JP5168844B2 - Method for producing aromatic polycarbonate - Google Patents

Description

  The present invention relates to a method for producing an aromatic polycarbonate, and more particularly to a method for producing an aromatic polycarbonate with reduced generation of foreign matter.

  Conventionally, aromatic polycarbonates are produced by a method in which bisphenols such as bisphenol A are directly reacted with phosgene (interface method), or by bisphenols such as bisphenol A and carbonic acid diesters such as diphenyl carbonate by transesterification. A method of condensation reaction (melting method) is known. Among them, the melting method by transesterification has an advantage that an aromatic polycarbonate can be produced at a lower cost than the interface method.

The melting method by the transesterification reaction is usually performed on a raw material mixture prepared in advance through a multistage polycondensation step using a plurality of reactors in the presence of a transesterification reaction catalyst (see Patent Document 1).
Many examples of aromatic polycarbonate produced by the melting method have been reported so far. For example, the temperature difference between the polymer temperature and the heating medium in the reactor is set to 100 ° C. or less when the intrinsic viscosity [η] of the produced aromatic polycarbonate is 0.2 or less, and [η] exceeds 0.2 to When the temperature is 35 or less, the temperature is set to 80 ° C. or less, and when [η] exceeds 0.35, the temperature is set to 50 ° C. or less (see Patent Document 2). A method of automatically controlling the temperature and pressure by changing them according to a pre-installed program (see Patent Document 3). The difference between the outer wall surface temperature of a pipe for transferring a high molecular weight molten polymer and the temperature of the molten polymer in the polymerization vessel is And a method of making the temperature range from -3 ° C to 50 ° C (see Patent Document 4).

Moreover, the aromatic dihydroxy compound and the diaryl carbonate, which are vacuum-substituted using an inert gas, are transferred to a raw material dissolution and mixing tank heated to 115 to 220 ° C., and the reaction rate is adjusted to a range of 5 to 95%. , A method of transferring to a post-process and polymerizing (see Patent Document 5 and Patent Document 6), after preparing a polycarbonate prepolymer, a step of controlling the hydroxyl group terminal ratio of a plurality of prepolymers, Examples include a method of continuously producing polycarbonates having different molecular weights simultaneously (see Patent Document 7), and a production method in which one early polymerization step and a plurality of later polymerization steps are combined (see Patent Document 8).
Furthermore, the manufacturing method (refer patent document 9) etc. which make the surface temperature of a reactor material the temperature of 230 degreeC or more, and suppress the crystallization of the low-order polycondensate of the polycarbonate produced | generated in the middle stage of a polycondensation reaction are mentioned.

JP 05-239334 A Japanese Patent Laid-Open No. 06-065365 Japanese Patent Laid-Open No. 06-065366 Japanese Patent Laid-Open No. 10-330474 JP 2003-034719 A JP 2003-034720 A JP 2003-192882 A Japanese Patent Laid-Open No. 2004-026916 JP 2000-198839 A

By the way, when producing an aromatic polycarbonate using a production apparatus connected with a plurality of vertical reactors, it is connected to the latter stage because the self-cleaning property is insufficient due to a decrease in the reflux amount during a long-term continuous operation. In such a reactor, the polymer scattered and adhering to the gas phase part of the reactor or the like may receive a thermal history to produce a high melting point product.
If such a high melting point compound is mixed in the reaction solution, it may cause troubles such as blocking the gear pump that draws out the reaction solution or mixing foreign substances into the aromatic polycarbonate product. It is said that.

This invention is made | formed in order to solve the subject in manufacture of the aromatic polycarbonate by such a melting method.
That is, an object of the present invention is to provide a method for producing an aromatic polycarbonate with reduced melting point in the production of an aromatic polycarbonate by a melting method.

