JPH08245780A - Production of polycarbonate - Google Patents

Abstract

PURPOSE: To provide a method for producing a polycarbonate capable of not only efficiently recovering and reusing an unreacted phenol compound in drain without using a prescribed apparatus and reducing a polycarbonate production unit but also supplying a polycarbonate having excellent qualities. CONSTITUTION: In a method for reacting an alkali aqueous solution of a phenol compound containing a dihydric phenol with phosgene in the presence of an organic solvent to produce a polycarbonate through a polycarbonate oligomer, a drain containing an unreacted phenol compound generated from the reaction system is brought into contact with a solution of the polycarbonate oligomer to transfer the unreacted phenol compound into the solution of the polycarbonate oligomer and to polymer and treat the solution of the polycarbonate oligomer containing the unreacted phenol compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polycarbonate, and more particularly to a method for producing a polycarbonate which enables recovery and reuse of unreacted phenol compounds in wastewater produced during the production of a polycarbonate.

[0002]

2. Description of the Related Art As a method for producing a polycarbonate, an alkaline aqueous solution of a phenol compound containing a dihydric phenol such as bisphenol A and phosgene are contacted in the presence of an organic solvent to carry out polycondensation at the interface between the aqueous phase and the organic phase. The interfacial polycondensation method for obtaining a polycarbonate by reacting is widely adopted.

According to the interfacial polycondensation method, a large amount of waste water is generated after the polymerization step and the washing step. This wastewater contains unreacted dihydric phenol used as a raw material and unreacted monohydric phenol used as a molecular weight regulator, and COD
(Chemical oxygen demand) is high, and its treatment is a problem.

In particular, in order to reduce the amount of unreacted dihydric phenol, the amount of dihydric phenol as a raw material is reduced to a value close to the equivalent of the chloroformate group that reacts with the phenolic hydroxyl group, and the resulting polycarbonate is chlorinated. It has been clarified that the formate group remains, the reaction takes a long time, and the product quality is adversely affected. Therefore, in the industrial production of polycarbonate, the dihydric phenol as a raw material is changed to phosgene. Since it is used in excess, the problem of treating wastewater containing unreacted phenolic compounds becomes more serious.

The following method is known as a method for treating the above wastewater containing unreacted dihydric phenol, monohydric phenol and the like (hereinafter, these may be collectively referred to as a phenol compound).

(A) Method of oxidative decomposition treatment or microbial decomposition treatment of waste water (b) Method of filtering precipitate of phenol compound obtained by acid precipitation treatment of waste water and reusing it for polycarbonate production (c) Waste water After acidifying the organic matter, extraction treatment with an organic solvent, and reusing the obtained organic solvent solution of the phenol compound in the production of polycarbonate

[0007]

Among the above three methods, the method (a) requires (i) an apparatus for oxidative decomposition treatment or microbial decomposition treatment, and (ii) for oxidative decomposition treatment. It is necessary to use an oxidizing agent for the above, and a microorganism for the microbial decomposition treatment, and special consideration must be given to the handling of these during the treatment. (Iii) Phenol compounds can be obtained by both the oxidative decomposition treatment and the microbial decomposition treatment. Since it decomposes and disappears, it cannot be reused, resulting in a loss of raw materials.

Further, the above method (b) is superior to the above method (a) in that the phenol compound can be recovered and reused, but the phenol compound obtained by filtration after acid precipitation has many impurities. In order to reuse polycarbonate in the production of polycarbonate, a purification step and a drying step are required. For this reason, not only the processing operation becomes complicated, but also the construction cost and the operation cost of the processing apparatus increase.

