JP2005146047A - Method for producing aromatic polycarbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out a distillation process of a diphenyl carbonate producing process while preventing clogging of piping, facilitating recovery of an organic component sucked to a vacuum apparatus side and keeping a sufficient degree of vacuum. <P>SOLUTION: In the subject method for producing an aromatic polycarbonate, which has a diphenyl carbonate production process for producing diphenyl carbonate through a reaction process using phenol and a carbonyl compound as raw materials and the distillation process and by which an aromatic polycarbonate is produced by using diphenyl carbonate obtained by the diphenyl carbonate production process and bisphenol A, the distillation process is carried out under reduced pressure and an ejector using phenol as a drive force is used as a pressure reduction means therefor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a method for producing an aromatic polycarbonate, and more particularly to a method for producing an aromatic polycarbonate using an ejector using phenol as a driving source and a reduced pressure in a distillation step of a diphenyl carbonate production step.

  Aromatic polycarbonate is made from diphenyl carbonate and bisphenol A. The diphenyl carbonate is produced by reacting phenol and a carbonyl compound. In this reaction, the diphenyl carbonate obtained is purified by a distillation step. This purification step is generally performed under reduced pressure, and a liquid ring pump is used as a means for reducing the pressure.

  However, when a liquid ring pump is used, a low boiling point organic component may be mixed into the liquid ring pump liquid or lubricating oil, and the degree of vacuum may decrease. In addition, the organic component carbide may adhere to the inner wall of the liquid ring pump.

  On the other hand, it is conceivable to use an ejector using water as a drive source for a water flow type decompression pump or the like. When this is used, a small amount of organic components such as diphenyl carbonate and phenol are pulled to the ejector side in any way. Since these organic components are insoluble in water, they exist in water as droplets or solids. Furthermore, these organic components are sent to the production process of diphenyl carbonate after recovery, but the presence of water is not preferred. For these reasons, recovery of these organic components tends to be difficult.

  Further, when a large amount of diphenyl carbonate comes into contact with water, diphenyl carbonate may be precipitated, and the piping may be blocked.

  In addition, in order to effectively use water, water used as a drive source is often circulated and reused. In this case, since the low boiling organic component is mixed in the water, the degree of vacuum may decrease.

  Therefore, the present invention prevents the clogging of the piping, facilitates the recovery of the organic component pulled to the decompression device side, and performs the distillation process of the diphenyl carbonate manufacturing process while maintaining a sufficient degree of vacuum. Objective.

  The present invention has a diphenyl carbonate production process in which diphenyl carbonate is produced through a reaction process and a distillation process using phenol and a carbonyl compound as raw materials, and aroma is obtained using diphenyl carbonate and bisphenol A obtained in the diphenyl carbonate production process. In the method for producing an aromatic polycarbonate for producing an aromatic polycarbonate, the above-mentioned problem was solved by performing the distillation step under reduced pressure and using an ejector using phenol as a driving source as the decompression means. .

  According to this invention, since the ejector using phenol as a drive source is used, the degree of vacuum can be improved as compared with the case where water is used as the drive source.

  Moreover, since phenol is used, organic components such as diphenyl carbonate and phenol that are pulled toward the decompression device are dissolved in phenol. For this reason, blockage of piping is prevented. And since phenol is one of the manufacturing raw materials of diphenyl carbonate, it becomes easy to send these organic components to the manufacturing process of diphenyl carbonate together with phenol.

  Furthermore, since the phenol used as the drive source of the ejector is one of the raw materials for producing diphenyl carbonate, the phenol once used as the drive source can be sent to the production process of diphenyl carbonate. For this reason, it is not necessary to repeatedly use phenol as a driving source, and low-boiling organic components are unlikely to accumulate in phenol, and the degree of vacuum can be maintained.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing an aromatic polycarbonate (PC) according to the present invention has a diphenyl carbonate (DPC) production process for producing diphenyl carbonate (DPC) through a reaction process and a distillation process using phenol (PL) and a carbonyl compound as raw materials. In this method, aromatic polycarbonate (PC) is produced using diphenyl carbonate (DPC) and bisphenol A (BPA) obtained in the diphenyl carbonate (DPC) production process.