Thus, according to the present invention, when an aromatic polycarbonate is produced using an aromatic dihydroxy compound and a carbonic acid diester as raw materials, a reaction with the reaction liquid temperature T ₁ (° C.) in at least one reactor is performed. reaction temperature T ₂ in the reactor following the vessel and _(℃), but the production method of an aromatic polycarbonate and satisfies the following formula (1) is provided.
T ₂ <T ₁ formula (1)

Here, in this method for producing an aromatic polycarbonate, it is preferable that at least one of the plurality of reactors is a vertical reactor.
Moreover, it is preferable that the reactor whose reaction solution temperature is T ₁ (° C.) is a vertical reactor.

Furthermore, in the method for producing the aromatic polycarbonate, it is preferable that the reaction liquid temperature T ₁ (° C.) and the reaction liquid temperature T ₂ (° C.) further satisfy the following formula (2).
260 ° C. <T ₂ <T ₁ <280 ° C. Formula (2)
Moreover, it is preferable that the viscosity average molecular weight of the polymer in the reactor having the reaction liquid temperature T ₁ (° C.) is 4,000 to 14,000.

  Furthermore, when connecting multiple reactors, the vertical reactor is connected to the tail of the multiple reactors connected in series, and the reactor following this vertical reactor is a horizontal type. A reactor is preferred.

  According to the present invention, an aromatic polycarbonate having a reduced melting point can be produced.

  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.

(Aromatic polycarbonate)
In the present invention, the aromatic polycarbonate 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 an aromatic polycarbonate 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 excessively small, the terminal OH groups of the resulting aromatic polycarbonate increase, and the thermal stability of the resin tends to deteriorate. In addition, when the molar ratio is excessively large, the transesterification reaction rate decreases, and it becomes difficult to produce an aromatic polycarbonate having a desired molecular weight, and the residual amount of carbonic acid diester in the resin increases. This may cause odors during molding or when formed into a molded product, which is not preferable.

(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 basic phosphorus compounds include trivalent phosphorus 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 of aromatic dihydroxy compound and carbonic acid diester compound as raw materials is prepared (primary process), and these compounds are melted in the presence of a transesterification catalyst in a molten state. The polycondensation reaction is carried out in multiple stages (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. As the reactor, a plurality of vertical reactors and then at least one horizontal reactor are used. Usually, these reactors are installed in series and processed continuously.
After the polycondensation step, the reaction is stopped and the unreacted raw material and reaction by-products in the polymerization reaction solution are devolatilized and removed, the step of adding a thermal stabilizer, mold release agent, colorant, etc., aromatic polycarbonate is specified A step of forming a pellet having a particle size of may be appropriately added.
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 usually selected from the range of 20 ° C. to 180 ° C., preferably 125 ° C. to 160 ° C.
At this time, the ratio of the aromatic dihydroxy compound and the carbonic acid diester is adjusted so that the carbonic acid diester becomes excessive, and the carbonic acid diester is usually 1.01 mol to 1.30 mol with respect to 1 mol of the aromatic dihydroxy compound. Preferably, it is 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 compound 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 multi-stage reactor, in order to more effectively remove by-product phenol out of the system as the polycondensation reaction proceeds, the temperature is set to higher temperature and higher vacuum stepwise within the above reaction conditions. . In addition, in order to prevent quality deterioration of the hue etc. of the aromatic polycarbonate obtained, 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 system, usually, a plurality of reactors including a vertical reactor 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.

  As the types of the stirring blades of the vertical reactor, 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 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 type stirring blade such as a disk type or a paddle type, HVR, SCR, N-SCR (manufactured by Mitsubishi Heavy Industries, Ltd.), Vivolak (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 compound 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 solvents, such as acetone, alcohol, toluene, and phenol, can also be selected.
The properties of water used for dissolving the catalyst are not particularly limited as long as the type 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, an aromatic polycarbonate is prepared by a raw material process for preparing raw material aromatic dihydroxy compounds and carbonic acid diester compounds, and a polycondensation reaction of these raw materials in a molten state using a plurality of reactors. It is manufactured through a condensation step.
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) ), And through a step (not shown) of forming the aromatic polycarbonate into pellets having a predetermined particle diameter, the pellets of the aromatic polycarbonate are formed.

