JP2008024807A - Method for producing aromatic polycarbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an aromatic polycarbonate, in which measurement of viscosity of an aromatic polycarbonate in which polymerization is advanced is stably carried out for a long period in production of the aromatic polycarbonate using a melting method. <P>SOLUTION: The method for producing the aromatic polycarbonate comprises using an aromatic dihydroxy compound and a carbonic diester as raw materials and using a plurality of reactors. In the production method, a vibration type inline viscometers are each attached to outlet passage of the reactors and polymer viscosities are measured and temperatures and pressures of reactors or agitating numbers of rotation of an agitators are controlled based on differences from target viscosities. According to the production method, measurement of viscosity of aromatic polycarbonate in which polymerization is in progress can stably be carried out even when production apparatus is operated for a long period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an aromatic polycarbonate using an in-line viscometer.

  Aromatic polycarbonate is excellent in heat resistance, impact resistance, dimensional stability and transparency, and is widely used as an engineering resin in many applications.

  As an industrial production method of an aromatic polycarbonate, an interface method in which an aromatic dihydroxy compound and phosgene are reacted at an interface by introducing phosgene in an alkali aqueous solution of an aromatic dihydroxy compound and a halogen-based organic solvent. A transesterification method (melting method) in which an aromatic dihydroxy compound and a carbonic acid diester are reacted in a molten state is known.

  When producing an aromatic polycarbonate by the transesterification method (melting method), it is necessary to make the degree of polymerization of the aromatic polycarbonate constant because of quality control requirements. For this reason, a production method using a viscometer for operation management There are some reports.

  For example, in order to bring the viscosity measured by the viscometer provided at the final reactor outlet closer to the target viscosity, the temperature and pressure of the reactor are changed in accordance with a program incorporated in advance (see Patent Document 1), Examples include a method of measuring the melt viscosity of polycarbonate with an online viscometer provided after the outlet of the final reactor, and controlling the degree of pressure reduction of the final reactor based on the measured value (see Patent Document 2).

  Further, as a method not using a viscometer, a method for obtaining an empirical formula indicating a quantitative relationship between plant operation information and a polymer fluid in advance and calculating a molecular weight of the polymer fluid being manufactured (see Patent Document 3), etc. Is mentioned.

Japanese Patent No. 3251346 JP 2003-192882 A JP 2004-125447 A

By the way, in the conventional manufacturing method of the polycarbonate provided with the viscometer, the viscosity of the polymer fluid is usually measured by connecting the viscometer to a bypass pipe provided separately from the main pipe (capillary inline viscometer).
However, in the melt polymerization method of aromatic polycarbonate, as the polymerization proceeds, branched polymers are formed by side reactions, and gelled products (micro unmelted products) are likely to be generated. The bypass piping provided with the viscometer is blocked, and it is difficult to stably operate the equipment.

The present invention has been made in view of the above-described problems of conventional techniques.
That is, an object of the present invention is to provide a method for producing an aromatic polycarbonate capable of stably measuring the viscosity of the aromatic polycarbonate even during long-term operation.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, it has been found that the polymer viscosity can be stably measured by directly inserting an in-line viscometer into the flow path of the molten polymer. Completed the invention.

  Thus, according to the present invention, there is provided a method for producing an aromatic polycarbonate using an aromatic dihydroxy compound and a carbonic acid diester as raw materials and using a plurality of reactors, wherein the detection is performed at the outlet flow path of at least one reactor of the plurality of reactors. A viscometer that directly inserts the end is provided to measure the polymer viscosity, and at least one of the reactor temperature, pressure, or stirring speed of the stirrer is controlled based on the difference between the polymer viscosity and the target viscosity. A method for producing an aromatic polycarbonate is provided.

