JPH0366338B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for continuously forming a hydrophilic polymer porous membrane. More specifically, it consists of a casting section that essentially casts the polymer solution to a predetermined thickness, and an organic solvent gas atmosphere section that continues to move the cast material in one direction under an organic solvent gas atmosphere. The atmosphere section is provided with at least one set of supply ports and exhaust ports for an organic solvent gas supplied from an organic solvent gas supply section having a predetermined composition, such that the supply port is in front of the exhaust port. An organic solvent gas dust removal section that allows flow in the direction of movement of the rolled material, controls the supply amount of the organic solvent gas and the exhaust amount of the organic solvent gas atmosphere section, and into which the organic solvent gas atmosphere section is introduced. The present invention also relates to a membrane forming apparatus for a porous hydrophilic polymer membrane characterized by having a laminar flow section. In general, a so-called laboratory-defined film forming apparatus is known as a film forming apparatus for producing a porous polymer membrane from a polymer solution. It is being The porous membrane obtained using this device has the drawback that not only is there non-uniformity locally on the porous membrane, but also the reproducibility of the performance of the obtained porous membrane is poor, making it difficult to produce it industrially. is extremely difficult. As a result of intensive studies to improve these drawbacks, the present inventors found that, following the casting section where the polymer solution is essentially cast to a predetermined thickness, the cast material is treated with an organic solvent gas. By providing an organic solvent gas atmosphere section that moves in one direction under the atmosphere, and configuring the organic solvent gas atmosphere section so that the organic solvent gas composition and concentration can be set within a predetermined range, any hydrophilic polymer solution can be processed. They have completed the apparatus of the present invention, which can continuously produce porous membranes from raw materials. Films are formed in an atmosphere where the temperature and humidity are controlled at a constant level, in the case of a conventional apparatus that is close to a closed system, or an open system. Under such conditions, the concentration of the organic gas that directly contacts the cast material after casting is not constant, and furthermore, it is impossible to keep the gas concentration within the container constant during film formation. That is, not only does the gas concentration change over time, but also the gas convects within the container due to the evaporation of the gas from the cast material or a change in the temperature of the cast material due to latent heat of evaporation. For this reason, only films with poor uniformity could be produced, and the film forming apparatus lacked versatility. However, by using the apparatus of the present invention, a porous membrane can be obtained from any hydrophilic polymer solution. The porous membrane in the present invention is a porous membrane produced by a microphase separation method, with an average pore diameter of 0.01 μm or more, a porosity of 50% or more, and a pore density of 6 × 10 ⁸ /cm ³
This means a membrane in which the presence of pores is clearly demonstrated by electron microscopy, and is different from a membrane for reverse osmosis. A casting part (applicator and fixed gate) that casts the polymer solution to a predetermined thickness is essential, and by keeping the thickness of the cast material constant,
It becomes possible to eliminate local unevenness in the pore characteristics of the resulting porous membrane. Following this casting section, the solution after casting comes into contact with an organic solvent gas atmosphere controlled to have a constant organic solvent gas concentration. By coming into contact with this organic solvent gas, it becomes possible to cause microphase separation on the surface of the casting solution. It is essential to generate microphase separation in order to obtain a porous membrane with a pore size of 0.01 μm or more, and the greatest technical challenge in obtaining a uniform porous membrane is to uniformly generate microphase separation points locally. That's the point. This can be achieved by moving the solution after casting in an organic solvent gas atmosphere having a constant composition. The reason for using organic solvent gas is to increase the versatility of manufacturing porous membranes. Organic solvent gas can also be used to form porous membranes from cellulose copper ammonia solution, which was impossible with conventional methods. It is quite possible. In an atmosphere containing only inorganic gases, it is difficult to cause the microphase separation described below, and
The physicochemical properties of atmospheric gases change significantly when mixed with trace amounts of water. The organic solvent gas atmosphere concentration is controlled by the supply gas concentration, its amount, and exhaust volume, and at least one set of organic solvents is provided in the organic solvent gas atmosphere part so that the organic solvent gas moves in one direction together with the casting solution. By providing a solvent gas supply port and an exhaust port and setting the atmosphere to a predetermined gas concentration, it becomes possible for the polymer solution to uniformly generate a microphase separation state under the atmosphere, and as a result, A porous polymer membrane with less unevenness in membrane formation can be obtained. Furthermore, by installing an attached device that sets the temperature in the organic solvent gas atmosphere to a predetermined temperature and performs dust removal and laminar flow on the organic solvent gas introduced into the organic solvent gas atmosphere, reproducibility can be improved. Polymer porous membranes with excellent properties can be manufactured continuously on an industrial scale. Below, based on drawings showing embodiments of the present invention,
The configuration of the present invention will be explained in detail. In FIG. 1, a fixed amount of polymer solution is supplied into an applicator 6 from a compressor 1, a stock solution tank 2, a filter 3, an air extraction tank 4, and a polymer solution supply section of a gear pump 5. The bottom surface of the applicator 6 opens onto a glass plate 21 that is continuously fed by a drive motor 20.
