JP2009096172A - Dope changeover method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively replace an old dope adhered to a dope supplying pipe with a new dope. <P>SOLUTION: A new dope 81 is supplied to a dope supplying pipe 71 adhered with an old dope already supplied in a solution film forming apparatus. An auxiliary dope 78 is sent in parallel with sending the new dope 81. The auxiliary dope 78 flows so as to contact with the inside wall of the dope supplying pipe 71. A main liquid flow 79 and a sub-liquid flow 80 are formed in the dope supplying pipe 71. The movement resistance of the auxiliary dope 78 is smaller than that of the new dope 81 near the inside wall of the dope supplying pipe 71. The old dope is substituted of a new dope 81 by supplying the auxiliary dope 78. The old dope is substituted for the new dope 81 by adding the auxiliary dope 78. The old dope is effectively substituted. The old dope is effectively substituted for the new dope 81. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dope switching method and apparatus.

  A TAC film manufactured by a solution casting method using a polymer such as cellulose triacetate (hereinafter referred to as “TAC”) as a raw material has different optical characteristics depending on the liquid crystal system and the user. Therefore, it is necessary to produce a wide variety of optical films according to various required performances.

Changing the type of optical film involves changing polymer raw materials, additives, and solvents. Therefore, for the purpose of producing a wide variety of optical films, the formulation of a polymer solution (hereinafter referred to as “dope”) as a raw material of the film may be changed (for example, see Patent Document 1).
Japanese Patent Laying-Open No. 2005-104148

  In the solution casting line, the dope preparation, filtration, storage, and liquid delivery facilities are large-scale. Further, the dope used in the solution casting method is generally highly viscous. Therefore, when the dope recipe is changed, the existing dope before the change (hereinafter referred to as “old dope”) remains attached to the wall surface of each facility, and therefore it is necessary to remove this by some means. . However, it is difficult to perform general cleaning because the facilities are extensive and each facility is large.

  For this reason, the extrusion substitution which replaces the old dope with the new dope is performed by passing a new dope. However, this extrusion replacement requires a liquid amount 3 to 5 times the dope holding amount of the equipment due to complete mixing in the tank and laminar flow in the pipe. Since the dope during the extrusion substitution is in a state where old and new dopes are mixed, it cannot be used as a product even if the film is formed. In addition, since the additive is also in a state where old and new dopes are mixed, it is impossible to recycle as a dope raw material into a chip because it is difficult to specify the amount of the additive, There is a problem that raw materials are wasted. Therefore, a problem arises in terms of cost, and this is a great restriction on the diversification of solution casting in film production facilities.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a dope switching method and apparatus capable of reducing the amount of a new dope to be sent to replace an old dope. .

  In the dope switching method of the present invention, a dope comprising a polymer and a solvent is sent to a casting die through a dope supply pipe, and the dope is cast on a support that runs endlessly from the casting die to form a casting film. Then, after the casting film has self-supporting property, the film is peeled off from the support and dried to form a film. In the dope switching method for switching to the dope, the dope switching step for switching the supply dope to the dope supply pipe from the old dope to the new dope, and the sub-dope having a lower viscosity than the new dope on the upstream side of the dope supply pipe Supply along the inner wall surface of the dope supply pipe, forming a main liquid flow by the new dope at the center of the dope supply pipe, and around the main liquid flow And having a secondary liquid flow forming step of forming a secondary liquid flow by an inner wall surface said auxiliary doping along the-loop supply pipe.

  It is preferable to have the process of stopping the said secondary liquid formation process after progress of predetermined time. When the diameter of the main liquid flow is d1 [m] and the thickness in the radial direction of the sub liquid flow is d2 [m], (d1 / d2) is preferably 2 or more and 100 or less. When the viscosity of the new dope is μ1 [Pa · s] and the viscosity of the sub-dope is μ2 [Pa · s], (μ2 / μ1) is preferably 0.001 or more and 0.9 or less.

  It is preferable that the inner wall surface temperature of the dope supply pipe is higher than the temperature of the main liquid flow at the radial center of the dope supply pipe in the range of 0.5 [° C.] to 35 [° C.].

  The dope switching device of the present invention forms a cast film by feeding a dope comprising a polymer and a solvent to a casting die through a dope supply pipe and casting the dope on a support that runs endlessly from the casting die. Then, after the casting film has self-supporting property, it is peeled off from the support and dried to form a film. In the dope switching device for switching to a sub-dope supply head having a supply port for supplying a sub-dope having a viscosity lower than that of the new dope along the inner wall surface of the dope supply pipe on the upstream side of the dope supply pipe; And a sub-dope supply unit for supplying a diluted dope obtained by diluting the new dope to the sub-dope supply head.

  The sub-dope supply head preferably includes an annular supply port formed over the entire circumference of the inner wall surface.

