JP2000128975A - Production of aromatic polycarbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for the production of an aromatic polycarbonate, free from the problems of adhesion and clogging with a distillate to dispense with a switching operation and accompanying complicate piping and operation, saving the energy for melting a solidified material, enabling easy separation of a compound for scrubbing liquid, the unreacted material and accompanying condensate and capable of stably producing an aromatic polycarbonate for a long period. SOLUTION: An aromatic polycarbonate is produced by transesterification reaction using an aromatic dihydroxy compound and a diaryl carbonate as raw materials and extracting a distillate containing by-produced aromatic monohydroxy compound, unreacted aromatic dihydroxy compound and diaryl carbonate and accompanying condensate from the polymerizer under reduced pressure. In the above process, the distillate is condensed and dissolved with a scrubber containing a compound for scrubbing liquid satisfying the following conditions. (a) The vapor pressure at 190 deg.C is 50-500 mmHg, (b) the melting point is <=30 deg.C and (c) the solubility of an aromatic polycarbonate having a number-average molecular weight of 2,500 in the compound is >=5 wt.% at 25 deg.C.

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 apparatus is corroded by by-produced hydrogen chloride and sodium chloride and a chlorine-containing compound such as methylene chloride used in large quantities as a solvent. In addition, there were problems such as difficulty in separating impurities such as sodium chloride and residual methylene chloride which adversely affect the physical properties of the polymer.

On the other hand, a method for producing an aromatic polycarbonate from an aromatic dihydroxy compound and a diaryl carbonate, for example, a transesterification method in which bisphenol A and diphenyl carbonate are transesterified in a molten state and polymerization is performed while extracting phenol produced as a by-product, has been previously used. Known from. Unlike the interfacial polycondensation method, the transesterification method has advantages such as using no solvent.

Conventionally, various polymerization apparatuses have been known as polymerization apparatuses for producing an aromatic polycarbonate by a transesterification method. In these, aromatic monohydroxy compounds and the like by-produced as the polymerization proceeds are led to a condenser to be condensed. However, as described above, when the aromatic monohydroxy compound generated from the polymerization vessel is immediately led to the condenser to be condensed, it is necessary to lower the temperature of the condenser in order to condense, and the aromatic monohydroxy compound and unreacted materials are required. Distillates such as condensates are attached to the inside of the condenser and to the exhaust pipe connecting the condenser and the vacuum device, and gradually reduce the vacuum pumping capacity. Has the problem of making it impossible.

In order to solve this problem, various devices have been devised for condensing distillates such as aromatic monohydroxy compounds. For example, JP-A-6-49197 discloses a method using a freeze condenser having a heat exchanger using a refrigerant at -10 to 40 ° C. In this method, in order to solidify distillates such as aromatic monohydroxy compounds, two or more freeze condensers are provided in parallel, and while one is operating, the other is heated to solidify the solidified product. A switching operation of dissolving the is required. In this method, the apparatus and piping connecting the apparatuses are complicated and the operation is complicated, and a large amount of energy is required for a heating operation for melting the solidified material at the time of switching.

In Japanese Patent Application Laid-Open No. 6-65367, 1
A method using a scrubber using a compound having a vapor pressure at 90 ° C. of 10 mmHg or less as a scrubbing liquid is specifically disclosed. This method also describes that unreacted substances and low-polymerized substances are solidified in the scrubber. In the embodiment, three scrubbers are provided in parallel and the operation is performed by switching these scrubbers. Therefore, the apparatus and the piping connecting the apparatuses are complicated, the operation is complicated, and a large amount of energy is required for a heating operation for melting the solidified material at the time of switching. Has the same problem as

In JP-A-6-6553, a compound having a very high boiling point having a vapor pressure at 190 ° C. of 10 mmHg or less is used as a scrubbing liquid. The reason for using a compound having a very high boiling point as the scrubbing liquid in this way is to separate the aromatic monohydroxy compound from the scrubbing liquid and to recover the aromatic monohydroxy compound in order to reuse the scrubbing liquid. For easy separation. However, compounds having such a vapor pressure have a problem that, although separation from an aromatic monohydroxy compound is easy, separation from unreacted aromatic dihydroxy compounds, diaryl carbonates, and condensates is difficult. Had.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an aromatic polycarbonate obtained by extracting a distillate consisting of an aromatic monohydroxy compound by-product or an unreacted product and an accompanying condensate by a transesterification method from a polymerization vessel. In the method of producing, because there is no problem of sticking and clogging by the distillate, there is no need for a switching operation and complicated piping and operation associated therewith, and no energy for melting the solidified product is required. An object of the present invention is to provide an industrially preferable method for producing an aromatic polycarbonate, which can easily separate an unreacted product and an accompanying condensate from a compound for the above scrubbing liquid and can stably produce an aromatic polycarbonate for a long period of time.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, using a scrubber using a specific scrubbing liquid, continuously dissolving distillate in the scrubbing liquid. It has been found that the object can be achieved by continuously extracting the scrubbing liquid, and the present invention has been completed.

