Low-temperature rapid curing non-oriented silicon steel coating and preparation method thereof

Abstract

The application belongs to the technical field of paint preparation, and provides a low-temperature fast-curing non-oriented silicon steel paint and a preparation method thereof; first, an epoxy resin is subjected to an amination ring-opening reaction with diethanolamine to prepare a water-based cationic epoxy resin; second, a polyurethane-acrylate copolymer emulsion is synthesized through polycondensation and grafting reaction; third, a reactive organosilicon-acrylate copolymer emulsion is prepared by using emulsion polymerization technology; finally, the three polymer emulsions with different functions are compounded with an aluminum dihydrogen phosphate solution to obtain the final paint; the paint prepared by the application does not contain harmful heavy metals such as chromium, can be rapidly crosslinked and solidified at a relatively low temperature, the formed coating has excellent electrical insulation, adhesion, corrosion resistance and heat resistance, the production energy consumption is reduced and the environmental protection performance is improved, and the application is suitable for surface insulation treatment of high-performance non-oriented silicon steel.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, and relates to a low-temperature rapid curing non-oriented silicon steel coating and its preparation method. Background Technology

[0002] Non-oriented silicon steel is an important functional metallic material, mainly used in the cores of motors and generators. For cold-rolled non-oriented silicon steel used in motor manufacturing, the eddy current loss of the steel sheet is proportional to the square of its thickness. Therefore, in the manufacture of cores, thinned non-oriented silicon steel sheets need to be stacked together. In order to effectively confine the eddy currents within each stack, an insulating coating is often applied to the surface of the non-oriented silicon steel.

[0003] Currently, the insulating coatings used for non-oriented silicon steel are mostly chromate semi-organic coatings, which have several limitations. They cause significant environmental pollution, consume a lot of energy, and require curing at furnace temperatures of 500-600℃, increasing production costs. Furthermore, the core processing involves multiple steps such as lamination, welding, and heat treatment, placing high demands on coating performance. The preparation of the insulating coating is the final step in the production of non-oriented silicon steel, and its insulation performance, adhesion, and corrosion resistance directly affect the overall performance of the steel. The coating must not only have high surface resistivity but also excellent adhesion to withstand the enormous shear forces during high-speed stamping without peeling off. It should also possess good weldability and corrosion resistance. Therefore, developing a low-temperature, rapid-curing coating for non-oriented silicon steel is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a low-temperature, rapid-curing, non-oriented silicon steel coating and its preparation method. By mixing waterborne cationic epoxy resin, polyurethane-acrylate copolymer emulsion, and organosilicon-acrylate copolymer emulsion, and then compounding them with an aqueous solution of aluminum dihydrogen phosphate, a dense and comprehensive insulating coating can be formed at a lower temperature, thereby meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a low-temperature rapid-curing non-oriented silicon steel coating, the method comprising:

[0007] S1, after mixing epoxy resin with propylene glycol methyl ether, diethanolamine is added dropwise to react. The reaction system is cooled and lactic acid solution is added to adjust the pH. Deionized water is added under stirring to obtain waterborne cationic epoxy resin.

[0008] S2, Trimethylolpropane, adipic acid and p-toluenesulfonic acid are mixed and reacted to obtain hyperbranched polyester alcohol. Hyperbranched polyester alcohol, polytetrahydrofuran ether diol, dimethylolpropionic acid, isophorone diisocyanate and dibutyltin dilaurate are dispersed in methyl ethyl ketone and reacted. Hydroxyethyl acrylate is added and the reaction continues. Triethylamine is added, stirred and deionized water is added to obtain an aqueous hyperbranched polyurethane-acrylate copolymer emulsion.

[0009] S3, methyl methacrylate, butyl acrylate, polydimethylsiloxane-methyl methacrylate, glycidyl methacrylate, the first part of sodium dodecyl sulfate and the first part of deionized water are mixed to obtain a pre-emulsion. The second part of deionized water, the second part of sodium dodecyl sulfate and potassium persulfate are mixed and added to the pre-emulsion for reaction. After the reaction is completed, the mixture is cooled to room temperature and the pH value is adjusted to 7-8 using ammonia water to obtain an organosilicon-acrylate copolymer emulsion.

[0010] S4, a low-temperature, fast-curing, non-oriented silicon steel coating is obtained by mixing waterborne cationic epoxy resin, waterborne hyperbranched polyurethane-acrylate copolymer emulsion, organosilicon-acrylate copolymer emulsion, aluminum dihydrogen phosphate solution, and deionized water.

[0011] Specifically, it includes:

[0012] S1. After mixing epoxy resin and propylene glycol methyl ether evenly, adjust the temperature to the first temperature, add diethanolamine dropwise under stirring, and after the addition is complete, raise the temperature to the second temperature to react. Cool the reaction system to the third temperature and add lactic acid solution until the pH of the reaction solution is 6-7. Add deionized water under stirring, cool the product to room temperature and filter it with a 200-mesh filter cloth to obtain waterborne cationic epoxy resin.

