JPH11310632A - Method for producing polycarbonate - Google Patents

Abstract

(57) [Problem] To efficiently produce a high molecular weight polycarbonate excellent in hue. SOLUTION: In a pre-polycondensation step, an aromatic dihydroxy compound and a carbonic acid diester are subjected to a polycondensation reaction to form a prepolymer having a viscosity average molecular weight of 4000 to 15,000,
In the post-polycondensation step, a horizontally disposed cylindrical container, a pair of rotating shafts separately disposed at both longitudinal ends in the container, and a stirring blade attached between the rotating shafts. With
Using a uniaxial stirring type horizontal reaction device having no stirring center shaft member penetrating the inside of the container, the viscosity average molecular weight is from 18,000 to
A 40,000 high molecular weight polycarbonate is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a corresponding polycarbonate from an aromatic dihydroxy compound and a carbonic acid diester by a transesterification reaction.

[0002]

2. Description of the Related Art Polycarbonate has excellent mechanical properties such as impact resistance, heat resistance, transparency and the like, and is therefore used in a wide range of fields such as bottles for soft drinks, electronic substrates and optical materials. . As a method for producing such a polycarbonate, a method is known in which an aromatic dihydroxy compound such as bisphenol A and a diester carbonate such as diphenyl carbonate are transesterified in a molten state, and a corresponding polycarbonate is produced by polycondensation. For example, Japanese Patent Publication No. 52-36159 discloses a method in which bisphenol A and diphenyl carbonate are transesterified in a molten state, and phenol by-produced is eliminated to obtain a polycarbonate. In this method, the reaction temperature is gradually increased from about 150 ° C., which is the minimum temperature required for starting the transesterification reaction, to about 350 ° C. under stirring and mixing in order to rapidly remove phenol by-produced from the reaction mixture. At the same time, raise the reaction pressure from atmospheric pressure to about 0.1 mmHg
The method of gradually lowering to the extent is adopted. However, as the reaction is completed, the viscosity of the reaction mixture becomes extremely high (for example, about 10,000 to 100,000 poise or more), which makes it difficult to efficiently remove by-produced phenol.

[0003] In order to solve this problem, the above-mentioned transesterification is carried out by a pre-polycondensation step of forming a low-molecular-weight prepolymer under ordinary stirring conditions in a state where the viscosity of the reaction mixture is relatively low; In the state where the viscosity of the mixture becomes high, the reaction is performed in two stages, that is, a post-polycondensation step in which a high molecular weight polymer is produced using a horizontal reactor, and a device having a special stirring type is used in the post-polycondensation step. Various methods have been proposed. For example, JP-A-63-23926 discloses that in the post-polycondensation step,
A method of performing a polycondensation reaction using a twin-screw vented kneading extruder having blades combining a screw and a paddle is disclosed. However, this method is not always satisfactory in terms of the hue of the polycarbonate obtained.

JP-A-2-153925 discloses a first polycondensation reaction step (pre-polycondensation step) in which a polycondensation reaction is carried out in a tank-type reaction tank, and the polycarbonate obtained in the first polycondensation reaction step is horizontally separated. A horizontal stirring polymerization having a rotating shaft and mutually discontinuous stirring blades mounted substantially at right angles to the horizontal rotating shaft, and in which the ratio of the length of the horizontal rotating shaft to the rotating diameter of the stirring blade is within a specific range. A method for producing polycarbonate comprising a second polycondensation reaction step (post-polycondensation step) in which a polycondensation reaction is carried out by supplying to a tank is disclosed. However, according to this method, the polymer stays in a portion of the horizontal rotating shaft that does not have the stirring blade, causing coloring or generation of unnecessary gel.

JP-A-9-286850 discloses a pre-polycondensation step using a vertical stirring reactor, a pre-polycondensation step using a vertical stirring reactor equipped with double helical ribbon blades, a lattice stirring blade. And a post-polycondensation step using a horizontal reactor equipped with a process for producing polycarbonate. However, in this method, in the relatively low viscosity stage in the first half of the post-polycondensation step, the stirring efficiency is not so improved, and the surface renewability of the reaction mixture cannot be said to be high. Therefore, a long residence time is required,
The hue of polycarbonate is also likely to deteriorate.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for efficiently producing a high-molecular-weight polycarbonate having an excellent hue.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, in the post-polycondensation step where the reaction mixture is extremely viscous, a stirring center shaft member penetrating the inside of the vessel is provided. It has been found that the use of a single-shaft agitated horizontal reactor having no agitator significantly improves the efficiency of agitation, thus completing the present invention.

That is, the present invention provides a method for producing a corresponding polycarbonate by subjecting an aromatic dihydroxy compound and a carbonic acid diester to a transesterification reaction,
(1) A polycondensation reaction between an aromatic dihydroxy compound and a carbonic acid diester results in a viscosity average molecular weight of 4,000 to 1,500.
(2) a pre-polycondensation step for producing a prepolymer of
The prepolymer generated in the pre-polycondensation step is a cylindrical container placed horizontally, a pair of rotating shafts separately disposed at both ends in the longitudinal direction in the container, and between the rotating shafts. A polycondensation reaction using at least a uniaxial stirring type horizontal reactor having no stirring center shaft member penetrating through the inside of the vessel and having a stirring blade attached thereto was performed, and the viscosity average molecular weight was 18,000.
A polycondensation step of producing a high molecular weight polycarbonate of ４０40000.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a polycarbonate is produced by subjecting an aromatic dihydroxy compound and a carbonic acid diester to a transesterification reaction.

[Aromatic dihydroxy compound] The aromatic dihydroxy compound includes a compound represented by the following formula (1).

