Aromatic Polycarbonate Production via Inverted Reactor Temperature Gradient
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Solution Overview
Problem
In the production of aromatic polycarbonates using a series-connected vertical and horizontal reactor system, issues arise with the formation of high melting point products leading to clogged gear pumps and contamination, and insufficient rejection efficiency of phenol by-products, disrupting polycondensation reactions.
Innovation Solution
A production method where the molten reactant temperatures in consecutive reactors are controlled such that T2 < T1, with specific temperature ranges (260° C. < T2 < T1 < 280° C.), and including conditions like increased evaporation surface area and stirring power to minimize high melting point product formation and optimize phenol removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature in the final vertical reactor is increased to remove phenol by-products, then the polycondensation reaction efficiency is improved, but high melting point products form and cause gear pump clogging
Solution Approach 1:
The patent inverts the conventional temperature gradient approach by setting the final vertical reactor temperature lower than the horizontal reactor temperature (T1 > T2), preventing high melting point product formation in the vertical reactor while maintaining effective phenol removal through the horizontal reactor's higher temperature and large evaporation surface area
Solution Approach 2:
The patent changes the temperature parameter distribution across reactors, specifically setting T1 (vertical reactor) between 260-280°C and T2 (horizontal reactor) between 260-300°C with T1 > T2, optimizing both phenol removal and preventing harmful high melting point product formation
2Quantity of substance
If the residence time in reactors is increased to improve polymerization, then the molecular weight increases, but the thermal history increases causing hue deterioration
Solution Approach 1:
The patent segments the polymerization process into multiple reactors with different temperature and residence time characteristics, allowing optimized control of each stage to achieve high molecular weight while minimizing cumulative thermal history and hue deterioration
3Productivity
If the evaporation surface area is increased to remove phenol by-products, then the reaction efficiency is improved, but the risk of high melting point product formation increases
Solution Approach 1:
The patent applies different temperature conditions to different locations in the system: the horizontal reactor has large evaporation surface area with higher temperature (T2) optimized for phenol removal, while the vertical reactor has lower temperature (T1) optimized for preventing high melting point product formation
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
This method effectively reduces high melting point product formation, prevents gear pump clogging, and enhances the hue and molecular weight of the aromatic polycarbonate, ensuring stable and high-quality production.
Implementation Method 1
polycondensation reacting bisphenols such as bisphenol A and carbonic diesters such as diphenyl carbonate by an ester exchange reaction
Implementation Method 2
method of polycondensation reacting bisphenols such as bisphenol A and carbonic diesters such as diphenyl carbonate by an ester exchange reaction
Implementation Method 3
setting operation conditions of a reactor to higher temperature and vacuum conditions as increasing stages to effectively remove phenol by-produced
Implementation Method 4
temperature difference between a polymer temperature and a heating medium in a reactor
Implementation Method 5
surface temperature of a reactor material is controlled to a temperature of 230° C. or higher, thereby suppressing crystallization of a low-order polycondensate
Data Source
AI summary
The object of the present invention is to provide a production method of a high molecular weight aromatic polycarbonate containing a reduced amount of a high melting point product, and having less thermal history received and excellent hue by a melt process. The present invention relates to a production method of an aromatic polycarbonate, characterized in that in producing an aromatic polycarbonate using an aromatic dihydroxy compound and a carbonic diester as raw materials and using plural reactors, a molten reactant temperature T1 (° C.) in at least one reactor A and a molten reactant temperature T2 (° C.) in a reactor B subsequent to the reactor A are satisfied with the relationship of T2<T1, and an evaporation surface area per unit treatment amount of a molten reactant in the reactor to which a molten reactant having a limiting viscosity of 0.1 dl/g or more is supplied is 1.0 m2·hr/m3 or more.