JP2016083932A - Method and device for manufacturing solution membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for manufacturing a solution membrane by suppressing wave-like deformation of a belt for long time and stripe-like deformation of the film for long time.SOLUTION: A belt 21 formed with a ring shape equipped to a flow casting unit 15 of a device for manufacturing a solution 10 continuously runs to a longer direction by being wound up to a roller 22. The belt 21 is formed by austenitic stainless steel and contains Ni, Cr, Mo and Cu. The percentage content of Cu is in a range of 0.04 mass% to 1.00 mass%. A dope 11 is continuously flowed from a flow casting die 24 to the belt 21 and a flow casting membrane 26 is formed. A film 12 is formed by peeling off the flow casting membrane 26 from the belt 21 and the film 12 is dried.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solution casting method and apparatus.

  The solution casting method is a method of forming a film from a polymer solution obtained by dissolving a polymer in a solvent. When producing a long film by the solution casting method, the polymer solution is continuously discharged from the casting die to the traveling support to form a casting film, and the casting film is peeled off from the support. Take and dry. The belt used as the support is formed in an annular shape and is stretched over a plurality of rollers and travels in the longitudinal direction. Thus, the belt circulates between a casting position where the polymer solution is cast and a peeling position where the cast film is peeled off. As a material for the belt, for example, austenitic stainless steel is used.

  The belt is made to have a uniform thickness as much as possible in order to produce a film having a uniform thickness and a smooth film surface. However, even if the thickness is uniform, waviness, that is, wave-like deformation (hereinafter referred to as wave-like deformation) may occur in the belt due to continuous use. This wave-like deformation is formed extending in the longitudinal direction of the belt, and in some cases, extending over the entire circumference of the annular belt. A plurality of wavy deformations occur in the width direction of the belt. Although the difference in height between the belt surface where the wavy deformation has occurred and the belt surface where the wavy deformation has not occurred is a very slight difference of about 2 μm to 3 μm, such wavy deformation is a film. Deformation (hereinafter referred to as streak deformation) extending in a line shape in the longitudinal direction of the film is generated on the film surface, resulting in a deterioration in film quality.

  In order to suppress such streak deformation of the film, Patent Document 1 discloses a solution using a belt that is made of stainless steel having an austenitic crystal structure and that specifies the degree of unevenness of the casting surface on which the polymer solution is cast. A film forming method and apparatus are proposed. This solution casting method and apparatus suppress the martensitic transformation of austenitic stainless steel in the belt, and suppress the streak deformation in the film due to the martensitic transformation.

Japanese Patent Laid-Open No. 2007-083451

  Since the solution casting method and apparatus of Patent Document 1 suppress martensite transformation, there is a certain effect of suppressing streak deformation of the film. However, even if the method of Patent Document 1 is used, depending on the belt, a wave-like deformation occurs due to continuous use for a long period of time, and this wave-like deformation still causes a line-like deformation in the film.

  Then, an object of this invention is to provide the solution casting method and apparatus which suppress the wave-like deformation of a belt for a long time, and suppress the streak deformation in a film for a long time.

  In order to solve the above-mentioned problems, the solution casting method of the present invention continuously flows out a polymer solution in which a polymer is dissolved in a solvent from a casting die onto a belt formed in an annular shape and continuously running in the longitudinal direction. Thus, the method includes a step of forming a cast film on the belt, and a step of peeling the cast film from the belt and drying. The belt is made of Ni, Cr, Mo, and 0.04% by mass or more. It is formed from an austenitic stainless steel containing Cu within a range of 0.000 mass% or less.

  Stainless steel is composed of Ni in the range of 10.00 mass% or more and 14.00 mass% or less, Cr in the range of 16.00 mass% or more and 18.00 mass% or less, and 2.00 mass% or more and 3.00 mass%. It is preferable that Mo in the range of% or less is included.

  The belt preferably has an elongation at break within a range of 10% to 20%. The crystal grain size of stainless steel in the belt is preferably in the range of 20 μm to 80 μm.

  The present invention provides a solution casting apparatus for producing a film from a polymer solution in which a polymer is dissolved in a solvent, and is formed in an annular shape and continuously runs in the longitudinal direction. Ni, Cr, Mo, and 0.04% by mass or more. A belt formed from an austenitic stainless steel containing Cu in a range of not more than 00% by mass, a casting die for continuously flowing the polymer solution to the belt, and drying for drying the film formed by peeling off the belt And a machine.

