Corona-resistant polyimide film special for high-voltage motor and preparation method of corona-resistant polyimide film

Abstract

The invention provides a corona-resistant polyimide film special for a high-voltage motor and a preparation method of the corona-resistant polyimide film. The corona-resistant polyimide film takes amino-benzene-containing derivatives and aliphatic siloxane diamine and dianhydride monomers as polymeric monomers. Wherein the amino-containing benzene derivative contains three-molecular-weight amino, so that a multi-branched structure is formed in the polyimide, the regularity of a molecular chain is changed, aliphatic siloxane diamine locally forms microcrystals in the polyimide, and the internal structure of the polyimide is changed through introduction of aliphatic siloxane diamine and aliphatic siloxane diamine. By adjusting the ratio of the two, the finally obtained polyimide has excellent water resistance and corona resistance, and can be used in a 800V high-voltage motor.

Description

Technical Field

[0001] The invention relates to polymer materials, in particular to a corona-resistant polyimide film special for high-voltage motors and a preparation method thereof. Background Art

[0002] Polyimide (PI) is a type of polymer material with an imide ring structure. The main chain contains a very stable aromatic heterocyclic structure, which makes it have excellent heat resistance, mechanical properties and electrical properties. Therefore, it is widely used in the fields of motor turn-to-turn insulation and cable wrapping insulation. In recent years, the rapid development of China's high-speed rail technology has brought many new problems to electrical equipment. The variable frequency speed motor is one of the most important equipment of high-speed EMUs and is used as a power driver for high-speed rail. Its safe operation is currently a research hotspot at home and abroad.

[0003] The variable frequency motor mainly adopts pulse width modulation (PWM) drive technology, and its performance is the key to ensure the stable operation of high-speed trains. However, the partial discharge caused by the pulse overvoltage of PWM technology will cause the inter-turn insulation material of the variable frequency motor to age rapidly, and be broken down by corona in a short time, causing the motor to fail. Therefore, it is very important to improve the corona performance of the inter-turn insulation material of the variable frequency motor.

[0004] Polyimide film has been used as a winding insulation material in the insulation system of traction motors for more than 40 years. However, with the rapid development of frequency conversion technology in the motor field, pure polyimide film is difficult to meet higher corona resistance requirements. Studies have found that by doping a certain amount of inorganic nanoparticles, the dielectric properties of polyimide film can be improved, and the corona resistance of the insulation material can be greatly improved.

[0005] At present, the following aspects of corona-resistant polyimide film also need to be paid attention to: 1. The dispersion state of nanoparticles will affect the corona resistance of the film. Physical crosslinking or chemical crosslinking can be used to increase the compatibility between the polymer and the inorganic filler to form an organic-inorganic network structure, which not only reduces the agglomeration of nanoparticles in the polymer matrix, but also improves the structural stability and voltage shock resistance of the hybrid film; 2. Since the increase in the amount of nanoparticle doping will cause the mechanical properties of the film to show a downward trend, the structure of the film can be involved. The "less doping, multi-layer film" method can be used to improve the corona resistance life while ensuring the excellent other physical properties of the film; 3. Superconducting motors have large transmission capacity, low loss, and greatly improved resource utilization, and are the future development direction of power system technology. Summary of the invention

[0006] The invention provides a corona-resistant polyimide film specially used for a high-voltage motor and a preparation method thereof. The corona-resistant polyimide film has excellent water resistance and corona resistance and can be used in an 800V high-voltage motor.

[0007] A corona-resistant polyimide film specially used for high-voltage motors comprises the following raw materials, measured by weight: 80-100 parts of pyromellitic dianhydride, 40-50 parts of 4,4-diaminodiphenyl ether, 20-50 parts of acetic anhydride, 10-13 parts of aminobenzene derivatives, 50-70 parts of aliphatic siloxane diamine, 8-50 parts of inorganic fillers and 510-850 parts of organic solvents; wherein the aminobenzene derivatives contain a molecular weight of amino groups.

[0008] In some embodiments of the present invention, the amino-containing benzene derivative is at least one of tris(4-aminophenyl)amine, 2,4,6-tris(4-aminophenyl)-pyridine, and 1,3,5-tris(4-aminophenoxy)benzene.

[0009] In some embodiments of the present invention, the long-chain aliphatic siloxane diamine is at least one of 1,3-diaminoethyldisiloxane (CAS=5678-37-5), 1,3-diaminopropyldisiloxane (CAS=6006-41-3), 1,3-bis(2-aminoethylaminopropyl)disiloxane (CAS=6048-96-0), 1,3-diaminomethyltetramethyldisiloxane (CAS=5724-63-0), 1,3-bis(2-aminoethylaminomethyl)tetramethyldisiloxane (CAS=83936-41-8), and 1,5-diaminomethylhexamethyltrisiloxane (CAS=75754-72-2).

