KR101810726B1

KR101810726B1 - Control method for safe continuous manufacturing of polycarbonate oligomer

Info

Publication number: KR101810726B1
Application number: KR1020137024886A
Authority: KR
Inventors: 가즈히로 세키구치; 히로아키 모테기; 도시유키 야스다
Original assignee: 이데미쓰 고산 가부시키가이샤
Priority date: 2011-03-31
Filing date: 2011-06-28
Publication date: 2017-12-19
Also published as: CN102286145B; KR20140007445A; TWI504634B; JP2012214631A; CN102286145A; TW201239002A; WO2012132029A1; JP5775345B2

Abstract

A method for safely manufacturing a polycarbonate oligomer, which is capable of automatically detoxifying harmful phosgene even in the event of an abnormality without leaking out of the system.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a control method for secure continuous production of a polycarbonate oligomer,

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

In general, as a production method of a polycarbonate, there are known an interfacial polymerization method in which biphasic phenols (bisphenols) are directly reacted with phosgene, and an ester exchange method in which bisphenols and diphenyl carbonate are reacted under solventless conditions. However, Since the carbonate is obtained, the interface method becomes mainstream (see, for example, Patent Document 1).

In the interfacial method, bisphenols, alkali compounds such as sodium hydroxide and phosgene are used as raw materials of the polycarbonate, and if necessary, a terminal stopper (molecular weight regulator) is added. In an industrial production plant for polycarbonate, phosgene is generally blown into an alkali aqueous solution of bisphenols to produce a polycarbonate oligomer having a reactive chloroformate group, and simultaneously or sequentially with the polycarbonate oligomer, a polycarbonate oligomer And an alkali aqueous solution of a bisphenol are reacted to produce a polycarbonate.

Patent Document 2 discloses a method of storing liquid liquefied phosgene obtained by distillation purification of phosgene and producing polycarbonate using the liquefied phosgene.

However, since phosgene is highly toxic, it is not preferable from the viewpoint of safety to store it. For example, there is a risk that phosgene leaks if the liquefied phosgene reservoir is destroyed by corrosion or the like. Such a risk can be reduced by installing a phosgene detoxification facility. However, because the amount of phosgene retained is large, it takes time to detoxify the phosgene, and in order to detoxify in a short time, a large-scale facility is required.

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

Japanese Laid-Open Patent Publication No. 2004-331916 Japanese Patent Application Laid-Open No. 2001-261321 International Publication No. 2007/083721

However, in any of the above documents, it is assumed that an accident occurs in which the pressure in the oligomer reactor becomes abnormal due to reaction abnormality or oligomer deposition by the organic solvent supply trouble to the oligomer reactor and obstruction of the reactor, And does not disclose a method for producing polycarbonate while detoxifying harmful phosgene without leaking out of the system.

A problem to be solved by the present invention is to provide a method for continuously producing a polycarbonate oligomer in the production of polycarbonate, a method for automatically stopping the apparatus even in the event of an abnormality and for removing harmful phosgene without leaking outside the system And the like.

The above problem is solved by a control method of continuous production of the polycarbonate oligomer described below.

(1) for continuously producing a phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to a phosgene reactor, and a step (1) for continuously producing a phosgene gas, an alkali aqueous solution of a dihydric phenol, and an organic A process for controlling continuous production of a polycarbonate oligomer comprising continuously (2) continuously feeding a solvent into an oligomer reactor to continuously prepare a reaction mixture containing a polycarbonate oligomer,

The supply of the chlorine and the carbon monoxide in the step (1) is stopped, the supply of the phosgene gas to the oligomer reactor is stopped, and the supply of the phosgene to the oligomer reactor is stopped when the following conditions (i) and / A method for controlling continuous production of a polycarbonate oligomer wherein a toxic gas containing a gas is transferred to a detoxifying means to render it harmless.

Condition (i): When 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, even when an accident such as reaction abnormality or precipitation of oligomer by the organic solvent supply trouble to the oligomer reactor and clogging of the reactor occurs in the continuous production of the polycarbonate oligomer by the interfacial method, The supply of chlorine and carbon monoxide as raw materials of the phosgene and the supply of phosgene to the oligomer reactor are automatically stopped and the phosgene in the system is automatically controlled to be transported to the detoxification means to safely manufacture the polycarbonate oligomer without leaking the phosgene out of the system .

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process diagram showing an outline of a preferred embodiment of a control method for continuous production of the polycarbonate oligomer of the present invention. Fig.

