High-temperature-resistant insulating spray paint as well as preparation and use methods thereof

Abstract

The invention relates to the technical field of insulating materials, in particular to high-temperature-resistant insulating spray paint as well as a preparation method and a use method thereof. The polyimide adhesive comprises the following components: a polyimide solution, an inorganic filler, a thixotropic agent and a diluent, wherein the weight ratio of the polyimide solution to the inorganic filler to the thixotropic agent is 1: (0.1-0.6): (0.001-0.02). The weight ratio of the polyimide solution to the inorganic filler to the thixotropic agent is 1: (0.1-0.6): (0.001-0.02), so that the insulating property of a paint film can be improved; the molar ratio of the dianhydride to the diisocyanate is 1: (0.92-0.98), the rotary viscosity of the polyimide solution at 25 DEG C can be stabilized at 1500-3500 cP, and the situation that the spraying performance is affected due to the fact that the viscosity of the system is too large is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of insulating materials, and in particular to a high temperature resistant insulating spray paint and a preparation and use method thereof. Background Art

[0002] The insulation treatment of metal surface is to improve its insulation performance by coating, wrapping, spraying or depositing an insulating layer. It is widely used in the fields of electronics and electrical engineering, wires and cables, rail transit and lithium batteries. The spraying process is divided into powder electrostatic spraying and solution spraying. The former often uses epoxy resin and acrylic resin powder, which has low cost and high utilization rate, but the thickness is large and it is difficult to withstand high temperature; the latter has low slurry utilization rate, but a large performance window, and high temperature resistant medium can broaden the temperature resistance range. With the urgent demand for high-temperature insulation in industries such as new energy vehicles and rail transit, materials such as polyimide film are often used to solve it. Polyimide tape is suitable for small area insulation, while large area insulation such as electric vehicle water cooling plates and battery casings requires high metal surface flatness and avoidance of bubbles. In the field of lithium batteries, it is also necessary to ensure that the insulation layer is resistant to electrolyte corrosion.

[0003] Chinese invention patent CN102643603B discloses a high temperature resistant insulating liquid coating and its spraying method. It is composed of insulating resin, diluent and filler. The insulating resin and diluent are evenly mixed according to the coating viscosity value of 2-6cP; spraying is carried out according to the steps of surface treatment of the product to be sprayed, preheating of the sprayed product, coating blending, rotary coating, false burning, main burning, and testing. The high temperature resistant insulating liquid coating of the invention has both high temperature resistance and insulation effects. The surface of the product sprayed with the coating can be well protected, but its electrolyte resistance performance has not been explored, which limits its application in the field of lithium batteries. Summary of the invention

[0004] The first aspect of the present invention provides a high temperature resistant insulating spray paint, the components of which include: a polyimide solution, an inorganic filler, a thixotropic agent and a diluent, wherein the weight ratio of the polyimide solution, the inorganic filler and the thixotropic agent is 1: (0.1-0.6): (0.001-0.02).

[0005] Preferably, the weight ratio of the polyimide solution, the inorganic filler and the thixotropic agent is 1:(0.15-0.55):(0.005-0.02).

[0006] The present application study found that the weight ratio of the polyimide solution, inorganic filler and thixotropic agent is 1: (0.1-0.6): (0.001-0.02), which can improve the insulation performance of the paint film. It may be that the chemical composition, crystal structure, and particle morphology of the inorganic filler in a specific ratio interact with the system to improve the density of the coating, thereby reducing the pores and defects in the coating and improving the insulation performance of the coating. The addition of a specific thixotropic agent achieves a good balance between the density and insulation performance of the coating by affecting the fluidity and deformability of the coating. At the same time, the compatibility of the polyimide solution in the inorganic filler and the thixotropic agent is improved, and the interlayer interface defects in the coating are avoided, thereby improving the insulation performance.

[0007] The rotational viscosity of the polyimide solution at 25° C. is 1500-3500 cP.

