Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1996-01-11
1997-07-22
Mosley, Terressa
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
526 59, 528198, C08G 6400
Patent
active
056504802
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for preparing a polycarbonate. More specifically, it relates to a process for efficiently preparing a polycarbonate, which is free from residence burn and excellent in quality and color tone, without impairing its hydrolysis resistance from a dihydroxy compound and a carbonic acid diester in accordance with an ester exchange method by adjusting the concentration of oxygen in an atmosphere where the ester exchange is carried out.
BACKGROUND ART
In general, as methods for preparing a polycarbonate (hereinafter referred to as "PC"), there are known a method which comprises directly reacting an aromatic dihydroxy compound such as bisphenol A with phosgene (an interfacial method), and another method which comprises carrying out an ester exchange reaction between an aromatic dihydroxy compound such as bisphenol A and a carbonic acid diester such as diphenyl carbonate in a melting state (a melting method).
In the PC preparation methods, the above-mentioned interfacial method has some problems. For example, (1) harmful phosgene must be used, (2) chlorine-containing compounds such as hydrogen chloride and sodium chloride as by-products accelerate the corrosion of the manufacturing apparatus, and (3) it is difficult to separate impurities such as sodium hydroxide with which the resin is contaminated and which has a harmful influence on the physical properties of the polymer.
On the other hand, the above-mentioned melting method has an advantage that the PC can be manufactured more inexpensively as compared with the interfacial method. In the melting method, however, the reaction is done at a high temperature of 280.degree. to 310.degree. C. for a long period of time, and therefore this method has a large drawback that a problem regarding the coloring of the resin is unavoidable.
In such a melting method, various improved techniques have been suggested in order to decrease this coloring phenomenon. For example, Japanese Patent Publication No. 39972/1986 and Japanese Patent Application Laid-open No. 223036/1988 have disclosed methods using specific catalysts. Furthermore, Japanese Patent Application Laid-open Nos. 151236/1986 and 158719/1987 have disclosed methods in which an antioxidant is added in the second half of reaction. Moreover, in Japanese Patent Application Laid-open No. 62522/1986, the use of a twin-screw bent type kneading extruder in the second half of reaction has been disclosed, and in Japanese Patent Application Laid-open No. 153925/1990, an improved technique regarding a process has been disclosed in which a transverse type stirring polymerizer is used. Additionally, in Japanese Patent Application Laid-open No. 175722/1990, a method has been disclosed in which the content of hydrolyzable chlorine in a monomer is controlled to a certain level or less.
However, the problem of the coloring has not completely been solved yet, and a technique for obtaining the satisfactory PC has not been attained so far.
DISCLOSURE OF THE INVENTION
Under the above-mentioned circumstances, the present inventors have intensively researched with the intention of improving an ester exchange process by which the drawbacks of the above-mentioned conventional methods can be solved and the PC having an excellent color tone can efficiently be prepared.
As a result, it has been found that the above-mentioned problems can be solved by adjusting the concentration of oxygen in an atmosphere where an ester exchange reaction is carried out, when the PC is prepared by the ester exchange process. In consequence, the present invention has been completed on the basis of such a knowledge.
That is to say, according to the present invention, there can be provided a process for preparing a polycarbonate from a dihydroxy compound (A) and a carbonic acid diester (B) in accordance with an ester exchange method, said process comprising the step of adjusting, to 2 ppm or less, the concentration of oxygen in an atmosphere where an ester exchange reaction is carried out.
BEST MODE FO
REFERENCES:
patent: 5349042 (1994-09-01), Kuze et al.
patent: 5459225 (1995-10-01), Kuze et al.
Kuze Shigeki
Okumura Ryozo
Takahashi Seiji
Idemitsu Petrochemical Co. Ltd.
Mosley Terressa
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