JPH06100687A - Production of aromatic polycarbonate - Google Patents

Abstract

PURPOSE:To stabilize the flow rate of an arom. polycarbonate when it is being discharged from a reactor. CONSTITUTION:A concaved part is formed at the bottom of a reactor and an arom. polycarbonate is discharged from the bottom of the concaved part in the process for producing the polycarbonate by melt polycondensing an arom. dihydroxy compd. with a carbonic diester using at least two reactors installed in series.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an aromatic polycarbonate, and more particularly to stabilization of a polymer withdrawal flow rate from a reactor.

[0002]

2. Description of the Related Art Aromatic polycarbonates are widely used because they are excellent in mechanical properties such as impact resistance, heat resistance and transparency. As a method for producing an aromatic polycarbonate, a method in which an aromatic dihydroxy compound such as bisphenol A is directly reacted with phosgene (interfacial method), or an aromatic dihydroxy compound such as bisphenol A and a diaryl carbonate such as diphenyl carbonate are in a molten state A method of transesterification (polycondensation reaction) is known. Current,
The former method is generally used, but the latter method is considered to be promising in the future because it does not use a troublesome compound such as phosgene.

In the latter method, generally, bisphenol A (melting point 156 ° C.) and diphenyl carbonate (melting point 80 ° C.) are heated and melted, and a catalyst is added to a mixed solution of both compounds to cause polycondensation. In a continuous manufacturing process,
The produced polymer is continuously extracted by a pump (for example, a gear pump), supplied to an extruder, and made into chips. However, there is a drawback that the flow rate of the withdrawal by the pump becomes unstable due to the high polymer viscosity in the reactor. As a method for stabilizing the flow rate of polymer withdrawal from the reactor, a device in which a retention pot for the polymer is installed in the pipe between the reactor and the polymer withdrawal pump is used for polymers with relatively low melt viscosity such as polyethylene terephthalate. Is commonly used. However, even when this method was used for producing aromatic polycarbonate, the pumping flow rate could not be stabilized.

[0004]

The process of the present invention aims at stabilizing the polymer withdrawal flow rate from the reactor.

[0005]

The present invention provides a method for producing an aromatic polycarbonate by melt polycondensation of an aromatic dihydroxy compound and a carbonic acid diester using at least two reactors in series. The method is characterized in that a concave recess is provided at the bottom of the polymer, and the polymer is extracted from the bottom of the concave recess.

That is, the inventors of the present invention have the above-mentioned drawback that the flow rate of the polymer is not stable when the polymer is withdrawn from the reactor in the method for producing an aromatic polycarbonate. It was found that the cause was that the gas was entrained in the polymer due to its high viscosity and the pump caused the pump to empty. Especially in a horizontal reactor where the rotation axis of the stirring blade is horizontal, the polymer is scraped up by the blade of the stirrer and entrains gas, and at the same time the bottom of the reactor is emptied temporarily and the gas exits to the suction side of the polymer extraction pump. It is harder to stabilize the flow rate because it entrains. Further, even when using a device in which a retention pot for the polymer is installed in the pipe between the reactor and the polymer extraction pump as described above, the reason why the above defects cannot be removed is that the viscosity of the polymer is high. This is because the gas entrained in the polymer cannot be sufficiently released in the pipe and the retention pot, and the gas is entrained in the pump and the pump cannot perform emptying to stabilize the withdrawal flow rate of the polymer. I found something.

Therefore, by providing a recessed indentation at the bottom of the reactor which is not affected by the above-mentioned agitator and allowing the polymer to stay for a certain period of time, even in the case of high viscosity polymer, the gas temporarily entrapped is sufficiently released. As a result, the method of the present invention capable of stabilizing the flow rate of polymer withdrawal has been completed.

In particular, in the method of producing aromatic polycarbonate pellets by directly feeding the produced aromatic polycarbonate in a molten state to an extruder, the presence of gas in the fed polymer causes frequent strand breakage, which is not preferable. Therefore, at least by providing a concave recess at the bottom of the final reactor, it is possible to sufficiently release the temporarily entrained gas there, and to stably supply the gas-free polymer to the extruder. it can.

Further, by providing the concave recess, even if the liquid level of the polymer in the reactor is lowered to the vicinity of the bottom of the reactor, the flow rate of the polymer withdrawn due to gas entrainment does not change at all.

