Polyamide-imide-modified polyurethane insulation enamel composition

A polyamide-imide-modified polyurethane varnish composition prepared by mixing a first intermediate reaction product with a second intermediate reaction product wherein:

• (a) said first intermediate reaction product is an isocyanate compound prepared by a process comprising the following steps:
• (I) preparing a first reaction mixture containing a phenol, a diisocyanate, and a dihydroxy compound in a first organic solvent, and reacting said first reaction mixture at room temperature;
• (ii) adding a diacid compound or trimellitic anhydride or mixture thereof to said first reaction mixture, and reacting at 100.degree..about.140.degree. C.;
• wherein said diisocyanate is stoichiometrically equivalent to the sum of said phenol, said dihydroxy compound, and said diacid compound or said trimellitic anhydride or mixture thereof, and
• (b) said second intermediate reaction product is a hydroxy compound is prepared by a process comprising the following steps:
• (I) preparing a second reaction mixture containing a diisocyanate and a dihydroxy compound in a second organic solvent, and reacting said second reaction mixture at room temperature;
• (ii) adding a trihydroxy compound to said second reaction mixture, and reacting at room temperature.

A method for preparing a polyamide-imide-modified polyurethane varnish composition for coating a conductive wire to form a varnished wire, said method comprising the following steps:

• (a) preparing a first intermediate reaction product, which is an isocyanate compound, by a first intermediate process comprising the following steps:
• (I) preparing a first reaction mixture containing a phenol, a diisocyanate, and a dihydroxy compound in a first organic solvent, and reacting said first reaction mixture at room temperature;
• (ii) adding a diacid compound or trimellitic anhydride or mixture thereof to said first reaction mixture, and reacting at 100.degree..about.140.degree. C.;
• wherein said diisocyanate is stoichiometrically equivalent to the sum of said phenol, said dihydroxy compound, and said diacid compound or said trimellitic anhydride or mixture thereof;
• (b) preparing a second intermediate reaction product, which is a hydroxy compound, by a second intermediate process comprising the following steps:
• (I) preparing a second reaction mixture containing a diisocyanate and a dihydroxy compound in a second organic solvent, and reacting said second reaction mixture at room temperature;
• (ii) adding a trihydroxyl compound to said second reaction mixture, and reacting at room temperature;
• and
• (c) mixing said first intermediate reaction product, said second intermediate reaction product, and a diluent to form said polyamide-imide-modified polyurethane varnish composition.