A high-temperature resistant enameled wire coating and its preparation method

Abstract

This invention relates to the field of enameled wire coating technology, specifically to a high-temperature resistant enameled wire coating and its preparation method. The coating of this invention is prepared by reacting toluene diisocyanate and hexamethylene diisocyanate with polyether glycol. The prepared enameled wire coating has a water contact angle of 97.3° and good hydrophobicity. By adding two isocyanate-containing substances to prepare a polyurethane coating and controlling an appropriate ratio, the tensile strength of the prepared enameled wire coating is improved, reaching 67.2 mPa. The final coating prepared by this invention has a pencil hardness of HB. The optimal catalyst is dibutyltin dibutylsilicate. The addition of polyethyleneimine, which is embedded in the branched portion of the prepolymer long chain, acts as a hard segment molecular chain, thus resulting in high pencil hardness. The coating of this invention incorporates nano-silica, whose residual hydroxyl groups readily interact strongly with the substrate, resulting in strong adhesion and good heat resistance, making it suitable for high-temperature special applications.

Description

Technical Field

[0001] This invention relates to the field of enameled wire coating technology, specifically to a high-temperature resistant enameled wire coating and its preparation method. Background Technology

[0002] With the rapid development of power electronics technology, the requirements for the performance of enameled wire are becoming increasingly stringent. As a key material for electrical equipment such as motors and transformers, the performance of enameled wire directly affects the operational stability and service life of these devices. High-temperature resistant enameled wire coatings are one of the important development directions in enameled wire technology. These coatings can maintain excellent electrical and mechanical properties in high-temperature environments, which is of great significance for improving the safety and reliability of electrical equipment.

[0003] High-temperature resistant enameled wire coatings possess the following performance characteristics: First, they exhibit high thermal stability, enabling prolonged operation at high temperatures without failure. Second, they possess excellent electrical properties, such as low resistance and high insulation strength, meeting the requirements of electrical equipment. Furthermore, they should also possess superior mechanical properties, such as high tensile strength and high abrasion resistance, resisting external environmental erosion and damage to the conductor. With the rapid development of new energy, electric vehicles, aerospace, and other fields, the demand for high-temperature resistant enameled wires is increasing daily. As a key technology for improving the performance of enameled wires, high-temperature resistant enameled wire coatings have broad application prospects.

[0004] In recent years, research on high-temperature resistant enameled wires has mainly focused on the selection of coating materials, optimization of preparation processes, and performance improvement. Currently, the main coating materials used for high-temperature resistant enameled wire coatings include polyimide, silicone, and polyurethane, which possess high thermal stability. However, the types of commercially available high-temperature resistant coatings are limited, and their properties vary, making the selection of the most suitable coating a significant challenge. Furthermore, high-temperature resistant enameled wire coatings need to operate under special environments, thus requiring higher standards for hydrophobicity, adhesion, and high-temperature resistance. However, some coatings sacrifice other properties while improving temperature resistance. For example, the high-temperature resistant coating synthesized by Peng Liu, Xi Tan, Hao Ren, Wei Liu, Linwen Jiang, and Xiaofeng Zhang (Synthesis and characterization of high-temperature resistant yttrium-doped lanthanum monazite coatings on SiC fibers, Surface & Coatings Technology, 2022, 56, 458-467) exhibits strong high-temperature resistance but poor pencil hardness. The reference Shupei Liu, Xinfang Zhang, Chijia Wang, Changqing Yin, Jinsong Rao, Yuxin Zhang, Dusan Losic, Long-term high-temperature resistant biotemplated compositecoating for AZ91D magnesium alloy protection, Journal of Magnesium and Alloys, 2022, 34, 231-241, describes a magnesium alloy template with strong high-temperature resistant coating adhesion but poor hydrophobicity. Therefore, optimizing other properties while ensuring high-temperature resistance remains a challenging technical problem to solve.

