Water-based glass mirror back coating as well as preparation method and application thereof

Abstract

The invention discloses a water-based glass mirror back coating as well as a preparation method and application thereof, and belongs to the field of coatings. The coating is prepared from the following raw materials: waterborne acrylic epoxy modified alkyd resin, an adhesion promoter, a defoaming agent, an anti-settling thixotropic agent, a dispersing agent, a thickening agent, a flash rust inhibitor, pigment and filler, deionized water, a base material wetting agent, a cosolvent, a drier and n-butylated urea formaldehyde resin. The waterborne acrylic epoxy modified alkyd resin with excellent corrosion resistance, thermal stability, weather resistance, impact resistance and film-forming property is obtained through epoxy resin and acrylic resin modified alkyd, and the waterborne glass mirror back coating is prepared by taking the waterborne acrylic epoxy modified alkyd resin as a main raw material. The problems of poor solvent resistance, short neutral salt spray resistance time, poor hardness and the like of the existing water-based glass mirror coating can be well solved.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a water-based glass mirror back coating and a preparation method and application thereof. Background Art

[0002] The raw materials for the production of silver-plated glass mirrors mainly include: flat glass, plating solution and silver-plated glass mirror back coating, of which the annual demand for silver-plated glass mirror back coating exceeds 20,000 tons. As environmental protection requirements become increasingly stringent, the solvent-based silver-plated glass mirror back coating currently used can no longer meet environmental protection requirements. It has become inevitable that water-based copper-free silver-plated glass mirror back coating will replace solvent-based silver-plated glass mirror back coating, but the research and development of water-based copper-free silver-plated glass mirror back coating has not made substantial progress.

[0003] Patent CN103849184A discloses a water-based mirror back paint and a preparation method thereof, which is composed of a water-based self-drying epoxy resin, which is synthesized from tung oil acid, linseed oil, methyl methacrylate, methacrylic acid, and epoxy resin, and is prepared with a drying agent cobalt material. It is a double-coat of primer and topcoat, but its hardness is only 1H, and its resistance to xylene, ferric chloride, corrosion resistance, and moisture and heat resistance are not up to standard.

[0004] Patent CN107652820A discloses a lead-free, environmentally friendly silver mirror back protective coating, which is composed of water-based hydroxy acrylic resin, water-based epoxy ester resin, hexamethoxy melamine formaldehyde resin, water-based TDI polyurethane blocked cross-linking agent, aluminum tripolyphosphate, methylbenzotriazole, pyridine blocked p-toluenesulfonic acid, etc. It has poor resistance to xylene, ferric chloride, corrosion resistance, and moisture and heat resistance.

[0005] Patent CN110577775A discloses an improved water-based mirror back paint and a preparation method thereof, which is composed of two components, wherein component a is a water-soluble epoxy resin, a water-soluble amino resin, a water-soluble acrylic resin, a water-soluble fluorocarbon resin, and a polyethylene wax, and component b is a flame retardant, a nano-silver antibacterial agent, and a silicone resin. The paint has poor resistance to xylene, resistance to ferric chloride, neutral salt spray test, copper accelerated acetic acid test, and resistance to moisture and heat, and the two-component paint is not suitable for the curtain shower process.

[0006] Patent CN103725146A discloses a water-based ultra-fast-drying aluminum mirror back protective coating, which is composed of water-dispersible epoxy-modified acrylic resin and methylated urea-formaldehyde resin. The salt spray resistance test is only 264 hours, and other properties such as resistance to xylene wiping, chemical resistance, and moisture and heat resistance are not up to standard.

[0007] Patent CN107652888A discloses a water-based silicone mirror back protective coating, which is composed of water-based silicone resin, hexamethoxymelamine formaldehyde resin, aluminum tripolyphosphate, and zinc oxide. Its hardness, xylene resistance, chemical resistance, neutral salt spray test, copper accelerated acetic acid test, and moisture and heat resistance all fail to pass the test.

[0008] Patent CN107652830A discloses a mirror back protective coating based on water-based epoxy, which is composed of two components, wherein component A is water-based epoxy resin, silane coupling agent, and water-based acrylic resin, and component B is water-based modified fatty amine. The two-component coating is obviously not suitable for the large-scale curtain-drying production process of aluminum-plated mirrors.

