JP6646398B2 - Method for producing aromatic polycarbonate - Google Patents

Description

  The present invention relates to a method for producing an aromatic polycarbonate.

  It is widely known that aromatic polycarbonates have excellent impact resistance and transparency. As a method for producing an aromatic polycarbonate, an aromatic dihydroxy compound and a diaryl carbonate are reacted at a high temperature and a reduced pressure in the presence of a transesterification catalyst to remove a generated aromatic monohydroxy compound out of the system. There are a synthetic method and an interfacial polymerization method in which an aromatic dihydroxy compound and phosgene are reacted in a mixture of an organic solvent and an aqueous alkaline solution.

  In the interfacial polymerization method, compared with the melt polymerization method, toxic phosgene must be used, and the equipment is corroded by by-products such as hydrogen chloride and sodium chloride and chlorine-containing compounds such as methylene chloride used in large quantities as a solvent. In addition, there is a problem that it is difficult to separate impurities such as sodium chloride, which adversely affects the physical properties of the polymer, and residual methylene chloride. Therefore, a number of melt polymerization methods have been proposed as methods for producing aromatic polycarbonate.

  In the melt polymerization method, an aromatic dihydroxy compound and a diaryl carbonate are used as raw materials. It is known that an aromatic dihydroxy compound is easily decomposed and colored due to its low heat resistance when handled in a molten state at a temperature equal to or higher than its melting point, thereby causing a deterioration in the hue of the polymer. For this reason, when preparing a raw material mixture containing an aromatic dihydroxy compound in the melt polymerization method, generally, a method of mixing a molten diaryl carbonate and a molten aromatic dihydroxy compound, and weighing the molten diaryl carbonate. A method is used in which a solid (powder, prill-like, etc.) aromatic dihydroxy compound is weighed, supplied, mixed and dissolved. In the former case, there is a restriction that the molten aromatic dihydroxy compound must be used in a short storage time. Therefore, the latter is superior in consideration of storage stability. However, even in the latter case, if the charged molar ratio of the diaryl carbonate and the aromatic dihydroxy compound fluctuates, the ratio of polymer terminal hydroxyl groups of the prepolymer or polymer fluctuates. It is known that the amount of terminal hydroxyl groups needs to be adjusted.

  As a method for solving the above problem, for example, Patent Literature 1 describes a required charging accuracy of a diaryl carbonate and an aromatic dihydroxy compound. That is, the diaryl carbonate is mixed so that the fluctuation range of the molar ratio of the charge used in the ratio of 1.05 mol to 1.20 mol per 1 mol of the aromatic dihydroxy compound is within ± 0.005 mol. Is described as being preferred. Further, as a method for controlling the molar ratio, there is exemplified a method in which diphenyl carbonate is heated to about 100 ° C. and weighed in a liquid state using a mass flow meter, and the weighing accuracy is within ± 0.5% by mass, preferably 0% by mass. It is stated that a measuring tank within .25% by mass is desirable. Patent Document 1 discloses a method in which the weight of an aromatic dihydroxy compound storage tank is weighed before and after the supply, and the actual supply amount of the aromatic dihydroxy compound is determined from the difference between the two. A method for weighing an aromatic dihydroxy compound and the like are described.

International Publication No. 2005/121213

However, when the present inventor examined Patent Document 1, it was found that by controlling the fluctuation range of the molar ratio of charging to ± 0.005 mol, although an effect was seen in terms of color tone and the like, the viewpoint of pressure control of the polymerization reactor was observed. It became clear that simply using a measuring tank with high weighing accuracy was not enough. That is, since the polymer terminal hydroxyl group ratio is affected by the molar ratio of the aromatic dihydroxy compound and the dialkyl carbonate, in order to obtain a desired value of the polymer terminal hydroxyl group ratio and the molecular weight of the obtained aromatic polycarbonate, the molar ratio of the charge is adjusted. It is necessary to frequently adjust the pressure of the polymerization reactor in accordance with the fluctuation. For example, if the precision of the molar ratio between the aromatic dihydroxy compound and the dialkyl carbonate fluctuates by ± 0.3%, the molecular weight and the ratio of polymer terminal hydroxyl groups may not be maintained in a desired range unless the pressure is fluctuated by ± 15 Pa or more.
The present invention has been made in view of the above circumstances, and in a method for producing an aromatic polycarbonate by a melt polymerization method using an aromatic dihydroxy compound and a diaryl carbonate as raw materials, a method in which a diaryl carbonate and an aromatic dihydroxy compound in a dissolved mixture are used. It is an object of the present invention to provide a production method capable of easily controlling the pressure of a polymerization vessel by suppressing the fluctuation of the actual charged molar ratio.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, the raw material diaryl carbonate and aromatic dihydroxy compound were converted into the majority of diaryl carbonate, then the aromatic dihydroxy compound, and then the measured aromatic dihydroxy compound. The first object is achieved by supplying the compound to the mixing tank in the order of the amount of the compound, the amount of the diaryl carbonate calculated so that the charged molar ratio becomes a predetermined value, and preparing the dissolved mixture. It was found that the present invention was obtained, and the present invention was completed.

That is, the present invention is as follows.
[1] A method for producing an aromatic polycarbonate by reacting an aromatic dihydroxy compound and a diaryl carbonate in a polymerization vessel,
A step of supplying the diaryl carbonate at 90 to 220 ° C. to a mixing tank at 75 to 99% by mass of the total supply amount of the diaryl carbonate, which is determined from a target molar ratio of the aromatic dihydroxy compound and the diaryl carbonate. (A) and
A step (B) of supplying the aromatic dihydroxy compound to the mixing tank adjusted to a liquid temperature of 135 to 220 ° C. after the step (A);
After the step (B), the diaryl carbonate is further supplied to the mixing tank so that the charged molar ratio of the aromatic dihydroxy compound and the diaryl carbonate in the mixing tank is within a predetermined range, and the mixture is dissolved. (C) preparing a mixture;
Including
Prior to said step (B), further seen including the step of metering the aromatic dihydroxy compound, with a metering vessel for installation aromatic dihydroxy compound independently stand,
The independent gantry is a gantry supported on a foundation independent of a foundation for directly or indirectly supporting the mixing tank,
The aromatic dihydroxy compound is bisphenol A,
A method for producing an aromatic polycarbonate.
[2] The melted mixture at 135 to 220 ° C. is supplied to a first melted mixture storage tank, and the melted mixture is kept at 160 to 220 ° C. for 1 to 12 hours in the first melted mixture storage tank. (D-1) obtaining a reaction mixture of
Supplying the first reaction mixture to a polymerization step for obtaining a prepolymer or polymer having a number average molecular weight of 400 or more by polymerization (E-1);
The dissolution mixture at 135 to 220 ° C. is supplied to a second dissolution mixture storage tank, and the dissolution mixture is kept at 160 to 220 ° C. for 1 to 12 hours in the second dissolution mixture storage tank to perform a second reaction. A step (D-2) of obtaining a mixture;
Supplying the second reaction mixture to the polymerization step (E-2) when the first reaction mixture in the first dissolved mixture storage tank is reduced to a predetermined amount, [1]. 5. The method for producing an aromatic polycarbonate according to the above.
[3] The method for producing an aromatic polycarbonate according to [2], wherein the aromatic polycarbonate is produced continuously.
[4] In the step (B), the aromatic dihydroxy compound is supplied to the mixing tank by being accompanied by an inert gas, and at the end of the supply, the aromatic dihydroxy compound and the inert gas are mixed. The method for producing an aromatic polycarbonate according to any one of [1] to [3], wherein a linear velocity of the inert gas in a pipe supplied into the tank is adjusted to 0.1 to 500 m / sec.
[5] In the step (B), the aromatic dihydroxy compound is supplied to the mixing tank by entraining the inert gas, which has been pressurized in the measuring tank, with the aromatic dihydroxy compound. The method for producing an aromatic polycarbonate according to [1] or [2], wherein a linear velocity of the inert gas in a pipe for supplying the inert gas into the mixing tank is adjusted to 0.1 to 500 m / sec.
[6] The method according to any one of [1] to [5], further including a step of adding a transesterification catalyst to the mixing tank after the step (A) and before the step (B). A method for producing the aromatic polycarbonate according to the above.

  According to the present invention, in a method of producing an aromatic polycarbonate by a melt polymerization method using an aromatic dihydroxy compound and a diaryl carbonate as raw materials, the actual charged molar ratio of the diaryl carbonate and the aromatic dihydroxy compound in the dissolved mixture is adjusted. By suppressing the fluctuation, it is possible to provide a production method capable of easily controlling the pressure of the polymerization reactor.

It is a flow figure showing an example of the manufacturing device used for the manufacturing method of the aromatic polycarbonate of this embodiment. It is a figure showing typically an example of an independent stand concerning this embodiment. It is a figure which shows typically an example of the flow of the steam when using steam as a heat source of the heating means of a mixing tank. It is a figure which shows another example of the flow of the steam when steam is used as a heat source of the heating means of a mixing tank.

  Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary, but the present invention is limited to the following present embodiment. Not something. The present invention can be variously modified without departing from the gist thereof. In the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  The method for producing an aromatic polycarbonate of the present embodiment is a method for producing an aromatic polycarbonate by reacting an aromatic dihydroxy compound and a diaryl carbonate in a polymerization vessel, and aims at a diaryl carbonate at 90 to 220 ° C. A step (A) of supplying 75 to 99% by mass of the total supply amount of the diaryl carbonate obtained from the charged molar ratio of the aromatic dihydroxy compound and the diaryl carbonate (hereinafter, simply referred to as “charged molar ratio”) to the mixing tank; After the step (A), the step (B) of supplying the aromatic dihydroxy compound to the mixing tank adjusted to a liquid temperature of 135 to 220 ° C., and after the step (B), the charged molar ratio in the mixing tank is Step (C) of further supplying diaryl carbonate to the mixing tank so as to be within a predetermined range to prepare a dissolved mixture. It is intended to include. FIG. 1 is a flowchart showing an example of a production apparatus used in the method for producing an aromatic polycarbonate of the present embodiment. Hereinafter, the method for producing the aromatic polycarbonate of the present embodiment will be described in more detail with reference to this flowchart.

The step (A) is a step of supplying the diaryl carbonate at 90 to 220 ° C. to the mixing tank in an amount of 75 to 99% by mass of the total amount of the diaryl carbonate obtained from the target charging molar ratio.
In FIG. 1, the raw material diaryl carbonate is stored in a storage tank 10. The temperature at the time of storage is preferably from 82 to 120 ° C from the viewpoint of avoiding thermal denaturation of the diaryl carbonate. The total supply amount of diaryl carbonate is a planned supply amount of diaryl carbonate, which is obtained from a planned supply molar ratio (ie, a target supply molar ratio). Of the total supply amount, 75 to 99% by mass of diaryl carbonate is measured from the storage tank 10 by the diaryl carbonate measuring device 13 provided in the transfer pipe from the storage tank 10 to the mixing tank 7. It is transferred to the preheater 11 by a transfer pump (not shown), preheated to 90 to 220 ° C. by the preheater 11, and supplied to the mixing tank 7 (hereinafter, this supply is referred to as “large supply”). By setting the temperature of the diaryl carbonate at this time to 90 ° C. or more, the diaryl carbonate becomes a liquid, which facilitates the transfer, and the mixing tank 7 receiving the diaryl carbonate can be adjusted to a predetermined temperature in a short time. By setting the temperature to 220 ° C. or lower, there is an effect that discoloration of the obtained aromatic polycarbonate can be prevented.
The mixing tank 7 is preferably provided with a stirring blade (not numbered), and preferably, when the stirring blade is completely immersed in the diaryl carbonate, the mixing tank 7 Stirring is started.

  When a transesterification catalyst is used for the reaction between the aromatic dihydroxy compound and the diaryl carbonate, a step of adding the transesterification catalyst to the mixing tank 7 after the step (A) and before the step (B) described below is further performed. It is preferable to include. By mixing the transesterification catalyst with the diaryl carbonate before mixing the aromatic dihydroxy compound and the diaryl carbonate, it is possible to further suppress the spread of the molecular weight distribution, and at the time of injection molding of the obtained aromatic polycarbonate in a mold. Generation of mold deposit can be further prevented, and generation of a gel-like high molecular weight substance in the aromatic polycarbonate can be further suppressed.

  The step (B) is a step of supplying the aromatic dihydroxy compound to the mixing tank 7 after the step (A). In the step (B), the temperature of the liquid containing the diaryl carbonate accommodated in the mixing tank 7 is adjusted to 135 to 220 ° C. For example, the aromatic dihydroxy compound is stored in a storage tank (for example, a storage hopper, not shown) for the aromatic dihydroxy compound or a facility for producing the aromatic dihydroxy compound (not shown) using the bucket conveyor 1. While being measured by the load cell 3, it is supplied to a measuring tank 2 for an aromatic dihydroxy compound installed on an independent stand (exemplified as an independent stand 20 in FIG. 2 described later). Here, the “independent gantry” means a gantry supported on a foundation independent of a foundation for directly or indirectly supporting the mixing tank 7. An example of “indirect” support is to support a gantry on which the mixing tank 7 is installed. By installing the measuring tank 2 on the independent stand, the vibration transmitted from the mixing tank 7 to the measuring tank 2 can be further suppressed. Next, the aromatic dihydroxy compound is supplied from the measuring tank 2 to the mixing tank 7 adjusted to a liquid temperature of 135 to 220 ° C. using the rotary valve 5. The supply amount of the aromatic dihydroxy compound is the total amount of the planned charge. Next, the atmosphere in the mixing tank 7 is changed to a gas different from oxygen and water vapor (preferably an inert gas such as nitrogen) in order to remove oxygen and moisture mixed into the aromatic dihydroxy compound and brought into the mixing tank 7. (Hereinafter, this gas is referred to as “replacement gas”). The supply amount of the aromatic dihydroxy compound to the measuring tank 2 is determined from the difference in mass between the measuring tank 2 before and after the supply. When an inert gas such as nitrogen is used as the replacement gas, its purity is preferably 99.999% by mass or more, and more preferably 99.9999% by mass, unless otherwise specified. Hereinafter, an inert gas such as nitrogen is referred to as “inert gas”.

