Insulating paint with high partial discharge inception voltage and preparation method and application thereof

Abstract

The application belongs to the technical field of high polymer materials, and provides an insulating paint with high partial discharge inception voltage, a preparation method and application thereof. At least one of long-chain alkyl citrate foaming agent, long-chain alkyl terephthalate foaming agent and long-chain alkyl dibasic fatty acid ester foaming agent is added into a base resin as a foaming agent, and the obtained insulating paint can obtain a polymer insulating layer with a bubble layer after coating and curing, wherein a large number of hole structures are contained, and the PDIV is high. The foaming agent used in the application has high safety, the preparation process of the polymer insulating layer with bubbles is simple and easy to operate, and the prepared paint film will not produce defects such as paint tumor or large bubbles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, and more particularly to an insulating paint with high partial discharge inception voltage and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of new energy vehicles, new technical challenges have appeared in the winding insulation system of electric drive motors, especially in the application and development of 800V or even 1000V drive motors, which require more compact size and stronger power of the motor. The motor is driven at high voltage to obtain high output, and under normal circumstances, these electric motors are driven by inverters to achieve fine control and energy saving. Therefore, in the insulating electromagnetic wire constituting the motor coil, due to the superposition of high voltage and inverter surge, the risk of partial discharge is increased. When partial discharge occurs, the organic polymer insulating coating is gradually eroded by electricity, the insulating layer becomes thin, and finally leads to insulation failure.

[0003] At a certain voltage, an insulation coating with low partial discharge inception voltage (PDIV) is prone to partial discharge, which often leads to insulation failure. Therefore, the insulation coating needs high PDIV (for example, according to the requirements of GBT 22720.1-2008, the phase-to-phase PDIV is greater than 2 times the voltage value) to avoid partial discharge at the rated voltage. The PDIV of the insulation coating is usually determined by the dielectric constant of the polymer material constituting the insulation coating and the thickness of the insulation coating, and the PDIV can be increased by reducing the relative dielectric constant of the polymer insulation material and / or increasing the coating thickness. On the one hand, the thickest flat wire film on the market has reached 350μm, but its PDIV still cannot meet the requirements of end customers. On the other hand, there are usually the following methods to reduce the relative dielectric constant of the polymer insulation material: (1) adding fluorine-containing monomers or diamondoid derivative monomers, such as the fluorine-containing monomers disclosed in US2015238072, but generally the cost of such monomers is too high to be widely used in the enameled wire industry. (2) Adding low relative dielectric constant material fillers (Xu, Liu Z J. Research progress of new low relative dielectric constant materials [J]. Micro-nano electronic technology, 2003) to reduce the relative dielectric constant of the whole system, but generally a large amount of fillers need to be added, and there are problems such as poor compatibility between fillers and resin, poor adhesion of paint film, and poor heat resistance. (3) Adding a foaming agent in the polymer material to form bubbles, and the relative dielectric constant of the gas is very low, which can reduce the relative dielectric constant of the paint film and improve the PDIV performance (Carter K R, Dolden J G, Hawker C J, et al. Progress in Polyimide Chemistry II [M]. Springer, 2003). In polyimide, add high molecular materials such as acrylate which is easy to decompose, and form a honeycomb-like porous material by high-temperature decomposition foaming method, with a decomposition temperature as high as 350℃ or above. However, when this material is applied to the preparation of enameled wire, due to the limitation of enameled process conditions, the surface temperature of the enameled wire is much lower than the complete decomposition temperature of the acrylate-based high molecular material in each coating, and it cannot be produced under normal process conditions. Japanese patent JP6306220B2 uses polymethyl methacrylate (PMMA) and silicone to prepare hollow microspheres to form a bubble material, but the preparation process of such hollow microspheres is complex. US9142334 molds a thermoplastic resin into an electromagnetic wire, then alternately stacks and winds the electromagnetic wire with a partition plate on a bobbin to form a roll, maintains the obtained roll in a pressurized inert gas (such as CO2) atmosphere to introduce the inert gas into the roll, and then further heats the roll to the softening temperature of the thermoplastic resin or higher under normal pressure to foam the resin, but the above process is too complex and requires high-pressure equipment, which cannot be mass-produced.In addition, there are also phthalate foaming agents such as dibutyl phthalate (DBP) to foam the polyimide polymer film (Morphology and properties of porous polyimide films prepared through thermally induced phase separation[J]. Rsc Advances, 2015. and A new route of fabricating porous polyimide membranes[J]. Journal of Minerals, Metallurgy and Materials, 2010. and Chinese patent CN114716858A), but phthalate foaming agents are confirmed to interfere with human endocrine, affect the reproductive system, and cause various diseases. The European Chemicals Agency (ECHA) classifies phthalate foaming agents such as DBP, di(2-ethylhexyl) phthalate (DEHP), and butyl benzyl phthalate (BBP) as CMR (carcinogenic, mutagenic, and reproductive toxic) substances. Chinese patents CN1914262A and CN114716858A use foaming agents to chemically react at high temperatures to decompose into gaseous products, thereby forming pores in the cured thermosetting polymer film, but due to the large temperature difference between the inner and outer layers, the decomposition rate of the foaming agent is large, resulting in different pore sizes, and the appearance of the polymer film will have defects such as warts or large bubbles, which is not suitable for use in insulating paint.