[0005] In addition, the tensile strength of the coating is also an important factor to consider. Under harsh environments such as high temperature and high humidity, the coating may experience aging and cracking, which requires solutions through material modification and process optimization. The quality of high-temperature resistant enameled wire coatings varies considerably, necessitating a comprehensive consideration of factors such as materials, processes, performance, and production costs.

[0006] To address this, a high-temperature-resistant enameled wire coating and its preparation method are proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a high-temperature resistant enameled wire coating and its preparation method. A polyurethane coating is prepared by polymerizing toluene diisocyanate and hexamethylene diisocyanate with polyether glycol. The prepared enameled wire coating has a water contact angle of 97.3°, exhibiting good hydrophobicity; the film tensile strength is 67.2 mPa. The tensile strength of the enameled wire coating is improved by adding two isocyanate-containing substances in a controlled ratio. The final enameled wire coating prepared by this invention has a pencil hardness of HB, with dibutyltin dibutylsilicate being the optimal catalyst. The addition of polyethyleneimine further enhances the pencil hardness. The coating obtained by this invention exhibits good adhesion and superior heat resistance; at an external temperature of 500°C, the thermal weight loss rate is 59%, making it suitable for high-temperature applications.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for preparing a high-temperature resistant enameled wire coating, characterized in that: the high-temperature resistant enameled wire coating comprises the following components:

[0010] Toluene diisocyanate 1-30g, hexamethylene diisocyanate 1-20g, polyether glycol 0.5-20g, polyethyleneimine 0.5-5g, catalyst 0.3-1.1g, solid filler 1-5g, defoamer 1-5g;

[0011] The method for preparing the high-temperature resistant enameled wire coating includes the following steps:

[0012] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine are used as raw materials; the raw materials are placed in an oven and dried for 2-10 hours at a temperature of 50-100 degrees Celsius; the dried raw materials are then cooled to room temperature before use.

[0013] Weigh 1-30g of dried toluene diisocyanate and 1-20g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 0.5-20g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 0.5-5g of polyethyleneimine and the catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 65-110°C and stir under nitrogen in an oil bath for 3-12 hours to obtain an intermediate product.

[0014] The intermediate product was mixed with solid filler and defoamer, and stirred with a glass rod at room temperature to obtain a high-temperature resistant enameled wire coating.

[0015] Preferably, the drying time is 3-10 hours; the oven temperature is 50-90 degrees Celsius.

[0016] Preferably, the amount of toluene diisocyanate added is 1-25g.

[0017] Preferably, the molar ratio of toluene diisocyanate to hexamethylene diisocyanate is 10-1:10.

[0018] Preferably, the amount of polyether diol added is 0.5-15g.

[0019] Preferably, the catalyst is one of dibutyltin diceryl silicate and platinum chloride; the amount of catalyst added is 0.3-1.0g.

[0020] Preferably, the intermediate product is prepared by heating to 70-110°C and reacting in an oil bath with stirring for 3-10 hours.

[0021] Preferably, the solid filler is nano-silica with a particle size of 50-500 nm.

[0022] Preferably, the defoamer is one of an organosilicon defoamer or a calcium carbonate defoamer.

[0023] A high-temperature resistant enameled wire coating is characterized in that: the high-temperature resistant enameled wire coating is a polyurethane coating polymerized from toluene diisocyanate, hexamethylene diisocyanate, and polyether glycol; the high-temperature resistant enameled wire coating is prepared by the preparation method described above; the high-temperature resistant enameled wire coating has a water contact angle of 97.3°, exhibiting good hydrophobicity; the high-temperature resistant enameled wire coating has a tensile strength of 67.2 mPa; the high-temperature resistant enameled wire coating has a pencil hardness of HB; the high-temperature resistant enameled wire coating has an adhesion of 49.5 mPa; and the high-temperature resistant enameled wire coating has a thermal weight loss rate of 59%, exhibiting strong heat resistance.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. In this invention, the raw materials are dried in an oven at 60 degrees Celsius for 7 hours. The enameled wire coating prepared under these drying conditions has a water contact angle of 97.3°, exhibiting good hydrophobicity. This is because the isocyanate groups at the active end of toluene diisocyanate and hexamethylene diisocyanate undergo a side reaction with the water in the system. The internal chemical bonds in the byproduct urea easily form intermolecular hydrogen bonds, making the byproducts more likely to aggregate, thus causing the coating surface to become rough and the contact angle to decrease, thereby affecting the hydrophobicity of the coating surface.