Embedded image (In the formula, A is a single bond, a linear or branched alkylene group having 1 to 8 carbon atoms which may be substituted with a phenyl group, and may have a phenylene group between carbon atoms. Divalent cyclic hydrocarbon group, -O-, -S-, -CO
-, - SO- or -SO ₂ - indicates, X and Y is a substituent on the benzene ring, the same or different and each represents a halogen atom or a hydrocarbon group having 1 to 6 carbon atoms, m and n
Are the same or different and each represent an integer of 0 to 4) As typical examples of the compound represented by the formula (1),
Dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl; bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane,
1,2-bis (4-hydroxyphenyl) ethane, 2,
2-bis (4-hydroxyphenyl) propane, 1,1
-Bis (4-hydroxyphenyl) butane, 1,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4
-Hydroxyphenyl) -2-methylpropane, 2,2
-Bis (4-hydroxyphenyl) pentane, 2,2-
Bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (4-hydroxyphenyl) octane, 1,1-bis (4-hydroxyphenyl) -1,1
-Diphenylmethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) -2-phenylethane, 2,2-bis (3,5-dibromo-4) -Hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3-
Isopropylphenyl) propane, 2,2-bis (4-
(Hydroxy-3-s-butylphenyl) propane, 2,
2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3-t
Bis (hydroxyaryl) alkanes such as -butylphenyl) propane; 1,1'-bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,1'-
Bis (hydroxyaryl) dialkylbenzenes such as bis (4-hydroxyphenyl) -m-diisopropylbenzene; 1,1-bis (4-hydroxyphenyl)
Bis (hydroxyaryl) such as cyclopentane and 1,1-bis (4-hydroxyphenyl) cyclohexane
Cycloalkanes; bis (hydroxyaryl) ethers such as bis (4-hydroxyphenyl) ether;
Bis (hydroxyaryl) sulfides such as bis (4-hydroxyphenyl) sulfide; bis (hydroxyaryl) ketones such as bis (4-hydroxyphenyl) ketone; bis (hydroxyaryl) such as bis (4-hydroxyphenyl) sulfoxide ) Sulfoxides; and bis (hydroxyaryl) sulfones such as bis (4-hydroxyphenyl) sulfone.

Further, as the aromatic dihydroxy compound,
In addition to the compound represented by the formula (1), dihydroxybenzene, dihydroxynaphthalene and the like can also be used. The aromatic dihydroxy compounds may be used alone, or two or more aromatic dihydroxy compounds may be used in combination to obtain a copolymer.

[Carboxylic Diester] As the carbonic diester, diphenyl carbonate, ditolyl carbonate,
Bis (2-chlorophenyl) carbonate, bis (3-
Diaryl carbonates such as chlorophenyl) carbonate, bis (4-chlorophenyl) carbonate, bis (2,4,6-trichlorophenyl) carbonate, di (m-cresyl) carbonate and dinaphthyl carbonate; dimethyl carbonate, diethyl carbonate,
Dialkyl carbonates such as dibutyl carbonate;
And dicycloalkyl carbonates such as dicyclohexyl carbonate.

Of these, diaryl carbonates such as diphenyl carbonate are preferred.

In addition, a dicarboxylic acid or a dicarboxylic acid ester can be used together with the above-mentioned carbonic acid diester. Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid. Examples of the dicarboxylic acid ester include esters of the above-mentioned aromatic carboxylic acids such as diphenyl terephthalate, dimethyl terephthalate, and diphenyl isophthalate (particularly, aromatic carboxylic acid aryl esters). Dicarboxylic acids and dicarboxylic esters may be used alone or
A mixture of more than one species can be used. The amount of the dicarboxylic acid or dicarboxylic acid ester to be used is, for example, about 0 to 50 mol%, preferably about 0 to 30 mol%, based on the total amount of the carbonic acid diester and the dicarboxylic acid or dicarboxylic acid ester.

When a dicarboxylic acid or a dicarboxylic acid ester is used in combination with a carbonic acid diester, a polyester polycarbonate is obtained. The method for producing the polycarbonate of the present invention includes such a method for producing a polyester polycarbonate.

The amount of the carbonic acid diester used is, for example, 1.0 to 1.7 mol, preferably 1.01 to 1.5 mol, more preferably 1.015 to 1. mol, per mol of the aromatic dihydroxy compound. It is about 2 mol.

[Transesterification Catalyst] The reaction between an aromatic dihydroxy compound and a carbonic acid diester proceeds in the presence of a transesterification catalyst.

As the transesterification catalyst, any known transesterification catalyst can be used. The transesterification catalysts can be used alone or as a mixture of two or more. Preferred transesterification catalysts include basic catalysts. Examples of the basic catalyst include a nitrogen-containing basic compound, an alkali metal compound, an alkaline earth metal compound, and the like. The basic catalysts can be used alone or in combination of two or more.

The nitrogen-containing basic compound includes an electron-donating nitrogen-containing heterocyclic compound or a salt thereof, a chain amine or a salt thereof,
Ammonium hydroxides and the like.

Representative examples of the electron-donating nitrogen-containing heterocyclic compound include 2-aminopyridine, 4-aminopyridine, 2-hydroxypyridine, 4-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine,
Pyridines such as -dimethylaminopyridine, 4-diethylaminopyridine, 4-pyrrolidinopyridine, 4- (4-methylpyrrolidinyl) pyridine and 4- (4-methyl-1-piperidinyl) pyridine; quinolines such as aminoquinoline Imidazoles such as imidazole, 2-dimethylaminoimidazole, 2-methoxyimidazole, 2-methylimidazole, 4-methylimidazole and 2-mercaptoimidazole; benzimidazoles such as benzimidazole; diazabicyclooctane (DABCO); 1,8-diazabicyclo [5.4.
0] -7-undecene (DBU) and the like (particularly, polycyclic amines having a nitrogen atom at a bridgehead position). As chain amines, tertiary amines such as trimethylamine, triethylamine, N, N-dimethylaniline; dimethylamine, diethylamine,
Secondary amines such as N-methylaniline; primary amines such as methylamine, ethylamine, benzylamine and aniline. Examples of the ammonium hydroxides include tetramethylammonium hydroxide, tetraethylammonium hydroxide and the like. Examples of the salt of the electron-donating nitrogen-containing heterocyclic compound and the chain amine include organic acid salts such as formates, acetates, and oxalates; carbonates, nitrates, nitrites, sulfates, phosphates, and fluorides. Examples thereof include inorganic acid salts such as borate and borohydride.

Among the nitrogen-containing basic compounds, one or a combination of two or more selected from electron-donating nitrogen-containing heterocyclic compounds and salts thereof are particularly preferable.

Representative examples of alkali metal compounds include hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and cesium hydroxide; carbonates such as lithium carbonate, sodium carbonate, potassium carbonate and cesium carbonate; Bicarbonates such as lithium hydrogen, sodium bicarbonate and potassium bicarbonate; borates such as lithium borate, sodium borate and potassium borate; hydrogen such as lithium borohydride, sodium borohydride and potassium borohydride Boride; dilithium hydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate; dihydrogen phosphate; lithium acetate, sodium acetate, potassium acetate, lithium stearate, sodium stearate, potassium stearate; Lithium benzoate, sodium benzoate, benzo Organic acid salts such as potassium, lithium methoxide, sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide,
Alkoxides such as cesium methoxide; phenols such as dilithium salts of bisphenol A, disodium salts of bisphenol A, dipotassium salts of bisphenol A, lithium salts of phenol, sodium salts of phenol, potassium salts of phenol, and cesium salts of phenol And the like. Among these alkali metal compounds, lithium compounds such as lithium hydroxide and lithium borate are particularly preferable.