[0008] Preferably, the rotational viscosity of the polyimide solution at 25° C. is 1700-3200 cP.

[0009] The molar ratio of the dibasic anhydride to the diisocyanate is 1:(0.92-0.98).

[0010] Preferably, the molar ratio of the dianhydride to the diisocyanate is 1:(0.94-0.98).

[0011] The dibasic anhydride includes at least one of metaphthalic anhydride (TMA), pyrophthalic anhydride (PMDA), ketone anhydride (BTDA), diphenyl ether dianhydride (ODPA), and biphenyl dianhydride (BPDA).

[0012] The diisocyanate includes at least one of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI, diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI).

[0013] Preferably, the raw materials for preparing the polyimide solution further include a solvent and a catalyst, and the amount of the solvent added to the polyimide solution is 60-80wt%.

[0014] The solvent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, and butyrolactone.

[0015] The catalyst includes at least one of triethylamine, triethylenediamine, ethyl tin octoate, dibutyltin dilaurate, iron octoate, cobalt octoate, tetraisobutyl titanate, potassium fluoride and potassium chloride.

[0016] The preparation method of the polyimide solution comprises the following steps: mixing all components and reacting them at 80° C. to 120° C. for 6 to 12 hours.

[0017] Preferably, the particle size of the inorganic filler is 2-10 microns.

[0018] Preferably, the thixotropic agent includes at least one of polyamide wax, fumed silica, and polyvinyl alcohol.

[0019] Preferably, the diluent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, propylene carbonate, cyclopentane, butyrolactone, toluene, xylene and cyclohexanone.

[0020] The inorganic filler unit includes at least one of boron nitride, boron nitride, aluminum oxide, titanium dioxide, kaolin, boehmite, magnesium oxide and silicon nitride.

[0021] The second aspect of the present invention provides a method for preparing a high temperature resistant insulating spray paint, comprising the following steps: uniformly mixing all components and homogenizing; the homogenization pressure is 1-50MPa, and the homogenization flow rate is 5-50L / h.

[0022] Preferably, the homogenization pressure is 1-5 MPa, and the homogenization flow rate is 5-50 L / h.

[0023] The rotational viscosity of the high temperature resistant insulating spray paint at 25° C. is 500-1250 cP.

[0024] Preferably, the rotational viscosity of the high temperature resistant insulating spray paint at 25° C. is 650-1250 cP.

[0025] The third aspect of the present invention provides a method for using a high temperature resistant insulating spray paint, comprising the following steps: first pre-treating the metal substrate; then spraying and drying; and then repeating the spraying and drying.

[0026] Preferably, the metal substrate includes one of an aluminum substrate, a copper substrate and an iron substrate.

[0027] Preferably, the pre-treatment includes grinding, roughening, washing and drying.

[0028] Preferably, the grinding is performed using a grinding wheel with a mesh size of 300 to 1000.

[0029] Preferably, the spraying and drying are repeated 2-5 times.

[0030] The caliber of the spray gun used for the spraying is 0.8-2.5 mm, and the pressure of the spraying is 0.3-1 MPa.

[0031] Preferably, the caliber of the spray gun used for the spraying is 1.5-2.0 mm, and the spraying pressure is 0.4-0.8 MPa.

[0032] Preferably, the drying is carried out by hot air tunnel heating drying, with an air volume of 30 to 200 m 3 / h, the tunnel length is 20-30m, the drying line speed is 0.5-2m / min, and the tunnel temperature is 60-250℃.

[0033] Beneficial Effects

[0034] 1. The weight ratio of polyimide solution, inorganic filler and thixotropic agent is 1:(0.1-0.6):(0.001-0.02), which can improve the insulation performance of the paint film.

[0035] 2. The molar ratio of dianhydride to diisocyanate is 1:(0.92-0.98), which can stabilize the rotational viscosity of the polyimide solution at 1500-3500 cP at 25°C, avoiding excessive viscosity of the system affecting the spraying performance.

