KR101997270B1 - Polymer solution filtering method and apparatus, polymer purifying method, and solution film forming method - Google Patents

Abstract

The present invention relates to a filtration method and apparatus for a polymer solution, a polymer purification method, and a solution film formation method. In the dissolving tank 6, the raw material cellulose acylate 17 is dissolved in methylene chloride 18 to form a dope 21. The dope 21 is filtered by the filter 12 of the auxiliary filter system. A solvent is added to the dope 21 at the upstream side of the filter 12 by the solvent addition unit 13 at the start of filtration to lower the viscosity of the dope 21. [ The flow rate of the dope 21 is increased in response to the viscosity decrease, and the throughput is improved. The dope 21 is heated by the temperature regulator 23b. The amount of solvent corresponding to the viscosity decrease of the dope 21 due to heating is determined and the amount of the solvent added in the solvent addition unit 13 is reduced by this amount. It is possible to avoid the incorporation of the filter aid into the dope 21 caused by the separation of the filter aid when the filtration is started or when the filtration is stopped.

Description

TECHNICAL FIELD [0001] The present invention relates to a polymer solution filtration method and apparatus, a polymer purification method, and a solution film formation method.

The present invention relates to a filtration method and apparatus for filtering a polymer solution with a filter aid, a polymer purification method, and a solution film formation method.

BACKGROUND ART Various display devices such as a liquid crystal display use various polymer films including a protective film for a polarizing plate and a viewing angle enlarging film. Examples of the method for producing such a polymer film for optical use include a melt film-forming method, a solution film-forming method, and the like. In the solution film-forming method, a polymer solution containing a polymer and a solvent (hereinafter referred to as " dope ") is formed on a running support to form a coherent film, then the coherent film is peeled off from the support, Since there is no heating process, there is no problem of damage to the film due to heat such as the melt film forming method. Therefore, it is optimal as a method for producing a polymer film which requires high transparency and stable optical characteristics.

Incidentally, in the dope, impurities such as dust and dirt mixed in the raw material of the original dope and mixed in preparation of the dope may be mixed as a foreign matter insoluble in the solvent of the dope. However, when a dopant containing an impurity is used, impurities are precipitated as impurities on the support, and it becomes difficult to separate the flexible film from the support. In addition, in the finished film, problems such as light scattering Cause. For this reason, it is necessary to remove impurities in the dope as much as possible before providing the dope to the softener.

Therefore, in general, in the solution film-forming method, the dope before being softened is filtered with a porous filter medium for the purpose of removing impurities in the dope. As the filter medium, a filter, a metal filter, a filter cloth or the like is used. However, there is a problem in that the filtration efficiency is lowered because the filtration material is occluded, the filtration time becomes longer, and the filtration flow rate decreases as time elapses from the start of filtration of any filter material.

In addition, in the case of using only a filter material such as a filter, a metal filter, a filter cloth or the like, it is difficult to remove impurities showing poor solubility in a solvent. Thus, for example, Patent Document 1 proposes an auxiliary filtration method for removing impure substances by using a filter aid in addition to the filter medium. As the filter aid, for example inert particles or powder such as silicon dioxide (SiO ₂ ) are used. This filter aid is used by being deposited randomly on a filter medium support such as a gold mesh filter. When the dope is passed through the filter medium having such a sediment layer formed thereon, irrespective of whether it is poorly soluble or not, impurities can be adsorbed on the filter aid and recovered, and a good dope with high clarity can be obtained. In addition, if a filter aid is used, clogging of the filter medium can be suppressed, and productivity is expected to be improved.

Japanese Patent Application Laid-Open No. 2009-214057

However, in the filtration system using the filter aid, the filtration aid is peeled off from the filter medium support due to abrupt fluctuation of the filtration pressure during filtration, and flows downstream, which may cause a failure of the foreign matter. Therefore, there is a demand to suppress the fluctuation of the filtration pressure as much as possible. Therefore, it is necessary to increase the filtrate flow rate gently to suppress the fluctuation of the filtration pressure from the start of filtration to the steady state, or from the steady state to the filtration stop. However, if the filtration flow rate is increased gently, the time required for the process of gently increasing the filtration flow rate is prolonged, and the productivity is lowered.

Disclosure of the Invention Problems to be Solved by the Invention It is an object of the present invention to provide a polymer solution which suppresses the fluctuation of filtration pressure in a transient state such as at the start and end of filtration and prevents the filtration aid from flowing downstream, A filtration method and apparatus, a polymer purification method, and a solution film formation method.

The filtration method of the polymer solution of the present invention is a filtration method for filtrating a polymer solution containing a polymer and a solvent by using a filter having a filtration aid agent, wherein a solvent is added to the polymer solution on the upstream side of the filter, And a solvent addition step of lowering the viscosity and suppressing the fluctuation of the pressure loss of the filter within a certain range.

A heating step of heating the polymer solution sent to the filter to gradually decrease the viscosity of the polymer solution and a step of adjusting the amount of solvent added in the solvent addition step corresponding to the viscosity decrease And a solvent addition diminution step of decreasing the solvent addition amount.

The method for purifying a polymer of the present invention comprises a dissolving step of dissolving a polymer in a solvent to obtain a polymer solution, a filtration step of using a filtration method of the polymer solution, and a step of mixing the polymer and the solvent, And a polymer precipitation step of dispersing the polymer solution obtained through the filtration process on the liquid containing the polymer solution and drying the solvent to precipitate the polymer.

In the dissolving step, the concentration of the polymer solution is preferably 2% by mass or more and 19% by mass or less. In the filtration step, it is preferable to perform auxiliary filter filtration with an absolute filtration accuracy of 2 탆 or more and 30 탆 or less. The solvent is preferably a single kind of solvent. It is also preferable that the polymer is cellulose acylate, the solvent is methylene chloride, and the liquid is water. In the polymer precipitation step, the temperature of the cellulose acylate solution is preferably 20 占 폚 to 120 占 폚, and the water temperature is preferably 40 占 폚 to 100 占 폚.

The solution film-forming method of the present invention comprises a dissolution step of dissolving a precipitated polymer obtained by the above-mentioned polymer purification method into a solvent to form a polymer solution, and a step of mixing the additive with the polymer solution obtained from this dissolution step, A softening step of forming a flexible film by flowing the polymer solution to which the additive liquid has been added in a soft dope from a flexible die into a flexible support, and a drying step of peeling the flexible film from the flexible support and drying.