The control method of the continuous production of the polycarbonate oligomer of the present invention continuously monitors the pressure P1 of the phosgene gas supplied to the oligomer reactor and the inlet pressure P2 in the oligomer reactor in the continuous production of the polycarbonate oligomer by the interfacial method The supply of the chlorine and the carbon monoxide as the raw materials of the phosgene and the supply of the phosgene to the oligomer reactor are automatically stopped and the phosgene in the system is removed as a detoxification means And then automatically controlling the transporting operation.

[Production of polycarbonate]

The control method of the continuous production of the polycarbonate oligomer of the present invention is applied to the interfacial method in which the divalent phenol and phosgene are directly reacted, and is applied in the continuous reaction method.

The method for continuously producing the polycarbonate oligomer according to the present invention comprises the steps of (1) continuously producing phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to a phosgene reactor, and (3) (2) continuously feeding a continuously prepared aqueous solution of phosgene gas, an aqueous alkali solution of a dihydric phenol and an organic solvent into an oligomer reactor, thereby continuously producing a reaction mixture containing a polycarbonate oligomer.

&Lt; Process (1) >

Process (1) is a process for continuously producing phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to a phosgene reactor.

From the viewpoint of the quality of the polycarbonate oligomer, carbon monoxide is preferably prepared by reacting oxygen with coke, petroleum, natural gas, alcohol or the like, and purifying at a purity of 95 vol% or more. Particularly, it is preferable that the content of the sulfur component is 50 ppm or less. The ratio (molar ratio) of chlorine to carbon monoxide 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 (Kokoku) No. 55-14044. As the catalyst, a catalyst containing activated carbon as a main component can be used. Since the reaction is an exothermic reaction, it is preferable to cool the phosgene reactor to maintain the internal temperature of the reactor at 350 DEG 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 viewpoints of cost and quality of the polycarbonate oligomer. That is, a phosgene gas having a purity of 99 to 70% by volume is preferable.

&Lt; Process (2) >

The step (2) is a step of continuously feeding a continuously prepared phosgene gas, an aqueous alkali solution of a dihydric phenol and an organic solvent into the oligomer reactor in the step (1) to continuously prepare a reaction mixture containing a polycarbonate oligomer Process.

Examples of raw materials in the production of the polycarbonate include phosgene gas, divalent phenols (bisphenols), alkaline compounds used for dissolving the divalent phenols, and organic solvents. If necessary, monovalent phenol Or other additives may be used.

As the phosgene gas, the phosgene gas continuously produced in the above step (1) is used.

As the dihydric phenols, 2,2-bis (4-hydroxyphenyl) propane (collectively, bisphenol A; BPA) is preferable in view of the physical properties of the polycarbonate. Examples of the dihydric phenols other than bisphenol A include bis (4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) ethane; Bis (4-hydroxyphenyl) alkane such as 1,2-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) cyclohexane; Dihydroxydiphenyl, bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) cycloalkane such as 1,1-bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfide, bis Hydroquinone, and the like. These bifunctional phenols may be used singly or in combination of two or more kinds.

As the alkali compound used for dissolving the dihydric phenols, sodium hydroxide is preferable.

The organic solvent may be any one which dissolves the polycarbonate oligomer. 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, chlorinated solvents are preferable, and methylene chloride is particularly preferably used in view of solubility of the polycarbonate oligomer. In addition to the organic solvents exemplified above, a solvent such as an alkane or the like called a poor solvent may be used as long as the solubility of the polycarbonate oligomer is not lowered.

One kind of organic solvent may be used alone, or two or more kinds may be mixed and used.

Examples of the monohydric phenol used as the molecular weight modifier include phenol, p-cresol, p-tert-butylphenol, p-tert-octylphenol, p-cumylphenol and nonylphenol. Among them, p-tert-butylphenol and phenol are preferable from the standpoints of cost and ease of availability.

For the production of the polycarbonate oligomer, a polymerization catalyst such as a tertiary amine or a quaternary amine may be used if necessary. As the polymerization catalyst, TEA (triethylamine) is preferable.

As the oligomer reactor, a reactor having a tubular structure having a mixing portion in which a reactor of a continuous reaction system is used and a reaction raw material is mixed is preferably used.

Also, the oligomer reactor is installed in the building and isolated from the outside. The inside of the building is always replaced with air, and the ventilation air inside is sent to the detoxification means by a blower or the like.

