Liquid crystal polymer paint for enameled wire and enameled wire

Abstract

The present invention belongs to the technical field of enameled wires, and particularly relates to a liquid crystal polymer paint for enameled wires and an enameled wire. The liquid crystal polymer paint for enameled wires comprises a modified LCP and a diluent, the diluent being DMF or DMAC, and the modified LCP is obtained by a condensation polymerization reaction of a monomer, acetic anhydride and a modified monomer, and the modified monomer is glycerol or trimellitic anhydride. The enameled wire comprises a flat copper wire, a primer coated on the surface of the flat copper wire, and a topcoat coated on the surface of the primer, the primer being a liquid crystal polymer paint for enameled wires modified with trimellitic anhydride, and the topcoat being a liquid crystal polymer paint for enameled wires modified with glycerol. The technical solution provided by the present invention, through graft modification of LPC, enables it to be dissolved in a solvent, so that it can be used as a paint, especially as an enameled wire, having the advantages of oil resistance, high temperature resistance, stable electrical properties, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of enameled wires, and in particular relates to a liquid crystal polymer paint for enameled wires and the enameled wires. Background Art

[0002] The motors of new energy electric vehicles are gradually developing towards lightweight and miniaturization, which requires optimization of motor windings, etc. After optimization, the heat dissipation method in the existing solution is no longer applicable, so oil cooling with better cooling effect is required.

[0003] At present, the materials of enameled flat wires used for windings are generally polyimide, polyamide-imide, etc. If the enameled wires made of such materials are exposed to oil for a long time, their corona resistance and PDIV value will decrease, and the paint layer will easily become brittle and fall off, greatly shortening their service life and failing to meet the requirements of oil-cooling conditions.

[0004] In order to prepare enameled wire that can be used in oil cooling conditions, researchers generally use a variety of methods to solve the problem.

[0005] For example, Chinese patent CN111627618 provides an enameled wire for automotive oil-cooled drive motors, which is coated with a combination of three different types of insulating paints, specifically high-adhesion polyamide-imide paint, corona-resistant polyimide paint, and oil-resistant and hydrolysis-resistant polyamide-imide paint.

[0006] Chinese patent CN111508639 provides an ATF oil-resistant and corona-resistant enameled wire with 5 layers of coating, specifically pit-resistant oil-resistant corona-resistant protective coating, corona-resistant polyamide-imide coating, oil-resistant corona-resistant protective coating, corona-resistant polyamide-imide coating and oil-resistant corona-resistant protective coating. The prepared enameled wire was immersed in ATF oil and subjected to 8 cycles of switching cycles between 155°C and -45°C, and no significant changes were observed in various properties.

[0007] The current methods are inseparable from the original main material, so its oil resistance cannot produce qualitative changes. The multi-layer structure is complex and difficult to process. The most critical thing is that since the main material has not changed, no matter how the composite modification is carried out, its heat resistance will be limited. Therefore, the amount of oil used as a heat dissipation medium is bound to be large, which will limit the reduction of the motor size.

[0008] Liquid crystal polymer (LCP) is a kind of liquid crystal polymer composed of rigid molecular chains, with the fluidity of the liquid crystal state and the physical properties of crystals. Liquid crystal polymers have high strength and high modulus mechanical properties, and excellent electrical insulation properties. As electrical application parts, when continuously used at a temperature of 200 - 300 °C, their electrical properties are not affected. The melt viscosity of LCP is low and the fluidity is good. It will not be dissolved and will not cause stress cracking after contacting with common solvents, fuel oils, detergents and hot water. If its unique properties can be used as the paint for enameled wires, it can perfectly solve the current problems such as the material not being oil-resistant, the continuous use temperature not being high enough, and the insufficient strength. However, there is a key obstacle to using LCP as a paint, that is, it is difficult to dissolve in solvents and cannot be constructed. Summary of the Invention

[0009] The present invention provides a liquid crystal polymer paint for enameled wires and an enameled wire, aiming to solve the problem that current LCP is difficult to dissolve in solvents and cannot be used as the paint for enameled wires.

[0010] To solve the above technical problems, the technical solution of the present invention is: the liquid crystal polymer paint for enameled wires includes modified LCP and a diluent. The diluent is DMF (N,N-dimethylformamide) or DMAC (dimethylacetamide). The modified LCP is obtained by condensation polymerization of monomers, acetic anhydride and modified monomers. The modified monomers are glycerol or trimellitic anhydride.

