Water-based single-component heat-cured self-bonding coating for thin-gauge silicon steel sheets and preparation method

Abstract

This invention relates to an aqueous one-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets and its preparation method. The aqueous one-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets comprises the following components: modified epoxy resin, modified silica, additives, and deionized water. The modified epoxy resin is obtained by first blending polytetrahydrofuran glycol, sorbitol, and isophorone diisocyanate, and then reacting them with the epoxy resin. The modified silica is obtained by blending silica containing double bonds, isocyanate-modified acrylate monomers containing epoxy groups, and trimethylolpropane triacrylate. The modified epoxy resin of this invention introduces polyurethane and a network structure, which can improve insulation performance, compatibility, and heat resistance. The modified silica of this invention introduces urethane groups, epoxy groups, a network structure, and benzene rings, which can improve compatibility, adhesion, and heat resistance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets and its preparation method. Background Technology

[0002] Silicon steel sheets are soft magnetic materials made of iron-silicon alloys containing 0.5-4.5% silicon. Their core characteristics are low iron loss and high magnetic induction, making them a key material for manufacturing the cores of transformers, motors, and electrical appliances, directly determining the efficiency, size, and energy consumption of electromagnetic equipment. Coatings for silicon steel sheets are functional coatings applied to the surface of the sheets. Their core functions are insulation, rust prevention, and adhesion assistance, directly determining the electromagnetic performance, processability, and reliability of the core. They are a crucial supporting material in the silicon steel sheet industry chain.

[0003] The main components of coatings for silicon steel sheets include film-forming resins, fillers, additives, and solvents. Among them, film-forming resins include epoxy resins, acrylates, polyurethanes, and silicone-modified resins; fillers include silica, talc, calcium carbonate, alumina, and aluminum nitride; additives include curing agents, wetting and dispersing agents, leveling agents, and defoamers; and solvents include deionized water, alcohol solvents, ester solvents, and aromatic solvents.

[0004] Currently, although there are many types of coatings for common silicon steel sheets on the market, some problems still exist, such as: insufficient adhesion, which leads to easy peeling and flaking of the coating, direct exposure of the silicon steel sheet, rust and corrosion, and shortening the life of the iron core; insufficient insulation, which leads to leakage and short circuits between sheets, a sharp increase in eddy current losses, severe heating of the iron core, a significant decrease in the efficiency of motors and transformers, and easy breakdown under high voltage, causing equipment failure, tripping, or even burnout; and insufficient heat resistance, which leads to softening and decomposition of the coating at high temperatures, causing a rapid decline in insulation and adhesion, leading to a vicious cycle.

[0005] In conclusion, it is necessary to develop a new technical solution to address the shortcomings of existing technologies. Summary of the Invention

[0006] This invention provides an aqueous one-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets and its preparation method. The aqueous one-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets comprises the following components: modified epoxy resin, modified silica, additives, and deionized water. The modified epoxy resin and modified silica of this invention incorporate multiple functional groups, improving insulation, heat resistance, and other properties, and have promising application prospects.

[0007] One object of the present invention is to provide a water-based one-component thermosetting self-adhesive coating for thin silicon steel sheets, wherein the water-based one-component thermosetting self-adhesive coating for thin silicon steel sheets comprises the following components in parts by weight: 50-90 parts of modified epoxy resin 1-8 parts of modified silica 2-40 parts of auxiliary agent 15-60 parts deionized water; The modified epoxy resin is obtained by first blending polytetrahydrofuran diol, sorbitol, and isophorone diisocyanate, and then reacting them with epoxy resin. The modified silica is obtained by first blending silica and KH570 to obtain silica containing double bonds, then blending toluene diisocyanate, 2-hydroxypropyl methacrylate, and epoxy resin to obtain isocyanate-modified acrylate monomers containing epoxy groups, and finally blending the silica containing double bonds, the isocyanate-modified acrylate monomers containing epoxy groups, and trimethylolpropane triacrylate.

[0008] Furthermore, the additive is selected from one or more of the following: diluent, emulsifier, curing agent, wetting agent, defoamer, leveling agent, and preservative.

[0009] Furthermore, the particle size of the silicon dioxide is 10-30 nm.