  According to the dope switching method and apparatus of the present invention, when replacing the old dope already existing in the pipe of the solution manufacturing facility with the new dope, the sub-dope having a viscosity smaller than the viscosity of the new dope contacts the inner wall of the pipe. Since it flows, the replacement | exchange of the old dope adhering to the pipe inner wall by a new dope can be performed efficiently. Accordingly, it is possible to reduce the amount of the new dope that is fed to replace the old dope.

  As shown in FIG. 1, a solution casting apparatus 10 for carrying out the present invention includes a raw material dope preparation unit 11 and a film forming unit 12.

  The raw material dope preparation unit 11 includes a measuring instrument 14, a solvent tank 15, an additive tank 16, a dissolution tank 17, a storage tank 18, a storage tank 44, and a filtration unit 45. A polymer 20 is placed in the meter 14, and the polymer 20 is weighed and put into the dissolution tank 17. A solvent 21 is stored in the solvent tank 15, and the input amount to the dissolution tank 17 is adjusted by controlling the open / close valve 23. An additive 22 is stored in the additive tank 16, and the input amount to the dissolution tank 17 is adjusted by controlling the open / close valve 24.

  The polymer 20 according to the present invention is not particularly limited as long as it is applicable to the solution casting method. Among these, if cellulose acylate is used, a film having high transparency and excellent optical properties can be obtained, and therefore, it is suitable for optical applications such as a protective film for polarizing plates and an optical compensation film. Among them, when cellulose acetate is used, and particularly cellulose triacetate having an average degree of acetylation of 57.5% to 62.5% is used, a film having excellent optical properties can be obtained. The above-mentioned degree of acetylation means the amount of bound acetic acid per unit weight of cellulose, and can be determined according to the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like). In this embodiment, granular cellulose triacetate is used. In addition, when using a granular polymer, it is preferable that 90 weight% or more is a particle size of 0.1-4 mm from a compatible viewpoint with a solvent, More preferably, a particle size is 1-4 mm. It is.

  The solvent 21 is preferably a halogenated hydrocarbon, an ester, a ketone, an ether, an alcohol, or the like, but is not particularly limited, and may be appropriately selected in consideration of the solubility in the polymer to be used. The solvent 21 may be one type of compound or a mixed solvent in which a plurality of compounds are mixed. Specifically, halogenated hydrocarbons (eg, dichloromethane, etc.), esters (eg, methyl acetate, methyl formate, ethyl acetate, amyl acetate, butyl acetate, etc.), ketones (eg, acetone, methyl ethyl ketone, cyclohexanone, etc.) ), Ethers (eg, dioxane, dioxolane, tetrahydrofuran, diethyl ether, methyl-t-butyl ether, etc.), alcohols (eg, methanol, ethanol, etc.) and the like.

  What is necessary is just to select the additive 22 suitably according to the characteristic of the desired film. For example, a plasticizer, an ultraviolet absorber, a peeling accelerator, a fluorine surfactant, and the like can be given. Among these, as the plasticizer, phosphate ester type (for example, triphenyl phosphate (hereinafter referred to as TPP), tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl Phosphates, etc.), phthalate esters (eg, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, etc.), glycolate esters (eg, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate) Methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc.). Among these, TPP is particularly preferable for making cellulose acylate into a film. In addition, a well-known thing can be used for a plasticizer besides the above, and it does not specifically limit. Further, as the ultraviolet absorber, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds are preferable, and among them, benzotriazole compounds and benzophenone compounds are preferable. Compounds are particularly preferred.

  The dissolution tank 17 includes a stirring blade 27 that is rotated by a motor 26. As the stirring blade 27 rotates, the polymer 20, the solvent 21, and the additive 22 in the dissolution tank 17 are stirred. By this stirring, a crude solution 30 in which the solute such as the polymer 20 is not completely dissolved in the solvent is obtained.

  The crude solution 30 in the dissolution tank 17 is temporarily stored in the storage tank 18. As a result, the dissolution tank 17 is emptied, and a continuous batch system in which the crude dissolution solution 30 is repeatedly formed becomes possible. The storage tank 18 is also provided with a stirring blade 32 that is rotated by a motor 31. By rotating the stirring blade 32, the crude solution 30 is stirred and made uniform.

  The crude solution 30 in the storage tank 18 is sent to the heater 40 via the pump 35 and the pipe 36. As the heater 40, an in-line mixer such as a multi-tube heat exchanger or a static mixer is used. The crude solution 30 is heated by the heater 40. The heating temperature is preferably 50 to 120 ° C., and the heating time is preferably 5 to 30 minutes. By this heating, the solute such as polymer 20 necessary for solution film formation is completely dissolved without being modified, and the raw material dope 41 is prepared. Thus, the raw material dope 41 prepared is made into 14 to 24 weight% as solid content concentration of a cellulose ester. In addition, you may concentrate the raw material dope 41 by the flash concentration method etc. as needed.