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 stirring blade 10a.

  The four reactors are equipped with distilling tubes 8a, 8b, 8c, and 8d for discharging by-products generated by the polycondensation reaction. 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.

In the apparatus for producing an aromatic polycarbonate shown in FIG. 1, a DPC melt prepared at a predetermined temperature in a nitrogen gas atmosphere and a BPA powder weighed 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 a catalyst, aqueous cesium carbonate 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 provided with cold traps (not shown), and byproducts are continuously solidified and recovered. .

In the present embodiment, in the production apparatus shown in FIG. 1, three vertical reactors (first vertical reactor 6a, second vertical reactor 6b, and third vertical reactor 6c) connected in series. In the polycondensation in at least the third vertical reactor 6c connected to the tail and the fourth horizontal reactor 9a, the aromatic polycarbonate is satisfied under the condition satisfying the relationship of the following formula (1): Is manufactured.
T ₂ <T ₁ formula (1)
In the formula (1), T ₁ is the reaction liquid temperature in the third vertical reactor 6c (unit: ° C.). T ₂ is the reaction liquid temperature in the fourth horizontal reactor 9a (unit: ° C.).

Here, by setting the reaction liquid temperature T ₁ in the third vertical reactor 6c to be higher than the reaction liquid temperature T ₂ in the fourth horizontal reactor 9a (T ₂ <T ₁ ), the third vertical reactor 6 Generation | occurrence | production of the high melting point thing in 6c can be reduced, and the stable manufacture driving | operation can be performed. Moreover, the foreign material mixed in the aromatic polycarbonate product finally obtained is significantly reduced.

At this time, the reaction mixture temperatures _{T 1} in the third vertical reactor 6c is usually, 240 ° C. to 300 ° C., preferably from 260 ° C. to 280 ° C.. Reaction temperature _{T 2} in the fourth horizontal reactor 9a is generally, 240 ° C. to 300 ° C., preferably, 260 ° C. to 280 ° C..
That is, during the polycondensation in the third vertical reactor 6c and the subsequent fourth horizontal reactor 9a, it is preferable to produce an aromatic polycarbonate under the conditions satisfying the relationship of the following formula (2). .
260 ° C. <T ₂ <T ₁ <280 ° C. Formula (2)

In the case of the reaction temperature T ₁ is excessively high temperature in the third vertical reactor 6c, there is a tendency that the color tone of the resulting polymer is deteriorated (yellowing). In the case of the low-temperature reaction liquid temperature T ₂ is excessively in the fourth horizontal reactor 9a, since higher melt viscosity of the polymer, deteriorates flowability, is likely to occur long residence-deposition in the reactor interior, There is a tendency that the generation of crystallized foreign matters increases.

  In this case, when the viscosity average molecular weight (Mv) of the polymer produced in the third vertical reactor 6c is about 4,000 to 14,000, the third vertical reactor 6c and the fourth horizontal reactor 9a. It is desirable that the operation of the aromatic polycarbonate in is performed so as to satisfy the condition of the formula (1) or the formula (2) described above. When the viscosity average molecular weight (Mv) of the reaction solution is within the above-described range, the effect of reducing the generation of the high melting point product in the third vertical reactor 6c is great.

Here, the viscosity average molecular weight (Mv) of the aromatic polycarbonate is obtained from the following formula based on the intrinsic viscosity [η] (unit: dl / g) measured at 20 ° C. in methylene chloride using an Ubbelohde viscometer. It is done.
[Η] = 1.23 × 10 ⁻⁴ × (Mv) ^0.83
The intrinsic viscosity “η” is a linear concentration (C) obtained by plotting the specific viscosity (η _sp / C) of the diluted methylene chloride solution at 20 ° C. and the concentration (C) of the diluted methylene chloride solution. ) Are extrapolated to zero.

