An aqueous PI resin and its application in an aqueous insulating paint

Abstract

The present invention relates to an aqueous PI resin and its application in an aqueous insulating paint. The aqueous PI resin is prepared by the following method: By weight, 80 - 130 parts of tung oil anhydride, 100 parts of polyfunctional epoxy resin, 20 - 50 parts of p-aminobenzoic acid and 210 - 270 parts of diethylene glycol tert-butyl ether are mixed and dispersed evenly, then heated to 120 °C while dispersing and maintained for 3 h, and then cooled, filtered and discharged. When the aqueous PI resin of the present invention is applied to an aqueous insulating paint, the film has a fast curing speed and low dielectric loss. At the same time, the coating has good heat resistance, adhesion, acid and alkali resistance, electrical properties, hardness and flexibility, and can meet the requirements of the product performance for both enameled wire paint and silicon steel sheet paint. Moreover, it is environmentally friendly and has low VOC emissions.

Description

Technical Field

[0001] The present invention belongs to the field of waterborne insulating paints, and particularly relates to a waterborne PI resin and its application in waterborne insulating paints. Background Art

[0002] Insulating paint is an important insulating material based on polymer materials that can be cured into an insulating film or an insulating integral under certain conditions. According to the scope of use, insulating paints can be divided into five categories: impregnating paints, enamelled wire paints, covering paints, silicon steel sheet paints, and anti-corona paints.

[0003] Among them, enamelled wire paint is mainly used for coating the insulation of enamelled wire cores. Since the wire will be subjected to the action of heat, chemicals, and various mechanical forces during processes such as winding coils and inserting wires, it is required that the enamelled wire paint has good coating properties (i.e., can be evenly coated), strong film adhesion, a smooth, soft, and tough surface, certain wear resistance and elasticity, good electrical properties, heat resistance, solubility resistance, and no corrosion to the conductor.

[0004] Silicon steel sheet paint is used to coat silicon steel sheets to reduce the eddy current loss of the iron core and enhance the corrosion resistance. After the silicon steel sheet paint is coated, it needs to be dried at high temperature for a short time. Its characteristics are thin coating, strong adhesion, hardness, smoothness, uniform thickness, oil resistance, moisture resistance, and good electrical properties.

[0005] Traditional insulating paints are solvent-based products with a VOC content as high as nearly 70%. Therefore, waterborne insulating paints have been the focus of development in recent years. However, both enamelled wire paints and silicon steel sheet paints have high requirements for the electrical properties, adhesion, high-temperature resistance, etc. of the coating, and there is still room for improvement in existing waterborne insulating paints. For example, in the invention patent application with the application number 202311812016.8, the applicant once proposed a waterborne insulating paint that can meet the requirements in fields such as automotive motor flat wires, capillary tubes of the thermal management system, and radiator electrical appliances, and is particularly suitable for wire materials such as enamelled copper and aluminum tubes / wires and magnet wires. However, its curing speed is average and further improvement is needed. Summary of the Invention

[0006] Aiming at the above problems existing in the prior art, the present invention synthesizes a waterborne PI (polyimide) resin and applies it to enamelled wire paint and silicon steel sheet paint, which can significantly shorten the curing time, reduce the dielectric loss, and at the same time, the coating has good heat resistance, adhesion, acid and alkali resistance, electrical properties, hardness, and flexibility, can meet the performance requirements of both enamelled wire paint and silicon steel sheet paint, and is environmentally friendly with less VOC emissions.

[0007] The present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, an aqueous PI resin is provided, and the aqueous PI resin is prepared by the following method: By weight, 80 - 130 parts of tung oil anhydride, 100 parts of polyfunctional epoxy resin, 20 - 50 parts of p-aminobenzoic acid, and 210 - 270 parts of diethylene glycol tert-butyl ether are mixed and dispersed evenly, then heated to 120°C while dispersing and maintained for 3 h, and then cooled, filtered, and discharged.

[0009] The polyimide aqueous resin is prepared by the prior reaction of tung oil anhydride and polyfunctional epoxy resin under the catalytic action of p-aminobenzoic acid in the solvent diethylene glycol tert-butyl ether, and can be further used for preparing aqueous insulating paint.

