CN105524264B

CN105524264B - Production apparatus for aromatic polycarbonate

Info

Publication number: CN105524264B
Application number: CN201510679228.2A
Authority: CN
Inventors: 长谷川和美
Original assignee: Asahi Kasei Corp
Current assignee: Asahi Kasei Corp
Priority date: 2014-10-21
Filing date: 2015-10-19
Publication date: 2019-12-31
Anticipated expiration: 2035-10-19
Also published as: CN105524264A; JP2016079400A; JP6554012B2; CN105524265B; JP6646398B2; CN105524265A; JP2016079399A

Abstract

The present invention provides an apparatus for producing an aromatic polycarbonate. It is possible to prevent the breakage of the heating unit even if a large amount of steam is circulated. An apparatus for producing an aromatic polycarbonate, comprising a mixing tank for reacting an aromatic dihydroxy compound and a diaryl carbonate, wherein the apparatus comprises at least one heating means for heating the mixing tank, the heating means being selected from the group consisting of an inner coil provided in the mixing tank, an outer jacket provided outside the mixing tank, and an outer coil provided outside the mixing tank; the heating unit uses steam as a heating medium, and has 2 or more steam outlets, and the 2 or more steam outlets are independently connected to the drain drum.

Description

Production apparatus for aromatic polycarbonate

[ technical field ] A method for producing a semiconductor device

The present invention relates to an apparatus for producing an aromatic polycarbonate.

[ background of the invention ]

Aromatic polycarbonates are known to have excellent impact resistance, transparency, and the like. As a method for producing an aromatic polycarbonate, there are the following methods: a melt polymerization method in which an aromatic dihydroxy compound and a diaryl carbonate are reacted at high temperature and under reduced pressure in the presence of a transesterification catalyst, and the produced aromatic monohydroxy compound is discharged out of the system; and an interfacial polymerization method in which an aromatic dihydroxy compound is reacted with phosgene in a mixed solution of an organic solvent and an aqueous alkali solution.

The interfacial polymerization method has the following problems compared with the melt polymerization method: the use of toxic phosgene is necessary; corrosion of the apparatus by the action of chlorine-containing compounds such as hydrogen chloride and sodium chloride which are by-produced and methylene chloride which is used in a large amount as a solvent; impurities such as sodium chloride or the like which adversely affect the physical properties of the polymer, or residual methylene chloride are difficult to separate; and so on. Accordingly, as a method for producing an aromatic polycarbonate, a large number of melt polymerization methods have been proposed.

In the melt polymerization method, an aromatic dihydroxy compound and a diaryl carbonate are used as raw materials (for example, see patent document 1). It is known that an aromatic dihydroxy compound is easily decomposed or colored due to its low heat resistance when it is treated in a molten state at a temperature equal to or higher than its melting point, and this is a cause of deterioration in the color tone of the polymer. Therefore, in the melt polymerization method, in the case of preparing a raw material mixture containing an aromatic dihydroxy compound, the following method is generally used: a method of mixing a molten diaryl carbonate with a molten aromatic dihydroxy compound; and a method of measuring the amount of the molten diaryl carbonate, and mixing and dissolving the aromatic dihydroxy compound in a solid (powder, pellet, or the like) state by measuring the amount of the aromatic dihydroxy compound. In the former case, there is a limitation that the molten aromatic dihydroxy compound must be used within a short storage time, and in the latter case, the storage stability is considered to be excellent. However, in the latter case, when the solid aromatic polycarbonate having a melting point of the diaryl carbonate or lower is supplied in a short time, the temperature in the mixing tank for mixing the raw materials is rapidly lowered, and the diaryl carbonate may be solidified and precipitated. When the diaryl carbonate precipitates in the mixing tank, an extra time is required for preparing a homogeneous raw material melt mixture, and there is a problem that the raw material is colored.

[ Prior art documents ]

[ patent document ]

Patent document 1: international publication No. 2005/121213

[ summary of the invention ]

[ problem to be solved by the invention ]

As a strategy for preventing the precipitation of the diaryl carbonate, for example, the following methods are available: a large amount of steam (hereinafter also referred to as "steam") or heat medium oil is circulated through a heating unit such as a coil or a jacket provided in the mixing tank to rapidly adjust the temperature in the mixing tank. Since the value of the total heat transfer coefficient of steam is generally larger than that of the heat medium oil, it is preferable to use a method of circulating steam inside the heating unit. However, when a large amount of steam flows through the heating unit, a steam hammer is generated inside the heating unit, and if the above-described strategy is repeatedly performed for a long period of time, there is a problem that the heating unit is damaged by the steam hammer.

Accordingly, an object of the present invention is to provide an apparatus for producing an aromatic polycarbonate, which can prevent a heating unit from being damaged even when a large amount of steam is circulated.

[ MEANS FOR solving PROBLEMS ] to solve the problems

The present inventors have conducted extensive studies to achieve the above object, and as a result, have found that the above object can be achieved by setting the steam outlet from the heating means to a predetermined form, and have completed the present invention.

Namely, the present invention is as follows.

[1] An apparatus for producing an aromatic polycarbonate, which comprises a mixing tank for reacting an aromatic dihydroxy compound with a diaryl carbonate,

the manufacturing apparatus comprises at least one heating means for heating the mixing tank, the heating means being selected from the group consisting of an inner coil provided in the mixing tank, an outer jacket provided outside the mixing tank, and an outer coil provided outside the mixing tank;

the heating unit uses steam as a heating medium, and has 2 or more steam outlets, and the 2 or more steam outlets are independently connected to the drain drum.

[2] An apparatus for producing an aromatic polycarbonate, which comprises a mixing tank for reacting an aromatic dihydroxy compound with a diaryl carbonate,

the manufacturing apparatus includes an internal coil for heating the mixing tank, the internal coil being provided in the mixing tank;

the inner coil uses steam as a heating medium, has 2 or more steam outlets, and pipes connected to the steam outlets are connected to a drain drum by large-diameter pipes having a pipe diameter 2 to 20 times as large as that of the pipes connected to the steam outlets.

[3] The apparatus for producing an aromatic polycarbonate as described in [1] or [2], further comprising a LIC control device for controlling a discharge amount of the water vapor condensate from the drain drum, and/or a vapor trap for selectively discharging the water vapor condensate from the drain drum.

[ Effect of the invention ]

According to the present invention, it is possible to provide an apparatus for producing an aromatic polycarbonate, which can prevent a heating unit from being damaged even when a large amount of steam is circulated.

[ description of the drawings ]

FIG. 1 is a flowchart showing an example of a production apparatus used in a method for producing an aromatic polycarbonate.

Fig. 2 is a diagram schematically showing an example of the stand.

Fig. 3 is a diagram schematically showing an example of a flow path of steam in a case where the steam is used as a heat source of a heating means of a mixing tank.

Fig. 4 is a view schematically showing another example of the flow path of steam in the case where the steam is used as a heat source of the heating unit of the mixing tank.

[ detailed description ] embodiments

The present embodiment (hereinafter, simply referred to as "the present embodiment") will be described in detail below with reference to the drawings as necessary, but the present invention is not limited to the present embodiment described below. The present invention can be variously modified within a range not departing from the gist thereof. In the drawings, the same elements are denoted by the same reference numerals, and redundant description thereof is omitted. The dimensional ratios in the drawings are not limited to the illustrated ratios.

The method for producing an aromatic polycarbonate according to 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 comprises the steps of: a step (A) in which a diaryl carbonate having a temperature of 90 to 220 ℃ is supplied to a mixing tank in an amount of 75 to 99 mass% of the total amount of diaryl carbonate supplied, the amount being determined from a target molar ratio of aromatic dihydroxy compound to diaryl carbonate (hereinafter referred to simply as "molar ratio of charge"); a step (B) of supplying the aromatic dihydroxy compound to a mixing tank having a liquid temperature adjusted to 135 to 220 ℃ after the step (A); and (C) preparing a dissolution mixture by further supplying a diaryl carbonate to the mixing tank after the step (B) so that the molar ratio of the materials charged into the mixing tank is within a predetermined range. FIG. 1 is a flowchart showing an example of a production apparatus used in the method for producing an aromatic polycarbonate according to the present embodiment. The method for producing an aromatic polycarbonate according to the present embodiment will be described in more detail below with reference to the flowchart.

The step (A) is a step of supplying a diaryl carbonate of 90 to 220 ℃ in an amount of 75 to 99 mass% of the total amount of the diaryl carbonate supplied at the target charging molar ratio to a mixing tank.

In FIG. 1, a raw material diaryl carbonate is stored in a storage tank 10. The temperature during storage is preferably 82 to 120 ℃ from the viewpoint of avoiding thermal denaturation of the diaryl carbonate. The total amount of diaryl carbonate fed is an estimated amount of diaryl carbonate fed determined from a predetermined feed molar ratio (i.e., a target feed molar ratio). Of the total supply amount, 75 to 99 mass% of diaryl carbonate is fed from the storage tank 10to the preheater 11 for diaryl carbonate by a feed pump (not shown) while being metered by a diaryl carbonate meter 13 provided in a feed pipe leading from the storage tank 10to the mixing tank 7, preheated to 90 to 220 ℃ by the preheater 11, and supplied to the mixing tank 7 (hereinafter, this supply is referred to as "large supply"). When the temperature of the diaryl carbonate at this time is 90 ℃ or higher, the diaryl carbonate is in a liquid state and can be easily transported, and the mixing tank 7 containing the diaryl carbonate can be adjusted to a predetermined temperature in a short time; when the temperature is 220 ℃ or lower, the discoloration of the obtained aromatic polycarbonate can be prevented.

The mixing tank 7 is preferably provided with a stirring paddle (not shown), and the stirring in the mixing tank 7 is preferably started when the stirring paddle is completely immersed in the diaryl carbonate.

When a transesterification catalyst is used for the reaction of the aromatic dihydroxy compound and the diaryl carbonate, it is preferable to further include a step of adding a transesterification catalyst to the mixing tank 7 after the step (a) and before the step (B) described later. By mixing the ester exchange catalyst with the diaryl carbonate before mixing the aromatic dihydroxy compound with the diaryl carbonate, the broadening of the molecular weight distribution can be further suppressed, the mold deposit of the obtained aromatic polycarbonate in a mold during injection molding can be further prevented, and the formation of a gel-like high molecular weight material 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 liquid temperature of the diaryl carbonate-containing liquid contained in the mixing tank 7 is adjusted to 135 to 220 ℃. For example, when the aromatic dihydroxy compound is measured by the load cell 3, the aromatic dihydroxy compound is supplied from a storage tank (for example, a storage hopper) (not shown) of the aromatic dihydroxy compound located at the front stage or an apparatus (not shown) for producing the aromatic dihydroxy compound to the measuring tank 2 for the aromatic dihydroxy compound provided in an independent stand (illustrated as an independent stand 20 in fig. 2 described later) by using the bucket conveyor 1. Here, the "independent stand" refers to a stand supported on a base independent from a base for directly or indirectly supporting the mixing tub 7. As an example of the "indirect" support, a stand provided with the mixing tank 7 is supported. By providing the measuring tank 2 on a separate stand, the vibration transmitted from the mixing tank 7 to the measuring tank 2 can be further suppressed. Next, the aromatic dihydroxy compound was supplied from the measuring tank 2 to the mixing tank 7 adjusted to a liquid temperature of 135 to 220 ℃ by using the rotary valve 5. The amount of the aromatic dihydroxy compound supplied was the entire amount of the expected charged amount. Next, in order to remove oxygen and moisture mixed into the aromatic dihydroxy compound and taken into the mixing tank 7, the atmosphere in the mixing tank 7 is replaced with a gas (preferably an inert gas such as nitrogen) different from oxygen and water vapor (hereinafter, this gas is referred to as "replacement gas"). The amount of the aromatic dihydroxy compound supplied to the measuring tank 2 was determined from the mass difference between the measuring tanks 2 before and after the supply. When an inert gas such as nitrogen is used as the substitution gas, the purity is not particularly limited, but is preferably 99.999% by mass or more, and more preferably 99.9999% by mass. In addition, an inert gas such as nitrogen is hereinafter referred to as "inert gas".

The step (C) is a step of preparing a dissolution mixture by further supplying diaryl carbonate to the mixing tank 7 after the step (B) so that the charging molar ratio in the mixing tank 7 is within a predetermined range. The amount of diaryl carbonate to be additionally supplied to the mixing tank 7 is determined so that the above-mentioned charging molar ratio falls within a predetermined range.

For example, the amount of diaryl carbonate to be additionally supplied is determined so as to be a predetermined molar ratio of the amount of the aromatic dihydroxy compound to be actually supplied to the mixing tank 7 in the step (B). Then, a necessary amount of diaryl carbonate is transferred from the storage tank 10to the preheater 11 by a transfer pump while measuring the diaryl carbonate by a meter 13 provided in a transfer pipe leading from the storage tank 10to the mixing tank 7. The diaryl carbonate is preheated in the preheater 11 and supplied to the mixing tank 7 whose liquid temperature is adjusted to 135 to 220 ℃ (hereinafter, this supply is referred to as "small supply").

In this step (C), the charging molar ratio in the dissolution mixture is adjusted to be within a predetermined range. The "predetermined range" of the charging molar ratio is a range in which the target value (target value) of the charging molar ratio is added to the fluctuation range of the target value, and is not particularly limited, and for example, the target value of the charging molar ratio may be in the range of 0.9 to 1.3, and more preferably 1.0 to 1.25. The target value of the charging molar ratio may vary within ± 0.003, preferably within ± 0.0015, for example.