  Stainless steel is composed of Ni in the range of 10.00 mass% or more and 14.00 mass% or less, Cr in the range of 16.00 mass% or more and 18.00 mass% or less, and 2.00 mass% or more and 3.00 mass%. It is preferable that Mo in the range of% or less is included.

  The breaking elongation of the belt is preferably in the range of 10% to 20%. The crystal grain size of stainless steel in the belt is preferably in the range of 20 μm to 80 μm.

  According to the present invention, the wavy deformation of the belt is suppressed for a long time, and the streak deformation in the film is suppressed for a long time.

1 is a schematic view of a solution casting apparatus embodying the present invention. It is a graph showing the relationship between the breaking elongation of a belt and the crystal grain diameter of stainless steel.

  A solution casting apparatus 10 shown in FIG. 1 is for continuously producing a film 12 from a dope 11. The dope 11 is a polymer solution in which a polymer is dissolved in a solvent. In this embodiment, cellulose triacetate (TAC) is used as the polymer, and a mixture of dichloromethane and methanol is used as the solvent, but the polymer and the solvent are not limited to these. Details of the polymer and the solvent that can be used in the present invention will be described later. The dope 11 may include various additives such as a plasticizer, an ultraviolet absorber, and a retardation control agent, and a matting agent for preventing the films 12 from sticking to each other.

  The solution casting apparatus 10 includes a casting unit 15, a tenter 16, a roller dryer 17, and a winder 18 in order from the upstream side. The casting unit 15 includes a belt 21 formed in an annular shape, a pair of rollers 22 that support the belt 21 on the circumferential surface and travel in the longitudinal direction, a casting die 24, and a peeling roller 25. At least one of the pair of rollers 22 rotates in the circumferential direction, and by this rotation, the wound belt 21 continuously travels in the longitudinal direction. The casting die 24 is disposed above one of the pair of rollers 22 in this example, but may be disposed above the belt 21 between one and the other of the pair of rollers 22.

  The belt 21 is a casting film support described later. For example, the length is in the range of 55 m to 200 m, the width is in the range of 1.5 m to 5.0 m, and the thickness is 1.0 mm to 2.0 mm. Within the following range. In the following description, one belt surface on which the dope 11 is cast to form the casting film 26 is referred to as a casting surface.

  The belt 21 is made of austenitic stainless steel. The belt 21 is made by abutting and welding one end and the other end in the longitudinal direction of a stainless steel made into a long belt material by rolling and polishing the welded portion. The stainless steel of the belt 21 includes Ni (nickel), Cr (chromium), Mo (molybdenum), and Cu (copper). The Cu content is in the range of 0.04% by mass or more and 1.00% by mass or less, so that the belt 21 can be reliably prevented from undulating deformation even when used for a long time. Cu is more preferably in the range of 0.30 mass% or more and 1.00 mass% or less.

  It is presumed that the martensitic transformation of austenite is related to the wavy deformation, and it is considered that the martensitic transformation as a change in crystal structure is suppressed by setting the content ratio of the above component elements and Cu. In particular, it is presumed that the austenite crystal structure is stabilized by setting the Cu content to the above-described content. As what contains said component element, what adjusted the component element so that Cu may be contained in 0.04 mass% or more and 1.00 mass% or less in SUS316 is mentioned, for example. In SUS316, Cu having a Cu content of less than 0.04% by mass tends to cause wavy deformation when used as a belt for a long period of time. On the other hand, if the Cu content is more than 1.00% by mass, the ductility becomes too high and the film tends to be deformed, so that it cannot be used as the belt 21.

  The stainless steel of the belt 21 has a Ni content in the range of 10.00% to 14.00% by mass, a Cr content in the range of 16.00% to 18.00% by mass, Mo Is preferably in the range of 2.00% by mass or more and 3.00% by mass or less, so that the belt 21 can be more reliably suppressed from wavy deformation even when used for a long period of time.

  The Cu content is more preferably in the range of 0.30 mass% or more and 1.00 mass% or less. The Ni content is more preferably in the range of 11.00% to 14.00% by mass, and the Cr content is in the range of 17.00% to 18.00% by mass. Is more preferable, and the Mo content is more preferably in the range of 2.50% by mass to 3.00% by mass.

  The belt 21 may contain, for example, C (carbon), N (nitrogen), and Mn (manganese) in addition to the above four elements, and these elements are also contained in a certain range so that the austenite series is included. It has the effect of stabilizing the crystal structure. Details of the elements contained in the belt 21 and how to obtain the content will be described later.

