JP2006188052A - Solution film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solution film forming method capable of producing a film, which is better in heat and moisture resistance and easier to make orientation than TAC film, without producing defects in quality in the casting process. <P>SOLUTION: A dope is made from cellulose acetate propionate (CAP) or cellulose acetate butyrate (CAB) and a solvent mixture having dichloromethane as the main solvent. The drying speed of the dope immediately after its discharge from a cast die 43 is set to ≤4 kg/min per kg of the solid component. The discharge speed of the dope 27 from the cast die 43 is set to ≥3 m/min. Because the occurrence of the skinning in the cast bead is suppressed, no quality defects are generated in the film. The obtained film, therefore, is excellent in optical characteristics and better in heat and moisture resistance than TAC film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solution casting method.

  A film formed from cellulose acylate, in particular, 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 support. Further, since the TAC film is excellent in optical isotropy, it is used for a polarizing plate protective film, an optical compensation film (for example, a viewing angle widening film, etc.) of a liquid crystal display device whose market is expanding in recent years. Yes.

  The TAC film is usually produced by a solution casting method. According to the solution casting method, a film superior in physical properties such as optical properties can be produced as compared with other film production methods such as a melt casting method. In the solution casting method, a polymer solution (hereinafter referred to as a dope) is prepared by dissolving a polymer or the like in a mixed solvent containing dichloromethane or methyl acetate as a main solvent. The dope is cast on a support from a casting die to form a casting film. After the cast film becomes self-supporting on the support, the cast film is peeled off from the support as a wet film containing a solvent, dried and then wound up as a film ( For example, refer nonpatent literature 1).

  In order to prevent defects such as streaks and unevenness from occurring in the film, a casting die has been proposed (see, for example, Patent Document 1). In particular, various proposals have been made for a casting die for casting a dope using TAC as a raw material (see, for example, Patent Documents 2 to 4).

It has also been proposed to use another cellulose acylate instead of TAC in order to increase the wet heat durability of the film. For example, in acylating cellulose, acylation with an acetyl group (—CO—CH ₃ ) and acylation with a propionyl group (—CO—C ₂ H ₅ ) are performed, and cellulose acylate propionate (hereinafter referred to as CAP). ) And using this CAP as a film raw material is known (for example, see Patent Document 5). The obtained CAP film is superior in wet heat durability to the CAP film due to the non-hydrophilicity of the acyl group in the side chain of CAP. In addition, CAP has a longer side chain acyl group than TAC, and thus has higher lipophilicity, which generally improves the solubility in organic solvents and facilitates the preparation of a dope. .

Furthermore, since the CAP film has a bulky propionyl group, orientation is likely to occur. For this reason, in-plane retardation (Re) and thickness direction retardation (Rth) can be increased. Therefore, it is preferably used as an optical film of a vertical alignment (VA) type liquid crystal display device that requires optical compensation. Such characteristics of CAP are common to cellulose acetate butyrate (CAB).
Japan Society for Invention and Innovation Public Technical Bulletin No. 2001-1745 JP-A-8-025381 JP 2001-071338 A JP 2002-254453 A JP 2004-066663 A JP 2001-188128 A

  However, the solution casting methods described in Patent Documents 1 to 4 use TAC as a raw material, and are not suitable as a method for forming CAP or CAB into a film. Further, the solution casting method described in Patent Document 5 is also performed under substantially the same conditions as in the case of a TAC raw material, and is a good method for producing a CAP film or CAB film for optical use. Absent.

  For example, since CAP and CAB have better solubility in solvents compared to TAC, there is a difference that the gel strength of the cast film is small. Therefore, when stripping the cast film, it is stripped more than TAC. A problem is likely to occur. Defective stripping means that the cast film is not peeled off on the support, the stripping force when stripping is not constant, the surface condition (planar) of the stripped film is rough, or the film is torn. This is a phenomenon such as. In addition, CAP and CAB have a lower reactivity of propionylation and butyrylation than acetylation at the time of synthesis, and therefore, TAC is not esterified among hydroxyl groups (-OH) of cellulose. There is also a difference that there are many. Since the hydroxyl group has higher affinity with the casting die surface than the esterified acyl group, CAP and CAB have high adhesion to the casting die, and a part of the dope becomes a foreign substance to cast the bead. May occur during. If foreign matter is generated in the casting bead, the casting bead has a problem that streaks are generated starting from the foreign matter. Further, even if the foreign matter is very small, it grows as a nucleus and becomes a so-called burrs. When the river burr becomes a certain size, it may fall from the casting bead onto the casting film and cause defects in the film.

  An object of this invention is to provide the solution casting method which can manufacture the film which is more excellent in heat-and-moisture resistance than TAC, and is easy to orient so that a quality defect may not arise in a casting process.

  As a result of intensive studies by the inventor, when casting a dope, the dope (casting bead) drying speed, the dope discharge speed, the dope peeling force at the lip of the casting die, and the stretching force of the casting bead It has been found that the occurrence of burrs can be prevented by adjusting the above and that casting can be performed stably when CAP or CAB (cellulose acetate butyrate) is used as a raw material.

In the solution casting method of the present invention, a dope comprising a solid component containing cellulose acylate and a solvent is discharged from a casting die to form a casting film on a support, and the casting film is formed from the support. In the solution casting method as a peeling film, the drying rate of the dope immediately after being discharged from the casting die is 4 kg / min or less per 1 kg of the solid component, and the cellulose acylate is represented by the following formula (I) and It is configured to satisfy (II). In the formulas (I) and (II), A represents the degree of substitution of the acetyl group with respect to the hydrogen atom of the cellulose hydroxyl group, and B represents the propionyl group, butyryl group, pentanoyl group, hexanoyl group with respect to the hydrogen atom of the cellulose hydroxyl group. Represents the total substitution degree.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 1.25 ≦ B ≦ 3.0

  The discharge speed for discharging the dope from the casting die is preferably 3 m / min or more. An angle θ formed by the direction in which the dope is discharged from the casting die and a straight line passing through the center of the discharge port of the casting die among the normal lines on the surface on which the casting film of the support is formed is 0 degree or more and 60 degrees. The distance between the support and the casting die on the straight line is preferably 0.5 mm or more and 5 mm or less. The peeling resistance between the dope and the lip tip of the casting die is 40 g / cm or less, and the shear viscosity η (Pa · s) of the dope during casting and the elongation of the dope from the casting die to the support It is preferable that the relationship with the speed ε (1 / sec) satisfies 150 Pa <3 · η · ε <15000 Pa. The storage elastic modulus of the dope at a shear rate of 100 (1 / sec) to 6500 (1 / sec) is preferably 10 Pa to 400 Pa.

  It is preferable that the concentration of the solid component on the surface of the dope immediately after being discharged from the casting die is 16 wt% or more and 25 wt% or less.

  The present invention includes a solution casting method in which the casting is performed by co-casting or sequential co-casting.

  According to the solution casting method of the present invention, a dope composed of a solid component containing cellulose acylate and a solvent is discharged from a casting die to form a casting film on a support, and the casting from the support is performed. In the solution casting method in which the film is peeled off, the dope drying rate immediately after discharge is 4 (kg · solvv) / (kg · solid) · min or less, that is, the dope drying rate immediately after discharge is the solid component Since the cellulose acylate satisfies the formulas (I) and (II) at a rate of 4 kg / min or less per kg, a cellulose acylate film in which casting failure is suppressed can be obtained. Thereby, the obtained cellulose acylate film has no thickness unevenness and can be preferably used as an optical film excellent in flatness.

The solution casting method of the present invention comprises:
(1) The speed at which the dope is discharged from the casting die, that is, the discharge speed is 3 m / min or more.
(2) The angle θ formed by the direction in which the dope is discharged from the casting die and the straight line passing through the center of the discharge port of the casting die among the normals on the surface of the support on which the casting film is formed is 0 degree. More than 60 degrees,
(3) The distance between the support and the casting die on the straight line is 0.5 mm or more and 5 mm or less.
(4) The peeling resistance between the dope and the lip tip of the casting die is 40 g / cm or less.
(5) The relationship between the shear viscosity η (Pa · s) of the dope during casting and the elongation rate ε (1 / sec) of the dope from the casting die to the support is 150 Pa <3 · η.・ The condition of ε <15000 Pa is satisfied.
(6) The storage elastic modulus of the dope at a shear rate of 100 (1 / sec) to 6500 (1 / sec) is 10 Pa to 400 Pa.
As a result, the above-described effect can be further improved, so that the above-described effect can be improved without requiring a special device, that is, without increasing the production cost. The film manufactured by this invention can be used as a polarizing plate protective film and an optical functional film. A polarizing plate can be obtained by covering at least one surface of the polarizing film with the polarizing plate protective film. In addition, a liquid crystal display device having excellent optical characteristics can be produced using such a polarizing plate and the optical functional film.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments listed here.

