-free silver-plated glass mirror back coatings has become inevitable. However, the research and development of water-based, copper-free silver-plated glass mirror back coatings has not yet made substantial progress.

[0003] Patent CN103849184A discloses a water-based mirror back paint and its preparation method. Its composition is a water-based self-drying epoxy resin, which is synthesized from tung oil acid, linseed oil, methyl methacrylate, methacrylic acid, and epoxy resin, and prepared by adding cobalt material as a drying agent. It is a double-coated primer and topcoat, but its hardness is only 1H, and its resistance to xylene, ferric chloride, corrosion resistance, and damp heat resistance are all substandard.

[0004] Patent CN107652820A discloses a lead-free, environmentally friendly protective coating for the back of a silver mirror. Its composition includes water-based hydroxyl acrylic resin, water-based epoxy ester resin, hexamethoxymelamine-formaldehyde resin, water-based TDI polyurethane blocking crosslinking agent, aluminum tripolyphosphate, methylbenzotriazole, pyridine-blocked p-toluenesulfonic acid, etc. However, its resistance to xylene, ferric chloride, corrosion resistance, and damp heat resistance all fail to meet the requirements.

[0005] Patent CN110577775A discloses an improved water-based mirror back paint and its preparation method. The paint is composed of two components, wherein component a is water-soluble epoxy resin, water-soluble amino resin, water-soluble acrylic resin, water-soluble fluorocarbon resin, and polyethylene wax, and component b is flame retardant, nano-silver antibacterial agent, and organosilicon resin. However, it failed the tests for xylene resistance, ferric chloride resistance, neutral salt spray test, copper-accelerated acetic acid test, and damp heat resistance. Moreover, the two-component design is not suitable for curtain coating processes.

[0006] Patent CN103725146A discloses a water-based ultra-fast drying protective coating for the back of aluminum mirrors. Its composition is water-dispersible epoxy-modified acrylic resin and methylated urea-formaldehyde resin. It only passes the salt spray test for 264 hours, and other properties such as resistance to xylene wiping, chemical resistance, and damp heat resistance fail to meet the requirements.

[0007] Patent CN107652888A discloses a water-based organosilicon mirror back protective coating, which is composed of water-based organosilicon resin, hexamethoxymelamine formaldehyde resin, aluminum tripolyphosphate, and zinc oxide. However, it failed the tests for hardness, xylene resistance, chemical resistance, neutral salt spray test, copper-accelerated acetic acid test, and damp heat resistance.

[0008] Patent CN107652830A discloses a water-based epoxy-based protective coating for the back of a mirror. The coating is a two-component system, in which component A is water-based epoxy resin, silane coupling agent, and water-based acrylic resin, and component B is water-based modified aliphatic amine. The two-component system is obviously not suitable for the large-scale curtain coating production process of aluminized mirrors.

[0009] Patent CN109251611A discloses a fast-drying water-based protective coating for aluminum-plated mirror backs, which is composed of water-based pure acrylic resin, water-based epoxy-modified alkyd resin, and fully methylated amino resin. However, it failed the tests for hardness, xylene resistance, chemical resistance, neutral salt spray test, copper-accelerated acetic acid test, and damp heat resistance.

[0010] Patent CN109337475A discloses a water-based protective coating for aluminum-plated mirror backs, which consists of water-based pure acrylic resin, water-based epoxy-modified alkyd resin, and fully methylated amino resin. Its neutral salt spray test results are only 258 hours, and its chemical resistance is 4 hours. However, its hardness, xylene wiping resistance, and damp heat resistance all fail to meet the requirements.

