JPH04106125A - Production of polycarbonate - Google Patents

Abstract

PURPOSE:To produce a polycarbonate having a high molecular weight and improved colorlessness, transparency and production efficiency by melt- polycondensing a dihydroxy compound with a bisaryl carbonate by transesterification in four specified steps. CONSTITUTION:In step 1, a monomer mixture comprising a dihydroxy compound (A) and a bisaryl carbonate (B) is molten in a tank for melting feeds. In step 2, this mixture is polymerized on a horizontal twin-screw polymerizer to obtain a polycarbonate prepolymer of a viscosity-average molecular weight of 5000-30000. In step 3, the obtained prepolymer is received in at least one hold tank. In step 4, it is reacted on at least one paddle-type self-cleaning extruder to melt-polycondense components A and B by transesterification and to thereby obtain a polycarbonate of a viscosity-average molecular weight of 12000-60000.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing polycarbonate, and more specifically, a method for producing polycarbonate by melt polycondensing a divalent hydroxy compound and a bisaryl carbonate by a transesterification method. It relates to a manufacturing method.

BACKGROUND OF THE INVENTION Polycarbonate is a general purpose engineering thermoplastic that has a wide range of uses, particularly for injection molding or as glass sheets in place of window panes.

Conventionally, interfacial polycondensation methods, transesterification methods, and the like have been applied to the production of these polycarbonates.

Although the interfacial polycondensation method is generally effective for producing polycarbonate, it has drawbacks such as the use of toxic phosgene and the fact that chlorine ions remain in the polycarbonate produced. In order to eliminate these drawbacks, a method for manufacturing polycarbonate by using liquid trichloromethyl chloroformate, which is a dimer of phosgene, instead of toxic phosgene, and carrying out an interfacial polycondensation reaction with a special dihydric phenol has been disclosed. It is disclosed in Publication No. 182336/1983. However, as a special dihydric phenol, 9
, 9-bis(4-hydroxyphenyl)fluorenes. In addition, a method for obtaining polycarbonate from 2,2-bis(4-hydroxyphenyl)propane using triphosgene instead of toxic phosgene is described in Angew, Chem, (Angevante,
922 (1987), German patent DE
No. 3,440,141, a reaction mechanism in which phosgene is generated has also been proposed.

In the transesterification reaction, a transesterification catalyst is added to diphenyl carbonate and an aromatic dihydroxy compound, and a prepolymer is synthesized while distilling phenol under heating and reduced pressure.Finally, the prepolymer is heated to 290°C or higher under high vacuum. High molecular weight polycarbonate is obtained by distilling phenol out (U.S. Pat. No. 4,345,062), but unlike engineering plastics, other high molecular weight polycarbonates have extremely high melt viscosity, so the reaction conditions are Requires high temperatures of 290°C or higher,
In addition, high vacuum (10-2 Torr) is required to distill off phenol with a high boiling point, making it difficult to industrialize from the equipment standpoint.Furthermore, phenol remains in the polycarbonate produced, resulting in poor hue and physical properties. It is known to have undesirable effects.

However, since the transesterification method can carry out the reaction by melt polycondensation and is an industrially economical method, various studies have been made. In particular, as the polycondensation reaction approaches completion, the viscosity of the reaction system increases, so attempts have been made to use various types of equipment to handle highly viscous reaction products. For example, Tokuko Sho 52-3615
9, JP 2-86618, JP 2-15392
3 to 153927, etc. are disclosed. Tokuko Sho 52-3
6159 uses a screw evaporator-type intermeshing twin-screw extruder, but it has the disadvantage that black foreign matter is likely to be generated in the retention area of the screw groove, and it is difficult to control the residence time and the heat history However, there are difficulties in terms of the degree of coloration of the product and the efficient removal of by-product distillates such as phenol. Also, Unexamined Japanese Patent Publication No. 2-15
3923 to 153927 use a horizontal stirred polymerization tank, which allows for a large hold-up, but increases the liquid thickness, and distillation of by-products such as phenol from the high viscosity reaction liquid becomes rate-limiting. It is necessary to increase the residence time. Therefore, exposure to thermal history at high temperatures causes coloring of the reaction product. It is difficult to say that this method is sufficient as a method for producing colorless and transparent high molecular weight polycarbonate industrially and efficiently.

