JPH0762076A - Production of polycarbonate - Google Patents

Abstract

PURPOSE:To obtain the subject polycarbonate free from retention burning, and excellent in quality and color tone without the hydrolysis resistance of the polycarbonate by preliminarily washing a reactor with an alkali and furthermore washing the reactor with an acid, when raw materials are subjected to transesterification. CONSTITUTION:When (A) a dihydroxy compound and (B) a carbonate diester are subjected to transesterification to obtain the objective carbonate, a reactor for performing the transesterification is preliminarily washed with an alkali such as lithium hydroxide and furthermore washed with an acid such as hydrochloric acid. The component A is preferably an aromatic dihydroxy compound of the formula (R is halogen, 1-8C alkyl; m is 0-4; z is single bond, 1-8C alkylene, 2-8C alkylidene, etc.).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing polycarbonate. Specifically, in producing a polycarbonate from a dihydroxy compound and a carbonic acid diester by a transesterification method, a reactor for carrying out the transesterification reaction is washed with an alkali in advance, and then washed with an acid to be used to improve hydrolysis resistance. The present invention relates to a method for efficiently producing a polycarbonate having excellent color tone, which is excellent in quality without retention burn without being damaged.

[0002]

2. Description of the Related Art Generally, as a method for producing a polycarbonate (hereinafter referred to as PC), a method in which an aromatic dihydroxy compound such as bisphenol A is directly reacted with phosgene (interfacial polycondensation) Or a method (melting method) in which an aromatic dihydroxy compound such as bisphenol A and a carbonic acid diester such as diphenyl carbonate are transesterified in a molten state. In the interfacial polycondensation method in the production method of PC, toxic phosgene must be used, the production equipment is corroded by chlorine-containing compounds such as hydrogen chloride and sodium chloride produced as a by-product, and hydroxylation mixed in the resin. There are various problems such as difficulty in separating impurities such as sodium that adversely affect the physical properties of the polymer.

On the other hand, the melting method has an advantage that PC can be manufactured at a lower cost than the interfacial polycondensation method, but usually, the reaction is carried out at a high temperature of 280 to 310 ° C. for a long time. In addition, it has a big drawback that it cannot escape from the coloring problem of the resin. In such a melting method, various improved techniques have been proposed in order to reduce this coloring. For example, JP-B-61-39972 and JP-A-63-223036 disclose a method of using a specific catalyst. Also, JP-A-61-151
Japanese Patent Laid-Open No. 236 and Japanese Patent Laid-Open No. 62-158719 disclose a method of adding an antioxidant in the latter stage of the reaction. And, in JP-A-61-62522, etc.,
In the latter stage of the reaction, a twin-screw vent type kneading extruder was used.
Japanese Patent Laid-Open No. 153925 discloses a process improvement technique such as using a horizontal stirring polymerization tank. Further, Japanese Patent Application Laid-Open No. 2-175722 discloses a method in which the content of hydrolyzable chlorine in a monomer is set to a certain level or less. However, the problem of coloring has not been completely solved yet, and the actual situation is that a satisfactory PC has not been obtained yet.

[0004]

Therefore, the present inventors have
In view of the above situation, the inventors have conducted earnest studies to solve the above-mentioned drawbacks of the conventional method and to develop a method capable of efficiently producing a PC having an excellent color tone by a transesterification method. As a result, in the production of PC by the transesterification method, the reactor for transesterification reaction was previously washed with alkali and then washed with acid, and then used.
It has been found that the above problems can be solved. The present invention has been completed based on such findings. That is, according to the present invention, when a polycarbonate is produced from a (A) dihydroxy compound and a (B) carbonic acid diester by a transesterification method, a reactor for carrying out the transesterification reaction is preliminarily washed with an alkali, and then washed with an acid. The present invention provides a method for producing a polycarbonate, which is characterized by being used.

