Polyamide-imide resin insulating coating material, insulated wire and method of making the same

1. A polyamide-imide resin insulating coating material, comprising:

a polyamide-imide resin obtained by reacting, in a mixed solvent, an isocyanate component comprising (i) 4,4′-diphenylmethane diisocyanate and (ii) an isomer of 4,4′-diphenylmethane diisocyanate other than 4,4′-diphenylmethane diisocyanate, with an acid component comprising a trimellitic anhydride, wherein:

a total compounding ratio, obtained by averaging a compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate component and a compounding ratio of the trimellitic anhydride in the acid component, is in the range of 85 to 98 mol %;

the mixed solvent comprises γ-butyrolactone as a main solvent and at least one nitrogen-containing high boiling point polar solvent selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC); and

an organo-silica sol comprising γ-butyrolactone as a main dispersion solvent of the organo-silica sol;

wherein the organo-silica sol is dispersed in the polyamide-imide resin insulating coating material; and

γ-butyrolactone accounts for 70% by weight or more of the amount of all solvents of the polyamide-imide resin insulating coating material.

2. The polyamide-imide resin insulating coating material according to claim 1 , wherein a silica component of the organo-silica sol accounts for 1 to 100 phr (parts per hundred parts of resin) by weight of a resin component of the polyamide-imide resin insulating coating material.

3. A method of making a polyamide-imide resin insulating coating material, comprising:

reacting an isocyanate component comprising (i) 4,4′-diphenylmethane diisocyanate and (ii) an isomer of 4,4′-diphenylmethane diisocyanate other than 4,4′-diphenylmethane diisocyanate, with an acid component comprising a trimellitic anhydride by using a mixed solvent comprising γ-butyrolactone as a main solvent and at least one nitrogen-containing high boiling point polar solvent selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC) to synthesize the polyamide-imide resin insulating coating material,

wherein a total compounding ratio, obtained by averaging a compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate component and a compounding ratio of the trimellitic anhydride in the acid component, is in the range of 85 to 98 mol %; and

mixing the polyamide-imide resin insulating coating material with an organo-silica sol comprising γ-butyrolactone as a main dispersion solvent, wherein the organo-silica sol is dispersed in the polyamide-imide resin insulating coating material, and γ-butyrolactone accounts for 70% by weight or more of the amount of all solvents of the polyamide-imide resin insulating coating material.

4. The method according to claim 3 , wherein: the acid component comprises 80 mol % or more of trimellitic anhydride and 20 mol % or less of a tetracarboxylic dianhydride.

5. The method according to claim 3 , wherein: the acid component comprises 80 mol % or more of trimellitic anhydride and 20 mol % or less of tricarboxylic acid.

6. A method of making an insulated wire, comprising:

preparing a polyamide-imide resin insulating coating material by reacting an isocyanate component comprising (i) 4,4′-diphenylmethane diisocyanate and (ii) an isomer of 4,4′-diphenylmethane diisocyanate other than 4,4′-diphenylmethane diisocyanate, with an acid component comprising a trimellitic anhydride by using a mixed solvent comprising γ-butyrolactone as a main solvent and at least one nitrogen-containing high boiling point polar solvent selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC) to synthesize the polyamide-imide resin insulating coating material,

wherein a total compounding ratio, obtained by averaging a compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate component and a compounding ratio of the trimellitic anhydride in the acid component, is in the range of 85 to 98 mol %; and

mixing the polyamide-imide resin insulating coating material with an organo-silica sol comprising γ-butyrolactone as a main dispersion solvent, wherein the organo-silica sol is dispersed in the polyamide-imide resin insulating coating material, and γ-butyrolactone accounts for 70% by weight or more of the amount of all solvents of the polyamide-imide resin insulating coating material; and

coating the polyamide-imide resin insulating coating material and the organo-silica sol dispersed in the insulating coating material on a conductor, and then baking the polyamide-imide resin insulating coating material to form a coating film on the conductor.

