Synthesis of the High Molecular Weight Polycarbonate by Interfacial Polycondensation of Bisphenol A and Triphosgene

摘要

Aromatic polycarbonate is a light weight, high-performance plastic found in commonly used items such as automobiles, cell phones, computers and other business equipment, sporting goods, consumer electronics, household appliances, CDs, DVDs, food storage containers and bottles. Polycarbonate of bisphenol A is the most important species, which possess good comprehensive properties, especially outstanding impact strength, high transparency, excellent dimensional stability and electrical insulation. At present, two methods are used in industry to produced PC of bisphenol A: interfacial polycondensation and melt trans-esterification. First process for making polycarbonate is based on the reaction between phosgene (COCl_2) and bisphenol A. The other process makes use of another activated derivative of carbonic acid diphenylcarbonate. The reaction between bisphenol A and diphenylcarbonate to make polycarbonate is carried out in a molten state at high temperature. The major drawbacks of conventional interfacial process are environmental and safety problems involved in using highly toxic and corrosive COCl_2 as the reactant. The trans-esterification is more safe method, but the reaction should carry out at elevated temperature, and the viscosity of reaction system is high at the later of reaction. It is difficult to remove the by-product phenol and obtain the high grade PC. Triphosgene (bis(trichloromethyl) carbonate) is a stable, crystalline solid which has proved to be a useful substitute for phosgene. It is safer and more convenient to handle, transport and store. Exact amounts may be weighed easily and used to perform desired chemical reaction.