The method (c) is also superior to the method (a) in that the phenol compound can be recovered and reused. However, the wastewater generated after the polycarbonate polymerization step and after the washing step generally contains a relatively large amount (for example, 0.1 to 50 g / liter) of a phenol compound, and the phenol compound is removed by solvent extraction according to the method (c). For extraction, it is necessary to take measures such as (i) using a large amount of organic solvent as the extraction solvent and (ii) performing the extraction in multiple stages. And when the above means (i) is taken, the concentration of the phenol compound in the extract is low, so the extract must be concentrated to increase the concentration of the phenol compound before it can be circulated to the reaction system, and therefore the concentration step Is required. Further, when the above-mentioned means (ii) is adopted and a multistage extraction process is carried out, the processing operation becomes complicated and the processing equipment cost becomes high.

Therefore, the object of the present invention is to solve the above-mentioned drawbacks of the prior art, and (1) to recover and reuse unreacted phenol compounds in wastewater efficiently without using a special device, and to produce a polycarbonate production unit. It is to provide a novel method for producing a polycarbonate, which has advantages such as reduction of (2) and excellent quality of the obtained polycarbonate.

[0011]

Means for Solving the Problems As a result of studies to achieve the above object, the present inventors have made an alkaline aqueous solution of a phenol compound containing a dihydric phenol and phosgene react in the presence of an organic solvent, When producing a polycarbonate via a polycarbonate oligomer, the wastewater containing the unreacted phenol compound generated from the reaction system is contacted with the polycarbonate oligomer solution to transfer the unreacted phenol compound to the polycarbonate oligomer solution, and the unreacted phenol compound-containing polycarbonate It has been found that the above objects are achieved by polymerizing the oligomer solution.

The present invention has been completed based on the above findings, and in a method for producing a polycarbonate through a polycarbonate oligomer by reacting an aqueous alkaline phenol compound solution containing a dihydric phenol with phosgene in the presence of an organic solvent. Characterized in that the wastewater containing the unreacted phenol compound generated from the reaction system is contacted with the polycarbonate oligomer solution to transfer the unreacted phenol compound to the polycarbonate oligomer solution, and the unreacted phenol compound-containing polycarbonate oligomer solution is polymerized. A method of manufacturing a polycarbonate is described.

The present invention will be described in detail below.

The present invention is a method for producing a polycarbonate by reacting (A) an alkaline aqueous solution of a phenolic compound containing a dihydric phenol with phosgene in the presence of an organic solvent, and (B) an unreacted product generated from a reaction system. It is characterized in that waste water containing a phenol compound is brought into contact with the polycarbonate oligomer solution to transfer the unreacted phenol compound to the polycarbonate oligomer solution, and the unreacted phenol compound-containing polycarbonate oligomer solution is polymerized.

That is, the present invention is based on the conventional interfacial polycondensation method, as is clear from the above requirement (A).
The novel characteristic requirement (B) is adopted in the interfacial polycondensation method.

Therefore, the above prerequisite (A) will be described first, and then the new characteristic requirement (B) will be described.

Prerequisites (A) The phenol compound used in the production of a polycarbonate by the interfacial polycondensation method includes a dihydric phenol as a raw material, a monohydric phenol as a molecular weight controlling agent, and a trivalent or more phenol as a branching agent. These will be specifically described below.

(1) Dihydric Phenol The dihydric phenol used as a raw material has the general formula (I)

Embedded image [Wherein R is a halogen atom (for example, chlorine,
Bromine, fluorine, iodine) or an alkyl group having 1 to 8 carbon atoms (eg, methyl group, ethyl group, propyl group, n-butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, etc.). When there are plural, they may be the same or different, and m is 0-4.
Is an integer. Z is a single bond, an alkylene group having 1 to 8 carbon atoms or an alkylidene group having 2 to 8 carbon atoms (for example, methylene group, ethylene group, propylene group, butylene group, penterylene group, hexylene group, ethylidene group, isopropylidene group). Ridene group, etc.), C5-C15 cycloalkylene group or C5-C15 cycloalkylidene group (for example, cyclopentylene group, cyclohexylene group,
Cyclopentylidene group, cyclohexylidene group, etc.),
Or --S--, --SO--, --SO2-, --O--, --CO--
Bond or general formula (II) or (III)

Embedded image Indicates a bond represented by. ] The dihydric phenol represented by these is mentioned.