[0004] Therefore, it is urgent to develop an insulating paint that can produce a polymer insulating layer containing bubbles after curing, without using toxic foaming agents, and the preparation process of the insulating layer containing bubbles is simple, without using high-pressure equipment, and the prepared paint film will not have defects such as warts or large bubbles. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides an insulating paint with high partial discharge inception voltage and a preparation method and application thereof. The insulating paint provided by the present application does not contain toxic foaming agents, is coated on a device, and can produce a polymer insulating layer containing a bubble layer after curing, with high PDIV (compared with the same resin, the highest can be increased by more than 15%), simple preparation process, without using high-pressure equipment, and the prepared paint film will not have defects such as warts or large bubbles, with less than 0.1% of particle percentage in HVC data in line particle detection.

[0006] The first aspect of the present application provides an insulating paint with high partial discharge inception voltage.

[0007] Specifically, an insulating paint with high partial discharge inception voltage comprises a base resin and a blowing agent, wherein the blowing agent comprises at least one of long-chain alkyl citrate blowing agent, long-chain alkyl terephthalate blowing agent, and long-chain alkyl long-chain alkyl dibasic fatty acid ester blowing agent.

[0008] The blowing agent with long carbon chain structure is selected in the present application. When the insulating paint of the present application is coated, the long chain of the blowing agent is disentangled and inserted between the polymer molecules of the base resin during the heating and curing process, which weakens the attraction between the polymer molecules of the base resin and increases the mobility of the polymer molecular chain. The plasticity of the polymer is increased. In the later curing stage, the polymer chain segment movement is limited due to the partial residual of the blowing agent in the insulating paint. After further strengthening baking, the blowing agent of the present application slowly evaporates from the film, and the insulating paint film restores the original space of the blowing agent droplets after passing through the cooling channel, and an insulating paint film containing pores is obtained.

[0009] The partial discharge inception voltage is the lowest voltage at which the partial discharge exceeds a certain specified value observed from the test device during voltage rising. With the continuous increase of system voltage, the partial discharge of the motor under working voltage is an important reason for the aging and development of insulation to breakdown. According to the requirement of GBT 22720.1-2008, the interphase PDIV is greater than or equal to 2 times the voltage value. In order to prevent partial discharge from occurring at the rated voltage.

[0010] Preferably, the boiling point of the blowing agent is 250-400℃, and / or the thermal decomposition temperature of the blowing agent is greater than or equal to 300℃. The blowing agent selected in the present application has the characteristics of high temperature resistance and is not easy to be decomposed during the curing process of the insulating paint.

[0011] Further preferably, the boiling point of the blowing agent is 294-400℃, and / or the thermal decomposition temperature of the blowing agent is 300-360℃.

[0012] Preferably, the mass of the blowing agent accounts for 4%-40% of the total mass of the insulating paint.

[0013] Further preferably, the mass of the blowing agent accounts for 5%-30% of the total mass of the insulating paint.