  Belts used for solution casting are periodically polished to make the casting surface, which is the belt surface on which the casting film is formed, into a mirror state, but the casting surface after this polishing treatment is cracked. (Cracking) may be observed. This crack extends in the width direction orthogonal to the longitudinal direction of the belt, and has a length of approximately 300 μm to 400 μm and a depth of approximately 10 μm. This crack disappears by further polishing treatment. However, when casting is performed in the presence of the crack, the smoothness of the film surface of the obtained film is impaired. Therefore, the belt 21 preferably has an elongation at break within a range of 10% to 20%. When the breaking elongation is 10% or more, cracks on the casting surface after the polishing treatment are suppressed as compared with the case where the breaking elongation is less than 10%. Further, since the elongation at break is 20% or less, the belt 21 hardly stretches in the longitudinal direction even if the belt 21 is wound around the pair of rollers 22 and travels for a long time, compared with the case where the elongation is larger than 20%. Continuous production is more reliable. The standard product SUS316 has an elongation at break of 40% or more, but the belt 21 has an extremely small elongation at break as compared with the standard product SUS316 as described above.

  The breaking elongation of the belt 21 is more preferably in the range of 12.0% to 20.0%. Details of how to obtain the elongation at break will be described later.

  The crystal grain size of the stainless steel in the belt 21 is preferably in the range of 20 μm to 80 μm. Since the crystal grain size of the stainless steel constituting the belt 21 is 20 μm or more, the elongation at break of the belt 21 is more surely within the above range compared to the case of less than 20 μm. Suppressed reliably. Since the crystal grain size is 80 μm or less, the strength is improved as compared with the case where the crystal grain size is larger than 80 μm, and thus cracks are less likely to occur. The crystal grain size is more preferably in the range of 25.0 μm or more and 75.0 μm or less, and further preferably in the range of 30.0 μm or more and 70.0 μm or less. Details of how to obtain the crystal grain size will be described later.

  The casting die 24 continuously flows out the supplied dope 11 from an outlet 24 a facing the belt 21. By continuously flowing out the dope 11 to the running belt 21, the dope 11 is cast on the belt 21, and a casting film 26 is formed on the belt 21. In FIG. 1, a reference numeral PC is given to a position where the dope 11 comes into contact with the belt 21 and a casting film 26 starts to be formed (hereinafter referred to as a casting position).

  The pair of rollers 22 includes a temperature controller (not shown) that adjusts the peripheral surface temperature. The temperature of the casting film 26 is adjusted via the belt 21 by the roller 22 whose peripheral surface temperature is adjusted. In the case of a so-called dry gelation method in which the casting film 26 is heated (hardened) by promoting drying, the peripheral surface temperature of the roller 22 is, for example, in the range of 15 ° C. or more and 35 ° C. or less. Good. Further, in the case of a so-called cooling gelation method in which the casting film 26 is cooled and solidified, the peripheral surface temperature of the roller 22 is preferably within a range of −15 ° C. or more and 5 ° C. or less. Due to such gelation, the cast film 26 becomes hard enough to be conveyed.

  With respect to the dope 11 from the casting die 24 to the belt 21, a so-called bead, a decompression chamber (not shown) may be provided upstream in the traveling direction of the belt 21. The decompression chamber sucks the atmosphere in the area upstream of the dope 11 that has flowed out to decompress the area. Further, a blower (not shown) for promoting the drying of the casting film 26 may be provided to face the belt 21.

  The casting film 26 is hardened on the belt 21 to such an extent that it can be conveyed to the tenter 16, and then peeled off from the belt 21 in a state containing a solvent. The peeling roller 25 is for continuously peeling the casting film 26 from the belt 21. The peeling roller 25 supports the film 12 formed by peeling from the belt 21 from below, for example, and keeps the peeling position PP where the casting film 26 peels from the belt 21 constant. The peeling method may be any of a method of pulling the film 12 downstream, a method of rotating the peeling roller 25 in the circumferential direction, and the like.

  In the case of the dry gelation method, the stripping from the belt 21 is performed, for example, while the solvent content of the cast film 26 is in the range of 3% by mass or more and 100% by mass or less. In some cases, for example, it is performed while the solvent content of the cast film 26 is in the range of 100% by mass to 300% by mass. In the present specification, the solvent content (unit:%) is a value based on the dry weight, and specifically, when the mass of the solvent is x and the mass of the film 12 for obtaining the solvent content is y. And {x / (y−x)} × 100.

  As described above, the casting unit 15 forms the film 12 from the dope 11. The belt 21 circulates between the casting position PC and the stripping position PP, so that the casting of the dope 11 and the stripping of the casting film 26 are repeated.