First, in the present invention, there are various dihydroxy compounds used as the component (A).
For example, selected from aromatic dihydroxy compounds, aliphatic dihydroxy compounds, bisesters of aromatic dihydroxy compounds, bisesters of aliphatic dihydroxy compounds, carbonates of aromatic dihydroxy compounds, and carbonates of aliphatic dihydroxy compounds. At least one compound. The aromatic dihydroxy compound used as one of the components (A) has the general formula (I)

[0006]

[Chemical 1]

[Wherein R is a halogen atom (for example, chlorine, bromine, fluorine, iodine) or an alkyl group having 1 to 8 carbon atoms (for example, methyl group, ethyl group, propyl group, n-butyl group, Isobutyl group, amyl group, isoamyl group, hexyl group, etc.) and when this R is plural,
They may be the same or different,
m is an integer of 0-4. 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.), C5-15
Cycloalkylene group or cycloalkylidene group having 5 to 15 carbon atoms (for example, cyclopentylene group, cyclohexylene group, cyclopentylidene group, cyclohexylidene group, etc.), or -S-, -SO-, -SO ₂ -, -O
-, -CO- bond or general formula (II) or (II ')

[0008]

[Chemical 2]

The bond represented by ] The aromatic dihydroxy compound represented by these is mentioned. Examples of such aromatic dihydroxy compounds include bis (4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) ethane; 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A : BPA);
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 Such as bis (hydroxyaryl) alkanes; 1,1-bis (4-hydroxyphenyl) cyclopentane; 1,1-bis (4
-Hydroxyphenyl) cyclohexane; 1,1-bis (4-hydroxyphenyl) -3,5,5-trimethylcyclohexane and other bis (hydroxyaryl) cycloalkanes; 4,4-dihydroxydiphenyl ether; 4,4'-dihydroxy Dihydroxy aryl ethers such as -3,3'-dimethylphenyl ether;
4,4'-dihydroxydiphenyl sulfide; 4,
Dihydroxydiaryl sulfides such as 4'-dihydroxy-3,3'-dimethyldiphenyl sulfide;
4,4'-dihydroxydiphenyl sulfoxide; 4,
Dihydroxyaryl sulfoxides such as 4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide; 4,4'-dihydroxydiphenyl sulfone; 4,
Dihydroxydiarylsulfones such as 4'-dihydroxy-3,3'-dimethyldiphenylsulfone, dihydroxybenzene, halogen and alkyl substituted dihydroxybenzenes, for example 1,4-dihydroxy-2,5-
Dichlorobenzene; 1,4-dihydroxy-3-methylbenzene and the like can be mentioned.

There are various kinds of aliphatic dihydroxy compounds as the component (A). For example, butane-1,4-diol; 2,2-dimethylpropane-
1,3-diol; hexane-1,6-diol; diethylene glycol; triethylene glycol; tetraethylene glycol; octaethylene glycol; dipropylene glycol; N, N-methyldiethanolamine; cyclohexane-1,3-diol; cyclohexane -1,4-diol; 1,4-dimethylolcyclohexane; p-xylylene glycol; 2,2-bis-
Ethoxylated or propoxylated products of (4-hydroxycyclohexyl) -propane and dihydric alcohols or phenols such as bis-oxyethyl-bisphenol A; bis-oxyethyl-tetrachlorobisphenol A or bis-oxyethyl-tetrachlorohydroquinone. To be

Examples of the bisester of an aromatic dihydroxy compound, the bisester of an aliphatic dihydroxy compound, the carbonate of an aromatic dihydroxy compound, or the carbonate of an aliphatic dihydroxy compound used as the component (A) include The bisesters of the above compounds have the general formula (III)

[0012]

[Chemical 3]

[Wherein R ¹ represents a residue obtained by removing two hydroxyl groups from the above aliphatic dihydroxy compound, and R ² represents an alkyl group having 1 to 6 carbon atoms or 4 to 4 carbon atoms.
A cycloalkyl group having 7 is shown. ] The compound represented by the general formula (IV)

[0014]

[Chemical 4]

[In the formula, Ar ¹ represents a residue obtained by removing two hydroxyl groups from the aromatic dihydroxy compound, and R ² has the same meaning as described above. ] The compound represented by the general formula (V)

[0016]

[Chemical 5]

[In the formula, Ar ² represents an aryl group, and R ¹ is the same as above. ] Or a compound represented by the general formula (V
I)

[0018]

[Chemical 6]

[In the formula, Ar ¹ and Ar ² are the same as defined above. ] The compound represented by these is mentioned. Further, the carbonates of the above compounds have the general formula (VII)

[0020]

[Chemical 7]

[In the formula, R ¹ and R ² are the same as defined above. ] The compound represented by the general formula (VIII)

[0022]

[Chemical 8]

[In the formula, R ² and Ar ¹ are the same as defined above. ] The compound represented by the general formula (IX)

[0024]

[Chemical 9]

[In the formula, R ¹ and Ar ² are the same as defined above. ] The compound or general formula (X) represented by

[0026]

[Chemical 10]

[In the formula, Ar ¹ and Ar ² are the same as defined above. ] The compound represented by these is mentioned. In the present invention, as the dihydroxy compound as the component (A), the above compounds are appropriately selected and used. Among these, it is preferable to use bisphenol A which is an aromatic dihydroxy compound. When bisphenol A is used, an adduct of bisphenol A and phenol or a mixture of the adduct and phenol can be used.

