JPH09255771A - Preparation of aromatic polycarbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an arom. polycarbonate which has uniform mol.wt. and possesses high quality free from coloring without fixation and clogging troubles derived from phenol or the like while continuously and stably maintaining vacuum for a long period of time by providing a wet vacuum pump using a sealing liq. contg. an arom. monohydroxy compd. and suitably withdrawing the sealing liq. SOLUTION: This process for preparing an arom. polycarbonate comprises preparing an arom. polycarbonate from an arom. dihydroxy compd. and a diallyl carbonate by transesterification while withdrawing an arom. monohydroxy compd. as a by-product using a vacuum pump under reduced pressure, wherein the whole or a part of the arom. hydroxy compd. produced as a by-product in a polymerizer is dissolved and/or mixed in a sealing liq. for a wet pump. and the sealing liq. is withdrawn either continuously or batchwise while maintaining the concn. of the by-product in the sealing liq. at not less than 1wt.%. The temp. of the wet vacuum pump is kept at -10 to 100 deg.C. If necessary, a dry vacuum pump may be provided between a polymerizer and a wet vacuum pump to enhance the degree of vacuum to a desired value.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a method for producing an aromatic polycarbonate.

[0002]

2. Description of the Related Art In recent years, aromatic polycarbonates have been widely used in many fields as engineering plastics having excellent heat resistance, impact resistance and transparency. Various studies have hitherto been made on the method for producing the aromatic polycarbonate, and among them, an aromatic dihydroxy compound, for example, 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A) and phosgene. Has been industrialized.

However, in this interfacial polycondensation method, toxic phosgene must be used, and the equipment is corroded by hydrogen chloride and sodium chloride produced as by-products and chlorine-containing compounds such as methylene chloride used in large amounts as a solvent. However, there is a problem that impurities such as sodium chloride, which adversely affect the physical properties of the polymer, and separation of residual methylene chloride are difficult.

On the other hand, as a method for producing an aromatic polycarbonate from an aromatic dihydroxy compound and a diaryl carbonate, for example, a transesterification of bisphenol A and diphenyl carbonate in a molten state is carried out, and an ester is polymerized while extracting by-product phenol. Exchange methods have been known for some time. Unlike the interfacial polycondensation method, the transesterification method has advantages such as not using a solvent.

Conventionally, various polymerization apparatuses are known as a polymerization apparatus for producing an aromatic polycarbonate by a transesterification method. These lead phenol and the like, which are by-produced as the polymerization progresses, to a condenser to be condensed. However, when the phenol generated from the polymerization reactor is immediately introduced into the condenser and condensed, the temperature of the condenser must be kept at a low temperature below the freezing point of phenol in order to condense it. Substances and low-polymerization substances adhere to the inside of the condenser and to the exhaust pipe connecting the condenser and the vacuum pump, gradually reducing the vacuum suction capacity and finally blocking the pipe, making continuous operation of the device impossible. Have the problem of doing.

In order to solve this problem, various measures have been taken to remove phenol and the like. For example, in Japanese Unexamined Patent Publication No. 6-49197, a method of switching two or more freeze condensers having a heat exchange section using a refrigerant of −10 to 40 ° C., and in Japanese Unexamined Patent Publication No. 6-65367, vapor pressure at 190 ° C. Specifically disclosed is a method in which two or more scrubbers having a scrubbing liquid of 10 mmHg or less are used.

[0007] In all of these methods, two or more condensers are provided in parallel and operated in a switching system. That is, when phenol or the like is accumulated in one condenser, another condenser is switched to use another condenser, and the condenser in which phenol or the like is accumulated is subjected to a cleaning treatment or the like. In all of these methods, the apparatus becomes complicated and the operation becomes complicated, and a large amount of energy is required for the heating operation for cooling and phenol recovery. Further, when the switching operation is performed, a trace amount of oxygen is likely to be mixed into the polymerization system, and the problem that the aromatic polycarbonate is colored is likely to occur. Furthermore, the former method has a problem that the molecular weight of the aromatic polycarbonate fluctuates due to pressure fluctuations during operation, and the latter method has many troubles such as clogging of equipment due to solidification precipitation of phenol etc. in the scrubbing liquid. However, there is a problem that is industrially unfavorable.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is, in a method for producing an aromatic polycarbonate by a transesterification method, fixing and blocking of phenol or the like inside a condenser or an exhaust pipe connecting the condenser and a vacuum pump. A trouble-free, vacuum suction capacity reduction, and continuous production of uncolored aromatic polycarbonate with a constant molecular weight for a long time without the need to operate while switching between two or more condensers in parallel It is an object of the present invention to provide an industrially preferable method that can be performed.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a wet vacuum pump using a sealing liquid containing an aromatic monohydroxy compound is used as the vacuum pump. It was found that the purpose can be achieved by extracting the sealing liquid continuously or batchwise,
The present invention has been completed.

That is, according to the present invention, (A) an aromatic polycarbonate is produced from an aromatic dihydroxy compound and a diaryl carbonate by extracting an aromatic monohydroxy compound by-produced by a transesterification method under reduced pressure using a vacuum pump. At this time, a wet vacuum pump is used as the vacuum pump, and all or part of the aromatic monohydroxy compound by-produced in the polymerization vessel is dissolved and / or mixed in the sealing liquid of the wet vacuum pump to obtain an aromatic monohydroxy compound. The method for producing an aromatic polycarbonate, wherein the sealing liquid is continuously or batchwise extracted from the wet vacuum pump while maintaining the concentration in the sealing liquid of 1% by weight or more, and (B) is extracted from the polymerization vessel. 3% by weight or more of the aromatic monohydroxy compound based on the total amount of the aromatic monohydroxy compound The method of producing the aromatic polycarbonate (A) described above, wherein the extracting and dissolving and / or mixed in the sealing liquid of the wet vacuum pump, (C)
A method for producing an aromatic polycarbonate according to the above (A) or (B), characterized in that a dry vacuum pump is provided between the polymerizer and the wet vacuum pump, (D) The temperature of the wet vacuum pump is -10 to 100 ° C. The method for producing an aromatic polycarbonate according to (A), (B) or (C) above, wherein (E) the exhaust port of the wet vacuum pump is connected to a detoxification tower. ), (B),
A method for producing an aromatic polycarbonate of (C) or (D) is provided.