[0036] 3. The spray paint of this application performs pretreatment of the metal substrate before spraying, and at the same time limits the caliber of the spray gun, the working pressure adjustment of the spray gun, the multiple operations of the insulation layer and the drying process. This can effectively improve the atomization effect of the spray paint and the quality of the paint film, thereby improving the pressure resistance and insulation performance of the paint film.

[0037] 4. The particle size of the inorganic filler is 2-10 microns, which can improve the paint film's resistance to electrolytes, acids and alkalis.

[0038] 5. The spray paint prepared in the present application has good adhesion to the metal substrate and effectively improves the friction resistance. DETAILED DESCRIPTION

[0039] Example 1

[0040] A high temperature resistant insulating spray paint comprises the following components: a polyimide solution, an inorganic filler (boron nitride), a thixotropic agent (polyamide wax) and a diluent (N,N-dimethylformamide), wherein the weight ratio of the polyimide solution, the inorganic filler and the thixotropic agent is 1:0.15:0.005.

[0041] The preparation method of the polyimide solution is as follows: in a reaction kettle, phthalic anhydride (19.212Kg), ketone anhydride (3.222Kg), composite catalyst potassium fluoride / ethyl tin octoate (60g / 75g) and N-methylpyrrolidone (57.840Kg) are added respectively, stirred at 90°C for 1h, toluene diisocyanate (18.390Kg) is added, a large amount of gas escapes, stirred for 1h, heated to 120°C, and continued to stir for 4h to obtain a polyimide solution with a solid content of 35wt% and a viscosity of 3120 (cP, 25°C).

[0042] A method for preparing a high-temperature resistant insulating spray paint comprises the following steps: adding 1.50 kg of boron nitride powder to 10.00 kg of the polyimide solution prepared above, adding 2.74 kg of N,N-dimethylformamide diluent, and adding 50 g of polyamide wax. After mixing, the mixture is put into a homogenizer for grinding and homogenization. The homogenization pressure is 1 MPa. The final spray paint has a solid content of 35 wt % and a viscosity of 650 (cP, 25° C.).

[0043] A method for using a high-temperature resistant insulating spray paint comprises spraying the spray paint on a polished, water-washed and dried aluminum substrate in a Class 10,000 clean room using a nozzle of 1.5 mm at a pressure of 0.4 MPa, drying the paint in a 25-meter tunnel oven at 80-120° C. with a line speed of 1 m / min, testing a surface dry paint film thickness of 30-35 microns, spraying the paint twice, drying the paint in a 25-meter tunnel oven at 80-120° C. with a line speed of 1 m / min, testing a surface dry paint film thickness of 70-80 microns, spraying the paint three times, drying the paint in a 25-meter tunnel oven at 80-120° C. with a line speed of 1 m / min, testing a surface dry paint film thickness of 110-120 microns, and finally raising the temperature of the tunnel oven to 150-220° C. with a line speed of 0.5 m / min to complete final paint film curing and molding, with a final paint film thickness of 100-110 microns.

[0044] Example 2

[0045] A high temperature resistant insulating spray paint comprises: a polyimide solution, an inorganic filler (boehmite, Anhui Yishitong brand 613), a thixotropic agent (polyvinyl alcohol) and a diluent (N, N-dimethylacetamide), wherein the weight ratio of the polyimide solution, the inorganic filler and the thixotropic agent is 1:0.525:0.013.

[0046] The preparation method of the polyimide solution is as follows: in a reaction kettle, phthalic anhydride (19.212Kg), ketone anhydride (3.222Kg), composite catalyst potassium fluoride / ethyl tin octoate (60g / 75g) and N-methylpyrrolidone (57.840Kg) are added respectively, stirred at 90°C for 1h, toluene diisocyanate (18.390Kg) is added, a large amount of gas escapes, stirred for 1h, heated to 120°C, and continued to stir for 4h to obtain a polyimide solution with a solid content of 35wt% and a viscosity of 3120 (cP, 25°C).