  The raw material dope 41 heated by the heater 40 is sent to the cooler 42. The cooler 42 cools the material dope 41 to the boiling point of the main solvent or less. The cooled raw material dope 41 is stored in the storage tank 44 via the pump 43. Thereafter, it is sent to the filtration unit 45 and filtered to produce the casting dope 46. The cast dope 46 is sent to the film forming unit 12 via a dope supply pipe 71 having a dope switching unit 47. In addition, the filtration unit 45 is provided with a plurality of filters, and when filtering on the one hand, the filter is washed on the other side so that continuous filtration is possible.

  The film forming unit 12 includes a casting chamber 51, a transfer section 52, a tenter 53, a drying chamber 54, and a winder 55, and a film 56 is made using the casting dope 46. In the casting chamber 51, a casting die 57 in which a discharge port for the casting dope 46 is formed, a casting drum 58 acting as a support, and a peeling roller 59 are arranged.

  The casting dope 46 from which impurities have been removed is cast on a casting drum 58 that is rotating endlessly through a casting die 57, thereby forming a casting film 61. The surface temperature of the casting drum 58 is preferably substantially constant within a range of −10 ° C. to 10 ° C. If the casting dope 46 is cast on such a casting drum 58, the casting dope 46 is quickly cooled, so that a gel-like casting film 61 is formed within a short time. As the casting drum 58 rotates, the casting film 61 is gelled, and the casting film 61 that has become self-supporting is peeled off from the casting drum 58 as a wet film 62 while being supported by the peeling roller 59. It is done.

  In the transfer section 52, the wet film 62 is supported by a large number of rollers, and drying proceeds while being conveyed. In the tenter 53, both end portions of the wet film 62 are held and conveyed by holding means such as pins, and drying is advanced. Thereafter, the dried air is sent to the film 56 in a state where the film 56 is stretched between a number of rollers in the drying chamber 54, and drying proceeds. Thereafter, the film 56 is wound around the winding shaft 63 in a roll shape.

  In addition, from the structure of casting die, decompression chamber, support, etc., co-casting, peeling method, stretching, drying conditions of each step, handling method, curling, winding method after flatness correction, solvent recovery method, film The recovery method is described in detail in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  Regarding specific uses of the cellulose ester film obtained by the above process, in Japanese Patent Application Laid-Open No. 2005-104148, for example, in paragraphs [1088] to [1265], TN type, STN type, VA type, OCB type, reflective type, and other examples are described in detail, and these descriptions can also be applied to the present invention.

  Hereinafter, switching between old and new dope will be described. The raw material dope preparation unit 11 and the film forming unit 12 are connected by a dope supply pipe 71 having a dope switching unit 47. The old dope that has already been fed remains in the dope supply pipe 71 and the film forming unit 12. Generally, since the dope solution has a high viscosity, it tends to adhere and remain on the dope supply pipe 71 and the wall surface of each device. Therefore, when the new dope is fed from the raw material dope preparation unit 11 to the film forming unit 12 in this state, the dope in which the old dope and the new dope are mixed is sent to the film forming unit 12, and the old dope is converted into the new dope. In order to replace it, a large amount of a new dope to be fed is required.

  Since the film forming unit 12 requires a great deal of labor before starting casting, it is preferable to operate continuously from the viewpoint of film production efficiency. For this reason, at the time of switching between the old and new dopes, a film made of a dope mixed with old and new dopes is produced. This film cannot be a product and is discarded. Therefore, the dope switching unit 47 is provided in the dope supply pipe 71 in order to reduce the waste film from the viewpoint of film production efficiency.

  The dope switching unit 47 can be applied to various dope supply pipes connecting the raw material dope preparation unit 11 and the film forming unit 12. For example, it can also be provided in a pipe connecting the heater 40 and the cooler 42. In the present embodiment, a dope supply pipe connecting the raw material dope preparation unit 11 and the film forming unit 12 will be described as an example.

  2 and 3 showing the dope switching unit according to the first embodiment of the present invention, a dope supply pipe 71 is provided with a sub-dope supply head 72 via flanges 71a and 72b. A new dope 81 that is newly switched from the new dope supply unit 73 is supplied to the dope supply pipe 71. The dope dilution unit 74 is connected to the new dope supply unit 73. The dope dilution unit 74 supplies the main solvent of the new dope 81, mixes the main solvent with the new dope 81 to form a diluted dope, and uses this diluted dope as the subdope 78 to supply the subdope. Supply to the head 72.

