JP2724217B2 - Method for producing polycarbonate oligomer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polycarbonate oligomer.

[Prior art] Polycarbonate low molecular weight products, especially dimerized monohydric phenols used as molecular weight regulators, cause clogging of vent lines in extruders and adhesion of molds during molding to deteriorate the quality. Has become the causative substance.

The phosgenation reaction of alkali hydroxide of dihydric phenol with phosgene generates a large amount of heat of reaction, and unless the heat is removed efficiently, the system will be in a boiling state and the reactor will be in a state where phosgene is not reacted. The phenomenon of blowing through the exit occurs. Moreover, according to the description of many patent specifications, the decomposition reaction of phosgene increases unless the phosgenation reaction is controlled at a low temperature.

It is known that the position or timing of supplying the molecular weight regulator to the process is at the time of a phosgenation reaction or at the time of a polycondensation reaction using an oligomer as a starting material. For example, Japanese Patent Application Laid-Open No. 62-89723 describes that a molecular weight modifier is added before or immediately after the introduction of phosgene, but there is no further description about the timing of addition. If the molecular weight regulator is added before the phosgenation reaction is completed, a dimer of monohydric phenol is generated, which leads to a deterioration in quality when producing polycarbonate. In addition, JP
JP-A-150496 also describes that a molecular weight modifier is added to a reactor in a feedstock or before a catalyst is added, but there is no specific description of the timing of addition.

JP-A-63-314237 points out that the presence of low-molecular-weight oligomers poses a problem during molding, and the production method described in the publication discloses the use of bischloroformate which has already completed the phosgenation step. It is characterized by reacting with a phenol. However, in this method, in the oligomer produced on the way, the number of hydroxyl groups increases due to the decrease in pH, so that low molecular weight substances increase during the reaction for increasing the molecular weight, and the same problem as described above remains.

On the other hand, if an oligomer is produced without adding a monohydric phenol, and then a monohydric phenol is added during a condensation reaction for increasing the molecular weight using the oligomer, the end-blocking rate of the monohydric phenol is reduced, and the hydroxyl group is reduced. It is known that the terminal polymer tends to remain, so that the washing property in the polymer washing step is reduced, and the heat resistance of the product is poor due to the remaining impurities.

Further, there are many patent specifications which disclose a method of controlling the temperature in order to suppress a decomposition reaction or a side reaction in a phosgenation reaction or an oligomerization reaction. For example, in JP-A-55-52321, the phosgenation reaction is carried out at a temperature of 10 ° C. or less.
In JP-A-58-108226, 2-30 ° C., JP-A-62-1673
No. 21, the first reactor is 10 to 25 ° C., the second reactor is 10 to 25 ° C.
Many attempts have been made to maintain the temperature at a low temperature, such as at 30 ° C. However, the calorific value of the phosgenation reaction and the oligomerization reaction is about 25 kc / mol of NaCl.
Since it is very large at al / mol, equipment such as pre-cooling the raw material and circulating a large amount of the reaction solution inside and outside of the reactor was required, and the apparatus and process were very complicated.

[Problems to be Solved by the Invention] Accordingly, an object of the present invention is to suppress the decomposition reaction of phosgene and reduce the production of diphenyl carbonates, which are dimers of monohydric phenols, particularly low molecular weight compounds. In addition, by producing oligomers having a reduced number of hydroxyl terminals, the amount of low molecular weight products produced after polymerization is reduced, the hue of molded products is improved, and the amount of adhered molds in multilayer blow molding is reduced. It is to provide a method that can do.

[Means for Solving the Problems] The object of the present invention is to provide, according to the present invention, a method in which an alkali aqueous solution containing an alkali metal salt of a polyhydric phenol is reacted with phosgene in the presence of an inert organic solvent to obtain a number average molecular weight of 300. In a method for continuously producing a polycarbonate oligomer of up to 10,000, (a) in a tubular reactor in which the system is pressurized to a saturated vapor pressure or higher of an inert organic solvent, the hydroxyl group of the polyhydric phenol in the alkaline aqueous solution is Gram equivalent ratio of alkali metal atom is
The alkaline aqueous solution and phosgene are supplied to perform the phosgenation reaction so that the molar ratio of the polyhydric phenol to phosgene is 0.55 to 0.95, and the phosgenation reaction is carried out. A monohydric phenol is supplied into the reactor or at the outlet of the tubular reactor to partially terminate the chloroformate group-terminated compound produced in the step (a), and then (c) the next reactor The reaction can be achieved by a method for producing a polycarbonate oligomer, wherein the oligomerization reaction is carried out until the pH after the reaction reaches 5 to 10.