That is, the present invention provides: (A) a distillate comprising an aromatic monohydroxy compound, an unreacted aromatic dihydroxy compound and a diaryl carbonate, and an accompanying condensate, starting from an aromatic dihydroxy compound and a diaryl carbonate; In a method for producing an aromatic polycarbonate by a transesterification method while extracting a substance from a polymerization vessel under reduced pressure, the above distillate is condensed with a scrubber having the following scrubbing liquid,
A method for producing an aromatic polycarbonate characterized by dissolving, a scrubbing liquid: a compound for a scrubbing liquid satisfying the following (a) to (c). (A) The vapor pressure at 190 ° C. is 50 to 500 mmHg.
(B) a melting point of 30 ° C. or lower, and (c) an aromatic polycarbonate having a number average molecular weight of 2,500 at 25 ° C.
Dissolves by weight or more. (B) The method according to (A), wherein the scrubbing solution is introduced into a distillation column, and is separated into an aromatic monohydroxy compound, a compound for scrubbing solution, unreacted diaryl carbonate, unreacted aromatic dihydroxy compound, and a condensate. (A) or (B), wherein the compound for a scrubbing liquid is an alkylaryl carbonate.
(D) The method for producing an aromatic polycarbonate according to (A), (B) or (C), wherein the compound for a scrubbing liquid is methylphenyl carbonate. Is what you do.

Conventionally, in a method for producing an aromatic polycarbonate by a transesterification method, an attempt has been made to operate while switching two or more condensers in parallel, and as described above, there have been many problems. . However, by condensing and dissolving the distillate with the scrubber containing the scrubbing liquid containing the compound for a scrubbing liquid of the present invention, solidification of the distillate in the scrubber is completely eliminated, and the scrubbing liquid can be continuously extracted from the scrubber. If the switching operation becomes unnecessary, it becomes clear that the aromatic polycarbonate can be stably produced for a long period of time because sticking and clogging troubles in the scrubber and piping do not occur.
Moreover, since the compound for scrubbing liquid used in the present invention has a vapor pressure of 50 to 500 mmHg at 190 ° C., not only is it easy to separate from the aromatic monohydroxy compound, but also by using a distillation column, Unreacted aromatic dihydroxy compounds and diaryl carbonates,
And it is also easy to separate from the condensate, and it is extremely easy to recover the compound for scrubbing liquid. That is, according to the present invention, it has been clarified that when producing an aromatic polycarbonate by a transesterification method, the problems caused in condensing the distillate can all be simultaneously solved.

Further, when the compound for scrubbing liquid is an alkylaryl carbonate, since the alkylaryl carbonate is an intermediate in producing a diaryl carbonate from a dialkyl carbonate and an aromatic monohydroxy compound, it is by-produced. Without separation from the aromatic monohydroxy compound or unreacted diaryl carbonate, it can be reused as a reaction raw material for producing diaryl carbonate. This is particularly useful when consistently producing an aromatic polycarbonate and its raw material, and is one of the major 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 (In the formula, 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 number 1 to 30.) In the divalent aromatic groups Ar ¹ and Ar ² , another substituent in which one or more hydrogen atoms do not affect the reaction, for example,
Halogen atom, alkyl group having 1 to 10 carbon atoms, 1 carbon atom
It may be substituted by 10 to 10 alkoxy groups, phenyl groups, phenoxy groups, vinyl groups, cyano groups, ester groups, amide groups, nitro groups and 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 naphthylene, substituted or unsubstituted biphenylene, and substituted or unsubstituted pyridylene. The substituent here is as described above. The divalent alkane group Y is, for example, an organic group represented by the following formula 1.

[0016]

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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 alkyl group having 6 to 10 carbon atoms. k is 3 ~
Represents an integer of 11, R ⁵ and R ⁶ are individually selected for each X, and each independently represents hydrogen or an alkyl group having 1 to 6 carbon atoms, and X represents carbon. R ¹ ,
In R ² , R ³ , R ⁴ , R ⁵ and R ⁶ , other substituents as long as one or more hydrogen atoms do not adversely affect the reaction,
For example, those substituted by 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, an ester group, an amide group, a nitro group, etc. May be. Examples of such a divalent aromatic group Ar include those represented by the following formula (2).

[0018]

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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 cycloalkyl having 5 to 10 ring carbon atoms) An alkyl group or a phenyl group, wherein m and n are 1
When m is 2 to 4, each R ⁷ may be the same or different, and when n is 2 to 4, each R ⁸ may be the same or different. There may be. Further, the divalent aromatic group Ar may be represented by the following formula.

-Ar ¹ -Z-Ar ^2- (wherein, 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).

[0021]

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(Wherein R ⁷ , R ⁸ , m and n are as described above.) Further, specific examples of the divalent aromatic group Ar include substituted or unsubstituted phenylene, substituted or unsubstituted And substituted or unsubstituted pyridylene. The aromatic dihydroxy compound used in the present invention may be a single kind or two or more kinds. 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.

