WO2012132030A1

WO2012132030A1 - Control method for safe continuous manufacturing of polycarbonate oligomer

Info

Publication number: WO2012132030A1
Application number: PCT/JP2011/064828
Authority: WO
Inventors: 和宏関口; 広明茂木; 俊之安田
Original assignee: 出光興産株式会社
Priority date: 2011-03-31
Filing date: 2011-06-28
Publication date: 2012-10-04
Also published as: KR20140010091A; TWI503350B; JP2012214632A; CN102336899B; KR101823723B1; TW201239000A; CN102336899A; JP5775346B2

Abstract

A control method for safely manufacturing a polycarbonate oligomer, wherein the control method automatically detoxifies toxic phosgene without leakage to outside the system in the event of an abnormality.

Description

Control method for safe continuous production of polycarbonate oligomers

The present invention relates to a control method for safe continuous production of polycarbonate oligomer.

In general, as a method for producing polycarbonate, an interfacial method in which dihydric phenols (bisphenols) and phosgene are directly reacted and a transesterification method in which bisphenols and diphenyl carbonate are reacted under a solvent-free condition are known. The interface method has become the mainstream from the viewpoint of obtaining a polycarbonate with good quality (see, for example, Patent Document 1).
In the interfacial method, bisphenols, alkali compounds such as sodium hydroxide and phosgene are used as raw materials for polycarbonate, and a terminal terminator (molecular weight regulator) or the like is added as necessary. Further, in an industrial production plant for polycarbonate, phosgene is generally blown into an alkaline aqueous solution of bisphenols to produce a polycarbonate oligomer having a reactive chloroformate group. Polycarbonate is produced by reacting with an alkaline aqueous solution of bisphenols.

Patent Document 2 discloses a method of storing liquefied phosgene obtained by distillation purification of phosgene and producing a polycarbonate using the liquefied phosgene.
However, since phosgene is highly toxic, it is not desirable to store it from the viewpoint of safety. For example, when a liquefied phosgene storage tank is damaged due to corrosion or the like, there is a risk that phosgene leaks. Such risks can be reduced by installing phosgene abatement equipment, but it takes time to remove phosgene due to the large amount of phosgene held, but to eliminate it in a short time. Requires large-scale equipment and is costly.

Patent Document 3 discloses a continuous production method of a polycarbonate oligomer that is directly used for producing a polycarbonate oligomer without liquefying phosgene gas obtained by reacting chlorine and carbon monoxide. According to this method, the amount of phosgene retained in the system can be reduced as compared with the method using liquefied phosgene.

JP 2004-331916 A JP 2001-261321 A International Publication No. 2007/083721

However, in any of the above patent documents, it is not assumed that an accident such as the precipitation of the oligomer due to a trouble in the supply of the raw material to the oligomer reactor and the blockage of the inside of the reactor occurs. It does not disclose a method for producing polycarbonate while detoxifying without leaking outside.

The problem to be solved by the present invention is that in the method of continuously producing a polycarbonate oligomer during the production of polycarbonate, even when an abnormality occurs, the apparatus is automatically stopped and harmful phosgene is leaked out of the system. It is to provide a method for abatement without doing.

The said subject is solved by the control method of the following polycarbonate oligomer continuous manufacture.
Step (1) for continuously producing phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to the phosgene reactor, and phosgene gas continuously produced in step (1), divalent A method for controlling polycarbonate oligomer continuous production comprising the step (2) of continuously producing a reaction mixture containing a polycarbonate oligomer by continuously supplying an alkaline aqueous solution of phenol and an organic solvent to an oligomer reactor,
When the following conditions (i) and / or (ii) are satisfied, the supply of chlorine and carbon monoxide in the step (1) is stopped, the supply of phosgene gas to the oligomer reactor is stopped, and the phosgene gas A control method for continuous production of polycarbonate oligomers, wherein a toxic gas containing is transferred to a detoxifying means and rendered harmless.
Condition (i): Flow rate of solvent supplied to the oligomer reactor (F2 [kg / h]), alkaline aqueous solution flow rate of dihydric phenol compound (F3 [kg / h]), and dihydric phenol compound concentration (a [mass%]) When the value of the parameter <F2 / (F3 × a / 100)> using) is 3.27 or less.
Condition (ii): phosgene gas flow rate (F1 [kg / h]) supplied to the oligomer reactor, alkaline aqueous solution flow rate of dihydric phenol compound (F3 [kg / h]) and dihydric phenol compound concentration (a [mass%]) The value of the parameter <(F3 × a / 100) / F1> using) is 1.23 or less.

