A novel non-phosgene polycarbonate production process using by-product CO2as starting material

Abstract

Asahi Kasei Corp. has succeeded in the development of a new green process for producing an aromatic polycarbonate based on bisphenol-A (hereafter usually abbreviated as PC) without using phosgene and methylene chloride. The new PC production process is the world's first to use carbon dioxide (CO₂) as a starting material. Until Asahi Kasei's new process was revealed, all of the PC in the world has been produced using carbon monoxide (CO) made from cokes or lower hydrocarbons and oxygen as a starting material. Furthermore, more than about 93% of the PC has been produced by the so-called “phosgene process” which uses phosgene made from CO and chlorine (Cl₂) as a monomer. However, the phosgene process inherently involves a number of environmental and economic shortcomings in addition to the high toxicity of phosgene itself and the high carcinogenic probability of methylene chloride itself. Asahi Kasei's new process enables high-yield production of the two important products for our citizens’ lives, high-quality PC and high-purity monoethylene glycol (MEG), starting from ethylene oxide (EO), carbon dioxide (CO₂) and bisphenol-A. This new technology not only overcomes the environmental and economic problems existing in the phosgene process, but also achieves resource conservation, and energy conservation. Furthermore, the new process contributes to the earth environment by the reduction of CO₂ emissions (173 tons per thousand tons of product PC). Commercial application of the new process was carried out at the 50,000 ton year⁻¹ PC plant of Chimei-Asahi Corporation, a joint venture between Asahi Kasei Corporation and Chi Mei Corporation, which was newly constructed in Taiwan and has been successfully operating since June 2002. In recognition of the outstanding advance in ecological and sustainable performance that this technology represents, Japan's Minister of Economy, Trade and Industry conferred the Green and Sustainable Chemistry Award of 2003 on us. Furthermore, the Chairman of Japan Chemical Industry Association also conferred the 35th Japan Chemical Industry Association Award of 2003 on us as an outstanding chemical technology. An outline of this new non-phosgene PC process embodying the spirit of Green and Sustainable Chemistry is given here.