A high-hardness water-based coating and its preparation method

Abstract

This invention discloses a high-hardness waterborne coating and its preparation method, belonging to the field of coating technology. By weight, it comprises the following raw materials: 50-80 parts modified waterborne alkyd resin, 10-15 parts nano-silica modified waterborne epoxy resin, 2-8 parts film-forming aid, 10-15 parts pigment, 5-8 parts filler, 0.5-0.8 parts dispersant, 0.1-0.3 parts defoamer, 0.1-0.5 parts leveling agent, and 20-35 parts water. The high-hardness waterborne coating prepared by this invention has the characteristics of high hardness, good toughness, good water resistance, high adhesion, and high stability, and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically a high-hardness water-based coating and its preparation method. Background Technology

[0002] Water-based coatings are coatings that use water as a solvent. Their main components include polymer emulsions, pigments, fillers, and additives. After application, the water evaporates, and the film-forming substances cross-link and cure to form a paint film. Due to their advantages such as environmental friendliness, non-flammability, and low volatile organic compound emissions, they are widely used in construction, furniture, automobiles, and other fields.

[0003] Currently, commonly used resins for waterborne coatings include waterborne acrylic resins, waterborne polyurethane resins, waterborne epoxy resins, and waterborne alkyd resins. Among these, waterborne alkyd resins are widely used due to their low cost, wide availability of raw materials, and good gloss, fullness, and flexibility. However, waterborne alkyd resin molecules contain numerous polar groups such as ester bonds and hydroxyl groups. The interactions between these groups are relatively weak, the molecular chains are not very rigid, and their crosslinking density is relatively low, making it difficult to form the highly crosslinked and compact structure found in some high-performance resins. This affects the hardness of the paint film. Furthermore, the ester bonds in alkyd resins are prone to hydrolysis in water, especially under high temperature and humidity conditions. Hydrolysis leads to the breakage of resin molecular chains, a decrease in molecular weight, and consequently, a decline in the mechanical properties and hardness of the paint film, resulting in chalking and peeling. Therefore, modifying alkyd resins to prepare high-hardness waterborne alkyd resin coatings is of great significance for extending the performance and service life of coatings. Summary of the Invention

[0004] To address the above problems, the present invention aims to provide a high-hardness water-based coating and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A high-hardness waterborne coating, by weight, is composed of the following raw materials: 50-80 parts of modified waterborne alkyd resin, 10-15 parts of nano-silica modified waterborne epoxy resin, 2-8 parts of film-forming aid, 10-15 parts of pigment, 5-8 parts of filler, 0.5-0.8 parts of dispersant, 0.1-0.3 parts of defoamer, 0.1-0.5 parts of leveling agent, and 20-35 parts of water;

[0007] The modified waterborne alkyd resin is prepared by modifying alkyd resin with a modified styrene-maleic anhydride copolymer, wherein polyetheramine is grafted onto the modified styrene-maleic anhydride copolymer.

[0008] The modified styrene-maleic anhydride copolymer was prepared according to the following method:

[0009] The styrene-maleic anhydride copolymer was added to cyclohexanone and stirred until dissolved. Then, polyetheramine was added and the mixture was stirred and reacted at 90-100°C for 2-5 hours. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

[0010] The mass ratio of the styrene-maleic anhydride copolymer, cyclohexanone, and polyetheramine is 1:5 to 10:1.5 to 2.5.

[0011] The polyetheramine is polyetheramine ED-600 or polyetheramine ED-900.

[0012] The film-forming aid is propylene glycol monoether, dipropylene glycol butyl ether, or diethylene glycol monobutyl ether.

[0013] The pigment is titanium dioxide, iron oxide yellow, iron oxide red, iron oxide blue, or carbon black.

[0014] The filler is calcium carbonate, talc, or zinc phosphate.

[0015] The dispersant is sodium polyacrylate or fatty alcohol polyoxyethylene ether.

[0016] The defoamer is an organosilicon defoamer or polyoxypropylene ethylene glycerol ether.

[0017] The leveling agent is a polyacrylic acid or silicone leveling agent.

