JPH04249531A - Production of polycarbonate - Google Patents

Abstract

PURPOSE:To produce a high-quality arom. polycarbonate substantially free from any impurity without using a material harmful to a human body. CONSTITUTION:A bisphenol and diphenyl carbonate are melt polymerized to give a prepolymer having a viscosity-average mol.wt. of 2000-20,000, which is converted into a slurry using a medium incapable of dissolving the prepolymer. The slurry is further polymerized at 150-350 deg.C or in a molten state. A linear hydrocarbon, a cyclic hydrocarbon, an ether, a ketone, etc., are used as the medium. Thus, a high-quality arom. polycarbonate free from any impurity is produced safely and efficiently. Since a low-boiling medium can be used, the removal of the medium is easy.

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 polycarbonate, and more particularly to a method for producing polycarbonate useful as a raw material for various structural materials, functional materials, and the like.

0002

BACKGROUND OF THE INVENTION Aromatic polycarbonates are engineering plastics with excellent heat resistance, impact resistance, transparency, etc., and are used in various fields. Various techniques have been studied for producing this aromatic polycarbonate, and currently, an interfacial polymerization method of bisphenol and phosgene has been industrialized.

In the interfacial polymerization method using phosgene,
There are problems such as (1) the use of toxic phosgene, (2) chlorine-containing compounds such as by-product HCl and NaCl corrode the equipment metal, and (3) NaCl etc. mixed into the resin. Furthermore, methylene chloride used as a reaction solvent remains in the resin, causing foaming of the resin during molding. Additionally, hydrochloric acid gas resulting from the decomposition of methylene chloride causes corrosion of the molding machine. As described above, the phosgene interfacial polymerization method currently being industrialized also has many problems.

[0004] In addition, a melting method for producing polycarbonate from a phenol compound and diaryl carbonate using a transesterification reaction is also known. The melting method involves distilling off by-product phenol and finally unreacted diaryl carbonate from high viscosity polycarbonate.
It is necessary to increase the degree of polymerization, and usually requires a high temperature of 280 to 350°C and a high vacuum of 1 mmHg or less. Therefore, special equipment is required, and the reaction conditions are harsh, so there are problems with quality deterioration, such as side reactions such as crosslinking and branching, and coloring due to decomposition.

[0005] Condensation systems such as polyethylene terephthalate (PET) and nylon 66 are also produced by melt polymerization. At this time, it is also known to increase the degree of polymerization by performing solid phase polymerization under reduced pressure and flowing dry nitrogen or the like at a temperature that allows the solid phase state to be maintained. Recently, studies have been conducted to produce polycarbonate using this method (Japanese Patent Application Laid-Open No. 1-15
No. 8033, Japanese Unexamined Patent Publication No. 2-180925). However, although this method has the advantage that polymerization proceeds at low temperatures, it has the problem of requiring a very long time.

[0006]

[Problems to be Solved by the Invention] Therefore, the present inventors have overcome the problems of the above-mentioned conventional methods, and have developed a method that does not use substances harmful or corrosive to the human body, and does not use substances such as chlorine compounds. We have conducted intensive research to develop a method for producing high-quality aromatic polycarbonate that is substantially free of such impurities.

[0007]

[Means for Solving the Problems] As a result, it has been found that the above problems can be achieved by further polymerizing a prepolymer produced by melt polymerization in a slurry state in a medium that does not dissolve the prepolymer. . The present invention was completed based on this knowledge.

That is, the present invention provides the following general formula (I)

[
[Formula X1 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and Y represents a single bond, -O-, -S-, -SO2-, Number of carbon atoms: 1-6
A methylene group substituted with one or two alkyl groups, a methylene group substituted with one or two aryl groups having 6 to 12 carbon atoms, or an alicyclic group having 4 to 8 carbon atoms,
n is an integer from 1 to 4. ] Bisphenol represented by the following general formula (II)

[Formula X2 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and n is 1
It is an integer of ~4. ] The diaryl carbonate represented by is reacted to form the following general formula (III)

embedded image [In the formula, X1, Y and n are the same as above. ] In producing a polycarbonate having a repeating unit represented by
20,000 of a prepolymer is prepared and then the degree of polymerization is determined by slurrying the prepolymer using a medium that does not dissolve the prepolymer at a temperature range of 150 to 350°C, or while the prepolymer is in the molten state. The present invention provides a method for producing polycarbonate, which is characterized by increasing the polycarbonate.