The amount of the raw material supplied to the oligomer reactor in the step (2) and the reaction conditions are appropriately determined according to the scale and production amount of the apparatus.

For example, preferable conditions for producing polycarbonate oligomer of about 200 kg per hour are described below, but the present invention is not limited thereto. The 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 boiling point (7.8 ° C) to 90 ° C of phosgene. As the alkaline aqueous solution of the bifunctional phenol, an aqueous solution of sodium hydroxide of bisphenol A is preferable and supplied in a predetermined concentration and adjusted in advance. In the sodium hydroxide aqueous solution of bisphenol A, the preferred bisphenol A concentration is 12.5 to 14.0 mass%, and the preferable sodium hydroxide concentration is 5.1 to 6.1 mass%. The preferred flow rate of 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 the 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 so as to obtain optimum properties. However, the molecular weight measured by VPO (vapor pressure osmometry) is preferably about 600 to 5,000.

The reaction mixture containing the polycarbonate oligomer is also a mixture of an aqueous phase in which a polycarbonate oligomer is dissolved in the organic solvent and an aqueous phase containing an aqueous alkali solution. The reaction mixture is introduced into a condensation reactor and subjected to a condensation reaction to produce a polycarbonate.

After completion of the condensation reaction, the reaction solution is washed by a known method, concentrated, and pulverized to give a powdery polycarbonate, which can then be pelletized by an extruder or the like.

[Control method for continuous production of polycarbonate oligomer]

In the oligomer reactor, a predetermined amount of a phosgene gas, an aqueous alkali solution of a dihydric phenol and an organic solvent are continuously supplied. The supply pressure P1 of the phosgene gas and the inlet pressure P2 of the oligomer reactor are appropriately set according to the size, shape and the like of the phosgene reactor or the oligomer reactor. Usually, the supply pressure P1 of the phosgene gas is 0.4-0.5 MPaG , The inlet pressure (P2) in the oligomer reactor is 0.15 to 0.35 MPaG, and the pressure difference (P1 - P2) in both is continuously operated to a differential pressure of 0.105 MPa to 0.35 MPa.

(I) and / or (ii) satisfy the following conditions (i) and (ii) with respect to the pressure P1 of the phosgene gas supplied to the oligomer reactor and the inlet pressure P2 in the oligomer reactor in the control method for continuous production of polycarbonate oligomer of the present invention When the condition is satisfied, the automatic system stops the production and supply of the phosgene, and the toxic gas containing the phosgene gas in the system is transferred to the detoxifying means to be harmless .

The condition (i) is a case where the pressure difference (P1 - P2) between the supply pressure P1 of the phosgene gas supplied to the oligomer reactor and the inlet pressure P2 within the oligomer reactor becomes 0.1 MPa or less.

For example, when the organic solvent can not be supplied by a pump for supplying an organic solvent by a certain trouble or the supply amount thereof is lowered, the concentration of the polycarbonate oligomer in the oligomer reactor becomes high and the resulting polycarbonate oligomer precipitates Closing the outlet of the oligomer reactor raises the pressure in the oligomer reactor. As a result, there is a risk that the solvent or the oligomer raw material flows back to the phosgene reactor and the operating voltage rises above the design pressure due to the evaporation of the solvent, and the phosgene leaks out of the system.

Therefore, in the present invention, 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 from the viewpoint of safety, . However, if the automatic system is frequently activated by troubles such as transient troubles, it becomes difficult to operate efficiently. Therefore, from the viewpoint of efficient operation after securing the safety, The value of the difference P1 - P2 may be set to 0.09 MPa or less, or to 0.049 MPa or less.

The condition (ii) is the case where the inlet pressure P2 in the oligomer reactor becomes 0.13 MPaG or less.

The lowering of the inlet pressure in the oligomer reactor is expected to be caused by poor supply of an aqueous solution of an organic solvent or an alkaline aqueous solution of a dihydric phenol, defective reaction, etc. Thus, some of the phosgene is not consumed in the oligomer reactor, , There is a risk that the phosgene leaks out of the system or the generated polycarbonate oligomer precipitates to block the outlet of the oligomer reactor and the organic solvent or the oligomer raw material flows back to the phosgene reactor and the operating voltage rises above the design pressure due to evaporation of the solvent, Therefore, there is a risk that the phosgene leaks out of the system.

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, from the standpoint of efficient operation after securing safety, the conditions under which the automatic system is started are that the inlet pressure in the oligomer reactor (P2) is 0.12 MPaG or less, or 0.049 MPaG or less.

