JP3251346B2 - Manufacturing method of aromatic polycarbonate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an aromatic polycarbonate.

[0002]

2. Description of the Related Art Aromatic polycarbonates are widely used because they have excellent mechanical properties such as impact resistance, and also have excellent 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 ester exchange between an aromatic dihydroxy compound such as bisphenol A and a carbonic acid diester such as diphenyl carbonate is used. A method of performing a reaction (polycondensation reaction) and the like are known. The former method is currently generally practiced, but the latter method is considered to be promising because it does not use cumbersome compounds such as phosgene.

[0003] Generally, bisphenol A (melting point 156)
C.) and diphenyl carbonate (melting point 80 ° C.) separately or mixed and heated and melted. After adding a catalyst to a mixed solution of both compounds, the mixture is heated to the reaction temperature and polycondensed in a reactor.

[0004] As a method for keeping the degree of polymerization of the aromatic polycarbonate formed in the polycondensation constant, sampling is performed at predetermined time intervals at outlets of each of the reactors arranged in multiple stages, the viscosity is measured, and the viscosity is measured. A method of appropriately changing the temperature or pressure of each reactor to keep the temperature constant has been performed.

However, the above method is effective when the polymerization rate is relatively low, but the free surface area of the polymer,
In a reactor in which the polymerization rate can be considerably increased by the effective free surface renewal or the like, the following control method has insufficient followability, and it is difficult to produce a product having a uniform molecular weight.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a method for producing an aromatic polycarbonate having a uniform molecular weight.

[0007]

SUMMARY OF THE INVENTION The present invention provides a method for producing an aromatic polycarbonate by melt-polycondensing an aromatic dihydroxy compound and a carbonic acid diester using at least two reactors in series. A viscometer is provided at the reactor outlet to measure the viscosity of the polymer, and the temperature and / or pressure of the reactor are automatically controlled by changing the temperature and / or pressure according to a pre-installed program so that the viscosity approaches the target viscosity. It is a method characterized by the following.

[0008] The process of the present invention regulates the temperature and / or pressure at the reactor based on the viscosity of the polymer at the reactor outlet. That is, focusing on the fact that there is a certain relationship between the viscosity and the molecular weight of the polymer, and by rapidly measuring the viscosity online, the temperature and / or pressure of the reactor are automatically and immediately controlled to reduce the viscosity. By keeping it constant, the molecular weight of the polymer is made uniform.

As described above, according to the method of the present invention, the polymerization temperature and / or pressure can be automatically and rapidly controlled in accordance with the viscosity of the polymer, that is, the molecular weight of the polymer, and the molecular weight of the aromatic polycarbonate to be produced can be controlled automatically. Control can be performed stably with high accuracy.

Here, the viscosity and the molecular weight of the aromatic polycarbonate which is a polymer have a substantially linear relationship. Therefore, by continuously measuring the viscosity, the molecular weight of the produced aromatic polycarbonate can be continuously known. The molecular weight of the polycarbonate is
It can be controlled by the polymerization conditions in the reactor, ie, the temperature and / or pressure. FIG. 1 shows the relationship between temperature or pressure and the molecular weight of the generated aromatic polycarbonate.

In the present invention, by incorporating a program in which the above relationship is expressed in a computer in advance and automatically controlling the temperature and / or pressure of the reactor using the viscosity measured online, the desired target viscosity is obtained. Can be approached.

The viscometer used in the present invention may be any viscometer that is a commonly used online viscometer. The viscometer is installed at least at the outlet of the final reactor. Preferably, it is installed at the outlet of each reactor, but it is not necessary to install it in all reactors. For example, by installing a viscometer only at the outlet of the final reactor, and by automatically controlling the temperature and / or pressure of the final reactor or a further upstream reactor based on the viscosity, the molecular weight of the polymer is made uniform. be able to.

The automatic control according to the present invention can be used not only for controlling the molecular weight in a steady state, but also for controlling the start-up from the start-up to the steady state quickly.

As the reactor used in the present invention, any known reactor can be used. The reactor may be a continuous type or a semi-continuous type, but a continuous type is preferred. In general, different stirring modes of the reactor are used for the pre-polymerization stage where the viscosity of the reaction system is low and the post-polymerization stage where the viscosity is high. For example, examples of the reactor include a vertical stirring polymerization tank and a horizontal stirring polymerization tank.

FIG. 2 shows an example of an apparatus for implementing the method of the present invention.
Shown in The stirring tank 4 has stirring blades attached to a vertical rotation shaft, and continuously supplies the above-mentioned aromatic dihydroxy compound and carbonic acid diester through the pipes 1 and 2, respectively. The stirring tank atmosphere is substantially free of oxygen, and the stirring tank is purged with, for example, nitrogen gas. A catalyst is supplied to the stirring tank through a pipe 3 and mixed with the reaction raw materials. A plurality of stirring tanks can be provided in series to form a uniform solution.