[material]
The polymer used in the present invention is cellulose acylate. Among them, cellulose acylate satisfying the following formulas (I) and (II) is used.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 1.25 ≦ B ≦ 3.0
In the formula, A and B represent the substitution degree of the acyl group (—CO—R) substituted on the hydroxyl group of cellulose, and A represents the substitution degree of the acetyl group (—CO—CH ₃ ). B represents a propionyl group (—CO—C ₂ H ₅ ), a butyryl group (—CO—C ₃ H ₇ ), a pentanoyl group (—CO—C ₄ H ₉ ), a hexanoyl group (— CO—C ₅ H ₁₁ ). In addition, when B is a propionyl group, it is called CAP (cellulose acetate propionate), and when B is a butyryl group, it is called CAB (cellulose acetate butyrate). Preferably 2.6 ≦ A + B ≦ 3.0 and 1.3 ≦ B ≦ 2.97, and more preferably 2.67 ≦ A + B ≦ 2.97 and 1.4 ≦ B ≦ 2.97.

  90% by mass or more of CAP and CAB are preferably particles having a particle size of 0.1 mm to 4 mm.

  Solvents for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, n-butanol, Diethylene glycol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). In the present invention, the dope means a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  Among these, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. From the viewpoint of physical properties such as the solubility of cellulose acylate, the peelability of the cast film from the support, the mechanical strength of the film, and the optical properties of the film, an alcohol having 1 to 5 carbon atoms is used in addition to dichloromethane. It is preferable to mix one to several kinds. 2 mass%-25 mass% are preferable with respect to the whole solvent, and, as for content of alcohol, 5 mass%-20 mass% are more preferable. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, but methanol, ethanol, n-butanol or a mixture thereof is preferably used.

  By the way, recently, for the purpose of minimizing the influence on the environment, studies have been conducted on the solvent composition when dichloromethane is not used. For this purpose, ethers having 4 to 12 carbon atoms, carbon atoms A ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferably used. These may be used in combination as appropriate. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester, and alcohol (that is, —O—, —CO—, —COO—, and —OH) can also be used as the solvent.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148. These descriptions can be applied to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, release accelerators, etc. It is described in detail in paragraphs [0196] to [0516] of JP-A-2005-104148, and can be applied to the present invention.

[Dope production method]
First, a dope is manufactured using the above raw materials. FIG. 1 shows a dope production line 10. An example in which CAP is used as the dope material will be described. The dope production line 10 has a solvent tank 11 for storing a solvent, a dissolution tank 12 for mixing the solvent and CAP, a hopper 13 for supplying CAP, and an additive for storing the additive. An additive tank 14, a heating device 15 for heating the swelling liquid described later, a temperature controller 16 for adjusting the temperature of the prepared dope, and a filtering device 17 are provided. The dope production line 10 further includes a flash device 30 for concentrating the prepared dope, a filtration device 31, a recovery device 32 for recovering the solvent, and a regeneration device 33 for regenerating the recovered solvent. Provided. The dope production line 10 is connected to the film production line 40 via a stock tank 41.

  The dope is manufactured by the following method using the dope manufacturing line 10. First, the valve 18 is opened, and the solvent is sent from the solvent tank 11 to the dissolution tank 12. Next, the CAP placed in the hopper 13 is fed into the dissolution tank 12 while being weighed. In addition, the required amount of the additive solution is sent from the additive tank 14 to the dissolution tank 12 by opening and closing the valve 19.

  As a method of sending the additive to the dissolution tank 12, there are a method of sending it as a solution when it is solid at room temperature, a method of sending it in its liquid state when it is liquid at room temperature, and the like. In the case where the additive is solid, there is a method in which the additive is fed into the dissolution tank 12 as a solid using a hopper or the like. When a plurality of types of additives are added, a solution in which a plurality of types of additives are dissolved may be placed in the additive tank 14. It is also possible to put a solution in which the additive is dissolved in each of the plurality of additive tanks, and send the additive solution to the dissolution tank 12 from each additive tank through an independent pipe.

  In the above description, the order of putting in the dissolution tank 12 is the solvent, the CAP, and the additive, but is not limited to this order. For example, a predetermined amount of solvent can be fed after the CAP is metered into the dissolution tank 12. The solvent may be a mixture of a plurality of compounds. Further, the additive does not necessarily need to be put in the dissolution tank 12 in advance, and can be mixed in a mixture of CAP and a solvent in a later step.

  As shown in FIG. 1, the dissolution tank 12 includes a jacket 20 that covers the outer surface thereof, and a first stirrer 22 that is rotated by a motor 21. Furthermore, it is preferable that a second agitator 24 that is rotated by a motor 23 is attached to the dissolution tank 12. The first stirrer 22 is preferably provided with an anchor blade, and the second stirrer 24 is preferably a dissolver type eccentric stirrer. However, the types of the first stirrer 22 and the second stirrer 24 are not limited to this. And it is preferable that the melting tank 12 is temperature-controlled with the heat-transfer medium sent inside the jacket 20, and is made constant temperature in the range of -10 degreeC-55 degreeC. Under the above conditions, a swelling liquid 25 in which CAP is swollen in a solvent is obtained.

  Next, the swelling liquid 25 is sent to the heating device 15 by the pump 26. The heating device 15 is preferably a jacketed pipe, and further preferably has a pressurizing mechanism for pressurizing the swelling liquid 25. By using such a heating device 15, a dope 27 in which the solid content in the swelling liquid 25 is dissolved under heating conditions or pressure heating conditions is obtained. Hereinafter, this method is referred to as a heating dissolution method. In the heating dissolution method, it is preferable that the temperature of the swelling liquid 25 is heated so as to be substantially constant in the range of 50 ° C to 120 ° C.

  Instead of the heating dissolution method, a cooling dissolution method can be applied. In this cooling dissolution method, the swelling liquid 25 is preferably cooled so as to be constant in the range of −100 ° C. to −30 ° C. By appropriately selecting the heating dissolution method and the cooling dissolution method described above, CAP can be sufficiently dissolved in a solvent. After the dope 27 is brought to about room temperature by the temperature controller 16, the dope 27 is filtered by the filtering device 17 to remove impurities contained in the dope 27. The filtration filter used for the filtration device 17 preferably has an average pore diameter of 100 μm or less. The filtration flow rate is preferably 50 L / hr or more. The dope 27 after filtration is sent to the stock tank 41 in the film production line 40 through the valve 28 and stored therein.

  By the way, as described above, the method of once preparing the swelling liquid 25 and then using the swelling liquid 25 as the dope 27 requires a longer time as the concentration of CAP is increased, resulting in production efficiency and production cost. May be a problem. In such a case, it is preferable to once prepare a dope having a concentration lower than the target concentration and then perform a concentration step of concentrating the dope so as to obtain the target concentration. In the concentration step of this embodiment, the dope filtered by the filtering device 17 is sent to the flash device 30 via the valve 28, and a part of the solvent in the dope is evaporated in the flash device 30. The solvent gas generated by the evaporation is condensed by a condenser (not shown) to become a liquid and is recovered by the recovery device 32. The recovered solvent is regenerated as a dope preparation solvent by the regenerator 33 and reused. This reuse is effective in terms of cost.

  Further, the concentrated dope 27 is extracted from the flash device 30 by the pump 34. Furthermore, it is preferable that a bubble removal process is performed to remove bubbles generated in the dope 27. As this defoaming method, various known methods are applied, for example, an ultrasonic irradiation method. The dope 27 is subsequently sent to the filtering device 31 to remove foreign matter. In addition, it is preferable that the temperature of dope 27 in the case of filtration is constant in the range of 0 degreeC-200 degreeC. The dope 27 is sent to the stock tank 41 and stored.

  By the above method, the dope 27 having a CAP concentration of 5% by mass to 40% by mass can be manufactured. More preferably, the CAP concentration is from 15% by mass to 30% by mass, and most preferably from 17% by mass to 25% by mass. In addition, the concentration of the additive (mainly a plasticizer) is preferably in the range of 1 to 20 when the mass of the entire solid content in the dope is 100. In addition, about the raw material in the solution casting method which obtains a CAP film, the raw material, the additive dissolution method and addition method, the filtration method, and the dope production method such as defoaming, paragraph [0517] of JP-A-2005-104148 To [0616] paragraph. These descriptions are also applicable to the present invention.

[Solution casting method]
Next, a method for producing a film using the dope 27 will be described. FIG. 2 is a schematic view showing a film production line 40. FIG. 3 is an enlarged view of the vicinity of the casting die of FIG. However, the present invention is not limited to the film production line as shown in FIGS. The film production line 40 includes a stock tank 41, a filtration device 42, a casting die 43, a casting band 46 stretched around rotating rollers 44 and 45, a tenter dryer 47, and the like. Further, an ear-cutting device 50, a drying chamber 51, a cooling chamber 52, a winding chamber 53, and the like are arranged.

  An agitator 61 that is rotated by a motor 60 is attached to the stock tank 41. The stock tank 41 is connected to the casting die 43 via the pump 62 and the filtration device 42.

As a material of the casting die 43, precipitation hardening type stainless steel is preferable, and its thermal expansion coefficient is preferably 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. And what has corrosion resistance substantially equivalent to SUS316 in the forced corrosion test with electrolyte aqueous solution can also be used as a material of this casting die 43. FIG. The material of the casting die 43 is preferably one having corrosion resistance that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months. It is preferable that the casting die 43 is manufactured by grinding a material that has passed one month or more after casting. This prevents the dope 27 from flowing uniformly in the casting die 43 and prevents streaks from being generated in the casting film. The surface finish accuracy of the liquid contact surface of the casting die 43, that is, the portion of the casting die 43 in contact with the dope 27 is 1 μm or less in terms of surface roughness, and the straightness is 1 μm / m or less in any direction. preferable. The clearance of the slit of the casting die 43 can be adjusted in a range of 0.5 mm to 3.5 mm by automatic adjustment. Further, the shear rate inside the casting die 43 is preferably 1 (1 / sec) to 5000 (1 / sec).

