JP5464166B2 - Method for purifying carbonic acid diester and method for producing polycarbonate resin - Google Patents

Description

  The present invention relates to a carbonic acid diester composition and the like, and more particularly, to a carbonic acid diester composition used for production of a polycarbonate resin.

  Conventionally, as a method for producing an aromatic polycarbonate resin, an interface method in which bisphenols and phosgene are directly reacted and a melting method in which a bisphenol and a carbonic acid diester are polycondensed by an ester exchange reaction are known. Among them, the melting method by transesterification has an advantage that an aromatic polycarbonate resin can be produced at a lower cost than the interface method.

  In the melting method, a large amount of by-products such as phenol is produced during the transesterification reaction between the bisphenols and the carbonic acid diester. Moreover, it is necessary to recover unreacted carbonic acid diester by a predetermined operation. For this reason, Patent Document 1 reports a method for recovering unreacted carbonic acid diester with high purity.

JP 2002-226573 A

By the way, in the melting method, in addition to byproduct phenol, for example, alkylphenol such as isopropenylphenol is also produced as a byproduct. Such isopropenylphenol is likely to cause the color tone of the polycarbonate resin to deteriorate, so it needs to be reduced.
Further, since the unreacted carbonic acid diester is distilled together with by-product phenol in the production process of the polycarbonate resin, it is necessary to purify it efficiently and to circulate and supply it to the production process of the polycarbonate resin.

The present invention has been made to solve the above-described problems.
That is, an object of the present invention is to provide a method for producing a polycarbonate resin that efficiently recycles unreacted carbonic acid diesters in the production process of polycarbonate resin, reduces consumption of raw materials and waste, and obtains a polycarbonate resin with good color tone. It is to provide.

Thus, according to the present invention, the following (1) to (13) are provided.
(1) In a polycarbonate production process by transesterification of a dihydroxy compound and a carbonic acid diester, a distillate containing mainly a by-product monohydroxy compound is separated from the polycarbonate production process by distillation, and a carbon number of 1 to A carbonic acid diester composition, wherein the content of an alkylphenol having an alkyl group having 5 carbon atoms is 100 ppm by weight or less.
(2) The carbonic acid diester composition as described in (1) above, wherein the alkylphenol is isopropenylphenol.

(3) A polycarbonate production process for producing a polycarbonate by a transesterification reaction between a dihydroxy compound and a carbonic acid diester, and a by-product mono product that distills a distillate mainly containing a by-product monohydroxy compound by-produced in the polycarbonate production process. A hydroxy compound distillation step, wherein the content of the alkylphenol separated from the distillate in the by-product monohydroxy compound distillation step and having an alkyl group having 1 to 5 carbon atoms is 100 ppm by weight or less A method for producing a polycarbonate resin, comprising recycling a carbonic acid diester to the polycarbonate production process.
(4) A mixture of the carbonic acid diester composition recycled to the polycarbonate production process and a carbonic acid diester produced using a monohydroxy compound and a carbonyl compound is used as a raw material for the polycarbonate production process. The manufacturing method of the polycarbonate resin as described in said (3).
(5) The method for producing a polycarbonate resin according to the above (4), wherein the mixture has a content of alkylphenol having an alkyl group having 1 to 5 carbon atoms of 30 ppm by weight or less.

(6) Polycarbonate production process by transesterification reaction of dihydroxy compound and carbonic acid diester, and by-product monohydroxy compound distillation process of distilling distillate mainly containing by-product monohydroxy compound by-produced in the polycarbonate production process And the by-product monohydroxy compound distillation step includes a first distillation step of distilling the by-product monohydroxy compound, and distilling a carbonic acid diester contained in the distillation residue obtained in the first distillation step. A second distilling step, wherein in the second distilling step, 90% by weight of the amount of the distillation residue obtained in the first distilling step is distilled from the top of the distillation column. Purification method.
(7) In the second distillation step, 5% by weight of the distillation residue amount in the first distillation step is withdrawn from the top of the distillation column, and 10% by weight is withdrawn from the bottom of the distillation column, and the remainder is purified product. The method for purifying a carbonic acid diester as described in (6) above.
(8) The method for purifying a carbonic acid diester according to (6), wherein a basic substance is added in the second distillation step.