Conventionally, in the method for producing an aromatic polycarbonate by the transesterification method, as described above, it has been attempted to equip two or more condensers in parallel and operate while switching. However, surprisingly, the total amount or a part of the aromatic monohydroxy compound produced as a by-product in the polymerization vessel is continuously dissolved and / or mixed in the sealing liquid of the wet vacuum pump to adjust the concentration of the aromatic monohydroxy compound to 1%.
By keeping the liquid content of at least 10% by weight and extracting the sealing liquid continuously or batchwise from the wet vacuum pump, a low-temperature condenser that causes sticking and clogging becomes unnecessary, and the fragrance can be removed without performing a switching operation. It has been revealed that the group polycarbonate can be continuously produced for a long time.

That is, 3% by weight or more of the aromatic monohydroxy compound with respect to the total amount of the aromatic monohydroxy compound withdrawn from the polymerization vessel is dissolved and / or mixed in the sealing liquid of the wet vacuum pump and withdrawn, As described above, since it is not always necessary to provide a condenser between the polymerization vessel and the vacuum pump, and it is not necessary to lower the temperature for condensation, the clogging of the aromatic monohydroxy compound does not occur. Further, when the aromatic monohydroxy compound is accumulated in the sealing liquid, only a part of the sealing liquid needs to be extracted. Such a withdrawal operation can be performed by a batch operation, but can also be performed continuously, and there is no complexity of the switching operation as in the past. Furthermore, there is no pressure fluctuation during operation, and there is no fluctuation in the molecular weight of the aromatic polycarbonate.

Further, if necessary, a dry type vacuum pump may be installed between the polymerization vessel and the wet vacuum pump to increase the degree of vacuum to a desired degree of vacuum. This is particularly useful in the latter half of the polymerization reactor, which usually requires a high vacuum, and is one of the great features of the present invention. Hereinafter, the present invention will be described in detail.

In the present invention, the aromatic dihydroxy compound is a compound represented by the following formula. HO-Ar-OH (wherein, Ar represents a divalent aromatic group). The divalent aromatic group Ar is preferably, for example, one represented by the following formula. -Ar ¹ -Y-Ar ^2- (wherein, Ar ¹ and Ar ² each independently represent a divalent carbocyclic or heterocyclic aromatic group having 5 to 70 carbon atoms, and Y represents carbon Represents a divalent alkane group having the numbers 1 to 30).

In the divalent aromatic groups Ar ¹ and Ar ² ,
One or more hydrogen atoms are other substituents that do not adversely affect the reaction, for example, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, It may be substituted with a cyano group, an ester group, an amide group, a nitro group or the like.

Preferred specific examples of the heterocyclic aromatic group include an aromatic group having one or more ring-forming nitrogen, oxygen or sulfur atoms. The divalent aromatic groups Ar ¹ and Ar ² represent groups such as substituted or unsubstituted phenylene, substituted or unsubstituted biphenylene, and substituted or unsubstituted pyridylene. The substituent here is as described above.

The divalent alkane group Y is, for example,
Is an organic group represented by

[0018]

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(Wherein R ¹ , R ² , R ³ , and R ⁴ each independently represent hydrogen, an alkyl group having 1 to 10 carbon atoms,
10 alkoxy groups, a cycloalkyl group having 5 to 10 ring carbon atoms, a carbocyclic aromatic group having 5 to 10 ring carbon atoms,
Represents a carbocyclic aralkyl group having 6 to 10 carbon atoms. k is 3
And R ⁵ and R ⁶ are independently selected for each X, independently of one another, hydrogen or C 1
And X represents an alkyl group, and X represents carbon. Also,
In R ¹ , R ² , R ³ , R ⁴ , R ⁵ , and R ⁶ , other substituents such as a halogen atom and an alkyl having 1 to 10 carbon atoms are used as long as one or more hydrogen atoms do not adversely affect the reaction. It may be substituted by a group, an alkoxy group having 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group, a nitro group, or the like. Examples of such a divalent aromatic group Ar include those represented by the following formula (2).

[0020]

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(Wherein R ⁷ and R ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and a cyclo group having 5 to 10 ring carbon atoms) An alkyl group or a phenyl group, m and n
Is an integer of 1 to 4, and when m is 2 to 4, each R ⁷ may be the same or different, and n is 2 to 4
In this case, each R ⁸ may be the same or different. Further, the divalent aromatic group Ar may be represented by the following formula. —Ar ¹ —Z—Ar ² — (In the formula, Ar ¹ and Ar ² are as described above, and Z is a single bond or —O—, —CO—, —S—, —SO ₂ —, —SO—,
_{-COO -, - CON (R 1} ) - represents a divalent group, such as. Here, R ¹ is as described above. Examples of such a divalent aromatic group Ar include those represented by the following formula (3).

[0022]

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(In the formula, R ⁷ , R ⁸ , m and n are as described above.) The divalent aromatic group Ar is a substituted or unsubstituted phenylene, a substituted or unsubstituted biphenylene, It may be a substituted or unsubstituted pyridylene or the like. The substituents here are
A halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, which does not adversely affect the reaction,
Examples thereof include an ester group, an amide group, a nitro group and the like.

