JP5775345B2 - Control method for continuous production of polycarbonate oligomer - Google Patents

Description

  The present invention relates to a method for controlling the continuous production of polycarbonate oligomers.

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 Pamphlet

  However, in any of the above-mentioned patent documents, there was an accident in which the pressure in the oligomer reactor was abnormal, such as an oligomer being deposited due to a reaction abnormality or an organic solvent supply trouble to the oligomer reactor, and the reactor was blocked. The case is not assumed, and a method for producing polycarbonate while detoxifying harmful phosgene without leaking out of the system is not disclosed.

  The problem of the present invention is that the polycarbonate oligomer is continuously produced in the production of polycarbonate, and even in the event of an abnormality, the apparatus is automatically stopped and harmful phosgene is removed without leaking out of the system. It is to provide a way to harm.

The problems of the present invention are solved by the following method for controlling the continuous production of polycarbonate oligomers.
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): The value of the pressure difference (P1-P2) between the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor becomes 0.1 MPa or less.
Condition (ii): When the inlet pressure (P2) in the oligomer reactor becomes 0.13 MPaG or less.

  According to the method of the present invention, in the continuous production of polycarbonate oligomers by the interfacial method, even when an accident such as the occurrence of a reaction abnormality or an organic solvent supply trouble to the oligomer reactor causes the oligomer to precipitate and the reactor is blocked. In addition to automatically stopping the supply of chlorine and carbon monoxide as phosgene raw materials and the supply of phosgene to the oligomer reactor, the phosgene is automatically controlled to transfer the phosgene in the system to the detoxifying means, and phosgene is removed from the system. Polycarbonate oligomer can be produced safely without leakage.

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 of the present invention constantly monitors the pressure (P1) of phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor in the continuous production of polycarbonate oligomer by the interfacial method. When conditions (i) and / or (ii) described later are satisfied, supply of chlorine and carbon monoxide as phosgene raw materials and supply of phosgene to the oligomer reactor are automatically stopped and phosgene in the system is removed. It is a method of automatic control so that it is transferred to the harm 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 ratio of chlorine to carbon monoxide (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 the 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 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 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. Among 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. A preferable flow rate of the phosgene gas obtained by the step (1) is 3.7 to 4.1 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 is 12.5 to 14.0% by mass, and the preferred sodium hydroxide concentration is 5.1 to 6.1% by mass. A preferable flow rate of the aqueous sodium hydroxide solution of bisphenol A is 42 to 46 kg / h. The flow rate of the organic solvent such as methylene chloride is preferably 20 to 24 kg / h.

  In step (2), a reaction mixture containing a polycarbonate oligomer having a chloroformate group is obtained. The property of the polycarbonate oligomer is not particularly limited, and reaction conditions may be set as appropriate so that the optimum property is obtained. The molecular weight measured with a VPO (vapor pressure osmometer) is about 600 to 5,000. 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 (P1) of the phosgene gas and the inlet pressure (P2) in the oligomer reactor are appropriately set depending on the size, shape, etc. of the phosgene reactor and the oligomer reactor. Usually, the supply pressure (P1) of the phosgene gas is 0.4 to 0.5 MPaG, the inlet pressure (P2) in the oligomer reactor is 0.15 to 0.35 MPaG, and the pressure difference between them (P1−P2) is 0.105 MPa to 0.35 MPa. It is continuously operated to become.
In the control method for continuous production of polycarbonate oligomer of the present invention, the following conditions (i) and / or (ii) are used for the pressure (P1) of phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor. If the conditions are met, the production and supply of phosgene will be stopped by the automatic system, and the toxic gas containing phosgene gas in the system will be transferred to the detoxification means to make it harmless. .
Condition (i): The value of the pressure difference (P1-P2) between the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor becomes 0.1 MPa or less.
Condition (ii): When the inlet pressure (P2) in the oligomer reactor becomes 0.13 MPaG or less.

<Condition (i)>
Condition (i) is when the pressure difference (P1-P2) between the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor is 0.1 MPa or less. It is.
For example, when the organic solvent cannot be supplied with a pump that supplies the organic solvent due to some trouble, or when the supply amount decreases, the concentration of the polycarbonate oligomer increases in the oligomer reactor, and the generated polycarbonate oligomer precipitates to form the oligomer. When the reactor outlet is blocked, the pressure in the oligomer reactor increases. As a result, 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, and there is a risk that phosgene leaks out of the system.
Therefore, in the present invention, from the viewpoint of safety, when the value of the pressure difference (P1-P2) between the supply pressure (P1) of the phosgene gas and the inlet pressure (P2) in the oligomer reactor becomes 0.1 MPa or less. Start the automated system. 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 pressure difference (P1-P2) value is 0.09 MPa or less, and may be set when the value is 0.049 MPa or less.