Representative examples of the alkaline earth metal compounds include hydroxides such as magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide; carbonates such as magnesium carbonate, calcium carbonate, strontium carbonate and barium carbonate. Borates such as magnesium borate, calcium borate, strontium borate, barium borate; magnesium acetate, calcium acetate, strontium acetate, barium acetate, magnesium stearate, calcium stearate, strontium stearate, barium stearate, etc. Organic acid salts and the like can be mentioned. Among these alkaline earth metal compounds, alkaline earth metal borates such as magnesium borate are preferred.

As the transesterification catalyst, in addition to the above,
For example, ammonium borate; transition metal salts of boric acid such as copper borate and manganese borate; phosphonium hydroxides such as tetrabutylphosphonium hydroxide and tetraphenylphosphonium hydroxide can also be used.

The amount of the transesterification catalyst used is, for example, 10 ^-9 to 10 based on 1 mol of the aromatic dihydroxy compound.
^-1 mol, preferably about 10 ^-8 to 10 ^-2 mol.

In the method of the present invention, when a basic catalyst is used as the transesterification catalyst, it is preferable to use a neutralizing agent for the basic catalyst in combination. By using the neutralizing agent, the physical properties of the polycarbonate, particularly the hue, can be greatly improved. As the neutralizing agent, an acid, an acid salt of an acid, an acidic substance such as an ester, or an equivalent thereof can be used. In particular, as the neutralizing agent, a weakly acidic substance such as a weak acid, a salt of a weak acid exhibiting an acidity, an acid salt of a weak acid, an ester of a weak acid, or an equivalent thereof is preferable. Examples of the weak acid include inorganic acids such as boric acid and phosphorous acid; and organic acids such as acetic acid. Examples of the acidic weak acid salt or the acidic weak acid salt include hydrogen phosphites such as ammonium hydrogen phosphite. Particularly preferred neutralizing agents include boric acid, hydrogen phosphite and the like. The neutralizing agents can be used alone or in combination of two or more.

The amount of neutralizing agent is the relative transesterification catalyst 1 mol, for example from ^10-5 to ³ mol, preferably ^10-3 to ² moles.

In the transesterification reaction (polycondensation reaction), various phenols and carbonic acid diesters can be used as a terminal blocking agent. Examples of phenols include p-phenylphenol, p-cumylphenol, pt-butylphenol and the like.
In addition, the carbonic acid diester as the terminal blocking agent includes 2-methoxycarbonyl-5-t-butylphenylphenyl carbonate and the like. The amount of the terminal blocking agent used is, for example, 0 to 1 mol of the aromatic dihydroxy compound.
It is about 0.1 mol, preferably about 0 to 0.07 mol.

[Pre-polycondensation step (1)] In the method of the present invention, the polycarbonate is subjected to (1) a pre-polycondensation step,
(2) It is manufactured through a post-polycondensation step. FIG. 1 is a flow sheet diagram showing an example of a production flow in the method of the present invention.

In the pre-polycondensation step (1), an aromatic dihydroxy compound and a carbonic acid diester are subjected to a polycondensation reaction to produce a prepolymer having a viscosity average molecular weight of 4,000 to 15,000.

The pre-polycondensation step (1) is not particularly limited as long as it can produce a prepolymer having the above-mentioned viscosity average molecular weight. A polycondensation reaction is carried out while distilling off the compound to give a viscosity average molecular weight of 30.
A first pre-polycondensation step (1c) for producing a prepolymer of 00 to 5000 and a second pre-polycondensation step (1d) for further proceeding the polycondensation reaction to produce a prepolymer having an average viscosity of 4000 to 15000. It is preferable to carry out in two stages.

The mixed solution subjected to the polycondensation reaction in the first pre-polycondensation step (1c) is not particularly limited, but is a mixture of a carbonic acid diester, or a carbonic acid diester and a transesterification catalyst in the substantial absence of oxygen. A dissolving step (1a) of dissolving an aromatic dihydroxy compound and a transesterification catalyst or an aromatic dihydroxy compound in a molten mixture containing the mixture to prepare a mixture containing a diester carbonate, an aromatic dihydroxy compound and a transesterification catalyst; The mixed solution obtained in the dissolving step (1a) is supplied to an aging tank, and a polycondensation reaction is performed without substantially distilling off the by-produced hydroxy compound to form a prepolymer. It is preferable to use an aging solution obtained through

As the dissolving tank A used in the dissolving step (1a), a vertical stirring tank having a general stirring device equipped with a vertical rotating shaft and a stirring blade can be used. In the dissolving step (1a), for example, the diester carbonate is supplied through the pipe 1 while stirring, and the pipe 2 is melted in a state where the diester carbonate is melted.
a and 2b to supply an aromatic dihydroxy compound and a transesterification catalyst to dissolve in the carbonic acid diester, or supply a carbonic acid diester and a transesterification catalyst through pipes 1 and 2b and, in a molten state, to supply an aromatic This is performed by supplying and dissolving the dihydroxy compound. When a neutralizing agent for the transesterification catalyst is used, it may be added at this stage. The neutralizing agent can be added in a subsequent step, for example, in the aging step (1b), the first pre-polycondensation step (1c), the second pre-polycondensation step (1d), or the like.

The atmosphere in the dissolving tank A is kept at a slight pressurized state, preferably about 10 to 100 mmH ₂ O, by constantly passing an inert gas such as nitrogen to avoid mixing of oxygen.

As the material of the dissolving tank A, stainless steel, for example, SUS-304 or SUS-316 may be used. In order to prevent an adverse effect on the hue, at least the liquid-contacting portion has an iron component (as iron; hereinafter, the content of "iron component" means a value in terms of iron) of 20% by weight or less, preferably 10% by weight or less. More preferably, the material is 5% by weight or less. For example, Hastelloy,
It is desirable to use nickel, titanium, zirconium, molybdenum, tantalum, an alloy thereof, a resin such as a fluorinated resin or a polyolefin resin, glass, or the like, or to line the inside of the melting tank A with the above material. In particular, when a dissolving tank A made of nickel (including nickel lining; hereinafter, “made of nickel” includes nickel lining) or hastelloy, a polycarbonate having an excellent hue can be obtained.

The temperature of the dissolving step (1a) is usually not lower than the melting point of the carbonate diester to be used, for example, about 50 to 270 ° C., preferably about 80 to 150 ° C.

