JP4695410B2 - Method for preparing dope and method for producing polymer film - Google Patents

Description

The present invention relates to a method for preparing a dope and a method for producing a polymer film .

  A TAC film formed from cellulose acylate, particularly cellulose triacetate (hereinafter referred to as TAC) having an average degree of acetylation of 57.5% to 62.5% is a photographic photosensitive material because of its toughness and flame retardancy. It is used as a film base. Moreover, since the TAC film is excellent in optical isotropy, it is used as a polarizing plate protective film and an optical compensation film for liquid crystal display devices whose market is expanding in recent years.

  The TAC film is generally produced by a solution casting method. The solution casting method can produce a film having excellent physical properties such as optical properties as compared with other production methods such as a melt casting method. In the solution casting method for obtaining a TAC film, a polymer solution (hereinafter also referred to as a dope) in which TAC is dissolved in a mixed solvent containing dichloromethane or methyl acetate as a main solvent is prepared. The dope is cast on a metal support polished by a casting die to form a casting film. After the cast film becomes self-supporting, it is peeled off from the metal support and transported while being dried by a transporting means such as a tenter dryer or a roller.

When a dope is prepared using TAC as a polymer, since the solubility in a solvent is poor, it is difficult to prepare the dope. For example, when preparing a polymer having a polymer concentration of 20% by weight to 30% by weight, dissolution may not be sufficiently performed, and an undissolved product may remain even after stirring. Therefore, it is considered that a dope having a low polymer concentration (hereinafter referred to as low concentration dope or dilute dope) is prepared in advance, and then the dope is concentrated to a high concentration (hereinafter, this concentrated dope is highly concentrated). Called concentration dope). As such a method, many methods described below are known. The organic solvent is charged into a tilting mixer and transferred while cooling. The polymer is transferred into the organic solvent while being swollen. The polymer concentration of the mixture containing the swollen polymer is increased by separating the organic solvent in which the polymer is not swollen by an organic solvent separator having a mesh on the outlet side of the mixer (see, for example, Patent Document 1). A flash concentration method is also known. A polymer solution is ejected from above the flash drum using a feed nozzle, and a part of the solvent in the solution is volatilized to form a vaporized solvent. The vaporized solvent is discharged using an exhaust line. Further, the concentrated polymer solution is retained under the flash drum and extracted with a gear pump (for example, see Patent Document 2). Furthermore, a method is also known in which a crude concentration is dissolved at a polymer concentration lower than 20% by weight to 30% by weight by a flash concentration method and then concentrated to a polymer concentration of 20% by weight to 30% by weight by flash concentration (eg, patent References 3 and 4).
JP-A-11-323017 Japanese Patent Laid-Open No. 2001-40031 US Pat. No. 2541012 U.S. Pat. No. 4,414,341

  The method for concentrating a polymer solution disclosed in Patent Document 1 removes an organic solvent other than the mixture. Therefore, when the organic solvent dissolves the polymer to form a solution, the polymer solution is removed and the solution is lost. In addition, the step of swelling the polymer has a problem that the reproducibility is poor and it is difficult to keep the polymer composition ratio in the mixture constant.

  In the flash concentration disclosed in Patent Document 2, the wall surface of the flash tank is set to be equal to or higher than the boiling point temperature of the solvent. Therefore, when a polymer solution adheres to the wall surface, a solute polymer remains on the wall surface. In addition, a baffle plate (skirt) is attached around the feed nozzle to prevent the polymer solution from being scattered by the baffle plate when the polymer solution is ejected. When is volatilized, the polymer remains as a foreign substance at that location. When the foreign matter remaining on the wall surface or the baffle plate is contained in the concentrated polymer solution that stays when dropped, a film is formed using the dope.

  In the methods described in Patent Documents 3 and 4, a solute such as a polymer is mixed in a solvent recovered by concentration, and then when water is adjusted in a dehydration step using a distillation tower or the like, a polymer or the like is used in that step. There is also a problem that clogging occurs due to precipitation of the solute. Further, when a dope with a low polymer concentration is flashed, impurities (also referred to as skinning) due to non-uniformity of gel or dope polymer concentration may occur, and the quality of the dope may be impaired. Furthermore, the temperature of the dope may rise due to the rotation of the stirring blade for stirring the dope in the flash tank. At this time, the temperature of the dope becomes higher than the desired temperature, and the volatilization of the solvent proceeds, so that concentration may proceed excessively.

  An object of the present invention is to provide a method for preparing a dope in which a foreign substance such as a gel substance or a skin is not mixed in a concentrated dope. Another object of the present invention is to provide a method for preparing a dope that makes the polymer concentration of the dope uniform before and after concentration.

The dope preparation method of the present invention is a dope preparation method comprising a polymer and a solvent, wherein the polymer is dissolved in the solvent by heating using a heat exchanger, and the polymer concentration is 15 wt% or more and 20 wt% or less. A dope is prepared, the heating temperature is set to be equal to or higher than the boiling point of the solvent, and the diluted dope is stirred using a static mixing stirring means, and then the diluted dope is concentrated to have a polymer concentration of 20 wt% to 30 wt%. the following dope, when performing pre-Symbol heating, using a plurality of heating units including a static mixing and stirring means provided on the downstream side of the heat exchanger the heat exchanger, in a single heat exchanger The temperature of the diluted dope is set to 20 ° C. or higher and 70 ° C. or lower .

It is preferable to provide a thermometer downstream of the static mixing and stirring means, measure the temperature of the diluted dope using the thermometer, and adjust the temperature of the heat exchanger based on the measurement result. The flow rate of the diluted dope fed to the static mixing and stirring means is 30 L / min or more and 150 L / min or less, the diameter of the tube of the static mixing and stirring means is 50 mm or more and 200 mm or less, and the static mixing and stirring means It is preferable to set the number of baffle plates provided in 4 to 20 or less. It is preferable to use a spiral heat exchanger for the heat exchanger. Moreover, the manufacturing method of the polymer film of this invention is characterized by manufacturing a polymer film using the dope prepared by said dope preparation method . It is preferable that 60% by weight or more of the polymer film is formed from the dope.