Step (C) is a step in which diaryl carbonate is further supplied to the mixing tank 7 so that the charged molar ratio in the mixing tank 7 falls within a predetermined range after the step (B) to prepare a dissolved mixture. . The amount of the diaryl carbonate additionally supplied to the mixing tank 7 is determined so that the charged molar ratio is within a predetermined range.
For example, an additional supply amount of diaryl carbonate is determined based on the amount of the aromatic dihydroxy compound actually supplied to the mixing tank 7 in the step (B) so that a predetermined charging molar ratio is obtained. Next, a required amount of diaryl carbonate is transferred from the storage tank 10 to the preheater 11 by the transfer pump while being measured by the diaryl carbonate measuring device 13 provided in the transfer pipe from the storage tank 10 to the mixing tank 7. . Further, the diaryl carbonate is preheated by the preheater 11 and supplied to the mixing tank 7 adjusted to a liquid temperature of 135 to 220 ° C. (hereinafter, this supply is referred to as “small supply”).
By this step (C), the charged molar ratio in the dissolved mixture is adjusted within a predetermined range. Here, the "predetermined range" of the charged molar ratio is a range in which a target charged molar ratio value (target value) and a fluctuation range from the target value are combined, and are not particularly limited. The target value of the molar ratio may be from 0.9 to 1.3, more preferably from 1.0 to 1.25. Further, the fluctuation range of the charged molar ratio from the target value may be, for example, within ± 0.003, and preferably within ± 0.0015.

  In this specification, the `` dissolved mixture '' is a mixture in which at least a diaryl carbonate and an aromatic dihydroxy compound are dissolved and mixed in a mixing tank, and another optional component such as a transesterification catalyst is dissolved and mixed therein. You may. The “reaction mixture” is a solution in which the dissolved mixture is kept at 160 to 220 ° C. for 1 to 12 hours in a dissolved mixture storage tank described below. Further, in the present embodiment, a step of polymerizing the reaction mixture to obtain a prepolymer or polymer having a number average molecular weight (hereinafter, referred to as “Mn”) of 400 or more is referred to as a “polymerization step”. Here, “prepolymer” refers to those having Mn of 400 to 7000, and “polymer” refers to those having Mn of more than 7000.

In the present embodiment, as shown in FIG. 1, it is preferable that the steps (D-1) and (D-2) in the dissolution mixture storage tanks 12A and 12B be advanced in a batch manner. That is, in the step (D-1), the dissolution mixture prepared in the step (C) is supplied to the first dissolution mixture storage tank 12A at 135 to 220 ° C., and the dissolution mixture is dissolved in the dissolution mixture storage tank 12A. Hold at 160-220 ° C. for 1-12 hours to obtain a first reaction mixture with a predetermined equilibrium reaction rate. Further, in the step (E-1), the first reaction mixture is supplied to a polymerization step.
On the other hand, in the step (D-2), while the dissolved mixture is held in the dissolved mixture storage tank 12A and / or while the first reaction mixture is supplied to the polymerization step, the mixture is prepared by the step (C). The dissolved mixture thus obtained is supplied to the second dissolved mixture storage tank 12B at 135 to 220 ° C., and the dissolved mixture is kept at 160 to 220 ° C. for 1 to 12 hours in the dissolved mixture storage tank 12B, and a predetermined equilibrium reaction is performed. % Of the second reaction mixture.
Next, in the step (E-2), when the first reaction mixture in the first dissolution mixture storage tank 12A has decreased to a predetermined amount, the second reaction mixture obtained in the step (D-2) is removed. The supply to the polymerization step is started. Further, step (D-1) proceeds while the dissolved mixture is held in the dissolved mixture storage tank 12B and / or while the second reaction mixture is being supplied to the polymerization step. The supply of the reaction mixture to the polymerization step can be performed continuously by repeating the above operations alternately.
Here, "equilibrium reaction rate" means the conversion of the aromatic dihydroxy compound in the dissolved mixture that has reached equilibrium. Further, the "predetermined amount" is a predetermined amount, for example, may be an amount guaranteed for normal operation of the dissolved mixture storage tank, and more specifically, the reaction mixture from the dissolved mixture storage tank. The amount may be such that cavitation of a transfer pump used to transfer the mixture can be suppressed.

In order to make the preparation of the dissolution mixture more stable and easy, the volumes of the mixing tank 7 and the dissolution mixture storage tanks 12A and 12B are made substantially equal to each other, and almost all of the dissolution mixture prepared in the mixing tank 7 is dissolved mixture. It is more preferable to supply to the storage tank 12A or 12B. Here, the “total amount” refers to the amount of the dissolved mixture supplied to the dissolved mixture storage tank 12A or 12B after the supply of the dissolved mixture to the dissolved mixture storage tank 12A or 12B is started until the mixing tank 7 becomes almost empty. Means quantity. For example, after the supply of the dissolved mixture to the dissolved mixture storage tank 12A or 12B is started, a level (liquid level) switch provided at the bottom of the mixing tank 7 is operated, and the dissolved mixture storage tank 12A Or the amount until the transfer pump 8A (to be described in detail later) for transferring the dissolved mixture to the dissolved mixture tank 12B is stopped, or the transfer pump 8A after the supply of the dissolved mixture to the dissolved mixture storage tank 12A or 12B is started. This is the amount from when the undercurrent (current value) of 8A is detected until the transfer pump 8A stops. Between the level switch at the bottom of the mixing tank 7 and the transfer pump 8A (including the suction side (suction) pipe of the transfer pump 8A), a small amount of the dissolved mixture may remain.
Switching between the dissolution mixture storage tanks 12A and 12B is preferably controlled appropriately in accordance with the rate of polymerization to the prepolymer or polymer so that the polymerization process can be continuously performed. In addition, two or more dissolution mixture storage tanks 12A and 12B may be provided in parallel with the process flow, and two or more dissolution mixture storage tanks may be provided in series with the process flow.

  Hereinafter, the method for producing the aromatic polycarbonate of the present embodiment and the production apparatus used for the production method will be described in more detail, focusing on each device that can be included in the production apparatus.

[Measurement of diaryl carbonate]
In this embodiment, in order to improve the accuracy of the charged molar ratio, the supply amount of the diaryl carbonate to the mixing tank 7 is set to 75 times the supply amount of the diaryl carbonate obtained from the target charged molar ratio for the first time (large supply). ~ 99% by weight. The large supply amount is preferably from 80 to 95% by mass, more preferably from 85 to 95% by mass. After the aromatic dihydroxy compound is supplied to the mixing tank 7 by not supplying the large amount of the diaryl carbonate all at once, the second (small supply) is performed based on the actually measured supply amount of the aromatic dihydroxy compound. The supply amount can be adjusted, and the accuracy of the charged molar ratio can be increased. When the amount of the large supply is 99% by mass or less, the adjustment with the small supply becomes easier. If the amount of the large supply is 75% by mass or more, the liquid level in the mixing tank 7 after the supply of the diaryl carbonate becomes higher than the stirring blades of a general mixing tank, thereby preventing breakage of the stirrer. it can. If the large supply amount is 75% by mass or more, the lump of the aromatic dihydroxy compound generated when the aromatic dihydroxy compound is supplied to the mixing tank 7 can be prevented. Furthermore, if the large supply amount is 75% by mass or more, when the internal coil is provided in the mixing tank 7, the discoloration of the aromatic dihydroxy compound attached to the internal coil can be prevented. .

[Diaryl carbonate measuring device 13]
The meter 13 can be used for measuring the diaryl carbonate. Examples of the measuring device 13 include known flow meters, such as an ultrasonic flow meter, a vortex flow meter, a positive displacement flow meter, an area flow meter, and a Coriolis integrating flow meter. Is preferred. Coriolis-type integrating flow meters are more preferable because of their high accuracy.
When the measuring device 13 is installed in a pipe, the measuring (weighing) accuracy is easily deteriorated due to the influence of external vibration or the like. Therefore, a measuring device with high weighing accuracy is preferable. Specifically, the weighing accuracy of the weighing device 13 is preferably within ± 0.5% by mass, and more preferably within ± 0.25% by mass. It is more preferable that the weighing accuracy after the weighing device 13 is installed in the pipe be within ± 0.15% by mass. It is preferable that two or more weighing devices 13 are installed along the pipe at intervals of 0.5 m or more. When two or more weighing devices are installed, it is preferable to use weighing devices having the same weighing accuracy, and it is preferable to use one weighing device as a main weighing device and perform a back check with another weighing device. In addition, when the weighing error between weighing instruments becomes large or when the weighing instrument used mainly breaks down, an interlock to stop receiving the weighing instruments shall be provided, or in addition to or instead of weighing for other back checks. It is also preferable to install a vessel so that it can be switched on a display screen of a DCS (distributed control system) used to control the operation of the aromatic polycarbonate production apparatus or inside a measuring instrument for back check. . Further, the measuring instrument may be back-checked with a liquid level gauge installed in the mixing tank 7.

[Diaryl carbonate preheater 11]
In the manufacturing apparatus of the present embodiment, a diaryl carbonate preheater 11 can be provided between the storage tank 10 and the mixing tank 7. As the preheater 11, a known heater can be used, and examples thereof include a double-tube heat exchanger and a multi-tube heat exchanger. Further, a double-tube heat exchanger is used to transfer diaryl carbonate. It may be used as a preheater 11 as a vessel. The diaryl carbonate is supplied to the mixing tank 7 while being heated or maintained at 90 to 220 ° C., preferably 100 to 210 ° C., more preferably 110 to 200 ° C. in the preheater 11. It is preferable that the flange portion of the preheater 11 has a structure in which diaryl carbonate does not stay in gaps between the flanges.

Examples of a heat source for heating and maintaining the temperature by the preheater 11 include hot oil circulated between the hot oil boiler and steam. When steam is used as the heat source, the temperature of the diaryl carbonate in the preheater 11 and / or the temperature of the diaryl carbonate in the outlet pipe of the preheater 11 is controlled while the diaryl carbonate is received (supplied) into the mixing tank 7 ( (TIC control method). After the diaryl carbonate is received in the mixing tank 7, the pressure may be switched from the TIC control method to the pressure control (PIC control method) for controlling the pressure of the preheater 11 on the heat source (for example, steam) side. Alternatively, TIC control for switching the temperature sensor from the temperature sensor of the diaryl carbonate in the pipe to the temperature sensor detecting the surface temperature or the internal temperature of the preheater 11 between the time when the diaryl carbonate is received into the mixing tank 7 and the time when the reception is stopped. A scheme may be used.
The heat source used for keeping the heat of the measuring device 13 and the transfer pump of the diaryl carbonate is preferably steam at 110 to 200 ° C, and the heat source of the preheater 11 is preferably steam at 120 to 220 ° C.

  When a preheater 11 is provided between the storage tank 10 and the mixing tank 7, the diaryl carbonate is heated by the preheater 11, so that the temperature of the storage tank 10 needs to be raised to a desired temperature in the mixing tank 7. There is no. In addition, from the viewpoint of ensuring the fluidity of the diaryl carbonate and preventing its discoloration, at least one or both of the temperature of the transfer pipe between the storage tank 10 and the mixing tank 7 and the temperature of the preheater 11 are set to 82 to 120 ° C. Can be reduced to In this case, it is necessary to add a heating means so that the mixing tank 7 itself can be heated to 135 to 220 ° C.

[Measurement of aromatic dihydroxy compound]
As a method of measuring the aromatic dihydroxy compound supplied to the mixing tank 7, for example, the mass of an aromatic dihydroxy compound storage hopper (not shown) is supplied to the mixing tank 7 from the storage hopper. There is a method of measuring before and after to determine the actual supply amount of the aromatic dihydroxy compound supplied to the mixing tank 7. Alternatively, as shown in FIG. 1, a scheduled supply amount or an aromatic dihydroxy compound larger than the planned supply amount is received in a measuring tank 2 in which a load cell 3 described later is installed, and oxygen and moisture in the atmosphere are replaced with an inert gas. After that, a predetermined amount is supplied to the mixing tank 7 according to the indicated value of the load cell 3, and the actual supply amount of the aromatic dihydroxy compound supplied to the mixing tank 7 is obtained from the difference in mass between the measuring tank 2 before and after the supply. Is mentioned.
However, in any of the methods, when the measuring tank 2 and the load cell 3 are installed on a pedestal that is affected by external influences such as wind, external vibration, and outside air temperature, the measuring accuracy may be deteriorated. From the viewpoint of eliminating such external influences as much as possible and further improving the measurement accuracy of the aromatic dihydroxy compound, two or more measurement points are provided on the measurement tank 2 using the measurement tank 2 installed on the independent stand 20. Is preferably provided.

  As at least a part of a pipe between the bucket conveyor 1 and the measuring tank 2 and a pipe for supplying the aromatic dihydroxy compound from the measuring tank 2 to the mixing tank 7, the measuring tank 2 is connected to the bucket conveyor 1 and the mixing tank 7. It is preferable to use the flexible tube 6 from the viewpoint of hardly being affected by vibration. Furthermore, it is preferable to connect a pressure equalizing pipe (not shown) to these pipes. By providing the equalizing pipe, the mass of the aromatic dihydroxy compound supplied to the measuring tank 2 can be measured more accurately. In order to prevent the powder of the aromatic dihydroxy compound from staying in the bellows portion of the flexible tube 6, the pressure equalizing pipe preferably includes a flexible tube having an insertion pipe at a connection portion with the pipe. Further, when the equalizing pipe includes a flexible tube, it is preferable that the bellows portion of the flexible tube can be purged with an inert gas. The material of the flexible tube 6 and the flexible tube in the pressure equalizing pipe may be any material having the same pressure resistance as the measuring tank 2, and PTFE (polytetrafluoroethylene) and SUS (stainless steel) are preferable.

  A preferred method for measuring the aromatic dihydroxy compound is shown below. That is, the planned supply amount of the aromatic dihydroxy compound is received in the measuring tank 2 provided with the load cell 3 having two or more measurement points installed on the independent stand 20. Next, oxygen and moisture contained in the atmosphere in the measuring tank 2 are replaced with an inert gas. Next, just before the aromatic dihydroxy compound is supplied to the mixing tank 7, the measuring tank 2 is weighed by the load cell 3, and then the entire amount of the aromatic dihydroxy compound is supplied to the mixing tank 7. Next, the electric vibrator and / or the air knocker attached to the cone portion of the measuring tank 2 are operated to drop the aromatic dihydroxy compound attached to the cone portion into the mixing tank 7. That is, the mixing tank 7 is located below the measuring tank 2 in the vertical direction. Next, the empty mass of the measuring tank 2 is measured by the load cell 3, and the actual supply amount of the aromatic dihydroxy compound is determined from the difference in mass before and after the supply of the aromatic dihydroxy compound to the mixing tank 7. Further, the supply amount of the aromatic dihydroxy compound can be back-checked with the indicated value of the liquid level meter in the mixing tank 7.