In the present specification, the "dissolution mixture" is a mixture of at least a diaryl carbonate and an aromatic dihydroxy compound dissolved and mixed in a mixing tank, and other optional components such as a transesterification catalyst may be dissolved and mixed therein. The "reaction mixture" is a dissolution mixture obtained by holding the dissolution mixture at 160 to 220 ℃ for 1 to 12 hours in a dissolution mixture tank described later. Further, in the present embodiment, a step of polymerizing the reaction mixture to obtain a prepolymer or a 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" means a material having an Mn of 400 to 7000 and "polymer" means a material having an Mn exceeding 7000.

In the present embodiment, as shown in FIG. 1, it is preferable to perform the step (D-1) and the step (D-2) in a batch manner in the respective dissolution mixture tanks 12A and 12B. That is, in the step (D-1), the dissolution mixture prepared in the step (C) is supplied to the 1 st dissolution mixture tank 12A at 135 to 220 ℃ and the dissolution mixture is held in the dissolution mixture tank 12A at 160 to 220 ℃ for 1 to 12 hours, whereby the 1 st reaction mixture having a predetermined equilibrium reaction rate is obtained. Further, in the step (E-1), the 1 st reaction mixture is supplied to the polymerization step.

In the step (D-2), while the dissolution mixture is held in the dissolution mixture tank 12A and/or while the 1 st reaction mixture is supplied to the polymerization step, the dissolution mixture prepared in the step (C) is supplied to the 2 nd dissolution mixture tank 12B at 135 to 220 ℃, and the dissolution mixture is held at 160 to 220 ℃ for 1 to 12 hours in the dissolution mixture tank 12B, whereby the 2 nd reaction mixture having a predetermined equilibrium reaction rate is obtained.

Then, in the step (E-2), the supply of the 2 nd reaction mixture obtained in the step (D-2) to the polymerization step is started at a timing when the 1 st reaction mixture in the 1 st dissolution mixture tank 12A is decreased to a predetermined amount. Further, the step (D-1) is carried out while the dissolution mixture is held in the dissolution mixture tank 12B and/or while the 2 nd reaction mixture is supplied to the polymerization step. The supply of the reaction mixture to the polymerization step can be continuously performed by repeating the above-described operations alternately.

Here, the "equilibrium reaction rate" means a conversion rate of the aromatic dihydroxy compound in the dissolution mixture which reaches equilibrium. Further, the "prescribed amount" is a predetermined amount, and may be, for example, an amount that ensures normal operation of the dissolution mixture tank, and more specifically, an amount that can suppress a cavitation phenomenon of a transfer pump for transferring the reaction mixture from the dissolution mixture tank.

In order to more stably and easily prepare the dissolution mixture, it is more preferable that the mixing tank 7 and each of the dissolution mixture storage tanks 12A and 12B have substantially the same volume, and substantially the entire amount of the dissolution mixture prepared in the mixing tank 7 is supplied to the dissolution mixture storage tank 12A or 12B. Here, the "total amount" refers to the amount of the dissolution mixture supplied to the dissolution mixture tank 12A or 12B from the start of supply of the dissolution mixture to the dissolution mixture tank 12A or 12B to the point where the mixing tank 7 is substantially empty. For example, the amount is an amount from the start of supply of the dissolution mixture to the dissolution mixture tank 12A or 12B to the start of a level switch provided at the bottom (bottom) of the mixing tank 7, and the stop of a transfer pump 8A (described later in detail) for transferring the dissolution mixture from the mixing tank 7 to the dissolution mixture tank 12A or 12B, or an amount from the start of supply of the dissolution mixture to the dissolution mixture tank 12A or 12B to the stop of the transfer pump 8A when the shortage of current (current value) of the transfer pump 8A is detected. A small amount of the dissolved mixture may remain between the horizontal switch at the bottom of the mixing tank 7 and the transfer pump 8A (including a suction-side pipe of the transfer pump 8A).

The switching between the dissolution mixture tanks 12A and 12B is preferably appropriately controlled so as to continuously perform the first polymerization step in consideration of the polymerization rate of the prepolymer or the polymer. The dissolving mixture tanks 12A and 12B may be arranged in parallel with the process flow path by 2 or more, and may be arranged in series with the process flow path by 2 or more.

Hereinafter, the method for producing an aromatic polycarbonate and the production apparatus used in the method of producing an aromatic polycarbonate according to the present embodiment will be described in further detail, focusing on the respective facilities that can be included in the production apparatus.

[ measurement of diaryl carbonate ]

In the present embodiment, in order to improve the accuracy of the charging molar ratio, the 1 st (large) supply of the diaryl carbonate to the mixing tank 7 is controlled to 75 to 99 mass% of the supply amount of the diaryl carbonate determined from the target charging molar ratio. The amount of the large supply is preferably 80 to 95% by mass, more preferably 85 to 95% by mass. By making the amount of the large supply not the entire amount of the diaryl carbonate to be supplied at once, the amount of the 2 nd (small supply) supply can be adjusted based on the actually measured amount of the aromatic dihydroxy compound after the aromatic dihydroxy compound is supplied to the mixing tank 7, and the accuracy of the charged molar ratio can be improved. When the amount of the large supply is 99 mass% or less, the adjustment during the small supply is easier. In addition, when the amount of the diaryl carbonate to be supplied is 75 mass% or more, the liquid surface of the mixing tank 7 after the diaryl carbonate is supplied is higher than the height of the stirring blade of a normal mixing tank, and thus the stirrer can be prevented from being damaged. In addition, when the large supply amount is 75 mass% or more, the blocking of the aromatic dihydroxy compound generated when the aromatic dihydroxy compound is supplied to the mixing tank 7 can be prevented. Further, even when the amount of the large supply is 75 mass% or more, the discoloration of the aromatic dihydroxy compound adhered to the inner coil can be prevented when the inner coil is provided in the mixing tank 7.

[ diaryl carbonate meter 13]

The metering device 13 can be used for metering diaryl carbonate. The meter 13 may be, for example, a known flowmeter such as an ultrasonic flowmeter, a vortex flowmeter, a volumetric flowmeter, an area flowmeter, or a coriolis cumulative flowmeter, and is preferably a cumulative flowmeter. Coriolis type cumulative flow meters are preferred for their high accuracy.

When the meter 13 is installed in the pipe, the accuracy of measurement (weighing) is likely to be reduced by the influence of vibration from the outside, and therefore, a meter with high weighing accuracy is preferable. Specifically, the weighing accuracy of the meter 13 is preferably within ± 0.5 mass%, more preferably within ± 0.25 mass%. It is more preferable that the weighing accuracy after the meter 13 is set in the pipe is within ± 0.15 mass%. Preferably, the number of meters 13 is 2 or more at intervals of 0.5m or more along the pipe. When 2 or more meters are provided, it is preferable to use meters having the same weighing accuracy, and it is preferable to check with other meters using 1 meter as a main meter. Further, when the measurement error between the meters becomes large or when the meter mainly used is out of order, it is preferable to provide an interlock for stopping retraction, or to provide another meter for checking in addition to or instead of the interlock, so that the interlock can be switched on a display screen of a DCS (distributed control system) for managing the operation of the aromatic polycarbonate production apparatus or inside the meter for checking. Furthermore, the meter may be checked by a liquid level meter provided in the mixing tank 7.

[ diaryl carbonate preheater 11]

In the production apparatus of the present embodiment, a diaryl carbonate preheater 11 may 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 pipe heat exchanger and a multi-pipe heat exchanger, and a pipe for conveying the diaryl carbonate can be used as the preheater 11. The diaryl carbonate is heated or maintained at 90 to 220 ℃, preferably 100to 210 ℃, and more preferably 110 to 200 ℃ by the preheater 11 and then supplied to the mixing tank 7. The flange portion of the preheater 11 is preferably configured such that the diaryl carbonate does not stay in the gap between the flanges.

Examples of the heat source for heating and heat-insulating by the preheater 11 include hot oil and steam circulating between the preheater and a hot oil boiler. 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 can be controlled while the diaryl carbonate is being taken (supplied) into the mixing tank 7 (TIC control method). After the diaryl carbonate is charged into the mixing tank 7, the TIC control mode may be switched to a pressure control (PIC control mode) for controlling the pressure on the heat source (e.g., steam) side of the preheater 11. Alternatively, a TIC control method may be used in which the temperature sensor is switched to a temperature sensor for detecting the surface temperature or the internal temperature of the preheater 11 by the temperature sensor for the diaryl carbonate in the pipe when the diaryl carbonate is fed into the mixing tank 7 or when the feeding is stopped.

The heat source used for keeping the temperature of the meter 13 and the diaryl carbonate feed pump is preferably steam of 110 to 200 ℃, and the heat source of the preheater 11 is preferably steam of 120 to 220 ℃.

When the preheater 11 is provided between the storage tank 10 and the mixing tank 7, the diaryl carbonate is heated by the preheater 11, and therefore, it is not necessary to increase the temperature of the storage tank 10to a temperature desired for the mixing tank 7. In addition, from the viewpoint of preventing discoloration while securing fluidity of the diaryl carbonate, at least one or both of the temperatures of the transfer piping between the storage tank 10 and the mixing tank 7 and the preheater 11 may be reduced to 82 ℃ to 120 ℃. In this case, a heating means capable of heating the mixing tank 7 itself to 135 to 220 ℃ is required.

[ measurement of aromatic dihydroxy Compound ]

Examples of the method for measuring the aromatic dihydroxy compound supplied to the mixing tank 7 include the following methods: the mass of the storage hopper (not shown) for the aromatic dihydroxy compound is measured before and after the aromatic dihydroxy compound is supplied from the storage hopper (not shown) for the aromatic dihydroxy compound to the mixing tank 7, and the actual supply amount of the aromatic dihydroxy compound to the mixing tank 7 is determined. Alternatively, the following methods may be mentioned: as shown in FIG. 1, the expected supply amount or more of the aromatic dihydroxy compound than the expected supply amount is taken in a measuring tank 2 provided with a load cell 3 described later, oxygen and moisture in the atmosphere are replaced with an inert gas, a predetermined amount is supplied to a mixing tank 7 in accordance with the instruction value of the load cell 3, and the actual supply amount of the aromatic dihydroxy compound supplied to the mixing tank 7 is determined from the mass difference of the measuring tank 2 before and after the supply.

However, in either method, when the measuring tank 2 or the weighing sensor 3 is installed on a stand which is affected by external factors such as wind, external vibration, and outside air temperature, the measurement accuracy may be deteriorated. From the viewpoint of eliminating such an external influence as much as possible and further improving the measurement accuracy of the aromatic dihydroxy compound, it is preferable to use a measuring tank 2 provided in the independent stand 20, and to provide a load cell 3 having 2 or more measuring points in the measuring tank 2.

From the viewpoint that the measuring tank 2 is less susceptible to the influence of vibrations from the bucket conveyor 1 or the mixing tank 7, the flexible pipe 6 is preferably used as at least a part of the piping between the bucket conveyor 1 and the measuring tank 2 and the piping for supplying the aromatic dihydroxy compound from the measuring tank 2 to the mixing tank 7. Further, a pressure equalizing pipe (not shown) is preferably connected to these pipes. By providing the pressure 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 equalizer tube is preferably provided with a flexible tube having an insertion tube at a portion connected to the above tube. Further, when the equalizer pipe includes a flexible pipe, it is also preferable that the bellows portion of the flexible pipe be purged with an inert gas. The flexible tube 6 and the equalizer tube may be made of a material having pressure resistance equivalent to that of the measuring tank 2, and PTFE (polytetrafluoroethylene) and SUS (stainless steel) are preferable.

The preferred method of metering the aromatic dihydroxy compound is as follows. That is, the aromatic dihydroxy compound of the expected supply amount is received in the measuring tank 2 provided with the load cell 3 having 2 or more measuring points provided in the independent stand 20. Next, oxygen and moisture contained in the atmosphere in the measuring tank 2 are replaced with an inert gas. Next, immediately before the aromatic dihydroxy compound is supplied to the mixing tank 7, the weighing cell 3 measures the amount of the aromatic dihydroxy compound in the measuring tank 2, and thereafter the entire amount of the aromatic dihydroxy compound is supplied to the mixing tank 7. Then, an electric vibrator and/or an air vibrator attached to the tapered portion of the measuring tank 2 is activated to peel off the aromatic dihydroxy compound attached to the tapered 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 mass of the empty measuring tank 2 is measured by the load cell 3, and the actual amount of the aromatic dihydroxy compound supplied is determined from the difference in mass between before and after the supply of the aromatic dihydroxy compound to the mixing tank 7. Further, the supply amount of the aromatic dihydroxy compound may be checked by the indication value of the level meter in the mixing tank 7.

[ independent stand 20]

Fig. 2 is a diagram schematically showing an example of the independent stand of the present embodiment. In the example shown in fig. 2, the building for accommodating the measuring tank 2 is preferably a double structure or more of the independent stand 20 and a wind shielding stand (not shown) provided outside thereof, and the base of the independent stand 20 and the base of the wind shielding stand are provided independently of each other. By making the base stand alone, external influences such as vibrations on the stand 20 can be eliminated as much as possible. Further, in order to further prevent external influence on the independent rack 20, it is preferable that a support portion (support) of the piping, the electric and instrument cable raceway is connected to the wind shielding rack. Further, it is preferable that the cables (wires and the like) spanning the wind shielding frame and the independent frame 20 have flexibility. The walls, windows, doors, and the like of the wind screen stand are preferably configured to prevent external wind from entering. Further, by providing a wall outside the wind screen stand, the influence of the outside air temperature can be reduced. The weighing tank 2 is provided on the independent stand 20 via the load cell 3. Since the load cell 3 provided 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 set within ± 0.15 mass%.