In the method of the present invention, as mentioned above, first, bisphenol represented by the general formula (I) and the general formula (
A prepolymer is produced by melt polymerizing the diaryl carbonate represented by II). Here, the bisphenol used as a raw material is represented by general formula (I). In the formula, X1 is a hydrogen atom, having 1 to 6 carbon atoms
represents an alkyl group (e.g., methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, etc.) or an aryl group having 6 to 12 carbon atoms (e.g., phenyl group, naphthyl group, etc.), and Y is a single bond. , -O-, -S-, -S
O2 −, methylene group substituted with one or two alkyl groups having 1 to 6 carbon atoms (e.g., 2,2-propylidene group; 2,2-butylidene group; 3,3-pentylidene group, etc.), Methylene groups substituted with one or two aryl groups having 6 to 12 carbon atoms (e.g., phenylmethylene group, diphenylmethylene group, etc.) or alicyclic groups having 4 to 8 carbon atoms (e.g., cyclohexylidene group, etc.) ) is shown. Moreover, n is an integer of 1-4. Specific examples of bisphenol represented by general formula (I) include 2,2-bis(4
-hydroxyphenyl)propane; 2,2-bis(4-
2,2-bis(4-hydroxyphenyl)pentane; 3,3-bis(4-hydroxyphenyl)pentane; 2,2-bis(3-methyl-
4-hydroxyphenyl)propane; 2,2-bis(3
-phenyl-4-hydroxyphenyl)propane; 1,
1-bis(4-hydroxyphenyl)cyclohexane;
1,1-bis(4-hydroxyphenyl)-1,1-diphenylmethane; 1,1-bis(4-hydroxyphenyl)-1-phenylmethane; 1,1-bis(4-hydroxyphenyl)-1-phenyl Examples include ethane; 4,4'-dihydroxydiphenyl;4,4'-dihydroxydiphenylether;4,4'-dihydroxydiphenylsulfide;4,4'-dihydroxydiphenyl sulfone.

Further, in the diaryl carbonate represented by the general formula (II), X2 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group,
propyl group, butyl group, pentyl group, hexyl group, etc.)
Or it represents an aryl group having 6 to 12 carbon atoms (eg, phenyl group, naphthyl group, etc.). n is the number of X2 and is 1
Indicates an integer of ~4. Specific examples of these diaryl carbonates include diphenyl carbonate, di-p-tolyl carbonate, phenyl-p-tolyl carbonate, and the like.

In the present invention, bisphenol represented by the general formula (I) and diaryl carbonate represented by the general formula (II) are prepolymerized by a known transesterification method (melt polymerization method). diaryl carbonate in a molar ratio of 1:1.0 to
After introducing into the reaction vessel at a ratio of 2.0, preferably 1:1.0 to 1.2, deaeration under reduced pressure and replacement with inert gas are performed. Thereafter, the reaction vessel is heated to melt the contents, and the reaction is carried out at an internal temperature of 100 to 320°C, preferably 180 to 250°C. At this time, at low temperatures the reaction rate is slow and polymerization takes a long time, and at high temperatures problems such as coloring occur. The reaction time is usually 5 minutes to 100 hours, preferably 15 minutes to 5 hours.

[0012] Under an inert gas flow or under reduced pressure,
The reaction proceeds while the by-produced phenol is distilled off, and after the reaction time is over, the degree of vacuum is increased to completely distill off the phenol and remaining monomers.

