JPH0632887A - Production of aromatic polycarbonate - Google Patents

Abstract

PURPOSE:To obtain an aromatic polycarbonate having excellent color tone. CONSTITUTION:A powdery aromatic dihydroxy compound is mixed with a carbonic acid diester substantially in the absence of oxygen to form a melt, which is subjected to polycondensation reaction to produce an aromatic polycarbonate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aromatic polycarbonate, which provides an aromatic polycarbonate having an excellent hue.

[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 carbonic acid diester such as diphenyl carbonate are melted A method of transesterification (polycondensation reaction) is known. Although the former method is generally practiced at present, the latter method is considered to be promising in the future because it does not use a troublesome compound such as phosgene.

Generally, bisphenol A (melting point: 156 ° C.) and solid diphenyl carbonate (melting point: 80 ° C.), which are available as solids, are separately or mixed and heated to melt, and a catalyst is added to a mixed solution of both compounds. In addition, polycondensation is performed.

However, there is a drawback in that the product polycarbonate is colored because it is exposed to high temperatures for a long time due to the reaction in the molten state.

[0005] Aromatic polycarbonates are often used for optical applications, and therefore, it is desired to have a hue as excellent as possible, that is, a material having less yellowness and good transparency.
For that purpose, various catalyst systems have been proposed (JP-A-4-89824 and JP-A-3-203928).

Also known is an attempt to reduce the coloring of the product polycarbonate by using a high-purity aromatic dihydroxy compound. In order to obtain a highly pure aromatic dihydroxy compound, a recrystallization method, a distillation method and an adduct formation method are known. Further, a method is known in which the adduct itself is used as a reaction raw material to perform melt polycondensation with a carbonic acid diester (JP-A-4-20523).
issue).

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to produce an aromatic polycarbonate having an excellent hue.

[0008]

The present invention is a method for producing an aromatic polycarbonate by melt polycondensation of an aromatic dihydroxy compound and a carbonic acid diester, wherein the powdered aromatic dihydroxy compound and the molten carbonic acid diester are oxygenated. Is mixed in the substantial absence of to form a solution, and the solution is subjected to a polycondensation reaction.

The aromatic dihydroxy compound and the carbonic acid diester are heated to a temperature at which a uniform solution is formed, generally 50 to 270.
It is maintained at a temperature of ° C, preferably below the melting point of the aromatic dihydroxy compound. For example, as an aromatic dihydroxy compound, bisphenol A (melting point 156
C.) is used as the carbonic acid diester (melting point 80.degree. C.), the powdery bisphenol A is dissolved in the melted liquid diphenyl carbonate, so that it is lower than the melting point of bisphenol A.
A homogeneous solution can be made at 0 ° C. Further, when phenol is present in the system, a homogeneous solution can be formed at a lower temperature, for example, 50 ° C. or higher. Therefore, it is preferable to add phenol. Since the phenol is distilled off during the polymerization, it has no adverse effect on the aromatic polycarbonate produced. When the solution forming temperature is set below the melting point of the aromatic dihydroxy compound, the hue of the aromatic polycarbonate is remarkably good.

In the present invention, the aromatic dihydroxy compound is mixed in powder form. The particle size of the powder is not particularly limited, but in order to quickly form a good homogeneous solution,
It is preferably about 0.1 to 5 mm.

The carbonic acid diester is mixed in a molten state from the carbonic acid diester manufacturing process. Therefore, compared with the case of using the solid carbonic acid diester, the heat history is small and the influence of oxygen can be extremely reduced.

Further, in order to prevent the deterioration of the hue of the aromatic polycarbonate, they are mixed in the substantial absence of oxygen, for example, in a nitrogen atmosphere.