As the aging tank B used in the aging step (1b), a conventional vertical stirring tank having a vertical rotating shaft and stirring blades can be used as in the dissolution tank A. In the aging step (1b), a mixed solution containing the carbonic acid diester, the aromatic dihydroxy compound, the transesterification catalyst, and, if necessary, the neutralizing agent for the transesterification catalyst obtained in the dissolving step (1a) is supplied to a pump 3 Thus, the transesterification reaction (polycondensation reaction) proceeds without substantially distilling off the by-produced hydroxy compound through the pipe 4 to produce a low molecular weight prepolymer (oligomer). The viscosity average molecular weight of this prepolymer is, for example, about 100 to 4000, preferably about 500 to 3000. The molecular weight can be adjusted by the reaction temperature, the residence time of the reaction solution, and the like. In addition,
The dissolving tank A can also be used as the aging tank B, and the mixture can be transferred to the aging step without transferring the liquid mixture.

The atmosphere in the aging tank B is preferably purged with an inert gas such as nitrogen gas so that oxygen is substantially absent. As in the case of the dissolving tank A, at least the liquid contacting part is made of iron in order to prevent the iron component from being eluted by the by-produced hydroxy compound (phenols) and deteriorating the hue of the polycarbonate. It is desirable to use a material having a component of 20% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less. A particularly preferred material is nickel.

The temperature in the aging step (1b) is a temperature at which transesterification proceeds, for example, 150 to 270 ° C., preferably 150 to 220 ° C., more preferably 160 to 220 ° C.
It is about 200 ° C. In addition, the aging step (1b) is usually performed under normal pressure or slight pressure so as not to distill out the by-produced hydroxy compound.

In the aging step (1b), the transesterification reaction proceeds without substantially distilling off the by-produced hydroxy compound, so that the molar balance between the carbonic acid diester and the aromatic dihydroxy compound used as the raw materials does not break down. . Therefore, a polycarbonate having a desired terminal group ratio (for example, a ratio of hydroxyaryl terminal groups to other terminal groups) and an average molecular weight can be obtained.

In the first pre-polycondensation step (1c), for example, a first pre-polycondensation tank C provided with a distillation column D for distilling off a hydroxy compound by-produced by a reaction between a carbonic acid diester and an aromatic dihydroxy compound is used. It can be performed using: As the first pre-polycondensation tank C, a vertical stirring device having a stirring blade having a vertical rotation axis can be used.

In the first pre-polycondensation step (1c), the aging solution obtained in the aging step is supplied to the first pre-polycondensation tank C through a pipe 6 using a pump 5, and a hydroxy compound produced as a by-product is supplied to a pipe. 7, the ester exchange reaction (polycondensation reaction) is further advanced while distilling off through the pipe 8, and a prepolymer having a viscosity average molecular weight of 3,000 to 5,000, preferably 3,500 to 4,500 is produced. The molecular weight can be controlled by the reaction temperature, the residence time of the reaction solution, and the like. The aging tank B may be used also as the first pre-polycondensation tank C, and the process may be shifted to the first pre-polycondensation step without transferring the aging liquid. The first pre-polycondensation tank C may be a single tank, but two or more tanks (for example, about 2 to 4 tanks) may be provided in series.

The material of the first pre-polycondensation tank C is
As in the case of the above, in order to prevent the iron component from being eluted by the by-produced hydroxy compound and deteriorating the hue of the polycarbonate, at least the liquid-contacting portion has an iron component of 20% by weight or less, preferably 10% by weight or less, more preferably Is preferably 5% by weight or less. Of these, nickel is preferred.

The reaction temperature in the first prepolycondensation step (1c) is, for example, 150 to 280 ° C., preferably 160 to 26 ° C.
It is about 0 ° C. The pressure is less than normal pressure, for example, 1 to
It is about 400 mmHg, preferably about 50 to 400 mmHg, and more preferably about 100 to 300 mmHg.

The distillation column D only needs to be able to separate the hydroxy compound by-produced from the carbonic acid diester and substances having a higher boiling point than the carbonic acid diester (such as an aromatic dihydroxy compound and a transesterification catalyst). Can be used. The distillation column D may be of any type, such as a tray column or a packed column. Distilled hydroxy compound, as it is or if necessary,
Further, by purifying using a separation and purification means such as a distillation column, it can be reused as a raw material of carbonic acid diester. The hydroxy compound distilled in a later step may be purified by the above separation and purification means and reused as a raw material for the carbonic acid diester. The unreacted carbonic diester and aromatic dihydroxy compound are usually refluxed into the reaction system through the pipe 9.

The material of the distillation column D is SUS-304 or SU
Although stainless steel such as S-316 may be used, as in the case of the melting tank A, at least the liquid contact part has an iron component 2
It is preferably formed of a material (particularly nickel and its lining, plating, etc.) of 0% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less.

The second pre-polycondensation step (1d) is performed using a vertical stirrer equipped with a stirrer having a vertical rotation axis, preferably a vertical stirrer E equipped with a double helical ribbon stirrer. .

In this step (1d), the prepolymer obtained in the first pre-polycondensation step (1c) is
The ester exchange reaction (polycondensation reaction) is further supplied to the second pre-polycondensation tank E through the pipe 11 while keeping the inside of the tank under reduced pressure by the vent pipe 12, and the viscosity average molecular weight is 4,000 to 15,000, preferably 6000-1300
Produce about 0 prepolymer. The by-produced hydroxy compound may be distilled off using the same distillation column as described above. The second pre-polycondensation tank E may be a single tank, but two or more tanks (for example, about 2 to 4 tanks) may be provided in series.

The material of the second pre-polycondensation tank E is
As in the case of the above, in order to prevent the reduction of the hue of the polycarbonate, at least the liquid contact portion is made of a material (for example, nickel) having an iron component of 20% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less. It is desirable.

The reaction temperature in the second pre-polycondensation step (1d) is, for example, 150 to 280 ° C., preferably 200 to 27.
It is about 0 ° C. The pressure is, for example, 0.1 to 30 m.
mHg, preferably about 0.5 to 20 mmHg, and more preferably about 1 to 10 mmHg.

[Post-polycondensation step (2)] One of the main features of the present invention is that, in the post-polycondensation step (2), a cylindrical container placed horizontally and two longitudinal ends in the container are provided. A single-shaft agitated horizontal reactor F having no stirring center shaft member penetrating inside the vessel, comprising a pair of rotating shafts separately disposed and a stirring blade attached between the rotating shafts. At least one is used.

FIG. 2 is a partial cross-sectional side view showing an example of the horizontal reaction apparatus F. 3 to 7 are front views showing a partition plate in the apparatus shown in FIG. FIG. 8 is a front view showing an end member in the apparatus of FIG.