The aromatic dihydroxy compound used in the present invention may be a single type or two or more types. A typical example of the aromatic dihydroxy compound is bisphenol A. The diaryl carbonate used in the present invention is represented by the following chemical formula 4.

[0025]

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(In the formula, Ar ³ and Ar ⁴ each represent a monovalent aromatic group.) Ar ³ and Ar ⁴ each represent a monovalent carbocyclic or heterocyclic aromatic group. ³ , in Ar ⁴ , one or more hydrogen atoms has another substituent that does not adversely affect the reaction;
For example, a halogen atom, an alkyl group having 1 to 10 carbon atoms,
It may be substituted by an alkoxy group having 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group, a nitro group, or the like. A
r ³ and Ar ⁴ may be the same or different.

Representative examples of the monovalent aromatic groups Ar ³ and Ar ⁴ include phenyl group, naphthyl group, biphenyl group and pyridyl group. These may be substituted with one or more types of the above-mentioned substituents. Preferred Ar ³
Examples of Ar ⁴ and Ar ⁴ include, for example,

[0028]

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A typical example of the diaryl carbonate is represented by the following chemical formula 6.

[0030]

[Chemical 6]

(Wherein R ⁹ and R ¹⁰ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms,
An alkoxy group having 10; a cycloalkyl group having 5 to 10 ring carbon atoms; or a phenyl group;
When p is 2 or more, each R ⁹ may be different, and when q is 2 or more,
Each R ¹⁰ may be different. Among these diphenyl carbonates, unsubstituted diphenyl carbonate, ditolyl carbonate, di-t
Symmetric diaryl carbonates, such as lower alkyl-substituted diphenyl carbonates such as -butylphenyl carbonate, are preferred, with diphenyl carbonate being the simplest diaryl carbonate being particularly preferred.

These diaryl carbonates may be used alone or in combination of two or more. The usage ratio (charge ratio) of the aromatic dihydroxy compound and the diaryl carbonate varies depending on the type of the aromatic dihydroxy compound and the diaryl carbonate used, the polymerization temperature and other polymerization conditions. On the other hand, it is usually 0.8 to 2.5 mol, preferably 0.9 to
It is used in a proportion of 2.0 mol, more preferably 0.95 to 1.5 mol.

In producing an aromatic polycarbonate by reacting an aromatic dihydroxy compound and a diaryl carbonate, the reaction temperature is usually selected in the range of 50 to 350 ° C, preferably 100 to 290 ° C. Aromatic monohydroxy compounds are produced as the reaction progresses. The aromatic monohydroxy compound of the present invention is represented by the following chemical formula 7.

[0034]

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(In the formula, R ⁹ and p are as described above.) The reaction rate can be increased by removing the aromatic monohydroxy compound, diaryl carbonate and the like out of the reaction system under reduced pressure. The preferred reaction pressure varies depending on the type and molecular weight of the aromatic polycarbonate to be produced, the polymerization temperature, etc., but when producing an aromatic polycarbonate from bisphenol A and diphenyl carbonate, for example,
When the number average molecular weight is 1000 or less, 50 mmHg
~ Normal pressure is preferable, and number average molecular weight is 1000 to 2
In the range of 000, the range of 3 mmHg to 50 mmHg is preferable, and in the range of the number average molecular weight of 2000 or more, 2
It is preferably 0 mmHg or less, more preferably 10 mmHg or less, and particularly preferably 2 mmHg or less.

The transesterification reaction can be carried out without adding a catalyst, but it is carried out in the presence of a catalyst, if necessary, in order to increase the polymerization rate. The polymerization catalyst is not particularly limited as long as it is used in this field, and hydroxides of alkali metals and alkaline earth metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide are used. Alkali metal salts, alkaline earth metal salts, and quaternary ammonium salts of boron or aluminum hydrides such as lithium aluminum hydride, sodium borohydride, and tetramethylammonium borohydride;
Alkali metal and alkaline earth metal hydrogen compounds such as lithium hydride, sodium hydride and calcium hydride; alkali metal and alkaline earth metal alkoxides such as lithium methoxide, sodium ethoxide and calcium methoxide; lithium Phenoxide, sodium phenoxide, magnesium phenoxide, LiO
-Ar-OLi, NaO-Ar-ONa (Ar is an aryl group) and other alkali metal and alkaline earth metal aryloxides; lithium acetate, calcium acetate, sodium benzoate and other alkali metal and alkaline earth metal organic acids Salts; zinc compounds such as zinc oxide, zinc acetate, zinc phenoxide; boron oxide, boric acid, sodium borate, trimethyl borate, tributyl borate, triphenyl borate, (R ₁ R ₂ R ₃ R ₄ ) NB (R ₁ R ₂ R ₃ R ₄ ) or (R
₁ R ₂ R ₃ R ₄ ) PB (R ₁ R ₂ R ₃ R ₄ ) Ammonium borate or phosphonium borate (R ₁ , R ₂ , R ₃ ,
R ₄ is as described in Chemical formula 3 above. Compounds such as); silicon oxide, sodium silicate, tetraalkyl silicon, tetraaryl silicon, diphenyl-ethyl-
Silicon compounds such as ethoxysilicon; germanium oxide, germanium tetrachloride, germanium ethoxide,
Germanium compounds such as germanium phenoxide; tin compounds such as tin compounds and organotin compounds combined with an alkoxy or aryloxy group such as tin oxide, dialkyltin oxide, dialkyltin carboxylate, tin acetate, and ethyltin tributoxide ;
Lead compounds such as lead oxide, lead acetate, lead carbonate, basic carbonate, alkoxide or aryloxide of lead and organic lead; onium compounds such as quaternary ammonium salt, quaternary phosphonium salt and quaternary arsonium salt Antimony compounds such as antimony oxide and antimony acetate;
Manganese compounds such as manganese acetate, manganese carbonate and manganese borate; titanium compounds such as titanium oxide, titanium alkoxide or aryloxide; zirconium compounds such as zirconium acetate, zirconium oxide, zirconium alkoxide or aryloxide, zirconium acetylacetone And the like.

