Coating liquid for improving compatibility of silicon steel and insulating paint as well as preparation method and application of coating liquid

Abstract

The invention discloses a coating liquid for improving compatibility of silicon steel and insulating paint as well as a preparation method and application of the coating liquid, and belongs to the technical field of silicon steel sheet insulating coatings. The coating comprises a stabilizer solution and an insulating solution, the insulating liquid comprises the following raw materials: 1-10% of zinc chromate, 1-10% of magnesium chromate, 1-10% of calcium chromate, 1-5% of glycerol, 1-7% of boric acid, 1-8% of an acrylic emulsion and the balance of water; the stabilizer solution is prepared from the following raw materials in parts by mass: 0.25 to 0.5 part of trisodium citrate, 0.25 to 0.5 part of EDTA (Ethylene Diamine Tetraacetic Acid) disodium and 5.0 to 10.0 parts of water. According to the insulating liquid disclosed by the invention, the ternary chromate is used as an inorganic framework, the acrylic emulsion is used as an organic bridging phase, and the stabilizer is supplemented to form a two-component system, so that the interfacial compatibility between the silicon steel surface and the water-soluble insulating paint is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of insulating coating technology for silicon steel sheets, specifically improving the compatibility of silicon steel with insulating varnish coating liquid, its preparation method and application. Background Technology

[0002] Cold-rolled non-oriented silicon steel sheets require an insulating coating on their surface. This coating must not only have good insulation properties but also good punching performance, adhesion, and corrosion resistance. Currently, the mainstream thin coating for silicon steel in China is a semi-organic chromium-containing thin coating.

[0003] Silicon steel sheet insulating varnish, as a key protective material for the surface of iron core laminations, is divided into organosilicon silicon steel sheet varnish and water-soluble silicon steel sheet varnish according to product requirements. Among them, water-soluble silicon steel sheet varnish has broad application prospects due to its advantages of low baking temperature, short curing time, and more environmentally friendly use of water as a diluent. In particular, the C6 type water-soluble silicon steel sheet varnish containing fillers has low leakage current and low thermal shrinkage rate of the varnish film in the Franklin burn-off test, which can effectively overcome the creep shrinkage problem in long iron core motors during operation, and is often used as the C-type base coating.

[0004] However, when existing silicon steel is used in combination with water-soluble silicon steel sheet paint, there are obvious compatibility defects. The coating is prone to peeling and flaking, which seriously affects the insulation performance and service life of the motor core. Summary of the Invention

[0005] To overcome the aforementioned technical problems, this invention provides an improved coating liquid for the compatibility of silicon steel and insulating varnish, its preparation method, and its application. The insulating liquid of this invention uses ternary chromate as the inorganic framework and acrylic emulsion as the organic bridging phase, supplemented with a stabilizer to form a two-component system, significantly improving the interfacial compatibility between the silicon steel surface and water-soluble insulating varnish.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] This invention discloses an improved coating liquid for silicon steel and insulating varnish, comprising a stabilizer solution and an insulating liquid; The insulating liquid comprises the following raw materials by mass fraction: 1-10% zinc chromate, 1-10% magnesium chromate, 1-10% calcium chromate, 1-5% glycerol, 1-7% boric acid, 1-8% acrylic emulsion, and the balance being water.

[0008] In some preferred embodiments, the insulating liquid comprises the following raw materials by mass fraction: 3-7% zinc chromate, 2-6% magnesium chromate, 2-5% calcium chromate, 1-3% glycerol, 1-4% boric acid, 2-5% acrylic emulsion, and the balance being water.

[0009] The stabilizer solution comprises the following raw materials in parts by weight: 0.25-0.5 parts of trisodium citrate (CAS No.: 68-04-2), 0.25-0.5 parts of disodium EDTA (CAS No.: 139-33-3), and 5.0-10.0 parts of water.

[0010] The raw materials for preparing the acrylic emulsion include a pre-emulsion; preferably, the raw materials for preparing the acrylic emulsion are a pre-emulsion and an aqueous solution of sodium bicarbonate.

