JPH11310631A - Production method of 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,
An annular support plate attached to the two rotating shafts at right angles to the axis in a first post-polycondensation step, and a scraping plate attached to the tip of the support plate at right angles to the support plate. The polymer having a viscosity average molecular weight of 15,000 to 18,000 was obtained using a horizontal reaction apparatus having a stirring blade composed of the following. In the second post-polycondensation step, two rotating ear shafts and a rod-shaped member attached between the rotating ear shafts The viscosity average molecular weight was 18,000 using a horizontal reactor having a grid-type stirring blade connected to a rectangular frame.
This produces ~ 40,000 polycarbonate.

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, in the latter half of the reaction, the polymer stays in a portion of the horizontal rotating shaft that does not have a 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 inventors of the present invention have made intensive studies to achieve the above object, and as a result, the reaction mixture adapted to the respective viscosity ranges according to the change in the viscosity of the reaction mixture with the progress of the reaction. By selecting the device and stirring type,
The inventors have found that the above objects are achieved, and have completed 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 produced in the pre-polycondensation step is transferred to a horizontally disposed cylindrical container, two rotating shafts juxtaposed in the container, and shafts corresponding to the two rotating shafts, respectively. A plurality of agitating blades each comprising: a plurality of annular support plates mounted at right angles to the support plate; and scraping plates mounted at respective ends of the annular support plates at right angles to the support plate. And the corresponding stirring blades respectively attached to the two rotating shafts are arranged so as to have a phase angle of 90 degrees when viewed from the axial direction, and the two rotating shafts Is supplied to a horizontal reaction apparatus equipped with a rotation mechanism that rotates while holding the tip of one stirring blade so as to pass close to the other rotation axis, to further advance the polycondensation reaction, and to obtain a viscosity average molecular weight of 15,000. The first to produce ~ 18000 polycarbonate A post-polycondensation step, and (3) a cylindrical container placed horizontally with the polycarbonate produced in the first post-condensation step, and two rotary ear shafts arranged side by side at both longitudinal ends in the container. And a grid-type stirring blade connected to a plurality of rod-shaped rectangular frames attached between the rotating ear shafts at both ends of the container, and the two rotating ear shafts are rod-shaped of one stirring blade. The rectangular frame is supplied to a horizontal reactor equipped with a rotation mechanism that rotates while holding the tip of the rectangular stirring blade close to the rotation center of the other stirring blade to further advance the polycondensation reaction, and to obtain a viscosity average molecular weight of 18,000. ~ 400
And a second post-polycondensation step to produce a high molecular weight polycarbonate of No. 00.

[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.

Incidentally, 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 of known transesterification catalysts 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, 4-dimethylaminopyridine,
4-diethylaminopyridine, 4-pyrrolidinopyridine, 4- (4-methylpyrrolidinyl) pyridine, 4-
Pyridines such as (4-methyl-1-piperidinyl) pyridine; quinolines such as aminoquinoline; imidazole, 2-dimethylaminoimidazole, 2-methoxyimidazole, 2-methylimidazole, 4-methylimidazole, 2-mercaptoimidazole and the like Imidazoles; benzimidazoles such as benzimidazole; diazabicyclooctane (DABCO), 1,8-
Diazabicyclo [5.4.0] -7-undecene (DB
U) and the like (particularly, polycyclic amines having a nitrogen atom at the bridgehead position). Examples of chain amines include trimethylamine, triethylamine, N,
Tertiary amines such as N-dimethylaniline; secondary amines such as dimethylamine, diethylamine and N-methylaniline
Primary amines such as primary amines such as methylamine, ethylamine, benzylamine and aniline. Examples of the ammonium hydroxides include tetramethylammonium hydroxide, tetraethylammonium hydroxide and the like. Salts of the electron-donating nitrogen-containing heterocyclic compound and chain amines include formate, acetate,
Organic acid salts such as oxalates; inorganic acid salts such as carbonates, nitrates, nitrites, sulfates, phosphates, fluoroborates, and borohydrides can be exemplified.