  The tip of the casting die 43, that is, the tip of the lip, preferably has a Vickers hardness Hv of 400 or more, more preferably 600 or more, and most preferably 1100 or more. If Hv is less than 400, the lip is liable to be damaged, which is not preferable. Also, the surface tension at the tip of the casting die 43 is preferably as large as possible. This is because the higher the surface tension of the casting die, the better the wettability with the solvent and the less likely to cause burrs. Specifically, the surface tension is preferably 380 μN / cm or more, more preferably 390 μN / cm or more, and most preferably 400 μN / cm or more. If the surface tension is less than 380 μN / cm, there is a risk that it is easy to form a power burr at the dope contact interface.

  About the corner | angular part of the liquid-contacting part of the lip | tip end of the casting die 43, it is preferable that the chamfer radius R shall be 5 micrometers or more and 50 micrometers or less over the whole width. Thereby, a casting bead is preferably formed and its shape can be maintained. If the chamfer radius is less than 5 μm, defects such as streaks are likely to occur in the casting bead. Further, if the chamfer radius exceeds 50 μm, it may be difficult to make the lip clearance of the casting die 43 substantially uniform, and there is a possibility that unevenness of thickness occurs in the casting film. The center line average roughness at the tip of the casting die 43 is preferably 0.013 μm or more and 1.6 μm or less. If the center line average roughness is less than 0.013 μm, ultra-precise machining is required, resulting in high costs. Further, if the center line average roughness exceeds 1.6 μm, defects such as streaks and unevenness may occur in the casting bead.

  The width of the casting die 43 is not particularly limited, but is preferably 1.01 to 1.3 times the width of the film as the final product. Further, it is preferable to attach a temperature controller to the casting die 43 so that the temperature of the dope during film formation is maintained at a predetermined temperature. The casting die 43 is preferably a coat hanger type. The casting die 43 is preferably provided with a plurality of thickness adjusting bolts (heat bolts) at predetermined intervals in the width direction and an automatic thickness adjusting mechanism using the heat bolts. In particular, it is preferable to set a heat bolt profile according to the amount of pump 56 (preferably a high-precision gear pump) according to a preset program. Further, a thickness meter (for example, an infrared thickness meter) (not shown) may be provided in the film production line 50, and feedback control may be performed by an adjustment program based on a profile by the thickness meter. The difference in thickness between any two points in the width direction excluding the casting edge of the product film is within 1 μm, and the difference between the minimum value and the maximum value in the width direction is preferably 3 μm or less, preferably 2 μm or less. More preferably. The thickness accuracy is preferably ± 1.5 μm or less.

More preferably, a cured film is formed at the lip end of the casting die 43. The method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding method. When ceramic is used as the material of the cured film, it can be ground, has low porosity, is not brittle, has excellent corrosion resistance, has excellent adhesion to the casting die 43, and does not adhere to the dope Is preferred. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, and WC is particularly preferable. The WC coating can be performed by a thermal spraying method.

  In order to prevent the dope flowing out from the casting die 43 from locally drying and solidifying at the slit end, it is preferable to attach a solvent supply device (not shown) to the slit end. The solvent supply device supplies a solvent capable of dissolving the dope to a predetermined position of the casting die at a predetermined flow rate. Examples of the solvent in this case include a mixture of 86.5 parts by mass of dichloromethane, 13 parts by mass of acetone, and 0.5 parts by mass of n-butanol. The solvent supply position is preferably near both ends of the casting bead, the end of the die slit, and the periphery of the three-phase contact line formed by the outside air. The flow rate when supplying the solvent is preferably 0.1 mL / min to 1.0 mL / min with respect to each one side of the end. By using the solvent supply device in this way, it is possible to prevent foreign matter from being mixed into the cast film. Note that the pump for supplying the solvent preferably has a pulsation rate of 5% or less.

  A casting band 46 is provided below the casting die 43 so as to span the rotating rollers 44 and 45. The rotating rollers 44 and 45 are rotated by a driving device (not shown), and the casting band 46 travels endlessly with the rotation. It is preferable to set the moving speed of the casting band 46, that is, the casting speed within a range of 10 m / min to 200 m / min. In order to set the surface temperature of the casting band 46 to a predetermined value, it is preferable that the heat transfer medium circulating device 63 is attached to the rotating rollers 44 and 45. It is preferable that the casting band 46 can be adjusted to a constant surface temperature in the range of −20 ° C. to 40 ° C. A heat transfer medium flow path (not shown) is formed in the rotation rollers 44 and 45, and the temperature of the rotation rollers 44 and 45 passes through the heat transfer medium maintained at a predetermined temperature. Is held at a predetermined value.

  The width of the casting band 46 is not particularly limited, but is preferably in the range of 1.05 to 1.5 times the casting width of the dope 27. Moreover, it is preferable that the length is 60 m to 120 m, the thickness is 1 mm to 2 mm, and the surface roughness is polished to be 0.05 μm or less. The casting band 46 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. Further, the thickness unevenness of the entire casting band 46 is preferably 0.5% or less.

  The positional relationship between the casting die 43 and the casting band 46 as a support will be described. The direction in which the dope is discharged from the discharge port 43a is represented by a straight line L1. Moreover, in the figure which looked at the casting die | dye 43 and the casting band 46 from the side surface like FIG. 3, let the straight line which passes along the discharge outlet 43a among the normal lines in the exposed surface of the casting band 46 be L2. The distance L (mm) between the discharge port 43a and the casting band 46 shown in FIG. 3 is preferably 0.5 mm or more and 5 mm or less, more preferably 1 mm or more and 4 mm or less, and most preferably 1 mm or more and 3 mm or less. It is. In this case, the distance L (mm) is a distance measured on the straight line L2. If the distance L (mm) is less than 0.5 mm, the tip of the lip and the casting band 46 may come into contact with each other due to the positional fluctuation in the vertical direction of the casting band 46 accompanying the rotation of the rotary roller 45. If the distance L (mm) exceeds 5 mm, the formation of the casting bead 69a may become unstable.

  The angle formed by the straight line L1 and the straight line L2 is referred to as a casting die angle θ in the following description. The angle θ of the casting die is positive when the straight line L1 is rotated up to 90 degrees counterclockwise of the straight line L2 with the central portion of the discharge port 43a where the straight line L1 and the straight line L2 intersect as the rotation center. The value, the position rotated clockwise by less than 90 is shown as a negative value. The angle θ (degree) of the casting die is preferably 0 degree or more and 60 degrees or less, more preferably 5 degrees or more and 60 degrees or less, and most preferably 10 degrees or more and 60 degrees or less. The casting die angle θ of 0 degrees means that the straight line L1 overlaps the straight line L2. If the angle θ of the casting die is less than 0 degree, the discharge port 43a is directed so that the direction of discharge of the dope 27 is opposite to the direction of travel of the casting band 46, so that the downstream side A large amount of the dope 27 adheres to the lip tip 43b, making it difficult to form the casting bead 69a. If the angle θ of the casting die exceeds 60 degrees, the casting die 43 is inclined too much with respect to the casting band 46, so that a large amount of dope adheres to the upstream lip tip 43c and casting occurs. May be difficult.

It is also possible to use a drum (not shown) as a support instead of the casting band 46. In this case, it is preferable that the rotation can be performed with high accuracy so that the rotation unevenness is 0.2 mm or less. In this case, the average roughness of the drum surface is preferably 0.01 μm or less. Therefore, the surface of the drum is subjected to chrome plating or the like to provide sufficient hardness and durability. It should be noted that surface defects of the support (the casting band 46 and the rotating rollers 44 and 45 supporting the casting band 46 and the drum) need to be minimized. Specifically, there is no pinhole of 30 μm or more, and the number of pinholes of 10 μm or more and less than 30 μm is 1 / m ² or less, and the number of pinholes of less than 10 μm is preferably ² / m ² or less.

  The casting die 43, the casting band 46, and the like are housed in a casting chamber 64. The casting chamber 64 is provided with a temperature control facility 65 for keeping the internal temperature at a predetermined value and a condenser (condenser) 66 for condensing and recovering the volatile organic solvent. A recovery device 67 for recovering the condensed and liquefied organic solvent is provided outside the casting chamber 64. Further, a decompression chamber 68 for controlling the pressure of the back surface portion of the casting bead formed from the casting die 43 to the casting band 46, that is, the upstream area of the casting bead in the traveling direction of the casting band is disposed. It is preferable that this is also used in this embodiment.

  Air ducts 70, 71, 72 are provided near the peripheral surface of the casting band 46 in order to evaporate the solvent in the casting film 69. Of these air ducts, a wind shield 73 is preferably provided in the vicinity of the air outlet (not shown) of the most upstream air duct 70. This is for suppressing deterioration of the surface condition of the casting film 69 due to the blowing of dry air to the casting film 69 immediately after casting.

  The crossover portion 80 is provided with a blower 81, and the ear-cutting device 50 downstream of the tenter dryer 47 is used for finely cutting the waste at the side end (referred to as an ear) of the cut film 82. Crusher 90 is connected.