According to a method for the preparation of the dope of the present invention, it is possible to obtain a high concentration dope it becomes possible to shorten the preparation time for de-loop. The dope can be preferably used in a solution casting method.

  Although the polymer used for this invention is not specifically limited, It is preferable to use a cellulose ester. Among cellulose esters, it is preferable to use cellulose acylate, and it is particularly preferable to use cellulose acetate. Furthermore, in cellulose acetate, it is preferable to use TAC having an average degree of acetylation of 57.5% to 62.5%. The degree of acetylation means the amount of bound acetic acid in cellulose acetate. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).

The cellulose acylate used in the present invention is preferably a cellulose acylate in which the degree of substitution of the cellulose with a hydroxyl group satisfies all of the following formulas (I) to (III).
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9
However, A and B represent the substituent of the acyl group substituted by the hydroxyl group of a cellulose, A is a substitution degree of an acetyl group, or B is a substitution degree of a C3-C22 acyl group. .

  In the present invention, cellulose acylate particles are used, and 90% by weight or more of the particles used have a particle diameter of 0.1 mm to 4 mm, preferably 1 mm to 4 mm. Also, preferably 95% by weight or more, more preferably 97% by weight or more, still more preferably 98% by weight or more, and most preferably 99% by weight or more of particles have a particle size of 0.1 mm to 4 mm. Furthermore, it is preferable that 50% by weight or more of the particles used have a particle diameter of 2 mm to 3 mm. More preferably 70% by weight or more, still more preferably 80% by weight or more, and most preferably 90% by weight or more of the particles have a particle size of 2 mm to 3 mm. The particle shape of the cellulose acylate is preferably as close to a sphere as possible.

  Examples of the solvent used in the present invention include aromatic hydrocarbons, halogenated hydrocarbons, esters, alcohols, ketones, and ethers, but are not particularly limited. A solvent will not be specifically limited if it is the purity of a commercial item. The solvent may be used alone (100% by weight) or a mixture of halogenated hydrocarbons, esters, alcohols, ketones, ethers, and the like. Specifically, aromatic hydrocarbons (for example, benzene, toluene, etc.), halogenated hydrocarbons (for example, dichloromethane, etc.), esters (methyl acetate, methyl formate, ethyl acetate (ethyl acetate), amyl acetate) , Butyl acetate, etc.), alcohols (eg, methanol, ethanol, n-butanol, etc.), ketones (eg, acetone, methyl ethyl ketone, cyclohexanone, etc.), ethers (eg, dioxane, dioxolane, tetrahydrofuran, diethyl ether, methyl- t-butyl ether, methyl cellosolve, etc.). In addition, when using a mixed solvent for a solvent, it is preferable to use dichloromethane and methyl acetate as a main solvent.

  A halogenated hydrocarbon having 1 to 7 carbon atoms is preferably used, and dichloromethane is most preferably used. From the viewpoint of physical properties such as optical properties such as solubility of TAC, peelability from the support, mechanical strength of the film, etc., it is preferable to mix one to several alcohols having 1 to 5 carbon atoms in addition to dichloromethane. . The content of the alcohol is preferably 2% by weight to 25% by weight and more preferably 5% by weight to 20% by weight with respect to the whole solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  Recently, a solvent composition not using dichloromethane has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 4 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are used by being appropriately mixed. These ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  Additives added to the dope include plasticizers, UV inhibitors, matting agents (eg, silicon dioxide, zirconium oxide, etc.), fluorine-based interfacial agents, release accelerators (eg, amino acids, carboxylic acids, etc.), and deterioration prevention. Agents (eg, amines, aromatic base compounds, etc.), retardation control agents (eg, aromatic compounds containing an aromatic hydrocarbon ring or aromatic heterocycle), oil gelling agents, etc. It is not limited. The additive may be added when the polymer is dissolved in the solvent, or may be added after the polymer is dissolved in the solvent. Furthermore, a solution in which an additive is dissolved in a solvent may be added to the solvent, the dope, etc. In this case, it may be added batchwise or continuously in-line.

  Examples of the plasticizer include phosphoric acid esters (for example, triphenyl phosphate (hereinafter referred to as TPP), tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate (hereinafter referred to as BDP), trioctyl. Phosphate, tributyl phosphate, etc.), phthalate esters (eg, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, etc.), glycolate esters (eg, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl) Ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc.) and other plasticizers can be used.

  Details of cellulose acylate are described in Japanese Patent Application No. 2003-319673, [0141] to [0192]. These descriptions are also applicable to the present invention. Further, as a solvent for cellulose acylate and other additives, plasticizers, deterioration inhibitors, optical anisotropy control agents, dyes, matting agents, release agents, etc. are also disclosed in Japanese Patent Application No. 2003-319673 [0193]. To [0531].

  The ultraviolet absorber preferably used for the cellulose acylate film of the present invention will be described. The cellulose acylate film of the present invention is used for a polarizing plate or a liquid crystal display member because of its high dimensional stability, but an ultraviolet absorber is preferably used from the viewpoint of preventing deterioration of the polarizing plate or the liquid crystal. As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specific examples of ultraviolet absorbers preferably used in the present invention include, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and other ultraviolet absorbers. Can be used. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds.

  Although the specific example as a benzotriazole type ultraviolet absorber is listed below, this invention is not limited to these. 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3) '-Tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy -3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethyl) Butyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)- -Chlorobenzotriazole, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoyl) Phenylmethane), (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2 (2'-hydroxy- 3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2'-hydroxy-3', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole, 2, 6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl -4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3 5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4 -Hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydride) Cinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4) -Hydroxybenzyl) -isocyanurate and the like. In particular, (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2 (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole, 2,6-di -Tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl -5-methyl-4-hydroxyphenyl) propionate], for example, N, N'-bis [3- (3,5-di-tert-butyl-4-hydroxy) Roxyphenyl) propionyl] hydrazine and other hydrazine-based metal deactivators and phosphorus-based processing stabilizers such as tris (2,4-di-tert-butylphenyl) phosphite may be used in combination. The amount is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to cellulose acylate.