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 preferred.

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.

[0024] 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 produced through a first post-polycondensation step and (3) a second 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 form 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.

Prior to the first pre-polycondensation step (1c), an aromatic dihydroxy compound and an ester are added to a molten mixture containing a carbonic acid diester or a carbonic acid diester and a transesterification catalyst in the substantial absence of oxygen. Dissolving an exchange catalyst or an aromatic dihydroxy compound, dissolving step (1a) of preparing a mixed solution containing a carbonic acid diester, an aromatic dihydroxy compound and a transesterification catalyst, and supplying the obtained mixed solution to an aging tank; It is preferable to provide a ripening step (1b) in which a polycondensation reaction is performed without substantially distilling off the by-produced hydroxy compound to form a prepolymer.

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 stirring blades 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 always kept at a slight pressurized state of about 10 to 100 mmH ₂ O by constantly passing an inert gas such as nitrogen in order 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, but the iron component is eluted by an acidic substance such as an aromatic dihydroxy compound to form a polycarbonate. 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 higher than the melting point of the carbonate diester used, for example, 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 rotation 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, for example, an inert gas such as nitrogen gas so that substantially no oxygen is present. 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., and 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 provided. 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 pre-polycondensation 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 by-produced hydroxy compounds from carbonic acid diesters and substances having a higher boiling point than carbonic acid diesters (such as aromatic dihydroxy compounds and transesterification catalysts). 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. Unreacted carbonic acid 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 carried out by using a vertical stirrer equipped with a stirring blade 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.

[First post-polycondensation step (2)] One of the main features of the present invention is that, in the first post-polycondensation step (2), a horizontally disposed cylindrical container and a parallel inside the container are provided. Established 2
A plurality of rotating shafts, a plurality of annular supporting plates attached to the two rotating shafts in a direction perpendicular to the shafts respectively, and a supporting plate at each end of the annular supporting plate. A plurality of agitating blades, each of which is constituted by a scraper plate mounted at right angles to the rotating shaft, and a corresponding agitating blade mounted on each of the two rotating shafts has a plurality of agitating blades as viewed from the axial direction.
And a rotation mechanism that rotates the two rotating shafts while holding the two rotating shafts such that the tip of one stirring blade passes close to the other rotating shaft. The point is that a horizontal reaction apparatus F is used.

FIG. 2 is a partial sectional plan view showing an example of the horizontal reaction apparatus F. 3 is a sectional view taken along the line III-III of FIG. 2, and FIG. 4 is a sectional view taken along the line IV-IV of FIG.

This reaction apparatus is installed substantially horizontally, and is provided with a cylindrical container 21 provided with a heating device (heat medium jacket or the like) 22 and two rotating shafts 23 a provided in parallel in the container 21. , 23b, a semi-disk-shaped weir 24 for partitioning the lower half of the container 21 into a plurality of chambers, and a pair of symmetrically fixed to the rotating shafts 23a, 23b in a direction perpendicular to the axes. Agitating blades 25a and 25b each composed of an annular support plate 26 and a scraping plate 27 fixed to the end of the support plate 26 at right angles. Stirring blades 25a, 2
5b are attached to each other with a phase angle of 90 degrees with each other. Also, the rotating shafts 23a, 23b
Is connected to a driving device (not shown),
The tips of 5a and 25b are rotating shafts 23b and 23a, respectively.
It is held so as to pass close to. The container 21 has an inlet nozzle 28, an outlet nozzle 29 and an exhaust nozzle 3.
0 is attached. The exhaust nozzle 30 is connected to a vent conduit 15 communicating with a decompression means (not shown), and the inside of the container 21 is maintained at a reduced pressure.