When a catalyst is used, these catalysts may be used alone or in combination of two or more. The amount of these catalysts to be used is generally selected in the range of 10 ^-8 to 1% by weight, preferably 10 ^-7 to 10 ^-1 % by weight, based on the aromatic dihydroxy compound as the raw material. The wet vacuum pump used in the present invention is a vacuum pump that increases the degree of vacuum by using a liquid or a condensable gas. Specifically, various known wet vacuum pumps such as a liquid ring pump, an oil rotary pump, a zet pump, a steam ejector, an oil ejector, an oil diffusion ejector and an oil diffusion pump can be used (Japan Chemical Industry Association). Edited by Maruzen Co., Ltd .; revised edition of Chemical Engineering Handbook; March 18, 1988
Issued daily; P319; see Table 5.26). Among these wet vacuum pumps, a liquid ring pump, an oil rotary pump, and a zet pump are preferable. The material that can be used for the wet vacuum pump is not particularly limited, but iron-based metals, non-ferrous metals, and ceramics are used. Specific examples include cast iron,
Examples include stainless steel, titanium, aluminum alloys, copper alloys and the like.

The sealing liquid in the present invention means a liquid or a condensable gas used to increase the degree of vacuum in a wet vacuum pump. It is necessary that the concentration of the aromatic monohydroxy compound in the sealing liquid of the present invention is maintained at 1% by weight or more, preferably 5% by weight or more. If the concentration of the aromatic monohydroxy compound is less than 1% by weight, the amount of the sealing liquid extracted together with the aromatic monohydroxy compound produced as a by-product in the polymerization vessel becomes extremely large, which is not preferable. The components of the sealing liquid other than the aromatic monohydroxy compound are not particularly limited, but those having a boiling point equal to or higher than that of phenol are preferable for increasing the degree of vacuum. As a specific example, the carbon number is 2 to 8.
, Polyalkylene glycols having a molecular weight of 106 to 6000, alcohols having 8 to 18 carbon atoms, higher aliphatic hydrocarbons having 10 to 18 carbon atoms, and total number of carbon atoms in the alkyl group to be substituted. Is a 4-54 item,
Di- or tri-alkyl-substituted benzene, mono-, di-, tri- or tetra-alkyl-substituted biphenyl having a total number of carbon atoms of the substituting alkyl group, mono-, di-, tri- or di-alkyl having a total number of carbon atoms of the substituting alkyl group of 1-72 Examples thereof include tetraalkyl-substituted diphenyl ether and silicone oil.

In a preferred embodiment of the present invention, the amount of the aromatic monohydroxy compound extracted from the polymerization vessel is 3 with respect to the total amount.
An aromatic monohydroxy compound in an amount of not less than 7% by weight, preferably not less than 7% by weight, more preferably not less than 10% by weight is dissolved and / or mixed in a sealing liquid from a wet vacuum pump and extracted. The remaining aromatic monohydroxy compounds other than those extracted from the wet vacuum pump are extracted from the condenser and the scrubber. At this time, it is not necessary to completely extract the aromatic monohydroxy compound in the condenser or the abatement tower, and therefore the temperature of the condenser is operated at a temperature higher than the freezing point of the aromatic monohydroxy compound, which causes clogging trouble. The absence of this is also a major feature of the present invention. Further, when the aromatic monohydroxy compound is extracted from the polymerization vessel, the diaryl carbonate, aromatic dihydroxy compound, and the like that are extracted at the same time can be extracted by dissolving or mixing all or part of them in the sealing liquid of the wet vacuum pump. I can.

Further, as a preferred embodiment of the present invention, there is a method of providing one or more dry vacuum pumps between the polymerization vessel and the liquid ring pump in order to obtain a high vacuum. As a specific example, various well-known dry vacuum pumps such as reciprocating pumps, mechanical boosters (roots type, screw type), and gas ejectors can be used (edited by the Chemical Industry Association of Japan; published by Maruzen Co., Ltd .; chemical engineering). Fifth edition revised handbook; issued March 18, 1988; P31
9; see Tables 5 and 26). The dry vacuum pump is preferably used at a temperature equal to or higher than the melting point of the aromatic monohydroxy compound.

In the present invention, the temperature of the sealing liquid of the wet vacuum pump is -10 to 100 ° C, more preferably 40 to 80 ° C.
° C. When it is higher than 100 ° C, it becomes difficult to increase the degree of vacuum, and when it is lower than -10 ° C, precipitation of an aromatic monohydroxy compound is likely to occur in the vacuum pump. further,
In the present invention, a method of connecting the exhaust port 11 of the wet vacuum pump to the abatement tower is also mentioned as a preferable embodiment. A trace amount of the aromatic monohydroxy compound which is not dissolved and / or mixed in the sealing liquid can be absorbed by the abatement tower.

