JP5245272B2 - Method for producing aromatic polycarbonate - Google Patents

Description

  The present invention relates to a method for producing an aromatic polycarbonate by a transesterification reaction, and more particularly to a method for producing an aromatic polycarbonate in which the exchange frequency of a filter for filtering a raw material is reduced.

  In recent years, polycarbonate resins have been widely used in OA parts, automobile parts, building materials, and the like as engineering plastics having excellent mechanical properties such as impact resistance, heat resistance, and transparency. In particular, taking advantage of properties such as impact resistance and transparency, it is widely used as an optical material in applications such as optical lenses, recording disks, sheets, and bottles.

As a method for producing the aromatic polycarbonate, a so-called interface method using an aromatic diol such as a bisphenol compound and phosgene as raw materials has been industrialized.
However, this method has problems such as the use of phosgene, which is harmful to the human body, the need for a solvent such as dichloromethane, which has a high environmental load, and the incorporation of a large amount of by-product sodium chloride into the polymer. It has been pointed out.
On the other hand, a method for obtaining an aromatic polycarbonate while transesterifying an aromatic diol and a carbonic acid diester in a molten state and removing low-molecular weight substances such as phenol as a by-product from the system has also been known as a so-called melting method for a long time. . The melting method has an advantage that an aromatic polycarbonate can be produced without the above-mentioned problems due to the interface method.

By the way, the aromatic polycarbonate is used as an optical material for an optical lens and a recording disk as described above. In particular, the contamination of foreign matters becomes a fatal problem in these applications.
As a method for reducing foreign matter in an aromatic polycarbonate, a method is disclosed in which an aromatic dihydroxy compound and a carbonic acid diester obtained by filtering and removing foreign matter using a filter are used as raw materials (see, for example, Patent Document 1).
Further, a method is disclosed in which an aromatic dihydroxy compound and a carbonic acid diester as raw materials are mixed and melted and then filtered using a filter that has been subjected to a specific treatment (see, for example, Patent Document 2).
Or the method etc. which prescribe | regulate the flow volume of the raw material liquid processed with a filter, and the filtration area of a filter are disclosed (for example, refer patent document 3).

JP-A-5-239334 JP 2003-048975 A Japanese Patent Laid-Open No. 2002-256071

However, since the filter for filtering the raw material gradually closes with time, the filter is usually replaced with a new filter or a washed filter when the differential pressure before and after the filter reaches a certain level.
However, since the melting point of aromatic dihydroxy compounds, carbonic acid diesters, and mixtures thereof used as raw materials for melt-processed aromatic polycarbonates is significantly higher than room temperature, there is a problem that the replacement work of the raw material filter involves a great risk. Although there is a method of increasing the filtration area per unit flow rate in order to reduce the filter replacement frequency, there is a problem that the apparatus becomes excessive and the risk of filter replacement work is further increased.
The problem as described above becomes more serious when a raw material contains a transesterification catalyst due to a small amount of the precipitation catalyst, and thus a drastic solution has been demanded.

The present invention has been made in view of the above-described problems of conventional techniques.
In other words, an object of the present invention is to provide a method for producing an aromatic polycarbonate capable of reducing the replacement frequency of a filter for filtering a raw material.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, it has been found that if a plurality of filters for filtering the raw material are used, the replacement frequency of the filter can be reduced, and the present invention has been completed based on such knowledge.

  Thus, according to the present invention, in the method for producing an aromatic polycarbonate using an aromatic dihydroxy compound and a carbonic acid diester as raw materials, the raw material in a molten state is filtered using a plurality of filters arranged in series, and then to the reactor. A method for producing an aromatic polycarbonate is provided.

Here, the raw material is preferably a mixture of an aromatic dihydroxy compound and a carbonic acid diester, and it is preferable that the raw material further contains a transesterification catalyst.
Further, in the filter, when the opening on the upstream side is A μm and the opening on the downstream side is B μm, in at least one combination, A is preferably larger than B (A> B), More preferably, A is 8 or more on the most upstream side, and B is 2 or less on the most downstream side.
And it is preferable that there are at least three filters, and at least one of the filters is preferably a pleated type.
On the other hand, the flow rate of at least one filter surface of the raw material filter in the molten state is preferably 1 m / h to 20 m / h, and the flow rate of the raw material filter in the molten state is (1) the filter If the mesh opening is less than 5 μm, the condition is 1 m / h to 5 m / h, and (2) if the filter opening is 5 μm or more, the condition is 5 m / h to 20 m / h. More preferably.
Furthermore, it is preferable that a static mixer is further arranged between the raw material preparation tank and the reactor, and the raw materials are preferably mixed using the static mixer, and the transesterification catalyst is placed in the raw material between the raw material preparation tank and the reactor. It is preferable to add to.