[0009] Patent CN109251611A discloses a quick-drying water-based mirror back aluminum-plated protective coating, which is composed of water-based pure acrylic resin, water-based epoxy-modified alkyd resin, and fully methylated amino resin. Its hardness, xylene resistance, chemical resistance, neutral salt spray test, copper accelerated acetic acid test, and moisture and heat resistance all fail to pass the test.

[0010] Patent CN109337475A discloses a water-based mirror back aluminum-plated protective coating, which is composed of water-based pure acrylic resin, water-based epoxy-modified alkyd resin, and fully methylated amino resin. Its neutral salt spray test is only 258 hours, and its chemical resistance is 4 hours, but its hardness, resistance to xylene wiping, and resistance to moisture and heat do not pass the test.

[0011] In summary, the performance of the current water-based aluminum-plated glass mirror back coating has certain defects. Therefore, the research and development of high-performance water-based silver-plated glass mirror back coating is urgent. Summary of the invention

[0012] The purpose of the present invention is to provide a water-based glass mirror back coating and a preparation method and application thereof, so as to overcome the shortcomings of the prior art, such as failure to meet environmental protection requirements, poor solvent resistance, short neutral salt spray resistance time, and poor hardness of the water-based glass mirror coating.

[0013] In order to achieve the above object, the present invention adopts the following technical solution:

[0014] The invention provides a water-based glass mirror back coating, which comprises the following raw materials in parts by weight: 25-35 parts of water-based acrylic epoxy modified alkyd resin, 0.5-1 parts of adhesion promoter, 0.3-1 parts 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 parts of flash rust inhibitor, 20-40 parts of pigment and filler, 20-45 parts of deionized water, 0.5-1 parts of substrate wetting agent, 1-5 parts of cosolvent, 0.1-0.5 parts of drying agent and 3-6 parts of n-butylated urea formaldehyde resin.

[0015] Furthermore, the defoaming agent is a polyether siloxane modified defoaming agent, the substrate wetting agent is a polyether modified wetting agent, the color filler is at least one of aluminum tripolyphosphate, hollow glass microspheres, red iron oxide, 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 high-activity iron complex.

[0016] Preferably, the defoaming agent is Digo 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 polyvalent organic amine chelate, and the drying agent is a highly active iron complex.

[0017] Furthermore, the water-based 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 oligomers, 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 partial anhydride, 7-12 parts of epoxy resin, 15-20 parts of dilution solvent, and 4-7 parts of neutralizer.

[0018] Preferably, the grafting catalyst is organic tin, the dilution solvent is a mixture of ethylene glycol butyl ether and isobutyl alcohol 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 preparation method of the waterborne acrylic epoxy modified alkyd resin is as follows:

[0020] S1: Add linoleic acid, isophthalic acid, trimethylolpropane, pentaerythritol and grafting catalyst into a reactor containing polyacrylic acid oligomer prepared in advance, stir and heat, when the temperature reaches 60-100°C, the materials melt, continue to heat to 200±5°C, and keep the temperature to react until the reaction product becomes transparent and then cool down;

[0021] S2: When the temperature drops to 140-180°C, add hexahydrophthalic anhydride and tert-butylbenzoic acid, continue to raise the temperature to 180-200°C, and keep reacting at this temperature until the acid value reaches 30-35 mgKOH / g, then cool down;

[0022] S3: When the temperature drops to 140-160°C, add epoxy resin, continue to heat to 167-180°C, and maintain the temperature until the reaction acid value is below 20 mgKOH / g;

[0023] S4: then add partial anhydride, keep at 180℃ for 1.5h, control the acid value at 35-45mgKOH / g, then cool to 140℃, transfer to the dilution tank, add dilution solvent for dilution;

[0024] S5: Add neutralizing agent into the dilution tank and stir for 15 to 30 minutes to obtain waterborne acrylic epoxy modified alkyd resin. Filter at 80°C to control the fineness to be below 20 um and package.

[0025] Further, the preparation method of polyacrylic acid oligomer is as follows:

[0026] S1: Weigh 40g of xylene, pump it into a reactor through a vacuum machine, stop the vacuum, start stirring and heat up; evenly dissolve 24-32g of dicumyl peroxide in 40-50g of styrene to prepare a solution a; add a monomer mixture into the reactor, wherein the monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate, and the ratio of methacrylic acid monomer, methyl methacrylate and styrene is 70-77:110-120:40-50;

