JPH02233733A - Production of polycarbonate and device therefor - Google Patents

Abstract

PURPOSE:To obtain the title polymer free from change of hue by heating a mixture of a polycarbonate and a fluorine-containing organic solvent in a device having part which is brought into contact with the mixture and made of a material of a metal or alloy containing specific amounts of copper and nickel. CONSTITUTION:A mixture of a polycarbonate prepared by subjecting bisphenol A, etc., and phosgene to interfacial polycondensation in a chlorine-containing organic solvent (e.g. methylene chloride) and the chlorine-containing organic solvent is introduced to a main body 2 of a solvent removal device 1 having part which is brought into contact with the mixture of the polycarbonate and the chlorine-containing organic solvent and made of a material comprising a metal or alloy containing >=85% copper and/or nickel, the mixture is heat- treated by a heat-exchanger 3 to evaporate and remove the chlorine-containing organic solvent and the polycarbonate is recovered as a molten polymer from an exhaust port 4 at the bottom of the main body 2.

Description

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

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

However, the melt transesterification method has the drawbacks of long processing times at high temperatures and poor product color, so the phosgene method is currently the mainstream. However, this phosgene method requires a concentration (flaking) step after washing the polycarbonate solution (polymer solution) produced by polymerization. It is necessary to perform the drying (solvent removal) step and the granulation (pelletization) step in sequence using respective devices. In 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 devised to recover 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. 39-1959, Japanese Patent Publication No. 14474-1974, etc. In addition, 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 a polymer solution with hot water and distilling off the solvent together with water vapor to obtain a polymer as a slurry is also described. Tokukai Showa 6
It is described in Publication 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 in which a polymer solution is heated in a specific heat exchanger to devolatilize it to 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 particularly characterized by its transparency, and deterioration in transparency due to the above-mentioned thermal deterioration, that is, poor hue, can be a serious drawback. 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.
Under such conditions, residual solvent increases. Therefore, 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. This coloration due to thermal deterioration of polymers is a problem associated with all equipment such as extruders that perform processing at temperatures above the glass transition point (Tg) of the polymer. This effect was particularly significant when a large amount of a chlorine-containing organic solvent such as methylene chloride, which is preferably used as a solvent for polycarbonate, was contained. This is because the chlorine-containing organic solvent decomposes to generate hydrochloric acid, which forms metal chloride when it comes into contact with the processing equipment, and this metal chloride acts as a catalyst, causing polymer deterioration. It is thought to promote coloring. This is true not only for polycarbonate but also for all polyester resins in a broad sense including oxygen-containing ester bonds, but is particularly remarkable for polycarbonate.

In order to prevent the effects of decomposition of the above-mentioned chlorine-containing organic solvent, it is necessary to use materials that do not react with the generated hydrochloric acid, such as inorganic materials such as glass. It is possible to use precious metals such as gold, which do not corrode in practical terms, but this is difficult to implement due to cost and strength issues, manufacturing issues, and in the case of inorganic materials, heat transfer issues. there were.

[Means to solve the problem]

Therefore, the present inventor has devised a polycarbonate manufacturing method and method that eliminates the drawbacks of the above-mentioned conventional techniques, reduces construction costs and running costs, reduces residual solvent in recovered polycarbonate, and improves hue due to thermal deterioration of recovered polycarbonate. We conducted extensive research to develop this device. As a result, it was discovered that the intended purpose could be achieved by forming the processing device using a specific material. The present invention was completed based on this knowledge.

That is, in the present invention, when heat treating a mixture consisting of polycarbonate and a chlorine-containing organic solvent, the material of the part that comes into contact with the polycarbonate mixture is made of a metal or alloy having a copper and/or nickel content of 85% or more. The present invention provides a method for producing polycarbonate, which is characterized in that the material is introduced into a processing equipment under heating conditions for treatment. The present invention also provides an apparatus for producing polycarbonate, characterized in that the material is a metal or alloy having a copper and/or nickel content of 85% by weight or more.

In the method of the present invention, the polycarbonate used as a raw material is obtained by a conventional polycondensation reaction. For example, according to the phosgene method, polycarbonate and its copolymer are obtained by polycondensing dihydric phenol as a raw material monomer and phosgene in a chlorinated organic solvent such as methylene chloride using a tertiary amine such as triethylamine as a catalyst. Polymers can be used.

As the raw material monomer, it is preferable to use commonly used bisphenol A, but other dihydric phenols include, for example, 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) sulfoxide;
hydroxyphenyl)ketone or 2,2-bis(3
Mention may be made of halogenated bisphenols such as ',5'-dibromo-4'-hydroxyphenyl)propane. Furthermore, a mixture of trihydric or higher polyhydric phenols, such as phloroglucin and phloroglucide, can also be used.

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 process of manufacturing polycarbonate.