[Production of bisphenol A and production of aromatic polycarbonate]
The bisphenol A (BPA) is synthesized using phenol (PL) and acetone (A) as raw materials. The obtained bisphenol A (BPA) is purified through the steps of low boiling point removal, crystallization / separation, heating and melting, phenol (PL) removal, and granulation.

  The aromatic polycarbonate (PC) is polymerized in a polymerization tank using the above-mentioned diphenyl carbonate (DPC) and bisphenol A (BPA) as raw materials and adding a basic catalyst such as an alkaline aqueous solution. It is manufactured by. As this polymerization proceeds, by-product phenol (s-PL) is distilled off and recovered, and an aromatic polycarbonate having a desired degree of polymerization is obtained.

[Diphenyl carbonate production process]
The diphenyl carbonate (DPC) production process is a process of producing diphenyl carbonate (DPC) using phenol (PL) and a carbonyl compound as raw materials. This carbonyl compound can be used without limitation as long as it can form a carbonyl group of diphenyl carbonate. Examples of such carbonyl compounds include phosgene (CDC), carbon monoxide, dialkyl carbonate and the like. In the following, a process for producing diphenyl carbonate (DPC) by using phosgene (CDC) as a carbonyl compound and passing through a washing process and a distillation process after the reaction will be described.

  The manufacturing process of the said diphenyl carbonate (DPC) is comprised from the process shown in FIG. Specifically, phenol (PL) and phosgene (CDC) are used as raw materials, and a reaction step of introducing this and the basic compound catalyst (C1) into the DPC reactor 1 is performed. Although the reaction conditions at this time are not specifically limited, 50-180 degreeC and normal pressure under a phenol (PL) in a molten state are preferable. In addition, the mixing ratio (molar ratio) of phenol (PL) and phosgene (CDC) is 0.40 to 0.49 mol with respect to 1 mol of phenol (PL) from the viewpoint of complete consumption of phosgene (CDC). preferable.

  The phenol (PL) used as a raw material at this time contains the by-product phenol (s-PL) as a part or all of the by-product phenol (s-PL). As will be described later, it is preferable to use by-product phenol used as a drive source of the ejector.

  The diphenyl carbonate (DPC) -containing reaction solution a produced in the above reaction step is sent to the dehydrochlorination tower 2, and the dehydrochlorination step is performed. The hydrochloric acid gas (D1) generated in the reactor 1 and the dehydrochlorination tower 2 is recovered and sent to a hydrochloric acid treatment step (not shown).

Subsequently, the obtained dehydrochlorination treatment liquid b is sent to the mixing tank 3 and mixed with a diphenyl carbonate (DPC) -containing recovery liquid d described later. And the neutralization process of neutralizing the hydrochloric acid which was sent to the alkali neutralization tank 4 and was not able to be removed with the said dehydrochlorination tower with the alkaline aqueous solution (E1) is performed.
And the obtained neutralization process liquid e is sent to the water-washing tank 5, and the water-washing process wash | cleaned with water (W) is performed.

  The water washing treatment liquid f obtained in the water washing step is sent to the distillation tower, where the distillation step is performed. In FIG. 1, two distillation columns are used, but the present invention is not limited to this. When two distillation columns are used, a mixed gas (F) containing water, a basic compound catalyst, and phenol (PL) is recovered in the first distillation column 6 for removing low boiling points, and a part of the reaction raw material Can be reused as.

  And the 1st distillation residue g1 of the said 1st DPC distillation column 6 is again distilled in the 2nd DPC distillation column 7 for high boiling point removal, and the refined diphenyl carbonate (DPC) which is a product is collect | recovered as a distillate. . And the distillation residue g2 is collect | recovered from the distillation kettle remainder side.

