Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1992-11-02
1995-05-23
Kight, III, John
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
528198, 528481, 528502, 526 65, C08G 6400
Patent
active
054183146
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INDUSTRIAL APPLICATION
The present Invention relates to a process for producing a polycarbonate. More particularly, the present invention is concerned with a process for producing a polycarbonate by subjecting a dihydroxy compound and a bisaryl carbonate to melt polycondensation through transesterification.
BACKGROUND ART
Polycarbonates are a general-purpose engineering thermoplastic and have found a wide range of applications, particularly in injection molding or a glass sheet as an alternative to a windowpane.
Interfacial polycondensation, transesterification and other methods have hitherto been applied to the production of these polycarbonates. Although interfacial polycondensation is generally effective for the production of a polycarbonate, it has drawbacks such as the use of toxic phosgene as a starting compound for the reaction and the remaining chlorine ions generated during the reaction in the resultant polycarbonate.
In order to eliminate the above-described drawbacks of the interfacial polycondensation, Japanese Patent Publication-A No. 182336/1988 discloses a process for producing a polycarbonate wherein a liquid trichloromethyl chloroformate as a dimer of phosgene is used instead of the toxic phosgene and subjected to interfacial polycondensation with a special dihydric phenol. This document, however, cites only 9,9-bis(4-hydroxyphenyl)fluorenes as the special dihydric phenol.
Angew. Chem., 99, 922 (1987) and German Patent DE 3440141 describe a process for producing a polycarbonate wherein triphosgene is used instead of the toxic phosgene and reacted with 2,2-bis(4-hydroxyphenyl)propane. This process, however, involves also a reaction mechanism whereby phosgene is generated.
In a process for producing a polycarbonate known in the art regarding the transesterification, a high-molecular-weight polycarbonate is produced by adding a transesterification catalyst to diphenyl carbonate and an aromatic dihydroxy compound as the starting compounds for the reaction, heating the mixture under reduced pressure to prepare a prepolymer while distilling off phenol and finally heating the prepolymer to 290.degree. C. or above in a high vacuum to distill off phenol (see U.S. Pat. No. 4,345,062). However, it is known that, unlike other engineering plastics, the melt viscosity of the high-molecular-weight polycarbonate is so high that the reaction should be conducted at a temperature as high as 290.degree. C. or above and that a high vacuum (10.sup.-2 Torr) is necessary for distilling off phenol having a high boiling point, so that the industrialization of this process is difficult also from the viewpoint of facilities, and the remaining phenol in the resultant polycarbonate has an adverse effect on the hue and properties of the polycarbonate.
However, various studies have been made on the transesterification because it can be conducted through melt polycondensation and is a technique which is excellent in profitability from the viewpoint of industry. In particular, since the viscosity of the reaction system becomes high when the polycondensation approaches completion, attempts have been made to use various types of apparatuses for the purpose of treating a reaction product having a high viscosity (Japanese Patent Publication-B No. 36159/1977 and Japanese Patent Publication-A Nos. 86618/1990 and 153923 to 153927/1990).
In the Japanese Patent Publication-B No. 36159/1977, the use of an intermeshing twin-screw extruder of a screw evaporator type is disclosed. This extruder, however, has problems of forming a black foreign matter in the residence section of screw grooves, the difficulty of controlling the residence time, the occurrence of coloring of the product due to the heating and the difficulty of efficiently removing distillates such as phenol as a by-product.
In the Japanese Patent publication-A Nos. 153923 to 153927/1990, use is made of a horizontal agitating polymerization tank. When this tank is used, although a large hold-up volume can be attained, the solution thickness becomes so large tha
REFERENCES:
patent: 3819332 (1974-06-01), Jaccard et al.
patent: 4313870 (1982-02-01), Imai et al.
patent: 5097002 (1992-03-01), Sakashita et al.
Japanese patent Laid Open Specification 51-121097 T. Fujiwara et al. Oct. 22, 1976.
Fukuda Yutaka
Kanno Tatsuya
Kuwana Takaaki
Oshino Yasuhiro
Yamamoto Tsutomu
Daicel Chemical Industries Ltd.
Kight III John
Mosley T.
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