The filtration apparatus of the present invention comprises a filter for filtering a polymer solution containing a polymer and a solvent by using a filter aid, and a solvent for adding a solvent to the polymer solution on the upstream side of the filter to lower the viscosity, And a solvent addition unit for inhibiting the solvent addition within a certain range. It is also possible to use a heating unit that heats the polymer solution sent to the filter and diminishes the viscosity of the polymer solution and a control unit that decreases the amount of solvent added by the solvent adding unit in correspondence with the viscosity decrease of the polymer solution by the heating unit .

According to the present invention, abrupt fluctuation of the filtration pressure from the start of filtration to the steady state or from the steady state to the filtration stop can be suppressed, and the outflow of the filtration aid into the polymer solution can be eliminated. Further, the amount of filtration at the time of starting filtration or at the end of filtration can be improved, and a filtration process with a good efficiency can be performed. By the filtration treatment having a good efficiency, the purification of the polymer and the solution film formation can be efficiently carried out.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view showing the outline of a polymer refining facility of the present invention. Fig.
2 is a cross-sectional view showing a filter medium of a filter.
3 is a perspective view schematically showing a solvent addition unit and a static mixer.
4 is a graph showing an example of the relationship between the dope concentration and the viscosity in the polymer solution.
5 is a graph for explaining the relationship between the pressure loss and the solid throughput.
6 is a graph showing the changes in the flow rate of the dope, the pressure loss, the dope temperature, and the amount of the solvent added in the filtration start treatment of the filter without changing the dope temperature and the solvent addition amount.
FIG. 7 is a graph showing the changes in the flow rate of the dope, the pressure loss, the dope temperature, and the amount of the solvent added in the filtering start treatment of the filter in the state where the dope is gradually heated.
8 is a graph showing changes in the flow rate of the dope, the pressure loss, the dope temperature, and the amount of the solvent added in the filtration start treatment of the filter in the state where the amount of solvent added is increased while heating the dope.
9 is a side view schematically showing a precipitator and a vibrating body.
10 is a side view schematically showing a solution film-forming apparatus.
11 is a sectional view showing a dynamic mixer.

1, the polymer refining equipment 5 includes a melting tank 6, a dope supply line 7, a precipitator 8, a vibrating body 9, a hot air dryer 10, , And a crusher (19). The dope supply line 7 has a switching valve 7a, a pump 11, a filter 12, a solvent addition unit 13, a static mixer 14, and a pressure control valve 7b .

A raw material cellulose acylate (hereinafter referred to as a raw material CA) 17 as raw material polymer is fed into the dissolution tank 6. A solvent reservoir tank 16 is connected to the dissolution tank 6 through a solvent supply conduit 15. Methylene chloride (18) as a solvent is stored in the solvent storage tank (16). Then, the methylene chloride 18 is injected into the dissolution tank 6 from the solvent storage tank 16 through the solvent supply conduit 15. The dissolving tank 6 has an agitator 6a. The dissolution of the raw CA 17 in the methylene chloride 18 is promoted by the agitator 6a to obtain a polymer solution (dope) 21 in which the raw material CA 17 is dissolved in methylene chloride 18 Loses. The concentration of the raw material CA 17 (the concentration of the polymer solution) in the dope 21 is, for example, 7 mass%. The dope concentration is 2 mass% or more and 19 mass% or less, preferably 5 mass% or more and 14 mass% or less. When the dope concentration is less than 2 mass%, the solvent removal cost becomes high, which is not preferable. On the other hand, if it exceeds 19 mass%, the viscosity becomes high and the pressure loss due to filtration becomes high, which is not preferable.

In the dissolving tank 6, the temperature of the dope 21 is maintained at, for example, 120 DEG C by the heating / heating effect by the jacket 6b. The dope 21 may be heated by a heating device separately provided on the downstream side of the dissolution tank 6 to heat the dope 21 to a predetermined temperature. The temperature of the dope 21 is preferably 20 占 폚 to 120 占 폚. If the temperature of the dope 21 is lower than 20 캜, it is necessary to cool it and the energy required for evaporation becomes large. On the other hand, if it exceeds 120 ° C, corrosion of the piping material is liable to occur, which is not preferable. The holding temperature of the dope 21, for example, 120 DEG C is up to the pressure regulating valve 7b, and becomes about 40 DEG C in a state of being ejected from the first nozzle 25 as described later. The obtained dope 21 is sent to the filter 12 of the dope supply line 7.

The filter 12 removes impurities of, for example, about 5 mu m from the dope 21 that has been sent. The filter 12 is an assistant filtration system, and the absolute filtration accuracy is in the range of 2 to 30 μm, and the absolute filtration accuracy is determined depending on the use of the final product, for example, the optical film and the use site. The absolute filtration accuracy of 5 占 퐉 or less means that the size that can be removed by 99.9% or more is 5 占 퐉.

As shown in Fig. 2, the filter medium 12a in the filter 12 is composed of a metal mesh filter 12b and a deposit layer 12d of the filter aid 12c. Since the filter 12 before use has only the network filter 12b and filtration can not be performed in this state, a deposited layer 12d having a certain thickness is formed on the network filter 12b. This initial deposit layer 12d becomes the precoat 12e. In order to form the precoat 12e, the precoated liquid circulating unit (not shown) circulates the precoated liquid in the filter 12 for a predetermined time. Foreign matter 21a such as impurities in the dope 21 is trapped when passing through the filter medium 12a.

A solvent addition unit 13 and a static mixer 14 are arranged in series on the upstream side of the dope supply line 7 with respect to the filter 12 as shown in Fig. As shown in Fig. 3, the solvent addition unit 13 has an addition nozzle 13a disposed in the dope supply line 7. As shown in Fig. The addition nozzle 13a sends the methylene chloride 18 into the dope 21 from the flattened nozzle orifice 13b.

The static mixer 14 is constituted by arranging a plurality of first elements 14b and second elements 14c arranged in series in the flow path 14a of the dope supply line 7. [ The first element 14b and the second element 14c are composed of different kinds of elements that change the angle or direction of mixing. In addition, the kind of the heterogeneous elements and the number of series arrangement may be changed as appropriate. By passing through these elements 14b and 14c, the methylene chloride 18 is uniformly mixed in the dope 21, and the concentration of the dope 21 is lowered.

Next, the pressure loss in the filter 12 will be described. It is perfectly reasonable to apply the Hagen-Poiseuille equation, which represents the pressure loss to the laminar flow, to the pressure loss in the filter 12. This Hagen-Poissy equation is shown below.

Ff = (ΔPf / ρ) = 32 · μ · L · u / (ρ · D 2)

Ρ is the density of the fluid, μ is the viscosity, L is the path length, u is the average flow velocity, and D is the path cross-sectional area. According to this Hagen-Poissy equation, the pressure loss? Pf at the time of filtration is found to be proportional to the viscosity μ and the average flow velocity u. That is, in the case of using this formula, the pressure loss? Pf in the filter can be expressed by the following formula (1) Lt; / RTI > The fluid density p is almost constant and can be ignored in this case. Therefore, the variation of the filter pressure loss? P, which causes the auxiliary agent leakage (the filtration aid 12c flowing downstream of the mesh filter 12b) by increasing the flow velocity u inversely, It can be eliminated.