(9) The basic substance is at least one selected from alkali metals, alkaline earth metals, and / or oxides, hydroxides, and carbonates thereof. Of carbonic acid diester.
(10) The method for purifying a carbonic acid diester according to (8) or (9) above, wherein the basic substance is sodium hydroxide or potassium hydroxide.
(11) The method for purifying a carbonic acid diester according to any one of (6) to (10), wherein the dihydroxy compound is a bisphenol.

(12) Recycling the carbonic acid diester obtained by the carbonic acid diester purification method according to any one of (6) to (11) above to a polycarbonate production process by an ester exchange reaction between a dihydroxy compound and a carbonic acid diester. A process for producing a polycarbonate resin characterized by the above.
(13) A mixture of a carbonic acid diester obtained by the carbonic acid diester purification method according to any one of (6) to (11) above and a carbonic acid diester produced from a monohydroxy compound and a carbonyl compound, A method for producing a polycarbonate resin, characterized in that the polycarbonate resin is used as a raw material in a polycarbonate production process by transesterification of a diester with a carbonic acid diester.

  According to the present invention, an unreacted carbonic acid diester in a polycarbonate resin production process can be efficiently recycled, consumption of raw materials and waste can be reduced, and a polycarbonate resin having a good color tone can be obtained.

It is a manufacturing process flowchart of a polycarbonate manufacturing method. It is another manufacturing-process flowchart of a polycarbonate manufacturing method. It is a figure which shows the example of a manufacturing apparatus of a polycarbonate.

  Hereinafter, modes for carrying out the present invention (hereinafter, embodiments of the present invention) will be described in detail. 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)
The polycarbonate resin used in the present embodiment is produced by a transesterification reaction between a dihydroxy compound and a carbonic acid diester.
Here, an aromatic dihydroxy compound is mentioned as a preferable compound as a dihydroxy compound. The polycarbonate resin is preferably an aromatic polycarbonate resin produced by melt polycondensation based on a transesterification reaction between an aromatic dihydroxy compound and a carbonic acid diester.
Hereinafter, a method (melting method) for producing an aromatic polycarbonate resin by continuously performing a melt polycondensation reaction in the presence of an ester exchange catalyst using an aromatic dihydroxy compound and a carbonic acid diester as raw materials 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 Examples thereof include a group and 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 with respect to the aromatic 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.

(Manufacturing process of carbonic acid diester)
The above-mentioned carbonic acid diester is usually produced by a synthetic reaction using an aromatic monohydroxy compound such as phenol and a carbonyl compound as raw materials in the presence of an alkaline catalyst.
The carbonyl compound is not particularly limited as long as it forms a carbonyl group of a carbonic acid diester, and examples thereof include carbonyl chloride (phosgene), carbon monoxide, and dialkyl carbonate. Of these, carbonyl chloride (phosgene) is preferred.
Moreover, pyridine etc. are mentioned as an alkaline catalyst.

The conditions for the synthesis reaction are not particularly limited, but when phenol is used as the aromatic monohydroxy compound, it is preferably 50 ° C. to 180 ° C. at which phenol is in a molten state under normal pressure. Moreover, the mixing ratio (molar ratio) of the aromatic monohydroxy compound and the carbonyl compound is usually preferably 0.40 mol to 0.49 mol with respect to 1 mol of the aromatic monohydroxy compound.
As described above, the carbonic acid diester used in the present embodiment can be subjected to dehydrochlorination treatment and removal after the reaction step of carrying out the synthesis reaction in the presence of an alkaline catalyst using aromatic monohydroxy compound and carbonyl compound as raw materials. It is produced through a washing step of neutralizing a non-hydrochloric acid with an alkaline aqueous solution and washing with water, and further a distillation step.

(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, for example, basic compounds such as alkali metal compounds, beryllium compounds or magnesium compounds, alkaline earth metal compounds, basic boron compounds, basic phosphorus compounds, basic ammonium compounds, and amine compounds can be used.
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 the beryllium compound or magnesium compound include inorganic compounds such as beryllium or magnesium hydroxide and carbonates; salts of beryllium or magnesium with alcohols, phenols, and organic carboxylic acids.

