JP5380934B2 - Method for producing polycarbonate resin - Google Patents

Description

  The present invention relates to a method for producing a polycarbonate resin, and more particularly to a method for producing a polycarbonate resin with reduced volatile impurities such as phenol.

  Polycarbonate resins are excellent in mechanical properties such as heat resistance and impact resistance and dimensional stability, and are also excellent in transparency, and are used in various applications.

  By the way, as a method for producing a polycarbonate resin, there are a melting method (transesterification method), a phosgene method (interfacial polymerization method), etc. In any method, unreacted raw materials, low molecular weight products, reaction solvents, etc. Obtained as a polycarbonate resin containing volatile impurities. Examples of the low molecular weight product include phenol in a melting method. That is, in the melting method, phenol produced in the transesterification reaction is distilled off under reduced pressure, but phenol remains in the reaction liquid and is contained in the polycarbonate resin as an equilibrium relationship between the reaction liquid phase and the gas phase. The

  Conventionally, as a method for producing a polycarbonate resin having a reduced content of volatile impurities, for example, when a polycarbonate resin is melted and extruded into pellets, nitrogen or water is supplied to an extrusion kneading part of a melt extruder to perform a decompression process. (Patent Documents 1 and 2), a method of adding saturated aliphatic hydrocarbons or aromatic hydrocarbons (Patent Documents 3 and 4), a method of supplying carbon dioxide in a pressurized state and performing a decompression process (Patent Document 5) Also known is a method (Patent Document 6) in which a polycarbonate resin and water are kneaded at 0.3 to 10 MPa using a multistage vent type melt extruder and subjected to reduced pressure treatment.

JP-A-9-59367 JP-A-9-59368 JP-A-9-67433 JP-A-9-157375 JP 2000-302879 A JP 2001-31753 A

  An object of the present invention is to provide a method for producing a polycarbonate resin having a very low content of volatile impurities such as phenol.

  As a result of intensive studies to solve the above problems, the present inventors have obtained the following surprising findings. That is, in general, in the production of polycarbonate resin, a polymer filter is disposed at the outlet of the melt extruder in the pelletizing process for the purpose of removing foreign matters such as fisheye, but on the other hand, phenol is regenerated in the polymer filter. . Such regeneration of phenol is related to catalytic action by the constituent metal of the polymer filter or decomposition of carbonic acid diester or polymer due to shear heat generation in the polymer filter. Therefore, even if a vent-type melt extruder is used to remove volatile impurities, the polymer filter does not sufficiently exhibit the removal effect of phenol remaining as volatile impurities, resulting in a sufficient phenol content. It is difficult to produce a reduced polycarbonate resin.

The present invention has been completed based on the above findings and has been completed. The gist of the present invention is to prepare a polycarbonate resin having a reduced volatile impurity content by melting and devolatilizing a polycarbonate resin containing volatile impurities. A manufacturing method using a device in which a polymer filter is arranged between at least two vent-type melt extruders connected in series and no polymer filter is arranged after the last vent-type melt extruder Thus, the present invention resides in a method for producing a polycarbonate resin, characterized by melting and devolatilizing after passing through a polymer filter.

  According to the present invention, it is possible to produce a polycarbonate resin having an extremely low content of volatile impurities such as phenol and having excellent thermal stability during molding.

  Hereinafter, the present invention will be described in detail. The polycarbonate resin is an optionally branched thermoplastic polycarbonate polymer or copolymer obtained by reacting a dihydroxy compound or a small amount thereof with phosgene or a carbonic acid diester.

  Examples of the method for producing the polycarbonate resin include a melting method (transesterification method), a phosgene method (interfacial polymerization method), and the like.