The molecular weight of the prepolymer obtained by this melt polymerization is 2,000 to 20, in terms of viscosity average molecular weight (Mv).
000, preferably in the range of 4,000 to 12,000. At this time, if the molecular weight is lower than 2000, a long time will be required for post-polymerization, and if the molecular weight exceeds 20,000, there is no need to further increase the molecular weight.

After the prepolymer is prepared as described above, an inert medium that does not dissolve the prepolymer is introduced into the reaction vessel, and the prepolymer is turned into a slurry or molten state to further proceed with polymerization. . Examples of media that can be used here include hydrocarbons having 5 to 20 carbon atoms (e.g., linear hydrocarbons, such as hexane, n-dodecane, etc., or cyclic hydrocarbons, such as cyclohexane), ether-based media (e.g., diethyl ether, etc.), ketone media (eg, acetone, methyl isobutyl ketone, etc.), and the like are suitable.

[0015] When the above-mentioned non-solvent medium is added to the prepolymer, the prepolymer may be obtained as it is by prepolymerization, or it may be crystallized in advance using an appropriate means. Viscosity average molecular weight 2 prepared in the present invention,
000 to 20,000, crystallization proceeds rapidly in the above medium, and even the prepolymer, which had a high viscosity, is easily crystallized and pulverized into a slurry state. Pre-crystallized prepolymers also remain in a slurry state. The crystallized prepolymer does not melt even at temperatures higher than the glass transition temperature of the amorphous state, and can maintain a slurry state under medium reflux. Furthermore, when the temperature is raised to a temperature exceeding the melting point of the prepolymer, the prepolymer becomes molten and mixed with the medium, thereby reducing the viscosity, improving stirring efficiency, and promoting high molecular weight. Ru.

[0016] In the polymerization reaction in a slurry state, the temperature inside the reactor is set at 150 to 350°C, preferably 200 to 280°C.
The process can be carried out at normal pressure or under elevated pressure within the temperature range of refluxing the medium. In addition, the polymerization reaction in the molten state is
The melting point varies depending on the chemical structure and degree of polymerization of the oligomer used, so the reaction temperature cannot be determined unconditionally.
The reaction may be carried out at a temperature slightly higher than the melting point of the oligomer. The reaction time is usually 5 minutes to 100 hours, preferably 10 minutes to 48 hours. Once the reaction time is over,
The medium is removed under reduced pressure.

[0017] In the method of the present invention, in both the slurry state and the molten state, heat propagation is carried out efficiently because a liquid medium having a larger heat capacity than a gas such as dry nitrogen gas in the conventional method is used. Therefore, the reaction time can be shortened compared to the general solid phase polymerization method, and temperature control is easier than the dry solid phase polymerization method.

[0018] Furthermore, compared to heat treatment or crystallization by solution drying, the method of the present invention, which involves dipping in a solvent, has more voids in the powder;
In addition to increasing the efficiency of heat propagation, it is also advantageous for final medium removal. Furthermore, since the method of the present invention allows the use of low boiling point media, media removal can be performed very efficiently and easily.

[0019]

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 2,2-bis(4-hydroxyphenyl)propane 45
．． 6g and 44.94g of diphenyl carbonate at 30
The mixture was placed in a 0 ml separable flask, and degassing, drying, and introduction of pure argon were repeated several times, and the flask was heated to 180°C. After the contents were melted, the internal temperature was raised to 230°C and held for 30 minutes. After reducing the pressure to 50 mmHg and maintaining it for 60 minutes, the pressure was reduced to 1 mmHg or less to distill off the produced phenol. Then, it was cooled to room temperature. The prepolymer obtained at this time has an intrinsic viscosity (ηsp/c)=0.25
2 dl/g, viscosity average molecular weight (Mv) = 7,800.

After crushing the obtained prepolymer, about 4
0 g was put into a 300 ml glass autoclave, and then 100 ml of hexane was added. After the autoclave was sealed, it was kept under pressure and heated to an internal temperature of 200°C. The contents were in a slurry state. At this time, the temperature was controlled while paying attention to the pressure.

