JPH107784A - Production of polycarbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process whereby a high-quality polycarbonate is efficiently produced by polymerizing a prepolymer in the solid state or swelled solid state under specified conditions. SOLUTION: A polycarbonate prepolymer is polymerized in the solid state or swelled solid state while the concn. of oxygen in the vapor phase is kept at 2ppm or lower. Moreover, the concn. of water in the reaction system is pref. 2ppm or lower. After the prepolymer is prepd. by prepolymerizing a dihydroxy compd. and a carbonic diester or phosgene, the prepolymer in the crystalline state is polymerized in the solid state or swelled solid state. Pref. a nitrogen-contg. org. basic compd. is used as the catalyst in preparing the prepolymer. The prepolymer is polymerized in the solid state or swelled solid state in the presence of a quat. phosphonium salt as the catalyst.

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 a polycarbonate, and more particularly, to a method for efficiently producing a polycarbonate having excellent quality by polymerizing a polycarbonate prepolymer in a solid state or a swollen solid state. It is about.

[0002]

2. Description of the Related Art Polycarbonate can be produced by directly reacting an aromatic dihydroxy compound such as bisphenol A with phosgene (interfacial method) or by melting an aromatic dihydroxy compound such as bisphenol A and a diester carbonate such as diphenyl carbonate. A method of performing a transesterification reaction (melting method / solid phase method) in a solid state or a solid state is known.

[0003] The interface method has disadvantages such as the use of toxic phosgene and the corrosion of the apparatus by a by-product chlorine-containing compound. On the other hand, in the melting method, usually 280
In order to react for a long time under high temperature of ℃ ~ 310 ℃,
There were problems such as the inevitable coloring of the obtained polycarbonate and the inability to obtain a high molecular weight product. In order to solve these problems in the melting method, various improved methods have been proposed, such as a method using a specific catalyst and a method of adding an antioxidant at a later stage of the polymerization reaction. Among them, it is disclosed that a polycarbonate having excellent hydrolysis resistance and color tone can be obtained by lowering the oxygen concentration of a polymerization system at the time of performing a transesterification reaction to a certain fixed value or less (Japanese Patent Application Laid-Open No. 26
No. 010), no satisfactory burn-in or color tone has yet been obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional method for producing a polycarbonate and to provide a method for efficiently producing a polycarbonate having excellent quality. Things.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has prepared a polycarbonate prepolymer (hereinafter sometimes abbreviated as "prepolymer"). When the prepolymer is polymerized in the solid state or swollen solid state, the oxygen concentration in the gas phase is 2p
pm or less, and when the water concentration is 2
It has been found that by polymerizing in a state of not more than ppm, a polycarbonate having excellent quality can be efficiently produced and the above object can be achieved. The present invention has been completed based on such findings.

That is, according to the present invention, (1) when producing a polycarbonate by polymerizing a polycarbonate prepolymer in a solid state or a swollen solid state, the oxygen concentration in the gas phase is 2 ppm or less, preferably the water concentration Is 2pp
It is intended to provide a method for producing a polycarbonate obtained by polymerizing in a state of m or less.

In a preferred embodiment for carrying out the present invention, (2) a polycarbonate prepolymer is prepared by using a nitrogen-containing organic basic compound as a catalyst when preparing the polycarbonate prepolymer. (3) The method according to the above (1) or (2), wherein after preparing the polycarbonate prepolymer, the prepolymer is polymerized in a solid state or a swollen solid state using a quaternary phosphonium salt as a catalyst. (4) The method according to (1) to (4), wherein the production of the polycarbonate is carried out by a transesterification reaction using a dihydroxy compound and a carbonic acid diester.
A method for producing a polycarbonate according to any one of (3).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, preferably,
Dihydroxy compound of component (A) as raw material and (B)
A prepolymer is prepared by prepolymerization using the component carbonic acid diester or phosgene and, if necessary, a terminal terminator or a branching agent, and then the crystallized prepolymer is polymerized in a solid state or a swollen solid state. Thereby, a polycarbonate is produced.

As a catalyst, a nitrogen-containing organic basic compound is preferably used at the time of preliminary polymerization, and a quaternary phosphonium salt is preferably used at the time of polymerization in a solid state or a swollen solid state. (1) Raw material (A) Dihydroxy compound For example, an aromatic dihydroxy compound and an aliphatic dihydroxy compound are mentioned, and at least one compound selected from these is used.