[0011] In summary, current water-based aluminized glass mirror back coatings all have certain performance defects. Therefore, the research and development of high-performance water-based silver-plated glass mirror back coatings is urgently needed. Summary of the Invention

[0012] The purpose of this invention is to provide a water-based glass mirror back coating, its preparation method, and its application, so as to overcome the shortcomings of the existing technology, such as not meeting environmental protection requirements, poor solvent resistance, short neutral salt spray resistance time, and poor hardness.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] This invention provides a water-based glass mirror back coating, comprising the following raw materials in parts by weight: 25-35 parts of water-based acrylic epoxy modified alkyd resin, 0.5-1 part of adhesion promoter, 0.3-1 part of defoamer, 0.1-0.5 parts of anti-settling thixotropic agent, 1.2-2 parts of dispersant, 0.2-0.8 parts of thickener, 0.5-1 part of flash rust inhibitor, 20-40 parts of pigments and fillers, 20-45 parts of deionized water, 0.5-1 part of substrate wetting agent, 1-5 parts of co-solvent, 0.1-0.5 parts of drying agent, and 3-6 parts of n-butylated urea-formaldehyde resin.

[0015] Furthermore, the defoamer is a polyether siloxane modified defoamer, the substrate wetting agent is a polyether modified wetting agent, the pigment and filler is at least one of aluminum tripolyphosphate, hollow glass microspheres, iron oxide red, and mica powder, the anti-settling thixotropic agent is fumed silica, the dispersant is a high molecular weight block copolymer, the cosolvent is at least one of dipropylene glycol methyl ether and diethylene glycol butyl ether, and the drying agent is a highly active iron complex.

[0016] Preferably, the defoamer is DIGIC 810, the substrate wetting agent is at least one of HY6085 and HY6083, the anti-settling thixotropic agent is Evonik fumed silica, the dispersant is BYK-91, the adhesion promoter is Dow Corning OFS-6040, the thickener is an associative medium-shear polyurethane thickener, the flash rust inhibitor is a poly-organic amine chelate, and the drying agent is a highly active iron complex.

[0017] Further, the waterborne acrylic epoxy-modified alkyd resin is composed of the following raw materials in parts by weight: 15-30 parts of linoleic acid, 5-20 parts of polyacrylic acid oligomer, 5-15 parts of isophthalic acid, 5-15 parts of trimethylolpropane, 3-8 parts of pentaerythritol, 5-7 parts of hexahydrophthalic anhydride, 4-5 parts of tert-butylbenzoic acid, 0.1-2 parts of grafting catalyst, 1-8 parts of meta-anhydride, 7-12 parts of epoxy resin, 15-20 parts of diluent, and 4-7 parts of neutralizer.

[0018] Preferably, the grafting catalyst is organotin, the diluent is a mixture of ethylene glycol butyl ether and isobutanol in a mass ratio of 7:3, and the neutralizing agent is a mixture of triethylamine and dimethylethanolamine in a mass ratio of 1:1.

[0019] Preferably, the waterborne acrylic epoxy-modified alkyd resin is prepared as follows:

[0020] S1: Add linoleic acid, isophthalic acid, trimethylolpropane, pentaerythritol, and grafted catalyst to a reactor containing pre-prepared polyacrylic acid oligomers, start stirring and heat up. When the temperature reaches 60-100℃, the material melts. Continue heating to 200±5℃ and maintain the reaction at this temperature until the reaction product becomes transparent, then cool down.

[0021] S2: When the temperature drops to 140-180℃, add hexahydrophthalic anhydride and tert-butylbenzoic acid, continue to raise the temperature to 180-200℃, and maintain the reaction at this temperature until the acid value is 30-35 mg KOH / g, then cool down.

[0022] S3: When the temperature drops to 140-160℃, add epoxy resin, continue to raise the temperature to 167-180℃, and maintain the reaction acid value at the temperature to below 20mgKOH / g;

[0023] S4: Then add the anhydride and keep it at 180℃ for 1.5h, keeping the acid value at 35-45mgKOH / g. Then cool down to 140℃, transfer to a dilution tank and add dilution solvent to dilute.

[0024] S5: Add neutralizing agent to dilution tank and stir for 15-30 minutes to obtain water-based acrylic epoxy modified alkyd resin. Filter at 80℃, control the fineness to below 20μm, and package.

[0025] Furthermore, the preparation method of polyacrylic acid oligomers is as follows:

[0026] S1: Weigh 40g of xylene and evacuate it into the reactor using a vacuum pump. Stop the vacuum and start stirring and heating. Dissolve 24-32g of dicumyl peroxide in 40-50g of styrene to prepare solution a. Add the monomer mixture to the reactor. The monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate. The ratio of methacrylic acid monomer, methyl methacrylate, and styrene is 70-77:110-120:40-50.

