| Popis: |
POLYCARBONATES are obtainable by interracial polycondensation through the interaction of phosgene with sodium salts of diphenols in the presence of small amounts of tertiary amines used as catalysts. The phosgene is introduced into the organic phase, while the aqueous phase contains an alkaline solution of the diphenol and the optimum excess of alkali required for the preparation of polycarbonate of the highest molecular weight. The production of polycarbonates by interracial polycondensation therefore involves the participation of four main components: phosgene, diphenol, sodium hydroxide and the catylyst (triethylamine). The process will be determined by the ratio of the rates of two main types of reaction: those resulting in growth of the macromolecular chain, and those leading to chain termination. Without further reference to the factors considered in previous investigations [1-3] determining the optimum conditions for the process (the effect of the ratio of the components, the effect of an excess of one or other component, etc.) we have now attempted to analyse the processes limiting or facilitating chain propagation. |