[0010] In some embodiments of the present invention, the inorganic filler is at least one of fumed alumina, talc, nano titanium dioxide and nano boron nitride.

[0011] In some embodiments of the present invention, the mass ratio of the amino-containing benzene derivative to the long-chain aliphatic siloxane diamine is 1-1.2:5-5.5.

[0012] The reason why the use mass ratio of the aminobenzene derivatives to the aliphatic siloxane diamine is to be optimized is that: the introduction of the aminobenzene derivatives can greatly change the regularity of the polyimide molecular chain, greatly increase the free volume of the material, and reduce the dielectric constant of the material, thereby obtaining good corona resistance; however, the branched polyimide molecules contain larger groups and asymmetric structures, and it is difficult to form a tight stacking structure between the segments, causing the polymer to be fluffy and coiled inside. Even if the introduction of the aliphatic siloxane diamine can form microcrystals locally, hindering the penetration and diffusion of water molecules, water molecules will also use the coil-like structure to infiltrate along the gaps between the polymers, resulting in a greater impact on the hydrophobicity of the polyimide. The immersion of water molecules will also increase the corona strength of the polyimide, which may cause rapid aging of the material. In view of this, the inventors have optimized the use mass ratio of the aminobenzene derivatives to the long-chain aliphatic siloxane diamine through experiments to obtain a hydrophobic and corona-resistant polyimide film.

[0013] The method for preparing the corona-resistant polyimide film for high-voltage motors described above comprises the following steps: S1: dissolving pyromellitic anhydride and 4,4-diaminodiphenyl ether, aminobenzene derivatives, and aliphatic siloxane diamine in an organic solvent respectively, then adding the pyromellitic anhydride solution to the 4,4-diaminodiphenyl ether solution under stirring, reacting at 30-50° C., and simultaneously adding acetic anhydride and aminobenzene derivative solution and long-chain aliphatic siloxane diamine solution in batches for multiple times, reacting for 6-12 hours, and obtaining a polyamic acid glue solution; S2: adding a solution containing dispersed inorganic fillers to the polyamic acid adhesive obtained in S1, stirring evenly at a temperature not higher than 25° C., and removing impurities by filter pressing; S3: Pour the purified glue onto the rolling steel belt, and use a film laying tool to evenly spread the glue on the steel plate according to the required thickness, and spread the film at a constant speed; S4: sending the steel plate with the adhesive solution into a preheating furnace, maintaining it at high temperature for 10-30 minutes, performing a dehydration cyclization treatment, and then performing thermal imidization and stretching to obtain the corona-resistant polyimide film specially used for high-voltage motors.

[0014] Furthermore, the solid content of the solution in which the inorganic filler is dispersed in S2 is 10-30%.

[0015] Furthermore, the stirring speed in S1 and S2 is 200-300 r / min and the time is 30-60 min.

[0016] Furthermore, the temperature of the dehydration cyclization in S4 is 120-250°C.

[0017] Furthermore, in S4, the temperature raising program of the thermal imidization is: 100-110°C for 10-20s, 110-120°C for 30-40s, 120-130°C for 40-50s, and 140-145°C for 1-3min.

[0018] Furthermore, the temperature of the stretching and shaping in S4 is 450-550°C.

[0019] Beneficial effects: Compared with the prior art, the present invention creatively uses special aminobenzene derivatives and aliphatic siloxane diamine as modified monomers for preparing polyimide, and the obtained polyimide contains both a branched structure and a flexible chain structure with a high local symmetry. By adjusting the mass ratio of the aminobenzene derivatives and aliphatic siloxane diamine, the corona resistance and hydrophobicity of the polyimide are double enhanced, so that it can be used in 800V high-voltage motors. DETAILED DESCRIPTION

[0020] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0021] Example 1 S1: 800g of pyromellitic anhydride, 400g of 4,4-diaminodiphenyl ether, 100g of tris(4-aminophenyl)amine, and 500g of 1,3-diaminoethyldisiloxane were dissolved in 1000ml of dimethylformamide, and then the pyromellitic anhydride solution was added to the 4,4-diaminodiphenyl ether solution at a stirring speed of 200r / min (30min), and the reaction was carried out at 30°C. At the same time, 200g of acetic anhydride and a solution of tris(4-aminophenyl)amine and 1,3-diaminoethyldisiloxane were added in batches for multiple times, and the reaction was carried out for 6h to obtain a polyamic acid glue solution; S2: Add a dimethylformamide solution (solid content 30%) in which 80 g of fumed alumina is dispersed to the polyamic acid glue obtained in S1, stir evenly at a speed of 200 r / min at 25°C (30 min), and remove impurities by filter pressing; S3: Pour the purified glue onto the rolling steel belt, and use a film laying tool to evenly spread the glue on the steel plate according to the required thickness, and spread the film at a constant speed; S4: sending the steel plate with the adhesive solution into a preheating furnace, maintaining it at 120°C for 10 minutes, performing a dehydration cyclization treatment, and then performing thermal imidization (residence time at 100°C for 20 seconds, residence time at 110°C for 40 seconds, residence time at 120°C for 50 seconds, and residence time at 140°C for 3 minutes) and stretching and shaping at 450°C to obtain the corona-resistant polyimide film specially used for high-voltage motors.