  The sub dope supply head 72 has a double piping structure by a partition pipe 75 and an attachment portion 76 of the partition pipe. The attachment portion 76 is formed at the upstream end of the partition pipe 75 in the dope flow direction, and the downstream end of the dope flow direction is open. A space defined by the partition pipe 75 and the inner wall surface of the dope supply pipe 71 also serves as the sub-dope buffer unit 77 so that the sub-dope 78 is filled. As shown in FIG. 3, the dope supply pipe 71 is provided with a supply port for the secondary dope 78, and the secondary dope 78 is supplied to the supply port from the dope dilution section 74. As shown in FIG. 3, the supply port of the sub dope 78 may be one, or a plurality of appropriate pitches may be formed in the circumferential direction of the dope pipe.

  When the old dope is switched to the new dope 81, the sub dope 78 obtained by diluting the new dope 81 is supplied to the sub dope supply head 72 correspondingly. Therefore, the dope flowing through the dope supply pipe 71 is in a two-layer flow state of the main liquid flow 79 by the new dope 81 and the sub liquid flow 80 by the sub dope 78.

  As shown in FIG. 4, the velocity distribution in the radial direction of the dope pipe of the new dope flowing through the dope pipe is shown. FIG. 5 shows the velocity distribution of the new dope in the conventional dope supply pipe.

  In the case of this embodiment of FIG. 4, in addition to the main liquid flow 82 by the new dope 81, a sub liquid flow 84 by the sub dope 83 is formed along the inner peripheral surface of the dope supply pipe 71 on the entire circumference. . Since the secondary dope 83 is obtained by diluting the new dope 81, the secondary liquid stream 84 has a lower viscosity than the new dope 81 of the main liquid stream 82. For this reason, compared with the case where the main liquid flow 82 is used, the movement resistance of the sub liquid flow 84 becomes small. Therefore, as shown in FIG. 4, the velocity distribution 92 is substantially uniform over the entire radial direction of the dope supply pipe 71. On the other hand, in the conventional type in which the sub-liquid flow 84 is not formed by the sub-dope 83, as can be seen from the velocity distribution 92 in FIG. The closer to the inner wall surface, the lower the dope flow velocity, and a mountain-shaped velocity distribution occurs in the radial direction of the supply pipe. For this reason, in the conventional type, the replacement of the old dope does not progress easily, but in the case of this embodiment, the velocity distribution is almost uniform in the radial direction of the supply pipe, and close to the inner wall surface. In this case, since the dope flow speed does not decrease, the old dope 93 attached to the inner wall surface of the dope pipe is efficiently replaced.

  Here, when the viscosity of the new dope 81 is μ1 [Pa · s] and the viscosity of the sub-dope 83 is μ2 [Pa · s], μ2 / μ1 is 0.001 or more and 0.9 or less. Preferably, μ2 / μ1 is 0.002 or more and 0.3 or less, and more preferably 0.004 or more and 0.1 or less. When μ2 / μ1 is less than 0.001, the sub-dope 83 is too low in viscosity with respect to the main liquid flow 82 of the new dope 81, and the flow is in the form of drops or streaks due to the influence of surface tension. , And it is difficult to maintain a stable laminar flow state, and the secondary liquid flow 84 tends to be difficult to be formed. When μ2 / μ1 exceeds 0.9, the viscosity of the sub-dope 83 increases, and even if the sub-liquid flow 84 is formed, the old dope 93 is hardly replaced by the new dope 81 and the sub-dope 83. Tend. For this reason, both cases are not preferable.

  As a method for measuring the viscosity, for example, a rotational viscometer, falling ball viscometer or vibration viscometer defined in JIS Z 8803 “Liquid Viscosity—Measurement Method” is used. The viscosity value is measured with a rotational viscometer.

  Each viscosity ratio (μ2 / μ1) between the new dope 81 and the sub-dope 83 is prepared by diluting the new dope 81 with a solvent. For this reason, a part of the new dope 81 is branched from the new dope supply unit 73 and diluted with the main solvent of the new dope 81 to adjust the viscosity ratio to a desired value. The solvent is not particularly limited as long as it dissolves the solute. For example, any of dichloromethane, chloroform, carbon tetrachloride, cyclohexane, methyl acetate, or a mixture thereof is used.

