JP2002265586A - Process for producing polycarbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a stable polycarbonate with a controlled molecular weight. SOLUTION: In the process for producing a polycarbonate by subjecting a carbonic diester and a dihydroxy compound to melt polymerization in the presence of an alkali metal and/or alkaline earth metal catalyst, a laser liquid level meter is used for the control of the liquid level of a reaction mixture having a viscosity of 30 Pa.s or higher in a polymerizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is characterized in that, in a polymerization reactor in which a reaction mixture having a high viscosity exists, a liquid level is controlled using a laser liquid level meter in order to obtain a resin having a stable molecular weight. The present invention relates to a method for producing a melt-polymerized polycarbonate resin.

[0002]

2. Description of the Related Art As a method of producing a polycarbonate resin, an interfacial polycondensation method of bisphenol A and phosgene is predominant, but there is a problem in safety by using toxic phosgene, and methylene chloride is used as a solvent. Is also not preferable from the viewpoint of environmental destruction. Therefore, recently, a method for continuously producing a polycarbonate resin having a good hue by connecting a plurality of reaction tanks in series by a transesterification method not using phosgene or methylene chloride has been reviewed. There is also a method using a batch reaction apparatus, but with scale-up, the surface renewability in the high viscosity region in the latter half of the polymerization is reduced and the polymerization time is increased, and the resin is colored because the time required for resin withdrawal is increased. Therefore, it is not preferable. When a polycarbonate resin is produced by continuously polymerizing by a transesterification method, it is usually heated to a temperature of 200 ° C. or higher,
Polycondensation is carried out by distilling off by-products while reducing the pressure in the molten state. In the latter half of the polymerization, the viscosity of the reaction mixture becomes several tens to several thousand P
a · s. A differential pressure type liquid level meter is generally used as an instrument for controlling the liquid level in a reaction tank for stirring and polymerizing such a high-temperature, high-viscosity reaction mixture. Other instruments for controlling the liquid level include a capacitance liquid level meter and an ultrasonic liquid level meter.In the case of a capacitance liquid level meter, a reaction mixture having a high viscosity adheres to a rod. , Because it is difficult to peel off, there are many malfunctions and it is difficult to use,
In the case of an ultrasonic liquid level meter as well, an instrument must be installed inside the tank, and it cannot be used in a polymerization apparatus having a high temperature and a high degree of reduced pressure. Although the differential pressure type liquid level meter can be used even in a high temperature and high viscosity region, the sensitivity is greatly reduced due to the influence of agitation and the flow direction when the liquid moves to the next reaction tank. Due to such a decrease in sensitivity, the liquid level fluctuates, that is, the residence time (reaction time) in the tank fluctuates, so that it is difficult to control the molecular weight of the produced resin. Such a variation in molecular weight is not preferable in terms of the characteristics of the product, and there has been a problem in controlling the liquid level in the reaction tank stably. As a liquid level meter used for a reaction mixture in a high-viscosity region, a γ-ray type liquid level meter is used, but it is expensive, and the area around the γ-ray passing area is a restricted area, so it is widely used. There are many problems, such as the need to secure a space, and further hindrance to maintenance of nearby equipment. Here, in the present specification, the term "reaction mixture" refers to a polycondensation reaction in a step of producing a polycarbonate by subjecting a mixture mainly containing a dihydroxy compound and a carbonic acid diester to a melt polycondensation reaction in the presence of a transesterification catalyst or the like. Means the mixture at the time of starting and ending or at the time of progress.

[0003]

In the case of producing a polycarbonate by a melt polymerization method using a continuous reaction apparatus, an inexpensive and simple method capable of controlling the liquid level in a tank constantly under high temperature and high viscosity conditions is required. Had been.

[0004]

Means for Solving the Problems In view of the above circumstances, the present inventors have made intensive studies and as a result, the following method is used to keep the liquid level in the tank constant and stably control the molecular weight of the polycarbonate. It is intended to provide a manufacturing method.