[0023]

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(Wherein, Ar^Three, Ar^FourAre monovalent
Represents an aromatic group. ) Ar^ThreeAnd Ar^FourIs a monovalent carbocyclic or heterocyclic aromatic
Which represents an Ar group^Three, Ar^FourIn one or more
Other substituents that do not adversely affect the reaction,
For example, a halogen atom, an alkyl group having 1 to 10 carbon atoms,
C1-C10 alkoxy, phenyl, phenoxy
Group, vinyl group, cyano group, ester group, amide group,
It may be substituted by a toro group or the like. Ar
^Three, Ar ^FourCan be the same or different
There may be. Monovalent aromatic group Ar^ThreeAnd Ar^FourRepresentative of
Examples include phenyl, naphthyl, biphenyl,
Pyridyl groups can be mentioned. These are the above 1
It may be substituted with more than one kind of substituent. Preferred A
r^ThreeAnd Ar^FourAs, for example,
Is mentioned.

[0025]

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Representative examples of the diaryl carbonate include those represented by the following formula (6).

[0027]

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(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 butyl phenyl carbonate, are preferred, but diphenyl carbonate, which is the diaryl carbonate having the simplest structure, is 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 depends on the type of the aromatic dihydroxy compound and the diaryl carbonate used,
Depending on the polymerization temperature and other polymerization conditions, the diaryl carbonate is usually 0.9 to 2.5 mol, preferably 0.9 to 2.5 mol, per mol of the aromatic dihydroxy compound.
2.0 moles, more preferably 0.98 to 1.5 moles.

The number average molecular weight of the aromatic polycarbonate obtained by the method of the present invention is usually in the range of 500 to 100,000, preferably in the range of 2000 to 30,000. In producing an aromatic polycarbonate by reacting an aromatic dihydroxy compound with a diaryl carbonate, the reaction temperature is usually selected from the range of 50 to 350 ° C, preferably 100 to 290 ° C. As the reaction proceeds, an aromatic monohydroxy compound is by-produced. The aromatic monohydroxy compound by-produced in the present invention is represented by the following formula (7).

[0031]

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(In the formula, R ⁹ and p are as described above.) The aromatic monohydroxy compound is removed to the outside of the reaction system under reduced pressure to form an aromatic polycarbonate production reaction rate (hereinafter referred to as polymerization rate). ) Is increased. The preferred reaction pressure varies depending on the type and molecular weight of the aromatic polycarbonate to be produced, the polymerization temperature, and the like. For example, when producing an aromatic polycarbonate from bisphenol A and diphenyl carbonate, the number average molecular weight is 1000
In the following range, the range of 50 mmHg to normal pressure is preferable,
When the number average molecular weight is in the range of 1,000 to 2,000, it is 3 to 50.
The range of mmHg is preferred, and when the number average molecular weight is in the range of 2,000 or more, it is preferably 20 mmHg or less, particularly preferably 10 mmHg or less, and further preferably 2 mmHg or less. In the present invention, the vacuum device for reducing the pressure of the polymerization vessel is not particularly limited, and various known vacuum pumps can be used.

When the by-produced aromatic monohydroxy compound is extracted out of the reaction system, unreacted aromatic dihydroxy compound, diaryl carbonate, and condensate are simultaneously extracted from the polymerization vessel to the outside of the reaction system. The distillate in the present invention refers to a compound composed of an aromatic monohydroxy compound by-produced, an unreacted aromatic dihydroxy compound and diaryl carbonate, and an accompanying condensate. The accompanying condensate refers to a low-molecular-weight aromatic polycarbonate vapor, a low-molecular-weight aromatic polycarbonate, an aromatic polycarbonate, and the like, which are entrained and entrained in a by-produced aromatic monohydroxy compound and the like. The low molecular weight aromatic polycarbonate generally indicates an aromatic polycarbonate having a number average molecular weight of about 300 to 3000.

The present invention is a process for producing an aromatic polycarbonate, characterized in that the distillate is condensed with a scrubber and simultaneously dissolved in a scrubbing solution. It is necessary that the scrubbing liquid contains a compound for a scrubbing liquid that satisfies the requirements of (a) to (c). (A) The vapor pressure at 190 ° C. is 50 to 500 mmHg.
(B) a melting point of 30 ° C. or lower, and (c) an aromatic polycarbonate having a number average molecular weight of 2,500 at 25 ° C.
Wt% or more can be dissolved. In the present invention,
The scrubbing liquid is composed of a compound for a scrubbing liquid and a distillate, and the amount of the compound for a scrubbing liquid contained in the scrubbing liquid is usually 5 to 99% by weight, preferably 15 to 99% by weight.
To 90% by weight, more preferably 30 to 80% by weight.