  By satisfying the above-described production conditions, an aromatic polycarbonate having a viscosity average molecular weight (Mv) of about 15,000 and excellent in hue and useful as an optical polycarbonate can be finally produced.

Here, the application of the formula (1) or the formula (2) in the third vertical reactor 6c and the fourth horizontal reactor 9a in the aromatic polycarbonate production apparatus shown in FIG. 1 has been described in detail. The relationship of the formula (1) or the formula (2) is not limited to this combination of reactors. For example, the first vertical reactor 6a and the second vertical reactor 6b, the second vertical reactor 6b and the second The present invention can also be applied to a polycondensation reaction in the 3-tubular reactor 6c.
In the method for producing an aromatic polycarbonate to which the present embodiment is applied, as shown in FIG. 1, a production apparatus in which a plurality of vertical reactors and a horizontal reactor equipped with a stirrer in a polycondensation step are connected in series. Among the three vertical reactors, at least in the third vertical reactor 6c connected at the end and the fourth horizontal reactor 9a following this, the above formula (1) or formula (2) is used. It is preferable to produce an aromatic polycarbonate under the conditions satisfying the relationship (1).

  Hereinafter, the present invention will be described more specifically based on examples. In addition, this invention is not limited to a following example, unless it deviates from the summary. In addition, the analysis of the aromatic polycarbonate used by an Example and a comparative example was performed with the following measuring methods.

(1) Viscosity average molecular weight (Mv)
It calculated | required from the following formula | equation based on the intrinsic viscosity [(eta)] of the aromatic polycarbonate (sample) measured using the Ubbelohde viscometer at 20 degreeC, using methylene chloride as a solvent.
(Η _sp /C)=〔ita〕×(1tasu0.28Ita _sp)
[Η] = 1.23 × 10 ⁻⁴ × (Mv) ^0.83
(In the formula, η _sp is a specific viscosity measured at 20 ° C. for a methylene chloride solution of an aromatic polycarbonate, and C is a concentration of the methylene chloride solution. As the methylene chloride solution, the concentration of the aromatic polycarbonate is 0.6 g / dl is used.)
For the intrinsic viscosity “η”, the concentration (C) of the straight line obtained by plotting the measured value of the specific viscosity (η _sp / C) at 20 ° C. and the concentration (C) of the methylene chloride diluted solution was set to 0. Extrapolated section.

(2) Hue (YI)
Using an aromatic polycarbonate (sample) dried at 130 ° C. for 5 hours, a press sheet having a length of 100 mm × width of 100 mm × thickness of 3 mm was formed at 280 ° C. by an injection molding machine.
Next, a tristimulus value XYZ which is an absolute value of the color is measured with a color tester (SC-1-CH manufactured by Suga Test Instruments Co., Ltd.) for this press sheet, and YI which is an index of yellowness is represented by the following relational expression. The value was calculated.
YI = (100 / Y) × (1.28 × X−1.06 × Z)
The larger this YI value, the more yellow it is colored.

Example 1
A melt was prepared by mixing diphenyl carbonate (DPC) and bisphenol A (BPA) at a constant molar ratio (DPC / BPA = 1.060) under a nitrogen gas atmosphere.
Next, as described in FIG. 1, an aromatic polycarbonate was produced by a production apparatus in which three vertical reactors equipped with a stirrer and one horizontal reactor were connected in series.
First, the above-mentioned mixed molten solution is continuously supplied into the first vertical reactor having a capacity of 100 L controlled at 220 ° C. and 1.33 × 10 ⁴ Pa through the raw material introduction pipe at a flow rate of 88.7 kg / hour. did. In the first vertical reactor, the liquid level was kept constant while controlling the valve opening degree provided in the polymer discharge line at the bottom of the reactor so that the average residence time was 60 minutes.
Moreover, simultaneously with the start of the supply of the above melt into the first vertical reactor, a 1 wt% aqueous cesium carbonate solution was continuously supplied as a catalyst at a ratio of 0.4 µmol per 1 mol of bisphenol A.