Here, the viscometer is preferably one that reciprocally twists and vibrates the detection end at a high frequency and measures the polymer viscosity,
It is preferable that the liquid contact portion at the detection end of the viscometer is made of a material having corrosion resistance to the by-product monohydroxy compound.
Also, in order to avoid breakage of the detection end of the viscometer due to the flow stress of the polymer due to the circulation of the high viscosity polymer, the detection end of the viscometer corresponds to the flow direction of the polymer in the outlet channel of the reactor. It is inserted into the flow path with the same direction or with an inclination within 75 ° from the same direction, or into the flow path with an inclination within 15 ° from the direction opposite to or in the direction of polymer flow in the outlet flow path of the reactor. It is preferable to install so as to be inserted.
Here, the inclination formed by the polymer flow direction in the pipe and the detection end of the viscometer is formed by the flow direction of the polymer in the pipe near the detection end of the viscometer and the insertion direction of the detection end of the viscometer. An angle (0 ° or more and less than 90 °). Even when the flow direction and the insertion direction of the detection end face each other, the angle between the two is defined similarly.
Moreover, when attaching, it is preferable to construct so as to eliminate the dead space in order to prevent the molten polymer from staying at the attachment location and causing burns and foreign matters.

  According to the present invention, even when the production apparatus is operated for a long period of time, it is possible to stably measure the viscosity of the aromatic polycarbonate whose polymerization is in progress.

  The best mode for carrying out the present invention (hereinafter, an embodiment of the present invention) will be described in detail below. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention. The drawings used are for explaining the present embodiment and do not represent the actual size.

(Polycarbonate resin)
In the present invention, the polycarbonate resin is produced by melt polycondensation based on an ester exchange reaction between an aromatic dihydroxy compound and a carbonic acid diester.
Hereinafter, a method for producing a polycarbonate resin by using an aromatic dihydroxy compound and a carbonic acid diester as raw materials and continuously performing a melt polycondensation reaction in the presence of a transesterification catalyst will be described.

(Aromatic dihydroxy compounds)
Examples of the aromatic dihydroxy compound used in the present embodiment include compounds represented by the following general formula (1).

Here, in the general formula (1), A is a single bond or an optionally substituted linear, branched or cyclic divalent hydrocarbon group having 1 to 10 carbon atoms, or -O-, A divalent group represented by —S—, —CO— or —SO ₂ —. X and Y are a halogen atom or a C1-C6 hydrocarbon group. p and q are integers of 0 or 1. X and Y and p and q may be the same or different from each other.

Specific examples of the aromatic dihydroxy compound include, for example, bis (4-hydroxydiphenyl) methane, 2,2-bis (4-hydroxyphenyl) propane, and 2,2-bis (4-hydroxy-3-methylphenyl) propane. 2,2-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3) , 5-dibromophenyl) propane, 4,4-bis (4-hydroxyphenyl) heptane, bisphenols such as 1,1-bis (4-hydroxyphenyl) cyclohexane; 4,4′-dihydroxybiphenyl, 3,3 ′ , 5,5'-tetramethyl-4,4'-dihydroxybiphenyl and the like; bis (4-hydroxyphenyl) sulfo Bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) ketone and the like.
Among these, 2,2-bis (4-hydroxyphenyl) propane (“bisphenol A”, hereinafter sometimes abbreviated as BPA) is preferable. These aromatic dihydroxy compounds can be used alone or in admixture of two or more.

(Carbonated diester)
Examples of the carbonic acid diester used in the present embodiment include compounds represented by the following general formula (2).

Here, in general formula (2), A 'is a C1-C10 linear, branched or cyclic monovalent hydrocarbon group which may be substituted. Two A ′ may be the same or different from each other.
In addition, as a substituent on A ′, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group, Examples thereof include a nitro group.

Specific examples of the carbonic acid diester include substituted diphenyl carbonates such as diphenyl carbonate and ditolyl carbonate, and dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-t-butyl carbonate.
Among these, diphenyl carbonate (hereinafter sometimes abbreviated as DPC) and substituted diphenyl carbonate are preferable. These carbonic acid diesters can be used alone or in admixture of two or more.