(Means for Solving the Problems) The present invention overcomes the drawbacks of the conventional method for producing polycarbonate by transesterification reaction, and provides a method for efficiently producing polycarbonate that is colorless and transparent and has a high molecular weight. It is.

The present inventors have discovered that (
1) When producing polycarbonate by melt polycondensing a divalent hydroxy compound and a bisaryl carbonate by a transesterification method, as a first step, a raw material melting tank is provided to melt the monomer, and after melting the monomer mixture, The second step includes a step of producing a polycarbonate prepolymer with a viscosity average molecular weight of 5.000 to 30,000 in a horizontal biaxial polymerization machine, and the third step includes:
After the prepolymer obtained in the second step is received in at least one hold tank, the fourth step is to use at least one paddle-type self-cleaning twin-screw extruder so that the viscosity average molecular weight is 12 ;000~60,
000 polycarbonate, or by performing polycondensation in the third and fourth steps without going through the hold tank in the second step in step (1), colorless and transparent high molecular weight polycarbonate can be produced industrially. The inventors have discovered scales that can be manufactured efficiently and have completed the present invention.

Examples of the divalent hydroxy compound used in the present invention include compounds represented by the following (1) to (IV).

(In the formula, R1, R2) R3+ R4r R5 each represents a hydrogen atom, a straight chain or branched alkyl group having 1 to 8 carbon atoms, or a phenyl group, X represents a halogen atom, and n = o ~ 4. m=1 to 4. ) Specifically, 2,
2. Bis-(4-hydroxyphenyl)propane, 2,
2-bis-(4-hydroxyphenyl)butane, 2,2
-bis-(4-hydroxyphenyl)-4-methylpentane, 2,2-bis-(4-hydroxyphenyl)octane, 4,4'-dihydroxy-2,2,2-triphenylethane, 2,2- Bis-(3,5-dibromo-4-
hydroxyphenyl)propane, 2,2-bis-(4-
Hydroxy, 3-methylphenyl)propane, 2,2.
bis, (4-hydroxy-3, isobrobylfunyl)
Propane, 2,2-bis-(4-hydroxy-3-se
e, butylphenyl)propane, 2.2-his-(3
,5-dimethyl-4,hydroxyphenyl)propane,
2.2-bis-(4-hydroxy-3-tert-butylphenyl)propane, 1,1'-bis-(4-hydroxyphenyl)-P-diisopropylbenzene, 1,
Examples include 1'-bis-(4-hydroxyphenyl) 0m, diisopropylbenzene, and 1,1-bis-(4-hydroxyphenyl)cyclohexane. Furthermore, it is also possible to produce a copolymerized polycarbonate by combining two or more of these divalent hydroxy compounds. Examples of bisaryl carbonates include diphenyl carbonate, bis(2,4-dichlorophenyl) carbonate, bis(2,4,6-)dichlorophenyl) carbonate, bis(2-cyanophenyl) carbonate, bis(0-nitro phenyl) carbonate, ditolyl carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, and the like. Preferably it is diphenyl carbonate. Further, in the present invention, a polymerization catalyst can be used if desired, and a transesterification catalyst is usually used as the polymerization catalyst.

