Preparation method of polyimide film resistant to electric breakdown

Abstract

The present invention discloses a preparation method of an electric breakdown-resistant polyimide film, which consists of the following steps. Step S1: Dissolve an organoelement compound in an organic solvent to obtain an organoelement compound solution. Step S2: Introduce nitrogen into the organoelement compound solution and add a diamine compound. Step S3: After the diamine compound is completely dissolved, add a dianhydride compound and react to obtain a polyamic acid solution containing an organoelement compound. Step S4: Obtain the electric breakdown-resistant polyimide film through imidization. By adding an organoelement compound, the present invention eliminates processes such as coupling agent hydrolysis, adding inorganic nanoparticles under stirring, filtration, drying, and pulverization in the prior art for preparing an electric breakdown-resistant polyimide film by adding inorganic nanoparticles, shortens the preparation process route of the electric breakdown-resistant polyimide film, reduces the production cost, and improves the breakdown voltage and tensile strength of the product.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulating materials, and particularly relates to a preparation method of an electric breakdown-resistant polyimide film. Background Art

[0002] With the rapid development of high-speed railways in China, the popularization of the core of high-speed trains has become crucial. The variable-frequency traction motor is one of the core equipment of high-speed trains, and the speed regulation, control, and inter-turn insulation between stator windings under high-frequency pulses are also the key research points at home and abroad. The variable-frequency traction motor adjusts its speed through PWM (Pulse Width Modulation) technology. Due to the short rise time and high frequency of the pulses, combined with the impedance mismatch between the cable and the motor terminal, overvoltage will be generated, which will impact the inter-turn insulation of the variable-frequency motor, causing the winding insulation of the variable-frequency traction motor to fail and threatening the safety of train operation. Therefore, it is particularly important to improve the insulation performance of the inter-turn insulation of the variable-frequency traction motor.

[0003] Polyimide (PI), as an excellent insulating material, has excellent thermal stability, mechanical properties, and insulation performance. Polyimide film has been used as the winding insulation material in the insulation system of traction motors for more than 40 years. However, with the rapid development of variable-frequency technology in the motor field, pure polyimide film is difficult to meet the higher corona resistance requirements. In recent years, it has been found that by doping a certain amount of inorganic nanoparticles, the dielectric properties of polyimide film can be improved, and at the same time, the corona resistance of insulating materials can be significantly enhanced. These inorganic nanoparticles include SiO2, TiO2, ZnO, MgO, and Al2O3, etc. In particular, the corona resistance performance of the polyimide film Kapton 100CR prepared by DuPont by adding inorganic nanoparticle Al2O3 is far ahead.

[0004] However, in the process of preparing polyimide corona-resistant film by adding the above inorganic nanoparticles, the inorganic nanoparticles need to be specially processed before use. Its processing technology includes coupling agent hydrolysis, adding inorganic nanoparticles under stirring, filtration, drying, crushing, ultrasonic dispersion, polymerization and other processes, which have many processes, a long cycle, and the tensile strength of the polyimide film added with inorganic nanoparticles has been reduced to varying degrees, affecting its application range. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of an electric breakdown-resistant polyimide film to solve the problems of long process cycle, many processes, high cost, and the decrease in the strength of polyimide film existing in the method of preparing an electric breakdown-resistant polyimide film by adding inorganic nanoparticles in the background art.

[0006] The present invention adopts the following technical scheme: A preparation method of an electric breakdown-resistant polyimide film, which consists of the following steps.

[0007] Step S1: Dissolve the organoelement compound in an organic solvent to obtain an organoelement compound solution.

[0008] Step S2: Introduce nitrogen gas into the organoelement compound solution and add a diamine compound.

[0009] Step S3: After the diamine compound is completely dissolved, add a dianhydride compound and react to obtain a polyamic acid solution containing the organoelement compound.

[0010] Step S4: Obtain a polyimide film with high resistance to electric breakdown through imidization.

[0011] Furthermore, the organoelement compound is one or a combination of several of an aluminum organic compound, a zinc organic compound, a magnesium organic compound, a zirconium organic compound, or a silicon organic compound.

