JP5329585B2 - Cellulose acylate solution and method for producing the same, and solution casting method - Google Patents

Description

  The present invention relates to a cellulose acylate solution, a production method thereof, and a solution casting method.

  As is well known, the solution casting method is a method in which a dope prepared by dissolving a polymer in a solvent is cast on a support to form a cast film, and the cast film is peeled off as a wet film and dried. It is a method of manufacturing. Cellulose acylate films often used for optical applications are produced by such a solution casting method. In recent years, with the rapid market expansion of liquid crystal displays, the demand for cellulose acylate films as viewing angle widening films and polarizing plate protective films constituting liquid crystal displays is also rapidly increasing. Therefore, it is necessary to greatly increase the production amount of existing equipment.

  In order to increase the production of film with existing solution casting equipment, a belt or drum as a support is moved at a higher speed. The support is repeatedly cast with the dope and stripped of the cast film, and the number of repetitions per unit time increases as the film production rate increases. Although there are variations depending on the composition of the dope, casting conditions, stripping conditions, etc., the support becomes dirty more quickly as the film production rate is increased.

  As the contamination of the support, there is one in which the substance contained in the casting film gradually increases to the extent that it is not visually confirmed and becomes cloudy. In the following description, the clouding phenomenon confirmed in this way is referred to as plate-out. Various proposals have been made as a method for preventing this plate-out. For example, in Patent Document 1, the concentration of a compound extracted from cellulose acylate under specific extraction conditions, and further a cellulose acylate solution Discloses a method for producing a cellulose acylate film in which the concentration of calcium, magnesium, sulfuric acid, and the like contained in is in a specific range, thereby reducing the amount of dirt generated on the drum.

  Moreover, in patent document 2, the ratio of the mass of a cellulose acylate and the mass of magnesium is made into the predetermined range, and, thereby, plate-out is prevented. Furthermore, in Patent Document 3, the amount of calcium, the amount of magnesium, and the amount of sulfuric acid in the dope are within a predetermined range, and a compound having a predetermined skeleton is included in the dope. This suppresses plate-out and prevents yellowing of the film.

JP 2006-199029 A JP 2008-063403 A JP 2009-161702 A

  There is certainly a case where plate-out is prevented by using cellulose acylate having a low calcium concentration as described in Patent Document 1. However, plate-out may also occur by the method of Patent Document 1. In the methods of Patent Documents 2 and 3, plate-out may be prevented, but even if this method is used, plate-out may still occur and it cannot be said that it is a complete suppression method. In addition, the plate-out is particularly likely to occur in the case of so-called cooling casting in which the casting film is cooled and solidified on the support. In other words, although the conventional cleaning method is effective for suppressing plate-out, there are components that cannot be removed.

  Then, an object of this invention is to provide the cellulose acylate solution which suppresses generation | occurrence | production of plate-out, its manufacturing method, and a solution casting method.

In order to solve the above-mentioned problems, the present invention provides a cellulose acylate solution produced by casting a solution on a support to form a cellulose acylate film, wherein the cellulose acylate is 20 ° C. or higher and 40 ° C. or lower. a melting step of generating a cellulose acylate solution by dissolving in a solvent at a temperature range, the hydrogen ion exponent pH is heated 3 to 5 inclusive range 囲Nia Ru cellulose acylate solution, 90 ° C. 8 0 ° C. or higher By maintaining the temperature within the following temperature for 90 minutes to 240 minutes , the molecular weight is in the range of 500 to 1000, and the mass ratio of the fatty acid ester in which at least 80% of the molecular weight is occupied by methylene groups is 9.0. It has the heating process which makes it ^x10 < ^-3> % or less, and is comprised.

When the hydrogen ion exponent pH of the cellulose acylate solution that has undergone the heating step is smaller than 4.5, it is preferable to add 4.5 or more by adding sodium acetate to the cellulose acylate solution.

Cellulose acylate, particularly large effect when the cellulose obtained from conifer is obtained is acylated.

The solution film- forming method of the present invention comprises a dissolution step of producing a cellulose acylate solution by dissolving cellulose acylate in a solvent in a temperature range of 20 ° C. to 40 ° C., and a hydrogen ion exponent pH of 3 to 5 and heating the range 囲Nia Ru cellulose acylate solution, at 8 0 ° C. or higher 90 ° C. in a temperature below, by holding 90 minutes or more 240 minutes or less, the molecular weight is in the range of 500 to 1000, A heating step in which the mass proportion of the fatty acid ester in which at least 80% of the molecular weight is occupied by a methylene group is 9.0 × 10 ⁻³ % , and the cellulose acylate solution that has undergone the heating step are cast on a support and peeled off. And a film forming step of drying into a cellulose acylate acylate film.

When the hydrogen ion exponent pH of the cellulose acylate solution that has undergone the heating step is smaller than 4.5, it is preferable to add 4.5 or more by adding sodium acetate to the cellulose acylate solution. The cellulose acylate is preferably an acylated cellulose obtained from a conifer.

  According to the present invention, plate-out in solution casting can be suppressed.

