JP3483409B2 - Heating method for polycarbonate manufacturing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bisphenol A
In a device that produces a polycarbonate by transesterification by reacting with a carbonate diester under heating and melting, when the production device is shut down due to some trouble or when a new production is started, the polycarbonate remains in the production device. And a method for raising the temperature of the apparatus. [0002] Aromatic polycarbonate is a resin excellent in various strengths and excellent in transparency, and is used in a wide range of fields. As an industrial production method of this polycarbonate, an interfacial polymerization method in which bisphenol A and phosgene are reacted in a methylene chloride solvent is generally used, but this method requires the use of phosgene or methylene chloride which is industrially difficult to handle. Therefore, in recent years, a method of producing a polycarbonate by using a diester carbonate such as diphenyl carbonate and an aromatic diol compound such as bisphenol A as a reaction raw material in a molten state without a solvent, without using these compounds, has recently been proposed. It has been proposed and partially put into practical use (Japanese Patent Application Laid-Open No. 2-153925,
99552, JP-A-63-51429, etc.). However, in the production of polycarbonate by the transesterification method, when the polymerization apparatus is stopped or cooled for repairing or inspecting the apparatus, the viscosity of the polycarbonate in the apparatus is high, and the polycarbonate tends to remain in the apparatus. For this reason, the production apparatus is heated to restart the reaction, and crystals that do not melt even when the inside of the apparatus is heated to a predetermined reaction temperature (200 to 320 ° C.) are generated in the course of cooling and heating, and There were problems such as blockage and incorporation of high-melting-point crystallized products into products. As means for solving such a problem, Japanese Unexamined Patent Publication No.
Japanese Patent Publication No. -200008 discloses that after a polycarbonate is produced by reacting a carbonic acid diester with a dihydroxyaryl compound, prior to initiating the reaction, a reaction apparatus in which a portion in contact with the reaction mixture is washed with a phenolic compound is used. suggest. JP-A-8-165342 discloses a tank-type precondensation reaction of a resin production apparatus in which a polycarbonate production apparatus includes a tank-type precondensation reactor and a horizontal or vertical twin-screw post-condensation machine with a vent. Only the vessel portion is washed with a solvent, and as a processing step after the washing, a method for washing and drying a resin manufacturing apparatus, characterized in that it is dried substantially in the absence of oxygen, is excellent in polycarbonate solubility. Phenol, benzyl alcohol, pyridine, dimethylformamide, ethyl acetate and tetrahydrofuran are mentioned as washing solvents. The purpose of these proposed methods is to improve the deterioration of the surface of the device, and not only does not address the problem of clogging of the device at all, but also causes problems such as deterioration of the sealing material due to the use of a solvent and loss of the hermeticity of the device. there were. An object of the present invention is to provide an apparatus in which a polycarbonate produced by a transesterification method in which a diol compound and a carbonic acid diester are reacted under heat and melt is used for starting a polymerization reaction. It is another object of the present invention to provide a method for preventing clogging of a device by a crystallized polycarbonate remaining in the device and mixing of the crystallized product into a product. The present inventors have conducted intensive studies on the crystallization behavior of polycarbonate remaining in the apparatus when the production apparatus is stopped, and as a result, have found that when the apparatus is restarted, the apparatus is raised. By controlling the temperature rate, we found conditions to suppress the generation of high melting point crystals that could cause device blockage, etc.
The present invention has been completed. That is, in the present invention, the viscosity average molecular weight obtained by reacting bisphenol A and carbonic acid diester under heat and melting is 2,000 to 25,000.
When the temperature of the polymerization apparatus in which the polycarbonate remains is raised from a temperature of 240 ° C. or less to at least 20 ° C. and heated to a temperature in the range of 200 ° C. to 320 ° C., the polymerization apparatus is heated to 0.2 ° C. An object of the present invention is to provide a method for increasing the temperature of a polycarbonate production apparatus, wherein the heating is performed at a temperature increase rate of higher than 20 ° C./min. Hereinafter, the method for raising the temperature of the transesterification polycarbonate polymerization apparatus of the present invention will be described more specifically. A method for producing a polycarbonate by a transesterification method; a method for producing a polycarbonate by a transesterification method comprises transesterifying a carbonic acid diester such as diphenyl carbonate and a diol compound such as bisphenol A in a molten state to produce an aromatic polycarbonate. This method is known as described in the above-mentioned patent publications. The diol compound used in the present invention is bisphenol A, but can be copolymerized with other monomers as long as the crystallization behavior is not largely changed. For example, bisphenol A can be up to 30 mol%, preferably up to 10 mol% of the diol compound. It can be replaced with another diol compound other than A. When a branched polycarbonate is produced, a small amount of a monomer required for branching, such as a trivalent or higher polyhydric phenol, can be copolymerized. Specific examples of the copolymerizable diol compound include those having 2 carbon atoms.