FIG. 1 shows a specific example of the case where the wet vacuum pump is a liquid ring pump. The aromatic monohydroxy compound is inhaled through the intake port 1. On the other hand, the sealing liquid 2 containing 1% by weight or more of the aromatic monohydroxy compound enters from the liquid inlet 3. At this time, in the pump body 4, the aromatic monohydroxy compound sucked from the intake port 1 is dissolved and / or mixed with the sealing liquid 2 that has entered from the liquid inlet 3. Both the sealing liquid 2 in which the aromatic monohydroxy compound is dissolved and / or mixed and the gas insoluble in the sealing liquid are discharged from the discharge port 5 to the gas-liquid separation / sealing liquid storage tank 6. In the gas-liquid separation / sealing liquid storage tank 6, the gas that is not dissolved in the sealing liquid is discharged from the exhaust port 7 as exhaust gas. On the other hand, the sealing liquid 2 in which the aromatic monohydroxy compound is dissolved and / or mixed is transferred from the liquid outlet 8 to the heat exchanger 9. In the heat exchanger 9, the temperature of the sealing liquid 2 is controlled to a predetermined temperature in the range of -10 to 100 ° C, preferably 40 to 80 ° C. Sealing liquid 2 in which the aromatic monohydroxy compound flowing out from the heat exchanger 9 is dissolved and / or mixed 2
Are circulated by entering the pump body 4 from the liquid inlet 3 again. Further, since the sealing liquid 2 is diluted by dissolving or mixing the aromatic monohydroxy compound, the sealing liquid 2
In order to maintain the composition of, the makeup sealing liquid 11 may be newly injected from the liquid injection port 10 of the gas-liquid separation / sealing liquid storage tank,
It is not always necessary to inject. There is no particular limitation on the concentration of the aromatic monohydroxy compound in the makeup sealing liquid 11.
The amount of increase in the case of injecting the makeup sealing liquid 11 and the amount of increase due to the dissolution and / or mixing of the aromatic monohydroxy compound are overflown from the liquid outlet 12 of the gas / liquid separation / sealing liquid storage tank 6 or by a pump. Pull out. The injection of the makeup sealing liquid 11 and the withdrawal of the sealing liquid 2 may be a continuous type or a batch type.

Next, an example of a preferable process flow used in the present invention will be described with reference to FIG. In FIG. 2, three agitated tank type polymerizers in the pre-polymerization step, a cylindrical perforated plate type polymerizer having a perforated plate in the post-polymerization step, and a cylindrical perforated plate type having a perforated plate and a plurality of columnar supports. One polymerization vessel is used for each.

In the prepolymerization step, the aromatic dihydroxy compound and the diaryl carbonate are introduced into the stirring tank type first (A) polymerization vessel 3 from the raw material supply port 1. The stirring tank type first (B) polymerization vessel 3'is
(A) It is exactly the same as the polymerizer, and can be used by switching when operating in batch. The inside of the polymerization vessel is under an atmosphere of an inert gas such as nitrogen, and is usually controlled near normal pressure. The polymerization intermediate 4 obtained by reacting for a predetermined time under stirring is discharged from the discharge port 5, continuously transferred by the transfer pump 6, and introduced into the stirring tank type second polymerization device 8 from the supply port 7. The inside of the polymerization vessel is controlled to a predetermined pressure, and the aromatic monohydroxy compound distilled out is introduced from the vent port 9 into the distillation column 10 for purification. After the aromatic monohydroxy compound is cooled in the condenser 11, it is taken out of the system by the liquid withdrawing pump 12, and unreacted substances and low-polymerized substances are returned from the liquid return port 13 to the polymerization vessel. The polymerization intermediate 14 which has reached a predetermined molecular weight under stirring is
It is discharged from the discharge port 15 while being controlled so as to keep the amount of the polymer melt in the polymerization vessel constant, and is transferred by the transfer pump 16.

In the post-polymerization step, the polymerization intermediate 14 is supplied from the supply port 17 to the circulation line 18. It is introduced into the inside of the perforated plate-type first polymerization vessel 20 through the perforated plate 19 and becomes a film-like, thread-like, droplet-like, or mist-like polymerization intermediate 21. The polymerization intermediate 21 is allowed to fall freely inside the polymerization vessel. The inside of the polymerization vessel is controlled to a predetermined pressure, such as an aromatic monohydroxy compound distilled from a molten mixture or a polymerization intermediate, and an inert gas such as nitrogen introduced from a gas supply port 22 as necessary. Is discharged from the vent port 23. The polymerization intermediate which has reached the bottom of the polymerization vessel in the form of film, thread, droplet, or mist is supplied again from the perforated plate 19 to the inside of the polymerization vessel through a circulation line 18 equipped with a circulation pump 24. The polymerization intermediate 25 having reached a predetermined molecular weight is discharged from the discharge port 27 by the transfer pump 26, and the supply port 2
8 to be introduced into the inside of the porous second polymerization vessel 30 through the perforated plate 29, and along with the columnar support 31, a polymerization intermediate 32 in the form of film or thread is formed. The polymerization intermediate 32 is dropped along with the inside of the polymerization vessel along with the cylindrical support 31. The inside of the polymerization vessel is controlled to a predetermined pressure, and the aromatic monohydroxy compound distilled from the polymerization intermediate and the inert gas such as nitrogen introduced from the gas supply port 33 as necessary are vented. It is discharged from the mouth 34. The polymer is discharged from the discharge port 36 by the discharge pump 35.

Here, a specific vacuum pump according to the present invention is used as the vacuum pump for depressurizing the polymerization tanks after the second stirring tank type second polymerization tank. In FIG. 2, the stirring tank type second
The polymerizer 8 is connected to a liquid ring pump 42 similar to that shown in FIG. 1 via a distillation column 10, a condenser 11, and a pipe 37. Cylindrical third polymerization vessel 20 having a perforated plate
Is a roots-type mechanical booster 4 connected in series in front of a liquid ring pump 42 via a pipe 38.
0 and 41 are connected. Similarly, the cylindrical polymerization vessel 30 having a plurality of columnar supports is also connected via a pipe 39.
It is connected to two roots type mechanical boosters 40 and 41 which are connected in series in front of the liquid ring pump 42. The exhaust gas of the liquid ring pump 42 is connected to the abatement tower 44 via a pipe 43. The aromatic monohydroxy compound absorbed in the sealing liquid is continuously or batchwise extracted from the liquid sealing pump 42.