Moreover, the ultraviolet absorber described in JP-A-6-148430 can also be preferably used. The ultraviolet absorber described above preferably used in the present invention has high transparency, is excellent in the effect of preventing the deterioration of the polarizing plate and the liquid crystal element, and is particularly preferably a benzotriazole-based ultraviolet absorber with less unnecessary coloring. The amount of the UV absorber used is not uniform depending on the type of compound and the use conditions, but is usually preferably 0.2 to 5.0 g, more preferably 0.4 to 1.5 g per 1 m ^{2 of the} cellulose acylate film. Preferably, 0.6g-1.0g is especially preferable.

In addition, the light stabilizers listed in the catalog “Adeka Stub”, an outline of additives for Asahi Denka Plastics, can also be used. Light stabilizers and UV absorbers from Ciba Special Chemicals' Tinuvin Product Guide can also be used. SEESORB, SEENOX, SEETEC, etc. can also be used in the catalog of SHIPRO KASEI KAIYA. Jouhoku Chemical's UV absorbers and antioxidants can also be used. UV absorbers from Kyosho's VIOSORB and Yoshitomi Pharmaceutical can also be used.

  Regarding the spectral transmittance in the ultraviolet region, Japanese Patent Application Laid-Open No. 2003-043259 discloses a 390 nm necessary for obtaining an optical film, a polarizing plate and a display device excellent in color reproducibility and durability in ultraviolet irradiation. An optical film having a spectral transmittance of 50% to 95% at 350 nm and a spectral transmittance of 350% at 350 nm is described.

  A polymer, a solvent, and a desired additive are put into a mixing tank 11 of a dope preparation line 10 shown in FIG. The mixing tank 11 includes a stirring blade 13 that is rotated by a motor 12. By rotating the stirring blade 13, the polymer, the solvent and the additive are mixed to form a mixed solution 14. The polymer concentration of the mixed solution 14 is preferably 15% by weight or more and 20% by weight or less. If it is less than 15% by weight, it may not be concentrated to the polymer concentration of the dope that is preferably used in the solution casting method even if the subsequent concentration is performed. In addition, the preparation of a low concentration dope exceeding 20% by weight has a low solubility in a solvent of a polymer (particularly, TAC), and therefore it takes a long time to prepare and may cause a high cost.

  The liquid mixture 14 is fed to the heater 20 and heated while adjusting the liquid feed flow rate by the pump 15. It is preferable to use a heat exchanger for the heater 20. The heat exchanger is not particularly limited. For example, a multi-tube cylindrical heat exchanger, a plate heat exchanger, a spiral heat exchanger, or a static mixing stirrer with a double-tube structure can be used. It is preferable to use a heat exchanger.

  The mixed solution 14 is heated and dissolved by the heater 20 to obtain a low concentration dope. Thereafter, it is preferable to feed the mixture to a static mixing stirrer and mix them in order to make the composition of the low concentration dope more uniform. A static mixer 21 is usually used for the static mixing stirrer. The temperature of the low-concentration dope delivered from the static mixer 21 is measured using a thermometer 22. The temperature of the low-concentration dope measured by the thermometer 22 is transmitted to the controller 23. The controller 23 determines whether or not the temperature of the low concentration dope is a desired temperature. If it is not the desired temperature, a signal for changing the heating condition of the heater 20 is transmitted to the heater 20. The heater 20 changes the heating condition based on the signal. For example, when a heat exchanger is used for the heater 20, the temperature and flow rate of the heat transfer medium are adjusted. Note that the heating temperature of the low-concentration dope is not less than the boiling point of the solvent.

  The form of the static mixer 21 is not particularly limited. The flow rate of the low concentration dope is preferably 30 L / min or more and 150 L / min or less, more preferably 50 L / min or more and 80 L / min or less. The inner diameter D1 (mm) of the pipe of the static mixer 21 is preferably 50 mm or more and 200 mm or less, more preferably 80 mm or more and 130 mm or less. The number of blades (baffle plates) 21a is preferably 4 or more and 20 or less, and more preferably 4 or more and 18 or less.

  It is preferable to send the low-concentration dope to the filtration device 24 to remove foreign matters in the low-concentration dope because foreign matters are prevented from being mixed into the high-concentration dope obtained at the time of subsequent concentration. . In the present invention, the low-concentration dope is sufficiently mixed and stirred by the static mixer 21 after being melted by heating, so that the content of insoluble matter and gel-like substance is extremely suppressed. Therefore, even if low concentration dope is filtered by the filtering device 24, the filtration load is reduced. However, even if the filtering device 24 is arranged on the upstream side of the heater 20, there is an effect of removing foreign matters such as insoluble matters and gel-like substances. As a result, the variation in the polymer concentration of the low-concentration dope can be within ± 1% by weight.

  The low concentration dope is passed through the pressure regulating valve 25 and the pressure is measured by the pressure gauge 26. The pressure value is transmitted to the controller 23. The controller 23 determines whether or not the pressure value has reached a pressure necessary for flash concentration. The pressure for flash concentration will be described later. When the pressure value is not a desired value, a signal for performing opening / closing control of the pressure regulating valve 25 is transmitted. The pressure regulating valve 25 opens and closes the valve based on the signal.

  As shown in FIG. 2, the low-concentration dope 16 adjusted to a desired temperature and pressure is ejected from the flash pipe 27 into the flash tank 30 (hereinafter, used in the same meaning as flash). At the time of jetting, a part of the solvent is evaporated from the low concentration dope 16 and stored in the flash tank 30 as a concentrated dope (hereinafter referred to as high concentration dope). Thereby, the high concentration dope 17 having a polymer concentration of 20 wt% or more and 30 wt% or less is obtained. This concentration method will be described in detail later.

  The high concentration dope 17 is extracted from the flash tank 30 by the pump 50. Thereafter, the temperature of the high concentration dope 17 is adjusted by the temperature controller 51. The temperature controller 51 is preferably a heat exchanger, and most preferably a spiral heat exchanger. The heat transfer medium is not particularly limited, but it is preferable to use hot water from the viewpoint of cost. The temperature of the hot water is appropriately adjusted depending on the preparation solvent for the high concentration dope 17. For example, when using a dichloromethane-based mixed solvent, it is preferable to set the temperature range from 30 ° C to 40 ° C. Moreover, when using a methyl acetate type mixed solvent, it is preferable to set it as the range of 20 to 50 degreeC.