On the other hand, in the present invention, there are various carbonic acid diesters used as the component (B). For example, it is at least one compound selected from diaryl carbonate compounds, dialkyl carbonate compounds or alkylaryl carbonate compounds. The diaryl carbonate compound used as one of the components (B) has the general formula (XI)

[0029]

[Chemical 11]

[In the formula, Ar ² is the same as described above. ] The compound or general formula (X) represented by

[0031]

[Chemical 12]

[In the formula, Ar ¹ and Ar ² are the same as defined above. ] It is a compound represented by these. The dialkyl carbonate compound has the general formula (XII)

[0033]

[Chemical 13]

[In the formula, R ² is the same as above. ] Or a compound represented by the general formula (VIII)

[0035]

[Chemical 14]

[In the formula, R ² and Ar ¹ are the same as defined above. ] It is a compound represented by these. The alkyl aryl carbonate compound has the general formula (XIII)

[0037]

[Chemical 15]

[In the formula, R ² and Ar ² are the same as defined above. ] Or a compound represented by the general formula (XIV)

[0039]

[Chemical 16]

[In the formula, R ² , Ar ¹ and Ar ² are the same as defined above. ] It is a compound represented by these. Here, examples of the carbonic acid diaryl compound include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, and bisphenol A bisphenyl carbonate.
Examples of the dialkyl carbonate compound include diethyl carbonate, dimethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, bisphenol A bismethyl carbonate and the like. Examples of the alkyl aryl carbonate compound include methylphenyl carbonate, ethylphenyl carbonate, butylphenyl carbonate, cyclohexylphenyl carbonate, bisphenol A methylphenyl carbonate and the like. In the present invention, as the carbonic acid diester as the component (B), the above compounds are appropriately selected and used. Among these, diphenyl carbonate is preferably used.

The production method of the present invention is to obtain a polycarbonate by a transesterification reaction using the components (A) and (B). In order to produce a polycarbonate by this transesterification reaction, in addition to the above-mentioned components (A) and (B), if necessary, the following terminal terminator can be used. Specific examples of such an end terminating agent include on-butylphenol; mn-
Butylphenol; pn-butylphenol; o-isobutylphenol; m-isobutylphenol; p-
Isobutylphenol; ot-butylphenol; m
-T-butylphenol; pt-butylphenol;
nn-pentylphenol; mn-pentylphenol; pn-pentylphenol; nn-hexylphenol; mn-hexylphenol; pn-hexylphenol; o-cyclohexylphenol; m
-Cyclohexylphenol; p-cyclohexylphenol; o-phenylphenol; m-phenylphenol; p-phenylphenol; nn-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

[0042]

[Chemical 17]

Examples of the compound represented by:

[0044]

[Chemical 18]

Examples thereof include monohydric phenols. Of these phenols, although not particularly limited in the present invention, p-tert-butylphenol; p-cumylphenol; p-phenylphenol and the like are preferable. Also, the formula

[0046]

[Chemical 19]

Examples thereof include compounds represented by Furthermore, in the present invention, phloroglucin; trimellitic acid; 1,1,1-tris (4-hydroxyphenyl) ethane; 1- [α-methyl-α- (4′-hydroxyphenyl) ethyl], if necessary. -4- [α ', α'-bis (4 "-hydroxyphenyl) ethyl] benzene; α,
α ′, α ″ -tris (4-hydroxyphenyl) -1,
3,5-triisopropylbenzene; isatin bis (o
-Cresol) or the like can be used as a branching agent.
Further, although a catalyst is not particularly required in the present invention, a known catalyst may be used for promoting the transesterification reaction. Specific examples of such a catalyst include simple substance of alkali metal or alkaline earth metal, oxide, hydroxide, amide compound, alcoholate, phenolate, or Zn.
Basic metal oxides such as O, PbO and Sb ₂ O ₃ , organic titanium compounds, soluble manganese compounds, Ca, Mg,
Acetates of Zn, Pb, Sn, Mn, Cd, Co or nitrogen-containing basic compounds and boron compounds, nitrogen-containing basic compounds and alkali (earth) metal compounds, nitrogen-containing basic compounds and alkali (earth) metals Examples thereof include a combined catalyst of a compound and a boron compound.