[0012] Furthermore, the aluminum organic compound is trimethylaluminum, triethylaluminum, triethanolaluminum, triisopropanolaluminum, or tributanolaluminum.

[0013] Furthermore, the zinc organic compound is diethylzinc, dimethanolzinc, diethanolzinc, or zinc dimethylimidazole.

[0014] Furthermore, the magnesium organic compound is dimethylmagnesium, diethylmagnesium, or diphenylmagnesium.

[0015] Furthermore, the silicon organic compound is tetramethylsiloxane or tetraethylsiloxane.

[0016] Furthermore, the zirconium organic compound is tetramethoxy zirconium, tetraethoxy zirconium, tetrapropoxy zirconium, or tetrabutoxy zirconium.

[0017] Furthermore, the molar ratio of the diamine compound to the dianhydride compound is 1:1, and the molar ratio of the organoelement compound to the diamine compound is 1 - 10:100.

[0018] Furthermore, in Step S3, after the diamine compound is completely dissolved, the temperature is lowered to 0°C, and then the dianhydride compound is added.

[0019] Furthermore, the reaction conditions after adding the dianhydride compound in Step S3 are: the temperature does not exceed 20°C, and the reaction lasts for 8 - 10 hours.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. By adding the organoelement compound, the present invention eliminates the processes of coupling agent hydrolysis, adding inorganic nanoparticles under stirring, filtration, drying, and pulverization in the process of preparing a polyimide film with high resistance to electric breakdown in the prior art, shortens the preparation process route of the polyimide film with high resistance to electric breakdown, and reduces the production cost.

[0022] 2. The organoelement compound added in the present invention can be dissolved in the solvent used for synthesizing polyimide, evenly distributed in the reaction solution and participate in the synthesis reaction of polyimide. Compared with the process method of preparing a polyimide film with resistance to electric breakdown by adding inorganic nanoparticles, the tensile strength of the polyimide film with resistance to electric breakdown is not reduced. Specific Embodiments

[0023] The present invention will be described in detail below in conjunction with specific embodiments.

[0024] It should be noted that the ratios in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the implementation conditions of the present invention. Therefore, they do not have substantial technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size, without affecting the efficacy that the present invention can produce and the purpose that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0025] The present invention discloses a method for preparing a polyimide film with resistance to electric breakdown, which consists of the following steps:

[0026] Step S1: Dissolve the organoelement compound in an organic solvent and stir at a speed of 50 rpm to 100 rpm to obtain an organoelement compound solution.

[0027] Step S2: Introduce nitrogen into the organoelement compound solution. Introducing nitrogen is to expel oxygen and moisture in the reactor, and then add a diamine compound.

[0028] Step S3: After the diamine compound is completely dissolved, add a dianhydride compound and react to obtain a polyamic acid solution containing an organoelement compound.

[0029] Step S4: Obtain a polyimide film with resistance to electric breakdown through imidization.

[0030] Among them, the organoelement compound is one or a combination of an aluminum organic compound, a zinc organic compound, a magnesium organic compound, a zirconium organic compound or a silicon organic compound.

[0031] Among them, the aluminum organic compound is trimethylaluminum, triethylaluminum, triethanolaluminum, triisopropanolaluminum or tributanolaluminum.

[0032] Among them, the zinc organic compound is diethylzinc, dimethanolzinc, diethanolzinc or zinc dimethylimidazole.

[0033] Among them, the magnesium organic compound is dimethylmagnesium, diethylmagnesium or diphenylmagnesium.

[0034] Among them, the silicon organic compound is tetramethylsiloxane or tetraethylsiloxane.

[0035] Among them, the organozirconium compound is zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetrapropoxide or zirconium tetrabutoxide.

[0036] Among them, the molar ratio of the diamine compound to the dianhydride compound is 1:1, and the molar ratio of the organoelement compound to the diamine compound is 1 - 10:100.

[0037] Among them, in step S1, the organic solvent is N,N-dimethylacetamide or N-methylpyrrolidone.

[0038] Among them, in step S3, after the diamine compound is completely dissolved, the temperature is lowered to 0 °C, and then the dianhydride compound is added. The reaction conditions after adding the dianhydride compound in step S3 are: the temperature does not exceed 20 °C, and the reaction is carried out for 8 - 10 hours.