Up to 20 substituted or unsubstituted straight-chain, branched or cyclic diols, and aromatic diol compounds represented by the following general formula (1). [0008] (Wherein A is a single bond, a substituted or unsubstituted linear, branched or cyclic divalent hydrocarbon group having 1 to 10 carbon atoms, and -O-, -S-, -CO -, -SO _2- , selected from the group consisting of divalent groups represented by
And Y are the same or different from each other and are selected from halogen or a hydrocarbon group having 1 to 6 carbon atoms, and p and q are 0 or an integer of 1 to 2. [0010] Some representative examples include, for example, bis (4-hydroxyphenyl) methane, 2,2-bis (4
-Hydroxy-3-methylphenyl) propane, 2,2
-Bis (4-hydroxy-3-t-butylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dibromo Bisphenols such as phenyl) propane, 4,4-bis (4-hydroxyphenyl) heptane and 1,1-bis (4-hydroxyphenyl) cyclohexane; 4,4′-dihydroxybiphenyl,
Biphenols such as 4'-dihydroxy-3,3 ', 5,5'-tetramethyl-biphenyl; bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ether And bis (4-hydroxyphenyl) ketone. Carbonic acid diesters: Carbonic acid diesters include dimethyl carbonate, diphenyl carbonate,
Ditolyl carbonate, bis (4-chlorophenyl) carbonate, bis (2,4,6-trichlorophenyl)
There are carbonates and the like. In the melt polymerization reaction between an aromatic diol compound and a carbonic acid diester, an ester exchange catalyst is usually used.
A transesterification catalyst is used. Examples of the transesterification catalyst include alkali metal compounds, alkaline earth metal compounds, quaternary ammonium salts, and phosphonium salts. Specific examples of such alkali metal compounds and alkaline earth metal compounds include alkali metal compounds. And organic acid salts, inorganic acid salts, oxides, hydroxides, hydrides and alcoholates of alkaline earth metals. More specifically, as the alkali metal compound, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, bisphenol A Disodium salt, dipotassium salt, dilithium salt, phenol sodium salt, potassium salt and lithium salt. In addition, cesium hydroxide, cesium carbonate, inorganic cesium salts such as cesium bicarbonate, cesium acetate, organic acid cesium salts such as cesium stearate, cesium methylate, cesium alcoholate such as cesium ethylate, cesium phenolate, bisphenol A of bisphenol A And cesium salts of phenols such as cesium salts. Further, as the alkaline earth metal compound, specifically, calcium hydroxide, barium hydroxide,
Examples include magnesium hydroxide, strontium hydroxide, calcium hydrogen carbonate, barium hydrogen carbonate, magnesium hydrogen carbonate, strontium hydrogen carbonate, calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, and the like. These compounds are used alone or in combination. In the present invention, a basic compound other than the above-mentioned alkali metal compound and / or alkaline earth metal compound can be used as the catalyst. Such basic compounds include, for example, nitrogen-containing basic compounds and phosphonium hydroxy compounds which are easily decomposable or volatile at high temperatures, rarely remain in the final aromatic polycarbonate, and do not adversely affect physical properties such as hue. And specifically, the following compounds. Examples of the nitrogen-containing basic compound include ammonium hydroxides having alkyl, aryl, and alkylaryl groups such as tetramethylammonium hydroxide (Me ₄ NOH) and tetraethylammonium hydroxide (Et ₄ NOH), trimethylamine, and the like. Tertiary amines such as triethylamine, R ₂ NH (wherein R
Is an alkyl group such as methyl and ethyl, and an aryl group such as phenyl and toluyl, etc.), primary amines represented by RNH ₂ (where R is the same as described above), 2-methyl imidazole, 2-phenylimidazole such as imidazole, iminocarboxylic acid derivative or a salt thereof nitrilotriacetic sodium acetate or ammonia, tetramethylammonium borohydride (Me ₄ NBH _4),, tetrabutylammonium borohydride (Bu ₄ NBH ₄ And the like. Examples of the phosphonium hydroxide compound include tetraethylphosphonium hydroxide, tetrabutylphosphonium hydroxide, tetraphenylphosphonium hydroxide, methyltriphenylphosphonium hydroxide, allyltriphenylphosphonium hydroxide and the like. Of these, tetraalkylammonium hydroxide, tetrabutylphosphonium hydroxide and tetraphenylphosphonium hydroxide are preferably used. These compounds are used alone or in combination with the aforementioned alkali metal compounds and alkaline earth metal compounds. These catalysts are used in an amount of 1 × 10 ^-8 to 1 × 10 ^-1 mol per 1 mol of the aromatic diol compound,
Preferably, 1 × 10 ⁻⁷ to 1 × 10 ⁻² mol is used. When a basic compound is used as the catalyst, the basic compound is usually 1 × based on 1 mole of the aromatic diol compound.