Examples of solvents that can be used include methylene chloride, which is usually preferred, as well as tetrachloroethane, trichloroethane, and the like. Dichloroethane, trichlorethylene, dichloroethylene. In the present invention, examples include chloroform, chlorobenzene, o-, m- or p-dichlorobenzene, mixtures of two or more of these, or mixtures containing these as main components. In heat-treating the mixture, it is necessary that the material of the processing device that comes into contact with the mixture be a metal or alloy containing 85% by weight or more of copper and/or nickel. That is, at least the portion that comes into contact with the polycarbonate is heat-treated using a processing device made of pure copper, pure nickel, or an alloy containing 85% by weight or more of these. Other components of alloys containing copper and nickel other than pure metals include metals that are normally included to provide strength and workability, such as iron. Chromium, zinc, etc. can be used.

Specific examples of alloys include nickel 200 (nickel 98% by weight or more copper 0.13% by weight), Monel 400 (copper 0.13% by weight),
66% by weight of nickel, 31.5% by weight of copper. iron (1.35% by weight), cupronickel (nickel 30% by weight, copper 6%)
9% by weight, iron: 0.6% by weight), red copper (copper: 86% by weight, iron: 0.05% by weight, zinc: 14% by weight).

Here, the material of the part of the processing equipment that comes into contact with the polycarbonate has a copper and/or nickel content of 85% by weight.
If it is less than that, the hue improvement which is the objective of the present invention cannot be sufficiently achieved.

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. Examples of industrially used equipment include equipment such as solvent removal equipment and extrusion processing equipment.

FIG. 1 is an explanatory diagram showing an example of a solvent removal device. The configuration of this solvent removal device l is a commonly used one,
A heat exchanger 3 is placed on the top of the main body 2, a heating medium and a polycarbonate solution 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. The polycarbonate is then 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, has a copper and/or nickel content of 8.
It is necessary to form the metal or alloy with a composition of 5% by weight or more. 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 zero body 2 including piping etc., the heat exchanger 3, etc. are all made of the above-mentioned composition. It can also be made of metal or alloy.

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 inside a casing 12 and a deaeration means 14. In the case of such an extrusion processing apparatus 11, the inner circumferential surface of the casing 12 and the surface of the screw 13 that come into contact with the polycarbonate containing the chlorine-containing organic solvent need to be formed of a metal or alloy having the above-mentioned composition. Furthermore, the surfaces of the hopper 15 and the like or the entire extrusion processing apparatus 11 may be formed of metals or alloys having the above composition.

Note that the content of copper and/or nickel is 85% by weight.
Parts made of metals or alloys with the above compositions may be formed integrally with these metals or alloys, but they may be formed by plating, thermal spraying,
A similar effect can be obtained by forming a layer of these metals or alloys on the surface by adhesion or the like.

〔Example〕

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

Reference Example First, as a standard for determining the influence of metal materials on heat treatment, a polycarbonate solution was heat treated using a glass instrument.

As a heat treatment apparatus, a peach having the configuration shown in FIG. 3 was used. That is, the sample was put into a semi-cylindrical glass port 20 with a radius of 15 mm and a length lOO, inserted into a bottomed glass tube 21 made of quartz glass, and then placed in an electric furnace (Toyo Kagaku Sangyo).
RONT-2 (1.2k) heated at 22. A three-necked flask 23 is connected to the opening side of the glass tube 21, and a nitrogen gas introduction pipe 24 and a vent pipe 25 are connected thereto.

In addition, as a sample, polycarbonate obtained by interfacial polycondensation of bisphenol A and phosgene (manufactured by Idemitsu Petrochemical Co., Ltd.; Taflon A2200) was mixed with methylene chloride (
Dissolved in Wako Pure Chemical Industries (special grade), concentration 25% by weight,
A polycarbonate solution with a water content of 1300 ppa+ was prepared.

Approximately 5 ml of this polycarbonate solution was charged into the glass port 20 and heat-treated at 300° C. for 30 minutes under a nitrogen gas flow. Then let it cool naturally to room temperature.
When the resin obtained in the glass port was dissolved again in methylene chloride, no undissolved matter was observed. In addition, we dissolved a polycarbonate plate with known Yl (yellowness) and measured the light transmittance, and from that value, calculated the hue of the experimentally obtained solution by interpolation. was.

Examples 1 to 5 and Comparative Examples 1 to 7 Using the same heat treatment equipment and polycarbonate solution as in the above reference example, each metal piece (5x7 0x 0.5 + n + n) shown in Table 1 and the polycarbonate solution were applied to the glass port. and heat treatment was performed under the same conditions as in the reference example. The state of dissolution of the resin in methylene chloride and the equivalent plate YI after cooling were measured. These results are shown in Table 1.

(The following is a blank space) Example 6 Polycarbonate was heated using the solvent removal device 30 shown in FIG. 4 to remove the solvent.

This solvent removal device 3o 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 3l to bring the inside of the zero body 3l into a predetermined reduced pressure state and to discharge the evaporated solvent.

The maximum diameter of the upper part of the zero body 31 of this solvent removal device 30 is 5.
00mm, height 2000mm, and internal volume approximately 0.2mm. In addition, a polymer pump was installed at the bottom of the main body to discharge molten polycarbonate.