In the present invention, a scrubber is an apparatus of the type in which a liquid is dispersed in a gas as a number of fine droplets and / or liquid film pieces. A scrubbing liquid refers to a liquid that is dispersed in a gas as fine droplets and / or liquid film pieces by a scrubber. Specifically, various known scrubbers such as a packed tower, an ejector, a rotary spray tower, and a venturi can be used (edited by The Chemical Industry Association; published by Maruzen Co., Ltd .; Chemical Engineering Handbook Revised 5th Edition; Showa 6)
Published March 18, 3; P781; see Table 17.5).
The most preferred form of the scrubber is a fixed spray tower having a heat exchanger as in the present invention, but among these known scrubbers, a rotary spray tower having a heat exchanger can also be preferably used. . The temperature of the scrubbing liquid is usually 0 to 100 ° C, preferably 5 to 80 ° C, and more preferably 15 to 50 ° C, although it depends on the conditions of the polymerization reactor to which the scrubber is connected.

The scrubbing solution of the present invention comprises (a) 190
The vapor pressure at 50 ° C. is 50 to 500 mmHg,
(B) a melting point of 30 ° C. or lower, and (c) a number average molecular weight of 2
Contains a compound for a scrubbing liquid capable of dissolving at least 5% by weight of 500 aromatic polycarbonates at 25 ° C. The vapor pressure of the compound for scrubbing liquid is 50 to 50.
0 mmHg, preferably 80-450 mmHg,
More preferably, it is 100 to 400 mmHg. When the vapor pressure of the compound for scrubbing liquid is lower than 50 mmHg, separation of the unreacted aromatic dihydroxy compound and diaryl carbonate in the distillate from the compound for scrubbing liquid by a distillation column becomes difficult, and
If it is higher, it becomes difficult to separate the compound for scrubbing liquid from the aromatic monohydroxy compound.

The melting point of the compound for scrubbing solution is 30 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 ° C. or lower. The lower limit of the melting point is not particularly limited, and the lower the melting point, the lower the operating temperature of the scrubber. This is preferable.
When the melting point of the compound for scrubbing liquid is higher than 30 ° C., it is necessary to raise the temperature of the scrubber to at least higher than 30 ° C., and the vapor pressure of the distillate increases, which is not preferable because it is difficult to condense in the scrubber. The compound for a scrubbing liquid can dissolve an aromatic polycarbonate having a number average molecular weight of 2,500 at 25 ° C. at 5% by weight or more, preferably 7% by weight or more, more preferably 10% by weight or more. The compound for scrubbing liquid has a number average molecular weight of 25.
If the aromatic polycarbonate of No. 00 cannot be dissolved at 25 ° C. in an amount of 5% by weight or more, the condensate solidifies in the scrubber and causes troubles such as clogging. It is difficult to stably produce an aromatic polycarbonate for a long period of time.

The compound for a scrubbing solution is the compound (a)
Any compound may be used as long as it satisfies (c) to (c).
And alkylaryl carbonates represented by

[0039]

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(In the formula, R ¹⁰ represents an alkyl group having 1 to ¹⁰ carbon atoms. Ar ⁵ is the same as Ar ^3. ) Particularly preferred alkyl aryl carbonates include:
Methyl phenyl carbonate is mentioned. In the present invention, the distillation column refers to a column-type apparatus that separates each component by utilizing a difference in partial pressure of each component under the condition that the liquid mixture is heated and all the components become vapor. Specifically, various known distillation towers such as a cap tower, a perforated plate tower, a perforated tower, and a packed tower can be used (Shigefumi Fujita; published by Iwanami Shoten; Chemical Engineering I Second Edition; April 1967) Issued the first print on 28th; P
106; see FIG. 6.1). Among these distillation columns, packed columns are preferred. The scrubbing liquid is composed of an aromatic monohydroxy compound, a compound for scrubbing liquid, unreacted diaryl carbonate, unreacted dihydroxy compound and condensate.
There are no particular restrictions on the number of distillation columns used to separate the components.

The scrubber of the present invention will be described with reference to the drawings. The scrubber 28 of FIG. 1 is a specific example of the scrubber of the present invention. The distillate from the polymerization vessel is introduced into the scrubber 28 from a feed port 49. On the other hand, there is a heat exchanger 57 cooled by a refrigerant inside the scrubber, and the scrubbing liquid is sprayed into the scrubber from the spray ports 61 and 62 through the pipes 58 and 59 above and below the heat exchanger. Is done. The vent port 33 is connected to a vacuum pump, and the inside of the scrubber 28 including the heat exchanger 57 is placed under vacuum. Therefore, the distillate introduced into the scrubber exchanges heat with the scrubbing liquid and passes through the heat exchanger to condense. At this time, the distillate is dissolved in the scrubbing liquid, and the distillate and the scrubbing liquid in which the distillate is dissolved collectively collect at the bottom of the scrubber, and a part of the distillate is reused as the scrubbing liquid through the pump 29. The part is withdrawn from the outlet 31 to separate and collect distillate. Further, the wall surface of the heat exchanger 57 is
Is kept wet by the scrubbing liquid sprayed from the spray port 61 through the spray port 61, and no blockage due to fixation of condensate or the like occurs. In order to keep the amount of the scrubbing liquid circulating in the system constant, the scrubbing liquid compound is made up from the supply port 32 by the amount of the liquid extracted through the discharge port 31.

