JP2009242492A - Method for producing porous film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a porous film having a plurality of apertures formed regularly and having excellent solvent resistance. <P>SOLUTION: A flow casting solution 58 is prepared by dissolving a cellulose acylate 56 as a polymer having an ester bond (-O-CO-) in the side chain in a solvent 57. When the flow casting solution 58 is flow cast on a support 52, a flow casting film 62 is formed. Water drops occur on the flow casting film 62 by dew condensation. Until a solvent content of the flow casting film 62 reaches 10 wt.%, the solvent 57 is evaporated from the flow casting film 62. In this process, the water drops occurring by dew condensation are not evaporated. A basic water solution 73 is brought into contact with the flow casting film 62 having the solvent content reaching 10 wt.% for saponifying the cellulose acylate. Then, after washing the flow casting film 62 with wash water 81 to remove a base 71, the flow casting film 62 is dried. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a porous film.

  Today, in the optical field and the electronic field, demands for higher integration, higher information density, and higher definition of image information are increasing. Therefore, there is a strong demand for films used in these fields to have a finer structure. A film having a fine structure is also required in the medical field and the like. As a film required in the medical field, there are a film used for cell culture and a film used as a blood filtration membrane.

As a film having a fine structure, there is a film having a honeycomb structure in which a large number of fine pores of μm level are formed. As a method for producing such a honeycomb structure film, a solution in which a predetermined polymer compound is dissolved in a hydrophobic organic solvent is cast to evaporate the organic solvent, and at the same time, dew condensation is caused on the surface of the cast liquid. A method of evaporating minute water droplets generated by condensation has been proposed (for example, see Patent Document 1). A film produced by such a method is called a self-assembled film because of the formation behavior of the microstructure.
JP 2002-335949 A

  By the way, the honeycomb structure film has been further expanded in use due to its fine structure, and may be required to have resistance to organic solvents, that is, solvent resistance. However, in order to produce a honeycomb structure film having pores on the μm scale by the method of Patent Document 1, the thickness of the film itself must be several μm, or even several tens of μm even if it is thick. Moreover, the polymer which can manufacture a honeycomb structure film by the method of patent document 1 is restricted to what is called a hydrophobic polymer which melt | dissolves in a hydrophobic solvent from viewpoints of the regularity of the aspect of a hole, etc. at present. Therefore, it cannot be said that the obtained honeycomb structure film is excellent in solvent resistance.

  Then, an object of this invention is to provide the manufacturing method of the porous film in which a some hole is formed regularly and excellent in solvent resistance.

  The present invention includes a casting process in which a solution containing a polymer compound and a solvent is cast on a support to form a casting film, a dew condensation process for generating water droplets on the casting film by condensation, and a solvent. A porous film having a pore forming step in which a cast film is made into a porous film having a plurality of pores by evaporating water droplets and a water droplet, wherein the polymer compound has an ester bond (—O—CO—) in the side chain. And the pore forming step is a step of saponifying the polymer compound by bringing the casting membrane into contact with the basic aqueous solution after the solvent has evaporated and the content of the casting membrane has reached 10% by weight. And a step of drying the cast film in which the polymer compound is saponified.

Further, when the glass transition point of the polymer compound is Tg, the pore forming step is performed in advance so that the temperature of the cast film when saponified is in the range of room temperature to Tg. It is preferable to have a step of adjusting the temperature and a step of washing the saponified cast film with water before drying. The base concentration in the basic aqueous solution is preferably in the range of 1 × 10 ⁻⁴ mol / m ³ or more and 5 × 10 ⁻³ mol / m ³ or less.

  It is preferable that the basic aqueous solution contains at least one surfactant among a cationic surfactant, an anionic surfactant, and an amphoteric surfactant. The concentration of the surfactant in the basic aqueous solution is preferably in the range of 0.01% by mass to 10% by mass.

  The basic aqueous solution preferably contains an alcohol having 1 to 4 carbon atoms in the range of 3 wt% to 85 wt%. And it is preferable that the said high molecular compound is a cellulose acylate.

  According to the present invention, it is possible to produce a porous film in which a plurality of pores are regularly formed and excellent in solvent resistance.

