Aqueous solutions of polyamide acids which can be precursors of polyimide polymers
Patent 4014834 Issued on March 29, 1977. Estimated Expiration Date: 
March 29, 1994. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
March 29, 1994. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3448068 3507765 3528937 3541036 3663728 3804793 3891601 InventorAssigneeApplicationNo. 05/546998 filed on 02/04/1975US Classes:524/104, Five-membered nitrogen ring524/173, Sulfur directly bonded to oxygen and devoid of an aryl group, e.g., dimethyl sulfoxide, etc.524/210, N-C=X group wherein X is a chalcogen524/233, Dialkyl amides, e.g., dimethyl formamide, dimethyl acetamide, etc.524/234, Two or more N-C nitrogen nonreactant materials or with an organo oxygen or nitrogen-containing nonreactant material524/348, Two or more aryl-OH DNRM compounds524/84, Five-membered sulfur ring525/180, Polycarboxylic acid or derivative contains three or more carboxylic acid groups; or polyamine contains three or more amino groups; or from an amino containing polycarboxylic acid or derivative other than amine solely in salt form; or from polyamino carboxylic acid or derivative other than wherein amino groups are solely in salt form525/420, Solid polymer derived from an amino carboxylic acid or derivative; from a polyamine and a polycarboxylic acid or derivative; from at least one lactam; or from a polyamine salt of a polycarboxylic acid525/426Mixed with ethylenically unsaturated reactant or polymer therefromExaminersPrimary: Lieberman, Allan M.AbstractHigh solids, low viscosity, stable aqueous solutions of polyamide acids, which are precursors of polyimide polymers, can be prepared from the polyamide acids, a tertiary amine, a coalescing agent such as N-methylpyrrolidone, and a viscosity reducing agent such as furfuryl alcohol. These aqueous solutions are capable of depositing a uniform film and of being cured into polyimides.Other References
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