From the scrubbing liquid extracted from the discharge port 31, a compound for a scrubbing liquid (for example, methylphenyl carbonate) can be recovered by a distillation tower or the like. For example, by a distillation column having two side cuts, a by-product monohydroxy compound, a compound for a scrubbing solution (eg, methylphenyl carbonate),
It is separated into four components of unreacted diaryl carbonate, unreacted dihydroxy compound and condensate, and can be recovered from the top, upper side cut, lower side cut and column bottom, respectively. Further, the components may be separated into four components using a plurality of distillation columns. For example, first, a by-product monohydroxy compound and a compound for scrubbing liquid, an unreacted diaryl carbonate, an unreacted dihydroxy compound and a condensate are separated into three components in a distillation column having one side cut, and the top, side cut, and Collect from the bottom of the tower. Next, the component recovered from the top is led to another distillation column, separated into a by-product monohydroxy compound and a compound for scrubbing liquid, and recovered from the top and bottom, respectively. Thus, it can be separated into four components.

In the case of the compound for scrubbing liquid of the present invention,
It is a great feature of the present invention that the aromatic monohydroxy compound and the unreacted diaryl carbonate can be easily separated from each other and the recovery rate is high. If the compound for the scrubbing liquid is an alkylaryl carbonate, it can be used as an intermediate when producing a diaryl carbonate from an aromatic monohydroxy compound. In that case, even if alkylaryl carbonate is contained in the recovered aromatic monohydroxy compound and diaryl carbonate, there is no particular disadvantage, and the separation operation can be further facilitated. It is.

The aromatic polycarbonate of the present invention is obtained by subjecting the aromatic dihydroxy compound and diaryl carbonate to a polycondensation by transesterification in a molten state while heating in the presence or absence of a catalyst. And the polymerization vessel is not particularly limited. For example, a stirred tank reactor, a thin film reactor, a centrifugal thin film evaporation reactor, a surface renewal type twin-screw kneading reactor, a twin-screw horizontal stirring reactor, a wet-wall reactor, and a perforated plate type for free-fall polymerization Reactor,
A polymerizer which melts and drops the prepolymer along the support to progress the polymerization, for example, a perforated plate reactor with a wire or the like is used, and a polymerizer alone or in combination thereof is used.

For example, in the early stage of polymerization, a molten prepolymer is produced from an aromatic dihydroxy compound and diaryl carbonate by using a vertical stirring tank, and a molten prepolymer is produced.
Surface renewal type twin-screw kneading reactor, twin-screw horizontal stirring reactor, wet-wall reactor, perforated plate reactor for free fall polymerization, prepolymer is melted and dropped along the support to promote polymerization A method of polymerizing using a polymerization vessel or the like is one of preferred embodiments of the present invention. A particularly preferred polymerization vessel used in the polymerization step is a polymerization vessel in which the prepolymer is melted and dropped along the support to progress the polymerization.
A preferred embodiment of the present invention is a method in which the prepolymer is melted down in a foamed state along the support and polymerized using a polymerization vessel that proceeds with polymerization.

In a polymerization vessel in which the prepolymer is melted and dropped along the support to progress the polymerization, the prepolymer is usually supplied from a perforated plate and then falls along the support. The perforated plate is usually selected from a flat plate, a corrugated plate, a plate having a thick central portion, and the like, and the shape of the perforated plate is generally selected from shapes such as a circle, an ellipse, a triangle, and a polygon. .

The holes of the perforated plate are usually selected from shapes such as a circle, an ellipse, a triangle, a slit, a polygon, and a star. The cross-sectional area of the hole is usually 0.01-100 cm ²
, Preferably 0.05 to 10 cm ² , particularly preferably 0.1 to ⁵ cm ² . The distance between the holes is usually the distance between the centers of the holes, which is 1 to 500 mm.
And preferably 25 to 100 mm. The hole of the perforated plate may be a hole penetrating the perforated plate or a case where a tube is attached to the perforated plate. Further, it may be tapered.

The term "support" refers to a material in which the ratio of the length in the vertical direction to the cross section in the horizontal direction is very large with respect to the average length of the outer circumference in the horizontal direction. The ratio is usually 1
0 to 1,000,000, preferably 50 to 1
00000. The shape of the cross section in the horizontal direction is generally selected from shapes such as a circle, an ellipse, a triangle, a square, a polygon, and a star. The shape of the cross section may be the same or different in the length direction. The support may be hollow. The support may be a single support such as a wire, or a combination of a plurality of supports by a method such as twisting. Further, it may be a wire mesh or a punching plate. The surface of the support may be smooth or uneven, or may partially have protrusions or the like. The material of the support is usually selected from metals such as stainless steel, carbon steel, Hastelloy, nickel, titanium, chromium, and other alloys, and high heat-resistant polymer materials. . Further, the surface of the support may be subjected to various treatments such as plating, lining, passivation treatment, acid washing, and phenol washing as required. The support may be directly connected to the hole of the perforated plate or may be apart from the hole. Preferred specific examples include those in which each support penetrates and connects near the center of each hole in the perforated plate, those in which the support is connected to the outer peripheral portion of each hole in the perforated plate, and the like. . The lower end of the support may be in contact with the bottom liquid level of the polymerization vessel or may be apart therefrom.