The production method of the present invention comprises the above-mentioned component (A),
When a polycarbonate is produced by a transesterification reaction using a terminal terminating agent, a branching agent or the like as the component (B) and other components, the reactor in which the transesterification reaction is carried out is preliminarily washed with an alkali and further washed with an acid. This is a major feature. Here, there are various reactors for carrying out the transesterification reaction, which may be appropriately selected and used depending on the situation. As the material of the reactor, stainless steel such as SUS304 and SUS316L, nickel, titanium nitride, or the like can be used. Particularly, nickel or titanium nitride is preferably used. In the present invention, when a transesterification reaction is carried out using a reactor made of such a material, the reactor is used after being washed with an alkali and then with an acid. The alkaline compound used for the alkali cleaning of this reactor is not particularly limited, and examples thereof include lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate and the like. These alkaline compounds are usually provided as an aqueous solution having a concentration of 0.001 to 2 N, preferably 0.01 to 1 N, and particularly preferably 0.05 to 0.5 N when the reactor is washed with alkali. It The acidic substance used for the acid washing is not particularly limited, but examples thereof include mineral acids such as hydrochloric acid, sulfuric acid and nitric acid. When acid-washing the reactor, these acidic substances are usually provided as an aqueous solution having a concentration of 0.001 to 2N, preferably 0.01 to 2N, and particularly preferably 0.05 to 1.5N. It

In the production method of the present invention, the reactor is preliminarily washed with an alkali using an aqueous solution of the alkaline compound and the acidic substance at a specified concentration, and further subjected to washing treatment in the order of acid washing, and then the transesterification reaction is carried out. . Various methods can be adopted for cleaning the reactor, and there is no particular limitation. For example, first, an aqueous solution of an alkaline compound is supplied to the reactor, and the mixture is thoroughly stirred at room temperature with a stirrer equipped in the reactor to wash with alkali, and then the aqueous solution of the alkaline compound is discarded. Next, an aqueous solution of the acidic substance is supplied, and after washing with an acid in the same manner, the aqueous solution of the acidic substance is discarded. Furthermore, after the alkaline cleaning and the acid cleaning, the reactor is thoroughly washed with water, for example, dry nitrogen gas is flowed and dried, and then the components (A) and (B) are supplied as the main components to carry out the transesterification reaction. By doing so, the desired polycarbonate can be obtained. In addition, as a method of alkali / acid cleaning, for example, a circulating method of an aqueous solution can be adopted. Without carrying out such alkali / acid cleaning, or only alkali cleaning or acid cleaning alone, the desired polycarbonate cannot be obtained. In the present invention, the reactor is cleaned in the order of alkali cleaning and acid cleaning, and further, if the contact parts such as the piping part, the auxiliary device, etc. in contact with the raw material or the produced polymer are alkali-acid cleaned, Be effective. Examples of these accessory devices and the like include, for example, stirring blades and shafts equipped in the reactor, instrumentation parts such as temperature sensors, piping parts or piping members adjacent to the reactor (for example, flanges, etc.)
Etc.

In the production method of the present invention, specifically, the reaction may be carried out under the above-mentioned conditions according to a known transesterification method. The procedure and conditions of the production method of the present invention will be specifically described below. That is, in the reactor which has been previously subjected to the alkali / acid washing treatment, sufficiently washed with water and dried as described above, first, the dihydroxy compound of the component (A) and the carbonic acid diester of the component (B) are added to the dihydroxy compound. Then, the carbonic acid diester is charged at a ratio of 1 to 1.5 times, and then a normal transesterification reaction is carried out. Depending on the situation, the amount of carbonic acid diester is 1.02 to 1.20, which is a slight excess with respect to the dihydroxy compound.
A double mole is preferable. In the above transesterification reaction, the amount of the terminal terminating agent composed of the monohydric phenol or the like is in the range of 0.05 mol% to 10 mol% with respect to 1 mol of the dihydroxy compound as the component (A). And, because the hydroxyl group terminal of the obtained polycarbonate is sealed,
A polycarbonate having excellent heat resistance and water resistance can be obtained. The total amount of such a terminal terminator composed of the monohydric phenol may be added to the reaction system in advance.
Further, it may be added in part to the reaction system in advance and the rest may be added as the reaction progresses. Moreover, in some cases,
After the transesterification reaction between the dihydroxy compound (A) and the carbonic acid diester (B) partially proceeds, the whole amount may be added to the reaction system.