  Examples of the dihydroxy compound used as a raw material include 2,2-bis (4-hydroxyphenyl) propane (alias: bisphenol A), 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane (alias: Tetrabromobisphenol A), bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxy) Phenyl) octane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 1,1-bis (3-tert-butyl-4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-) 3,5-dimethylphenyl) propane, 2,2-bis (3-bromo-4-hydroxyphenyl) propane, 2,2 Bis (3,5-dichloro-4-hydroxyphenyl) propane, 2,2-bis (3-phenyl-4-hydroxyphenyl) propane, 2,2-bis (3-cyclohexyl-4-hydroxyphenyl) propane, 1 , 1-bis (4-hydroxyphenyl) -1-phenylethane, bis (4-hydroxyphenyl) diphenylmethane, 2,2-bis (4-hydroxyphenyl) -1,1,1-trichloropropane, 2,2- Bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexachloropropane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane Bis (hydroxyaryl) alkanes such as 1,1-bis (4-hydroxyphenyl) cyclopentane, 1,1-bis (4-hydroxy) Enyl) cyclohexane, bis (hydroxyaryl) cycloalkanes such as 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, Cardiostructure-containing bisphenols such as 9-bis (4-hydroxy-3-methylphenyl) fluorene; dihydroxydiaryl ethers such as 4,4′-dihydroxydiphenyl ether and 4,4′-dihydroxy-3,3′-dimethyldiphenyl ether Dihydroxydiaryl sulfides such as 4,4′-dihydroxydiphenyl sulfide and 4,4′-dihydroxy-3,3′-dimethyldiphenyl sulfide; 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxy-3, 3'-dimethyldiphenyl Dihydroxydiaryl sulfoxides such as sulfoxide; dihydroxydiaryl sulfones such as 4,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxy-3,3′-dimethyldiphenylsulfone; hydroquinone, resorcin, 4,4′-dihydroxydiphenyl Etc. Among these, bis (4-hydroxyphenyl) alkanes are preferable, and bisphenol A is particularly preferable from the viewpoint of impact resistance. Furthermore, for the purpose of enhancing flame retardancy, a compound in which one or more tetraalkylphosphonium sulfonates are bonded to the above-mentioned dihydroxy compound can also be used. These dihydroxy compounds may be used in combination of two or more.

  In order to obtain a branched polycarbonate resin, in the interfacial polymerization method, phloroglucin, 4,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptene-2, 4,6-dimethyl-2,4, 6-tris (4-hydroxyphenyl) heptane, 2,6-dimethyl-2,4,6-tris (4-hydroxyphenyl) heptene-3, 1,3,5-tris (4-hydroxyphenyl) benzene, 1 , 1,1-tris (4-hydroxyphenyl) ethane, 3,3-bis (4-hydroxyaryl) oxindole (also known as isatin bisphenol), 5-chloroisatin, 5,7-dichloroisa Chin, 5-bromoisatin and the like may be used as part of the dihydroxy compound, and the amount used may be dihydroxy. To compound, usually 0.01 to 10 mol%, preferably 0.1 to 2 mol%. On the other hand, in the melting method, the addition of the branching agent is optional, and a branched polycarbonate resin can be obtained by adjusting the reaction temperature and the amount of catalyst.

  The reaction by the interfacial polymerization method is carried out as follows using a dihydroxy compound and, if necessary, a molecular weight modifier (terminal terminator) and an antioxidant for preventing the dihydroxy compound from being oxidized. That is, in the presence of an organic solvent inert to the reaction and an aqueous alkaline solution, the pH is usually maintained at 9 or higher, phosgene is reacted, and then a polymerization catalyst such as a tertiary amine or quaternary ammonium salt is added to the interface. Polymerization is performed to obtain a polycarbonate. The reaction temperature is, for example, 0 to 40 ° C., and the reaction time is, for example, several minutes (for example, 10 minutes) to several hours (for example, 6 hours).

  Examples of the organic solvent inert to the reaction include chlorinated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, monochlorobenzene and dichlorobenzene, and aromatic hydrocarbons such as benzene, toluene and xylene. It is done. Moreover, as an alkali compound used for alkaline aqueous solution, hydroxide of alkali metals, such as sodium hydroxide and potassium hydroxide, is mentioned.