  The distillation conditions in the first DPC distillation column 6 are not particularly limited as long as water, the basic compound catalyst, and phenol (PL) are distilled and diphenyl carbonate (DPC) remains. 3-13 kPa is preferred. The temperature becomes the boiling point under that pressure. The distillation conditions in the second DPC distillation column 7 are not particularly limited as long as diphenyl carbonate (DPC) is distilled and impurities having a higher boiling point than diphenyl carbonate (DPC) remain. The pressure is preferably 150 to 220 ° C. under a reduced pressure condition of 3 to 6.5 kPa.

  The distillation step in the second DPC distillation column 7 is performed under reduced pressure as described above. As this decompression means, as shown in FIG. 2, an ejector 11 using phenol as a drive source is used.

  Specifically, the distillate p distilled in the second DPC distillation column 7 is condensed in the condenser 12 and temporarily stored in the tank 13. Then, a part is returned to the second DPC distillation column 7 by the pump 14 and the rest is recovered as diphenyl carbonate (DPC).

  The ejector 11 for reducing the pressure is connected to a pressure reducing pipe 15 connected to the condenser 12. Since the decompression pipe 15 connected to the ejector 11 is connected by the condenser 12, the distillate p containing gaseous diphenyl carbonate (DPC) can be prevented from being pulled by the ejector 11 while remaining in the gaseous state.

  The ejector 11 uses liquid phenol (PL) as a drive source. Since liquid phenol (PL) is used as a drive source, a degree of vacuum of several Torr can be obtained, and energy for gasification can be reduced. Furthermore, a pressure reducing device that uses an ejector that uses phenol vapor as a drive source and condenses the scattered matter sucked by the ejector with a barometric condenser that uses a phenol solution as a coolant is used in front of the liquid ejector. It is also possible. Moreover, the scattered matter of distillate p, such as diphenyl carbonate (DPC) pulled to the decompression device side, dissolves in phenol (PL). And since phenol (PL) is one of the manufacturing raw materials of diphenyl carbonate (DPC), by returning this to the reaction process of the said diphenyl carbonate (DPC) manufacturing process, phenol (PL) is diphenyl carbonate (DPC). Since the scattered product of the distillate p dissolved in phenol (PL) is returned to the diphenyl carbonate (DPC) step, the yield can be improved.

  Phenol (PL) used as a drive source for the ejector may be used in a partly circulated manner or may be used only once. This is because this phenol (PL) can be used as a raw material of diphenyl carbonate (DPC) as described above. When this phenol (PL) is not circulated and used, there is no need to cool, and the cooling source can be saved.

  As a phenol (PL) used as a drive source of the ejector, a by-product phenol (s-PL) produced as a by-product when the aromatic polycarbonate (PC) is produced is preferable. Since this byproduct phenol (s-PL) has a low low boiling point, when used as a drive source for the ejector, the degree of vacuum can be kept high. In addition, the by-product phenol (s-PL) may need to be purified. In this case, if the purification step is applied after the use as the driving source, the purification step may be reduced. Furthermore, when using the ejector which uses the above-mentioned phenol vapor | steam as a drive source, it is also possible to pressurize and use a part of by-product phenol vapor | steam byproduced when manufacturing the said aromatic polycarbonate.

  The phenol (PL) used as the ejector 11 is temporarily stored in the tank 16 and can be used as at least a part of the raw material of the diphenyl carbonate (DPC) production process after undergoing a purification process as necessary.

  You may provide the valve | bulb 17 for sending a phenol (PL) vapor | steam in the part by the side of the condenser 12 of said pressure reduction piping 15. FIG. If it does in this way, when the scattered matter of the said distillate p in the piping 15 for pressure reduction, especially diphenyl carbonate (DPC) precipitate, this can be dissolved. The fed phenol (PL) vapor is combined with the drive source phenol (PL) by the ejector 11 and sent to the tank 16.

  As a device for preventing the vacuum degree from being lowered by the ejector 11, there is a method in which the decompression pipe 15 is provided so as to be inclined downward from the condenser 12 side toward the ejector 11 side. If it does in this way, even if the scattered matter of the said distillate p liquefies in the piping 15 for pressure reduction, it can prevent staying here.