10 ^-6 to 1 × 10 ^-1 mol, preferably 1 × 10 ^-5 to 1 ×
It is used in an amount of 10 ^-2 mol. Melt polycondensation: The polycarbonate is produced by the transesterification method by a known aromatic polycondensation method. That is, a reaction is carried out under normal pressure or reduced pressure at a temperature of 200 to 320 ° C. using the above-mentioned raw materials, and a melt polycondensation reaction is carried out while removing by-products such as phenol by a transesterification reaction. The reaction is usually carried out in two or more multi-step processes under different temperature and pressure conditions. The reaction time of each stage is appropriately determined depending on the degree of progress of the reaction, but from the viewpoint of the hue of the polymer, it is 0.1 to 0.1.
Preferably, it is 5 hours. Melt polycondensation can be carried out batchwise or continuously. Next, a method for producing an aromatic polycarbonate according to the present invention will be described. In the present invention, any device can be used as the reaction device. Normally, turbine blades, paddle blades, anchor blades, full zone blades (manufactured by Shinko Pantech Co., Ltd.), and Sun Meller blades (Mitsubishi Heavy Industries, Ltd.)
), Max Blend Tsubasa (Sumitomo Heavy Industries, Ltd.)
), A helical ribbon blade, a twisted lattice blade (manufactured by Hitachi, Ltd.), and one or more vertical polymerization tanks, followed by a horizontal uniaxial polymerization tank such as a disk type or a cage type, or an HVR. , SCR, N-SCR (Mitsubishi Heavy Industries, Ltd.)
), A bivolak (manufactured by Sumitomo Heavy Industries, Ltd.), or a horizontal twin-screw polymerization tank equipped with spectacle wings and lattice wings (manufactured by Hitachi, Ltd.). Next, FIG. 1 shows one of the apparatuses used in the continuous polymerization method.
An example will be described using bisphenol A as an example of an aromatic diol and diphenyl carbonate as an example of a carbonic acid diester compound as a monomer of a reaction raw material. In FIG. 1, five polymerization tanks are installed in series. In the figure, 1 is a raw material introduction pipe, 2 is a transesterification catalyst introduction pipe, 3 is a by-product discharge pipe, 4, 4 ', 4 ", and 4'" are vertical polymerization tanks, and 5 is a max blend stirring blade. , 6
Is a double helical ribbon wing. 7 is a schematic horizontal sectional view of the horizontal polymerization tank, 8 and 9 are lattice blades, and 10 is the first.
