JP2883433B2 - Production method of polycarbonate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polycarbonate, and more specifically, a polyhydric hydroxy compound and a bisaryl carbonate are melt-polycondensed by a transesterification method,
The present invention relates to a method for producing polycarbonate.

[Problems to be solved by conventional technology and invention]

Polycarbonate is a general engineering thermoplastic that has a wide range of uses, especially for injection molding or as a glass sheet instead of window glass.

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

The interfacial polycondensation method is generally effective for producing polycarbonate, but has drawbacks such as the use of toxic phosgene and the occurrence of chloride ions remaining in the produced polycarbonate. In order to solve these drawbacks, a method of producing a polycarbonate by interfacial polycondensation reaction with a special dihydric phenol using a liquid trichloromethyl chloroformate, which is a dimer of phosgene, instead of toxic phosgene is disclosed in Japanese Patent Application Laid-Open No. H11-163,873. It is disclosed in JP-A-63-182336. However, 9,9-
There is only description of bis (4-hydroxyphenyl) fluorenes. Also, a method for obtaining polycarbonate from 2,2-bis (4-hydroxyphenyl) propane using triphosgene instead of toxic phosgene is known.
Angew.Chem (Angewandte Chemie) 99, 922 (1987),
As described in DE 3440141, a reaction mechanism for generating phosgene has also been proposed.

In the transesterification reaction, a transesterification catalyst is added to diphenyl carbonate and an aromatic dihydroxy compound, a prepolymer is synthesized while distilling phenol under heating and reduced pressure, and finally heated to 290 ° C or higher under high vacuum. A high molecular weight polycarbonate is obtained by distilling phenol (US Pat. No. 4,434,062). However, unlike other engineering plastics, the high molecular weight polycarbonate has an extremely high melt viscosity, so that the reaction condition is 290. Requires high temperature of over ℃ and high vacuum (10 ^-2 Torr) to remove high boiling phenol
Therefore, it is known that industrialization is difficult from the viewpoint of equipment, and that phenol remains in the produced polycarbonate, which adversely affects hue and physical properties.

However, the transesterification method can be reacted by melt polycondensation, and has been studied variously because it is industrially economical. In particular, since the viscosity of the reaction system increases as the polycondensation reaction approaches completion, various types of apparatuses have been used to handle high-viscosity reaction products. For example, Japanese Patent Publication No. 52-36159
JP, JP-A-2-86618, JP-A-2-153923-1
No. 53927 is disclosed. In Japanese Patent Publication No. 52-36159, a screw evaporator-type meshing twin-screw extruder is used, but it has a disadvantage that black foreign matter is easily generated in a retaining portion of a screw groove portion. It is difficult to control the time, and there is a problem in that the degree of coloring of the product due to the heat history and the distillate such as phenol by-produced are efficiently removed. Also, JP-A-2-153923-1539
No. 27 uses a horizontal stirring polymerization tank.However, although a large hold-up can be obtained, the liquid thickness increases, and the distillation of phenol and the like by-produced from the high-viscosity reaction solution is rate-determining. You need to increase the time. Therefore, by receiving a heat history at a high temperature, it becomes a factor of coloring the reaction product.

These methods cannot be said to be sufficient as industrially efficient methods for producing colorless and transparent polycarbonate.

Accordingly, an object of the present invention is to overcome the drawbacks of such a conventional method for producing a polycarbonate by transesterification and to provide a method for efficiently producing a colorless, transparent, high-molecular-weight polycarbonate.

[Means for solving the problem]

The present inventors, in a method for producing polycarbonate,
It was found that colorless, transparent, high-molecular-weight polycarbonate can be efficiently produced by a method in which a reaction is performed in a tank-type reaction tank or horizontal polymerization machine and a paddle-type self-cleaning twin-screw extruder to increase the viscosity average molecular weight stepwise. Thus, the present invention has been completed.