[ measuring tank 2 for aromatic dihydroxy Compound ]

The volume of the measuring tank 2 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 taken in, from the viewpoints of securing a space volume when taking in the aromatic dihydroxy compound, suppressing powder scattering of the aromatic dihydroxy compound, and shortening the time required for pressure reduction or nitrogen gas replacement. The capacity of the metering tank 2 is preferably 250m³Below, more preferably 150m³The following. By setting the measuring tank 2 to 250m³Can prevent the settingThe strength required for the stand becomes too high, or the construction in which the measuring tank 2 is installed must be very large.

It is preferable to prevent the diaryl carbonate, the aromatic dihydroxy compound, and if necessary, the aromatic monohydroxy compound from adhering to piping or the like by increasing the pressure in the measuring tank 2 to a higher pressure than the pressure in the mixing tank 7 and facilitating the flow of the inert gas from the measuring tank 2 to the mixing tank 7. In this case, the pressure of the measuring tank 2 may be higher than the pressure of the mixing tank 7, and when the measuring tank 2 is provided at a position higher than the mixing tank 7 (i.e., at the upper side in the vertical direction), the pressure of the measuring tank 2 is preferably 0.1kPaG to 1000kPaG, more preferably 0.1kPaG to 500kPaG, and still more preferably 0.05kPaG to 20 kPaG. When the aromatic dihydroxy compound is pneumatically transferred from the metering tank 2 to the mixing tank 7, the pressure in the metering tank 2 is preferably 50kPaG to 1000 kPaG. The pressure in the measuring tank 2 is preferably adjusted by PIC control and kept within a predetermined range (the fluctuation range varies depending on the accuracy of the meter, and is, for example, ± 0.01kPaG to ± 0.05kPaG in the case where the set value is 6 kPaG). When the aromatic dihydroxy compound is taken into the measuring tank 2, the pressure of the bucket conveyor 1 is preferably higher than the pressure of the measuring tank 2 by using a sequence control or the like. In the present specification, the pressure (for example, "kPaG" or the like) to which "G" is attached to the end of the unit is a gauge pressure, and the pressure (for example, "Paa" or the like) to which "a" is attached to the end of the unit and the pressure (for example, "kPa" or the like) to which neither is attached represent absolute pressures.

From the viewpoint of facilitating the pressure control of each polymerization vessel described later, it is preferable that the blending time of the dissolution mixture from when the diaryl carbonate is taken into the mixing tank 7 to when the transesterification reaction in the dissolution mixture storage tank 12A or 12B reaches equilibrium is within 12 hours, more preferably within 8 hours. In order to achieve such blending time, it is preferable that the time from the entry of the aromatic dihydroxy compound into the intake port of the measuring tank 2 to the discharge thereof from the discharge port is short. From such a viewpoint, the size of the piping for taking in and discharging the aromatic dihydroxy compound connected to the upper and lower portions of the measuring tank 2 is preferably a piping diameter capable of taking in or discharging the entire amount of the aromatic dihydroxy compound within 2 hours, and more preferably a piping diameter capable of taking in or discharging within 1.5 hours.

When the aromatic dihydroxy compound is taken into the measuring tank 2 by the bucket conveyor 1, it is preferable that a connecting portion between the outlet of the bucket conveyor 1 and a valve which can be provided in front of the inlet of the aromatic dihydroxy compound in the measuring tank 2 is tapered as shown in fig. 1. The apex angle of the conical shape of the connecting portion is preferably 20 to 90 degrees, more preferably 30to 90 degrees.

Preferably, the lower portion of the metering tank 2 is also tapered. In this case, the angle of the apex of the tapered shape at the lower portion of the measuring tank 2 may be an angle at which the aromatic dihydroxy compound does not stagnate. The angle of the apex of the tapered shape at the lower portion of the measuring tank 2 is preferably 20 to 75 degrees, more preferably 20 to 60 degrees. In order to prevent the powder of the aromatic dihydroxy compound from being accumulated, it is preferable to install an electric vibrator and/or an air shaker in the lower portion of the tapered shape of the measuring tank 2. After the entire amount of the aromatic dihydroxy compound is supplied to the mixing tank 7, the measuring tank 2 is preferably vibrated for several seconds to several minutes by an electric vibrator and/or an air shaker in order to peel off powder adhering to the wall surface of the measuring tank 2. In addition, in order to prevent the aromatic dihydroxy compound from being pulverized by the impact when the aromatic dihydroxy compound is received in the measuring tank 2, a spiral chute for sliding the aromatic dihydroxy compound down at the upper portion thereof may be provided inside the measuring tank 2.

An exhaust pipe (not shown) may be connected to the measuring tank 2, and a pressure control valve may be provided in the exhaust pipe. In view of the operation of extracting gas from the measuring tank 2 when the aromatic dihydroxy compound is taken in and the operation of replacing the pressure with inert gas by reducing the pressure, it is preferable to provide an automatic valve such as a 1-20 inch ball valve in a bypass of the pressure control valve. The pipe diameter of the exhaust pipe is preferably determined in consideration of the time taken for pressure reduction.

A pipe for introducing an inert gas for pressurization can be connected to the measuring tank 2, and an automatic valve such as a 1-20 inch ball valve is preferably provided in a bypass of the pressure control valve. In order to quickly actuate an automatic valve of 6 inches or more, it is also preferable to provide a buffer tank of meter air for the automatic valve. The pipe for introducing the inert gas is preferably a pipe diameter capable of performing pressure reduction to micro-pressure in a short time. In order to prevent the pressure inside the piping from being reduced, it is more preferable to provide a buffer tank in the middle of the piping.

In order to prevent powder or the like of the aromatic dihydroxy compound from entering the meter connectable to the exhaust pipe of the measuring tank 2, it is preferable that the mounting nozzle or the like of the meter is connected perpendicularly downward from the upper side in the vertical direction with respect to the exhaust pipe. When a control valve is provided in the exhaust pipe, it is preferable that the tip pipes from the flange portions on the inlet side and the outlet side of the control valve are installed so as to face downward in the vertical direction so that the powder of the aromatic dihydroxy compound does not block the control valve. When the exhaust pipe is clogged with powder of the aromatic dihydroxy compound or the like, it is preferable that the powder or the like can be removed by flowing an inert gas through the pipe. In this case, the pipe for supplying the inert gas to the exhaust pipe is preferably connected to the exhaust pipe so as to be perpendicular to the exhaust pipe from the upper side in the vertical direction downward.

When the oxygen and the moisture present in the measuring tank 2 are replaced with the inert gas, the inert gas may be introduced into the measuring tank 2 after or while reducing the pressure in the measuring tank 2. In this case, since the powder of the aromatic dihydroxy compound may fly in the measuring tank 2 and may block the exhaust pipe, it is preferable to provide a bag filter for removing the powder of the aromatic dihydroxy compound in the exhaust pipe of the measuring tank 2. The piping from the measuring tank 2 to the bag filter is preferably provided at an angle of 30to 90 degrees downward with respect to the horizontal direction, and more preferably at an angle of 60 to 90 degrees.

In order to control the pressure in the measuring tank 2, it is preferable to use division control or the like. The exhaust capacity of the pressure control valve of the exhaust pipe preferably has an exhaust capacity (Nm) 1 to 5 times the capacity of the measuring tank 2³/hr), more preferably 1.5 to 3 times. Preferably, a pressure control valve is also provided in the pipe for supplying the inert gas, and the pressure control valve is preferably set to 1 at a timeThe volume of the measuring tank 2 is 0.3 to 2 times (Nm) in hours³/hr) supply capacity. The size of the pressure control valve (the diameter of the internal valve), the pressure control valve of the exhaust pipe, and the pressure control valve of the pipe for supplying the inert gas are preferably 1/2 inches to 2 inches. In the case of the division control, it is also preferable to provide a dead zone (a range of input signals in which the valve body does not operate in association with a change in the input signal).

When the measuring tank 2 is provided on the upper side of the mixing tank 7 in the vertical direction and the aromatic dihydroxy compound is taken into the measuring tank 2 by the bucket conveyor 1, a ball valve 4 (preferably a 4-face valve seat) as an automatic shut-off valve may be attached to the lower side of the measuring tank 2, and a rotary valve 5 (or a screw conveyor (not shown)) may be attached to the lower side thereof. Further, a short pipe may be provided between the rotary valve 5 and the ball valve 4 on the lower side of the measuring tank 2. These devices are preferably supported by support members extending from the lower part of the preferably conical shape of the metering slot 2. The aromatic dihydroxy compound can be taken in from the metering tank 2 to the mixing tank 7 by pneumatic transmission. In the case of pneumatic transmission, plug transmission in which the aromatic dihydroxy compound moves in the supply pipe in a plug state in which the aromatic dihydroxy compound is aggregated is preferable in terms of preventing adhesion of the aromatic dihydroxy compound powder to the pipe. Preferably, the gas used for pneumatic transmission is an inert gas. In the case of pneumatic transmission, a feedenser system can be mentioned as an example of a method of transmitting the aromatic dihydroxy compound from the measuring tank 2 to the mixing tank 7. In the case of pneumatic transmission, the position of the measuring tank 2 may be either the upper side or the lower side in the vertical direction with respect to the upper portion of the mixing tank 7.

[ weighing cell 3]

As described above, the load cell 3 that can be provided in the measuring tank 2 is preferably 2 points or more, more preferably 3 points or 4 points, and even more preferably 3 points, having a measuring point of 2 points or more. The weighing accuracy after the load cell 3 is attached to the measuring tank 2 is preferably within ± 0.5 mass%, more preferably within ± 0.25 mass%, and still more preferably within ± 0.15 mass%.

[ ball valve 4]

The metering tank 2 has an inlet and an outlet for the aromatic dihydroxy compound on the upper and lower sides thereof, and preferably has a ball valve 4 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. In the case of a ball valve, in order to prevent powder of the aromatic dihydroxy compound from entering the ball inside the ball valve, an automatic valve having a 4-face valve seat is preferred. It is also preferable to provide a buffer tank of instrument air in view of ensuring more rapid action even if the size of the automatic valve is increased. The ball valve 4 is preferably supported by a support member extending from an upper portion or a lower portion of the metering tank 2.

The pipe connected to the ball valve 4 is preferably heated to 40 to 160 ℃ so that the aromatic dihydroxy compound melts even if it adheres thereto. It is preferable that the ball valve 4 is purged with an inert gas because the aromatic dihydroxy compound is prevented from adhering to the ball valve 4.

[ Rotary valve 5]

The rotary valve 5 (or screw conveyor) is preferable in terms of feeding the aromatic dihydroxy compound into the mixing tank 7 at a constant speed as much as possible. At the outlet of the rotary valve 5 (or screw conveyor) a short and/or flexible pipe 6 can be installed. The flexible tube 6 is preferably provided with an inner cannula (not shown). In the case of using the flexible pipe 6 having the inner insertion tube, it is also preferable that the pipe connected to the flexible pipe 6 is a reduced diameter pipe in order to prevent the inner insertion tube from contacting the wall surface of the pipe. The inclination angle of the pipe from the flexible pipe 6 to the upper nozzle of the mixing tank 7 is preferably 30to 90 degrees, and more preferably 60 to 75 degrees with respect to the horizontal direction. The pipe diameter from the measuring tank 2 to the mixing tank 7 including the short pipe and the flexible pipe 6 is preferably a pipe diameter capable of supplying the entire amount of the aromatic dihydroxy compound measured in the measuring tank 2 to the mixing tank 7 in a time of 0.25 to 2 hours.

A pipe (not shown) for introducing an inert gas may be connected to the shaft of the rotary valve 5. In order to prevent air leakage from the shaft of the rotary valve 5 and powder of the aromatic dihydroxy compound from entering the gap between the shaft and the body, it is preferable to allow the inert gas to flow to the process side and the large side of the rotary valve 5The gas side. The purge amount of the inert gas is preferably 0.1Nm³/hr～20Nm³Perhr, more preferably 0.3Nm³/hr～10Nm³And/hr. In order to prevent the powder of the aromatic dihydroxy compound from entering the gap between the shaft and the body, it is also preferable to provide a structure in which horizontal plates are attached to both sides of the rotary valve on the bearing side.

[ supply of aromatic dihydroxy Compound to mixing tank 7]

In the step (B) of supplying the aromatic dihydroxy compound to the mixing tank 7, it is preferable to control 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, from the viewpoint of preventing the aromatic dihydroxy compound from scattering into the exhaust pipe connectable 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, a gas may be blown into the mixing tank 7, and the aromatic dihydroxy compound may be supplied to the mixing tank 7 together with 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 "the linear velocity of the gas supplied to the mixing tank") is defined as follows.

Linear velocity (m/sec) of gas supplied to the mixing tank (maximum flow rate (Nm) of gas supplied to the mixing tank 7)³Sec)/(cross-sectional area of gas flow in mixing tank 7 (m)²))

Here, the "maximum flow rate of the gas supplied to the mixing tank 7" may be "the maximum flow rate of the gas blown into the mixing tank 7", and for example, in the case where an exhaust pipe for the gas provided with a pressure control valve is provided to control the pressure in the mixing tank 7, the maximum flow rate of the gas in the pressure control valve may be checked. The "maximum flow rate" refers to the maximum flow rate among the flow rates at the respective times. The "cross-sectional area of the gas flow in the mixing tank 7" refers to a cross-sectional area orthogonal to the gas flow direction in the region where the gas flows, and when the mixing tank 7 has a straight cylindrical portion and the gas flows from one end to the other end of the straight cylindrical portion, it refers to a cross-sectional area orthogonal to the axial direction of the straight cylindrical portion. The linear velocity of the gas supplied to the mixing tank is preferably 0.005m/sec to 0.05 m/sec. By controlling the linear velocity of the gas supplied from the mixing tank to 0.005m/sec to 0.05m/sec, the powder of the aromatic hydroxy compound can be more effectively dropped into the liquid phase in the mixing tank 7, and the scattering into the exhaust pipe can be further suppressed. When the linear velocity of the gas supplied from the mixing tank is 0.05m/sec or less, the powder of the aromatic dihydroxy compound associated with the inert gas discharged from the mixing tank 7 can be more effectively prevented from entering the exhaust pipe, and problems such as clogging of the exhaust pipe and deviation of the charged molar ratio from the target can be further suppressed.