[0010] Preferably, the polyfunctional epoxy resin is phenolic epoxy resin, such as 638s, etc.

[0011] The present invention also provides an aqueous insulating paint, including the above-mentioned aqueous PI resin.

[0012] The present invention also provides an aqueous insulating paint for enameled wire, and each 100 parts by weight of the raw materials is composed of the following components: 40 - 60 parts of the above-mentioned aqueous PI resin, 2.5 - 6.5 parts of diethanolamine, 0 - 10 parts of solvent, 0.2 - 2 parts of wetting agent, and the balance of deionized water.

[0013] Preferably, the wetting agent is composed of BYK349 and Degussa 4100, and the weight ratio is 1:1.

[0014] Preferably, the solvent is one or two of diethylene glycol butyl ether and diethylene glycol tert-butyl ether.

[0015] The present invention also provides an aqueous insulating paint for silicon steel sheets, and each 100 parts by weight of the raw materials is composed of the following components: 57 parts of the aqueous PI resin as described in claim 1 or 2, 4 - 10 parts of diethanolamine, 0 - 10 parts of solvent, 0.1 - 1.5 parts of wetting agent, 0.1 - 1.5 parts of defoaming agent, and the balance of deionized water.

[0016] Wherein the silicon steel sheets may be electrical steel coils, silicon steel sheets, etc.

[0017] Preferably, the solvent is one or two of diethylene glycol butyl ether and diethylene glycol tert-butyl ether.

[0018] Preferably, the wetting agent is Degussa 4100.

[0019] Preferably, the defoaming agent is Efka 2524.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention synthesizes an aqueous PI resin and applies it to an aqueous insulating paint, resulting in an insulating paint with a fast curing speed, low dielectric loss, and being safe, environmentally friendly, without the volatilization of pungent odors; having a temperature resistance of ≥310 °C; having good coating adaptability, good adhesion, and good acid and alkali resistance on metal substrates such as copper, aluminum, and steel; having a strong electric breakdown resistance, with the normal breakdown voltage of the coating being ≧3200 V / 10 μm, which is 40% or more higher than that of ordinary coatings; having good coating compactness, no pinholes, and good flexibility, completely overcoming the disadvantages of oil-based PI thick coatings becoming hard and brittle with many pinholes and slow drying; and can be applied to insulating paints for enamelled wires and / or silicon steel sheet coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the dielectric loss test result of the sample in Example 3 of the present invention;

[0023] Figure 2 It is the dielectric loss test result of the sample in Example 4 of the present invention;

[0024] Figure 3 It is the dielectric loss test result of the sample in Example 5 of the present invention;

[0025] Figure 4 It is the schematic diagram of enamelled wire coating in the embodiment of the present invention;

[0026] Figure 5 It is the schematic diagram of the enamelled wire after coating;

[0027] Figure 6 It is one of the schematic diagrams of silicon steel sheets;

[0028] Figure 7 It is another schematic diagram of silicon steel sheets. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings and embodiments. Preferred embodiments of the present invention are given in the embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] Unless otherwise specified, the reagents used in the following examples are commercially available; unless otherwise specified, the methods used in the following examples can be achieved by conventional methods.

[0032] Waterborne PI resin

[0033] Raw material composition of the waterborne PI resin in Examples 1 to 3 in Table 1

[0034] Example 1 Example 2 Example 3 Tung oil anhydride 80 100 130 638S 100 100 100 p-Aminobenzoic acid 34 20 50 Diethylene glycol tert-butyl ether 214 238 270

[0035] Example 1

[0036] According to parts by weight, 80 parts of tung oil anhydride, 100 parts of polyfunctional epoxy resin, 34 parts of p-aminobenzoic acid and 214 parts of diethylene glycol tert-butyl ether are mixed and dispersed evenly, then heated to 120 °C while dispersing and maintained for 3 h, and then cooled, filtered and discharged to obtain a waterborne modified PI resin.

[0037] The obtained sample has a yellow transparent liquid appearance, solid content: 57% (150 °C / 90 min), viscosity: 1100 mPa·s / 33 °C.