That is, the present invention relates to a method for producing a polycarbonate by melt-polycondensing a divalent hydroxy compound and a bisaryl carbonate by a transesterification method, wherein the monomer is melted in a regulating tank as a first step, and the monomer is melted as a second step. After performing a polycondensation reaction in a tank-type reaction tank while melting the mixture to obtain a polycarbonate having a viscosity-average molecular weight of 5,000 to 30,000, at least 1
Using a paddle-type self-cleaning twin-screw extruder having at least one group, a method for producing a polycarbonate characterized by obtaining a polycarbonate having a viscosity average molecular weight of 12,000 to 60,000, and after the first step, after the first step, the monomer as a second step A polycondensation reaction is performed in a tank-type reaction vessel under melting of the mixture to generate a polycarbonate prepolymer having a viscosity average molecular weight of 5,000 to 20,000, and a polycondensation reaction of the prepolymer obtained in the second step as the third step is performed. Further proceeding in a tank type reaction vessel or horizontal polymerization machine, after obtaining a polycarbonate having a viscosity average molecular weight of 10,000 to 30,000, as a fourth step, using at least one or more paddle type self-cleaning twin-screw extruder, the viscosity average It is intended to provide a method for producing a polycarbonate, characterized in that a polycarbonate having a molecular weight of 12,000 to 60,000 is obtained.

Examples of the divalent hydroxy compound used in the present invention include:
For example, the following general formula (I), (II), (III) or (IV)
The compound represented by these is mentioned.

(Wherein R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each a hydrogen atom,
Represents a straight-chain or branched alkyl group or a phenyl group, X represents a halogen atom, n = 0 to 4, m
= 1-4. ) 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-hydroxy Phenyl) propane, 2,2-bis- (4-hydroxy-3-methylphenyl) propane, 2,2-bis- (4
-Hydroxy-3-isopropylphenyl) propane,
2,2-bis- (4-hydroxy-3-sec.butylphenyl) propane, 2,2-bis- (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis- (4-hydroxy -3-tert-butylphenyl) propane, 1,
1'-bis- (4-hydroxyphenyl) -p-diisopropylbenzene, 1,1'-bis- (4-hydroxyphenyl) -m-diisopropylbenzene, 1,1-bis-
(4-hydroxyphenyl) cyclohexane and the like. Furthermore, it is also possible to produce a copolymerized polycarbonate by combining these two or three or more divalent hydroxy compounds.

As the bisaryl carbonate used in the present invention, diphenyl carbonate, bis (2,4-dichlorophenyl) carbonate, bis (2,4,6-trichlorophenyl) carbonate, bis (2-cyanophenyl) carbonate, bis (o) -Nitrophenyl) carbonate,
Examples include ditolyl carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, and the like. Preferably, it is diphenyl carbonate.

In the present invention, a polymerization catalyst can be used if desired, and a normal transesterification catalyst can be used as the polymerization catalyst.

Representative examples of the transesterification catalyst that can be used in the present invention include (a) lithium borohydride, sodium borohydride, potassium borohydride, rubidium borohydride, and hydrogenation catalysts similar to metal-containing catalysts. Cesium borohydride, beryllium borohydride, magnesium borohydride, calcium borohydride, strontium borohydride, barium borohydride, aluminum borohydride, titanium borohydride, tin borohydride, germanium borohydride, tetraphenoxy Lithium, sodium tetraphenoxy, potassium tetraphenoxy, tetraphenoxyrubidium, tetraphenoxycesium, sodium thiosulfate, beryllium oxide,
Magnesium oxide, tin (IV) oxide, dibutyltin oxide, beryllium hydroxide, magnesium hydroxide, 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, bismuth trimethylcarboxylate and the like.

(B) As a catalyst similar to the electron donating amine compound, N, N-dimethyl-4-aminopyridine, 4-diethylaminopyridine, 4-aminopyridine, 2-aminopyridine, 2-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine, 4-hydroxypyridine,
Examples thereof include 2-dimethylaminoimidazole, 2-methoxyimidazole, 2-mercaptoimidazole, aminoquinoline, imidazole, 2-methylimidazole, 4-methylimidazole, and diazabicyclooctane (DABCO).