The prepolymer, 11 is the second prepolymer, 12 is the third prepolymer, 13 is the fourth prepolymer, and 14 is the final product polymer. In the reaction, first, a molten mixture of bisphenol A as an aromatic diol compound and diphenyl carbonate as a carbonic acid diester is introduced into the first polymerization tank through a raw material introduction pipe 1 under an atmosphere of an inert gas such as nitrogen gas. Further, an alkali metal compound and / or an alkaline earth metal compound and / or a basic compound as a catalyst are continuously supplied into the above-mentioned polymerization tanks through a catalyst introduction pipe 2, and in each polymerization tank, by-products are produced. While removing the phenol from the by-product discharge pipe 3, the polymerization tanks of 3 to 7 stages (FIG. 1)
In this case, five units are used. The reaction conditions are as follows: temperature: 200 to 320
° C, more preferably 200-280 ° C, pressure: normal pressure ~
0.01 Torr, average residence time: in the range of 5 to 150 minutes. In each polymerization tank, in order to more effectively discharge phenol by-produced as the reaction proceeds, the above reaction conditions are set in stages. Set higher temperature and higher vacuum within the range. In order to prevent deterioration of the hue of the polycarbonate obtained, it is preferable to set the temperature as low as possible and the residence time as low as possible. The ratio of diphenyl carbonate and bisphenol A supplied to the first polymerization tank is 1.010 to 1.30.
0 (diphenyl carbonate / bisphenol A) is preferred. In each polymerization tank, polycarbonate (including its prepolymer) having various viscosity average molecular weights is produced depending on the degree of polycondensation. In this apparatus, it is preferable that a polycarbonate having a viscosity average molecular weight of 10,000 can be obtained in the third and subsequent polymerization tanks. <Method of increasing the temperature of the manufacturing apparatus> The method of increasing the temperature of the manufacturing apparatus is as follows.
This is performed in order to prevent a polymer produced beforehand and remaining in the reactor from generating crystals having a high melting point exceeding the ultimate temperature of the reactor and causing troubles such as blockage of the reactor. That is, the viscosity average molecular weight of the polymer in the reactor is 2,000 to 25,000, preferably 2,000 to 20,
000, more preferably 3,000 to 15,000, the production apparatus in which the polycarbonate remaining is heated from a state in which stirring is stopped or substantially in a state in which the flow of contents is stopped, and the apparatus temperature before the temperature rise is 240 ° C. or lower, preferably 150 ° C or lower to 200 ° C to 320 ° C, preferably 230 to 300 ° C
Up to 20 ° C. or higher, preferably 50 ° C. or higher, more preferably 80 ° C. or higher, the heating rate of the apparatus should be more than 0.2 ° C./min and 20 ° C./min or less, preferably 0.5 ° C.
/ Min or more, more preferably at 1 ° C / min or more. When the molecular weight of the polymer in the apparatus is smaller than 2,000, no problem occurs because the crystal does not increase in melting point even if crystallization occurs. When the molecular weight of the polymer exceeds 25,000, the rate of crystal formation is extremely low, and no problems such as device blockage occur. If the temperature rise rate of the apparatus is 0.2 ° C./min or less, the ultimate temperature of the apparatus becomes 200 due to crystallization of the polymer in the apparatus and increase of the melting point of the generated crystals.
At any temperature in the range of -320 ° C, crystals of the polymer remain, causing problems such as device blockage. The upper limit of the heating rate is not particularly limited when it exceeds 0.2 ° C./min, and is determined by the structural limitation of the apparatus, the balance between the capacity of the heat source for heating the apparatus and the heat capacity of the apparatus, and the like. In general, if the temperature rise rate of the device exceeds 20 ° C./min, the hermeticity of the device may be impaired due to the difference in thermal expansion between the sealing portion of the device and the tank or the like. Preferably, a heating rate of 10 ° C./min or less is preferable. The heating method may be a constant heating rate or not a constant heating rate as long as the above conditions are satisfied. The temperature rise may be continuous or stepwise. Incidentally, the stepwise heating includes two or more heating steps with a temperature difference of less than 20 ° C. at a heating rate exceeding 0.2 ° C./min,
In this method, the temperature is raised to 0 ° C. or more. If the temperature before the heating of the apparatus exceeds 240 ° C., the crystallization of the polymer is slow and no problems such as clogging occur. If the temperature after heating is lower than 200 ° C., the polymer having a viscosity average molecular weight of 2,000 to 25,000 easily undergoes crystallization during the polymerization reaction, and does not become a polymerization reaction in a molten state. If the temperature difference before and after the temperature rise of the apparatus is less than 20 ° C., sufficient crystallization and high melting point of the crystal do not occur, and problems such as blockage of the apparatus do not occur. The type of the reaction apparatus is not limited to the apparatus shown in FIG. 1, and there is no particular limitation as long as a polymer having a molecular weight within the above range remains, and a vertical polymerization tank equipped with various stirring blades. A horizontal uniaxial or / and horizontal biaxial polymerization tank or the like can be used. The atmosphere during the temperature rise of the apparatus is not particularly limited. However, from the viewpoint of the quality of the polymer after the temperature rise, it is preferably carried out in an inert gas such as nitrogen gas at normal pressure or reduced pressure. EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition,
The manufacturing apparatus shown in FIG. 1 was used. The viscosity average molecular weight (Mv) of the polycarbonate was measured using an Ubbelohde viscometer to measure the intrinsic viscosity [η] at 20 ° C. in methylene chloride. Was determined for the viscosity average molecular weight (Mv). [Η] = 1.23 × 10 ⁻⁴ × (Mv) ^0.83 Synthesis Example 1 Under a nitrogen gas atmosphere, bisphenol A and diphenyl carbonate were mixed at a constant molar ratio (DPC / BPA molar ratio =
1.040) together with the adjusted melt mixture.
