JPH0391539A - Process and apparatus for producing polycarbonate - Google Patents

Abstract

PURPOSE:To obtain a polycarbonate suppressed from deteriorating in a hue and excelling in transparency while preventing it from decreasing in a mol.wt. by treating a mixture of a polycarbonate with a chlorinated organic solvent in a treatment apparatus made of a specified material under specified heating conditions. CONSTITUTION:A mixture comprising a polycarbonate and a chlorinated organic solvent (e.g. methylene chloride) is treated in a treatment apparatus whose part in contact with the mixture is made of a ceramics under specified heating conditions.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention relates to a polycarbonate production method and an apparatus thereof, and more specifically, to a process for recovering polycarbonate dissolved in a chlorinated organic solvent, which improves hue deterioration. The present invention relates to a method and apparatus for producing polycarbonate.

[Prior Art and Problems to be Solved by the Invention 1 Generally, the phosgene method or the melt transesterification method is employed as an industrial method for producing polycarbonate.

However, the melt transesterification method has disadvantages in that it requires a long processing time at high temperatures and the color of the product deteriorates, so the phosgene method is currently the mainstream.

However, in this phosgene method, after washing the polycarbonate solution (polymer solution) produced by polymerization, it is necessary to sequentially perform a concentration (flake formation) process, a drying (solvent removal) process, and a granulation (pelletization) process using separate equipment. Among these processes, the burden of concentration and drying is heavy, requiring large equipment such as kneaders and dryers, and the operating costs are high.

Therefore, it is desired to simplify both steps, and various methods have been proposed for recovering the polymer from the polymer solution.

For example, a method of isolating a polymer by adding a poor solvent to a polymer solution is disclosed in Japanese Patent Publication No. 37-5599.
It is described in Japanese Patent Publication No. 18399, Japanese Patent Publication No. 1959, Japanese Patent Publication No. 42-14474, etc. Further, a method of gelling and pulverizing a polymer solution using a kneader or the like is described in Japanese Patent Publication No. 15899/1989, and a method of contacting the polymer solution with hot water and distilling off the solvent together with water vapor to obtain the polymer as a slurry. was published in 1976
It is described in Japanese Patent No. 0-115625.

Each of these polymer recovery methods has its advantages and disadvantages, but each method requires a large number of steps, resulting in large construction costs and running costs.

As a simple and economical method for producing polycarbonate that solves these drawbacks, JP-A-62-183801 discloses a method for heating a polymer solution in a specific heat exchanger to devolatilize it and obtain polycarbonate in a molten state. A method is disclosed. However, this method poses problems such as coloring of the polycarbonate due to thermal deterioration and residual solvent in the recovered polycarbonate.

As is well known, polycarbonate is characterized by excellent impact resistance and especially good transparency, and the deterioration of transparency due to the above-mentioned thermal deterioration, that is, poor hue, is a serious drawback. obtain. In order to solve this problem of thermal deterioration, it is best to lower the temperature during heating devolatilization as much as possible and shorten the heating time, but under such conditions the residual solvent increases. In order to sufficiently remove the residual solvent, it is necessary to increase the devolatilization temperature and to lengthen the devolatilization time.

Therefore, with the above method, it is difficult to obtain a polycarbonate that has excellent hue and is free from residual solvent problems.

Coloring due to thermal deterioration of this polymer is 1. This is a problem that relates to devices in general, such as extruders, that perform processing at temperatures above the glass transition point (Tg) of the polymer. In particular, the influence was significant when a large amount of chlorine-containing organic solvents such as methylene chloride (methylene chloride), which is preferably used as a solvent for polycarbonate, and metal impurities were contained. That is, in the former case, the chlorine-containing organic solvent decomposes to generate hydrochloric acid, which forms metal chloride when it comes into contact with the treatment equipment, and this metal chloride acts as a catalyst, causing polymer deterioration and coloration. It is thought that this will promote This is not limited to polycarbonate, but applies to all polyester resins in a broad sense that include chlorine-containing ester bonds, but it is particularly noticeable in polycarbonate, and in the latter case, due to the decomposition effect of the solvent, it is difficult to use for high-temperature treatment. It is thought that the contaminants come from the equipment used.