  By the way, the distillation residue g2 in the second DPC distillation column 7 includes a methyl substitution product of diphenyl carbonate reacted with methylphenol, which is a phenol-containing impurity, and a bromine substitution product of diphenyl carbonate reacted with residual bromine in phosgene (CDC). It contains impurities at the center, but also contains diphenyl carbonate (DPC). For this reason, this distillation residue g2 may be distilled again to recover diphenyl carbonate (DPC). That is, as shown in FIG. 1, the distillation residue g <b> 2 in the second DPC distillation column 7 is subjected to a recovery distillation step using the DPC recovery distillation column 8. Thereby, the diphenyl carbonate (DPC) -containing recovery liquid d can be recovered by distillation. By sending this to the mixing tank 3 as described above, it can be re-introduced into the washing / distilling step, and the recovery efficiency of diphenyl carbonate (DPC) can be further improved. Then, the recovered distillation residue (X1) in which the methyl-substituted product or bromine-substituted product of diphenyl carbonate (DPC) is concentrated is recovered from the remaining side of the distillation kettle.

  The distillation conditions in the recovery distillation column 8 are not particularly limited as long as diphenyl carbonate (DPC) is distilled and impurities having a higher boiling point than diphenyl carbonate (DPC) remain. 6.5 kPa and 150-220 ° C are preferred.

Hereinafter, the present invention will be described using experimental examples.
(Example 1)
[Production example of diphenyl carbonate]
An example of producing diphenyl carbonate from commercially available phenol and phosgene is shown below.
<Reaction process>
While continuously supplying molten commercial phenol and pyridine catalyst to the reactor, phosgene gas was continuously supplied under mixing at 150 ° C. The hydrogen chloride gas produced as a by-product in the phosgenation reaction was cooled to 10 ° C., the condensate was returned to the reactor, and the uncondensed gas was discharged after neutralization with an alkaline aqueous solution. On the other hand, a reaction solution containing about 91% by weight of diphenyl carbonate was continuously extracted from the reactor. The reaction rate of phosgene in the reaction step was almost 100%.

<Washing process>
The reaction solution and about 5 wt% sodium hydroxide aqueous solution were respectively supplied to a neutralization mixing tank made of Teflon lining, and mixed at 80 ° C. for about 10 minutes to adjust to pH 8.5. After neutralization, the organic phase after neutralization was transferred to a washing and mixing tank. In the water washing and mixing tank, it is washed with warm water corresponding to about 30% by weight with respect to the organic phase, the aqueous phase is separated, and crude diphenyl carbonate (water 1% by weight, pyridine 2% by weight, phenol 8% by weight, diphenyl carbonate 89%). Weight% content).

<Low boiling distillation process>
Next, the crude diphenyl carbonate was continuously fed to the middle stage of the low boiling distillation column at about 30 kg / hr. The low boiling distillation column has an inner diameter of 150 mm, a height of 4.0 m, a condenser at the top, a raw material supply unit at the center, and a sulzer packing (manufactured by Sumitomo Heavy Industries, Ltd.) packed in the concentration unit and the recovery unit. A continuous distillation column having 8 theoretical plates was used. Distillation of water, pyridine and phenol, which are lower boiling substances than diphenyl carbonate, by distillation under the conditions of a vacuum of 20 torr, a heating medium oil temperature of about 220 ° C., a top temperature of 80 to 100 ° C., a tower middle stage temperature of 160 ° C., and a reflux ratio of 1. Left. From the bottom of the column, diphenyl carbonate (water 10 wt ppm or less, pyridine 1 wt ppm or less, phenol 50 wt ppm) was continuously extracted at about 26 kg / hr.