  Examples of the molecular weight regulator include compounds having a monovalent phenolic hydroxyl group, and specific examples thereof include m-methylphenol, p-methylphenol, m-propylphenol, p-propylphenol, p-tert-butylphenol. , P-long chain alkyl-substituted phenol and the like. The usage-amount of a molecular weight regulator is 50-0.5 mol normally with respect to 100 mol of dihydroxy compounds, Preferably it is 30-1 mol.

  The melt transesterification method is performed, for example, as a transesterification reaction between a carbonic acid diester and a dihydroxy compound.

  Examples of the carbonic acid diester include compounds represented by the following general formula (1).

  Here, in the general formula (1), A ′ is a linear, branched or cyclic monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted. Two A's may be the same or different from each other. In addition, as a substituent on A ′, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide Examples include a group and a nitro group.

  Specific examples of the carbonic acid diester include substituted diphenyl carbonates such as diphenyl carbonate and ditolyl carbonate, and dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-t-butyl carbonate. Among these, diphenyl carbonate (hereinafter sometimes abbreviated as DPC) and substituted diphenyl carbonate are preferable. These carbonic acid diesters can be used in combination of two or more.

  The carbonic acid diester may be partially substituted with dicarboxylic acid or dicarboxylic acid ester, and the ratio is usually 50 mol% or less, preferably 30 mol% or less. Examples of typical dicarboxylic acid or dicarboxylic acid ester include terephthalic acid, isophthalic acid, diphenyl terephthalate, and diphenyl isophthalate. When substituted with such a dicarboxylic acid or dicarboxylic acid ester, a polyester carbonate is obtained.

  In the polycarbonate produced by the transesterification method, the carbonic acid diester (including the above-mentioned substituted dicarboxylic acid or dicarboxylic acid ester; the same shall apply hereinafter) is used in excess relative to the dihydroxy compound. That is, the ratio (molar ratio) of the carbonic acid diester to the dihydroxy compound is usually 1.00 to 1.30, preferably 1.01 to 1.20, and more preferably 1.05 to 1.20. When the molar ratio is excessively small, the terminal OH groups of the obtained polycarbonate resin increase, and the thermal stability of the resin tends to deteriorate. In addition, when the molar ratio is excessively large, the transesterification reaction rate decreases, and it becomes difficult to produce a polycarbonate resin having a desired molecular weight, and the residual amount of carbonic acid diester in the resin increases. It may cause odors during molding and molding.

  Generally, a polycarbonate having a desired molecular weight and a terminal hydroxyl group amount can be obtained by adjusting the mixing ratio of the carbonic acid diester and the dihydroxy compound or adjusting the degree of vacuum during the reaction. As a more aggressive method, there is a well-known adjustment method in which a terminal terminator is added separately during the reaction. In this case, examples of the terminal terminator include monohydric phenols, monovalent carboxylic acids, and carbonic acid diesters. The amount of terminal hydroxyl groups greatly affects the thermal stability, hydrolysis stability, color tone, etc. of the product polycarbonate resin. The amount of terminal hydroxyl groups is usually 1,000 ppm or less, preferably 700 ppm or less in order to give practical physical properties although it depends on the use.

Usually, when a polycarbonate is produced by a transesterification method, a transesterification catalyst is used. The transesterification catalyst is not particularly limited, but an alkali metal compound and / or an alkaline earth metal compound is preferable. In addition, a basic compound such as a basic boron compound, a basic phosphorus compound, a basic ammonium compound, or an amine compound can be used in combination. Among these transesterification catalysts, alkali metal compounds are preferable from a practical viewpoint. These transesterification catalysts may be used in combination of two or more. The amount of the transesterification catalyst used is usually 1 × 10 ⁻⁹ to 1 × 10 ⁻¹ mol, preferably 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol, more preferably 1 × 10 to 1 mol of the dihydroxy compound. It is the range of ⁻⁷ to 1 × 10 ⁻⁶ mol.