In order to prevent the effects of decomposition of the above-mentioned chlorine-containing organic solvents, it is recommended to use materials that do not react with the generated hydrochloric acid, such as inorganic materials such as ceramics, and precious metals such as gold that cannot practically corrode. However, it was considered difficult to implement due to cost and strength issues, manufacturing issues, and in the case of inorganic materials, heat transfer issues.

[Means for Solving the Problems 1] Therefore, the present inventor solved the drawbacks of the above-mentioned conventional techniques, reduced construction costs and running costs, reduced the residual solvent in recovered polycarbonate, and reduced the hue due to thermal deterioration of recovered polycarbonate. We conducted extensive research to develop an improved polycarbonate manufacturing method and equipment. As a result, it was discovered that the intended purpose could be achieved by forming the processing device using a specific material. In other words, during the manufacturing process, coloring due to thermal deterioration of polycarbonate is most likely to occur during the polycarbonate melting process, solvent removal process, and extrusion process. It was found that the deterioration at this point was hardly a problem because the flow was smooth and the residence time was short. On the other hand, it was found that in the solvent removal step and the extrusion treatment step, polycarbonate tends to adhere to the inside of the device and stay there for a long time, which has the greatest effect on coloration due to thermal deterioration.

As a result, it has been found that discoloration can be significantly suppressed by providing means for preventing solvent decomposition and metal impurity incorporation into the equipment used in the solvent removal and extrusion processes. On the other hand, since polycarbonate is melted in a solution heating section and then supplied to a solvent removal device or an extrusion processing device, it has been found that even if heat transfer is somewhat low in these devices, it has little effect on quality.

For these reasons, during the polycarbonate manufacturing process,
It has been discovered that the intended purpose can be achieved by using ceramics in the parts of the equipment used in the solvent removal process and the extrusion process that come into contact with polycarbonate. In particular, it has been found that the use of oxide ceramics as the ceramic is more effective in suppressing coloring.The present invention was completed based on this knowledge.

That is, in heat treating a mixture consisting of polycarbonate and a chlorine-containing organic solvent, the present invention provides that the above mixture is heated under predetermined heating conditions in a processing apparatus in which the material of the part that comes into contact with the mixture is made of ceramic. The present invention provides a method for producing polycarbonate, which is characterized in that the polycarbonate is introduced and treated, and at the same time, the present invention is characterized in that the material of the part that comes into contact with the mixture consisting of polycarbonate and a chlorine-containing organic solvent is made of ceramic. The present invention also provides an apparatus for producing polycarbonate.

In the method of the present invention, the polycarbonate used as a raw material is obtained by a normal polycondensation reaction.1For example, according to the phosgene method, dihydric phenol and phosgene as raw material monomers are mixed with a chlorinated organic compound such as methylene chloride. Polycarbonate and copolymers thereof obtained by polycondensation reaction in a solvent using a tertiary amine such as triethylamine as a catalyst can be used.

The dihydric phenol used in the above raw material monomer includes various bisphenols, but especially 2゜2-bis(4
°-Hydroxyphenyl)propane (hereinafter referred to as bisphenol A) is preferred, and part or all of bisphenol A may be replaced with other dihydric phenols.
Examples of dihydric phenols other than bisphenol A include hydroquinone; 4,4'-dihydroxydiphenyl;bis(4-hydroxyphenyl)alkane; bis(
4-hydroxyphenyl)cycloalkane; bis(4-
Hydroxyphenyl>sulfide;bis(4-hydroxyphenyl)sulfoxide;bis(4-hydroxyphenyl>sulfone); bis(4-hydroxyphenyl)ketone or 2,2-bis(3',5°-dibromo-4'
-Hydroxyphenyl> Halogenated bisphenols such as propane can be mentioned. Furthermore, trivalent or higher polyhydric phenols, such as phloroglucin and phloroglucide, can also be used in combination.

Further, as mentioned above, the chlorine-containing organic solvent is used as a solvent for raw materials in the manufacturing process, and the removal of this solvent can be said to be unavoidable in the manufacturing of polycarbonate.

