High molecular weight polyamide-imides having a reduced viscosity of 0.3 dl/g or above and exhibiting excellent heat resistance and melt flowability is produced with good economic efficiency by a process, which process comprises the two reaction stages:
(a) a first reaction stage which comprises reacting (I) a trimellitic acid derivative and (II) an aromatic diamine in the presence of a polar solvent in the presence of a first dehydration catalyst until a polyamide-imide resin having a reduced viscosity of 0.2 to 0.5 dl/g as measured at a concentration of 0.5 g/dl in dimethylformamide at 30°C is produced; and
(b) a second reaction stage which comprises adding a phosphorous ester as a second dehydration catalyst to the reaction mixture resulting from the first reaction stage and further reacting the reaction mixture until a high molecular weight polyamide-imide resin having a reduced viscosity of 0.3 dl/g or above as measured at a concentration of 0.5 g/dl in dimethylformamide at 30 °C is produced.
高分子量聚酰胺-
酰亚胺的粘度降低到 0.3 dl/g 或以上,并具有优异的耐热性和熔体流动性,其生产工艺具有良好的经济效益,该工艺包括两个反应阶段:
(a) 第一反应阶段,包括在极性溶剂中,在第一脱
水催化剂存在下,使(I)偏苯三 酸衍
生物和(II)芳香族二胺反应,直至生成聚酰胺-
酰亚胺树脂,该
树脂在 30℃的二甲基甲酰胺中,浓度为 0.5 克/分升时,粘度降低到 0.2 至 0.5 分升/克;以及
(b) 第二反应阶段,包括向第一反应阶段产生的反应混合物中加入
磷酯作为第 二脱
水催化剂,并使反应混合物进一步反应,直至生成高分子量聚酰胺酰
亚胺树脂,该
树脂在二甲基甲酰胺中的浓度为 0.5 克/分升,温度为 30 摄 氏度时,其粘度降低至 0.3 分升/克或以上。