[0013] S2, under a nitrogen atmosphere, trimethylolpropane, adipic acid, and p-toluenesulfonic acid are mixed and the temperature is adjusted to the fourth temperature and stirred to obtain hyperbranched polyester alcohol. Hyperbranched polyester alcohol, polytetrahydrofuran ether glycol, dimethylolpropionic acid, isophorone diisocyanate, and dibutyltin dilaurate are dispersed in methyl ethyl ketone and the temperature is adjusted to the fifth temperature and refluxed. The reaction system is cooled to 60-65°C, hydroxyethyl acrylate is added and the reaction continues. The reaction system is cooled to 40-45°C, triethylamine is added and stirred, and deionized water is added. The mixture is then rotary evaporated and filtered to obtain an aqueous hyperbranched polyurethane-acrylate copolymer emulsion.

[0014] S3, methyl methacrylate, butyl acrylate, polydimethylsiloxane-methacrylate, glycidyl methacrylate, sodium dodecyl sulfate (SMS) and deionized water (SDR) are mixed and homogenized to obtain a pre-emulsion. Under a nitrogen atmosphere, deionized water (SMS), sodium dodecyl sulfate (SMS) (SMS) and potassium persulfate (PS) are mixed and added to the pre-emulsion. The temperature is adjusted to the first temperature for reaction. After the reaction is completed, the mixture is cooled to room temperature. The pH is adjusted to 7-8 using ammonia and filtered through a 200-mesh filter cloth to obtain an organosilicon-acrylate copolymer emulsion.

[0015] S4, a low-temperature, fast-curing, non-oriented silicon steel coating is obtained by mixing waterborne cationic epoxy resin, waterborne hyperbranched polyurethane-acrylate copolymer emulsion, organosilicon-acrylate copolymer emulsion, aluminum dihydrogen phosphate solution, and deionized water.

[0016] In S1, the hydrophobic linear epoxy resin is modified into a cationic prepolymer that can be stably dispersed in water. The nitrogen atom in the diethanolamine molecule acts as a nucleophilic center, attacking the epoxy ring at the end group of the epoxy resin, causing the epoxy ring to open. This process forms a new carbon-nitrogen bond and converts the original secondary amine into a tertiary amine structure, while simultaneously generating a new secondary hydroxyl group on an adjacent carbon atom. Since each diethanolamine molecule contains two hydroxyl groups, and the ring-opening reaction itself generates one hydroxyl group, this reaction not only introduces the tertiary amine group necessary for subsequent water-based conversion into the epoxy resin backbone, but also increases the hydroxyl density on the molecular chain, providing sufficient reaction sites for the final crosslinking and curing of the coating. In the neutralization and salt formation process, the added lactic acid, as a weak organic acid, has its carboxyl group providing protons that combine with the lone pair electrons of the tertiary amine group on the resin molecular chain to form a quaternary ammonium cation and the corresponding lactate anion. The quaternary ammonium salt structure endows the polymer chain with hydrophilicity. Through electrostatic repulsion between cations and hydration with water molecules, a thermodynamically stable cationic aqueous dispersion is formed.

[0017] In S2, under the acid catalysis of p-toluenesulfonic acid, the hydroxyl groups of trimethylolpropane and the carboxyl groups of adipic acid undergo esterification to form ester bonds. Because the trimethylolpropane molecule has three reaction sites, new branching centers are continuously introduced during the reaction, causing the polymer chain to grow in a three-dimensional dendritic manner rather than linearly, ultimately forming a hyperbranched polyester alcohol. The numerous hydroxyl groups on the surface of the hyperbranched polyester alcohol, the terminal hydroxyl groups of the polyether glycol, and the hydroxyl groups of dimethylolpropionic acid react with the isocyanate groups of excess isophorone diisocyanate to undergo polyurethaneization, forming a prepolymer with the hyperbranched polyester as the core and extending polyether / polyurethane segments, the chain arms ending in active isocyanate groups. Subsequently, the hydroxyl groups of hydroxyethyl acrylate react with these terminal isocyanate groups to complete the end-capping, thereby introducing acrylic double bonds that can participate in subsequent crosslinking. Finally, the carboxyl groups of dimethylolpropionic acid in the chain segments are neutralized by triethylamine to form a salt, and then water is added for reverse emulsification to form a stable aqueous dispersion.