  As a method for adjusting the viscosity ratio between the new dope 81 and the sub dope 83, the temperature distribution may be changed in the radial direction of the dope supply pipe. Since the viscosity of the solution changes depending on the temperature, this property is used. Generally, when the temperature of the liquid is increased, the viscosity tends to decrease. Therefore, when the temperature of the new dope 81 at the center of the dope supply pipe 71 is T1 [° C.] and the temperature of the inner wall of the dope supply pipe 71 is T2 [° C.], T2 is in the range from 0.5 ° C. to 35 ° C. from T1. It is preferable to make it high. The temperature difference is preferably 5 ° C. or more and 35 ° C. or less, more preferably 10 ° C. or more and 30 ° C. or less. When the temperature difference is less than 0.5 ° C., a viscosity ratio sufficient to increase the dope substitution efficiency cannot be obtained, and when the temperature difference exceeds 35 ° C., the viscosity is close to the boiling point of the dope or the boiling point is reduced. There is a tendency that it is difficult to maintain a stable laminar flow state. For this reason, both cases are not preferable. In addition, you may use together the viscosity ratio adjustment method by this temperature difference, and the viscosity ratio adjustment method by the change of the dilution rate of the main dope.

  When the thickness of the main liquid flow 82 is d1 [m] and the thickness of the sub liquid flow 84 is d2 [m], the thickness ratio (d1 / d2) is 2 or more and 100 or less. This thickness ratio is preferably 5 or more and 100 or less, more preferably 10 or more and 50 or less. This thickness ratio is obtained from the thickness at the outlet of the sub-dope supply head 72. When the thickness ratio is less than 2, the decrease in the concentration of the main liquid stream 82 becomes large downstream, and when it exceeds 100, it is difficult to maintain a stable laminar flow state of the secondary liquid stream 84, both of which are not preferable. .

  The inflow of the sub dope is stopped after a lapse of a certain time after completion of the dope replacement, and the formation of the sub liquid flow 84 is stopped. The completion time of the dope replacement is obtained in advance by experiments or the like. In addition, you may determine whether dope substitution was completed by sampling dope in the most downstream part of the dope supply piping 71. FIG. Further, replacement of old and new dopes may be detected from the result of the component using an online component analyzer.

  Next, a second embodiment will be described with reference to FIG. In the second embodiment, the dope supply head 101 is provided on the outside of the dope pipe, whereas the dope supply head is formed of a partition pipe and an attachment portion formed in the dope pipe in the first embodiment. Is different in that. Since the new dope supply unit and the dope dilution unit are the same as those in the first embodiment, description thereof will be omitted.

  The dope supply pipe 102 is divided in the middle, and includes an upstream pipe 103 and a downstream pipe 104. The divided portion is a sub dope supply port 105. A supply head jacket 106 is attached to the upstream pipe 103, and the sub dope is supplied into the jacket from the supply port 106a. A shutter sleeve 107 that closes the sub-dope supply port is attached as necessary. The shutter sleeve 107 is shifted by the shift mechanism 110 between an open position where the sub dope supply port is opened and a closed position where the sub dope supply port is closed.

  In the case of the dope supply pipe 102 in the second embodiment, the thickness d1 [m] of the main liquid flow 108 formed by the new dope and the thickness d2 [m] of the sub liquid flow 109 formed by the subdope are subdope. Is supplied to the dope supply pipe 102, a main liquid flow 108, a sub liquid flow 109, and a two-layer flow are formed in the dope supply pipe 102.

  Of these two layer flows, the diameter of the main liquid flow 108 is d1 [m], and the radial thickness of the sub-liquid flow 109 is d2 [m]. The ratio of the viscosity of the new dope and the sub-dope, the temperature setting, the velocity distribution of the flow of the new dope and the sub-dope, and the like are the same as in the first embodiment, and thus the description thereof is omitted.

  7 and 8 showing the third embodiment, a supply head jacket 111 is slidably attached by a shift mechanism 114 between an upstream pipe 112 and a downstream pipe 113.

  When supplying the sub dope, as shown in FIG. 7, the supply head jacket 111 is shifted to the right by the shift mechanism 114, the sub dope supply port 115 is opened, and the sub dope is supplied to the main liquid flow and the inner wall surface of the dope pipe. It flows as a laminar flow. When the supply of the sub dope is stopped, the supply head jacket 111 is shifted to the left by the shift mechanism 114 as shown in FIG. 8 and the sub dope supply port 115 is closed by the small diameter portion 111 a of the supply head jacket 111. . A sealing member such as an O-ring 116 is inserted in the sliding portion of each jacket so that the dope does not leak from the sliding portion.

  The thickness d1 of the main liquid flow and the thickness d2 of the sub liquid flow are determined in the same manner as in the second embodiment. The viscosity ratio between the new dope and the sub-dope, the temperature setting, the velocity distribution of the flow of the new dope and the sub-dope, and the like are the same as in the first embodiment. Therefore, explanation is omitted.

  The sub dope supply port 115 may be opened in the entire circumferential direction of the dope supply pipe, or may be constituted by a plurality of round holes provided at appropriate pitches in the circumferential direction of the dope supply pipe.