<High boiling distillation process>
Furthermore, this diphenyl carbonate (the bottoms of the low boiling distillation column) was continuously supplied to the high boiling distillation column. The high boiling distillation column has an inner diameter of 200 mm, a height of 4.0 m, a condenser at the top, a raw material supply unit at the center, and packed with sulzer packing (manufactured by Sumitomo Heavy Industries, Ltd.) in the concentration unit and recovery unit, 8 theoretical plates A staged continuous distillation column was used. Distilled at a pressure of 20 torr, a heating medium oil temperature of about 240 ° C., a top temperature of about 180 ° C., and a reflux ratio of 0.5, purified diphenyl carbonate was obtained from the top at about 23.5 kg / hr, which was higher Boils (diphenyl carbonate containing about 350 ppm by weight and about 40 ppm by weight of alkyl and bromine substituents of diphenyl carbonate, respectively) were purged at about 2.5 kg / hr. The purified diphenyl carbonate was a high-purity product containing 80 ppm by weight of phenol.
In the low boiling distillation and high boiling distillation, by-product phenol recovered during the production of the aromatic polycarbonate described later was adjusted to 50 ° C. and supplied to the ejector at about 27 kg / hr, and the system was depressurized. Furthermore, each vacuum degree was adjusted by restricting the valve between the condenser and the ejector.

[Production example of aromatic polycarbonate]
The example which manufactures an aromatic polycarbonate from the said diphenyl carbonate and bisphenol A is described below.

<Polymerization process>
The above-mentioned diphenyl carbonate and bisphenol A were melt-mixed at a 0.977 weight ratio in a nitrogen gas atmosphere, and continuously fed into a first vertical stirring polymerization tank controlled at 210 ° C. and 100 Torr in a nitrogen atmosphere, and the average residence time was The liquid level was kept constant while controlling the valve opening degree provided in the polymer discharge line at the bottom of the tank so as to be 60 minutes. At the same time as the supply of the raw material mixture was started, cesium carbonate in an aqueous solution as a catalyst was continuously supplied at a flow rate of 0.5 × 10 −6 mol to 1 mol of bisphenol A. The polymerization solution discharged from the bottom of the tank was successively continuously supplied to the second and third vertical polymerization tanks and the fourth horizontal polymerization tank. During the reaction, the liquid level was controlled so that the average residence time in each tank was 60 minutes, and at the same time, the by-produced phenol was distilled off. The gas evaporating from the first and second polymerization tanks was condensed and liquefied by a multistage condenser, a part was refluxed to each polymerization tank, and the rest was collected in a byproduct phenol tank. On the other hand, the gas evaporating from the third and fourth polymerization tanks was solidified in one of the two freeze condensers in parallel, and the solidified part was melted by switching operation with the other freeze condenser and recovered in the byproduct phenol tank. .

  The polymerization conditions in each reaction tank were as follows: first polymerization tank (210 ° C., 100 Torr), second polymerization tank (240 ° C., 15 Torr), third polymerization tank (260 ° C., 0.5 Torr), fourth polymerization tank (280 ° C. 0.5 Torr).

  The polymer obtained above was introduced in a molten state into a twin-screw extruder (manufactured by Kobe Steel, Ltd., screw diameter 0.046 m, L / D = 40.2), and p equivalent to 5 ppm by weight per polycarbonate. -Pelletized with continuous addition of butyl toluenesulfonate. The polycarbonate thus obtained had a viscosity average molecular weight (Mv) of 21,000 and an initial hue YI of 1.7.

  Moreover, as a result of analyzing the contents of the by-product phenol tank recovered from the polymerization step, phenol was 94.2% by weight, diphenyl carbonate was 5.0% by weight, bisphenol A and oligomer components were each 0.5% by weight. 0.3 wt% was detected. This by-product phenol was supplied as a drive source to an ejector used in the diphenyl carbonate distillation step.