It is the schematic of the solution casting apparatus which enforces the solution casting method of this invention. It is the schematic of the dope manufacturing equipment which enforces the manufacturing method of the dope of this invention. It is a flowchart which shows the manufacturing method of dope of this invention. It is a flowchart which calculates | requires the mass ratio of fatty acid ester. It is a flowchart which calculates | requires the hydrogen ion index | exponent pH of dope.

<Solution casting method>
The solution casting method of the present invention is performed by, for example, the solution casting equipment 10 shown in FIG. The solution casting apparatus 10 includes a casting device 15, a tenter 17, a roller drying device 21, and a winding device 27 in order from the upstream side. The casting apparatus 15 forms a polymer film (hereinafter simply referred to as “film”) 12 from a cellulose acylate solution (hereinafter referred to as “dope”) 11 in which cellulose acylate as a polymer component is dissolved in a solvent. The tenter 17 proceeds to dry the film 12 while holding each side of the film 12 with the holding means 16. The roller drying device 21 dries while supporting the film 12 with a plurality of rollers 20. The second tenter 23 holds each side portion of the film 12 by the holding means 22 and applies a tension in the width direction to the film 12. Note that a slitter (not shown) may be provided downstream of the tenter 17, and the holding marks on the respective sides held by the holding means 16 of the tenter 17 may be cut off. The winding device 27 rolls the film 12 around a winding core to form a roll.

  In the present specification, the solvent content (unit:%) is a value based on the dry weight. Specifically, when the mass of the solvent is x and the mass of the film 12 is y, {x / (Y−x)} × 100.

  The casting apparatus 15 includes a drum 30 as a casting support, and a casting die 35 that flows out the dope 11 above the drum 30. By continuously flowing out the dope 11 from the casting die 35 to the drum 30 being conveyed, the dope 11 is cast on the drum 30 to form a casting film 36. In FIG. 1, a reference numeral PC is given to a position where the dope 11 starts to contact the drum 30 (hereinafter referred to as a casting position).

  The drum 30 includes a temperature controller (not shown) that controls the peripheral surface temperature. The temperature of the casting film 36 is adjusted by the drum 30 whose peripheral surface temperature is controlled. For example, in the case of cooling casting, when the peripheral surface temperature is in the range of −15 ° C. or more and 10 ° C. or less, the casting film 36 is cooled and gelled. Due to this gelation, the casting film 36 is hardened to such an extent that it can be conveyed. When the peripheral surface temperature of the drum 30 is as low as −15 ° C. or more and 10 ° C. or less, plate-out is particularly likely to occur according to the conventional method. On the other hand, according to the present invention, since the dope 11 described later is used, even if the plate-out is cooling casting, it is difficult to occur.

  Note that an endless band (not shown) formed in an annular shape may be used as the casting support instead of the drum 30. When the band is used as a casting support, the band is wound around the circumferential surface of a pair of rollers (not shown) that rotate in the circumferential direction. At least one of the pair of rollers may be a driving roller having a driving unit. As the drive roller rotates in the circumferential direction, the band in contact with the circumferential surface is conveyed. By this conveyance, the band circulates and continuously travels in the longitudinal direction. When the band is used as a casting support, a pair of rollers is provided with a temperature controller (not shown) for controlling the circumferential surface temperature of the roller, and the circumferential surface of the roller is controlled by controlling the circumferential surface temperature of the roller. The temperature of the band that contacts the surface may be controlled.

  Regarding the dope 11 from the die 31 to the drum 30, a so-called bead, a decompression chamber (not shown) is provided upstream in the rotation direction of the drum 30. The decompression chamber sucks the atmosphere in the upstream area of the flowed out dope 11 and decompresses the area.

  The cast film 36 is hardened to such an extent that it can be conveyed to the tenter 17, and then peeled off from the drum 30 in a state containing a solvent. In the case of cooling casting, stripping is preferably performed while the solvent content is in the range of 150% by mass to 280% by mass.

  At the time of stripping, the film 12 is supported by a stripping roller (hereinafter referred to as a stripping roller) 37, and the stripping position PP where the casting film 36 is stripped from the drum 30 is held constant. The stripping roller 37 may be a driving roller that includes driving means and rotates in the circumferential direction. On the rotating drum 30, the casting of the dope 11 and the stripping of the casting film 36 are repeated.

  A blower (not shown) may be arranged on the conveyance path between the casting device 15 and the tenter 17. The film 12 is dried by the air blown from the blower.

  The cast film 36 that has been peeled off, that is, the film 12 is guided to the tenter 17. The holding means 16 of the tenter 17 is a clip.

  The tenter 17 applies the tension in the width direction while holding the film 12 by the holding means 16 and transports it in the longitudinal direction, and widens the width of the film 12. The tenter 17 is formed with a preheating area, an extension area, and a relaxation area in order from the upstream side. There may be no relaxation area.