That is, the present invention provides (1) a method for continuously producing a polycarbonate in which a diester carbonate and a dihydroxy compound are melt-polymerized in the presence of an alkali metal and / or alkaline earth metal catalyst, wherein the viscosity of the reaction mixture is 30 Pa · s. (2) A method for producing a polycarbonate using a laser liquid level meter for controlling the liquid level of a reactor as described above; and (2) using an aromatic dihydroxy compound in the range of 20% to 100% as at least one dihydroxy compound. 1) a method for producing a polycarbonate;
(3) The method for producing a polycarbonate according to the above (1), wherein a dihydroxy compound having an alicyclic structure is used in the range of 20% to 80% as at least one dihydroxy compound;
(4) The method for producing a polycarbonate according to the above (1), wherein the aromatic carbonic acid diester is diphenyl carbonate.

Hereinafter, the present invention will be described in detail. In the present invention, the dihydroxy compound used in the transesterification method is a per se known dihydroxy compound,
An aromatic dihydroxy compound, an aliphatic dihydroxy compound, an alicyclic dihydroxy compound and the like can be mentioned. The dihydroxy compound is appropriately selected or combined depending on the use of the obtained polycarbonate. In the case of polycarbonate for optical use, a combination of an aromatic dihydroxy compound and an aliphatic dihydroxy compound having an alicyclic structure is preferable. In the present invention, the aromatic dihydroxy compound is a compound represented by the following general formula (II).

[0007]

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(In the above formula (II), X is

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Wherein R ₃ and R ₄ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or a phenyl group, and R ₃ and R ₄ may combine to form a ring. R
₁ and R ₂ are a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or halogen, and R ₁ and R ₂ may be the same or different. Further, m and n represent the number of substituents and are integers of 0 to 4. )

As the aromatic dihydroxy compound represented by the general formula (II), for example, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis ( 4-hydroxy-3
-Methylphenyl) propane, 2,2-bis (4-hydroxy-3-t-butylphenyl) propane, 2,2-
Bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 4,4-bis (4-hydroxyphenyl) heptane, 1,1 Bisphenols such as -bis (4-hydroxyphenyl) cyclohexane;
4'-dihydroxydibiphenyl, 3,3 ', 5,5'
Biphenols such as -tetramethyl-4,4'-dihydroxybiphenyl; bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) Ether and bis (4-hydroxyphenyl) ketone. Further, two or more aromatic dihydroxy compounds represented by the formula (II) can be used in combination.

In the present invention, the aliphatic di-containing compound having an alicyclic structure
Examples of the hydroxy compound include tricyclo (5.
2.1.0^2,6) Decane dimethanol, β, β, β ',
β'-tetramethyl-2,4,8,10-tetraoxa
Spiro [5,5] undecane-3,9-diethanol
(Spiroglycol), pentacyclo [9.2.1.1]
^3,9. 0^2,10. 0^4,8] Pentadecane dimethanol, pen
Tacyclo [9.2.1.1^4,7. 0^2,10. 0^3,8] Penta
Decane dimethanol, 2,6-decalin dimethanol
Or 1,4-cyclohexanedimethanol, etc.
Can be Among these, in particular, tricyclo (5.2.
1.0^2,6) Decandimethanol (hereinafter abbreviated as TCDDM)
Is preferred. Aliphatic dihydro having the above alicyclic structure
Xy compounds contain carbonyl groups contained as impurities
The amount is 1.0 mg / g or less in terms of KOH, preferably 0.1 mg / g.
5 mg / g, more preferably 0.1 mg / g or less
Is used. In addition, chlorine and all metal ions
About 1 ppm or less
No.

In the present invention, the carbonic acid diester is a known carbonic acid diester used in the transesterification method, and examples thereof include an aromatic carbonic acid diester and an aliphatic carbonic acid diester. Considering the physical properties of the obtained polycarbonate, Aromatic carbonic acid diesters are preferred. In the present invention, the aromatic carbonic diester is represented by the following general formula (II)
It is a compound represented by I).

[0013]

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(Wherein Ar is a monovalent aromatic group;
May be the same or different. )

The aromatic carbonic diester represented by the general formula (III) is, for example, diphenyl carbonate, ditolyl carbonate, dixylyl carbonate, bispropylphenyl carbonate, bisoctylphenyl carbonate, bisnonylphenyl carbonate, bismethoxyphenyl. Examples thereof include substituted diphenyl carbonates such as carbonate and bisethoxyphenyl carbonate. Particularly preferred is diphenyl carbonate, and the chlorine content is preferably 1 ppm or less. The aromatic carbonic acid diester is preferably used in an amount of 0.97 to 1.2 mol, particularly preferably 0.99 to 1.1, per 1 mol of the total of the dihydroxy compound.
It is an amount of 0 mol.