  ADVANTAGE OF THE INVENTION According to this invention, in manufacture of an aromatic polycarbonate, the replacement frequency of the filter which filters a raw material can be reduced.

  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 hydrocarbon group having 1 to 6 carbon atoms. p and q are integers of 0-2. 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 the general formula (2), A ′ is an optionally substituted linear, branched or cyclic monovalent hydrocarbon group having 1 to 10 carbon atoms. 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, and an ester group Amide group, nitro group and the like.

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, the molar ratio of the carbonic acid diester to the aromatic dihydroxy compound is preferably 1.01 or more, particularly preferably 1.02 or more, preferably 1.30 or less, particularly preferably 1.20 or less. . 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 or an alkaline earth metal compound has a great effect in terms of reducing the replacement frequency of a filter that filters the target raw material of the present embodiment. These transesterification catalysts may be used alone or in combination of two or more.
The amount of the transesterification catalyst used is usually preferably 1 × 10 ⁻⁹ mol or more, particularly preferably 1 × 10 ⁻⁷ mol or more, and more preferably 1 × 10 ^{−1 with} respect to 1 mol of the aromatic dihydroxy compound. It is used in a range of not more than mol, particularly preferably not more than 1 × 10 ⁻² mol.

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, methyltriphenylammonium hydroxide Sid, butyl triphenyl ammonium hydroxide, and the like.

  Examples of amine compounds 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, but a continuous system is preferable from the viewpoint of productivity and quality stability. In the case of a continuous type, the reactor is generally composed of a plurality of reactors arranged in series, and preferably, a plurality of vertical reactors and then at least one horizontal reactor are used.
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 melt mixing temperature is preferably 120 ° C. or higher, particularly preferably 125 ° C. or higher, and more preferably 180 ° C. or lower, particularly preferably Is selected from a range of 160 ° C. or lower.
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, and the ratio of the carbonic acid diester to the 1 mol of the aromatic dihydroxy compound is preferably 1.01 mol or more. In particular, the amount is adjusted to 1.02 mol or more, preferably 1.30 mol or less, particularly preferably 1.20 mol or less.

(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 per stage: 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 carried out in a multistage system, it is preferable to increase the average molecular weight of the polycarbonate resin by providing a plurality of vertical reactors and / or at least one reactor excellent in thin film evaporation performance following this. Let Usually 3 to 6 reactors, preferably 4 to 5 reactors are installed.
Here, as a reactor having excellent thin film evaporation performance, for example, a thin film reactor, a centrifugal thin film evaporation reactor, a surface renewable biaxial kneading reactor, a biaxial horizontal stirring reactor, a wet wall reactor, a free 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.

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 device)
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 reaction is stopped and the unreacted raw materials and reaction byproducts in the polymerization reaction solution are devolatilized and removed, the step of adding a heat stabilizer, a release agent, a colorant, etc., the aromatic polycarbonate having a predetermined particle size The pellet of polycarbonate resin is formed through the step of forming the pellet.

In the raw material process, a first raw material preparation tank 2a and a second raw material preparation 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 preparation tank 2a and the second raw material preparation tank 2b, respectively.
The first raw material preparation 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.

In the apparatus for producing an aromatic polycarbonate resin 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 supplied to a DPC supply port 1a-1. And the BPA supply port 1b are continuously supplied to the first raw material preparation tank 2a. When the liquid level of the first raw material preparation 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 preparation tank 2b.
Next, the raw material mixture is continuously supplied to the first vertical reactor 6a via the raw material supply pump 4a. The raw material mixture melted at this time passes through the filter unit 20 and is filtered. 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.
The filter unit 20 will be described in detail later.

  In the first vertical reactor 6a, in a nitrogen atmosphere, for example, the temperature is 220 ° C., the pressure is 13.33 kPa (100 Torr), the rotation speed of the stirring blade 7a is maintained at 160 rpm, and the by-produced phenol is distilled 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 to 120 minutes. 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 generally 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.