  Examples of the alkaline earth metal compound include inorganic alkaline earth metal compounds such as alkaline earth metal hydroxides and carbonates; alkaline earth metal alcohols, phenols, salts with organic carboxylic acids, and the like. It is done. 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 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, a method for producing a polycarbonate to which the present embodiment is applied will be described by taking an example of a method for producing an aromatic polycarbonate.
FIG. 1 is a manufacturing process flow chart of a polycarbonate manufacturing method. Here, a process flow in the case where a polycarbonate manufacturing process for manufacturing a polycarbonate resin and a carbonic acid diester manufacturing process for manufacturing a raw material carbonic acid diester are provided together will be described.

As shown in FIG. 1, in a predetermined aromatic dihydroxy compound manufacturing process, an aromatic dihydroxy compound used as a raw material for an aromatic polycarbonate is manufactured (step 101: indicated as S101 in FIG. 1, hereinafter the same). . Moreover, in this Embodiment, a carbonic acid diester compound is manufactured by a predetermined carbonic acid diester manufacturing process (step 102), and it refine | purifies through a predetermined carbonic acid diester refinement | purification process (step 103).
Next, an aromatic polycarbonate is produced using these raw materials (polycarbonate production process: step 104).

In the production of aromatic polycarbonate, a raw material mixed melt of raw material aromatic dihydroxy compound and carbonic acid diester compound is prepared (primary process), and these compounds are melted in the presence of a transesterification catalyst in a molten state. It is carried out by carrying out polycondensation reaction in multiple stages using a reactor (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. The reactor uses a plurality of vertical stirring reactors followed by at least one horizontal stirring reactor. Usually, these reactors are installed in series and processed continuously.
After the polycondensation step, stop the reaction, devolatilize and remove unreacted raw materials and reaction by-products in the polymerization reaction solution, add a heat stabilizer, mold release agent, colorant, etc., aromatic polycarbonate You may add suitably the process etc. which form in the pellet of a predetermined particle size.
Next, each process of a polycarbonate manufacturing process is demonstrated.

(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 raw material mixed melt. 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 adjusts so that it may become a ratio of 1.02 mol-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 order to prevent quality degradation such as hue of the aromatic polycarbonate to be produced, it is preferable to set a low temperature and a short residence time as much as possible.

When the polycondensation step is performed in a multistage manner, usually, a plurality of reactors including a vertical stirring 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, or the like is used.

  Examples of the types of the stirring blades of the vertical stirring reactor include 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 blend blades (manufactured by Sumitomo Heavy Industries, Ltd.), helical ribbon blades, twisted lattice blades (manufactured by Hitachi, Ltd.), and the like.

  Moreover, a horizontal stirring reactor means that the rotating shaft of a stirring blade is a horizontal type (horizontal direction). As a stirring blade of a horizontal stirring reactor, for example, a uniaxial 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 biaxial stirring blades such as spectacle blades and lattice blades (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 nature of the water used for dissolving the catalyst is 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 preferable.

(By-product monohydroxy compound distillation process)
Next, the byproduct monohydroxy compound distillation step will be described.
As the polycondensation reaction proceeds in the polycarbonate production process described above, the by-product monohydroxy compound is removed from the system.
In the present embodiment, the by-product monohydroxy compound is first extracted from the top of the distillation column in the first distillation step (step 105), and the carbonic acid diester production step and / or the aromatic dihydroxy compound. Recycle to the manufacturing process (step 106). Further, the high boiling point component separated from the monohydroxy compound is extracted as a residual component in the distillation column and sent to the second distillation step.
In the second distillation step (step 107), first, less than 5% by weight (initial distillation) of the high-boiling fraction separated in the first distillation step is extracted. Subsequently, 5% to 90% by weight of a high-boiling fraction is distilled, and a carbonic acid diester having an alkylphenol having an alkyl group having 1 to 5 carbon atoms is not more than 100 ppm by weight from the top of the distillation column. Extract. The remainder is treated as a distillation residue. In addition, this distillation process may be a batch type or a continuous type.

