Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1997-09-19
1998-11-24
Mosley, Terressa
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C08G 6400
Patent
active
058408266
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of The Invention
The present invention relates to a method for producing an aromatic polycarbonate. More particularly, the present invention is concerned with a method for producing an aromatic polycarbonate, comprising subjecting to a transesterification reaction in a polymerizer at least one polymerizable material selected from the group consisting of a molten monomer mixture of an aromatic dihydroxy compound and a diaryl carbonate, and a molten prepolymer obtained by a process comprising reacting an aromatic dihydroxy compound with a diaryl carbonate, wherein the polymerizable material is present in the form of a liquid mass in the polymerizer and wherein the liquid mass of polymerizable material being transesterified in the polymerizer has an exposed surface, and wherein the transesterification reaction of the liquid mass of polymerizable material is performed under reaction conditions such that an evaporation surface area S (m.sup.2) which is defined as the area (m.sup.2) of the exposed surface of the liquid mass of polymerizable material, the volume V (m.sup.3) of the liquid mass of polymerizable material in the polymerizer, and the number average molecular weight Mn of the aromatic polycarbonate to be produced satisfy specific relationships. According to the method of the present invention, not only can a high quality aromatic polycarbonate having high heat resistance be obtained at high polymerization rate without suffering problems (such as discoloration, entry of impurities and generation of a thermal decomposition product) which are likely to be encountered in the production by a conventional method, but also a very large motive power for agitation is not needed and a scale-up of the polycarbonate production is easy. Therefore, the method of the present invention is commercially advantageous.
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 transesterification 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 transesterification process has an advantage in that a solvent need not be used. However, the transesterification 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 by the transesterification process. A vertical agitation type polymerizer vessel equipped with an agitator is widely used. The vertical a
REFERENCES:
patent: 3888826 (1975-06-01), Yamana et al.
patent: 5596067 (1997-01-01), Komiya et al.
Fukuoka Shinsuke
Kawamura Mamoru
Komiya Kyosuke
Asahi Kasei Kogyo Kabushiki Kaisha
Mosley Terressa
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