  FIG. 1 is a schematic view of a porous film produced according to the present invention. (A) is a top view of the porous film 10, (B) is sectional drawing which follows the bb line of (A), (C) is sectional drawing which follows the cc line of (A). The porous film 10 in which the plurality of holes 15 are formed is formed so as to overlap the support. The smaller the hole 15 is formed, the smaller the thickness of the porous film 10 is. Therefore, the handling properties such as conveyance become difficult, so the product may be formed in a form overlapping the support. And it may be used with the aspect which overlapped with the support body, or it may be used by peeling from a support body.

  The plurality of holes 15 are formed side by side in the surface direction of the porous film 10. As shown in FIG. 1A, the holes 15 are formed inside the porous film 10 so that the porous film 10 has a so-called honeycomb structure having a honeycomb shape. The holes 15 have a substantially constant shape and size, and are regularly arranged. And the hole 15 is formed so that it may penetrate the porous film 10 in the thickness direction, as shown to FIG. 1 (B) and (C). Therefore, when the porous film 10 overlaps the support, the support appears to be exposed in the holes 15 of the porous film 10.

  The diameter D of the hole 15 is larger than the diameter of the opening of the hole 15 (hereinafter referred to as the opening diameter) AP on the surface of the porous film 10. Moreover, the diameter D of a hole is larger than the distance L between the centers of adjacent holes, and the adjacent holes 15 are connected inside. Therefore, a communication path is formed in the porous film 10 in the surface direction of the porous film 10. The opening diameter AP of the hole 15 is constant in the range of 0.05 μm to 100 μm, and the center-to-center distance L between the adjacent holes 15 is constant in the range of 0.1 μm to 120 μm. The thickness T is in the range of 0.05 μm or more and 100 μm or less.

  In the unit area in the plan view, the porous film 10 has a porosity (%) determined by 100 × S2 / S1, where S1 is the total projected area and S2 is the sum of the projected areas (opening areas) of the holes. It is at least 30%, more preferably 50% or more and 95% or less, and the porosity is very high.

  The porous film 10 is made of a saponified polymer compound. In addition, not all the molecules of the polymer compound constituting the porous film 10 need to be saponified, and at least the polymer compound forming the exposed surface is saponified among the polymer compounds constituting the porous film 10. For this reason, the porous film 10 is excellent in solvent resistance compared with the conventional porous film which consists of a high molecular compound.

  2A and 2B are cross-sectional views of a porous film 20 of another embodiment manufactured according to the present invention. Each plan view of the porous film 20 and the porous film 30 is the same as FIG.

  In the porous film 20, a large number of holes 25 are formed side by side in the surface direction of the porous film 20 in the same manner as the porous film 10 (see FIG. 1), and the holes 25 having a substantially constant shape and size are regularly arranged. is doing. The holes 25 are formed as depressions on one surface side of the porous film 20. In the case of a mode in which holes 25 are formed on the surface not in contact with the support, that is, the exposed surface, and overlapped with the support as a product at the time of manufacturing, the smooth other surface without the holes 25 is in contact with the support. It is said. In this porous film 20, adjacent holes 25 are not continuous inside, and there is no communication path.

  In the porous film 30, as in the porous film 20, the holes 35 are formed as depressions on the exposed surface side of the porous layer 21. The hole 35 is a dent deeper than the hole 25 of the porous film 20, and the diameter D of the hole is larger than the opening diameter AP. However, unlike the porous film 10, the adjacent hole 35 and the hole 35 are not connected, and there is no communication path.

  In each of the porous films 20 and 30, the holes 25 and 35 are independently formed, but the present invention is not limited to this embodiment. For example, the holes may be formed so that the recesses are continuous, that is, the center distance D between adjacent recesses is smaller than the opening diameter AP or the diameter D. In addition, since the porosity of the porous films 20 and 30 and the material which comprises the porous films 20 and 30 are the same as the porous film 10, description is abbreviate | omitted.