[0018] In S3, potassium persulfate decomposes under heating conditions to generate sulfate radicals. These radicals initiate monomer polymerization in the aqueous phase, forming short-chain oligomer radicals with charged end groups. A pre-emulsion containing four functional monomers is dropwise added to a solution containing an initiator, ensuring that the instantaneous monomer concentration remains low. This allows monomers with different reactivity to copolymerize more uniformly onto the same polymer backbone, rather than forming a mixture of block copolymers or pure homopolymers. Ultimately, copolymer latex particles are formed with polyacrylate as the main chain, laterally grafted with numerous low surface energy polydimethylsiloxane segments and reactive epoxy groups.

[0019] In S4, the aqueous cationic epoxy resin molecular chain is rich in primary and secondary hydroxyl groups, while aluminum dihydrogen phosphate dissociates and hydrates in the aqueous medium, forming an aluminum oligophosphate species with a large number of active phosphorus hydroxyl groups. Under heating conditions, the alcohol hydroxyl groups of the resin undergo a nucleophilic condensation reaction with the phosphorus hydroxyl groups of the phosphate species, losing water molecules to form stable POC covalent bonds. This reaction proceeds efficiently under the acidic catalysis of aluminum dihydrogen phosphate itself, thereby constructing a three-dimensional network structure with aluminum phosphate oxygen bonds as the inorganic framework and flexible epoxy segments as organic bridges at a relatively low temperature. At the same time, the quaternary ammonium salt groups of the cationic epoxy resin in the system interact with the phosphate anions through electrostatic attraction, further enhancing the interfacial bonding between the organic and inorganic phases. The system achieves rapid curing at low temperatures, mainly due to the inherent high reactivity and autocatalytic properties of the aluminum dihydrogen phosphate system. It eliminates the need for the high-temperature unsealing process required by traditional crosslinking agents. The evaporation of moisture itself can promote the condensation reaction equilibrium to shift to the forward direction, while external heating provides the necessary activation energy for molecular chain segment movement and chemical bond formation, enabling the formation of a dense crosslinked network to be completed efficiently within a relatively low temperature range.

[0020] As a preferred technical solution of the present invention, in S1, the mass ratio of epoxy resin, propylene glycol methyl ether, diethanolamine and deionized water is (100-105):50:(40-52.5):200, for example, it can be (100, 100.5, 101, 101.5, 102, 102.5, 103, 103.5, 104, 104.5 or 105):50:(40, 41.25, 42.5, 43.75, 45, 46.25, 47.5, 48.75, 50, 51.25 or 52.5):200, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] In some alternative embodiments, the epoxy resin is epoxy resin E44.

[0022] In some alternative embodiments, the first temperature is 80-85°C, for example, it can be 80°C, 80.5°C, 81°C, 81.5°C, 82°C, 82.5°C, 83°C, 83.5°C, 84°C, 84.5°C or 85°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0023] In some optional embodiments, the diethanolamine is added over a period of 2 hours.

[0024] In some alternative embodiments, the second temperature is 90-95°C, for example, it can be 90°C, 90.5°C, 91°C, 91.5°C, 92°C, 92.5°C, 93°C, 93.5°C, 94°C, 94.5°C or 95°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0025] In some alternative embodiments, the reaction time at the second temperature is 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0026] In some alternative embodiments, the third temperature is 60-65°C, for example, it can be 60°C, 60.5°C, 61°C, 61.5°C, 62°C, 62.5°C, 63°C, 63.5°C, 64°C, 64.5°C or 65°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the lactic acid solution has a mass fraction of 85 wt.%.