[0047] A method for preparing a high-temperature resistant insulating spray paint comprises the following steps: adding 5.25 kg of boehmite powder to 10 kg of the polyimide solution unit prepared above, adding 6.82 kg of N,N-dimethylacetamide diluent, and adding 130 g of polyvinyl alcohol. After mixing, the mixture is put into a homogenizer for grinding and homogenization. The homogenization pressure is 1 MPa. The final solid content of the spray paint is 40 wt % and the rotational viscosity is 750 (cP, 25° C.).

[0048] A method for using a high-temperature resistant insulating spray paint comprises spraying the spray paint on a polished, washed and dried aluminum substrate in a Class 10,000 clean room using a nozzle of 1.8 mm in diameter at a pressure of 0.6 MPa, drying the paint in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min, and testing a surface dry paint film thickness of 45 to 50 microns. The paint is then sprayed a second time, and then dried in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min. The surface dry paint film thickness is tested to be 120 to 130 microns. The temperature of the tunnel oven is finally raised to 170°C with a line speed of 0.5 m / min to complete final paint film curing and molding, and the final paint film thickness is 110 to 120 microns.

[0049] Example 3

[0050] A high temperature resistant insulating spray paint comprises: a polyimide solution, an inorganic filler (kaolin), a thixotropic agent (fumed silica) and a diluent (N,N-dimethylformamide), wherein the weight ratio of the polyimide solution, the inorganic filler and the thixotropic agent is 1:0.3:0.005.

[0051] The preparation method of the polyimide solution is as follows: in a reaction kettle, phthalic anhydride (19.212Kg), biphenyl dianhydride (2.942Kg), a composite catalyst triethylamine / potassium chloride (75g / 80g) and N,N-dimethylacetamide (89.56Kg) are added respectively, stirred at 90°C for 1h, isophorone diisocyanate (2.134Kg) and diphenylmethane diisocyanate (23.774Kg) are added, a large amount of gas escapes, stirred for 1h, heated to 120°C, and continued to stir for 4h to obtain a polyimide solution with a solid content of 30% and a viscosity of 1740 (cP, 25°C).

[0052] A method for preparing a high-temperature resistant insulating spray paint comprises adding 3 kg of kaolin powder to 10 kg of the polyimide solution unit prepared above, then adding 3.75 kg of N,N-dimethylformamide diluent, and then adding 50 g of fumed silica. After mixing, the mixture is put into a homogenizer for grinding and homogenization. The homogenization pressure is 1.5 MPa. The final spray paint has a solid content of 36 wt% and a rotational viscosity of 1250 (cP, 25°C).

[0053] A method for using a high-temperature resistant insulating spray paint comprises spraying the spray paint on a polished, washed and dried aluminum substrate in a Class 10,000 clean room using a nozzle of 2.0 mm in diameter at a pressure of 0.8 MPa, drying the paint in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min, testing a surface dry paint film thickness of 30 to 35 microns, spraying the paint twice, drying the paint in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min, testing a surface dry paint film thickness of 70 to 80 microns, spraying the paint three times, drying the paint in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min, testing a surface dry paint film thickness of 120 to 130 microns, and finally raising the temperature of the tunnel oven to 170°C with a line speed of 0.5 m / min to complete final paint film curing and molding, with a final paint film thickness of 115 to 125 microns.

[0054] Comparative Example 1

[0055] The specific implementation method is the same as Example 1; the difference is that the preparation method of the polyimide solution described in Comparative Example 1 is as follows: in a reaction kettle, phthalic anhydride (19.212Kg), phthalic anhydride monomer (2.942Kg), composite catalyst triethylamine / ethyl tin octoate (55g / 55g) and N-methylpyrrolidone (73.776Kg) are added respectively, stirred at 90°C for 1h, diphenylmethane diisocyanate monomer (27.252Kg) is added, a large amount of gas escapes, stirring is continued for 1h, the temperature is raised to 120°C, and stirring is continued for 4h to obtain a polyimide solution with a solid content of 35wt% and a viscosity of 24572 (cP, 25°C).