  The drying chamber 51 is provided with a large number of rollers 91, and an adsorption / recovery device 92 for adsorbing / recovering the solvent gas generated by evaporation is attached. In FIG. 2, the cooling chamber 52 is provided downstream of the drying chamber 51, but a humidity control chamber (not shown) may be provided between the drying chamber 51 and the cooling chamber 52. A forced static elimination device (static elimination bar) 93 for setting the charged voltage of the film 82 within a predetermined range (for example, −3 kV to +3 kV) is provided downstream of the cooling chamber 52. In FIG. 2, an example in which the forced static elimination device 93 is installed on the downstream side of the cooling chamber 52 is illustrated, but the present invention is not limited to this installation position. Furthermore, in this embodiment, a knurling roller 94 for applying knurling to both edges of the film 82 by embossing is appropriately provided downstream of the forced static elimination device 93. The winding chamber 53 is provided with a winding roller 95 for winding the film 82 and a press roller 96 for controlling the tension at the time of winding.

  Next, an example of a method for manufacturing the film 82 using the film manufacturing line 40 as described above will be described. The dope 27 is always made uniform by the rotation of the stirrer 61. The dope 27 can be mixed with additives such as a plasticizer and an ultraviolet absorber even during the stirring. When storing the dope 27, the storage elastic modulus of the dope 27 at a shear rate of 100 to 6500 (1 / sec) is preferably 10 Pa or more and 400 Pa or less, more preferably 30 Pa or more and 400 Pa or less, and most preferably 50 Pa or more and 400 Pa or less. In this case, the dope temperature is preferably in the range of 20 ° C to 50 ° C. If the storage modulus is less than 10 Pa, the bead take-up force may be insufficient. On the other hand, when the storage elastic modulus exceeds 400 Pa, there is a risk of occurrence of uneven thickness of the casting bead or deterioration of the surface condition.

The dope 27 is sent to the filtering device 42 by the pump 62 and filtered there, and then is cast from the casting die 43 onto the casting band 46. The driving of the rotating rollers 44 and 45 is preferably adjusted so that the tension generated in the casting band 46 is 10 ⁴ N / m to 10 ⁵ N / m. Further, the relative speed difference between the casting band 46 and the rotating rollers 44 and 45 is adjusted to 0.01 m / min or less. It is preferable that the speed fluctuation of the casting band 46 is 0.5% or less, and the amount of positional deviation in the width direction that occurs when the casting band 46 rotates once, that is, the meandering width is suppressed to within 1.5 mm. In order to control the meandering width, a detector (not shown) for detecting the positions of both ends of the casting band 46 is provided, and feedback is provided to a position controller (not shown) of the casting band 46 based on the measured value. More preferably, the position of the casting band 46 is adjusted by performing control. Furthermore, although the position of the casting band 46 directly below the casting die 43 may fluctuate in the vertical direction as the rotary roller 55 rotates, it is preferable to suppress this fluctuation amount to 200 μm or less. The temperature of the casting chamber 64 is preferably set to −10 ° C. to 57 ° C. by the temperature control equipment 65. The solvent evaporated inside the casting chamber 64 is recovered by the recovery device 67 and then regenerated and reused as a dope preparation solvent.

  A casting bead 69 a is formed from the casting die 43 to the casting band 46, and a casting film 69 is formed on the casting band 46. The temperature of the dope 27 at the time of casting is preferably constant in the range of −10 ° C. to 57 ° C. Further, in order to stabilize the casting bead 69a, it is preferable that the area on the back surface side of the bead is decompressed to a range of −2000 Pa to −10 Pa from the area on the front surface side using the decompression chamber 68. Further, it is preferable that a jacket (not shown) is attached to the decompression chamber 68 and the temperature is controlled so that the internal temperature is kept at a predetermined temperature. The temperature of the decompression chamber 68 is not particularly limited, but is preferably set to be equal to or higher than the condensation point of the organic solvent used for the dope. Further, in order to keep the shape of the casting bead 69a in a desired shape, a suction device (not shown) is attached to the edge portion of the casting die 43, and the edge is sucked with an air volume in the range of 1 L / min to 100 L / min. It is preferable.

  The discharge speed of the dope 27 from the casting die 43 is preferably 3 m / min or more, and more preferably 5 m / min or more. By setting the discharge speed to 3 m / min or more, the residence of the dope 27 at the discharge port of the casting die is suppressed. Further, the lower limit of the discharge speed is not particularly limited, but if it is less than 3 m / min, the productivity is lowered, which is not preferable. The discharge speed of the dope 27 can be obtained by dividing the dope flow rate by the area of the discharge port 43a. Further, the discharge speed of the dope 27 can be controlled by adjusting the clearance of the discharge port 43a or by increasing or decreasing the dope flow rate.

  The peeling resistance between the dope 27 and the lip tip of the casting die 43 is preferably 40 g / cm or less, more preferably 20 g / cm or less, and most preferably 5 g / cm or less. When the peeling resistance exceeds 40 g / cm, the dope 27 is likely to adhere to the casting die 43, which causes the generation of burrs. The peeling resistance between the dope 27 and the lip tip of the casting die 43 is a force required to dry the dope with the casting die 43 and peel it off, and is also called a peeling load. The measurement can be performed by a load cell, specifically by the following method. The dope 27 is dropped on a metal plate having the same material and the same surface roughness as the casting die 43, spread to a uniform thickness using a doctor blade, and dried. Make a notch of equal width in the dope 27 dried with a cutter knife, peel off the end of the piece by hand and pinch it with a clip connected to the strain gauge, and measure the load change while pulling up the strain gauge in an oblique 45 degree direction. . In addition, adjustment of peeling resistance is mainly performed by determining these suitably based on the relationship between the surface material of the casting die lip tip and the composition of the dope.

  Further, the shear viscosity η (Pa · s) of the dope 27 and the elongation rate ε (1 / sec) of the casting bead 69a at the time of casting, that is, when discharged from the casting die, are 150 Pa <3 · η · The condition of ε <15000 Pa is preferably satisfied, and more preferably 500 Pa <3 · η · ε <10000 Pa. If the value of (3 · η · ε) is less than 150 Pa, the dope may stay at the tip of the die lip. Further, if the value of (3 · η · ε) exceeds 15000 Pa, the flatness of the cast film 69 may be deteriorated.

In this specification, the extension speed ε of the casting bead 69a is a numerical value at the center of the discharge port 43a. It can be obtained using the formula described in JP-A-2001-71338, [0020]. In this specification, the elongation rate ε is the elongation strain rate in the publication. Specifically: The shear viscosity η, the extension stress τ, the discharge speed v1, the contact start point speed v2, the tip lip clearance CL, the film 82 thickness t, the cast bead at the center of the discharge port 43a. Let L be the length of 69a. The contact start point speed is the flow speed of the casting bead 69 at the position where the casting bead 69a starts to contact the casting band 46, and may be replaced with the speed of the casting band 46 or the casting speed. . Then, the extension speed ε is obtained using the following equation. Therefore, the extension speed ε can be adjusted by controlling the shear viscosity η, the discharge speed v1, the contact start point speed v2, the clearance CL of the tip lip, the thickness t of the film 82, and the length L of the casting bead 69a. it can.
τ = ε * η
= (V2-v1) / L * η
= (V2-t / CL * v2) L * η

  The casting film 69 is moved by the running of the casting band 46. At this time, drying air is applied by the air ducts 70, 71, 72 to promote the evaporation of the solvent. Since the surface shape of the casting film 69 may fluctuate due to the blowing of the dry air, the fluctuation is suppressed by using the wind shielding plate 73. The surface temperature of the casting band 46 is preferably -20 ° C to 40 ° C.

  In order to suppress the evaporation of the solvent from the casting bead 69a and the occurrence of defects such as unevenness in the thickness of the casting bead 69a and the occurrence of burrs, the drying speed of the casting bead is set to 4 (kg · solvv) / (kg · solid) · min or less, preferably 3.5 (kg · solv) / (kg · solid) · min or less, more preferably 3.0 (kg · solv) / (kg · solid) · Most preferably, it is not more than min. The value of the drying rate indicates the mass (kg) of the solvent that evaporates per minute with respect to 1 kg of the solid component of the casting bead 69a. The drying speed is adjusted by adjusting the temperature of the casting die, the dope formulation (for example, containing an additive), the atmospheric temperature in the casting chamber, the temperature of the drying air from the air ducts 70, 71, 72, the humidity, and the wind speed. This can be done easily by adjusting.

  It is preferable that the solid content concentration on the surface of the casting bead 69a immediately after coming out of the casting die 43 is 16% by weight or more and 25% by weight or less. If this solid content concentration is less than 16% by weight, the viscosity of the casting bead 69a is too low and the tensile stress is insufficient, so that it becomes difficult to peel off when the casting bead 69a adheres to the lip tip portions 43b and 43c. On the other hand, if it exceeds 25% by weight, there may be a problem that the state of the sharkskin surface formed by the discharge ports 43a deteriorates. The sharkskin surface is the surface of the casting bead 69a that is in the form of a husk. Since the solid content concentration on the surface of the casting bead 69a immediately after coming out of the casting die 43 is difficult to measure on-line in the production line, the solid content concentration of the dope 27 fed to the casting die 43 is determined. This value may be used.