[0026] 2. In this invention, the enameled wire coating film is prepared using 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate. These two are added to anhydrous tetrahydrofuran, and 8g of polyether glycol is also added. The resulting enameled wire coating film has a tensile strength of 67.2 mPa. This invention prepares a polyurethane coating by adding two isocyanate-containing substances and controlling the appropriate ratio, thereby improving the tensile strength of the prepared enameled wire coating film. The toluene diisocyanate group has a symmetrical spatial structure and contains a benzene ring in its molecular structure. After the reaction, the long chain of the product contains a benzene ring, increasing the cohesive energy of the long chain. Furthermore, the long chain contains ether bonds, which can rotate, thus improving the resistance to breakage.

[0027] 3. In this invention, 4g of polyethyleneimine and 0.8g of dibutyltin distillate catalyst were added, and the mixture was stirred in an oil bath at 70°C for 8 hours under nitrogen purging. The resulting enameled wire coated pencil had a hardness of HB. The optimal catalyst was dibutyltin distillate. Toluene diisocyanate and hexamethylene diisocyanate provided isocyanate groups, which, after prepolymerization with hydroxyl groups, were added to allow polyethyleneimine fragments to embed into the branched portions of the prepolymer long chain, acting as hard segments of the molecular chain, thus resulting in a high pencil hardness.

[0028] 4. The solid filler used in this invention is 3g of solid nano-silica with a particle size of 300-400nm, resulting in the coating with the best adhesion, at 49.5mPa. Nano-silica easily undergoes physical blending with intermediate products, and its residual hydroxyl groups readily interact strongly with the substrate coating layer, thus exhibiting strong adhesion. The use of 300-400nm nano-silica is optimal for this invention.

[0029] 5. The enameled wire coating prepared by using 2.5g of organosilicon defoamer in this invention exhibits the best heat resistance. When the external temperature reaches 500℃, the thermal weight loss rate is 59%. This is because the cross-linked siloxane structure of the organosilicon defoamer forms a non-polar dense three-dimensional structure with a large bond energy of Si-O bonds. External heat makes it difficult to destroy these chemical bonds, resulting in a coating with strong heat resistance that can be applied in high-temperature special fields. Attached Figure Description

[0030] Figure 1 This is a diagram illustrating the modification mechanism of the present invention;

[0031] Figure 2 Thermogravimetric analysis of the enameled wire coating in Embodiment 40 of the present invention;

[0032] Figure 3 The thermal decomposition temperature is specified in some embodiments of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Please see Figures 1 to 3 This invention provides a high-temperature resistant enameled wire coating and its preparation method, the technical solution of which is as follows:

[0035] Example 1

[0036] The high-temperature resistant enameled wire coating comprises the following components:

[0037] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0038] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0039] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 3 hours at a temperature of 75 degrees Celsius; the dried raw materials were then cooled to room temperature before use.

[0040] Weigh 11g of dried toluene diisocyanate and 6g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 3g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 0.5g of polyethyleneimine and 0.3g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0041] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0042] The reagents used in this embodiment and their manufacturers: toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, dibutyltin disilicate, and calcium carbonate were all purchased from Shanghai Aladdin Reagent Co., Ltd.; nano silica was purchased from Nantong Xinxing Materials Co., Ltd.; and organosilicon defoamer was purchased from Shandong Bolai Co., Ltd.