[0011] The preemulsion comprises the following raw materials in parts by weight: 20.0~25.0 parts methyl methacrylate (MMA, CAS No.: 80-62-6), 15.0~20.0 parts ethyl acrylate (EA, CAS No.: 140-88-5), and 3.0~5.0 parts... N 1-Hydroxyethylacrylamide (HEMAA, CAS No.: 7646-67-5), 3-5 parts allyloxyisomeric alcohol ether sulfate ammonium salt (brand name SR-10), 0.5-1.0 parts potassium persulfate, 0.3-0.6 parts isooctyl 3-mercaptopropionate (IOMP, CAS No.: 30374-01-7) and 15-20 parts water; Among them, IOMP is used as a chain transfer agent, MMA, EA and HEMAA are all monomers, and SR-10 is a surfactant.

[0012] And / or, the sodium bicarbonate aqueous solution comprises 1.0 to 2.0 parts sodium bicarbonate and 25.0 to 30.0 parts water.

[0013] The present invention also provides a method for preparing the aforementioned coating liquid with improved compatibility between silicon steel and insulating varnish, comprising the following steps: S1. Under nitrogen protection, a pre-emulsion is added dropwise to an aqueous sodium bicarbonate solution to obtain an acrylic emulsion; S2. Mix the raw materials for preparing the insulating liquid and the stabilizer solution according to the required ratio to obtain the insulating liquid and the stabilizer solution respectively; S3. Mix the stabilizer solution and the insulating liquid, and filter them to obtain a coating liquid that improves the compatibility between silicon steel and insulating varnish.

[0014] In S1, the preparation process of the pre-emulsion involves first dissolving allyloxyisomeric alcohol ether sulfate ammonium salt and potassium persulfate in water, then adding methyl methacrylate, ethyl acrylate, and... N The pre-emulsion can be obtained by mixing hydroxyethyl acrylamide and isooctyl 3-mercaptopropionate.

[0015] In S1, the sodium bicarbonate aqueous solution needs to be added dropwise at 70~90℃ to form a pre-emulsion; In S1, the dropping rate is 5~10 mL / min. After dropping, the temperature is maintained and stirring is continued for 0.5~2 h. Finally, the temperature is lowered to ≤40℃ and the pH is adjusted to 6~8.

[0016] In S2, the preparation process of the insulating liquid involves dissolving boric acid in water, then adding zinc chromate, magnesium chromate, and calcium chromate, adjusting the pH to 5.5-6.5 using magnesium oxide or magnesium hydroxide, and finally adding acrylic emulsion and glycerol. In S3, the mixing is performed by stirring at 250-350 rpm for 15-20 minutes.

[0017] The aforementioned coating liquid for improving the compatibility between silicon steel and insulating varnish, or the coating liquid for improving the compatibility between silicon steel and insulating varnish prepared by the aforementioned method, is applied between non-oriented silicon steel and water-soluble silicon steel insulating varnish.

[0018] The coating process includes the following steps: Step 1: Pre-treat the non-oriented silicon steel, including degreasing, pickling, washing and drying; Furthermore, the degreasing is performed by treating with a sodium hydroxide solution with a mass concentration of 5-8% at 50-60°C for 10-15 minutes; Furthermore, the pickling is performed using a hydrochloric acid solution with a mass concentration of 8-12% at 40-50°C for 5-8 minutes. Furthermore, the drying process involves hot drying at 100-120°C for 5-8 minutes; Step 2: Apply the improved compatibility coating liquid between silicon steel and insulating varnish to the pretreated non-oriented silicon steel surface using a roller coating method. The coating speed is 15~25m / min, and the wet film thickness is 15~25μm. Place the coated substrate in an oven and preheat it at 80~100℃ for 5~8min, then raise the temperature to 180~220℃ to cure for 10~15min, and cool it to room temperature (20~30℃) to obtain the improved compatibility coating between silicon steel and insulating varnish. Step 3: Apply water-soluble silicon steel insulating varnish to the surface of the improved silicon steel and insulating varnish compatibility coating, with a coating thickness of 20~30μm, and cure at 160~180℃ for 20~30min.

[0019] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs a two-component coating solution consisting of a stabilizer solution and an insulating liquid. The insulating liquid uses a zinc / magnesium / calcium ternary chromate as its inorganic framework, with boric acid promoting the dehydration and polymerization of the chromate to form a dense inorganic film. An acrylic emulsion provides organic elastic segments, and glycerol enhances the film's flexibility. In the stabilizer solution, trisodium citrate and disodium EDTA form a chelating-buffering bifunctional system, both chelating metal ions on the silicon steel surface to prevent coating failure and stabilizing the chromate dispersion.