In the present invention, a polyhydric phenol, that is, a dihydric or trihydric or higher phenol is used as a starting material monomer for producing a polycarbonate oligomer. There are various bisphenols as dihydric phenols.
-Bis (4'-hydroxyphenyl) propane (hereinafter, referred to as
Bisphenol A) is preferred. Further, a compound in which part or all of bisphenol A is substituted with another dihydric phenol can also be used. Examples of the dihydric phenol other than bisphenol A include, for example, hydroquinone;
4,4'-dihydroxydiphenyl; bis (4-hydroxyphenyl) alkane; bis (4-hydroxyphenyl) cyclocarban; bis (4-hydroxyphenyl)
Bis (4-hydroxyphenyl) sulfoxide; bis (4-hydroxyphenyl) sulfone; bis (4-hydroxyphenyl) ketone; bis (4-hydroxyphenyl) ether; 2,2-bis (3 ', 5'- Dimethyl-4'-hydroxyphenyl) propane or 2,2
Halogenated bisphenols such as -bis (3 ', 5'-dibromo-4'-hydroxyphenyl) propane.

Examples of trihydric or higher polyhydric phenol include phloroglucin; phloroglucid; 4,6-dimethyl-2,4,6-tri (4'-hydroxyphenyl) -heptene-2; 4,6-
Dimethyl-2,4,6-tri (4'-hydroxyphenyl)
Heptane; 1,3,5-tri (4'-hydroxyphenyl)-
Benzene; 1,1,1-tri- (4'-hydroxyphenyl)
Ethane; 2,2-bis (4,4-bis (4'-hydroxyphenyl) cyclohexyl) -propane; 2,6-bis (2'-
Hydroxy-3'-methyl-benzyl) -4-methylphenyl; 2,6-bis (2'-hydroxy-3'-isopropyl-benzyl) -isopropylphenyl; bis (2-
Hydroxy-3-methyl-benzyl-4-methylphenyl) methane; tetra (4-hydroxyphenyl) methane; tri- (hydroxyphenyl) phenylmethane; triphenol; bis (2,4-dihydroxyphenyl) ketone; 1,4 -Bis (4 ', 4 "-dihydroxytriphenyl-methyl) benzene, etc. Each of the compounds exemplified above as polyhydric phenols may have a halogen substituent. Can also be used.

The molecular weight regulators which can be used in the process of the present invention include monohydric phenols, such as phenols, alkylphenols having alkyl substituents having 1 to 10 carbon atoms, especially p-cresol, p-cumylphenol, and most Preferably, pt-butylphenol can be mentioned. The monohydric phenols may further have a halogen substituent.

Examples of the alkali that forms an alkali metal salt of a polyhydric phenol include alkali hydroxides, particularly strongly basic hydroxides,
For example, sodium hydroxide and potassium hydroxide can be mentioned.

As the inert organic solvent, any compound that dissolves polycarbonate can be used. Examples thereof include halogenated hydrocarbons such as methylene chloride, tetrachloroethane, 1,2-dichloroethylene, chloroform, trichloroethane, dichloroethane, and chlorobenzene. be able to.

The method of the present invention comprises a three-stage method of (i) a phosgenation reaction, (ii) a partial termination reaction of a chloroformate group, and (iii) an oligomerization reaction. Up to 10,000 polycarbonate oligomers can be produced. In the step (a), a phosgenation reaction is carried out by using a tubular reactor in the presence of an inert organic solvent with a polyhydric, ie, dihydric or trivalent, alkali hydroxide of phenol and phosgene. . At this time, each raw material is introduced at the following supply ratio. That is, the equivalent ratio of the alkali metal atom to the hydroxyl group of the polyhydric phenol in the aqueous alkali solution is set to 0.9 to 1.5, preferably 0.95 to 1.2. If it is less than 0.9, phenols are precipitated, causing troubles in operation, and if it exceeds 1.5, the decomposition reaction of phosgene increases, which is not preferable.

The molar ratio of polyhydric phenol to phosgene is between 0.55 and 0.5.
95, preferably a ratio of 0.6 to 0.75. If it is less than 0.55, it becomes difficult to recover the oligomer due to its high molecular weight,
If it exceeds 0.95, the decomposition reaction of phosgene increases, which is not preferable.