Examples of such dihydric phenols include bis (4-hydroxyphenyl) methane; bis (3
-Methyl-4-hydroxyphenyl) methane; bis (3
-Chloro-4-hydroxyphenyl) methane; bis (3,5-dibromo-4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) ethane;
1,1-bis (2-t-butyl-4-hydroxy-3-
Methylphenyl) ethane; 1,1-bis (2-t-butyl-4-hydroxy-3-methylphenyl) ethane; 1
-Phenyl-1,1-bis (3-fluoro-4-hydroxy-3-methylphenyl) ethane; 2,2-bis (4
-Hydroxyphenyl) propane (commonly called bisphenol A: BPA); 2,2-bis (3-methyl-4-hydroxyphenyl) propane; 2,2-bis (2-methyl-)
4-hydroxyphenyl) propane; 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane; 1,1-bis (2-t-butyl-4-hydroxy-)
5-Methylphenyl) propane; 2,2-bis (3-chloro-4-hydroxyphenyl) propane; 2,2-bis (3-fluoro-4-hydroxyphenyl) propane; 2,2-bis (3-bromo) -4-Hydroxyphenyl) propane; 2,2-bis (3,5-difluoro-4)
-Hydroxyphenyl) propane; 2,2-bis (3,3
5-dichloro-4-hydroxyphenyl) propane;
2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane; 2,2-bis (4-hydroxyphenyl) butane; 2,2-bis (4-hydroxyphenyl)
Octane; 2,2-bis (4-hydroxyphenyl) phenylmethane; 2,2-bis (4-hydroxy-1-methylphenyl) propane; 1,1-bis (4-hydroxy-t-butylphenyl) propane; 2,2-bis (4
-Hydroxy-3-bromophenyl) propane; 2,2
-Bis (4-hydroxy-3,5-dimethylphenyl)
Propane: 2,2-bis (4-hydroxy-3-chlorophenyl) propane; 2,2-bis (4-hydroxy-)
3,5-Dichlorophenyl) propane; 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane; 2,2-bis (3-bromo-4-hydroxy-5)
Chlorophenyl) propane; 2,2-bis (3-phenyl-4-hydroxyphenyl) propane; 2,2-bis (4-hydroxyphenyl) butane; 2,2-bis (3
-Methyl-4-hydroxyphenyl) butane; 1,1-
Bis (2-butyl-4-hydroxy-5-methylphenyl) butane; 1,1-bis (2-t-butyl-4-hydroxy-5-methylphenyl) butane; 1,1-bis (2-t-) Butyl-4-hydroxy-5-methylphenyl) isobutane; 1,1-bis (2-t-amyl-4-
Hydroxy-5-methylphenyl) butane; 2,2-bis (3,5-dichloro-4-hydroxyphenyl) butane; 2,2-bis (3,5-dibromo-4-hydroxyphenyl) butane; 4,4 -Bis (4-hydroxyphenyl) heptane; 1,1-bis (2-t-butyl-4-
Hydroxy-5-methylphenyl) heptane; 2,2-
Bis (4-hydroxyphenyl) octane; 1,1-
Bis (hydroxyaryl) alkanes such as (4-hydroxyphenyl) ethane; 1,1-bis (4-hydroxyphenyl) cyclopentane; 1,1-bis (4-hydroxyphenyl) cyclohexane; 1,1-bis ( Three
-Methyl-4-hydroxyphenyl) cyclohexane;
1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane; 1,1-bis (3-phenyl-4-hydroxyphenyl) cyclohexane; 1,1-
Bis (hydroxyaryl) such as bis (4-hydroxyphenyl) -3,5,5-trimethylcyclohexane
Cycloalkanes; bis (4-hydroxyphenyl) ether; bis (4, -hydroxy-3-methylphenyl) ether and other bis (hydroxyaryl) ethers; bis (4-hydroxyphenyl) sulfide; bis (3-methyl) Bis (hydroxyaryl) sulfides such as -4-hydroxyphenyl) sulfide; bis (4-hydroxyphenyl) sulfoxide; bis (3-
Methyl-4-hydroxyphenyl) sulfoxide; bis (hydroxyaryl) sulfoxides such as bis (3-phenyl-4-hydroxyphenyl) sulfoxide;
Bis (4hydroxyphenyl) sulfone; Bis (3-methyl-4-hydroxyphenyl) sulfone; Bis (3-
Bis (hydroxyaryl) sulfones such as phenyl-4-hydroxyphenyl) sulfone, 4,4′-dihydroxybiphenyl; 4,4′-dihydroxy-2,
2'-dimethylbiphenyl;4,4'-dihydroxy-
3,3'-Dimethylbiphenyl;4,4'-Dihydroxy-3,3'-dicyclohexylbiphenyl; 3,3 '
Examples thereof include dihydroxybiphenyls such as -difluoro-4,4'-dihydroxybiphenyl.