In the control method for continuous production of the polycarbonate oligomer of the present invention, the operations (a), (b) and (c) below are automatically carried out when the above conditions (i) and / It prevents harmful phosgene leakage and is harmless.

(a) The supply of chlorine and carbon monoxide in the step (1) for continuously producing the phosgene gas is stopped. This is an operation for stopping the production of the phosgene gas for the purpose of not increasing the amount of the phosgene gas in the system.

(b) stop feeding the phosgene gas to the oligomer reactor. This is an operation for preventing the leakage of phosgene because some phosgene is not consumed in the oligomer reactor and there is a possibility that the phosgene flows to the downstream process while being unreacted.

(c) The toxic gas containing the phosgene gas in the system is transferred to the detoxifying means and rendered harmless. This is an operation for detoxifying the phosgene gas in the system from the viewpoint of higher safety in addition to preventing increase and leakage of phosgene by the operations of (a) and (b) described above and blocking the system.

&Lt;

The detoxification means is a facility for detoxifying the poisonous gas containing the phosgene gas by releasing it, and known ones can be used. As specific examples, there may be mentioned a release facility for releasing, an absorption tower for bringing the toxic gas into contact with the release agent, and the like. It is also possible to use a tower-type desalting plant described in JP-A-6-319946 or JP-A-2005-305414.

For acid gases such as phosgene and chlorine, an alkaline substance is used as the release agent. The alkaline substance used as the releasing agent is not particularly limited, but sodium hydroxide and potassium hydroxide are generally used. In addition, they are usually used as an aqueous solution.

In the case where the detoxification means is a decomposition tower, the structure of the decomposition tower is not particularly limited. As a typical example, the decomposition is carried out by spraying the decompression from the upper part of the column with a spray or the like, . A filler such as a lashing ring may be filled between the discharge port of the release port and the inlet port of the gas so as to increase the contact efficiency between the release port and the gas. The number of the disposal tower is not particularly limited, and it is designed so that the toxic gas concentration in the detoxication process gas is lowered to a predetermined concentration or lower, which is preferably not detected.

The deterrent means are always operated against unpredictable events without the leakage of toxic gases. Further, the ventilation air in the building in which the oligomer reactor is installed is sent to the detoxifying means by a blower or the like, and is harmlessly discharged to the outside.

One preferred embodiment of the present invention will be described with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart outlining one preferred embodiment of a control method for continuous production of a polycarbonate oligomer of the present invention.

Typically, during operation, chlorine and carbon monoxide of the raw materials for producing phosgene are supplied to the phosgene reactor through the regulating valve, and phosgene gas is produced in the phosgene reactor. Since the reaction is an exothermic reaction, the phosgene reactor is cooled by cooling water.

The phosgene gas (reaction product) containing unreacted carbon monoxide is introduced into the oligomer reactor through the regulating valve. In the oligomer reactor, in addition to the phosgene gas, an alkali aqueous solution of divalent phenol (specifically, for example, an aqueous sodium hydroxide solution of bisphenol A) and an organic solvent (specifically, for example, methylene chloride) , An emulsion solution containing a polycarbonate oligomer is prepared.

Further, the control valve formed in the supply path of chlorine and carbon monoxide automatically controls these flow rates, and the regulating valve formed in the supply path to the oligomer reactor of the phosgene gas controls the supply pressure of the phosgene gas supplied to the oligomer reactor.

The pressure P1 of the phosgene gas supplied to the oligomer reactor and the inlet pressure P2 in the oligomer reactor are always monitored using a pressure gauge and the value is sent to the automatic control device (indicated by the dotted line in the figure).

If the above conditions (i) and / or (ii) are satisfied with respect to the pressures (P1) and (P2), the automatic control device supplies the chlorine and the carbon monoxide A control valve formed in the supply passage for the oligomer reactor of the phosgene gas, and a regulating valve formed in the flow path for the detoxification device are simultaneously sent (arrows in bold solid lines in the figure).

By the signal from the automatic control device, the control valve formed in the supply path of chlorine and carbon monoxide is closed to stop the supply of chlorine and carbon monoxide. Further, the control valve formed in the supply passage for the oligomer reactor of the phosgene gas is closed to stop the supply of the phosgene gas to the oligomer reactor.