[0021] 2. The acrylic emulsion of the present invention contains... N - Hydroxyethyl acrylamide (HEAA) is copolymerized with methyl methacrylate (MMA). The hydroxyl groups of HEAA can form hydrogen bonds with the carboxyl / hydroxyl groups of insulating varnish, thus solving the problem of insufficient bridging ability in traditional emulsions. 3. The improved compatibility coating liquid of silicon steel and insulating varnish of the present invention can be directly coated on the surface of non-oriented silicon steel, improving the compatibility problem between silicon steel and water-soluble insulating varnish; furthermore, it solves the problem of core insulation failure in high-end fields such as ultra-high voltage motors and new energy servo motors. Detailed Implementation

[0022] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0024] The "range" disclosed in this invention is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0025] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0026] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0027] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0028] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0029] Unless otherwise specified, the term "or" is inclusive in this invention. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0030] The raw material information used in the following examples is as follows: The grade of the water-soluble silicon steel insulating varnish is HRT1260-1; The allyloxyisomeric alcohol ether sulfate ammonium salt, brand name SR-10, was purchased from Nantong Aochen Chemical Co., Ltd.; including but not limited to the above manufacturers and models.

[0031] Example 1 The improved compatibility coating liquid between silicon steel and insulating varnish in this embodiment consists of a stabilizer solution and an insulating liquid. The raw materials for the stabilizer solution, by mass fraction, are: 0.4 parts trisodium citrate, 0.4 parts disodium EDTA, and 8 parts water.

[0032] The raw materials of the insulating fluid, by mass fraction, are: 5% zinc chromate, 5% magnesium chromate, 5% calcium chromate, 1% glycerol, 2% boric acid, 2% acrylic emulsion and the balance water; Acrylic emulsions consist of a pre-emulsion and an aqueous solution of sodium bicarbonate; The raw materials for the preemulsion are: 20 parts methyl methacrylate (MMA), 15 parts ethyl acrylate (EA), and 3 parts... N 1-Hydroxyethylacrylamide (HEMAA), 3 parts SR-10, 0.8 parts potassium persulfate, 0.3 parts isooctyl 3-mercaptopropionate (IOMP chain transfer agent), and 20 parts water; The raw materials for the sodium bicarbonate aqueous solution are: 2.0 parts sodium bicarbonate and 25 parts water.

[0033] The preparation method of the improved silicon steel and insulating varnish compatibility coating liquid in this embodiment is as follows: S1. Preparation of preemulsion: According to the above ratio, first dissolve SR-10 and potassium persulfate in water, then add three monomers MMA, EA, and HEMAA and IOMP chain transfer agent, stir and mix well to obtain the preemulsion; Under nitrogen protection, the above pre-emulsion was added dropwise to a sodium bicarbonate aqueous solution at a temperature of 80℃ and a stirring speed of 500rpm at a dropping rate of 10mL / min. After the addition, the temperature was maintained and stirring was continued for 1.5h. Finally, the temperature was lowered to ≤40℃ and the pH was adjusted to 7 with ammonia water to obtain an acrylic emulsion. S2. Preparation of insulating liquid and stabilizer solution: Preparation of insulating fluid: Dissolve boric acid in water, add zinc chromate, magnesium chromate and calcium chromate, adjust the pH to 6.0 with magnesium oxide, and finally add acrylic emulsion and glycerol, and stir at 300 rpm for 20 min. Preparation of stabilizer solution: Add trisodium citrate and disodium EDTA to water and mix well; S3. Mix the stabilizer solution and insulating liquid for 15 minutes, then filter through a 150-mesh filter cloth to obtain a coating liquid that improves the compatibility between silicon steel and insulating varnish.

[0034] Example 2 The difference between this embodiment and Embodiment 1 is as follows: The raw materials of the insulating fluid, by mass fraction, are: 3% zinc chromate, 6% magnesium chromate, 2% calcium chromate, 3% glycerol, 1% boric acid, 5% acrylic emulsion and the balance water; The other raw materials, steps and parameters are the same as in Example 1.

[0035] Example 3 The difference between this embodiment and Embodiment 1 is as follows: The raw materials of the insulating liquid, by mass fraction, are: 7% zinc chromate, 2% magnesium chromate, 3% calcium chromate, 2% glycerol, 3% boric acid, 3% acrylic emulsion and the balance water; The other raw materials, steps and parameters are the same as in Example 1.

