The production of low color polyetherimides, including its intermediates, such as bisimides and diaryl diether dianhydrides, may be affected by producing an improved purity intermediate of 4-nitro-N-alkylphthalimide. A salt, such as alkali metal carbonate or alkali metal hydrogen carbonate, is added to an aqueous mixture of 4-nitro-N-alkylphthalimide and 3-nitro-N-alkylphthalimide to selectively hydrolyze the imide linkage of 3-nitro-N-alkylphthalimide forming a water-soluble acid-amide salt. An organic solvent is added to this salt mixture to phase separate 4-nitro-N-alkylphthalimide having dissolved in the organic solvent from acid-amide salt of 3-nitro-N-alkylphthalimide having dissolved in water.
生产低色差聚醚
酰亚胺,包括其中间体,如双亚
酰亚胺和二芳基
二醚二酐,可能会受到生产改进纯度的4-硝基-N-烷基邻苯二甲
酰亚胺中间体的影响。将盐,如碱
金属
碳酸盐或碱
金属氢
碳酸盐,加入到4-硝基-N-烷基邻苯二甲
酰亚胺和
3-硝基-N-烷基邻苯二甲
酰亚胺的
水溶混合物中,选择性
水解
3-硝基-N-烷基邻苯二甲
酰亚胺的亚醯胺键,形成
水溶性酸酰胺盐。然后向这个盐混合物中加入有机溶剂,将溶解在有机溶剂中的4-硝基-N-烷基邻苯二甲
酰亚胺与溶解在
水中的
3-硝基-N-烷基邻苯二甲
酰亚胺的酸酰胺盐进行相分离。