Each of the polymerization units, circulation line, transfer line, discharge line, etc. is heated by a jacket or heater and kept warm.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to examples. Note that the molecular weight is a number average molecular weight (hereinafter, referred to as M) measured by gel permeation chromatography (GPC).
Abbreviated as n. ). The color was measured by a CIELAB method at a test piece thickness of 3.2 mm, and the yellowness was indicated by a b ^* value.

[0049]

Example 1 An aromatic polycarbonate was produced by a process as shown in FIG. However, the first agitating tank polymerization device was operated in batches while switching between (A) and (B), and the second agitating tank polymerization device was operated continuously. Stirring tank 1st polymerization vessel (A), the internal volume of (B) is 100 liters, stirring tank 2nd
The inner volume of the polymerization vessel was 50 liters, and the stirring blades were all anchor type. Bisphenol A as the aromatic dihydroxy compound, diphenyl carbonate as the diaryl carbonate (molar ratio of bisphenol A to 1.0)
6) was introduced into the stirring tank type first (A) and (B) polymerizers, and the molten mixture was introduced into the stirring tank type second polymerizer at 2 liter / hr.
Supplied with The stirring tank type first (A), (B) polymerization vessel is 17
0 ° C, atmospheric pressure, 240 ° C, 5 mm for the second tank of stirring tank type
The composition of the liquid seal of the liquid ring pump before starting the operation was 80.0% by weight of phenol and diphenyl carbonate 19.
A mixed solution of 0 wt% and bisphenol A 1.0 wt% was used. The liquid ring pump was operated at 60 ° C. Further, the sealing liquid was not supplied, and the sealing liquid increasing with the operation was periodically extracted. It operated continuously for 1000 hours under these conditions. As a result, the polymerizer was stably operated at a constant pressure, and the change with time of Mn was 2810 after 200 hours and 2870 after 400 hours.
600 hours later 2850, 800 hours later 2820, 100
A colorless and transparent aromatic polycarbonate (b ^* value 3.1) which was stable at 2850 after 0 hours was obtained. In addition, the composition of phenol in the liquid seal of the liquid ring pump during operation is always 8
The composition of the liquid seal of the liquid ring pump after the operation is 0.0 wt% or more, and the composition of the liquid seal is 95.2 wt% phenol, 4.7 wt% diphenyl carbonate, and 0.1 wt% bisphenol A.
Met. Further, the amount of phenol extracted from the liquid ring pump was 16% by weight based on the total amount of phenol extracted from the polymerization vessel.

[0050]

Example 2 An aromatic polycarbonate was produced by the process shown in FIG. However, the first tank of the stirring tank in the prepolymerization step was operated in a batch manner while switching between (A) and (B), and the second tank of the stirring tank was continuously operated. The internal volume of the stirring tank first polymerization vessel (A), (B) is 100 liters, the internal volume of the stirring tank second polymerization vessel is 50 liters,
The stirring blades are all anchor type. The perforated plate type first polymerization vessel which was dropped from the perforated plate having the circulation line in the post-polymerization step was continuously operated. The perforated plate type first polymerizer is equipped with a perforated plate having 40 holes each having a hole diameter of 3.5 mm, and the dropping height is 4 m. Bisphenol A as the aromatic dihydroxy compound and diphenyl carbonate as the diaryl carbonate (molar ratio of bisphenol A to 1.
03) was introduced into the stirring tank type first (A) and (B) polymerization vessels,
4 liter / h of the molten mixture was added to the second tank of the stirring tank type.
r. The stirring tank type first (A) and (B) polymerizers have a temperature of 180 ° C., the pressure is atmospheric pressure, and the stirring tank type second polymerizer has a temperature of 2
30 ° C., pressure 50 mmHg, perforated plate type first polymerization vessel temperature 260 ° C., pressure 1.5 mmHg, circulation flow rate 100 liters / hr, nitrogen gas flow rate 1 liters / hr, liquid sealing of liquid ring pump before start of operation As the composition, a mixed solution of 96.0% by weight of tetraethylene glycol and 4.0% by weight of phenol was used. The liquid ring pump was operated at 45 ° C. The sealing liquid to be supplied is 99.5% by weight of tetraethylene glycol,
A mixed liquid having a composition of 0.5% by weight of phenol was used, and the supply was performed so that the composition of phenol in the sealing liquid was kept at 5.0% by weight. The sealing liquid, which increases with the operation, was withdrawn periodically. It operated continuously for 500 hours on this condition. as a result,
The polymerizer was stably operated at a constant pressure, and the change with time of Mn was 5980 after 100 hours and 5970 and 30 after 200 hours.
A colorless and transparent aromatic polycarbonate (b ^* value 3.4) was obtained, which was stable at 5960 after 0 hours, 6010 after 400 hours, and 5980 after 500 hours. The Mn of the aromatic polycarbonate extracted every 5 hours from 230 hours to 250 hours was 598 after 230 hours.
0,235 hours later 5990, 240 hours later 5970,2
It was very stable at 5990 after 45 hours and 5980 after 250 hours. The amount of phenol extracted from the liquid ring pump was 21% by weight based on the total amount of phenol extracted from the polymerization vessel.