<Condition (ii)>
Condition (ii) is when the inlet pressure (P2) in the oligomer reactor becomes 0.13 MPaG or less.
The inlet pressure drop in the oligomer reactor is expected to be caused by poor supply of organic solvent or alkaline aqueous solution of dihydric phenol, poor reaction, etc., so that some phosgene is not consumed in the oligomer reactor and unreacted As it flows to the downstream process, the danger of phosgene leaking out of the system and the generated polycarbonate oligomers precipitate, block the outlet of the oligomer reactor, and the organic solvent and oligomer raw material flow back to the phosgene reactor. This indicates that there is a risk that phosgene leaks out of the system due to the operating pressure rising above the design pressure due to evaporation or the like.
Therefore, in the present invention, from the viewpoint of safety, the automatic system is started when the inlet pressure (P2) in the oligomer reactor becomes 0.13 MPaG 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 inlet pressure (P2) in the oligomer reactor is 0.12 MPaG or less, and may be set when the pressure is 0.049 MPaG or less.

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 the leakage of toxic phosgene 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. Also, tower-type abatement equipment described in JP-A-6-319946 and JP-A-2005-305414 can be used.

  For acidic gases such as phosgene and chlorine, an alkaline substance is 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.

  The abatement means is always operated in preparation for 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 pressure (P1) of the phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor are constantly monitored using a pressure gauge, and the values are sent to the automatic controller (see FIG. Middle dotted arrow).
When an abnormal situation occurs, that is, when the above conditions (i) and / or (ii) are satisfied for the pressures (P1) and (P2), supply of chlorine and carbon monoxide from the automatic control device Signals are sent all at once to the control valve provided in the passage, the control valve provided in the supply passage to the oligomer reactor of phosgene gas, and the control valve provided in the flow path to the abatement device (the thicker in the figure). Solid arrows).
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.

  As mentioned above, although one preferable embodiment of this invention was described referring drawings, this 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 described more specifically 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 pressure (P1) of phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor are monitored by a pressure gauge, and the supply pressure (P1) of phosgene gas supplied to the oligomer reactor is monitored. ) And the pressure difference (P1-P2) of the inlet pressure (P2) in the oligomer reactor becomes 0.1 MPa or less (condition (i)) or the inlet pressure (P2) in the oligomer reactor is 0. When the pressure is less than 13 MPaG (condition (ii)), the control valve provided in the chlorine and carbon monoxide supply passage and the control valve provided in the supply passage to the oligomer reactor of phosgene gas are closed, and In addition, an automatic control device was designed to perform control so as 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 filled with commercially available granular activated carbon (coconut shell activated carbon pulverized to a diameter of 1.2 to 1.4 mm) 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 (P1) of the phosgene gas supplied to the oligomer reactor was set to 0.45 MPaG.
In the oligomer reactor, phosgene gas 3.9 kg / h, bisphenol A (BPA) dissolved in 6% strength by weight sodium hydroxide aqueous solution, obtained by dissolving 13.5% by weight BPA aqueous sodium hydroxide 44 kg / h, chloride A methylene chloride solution (0.46 kg / h) of p-tert-butylphenol having a concentration of 25% by weight for adjusting the molecular weight was supplied to prepare a polycarbonate oligomer solution. At this time, the inlet pressure (P2) in the oligomer reactor was 0.20 MPaG.