Moreover, said carbonic acid diester may substitute the quantity of the 50 mol% or less preferably 30 mol% or less with the dicarboxylic acid or dicarboxylic acid ester preferably.
Typical dicarboxylic acids or dicarboxylic acid esters include terephthalic acid, isophthalic acid, diphenyl terephthalate, diphenyl isophthalate, and the like. When substituted with such a dicarboxylic acid or dicarboxylic acid ester, a polyester carbonate is obtained.

These carbonic acid diesters (including the above-mentioned substituted dicarboxylic acid or dicarboxylic acid ester, the same shall apply hereinafter) are used in excess relative to the dihydroxy compound.
That is, it is usually used in a molar ratio of carbonic acid diester 1.01-1.30, preferably 1.02-1.20, relative to the aromatic dihydroxy compound. When the molar ratio is smaller than 1.01, the terminal OH group of the obtained polycarbonate resin increases, and the thermal stability of the resin tends to deteriorate. In addition, when the molar ratio is larger than 1.30, the transesterification reaction rate decreases, and it becomes difficult to produce a polycarbonate resin having a desired molecular weight, and the residual amount of carbonic acid diester in the resin increases. This is not preferable because it may cause odor of the molded product or the molded product.

(Transesterification catalyst)
The transesterification catalyst used in the present embodiment is not particularly limited, and is usually a catalyst used when producing polycarbonate by the transesterification method. In general, examples include basic compounds such as alkali metal compounds, beryllium or magnesium compounds, alkaline earth metal compounds, basic boron compounds, basic phosphorus compounds, basic ammonium compounds, and amine compounds.
Among these transesterification catalysts, an alkali metal compound is practically desirable. These transesterification catalysts may be used alone or in combination of two or more.
The transesterification catalyst is generally used in an amount of 1 × 10 ⁻⁹ to 1 × 10 ⁻¹ mol, preferably 1 × 10 ⁻⁷ to 1 × 10 ⁻² mol, relative to 1 mol of the aromatic dihydroxy compound. It is done.

Examples of the alkali metal compound include inorganic alkali metal compounds such as alkali metal hydroxides, carbonates and hydrogencarbonate compounds; organic alkali metal compounds such as salts with alkali metal alcohols, phenols and organic carboxylic acids. It is done. Here, examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium.
Among these alkali metal compounds, cesium compounds are preferable, and cesium carbonate, cesium hydrogen carbonate, and cesium hydroxide are particularly preferable.

  Examples of beryllium or magnesium compounds and alkaline earth metal compounds include inorganic alkaline earth metal compounds such as beryllium, magnesium, hydroxides and carbonates of alkaline earth metals; alcohols of these metals, phenols, organic And salts with carboxylic acids. Here, examples of the alkaline earth metal include calcium, strontium, and barium.

  Examples of basic boron compounds include sodium salts, potassium salts, lithium salts, calcium salts, magnesium salts, barium salts, strontium salts, and the like of boron compounds. Here, as the boron compound, for example, tetramethylboron, tetraethylboron, tetrapropylboron, tetrabutylboron, trimethylethylboron, trimethylbenzylboron, trimethylphenylboron, triethylmethylboron, triethylbenzylboron, triethylphenylboron, tributyl Examples include benzylboron, tributylphenylboron, tetraphenylboron, benzyltriphenylboron, methyltriphenylboron, and butyltriphenylboron.

  Examples of the basic phosphorus compound include trivalent phosphine compounds such as triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, and tributylphosphine, or derivatives thereof. And quaternary phosphonium salts.

  Examples of the basic ammonium compound include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylbenzylammonium hydroxide, trimethylphenylammonium hydroxide, Triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide, triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide, tributylphenylammonium hydroxide, tetraphenylammonium hydroxide, benzyltriphenylammonium hydroxide, methyltol Phenyl ammonium hydroxide, butyltriphenyl ammonium hydroxide, and the like.

  Examples of the amine compound include 4-aminopyridine, 2-aminopyridine, N, N-dimethyl-4-aminopyridine, 4-diethylaminopyridine, 2-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine, 2 -Dimethylaminoimidazole, 2-methoxyimidazole, imidazole, 2-mercaptoimidazole, 2-methylimidazole, aminoquinoline and the like.