[0022] Example 2 S1: 900g of pyromellitic anhydride and 450g of 4,4-diaminodiphenyl ether, 110g of 2,4,6-tris(4-aminophenyl)-pyridine, and 600g of 1,3-bis(2-aminoethylaminopropyl)disiloxane were dissolved in 1000ml of dimethylformamide, and then the pyromellitic anhydride solution was added to the 4,4-diaminodiphenyl ether solution at a stirring speed of 250r / min (40min), and the reaction was carried out at 40°C. At the same time, 300g of acetic anhydride and a solution of 2,4,6-tris(4-aminophenyl)-pyridine and 1,3-bis(2-aminoethylaminopropyl)disiloxane were added in batches for multiple times, and the reaction was carried out for 9h to obtain a polyamic acid glue solution; S2: Add dimethylformamide solution (solid content 20%) dispersed with 250g of inorganic filler (fumed alumina + talc) to the polyamic acid adhesive obtained in S1, stir evenly at 250r / min at 20°C (40min), and remove impurities by filter pressing; S3: Pour the purified glue onto the rolling steel belt, and use a film laying tool to evenly spread the glue on the steel plate according to the required thickness, and spread the film at a constant speed; S4: The steel plate coated with the adhesive is sent into a preheating furnace and maintained at 200°C for 20 minutes for dehydration cyclization, followed by thermal imidization (105°C for 15 seconds, 115°C for 35 seconds, 125°C for 45 seconds, 140°C for 2 minutes) and stretching and shaping at 500°C to obtain the corona-resistant polyimide film specially used for high-voltage motors.

[0023] Example 3 S1: 1000g of pyromellitic anhydride and 500g of 4,4-diaminodiphenyl ether, 130g of 1,3,5-tris(4-aminophenoxy)benzene, and 700g of 1,3-bis(2-aminoethylaminomethyl)tetramethyldisiloxane were dissolved in 1000ml of dimethylformamide, and then the pyromellitic anhydride solution was added to the 4,4-diaminodiphenyl ether solution at a stirring speed of 300r / min (60min), and the reaction was carried out at 50°C. At the same time, 500g of acetic anhydride and a solution of 1,3,5-tris(4-aminophenoxy)benzene and 1,3-bis(2-aminoethylaminomethyl)tetramethyldisiloxane were added in batches for multiple times, and the reaction was carried out for 12h to obtain a polyamic acid glue solution; S2: Add dimethylformamide solution (solid content 10%) dispersed with 500g of inorganic filler (talcum powder + nano silicon nitride) to the polyamic acid adhesive obtained in S1, stir evenly at 300r / min at 15°C (60min), and remove impurities by filter pressing; S3: Pour the purified glue onto the rolling steel belt, and use a film laying tool to evenly spread the glue on the steel plate according to the required thickness, and spread the film at a constant speed; S4: The steel plate coated with the adhesive is sent into a preheating furnace and maintained at 250°C for 20 minutes for dehydration and cyclization, followed by thermal imidization (105°C for 15 seconds, 115°C for 35 seconds, 125°C for 45 seconds, and 140°C for 2 minutes) and stretching and shaping at 550°C to obtain the corona-resistant polyimide film specially used for high-voltage motors.

[0024] Example 4 The process is the same as in Example 2, except that the amount of 1,3-bis(2-aminoethylaminopropyl)disiloxane used is 550 g.

[0025] Comparative Example 1 The process is the same as in Example 4, except that 2,4,6-tris(4-aminophenyl)-pyridine is not added.

[0026] Comparative Example 2 The process is the same as in Example 4, except that 1,3-bis(2-aminoethylaminopropyl)disiloxane is not added.

[0027] Comparative Example 3 The process is the same as in Example 4, except that 2,4,6-tris(4-aminophenyl)-pyridine and 1,3-bis(2-aminoethylaminopropyl)disiloxane are not added.

[0028] Performance Testing According to GB / T13542.2-2009 standard, the tensile strength, electrical strength and corona resistance of the films obtained in Examples 1-4 and Comparative Examples 1-3 were tested.

