Modified inorganic filler and preparation method thereof, polyimide wire enamel and preparation method thereof, and enameled wire

Abstract

The invention discloses a modified inorganic filler, which comprises an inorganic filler core and a coating layer coated outside the inorganic filler core, the surface of the inorganic filler core is subjected to graft modification by mercaptoethanol and dodecyl trimethoxysilane, the coating layer comprises a titanium dioxide layer and a polymethyl methacrylate layer; the titanium dioxide layer is coated outside the inorganic filler core; the polymethyl methacrylate layer is grafted outside the titanium dioxide layer. The invention also provides a preparation method of the modified inorganic filler, polyimide wire enamel and a preparation method thereof, and an enameled wire. According to the invention, a modified inorganic filler with a three-layer core-shell structure is designed, and a spherical inorganic filler core is used as a core, so that high doping amount and high corona resistance effect of a filler system in wire enamel are ensured; the introduction of the intermediate TiO2 layer and the introduction of the PMMA outer layer cooperate with the inorganic filler core, so that the corona resistance is improved.

Claims

1. A modified inorganic filler, comprising an inorganic filler core and a coating layer coated outside the inorganic filler core, characterized in that, The surface of the inorganic filler core is graft-modified with mercaptoethanol and dodecyltrimethoxysilane. The coating layer includes a titanium dioxide layer coated outside the inorganic filler core and a polymethyl methacrylate layer grafted outside the titanium dioxide layer.

2. The modified inorganic filler according to claim 1, wherein, The inorganic filler core includes one or more of spherical alumina, spherical silica, spherical glass microbeads, and spherical zirconia. The particle size of the inorganic filler core does not exceed 3 microns, the thickness of the titanium dioxide layer does not exceed 2 microns, and the thickness of the polymethyl methacrylate layer does not exceed 1 micron.

3. A method for preparing a modified inorganic filler as described in claim 1 or 2, characterized in that, It includes the following steps: (1) Disperse the inorganic filler core in a solvent, and slowly dropwise add mercaptoethanol and dodecyltrimethoxysilane respectively and stir to react to obtain a bifunctional group-modified inorganic filler core; (2) Disperse the above bifunctional group-modified inorganic filler core in a solvent, add tetrabutyl titanate and water, adjust the pH value and stir to react, and obtain a bifunctional group-modified inorganic filler core with a titanium dioxide layer coated on the surface through the sol-gel method; (3) Uniformly disperse the above bifunctional group-modified inorganic filler core with a titanium dioxide layer coated on the surface in a solution containing methyl methacrylate monomer and initiator, stir to react, and in-situ polymerize to obtain the modified inorganic filler.

4. The preparation method according to claim 3, characterized in that, In step (1), the solvent is an ethanol-water mixed solvent, and the volume ratio of ethanol to water is (3 - 10):

1. The mass ratio of mercaptoethanol to the inorganic filler core is (1.5 - 5):1, and the mass ratio of dodecyltrimethoxysilane to the inorganic filler core is (1 - 5):

1. First, dropwise add mercaptoethanol, stir and react at 50 - 80 °C for 1 - 3 h, then dropwise add dodecyltrimethoxysilane and stir to react. The reaction temperature during stirring is 60 - 85 °C, and the reaction time is 4 - 8 h.

5. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of tetrabutyl titanate to the inorganic filler core is (3 - 10):1, and the mass ratio of water to tetrabutyl titanate is 1:(1 - 3). The pH value during adjusting the pH value and stirring to react is 1 - 5, the reaction temperature is 50 - 80 °C, and the reaction time is 2 - 4 h.

6. The preparation method according to claim 3, characterized in that, In step (3), the mass ratio of methyl methacrylate monomer to the titanium dioxide layer is (10 - 100):1, and the mass ratio of the initiator to the titanium dioxide layer is 1:(1 - 10). The initiator includes one or more of azobisisobutyronitrile, benzoyl peroxide, and methyl ethyl ketone peroxide. The reaction temperature of the stirring reaction is 50 - 90 °C, and the reaction time is 4 - 10 h.

7. A polyimide enamel wire paint, characterized in that, It includes the following components in parts by weight: 10 - 50 parts of polyamic acid; 10 - 50 parts of modified inorganic filler; 50 - 90 parts of solvent; The modified inorganic filler is the modified inorganic filler described in claim 1 or 2 or the modified inorganic filler prepared by the preparation method described in any one of claims 3 - 6. The solvent includes one or more of DMAc, DMF, and NMP. The viscosity of the polyimide enameled wire paint is 100 - 10000 cP, and the solid content is 10 - 50%.

8. A method for preparing the polyimide enameled wire paint according to claim 7, characterized in that, It includes the following steps: adding the modified inorganic filler into a solvent, dispersing it evenly, then adding a diamine monomer, and then adding a dianhydride monomer in batches for reaction, and defoaming under vacuum to obtain the polyimide enameled wire paint.

9. The preparation method according to claim 8, wherein The diamine monomer includes one or more of 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane, 3,4'-diaminodiphenyl methane, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 4,4'-diaminodiphenyl sulfone, and 4,4'-diaminobenzophenone; the dianhydride monomer includes one or more of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, bisphenol A type diether dianhydride, 4,4'-biphenyl ether dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 1,2,4,5-cyclohexanetetracarboxylic dianhydride; the molar ratio of the diamine monomer to the dianhydride monomer is 1:(0.9 - 1.1).

10. An enameled wire, characterized in that, It is obtained by curing the polyimide enameled wire paint described in claim 7 or the polyimide enameled wire paint prepared by the preparation method described in claim 8 or 9.

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