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

Abstract

A polyamide-imide resin insulating coating material, which is obtained by reacting an isocyanate component with an acid component, has a main solvent component of γ-butyrolactone. In the coating material, a total compounding ratio of 4,4′-diphenylmethane diisocyanate (MDI) and trimellitic anhydride (TMA) is 85 to 98 mol %, where the total compounding ratio is given by averaging a compounding ratio of MDI to the isocyanate component and a compounding ration of TMA to the acid component.

What is claimed is: 
     
         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 the compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate components and the compounding ratio of the trimellitic anhydride in the acid components, is in the range of 85 to 98 mol %; and   the mixed solvent comprises ybutyrolactone 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).   
     
     
         2 . 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 the compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate components and the compounding ratio of the trimellitic anhydride in the acid components, is in the range of 85 to 98 mol %.   
     
     
         3 . The method according to  claim 2 , wherein: the acid component comprises 80 mol % or more of trimellitic anhydride and 20 mol % or less of a tetracarboxylic dianhydride. 
     
     
         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 tricarboxylic acid. 
     
     
         5 . 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′-diphenylrnethane diisocyanate other than 4,4′-diphenylrnethane 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 the compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate components and the compounding ratio of the trimellitic anhydride in the acid components, is in the range of 85 to 98 mol %; and   coating the polyamide-imide resin insulating coating material on a conductor, and then baking the polyamide-imide resin insulating coating material to form a coating film on the conductor.   
     
     
         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 4J4′-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 defined by averaging the compounding ratio of the 4,4′-diphenylmethane diisocyanate in the isocyanate components and trimellitic anhydride in the acid components is in the range of 85 to 98 mol %, where the compounding ratio is given by averaging a compounding ratio of the MDI to the isocyanate component and a compounding ratio of the TMA to the acid component;   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.   
     
     
         7 . 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 %. 
     
     
         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 100 mol %. 
     
     
         9 . 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.   
     
     
         10 . The method according to  claim 2 , 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. 
     
     
         11 . The method according to  claim 5 , 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 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.