[0014] Preferably, the long-chain alkyl citrate blowing agent has the molecular structure shown in the following formula (I):

[0015]

[0016] wherein R1 is one of hydrogen atom, acetyl group and butyryl group, and R2-R4 are independently selected from C4-C6 aliphatic hydrocarbon group.

[0017] Further preferably, the long-chain alkyl citrate foaming agent is at least one of triethyl citrate (TEC), acetyl triethyl citrate (ATEC), tripropyl citrate (TPC), n-tri-butyl citrate (TBC), acetyl n-tri-butyl citrate (ATBC), acetyl tri-n-hexyl citrate (ATHC), butyryl tri-n-hexyl citrate (BTHC).

[0018] Preferably, the long-chain alkyl phthalate foaming agent has a molecular structure as shown in the following formula (II):

[0019]

[0020] wherein R5-R6 are independently selected from C4-C6 aliphatic hydrocarbon group or C4-C6 hydrocarbon group hydroxyl.

[0021] Further preferably, the long-chain alkyl phthalate foaming agent is at least one of dioctyl phthalate (DOTP), diethyl phthalate (DEP), di(2-propylheptyl) phthalate (DPHTP), bis(2-hydroxyethyl) phthalate (BHET).

[0022] Preferably, the long-chain alkyl dibasic fatty acid ester foaming agent has a molecular structure as shown in the following formula (III):

[0023]

[0024] wherein R7 is C4-C10 aliphatic hydrocarbon group, and R8-R9 are independently selected from C2-C8 aliphatic hydrocarbon group.

[0025] Further preferably, the long-chain alkyl dibasic fatty acid ester foaming agent is at least one of dioctyl sebacate (DOS), dibutyl sebacate (DBS), dioctyl azelate (DOZ), dioctyl adipate (DOA), dibutyl adipate (DBA).

[0026] Preferably, the base resin comprises at least one of polyimide (PI), polyamide-imide (PAI), polyester, polyester-imide.

[0027] The second aspect of the present application provides a preparation method of the insulating paint with high partial discharge inception voltage.

[0028] The preparation method of the insulating paint with high partial discharge inception voltage comprises the following steps:

[0029] Mixing the base resin and the foaming agent to obtain the insulating paint.

[0030] The third aspect of the present application provides an application of the insulating paint with high partial discharge inception voltage.

[0031] Use of an insulating paint with high partial discharge inception voltage in insulating materials, electronic devices.

[0032] A bubble-containing polymer insulating layer coated insulating device is prepared by using the insulating paint.

[0033] Preferably, the bubble-containing polymer insulating layer coated insulating device is prepared by coating the insulating paint on a device substrate and curing.

[0034] Preferably, the curing temperature is 400-600℃.

[0035] Further preferably, the curing temperature is 530-600℃.

[0036] Preferably, the device substrate is made of copper or aluminum.

[0037] Preferably, the device is an electromagnetic wire.

[0038] Compared with the prior art, the present application has the following advantages:

[0039] By using at least one of long-chain alkyl citrate foaming agent, long-chain alkyl terephthalate foaming agent, long-chain alkyl dibasic fatty acid ester foaming agent as a foaming agent added to the matrix resin, the obtained insulating paint can obtain a bubble-containing polymer insulating layer after coating and curing, which contains a large number of pore structures, has high PDIV, does not need to use toxic foaming agent, and does not need to use high-pressure equipment, and has high safety. The preparation process of the bubble-containing polymer insulating layer of the present application is simple and easy to operate, and the prepared paint film will not produce defects such as paint tumor or large bubbles, the in-line particle detection HVC data is less than 0.1%, and is consistent with the conventional insulating paint production process. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Scanning electron microscope (SEM) of the bubble-containing polymer insulating layer prepared for Example 6 of the present application. DETAILED DESCRIPTION

[0041] In order to make those skilled in the art more clearly understand the technical solutions described in the present application, the following examples are listed for illustration. It should be pointed out that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0042] The raw materials, reagents or devices used in the following examples, unless otherwise specified, can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0043] Example 1

[0044] An insulating paint with high partial discharge inception voltage, comprising a base resin PAI and long-chain alkyl citrate foaming agent TBC. The specific components and amounts are shown in Table 1.