The carbonic acid diester obtained in the second distillation process is circulated and supplied to the carbonic acid diester purification process (carbonic acid diester recycling process: step 108), and is used as a raw material for the polycarbonate production process through a predetermined distillation operation.
Here, the conditions for the first distillation step are not particularly limited. Usually, when the carbonic acid diester is diphenyl carbonate, the column top temperature is 100 ° C. to 150 ° C., and the pressure is 100 Torr to 300 Torr. The conditions for the second distillation step are not particularly limited, but are usually a tower top temperature of 80 ° C to 120 ° C and a pressure of 30 Torr to 80 Torr.

Thus, by removing less than 5% by weight of distillate in the second distillation step, it is possible to remove most of the components other than the carbonic acid diester contained in the high-boiling product obtained in the first distillation step. it can.
Examples of components other than the carbonic acid diester contained in the high-boiling product obtained in the first distillation step include phenol and alkylphenol having an alkyl group having 1 to 5 carbon atoms. Specific examples of the alkylphenol include isopropenylphenol.

In the present embodiment, the content of the alkylphenol having an alkyl group having 1 to 5 carbon atoms is 100 ppm by weight or less, preferably 50 ppm by weight or less, more preferably 30 ppm by weight or less by the distillation operation described above. Certain carbonic acid diesters can be obtained.
In particular, by using a carbonic acid diester having a content of isopropenylphenol reduced to 100 ppm by weight or less as a raw material in the polycarbonate production process, it is possible to prevent the color tone of the obtained polycarbonate resin from being lowered.

Next, the process flow when the polycarbonate production process and the carbonic acid diester production process are not provided will be described.
FIG. 2 is a flowchart of another manufacturing process of the polycarbonate manufacturing method. As shown in FIG. 2, the aromatic dihydroxy compound is produced in a predetermined production process (aromatic dihydroxy compound production process) as described above (step 201: indicated as S201 in FIG. 2, the same applies hereinafter). . Moreover, in this Embodiment, a carbonic acid diester compound is manufactured by another carbonic acid diester manufacturing process (step 202). Next, an aromatic polycarbonate is produced using these raw materials (polycarbonate production process: step 203).
On the other hand, the by-product monohydroxy compound is removed out of the system as the polycondensation reaction proceeds. In the byproduct monohydroxy compound distillation step, the byproduct monohydroxy compound is extracted from the top of the distillation column in the first distillation step (step 204), and the aromatic dihydroxy compound production step and / or other carbonic acid diester production is produced. Recycle to process (step 205). Moreover, the high boiling point component separated from the monohydroxy compound is sent to the second distillation step.
In the second distillation step (step 206), first, less than 5% by weight (initial distillation) of the high-boiling fraction separated in the first distillation step is extracted. Subsequently, 5% to 90% by weight of a high-boiling fraction is distilled, and a carbonic acid diester having an alkylphenol having an alkyl group having 1 to 5 carbon atoms is not more than 100 ppm by weight from the top of the distillation column. Extract. The remainder is treated as a distillation residue. In addition, this distillation process may be a batch type or a continuous type.

In the present embodiment, the carbonic acid diester extracted from the top of the distillation column in the second distillation process is circulated and supplied as a raw material in the above-described polycarbonate production process (carbonic acid diester recycling process: step 207).
A mixture of such a carbonic acid diester to be recycled and a synthetic carbonic acid diester previously produced in another carbonic acid diester production process can be used in the polycarbonate production process as a raw material in which the content of components other than the carbonic acid diester is greatly reduced. it can.
At this time, the content of the alkylphenol contained in the mixture of the recycled carbonic acid diester used in the polycarbonate production process and the synthetic carbonic acid diester previously produced in the other carbonic acid diester production process is not particularly limited, but is 30% by weight with respect to the carbonic acid diester. ppm or less, preferably 20 ppm by weight or less.
In particular, by using a carbonic acid diester mixture in which the content of isopropenylphenol is reduced to 30 ppm by weight or less as a raw material, it is possible to prevent the color tone of the polycarbonate from being lowered.