[0036] Example 4 The difference between this embodiment and Embodiment 1 is as follows: The preemulsion comprises the following raw materials in parts by weight: 25 parts methyl methacrylate, 20 parts ethyl acrylate, 5 parts N-hydroxyethyl acrylamide, 5 parts SR-10, 1.0 parts potassium persulfate, 0.6 parts isooctyl 3-mercaptopropionate, and 15 parts water; The other raw materials, steps and parameters are the same as in Example 1.

[0037] Example 5 The difference between this embodiment and Embodiment 1 is as follows: In S2, magnesium oxide was used to adjust the pH to 6.5; The other raw materials, steps and parameters are the same as in Example 1.

[0038] Example 6 The difference between this embodiment and Embodiment 1 is as follows: In S2, magnesium oxide was used to adjust the pH to 5.5; The other raw materials, steps and parameters are the same as in Example 1.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: This comparative example of the improved compatibility coating liquid between silicon steel and insulating varnish does not contain a stabilizer solution and consists only of insulating liquid; The other raw materials, steps and parameters are the same as in Example 1.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: The raw materials for the insulating liquid are: 5% zinc chloride, 20 parts chromic anhydride, 3% glycerol, 0.1% boric acid, 10% acrylic emulsion, and the balance water; The other raw materials, steps and parameters are the same as in Example 1.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: The raw materials for the preemulsion are: 20 parts methyl methacrylate, 15 parts ethyl acrylate, 3 parts SR-10, 0.8 parts potassium persulfate, 0.3 parts isooctyl 3-mercaptopropionate and 20 parts water; other raw materials, steps and parameters are the same as in Example 1.

[0042] Application examples (1) The non-oriented cold-rolled silicon steel sheet is pretreated by first degreasing in a 7% sodium hydroxide solution at 50°C for 10 min; then pickling in a 10% hydrochloric acid solution at 40°C for 5 min; and finally drying at 100°C for 7 min. (2) The improved silicon steel and insulating varnish compatibility coating liquid prepared in the above examples and comparative examples was coated on the surface of the pretreated non-oriented cold-rolled silicon steel sheet by roller coating. The coating speed was 22 m / min and the wet film thickness of the coating was 25 μm. The coated substrate was placed in an oven, preheated at 100°C for 5 min, then heated to 200°C for 10 min and cooled to room temperature (20~30°C) to obtain the improved silicon steel and insulating varnish compatibility coating. (3) Apply water-soluble silicon steel insulating varnish (HRT1260-1) to the surface of the coating to improve the compatibility between silicon steel and insulating varnish, with a coating thickness of 30μm, and cure at 180℃ for 20min.

[0043] Test Example 1 The improved silicon steel and insulating varnish compatibility coating obtained in step (2) above was subjected to the following tests, and the test results are shown in Table 1; Gloss test shall be performed in accordance with GB9754-2007; coating resistance test shall be performed in accordance with GB / T 1410-2006.

[0044] Table 1

[0045] Test Example 2 The cured HRT1260-1 insulating varnish layer was subjected to the following tests, and the test results are shown in Table 2. The adhesion test was conducted according to GB / T2522-2007 "Test Method for Adhesion of Coatings on Electrical Steel Sheets (Strips)". The cross-cut test was used with a grid spacing of 1 mm. After the grid was drawn, the coating was adhered with tape and then quickly peeled off. The extent of paint peeling was observed. The adhesion level was divided into 0-5, with 0 being the best (no peeling) and 5 being the worst (large-area peeling). The damp heat resistance test shall be conducted in accordance with GB / T1740-2021, using a damp heat chamber. The test conditions are a temperature of 40±2℃ and a relative humidity of 95±2%. The condition of the insulating varnish layer shall be observed every 24 hours. The test shall be stopped when blistering (level ≥2), cracking or peeling area ≥5% occurs, and the test time at this time shall be recorded in hours.

[0046] Table 2

[0047] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this invention. It should be understood that the above descriptions are merely specific embodiments of this invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A coating liquid for improving the compatibility of silicon steel and insulating varnish, characterized in that, Includes stabilizer solution and insulating liquid; The insulating liquid comprises the following raw materials by mass fraction: 1-10% zinc chromate, 1-10% magnesium chromate, 1-10% calcium chromate, 1-5% glycerol, 1-7% boric acid, 1-8% acrylic emulsion, and the balance being water.