[0043] Example 2

[0044] The high-temperature resistant enameled wire coating comprises the following components:

[0045] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0046] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0047] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 4 hours at a temperature of 80 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0048] Weigh 11g of dried toluene diisocyanate and 6g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 3g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 0.5g of polyethyleneimine and 0.3g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0049] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0050] Example 3

[0051] The high-temperature resistant enameled wire coating comprises the following components:

[0052] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0053] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0054] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 5 hours at a temperature of 90 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0055] Weigh 11g of dried toluene diisocyanate and 6g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 3g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 0.5g of polyethyleneimine and 0.3g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0056] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0057] The drying time and temperature of the raw materials in Examples 4-8 are shown in Table 1 below. The other steps are the same as in Example 1.

[0058] Table 1. Drying time and temperature for Examples 4-8

[0059]

[0060]

[0061] Comparative Example 1

[0062] Toluene diisocyanate and hexamethylene diisocyanate are not dried; the remaining steps are the same as in Example 1.

[0063] Comparative Example 2

[0064] Toluene diisocyanate and hexamethylene diisocyanate were added to ordinary tetrahydrofuran, which is not an ultra-dry solvent. The remaining steps were the same as in Example 1.

[0065] Example 9

[0066] The water contact angles of the high-temperature resistant enameled wire coatings prepared in Examples 1-8 and Comparative Examples 1-2 were tested to evaluate their hydrophobicity. The contact angles were measured using a contact angle meter (DSA30), and the results are shown in Table 2.

[0067] Table 2 Results of water contact angle test

[0068] Contact angle (°) Example 1 76.3 Example 2 61.2 Example 3 68.5 Example 4 71.3 Example 5 88.5 Example 6 91.2 Example 7 97.3 Example 8 94.1 Comparative Example 1 71.1 Comparative Example 2 74.0

[0069] In Example 7, the raw materials were dried in an oven at 60°C for 7 hours. The enameled wire coating prepared under these drying conditions had a water contact angle of 97.3°, indicating good hydrophobicity. In Comparative Example 1, the raw materials were not dried, resulting in a final enameled wire coating with a contact angle of 71.1°, indicating poor hydrophobicity. In Comparative Example 2, the lack of an ultra-drying solvent resulted in a final enameled wire coating with a contact angle of 74°, also indicating poor hydrophobicity. The high-temperature drying in Examples 2, 3, and 4 affected the spatial structure of the isocyanate. Therefore, the drying methods in other examples resulted in coatings with lower hydrophobicity than those in Example 7. This is because the isocyanate groups at the active end of toluene diisocyanate and hexamethylene diisocyanate react with water in the system to form a byproduct, urea. The urea bonds within the urea readily form intermolecular hydrogen bonds. The presence of hydrogen bonds makes byproducts more likely to aggregate, leading to a rougher coating surface, a smaller contact angle, a larger contact area with water, and easier wetting, thus affecting the hydrophobicity of the coating surface. Therefore, the raw material drying method of Example 7 was subsequently adopted.

[0070] Example 10

[0071] The high-temperature resistant enameled wire coating comprises the following components:

[0072] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0073] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0074] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 7 hours at a temperature of 60 degrees Celsius; the dried raw materials were then cooled to room temperature before use.

[0075] Weigh 18g of dried toluene diisocyanate and 8g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 5g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 0.5g of polyethyleneimine and 0.3g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0076] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0077] Example 11

[0078] The high-temperature resistant enameled wire coating comprises the following components:

[0079] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0080] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0081] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 7 hours at a temperature of 60 degrees Celsius; the dried raw materials were then cooled to room temperature before use.

[0082] Weigh 20g of dried toluene diisocyanate and 13g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 6g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 0.5g of polyethyleneimine and 0.3g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0083] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0084] Example 12

[0085] The high-temperature resistant enameled wire coating comprises the following components:

[0086] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0087] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0088] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 7 hours at a temperature of 60 degrees Celsius; the dried raw materials were then cooled to room temperature before use.

