Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-11-22
2001-07-24
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
Reexamination Certificate
active
06265524
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an economically advantageous process for producing polycarbonate having a high molecular weight and excellent color. More specifically, it relates to a process for producing polycarbonate through an ester interchange reaction between an aromatic dihydroxy compound and an aromatic carbonic acid diester produced by a specific process.
PRIOR ART
Polycarbonate is widely used for such applications as optical disks, mechanical parts and the like due to its excellent transparency, mechanical properties and thermal properties.
As a conventional industrial process for producing such polycarbonate, an interfacial polycondensation process in which an aromatic dihydroxy compound is reacted with phosgene and one in which an ester interchange reaction between an aromatic dihydroxy compound and an aromatic carbonic acid diester typified by diphenyl carbonate is carried out in a molten state are widely used.
To produce polycarbonate through an ester interchange reaction between an aromatic dihydroxy compound and an aromatic carbonic acid diester, an ester interchange catalyst typified by a basic compound is used to perform ester interchange in a molten state while heating at a temperature of 160 to 300° C., and the reaction product is directly pelletized after the completion of the reaction to produce a product. Therefore, this process is simpler and more economical than the interfacial polycondensation process.
An aromatic carbonic acid diester is generally produced through a dehydrochlorination reaction between an aromatic monohydroxy compound and phosgene, that is, so-called phosgene process. This process, however, involves safety and environmental problems because of the use of phosgene. Further, since the obtained aromatic carbonic acid diester contains an organic acid typified by phenyl chloroformate as a reaction intermediate, an ester interchange reaction is impeded when an aromatic polycarbonate is to be produced through the ester interchange reaction. Therefore, purification for removing the organic acid, for example, purification by washing with hot water as disclosed by JP-B 38-1373 (the term “JP-B” as used herein means an “examined Japanese patent publication”), must be carried out.
An aromatic carbonic acid diester obtained through an ester interchange reaction between an alkyl carbonate typified by dimethyl carbonate and an aromatic monohydroxy compound without using phosgene increases the costs of an aromatic carbonic acid diester due to its low reaction yield, which induces an increase in the costs of the obtained aromatic polycarbonate. Therefore, it is not practical. However, since it does not contain an organic acid as a reaction intermediate unlike the above aromatic carbonic acid diester obtained by using phosgene, the need for washing with hot water to remove the organic acid is low and simple purification such as distillation may be carried out.
As a process for obtaining an aromatic carbonic acid diester at a low cost without using phosgene, JP-A 8-333307 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) proposes a process for obtaining an aromatic carbonic acid diester through the decarbonylation reaction of an aromatic oxalic acid diester.
Although the aromatic oxalic acid diester can be produced through an ester interchange reaction between an alkyl oxalate typified by dimethyl oxalate and an aromatic monohydroxy compound, the reaction rate of an ester interchange reaction between an alkyl oxalate and an aromatic monohydroxy compound is extremely high. Further, the yield of an aromatic carbonic acid diester produced through the decarbonylation reaction of an aromatic oxalic acid diester is also high. Consequently, an aromatic carbonic acid diester can be produced by the above process at a low cost.
In the decarbonylation reaction of an aromatic oxalic acid diester described in the above publication, an organic phosphorus compound is used as a catalyst. Typical examples of the organic phosphorus compound include phosphonium salts, phosphine, phosphine dihalide and phosphine oxide. Phosphonium halide, phosphine dihalide and a combination of phosphine or phosphine oxide and a halogen compound are preferred as a catalyst. In the decarbonylation reaction described in the above publication, an organic phosphorus compound containing halogen is inevitably used to obtain an aromatic carbonic acid diester at a high yield.
An aromatic carbonic acid diester produced through the above decarbonylation reaction does not contain an organic acid as a reaction intermediate impurity unlike an aromatic carbonic acid diester synthesized by the phosgene process. However, according to studies conducted by the inventors of the present invention, it has been revealed that when an aromatic polycarbonate is produced through an ester interchange reaction between an aromatic carbonic acid diester obtained by the above decarbonylation reaction and an aromatic dihydroxy compound, the obtained aromatic polycarbonate does not have a sufficiently high molecular weight and satisfactory color.
Problems that the Invention tries to Solve
The present inventors have conducted intensive studies to produce an aromatic polycarbonate having a high molecular weight and excellent color from an aromatic carbonic acid diester obtained through the above decarbonylation reaction and an aromatic dihydroxy compound and have found that it is effective in producing the aromatic polycarbonate to control the content of hydrolyzable halogen contained in the aromatic carbonic acid diester to a value lower than a predetermined value. The present invention has been accomplished based on this finding.
Means for Solving the Problem
That is, according to the present invention, there is provided a process for producing an aromatic polycarbonate through an ester interchange reaction between an aromatic carbonic acid diester and an aromatic dihydroxy compound, wherein the aromatic carbonic acid diester is obtained through the decarbonylation reaction of an aromatic oxalic acid diester represented by the following general formula (1):
wherein two Ar's are the same or different aromatic hydrocarbon groups having 6 to 14 carbon atoms, and contains 5 ppm or less of hydrolyzable halogen.
The process for producing an aromatic polycarbonate according to the present invention will be described in detail hereinafter.
In the present invention, the aromatic polycarbonate is produced through an ester interchange reaction between an aromatic dihydroxy compound and an aromatic carbonic acid diester, and a characteristic feature is that there is used the aromatic carbonic acid diester obtained through the decarbonylation reaction of an aromatic oxalic acid diester represented by the above general formula (1).
The aromatic dihydroxy compound may be one which is generally used as a dihydroxy component of an aromatic polycarbonate. More specifically, an aromatic dihydroxy compound represented by the following general formula (3) is used.
wherein W is —O—, —S—, —SO—, —SO
2
—,
In the above general formula (3), n is an integer of 0 to 4, R
5
and R
6
are the same or different and each a halogen atom or hydrocarbon group having 1 to 12 carbon atoms. The halogen atom is preferably a chlorine atom, bromine atom or iodine atom. The hydrocarbon group is advantageously an aliphatic hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 5 carbon atoms, such as methyl group or ethyl group, or an aromatic hydrocarbon group having 6 to 12 carbon atoms, such as phenyl group. R
7
and R
8
are the same or different and each a halogen atom, hydrogen atom or hydrocarbon group having 1 to 12 carbon atoms. Illustrative examples of the hydrocarbon group are the same as those listed for the above R
5
and R
6
. R
9
is an alkylene group having 3 to 8 carbon atoms.
Illustrative examples of the aromatic dihydroxy compound include bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4-bis(4-hydroxyphenyl)heptan
Sasaki Katsushi
Sawaki Toru
Takemoto Hidemi
Boykin Terressa M.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Teijin Limited
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