According to the method of the present invention, in the continuous production of polycarbonate oligomer by the interfacial method, even when an accident such as the oligomer being deposited due to the trouble of supplying the raw material to the oligomer reactor and the inside of the reactor clogging occurs, the phosgene raw material is used. The supply of certain chlorine and carbon monoxide and the supply of phosgene to the oligomer reactor are automatically stopped and the phosgene in the system is automatically controlled so as to be transferred to the detoxifying means, so that phosgene does not leak out of the system. Polycarbonate oligomer can be produced safely.

It is process drawing which shows the outline of one preferable embodiment of the control method of the polycarbonate oligomer continuous manufacture of this invention.

The method for controlling the continuous production of polycarbonate oligomer according to the present invention includes the flow rate of phosgene gas (F1), the flow rate of solvent (F2) supplied to the oligomer reactor, the flow rate of alkaline aqueous solution of dihydric phenol compound (F3). ) And dihydric phenol compound concentration (a [mass%]) are constantly monitored, and supply of chlorine and carbon monoxide as the phosgene raw material and oligomer reaction when the conditions (i) and / or (ii) described below are satisfied In this method, the supply of phosgene to the vessel is automatically stopped and the phosgene in the system is automatically controlled so as to be transferred to the abatement means.

[Manufacture of polycarbonate]
The method for controlling the continuous production of polycarbonate oligomer of the present invention is applied to an interfacial method in which a dihydric phenol and phosgene are directly reacted, and is applied in a continuous reaction system.
The method for continuously producing a polycarbonate oligomer in the present invention includes a step (1) of continuously supplying phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to a phosgene reactor, and the above-described step. Step (2) for continuously producing a reaction mixture containing a polycarbonate oligomer by continuously supplying the phosgene gas continuously produced in (1), an alkaline aqueous solution of dihydric phenol and an organic solvent to an oligomer reactor. It is a method including.

<Step (1)>
Step (1) is a step of continuously producing phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to the phosgene reactor.
From the viewpoint of the quality of the polycarbonate oligomer, carbon monoxide is preferably produced by reacting coke, petroleum, natural gas, alcohol or the like with oxygen and purified to a purity of 95% by volume or more. In particular, the sulfur component content is preferably 50 ppm or less. The chlorine (carbon monoxide) ratio (molar ratio) is preferably 1: 1.01 to 1: 1.3, more preferably 1: 1.02 to 1: 1.2.
The reaction can be carried out by a known method described in, for example, Japanese Patent Publication No. 55-14044. As the catalyst, a catalyst mainly composed of activated carbon can be used. Moreover, since the reaction is an exothermic reaction, it is preferable to cool the phosgene reactor and keep the reactor internal temperature at 350 ° C. or lower.

The phosgene gas obtained in step (1) usually contains unreacted carbon monoxide. The content of carbon monoxide in the phosgene gas is preferably 1 to 30% by volume, more preferably 2 to 20% by volume, from the viewpoint of cost and the quality of the polycarbonate oligomer. That is, phosgene gas having a purity of 99 to 70% by volume is preferable.

<Step (2)>
In the step (2), the phosgene gas continuously produced in the step (1), the alkaline aqueous solution of dihydric phenol and the organic solvent are continuously supplied to the oligomer reactor, and the reaction mixture containing the polycarbonate oligomer is continuously added. Manufacturing process.

Examples of raw materials in the production of polycarbonate include phosgene gas, dihydric phenols (bisphenols), alkali compounds used to dissolve dihydric phenols, and organic solvents. Polyhydric phenols and other additives may be used.
As the phosgene gas, the phosgene gas continuously produced in the step (1) is used.