Fig. 4 shows an example of the relationship between the dope concentration and the viscosity? In a general polymer solution. In a considerable number of polymer solutions, the viscosity mu increases exponentially as the dope concentration increases. Therefore, when the concentration of the dope 21 is reduced from, for example, 8 mass% to 4 mass%, the viscosity decreases from "16" to "4", and becomes 1/4 of the value before the drop.

5 is a graph showing the relationship between the pressure loss? P and the solid throughput. The pressure loss (? P) is an important factor determining the filtration life. When this pressure loss? P is regarded as a constraint, the processing amount is increased as the concentration is low. The pressure loss? P is expressed as a function of the viscosity μ × the flow rate u as described above. The solids throughput is expressed as a function of the dope concentration x flow rate u. The viscosity μ is a function of the square of the dope concentration. Therefore, as shown in Fig. 4, when the dope concentration is reduced from half, for example, from 8 mass% to 4 mass%, the viscosity 占 becomes 1/4. As shown in Fig. 5, when the pressure loss? P is, for example, "8", the flow rate is four times and the solid content concentration is half, so that when the dope concentration is 8 mass% , Whereas when the dope concentration is 4% by mass, the solid content throughput is " 8 ", and the solid content throughput is doubled. As described above, it can be seen that by lowering the concentration of the dope 21 even at the same pressure loss, the solid content throughput can be greatly increased and the throughput can be expected to be improved. In addition, the pressure loss? P in Fig. 5 is a numerical value based on the processing amount of the dope concentration of 4 mass% set as 1. Also, the viscosity 占 in Fig. 4 is 1 when the dope concentration is 2 mass%, and is numerically expressed based on this value.

In addition, in the conventional filtration method, the following two methods can be selected from the viewpoint of auxiliary agent leakage and filtration efficiency.

(1) As shown by the solid line L1 in Fig. 6 (A), the auxiliary agent is allowed to leak and filtration is performed to increase the throughput.

(2) As shown by the broken line L2 in Fig. 6 (A), filtration is performed by sacrificing the throughput and lengthening the low flow rate period so as not to cause auxiliary agent leakage.

In the case of performing filtration by allowing the auxiliary agent leakage in the above (1), the flow rate Q1 is raised early, and the throughput becomes large. However, since the amount of pressure loss change per unit time < RTI ID = 0.0 > P1 / t0 < / RTI > increases, auxiliary material leakage tends to occur and a high precision filter is required at the rear end. And the disadvantage that the throughput increases.

In the case of sacrificing the throughput of the above (2), there is an advantage that the auxiliary pressure leakage amount does not occur because the pressure loss change amount per unit time? P2 / t0 is small, but the flow rate Q is low Since the state continues, the throughput decreases and the start-up time becomes longer. Therefore, there is a disadvantage that the production capacity is lowered. In Fig. 6, the temperature of the dope 21 is constant, and there is no need to add a solvent, which is " 0 ".

Therefore, in the present invention, paying attention to the fact that the pressure loss? P can be arranged in the Hagen-Poissy equation, by performing the following control, the pressure loss? P is kept within a certain range, The filtration process is performed with good efficiency. In order to keep the pressure loss [Delta] P constant in the Hagen-Poisson formula, the product u · μ of the average flow velocity u of the fluid and the viscosity μ can be made constant. For high productivity, as shown in Fig. 7, there is a method of increasing the average flow velocity u in correspondence to a decrease in the viscosity 占 by increasing the temperature of the dope 21, and a method of increasing the average flow velocity u as shown in Fig. 21) is increased and solvent addition is performed to increase the average flow velocity u.

FIG. 7 shows that by increasing the temperature of the dope 21, the viscosity μ is lowered and the average flow velocity u is increased in correspondence with the viscosity decrease, thereby improving the filtration efficiency. In the first step for raising the flow rate Q to the target value Q1, the dope temperature is elevated in terms of efficiency, for example, in a full capacity. At this time, the temperature rise is performed while monitoring the pressure loss change amount? P3 / t0, which is a time change of the pressure loss? P. 6 and 7, since the solvent is not added, the dope density p is fixed, and the transition of the flow rate Q and the pressure loss? P is almost the same.

Fig. 7 (C) shows the temperature change of the dope 21 over time. The upper limit of the increase of the dope temperature is determined in consideration of the following. First, if the facility capacity is excessively high, the investment cost becomes large, which is undesirable. In addition, if the heat source temperature is excessively high, the polymer solution may boil up, causing problems such as precipitation of solid matter and generation of bubbles, which is not preferable. Therefore, a proper value is determined in consideration of both.

As shown in Fig. 7, when only the temperature is increased, the pressure loss change amount? P3 / t0 per unit time is small. At the same time, control is performed to limit the pressure loss change amount? P3 / t0 per unit time to the allowable range. Actually, the pressure loss change amount? P3 / t0 per unit time is measured, and if the value is an unacceptable value, control is performed so as to reduce the rising speed of the flow velocity. In this embodiment, the throughput is moderate, but since the pressure loss change amount? P3 / t0 per unit time is small, auxiliary agent leakage is eliminated.

8 shows a case where the solvent T is added to the dope 21 in addition to increasing the temperature T of the dope 21 and the viscosity μ is decreased to increase the average flow velocity u . In addition to the temperature rise of the dope 21, when the solvent is added to lower the dope concentration, the viscosity? Of the dope 21 is further lowered. In the first step for raising the flow rate Q to the target value Q2, the temperature is increased by the full capacity and the amount of the solvent is increased. As the temperature continues to rise, the amount of solvent added is increased with respect to the amount required to lower the viscosity further.

Even in the second step in which the dope flow rate Q is constant (= Q2), the dope temperature T continues to rise. When the amount of solvent added is constant, the viscosity? Of the dope 21 decreases and the pressure loss? P decreases. Therefore, the solvent addition amount X is gradually reduced by an amount corresponding to the lowering of the pressure loss? P. At the end of the second step, the dope temperature T reaches the maximum value T3. In the subsequent third step, the increasing rate of the pressure loss? P is controlled by gradually decreasing the amount X of the solvent added.