  Examples of the alkali metal compound include inorganic alkali metal compounds such as alkali metal hydroxides, carbonates and hydrogencarbonate compounds; organic alkali metal compounds such as alkali metal alcohols (or phenols) and salts with organic carboxylic acids. Can be mentioned. Here, examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium. Among these alkali metal compounds, cesium compounds are preferable, and cesium carbonate, cesium hydrogen carbonate, or cesium hydroxide is particularly preferable.

  The transesterification reaction between the dihydroxy compound and the carbonic acid diester can be carried out as follows.

  First, as a raw material preparation step, a batch, semi-batch or continuous stirring tank type apparatus is used in an inert gas atmosphere such as nitrogen or argon to prepare a raw material mixed melt. For example, when bisphenol A is used as the dihydroxy compound and diphenyl carbonate is used as the carbonic acid diester, the melt mixing temperature is usually in the range of 120 ° C. to 180 ° C., preferably 125 ° C. to 160 ° C.

  Next, as a polycondensation step, an ester exchange reaction between the dihydroxy compound and the carbonic acid diester compound is performed. The transesterification reaction is usually carried out continuously in a multistage system of two or more stages, preferably 3 to 7 stages. Specific reaction conditions for each tank are temperature: 150 to 320 ° C., pressure: normal pressure to reduced pressure (0.01 Torr: 1.3 Pa), and average residence time: 5 to 150 minutes.

  In each multi-stage reactor, in order to more effectively remove the by-product phenol as the polycondensation reaction proceeds, the temperature is gradually increased to a higher vacuum within the above reaction conditions. Ultimately, the pressure is reduced to 2 Torr (266.6 Pa) or less. Thereby, a melt polycondensation reaction can be performed while removing by-products such as hydroxy compounds. In order to prevent deterioration in quality such as hue of the polycarbonate resin obtained, conditions of a low temperature and a short residence time are preferable within the above range.

  The melt polycondensation can be carried out batchwise or continuously, but the continuous method is preferred in consideration of the stability of the resin composition of the present invention. As a catalyst deactivator in the transesterification polycarbonate, a compound that neutralizes the catalyst, for example, a sulfur-containing acidic compound or a derivative formed therefrom can be used. The usage-amount of the compound which neutralizes a catalyst is 0.5-10 equivalent normally with respect to the alkali metal which the said catalyst contains, Preferably it is the range of 1-5 equivalent. In addition, the ratio of the compound that neutralizes the catalyst to the polycarbonate is usually in the range of 1 to 100 ppm, preferably 1 to 20 ppm.

  The viscosity average molecular weight of the polycarbonate resin is not particularly limited, but is usually 13,000 or more, preferably 15,000 or more. In addition, said viscosity average molecular weight means the value converted from the solution viscosity measured at the temperature of 20 degreeC, using a methylene chloride as a solvent.

  The present invention relates to a method for producing a polycarbonate resin having a reduced volatile impurity content by melting and devolatilizing a polycarbonate resin containing volatile impurities, the feature of which is to melt and devolatilize after passing through a polymer filter. In the point.

  The polymer filter in the present invention is a filter that removes foreign substances present in the polycarbonate resin by filtration, and in general, known types such as a candle type, a pleat type, and a leaf disk type can be used. In particular, a leaf disk type polymer filter is preferable. The leaf disk type is usually a disk shape, and one or more layers of woven wire meshes having various wire diameters and aperture ratios are used. The types of weaving include plain weave, twill weave, plain tatami weave, twill tatami weave, and may be non-woven fabric. As the material, stainless steel such as SUS-316 or SUS-316L is usually used, but sintered metal or resin can also be used. The absolute filtration accuracy is usually 0.5 μm to 50 μm, preferably 0.5 μm to 20 μm.

  The method of melt devolatilization is not particularly limited, and examples thereof include a method using a vent type melt extruder, a method using a thin film evaporator, and a method of melting and stirring in a stirring tank. Among these, a method using a vent type melt extruder and a method using a thin film evaporator are preferable, and the former is particularly preferable.