[0028] As a preferred embodiment of the present invention, in S2, the mass ratio of trimethylolpropane, adipic acid, and p-toluenesulfonic acid is (67-70):(73-75):(0.8-1.2), for example, it can be (67, 67.3, 67.6, 67.9, 68.2, 68.5, 68.8, 69.1, 69.4, 69.7 or 70):(73, 73.2, 73.4, 73.6, 73.8, 74.0, 74.2, 74.4, 74.6, 74.8 or 75):(0.8, 0.84, 0.88, 0.92, 0.96, 1.0, 1.04, 1.08, 1.12, 1.16 or 1.2), but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the fourth temperature is 180-190°C, for example, it can be 180°C, 181°C, 182°C, 183°C, 184°C, 185°C, 186°C, 187°C, 188°C, 189°C or 190°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the stirring reaction time at the fourth temperature is 4-5 hours, for example, 4.0 hours, 4.1 hours, 4.2 hours, 4.3 hours, 4.4 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.8 hours, 4.9 hours, or 5.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the mass ratio of the hyperbranched polyester alcohol, polytetrahydrofuran ether diol, dimethylolpropionic acid, isophorone diisocyanate, dibutyltin dilaurate, methyl ethyl ketone, hydroxyethyl acrylate, triethylamine, and deionized water is (30-35):(50-55):(6-7):(42-45):(0.3-0.5):80:(5.8-6.5):(5-6):250, for example, it can be (30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5 or 35):(50, 50.5, 51, 51.5, 52, 52.5, 53, 53.5, 54, 54.5 or 55):(6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6). 6.7, 6.8, 6.9 or 7.0: (42, 42.3, 42.6, 42.9, 43.2, 43.5, 43.8, 44.1, 44.4, 44.7 or 45): (0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48 or 0.5): 80: (5.8) 5.87, 5.94, 6.01, 6.08, 6.15, 6.22, 6.29, 6.36, 6.43 or 6.5: (5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 or 6.0): 250, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0032] In some alternative embodiments, the fifth temperature is 80-85°C, for example, it can be 80°C, 80.5°C, 81°C, 81.5°C, 82°C, 82.5°C, 83°C, 83.5°C, 84°C, 84.5°C or 85°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the reflux reaction time at the fifth temperature is 3-4 hours, for example, 3.0 hours, 3.1 hours, 3.2 hours, 3.3 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.7 hours, 3.8 hours, 3.9 hours, or 4.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0034] As a preferred embodiment of the present invention, in S3, the mass ratio of methyl methacrylate, butyl acrylate, polydimethylsiloxane-methyl methacrylate, glycidyl methacrylate, the first part sodium dodecyl sulfate, the first part deionized water, the second part deionized water, the second part sodium dodecyl sulfate, and potassium persulfate is (40-43):(45-48):(8-10):(5-6):(2-2.5):80:(120-13) 0): (0.5-0.6): (0.5-0.6), for example, it could be (40, 40.3, 40.6, 40.9, 41.2, 41.5, 41.8, 42.1, 42.4, 42.7 or 43): (45, 45.3, 45.6, 45.9, 46.2, 46.5, 46.8, 47.1, 47.4, 47.7 or 48): (8.0, 8.2, 8.4, 8.6, 8.8, 9 0, 9.2, 9.4, 9.6, 9.8 or 10.0: (5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 or 6.0): (2.0, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45 or 2.5): 80: (120, 121, 122, 123, 124, 125, 126, 12) 7, 128, 129 or 130: (0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59 or 0.6), but not limited to the listed values; other unlisted values ​​within this range also apply.

[0035] In some alternative embodiments, the reaction time at the first temperature is 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the ammonia solution has a mass fraction of 15 wt.%.

[0037] As a preferred embodiment of the present invention, in S4, the mass ratio of the waterborne cationic epoxy resin, the waterborne hyperbranched polyurethane-acrylate copolymer emulsion, the organosilicon-acrylate copolymer emulsion, and the aluminum dihydrogen phosphate solution is 200:(15-20):(2-3):20. For example, it can be 200:(15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5 or 20):(2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0):20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the waterborne cationic epoxy resin has a solid content of 50%.

[0039] In some optional embodiments, the aluminum dihydrogen phosphate solution has a mass fraction of 50 wt.%.

[0040] In some optional embodiments, the solid content of the low-temperature rapid-curing non-oriented silicon steel coating is 20%.

[0041] Secondly, the present invention provides a low-temperature rapid curing non-oriented silicon steel coating prepared by the preparation method described in the first aspect.

[0042] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention adopts a water-based system, and the formula does not contain any toxic heavy metal elements such as chromium and lead, thus eliminating the serious environmental and human health hazards caused by traditional chromate coatings; it adopts a phosphate low-temperature curing system, which can achieve rapid cross-linking and curing at temperatures far lower than those of traditional chromate coatings, significantly reducing energy consumption and carbon emissions in the silicon-steel production process; this invention achieves an improvement in the overall performance of the coating, and the final coating, while maintaining high insulation, also meets the requirements for core processing and use in terms of adhesion, corrosion resistance, and thermal shock resistance. Detailed Implementation

[0043] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0044] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0045] Example 1

[0046] This embodiment provides a low-temperature rapid-curing non-oriented silicon steel coating and its preparation method. The preparation method specifically includes the following steps:

[0047] S1, after mixing 102g of epoxy resin with 50g of propylene glycol methyl ether evenly, the temperature was adjusted to 82℃, and 45g of diethanolamine was added dropwise under stirring. The time for adding diethanolamine was 2h. After the addition was completed, the temperature was raised to 92℃ and the reaction was carried out for 2.5h. The reaction system was cooled to 62℃ and 85wt.% lactic acid solution was added until the pH of the reaction solution was 6.5. 200g of deionized water was added under stirring. The product was cooled to room temperature and filtered through a 200-mesh filter cloth to obtain waterborne cationic epoxy resin.