[0038] Example 2

[0039] According to parts by weight, 100 parts of tung oil anhydride, 100 parts of polyfunctional epoxy resin, 40 parts of p-aminobenzoic acid and 238 parts of diethylene glycol tert-butyl ether are mixed and dispersed evenly, then heated to 120 °C while dispersing and maintained for 3 h, and then cooled, filtered and discharged to obtain a waterborne modified PI resin.

[0040] The obtained sample has a yellow transparent liquid appearance, solid content: 58% (150 °C / 90 min), viscosity: 1250 mPa·s 33 °C.

[0041] Example 3

[0042] According to parts by weight, 130 parts of tung oil anhydride, 100 parts of polyfunctional epoxy resin, 50 parts of p-aminobenzoic acid and 270 parts of diethylene glycol tert-butyl ether are mixed and dispersed evenly, then heated to 120 °C while dispersing and maintained for 3 h, and then cooled, filtered and discharged to obtain a waterborne modified PI resin.

[0043] The obtained sample has a yellow transparent liquid appearance, solid content: 57% (150 °C / 90 min), viscosity: 1160 mPa·s / 33 °C.

[0044] Waterborne insulating paint for enameled wire

[0045] Formulations of each example and comparative example of the waterborne insulating paint for enameled wire in Table 2

[0046]

[0047] Examples 4 to 6

[0048] By weight, 55 parts of the waterborne modified PI resin prepared in Examples 1 to 3 were neutralized with 5.5 parts of diethanolamine, 0.3 part of BYK349 wetting agent, 0.3 part of Disperbyk 4100 wetting agent, and 38.9 parts of deionized water. After stirring evenly, it was filtered and packaged to obtain the waterborne insulating paint for enameled wire. Table 2 shows the test results of the apparent properties of each sample.

[0049] Comparative Example 1

[0050] The difference from Example 4 is that only the single Disperbyk 4100 wetting agent was used.

[0051] Comparative Example 2

[0052] The difference from Example 4 is that only the single BYK349 wetting agent was used.

[0053] Comparative Example 3

[0054] The difference from Example 4 is that the proportion of the wetting agent is different.

[0055] Comparative Example 4

[0056] The insulating paint in Example 3 of the applicant's prior application 202311812016.8.

[0057] Table 3 Test results of the apparent properties of each sample of the waterborne insulating paint for enameled wire

[0058]

[0059]

[0060] Furthermore, the above samples were subjected to a coating experiment using a 4-head DV60 medium-speed enameled wire machine (reference Figure 1 ). The coating experiment was carried out using the same primer and the same wire. The curing process and main performance indicators are shown in Table 3. It can be seen that compared with the comparative examples, which contain only one wetting agent or the proportion of the wetting agent is not 1:1, and the waterborne insulating paint in the previous application, the dielectric loss of the insulating paint in the examples of this application is significantly reduced, and the curing speed is increased. The curing wire speed is increased from the original maximum of 24 m / min to 40 - 90 m / min. Figure 1-3 They are the test results of the dielectric loss of the samples of Examples 4 - 6 respectively, Figure 4 is a schematic diagram of the enameled wire coating, Figure 5 is a schematic diagram of the coated enameled wire.

[0061] Table 4 Curing process and main performance indicators of each sample of the waterborne insulating paint for enameled wire

[0062]

[0063]

[0064] Water-based insulating paint for silicon steel sheets

[0065] Table 5 Formulations of Examples and Comparative Examples of Water-based Insulating Paint for Silicon Steel Sheets

[0066]

[0067] Examples 7 - 9

[0068] By weight, 57 parts of the water-based modified PI resin prepared in Examples 1 - 3 were neutralized with 5.7 parts of diethanolamine, then 10 parts of diethylene glycol butyl ether, 0.6 part of Disperbyk 4100 wetting agent, 0.5 part of Efka 2524 defoaming agent, and 26.2 parts of deionized water were added. After stirring evenly, it was filtered and packaged to obtain the water-based insulating paint for coating silicon steel sheets.

[0069] Comparative Example 5

[0070] The difference from Example 7 is that it does not contain a defoaming agent.