  Specifically, when CAB is used as the polymer and the polymer concentration in the dope is 19% by weight to 28% by weight, the temperature of the casting die is 10 ° C. to 40 ° C., the solvent is dichloromethane, A TPP / BDP was added at 3% by weight based on solid content, and 4% by weight of N, N′-dimetatolyl-N ″ -p-methoxyphenyl-1,3,5-triazine-2,4,6-triamine was added. Dope is used. Moreover, the atmospheric temperature in a casting chamber is hold | maintained at 15 degreeC-45 degreeC, and the dry wind from the ventilation duct 70 shall be 15 degreeC-45 degreeC, and wind speed 2m / s-15m / s. Moreover, the dry air from the ventilation duct 72 shall be 15 to 45 degreeC, and the wind speed shall be 1 m / s-5 m / s.

  After the casting film 69 has self-supporting properties, the casting film 69 is peeled off from the casting band 46 while being supported by the peeling roller 75 as a wet film 74. The amount of residual solvent at the time of stripping is preferably 20% by mass to 250% by mass based on the solid content. Thereafter, the transfer section 80 provided with a large number of rollers is conveyed, and the wet film 74 is fed into the tenter dryer 47. In the transfer part 80, the drying of the wet film 74 is advanced by sending the drying air of desired temperature from the air blower 81. FIG. At this time, the temperature of the drying air is preferably 20 ° C to 50 ° C. In the transition section 80, it is also possible to apply a draw tension to the wet film 74 by making the rotation speed of the downstream roller faster than the rotation speed of the upstream roller.

  The wet film 74 sent to the tenter dryer 47 is dried while being conveyed while being gripped by clips at both ends. Moreover, it is preferable to divide the inside of the tenter dryer 47 into temperature zones and adjust the drying conditions appropriately for each of the zones. It is also possible to stretch the wet film 74 in the width direction using the tenter dryer 47. Thus, it is preferable to stretch at least one direction between the casting direction and the width direction of the wet film 74 by 0.5% to 300% by the crossover part 80 and / or the tenter dryer 47.

  The wet film 74 is dried to a predetermined residual solvent amount by the tenter dryer 47 and then sent to the downstream side as a film 82. Both edges of the film 82 are cut at both edges by the edge-cutting device 50. The cut side end portion is sent to the crusher 90 by a cutter blower (not shown). The crusher 90 pulverizes the film side end portion into a chip. Since this chip is reused for dope preparation, this method is effective in terms of cost. In addition, although it can also abbreviate | omit about the cutting process of this film both ends, it is preferable to carry out in any one from the said casting process to the process of winding up the said film.

  The film 82 from which both side ends have been removed is sent to the drying chamber 51 and further dried. Although the temperature in the drying chamber 51 is not specifically limited, It is preferable that it is the range of 50 to 160 degreeC. In the drying chamber 51, the film 82 is conveyed while being wound around a roller 91, and the solvent gas generated by evaporation here is adsorbed and recovered by an adsorption recovery device 92. The air from which the solvent component has been removed is blown again as dry air inside the drying chamber 51. The drying chamber 51 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, when a preliminary drying chamber (not shown) is provided between the ear opener 50 and the drying chamber 51 and the film 82 is preliminarily dried, the film temperature is prevented from rising rapidly in the drying chamber 51. The shape change of the film 82 can be further suppressed.

  The film 82 is cooled to approximately room temperature in the cooling chamber 52. Note that a humidity control chamber (not shown) may be provided between the drying chamber 51 and the cooling chamber 52, and air adjusted to a desired humidity and temperature can be blown onto the film 82 in the humidity control chamber. It is preferable. Thereby, generation | occurrence | production of the curling of the film 82 and the winding defect at the time of winding can be suppressed.

  Further, the forcible charge removal device (charge removal bar) 93 sets the charged voltage while the film 82 is being conveyed to a predetermined range (for example, −3 kV to +3 kV). FIG. 2 illustrates an example provided on the downstream side of the cooling chamber 52, but the position is not limited thereto. Furthermore, it is preferable to provide a knurling roller 94 to give knurling to both edges of the film 82 by embossing. In addition, it is preferable that the unevenness | corrugation of the knurled location is 1 micrometer-200 micrometers.

  Finally, the film 82 is taken up by the take-up roller 95 in the take-up chamber 53. At this time, it is preferable to wind the sheet while applying a desired tension with the press roller 96. More preferably, the tension is gradually changed from the start to the end of winding. The film 82 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). Moreover, it is preferable that the width | variety of the film 82 is 600 mm or more, and it is more preferable that they are 1400 mm or more and 1800 mm or less. The present invention is also effective when it is larger than 1800 mm. The present invention is also applied when a thin film having a thickness of 15 μm or more and 100 μm or less is manufactured.

  In the solution casting method of the present invention, when casting the dope, two or more kinds of dopes can be simultaneously laminated or sequentially laminated. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. It is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5% to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. 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, it is preferable that the dope which contact | connects an external field has a larger alcohol composition ratio than an internal dope among the casting beads formed from a die slit to a support body.

  From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for each process, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method The details are described in paragraphs [0617] to [0889] of JP-A-2005-104148. These descriptions are also applicable to the present invention.

[Performance / Measurement method]
(Curl degree / thickness)
The performance of the wound cellulose acylate film and the measurement method thereof are described in paragraphs [0112] to [0139] of JP-A-2005-104148. These are also applicable 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]
(Antistatic, hardened layer, antireflection, easy adhesion, antiglare)
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 paragraphs [0890] to [1087] of JP-A-2005-104148. Detailed conditions and methods are also described. These are also applicable to the present invention.

(Use)
The cellulose acylate film is particularly useful as a polarizing plate protective film. Usually, two polarizing plates each having a cellulose acylate film bonded to a polarizer are bonded to a liquid crystal layer to produce a liquid crystal display device. However, the arrangement of the liquid crystal layer and the polarizing plate is not limited, and various known arrangements can be employed. Japanese Patent Application Laid-Open No. 2005-104148 describes TN type, STN type, VA type, OCB type, reflection type, and other examples in detail as a liquid crystal display device. 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 descriptions are also applicable to the present invention. Details are described in paragraphs [1088] to [1265] of JP-A-2005-104148.

  Moreover, the CAP film and CAB film which are excellent in an optical characteristic can be obtained with the manufacturing method of this invention. The CAP film and CAB film can be used as a polarizing plate protective film or a base film for photographic photosensitive materials. Furthermore, it can also be used as an optical compensation film for improving the viewing angle dependency of a liquid crystal display device for television applications. In particular, it is effective for applications that also serve as a protective film for a polarizing plate. Therefore, it is used not only in the conventional TN mode but also in the IPS mode, OCB mode, VA mode, and the like. Moreover, you may comprise a polarizing plate using the said film for polarizing plate protective films.

  Examples are given below, but the present invention is not limited thereto. Experiments 1 to 3 are embodiments in the present invention, and Experiments 4 to 7 are comparative experiments for the present invention. Further, in the description, the experiment 1 will be described in detail, and the description of the same conditions as the experiment 1 will be omitted for the experiments 2 to 7.

[Experiment 1]
Next, examples of the present invention will be described. The composition of the components of the dope used for film production is shown below.

[composition]
Cellulose acetate butyrate (CAB; acetyl substitution degree 1.00, butyryl substitution degree 1.70, total substitution degree 2.70, viscosity average polymerization degree 220, water content 0.2 mass%, viscosity 6 mass% in dichloromethane solution 190 mPa · s, powder having an average particle diameter of 1.5 mm and a standard deviation of 0.5 mm) 100 parts by weight dichloromethane (first solvent) 293 parts by weight methanol (second solvent) 53 parts by weight 1-butanol (third Solvent) 13 parts by weight N, N′-dimetatolyl-N ″ -p-methoxyphenyl-1,3,5-triazine-2,4,6-triamine 4 parts by weight Plasticizer A (triphenyl phosphate) 2 parts by weight Part plasticizer B (biphenyldiphenyl phosphate) 1 part by weight Release agent (citric acid ethyl ester) 0.2 part by weight

  Here, the used CAB has a residual acetic acid content of 0.1% by mass or less, a residual butanoic acid content of 0.1% by mass or less, a Ca content of 80 ppm, a Mg content of 22 ppm, and a Fe content of 0.1%. It was 5 ppm and further contained 105 ppm of sulfur as a sulfate group. Further, the substitution degree of the 6-position acetyl group was 0.33, the substitution degree of the 6-position butyryl group was 0.57, and the ratio to the total acyl group was 33%. The methanol extract was 5% by mass or less, and the weight average molecular weight / number average molecular weight ratio was 2.8. The yellow index was 1.6, the haze was 0.07, the transparency was 92.9%, and the Tg (glass transition temperature; measured by DSC) was 128 ° C. This CAB is synthesized using cellulose collected from cotton as a raw material.