In the present embodiment, it is preferable to add a basic substance in the byproduct monohydroxy compound distillation step to separate the byproduct monohydroxy compound and the carbonic acid diester.
Here, although it does not specifically limit as a basic substance, For example, an alkali metal, alkaline-earth metal, these oxides, hydroxide, carbonate etc. are mentioned. Among these, sodium hydroxide and potassium hydroxide are preferable. Each of these basic substances can be used alone, or a plurality of basic substances can be used.
The addition amount of the basic substance in the by-product monohydroxy compound distillation step is not particularly limited, but is usually 0.1 ppm to 1% by weight, preferably 1 ppm to 1000 ppm, more preferably 10 ppm by weight. -200 ppm by weight.

(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. 3 is a diagram showing an example of an apparatus for producing an aromatic polycarbonate. In the production apparatus shown in FIG. 3, the aromatic polycarbonate is 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 manufactures through a condensation process.
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) ), An aromatic polycarbonate pellet is formed through a step (not shown) of forming the aromatic polycarbonate into a pellet having a predetermined particle diameter.

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.
Further, diphenyl carbonate (hereinafter sometimes referred to as DPC), which is a carbonic acid diester, is supplied in a molten state from the DPC supply port 1a-1 to the first raw material mixing tank 2a, and from the BPA supply port 1b. Then, 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, and the fourth horizontal reactor 9a is stirred. Wings 10a are provided.
The four reactors are equipped with distillation tubes 8a, 8b, 8c, and 8d for discharging by-products generated by the polycondensation reaction.
Further, the distillation of the first distillation column 91a, the second distillation column 91b, and the second distillation column 91b for purifying by-product phenol etc. distilled through the distillation pipes 8a, 8b, 8c, 8d. A third distillation column 91c for distilling the residual components in the column is provided.

  In the apparatus for producing aromatic polycarbonate shown in FIG. 3, a DPC melt prepared at a predetermined temperature in a nitrogen gas atmosphere and a BPA powder weighed in a nitrogen gas atmosphere are supplied to a DPC supply port 1a-1 and a BPA supply, respectively. It is continuously supplied from the 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), a rotating speed of a stirring blade is maintained at 160 rpm, and 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.

  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 to perform polycondensation. Allow the reaction to proceed. 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 distilled from the distillation pipes 8b, 8c and 8d.

In the present embodiment, phenol produced as a by-product in the polycondensation reaction is distilled from the distillation pipes 8b, 8c, and 8d attached to the first vertical reactor 6a to the fourth horizontal reactor 9a, respectively.
In the first distillation step, by-product phenol is separated from main distillate (phenol) and high boiling point (substantially DPC) using two distillation columns (first distillation column 91a and second distillation column 91b). To do. That is, byproduct phenol is first extracted from the top piping 92a in the first distillation column 91a. Next, the remaining fraction extracted from the first distillation column 91a is continuously sent to the second distillation column 91b via the column bottom pipe 93a, and is sent from the column top pipe 92b of the second distillation column 91b. (Phenol) is extracted, and a high boiling point component (approximately DPC) is extracted from the tower bottom pipe 93b as a residual component in the distillation column.

Next, in the second distillation step, the carbonic acid diester (DPC) is distilled using two distillation columns (the third distillation column 91c and the fourth distillation column 91d). That is, first, in the third distillation column 91c, less than 5% by weight (initial distillation) of the high boiling point component (approximately DPC) extracted from the bottom piping 93b of the second distillation column 91b is extracted from the column top piping 92c.
Subsequently, in the fourth distillation column 91d, 5% by weight to 90% by weight of the high boiling point sent via the tower bottom pipe 93c is distilled, and the alkyl having 1 to 5 carbon atoms is distilled from the tower top pipe 92d. A carbonic acid diester having a content of alkylphenol having a group of 100 ppm by weight or less is extracted. The remainder is discharged as a distillation residue from the tower bottom pipe 93d. Carbonic acid diester (DPC) distilled from the top of the fourth distillation column 91d is circulated and supplied to the first raw material mixing tank 2a via the DPC supply port 1a-1 by the tower top pipe 92d.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples, unless the summary is exceeded. In addition, the physical property of the obtained polycarbonate resin is measured by the following method.
(1) Viscosity average molecular weight (Mv)
A polycarbonate resin is dissolved in dichloromethane to prepare a solution having a concentration (C) of 600 g / L. Next, using a Ubbelohde capillary viscometer, the flow rate (t ₀ ) of the solvent (dichloromethane) and the flow rate (t) of the sample solution are measured in a constant temperature water bath set at a temperature of 20 ° C. To determine the viscosity average molecular weight (Mv).
η _sp = (t / t ₀ ) −1
a = 0.28 × η _sp +1
b = 10 × (η _sp / C)
[Η] = b / a
Mv = 51400 × [η] exp 1.205