[0048] S2, under a nitrogen atmosphere, 68g of trimethylolpropane, 74g of adipic acid, and 1.0g of p-toluenesulfonic acid were mixed and the temperature was adjusted to 185℃ and stirred for 4.5h to obtain hyperbranched polyester alcohol. 32g of hyperbranched polyester alcohol, 52g of polytetrahydrofuran ether glycol, 6.5g of dimethylolpropionic acid, 43g of isophorone diisocyanate, and 0.4g of dibutyltin dilaurate were dispersed in 80g of butanone and the temperature was adjusted to 82℃ and refluxed for 3.5h. The reaction system was cooled to 62℃, 6.0g of hydroxyethyl acrylate was added, and the reaction continued for 1.5h. The reaction system was cooled to 42℃, 5.5g of triethylamine was added, stirred, and 250g of deionized water was added. The mixture was then rotary evaporated and filtered to obtain an aqueous hyperbranched polyurethane-acrylate copolymer emulsion.

[0049] S3, 41g methyl methacrylate, 46g butyl acrylate, 9g polydimethylsiloxane-methacrylate, 5.5g glycidyl methacrylate, 2.2g sodium dodecyl sulfate and 80g deionized water were mixed and homogenized to obtain a pre-emulsion. Under a nitrogen atmosphere, 125g deionized water, 0.55g sodium dodecyl sulfate and 0.55g potassium persulfate were mixed and added to the pre-emulsion. The temperature was adjusted to 82℃ and the reaction was carried out for 2.5h. After the reaction was completed, the mixture was cooled to room temperature, and the pH value was adjusted to 7.5 with 15wt.% ammonia water. The mixture was then filtered through a 200-mesh filter cloth to obtain an organosilicon-acrylate copolymer emulsion.

[0050] S4. 200g of waterborne cationic epoxy resin with a solid content of 50%, 18g of waterborne hyperbranched polyurethane-acrylate copolymer emulsion, 2.5g of organosilicon-acrylate copolymer emulsion, 20g of aluminum dihydrogen phosphate solution with a mass fraction of 50wt.% are mixed with deionized water to obtain a low-temperature rapid curing non-oriented silicon steel coating, wherein the solid content of the low-temperature rapid curing non-oriented silicon steel coating is 20%.

[0051] Example 2

[0052] This embodiment provides a low-temperature rapid-curing non-oriented silicon steel coating and its preparation method. The preparation method specifically includes the following steps:

[0053] S1, after mixing 104g of epoxy resin and 50g of propylene glycol methyl ether evenly, the temperature was adjusted to 84℃, and 50g of diethanolamine was added dropwise under stirring. The time for adding diethanolamine was 2h. After the addition was completed, the temperature was raised to 94℃ and the reaction was carried out for 2.8h. The reaction system was cooled to 64℃ and 85wt.% lactic acid solution was added until the pH of the reaction solution was 6.8. 200g of deionized water was added under stirring. The product was cooled to room temperature and filtered through a 200-mesh filter cloth to obtain waterborne cationic epoxy resin.

[0054] S2, under a nitrogen atmosphere, 69g of trimethylolpropane, 73.5g of adipic acid, and 0.9g of p-toluenesulfonic acid were mixed and the mixture was stirred at 182℃ for 4.2h to obtain hyperbranched polyester alcohol. 34g of hyperbranched polyester alcohol, 54g of polytetrahydrofuran ether glycol, 6.2g of dimethylolpropionic acid, 44g of isophorone diisocyanate, and 0.35g of dibutyltin dilaurate were dispersed in 80g of butanone and refluxed at 84℃ for 3.2h. The reaction system was then cooled to 64℃, and 6.3g of hydroxyethyl acrylate was added to continue the reaction for 1.8h. The reaction system was then cooled to 44℃, and 5.2g of triethylamine was added and stirred, followed by the addition of 250g of deionized water. The mixture was then rotary evaporated and filtered to obtain an aqueous hyperbranched polyurethane-acrylate copolymer emulsion.

[0055] S3, 42.5g methyl methacrylate, 47.5g butyl acrylate, 8.5g polydimethylsiloxane-methacrylate, 5.2g glycidyl methacrylate, 2.4g sodium dodecyl sulfate and 80g deionized water were mixed and homogenized to obtain a pre-emulsion. Under a nitrogen atmosphere, 122g deionized water, 0.52g sodium dodecyl sulfate and 0.58g potassium persulfate were mixed and added to the pre-emulsion. The temperature was adjusted to 84℃ and the reaction was carried out for 2.2h. After the reaction was completed, the mixture was cooled to room temperature, and the pH value was adjusted to 7.2 with 15wt.% ammonia water. The mixture was then filtered through a 200-mesh filter cloth to obtain an organosilicon-acrylate copolymer emulsion.

[0056] S4. 200g of waterborne cationic epoxy resin with a solid content of 50%, 16g of waterborne hyperbranched polyurethane-acrylate copolymer emulsion, 2.8g of organosilicon-acrylate copolymer emulsion, 20g of aluminum dihydrogen phosphate solution with a mass fraction of 50wt.% are mixed with deionized water to obtain a low-temperature rapid curing non-oriented silicon steel coating, wherein the solid content of the low-temperature rapid curing non-oriented silicon steel coating is 20%.