[0018] The preparation method of the modified waterborne alkyd resin includes the following steps:

[0019] By weight, 12-20 parts of linoleic acid, 10-15 parts of trimethylolpropane, 8-12 parts of phthalic anhydride, 3-5 parts of modified styrene-maleic anhydride copolymer, and 1-2 parts of xylene were added to a reactor. The mixture was stirred and heated to 180°C and kept at that temperature for 1-3 hours. The temperature was then increased to 190-230°C and reacted for 3-8 hours until the acid value reached 10-15 mg KOH / g. Xylene was removed by vacuuming, and the temperature was lowered to 180°C. 3-5 parts of trimellitic anhydride were added, and the reaction was continued until the acid value reached 35-50 mg KOH / g. The temperature was then lowered to 60-80°C, and 4-5 parts of triethylamine were added for neutralization reaction for 0.5-1 hour. Finally, water was added for high-speed emulsification and dispersion for 30 minutes. The mixture was then filtered to obtain the modified waterborne alkyd resin.

[0020] The nano-silica-modified waterborne epoxy resin was prepared according to the following method:

[0021] 1) Add nano-silica to an organic solvent with a water content of less than 10 ppm, then add 3-chloropropyltriethoxysilane, heat to 40-50℃, stir and react for 10-24 h to obtain silanized silica;

[0022] 2) Add the silanized silica, bisphenol A epoxy resin and sodium hydride obtained in step 1) to tetrahydrofuran, stir and mix evenly, heat to 50-80℃, react for 3-5 hours, add water to quench the reaction, then add dichloromethane for extraction, and remove the solvent by vacuum distillation of the obtained organic layer to obtain nano silica modified epoxy resin.

[0023] 3) Add the nano-silica modified epoxy resin and waterborne epoxy emulsifier obtained in step 2) into the reactor, disperse them evenly at high speed at 50-55℃, then add water dropwise and stir for 0.5-1h to obtain nano-silica modified waterborne epoxy resin.

[0024] The organic solvent mentioned in step 1) is tetrahydrofuran or toluene.

[0025] The mass ratio of nano-silica, organic solvent and 3-chloropropyltriethoxysilane in step 1) is 1:5 to 10:2 to 4.

[0026] The mass ratio of silanized silica, bisphenol A epoxy resin, sodium hydride, tetrahydrofuran, water and dichloromethane in step 2) is 0.2-0.4:1:0.1-0.2:5-10:3-5:3-5.

[0027] In step 3), the mass ratio of the nano-silica modified epoxy resin, the waterborne epoxy emulsifier, and water is 1:0.1-0.2:0.7-0.9.

[0028] The preparation method of the high-hardness water-based coating includes the following steps:

[0029] By weight, 50-80 parts of modified waterborne alkyd resin, 10-15 parts of pigment, 5-8 parts of filler, 0.5-0.8 parts of dispersant, and 20-35 parts of water are added to a high-speed disperser and stirred and dispersed evenly at 1500-2000 r / min. Then, 10-15 parts of nano-silica modified waterborne epoxy resin are added and stirred for 10-30 min. Finally, 2-8 parts of film-forming aid, 0.1-0.3 parts of defoamer, and 0.1-0.5 parts of leveling agent are added and stirred and dispersed at 500-800 r / min for 0.5-1 h to obtain a high-hardness waterborne coating.

[0030] The present invention has the following advantages over the prior art:

[0031] The high-hardness waterborne coating of the present invention comprises a waterborne epoxy resin modified with nano-silica and a waterborne alkyd resin modified with nano-silica. The waterborne alkyd resin is modified using a modified styrene-maleic anhydride copolymer. The epoxy groups can react with the active amine groups in the modified styrene-maleic anhydride copolymer to form a stable three-dimensional network structure. The rigid structure of styrene can improve the hardness and glass transition temperature of the coating, increasing the mechanical strength of the waterborne coating. Simultaneously, the cross-linked network structure blocks the ester groups in the alkyd resin, reducing hydrolysis and increasing the stability of the coating. Modifying the epoxy resin with nano-silica increases the compatibility between the nano-silica and the resin, allowing the nano-silica to be more stably dispersed in the coating, further increasing the hardness of the coating.

[0032] The high-hardness waterborne coating of the present invention utilizes the reaction of polyetheramine and maleic anhydride groups to form amide bonds, while introducing flexible ether chains, which improves the toughness of the waterborne coating and its adhesion to the substrate; at the same time, it can improve the water solubility of styrene-maleic anhydride copolymer; due to the hydrophobicity of styrene and silane chains, the waterborne coating can reduce water absorption rate and improve water resistance after film formation, and reduce the occurrence of hydrolysis reaction.