  The arrangement of the holes 15, 25, and 35 of the porous films 10, 20, and 30 is such that the density and size of water droplets, which will be described later, the drying speed, and the solution to be cast (hereinafter referred to as the casting solution). It varies depending on the solid content concentration, the timing of evaporation of the solvent from the cast film, and the like. However, since the manufacturing process is basically the same, the manufacturing method of the porous film 10 will be described below, and the description of the porous films 20 and 30 will be omitted.

  The porous film 10 is formed by casting a casting solution containing a polymer compound and a solvent on a support. The casting solution will be described below.

[Polymer compound]
The polymer compound as a component of the casting solution may be any compound having an ester bond (—O—CO—) in the side chain. Although there are many polymer compounds having an ester bond in the side chain, cellulose acylate is a preferred example from the viewpoint that it can be stably obtained, is stable as a commercial product, and is suitable for casting. As mentioned.

  Of the cellulose acylates, triacetyl cellulose (TAC), diacetyl cellulose (DAC), cellulose propionate (CAP), and cellulose butyrate (CAB) are more preferable. Note that at least two of TAC, DAC, CAP, and CAB can be used in combination.

[solvent]
The solvent of the casting solution is preferably an organic compound. The solvent may be a simple substance or a mixture, and is not particularly limited as long as it dissolves the polymer compound to be used.

  When cellulose acylate is used as the polymer component of the casting solution, examples of the solvent include the following. Aromatic hydrocarbons (eg benzene, toluene etc.), halogenated hydrocarbons (eg dichloromethane, chlorobenzene, carbon tetrachloride, 1-bromopropane etc.), cyclohexane, ketones (eg acetone, methyl ethyl ketone etc.), esters (eg , Methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (for example, tetrahydrofuran, methyl cellosolve, etc.). Among these, a plurality of compounds may be used in combination as a solvent. Moreover, you may use what added alcohol etc. to the simple substance or mixture of these compounds.

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

  In addition, by using two or more different compounds as solvent components and appropriately changing the ratio, the rate of formation of water droplets to be described later, the depth of penetration of water droplets into the coating film to be described later, and the like are controlled. Can do.

  In the casting solution, the polymer compound is preferably 0.02 part by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the organic solvent as described above. Thereby, the high quality porous film 10 can be formed with high productivity. When the polymer compound is less than 0.02 parts by weight with respect to 100 parts by weight of the organic solvent, the solvent ratio in the solution is too large and the time required for evaporation becomes long, so that the productivity of the porous film 10 is deteriorated, The regularity of water droplets may not be expressed. On the other hand, when the polymer compound exceeds 30% by weight, water droplets generated by condensation cannot deform the solution constituting the casting film, and thus the porous film 10 with uneven unevenness is formed. Sometimes.

  The film production process includes a casting process in which a solution is cast on a support to form a casting film, a condensation process in which water droplets are formed on the casting film by condensation, a solvent and the water droplets from the casting film. And a hole forming step in which the casting film is made into a porous film 10 having a plurality of holes by evaporating. The casting process, the dew condensation process, and the hole forming process are successively performed in this order in the present embodiment, but are not limited to this mode. That is, the casting process, the dew condensation process, and the hole forming process may not be performed continuously, and may be performed in a so-called batch method in which these processes are performed independently. Further, each step in the hole forming step may be carried out by a batch method instead of a continuous method.

  Further, the pore forming step includes a first drying step for evaporating the solvent from the casting membrane until the solvent content in the casting membrane reaches 10% by weight, and a basic step for the casting membrane and the basic after the solvent evaporation step. It is preferable to have a saponification process which saponifies the polymer compound contained in a cast film by making it contact with aqueous solution, and a 2nd drying process which dries the cast film which passed through the saponification process. These steps may be carried out by either a continuous method or a batch method.

  Furthermore, in the hole forming step, the temperature of the cast film before saponification is adjusted in advance so that the temperature of the cast film when saponified is room temperature or higher, and the cast film that has undergone the saponification process. Is preferably washed with water before the second drying step to remove the basic aqueous solution attached to or contained in the cast film.