[0022] 10°C/1hr while changing the pressurizing conditions.
The temperature was raised every hour at a rate of 250°C, and after reaching 250°C, it was held for 7 hours. After the reaction was stopped, it was cooled to room temperature, and then the pressure was reduced. Under slight heating, hexane was distilled off under reduced pressure, and ηsp/c=
A finely powdered polycarbonate of 0.61 dl/g and Mv=25,600 was obtained.

Example 2 The same procedure as in Example 1 was carried out except that the medium was changed to cyclohexane. The prepolymer obtained at this time is η
sp/c=0.252 dl/g, Mv=7,800.

The final polycarbonate has ηsp/c=0
．． It was 518 dl/g, Mv=21,300.

Example 3 100 ml of n-dodecane was added to the prepolymer obtained in the same manner as in Example 1, the temperature was raised to 215° C. under normal pressure, and the mixture was kept in a slurry state for 12 hours under stirring to increase the molecular weight. The reaction was carried out. After the reaction, under reduced pressure, n
- Dodecane is distilled off, ηsp/c=0.521dl/g
, Mv=21,500, a white powdery polycarbonate was obtained.

Example 4 The medium was changed to n-tetradecane and the mixture was heated to 250 ml at normal pressure.
The procedure of Example 3 was repeated except that the temperature was raised to 0.degree. C. and the polymerization reaction was carried out in a state in which the prepolymer was molten. As a result, ηsp/c=0.510dl/g, Mv=
20,500 white powder polycarbonate was obtained.

Comparative Example 1 Same as Example 1, ηsp/c=0.235dl/g
, Mv=8,600 was prepared. This prepolymer was crushed, immersed in acetone for 2 hours to crystallize it, filtered, and dried. 40 g of this prepolymer was placed in a flask and heated in an oil bath at 190° C. for 6 hours while introducing a small amount of nitrogen gas under reduced pressure of 5 mmHg. Next, the temperature was raised to 220°C over 6 hours at 5°C/hr, and
When held at 20°C for 8 hours to perform solid phase polymerization, ηs
A polycarbonate with p/c=0.441 dl/g and Mv=17,800 was obtained.

[0028]

[Effects of the Invention] According to the method of the present invention, high-quality aromatic polycarbonate substantially free of impurities such as chlorine compounds can be efficiently produced without using substances harmful to the human body or corrosive. can be manufactured. In addition, compared to conventional solid phase polymerization methods, by introducing a medium to make the prepolymer into a slurry or molten state, temperature control is easy, heat propagation is uniform, and the process can be carried out at relatively low temperatures.
Moreover, a high molecular weight polycarbonate can be produced in a short time, and furthermore, since a low boiling point medium can be used, the medium can be removed very easily.

[Chemical formula 1]

[Chemical formula 1]

Claims (2)

[Claims] Claim 1: The following general formula (I) [Formula X1 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and Y represents a single bond, -O-, -S-, -SO2 -, methylene group substituted with 1 or 2 alkyl groups having 1 to 6 carbon atoms, 1 or 2 substituted with aryl groups having 6 to 12 carbon atoms
represents a substituted methylene group or an alicyclic group having 4 to 8 carbon atoms, and n is an integer of 1 to 4. ] and the following general formula (II) [Formula X2 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and n is 1
It is an integer of ~4. ] A diaryl carbonate represented by is reacted to form the following general formula (III) [In the formula, X1 , Y and n are the same as above. ] In producing a polycarbonate having a repeating unit represented by
20,000 of a prepolymer is prepared and then the degree of polymerization is determined by slurrying the prepolymer using a medium that does not dissolve the prepolymer at a temperature range of 150 to 350°C, or while the prepolymer is in the molten state. A method for producing polycarbonate, characterized by increasing the amount of polycarbonate. 2. The method for producing polycarbonate according to claim 1, wherein the medium that does not dissolve the prepolymer is a hydrocarbon having 5 to 20 carbon atoms, an ether medium, or a ketone medium.