[0039] Among them, in step S4, imidization is carried out according to the following procedure: 80 °C, 2 min; 130 °C, 6 min; 160 °C, 2 min; 180 °C, 2 min; 200 °C, 2 min; 250 °C, 2 min; 300 °C, 2 min; 350 °C, 2 min; 400 °C, 2 min.

[0040] Among them, the particle size of the organoelement compound is not more than 100 nanometers; the stirring speed is 50 revolutions / min - 100 revolutions / min.

[0041] Among them, the nitrogen is high-purity nitrogen, and its flow rate is 2 liters / min - 5 liters / min; the purity of the diamine is not less than 99.5% and the water content is not more than 100 ppm;

[0042] Among them, the purity of the dianhydride is not less than 99.5% and the water content is not more than 100 ppm; the dianhydride is added in 5 times, and the amount of the dianhydride added for the 5th time is 97.5% of the total amount of the dianhydride. Controlling the purity and water content of the dianhydride can affect the quality of the synthesized polyamic acid product. Controlling the feeding speed of the dianhydride can not only ensure the smooth progress of the reaction, but also ensure the quality of the polyamic acid. Adding the dianhydride in 5 times is to avoid concentrated heat release during the reaction. For the amount of the dianhydride added for the 5th time being 97.5% of the total amount of the dianhydride, this can not only control the heat release, but also adjust the viscosity of the reactants and prevent the formation of gel locally.

[0043] Example 1

[0044] Step S1: Dissolve 0.005 mol of the organoelement compound aluminum triethanolate containing aluminum in 230 grams of N,N-dimethylacetamide at room temperature to obtain an organoelement compound solution.

[0045] Step S2: Pass nitrogen into the organoelement compound solution, and add 0.1 mol of m-phenylenediamine under stirring.

[0046] Step S3: After m - phenylenediamine is completely dissolved, cool the temperature to 0 °C, then add 0.1 mol of 4,4'-oxydiphthalic anhydride, and control the temperature of the reaction solution not to exceed 20 °C, and react for 8 hours.

[0047] Step S4: Obtain the electrically breakdown - resistant polyimide film A1 through imidization. That is, take an appropriate amount of the reaction solution and evenly coat it on the substrate, and perform imidization according to the following procedure: 80 °C, 2 min; 130 °C, 6 min; 160 °C, 2 min; 180 °C, 2 min; 200 °C, 2 min; 250 °C, 2 min; 300 °C, 2 min; 350 °C, 2 min; 400 °C, 2 min.

[0048] Prepare the blank control A0 without adding organoelement compounds and with the same other steps and conditions as in this example. Perform performance tests on the prepared electrically breakdown - resistant polyimide films A1 and A0, and the specific test data are shown in Table 1.

[0049] Table 1 Test data

[0050]

[0051] Example 2

[0052] Step S1: Dissolve 0.001 mol of the organoelement compound aluminum tri - n - butoxide containing aluminum in 283 g of N,N - dimethylacetamide at room temperature to obtain the organoelement compound solution.

[0053] Step S2: Pass nitrogen into the organoelement compound solution, and add 0.1 mol of m - phenylenediamine with stirring.

[0054] Step S3: After m - phenylenediamine is completely dissolved, cool the temperature to 0 °C, then add 0.1 mol of 4,4'-oxydiphthalic anhydride, and control the temperature of the reaction solution not to exceed 20 °C, and react for 10 hours.

[0055] Step S4: Obtain the electrically breakdown - resistant polyimide film B1 through imidization. That is, take an appropriate amount of the reaction solution and evenly coat it on the substrate, and perform imidization according to the following procedure: 80 °C, 2 min; 130 °C, 6 min; 160 °C, 2 min; 180 °C, 2 min; 200 °C, 2 min; 250 °C, 2 min; 300 °C, 2 min; 350 °C, 2 min; 400 °C, 2 min.

[0056] Prepare the blank control B0 without adding organoelement compounds and with the same other steps and conditions as in this example. Perform performance tests on the prepared electrically breakdown - resistant polyimide films B1 and B0, and the specific test data are shown in Table 2.

