JPS6029282B2 - Semipermeable membrane and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the technical field of semipermeable membranes for ultrafiltration and microfurnace applications.

More specifically, the molecular weight fractionation characteristics of a semipermeable membrane having an oblique porous layer, in other words, the membrane manufacturing technology that allows the membrane to be manufactured by freely changing the pore size at the joints of the semipermeable membrane, and its technology. The present invention relates to a semipermeable membrane with a characteristic structure obtained by. The purpose is to provide a technology that can be manufactured using the same polymer material over a wide range and with the size of the joints arbitrarily controlled, and to provide a semipermeable membrane obtained using this technology. . Separation methods using semipermeable membranes include evaporation method, ion exchange membrane method,
Compared to separation methods such as adsorption, the operation energy cost is very low and the operation is simple, so in recent years it has become popular.
It has come to be used for purposes such as improving separation processes and treating wastewater in a wide range of fields such as the food industry, pharmaceutical industry, electronics industry, painting industry, machinery industry, and chemical industry.

The substances to be separated in these fields include salts, proteins,
It contains various substances ranging from low molecular weight substances to high molecular weight substances such as viruses, colloids, emulsions, and polymer latexes, and several types of semipermeable membranes are already on the market for the purpose of efficiently separating substances depending on the substance to be separated. There is. However, the fractional molecular weight of a semipermeable membrane, or in other words, the composition of the membrane-forming stock solution,
It is determined by coagulation conditions, post-solidification heat treatment conditions, etc., and the range in which the pore size of semipermeable membranes made of the same material can be changed is currently extremely narrow considering membrane formability and membrane strength. Therefore, semipermeable membranes made of the same membrane material are limited in their fields of use, and semipermeable membranes made of various membrane materials must be prepared depending on the objects to be separated. Also, depending on the relationship between the membrane material and the object to be separated, some membranes may not be usable, or the other components of the object to be separated may have the same composition but differ only in molecular weight, so the membrane may be changed to one made of a different material. If this becomes necessary, it may be necessary to control the substances to be separated under usage conditions that are compatible with the membrane material. These restrictions not only complicate the separation operation, but also increase the price of the membrane because there is a limit to the amount of membranes made of the same material that can be used.Furthermore, the method of use must be changed for each material, which makes separation difficult. It also increases costs. The inability to freely change the pore diameter of semipermeable membranes made of the same material is a major factor that hinders the widespread use of the negative separation method, which has excellent features. In order to eliminate the inconvenience brought about by the narrow change in pore size of semipermeable membranes, the inventors of the present invention conducted intensive studies with the goal of increasing the change in pore size, and found that semipermeable membranes made of the same membrane material We have developed a technology that allows the pore size to be changed over a wide range and arbitrarily, and using this technology, we can manufacture semipermeable membranes, making it possible to treat various substances to be separated using semipermeable membranes made of the same membrane material. This made it possible to provide a membrane material most suitable for the object to be separated.

Currently, the porous layer has a network structure that becomes denser as it approaches the pus surface, that is, the pore diameters are almost uniform at equal distances from the abdominal surface, and the pore diameters on the pus surface are the smallest and towards the inside of the membrane. Ultra-furnace filtration membranes or MIKU membranes have excellent permeability properties and have a porous layer with continuously increasing pore diameters.

It is known as a filter membrane. Since such a porous layer is called a graded porous layer, such a porous layer will also be referred to as a graded porous layer in the present invention. Also, at this time, the oblique porous layer does not exist alone, but has a uniform pore diameter that is the same as or larger than the maximum pore diameter of this layer, or the minimum pore diameter is the same as that of the oblique porous layer. A membrane that has a silk-like porous layer that has the same maximum pore size as that of a slanted porous layer is known as an improved membrane that has good permeability despite its high membrane strength. ing. The mesh size of the network structure layer continuous to the graded porous layer is generally 50
0A to IA, but it is also known that the permeability can be further improved by inserting cavities with large pore diameters whose long axes are perpendicular to the membrane surface in the layer. As mentioned above, it is said that even in the case of a membrane with a misalignment, a mirror-slanted porous layer cannot actually be formed unless it has a thickness of at least 3 mm or more, particularly preferably 10 mm or more. The maximum thickness of the oblique porous layer is not particularly defined, but there is a physical limit to uniformly increasing the pore diameters at equal distances from the ventral surface.
It is generally said to be less than 100, more commonly less than 50 Buddhas. Various methods for producing semipermeable membranes having such oblique porous layers have been reported so far.