As the dihydric phenols, 2,2-bis (4-hydroxyphenyl) propane (common name, bisphenol A; BPA) is preferable from the viewpoint of the physical properties of the polycarbonate. Examples of dihydric phenols other than bisphenol A include bis (4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) ethane; bis (1,2-bis (4-hydroxyphenyl) ethane, etc. 4-hydroxyphenyl) alkane, 1,1-bis (4-hydroxyphenyl) cyclohexane; bis (4-hydroxyphenyl) cycloalkane such as 1,1-bis (4-hydroxyphenyl) cyclodecane, 4,4′-dihydroxy Diphenyl, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) ether, bis (4 -Hydroxyphenyl) ketone, hydroxy Non etc. are mentioned. These dihydric phenols may be used individually by 1 type, and may mix and use 2 or more types.
Sodium hydroxide is preferred as the alkaline compound used to dissolve the dihydric phenols.
The alkaline aqueous solution of dihydric phenol is supplied after being adjusted to a predetermined concentration in advance. At this time, the concentration (a [mass%]) is monitored online using an analyzer such as titration. Although there is no restriction | limiting in particular in the measuring method, For example, the method etc. which obtain | require the density | concentration by titration using hydrochloric acid are mentioned.

The organic solvent only needs to dissolve the polycarbonate oligomer, and examples thereof include chlorinated solvents such as methylene chloride, dichloroethane, chloroform, chlorobenzene, and carbon tetrachloride, and cyclic oxy compounds such as dioxane. In the present invention, a chlorinated solvent is preferable, and methylene chloride is particularly preferably used from the viewpoint of the solubility of the polycarbonate oligomer. In addition to the organic solvents mentioned above, solvents such as alkanes called poor solvents may be used as long as the solubility of the polycarbonate oligomer is not lowered.
An organic solvent may be used individually by 1 type, and may mix and use 2 or more types.

Examples of the monohydric phenol used as the molecular weight regulator include phenol, p-cresol, p-tert-butylphenol, p-tert-octylphenol, p-cumylphenol, nonylphenol and the like. Of these, p-tert-butylphenol and phenol are preferable from the viewpoints of cost and availability.

For the production of the polycarbonate oligomer, a polymerization catalyst such as a tertiary amine or a quaternary amine can be used as necessary. As the polymerization catalyst, TEA (triethylamine) is preferable.
As the oligomer reactor, a continuous reaction type reactor is used, and a reactor having a tubular structure having a mixing section for mixing reaction raw materials is preferably used.
The oligomer reactor is installed in the building and isolated from the outside. The inside of the building is constantly changing air, and the ventilation air inside is sent to the abatement means by a blower or the like.

The amount of raw material supplied to the oligomer reactor and the reaction conditions in the step (2) are appropriately determined depending on the scale of the apparatus and the production amount.
As an example, preferable conditions for producing about 200 kg of polycarbonate oligomer per hour will be described below, but the present invention is not limited thereto. The flow rate (F1) of the phosgene gas obtained by the step (1) is preferably 3.7 to 4.1 kg / h. The flow rate (F2) of an organic solvent such as methylene chloride is preferably 20 to 24 kg / h. The temperature of the phosgene gas is preferably in the range of the boiling point of phosgene (7.8 ° C.) to 90 ° C. As the alkaline aqueous solution of dihydric phenol, a sodium hydroxide aqueous solution of bisphenol A is preferable, and is adjusted and supplied in advance to have a predetermined concentration. In the aqueous sodium hydroxide solution of bisphenol A, the preferred bisphenol A concentration (a) is 12.5 to 14.0% by mass, and the preferred sodium hydroxide concentration is 5.1 to 6.1% by mass. The flow rate (F3) of the aqueous sodium hydroxide solution of bisphenol A is preferably 42 to 46 kg / h.

In step (2), a reaction mixture containing a polycarbonate oligomer having a chloroformate group is obtained. The properties of the polycarbonate oligomer are not particularly limited, and the reaction conditions may be set as appropriate so that the properties are appropriate, but the molecular weight measured by a VPO (vapor pressure osmometer) is about 600 to 5000. Those are preferred.

The reaction mixture containing the polycarbonate oligomer is a mixture of an organic phase in which the polycarbonate oligomer is dissolved in the organic solvent and an aqueous phase containing an alkaline aqueous solution. A polycarbonate can be produced by introducing this reaction mixture into a condensation reactor and subjecting it to a condensation reaction.
In addition, after the condensation reaction is completed, the reaction solution is washed by a known method, concentrated, and pulverized to obtain a powdery polycarbonate, which is further pelletized by processing with an extruder or the like. can do.