  The high concentration dope 17 is fed from the temperature controller 51 to the static mixer 52. The high-concentration dope 17 is mixed and stirred by the static mixer 52 to be uniform. Thereafter, foreign matter, insoluble matter, and gel-like substance are removed by the filtering device 53. Also in this case, the high concentration dope 17 is sufficiently mixed by the static mixer 52. Impurities in the high-concentration dope 17, especially gel-like substances, are extremely small, and the filtration load of the filtration device 53 is reduced. Further, the high-concentration dope 17 from which foreign matters such as skinning, undissolved materials, insoluble materials, etc. are sufficiently removed can be preferably used as a dope for film formation.

  By performing the above-described method using a low-concentration dope having a polymer concentration, the polymer concentration variation of the high-concentration dope 17 is adjusted within ± 1% by weight. The filter medium (filter) used for the filtration device 53 is not particularly limited. However, when the high-concentration dope 17 produced by the dope preparation method according to the present invention is used for film formation, a filter having a nominal diameter of 3 μm or more and 100 μm or less is used in order to remove minute foreign matters. Is preferred.

  The high concentration dope 17 stays in the flash tank 30 shown in FIG. The stirring blade 32 is connected to a motor 34 via a shaft 33. The high concentration dope 17 is stirred by rotating the stirring blade 32. A jacket 35 is attached to the flash tank 30 and a heat transfer medium 36 is fed between them. A flash pipe 27 is provided above the flash tank 30. The capacitor 37 is attached via a pipe 38.

The height of the uppermost part (hereinafter referred to as the uppermost part of the stirring blade) 32a of the stirring blade 32 and the liquid surface 17a of the high concentration dope 17 is L1 (mm). The height of the liquid surface 17a and the tip part (hereinafter referred to as the flash pipe tip) 27a which is the discharge port of the flash pipe is defined as L2 (mm). The height of the liquid surface 17a and the tip portion (hereinafter referred to as the pipe tip) 38a which is the suction port of the pipe 38 is L3 (mm). The volume V (m ³ ) of the flash tank 30 is not particularly limited, but a specific example is given. Volume V (m ³⁾ is in the range of 3.0m ³ ~10.0m ^3, the height H of the flash tank 30 (mm) is in the range of 1000Mm～4000mm, the diameter of the flash tank D2 (mm) is 1000Mm～ A range of 3000 mm is preferable. Further, the height L1 (mm) during steady operation is preferably within 800 mm, more preferably within 500 mm, and most preferably within 300 mm. The height L2 (mm) during steady operation is preferably in the range of 100 mm to 1000 mm, and the height L3 (mm) during steady operation is preferably in the range of 200 mm to 1000 mm. Further, the ratio between the volume (hereinafter referred to as the liquid phase volume) Vl (m ³ ) in which the high concentration dope 17 is placed and the volume of the gas phase space 39 (hereinafter referred to as the gas phase volume) Vg (m ³ ). Vl: Vg = 4: 6 to 9: 1 is preferable.

  It is preferable to use hot water for the heat transfer medium 36. The temperature of the heat transfer medium 36 differs depending on the dope solvent. For example, when a dichloromethane-based mixed solvent is used, it is preferably in the range of 30 ° C. to 40 ° C., and when a methyl acetate-based mixed solvent is used, it is preferably in the range of 20 ° C. to 50 ° C. Further, the shape of the flash pipe 27 is not limited to the illustrated form. For example, it is possible to use a tapered shape, an enlarged shape, or a nozzle whose tip is cut obliquely.

The low concentration dope 16 is ejected from the flash pipe 27. In this case, the pressure P (MPa) of the low-concentration dope 16 is set to 2.0 MPa> P (MPa) ≧ {P0 + (T−40) × A} MPa (1)
It is preferable to set it as the range. P0 (MPa) is a theoretical value of the vapor pressure calculated from the maximum temperature T (° C.) of the low-concentration dope 16 in the heating part. The temperature of the heater 20 (see FIG. 1) is adjusted so that the maximum temperature T (° C.) is in the range of 60 ° C. to 120 ° C. A (MPa / ° C.) is a constant determined according to the type of solvent, and is 0.01 (MPa / ° C.) for a dichloromethane-based mixed solvent, and 0 (MPa / ° C.) for a methyl acetate-based mixed solvent. 008 (MPa / ° C.).

  When the low-concentration dope 16 is ejected toward the high-concentration dope 17, a part of the solvent in the low-concentration dope 16 volatilizes to become a vaporized solvent and exists in the gas phase space 39. The vaporized solvent is sent to the condenser 37 through the pipe 38. The condenser 37 is cooled, and the vaporized solvent is condensed and recovered as a liquid. Use of this recovered solvent as a solvent for preparing the low-concentration dope 16 is advantageous in terms of cost. Although the cooling temperature of the capacitor | condenser 37 is not specifically limited, When using a dichloromethane type mixed solvent, it is preferable to set it as the range of 0 degreeC-30 degreeC. Moreover, when using a methyl acetate type mixed solvent, it is preferable to set it as the range of 0 degreeC-50 degreeC. At this time, the pressure in the flash tank 30 is preferably adjusted to atmospheric pressure ± 0.01 MPa in order to perform uniform concentration.

  The high-concentration dope 17 is kept warm by the heat transfer medium 36 and is kept in gas-liquid equilibrium by stirring with the stirring blade 32. Since the vaporized solvent in the gas phase space 39 is in vapor-liquid equilibrium with the solvent of the high concentration dope 17, a part of the vaporized solvent is liquefied, but the other part is condensed by the condenser 37 through the pipe 38. Liquefaction. In order to keep the high-concentration dope 17 in a steady state, it is preferable to adjust the temperature while stirring with the stirring blade 32. In addition, the rotational speed of the stirring blade 32 is not particularly limited, but is preferably in the range of 2.5 rpm to 25 rpm.