[0089] Weigh 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 8g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 0.5g of polyethyleneimine and 0.3g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0090] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0091] The components and dosages of Examples 13-19 are shown in Table 3 below, and the other steps are the same as those of Example 4.

[0092] Table 3. Partial components and dosages of Examples 13-19

[0093] Toluene diisocyanate Hexamethylene diisocyanate polyether diol Example 13 3.2 12.2 1.0 Example 14 5.1 16.3 1.5 Example 15 7.9 12.2 2.3 Example 16 11.5 8.5 6.8 Example 17 13.2 6.0 9.5 Example 18 16.0 3.4 12.2 Example 19 25.3 1.5 14.1

[0094] Comparative Example 3

[0095] Without adding hexamethylene diisocyanate, the remaining steps are the same as in Example 4.

[0096] Comparative Example 4

[0097] Without adding toluene diisocyanate, the remaining steps are the same as in Example 4.

[0098] Example 20

[0099] The tensile strength of the high-temperature resistant enameled wire coatings prepared in Examples 10-19 and Comparative Examples 3-4 was tested. The test methods were ASTM D638-2010. The test results are shown in Table 4 below.

[0100] Table 4 Tensile strength of materials prepared in Examples 10-19 and Comparative Examples 3-4

[0101] Tensile strength (mPa) Example 10 51.3 Example 11 49.2 Example 12 67.2 Example 13 41.2 Example 14 59.3 Example 15 49.6 Example 16 51.2 Example 17 55.2 Example 18 61.7 Example 19 53.4 Comparative Example 3 28.5 Comparative Example 4 25.3

[0102] In Example 12, the enameled wire coating was prepared using 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate. These two were added to anhydrous tetrahydrofuran, and 8g of polyether glycol was also added. The resulting enameled wire coating had a tensile strength of 67.2 mPa. In Comparative Example 3, without the addition of hexamethylene diisocyanate, the tensile strength of the enameled wire coating was 28.5 mPa. This demonstrates that by adding two isocyanate-containing substances to prepare a polyurethane coating and controlling the appropriate ratio, the tensile strength of the prepared enameled wire coating can be significantly improved. This is because the toluene diisocyanate group has a symmetrical spatial structure, enhancing the molecular forces between adjacent molecules and thus improving the tensile strength of the material. Furthermore, its molecular structure contains a benzene ring. After the isocyanate group undergoes a cross-linking reaction with the hydroxyl groups of the polyether glycol, the long chain of the product contains a benzene ring. The aromatic ring in the long chain is a conjugated region, which simultaneously increases the cohesive energy of the long chain in the coating's chemical structure, making it easier to resist external stress. Furthermore, polyether glycol contains ether bonds, which are rotatable. When external forces are applied to the coating surface, these rotatable ether bonds buffer the force, thus improving its fracture resistance. Therefore, the coating film prepared by this method exhibits good tensile properties.

[0103] Example 21

[0104] The high-temperature resistant enameled wire coating comprises the following components:

[0105] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0106] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0107] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 4 hours at a temperature of 80 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0108] Weigh 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 8g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 1g of polyethyleneimine and 0.4g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0109] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0110] Example 22

[0111] The high-temperature resistant enameled wire coating comprises the following components:

[0112] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0113] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0114] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 4 hours at a temperature of 80 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0115] Weigh 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 8g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 2.5g of polyethyleneimine and 0.7g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 3 hours to obtain an intermediate product.

[0116] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0117] Example 23

[0118] The high-temperature resistant enameled wire coating comprises the following components:

[0119] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0120] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0121] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 4 hours at a temperature of 80 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0122] Weigh 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 8g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 4g of polyethyleneimine and 0.8g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 70°C and stir under nitrogen in an oil bath for 8 hours to obtain an intermediate product.

[0123] The intermediate product is combined with solid filler nano-silica and organosilicon defoamer to obtain a high-temperature resistant enameled wire coating.