The regulating valve formed in the flow path to the detoxication apparatus is normally closed during operation but is opened by a signal from the automatic control apparatus and the toxic gas containing the phosgene gas in the system is transferred to the detoxication apparatus. In the detoxification apparatus, the toxic gas containing the phosgene gas is harmless.

As described above, one preferred embodiment of the present invention has been described with reference to the drawings, but the present invention is not limited thereto. For example, although not shown in FIG. 1, each fluid supply stop valve may be formed in addition to the control valve.

Example

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

Example 1-1

(Automatic control device)

As shown in Fig. 1, the pressure P1 of the phosgene gas supplied to the oligomer reactor and the inlet pressure P2 of the oligomer reactor are monitored by a pressure gauge to determine the supply pressure P1 of the phosgene gas supplied to the oligomer reactor, When the value of the pressure difference (P1 - P2) of the inlet pressure P2 in the reactor becomes 0.1 MPa or less (condition (i)) or the inlet pressure P2 in the oligomer reactor becomes 0.13 MPaG or less The control valve formed in the supply path for the chlorine and the carbon monoxide and the control valve formed in the supply path for the oligomer reactor of the phosgene gas are closed and the control valve formed in the flow path for the decomposition device is opened Is designed.

(Detoxification device)

A distillation column with a column diameter of 600 mm and a packed bed height of 10 m filled with Cascade Mini Ring (CMR) (trade name, manufactured by Matsui Machine Co., Ltd.) was used as a detoxification apparatus. In the decomposition column, an aqueous solution of sodium hydroxide having a concentration of 10% by mass was circulated at 2 m < 3 > / h as the release. Aqueous sodium hydroxide solution was supplied from the top of the column and toxic gas was supplied from the bottom.

(Preparation of phosgene)

As the phosgene reactor, a shell-and-tube reactor in which commercially available granular activated carbon (palm shell activated carbon pulverized with a diameter of 1.2 to 1.4 mm) was filled in the tube was used.

1.2 kg / h of carbon monoxide and 2.8 kg / h of chlorine were supplied to the phosgene reactor, and 3.9 kg / h of phosgene gas was prepared. In the shell part of the phosgene reactor, 90 ° C water was passed through to remove reaction heat.

(Preparation 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 占 폚. The phosgene gas was continuously supplied to the oligomer reactor from the upstream phosgene production process, and the supply pressure P1 of the phosgene gas supplied to the oligomer reactor was set to 0.45 MPaG.

44 kg / h of a BPA sodium hydroxide aqueous solution having a concentration of 13.5% by mass obtained by dissolving bisphenol A (BPA) in a 6 mass% sodium hydroxide aqueous solution of a phosgene gas of 3.9 kg / h, 22 kg / h of methylene chloride, 0.46 kg / h of a methylene chloride solution of p-tert-butylphenol having a concentration of 25% by mass for regulating the polymerization 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 intensively increasing the pressure in the oligomer reactor by tightening the outlet valve of the oligomer reactor, the inlet pressure (P2) in the oligomer reactor is set to 0.35 MPaG, the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor, The value of the pressure difference (P1 - P2) of the inlet pressure (P2) in the oligomer reactor was 0.1 MPa.

As a result, the supply of chlorine and carbon monoxide to the phosgene reactor was stopped by the automatic control device, the supply of the phosgene gas to the oligomer reactor was stopped, and the phosgene gas produced by the phosgene reactor was transferred to the detoxification apparatus. As a result of performing the component measurement on the gas discharged from the outlet of the decomposition tower, the phosgene was not detected and was harmless.

Examples 1-2

The pressure in the oligomer reactor was intentionally increased by tightening the outlet valve of the oligomer reactor so that the inlet pressure (P2) in the oligomer reactor was 0.36 MPaG, the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor, Except that the value of the pressure difference (P1 - P2) of the inlet pressure (P2) in the reactor was 0.09 MPa.

As a result, in the same manner as in Example 1-1, the supply of chlorine and carbon monoxide to the phosgene reactor was stopped by the automatic control device, the supply of the phosgene gas to the oligomer reactor was stopped, and the phosgene produced by the phosgene reactor The gas was transferred to the detoxification unit. As a result of performing the component measurement on the gas discharged from the outlet of the decomposition tower, the phosgene was not detected and was harmless.

Example 1-3

The inlet pressure (P2) of the oligomer reactor was adjusted to 0.41 MPaG by intentionally raising the pressure in the oligomer reactor by tightening the outlet valve of the oligomer reactor, the supply pressure (P1) of the phosgene gas supplied to the oligomer reactor, The polycarbonate oligomer was produced in the same manner as in Example 1-1 except that the value of the pressure difference (P1 - P2) of the inlet pressure P2 within the reactor was 0.04 MPa.