When the supply of the aromatic dihydroxy compound to the mixing tank 7 was terminated, the gas having pressurized the measuring tank 2 was in a state of flowing into the mixing tank 7 (through-flow (blown き removed け)). When the pressure in the measuring tank 2 is in the through-flow state, the pressure in the mixing tank 7 is easily equalized to (isobaric +0.05kPa) temporarily. By achieving an appropriate flow-through state, the aromatic dihydroxy compound temporarily adhering to the 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") can be more reliably contained in the mixing tank 7, and furthermore, the diaryl carbonate or the aromatic monohydroxy compound and the dissolved mixture thereof scattered from the mixing tank 7 can be prevented from adhering to the supply pipe for the aromatic dihydroxy compound. Therefore, control of the gas flow rate in the through-flow state is important.

However, the flow rate of the gas in the through-flow state varies depending on the method (equipment) of supplying the aromatic dihydroxy compound to the mixing tank 7, the pressure of the measuring tank 2, the gap of the rotary valve 5 or the like, the pipe diameter of the supply pipe for the aromatic dihydroxy compound, and the supply amount of the gas. Therefore, in the present embodiment, the linear velocity of the gas in the state of flowing through the supply pipe for supplying the aromatic dihydroxy compound to the mixing tank 7 (hereinafter referred to as "linear velocity of flowing gas") is defined as follows.

Linear velocity (m/sec) of through-flow gas (gas flow rate (Nm) in supply pipe for aromatic dihydroxy compound)³Sec)/(cross-sectional area of supply pipe for aromatic dihydroxy Compound(m²))

The gas flow rate is, for example, a gas flow rate when a nozzle extending from the upper part of the mixing tank 7 to which a supply pipe for an aromatic dihydroxy compound is connected flows through a flange part (1 st flange part) of the first nozzle on the mixing tank 7 side within 1 minute on the assumption that the same amount of inert gas as the capacity of the measuring tank 2 flows, and in this case, the cross-sectional area of the supply pipe is a cross-sectional area determined from the inner diameter of the 1 st flange part.

When the aromatic dihydroxy compound is supplied from the measuring tank 2 to the mixing tank 7 by pneumatic conveyance, the linear velocity of the gas flowing through the mixing tank is preferably 0.1m/sec to 500m/sec, more preferably 1m/sec to 300m/sec, and still more preferably 20m/sec 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 linear velocity of the gas passing through the flow is preferably 1m/sec to 100m/sec, more preferably 2m/sec to 60m/sec, and still more preferably 4m/sec to 35 m/sec. When the linear velocity of the gas flowing through is in the range of 0.1m/sec to 500m/sec, the powder of the aromatic dihydroxy compound adhering to the supply pipe of the aromatic dihydroxy compound can be more effectively and reliably peeled off into the mixing tank 7, the diaryl carbonate or the aromatic monohydroxy compound can be further prevented from adhering to the supply pipe, and the linear velocity of the gas required to supply the entire amount of the aromatic dihydroxy compound to the mixing tank 7 can be more reliably ensured. The prevention of adhesion of the aromatic dihydroxy compound and the diaryl carbonate to the supply pipe of the aromatic dihydroxy compound is effective in maintaining the molar ratio of the ingredients in the dissolution mixture in the mixing tank 7 within a predetermined range.

Further, since the effect of maintaining the charging molar ratio within the predetermined range can be further exhibited as long as the state of the through-flow is short, the time of the through-flow is preferably 0.01 to 8 minutes, more preferably 0.1 to 5 minutes, and still more preferably 0.2 to 3 minutes.

When the pressure in the mixing tank 7 rises in the through-flow state, it is also preferable to provide a ball valve type shield valve in a bypass of the pressure control valve in the exhaust pipe in order to discharge the through-flowing inert gas.

The aromatic dihydroxy compound before being supplied to the mixing tank 7 may be in the form of a solid powder or a liquid as described above. When the aromatic dihydroxy compound is in a liquid state, the mass of the aromatic dihydroxy compound supplied to the mixing tank 7 can be directly weighed without using the measuring tank 2 by measuring the aromatic dihydroxy compound with a coriolis type cumulative flowmeter or the like. In the case where the aromatic dihydroxy compound is in a liquid state, when the aromatic dihydroxy compound is not supplied to the mixing tank 7, it is preferable to provide a circulation line between the storage tank of the aromatic dihydroxy compound and the distillation system of the aromatic dihydroxy compound to circulate the aromatic dihydroxy compound between the storage tank and the distillation system in order to prevent coloration. In this case, it is also preferable that a pipe for returning the aromatic dihydroxy compound to the storage tank of the aromatic dihydroxy compound is connected to the inlet of the storage tank of 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 (e.g., an L-shaped three-way valve and a T-shaped three-way polymer valve), and the supply pipe of the aromatic dihydroxy compound is preferably a jacket pipe capable of being uniformly heated.

[ mixing tank 7]

In the mixing tank 7, provided are, as necessary: heating means such as an internal coil provided in the mixing tank 7, an external jacket provided outside the mixing tank 7, or an external coil provided outside the mixing tank 7; a stirring device; and a transfer pump 8A for performing circulation or transfer of the dissolution mixture. The mixing tank 7 is a tank for dissolving the aromatic dihydroxy compound and the diaryl carbonate to prepare a dissolved mixture, or a tank for adding a transesterification catalyst to the aromatic dihydroxy compound and the diaryl carbonate and reacting a part or substantially all of them to prepare a dissolved mixture. The mixing tank 7 may be used alone or in plural. As the stirring device provided in the mixing tank 7, a known stirring tank and a known stirring paddle may be used as long as they have a function of obtaining a more uniform dissolved mixture. When the aromatic dihydroxy compound at normal temperature (i.e., solid) 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 is, the more likely the internal temperature of the mixing tank 7 is decreased by melting of the aromatic dihydroxy compound accompanied by heat absorption. As a result, there is also a possibility that a diaryl carbonate precipitates or the aromatic dihydroxy compound is not completely melted. In order to prevent this, a double-pipe or multi-pipe heat exchanger (not shown) may be provided outside the mixing tank 7, and the contents containing the aromatic dihydroxy compound, diaryl carbonate, aromatic monohydroxy compound, and, if necessary, the transesterification catalyst may be circulated between the heat exchanger and the mixing tank 7, and the liquid temperature of the contents may be adjusted to a desired temperature.

When the aromatic dihydroxy compound is supplied to the mixing tank 7, if a part of the aromatic dihydroxy compound is in an unmelted slurry state, the transesterification reaction may proceed unevenly. When the liquid temperature in the mixing tank 7 is 135 ℃ or higher, the aromatic dihydroxy compound can be prevented from being in a slurry state in the mixing tank 7; when the temperature is 220 ℃ or lower, coloration of the aromatic dihydroxy compound can be prevented. Therefore, the liquid temperature of the contents of the mixing tank 7 was adjusted to 135 to 220 ℃. The liquid temperature in the mixing tank 7 is more preferably 140 to 210 ℃ and still more preferably 145 to 200 ℃.

In order to prevent the adhesion of the vapor of the aromatic dihydroxy compound, the scattered diaryl carbonate, and the aromatic monohydroxy compound produced by the reaction to the supply pipe, a ball valve (not shown) having a 4-face valve seat is preferably attached to the mixing tank 7 in the vicinity of the supply port of the aromatic dihydroxy compound. In the mixing tank 7, it is preferable that an inert gas is constantly circulated through the installation nozzle of the ball valve in order to prevent the steam of the diaryl carbonate and the aromatic monohydroxy compound produced by the reaction from flowing into the installation nozzle and adhering to the installation nozzle. The flow rate of the inert gas flowing through the installation nozzle is preferably 1Nm³/hr～5Nm³/hr。

When the aromatic dihydroxy compound and the diaryl carbonate are taken into the mixing tank 7, the pressure in the gas phase part of the mixing tank 7 is increased. In order to reduce the increased pressure, the mixing tank 7 is preferably provided with a gas discharge pipe for rapidly discharging the inert gas and the like to the outside of the mixing tank 7. The exhaust pipe is preferably heated to 45 to 220 ℃, more preferably 45 to 190 ℃, and still more preferably 45 to 160 ℃ until reaching the scrubber 9 described later from the mixing tank 7. When the temperature of the exhaust pipe is set to 45 ℃ or higher, the curing of the aromatic monohydroxy compound can be further suppressed. When the temperature of the exhaust pipe is 220 ℃ or lower, it is possible to more effectively prevent the aromatic dihydroxy compound colored in the exhaust pipe from flowing back into the mixing tank 7 to deteriorate the quality of the aromatic polycarbonate.

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

When the scrubber 9 is a jet pump system in which a scrubbing liquid circulates, the pressure in the exhaust pipe extending from the mixing tank 7 can be slightly reduced, and therefore, it is preferable that the vapor or the condensate of the aromatic monohydroxy compound, the diaryl carbonate, and the aromatic dihydroxy compound is less likely to remain in the exhaust pipe.

After the supply of the aromatic dihydroxy compound to the mixing tank 7 is terminated and/or after the diaryl carbonate is supplied in a small amount, the content of the mixing tank 7 is preferably bubbled with an inert gas in order to remove oxygen and moisture mixed into the mixing tank 7 together with the aromatic dihydroxy compound. The bubbling flow rate of the inert gas is preferably 0.01 to 0.5 times the volume of the mixing tank 7 per 1 hour (Nm)³Hr), more preferably 0.05 to 0.4 times, still more preferably 0.1 to 0.25 times. The time for bubbling is preferably 5 minutes or more, and preferably bubbling is continued until immediately before the dissolution mixture is transferred to the dissolution mixture storage tanks 12A and/or 12B described later.

In the mixing tank 7, depending on the temperature at which the diaryl carbonate is taken in, the liquid level in the mixing tank 7 may rise, and the liquid temperature in the mixing tank 7 may decrease until the stirring is started. When the liquid temperature in the mixing tank 7 is lowered, the mixing tank 7 is depressurized if the supply amount of the gas (the total amount of the gas for supplying the substitution gas and the aromatic dihydroxy compound to the mixing tank 7) is small. In order to prevent the mixing tank 7 from being depressurized, it is preferable to switch between a temperature control method (TIC control method) of controlling the liquid temperature in the mixing tank 7 and a pressure control method (PIC control method) of controlling the pressure of steam that can be used as a heat source. Alternatively, in order to prevent the pressure in the mixing tank 7 from being reduced, when the mixing tank 7 is provided with a gas exhaust pipe provided with a pressure control valve, it is preferable to increase the supply capacity of the pressure control valve or provide a double pressure control valve for the gas.

The heat source of the heating unit of the mixing tank 7 preferably uses steam. Preferable examples of the heating means include an inner coil, an outer jacket, and an outer coil. Any one of them may be used alone, or 2 or more of them may be used in combination. When the internal coil is used, the internal coil is preferably arranged 2 to 6-fold.

When steam is used as a heat source in supplying the aromatic dihydroxy compound to the mixing tank 7 or in raising the temperature of the liquid in the mixing tank 7, a large amount of steam condensate (hereinafter also referred to as "steam drain") is likely to be generated because the temperature difference between the steam in the heating means, particularly the inner coil and/or the outer jacket, and the temperature in the mixing tank 7 is likely to increase. The steam and steam vent water are preferably returned to a steam recovery system comprising a steam recovery device. The steam recovery device is a heating/pressurizing device as necessary in order to recover steam and steam waste water and reuse the steam and steam waste water as a heat source of the heating unit. In the case where the steam drainage is to be returned to the steam recovery system, if the pressure of the steam drainage is lower than that of the steam recovery system, the steam drainage may not be returned to the steam recovery system in the steam trap located therebetween. In this case, a steam hammer is likely to occur in the vicinity of the position where the steam drain joins the steam recovery system. Since the heating unit may be damaged if the steam hammer is frequently generated, the following method may be employed, for example, to prevent such damage. The "steam trap" refers to a member that selectively traps drain water from the mixed drain water and steam.

Here, fig. 3 is a diagram schematically showing an example of a manner in which a plurality of steam pipes are independently connected to each drain drum in a steam drain discharge facility that recovers steam and steam drain from an outlet from the mixing tank 7 in the case where steam is used as a heat source of a heating unit (for example, an inner coil and/or an outer jacket or an outer coil, hereinafter collectively referred to as "inner coil or the like") of the mixing tank 7. Fig. 4 is a diagram schematically showing an example of a manner in which, when steam is used as a heat source of the heating unit of the mixing tank 7, a part of the plurality of steam pipes are joined after the outlet from the mixing tank 7 and connected to a drain drum in the steam drain discharge facility. In fig. 4, the pipe diameter of the steam pipe after the joining is, for example, 2 to 20 times the pipe diameter of the steam pipe before the joining. These fig. 3 and 4 are the cases where both an inner coil and an outer jacket are used as the heating unit.

(1) The inner coil includes a plurality of steam pipes which are independently connected to the steam drain drum 22 in the steam drain discharge facility 21 (see fig. 3) when they do not meet at the outlet from the mixing tank 7.

(2) The inner coil includes a plurality of steam pipes, which are joined together in a steam drain discharge facility 21 connected to an outlet from the mixing tank 7 to form 1 large-diameter pipe, and when the large-diameter pipe is connected to the drain drum 22, the pipe diameter of the large-diameter pipe is, for example, 2 to 20 times the pipe diameter of each steam pipe of the inner coil (see fig. 4).