This reaction apparatus is installed substantially horizontally, and is separated into a cylindrical container 21 provided with a heating device (heat medium jacket or the like) (not shown), and two longitudinal ends in the container 21. Of a pair of rotating shafts 22a, 22
b, a pair of plate-like end members 29 attached to the rotating shafts 22a and 22b in a direction perpendicular to the shafts, and the pair of end members 29 at a position separated from the rotation center axis. A plurality of (four) rod-shaped connecting members 40 and a plurality of partition plates 2 attached to the connecting members 40 in a vertical direction.
3, 24, 25, 26 and a scraping plate 28a, which is attached to the tip of each of the partition plates in a direction perpendicular to the partition plate.
A stirring blade constituted by 28b, 28c, 28d, an intermediate plate constituted by a partition plate 27, and a scraping blade 30 provided between an end member 29 and inner walls at both ends in the longitudinal direction of the container 21.
And a reinforcing member 41 for reinforcing the end member 29. The rotating shaft 22a is connected to a driving device (not shown). The scraping blade 30 is formed in an S-shape (propeller shape) when viewed from the rotation axis direction. The container 21 is provided with an inlet nozzle 43a, an outlet nozzle 43b, and an exhaust nozzle (not shown). The exhaust nozzle is connected to a vent conduit 15 leading to a decompression means (not shown), and the inside of the container 21 is kept at a reduced pressure.

The partition plates 23, 24, 25, 26, 27
Has a function of preventing a short path in the longitudinal direction of the reaction solution in the container. The shape of the partition plate is a donut shape having an opening 42 at the center. In addition, the partition plate 24,
26 has an opening 42 in addition to the center. The size of the opening 42 and the interval between the partition plates are
Can be set appropriately according to the position in the longitudinal direction in the inside, that is, the viscosity of the liquid. Since the molecular weight increases with the progress of the reaction, the viscosity increases in the vessel 21 as it goes downstream. It is preferable that the opening area of the opening of the partition plate and the interval between the partition plates are set to be larger as going to the downstream side (high viscosity side).

The shape of the scraping plate attached to each partition plate,
The size, number, and mounting angle when viewed from the rotation axis direction are also
It can be appropriately selected depending on the position in the container 21. In the above example, each scraping plate has a rectangular shape. The scraping plates 28a and 28b attached to the partition plate 23
When viewed from the direction of the rotation axis, they are arranged at an angle with respect to the diameter direction. On the other hand, the scraping plates 28c and 28d
Are arranged in the diameter direction when viewed from the rotation axis direction. In consideration of the viscosity of the reaction solution, it is desirable that the size (width) of the scraping plate and the number of the scraping plates be reduced toward the downstream side. The number of scraping plates attached to each partition plate is, for example, about 2 to 24, and preferably about 3 to 18. When viewed from the side of the container, the scraping plate is preferably continuous in the longitudinal direction.
The scraping plate can be attached to the partition plate by, for example, fitting and fixing the corresponding notch provided in the partition plate.

The distance between the tip of the stirring blade and the inner wall of the vessel can be appropriately set in a range where no dead space is generated, for example, in a range of about 1 to 50 mm. The number of rotations of the rotating shafts 22a and 22b can be selected within a range that does not impair the stirring efficiency, and is, for example, about 0.5 to 20 rpm, and preferably about 1 to 10 rpm.

The scraping blade 30 has a screw function of pushing the reaction solution back into the container 21. Scraping wings 30
The distance between the container and the inner wall of the container 21 is in a range in which a dead space does not occur, for example, about 1 to 50 mm.

The end member 29 is also provided with an opening 42 through which the reaction solution passes. In addition, the end member 29 does not necessarily have to be plate-shaped, and for example, may be formed in a lattice shape, a radial shape, or the like by combining a plurality of narrow members. Also, the number of the connecting members 40 may be at least two, and is preferably about three to eight.

The viscosity-average molecular weight of the specific range (namely, 4000 to 150) formed in the pre-polycondensation step (1).
The prepolymer having (00) is supplied from the inlet nozzle 43a into the container 21 by the pump 13 through the pipe 14, and is heated by the heating device. Then, the supplied prepolymer is rotated by a rotating shaft 2 as shown by the arrow in the figure.
Due to the rotation of 2a and 22b, it is moved in the direction of the outlet nozzle 43b while being subjected to the stirring and the surface renewal action by the stirring blade, and is taken out from the outlet nozzle 43b. During this time, the transesterification reaction (polycondensation reaction) further proceeds, and the viscosity average molecular weight is 18,000 to 40,000, preferably 1850.
A high molecular weight polycarbonate of about 0-35,000 is obtained. The molecular weight can be adjusted by the reaction temperature, the residence time of the reaction solution, and the like. Volatile substances such as a hydroxy compound by-produced in the reaction are discharged from an exhaust nozzle, and if necessary, purified and recovered by using the same distillation column as described above.

One horizontal reactor F may be provided, but two or more reactors (for example, about 2 to 3 reactors) may be provided in series. When producing polycarbonate using two or more groups, depending on the viscosity of the reaction solution, the shape and spacing of the partition plate,
The size and number of scraping plates can be set as appropriate. For example,
As we go to the later stage, while increasing the spacing of the dividers,
Set the size and number of scraping plates attached to the partition plate small.

The material of the horizontal reaction apparatus F may be the same as that of the dissolving tank A in order to prevent corrosion by the by-produced hydroxy compound. Because of its low concentration, it may be made of a material having relatively low corrosion resistance. From a practical viewpoint, stainless steel such as SUS304 and SUS316 is preferable. It is desirable to provide a preheater at the entrance of the horizontal reactor F. When the preheater is provided, the temperature difference between the liquid supplied to the horizontal reactor F and the reactor becomes smaller, the surface of the reaction liquid (resin) is smoothly renewed, and the evaporation efficiency of the by-product hydroxy compound is improved. I do.

The reaction temperature in the post-polycondensation step (2) is as follows:
For example, 240 to 320 ° C, preferably 250 to 310 ° C
It is about. The pressure is 10 mmHg or less, preferably 1 mmHg or less.

In this reaction apparatus, the reaction liquid (polymer) is stirred by a single-axis stirring type stirring device having no stirring center shaft member penetrating the inside of the vessel. Therefore, the reaction using the stirring device having the stirring center shaft member is performed. Unlike the device, the polymer does not stay on the shaft, and the gelling or coloring of the polymer can be suppressed. Further, the flow of the entire reaction solution in the container 21 can be maintained in a state close to the piston flow.
Therefore, it is possible to obtain a polycarbonate having high quality, particularly excellent hue, with high efficiency.

