High-purity biphenyltetracarboxylic dianhydride and process for producing the same
View Patent ↗There is provided biphenyltetracarboxylic dianhydride containing biphenyltetracarboxylic monoanhydride in an amount of not more than 0.4%. By using the biphenyltetracarboxylic dianhydride as a raw material, it is possible to produce polyimide or polyamic acid having an increased molecular weight.
1. A process for producing purified biphenyltetracarboxylic dianhydride containing biphenyltetracarboxylic monoanhydride in an amount of not more than 0.4% comprising pulverizing the biphenyltetracarboxylic dianhydride under an inert gas atmosphere having a water content of not more than 200 ppm and a temperature of not more than 30° C.
2. A process for producing purified biphenyltetracarboxylic dianhydride containing biphenyltetracarboxylic monoanhydride in an amount of not more than 0.4% wherein in a temperature rise process including heating said biphenyltetracarboxylic dianhydride from 20° C. to 248° C. and then maintaining a temperature of the biphenyltetracarboxylic dianhydride at 248° C. for 30 minutes after reaching 248° C., a total amount of water vaporized from the biphenyltetracarboxylic dianhydride during a whole period of the temperature rise process is not more than 500 ppm, and an amount of water vaporized from the biphenyltetracarboxylic dianhydride during a period of the temperature rise process subsequent to a time at which the temperature of the biphenyltetracarboxylic dianhydride reaches 210° C. is not more than 200 ppm;
said process comprising pulverizing the biphenyltetracarboxylic dianhydride under an inert gas atmosphere having a water content of not more than 200 ppm and a temperature of not more than 30° C.