[0033] The high-hardness waterborne coating prepared by this invention has the characteristics of high hardness, good toughness, good water resistance, high adhesion and high stability, and has broad application prospects. Detailed Implementation

[0034] To better understand the technical solution of the present invention, the following detailed embodiments further illustrate the above-mentioned content of the present invention. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention.

[0035] Example 1: Preparation of modified styrene-maleic anhydride copolymer

[0036] 0.1 kg of styrene-maleic anhydride copolymer was added to 0.5 kg of cyclohexanone and stirred until dissolved. Then, 0.15 kg of polyetheramine ED-600 was added and stirred at 90 °C for 5 h. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

[0037] Preparation of modified waterborne alkyd resin

[0038] 1.2 kg of linoleic acid, 1 kg of trimethylolpropane, 0.8 kg of phthalic anhydride, 0.3 kg of modified styrene-maleic anhydride copolymer, and 0.1 kg of xylene were added to a reactor, stirred, heated to 180 °C, and kept at that temperature for 1 h. The temperature was then increased to 190 °C and reacted for 8 h until the acid value reached 15 mg KOH / g. Xylene was removed by vacuuming, and the temperature was lowered to 180 °C. 0.3 kg of trimellitic anhydride was added, and the reaction was continued until the acid value reached 35 mg KOH / g. The temperature was then lowered to 60 °C, and 0.4 kg of triethylamine was added to neutralize the reaction for 0.5 h. Finally, water was added and the mixture was emulsified and dispersed at high speed for 30 min. The mixture was then filtered to obtain the modified waterborne alkyd resin.

[0039] Preparation of waterborne epoxy resin modified with nano-silica

[0040] 1) Add 1 kg of nano-silica to 5 kg of tetrahydrofuran with a water content of less than 10 ppm, then add 2 kg of 3-chloropropyltriethoxysilane, heat to 40 °C, stir and react for 24 h to obtain silanized silica;

[0041] 2) Add the silanized silica, bisphenol A epoxy resin and sodium hydride obtained in step 2) to tetrahydrofuran, stir and mix evenly, heat to 50-80℃, react for 3-5 hours, add water to quench the reaction, then add dichloromethane for extraction, and remove the solvent by vacuum distillation of the obtained organic layer to obtain nano silica modified epoxy resin.

[0042] 3) Add the nano-silica modified epoxy resin and waterborne epoxy emulsifier obtained in step 2) into the reactor, disperse them evenly at high speed at 50-55℃, then add water dropwise and stir for 0.5-1h to obtain nano-silica modified waterborne epoxy resin.

[0043] 2) Add 0.2 kg of silanized silica obtained in step 1), 1 kg of bisphenol A epoxy resin and 0.1 kg of sodium hydride to 5 kg of tetrahydrofuran, stir and mix evenly, heat to 50°C and react for 5 h. After the reaction is completed, add 3 kg of water to quench the reaction, then add 3 kg of dichloromethane for extraction. Remove the solvent from the obtained organic layer by vacuum distillation to obtain nano-silica modified epoxy resin.

[0044] 3) Add 1 kg of nano-silica modified epoxy resin obtained in step 2) and 0.1 kg of waterborne epoxy emulsifier to the reactor, disperse them evenly at high speed at 50°C, then add 0.7 kg of water dropwise, stir and disperse for 0.5 h to obtain nano-silica modified waterborne epoxy resin.

[0045] Preparation of high-hardness waterborne coatings

[0046] Add 5 kg of modified waterborne alkyd resin, 1 kg of titanium dioxide pigment, 0.5 kg of calcium carbonate filler, 0.05 kg of sodium polyacrylate dispersant, and 2 kg of water to a high-speed disperser and stir and disperse evenly at 1500 r / min. Then add 1 kg of nano-silica modified waterborne epoxy resin and stir and react for 10 min. Finally, add 0.2 kg of film-forming aid propylene glycol monoether, 0.01 kg of silicone defoamer, and 0.01 kg of silicone leveling agent and stir and disperse at 500 r / min for 0.5 h to obtain a high-hardness waterborne coating.