[Control method for continuous production of polycarbonate oligomer]
A predetermined amount of phosgene gas, an aqueous alkali solution of dihydric phenol, and an organic solvent are continuously supplied to the oligomer reactor. The supply pressure of phosgene gas and the inlet pressure in the oligomer reactor are appropriately set according to the size, shape, etc. of the phosgene reactor and oligomer reactor. Usually, the supply pressure (P1) of phosgene gas is 0.4 to 0.00. Continuous operation was performed so that the pressure in the oligomer reactor was 5 MPaG, the inlet pressure (P2) in the oligomer reactor was 0.15 to 0.35 MPaG, and the pressure difference between the two (P1−P2) was 0.105 MPa to 0.35 MPa. The

In the method for controlling the continuous production of polycarbonate oligomer of the present invention, the phosgene gas flow rate (F1), the solvent flow rate (F2), the alkaline aqueous solution flow rate (F3) of the dihydric phenol compound and the dihydric phenol compound concentration (a [ Mass%]) is constantly monitored whether the following conditions (i) and / or (ii) are satisfied, and when the conditions are satisfied, the automatic system stops the production and supply of phosgene, Toxic gas containing phosgene gas is transferred to the detoxification means to make it harmless.
Condition (i): Flow rate of solvent supplied to the oligomer reactor (F2 [kg / h]), alkaline aqueous solution flow rate of dihydric phenol compound (F3 [kg / h]), and dihydric phenol compound concentration (a [mass%]) When the value of the parameter <F2 / (F3 × a / 100)> using) is 3.27 or less.
Condition (ii): phosgene gas flow rate (F1 [kg / h]) supplied to the oligomer reactor, alkaline aqueous solution flow rate of dihydric phenol compound (F3 [kg / h]) and dihydric phenol compound concentration (a [mass%]) The value of the parameter <(F3 × a / 100) / F1> using) is 1.23 or less.

<Condition (i)>
Condition (i) is that the solvent flow rate (F2 [kg / h]) supplied to the oligomer reactor, the alkaline aqueous solution flow rate of the dihydric phenol compound (F3 [kg / h]) and the dihydric phenol compound concentration (a [mass%] ]) Using the parameter <F2 / (F3 × a / 100)> is 3.27 or less. This parameter defines the balance between the solvent flow rate supplied to the oligomer reactor and the alkaline aqueous solution flow rate of the dihydric phenol compound.

A predetermined amount of phosgene gas, an alkaline aqueous solution of dihydric phenol, and an organic solvent are continuously supplied to the oligomer reactor. However, when the solvent supply amount is insufficient due to a trouble such as a solvent supply pump, the polycarbonate produced in the oligomer reactor There is a possibility that the oligomer concentration becomes high, and as a result, the polycarbonate oligomer precipitates and closes the outlet of the oligomer reactor. Then, the pressure in the oligomer reactor rises, the solvent or oligomer raw material flows back into the phosgene reactor, the operating pressure rises above the design pressure due to evaporation of the solvent, etc., and there is a risk that phosgene leaks out of the system .
Therefore, in the present invention, from the viewpoint of safety, the flow rate of the solvent supplied to the oligomer reactor (F2 [kg / h]), the alkaline aqueous solution flow rate of the dihydric phenol compound (F3 [kg / h]), and the dihydric phenol compound The automatic system is activated when the value of the parameter <F2 / (F3 × a / 100)> using the concentration (a [mass%]) becomes 3.27 or less. However, if the automatic system is frequently started due to temporary troubles, etc., it will be difficult to operate efficiently. From the viewpoint of operating efficiently while ensuring safety, the automatic system May be set when the value of the parameter <F2 / (F3 × a / 100)> is 2.52 or less, and may be set when the value is 2.43 or less.

During normal operation, the value of the parameter <F2 / (F3 × a / 100)> is preferably 3.30 to 4.60, more preferably 3.60 to 4 from the viewpoint of productivity and the like. .10.