In carrying out the transesterification reaction according to the method of the present invention, the reaction temperature is not particularly limited,
It is usually in the range of 100 ° C to 330 ° C, preferably 18 ° C.
A method of raising the temperature from 0 ° C to 300 ° C, more preferably 180 ° C to 300 ° C gradually according to the progress of the reaction is preferable. If the transesterification reaction is lower than 100 ° C., the progress of the reaction is slow, and if it exceeds 330 ° C., thermal deterioration of the polymer may occur, which may not be preferable. The reaction pressure is set according to the vapor pressure of the monomer used and the reaction temperature. This is not limited as long as it is set so that the reaction is efficiently performed. Usually, in the initial stage of the reaction, 1 to 50 atm (760 to 38,000 to
rr) to atmospheric pressure (normal pressure) or pressurized state,
In the latter half of the reaction, a reduced pressure condition, preferably finally
It is often set to 0.01 to 100 torr. Furthermore, the reaction time may be up to the target molecular weight, usually 0.2
It is about 10 hours.

The above reaction is carried out in the absence of an inert solvent, and if necessary, 1 to
It may also be carried out in the presence of 150% by weight of an inert solvent. Here, examples of the inert solvent include aromatic compounds such as diphenyl ether, halogenated diphenyl ether, benzophenone, polyphenyl ether, dichlorobenzene, and methylnaphthalene, carbon dioxide, gases such as dinitrogen monoxide and nitrogen, and chlorofluorohydrocarbons. Examples thereof include alkanes such as ethane and propane, cyclohexane, cycloalkanes such as tricyclo (5,2,10) -decane, cyclooctane and cyclodecane, and alkenes such as ethene and propene. In addition, in this invention, an antioxidant can be used as needed. Specific examples include phosphorus-based antioxidants such as tris (nonylphenyl) phosphite, trisphenylphosphite, 2-ethylhexyldiphenylphosphite, trimethylphosphite, triethylphosphite, tricresylphosphite, and triarylphosphite. There is.

In the present invention, as the reaction proceeds, phenols corresponding to the carbonic acid diester used,
Alcohols or their esters and inert solvent are desorbed from the reactor. These desorbed substances can be separated, purified and recycled for use, and it is preferable to have a facility for removing them. And, the present invention can be carried out batchwise or continuously, and any equipment can be used. In the case of continuous production, it is preferable to use at least two reactors and set the above reaction conditions. The reactor used in the present invention is provided with a coating of the above-mentioned material on its inner wall,
The structure is not particularly limited as long as it has a normal stirring function. However, since the viscosity increases in the latter stage of the reaction, it is preferable to have a high-viscosity stirring function. Further, the shape of the reactor is not limited to a tank type, and may be an extruder type reactor or the like.

The PC thus obtained may be granulated as it is, or may be molded by using an extruder or the like. Further, the PC obtained by the present invention can be used by blending well-known additives such as a plasticizer, a pigment, a lubricant, a release agent, a stabilizer and an inorganic filler. Further, the obtained PC can be blended with a polymer such as polyolefin, polystyrene, polyester, polysulfonate, polyamide and polyphenylene oxide. In particular, OH group, COOH group, NH ₂
It is effective when used in combination with a polyphenylene ether having a terminal group such as a group, a polyether nitrile, a terminal-modified polysiloxane compound, a modified polypropylene, and a modified polystyrene.