  The stoppage of the inflow of the sub-dope may be performed at once after completion of the dope replacement, or may be performed gradually. When gradually reducing the sub-dope, it is preferable to use a sub-dope supply head 118 in which the opening area of the sub-dope supply port 115 can be changed as shown in FIGS. For example, in the supply head jacket 111 shown in FIGS. 7 and 8, the opening area of the sub-dope supply port 115 formed in an annular shape can be freely changed by the shift mechanism 114.

  Further, since the sub-dope is a dilution of the new dope, the amount of inflow of the sub-dope may be gradually decreased while the sub-dope is kept flowing. Further, when the dope supply pipe 71 is always open with respect to the new dope supply unit 73 (see FIG. 2), the dope dilution unit 74 (see FIG. 2) is not functioned, and the new dope is doped instead of the sub dope. You may supply to supply piping.

  It should be noted that the timing of injecting the sub-dope to form the sub-liquid flow may be when the old dope is replaced with the new dope, or even when the old dope is replaced with the new dope at an appropriate time. May be replaced with new dope.

  The present invention may be applied not only when the old dope is switched to the new dope but also when the prescription of the old dope is slightly changed. Moreover, in the said embodiment, although this invention is applied to piping (refer FIG. 1) between the raw material dope preparation unit 11 and the film forming unit 12, applicable piping for this invention is not restricted to this. . For example, you may provide a dope switching unit with respect to piping of each part, such as piping which connects the heater 40 and the cooler 42 in the raw material dope preparation unit 11. FIG. In addition, the present invention can be applied not only to piping but also to a component having a portion that becomes a dope channel.

  Next, specific examples of the present invention will be described. Dope A and dope B using cellulose triacetate and dichloromethane as the main solvent were prepared as new and old dopes. Then, using the dope switching unit 47 shown in FIG. 2, the dope A was flown as the old dope, and then the dope B was flowed through the dope supply pipe as the new dope to perform extrusion substitution. In order to confirm the effect of the present invention, a concentration sensor was provided at a position 5 m downstream from the dope switching unit 47. By measuring the concentration at this position, the rate of extrusion substitution was investigated using a stainless steel pipe of length 5 m and 80 A (dope supply pipe JIS schedule 10S (inner diameter 83 mm, wall thickness 3 mm)) as an experimental model. . Here, the liquid feeding rate means the ratio of the integrated amount for feeding the new dope to the capacity of the pipe. The sub-dope supply head 72 of the dope switching unit 47 also uses the same pipe as the dope supply pipe 71. At this time, the viscosities of dope A and dope B were substantially the same, and the flow rate of dope B was 20 L / min. In addition, a secondary liquid flow was formed around the main liquid flow using the secondary dope supply head 72 shown in FIG. 2 of the present embodiment.

  The dope replacement ratio for replacing the old dope with the new dope and the liquid feeding rate indicating the ratio of the new dope liquid feeding amount to the pipe capacity were measured. The dope substitution rate is expressed as a percentage. When 0%, the old dope occupies 100%. At 100%, the old dope becomes 0 and the new dope becomes 100%. In order to measure the dope substitution rate, the dope B was a transparent dope without a black dye, a black dye was put in the dope A, and the concentration by this black dye was measured to obtain the dope substitution rate. And the liquid feeding rate was obtained from the liquid feeding amount of dope.

  At this time, the viscosity μ1 [Pa · s] of the main liquid flow of the dope B is 30, and the viscosity of the secondary liquid flow μ2 [Pa · s is adjusted by diluting the dope B with dichloromethane as a subdope and adjusting the solvent content. ] Was 1.5, and μ2 / μ1 was 0.05. The thickness d1 [mm] of the main liquid flow was 81.5, the thickness d2 [mm] of the auxiliary liquid flow was 1.5, and the thickness ratio d1 / d2 was 54. The temperature T1 [° C.] of the main liquid flow was set to 35, the inner wall temperature T2 [° C.] of the pipe was set to 37, and the temperature difference ΔT of T2 with respect to T1 was set to 2.

  The conditions were the same as in Example 1 except that the thickness d1 [mm] of the main liquid flow was 41.5, the thickness d2 [mm] of the auxiliary liquid flow was 41.5, and the thickness ratio d1 / d2 was 1.

  The conditions were the same as in Example 1, except that the main liquid flow thickness d1 [mm] was 56.0, the sub liquid flow thickness d2 [mm] was 27.0, and the thickness ratio d1 / d2 was 2.

  The conditions were the same as in Example 1 except that the thickness d1 [mm] of the main liquid flow was 79.0, the thickness d2 [mm] of the auxiliary liquid flow was 4.0, and the thickness ratio d1 / d2 was 20.

  The conditions were the same as in Example 1 except that the thickness d1 [mm] of the main liquid flow was 82.1, the thickness d2 [mm] of the auxiliary liquid flow was 0.9, and the thickness ratio d1 / d2 was 91.