[0056] The above polyimide solution was used to prepare a spray paint according to Example 1. The final spray paint had a solid content of 35 wt % and a viscosity of 21100 (cP, 25° C.).

[0057] Comparative Example 2

[0058] A spray paint comprises: a polyimide solution, an inorganic filler (boehmite), a thixotropic agent (polyvinyl alcohol) and a diluent (N, N-dimethylacetamide), wherein the weight ratio of the polyimide solution, the inorganic filler and the thixotropic agent is 1:0.65:0.0148.

[0059] A method for preparing a spray paint, comprising adding 6.5 kg of boehmite powder to 10 kg of a polyimide solution unit prepared in Example 2, adding 8.72 kg of N,N-dimethylacetamide diluent, and adding 148 g of polyvinyl alcohol. After mixing, the mixture is put into a homogenizer for grinding and homogenization. The homogenization pressure is 1 MPa. The final spray paint has a solid content of 40 wt % and a rotational viscosity of 650 (cP, 25° C.).

[0060] A method for using a spray paint comprises spraying the spray paint on a polished, washed and dried aluminum substrate in a Class 10,000 clean room using a nozzle of 1.8 mm in diameter at a pressure of 0.6 MPa, drying the paint in a 25-meter tunnel oven at 100° C. with a line speed of 1 m / min, and testing a surface dry paint film thickness of 45 to 50 microns; spraying the paint a second time, and then drying the paint in a 25-meter tunnel oven at 100° C. with a line speed of 1 m / min, and testing a surface dry paint film thickness of 120 to 130 microns; finally, the temperature of the tunnel oven is raised to 170° C. with a line speed of 0.5 m / min, and the final paint film curing and molding is completed, and the final paint film thickness is 110 to 120 microns.

[0061] Comparative Example 3

[0062] A method for using a spray paint, using the spray paint formula prepared in Example 3, spraying the spray paint on a polished, washed and dried aluminum substrate in a Class 10,000 clean room using a 2.5 mm caliber nozzle at a pressure of 0.4 MPa, drying in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min, testing a surface dry paint film thickness of 30 to 55 microns, spraying twice, drying in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min, testing a surface dry paint film thickness of 65 to 85 microns, spraying three times, drying in a 25-meter tunnel oven at 100°C with a line speed of 1 m / min, testing a surface dry paint film thickness of 105 to 130 microns, and finally raising the tunnel oven temperature to 170°C with a line speed of 0.5 m / min to complete final paint film curing and molding, and the final paint film thickness is 115 to 135 microns.

[0063] Performance Testing Methods and Data

[0064] The paint films prepared in the examples and comparative examples were subjected to performance tests, and the test data are listed in Table 1.

[0065] “-” means no test was performed.

[0066] 1. Insulation withstand voltage: Refer to GB / T 1408.1, DC 3000V, 60s, <3mA is qualified.

[0067] 2. Insulation resistance: Refer to GB / T 10064, AC 1000V, 60s, >1000MΩ is qualified.

[0068] 3. Acid resistance: Put the paint film sample into 0.1molL hydrochloric acid solution and soak it at 25℃ for 24 hours. The paint film is not damaged, DC3000V.60s, <3mA and AC 1000v.60s, >1000MΩ, which is qualified.

[0069] 4. Alkali resistance: Put the paint film sample into 0.1molL sodium hydroxide dilution and soak it at 25℃ for 24 hours. The paint film is not damaged, DC 3000V.60s, <3mA and AC 1000v.60s, >1000MΩ, which is qualified.

[0070] 5. Electrolyte resistance: Put the paint film sample into the electrolyte (EC / EMCDEC=5 / 32w%) and place it in a 60℃ oven for 7 days. The paint film is qualified if it is not damaged, DC 3000V.60s, <3mA and AC 1000v.60s, >1000MΩ.