A fixed gate 7 applies the polymer solution in the applicator 6 to a constant thickness on the glass plate 21 at a speed set by the drive motor 20. By changing the thickness of the fixed gate 7 and the speed of the drive motor 20, porous membranes with different thicknesses can be obtained. The applicator 6 and the fixed gate 7 substantially form a casting section for casting the polymer solution to a predetermined thickness. Following the casting section, an organic solvent gas atmosphere section 8 is provided in which the polymer solution applied to a certain thickness on the glass plate 21 is brought into contact with an organic solvent gas. This organic solvent gas atmosphere section 8 is provided with a supply port 10 and an exhaust port 10' for the organic solvent gas supplied from the organic solvent gas supply section 9. The exhaust port 10' opens from inside the box-shaped box having the dust removal section 11 to the outside. As shown in FIG. 2, the dust removal section 11 has a box-shaped side wall member 12 with a large number of holes 13, and a filter 14, for example, a DOP, on the side wall member 12.
It is equipped with a filter of 0.45 μm measured from the measurement, and the box-shaped side wall corresponding to the moving direction of the cast material forms the dust removal section 11, and the other box-shaped side wall is attached to the side wall of the organic solvent gas atmosphere 8. It is glued. Therefore, the organic solvent gas having a predetermined composition supplied from the organic solvent gas supply section 9 is sent through the dust removal section 11. Since the dust removal section 11 is for removing dust by passing organic solvent gas, in FIG.
The side wall of the exhaust port 10' that is in contact with the end surface of the organic solvent gas atmosphere section 8 does not need to be formed into the dust removal section 11, and the dust removal section 11 is not necessarily formed as a box-shaped side wall as described above. It doesn't require that. As shown in FIG. 4, between the box shapes having the dust removal section 11, there is an organic solvent laminar flow section 17 in which a filter 15 similar to that described above is sandwiched between about 30 meshes of wire meshes 16, 16. is provided so that it is almost flush with the bottom of the box shape, and the dust removal section 1
In addition to step 1, dust removal and laminar flow of the organic solvent gas are performed. Then, the exhaust port 10' and the supply port 1 near it
An organic solvent gas shielding plate 18 is provided in the middle of the exhaust port 10'. Not provided. The organic solvent gas sent through the dust removal section 11 passes through the organic solvent laminar flow section 17 and enters the passage of the casting section formed below. is provided in front of the exhaust port 10', the organic solvent gas flows in the direction of movement of the cast material, passes through the dust removal section 11 of the exhaust port 10', and flows out through the exhaust port 10'. . A heat medium circulation pipe 19 is provided below the passage of the organic solvent gas atmosphere 8 in the casting part.