  A blower (not shown) for promoting the drying of the film 12 may be disposed on the conveyance path between the casting unit 15 and the tenter 16. The film 12 formed by being peeled off is guided to a tenter 16. The tenter 16 includes a plurality of clips 31 that hold the sides of the long film 12, a pair of rails (not shown), and a chain (not shown). Instead of the clip 31, a plurality of pins (not shown) are arranged in an upright posture on the upper surface of the base, and a pin plate (not shown) that holds the film 12 by piercing each pin on the side of the film 12 is used. May be.

  The rails are installed on each side of the film 12 conveyance path. The chain is stretched over a driving sprocket and a driven sprocket (not shown), and is attached so as to be movable along the rail. The clips 31 are attached to the chain at predetermined intervals, and the clips 31 circulate along the rails by the rotation of the driving sprocket. The clip 31 starts holding the guided film 12 near the entrance of the tenter 16, moves toward the exit, and releases the hold near the exit. The clip 31 whose holding has been released moves again to the vicinity of the entrance, and holds the newly guided film 12. Thus, the clip 31 grips each side part of the film 12 and conveys it in the longitudinal direction.

  The tenter 16 has a function as a first dryer, and includes a blower 32 above the conveyance path of the film 12. On the lower surface of the blower 32, an outlet (not shown) through which the dry gas flows out is formed, and the dry gas is blown out toward the film 12 that passes therethrough. In addition, you may provide the air blower which has the same structure under the conveyance path of the film 12. FIG.

  The roller dryer 17 is a second dryer and includes a plurality of rollers 33 and an air conditioner (not shown). Each roller 33 supports the film 12 on the peripheral surface. The film 12 is wound around a roller 33 and conveyed. The air conditioner adjusts the temperature and humidity inside the roller dryer 17. The winder 18 is for winding the film 12 into a roll.

  The element contained in the belt 21 and how to obtain the content thereof will be described below. The element contained in the belt 21 and the content rate are samples sampled from any of the stainless steel before the belt material described above, the belt material, and the remaining belt material remaining after the belt 21 is formed. Can be obtained using In this embodiment, a sample sampled from stainless steel before being used as a belt material is used.

  C (carbon) and S (sulfur) can be determined by a combustion-infrared absorption method. In the present embodiment, the contents of C and S are obtained by this combustion-infrared absorption method according to Japanese Industrial Standard JIS G 1215-4. As an apparatus to be used, for example, there is EMIA-920V2 manufactured by Horiba Ltd.

  Si (silicon) can be determined by a weight method. In the present embodiment, the Si content is determined by a weight method according to JIS G1212.

  N (nitrogen) can be determined by an inert gas melting-heat conduction method. In the present embodiment, the N content is determined by this inert gas melting-heat conduction method according to JIS G 1228. As an apparatus to be used, for example, EMGA-930 manufactured by Horiba Ltd. is available.

  For elements other than C, S, Si, and N, ICP emission spectroscopy (Inductively Coupled Plasma-AES (Atomic Emission Spectroscopy), Inductively Coupled Plasma-OES (Optical Emission Spectrometry), high frequency inductively coupled plasma emission spectroscopy ). That is, Ni, Cr, Mo, and Cu are obtained by ICP emission spectroscopic analysis. In the present embodiment, the contents of Ni, Cr, Mo, and Cu are obtained by this ICP emission spectroscopic analysis method according to JIS K 0133. As an apparatus to be used, for example, there is ICPE-9000 manufactured by Shimadzu Corporation. The content ratios of Ni, Cr, Mo, and Cu can be adjusted by changing the blending of raw materials during refining so as to have a target composition.

  For the elongation at break of the belt 21 and the crystal grain size described above, a sample sampled from either the belt material or the belt material residue can be used. In the present embodiment, the elongation at break is determined according to JIS Z 2241. As an apparatus to be used, for example, Autograph AG-Xplus series manufactured by Shimadzu Corporation can be cited, which is also used in this embodiment. A sample (sample) for measurement is a JIS No. 13B test piece (the width of the parallel part is 12.5 mm and the length of the parallel part is 60 mm), and two samples are prepared by sampling. In sampling, the longitudinal direction of the sample is aligned with the longitudinal direction of the belt 21. For each of these samples, the elongation at break is determined by conducting a tensile test at a tensile rate of 5 mm / min, and the average value is taken as the value of the elongation at break.