(C) carbonic acid, acetic acid, formic acid, nitric acid, nitrous acid, oxalic acid, fluorinated boronic acid,
And hydrofluoric acid salts.

(D) As a catalyst similar to the electron donating phosphorus compound,
Triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tri-o-dimethoxyphenylphosphine, tri-p-tolylphosphine, tri-o-tolylphosphine, tributylphosphite , Triphenyl phosphite, tri-p-tolyl phosphite, tri-o-tolyl phosphite and the like.

Further, (e) a catalyst similar to the borane complex includes a complex of borane and the following compound, that is, ammonia, dimethylamine, trimethylamine, triethylamine, t
-Butylamine, dimethylaniline, pyridine, dimethylaminopyridine, morpholine, piperazine, pyrrole, tetrahydrofuran, dimethylsulfide, tri-
Complexes with n-butylphosphine, triphenylphosphine, triphenylphosphite, and the like are included.

One of these catalysts may be used alone, or two or more of them may be used in combination. The amount of the catalyst used is usually 1 × 10 ⁻⁶ to 1 mol based on the divalent hydroxy compound. Although it is possible, it is preferably 5 × 10 ^{−5 to} 5 × 10 ⁻² mol. If the amount of the catalyst used is less than 1 × 10 ^-6 mol, the polymerization rate becomes slow and causes coloration. On the other hand, if it exceeds 1 mol, the catalyst remaining in the obtained polycarbonate adversely affects the physical properties, for example, causes a mechanical deterioration in physical properties.

In the present invention, a two-stage reaction system is generally used as a method for producing a polycarbonate by a transesterification method using a divalent hydroxy compound and a bisaryl carbonate. That is, in the presence of a transesterification catalyst, the raw material is subjected to a first-stage reaction in which a relatively low-molecular-weight polycarbonate is produced in a molten state by a transesterification reaction, and polymerization is further promoted under a higher viscosity to produce a target high-molecular-weight polycarbonate. This is the second stage reaction obtained.

The reaction temperature in the first-stage reaction is from 100 ° C to 300 ° C, preferably from 130 ° C to 280 ° C. Reaction temperature
If the temperature is lower than 100 ° C., the reaction rate becomes slow, and if it is higher than 300 ° C., side reactions tend to occur. After removing the distillate of a predetermined phenol or the like under reduced pressure, a higher molecular weight can be obtained in the second stage reaction.

The reaction temperature in the second stage reaction is from 180 ° C to 350 ° C, preferably from 200 ° C to 320 ° C. Reaction temperature
If the temperature is lower than 180 ° C., it is difficult to remove phenol and the like for increasing the molecular weight, and if it is higher than 350 ° C., the coloring and side reaction of the resin are undesirably promoted. Further, this reaction is preferably performed under a high vacuum, and the degree of vacuum is 10
Torr or less, preferably 1 Torr or less.

As the catalyst addition time, it is also possible to initially charge the catalyst all at once or to use an appropriate catalyst for each of the first-stage reaction and the second-stage reaction.

Further, details of the production method of the present invention will be described, but the production method of the present invention is not limited thereto.

Production method (I) First, the first step may be performed in a general stirring tank.
Such a stirring tank is an adjusting tank for melting and dissolving the raw material monomers, such as a divalent hydroxy compound and bisaryl carbonate.