In the present invention, an alkali metal compound or an alkaline earth metal compound is used as a catalyst. Such compounds include organic acid salts such as alkali metals and alkaline earth metals, inorganic salts, oxides, hydroxides,
A hydride or an alkoxide is preferably used,
These compounds can be used alone or in combination.

Examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium hydrogen carbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium carbonate, sodium acetate, potassium acetate, and cesium acetate. , Lithium acetate, sodium stearate, potassium stearate, cesium stearate, lithium stearate, sodium borohydride, sodium borohydride, sodium benzoate, potassium benzoate, cesium benzoate, lithium benzoate, hydrogen hydrogen phosphate 2 Sodium, hydrogen phosphate 2
Potassium, dilithium hydrogen phosphate, sodium diphosphate, potassium diphosphate, lithium diphosphate, disodium phenyl phosphate, disodium salt of bisphenol A, 2 potassium salt, 2 cesium salt, 2 lithium salt, phenol Sodium salt, potassium salt, cesium salt, lithium salt and the like can be mentioned.

Further, as the alkaline earth metal compound,
For example, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium bicarbonate, calcium bicarbonate, strontium bicarbonate,
Examples include barium hydrogen carbonate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, magnesium stearate, calcium stearate, calcium benzoate, magnesium phenyl phosphate and the like.

These catalysts are used in an amount of 10 ^-9 to 10 ^-3 mol, preferably 1 to ³ mol, per mol of the total of the dihydroxy compound.
It is used in an amount of ^0-7 to ^10-5 mol.

In the process for producing a transesterification polycarbonate of the present invention, particularly when an aromatic-aliphatic copolymer polycarbonate is produced, the structural unit (A) derived from the aromatic dihydroxy compound used as a raw material and the aliphatic dihydroxy compound ( Molar ratio (A) of the structural unit (B) derived from an aliphatic dihydroxy compound preferably having an alicyclic structure)
/ (B) is preferably from 100/0 to 20/80, and more preferably from 70/20 to 20/80. The reason for this is that the molar ratio of structural units (A) /
If (B) is lower than 20/80, the heat resistance becomes poor, and the addition of an aliphatic dihydroxy compound (preferably, an aliphatic dihydroxy compound having an alicyclic structure) results in a good Abbe number and optical properties. This is because the material has preferable physical properties. Their mixing ratio can be changed depending on the intended use of the resin to be produced.

As the catalyst deactivator, for example, phosphoric acid,
Phosphorous acid, hypophosphorous acid, phenylphosphoric acid, phenylphosphine, phenylphosphinic acid, phenylphosphonic acid,
Diphenyl phosphate, diphenyl phosphite, diphenyl phosphine, diphenyl phosphine oxide,
Diphenyl phosphinic acid, monomethyl acid phosphate, monomethyl acid phosphite, dimethyl acid phosphate, dimethyl acid phosphite, monobutyl acid phosphate, monobutyl acid phosphite, dibutyl acid phosphate, dibutyl acid phosphite, monostearyl acid phosphate, distearyl acid Phosphorus-containing acidic compounds such as phosphate, p-toluenesulfonic acid, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, p-toluenesulfonic acid
-Propyl toluenesulfonate, butyl p-toluenesulfonate, pentyl p-toluenesulfonate, hexyl p-toluenesulfonate, octyl p-toluenesulfonate, phenyl p-toluenesulfonate, phenethyl p-toluenesulfonate, p- Aromatic sulfonic acid compounds such as naphthyl toluenesulfonate are exemplified.

The amount of the phosphorus-containing acidic compound or aromatic sulfonic acid compound to be added is 1/5 to 20 times the neutralization equivalent to the alkali metal and / or alkaline earth metal catalyst.
The amount is preferably 1/2 to 10 times the amount. If the amount is less than this, the desired effect cannot be obtained. If the amount is excessive, the heat resistance and mechanical properties decrease, which is not appropriate.