  The tenter 17 includes a pair of rails (not shown) and a chain (not shown). The rails are installed on both sides of the conveyance path of the film 12, and the pair of rails are spaced apart at a predetermined interval. This rail interval is constant in the preheating area, gradually increases in the extending area as it goes downstream, and is constant in the relaxation area. In addition, you may make it the rail space | interval of a relaxation area become narrow gradually as it goes downstream.

  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 plurality of holding means 16 are attached to the chain at a predetermined interval. Due to the rotation of the driving sprocket, the holding means 16 circulates along the rail.

  The holding means 16 starts holding the guided film 12 near the entrance of the tenter 17, moves toward the exit, and releases the hold near the exit. The holding means 16 released from the holding moves again to the vicinity of the entrance and holds the newly guided film 12.

  The preheating area, the stretching area, and the relaxation area are formed as spaces by sending dry air from the duct 31 and do not have a clear boundary. The duct 31 is provided above the conveyance path of the film 12. The duct 31 has a slit for sending dry air, and is supplied from a blower (not shown). The blower sends dry air adjusted to a predetermined temperature and humidity to the duct 31. The duct 31 is arranged so that the slit faces the conveyance path of the film 12. Each slit has a shape extending long in the width direction of the film 12 and is formed at a predetermined interval in the transport direction. A duct having the same structure may be provided below the conveyance path of the film 12 or may be provided both above and below the conveyance path of the film 12.

  While the film is being transported by the tenter 17, the film is dried by the drying air from the duct 31, and the width can be changed by the holding means 16 at a predetermined timing.

  The atmosphere inside the roller dryer 21 is adjusted by an air conditioner (not shown) such as temperature and humidity. In the roller drying device 21, the film 12 is wound around a large number of rollers 20 and conveyed. Also in the roller drying device 21, the solvent evaporates from the film 12. In the roller drying device 21, it is preferable to perform the drying process until the solvent content becomes 5% by mass or less.

  When the film 12 is sent to the winding device 27, it is wound into a roll. Note that a tenter (not shown) may be further provided downstream of the roller drying device 21 in order to develop the desired characteristics in the film 12. This tenter has the same structure as the tenter 17.

  The obtained film 12 can be used as an optical film. Examples of the optical film include a protective film for a polarizing plate and a retardation film.

<Dope>
The dope 11 reduces the amount of fatty acid ester represented by the following formula (1) as much as possible. Specifically, in the present invention, the mass ratio of the fatty acid ester of the formula (1) in the dope 11 is suppressed to 0.0100% or less. Thereby, the plate-out in a support body is suppressed not only in dry casting but also in cooling gelation casting. In the formula (1), R ¹ and R ² represent an alkyl group. Here, the fatty acid ester of the formula (1) has a molecular weight in the range of 500 to 1,000, and at least 80% of the molecular weight is occupied by a methylene group (—CH ₂ —).

  The mass ratio of the fatty acid ester of the formula (1) in the dope 11 is more preferably suppressed to 0.0010% or less. In addition, the smaller the mass ratio of the fatty acid ester of the formula (1), the better, and most preferably 0 (zero). However, if the mass ratio is to be as close to 0 (zero) as possible, the mixing process in the mixing apparatus 41 (see FIG. 2) in the method for manufacturing the dope 11 described later to the heating process in the heating apparatus 45 (see FIG. 2). Since the number of repetitions is increased, it is not economically preferable.

The fatty acid ester of the formula (1) has a carbon number (C number) of generally 29 or more, preferably 40 or more and 70 or less. That is, (carbon number of R ¹ ) + (carbon number of R ² ) is 29 or more, preferably 40 or more and 70 or less.

  When cellulose acylate is obtained by acylating cellulose obtained from coniferous trees, the content of the fatty acid ester of formula (1) is particularly large, and plate-out is very likely to occur. Therefore, when cellulose acylate obtained by acylating cellulose obtained from conifers is used as the polymer component of the dope 11, the content of the fatty acid ester of the formula (1) in the dope 11 is reduced to a mass ratio. By suppressing the content to 0.01% or less, the plate-out suppression effect is particularly prominent.

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.
2.5 ≦ 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 for obtaining a polymer solution used for solution casting can be obtained, and a polymer solution having a low filterability and a preferable viscosity can be produced. In particular, when a non-chlorine organic solvent is used, the above cellulose acylate is preferable.

  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.

<Dope manufacturing equipment and manufacturing method>
Below, the manufacturing equipment and manufacturing method of dope 11 are explained. The dope 11 includes cellulose acylate and a solvent as basic components. However, a plasticizer is often included in the dope 11 in consideration of the process of manufacturing the film 12 and the storage, transportation, and use of the film 12. Therefore, in the following description, a case where a plasticizer is also used as a dope component is taken as an example. Moreover, in the following description, the case where TAC (cellulose triacetate) is used as the cellulose acylate is taken as an example, but as described above, the cellulose acylate is not limited to TAC. In the present embodiment, a mixture of dichloromethane, methanol, and butanol is used as the solvent.

  As shown in FIG. 2, the dope manufacturing facility 40 includes a mixing device 41, a dissolving device 42, a concentrating device 43, a recovery / purification device 44, and a heating device 45.