The viscosity average molecular weight of the prepolymer supplied to the reactor F is in the above range (4000 to 150).
If the ratio is larger or smaller than (00), the stirring efficiency and the surface renewal efficiency of the reaction solution decrease, and the reaction efficiency also decreases.
Also, in the post-polycondensation step (2), when the reaction apparatus G used in the second post-polycondensation step (2b) described later is used directly without using the reaction apparatus F, the viscosity of the reaction solution is increased. If it is too low, high reaction efficiency cannot be obtained, and it is necessary to increase the average residence time of the reaction solution, and the hue of the obtained polycarbonate tends to deteriorate.

[First post-polycondensation step (2a) and second post-polycondensation step (2b)] In the method of the present invention, the post-polycondensation step (2) can be carried out in two stages. For example,
In the post-polycondensation step (2), the viscosity-averaged 4000-15000 prepolymer produced in the second pre-polycondensation step (1d) is further subjected to a polycondensation reaction, for example, with a viscosity-average molecular weight of 15
000 to 18000, preferably 16000 to 1750
The first post-polycondensation step (2a) for producing about 0 polycarbonate and the polycarbonate produced in the first post-polycondensation step (2a) are further subjected to a polycondensation reaction to obtain a high viscosity average molecular weight of 18,000 to 40,000. And a second post-polycondensation step (2b) for producing a molecular weight polycarbonate.

The first post-polycondensation step (2a) can be performed using the single-screw stirring type horizontal reaction apparatus F. The reaction temperature in the second post-polycondensation step (2a) is, for example, 24
0 to 320 ° C, preferably about 250 to 310 ° C, and the pressure is 10 mmHg or less, preferably 1 mmHg.
It is as follows. The molecular weight of the polycarbonate to be produced is
It can be adjusted by the reaction temperature or the liquid residence time.

The reaction device used in the second post-polycondensation step (2b) may be any device that can obtain high stirring efficiency for a high viscosity liquid. Examples of such a reaction device include:
A cylindrical container installed horizontally, two rotary ear shafts juxtaposed at both longitudinal ends of the container, and a plurality of rod-shaped rectangular frames attached between the rotary ear shafts at both ends of the container. And a grid-type stirring blade connected to
A horizontal reaction device G provided with a rotating mechanism for rotating the rotating ear shaft while holding it so that the tip of the rod-shaped rectangular frame of one stirring blade passes close to the rotation center of the other stirring blade.

FIG. 9 is a partially sectional plan view showing an example of the above-mentioned horizontal reactor G. FIG. 10 is a sectional view taken along line XX of FIG. 9, and FIG. 11 is a perspective view showing a stirring blade of the horizontal reactor G of FIG.

The reactor G is installed substantially horizontally, and is provided with a cylindrical container 31 provided with a heating device (heat medium jacket or the like) (not shown), and both ends of the container 31 in the longitudinal direction. Two rotating ear shafts 32a and 32b
Between the left and right rotating ear shafts 32a, 32a, and 32
b, 32b, and lattice-type stirring blades 34a and 34b. The rotating ear shafts 32a and 32b are supported by bearings 35 fixed to the side surface of the container 31, and one of the left and right rotating ear shafts is a driving device (not shown).
It is connected to. The lattice type stirring blades 34a and 34b are
Each is formed by connecting a plurality of rod-shaped rectangular frames 33a and 33b with a phase angle of 90 degrees. Further, the stirring blades 34a, 34b are provided with rotating ear shafts 32a, 32b.
When viewed from the direction, the rod-shaped rectangular frames 33a and 33b have a phase angle of 45 degrees with each other, and the tip of one of the rod-shaped rectangular frames 33a and 33b has the other rod-shaped rectangular frames 33b and 33b.
a so as to pass as close as possible to the center of rotation of the container 3a.
1. Rotate at the same speed in opposite directions to each other so as to lift the reaction solution from the bottom to the top inside the container 31 near the inner wall surface. The container 31 has an inlet nozzle 36 and an exhaust nozzle 3
7, and an outlet nozzle (not shown) provided on the opposite side of the exhaust nozzle 37. It is desirable to provide a preheater (not shown) in front of the inlet nozzle 36. The exhaust nozzle 37 is connected to the vent conduit 18 that leads to a pressure reducing means (not shown), and the inside of the container 31 is kept at a reduced pressure.

The ratio of the vertical and horizontal lengths of the bar-shaped rectangular frames 33a and 33b is, for example, about 1/3 to 3/1. Rod-shaped rectangular frame 3
The connection number of 3a and 33b is, for example, about 4 to 12. The phase angle between adjacent rod-shaped rectangular frames is not limited to 90 degrees,
For example, an appropriate angle such as 30 degrees, 45 degrees, or 60 degrees can be adopted. Further, the rod-shaped rectangular frame is formed at an appropriate angle in two or more directions when viewed from the direction of the rotating ear axis (for example, 1).
A stirrer may be formed by connecting adjacent rod-shaped rectangular frames at an appropriate (eg, 60 °) phase angle with an angle of 20 °).

The polycarbonate produced in the first post-polycondensation step (2a), for example, having a viscosity-average molecular weight of 15,000 to 18000, is supplied to the inlet nozzle 36 through the pipe 17 by the pump 16 connected to the outlet nozzle 30b of the horizontal reactor F. From the container 31 and heated by a heating device (not shown). Then, the supplied polycarbonate moves toward the outlet nozzle while being stirred and mixed by the stirring blades 34a and 34b, and is taken out of the pipe 20 from the outlet nozzle by using the pump 19. During this time, the transesterification reaction (polycondensation reaction) further proceeds, and a high-molecular-weight polycarbonate having a viscosity-average molecular weight of 18,000 to 40,000, preferably about 18,500 to 35,000 is obtained. The molecular weight of the polycarbonate can be adjusted by the reaction temperature, the liquid residence time, and the like. Volatile substances such as hydroxy compounds by-produced in the reaction are exhausted by the exhaust nozzle 37.
And can be purified and recovered by using a distillation column similar to the above, if necessary.

One horizontal reactor G may be provided, but two or more reactors (for example, about two to three reactors) may be provided in series.
As the material of the horizontal reactor G, a material having high corrosion resistance similar to that of the dissolution tank A may be used. However, in the second post-polycondensation step (2b), the concentration of the hydroxy compound is small. It may be made of a relatively low corrosion resistant material. From a practical viewpoint, stainless steel such as SUS304 and SUS316 is preferable.

The reaction temperature in the second post-polycondensation step (2b) is, for example, 240 to 320 ° C., preferably 250 to 31 ° C.
The temperature is about 0 ° C., and the pressure is 10 mmHg or less, preferably 1 mmHg or less.