[0011] Due to the addition of modified monomers, hydroxyl groups and carboxyl groups are branched out on the main chain of the synthesized LCP, so that the synthesized LCP can be dissolved in polar solvents, making it possible to be used as a paint.

[0012] Optionally, the monomers are selected from at least two condensable monomers among p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, hydroquinone, 2,6-naphthalenediol, terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid.

[0013] Optionally, in 100 parts by molar amount of the total of the monomers and modified monomers, it includes 50 - 60 parts of p-hydroxybenzoic acid, 20 - 30 parts of 2-hydroxy-6-naphthoic acid, 5 - 10 parts of hydroquinone and / or glycerol, and 5 - 10 parts of terephthalic acid and / or trimellitic anhydride.

[0014] Optionally, the preparation method of the modified LCP includes the following steps: putting the monomers, modified monomers and acetic anhydride into a reaction kettle, heating up for reaction until the hydroxyacylation is completed, and then evacuating and continuing to heat up for polycondensation reaction.

[0015] Optionally, the weight-average molecular weight of the modified LCP is controlled at 25000 - 75000.

[0016] Optionally, the liquid crystal polymer paint for enameled wire has a viscosity of 1000 - 3000 cps at 23 ± 2°C.

[0017] Optionally, the solid content (150°C, 2h, %) of the liquid crystal polymer paint for enameled wire is controlled at 20 ± 5.

[0018] The present invention also provides an enameled wire, which includes a copper flat wire, a primer coated on the surface of the copper flat wire, and a topcoat coated on the surface of the primer. The primer is a trimellitic anhydride - modified liquid crystal polymer paint for enameled wire, and the topcoat is a glycerol - modified liquid crystal polymer paint for enameled wire.

[0019] Optionally, the terminal carboxyl group content in the primer is 900 - 1200 ppm.

[0020] Optionally, the terminal hydroxyl group content in the topcoat is 150 - 300 ppm.

[0021] The technical solution provided by the present invention, through graft modification of LPC, enables it to be dissolved in a solvent, and thus can be used as a paint material, especially as an enameled wire, which has the advantages of oil - resistance, high - temperature resistance, and stable electrical performance. Detailed Embodiments

[0022] For ease of understanding, the liquid crystal polymer paint for enameled wire and the enameled wire are described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0023] The reagents used in this embodiment are all commercially available products unless otherwise specified, and the production processes adopted in this embodiment are all carried out using existing process procedures unless otherwise specified.

[0024] Example 1: Glycerol - modified LCP

[0025] The modified LCP is obtained by condensation polymerization of monomers, acetic anhydride, and a modifying monomer. The modifying monomer is glycerol. The monomers, modifying monomer, catalyst, and acetic anhydride are put into a reaction kettle, and the temperature is raised for reaction until hydroxyacylation is completed, and then the vacuum is pumped and the temperature is further raised for polycondensation reaction. In this embodiment, the catalyst is sodium acetate.

[0026] The components of Examples 1 - 3 are shown in Table 1 in terms of molar ratio.

[0027] Table 1

[0028] p-Hydroxybenzoic acid (parts) 2-Hydroxy-6-naphthoic acid (parts) Glycerol (parts) Hydroquinone (parts) Terephthalic acid (parts) Example 1 60 25 1 5 10 Example 2 50 30 2 5.5 7.5 Example 3 55 20 1 8 7.5

[0029] The dosage of acetic anhydride is 1.2 times the molar amount of acylation reaction, and the weight - average molecular weight of the synthesized modified LCP is 30000 - 60000.

[0030] Examples 4 - 6: Trimellitic Anhydride Modified LCP

[0031] The modified LCP is obtained by condensation polymerization of monomers, acetic anhydride and modified monomers, and the modified monomer is trimellitic anhydride. The monomers, modified monomers, catalyst and acetic anhydride are put into a reaction kettle, and the temperature is raised for reaction until hydroxyacylation is completed, and then the vacuum is pumped and the temperature is further raised for polycondensation reaction. In this example, the catalyst is sodium acetate.

[0032] The components of Examples 4 - 6 are shown in Table 2 according to the molar ratio.

[0033] Table 2

[0034] p-Hydroxybenzoic acid (parts) 2-Hydroxy-6-naphthoic acid (parts) Hydroquinone (parts) Trimellitic anhydride (parts) Terephthalic acid (parts) Example 4 60 20 7.5 7 2 Example 5 50 30 10 5 2 Example 6 55 25 6 9 1

[0035] The dosage of acetic anhydride is 1.2 times the molar amount of acylation reaction, and the weight - average molecular weight of the synthesized modified LCP is in the range of 42000 - 73000.