Typical examples of transesterification catalysts that can be used in the present invention include <a) Catalysts similar to metal-containing catalysts such as lithium borohydride, sodium borohydride, potassium borohydride, rubidium borohydride, Cesium boron, beryllium borohydride, magnesium borohydride, calcium borohydride, strontium borohydride, barium borohydride, aluminum borohydride, titanium borohydride, tin borohydride,
Germanium borohydride, lithium tetraphenoxy, sodium tetraphenoxy, potassium tetraphenoxy, tetraphenoxyrubidium, tetraphenoxycesium, sodium 1,000 sulfate, beryllium oxide, magnesium oxide, tin(IV) oxide, dibutyltin oxide, beryllium hydroxide, water Magnesium oxide, germanium hydroxide, beryllium acetate, magnesium acetate, tin (IV) acetate, germanium acetate, lithium carbonate, sodium carbonate, potassium carbonate, beryllium carbonate, magnesium carbonate, tin (IV) carbonate, germanium carbonate, tin (IV) nitrate ), germanium nitrate, antimony trioxide,
Examples include bismuth trimethyl carboxylate.

(b) Catalysts similar to electron-donating amine compounds include:
N,N-dimethyl-4-aminopyridine, 4-diethylaminopyridine, 4-aminopyridine, 2-aminopyridine, 2-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine, 4-hydroxypyridine, 2
-dimethylaminoimidazole, 2-methoxyimidazole, 2-mercaptoimidazole, aminoquinoline,
Examples include imidazole, 2-methylimidazole, 4-methylimidazole, diazabicyclooctane (DABCO), and the like.

Further, (C) carbonic acid, acetic acid, formic acid, nitric acid, nitrous acid, oxalic acid, fluoroboric acid, hydrofluoride, etc. of the electron-donating amine compounds mentioned above may be mentioned.

Examples of catalysts similar to (d) as child-donating phosphorus compounds include triethylphosphine, tri-n-propylphosphine,
tri-isopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tri-low dimethoxyphenylphosphine, tri-p-tolylphosphine, tri-〇-)lylphosphine, tributylphosphine,
Examples include triphenyl phosphite, tri-p-tolyl phosphite, tri-o-tolyl phosphite, and the like.

Furthermore, (e) catalysts similar to borane complexes include complexes of borane and the following compounds, namely ammonia, dimethylamine, trimethylamine, triethylamine, t-
Butylamine, dimethylaniline, pyridine, dimethylaminopyridine, morpholine, piperazine, virol,
Tetrahydrofuran, dimethyl sulfide, tri-n-
Examples include complexes of butylphosphine, triphenylphosphine, triphenylphosphite, and the like.

These catalysts may be used alone or in combination of two or more, and the amount used is usually in the range of lXl0-6 to 1 mol based on the divalent hydroxy compound. , preferably 5X 10-5 to 5X
It is 10-2 mol. If the amount is less than 5×10 −5 mol, the polymerization rate will be slow and cause coloring. When the amount exceeds 5×10 −2 mol, the catalyst remaining in the resulting polycarbonate becomes a factor that adversely affects physical properties, for example, decreases in mechanical properties.

In the present invention, a two-stage reaction system is generally used to produce polycarbonate by transesterifying a divalent hydroxy compound and a bisaryl carbonate. That is, the first stage reaction involves transesterifying the raw materials in the presence of a transesterification catalyst to produce a polycarbonate prepolymer in a molten state, and the second stage reaction involves proceeding with polymerization at a higher viscosity to produce a high molecular weight polycarbonate. In the first stage reaction, the reaction temperature is 100
In the range of 300°C or higher, preferably 130°C
It ranges from °C to 280 °C. If the temperature is less than 130°C, the reaction rate will be slow, and if it exceeds 280°C, side reactions will likely occur. After removing certain distillates such as phenol under reduced pressure, a second stage reaction is performed to further increase the molecular weight. The reaction temperature is 180°C or higher and 350°C.
preferably from 200°C to 320°C
is within the range of If the temperature is less than 200°C, it will be difficult to remove phenol etc. for measuring high molecular weight, and if it exceeds 320°C, coloring of the resin and side reactions will be promoted, which is not desirable. Furthermore, this reaction is carried out under high vacuum, and the degree of vacuum is I
QTorr or less, preferably ITorr or less.