Here, by restricting the outlet valve of the oligomer reactor, the pressure in the oligomer reactor is intentionally increased, the inlet pressure (P2) in the oligomer reactor is set to 0.35 MPaG, and the oligomer reactor is supplied to the oligomer reactor. The value of the pressure difference (P1-P2) between the supply pressure (P1) of phosgene gas and the inlet pressure (P2) in the oligomer reactor was set to 0.1 MPa.
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
By restricting the outlet valve of the oligomer reactor, the pressure in the oligomer reactor is intentionally increased, the inlet pressure (P2) in the oligomer reactor is set to 0.36 MPaG, and phosgene gas supplied to the oligomer reactor is supplied. A polycarbonate oligomer was produced in the same manner as in Example 1-1 except that the pressure difference (P1-P2) between the pressure (P1) and the inlet pressure (P2) in the oligomer reactor was 0.09 MPa. It was.
As a result, as in Example 1-1, the automatic control device stopped the supply of chlorine and carbon monoxide to the phosgene reactor, stopped 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 1-3
By restricting the outlet valve of the oligomer reactor, the pressure in the oligomer reactor is intentionally increased so that the inlet pressure (P2) in the oligomer reactor is 0.41 MPaG, and phosgene gas is supplied to the oligomer reactor. A polycarbonate oligomer was produced in the same manner as in Example 1-1 except that the pressure difference (P1-P2) between the pressure (P1) and the inlet pressure (P2) in the oligomer reactor was 0.04 MPa. It was.
As a result, as in Example 1-1, the automatic control device stopped the supply of chlorine and carbon monoxide to the phosgene reactor, stopped 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 1-1
The pressure inside the oligomer reactor was intentionally increased by not using the automatic controller and by restricting the outlet valve of the oligomer reactor, so that the inlet pressure (P2) in the oligomer reactor was 0.40 MPaG. Example 1 except that the pressure difference (P1-P2) between the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor was 0.05 MPa. In the same manner as in Example 1, an attempt was made to produce a polycarbonate oligomer.
However, when the outlet valve of the oligomer reactor was gradually throttled, the pressure in the oligomer reactor suddenly increased. If the operation of further reducing the outlet valve of the oligomer reactor is continued, the reaction liquid inside the oligomer reactor flows back to the phosgene reactor, the methylene chloride evaporates and the pressure in the phosgene reactor rises, and the phosgene reaction This operation was stopped because the vessel was damaged and phosgene was expected to leak out of the system.

Example 2-1
Example 1 except that the pressure in the oligomer reactor was intentionally reduced by restricting the control valve for supplying methylene chloride, and the inlet pressure (P2) in the oligomer reactor was set to 0.13 MPaG. In the same manner as in No. 1, a polycarbonate oligomer was produced.
As a result, as in Example 1-1, the automatic control device stopped the supply of chlorine and carbon monoxide to the phosgene reactor, stopped 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 2-2
Example 2 except that the pressure in the oligomer reactor was intentionally reduced by restricting the control valve for supplying methylene chloride, and the inlet pressure (P2) in the oligomer reactor was set to 0.12 MPaG. In the same manner as in No. 1, a polycarbonate oligomer was produced.
As a result, as in Example 2-1, the automatic control device stopped the supply of chlorine and carbon monoxide to the phosgene reactor, stopped 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
Example 2 except that the pressure in the oligomer reactor was intentionally lowered by restricting the control valve for supplying methylene chloride, and the inlet pressure (P2) in the oligomer reactor was set to 0.045 MPaG. In the same manner as in No. 1, a polycarbonate oligomer was produced.
As a result, as in Example 2-1, the automatic control device stopped the supply of chlorine and carbon monoxide to the phosgene reactor, stopped 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
The pressure inside the oligomer reactor was intentionally lowered by not using an automatic control device and by restricting the control valve for supplying methylene chloride, so that the inlet pressure (P2) in the oligomer reactor was reduced to 0. 0. A polycarbonate oligomer was produced in the same manner as in Example 2-1, except that the pressure was 13 MPaG.
However, by restricting the control valve for supplying methylene chloride, the inlet pressure (P2) in the oligomer reactor decreased to 0.13 MPaG, but then the pressure started to increase because the oligomer precipitated. When the operation of further reducing the methylene chloride supply control valve is continued, oligomer precipitation proceeds, the reaction solution inside the oligomer reactor flows back to the phosgene reactor, the methylene chloride evaporates and the phosgene reactor is This operation was stopped because it was assumed that phosgene would leak out of the system.

  According to the method of the present invention, a polycarbonate oligomer can be continuously produced safely. In particular, even in the event of an accident in which the pressure in the oligomer reactor becomes abnormal, such as the reactor being clogged due to oligomer precipitation, the production and supply of phosgene is urgently stopped by automatic control, and the phosgene gas in the system The poisonous gas containing is made harmless and the poisonous gas does not leak out of the system.

Claims (2)

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 Continuous production of a polycarbonate oligomer 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 (however, the above step (2)) The reaction mixture obtained in step 1 is cooled via an external heat exchanger using a circulation pump, and a part of the reaction mixture is returned to the oligomer reactor again, except for the continuous production of polycarbonate oligomer). ,
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): The value of the pressure difference (P1-P2) between the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor and the inlet pressure (P2) in the oligomer reactor becomes 0.1 MPa or less.
Condition (ii): When the inlet pressure (P2) in the oligomer reactor becomes 0.13 MPaG or less.   The method for controlling polycarbonate oligomer continuous production according to claim 1, wherein the detoxifying means is a means for detoxifying a toxic gas containing phosgene gas by contacting with an alkaline aqueous solution.

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