[Independent stand 20]
FIG. 2 is a diagram schematically illustrating an example of the independent stand according to the present embodiment. In the example shown in FIG. 2, the building accommodating the weighing tank 2 has a double structure of an independent gantry 20 and a wind gantry (not shown) provided outside the gantry 20. It is preferable that the foundation of the windshield mount and the foundation of the windbreak stand are independently installed. By making the foundation independent, external influences such as vibration on the independent stand 20 can be eliminated as much as possible. Further, in order to further prevent external influences on the independent gantry 20, it is preferable that the support portion of the pipe, electric and instrumentation cable ducts is connected to the wind gantry. Further, it is also preferable that a cable (such as an electric wire) straddling the wind-guard stand and the independent stand 20 has flexibility. It is also preferable that the walls, windows, doors, and the like of the wind-guard stand have a structure that makes it difficult for wind to enter from outside. Further, by providing an additional wall outside the wind-guard stand, the influence of the outside air temperature can be reduced. The measuring tank 2 is installed on the independent stand 20 via the load cell 3. Since the load cell 3 installed on the independent stand 20 is not affected by external vibration or the like, the weighing accuracy in a state where the load cell 3 is attached to the measuring tank 2 can be within ± 0.15% by mass.

[Measurement tank 2 for aromatic dihydroxy compound]
From the viewpoint of securing the space volume when the aromatic dihydroxy compound is received, suppressing the scattering of the aromatic dihydroxy compound powder, and shortening the time required for decompression and nitrogen replacement, the capacity of the measuring tank 2 is increased. Is preferably 1.5 to 2.5 times, more preferably 1.5 to 2.2 times the volume of the aromatic dihydroxy compound to be accepted. The capacity of the measuring tank 2 is preferably 250 m ³ or less, more preferably 150 m ³ or less. By setting the measuring tank 2 to 250 m ³ or less, it is possible to prevent the strength required for the gantry to be installed from becoming too large and the building in which the measuring tank 2 is installed to be extremely large.

  By making the pressure in the measuring tank 2 higher than the pressure in the mixing tank 7 to make it easier for the inert gas to flow from the measuring tank 2 to the mixing tank 7, the diaryl carbonate and the aromatic dihydroxy compound, and in some cases, the aromatic monohydroxy compound, It is preferable to prevent the hydroxy compound from adhering to a pipe or the like. In this case, the pressure of the measuring tank 2 only needs to be higher than the pressure of the mixing tank 7. When the measuring tank 2 is installed at a position higher than the mixing tank 7 (that is, above the vertical direction), 0.1 to 1000 kPaG is preferred, 0.1 to 500 kPaG is more preferred, and 0.05 to 20 kPaG is even more preferred. When the aromatic dihydroxy compound is transported by force from the measuring tank 2 to the mixing tank 7, the pressure in the measuring tank 2 is preferably 50 to 1000 kPaG. The pressure of the measuring tank 2 is adjusted by the PIC control, and is maintained within a predetermined range (a fluctuation range varies depending on the accuracy of an instrument, for example, ± 0.01 kPaG to ± 0.05 kPaG when the setting is 6 kPaG). Is preferred. When the aromatic dihydroxy compound is received in the measuring tank 2, the pressure of the bucket conveyor 1 is preferably made higher than the pressure of the measuring tank 2 by using sequence control or the like. In this specification, a pressure suffixed with “G” (eg, “kPaG” or the like) means a gauge pressure, and a pressure suffixed with “a” (eg, “ "Paa" etc.) and a blank pressure (for example, "kPa" etc.) indicate an absolute pressure.

  From the viewpoint of facilitating the pressure control of each polymerization vessel described later, the preparation time of the dissolved mixture from the reception of the diaryl carbonate to the mixing tank 7 until the transesterification reaction reaches equilibrium in the dissolved mixture storage tank 12A or 12B, It is desirable that the time is preferably within 12 hours, more preferably within 8 hours. In order to achieve such a mixing time, it is preferable that the time from when the aromatic dihydroxy compound is received at the receiving port of the measuring tank 2 to when it is discharged at the discharging port is short. From such a viewpoint, the size of the piping for receiving and discharging the aromatic dihydroxy compound connected to the upper part and the lower part of the measuring tank 2 is such that the total amount of the aromatic dihydroxy compound can be received or discharged within two hours. It is preferable that the pipe diameter be a pipe diameter that can be received or discharged within 1.5 hours.

  When the aromatic dihydroxy compound is received into the measuring tank 2 via the bucket conveyor 1, the connection between the outlet of the bucket conveyor 1 and the valve which may be provided in front of the inlet of the aromatic dihydroxy compound in the measuring tank 2 is shown in FIG. It is preferable to have a cone shape as shown in FIG. The cone shape of the connecting portion preferably has an apex angle of 20 to 90 degrees, more preferably 30 to 90 degrees.

  It is preferable that the lower part of the measuring tank 2 also has a cone shape. In this case, the angle of the vertex in the cone shape at the lower part of the measuring tank 2 may be an angle at which the aromatic dihydroxy compound does not stay. The angle of the vertex in the cone shape at the bottom of the measuring tank 2 is preferably 20 to 75 degrees, more preferably 20 to 60 degrees. An electric vibrator and / or an air knocker is preferably attached to the cone-shaped lower part of the measuring tank 2 so that the aromatic dihydroxy compound powder does not stay. After the entire amount of the aromatic dihydroxy compound is supplied to the mixing tank 7, in order to remove the powder adhering to the wall surface of the measuring tank 2, the electric motor vibrator and / or an air knocker is used for several seconds to several minutes. Is preferably vibrated. Further, in order to prevent the aromatic dihydroxy compound from being powdered by the impact when the aromatic dihydroxy compound is received into the measuring tank 2, a spiral spiral for the aromatic dihydroxy compound to slide down on the inside of the measuring tank 2. A shooter may be provided.

  A vent pipe (not shown) may be connected to the measuring tank 2, and the vent pipe may be provided with a pressure control valve. In consideration of the work of extracting the gas from the measuring tank 2 when the aromatic dihydroxy compound is received and the work of reducing the pressure and replacing with an inert gas, a ball valve of 1 to 20 inches or the like is provided in the bypass of the pressure control valve. Is preferably provided. It is preferable that the pipe diameter of the vent pipe is determined by assuming a time for reducing the pressure.

  A pipe for introducing an inert gas for pressurization may be connected to the measuring tank 2, and an automatic valve such as a ball valve of 1 to 20 inches is also provided on the bypass of the pressure control valve. Is preferred. It is also preferable to provide an instrumented air buffer drum for the automatic valve in order to speed up the operation of the automatic valve of 6 inches or more. It is preferable that the pipe for introducing the inert gas has a pipe diameter that allows a short period of time from depressurization to slight pressurization. It is more preferable to provide a buffer drum in the middle of the pipe so that the inside of the pipe is not depressurized.

  In order to prevent intrusion of the aromatic dihydroxy compound powder or the like into a meter that can be connected to the vent pipe of the measuring tank 2, the mounting nozzle or the like of the meter is vertically connected to the vent pipe from the upper side in the vertical direction to the lower side. Is preferred. When a control valve is provided in the vent pipe, the pipe from the flanges on the inlet and outlet sides of the control valve should be vertically downward to prevent the aromatic dihydroxy compound powder from clogging the control valve. Preferably, it is attached. Further, when the vent pipe is clogged with a powder of an aromatic dihydroxy compound, it is preferable that an inert gas be flowed into the pipe so that the powder and the like can be removed. In that case, it is preferable that the pipe for supplying the inert gas to the vent pipe be connected vertically from the vertical upper side to the lower side with respect to the vent pipe.

  When replacing the oxygen and moisture present in the measuring tank 2 with an inert gas, the inert gas may be introduced into the measuring tank 2 after or under reduced pressure in the measuring tank 2. At this time, there is a possibility that the powder of the aromatic dihydroxy compound soars in the measuring tank 2 and closes the vent pipe. Preferably, a filter is provided. The piping from the measuring tank 2 to the bag filter is preferably installed at an angle of 30 to 90 degrees downward with respect to the horizontal direction, and more preferably 60 to 90 degrees.

Preferably, split control or the like is used to control the pressure of the measuring tank 2. The exhaust capacity of the pressure control valve in the vent pipe preferably has an exhaust capacity (Nm ³ / hr) of 1 to 5 times the capacity of the measuring tank 2, and more preferably 1.5 to 3 times. It is preferable that a pressure control valve is also provided in a pipe for supplying the inert gas, and the pressure control valve supplies 0.3 to 2 times (Nm ³ / hr) of the capacity of the measuring tank 2 per hour. It is preferable to have the ability. The size of the pressure control valve (the diameter of the inner valve) is preferably 1/2 to 2 inches for both the pressure control valve of the vent pipe and the pressure control valve of the pipe for supplying the inert gas. When performing split control, it is also preferable to provide a dead zone (a range of an input signal in which the valve element does not operate in accordance with the change of the input signal).

  When the measuring tank 2 is provided vertically above the mixing tank 7 and the aromatic dihydroxy compound is received in the measuring tank 2 by the bucket conveyor 1, an automatic shut-off valve is provided below the measuring tank 2 (preferably a four-sided sheet). ) A rotary valve 5 (or a screw conveyor (not shown)) may be attached to the ball valve 4 and further below the ball valve 4. Further, a short pipe may be provided between the rotary valve 5 and the ball valve 4 below the measuring tank 2. These devices are preferably supported by a support member extending from a preferably cone-shaped lower part of the measuring tank 2. The aromatic dihydroxy compound may be received from the measuring tank 2 into the mixing tank 7 by pneumatic transportation. In the case of pneumatic transportation, from the viewpoint of preventing the aromatic dihydroxy compound powder from adhering to the pipe, plug transportation in which the aromatic dihydroxy compound moves in the supply pipe in a plug state in which it is aggregated is preferable. Further, the gas used for the pneumatic transportation is preferably an inert gas. In the case of pneumatic transportation, a feeder system is an example of a system for transporting the aromatic dihydroxy compound from the measuring tank 2 to the mixing tank 7. In the case of pneumatic transportation, the position where the measuring tank 2 is installed may be vertically above or below the upper part of the mixing tank 7.

[Load cell 3]
The load cell 3 that can be provided in the measuring tank 2 is preferably a two-point type having two or more measurement points as described above, more preferably a three-point type or a four-point type, and more preferably a three-point type. Is more preferable. The weighing accuracy after attaching the load cell 3 to the measuring tank 2 is preferably within ± 0.5% by mass, more preferably within ± 0.25% by mass, and further preferably within ± 0.15% by mass.

[Ball valve 4]
The upper and lower sides of the measuring tank 2 have an inlet and an outlet for the aromatic dihydroxy compound, and it is preferable that the ball valve 4 is provided on at least one of them. Further, it is preferable that the ball valve 4 on the discharge port side is directly attached to the flange. The ball valve is preferably an automatic valve having a four-sided valve seat in order to prevent the powder of the aromatic dihydroxy compound from entering the back side of the ball of the ball valve. Even if the size of the automatic valve becomes large, it is also preferable to provide a buffer drum for instrumentation air from the viewpoint of ensuring quick operation. The ball valve 4 is preferably supported by a support member extending from the upper or lower part of the measuring tank 2.

  The pipe connected to the ball valve 4 is preferably heated to 40 to 160 ° C. so that the pipe is melted even if the aromatic dihydroxy compound adheres. In addition, purging the ball valve 4 with an inert gas is preferable because the aromatic dihydroxy compound can be prevented from adhering to the ball valve 4.

[Rotary valve 5]
The rotary valve 5 (or screw conveyor) is preferable from the viewpoint of supplying the aromatic dihydroxy compound to the mixing tank 7 at a constant speed as much as possible. A short pipe and / or a flexible tube 6 may be attached to the outlet of the rotary valve 5 (or the screw conveyor). The flexible tube 6 preferably has an intubation tube (not shown). When using the flexible tube 6 provided with the inner tube, it is also preferable that the tube connected to the flexible tube 6 is a reducer in order to prevent the inner tube from contacting the wall surface of the tube. The inclination angle of the pipe from the flexible tube 6 to the upper nozzle of the mixing tank 7 is preferably 30 to 90 degrees, more preferably 60 to 75 degrees, with respect to the horizontal direction. The diameter of the pipe from the measuring tank 2 including the short pipe and the flexible tube 6 to the mixing tank 7 is such that the entire amount of the aromatic dihydroxy compound measured in the measuring tank 2 can be supplied to the mixing tank 7 in 0.25 to 2 hours. It is preferably a diameter.

A pipe (not shown) for introducing an inert gas may be connected to the shaft of the rotary valve 5. Inactive on both the process side and the atmosphere side of the rotary valve 5 to prevent air from leaking from the shaft of the rotary valve 5 and powder of the aromatic dihydroxy compound from entering the gap between the shaft and the main body. It is preferable to allow the gas to flow. The purge amount of the inert gas is preferably 0.1 to 20 Nm ³ / hr, and more preferably 0.3 to 10 Nm ³ / hr. In order to prevent the powder of the aromatic dihydroxy compound from entering the gap between the shaft portion and the main body, a structure in which horizontal plates are attached to both sides of the rotary valve on the bearing side is also preferable.

[Supply of aromatic dihydroxy compound to mixing tank 7]
In the step (B) of supplying the aromatic dihydroxy compound to the mixing tank 7, controlling the speed at which the aromatic dihydroxy compound supplied to the mixing tank 7 passes through the gas phase portion of the mixing tank 7 involves controlling the aromatic It is preferable from the viewpoint of preventing the dihydroxy compound from scattering to a vent pipe that can be connected to the mixing tank 7. The aromatic dihydroxy compound can be supplied to the mixing tank 7 by being accompanied by a gas (preferably an inert gas). For example, an aromatic dihydroxy compound can be supplied to the mixing tank 7 by blowing a gas into the mixing tank 7 and accompanying the gas. In the present embodiment, the linear velocity of the gas when the aromatic dihydroxy compound is supplied to the mixing tank 7 (hereinafter, referred to as “mixing tank supply gas linear velocity”) is defined as follows.
Linear velocity of gas supplied to mixing tank (m / sec) = (maximum flow rate of gas supplied to mixing tank 7 (Nm ³ / sec)) ÷ (cross-sectional area of gas flow in mixing tank 7 (m ² ))
Here, the “maximum flow rate of the gas supplied to the mixing vessel 7” may be “the maximum flow rate of the gas blown into the mixing vessel 7”. For example, in order to control the pressure in the mixing vessel 7, When a gas vent pipe provided with a pressure control valve is provided, it can be confirmed by the maximum flow rate of gas at the pressure control valve. The “maximum flow rate” indicates the maximum flow rate among the flow rates at each time point. Further, the “cross-sectional area of the gas flow in the mixing tank 7” means a cross-sectional area orthogonal to the gas flow direction in a region where the gas flows, and the mixing tank 7 has a straight body, When gas flows from one end to the other end, it indicates a cross-sectional area of a cross section orthogonal to the axial direction of the straight body portion. The mixing tank supply gas linear velocity is preferably 0.005 to 0.05 m / sec. By controlling the linear velocity of the gas supplied to the mixing tank to 0.005 to 0.05 m / sec, the powder of the aromatic dihydroxy compound is efficiently dropped into the liquid phase of the mixing tank 7 and the scattering to the vent pipe is further suppressed. be able to. When the linear velocity of the gas supplied to the mixing tank is 0.05 m / sec or less, it is possible to more effectively prevent the aromatic dihydroxy compound powder accompanying the inert gas discharged from the mixing tank 7 from entering the vent pipe. Thus, problems such as blockage of the vent pipe and the charged molar ratio deviating from the target can be further suppressed.