[0047] Example 2: Preparation of modified styrene-maleic anhydride copolymer

[0048] 0.1 kg of styrene-maleic anhydride copolymer was added to 0.6 kg of cyclohexanone and stirred until dissolved. Then, 0.18 kg of polyetheramine ED-900 was added and stirred at 97 °C for 3 h. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

[0049] Preparation of modified waterborne alkyd resin

[0050] 1.4 kg of linoleic acid, 1.1 kg of trimethylolpropane, 0.9 kg of phthalic anhydride, 0.35 kg of modified styrene-maleic anhydride copolymer, and 0.15 kg of xylene were added to a reactor, stirred, heated to 180 °C, and reacted for 1.5 h. The temperature was then increased to 200 °C and reacted for 7 h until the acid value reached 13 mg KOH / g. Xylene was removed by vacuum, and the temperature was lowered to 180 °C. 0.35 kg of trimellitic anhydride was added, and the reaction was continued until the acid value reached 40 mg KOH / g. The temperature was then lowered to 70 °C, and 0.4 kg of triethylamine was added for neutralization and reaction for 0.6 h. Finally, water was added and emulsified at high speed for 30 min. The mixture was then filtered to obtain the modified waterborne alkyd resin.

[0051] Preparation of waterborne epoxy resin modified with nano-silica

[0052] 1) Add 1 kg of nano-silica to 6 kg of toluene with a water content of less than 10 ppm, then add 2.5 kg of 3-chloropropyltriethoxysilane, heat to 45 °C, stir and react for 20 h to obtain silanized silica;

[0053] 2) Add 0.25 kg of silanized silica obtained in step 1), 1 kg of bisphenol A epoxy resin and 0.12 kg of sodium hydride to 6 kg of tetrahydrofuran, stir and mix evenly, heat to 60 °C and react for 4.5 h. After the reaction is completed, add 3.5 kg of water to quench the reaction, and then add 4 kg of dichloromethane for extraction. Remove the solvent from the obtained organic layer by vacuum distillation to obtain nano-silica modified epoxy resin.

[0054] 3) Add 1 kg of nano-silica modified epoxy resin obtained in step 2) and 0.12 kg of waterborne epoxy emulsifier to the reactor, disperse them evenly at high speed at 52°C, then add 0.75 kg of water dropwise, stir and disperse for 0.6 h to obtain nano-silica modified waterborne epoxy resin.

[0055] Preparation of high-hardness waterborne coatings

[0056] 6 kg of modified waterborne alkyd resin, 1.1 kg of iron oxide red pigment, 0.6 kg of zinc phosphate filler, 0.06 kg of fatty alcohol polyoxyethylene ether dispersant, and 2.2 kg of water were added to a high-speed disperser and stirred and dispersed evenly at 1600 r / min. Then, 1.2 kg of nano-silica modified waterborne epoxy resin was added and stirred and reacted for 20 min. Finally, 0.3 kg of film-forming aid dipropylene glycol butyl ether, 0.02 kg of organosilicon defoamer, and 0.02 kg of leveling agent polyacrylic acid were added and stirred and dispersed at 600 r / min for 0.6 h to obtain a high-hardness waterborne coating.

[0057] Example 3: Preparation of modified styrene-maleic anhydride copolymer

[0058] 0.1 kg of styrene-maleic anhydride copolymer was added to 0.7 kg of cyclohexanone and stirred until dissolved. Then, 0.2 kg of polyetheramine ED-600 was added and stirred at 95 °C for 3.5 h. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

[0059] Preparation of modified waterborne alkyd resin

[0060] 1.5 kg of linoleic acid, 1.2 kg of trimethylolpropane, 1 kg of phthalic anhydride, 0.4 kg of modified styrene-maleic anhydride copolymer, and 0.15 kg of xylene were added to a reactor, stirred, heated to 180 °C, and kept at that temperature for 2 h. The temperature was then increased to 210 °C and reacted for 5 h until the acid value reached 12 mg KOH / g. Xylene was removed by vacuuming, and the temperature was lowered to 180 °C. 0.4 kg of trimellitic anhydride was added, and the reaction was continued until the acid value reached 40 mg KOH / g. The temperature was then lowered to 65 °C, and 0.45 kg of triethylamine was added to neutralize the reaction for 0.7 h. Finally, water was added and emulsified at high speed for 30 min. The mixture was then filtered to obtain the modified waterborne alkyd resin.