  FIG. 3 is a schematic view of a film production facility for producing the porous film 10. The film manufacturing equipment 41 has a casting chamber 42 for partitioning a space for performing a casting process, a dew condensation process, and a hole forming process from an external space. The casting chamber 42 includes a first area 45 that performs a casting process and a dew condensation process, a second area 46 that performs a first drying process and a temperature adjustment process, and a third area 47 that performs a saponification process. The fourth area 48 for performing the cleaning process and the fifth area 49 for performing the second drying process are partitioned, and each partition member 51 that partitions each area has an opening serving as a conveyance path for the support 52. (Not shown) is provided. The travel path of the support body 52 in the first area 45 to the second area 49 is determined by the positions of a plurality of rollers 53 that support the support body 52 on the circumferential surface. Among these rollers 53 are drive rollers, and the support 52 is continuously conveyed by the rotation of these drive rollers. The temperature of the peripheral surface of each roller 53 is independently adjusted by a temperature controller (not shown), and the temperature of the support 52 is controlled by contacting each roller 53.

[First area 45]
The casting solution 58 containing the cellulose acylate 56 and the solvent 57 is sent to the casting die 61 in the first area 45 and flows out from the casting die 61 onto the traveling support 52, thereby casting. Is done. The outlet of the casting die 61 faces the roller 53 through the travel path of the support body 52. As a result, the casting solution 58 starts to contact the support 52 in the contact range where the support 52 is in contact with the roller 53, and a casting film 62 is formed downstream of the contact start position.

  It is preferable to cast the casting solution 58 so that the thickness of the casting film 62 in the first area is constant within a range of 0.01 mm to 1 mm. Thereby, the uniform porous film 10 can be formed, and the production efficiency is improved. Even if the thickness of the casting film 62 is in the range of 0.01 mm to 1 mm, uniform water droplets may not be formed if the thickness varies. If the thickness is less than 0.01 mm, the casting film 62 itself is not uniformly formed, and the casting solution 58 is partially repelled on the support 52 to cover the support 52 with the casting solution 58. May not be possible. On the other hand, if it is thicker than 1 mm, the time required for drying becomes too long, and the production efficiency may be poor.

  In the first area 45, a blower suction unit 63 is provided downstream of the casting die 61 in the traveling direction of the support body 52. The blower suction unit 63 is provided above the traveling path of the casting film 62, and has a blower port 63 a through which humidified air flows out in the vicinity of the casting film 62, and an intake port 63 b that sucks gas around the casting film 62. And a blower controller (not shown) that independently controls the temperature, humidity, and wind speed of the dry air in the blower system, and the suction force in the intake system.

Here, let TD be the dew point of the wind from the air outlet 63a, TS be the surface temperature of the casting film 62, and let ΔT be the value obtained by TD-TS. It is preferable to control at least one of the surface temperature TS and the dew point TD so that ΔT satisfies the following formula (1). The surface temperature TS of the casting film 62 not only in the first area 45 but also in the second area 46 to the fifth area 49 is cast by a non-contact temperature measuring means such as a commercially available infrared thermometer. The film 62 can be measured near the traveling path. When ΔT is 0 ° C. or lower, water droplets are difficult to be generated. On the other hand, when ΔT is higher than 30 ° C., water droplets are suddenly generated, and the size of the water droplets becomes uneven, There are cases in which they do not line up on a plane but overlap in three dimensions. In the first area 45, it is preferable to gradually change ΔT from a large value to a small value as it goes downstream. Thereby, the generation speed of the water droplets and the size of the generated water droplets can be controlled, and the two-dimensional water droplets having a uniform diameter in the surface direction of the casting film 62 can be formed.
0 ° C <ΔT ≦ 30 ° C (1)

  A temperature control plate (not shown) extending in the traveling direction of the support 52 is provided on the non-casting surface side of the support 52, and the temperature of the support 52 is controlled by a roller 53 and a temperature control plate. The surface temperature TS of the cast film is controlled by 52. However, it may be controlled by either the roller 53 or the temperature control plate. Further, the dew point TD is controlled by controlling the condition of the humidified air emitted from the blower suction unit 63.