[0027] S2: Heat the reactor to 130°C, and evenly add solution a at a rate of 180±2L / h at 130±2°C. Add the solution within 3h±10min and keep warm 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 temperature of 110-115°C at a rate of 130±2L / h, add it three times, add 1 / 3 each time, and add it within 10 minutes each time. After the first two additions, keep warm for 50 minutes, and keep warm for the last time for 1.5 hours. After the heat preservation is completed, take samples to measure the viscosity. The viscosity is required to reach 6-10s. If the viscosity is lower than 6s, continue to keep warm and measure the sample once every 0.5h until the viscosity is qualified;

[0029] S4: After the viscosity is qualified, the temperature is raised to 120°C for vacuum dehydration until no water is removed, the temperature is lowered to 100°C, the viscosity is adjusted to qualified with xylene, and the temperature is lowered to below 80°C 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 water-based acrylic epoxy modified alkyd resin into the preparation tank, start stirring at a speed of 300-500r / min, and add part of deionized water, dispersant, defoamer, and anti-settling thixotropic agent in sequence; after the addition is completed, increase the speed to 700-900r / min, stir for 20-30min, then add pigments, fillers, and cosolvents and continue stirring until they are evenly dispersed;

[0032] S2: conveying the slurry obtained in step S1 to a sand mill for grinding, grinding the slurry to a fineness of less than 30 μm, and controlling the temperature to ≤45° C. during the grinding process;

[0033] S3: The slurry obtained in step S2 is transferred into a dilution basin, and the remaining deionized water, adhesion promoter, thickener, flash rust inhibitor, substrate wetting agent, drying agent, and n-butylated urea formaldehyde resin are added in sequence under stirring, and the mixture is stirred at a speed of 500-800 r / min for 20-30 min, and the viscosity is adjusted to meet the requirements to obtain a finished coating product.

[0034] The present invention also provides the use of the above-mentioned water-based glass mirror back coating in a molten salt tower power station heliostat. By applying the water-based glass mirror back coating of the present invention on the back of the molten salt tower power station heliostat, the light supplement efficiency can be improved, helping the solar panels to improve the power generation efficiency.

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

[0036] (1) The present invention obtains a water-based acrylic epoxy modified alkyd resin with excellent corrosion resistance, thermal stability, weather resistance, impact resistance and film-forming properties by modifying alkyd with epoxy resin and acrylic resin, and uses the water-based acrylic epoxy modified alkyd resin as the main raw material to prepare a water-based glass mirror back coating, which can well solve the problems of poor solvent resistance, short neutral salt spray resistance time, poor hardness, etc. of the existing water-based glass mirror coating. The weather resistance is greatly improved compared with the traditional modified resin, and it also has excellent salt spray resistance.

[0037] (2) The water-based glass mirror coating of the present invention has excellent water resistance, and the paint film is good without losing gloss after long-term immersion in the water-based paint; the drying time is fast, and it can be dried by itself or baked; the hardness is high, and the medium resistance is excellent.

[0038] (3) The water-based glass mirror coating of the present invention is applied to the back coating of heliostats, which can improve the lighting efficiency, make the mirror reflectivity reach 95%, reduce the weight by 10%, help improve the efficiency of solar panels, and increase the power generation gain by 1.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[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 DESCRIPTION

[0040] The technical solution of the present invention will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] (1) Preparation of polyacrylic acid oligomers

[0043] S1: Weigh 40g of xylene, pump it into the reactor through a vacuum machine, stop the vacuum, start stirring and heat up; dissolve 24g of diisopropylbenzene peroxide in 40g of styrene to prepare solution a; add a monomer mixture into the reactor, the monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate, and the ratio of methacrylic acid monomer, methyl methacrylate and styrene is 70:110:40;

[0044] S2: Heat the reactor to 130°C, and evenly add solution a at a rate of 180±2L / h at 130±2°C. Add the solution within 3h±10min and keep warm 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 a rate of 130±2L / h at a temperature of 110°C, add 1 / 3 each time, and add within 10 minutes each time. After the first two additions, keep warm for 50 minutes, and keep warm for the last time for 1.5 hours. After the heat preservation is completed, take samples to measure the viscosity. The viscosity is required to reach 6-10s. If the viscosity is lower than 6s, continue to keep warm and measure the sample once every 0.5h until the viscosity is qualified;

[0046] S4: After the viscosity is qualified, the temperature is raised to 120°C for vacuum dehydration until no water is removed, the temperature is lowered to 100°C, the viscosity is adjusted to qualified with xylene, and the temperature is lowered to below 80°C to obtain polyacrylic acid oligomer for standby 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 into a reactor containing 10g of polyacrylic acid oligomer, stir and heat to 200±5°C, and keep the temperature to react until the reaction product becomes transparent, then cool down;