The aromatic dihydroxy compound used as one of the components (A) has the general formula (I)

[0011]

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The compounds represented by the following formulas can be mentioned.
In the above general formula (I), R ³ and R ⁴ are each a halogen atom of fluorine, chlorine, bromine or iodine or an alkyl group having 1 to 8 carbon atoms, for example, a methyl group, an ethyl group, n-
Propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl,
It represents a hexyl group, a cyclohexyl group, a hebutyl group, an octyl group, or the like. R ³ and R ⁴ may be the same or different. The plurality of R ³ when there are a plurality of R ³ may be the same or different, a plurality of R ⁴ if R ⁴ there are a plurality may be the same or different. m and n are each an integer of 0-4. Z is a single bond, an alkylene group having 1 to 8 carbon atoms, an alkylidene group having 2 to 8 carbon atoms, a cycloalkylene group having 5 to 15 carbon atoms, a cycloalkylidene group having 5 to 15 carbon atoms, or -S-, −
SO—, —SO ₂ —, —O—, —CO— bond or formula (II), (II ′)

[0013]

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[0014] The bond represented by Examples of the alkylene group having 1 to 8 carbon atoms and the alkylidene group having 2 to 8 carbon atoms include:
Examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, an ethylidene group, an isopropylidene group and the like. As a cycloalkylene group having 5 to 15 carbon atoms and a cycloalkylidene group having 5 to 15 carbon atoms, Examples thereof include a cyclopentylene group, a cyclohexylene group, a cyclopentylidene group, and a cyclohexylidene group.

In a preferred production method of the present invention,
As the dihydroxy compound of the component (A), one or more of the above compounds are appropriately selected and used, and among these, bisphenol A which is an aromatic dihydroxy compound is preferably used. Further, diesters of dihydroxy compounds, dicarbonates of dihydroxy compounds, monocarbonates of dihydroxy compounds, and the like can also be used.

Component (B) Various carbonic acid diesters are used. For example, it is at least one compound selected from diaryl carbonate compounds, dialkyl carbonate compounds and alkylaryl carbonate compounds.

The diaryl carbonate compound used as one of the components (B) has the general formula (III)

[0018]

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Wherein Ar ¹ and Ar ² each represent an aryl group, which may be the same or different, or a compound of the general formula (IV)

[0020]

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(Wherein, Ar ³ and Ar ⁴ each represent an aryl group, which may be the same or different, and D ¹ represents a residue obtained by removing two hydroxyl groups from the aromatic dihydroxy compound. ). The dialkyl carbonate compound is represented by the general formula (V)

[0022]

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(Wherein R ⁵ and R ⁶ each have 1 carbon atom)
And represents an alkyl group having from 6 to 6 or a cycloalkyl group having from 4 to 7 carbon atoms, which may be the same or different. Or a compound represented by the general formula (VI)

[0024]

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Wherein R ⁷ and R ⁸ each have 1 carbon atom
And a cycloalkyl group having 4 to 7 carbon atoms, which may be the same or different, and D ² represents a hydroxyl group 2 from the aromatic dihydroxy compound.
The residue excluding the number is shown. ). The alkylaryl carbonate compound is represented by the general formula (VII)

[0026]

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(Wherein, Ar ⁵ represents an aryl group, R ⁹ represents an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 47 carbon atoms), or a compound represented by the general formula (VIII)

[0028]

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(Wherein, Ar ⁶ is an aryl group, R ¹⁰ is an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 4 to 7 carbon atoms, and D ³ is a group obtained by removing two hydroxyl groups from the aromatic dihydroxy compound. The compound is a compound represented by the following formula: As the carbonic acid diester of the component (B), one or more of the above compounds are appropriately selected and used, and among these, diphenyl carbonate is preferably used.

Phosgene It is also possible to use phosgene as the component (B). In this case, it is necessary to use an appropriate amount of the monohydroxy compound. (2) Preparation of Prepolymer by Prepolymerization In the prepolymerization, the dihydroxy compound of component (A) and the carbonic acid diester or phosgene of component (B) are used as raw materials, and if necessary, a terminal terminator or a branching agent is used. , Prepare a prepolymer. In this case, it is preferable to use a nitrogen-containing organic basic compound as the polymerization catalyst.

Specific preferred procedures and conditions of the production method will be described. Method of Prepolymerization (i) A prepolymer can be prepared by treating a dihydroxydiaryl compound and a diarylcarbonate with heating to remove an aromatic monohydroxy compound. The polymerization average molecular weight of the prepolymer produced in this prepolymerization step is preferably 2000
It is selected in the range of ２０20,000. This prepolymerization reaction,
It is preferably carried out in the molten state. In this case, for example, a solvent inert to the reaction, such as methylene chloride or chloroform, may be used. However, the reaction is usually carried out without a solvent and in a molten state.

The use ratio (preparation ratio) of the diaryl carbonate and the dihydroxydiaryl compound varies depending on the kind used, the reaction temperature, and the reaction conditions. , Usually 0.9 to 2.5 mol, preferably 0.95 to 2.0 mol, more preferably 0.9.
It is used in a ratio of 8 to 1.5 mol.

