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AssigneeBayer Aktiengesellschaft
InventorsChristian Kords, Jurgen Heuser, Antonio Ortiz
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A process for preparing an emulsion is disclosed. The process entails mixing an aqueous mineral acid that contains phosphorous in an organic solvent, the mixing being continuous and with the degree of intensity sufficient to form a homogeneous emulsion. The emulsion prepared by the process is useful in the process of preparing polycarbonate by the interfacial process. Accordingly the washed organic polycarbonate that has been washed without the use of a phosphorous containing mineral acid solution is mixed with the novel emulsion. The resulting polycarbonate is characterized by its improved thermal stability.
A process for preparing an emulsion comprising mixing an aqueous mineral acid that contains phosphorous in an organic solvent, the mixing being continuous and with the degree of intensity sufficient to form a homogeneous emulsion.
Dependencies are inferred from the claim text.
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Macromolecular compounds obtained by reactions forming a carbonic ester link in the main chain of the macromolecule: post-polymerisation treatment
Using carbonyl halides: and phenols
Macromolecular compounds obtained otherwise than by reactions only involving unsaturated carbon-to-carbon bonds
Term end not estimated
The invention relates to a process for the preparation of polycarbonates and more particularly the interfacial polycondensation process.
For the preparation of polycarbonates by the so-called interfacial process, dihydroxydiarylalkanes in the form of their alkali salts are reacted with phosgene in heterogeneous phase in the presence of inorganic bases such as sodium hydroxide solution and an organic solvent in which the product polycarbonate is readily soluble. During the reaction, the aqueous phase is distributed in the organic phase, and after the reaction the organic polycarbonate-containing phase is separated from the aqueous phase and washed several times with an aqueous liquid, during which electrolytes, residual monomers and catalyst inter alia are removed. The washing liquid is then separated off as far as possible. Finally, the polycarbonate is freed of the organic solvent and converted into a form which may readily be processed further, for example granular form.
This known interfacial process is described by way of example and in detail in the following publications:
A PC solution, washed with HCl is, after washing, emulsified with an emulsion of 8% phosphoric acid in an amount of 1000 ppm in a mixture of 90% monochlorobenzene and 10% dichloromethane by means of a continuously operating mixing pump, and is mixed into the PC solution by way of the mixing chamber of a disk separator. The polycarbonate is then isolated in the conventional manner. The amount of phosphoric acid, based on polycarbonate, is 3 ppm. The mold release agent is metered in as in the Comparative Example, but without the addition of the phosphoric acid, and mixed in; the mold release agent is present in the granules in unchanged form, the yellowness index is from 1.2 to 1.3. The mold release agent does not change even during processing to CD molded articles.
If the result of the process according to the prior art (Comparison Example) is compared with that of the process according to the invention, it will immediately be seen that, on the one hand, the polycarbonate obtained by the process according to the invention surprisingly exhibits a superior yellowness index and, on the other hand, in contrast to the prior art, the mold release agent does not change during further processing. This performance is deemed surprising and unexpected in view of the art.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations may be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.