Abstract Wire coating solutions are provided by reacting trimellitic anhydride with an organic diisocyanate in substantially equimolar proportions, the reaction being carried out at a moderate temperature up to about 275* F. in organic solvent solution medium to produce an amide reaction product having a single anhydride group and a single isocyanate group. The amide-forming reaction is continued until the theoretical amount of carbon dioxide is removed. The reaction product is then blocked with a monofunctional blocking agent such as phenol in order to block the isocyanate functionality and convert the anhydride functionality to a carboxy ester. Polymerization is then carried out by raising the temperature to progressively unblock the isocyanate functionality for reaction with the free carboxy groups which are available. This polymerization produces an organic solvent-soluble polyamide polymer in solution in the solvents used. When the polyamide polymer is coated on a base such as wire and baked, the phenol blocking agent is removed and insolubilization takes place primarily by imide formation.
A method as recited in claim 1 in which the molar proportion of trimellitic anhydride and organic diisocyanate does not exceed 1:1.2, and the reaction product which is produced is mixed with phenol.
Claim 2
Dependent Claim
14 words
A method as recited in claim 1 in which said solvent comprises N-methyl pYrrolidone.
Claim 3
Dependent Claim
13 words
A method as recited in claim 1 in which said diisocyanate is diphenylmethane-4,4''-diisocyanate.
Claim 4
Dependent Claim
16 words
A wire coating solution comprising an organic solvent-soluble polyamide polymer produced as recited in claim 1.
Claim 5
Independent Claim
114 words
A method of producing an organic solvent-soluble polyamide polymer capable of curing with the formation of imide linkages comprising reacting trimellitic anhydride and organic diisocyanate containing isocyanate groups as the sole functional group in molar proportions of from 1:0.95 to 1:1.4, said reaction being carried out in organic solvent solution at a temperature up to about 275* F. until about one molar proportion of carbon dioxide is liberated per mol of trimellitic anhydride, adding to the reaction product so-produced a monohydric phenol and heating the phenol-containing product to cause polymerization and the formation of a solvent-soluble polyamide polymer which is curable by baking with the product being insolubilized through the formation of imide groups.