The concave recessed portion provided at the bottom of the reactor of the present invention is used as a polymer reservoir, and is capable of sufficiently releasing the gas temporarily entrapped without being affected by the above-mentioned effects of the stirrer. If so, there are no particular restrictions on its shape, dimensions, and the like.

The recessed portion may be installed in any reactor, and in the method of producing polycarbonate pellets by directly feeding the produced aromatic polycarbonate in a molten state to the extruder, at least the final reactor is Installed on the bottom.

Further, the reactor having the above-mentioned recessed indentation at the bottom of the reactor may be either a vertical reactor or a horizontal reactor, but preferably a horizontal reaction in which the rotation axis of the stirring blade is horizontal. It is a vessel. The horizontal reactor has, for example, one or more horizontal rotating shafts, and one type of stirring blades such as a disc type, a wheel type, a paddle type, a rod type, and a window frame type is provided on the horizontal rotating shaft. Alternatively, a horizontal type high-viscosity liquid treatment device or the like in which two or more types are combined and at least two or more stages are installed per rotary shaft and the reaction solution is scraped up or spread by the stirring blades to renew the surface of the reaction solution may be used.

The polymer is preferably withdrawn from the bottom of the recessed recess provided in the bottom of the reactor, preferably by a pump, and optionally, immediately after withdrawal, is fed to the extruder. Any known pump can be used as long as it can transfer a polymer, and a gear pump, a screw pump and the like are preferable. Also, the pump is preferably installed at a position as close as possible from the concave recess.

An example of the method for producing a polycarbonate according to the present invention will be described below with reference to FIG.

The stirring tank 4 has a stirring blade mounted on a vertical rotating shaft, and an aromatic dihydroxy compound and a carbonic acid diester are continuously supplied to the stirring blade through pipes 1 and 2, respectively. In the stirred tank atmosphere so that oxygen is substantially absent,
For example, the stirring tank is purged with nitrogen gas. The catalyst is supplied to the stirring tank through the pipe 3 and mixed with the reaction raw material. It is also possible to provide a plurality of stirring tanks in series to form a uniform solution.

The mixed raw materials are supplied to the prepolymerization tank 8 through the pipe 6 by the pump 5. The pre-polymerization tank is equipped with a stirring blade having a vertical rotation axis. The inside of the tank is kept at a reduced pressure by the venting conduit 7 provided at the upper part. The by-produced phenol and a part of the unreacted monomer sucked through the conduit 7 are rectified, the phenol is discharged out of the system, and the unreacted monomer is returned to the polymerization tank. Also, piping 3
It is also possible to supply a further catalyst through ′.

One or more pre-polymerization tanks 8 can be provided in series, and preferably two to four pre-polymerization tanks 8 are provided. The reaction temperature in the first prepolymerization tank is usually 50 to 270 ° C., preferably 150 to 260.
C., and the pressure can be reduced from normal pressure to 6 mmHg, and the lower limit is preferably 400 to 6 mm.
Hg, particularly preferably in the range of 300 to 6 mmHg can be set.

The reaction temperature in the second and subsequent prepolymerization tanks is usually 180 to 300 ° C., preferably 200 to 280.
C., and the pressure is in the range of 1 to 50 mmHg, preferably 1 to 30 mmHg.

The aromatic polycarbonate having a certain degree of polymerization as described above has an intrinsic viscosity [η] measured in a methylene chloride solution at 20 ° C. of 0.05 to 0.5 dl.
/ G, preferably 0.10 to 0.45 dl / g, and more preferably 0.10 to 0.4 dl / g.

Next, the reaction mixture is fed to a horizontal stirring polymerization tank 12
Supply to. This horizontal stirring polymerization tank is the above-mentioned horizontal high-viscosity liquid processing apparatus. The reaction temperature there is usually 240-
320 ° C, preferably in the range of 250-310 ° C,
The pressure is 20 mmHg or less, preferably 10 mmHg
It is the following.