7. A method of making an insulated wire, comprising:

preparing a polyamide-imide resin insulating coating material by reacting an isocyanate component comprising (i) 4,4′-diphenylmethane diisocyanate and (ii) an isomer of 4,4′-diphenylmethane diisocyanate other than 4,4′-diphenylmethane diisocyanate, with an acid component comprising a trimellitic anhydride by using a mixed solvent comprising γ-butyrolactone as a main solvent and at least one nitrogen-containing high boiling point polar solvent selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAC) to synthesize the polyamide-imide resin insulating coating material,

wherein a total compounding ratio, obtained by averaging a compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate component and a compounding ratio of the trimellitic anhydride in the acid component, is in the range of 85 to 98 mol %;

mixing the polyamide-imide resin insulating coating material with an organo-silica sol comprising γ-butyrolactone as a main dispersion solvent, wherein the organo-silica sol is dispersed in the polyamide-imide resin insulating coating material, and γ-butyrolactone accounts for 70% by weight or more of the amount of all solvents of the polyamide-imide resin insulating coating material;

forming an organic insulation coating layer on the surface of a conductor, and

coating the polyamide-imide resin insulating coating material on the organic insulation coating layer, and then baking the polyamide-imide resin insulating coating material to form a coating film on the organic insulation coating layer.

8. The polyamide-imide resin insulating coating material according to claim 1 , wherein: the compounding ratio of the trimellitic anhydride to the acid component is 80 to 98 mol %.

9. The polyamide-imide resin insulating coating material according to claim 1 , wherein: the compounding ratio of the trimellitic anhydride to the acid component is 80 to 100 mol %.

10. The polyamide-imide resin insulating coating material according to claim 3 , wherein: the organo-silica sol is uniformly dispersed in the polyamide-imide resin insulating coating material.

11. The polyamide-imide resin insulating coating material according to claim 1 , wherein:

the acid component further comprises an acid other than the trimellitic anhydride, the acid other than the trimellitic anhydride is an aromatic tetracarboxylic dianhydride selected from 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, and 4,4′-oxydiphthalic dianhydride; an alicyclic tetracarboxylic dianhydride selected from butanetetracarboxylic dianhydride and 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride; or a tricarboxylic acid selected from trimesic acid and tris-(2-carboxyethyl)isocyanurate.

12. The method according to claim 3 , wherein:

the acid component further comprises an acid other than the trimellitic anhydride, the acid other than the trimellitic anhydride is an aromatic tetracarboxylic dianhydride selected from 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, and 4,4′-oxydiphthalic dianhydride; an alicyclic tetracarboxylic dianhydride selected from butanetetracarboxylic dianhydride and 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride; or a tricarboxylic acid selected from trimesic acid and tris-(2-carboxyethyl)isocyanurate.

13. The method according to claim 6 , wherein:

the acid component further comprises an acid other than the trimellitic anhydride, the acid other than the trimellitic anhydride is an aromatic tetracarboxylic dianhydride selected from 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, and 4,4′-oxydiphthalic dianhydride; an alicyclic tetracarboxylic dianhydride selected from butanetetracarboxylic dianhydride and 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride; or a tricarboxylic acid selected from trimesic acid and tris-(2-carboxyethyl)isocyanurate.

14. The method according to claim 7 , wherein:

the acid component further comprises an acid other than the trimellitic anhydride, the acid other than the trimellitic anhydride is an aromatic tetracarboxylic dianhydride selected from 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride, 3 , 3 ′, 4 , 4 ′-benzophenone tetracarboxylic dianhydride, and 4,4′-oxydiphthalic dianhydride; an alicyclic tetracarboxylic dianhydride selected from butanetetracarboxylic dianhydride and 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylicanhydride; or a tricarboxylic acid selected from trimesic acid and tris-(2-carboxyethyl)isocyanurate.

15. The polyamide-imide resin insulating coating material according to claim 1 , wherein the solvent for the polyamide-imide resin insulating coating material is a mixed solvent comprising 73-88% by weight of said γ-butyrolactone.

16. The method according to claim 3 , wherein the solvent for the polyamide-imide resin insulating coating material is a mixed solvent comprising 73-88% by weight of said γ-butyrolactone.

17. The method according to claim 6 , wherein the solvent for the polyamide-imide resin insulating coating material is a mixed solvent comprising 73-88% by weight of said γ-butyrolactone.

18. The method according to claim 7 , wherein the solvent for the polyamide-imide resin insulating coating material is a mixed solvent comprising 73-88% by weight of said γ-butyrolactone.