  Plate-shaped stainless steel originally has an allowance of 40% or more after hot rolling (hot rolling), and the elongation after hot rolling is the elongation (unit:%) in cold rolling (cold rolling). The elongation at break (unit:%) is the sum. The larger the amount of cold rolling (the amount to be stretched) is, the smaller the elongation at break of stainless steel is. Therefore, in order to adjust the elongation at break, it is preferable to adjust the amount of cold rolling. The hot rolling is a method of processing at a temperature higher than the recrystallization temperature of the metal, and the cold rolling is a method of processing at a temperature lower than the recrystallization temperature of the metal.

  The belt material residue is cut in a direction corresponding to the longitudinal direction of the belt 21, the cut surface is polished so as to be a mirror surface, and the polished surface is etched. For etching, an aqua regia aqueous solution is used for the appearance of the metal structure, and a nitric acid electrolysis method may be applied to the appearance of the grain boundary. As the aqua regia aqueous solution, in this embodiment, a mixed solution of concentrated hydrochloric acid and concentrated nitric acid is used. The nitric acid electrolysis is a method in which etched stainless steel is immersed in nitric acid to corrode, and the grain boundary is revealed by utilizing the difference in the corrosion rate between the crystal part and the grain boundary part. After etching, the etched surface can be observed with an optical microscope at a magnification of, for example, 100 times or 200 times to determine the crystal grain size. In this embodiment, Olympus Corporation system industry microscope BX51M is used as an optical microscope.

  The crystal grain size can be adjusted by the processing temperature in hot rolling and the processing amount (the amount to be extended). The crystal grain size increases as the processing temperature in hot rolling is higher.

  As shown in FIG. 2, there is a correlation between the elongation at break and the crystal grain size, and the elongation at break increases as the crystal grain size increases. A large elongation at break means that the amount of processing in cold rolling is small and the amount of processing in hot rolling is increased accordingly. Thus, as a result, the crystal grain size tends to increase as the elongation at break increases.

The Md30 of the stainless steel constituting the belt 21 is preferably 21 ° C. or lower. As is well known, Md30 is a temperature at which 50% of the metal crystal lattice transforms to martensite when an elongation strain of 30% is applied, and is determined in units of ° C. The martensitic transformation due to stress during processing, polishing, running in casting, etc. is more likely to occur at lower temperatures, and the smaller the Md30 value, the lower the temperature at which martensitic transformation occurs. This Md30 has a correlation with the Cu content in the belt 21, and can be used as a guideline for setting Cu to any content within the above-mentioned range. Md30 can be obtained by the following equation. In the following formula, “C”, “N”, “Si”, “Mn”, “Ni”, “Cu”, “Mo”, and “Nb” are the respective contents (mass%) of these elements. And “v” indicates the crystal grain size number.
Md30 (unit: ° C) = 431-462 (C + N) -9.2Si-8.2Mn-13.7Cr-9.5 (Ni + Cu) -18.5Mo-68Nb-1.42 (v-8.0)

In the present embodiment, since the stainless steel used does not contain Nb and N (but does not contain), the content rate is calculated as 0%. Although Cu has a low content, it is used in the calculation because it has the effect of increasing ductility. As other elements, C, Si, and Mn are contained in a range of C <0.08 mass%, Si <1.00 mass%, and Mn <2.00 mass%. The crystal grain size number v is determined according to JIS G 0551. The grain size number v is a value of G calculated by the formula m = 8 × 2 ^G using the average number of crystal grains m per 1 mm ^{2 of the} cross section of the test piece. v is a positive number, 0 (zero), or a negative number.

  The operation of the above configuration will be described. The dope 11 is continuously discharged from the casting die 24 toward the traveling belt 21. As a result, the casting film 26 is continuously formed on the belt 21 (casting step). The casting film 26 is hardened by temperature adjustment on the belt 21 and is peeled off from the belt 21 at the peeling position PP in a state containing a solvent.

  The film 12 formed by peeling off the casting film 26 from the belt 21 is guided by the tenter 16 and conveyed with the side portion gripped by the clip 31. The film 12 being transported is dried by the dry gas blown from the blower 32 (first drying step). The film 12 is released from the grip by the clip 31 at the downstream end of the tenter 16 and guided to the roller dryer 17. In the roller dryer 17, the film 12 is further dried while being supported by each roller 33 and conveyed (second drying step). Thus, the step of drying the film 12 (drying step) is performed by both the tenter 16 and the roller dryer 17. The dried film 12 is wound into a roll by a winder 18. Note that a slitter (not shown) may be provided downstream of the tenter 16 so as to cut off the grip of the film 12 by the clip 31.