Comparative Example 1-1

The pressure in the oligomer reactor was intentionally increased by tightening the outlet valve of the oligomer reactor and the inlet pressure (P2) in the oligomer reactor was set to 0.40 MPaG, and the amount of phosgene supplied to the oligomer reactor Polycarbonate oligomer was produced in the same manner as in Example 1-1 except that the pressure difference (P1 - P2) between the gas supply pressure (P1) and the inlet pressure (P2) in the oligomer reactor was 0.05 MPa I tried.

However, as the exit valve of the oligomer reactor was slowly tightened, the pressure in the oligomer reactor rose sharply. When the operation for tightening the outlet valve of the abnormal oligomer reactor is continued, the reaction liquid inside the oligomer reactor flows back to the phosgene reactor, the methylene chloride evaporates, the pressure in the phosgene reactor rises and the phosgene reactor breaks, This operation was aborted because it was assumed to leak outside.

Example 2-1

Except that the pressure in the oligomer reactor was intentionally lowered by tightening the control valve for supplying methylene chloride so that the inlet pressure P2 in the oligomer reactor was adjusted to 0.13 MPaG to obtain a polycarbonate oligomer .

Example 2-2

Except that the pressure in the oligomer reactor was intentionally lowered by tightening the control valve for feeding methylene chloride so that the inlet pressure P2 in the oligomer reactor was adjusted to 0.12 MPaG to obtain a polycarbonate oligomer .

As a result, in the same manner as in Example 2-1, the supply of chlorine and carbon monoxide to the phosgene reactor was stopped by the automatic control device, the supply of the phosgene gas to the oligomer reactor was stopped, and the phosgene produced by the phosgene reactor The gas was transferred to the detoxification unit. As a result of performing the component measurement on the gas discharged from the outlet of the decomposition tower, the phosgene was not detected and was harmless.

Example 2-3

Except that the pressure in the oligomer reactor was intentionally lowered by tightening the control valve for feeding methylene chloride so that the inlet pressure (P2) in the oligomer reactor was 0.045 MPaG, the polycarbonate oligomer .

Comparative Example 2-1

Example 2 was repeated except that the automatic control device was not used and the pressure in the oligomer reactor was intentionally lowered by tightening the control valve for supplying methylene chloride so that the inlet pressure P2 in the oligomer reactor was 0.13 MPaG. -1, a polycarbonate oligomer was prepared.

However, by tightening the control valve for supplying methylene chloride, the inlet pressure (P2) in the oligomer reactor dropped to 0.13 MPaG, but then the pressure began to rise because of oligomer deposition. When the operation for tightening the control valve for feeding methylene dichloride is continued, the precipitation of the oligomer proceeds and the reaction liquid in the oligomer reactor flows back to the phosgene reactor, the methylene chloride evaporates and the phosgene reactor is broken, This operation was stopped because leakage was assumed.

Industrial availability

According to the method of the present invention, a polycarbonate oligomer can be continuously produced safely. Particularly, even when an accident occurs in which the pressure in the oligomer reactor is blocked due to the precipitation of oligomers, the production and supply of the phosgene are stopped automatically by automatic control, and the phosgene gas The toxic gas containing the toxic gas is made harmless and the toxic gas is not leaked out of the system.

Claims

(1) for continuously producing phosgene gas containing unreacted carbon monoxide by supplying chlorine and carbon monoxide to a phosgene reactor, and a step (1) for continuously producing a phosgene gas, an alkali aqueous solution of dihydric phenol, and an organic A process for controlling continuous production of polycarbonate oligomer comprising continuously (2) continuously supplying a solvent to an oligomer reactor to continuously prepare a reaction mixture containing a polycarbonate oligomer,
The supply of the chlorine and the carbon monoxide in the step (1) is stopped, the supply of the phosgene gas to the oligomer reactor is stopped, and the supply of the phosgene to the oligomer reactor is stopped when the following conditions (i) and / A method for controlling continuous production of a polycarbonate oligomer wherein a toxic gas containing a gas is transferred to a detoxifying means to render it harmless.
Condition (i): When 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 according to claim 1,
Wherein said detoxifying means is a means for detoxifying a toxic gas containing a phosgene gas by contacting with an alkaline aqueous solution.