Polycarbonate Production Using Chlorohydrocarbon Solvent
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Solution Overview
Problem
The production of polycarbonates by the interfacial process requires high-purity organic solvents, which are costly and inconvenient to maintain due to the need for frequent purification and replacement, especially when impurities like carbon tetrachloride and chloroethane are present, affecting the optical and rheological properties of the final product.
Innovation Solution
A process using an organic solvent based on chlorohydrocarbons with elevated contents of carbon tetrachloride (0.05% to 7% by weight) and chloroethane (0.3% to 10% by weight), such as methylene chloride, chlorobenzene, and chloroform, allows for the production of polycarbonates without impairing their optical and rheological properties, enabling less frequent solvent replacement and reduced purification needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-purity organic solvents are used in the interfacial process for polycarbonate production, then the optical and rheological properties of the polycarbonate product are maintained, but the cost and operational convenience deteriorate due to frequent purification and replacement requirements
Solution Approach 1:
The invention changes the chemical composition parameters of the organic solvent system by introducing specific chlorohydrocarbons (methylene chloride, chloroform, chlorobenzene) with controlled impurity levels. This parameter change allows the solvent to tolerate higher carbon tetrachloride and chloroethane contents while maintaining polycarbonate product quality, thereby reducing purification frequency and operational costs
Solution Approach 2:
The invention uses a composite solvent system comprising multiple chlorohydrocarbon components rather than a single pure solvent. This composite approach (methylene chloride + chloroform + chlorobenzene in specific ratios) creates a synergistic effect that maintains solvent effectiveness while tolerating higher impurity levels, reducing the need for frequent purification and replacement
2Ease of manufacture
If the organic solvent contains elevated levels of carbon tetrachloride and chloroethane, then the solvent replacement frequency and purification costs are reduced, but the optical and rheological properties of the polycarbonate product are impaired
Solution Approach 1:
The invention establishes specific parameter ranges for carbon tetrachloride (0.05-7% by weight) and chloroethane (0.3-10% by weight) in the organic solvent, along with controlled ratios of methylene chloride to chlorobenzene/chloroform. These parameter changes define the optimal composition window that allows higher impurity tolerance while maintaining product quality
Solution Approach 2:
The invention applies local quality control by specifying different concentration ranges for different solvent components and impurities. Rather than requiring uniform high purity across all components, the patent allows localized variations (higher carbon tetrachloride/chloroethane content) in specific solvent regions while maintaining overall product quality through controlled composition ratios
3Productivity
If phosgene excess is increased to accelerate reaction and improve phase separation in the interfacial process, then the reaction rate and phase separation are enhanced, but the amount of byproducts (common salt and alkali metal carbonate compounds) increases
Solution Approach 1:
The invention optimizes the phosgene to diphenoxide molar ratio parameter, establishing it within 10-30% excess rather than the conventional 20 mol% or higher. This parameter optimization achieves adequate reaction acceleration and phase separation while minimizing excess phosgene that would decompose into harmful byproducts
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 maintains the optical and rheological quality of polycarbonates, with yellowness index values not exceeding 2.0 and relative solution viscosities within standard ranges, while reducing the frequency of plant shutdowns and minimizing solvent purification costs.
Implementation Method 1
a diphenol initially charged in aqueous alkaline solution or suspension or a mixture of two or more different diphenols initially charged in aqueous alkaline solution or suspension is in the presence of an inert organic solvent or solvent mixture reacted with a carbonyl halide
Implementation Method 2
The incipient oligocarbonates primarily present in the organic phase are subjected to condensation with the aid of suitable catalysts to afford high molecular weight polycarbonates dissolved in the organic phase
Data Source
AI summary
The present invention relates to a process for producing a polycarbonate from a diphenol or two or more different diphenols and a carbonyl halide by the interfacial process. It is a feature of the process according to the invention that it is carried out on the basis of a chlorohydrocarbon or a mixture of a mixture of two or more chlorohydrocarbons using an organic solvent. An organic solvent is also provided.