  The shape of the agitating blade 32 is not particularly limited, but it is an irrigation type, a bull margin type, a turbine type, a spiral band type, a spiral shaft type, a propeller type, a paddle type, an inclined paddle type, a curved paddle type, and a max. Blends (registered trademark; manufactured by Sumitomo Heavy Industries, Ltd.) can be used.

  Another embodiment of the dope preparation method according to the present invention will be described with reference to FIG. In addition, about the same location as the dope preparation line 10 of FIG. 1, the same code | symbol is attached | subjected and description is abbreviate | omitted. The liquid mixture 14 is sent to the heater 60 by the pump 15 and heated. Thereafter, the liquid is fed to the static mixer 61 to obtain a mixed liquid (hereinafter referred to as an intermediate liquid). The temperature of the intermediate liquid sent out from the static mixer 61 is measured with a thermometer 62. The temperature measured by the thermometer 62 is transmitted to the controller 63. The controller 63 determines whether or not the temperature is a desired temperature. If the temperature is not the desired temperature, the controller 63 transmits a signal to the heater 60 to adjust the heating conditions.

  The intermediate liquid is sent to the second heater 64. The intermediate liquid is further heated by the heater 64 and the dissolution proceeds sufficiently. Thereafter, the liquid is fed to the static mixer 65. It is fed out after being mixed by the static mixer 65 and made into a low concentration dope sufficiently dissolved. The temperature of the low concentration dope is measured with a thermometer 66. The measured temperature is transmitted to the controller 63. The controller 63 determines whether or not the temperature is appropriate. When the temperature is inappropriate, a signal is transmitted to the heater 64 to adjust the heating condition of the heater 64. In addition, it is preferable to use a heat exchanger for the heaters 60 and 64, and it is more preferable to use a spiral heat exchanger. Thus, when preparing a low-concentration dope from a mixed solution, a low-concentration dope in which dissolution is in progress even if the maximum heating temperature is lowered by 5 ° C to 10 ° C is obtained by preparing a semi-dissolved intermediate solution once. be able to. Therefore, modification of the solute component (particularly polymer) due to heating can be suppressed.

  The form of the static mixers 61 and 65 is not particularly limited. The flow rate of the low concentration dope is preferably 30 L / min or more and 150 L / min or less, more preferably 50 L / min or more and 80 L / min or less. The inner diameter of the pipes of the static mixers 61 and 65 is preferably 50 mm or more and 200 mm or less, and more preferably 80 mm or more and 130 mm or less. The number of blades (baffle plates) 21a is preferably 4 or more and 20 or less, and more preferably 4 or more and 18 or less.

  The low concentration dope is sent to the filtering device 67. Since this low-concentration dope has passed through a unit composed of a heater and a static mixer (a heater 60 and a static mixer 61 and a heater 64 and a static mixer 65) twice, undissolved substances, gel substances, etc. Inclusion is extremely suppressed. Therefore, even if the insoluble matter in the low-concentration dope 16 is filtered by the filtering device 67, the filtering load on the filtering device 67 can be reduced.

After the low concentration dope passes through the pressure adjustment valve 68, the pressure is measured by the pressure gauge 69. The pressure value is transmitted to the controller 63. The controller 63 has the formula (1) in which the pressure P (MPa) of the low concentration dope is explained above.
2.0 MPa> P (MPa) ≧ {P0 + (T−40) × A} MPa (1)
If it is not appropriate, a signal is transmitted to the pressure regulating valve 68 to control the opening and closing of the pressure regulating valve 68 so as to adjust to a desired pressure range. Thereafter, the low-concentration dope is ejected from the flash pipe 27 into the flash tank 30 and concentrated. Thereafter, the concentrated high-concentration dope 70 is extracted from the flash tank 30 using the pump 50 and the same operation as that of the dope preparation line 10 of FIG. 1 is performed.

  When the temperature of the low-concentration dope is raised, if it is suddenly raised, temperature adjustment may be difficult. In that case, it is preferable to raise the temperature sequentially using a plurality of heaters (preferably heat exchangers) as shown in FIG. Also in this case, it is preferable to attach a static mixer to the secondary side of each heater (heat exchanger) and use it as a heating / mixing unit. It is preferable that the temperature elevation temperature in each unit is in a temperature range of 20 ° C. to 70 ° C. per unit. If the temperature is lower than 20 ° C., a large number of units are required to bring the low-concentration dope to a desired temperature, which is disadvantageous in terms of cost. In addition, the liquid feeding time is inevitably long, and heating at a low temperature may occur, but there may be a case where solute, particularly polymer modification, cannot be ignored due to aging. Moreover, when it exceeds 70 degreeC, the difficulty in temperature adjustment may arise and the advantage using many units is lost.

  As shown in FIG. 4, the film forming apparatus 80 includes a band zone 81 and a drying zone 82. A high concentration dope tank (hereinafter referred to as a tank) 83 is connected to the film-forming apparatus 80 via a pump 84 and a filtration device 85. The tank 83 is provided with a stirring blade 86. The stirring blade 86 is made uniform by rotating by the motor 87 and stirring the high concentration dope 17.

  The band zone 81 is provided with a casting belt 92 stretched around the support drums 90 and 91, and travels endlessly as the support drums 90 and 91 are rotated by a driving device (not shown). A casting die 93 is provided on the casting belt 92. The moving speed of the casting belt 92, that is, the casting speed is preferably 10 m / min to 200 m / min. In order to set the surface temperature of the casting belt 92 to a desired temperature, it is preferable that a heat transfer medium circulation device (not shown) is attached to the support drums 90 and 91. And what used the heat-transfer-medium flow path in the support drums 90 and 91 is used. The temperature of the support drums 90 and 91 is maintained at a predetermined temperature by passing through the heat transfer medium maintained at the predetermined temperature. Thereby, the surface temperature of the casting belt 92 is adjusted to a predetermined temperature. The surface temperature of the casting belt 92 is preferably −20 ° C. to 40 °.