[0051]

Example 3 An aromatic polycarbonate was produced by the process as shown in FIG. However, the same apparatus as in Example 2 was used except that two roots-type mechanical boosters were connected in series in front of the liquid ring pump, and the pre-polymerization step and the post-polymerization step were performed under the same conditions as in Example 2. I drove in.
The composition of the liquid seal of the liquid ring pump before the start of operation is phenol 8
Using a mixed solution of 5.0% by weight, 14.2% by weight of diphenyl carbonate and 0.8% by weight of bisphenol A, 7
It was operated at 0 ° C. Further, the sealing liquid was not supplied, and the sealing liquid increasing with the operation was periodically extracted. 750 in this condition
It was operated continuously for hours. As a result, the polymerization vessel was stably operated at a constant pressure, and the change with time of Mn was 602 after 150 hours.
0,300 hours later 5960, 450 hours later 5980,6
Aromatic polycarbonate (b ^* value of 3.) which is stable and stable at 5990 after 00 hours and 5970 after 750 hours.
3) was obtained. Further, the composition of the phenol of the liquid seal of the liquid ring pump during operation is always 85.0% by weight or more, and the composition of the liquid seal of the liquid ring pump after the operation is phenol 9%.
6.3% by weight, diphenyl carbonate 3.6% by weight,
It was 0.1% by weight of bisphenol A. The amount of phenol extracted from the liquid ring pump was 17% by weight based on the total amount of phenol extracted from the polymerization vessel.

[0052]

Comparative Example 1 An aromatic polycarbonate was produced by the process shown in FIG. However, an oil rotary pump was used as the vacuum pump, and the same apparatus as in Example 2 was used except that two oil rotary pumps were connected in parallel in front of the oil rotary pump, and a shell-and-tube freeze condenser was connected. The polymerization process was operated under the same conditions as in Example 2. The shell-and-tube freeze condensers (A) and (B) are batch-operated while periodically switching, and when one is in a regenerating operation, the other is connected to a reaction system.
The process stream was run from bottom to top and the coolant used was cold water at 5 ° C. For regeneration, steam at 180 ° C was used. Silicone oil was used as the sealing liquid for the oil rotary pump, and operation was performed at 25 ° C. without extracting the sealing liquid. It operated continuously for 500 hours on this condition. As a result, the Mn and color change of the obtained aromatic polycarbonate with time were 617 after 100 hours.
0 (b ^* value 3.4), after 5 hours 5990 (b ^* value 3.6), after 300 hours 6110 (b ^* value 3.
9), 5920 after 400 hours (b ^* value of 3.8), 50
After 0 hours, Mn was unstable with 6090 (b ^* value 3.9), and the color was not good. In addition, the shell and tube freeze condenser was switched after 240 hours. The Mn of the aromatic polycarbonate extracted every 5 hours from 230 hours before to 250 hours after that is 5950 after 230 hours and 583 after 235 hours.
0, 240 hours later 5740, 245 hours later 6230, 2
It was very unstable at 6180 after 50 hours. Further, the composition of phenol in the sealing liquid of the oil rotary pump after the operation was 1% by weight or less.

[0053]

Example 4 An aromatic polycarbonate was produced by the process as shown in FIG. However, the same apparatus as in Example 3 was used except that the horizontal stirring first polymerization vessel was used in the post-polymerization step, the pre-polymerization step was operated under the same conditions as in Example 3, and the horizontal stirring first polymerization in the post-polymerization step was performed. The vessel was operated at 280 ° C and 2 mmHg. The composition of the liquid seal of the liquid ring pump before the start of operation was 90.0% by weight of phenol and 9.
A mixture of 5% by weight and 0.5% by weight of bisphenol A was used, and operation was performed at 75 ° C. Further, the sealing liquid was not supplied, and the sealing liquid increasing with the operation was periodically extracted. It operated continuously for 500 hours on this condition. As a result, the polymerizer was stably operated at a constant pressure, and the change with time of Mn was 6220 after 100 hours, 6310 after 200 hours, and 628 after 300 hours.
A colorless and transparent aromatic polycarbonate (b ^* value 3.6) was obtained, which was stable at 0,400 hours, 6240, and 500 hours, 6270. In addition, the phenol composition of the liquid seal of the liquid ring pump during operation is always 90.0% by weight or more, and the composition of the liquid seal of the liquid ring pump after the operation is 95.3% by weight of phenol and 4% of diphenyl carbonate. It was 0.5% by weight and 0.2% by weight of bisphenol A. The phenol extracted from the liquid ring pump was 15% by weight based on the total amount of phenol extracted from the polymerization vessel.

[0054]