[0036] Examples 7 and 8: Enameled Wire

[0037] The production process of the enameled wire is as follows:

[0038] Preparation of topcoat: Dilute the modified LCP prepared in Examples 1 - 3 with DMAC, and the solid content (%) at 150 °C for 2 h is 20 ± 5. The content of terminal hydroxyl groups in the topcoat is 150 - 280 ppm, and at 23 ± 2 °C, the viscosity is 1000 - 1800 cps.

[0039] Preparation of primer: Dilute the modified LCP prepared in Examples 4 - 6 with DMAC, so that the solid content (%) at 150 °C for 2 h is 20 ± 5. The content of terminal carboxyl groups in the primer is 900 - 1200 ppm, and at 23 ± 2 °C, the viscosity is 2000 - 3000 cps.

[0040] Annealing: Anneal the flat copper wire in an annealing furnace to remove stress and soften the copper wire;

[0041] Painting: Uniformly coat the primer prepared in Example 5 (for Example 7) or Example 4 (for Example 8) on the surface of the wire, and then bake and cure; then, coat the topcoat prepared in Example 1 (for Example 7) or Example 3 (for Example 8), and conduct baking and curing;

[0042] Cooling and winding: After natural cooling, the winding machine winds the wire.

[0043] Comparative Example 1: Yingtong Wire YG180 - DD20

[0044] Comparative experiment:

[0045] For Examples 7 and 8 and Comparative Example 1, the following performance tests were conducted on the enameled wire paint, and the test results are shown in Table 3.

[0046] Table 3

[0047]

[0048] Oil immersion and high-temperature resistance test

[0049] Examples 7 and 8 were immersed in transmission oil (ATF oil). The temperature ranged from -40 to 155 °C, with 8 hours as one cycle. After 8 cycles, the mechanical and electrical properties were tested, and the test results are shown in Table 4.

[0050] Examples 7 and 8 were immersed in transmission oil (ATF oil). The temperature ranged from -40 to 155 °C, with 8 hours as one cycle. After 8 cycles, the mechanical and electrical properties were tested, and the test results are shown in Table 4.

[0051] Table 4

[0052]

[0053] It can be found that after the oil immersion experiment, there are no obvious changes in the mechanical and electrical properties.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An enameled wire, characterized in that, It includes copper rectangular wire, a primer coated on the surface of the copper rectangular wire, and a topcoat coated on the surface of the primer. The primer is a liquid crystal polymer paint for enameled wire, and the topcoat is a liquid crystal polymer paint for enameled wire; The liquid crystal polymer paint for enameled wire includes modified LCP and a diluent. The diluent is DMF or DMAC, and the modified LCP is obtained by condensation polymerization of monomers, acetic anhydride, and a modifying monomer; When the liquid crystal polymer paint for enameled wire is the primer, the modifying monomer is trimellitic anhydride; When the liquid crystal polymer paint for enameled wire is the topcoat, the modifying monomer is glycerol; The terminal carboxyl group content in the primer is 900 - 1200 ppm; The terminal hydroxyl group content in the topcoat is 150 - 300 ppm.

2. The enameled wire according to claim 1, characterized in that The monomers are selected from at least two condensable polymerizable monomers among p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, hydroquinone, 2,6-naphthalenediol, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid.

3. The enameled wire according to claim 2, characterized in that, The total of the monomers and the modifying monomer includes 50 - 60 parts of p-hydroxybenzoic acid, 20 - 30 parts of 2-hydroxy-6-naphthoic acid, 5 - 10 parts of hydroquinone or a composition of hydroquinone and glycerol, and 5 - 10 parts of trimellitic anhydride or a composition of trimellitic anhydride and terephthalic acid per 100 parts by molar amount.

4. The enameled wire according to claim 1, wherein The preparation method of the modified LCP includes the following steps: Put the monomers, the modifying monomer, and acetic anhydride into a reaction kettle, raise the temperature for reaction until hydroxyacylation is completed, and then evacuate and continue to raise the temperature for polycondensation reaction.

5. The enameled wire according to claim 1, characterized in that, The weight-average molecular weight of the modified LCP is controlled at 25000 - 75000.

6. The enameled wire according to claim 1, wherein The liquid crystal polymer paint for enameled wire has a viscosity of 1000 - 3000 cps at 23 ± 2 °C.

7. The enameled wire according to claim 1, wherein The solid content of the liquid crystal polymer paint for enameled wire is controlled at 20 ± 5% at 150 °C for 2 h.

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