[Second area 46]
In the second area 46, a plurality of air suction units 66 are arranged along the travel path of the support body 52. The most upstream air suction unit 66 is provided close to the partition member 51 between the first area 45 and the second area so as to be immediately downstream of the air suction unit 63 in the first area 45. This is for uniformly growing all the water droplets formed in the first area 45. The more the first area 45 and the second area 46 are separated from each other, that is, the longer the time from the formation of the water droplet to the entry into the second area 46, the more uneven the size of the water droplet when it has grown. End up. The number of blower suction units 66 is not particularly limited.

  Similar to the first area 45, a temperature control plate 67 that controls the temperature of the support body 52 is provided below the support body 52. The surface temperature TS of the casting film 62 is controlled by the temperature control plate 67 through the support body 52. The temperature control plate 67 has basically the same structure as the temperature control plate in the first area 45, and can change the temperature along the traveling direction of the support body 52.

In the second area 46, it is preferable to control at least one of the surface temperature TS of the casting film 62 and the dew point TD so that ΔT satisfies the following formula (2). The dew point TD is controlled by controlling the condition of the dry air from the air outlet 66a. By setting the conditions of the second area 46 in this way, it is possible to grow water droplets slowly and promote the arrangement of the water droplets by capillary force, thereby forming uniform water droplets densely.
0 ° C <ΔT ≦ 10 ° C (2)

  It is preferred to evaporate as much solvent from the coating as possible while growing the water droplets. By making the surface temperature TS and the dew point TD in the second area 46 within the above ranges, rapid evaporation can be suppressed despite sufficiently evaporating the solvent in the coating film. In the second area 46, it is preferable to evaporate the solvent in the casting film so that water drops remain, that is, the water drops do not completely evaporate. By passing through the process of evaporating the solvent in this way, the water droplets enter the casting film 62. In order to selectively evaporate only the solvent without evaporating the water droplets, it is preferable to use a solvent having a higher evaporation rate than the water droplets under the same temperature and pressure. It becomes easier to enter the inside of the casting film 62.

  In the second area 46, the solvent is evaporated from the cast film 62 until the solvent content reaches 10% by weight. This is because the cast film 62 to be subjected to the saponification step has a solvent content of 10% by weight or less. Therefore, in the second area 46, the solvent content may be lower than 10% by weight or zero. However, since it is preferable to suppress evaporation of water droplets in this second area, it is practically difficult to evaporate the solvent until the solvent content of the casting film 62 becomes zero.

  In addition, a solvent content can be calculated | required by arrange | positioning the non-contact-type thickness meter near the running path of the support body 52, and measuring the thickness of the cast film 62. In this case, the relationship between the solvent content and the thickness of the cast film 62 on which water droplets are formed is obtained in advance, and the thickness corresponding to the solvent content of 10% by weight is obtained from the relationship. Then, by measuring the thickness of the casting film 62, it can be confirmed whether or not the solvent content has reached 10% by weight.

  One of the plurality of blower suction units 66 on the most downstream side is preferably used mainly for adjusting the temperature of the casting film 62 rather than the evaporation amount of the solvent. This temperature adjustment is a temperature adjustment for the saponification step which is the next step. When the glass transition point of the polymer compound to be used is Tg, saponification is preferably performed on the casting film 62 at room temperature or higher and Tg or lower, more preferably at room temperature or higher and 60 ° C. or lower, as will be described later. In the process of the second area 46 prior to this temperature adjustment process, it is preferable to set the temperature below the dew point of the atmosphere (for example, 30 ° C. or less) in order to suppress the evaporation of water droplets. The membrane 62 is heated. In the present embodiment, this temperature adjustment for the saponification step is also performed by the temperature control plate.

[Third area]
In the third area 47, a first coating die 70 is provided above the traveling path of the support body 52. Then, the basic aqueous solution 73 in which the base 71 is contained in the water 72 flows out from the first coating die 70, and is applied onto the casting film 62 guided from the second area 46 and brought into contact therewith. This contact is performed in order to saponify the polymer compound of the casting film 62.

  The base 71 is preferably an alkali metal hydroxide. Of these, NaOH and KOH are more preferable. In addition, various bases described in JP-A-2003-313326, [0041] can also be used.