In addition to methylene chloride, which is usually preferably used, solvents used include, for example, tetrachloroethane, trichloroethane, dichloroethane, trichloroethylene, dichloroethylene, chloroform, chlorobenzene, o-, m- or p-dichlorobenzene, and two or more thereof. and mixtures containing these as main components.

In the present invention, when heat treating a mixture of polycarbonate and a chlorine-containing organic solvent as described above, it is necessary to use ceramic as the material of the treatment device for the portion that comes into contact with the mixture. Ceramics here refers to heat-resistant non-metallic inorganic materials such as oxides, carbides, nitrides, and sulfides. Ceramics are almost non-corrosive, so they may have excellent thermal and mechanical functions. For example, substantially most ceramics such as alumina, silicon carbide, silicon nitride, etc. can be used.

In particular, oxide ceramics densified by high-temperature firing, such as alumina, zirconia, and zircon.

The use of magnesia or the like is effective because it has better oxidation stability.

Note that the apparatus of the present invention can have exactly the same configuration as various types of equipment conventionally used in the production of polycarbonate, and only the material of the part that comes into contact with polycarbonate containing a chlorinated organic solvent is changed. can do.

In addition, as equipment for heat-treating polycarbonate solution, various equipment including heating containers and piping can be used as long as the mixture of polycarbonate and chlorine-containing organic solvent is heated to a temperature higher than the glass transition point of polycarbonate. Among the industrially used ones,
For example, devices such as a solvent removal device and an extrusion processing device can be mentioned.

FIG. 1 is an explanatory diagram showing an example of a solvent removal device. The configuration of this solvent removal device 1 is a commonly used one,
A heat exchanger 3 is disposed on the top of the main body 2, a heating medium and polycarbonate are introduced into the heat exchanger 3, the polycarbonate solution is heated by heat exchange, and the chlorine-containing organic solvent in the polycarbonate solution is evaporated and removed. Then, polycarbonate is taken out as a molten polymer from the outlet 4 at the bottom of the main body. In the solvent removal device 1 having such a configuration, at least the surface of the portion that comes into contact with the polycarbonate solution, for example, the flow path portion of the polycarbonate solution of the heat exchanger 3, needs to be formed of the above-mentioned silicon. Preferably, the same material is used for the lower part of the main body 2 through which the molten polycarbonate flows down from the heat exchanger 3 and the discharge port 4, and furthermore, the main body 2 including piping etc., the heat exchanger 3, etc. are all made of the above-mentioned ceramics. It can also be formed.

FIG. 2 is an explanatory diagram showing an example of an extrusion processing apparatus. This extrusion processing apparatus 11 is similar to a commonly used extrusion processing apparatus, and is equipped with a screw 13 in a casing 12 and a degassing means 14. In the case of such an extrusion processing apparatus 11, it is necessary to form the inner circumferential surface of the casing 12 and the surface of the screw 13, which are in contact with the polycarbonate containing the chlorine-containing organic solvent, with the above-mentioned ceramics. The surface can also be formed of the above ceramics.

Note that the portion formed of ceramic may be entirely integrated, but the same effect can be obtained by forming a ceramic layer on its surface by coating, adhesion, or the like.

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

Example 1 <Conditions> Polycarbonate was heated using the solvent removal device 30 shown in FIG. 3 to remove the solvent.

This solvent removal device 30 has a heat exchanger 32 disposed above the inside of a main body 31, and a discharge port 33 formed in the lower part.

This main body 31 is covered with a jacket 34, and is heated to a predetermined temperature by a heat medium supplied into the jacket 34. Further, an exhaust port 35 connected to a vacuum pump or the like is provided at the upper part of the main body 31 to bring the inside of the main body 31 into a predetermined reduced pressure state and to discharge the evaporated solvent.

The main body 31 of this solvent removal device 30 has a maximum diameter of 5 mm at the top.
00 mm, height 2000 mm, internal volume approximately 0.2 m
'is.