  The belt 21 contains Ni, Cr, Mo, and Cu is contained at a content within the range of 0.04 mass% or more and 1.00 mass% or less. The film 12 is manufactured for a long time. In the belt 21, the Ni content is in the range of 10.00% to 14.00% by mass, the Cr content is in the range of 16.00% to 18.00% by mass, and the Mo content is Is within the range of 2.00% by mass or more and 3.00% by mass or less, so that the wave-like deformation of the belt 21 can be more reliably suppressed for a long time, so that the film 12 without the streak-like deformation is more reliable. Produced for a long time. Furthermore, since the breaking elongation of the belt 21 is within the above range, no cracks are generated in the belt 21 even when the belt 21 is polished. Therefore, unevenness due to cracks does not occur on the film surface, and the film 12 having excellent smoothness can be obtained. Since the crystal grain size of the stainless steel constituting the belt 21 is within the above range, the belt 21 exhibits the breaking elongation within the above range more reliably. Therefore, even if the belt 21 is polished, cracks are not generated more reliably.

  The film 12 can be used as an optical film, for example. Examples of the optical film include a protective film for a polarizing plate and a retardation film. Although the said embodiment is an example which manufactures the film 12 of a single layer structure using 1 type of dope 11, the multilayer film may be sufficient as the film to manufacture. When a film having a multilayer structure is produced, a plurality of types of dopes may be cast by well-known co-casting or sequential casting.

  Although the said embodiment is an example using TAC as a polymer, it may replace with TAC and may be another cellulose acylate different from TAC, cyclic polyolefin, etc. Details of the cellulose acylate will be described below.

<Cellulose acylate>
Cellulose acylate has a ratio of esterifying the hydroxyl group of cellulose with carboxylic acid, that is, the acyl group substitution degree (hereinafter referred to as acyl group substitution degree) satisfies all the conditions of the following formulas (1) to (3). Particularly preferred are: In (1) to (3), A and B are both acyl group substitution degrees, the acyl group in A is an acetyl group, and the acyl group in B has 3 to 22 carbon atoms.
2.4 ≦ A + B ≦ 3.0 (1)
0 ≦ A ≦ 3.0 (2)
0 ≦ B ≦ 2.9 (3)

  Glucose units constituting cellulose and having β-1,4 bonds have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer in which some or all of the hydroxyl groups of cellulose are esterified, and the hydrogen of the hydroxyl group is substituted with an acyl group having 2 or more carbon atoms. Since the degree of substitution is 1 when esterification of one hydroxyl group in the glucose unit is 100%, in the case of cellulose acylate, the hydroxyl groups at the 2nd, 3rd and 6th positions are each 100% ester. The degree of substitution is 3.

  Here, the total acyl group substitution degree obtained by “DS2 + DS3 + DS6”, where the acyl group substitution degree at the 2-position in the glucose unit is DS2, the acyl substitution degree at the 3-position is DS3, and the acyl substitution degree at the 6-position is DS6 is 2. It is preferably from 00 to 3.00, more preferably from 2.22 to 2.90, and even more preferably from 2.40 to 2.88. Furthermore, “DS6 / (DS2 + DS3 + DS6)” is preferably 0.32 or more, more preferably 0.322 or more, and further preferably 0.324 to 0.340.

  There may be only one kind of acyl group, or two or more kinds. When there are two or more acyl groups, it is preferable that one of them is an acetyl group. The sum of the substitution degrees of the hydrogen at the 2-, 3- and 6-position hydroxyl groups with acetyl groups is DSA, and the sum of the substitution degrees with acyl groups other than the acetyl groups at the 2-, 3- and 6-positions is DSB. In this case, the value of “DSA + DSB” is preferably 2.2 to 2.86, and particularly preferably 2.40 to 2.80. DSB is preferably 1.50 or more, and particularly preferably 1.7 or more. In DSB, 28% or more is preferably 6-position hydroxyl group substitution, more preferably 30% or more, further preferably 31% or more, particularly preferably 32% or more substitution of 6-position hydroxyl group. It is preferable. In addition, the value of “DSA + DSB” at the 6-position of cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. By using the cellulose acylate as described above, preferable solubility can be obtained in order to produce a polymer solution used for solution casting.

  The acyl group having 2 or more carbon atoms may be an aliphatic group or an aryl group, and is not particularly limited. For example, there are cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester, etc., and these may each further have a substituted group. Propionyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group, t-butanoyl group, cyclohexane Examples thereof include a carbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable.

  When cellulose acylate is used as the polymer, the solvent for the dope 11 may be a known solvent for the dope when the cellulose acylate film is produced by solution casting. For example, dichloromethane, various alcohols, various ketones and the like. A plurality selected from these may be mixed and this mixture may be used as a solvent.