Examples of the dihydric phenol other than the above general formula (I) include dihydroxybenzenes, halogen- and alkyl-substituted dihydroxybenzenes. For example, resorcin, 3-methylresorcin, 3-ethylresorcin, 3-propylresorcin, 3-butylresorcin,
3-t-butylresorcin, 3-phenylresorcin,
3-cumylresorcin; 2,3,4,6-tetrafluororesorcin; 2,3,4,6-tetrabromoresorcin; catechol, hydroquinone, 3-methylhydroquinone, 3-ethylhydroquinone, 3-propylhydroquinone, 3 -Butyl hydroquinone, 3-t-butyl hydroquinone, 3-phenyl hydroquinone, 3-
Cumyl hydroquinone; 2,5-dichlorohydroquinone; 2,3,5,6-tetramethylhydroquinone;
2,3,4,6-tetra-t-butylhydroquinone;
2,3,5,6-tetrafluorohydroquinone; 2,
3,5,6-tetrabromohydroquinone and the like can be mentioned.

(2) Monohydric Phenol Specific examples of the monohydric phenol used as a molecular weight regulator include nn-butylphenol; mn-butylphenol; pn-butylphenol; o-isobutylphenol; m-isobutyl. Phenol; p-isobutylphenol; o-t-butylphenol; m-t-
Butylphenol; pt-butylphenol; on
-Pentylphenol; mn-pentylphenol;
p-n-pentylphenol; o-n-hexylphenol; m-n-hexylphenol; p-n-hexylphenol; o-cyclohexylphenol; m-cyclohexylphenol; p-cyclohexylphenol; o-phenylphenol; m- Phenylphenol; p-phenylphenol; on-nonylphenol; mn-nonylphenol; pn-nonylphenol; o-cumylphenol; m-cumylphenol;
p-cumylphenol; o-naphthylphenol; m-
Naphthylphenol; p-Naphthylphenol; 2,6
-Di-t-butylphenol; 2,5-di-t-butylphenol; 2,4-di-t-butylphenol; 3,
5-di-t-butylphenol; 2,5-dicumylphenol; 3,5-dicumylphenol; formula

Embedded image As a compound represented by or a chroman derivative, for example,
formula

[Chemical 4] Monohydric phenols such as compounds represented by

Among such phenols, p-tert
-Butylphenol; p-cumylphenol; p-phenylphenol and the like are preferable.

(3) Trivalent or higher phenols Examples of trivalent or higher phenols used as a branching agent include, for example, phloroglucin; phlorogluside; 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 "- Examples thereof include dihydroxytriphenyl-methyl) benzene, etc. Each compound exemplified above as a trivalent or higher valent phenol may have a halogen substituent, or a mixture of the above compounds may be used.