[0061] Preparation of waterborne epoxy resin modified with nano-silica

[0062] 1) Add 1 kg of nano-silica to 8 kg of toluene with a water content of less than 10 ppm, then add 3 kg of 3-chloropropyltriethoxysilane, heat to 48 °C, stir and react for 18 h to obtain silanized silica;

[0063] 2) Add 0.3 kg of silanized silica obtained in step 1), 1 kg of bisphenol A epoxy resin and 0.15 kg of sodium hydride to 7 kg of tetrahydrofuran, stir and mix evenly, heat to 65°C and react for 4 h. After the reaction is completed, add 4 kg of water to quench the reaction, and then add 4 kg of dichloromethane for extraction. Remove the solvent from the obtained organic layer by vacuum distillation to obtain nano-silica modified epoxy resin.

[0064] 3) Add 1 kg of nano-silica modified epoxy resin obtained in step 2) and 0.15 kg of waterborne epoxy emulsifier to the reactor, disperse them evenly at high speed at 53°C, then add 0.8 kg of water dropwise, stir and disperse for 0.7 h to obtain nano-silica modified waterborne epoxy resin.

[0065] Preparation of high-hardness waterborne coatings

[0066] 6.5 kg of modified waterborne alkyd resin, 1.2 kg of pigment iron oxide yellow, 0.7 kg of filler calcium carbonate, 0.07 kg of dispersant fatty alcohol polyoxyethylene ether, and 2.5 kg of water were added to a high-speed disperser and stirred and dispersed evenly at 1800 r / min. Then, 1.3 kg of nano silica-modified waterborne epoxy resin was added and stirred for 25 min. Finally, 0.4 kg of film-forming aid dipropylene glycol butyl ether, 0.02 kg of defoamer polyoxypropylene ethylene glycerol ether, and 0.03 kg of leveling agent polyacrylic acid were added and stirred and dispersed at 700 r / min for 0.8 h to obtain a high-hardness waterborne coating.

[0067] Example 4: Preparation of modified styrene-maleic anhydride copolymer

[0068] 0.1 kg of styrene-maleic anhydride copolymer was added to 0.9 kg of cyclohexanone and stirred until dissolved. Then, 0.23 kg of polyetheramine ED-900 was added and stirred at 92 °C for 4.5 h. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

[0069] Preparation of modified waterborne alkyd resin

[0070] 1.8 kg of linoleic acid, 1.3 kg of trimethylolpropane, 1.1 kg of phthalic anhydride, 0.4 kg of modified styrene-maleic anhydride copolymer, and 0.18 kg of xylene were added to a reactor, stirred, heated to 180 °C, and reacted for 2.5 h. The temperature was then increased to 220 °C and reacted for 4 h until the acid value reached 11 mg KOH / g. Xylene was removed by vacuum, and the temperature was lowered to 180 °C. 0.45 kg of trimellitic anhydride was added, and the reaction was continued until the acid value reached 45 mg KOH / g. The temperature was then lowered to 75 °C, and 0.48 kg of triethylamine was added to neutralize the reaction for 0.9 h. Finally, water was added and emulsified at high speed for 30 min. The mixture was then filtered to obtain the modified waterborne alkyd resin.

[0071] Preparation of waterborne epoxy resin modified with nano-silica

[0072] 1) Add 1 kg of nano-silica to 9 kg of tetrahydrofuran with a water content of less than 10 ppm, then add 3.5 kg of 3-chloropropyltriethoxysilane, heat to 48 °C, stir and react for 15 h to obtain silanized silica;

[0073] 2) Add 0.35 kg of silanized silica obtained in step 1), 1 kg of bisphenol A epoxy resin and 0.18 kg of sodium hydride to 8 kg of tetrahydrofuran, stir and mix evenly, heat to 70 °C and react for 3.5 h. After the reaction is completed, add 4.5 kg of water to quench the reaction, then add 4.5 kg of dichloromethane for extraction. Remove the solvent from the obtained organic layer by vacuum distillation to obtain nano-silica modified epoxy resin.

[0074] 3) Add 1 kg of nano-silica modified epoxy resin obtained in step 2) and 0.18 kg of waterborne epoxy emulsifier to the reactor, disperse them evenly at high speed at 54°C, then add 0.85 kg of water dropwise, stir and disperse for 0.8 h to obtain nano-silica modified waterborne epoxy resin.

