Method for stably producing an aromatic polycarbonate
A method for stably producing an aromatic polycarbonate, which comprises continuously reacting an aromatic dihydroxy compound with a diaryl carbonate in a closed, reactor-pipeline system, the closed, reactor-pipeline system comprising: a plurality of reactors which are liquid-tightly connected through a pipeline toward an outlet for a final aromatic polycarbonate product, the pipeline comprising one or more pipes, wherein the plurality of reactors include at least two reactors connected in series, and at least one filter secured in the pipe or pipes of the reactor-pipeline system, wherein the or each filter is simultaneously or separately taken out to the outside of the reactor-pipeline system and subjected to washing in the outside of the reactor-pipeline system, followed by returning of the resultant washed filter into the inside of the pipe or pipes of the reactor-pipeline system, the washing being performed with the below-mentioned washing agents used in the following order: an aqueous solution of a basic compound, an aromatic monohydroxy compound, and a molten mixture of an aromatic dihydroxy compound and a diaryl carbonate, the molten mixture containing a basic compound.
1. A method for producing an aromatic polycarbonate, which comprises continuously reacting an aromatic dihydroxy compound with a diaryl carbonate in a closed, reactor-pipeline system,
said closed, reactor-pipeline system comprising:
a plurality of reactors which are liquid-tightly connected through a pipeline toward an outlet for a final aromatic polycarbonate product, said pipeline comprising one or more pipes, wherein said plurality of reactors include at least two reactors connected in series, and
at least one filter secured in the pipe or pipes of said reactor-pipeline system,
said method further comprising:
a step of simultaneously or separately taking out the or each filter clogged with foreign matter to the outside of said reactor-pipeline system,
a step of subjecting the or each filter to washing in the outside of said reactor-pipeline system, and
a step of returning of the resultant washed filter into the inside of the pipe or pipes of said reactor-pipeline system,
wherein said washing is performed with the below-mentioned washing agents used in the following order:
an aqueous solution of a basic compound with a pH value of from 7.5 to 10,
an aromatic monohydroxy compound, and
a molten mixture of an aromatic dihydroxy compound and a diaryl carbonate, said molten mixture containing a basic compound in an amount of from 1 to 10,000 ppb.
2. The method according to claim 1 , wherein said aqueous solution of a basic compound has apH value of from 8 to 9.5.
3. The method according to claim 1 , wherein said basic compound is an alkali metal hydroxide.
4. The method according to claim 3 , wherein said alkali metal hydroxide is at least one member selected from the group consisting of sodium hydroxide and potassium hydroxide.
5. The method according to any one of claims 1 to 4 , wherein said aromatic dihydroxy compound is phenol.