The concentration of the base 71 in the basic aqueous solution 73 is preferably in the range of 1 × 10 ⁻⁴ mol / m ³ or more and 5 × 10 ⁻³ mol / m ³ . When the concentration of the base 71 is less than 1 × 10 ⁻⁴ mol / m ³ , the polymer compound of the cast film 62 may not be saponified to the extent that it can be said that the solvent resistance is excellent. On the other hand, if the concentration of the base 71 is higher than 5 × 10 ⁻³ mol / m ³ , the components of the porous film 10 may come out in the contacted basic aqueous solution.

The above value of the concentration of bases, OH of a basic aqueous solution 73 ^- amount of substance of (mol number) X1 (unit; mol) and the volume of the basic aqueous solution 73 Y1 (unit; ^{m 3)} when the The value obtained by X1 / Y1.

More preferably, the concentration of the base 71 in the basic aqueous solution 73 is in the range of 5 × 10 ⁻⁴ mol / m ^{3 to} 3 × 10 ⁻³ mol / m ³ .

  Since the porous film 10 has a very high porosity of 30% as described above, unlike the case of saponifying a film having a smooth surface, it repels a basic solution for saponification. Therefore, the cast film 62 which becomes the porous film 10 is not easily saponified. Therefore, the basic aqueous solution 73 more preferably includes a surfactant 76. As the surfactant 7, any one of a cationic surfactant (cationic surfactant), an anionic surfactant (nonionic surfactant), and an amphoteric surfactant is preferable. Thereby, the wettability with respect to the cast film 62 of the basic aqueous solution 73 is improved, and saponification comes to be accelerated | stimulated. In addition, the surfactant described in JP2003-313326A can be preferably used in the present invention.

  The concentration of the surfactant in the basic aqueous solution 73 is preferably in the range of 0.01 wt% to 10 wt%. If the concentration of the surfactant is less than 0.01% by weight, the saponification reaction may not proceed, and if it is greater than 10% by weight, the saponification reaction may not proceed.

  The concentration of the surfactant 76 in the basic aqueous solution 73 is more preferably in the range of 0.01% by mass to 5% by mass, and still more preferably in the range of 0.03% by mass to 3% by mass.

  The above-mentioned value of the concentration of the surfactant is 100 × Y2 // when the mass of the surfactant is X2 (unit: kg) and the mass of the solution containing the surfactant is Y2 (unit: kg). This is a value obtained from X2.

  The basic aqueous solution 73 preferably contains an alcohol having 1 to 4 carbon atoms, and the alcohol may be a monohydric alcohol or a polyhydric alcohol. A plurality of these may be mixed and used. Of these, isopropyl alcohol (IPA) 77 is particularly preferable. By containing IPA77, the surface tension of the basic aqueous solution 73 can be reduced. When a conventional basic aqueous solution such as that used for saponification is applied to the casting film 62, the basic aqueous solution is repelled by the surface irregularities due to the holes of the casting film 62 and the presence of water droplets in the concave portions, and saponification is not caused. It may be performed uniformly. This tendency is particularly strong when a porous film 10 having a porosity of at least 30% is manufactured. However, if alcohol having 1 to 4 carbon atoms, particularly IPA 77, is contained in the basic aqueous solution 73, the basic aqueous solution 73 is prevented from being repelled on the casting film 62, and the casting film 62 polymer compounds are uniformly saponified, that is, uniformly saponified.

  The concentration of IPA in the basic aqueous solution 73 is preferably in the range of 3% by mass to 85% by mass. When the concentration of the surfactant is less than 3% by mass, there may be no effect of addition of IPA as described above. When the concentration is greater than 85% by mass, the components of the porous film 10 are in contact with the basic aqueous solution 73. Or the cast film 62 may swell to break the porous structure.

  The IPA concentration in the basic aqueous solution 73 is more preferably in the range of 5% by mass to 70% by mass, and still more preferably in the range of 10% by mass to 50% by mass.

  The above IPA concentration is a value obtained by 100 × X3 / Y3 when the mass of IPA is X3 (unit: kg) and the mass of the basic aqueous solution 73 is Y3 (unit: kg). .