  The mixing device 41 includes a storage unit (not shown), a stirrer (not shown), and a temperature controller (not shown). The accommodating portion accommodates the TAC 48, the solvent 49 of the TAC 48, and the plasticizer 50. The stirrer is provided in the accommodating portion, and includes a stirring blade (not shown) and driving means (not shown) for driving the stirring blade to rotate. The stirring blade is housed inside the housing portion. The temperature controller controls the temperature inside the housing unit.

  When the TAC 48, the solvent 49, and the plasticizer 50 are sent, the mixing device 41 rotates the stirring blade while controlling the temperature inside the container.

  As the melting device 42, a static mixer is used in this embodiment. However, the dissolving device 42 is not limited to a static mixer. The static mixer used in this embodiment is a known static mixer. The static mixer includes a liquid feed pipe (not shown) through which a mixture of TAC 48, solvent 49, and plasticizer 50 passes from the mixing device 41, a temperature control unit (not shown) provided on the outer periphery of the liquid feed pipe, A plurality of elements (not shown) arranged in the liquid feeding direction so as to be arranged in the liquid feeding direction. Each element is formed by twisting a rectangular plate by 180 °. The temperature control unit includes a jacket that covers the outer periphery of the liquid feeding pipe and a temperature controller that controls the temperature of the jacket.

  When the mixture of the TAC 48, the solvent 49, and the plasticizer 50 is sent to the dissolving device 42, the dissolving device 42 guides the mixture downstream while controlling the temperature inside the liquid feeding pipe. The element shears the mixture directed downstream.

  The liquid feeding pipe L1 downstream of the dissolving apparatus 42 branches, the concentrating device 43 is connected to one branched liquid feeding pipe L2, and the heating device 45 is connected to the other liquid feeding pipe L3. A three-way valve 51 is provided at the branch position.

  The concentrating device 43 is a known flash unit, but is not limited thereto. The flash unit includes an accommodating portion (not shown) and a nozzle that flushes (injects) the dope 11 toward the inside of the accommodating portion. The container stores the dope 11 that has been flushed from the nozzle. A pipe L4 connected to the collection / purification device 44 is provided above the housing portion. A liquid feeding pipe L5 is provided below the housing portion. The liquid feeding pipe L5 is connected to a liquid feeding pipe L3 that is branched downstream of the melting device 42 and connected to the heating device 45. In FIG. 2, PJ <b> 1 is attached to a joining portion of the liquid feeding pipe L <b> 3 that connects the melting device 42 and the heating device 45 and the liquid feeding pipe L <b> 5 that extends from below the accommodating portion of the concentrating device 43.

  The recovery / purification device 44 is connected to a pipe L4 extending from above the accommodating portion of the concentrating device 43, and cools the solvent guided in a gaseous state from the concentrating device 43 into a liquid (not shown). Is provided. Further, the recovery / purification leaving stand 44 includes a purifying section (not shown) for purifying the solvent when the liquid solvent is guided by the cooler.

  The purification unit of the collection / purification device 44 is connected to the mixing device 41. A liquid feeding pipe L7 for feeding acetic acid 52 and a liquid feeding pipe L8 for feeding sodium acetate are connected to the liquid feeding pipe L6 connecting the purification unit of the recovery / purification apparatus 44 and the mixing apparatus 41, respectively. . A valve 56 is provided in the liquid feed pipe L7 for feeding the acetic acid 52, and a valve 57 is provided in the liquid feed pipe L8 for feeding the sodium acetate. Each valve 56, 57 has an opening adjustment function for adjusting the opening.

  The heating device 45 is basically the same static mixer as the melting device 42. However, the liquid feeding pipe (not shown) of the heating device 45 is made longer than the liquid feeding pipe (not shown) of the dissolving apparatus 42, so that the residence time in the liquid feeding pipe stays in the liquid feeding pipe of the dissolving apparatus 42. It takes longer than the time to do. In the present embodiment, the length of the liquid feeding tube of the heating device 45 is set to be not less than 2 times and not more than 3 times the length of the liquid feeding tube of the dissolving device 42. Instead of a mode in which the length of the liquid supply pipe of the heating device 45 is made longer than that of the liquid supply pipe of the dissolving device 42, a circulation pipe from the downstream to the upstream of the liquid supply pipe is provided in the liquid supply pipe of the heating device 45. It is good also as an aspect to provide. By circulating the circulation pipe and the liquid feeding pipe and repeatedly flowing the liquid feeding pipe of the heating device 45 5 to 10 times, the residence time in the liquid feeding pipe of the heating device 45 can be made longer.

  The heating device 45 is connected to the solution casting equipment 10. However, the heating device 45 does not necessarily have to be connected to the solution casting apparatus 10. For example, the heating device 45 may be connected to a storage container for storing the dope 11 instead of the solution casting apparatus 10.