In this reactor, the stirring blades 34a, 34b
Since the tips of the rod-shaped rectangular frames 33a, 33b pass close to the rotation centers of the opposing rod-shaped rectangular frames 33b, 33a, and the stirring action is performed by the rod-shaped structure, the reaction solution ( Adhesion and scaling of the polymer), and the dead space can be extremely reduced.
In addition, the flow of the entire reaction solution in the container 31 can be maintained close to the piston flow, and a good surface renewal effect can be obtained, so that a polycarbonate having excellent quality, particularly excellent hue, can be obtained.

If the viscosity average molecular weight of the polycarbonate supplied to the reactor G is out of the above range (15,000 to 18,000), the stirring efficiency and the surface renewal efficiency of the reaction solution are liable to decrease.

Further, it is preferable to provide a kneading step using a dynamic kneader after the second post-polycondensation step (3) using the reactor G. In this kneading step, various additives can be added to the polymer in a molten state and kneaded. Each of the above steps can be performed by any of a continuous system, a batch system, and a semi-batch system.

[0077]

According to the method of the present invention, in the post-polycondensation step, a reaction device equipped with a specific stirring device suitable for the viscosity of the reaction liquid (polymer) is used, so that good physical properties can be obtained.
Particularly, a high molecular weight polycarbonate having an excellent hue can be efficiently produced.

[0078]

EXAMPLES The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples. The physical properties of the produced polycarbonate were evaluated according to the following methods. (Viscosity average molecular weight (Mv)) The intrinsic viscosity [η] of the methylene chloride solution at 20 ° C. was measured using an Ubbelohde viscometer, and the viscosity average molecular weight (Mv) was determined based on the following equation. [Η] = 1.11 × 10 ⁻⁴ (Mv) ^0.82 (hue) The X, Y, and Z values (tristimulus values) of a 2 mm-thick injection plate were measured by using Color and Color De-produced by Nippon Denshoku Industries Co., Ltd.
Using a fference meter NDJ-1001DP, it was measured by a transmission method, and a YI value indicating a scale of yellowness was obtained, and this was used as an index of hue. The larger the YI value, the more colored.

Example 1 A polycarbonate was produced according to the production flow shown in FIG. (Dissolution step) Under a nitrogen atmosphere, 100 parts by weight of diphenyl carbonate, lithium borate dihydrate (transesterification catalyst) 0.0003 in a vertical stirring and dissolving tank A made of nickel.
A melt mixture of 9 parts by weight and 0.0046 parts by weight of boric acid (neutralizing agent) and 105 parts by weight of bisphenol A were continuously supplied and stirred at a temperature of 90 ° C. to prepare a mixed solution. The average residence time of the liquid was 3 hours.

(Maturation Step) Under a nitrogen atmosphere, the mixed solution obtained in the above-mentioned dissolution step is continuously supplied to a vertical stirring and maturation tank B made of nickel, and aged at a temperature of 180 ° C. under normal pressure to obtain an ester. The exchange reaction was allowed to proceed to produce a low molecular weight (viscosity average molecular weight 3000) prepolymer (oligomer). The average residence time was 3 hours.

(First Precondensation Step) The aging liquid obtained in the aging step is continuously supplied to a vertical stirring reactor C made of nickel, and stirred and mixed at a temperature of 220 ° C. under a pressure of 150 mmHg. Thus, a prepolymer having a viscosity average molecular weight of 4000 was obtained. The average residence time was 2 hours. The volatile substances were supplied to a distillation column D, which was nickel-plated on stainless steel, and distilled to distill phenol by-produced and reflux unreacted diphenyl carbonate and bisphenol A to the reaction system.

(Second Pre-Polycondensation Step) The prepolymer obtained in the first pre-polycondensation step is continuously supplied to a nickel vertical stirring reactor D equipped with a double helical ribbon stirrer. Under a pressure of 10 mmHg and stirring at a temperature of 260 ° C., a prepolymer having a viscosity average molecular weight of 10,000 was obtained. Phenol by-produced in the reaction was distilled out of the system. The average residence time was one hour.

(First Post-Polycondensation Step) The prepolymer obtained in the second pre-polycondensation step is continuously supplied to a horizontal reactor (reactor F) shown in FIGS.
Under a pressure of 270 ° C. to obtain a polycarbonate having a viscosity average molecular weight of 16,500. Phenol by-produced in the reaction was distilled out of the system. Average residence time is 40
Minutes.

(Second Post-Polycondensation Step) The polycarbonate obtained in the first post-polycondensation step was treated as shown in FIGS.
It is continuously supplied to an axial stirring type horizontal reactor [Reactor G: "Hitachi Lattice Blade Polymerizer" (trade name, manufactured by Hitachi, Ltd., material: stainless steel)] under a pressure of 0.3 mmHg, 270. Stir and mix at a temperature of ° C. Phenol by-produced in the reaction was distilled out of the system. The average residence time was one hour. The viscosity average molecular weight of the obtained polycarbonate was 28,000, and the hue YI was 0.5.

Comparative Example 1 In both the first post-polycondensation step and the second post-polycondensation step, a two-axis horizontal reactor having a stirring central shaft member [“Hitachi Glass Wing Polymerizer” manufactured by Hitachi, Ltd.] (Trade name), material stainless steel], and the same operation as in Example 1 was performed. However, in the first post-polycondensation step, an average residence time of 3 hours was required to obtain a polycarbonate having a viscosity average molecular weight of 16,500. In addition, in the second post-polycondensation step, it took 4 hours in average residence time to obtain a polycarbonate having a viscosity average molecular weight of 28,000. The hue YI of the polycarbonate obtained in the second post-polycondensation step was 20.

Comparative Example 2 In both the first post-polycondensation step and the second post-polycondensation step,
The same operation as in Example 1 was performed except that a two-axis stirring type horizontal reactor (Hitachi, Ltd., “Hitachi lattice wing polymerization machine” (trade name), material stainless steel) shown in Nos. 11 to 11 was used. Was. However, in the first post-polycondensation step, an average residence time of 1 hour was required to obtain a polycarbonate having a viscosity average molecular weight of 16,500. In addition, in the second post-polycondensation step, an average residence time of 1 hour was required to obtain a polycarbonate having a viscosity average molecular weight of 28,000. The hue YI of the polycarbonate obtained in the second post-polycondensation step was 2.0.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram showing an example of a production flow in a method of the present invention.

FIG. 2 is a partial cross-sectional side view illustrating an example of a horizontal reaction apparatus F.

FIG. 3 is a front view showing an example of a partition plate in the apparatus of FIG.