Further, the amount of the inert organic solvent is preferably set to 0.4 to 1.5 in volume ratio with respect to the alkali aqueous solution of the polyhydric phenol.
In the present specification, the phosgenation reaction means a reaction for converting a terminal hydroxyl group of phenol into a chloroformate.

Since the phosgenation reaction proceeds very quickly, it is completed within 10 seconds in a turbulent flow field, depending on the flow state in the pipe, when it is performed in a tubular reactor, and in 20 to 30 seconds even in the case of laminar flow. Terminate (complete consumption of phosgene). Therefore, the end time of the phosgenation reaction can be determined by the flow state and the residence time in the tube.

Since the phosgenation reaction is very fast and generates a large amount of reaction heat, it becomes more difficult to remove the heat as the reaction scale becomes larger. As described in the above-mentioned conventional patent specifications, in order to control the temperature to 10 to 20 ° C., it is necessary to take measures such as pre-cooling the raw material and using a very low-temperature refrigerant. It has been. However, according to the findings of the present inventors, if the pressure in the system is increased to a value higher than the saturated vapor pressure of the inert organic solvent at the system temperature to suppress the boiling of the inert organic solvent and the generated oligomer, the cooling simply proceeds. It was found that the phosgene decomposition reaction can be sufficiently suppressed only by cooling the jacket with water. For example, depending on the scale of the reaction, if the temperature after the end of the phosgenation reaction is 50 to 60 ° C., the phosgene decomposition rate is 30 ° C. by setting the internal pressure to ² to 3 kg / cm ² G. Can be about the same.

When a metal is used as the material of the phosgenation reactor, a high temperature causes a strong corrosive environment in the system, and a side reaction easily occurs using the eluted metal as a catalyst, so that Teflon lining, glass lining, It is preferable to use carbon, ceramic or the like.

In the step (b), the monohydric phenol as a molecular weight regulator supplied after completion of the phosgenation reaction is converted into an organic solvent solution or an aqueous alkali hydroxide solution in the tubular reactor or at the outlet of the tubular reactor (for example, (Reactor installed) to react. The supply amount is set according to the target molecular weight of the polymer.

In the oligomerization reaction of the next step (c), a tertiary amine such as a trialkylamine (preferably triethylamine) or a quaternary ammonium salt can be used as a catalyst. If a catalyst such as a tertiary amine is added before the end of the phosgenation reaction, a by-product with phosgene is generated,
It is not preferable because the quality is deteriorated. By adding a tertiary amine or quaternary ammonium salt as a catalyst, adding an alkali hydroxide, or adding an alkaline aqueous solution of a phenol, the pH at the reactor outlet is adjusted to 5 or less.
By controlling to -10, preferably 7-9, hydroxyl-terminated oligomers can be reduced. If the pH is less than 5, the number of hydroxyl terminal ends is extremely increased, and if the pH exceeds 10, the separation from the aqueous layer is deteriorated, and it becomes difficult to recover the solution by standing separation. The reaction temperature is preferably cooled to 20 to 30 ° C. from the viewpoint of suppressing the reaction of decomposing the chloroformate group of the oligomer.

Examples of the reactor used in the step (c) include a shell-and-tube heat exchanger having excellent cooling efficiency, and a stirred reactor having a jacket and an internal cooling pipe.

As the molecular weight after the completion of the oligomerization reaction, the number average molecular weight measured by an osmotic pressure method is 300 to 10,000, preferably 60.
It is preferably from 0 to 5000 in view of the aqueous phase separation at the time of oligomer recovery or the operability in increasing the molecular weight.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples, but these do not limit the scope of the present invention.

Example 1 A first tubular reactor having an inner diameter of 6 mm and a length of 12 m was immersed in a cooling bath at 30 ° C., and the outlet was provided with a jacket having an inner diameter of 1/2 inch and a length of 2 mm.
A polycarbonate oligomer was produced using a process in which a 0 m double tube type second tube reactor was connected, and the outlet was connected to a 30 l tank reactor.

First, 43.5 l / hr of an aqueous solution (Na / OH gram equivalent ratio = 1.04) in which bisphenol A was dissolved to a concentration of 14.0 wt% in a sodium hydroxide aqueous solution having a concentration of 6.0 wt%, and 18.5 l / hr of methylene chloride as a solvent. The mixture was supplied to the first tubular reactor at a flow rate of hr, and phosgene was blown into the reactor at a flow rate of 3.8 kg / hr (the molar ratio of bisphenol A / phosgene = 0.75). The residence time of the reaction solution at this time was 20 seconds.