In this embodiment in Fig. 8, since the pressure loss change amount DELTA P4 / t0 per unit time is small, leakage of the filtration aid agent does not occur. In practice, the temperature rise due to the heating of the dope 21 is made constant, and the flow rate is constantly raised. Then, the rise of the pressure loss change amount? P4 / t0 per unit time is measured to increase or decrease the addition amount of the solvent to limit the control range. Although the final pressure loss? P4 shown in Fig. 8 is higher than the final pressure loss? P3 in Fig. 7, the fact that the amount of change is important and the final pressure loss? P4 is high, It does not.

In the filtration start processing, the dope 21 is sent to the filter 12 to start filtration. 2, the filtration aid 12c is randomly deposited on the metal mesh filter 12b, so that the deposit layer 12d is formed on the surface of the filter medium 12b, . The initial state of the deposit layer 12d becomes the precoat 12e.

As shown in Fig. 1, the controller 23 adjusts the flow rate Q of the dope 21 by adjusting the rotational speed of the pump 11, and when the filtration is started as shown in Fig. 8 (A) The flow rate Q is increased from "0" to a predetermined amount Q2. The controller 23 controls the temperature regulator 23b so that the temperature regulator 23b heats the dope 21 to regulate the temperature of the dope 21 as shown in Fig. The temperature (T) is gradually increased. That is, the temperature regulator 23b functions as an embodiment of the heating unit. The controller 23 also controls the flow rate control valve 23a to increase the addition amount X of the methylene chloride 18 to the dope 21. [ When the dope flow rate Q reaches the target constant value Q2, the controller 23 controls the flow rate adjustment valve 23a so that the amount of methylene chloride The additive amount X of the additive 18 is decreased. That is, the controller 23 and the flow rate adjusting valve 23a function as one aspect of the control unit. Thereby, the transition from the filtration start process to the normal process can be performed.

Control parameters in the controller 23 include a dope flow rate, a dope temperature, and a solvent addition amount. It is preferable to carry out the control so that the boiling point of methylene chloride is 40 DEG C, the dope temperature is limited, and the amount of the solvent is not limited.

Before the start of the operation, the initial setting is performed. In the initial setting, the flow rate increase rate of the filtration, the heating rate of the dope 21, and the solvent addition amount are set. The flow rate increase rate of the filtration is determined in consideration of productivity. If the flow rate increase rate is too low, the advantage of using this method is eliminated. If it is excessively high, the amount of the solvent to be added is excessively increased, resulting in a large energy loss in the solvent removing step. Therefore, the flow rate increase rate is determined from the viewpoint of energy efficiency and productivity. The heating rate of the dope 21 is determined from the facility scale. For example, the heating rate of the dope 21 is set to a large value within a range that permits the boiling point of the solvent and the polymer denaturation. The amount of the solvent added is set to an optimum value in terms of energy efficiency and productivity.

After the initial setting, the pre-coat process is performed. In the pre-coat treatment, the filter aid 12c is sent from the not-shown pre-coat formation line, and the filter aid 12c is deposited on the metal mesh filter 12b as shown in Fig. 2, . Filtration is started after this pretreatment.

In the filtration process, the dope temperature first rises at a constant rate. Then, during this heating, the pressure loss change amount DELTA P4 / t0 per unit time is obtained at predetermined time intervals. When the pressure loss change amount? P4 / t0 exceeds a certain range, auxiliary agent leakage occurs. Therefore, as shown in Fig. 8 (C), a solvent is added so as to suppress the leakage of the auxiliary agent.

Table 1 shows the results when the pressure loss change amount? P4 / t0 (Mpa / h) is changed. In Table 1, " A " indicates that there is no auxiliary agent leakage due to the naked eye; " B " indicates auxiliary agent leakage due to visual examination; Quot; D " means a case where there is an auxiliary agent leakage, and a case where there is no filtering effect, respectively. From Table 1, when the pressure loss change amount? P4 / t0 exceeds 0.8 MPa / h, auxiliary agent leakage occurs. For this reason, it is preferable that the auxiliary agent leakage is somewhat left, but not more than 0.6 Mpa / h, which does not need to increase the filtration load in the next step. If it is 0.5 MPa / h or less, it is preferable because there is no filtration load in the next step. If it is 0.4 MPa / h or less, occurrence of auxiliary agent leakage was not observed although it was observed with naked eyes.

Pressure loss variation
ΔP4 / t0
(Mpa / h) 0.2 0.4 0.5 0.6 0.8 0.9 result A A B C D D

As described above, when the filtration start processing is terminated and the state is shifted to the steady state, the filtration processing is performed while maintaining this steady state. When the polymer refining equipment 5 is stopped, filtration stop processing is performed. In this filtration stop process, the dope temperature and the solvent addition amount are controlled by a pattern in which the time lapse is reversed from that in Fig. 8, so that the pressure loss change amount P4 / t0 per unit time becomes constant, " By performing the filtration stop treatment in this manner, filtration can be stopped efficiently without reducing the filtration throughput and eliminating leakage of the filtration aid.

In the filtration normal treatment, when the filtration pressure has reached a filtration limit due to accumulation of foreign matter 21a trapped by the filtration aid 12c or the like, the filter aid 12 is fed from the filter aid 12 12c are retrieved. Further, the filter 12 is washed with a solvent. Thereafter, as shown in Fig. 2, a new filtration aid 12c is sent from the precoat forming line, and the filtration aid 12c is deposited to form the precoat 12e on the metal mesh filter 12b. After the formation of the precoat 12e, the filtration start treatment is performed. Further, the recovery of the auxiliary agent after completion of the filtration and the formation of the precoat 12e are described in detail in, for example, Japanese Laid-Open Patent Publication No. 2009-66569, and a description thereof will be omitted.

As described above, in the filtration method of the present invention, attention is paid to the viscosity of the dope 21 in the filtration process from the start of filtration to the steady state, the filtration from the steady state to the stop of filtration, The filtration amount can be increased by controlling the temperature of the dope 21 and the amount of solvent added to the dope 21 as a factor for changing the amount of the filtration aid 12c and the filtration can be started or terminated without leakage of the filtration aid 12c.

The dope 21 filtered by the filter 12 of the present invention as described above is sent to the precipitator 8 where the polymer in the dope 21 is precipitated. As shown in Fig. 9, the precipitator 8 is a sealed type in which gas and liquid inside do not leak out to the outside, and for example, a horizontal cylindrical tank is used. Hot water 22 maintained at a temperature equal to or higher than the boiling point of methylene chloride 18 is stored in the precipitator 8 in order to evaporate the methylene chloride 18 in the dope 21.