In the method for producing a polycarbonate by the interfacial polycondensation method, an alkaline aqueous solution of a phenol compound containing a dihydric phenol and phosgene are reacted in the presence of an organic solvent. The alkaline aqueous solution of a phenol compound containing a dihydric phenol is a phenol compound containing a dihydric phenol dissolved in an alkaline aqueous solution such as a caustic alkaline aqueous solution, and a caustic soda aqueous solution is particularly preferable.

As the organic solvent used for the production of the polycarbonate by the interfacial polycondensation method, methylene chloride is particularly preferable, but in addition to this, chlorine-based organic solvents such as chloroform and chlorobenzene, and ether-based solvents such as dioxane and tetrahydrofuran are used. You can also

These solvents may contain a poor solvent to the extent that polycarbonate does not precipitate. Here, the poor solvent is an aromatic compound such as benzene, toluene or xylene, an alkane such as pentane, hexane, heptane or octane, a ketone such as acetone or methyl ethyl ketone, or a mixed solvent thereof.

By reacting an alkaline aqueous solution of a phenol compound containing a dihydric phenol with phosgene in the presence of an organic solvent, a polycarbonate oligomer is produced, and by polymerizing this, a desired polycarbonate is produced. The conditions for producing the polycarbonate oligomer and the conditions for producing the polycarbonate by polymerizing the oligomer are the same as the conditions in the conventional interfacial polycondensation method, and thus the description thereof is omitted.

In the production of polycarbonate by the interfacial polycondensation method as already described in the section of the prior art, in order to reduce the residual of chloroformate groups which adversely affect the quality of the polycarbonate product in the polycarbonate product, (a ) Measures such as excessive use of a phenolic compound with respect to phosgene, (b) decomposition of a chloroformate group by an excess of alkali by using an excess of alkali more than necessary amount are taken, (A), (b)
In either case, the phenol compound becomes excessive and the wastewater discharged from the reaction system contains a considerable amount of unreacted phenol compound.

Therefore, according to the present invention, in order to recover and reuse the phenol compound in the waste water, the characteristic requirement (B) described in detail below is adopted.

Characteristic Requirement (B) According to the present invention, the waste water containing the unreacted phenol compound generated from the reaction system is contacted with the polycarbonate oligomer solution.

Wastewater generated from the reaction system is typically wastewater generated after the polymerization step, wastewater generated after the cleaning step, and the like. All wastewater containing phenolic compounds generated in factories can be used in the present invention.

The pH of the waste water which is brought into contact with the polycarbonate oligomer solution is preferably 6-14. The reason is as follows. If the pH of the wastewater is less than 6, the unreacted phenolic compound in the wastewater does not react sufficiently with the polycarbonate oligomer and is only extracted into the oligomer solution by acid precipitation, which does not react in the wastewater according to the distribution ratio of phenols. Phenolic compounds remain. On the other hand, when the pH of the waste water exceeds 14, the decomposition of the oligomer in contact with the high pH waste water, especially the decomposition of the chloroformate group and the carbonate group is promoted.

Therefore, when the pH of the waste water is less than 6 or more than 14, the pH of the waste water is adjusted to the range of 6 to 14 by adding a pH adjusting agent such as alkali or acid before contacting with the oligomer solution. Preferably. The alkali added when the pH is less than 6 is preferably the same as the alkali used in the production of the polycarbonate, and therefore it is particularly preferable to use caustic alkali, especially caustic soda.

The polycarbonate oligomer solution is produced in the process of producing the polycarbonate, and since the medium is the organic solvent used in the reaction as described above, it functions as an extraction solvent for the phenol compound in the waste water. Therefore, when the waste water containing the unreacted phenol compound is brought into contact with the polycarbonate oligomer solution in the present invention, the unreacted phenol compound is transferred from the waste water to the polycarbonate oligomer solution. Then, the unreacted phenol compound transferred to the polycarbonate oligomer solution is incorporated into the polycarbonate polymer by reacting with the chloroformate group in the polycarbonate oligomer. By thus polymerizing the polycarbonate oligomer solution containing the unreacted phenol compound, a polycarbonate having excellent product quality can be obtained.