  Examples of the vent-type melt extruder include a vent-type single-screw or multi-screw extruder. In particular, a mesh-type twin-screw extruder is preferable, and the screw rotation direction may be the same direction rotation or different direction rotation. Moreover, there is no restriction | limiting in the number of vents, Usually, it selects suitably from the range of 1-10 steps. The resin temperature in the extruder is measured as the highest temperature shown during operation by a resin thermometer attached to the center and outlet of each barrel of the extruder, and the thermometer is a thermocouple type or contact infrared type. A thermometer such as is preferably used. Further, the resin supplied to the extruder may be in a molten state or a pellet state.

  In the present invention, a polycarbonate resin already pelletized by a melt extruder in which a polymer filter is disposed at the outlet of the melt extruder may be used as a raw material and devolatilized and melt extruded before molding. However, it is preferable to perform devolatilization melt extrusion using an apparatus in which a polymer filter is disposed between two vent-type melt extruders connected in series by piping. In this case, the arrangement position of the polymer filter is not particularly limited, and may be any of the outlet of the first vent-type melt extruder, the middle of the connection pipe, and the inlet of the last vent-type melt extruder.

  Preferably, the first vented melt extruder uses a co-directional screw rotary extruder and the last vent-type melt extruder uses a partially meshed different direction screw rotary extruder. Basically, the same direction rotation is the mixing action and the different direction rotation is mainly the kneading action. However, in terms of the removal of volatile impurities, that is, the devolatilization effect, the different direction screw rotation type. It is said that the extruder is superior in surface renewability, and in particular, the partial meshing type is superior. However, in general, since various additives are often added to the extruder, a co-directional screw rotary type extruder having a small dispersibility and a small amount of extrusion is preferably used. For this reason, it is important to make the structure which fully utilizes each characteristic, and as a result, it becomes possible to obtain a higher quality product.

  The molten resin temperature in the last vent-type melt extruder is preferably lower than the molten resin temperature in the first vent-type melt extruder. In order to efficiently remove volatile impurities such as phenol, it is necessary to suppress phenol regeneration due to decomposition of the polymer or carbonic acid diester, so that the molten resin temperature is preferably low. However, for example, when the first vent-type melt extruder is equipped with a polymer filter, if the resin temperature is too low, decomposition of the polymer and carbonic acid diester can be suppressed, but the differential pressure before and after filtration of the polymer filter is extremely high. It may rise and damage the polymer filter. In addition, when an additive or the like is added to the extruder, if the resin temperature is low, the resin viscosity becomes high, so that mixing and dispersibility deteriorate. For this reason, the molten resin temperature (T1) in the first vent type melt extruder is usually 200 to 400 ° C., preferably 250 to 380 ° C., and the molten resin temperature (T2) in the last vent type melt extruder is Usually, it is 200-350 degreeC, Preferably it is 220-330 degreeC. The difference between the molten resin temperatures (T1) and (T2) is usually 1 to 100 ° C, preferably 1 to 50 ° C.

  The molten resin residence time (θ1) in the last vent-type melt extruder is preferably shorter than the molten resin residence time (θ2) in the first vent-type melt extruder. From the viewpoint of removing volatile impurities, a shorter residence time of the molten resin is advantageous from the viewpoint of decomposition of the polymer and the carbonic acid diester. On the other hand, when adding various additives etc. with the first vent type melt extruder, if the residence time is short, the dispersibility deteriorates. For this reason, in the last vent type melt extruder, it is preferable that various additives are not added and the residence time of the extruder is shortened so that the effect of removing volatile impurities can be sufficiently exhibited. The molten resin residence time (θ1) in the first vent-type melt extruder is usually 0.1 to 60 minutes, preferably 1 to 30 minutes, and the molten resin residence time (θ2) in the last vent-type melt extruder is Usually, 0.1 to 60 minutes, preferably 0.5 to 20 minutes. The difference between the molten resin residence time (θ1) and (θ2) is usually 0.1 to 30 minutes, preferably 1 to 10 minutes. The residence time can be changed by the barrel length of the melt extruder.