(3) The thickness of the pipe used for the steel pipe for piping is increased by about 1 coil from the position at the front stage of the inlet from the inner coil to the mixing tank 7 and the position at the rear stage of the outlet from the mixing tank 7 (for example, from Sch10 to Sch160 in the thickness of the pipe in the thickness series number used).

(4) The coil diameter of the inner coil near the outlet of the mixing tank 7 is increased to 1.2 to 4 times by a reducing pipe.

Among the above, the methods (1) and (2) are more preferable in order to facilitate the discharge of the steam waste water and to prevent the steam waste water from accumulating in the steam coil.

When the steam-drained water from the inner coil or the like is recovered in a large-sized drainage drum, the capacity of the drainage drum is preferably 0.001 to 0.4 times, more preferably 0.0025 to 0.2 times, the maximum supply amount of steam per 1 hour (ton/hr; the total amount of steam used in the inner coil, the outer jacket, and the outer coil).

When the pressure in the drain drum 22 is lower than the pressure in the steam recovery device (for example, indicated by reference numeral 24 in fig. 3 and 4), it is preferable to drain the steam and the steam drain to a drain 25 or a drain drum (not shown) provided at the bottom (underground) and under atmospheric pressure. On the other hand, when the pressure in the drain drum 22 is higher than the pressure in the steam recovery facility 24, it is preferable to discharge the steam and the steam drain to the steam recovery facility 24 side.

In the case of recovering steam and steam drain from the steam outlet of the inner coil or the like of the mixing tank 7, it is preferable to collect the steam drain into an underground drum or the like and then pump the steam drain into a recovery system. The discharge of the steam drainage from the drainage drum is more preferably controlled by means of an LIC (Level Indication Control) in the drainage drum, its discharge, and/or via a steam trap (for example, indicated by the symbol 23 in fig. 3 and 4). When the LIC control (and the LIC control device used for the control) is used, if a large amount of steam drain is generated, the steam drain can be discharged to the outside of the system before the drain drum is full, and the steam drain is not easily left in the inner coil or the like, so that the damage of the inner coil or the like due to the steam hammer can be more reliably prevented. Further, when the steam trap 23 is used to recover steam exhaust with a pressure higher than the steam pressure of the steam recovery device 24, heat loss is less and it is a simpler device. When the LIC control is used in combination with the steam trap 23, it is more preferable that the steam trap 23 be able to return the steam-drain to the steam recovery facility 24 when the pressure of the steam-drain is lower than the steam pressure of the steam recovery facility 24 and the steam-drain is higher than the steam pressure of the steam recovery facility 24.

The inner coil is preferably provided with a support portion (hereinafter referred to as "support portion". not shown) for fixing it. The support part also serves as a baffle, and is preferably provided at 3 or more positions. The inner coil is preferably formed so as to penetrate the tube in a portion fixed to the support portion and in a region 20cm to 30cm from the portion along the extending direction of the inner coil. This is preferable because breakage of the internal coil can be prevented by using a U-shaped screw for fixing the internal coil to the support portion. The U-shaped screw used for fixing the inner coil is preferably double-threaded and welded to the support portion. Further, since the pressure of the mixing tank 7 increases when the steam leaks from the inner coil, it is also preferable to provide an interlock for stopping the supply of the steam into the inner coil.

[ scrubber 9]

The scrubber 9 is a usual capture system that circulates the scrubbing liquid and absorbs the vapor. For example, the scrubber 9 is a vertical tank connected to an exhaust pipe extending from the top of the mixing tank 7 at a substantially central portion in the vertical direction, and an exhaust pipe for discharging the gas having absorbed the steam is connected to an upper portion of the tank. Examples of the scrubber 9 include a packed tower, a jet pump, a rotary spray tower, and a venturi scrubber. The exhaust pipe from the scrubber 9 may be directly opened to the atmosphere or may be connected to an exhaust pipe from another device. Alternatively, the generated steam may be absorbed by circulating the cleaning liquid through an exhaust pipe extending from the top of the mixing tank 7. In this case, for example, a heat exchanger for cooling the washing liquid is provided in the circulation line of the washing liquid, and the washing liquid circulated is cooled to 0to 115 ℃ and returned to the scrubber 9.

The washing liquid is not particularly limited, and may be, for example, a solvent having low volatility capable of dissolving or decomposing and absorbing the aromatic dihydroxy compound and/or the diaryl carbonate, or a low-temperature liquid capable of cooling and solidifying the vapor. Examples of the washing liquid include aromatic monohydroxy compounds, diaryl carbonates, alkyl aryl carbonates, water, aqueous sodium hydroxide solutions, ethylene glycol, and triethylene glycol. These may be used in 1 kind or in combination of 2 or more kinds.

The washing liquid may contain an aromatic dihydroxy compound, and the melting point of the washing liquid and the temperature of the washing liquid to be circulated can be lowered by selecting the compounds contained in the washing liquid and the ratio thereof. For example, a mixture of about 45 mass% of 1 phenol (hereinafter, referred to as "PH") as an aromatic monohydroxy compound, about 54 mass% of 1 methylphenyl carbonate (hereinafter, referred to as "MPC") as an alkylaryl carbonate, and about 1 mass% or less of bisphenol a (hereinafter, referred to as "BPA") as an aromatic dihydroxy compound does not solidify at 0 ℃. In addition, for the mixture of MPC and PH, if the PH is 95 mass% or less, coagulation will not occur at 40 ℃. When an aromatic monohydroxy compound is used as the washing liquid, the temperature of the circulating liquid is preferably 42 to 115 ℃, more preferably 42 to 85 ℃, still more preferably 42 to 75 ℃, and particularly preferably 42 to 70 ℃. When a mixed solution of MPC containing 5% by mass or less of BPA and PH is used as the washing liquid, the temperature of the washing liquid is preferably 0to 115 ℃, more preferably 0to 85 ℃, still more preferably 0to 35 ℃, and particularly preferably 0to 20 ℃.

A method of collecting the vapor of the aromatic monohydroxy compound, diaryl carbonate, and aromatic dihydroxy compound by spraying and supplying the washing liquid into the scrubber 9 to bring the vapor into more sufficient contact with the washing liquid is also preferable. In the case where the aromatic dihydroxy compound or the like is not completely dissolved in the washing liquid, it is also preferable to remove the undissolved substance by a transfer pump which may be provided in the transfer line of the washing liquid from the scrubber 9 and/or a suction filter which may be provided on the suction side of a circulation pump which may be provided in the circulation line. When an aromatic monohydroxy compound produced as a by-product in the polymerization step is used as the washing liquid, the aromatic monohydroxy compound may contain moisture or an aromatic dihydroxy compound. In this case, the aromatic monohydroxy compound is preferably distilled by a distillation column capable of separating high-boiling components such as water and the aromatic dihydroxy compound.

When the concentration of the aromatic dihydroxy compound or diaryl carbonate in the washing liquid is not less than a certain concentration, it is preferable to continuously extract a part of the washing liquid and add a new washing liquid to continuously operate the scrubber 9. As a method of continuously withdrawing a part of the washing liquid, for example, preferred are: a level control method in which a part of the washing liquid is extracted so that the liquid level of the liquid located at the bottom (bottom) of the scrubber 9 is kept within a predetermined narrow range (for example, 0% when the washing liquid in the scrubber 9 is the smallest amount in the range in which the scrubber 9 can be operated and ± 1% of any value of 0% to 100% when the liquid level of the washing liquid in the scrubber 9 is the largest amount is 100%), and a semibatch method in which the liquid level of the washing liquid is controlled to 10% to 90%.

[ transfer pump 8A ]

The transfer pump 8A performs circulation for returning the dissolution mixture drawn out from the mixing tank 7 to the mixing tank 7 again, or transfers the dissolution mixture to the dissolution mixture storage tank 12A or 12B. When the transfer pump 8A sucks the unmelted aromatic dihydroxy compound into the transfer pump 8A, the pump is preferably a pump having a structure capable of pulverizing the unmelted aromatic dihydroxy compound.

A suction screen is preferably arranged on the suction side of the delivery pump 8A. 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 suction screen is exchanged or cleaned. When the diaryl carbonate is first supplied to the mixing tank 7, a part of the diaryl carbonate may be mixed into the suction-side pipe of the transfer pump 8A, and therefore, the dissolution mixture is transferred from the mixing tank 7 to the dissolution mixture storage tank 12A or 12B after a short-time circulation operation is performed between the mixing tank 7 and the transfer pump 8A before the dissolution mixture is transferred from the mixing tank 7 to the dissolution mixture storage tank 12A or 12B, whereby the diaryl carbonate can be suppressed from remaining in the suction-side pipe.

To prevent cavitation and liquid seal, it is preferred that the temperature of the body of the transfer pump 8A be lower than the temperature of the dissolving mixture. In order to prevent coloration, deterioration, and liquid seal of the dissolution mixture, the piping for transporting the dissolution mixture from the mixing tank 7 to the dissolution mixture storage tank 12A or 12B is also preferably heated by steam having a temperature lower than the temperature of the dissolution mixture or heat medium oil supplied from a heat medium boiler.

In order to prevent the idle operation of the transfer pump 8A, it is preferable that the transfer pump 8A is automatically stopped by detecting a decrease in the liquid level at the bottom of the mixing tank 7 by a liquid level switch (LIS) provided in a pipe connected to the bottom of the mixing tank 7. Similarly, in order to prevent the idle operation of the feed pump 8A, it is also preferable to detect a decrease in the current value of the feed pump 8A and automatically stop the same. In order to prevent the liquid level of the dissolution mixture tank 12A and/or 12B from being higher than the estimated value or prevent the pressure of the dissolution mixture tank 12A and/or 12B from abnormally rising, it is also preferable to stop the feed pump 8A using interlock.

[ dissolution mixture storage tanks 12A and 12B ]

The dissolution mixture tanks 12A and 12B are tanks for allowing the dissolution mixture prepared in the mixing tank 7 to react until a prescribed equilibrium reaction rate is reached. The dissolution mixture is preferably held in the dissolution mixture tanks 12A and 12B at a liquid temperature of 160 ℃ to 220 ℃ for 1 hour to 12 hours. The liquid temperature is preferably 160 to 220 ℃, more preferably 160 to 210 ℃, and still more preferably 180 to 200 ℃. 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 prepare a reaction mixture in which the dissolution mixture reaches the equilibrium reaction rate, it is preferable to keep the reaction mixture at 160 ℃ or higher for 1 to 12 hours. When the reaction mixture having the equilibrium reaction rate is supplied to the stirred tank type 1 st polymerizer 14 described later, it is preferable to further suppress the Mn of the prepolymer and/or the polymer and/or the ratio of the polymer terminal hydroxyl groups (hereinafter referred to as "OH%") from largely varying, and to more easily adjust the operating pressure of the main polymerizers 18A and 18B described later. Further, it is preferable to keep the temperature at 220 ℃ or lower because the aromatic polycarbonate as a final product is less likely to be colored. In order to confirm whether or not the reaction mixture has reached the equilibrium reaction rate, the reaction mixture was collected and measured by the method described in the following examples.

Further, as described later, in the case where the dissolution mixture is bubbled with an inert gas in the dissolution mixture tanks 12A and 12B, or in the case where mechanical seals of meters or stirrers which may be provided in the dissolution mixture tanks 12A and 12B are purged with a small amount of an inert gas, the inert gas used is discharged from the dissolution mixture tanks 12A and 12B to the outside of the system. In this case, the aromatic monohydroxy compound produced as a by-product may be discharged out of the system together with the inert gas. The holding time is preferably 12 hours or less from the viewpoint of suppressing the progress of the ester exchange reaction to an extent expected by increasing the amount of the discharged aromatic monohydroxy compound. This can further suppress the amount of the aromatic monohydroxy compound discharged from the dissolution mixture storage tanks 12A and 12B.

The dissolution mixture tanks 12A and 12B preferably include at least 1 of an internal coil and/or an external jacket, an addition nozzle for adding a transesterification catalyst, a stirring device, and a sampling (collection) nozzle for measuring an equilibrium reaction rate of the dissolution mixture. In addition, from the viewpoint of removing the moisture mixed with the aromatic dihydroxy compound, it is preferable to bubble the dissolution mixture in the dissolution mixture tanks 12A and 12B with an inert gas. The number of the dissolution mixture tanks is preferably 2 or more, preferably 2 or 3 as shown in the drawing. Thus, while the dissolving mixture is supplied to one of the 2 or more dissolving mixture tanks and the reaction mixture obtained therein is supplied to the polymerization step for obtaining the prepolymer or the polymer, the dissolving mixture is supplied to the other dissolving mixture tank and the reaction mixture is obtained therein. Thereafter, when the amount of the reaction mixture in the first part of the dissolution mixture storage tank is reduced to a predetermined amount, the reaction mixture obtained in the other part of the dissolution mixture storage tank may be supplied to the polymerization step for obtaining the prepolymer or the polymer. And, the dissolution mixture may be supplied to another part of the dissolution mixture storage tank therebetween, to obtain a reaction mixture therein. In this way, it is preferable that the tank for supplying the reaction mixture in the polymerization step be repeatedly switched to allow the entire apparatus to be continuously operated.

