Patent ID: 9481641
Filing Date: 2016-11-01
CPC Classification: C07C,C08G,Y02P

Claim Text:
1. A process for purifying a polycarbodiimide, comprising: (a) separating a carbodiimidization catalyst from an initial mixture comprising a polycarbodiimide and the carbodiimidization catalyst by subjecting the initial mixture to a first distillation, wherein a first bottom product and a first top product are obtained, wherein the first bottom product comprises the polycarbodiimide and carbodiimidization catalyst, a weight ratio of carbodiimidization catalyst relative to polycarbodiimide in the first bottom product is lower than a weight ratio of carbodiimidization catalyst relative to polycarbodiimide in the initial mixture and wherein the first top product comprises carbodiimidization catalyst; (b) adding an entrainer to the first bottom product obtained from (a) to obtain an intermediate mixture, wherein the entrainer has a boiling point which is lower than the boiling point of the polycarbodiimide; (c) further separating carbodiimidization catalyst from the polycarbodiimide by subjecting the intermediate mixture obtained from the adding (b) to a second distillation, wherein a second bottom product and a second top product are obtained, wherein the second bottom product comprises the polycarbodiimide and carbodiimidization catalyst, a weight ratio of carbodiimidization catalyst relative to polycarbodiimide in the second bottom product is lower than a weight ratio of carbodiimidization catalyst relative to polycarbodiimide in the first bottom product obtained from the separating (a), and wherein the second top product comprises carbodiimidization catalyst and entrainer.