  When the supply of the aromatic dihydroxy compound to the mixing tank 7 is completed, the gas pressurizing the measuring tank 2 immediately flows into the mixing tank 7 (blow-through). In the blow-by state, the pressure in the measuring tank 2 is likely to temporarily become the same pressure as the mixing tank 7 to (the same pressure + 0.05 kPa). By achieving an appropriate blow-through state, the gas temporarily adhered to a pipe for supplying the aromatic dihydroxy compound from the measuring tank 2 to the mixing tank 7 (hereinafter, simply referred to as "supply pipe for the aromatic dihydroxy compound"). The aromatic dihydroxy compound can be more reliably contained in the mixing tank 7, and the diaryl carbonate and the aromatic monohydroxy compound scattered from the mixing tank 7 and the dissolved mixture thereof are supplied to the aromatic dihydroxy compound. It can also be prevented from adhering to piping. Therefore, it is important to control the gas flow rate in the blow-by state.

However, the gas flow rate in the blow-by state depends on the method of supplying the aromatic dihydroxy compound to the mixing tank 7 (equipment), the pressure of the measuring tank 2 and the clearance of the rotary valve 5, the diameter of the supply pipe of the aromatic dihydroxy compound, the gas Varies depending on the supply amount of Therefore, in the present embodiment, the gas linear velocity in the blow-by state of the supply pipe of the aromatic dihydroxy compound in the mixing tank 7 (hereinafter, referred to as “blowing gas linear velocity”) is defined as follows.
Blow-through gas linear velocity (m / sec) = (gas flow rate in supply pipe for aromatic dihydroxy compound (Nm ³ / sec)) ÷ (cross-sectional area of supply pipe for aromatic dihydroxy compound (m ² ))
The gas flow rate is determined, for example, by setting the flange portion (first flange portion) of the first nozzle on the mixing tank 7 side of the nozzle extending from the top of the mixing tank 7 to which the supply pipe for the aromatic dihydroxy compound is connected, This is the gas flow rate assuming that the same amount of inert gas blows through in one minute. In this case, the cross-sectional area of the supply pipe is the cross-sectional area obtained from the inner diameter of the first flange portion.

When the aromatic dihydroxy compound is supplied from the measuring tank 2 to the mixing tank 7 by pneumatic transport, the blow-through gas linear velocity is preferably 0.1 to 500 m / sec, more preferably 1 to 300 m / sec, More preferably, it is 20 to 200 m / sec. When the aromatic dihydroxy compound is supplied from the measuring tank 2 to the mixing tank 7 using the rotary valve 5 or the like, the gas linear velocity of the blow-through is preferably 1 to 100 m / sec, more preferably 2 to 60 m / sec. -35 m / sec is more preferable. If the gas linear velocity of the blow-through is in the range of 0.1 to 500 m / sec, the powder of the aromatic dihydroxy compound adhering to the supply pipe of the aromatic dihydroxy compound can be more effectively and reliably dropped into the mixing tank 7. This makes it possible to further prevent the diaryl carbonate and the aromatic monohydroxy compound from adhering to the supply pipe, and to more reliably reduce the gas linear velocity required to supply the entire amount of the aromatic dihydroxy compound to the mixing tank 7. Can be secured. Preventing the aromatic dihydroxy compound and the diaryl carbonate from adhering to the supply pipe of the aromatic dihydroxy compound is effective for keeping the charged molar ratio of the dissolved mixture in the mixing tank 7 within a predetermined range.
Furthermore, if the blow-through state is short, the effect of keeping the charged molar ratio in a predetermined range is further exhibited, so the blow-through time is preferably 0.01 to 8 minutes, more preferably 0.1 to 5 minutes. Minutes, more preferably 0.2 to 3 minutes.

  It is also preferable to provide a ball valve type shut-off valve in the bypass of the pressure control valve of the vent pipe in order to discharge the blown-in inert gas when the pressure of the mixing tank 7 rises in the blow-by state.

  The aromatic dihydroxy compound before being supplied to the mixing tank 7 may be a solid powder as described above, or may be a liquid. When the aromatic dihydroxy compound is in a liquid state, the mass of the aromatic dihydroxy compound supplied to the mixing tank 7 is directly measured without using the measuring tank 2 by measuring the aromatic dihydroxy compound with a Coriolis-type integrating flow meter or the like. can do. When the aromatic dihydroxy compound is liquid, when the aromatic dihydroxy compound is not supplied to the mixing tank 7, a circulation line is provided between the aromatic dihydroxy compound storage tank and the aromatic dihydroxy compound distillation system in order to prevent coloring. Preferably, an aromatic dihydroxy compound is circulated between the storage tank and the distillation system. In this case, a pipe for returning the aromatic dihydroxy compound to the storage tank for the aromatic dihydroxy compound is preferably connected immediately before the inlet of the storage tank for the aromatic dihydroxy compound, and the pipe is preferably as short as possible. .

  When the aromatic dihydroxy compound is in a liquid state, the valve at the inlet of the mixing tank 7 is preferably a three-way valve (for example, an L-type three-way valve and a T-type three-way polymer valve). It is preferably a double tube that can be heated to a high temperature.

[Mixing tank 7]
The mixing tank 7 may be provided with a heating means such as an internal coil provided inside the mixing tank 7, an external jacket provided outside the mixing tank 7, or an external coil provided outside the mixing tank 7, as necessary. A stirrer and a transfer pump 8A for circulating and transferring the dissolved mixture are provided. The mixing tank 7 is a tank in which an aromatic dihydroxy compound and a diaryl carbonate are dissolved to prepare a dissolved mixture, or a transesterification catalyst is added to an aromatic dihydroxy compound and a diaryl carbonate to partially or almost entirely react. This is a tank for preparing a dissolved mixture. The mixing tank 7 may be used alone or in combination. As the stirring device provided in the mixing tank 7, a known stirring tank and stirring blade can be used as long as it has a function of obtaining a more uniform dissolved mixture. Further, when the room temperature (that is, solid) aromatic dihydroxy compound is supplied to the mixing tank 7 and mixed with the diaryl carbonate in the mixing tank 7, the higher the supply rate of the aromatic dihydroxy compound, the higher the heat absorption of the aromatic dihydroxy compound. The internal temperature of the mixing tank 7 tends to decrease due to the melting of the aromatic dihydroxy compound. As a result, the diaryl carbonate may precipitate or the aromatic dihydroxy compound may not completely melt. From the viewpoint of preventing this, a double-pipe or multi-pipe heat exchanger (not shown) is provided outside the mixing tank 7, and an aromatic dihydroxy compound is provided between the heat exchanger and the mixing tank 7. The content containing the compound, the diaryl carbonate, the aromatic monohydroxy compound and, if necessary, the transesterification catalyst may be circulated to adjust the liquid temperature of the content to a desired temperature.

  When a part of the aromatic dihydroxy compound is in a slurry state in which the aromatic dihydroxy compound is not melted when the aromatic dihydroxy compound is supplied to the mixing tank 7, the transesterification reaction may not proceed uniformly. When the liquid temperature in the mixing tank 7 is 135 ° C. or more, the aromatic dihydroxy compound can be prevented from being in a slurry state in the mixing tank 7, and when the liquid temperature is 220 ° C. or less, coloring of the aromatic dihydroxy compound can be prevented. Therefore, the liquid temperature of the contents in the mixing tank 7 is adjusted to 135 to 220 ° C. The liquid temperature in the mixing tank 7 is more preferably from 140 to 210 ° C, and still more preferably from 145 to 200 ° C.

In the vicinity of the supply port of the aromatic dihydroxy compound in the mixing tank 7, it is possible to prevent the vapor of the aromatic dihydroxy compound, the scattered diaryl carbonate, and the aromatic monohydroxy compound generated by the reaction from adhering to the supply pipe. From the viewpoint, it is preferable that a ball valve (not shown) of a four-sided seat be attached. In order to prevent the vapor of the aromatic monohydroxy compound generated by the reaction with the diaryl carbonate in the mixing tank 7 from flowing into and attaching to the mounting nozzle of the ball valve, it is preferable to always flow an inert gas through the mounting nozzle. . The flow rate of the inert gas flowing through the mounting nozzle is preferably from 1 to 5 Nm ³ / hr.

  When the aromatic dihydroxy compound and the diaryl carbonate are received in the mixing tank 7, the pressure in the gas phase of the mixing tank 7 increases. In order to reduce the increased pressure, it is preferable that the mixing tank 7 is provided with a vent pipe for quickly discharging an inert gas or the like out of the mixing tank 7. Between the mixing tank 7 and the scrubber 9 described below, the vent pipe is preferably heated to 45 to 220 ° C, more preferably to 45 to 190 ° C, and more preferably to 45 to 160 ° C. More preferred. By setting the temperature of the vent pipe to 45 ° C. or higher, solidification of the aromatic monohydroxy compound can be further suppressed. By setting the temperature of the vent pipe to 220 ° C. or lower, it is possible to more effectively prevent the aromatic dihydroxy compound colored in the vent pipe from flowing back to the mixing tank 7 and leading to deterioration in the quality of the aromatic polycarbonate.

  In order to prevent the aromatic dihydroxy compound from flowing backward from the vent pipe to the mixing tank 7, the vent pipe of the mixing tank 7 extends vertically upward and then has an angle of 0.05 degrees or more with respect to the horizontal direction. Thus, it is preferable that it is connected to a scrubber 9 provided vertically below the outlet nozzle of the vent pipe.

  When the scrubber 9 is an ejector system in which the scrubbing liquid is circulated, the pressure of the vent pipe extending from the mixing tank 7 can be slightly reduced, so that the vapor or condensate of the aromatic monohydroxy compound, the diaryl carbonate and the aromatic dihydroxy compound flows in the vent pipe. It is difficult to stay in the water, which is preferable.

After the supply of the aromatic dihydroxy compound to the mixing tank 7 is completed and / or after a small supply of the diaryl carbonate, oxygen and moisture mixed in the mixing tank 7 with the aromatic dihydroxy compound are removed. It is also preferable to bubble the contents of the mixing tank 7 with an inert gas. The bubbling flow rate of the inert gas is preferably 0.01 to 0.5 times the volume of the mixing tank 7 per hour (Nm ³ / hr), and more preferably 0.05 to 0.4 times. Times, more preferably 0.1 to 0.25 times. The bubbling time is preferably 5 minutes or more, and it is preferable to continue bubbling until immediately before transferring the dissolved mixture to the dissolved mixture storage tanks 12A and / or 12B described below.

  Depending on the temperature at which the mixing tank 7 receives the diaryl carbonate, the liquid level in the mixing tank 7 may rise, and the temperature of the liquid in the mixing tank 7 may decrease before stirring is started. When the liquid temperature in the mixing tank 7 is reduced, the mixing tank 7 is depressurized if the supply amount of gas (the total amount of gas used to supply the replacement gas and the aromatic dihydroxy compound to the mixing tank 7) is small. In order to prevent the pressure in the mixing tank 7 from being reduced, a temperature control method (TIC control method) for controlling the liquid temperature in the mixing tank 7 and a pressure control method (PIC control method) for controlling the pressure of the steam that can be used as a heat source ) Is preferable. Alternatively, when the mixing tank 7 is provided with a gas vent pipe provided with a pressure control valve in order to prevent the pressure of the mixing tank 7 from being reduced, the supply capacity of the pressure control valve can be increased, It is also preferable to provide two pressure control valves.

  It is preferable to use steam as a heat source of the heating means of the mixing tank 7. Preferred heating means include an inner coil, an outer jacket and an outer coil. These may be used alone or in combination of two or more. When an internal coil is used, it is preferable that the internal coil is arranged in two to six layers.

  When supplying the aromatic dihydroxy compound to the mixing tank 7 or raising the temperature of the liquid in the mixing tank 7, when using steam as a heat source, heating means, particularly steam of the inner coil and / or the outer jacket and the mixing tank 7 are used. Since the temperature difference from the internal temperature tends to be large, a large amount of steam condensate (hereinafter, also referred to as “steam drain”) tends to be generated. The steam and steam drain are returned to a steam recovery system, which preferably includes a steam recovery facility. The steam recovery facility is a facility for recovering steam and steam drain and heating and pressurizing as necessary in order to use the steam and the steam drain again as a heat source of the heating means. When attempting to return the steam drain to the steam recovery system, if the pressure of the steam drain is lower than the pressure of the steam recovery system, the steam trap located therebetween may not be able to return the steam drain to the steam recovery system. At that time, a steam hammer is likely to occur near a point where the steam drain joins the steam recovery system. If the steam hammer occurs frequently, the heating means may be damaged. For example, the following method can be employed to prevent such damage. The “steam trap” selectively collects drain from mixed drain and steam.