(Method for producing aromatic polycarbonate)
Next, the manufacturing method of an aromatic polycarbonate is demonstrated.
For the production of aromatic polycarbonate, a mixture containing an aromatic dihydroxy compound and a carbonic acid diester as raw materials is prepared (primary process), and a mixture of these compounds is reacted in a molten state in the presence of a transesterification reaction catalyst. The polycondensation reaction is performed in a multistage manner using a vessel (polycondensation step). The reaction system may be any of a batch system, a continuous system, or a combination of a batch system and a continuous system. In general, a plurality of vertical reactors and / or at least one horizontal reactor is used as the reactor. Usually, these reactors are installed in series and processed continuously.
After the polycondensation step, the reaction is stopped and the unreacted raw materials and reaction by-products in the reaction solution are devolatilized and removed, the step of adding a heat stabilizer, release agent, colorant, etc., polycarbonate resin You may add suitably the process etc. which form in the diameter pellet.
Next, each process of the manufacturing method will be described.

(Primary process)
The aromatic dihydroxy compound and carbonic acid diester used as the raw material for the aromatic polycarbonate are usually used in a batch, semi-batch or continuous stirring tank type apparatus in an atmosphere of an inert gas such as nitrogen or argon. Prepared as a molten mixture. For example, when bisphenol A is used as the aromatic dihydroxy compound and diphenyl carbonate is used as the carbonic acid diester, the temperature of the melt mixing is usually selected from the range of 120 ° C to 180 ° C, preferably 125 ° C to 160 ° C.
At this time, the mixing ratio of the aromatic dihydroxy compound and the carbonic acid diester is adjusted so that the carbonic acid diester becomes excessive. The carbonic acid diester is usually 1.01 mol to 1.30 mol with respect to 1 mol of the aromatic dihydroxy compound. , Preferably adjusted to a ratio of 1.02 mol to 1.20 mol.

(Polycondensation process)
The polycondensation by the transesterification reaction between the aromatic dihydroxy compound and the carbonic acid diester is usually carried out continuously in a multistage system of two or more stages, preferably 3 to 7 stages.
Specific reaction conditions are temperature: 150 ° C. to 320 ° C., pressure: normal pressure to 0.01 Torr (1.3 Pa), and average residence time: 5 minutes to 150 minutes.
In each reactor when the polycondensation process is performed in multiple stages, in order to more effectively discharge the by-product phenol with the progress of the polycondensation reaction, the reaction conditions are usually higher and higher in steps. Set to vacuum. In order to prevent quality deterioration such as hue of the obtained polycarbonate resin, it is preferable to set a low temperature and a short residence time as much as possible.

When the polycondensation step is performed in a multistage manner, usually, a plurality of vertical reactors and / or at least one horizontal reactor following the same are provided to increase the average molecular weight of the polycarbonate resin. Usually 3 to 6 reactors, preferably 4 to 5 reactors are installed.
Here, as a reactor, for example, a stirred tank reactor, a thin film reactor, a centrifugal thin film evaporation reactor, a surface renewal type biaxial kneading reactor, a biaxial horizontal type stirring reactor, a wet wall reactor, a free reactor A perforated plate reactor that polymerizes while dropping, a perforated plate reactor with wire that polymerizes while dropping along a wire, and the like are used.

  The types of stirring blades in the vertical reactor include, for example, turbine blades, paddle blades, fiddler blades, anchor blades, full zone blades (manufactured by Shinko Pantech Co., Ltd.), Sun Meller blades (manufactured by Mitsubishi Heavy Industries, Ltd.), Max. Examples thereof include blend blades (manufactured by Sumitomo Heavy Industries, Ltd.), helical ribbon blades, and twisted lattice blades (manufactured by Hitachi, Ltd.).