[0027] S2: Heat the reactor to 130℃, and add solution a uniformly at a rate of 180±2L / h at a temperature of 130±2℃. The addition is completed within 3h±10min, and the temperature is maintained for 75min.

[0028] S3: Dissolve 6-8g of dicumyl peroxide in 20-30g of xylene to prepare solution b; after the heat preservation in step S2 is completed, add solution b dropwise at a rate of 130±2L / h at a temperature of 110-115℃, in three parts, adding 1 / 3 each time, and completing the addition within 10 minutes each time. After the first two additions, keep the temperature for 50 minutes, and keep the temperature for 1.5 hours for the last time. After the heat preservation is completed, take a sample to measure the viscosity. The viscosity should reach 6-10s. If the viscosity is lower than 6s, continue to keep the temperature and measure the sample every 0.5 hours until the viscosity is qualified.

[0029] S4: After the viscosity is qualified, heat to 120℃ and dehydrate under vacuum until no water is removed. Cool down to 100℃, adjust the viscosity with xylene to qualified, and cool down to below 80℃ to obtain polyacrylic acid oligomer.

[0030] The present invention also provides a method for preparing the above-mentioned water-based glass mirror back coating, comprising the following steps:

[0031] S1: Add waterborne acrylic epoxy modified alkyd resin to the preparation tank, start stirring at a speed of 300-500 r / min, and add deionized water, dispersant, defoamer, and anti-settling thixotropic agent in sequence; after the addition is complete, increase the speed to 700-900 r / min and stir for 20-30 min. Then add pigments, fillers, and co-solvent and continue stirring until the dispersion is uniform.

[0032] S2: The slurry obtained in step S1 is fed to a sand mill for grinding. The fineness of the slurry is ground to below 30μm, and the temperature is controlled to be ≤45℃ during the grinding process.

[0033] S3: Transfer the slurry obtained in step S2 into a dilution basin, and add the remaining deionized water, adhesion promoter, thickener, flash rust inhibitor, substrate wetting agent, drying agent, and n-butylated urea formaldehyde resin in sequence while stirring. Stir at 500-800 r / min for 20-30 min, adjust the viscosity to meet the requirements, and obtain the finished coating product.

[0034] This invention also provides the application of the above-mentioned water-based glass mirror back coating in heliostats of molten salt tower power plants. By applying the water-based glass mirror back coating of this invention to the back of the heliostats of molten salt tower power plants, the supplementary lighting efficiency can be improved, thus helping the solar panels to improve power generation efficiency.

[0035] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0036] (1) This invention modifies alkyd with epoxy resin and acrylic resin to obtain a waterborne acrylic epoxy-modified alkyd resin with excellent corrosion resistance, thermal stability, weather resistance, impact resistance, and film-forming properties. The waterborne acrylic epoxy-modified alkyd resin is then used as the main raw material to produce a waterborne glass mirror back coating, which effectively solves the problems of poor solvent resistance, short neutral salt spray resistance time, and poor hardness in existing waterborne glass mirror coatings. The weather resistance is significantly improved compared to traditional modified resins, while also possessing excellent salt spray resistance.

[0037] (2) The water-based glass mirror coating of the present invention has excellent water resistance and the water-based paint film does not lose its gloss after long-term immersion; it dries quickly and can be air-dried or baked; it has high hardness and excellent resistance to media.

[0038] (3) The water-based glass mirror coating of the present invention is applied to the back coating of the heliostat, which can improve the supplementary light efficiency, so that the mirror reflectivity can reach 95%, reduce the weight by 10%, help the solar panel improve efficiency, and increase the power generation gain by 1.5%. Attached Figure Description

[0039] Figure 1 This is a particle size distribution diagram of the waterborne acrylic epoxy-modified alkyd resin in Test Example 2 of the present invention. Detailed Implementation

[0040] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0041] Example 1

[0042] (1) Preparation of polyacrylic acid oligomers

[0043] S1: Weigh 40g of xylene and evacuate it into the reactor using a vacuum pump. Stop the vacuum and start stirring and heating. Dissolve 24g of dicumyl peroxide in 40g of styrene to prepare solution a. Add the monomer mixture to the reactor. The monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate. The ratio of methacrylic acid monomer, methyl methacrylate, and styrene is 70:110:40.