As a method of dropping the prepolymer along the support through the perforated plate, a method of dropping the prepolymer by a liquid head or its own weight, or a method in which the prepolymer is pressed from the perforated plate by applying pressure using a pump or the like. Extrusion and the like. The number of pores is not particularly limited, and varies depending on conditions such as reaction temperature and pressure, the amount of catalyst, the range of the molecular weight to be polymerized, and the like.
When kg / hr production is required 10 to 10 ⁵ holes. After passing through the hole, the height of the drop along the support is preferably 0.3 to 50 m, more preferably 0.5 to 30 m. The flow rate of prepolymer passing through holes are different but normally, per hole by the molecular weight of the prepolymer, 10 ^-4 to 10 ⁴ liters / hr, preferably 10 ^-2 to 10 ² liters / hr, particularly preferably , 0.05 to 50 l / hr. The time required for dropping along the support is not particularly limited, but is usually in the range of 0.01 seconds to 10 hours. The polymer polymerized while being dropped along the support may be dropped into the liquid reservoir as it is, or may be forcibly taken into the liquid reservoir by a winder or the like. Further, the polymer after dropping along the support may be extracted as it is, but it is also a preferable method to circulate and polymerize while dropping again along the support. In this case, the residence time can be prolonged in the liquid reservoir, the circulation line, or the like after being dropped along the support according to the reaction time required for the polycondensation reaction. In addition, a new liquid surface area that can be formed per unit time can be obtained by circulating while being dropped along the support, so that the polymerization can easily proceed sufficiently to a desired molecular weight.

When the aromatic polycarbonate is produced in the present invention, one or more polymerizers are used. When two or more polymerizers are used, the scrubber of the present invention is installed in all the polymerizers. It may be installed in only one polymerization vessel. The scrubber of the present invention is preferably used in the latter half of the polymerization when the polymerization pressure decreases. In a particularly preferred embodiment, for example, the number average molecular weight is 100
In the initial stage of polymerization of 0 to 4000, a scrubber using the distillate itself as a scrubbing liquid is installed in the polymerization vessel, and the distillate is condensed at a temperature higher than the melting point of the aromatic monohydroxy compound to be distilled, and the number average molecular weight is 4000 or more. In the latter stage of the polymerization, a method of installing the scrubber of the present invention in a polymerization vessel and the like can be mentioned.

The polymerization can be carried out without adding a catalyst. However, in order to increase the polymerization rate, the polymerization is carried out in the presence of a catalyst if necessary. The polymerization catalyst is not particularly limited as long as it is used in this field, but hydroxides of alkali metals or alkaline earth metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide are used. , Alkali metal salts of boron or aluminum hydrides such as lithium aluminum hydride, sodium borohydride, tetramethylammonium borohydride,
Alkaline earth metal salts and quaternary ammonium salts; alkali metal or alkaline earth metal hydrogen compounds such as lithium hydride, sodium hydride and calcium hydride;
Alkoxides of alkali metals or alkaline earth metals such as lithium methoxide, sodium ethoxide, calcium methoxide; lithium phenoxide, sodium phenoxide, magnesium phenoxide, LiO—
Aryloxides of alkali metals or alkaline earth metals such as Ar-OLi and NaO-Ar-ONa (Ar is an aryl group); Organic acid salts of alkali metals or alkaline earth metals such as lithium acetate, calcium acetate and sodium benzoate 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 ) represented by ammonium borates,
(R ¹ , R ² , R ³ , R ⁴ ) phosphonium borates (R ¹ , R ² , R ³ , R ³ ) represented by PB (R ¹ , R ² , R ³ , R ⁴ )
⁴ is as described in Chemical formula 1. Compounds of boron 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 alkoxy or aryloxy groups such as tin oxide, dialkyltin oxide, dialkyltin carboxylate, tin acetate, 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 materials for the polymerization vessel and scrubber of the present invention are not particularly limited, and are usually selected from stainless steel, nickel, glass lining and the like.

[0053]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to examples.