  Moreover, a horizontal reactor means that the rotating shaft of a stirring blade is a horizontal type (horizontal direction). As a stirring blade of a horizontal reactor, for example, a single-shaft stirring blade such as a disk type or a paddle type, HVR, SCR, N-SCR (manufactured by Mitsubishi Heavy Industries, Ltd.), Violac (Sumitomo Heavy Industries, Ltd.) Or a biaxial stirring blade such as a spectacle blade or a lattice blade (manufactured by Hitachi, Ltd.).

In addition, the transesterification catalyst used for the polycondensation of the aromatic dihydroxy compound and the carbonic acid diester is usually prepared in advance as an aqueous solution. The concentration of the catalyst aqueous solution is not particularly limited, and is adjusted to an arbitrary concentration according to the solubility of the catalyst in water. Moreover, it can replace with water and other organic solvents, such as acetone, alcohol, toluene, and phenol, can also be used.
The water used for dissolving the catalyst is not particularly limited as long as the kind and concentration of impurities contained are constant, but usually distilled water, deionized water, and the like are preferably used.

(Manufacturing equipment)
Next, an example of a method for producing an aromatic polycarbonate to which the exemplary embodiment is applied will be specifically described with reference to the drawings.
FIG. 1 is a diagram showing an example of an apparatus for producing an aromatic polycarbonate. In the production apparatus shown in FIG. 1, the aromatic polycarbonate is prepared by preparing a raw material aromatic dihydroxy compound and a carbonic acid diester, and a polycondensation reaction of these raw materials in a molten state using a plurality of reactors. It is manufactured through processes.
Thereafter, the step of stopping the reaction and devolatilizing and removing unreacted raw materials and reaction byproducts in the polymerization reaction solution (not shown), and the step of adding a thermal stabilizer, a release agent, a colorant and the like (not shown) ), A pellet of polycarbonate resin is formed through a step (not shown) of forming an aromatic polycarbonate into pellets of a predetermined particle size.

In the raw material process, a first raw material mixing tank 2a and a second raw material mixing tank 2b connected in series, and a raw material supply pump 4a for supplying the prepared raw material to the polycondensation process are provided. For example, anchor-type stirring blades 3a and 3b are provided in the first raw material mixing tank 2a and the second raw material mixing tank 2b, respectively.
The first raw material mixing tank 2a is supplied with diphenyl carbonate (hereinafter referred to as DPC) in a molten state from the DPC supply port 1a-1 in a molten state, and from the BPA supply port 1b. Bisphenol A which is an aromatic dihydroxy compound (hereinafter sometimes referred to as BPA) is supplied in a powder state, and bisphenol A is dissolved in molten diphenyl carbonate.

  Next, in the polycondensation step, the first vertical reactor 6a, the second vertical reactor 6b and the third vertical reactor 6c connected in series, and the subsequent stage of the third vertical reactor 6c are connected in series. A connected fourth horizontal reactor 9a is provided. The first vertical reactor 6a, the second vertical reactor 6b, and the third vertical reactor 6c are provided with max blend blades 7a, 7b, 7c, respectively. The fourth horizontal reactor 9a is provided with a lattice blade 10a.

  The four reactors are equipped with distilling tubes 8a, 8b, 8c, and 8d for discharging by-products generated by the polycondensation reaction, respectively. The distillation pipes 8a, 8b, 8c and 8d are connected to the condensers 81a, 81b, 81c and 81d, respectively, and the respective reactors are kept in a predetermined reduced pressure state by the decompression devices 82a, 82b, 82c and 82d. Be drunk.

  Furthermore, in the present embodiment, a vibration type inline viscometer 20 is installed in the outlet channel 11 of the fourth horizontal reactor 9a so that the detection end (sensor unit) is directly inserted into the outlet channel 11. The polymer viscosity of the aromatic polycarbonate in a molten state fed from the bottom of the fourth horizontal reactor 9a is measured.

