BPDA Production via Controlled Dehydration and Sublimation
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Solution Overview
Problem
The existing process for producing biphenyltetracarboxylic acid dianhydride (BPDA) is inefficient, requiring long times to achieve high purity and leading to coloration issues, which affects the productivity and quality of the aromatic polyimide produced.
Innovation Solution
A process involving heating BPDA under specific conditions, using a heating device with hollow rotary shafts and rotary heating members, and subsequent sublimation purification to achieve high purity and reduce coloration, while maintaining high productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If preheating is carried out at an average temperature-rising rate not higher than 50° C./hr from 80° C. to the dehydrating temperature, then high purity BPDA with tri-derivative content less than 0.2 wt % is obtained, but the preheating time exceeds 9 hours and total process time becomes very long
Solution Approach 1:
The patent applies preliminary action by pre-drying BTC crystals at 80° C. to remove water attached to crystals and crystal water before the main dehydration reaction. This preliminary removal of moisture prevents side reactions and tri-derivative formation during subsequent high-temperature dehydration, ensuring high purity BPDA while allowing the main reaction to proceed efficiently at 250-300° C. for at least 3 hours without excessive total time
Solution Approach 2:
The patent optimizes parameter changes by carefully controlling the temperature-rising rate during preheating (not higher than 50° C./hr) to prevent premature dehydration and side reactions. Then it transitions to high-temperature dehydration at 250-300° C. with adequate heating power to complete the reaction in reasonable time. The use of strong heating medium (pressurized steam or heating oil) enables rapid heat transfer and reduces total process time while maintaining purity
2Productivity
If strong heating is applied to increase productivity, then production time is reduced, but coloration of BPDA occurs and purity is compromised
Solution Approach 1:
The patent applies preliminary action by pre-drying BTC crystals at 80° C. to remove water attached to crystals and crystal water before the main dehydration reaction. This preliminary removal of moisture prevents side reactions and tri-derivative formation during subsequent high-temperature dehydration, ensuring high purity BPDA while allowing the main reaction to proceed efficiently at 250-300° C. for at least 3 hours without excessive total time
Solution Approach 2:
The patent optimizes parameter changes by carefully controlling the temperature-rising rate during preheating (not higher than 50° C./hr) to prevent premature dehydration and side reactions. Then it transitions to high-temperature dehydration at 250-300° C. with adequate heating power to complete the reaction in reasonable time. The use of strong heating medium (pressurized steam or heating oil) enables rapid heat transfer and reduces total process time while maintaining purity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process significantly reduces production time, achieves high purity BPDA with minimal coloration, and results in a polyimide with excellent heat resistance and transparency, suitable for various applications.
Implementation Method 1
heating biphenyltetracarboxylic acid to produce biphenyltetracarboxylic acid dianhydride
Implementation Method 2
feed a heated heating medium to hollow portions of the rotary heating members via a hollow portion of the rotary shaft... to supply an amount of heat required for the reaction by heat transfer
Implementation Method 3
sublimation purification to achieve high purity and reduce coloration
Data Source
AI summary
To provide a process for producing BPDA whereby high productivity is attained while high purity is maintained.A process for producing biphenyltetracarboxylic acid dianhydride, which comprises heating biphenyltetracarboxylic acid to produce biphenyltetracarboxylic acid dianhydride, characterized in that the heating is carried out at a pressure of from 1×102 Pa to 1.1×105 Pa to a maximum temperature in a range of from 210° C. to 250° C. in such a manner that the temperature rising rate is higher than 50° C./hr for a period of at least ¼ of the time for the temperature rise from 60° C. to 210° C., and the temperature is maintained to be from 150° C. to 250° C. for from 0.5 to 10 hours.