A discharge nozzle 24 for discharging an inert gas (air, nitrogen, or the like) is disposed at the bottom of the precipitator 8. The temperature of the inert gas sent to the discharge nozzle 24 is maintained at 20 ° C or more and 100 ° C or less. Methylene chloride 18, which is a poorly soluble component for water, is dissipated into the inert gas discharged from the discharge nozzle 24. The initial concentration of methylene chloride in the inert gas bubbles is 0, while when the concentration of methylene chloride in the water is high, the concentration difference is used as a driving force to pass through the boundary membrane between water and air bubbles, and methylene chloride (18) Move. And, the higher the bubble temperature, the higher the saturated vapor pressure in the bubbles, so the amount of methylene chloride that can be moved increases. As a result, the evaporation of the methylene chloride 18 in the dope 21 is promoted and the efficiency is improved. If the temperature of the inert gas exceeds 100 ° C, there is a fear that the water boils, and as a result, the water content in the steam increases, so that the temperature is 100 ° C or lower.

The temperature of the hot water 22 supplied to the precipitator 8 is preferably 40 ° C or higher and 100 ° C or lower. If the temperature is lower than 40 占 폚, the methylene chloride 18 does not evaporate, and precipitation of the polymer becomes impossible. On the other hand, if it exceeds 100 캜, it is necessary to operate the pressurized pressure to keep the water in a liquid state, which is not preferable.

A first nozzle (25) and a second nozzle (26) are disposed on the inner surface of the precipitator (8). In addition, the stirring wing (27) is disposed inside the precipitator (8). The stirring blades 27 are constituted by fixing a plurality of blades 27b to the rotating shaft 27a. The stirring vane 27 is mounted in the precipitator 8 so that the rotating shaft 27a is horizontal. One end of the rotary shaft 27a extends outward from the extruder 8, and the motor 29 is connected to this. The rotation of the motor 29 causes the stirring vanes 27 to rotate so that the hot water 22 in the precipitator 8 is stirred to keep the water surface temperature constant.

The number of the rotary shafts 27a of the stirring blades 27 may be one or plural. In the case of a plurality of units, adjacent units may be rotated in the same direction or in the same direction. It is preferable that the hot water 22 flows from the vicinity of the water surface toward the discharge port 8a. The arrangement direction of the stirring blades 27 and the shape of the stirring blades are not limited to those shown in the drawings, but any other arrangement may be used as long as it can stir the hot water 22 in the precipitator 8.

As shown in Fig. 1, the first nozzle 25 is connected to a dope supply line 7. As a result, the dope 21 (see FIG. 9) is sprayed from the first nozzle 25 and scattered toward the water surface. The piping from the pressure regulating valve 7b to the first nozzle 25 of the precipitator 8 is formed to be short so that the dope 21 is stably flash evaporated in the precipitator 8. Although only one first nozzle 25 is disposed, the number of the nozzles 25 is not limited to one but may be appropriately increased.

A hot water supply line 28 is connected to the second nozzle 26. 9, the second nozzle 26 includes a nozzle head 26a arranged in the lengthwise direction of the precipitator 8 and a plurality of nozzle bodies 26a arranged at a predetermined pitch in the nozzle head 26a 26b. The hot water supply duct 28 sends the hot water 22 from the hot water storage tank 39 to the second nozzle 26. As a result, the hot water 22 is sprayed from the second nozzle 26 and scattered toward the water surface.

It is preferable that the dispersion of the dope 21 by the first nozzle 25 and the hot water 22 by the second nozzle 26 are uniformly performed in the width direction of the cylindrical tank. Thereby, precipitation of cellulose acylate can be efficiently carried out.

1, the hot water supply line 28 is provided with a pump 28b, a filter 28c, a check valve 28d, and a temperature controller 28e in addition to a suitably formed switch valve 28a . The pump 28b adjusts the flow rate of hot water by adjusting the number of revolutions. The filter 28c filters the foreign matter from the hot water 22. The temperature controller 28e performs final temperature adjustment of the temperature-adjusted hot water in the hot water storage tank 39. [ As a result, hot water 22 (see FIG. 9) heated at a proper temperature is injected from the second nozzle 26 toward the water surface at a predetermined flow rate.

The dope 21 injected from the first nozzle 25 comes into contact with the hot water 22 in the precipitator 8. As a result, The hot water 22 is heated and maintained at a boiling point or more of the methylene chloride 18. Therefore, the methylene chloride 18 in the dope 21 in contact with the hot water 22 is momentarily evaporated by the heating with the hot water 22, and the raw CA 17 is precipitated in the form of, for example, , Precipitated cellulose acylate (hereinafter referred to as precipitation CA) 30. In the present embodiment, hot water 22 heated (for example, 80 DEG C) above the boiling point of methylene chloride 18 from above the water surface is dispersed from the second nozzle 26, Thereby promoting evaporation of the chloride (18).

At one end of the precipitator 8, an outlet 8a of the precipitation CA 30 is opened. The hot water 22 near the water surface flows toward the discharge port 8a by the rotation of the stirring vane 27 so that the precipitation CA 30 advances toward the discharge port 8a. The plurality of nozzle bodies 26b of the second nozzle 26 are arranged so as to be inclined so that the spraying direction is directed toward the discharge direction of the precipitation CA 30. [ Therefore, the precipitation CA 30 is also fed toward the discharge port 8a by the extrusion of the hot water 22 injected from the second nozzle 26. [

A vibrating body 9 is disposed below the discharge port 8a. The precipitation CA 30 precipitated by the precipitator 8 overflows together with the hot water 22 from the discharge port 8a and is discharged from the precipitator 8 to the oscillator 9. [ In the vibrating body 9, the precipitation CA 30 is received from the body 9a. The hot water 22 passes through the body 9a and flows into the hot water recovery tank 9b. Then, the water is returned to the hot water storage tank 39 (see FIG. 1) by the water return duct 38.

The body 9a is vibrated by the vibration mechanism 9c. On the main body 9a, the precipitation CA 30 is shaken and sent out to the squeeze roller 33 by vibration. The squeeze rollers 33 and 34 sandwich the precipitation CA 30 from the up and down directions to squeeze moisture. Although two squeeze rollers 33 and 34 are provided, one or three or more of them may be used.

This moisture is returned to the hot water storage tank 39 (see FIG. 1) through the hot water recovery tank 9b and the water recovery pipe 38.

As shown in Fig. 1, the water return line 38 has a switching valve 38a, a pump 38b, a filter 38c, and a check valve 38d. When the foreign matter contained in the hot water 22 is filtered by the filter 38c, the hot water 22 is returned to the hot water storage tank 39.

The precipitator 8 and the vibrating body 9 are disposed in the same sealing tank 8b. A solvent return pipe 55 is connected to the sealed tank 8b. The methylene chloride 18 recovered through the solvent recovery pipe 55 is returned to the solvent storage tank 16 via the condenser 56 and the separation tank 57 and circulated . Similarly, the solvent return pipe 55 is also connected to the hot air dryer 10 and the crusher 19, which will be described later, and the methylene chloride 18 is circulated through the solvent return pipe 55.

