The invention aims to provide polyamic acid that can form a varnish with a low viscosity and serves to produce, through curing, coat film with good mechanical characteristics and further aims to produce cured coat film with good mechanical characteristics regardless of whether the molar concentration of the acid anhydride group in the acid dianhydride monomer and that of the amino group in the multivalent amine compound or diamine compound are identical to or different from each other. This objective is met by polyamic acid including a structure as represented by chemical formula (1) given below: (In chemical formula (1), δ represents an oxygen or sulfur atom and W represents an electron-withdrawing group, and R11 and R12 represent independently a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.
本发明旨在提供可形成低粘度清漆的聚酰胺酸,通过固化可生产出具有良好机械特性的 涂膜,并进一步旨在生产出具有良好机械特性的固化涂膜,无论酸酐单体中酸酐基团的摩尔 浓度与多价胺化合物或二胺化合物中
氨基的摩尔浓度是相同还是不同。包括如下
化学式(1)所示结构的聚酰胺可以达到这一目的:(在
化学式(1)中,δ 代表氧原子或
硫原子,W 代表抽电子基团,R11 和 R12 分别独立地代表氢原子或具有 1 至 10 个碳原子的烃基。