[0029] The test conditions are: experimental voltage 2kV, experimental frequency 20kHz, pulse rise time 50ns, bipolar pulse square wave, 6mm cylindrical electrode, nine groups of data are measured for each embodiment, and the median value is taken respectively.

[0030] The test results are as follows: Table 1 Performance test results of the films obtained in Examples 1-4 and Comparative Examples 1-3

[0031] From the data in Table 1, it can be seen that the polyimide films prepared in Examples 1-4 can achieve electrical strength and corona resistance at a high level, but the result of Example 4 is slightly better than that of Example 2, which shows that the use of aminobenzene derivatives and aliphatic siloxane diamines described in the present invention needs to be determined according to the situation to obtain a more effective product. The results of Comparative Examples 1-3 show that aminobenzene derivatives and aliphatic siloxane diamines are indispensable for improving the corona resistance of polyimide films, both play an important role, and the two also have a synergistic effect.

[0032] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A corona-resistant polyimide film for high-voltage motors, characterized in that: The invention comprises the following raw materials by weight: 80-100 parts of pyromellitic dianhydride, 40-50 parts of 4,4-diaminodiphenyl ether, 20-50 parts of acetic anhydride, 10-13 parts of aminobenzene derivatives, 50-70 parts of aliphatic siloxane diamine, 8-50 parts of inorganic filler and 510-850 parts of organic solvent; wherein the aminobenzene derivatives contain three molecular weight amino groups.

2. The corona-resistant polyimide film for high-voltage motors according to claim 1, characterized in that: The aminobenzene derivative is at least one of tris(4-aminophenyl)amine, 2,4,6-tris(4-aminophenyl)-pyridine and 1,3,5-tris(4-aminophenoxy)benzene.

3. The corona-resistant polyimide film for high-voltage motors according to claim 1, characterized in that: The aliphatic siloxane diamine is at least one of 1,3-diaminoethyl disiloxane, 1,3-diaminopropyl disiloxane, 1,3-bis(2-aminoethylaminopropyl) disiloxane, 1,3-diaminomethyltetramethyl disiloxane, 1,3-bis(2-aminoethylaminomethyl)tetramethyl disiloxane and 1,5-diaminomethylhexamethyltrisiloxane.

4. The corona-resistant polyimide film for high-voltage motors according to claim 1, characterized in that: The inorganic filler is at least one of fumed alumina, talcum powder, nano titanium dioxide and nano boron nitride.

5. The corona-resistant polyimide film for high-voltage motors according to claim 1, characterized in that: The mass ratio of the aminobenzene derivative to the long-chain aliphatic siloxane diamine is 1-1.2:5-5.

5.

6. The method for preparing the corona-resistant polyimide film for high-voltage motors according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1: dissolving pyromellitic anhydride and 4,4-diaminodiphenyl ether, aminobenzene derivatives, and aliphatic siloxane diamine in organic solvents respectively, then adding the pyromellitic anhydride solution to the 4,4-diaminodiphenyl ether solution under stirring, reacting at 30-50° C., and simultaneously adding acetic anhydride, aminobenzene derivative solution, and aliphatic siloxane diamine solution in batches for multiple times, reacting for 6-12 hours, and obtaining a polyamic acid glue solution; S2: adding a solution containing dispersed inorganic fillers to the polyamic acid adhesive obtained in S1, stirring evenly at a temperature not higher than 25° C., and removing impurities by filter pressing; S3: Pour the purified adhesive onto a rolling steel belt, and use a film laying cutter to evenly spread the adhesive onto the steel plate at a desired thickness, spreading the film at a constant speed; S4: sending the steel plate with the adhesive solution into a preheating furnace, maintaining it at high temperature for 10-30 minutes, performing a dehydration cyclization treatment, and then performing thermal imidization and stretching to obtain the corona-resistant polyimide film specially used for high-voltage motors.

7. The method for preparing the corona-resistant polyimide film for high-voltage motors according to claim 6, characterized in that: The solid content of the solution in which the inorganic filler is dispersed in S2 is 10-30%.

8. The method for preparing the corona-resistant polyimide film for high-voltage motors according to claim 6, characterized in that: The stirring speed in S1 and S2 is 200-300 r / min and the time is 30-60 min.

9. The method for preparing the corona-resistant polyimide film for high-voltage motors according to claim 6, characterized in that: The temperature of the dehydration cyclization in S4 is 120-250°C.

10. The method for preparing the corona-resistant polyimide film for high-voltage motors according to claim 6, characterized in that: In S4, the temperature raising program of the thermal imidization is: 100-110°C for 10-20s, 110-120°C for 30-40s, 120-130°C for 40-50s, and 140-145°C for 1-3min.

Images