[0044] S2: Heat the reactor to 130℃, and add solution a uniformly at a rate of 180±2L / h at a temperature of 130±2℃. The addition is completed within 3h±10min, and the temperature is maintained for 75min.

[0045] S3: Dissolve 6g of dicumyl peroxide in 20g of xylene to prepare solution b; after the heat preservation in step S2 is completed, add solution b dropwise at 130±2L / h at 110℃, in three parts, each time adding 1 / 3, and each time within 10min. After the first two additions, keep warm for 50min, and the last time keep warm for 1.5h. After the heat preservation is completed, take a sample to measure the viscosity. The viscosity should reach 6-10s. If the viscosity is lower than 6s, continue to keep warm. Take a sample every 0.5h until the viscosity is qualified.

[0046] S4: After the viscosity is qualified, heat to 120℃ and dehydrate under vacuum until no water is removed. Cool down to 100℃, adjust the viscosity with xylene to qualified, and cool down to below 80℃ to obtain polyacrylic acid oligomer for later use.

[0047] (2) Preparation of waterborne acrylic epoxy modified alkyd resin

[0048] S1: Add 20g of linoleic acid, 10g of isophthalic acid, 11g of trimethylolpropane, 3g of pentaerythritol, and 0.8g of organotin to a reactor containing 10g of polyacrylic acid oligomer. Start stirring and heat to 200±5℃, and maintain the temperature at this temperature until the reaction product becomes transparent, then cool down.

[0049] S2: When the temperature drops to 180℃, add 7g of hexahydrophthalic anhydride and 3g of tert-butylbenzoic acid, continue to raise the temperature to 200℃, and maintain the reaction at this temperature until the acid value is 30-35mgKOH / g, then cool down.

[0050] S3: When the temperature drops to 160℃, add 10g of epoxy resin, continue to raise the temperature to 180℃, and maintain the reaction acid value at the temperature below 20mgKOH / g;

[0051] S4: Then add 3g of metaanhydride, and continue to maintain at 180℃ for 1.5h, controlling the acid value at 35~45mgKOH / g. Then cool down to 140℃, transfer to a dilution tank and add 20g of diluent; the diluent is a mixture of ethylene glycol butyl ether and isobutanol in a weight ratio of 7:3.

[0052] S5: Add 4g of neutralizing agent to the dilution tank and stir for 15-30 minutes to obtain water-based acrylic epoxy modified alkyd resin. Filter at 80℃, control the fineness to below 20um, and package. The neutralizing agent is a mixture of triethylamine and dimethylethanolamine in a 1:1 weight ratio.

[0053] (3) Preparation of water-based glass mirror back coating

[0054] S1: Add 27g of waterborne acrylic epoxy modified alkyd resin to the preparation tank, start stirring at 300r / min, and add 30g of deionized water, 1.2g of dispersant, 0.3g of defoamer, and 0.19g of anti-settling thixotropic agent in sequence; after the addition is completed, increase the speed to 700r / min and stir for 30min. Then add 28g of pigments and fillers and 2g of cosolvent, and continue stirring until the dispersion is uniform.

[0055] S2: The slurry obtained in step S1 is fed to a sand mill for grinding. The fineness of the slurry is ground to below 30μm, and the temperature is controlled to be ≤45℃ during the grinding process.

[0056] S3: Transfer the slurry obtained in step S2 into a dilution basin, and add the remaining 15g of deionized water, 0.5g of adhesion promoter, 0.6g of thickener, 0.5g of flash rust inhibitor, 0.5g of substrate wetting agent, 0.2g of drying agent, and 3g of n-butylated urea-formaldehyde resin in sequence while stirring. Stir at 500r / min for 20min, adjust the viscosity to meet the requirements, and obtain the finished coating product.