The reaction temperature and reaction time vary depending on the type and amount of the starting materials and catalysts used, the required polymerization amount of the obtained prepolymer, other reaction conditions, and the like.
It is selected at a temperature of 50 ° C., preferably in the range of 1 minute to 100 hours. In order not to color the prepolymer, it is desirable to carry out the prepolymerization reaction at a temperature as low as possible and in a short time. In this reaction, a prepolymer having a relatively low molecular weight may be produced by this prepolymerization, so that a colorless and transparent prepolymer having a required degree of polymerization can be easily obtained under the above conditions. The pressure during the reaction is preferably from 1 Torr to 5 kg / cm ² G.

As a reactor used in such a prepolymer production step, any conventionally known polymerization reactor may be used. The reaction step may be performed in one step or may be performed by dividing into more steps. In addition, one or more reactors can be used by connecting them in series or in parallel. For this production, any of a batch method, a continuous method, and a method using a combination thereof may be used.

The terminal ratio of the prepolymer produced by this step is preferably phenyl carbonate terminal: hydroxyl terminal = 1: 4 to 4: 1, more preferably 1: 4.
1.5 to 1.5: 1, more preferably 1: 1 to 1.
The range is 1: 1. When the terminal ratio is out of the above range,
The final reached molecular weight is limited, and it is difficult to increase the molecular weight. (Ii) A prepolymer can also be prepared by a known method in which an aromatic dihydroxy compound and phosgene are reacted in the presence of the above-mentioned molecular weight regulator, acid binder and solvent. (Iii) Further, in order to obtain a spherical prepolymer, an organic solvent solution of the polycarbonate prepolymer is supplied to a granulation vessel in which the prepolymer powder obtained in the pre-polymerization step is present, and the organic solvent solution is mixed with a polycarbonate. The organic solvent may be evaporated while being in contact with the prepolymer powder to granulate into a spherical prepolymer. The prepolymer powder used here can be produced by the above method.

In this method, first, the concentration of the prepolymer obtained as described above in an organic solvent solution is adjusted to 1 to 5
It is preferably 0% by weight. In order to obtain a spherical prepolymer from a solution of the prepolymer in an organic solvent, first, the prepolymer powder is charged into a granulation container and kept in a stirred state. Next, an organic solvent solution of the prepolymer is supplied thereto. While the supplied organic solvent solution is in contact with the prepolymer powder being stirred, the organic solvent is evaporated on the powder, and the mixture is subsequently stirred and mixed to form a spherical shape close to a granulated and crystallized true spherical shape. A prepolymer can be obtained.

The spherical prepolymer granulated in the granulation vessel is taken out of the granulation vessel by appropriate means, and is used in the next step to produce polycarbonate by solid-state polymerization or swelling solid-state polymerization. You. In this granulation step, a prepolymer powder previously charged into a granulation container and stirred in advance of granulation can be obtained by a conventionally known method. For example, what was concentrated and pulverized using a kneader or the like can be used. The particle size of the prepolymer powder to be charged in the granulation container in advance is not particularly limited, but is preferably adjusted to about 0.5 to 3 mm. The charge amount is not particularly limited. The supply amount of the organic solvent solution of the prepolymer supplied to the granulation container is 500% by weight or less per hour based on the amount of the prepolymer powder uniformly stirred and existing in the granulation container. is there. The method of supplying the organic solvent solution of the prepolymer to the granulation container is not particularly limited.

When the prepolymer organic solvent solution is supplied to the granulation container, the granulation can be more effectively performed by simultaneously supplying a non-solvent or poor solvent of polycarbonate as a crystallization agent. Here, examples of the crystallization agent include linear or cyclic alkanes such as pentane, hexane, heptane, and octane; ketones such as acetone and methyl ethyl ketone; and aromatic compounds such as benzene, toluene, and xylene. .

When the crystallization agent is supplied at the same time, the amount of the crystallization agent mixed into the organic solvent solution of the prepolymer, that is, (crystallization agent) / (prepolymer organic solvent solution amount ×
(Concentration of solution of prepolymer) × 100% = Preferred amount is preferably 5 to 50% by weight based on the amount of prepolymer solids in the organic solvent solution of prepolymer. Further, the residence time of the spherical prepolymer in the granulation container is related to the supply amount of the organic solvent solution of the prepolymer.
About 6 hours. As the temperature for granulation, a temperature at which the organic solvent of the organic solvent solution of the prepolymer is maintained in an atmosphere that does not hinder evaporation is desired.
It is kept at ２００200 ° C. Pressure granulation vessel is held preferably in -500mmHg~10kg / cm ^2.

Catalyst in Prepolymerization It is preferable to use a nitrogen-containing organic basic compound as a catalyst. The nitrogen-containing organic basic compound is not particularly limited, and examples thereof include an aliphatic tertiary amine compound, an aromatic tertiary amine compound, and a nitrogen-containing heterocyclic compound. Moreover, the general formula _{^{(X) (NR 1 4)}} + (X 1) - quaternary ammonium salt represented by · · · (X) can be exemplified.