The second step may be performed in either a batch system or a continuous system. When the reaction is carried out batchwise, the reaction may be carried out using a single tank-type reaction vessel equipped with a usual stirrer, or may be carried out using a plurality of the reaction vessels. The stirrer is provided with turbine blades, paddle blades, anchor blades, helical ribbon blades, and improved types of these blades. From the viewpoint of molecular weight distribution and heat history, helical ribbon blades or blades used in improved high-viscosity tank types are particularly preferable. However, since the viscosity of the reaction product increases in the latter stage of the reaction, a tank-type reaction vessel equipped with a paddle type, lattice blade type, helicone blade type or the like as a stirrer for higher viscosity is also suitable. In the reaction of the second step, a transesterification catalyst was added while melting the divalent hydroxy compound and the bisaryl carbonate as raw material monomers in the tank-type reaction tank under a nitrogen purge, and the temperature was gradually increased with the progress of the reaction. By reducing the pressure gradually, by-product phenols are removed. In removing by-products such as phenol, the reaction tank is preferably provided with a distillation column in order to avoid as much as possible the raw materials in the system from being distilled off to the distillate side. In addition, a method of replenishing heat by installing a draft tube or the like in a reactor to compensate for a shortage of heat due to latent heat of vaporization with removal of by-products such as phenol is also included in the production method of the present invention. Reaction temperature is 13
The temperature is preferably from 0 ° C. to 300 ° C., and the degree of vacuum is preferably from 400 Torr to 0.5 Torr. The viscosity average molecular weight of the polycarbonate obtained in the second step is 5,000 to 30,000.

The third step is a step of further increasing the molecular weight of the polycarbonate obtained in the second step.

In the third step, the viscosity of the reaction mixture is very high, and a special polycondensation apparatus is required in the post-polycondensation step for synthesizing a high molecular weight polymer. Conventionally, a high-viscosity processing apparatus such as a (forced) thin film evaporator or a horizontal twin-screw polymerization apparatus has been used as an applicable apparatus.
A relatively long residence time is required for increasing the molecular weight, and it is difficult to obtain a polycarbonate polymer having a sufficiently high molecular weight, and it is difficult to say that the polycarbonate polymer is industrially effective. In the present invention, the aforementioned disadvantages can be overcome by using at least one or more paddle type self-cleaning twin-screw extruders in the third step. Here, the paddle shape refers to a blade that is discontinuous (that is, the valley portion of the blade does not have continuous connection) as compared with the screw, and includes a convex lens type or a pseudo triangle, but is not limited to these. Absent. In addition, the self-cleaning function means that the phases of a pair of left and right paddles incorporated in two shafts are out of phase, while maintaining a certain small gap so that the tip of one paddle cleans the side surface of the other paddle It is brought by rotating. Normal L / D =
In the range of 1 to 35 (L is the length of the jacket, D is the rotating diameter of the paddle), preferably L / D = 1 to 20. However, the present invention is not necessarily limited. The reaction temperature in the third step is usually from 200 ° C. to 320 ° C., and the degree of vacuum is from 1 Torr to 0.1 Torr. The residence time is between 0.2 and 2 hours, preferably between 0.4 and 1.0 hour, and is operated continuously. The surface of the reaction mixture is renewed in the system, and by-products such as phenol are removed from a distillation outlet connected to a vacuum system. The viscosity average molecular weight of the polycarbonate obtained in the third step is 12,000 to 60,000.

Production method (II) In another method of the present invention, the first step may be performed in the same manner as the first step of production method (I), and the second step is carried out in a tank-type reaction vessel while melting the monomer mixture. Perform a polycondensation reaction, to produce a polycarbonate prepolymer having a viscosity average molecular weight of 5,000 to 20,000, and further perform the polycondensation reaction of the prepolymer obtained in the second step as a third step in a tank-type reaction tank or a horizontal polymerization machine. Advance, viscosity average molecular weight is 10,000
A polycarbonate is obtained which is ~ 30000.

The second step of this method may be performed in either a batch system or a continuous system as in the second step of the production method (I).
When the reaction is carried out in a batch system, the reaction may be carried out using one or a plurality of tank-type reaction tanks equipped with a conventional stirrer as described above. The agitator is a turbine blade, paddle blade,
An anchor wing, a helical ribbon wing, and improved wings of these wings are provided. The viscosity average molecular weight of the polycarbonate prepolymer obtained in the second step is 5000 to 20
000.