(1-1) Dope Preparation A dope 27 was prepared using a dope production line 10 shown in FIG. The plurality of solvents were mixed and stirred well in a 4000 L stainless steel dissolution tank 12 having a stirring blade to obtain a mixed solvent. In addition, as each raw material of a solvent, that whose water content is 0.5 mass% or less was used. Next, flaky powder of CAB was gradually added from the hopper 13. The CAB powder is charged into the dissolution tank 12 and is initially stirred at a peripheral speed of 1 m / sec. With a dissolver type eccentric agitator 24 that stirs at a peripheral speed of 5 m / sec and with a stirrer 22 having an anchor blade on the central axis. Dispersed under for 30 minutes. The temperature at the start of dispersion was 25 ° C., and the final temperature reached 48 ° C. Further, the amount of the additive solution prepared in advance was adjusted from the additive tank 14 with the valve 19 so that the total amount became 2000 kg. After finishing the dispersion of the additive solution, the high speed stirring was stopped. And the peripheral speed of the anchor wing | blade of the stirrer 22 was 0.5 m / sec, and it stirred for further 100 minutes, the CAB flakes were swollen, and the swelling liquid 25 was obtained. Until the end of swelling, the inside of the dissolution tank 12 was pressurized to 0.12 MPa with nitrogen gas. At this time, the inside of the dissolution tank 12 maintained an oxygen concentration of less than 2 vol% and no problem in terms of explosion prevention. The water content in the swelling liquid 25 was 0.3% by mass.

(1-2) Dissolution / Filtration The swelling liquid 25 was sent from the dissolution tank 12 to the jacketed pipe 15 using the pump 26. The swelling liquid 25 was heated to 50 ° C. with the jacketed pipe 15 and further heated to 90 ° C. under a pressure of 2 MPa to be completely dissolved. The heating time at this time was 15 minutes. Next, the temperature of the dissolved liquid was lowered to 36 ° C. with the temperature controller 16 and passed through a filtering device 17 having a filter medium having a nominal pore diameter of 8 μm to obtain a dope (hereinafter referred to as a dope before concentration). At this time, the primary pressure in the filtration device 17 was 1.5 MPa, and the secondary pressure was 1.2 MPa. The filters, housings and pipes exposed to high temperatures were made of Hastelloy (trade name) alloy and had excellent corrosion resistance, and were equipped with a jacket for circulating a heat transfer medium for heat insulation and heating.

(1-3) Concentration / Filtration / Defoaming / Additive The dope before concentration thus obtained is flash-evaporated in the flash device 30 at normal pressure at 80 ° C., and the evaporated solvent is removed by a condenser. It was collected. The solid concentration of the dope 27 after flashing was 23% by weight. The condensed solvent was recovered by the recovery device 32 to be reused as a dope preparation solvent. Thereafter, the solution was regenerated by the regenerator 33 and then sent to the solvent tank 11. In the recovery device 32 and the regeneration device 33, distillation and dehydration were performed. The flash tank of the flash device 30 was provided with a stirrer (not shown) having an anchor blade on the stirring shaft, and the dope flashed with the stirrer at a peripheral speed of 0.5 m / sec was stirred for defoaming. The temperature of the dope in this flash tank was 25 ° C., and the average residence time of the dope in the tank was 50 minutes. The dope 27 was sampled and the shear viscosity measured at 25 ° C. was 450 Pa · s at a shear rate of 10 (sec ⁻¹ ).

  Next, bubbles were removed by irradiating the dope 27 with weak ultrasonic waves. Then, the filtration apparatus 31 was allowed to pass in the state pressurized to 1.5 MPa using the pump 34. In the filtering device 31, first, the sintered fiber metal filter having a nominal pore diameter of 10 μm was passed, and then the sintered fiber filter having the same pore diameter of 10 μm was passed. Respective primary pressures were 1.5 MPa and 1.2 MPa, and secondary pressures were 1.0 MPa and 0.8 MPa. The dope temperature after filtration was adjusted to 36 ° C., and the dope 27 was fed into a 2000 L stainless steel stock tank 41 and stored. The stock tank 41 has a stirrer 61 having an anchor blade on the central axis, and was constantly stirred at a peripheral speed of 0.3 m / sec. In addition, when the dope was prepared from the dope before concentration, no problem such as corrosion occurred at all in the wetted part of the dope.

  Moreover, the mixed solvent A with 86.5 mass parts of dichloromethane, 13 mass parts of acetone, and 0.5 mass part of 1-butanol was produced.

(1-4) Discharge / immediate addition / casting / bead depressurization A film 82 was produced using the film production line 40 shown in FIG. The dope 27 in the stock tank 41 was sent to the filtration device 42 by a high-precision gear pump 62. The gear pump 62 has a function of increasing the pressure on the primary side of the pump 62. The inverter pump performs feedback control on the upstream side of the gear pump 62 so that the pressure on the primary side becomes 0.8 MPa, and the liquid is sent. . A gear pump 62 having a volume efficiency of 99.2% and a discharge rate variation rate of 0.5% or less was used. The discharge pressure was 1.5 MPa. Then, the dope 27 that passed through the filtration device 42 was fed to the casting die 43.

  The casting die 43 was cast by adjusting the flow rate of the dope 27 at the discharge port of the casting die 43 so that the width of the casting die 43 was 1.8 m and the thickness of the dried film was 95 μm. The casting width of the dope 27 from the discharge port of the casting die 43 was 1700 mm. The casting speed was 8 m / min. In order to adjust the temperature of the dope 27 to 20 ° C., a jacket (not shown) was provided on the casting die 43 and the inlet temperature of the heat transfer medium supplied into the jacket was set to 20 ° C.

  The casting die 43 and the piping were all kept at 20 ° C. during film formation. As the casting die 43, a coat hanger type die was used. The casting die 43 was provided with thickness adjusting bolts at a pitch of 20 mm and equipped with an automatic thickness adjusting mechanism using a heat bolt. The heat bolt can set a profile according to the liquid feed amount of the gear pump 62 by a preset program, and is fed back by an adjustment program based on a profile of an infrared thickness meter (not shown) installed in the film production line 40. The thing which has the performance which can also be controlled was used. In the film excluding the edge 20 mm, the thickness difference between two arbitrary points 50 mm apart was within 1 μm, and the thickness variation in the width direction was adjusted to 3 μm / m or less. The overall thickness was adjusted to ± 1.5% or less.

  In addition, a decompression chamber 68 for decompressing this portion was installed on the primary side of the casting die 43. The degree of decompression of the decompression chamber 68 is adjusted so that a pressure difference of 1 Pa to 5000 Pa is generated before and after the casting bead, and this adjustment is made according to the casting speed. At that time, the pressure difference on both sides of the casting bead was set so that the length of the casting bead was 5 mm to 15 mm. The decompression chamber 68 was provided with a mechanism that can be set to a temperature higher than the condensation temperature of the gas around the casting portion. Labyrinth packings (not shown) were provided on the front and back surfaces of the beads at the die discharge port. Also, openings were provided at both ends of the die discharge port of the casting die. Further, an edge suction device (not shown) for adjusting the disturbance of both edges of the casting bead was attached to the casting die 43.

(1-5) Casting Die As the material of the casting die 43, precipitation hardening type stainless steel having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less was used. This had a corrosion resistance substantially equal to that of SUS316 in a forced corrosion test with an aqueous electrolyte solution. Further, even when immersed in a mixed solution of dichloromethane, methanol and water for 3 months, it had corrosion resistance that did not cause pitting (opening) at the gas-liquid interface. The finishing accuracy of the wetted surface of the casting die 43 was 1 μm or less in terms of surface roughness, the straightness was 1 μm / m or less in any direction, and the slit clearance was adjusted to 1.0 mm. About the corner | angular part of the liquid-contact part of the lip tip of the casting die 43, what was processed so that R might be set to 50 micrometers or less over the full width of a slit was used. The shear rate of the dope 27 inside the casting die 43 was in the range of 1 (1 / sec) to 5000 (1 / sec). Further, a WC (tungsten carbide) coating was performed on the lip end of the casting die 43 by a thermal spraying method to provide a cured film.

  Further, in order to prevent the dope 27 flowing out from being locally dried and solidified, the mixed solvent A for solubilizing the dope 27 is discharged from both sides of the casting bead to the discharge port of the casting die 43. Each 0.5 ml / min was supplied to the interface with the outlet. The pulsation rate of the pump supplying the mixed solvent A was 5% or less. Further, the pressure on the back side of the casting bead was lowered by 150 Pa from the front side by the decompression chamber 68. A jacket (not shown) was attached to make the internal temperature of the decompression chamber 68 constant at a predetermined temperature. A heat transfer medium adjusted to 35 ° C. was supplied into the jacket. The edge suction device can adjust the edge suction air volume so as to be in the range of 1 L / min to 100 L / min, and in the present embodiment, this is in the range of 30 L / min to 40 L / min. Adjusted appropriately.

(1-6) Metal Support A stainless steel endless band having a width of 2.1 m and a length of 70 m was used as the casting band 46 as a support. The casting band 46 was polished so that the thickness was 1.5 mm and the surface roughness was 0.05 μm or less. The material is made of SUS316 and has sufficient corrosion resistance and strength. The thickness unevenness of the entire casting band 46 was 0.5% or less. The casting band 46 was driven by two rotating rollers 44 and 45. At that time, the tension in the conveying direction of the casting band 46 was adjusted to 1.5 × 10 ⁵ N / m ² . Further, the relative speed difference between the casting band 46 and the rotating rollers 44 and 45 was adjusted to be 0.01 m / min or less. At this time, the speed fluctuation of the casting band 46 was set to 0.5% or less. Further, both end positions of the casting band 46 were detected and controlled so that the meandering in the width direction of one rotation was limited to 1.5 mm or less. The positional fluctuation in the vertical direction between the die lip tip and the casting band 46 immediately below the casting die 43 was set to 200 μm or less. The casting band 46 was installed in a casting chamber 64 having wind pressure fluctuation suppressing means (not shown). The dope 27 was cast from the casting die 43 on the casting band 46.