Further, as for the timing of adding the catalyst, it is also possible to use appropriate catalysts for the initial charge or for the first stage reaction and the second stage reaction.

Further, the present invention will be explained in detail.

First, the polycarbonate prepolymer production reaction in the second step may be carried out either batchwise or continuously.

Furthermore, the reaction may be carried out using a plurality of such reactors. In the horizontal biaxial polymerization machine described above under nitrogen purge, a transesterification catalyst is added while the divalent hydroxy compound and bisaryl carbonate are melted as raw material monomers, and in the case of a batch system, the temperature is gradually raised as the reaction progresses. , and by-product phenols are removed by gradually reducing the pressure. When removing by-products such as phenol, it is preferable to equip the reaction tank with a distillation column in order to avoid as much as possible the raw materials in the system being entrained and distilled off to the distillate side.The reaction temperature is 150°C ~ 300°C1 vacuum degree is 4QQToor~1
The Too(7) range is preferred. The viscosity average molecular weight of the polycarbonate prepolymer obtained in the second step is 5.0
00 to 20,000.

Next, as a third step, the prepolymer obtained in the second step is received in a hold tank. It is kept in a molten state in the hold tank, and if necessary, it is stirred by a stirrer.
Equalization will be achieved. At that time, it is fully possible to add additives such as hue improvers, antioxidants, and catalyst terminal cappers within the range that does not interfere with the reaction in the next step, and this method is also included in the present invention. It is something. The viscosity average molecular weight of the subsequently obtained polycarbonate ranges from 10,000 to 30,000. In the fourth step, which is the next step, the viscosity of the reaction mixture is very high, and a special polycondensation equipment is required in the post-polycondensation step to synthesize a high molecular weight polymer. Generally, high-viscosity processing equipment such as (forced) thin-film evaporators and horizontal biaxial polymerization machines are applicable, but black, burnt foreign matter may be generated, and the residence time may be relatively long due to the high molecular weight. It is difficult to obtain a polymer with a sufficient high molecular weight, and it is difficult to say that it is industrially effective.

In the fourth step of the present invention, the above-mentioned drawbacks can be overcome by using at least one paddle-type self-cleaning twin-screw extruder. In contrast to a screw, the paddle shape refers to a blade that is discontinuous (that is, the valley part of the blade is not continuous and connected), and includes, but is not limited to, a convex lens type or a pseudo-triangle. isn't it. In addition, the self-cleaning function is a pair of left and right paddles built into two shafts that are out of phase, creating a certain minute gap so that the tip of one paddle cleans the side of the other paddle. This is achieved by rotating while holding the Normally L/D = 1 to 35 (L is the length of the shut, F,
D is the rotating diameter of the paddle), preferably L/D=
It is 1 to 2 o.

However, the present invention is not necessarily limited to this. The reaction temperature is usually 220'C to 3500C, the degree of vacuum is 5 Torr to Q, and 1 Torr. Residence time is 0.
The duration is 2 hours to 2 hours, preferably 0.4 to 1.2 hours, and the operation is continuous. As the surface of the reaction mixture is renewed within the system, by-products such as phenol are removed from a distillation port connected to a vacuum system. The resulting polycarbonate has a viscosity average molecular weight of 12,000 to 60,000.

The paddle-type self-cleaning twin-screw extruder used in the present invention enables efficient surface renewal and removal of phenol, etc., which are by-products that increase liquid thickness.Furthermore, by controlling the residence time, colorless and transparent high molecular weight polycarbonate can be produced. can get.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

(Example) Example 1 4566 g of bisphenol A (20,0
mol), diphenyl carbonate 4392 g (20,5
2-methylimidazole (3.28 g (0.04 mol)) and sodium acetate (0.033 g (0.0004 mol) ), 260
The temperature was gradually raised to 'C' and then the pressure was reduced to 2 Torr to distill off the by-product phenol. After about 4 hours, a polycarbonate prepolymer having a viscosity average molecular weight of 16.000 was obtained.