<Condition (ii)>
Condition (ii) is as follows: the flow rate of phosgene gas supplied to the oligomer reactor (F1 [kg / h]), the flow rate of alkaline aqueous solution of dihydric phenol compound (F3 [kg / h]), and the concentration of dihydric phenol compound (a [mass%) ]) Using the parameter <(F3 × a / 100) / F1> is 1.23 or less. This parameter defines the balance between the phosgene gas flow rate supplied to the oligomer reactor and the alkaline aqueous solution flow rate of the dihydric phenol compound.

The oligomer reactor is continuously supplied with a predetermined amount of phosgene gas, an alkaline aqueous solution of dihydric phenol, and an organic solvent. However, when the supply amount of the alkaline aqueous solution of dihydric phenol is insufficient due to a trouble such as a dihydric phenol compound supply pump. Some phosgene is not consumed in the oligomer reactor, but flows unreacted to the downstream process, and there is a risk that phosgene leaks out of the system.
Therefore, in the present invention, from the viewpoint of safety, the phosgene gas flow rate (F1 [kg / h]) supplied to the oligomer reactor, the alkaline aqueous solution flow rate (F3 [kg / h]) of the dihydric phenol compound, and the dihydric phenol compound When the value of the parameter <(F3 × a / 100) / F1> using the concentration (a [mass%]) becomes 1.23 or less, the automatic system is activated. However, if the automatic system is frequently started due to temporary troubles, etc., it will be difficult to operate efficiently. From the viewpoint of operating efficiently while ensuring safety, the automatic system May be set when the value of the parameter <(F3 × a / 100) / F1> is 1.05 or less, and may be set when the value is 1.00 or less.

During normal operation, the value of the parameter <(F3 × a / 100) / F1> is preferably 1.28 to 2.00, more preferably 1.40 to 1 from the viewpoint of productivity and the like. .80.

In the method for controlling the continuous production of polycarbonate oligomer of the present invention, when the above conditions (i) and / or (ii) are satisfied, the following operations (a), (b) and (c) are automatically performed: Prevents toxic phosgene leakage and renders it harmless.
(A) The supply of chlorine and carbon monoxide in the step (1) for continuously producing phosgene gas is stopped. This is an operation of stopping the production of phosgene gas for the purpose of not increasing the amount of phosgene gas in the system.
(B) The supply of phosgene gas to the oligomer reactor is stopped. This is an operation for preventing leakage of phosgene because a part of phosgene may flow into a downstream process without being consumed in the oligomer reactor without being consumed.
(C) Toxic gas containing phosgene gas in the system is transferred to an abatement means and rendered harmless. This is an operation of detoxifying the phosgene gas in the system from the viewpoint of higher safety, in addition to preventing the increase and leakage of phosgene by the above operations (a) and (b) and confining it in the system. .

<Disinfection means>
The detoxifying means is equipment for detoxifying toxic gas containing phosgene gas with a detoxifying agent, and a known one can be used. Specific examples include a spraying device for a pesticide, an absorption tower for bringing a toxic gas into contact with the pesticide, and the like. In addition, tower-type detoxification equipment described in JP-A-6-319946, JP-A-2005-305414 and the like can also be used.

For acidic gases such as phosgene and chlorine, alkaline substances are used as a detoxifying agent. The alkaline substance used as the detoxifying agent is not particularly limited, but sodium hydroxide and potassium hydroxide are generally used. These are usually used as an aqueous solution.

When the detoxification means is a detoxification tower, the structure of the detoxification tower is not particularly limited, but as a typical example, the detoxifying agent is sprayed from the top of the tower in the form of a shower, etc. There are those that are removed by contact with gas. In order to improve the contact efficiency between the detoxifying agent and the gas, a filler such as Raschig ring may be filled between the detoxifying agent injection port and the gas inflow port. The number of detoxification towers is not particularly limited, and the toxic gas concentration in the detoxification treatment gas is preferably reduced to a level that is not detected so that the concentration is less than or equal to a predetermined concentration defined by environmental standards. Designed to.

Detoxification means always operate in case of unforeseen circumstances even if no toxic gas leaks. In addition, the ventilation air in the building where the oligomer reactor is installed is sent to an abatement means by a blower or the like to be rendered harmless and then released to the outside.

A preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a process diagram showing an outline of a preferred embodiment of the method for controlling the continuous production of polycarbonate oligomer of the present invention.
During normal operation, phosgene production raw material chlorine and carbon monoxide are supplied to the phosgene reactor through a control valve, and phosgene gas is produced in the phosgene reactor. Since the reaction is exothermic, the phosgene reactor is cooled by cooling water.
Phosgene gas (reaction product) containing unreacted carbon monoxide is introduced into the oligomer reactor through a control valve. In addition to phosgene gas, an alkaline aqueous solution of dihydric phenol (specifically, for example, a sodium hydroxide aqueous solution of bisphenol A) and an organic solvent (specifically, for example, methylene chloride) are also introduced into the oligomer reactor. By this reaction, an emulsion solution containing a polycarbonate oligomer is produced.
In addition, the control valve provided in the supply path of chlorine and carbon monoxide automatically controls these flow rates, and the control valve provided in the supply path to the oligomer reactor of phosgene gas supplies to the oligomer reactor. The supply pressure of phosgene gas is controlled.

The phosgene gas flow rate (F1), the solvent flow rate (F2), and the alkaline aqueous solution flow rate (F3) of the dihydric phenol compound supplied to the oligomer reactor are constantly monitored using a flow meter. In addition, the dihydric phenol alkaline aqueous solution has the dihydric phenol compound concentration (a) adjusted in advance to a predetermined concentration, and the concentration (a) is constantly monitored using a densitometer. These data are sent to the automatic control device (dotted arrows in the figure), and the automatic control device calculates the parameters defined in the above conditions (i) and (ii) based on the sent data. Is done.
When an abnormal situation occurs, that is, when the above condition (i) and / or (ii) is satisfied with respect to the parameter, the control valve provided in the supply path of chlorine and carbon monoxide from the automatic control device Signals are sent all at once to the control valve provided in the supply path to the oligomer reactor of phosgene gas and the control valve provided in the flow path to the abatement apparatus (thick solid line arrow in the figure).
The control valve provided in the supply path for chlorine and carbon monoxide is closed by a signal from the automatic control device, and the supply of chlorine and carbon monoxide is stopped. Moreover, the control valve provided in the supply path to the oligomer reactor of phosgene gas is closed, and the supply of phosgene gas to the oligomer reactor is stopped.
The control valve provided in the flow path to the abatement device is closed during normal operation, but is opened by a signal from the automatic control device, and toxic gas including phosgene gas in the system is transferred to the abatement device. . In the abatement apparatus, toxic gas including phosgene gas is rendered harmless.

The preferred embodiment of the present invention has been described above with reference to the drawings, but the present invention is not limited to this. For example, although not shown in FIG. 1, a shutoff valve for stopping fluid supply may be provided in addition to the control valve.

Hereinafter, the present invention will be more specifically described based on examples, but the present invention is not limited to these examples.

Example 1-1
(Automatic control device)
As shown in FIG. 1, the solvent flow rate (F2 [kg / h]) supplied to the oligomer reactor, the alkaline aqueous solution flow rate of the dihydric phenol compound (F3 [kg / h]), and the dihydric phenol compound concentration (a [mass] %]) When the value of the parameter <F2 / (F3 × a / 100)> is 3.27 or less (condition (i)) or the phosgene gas flow rate (F1 [kg / h]), the value of the parameter <(F3 × a / 100) / F1> using the flow rate of the alkaline aqueous solution of the dihydric phenol compound (F3 [kg / h]) and the concentration of the dihydric phenol compound (a [mass%]) Is 1.23 or less (condition (ii)), the control valve provided in the supply path for chlorine and carbon monoxide and the control valve provided in the supply path for the oligomer reactor of phosgene gas are closed. And We designed an automatic control device that performs control to open the control valve provided in the flow path to the abatement device.

(Abatement equipment)
As the abatement apparatus, an abatement tower having a tower diameter of 600 mm and a packed bed height of 10 m packed with Cascade Mini Ring (CMR) (trade name, manufactured by Matsui Machine Co., Ltd.) was used. A sodium hydroxide aqueous solution having a concentration of 10% by mass was circulated at 2 m ³ / h as a detoxifying agent in the detoxifying tower. Sodium hydroxide aqueous solution was supplied from the top of the tower, and toxic gas was supplied from the bottom.