[0075] Preparation of high-hardness waterborne coatings

[0076] 7.5 kg of modified waterborne alkyd resin, 1.3 kg of pigment iron blue, 0.75 kg of filler talc, 0.07 kg of dispersant sodium polyacrylate, and 3 kg of water were added to a high-speed disperser and stirred and dispersed evenly at 1900 r / min. Then, 1.4 kg of nano-silica modified waterborne epoxy resin was added and stirred for 28 min. Finally, 0.6 kg of film-forming aid diethylene glycol monobutyl ether, 0.02 kg of organosilicon defoamer, and 0.04 kg of leveling agent polyacrylic acid were added and stirred and dispersed at 750 r / min for 0.9 h to obtain a high-hardness waterborne coating.

[0077] Example 5: Preparation of modified styrene-maleic anhydride copolymer

[0078] 0.1 kg of styrene-maleic anhydride copolymer was added to 1 kg of cyclohexanone and stirred until dissolved. Then, 0.25 kg of polyetheramine ED-600 was added and stirred at 100 °C for 2 h. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

[0079] Preparation of modified waterborne alkyd resin

[0080] 2 kg of linoleic acid, 1.5 kg of trimethylolpropane, 1.2 kg of phthalic anhydride, 0.5 kg of modified styrene-maleic anhydride copolymer, and 0.2 kg of xylene were added to a reactor. The mixture was stirred and heated to 180°C and kept at that temperature for 3 hours. The temperature was then increased to 230°C and reacted for another 3 hours until the acid value reached 10 mg KOH / g. Xylene was removed by vacuuming, and the temperature was lowered to 180°C. 0.5 kg of trimellitic anhydride was added, and the reaction was continued until the acid value reached 50 mg KOH / g. The temperature was then lowered to 80°C, and 0.5 kg of triethylamine was added to neutralize the reaction for 1 hour. Finally, water was added and the mixture was emulsified and dispersed at high speed for 30 minutes. The mixture was then filtered to obtain the modified waterborne alkyd resin.

[0081] Preparation of waterborne epoxy resin modified with nano-silica

[0082] 1) Add 1 kg of nano-silica to 10 kg of tetrahydrofuran with a water content of less than 10 ppm, then add 4 kg of 3-chloropropyltriethoxysilane, heat to 50 °C, stir and react for 10 h to obtain silanized silica;

[0083] 2) Add 0.4 kg of silanized silica obtained in step 1), 1 kg of bisphenol A epoxy resin and 0.2 kg of sodium hydride to 10 kg of tetrahydrofuran, stir and mix evenly, heat to 80°C and react for 3 h. After the reaction is completed, add 5 kg of water to quench the reaction, then add 5 kg of dichloromethane for extraction. Remove the solvent from the obtained organic layer by vacuum distillation to obtain nano-silica modified epoxy resin.

[0084] 3) Add 1 kg of nano-silica modified epoxy resin obtained in step 2) and 0.2 kg of waterborne epoxy emulsifier to the reactor, disperse them evenly at high speed at 55°C, then add 0.9 kg of water dropwise, stir and disperse for 1 h to obtain nano-silica modified waterborne epoxy resin.

[0085] Preparation of high-hardness waterborne coatings

[0086] 8 kg of modified waterborne alkyd resin, 1.5 kg of titanium dioxide pigment, 0.8 kg of calcium carbonate filler, 0.08 kg of sodium polyacrylate dispersant, and 3.5 kg of water were added to a high-speed disperser and stirred and dispersed evenly at 2000 r / min. Then, 1.5 kg of nano-silica modified waterborne epoxy resin was added and stirred and reacted for 30 min. Finally, 0.8 kg of film-forming aid diethylene glycol monobutyl ether, 0.03 kg of silicone defoamer, and 0.05 kg of silicone leveling agent were added and stirred and dispersed at 800 r / min for 1 h to obtain a high-hardness waterborne coating.