  The casting die 93, the casting belt 92, and the like are preferably housed in the casting chamber. Temperature control equipment is attached to keep the temperature in the casting chamber at a predetermined value. The temperature of the casting chamber is preferably −10 ° C. to 57 ° C. Moreover, it is preferable to provide a condenser (condenser) for condensing and recovering the volatile organic solvent. The condensed and liquefied organic solvent is preferably reused as a dope preparation solvent after being recovered and regenerated by a recovery device.

  The high-concentration dope 17 is sent from the tank 83 by the pump 84, and after the foreign matter is removed by the filtration device 85, it is sent to the casting die 93. The high concentration dope 17 is cast on the casting belt 92 from the casting die 93. The casting width when casting is preferably 1000 mm or more, more preferably 1400 mm or more. At this time, a casting film 94 is formed by casting on the casting belt 92 while forming a casting bead. In addition, it is preferable that the temperature of dope for casting is -10 degreeC-57 degreeC. In order to stabilize the formation of the casting bead, the decompression chamber is preferably attached to the rear surface of the casting bead and adjusted to a desired pressure. The casting film 94 moves as the casting belt 92 travels. At this time, in order to volatilize the organic solvent in the casting film 94, it is preferable to provide a blower and blow dry air. The attachment position of the blower is preferably provided at the upper upstream side, the downstream side, and the lower part of the casting belt 92, but is not limited thereto. In addition, it is preferable that a wind shield device is provided in order to suppress the surface variation of the film surface caused by blowing dry air onto the cast film 94 immediately after formation. The casting belt 92 that is an endless belt is preferably made of stainless steel, copper or the like. Instead of the casting belt 92, a casting drum (rotating drum) can be used as a support. The casting drum is preferably made of stainless steel or steel and subjected to hard chrome plating. In this case, the surface temperature of the casting drum is preferably -20 ° C to 40 ° C.

  After the casting film 94 has a self-supporting property, it is peeled off from the casting belt 92 as a film 96 while being supported by the peeling roller 45. Thereafter, the transfer section provided with a large number of rollers 97 is conveyed and then fed into the tenter 98. In the crossing part, the drying of the film 96 is advanced by blowing dry air at a desired temperature from a blower (not shown). The drying air temperature is preferably 20 ° C to 250 ° C. It is also possible to impart a draw to the film 96 by making the rotational speed of the downstream roller faster than that of the upstream roller at the transition portion. The film 96 in the tenter 98 is dried while its both edges are held by clips and conveyed. While holding both edges of the film 96 with the tenter 98, drying can be performed and tension can be applied in the casting width direction. When the film 96 is stretched by applying tension in at least one of the casting width direction and the conveyance direction, it is possible to correct creases generated on the surface of the film 96. The contact surface of the roller 96 with the film 96 is not limited to one side as shown in the figure.

  Both edges of the film 96 are cut by an unillustrated ear clip device. Both the cut edges are sent to a crusher by a cutter blower. Both edges of the film are crushed by a crusher into chips. It is advantageous in terms of cost to reuse this chip for dope preparation. In addition, although the process of cut | disconnecting the both edges of this film can also be abbreviate | omitted, it is preferable to carry out in either from the said casting process to the process of winding up a film.

  The film 96 is sent to a drying zone 82 where a number of rollers 99 are provided. Although the temperature of the drying zone 82 is not specifically limited, It is preferable that it is the range of 80 to 160 degreeC. The method for transporting the film 96 to the drying zone 82 may be performed by either transport by the roller 97 or transport by the tenter 98. However, it is more preferable to use both in combination as shown in FIG. 4 because the direction in which the tension is applied can be selected. In the drying zone 82, the film 96 is conveyed while being wound around a roller 99, and the organic solvent is volatilized and dried. It is preferable that an adsorption recovery device is attached to the drying zone 82. The volatile solvent is adsorbed and recovered by an adsorption recovery device. The air from which the solvent component has been removed is blown into the drying zone 82 again as dry air. The drying zone 82 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, providing a predrying chamber (not shown) between the ear opener and the drying zone 82 to preliminarily dry the film 96 can suppress changes in the shape of the film due to a sharp rise in film temperature. preferable.

  The film 96 is conveyed to a cooling chamber (not shown) and cooled to approximately room temperature. A humidity control chamber may be provided between the drying zone 82 and the cooling chamber. Air adjusted to a desired humidity and temperature is blown onto the film 96 in a humidity control chamber. Thereby, generation | occurrence | production of the winding defect at the time of winding up the film 96 can be suppressed.

  It is preferable to provide a forced charge removal device (charge removal bar) so that the charged voltage while the film 96 is being conveyed falls within a predetermined range (for example, −3 kV to +3 kV). Furthermore, it is preferable to provide a knurling roller and to impart knurling to both edges of the film 96 by embossing. In addition, it is preferable that the unevenness | corrugation of the knurled location is 1 micrometer-200 micrometers.

  Finally, the film 96 is wound up by the winder 100. At this time, it is preferable to wind the sheet while applying a desired tension with a press roller. More preferably, the tension is gradually changed from the start to the end of winding. The film 96 to be wound is preferably at least 100 m or more in the longitudinal direction (casting direction). The width direction is preferably 600 mm or more, and more preferably 1400 mm or more and 1800 mm or less. Also, it is effective when it is larger than 1800 mm. The thickness of the film can be applied when producing a thin film having a thickness of 15 μm or more and 100 μm or less.

  Since the film 96 is formed using a very uniform dope, it is preferably used for a polarizing plate protective film, an optical compensation film, or a film base of a photographic photosensitive material used for a liquid crystal display device or the like. In addition, the present invention is effective when the width of the film to be formed is 1000 mm or more and 1800 mm or less, and is also effective when it exceeds 1800 mm. In addition, it becomes possible to obtain a film having excellent optical characteristics by forming a film using 60% by weight or more of the high-concentration dope prepared by the dope preparation method according to the present invention.