  The liquid feeding pipe L3 between the junction PJ1 and the heating device 45 is branched. A three-way valve 58 is provided at the branch position. The downstream end of the branched liquid supply pipe L9 is connected to a liquid supply pipe L10 that connects the heating device 45 and the solution film-forming facility 10. In the case where the heating device 45 is connected to a storage container that stores the dope 11 instead of the solution casting apparatus 10, the downstream end of the branched liquid supply pipe L9 may be connected to the storage container.

  In FIG. 2, reference numeral PJ <b> 2 is attached to the junction where the branched liquid supply pipe L <b> 9 and the liquid supply pipe L <b> 10 downstream of the heating device 45 are connected. A pipe L11 for feeding sodium acetate 61 is connected to the liquid feed pipe L10 downstream of the heating device 45 at the upstream position of the junction PJ2. The pipe L11 is provided with a valve 62 having an opening adjustment function for adjusting the opening.

  The dope manufacturing method by the dope manufacturing facility 40 will be described below with reference to FIG. First, when the TAC 41, the solvent 42 of the TAC 41, and the plasticizer 43 are sent to the mixing device 41, the mixing device 41 mixes them while heating them. Specifically, the storage unit of the mixing device 41 drives the stirrer to mix the stored TAC 48, the solvent 49, and the plasticizer 50. The temperature controller controls the temperature inside the container, and thereby adjusts the temperatures of the TAC 48, the solvent 49, and the plasticizer 50 that are accommodated.

  The mixture obtained by mixing in the mixing device 41 is sent to the dissolving device 42. When the mixture is sent, the dissolving device 42 dissolves the TAC 41 and the plasticizer in the solvent to make the dope 11. The temperature of the dope 11 set at the time of melting in the melting apparatus 42 is in the range of 20 ° C. or higher and 40 ° C. or lower.

  It is determined whether the concentration of the dope 11 is equal to or lower than a predetermined concentration. This concentration is the concentration of the solid content in the dope 11, and in this embodiment is the mass ratio of the TAC and the plasticizer in the dope 11. The predetermined density is individually set according to the film 12 to be manufactured. When the concentration of the dope 11 is a predetermined concentration, the dope 11 is sampled. If the predetermined concentration is not reached, the dope 11 is sent to the concentrator 43. The concentrator 43 concentrates the dope 11 to a predetermined concentration or less by flushing the dope 11. The concentrated dope 11 is sampled.

  The solvent 42, which has been gasified by flushing the dope 11 in the concentration device 43, is sent to the recovery / purification device 44. The recovery / purification device 44 cools the solvent 42 that has become a gas to form a liquid, and purifies the solvent 42 that has become a liquid to increase the purity. An example of the purification method is distillation.

  In the present embodiment, the dope 11 is sampled from the liquid feed path between the junction PJ and the three-way valve 58 downstream of the junction PJ in both cases of concentration and non-concentration. In FIG. 2, a symbol PS is attached to the sampling position. However, when the dope 11 is not concentrated, the dope 11 may be sampled at any location of the liquid supply pipes L1 and L3 provided from the dissolving device 42 to the three-way valve 56.

  Using the sampled dope 11, the mass ratio (content ratio) of the fatty acid ester of the formula (1) is obtained (reference S1 in FIG. 3). Here, the mass ratio of the fatty acid ester of the formula (1) represents the mass of the fatty acid ester of the formula (1) with respect to the total mass of the dope 11 as a percentage (unit:%). The mass ratio of the fatty acid ester of 1) is expressed as a percentage. Specifically, when the mass of the dope 11 is A and the mass of the fatty acid ester of the formula (1) is B, the mass ratio of the fatty acid ester is a value obtained by (B / A) × 100. In addition, how to obtain | require the mass ratio of the fatty acid ester of Formula (1) is later mentioned using another drawing.

  If the mass ratio of fatty acid ester is calculated | required, it will be determined whether the mass ratio is 0.01% or less. When the mass ratio of the fatty acid ester is 0.01% or less, the manufacturing process of the dope 11 is finished and used for the film forming process. In addition, when adding the additive (not shown) different from the plasticizer 43 to the dope 11, it is good to add those additives, before using for a film forming process.

  When the mass ratio of the fatty acid ester is larger than 0.01%, the sampling is performed again from the dope 11. Using the sampled dope 11, the hydrogen ion exponent pH of the dope 11 is obtained (reference S2 in FIG. 3). In addition, how to obtain the hydrogen ion exponent pH of the dope 11 will be described later using another drawing.

  When the hydrogen ion exponent pH of the dope 11 is obtained, it is determined whether or not the obtained value satisfies 3 ≦ pH ≦ 5. When 3 ≦ pH ≦ 5 is satisfied, a heating step for heating the dope 11 is performed.

  When 3 ≦ pH ≦ 5 is not satisfied, it is evaluated whether pH <3 or pH> 5. When pH <3, sodium acetate 53 is added to the solvent 42 sent to the mixing device 41, and the amount of sodium acetate added is increased to 3 or more. When pH> 5, acetic acid 52 is added to the solvent 42 sent to the mixing device 41, and the amount of acetic acid 52 added is increased to 5 or less. In this way, the pH of the dope 11 is adjusted to be in the range of 3 to 5. The value of acetic acid 52 or sodium acetate 53 to be added may be determined according to the pH of the dope 11. Based on this, the addition flow rate of acetic acid 52 or sodium acetate 53 with respect to the amount of solvent 42 fed may be set in the solution feeding pipe L6 of solvent 42 toward mixing device 41.