[0010] Another object of the present invention is to provide a method for preparing the water-based one-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet, the method comprising the following steps: S1. Under an inert atmosphere, polytetrahydrofuran diol, sorbitol, isophorone diisocyanate and catalyst are blended, heated and stirred to react, and a prepolymer is obtained. S2. Under an inert atmosphere, the prepolymer, epoxy resin, and catalyst are blended, heated, and stirred to react, thereby obtaining a modified epoxy resin. S3. Silica and KH570 are mixed and heated and stirred to react, yielding silica containing double bonds; S4. Under an inert atmosphere, toluene diisocyanate and 2-hydroxypropyl methacrylate are mixed, heated and stirred to react, and an intermediate product is obtained. S5. Under an inert atmosphere, the intermediate product, epoxy resin, and catalyst are blended and heated and stirred to obtain an isocyanate-modified acrylate monomer containing epoxy groups. S6. Under an inert atmosphere, the silica containing double bonds, the isocyanate-modified acrylate monomer containing epoxy groups, trimethylolpropane triacrylate, and the initiator are blended and heated and stirred to obtain modified silica. S7. The modified epoxy resin, modified silica and the remaining components are mixed and stirred evenly to obtain the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet.

[0011] Further, in step S1, the mass ratio of polytetrahydrofuran diol, sorbitol, and isophorone diisocyanate is (1-5):(0.01-0.1):(0.5-2).

[0012] Further, in step S2, the mass ratio of the prepolymer to the epoxy resin is (0.5-2):(5-15).

[0013] Furthermore, in step S3, the heating temperature is 50-80°C.

[0014] Furthermore, in step S4, the heating temperature is 70-90°C.

[0015] Furthermore, in step S5, the heating temperature is 70-90°C.

[0016] Further, in step S6, the mass ratio of the silicon dioxide containing double bonds, the isocyanate acrylate monomer containing epoxy groups, and the trimethylolpropane triacrylate is (1-3):(0.5-2):(0.5-2).

[0017] The present invention has the following beneficial effects: This invention provides an aqueous one-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets and its preparation method. The aqueous one-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets comprises the following components: modified epoxy resin, modified silica, additives, and deionized water. The modified epoxy resin is obtained by first blending polytetrahydrofuran glycol, sorbitol, and isophorone diisocyanate, and then reacting the remaining isocyanate groups with the hydroxyl groups of the epoxy resin. The modified silica is obtained by first blending silica and KH570 to obtain silica containing double bonds, then reacting toluene diisocyanate with the hydroxyl groups of 2-hydroxypropyl methacrylate and the hydroxyl groups of the epoxy resin to obtain an isocyanate-modified acrylate monomer containing epoxy groups, and finally, blending the silica containing double bonds, the isocyanate-modified acrylate monomer containing epoxy groups, and trimethylolpropane triacrylate to undergo a polymerization reaction.

[0018] The modified epoxy resin of this invention incorporates polyurethane and a network structure. Polyurethane can promote free diffusion of charge, reduce the risk of electric field concentration, thereby improving insulation performance. It can also improve the compatibility of each component and prevent aggregation. The network structure increases the degree of crosslinking and improves properties such as heat resistance and flexibility.

[0019] The modified silica of this invention incorporates urethane groups, epoxy groups, a network structure, and benzene rings. The urethane groups improve compatibility, while the epoxy groups enhance both the compatibility and adhesion of the components. The network structure increases the degree of crosslinking, thereby improving heat resistance and flexibility. The benzene rings further enhance compatibility with epoxy resins containing benzene rings. Furthermore, silica possesses high thermal stability, which also improves heat resistance. Moreover, the modified epoxy resin and modified silica incorporate various active groups and a network structure, thereby achieving a synergistic effect and jointly improving flexibility, adhesion, and other properties. Detailed Implementation

[0020] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0021] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0022] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0023] The embodiments of the present invention use the following raw materials: Polytetrahydrofuran diol: molecular weight 2000.

[0024] Catalyst T12: Dibutyltin dilaurate, purchased from Nantong Haotai Chemical Products Co., Ltd.

[0025] Epoxy resin: Bisphenol A epoxy resin E51, purchased from Sinopec Baling Petrochemical Co., Ltd.

[0026] Silica: Particle size 10-30nm.

[0027] Diluent: 1,4-Butanediol diglycidyl ether.

[0028] Emulsifier: LSC-206-1, purchased from Dalian Liansheng New Materials Group Co., Ltd.