  Examples of the present invention and comparative examples for the present invention will be described below.

[Example 1] to [Example 10]
The film 12 having a thickness of 40 μm and a width of 1500 mm was continuously applied for 3000 hours by ten solution casting apparatuses 10 in which the casting die 24 was replaced with a casting die (not shown) for co-casting three dopes. Example 1 to 10 were manufactured. The film 12 was wound into a roll by the winder 18 every 5000 m in length. Each solution casting apparatus 10 was provided with a slitter (not shown) between the tenter 16 and the roller dryer 17 for cutting off the grip marks of the tenter 16 by the clip 31 from the film 12. Further, each solution casting apparatus 10 was provided with a knurling machine (not shown) for imparting knurling (unevenness) to the side of the film 12 between the roller dryer 17 and the winder 18. The belts 21 of the solution casting apparatuses 10 of Examples 1 to 10 have different contents of Ni, Cr, Mo, and Cu, and the contents are shown in Table 1. The method for obtaining the content of Ni, Cr, Mo, Cu is as described above.

  The dope 11 used is of the following two types: a first dope and a second dope, in which the flow of the first dope is sandwiched between the flows of the second dope, from a casting die for co-casting (not shown) Leaked. The first dope and the second dope were prepared by dissolving the following TAC or the like in a solvent, filtered, and then guided to the casting die.

<First dope>
TAC (substitution degree 2.85, viscosity average polymerization degree 320) 100 parts by weight Additive A 8 parts by weight Dichloromethane 470 parts by weight Methanol 70 parts by weight UV absorber 0.3 parts by weight

  The above additive A has a number average molecular weight (Mn) of 1000 obtained by reacting adipic acid and ethylene glycol at a molar ratio of adipic acid: ethylene glycol = 50: 50 and end-capping with an acetyl group. It is a polyester compound. The number average molecular weight (Mn), mass average molecular weight (Mw), and molecular weight distribution (MWD) can be measured using gel permeation chromatography (GPC). Specifically, N-methylpyrrolidone can be used as a solvent, a polystyrene gel can be used, and the molecular weight can be obtained using a conversion molecular weight calibration curve obtained in advance from a constituent curve of standard monodisperse polystyrene. Additive A was also used for the following second dope. The fine particles used for the following second dope were silicon dioxide, the primary particle size was 20 nm, and the Mohs hardness was 7.0.

<Second dope>
TAC (substitution degree 2.85, viscosity average polymerization degree 320) 100 parts by mass Additive A 8 parts by mass Dichloromethane 520 parts by mass Methanol 80 parts by mass UV absorber 0.3 parts by mass Fine particles (such as NX90S manufactured by Aerosil) 0.05 Parts by mass

  The casting film 26 was dried so that the solvent content of the casting film 26 at the peeling position PP from the belt 21 was 30% by mass. The peeled film 12 was dried with a tenter 16 in a dry gas having a temperature of 120 ° C., and the solvent content of the film 12 at the outlet of the tenter 16 was set to 10% by mass or less. The film 12 that came out of the tenter 16 was guided to a slitter (not shown), and the side portions were cut so as to cut off the gripping marks by the clip 31 from the film 12. The film 12 was guided to a roller dryer 17 in which the internal temperature was adjusted within a range of 130 ° C. or higher and 140 ° C. or lower, and dried until the solvent content became 0.1% by mass or lower. After imparting knurling to the side of the film 12, the film 12 was wound up in a roll form by a winder 18 to 5000 m.

Each belt 21 was evaluated for wave-like deformation, and for the obtained film 12, streak-like deformation was evaluated by the following methods and criteria. The evaluation results are shown in Table 1.
1. Wave-like deformation of the belt 21 After the film 12 is continuously manufactured for 3000 hours as described above, the light of the fluorescent lamp is irradiated on the casting surface of the belt 21, and the fluorescent lamp is reflected on the casting surface. The contour (edge line) of the fluorescent lamp image reflected on the casting surface was visually observed from an oblique direction with respect to the casting surface to evaluate the degree of distortion. The evaluation criteria are as follows. A and B are acceptable and C is unacceptable.
A: No distortion B: Some distortion was confirmed, but not to affect the film surface C: Distortion was confirmed, which may affect the film surface

2. Stripe deformation of film 12 Each film 12 obtained is irradiated with light by a fluorescent lamp, the distortion of the outline of the fluorescent lamp reflected on the film 12 is confirmed, and the degree of this distortion is visually evaluated as the stripe deformation of the film. did. The evaluation criteria are as follows. A and B are acceptable and C is unacceptable.
A: No distortion B: Some distortion was confirmed, but there was no problem in practical use C: Distortion was severe and there was a problem as a product

[Comparative Example 1], [Comparative Example 2]
A film was produced from the dope 11 using a solution casting apparatus in which the belt 21 of Example 1 was replaced with a belt having Ni, Cr, Mo, and Cu contents shown in Table 1, and Comparative Example 1 and Comparative Example 2.