(Manufacture of phosgene)
As the phosgene reactor, a shell and tube reactor in which a commercially available granular activated carbon (coconut shell activated carbon pulverized to a diameter of 1.2 to 1.4 mm) was filled in a tube was used.
Carbon monoxide 1.2 kg / h and chlorine 2.8 kg / h were supplied to the phosgene reactor to produce phosgene gas 3.9 kg / h. 90 ° C. water was passed through the shell portion of the phosgene reactor to remove heat of reaction.

(Production of polycarbonate oligomer)
As the oligomer reactor, a tubular reactor having an inner diameter of 6 mm and a length of 30 m was used. The oligomer reactor was immersed in a cooling bath at 20 ° C. The phosgene gas was continuously supplied from the upstream phosgene production process to the oligomer reactor, and the supply pressure of the phosgene gas supplied to the oligomer reactor was set to 0.45 MPaG.
Concentration (a) obtained by dissolving bisphenol A (BPA) in phosgene gas and 6% strength by weight sodium hydroxide aqueous solution in an oligomer reactor, 13.5% by weight BPA aqueous sodium hydroxide solution, methylene chloride, for molecular weight adjustment A methylene chloride solution of p-tert-butylphenol having a concentration of 25% by mass was fed to prepare a polycarbonate oligomer solution. At this time, the supply flow rate (F1) of phosgene gas was 3.9 kg / h, the supply flow rate (F3) of the BPA sodium hydroxide aqueous solution was 44 kg / h, the supply flow rate (F2) of methylene chloride was 22 kg / h, p-tert- The supply flow rate of the methylene chloride solution of butylphenol was 0.46 kg / h. The value of F2 / (F3 × a / 100) is 3.70, and the value of (F3 × a / 100) / F1 is 1.52. The inlet pressure in the oligomer reactor was 0.20 MPaG.

Here, the methylene chloride flow rate (F2) supplied to the oligomer reactor was decreased to 19.3 kg / h, and the value of F2 / (F3 × a / 100) was intentionally set to 3.25.
As a result, the automatic control device stops the supply of chlorine and carbon monoxide to the phosgene reactor and the supply of phosgene gas to the oligomer reactor, and the phosgene gas generated in the phosgene reactor is removed from the abatement device. It was transferred to. When components were measured for the gas discharged from the exit of the detoxification tower, phosgene was not detected and was rendered harmless.

Example 1-2
Example 1 except that the methylene chloride flow rate (F2) supplied to the oligomer reactor was reduced to 14.9 kg / h and the value of F2 / (F3 × a / 100) was intentionally 2.51. Polycarbonate oligomer was produced in the same manner as -1.
As a result, as in Example 1-1, the supply of chlorine and carbon monoxide to the phosgene reactor was stopped and the supply of phosgene gas to the oligomer reactor was stopped by the automatic controller, and the phosgene reaction The phosgene gas generated in the vessel was transferred to the abatement device. When components were measured for the gas discharged from the exit of the detoxification tower, phosgene was not detected and was rendered harmless.

Example 1-3
Example 1 except that the methylene chloride flow rate (F2) supplied to the oligomer reactor was decreased to 14.4 kg / h and the value of F2 / (F3 × a / 100) was intentionally set to 2.42. Polycarbonate oligomer was produced in the same manner as -1.
As a result, as in Example 1-1, the supply of chlorine and carbon monoxide to the phosgene reactor was stopped and the supply of phosgene gas to the oligomer reactor was stopped by the automatic controller, and the phosgene reaction The phosgene gas generated in the vessel was transferred to the abatement device. When components were measured for the gas discharged from the exit of the detoxification tower, phosgene was not detected and was rendered harmless.

Comparative Example 1-1
A polycarbonate oligomer was produced in the same manner as in Example 1-1 except that the automatic controller was not used.
However, when the automatic control was not performed, the pressure in the oligomer reactor rapidly increased. If the operation is continued further, the reaction liquid inside the oligomer reactor flows backward to the phosgene reactor, the methylene chloride evaporates and the pressure in the phosgene reactor rises, the phosgene reactor breaks down, and the phosgene becomes a system. This operation was canceled because it was assumed to leak outside.

