Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Patent
1997-12-11
1999-07-27
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
059291923
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for producing an aromatic polycarbonate resin and, more specifically, to a process for producing an aromatic polycarbonate resin, which comprises the step of melt polycondensing an aromatic dihydroxy compound and an aromatic carbonic acid diester and which allows continuous operation to be performed on an industrial scale for a prolonged period of time.
PRIOR ART
Aromatic polycarbonate resins have excellent mechanical properties such as impact resistance as well as excellent heat resistance and transparency, and are widely used as a molding material. Such aromatic polycarbonate resins are produced by known methods including an interfacial method in which an aromatic dihydroxy compound such as bisphenol is allowed to react directly with phosgene; and a melt polycondensation method in which an aromatic dihydroxy compound such as bisphenol and an aromatic carbonic acid diester such as diphenyl carbonate are subjected to an ester exchange reaction in a molten state.
Of these production methods, the method of producing a polycarbonate by subjecting an aromatic dihydroxy compound and an aromatic carbonic acid diester to an ester exchange reaction is one in which an aromatic dihydroxy compound and an aromatic carbonic acid diester are heated up to 250 to 330.degree. C. to melt and subjected to an ester exchange reaction, in a molten state, at a reduced pressure in the presence of a catalyst such as an organic acid salt, inorganic acid salt, hydroxide, hydride or alcoholate of a metal.
In this ester exchange reaction, the operation of recovering the vapor of an aromatic monohydroxy compound as a by-product by a condenser is required and a scrubber type condenser which uses a cooled aromatic monohydroxy compound as a scrubbing solution is usable as the condenser. However, since the freezing point of the aromatic monohydroxy compound is high, the temperature of the scrubbing solution cannot be sufficiently lowered, whereby the recovery efficiency is low and it is difficult to maintain a degree of reduced pressure required for the reaction.
To solve the above problems, JP-A 6-065367 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") proposes a process which uses a high-boiling and low-melting compound other than the by-produced aromatic monohydroxy compound as a scrubbing solution. This publication lists tetraethylene glycol, dibenzyl toluene and mono- or dialkyl-substituted diphenyl ether in which the alkyl group has 8 to 18 carbon atoms as specific examples of the compound used as the scrubbing solution.
However, in this process, the scrubbing solution must be recycled after separating the by-produced aromatic monohydroxy compound from a large amount of the scrubbing solution. And, generally, the scrubbing solution must be recycled in an amount of hundreds times the quantity of the by-produced aromatic composition in order to achieve sufficient scrubbing. Consequently, this process invites increases in equipment costs and energy load, which are industrially disadvantageous.
Further, it cannot be said that the above process is suitable for a long-time continuous operation when it is carried out on an industrial scale. In other words, the above process makes impossible a long-time stable operation because unreacted products and oligomers contained in the vapor of the aromatic monohydroxy compound discharged from the reaction system are solidified, accumulated in the scrubber and deposited in a bottom portion of the scrubber, thereby clogging up an exhaust line. The solidification of the unreacted product and the oligomer in the scrubber is considered to depend on the composition and solubility of the scrubbing solution. The above publication describes that such solidification occurs in the scrubber in the above process (page 3, column 3, lines 36-40) and further that the line in the bottom portion of the scrubber began to get clogged after 7 days of continuous operation in Examples (page 4, column 6, lines 30-40).
REFERENCES:
patent: 5444148 (1995-08-01), Alewelt et al.
Patent Abstract of JP 06 065 367, Mar. 8, 1994.
Miyauti Tetsurou
Sasaki Katsushi
Wawaki Toru
Mosley Terressa
Teijin Limited
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