Here, FIG. 3 shows a case where steam is used as a heat source of the heating means of the mixing tank 7 (for example, an internal coil and / or an external jacket or an external coil; hereinafter, these are collectively referred to as “internal coil or the like”). FIG. 3 is a diagram schematically showing an example of a mode in which a plurality of steam pipes are independently connected to a drain drum in a steam drain discharge facility for collecting steam and steam drain from an outlet from a mixing tank 7. FIG. 4 shows that when steam is used as the heat source of the heating means of the mixing tank 7, a part of the plurality of steam pipes joins after the outlet from the mixing tank 7, and the steam pipes reach the drain drum in the steam drain discharge facility. It is a figure which shows an example of the aspect of a connection typically. In FIG. 4, the diameter of the steam pipe after merging is, for example, 2 to 20 times the diameter of the steam pipe before merging. FIGS. 3 and 4 show a case where an inner coil and an outer jacket are used as heating means.
(1) When there are a plurality of steam pipes as internal coils and they do not merge at the outlet from the mixing tank 7, the pipes are independently transferred to the drain drum 22 of the steam drain in the steam drain discharge facility 21. Connect (see FIG. 3).
(2) There are a plurality of steam pipes as internal coils, and they join in the steam drain discharge facility 21 connected to the outlet from the mixing tank 7 to form one large diameter pipe, and the large diameter pipe is a drain drum. In the case of connection to 22, the diameter of the large-diameter pipe is set to, for example, 2 to 20 times the diameter of each steam pipe of the internal coil (see FIG. 4).
(3) The wall thickness of the pipe used for the pipe steel pipe for about one coil is increased from the stage before the inlet of the internal coil to the mixing tank 7 and from the stage after the outlet from the mixing tank 7 (for example, the thickness of the pipe). The schedule number used for the thickness dimension is changed from Sch10 to Sch160).
(4) The diameter of the internal coil near the outlet from the mixing tank 7 is increased to 1.2 to 4 times by a reducer.

Among the above, the methods (1) and (2) are more preferable in order to make the discharge of the steam drain easier and make it difficult for the steam drain to accumulate in the steam coil.
When the steam drain from the internal coil or the like is collected in a large drain drum, the capacity of the drain drum is the maximum supply amount of steam per hour (ton / hr; the steam used in the internal coil, the outer jacket, and the outer coil). Is preferably 0.001 to 0.4 times, more preferably 0.0025 to 0.2 times.

  When the pressure in the drain drum 22 is lower than the pressure of the steam recovery equipment (for example, indicated by reference numeral 24 in FIGS. 3 and 4), the steam and the steam drain are drained to the drain 25 or an atmospheric pressure drain provided underground. It is preferable to discharge to a drum (not shown). On the other hand, when the pressure in the drain drum 22 is higher than the pressure in the steam collection facility 24, it is preferable to discharge the steam and the steam drain to the steam collection facility 24 side.

  When recovering steam and steam drain from a steam outlet such as an internal coil of the mixing tank 7, it is preferable that the steam drain is received by an underground drum or the like and then sent to a recovery system by a pump. In this case, the drain is connected to a pipe at the steam outlet. It is preferable to provide a drum because the steam drain can be discharged and collected more efficiently. The discharge of the steam drain from the drain drum is controlled by an LIC (Level Indication Control) in the drain drum, and / or via a steam trap (for example, indicated by reference numeral 23 in FIGS. 3 and 4). Is more preferable. With the use of the LIC control (and the LIC control device used for the control), when a large amount of steam drain is generated, the steam drain can be discharged out of the system before the drain drum becomes full, and the steam is discharged into an internal coil or the like. Since the drain hardly remains, damage to the internal coil and the like by the steam hammer can be more reliably prevented. In addition, if the steam drain is collected by using the steam trap 23 at a pressure higher than the steam pressure of the steam collecting facility 24, the facility can be simplified with less heat loss. When the LIC control and the steam trap 23 are used together, when the steam drain pressure is lower than the steam pressure of the steam recovery equipment 24, the steam is discharged outside the system. When the steam drain pressure is high, the steam trap 23 is used. This is more preferable because the steam drain can be returned to the steam recovery facility 24.

  It is preferable that the internal coil is provided with a support portion (hereinafter, referred to as “support”, not shown) for fixing the internal coil. The support also serves as a baffle and is preferably provided at three or more locations. The internal coil preferably has a configuration in which the internal coil passes through the pipe in a region fixed to the support and in a region of 20 to 30 cm along a direction in which the internal coil extends from the portion. This is preferable because the U-bolt for fixing the internal coil to the support can be used to prevent the internal coil from being damaged. The U-bolt used for fixing the internal coil is preferably a double nut and is welded to the support. Further, when steam leaks from the internal coil, the pressure in the mixing tank 7 increases. Therefore, it is preferable to provide an interlock for stopping the supply of steam into the internal coil.

[Scrubber 9]
The scrubber 9 is a general collection system that circulates scrubbing liquid and absorbs steam. For example, the scrubber 9 is a vertical tank in which a vent pipe extending from the top of the mixing tank 7 is connected to a substantially central portion in the vertical direction, and a gas after absorbing steam is discharged to the upper part of the tank. Exhaust pipe is connected. Examples of the embodiment of the scrubber 9 include a packed tower, an ejector, a rotary spray tower, and a venturi. The exhaust pipe from the scrubber 9 may be directly open to the atmosphere, or may be connected to a vent pipe from another facility. Alternatively, the generated steam may be absorbed by circulating the scrubbing liquid in a vent pipe extending from the top of the mixing tank 7. In this case, for example, a heat exchanger for cooling the scrubbing liquid is provided in the circulation line of the scrubbing liquid, and the temperature of the circulating scrubbing liquid is cooled to 0 to 115 ° C. and returned to the scrubber 9.

  The scrubbing liquid is not particularly limited, but is, for example, a low-volatile solvent capable of dissolving or decomposing and absorbing an aromatic dihydroxy compound and / or diaryl carbonate, or a low-temperature liquid capable of cooling and solidifying steam. Examples of the scrubbing liquid include an aromatic monohydroxy compound, a diaryl carbonate, an alkylaryl carbonate, water, an aqueous sodium hydroxide solution, ethylene glycol and triethylene glycol. These are used alone or in combination of two or more.

  The scrubbing liquid may contain an aromatic dihydroxy compound, and by selecting the compounds to be contained in the scrubbing liquid and their ratio, the melting point of the scrubbing liquid is reduced, and the temperature of the circulating scrubbing liquid is reduced. Can also. For example, about 45% by mass of phenol (hereinafter referred to as “PH”), which is one kind of aromatic monohydroxy compound, and methylphenyl carbonate (hereinafter, referred to as “MPC”), which is one kind of alkylaryl carbonate. ) And bisphenol A (hereinafter referred to as “BPA”), which is one type of aromatic dihydroxy compound, does not coagulate even at 0 ° C. Also, a mixture of MPC and PH does not solidify at 40 ° C. if the PH is 95% by mass or less. When an aromatic monohydroxy compound is used as the scrubbing liquid, the temperature of the circulating liquid is preferably 42 to 115 ° C, more preferably 42 to 85 ° C, still more preferably 42 to 75 ° C, and particularly preferably 42 to 70 ° C. When a mixed solution of MPC and PH containing BPA of 5% by mass or less is used as the scrubbing liquid, the temperature of the scrubbing liquid is preferably 0 to 115 ° C, more preferably 0 to 85 ° C, and still more preferably 0 to 35 ° C. ° C, particularly preferably 0 to 20 ° C.

  A method is also preferable in which the scrubbing liquid is sprayed into the scrubber 9 so that the vapor and the scrubbing liquid are brought into more sufficient contact to collect the vapors of the aromatic monohydroxy compound, diaryl carbonate, and aromatic dihydroxy compound. When the aromatic dihydroxy compound or the like is not completely dissolved in the scrubbing liquid, the aromatic dihydroxy compound is provided on the suction side of a transfer pump provided in a transfer line for the scrubbing liquid from the scrubber 9 and / or a circulation pump provided in a circulation line. It is also preferable to remove undissolved substances with a suction filter. When an aromatic monohydroxy compound produced as a by-product in the polymerization step is used as a scrubbing liquid, the aromatic monohydroxy compound may contain water or an aromatic dihydroxy compound. In that case, it is preferable to distill the aromatic monohydroxy compound in a distillation column capable of separating high-boiling components such as water and an aromatic dihydroxy compound.

  When the concentration of the aromatic dihydroxy compound or diaryl carbonate in the scrubbing liquid has reached a certain level or more, a new scrubbing liquid is added while continuously extracting a part of the scrubbing liquid, and the scrubber 9 is continuously operated. Is preferred. As a method of continuously extracting a part of the scrubbing liquid, for example, the liquid level at the bottom of the tank of the scrubber 9 is set within a predetermined narrow range (for example, the scrubbing liquid in the scrubber 9 removes the scrubber 9). When the liquid level of the scrubbing liquid is 0% when the liquid level is the smallest in the operable range and 100% when the liquid level of the scrubbing liquid is the largest, the arbitrary ± 1% of 0% to 100% ), And a semi-batch method in which the level of the scrubbing liquid is controlled between 10% and 90% is preferred.

[Transfer pump 8A]
The transfer pump 8A circulates the dissolved mixture extracted from the mixing tank 7 back to the mixing tank 7 or transfers the dissolved mixture to the dissolved mixture storage tank 12A or 12B. The transfer pump 8A is preferably a pump having a mechanism capable of pulverizing the unmelted aromatic dihydroxy compound when the unmelted aromatic dihydroxy compound is sucked into the transfer pump 8A.

  It is preferable that a suction strainer is provided on the suction side of the transfer pump 8A. When replacing or cleaning the suction strainer, a pipe for supplying the aromatic monohydroxy compound may be connected to the transfer pump 8A so that the adhered dissolved mixture can be washed with the aromatic monohydroxy compound. When the diaryl carbonate is first supplied to the mixing tank 7, a part of the diaryl carbonate may be mixed into the suction pipe of the transfer pump 8A, so that the dissolved mixture is supplied from the mixing tank 7 to the dissolved mixture storage tank 12A or 12B. Before being transferred to the mixing tank 7, a short circulation operation is performed between the mixing tank 7 and the transfer pump 8A, and then the dissolved mixture is transferred from the mixing tank 7 to the dissolved mixture storage tank 12A or 12B, whereby the diaryl to the suction side pipe is transferred. Residual carbonate can also be suppressed.

  The temperature of the main body of the transfer pump 8A is preferably lower than the temperature of the dissolved mixture in order to prevent cavitation and liquid sealing. The transfer pipe of the dissolved mixture from the mixing tank 7 to the dissolved mixture storage tank 12A or 12B is supplied from a steam or heat medium boiler at a temperature lower than the temperature of the dissolved mixture to prevent coloring, alteration and liquid sealing of the dissolved mixture. It is also preferable to heat with a heating medium oil.

  In order to prevent the idle operation of the transfer pump 8A, a level switch (LIS) provided in a pipe connected to the bottom of the mixing tank 7 detects a drop in the liquid level at the bottom of the mixing tank 7, and the transfer pump 8A Preferably stop automatically. Similarly, in order to prevent the idle operation of the transfer pump 8A, it is preferable to detect a decrease in the current value of the transfer pump 8A and automatically stop the operation. The transfer pump 8A is stopped by an interlock in order to prevent the liquid level of the dissolved mixture storage tanks 12A and / or 12B from becoming higher than expected and to prevent the pressure of the dissolved mixture storage tanks 12A and / or 12B from abnormally increasing. It is also preferred.

[Dissolution mixture storage tanks 12A and 12B]
The dissolution mixture storage tanks 12A and 12B are storage tanks for allowing the dissolution mixture prepared in the mixing tank 7 to react until a predetermined equilibrium reaction rate is reached. The dissolution mixture is kept in the dissolution mixture storage tanks 12A and 12B, preferably at a liquid temperature of 160 to 220 ° C. for 1 to 12 hours. The liquid temperature is preferably 160 to 220 ° C, more preferably 160 to 210 ° C, and still more preferably 180 to 200 ° C. Further, the holding time is preferably 1 to 12 hours, more preferably 1.2 to 8 hours, and still more preferably 1.5 to 6 hours. In order to make the dissolution mixture a reaction mixture that has reached an equilibrium reaction rate, it is preferable to maintain the mixture at 160 ° C. or higher for 1 to 12 hours. When the reaction mixture that has reached the equilibrium reaction rate is supplied to the below-described stirred tank type first polymerization vessel 14, the prepolymer and / or the Mn of the polymer and / or the ratio of polymer terminal hydroxyl groups (hereinafter, referred to as “OH%”) ) Can be further suppressed, and it becomes easier to adjust the operating pressure of the main polymerization units 18A and 18B described later, which is preferable. Further, it is preferable to maintain the temperature at 220 ° C. or lower because the aromatic polycarbonate as a final product is hardly colored. In order to confirm whether the reaction mixture has reached the equilibrium reaction rate, the reaction mixture may be sampled and measured according to the method described in the following Examples.

  In addition, as described later, when the dissolved mixture is bubbled with an inert gas in the dissolved mixture storage tanks 12A and 12B, or when a mechanical seal of an instrument or a stirrer which can be provided in the dissolved mixture storage tanks 12A and 12B has a small amount of inert gas. In the case of purging, the used inert gas is discharged out of the system from the dissolved mixture storage tanks 12A and 12B. At that time, an aromatic monohydroxy compound by-produced may be discharged out of the system along with the inert gas. From the viewpoint of suppressing the amount of the discharged aromatic monohydroxy compound from increasing and the transesterification reaction from proceeding more than expected, the holding time is preferably 12 hours or less. Thereby, the amount of the aromatic monohydroxy compound discharged from the dissolved mixture storage tanks 12A and 12B can be further suppressed.

  Dissolution mixture reservoirs 12A and 12B include an internal coil and / or outer jacket, an addition nozzle for adding the transesterification catalyst, a stirrer, and a sampling nozzle for measuring the equilibrium conversion of the dissolved mixture. Preferably, at least one of them is provided. In addition, bubbling the dissolved mixture in the dissolved mixture storage tanks 12A and 12B with an inert gas is preferable from the viewpoint of removing water mixed with the aromatic dihydroxy compound. Two or more dissolution mixture storage tanks are preferably provided as shown, and preferably two or three dissolution mixture storage tanks are provided. Thereby, the dissolution mixture is supplied to some of the dissolution mixture storage tanks of the two or more units, and while the resulting reaction mixture is supplied to the polymerization step for obtaining a prepolymer or a polymer, another part of the dissolution mixture is dissolved. The dissolution mixture is fed to the mixture reservoir, where the reaction mixture can be obtained. Thereafter, when the amount of the reaction mixture in the first part of the dissolved mixture storage tank is reduced to a predetermined amount, the reaction mixture obtained in the other part of the dissolved mixture storage tank is supplied to a polymerization step for obtaining a prepolymer or a polymer. can do. In the meantime, the dissolved mixture is supplied to another part of the dissolved mixture storage tank, where the reaction mixture can be obtained. In this way, by repeatedly switching the dissolution mixture storage tank for supplying the reaction mixture to the polymerization step, the whole apparatus can be continuously operated, which is preferable.