[0057] Example 2

[0058] (1) Preparation of polyacrylic acid oligomers

[0059] S1: Weigh 40g of xylene and evacuate it into the reactor using a vacuum pump. Stop the vacuum and start stirring and heating. Dissolve 32g of dicumyl peroxide in 50g of styrene to prepare solution a. Add the monomer mixture to the reactor. The monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate. The ratio of methacrylic acid monomer, methyl methacrylate, and styrene is 77:120:50.

[0060] S2: Heat the reactor to 130℃, and add solution a uniformly at a rate of 180±2L / h at a temperature of 130±2℃. The addition is completed within 3h±10min, and the temperature is maintained for 75min.

[0061] S3: Dissolve 8g of dicumyl peroxide in 30g of xylene to prepare solution b; after the heat preservation in step S2 is completed, add solution b dropwise at a rate of 130±2L / h at 115℃, in three parts, adding 1 / 3 each time, and finishing each addition within 10 minutes. After the first two additions, keep the temperature for 50 minutes, and keep the temperature for 1.5 hours for the last time. After the heat preservation is completed, take a sample to measure the viscosity. The viscosity should reach 6-10s. If the viscosity is lower than 6s, continue to keep the temperature. Take a sample every 0.5 hours until the viscosity is qualified.

[0062] S4: After the viscosity is qualified, heat to 120℃ and dehydrate under vacuum until no water is removed. Cool down to 100℃, adjust the viscosity with xylene to qualified, and cool down to below 80℃ to obtain polyacrylic acid oligomer for later use.

[0063] (2) Preparation of waterborne acrylic epoxy modified alkyd resin

[0064] S1: Add 28g of linoleic acid, 6g of isophthalic acid, 7g of trimethylolpropane, 6g of pentaerythritol, and 0.9g of organotin to a reactor containing 14g of polyacrylic acid oligomer. Start stirring and heat to 200±5℃, and maintain the temperature at this temperature until the reaction product becomes transparent, then cool down.

[0065] S2: When the temperature drops to 140℃, add 5g of hexahydrophthalic anhydride and 5g of tert-butylbenzoic acid, continue to raise the temperature to 180℃, and maintain the reaction at this temperature until the acid value is 30-35mgKOH / g, then cool down.

[0066] S3: When the temperature drops to 140℃, add 11g of epoxy resin, continue to raise the temperature to 180℃, and maintain the reaction acid value at the temperature below 20mgKOH / g;

[0067] S4: Then add 4g of metaanhydride, and continue to maintain at 180℃ for 1.5h, controlling the acid value at 35~45mgKOH / g. Then cool down to 140℃, transfer to a dilution tank and add 15g of diluent; the diluent is a mixture of ethylene glycol butyl ether and isobutanol in a weight ratio of 7:3.

[0068] S5: Add 4.4g of neutralizing agent to the dilution tank and stir for 30min to obtain water-based acrylic epoxy modified alkyd resin. Filter at 80℃, control the fineness to below 20um, and package. The neutralizing agent is a mixture of triethylamine and dimethylethanolamine in a 1:1 weight ratio.

[0069] (3) Preparation of water-based glass mirror back coating

[0070] S1: Add 33g of waterborne acrylic epoxy modified alkyd resin to the preparation tank, start stirring at a speed of 300-500 r / min, and add 25g of deionized water, 1.6g of dispersant, 0.5g of defoamer, and 0.5g of anti-settling thixotropic agent in sequence; after the addition is complete, increase the speed to 900 r / min and stir for 20 min. Then add 21g of pigments and fillers and 4g of cosolvent, and continue stirring until the dispersion is uniform.

[0071] S2: The slurry obtained in step S1 is fed to a sand mill for grinding. The fineness of the slurry is ground to below 30μm, and the temperature is controlled to be ≤45℃ during the grinding process.

[0072] S3: Transfer the slurry obtained in step S2 into a dilution basin, and add the remaining 11g of deionized water, 0.7g of adhesion promoter, 0.2g of thickener, 0.5g of flash rust inhibitor, 0.5g of substrate wetting agent, 0.3g of drying agent, and 4g of n-butylated urea-formaldehyde resin in sequence while stirring. Stir at 800r / min for 20min, adjust the viscosity to meet the requirements, and obtain the finished coating product.