At a flow rate of 1.064 mol / hour, a Max Blend blade was provided through a raw material introduction pipe at normal pressure under a nitrogen atmosphere.
The liquid is continuously supplied into the first vertical stirred polymerization tank having a capacity of 100 L controlled at 0 ° C., and the liquid level is controlled while controlling the valve opening provided in the polymer discharge line at the bottom of the tank so that the average residence time is 30 minutes. The level was kept constant. Simultaneously with the start of the supply of the raw material mixture, a 2% by weight aqueous cesium carbonate solution as a catalyst was 3.2 ml / hour (bisphenol A1).
(1 × 10 ⁻⁶ mol per mol).
The polymerization solution discharged from the bottom of the tank is continuously stirred in a second, third, and fourth tanks (second and third tanks: Max blend blades, fourth tank: double helical ribbon blades) with a vertical stirring polymerization tank having a capacity of 100 L. In addition, it was sequentially and continuously supplied to a 150-L capacity horizontal polymerization tank equipped with a fifth lattice blade. During the reaction, the liquid level is controlled so that the average residence time in each of the second to fifth polymerization tanks is 60 minutes.
At the same time, phenol by-produced was distilled off. Second
The reaction conditions in the fifth to fifth polymerization tanks are as follows: a second polymerization tank (210 ° C., 100 Torr, 110 rpm), a third polymerization tank (240 ° C., 15 Torr, 75 rpm), and a fourth polymerization tank (265 ° C., 0.5 Torr). , 25 rpm), 5th
In a polymerization tank (280 ° C, 0.5 Torr, 10 rpm)
As the reaction progressed, conditions were set to high temperature, high vacuum, and low stirring speed. The second, third, and
The viscosity average molecular weights of the respective polymers extracted from the fourth and fifth polymerization tanks were 1,600, 4,800 (resin A), 10,000 (resin C), and 17,000, respectively. Synthesis Example 2 A reaction was carried out in the same manner as in Synthesis Example 1 except that the temperatures of the third and fourth polymerization tanks were changed to 230 ° C. and 250 ° C., respectively. The viscosity average molecular weight of each polymer extracted from the fourth polymerization tank at the time when each tank was stabilized stably was 7,8.
00 (resin B). Synthesis Example 3 In Synthesis Example 1, the molar ratio of bisphenol A to diphenol carbonate was 1.02, the temperatures of the fourth and fifth tanks were 280 ° C. and 290 ° C., respectively, and the average residence time of the fifth tank. Was carried out in the same manner as in Synthesis Example 1 except that the reaction time was changed to 90 minutes.