The reaction liquid discharged from the bottom of the first vertical reactor is continuously continuously supplied to the second and third vertical reactors (capacity 100 L) and the fourth horizontal reactor (capacity 150 L). The molten polymer was extracted from the polymer outlet at the bottom of the reactor.
Next, this molten polymer is fed into a twin screw extruder, and butyl p-toluenesulfonate (4 times the amount of cesium carbonate used as a catalyst) is continuously fed and kneaded. And then formed into a strand shape and cut with a cutter to obtain a pellet (aromatic polycarbonate product).
The reaction conditions (reaction solution temperature, pressure, number of stirring) in the second vertical reactor are (250 ° C., 2.00 × 10 ³ Pa, 75 rpm).
The viscosity average molecular weight of the polymer discharged from the second vertical reactor was Mv = 3,800.

Next, the reaction liquid temperature T ₁ (° C.) in the third vertical reactor located at the end of the three vertical reactors, and the subsequent reaction liquid temperature T ₂ (° C.) in the fourth horizontal reactor. preparative, such that T 2 _{<T 1,} were set up as follows, respectively. The reaction conditions are shown in the order of (reaction solution temperature (° C.), pressure (Pa), number of stirring (rpm)).
Third vertical reactor (T ₁ : 272 ° C., 67 Pa, 75 rpm)
Fourth horizontal reactor (T ₂ : 265 ° C., 140 Pa, 5 rpm)
The liquid level was controlled so that the average residence time in each reactor was 60 minutes, and at the same time, by-produced phenol was distilled off.

When the production operation was continued for one month under the above conditions, no troubles in operation such as generation of a high melting point product and blockage / stop of the discharge gear pump based on this occurred.
The viscosity average molecular weight of the polymer discharged from the third vertical reactor was Mv = 7,000.
The viscosity average molecular weight of the finally obtained aromatic polycarbonate product was Mv = 15,000. The color tone was YI = 1.3, and no contamination was observed.

(Example 2)
The reaction conditions for the third vertical reactor were set to (T ₁ : 282 ° C., 100 Pa, 75 rpm), and the reaction conditions for the fourth horizontal reactor were set to (T ₂ : 275 ° C., 180 Pa, 5 rpm). An aromatic polycarbonate was produced under the same conditions as in Example 1.
When the production operation was continued for one month under the above conditions, as in the case of Example 1, no trouble in operation occurred and stable production operation could be performed.
The viscosity average molecular weight of the polymer discharged from the third vertical reactor was Mv = 7,400.
In addition, the viscosity average molecular weight of the aromatic polycarbonate product finally obtained was Mv = 15,200. The color tone was YI = 1.8, and no contamination was observed.

(Comparative Example 1)
The reaction liquid temperature T ₁ in the third vertical reactor is set to be lower than the reaction liquid temperature T ₂ in the fourth horizontal reactor (T ₂ > T ₁ ), and other conditions are the same as in Example 1. Aromatic polycarbonate was produced.
The reaction conditions (reaction liquid temperature (° C.), pressure (Pa), number of stirring (rpm)) of the third vertical reactor and the fourth horizontal reactor are as follows.
Third vertical reactor (T ₁ : 258 ° C., 67 Pa, 75 rpm)
Fourth horizontal reactor (T ₂ : 265 ° C., 100 Pa, 5 rpm)
When the production operation was continued for one month under the above conditions, a high melting point product was produced in the third vertical reactor. Since the high melting point product was mixed in the reaction solution, the discharge gear pump of the third vertical reactor was stopped twice. Moreover, unmelted material (foreign matter) was observed in the produced aromatic polycarbonate.
The viscosity average molecular weight of the polymer discharged from the third vertical reactor was Mv = 6,100.
The finally obtained aromatic polycarbonate product had a viscosity average molecular weight of Mv = 14,900 and a color tone of YI = 1.3.