As the rotating rollers 44 and 45, those capable of feeding a heat transfer medium therein were used so that the temperature of the casting band 46 could be adjusted. A 5 ° C. heat transfer medium was passed through the rotating roller 45 on the casting die 43 side, and a 40 ° C. heat transfer medium was passed through the other rotating roller 44 for drying. The surface temperature of the central part of the casting band 46 immediately before casting was 15 ° C., and the temperature difference between both side ends was 6 ° C. or less. The casting band 46 preferably has no surface defects, has no pinholes of 30 μm or more, has no pinholes of 10 μm to 30 μm, 1 pin / m ² or less, and ² pinholes of less than 10 μm / Those with m ² or less were used.

  The positions of the casting die 43 and the casting band 46 were determined so that the die height L (mm) of the casting die 43 was 1 mm and the angle θ (degree) of the casting die was 50 degrees.

(1-7) Casting Drying The temperature of the casting chamber 64 was kept at 35 ° C. using the temperature control equipment 65. The discharge speed of the dope 27 from the casting die 43 was 2.5 m / min. The drying speed of the casting bead 69a is shown in the “initial drying speed” column of Table 1. The unit of the initial drying speed is represented by the mass (kg) of the solvent that evaporates per minute per 1 kg of the solid component of the dope 27, and this is expressed as (kg · solv) / (kg / solid) / min. The casting film 69 formed from the dope 27 cast on the casting band 46 was first fed with a drying air flowing parallel to the casting film 69 to dry the casting film 69. The overall heat transfer coefficient from the dry air to the cast film 69 was 24 kcal / (m ² · hr · ° C.). As for the temperature of the drying air, 135 ° C. drying air was blown from the upstream air duct 70 above the casting band 46. Further, 140 ° C. dry air was blown from the downstream air duct 71, and 65 ° C. dry air was blown from the air duct 72 below the casting band 46. The saturation temperature of each drying wind was around -8 ° C. The oxygen concentration in the dry atmosphere on the casting band 43 was kept at 5 vol%. In order to maintain this oxygen concentration at 5 vol%, the air was replaced with nitrogen gas. Further, in order to condense and recover the solvent in the casting chamber 64, a condenser (condenser) 66 was provided, and the outlet temperature thereof was set to -10 ° C.

A wind shielding plate 73 is provided so that the dry air does not directly hit the casting bead and the casting film 69 for 5 seconds after casting, thereby suppressing the static pressure fluctuation in the vicinity of the casting die 43 to ± 1 Pa or less. . When the solvent ratio in the cast film 69 became 15% by weight on the dry basis, the film was peeled off as a film (hereinafter referred to as a wet film) 74 while being supported by the strip roller 75 from the cast band 46. The solvent content on the basis of the dry weight is a value calculated by {(xy) / y} × 100, where x is the film weight at the time of sampling and y is the weight after drying the sampling film. It is. The stripping tension is 1 × 10 ² N / m ^2, and the stripping speed (stripping roller draw) is 100.1% to 110% with respect to the speed of the casting band 46 in order to suppress stripping failure. Adjusted appropriately in range. The surface temperature of the peeled wet film 74 was 15 ° C. The drying speed on the casting band 46 was an average of 60% by mass dry weight reference solvent / min. The solvent gas generated by the drying was condensed and liquefied by a condenser 66 at −10 ° C. and recovered by a recovery device 67. The recovered solvent was adjusted so that the water content was 0.5% or less. The drying air from which the solvent was removed was heated again and reused as drying air. The wet film 74 was conveyed through the roller of the crossing section 80 and sent to the tenter dryer 47. In the crossover 80, 40 ° C. dry air was blown from the blower 81 to the wet film 74. In addition, a tension of about 30 N was applied to the wet film 74 while being transported by the roller of the crossing section 80.

(1-8) Tenter Transport / Drying / Ear Cutting The wet film 74 sent to the tenter dryer 47 is transported through the drying zone of the tenter dryer 47 while being fixed at both ends with clips. Dried. The clip was cooled by supplying a heat transfer medium at 20 ° C. The clip was conveyed by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the interior of the tenter dryer 47 was divided into three zones, and the drying air temperature in each zone was set to 90 ° C., 110 ° C., and 120 ° C. from the upstream side. The gas composition of the drying air was set to a saturated gas concentration at −10 ° C. The average drying speed in the tenter dryer 47 was 120% by mass (dry weight reference solvent) / min. The conditions of the drying zone were adjusted so that the amount of residual solvent in the film 82 was 7% by mass at the outlet of the tenter dryer 47. In the tenter dryer 47, it was stretched in the width direction while being conveyed. When the width of the wet film 74 before stretching was 100%, the film was stretched so that the width after stretching was 103%. The stretch ratio (tenter drive draw) from the peeling roller 75 to the entrance of the tenter dryer 47 was 102%.

  The stretching ratio in the tenter dryer 47 is any two at a difference of 10% or less between each of the substantial stretching ratios at any two points at a position 10 mm or more away from the biting start position by the clip and at a distance of 20 mm. The difference in the stretching ratio of points was 5% or less. The ratio of the length from the clip clamping start position to the clamping release position with respect to the length from the inlet to the outlet of the tenter dryer 47 was 90%. The solvent evaporated in the tenter dryer 47 was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (condenser) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The condensed solvent was reused after adjusting the water content to 0.5% by mass or less. Then, the film was sent out from the tenter dryer 47 as a film 82.

The ear-cutting device 50 cuts off both ends of the film 82 within 30 seconds from the exit of the tenter dryer 47. Ears 50 mm on both sides were cut with an NT-type cutter, and the cut ears were blown to a crusher 90 with a cutter blower (not shown) and crushed into chips of about 80 mm ² on average. This chip was used again as a raw material for dope production together with CAB flakes as a raw material for dope preparation. The oxygen concentration in the drying atmosphere of the tenter dryer 47 was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Before drying at a high temperature in a drying chamber 51 described later, the film 82 was preheated in a predrying chamber (not shown) to which 100 ° C. drying air was supplied.

(1-9) Post-drying / static elimination The film 82 was dried in the drying chamber 51 at a high temperature. The drying chamber 51 was divided into four sections, and drying air at 120 ° C., 130 ° C., 130 ° C., and 130 ° C. was supplied from a blower (not shown) from the upstream side. The conveying tension of the film 82 by the roller 91 was set to 100 N / m, and the film was dried for about 10 minutes until the residual solvent amount finally reached 0.3% by mass. The wrap angle of the roller 91 (film winding center angle) was 90 degrees and 180 degrees. The material of the roller 91 was made of aluminum or carbon steel, and hard chrome plating was applied to the surface. The roller 91 has a flat surface shape and a blasted matte surface. All film position fluctuations due to the rotation of the roller 91 were 50 μm or less. The roller deflection at a tension of 100 N / m was selected to be 0.5 mm or less.

  The solvent gas contained in the drying air was adsorbed and recovered using an adsorption recovery device 92. The adsorbent used here was activated carbon, and desorption was performed using dry nitrogen. The recovered solvent was reused as a dope preparation solvent with the water content adjusted to 0.3 mass% or less. The drying air contains plasticizers, UV absorbers and other high-boiling substances in addition to the solvent gas, so these were removed by a cooler and pre-adsorber to be removed by cooling and used for recycling. And adsorption / desorption conditions were set so that VOC (volatile organic compound) in the outdoor exhaust gas was finally 10 ppm or less. Moreover, the solvent amount collect | recovered by a condensation method among all the evaporation solvents was 90 mass%, and most of the remainder was collect | recovered by adsorption collection.

  The dried film 82 was conveyed to a first humidity control chamber (not shown). A drying air of 110 ° C. was supplied to the transition portion between the drying chamber 51 and the first humidity control chamber. Air having a temperature of 50 ° C. and a dew point of 20 ° C. was supplied to the first humidity control chamber. Further, the film 82 was conveyed to a second humidity control chamber (not shown) that suppresses the curling of the film 82. In the second humidity control chamber, air of 90 ° C. and humidity of 70% was directly applied to the film 82.

(1-10) Knurling and Winding Conditions The film 82 after humidity control was cooled to 30 ° C. or lower in the cooling chamber 52 and then subjected to ear cutting at both ends again with an ear cutting device (not shown). A forced charge removal device (charge removal bar) 93 was installed so that the charged voltage of the film 82 during conveyance was always in the range of −3 kV to +3 kV. Further, knurling was applied to both ends of the film 82 by a knurling roller 94. The knurling is imparted by embossing from one side of the film 82, the width for imparting the knurling is 10 mm, and the pressure applied by the knurling roller is such that the height of the irregularities is 12 μm higher than the average thickness of the film 81. It was set.