As described above, in the method of the present invention, since the aromatic dihydroxy compound is supplied in the form of powder, the powdery aromatic dihydroxy compound is heated to a temperature considerably higher than the melting point and melted as in the conventional method. It was made because of the lack of steps and the ability of the aromatic dihydroxy compound and the carbonic acid diester to form a homogeneous mutual solution at temperatures below the melting point of the aromatic dihydroxy compound, allowing polymerization to be initiated at relatively low temperatures. Aromatic polycarbonates have excellent hue.

The uniform solution can be formed by any of a batch system, a semi-continuous system and a continuous system, but a continuous system is preferred. For example, in the case of the batch system, a predetermined amount of molten carbonic acid diester is supplied to the mixing tank, and then a predetermined amount of powdered aromatic dihydroxy compound is supplied, and the mixture is stirred and mixed using a stirrer while heating. Form a homogeneous solution. Also,
In the case of the continuous system, a carbonic acid diester in a molten state and a powdered aromatic dihydroxy compound are continuously supplied at a predetermined ratio to a homogeneous solution which is previously formed in a mixing tank and is kept and stirred at a predetermined temperature. Form a homogeneous solution.

In the present invention, the aromatic dihydroxy compound has the following formula [I]:

[0016]

[Chemical 1] (Where X is

[0017]

[Chemical 2] -O-, -S-, -SO- or -SO _2- , R
₁ and R ₂ are hydrogen atoms or monovalent hydrocarbon groups,
R ₃ is a divalent hydrocarbon group. 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 generally available aromatic dihydroxy compounds contain impurities, in particular their structural isomers. For example, in the case of bisphenol A, 2- (4'-hydroxyphenyl) -2- (2'-hydroxyphenyl) propane is contained as an impurity, so it is preferable to purify it. Examples of the purification method include recrystallization with water or an organic solvent, distillation, or a method of forming an adduct with phenols.

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 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.
Examples thereof include those described in Japanese Patent Publication No. 175723.

Any known polymerization apparatus can be used, and it may be a continuous type, a semi-continuous type or a batch type, but a continuous type is preferable. In general, a reactor having a different stirring mode is used in the pre-polymerization stage in which the viscosity of the reaction system is low and the post-polymerization stage in which the viscosity is high.

An example is shown in FIG. The stirring tank 4 has a stirring blade mounted on a vertical rotating shaft, and the powdery aromatic dihydroxy compound and the molten carbonic acid diester are continuously supplied to the stirring blade 4 through pipes 1 and 2, respectively. In order to make oxygen substantially absent in the stirring tank atmosphere, 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.
The temperature in the stirred tank is preferably kept below the melting point of the aromatic dihydroxy compound. It is also possible to provide a plurality of stirring tanks in series to form a uniform solution. In such a case, set the first stirred tank to a much lower temperature,
A uniform solution can be formed at a relatively low temperature after the second stirring tank. It is presumed that this is because the aromatic dihydroxy compound and the carbonic acid diester react in the stirred tank to generate phenol.

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, preferably 2 to 4 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, for example, 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 has 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 or Two
This is a horizontal type high-viscosity liquid processing apparatus in which at least two stages are installed per rotary shaft in combination of two or more kinds, and the reaction solution is scraped or spread by the stirring blade to renew the surface of the reaction solution. 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.

At least one, preferably one or two horizontal stirring polymerization tanks are provided in series. A viscous polymer was taken out from the bottom of the last horizontal stirring polymerization tank by a 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 the polycondensation reaction is carried out in the horizontal stirring polymerization tank, the reaction can be further carried out by a twin-screw vent type extruder. When using a twin-screw vent type extruder, the polycondensation reaction has progressed considerably in the horizontal stirring polymerization tank in the previous stage, so the reaction conditions of the twin-screw vent extruder can be relaxed and the deterioration of the polycarbonate quality is prevented. It becomes possible to do.

The above reactors and reaction conditions are merely examples and are not limiting. For example, Japanese Patent Laid-Open No. 2-1539
Nos. 23 to 2-353927 and JP-A-2-1757.
The apparatus and conditions described in JP 22 can be used.

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.