  The conditions were the same as in Example 1 except that the thickness d1 [mm] of the main liquid flow was 82.2, the thickness d2 [mm] of the auxiliary liquid flow was 0.8, and the thickness ratio d1 / d2 was 103.

  The same conditions as in Example 1 except that the viscosity μ1 [Pa · s] of the main liquid flow was set to 100, the viscosity μ2 [Pa · s] of the auxiliary liquid flow was set to 0.01, and μ2 / μ1 was set to 0.0001. did.

  The same conditions as in Example 1 except that the viscosity μ1 [Pa · s] of the main liquid flow is 100, the viscosity μ2 [Pa · s] of the auxiliary liquid flow is 0.1, and μ2 / μ1 is 0.001. did.

  The same conditions as in Example 1 except that the viscosity μ1 [Pa · s] of the main liquid flow is 30, the viscosity μ2 [Pa · s] of the auxiliary liquid flow is 0.3, and μ2 / μ1 is 0.01. did.

  The conditions were the same as in Example 1, except that the viscosity of the main liquid flow [mu] 1 [Pa.s] was 30, the viscosity [mu] 2 [Pa.s] of the auxiliary liquid flow was 3, and [mu] 2 / [mu] 1 was 0.1.

  The conditions were the same as in Example 1 except that the viscosity of the main liquid flow [mu] 1 [Pa.s] was 30, the viscosity of the auxiliary liquid flow [mu] 2 [Pa.s] was 27, and [mu] 2 / [mu] 1 was 0.9.

  The conditions were the same as in Example 1, except that the viscosity of the main liquid flow [mu] 1 [Pa.s] was 30, the viscosity [mu] 2 [Pa.s] of the auxiliary liquid flow was 30, and [mu] 2 / [mu] 1 was 1.

  The temperature T1 [° C.] of the main liquid flow was set to 35, and the inner wall temperature T2 [° C.] of the pipe was set to 35.4. The temperature difference ΔT of T2 with respect to T1 was set to 0.4. As a result, the viscosity μ1 [Pa · s] of the main liquid flow was 30, the viscosity μ2 [Pa · s] of the main liquid flow was 1.7, and μ2 / μ1 was 0.06. Other conditions were the same as in Example 1.

  The temperature T1 [° C.] of the main liquid flow was set to 35, and the inner wall temperature T2 [° C.] of the pipe was set to 35.6. The temperature difference ΔT of T2 with respect to T1 was set to 0.6. As a result, the viscosity μ1 [Pa · s] of the main liquid flow was 30, the viscosity μ2 [Pa · s] of the main liquid flow was 1.7, and μ2 / μ1 was 0.06. Other conditions were the same as in Example 1.

  The temperature T1 [° C.] of the main liquid flow was set to 35, the inner wall temperature T2 [° C.] of the pipe was set to 39, and the temperature difference ΔT of T2 with respect to T1 was set to 4. As a result, the viscosity μ1 [Pa · s] of the main liquid flow was 30, the viscosity μ2 [Pa · s] of the secondary liquid flow was 27, and μ2 / μ1 was 0.9. Other conditions were the same as in Example 1.

  The temperature T1 [° C.] of the main liquid flow was 20, the inner wall temperature T2 [° C.] of the pipe was 38, and the temperature difference ΔT of T2 with respect to T1 was 18. As a result, the viscosity μ1 [Pa · s] of the main liquid flow was 100, the viscosity μ2 [Pa · s] of the secondary liquid flow was 0.1, and μ2 / μ1 was 0.001. Other conditions were the same as in Example 1.

  The temperature T1 [° C.] of the main liquid flow was set to 5, the inner wall temperature T2 [° C.] of the pipe was set to 38, and the temperature difference ΔT of T2 with respect to T1 was set to 33. As a result, the viscosity μ1 [Pa · s] of the main liquid flow was 200, the viscosity μ2 [Pa · s] of the secondary liquid flow was 4.0, and μ2 / μ1 was 0.02. Other conditions were the same as in Example 1.

  The temperature T1 [° C.] of the main liquid flow was set to 5, the inner wall temperature T2 [° C.] of the pipe was set to 42, and the temperature difference ΔT of T2 with respect to T1 was set to 37. As a result, the viscosity μ1 [Pa · s] of the main liquid flow was 200, the viscosity μ2 [Pa · s] of the secondary liquid flow was 2.5, and μ2 / μ1 was 0.01. Other conditions were the same as in Example 1.

[Comparative example]
As a comparative example, extrusion replacement of old and new dopes was performed on the dope supply pipe without using a sub-dope supply head. The wall surface temperature T2 in the pipe was set to 35 [° C.], which is the same as the temperature T1 of the main liquid flow. The other conditions were the same as in Example 1.