In the general formula (X), R ¹ is an organic group,
For example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a cyclohexyl group, an aryl group such as a cycloalkyl group, a phenyl group, a tolyl group, a naphthyl group, a biphenyl group;
And an arylalkyl group such as a benzyl group. The four R ^{1 's} may be the same or different, and two R ^{1' s} may combine to form a ring structure. X ¹
Represents a halogen atom, a hydroxyl group or BR ₄ . Where R
Represents a hydrogen atom or a hydrocarbon group such as an alkyl group or an aryl group, and the four Rs may be the same or different.

Such quaternary ammonium salts include:
For example, ammonium hydroxides having an alkyl group, an aryl group, an araryl group and the like, such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, tetramethylammonium borohydride, tetrabutylammonium Examples include basic salts such as borohydride, tetrabutylammonium tetraphenylborate, and tetramethylammonium tetraphenylborate.

Among these nitrogen-containing organic basic compounds,
Quaternary ammonium salts represented by the above general formula (I), such as tetramethylammonium hydroxide and tetrabutylammonium, have high catalytic activity, are easily thermally decomposed, and do not easily remain in the polymer. Hydroxide, tetramethylammonium borohydride and tetrabutylammonium borohydride are preferred, and tetramethylammonium hydroxide is particularly preferred.

Such a nitrogen-containing organic basic compound is one kind
They may be used, or two or more kinds may be used in combination.
The nitrogen-containing organic basic compound is preferably 10^-2-10^-8Mo
, More preferably 10^-3-10^-7Desirable to use mole
New The amount of the nitrogen-containing organic basic compound used is 10 ^-8Mole not
If it is full, the catalyst activity in the early stage of the reaction will be insufficient, and 10
^-2Exceeding the mole leads to an increase in cost, which is not preferable.

Crystallization of Prepolymer The method for crystallizing the prepolymer is not particularly limited, but a solvent treatment method and a heat crystallization method are preferably used. The former solvent treatment method is a method of crystallizing a prepolymer using a suitable solvent such as chloromethane, methylene chloride, chloroform and the like. The amount of solvent used is
Although it depends on various conditions, it is preferably selected in the range of 0.05 to 100 times by weight based on the prepolymer.

On the other hand, in the heat crystallization method, the prepolymer is heated at a temperature not lower than the glass transition temperature of the intended aromatic polycarbonate and lower than the temperature at which the prepolymer begins to melt. It is a way to make it. The temperature Tc (° C.) at which this heat crystallization is performed is not particularly limited as long as it is equal to or higher than the glass transition temperature of the target aromatic polycarbonate and lower than the melting temperature Tm (° C.) of the prepolymer. (3) Production of Polycarbonate by Polymerization In the present invention, after preparing a polycarbonate prepolymer, the prepolymer is polymerized in a solid state or a swollen solid state, preferably using a quaternary phosphonium salt as a polymerization catalyst. Further, the nitrogen-containing organic basic compound used in the above-mentioned preliminary polymerization may be used as a catalyst. Furthermore, a trivalent phosphorus compound or a pentavalent phosphorus compound can be used as a catalyst.

[0047] As the quaternary phosphonium salts quaternary phosphonium salt is not particularly limited, there are various things, but for example the general formula _{^{(IX) (PR 2 4)}} + (X 2) - in · · · (IX) The compounds represented are preferably used.

In the general formula (IX), R ² represents an organic group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group,
Examples include an alkyl group such as an octyl group and a cyclohexyl group, a cycloalkyl group, an aryl group such as a phenyl group, a tolyl group, a naphthyl group and a biphenyl group, and an arylalkyl group such as a benzyl group. The four R ² may be the same or different, and two R ²
May combine with each other to form a ring structure. X ² represents a halogen atom, a hydroxyl group, an alkyloxy group, an aryloxy group, (R′O) ₂ P (＝ O) O or BR ″ ₄ . Here, R 'represents a hydrocarbon group such as an alkyl group or an aryl group, and two R'Os may be the same or different. R ″ represents a hydrogen atom or a hydrocarbon group such as an alkyl group or an aryl group, and the four R ″ s may be the same or different.

Such quaternary phosphonium salts include:
For example, tetraphenylphosphonium hydroxide, tetranaphthylphosphonium hydroxide, tetra (chlorophenyl) phosphonium hydroxide, tetra (biphenyl) phosphonium hydroxide, tetratolylphosphonium hydroxide, tetramethylphosphonium hydroxide, tetraethylphosphonium hydroxide, tetrabutylphosphonium hydroxy (Aryl or alkyl) phosphonium hydroxides such as tetramethylphosphonium tetraphenylborate, tetraphenylphosphonium bromide, tetraphenylphosphonium phenolate, tetraphenylphosphonium tetraphenylborate, methyltriphenylphosphonium tetraphenylborate, benzyl Triphenylphosphonium La tetraphenylborate, biphenyl triphenylphosphonium tetraphenylborate, tetra-tolyl phosphonium tetraphenylborate, tetraphenylphosphonium phenolate, tetra (p-t
-Butylphenyl) phosphonium diphenyl phosphate, triphenylbutylphosphonium phenolate, triphenylbutylphosphonium tetraphenylborate and the like.