(2) Measurement of initial hue (YI) A polycarbonate resin was dried at 120 ° C. for 6 hours under a nitrogen atmosphere, and then 3 mm thick injection prepared at 360 ° C. by an injection molding machine (J-100, manufactured by Nippon Steel). About a molded piece, a YI value is measured using a color tester (SC-1-CH manufactured by Suga Test Instruments Co., Ltd.). The larger the YI value, the more colored it is.

(3) Amount of isopropenylphenol (IPP) The amount of isopropenylphenol (IPP) contained in the diphenyl carbonate composition is quantitatively analyzed by liquid chromatography and expressed as a weight ratio to the diphenyl carbonate composition.

(4) Operation of polycarbonate resin production apparatus In the production apparatus shown in Fig. 3, diphenyl carbonate (DPC) and bisphenol A (BPA) are melt-mixed in a nitrogen gas atmosphere at a (DPC / BPA) 0.977 weight ratio. A mixture is obtained. Next, this raw material mixture is continuously supplied into the first vertical reactor 6a controlled at 210 ° C. and 100 Torr under a nitrogen atmosphere, and provided in the polymer discharge line at the bottom of the tank so that the average residence time is 60 minutes. The liquid level is kept constant while controlling the valve opening.
At the same time as the supply of the raw material mixture into the first vertical reactor 6a is started, an aqueous cesium carbonate solution is continuously supplied as a catalyst at a flow rate of 0.5 × 10 ⁻⁶ mol to 1 mol of bisphenol A.

The polymerization reaction liquid discharged from the bottom of the first vertical reactor 6a is successively continuously supplied to the second vertical reactor 6b, the third vertical reactor 6c, and the fourth horizontal reactor 9a. During the polymerization reaction, the liquid level is controlled so that the average residence time of each reactor is 60 minutes, and at the same time, the by-produced phenol is distilled off.
The gas evaporating from the reactor is condensed and liquefied by a multistage condenser, a part is refluxed to each reactor, and the rest is recovered in a byproduct phenol tank. The polymerization conditions for each reactor are as follows.
(First vertical reactor 6a) 210 ° C., 100 Torr
(Second vertical reactor 6b) 240 ° C., 15 Torr
(Third vertical reactor 6c) 260 ° C., 0.5 Torr
(Fourth horizontal reactor 9a) 280 ° C., 0.5 Torr

The molten polymer extracted from the bottom of the fourth horizontal reactor 9a was introduced into a twin-screw extruder (Kobe Steel Co., Ltd., screw diameter 0.046 m, L / D = 40.2). Pelletize while continuously adding 5 ppm by weight of butyl p-toluenesulfonate.
The resulting polycarbonate resin has a viscosity average molecular weight Mv of 21,000 and an initial YI of 1.7.

The by-product phenol recovered in the polycarbonate resin production process described above is removed from the low-boiling components (mainly water) in the first distillation column 91a (top temperature 140 ° C., pressure 200 Torr), and then the second distillation column 91b ( Phenol is extracted from the top of the column at a column top temperature of 105 ° C. and a pressure of 50 Torr) to obtain a distillation column residual component.
The composition of the distillation column residual component is 1.9% by weight of phenol, 1.3% by weight of bisphenol A, 90.4% by weight of diphenyl carbonate, and 6.4% by weight of other components.