  Similar to the arrangement of the casting die 61, the outlet of the first coating die 70 faces the roller 53 via the travel path of the support 52. Thereby, the basic aqueous solution 73 starts to be applied to the casting film 62 in the contact range where the support 52 is in contact with the roller 53. The temperature of the cast film 62 at the start of coating is in the range of room temperature to Tg, more preferably room temperature to 60 ° C. Since this temperature is preferably as high as possible to increase the reactivity of saponification, the upper limit value is not particularly limited and may be determined according to the type of polymer component, and the polymer component has a glass transition point. In some cases, Tg is a guideline for the upper limit. A commercially available infrared thermometer 78 may be provided upstream of the application start position to measure the temperature of the casting film 62. Further, based on the measurement result of the thermometer 78, it is preferable to determine the set temperature of the temperature control plate 68 and the most downstream one of the plurality of blower suction units 66. As described above, since it is adjusted in advance in the second area 46, when the basic aqueous solution 73 is applied, the polymer compound forming the exposed surface of the cast film 62 starts to be saponified and starts to hydrolyze.

  In the third area 47, the temperature of the casting film 62 is preferably maintained in the range of room temperature to Tg, more preferably in the range of room temperature to 60 ° C. Also in this temperature range, the upper limit value is not particularly limited as in the temperature at the start of application. This is because since the solvent content has already reached 10% by weight, the pores hardly disappear even when the water droplets become smaller. In this way, in this third area, it is not necessary to maintain the size of the water droplets, so the upper limit value may be set so that the saponification reaction proceeds as much as possible using the glass transition point of the polymer as a guide. This is to sufficiently promote the hydrolysis reaction by saponification. A temperature control plate is also provided below the travel path of the support 52 in the third area 47, and the temperature of the casting film 62 is maintained in the above range via the support 52 by this temperature control plate.

  Instead of or in addition to the first coating die 70, a liquid tank containing the basic aqueous solution 73 may be provided. In this case, the casting film 62 is brought into contact with the basic aqueous solution 73 in the liquid tank by guiding it. In this case, a roller that contacts and supports the support 52 is disposed in the liquid tank. In order to ensure that the casting film 62 is immersed in the basic aqueous solution 73, it is preferable that the lower end of the roller be equal to or lower than the liquid level of the basic aqueous solution 73.

[Fourth area 48]
In the fourth area 48, a second coating die 80 is provided above the traveling path of the support body 52. Then, the washing water 81 flows out from the second coating die 80 and the casting film 62 guided from the third area 46 is washed. This washing is for removing the base 71 from the casting film 62. Therefore, it is preferable that the base 71 adhering to the casting film 62 and the base 71 contained therein are washed away by this washing step so that the amount of residual base in the casting film 62 is as zero as possible. .

  A container that receives the wash water flowing down from the casting film 62 and the support body 52 below the side end of the support body 52 at a downstream side from the position where the washed water 62 that has flowed out starts to contact the casting film 62. 82 is provided. Further, another coating die may be provided downstream of the second coating die 80 and cleaning may be performed a plurality of times.

  Instead of or in addition to the second coating die 80, a liquid tank containing the cleaning water 81 may be provided. In this case, the casting film 62 is brought into contact with the cleaning water 81 in the liquid tank by guiding it. In this case, a roller that contacts and supports the support 52 is disposed in the liquid tank. In order to ensure that the casting film 62 is immersed in the cleaning water 81, it is preferable that the lower end of the roller be equal to or lower than the liquid level of the cleaning water 81. In addition, when the liquid tank is arranged in series in the traveling direction of the support 52 and the immersion in the cleaning water 81 is performed a plurality of times, the cleaning effect becomes higher.

[Fifth area 49]
In the fifth area 49, a plurality of air suction units 86 are arranged along the travel path of the support body 52. By supplying dry air from the blower port 86a and sucking air by the suction port 86b, water droplets that are responsible for the formation of holes in the casting film 62 and the cleaning water 81 are evaporated. Even when the solvent 57 remains in the casting film 62, it is evaporated by this air suction. In addition, the number of ventilation suction units is not specifically limited, One may be sufficient.