[0057] Example 3

[0058] This embodiment provides a low-temperature rapid-curing non-oriented silicon steel coating and its preparation method. The preparation method specifically includes the following steps:

[0059] S1, 101g of epoxy resin and 50g of propylene glycol methyl ether were mixed evenly, and the temperature was adjusted to 81℃. Under stirring, 42g of diethanolamine was added dropwise over a period of 2 hours. After the addition was complete, the temperature was raised to 91℃ and the reaction was carried out for 2.2 hours. The reaction system was then cooled to 61℃ and 85wt.% lactic acid solution was added until the pH of the reaction solution was 6.2. Under stirring, 200g of deionized water was added. The product was cooled to room temperature and filtered through a 200-mesh filter cloth to obtain an aqueous cationic epoxy resin.

[0060] S2, under a nitrogen atmosphere, 67.5g of trimethylolpropane, 74.5g of adipic acid, and 1.1g of p-toluenesulfonic acid were mixed and the mixture was stirred at 188℃ for 4.8h to obtain hyperbranched polyester alcohol. 31g of hyperbranched polyester alcohol, 51g of polytetrahydrofuran ether glycol, 6.8g of dimethylolpropionic acid, 42.5g of isophorone diisocyanate, and 0.45g of dibutyltin dilaurate were dispersed in 80g of butanone and refluxed at 81℃ for 3.8h. The reaction system was then cooled to 61℃, and 5.9g of hydroxyethyl acrylate was added to continue the reaction for 1.2h. The reaction system was then cooled to 41℃, and 5.8g of triethylamine was added and stirred, followed by the addition of 250g of deionized water. The mixture was then rotary evaporated and filtered to obtain an aqueous hyperbranched polyurethane-acrylate copolymer emulsion.

[0061] S3, 40.5g methyl methacrylate, 45.5g butyl acrylate, 9.5g polydimethylsiloxane-methacrylate, 5.8g glycidyl methacrylate, 2.1g sodium dodecyl sulfate and 80g deionized water were mixed and homogenized to obtain a pre-emulsion. Under a nitrogen atmosphere, 128g deionized water, 0.58g sodium dodecyl sulfate and 0.52g potassium persulfate were mixed and added to the pre-emulsion. The temperature was adjusted to 81℃ and the reaction was carried out for 2.8h. After the reaction was completed, the mixture was cooled to room temperature, and the pH value was adjusted to 7.8 with 15wt.% ammonia water. The mixture was then filtered through a 200-mesh filter cloth to obtain an organosilicon-acrylate copolymer emulsion.

[0062] S4, 200g of waterborne cationic epoxy resin with a solid content of 50%, 19g of waterborne hyperbranched polyurethane-acrylate copolymer emulsion, 2.2g of organosilicon-acrylate copolymer emulsion, 20g of aluminum dihydrogen phosphate solution with a mass fraction of 50wt.% are mixed with deionized water to obtain a low-temperature rapid curing non-oriented silicon steel coating, wherein the solid content of the low-temperature rapid curing non-oriented silicon steel coating is 20%.

[0063] Example 4

[0064] This embodiment provides a low-temperature rapid-curing non-oriented silicon steel coating and its preparation method. The preparation method specifically includes the following steps:

[0065] S1, after mixing 105g of epoxy resin and 50g of propylene glycol methyl ether evenly, the temperature was adjusted to 85℃, and 52.5g of diethanolamine was added dropwise under stirring. The time for adding diethanolamine was 2h. After the addition was completed, the temperature was raised to 95℃ and the reaction was carried out for 3h. The reaction system was cooled to 65℃ and 85wt.% lactic acid solution was added until the pH of the reaction solution was 7. 200g of deionized water was added under stirring. The product was cooled to room temperature and filtered through a 200-mesh filter cloth to obtain waterborne cationic epoxy resin.

[0066] S2, under a nitrogen atmosphere, 70g of trimethylolpropane, 75g of adipic acid and 1.2g of p-toluenesulfonic acid were mixed and the temperature was adjusted to 190℃ and stirred for 5h to obtain hyperbranched polyester alcohol. 35g of hyperbranched polyester alcohol, 55g of polytetrahydrofuran ether glycol, 7g of dimethylolpropionic acid, 45g of isophorone diisocyanate and 0.5g of dibutyltin dilaurate were dispersed in 80g of butanone and the temperature was adjusted to 85℃ and refluxed for 4h. The reaction system was cooled to 65℃, 6.5g of hydroxyethyl acrylate was added and the reaction continued for 2h. The reaction system was cooled to 45℃, 6g of triethylamine was added and stirred, and 250g of deionized water was added. The mixture was then rotary evaporated and filtered to obtain an aqueous hyperbranched polyurethane-acrylate copolymer emulsion.