In order to adjust the pressure in the dissolution mixture tank 12A and/or 12B, a pipe for introducing an inert gas and a gas discharge pipe for discharging an inert gas may be provided above the dissolution mixture tank 12A and/or 12B. In the case where 2 or more dissolution mixture tanks are used as shown in the figure, a plurality of exhaust pipes may be connected by a pressure equalizing pipe. The exhaust pipe of the dissolution mixture tank preferably extends downward at least partially from the dissolution mixture tank toward the outlet of the exhaust pipe, and is connected to a scrubber. This can more effectively prevent the aromatic monohydroxy compound that may be accompanied by the inert gas discharged from the exhaust pipe from flowing back into the dissolved mixture storage tank, and the aromatic monohydroxy compound can be absorbed by the scrubber. The scrubber connected to the dissolution mixture tank may be the same scrubber 9 as the mixing tank 7 as shown in the drawing, or another scrubber may be provided. When steam is used as the heat source of the dissolution mixture storage tank, the piping at the steam outlet is preferably the same as that used for the heat source of the mixing tank.

[ transfer pumps 8B,8C ]

Transfer pumps 8B and 8C are used to perform circulation of returning the reaction mixture withdrawn from the dissolution mixture tanks 12A and 12B to the dissolution mixture tanks 12A and 12B again, or transfer the reaction mixture to the agitation tank type 1 st polymerizer 14. It is preferable that the suction filter on the suction side of the transfer pump 8B and/or 8C is connected to a pipe (not shown) for supplying an aromatic monohydroxy compound, and the attached dissolved mixture can be washed with the aromatic monohydroxy compound when the suction strainer of the transfer pump 8B and/or 8C is exchanged or cleaned. In order to more effectively prevent the cavitation phenomenon from occurring in the transfer pump 8B or 8C, regarding the switching between the dissolution mixture tanks 12A and 12B, it is preferable to perform the switching of the transfer pump in the following manner: when the liquid level of the liquid contained in one of the tanks, from which the reaction mixture is flowed out by the delivery pump, is below the level corresponding to 10 mass% of the amount of the dissolved mixture taken in, it can be flowed out from the other tank. The liquid level as a target for switching the transfer pump is more preferably a level corresponding to 5 mass% or less of the amount of the dissolved mixture taken in.

[ Filter (not shown) for filtering reaction mixture ]

A filter equipped with a filter element for removing foreign matters in the reaction mixture may be disposed between the dissolution mixture tanks 12A and 12B and the agitation tank type 1 st polymerizer 14. Foreign substances in the reaction mixture were removed by the filter. More than 1 filter can be arranged in series, more preferably more than 2 filters with the same or different pore sizes are arranged. Further, preliminary filters may be provided side by side so that the supply of the reaction mixture into the agitation type 1 st polymerizer 14 will not be stopped even when the filter element is clogged.

The filter element used is preferably of any of a candle type and a disk type. The structural material in the filter element may be a wire mesh, a metal sintered body, a metal fiber, a perforated metal plate, or the like, and may be used alone or in any combination. The pore size of the filter element is preferably 0.25 to 50 μm with a filtration accuracy of 98% or more, and more preferably, a filter element with a large pore size is used upstream and a filter element with a small pore size is used downstream.

The surface of the filter element may be treated with heat and/or acid. Before the filter element is used, it is also preferable to wash the filter element with 1 to 1000ppm of an alkali water (for example, an aqueous potassium hydroxide solution) and/or a dissolved mixture to which an aromatic monohydroxy compound is added at 45 to 180 ℃ in order to neutralize a reaction inhibitor such as a trace amount of an acid component adhering to the filter element or remove adsorbed oxygen or oil on the surface.

The material of the gasket used for fixing the filter element is preferably a material having a heat resistant temperature of 220 ℃ or higher. Further, it is preferable that the material is not deteriorated even when it is brought into contact with an aromatic dihydroxy compound, an aromatic monohydroxy compound, or a diaryl carbonate.

The transfer piping for transferring the reaction mixture from the dissolution mixture storage tanks 12A and 12B to the stirred tank type 1 polymerization vessel 14 preferably suppresses the temperature decrease of the reaction mixture therein by steam tracing and/or double pipe type from the viewpoint of reducing undissolved substances. Further, when the transfer pipe is a sleeve pipe, it can be used as a preheater for the reaction mixture, and it is also preferable that the heat source is heat medium oil or steam supplied from a heat medium boiler.

[ flow rate regulator (not shown) for reaction mixture ]

A flow rate regulator for adjusting the amount of the reaction mixture to be supplied is preferably provided at the inlet of the reaction mixture of the agitation type 1 st polymerizer 14. The flow rate regulator is preferably a combination of a flow rate regulating valve for the reaction mixture and an accumulation flow meter (not shown), and is further preferably provided with a jacket. The flow rate control valve for the reaction mixture is preferably provided on the side surface of the agitation type 1 st polymerizer 14 at a position corresponding to the liquid level in the liquid phase part of the polymerizer. The amount of the reaction mixture supplied is measured by the above-mentioned integrating flowmeter (provided immediately before a preheater for a reaction mixture described later is provided), and is controlled to a flow rate within a predetermined range by a flow rate control valve.

[ preheater for reaction mixture and prepolymer (not shown) ]

The supply pipe for supplying the reaction mixture from the dissolved mixture storage tank 12A or 12B to the stirred tank type 1 st polymerizer 14 may be provided with a preheater for the reaction mixture. The preheater for the reaction mixture is preferably capable of heating the reaction mixture to a temperature above the temperature in the dissolution mixture tank 12A or 12B and below the reaction temperature in the stirred tank type 1 st polymerizer 14. The preheater of the reaction mixture preferably can supply heat capable of vaporizing 0to 50 mass% of the amount of the aromatic monohydroxy compound vaporized in the stirred tank type 1 st polymerizer 14.

The supply pipe for supplying the prepolymer from the agitation type 1 st polymerization vessel 14 to the agitation type 2 nd polymerization vessel 15 may be provided with a preheater for the prepolymer. The preheater for the prepolymer preferably can supply heat capable of vaporizing 0to 50 mass% of the amount of the aromatic monohydroxy compound vaporized in the stirred tank type 2 nd polymerizer 15.

[ tank type 1 st polymerization vessel 14 and tank type 2 nd polymerization vessel 15]

The agitation tank type 1 st polymerizer 14 and the agitation tank type 2 nd polymerizer 15 are apparatuses for producing a prepolymer having Mn of 400 to 7000 from the reaction mixture. The form of the agitation tank type polymerizer is preferably a well-known vertical reactor in which the rotation axis of the agitation blade is vertical.

From the viewpoint of preventing the concentration of the aromatic dihydroxy compound in the reaction mixture from varying due to the discharge of the aromatic monohydroxy compound produced by the transesterification reaction to the outside of the system, 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 stirred tank type 1 st polymerization reactor 14 is preferably 1 hour to 24 hours, more preferably 2 hours to 12 hours, and still more preferably 3 hours to 8 hours.

The stirred tank type 1 st polymerizer 14 is preferably continuously operated under conditions of an internal temperature of 210 to 240 ℃ and a pressure of 6.65 to 13.3kPa (50to 100 Torr). The Mn of the prepolymer at the outlet of the agitation tank type 1 st polymerizer 14 is preferably 400 to 1200. The residence time of the reaction mixture and the prepolymer in the agitation tank type 1 st polymerizer 14 is preferably within 1.5 hours.

The prepolymer produced in the agitation type 1 st polymerization vessel 14 is continuously fed to the agitation type 2 nd polymerization vessel 15 by a feed pump (not shown) provided in a pipe connected to the bottom of the agitation type 1 st polymerization vessel 14. The form of the transfer pump is, for example, a gear pump. The prepolymer may be heated to 210 to 275 ℃ by providing a preheater in the middle of the prepolymer transport pipe from the agitation tank type 1 st polymerization vessel 14 to the agitation tank type 2 nd polymerization vessel 15. The transfer piping may be provided with a filter for removing solid components.

In order to more effectively and surely prevent the liquid seal and the coloration of the reaction mixture, it is preferable that the piping and the filter from the dissolution mixture tank 12A or 12B to the agitation tank type 1 st polymerizer 14 are themselves at the same temperature as or lower than the temperature of the reaction mixture with which they are brought into contact.

The stirred tank type 2 nd polymerizer 15 is preferably continuously operated under conditions of an internal temperature of 240 to 275 ℃ and a pressure of 1.3 to 3.99kPa (10to 30 Torr). The Mn of the prepolymer at the outlet of the agitation tank type 2 nd polymerizer 15 is preferably 2000 to 7000.

It is preferable that the molecular weight of each polymerization vessel can be confirmed by the rotational speed and discharge pressure of a transfer pump for drawing and transporting the prepolymer or the polymer, which is provided at the bottom of each polymerization vessel, and/or the viscometer provided in a discharge pipe, and/or the pressure at the inlet of the prepolymer or the polymer of the polymerization vessel.

Inert gas absorption apparatus (not shown)

The production apparatus of the present embodiment may be provided with an inert gas absorption device for absorbing an inert gas in the prepolymer or the polymer between the agitation type 1 st polymerization vessel 14 and the agitation type 2 nd polymerization vessel 15 and/or between the agitation type 2 nd polymerization vessel 15 and a main polymerization vessel 16 described later. The inert gas absorption apparatus causes the prepolymer or polymer to absorb an inert gas, thereby promoting, for example, the transesterification reaction described in International publication No. 99/64492. Examples of the inert gas absorption means include a vertical cylindrical tank (for example, a vertical cylindrical tank) in which a lead wire and/or a wire mesh are provided, and an agitation tank.

[ Main polymerizers 16,18A, and 18B ]

The main polymerizers 16,18A, and 18B are polymerizers for producing a prepolymer and a polymer having Mn of 4000 to 30000 from the prepolymer supplied from the agitation type 2 nd polymerizer 15. Examples of the form of the main polymerizers 16,18A, and 18B include known horizontal polymerizers such as a wire-type vertical cylindrical tank (for example, a vertical cylindrical tank) in which a prepolymer or a polymer is allowed to fall along a wire or a wire mesh to be polymerized, and a horizontal polymerizer in which the rotation axis of a paddle is horizontal. The number of the main polymerizers 16,18A, and 18B may be 1 or more, and all of them may be wire-type vertical cylindrical tanks or all of them may be horizontal polymerization tanks, or a combination of wire-type vertical cylindrical tanks and horizontal polymerization tanks. The number of main polymerizers is not particularly limited, and may be 3 as shown in the drawing, but is preferably 2 to 6. As shown in fig. 1, when the production apparatus of the present embodiment includes main polymerization vessels 16,18A, and 18B, the temperature and pressure in the main polymerization vessel 16 are not particularly limited as long as the desired prepolymer and polymer can be obtained, and the temperature is preferably 240 to 300 ℃ and the pressure is preferably 990Paa to 20 Paa. The temperature and pressure in the main polymerizers 18A and 18B are not particularly limited as long as the desired prepolymer and polymer can be obtained, and the temperature is preferably 250 to 300 ℃ and the pressure is preferably 500 to 20 Paa.

[ Material of the device, etc. ]

The material of each device and apparatus used in the present embodiment may be a known material, and for example, austenitic stainless steel, which is also called 18-8 stainless steel, is preferable. Specific examples thereof include SUS302, SUS304L, SUS309S, SUS310S, SUS316L, SUS317, SUS321, and SUS 347. More preferred materials are SUS304 and SUS 316. Further, these stainless steels may further contain niobium or vanadium. Examples of the method of incorporating these metal elements into stainless steel include a method of adding these metals to molten steel, or a method of adding these 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 10ppm to 1000 ppm.

The piping from the storage tank 10to the main polymerizers 18A and 18B, and the metal surfaces of the equipment may be subjected to finish polishing. The surface roughness of these metal surfaces is preferably 50 μm or less, more preferably 10 μm or less. In order to remove dirt, oil, reaction inhibitors (e.g., acids) attached to the metal surface, and adsorbed oxygen on the metal surface, the metal surface of the piping and equipment is preferably further cleaned with at least 1 kind selected from the group consisting of chemicals, warm water, dilute alkali, and a molten mixture of an aromatic monohydroxy compound, a diaryl carbonate, and an aromatic dihydroxy compound and a diaryl carbonate.

[ aromatic dihydroxy Compound ]

As the aromatic dihydroxy compound of 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, the aromatic dihydroxy compound may be used alone in 1 kind, or two or more kinds may be used in combination.

[ diaryl carbonate ]

As the diaryl carbonate of the present embodiment, for example, the diaryl carbonate described in patent document 1 is used. A particularly preferred diaryl carbonate is diphenyl carbonate (hereinafter "DPC"). The diaryl carbonate may be used alone or in combination of 2 or more. In addition, the diaryl carbonate may contain an aromatic monohydroxy compound such as PH, tert-butylphenol, and cumylphenol for the purpose of terminal conversion or molecular weight adjustment.

[ molar ratio of aromatic dihydroxy Compound to diaryl carbonate fed ]

The molar ratio of the aromatic dihydroxy compound to the diaryl carbonate charged into the mixing tank 7, that is, the charging molar ratio, is determined by the Mn or OH% of the objective aromatic polycarbonate, the kind of the aromatic dihydroxy compound and the diaryl carbonate used, the polymerization temperature, and other polymerization conditions. From the viewpoint of achieving a better polymerization reaction and effectively preventing coloration or a decrease in heat resistance, the charge amount of the diaryl carbonate is preferably 1.05 to 1.30, more preferably 1.05 to 1.25, and still more preferably 1.05 to 1.20 in a limited range on a molar basis relative to the charge amount of the aromatic dihydroxy compound. When the amount of diaryl carbonate added (molar ratio) is 1.05 or more, the coloring and heat resistance can be further improved; when the amount is 1.30 or less, the polymerization reaction proceeds more easily.