In addition to the compound represented by the above general formula (IX), for example, bis-tetraphenylphosphonium salt of 2,2-bis (4-hydroxyphenyl) propane,
Ethylenebis (triphenylphosphonium) dibromide, trimethylenebis (triphenylphosphonium)-
Bis (tetraphenyl borate) and the like can also be mentioned.

Among these quaternary phosphonium salts, tetraphenylphosphonium tetraphenylborate, biphenyltriphenylphosphonium tetraphenylborate and tetraphenylphosphonium tetraphenylborate are preferred because of their high catalytic activity, easy thermal decomposition and low persistence in the polymer. Cyclohexyltriphenylphosphonium tetraphenylborate is preferred.

The quaternary phosphonium salt may be used alone or in combination of two or more. The quaternary phosphonium salt is preferably used in an amount of 10 ⁻² to 10 based on 1 mol of the dihydroxy compound of the component (A) as a raw material.
^It is desirable to use ^-8 mol. If the amount of the quaternary phosphonium salt is less than 10 ^-8 mol, the catalytic activity in the latter half of the reaction will be insufficient, and if it exceeds 10 ^-2 mol, the cost will increase, which is not preferable.

Polymerization in Solid State The solid prepolymer in the crystallized state is
Further, a polymerization reaction is performed. In this case, it is preferable to carry out the polymerization by adding a quaternary phosphonium salt as a catalyst, but the reaction is accelerated by extracting the aromatic monohydroxy compound, diaryl carbonate or both, which are by-produced by the reaction, out of the system. Is done. For this purpose, an inert gas such as nitrogen, argon, helium, or carbon dioxide or a lower hydrocarbon gas is introduced to remove the gas together with the gas, a method of performing a reaction under reduced pressure, or a method of performing the reaction under reduced pressure. Are preferably used. When introducing entraining gases, it is desirable to heat these gases to a temperature near the reaction temperature.

The shape of the crystallized prepolymer for carrying out the solid-state polymerization reaction is not particularly limited, but is preferably in the form of pellets, beads or the like. As the reaction catalyst in this solid-phase polymerization, a quaternary phosphonium salt and other catalysts are used as needed, but they are added in the prepolymer production step, and the remaining one may be used as it is, or The catalyst may be added again in powder, liquid or gaseous state.

The polymerization reaction temperature Tp (° C.) and the reaction time vary depending on various conditions, but are preferably higher than or equal to the glass transition temperature of the target aromatic polycarbonate and the crystallization prepolymer during the solid phase polymerization is melted. Instead, the heating is performed by heating at a temperature in a range in which the solid phase is maintained for 1 minute to 100 hours. Such a temperature range is preferably about 150 to 260 ° C, particularly preferably about 180 to 230 ° C in the case of producing a polycarbonate of bisphenol A.

In the polymerization step, in order to apply heat to the polymer being polymerized as uniformly as possible or to favorably remove by-products, stirring is performed, the reactor is rotated itself, or heated gas is used. Is preferably used. In general, the weight average molecular weight of an industrially useful aromatic polycarbonate is 6,000.
Although it is about 200,000, a polycarbonate having such a degree of polymerization can be easily obtained by performing the solid phase polymerization step.

The crystallinity of the aromatic polycarbonate obtained by solid-state polymerization of the crystallized prepolymer is usually higher than the crystallinity of the original prepolymer.
In the method of the present invention, a crystalline aromatic polycarbonate powder is usually obtained. The crystalline aromatic polycarbonate powder can be directly introduced into an extruder and pelletized without cooling, or can be directly introduced into a molding machine without cooling and molded.

The ratio between the prepolymerization and the solid-phase polymerization which contribute to the polymerization may be changed in a wide range. Polymerization in Swelled Solid State This is a method in which the prepolymer obtained in the prepolymerization step is crystallized and then further polymerized by solid state polymerization in a state swollen by a swelling gas described later. This production method is a method for producing a polycarbonate by a transesterification reaction. In the case of removing or extracting and removing a low-molecular compound such as phenol as a by-product, from a polymer (prepolymer) in a swelling state by a swelling gas, De-brightening or extraction removal of low-molecular compounds is an application of the fact that mass transfer rate is faster than that of high-viscosity molten polymers or crystallized solids, and the reaction can be performed with high efficiency. .

The above method can be divided into a flake forming step of the prepolymer obtained as described above, and a high molecular weight converting step in which a high molecular weight is obtained by a solid phase polymerization method under the flow of a swelling solvent (swelling solid state polymerization step). The molecular weight of the prepolymer suitable for the flake forming step is 1500 in terms of viscosity average molecular weight (Mv).
~ 30000. If the molecular weight is lower than this range, the melting point is lowered, and it is necessary to lower the solid-state polymerization temperature.