  FIG. 9 shows the amount of new dope fed and the dope substitution rate. The vertical axis represents the substitution rate (%), and the horizontal axis represents the liquid feeding rate (liquid feeding amount / pipe capacity). The curve CA is of the conventional type, and the curve CB is of the first embodiment. It is a thing of the comparative example 1 shown below. The percentage of substitution is expressed in percentage. At 0%, the old dope occupies 100%, and at 100%, the old dope becomes 0 and the new dope indicates 100%.

  In the conventional type, a liquid feed amount of three times or more of the pipe capacity is required before being replaced with about 95%, whereas in the present embodiment, 95 is about 1.2 times the pipe capacity. The substitution rate is about 97% at about 1.5 times, and it can be seen that the substitution efficiency is improved.

  Table 1 shows each set value and the liquid feeding rate of dope B when the dope substitution rate becomes 95% in Examples 1 to 18 and Comparative Example 1.

  In the example satisfying the present invention, it is only necessary to feed the liquid twice as much as the pipe capacity at the maximum, and it can be seen that the replacement efficiency is improved as compared with Comparative Example 1 not satisfying the present invention.

It is the schematic which shows the solution casting apparatus which implements this invention. It is sectional drawing which shows the dope supply piping in which the dope switching unit of 1st Embodiment of this invention is provided. It is the III-III sectional view taken on the line in FIG. 2 of dope supply piping of 1st Embodiment of this invention. It is explanatory drawing which shows the velocity distribution of the new dope and sub dope in the dope supply piping which implemented this invention. It is explanatory drawing which shows the velocity distribution of the new dope in the conventional dope supply piping. It is sectional drawing which shows the dope supply piping of 2nd Embodiment of this invention. It is dope supply piping in which the dope switching unit of 3rd Embodiment of this invention is provided, and is sectional drawing which shows the state by which the sub dope supply port is open | released. It is sectional drawing which shows the state by which the dope switching unit of 3rd Embodiment of this invention is provided, it is dope supply piping, and the sub dope supply port is closed. It is explanatory drawing which shows the liquid feeding amount and dope substitution rate of the new dope shown by comparing the method of this invention and the conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solution film-forming equipment 47 Dope switching unit 71 Dope supply piping 72 Sub dope supply head 78 Sub dope 79 Main liquid flow 80 Sub liquid flow 81 New dope 93 Old dope

Claims (7)

A dope composed of a polymer and a solvent is sent to a casting die through a dope supply pipe, and the dope is cast on a support that runs endlessly from the casting die to form a casting film. In the dope switching method for switching from the old dope to the new dope by changing the prescription of the dope, with respect to the dope supply pipe in the solution casting equipment that is peeled off from the support after having support and dried to form a film,
A dope switching step of switching the dope supplied to the dope supply pipe from the old dope to the new dope;
On the upstream side of the dope supply pipe, a sub-dope having a viscosity lower than that of the new dope is supplied along the inner wall surface of the dope supply pipe, and a main liquid flow is formed by the new dope at the center of the dope supply pipe. And a sub liquid flow forming step of forming a sub liquid flow by the sub dope along the inner wall surface of the dope supply pipe around the main liquid flow.   The dope switching method according to claim 1, further comprising a step of stopping the sub-liquid flow forming step after a predetermined time has elapsed.   When the diameter of the main liquid flow is d1 [m] and the radial thickness of the sub-liquid flow is d2 [m], (d1 / d2) is 2 or more and 100 or less. Item 3. The dope switching method according to Item 1 or 2.   When the viscosity of the new dope is μ1 [Pa · s] and the viscosity of the sub-dope is μ2 [Pa · s], (μ2 / μ1) is 0.001 to 0.9. The dope switching method according to any one of claims 1 to 3.   The temperature of the inner wall surface of the dope supply pipe is increased in a range of 0.5 [° C.] or more and 35 [° C.] or less with respect to the temperature of the main liquid flow at the radial center of the dope supply pipe. The dope switching method according to any one of claims 1 to 4. A dope composed of a polymer and a solvent is sent to a casting die through a dope supply pipe, and the dope is cast on a support that runs endlessly from the casting die to form a casting film. In the dope switching device that switches from the old dope to the new dope by changing the dope prescription for the dope supply pipe in the solution casting equipment to be peeled off from the support after having support and dried to form a film,
On the upstream side of the dope supply pipe, a sub dope supply head having a supply port for supplying a sub dope having a viscosity lower than that of the new dope along the inner wall surface of the dope supply pipe,
A dope switching device comprising: a subdope supply unit that supplies a diluted dope obtained by diluting the new dope to the subdope supply head.   The dope switching device according to claim 6, wherein the sub-dope supply head includes an annular supply port formed over the entire circumference of the inner wall surface in the circumferential direction.

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