Any polymer known to have the ability to form a semipermeable membrane using the green method can be used, such as acrylonitrile polymers, acetyl cellulose, aromatic polyamides, polybenzimidazole, polyvinyl chloride,
Polymers such as polypiverazine, polysulfone, polymethyl methacrylate, and regenerated cellulose are used to make semipermeable membranes. These polymers are dissolved in a suitable solvent to form a stock solution, which is coagulated in a suitable coagulation chamber to form a film. Water or water-based coagulants are preferably used, but any coagulant that does not dissolve the polymer and is soluble in the polymer solvent can be used. Semipermeable membranes having a cline-type porous layer include, of course, any form such as a film, a tube, or a hollow fiber, but for film-like membranes, the undiluted solution is spread on a glass plate, etc., in the form of a thin film. It can be produced by casting, placing it together with a glass plate in a coagulation rack, solidifying it, and then washing it.

It can also be made by extruding from a slit-shaped T-die into a coagulation chamber. Furthermore, various methods for producing hollow fiber-like permeable membranes have been disclosed so far.

For example, Japanese Patent Application Laid-open No. 49-90684 discloses an acrylonitrile hollow fiber semipermeable membrane with high water permeability and a method for producing the same.
It is described that the structure has a silk-like porous layer containing 0 or more large cavities.

As is clear from the description, the semipermeable membrane having the graded porous layer 1 as shown in the schematic cross-sectional view of FIG. 1 is currently known as a semipermeable membrane with excellent permeability. The open waist has a large number of recesses 2 on its surface, as shown in the schematic cross-sectional view of FIG.

The depth of this recess is in the range of a size larger than the pore diameter of the outermost surface of the oblique-type porous layer and smaller than the thickness of the same layer,
It can take any size within that range. The semi-transparent graded porous layer of the present invention is essentially the same as that shown in Fig. 1, as will become clear from the manufacturing method described later. Holes with large diameters are exposed, and the deeper the depth of the recesses, the larger the pores on the surface of the recesses.

Therefore, even if a semipermeable membrane is made from the same material and has the same oblique porous layer, by changing the size of the recesses, it is possible to change the size of the molecules that pass through the semipermeable membrane. I can do it.

FIG. 3 is a schematic diagram showing the cross-sectional structure of the hollow fiber of the present invention.

The oblique porous layer is present on both the inner side 3 and the outer side 4, and the recesses are also present on both the inner side 5 and the outer side 6. FIG. 4 is a schematic cross-sectional view of another form of the hollow fiber of the present invention. 3 and 4 indicate inner and outer inclined porous layers, and 5 and 6 indicate inner and outer surface recesses.

7 indicates a cavity with a large pore size. These cavities are large cavities in the silk-like porous layer disposed in contact with the above-mentioned inclined porous layer, and are not related to the formation of surface recesses. Next, a method for manufacturing the semipermeable membrane of the present invention will be described.

The above-mentioned semipermeable membrane of the present invention has a solubility of 5 or less in the membrane-forming stock solution mainly consisting of a polymer and its solvent in the above-mentioned conventional method for manufacturing a semipermeable membrane having a graded porous layer. A liquid dispersant is uniformly dispersed in a stock solution, and a film is coagulated in a coagulation chamber that dissolves in the solvent but does not dissolve the dispersant, and then the dispersant is removed from the film. It is obtained by a method characterized by:

The polymer, solvent, coagulation margin, etc. in the method of the present invention are the same as those used in the production of a conventional membrane having an oblique porous layer. The dispersant used in the method of the present invention must first be in a liquid state in the film-forming stock solution, and secondly, it must be insoluble in the solvent of the stock solution.

The first reason is that liquid materials have better dispersibility than solid materials, and the cavities after the dispersant is removed tend to be uniform cavities. The solubility in the second solvent is
It is desirable that the amount is 5 or less, preferably zero, based on 100 parts of the solvent. If the solubility is high, the solubility of the polymer will decrease and the viscosity of the stock solution will increase, eventually making it impossible to form a film.
This is because it becomes impossible to change the amount of the dispersant added. The increase or decrease in the amount of dispersant added is related to the size of the dispersed particles, which ultimately determines the size of the cavities through which the dispersant has escaped and the recesses of the graded porous layer, so change the amount of dispersant added. The size of the possible is important. The amount of dispersant added varies depending on the composition of the film forming stock solution and the type of dispersant.
Although the range cannot be uniquely specified, the dispersant can be used in any amount within a range in which the dispersed phase of the dispersant does not invert to a continuous phase, preferably within 80% of the amount added that causes phase inversion.