Further, aromatic sulfonate phosphonium salts can also be preferably used. For example, tetrabutylphosphonium benzenesulfonate, tetrabutylphosphonium p-toluenesulfonate, tetrabutylphosphonium butylbenzenesulfonate, octylbenzene Examples include tetrabutylphosphonium sulfonic acid salt, tetrabutylphosphonium dodecylbenzenesulfonic acid salt, tetramethylphosphonium dodecylbenzenesulfonic acid salt, tetraethylphosphonium dodecylbenzenesulfonic acid salt, and tetrahexylphosphonium dodecylbenzenesulfonic acid salt.

The amount of the phosphonium aromatic sulfonic acid salt to be added is 1 to 30 with respect to the melt-polymerized polycarbonate.
The content is 0 ppm, preferably 10 to 100 ppm. If the content is less than this, the desired effect cannot be obtained. If the content is excessive, the heat resistance and mechanical properties are deteriorated, which is not appropriate.

In the present invention, it is desirable to add various known additives to the melt-polymerized polycarbonate together with the above-mentioned specific compound as long as the physical properties are not impaired.

Examples of the antioxidant include triphenyl phosphite, tris (4-methylphenyl) phosphite, tris (4-t-butylphenyl) phosphite, tris (monononylphenyl) phosphite and tris (2 -Methyl-4-ethylphenyl) phosphite,
Tris (2-methyl-4-t-butylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, tris (2,6-di-t-butylphenyl) phosphite, tris ( 2,4-di-t-butyl-
5-methylphenyl) phosphite, tris (monodinonylphenyl) phosphite, bis (monononylphenyl) pentaerythritol-di-phosphite, bis (2,4-di-t-butylphenyl) pentaerythritol-di- Phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-di-
Phosphite, bis (2,4,6-tri-t-butylphenyl) pentaerythritol-di-phosphite, bis (2,4-di-t-butyl-5-methylphenyl) pentaerythritol-di-phosphite 2,2-methylenebis (4,6-dimethylphenyl) octyl phosphite, 2,2-methylenebis (4-t-butyl-6-
Methylphenyl) octyl phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, 2,2-methylenebis (4,6-dimethylphenyl) hexyl phosphite, 2,2-methylenebis Phosphite compounds such as (4,6-di-t-butylphenyl) hexyl phosphite and 2,2-methylenebis (4,6-di-t-butylphenyl) stearyl phosphite, pentaerythrityl-tetrakis [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5
-Di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl)
Benzene, triethylene glycol-bis [3- (3-
t-butyl-5-methyl-4-hydroxyphenyl) propionate], 3,9-bis {2- [3- (3-t-
Butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl} -2,4.
8,10-tetraoxaspiro [5,5] undecane,
1,1,3-tris [2-methyl-4- (3,5-di-
Hindered phenol compounds such as [t-butyl-4-hydroxyphenylpropionyloxy) -5-t-butylphenyl] butane. These may be used alone or in combination of two or more.

The addition amount of these antioxidants is 0.005 to 100 parts by weight of the melt-polymerized polycarbonate.
0.1 part by weight, preferably 0.01 to 0.08 part by weight, more preferably 0.01 to 0.05 part by weight. If less than this, the desired effect cannot be obtained. However, the mechanical properties are deteriorated and are not suitable.

As the ultraviolet absorber, for example, 2- (5
-Methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5-di-t- Butyl-2-hydroxyphenyl) benzotriazole, 2- (3-t-butyl-
5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-butyl-2)
-Hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-amyl-2-hydroxyphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole ,
2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6-[(2H-benzotriazol-2-yl) phenol]], 2- (4,6-diphenyl-1 , 3,5-Triazin-2-yl) -5-[(hexyl) oxy] -phenol, 2,4-dihydroxobenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4-methoxy −
2'-carboxybenzophenone, dimethyl succinate-
1- (2-hydroxyethyl) -4-hydroxy-2,
2,6,6, -tetramethylpiperidine polycondensate, bis (1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,
6, -tetramethyl-4-piperidyl) sebacate and the like. These may be used alone or in combination of two or more.

As the release agent, those generally used may be used. For example, natural and synthetic paraffins, silicone oils, polyethylene waxes, beeswax, monoglyceride stearate, monoglyceride palmitate, pentaerythritol tetrastearate And the like, and these may be used alone or in combination of two or more.

Other flame retardants, antistatic agents, pigments, dyes and the like can be used alone or in combination as required. There are no particular restrictions on the timing of addition, the method of addition, and the form of addition, but it is preferable to add the catalyst simultaneously with or after the addition of the catalyst deactivator.