FIG. 4 is a front view showing an example of a partition plate in the apparatus of FIG.

FIG. 5 is a front view showing an example of a partition plate in the apparatus of FIG.

FIG. 6 is a front view showing an example of a partition plate in the apparatus of FIG.

FIG. 7 is a front view showing an example of a partition plate in the apparatus shown in FIG.

FIG. 8 is a front view showing an example of an end member in the apparatus shown in FIG.

FIG. 9 is a partial sectional plan view showing an example of a horizontal reaction device G.

FIG. 10 is a sectional view taken along line XX of FIG. 9;

FIG. 11 is a perspective view showing a stirring blade of the horizontal reactor G of FIG.

[Explanation of symbols]

 A dissolution tank B aging tank C 1st pre-polycondensation tank D distillation column E 2nd pre-polycondensation tank F 1st post-polycondensation tank G 2nd post-polycondensation tank 21, 31 Vessel 22a, 22b Rotating shaft 23, 24, 25, 26, 27 Partition plate 28a, 28b, 28c, 28d Scraper plate 29 End member 30 Scraper blade 32a, 32b Rotating ear axis 33a, 33b Rectangular rectangular frame 34a, 34b Lattice stirrer 40 Connecting member

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Kinoshita 794, Higashi-Toyoi, Kazamatsu, Kudamatsu, Yamaguchi Prefecture Inside the Kasado Plant of Hitachi, Ltd. In the Kasado factory of Hitachi, Ltd. (72) Inventor Seiji Motohiro 794, Higashi-Toyoi, Oaza, Kudamatsu-shi, Yamaguchi Prefecture In-house of Hitachi, Ltd. Address Kasado Factory, Hitachi, Ltd.

Claims (8)

[Claims] 1. A method for producing a corresponding polycarbonate by subjecting an aromatic dihydroxy compound and a carbonic acid diester to a transesterification reaction, wherein (1) a polycondensation reaction between the aromatic dihydroxy compound and a carbonic acid diester to obtain a viscosity average A pre-polycondensation step of producing a prepolymer having a molecular weight of 4,000 to 15,000, and (2) a pre-polycondensation step produced by the pre-polycondensation step;
It does not have a stirring center shaft member that penetrates the inside of the vessel, having a pair of rotating shafts separately disposed at both ends in the longitudinal direction in the vessel, and a stirring blade attached between the rotating shafts. A polycondensation reaction using at least a uniaxial stirring type horizontal reactor to produce a high molecular weight polycarbonate having a viscosity average molecular weight of 18,000 to 40,000, followed by a polycondensation step. 2. The pre-polycondensation step (1) comprises: (1c) a vertical type equipped with a distillation column for distilling a mixed solution containing a diester carbonate, an aromatic dihydroxy compound and a transesterification catalyst from a by-produced hydroxy compound. A first pre-polycondensation step of subjecting to a polycondensation reaction in a stirred reactor to produce a prepolymer having a viscosity average molecular weight of 3,000 to 5,000; and (1d) a prepolymer produced in the first pre-polycondensation step, Supply to a vertical stirring reactor equipped with a helical ribbon type stirrer,
The polycondensation reaction is further advanced, and the viscosity average molecular weight is 4000.
The method for producing a polycarbonate according to claim 1, further comprising a second pre-polycondensation step of producing a prepolymer of ~ 15,000. 3. A mixed solution to be subjected to a polycondensation reaction in the first pre-polycondensation step (1c) includes: (1a) a diester carbonate or a diester carbonate in a vertical stirring dissolution tank in the substantially absence of oxygen. And a melt mixture containing a transesterification catalyst and an aromatic dihydroxy compound and a transesterification catalyst, or an aromatic dihydroxy compound,
A dissolving step of preparing a mixed liquid containing the aromatic dihydroxy compound and the transesterification catalyst; and (1b) supplying the mixed liquid obtained in the dissolving step to a vertical stirring ripening tank to substantially remove the by-produced hydroxy compound. 3. The method for producing a polycarbonate according to claim 2, wherein a ripening solution obtained through a ripening step of forming a prepolymer by performing a polycondensation reaction without distilling off is used. 4. The post-polycondensation step (2) comprises the steps of: (2a) separating the prepolymer produced in the second pre-polycondensation step into a horizontally disposed cylindrical container and two longitudinal ends in the container. To a single-shaft agitated horizontal reactor having no stirring center shaft member penetrating the inside of the vessel, comprising a pair of rotating shafts arranged in a row and stirring blades mounted between the rotating shafts. (1) a first post-polycondensation step for further promoting the polycondensation reaction; and (2b) a polycarbonate container produced in the first post-polycondensation step; It has two rotating ear shafts arranged side by side at both ends, and a lattice-type stirring blade connecting a plurality of rod-shaped rectangular frames attached between the rotating ear shafts at both ends of the container, and The tip of the rod-shaped rectangular frame of one stirring blade is positioned at the center of rotation of the other stirring blade. The mixture is supplied to a two-axis stirring type horizontal reactor equipped with a rotation mechanism that rotates while holding and passing as in contact with each other to further advance the polycondensation reaction and produce a high molecular weight polycarbonate having a viscosity average molecular weight of 18,000 to 40,000. 2. The method according to claim 1, wherein the second polycondensation step is performed.
The method for producing the polycarbonate according to the above. 5. The method for producing a polycarbonate according to claim 4, wherein a polycarbonate having a viscosity average molecular weight of 15,000 to 18,000 is produced in the first post-polycondensation step (2a). 6. A single-screw agitated horizontal reactor used in the post-polycondensation step (2) is provided separately in a horizontally disposed cylindrical vessel and both longitudinal ends in the vessel. A pair of rotating shafts, a pair of end members attached to the respective rotating shafts in a direction perpendicular to the shafts, and a plurality of connecting members for connecting the pair of end members at positions separated from the center axis of rotation. And a stirring blade configured by a plurality of partition plates attached vertically to the connecting member and a scraping plate attached to a tip of the partition plate in a direction perpendicular to the partition plate. 2. The method for producing a polycarbonate according to 1. 7. A vertical stirring dissolution tank used in the dissolving step (1a), a vertical stirring aging tank used in the aging step (1b), a distillation column used in the first pre-polycondensation step (1c), and a vertical stirring reaction apparatus. ,
4. The production of the polycarbonate according to claim 3, wherein at least one of the vertical stirring reactors used in the second pre-polycondensation step (1d) has at least one liquid contact part made of a material having an iron component of 20% by weight or less. Law. 8. The method for producing a polycarbonate according to claim 7, wherein the material whose iron component is 20% by weight or less is nickel.