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Process for purification of polycarbonate-containing solutions by plate decantation

A polycarbonate and tray technology, which is applied in the field of purifying polycarbonate-containing solutions by tray decantation, can solve the problems of slow efficiency, time-consuming and expensive centrifuge installation and operation, etc.

Inactive Publication Date: 2003-12-10
SABIC GLOBAL TECH BV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] Phase separation and purification using centrifuges is time-consuming and expensive to install and operate
Furthermore, other alternative purification methods such as extraction using countercurrent water washes and gravity separation of the two phases are much slower and less efficient

Method used

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  • Process for purification of polycarbonate-containing solutions by plate decantation
  • Process for purification of polycarbonate-containing solutions by plate decantation
  • Process for purification of polycarbonate-containing solutions by plate decantation

Examples

Experimental program
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Effect test

Embodiment 1

[0033] A tray decanter was tested in a polycarbonate resin separation line consisting of three centrifuges. The first centrifuge is used for resin and brine separation. The second centrifuge is used for pickling the resin solution, reducing the chloride ion concentration in the third centrifuge, and preventing the third centrifuge from being excessively corroded.

[0034] To test the use of a tray decanter, a 200 liter decanter unit (ex Esmitec / FIB) was tested on the discharge of the feed pump of the resin separation line. The separated light and heavy organic phases from the top and bottom of the decanter are conveyed back to the inlet of the centrifuge feed pump.

[0035] The feed mixture to the decanter consisted of an aqueous phase (brine or wash water) and an organic phase (polycarbonate in dichloromethane). The feed mixture enters the decanter through the feed tube. The aqueous, ie light phase flows to the top of the decanter and the resin solution to the bottom. The...

Embodiment 2

[0041] The polycarbonate-containing reaction mixture can be prepared using an interfacial reaction method. Such a reaction mixture can use two tray decanters and three centrifuges, such as figure 1 Isolation and purification were carried out as indicated. Calculations were made using mass balances according to Example 1 assuming feed stream composition, entrained brine and polycarbonate content.

[0042] The results are summarized in Table 1, where PC = polycarbonate, MeCl 2 = dichloromethane, BPA = bisphenol A, TEA = triethylamine. The final effluent of the purified organic phase contained 0.5% by weight of water.

[0043] 10

[0044] image 3 An alternative separation network is shown comprising two tray decanters in series followed by two centrifuge trains each comprising 3 centrifuges arranged in parallel. The effluent 300 from a tray reactor producing polycarbonate using a two-phase interface process is introduced into a tray decanter 310 where the effl...

Embodiment 4

[0046] A reactor effluent solution with a polycarbonate concentration in the organic phase of 10-18% by weight and a brine or aqueous phase in a specific gravity of 1.0-1.16 is fed into a tray decanter and discharged continuously. The feed rate was maintained such that the retention time in the decanter was 10-30 minutes. Continuous operation and defined retention times create waves and turbulence around the interface, making observation of the interface difficult. Such as Figure 4 As shown, decanter 700 is fitted with a top-down sonar probe 720 (available from Accu-Gage Corporation). The effluent solution enters decanter 700 through feed port 730 . The effluent separates into an organic phase 740 and a brine phase 750 with an interface 760 therebetween. The lighter brine phase exits through brine outlet 770 at the top of the decanter and the heavier organic phase exits through organic phase outlet 780 at the bottom of the decanter. Optionally, additional trays can be ins...

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Abstract

This invention relates to an economical and efficient process for purifying a reaction mixture obtained in a two-phase interfacial reaction for the preparation of polycarbonate. More particularly, the method of the invention provides for separating the reaction mixture into an organic phase, which includes the desired polycarbonate and undesirable impurities, and an aqueous phase. The organic phase is further purified by using a plate decanter in combination with coalescence and centrifugation.

Description

[0001] The present invention relates to an improved method of purifying polycarbonate-containing solutions resulting from two-phase interface synthesis. The method of the present invention uses at least one tray decanter to separate and purify the polycarbonate-containing solution. Background of the invention [0002] There are a number of well-known methods for preparing polycarbonates from monomers. A preferred method is the two-phase interface method in which phosgene and an aromatic diphenol are contacted and condensed to form a high molecular weight polycarbonate. [0003] The reaction mixture obtained by the two-phase interface method is an emulsion of an organic phase and a basic aqueous phase. It was found that in order to recover the polycarbonate product from the organic phase, the reaction mixture must first be separated into an organic phase and an alkaline aqueous phase, and then the organic phase must be further treated to remove unwanted impurities including el...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D17/00B01D21/00C08G64/40
CPCB01D21/262C08G64/406B01D21/00B01D17/00B01D21/32B01D17/0211B01D17/0217B01D17/045B01D21/0039B01D21/26C08G64/40
Inventor C·A·M·范古尔M·H·奥耶瓦尔A·瓦伦C·廷尼M·朱
Owner SABIC GLOBAL TECH BV
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