  The heating device 45 heats the dope 11 whose pH is adjusted while sending it downstream. This heating is performed so that the temperature of the dope 11 is maintained in the range of 80 ° C. or higher and 90 ° C. or lower. By passing through this heating, the dope 11 has a mass ratio of the fatty acid ester of the formula (1) of 0.01% or less. By adjusting the pH and heating, the dope 11 does not generate plate-out even when cast into the drum 30 (FIG. 1). According to this method, the TAC and the plasticizer are not decomposed, or are suppressed to such a level that there is no practical problem even if they are decomposed. In addition, the fatty acid ester of the formula (1) is decomposed into fatty acid and alcohol through this heating, but these do not cause plate-out.

  Adjustment of the temperature of dope 11 is performed by controlling the temperature of the jacket which covers the outer periphery of a liquid feeding pipe with a temperature controller. The temperature of the dope 11 set during heating in the heating device 45 is higher than the temperature in the melting device 42.

  In the heating device 45, it is preferable that the time for maintaining the temperature of the dope 11 in the range of 80 ° C. or higher and 90 ° C. or lower is in the range of 60 minutes or longer and 240 minutes or shorter. By keeping the temperature of the dope 11 within the above range for this time, the fatty acid ester of the formula (1) is more reliably decomposed. Thereby, plate-out is prevented more reliably. The adjustment of the time for maintaining the temperature includes a method of adjusting the length of the liquid feeding tube and a method of adjusting the liquid feeding speed in the liquid feeding tube. This temperature holding time is extremely longer than the time for heating the dope 11 in the melting apparatus 42, and is 5 times or more and 10 times or less. For example, the heating time in the melting device 42 is not less than 10 minutes and not more than 60 minutes, which is much shorter than that in the heating device 45.

  The dope 11 that has been heated by the heating device 45 is preferably sampled and measured for pH. When the pH satisfies 4.5 ≦ pH ≦ 5.5, the manufacturing process of the dope 11 is terminated and guided to the solution casting apparatus 10 or the storage container. When the pH is lower than 4.5, it is preferable to adjust the pH to be 4.5 or more by adding sodium acetate 61 to the dope 11. In the case where cellulose acylate is used as the polymer component, the pH of the dope 11 is hardly higher than 5.5.

  It should be noted that the dope that has been heated by the heating device 45 is obtained by measuring the mass ratio of the fatty acid ester of the formula (1) before sampling for pH measurement as described above and confirming that it is 0.01 or less. May be.

  A method for obtaining the mass ratio of the fatty acid ester of the formula (1) using the sampled dope 11 (reference S1 in FIG. 3) will be described with reference to FIG.

  The sampled dope 11 includes a plasticizer 50. Depending on the type of plasticizer, the mass ratio of the fatty acid ester of formula (1) may not be accurately measured. Therefore, in this embodiment, the plasticizer is removed from the sampled dope 11, and this removal is performed by methanol extraction.

  A film is prepared with the dope 11 from which the plasticizer has been removed. In this embodiment, the film was cast and dried so as to be a film having a thickness of 80 μm. The drying conditions are 140 ° C. and 30 minutes. In addition, the temperature and time of the film as drying conditions are not limited to 140 ° C. and 30 minutes, and may be sufficiently dried to such an extent that TAC does not decompose, and may be the same as the drying conditions in the solution casting apparatus 10.

  The produced film is made fine by using a mixer or a mill to produce a chip. The size of the chip is not particularly limited, and may be, for example, about 5 mm × 5 mm.

  Soxhlet extraction is performed with 10 g of chips. The solvent used for Soxhlet extraction is preferably toluene. Extraction is repeated 50 times or more under normal pressure with 100 mL (milliliter) of toluene. Concentrate 100 mL of toluene (corresponding to the extract) used repeatedly for 50 extractions. The concentrate obtained by concentration is weighed. Let A (g) be the mass of the concentrate obtained by weighing. The concentrate is diluted with 1 mL of toluene, and the dilution obtained by dilution is subjected to a gas chromatograph mass spectrometer (GCMS). Examples of the GCMS column include DB-HT5 manufactured by Agilent. The measurement may be performed by holding at 100 ° C. for 1 minute, then increasing the temperature at a rate of 15 ° C./minute, and then holding at 400 ° C. for 9 minutes.

  A sample of fatty acid ester of formula (1) is prepared and subjected to GCMS. When this sample is measured by GCMS, the carbon number is generally in the range of 29 to 65. Therefore, based on the measurement result of this sample, the area S1 of the portion corresponding to the carbon number of 40 or more and 65 or less in the graph obtained by the measurement by GCMS is obtained, and the total area S2 is obtained as the obtained area S1. This value is taken as the mass ratio R1 of the fatty acid ester of the formula (1) in the concentrate.