[0124] The components and dosages of Examples 24-28 are shown in Table 5 below, and the other steps are the same as those of Example 21.

[0125] Table 5. Components and dosages of Examples 24-28

[0126] Polyethyleneimine dosage (g) Catalyst and its dosage (g) Example 24 0.5 Dibutyltin silicate 0.3g Example 25 0.5 Platinum chloride, 0.3g Example 26 1 Platinum chloride, 0.4g Example 27 2.5 Platinum chloride, 0.7g Example 28 4 No addition

[0127] Comparative Example 5

[0128] Without adding polyethyleneimine and catalyst, the remaining steps are the same as in Example 21.

[0129] Example 29

[0130] The high-temperature resistant enameled wire coatings prepared in Examples 21-28 and Comparative Example 5 were tested for pencil hardness. The test method according to the national standard GB / T 6739-2006 was used.

[0131] Table 6. Pencil hardness of the coatings prepared in Examples 21-29 and Comparative Example 5.

[0132] Pencil hardness Example 21 2B Example 22 B Example 23 HB Example 24 H Example 25 H Example 26 H Example 27 2H Example 28 2H Comparative Example 5 B

[0133] In Example 23 of this invention, 4g of polyethyleneimine and 0.8g of dibutyltin dimerose catalyst were added, and the mixture was stirred in an oil bath under nitrogen at 70°C for 8 hours. The final enameled wire coating pencil hardness was HB. The pencil hardness of the coating gradually increased with increasing polyethyleneimine content. The optimal catalyst was dibutyltin dimerose. This is because toluene diisocyanate and hexamethylene diisocyanate provide isocyanate groups, which, after prepolymerization with hydroxyl groups, allow the added polyethyleneimine to solidify the prepolymer with its free amino groups. Polyethyleneimine fragments are embedded into the branched portions of the prepolymer's long chains, acting as hard molecular chains. For details of the mechanism, see [link to relevant documentation]. Figure 1Therefore, the more polyethyleneimine added, the greater the pencil hardness. However, higher hardness often leads to coating cracking. Therefore, the method in Example 23 can ensure that the hardness is achieved without cracking during normal use.

[0134] Example 30

[0135] The high-temperature resistant enameled wire coating comprises the following components:

[0136] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0137] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0138] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 4 hours at a temperature of 80 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0139] Weigh 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 8g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 4g of polyethyleneimine and 0.8g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 80°C and stir under nitrogen in an oil bath for 5 hours to obtain an intermediate product.

[0140] Add 3g of solid filler nano-silica with a particle size of 100-200nm and an organosilicon defoamer to the intermediate product to obtain a high-temperature resistant enameled wire coating.

[0141] Example 31

[0142] The high-temperature resistant enameled wire coating comprises the following components:

[0143] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0144] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0145] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 4 hours at a temperature of 80 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0146] Weigh 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 8g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 4g of polyethyleneimine and 0.8g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 90°C and stir under nitrogen in an oil bath for 9 hours to obtain an intermediate product.

[0147] Add 3g of solid filler nano-silica with a particle size of 200-300nm and an organosilicon defoamer to the intermediate product to obtain a high-temperature resistant enameled wire coating.

[0148] Example 32

[0149] The high-temperature resistant enameled wire coating comprises the following components:

[0150] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, polyethyleneimine, catalyst, solid filler, defoamer;

[0151] The preparation method of high-temperature resistant enameled wire coating includes the following steps:

[0152] Toluene diisocyanate, hexamethylene diisocyanate, polyether glycol, and polyethyleneimine were used as raw materials; the raw materials were placed in an oven and dried for 4 hours at a temperature of 80 degrees Celsius; the dried raw materials were then cooled to room temperature for later use.