  The wavy deformation for the belt and the streak deformation for the film were evaluated using the same methods and criteria as in the examples. The evaluation results are shown in Table 1.

[Example 11] to [Example 19]
By using the same stainless steel as that used in Example 1 and changing the rolling conditions, belt materials having the elongation at break and the crystal grain size shown in Table 1 were prepared. Each belt 21 was made from the obtained belt material, and the film 12 was manufactured by the solution casting apparatus 10 provided with each belt 21, and it was set as Examples 11-19. Other conditions are the same as those in Examples 1-10.

  Each belt 21 was evaluated for cracks, and the resulting film 12 was evaluated for smoothness by the following methods and criteria.

3. Smoothness of the film 12 The crack of the belt 21 has an influence on the film surface and causes a convex deformation on the film surface. Then, the film surface of the film 12 was evaluated on the following reference | standard using the defect detection apparatus of patent 5258349 gazette. In addition, since the convex deformation tended to be higher as the length was longer, the convex deformation was confirmed with the length, and the evaluation of the convex deformation was evaluated for the smoothness of the film 12. It was. A and B are acceptable and C is unacceptable. The evaluation results are shown in Table 1.

A: Convex deformation was not confirmed on the film surface B: Convex deformation was observed on the film surface, but the length of the convex deformation was less than 500 μm C: Convex length of 500 μm or more on the film surface Deformed

4). Cracks in the belt 21 Cracks in the belt 21 were difficult to detect visually. Therefore, after identifying the position of the crack of the belt 21 from the position of the convex deformation observed on the film 12, the identified location was observed with a microscope. The microscope used was Keyence VHX-900, which was observed at a magnification of 50 times. The evaluation criteria are as follows. A and B are acceptable and C is unacceptable.

A: No cracks were observed B: Cracks were observed, but the crack length was less than 500 μm C: Cracks with a length of 500 μm or more were observed

DESCRIPTION OF SYMBOLS 10 Solution casting apparatus 11 Dope 12 Film 15 Casting unit 16 Tenter 17 Roller dryer 21 Belt 24 Casting die 26 Casting film

Claims (8)

Forming a casting film on the belt by continuously flowing out a polymer solution in which a polymer is dissolved in a solvent from a casting die onto a belt formed in an annular shape and continuously running in a longitudinal direction;
Peeling the cast film from the belt and drying,
The belt is formed from an austenitic stainless steel containing Ni, Cr, Mo, and Cu in a range of 0.04 mass% or more and 1.00 mass% or less. Method.   The stainless steel includes Ni in a range of 10.00 mass% to 14.00 mass%, Cr in a range of 16.00 mass% to 18.00 mass%, and 2.00 mass% to 3.00. The solution casting method according to claim 1, comprising Mo in a range of not more than mass%.   The solution casting method according to claim 1 or 2, wherein the belt has an elongation at break within a range of 10% to 20%.   4. The solution casting method according to claim 1, wherein a crystal grain size of the stainless steel in the belt is in a range of 20 μm to 80 μm. In a solution casting apparatus for producing a film from a polymer solution in which a polymer is dissolved in a solvent,
A belt formed of an austenitic stainless steel formed in an annular shape and continuously running in the longitudinal direction, and containing Ni, Cr, Mo, and Cu in a range of 0.04% by mass to 1.00% by mass;
A casting die for continuously flowing the polymer solution to the belt;
A solution casting apparatus comprising: a dryer for drying a film formed by peeling off the belt.   The stainless steel includes Ni in a range of 10.00 mass% to 14.00 mass%, Cr in a range of 16.00 mass% to 18.00 mass%, and 2.00 mass% to 3.00. The solution casting apparatus according to claim 5, comprising Mo in a range of mass% or less.   The solution casting apparatus according to claim 5 or 6, wherein the elongation at break of the belt is in the range of 10% to 20%.   The solution casting apparatus according to any one of claims 5 to 7, wherein a crystal grain size of the stainless steel in the belt is in a range of 20 µm or more and 80 µm or less.

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