[0029] Curing agent: GY HT110, purchased from Guangdong Guyan Electronic Materials Co., Ltd.

[0030] Wetting agent: propylene glycol.

[0031] Defoamer: BYK-028, purchased from BYK Chemical.

[0032] Leveling agent: BYK-333, purchased from BYK Chemicals.

[0033] Preservative: KATHON LXE, purchased from Jining Fangyu Chemical Co., Ltd.

[0034] Example 1 A water-based, one-component, thermosetting self-adhesive coating for thin-gauge silicon steel sheets, comprising the following components in parts by weight: 90 parts modified epoxy resin 8 parts of modified silica 9 parts diluent 9 parts emulsifier 4 parts of curing agent 2 parts wetting agent 0.2 parts defoamer 0.2 parts leveling agent 0.2 parts preservative 30 parts deionized water; The preparation method of the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet includes the following steps: S1. Under a nitrogen atmosphere, using anhydrous tetrahydrofuran as a solvent, polytetrahydrofuran diol, isophorone diisocyanate, and catalyst T12 were blended in a mass ratio of 3:1:0.004, heated to 70°C and stirred for 3 hours. Then, sorbitol (the mass ratio of isophorone diisocyanate to sorbitol was 1:0.1) was added, and the mixture was stirred at 70°C for 3 hours. The solvent was removed, and the mixture was dried to obtain the prepolymer. S2. Under a nitrogen atmosphere, the prepolymer, epoxy resin, and catalyst T12 are blended in a mass ratio of 1:6:0.01, heated to 80°C and stirred for 4 hours to obtain modified epoxy resin. S3. Using ethanol and water in a volume ratio of 1:1 as solvents, silica and KH570 were mixed in a mass ratio of 1:1.5, heated to 50°C and stirred for 24 hours, filtered, washed and dried to obtain silica containing double bonds. S4. Under a nitrogen atmosphere, toluene diisocyanate and 2-hydroxypropyl methacrylate were blended at a mass ratio of 1.2:1, heated to 80°C and stirred for 3 hours to obtain an intermediate product. S5. Under a nitrogen atmosphere, the intermediate product, epoxy resin, and catalyst T12 are blended in a mass ratio of 1:5:0.03, heated to 80°C and stirred for 5 hours to obtain an isocyanate-modified acrylate monomer containing epoxy groups. S6. Under a nitrogen atmosphere, using toluene as a solvent, the silica containing double bonds, the isocyanate acrylate monomer containing epoxy groups, trimethylolpropane triacrylate, and initiator BPO are blended in a mass ratio of 2:1:0.5:0.05, heated to 100°C and stirred for 2 hours, the solvent is removed and dried to obtain modified silica. S7. According to the above-mentioned mass proportions, the modified epoxy resin, modified silica and the remaining components are mixed and stirred evenly to obtain the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet.

[0035] Example 2 A water-based, one-component, thermosetting self-adhesive coating for thin-gauge silicon steel sheets, comprising the following components in parts by weight: 80 parts modified epoxy resin 7 parts modified silica 9 parts diluent 8 parts emulsifier 4 parts of curing agent 2 parts wetting agent 0.2 parts defoamer 0.3 parts leveling agent 0.1 parts preservative 25 parts deionized water; The preparation method of the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet includes the following steps: S1. Under a nitrogen atmosphere, using anhydrous tetrahydrofuran as a solvent, polytetrahydrofuran diol, isophorone diisocyanate, and catalyst T12 were blended in a mass ratio of 3:1:0.004, heated to 70°C and stirred for 3 hours. Then, sorbitol (the mass ratio of isophorone diisocyanate to sorbitol was 1:0.1) was added, and the mixture was stirred at 70°C for 3 hours. The solvent was removed, and the mixture was dried to obtain the prepolymer. S2. Under a nitrogen atmosphere, the prepolymer, epoxy resin, and catalyst T12 are blended in a mass ratio of 1:6:0.01, heated to 80°C and stirred for 4 hours to obtain modified epoxy resin. S3. Using ethanol and water in a volume ratio of 1:1 as solvents, silica and KH570 were mixed in a mass ratio of 1:1.5, heated to 55°C and stirred for 24 hours, filtered, washed and dried to obtain silica containing double bonds. S4. Under a nitrogen atmosphere, toluene diisocyanate and 2-hydroxypropyl methacrylate were blended at a mass ratio of 1.2:1, heated to 80°C and stirred for 3 hours to obtain an intermediate product. S5. Under a nitrogen atmosphere, the intermediate product, epoxy resin, and catalyst T12 are blended in a mass ratio of 1:5:0.03, heated to 80°C and stirred for 5 hours to obtain an isocyanate-modified acrylate monomer containing epoxy groups. S6. Under a nitrogen atmosphere, using toluene as a solvent, the silica containing double bonds, the isocyanate acrylate monomer containing epoxy groups, trimethylolpropane triacrylate, and initiator BPO are blended in a mass ratio of 2:1:0.5:0.05, heated to 100°C and stirred for 2 hours, the solvent is removed and dried to obtain modified silica. S7. According to the above-mentioned mass proportions, the modified epoxy resin, modified silica and the remaining components are mixed and stirred evenly to obtain the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet.