( Reference Example 1)
In the above-described polycarbonate resin production process, about 5,300 g of the distillation column residual component obtained in the second distillation column 91b is distilled with a theoretical plate number of 8 plates filled with Sulzer Packing (manufactured by Sumitomo Heavy Industries, Ltd.). Charge to the tower and perform distillation purification in batch.
In distillation purification, the temperature of the heating medium is gradually increased under the conditions of a vacuum degree of 20 Torr to 15 Torr and a reflux ratio of 1. 30% (1,500 g) of the total weight is taken from the initial distillate.
The diphenyl carbonate purity in this fractionated distillate is 87.44%, and isopropenylphenol is 36 ppm by weight.

The above-mentioned distillate (diphenyl carbonate 87.44%, isopropenyl phenol 36 wt ppm) and diphenyl carbonate flakes (manufactured by Mitsubishi Chemical Corporation) are mixed to prepare a DPC mixture having a weight ratio of 45/55. . 30.7 mol of this DPC mixture and an aqueous cesium carbonate solution (catalyst: cesium carbonate 0.5 (μmol / bisphenol A-mol)) were supplied to a 40 L first reactor controlled at 100 ° C., and then bisphenol A ( 29.3 mol of Mitsubishi Chemical Corporation) is supplied.
The operation of bringing the inside of the 40 L first reactor to 10 torr and then bringing it to atmospheric pressure with nitrogen is repeated 5 times to replace the inside with nitrogen. Next, the temperature is raised through a heating medium having a temperature of 230 ° C. to dissolve the above-mentioned DPC mixture, and then stirred at 300 rpm. While maintaining the internal temperature at 220 ° C., the pressure in the 40 L first reactor is increased over 40 minutes. Is reduced from 760 torr to 100 torr.

Subsequently, the oligomerization reaction is performed for 80 minutes while distilling off phenol while maintaining the pressure in the 40 L first reactor at 100 torr. After completion of the oligomerization, the pressure in the system is restored to 0.2 MPa with nitrogen, and this oligomer is pumped to a 40 L second reactor (atmospheric pressure) controlled at 300 ° C.
Subsequently, the inside of the 40L second reactor is released to atmospheric pressure, and the inside of the system is decompressed while stirring at 38 rpm. After the pressure in the 40 L second reactor reaches 0.5 torr, a condensation reaction is carried out for 90 minutes while maintaining 0.5 torr to carry out a polymerization reaction. The final internal temperature in the 40L second reactor is 280 ° C.
After the completion of the polymerization reaction, the pressure in the second reactor of 40 L is restored with nitrogen, and the polycarbonate polymer is extracted in a strand form from the bottom of the tank and pelletized with a rotary cutter.
The resulting polycarbonate has a viscosity average molecular weight Mv of 20,700 and an initial YI of 1.83.

( Reference Example 2)
In Reference Example 1, batch distillation purification of the residual components in the kettle was performed, and 30% to 85% of the total weight was fractionated from the initial distillate. Otherwise, the operation was performed under the same conditions as in Reference Example 1, To manufacture.

(Example 3)
In Reference Example 1, 13 mL of 1N sodium hydroxide aqueous solution was supplied to the top of the distillation column in the total reflux state, and the batch distillation purification of the distillation column kettle residue was performed by performing the same operation as in Reference Example 1 except for the following. The fraction from the initial distillate to 30% (1,500 g) of the total weight is fractionated.
The diphenyl carbonate purity of this fractionated distillate is 87.01%, and isopropenylphenol is not detected. A polycarbonate is produced in the same manner as in Reference Example 1 using this diphenyl carbonate.
The resulting polycarbonate has a viscosity average molecular weight Mv of 21,400 and YI of 1.76.

Example 4
In Reference Example 1, 13 mL of 1N sodium hydroxide aqueous solution was supplied to the top of the distillation column in the total reflux state, and the batch distillation purification of the distillation column kettle residue was performed by performing the same operation as in Reference Example 1 except for the following. A distillate from the initial distillate to 87% of the total weight is collected, and other operations are performed under the same conditions as in Reference Example 1 to produce polycarbonate.
Table 1 shows the amount of isopropenylphenol (IPP) in diphenyl carbonate (DPC) among the results of Reference Examples 1 to 2 and Examples 3 to 4.