Next, as a third step, the polycondensation of the polycarbonate prepolymer obtained in the second step is further advanced in a tank-type reaction vessel or a horizontal polymerization machine. The same type as the tank type reaction tank used in the above can be used. However, a tank-type reaction tank provided with a paddle type, lattice blade type, helicone blade type, or the like as a stirrer for higher viscosity is also suitable. In the present method, a horizontal polymerization machine can also be used. Here, a horizontal polymerization machine has one or two horizontal rotation shafts, and these have wings of a disk type, a pin type, an eyeglass type, a wheel type, etc., and usually has a residence time of 1 hour or more. In the horizontal type, it means a high hold type. The reaction temperature in the third step is 200 ° C ~ 3
The temperature at 20 ° C. and the degree of vacuum are preferably in the range of 10 Torr to 0.5 Torr. The viscosity average molecular weight of the polycarbonate obtained in the third step is
It is in the range of 10,000 to 30,000.

The fourth step is a step of further increasing the molecular weight of the polycarbonate obtained in the third step, using at least one or more paddle-type self-cleaning twin-screw extruders as in the third step of the production method (I), By carrying out the reaction under the same conditions, a polycarbonate having a viscosity average molecular weight of 12,000 to 60,000 is obtained.

〔Example〕

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example 1 Bisphenol A 4566 g (20 mol), diphenyl carbonate 4392 g (20.5 mol), 4-dimethylaminopyridine 4.88 g (0.04 mol) and sodium acetate 0.033 g (0.04 mol)
004 mol) was charged into 20 tank-type stirring tanks, and after purging with nitrogen, the mixture was heated to 180 ° C. and dissolved.

Next, the monomer mixture is supplied to a 20-tank type reaction tank equipped with a distillation column, and the pressure is reduced to 2 Torr while gradually raising the temperature from 180 ° C. to 260 ° C., and phenol produced as a by-product is distilled off. After about 4 hours, a polycarbonate prepolymer having a viscosity average molecular weight of 13,000 was obtained.

In addition, a paddle-type self-cleaning twin-screw extruder controlled at a temperature of 280 ° C and a pressure of 0.2 Torr by a gear pump (L / D = 8.9, paddle rotation diameter 50mm, shaft length 445.5m)
The above polycarbonate prepolymer was fed to m), and discharged by a gear pump at 850 g / Hr. Residence time is about 45 minutes. When the viscosity average molecular weight (v) of the obtained polycarbonate was measured, v = 28000.
The hue was A380-A580 = 0.110.

Here, the method of measuring the viscosity average molecular weight is to measure the intrinsic viscosity [η] of the methylene chloride solution at 20 ° C. using an Ubbelohde viscometer, and calculate the viscosity average molecular weight (v) by the following equation.
Was calculated.

[Η] = 1.11 × 10 ⁻⁴ (v) ^0.82 The hue was evaluated by measuring the difference in absorbance in the wavelength range of 380 μm and 580 μm with a UV measurement device using polycarbonate as a 10% methylene chloride solution. The larger the value, the more colored.

Example 2 In Example 1, after obtaining a polycarbonate prepolymer having a viscosity average molecular weight of 13000, the polycarbonate prepolymer was transferred to a 20-tank type reaction tank by a gear pump.
The polycondensation reaction was further promoted under the conditions of a temperature of 280 ° C. and a pressure of 1 Torr. At this stage, the viscosity average molecular weight of the polycarbonate is 20.
000.

In addition, a paddle-type self-cleaning twin-screw extruder controlled at a temperature of 280 ° C and a pressure of 0.2 Torr by a gear pump (L / D = 8.9, paddle rotation diameter 50mm, shaft length 445.5m)
The above polycarbonate was fed into m), and discharged with a gear pump at 800 g / Hr. Residence time is about 45 minutes. The viscosity average molecular weight of the obtained polycarbonate (
When v) was measured, v = 27,000. The hue is A
380-A580 = 0.101.