[0049] S2: When the temperature drops to 180°C, add 7g of hexahydrophthalic anhydride and 3g of tert-butylbenzoic acid, continue to raise the temperature to 200°C, and keep reacting at this temperature until the acid value reaches 30-35mgKOH / g, then cool down;

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

[0051] S4: Then add 3g of partial anhydride, continue to maintain at 180°C for 1.5h, control the acid value at 35-45mgKOH / g, then cool to 140°C, transfer to a dilution tank, add 20g of dilution solvent for dilution; the dilution solvent is a mixture of ethylene glycol butyl ether and isobutyl alcohol in a weight ratio of 7:3;

[0052] S5: Add 4 g of neutralizer into the dilution tank and stir for 15 to 30 minutes to obtain water-based acrylic epoxy modified alkyd resin, filter at 80°C, control the fineness to be below 20 um, and package; the neutralizer is a mixture of triethylamine and dimethylethanolamine in a weight ratio of 1:1.

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

[0054] S1: Add 27g of waterborne acrylic epoxy modified alkyd resin into the preparation tank, start stirring at a speed of 300r / min, and add 30g of partial 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, stir for 30min, then add 28g of pigment and filler, 2g of cosolvent, and continue stirring until the dispersion is uniform;

[0055] S2: conveying the slurry obtained in step S1 to a sand mill for grinding, grinding the slurry to a fineness of less than 30 μm, and controlling the temperature to ≤45° C. during the grinding process;

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

[0057] Example 2

[0058] (1) Preparation of polyacrylic acid oligomers

[0059] S1: Weigh 40g of xylene, pump it into the reactor through a vacuum machine, stop the vacuum, start stirring and heat up; evenly dissolve 32g of diisopropylbenzene peroxide in 50g of styrene to prepare solution a; add a monomer mixture into the reactor, the monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate, and the amount ratio of methacrylic acid monomer, methyl methacrylate and styrene is 77:120:50;

[0060] S2: Heat the reactor to 130°C, and evenly add solution a at a rate of 180±2L / h at 130±2°C. Add the solution within 3h±10min and keep warm for 75min.

[0061] S3: 8g of dicumyl peroxide is uniformly dissolved in 30g of xylene to prepare solution b; after the heat preservation in step S2 is completed, solution b is added dropwise at a rate of 130±2L / h at a temperature of 115°C, and the addition is completed in three times, with 1 / 3 added each time, and each time the addition is completed within 10 minutes. After the first two additions are completed, the temperature is kept for 50 minutes, and the last time is kept for 1.5 hours. After the heat preservation is completed, samples are taken to measure the viscosity, and the viscosity is required to reach 6-10s. If the viscosity is lower than 6s, continue to keep warm and measure the sample once every 0.5h until the viscosity is qualified;

[0062] S4: After the viscosity is qualified, the temperature is raised to 120°C for vacuum dehydration until no water is removed, the temperature is lowered to 100°C, the viscosity is adjusted to qualified with xylene, and the temperature is lowered to below 80°C to obtain polyacrylic acid oligomer for standby 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 into a reactor containing 14g of polyacrylic acid oligomer, stir and heat to 200±5°C, and keep the temperature to react until the reaction product becomes transparent, then cool down;

[0065] S2: When the temperature drops to 140°C, add 5g of hexahydrophthalic anhydride and 5g of tert-butylbenzoic acid, continue to raise the temperature to 180°C, and keep reacting at this temperature until the acid value reaches 30-35mgKOH / g, then cool down;

[0066] S3: When the temperature drops to 140°C, add 11g of epoxy resin, continue to heat to 180°C, and maintain the temperature until the reaction acid value is below 20mgKOH / g;

[0067] S4: Then add 4g of partial anhydride, continue to maintain at 180°C for 1.5h, control the acid value at 35-45mgKOH / g, then cool to 140°C, transfer to a dilution tank, add 15g of dilution solvent for dilution; the dilution solvent is a mixture of ethylene glycol butyl ether and isobutyl alcohol in a weight ratio of 7:3;

[0068] S5: Add 4.4 g of neutralizer into the dilution tank and stir for 30 min to obtain waterborne acrylic epoxy modified alkyd resin, filter at 80° C., control the fineness to be below 20 um, and package; the neutralizer is a mixture of triethylamine and dimethylethanolamine in a weight ratio of 1:1.