The timing of adding these catalyst deactivators, additives and the like to the transesterification polycarbonate is not limited. For example, a method in which the resin is added after the polycondensation reaction is completed while the resin is in a molten state, or a pellet once cooled. And then re-melting and mixing. Also, there is no limitation on the addition method, for example, a method of directly charging and mixing the polymerization vessel,
A method of kneading using a single-screw or twin-screw extruder or the like can be used. Examples of the form of addition include a method of adding the compound as it is without diluting, a method of adding the compound after dilution with a soluble solvent, and a method of adding the compound in the form of a master batch, but are not particularly limited.

After deactivation of the catalyst, a step of degassing and removing low boiling compounds in the polymer at a temperature of 200 to 310 ° C. under reduced pressure may be provided. For this purpose, paddle blades, lattice blades, spectacle blades, etc. A horizontal stirring device having a stirring blade having excellent surface renewability, a multi-vent twin screw extruder, or a thin film evaporator is preferably used.

When a multi-vent twin screw extruder is used in the method of adding a catalyst deactivator or other additives in the present invention, the temperature of the molten resin is preferably from 230 ° C to 33 ° C.
It is desirable to control at 0 ° C., more preferably within the range of 240 ° C. to 310 ° C. When the temperature is lower than this temperature, the additive is not dispersed, and the effect is not exhibited. On the other hand, if it is higher than this, thermal deterioration is accelerated and causes coloring.

When the resin of the present invention is used for optical applications, it is desirable to manufacture the resin in an environment such as a clean room or a clean booth in order to prevent foreign substances from being mixed into the product. In that case, it is effective to install a raw material filter, mount a cooling water filter used for pelletizing, or mount a polymer filter at the outlet of the extruder to prevent foreign matter from entering.

The weight average molecular weight of the polycarbonate obtained by the method of the present invention is in the range of 10,000 to 200,000, preferably in the range of 30,000 to 120,000.

The transesterification according to the present invention can be carried out by a known melt polycondensation method. That is, melt polycondensation is carried out from the dihydroxy compound and the diaryl compound in the presence of a catalyst while removing by-products by a transesterification reaction under normal pressure or reduced pressure while heating in the presence of a catalyst. The reaction is carried out in two or more stages,
The polymerization vessel used for the reaction is not particularly limited. For example, a stirred tank reactor, a thin film evaporation reactor, a biaxial horizontal stirring reactor,
Using a wet wall type reactor, a surface renewal type twin-screw kneading reactor, etc.
A polymerization vessel using these alone or in combination is used. It is also a preferable method to use an extruder or the like in combination with a polymerization device as an apparatus for adding a stabilizer, a deactivator or the like as an additive while the polycarbonate is in a molten state after the polymerization.

[0037]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

(1) Weight average molecular weight (Mw) GPC (Shodex GPC system 11)
And the molecular weight in terms of polystyrene (weight average molecular weight: M
w). Chloroform was used as a developing solvent. (2) Viscosity It was measured at each polymerization tank temperature using a B8L type viscometer (manufactured by Tokimec Co., Ltd.).