In the flake forming step, conventionally known methods such as a rolling granulation method, an extrusion granulation method, a compression granulation method, a melt granulation method, a spray drying granulation method, a fluidized bed granulation method, A crushing granulation method, a stirring granulation method, a liquid phase granulation method, a vacuum freeze granulation method, or the like can be used depending on the case. The shape of the flake is not particularly limited, but is preferably a pellet, a bead, or the like from the viewpoint of operability. Further, a stirring granulation method in which the prepolymer is once dissolved in a swelling solvent used in the next step, and a poor solvent for the polycarbonate is mixed therein while forming a flake is also effective. In the polymerization, flake drying is not particularly required.

Next, in the swelling solid phase polymerization step, the molecular weight of the prepolymer is further increased while maintaining the flakes in the solid state. This step is characterized in that solid phase polymerization is performed in a swelling solvent atmosphere, and the swelling effect improves the efficiency of removing phenol by-produced. Through this step, it is possible to lower the temperature as compared with a normal melt transesterification reaction, and further, it is possible to greatly shorten the reaction time as compared with a normal solid-state polymerization or melt transesterification.

The swelling solvent used here is a single swelling solvent capable of swelling polycarbonate under the following reaction conditions:
A mixture of these single swelling solvents, or a mixture of a single swelling solvent or a mixture thereof with a poor solvent of polycarbonate as a single or several kinds of mixtures is shown. The swelling state in this step refers to a state in which the prepolymer flakes, which are the reaction raw materials, are increased volumetrically or by weight above the thermal swelling value within the range of the reaction conditions shown below,
The swelling solvent is a single compound having a boiling point of completely vaporizing under the following reaction conditions, or a single compound having a vapor pressure of usually 50 mmHg or more, or a mixture thereof,
Simultaneously, it refers to one that can form the above-mentioned swollen state.

Such a swelling solvent is not particularly limited as long as it satisfies the above swelling conditions. For example, aromatic compounds and oxygen-containing compounds having a solubility parameter in the range of usually 4 to 20 (cal / cm ³ ) ^1/2 , preferably 7 to 14 (cal / cm ³ ) ^1/2 are applicable. Specific swelling solvents include, for example, benzene, toluene, xylene, ethylbenzene,
Aromatic hydrocarbons such as diethylbenzene, propylbenzene and dipropylbenzene; ethers such as tetrahydrofuran and dioxane; ketones such as methyl ethyl ketone and methyl isobutyl ketone. Among these, a single compound of an aromatic hydrocarbon having 6 to 20 carbon atoms or a mixture thereof is preferable.

The conditions of the poor solvent mixed with the swelling solvent are as follows. Under the following reaction conditions, the solubility of the polycarbonate in the solvent is 0.1% by weight or less, and the linear or branched polycarbonate is less likely to be involved in the reaction. A saturated hydrocarbon compound having 4 to 18 carbon atoms having a chain, or an unsaturated hydrocarbon compound having 4 to 18 carbon atoms and a low degree is preferred. If the boiling point of both the swelling solvent and the poor solvent exceeds 250 ° C., it becomes difficult to remove the residual solvent, and the quality may deteriorate, which is not preferable.

When a mixture of such a poor solvent and a swelling solvent is used, 1% by weight of the swelling solvent is contained in the mixed solvent.
The swelling solvent is preferably contained in the mixed solvent in an amount of at least 5% by weight. In this swelling solid-state polymerization step, the reaction temperature is preferably 100 to 240 ° C, and the pressure during the reaction is preferably 10 Torr to 5 kg /
It is carried out at cm ² G, particularly preferably at atmospheric pressure. If the reaction temperature is lower than the above range, the transesterification reaction does not proceed, and under the high temperature condition where the reaction temperature exceeds the melting point of the prepolymer, the solid state cannot be maintained, and phenomena such as fusion between particles occur. Properties are significantly reduced. Therefore, the reaction temperature must be lower than the melting point.

As a reaction catalyst in the swelling solid phase polymerization step, a quaternary phosphonium salt and other catalysts may be used, if necessary. Alternatively, the catalyst may be added again in a powder, liquid or gaseous state. The swelling solvent gas may be supplied to the reactor in a liquid state and vaporized in the reactor, or may be supplied to the reactor after being vaporized by a heat exchanger or the like in advance. The flow rate of the swelling solvent gas is 1
It should be at least 10 ^-3 cm / s, preferably 1 x 1
0 ^-3 cm / s or more is preferable. The gas supply amount was 0.5 liter per 1 g of prepolymer (standard state) / hr.
It is preferable to supply the above gas to the reactor. The flow rate of the swelling solvent gas is closely related to the reaction rate, and acts as a heat medium simultaneously with the phenol removal effect. Therefore, the reaction rate increases as the gas flow rate increases. There is no particular limitation on the reactor used for such swelling solid-state polymerization.