  The vent pressure in the last vented melt extruder is preferably lower than the vent pressure in the first vented melt extruder. It has been considered that lowering the vent pressure tends to be preferable from the viewpoint of removal of volatile impurities, that is, devolatilization efficiency. However, the removal of phenol, in particular, tends to depend greatly on the temperature of the molten resin. Even if the vent pressure is lowered while the resin temperature is high, the carbonic diester content decreases, but the phenol content increases conversely. There was found. Therefore, in the last vent-type melt extruder, the phenol removal efficiency can be increased by lowering the melt resin temperature and lowering the vent pressure. The vent pressure (P1) in the first vent-type melt extruder is usually 0.01-100 KPa, preferably 0.1-70 KPa, and the vent pressure (P2) in the last vent-type melt extruder is usually 0.00. 001 to 80 KPa, preferably 0.01 to 50 KPa. The difference between the vent pressures (P1) and (P2) is usually 0.01 to 100 KPa, preferably 0.1 to 80 KPa.

  In the present invention, it is preferable to use water as a devolatilization aid. The water supplied to the extruder is not particularly limited as long as it does not affect the quality of the polycarbonate resin, but water having a low electrical conductivity is preferable. The electrical conductivity of water is usually 1 mS / cm or less, preferably 1 μS / cm or less. The main purpose of devolatilization aid injection is to improve devolatilization while promoting diffusion of volatile impurities from the surface layer by lowering the partial pressure of volatile impurities due to evaporation of the devolatilization aid and the azeotropic effect. is there. However, if the injection amount of the devolatilization aid is small, sufficient devolatilization improvement cannot be achieved. Conversely, if the amount is too large, the polymer is hydrolyzed and the molecular weight of the polymer is lowered and the hue is deteriorated. For this reason, the injection amount of water as a devolatilization aid is usually 0.01 to 5% by weight, preferably 0.05 to 2% by weight, based on the amount of the extruded resin. Further, the devolatilization aid can be injected into either the first vent-type melt extruder, the last vent-type melt extruder, or both.

  The polycarbonate resin derived from the last vent-type melt extruder is usually pelletized according to a conventional method. In the case of using cooling water for cooling / cutting the polycarbonate resin during pelletization, the electric conductivity of the cooling water is preferably low, and is usually 1 mS / cm or less, preferably 1 μS / cm or less, as described above. . According to the present invention, a polycarbonate resin having a sufficiently reduced content of volatile impurities such as phenol can be produced. For example, the content of phenol is usually 20 ppm or less, preferably 15 ppm or less, more preferably 10 ppm or less.

  A preferred embodiment of the present invention employing a transesterification process for the production of polycarbonate resin comprises at least one reactor and at least one extruder, wherein at least one of the extruders is a vented melt extruder, Use a polycarbonate resin production system in which a polymer filter is provided on the inlet side of the vent type melt extruder (or the last vent type melt extruder when multiple vent type melt extruders are installed). This is a method in which a dihydroxy compound and a carbonic acid diester are transesterified in a reactor, and a volatile impurity content is melted and devolatilized by an extruder.

  For polycarbonate resin, conventionally known additives such as other thermoplastic resins, flame retardants, impact resistance improvers, antistatic agents, slip agents, antiblocking agents, lubricants, antifogging agents, natural, as necessary. Oils, synthetic oils, waxes, organic fillers, and inorganic fillers can be appropriately selected and used.

  The polycarbonate resin obtained by the production method of the present invention is used in various applications that require a small amount of volatile impurities, for example, optical applications such as optical disk substrates, optical fibers, lenses, and window materials; , Medical device applications such as syringes: Used suitably for applications such as tableware and beverage containers.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. The polycarbonate resin was analyzed by the following method.

(1) Viscosity average molecular weight (Mv):
Using an Ubbelohde viscometer, the intrinsic viscosity [η] was measured at 20 ° C. in methylene chloride, and the viscosity average molecular weight (Mv) was determined from the following formula.