Uniform dispersion of the dispersant can be achieved mechanically, but it is effective to add a dispersion aid such as a surfactant if necessary. Specific examples of dispersants include, for example, when water is used for coagulation, liquid paraffin, chlorinated paraffin, various vegetable oils such as olive oil and linseed oil, silicone oil, various organic heat agents such as hydrogenated triphenyl, and jetyl diphenyl. Select a polymer with extremely low solubility in the solvent from among widely used water-insoluble, relatively high viscosity, and low vapor pressure, such as media compounds, insulating oil, spindle oil, and other mineral oils. Can be used.

When a membrane is formed using a conventional combination of polymer, solvent, and coagulation phase that can produce a semipermeable membrane having a mirror-oblique porous layer, and using a stock solution containing a dispersed phase of a dispersant that satisfies the above conditions,
Since the dispersing agent does not dissolve in the coagulated phase, the obtained film is coagulated completely regardless of the presence of the dispersed phase, and a film having the same oblique-shaped porous layer as in the case where no dispersing agent is present is produced.
In addition, a mirror-oblique porous layer film is formed in which the dispersant particles are confined within the membrane structure or embedded and fixed on the membrane surface.

Therefore, if these dispersant particles are removed, a semipermeable membrane with a diagonal porous layer, which is completely different from a normal membrane except for the lack of membrane structure in the internal cavities or surface depressions based on the dispersant, will be obtained. . That is, the semipermeable membrane of the present invention as shown in FIGS. 2 to 4 and described above can be obtained. Furthermore, 2nd to 4th
In the figure, 2' and 5' are internal cavities based on the dispersant, and although this cavity is not related to the size of the furnace limit molecule, it is a cavity that contributes to improving permeability. In front of is a pore filled with dispersant. Next, a general method for manufacturing hollow fiber semipermeable membranes will be described. The above-mentioned dispersant is uniformly dispersed in a stock solution with an appropriate concentration in the range of 2 to 4% by weight, preferably 5 to 3% by weight, and then degassed in a furnace, and a nozzle having an annular orifice as shown in Fig. 5 is prepared. 8, as shown in FIG. 6, the stock solution is sent from the gap pump 9 and the coagulating liquid is sent from the gap pump 10, extruded, passed through the coagulation plate 11, and wound into a coil 12.

If the dispersant is extracted and removed after winding, a hollow fiber semipermeable membrane having inclined porous layers on both the inner and outer surfaces and a silk-like porous layer in the middle can be obtained. If a non-coagulating liquid is sent from the gear pump 10, a hollow fiber semipermeable membrane having a diagonal porous layer only on the outer surface can be obtained. When producing a film-like or tubular semipermeable membrane, the nozzle can be replaced with a T-die or one having a circular slit. Semipermeable membranes are generally heat-treated to stabilize their performance, but the semipermeable membrane according to the present invention is in the form of a membrane containing a dispersant in the graded porous layer and the silk-like porous layer. When heat-treated, the change in shape due to heat treatment is smaller than that of a system to which no dispersant is added, and therefore it can be heat-treated at a higher temperature, resulting in excellent thermal stability when put into practical use. . Additionally, when semipermeable membranes are used at high temperatures or under dry conditions,
In many cases, the entire semi-permeable waist shrinks and loses its performance as a semi-permeable membrane, but the semi-permeable membrane of the present invention retains its properties within the graded porous layer and the silk-like porous layer even under high temperature or dry conditions. The cavities after the dispersant that exists in the membrane acts as a buffer against membrane contraction, and the effect on the surface of the graded porous layer that has a separation function is small. It is possible to maintain water permeability even when the water is lost. As mentioned above, the semipermeable membrane of the present invention has an unprecedented structure, and because of this structure, it has excellent properties. It has great advantages. In addition, the semipermeable membrane retaining the liquid dispersant can be stored as it is and sold commercially.
After heat treatment by the user, the dispersant is removed and the semipermeable membrane can be used as a semipermeable membrane, so the semipermeable membrane in this state is also a very useful object of the present invention. . Examples are shown below.