[0036] Example 3 A water-based, one-component, thermosetting self-adhesive coating for thin-gauge silicon steel sheets, comprising the following components in parts by weight: 70 parts modified epoxy resin 6 parts of modified silica 8 parts diluent 7 parts emulsifier 4 parts of curing agent 2 parts wetting agent 0.1 parts defoamer 0.2 parts leveling agent 0.2 parts preservative 21 parts deionized water; The preparation method of the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet includes the following steps: S1. Under a nitrogen atmosphere, using anhydrous tetrahydrofuran as a solvent, polytetrahydrofuran diol, isophorone diisocyanate, and catalyst T12 were blended in a mass ratio of 3:1:0.004, heated to 70°C and stirred for 3 hours. Then, sorbitol (the mass ratio of isophorone diisocyanate to sorbitol was 1:0.1) was added, and the mixture was stirred at 70°C for 3 hours. The solvent was removed, and the mixture was dried to obtain the prepolymer. S2. Under a nitrogen atmosphere, the prepolymer, epoxy resin, and catalyst T12 are blended in a mass ratio of 1:6:0.01, heated to 80°C and stirred for 4 hours to obtain modified epoxy resin. S3. Using ethanol and water in a volume ratio of 1:1 as solvents, silica and KH570 were mixed in a mass ratio of 1:1.5, heated to 50°C and stirred for 24 hours, filtered, washed and dried to obtain silica containing double bonds. S4. Under a nitrogen atmosphere, toluene diisocyanate and 2-hydroxypropyl methacrylate were blended at a mass ratio of 1.2:1, heated to 85°C and stirred for 3 hours to obtain an intermediate product. S5. Under a nitrogen atmosphere, the intermediate product, epoxy resin, and catalyst T12 are blended in a mass ratio of 1:5:0.03, heated to 80°C and stirred for 5 hours to obtain an isocyanate-modified acrylate monomer containing epoxy groups. S6. Under a nitrogen atmosphere, using toluene as a solvent, the silica containing double bonds, the isocyanate acrylate monomer containing epoxy groups, trimethylolpropane triacrylate, and initiator BPO are blended in a mass ratio of 2:1:0.5:0.05, heated to 100°C and stirred for 2 hours, the solvent is removed and dried to obtain modified silica. S7. According to the above-mentioned mass proportions, the modified epoxy resin, modified silica and the remaining components are mixed and stirred evenly to obtain the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet.

[0037] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that sorbitol in S1 is replaced with polytetrahydrofurandiol, while the remaining components and preparation methods are the same as in Example 1.

[0038] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that S3 is modified as follows: Using ethanol and water in a volume ratio of 1:1 as solvents, silica and KH560 were mixed in a mass ratio of 1:1.5, heated to 50°C and stirred for 24 hours, filtered, washed and dried to obtain modified silica; S4-S6 were removed, and the remaining components and preparation methods were the same as in Example 1.

[0039] Test case The product samples prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests.

[0040] Test method: The sample curing steps for coating products include: grinding, cleaning, and drying the substrate surface, applying the sample, and heat curing at 120°C for 30 minutes to obtain the coating.

[0041] Hardness: The coating hardness was determined by pencil method according to GB / T 6739-2022.

[0042] Adhesion: Tested in accordance with GB / T 2522-2007, where adhesion is graded from best to worst as A, B, C, and D.

[0043] Water resistance: Tested according to GB / T 1733-1993.

[0044] Flexibility: Tested in accordance with GB / T 1731-2020.