[0071] 6. High temperature resistant insulation: 500±2℃ for 0.5h baking (oven). The paint film has no spontaneous combustion and no damage: DC 500V, 60s, <3mA is qualified.

[0072] 7. Hundred grid test: refer to GB / T 9826.

[0073] 8. Pencil hardness: refer to GB / T6739.

[0074] 9. Wear resistance: Taber abrasion tester, refer to GB-7012-T, load 1000g, rotation number 1000r, test mass loss.

[0075] The test instruments for test 1-6 are: electrical safety performance comprehensive analyzer (Qingdao Ainuo Intelligent Instrument Co., Ltd., AN9635HC).

[0076] Among them, the viscosity of Comparative Example 1 was too high to be sprayed into a film, so it was not tested.

[0077] Table 1

[0078]

[0079]

[0080] It can be seen from Table 1 that the spray paints prepared in Examples 1 to 3 have excellent high temperature insulation resistance, and also show good electrolyte resistance, acid and alkali resistance, friction resistance and good adhesion to metal substrates. Comparison of Example 1 with Comparative Example 1 shows that when the molar mass ratio of dianhydride and diisocyanate is greater than 0.98, the molecular weight of the polymer increases sharply, the viscosity increases sharply, and the subsequent polyimide solution cannot be compounded with the inorganic filler to prepare a spray paint with suitable viscosity and solid content. Comparison of Example 2 with Comparative Example 2 shows that both spray paints can form a good film, but the insulation performance test of Comparative Example 2 fails, and the DC3000V test is easily broken down, indicating that the addition of too high a proportion of inorganic fillers will bring about the risk of insulation failure. Comparing Example 3 with Comparative Example 3, it is found that the paint film prepared in Comparative Example 3 fails the voltage insulation test, indicating that when the spray paint is within a certain viscosity range, the air pressure must be flexibly adjusted according to the caliber of the spray gun during spraying. Otherwise, the atomization effect of the spray paint is too poor, affecting the quality of the formed paint film and thus affecting the performance of the paint film.

Claims

1. A high temperature resistant insulating spray paint, characterized in that: The components include: a polyimide solution, an inorganic filler, a thixotropic agent and a diluent, wherein the weight ratio of the polyimide solution, the inorganic filler and the thixotropic agent is 1: (0.1-0.6)：(0.001-0.02)。 2. The high temperature resistant insulating spray paint according to claim 1, characterized in that: The rotational viscosity of the polyimide solution at 25° C. is 1500-3500 cP.

3. The high temperature resistant insulating spray paint according to claim 2, characterized in that: The raw materials for preparing the polyimide solution include dibasic anhydride and diisocyanate, and the molar ratio of the dibasic anhydride to the diisocyanate is 1:(0.92-0.98).

4. The high temperature resistant insulating spray paint according to claim 3, characterized in that: The particle size of the inorganic filler is 2-10 microns.

5. The high temperature resistant insulating spray paint according to claim 1 or 4, characterized in that: The thixotropic agent includes at least one of polyamide wax, fumed silica and polyvinyl alcohol.

6. The high temperature resistant insulating spray paint according to claim 5, characterized in that: The diluent includes at least one of N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, propylene carbonate, sulfolane, butyrolactone, toluene, xylene and cyclohexanone.

7. A method for preparing the high temperature resistant insulating spray paint according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: mixing all components uniformly and performing homogenization; the homogenization pressure is 1-50MPa.

8. The method for preparing the high temperature resistant insulating spray paint according to claim 7, characterized in that: The rotational viscosity of the spray paint at 25° C. is 500-1250 cP.

9. A method for using the high temperature resistant insulating spray paint according to any one of claims 1 to 6, characterized in that: The following steps are involved: First, pre-treat the metal substrate; then spray and dry; then repeat spraying and drying.

10. The method for using the high temperature resistant insulating spray paint according to claim 9, characterized in that: The caliber of the spray gun used for the spraying is 0.8-2.5 mm, and the pressure of the spraying is 0.3-1 MPa.

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