[0153] Weigh 22g of dried toluene diisocyanate and 17g of dried hexamethylene diisocyanate, and add them to anhydrous tetrahydrofuran to form a mixture. Dissolve 8g of polyether glycol in anhydrous ethanol to form a polyether glycol solution. Add the polyether glycol solution to the mixture to form a further mixture. Add 4g of polyethyleneimine and 0.8g of dibutyltin disilicate catalyst to the mixture to obtain a reaction solution. Place the reaction solution in a three-necked flask, pre-stir at room temperature for 10-40 minutes, then heat to 100°C and stir under nitrogen in an oil bath for 7 hours to obtain an intermediate product.

[0154] Add 3g of solid filler nano-silica with a particle size of 300-400nm and 4g of organosilicon defoamer to the intermediate product to obtain a high-temperature resistant enameled wire coating.

[0155] Examples 33-38 and Comparative Example 6 used the following dosages and particle sizes of solid fillers as shown in Table 7.

[0156] Table 7. Solid filler dosage and particle size in Examples 33-38

[0157] Amount added (g) Particle size (nm) Example 33 1g 100-200 Example 34 1g 200-300 Example 35 1g 300-400 Example 36 5g 100-200 Example 37 5g 200-300 Example 38 5g 300-400 Comparative Example 6 0g -

[0158] Example 39

[0159] The high-temperature resistant enameled wire coatings prepared in Examples 30-38 and Comparative Example 6 were used to test the effect of solid filler particle size on coating adhesion. The test methods according to the national standard GB / T 9286-1998 were employed.

[0160] The test results are shown in Table 8 below. In Example 32 of this invention, 3g of solid nano-silica with a particle size of 300-400nm was used as the solid filler, resulting in the coating with the best adhesion, at 49.5mPa. Nano-silica easily undergoes physical blending with intermediate products, and the residual hydroxyl groups of nano-silica readily interact strongly with the coating layer on substrates such as metals or rubber, thus exhibiting strong adhesion. However, if the nano-silica particle size is too large, it can easily create micropores in the coating film; if the particle size is too small, it can easily enter the polymer cavity, leading to poor performance. Therefore, the 300-400nm nano-silica is optimal for this invention.

[0161] Table 8. Adhesion of the coatings obtained in Examples 30-38 and Comparative Example 6

[0162] Adhesion (mPa) Example 30 35.2 Example 31 39.4 Example 32 49.5 Example 33 41.3 Example 34 36.5 Example 35 31.1 Example 36 29.6 Example 37 32.1 Example 38 34.6 Comparative Example 6 26.8

[0163] Example 40

[0164] The defoamer used was 2.5g of silicone defoamer, and the dosage and steps of the remaining components were the same as in Example 30.

[0165] The defoamers and dosages used in Examples 41-46 are shown in Table 9 below.

[0166] Table 9. Defoamers and dosages in Examples 41-46

[0167] Defoamer Dosage (g) Example 41 silicone defoamer 1g Example 42 silicone defoamer 3.5g Example 43 Calcium carbonate 4g Example 44 Calcium carbonate 2.5g Example 45 Calcium carbonate 1g Example 46 Do not use 0g

[0168] Example 47

[0169] The high-temperature resistant enameled wire coatings prepared in Examples 30 and 40-46 above were tested for heat resistance. Thermogravimetric analysis was performed using a DTG-60H simultaneous thermal analyzer at a heating rate of 30°C / min, within a temperature range of 20–500°C. The decomposition temperature was recorded as the temperature at which a 5% mass loss was achieved.

[0170] Example 40: The enameled wire coating prepared using 2.5g of silicone defoamer exhibited the best heat resistance. At an ambient temperature of 500℃, the thermal weight loss rate was 59%. The statistical results of the thermal weight loss rate are shown below. Figure 2This is because the organosilicon defoamer is uniformly dispersed in the coating material, and the cross-linked siloxane structure forms a non-polar, dense three-dimensional structure. The Si-O bonds within this structure have high bond energies, making it difficult for external heat to break these chemical bonds, thus resulting in a coating with strong heat resistance. In contrast, Examples 43-45 used calcium carbonate as the defoamer, resulting in poorer heat resistance. Furthermore, the decomposition temperatures of the enameled wire coatings prepared in Examples 30 and 40-46 were recorded, and the results are shown in […]. Figure 3 The enameled wire coating prepared by the method of the present invention has the highest decomposition temperature of 200°C in Example 40, and the best heat resistance, so it can be applied to special high-temperature fields.

