Process for producing high-purity diphenyl carbonate on an industrial scale

Abstract

The invention aims at providing a specific process for producing high-purity diphenyl carbonate, which is necessary in producing high-quality and high-performance aromatic polycarbonates, from cyclic carbonates and phenol stably on an industrial scale (e.g., in an amount of one ton or above per hour) over a long period (e.g., for 1000 hours or longer, preferably 3000 hours or longer, still preferably 5000 hours or longer). The aim can be attained by a process for producing high-purity diphenyl carbonate necessary for the production of high-quality and high-performance aromatic polycarbonates from cyclic carbonates and phenol which comprises the step (I) of producing a dialkyl carbonate and a diol by use of a reaction-distillation column having a specific structure, the step (II) of producing diphenyl carbonate by use of two reaction-distillation columns having specific structures, and the step (III) of passing the diphenyl carbonate through a column (A) for separating high-boiling substances and a column (B) for purifying diphenyl carbonate to obtain high-purity diphenyl carbonate.

Description

Technical field [0001] The invention relates to an industrial preparation method of high-purity diphenyl carbonate. More specifically, the present invention relates to a method for preparing high-purity diphenyl carbonate required for the production of high-quality and high-performance aromatic polycarbonate from cyclic carbonate and phenol stably for a long period of time on an industrial scale. Background technique [0002] To prepare aromatic polycarbonate on an industrial scale through transesterification reaction, it is necessary to obtain a large amount of high-purity diphenyl carbonate on an industrial scale. Although aromatic dihydroxy compounds such as high-purity bisphenol A can be produced industrially in large quantities and are easily available, it is impossible to obtain large quantities of high-purity diphenyl carbonate on an industrial scale. Therefore, it needs to be prepared. [0003] As a method of producing diphenyl carbonate, a method of reacting phenol and p...

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Problems solved by technology

[0041] The purity of diphenyl carbonate obtained in the method of patent document 1 of (1) is low, and because it is a batch type, it is not suitable for industrial mass production

[0042] The method of the patent document 32 of (2) is batch type, although there is the titanium catalyst below 1ppm in the diphenyl carbonate that the method for patent document 33 obtains, still not as the raw material of the high-purity polycarbonate of preparation colorless Suitable

[0043] In the method of the patent document 29 of (3), because diphenyl carbonate is heated at high temperature at the tower bottom of 2 distillation towers namely light boiling separation tower, methyl phenyl carbonate separation tower, then in diphenyl carbonate The ester separation tower is at high temperature again, so the diphenyl carbonate is modified, resulting in a decrease in purity and a decrease in yield

[0044] In the method of obtaining diphenyl carbonate from the bottom of the tower of patent documents 14 and 30 in (4), the purity is low and it is not suitable for preparing the target polycarbonate

[0045] In the methods of Patent Documents 8 and 9 of (5), the reaction mixture containing catalyst, unreacted raw materials, and impurities, etc. derived from the bottom of the second reactive distillation tower is introduced from the top of the third reactive distillation tower. The diphenyl carbonate is taken out from the side of the tower, so it will bring in steam and mist of catalyst, impurities, raw materials, etc., and the obtained diphenyl carbonate has low purity

[0046] The production capacity of the method diphenyl carbonate of (6) is 6.7kg / hour (patent document 16, embodiment 3), 3.9kg / hour (patent document 17, embodiment 1), not industrial scale

The method of (7) is a preferred method, but the production capacity of diphenyl carbonate is 2kg / hour (Example 8 of Patent Document 35), which is a small amount and not on an industrial scale

However, these high-boiling by-products are difficult to separate, and the methods proposed so far have not been able to reduce these high-boiling by-products below sufficient levels

In particular, there has not been proposed a method for producing high-purity diphenyl carbonate required as a raw material for high-quality high-performance polycarbonate on an industrial scale with a production capacity of 1 ton / hour or more.

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