The viscosity-average molecular weight of the specific range produced in the pre-polycondensation step (1) (ie, 4000 to 150)
The prepolymer having (00) is supplied into the container 21 from the inlet nozzle 28 through the pipe 14 by the pump 13, and is heated by the heating device 22. Then, the supplied prepolymer is rotated by a rotating shaft 2 that rotates in the opposite directions from the inside of the container 21 to the outside as shown by the arrow in the figure.
With the rotation of 3a and 23b, the water flows sequentially into the next chamber over the weir 24 and is taken out from the outlet nozzle 29 while being stirred and renewed by the stirring blades 25a and 25b. During this time, the transesterification reaction (polycondensation reaction) further proceeds, and the viscosity average molecular weight is 15,000 to 1800.
0, preferably about 16000-17500 polycarbonate 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 hydroxy compounds by-produced in the reaction are discharged from the exhaust nozzle 30 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. 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, but at this stage, the concentration of the hydroxy compound is usually small. Therefore, 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 first post-polycondensation step (2) is, for example, 240 to 320 ° C., preferably 250 to 31 ° C.
It is about 0 ° C. The pressure is 10 mmHg or less, preferably 1 mmHg or less.

In this reactor, the stirring blades 25a, 25b
Is formed by a pair of annular support plates 26 fixed symmetrically in a direction perpendicular to the axis and a scraping plate 27 fixed to the tip of the support plate 26 in a direction perpendicular to the axis.
When 5a and 25b pass through the reaction liquid (polymer) in the lower half of the container 21, the reaction liquid is efficiently stirred and mixed by the scraping plate 27, and when passing through the space above the reaction liquid. It is necessary to increase the surface area of the liquid because the liquid adheres to the annular portion of the support plate 26 to form a thin film, and at the same time, the liquid drops from the periphery of the scraping plate 27 to form a rectangular thin film. And the surface renewal of the liquid can be performed extremely efficiently.

Further, the stirring blades 25a and 25b are
3a and 23b, a plurality of them are attached to each other with a phase angle of 90 degrees to each other, and one of the stirring blades 25
Since the tip of a, 25b, that is, the scraping plate 27 is formed so as to pass close to the other rotating shafts 23b, 23a, the stirring and mixing action of the reaction liquid and the surface renewal action are more effectively performed. . Further, the stirring blades 25a, 25b
, That is, the distance between the adjacent scraping plates 27 and the distance between the scraping plate 27 and the weir 24 can be set extremely small, so that the inner surface of the container 21 and the side surfaces of the weir 24 and the rotating shafts 23a and 23b can be set. The reaction solution attached around
The dead space in the vicinity of the wall surface of the container 21 and the weir 24 can be extremely reduced by being scraped off by the scraping plate 27.

As described above, in the present invention, in the first post-polycondensation step (2), the viscosity average molecular weight is 4000 to 1500.
The prepolymer having a specific molecular weight of 0 is supplied to the reactor F to further advance the polycondensation reaction, so that the reaction efficiency can be significantly improved.

Even if the viscosity average molecular weight of the prepolymer supplied to the reactor F is larger or smaller than the above range, the stirring efficiency and the surface renewal efficiency of the reaction solution are reduced, and the reaction efficiency is lowered. Become. Further, in the first post-polycondensation step (2), the above-mentioned second reaction apparatus
When the reactor G used in the post-polycondensation step (3) is used, the viscosity of the reaction solution is too low, high reaction efficiency cannot be obtained, and it is necessary to increase the average residence time of the reaction solution. The hue of the obtained polycarbonate tends to deteriorate.

[Second post-polycondensation step (3)] Another feature of the present invention is that, in the second post-polycondensation step (3), a horizontally disposed cylindrical container and two longitudinal ends in the container are provided. And two lattice-shaped agitating blades connected to a plurality of rod-shaped rectangular frames attached between the rotational ear shafts at both ends of the container. In that a horizontal reaction apparatus G having a rotation mechanism for rotating the rotating ear shaft while holding the tip of the rod-shaped rectangular frame of one stirring blade close to the rotation center of the other stirring blade is used. is there.