The heat exchanger 32 used is a plate fin type,
As shown in FIG. 5, the thickness is 0.2 mm. Wave height 5I [I
11 corrugated metal plate (slate fin plate) 36.
37 at right angles, 10 metal plates 36 on the polycarbonate solution flow path side and 1 metal plate 37 on the heat transfer path side.
They were laminated in such a manner that passages for the heat medium, that is, heating chambers, were arranged at both ends with 22 partition plates (tube plates) 38 having a thickness of 0.2 mm interposed therebetween. This heat exchanger unit has an external dimension of approximately 105 x length (L) x width (
V) The size was 150 x height (H) 70 (ffllll), and the polycarbonate solution was arranged so as to flow down in the height direction.

and parts, including the heat exchanger 32, that are expected to come into contact with polycarbonate containing a chlorine-containing 80 solvent at high temperatures;
In other words, the inner periphery of the lower part of the main body and the discharge port are all made of W4 (95% copper by weight).
above).

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 -740 mmHH. 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 52% per hour.

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

Shortly after supplying the polycarbonate solution, a polycarbonate melt was obtained 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 amount of residual methylene chloride in the obtained polycarbonate was as low as 52 ppm by weight, and the color tone was 3.2 as a transmission type YI, which was of good quality. Also, the molecular weight is 25,500
Good physical properties were obtained without any deterioration.

Comparative Example 8 Under exactly the same conditions as Example 6, the main body material was SUS316.
When a device named L was prepared and polycarbonate was obtained by removing the solvent in the same manner, its YI was 32, and when it was dissolved in methylene chloride, a large number of insoluble components were observed. When the main body was opened after two hours of operation, degraded polycarbonate was found adhering to the inner surface of the main body.

Example 7 An extruder with a screw diameter of 20 mm, a length of 45 c+a, a single-stage vent, and Monel 400 made of the material of the part that comes into contact with polycarbonate was produced. This extruder has a maximum capacity of 1. 5 kg/hour.

The pellets obtained in Example 6 above containing about 5,000 weight ρpm of methylene chloride were fed from a hopper in a commonly practiced manner and extruded at a temperature of 280°C to produce pellets.

Although some air bubbles were observed in the obtained pellets, there was no deterioration in the hue of the polymer as expected from conventional conditions, and the yellowness index (Yl) of the pellets was 3.8.

〔Effect of the invention〕

As explained above, according to the method of the present invention, it is possible to reduce the deterioration of hue in heat treatment steps such as heat treatment of a polycarbonate solution, for example, a step of evaporating and removing a solvent, or a step of performing an extrusion treatment. The characteristic of transparency can be fully demonstrated.

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. Furthermore, it has good thermal conductivity and is suitable for heat treatment.

Note that the apparatus of the present invention is applicable 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 the drawing]

Fig. 1 is an explanatory diagram showing an example of a solvent removal device, Fig. 2 is an explanatory diagram showing an example of an extrusion processing device, and Fig. 3 is a reference example, and experiments used in Examples 1 to 5 and Comparative Examples 1 to 7. An explanatory diagram of the device,
Figure 4 is a cross-sectional view of the solvent removal device used in Example 6;
The figure shows a heat exchanger unit of a plate-fin type heat exchanger installed in a solvent removal device. Fig. 5(a) is an enlarged perspective view of the main part, and Fig. 5(b) is an enlarged cross-section of the main part. FIG. 5(c) is an overall perspective view. 1: Solvent removal device, 3: Heat exchanger. 11: Extrusion processing device. l3: Screw 20: Glass port 22: Electric furnace, 24: Nitrogen gas introduction pipe. 30: Solvent removal device. 32: Heat exchanger, 34: Jacket 36.3'7: Metal plate. 2: Main body. 4: Discharge port, 12: Casing, 14: Hopper 21: Glass tube. 23: Three-necked flask 25: Vent pipe, 3l: Main body, 33: Discharge port. 35: Exhaust port, 38: Partition plate Fig. Fig. 4 Fig. Melted polymer tool nitrogen yarn (Q) Fig. Fig. 5

Claims (6)

[Claims] (1) When heat treating a mixture of polycarbonate and a chlorine-containing organic solvent, the material of the part that comes into contact with the polycarbonate mixture is made of a metal or alloy with a copper and/or nickel content of 85% or more. 1. A method for producing polycarbonate, which comprises introducing the polycarbonate into a processing apparatus under heating conditions for treatment. (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) In a polycarbonate manufacturing apparatus that heats a mixture consisting of polycarbonate and a chlorine-containing organic solvent,
An apparatus for producing polycarbonate, characterized in that the material of the part that comes into contact with the mixture is a metal or alloy having a copper and/or nickel content of 85% by weight or more. (5) The manufacturing apparatus according to claim 4, 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. (6) The manufacturing apparatus according to claim 4, wherein the processing apparatus is an extrusion processing apparatus for extruding a mixture of polycarbonate and a chlorine-containing organic solvent under heating.