The second tubular reactor was supplied with a solution of methylene chloride in which pt-butylphenol was dissolved to a concentration of 4% by weight at 3.3 l / hr.
The solution was supplied to a tank reactor having an internal volume of 30 l to react with 0.32 l / hr of a 6 wt% aqueous solution and 3 l / hr of a 6 wt% aqueous sodium hydroxide solution.

At this time, the outlet of the second tubular reactor was pressurized to 1.5 kg / cm ² G, and the pressure at the outlet of the first tubular reactor was 2.0 kg / cm ² G. The outlet temperature of the first tubular reactor was 48 ° C, and the outlet temperature of the second tubular reactor was 27 ° C. The Na ₂ CO ₃ concentration in the aqueous phase of the reaction solution at the outlet of the tank reactor was 0.05 mol / l, and the phosgene decomposition rate was calculated to be 5.6 mol%.

The overflowed reaction solution is separated in a stationary separation tank,
The methylene chloride phase was used as a starting oligomer. The oligomer had a number average molecular weight (Mn) of 920 and a chloroformate group concentration of 0.7 N. Further, the hydroxyl group terminal fraction measured by NMR was 6.5 mol%.

Next, a condensation reaction was carried out using the above-mentioned oligomer by the following method to obtain a polycarbonate. Oligomers
20 l / hr, an aqueous solution of bisphenol A dissolved in sodium hydroxide at a concentration of 6 wt% to a concentration of 14.0 wt%, 10 l / hr,
12.5 l / hr of methylene chloride as a solvent, 0.8 l / hr of a 25% by weight aqueous solution of sodium hydroxide, and 1 part of triethylamine as a catalyst
A 0.1% by weight aqueous solution of 0.17 l / hr is supplied to a 0.3 l pipeline homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), prepolymerized by high-speed stirring at 3000 rpm, and a 50-liter column reaction having three paddle blades. Then, the reaction was completed.

The polymerization liquid was allowed to stand and separated, and the obtained organic layer was purified by washing with an alkali, washing with an acid, and washing with water. After concentrating this polymer solution by heating flash operation and pulverizing with a kneader,
The obtained flake was dried and granulated.

The viscosity average molecular weight (Mv) of the obtained polymer is 24200,
The molecular weight distribution (Mw / Mn) is 2.12 and the pt-
When the dimer of butylphenol (di- (pt-butylphenol) carbonate) was measured, it was 10 ppm by weight.
It was below. Y1 of the plate on which the pellets after granulation were formed was 2.5. Furthermore, using a MAC-5SS-S type hollow molding machine of Mac International Associates, a multi-layer bottle with 0.5 liter of polypropylene was molded, and the time until roughening of the molded product due to adhesion of a low molecular weight mold was measured. The result was 36 hours. Table 1 shows the operation time and the evaluation results.

Comparative Example 1 A polycarbonate oligomer was produced by repeating the operation procedure described in Example 1 to obtain polycarbonate pellets, except that the supply position of 4 wt% methylene chloride of pt-butylphenol was changed to the first tube type. A reactor was used.

The viscosity average molecular weight of the obtained polymer was 24,400, and the measurement of the pt-butylphenol dimer in the flakes showed 310 ppm by weight. Y1 after plate formation was 3.0. It was 4 hours as a result of measuring the time until the roughening of the molded article occurred in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 A polycarbonate oligomer was produced by repeating the operation procedure described in Example 1, except that the cooling and pressurizing of the second tubular reactor were not performed, and the reactor was operated in a normal pressure system.

At this time, the pressure at the outlet of the first tube type reactor was 0.4 kg / cm ² G,
The temperature was boiling at 48 ° C. Further, the outlet temperature of the second tubular reactor was 40 ° C., which was also a boiling state. Unreacted phosgene was detected from the outlet of the bed reactor, and the concentration of Na ₂ CO ₃ in the aqueous phase of the reaction solution was as high as 0.08 mol / l, and the decomposition rate of phosgene was 9.0 mol%.

The viscosity average molecular weight of the polycarbonate prepared by performing the same treatment as described in Example 1 was 22,800, and the pt-butylphenol dimer in the flake was 90 ppm. In addition, Y1 after plate formation was 2.9, and the time until occurrence of rough surface of the molded product was 14 hours. Other evaluation results are as shown in Table 1.