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

[0070] S1: Add 33g of waterborne acrylic epoxy modified alkyd resin into the preparation tank, start stirring at a speed of 300-500r / min, and add 25g of partial deionized water, 1.6g 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 900r / min, stir for 20min, then add 21g of pigment and filler, 4g of cosolvent, and continue stirring until the dispersion is uniform;

[0071] S2: conveying the slurry obtained in step S1 to a sand mill for grinding, grinding the slurry to a fineness of less than 30 μm, and controlling the temperature to ≤45° C. during the grinding process;

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

[0073] Example 3

[0074] (1) Preparation of polyacrylic acid oligomers

[0075] S1: Weigh 40g of xylene, pump it into the reactor through a vacuum machine, stop the vacuum, start stirring and heat up; evenly dissolve 28g of diisopropylbenzene peroxide in 50g of styrene to prepare solution a; add a monomer mixture into the reactor, the monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate, and the ratio of methacrylic acid monomer, methyl methacrylate and styrene is 75:115:50;

[0076] S2: Heat the reactor to 130°C, and evenly add solution a at a rate of 180±2L / h at 130±2°C. Add the solution within 3h±10min and keep warm for 75min.

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

[0078] S4: After the viscosity is qualified, the temperature is raised to 120°C for vacuum dehydration until no water is removed, the temperature is lowered to 100°C, the viscosity is adjusted to qualified with xylene, and the temperature is lowered to below 80°C to obtain polyacrylic acid oligomer for standby 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 into a reactor containing 10g of polyacrylic acid oligomer, stir and heat to 200±5°C, and keep the temperature to react until the reaction product becomes transparent, then cool down;

[0081] S2: When the temperature drops to 160°C, add 6g of hexahydrophthalic anhydride and 5g of tert-butylbenzoic acid, continue to raise the temperature to 190°C, and keep reacting at this temperature until the acid value reaches 30-35mgKOH / g, then cool down;

[0082] S3: When the temperature drops to 150°C, add 11g of epoxy resin, continue to heat to 175°C, and maintain the temperature until the reaction acid value is below 20mgKOH / g;

[0083] S4: Then add 3g of partial anhydride, continue to maintain at 180°C for 1.5h, control the acid value at 35-45mgKOH / g, then cool to 140°C, transfer to a dilution tank, add 20g of dilution solvent for dilution; the dilution solvent is a mixture of ethylene glycol butyl ether and isobutyl alcohol in a weight ratio of 7:3;

[0084] S5: Add 4.4 g of neutralizer into the dilution tank and stir for 20 min to obtain water-based acrylic epoxy modified alkyd resin, filter at 80° C., control the fineness to be below 20 um, and package; the neutralizer is a mixture of triethylamine and dimethylethanolamine in a weight ratio of 1:1.

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

[0086] S1: Add 30g of waterborne acrylic epoxy modified alkyd resin into the preparation tank, start stirring at a speed of 400r / min, and add 35g of partial 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, stir for 25min, then add 24g of pigment and filler, 3g of cosolvent, and continue stirring until the dispersion is uniform;

[0087] S2: conveying the slurry obtained in step S1 to a sand mill for grinding, grinding the slurry to a fineness of less than 30 μm, and controlling the temperature to ≤45° C. during the grinding process;

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

[0089] Test Example 1

[0090] The performance tests were conducted on the water-based glass mirror back coatings prepared in Examples 1-3 of the present invention and a certain brand of commercially available water-based mirror back paint products. The test results are shown in the table below.

[0091]

[0092]

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

[0094] Test Example 2

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

[0096]

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

[0098] Application Examples

[0099] A 110MW molten salt tower power station under construction, the heliostat is designed to be 115m 2 A set of heliostats is equipped with 35 reflectors. The size of a single-sided heliostat with a traditional glass-steel structure is 3.3m 2(solar reserve), mirror reflectivity 93%. The water-based glass mirror back paint of Example 1 was used as a primer to coat the back of the heliostat, and the details are shown in the following table.

[0100]

[0101]

[0102] Compared with the existing coating scheme, the use of 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 collected relevant data, it is found that the power generation gain is 1.1% after the primer is applied.

[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 in the protection scope of the present invention.