The temperature control heating medium is circulated to control the organic solvent gas concentration in the organic solvent gas atmosphere section 8. It is preferable to provide at least two locations for temperature measurement, and a thermocouple (copper-constantan) is sufficient for temperature measurement. In the conventional apparatuses, there was no apparatus for forcibly supplying organic solvent gas and forcibly discharging organic solvent gas as described above. A forced change in the atmosphere composition has been considered undesirable in terms of film formation, but by incorporating such a system in the apparatus of the present invention, the organic solvent gas atmosphere measured by the gas chromatograph 8 The organic solvent gas concentration is uniform and stabilized, and convection of the organic solvent gas within the organic solvent gas atmosphere section 8 can be prevented. And the size of the porous membrane is 500
mm x 500 mm or more, there is no uneven film formation on the surface of one porous membrane, and porous membranes having a set pore diameter can be continuously formed industrially with good reproducibility. Next, an example of manufacturing a hydrophilic porous membrane using the apparatus of the present invention and a comparative example thereof will be described, but before that,
Definitions of characteristics, measurement methods, etc. in the detailed description up to now and in the manufacturing examples described later will be explained. Microphase separation refers to a state in which a concentrated phase or a dilute phase of a polymer is separated and stabilized as particles with a diameter of 0.01 μm to several μm in a solution. For example, the occurrence of microphase separation in a cellulose cupric ammonia solution appears as a devitrification phenomenon during membrane formation (cellulose cupric ammonia solution is a dark blue solution, and the solution becomes cloudy).
The occurrence of the phenomenon can be confirmed by visual observation, that is,
This is confirmed by the presence of particles with a diameter of 1 μm or more in the liquid when observed with an optical microscope. Copper ammonia solution A solution whose main components are copper and ammonia, and is a dark blue solvent system called Schuweitzer reagent.
It means a solvent system that can substantially dissolve cellulose, and also includes a solvent system in which cations other than copper or solvents other than ammonia are partially mixed. Average Molecular Weight By substituting the intrinsic viscosity number [η] (ml/g) measured in a cupric ammonia solution (20°C) into equation (1), the average molecular weight (degree average molecular weight) Mv is calculated. Mυ＝[η]×3.2×10 ³ (1) Average pore radius ₃ and pore density If the number of pores with a pore radius of r to r+dr per 1 cm of porous membrane is expressed as N(r) dr, then (N(r ) is the pore radius distribution function), the average pore radius ₃ and the pore density per 1 cm N are given by equations (2) and (3). ₃ =∫ ^∞ / ₀ r ³ N (r) dr / ∫ ^∞ / ₀ r ² N (r
) dr(2) N=∫ ^∞ ₀ N(r) dr (3) Take electron micrographs of the front and back surfaces using a scanning electron microscope. A pore size distribution function N(r) is calculated from the photograph by a known method and substituted into equation (2).
In other words, take a scanning electron micrograph of the area where you want to find the pore size distribution, and take a scanning electron micrograph of an appropriate size (for example, 20cm x 20cm).
cm) and draw 20 test lines (straight lines) at equal intervals on the resulting photograph, each of which crosses a large number of holes. Measure the length of the straight line that exists within the hole when it crosses the hole, and find this frequency distribution function. Using this frequency distribution function, N(r) is determined, for example, by the method of stereology (written by Norio Suwa, Quantitative Morphology, Iwanami Shoten). Porosity Pr Cut a planar porous membrane into a circular shape of 47mmφ,
The porous membrane is dried in vacuum to a moisture content of 0.5% or less. When the thickness of the porous membrane after drying is d (cm) and the weight is w (g), the porosity Pr (%) is given by equation (4). Pr (%) = (1-17.34 x d/1.50 x w) x 100 (4) Uniformity Local uniformity of the pore diameter and porosity of a porous membrane, within the range that can be observed with the naked eye (approximately 100 μm). Uniformity as defined refers to the uniformity of pore size and the uniformity of porosity from place to place. When a solution containing dispersed particles of an appropriate size is passed through, the particles are collected on the porous membrane approximately in proportion to the flow rate at each location. Therefore, by observing the filter after passing, it is possible to find out the non-uniformity of the flow rate depending on the location.
An ideal porous membrane must be able to capture particles uniformly over its entire surface. The measurement method involved cutting out a planar porous membrane into a circular shape of 47 mm diameter, and setting the porous membrane in a millipore filter. At this time, the porous membrane is set so that the evaporation surface is facing upward. next,
Pour 100 ml of water in which carbon black is dispersed at a rate of 0.01 g/g onto the surface of the porous membrane, apply pressure or vacuum, and filter all the poured liquid. Afterwards, measure the transparency of the liquid and examine whether carbon black has passed. Next, the porous membrane after drying was observed with the naked eye and with a magnifying glass, and non-uniformity in the amount of carbon black deposited was examined. Production example Cellulose linter (average molecular weight 2.33×10 ⁵ )
6.8% by weight of ammonia prepared by a known method,
After dissolving copper at a concentration of 6% by weight in a copper ammonia solution containing 3.1% by weight, the temperature of the organic solvent gas atmosphere was 25%.