Example 1 A first vertical stirring polymerization tank (reaction conditions: 1.33 × 10 ⁴ Pa, 205) under a nitrogen gas atmosphere substantially free of oxygen.
The raw material molar ratio (diphenyl carbonate / (BPZ + TCDDM)) at 1.0 ° C. and a stirring speed of 160 rpm is 1.01.
Sodium hydroxide is used as a catalyst in BPZ
(Mol), and 6 μmol of the first polymerization at a flow rate of 54.3 kg / h of a molten mixture prepared by mixing and preparing diphenyl carbonate and BPZ at a fixed ratio (diphenyl carbonate / BPZ (molar ratio) = 2.02). The TCDDM is continuously supplied to the tank at the same time, and the TCDDM is continuously supplied at a flow rate of 15.2 kg / h. The liquid level was kept constant while controlling the valve opening by interlocking with a control valve provided in the reaction mixture discharge line of No. 1. The polymerization liquid (prepolymer) discharged from the bottom of the tank is continuously supplied to the second, third, and fourth vertical polymerization tanks and the fifth horizontal polymerization tank (glass wing polymerization machine (trade name) manufactured by Hitachi, Ltd.) ). The average residence time was controlled to 60 minutes for each of the second to fourth vertical polymerization tanks, and 90 minutes for the fifth horizontal polymerization tank, and the phenol by-produced was also distilled off at the same time. . The polymerization conditions in each of the second to fifth polymerization tanks are respectively set in the second polymerization tank (220 ° C., 2.00 × 1).
0 ³ Pa, stirring speed 160 rpm), the third polymerization tank (23
0 ° C., 40 Pa, stirring speed 60 rpm), a fourth polymerization tank (240 ° C., 40 Pa, stirring speed 20 rpm), and a fifth horizontal polymerization tank (245 ° C., 40 Pa, stirring speed 5 rpm). As for the liquid level control after the second polymerization tank, a differential pressure type liquid level meter was used for the second polymerization tank similarly to the first polymerization tank, and a laser type liquid level meter was used for the third to fifth polymerization tanks. LM4 manufactured by Yokogawa Electric Corporation
Using the sample No. 00, an infrared laser was passed through the sight glass of the reaction tank from the outside of the apparatus and reflected on the cloudy liquid surface to measure the liquid level of the reaction mixture. The polymer discharged from the fifth horizontal polymerization tank is continuously melted to form a three-vent type 2
The extruder is introduced into a screw extruder (46 mm twin screw extruder manufactured by Kobe Steel Co., Ltd.), and an additive to be described later is added to the resin in the form of a master batch in the form of a master batch just before the vent port closest to the resin supply port.
t. %, Supplied by a side feed compactor, cooled with water, and pelletized.

Under the above-mentioned apparatus and operating conditions, continuous operation was performed for 50 hours, and after 40 hours, the produced resin was sampled at the outlet of the extruder every hour, and the weight average molecular weight was measured. Table 1 shows the evaluation results of the samples. The reaction mixture in each reaction tank was sampled every three hours, and the melt viscosity at each reaction temperature was measured.

Comparative Example 1 Using the same apparatus as in Example 1, the liquid level of the third and fourth polymerization tanks was controlled by a differential pressure level gauge, and the liquid level of the fifth polymerization tank was visually controlled. The procedure was performed in the same manner as in Example 1 except that the test was performed. Table 1 shows the evaluation results.

[0042]

[Table 1]

[0043]

According to the present invention, it is possible to stably produce a polycarbonate whose molecular weight is controlled while keeping the liquid level in the polymerization tank constant.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Sasaki 2-4-1, Hinagahigashi, Yokkaichi City, Mie Prefecture Inside the Yokkaichi Plant of Mitsubishi Gas Chemical Co., Ltd. (72) Inventor Toshihiro Nomura 2-4-1, Hinagahigashi, Yokkaichi-shi, Mie Prefecture F-term (reference) 4J029 AA03 AB04 AC02 AD01 BB09A BB09A BB12A BB13A BD09A BD10 BE05A BF14A BG08X BH02 DB07 DB13 HC05A JA091 JA121 JA253 JA261 JB171 JC363 JC453 JC583 JF021 JF031 JF041 JF051 KB03 LB09

Claims (5)

[Claims] 1. A method for producing a polycarbonate in which a carbonate diester and a dihydroxy compound are melt-polymerized in the presence of an alkali metal and / or alkaline earth metal catalyst, a reaction mixture having a viscosity of 30 Pa · s or more in a polymerization apparatus. A method for producing polycarbonate, comprising using a laser liquid level meter for liquid level control. 2. The method for producing a polycarbonate according to claim 1, wherein an aromatic dihydroxy compound is used in the range of 20% to 100% as at least one dihydroxy compound. 3. A dihydroxy compound having an alicyclic structure as at least one of the dihydroxy compounds in an amount of 20% or less.
3. The method for producing a polycarbonate according to claim 1, wherein the polycarbonate is used in a range of 80%. 4. The method for producing a polycarbonate according to claim 1, wherein the aromatic carbonic acid diester is diphenyl carbonate. 5. An aliphatic dihydroxy compound having an alicyclic structure, which is represented by the following formula (I):
2.1.0 ^2,6 ) 20% to 80% of decandimethanol
The method for producing a polycarbonate according to any one of claims 1 to 4, wherein the method is used in the range of: Embedded image