The mixed raw materials are supplied to a pre-polymerization tank 8 through a pipe 6 by a pump 5. The prepolymerization tank is provided with a stirring blade having a vertical rotation axis. The inside of the tank is kept at a reduced pressure by a vent conduit 7 provided at the top. By-product phenol and some unreacted monomer sucked through the conduit 7 are respectively rectified, phenol is discharged out of the system, and unreacted monomer is returned to the polymerization tank. Also, piping 3
The catalyst can be further supplied through the '.

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

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] of 0.05 to 0.5 dl measured in a methylene chloride solution at 20 ° C.
/ G, preferably 0.10 to 0.45 dl / g, more preferably 0.15 to 0.4 dl / g.

Next, the polymer is supplied to the horizontal stirring polymerization tank 12.
Supplied to At least one, preferably one or two, horizontal stirring polymerization tanks can be provided in series. The reaction temperature in the horizontal stirring polymerization tank is usually 240 to 32.
The temperature is 0 ° C., preferably 250 to 310 ° C., and the pressure is 20 mmHg or less, preferably 10 mmHg or less.

The above horizontal stirring polymerization tank has one or more horizontal rotating shafts, and the horizontal rotating shaft has a disk type,
One or more types of stirring blades such as wheel type, paddle type, rod type, window frame type, etc. are combined and installed at least two or more stages per rotation axis. The stirring blades lift or spread the reaction solution. This is a horizontal high-viscosity liquid treatment apparatus that renews the surface of the reaction solution by using the method.

The viscous polymer is taken out from the bottom of the last horizontal stirring polymerization tank by the gear pump 13 and supplied to the on-line viscometer 15 installed on the bypass line to measure the viscosity. The viscosity is controlled by automatically controlling the flow rate of the heat medium in the jacket 16 of the horizontal stirring polymerization tank by the flow control valve 17 and the temperature and / or pressure of the horizontal stirring polymerization tank by the pressure control valve 21 based on the above program. Retained in viscosity. The target viscosity is preferably an intrinsic viscosity [η] of 0.2 in a methylene chloride solution at 20 ° C.
1.0 to 1.0 dl / g, preferably 0.25 to 0.9 dl / g
g, more preferably a specific value ± 0.05 dl / g in the range of 0.30 to 0.8 dl / g, more preferably ± 0.03 dl / g.

After performing a polycondensation reaction in a horizontal stirring polymerization tank,
The reaction can be further performed in a twin-screw vented extruder. In the case of using a twin-screw vented extruder, the polycondensation reaction has progressed considerably in the horizontal stirring polymerization tank at the preceding stage, so the reaction conditions of the twin-screw vented extruder can be relaxed and the quality of polycarbonate is prevented from deteriorating. It is possible to do.

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

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

Here, the aromatic dihydroxy compound is represented by the following formula [I]

[0027]

Embedded image (Where X is

[0028]

Embedded image -O -, - S -, - SO- or -SO ₂ - and is, R
₁ and R ₂ are a hydrogen atom or a monovalent hydrocarbon group,
R ₃ is a divalent hydrocarbon group. The aromatic nucleus may have a monovalent hydrocarbon group. ).

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) Bis (hydroxyaryl) alkanes such as propane, 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′-dihydroxydiphenylether and 4,4′-dihydroxy-3,3′-dimethylphenylether;
4,4'-dihydroxydiphenyl sulfide, 4,4
Dihydroxydiaryl sulfides such as'-dihydroxy-3,3'-dimethyldiphenylsulfide;
4,4'-dihydroxydiphenylsulfoxide, 4,
Dihydroxydiarylsulfoxides such as 4'-dihydroxy-3,3'-dimethylphenylsulfoxide;4,4'-dihydroxydiphenylsulfone;
Examples include dihydroxydiarylsulfones such as 4'-dihydroxy-3,3'-dimethyldiphenylsulfone, and 2,2-bis (4-hydroxyphenyl) propane (so-called bisphenol A) is particularly preferred.

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 and the like. And diphenyl carbonate is particularly preferred.

The above-mentioned carbonic acid diester may contain a dicarboxylic acid or a 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, and preferably 0.001 to 0.03 mol, particularly 0 to 1 mol of the aromatic dihydroxy compound. It is 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 Catalyst systems consisting of esters can be used. A catalyst system comprising 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 JP-A-4-46928 can also be used. Also, Japanese Unexamined Patent Publication No.
A catalyst system comprising a nitrogen-containing basic compound and a boron compound described in Japanese Patent Application Laid-Open (JP-A) No. 6-284, can be used.

In the polymerization reaction, various phenols can be used as a terminal blocking agent.
No. 175723 can be mentioned.

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.

[0036]

EXAMPLES In Examples and Comparative Examples, intrinsic viscosity [η] of polymers was measured in methylene chloride at 20 ° C. using an Ubbelohde viscometer.

[0037]

Example 1 The polymerization reactor shown in FIG. 2 was used. There were two prepolymerization tanks and one horizontal stirring polymerization tank, and one on-line viscometer was installed at the exit of the horizontal stirring polymerization tank. The respective reaction conditions are as follows.