[0067] S3, 43g methyl methacrylate, 48g butyl acrylate, 10g polydimethylsiloxane-methacrylate, 6g glycidyl methacrylate, 2.5g sodium dodecyl sulfate and 80g deionized water were mixed and homogenized to obtain a pre-emulsion. Under a nitrogen atmosphere, 130g deionized water, 0.6g sodium dodecyl sulfate and 0.6g potassium persulfate were mixed and added to the pre-emulsion. The temperature was adjusted to 85℃ and reacted for 3h. After the reaction was completed, the mixture was cooled to room temperature, and the pH value was adjusted to 8 using 15wt.% ammonia water. The mixture was then filtered through a 200-mesh filter cloth to obtain an organosilicon-acrylate copolymer emulsion.

[0068] S4, 200g of waterborne cationic epoxy resin with a solid content of 50%, 20g of waterborne hyperbranched polyurethane-acrylate copolymer emulsion, 3g of organosilicon-acrylate copolymer emulsion, 20g of aluminum dihydrogen phosphate solution with a mass fraction of 50wt.% are mixed with deionized water to obtain a low-temperature rapid curing non-oriented silicon steel coating, wherein the solid content of the low-temperature rapid curing non-oriented silicon steel coating is 20%.

[0069] Comparative Example 1

[0070] This comparative example provides a low-temperature rapid curing non-oriented silicon steel coating and its preparation method. The difference between this and Example 1 is that water-based hyperbranched polyurethane-acrylate copolymer emulsion is not used in S4, while other process parameters and operating conditions are exactly the same as in Example 1.

[0071] Comparative Example 2

[0072] This comparative example provides a low-temperature rapid curing non-oriented silicon steel coating and its preparation method. The difference between this and Example 1 is that the organosilicon-acrylate copolymer emulsion is not used in S4, while the other process parameters and operating conditions are exactly the same as in Example 1.

[0073] Comparative Example 3

[0074] This comparative example provides a low-temperature rapid curing non-oriented silicon steel coating and its preparation method. The difference between this example and Example 1 is that the mass of aluminum dihydrogen phosphate solution in S4 is 30g, which is 10g more than in Example 1. Other process parameters and operating conditions are exactly the same as in Example 1.

[0075] Curing temperature test method: The prepared coating is applied to an 80mm×200mm 50AG800 sample using a 3μm wire bar applicator. After coating, the sample is dried in a constant temperature drying oven at different temperatures for 20 seconds. The dried sample is then tested using the ethanol wiping method and the water drop method to check whether it has been cured. Ethanol wiping method: Soak degreased cotton in ethanol and then wipe the coating surface back and forth 20 times. Observe the surface condition of the coating. If there is no change, the test is passed. Water drop method: Draw deionized water into a disposable dropper and then drop a drop onto the coating surface. Wipe off the water droplet after 3 minutes. If there is no change on the coating surface, the test is passed. If both test methods are passed, the coating is fully cured.

[0076] The flexibility test method is NB / T42003; the corrosion resistance test method is salt spray chamber treatment at 35℃ and 5% salt water for 8 hours; the fumigation resistance test method is to fill a beaker with water and boil it on an electric furnace, place the coated plate on the beaker for fumigation, record the fumigation status of the plate surface every 10 minutes, and record for a total of three times for half an hour; the insulation resistance test method is in accordance with GB / T2522-2017 "Test Method for Insulation Resistance and Adhesion of Coatings of Electrical Steel Strips (Sheets)", and the prepared coating is tested using the Changsha Tianheng TD8560 electrical steel surface insulation resistance testing system.

[0077] The test results are shown in Table 1.

[0078] Table 1. Test results of low-temperature rapid curing non-oriented silicon steel coatings in Examples 1-4 and Comparative Examples 1-3

[0079]

[0080] As shown in Table 1, compared to Example 1, Comparative Example 1 exhibits decreased flexibility, corrosion resistance, fumigation resistance, and insulation resistance; Comparative Example 2 also shows decreased flexibility, corrosion resistance, fumigation resistance, and insulation resistance; while Comparative Example 3 shows increased curing temperature, decreased flexibility, decreased corrosion resistance, decreased fumigation resistance, and increased insulation resistance. This is because the waterborne hyperbranched polyurethane-acrylate copolymer emulsion plays a crucial role in filling physical voids and increasing crosslinking density in the cured network. In Comparative Example 1, the cured network is relatively loose, leading to a significant decrease in the coating's shielding performance and corrosion resistance. Comparative Example 2, lacking the use of silicone-acrylate copolymer emulsion and the absence of low surface energy polydimethylsiloxane segments, allows corrosive media to more easily wet and remain on the coating surface, and water molecules to more easily penetrate the coating, thus resulting in decreased corrosion resistance, water boiling resistance, fumigation resistance, and insulation resistance. In Comparative Example 3, there was too much aluminum dihydrogen phosphate solution. Excessive inorganic phosphate network would make the coating hard and brittle, with greater internal stress. At the same time, the proportion of resin was relatively reduced, so the curing temperature increased, flexibility decreased, corrosion resistance decreased, fumigation resistance decreased, and insulation resistance increased.