Example 5 An aromatic polycarbonate was produced by the process as shown in FIG. However, the first tank of the stirring tank in the prepolymerization step was operated in a batch manner while switching between (A) and (B), and the second tank of the stirring tank was continuously operated. The internal volume of the stirring tank first polymerization vessel (A), (B) is 100 liters, the internal volume of the stirring tank second polymerization vessel is 50 liters,
The stirring blades are all anchor type. The perforated plate type first polymerizer which is dropped from the perforated plate having the circulation line in the post-polymerization step and the perforated plate type second polymerizer which is dropped from the perforated plate along with the columnar support were continuously operated. The perforated plate type first polymerizer is equipped with a perforated plate having 50 holes each having a hole diameter of 3.0 mm, and the dropping height is 4 m. The perforated plate type second polymerizer is equipped with a perforated plate having 25 holes each having a hole diameter of 4.0 mm, and all 25 ports of the perforated plate are provided with SUS316 wire of 1.0 mmφ vertically from the center of the holes. It is installed so as to hang down to the liquid reservoir at the bottom of the polymerizer. The height along which the wire is dropped is 8 m. 2 in series in front of liquid ring pump
A roots-type mechanical booster is connected.
Bisphenol A as an aromatic dihydroxy compound and diphenyl carbonate as a diaryl carbonate (molar ratio of bisphenol A to 1.02) are stirred tank type No. 1
(A) and (B) were introduced into the polymerization vessel, and the molten mixture was supplied to the second agitating tank type polymerization vessel at 3 liter / hr. The stirring tank type first (A) and (B) polymerization vessels have a temperature of 180 ° C. and atmospheric pressure, and the stirring vessel type second polymerization vessel has a temperature of 230 ° C. and a pressure of 60 mm.
Hg, the temperature of the porous plate type first polymerization vessel is 250 ° C., the pressure is 3 mm
Hg, circulation flow rate 80 liters / hr, nitrogen gas flow rate 2 liters / hr, perforated plate type second polymerizer at temperature 245 ° C., pressure 0.7 mmHg, nitrogen gas flow rate 1 liter / hr,
The composition of the liquid seal of the liquid ring pump was a mixture of phenol 75.0% by weight, diphenyl carbonate 23.6% by weight, and bisphenol A 1.4% by weight, and the mixture was operated at 70 ° C. Further, the sealing liquid was not supplied, and the sealing liquid increasing with the operation was periodically extracted. It operated continuously for 2500 hours under these conditions. As a result, the polymerization reactor was stably operated at a constant pressure, and the change with time of Mn was 10260, 10 and 10 after 500 hours.
00 hours later 10210, 1500 hours later 10270, 2
Aromatic polycarbonate (b ^*) that is stable and colorless and transparent (10190 after 000 hours and 10230 after 2500 hours ⁾
A value of 3.4) was obtained. Further, the composition of the phenol in the liquid seal of the liquid ring pump during operation is always 75.0% by weight or more, and the composition of the liquid seal of the liquid ring pump after operation is 95.1% by weight of phenol and 4% diphenyl carbonate. It was 0.7% by weight and bisphenol A was 0.2% by weight. The amount of phenol extracted from the liquid ring pump was 18% by weight based on the total amount of phenol extracted from the polymerization vessel.

[0055]

EFFECTS OF THE INVENTION In the method for producing an aromatic polycarbonate by the transesterification method, there is no sticking and blocking troubles due to phenol, etc., a stable vacuum can be maintained for a long period of time, and a high-quality product with a constant molecular weight and no coloration. It has become possible to obtain the aromatic polycarbonate of

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a liquid ring pump which is one of wet vacuum pumps that achieves the method of the present invention.

FIG. 2 is a system diagram showing an example of a process flow for achieving the method of the present invention.

FIG. 3 is a systematic diagram showing an example of a process flow for achieving the method of the present invention.

FIG. 4 is a system diagram showing an example of a process flow for achieving the method of the present invention.

FIG. 5 is a system diagram showing an example of a process flow for achieving the method of the present invention.

FIG. 6 is a system diagram showing a process flow of Comparative Example 1 which is a conventional technique.

FIG. 7 is a system diagram showing an example of a process flow for achieving the method of the present invention.

[Explanation of symbols]

In FIG. 1, 1 intake port 2 sealing liquid 3 liquid inlet 4 pump body 5 discharge port 6 gas-liquid separation / sealing liquid storage tank 7 exhaust port 8 liquid outlet 9 heat exchanger 10 liquid injection port 11 makeup sealing liquid 12 liquid outlet port diagram 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, 1 and 2 raw material supply port 3, 3'stirring tank type first polymerizer 4 polymerization intermediate 5 discharge port 6 transfer pump 7 supply port 8 stirring Second tank-type polymerization vessel 9 Vent port 10 Distillation column 11 Condenser 12 Liquid extraction pump 13 Liquid return port 14 Polymerization intermediate 15 Discharge port 16 Transfer pump 17 Supply port 18 Circulation line 19 Perforated plate 20 Perforated plate type first polymerization device 21 Polymerization Intermediate 22 Gas Supply Port 23 Vent Port 24 Circulation Pump 25 Polymerization Intermediate 26 Transfer Pump 27 Discharge Port 28 Supply Port 29 Perforated Plate 30 Perforated Plate Second Polymerizer 31 Cylindrical Support 32 During Polymerization Body 33 Gas supply port 34 Vent port 35 Discharge pump 36 Discharge port 37, 38, 39 Piping 40, 41 Roots type mechanical booster 42 Liquid ring pump 43 Piping 44 Detoxification tower 45, 45 'Shell and tube freeze condenser 46 Oil rotation Pump 47 Horizontal stirring first polymerizer

Claims (5)

[Claims] 1. A wet vacuum as a vacuum pump for producing an aromatic polycarbonate while extracting an aromatic monohydroxy compound by-produced by an ester exchange method from an aromatic dihydroxy compound and a diaryl carbonate under reduced pressure using a vacuum pump. Using a pump, the total amount or a part of the aromatic monohydroxy compound by-produced in the polymerization vessel is dissolved and / or mixed in the sealing liquid of the wet vacuum pump to adjust the concentration of the aromatic monohydroxy compound in the sealing liquid to 1
A method for producing an aromatic polycarbonate, characterized in that the sealing liquid is continuously or batchwise withdrawn from the wet vacuum pump while maintaining the content at not less than wt%. 2. An aromatic monohydroxy compound in an amount of 3% by weight or more based on the total amount of the aromatic monohydroxy compound extracted from the polymerization vessel is dissolved and / or mixed in a sealing liquid of a wet vacuum pump and extracted. The method for producing an aromatic polycarbonate according to claim 1. 3. The method for producing an aromatic polycarbonate according to claim 1, wherein a dry vacuum pump is provided between the polymerization vessel and the wet vacuum pump. 4. The temperature of the wet vacuum pump is -10 to 100.
4. The method for producing an aromatic polycarbonate according to claim 1, 2 or 3, wherein the temperature is ° C. 5. The method for producing an aromatic polycarbonate according to claim 1, wherein the exhaust port of the wet vacuum pump is connected to the abatement tower.