FIG. 5 is a partially sectional plan view showing an example of the horizontal reaction apparatus G. 6 is a sectional view taken along line VI-VI of FIG.
FIG. 6 is a perspective view showing a stirring blade of the horizontal reactor G of FIG. 5.

The reactor G is installed substantially horizontally, and is provided with a cylindrical container 31 provided with a heating device (such as a heating medium jacket) (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 having a viscosity-average molecular weight of 15,000 to 18,000 produced in the first post-polycondensation step (2) is supplied from the inlet nozzle 36 to the container through the pipe 17 by the pump 16 connected to the outlet nozzle of the horizontal reactor F. 31 and is heated by a heating device (not shown). And the supplied polycarbonate,
While being stirred and mixed by the stirring blades 34a and 34b, it moves toward the outlet nozzle, and the pump 1
9 and taken out of the pipe 20. During this time, a transesterification reaction (polycondensation reaction) further proceeds, and a viscosity average molecular weight of 18,000 to 40000, preferably 18500
A high molecular weight polycarbonate of up to about 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 discharged from 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, or two or more reactors (for example, about 2 to 3 reactors) may be provided in series.
As the material of the horizontal reaction device G, a material having high corrosion resistance similar to that of the dissolving tank A may be used, but in the second post-polycondensation step (3), the first post-polycondensation step (2) Similarly to the above, since the concentration of the hydroxy compound is low, 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.

The reaction temperature in the second post-polycondensation step (3) 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.

As described above, in the present invention, in the second post-polycondensation step (3), the viscosity average molecular weight is 15,000 to 180.
Since the polycarbonate having a specific molecular weight of 00 is supplied to the reactor G to further advance the polycondensation reaction, a high molecular weight polycarbonate having good quality can be produced extremely efficiently.

If the viscosity average molecular weight of the polycarbonate supplied to the reaction apparatus G is out of the above range, the stirring efficiency and the surface renewal efficiency of the reaction solution are lowered, and high reaction efficiency cannot be obtained. In the second post-polycondensation step, when the reaction apparatus used in the first post-polycondensation step (2) is used instead of the reaction apparatus G, the viscosity of the reaction solution is too high. Sufficient stirring efficiency cannot be obtained, and the quality of polycarbonate tends to deteriorate.

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.

[0069]

According to the method of the present invention, the post-polycondensation step is divided into two steps, and in each step, a reaction apparatus equipped with a specific stirring device suitable for the viscosity of the reaction solution (polymer) is provided. Since it is used, a high molecular weight polycarbonate having good physical properties, particularly excellent hue, can be efficiently produced.

[0070]

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 and lithium borate dihydrate (transesterification catalyst) were placed in a vertical stirring dissolution tank A made of nickel.
0.00039 parts by weight and boric acid (neutralizing agent) 0.00
46 parts by weight of the molten mixture 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.

(Aging Step) Under a nitrogen atmosphere, the mixed solution obtained in the above dissolving step is continuously supplied to a vertical stirring and aging 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 Pre-Polycondensation Step) The aging solution 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 substance was supplied to a distillation column D formed by plating nickel on stainless steel to perform distillation, thereby distilling off by-product phenol and refluxing 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 subjected to a horizontal reaction apparatus shown in FIGS. 2, 3 and 4 [reaction apparatus F: manufactured by Hitachi, Ltd.
"Hitachi Glasses Wing Polymerizer" (trade name), stainless steel], and continuously supplied under a pressure of 5 mmHg to 270
It stirred and mixed at the temperature of ° C, and obtained the polycarbonate of viscosity average molecular weight 16500. Phenol by-produced in the reaction was distilled out of the system. The average residence time was one hour.

(Second post-polycondensation step) The polycarbonate obtained in the first post-polycondensation step was converted into a horizontal reactor [reactor G: manufactured by Hitachi, Ltd., Hitachi Lattice Blade Polymerizer ”(trade name), material stainless steel], under a pressure of 0.3 mmHg,
The mixture was stirred and mixed at a temperature of 270 ° 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 hue YI was 1.0.