[0055]

The present invention will be further described in detail with reference to Examples and Comparative Examples. The present invention is not limited to the examples below. Example 1 A nickel steel autoclave (with a stirrer) having an internal volume of 1.4 liters was filled with a 0.1N aqueous sodium hydroxide solution, and stirred at room temperature for 30 minutes. Next, the sodium hydroxide aqueous solution was discarded, and then the solution was filled with a 1N hydrochloric acid aqueous solution and stirred in the same manner. Then, it was thoroughly washed with water and dried by flowing dry nitrogen. Bisphenol A was added to this autoclave.
228 g (1.0 mol) of (BPA) and 257 g (1.2 mol) of diphenyl carbonate were charged, and nitrogen substitution was carried out 5 times. Heat the mixture to 180 ° C and add bisphenol A
And melted the diphenyl carbonate. Then, as a catalyst, 2.5 mg (1 × 10 ⁻⁵ mol) of (C ₄ H ₉ ) ₄ NBH ₄ was used.
Was added, the temperature was raised to 220 ° C., stirring was started at the same time, and a small amount of nitrogen was passed through, and the produced phenol started to be distilled off. The temperature of the reaction product was maintained at 220 ° C. for 4 hours.
Thereafter, the temperature was gradually raised from 220 ° C. to 280 ° C. over 1 hour, and at the same time, the degree of vacuum was raised to remove the residual diphenyl carbonate and proceed with the transesterification reaction. Finally, with the pressure kept at 0.5 torr, 1
React with stirring for a while, and finally in the autoclave,
A viscous and transparent condensate (PC) was obtained. The viscous and transparent condensate obtained was dissolved in methylene chloride, and the viscosity average molecular weight was measured. Further, the obtained viscous and transparent condensate was crushed and pelletized at 270 ° C. using an extruder. The obtained pellets were injection-molded and subjected to YI, hydrolysis resistance and retention burn test.

Example 2 In Example 1, (C ₄ H ₉ ) ₄ NBH ₄ was used as a catalyst in 2.
0.2 mg of LiOH instead of ⁵ mg (1 × 10 ^-5 mol)
Example 1 was ^repeated except that (1 × 10 ⁻⁵ mol) was used. Example 3 The procedure of Example 1 was repeated, except that 6.8 g of p-cumylphenol (0.05 mol based on bisphenol A) was added as a terminal terminator. Example 4 The procedure of Example 1 was repeated, except that 28.2 g of diphenyl ether was added as an inert solvent and no catalyst was used. Example 5 The procedure of Example 1 was repeated, except that a titanium nitride autoclave was used instead of the nickel steel autoclave.

Comparative Example 1 The procedure of Example 1 was repeated except that the acid cleaning and the alkali cleaning of the autoclave were not performed. Comparative Example 2 The procedure of Example 1 was repeated, except that only the acid cleaning of the autoclave was performed. Comparative Example 3 The procedure of Example 1 was repeated, except that only the alkali cleaning of the autoclave was performed. Table 1 shows the measurement results of Examples 1 to 5 and Comparative Examples 1 to 3.

[0058]

[Table 1]

The viscosity average molecular weight measurement, YI, hydrolysis resistance and retention burn test were as follows. 1) Viscosity average molecular weight (Mv) The viscosity of a methylene chloride solution at 20 ° C was measured with an Ubbelohde type viscosity tube, and the intrinsic viscosity [η] was calculated from this, and then calculated by the following formula. [Η] = 1.23 × 10 ⁻⁵ × Mv ^0.83 2) YI (Yellow Index) Measured using a color meter SM-3 (manufactured by Suga Test Instruments Co., Ltd.) according to JIS K-7103-77. . 3) Hydrolysis resistance The plate (thickness 3 mm) was exposed to 121 ° C. steam for 48 hours, and then visually observed. 4) Residence burn test It was evaluated by the difference between YI when molded at 320 ° C. and YI when molded after being retained in the cylinder for 20 minutes.

[0060]

As described above, according to the present invention, when the transesterification reaction is carried out, the reactor is washed with an alkali in advance and further washed with an acid, so that the retention burn can be prevented without impairing the hydrolysis resistance. It is possible to produce a polycarbonate having excellent color tone as well as excellent quality. Therefore, the present invention can be effectively and widely used as a method for industrially producing a polycarbonate by a transesterification method.

Claims (2)

[Claims] 1. When a polycarbonate is produced from a (A) dihydroxy compound and a (B) carbonic acid diester by a transesterification method, a reactor for carrying out the transesterification reaction is washed with an alkali in advance and further washed with an acid before use. A method for producing a polycarbonate, comprising: 2. The method for producing a polycarbonate according to claim 1, wherein the material of the reactor for performing the transesterification reaction is nickel or titanium nitride.