[ polyfunctional Compound ]

Further, in order to impart a branched structure to the objective aromatic polycarbonate, a polyfunctional compound may be used. As polyfunctional compounds, for example, 1,1, 1-tris (4-hydroxyphenyl) ethane and 4- [4- [1, 1-bis (4-hydroxyphenyl) ethyl ] - α, α -dimethylbenzyl ] phenol are 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 still more preferably 0.3 to 0.8 mol% based on 100 mol% of the aromatic dihydroxy compound.

[ transesterification catalyst ]

In the present embodiment, a transesterification catalyst may not be used in the polymerization reaction of the aromatic dihydroxy compound and the diaryl carbonate, but a transesterification catalyst described in, for example, patent document 1 may be used as necessary in order to increase the polymerization rate. In the case of using a transesterification catalyst, 1 kind of the transesterification catalyst may be used alone, or 2 or more kinds may be used in combination. In addition, the amount of the transesterification catalyst to be used is preferably 50ppb to 300ppb, more preferably 60ppb to 200ppb, and further preferably 70ppb to 150ppb, with respect to the raw material aromatic dihydroxy compound, from the viewpoint of achieving a more satisfactory polymerization reaction in practical use and more effectively preventing coloration or reduction in heat resistance.

The transesterification catalyst may be added as it is, or may be diluted with water, an aromatic monohydroxy compound, a diaryl carbonate, or the like. In the case of using water, the water may be mixed into the aromatic monohydroxy compound by-produced in the polymerization reaction.

Preferred forms of the transesterification catalyst to be added include powders and tablets (tablets), and commercially available forms may be used as they are. Examples of the method of adding the transesterification catalyst include the following methods: a method in which a transesterification catalyst is added to a powdery aromatic dihydroxy compound and/or diaryl carbonate, and the mixture is compressed to charge a solid into a production apparatus; a method in which a transesterification catalyst is added to a container comprising a compression-molded aromatic dihydroxy compound and/or diaryl carbonate, and the mixture is charged into a production apparatus together with the container; a method in which an aromatic dihydroxy compound and/or a diaryl carbonate melted in a nitrogen glove box is stored in an SUS-made container having a truncated cone shape such that the diameter of the opening is larger than that of the bottom, a transesterification catalyst is added thereto, the mixture is cooled, and the resulting cured product is charged into a manufacturing apparatus; a method in which a transesterification catalyst is added to a container made of an aromatic polycarbonate (package including a film made of an aromatic polycarbonate), and the container is charged into a production apparatus. In the above method, since the diaryl carbonate, the dissolution mixture and the prepolymer melted in the production apparatus are immediately dissolved when the vessel composed of the aromatic dihydroxy compound, the diaryl carbonate and the aromatic polycarbonate is added to the vessel, it is effective to add a large amount of the ester exchange catalyst at a time when the progress of the reaction is delayed, particularly in the mixing tank 7, the dissolution mixture storage tanks 12A and 12B and the agitation tank type 1 st polymerizer 14. In addition, for the solid catalyst, in order to accurately measure the amount of addition, required by calculation, pulverization, etc., also preferably not grinding operation, and more than the calculated value of 0 ~ 100mg added. In this paragraph, it is preferable that the aromatic dihydroxy compound and the diaryl carbonate are used as raw materials in the production method of the present embodiment.

The transesterification catalyst may be added to the production apparatus through a nozzle. The nozzle used for the addition of the transesterification catalyst is preferably provided in the upper part of 1 or more kinds of equipment selected from the group consisting of the mixing tank 7, the dissolution mixture storage tanks 12A and 12B, the agitation tank type 1 st polymerizer 14, and the agitation tank type 2 nd polymerizer 15. The nozzle is preferably 2 inches to 4 inches in size, and a ball valve can be attached to the nozzle, and a short pipe with a manometer, an exhaust pipe, a pipe for supplying inert gas, and the like is preferably attached to the nozzle. In the case where the short pipe is provided with a pipe for supplying an inert gas to supply the transesterification catalyst, it is also preferable that the inert gas flows from the pipe for supplying the inert gas to the tank provided with the nozzle, thereby preventing the aromatic monohydroxy compound from adhering to the short pipe. In order to suppress the adhesion of the powder of the diaryl carbonate, the aromatic monohydroxy compound, and the aromatic dihydroxy compound, it is also preferable to constantly supply an inert gas to the lower part of the nozzle to which the transesterification catalyst is added. The flange for supplying the transesterification catalyst can preferably be closed by means of a flange-type clamp which can be opened in a simple and clean manner. 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 piping connecting the mixing tank 7 and the dissolution mixture storage tank 12A or 12B, and/or may be added to the reaction mixture in the middle of the transfer piping connecting the dissolution mixture storage tank 12A or 12B and the agitation tank type 1 st polymerization vessel.

[ catalyst deactivator ]

In the present embodiment, for example, a known catalyst deactivator described in patent document 1 can be used. The amount of the catalyst deactivator to be 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 1 mol of the transesterification catalyst. The catalyst deactivator is added, for example, in an extruder.

[ additives, others ]

The final aromatic polycarbonate obtained in the main polymerizers 18A and 18B can be sent out in a molten state from the main polymerizers 18A and 18B to the subsequent facilities 19A and 19B. The facilities 19A and 19B in the latter stage are not particularly limited as long as they are conventional facilities capable of storing the molten aromatic polycarbonate, and examples thereof include extruders, pelletizers, sifters, dryers, silos, and packing machines. For example, the molten aromatic polycarbonate may be fed to an extruder, and other resins such as ABS and PET, additives such as a heat stabilizer, an antioxidant, a light stabilizer, an ultraviolet absorber, a release agent, and a flame retardant, and any additives such as an organic or inorganic pigment or dye, a metal deactivator, an antistatic agent, a lubricant, and a nucleating agent may be mixed in the extruder. These other resins and optional additives may be used alone or in combination of 2 or more. The aromatic polycarbonate produced in the present embodiment may further contain 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 hydroxy acids such as lactic acid, p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

Further, pH that can be secondarily produced in the agitation type 1 st polymerizer 14, the agitation type 2 nd polymerizer 15, and the main polymerizers 16,18A, and 18B may be recovered by the transfer pump 17.

The above description shows that the production method of the present embodiment can continuously produce an aromatic polycarbonate. The aromatic polycarbonate obtained by the production method of the present embodiment can be molded into a molded article through a predetermined molding step. The molding step may be a known molding step, and for example, in the molding step, the aromatic polycarbonate may be molded by 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. The obtained molded article can be used in a wide range of applications such as automobiles, electric and electronic products, OA, optical media, building materials, and medical treatment.

The present embodiment can provide a method for efficiently producing an aromatic polycarbonate having little coloration by easily controlling the operating conditions during production. Further, a large amount of steam is circulated inside the heating coil provided in the mixing tank, whereby the temperature in the mixing tank can be quickly adjusted.

[ examples ] A method for producing a compound

The present invention will be described below by way of specific examples and comparative examples, but the present invention is not limited to these examples.

The measurement methods of the characteristics applied in the examples and comparative examples are described below.

(1) Equilibrium reaction rate

0.5g of the reaction mixture collected from the dissolution mixture tank and 0.05g of carbanilate as an internal standard substance were dissolved in 40mL of THF and used as a sample. The amounts of the respective components contained in the sample were measured using an ultra high performance liquid chromatography apparatus (product name "ACQUITYUPLC", manufactured by Waters Co., Ltd.), and the equilibrium reaction rates were derived based on the measurement results. As the eluent, a mixed eluent composed of distilled water and acetonitrile was used. The measurement conditions were as follows: first, the column temperature was set to 40 ℃, the ratio of distilled water to acetonitrile (distilled water/acetonitrile) in the mixed eluent was 80/20, the measurement was started, the ratio was changed to 30/70 by a time gradient of 4.5 minutes from 1.5 minutes after the start of the measurement, the ratio was maintained for 2 minutes, the ratio was changed to 0.1/99.9 by a time gradient of 2 minutes, the ratio was maintained for 0.9 minutes, and the ratio of distilled water/acetonitrile was thereafter changed to 80/20 by a time of 0.1 second. As the column, HSST 3(1.8 μm, length 100mm) column for the above-mentioned 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 absorption coefficient of the internal standard substance, and the amount of the unreacted aromatic dihydroxy compound was subtracted from the amount of the aromatic dihydroxy compound charged (the amount of the aromatic dihydroxy compound in the case where the total amount of each raw material charged was converted to 0.5g), to determine the reaction conversion rate of the aromatic dihydroxy compound, and this value was taken as the equilibrium reaction rate. For example, when BPA is used as the aromatic dihydroxy compound and DPC is used as the diaryl carbonate, the reaction conversion of BPA is determined by the following formula.

Sample size (0.5g) × (charge of BPA)/(charge of BPA + charge of DPC)

(Here, A represents the amount (g) of BPA in the case where the total amount of each raw material charged is 0.5 g.)

Reaction conversion (%) of BPA [ (a-amount of unreacted BPA in sample (g))/a ] × 100

(2) Number average molecular weight (Mn)

Mn was measured using Gel Permeation Chromatography (GPC). Tetrahydrofuran was used as a solvent, polystyrene gel was used as a gel, and the number average molecular weight was determined from a calibration curve of standard monodisperse polystyrene using a calibration curve of the converted molecular weight based on the following formula.

MPC＝0.3591×MPS^1.0388

(in this case, MPC represents the molecular weight of polycarbonate and MPS represents the molecular weight of polystyrene.)

(3) Melt Index (MI)

MI (g/10min) was measured according to ISO 1133 at 300 ℃ under a load of 1.2 kg. The larger MI means the more excellent fluidity.

(4) Proportion of terminal hydroxyl groups of Polymer (OH%)

As OH%, 0.3g of aromatic polycarbonate was dissolved in 5mL of deuterated chloroform and used at 23 ℃¹The terminal group was measured by an H-NMR apparatus (product name "EX-400" manufactured by Nippon electronics Co., Ltd.) and the ratio of the hydroxyl group terminal to the total terminal number was calculated as OH%.

(5) Color tone (b)^*Value)

Using the aromatic polycarbonates produced in examples and comparative examples, injection molding was carried out on a disk-shaped test plate having a diameter of 5.5cm and a thickness of 3.2mm under conditions of a cylinder temperature of 300 ℃ and a mold temperature of 90 ℃.

The chromaticity of the test plate was measured using a spectrophotometer in accordance with JIS Z8722 as a colorimeter. The color tone was measured by CIELAB method (Commission International de L' Eclairage 1976L) according to JIS Z8729^*a^*b^*Diagram (International Commission on illumination 1976L)^*a^*b^*Graph) is represented by b-value, which is an index of yellowness, in a colorimetric system.

Specifically, in b as a measurement standard^*The test plate was placed on a white board having a value of 1.97, 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, the mixing vessel 7 had a diameter of 3.8m and an internal volume of 80m³Is provided with 2 sections of impeller blades. A piping nozzle having a flange portion with an inner diameter of 400mm for introducing the aromatic hydroxy compound is connected to the upper portion of the mixing tank 7. The independent stand 20 shown in fig. 2 has an inner capacity of 90m³A metering tank 2 and a load cell 3. The independent stand 20 is built on an independent base, and is provided with flexible electric wiring, cables for instruments, and piping. The wind shielding stand (not shown) is arranged outside the independent stand 20The building on the base of the gantry 20 is fabricated independently of each other, and supports such as pipes are attached thereto. The measuring tank 2 is connected with a gas displacement of 150Nm³And/h an exhaust control valve for controlling the internal pressure by discharging the gas in the measuring tank 2.

A steam drain discharge device 21 (a portion enclosed by a dotted line) shown in fig. 3 is provided at a steam outlet of the inner coil provided in the mixing tank 7 and a steam outlet of the outer jacket provided on the outside. The inner capacity is 0.5m³The drain drum 22 of (a) is connected to a steam trap 23 having a treatment capacity of 18 ton/hr arranged in parallel. The pipe diameter of the steam outlet of the inner coil located in the steam drain 21 was 1.5 inches, the pipe diameter of the steam outlet of the outer jacket was 2.5 inches, the pipe diameter of the outlet of the drain drum 22 was 6 inches, the pipe diameter of the pipe from the steam trap 23 to the drain 25 was 6 inches, and the pipe diameter of the pipe from the steam trap 23 to the steam recovery device 24 was 4 inches. The set value (SV value) of the level control (LIC control) of the steam drainage in the drainage drum 22 was 3%. Further, the steam drain discharging device 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 inside the device 21. The vapor outlet of the vapor trap 23 is connected to a vapor recovery device 24 at a pressure of about 0.4MPaG (about 140 ℃).

The accuracy test of the load cell 3 was performed using 50 weights of 20kg and water. A weighing platform scale (weighing accuracy: 0.02% or less) of 1500kg at the maximum was used as the scale for measuring water. It was confirmed that 50 tons of water were added to the measuring tank 2 every 1 ton, and that the error between the indicated value of the load cell 3 and the cumulative value of the water charged was within ± 0.15 mass%. As the load cell, a 3-point type CC21Capacity:36tf (product name, manufactured by Daihu Kabushiki Kaisha) was used. Since the measuring tank 2 is provided on the independent stand 20, the indicated value of the load cell 3 does not change even if wind or external vibration is present.

As the meter 13 for diaryl carbonate, a coriolis type cumulative flowmeter was used. In order to check the accuracy of the diaryl carbonate meter 13, 50 tons of water were stored in the measuring tank 2, and after the diaryl carbonate meter 13 was filled with water, 10 tons of water were extracted at a flow rate at which accuracy was ensured, and it was confirmed that the indicated value of the load cell 3 and the indicated value of the meter 13 were matched. Next, 50 tons of water were filled into the measuring tank 2 through the measuring device 13, and the water was extracted while measuring 1 ton at a time by the scale, and it was confirmed that the cumulative value of the scale matches the value indicated by the load cell 3. The above operation was performed 2 times, and as a result, the accuracy of the meter 13 was within ± 0.15 mass%.