[0073] Example 3

[0074] (1) Preparation of polyacrylic acid oligomers

[0075] S1: Weigh 40g of xylene and evacuate it into the reactor using a vacuum pump. Stop the vacuum and start stirring and heating. Dissolve 28g of dicumyl peroxide in 50g of styrene to prepare solution a. Add the monomer mixture to the reactor. The monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate. The ratio of methacrylic acid monomer, methyl methacrylate, and styrene is 75:115:50.

[0076] S2: Heat the reactor to 130℃, and add solution a uniformly at a rate of 180±2L / h at a temperature of 130±2℃. The addition is completed within 3h±10min, and the temperature is maintained for 75min.

[0077] S3: Dissolve 7g of dicumyl peroxide in 30g of xylene to prepare solution b; after the heat preservation in step S2 is completed, add solution b dropwise at a rate of 130±2L / h at 115℃, in three parts, adding 1 / 3 each time, and finishing each addition within 10 minutes. After the first two additions, keep the temperature for 50 minutes, and the last time keep the temperature for 1.5 hours. After the heat preservation is completed, take a sample to measure the viscosity. The viscosity should reach 6-10s. If the viscosity is lower than 6s, continue to keep the temperature and measure the sample every 0.5 hours until the viscosity is qualified.

[0078] S4: After the viscosity is qualified, heat to 120℃ and dehydrate under vacuum until no water is removed. Cool down to 100℃, adjust the viscosity with xylene to qualified, and cool down to below 80℃ to obtain polyacrylic acid oligomer for later use.

[0079] (2) Preparation of waterborne acrylic epoxy modified alkyd resin

[0080] S1: Add 20g of linoleic acid, 10g of isophthalic acid, 8g of trimethylolpropane, 4g of pentaerythritol, and 0.9g of organotin to a reactor containing 10g of polyacrylic acid oligomer. Start stirring and heat to 200±5℃, and maintain the temperature at this temperature until the reaction product becomes transparent, then cool down.

[0081] S2: When the temperature drops to 160℃, add 6g of hexahydrophthalic anhydride and 5g of tert-butylbenzoic acid, continue to raise the temperature to 190℃, and maintain the reaction at this temperature until the acid value is 30-35mgKOH / g, then cool down.

[0082] S3: When the temperature drops to 150℃, add 11g of epoxy resin, continue to raise the temperature to 175℃, and maintain the reaction acid value at the temperature to below 20mgKOH / g;

[0083] S4: Then add 3g of metaanhydride, and continue to maintain at 180℃ for 1.5h, controlling the acid value at 35~45mgKOH / g. Then cool down to 140℃, transfer to a dilution tank and add 20g of diluent; the diluent is a mixture of ethylene glycol butyl ether and isobutanol in a weight ratio of 7:3.

[0084] S5: Add 4.4g of neutralizing agent to the dilution tank and stir for 20min to obtain water-based acrylic epoxy modified alkyd resin. Filter at 80℃, control the fineness to below 20um, and package. The neutralizing agent is a mixture of triethylamine and dimethylethanolamine in a 1:1 weight ratio.

[0085] (3) Preparation of water-based glass mirror back coating

[0086] S1: Add 30g of waterborne acrylic epoxy modified alkyd resin to the preparation tank, start stirring at 400r / min, and add 35g of deionized water, 1.3g of dispersant, 0.5g of defoamer, and 0.5g of anti-settling thixotropic agent in sequence; after the addition is completed, increase the speed to 800r / min and stir for 25min. Then add 24g of pigments and fillers and 3g of cosolvent, and continue stirring until the dispersion is uniform.

[0087] S2: The slurry obtained in step S1 is fed to a sand mill for grinding. The fineness of the slurry is ground to below 30μm, and the temperature is controlled to be ≤45℃ during the grinding process.

[0088] S3: Transfer the slurry obtained in step S2 into a dilution basin, and add the remaining 10g of deionized water, 0.7g of adhesion promoter, 0.3g of thickener, 0.5g of flash rust inhibitor, 0.5g of substrate wetting agent, 0.4g of drying agent, and 5g of n-butylated urea-formaldehyde resin in sequence while stirring. Stir at 600r / min for 25min, adjust the viscosity to meet the requirements, and obtain the finished coating product.