(2) Terminal hydroxyl group concentration:
Dissolve 0.1 g of resin in 10 ml of methylene chloride, and add 5 ml of 5% methylene chloride solution of acetic acid (Wako Pure Chemicals, reagent grade) and 2.5% methylene chloride solution of titanium tetrachloride (Wako Pure Chemicals, reagent grade). Color was developed by adding 10 ml, and the absorbance at a wavelength of 546 nm was measured using a spectrophotometer (“UV160 type” manufactured by Hitachi, Ltd.). Separately, the extinction coefficient was determined using a methylene chloride solution of dihydric phenol used during resin production, and the OH group concentration in the sample was quantified.

(3) Residual monomer amount:
Dissolve 1.2 g of resin in 7 ml of methylene chloride, add 23 ml of acetone to this while stirring, and reprecipitate. The supernatant is subjected to liquid chromatography (“LC-10AT” manufactured by Shimadzu, column: “MCI GEL ODS” ( 5 μm), 4.6 mm ID × 150 mm L, detector: UV 219 nm, eluent: acetonitrile / water = 4/6 volume ratio), the amount of residual phenol in the resin, the amount of residual bisphenol A (BPA), DPC) amount was quantified.

(4) Foreign matter amount:
After the resin pellets were dried at 120 ° C. for 6 hours or more under a nitrogen atmosphere, a 70 μm-thick film was formed using a single-screw 30 mm extruder manufactured by Isuzu Chemical Industries, Ltd. A 90 cm × 50 cm range (about 4 g) was cut out as a sample, a solid foreign substance (= fish eye) was marked using a stereomicroscope, the number of 10 μm or more was counted, and the number of foreign substances per 1 g was calculated.

Example 1:
A 140 ° C. molten mixture prepared by mixing bisphenol A and diphenyl carbonate at a constant molar ratio (DPC / BPA molar ratio = 1.103) under a nitrogen gas atmosphere is passed through a raw material introduction pipe at normal pressure, In a nitrogen atmosphere, the liquid was continuously supplied into the first vertical stirring polymerization tank controlled at 210 ° C., and the liquid opening was controlled while controlling the valve opening degree provided in the polymer discharge line at the bottom of the tank so that the average residence time was 60 minutes. The surface level was kept constant. Moreover, simultaneously with the start of the supply of the raw materials, an aqueous cesium carbonate solution as a catalyst was continuously supplied at a flow rate of 0.5 × 10 ⁻⁶ mol with respect to 1 mol of bisphenol A. The produced distillate such as phenol was continuously liquefied and recovered by a condenser provided in the distillation line of the polymerization tank. The reaction liquid discharged from the first polymerization tank was continuously introduced successively into the second, third and fourth vertical polymerization tanks and the fifth horizontal polymerization tank. The operation of each tank was set to a higher temperature and higher vacuum as the reaction progressed as follows.

  That is, the second polymerization tank is 210 ° C., 13300 Pa, 110 rpm, the third polymerization tank is 240 ° C., 1995 Pa, 75 rpm, the fourth polymerization tank is 260 ° C., 67 Pa, 75 rpm, the fifth polymerization tank is 265 ° C., 67 Pa, 5 rpm. During the reaction, the liquid level was controlled so that the average residence time of each tank was 60 minutes, and at the same time, by-product phenol was distilled off. The production rate of the polycarbonate resin is 50 kg / Hr.

  Next, the polymer melt withdrawn from the fifth polymerization tank was introduced into a twin-screw extruder-1 (screw diameter 46 mm, partially meshed screw type, same direction rotation) equipped with a three-stage vent port and a three-stage supply port. , P-toluenesulfonic acid butyl and tris (2,4-di-tert-butylphenyl) phosphate were supplied to the resin at 10 ppm and 1000 ppm, respectively. After circulation of a disk-type polymer filter (135 sheets of woven wire mesh leaf disk with an absolute filtration accuracy of 40 μm attached to the center post, hereinafter abbreviated as P / F), it was pelletized with water.