[0045] Corrosion resistance: The corrosion resistance of the coating is evaluated by scratch test. Take the prepared coating and scratch the surface of the coating. The scratches on the coating surface are of the same size. Then place the coating in salt spray test chamber. After 7 days of salt spray test, the surface of the coating is tested. The test standard refers to GB / T 10125-2021.

[0046] Heat resistance: The heat resistance level is tested according to GB / T11021-2007.

[0047] The test results are shown in Table 1.

[0048] Table 1 Test Results As can be seen from Table 1, the results of Examples 1-3 are better than those of Comparative Examples 1-2. This is because the modified epoxy resin of Comparative Example 1 did not introduce a network structure, which reduced the degree of crosslinking and thus reduced the performance. In contrast, the modified silica of Comparative Example 2 did not introduce urethane groups, a network structure, or benzene rings, which reduced the compatibility of the components and the degree of crosslinking, resulting in a decrease in performance.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A water-based, single-component, thermosetting self-adhesive coating for thin-gauge silicon steel sheets, characterized in that, The water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet comprises the following components in parts by weight: 50-90 parts of modified epoxy resin 1-8 parts of modified silica 2-40 parts of auxiliary agent 15-60 parts deionized water; The modified epoxy resin is obtained by first blending polytetrahydrofuran diol, sorbitol, and isophorone diisocyanate, and then reacting them with epoxy resin. The modified silica is obtained by first blending silica and KH570 to obtain silica containing double bonds, then blending toluene diisocyanate, 2-hydroxypropyl methacrylate, and epoxy resin to obtain isocyanate-modified acrylate monomers containing epoxy groups, and finally blending the silica containing double bonds, the isocyanate-modified acrylate monomers containing epoxy groups, and trimethylolpropane triacrylate.

2. The water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 1, characterized in that, The additives are selected from one or more of the following: diluents, emulsifiers, curing agents, wetting agents, defoamers, leveling agents, and preservatives.

3. The water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 1, characterized in that, The silicon dioxide has a particle size of 10-30 nm.

4. A method for preparing the water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to any one of claims 1-3, characterized in that, The preparation method of the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet includes the following steps: S1. Under an inert atmosphere, polytetrahydrofuran diol, sorbitol, isophorone diisocyanate and catalyst are blended, heated and stirred to react, and a prepolymer is obtained. S2. Under an inert atmosphere, the prepolymer, epoxy resin, and catalyst are blended, heated, and stirred to react, thereby obtaining a modified epoxy resin. S3. Silica and KH570 are mixed and heated and stirred to react, yielding silica containing double bonds; S4. Under an inert atmosphere, toluene diisocyanate and 2-hydroxypropyl methacrylate are mixed, heated and stirred to react, and an intermediate product is obtained. S5. Under an inert atmosphere, the intermediate product, epoxy resin, and catalyst are blended and heated and stirred to obtain an isocyanate-modified acrylate monomer containing epoxy groups. S6. Under an inert atmosphere, the silica containing double bonds, the isocyanate-modified acrylate monomer containing epoxy groups, trimethylolpropane triacrylate, and the initiator are blended and heated and stirred to obtain modified silica. S7. The modified epoxy resin, modified silica and the remaining components are mixed and stirred evenly to obtain the water-based single-component thermosetting self-adhesive coating for the thin-gauge silicon steel sheet.

5. The method for preparing the water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 4, characterized in that, In step S1, the mass ratio of polytetrahydrofuran diol, sorbitol, and isophorone diisocyanate is (1-5):(0.01-0.1):(0.5-2).

6. The method for preparing the water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 4, characterized in that, In step S2, the mass ratio of the prepolymer to the epoxy resin is (0.5-2):(5-15).

7. The method for preparing the water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 4, characterized in that, In step S3, the heating temperature is 50-80℃.

8. The method for preparing the water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 4, characterized in that, In step S4, the heating temperature is 70-90℃.

9. The method for preparing the water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 4, characterized in that, In step S5, the heating temperature is 70-90℃.

10. The method for preparing the water-based single-component thermosetting self-adhesive coating for thin-gauge silicon steel sheets according to claim 4, characterized in that, In step S6, the mass ratio of the double-bonded silica, the epoxy-containing isocyanate acrylate monomer, and the trimethylolpropane triacrylate is (1-3):(0.5-2):(0.5-2).

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