The polycarbonate oligomer in the polycarbonate oligomer solution preferably has a chloroformate group in an amount equal to or more than that required for the reaction of the unreacted phenol compound, in order to carry out the polymerization reaction optimally.

The content of residual chloroformate groups of the polycarbonate oligomer in the polycarbonate oligomer solution was previously determined by analysis, and at the same time, the content of unreacted phenol compound in the waste water was also determined by analysis. The polymerization reaction can be optimally performed by appropriately changing the amount of waste water supplied.

In order to accelerate the reaction between the unreacted phenol compound and the polycarbonate oligomer, a catalyst may be added at the time of contact between the waste water and the polycarbonate oligomer solution. As the catalyst, a known catalyst in the interfacial polycondensation method can be used. Examples of usable catalysts include tertiary amines and quaternary ammonium salts, and specific examples thereof include triethylamine, tri-n-butylamine, diethylaminopyridine, and tetramethylammonium chloride. Triethylamine (TEA) is particularly preferable. The optimum amount of these catalysts to be used may be experimentally confirmed according to the conditions such as the contact time between the waste water and the polycarbonate oligomer solution, the pH, etc. 1.0 (mo
1 catalyst / mol unreacted phenol / liter), preferably 0-0.5.

In the present invention, by contacting the wastewater from the reaction system with the polycarbonate oligomer solution, the unreacted phenol compound is transferred from the wastewater to the polycarbonate oligomer solution, and the unreacted phenol compound and the chloroformate group of the oligomer are added. The polymerization reaction of the oligomer including the reaction of is carried out all at once.
It is carried out by a liquid contact method, and for example, a method of stirring in a stirring tank, a method of mixing with a static mixer, a method of countercurrent or cocurrent contact in a packed column, and the like are used.

The contact time should be determined efficiently depending on each method, but it is about 30 seconds to 2 hours. If the contact time is less than 30 seconds, sufficient extraction and reaction cannot be expected, and if the contact time is 2 hours or more, the equipment used for contact becomes large.

The polycarbonate oligomer solution after contact with the waste water may be further subjected to a polymerization treatment after separating at least a part or all of the aqueous phase by a conventionally known method. On the other hand, although the unreacted phenol compound is significantly reduced in the aqueous phase, it may be subjected to the following treatment if necessary for further removal of the unreacted phenol compound.

(A) Method of extracting unreacted phenol compound by bringing it into contact with a polymerization solvent (b) Method of treatment by aeration (c) Method of treatment with microorganisms etc. The reaction phenol compound can be recovered more efficiently, and by reusing this solvent as the polymerization reaction solvent, further improvement in recovery efficiency can be expected, and the utilization rate of the phenol compound as a raw material can be almost the theoretical amount. It can be close to 100%.

[0042]

【Example】

Reference Example 1 (Example of Polycarbonate Production by Ordinary Interfacial Polycondensation Method) (1) Production of Polycarbonate Oligomer Bisphenol A (BPA) was dissolved in a caustic soda (NaOH) aqueous solution having a concentration of 6 wt% to prepare a BP having a concentration of 14.5 wt%.
An A-NaOH solution was obtained. The obtained BPA-NaOH solution was 40 l / hr, the concentration of 25 wt% p-tert-butylphenol (PTBP: molecular weight modifier) -methylene chloride (MC) solution was 0.35 l / hr, and the solvent methylene chloride (MC ) At a flow rate of 18.5 l / hr for 20
It was introduced into a tubular reactor having an inner diameter of 6 mm and a length of 30 m, which was soaked in a cooling bath at 0 ° C., and phosgene was blown thereinto at a flow rate of 3.8 kg / hr.