  In addition, the concentration of the concentrate obtained by extraction with toluene and concentration of the extract in the dope 11 excluding the plasticizer (hereinafter referred to as “concentration of the concentrate in the dope”) X (unit:%) is obtained. The concentration X of the concentrate in the dope is a percentage value obtained by [A / {(10 g / B) × 100}] × 100. “10 g” in this equation corresponds to 10 g as the mass of the chip used for Soxhlet extraction. B is the concentration of the solid component in the dope used to obtain the chip. Since the dope used for obtaining the chips has the plasticizer removed in advance, the solid component does not contain a plasticizer. (10 g / B) × 100 is the mass (unit: g) of the dope used to obtain the chip. A / {(10 g / B) × 100} is the ratio of the mass of the concentrate to the mass of the dope 11 excluding the plasticizer.

  Multiply the concentration X of the concentrate in the obtained dope and the mass ratio R1 of the fatty acid ester of the formula (1) in the concentrate. The value of X × R1 is defined as the mass ratio of the fatty acid ester of the formula (1) in the dope 11.

  When the plasticizer 50 is extracted with toluene even though the plasticizer 50 is removed, the extraction liquid obtained by Soxhlet extraction is subjected to known extraction such as liquid separation extraction, decantation, and chromatography. This removes the plasticizer 50 from the extract.

  Next, a method for obtaining the pH of the dope 11 using the sampled dope 11 (reference S2 in FIG. 3) will be described with reference to FIG.

  A film is prepared with the sampled dope 11. In addition, the thickness of a film is not specifically limited. The drying conditions when the cast dope 11 is peeled off and dried are 140 ° C. for 20 minutes. In addition, although the temperature and time of the film as drying conditions are not restricted to 140 degreeC for 20 minutes, drying is complete | finished in the state in which a solvent remains.

  The produced film is washed with water. Washing with water is performed by the following method in this embodiment. First, 6.5 g of film is put in methanol, and this methanol bath is subjected to ultrasonic waves. The mass of methanol is 35 g. However, the mass of methanol may be adjusted according to the mass of the film, and may be set to 35 g per 6.5 g of film. The time for ultrasonic waves is 3 hours. At the end of the 3 hour sonication, the film is removed from the methanol and placed in water. This water bath is subjected to ultrasound. The mass of water is 22 g. In addition, what is necessary is just to adjust the mass of water according to the mass of a film, and should just set it to 22g per 6.5g of films used for the methanol bath. The time for ultrasonic waves in the water bath is 3 hours. After 3 hours of sonication, remove the film from the water. The water from which the film is taken out is filtered, and the pH of the filtrate is measured. This pH is regarded as the pH of the dope 11.

  A compound having low solubility in the solvent 49 is mainly brought into cellulose acylate as an impurity contained in cellulose as a raw material. On the other hand, petroleum-derived compounds including solvents usually do not contain such impurities. Cellulose acylate contains a compound having low solubility in the solvent 49 derived from linter purified from cotton and wax components contained in pulp refined from wood. To remove this, it is desirable to remove the wax component as much as possible at the pulp or linter stage, but this is too expensive or too time consuming. Since such low-solubility compounds often contain ester groups, the ester can be decomposed to a molecular weight of 500 or less by performing treatment at high temperature, treatment with acid or alkali, oxidation reduction, enzyme treatment, etc. Control the content of these compounds. In addition, after manufacturing the dope 11, you may implement such a process in any of the process of manufacturing the dope 11, the manufacturing process of a cellulose acylate, and the manufacturing process of a pulp or a linter.

  Examples of the present invention and comparative examples for the present invention will be described below. Details are described in Example 1, and only the conditions different from Example 1 are described in the other Examples and Comparative Examples.

  Two types of dope 11 were manufactured by the dope manufacturing facility 40 under the following conditions and methods. This example is referred to as Example 1.

The prescriptions for the two types of dopes are as follows.
<First dope>
Cellulose acetate (acyl group substitution degree: 2.85) 100 parts by weight Triphenyl phosphate 13 parts by weight Dichloromethane 384 parts by weight Methanol 54 parts by weight n-butanol 15 parts by weight Matting agent (AS972, average primary particle size 10 nm) 0. 03 parts by mass

<Second dope>
Cellulose acetate (acyl group substitution degree: 2.85) 100 parts by weight Triphenyl phosphate 13 parts by weight Dichloromethane 314 parts by weight Methanol 44 parts by weight n-butanol 12 parts by weight

  The temperature at which the first dope 11 is heated and held in the heating device 45 and the time for which the temperature is held are shown in the “temperature” (unit: ° C.) column and “time” (unit: minute) column of Table 1, respectively. Show. In the first dope 11 sampled at the sampling position PS between the junction PJ1 and the three-way valve 58, the mass ratio of the fatty acid ester of the formula (1) was not less than 0.01%. And the mass ratio of the fatty acid ester of the formula (1) was 0.01% or less. The pH when the first dope 11 produced by adding the acetic acid 52 is supplied to the heating device 45 is shown in the “pH” column of Table 1. For confirmation, the first dope 11 was sampled downstream of the heating device 45, and the mass ratio of the fatty acid ester of the formula (1) was determined for the sampled first dope 11. The obtained mass ratio is shown in the “mass ratio” (unit:%) column of Table 1. Note that the second dope 11 is also manufactured by the same method and conditions as the first dope 11 and the same data is obtained, so the description is omitted.