The precipitation CA 30 coming out of the squeeze roller 34 is guided by the guide plate 35 and sent to the rotary valve 40. The rotary valve 40 has a plurality of valve plates 40b in the cylinder 40a and the front end of the valve plate 40b closely contacts the inner wall of the cylinder 40a and rotates, And the hermetic tank 8b. The precipitation CA 30 coming out of the rotary valve 40 is sent to the hot air dryer 10.

The hot air dryer 10 dries the precipitation CA 30 sent by the rotary valve 40 with hot air. The dried precipitation CA 30 is sent to the crusher 19 and crushed into a lump of a predetermined size. The precipitated CA 30 after the pulverization is filled in the flexible container bag 20.

As shown in Fig. 1, the hot water storage tank 39 has a heater 39a, a jacket 39b, and a stirrer 39c. The heater 39a heats the hot water 22 in the hot water storage tank 39 to a predetermined temperature. In the jacket 39b, the heating medium is circulated and the water in the hot water storage tank 39 is maintained at a constant temperature. When the hot water 22 of the hot water storage tank 39 becomes equal to or less than a predetermined amount, the predetermined amount of hot water 22 is replenished from the pure water storage tank 60 to the hot water storage tank 39 by the water supply pipe 51. The water supply line 51 has a switching valve 51a, a pump 51b, and a pure water filtration unit 51c. The pure water filtration apparatus 51c filters the impurities in the hot water 22.

The methylene chloride 18 used in the present embodiment is a substance whose utilization and disposal are monitored by the Pollutant Release and Transfer Register (PRTR) method from the concern of environmental load and toxicity to humans. For this reason, emissions to the outside of the factory building should be avoided. Therefore, in addition to increasing the airtightness of the building by, for example, a double structure, it is necessary to reduce the amount of methylene chloride gas leaking from each device as much as possible. For this reason, in the present embodiment, the methylene chloride 18 is circulated only in a closed circulation system. The precipitator 8, the vibrating body 9, the hot air dryer 10, the crusher 19, and the hot water storage tank 39 are separately sealed. The solvent return line 55 is connected to each of the sealed devices 8 to 10, 19, and 39, and is used again in the circulation system to prevent the methylene chloride gas from leaking to the outside.

The methylene chloride 18 evaporated inside the precipitator 8, the vibrating body 9, the hot air dryer 10, the crusher 19 and the hot water storage tank 39 flows through the solvent return line 55 to the condenser 56). The solvent return pipe 55 has a switching valve 55a and a pump 55b. The methylene chloride 18 sent from the solvent return line 55 is recycled separately from water as described later.

Although the illustration is omitted, the installation space of a building or each device is divided into an enclosed space. Then, the methylene chloride gas is recovered for each division unit, and adsorbed and recovered by an adsorption tower or the like. Therefore, even when the methylene chloride gas is blown from each of the devices 8 to 10, 19, and 39, it is eventually caught and never released outside the building.

In the condenser 56, a gas mixed with steam and methylene chloride sent from each of the devices 8 to 10, 19, and 39 is heat-exchanged with cold water, for example, to coagulate and liquefy. The coagulated liquid is sent to the separation tank (57). The separating tank 57 separates the liquid into methylene chloride 18 and hot water 22 depending on the specific gravity. The methylene chloride (18) is located in the lower layer, and the hot water (22) is located in the upper layer. Therefore, the separation tank 57 has a jacket 57a and a switching valve 57b. In the jacket 57a, for example, water is circulated as the temperature control medium, and the methylene chloride 18 and the hot water 22 are maintained at an appropriate temperature.

The hot water 22 separated from the separation tank 57 is sent to the pure water storage tank 60 and the methylene chloride 18 is sent to the solvent storage tank 16 for storage.

The hot water 22 supplied to the precipitator 8 is stored in the hot water storage tank 39. The hot water storage tank 39 has a jacket 39b and is maintained at a constant temperature by the flow of the temperature control medium. The water from the hot water storage tank 39 is sent to the second nozzle 26 in the precipitator 8 by the hot water supply line 28 and is scattered toward the water surface by the second nozzle 26. The temperature of the hot water 22 is adjusted by the temperature controller 28e. Further, the flow rate of the hot water 22 is controlled by controlling the rotation number of the pump 28b, so that the water surface in the precipitator 8 is maintained at a predetermined position.

Next, the operation of the present embodiment will be described. As shown in Fig. 1, when the precipitation CA 30 is produced, the raw CA 17 and the methylene chloride 18 are added to the dissolution tank 6 and stirred by an agitator 6a to be stirred for example, A dope 21 having a solution concentration of 7 mass% is produced. The dope 21 passes through the filter 12 and is sent to the first nozzle 25 of the extruder 8 with the pressure controlled by the pressure regulating valve 7b. In the present embodiment, since the concentration of the dope 21 is 7 mass%, the filtration load is small and high-performance filtration becomes possible.

As shown in Fig. 9, the dope 21 is sprayed toward the water surface in the precipitator 8 from the first nozzle 25 and diffuses into the water surface. The temperature of the hot water 22 is set to a temperature higher than the boiling point of the methylene chloride 18. Therefore, the methylene chloride 18 in the dope 21 in contact with the water surface is instantaneously evaporated by the heat from the hot water 22, and a precipitate CA 30 in the form of a filament is obtained. The precipitation CA 30 efficiently evaporates the methylene chloride 18 even by the hot water shower from the second nozzle 26. The precipitation CA 30 is sent to the discharge port 8a by spraying the hot water 22 from the agitating blades 27 and the second nozzle 26.

When the hot water 22 reaches the outlet 8a, the hot water 22 overflows together with the precipitation CA 30 and falls on the vibrating body 9. The precipitation CA 30 is discharged by the body 9a toward the rotary valve. The hot water 22 having passed through the body 9a is recovered by 9b.

As described above, the precipitation CA 30 from which the impurities and the like have been removed from the raw material CA 17 is obtained. This precipitation CA 30 is more likely to be dissolved in methylene chloride 18 and other various solvents than the raw CA 17. This is presumed to be due to dissolution once at the stage of the raw material CA 17 and disappearance of the unheated part in the raw material CA 17.

The methylene chloride 18 is used as the solvent for the raw CA 17 and the methylene chloride 18 is evaporated by the hot water 22 heated by the boiling point of the methylene chloride 18 or more. The precipitation CA 30 having excellent solubility can be made efficient by reducing the loss of heat energy. Further, by using a single kind of solvent, recovery and reuse of the subsequent solvent can be simplified.