[0035]

EXAMPLES In Examples and Comparative Examples, bisphenol A was used as an aromatic dihydroxy compound, diphenyl carbonate was used as a carbonic acid diester, and tetramethylammonium hydroxide and sodium hydroxide were used as catalysts.

The hue of the purified polycarbonate was measured by the following method. 3mm thick injection plate X, Y,
Z value is Color and Co of Nippon Denshoku Industries Co., Ltd.
lor Difference Meter ND-1
001D was used to measure by the transmission method, and the YI value was used as a measure of yellowness.

YI = (100 / Y) × (1.277X-
1.060Z)

[0038]

Example 1 The polymerization reactor shown in FIG. 1 was used. There are two pre-polymerization tanks and two horizontal stirring 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 100 210 210 1.0 Pre-polymerization tank B 20 240 0.5 0.5 Horizontal stirring polymerization tank A 3 285 0.5 Horizontal stirring polymerization tank B 0.3 290 0.5 Powdered bisphenol A (feed rate 36.0 kg / h
r), molten diphenyl carbonate (feed rate 34.7 kg / hr) directly fed from the diphenyl carbonate production process through a pipe, and tetramethylammonium hydroxide as a catalyst (feed rate 3.
6 g / hr), sodium hydroxide (feed rate 3.2 mg
/ Hr) was continuously supplied to a stirring tank maintained at the above temperature to prepare a homogeneous solution.

Subsequently, the solution was sequentially supplied to the pre-polymerization tank A, the pre-polymerization tank B, the horizontal stirring polymerization tank A and the horizontal stirring polymerization tank B at a supply rate of 36.0 kg / hr in terms of bisphenol A. Polymerization was performed under reaction conditions to produce a polycarbonate.

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

The hue was 1.44.

[0043]

Example 2 A polycarbonate was produced in the same manner as in Example 1 except that the temperature of the stirring tank was 140 ° C.

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

The hue was 1.47.

[0046]

Comparative Example 1 Polycarbonate was produced in the same manner as in Example 1 except that powdered bisphenol A was melted and the liquid temperature was 180 ° C. was supplied to a stirring tank, and the temperature of the stirring tank was 180 ° C. .

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

The hue was 1.72.

As described above, the aromatic polycarbonate obtained by the method of the present invention has a remarkably higher hue than that obtained by the method in which an aromatic dihydroxy compound is heated and melted at a temperature higher than the melting point before use. Was excellent.

[0050]

The aromatic polycarbonate produced according to the present invention has an excellent hue. There is no step to heat and melt the powdery aromatic dihydroxy compound to a temperature considerably higher than the melting point as in the conventional method, and the temperature of the aromatic dihydroxy compound and the carbonic acid diester far below the melting point of the aromatic dihydroxy compound. It is presumed that the effect of the present invention is brought about by the fact that a homogeneous mutual solution can be easily obtained with and the polymerization can be started from a relatively low temperature.

[Brief description of drawings]

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

[Explanation of symbols]

 1,2,6,10,14. Piping 3,3 '. Catalyst inlet 4. Stirring tank 5, 9, 13. Pump 7, 11. Vent conduit 8. Pre-polymerization tank 12. Horizontal stirring polymerization tank m ≧ 1, n ≧ 1

Claims (3)

[Claims] 1. A method for producing an aromatic polycarbonate by melt-polycondensing an aromatic dihydroxy compound and a carbonic acid diester, wherein the powdery aromatic dihydroxy compound and the molten carbonic acid diester are mixed in the substantial absence of oxygen. To form a solution, and subjecting the solution to a polycondensation reaction. 2. The method according to claim 1, wherein the aromatic dihydroxy compound is bisphenol A and the carbonic acid diester is diphenyl carbonate. 3. The method of claim 1 wherein the formation of the solution of powdered aromatic dihydroxy compound and molten carbonic acid diester is carried out at a temperature below the melting point of the aromatic dihydroxy compound.