[0054]

Example 1 An aromatic polycarbonate was produced by the process shown in FIG. The process of FIG. 1 includes three stirred tank-type polymerization reactors, a perforated-plate polymerization reactor having a circulation line, and a perforated-plate polymerization reactor having a cylindrical support. However, the first polymerization vessel in the stirring tank was operated in a batch while switching between (A) and (B), and the other polymerization vessels were operated continuously.
The inner volume of the first (A) polymerization tank 3 and the first (B) polymerization tank 3 'of the stirring tank are 100 liters, the inner volume of the second polymerization vessel 8 of the stirring tank is 50 liters, and both stirring blades are used. It is an anchor type. The perforated-plate type polymerization vessel 20 having a circulation line includes:
It is provided with a perforated plate 19 having forty holes having a diameter of 2 mm, and its falling height is 4 m. The perforated-plate type polymerization vessel 36 with a cylindrical support is provided with a perforated plate 35 having 20 holes having a diameter of 4 mm. S of 2 mm diameter vertically from the center of each hole
The US316L wire 37 is hung down to the liquid reservoir at the bottom of the polymerization vessel, and the falling height is 8 m.

Bisphenol A as an aromatic dihydroxy compound and diphenyl carbonate (a molar ratio of bisphenol A to 1.13) as a diaryl carbonate were supplied from the raw material supply ports 1 and 2 to a stirred tank type first (A) polymerizer under a nitrogen atmosphere. The prepolymer 4 in the polymerization vessel was introduced into the second polymerization vessel 8 of the stirred tank type by the transfer pump 6 at a rate of 10 liters / liter.
hr. The stirred tank type first polymerization vessel was at a temperature of 180 ° C. and atmospheric pressure, and the stirred tank type second polymerization vessel was at a temperature of 230 ° C. and a pressure of 5.
The operation was performed at 0 mmHg.

The first (B) polymerization vessel 3 'of the stirring vessel was exactly the same as the first (A) polymerization vessel 3 of the stirring vessel, and was used after being switched in batches. The distillate withdrawn from the stirred tank type second polymerization vessel 8 is introduced into a packed column type distillation column 10 through a vent port 9. Most of the aromatic monohydroxy compound in the distillate is cooled in the condenser 11 and then discharged out of the system by the transfer pump 12, and unreacted aromatic dihydroxy compound and diaryl compound accompanying the aromatic monohydroxy compound. Most of the carbonate and condensate are returned from the liquid return port 13 to the polymerization vessel. The prepolymer 14 is discharged from the discharge port 15 while keeping the liquid level in the polymerization vessel constant and keeping the residence time at 1.5 hours, and is transferred to the perforated plate polymerization vessel 20 by the transfer pump 16. The prepolymer 14 is supplied from a supply port 17 to a circulation line 18. The prepolymer 21 introduced into the perforated plate type polymerization vessel 20 through the perforated plate 19 falls freely inside the polymerization vessel, and the prepolymer reaching the bottom of the polymerization vessel is passed through a circulation pump 24.
Is supplied again from the perforated plate 19 to the inside of the polymerization vessel through the circulation line 18 provided with Prepolymer 2 at the bottom of the polymerization vessel
A part of 5 is discharged from the discharge port 27 by the transfer pump 26 while controlling the liquid level at the bottom of the polymerization vessel to be constant and keeping the residence time at 0.5 hour.
The mixture is supplied to a perforated plate type polymerization vessel 36 with a cylindrical support.

The operating conditions of the perforated-plate type polymerization vessel 20 are as follows.
70 ° C., pressure 10 mmHg, circulation flow rate 100 l /
hr. In addition, one nitrogen is supplied from the inert gas supply port 22.
Liter / hr. The prepolymer introduced into the inside of the porous polymerization vessel 36 with a cylindrical support through the porous plate 35 falls along the cylindrical support 37.
The aromatic polycarbonate 38 at the bottom of the polymerization vessel whose polymerization degree has risen is discharged from the discharge port 42 by the transfer pump 41 while keeping the liquid level at the bottom of the polymerization vessel constant and controlling the residence time to be 0.5 hour. . The operating conditions of the perforated-plate type polymerization vessel 36 with a cylindrical support were as follows:
° C, pressure 0.8 mmHg. Further, nitrogen is supplied from the inert gas supply port 39 at 1 liter / hr.
The aromatic monohydroxy compound and unreacted aromatic dihydroxy compound and diaryl carbonate distilled out of the perforated plate type polymerization vessel 20 and the perforated plate type polymerization vessel 36 with the cylindrical support, and the distillate composed of condensate and nitrogen, , Are introduced into scrubbers 28 and 43 through vent ports 23 and 40, respectively.