The precipitation CA 30 is divided by the vibrating body 9 to keep the precipitator 8 in a closed state so that a solvent such as methylene chloride 18 can be used without leaking outside the apparatus.

In the above embodiment, the methylene chloride 18 is used as the solvent for the raw CA 17, and the methylene chloride 18 is evaporated by the hot water 22 heated by the boiling point of the methylene chloride 18 . However, the present invention is not limited to these materials. As long as the solvent is a good solvent, another single solvent or a mixture of plural kinds of solvents may be used. In addition, if the liquid can be heated by the boiling point of the solvent or more, it is not limited to water, and other liquids may be used. When a solvent mixed with a plurality of kinds is used, a solvent mixed with a plurality of kinds recovered by the solvent recovery duct 55 is separated and recovered as a solvent or reused as a mixed solvent.

In the above embodiment, the precipitation CA 30 is sent in the direction of the discharge port by the flow of the hot water 22. Alternatively, or in addition thereto, it is sent to the discharge port 8a by a roller or other conveyance section .

The raw polymer is dissolved in a solvent as described above, and the polymer is precipitated after filtering the solution, whereby foreign matters in the polymer are removed. Further, a precipitated polymer having improved solubility in a solvent can be obtained. The precipitated polymer is stored, and the precipitated polymer is dissolved by the solvent at the time of film formation to form a soft-doped film.

[Solution forming equipment]

10, the solution film-forming equipment 68 has a mixing device 69, a flexible device 73, a pin tenter 74, a drying chamber 75, and a winding device 76. The mixing device 69 has a dissolving tank 80, a pump 81, a static mixer 82, a dynamic mixer 83, and a filter 84. The dissolution tank 80 has the same constitution as the dissolution tank 6, and the precipitation CA 30 and the solvent 79 for dissolving the precipitation CA 30, for example, are introduced. By stirring with the stirrer 80a after the addition, the precipitation CA 30 is dissolved in the solvent 79.

The soft dope 85 having a concentration of, for example, about 20% by mass in the dissolution tank 80 is used as the dissolution tank 80 in the dissolution tank 80 by using the precipitation CA 30, By a dissolving operation. Therefore, the running cost using a complicated device such as heating, pressurization and concentration required for dope preparation as in the prior art does not go through a high process, and high-precision filtration is also unnecessary, and the running cost for filtration can also be reduced.

Since the complicated device configuration is not employed and only the dissolving tank 80 is used, the passage capacity to the flexible die 78 of the flexible dope 85 can be reduced to about 1/30 of that of the conventional one. For this reason, when the flow rate of the new varieties is replaced by the new varieties with a flow rate of three times the flow rate of the new varieties through the flexible dope of the new varieties, the flow rate for replacement is about 1/30 Can be reduced. In addition, since the amount of the dope to be replaced is small, the time required for switching the new variety can be shortened and the new kind of dope can be efficiently switched.

The soft dope 85 dissolved in the dissolving tank 80 is sent to the static mixer 82 by the pump 81. At the inlet of the static mixer 82, an addition unit 71 having an addition nozzle 86 is disposed.

The addition unit 71 has two systems of additive liquid reservoirs 89a and 89b, a three-way valve 90 and a pump 91 in addition to the addition nozzle 86. [ The three-way valve 90 selects one of the additive liquids 93a as one of the additive liquid storage tanks 89a and 89b. The pump 91 sends the selected additive liquid 93a to the additive nozzle 86.

The static mixer 82 is constructed in the same manner as the static mixer 14 shown in Fig. 3, and a plurality of the first element 14b and the second element 14c are arranged in series. By passing through these elements 14b and 14c, the additive liquid 93a is mixed with the soft dope 85. [

11, the dynamic mixer 83 mixes the additive liquid 93a mixed with the static mixer 82 and the soft dope 85 in the pipe 83a through the stator 83b and the rotator 83c ). The rotator 83c is fixed to the drive shaft 83d. The rotator 83c rotates relative to the stator 83b by rotation of the drive shaft 83d. The drive shaft 83d is connected to a motor (not shown). Thereby, mixing of the soft doping 85 and the additive solution 93a is promoted, and the additive solution 93a is mixed more uniformly in the soft doping 85. [

At both ends of the pipe 83a, a seal member 83e and a labyrinth member 83f are disposed. On the circumferential surface of the labyrinth member 83f, a spiral protrusion 83g protrudes. The labyrinth member 83f is fixed to the drive shaft 83d and rotates integrally with the drive shaft 83d. The spiral ridges 83g of the right and left labyrinth member 83f have opposite spiral directions. When the drive shaft 83d rotates, the flexible dope 85 entering from the seal member 83e is returned to the pipe 83a by each spiral protrusion 83g. This prevents the soft dope 85 from leaking from the gap between the drive shaft 83d and the seal member 83e.

The soft dope 85 that has passed through the dynamic mixer 83 is filtered by the filter 84. Since the precipitation CA 30 has foreign matters removed from the sediment, the filtration load of the filter 84 is small and the filtration life is long. Thereafter, the flexible dope 85 is sent to the flexible die 78 and is flexible on the rotating flexible drum 95.

10, the flexible device 73 has a flexible die 78, a flexible drum 95, and a peeling roller 96, which are disposed in the flexible chamber 73a. The flexible drum 95 is rotated about its axis by a driving device (not shown). The flexible drum 95 is set at a temperature at which the flexible film 97 is cooled by a temperature controller (not shown).

The flexible die 78 continuously flows the flexible dope 85 toward the circumferential surface of the rotating flexible drum 95. In the flexible drum 95, a band-shaped flexible film 97 is formed by the flexible dope 85. By cooling, the flexible film 97 on the flexible drum 95 is brought into a state in which it can move freely and carry it. Thereafter, the flexible film 97 is peeled off from the flexible drum 95 by the peeling roller 96, and becomes a strip-shaped wet film 98.

In the crosslinking portion 99 between the flexible chamber 73a and the pin tenter 74, the conveying roller 99a introduces the wet film 98 into the pin tenter 74. The pin tenter 74 has a plurality of fin plates that penetrate and hold both side edges of the wet film 98. The drying wind is sent to the wet film 98 held by the moving fin plate. As a result, the wet film 98 is dried to form a strip-shaped film 100.

The ear cutting device 101 is formed on the downstream side of the pin tenter 74. The die cutting apparatus 101 cuts both side edges of the film 100. The cut edges of both sides are sent to the crusher by blowing and crushed. It is possible to use the crushed both side edge portions dissolved in the solvent instead of the raw CA (17) or precipitation CA (30) to reuse.