  In order to adjust the pressure in the dissolved mixture storage tanks 12A and / or 12B, a pipe for introducing an inert gas and a vent pipe for discharging the inert gas are provided above the dissolved mixture storage tanks 12A and / or 12B. Is also good. As shown in the figure, when two or more dissolved mixture storage tanks are used, a plurality of vent pipes may be connected by a pressure equalizing pipe. It is preferable that at least a part of the vent pipe of the dissolved mixture storage tank extends downward from the dissolved mixture storage tank toward the outlet of the vent pipe, and is connected to a scrubber. This makes it possible to more efficiently prevent the aromatic monohydroxy compound that can be entrained in the inert gas discharged from the vent pipe from flowing back to the dissolved mixture storage tank, and absorb the aromatic monohydroxy compound with a scrubber. Can be. As the scrubber connected to the dissolved mixture storage tank, the same scrubber 9 as the mixing tank 7 may be used as shown in the figure, or another scrubber may be provided. When using steam as the heat source for the molten mixture storage tank, it is preferable that the piping at the outlet of the steam be the same as when using steam as the heat source for the mixing tank.

[Transfer pumps 8B and 8C]
The transfer pumps 8B and 8C circulate the reaction mixture extracted from the dissolved mixture storage tanks 12A and 12B back to the dissolved mixture storage tanks 12A and 12B, or transfer the reaction mixture to the stirred tank type first polymerization vessel 14. Or something. The transfer pumps 8B and / or 8C are connected to a suction filter (not shown) for supplying an aromatic monohydroxy compound to the suction filter on the suction side, and exchange the suction strainers of the transfer pumps 8B and / or 8C. Alternatively, it is preferable that the attached dissolved mixture can be washed with the aromatic monohydroxy compound when cleaning. In order to more effectively prevent the transfer pump 8B or 8C from causing cavitation, switching between the dissolved mixture storage tanks 12A and 12B was carried out in one of the storage tanks from which the reaction mixture was flowing out by the transfer pump. It is preferable to switch the transfer pump so that the liquid can flow out of the other storage tank when the liquid level falls below a level corresponding to 10% by mass of the amount of the dissolved mixture received therein. More preferably, the liquid level, which is a guide for switching the transfer pump, is equal to or lower than the level corresponding to 5% by mass of the amount of the dissolved mixture received.

[Filter for filtering the reaction mixture (not shown)]
A filter provided with a filter element for removing foreign substances in the reaction mixture may be provided between the dissolving mixture storage tanks 12A and 12B and the first polymerization vessel 14 with stirring tank. This filter removes foreign substances in the reaction mixture. One or more filters may be provided in series, and it is more preferable that two or more filters having the same or different pore sizes are provided. Further, it is also preferable to provide a spare filter in parallel so that the supply of the reaction mixture to the first polymerization vessel 14 with stirring tank is not stopped even if the filter element is closed.

The filter element used is preferably either a candle type or a disk type. As the structural material inside the filter element, a wire mesh, a metal sintered body, a metal fiber, a punching metal, or the like can be used, and a single material or a combination thereof can be used. It is preferable to use a filter element having a pore size of 0.25 to 50 μm with a filtration accuracy of 98% or more, and it is more preferable to use a filter element with a large pore size upstream and a filter with a small pore size downstream.
The surface of the filter element may be heated and / or treated with an acid. Before using the filter element, 1 to 1000 ppm of alkaline water is used to neutralize a reaction inhibitor such as a trace amount of an acid component attached to the filter element or to remove adsorbed oxygen or oil on the surface. It is also preferable to wash with a dissolution mixture (for example, aqueous potassium hydroxide solution) and / or an aromatic monohydroxy compound at 45 to 180 ° C.

  The material of the gasket used when fixing the filter element preferably has a heat-resistant temperature of 220 ° C. or higher. Further, those which do not deteriorate even when contacted with an aromatic dihydroxy compound, an aromatic monohydroxy compound or a diaryl carbonate are preferred.

  From the viewpoint of reducing undissolved substances, the transfer pipe for transferring the reaction mixture from the dissolution mixture storage tanks 12A and 12B to the first polymerization vessel 14 of the stirring tank is formed by a steam trace and / or a double pipe system. It is preferable to suppress a decrease in the temperature. Further, when the transfer pipe is a double pipe type, it can be used as a preheater for the reaction mixture, and it is also preferable that the heat source is a heat transfer oil or steam supplied from a heat transfer boiler.

[Flow controller for reaction mixture (not shown)]
It is preferable that a flow controller for adjusting the supply amount of the reaction mixture be provided at the inlet of the reaction mixture of the first polymerization vessel 14 with the stirring tank. The flow controller is preferably a combination of a reaction mixture flow control valve and an integrating flow meter (not shown), and more preferably has a jacket. The flow rate control valve for the reaction mixture is preferably provided on the side surface of the first polymerization vessel 14 with a stirring tank and at the position of the liquid surface of the liquid phase portion in the polymerization vessel. The supply amount of the reaction mixture is measured by the above-mentioned integrating flow meter (provided before the reaction mixture preheater described later is provided), and is controlled to a flow rate within a predetermined range by a flow control valve.

[Preheater of reaction mixture and prepolymer (not shown)]
A preheater for the reaction mixture can be provided in the supply pipe for supplying the reaction mixture from the dissolution mixture storage tank 12A or 12B to the first polymerization vessel 14 with the stirring tank. The preheater for the reaction mixture is preferably capable of heating the reaction mixture to a temperature higher than the temperature in the dissolution mixture storage tank 12A or 12B and lower than the reaction temperature in the first polymerization vessel 14 with the stirring tank. It is preferable that the preheater of the reaction mixture is provided with a heat amount capable of evaporating 0 to 50% by mass of the amount of the aromatic monohydroxy compound evaporated in the first polymerization reactor 14 with a stirring tank.

  A prepolymer preheater can be provided in a supply pipe for supplying the prepolymer from the stirred tank type first polymerization device 14 to the stirred tank type second polymerization device 15. It is preferable that the prepolymer preheater is provided with a heat amount capable of evaporating 0 to 50% by mass of the amount of the aromatic monohydroxy compound evaporated in the stirred tank type second polymerization device 15.

[Agitated Vessel Type First Polymerizer 14, Agitated Vessel Type Second Polymerizer 15]
The stirred tank type first polymerization device 14 and the stirred tank type second polymerization device 15 are facilities for producing a prepolymer having Mn of 400 to 7000 from the reaction mixture. The type of the stirred tank polymerization reactor is preferably a known vertical reactor in which the rotation axis of the stirring blade is vertical.

  During the time from the start of the supply of the diaryl carbonate to the mixing tank 7 to the end of the supply of the reaction mixture to the first polymerization vessel 14 with the stirred tank, the aromatic monohydroxy compound generated by the transesterification reaction is discharged out of the system. From the viewpoint of preventing the concentration of the aromatic dihydroxy compound in the reaction mixture from fluctuating, the time is preferably 1 to 24 hours, more preferably 2 to 12 hours, and still more preferably 3 to 8 hours.

  The first polymerization vessel 14 with a stirring tank is preferably operated continuously at an internal temperature of 210 to 240 ° C. and a pressure of 6.65 to 13.3 kPa (50 to 100 Torr). The Mn of the prepolymer at the outlet of the first polymerization vessel 14 with a stirring tank is preferably 400 to 1200. The residence time of the reaction mixture and the prepolymer in the first polymerization vessel 14 with a stirring tank is preferably within 1.5 hours.

The prepolymer produced in the first polymerization vessel 14 of the stirring tank type is continuously stirred by a transfer pump (not shown) provided in a pipe connected to the bottom of the first polymerization vessel 14 of the stirring tank type. It is transferred to the double polymerization unit 15. As a type of the transfer pump, for example, a gear pump is used. A preheater may be provided in the middle of the prepolymer transfer pipe from the first polymerization reactor 14 to the second polymerization reactor 15 to heat the prepolymer to 210 to 275 ° C. The transfer pipe may be provided with a filter for removing solids.
In order to more effectively and reliably prevent the liquid ring and the coloring of the reaction mixture, the pipes and filters from the dissolution mixture storage tank 12A or 12B to the stirred tank type first polymerization vessel 14 reduce the temperature of the reaction mixture in contact with them. It is preferable to make the temperature equal to or lower than the temperature.

  The stirring tank type second polymerization vessel 15 is preferably continuously operated at an internal temperature of 240 to 275 ° C. and a pressure of 1.3 to 3.99 kPa (10 to 30 Torr). The Mn of the prepolymer at the outlet of the stirred tank type second polymerization vessel 15 is preferably 2000 to 7000.

  The rotation speed and discharge pressure of a transfer pump for extracting and transferring the prepolymer or polymer provided at the bottom of each polymerization vessel, and / or a viscometer provided at a discharge pipe, and / or It is preferable that the molecular weight of each polymerization vessel can be confirmed by the pressure of the polymer or the inlet of the polymer.

[Inert gas absorption equipment (not shown)]
The production apparatus according to the present embodiment includes an inert gas absorption facility for absorbing an inert gas into a prepolymer or a polymer between the first stirring type polymerization unit 14 and the second stirring type polymerization unit 15 and / or May be provided between the stirring type second polymerization device 15 and a main polymerization device 16 described later. The inert gas absorbing equipment makes a prepolymer or a polymer absorb an inert gas, for example, in order to promote a transesterification reaction described in WO 99/64492. Examples of the inert gas absorbing equipment include a vertical cylindrical tank (for example, a vertical cylindrical tank) in which a wire and / or a wire mesh is provided, and a stirring tank.

[Main polymerization units 16, 18A and 18B]
The main polymerization units 16, 18A and 18B are polymerization units for producing a prepolymer and a polymer having Mn of 4000 to 30,000 from the prepolymer supplied from the second stirring type polymerization unit 15. As a type of the main polymerization units 16, 18A and 18B, for example, a known wire-type vertical cylindrical tank (for example, a vertical cylindrical tank) in which a prepolymer or a polymer is dropped along a wire or a wire net and polymerized by being dropped. And a known horizontal polymerization vessel such as a horizontal polymerization tank in which the rotation axis of the stirring blade is horizontal. The main polymerization vessels 16, 18A and 18B are each one or more, and may be all wire-type vertical cylindrical tanks or all horizontal polymerization tanks, or may be a combination of a wire-type vertical cylindrical tank and a horizontal polymerization tank. . The number of main polymerizers is not particularly limited, and may be three as shown, but is preferably two to six. As shown in FIG. 1, when the manufacturing apparatus of the present embodiment includes the main polymerization reactors 16, 18 </ b> A and 18 </ b> B, the temperature and pressure in the main polymerization reactor 16 are within a range where desired prepolymers and polymers can be obtained. Although not particularly limited, preferably, the temperature is 240 to 300 ° C. and the pressure is 990 to 20 Paa. The temperature and pressure in the main polymerization units 18A and 18B are not particularly limited as long as the desired prepolymer and polymer can be obtained, but preferably the temperature is 250 to 300 ° C and the pressure is 500 to 20 Paa.

[Equipment material etc.]
The material of each device or device used in the present embodiment may be any known material, and for example, austenitic stainless steel, also called 18-8 stainless steel, is preferable. Specific examples include SUS302, SUS304, SUS304L, SUS309S, SUS310S, SUS316, SUS316L, SUS317, SUS321, and SUS347. More preferred materials are SUS304 and SUS316. Further, these stainless steels may further contain niobium or vanadium. Examples of a method of including these metal elements in stainless steel include a method of adding these metals to molten steel and a method of adding the metals by a method such as ion etching or vapor deposition. The total content of niobium and vanadium contained in the stainless steel is preferably from 10 to 1000 ppm.

  The metal surfaces of the piping and equipment from storage tank 10 to main polymerization vessels 18A and 18B may be buffed. The surface roughness of those metal surfaces is preferably 50 μm or less, more preferably 10 μm or less. The metal surfaces of piping and equipment must be cleaned with chemicals, hot water, dilute alkali, and to remove dirt, oil, and reaction inhibitors (such as acids) adhering to the metal surface and adsorbed oxygen on the metal surface. It is also preferable to be washed with at least one selected from the group consisting of an aromatic monohydroxy compound, a diaryl carbonate, and a molten mixture of an aromatic dihydroxy compound and a diaryl carbonate.

[Aromatic dihydroxy compound]
As the aromatic dihydroxy compound according to the present embodiment, for example, an aromatic dihydroxy compound described in Patent Document 1 is used. A particularly preferred aromatic dihydroxy compound is BPA. Further, as the aromatic dihydroxy compound, only one kind may be used alone, or two or more kinds may be used in combination.

[Diaryl carbonate]
As the diaryl carbonate according to the present embodiment, for example, a diaryl carbonate described in Patent Document 1 is used. A particularly preferred diaryl carbonate is diphenyl carbonate (hereinafter, referred to as "DPC"). The diaryl carbonate may be used alone or in combination of two or more. The diaryl carbonate may contain an aromatic monohydroxy compound such as PH, t-butylphenol, and cumylphenol for terminal conversion and molecular weight control.

[Charging molar ratio of aromatic dihydroxy compound and diaryl carbonate]
The molar ratio between the aromatic dihydroxy compound and the diaryl carbonate charged in the mixing tank 7, that is, the charged molar ratio is determined by the Mn and OH% of the target aromatic polycarbonate, the type of the aromatic dihydroxy compound and the diaryl carbonate to be used, and the polymerization. Determined by temperature, as well as other polymerization conditions. From the viewpoint of realizing a better polymerization reaction and more effectively preventing the coloring and the decrease in heat resistance, the charging ratio within a predetermined range is defined as a molar ratio of the charged amount of the diaryl carbonate to the charged amount of the aromatic dihydroxy compound. On the basis, it is preferably from 1.05 to 1.30, more preferably from 1.05 to 1.25, and even more preferably from 1.05 to 1.20. When the charged amount (molar ratio) of the diaryl carbonate is 1.05 or more, coloring and heat resistance can be further improved, and when the charged amount is 1.30 or less, the polymerization reaction more easily proceeds.

[Polyfunctional compound]
Further, a polyfunctional compound may be used to impart a branched structure to the target aromatic polycarbonate. Examples of the polyfunctional compound include 1,1,1-tris (4-hydroxyphenyl) ethane and 4- [4- [1,1-bis (4-hydroxyphenyl) ethyl] -α, α-dimethylbenzyl Phenol is preferably used. The amount of the polyfunctional compound to be used is preferably 0.2 to 1.0 mol%, more preferably 0.2 to 0.9 mol%, and more preferably 0.3 to 0.8 mol% based on 100 mol% of the aromatic dihydroxy compound. Mole% is more preferred.