For drying and pelletizing the high molecular weight polycarbonate, a conventional method can be used, and there is no particular limitation. When mixing the additives, it is preferable to apply the additive powder directly to the flakes before or after drying, or to spray the liquid and absorb the gas, but it is also possible to mix with an extruder during pelletization. . The mixing ratio between the inert gas and the swelling solvent may be such that the mixing solvent gas contains at least 1% by volume of the swelling solvent, and preferably 5% by volume or more of the swelling solvent is mixed with the mixed solvent. It is better to let it.

In the solid-state polymerization or swollen solid-state polymerization of the present invention, if necessary, it is preferable to use a terminal terminator such as pt-butylphenol, p-cumylphenol and p-phenylphenol. it can. further,
Known branching agents can be used as necessary. Further, if necessary, a known antioxidant may be added to the reaction system. As this antioxidant, a phosphorus-based antioxidant is preferably used.

Oxygen Concentration and Moisture Concentration in the Gas Phase in the Polymerization System In the present invention, the oxygen concentration in the gas phase in the reaction system in which the polymerization is performed needs to be 2 ppm or less. It is preferably at most 1 ppm, more preferably at most 0.5 ppm. In addition, the water concentration in the reaction system was 2 p.
pm or less, more preferably 1 ppm or less. When the oxygen concentration in the reaction system in which the polymerization is performed exceeds 2 ppm, the resulting resin tends to be colored, and the thermal stability is deteriorated. The water concentration in the reaction system was also 2
If it exceeds ppm, it is considered that hydrolysis occurs during the reaction, which is not preferable in that it has an adverse effect such as a decrease in catalytic activity.

The method for reducing the oxygen concentration in the reaction system to 2 ppm or less and the water concentration to 2 ppm or less is not particularly limited. For example, an oxygen removing tube incorporating an oxygen filter or the like before the polymerization vessel inlet, What is necessary is just to provide a water removal tube in which a moisture filter or the like is incorporated. The polycarbonate obtained by the present invention comprises a plasticizer, a pigment,
Known additives such as lubricants, release agents, stabilizers, inorganic fillers and the like can be used in combination. This polycarbonate is made of polyolefin, polystyrene,
It can be blended with polymers such as polyester, polysulfonate, polyamide and polyphenylene ether. In particular, it is effective to use in combination with polyphenylene ether, polyether nitrile, terminal-modified polysiloxane compound, modified polypropylene, modified polystyrene or the like having OH group, COOH group, NH ₂ group or the like at the terminal.

[0071]

Next, 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. Examples 1 and 2 228 g (1.0 mol) of bisphenol A (BPA), 225 g (1.05 mol) of diphenyl carbonate, and tetramethylammonium hydroxide (0.5 mol) were placed in a nickel steel autoclave with an internal volume of 1 liter and equipped with a stirrer.
Mmol), and the atmosphere was replaced with argon five times. Thereafter, the mixture is heated to 180 ° C. and heated under argon atmosphere for 3 hours.
The reaction was performed for 0 minutes. The temperature is then increased to 240 over 120 minutes.
At the same time, raise the degree of vacuum to 8 mmHg and react, further raise the temperature to 270 ° C over 30 minutes, and at the same time raise the degree of vacuum to 7 mmHg and react, and finally raise the degree of vacuum to 1 mmHg The reaction was performed for 5 minutes. After the reaction was completed, the inside of the reactor was returned to atmospheric pressure with argon, and the content of the prepolymer was taken out and pulverized.

The number average molecular weight ( ¹ H-
NMR) (calculated from NMR) was 4,500, and the terminal fraction of hydroxyl groups was 49.5%. The prepolymer thus obtained was dissolved in methylene chloride, and the catalyst shown in Table 1 was added. Then, paraxylene was added to precipitate a powder. A polymer powder was obtained. This powder is SUS of 10mm in diameter and 200mm in length
1 g was charged into the tube, and nitrogen was flowed at a rate of 50 ml / min at 220 ° C., and solid-state polymerization was performed for 90 minutes. At this time, an oxygen removing tube (indicating oxygen generator trap (manufactured by GL Science)) and a water removing tube (moisture filter (manufactured by GL Science)) were attached to the polymerization reaction inlet, and the oxygen concentration in the reaction system was set to 1. The polymerization was carried out at a concentration of 0 ppm or less and a water concentration of 0.5 ppm or less. After completion of the reaction, the obtained polycarbonate was allowed to stand at 340 ° C. for 90 minutes under a nitrogen stream, and the yellow index (YI) was measured (retention burn test).

Table 1 shows the results. Example 3 The same operation as in Example 1 was carried out except that only an oxygen removing tube (indicating oxygen trap (manufactured by GL Science)) was attached and a moisture removing tube (moisture filter (manufactured by GL Science)) was not attached. .