[0171] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the preparation of a high temperature resistant enameled wire paint, The application relates to a high-temperature-resistant enameled wire paint, which comprises the following components: toluene diisocyanate 1-30 parts, hexamethylene diisocyanate 1-20 parts, polyether glycol 0.5-20 parts, polyethylene imine 0.5-5 parts, a catalyst 0.3-1.1 parts, a solid filler 1-5 parts and a defoaming agent 1-5 parts; the solid filler is nano silicon dioxide with a particle size of 50-500 nm; The preparation method of the high-temperature-resistant enameled wire paint comprises the following steps: The toluene diisocyanate, the hexamethylene diisocyanate, the polyether glycol and the polyethylene imine are raw materials; the raw materials are dried in an oven for 2-10 hours; the oven temperature is 50-100 DEG C; the dried raw materials are cooled at room temperature and then stored; The dried toluene diisocyanate 1-30 g and the dried hexamethylene diisocyanate 1-20 g are added into anhydrous tetrahydrofuran to form a mixed solution; 0.5-20 g of polyether glycol is dissolved in anhydrous ethanol to form a polyether glycol solution; the polyether glycol solution is added into the mixed solution to form a mixture; 0.5-5 g of the polyethylene imine and the catalyst are added into the mixture to obtain a reaction solution; the reaction solution is placed in a three-necked flask, pre-stirred at room temperature for 10-40 min, then heated to 65-110 DEG C, and stirred in an oil bath under nitrogen for 3-12 hours to obtain an intermediate product; The intermediate product is added with the solid filler and the defoaming agent, and stirred at room temperature with a glass rod to obtain the high-temperature-resistant enameled wire paint.

2. The method for preparing high temperature resistant enameled wire paint according to claim 1, characterized in that: The drying time is 3-10 h; the oven temperature is 50-90 DEG C.

3. The method for preparing high temperature resistant enameled wire paint according to claim 1, characterized in that: The toluene diisocyanate is added in an amount of 1-25 g.

4. The method for preparing high temperature resistant enameled wire paint according to claim 1, characterized in that: The molar ratio of the toluene diisocyanate to the hexamethylene diisocyanate is 10-1:

10.

5. The method for preparing high temperature resistant enameled wire paint according to claim 1, characterized in that: The polyether glycol is added in an amount of 0.5-15 g.

6. The method for preparing a high-temperature resistant enameled wire enamel according to claim 1, characterized in that: The catalyst is one of dibutyltin dilaurate and platinum chloride; the catalyst is added in an amount of 0.3-1.0 g.

7. The method for preparing a high-temperature resistant enameled wire enamel according to claim 1, characterized in that: The intermediate product is heated to 70-110 DEG C and stirred in an oil bath for 3-10 h.

8. The method for preparing a high-temperature resistant enameled wire enamel according to claim 1, characterized in that: The defoaming agent is one of silicone defoaming agent and calcium carbonate defoaming agent.

9. A high temperature resistant enameled wire coating film, characterized by: The high-temperature-resistant enameled wire paint film is a polyurethane paint film formed by polymerization of toluene diisocyanate and hexamethylene diisocyanate with polyether glycol; the high-temperature-resistant enameled wire paint film is prepared by the preparation method in any one of claims 1-8; the high-temperature-resistant enameled wire paint film has a water contact angle of 97.3 DEG, good hydrophobicity, a tensile strength of 67.2 MPa, a pencil hardness of HB and an adhesion of 49.5 MPa.

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