  From the results shown in Table 1, the polycarbonate resin obtained from diphenyl carbonate (DPC), which is separated from by-product phenol and has an isopropenyl phenol (IPP) content of 100 ppm by weight or less, has an initial hue (YI) value. Is small and it can be seen that the color tone is good.

(Comparative Examples 1 to 6)
In Reference Example 1, 1N sodium hydroxide aqueous solution was not supplied in the total reflux state, and the batch distillation purification of the distillation column kettle was performed by performing the same operation as in Reference Example 1 except that, and from the initial distillate. Each distillate shown in Table 2 is collected.
This diphenyl carbonate and diphenyl carbonate obtained in advance by another diphenyl carbonate purification step are mixed at a ratio shown in Table 2, and a polycarbonate is produced in the same manner as in Reference Example 1 except that.
Table 2 shows the amount of isopropenylphenol (IPP) in diphenyl carbonate (DPC) in Comparative Examples 1 to 6.

  From the results shown in Table 2, diphenyl carbonate (DPC) separated from by-product phenol and having an isopropenyl phenol (IPP) content of more than 100 ppm by weight, and diphenyl carbonate previously obtained by another diphenyl carbonate purification step, It can be seen that the polycarbonate resin obtained from the above mixture has a large initial hue (YI) value and poor color tone.

As described above in detail, in the present embodiment, it is understood that a polycarbonate resin having a good color tone can be obtained by efficiently recycling the unreacted carbonic acid diester.
The polycarbonate resin obtained in the present embodiment is useful as a resin agent used for, for example, an optical disk substrate, a transport container for precision electronic members of ICs and LEDs, a housing for electronic devices, and the like.

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, 91a ... 1st distillation column, 91b ... 2nd distillation column, 91c ... 3rd distillation column, 91d ... 4th distillation column

Claims (8)

Polycarbonate production process by transesterification of dihydroxy compound and carbonic acid diester;
A by-product monohydroxy compound distillation step for distilling a distillate mainly containing a by-product monohydroxy compound by-produced in the polycarbonate production process,
The by-product monohydroxy compound distillation step includes:
A first distillation step of distilling the by-product monohydroxy compound;
A second distillation step of distilling the carbonic acid diester contained in the distillation residue obtained in the first distillation step,
In the second distillation step, a basic substance is added, by distillation of the 5 wt% amount to 90 wt% of the said distillation residual amount obtained in the first distillation step from the top of the distillation column, 1 carbon atoms A method for purifying a carbonic acid diester comprising obtaining a carbonic acid diester having a content of alkylphenol having an alkyl group having 5 carbon atoms of 100 ppm by weight or less . 2. The method for purifying a carbonic acid diester according to claim 1, wherein an amount of the basic substance added in the second distillation step is 0.1 wt ppm to 1 wt%. The carbonic acid according to claim 1 or 2 , wherein the basic substance is at least one selected from alkali metals, alkaline earth metals, and / or oxides, hydroxides, and carbonates thereof. Diester purification method. The method for purifying a carbonic acid diester according to any one of claims 1 to 3 , wherein the basic substance is sodium hydroxide or potassium hydroxide. Wherein in the second distillation step, the purification process of the carbonic acid diester of claim 1 to 4, characterized in that to leave vent from the top of the distillation column less than 5% by weight of the distillation residual amount of the first distillation step. The method for purifying a carbonic acid diester according to any one of claims 1 to 5 , wherein the dihydroxy compound is a bisphenol. A polycarbonate resin obtained by recycling the carbonic acid diester according to any one of claims 1 to 6 to a polycarbonate production process by transesterification of a dihydroxy compound and a carbonic acid diester. Production method. Transesterification of a mixture of a carbonic acid diester obtained by the method for purifying a carbonic acid diester according to any one of claims 1 to 6 and a carbonic acid diester produced from a monohydroxy compound and a carbonyl compound, with a dihydroxy compound and a carbonic acid diester A method for producing a polycarbonate resin, which is used as a raw material for a polycarbonate production process by reaction.

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