  Here, the vibration type in-line viscometer applies high-frequency reciprocal torsional vibration to the detection end (sensor unit) protruding into the polymer fluid, and uses the resonance characteristics that change with the viscosity change of the polymer fluid to It is a viscometer that derives the loss and derives the viscosity value. As such a vibration type in-line viscometer, for example, the ML series Inc. XL series etc. are mentioned.

In the polycarbonate resin manufacturing apparatus shown in FIG. 1, a DPC melt prepared at a predetermined temperature in a nitrogen gas atmosphere and a BPA powder measured in a nitrogen gas atmosphere are respectively connected to a DPC supply port 1a-1 and a BPA. It is continuously supplied from the supply port 1b to the first raw material mixing tank 2a. When the liquid level of the first raw material mixing tank 2a exceeds the same height as the highest position in the transfer pipe, the raw material mixture is transferred to the second raw material mixing tank 2b.
Next, the raw material mixture is continuously supplied to the first vertical reactor 6a via the raw material supply pump 4a. As the catalyst, an aqueous cesium carbonate solution is continuously supplied from the catalyst supply port 5a in the middle of the transfer pipe of the raw material mixture.

  In the first vertical reactor 6a, under a nitrogen atmosphere, for example, a temperature of 220 ° C., a pressure of 13.33 kPa (100 Torr), the rotation speed of the Max Blend blade 7a is maintained at 160 rpm, and by-produced phenol is removed from the distillation pipe 8a. The polycondensation reaction is carried out while keeping the liquid level constant so that the average residence time is 60 minutes while distilling. Next, the polymerization reaction liquid discharged from the first vertical reactor 6a is continuously continuously supplied to the second vertical reactor 6b, the third vertical reactor 6c, and the fourth horizontal reactor 9a. The condensation reaction proceeds. The reaction conditions in each reactor are set so as to become high temperature, high vacuum, and low stirring speed as the polycondensation reaction proceeds. During the polycondensation reaction, the liquid surface level is controlled so that the average residence time in each reactor is, for example, about 60 minutes. In each reactor, by-produced phenol is added to the distillation tubes 8b, 8c, Distilled from 8d.

  In the present embodiment, by-products such as phenol are continuously liquefied and recovered from the condensers 81a and 81b attached to the first vertical reactor 6a and the second vertical reactor 6b, respectively. The Further, condensers 81c and 81d attached to the third vertical reactor 6c and the fourth horizontal reactor 9a are respectively provided with cold traps (not shown) so that by-products are continuously condensed and solidified and recovered. Is done.

Next, in the present embodiment, the polymer viscosity of the aromatic polycarbonate is measured by the vibration type in-line viscometer 20 in which the detection end (sensor unit) is directly inserted into the outlet channel 11 of the fourth horizontal reactor 9a. . Then, the measured value is transferred to a control device (not shown), and the temperature and pressure of the fourth horizontal reactor 9a and the stirring rotation speed of the lattice blade 10a are controlled based on the difference from the preset target viscosity.
As a specific control method, for example, when the measured value is lower than the target viscosity, in order to promote the polycondensation reaction, the temperature is increased, the pressure is decreased, and the stirring rotational speed is further increased. On the other hand, when the measured value exceeds the target viscosity, the above reverse adjustment may be performed.

Next, a method for attaching the vibration type inline viscometer will be described.
FIG. 2 is a diagram for explaining an installation example of a vibration type inline viscometer.
FIG. 2 (a) shows that the vibration type inline viscometer 20a is fixed to the outlet channel 11 of the reactor by bolts and nuts via the flange 22, and the detection end (sensor part) 21a is the same as the polymer flow direction. It is inserted directly with an inclination within 75 ° from the direction.
On the other hand, in FIG. 2B, the vibration-type in-line viscometer 20b is fixed to the bent portion of the outlet flow path 11 of the reactor via a flange 22 with bolts and nuts, and the detection end (sensor portion) 21b is a polymer. It is inserted so that it may oppose with respect to the flow direction.
As described above, the detection end is installed so as to be inserted at the same direction as the flow direction of the polymer fluid or at an inclination within 75 ° from the same direction, or at an inclination within 15 ° from the direction opposite to or from the opposite direction. Thus, the stress due to the polymer flow to the detection end (sensor part) can be reduced, and troubles such as breakage can be prevented.
In addition, by making the upper flange a stamped lid structure, it is possible to eliminate the dead space at the location where the outlet channel 11 and the viscometer are attached, and it is possible to prevent the occurrence of burns and foreign matters due to polymer retention in this portion. preferable.