[0071] Comparative Example 6

[0072] The difference from Example 7 is that it does not contain a wetting agent.

[0073] Comparative Example 7

[0074] The difference from Example 7 is that the proportions of the wetting agent and the defoaming agent are different.

[0075] The test results of the apparent properties of the water-based insulating paints obtained in Examples 7 - 9 and Comparative Examples 5 - 7 are shown in Table 6.

[0076] Table 6 Test Results of the Apparent Properties of Each Water-based Self-adhesive Insulating Paint in Examples 7 - 9

[0077]

[0078] Furthermore, the above samples were coated on the surface of silicon steel sheets by roll coating as Figure 6 shown, and then baked and cured in a chain-type tunnel furnace. At the same time, a comparison was made with the insulating paints of Comparative Examples 4 - 7.

[0079] The specific curing process and main performance indicators are shown in Table 7.

[0080] Table 7 Curing Process and Main Performance Indicators of Water-based Insulating Paint for Silicon Steel Sheets

[0081]

[0082] It can be seen that when only a wetting agent or a defoaming agent is added alone, the film properties are affected. Only when Disperbyk 4100 wetting agent and Efka 2524 defoaming agent are used in combination and the ratio is appropriate can better effects be achieved. Moreover, compared with the waterborne insulating paint in the previous application, the curing ability is significantly improved, and the curing time is reduced from 1 minute and 40 seconds before to 50 seconds now.

[0083] In addition to Figure 6 the silicon steel sheets shown, the insulating paint of the present invention can also be used for silicon steel sheets such as Figure 7 those shown.

[0084] In summary, it can be seen that the solution of the present invention first reacts in the solvent diethylene glycol tert-butyl ether under the catalysis of p-aminobenzoic acid through tung oil anhydride and polyfunctional epoxy resin to prepare a polyimide waterborne resin. Further, by adding appropriate wetting agents, defoaming agents, etc., it can be used to prepare a waterborne insulating paint. The obtained waterborne paint has a fast curing speed, low dielectric loss, and excellent properties in all aspects.

[0085] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0086] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A waterborne PI resin, characterized in that, The aqueous PI resin is prepared by the following method: By weight, 80 - 130 parts of tung oil anhydride, 100 parts of multi-functional epoxy resin, 20 - 50 parts of p-aminobenzoic acid and 210 - 270 parts of diethylene glycol tert-butyl ether are mixed and dispersed evenly, then heated to 120 °C while dispersing and maintained for 3 h, and then cooled, filtered and discharged. The multi-functional epoxy resin is phenolic epoxy resin.

2. An aqueous insulating paint, comprising the aqueous PI resin as described in Claim 1.

3. An aqueous insulating paint for enameled wire, characterized in that, Per 100 parts by weight of the raw materials consists of the following components: 40 - 60 parts of the aqueous PI resin as described in Claim 1, 2.5 - 6.5 parts of diethanolamine, 0 - 10 parts of solvent, 0.2 - 2 parts of wetting agent, and the balance deionized water.

4. The water-based insulating paint for enameled wire according to claim 3, characterized in that, The wetting agent consists of BYK349 and Degussa 4100, with a weight ratio of 1:

1.

5. The aqueous insulating paint for enameled wire according to claim 3, characterized in that, The solvent is one or both of diethylene glycol butyl ether and diethylene glycol tert-butyl ether.

6. An aqueous insulating paint for silicon steel sheets, characterized in that, Per 100 parts by weight of the raw materials consists of: 57 parts of the aqueous PI resin as described in Claim 1, 4 - 10 parts of diethanolamine, 0 - 10 parts of solvent, 0.1 - 1.5 parts of wetting agent, 0.1 - 1.5 parts of defoaming agent, and the balance deionized water.

7. The water-based insulating paint for silicon steel sheets according to claim 6, characterized in that, The solvent is one or both of diethylene glycol butyl ether and diethylene glycol tert-butyl ether.

8. The water-based insulating paint for silicon steel sheets according to claim 6, wherein, The wetting agent is Degussa 4100.

9. The aqueous insulating paint for silicon steel sheets according to claim 6, characterized in that, The defoaming agent is Efka 2524.

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