The viscosity average molecular weight of the polymer withdrawn from the fifth polymerization tank at the time when each tank was stabilized stably was 27,000 (resin F). Synthesis Example 4 In Synthesis Example 1, the molar ratio of bisphenol A to diphenol carbonate was 1.05, the amount of catalyst was tripled, the temperature of the fourth tank was 240 ° C., and the average residence time of the fourth tank was 30. The reaction was conducted in the same manner as in Synthesis Example 1 except that the reaction time was changed to minutes. The viscosity average molecular weight of the polymer withdrawn from the fourth polymerization tank at the time when each tank was stabilized stably was 16,400 (resin D). Synthesis Example 5 In Synthesis Example 1, the molar ratio of bisphenol A to diphenol carbonate was 1.04, and the catalyst was 1.7 × 10 ^{− with} sodium tetraphenylboron in place of cesium carbonate per mole of bisphenol A. ^The reaction was carried out in the same manner as in Synthesis Example 1 except that ⁶ mol, the temperature of the third tank was 240 ° C., and the average residence time of the third tank was 30 minutes. The viscosity average molecular weight of the polymer withdrawn from the fourth polymerization tank at the time when each tank was stabilized stably was 4,500 (resin E). Examples 1 to 10 and Comparative Example 1 During the continuous polymerization of Synthesis Examples 1 to 5, an emergency stop was carried out, and the polymer in each polymerization tank was taken out. Was lowered to 50 ° C. or lower. Next, the respective polymerization tanks were heated under the temperature increasing conditions shown in Table 1, and when the temperature reached the set temperature of each polymerization tank of Synthesis Examples 1 to 5, the operation was restarted. In Examples 1 to 5, there was no blockage of the piping system of each polymerization tank. In Comparative Example 1, a part of the piping was blocked in polymerization tanks 4 and 5. [Table 1] Reference Examples 1 to 10 and Reference Comparative Examples 1 to
12 Resins A to F, each of which is a polymer obtained in Synthesis Examples 1 to 5, are each 0.1 mm.
A 5 g test tube was treated in a nitrogen atmosphere at 300 ° C. for 10 minutes and then quenched, heated in a cast heater under the conditions shown in Table 2, allowed to cool to room temperature, and then cooled to a differential scanning calorimeter (DSC). ), The crystal melting point is calculated from the melting peak temperature by JP
oly. Sci. Based on the heat of fusion of perfect crystals described in B8, 645, 1970, the degree of crystallinity was determined by measuring the heat of crystal fusion. Table 2 shows the results. [Table 2] As can be understood from Table 2, in the examples of the present invention, if the heating rate is set appropriately, it is presumed that crystallized polycarbonate does not form and no clogging of piping or the like occurs. If the rate of temperature rise is slow even though the temperature and molecular weight are satisfied (Comparative Example 1), a crystallized polymer is produced (Reference Comparative Example 1), and the tube is clogged. In the case of a resin having a high viscosity molecular weight of 27,000, crystallization does not occur even when subjected to a heat history (Reference Comparative Example 11), so it is presumed that the tube will not be blocked. Also, when the temperature change range is narrow (Reference Comparative Example 12), no crystallization of polycarbonate is observed, and it is assumed that there is no blockage of the tube. According to the method for raising the temperature of the transesterification polycarbonate polymerization apparatus according to the present invention, when the apparatus is started after the apparatus is stopped, there is no trouble such as apparatus blockage, and the apparatus can be shifted to the steady operation in a short time. Efficient production becomes possible.

[Brief description of the drawings] FIG. 1 is a diagram showing an apparatus for producing polycarbonate. [Explanation of symbols] 1 Raw material introduction pipe 2 Catalyst introduction pipe 3 By-product discharge pipe 4, 4 ', 4' ', 4' '' vertical polymerization tank 5 stirring blade 7 Horizontal polymerization tank 10 Prepolymer 14 Final product polycarbonate

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsushige Hayashi 2-4-1-16 Hinagahigashi, Yokkaichi-shi, Mie Mitsubishi Gas Chemical Co., Ltd. Yokkaichi Plant (56) References JP-A-6-200008 (JP, A (58) Fields surveyed (Int. Cl. ⁷ , DB name) C08G 64/00-64/42

Claims (1)

(57) [Claims 1] A viscosity average molecular weight obtained by reacting bisphenol A with a carbonic acid diester under heating and melting is 2,2.
When the temperature of the polymerization apparatus in which the polycarbonate of 2,000 to 25,000 remains is raised from a temperature of 240 ° C. or lower to a temperature of at least 20 ° C. and heated to a temperature of 200 ° C. to 320 ° C., the polymerization is performed. A method for increasing the temperature of a polycarbonate production apparatus, comprising heating the apparatus at a rate of more than 0.2 ° C./min and not more than 20 ° C./min.