Next, the filter unit 20 will be described in detail.
FIG. 2 is a diagram illustrating an example of the configuration of the filter unit 20.
As shown in FIG. 2, the filter unit 20 includes three filters 21, 22, and 23 connected in series.
Here, when the aperture on the upstream side of the filter is A μm and the aperture on the downstream side is B μm, A is preferably larger than B (A> B) in at least one combination. When this condition is satisfied, the filter is more difficult to block, and the frequency of filter replacement can be reduced.
A and B are preferably 8 or more, more preferably 10 or more on the most upstream side, and B is preferably 2 or less, more preferably 1 or less on the most downstream side. When A and B are excessively out of this range, there is a tendency that the removal of foreign matters becomes insufficient and the filter is likely to be clogged.

  Further, any type of filter can be used, and the filter medium constituting the filter may be any of metal wind, laminated metal mesh, metal nonwoven fabric, porous metal plate, etc., but from the viewpoint of filtration accuracy, a laminated metal mesh or A metal nonwoven fabric is preferable, and among these, a type in which a metal nonwoven fabric is sintered and fixed is preferable. The shape of the filter may be any type such as a basket type, a disc type, a leaf disc type, a tube type, a flat cylindrical type, a pleated cylindrical type, etc. Among them, a pleated type is more preferable.

  There is no particular limitation on the material of the filter, and metal, resin ceramic, etc. can be used, but from the viewpoint of heat resistance and color reduction, a metal filter having an iron content of 80% or less is preferable. Of these, stainless steel such as SUS304, SUS316, SUS316L, and SUS310S is preferable.

Here, the aperture means the value of χ when the βχ value represented by the following formula (1) measured in accordance with ISO16889 is 1000.

βχ = (number of particles on the primary side larger than χ μm) / (number of particles on the secondary side larger than χ μm) (1)
Further, the upstream means the raw material preparation tank side with respect to the direction in which the raw material mixture flows, and the downstream means the reactor side with respect to the direction in which the raw material mixture flows.

From the viewpoint of productivity and filter life, the flow rate of the raw material in the molten state on the filter surface is preferably 1 m / h to 20 m / h. If the flow rate is too small, the equipment becomes excessive, and if it is too large, the filter life tends to be short.
In particular, when the aperture of the filter is less than 5 μm, the flow rate is 1 m / h to 5 m / h, particularly 2 m / h to 3 m / h, and the aperture of the filter is 5 μm or more. The flow rate on the filter surface is preferably 5 m / h to 20 m / h, more preferably 6 m / h to 10 m / h.
Although there is no restriction | limiting in the temperature of the raw material fluid at the time of letting the filter in this Embodiment pass, Since raw materials will solidify when too low, and there exist malfunctions, such as thermal decomposition, when too high, Usually 100 to 200 degreeC, Preferably It is 120 to 180 ° C, particularly preferably 125 to 160 ° C.

As shown in FIG. 2, the static mixer 24 may be provided before or after the three filters, preferably at the preceding stage, but may be omitted.
When the number of filters is one, the filter often closes in a short operation. Therefore, in the present embodiment, a plurality of filters are used, but preferably three or more. By adopting this configuration, it is very difficult to block the filter, and an excellent effect is achieved in that the frequency of filter replacement can be reduced.
In the present embodiment, what is filtered by the filter unit 20 is a raw material mixture of an aromatic dihydroxy compound and a carbonic acid diester. However, these raw materials may be mixed and then mixed.
In the present embodiment, the addition position of the catalyst is not limited, and may be added in any of the reactor, between the raw material preparation tank, the raw material preparation tank and the reactor, but the stabilization of the addition amount, the thermal stability of the raw material From this point of view, it is preferable to add a catalyst between the raw material preparation tank and the reactor as shown in FIG. 1, and in particular, as shown in FIG. 1, the filter part is in a state where the raw material mixture and the transesterification catalyst are all mixed. Passing through 20 is preferred.
However, in the present embodiment, the position of the filter portion is not limited to 20, and the raw material in a molten state is filtered using a plurality of filters arranged in series, and then supplied to the reactor. Just do it.
That is, in FIG. 1, the filter unit may be installed at any of positions 20-1, 20-2, and 20 and a plurality of filter units may be installed. Or each filter of a filter part may be installed over multiple places of 20-1, 20-2, and 20. However, it is preferable that at least one filter is installed at 20 from the viewpoint of removing foreign substances immediately before transfer to the reaction vessel.

  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.