Claims

1. A water-based glass mirror back coating, characterized in that: The invention comprises the following raw materials in parts by weight: 25-35 parts of waterborne acrylic epoxy modified alkyd resin, 0.5-1 parts of adhesion promoter, 0.3-1 parts 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 parts of flash rust inhibitor, 20-40 parts of pigment and filler, 20-45 parts of deionized water, 0.5-1 parts of substrate wetting agent, 1-5 parts of cosolvent, 0.1-0.5 parts of drying agent, and 3-6 parts of n-butylated urea formaldehyde resin; The substrate wetting agent is a polyether modified wetting agent, the pigment filler is at least one of aluminum tripolyphosphate, hollow glass microspheres, red iron oxide, 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 high-activity iron complex; The water-based 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 partial anhydride, 7-12 parts of epoxy resin, 15-20 parts of dilution solvent, and 4-7 parts of neutralizer; The preparation method of the polyacrylic acid oligomer is as follows: S1: Weigh 40g of xylene, pump it into a reactor through a vacuum machine, stop the vacuum, start stirring and heat up; evenly dissolve 24-32g of dicumyl peroxide in 40-50g of styrene to prepare a solution a; add a monomer mixture into the reactor, wherein the monomer mixture is a mixture of methacrylic acid monomer and methyl methacrylate, and the ratio of methacrylic acid monomer, methyl methacrylate and styrene is 70-77:110-120:40-50; S2: Heat the reactor to 130°C, and evenly add solution a at a rate of 180±2L / h at 130±2°C. Add the solution within 3h±10min and keep warm 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 temperature of 110-115°C at a rate of 130±2L / h, add it three times, add 1 / 3 each time, and add it within 10 minutes each time. After the first two additions, keep warm for 50 minutes, and keep warm for the last time for 1.5 hours. After the heat preservation is completed, take samples to measure the viscosity. The viscosity is required to reach 6-10s. If the viscosity is lower than 6s, continue to keep warm and measure the sample once every 0.5h until the viscosity is qualified; S4: After the viscosity is qualified, the temperature is raised to 120°C for vacuum dehydration until no water is removed, the temperature is lowered to 100°C, the viscosity is adjusted to qualified with xylene, and the temperature is lowered to below 80°C to obtain polyacrylic acid oligomer.

2. The water-based glass mirror back coating according to claim 1, characterized in that: The defoaming agent is Digo 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 polyvalent 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 organic tin, the dilution solvent is a mixture of ethylene glycol butyl ether and isobutyl alcohol in a mass ratio of 7:3, and the neutralizer 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 grafting catalyst into a reactor containing polyacrylic acid oligomer prepared in advance, stir and heat, when the temperature reaches 60-100°C, the materials melt, continue to heat to 200±5°C, and keep the temperature to react until the reaction product becomes transparent and then cool down; S2: When the temperature drops to 140-180°C, add hexahydrophthalic anhydride and tert-butylbenzoic acid, continue to raise the temperature to 180-200°C, and keep reacting at this temperature until the acid value reaches 30-35 mgKOH / g, then cool down; S3: When the temperature drops to 140-160°C, add epoxy resin, continue to heat to 167-180°C, and maintain the temperature until the reaction acid value is below 20 mgKOH / g; S4: then add partial anhydride, keep at 180℃ for 1.5h, control the acid value at 35-45mgKOH / g, then cool to 140℃, transfer to the dilution tank, add dilution solvent for dilution; S5: Add neutralizing agent into the dilution tank and stir for 15-30 minutes to obtain waterborne acrylic epoxy modified alkyd resin. Filter at 80°C to control the fineness to be below 20 um 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: The following steps are involved: S1: Add water-based acrylic epoxy modified alkyd resin into the preparation tank, start stirring at a speed of 300-500r / min, and add part of deionized water, dispersant, defoamer, and anti-settling thixotropic agent in sequence; after the addition is completed, increase the speed to 700-900r / min, stir for 20-30min, then add pigments, fillers, and cosolvents and continue stirring until they are evenly dispersed; S2: conveying the slurry obtained in step S1 to a sand mill for grinding, grinding the slurry to a fineness of less than 30 μm, and controlling the temperature to ≤45°C during the grinding process; S3: The slurry obtained in step S2 is transferred into a dilution basin, and the remaining deionized water, adhesion promoter, thickener, flash rust inhibitor, substrate wetting agent, drying agent, and n-butylated urea formaldehyde resin are added in sequence under stirring, and the mixture is stirred at a speed of 500-800 r / min for 20-30 min, and the viscosity is adjusted to meet the requirements to obtain a finished coating product.

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

Images