[0089] Test Example 1

[0090] The performance of the water-based glass mirror back coating prepared in Examples 1-3 of this invention and a commercially available water-based mirror back paint product of a certain brand were tested. The test results are shown in the table below.

[0091]

[0092]

[0093] Test results show that the water-based glass mirror back coating of the present invention has excellent solvent resistance, salt spray resistance, media resistance, water resistance, thermal stability, high hardness, and short drying time.

[0094] Test Example 2

[0095] The waterborne acrylic epoxy-modified alkyd resin in Example 1 of this invention was analyzed using a laser particle size analyzer, and the results are shown in [Figure Number]. Figure 1 And the table below.

[0096]

[0097] The test results show that the waterborne acrylic epoxy modified alkyd resin of the present invention has a relatively uniform particle size distribution.

[0098] Application examples

[0099] A 110MW molten salt tower power plant under construction has a heliostat designed to be 115m long. 2 A single heliostat consists of 35 reflecting mirrors. A traditional glass-steel single-sided heliostat measures 3.3 meters. 2(solar reserve), with a mirror reflectivity of 93%. The water-based glass back coating of Example 1 was used as a primer to coat the back of the heliostat, as detailed in the table below.

[0100]

[0101]

[0102] Compared with existing coating schemes, using the water-based glass mirror back coating of Example 1 as a primer to coat the back of the heliostat can reduce the overall weight, and according to the relevant data collected, the power generation gain is 1.1% after applying this primer.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the technical solution and conceptual invention of the present invention should be included within the protection scope of the present invention.

Claims

1. A water-based glass mirror back coating, characterized in that, The raw materials comprise the following parts by weight: 25-35 parts of waterborne acrylic epoxy modified alkyd resin, 0.5-1 part of adhesion promoter, 0.3-1 part of defoamer, 0.1-0.5 parts of anti-settling thixotropic agent, 1.2-2 parts of dispersant, 0.2-0.8 parts of thickener, 0.5-1 part of flash rust inhibitor, 20-40 parts of pigments and fillers, 20-45 parts of deionized water, 0.5-1 part of substrate wetting agent, 1-5 parts of co-solvent, 0.1-0.5 parts of drier, and 3-6 parts of n-butylated urea-formaldehyde resin; The substrate wetting agent is a polyether-modified wetting agent; the pigment and filler are at least one of aluminum tripolyphosphate, hollow glass microspheres, iron oxide red, and mica powder; the anti-settling thixotropic agent is fumed silica; the dispersant is a high molecular weight block copolymer; the co-solvent is at least one of dipropylene glycol methyl ether and diethylene glycol butyl ether; and the drying agent is a highly active iron complex. The waterborne acrylic epoxy-modified alkyd resin is composed of the following raw materials in parts by weight: 15-30 parts of linoleic acid, 5-20 parts of polyacrylic acid oligomer, 5-15 parts of isophthalic acid, 5-15 parts of trimethylolpropane, 3-8 parts of pentaerythritol, 5-7 parts of hexahydrophthalic anhydride, 4-5 parts of tert-butylbenzoic acid, 0.1-2 parts of grafting catalyst, 1-8 parts of metahydric anhydride, 7-12 parts of epoxy resin, 15-20 parts of diluent, and 4-7 parts of neutralizer. The preparation method of the polyacrylic acid oligomer is as follows: S1: Weigh 40g of xylene and evacuate it into the reactor using a vacuum pump. Stop the vacuum and start stirring and heating. Dissolve 24-32g of dicumyl peroxide in 40-50g of styrene to prepare solution a. Add the monomer mixture to the reactor. The monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate. The ratio of methacrylic acid monomer, methyl methacrylate, and styrene is 70-77:110-120:40-50. S2: Heat the reactor to 130℃, and add solution a uniformly at a rate of 180±2L / h at a temperature of 130±2℃. The addition is completed within 3h±10min, and the temperature is maintained for 75min. S3: Dissolve 6-8g of dicumyl peroxide in 20-30g of xylene to prepare solution b; after the heat preservation in step S2 is completed, add solution b dropwise at a rate of 130±2L / h at a temperature of 110-115℃, in three parts, adding 1 / 3 each time, and completing the addition within 10 minutes each time. After the first two additions, keep the temperature for 50 minutes, and keep the temperature for 1.5 hours for the last time. After the heat preservation is completed, take a sample to measure the viscosity. The viscosity should reach 6-10s. If the viscosity is lower than 6s, continue to keep the temperature and measure the sample every 0.5 hours until the viscosity is qualified. S4: After the viscosity is qualified, heat to 120℃ and dehydrate under vacuum until no water is removed. Cool down to 100℃, adjust the viscosity with xylene to qualified, and cool down to below 80℃ to obtain polyacrylic acid oligomer.