[0057] Table 2 Test data

[0058]

[0059] Example 3

[0060] Step S1: Dissolve 0.005 mol of the organometallic compound zinc diethanolate containing zinc in 251 g of N,N'-dimethylacetamide at room temperature to obtain an organometallic compound solution.

[0061] Step S2: Pass nitrogen into the organometallic compound solution, and add 0.1 mol of m-phenylenediamine with stirring.

[0062] Step S3: After the m-phenylenediamine is completely dissolved, cool the temperature to 0 °C, then add 0.1 mol of 4,4'-biphenyl ether dianhydride, and control the temperature of the reaction solution not to exceed 20 °C, and react for 9 hours.

[0063] Step S4: Obtain the electrically breakdown-resistant polyimide film C1 through imidization, that is, take an appropriate amount of the reaction solution and uniformly coat it on a substrate, and perform imidization according to the following procedure: 80 °C, 2 min; 130 °C, 6 min; 160 °C, 2 min; 180 °C, 2 min; 200 °C, 2 min; 250 °C, 2 min; 300 °C, 2 min; 350 °C, 2 min; 400 °C, 2 min.

[0064] Prepare a blank control C0 without adding the organometallic compound, and with other steps and conditions the same as this example. Perform performance tests on the prepared electrically breakdown-resistant polyimide films C1 and C0, and the specific test data are shown in Table 3.

[0065] Table 3 Test Data

[0066]

[0067] Example 4

[0068] Step S1: Dissolve 0.005 mol of the organometallic compound diphenylmagnesium containing magnesium in 371 g of N-methylpyrrolidone at room temperature to obtain an organometallic compound solution.

[0069] Step S2: Pass nitrogen into the organometallic compound solution, and add 0.1 mol of m-phenylenediamine with stirring.

[0070] Step S3: After the m-phenylenediamine is completely dissolved, cool the temperature to 0 °C, then add 0.1 mol of 4,4'-biphenyl ether dianhydride, and control the temperature of the reaction solution not to exceed 20 °C, and react for 8 hours.

[0071] Step S4: Obtain the electrically breakdown-resistant polyimide film D1 through imidization. That is, take an appropriate amount of the reaction solution, uniformly coat it on a substrate, and perform imidization according to the following procedure: 80°C for 2 minutes; 130°C for 6 minutes; 160°C for 2 minutes; 180°C for 2 minutes; 200°C for 2 minutes; 250°C for 2 minutes; 300°C for 2 minutes; 350°C for 2 minutes; 400°C for 2 minutes.

[0072] Prepare a blank control D0 without adding element organic compounds, and with other steps and conditions the same as in this example. Perform performance tests on the prepared electrically breakdown-resistant polyimide films D1 and D0. The specific test data are shown in Table 4.

[0073] Table 4 Test Data

[0074]

[0075] Example 5

[0076] Step S1: Dissolve 0.005 mol of the element organic compound tetraethylsiloxane containing silicon in 300 grams of N-methylpyrrolidone at room temperature to obtain an element organic compound solution.

[0077] Step S2: Pass nitrogen into the element organic compound solution, and add 0.1 mol of m-phenylenediamine under stirring.

[0078] Step S3: After the m-phenylenediamine is completely dissolved, cool down to 0°C, then add 0.1 mol of 4,4'-biphenyl ether dianhydride, and control the temperature of the reaction solution not to exceed 20°C, and react for 9 hours.

[0079] Step S4: Obtain the electrically breakdown-resistant polyimide film E1 through imidization. That is, take an appropriate amount of the reaction solution, uniformly coat it on a substrate, and perform imidization according to the following procedure: 80°C for 2 minutes; 130°C for 6 minutes; 160°C for 2 minutes; 180°C for 2 minutes; 200°C for 2 minutes; 250°C for 2 minutes; 300°C for 2 minutes; 350°C for 2 minutes; 400°C for 2 minutes.

[0080] Prepare a blank control E0 without adding element organic compounds, and with other steps and conditions the same as in this example. Perform performance tests on the prepared electrically breakdown-resistant polyimide films E1 and E0. The specific test data are shown in Table 5.