Example 1
Bisphenol A as the aromatic dihydroxy compound, diphenyl carbonate as the carbonic acid diester, and a heat medium jacket and a heat medium coil inside so that diphenyl carbonate / bisphenol A = 1.065 (mol / mol). Was continuously fed to a raw material preparation tank maintained at 150 ° C., and mixed and melted.
This raw material mixture is extracted from the pipe at the bottom of the raw material preparation tank, and an aqueous solution of cesium carbonate is added to the pipe by controlling the flow rate to 0.5 μmol as cesium carbonate with respect to 1 mol of raw material bisphenol A. Then, the solution was supplied to three filter units arranged in series through a pipe equipped with a static mixer and filtered. Each filter has a structure in which a medium obtained by sintering a metal nonwoven fabric made of SUS316 is processed into a pleated shape, and the openings are 10 μm, 5 μm, and 1 μm in order from the upstream. At this time, the flow velocity on the filter surface was 7 m / h, 6 m / h, and 2 m / h in order from the upstream. In this state, continuous operation was performed for one year, but the pressure difference that served as a reference for replacing the filter was not reached.

(Example 2)
In Example 1, the operation was performed in the same manner as in Example 1 except that the flow velocity on the filter surface was set to 28 m / h, 10 m / h, and 6 m / h in order from the upstream. When continuously operated in this state, the pressure difference reached the standard for replacing the filter after 30 days.

(Comparative Example 1)
In Example 1, the operation was performed in the same manner as in Example 1 except that only one filter having an aperture of 1 μm was used. The filter had to be replaced because the pressure difference reached the standard for replacing the filter in two weeks.

  As mentioned above, according to the manufacturing method of the aromatic polycarbonate explained in full detail in this Embodiment, the replacement frequency of the filter which filters a raw material can be reduced. As a result, it is possible to reduce the risk at the time of filter replacement and the frequency of operation stoppage accompanying the filter replacement, and it is possible to obtain an excellent effect that an aromatic polycarbonate with little foreign matter can be stably obtained.

It is a figure which shows an example of the manufacturing apparatus of an aromatic polycarbonate. It is a figure explaining an example of composition of a filter part.

Explanation of symbols

2a ... 1st raw material preparation tank, 2b ... 2nd raw material preparation 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 ... Third vertical reactor, 7a, 7b, 7c, 10a ... Stirrer blades, 8a, 8b, 8c, 8d ... Distillation tube, 9a ... Fourth horizontal reactor, 20, 20-1 , 20-2 ... Filter section, 21, 22, 23 ... Filter, 24 ... Static mixer

Claims (10)

In a method for producing an aromatic polycarbonate using an aromatic dihydroxy compound and a carbonic acid diester as raw materials,
After filtering the raw material in a molten state using a plurality of filters arranged in series, supply to the reactor ,
A method for producing an aromatic polycarbonate, wherein a flow rate of the raw material in a molten state on at least one filter surface of the filter is from 1 m / h to 20 m / h .   The method for producing an aromatic polycarbonate according to claim 1, wherein the raw material is a mixture of an aromatic dihydroxy compound and a carbonic acid diester.   The method for producing an aromatic polycarbonate according to claim 1, wherein a transesterification catalyst is further added to the raw material, and filtration is performed using the plurality of filters.   The filter is characterized in that A is larger than B (A> B) in at least one combination when the opening on the upstream side is A μm and the opening on the downstream side is B μm. The method for producing an aromatic polycarbonate according to any one of claims 1 to 3.   The method for producing an aromatic polycarbonate according to claim 4, wherein A is 8 or more on the most upstream side, and B is 2 or less on the most downstream side.   The method for producing an aromatic polycarbonate according to any one of claims 1 to 5, wherein the filter includes at least three groups.   The method for producing an aromatic polycarbonate according to any one of claims 1 to 6, wherein at least one of the filters is a pleated type. The production of an aromatic polycarbonate according to any one of claims 1 to 7 , wherein the flow rate of the raw material in the molten state on the filter surface satisfies the following conditions (1) and (2): Method.
(1) When the aperture of the filter is less than 5 μm, it is 1 m / h to 5 m / h.
(2) When the aperture of the filter is 5 μm or more, it is 5 m / h to 20 m / h. The method for producing an aromatic polycarbonate according to any one of claims 1 to 8, wherein the raw material in the molten state is prepared in a raw material preparation tank . The method for producing an aromatic polycarbonate according to claim 9 , wherein the transesterification catalyst is added to the raw material between the raw material preparation tank and the reactor.

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