The main body 31 is entirely made of 5US304, and the parts where polycarbonate containing a chlorine-containing organic solvent is likely to come into contact at high temperatures, that is, the inner periphery of the lower part of the main body and the discharge port, are coated with ceramics by thermal spraying with alumina. I did this.

The heat exchanger 32 used is a plate fin type,
As shown in Fig. 4, corrugated metal plates (slate fin plates) 36, 37 with a thickness of 0.2 mm and a wave height of 5 mm are combined at right angles, 10 metal plates 36 on the flow path side of the polycarbonate solution, and a heating medium. There are 11 metal plates 37 on the passage side, and 22 partition plates (tube plates) 38 with a thickness of 0 and 2 mm are used to connect the two, with heat medium passages, that is, heating chambers, arranged at both ends. This laminated heat exchanger unit has an external dimension of approximately 105 mm in length (L) x 1 mm in width (V).
The size was 50 x height (H) 70 (mm), and the polycarbonate solution was arranged so as to flow down in the height direction. This heat exchanger 32 was also formed using 5US304 in consideration of heat transfer.

The heat exchanger and main body of the solvent removal apparatus constructed as described above were heated to 300° C., and the main body was adjusted to a degree of vacuum of -749 mmHg. A polycarbonate solution prepared by dissolving polycarbonate having a viscosity average molecular weight of 26,000 using methylene chloride as a solvent and adjusting the concentration to about 20% by weight was supplied to this solvent removal device at a rate of 5 J2 per hour.

The water content in this polycarbonate solution was 1300 ppm by weight, and the dissolved oxygen concentration was 52 ppm by weight.

<Results> After supplying the polycarbonate solution, we were able to obtain a molten polycarbonate from the polymer pump at the bottom of the main body. Further, a pelletizer was attached to the outlet of this solvent removal device, and the obtained polycarbonate was pelletized. The color tone of the obtained polycarbonate was transmission type Yl (
It was of good quality with a yellowness index of 3.2. The molecular weight of the polycarbonate was 25,500 without any decrease, and the amount of residual methylene chloride (methylene chloride) was as low as 60 ppm by weight, resulting in good physical properties.

Example 2 Conditions> The ceramic-coated part of the device body was
Example 1 except that zirconia was thermally sprayed and coated.
Polycarbonate was obtained under the same conditions.

Results> The color tone of the obtained polycarbonate was 2.9 in terms of Yl, the residual molecular weight was 26,000, which was not lowered, and the residual methylene chloride was as low as 55 ppm by weight, so good physical properties were obtained.

Example 3 <Conditions> The ceramic-coated part of the device body was
Polycarbonate was obtained under the same conditions as in Example 1 except that magnesium oxide was thermally sprayed and coated.

Results> The color tone of the obtained polycarbonate was 3.2 in YI, the residual molecular weight was 25,300, which was not decreased, and the residual methylene chloride was as low as 58 ppm by weight, so good physical properties were obtained.

Example 4 Conditions> The ceramic-coated part of the device body was
Example 1 except that chromium oxide was thermally sprayed and coated.
Polycarbonate was obtained under the same conditions.

Results> The color tone of the obtained polycarbonate was 2.8 in Yl, the residual molecular weight was 25,200, which was not decreased, and the residual methylene chloride was as low as 54 ppm by weight, and good physical properties were obtained.

Example 5 <Conditions> The ceramic-coated part of the device body was
Polycarbonate was obtained under the same conditions as in Example 1 except that silicon carbide was coated by thermal spraying.

<Results> The color tone of the obtained polycarbonate was 3.0 in YI, the residual molecular weight was 25,700, which was not decreased, and the residual methylene chloride was as low as 63 ppm by weight, and good physical properties were obtained.

After the experiment, when we checked the inside of the main body, we found that there was a slight amount of polymer deterioration attached, but it had almost no effect on the quality.

Example 6 Conditions> The ceramic-coated part of the device body was
Polycarbonate was obtained under the same conditions as in Example 1 except that zinc sulfide was thermally sprayed and coated.

Results> The color tone of the obtained polycarbonate was 3.1 in terms of YI, the residual molecular weight was 25,800, which was not decreased, and the residual methylene chloride was as low as 57 ppm by weight, and good physical properties were obtained.

