Method for producing polycarbonates
View Patent ↗The invention relates to a continuous method for producing polycarbonates by transesterifying diaryl carbonates with dihydroxyaryl compounds in the presence of quaternary onium compounds. The invention also relates to polycarbonates produced thereby and products produced from said polycarbonates.
1. Continuous process for the production of polycarbonates by the transesterification of diaryl carbonates with dihydroxyaryl compounds characterised in that condensation is affected in the presence of quaternary onium compounds as catalysts, wherein the final polycondensation stage is affected without the further addition of catalyst, and in that an oligocarbonate is produced using quaternary onium compounds as catalysts which can be decomposed, substantially without leaving a residue, after preliminary condensation without separation of the monohydroxyaryl compound formed, and in a plurality of subsequent flash/evaporator stages in which the temperature is elevated stepwise and the pressure is decreased stepwise, which oligocarbonate is thereafter condensed to form the finished polycarbonate in one or two successive basket-type reactors, without the addition of further amounts of the catalyst used or of a new, different catalyst, whilst the temperature is further elevated and the pressure is further reduced.
2. Polycarbonate, characterised in that it can be obtained by the continuous process according to claim 1 .
3. Polycarbonate according to claim 2 , characterised in that it is low in alkali and alkaline-earth ions.
4. Polycarbonate according to claim 2 , characterised in that incorporated cleavage and decomposition products from the transesterification process are not detectable.
5. Polycarbonate according to claim 2 , characterised in that it contains less than 1 ppm of phosphorus.
6. Products made from polycarbonate, characterised in that they are produced from polycarbonate according to claim 2 .
7. Storage media, characterised in that they are produced from a polycarbonate according to claim 2 .
8. Process according to claim 1 , characterised in that the onium compound is tetraphenylphosphonium phenolate.
9. Process according to claim 8 , characterised in that the tetraphenylphosphonium phenolate is added in a phenolic solution.
10. Process according to claim 1 , characterised in that the catalyst is used in amounts of 10 −8 to 10 −3 mol per mol bisphenol.
11. Process according to claim 1 , characterised in that the reactors and apparatus as well as pumps, pipelines and fittings are produced from stainless steels of the type Cr NI (Mo) 18/10 for processing temperatures up to about 290° C. and are produced from Ni base alloys of type C for temperatures above about 290° C.