| 摘要 |
PURPOSE: A method for preparing polycarbonate is provided to efficiently reduce the amount of discharged methylene chloride, the used amount of steam, and production costs by collecting methylene chloride using two adsorption towers alternatively performing an adsorption process including an ion exchange resin. CONSTITUTION: A method for preparing polycarbonate from aromatic dihydroxy compounds or substituted aromatic bischloroformate using methylene chloride as a solvent comprises a step of collecting methylene chloride using first and second adsorption towers. The collection step for methylene chloride comprises the steps of: (a) passing a reactant containing methylene chloride through an adsorption tower to adsorb the reactant by an ion exchange resin inside the adsorption tower; and (b) after completion of the step (a), supplying detaching water inside the adsorption tower to detach methylene chloride remaining inside the tower, and supplying purified water inside the adsorption tower to remove methylene chloride remaining inside the tower. After completion of the step (a) in a first adsorption tower, the step (a) in a second adsorption tower starts. The steps (a) and (b) are consecutively performed in two adsorption towers. During the step (a) in the first adsorption tower, the step (b) is progressed in the second adsorption tower, and during the step (b) in the first adsorption tower, the step (a) is progressed in the second adsorption tower.
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