Example 3 In Example 2, 3.28 g of 2-methylimidazole (0.04
Mol), and the viscosity average molecular weight was 1400 in the tank type reaction vessel used in Example 2 under the same charging conditions as in Example 2.
After obtaining a polycarbonate prepolymer of No. 0, polycondensation was further carried out in a similar horizontal reaction layer with a gear pump to obtain a polycarbonate having a viscosity average molecular weight of 18,000.

Next, this reaction mixture was fed into a paddle type self-cleaning twin-screw extruder controlled at a temperature of 280 ° C. and a pressure of 0.2 Torr by a gear pump, and discharged by a gear pump at 900 g / Hr. The viscosity average molecular weight of the obtained polymer was 29,000. The hue was A380-A580 = 0.105.

Example 4 A polycarbonate prepolymer having a viscosity average molecular weight of 14,000 was obtained in a tank-type reaction tank under the same charging conditions as in Example 2, and this was further charged into a horizontal polymerization machine with a gear pump, and the temperature was lowered.
The reaction was carried out at 280 ° C and a pressure of 1 Torr, and a polycarbonate having a viscosity average molecular weight of 20,000 was obtained.Then, the mixture was sent to a paddle type self-cleaning twin-screw extruder controlled at a temperature of 280 ° C and a pressure of 0.2 Torr by a gear pump, and 900 g / g Discharge was performed with Hr. The viscosity average molecular weight of the obtained polymer is 30.
000. The hue was A380-A580 = 0.102.

Comparative Example 1 After obtaining a polycarbonate under the same conditions as in Example 2,
Furthermore, instead of the paddle type self-cleaning twin-screw extruder, this polycarbonate is sent to a horizontal twin-screw polymerization machine,
At a temperature of 280 ° C. and a pressure of 0.2 Torr, the mixture was discharged at 800 g / Hr with a gear pump. The residence time was about 3 hours, and the viscosity average molecular weight of the obtained polymer was 22,000. The hue was A380-A580 = 0.27.

Comparative Example 2 After obtaining polycarbonate under the same conditions as in Example 2,
Further, this polycarbonate was fed into a screw evaporator instead of a paddle type self-cleaning twin-screw extruder, and discharged at 300 g and a pressure of 0.2 Torr by a gear pump at 900 g / Hr. The residence time was about 10 minutes, and the viscosity average molecular weight of the obtained polymer was 24,000. Further, the hue was A380-A580 = 0.50, and a black kogation was locally observed.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, a colorless and transparent high molecular weight polycarbonate can be manufactured efficiently.

Claims (2)

(57) [Claims] 1. A method for producing a polycarbonate by melt-polycondensing a divalent hydroxy compound and a bisaryl carbonate by a transesterification method, wherein the monomer is melted in a regulating tank as a first step, and the monomer is melted in a second step. A polycondensation reaction is performed in a tank-type reaction tank while the mixture is being melted to obtain a polycarbonate having a viscosity average molecular weight of 5,000 to 30,000, and then at least one paddle-type self-cleaning twin-screw extruder is used as a third step. And obtaining a polycarbonate having a viscosity average molecular weight of 12,000 to 60,000. 2. A method for producing a polycarbonate by subjecting a divalent hydroxy compound and a bisaryl carbonate to melt polycondensation by a transesterification method, wherein the monomer is melted in a regulating tank as a first step, and the monomer is melted as a second step. A polycondensation reaction is performed in a tank-type reaction vessel under melting of the mixture to generate a polycarbonate prepolymer having a viscosity average molecular weight of 5,000 to 20,000, and a polycondensation reaction of the prepolymer obtained in the second step as the third step is performed. Further proceed with a tank type reaction tank or horizontal polymerization machine, the viscosity average molecular weight is 10,000 ~ 300
A polycarbonate having a viscosity-average molecular weight of 12,000 to 60,000 using a paddle-type self-cleaning twin-screw extruder of at least one unit as a fourth step after obtaining a polycarbonate having a viscosity of 12,000 to 60,000. .