The reaction mixture discharged from the reactor was introduced into a separation tank to separate the aqueous phase, and the polycarbonate oligomer M
An organic phase consisting of C solution was obtained.

The properties of the obtained polycarbonate oligomer were analyzed and the results were as follows.

Average molecular weight: 860 (number average molecular weight is measured by vapor pressure osmometer (VPO)) Chloroformate group concentration: 0.68 (N) (as a solution of oligomer in organic solvent) (2) Production of polycarbonate (1) 20 liter / hr of MC solution of the polycarbonate oligomer obtained in 1), the concentration of 1 adjusted in (1)
4.5 wt% BPA-NaOH solution 11.5 l / hr, concentration 4 wt% triethylamine (TEA: catalyst)
An aqueous solution of 0.04 liter / hr and a concentration of 25 wt% NaO
The H aqueous solution was introduced into the tower reactor at a flow rate of 0.8 L / hr and the solvent MC was introduced at a flow rate of 13 L / hr for reaction. The residence time was 1 hour.

After this, the organic phase obtained by separating the aqueous phase from the reaction mixture which overflowed and came out was adjusted to pH 13.5.
Was sequentially washed with an aqueous solution of NaOH, an aqueous solution of hydrochloric acid (HCl) having a pH of 1.5, and pure water to obtain a clear MC solution of polycarbonate.

A white polycarbonate powder was obtained by pulverizing the obtained polycarbonate MC solution while evaporating and removing the solvent MC. The viscosity average molecular weight (Mv) of the obtained polycarbonate powder was 29400.

On the other hand, the unreacted phenol compound concentration and the NaOH concentration of the aqueous phase separated from the reaction mixture were measured to be 15 g / liter and 0.
It was 21N, and all were high concentration.

Example 1 Unreacted BPA concentration of 15 discharged in (2) of Reference Example 1
g / liter, 12 liters / hr of NaOH concentration of 0.21 N, and 20 liters / hr of MC solution of polycarbonate oligomer obtained in (1) of Reference Example 1 were continuously introduced into a vertical stirring tank, Aqueous NaOH solution was added so that the pH of the aqueous phase was 8.5. The residence time is set to 30 minutes, the mixture is stirred and the waste water is brought into contact with the MC solution of the polycarbonate oligomer, and the unreacted phenol compound is extracted from the aqueous phase to the organic phase and subjected to a polymerization process including a reaction between the unreacted phenol compound and the oligomer It was

The unreacted phenol compound concentration in the aqueous phase obtained by allowing the residence time to be 30 minutes and subjecting them to contact treatment and then separating them by standing was 500 mg / liter, and the unreacted phenol in the waste water used in this Example was Compound concentration is 15g /
Since it was liter, it was reduced to 3.3% (removal rate 96.7%).

Further, the viscosity average molecular weight (Mv) of the polycarbonate obtained by treating the organic phase composed of the MC solution of the polycarbonate obtained after the stationary separation in the same manner as in (2) of Reference Example 1 was 29200. .

A series of operations was continuously carried out for 72 hours, but it was found that stable operation was possible without any particular fluctuation in the process.

Examples 2 to 6 The procedure of Example 1 was repeated, except that the pH of the waste water, the contact time between the waste water and the polycarbonate oligomer solution, and the amount of catalyst supplied were changed as shown in Table 1.

Table 1 shows the concentration of unreacted phenol compound in the aqueous phase separated from the reaction mixture and the viscosity average molecular weight of the polycarbonate obtained by treating the organic phase in the same manner as in Example 1.

[0055]

[Table 1]

As is clear from Table 1, according to Examples 1 to 6 in which the wastewater containing unreacted phenol and the polycarbonate oligomer solution were contact-treated, the phenol compound in the wastewater generated by the reaction was 96.7 to 99. The removal rate was as high as 5%. The molecular weight of the obtained polycarbonate was 28800 to 29400, which was a satisfactory value.