Pressure (mmHg) Temperature (° C.) Average residence time (hr) Stirring tank Nitrogen atmosphere 200 0.5 Prepolymerization tank A 100 210 1.0 Prepolymerization tank B 15 250 0.5 Horizontal stirring polymerization tank 0.8 285 0.5 Bisphenol A (manufactured by Nippon GE Plastics)
0.44 mmol and 0.46 mmol of diphenyl carbonate (manufactured by Any) were continuously supplied to a stirring tank maintained at the above temperature. Further, 0.11 mol (2.5 × 10 4) of tetramethylammonium hydroxide was used as a catalyst.
^-4 mol / mol-bisphenol A) and 0.00044 mol of sodium hydroxide (1 × 10 ^-6 mol / mol-bisphenol A) were supplied to prepare a homogeneous solution.

Subsequently, the solution was supplied to pre-polymerization tank A and pre-polymerization tank B maintained at the above-mentioned reaction temperature to obtain a polymer having an intrinsic viscosity [η] of 0.32. The polymer was supplied to a horizontal stirring polymerization tank. The temperature and pressure of the horizontal stirring polymerization tank are as follows:
In order to keep the viscosity of the produced polymer constant, it was automatically controlled by an online viscometer installed at the outlet pipe. The target value of the intrinsic viscosity of the polymer is [η] = 0.4
9 (the control operation area was [η] = 0.49 ± 0.005). Further, the temperature of the horizontal stirring polymerization tank was fixed at 285 ° C. and the pressure was set at 0.8 ± 0.2 in accordance with the target viscosity value.
Automatically controlled at 6 mmHg.

The operation was continued for one month under the above conditions.
The variation of the intrinsic viscosity of the produced aromatic polycarbonate at the outlet of the horizontal stirring polymerization tank was in the range of [η] = 0.49 ± 0.01.

[0041]

Example 2 An aromatic polycarbonate was produced in the same manner as in Example 1 except that the temperature of the horizontal stirring polymerization tank was also controlled automatically. Further, the temperature of the horizontal stirring polymerization tank was 285 ± 20 ° C. and the pressure was 0.8 ± 0.6 mm corresponding to the target viscosity value.
Automatically controlled at Hg.

Under the above conditions, the operation was continued for 1.5 months. The variation of the intrinsic viscosity of the generated aromatic polycarbonate at the outlet of the horizontal stirring polymerization tank is [η] = 0.49 ± 0.00.
7 range.

[0043]

[Comparative Example 1] An intrinsic viscosity [η] of a polymer was measured by sequentially sampling without installing an on-line viscometer at the outlet of the horizontal stirring polymerization tank, and the intrinsic viscosity was set to the same target value as in Example 1. The temperature and pressure of the horizontal stirring polymerization tank were controlled to maintain the temperature. Other than that, it carried out similarly to Example 1.

The variation of the intrinsic viscosity of the produced aromatic polycarbonate at the outlet of the horizontal stirring polymerization tank is [η] = 0.49 ±
It was in the range of 0.1.

As described above, in the method of the present invention, the precision of controlling the molecular weight is higher than in the method of Comparative Example 1, and the resulting aromatic polycarbonate has a smaller range of variation in the molecular weight.

[0046]

According to the method of the present invention, the temperature and / or pressure of the polymerization can be quickly and automatically controlled in accordance with the viscosity of the polymer, that is, the molecular weight of the polymer. It can be performed with high accuracy and stability.

[Brief description of the drawings]

FIG. 1 shows the relationship between the molecular weight of an aromatic polycarbonate and the polymerization temperature and pressure.

FIG. 2 is a flow sheet of the method of the present invention.

[Explanation of reference numerals] 1, 2, 6, 10, 14. Piping 3, 3 '. Catalyst inlet 4. Stirrer tank 5, 9, 13. Pump 7,11. 7. Vent conduit Prepolymerization tank 12. Horizontal stirring polymerization tank 15. Online type viscometer 16. Heat medium jacket 17. Heat medium flow control valve 18, 18 '. Heat medium piping 19, 23, 24. Temperature and pressure control device 20. Vacuum pump 21. Pressure control valve 22. Cooler m ≧ 1

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiko Yamamoto 61-2-2 Waki, Waki-machi, Kuga-gun, Yamaguchi Japan Inside GE Plastics Co., Ltd. (72) Kotaro Kishimura Waka-machi, Kuga-gun, Yamaguchi No. 6 1-2 Ki, Japan GE Plastics Co., Ltd. (56) References JP-A-4-198213 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 64/00 -64/42

Claims (1)

(57) [Claims] 1. A method for producing an aromatic polycarbonate by melt-polycondensing an aromatic dihydroxy compound and a carbonic acid diester by using at least two reactors in series, wherein a viscometer is provided at least at a final reactor outlet. Measuring the viscosity of the polymer online, and automatically controlling the temperature and / or pressure of the reactor according to a pre-installed program based on the difference between the viscosity and the target viscosity.