Example 2 A polycarbonate oligomer and a polycarbonate were produced by repeating the operation procedure described in Example 1, except that the concentration of sodium hydroxide was 5.5% by weight, and bisphenol A was dissolved at a concentration of 14.0% by weight (Na / OH). 52.2 l / hr of aqueous solution (gram equivalent ratio = 0.95) (bisphenol
A / phosgene molar ratio = 0.90). Table 1 shows the operating conditions and the evaluation results.

Example 3 A polycarbonate oligomer and a polycarbonate were produced by repeating the operation procedure described in Example 1, except that the concentration of sodium hydroxide was 7.2% by weight and bisphenol A was dissolved at a concentration of 12.9% by weight (Na / OH). 34.8l / hr (bisphenol)
A / phosgene molar ratio = 0.60). Table 1 shows the operating conditions and the evaluation results.

Example 4 A polycarbonate oligomer and a polycarbonate were produced by repeating the operating procedure described in Example 1, except that the first tubular reactor and the second tubular reactor described in Example 1 were used as tubular reactors. 8 mm inner diameter, 3 length integrated with reactor
Using a 0 m reactor, this was immersed in a cooling bath at 30 ° C., each raw material was supplied under the same conditions as in Example 1, and pt-butylphenol was supplied from a nozzle attached at a position 15 m from the inlet, Further, only 6% by weight of sodium hydroxide was supplied to the oligomerization reactor at a rate of 5 l / hr. Table 1 shows the operating conditions and the evaluation results.

Comparative Example 3 The operating procedure described in Example 1 was repeated, except that the concentration of sodium hydroxide was 4.6% by weight, and bisphenol A was dissolved at a concentration of 14.0% by heating to 35 ° C. (Na / OH).
When the aqueous solution (gram equivalent ratio = 0.80) was supplied at 43.5 l / hr and phosgene was supplied at the same flow rate (bisphenol A / phosgene molar ratio = 0.75), bisphenol A was precipitated in the tubular reactor, Operation became impossible.

Comparative Example 4 The operating procedure described in Example 1 was repeated except that the concentration of sodium hydroxide was 7.2% by weight and bisphenol A was dissolved at a concentration of 11.3% by weight (Na / OH gram equivalent ratio =
The resulting aqueous solution was supplied at 32.3 l / hr (molar ratio of bisphenol A / phosgene = 0.45), and nothing was supplied to the oligomerization reactor. Under these conditions, the polymer was not evaluated because the decomposition rate of phosgene was as high as 15.5 mol% and the hydroxyl group end fraction of the oligomer was as high as 27.5 mol%.

Comparative Example 5 The operating procedure described in Example 1 was repeated, except that the concentration of sodium hydroxide was 6.0% by weight and bisphenol A was dissolved at a concentration of 14.0% by weight (Na / OH gram equivalent ratio =
1.04) The supplied aqueous solution was supplied at 60.9 l / hr (molar ratio of bisphenol A / phosgene = 1.05), and a 6% sodium hydroxide solution was supplied to the oligomerization reactor at 5 l / hr. However, under these conditions, the oligomer had a high molecular weight, the pressure increased in the tubular reactor, and the separation of the oligomer in the stationary separation tank for separating the aqueous phase became worse.

Comparative Example 6 The operating procedure described in Example 1 was repeated, except that p
-T-butylphenol was supplied to the third-stage stirred reactor, and a 1% by weight aqueous solution of triethylamine was supplied as a catalyst at a rate of 0.5 l / hr to the reactor. Under these conditions, the pH of the aqueous phase of the reaction solution dropped to 4.8, and the hydroxyl group end fraction of the oligomer increased to 17.1 mol%. When a polymer was prepared and evaluated in the same manner as in the method described in Example 1,
The molecular weight distribution Mw / Mn was as wide as 2.41, and the roughening time during blow molding was as short as 24 hours.