A concave recess 15 is provided at the bottom of the horizontal stirring polymerization tank 12, and the polymer polycondensed in the horizontal stirring polymerization tank is temporarily stored in the concave recess. The viscous polymer was taken out from the recessed portion by the gear pump 13, and the intrinsic viscosity [η] measured in a methylene chloride solution at 20 ° C was 0.20 to 1.0 dl / g, preferably 0.25 to 0. 9 dl / g, more preferably 0.
A polycarbonate is obtained which is 30-0.8 dl / g.
After carrying out a polycondensation reaction in a horizontal stirring polymerization tank, the polymer may be directly supplied in a molten state to an extruder to produce polycarbonate pellets.

The above reactors and reaction conditions are merely examples and are not limiting.

In the present invention, the polymer means a polymer of an aromatic dihydroxy compound and a carbonic acid diester.

The aromatic dihydroxy compound has the following formula [I]:

[0025]

(Where X is

[0026]

Embedded image is —O—, —S—, —SO— or —SO ₂ —, R ₁ and R ₂ are hydrogen atoms or a monovalent hydrocarbon group, and R ₃ is a divalent hydrocarbon group. Is. Further, the aromatic nucleus may have a monovalent hydrocarbon group. ) Is a compound represented by.

As such an aromatic dihydroxy compound,
For example, bis (4-hydroxyphenyl) methane, 1,1
-Bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4
-Hydroxyphenyl) octane, bis (4-hydroxyphenyl) phenylmethane, 2,2-bis (4-hydroxy-1-methylphenyl) propane, 1,1-bis (4-hydroxy-3-t-butylphenyl) Propane, bis (hydroxyaryl) alkanes such as 2,2-bis (4-hydroxy-3-bromophenyl) propane, 1,1-bis (4-hydroxyphenyl) cyclopentane, 1,1-bis (4- Bis (hydroxyaryl) cycloalkanes such as hydroxyphenyl) cyclohexane, dihydroxyaryl ethers such as 4,4′-dihydroxydiphenyl ether and 4,4′-dihydroxy-3,3′-dimethylphenyl ether,
4,4'-dihydroxydiphenyl sulfide, 4,4
Dihydroxydiaryl sulfides such as ′ -dihydroxy-3,3′-dimethyldiphenyl sulfide,
4,4'-dihydroxydiphenyl sulfoxide, 4,
Dihydroxy diaryl sulfoxides such as 4'-dihydroxy-3,3'-dimethylphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfone, 4,
Examples thereof include dihydroxydiarylsulfones such as 4′-dihydroxy-3,3′-dimethyldiphenylsulfone, and 2,2-bis (4-hydroxyphenyl) propane (so-called bisphenol A) is particularly preferable.

The carbonic acid diester is, for example, diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, diethyl carbonate, dimethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate or the like. And diphenyl carbonate is particularly preferable.

The carbonic acid diester as described above may contain a dicarboxylic acid or dicarboxylic acid ester in an amount of preferably 50 mol% or less, more preferably 30 mol% or less. Examples of the dicarboxylic acid or dicarboxylic acid ester include terephthalic acid, isophthalic acid, diphenyl terephthalate, and diphenyl isophthalate. When a dicarboxylic acid or a dicarboxylic acid ester is used in combination with a carbonic acid diester, a polyester polycarbonate is obtained.

The carbonic acid diester is used in an amount of 0.90 to 1.30 mol, preferably 0.95 to 1.20 mol, per 1 mol of the aromatic dihydroxy compound. A compound having three or more functional groups (preferably a phenolic hydroxyl group or a carboxyl group) in one molecule can be further added, preferably 0.001 to 0.03 mol, particularly 0 to 1 mol of the aromatic dihydroxy compound. Used in an amount of 0.001 to 0.01 mol. Examples of such compounds are described in JP-A-4-89824.

The polymerization reaction proceeds in the presence of a catalyst. As the catalyst, any known catalyst can be used.
For example, a catalyst system comprising (a) a nitrogen-containing basic compound and (b) an alkali metal compound or an alkaline earth metal compound described in JP-A-2-124934, or (c) boric acid or boric acid. A catalyst system consisting of esters can be used. It is also possible to use a catalyst system composed of an electron-donating amine compound and potassium borohydride or an alkali metal compound or an alkaline earth metal compound described in JP-A-4-46927 and 4-46928. Also, JP-A-60-51719
A catalyst system composed of a nitrogen-containing basic compound and a boron compound described in the publication can be used.