(Comparative Example 2)
The reaction liquid temperature T ₁ in the third vertical reactor and the reaction liquid temperature T ₂ in the fourth horizontal reactor are set to be equal (T ₂ = T ₁ ), and other conditions are the same as in Example 1. Aromatic polycarbonate was produced.
The reaction conditions (reaction liquid temperature (° C.), pressure (Pa), number of stirring (rpm)) of the third vertical reactor and the fourth horizontal reactor are as follows.
Third vertical reactor (T ₁ : 265 ° C., 67 Pa, 75 rpm)
Fourth horizontal reactor (T ₂ : 265 ° C., 100 Pa, 5 rpm)
When the production operation was continued for one month under the above conditions, a high melting point product was produced in the third vertical reactor. Since this high melting point product was mixed in the reaction solution, the discharge gear pump of the third vertical reactor was stopped once. Moreover, unmelted material (foreign matter) was observed in the produced aromatic polycarbonate.
The viscosity average molecular weight of the polymer discharged from the third vertical reactor was Mv = 6,600.
The finally obtained aromatic polycarbonate product had a viscosity average molecular weight of Mv = 15,300 and a color tone of YI = 1.3. The results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1.

As described above, as described in the present example, aromatic compounds are obtained by connecting three vertical reactors and one horizontal reactor in series using diphenyl carbonate (DPC) and bisphenol A (BPA) as raw materials. When producing polycarbonate, the reaction liquid temperature T ₁ (° C.) in the third vertical reactor located at the end of the three vertical reactors is changed to the reaction liquid temperature T ₂ in the subsequent fourth horizontal reactor. by (℃) higher than _(T 2 _{<T 1),} it can be seen that it is possible to reduce the occurrence of high melting point compound in the third vertical reactor.
At this time, when the viscosity average molecular weight (Mv) of the polymer in the third vertical reactor is 4,000 to 14,000, the effect of reducing the generation of the high melting point product in the third vertical reactor is great.
Furthermore, since the viscosity average molecular weight (Mv) of the aromatic polycarbonate produced under such conditions is about 15,000 and the YI value indicating the color tone is small, it can be suitably used as an optical polycarbonate.

It is a figure which shows an example of the manufacturing apparatus of an aromatic polycarbonate.

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 ... Stirring blade, 11 ... Exit piping, 81a, 81b, 81c, 81d ... Condenser, 82a, 82b, 82c, 82d ... Pressure reducing device

Claims (5)

When an aromatic dihydroxy compound and a carbonic acid diester are used as raw materials and an aromatic polycarbonate is produced using a plurality of reactors,
The reaction liquid temperature T ₁ (° C.) in at least one vertical reactor and the reaction liquid temperature T ₂ (° C.) in the reactor following the vertical reactor satisfy the following formula (1): A method for producing an aromatic polycarbonate.
T ₂ <T ₁ formula (1)   The method for producing an aromatic polycarbonate according to claim 1, wherein at least one of the plurality of reactors is a vertical reactor. The reaction mixture temperature T _{1 (°} C.) and the reaction temperature T _{2 (°} C.), but the production method of an aromatic polycarbonate according to claim 1 or 2, characterized in that to satisfy further the following formula (2).
260 ° C. <T ₂ <T ₁ <280 ° C. Formula (2) The aromatic polycarbonate production according to any one of claims 1 to 3 , wherein the viscosity average molecular weight of the polymer in the reactor at the reaction liquid temperature T ₁ (° C) is 4,000 to 14,000. Method. The vertical reactor is connected to the last of a plurality of reactors connected in series, and the reactor following the vertical reactor is a horizontal reactor. Item 5. A method for producing an aromatic polycarbonate according to any one of Items 1 to 4 .

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