Comparative Example 1 In both the first post-polycondensation step and the second post-polycondensation step, the horizontal reaction apparatus shown in FIGS. 2, 3 and 4 [“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, the viscosity average molecular weight is 1
An average residence time of 3 hours was required to obtain 6500 polycarbonate. 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 each of the first post-polycondensation step and the second post-polycondensation step, the horizontal reactor shown in FIGS. 5, 6 and 7 [“Hitachi Lattice Blade 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, the viscosity average molecular weight is 1
An average residence time of 1 hour was required to obtain 6500 polycarbonate. 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 partially sectional plan view showing an example of a horizontal reaction apparatus F.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is a partially sectional plan view showing an example of a horizontal reaction device G.

FIG. 6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 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 23a, 23b Rotating shaft 25a, 25b Stirring Blade 26 Annular support plate 27 Scraping plate 32a, 32b Rotating ear axis 33a, 33b Rectangular rectangular frame 34a, 34b Grid-type stirring blade

 ──────────────────────────────────────────────────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 (5)

[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;
Two rotating shafts juxtaposed in the container, a plurality of annular supporting plates respectively corresponding to the two rotating shafts and mounted in a direction perpendicular to the axes, and the annular supporting plate A plurality of agitating blades each of which is constituted by a scraping plate attached at a right angle to the support plate at each end, and a corresponding agitator attached to each of the two rotating shafts. The blades are arranged so as to have a phase angle of 90 degrees when viewed from the axial direction, and hold the two rotating shafts so that the tip of one stirring blade passes close to the other rotating shaft. To a horizontal reaction apparatus equipped with a rotation mechanism for rotating while rotating, to further advance the polycondensation reaction, and to obtain a viscosity average molecular weight of 15,000.
A first post-polycondensation step of producing a polycarbonate of ~ 18000, and (3) a polycarbonate container which is horizontally placed and a polycarbonate container which is produced in the first post-polycondensation step. It has two rotating ear shafts arranged side by side, and a grid-type stirring blade connected to a plurality of rod-shaped rectangular frames attached between the rotating ear shafts at both ends of the container. The rotary ear shaft is supplied to a horizontal reactor equipped with a rotating mechanism that rotates while holding the tip of the rod-shaped rectangular frame of one stirring blade so as to pass close to the rotation center of the other stirring blade, and performs polycondensation. Let the reaction proceed further,
A second post-polycondensation step of producing a high molecular weight polycarbonate having a viscosity average molecular weight of 18,000 to 40,000. 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 average viscosity is 4000 to 15
And a second pre-polycondensation step of producing 000 prepolymers. 3. The pre-polycondensation step (1) comprises: (1a) a molten mixture containing a carbonic acid diester or a carbonic acid diester and a transesterification catalyst in a vertical stirring dissolution tank in the substantial absence of oxygen. Dissolving the aromatic dihydroxy compound and the transesterification catalyst or the aromatic dihydroxy compound to prepare a mixed solution containing the carbonic acid diester, the aromatic dihydroxy compound and the transesterification catalyst, and (1b) the dissolving step An aging step of supplying the obtained mixed liquid to a vertical stirring aging tank and subjecting the by-product hydroxy compound to a polycondensation reaction without substantially distilling off the hydroxy compound to form a prepolymer; and (1c) the aging step Is supplied to a vertical stirring reactor equipped with a distillation tower for distilling off the by-produced hydroxy compound, and the polycondensation reaction is further advanced to obtain a viscosity average molecular weight of 300. A first pre-polycondensation step for producing 0 to 5000 prepolymers, and (1d) supplying the prepolymer produced in the first pre-polycondensation step to a vertical stirring reactor equipped with a double helical ribbon stirrer. To further advance the polycondensation reaction, the viscosity average 4000 ~ 150
And a second pre-polycondensation step of forming a prepolymer of No. 00. 4. 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 reactor. ,
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. 5. The method for producing a polycarbonate according to claim 4, wherein the material whose iron component is 20% by weight or less is nickel.