[Measurement of viscosity average molecular weight (Mv)]
The viscosity average molecular weight (Mv) is calculated from the specific viscosity (ηsp) measured at 20 ° C. with a Ubbelohde viscometer using a methylene chloride solution having a polycarbonate concentration (C) of 0.6 g / dl. This is a value calculated using an equation.
ηsp / C = [η] (1 + 0.28 ηsp)
[Η] = 1.23 × 10 ⁻⁴ (Mv) ^0.83

[Initial hue (YI)]
The initial hue (YI) was obtained by drying polycarbonate resin at 120 ° C. for 6 hours in a nitrogen atmosphere, and then producing a 3 mm thick injection molded piece at 360 ° C. using a J-100 injection molding machine manufactured by Nippon Steel. The YI value was measured by SC-1 manufactured by Suga Test Instruments Co., Ltd. (This YI value indicates that the larger the color, the more colored it is).

(Example 2)
Diphenyl carbonate and aromatic polycarbonate were produced by purifying the by-product phenol after being used as an ejector driving source in the diphenyl carbonate distillation step, and using it as a raw material for diphenyl carbonate.

[Purification of by-product phenol]
As a result of analyzing the byproduct phenol after being used as an ejector drive source in the diphenyl carbonate distillation step, water was 1000 ppm by weight, phenol was 93.8% by weight, diphenyl carbonate was 5.1% by weight, bisphenol A and oligomers Components were detected at 0.5 wt% and 0.3 wt%, respectively.
This byproduct phenol was continuously purified in the following two distillation columns. The first distillation column was 200 Torr and the reflux ratio was 2, and the contained water was partially distilled off together with phenol, and the bottoms were continuously supplied to the second distillation column. In the second distillation column, purified phenol is obtained from the top at 50 Torr and a reflux ratio of 0.5, and diphenyl carbonate, bisphenol A, and oligomer are obtained from the bottom by 70 wt%, 7 wt%, and 4 wt%, respectively. % Containing phenol mixture was continuously purged.

[Production of diphenyl carbonate and aromatic polycarbonate]
Example of production of diphenyl carbonate and aromatic polycarbonate of Example 1 except that purified phenol obtained by purification of the byproduct phenol was used instead of the commercially available phenol used in the production example of diphenyl carbonate of Example 1. The same operation was performed to produce diphenyl carbonate and aromatic polycarbonate. As a result, the phosgene reaction rate in the reaction process, and the quality of the obtained diphenyl carbonate and further the aromatic polycarbonate were not changed.

Process drawing which shows the example of the scheme of the diphenyl carbonate (DPC) manufacturing process based on this invention Process drawing which shows the example of the scheme of the distillation process of the diphenyl carbonate (DPC) manufacturing process concerning this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DPC reactor 2 Dehydrochlorination tower 3 Mixing tank 4 Alkali neutralization tank 5 Water washing tank 6 1st DPC distillation tower 7 2nd DPC distillation tower 8 DPC recovery distillation tower 11 Ejector 12 Condenser 13 Tank 14 Pump 15 Decompression piping 16 Tank 17 valve

C1 Alkaline catalyst CDC Phosgene D2 Neutralized wastewater D3 Aqueous wastewater DPC Diphenyl carbonate E1 Alkaline aqueous solution F Mixed gas PL Phenol s-PL Byproduct phenol X1 Recovered distillation residue

a DPC-containing reaction solution b Dehydrochlorination treatment solution d DPC-containing recovery solution e Neutralization treatment solution f Washing treatment solution g1 First distillation residue g2 Second distillation residue p Distillate

Claims (3)

It has a diphenyl carbonate production process for producing diphenyl carbonate through a reaction process and a distillation process using phenol and a carbonyl compound as raw materials, and an aromatic polycarbonate is produced using diphenyl carbonate and bisphenol A obtained in this diphenyl carbonate production process In the method for producing an aromatic polycarbonate,
The distillation step is performed under reduced pressure, and an ejector using phenol as a drive source is used as the decompression means.   2. The method for producing an aromatic polycarbonate according to claim 1, wherein the phenol used as a drive source of the ejector is a by-product phenol produced as a by-product when the aromatic polycarbonate is produced.   3. The method for producing an aromatic polycarbonate according to claim 1, wherein phenol used as a drive source of the ejector is used as at least a part of a raw material in the diphenyl carbonate production process.

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