[0087] Example 6: Preparation of modified styrene-maleic anhydride copolymer

[0088] 0.1 kg of styrene-maleic anhydride copolymer was added to 0.8 kg of cyclohexanone and stirred until dissolved. Then, 0.2 kg of polyetheramine ED-600 was added and stirred at 100 °C for 5 h. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

[0089] Preparation of modified waterborne alkyd resin

[0090] 1.2 kg of linoleic acid, 1.5 kg of trimethylolpropane, 0.8 kg of phthalic anhydride, 0.5 kg of modified styrene-maleic anhydride copolymer, and 0.2 kg of xylene were added to a reactor, stirred, and heated to 180°C. The mixture was kept at this temperature for 3 hours, then heated to 230°C and reacted for 8 hours until the acid value reached 15 mg KOH / g. The xylene was removed by vacuuming, and the temperature was lowered to 180°C. 0.5 kg of trimellitic anhydride was added, and the mixture was kept at this temperature until the acid value reached 45 mg KOH / g. The temperature was lowered to 60°C, and 0.5 kg of triethylamine was added to neutralize the mixture for 1 hour. Finally, water was added and the mixture was emulsified and dispersed at high speed for 30 minutes. The mixture was then filtered to obtain the modified waterborne alkyd resin.

[0091] Preparation of waterborne epoxy resin modified with nano-silica

[0092] 1) Add 1 kg of nano-silica to 8 kg of toluene with a water content of less than 10 ppm, then add 3 kg of 3-chloropropyltriethoxysilane, heat to 50 °C, stir and react for 24 h to obtain silanized silica;

[0093] 2) Add 0.3 kg of silanized silica obtained in step 1), 1 kg of bisphenol A epoxy resin and 0.15 kg of sodium hydride to 7 kg of tetrahydrofuran, stir and mix evenly, heat to 55°C and react for 5 h. After the reaction is completed, add 3 kg of water to quench the reaction, and then add 5 kg of dichloromethane for extraction. Remove the solvent from the obtained organic layer by vacuum distillation to obtain nano-silica modified epoxy resin.

[0094] 3) Add 1 kg of nano-silica modified epoxy resin obtained in step 2) and 0.15 kg of waterborne epoxy emulsifier to the reactor, disperse them evenly at high speed at 55°C, then add 0.8 kg of water dropwise, stir and disperse for 1 h to obtain nano-silica modified waterborne epoxy resin.

[0095] Preparation of high-hardness waterborne coatings

[0096] Add 5 kg of modified waterborne alkyd resin, 1.2 kg of pigment iron oxide yellow, 0.8 kg of filler calcium carbonate, 0.08 kg of dispersant fatty alcohol polyoxyethylene ether, and 3.5 kg of water to a high-speed disperser and stir and disperse evenly at 2000 r / min. Then add 1.5 kg of nano silica-modified waterborne epoxy resin and stir and react for 20 min. Finally, add 0.5 kg of film-forming aid dipropylene glycol butyl ether, 0.02 kg of defoamer polyoxypropylene ethylene glycerol ether, and 0.05 kg of organosilicon leveling agent. Stir and disperse at 800 r / min for 0.5 h to obtain a high-hardness waterborne coating.

[0097] The high-hardness water-based coatings prepared in Examples 1 to 6 were sprayed onto the test plates and tested according to the method in HG / T4847-2015. The test results are shown in Table 1.

[0098] Table 1 Performance parameters of the coating

[0099]

[0100] As can be seen from the results in Table 1, the high-hardness waterborne coating prepared by this invention has the characteristics of high hardness, good toughness, good water resistance, high adhesion and high stability, and has broad application prospects.

[0101] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A high-hardness water-based coating, characterized in that: By weight, it is composed of the following raw materials: 50-80 parts modified waterborne alkyd resin, 10-15 parts nano-silica modified waterborne epoxy resin, 2-8 parts film-forming aid, 10-15 parts pigment, 5-8 parts filler, 0.5-0.8 parts dispersant, 0.1-0.3 parts defoamer, 0.1-0.5 parts leveling agent, and 20-35 parts water; The modified waterborne alkyd resin is prepared by modifying alkyd resin with a modified styrene-maleic anhydride copolymer, wherein polyetheramine is grafted onto the modified styrene-maleic anhydride copolymer. The modified styrene-maleic anhydride copolymer was prepared according to the following method: The styrene-maleic anhydride copolymer was added to cyclohexanone and stirred until dissolved. Then, polyetheramine was added and the mixture was stirred and reacted at 90-100°C for 2-5 hours. The solvent was removed by vacuum distillation to obtain the modified styrene-maleic anhydride copolymer.

2. The high-hardness water-based coating as described in claim 1, characterized in that: The mass ratio of the styrene-maleic anhydride copolymer, cyclohexanone, and polyetheramine is 1:5 to 10:1.5 to 2.

5.