After the experiment, when we checked the inside of the main body, we found that there was a slight amount of polymer deterioration attached, but it had almost no effect on the quality.

Comparative Example 1 Conditions> Example 1 except no ceramic coating
Polycarbonate was obtained under the same conditions.

<Results> The color tone of the obtained polycarbonate was YI 46,
Residual methylene chloride was 61 ppm by weight.

Furthermore, when dissolved in methylene chloride, numerous undissolved fragments were observed. Furthermore, when the machine was opened after two hours of operation, degraded polycarbonate was found inside the main body.

Comparative Example 2 <Conditions> A polycarbonate was obtained under the same conditions as in Example 1 except that the material of the main body was titanium and no ceramic coating was applied.

<Results> The color tone of the obtained polycarbonate was 82 in YI;
Residual methylene chloride was 57 ppm by weight.

Furthermore, when dissolved in methylene chloride, numerous undissolved fragments were observed. When the machine was opened after operating for two more hours, degraded polycarbonate was found attached to the inner peripheral surface of the main body. When the adhered polymer was removed and the surface condition was observed, numerous pores were observed.

The results of Examples 1 to 6 and Comparative Example 1.2 are shown in Table 1.

The following margin [Advantageous Effects of the Invention 1] As explained above, according to the method of the present invention, the reduction in molecular weight during heat treatment of a polycarbonate solution, such as a step of evaporating the solvent or a step of extrusion, can be avoided. In addition to preventing this, deterioration of hue can be reduced, and transparency, which is a characteristic of polycarbonate, can be fully exhibited.

Furthermore, since the device of the present invention uses materials that are relatively easy to obtain, it is easy to manufacture and can be manufactured at low cost.

Note that the apparatus of the present invention can be applied not only to the production of the above-mentioned polycarbonate but also to the production of polymers such as polyester, polysulfonate, polyamide, polyphenylene oxide, and the like.

Therefore, the present invention can be effectively and widely used in the production of high quality polycarbonate and also in the production of other polymers.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an example of the solvent removal device of the present invention;
FIG. 2 is a partially cutaway diagram showing an example of the extrusion processing apparatus of the present invention;
FIG. 3 is a cross-sectional view of the solvent removal device used in Examples and Comparative Examples, and FIG. 4 is an enlarged perspective view of the main part of a plate-fin type heat exchanger provided in the solvent removal device. 1: Solvent removal device 3: Heat exchanger 11: Extrusion processing device 13 Varnish screw 30: Solvent removal device 32: Heat exchanger 34: Jacket 36.37: Metal plate 2: Main body 4: Discharge port 12: Casing 14: Hopper 31 = Main body 33: Exhaust port 35: Exhaust port

Claims (7)

[Claims] (1) When heat-treating a mixture consisting of polycarbonate and a chlorine-containing organic solvent, the mixture is introduced under predetermined heating conditions into a processing device in which the material of the part that comes into contact with the mixture is made of ceramics. A method for producing polycarbonate, characterized by: (2) The manufacturing method according to claim 1, wherein the processing device is a solvent removal device that heats a mixture of polycarbonate and a chlorine-containing organic solvent to evaporate and remove the chlorine-containing organic solvent. (3) The manufacturing method according to claim 1, wherein the processing device is an extrusion processing device that extrudes a mixture of polycarbonate and a chlorine-containing organic solvent under heating. (4) The manufacturing method according to claim 1, wherein the ceramic is an oxide ceramic. (5) In a polycarbonate manufacturing apparatus that heats a mixture consisting of polycarbonate and a chlorine-containing organic solvent,
An apparatus for manufacturing polycarbonate, characterized in that the material of the part that comes into contact with the mixture is ceramic. (6) The manufacturing apparatus according to claim 5, wherein the processing apparatus is a solvent removal apparatus that heats a mixture of polycarbonate and a chlorine-containing organic solvent to remove the chlorine-containing organic solvent. (7) The manufacturing apparatus according to claim 5, wherein the processing apparatus is an extrusion processing apparatus for extruding a mixture of polycarbonate and a chlorine-containing organic solvent under heating.