Comparative Example 7 Bisphenol was added to a 6.0 wt% aqueous sodium hydroxide solution in a one-necked flask equipped with a stirrer, a reflux condenser, a pH electrode and a phosgene blowing tube so as to have the same chemical ratio as in Example 1. A is dissolved and the concentration is 14.0% by weight
43.5 ml of the prepared aqueous solution (Na / OH gram equivalent ratio = 1.04) and 185 ml of methylene chloride as a solvent were charged, and phosgene was blown into this at 633 mg / min for 1 hour. Subsequently, after stirring for 10 minutes, 33 ml of a 4% by weight methylene chloride solution in which pt-butylphenol was dissolved was added, and the mixture was further stirred for 10 minutes. Next, 1% by weight of triethylamine as a catalyst
3.2 ml of an aqueous solution and 30 ml of a 6% aqueous sodium hydroxide solution were added and stirred for 30 minutes to obtain an oligomer. After the end of the reaction
pH was 3.7. Further, the phosgene decomposition rate was 21.0 mol% and the hydroxyl group terminal fraction was 42.4 mol%, which were extremely high as compared with the tubular reactor. Table 1 summarizes the operating conditions and evaluation results.

Example 5 A polycarbonate oligomer was prepared by repeating the procedure described in Example 1, except that dihydric bisphenol A was added to 6.2 wt% sodium hydroxide at a concentration of 14.0 wt%.
An aqueous solution (Na / OH gram equivalent ratio = 1.06) in which trivalent 1,1,1-tri (4'-hydroxyphenyl) ethane was dissolved at a concentration of 0.16% by weight at 43.0 l / hr. ,
Then, methylene chloride as a solvent was supplied to each of the first tubular reactors at a rate of 18.5 l / hr, and phosgene was further blown at a flow rate of 3.8 kg / hr. Table 1 shows the operating conditions and the evaluation results.
In Table 1, the ratio of BPA / CDC (the meaning will be described later) is represented by the ratio of the total number of moles of dihydric phenol and trihydric phenol to the number of moles of phosgene.

Abbreviations and measurement methods in the following Table 1 are as follows.

BPA: bisphenol A, CDC: phosgene, PTBP: pt-butylphenol, Rx: reactor phosgene decomposition rate (mol%): concentration of Na ₂ CO ₃ in the aqueous phase after completion of the oligomerization reaction (mol / l) × Water phase flow rate (l / h) x 1
00 / phosgene supply amount (mol / h).

Oligomer hydroxyl terminal end fraction (mol%): Determined by proton absorption using a nuclear magnetic resonance apparatus GSX-400 (manufactured by JEOL Ltd.).

Y1: A plate of 80 mm × 80 mm was molded, and the transmission type Y1 was measured.

Skin roughening time during blow molding: Using a MAC-5SS-S type hollow molding machine manufactured by Mac International Associates, a multi-layer bottle with 0.5 liter polypropylene is molded, and the surface roughness of the molded product due to adhesion of a low molecular weight mold. The time to onset was measured.

Number average molecular weight (Mn) of oligomer: Measured by vapor pressure osmometer (VPO).

Viscosity average molecular weight (Mv) of polymer: Based on the intrinsic viscosity measured in methylene chloride at 20 ° C., it was calculated by Schnell's formula.

Molecular weight distribution (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn): Measured by GPC.

The amount of the dimer of PTBP (pt-butylphenol) (pp
m): Measured by liquid chromatography.

[Effects of the Invention] The oligomer produced by the method of the present invention has a small number of hydroxyl group terminals and a low content of low molecular weight substances. Further, the polycarbonate prepared from the oligomer produced by the method of the present invention has a narrow molecular weight distribution and an improved hue. Furthermore, there is little adhesion to the mold at the time of multilayer blow molding, and roughening of the molded product is suppressed.

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Claims (1)

(57) [Claims] A method for continuously producing a polycarbonate oligomer having a number average molecular weight of 300 to 10,000 by reacting an aqueous alkali solution containing an alkali metal salt of a polyhydric phenol with phosgene in the presence of an inert organic solvent. (A) The gram equivalent ratio of the alkali metal atom to the hydroxyl group of the polyhydric phenol in the aqueous alkali solution is set in a tubular reactor in which the system is pressurized to a pressure higher than the saturated vapor pressure of the inert organic solvent.
The alkaline aqueous solution and phosgene are supplied to perform the phosgenation reaction so that the molar ratio of the polyhydric phenol to phosgene is 0.55 to 0.95, and the phosgenation reaction is carried out. A monohydric phenol is supplied into the reactor or at the outlet of the tubular reactor to partially terminate the chloroformate group-terminated compound produced in the step (a), and then (c) the next reactor Wherein the oligomerization reaction is performed until the pH after the reaction is 5 to 10.