Corona-resistant N-grade insulation paper for variable frequency motor and preparation method thereof

Patent metadata

Field	Value
Publication number	US-12110638-B1
Application number	US-202418424253-A
Country	US
Kind code	B1
Filing date	Jan 26, 2024
Priority date	Sep 11, 2023
Publication date	Oct 8, 2024
Grant date	Oct 8, 2024

Abstract

Disclosed are a corona-resistant N-grade insulation paper for a variable frequency motor and a preparation method thereof. The insulation paper has a sandwich structure, aramid nanofibers and mica nanosheets are taken as a sandwich material of the sandwich structure, aramid nanofibers and silicon carbide nanowires being taken as upper and lower surface layer materials, and three layers of materials are electrostatically sprayed and thermo-compressed to prepare the insulation paper. According to the present disclosure, by introducing mica sheets and the silicon carbide nanowires into the aramid nanofibers, the highly ordered arrangement inside the sandwich structure is realized through electrostatic spraying, which improves the temperature resistance and corona resistance of the insulation paper.

First claim

The invention claimed is:

1. A corona-resistant N-grade insulation paper for a variable frequency motor, comprising a sandwich structure, wherein
aramid nanofibers and mica nanosheets are taken as a sandwich material of the sandwich structure, aramid nanofibers and silicon carbide nanowires being taken as upper and lower surface layer materials of the sandwich material.

2. The corona-resistant N-grade insulation paper for a variable frequency motor according to claim 1 , wherein the aramid nanofiber has a diameter of 10-50 nm and a length of more than 3 μm, the mica nanosheet has a particle size of 2-10 μm and a thickness of less than 10 nm, and the silicon carbide nanowire has a diameter of 80-500 nm and a length of greater than 5 μm,
the aramid nanofibers being para-aramid nanofibers, and
the mica nanosheets being synthetic mica nanosheets.

3. The corona-resistant N-grade insulation paper for a variable frequency motor according to claim 1 , wherein a mass ratio of the aramid nanofibers to the mica nanosheets is (9-5):(1-5).

4. The corona-resistant N-grade insulation paper for a variable frequency motor according to claim 1 , wherein a mass ratio of the aramid nanofibers to the silicon carbide nanowires is 9:1.

5. A preparation method for a corona-resistant N-grade insulation paper for a variable frequency motor according to claim 1 , comprising the steps of:
1) Taking aramid nanofibers and silicon carbide nanowires as raw materials to prepare a surface layer composite slurry;
2) Taking aramid nanofibers and synthetic mica nanosheets as raw materials to prepare a sandwich composite slurry;
3) Spraying the surface layer composite slurry on a substrate through electrostatic spraying to form a lower surface layer gel;
4) Spraying the sandwich composite slurry on an upper surface of the lower surface layer gel through electrostatic spraying to form a sandwich gel;
5) Spraying the surface layer composite slurry on an upper surface of the sandwich gel again through electrostatic spraying to form an upper surface layer gel;
6) Drying the prepared three-layer gel under vacuum at 50-73° C. for 36-48 h to obtain a sandwich insulation rough paper; and
7) Performing thermo-compression formation on the sandwich insulation rough paper at 20 Mpa at 175-195° C. to obtain the corona-resistant N-grade insulation paper for a variable frequency motor having a sandwich structure.

6. The preparation method according to claim 5 , wherein both the lower surface layer gel and the upper surface layer gel have a thickness of 200 μm-500 μm; and the sandwich gel has a thickness of 500 μm-1000 μm.

7. The preparation method according to claim 5 , wherein the preparation of the surface layer composite slurry comprises the steps of:
adding the aramid nanofibers and the silicon carbide nanowires into 400 mL of deionized water in a mass ratio of 9:1, and uniformly mixing and pulping the same by high-speed shearing at 10000-15000 rpm for 15 min to obtain the surface layer composite slurry.

8. The preparation method according to claim 5 , wherein the preparation of the sandwich composite slurry comprises the steps of:
adding the aramid nanofibers and the mica nanosheets into 400 mL of deionized water in a mass ratio of (9-5):(1-5), and uniformly mixing and pulping the same by high-speed shearing at 10000-25000 rpm for 15 min to obtain the sandwich composite slurry.

9. The preparation method according to claim 5 , wherein the preparation of the aramid nanofibers comprises the steps of:
placing aramid fibres, after being cleaned by acetone and dried, in a low-temperature plasma treatment instrument with a power of 200 W and a vacuum degree of 100 Pa to be treated for 6 min by introducing argon gas with a flow rate of 30 mL/min; and
placing the plasma-treated aramid fibers with potassium hydroxide and dimethyl sulfoxide in a ratio of 1 g: 1.5 g: 500 mL in a sealed container, and stirring mechanically at a rotation speed of 1000 rpm at room temperature for 7 d continuously to obtain aramid nanofibers stably dispersed in a potassium hydroxide/dimethyl sulfoxide system.

10. The preparation method according to claim 5 , wherein the preparation of the mica nanosheets comprises the steps of:
adding synthetic mica and hexadecyl trimethyl ammonium bromide into deionized water to obtain a mica dispersion liquid, a ratio of the synthetic mica, hexadecyl trimethyl ammonium bromide and the deionized water being 10 g: 10 g: 500 ml;
stirring the mica dispersion liquid in a water bath at 80° C. for 2 h to fully dissolve hexadecyl trimethyl ammonium bromide;
sonicating the fully dissolved mica dispersion liquid in the water bath for 6 h, and stripping mica through the ultrasonic cavitation effect and the intercalation assistance of hexadecyl trimethyl ammonium bromide to obtain the mica nanosheets, an ultrasonic power being 300-350 W;
centrifuging the sonicated mica nanosheet dispersion solution and repeatedly washing the same with deionized water to remove residual hexadecyl trimethyl ammonium bromide on surfaces of the mica nanosheets, a centrifugation speed being 4500-5000 rpm; and
drying the obtained solid under vacuum at 80° C. for 12 h to obtain the synthetic mica nanosheets.

Assignees

• Univ Sichuan

Inventors

• Ren Junwen
• Qing Qiuwanyu
• Jia Shenli
• Zhao Lihua
• Wang Zi
• Teng Fuli
• Jiang Guoqing

Classifications

• D21H17/68

  siliceous, e.g. clays · CPC title

• D21F5/18

  Drying webs by hot air · CPC title

• D21H13/38

  siliceous · CPC title

• D21H27/38 Primary

  at least one of the sheets having a fibrous composition differing from that of other sheets · CPC title

• D21F11/00

  Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines · CPC title