  Then, the film 82 was conveyed to the winding chamber 53. The winding chamber 53 was kept at a room temperature of 28 ° C. and a humidity of 70%. Inside the winding chamber 53, an ion wind static eliminating device (not shown) was also installed so that the charged voltage of the film 82 was −1.5 kV to +1.5 kV. The product width of the film (thickness 95 μm) 82 thus obtained was 1475 mm. The diameter of the winding roller 95 was 169 mm. The tension pattern was such that the winding start tension was 300 N / m and the winding end was 200 N / m. The total winding length was 3940 m. The fluctuation range of winding deviation at the time of winding (sometimes referred to as oscillating width) was ± 5 mm, and the winding deviation period with respect to the winding roller 95 was 400 m. The pressing pressure of the press roller 96 against the winding roller 95 was set to 50 N / m. The temperature of the film 82 at the time of winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.3% by mass. Throughout the entire process, the average drying rate was 20% by mass (dry weight reference solvent) / min. Moreover, there was no winding looseness and wrinkles, and no winding slip occurred in the impact test at 10G. The roll appearance was also good. When the thickness and appearance inspection of the obtained film 82 in the casting direction and the width direction were performed, the film had no unevenness in the thickness direction, and the flatness was very good. In addition, about the evaluation result of the surface state of such a film, it shows in the "film surface state" column of Table 1. In the “Film surface” column, ◎ indicates that the unevenness is not observed and the flatness is very good, ◎, the case where the unevenness is hardly recognized and the flatness is good, ○, there are unevenness and cannot be used depending on the application When it was judged that it was such flatness, Δ, and when it was regarded as a defective product with large irregularities, it was marked as x.

  The film roll of the film 82 was stored in a storage rack at 25 ° C. and 55% RH for 1 month and further examined in the same manner as described above. As a result, no significant change was observed. Further, no adhesion was observed in the roll. In addition, after the film 82 was formed, no cast film 69 was left on the casting band 46.

[Experiment 2]
The dope had the same formulation as Experiment 1 and the same solid content concentration. The casting die height L (mm) was 1 mm, and the casting die angle θ (degrees) was 50 degrees. The casting die temperature was 30 ° C., and the dope discharge speed was 3.5 m / min. The moving speed of the casting band 46, that is, the casting speed was 11 m / min. The initial drying speed was 4 (kg · solvv) / (kg · solid) · min. When the amount of residual solvent in the cast film 69 became 50% by weight or less, the film was peeled off as the wet film 74, and the same drying treatment as in Experiment 1 was performed to obtain a film 82 having a thickness of 95 μm. When the thickness distribution in the casting direction and the width direction of the obtained film 82 and the appearance inspection were performed, there was no unevenness in the thickness direction and the flatness was good.

[Experiment 3]
The dope was manufactured with the same formulation as in Experiment 1, and the solid concentration was 25% by weight. The casting die 43 was arranged above the casting band 46 so that the casting die height L (mm) was 3 mm and the casting die angle θ (degree) was 10 degrees. The casting die temperature was 30 ° C., and the dope discharge speed was 7 m / min. The casting speed was 20 m / min, and the initial drying speed was 4 (kg · solvv) / (kg · solid) · min. And when the amount of residual solvent in the casting film 69 became 50 weight% or less, it peeled off from the casting band 46 as the wet film 74. FIG. Then, the drying process was performed on the same conditions as Experiment 1, and the film 82 with a thickness of 95 micrometers was obtained. When the thickness distribution and appearance inspection of the obtained film in the casting direction and the width direction were performed, there was no unevenness in the thickness direction and the flatness was good.

[Experiment 4]
In Experiment 4 as a comparative example, the dope formulation and the solid content concentration were the same as those in Experiment 1. The casting conditions were the same as those in Experiment 1 except that the casting die temperature was 30 ° C. and the initial drying rate was 4 (kg · solv) / (kg · solid) · min. When the thickness distribution in the casting direction and the width direction of the obtained film and the appearance inspection were performed, the obtained film had irregularities and was flat so that it could not be used depending on the application.

[Experiment 5]
In Experiment 5, which is a comparative example, the dope formulation and the solid content concentration were the same as in Experiment 1. The casting die 43 was arranged such that the height L (mm) of the casting die 43 was 3 mm and the angle θ (degree) of the casting die was −10 degrees. The temperature of the casting die 43 is 36 ° C., the discharge speed of the dope 27 from the casting die 43 is 7 m / min, the casting speed is 20 m / min, and the initial drying speed is 4 (kg · solv) / (kg · solid). ) · The test was performed under the same conditions as in Experiment 1 except that the value was set to min. When the residual solvent ratio in the cast film became 15% by weight or less, it was peeled off from the cast band 46 as a wet film. Thereafter, the same drying treatment as in Experiment 1 was performed to obtain a film. When the thickness distribution in the casting direction and the width direction of the obtained film and the appearance inspection were performed, the obtained film had irregularities and was flat so that it could not be used depending on the application.

[Experiment 6]
The dope components were the same as those in Experiment 1, but the solid content concentration was 26% by weight. The initial drying speed was 4.5 (kg · solv) / (kg · solid) · min, the casting die angle θ was −10 degrees, and the casting die temperature was 36 ° C. Other conditions are the same as those in Experiment 3. The film was a defective product with large irregularities.

[Experiment 7]
The casting die 43 was arranged such that the height L (mm) of the casting die 43 was 0.3 mm and the angle θ (degree) of the casting die was 10 degrees. The other conditions are the same as in Experiment 5. The resulting film had irregularities and was flat so that it could not be used depending on the application.

[Experiment 1] to [Experiment 7]
The composition of the dope components was changed to the following, and the same procedure as in Example 1 was performed. In addition, the other conditions of Experiments 1 to 7 in Example 2 are the same corresponding to the same experiment numbers of Experiments 1 to 7 of Example 1.
[composition]
Cellulose acetate propionate (CAP; acetyl substitution degree 0.20, propionyl substitution degree 2.50, total substitution degree 2.70, viscosity average polymerization degree 270, water content 0.2 mass%, 6 mass% in dichloromethane solution (Powder having a viscosity of 250 mPa · s and an average particle diameter of 1.5 mm and a standard deviation of 0.5 mm) 100 parts by weight dichloromethane (first solvent) 293 parts by weight methanol (second solvent) 53 parts by weight 1-butanol (first 3 solvents) 13 parts by weight N, N′-dimethatryl-N ″ -p-methoxyphenyl-1,3,5-triazine-2,4,6-triamine 4 parts by weight plasticizer A (triphenyl phosphate) 2 Parts by weight plasticizer B (biphenyldiphenyl phosphate) 1 part by weight release agent (ethyl citrate) 0.2 parts by weight

  Here, the used CAP has a residual acetic acid content of 0.1% by mass or less, a residual propionic acid of 0.1% by mass or less, a Ca content of 80 ppm, a Mg content of 22 ppm, and a Fe content of 0.00. It was 5 ppm and further contained 105 ppm of sulfur as a sulfate group. Further, the substitution degree of the 6-position acetyl group was 0.11, the substitution degree of the 6-position propionyl group was 0.69, and the ratio to the total acyl group was 33%. The methanol extract was 5% by mass or less, and the weight average molecular weight / number average molecular weight ratio was 2.8. The yellow index was 1.6, the haze was 0.07, the transparency was 92.9%, and the Tg (glass transition temperature; measured by DSC) was 128 ° C. This CAP is synthesized using cellulose collected from cotton as a raw material.

It is the schematic of the manufacturing line which manufactures the dope used for the solution casting method concerning this invention. It is the schematic of the manufacturing line for enforcing the solution casting method concerning this invention. FIG. 3 is an enlarged view of a main part of FIG. 2.

Explanation of symbols

27 Dope 40 Film Production Line 43 Casting Die 43a Discharge Port 46 Casting Band 69 Casting Film 69a Casting Bead 74 Wet Film 82 Film L Casting Die Height L1 Dope Discharge Direction L2 Casting Surface of Casting Band Straight line that passes through the center of the discharge port of the casting die among the normal lines.

Claims (5)

A solution casting method in which a dope composed of a solid component containing cellulose acylate and a solvent is discharged from a casting die to form a casting film on a support, and the casting film is peeled off from the support. In
The drying rate of the dope immediately after being discharged from the casting die is 4 kg / min or less per kg of the solid component,
A solution casting method, wherein the cellulose acylate satisfies the following formulas (I) and (II).
(I) 2.5 ≦ A + B ≦ 3.0
(II) 1.25 ≦ B ≦ 3.0
However, in formula (I) and (II), A represents the substitution degree of the acetyl group with respect to the hydrogen atom of the hydroxyl group of a cellulose, B represents the propionyl group, butyryl group, pentanoyl group, and hexanoyl group with respect to the hydrogen atom of the cellulose hydroxyl group. Represents the sum of the degree of substitution.   2. The solution casting method according to claim 1, wherein a discharge speed at which the dope is discharged from the casting die is 3 m / min or more. An angle θ formed by the direction in which the dope is discharged from the casting die and a straight line passing through the center of the discharge port of the casting die among the normal lines on the surface of the support on which the casting film is formed. 0 degree or more and 60 degrees or less,
The solution casting method according to claim 1 or 2, wherein a distance between the support and the casting die on the straight line is 0.5 mm or more and 5 mm or less. The peeling resistance between the dope and the lip tip of the casting die is 40 g / cm or less,
Further, the relationship between the shear viscosity η (Pa · s) of the dope during casting and the elongation rate ε (1 / sec) of the dope from the casting die to the support is 150 Pa <3 · η · ε. The solution casting method according to any one of claims 1 to 3, wherein <15000 Pa is satisfied. 5. The solution casting according to claim 1, wherein the concentration of the solid component on the surface of the dope immediately after being discharged from the casting die is 16 wt% or more and 25 wt% or less. Method.

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