[0045] The preparation method of the above-mentioned insulating paint with high partial discharge inception voltage, comprising the following steps:

[0046] In 950g of polyamide-imide PAI, 50g of TBC is added, stirred thoroughly, and deaerated by standing to obtain an insulating paint, which is clear and transparent without turbidity and stratification.

[0047] Example 2

[0048] An insulating paint with high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0049] In 900g of polyamide-imide PAI, 100g of TBC is added, stirred thoroughly, and deaerated by standing to obtain an insulating paint, which is clear and transparent without turbidity and stratification.

[0050] Example 3

[0051] An insulating paint with high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0052] In 910g of polyamide-imide PAI, 90g of TEC is added, stirred thoroughly, and deaerated by standing to obtain an insulating paint, which is clear and transparent without turbidity and stratification.

[0053] Example 4

[0054] An insulating paint with high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0055] In 800g of polyamide-imide PAI, 200g of ATBC is added, stirred thoroughly, and deaerated by standing to obtain an insulating paint, which is clear and transparent without turbidity and stratification.

[0056] Example 5

[0057] An insulating paint with high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0058] In 950g of polyamide-imide PI, 50g of TBC is added, stirred thoroughly, and deaerated by standing to obtain an insulating paint, which is clear and transparent without turbidity and stratification.

[0059] Example 6

[0060] An insulating paint with high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0061] In 900 g of polyimide PI, 100 g of DOTP is added, stirred thoroughly, and left to stand to remove bubbles to obtain an insulating paint, which is clear and transparent in state without turbidity and stratification.

[0062] Example 7

[0063] An insulating paint with a high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0064] In 800 g of polyimide PI, 200 g of TBC is added, stirred thoroughly, and left to stand to remove bubbles to obtain an insulating paint, which is clear and transparent in state without turbidity and stratification.

[0065] Example 8

[0066] An insulating paint with a high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0067] In 700 g of polyimide PI, 300 g of ATBC is added, stirred thoroughly, and left to stand to remove bubbles to obtain an insulating paint, which is clear and transparent in state without turbidity and stratification.

[0068] Example 9

[0069] An insulating paint with a high partial discharge inception voltage, the specific components and amounts are shown in Table 1, and the preparation method comprises the following steps:

[0070] In 800 g of polyimide PI, 200 g of DBA is added, stirred thoroughly, and left to stand to remove bubbles to obtain an insulating paint, which is clear and transparent in state without turbidity and stratification.

[0071] Comparative Example 1

[0072] This comparative example provides a polyamide-imide PAI, TONGMID 595 / 36MB (Alliant) insulating paint.

[0073] Comparative Example 2

[0074] This comparative example provides a polyimide PI, TONGTHERM 537 / 30 (Alliant) insulating paint.

[0075] Comparative Example 3

[0076] This comparative example provides an insulating paint, which is different from Example 3 in that TEC is replaced by an equal amount of DBP, and the preparation method is as follows:

[0077] In 910 g of polyamide-imide PAI, 90 g of DBP is added, stirred thoroughly, and left to stand to remove bubbles to obtain an insulating paint, which is clear and transparent in state without turbidity and stratification.

[0078] Comparative Example 4

[0079] This comparative example provides an insulating paint, which is different from Example 7 in that TBC is replaced by an equal amount of DBP, and the preparation method is as follows:

[0080] In 800 g of polyimide PI, 200 g of DBP is added, stirred thoroughly, and deaerated by standing, to obtain an insulating paint, which is clear and transparent in state, without turbidity and stratification phenomenon.

[0081] Application Example

[0082] The insulating paint prepared in each of the above examples and comparative examples is respectively coated on a 0.70 mm enameled round copper wire, and then cured, with a curing oven temperature of 530°C and a vehicle speed of 13 m / min, to obtain a paint film with a film thickness of 60 μm.