°C, gas composition is 18% acetone, ammonia
The composition and flow rate of the organic solvent gas supply section and the amount of organic solvent gas exhaust were set so that the concentrations were 21.6%, water 20.4%, and N ₂ 40%, and using a fixed gate with a thickness of 300 μm,
A cellulose copper ammonia solution with a thickness of 300 μm was continuously cast on a glass plate at a speed of 0.2 m/min.
The cast product was immediately placed in the set organic solvent gas atmosphere and left to stand for 8 minutes, and it was confirmed that microphase separation had occurred on the surface of the cast film. Note that during this standing time, no dilute phase was leached onto the membrane surface. Next, the cast material was immersed for 15 minutes in a mixed solution (20°C) with an acetone/water ratio of 33.6% by weight and an ammonia/water ratio of 0.8% by weight, and then immersed in a 2% by weight sulfuric acid aqueous solution at 20°C for 10 minutes. After soaking, wash with water, then absorb the moisture with paper, immerse in acetone at 20℃ for 15 minutes, replace the moisture in the membrane with acetone, sandwich it between paper and air dry at 30℃, and make a 100μm thick film. A porous membrane was obtained.
Table 1 shows the properties of the porous membrane obtained. Comparative Examples 1 to 3 The cellulose copper ammonia solution used in the production example was cast onto a glass plate using a fixed gate with a thickness of 300 μm,
Acetone was placed in a desiccator in advance, the acetone was bubbled with nitrogen gas, and the cast product was placed in a closed desiccator in which the acetone gas was forcibly evaporated, and left for various times shown in Table 1, and then, The cast product was immersed in a mixed solution (20°C) with an acetone/water ratio of 33.6% by weight and an ammonia/water ratio of 0.8% by weight for 15 minutes, and then immersed in a 2% by weight sulfuric acid aqueous solution at 20°C for 10 minutes. After soaking, wash with water, absorb moisture with paper, and soak in acetone at 20℃ for 15 minutes.
After soaking for a minute, the water in the membrane was replaced with acetone.
It was sandwiched between paper and air-dried at 30°C. The characteristic values of the obtained porous membrane are shown in Table 1.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a schematic diagram of the apparatus of the present invention, FIG. 2 is an enlarged perspective view of the organic solvent gas supply port, exhaust port, and dust removal section of the present invention, and FIG. 3 is an enlarged sectional view of the dust removal section.
FIG. 4 is an enlarged sectional view of the organic solvent gas laminar flow section. 1... Compressor, 2... Raw solution tank, 3... Filter, 4... Bleed tank, 5... Gear pump, 6
...Applicator, 7...Fixed gate, 8...
Organic solvent gas atmosphere part, 9... Organic solvent gas supply part, 10... Supply port, 10'... Exhaust port, 11...
...Dust removal part, 12... Side wall member, 13... Hole, 14
...Filter, 15...Filter, 16...
Wire mesh, 17... Organic solvent laminar flow section, 18... Organic solvent gas shielding plate, 19... Heat medium circulation pipe, 20
...Drive motor, 21...Glass plate.

Claims (1)

[Claims] 1 Consists of a casting section that essentially casts a polymer solution to a predetermined thickness, and an organic solvent gas atmosphere section that continues to move the cast material in one direction under an organic solvent gas atmosphere. At least one set of supply port and exhaust port for organic solvent gas supplied from an organic solvent gas supply section having a predetermined composition are provided such that the supply port is in front of the exhaust port, and the organic solvent gas is supplied to the cast material. In addition to making it flow in the direction of movement,
A hydrophilic device capable of controlling the supply amount of organic solvent gas and the exhaust amount of the organic solvent gas atmosphere section, and having an organic solvent gas dust removal section and a laminar flow section into which the organic solvent gas atmosphere section is introduced. Film forming equipment for porous polymer membranes.