[0081] Table 5 Test Data

[0082]

[0083] Example 6

[0084] Step S1: Dissolve 0.01 mol of the organo-elemental compound tetraethoxyzirconium containing zirconium in 355 g of N-methylpyrrolidone at room temperature to obtain an organo-elemental compound solution.

[0085] Step S2: Introduce nitrogen into the organo-elemental compound solution, and add 0.1 mol of m-phenylenediamine with stirring.

[0086] Step S3: After the m-phenylenediamine is completely dissolved, cool the temperature to 0 °C, then add 0.1 mol of 4,4'-biphenyl ether dianhydride, control the temperature of the reaction solution not to exceed 20 °C, and react for 10 hours.

[0087] Step S4: Obtain the polyimide film F1 with high resistance to electric breakdown through imidization. That is, take an appropriate amount of the reaction solution and uniformly coat it on a substrate, and perform imidization according to the following procedure: 80 °C, 2 min; 130 °C, 6 min; 160 °C, 2 min; 180 °C, 2 min; 200 °C, 2 min; 250 °C, 2 min; 300 °C, 2 min; 350 °C, 2 min; 400 °C, 2 min.

[0088] A blank control F0 was prepared without adding the organo-elemental compound, and other steps and conditions were the same as those in this example. The performance tests were carried out on the prepared polyimide films F1 and F0 with high resistance to electric breakdown. The specific test data are shown in Table 6.

[0089] Table 6 Test Data

[0090]

[0091]

[0092] It can be seen from Tables 1-6 that adding the organo-elemental compound can improve the electric breakdown resistance of the polyimide film without reducing its tensile strength.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of an electrically breakdown-resistant polyimide film, characterized in that, It consists of the following steps: Step S1: Dissolve the organoelement compound in an organic solvent to obtain an organoelement compound solution. Step S2: Introduce nitrogen into the organoelement compound solution and add a diamine compound. Step S3: After the diamine compound is completely dissolved, add a dianhydride compound and react to obtain a polyamic acid solution containing the organoelement compound. Step S4: Obtain a polyimide film resistant to electrical breakdown through imidization. Among them, the purity of the dianhydride compound is not less than 99.5% and the water content is not more than 100 ppm; the dianhydride is added in 5 times, and the amount of the dianhydride added in the 5th time is 97.5% of the total amount of the dianhydride. The dianhydride compound is 4,4 ， -biphenyl ether dianhydride; The organoelement compound is one or a combination of an aluminum organic compound, a zinc organic compound, a magnesium organic compound, or a zirconium organic compound. The molar ratio of the diamine compound to the dianhydride compound is 1:1, and the molar ratio of the organoelement compound to the diamine compound is 1-10:

100.

2. The preparation method of a polyimide film resistant to electric breakdown according to claim 1, characterized in that, The aluminum organic compound is trimethylaluminum, triethylaluminum, triethanolaluminum, triisopropanolaluminum, or tributylaluminum.

3. The preparation method of an electrically breakdown-resistant polyimide film according to claim 1, characterized in that, The zinc organic compound is diethylzinc, dimethanolzinc, diethanolzinc, or zinc dimethylimidazole.

4. The preparation method of a polyimide film resistant to electric breakdown according to claim 1, characterized in that, The magnesium organic compound is dimethylmagnesium, diethylmagnesium, or diphenylmagnesium.

5. The preparation method of an electric breakdown resistant polyimide film according to claim 1, characterized in that, The zirconium organic compound is tetramethoxyzirconium, tetraethoxyzirconium, tetrapropoxyzirconium, or tetrabutoxyzirconium.

6. The preparation method of a polyimide film resistant to electric breakdown according to claim 1, characterized in that, In step S3, after the diamine compound is completely dissolved, the temperature is lowered to 0 °C, and then the dianhydride compound is added.

7. The preparation method of a polyimide film resistant to electric breakdown according to claim 6, characterized in that, The reaction conditions after adding the dianhydride compound in step S3 are: the temperature does not exceed 20 °C, and the reaction is carried out for 8-10 hours.

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