In the drying chamber 75, a plurality of rollers 75a are arranged, and the film is rolled thereon. The temperature and humidity of the atmosphere in the drying chamber 75 are controlled by an unillustrated air conditioner and the film 100 is passed through the drying chamber 75 so that the film 100 is dried.

Between the drying chamber 75 and the winding device 76 are provided a cooling chamber 102 for cooling the film 100, a forced static electricity eliminating device (static electricity bar) for discharging the film 100, And a knurling-imparting roller for imparting knurling to the knurl. The winding device 76 has a press roller, and winds the film 100 on the winding core.

The film 100 thus obtained can be used particularly for a retardation film or a polarizing plate protective film. The width of the film 100 is preferably 600 mm or more, more preferably 1400 mm or more and 2500 mm or less. The width of the film 100 may be larger than 2500 mm. The film thickness of the film 100 is preferably 15 mu m or more and 120 mu m or less.

(Polymer)

The polymer is not particularly limited as long as it is a thermoplastic resin, and examples thereof include a cellulose acylate, a lactone ring-containing polymer, a cyclic olefin, and a polycarbonate. Of those, preferred are cellulose acylate and cyclic olefins. Of these, cellulose acylate containing an acetate group and a propionate group, and cyclic olefins obtained by addition polymerization are more preferable, and cyclic olefins obtained by addition polymerization Olefins.

(Cellulose acylate)

There may be only one acyl group used for the cellulose acylate, or two or more acyl groups may be used. When two or more kinds of acyl groups are used, one of them is preferably an acetyl group. It is preferable that the ratio of the esterification of the hydroxyl group of cellulose to the carboxylic acid, that is, the substitution degree of the acyl group satisfies all of the following formulas (I) to (III). In the following formulas (I) to (III), A and B represent substitution degrees of an acyl group, A represents a substitution degree of an acetyl group, and B represents an acyl group substitution of 3 to 22 carbon atoms . It is also preferable that 90 mass% or more of triacetyl cellulose (TAC) is 0.1 mm or more and 4 mm or less.

(I) 2.0?? +?? 3.0

(II) 1.0??? 3.0

(III) 0??? 2.9

The total degree of substitution? +? Of the acyl group is more preferably 2.20 or more and 2.90 or less, and particularly preferably 2.40 or more and 2.88 or less. The substitution degree B of the acyl group having 3 to 22 carbon atoms is more preferably 0.30 or more, and particularly preferably 0.5 or more.

Details of the cellulose acylate are described in paragraphs [0140] to [0195] of Japanese Laid-Open Patent Publication No. 2005-104148. These substrates are also applicable to the present invention. The additives such as a solvent and a plasticizer, an anti-deterioration agent, an ultraviolet absorber (UV agent), an optically anisotropic control agent, a retardation control agent, a dye, a matting agent, a stripping agent and a peeling accelerator are likewise disclosed in Japanese Patent Laid-Open No. 2005-104148 Are described in detail in paragraphs [0516] to [0516]. Cellulose as a raw material of cellulose acylate may be obtained from any of linter and pulp.

Further, although the flexible drum 95 is used as the support, a flexible band may be used. In this case, a flexible band is spread over a pair of drums whose horizontal rotary shafts are arranged, and the flexible band is caused to run by rotating the drum.

Although the flexible film 97 is in a state in which the flexible film 97 can be peeled off by the cooling gelling method of cooling the flexible film 97 on the flexible drum 95, the present invention is not limited to this, and a flexible film on a support such as a drum, The flexible film may be in a state in which it can be peeled off by a drying method of drying.

5: Polymer refining equipment
6: Fusion tank
7: Doping supply line
8: Precipitator
9: Vibrating body
10: Hot air dryer
11: Pump
12: Filter
12a: Filter medium
12b: Filter filter
12c: Filtration aid
12d:
12e: Precote
13a: addition nozzle
13: Solvent addition unit
14: Static mixer
17: raw material CA (raw material cellulose acylate)
18: Methylene chloride
21: Dof
22: Hot water
28: Hot water supply line
30: discharged CA (precipitated cellulose acylate)
37: overflow recovery unit
38: Water recovery pipe
39: Hot water storage tank
55: Solvent recovery pipe

Claims (11)

A filtration method for filtering a polymer solution containing a polymer and a solvent using a filter having a filter aid,
A solvent addition step of adding the solvent to the polymer solution on the upstream side of the filter to lower the viscosity of the polymer solution and to suppress the fluctuation of the pressure loss of the filter within a certain range;
A heating step of heating the polymer solution sent to the filter to gradually decrease the viscosity of the polymer solution;
And a solvent addition dimerization step of decreasing the amount of the solvent added in the solvent addition step in correspondence with the viscosity decrease of the polymer solution by the heating step. delete A dissolution step of dissolving the polymer in a solvent to obtain a polymer solution,
A filtration step using the filtration method of the polymer solution according to claim 1;
And a polymer precipitation step of dispersing the polymer solution that has been subjected to the filtration step in a liquid which is incompatible with the polymer and the solvent and heated to a temperature higher than the boiling point of the solvent and drying the solvent to precipitate the polymer Lt; / RTI > The method of claim 3,
In the dissolution step, the concentration of the polymer solution is 2 mass% or more and 19 mass% or less. 5. The method of claim 4,
Wherein the filtration step is performed by filtration of an auxiliary agent having an absolute filtration accuracy of 2 탆 or more and 30 탆 or less. 6. The method of claim 5,
Wherein the solvent is a single kind of solvent. The method according to claim 6,
Wherein the polymer is a cellulose acylate, the solvent is methylene chloride, and the liquid is water. 8. The method of claim 7,
Wherein the temperature of the cellulose acylate solution is 20 占 폚 or higher and 120 占 폚 or lower and the temperature of the water is 40 占 폚 or higher and 100 占 폚 or lower in the polymer precipitation step. A dissolution step of dissolving the precipitated polymer obtained by the polymer purification method according to any one of claims 3 to 8 in a solvent to prepare a polymer solution,
An adding step of adding an additive liquid mixed with an additive to the polymer solution obtained from the dissolving step in-line,
A softening step of flowing a polymer solution to which the additive liquid is added as a soft dope from a flexible die to a flexible support to form a flexible film,
And a drying step of peeling the flexible film from the flexible support and drying the flexible film. A filter for filtering a polymer solution containing a polymer and a solvent by using a filter aid,
A solvent addition unit for adding the solvent to the polymer solution on the upstream side of the filter to lower the viscosity of the polymer solution and to suppress the fluctuation of the pressure loss of the filter within a certain range;
A heating unit for heating the polymer solution sent to the filter to diminish the viscosity of the polymer solution,
And a control unit for decreasing an amount of the solvent added by the solvent addition unit in response to a decrease in viscosity of the polymer solution by the heating unit. delete

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