  A film 12 was produced by the solution casting apparatus 10 by co-casting using the first and second dopes 11 in which the mass ratio of the fatty acid ester of the formula (1) was adjusted. These dopes 11 were co-cast after filtration. The co-casting is a co-casting of three layers, and the following first dope is used as a dope for the surface layer exposed on the surface, and the following second dope is a core between each surface layer. Used as dope for layer. That is, the co-casting was performed so that the first dope, the second dope, and the first dope overlapped in this order. The co-casting was performed by flowing out of the casting die so that the layer made of the first dope 11 was 3 μm and the layer made of the second dope 11 was 74 μm in the casting film 36. The casting was performed using a casting die equipped with a feed block. In addition, each dope 11 flowed out from the casting die in the state heated and maintained at 35 degreeC. The temperature of the peripheral surface of the drum 30 was set to -7 ° C. After the cast film 36 was peeled off, the film 12 was obtained by drying at 120 ° C. for 10 minutes using the tenter 17 and the roller drying device 21.

The occurrence of plate-out in the drum 30 was evaluated. Specifically, the time until dirt (cloudiness) occurred on the peripheral surface of the drum 30 was evaluated by the following criteria, and this was regarded as plate-out evaluation. The occurrence of contamination was confirmed visually. A to D are in a practical range.
A: 48 hours or more B: 24 hours or more but less than 48 hours C; 12 hours or more but less than 24 hours D: 10 hours or more but less than 12 hours E: Less than 10 hours

  The temperature at which the first and second dopes 11 are heated and held in the heating device 45, the time during which the temperature is held, and the pH of the first and second dopes 11 that are provided to the heating device 45 are the same as those in Example 1. It implemented instead of these conditions. Each condition and example number are as shown in Table 1.

[Comparative example]
In the comparative example, in the dope sampled at the sampling position PS between the junction PJ1 and the three-way valve 58, the mass ratio of the fatty acid ester of the formula (1) was not 0.01% or less. However, acetic acid 52 was not added to solvent 49. In addition, the heating device 45 did not heat the first and second dopes. A film having a three-layer structure was produced from the first and second dopes thus obtained by co-casting.

DESCRIPTION OF SYMBOLS 10 Solution casting equipment 11 Dope 12 Film 40 Dope manufacturing equipment 45 Heating apparatus

Claims (6)

In the method for producing a cellulose acylate solution in which a cellulose acylate film is formed by casting on a support in solution casting,
A dissolving step for producing a cellulose acylate solution by dissolving cellulose acylate in a solvent in a temperature range of 20 ° C. or higher and 40 ° C. or lower;
The cellulose acylate solution the hydrogen ion exponent pH is in the range of 3 to 5 by heating at 80 ° C. or higher 90 ° C. in a temperature below, by holding 90 minutes or more 240 minutes or less, a molecular weight of 500 A heating step within a range of 1000 or less and a mass ratio of a fatty acid ester in which at least 80% of the molecular weight is occupied by a methylene group is 9.0 × 10 ⁻³ % or less;
A method for producing a cellulose acylate solution, comprising: When the cellulose acylate solution having undergone the heating step has a hydrogen ion exponent pH of less than 4.5, the cellulose acylate solution is adjusted to 4.5 or more by adding sodium acetate to the cellulose acylate solution. The method for producing a cellulose acylate solution according to claim 1 . The method for producing a cellulose acylate solution according to claim 1 or 2 , wherein the cellulose acylate is obtained by acylating cellulose obtained from a conifer. A dissolving step for producing a cellulose acylate solution by dissolving cellulose acylate in a solvent in a temperature range of 20 ° C. or higher and 40 ° C. or lower;
The cellulose acylate solution the hydrogen ion exponent pH is in the range of 3 to 5 by heating at 80 ° C. or higher 90 ° C. in a temperature below, by holding 90 minutes or more 240 minutes or less, a molecular weight of 500 A heating step in which the mass ratio of the fatty acid ester in which the methylene group occupies at least 80% of the molecular weight is 9.0 × 10 ⁻³ % or less,
The cellulose acylate solution through the heating step, peeled cast onto a support, a solution casting method characterized in that it comprises a film forming step of the cellulose acylate film was dried. When the cellulose acylate solution having undergone the heating step has a hydrogen ion exponent pH of less than 4.5, the cellulose acylate solution is adjusted to 4.5 or more by adding sodium acetate to the cellulose acylate solution. The manufacturing method of the cellulose acylate solution of Claim 4 . 6. The solution casting method according to claim 4 , wherein the cellulose acylate is obtained by acylating cellulose obtained from coniferous trees.

Images