  A vacuum dryer may be used in place of the blower suction unit 86. By performing the drying under reduced pressure, it becomes easier to adjust the evaporation rates of the solvent and the water droplets, respectively, and therefore the drying under reduced pressure is particularly effective when the solvent remains in the casting film 62.

  The film manufacturing equipment 41 further winds the delivery means (not shown) for feeding the long support body 52 wound in a roll shape to the first area 45 and the porous film 10 in a state of being overlapped with the support body 52. Winding means (not shown). Moreover, it may replace with a winding-up means, and the function provision means for providing another function to the porous film 10 or the processing means which processes the porous film 10 in a predetermined shape may be used.

  In addition, it is preferable that the wind speed of the air sent out from the ventilation suction units 63, 66, 86 is set according to the traveling speed of the support body 52. The relative speed of the support 52 with respect to the traveling speed is preferably in the range of 0.02 m / second to 2 m / second.

  As a casting method of the casting solution 58 and a coating method of the basic aqueous solution 73, a method of spreading and spreading each liquid on a stationary support, and a method of discharging each liquid from the die onto the traveling support Any method can be used in the present invention. The former is generally suitable for producing a variety of products with a small amount of production, that is, for the production of a small variety of products, and the latter is generally suitable for mass production. In the latter method, when the liquid is continuously discharged, a long multilayer film can be formed, and the liquid is intermittently discharged, that is, the liquid flow from the die is turned on / off in a predetermined time. By repeating, a plurality of porous films having a predetermined length can be manufactured continuously.

  The porous film obtained by the above manufacturing method has a plurality of holes regularly formed. And since the high molecular compound which has an ester bond is saponified, this porous film is excellent in solvent resistance.

(A) is a top view of the porous film manufactured by this invention, (B) is sectional drawing which follows the bb line of (A), (C) is sectional drawing which follows the cc line of (A). is there. (A) is sectional drawing of the porous film which is another embodiment, (B) is sectional drawing of the porous film which is another embodiment. It is the schematic of a film manufacturing equipment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20,30 Porous film 15,25,35 Hole 52 Support body 56 Casting die 58 Casting solution 63,66,86 Air blow suction unit 70 Coating die 73 Basic aqueous solution 81 Washing water

Claims (7)

A casting process in which a solution containing a polymer compound and a solvent is cast on a support to form a casting film, a condensation process in which water droplets are formed on the casting film by condensation, the solvent and the solvent In a method for producing a porous film, the method includes a step of forming a pore film by evaporating water droplets to make the cast film a porous film having a plurality of pores.
The polymer compound has an ester bond (—O—CO—) in the side chain,
The hole forming step includes
After the solvent has evaporated and the content of the cast film reaches 10% by weight, the cast film is brought into contact with a basic aqueous solution to saponify the polymer compound;
And a step of drying the cast film in which the polymer compound is saponified. When the glass transition point of the polymer compound is Tg,
The hole forming step includes
Adjusting the temperature of the casting film in advance so that the temperature of the casting film when saponified is in the range of room temperature to Tg;
Washing the saponified cast film with water before drying;
The method for producing a porous film according to claim 1, comprising: ^{3. The} method for producing a porous film according to claim 1, wherein the concentration of the base in the basic aqueous solution is in the range of 1 × 10 ⁻⁴ mol / m ³ or more and 5 × 10 ⁻³ mol / m ³ or less. .   The said basic aqueous solution contains at least any one surfactant among a cationic surfactant, an anionic surfactant, and an amphoteric surfactant, The Claim 1 thru | or 3 characterized by the above-mentioned. A method for producing a porous film.   The method for producing a porous film according to claim 4, wherein the concentration of the surfactant in the basic aqueous solution is in the range of 0.01% by mass to 10% by mass.   6. The porous film according to claim 1, wherein the basic aqueous solution contains an alcohol having 1 to 4 carbon atoms in a range of 3 wt% to 85 wt%. Production method.   The method for producing a porous film according to any one of claims 1 to 6, wherein the polymer compound is cellulose acylate.

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