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

DPC maintained at 120 ℃ in a DPC storage tank 10 was heated to 160 ℃ by a preheater 11, and a predetermined amount of DPC was calculated so that the total feed molar ratio of DPC to BPA was 1.17 relative to 22.5 tons of BPA. A predetermined amount of DPC of 94.29 mass% (23.3 tons) of this charge was fed to the mixing tank 7 (large feed).

Next, as a transesterification catalyst, commercially available potassium hydroxide (grade 1 reagent (purity: 85%)) pastilles were added in an amount of about 120 mass ppb in terms of potassium atoms with respect to 22.5 tons of BPA.

The BPA in the measuring tank 2 was replaced with nitrogen, and the entire amount was fed to the mixing tank 7 after the replacement with nitrogen for 0.75 hour. In supplying BPA, the internal pressure of the gauge 2 for an aromatic dihydroxy compound was maintained at 7kPaG and the internal pressure of the mixing tank 7 was maintained at 6kPaG by pressure control (PIC control). Steam of 200 ℃ is supplied to the inner coil and the outer jacket of the mixing tank 7 at a rate of 0.1 to 8 tons/hr, and the liquid temperature in the mixing tank 7 is maintained at 140 to 160 ℃. The linear velocity of the gas in the gas phase part of the mixing tank 7 during the supply of BPA from the metering tank 2 is 0.04m/sec or less. The linear velocity of the gas flowing through the reactor at the termination of the supply was 12m/sec, and the flow time was 3 minutes.

The amount of DPC to be added was calculated in accordance with the desired molar ratio of BPA to DPC charged, with respect to the difference in indicated values of the load cell between before and after BPA supply (actual supply amount) of 22.5 tons, and 1.41 tons of DPC obtained by calculation was supplied to the mixing tank 7 (small supply). Thereafter, the liquid temperature in the mixing tank 7 was raised to 195 ℃. Since the steam drain discharging means 21 shown in fig. 3 was provided, no steam hammering occurred in the inner coil in the mixing tank 7 in the middle of the temperature rise of the liquid temperature of the dissolved mixture to 195 ℃. Further, the steam drain was smoothly discharged.

After the preparation of the dissolved mixture, the dissolved mixture was supplied to an internal capacity of 80m over a period of 0.75 hours³The dissolution mixture tank 12A of (4) is maintained at 195 ℃. Immediately after the dissolution mixture was supplied to the dissolution mixture storage tank 12A, the liquid temperature in the mixing tank 7 was lowered to about 160 ℃, and 94.29 mass% (23.3 tons) of DPC, which was a predetermined amount charged, was supplied again to the mixing tank 7, and the dissolution mixture was prepared in the same manner as described above.

The reaction mixture was kept in the dissolution mixture tank 12A for 3.9 hours, and the reaction mixture having an equilibrium reaction rate of 80% was filtered at a flow rate of 12 tons/hr through 2 polymer filters (not shown, having a pore size of 5 μm on the upstream side and a pore size of 2.5 μm on the downstream side) having different pore sizes and disposed in series between the dissolution mixture tank 12A and the agitation tank type 1 st polymerizer 14. The filtered reaction mixture is heated by a preheater (not shown) and supplied to the stirred tank type 1 st polymerizer 14. The liquid temperature at the outlet of the preheater was 200 ℃.

At the time when the level of the reaction mixture in the dissolution mixture tank 12A is lower than a prescribed value, the supply source of the reaction mixture to the stirred tank type 1 st polymerizer 14 is switched from the dissolution mixture tank 12A to the dissolution mixture tank 12B. The reaction mixture was continuously supplied to the stirred tank type 1 st polymerizer 14 by repeating the operation of alternately switching the supply source dissolved mixture tanks 12A and 12B every 3.9 hours.

The dissolution mixture was supplied from the mixing tank 7 to the dissolution mixture storage tank 12A or 12B, and held for 3.9 hours (immediately before starting the supply to the agitation tank type 1 st polymerizer 14) at 4Nm³Per hr, nitrogen bubbling was performed therein.

The reaction mixture was polymerized while removing the generated PH under reduced pressure with stirring in the stirred tank type 1 st polymerization vessel 14 and the stirred tank type 2 nd polymerization vessel 15 to obtain a prepolymer. At this time, the temperature of the agitation type 1 st polymerizer 14 was 220 ℃ and the pressure was 9.3kPa, and the temperature of the agitation type 2 nd polymerizer 15 was 268 ℃ and the pressure was 2.66 kPa. The liquid level in the stirred tank type 1 st polymerizer 14 was adjusted by LIC control using a gear pump at the bottom, and the amount of the reaction mixture supplied was adjusted by FIC control. The liquid level of the agitation tank type 2 nd polymerizer 15 was adjusted by LIC control using a gear pump at the bottom. The PH produced as a by-product in the stirred tank type 1-polymerization vessel 14, the stirred tank type 2-polymerization vessel 15, the main polymerization vessel 16, the main polymerization vessel 18A and the main polymerization vessel 18B is recovered by a by-product phenol recovery facility and a transfer pump 17 and used as a raw material in the DPC production process (not shown).

The obtained prepolymer was continuously fed to the main polymerization reactor 16 by a gear pump provided in a pipe connected to the bottom of the stirring tank type 2 nd polymerization reactor 15, and further polymerized therein under reduced pressure. The temperature of the main polymerizer 16 was 270 ℃ and the pressure was 600 Paa.

The polymer polymerized by the main polymerizer 16 is continuously supplied to the main polymerizers 18A and 18B, wherein an aromatic polycarbonate having an MI of 22. + -. 0.3g/10min is produced. The amount of the aromatic polycarbonate produced was 6.6 tons per 1 hour. The temperature of the main polymerizers 18A and 18B was 270 ℃ and the pressure was 140. + -. 2 Paa. The production conditions are shown in Table 1. Further, the evaluation results of the properties of the aromatic polycarbonate 1000 hours after the start of the operation and 10000 hours after the start of the operation are shown in Table 1.

< example 2>

An aromatic polycarbonate was produced in the same manner as in example 1, except that a steam vent of the inner coil provided in the mixing tank 7 and a steam vent of the outer jacket provided on the outside were provided with a steam drain discharge facility 21 shown in FIG. 4. The pipe diameter of the steam outlet of the inner coil was 1.5 inches, and among the pipes connected from the steam outlet of the inner coil to the drain drum 22, the pipe diameter of the large-diameter pipe directly connected to the drain drum 22 was 10 inches, the pipe diameter of the steam outlet of the outer jacket was 2.5 inches, the pipe diameter of the outlet of the drain drum 22 was 6 inches, the pipe diameter of the pipe from the steam trap 23 to the drain 25 was 6 inches, and the pipe diameter of the pipe from the steam trap 23 to the steam recovery device 24 was 4 inches. By providing the steam drain discharging means 21 shown in fig. 4, no steam hammer is generated in the inner coil in the mixing tank 7 while the liquid temperature in the mixing tank 7 is raised to 195 ℃. And the discharge of the steam drainage is also smooth. The results are shown in Table 1.

< example 3>

An aromatic polycarbonate was produced in the same manner as in example 2, except that the pipe diameter of the large-diameter pipe directly connected to the drain drum 22 was changed from 10 inches to 3 inches in the pipe connected to the drain drum 22 from the vapor outlet of the inner coil. During the supply of BPA to the mixing tank 7, during the small supply of DPC, and during the temperature increase of the liquid temperature in the mixing tank 7 to 195 ℃, a vapor hammer was generated at the inner coil, but the inner coil and the like were not damaged, and the operation was continued while maintaining this state. The results are shown in Table 1.

< comparative example 1>

An aromatic polycarbonate was produced in the same manner as in example 1, except that the drain drum 22 of the steam drain facility 21 was changed to a 2.5-inch pipe provided with a liquid level meter, and the pipes of the plurality of steam outlets of the inner coil were independently connected to the 2.5-inch pipe. During the small supply of DPC and the process of raising the temperature of the liquid in the mixing tank 7 to 195 ℃, the 2.5-inch pipe provided in place of the drain drum 22 was filled with water, and a steam hammer was vigorously generated in the inner coil provided in the mixing tank 7. The operation was continued in this state, and after 5500 hours, cracks were generated in a part of the inner coil of the mixing tank 7, and thus the supply of steam to the inner coil and the outer jacket of the mixing tank 7 was stopped. Next, after the entire amount of the dissolution mixture in the mixing tank 7 is supplied to the dissolution mixture storage tanks 12A and 12B, the operation of the mixing tank 7 is stopped. The operation was continued while maintaining this state until substantially the entire amounts of the reaction mixture, prepolymer and polymer in the stirred tank type 1 st polymerizer 14 to main polymerizers 18A,18B were discharged, after which the operation of the whole system was stopped. Compared with the polymer obtained up to 5500 hours ago, from the time when the operation of the mixing tank 7 was stopped to the time when the entire system was completedThe polymer obtained during the shutdown was found to have MI fluctuation and color tone deterioration (MI was changed from 22. + -. 0.3 to 23. + -.1, b)^*The value changed from 1.2 to 1.5). The results are shown in Table 1.

< comparative example 2>

An aromatic polycarbonate was produced in the same manner as in example 2, except that the pipe diameter of a large-diameter pipe directly connected to the drain drum 22 was changed from 10 inches to 2.5 inches among pipes connected to the drain drum 22 from the vapor outlet of the inner coil. During the small supply of DPC and during the temperature raising of the liquid temperature in the mixing tank 7 to 195 ℃, a steam hammer is violently generated in the inner coil provided in the mixing tank 7. The operation was continued in this state, and after 6000 hours, cracks were generated in a part of the inner coil of the mixing tank 7, and thus the supply of steam to the inner coil and the outer jacket of the mixing tank 7 was stopped. Next, after the entire amount of the dissolution mixture in the mixing tank 7 is supplied to the dissolution mixture storage tanks 12A and 12B, the operation of the mixing tank 7 is stopped. The operation was continued while maintaining this state until substantially the entire amounts of the reaction mixture, prepolymer and polymer from the agitation tank type 1 st polymerizer 14 to the main polymerizers 18A,18B were discharged, after which the operation of the whole system was stopped. In the polymer obtained from the time point after the operation stop of the mixing tank 7 to the time point when the operation of the whole system was stopped, the MI was varied from 22. + -. 0.3 to 23. + -. 1, and b was deteriorated as compared with the polymer obtained before the time point of 6000 hours (MI was changed from 22. + -. 0.3 to 23. + -. 1, b)^*The value changed from 1.2 to 1.4). The results are shown in Table 1.

[ TABLE 1]

⁽¹⁾The drain drum 22 was changed to a 2.5 inch pipe.

⁽²⁾The pipe diameter of the large-diameter pipe directly connected to the drain drum 22 was changed from 10 inches to 2.5 inches.

[ INDUSTRIAL APPLICABILITY ]

In the case of using the apparatus for producing an aromatic polycarbonate of the present invention, even if a large amount of steam is circulated inside a heating means such as a coil or a jacket provided in a mixing tank for mixing a diaryl carbonate and an aromatic polycarbonate, a hammer of steam is not generated inside the heating means, and thus the breakage of the heating means can be prevented, and the aromatic polycarbonate can be stably produced for a long period of time. Therefore, the apparatus for producing an aromatic polycarbonate of the present invention is industrially useful particularly as an apparatus for industrially producing an aromatic polycarbonate on a large scale.

[ description of symbols ]

1 … bucket conveyor, 2 … metering tank, 3 … load cell, 4 … ball valve, 5 … rotary valve, 6 … flexible pipe, 7 … mixing tank, 8A,8B,8C, 17 … transfer pump, 9 … scrubber, 10 … storage tank, 11 … preheater, 12A,12B … dissolved mixture storage tank, 13 … meter, 14 … agitation tank type 1 st polymerizer, 15 … agitation tank type 2 nd polymerizer, 16,18A,18B … main polymerizer, equipment at the rear stage of 19a … main polymerizer 18A, equipment at the rear stage of 19B … main polymerizer 18B, 20 … independent stand, 21 … steam drain discharge equipment, 22 … drain drum, 23 … steam trap, 24 … steam recovery equipment, 25 … drain.

Claims

1. An apparatus for producing an aromatic polycarbonate, which comprises a mixing tank for reacting an aromatic dihydroxy compound with a diaryl carbonate,

the manufacturing apparatus has at least one heating unit for heating the mixing tank, the heating unit being selected from the group consisting of an inner coil provided in the mixing tank, an outer jacket provided outside the mixing tank, and an outer coil provided outside the mixing tank;

the heating unit uses water vapor as a heating medium and is provided with more than 2 water vapor outlets, and the more than 2 water vapor outlets are respectively and independently connected with the drainage drum so that the steam drainage from the water vapor outlets is continuously drained into the drainage drum;

the drain drum is connected to a drain and a vapor recovery device to allow the vapor drain to be discharged into the drain and/or the vapor recovery device.

2. An apparatus for producing an aromatic polycarbonate, which comprises a mixing tank for reacting an aromatic dihydroxy compound with a diaryl carbonate,

the inner coil uses steam as a heating medium, has more than 2 steam outlets, and a pipe connected with each steam outlet is connected with a drainage drum through a large-diameter pipe so as to continuously discharge steam drainage from the steam outlet into the drainage drum, wherein the pipe diameter of the large-diameter pipe is 2-20 times of the pipe diameter of the pipe connected with the steam outlet;

3. The production apparatus for an aromatic polycarbonate according to claim 1 or 2, further comprising a LIC control device for controlling a discharge amount of water vapor condensate from the drain drum, and/or a vapor trap for selectively discharging the water vapor condensate from the drain drum.