[Transesterification catalyst]
In the present embodiment, the polymerization reaction between the aromatic dihydroxy compound and the diaryl carbonate does not require the use of a transesterification catalyst. However, in order to increase the polymerization rate, if necessary, for example, it is described in Patent Document 1. A transesterification catalyst may be used. When a transesterification catalyst is used, one transesterification catalyst may be used alone, or two or more transesterification catalysts may be used in combination. The amount of the transesterification catalyst used is preferably 50 to the amount of the raw material aromatic dihydroxy compound from the viewpoint of realizing a polymerization reaction which is practically better, and more effectively preventing coloring and a decrease in heat resistance. -300 ppb, more preferably 60-200 ppb, even more preferably 70-150 ppb.

The transesterification catalyst may be added as it is, or may be diluted with water, an aromatic monohydroxy compound, diaryl carbonate, or the like. However, when water is used, water may be mixed into the aromatic monohydroxy compound by-produced in the polymerization reaction.
Further, as a preferable form of the transesterification catalyst to be added, a powder or a tablet (tablet) is mentioned, and a commercially available one may be used as it is. Examples of the method of adding a transesterification catalyst include a method of adding a transesterification catalyst to a powdery aromatic dihydroxy compound and / or diaryl carbonate, compressing and solidifying the resulting mixture into a production apparatus, and a method of compressing and molding an aromatic compound. A method in which a transesterification catalyst is added to a container made of an aromatic dihydroxy compound and / or a diaryl carbonate, and the whole container is charged into a production apparatus. The aromatic dihydroxy compound and / or diaryl carbonate melted in a nitrogen glove is placed in an opening. A method in which the solidified material is accommodated in a SUS container having a tapered shape so that the diameter is larger than the diameter of the bottom portion, and a transesterification catalyst is added thereto, and the solidified material is cooled, and then put into a manufacturing apparatus. Container made of aromatic polycarbonate (by film made of aromatic polycarbonate) It was added transesterification catalyst in.), Including packaging, and a method of introducing to the each container manufacturing device. According to the above-described method, a container made of an aromatic dihydroxy compound, a diaryl carbonate, and an aromatic polycarbonate is immediately dissolved when added to a molten diaryl carbonate, a dissolved mixture, and a prepolymer in a production apparatus. 7. In the dissolution mixture storage tanks 12A and 12B and the stirred tank type first polymerization vessel 14, when the progress of the reaction is slow, a large amount of transesterification catalyst can be added at once, which is effective. In addition, for the solid catalyst, it is necessary to perform pulverization and the like in order to accurately measure the amount of addition calculated by the calculation. Therefore, do not perform operations such as pulverization, and charge an excess of 0 to 100 mg from the calculated value. Is also preferred. In this paragraph, the aromatic dihydroxy compound and the diaryl carbonate are preferably used as raw materials in the production method of the present embodiment.

  The transesterification catalyst may be added via a nozzle into the production equipment. The nozzle used for adding the transesterification catalyst is one selected from the mixing tank 7, the dissolved mixture storage tanks 12A and 12B, the stirred tank type first polymerization device 14, and the stirred tank type second polymerization device 15. It is preferable to be provided above the above devices. The size of the nozzle is preferably 2 to 4 inches, a ball valve may be attached to the nozzle, and a short pipe provided with a pressure gauge, a vent pipe, a pipe for supplying an inert gas, and the like above the nozzle. Is also preferable. When supplying a transesterification catalyst by attaching a pipe for supplying an inert gas to the short pipe, by generating a flow of the inert gas from the pipe for supplying the inert gas to a tank provided with a nozzle. It is also preferable to prevent the aromatic monohydroxy compound from adhering to the short tube. It is also preferable to always flow an inert gas below the nozzle to which the transesterification catalyst is added so as to suppress the adhesion of the powder of the diaryl carbonate, the aromatic monohydroxy compound, and the aromatic dihydroxy compound. The flange for supplying the transesterification catalyst is preferably one that can be stopped by a sanitary type flange type clip that can be easily opened. It is also preferable to automatically supply the transesterification catalyst. Further, the transesterification catalyst may be added to the dissolution mixture in the middle of the transfer pipe connecting the mixing tank 7 and the dissolution mixture storage tank 12A or 12B, and / or the dissolution mixture storage tank 12A or 12B and the stirring tank type. One may be added to the reaction mixture in the middle of the transfer pipe connecting the polymerization reactor.

[Catalyst deactivator]
In the present embodiment, for example, a known catalyst deactivator described in Patent Document 1 may be used. The amount of the catalyst deactivator used is preferably 0.5 to 50 mol, more preferably 0.5 to 10 mol, and still more preferably 0.8 to 5 mol per mol of the transesterification catalyst. It is. The catalyst deactivator is added, for example, in an extruder.

[Additives, other]
The aromatic polycarbonate obtained in the final main polymerization reactors 18A and 18B may be sent in a molten state from the main polymerization reactors 18A and 18B to the subsequent devices 19A and 19B. The subsequent devices 19A and 19B are not particularly limited as long as they are devices that conventionally receive the molten aromatic polycarbonate, and include, for example, an extruder, a pelletizer, a sieve, a dryer, a silo, and a packaging machine. For example, a melted aromatic polycarbonate is supplied to an extruder, where other resins such as ABS and PET, heat stabilizers, antioxidants, light stabilizers, ultraviolet absorbers, release agents, flame retardants are used. And other additives such as organic and inorganic pigments and dyes, metal deactivators, antistatic agents, lubricants and nucleating agents. These other resins and optional additives may be used alone or in combination of two or more. Further, the aromatic polycarbonate produced according to the present embodiment is, for example, an aliphatic dihydroxy compound (diol) such as ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and 1,10-decanediol. Dicarboxylic acids such as succinic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, cyclohexanecarboxylic acid and terephthalic acid; and, for example, lactic acid, P-hydroxybenzoic acid and 6-hydroxy-2 -Oxy acids such as naphthoic acid may be contained.

  Further, PH which may be by-produced in the first polymerization tank 14 with the stirring tank, the second polymerization tank 15 with the stirring tank, and the main polymerization tanks 16, 18A and 18B may be collected by the transfer pump 17.

  As is clear from the above description, according to the production method of the present embodiment, an aromatic polycarbonate can be produced continuously. The aromatic polycarbonate obtained by the production method of the present embodiment can be formed into a molded article through a predetermined molding step. The molding step may be a known molding step. For example, in the molding step, an aromatic polycarbonate is molded using an injection molding machine, an extrusion molding machine, a blow molding machine, a sheet molding machine, or the like to obtain a molded product. Can be. The obtained molded article can be used for a wide range of applications such as automobiles, electricity, electronics, OA, optical media, building materials and medical treatment.

  According to the present embodiment, it is possible to provide a method for easily controlling an operating condition at the time of production and efficiently producing an aromatic polycarbonate with little coloring. Further, by flowing a large amount of steam into the heating coil installed in the mixing tank, the temperature in the mixing tank can be quickly adjusted.

  Hereinafter, the present invention will be described with reference to specific examples and comparative examples, but the present invention is not limited to these examples.

  The method of measuring each property applied in the examples and comparative examples will be described below.

(1) Equilibrium Reaction Rate 0.5 g of the reaction mixture collected from the dissolution mixture storage tank and 0.05 g of phenylurethane as an internal standard substance were dissolved in 40 mL of THF, and used as a sample. The amount of each component contained in the sample was measured using an ultra high performance liquid chromatography device (product name "ACQUITY UPLC", manufactured by Waters), and the equilibrium reaction rate was derived based on the measurement results. Note that a mixed eluent composed of distilled water and acetonitrile was used as the eluent. The measurement conditions were as follows. First, the column temperature was set to 40 ° C., the ratio of distilled water to acetonitrile in the mixed eluent (distilled water / acetonitrile) was set to 80/20, and the measurement was started. Thereafter, the ratio of distilled water / acetonitrile is gradient to 30/70 over 4.5 minutes, the ratio is maintained for 2 minutes, and then the ratio of distilled water / acetonitrile is 0.1 / 99. 9 and the ratio was maintained for 0.9 minutes, and then the conditions were adjusted to a distilled water / acetonitrile ratio of 80/20 over 0.1 seconds. As the column, a column of HSS T3 (1.8 μm, length 100 mm) for the ultra high performance liquid chromatography device was used.
The detection of each component was performed using a UV detector having a detection wavelength of 254 nm. The amount of the unreacted aromatic dihydroxy compound in the reaction mixture in the sample was determined from the extinction coefficient of the internal standard substance, and the amount of the charged aromatic dihydroxy compound (the aromatic content when the total amount of the charged raw materials was converted to 0.5 g) The amount of unreacted aromatic dihydroxy compound was subtracted from the amount of aromatic dihydroxy compound) to determine the reaction conversion of the aromatic dihydroxy compound, and this value was used as the equilibrium reaction rate. For example, when BPA was used as the aromatic dihydroxy compound and DPC was used as the diaryl carbonate, the reaction conversion of BPA was determined from the following formula.
A = Sample amount (0.5 g) × (BPA preparation amount) / (BPA preparation amount + DPC preparation amount)
(Here, A indicates the amount (g) of BPA when the total amount of the charged raw materials is converted to 0.5 g.)
BPA reaction conversion (%) = [(A-Amount of unreacted BPA in sample (g)) / A] × 100

(2) Number average molecular weight (Mn)
Mn was measured using gel permeation chromatography (GPC). Using tetrahydrofuran as a solvent and a polystyrene gel as a gel, it was determined from a calibration curve of standard monodisperse polystyrene using a reduced molecular weight calibration curve according to the following equation.
MPC = 0.3591 x MPS 1.0388
(Here, MPC indicates the molecular weight of polycarbonate, and MPS indicates the molecular weight of polystyrene.)

(3) Melt index (MI)
The MI (g / 10 min) was measured under the conditions of 300 ° C. and 1.2 kg load according to ISO 1133. The larger the MI, the better the fluidity.

(4) Polymer terminal hydroxyl group ratio (OH%)
OH% was obtained by dissolving 0.3 g of an aromatic polycarbonate in 5 mL of deuterated chloroform and using a ¹ H-NMR apparatus (manufactured by JEOL Ltd., product name “EX-400”) at 23 ° C. It was measured and calculated as the ratio of hydroxyl terminal to the total number of terminals.

(5) Hue (b ^* value)
A disk-shaped test plate having a diameter of 5.5 cm and a thickness of 3.2 mm was injection-molded under the conditions of a barrel temperature of 300 ° C. and a mold temperature of 90 ° C. using the aromatic polycarbonates produced in Examples and Comparative Examples.
The chromaticity of the test plate was measured using a spectrophotometer according to JIS Z8722 as a colorimeter. The color tone was represented by a b * value as an index of yellowness, which is a CIELAB method (Commission Internationale del'Eclairage 1976 L ^* a ^* b ^* Diagram) color system based on JIS Z8729.
Specifically, the test plate was placed on a white plate having a b ^* value of 1.97 as a measurement reference, and the b ^* value of the test plate was measured by a reflection method.

<Example 1>
The manufacturing apparatus shown in FIG. 1 was used. More specifically, as the mixing tank 7, a vertical stirring tank provided with two-stage paddle blades having a diameter of 3.8 m and an internal capacity of 80 m ³ was used. A piping nozzle for charging an aromatic dihydroxy compound having an inner diameter of a flange portion of 400 mm was connected to an upper portion of the mixing tank 7. Independently stand 20 shown in FIG. 2, the metering chamber 2 and the load cell 3 having an inner volume 90m ³ was installed. The independent gantry 20 was built on an independent foundation and provided with flexible electrical wiring, instrumentation cables, and piping. The wind-guard stand (not shown) is a building that is built on a foundation made independently of the foundation of the independent stand 20 outside the independent stand 20, and supports such as piping are attached. I was The measuring tank 2 was connected to a vent control valve having an exhaust amount of 150 Nm ³ / h for controlling the internal pressure by discharging gas inside the measuring tank 2.

At the steam outlet of the internal coil provided in the mixing tank 7 and the steam outlet of the outer jacket provided outside, a steam drain discharge facility 21 (portion surrounded by a broken line) shown in FIG. 3 is installed. Was. A steam trap 23 having a processing capacity of 18 tons / hr provided in parallel was connected to the drain drum 22 having an internal capacity of 0.5 m ³ . The pipe diameter at the steam outlet of the internal coil in the steam drain discharge facility 21 is 1.5 inches, the pipe diameter at the steam outlet of the outer jacket is 2.5 inches, the pipe diameter at the outlet of the drain drum 22 is 6 inches, and the steam trap is used. The pipe diameter from the pipe 23 to the drain 25 was 6 inches, and the pipe diameter from the steam trap 23 to the steam recovery facility 24 was 4 inches. The set value (SV value) of the level control (LIC control) of the steam drain in the drain drum 22 was 3%. Further, the steam drain discharge facility 21 has a function of discharging steam to the atmosphere side of the drain drum 22 when the temperature of the steam drain is lower than the temperature in the facility 21. The steam outlet of the steam trap 23 is connected to a steam recovery facility 24 having a pressure of about 0.4 MPaG (about 140 ° C.).

  The accuracy of the load cell 3 was checked using 50 weights of 20 kg and water. A scale for measuring water used was a 1500 kg maximum scale (weighing accuracy: 0.02% or less). 50 tons of water were put into the measuring tank 2 by 1 ton each, and it was confirmed that the error between the indicated value of the load cell 3 and the integrated value of the supplied water was within ± 0.15% by mass. As a load cell, a three-point type CC21 Capacity: 36 tf (product name, manufactured by Daiwa Seiko Co., Ltd.) was used. Since the measuring tank 2 was installed on the independent stand 20, the indicated value of the load cell 3 did not change even when there was wind or external vibration.

  A Coriolis-type integrating flow meter was used as the diaryl carbonate measuring device 13. In order to check the accuracy of the diaryl carbonate measuring device 13, 50 tons of water are stored in the measuring tank 2, and the diaryl carbonate measuring device 13 is filled with water. Was extracted, and it was confirmed that the indicated value of the load cell 3 and the indicated value of the measuring device 13 were the same. Next, the measuring tank 2 is filled with 50 tons of water via the measuring device 13, and water is extracted while being weighed with a scale of 1 ton, and it is confirmed that the integrated value of the scale matches the indicated value of the load cell 3. confirmed. When the above operation was performed twice, the accuracy of the measuring device 13 was within ± 0.15% by mass.

  Next, the measuring tank 2 was dried and replaced with nitrogen. Using the bucket conveyor 1, BPA was supplied to the measuring tank 2 until the indicated value of the load cell 3 became about 22.5 tons.