[0081] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a low-temperature, rapid-curing, non-oriented silicon steel coating, characterized in that, The preparation method includes: S1, after mixing epoxy resin with propylene glycol methyl ether, diethanolamine is added dropwise to react. The reaction system is cooled and lactic acid solution is added to adjust the pH. Deionized water is added under stirring to obtain waterborne cationic epoxy resin. S2, Trimethylolpropane, adipic acid and p-toluenesulfonic acid are mixed and reacted to obtain hyperbranched polyester alcohol. Hyperbranched polyester alcohol, polytetrahydrofuran ether diol, dimethylolpropionic acid, isophorone diisocyanate and dibutyltin dilaurate are dispersed in methyl ethyl ketone and reacted. Hydroxyethyl acrylate is added and the reaction continues. Triethylamine is added, stirred and deionized water is added to obtain an aqueous hyperbranched polyurethane-acrylate copolymer emulsion. S3, methyl methacrylate, butyl acrylate, polydimethylsiloxane-methyl methacrylate, glycidyl methacrylate, the first part of sodium dodecyl sulfate and the first part of deionized water are mixed to obtain a pre-emulsion. The second part of deionized water, the second part of sodium dodecyl sulfate and potassium persulfate are mixed and added to the pre-emulsion for reaction. After the reaction is completed, the mixture is cooled to room temperature and the pH value is adjusted to 7-8 using ammonia water to obtain an organosilicon-acrylate copolymer emulsion. S4, waterborne cationic epoxy resin, waterborne hyperbranched polyurethane-acrylate copolymer emulsion, organosilicon-acrylate copolymer emulsion, aluminum dihydrogen phosphate solution and deionized water are mixed to obtain a low-temperature fast-curing non-oriented silicon steel coating. The mass ratio of the aqueous cationic epoxy resin, the aqueous hyperbranched polyurethane-acrylate copolymer emulsion, the organosilicon-acrylate copolymer emulsion, and the aluminum dihydrogen phosphate solution is 200:(15-20):(2-3):

20.

2. The method for preparing a low-temperature rapid-curing non-oriented silicon steel coating according to claim 1, characterized in that, In S1: The mass ratio of epoxy resin, propylene glycol methyl ether, diethanolamine and deionized water is (100-105):50:(40-52.5):

200.

3. The method for preparing a low-temperature rapid-curing non-oriented silicon steel coating according to claim 1, characterized in that, In S1: The lactic acid solution has a mass fraction of 85 wt.%.

4. The method for preparing a low-temperature rapid-curing non-oriented silicon steel coating according to claim 1, characterized in that, In S2: The mass ratio of trimethylolpropane, adipic acid and p-toluenesulfonic acid is (67-70):(73-75):(0.8-1.2).

5. The method for preparing a low-temperature rapid-curing non-oriented silicon steel coating according to claim 1, characterized in that, In S2: The mass ratio of the hyperbranched polyester alcohol, polytetrahydrofuran ether diol, dimethylolpropionic acid, isophorone diisocyanate, dibutyltin dilaurate, methyl ethyl ketone, hydroxyethyl acrylate, triethylamine and deionized water is (30-35):(50-55):(6-7):(42-45):(0.3-0.5):80:(5.8-6.5):(5-6):

250.

6. The method for preparing a low-temperature rapid-curing non-oriented silicon steel coating according to claim 1, characterized in that, In S3: The mass ratio of the methyl methacrylate, butyl acrylate, polydimethylsiloxane-methyl methacrylate, glycidyl methacrylate, first part sodium dodecyl sulfate, first part deionized water, second part deionized water, second part sodium dodecyl sulfate and potassium persulfate is (40-43):(45-48):(8-10):(5-6):(2-2.5):80:(120-130):(0.5-0.6):(0.5-0.6).

7. The method for preparing a low-temperature rapid-curing non-oriented silicon steel coating according to claim 1, characterized in that, In S3: The ammonia solution has a mass fraction of 15 wt.%.

8. The method for preparing a low-temperature rapid-curing non-oriented silicon steel coating according to claim 1, characterized in that, In S4: The solid content of the waterborne cationic epoxy resin is 50%. The aluminum dihydrogen phosphate solution has a mass fraction of 50 wt.%.

9. A low-temperature rapid-curing non-oriented silicon steel coating obtained by the preparation method according to any one of claims 1-8.

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