2. The water-based glass mirror back coating according to claim 1, characterized in that: The defoamer is DIG810, the substrate wetting agent is at least one of HY6085 and HY6083, the anti-settling thixotropic agent is Evonik fumed silica, the dispersant is BYK-91, the adhesion promoter is Dow Corning OFS-6040, the thickener is an associative medium-shear polyurethane thickener, the flash rust inhibitor is a poly-organic amine chelate, and the drying agent is a highly active iron complex.

3. The water-based glass mirror back coating according to claim 1, characterized in that: The grafting catalyst is organotin, the diluent is a mixture of ethylene glycol butyl ether and isobutanol in a mass ratio of 7:3, and the neutralizing agent is a mixture of triethylamine and dimethylethanolamine in a mass ratio of 1:

1.

4. The water-based glass mirror back coating according to claim 1, characterized in that, The preparation method of the waterborne acrylic epoxy-modified alkyd resin is as follows: S1: Add linoleic acid, isophthalic acid, trimethylolpropane, pentaerythritol, and grafted catalyst to a reactor containing pre-prepared polyacrylic acid oligomers, start stirring and heat up. When the temperature reaches 60-100℃, the material melts. Continue heating to 200±5℃ and maintain the reaction at this temperature until the reaction product becomes transparent, then cool down. S2: When the temperature drops to 140-180℃, add hexahydrophthalic anhydride and tert-butylbenzoic acid, continue to raise the temperature to 180-200℃, and maintain the reaction at this temperature until the acid value is 30-35 mg KOH / g, then cool down. S3: When the temperature drops to 140-160℃, add epoxy resin, continue to raise the temperature to 167-180℃, and maintain the reaction acid value at the temperature to below 20mgKOH / g; S4: Then add the anhydride and keep it at 180℃ for 1.5h, keeping the acid value at 35-45mgKOH / g. Then cool down to 140℃, transfer to a dilution tank and add dilution solvent to dilute. S5: Add neutralizing agent to dilution tank and stir for 15-30 minutes to obtain water-based acrylic epoxy modified alkyd resin. Filter at 80℃, control the fineness to below 20μm, and package.

5. The method for preparing the water-based glass mirror back coating according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Add waterborne acrylic epoxy modified alkyd resin to the preparation tank, start stirring at a speed of 300-500 r / min, and add deionized water, dispersant, defoamer, and anti-settling thixotropic agent in sequence; after the addition is complete, increase the speed to 700-900 r / min and stir for 20-30 min. Then add pigments, fillers, and co-solvent and continue stirring until the dispersion is uniform. S2: The slurry obtained in step S1 is fed to a sand mill for grinding. The fineness of the slurry is ground to below 30μm, and the temperature is controlled to be ≤45℃ during the grinding process. S3: Transfer the slurry obtained in step S2 into a dilution basin, and add the remaining deionized water, adhesion promoter, thickener, flash rust inhibitor, substrate wetting agent, drying agent, and n-butylated urea formaldehyde resin in sequence while stirring. Stir at 500-800 r / min for 20-30 min, adjust the viscosity to meet the requirements, and obtain the finished coating product.

6. The application of the water-based glass mirror back coating as described in any one of claims 1 to 4 or the water-based glass mirror back coating prepared by the preparation method described in claim 5 in the heliostat of a molten salt tower power station.

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