  The film casting apparatus 80 shown in FIG. 4 uses a casting die 93 for single layer casting. However, the film production method is not limited to single layer casting. A co-casting method using a multi-manifold casting die or a feed block attached to the upstream side of the casting die, a plurality of casting dies (may be a co-casting die) are arranged on the support, A sequential casting method that sequentially casts the dope is also applicable. In addition, it is preferable to use at least one dope obtained by the dope preparation method according to the present invention for multi-layer casting such as co-casting and sequential casting. Most preferably, a high-concentration dope obtained by the dope preparation method according to the present invention is used for all the dopes used for multilayer casting.

  The film composed of multiple layers by co-casting preferably has a layer thickness on the air side and / or a layer on the support side of 0.5% to 30% of the total film thickness. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope is cast from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, when casting dope from a die slit to a support body, it is preferable that internal dope is enveloped by dope with a larger composition ratio of alcohol than the dope.

  Solvent recovery method from structure of casting die, vacuum chamber, support, etc. in casting, co-casting, peeling method, stretching, drying conditions of each process, handling method, curling, winding method after flatness correction The film collection method is described in detail from [0610] to [0842] of Japanese Patent Application No. 2003-319673, and these descriptions can also be applied to the present invention.

[Performance / Measurement method]
The performance of the cellulose acylate film wound up and the measuring method thereof are described in detail from [0114] to [0140] of Japanese Patent Application No. 2003-319673, and these descriptions can also be applied to the present invention.

[surface treatment]
It is preferable that at least one surface of the cellulose acylate film is surface-treated. The surface treatment is preferably at least one of vacuum glow discharge treatment, atmospheric pressure plasma discharge treatment, ultraviolet irradiation treatment, corona discharge treatment, flame treatment, acid treatment or alkali treatment.

[Functional layer]
At least one surface of the cellulose acylate film may be undercoated. Furthermore, it is preferable to use the cellulose acylate film as a base film as a functional material provided with another functional layer. The functional layer is preferably provided with at least one layer selected from an antistatic layer, a cured resin layer, an antireflection layer, an easy adhesion layer, an antiglare layer and an optical compensation layer.

The functional layers preferably contain at least one surfactant 0.1mg / m ² ~1000mg / m ² containing. Further, the functional layers preferably contain at least one sort of plasticizers in the 0.1mg / m ² ~1000mg / m ² containing. Further, the functional layers preferably contain at least one sort of matting agents in the 0.1mg / m ² ~1000mg / m ² containing. Further, the functional layers preferably contain at least one sort of antistatic agents 1mg / m ² ~1000mg / m ² containing. In addition to the above, the method for applying a surface treatment functional layer for realizing various functions and properties on the cellulose acylate film is described in detail in [0843] to [1079] of Japanese Patent Application No. 2003-319673, The method is also described. These are also applicable to the present invention.

  The cellulose acylate film is particularly useful as a polarizing plate protective film. Two polarizing plates to which a cellulose acylate film is bonded are usually bonded to a liquid crystal layer to produce a liquid crystal display device. However, this arrangement may be at any position. Japanese Patent Application No. 2003-319673 describes in detail TN type, STN type, VA type, OCB type, reflection type, and other examples of liquid crystal display devices. This method can also be applied to the present invention. The application also describes a cellulose acylate film provided with an optically anisotropic layer and a cellulose acylate film provided with antireflection and antiglare functions. Furthermore, the use as an optical compensation film is also described as a biaxial cellulose acylate film imparting moderate optical performance. This can also be used as a polarizing plate protective film. These restrictions can also be applied to the present invention. Details are described in [1080] to [1252] of Japanese Patent Application No. 2003-319673.

  The dope preparation method of the present invention was performed as Example 1 using a dichloromethane-based mixed solvent as a solvent. The dope preparation line 10 shown in FIG. 1 was used for preparation of the high concentration dope. As the solvent, dichloromethane and mixed alcohol (mixing ratio methyl alcohol: butyl alcohol (1-butanol) = 95: 5, where the composition ratio is weight ratio) were mixed at a ratio of 83:17 (weight ratio). Further, TAC having an acetylation degree of 61.0% was used. As the plasticizer, a mixture of TPP and BDP at a weight ratio of 2: 1 was used. The polymer tank of the low concentration dope was placed in the mixing tank 11 so as to be 19.0% by weight. The mixed liquid 14 was obtained by rotating the motor 12 with a stirrer power of 45 kW at a rotation speed of 80 rpm for 50 minutes. As the heater 20, a spiral heat exchanger (manufactured by Croce Co., Ltd.) was used. The static mixer 21 used had an inner diameter D1 of 100 mm and 18 blades 21a. Steam was used as the heat transfer medium of the spiral heat exchanger 20.

  The pump 15 sent the mixed liquid 14 at a flow rate of 70 L / min to the spiral heat exchanger 20 and the static mixer 21 to obtain a low concentration dope. The temperature of the low-concentration dope was measured with the thermometer 22, and the supply conditions of the heat transfer medium of the spiral heat exchanger 20 were adjusted so that the temperature range was 88 ° C to 92 ° C. The pressure of the low concentration dope was measured with the pressure gauge 26, and the result was transmitted to the controller 23 to control the opening / closing of the pressure adjusting valve 25. The maximum temperature T reached when the low-concentration dope was heated was 91 ° C. The pressure P at this time was adjusted to be 1.3 MPa ± 0.2 MPa. The low concentration dope 16 was ejected from the flash pipe 27 into the flash tank 30.

Between the flash tank 30 and the jacket 35, 35 degreeC warm water was supplied as the heat-transfer medium 36 (refer FIG. 2). The volume V of the flash tank 30 was 7 m ³ , and the residence amount of the high-concentration dope 17 was adjusted so that the ratio of the liquid phase volume Vl to the gas phase volume Vg was 4: 1. The stirring blade 32 was an inclined paddle type, and was rotated at a rotation speed of 15 rpm. The height L1 between the stirring blade uppermost portion 32a and the liquid level 17a is in the range of 200 mm ± 200 mm, the height L2 between the flash pipe tip 27a and the liquid level 17a is in the range of 500 mm ± 200 mm, and the pipe tip 38a And the liquid surface 17a have a height L3 in the range of 600 mm ± 200 mm. Further, the cooling temperature of the capacitor 37 was set to 7 ° C. ± 5 ° C.