In addition, it is preferable that the liquid-contact part of a vibration type in-line viscometer is comprised by the material which has corrosion resistance with respect to the monohydroxy compound byproduced, or is coat | covered. For example, SUS304, SUS304L, SUS316, SUS316L, or the like is preferably used as the material. Further, the surface polishing is preferable because elution of the material is suppressed and deterioration of the polymer color tone can be prevented.
Examples of the method for coating the surface of the wetted part include a method of performing durable resin coating.

EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited by these Examples, unless the summary is exceeded.
In addition, the viscosity average molecular weight (Mv) of the obtained aromatic polycarbonate was performed by the following method.

[Measurement of viscosity average molecular weight (Mv)]
Using an Ubbelohde viscometer, the intrinsic viscosity [η] at 20 ° C. in methylene chloride of an aromatic polycarbonate (sample) was measured, and the viscosity average molecular weight (Mv) was determined from the following formulas (1) and (2). .

(In formula (1), η _sp is the specific viscosity of a methylene chloride solution of polycarbonate resin measured at 20 ° C., and C is the concentration of this methylene chloride solution. (Use 6g / dl.)

(Example 1)
A melt prepared by mixing and preparing diphenyl carbonate and bisphenol A at a constant molar ratio (DPC / BPA = 1.040) under a nitrogen gas atmosphere at a flow rate of 88.7 kg / hour through a raw material introduction pipe, It was continuously fed into a 100 L first vertical reactor controlled at 220 ° C. and 1.33 × 10 ⁴ Pa, and provided in the polymer discharge line at the bottom of the reactor so that the average residence time was 60 minutes. The liquid level was kept constant while controlling the valve opening.
At the same time as the supply of the mixture was started, a 1 wt% aqueous cesium carbonate solution was continuously supplied as a catalyst at a ratio of 1.0 µmol per 1 mol of bisphenol A.

  The reaction liquid discharged from the bottom of the reactor is continuously continuously supplied to the second vertical reactor, the third vertical reactor (capacity 100 L), and the fourth horizontal reactor (capacity 150 L). Aromatic polycarbonate was extracted from the polymer outlet at the bottom of the vessel.

Next, in the molten state, this aromatic polycarbonate was fed into a twin-screw extruder, and butyl p-toluenesulfonate (4 times molar amount relative to cesium carbonate used as a catalyst) was continuously added. The mixture was kneaded and formed into a strand shape through a die and cut with a cutter to obtain a pellet.
The reaction conditions in the second vertical reactor to the third vertical reactor are respectively the second vertical reactor (240 ° C., 2.00 × 10 ³ Pa, 75 rpm) and the third vertical reactor (270 ° C.). 67 Pa, 75 rpm). The reaction conditions of the fourth horizontal reactor were automatically controlled by a vibrating in-line viscometer installed in a pipe corresponding to the outlet channel so as to keep the viscosity of the produced aromatic polycarbonate constant.

The target value of the viscosity average molecular weight of the aromatic polycarbonate was Mv = 26000.
Further, according to the target viscosity value, the stirring rotation speed of the fourth horizontal reactor was fixed at 5 rpm, the temperature was automatically controlled within a range of 285 ± 2 ° C., and the pressure was 70 ± 10 Pa.
During the reaction, the liquid surface level is controlled so that the average residence time of the second vertical reactor to the fourth horizontal reactor is 60 minutes, and at the same time, by-product phenol is distilled off. It was.

  The operation was continued for 2 months under the above conditions. The variation of the viscosity average molecular weight of the produced aromatic polycarbonate was in the range of Mv = 26000 ± 250.

