Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1995-09-01
1997-01-21
Seidleck, James J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
159 131, 159 134, 159 482, 159DIG10, 26421124, 264 85, 425 721, 528198, 528199, 526 67, C08G 6400
Patent
active
055960677
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This is a 371 of PCT/JP94/01202 filed Jul. 21, 1994 and published as WO95/03351 Feb. 2, 1995.
1. Field of The Invention
The present invention relates to a method for producing an aromatic polycarbonate.
2. Prior Art
In recent years, aromatic polycarbonates have been widely used in various fields as engineering plastics having excellent heat resistance, impact resistance and transparency. With respect to methods for producing aromatic polycarbonates, various studies have heretofore been made. Of the methods studied, a process utilizing an interfacial polycondensation between an aromatic dihydroxy compound, such as 2,2-bis(4-hydroxyphenyl)propane (hereinafter, frequently referred to as "bisphenol A"), and phosgene has been commercially practiced.
However, the interfacial polycondensation process has problems in that it is necessary to use phosgene, which is poisonous, that a reaction apparatus is likely to be corroded with chlorine-containing compounds, such as hydrogen chloride and sodium chloride, which are by-produced, and methylene chloride which is used as a solvent in a large quantity, and that difficulties are encountered in separating and removing impurities, such as sodium chloride, and residual methylene chloride, which adversely affect properties of a produced polymer.
With respect to a method for producing an aromatic polycarbonate from an aromatic dihydroxy compound and a diaryl carbonate, in a conventionally known melt polycondensation process a polycarbonate is produced by performing an ester exchange reaction between bisphenol A and diphenyl carbonate in the molten state, while removing a by-produced phenolic compound (phenol). Unlike the interfacial polycondensation process, the melt polycondensation process has an advantage in that a solvent need not be used. However, the melt polycondensation process has a serious problem, namely; since the viscosity of polymer being formed increases during the progress of the polymerization reaction, it becomes difficult to remove by-produced phenol from the polymerization reaction system efficiently, thus making-it difficult to achieve a high degree of polymerization with respect to polycarbonate produced.
Various polymerizers have been known for use in producing aromatic polycarbonates. An agitation type polymerizer vessel equipped with an agitator is widely used. The agitation type polymerizer vessel equipped with an agitator is advantageous in that it exhibits high volumetric efficiency and has a simple construction, so that polymerization on a small scale can be efficiently carried out. However, the agitation type polymerizer vessel has a problem in that, as mentioned above, the by-produced phenol becomes difficult to remove from the polymerization reaction system efficiently in the production of aromatic polycarbonates on a commercial scale, so that it is difficult to achieve a high degree of polymerization with respect to produced polycarbonate.
Specifically, a large-scale agitation type polymerizer vessel generally has a greater ratio of liquid volume to vaporization area than a small-scale one. In other words, the depth of a reaction mixture in the polymerizer is large. In such a case, even if the degree of vacuum of the polymerization reaction zone is raised in order to achieve a high degree of polymerization in the lower part of the agitation vessel, the polymerization proceeds under virtually high pressure due to the weight of the reaction mixture, so that phenol and the like cannot be efficiently removed.
To solve the above-mentioned problem, various attempts have been made to remove phenol and the like from high viscosity polymer being formed. For example, Examined Japanese Patent Application Publication No. 50-19600 discloses a screw type polymerizer having a vent. Examined Japanese Patent Application Publication No. 53-5718 discloses a thin film evaporation type reactor, such as a screw evaporator and a centrifugal film evaporator. Further, Unexamined Japanese Patent Application Laid-Open Specification No. 2-15
REFERENCES:
patent: 2719776 (1955-10-01), K ummel
patent: 3110547 (1963-11-01), Emmert
patent: 3888826 (1975-06-01), Yamana
patent: 5225526 (1993-07-01), Fukawa et al.
Kawakami Yoshifumi
Komiya Kyosuke
Okamoto Hiroshige
Asahi Kasei Kogyo Kabushiki Kaisha
Mosley Terressa M.
Seidleck James J.
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