Example 2-1
The BPA sodium hydroxide aqueous solution flow rate (F3) supplied to the oligomer reactor was decreased to 35.5 kg / h, and the value of (F3 × a / 100) / F1 was intentionally set to 1.23, A polycarbonate oligomer was produced in the same manner as in Example 1-1.
As a result, as in Example 1-1, the supply of chlorine and carbon monoxide to the phosgene reactor was stopped and the supply of phosgene gas to the oligomer reactor was stopped by the automatic controller, and the phosgene reaction The phosgene gas generated in the vessel was transferred to the abatement device. When components were measured for the gas discharged from the exit of the detoxification tower, phosgene was not detected and was rendered harmless.

Example 2-2
The BPA sodium hydroxide aqueous solution flow rate (F3) supplied to the oligomer reactor is decreased to 30.1 kg / h, and the value of (F3 × a / 100) / F1 is intentionally set to 1.04, A polycarbonate oligomer was produced in the same manner as in Example 2-1.
As a result, as in Example 2-1, the automatic control device stopped the supply of chlorine and carbon monoxide to the phosgene reactor and the supply of phosgene gas to the oligomer reactor, and the phosgene reaction The phosgene gas generated in the vessel was transferred to the abatement device. When components were measured for the gas discharged from the exit of the detoxification tower, phosgene was not detected and was rendered harmless.

Example 2-3
The BPA sodium hydroxide aqueous solution flow rate (F3) supplied to the oligomer reactor was decreased to 28.7 kg / h, and the value of (F3 × a / 100) / F1 was intentionally set to 0.99, A polycarbonate oligomer was produced in the same manner as in Example 2-1.
As a result, as in Example 2-1, the automatic control device stopped the supply of chlorine and carbon monoxide to the phosgene reactor and the supply of phosgene gas to the oligomer reactor, and the phosgene reaction The phosgene gas generated in the vessel was transferred to the abatement device. When components were measured for the gas discharged from the exit of the detoxification tower, phosgene was not detected and was rendered harmless.

Comparative Example 2-1
A polycarbonate oligomer was produced in the same manner as in Example 2-1, except that the automatic controller was not used.
However, if automatic control is not performed, since the BPA sodium hydroxide aqueous solution flow rate is smaller than the phosgene gas flow rate supplied to the oligomer reactor, a phosgene gas having a stoichiometric ratio or more is supplied to the oligomer reactor. This operation was stopped because it was assumed that phosgene leaked out of the system by flowing into the downstream process without being consumed without being consumed.

According to the method of the present invention, a polycarbonate oligomer can be continuously produced safely. In particular, even when an accident such as oligomer precipitation due to a raw material supply trouble to the oligomer reactor occurs and the inside of the reactor is blocked, the production and supply of phosgene is stopped urgently by automatic control. Toxic gas containing phosgene gas is made harmless, and toxic gas does not leak out of the system.

Claims

Step (1) for continuously producing phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to the phosgene reactor, and phosgene gas continuously produced in step (1), divalent A method for controlling polycarbonate oligomer continuous production comprising the step (2) of continuously producing a reaction mixture containing a polycarbonate oligomer by continuously supplying an alkaline aqueous solution of phenol and an organic solvent to an oligomer reactor,
When the following conditions (i) and / or (ii) are satisfied, the supply of chlorine and carbon monoxide in the step (1) is stopped, the supply of phosgene gas to the oligomer reactor is stopped, and the phosgene gas A control method for continuous production of polycarbonate oligomers, wherein a toxic gas containing is transferred to a detoxifying means and rendered harmless.
Condition (i): Flow rate of solvent supplied to the oligomer reactor (F2 [kg / h]), alkaline aqueous solution flow rate of dihydric phenol compound (F3 [kg / h]), and dihydric phenol compound concentration (a [mass%]) When the value of the parameter <F2 / (F3 × a / 100)> using) is 3.27 or less.
Condition (ii): phosgene gas flow rate (F1 [kg / h]) supplied to the oligomer reactor, alkaline aqueous solution flow rate of dihydric phenol compound (F3 [kg / h]) and dihydric phenol compound concentration (a [mass%]) The value of the parameter <(F3 × a / 100) / F1> using) is 1.23 or less.
The method for controlling the continuous production of polycarbonate oligomer according to claim 1, wherein the detoxifying means is a means for detoxifying the toxic gas containing phosgene gas by contacting with an alkaline aqueous solution.