(Example 2)
An aromatic polycarbonate was produced in the same manner as in Example 1 except that the stirring rotation speed of the fourth horizontal reactor was controlled in the range of 3 rpm to 5 rpm.
The operation was continued for 2 months under the above conditions. The variation of the viscosity average molecular weight of the produced aromatic polycarbonate was in the range of Mv = 26000 ± 200.

(Comparative Example 1)
In Example 1, a vibration type inline viscometer was not installed, a bypass pipe was provided in the outlet channel of the fourth horizontal reactor, and a capillary viscometer was installed in the bypass pipe. Thus, an aromatic polycarbonate was produced. Although the operation was scheduled to continue for two months, the viscometer capillary tube gradually closed, and the viscometer derived value was deviated from the Mv of the aromatic polycarbonate produced by the flow rate fluctuation, and the operation was interrupted at 1.7 months.

  As mentioned above, according to the manufacturing method of the aromatic polycarbonate explained in full detail in this Embodiment, even if a manufacturing apparatus is drive | operated for a long period of time, the viscosity measurement of the aromatic polycarbonate which superposition | polymerization advanced can be performed stably. As a result, a stable operation of the production apparatus can be realized, and an excellent effect that an aromatic polycarbonate resin having a certain quality can be produced is achieved.

It is a figure which shows an example of the manufacturing apparatus of an aromatic polycarbonate. It is a figure explaining the example of installation of a vibration type in-line viscometer. FIG. 2 (a) is an example in which the detection end is attached with an inclination within 75 ° from the polymer flow direction. FIG. 2B is an example in which the detection end is attached to the flow path bending portion in the polymer flow direction using a flange of the seal lid structure.

Explanation of symbols

2a ... 1st raw material mixing tank, 2b ... 2nd raw material mixing tank, 3a, 3b ... Anchor type stirring blade, 4a ... Raw material supply pump, 5a ... Catalyst supply port, 6a ... 1st vertical reactor, 6b ... 2nd Vertical reactor, 6c ... 3rd vertical reactor, 7a, 7b, 7c ... Max blend blade, 8a, 8b, 8c, 8d ... Distillation tube, 9a ... Fourth horizontal reactor, 10a ... Grid blade, 11 ... exit flow path, 20, 20a, 20b ... vibrating in-line viscometer, 21a, 21b ... detection end (sensor part), 23 ... dead space, 24 ... structure without dead space, 81a, 81b, 81c, 81d ... Condenser, 82a, 82b, 82c, 82d ... Connection piping to decompression device

Claims (5)

A method for producing an aromatic polycarbonate using an aromatic dihydroxy compound and a carbonic acid diester as raw materials, and using a plurality of reactors,
Measuring a polymer viscosity by providing a viscometer that directly inserts a detection end into an outlet channel of at least one of the plurality of reactors;
A method for producing an aromatic polycarbonate, comprising controlling at least one of a temperature and a pressure of the reactor or a stirring rotational speed of a stirrer based on a difference between the polymer viscosity and a target viscosity.   The method for producing an aromatic polycarbonate according to claim 1, wherein the viscometer measures the polymer viscosity by causing the detection end to reciprocate torsionally vibrate at a high frequency.   3. The method for producing an aromatic polycarbonate according to claim 1, wherein the viscometer comprises a liquid contact portion at the detection end made of a material having corrosion resistance to the by-product monohydroxy compound.   The detection end of the viscometer is inserted in the flow path at the same direction as the polymer flow direction in the outlet flow path of the reactor or with an inclination within 75 ° from the same direction, or in the outlet flow path of the reactor The method for producing an aromatic polycarbonate according to any one of claims 1 to 3, wherein the aromatic polycarbonate is inserted into the flow path in a direction opposite to the flow direction of the polymer or an inclination within 15 ° from the opposite direction. .   The method for producing an aromatic polycarbonate according to claim 4, wherein the viscometer is attached to a bent portion of an outlet flow path of the reactor.

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