In the polymerization reaction, various phenols can be used as the terminal blocking agent, and for example, Japanese Patent Laid-Open Publication No. Hei 2
Examples thereof include those described in Japanese Patent Publication No. 175723.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0034]

EXAMPLES In Examples and Comparative Examples, the intrinsic viscosity of polymerization products was measured in methylene chloride at 20 ° C. using an Ubbelohde viscometer.

[0035]

Example 1 The polymerization reactor shown in FIG. 1 was used. There are two pre-polymerization tanks. The respective reaction conditions are as follows.

Pressure (torr) Temperature (° C.) Average residence time (hr) Stirring tank Nitrogen atmosphere 130 2.0 Pre-polymerization tank A 100 210 1.0 1.0 Pre-polymerization tank B 20 240 0.5 0.5 Horizontal stirring polymerization tank 0.15 ~ 1.5 290 0.5 Bisphenol A (Japan GE Plastics Co., Ltd.)
0.44 kmole, diphenyl carbonate (manufactured by Any Co.) 0.46 kmole, tetramethylammonium hydroxide 0.11 mol as a catalyst, sodium hydroxide 0.00044 mol (1 × 10 ⁻⁶ mol / mol-bisphenol) The ratio of A) was supplied to a stirring tank maintained at the above temperature to prepare a uniform solution.

Subsequently, the solution is polycondensed in the prepolymerization tank A and the prepolymerization tank B under the reaction conditions described above, and then supplied to a horizontal stirring polymerization tank having a concave depression at the bottom, and under the reaction conditions described above. Polycondensation was carried out to produce a polycarbonate. The flow rate of the polymer withdrawn from the horizontal stirring polymerization tank was stable.

The intrinsic viscosity of the obtained polycarbonate is
It was 0.50 dl / g in methylene chloride at 20 ° C.

[0039]

Example 2 Polycarbonate was produced using the same equipment as in Example 1 under the same conditions. The polycarbonate was directly fed to the extruder in a molten state from a horizontal stirring polymerization tank by a gear pump to produce polycarbonate pellets.

The feeding stability of the polymer to the extruder was good, and strand breakage did not occur.

[0041]

Comparative Example 1 Polycarbonate was produced under the same conditions as in Example 1 except that a horizontal stirring polymerization tank having no recessed depression at the bottom was used.

The gear pump for polymer withdrawal in the horizontal stirring polymerization tank was frequently evacuated, and the flow rate was unstable. Further, when the polymer was directly supplied to an extruder in a molten state, strand breakage occurred frequently.

As described above, by using the method of the present invention, a polycarbonate having a high intrinsic viscosity can be stably discharged from the horizontal stirring polymerization tank, and the polymer can be directly supplied to the extruder in a molten state. Supply stability is good and strand breakage does not occur.

[0044]

According to the method of the present invention, the polymer can be stably withdrawn from the reactor.

[Brief description of drawings]

FIG. 1 is a flow sheet of the present invention.

[Explanation of symbols]

 1,2,6,10,14. Piping 3,3 '. Catalyst introduction piping 4. Stirring tank 5. Pump 9,13. Gear pump 7,11. Vent conduit 8. Pre-polymerization tank 12. Horizontal stirring polymerization tank 15. Recessed indentation m ≧ 1

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kotaro Kishimura 6-1-2 Waki, Waki-machi, Kuga-gun, Yamaguchi Japan GE Plastics Co., Ltd.

Claims (3)

[Claims] 1. A method for producing an aromatic polycarbonate by melt polycondensation of an aromatic dihydroxy compound and a carbonic acid diester using at least two reactors in series, wherein a recessed recess is provided at the bottom of the reactor. A method of extracting polymer from the bottom of the recess. 2. The method according to claim 1, wherein the reactor provided with the concave recess is a horizontal reactor in which a rotation axis of a stirring blade is horizontal. 3. An aromatic polycarbonate is produced by melt polycondensation of an aromatic dihydroxy compound and a carbonic acid diester using at least two reactors in series, and then a polymer in a molten state is directly extruded from the reactor. In the method for producing aromatic polycarbonate pellets by supplying to a machine, the final reactor is a horizontal reactor in which the rotation axis of the stirring blades is horizontal, and at least the bottom portion of the final reactor is provided with a concave indentation, A method characterized in that the polymer is withdrawn from the bottom of the recess and the polymer withdrawn from the recess of the bottom of the final reactor is directly fed to the extruder.