To each scrubber, methylphenyl carbonate is supplied from a supply port 32 and a supply port 47, and a scrubbing liquid composed of the distillate and methylphenyl carbonate is supplied to a circulation pump 29 and a circulation pump 44.
And is sprayed into the scrubber from the spray ports 61, 62, 63 and 64. In both the scrubber 28 and the scrubber 43, the concentration of methylphenyl carbonate in the scrubbing liquid is 60% by weight. Methyl phenyl carbonate has a vapor pressure of 40 at 190 ° C.
0 mmHg, melting point is −20 ° C. or less, Mn 2500
5% by weight or more can be dissolved at 25 ° C. The scrubber 28 has a gas phase temperature of 40 ° C.
The scrubber 43 is controlled at a gas phase temperature of 15 ° C. The distillate condensed in the scrubber is discharged to the tank 50 from the outlet 31 and the outlet 46 together with methylphenyl carbonate. The distillate of the tank 50 and methylphenyl carbonate are supplied to a packed column distillation column 52 having two side cuts via a transfer pump 51, and the by-product monohydroxy compound, methylphenyl carbonate, unreacted diaryl carbonate, The unreacted dihydroxy compound and the condensate are separated into four components, which are recovered from the top, the upper side cut, the lower side cut, and the bottom, respectively. The packed plate type distillation column 52 has 20 theoretical plates, and is operated at a bottom temperature of 228 ° C., a top pressure of 400 mmHg, and a reflux ratio of 3. The recovered methylphenyl carbonate is transferred from the upper side cut port 53 to the tank 54, and is made up into a scrubber through the supply ports 32 and 47 to be reused.

Under these conditions, an aromatic polycarbonate was produced continuously for 1000 hours. As a result, the polymerization reactor was operated at a constant pressure, and an aromatic polycarbonate having a number average molecular weight of 11,000 could be produced stably. No precipitation or blockage of solid matter was seen on the scrubber and vent pipe,
Switching operation of the scrubber was not required at all. The ratio of methylphenyl carbonate recovered from the side cut upper side cut to the methylphenyl carbonate supplied from the tank 50 to the packed tower distillation column 52 was 99.5%, and methylphenyl carbonate was removed from the distillate. It could be easily separated and recovered.

[0060]

Comparative Example 1 An aromatic polycarbonate was produced in the same manner as in Example 1 except that tetraethylene glycol was used as the scrubber compound for the scrubbers 28 and 43. Forty hours after the start of the operation, the spray port 63 was closed and the operation became impossible.

[0061]

According to the present invention, there is no sticking or blockage of the distillate by the scrubber, and there is no need for a switching operation, so that complicated piping and operation are not required, and energy for melting the solidified material is not required, and The compound for the scrubbing liquid can be easily separated and recovered from the scrubbing liquid, and the aromatic polycarbonate can be stably produced for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a process used in the present invention.

[Explanation of symbols]

 1, 1 ', 2, 2' Raw material supply port 3 Stirring tank first (A) polymerizer 3 'Stirring tank first (B) polymerizer 4, 4', 14, 21, 25 Prepolymer 5, 5 ' 15, 27, 31, 42, 46 Discharge port 6, 12, 16, 26, 41, 51 Transfer pump 7, 17, 32, 34, 47, 49 Supply port 8 Stirring tank second polymerization device 9, 23, 33, 40, 48 Vent port 10, 52 Packing tower type distillation column 11 Condenser 13 Liquid return port 18, 30, 45 Circulation line 19, 35 Perforated plate 20 Perforated plate type polymerizer 22, 39 Inert gas supply port 24, 29, 44 Circulating pump 28, 43 Scrubber 36 Perforated plate type polymerizer with cylindrical support 37 Cylindrical support 38 Aromatic polycarbonate 50, 54 Tank 53 Upper side cut port 55, 56 Vacuum pump 57, 60 Heat exchanger 58, 5961, 62, 63, 64 spray nozzle

Continued on the front page F term (reference) 4J029 AA10 AB04 AC01 AD01 BB08A BB08B BB12A BB12B BB12C BB13A BD01 BE05A BE05B BE07 BF03 BF14A BF14B BG06X BG06Y BG07X BG08X BG08Y BH02 DB07 DB02 DB07

Claims (4)

[Claims] 1. A distillate containing an aromatic dihydroxy compound and a diaryl carbonate as raw materials, and a distillate containing an aromatic monohydroxy compound produced as a by-product, an unreacted aromatic dihydroxy compound and a diaryl carbonate, and an accompanying condensate, are polymerized under reduced pressure. A process for producing an aromatic polycarbonate by a transesterification method while extracting from a distillate, wherein the distillate is condensed and dissolved by a scrubber having a scrubbing solution described below. Scrubbing solution: contains a compound for scrubbing solution satisfying the following (a) to (c). (A) The vapor pressure at 190 ° C. is 50 to 500 mmHg.
(B) a melting point of 30 ° C. or lower, and (c) an aromatic polycarbonate having a number average molecular weight of 2,500 at 25 ° C.
Dissolves by weight or more. 2. The method according to claim 1, wherein the scrubbing solution is introduced into a distillation column, and is separated into an aromatic monohydroxy compound, a compound for scrubbing solution, unreacted diaryl carbonate, unreacted aromatic dihydroxy compound and a condensate. A method for producing the aromatic polycarbonate according to the above. 3. The method for producing an aromatic polycarbonate according to claim 1, wherein the compound for the scrubbing liquid is an alkylaryl carbonate. 4. The compound for a scrubbing liquid is methyl phenyl carbonate.
Or a method for producing an aromatic polycarbonate according to item 3.