The results are shown in Table 1. Comparative example 1 It carried out similarly to Example 1 except not using an oxygen removal tube and a water removal tube. The oxygen concentration in the reaction system is 5 ppm,
The water concentration was 5 ppm. The results are shown in Table 1. Examples 4 and 5 Examples 1 and 2 were carried out in the same manner as in Examples 1 and 2, except that paraxylene was flowed at a rate of 20 g / hour instead of flowing nitrogen at a rate of 50 ml / min. Here, paraxylene was subjected to atmospheric pressure distillation under nitrogen through an oxygen removing tube (indicating oxygen generator trap (manufactured by GL Science)) and a moisture removing tube (moisture filter (manufactured by GL Science)), and then the same process was performed. 12 with nitrogen
Time bubbling. The oxygen concentration in the reaction system was 1.0 ppm or less, and the water concentration was 1 ppm.

The results are shown in Table 1. Comparative example 2 It carried out similarly to Example 4 except having used commercially available para-xylene (made by Wako Pure Chemical Industries). At this time, the oxygen concentration in the reaction system was 5 ppm or more, and the water concentration was 10 ppm or more.
The results are shown in Table 1. Example 6 In a container with a stirrer having an inner volume of 50 liters, 9.2 mol of bisphenol A as a dihydric phenol, 9.4 liters of a 2.0 N aqueous sodium hydroxide solution and 8 liters of methylene chloride were stirred, and phosgene was sufficiently added thereto. 3 as excess
Blow for 0 minutes.

Then, 0.18 mol of phenol was reacted, 0.4 mol of bisphenol A, 0.022 mol of triethylamine and 4.5 liter of 0.2N aqueous sodium hydroxide were added, and the mixture was reacted for 40 minutes. The phases were separated from the organic phase. Thus, a methylene chloride solution of the PC oligomer was obtained. Eight liters of this methylene chloride solution of the PC oligomer, 2.5 mol of bisphenol A, 0.18 mol of methyl chloroformate, 400 g of a 7.25% by weight aqueous sodium hydroxide solution, 0.017 mol of triethylamine and 8 liter of methylene chloride were mixed. The mixture was stirred at 500 rpm and reacted for 60 minutes.

After the reaction, the aqueous phase and the organic phase are separated, and the organic phase is separated from water, alkali (0.01N aqueous sodium hydroxide solution),
An organic solvent solution of PC prepolymer was sequentially washed with an acid (0.1N hydrochloric acid) and pure water. The methylene chloride was removed from a part of this to obtain a prepolymer powder, and the viscosity average molecular weight was measured to be 8,700. The prepolymer thus obtained was pulverized while removing and evaporating methylene chloride from the organic solvent solution of the prepolymer to obtain a prepolymer powder.

A polycarbonate was obtained in the same manner as in Example 1 except that the thus obtained prepolymer was used. The results are shown in Table 1. Comparative example 3 It carried out similarly to Example 6 except not using an oxygen removal pipe and a water removal pipe. The oxygen concentration in the reaction system is 5 ppm,
The water concentration was 5 ppm.

The results are shown in Table 1. In the table, the viscosity average molecular weight Mv is the intrinsic viscosity [η] in methylene chloride at 20 ° C.
Was calculated from the equation [η] = 1.23 × 10 ⁻⁵ × Mv ^0.83 . The retention burn test was conducted by leaving a polycarbonate sample as a sample at 340 ° C. for 90 minutes under a nitrogen stream, and then applying an 8% methylene chloride solution of the sample to a color meter SM-3 (Suga test) using a quartz cell having an optical path length of 57 mm. Machine)
(YI (yellow index)).

[0080]

[Table 1]

[0081]

According to the present invention, in the production of a polycarbonate, the catalyst activity is sufficiently high, the reaction rate can be improved, and the polycarbonate having little retention burn and excellent color quality can be efficiently produced. be able to.

Claims (5)

[Claims] 1. A method for producing a polycarbonate, comprising producing a polycarbonate by polymerizing a polycarbonate prepolymer in a solid state or a swollen solid state, wherein the oxygen concentration in the gas phase is 2 ppm or less. Method. 2. When producing a polycarbonate by polymerizing a polycarbonate prepolymer in a solid state or a swollen solid state, the oxygen concentration in the gas phase is 2 ppm or less,
A method for producing a polycarbonate which is polymerized in a state where the water concentration is 2 ppm or less. 3. The method for producing a polycarbonate according to claim 1, wherein a nitrogen-containing organic basic compound is used as a catalyst when preparing the polycarbonate prepolymer. 4. The method according to claim 1, wherein after preparing the polycarbonate prepolymer, the prepolymer is polymerized in a solid state or a swollen solid state using a quaternary phosphonium salt as a catalyst. Production method of polycarbonate. 5. In producing a polycarbonate,
The method for producing a polycarbonate according to any one of claims 1 to 4, wherein the reaction is carried out by a transesterification reaction using a dihydroxy compound and a carbonic acid diester.