[0083] Product Effect Test

[0084] The paint film obtained in the above application example is subjected to performance test, and the test method is as follows:

[0085] 1. Average bubble pore size

[0086] The average bubble diameter is measured from the scanning electron microscope (SEM) photograph of the cross section of the enameled wire. The SEM graph of the insulating layer prepared by the present application is shown in FIG. 1, from which it can be seen that the coating contains a large number of hole structures, and the bubble pore size is shown in Table 1. Figure 1

[0087] 2. Breakdown voltage

[0088] Tested according to the test method of standard IEC 60851-5.

[0089] 3. Partial discharge inception voltage (PDIV)

[0090] The peak-to-peak voltage (Vpp) above 100 pc of discharge is measured as the partial discharge inception voltage, with a sine wave, 50 Hz, and a voltage rise rate of 10 v / s.

[0091] 4. Wire particle detection

[0092] The particle size and particle percentage are detected by dynamic analysis using the online detection equipment, Lear Fusion system of New Material Science Technology (Shanghai) Co., Ltd.

[0093] The components and contents of the insulating paint of each of the examples and comparative examples, and the corresponding performance test results are shown in Table 1.

[0094] Table 1 Components and contents of each example and comparative example, and performance test results

[0095] ​

[0096] From the results of the above table, the paint film prepared by examples 1-9 has high PDIV, not less than 803V, even up to 1029V, and the particle percentage is less than 0.1%, indicating that the prepared paint film will not produce paint tumor or air bubble defects. Among them, examples 1-4, using PAI as the base paint, the PDIV is between 803-887V, higher than the PDIV (759V) of comparative example 1. Examples 5-9, using PI as the base paint, the PDIV is between 990-1029V, higher than the PDIV (889V) of comparative example 2; and the foaming agent used in the present application is safe, and does not involve the use of high-pressure equipment.

[0097] The two kinds of insulating paint provided by comparative example 1 and comparative example 2 have low PDIV due to the absence of foaming agent.

[0098] Comparative example 3 and example 3, because comparative example 3 replaces TEC with DBP, resulting in a decrease in PDIV, and DBP is toxic and has low safety.

[0099] Comparative example 4 and example 7, because comparative example 4 replaces TBC with DBP, resulting in a decrease in PDIV, and DBP is toxic and has low safety.

Claims

1. A type of enameled insulating device with a bubble-containing polymer insulating layer, characterized in that, The enameled insulating device with a bubble-containing polymer insulating layer is made by coating a device substrate with an insulating varnish with a high partial discharge initiation voltage and then curing it. The curing temperature is 400-600℃; The insulating varnish with high partial discharge initiation voltage includes a base resin and a foaming agent, wherein the foaming agent includes at least one of long-chain alkyl citrate foaming agents, long-chain alkyl terephthalate foaming agents, and long-chain alkyl dicarboxylic acid ester foaming agents. The long-chain alkyl citrate foaming agent has the molecular structure shown in formula (Ⅰ): R1 is one of hydrogen atom, acetyl group, and butyryl group, and R2-R4 are independently selected from C4-C6 aliphatic hydrocarbon groups; The long-chain alkyl terephthalate foaming agent has the molecular structure shown in formula (II): R5-R6 are each independently selected from C4-C6 aliphatic hydrocarbon groups or C4-C6 hydrocarbon hydroxyl groups; The long-chain alkyl dicarboxylic acid ester foaming agent has the molecular structure shown in formula (Ⅲ): Among them, R7 is a C4-C10 aliphatic hydrocarbon group, and R8-R9 are independently selected from C2-C8 aliphatic hydrocarbon groups.

2. The enameled insulating device according to claim 1, characterized in that, The foaming agent has a boiling point of 250-400℃ and a thermal decomposition temperature of 300℃ or higher.

3. The enameled insulating device according to claim 1, characterized in that, The foaming agent accounts for 4%-40% of the total mass of the insulating varnish.

4. The enameled insulating device according to claim 1, characterized in that, The matrix resin includes at least one of polyimide, polyamide-imide, polyester, and polyesterimide.

5. The enameled insulating device according to any one of claims 1-4, characterized in that, The method for preparing the insulating varnish with high partial discharge initiation voltage includes the following steps: The matrix resin and the foaming agent are mixed to obtain the insulating varnish with high partial discharge initiation voltage.

Images