Comparative Example 1 In order to reduce the content of unreacted phenol compound in the waste water discharged after the polymerization, BPA-having a concentration of 14.5 wt% was used.
Change the amount of NaOH solution from 11.5 l / hr to 10.5
The polymerization reaction was performed in the same manner as in (2) of Reference Example 1 except that the rate was decreased to 1 / hr. As a result, the content of unreacted phenol compound contained in the wastewater after polymerization was 90
Although it decreased to 0 mg / liter, the viscosity average molecular weight (Mv) of the sample 1 hour after the initiation of polymerization was 24500, which was lower than that obtained in (2) of Reference Example 1. The amount of chlorine (Cl) derived from the residual chloroformate group in the polycarbonate was 45 wt-ppm, and the reaction was not completed with the same residence time of 1 hour as (2) in Reference Example 1.

From the results of Comparative Example 1, the amount of the phenol compound in the waste water is reduced only by decreasing the supply amount of the dihydric phenol as the raw material, but the reaction is prolonged and the product quality is deteriorated. Turned out to be.

Reference Example 2 (Example of Polycarbonate Production by Ordinary Interfacial Polycondensation) As a raw material dihydric phenol A NaOH solution, BPA was used.
12.5 wt%, tetrabromobisphenol (TB
Concentration of BPA and TBA is 6 so that A) is 2.0 wt%
A polycarbonate oligomer solution was obtained in the same manner as in (1) and (2) of Reference Example 1, except that a solution obtained by dissolving in a wt% NaOH aqueous solution was used. A polycarbonate having an average molecular weight of 28700 was obtained. BP in wastewater generated after polymerization
A concentration is 10.1 g / liter, TBA concentration is 1.2 g
/ Liter.

Example 7 MC of the polycarbonate oligomer obtained in Reference Example 2
20 liters / hr of the solution and 12 liters / hr of the waste water generated in Reference Example 2 were contacted in the same manner as in Example 1 to extract the unreacted phenol compound being discharged into an oligomer solution and polymerize the oligomer. Was done. The BPA concentration and TBA concentration in the aqueous phase obtained after the polymerization treatment were 175 mg / liter and 30 mg / liter, respectively, and the removal rates were 98.3% and 97.5%. The viscosity average molecular weight of the obtained polycarbonate is also 29,200.
And was satisfactory.

[0061]

EFFECT OF THE INVENTION According to the method for producing a polycarbonate of the present invention, unreacted phenol compounds in wastewater can be efficiently recovered and reused without using a special device, and not only the production unit of polycarbonate can be reduced, The special effect is obtained that the quality of the obtained polycarbonate is excellent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eizo Saito 1 Inezaki Kaigan, Ichihara-shi, Chiba Idemitsu Petrochemical Co., Ltd. Within

Claims (6)

[Claims] 1. A method for producing a polycarbonate through a polycarbonate oligomer by reacting an alkaline aqueous solution of a phenol compound containing a dihydric phenol with phosgene in the presence of an organic solvent, which comprises an unreacted phenol compound generated from a reaction system. A method for producing a polycarbonate, which comprises contacting wastewater with a polycarbonate oligomer solution to transfer an unreacted phenol compound to the polycarbonate oligomer solution, and polymerizing the unreacted phenol compound-containing polycarbonate oligomer solution. 2. The method according to claim 1, wherein the wastewater generated from the reaction system is wastewater after the polymerization step and / or wastewater after the washing step. 3. The method according to claim 1, wherein the pH of the wastewater contacted with the polycarbonate oligomer solution is 6-14. 4. The pH of the wastewater by adding a pH adjuster to the wastewater
The method of claim 3, wherein: 5. The method of claim 4, wherein the pH adjusting agent is caustic. 6. The method according to claim 1, wherein a catalyst is added at the time of contact between the waste water and the polycarbonate oligomer solution.