3. The high-hardness water-based coating as described in claim 1, characterized in that: The polyetheramine is polyetheramine ED-600 or polyetheramine ED-900.

4. The high-hardness water-based coating as described in claim 1, characterized in that: The film-forming aid is propylene glycol monoether, dipropylene glycol butyl ether, or diethylene glycol monobutyl ether; the pigment is titanium dioxide, iron oxide yellow, iron oxide red, iron blue, or carbon black; the filler is calcium carbonate, talc, or zinc phosphate; the dispersant is sodium polyacrylate or fatty alcohol polyoxyethylene ether; the defoamer is an organosilicone defoamer or polyoxypropylene ethylene glycerol ether; and the leveling agent is polyacrylic acid or organosilicone leveling agent.

5. The high-hardness water-based coating as described in claim 1, characterized in that: The preparation method of the modified waterborne alkyd resin includes the following steps: By weight, 12-20 parts of linoleic acid, 10-15 parts of trimethylolpropane, 8-12 parts of phthalic anhydride, 3-5 parts of modified styrene-maleic anhydride copolymer, and 1-2 parts of xylene were added to a reactor. The mixture was stirred and heated to 180°C and kept at that temperature for 1-3 hours. The temperature was then increased to 190-230°C and reacted for 3-8 hours until the acid value reached 10-15 mg KOH / g. Xylene was removed by vacuuming, and the temperature was lowered to 180°C. 3-5 parts of trimellitic anhydride were added, and the reaction was continued until the acid value reached 35-50 mg KOH / g. The temperature was then lowered to 60-80°C, and 4-5 parts of triethylamine were added for neutralization reaction for 0.5-1 hour. Finally, water was added for high-speed emulsification and dispersion for 30 minutes. The mixture was then filtered to obtain the modified waterborne alkyd resin.

6. The high-hardness water-based coating as described in claim 1, characterized in that: The nano-silica-modified waterborne epoxy resin was prepared according to the following method: 1) Add nano-silica to an organic solvent with a water content of less than 10 ppm, then add 3-chloropropyltriethoxysilane, heat to 40-50℃, stir and react for 10-24 h to obtain silanized silica; 2) Add the silanized silica, bisphenol A epoxy resin and sodium hydride obtained in step 1) to tetrahydrofuran, stir and mix evenly, heat to 50-80℃, react for 3-5 hours, add water to quench the reaction, then add dichloromethane for extraction, and remove the solvent by vacuum distillation of the obtained organic layer to obtain nano silica modified epoxy resin. 3) Add the nano-silica modified epoxy resin and waterborne epoxy emulsifier obtained in step 2) into the reactor, disperse them evenly at high speed at 50-55℃, then add water dropwise and stir for 0.5-1h to obtain nano-silica modified waterborne epoxy resin.

7. The high-hardness water-based coating as described in claim 6, characterized in that: The organic solvent mentioned in step 1) is tetrahydrofuran or toluene; the mass ratio of nano-silica, organic solvent and 3-chloropropyltriethoxysilane mentioned in step 1) is 1:5 to 10:2 to 4.

8. The high-hardness water-based coating as described in claim 6, characterized in that: The mass ratio of silanized silica, bisphenol A epoxy resin, sodium hydride, tetrahydrofuran, water and dichloromethane in step 2) is 0.2-0.4:1:0.1-0.2:5-10:3-5:3-5.

9. The high-hardness water-based coating as described in claim 6, characterized in that: In step 3), the mass ratio of the nano-silica modified epoxy resin, the waterborne epoxy emulsifier, and water is 1:0.1-0.2:0.7-0.

9.

10. The method for preparing the high-hardness waterborne coating according to claim 1, characterized in that: Includes the following steps: By weight, 50-80 parts of modified waterborne alkyd resin, 10-15 parts of pigment, 5-8 parts of filler, 0.5-0.8 parts of dispersant, and 20-35 parts of water are added to a high-speed disperser and stirred and dispersed evenly at 1500-2000 r / min. Then, 10-15 parts of nano-silica modified waterborne epoxy resin are added and stirred for 10-30 min. Finally, 2-8 parts of film-forming aid, 0.1-0.3 parts of defoamer, and 0.1-0.5 parts of leveling agent are added and stirred and dispersed at 500-800 r / min for 0.5-1 h to obtain a high-hardness waterborne coating.

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