  A part of the solvent of the low-concentration dope 16 became a vaporized solvent, condensed and liquefied by the capacitor 37, and recovered as a solvent. This recovered solvent was reused as a solvent for preparing the low concentration dope 16. The high-concentration dope 17 prepared from the low-concentration dope 16 was 23% by weight when its polymer concentration was measured by an absolutely dry method. The high-concentration dope 17 was extracted at a flow rate of 50 L / min using the pump 50.

  A spiral heat exchanger was used as the temperature controller 51. Hot water was used as the heat transfer medium, and the temperature was adjusted to 35 ° C. The static mixer 52 used had an inner diameter of 100 mm and six blades. Further, a sintered metal was used for the filter medium of the filter device 53, and a nominal diameter of 10 μm was used.

  After the high-concentration dope 17 was fed to the spiral heat exchanger, the static mixer 52 and the filtration device 53, it was used as a dope for film formation. The film was formed using the film forming apparatus 80 shown in FIG. The high concentration dope 17 was put in the tank 83 and the stirring blade 86 was rotated to maintain a uniform state.

  The high concentration dope 17 was fed to the casting die 93 using the pump 84. The film was cast on the casting belt 92 from the casting die 93 so that the film thickness of the dried film was 80 μm. The casting width was 2000 mm. The temperature of the casting belt 92 was adjusted with a temperature controller (not shown) so as to be about 25 ° C. A casting film 94 was formed on the casting belt 92, and after the casting film 94 had self-supporting properties, it was peeled off as a film 96 while being supported by a peeling roller 95. By adjusting the speed of the roller 97, the film 96 was stretched by 10% in the transport direction. Thereafter, the film 96 was conveyed into a tenter dryer 98 maintained at 140 ° C. The film 96 was allowed to dry by passing through the tenter dryer 98 for 0.5 minutes. At this time, 20% stretching was applied in the casting width direction of the film 96. Then, the film 96 was conveyed to the drying zone 82 adjusted to a temperature range of 120 ° C to 145 ° C. The film 96 was conveyed for 10 minutes while being wound around a roller 99, and then wound up by a winder.

  The film 96 was measured for in-plane retardation (Re) and thickness direction retardation (Rth) at a wavelength of 632.8 nm using an ellipsometer (an ellipsometer). Film could be obtained.

  Example 2 will be described. The description of the same experimental conditions as in Example 1 is omitted. The high concentration dope was prepared using the dope preparation line shown in FIG. The polymer concentration of the low concentration dope was adjusted to 19.0% by weight from TAC, a mixed solvent, and a plasticizer. The low concentration dope was placed in the mixing tank 11 and stirred to obtain a mixed solution 14. The liquid feed flow rate of the mixed liquid 14 was fed by the pump 15 to the spiral heat exchanger as the heater 60 and the static mixer 61. Hereinafter, this mixed solution is referred to as an intermediate solution. The temperature of the intermediate liquid was measured with the thermometer 62, and the supply conditions of the heat transfer medium of the spiral heat exchanger were adjusted so that the temperature range was 48 ° C to 50 ° C.

  The intermediate solution was then sent to a spiral heat exchanger as a heater 64 and to a static mixer 65 to obtain a low concentration dope. The temperature of the low concentration dope was measured with the thermometer 66, and the supply conditions of the heat transfer medium of the spiral heat exchanger were adjusted so that the temperature range was 83 ° C to 85 ° C. In Example 2, unlike Example 1, when preparing a low-concentration dope from a mixed solution, an intermediate solution that is in a semi-dissolved state is prepared. Therefore, even if the maximum temperature in the heat exchanger is lowered by about 5 ° C., the solubility is high. It was possible to obtain a low-concentration dope excellent in the above. Thereafter, a film was produced after flash concentration using this low-concentration dope under the same conditions as in Example 1. The optical properties of the obtained film were excellent in optical properties similar to those obtained in Example 1.

  The dope preparation method of the present invention is also applicable when obtaining a solution by dissolving a hardly soluble solute in a solvent.

It is explanatory drawing which showed the implementation method of the preparation method of dope. Example 1 It is a principal part enlarged view of FIG. It is explanatory drawing which showed the other implementation method of the preparation method of dope. (Example 2) It is explanatory drawing which showed the implementation method of the solution casting method. Example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dope preparation line 16 Low concentration dope 17 High concentration dope 17a Liquid level 20 Heater 21 Static mixer 27 Flash pipe 30 Flash tank

Claims (6)

In a method for preparing a dope comprising a polymer and a solvent,
The polymer is heated and dissolved in the solvent using a heat exchanger to prepare a diluted dope having a polymer concentration of 15% by weight to 20% by weight,
The heating temperature is not less than the boiling point of the solvent,
After stirring the diluted dope using a static mixing stirring means, the diluted dope is concentrated to obtain a dope having a polymer concentration of 20 wt% or more and 30 wt% or less ,
When performing the heating, using a plurality of heating units including a heat exchanger and static mixing and stirring means provided on the downstream side of the heat exchanger,
A method for preparing a dope, wherein a temperature rise temperature of the diluted dope in one heat exchanger is set to 20 ° C. or more and 70 ° C. or less. A thermometer is provided downstream of the static mixing and stirring means,
The method for preparing a dope according to claim 1 , wherein the temperature of the diluted dope is measured using the thermometer, and the temperature of the heat exchanger is adjusted based on the measurement result. The flow rate of the diluted dope fed to the static mixing and stirring means is 30 L / min to 150 L / min,
The diameter of the tube of the static mixing and stirring means is 50 mm or more and 200 mm or less,
The dope preparation method according to claim 1 or 2, wherein the number of baffle plates provided in the static mixing and stirring means is 4 or more and 20 or less. The dope preparation method according to any one of claims 1 to 3, wherein a spiral heat exchanger is used as the heat exchanger. Method for producing a polymer film characterized in that with the claims 1 to 4 wherein the dope is prepared by a process for the preparation of any one described dope to produce a polymer film. 6. The method for producing a polymer film according to claim 5, wherein 60% by weight or more of the polymer film is formed from the dope.

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