  Thereafter, the pellets dried at 120 ° C. for 6 hours were introduced into a twin-screw extruder-2 (screw diameter 46 mm, partially meshed screw type, rotating in the same direction) equipped with a two-stage vent port and a water inlet between the vent ports. The mixture was melt-kneaded, devolatilized at each vent, and then pelletized with water without passing through P / F. The operating conditions of Extruder-1 and Extruder-2 are shown in Table 1. In addition, the average residence time was calculated | required by time until 0.5g of bluing agents were added from the feed port for extruder resin introduction | transduction, and it discharged | emitted from die | dye. Table 2 shows the physical property evaluation results of the P / F inlet resin and the P / F outlet resin (pellet) of the biaxial extruder-1 and the outlet resin (pellet) of the biaxial extruder-2.

Example 2:
Except for pelletizing using a devolatilizing extruder in which a twin-screw extruder-1 (equipped with P / F) and a twin-screw extruder-2 (without P / F) were connected in series, the same as in Example 1 An aromatic polycarbonate resin was produced by the method, and physical properties were evaluated. The operating conditions and physical property evaluation results of the twin-screw extruder-2 are shown in Tables 1 and 2.

Example 3 and Example 4:
The molar ratio of bisphenol A to diphenyl carbonate (DPC / BPA molar ratio) was adjusted to 1.065, the P / F opening was 40 μm, and the twin screw extruder-2 was set to “3-stage vent port and 2-stage feed port. (Screw diameter 30 mm, partially meshed screw type, different direction rotation), and the operating conditions of the twin screw extruder-1 and the twin screw extruder-2 as shown in Table 1 were used. Except for the above, an aromatic polycarbonate resin was produced in the same manner as in Example 2, and the physical properties were evaluated. The average residence time was determined by adjusting the amount of resin introduced into the extruder. The physical property evaluation results are shown in Table 2.

Comparative Example 1 and Comparative Example 2:
The aromatic polycarbonate resin was prepared in the same manner as in Example 1 except that the operating conditions of the twin screw extruder-1 and P / F were changed as shown in Table 1 without using the twin screw extruder-2. Manufactured and evaluated for physical properties. The physical property evaluation results are shown in Table 2.

Comparative Example 3:
A polycarbonate was produced in the same manner as in Example 2 except that the operating conditions of the biaxial extruder-1 were changed as shown in Table 1 without using the biaxial extruder-2, and the physical properties were evaluated. went. The physical property evaluation results are shown in Table 2.

Claims (8)

A method for producing a polycarbonate resin having a reduced volatile impurity content by melting and devolatilizing a polycarbonate resin containing volatile impurities , wherein the polymer is interposed between at least two vent-type melt extruders connected in series. A method for producing a polycarbonate resin, characterized in that a filter is disposed, and a device in which a polymer filter is not disposed after the last vent-type melt extruder is used to melt and volatilize after passing through the polymer filter. The manufacturing method according to claim 1, wherein the first vent-type melt extruder uses a same-direction screw rotary extruder, and the last vent-type melt extruder uses a partially meshed different-direction screw rotary extruder. The production method according to claim 1 or 2 , wherein a molten resin temperature in the last vent-type melt extruder is lower than a molten resin temperature in the first vent-type melt extruder. The manufacturing method according to any one of claims 1 to 3, wherein a molten resin residence time in the last vent-type melt extruder is shorter than a molten resin residence time in the first vent-type melt extruder. The manufacturing method according to any one of claims 1 to 4, wherein a vent pressure in the last vent-type melt extruder is lower than a vent pressure in the first vent-type melt extruder. The method according to any one of claim 1 to 5 used a de揮助agent in an extruder. Including at least one reactor and at least one extruder, wherein at least one of the extruders is a vent-type melt extruder, and an inlet side of the vent-type melt extruder (a plurality of vent-type melt extruders are arranged) In the case of the last vent-type melt extruder, use a polycarbonate resin production device equipped with a polymer filter), in the reactor, diesterify the dihydroxy compound and carbonic acid diester, The manufacturing method of any one of Claims 1-6 which performs melt devolatilization of a volatile impurity content. The method according to any one of claims 1 to 7 , wherein the polycarbonate resin has a viscosity average molecular weight of 13,000 to 30,000.