2. The coating liquid for improving the compatibility of silicon steel and insulating varnish as described in claim 1, characterized in that, The stabilizer solution comprises the following raw materials in parts by weight: 0.25-0.5 parts trisodium citrate, 0.25-0.5 parts disodium EDTA, and 5.0-10.0 parts water; And / or, the insulating liquid comprises the following raw materials by mass fraction: 3-7% zinc chromate, 2-6% magnesium chromate, 2-5% calcium chromate, 1-3% glycerol, 1-4% boric acid, 2-5% acrylic emulsion, and the balance being water.

3. The coating liquid for improving the compatibility of silicon steel and insulating varnish as described in claim 1, characterized in that, The raw materials for preparing the acrylic emulsion include a pre-emulsion; And / or, the raw materials for preparing the acrylic emulsion are a pre-emulsion and an aqueous solution of sodium bicarbonate.

4. The coating liquid for improving the compatibility between silicon steel and insulating varnish as described in claim 3, characterized in that, The preemulsion comprises the following raw materials in parts by weight: 20.0-25.0 parts methyl methacrylate, 15.0-20.0 parts ethyl acrylate, and 3.0-5.0 parts... N 1-Hydroxyethylacrylamide, 3-5 parts allyloxyisomeric alcohol ether sulfate ammonium salt, 0.5-1.0 parts potassium persulfate, 0.3-0.6 parts isooctyl 3-mercaptopropionate and 15-20 parts water; And / or, the sodium bicarbonate aqueous solution comprises 1.0 to 2.0 parts sodium bicarbonate and 25.0 to 30.0 parts water.

5. The method for preparing the coating liquid for improving the compatibility of silicon steel and insulating varnish as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Under nitrogen protection, a pre-emulsion is added dropwise to an aqueous sodium bicarbonate solution to obtain an acrylic emulsion; S2. Mix the raw materials of the insulating liquid and the stabilizer solution according to the required ratio to obtain the insulating liquid and the stabilizer solution; S3. Mix the stabilizer solution and the insulating liquid, and filter them to obtain a coating liquid that improves the compatibility between silicon steel and insulating varnish.

6. The method for preparing the coating liquid for improving the compatibility between silicon steel and insulating varnish as described in claim 5, characterized in that, The pre-emulsion is prepared by first dissolving allyloxyisomeric alcohol ether sulfate ammonium salt and potassium persulfate in water, and then adding methyl methacrylate, ethyl acrylate, and... N The pre-emulsion can be obtained by mixing hydroxyethyl acrylamide and isooctyl 3-mercaptopropionate.

7. The method for preparing the coating liquid for improving the compatibility between silicon steel and insulating varnish as described in claim 6, characterized in that, In S1, the sodium bicarbonate aqueous solution needs to be added dropwise at 70~90℃ to form a pre-emulsion; And / or, in S1, the dropping rate is 1.0~1.5 ml / min, the temperature is maintained after dropping and stirring is continued for 0.5~2 h, and finally the temperature is lowered to ≤40℃ and the pH is adjusted to 6~8.

8. The method for preparing the coating liquid for improving the compatibility between silicon steel and insulating varnish as described in claim 5, characterized in that, In S2, the preparation process of the insulating liquid involves dissolving boric acid in water, then adding zinc chromate, magnesium chromate, and calcium chromate, adjusting the pH to 5.5-6.5, and finally adding acrylic emulsion and glycerol.

9. The application of the improved silicon steel and insulating varnish compatibility coating liquid as described in any one of claims 1 to 4, or the improved silicon steel and insulating varnish compatibility coating liquid prepared by the preparation method as described in any one of claims 5 to 8, characterized in that, It is coated between non-oriented silicon steel and water-soluble silicon steel insulating varnish.

10. The application of the improved compatibility coating liquid between silicon steel and insulating varnish as described in claim 9, characterized in that, The coating process includes the following steps: Step 1: Pre-treat the non-oriented silicon steel, including degreasing, pickling, washing and drying; Step 2: Apply the improved compatibility coating liquid between silicon steel and insulating varnish to the pretreated non-oriented silicon steel surface using a roller coating method and dry and cure to obtain the improved silicon steel and insulating varnish coating. Step 3: Apply water-soluble silicon steel insulating varnish to the surface of the improved silicon steel and insulating varnish compatibility coating and heat cure it.

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