  The DPC maintained at 120 ° C. in the DPC storage tank 10 is heated to 160 ° C. by the preheater 11, and the total charged molar ratio of DPC and BPA with respect to 22.5 tons of BPA becomes 1.17. Thus, the planned amount of DPC to be charged was calculated. DPC of 94.29% by mass (23.3 tons) of the planned charge was supplied to the mixing tank 7 (large supply).

  Next, as an ester exchange catalyst, tablets of commercially available potassium hydroxide (primary reagent (purity: 85%)) were added to 22.5 tons of BPA so as to have a weight of about 120 mass ppb in terms of potassium atom.

  The BPA in the measuring tank 2 was purged with nitrogen, and the whole amount was supplied to the mixing tank 7 purged with nitrogen over 0.75 hours. During the supply of BPA, the internal pressure of the meter 2 for the aromatic dihydroxy compound was maintained at 7 kPaG and the internal pressure of the mixing tank 7 was maintained at 6 kPaG by pressure control (PIC control). Steam at 200 ° C. was supplied to the inner coil and the outer jacket of the mixing tank 7 at 0.1 to 8 tons / hr, and the liquid temperature in the mixing tank 7 was maintained at 140 to 160 ° C. The gas linear velocity in the gas phase of the mixing tank 7 during the supply of BPA from the measuring tank 2 was 0.04 m / sec or less. The gas linear velocity of the blow-through at the end of the supply was 12 m / sec, and the blow-through time was 3 minutes.

  With respect to the difference of 22.5 tons (actual supply amount) of the load cell indicated values before and after the supply of BPA, the additional DPC supply amount is calculated so that the desired molar ratio between BPA and DPC is obtained. The obtained 1.41 tons of DPC was supplied to the mixing tank 7 (small supply). Thereafter, the liquid temperature in the mixing tank 7 was raised to 195 ° C. By installing the steam drain discharge facility 21 shown in FIG. 3, no steam hammer was generated in the internal coil in the mixing tank 7 while the temperature of the solution was raised to 195 ° C. In addition, steam drain emissions were favorable.

After preparing the melt mixture, the melt mixture was supplied to a melt mixture storage tank 12A having an internal volume of 80 m ³ over 0.75 hours, and the inside thereof was maintained at 195 ° C. Immediately after the dissolution mixture is supplied to the dissolution mixture storage tank 12A, the liquid temperature in the mixing tank 7 is lowered to about 160 ° C., and DPC of 94.29% by mass (23.3 tons) of the planned charge is again supplied to the mixing tank 7. Feed and dissolve mixture prepared as described above.

  The reaction mixture, which was held in the dissolution mixture storage tank 12A for 3.9 hours and reached an equilibrium reaction rate of 80%, was flowed at a flow rate of 12 tons / hr between the dissolution mixture storage tank 12A and the stirred tank type first polymerization vessel. Filtration was carried out using two polymer filters (not shown, having a pore size of 5 μm on the upstream side and 2.5 μm on the downstream side) provided in series and having different pore sizes. The reaction mixture after filtration was heated by a preheater (not shown) and supplied to the first polymerization vessel 14 with a stirring tank. The liquid temperature at the outlet of the preheater was 200 ° C.

  When the level of the reaction mixture in the dissolution mixture storage tank 12A became lower than a predetermined value, the supply source for supplying the reaction mixture to the first polymerization reactor 14 with the stirring tank was switched from the dissolution mixture storage tank 12A to the dissolution mixture storage tank 12B. The supply of the reaction mixture to the stirring tank type first polymerization vessel 14 was continuously performed by repeating an operation of alternately switching the supply source dissolution mixture storage tanks 12A and 12B every 3.9 hours.

The dissolved mixture is supplied from the mixing tank 7 to the dissolved mixture storage tank 12A or 12B, and is held there for 3.9 hours (until immediately before the supply to the stirred tank type first polymerization vessel 14 is started), 4 Nm ³ / hr And nitrogen bubbling was performed.

  Stirring was performed under reduced pressure in the first polymerization vessel 14 and the second polymerization vessel 15 with stirring tank, and the reaction mixture was polymerized while removing generated PH to obtain a prepolymer. At that time, the temperature of the stirred tank type first polymerization vessel 14 was 220 ° C. and the pressure was 9.3 kPa, and the temperature of the stirred tank type second polymerization vessel 15 was 268 ° C. and the pressure was 2.66 kPa. The liquid level of the first polymerization vessel 14 was adjusted by LIC control using a bottom gear pump, and the supply amount of the reaction mixture was adjusted by FIC control. The liquid level of the stirred tank type second polymerization vessel 15 was adjusted by LIC control using a bottom gear pump. The PH produced as a by-product in the first polymerization vessel 14 with the stirring tank, the second polymerization vessel 15 with the stirring vessel, the main polymerization vessel 16, the main polymerization vessel 18A and the main polymerization vessel 18B is converted into a by-product phenol recovery facility and a transfer pump And used as a raw material in a DPC manufacturing process (not shown).

  The obtained prepolymer was continuously transferred to the main polymerization unit 16 by a gear pump provided in a pipe connected to the bottom of the second stirred tank type polymerization unit 15, where it was further polymerized under reduced pressure. The temperature of the main polymerization vessel 16 was 270 ° C., and the pressure was 600 Paa.

The polymer polymerized in the main polymerization unit 16 was continuously supplied to the main polymerization units 18A and 18B, where an MI having an MI of 22 ± 0.3 g / 10 min was produced. The production amount of the aromatic polycarbonate was 6.6 tons per hour. The temperature of the main polymerization reactors 18A and 18B was 270 ° C., and the pressure was 140 ± 2 Paa.
Table 1 shows the production conditions and the results of evaluating the properties of the produced aromatic polycarbonate.

<Example 2>
An aromatic polycarbonate was produced in the same manner as in Example 1, except that the large supply amount of DPC was changed to 21.3 tons (86.2 mass%) and the small supply amount was changed to 3.41 tons. Table 1 shows the results.

< Reference Example 1 >
In place of the independent stand, a stand without independence, that is, an aromatic polycarbonate was prepared in the same manner as in Example 1 except that a measuring tank having an internal capacity of 90 m ³ was installed on a stand sharing a base with the mixing tank. Manufactured. The indicated value of the load cell 3 was affected by external vibration and wind, and there was an error in the amount of BPA supplied to the mixing tank 7. As a result, the charged molar ratio of DPC and BPA was shifted, and the pressure adjustment range of the main polymerization reactors 18A and 18B was slightly larger than that of Example 1, and the MI and OH of the produced aromatic polycarbonate were There was a small variation in%. Table 1 shows the results.

<Example 4>
Example 1 except that the inner diameter of the flange portion of the piping nozzle for introducing the aromatic dihydroxy compound was changed to 250 mm, and the gas linear velocity of the blow-through at the end of the supply of BPA to the mixing tank 7 was changed to 30.6 m / sec. In the same manner as in 1, an aromatic polycarbonate was produced. Table 1 shows the results.

<Example 5>
The embodiment is the same as the embodiment except that the steam drain of the internal coil provided in the mixing tank 7 and the steam outlet of the outer jacket provided outside are provided with the steam drain discharge equipment 21 shown in FIG. In the same manner as in Example 1, an aromatic polycarbonate was produced. The diameter of the pipe at the steam outlet of the internal coil is 1.5 inches. Of the pipes connected from the steam outlet of the internal coil to the drain drum 22, the diameter of the large-diameter pipe directly connected to the drain drum 22 is 10 inches. The diameter of the pipe at the outlet is 2.5 inches, the diameter of the pipe at the outlet of the drain drum 22 is 6 inches, the diameter of the pipe from the steam trap 23 to the drain groove 25 is 6 inches, and the diameter of the pipe from the steam trap 23 to the steam recovery facility 24. The diameter was 4 inches. By installing the steam drain discharge facility 21 shown in FIG. 4, no steam hammer was generated in the internal coil in the mixing tank 7 while the temperature of the liquid in the mixing tank 7 was raised to 195 ° C. In addition, steam drain emissions were favorable. Table 1 shows the results.

<Example 6>
Aromatic polycarbonate was produced in the same manner as in Example 5, except that the diameter of the large-diameter pipe directly connected to the drain drum 22 from the steam outlet of the internal coil to the drain drum 22 was changed from 10 inches to 3 inches. Was manufactured. During the supply of BPA to the mixing tank 7, during the small supply of DPC, and while increasing the temperature of the liquid in the mixing tank 7 to 195 ° C, a steam hammer was generated in the internal coil. Table 1 shows the results.

<Comparative Example 1>
An aromatic polycarbonate was produced in the same manner as in Example 1 except that the large supply amount of DPC was 17.0 tons (68.8% by mass) and the small supply amount was 7.71 tons. However, when 3 tons of BPA was supplied to the mixing tank 7, the stirrer tripped, and the operation could not be continued. In order to restart the operation, the supply of BPA was temporarily stopped, and 6.3 tons of the small supply of DPC were additionally supplied to the mixing tank 7. Thereafter, the remaining BPA was supplied after the liquid temperature in the mixing tank 7 reached 160 ° C. Next, 1.41 tons was supplied to the mixing tank 7 by the second small supply of DPC. It took two hours to deal with this trouble. Further, a part of BPA was discolored and the hue of the product was deteriorated. Table 2 shows the results.

<Comparative Example 2>
An aromatic polycarbonate was produced in the same manner as in Example 1 except that the entire amount of the planned charge was supplied in the first supply of DPC, and no small supply was performed. Since the supply amount of DPC cannot be adjusted with respect to the fluctuation of the input amount of BPA, it is necessary to adjust the pressure of the main polymerization reactors 18A and 18B, and the fluctuation of MI of the aromatic polycarbonate has also increased. Table 2 shows the results.

<Comparative Example 3>
An aromatic polycarbonate was produced in the same manner as in Example 1, except that the liquid temperature in the mixing tank 7 was changed from 140 to 160 ° C to 110 to 130 ° C. After the small supply of DPC, when the dissolved mixture was collected from the mixing tank 7, a part of the BPA was in an unmelted slurry state. The fluctuation of Mn at the outlet of the stirred tank type second polymerization vessel 15 was large, and the pressure of the main polymerization vessels 18A and 18B was greatly changed, but the desired aromatic polycarbonate could not be obtained. Table 2 shows the results.

  The method for producing an aromatic polycarbonate according to the present invention is a method for producing an aromatic polycarbonate in which the pressure in a polymerization reactor is easily controlled, the impact resistance is excellent, and the coloration is small. There is industrial applicability as a technique for producing polycarbonate.

DESCRIPTION OF SYMBOLS 1 ... Bucket conveyor, 2 ... Measuring tank, 3 ... Load cell, 4 ... Ball valve, 5 ... Rotary valve, 6 ... Flexible tube, 7 ... Mixing tank, 8A, 8B, 8C, 17 ... Transfer pump, 9 ... Scrubber, 10 ... storage tank, 11 ... preheater, 12A, 12B ... dissolved mixture storage tank, 13 ... measuring device, 14 ... stirred tank type first polymerization device, 15 ... stirred tank type second polymerization device, 16, 18A, 18B ... main polymerization Vessel, 19A: Equipment after main polymerization vessel 18A, 19B: Equipment after main polymerization vessel 18B, 20 ... Independent stand, 21 ... Steam drain discharge equipment, 22 ... Drain drum, 23 ... Steam trap, 24 ... Steam recovery Equipment, 25 ... drain.

Claims (6)

A method for producing an aromatic polycarbonate by reacting an aromatic dihydroxy compound and a diaryl carbonate in a polymerization vessel,
A step of supplying the diaryl carbonate at 90 to 220 ° C. to a mixing tank at 75 to 99% by mass of the total supply amount of the diaryl carbonate, which is determined from a target molar ratio of the aromatic dihydroxy compound and the diaryl carbonate. (A) and
A step (B) of supplying the aromatic dihydroxy compound to the mixing tank adjusted to a liquid temperature of 135 to 220 ° C. after the step (A);
After the step (B), the diaryl carbonate is further supplied to the mixing tank so that the charged molar ratio of the aromatic dihydroxy compound and the diaryl carbonate in the mixing tank is within a predetermined range, and the mixture is dissolved. (C) preparing a mixture;
Including
Prior to said step (B), further seen including the step of metering the aromatic dihydroxy compound, with a metering vessel for installation aromatic dihydroxy compound independently stand,
The independent gantry is a gantry supported on a foundation independent of a foundation for directly or indirectly supporting the mixing tank,
The aromatic dihydroxy compound is bisphenol A,
A method for producing an aromatic polycarbonate. Supplying the dissolved mixture at 135 to 220 ° C. to a first dissolved mixture storage tank, and holding the dissolved mixture at 160 to 220 ° C. for 1 to 12 hours in the first dissolved mixture storage tank to form a first reaction mixture; (D-1) obtaining
Supplying the first reaction mixture to a polymerization step for obtaining a prepolymer or polymer having a number average molecular weight of 400 or more by polymerization (E-1);
Supplying the dissolved mixture at 135 to 220 ° C. to a second dissolved mixture storage tank and holding the dissolved mixture at 160 to 220 ° C. for 1 to 12 hours in the second dissolved mixture storage tank to perform a second reaction; A step (D-2) of obtaining a mixture;
(E-2) supplying the second reaction mixture to the polymerization step when the first reaction mixture in the first dissolution mixture storage tank is reduced to a predetermined amount;
The method for producing an aromatic polycarbonate according to claim 1, comprising:   The method for producing an aromatic polycarbonate according to claim 2, wherein the aromatic polycarbonate is produced continuously.   In the step (B), the aromatic dihydroxy compound is supplied to the mixing tank by entraining it with an inert gas, and at the end of the supply, the aromatic dihydroxy compound and the inert gas are introduced into the mixing tank. The method for producing an aromatic polycarbonate according to any one of claims 1 to 3, wherein a linear velocity of the inert gas in a supply pipe is adjusted to 0.1 to 500 m / sec.   In the step (B), the aromatic dihydroxy compound is supplied to the mixing tank by entraining the inert gas, which has been pressurized in the measuring tank, with the aromatic dihydroxy compound. The method for producing an aromatic polycarbonate according to claim 1 or 2, wherein a linear velocity of the inert gas in a pipe for supplying a gas into the mixing tank is adjusted to 0.1 to 500 m / sec.   The aromatic polycarbonate according to any one of claims 1 to 5, further comprising a step of adding a transesterification catalyst to the mixing tank after the step (A) and before the step (B). Manufacturing method.