Next, transfer the liquid to the hold tank of 121 using a gear pump and
A temperature of 0°C was maintained under nitrogen. Next, the liquid was transferred using a gear pump and sent to a paddle-type self-cleaning twin-screw extruder (L/D = 8.9°, paddle rotation diameter 50 mm, shaft length 445.5 mm) controlled at 0.2 Torr, at 800 g / Hr. Discharge was performed using a gear pump. The residence time is approximately 45 minutes. The viscosity average molecular weight of the obtained polymer was 30,000. Moreover, the hue was A380-A380=0.100.

Here, the method for measuring the viscosity average molecular weight is to measure the intrinsic viscosity of a methylene chloride solution at 20'C using an Ubbelohde viscometer, and calculate the viscosity average molecular weight (V) using the following formula.
was calculated.

[r1]=1.11X10-'(Mv)O-82 Also,
Hue evaluation is performed by measuring and displaying the difference in absorbance in the wavelength range of 380 pm and 580 pm using a UV measuring device using a 10% methylene chloride solution of polycarbonate, and the larger the value, the more colored it is. .

Example 2 Under the same charging conditions as in Example 1, 4-dimethylaminopyridine was used instead of 2-methylimidazole as a catalyst.
88 g (0.04 mol) was charged into a 201 horizontal twin-screw polymerization machine, and the temperature was gradually raised from 180°C to 260°C under a nitrogen purge, and the pressure was reduced to 4 Torr to distill off the by-produced phenol. After about 4 hours, the viscosity average molecular weight was 13.
000 polycarbonate was obtained. Next, the above prepolymer was charged into a similar horizontal biaxial polymerization machine at 280°C, 22To
Polycondensation was proceeded under the conditions of rr. The viscosity average molecular weight of the obtained polymer was 19,000. Next, it was fed into a paddle-type self-cleaning twin-screw extruder controlled at 280°C, Q, and 2 Torr using a gear pump.
Drainage was carried out at g/hr. Residence time was approximately 45 minutes. The viscosity average molecular weight of the obtained polymer was 32,00
It was 0. Also, the hue is A380-A5B□ = 0
．． 090 Ara 7':.

Comparative Example 1 Under almost the same conditions as Example 1, a horizontal twin-screw polymerization machine was used instead of the paddle-type self-cleaning twin-screw extruder, and 2
800g/Hr under the conditions of 80°C, Q, 2 Torr
It was discharged using a gear pump. The residence time was about 3 hours, and the viscosity average molecular weight of the obtained polymer was 25,000. The hue was A380-A380'' 0.17.

Comparative Example 2 Under almost the same conditions as Example 1, a screw evaporator was used instead of the paddle-type self-cleaning twin-screw extruder,
900g/H at 280°C and 0.2 Torr
It was discharged using a gear pump. The residence time was about 10 minutes, and the viscosity average molecular weight of the obtained polymer was 24,000.
Met. Hue is A380-A380” 0-20
A black scorch-like substance was observed at the report office.

(Effects of the Invention) According to the present invention, a colorless, transparent, high molecular weight polycarbonate can be efficiently produced.

Claims (2)

[Claims] (1) In a method for producing polycarbonate by melt polycondensing a divalent hydroxy compound and a bisaryl carbonate by a transesterification method, the first step includes a raw material melting tank for melting the monomers, and after melting the monomer mixture. As a second step, a horizontal biaxial polymerization machine is used to produce a polycarbonate prepolymer having a viscosity average molecular weight of 5,000 to 30,000, and as a third step, the prepolymer obtained in the second step is After passing through at least one hold tank, the fourth step is to use at least one paddle-type self-cleaning twin-screw extruder to achieve a viscosity average molecular weight of 12,000 to 60,000.
1. A method for producing polycarbonate, characterized by obtaining a polycarbonate of 0.00. (2) A method for producing polycarbonate according to claim 1, in which polycondensation is carried out in the third and fourth steps without going through a hold tank in the second step.