In addition, prior to the examples, parameters used to express the characteristics of the semipermeable membrane will be summarized. Water permeability (skin ['min・atm.): In the case of hollow fiber semipermeable membrane,
A certain number of hollow fiber semipermeable membranes, the outer and inner diameters of which have been measured in advance, are attached at one end as shown in Figure T, and a pressure difference of 1 atm is created between the injection side and the outlet side, and the distilled water per unit time is Measure the amount of permeation.

In FIG. 7, 13 is the hollow fiber east, 14 is the adhesive portion of the hollow fiber east end, and 15 is the injection port for the test liquid. Next, the hollow fiber inner wall area is calculated and taken as the effective membrane area. The permeation rate of distilled water is divided by the effective membrane area to calculate the water permeability as a value per unit area. On the other hand, in the case of a film-like semipermeable membrane, measurement is performed using a permeation cell as shown in FIG. 8 with a pressure difference of 1 atmosphere. In FIG. 8, 16 is a loss plate, 17 is a film-like semipermeable membrane, and 18 is a porous plate. Peacock: The diameter of the pore is so small that it cannot be measured directly, so the following two methods were used to determine the size of the peacock.

Regarding the pore size in the field of ultrafiltration, three aqueous solutions of globular proteins of different sizes are passed through three filters, and the minimum molecular weight that cannot completely (100%) pass through the semipermeable membrane is determined by analysis of the reactor liquid. The molecular weight was used as a guideline for the pore size. Table 1 shows a list of the globular proteins used. Table 1 Globular protein molecular weight for peacock measurement Thyroglobulin (cow) 669.000 Urease 480.000 Fibrinogen 300.000 Catalase 250.0007
- Globulin 160.0008
- Globulin 90.000 Hemoglobin 63.000 Ovalbumin 45.000 Q-Chymotrivcin 24.500 Titoku.

Mu 13,000 Insulin 5.700 Bacitracin 1.400 Also, for the pore diameter of the microfurnace field, use the measuring device shown in Figure 7 to pump air instead of water into the hollow fiber east that has been submerged with water. The pressure (bubble point pressure) at which the air begins to escape after entering the hole was used as a guideline for the hole. Examples are shown below.

Example 1 Acrylonitrile 90 mol%, methyl acrylate 10
A copolymer consisting of mol% (intrinsic viscosity in N,N-dimethylformamide is 1.3) was dissolved in 65% nitric acid kept at -5°C to make a 15% by weight polymer solution, and then dispersed. Liquid paraffin containing 3% by weight of the surfactant Nonion P208 (manufactured by NOF Corporation) was added to the polymer solution at the ratio shown in Table 2, and the mixture was dispersed uniformly by stirring. .

Next, this was degassed under reduced pressure while being maintained at -5°C, and then degassed by standing still, and then spun using the apparatus shown in FIG. As for the spinning conditions, the annular orifice nozzle for the spinner was used, with the outer diameter of the capillary in the center being 0.8 legs, and the inner diameter of the stock solution extrusion nozzle being varied in the range of 1.5 to 2.5. ,
The stock solution is sent to the nozzle with a gap pump 9 at a rate of 13 to 44 [/min, and a gap pump 10 is sent to the center of the nozzle with a rate of 5.
Water was fed into the bath at a rate of 0 qo/min, and a full-length low bath filled with 20 qo of water was used for the condensation bath 11, and the winding speed was 10 m/min. Almost no liquid paraffin in the liquid paraffin was observed to flow out into the coagulation medium. The hollow fibers obtained by making shark threads were thoroughly washed with water, then heat treated with warm water at 6,000 °C for 30 minutes, and then the liquid paraffin fractionated in the dioxane-treated hollow fibers was extracted and removed, and then immersed in water. I crushed it.

The cross-sectional structure of these hollow fibers was as shown in FIG.

The obtained hollow fibers were installed in the apparatus shown in FIG. 7, and the water permeability, furnace excess molecular weight, valve point pressure, etc. were measured, and the results are shown in Table 2 together with other figures.

As can be seen from the data in Table 2, by changing the amount of liquid paraffin added, the pore diameter of the hollow fiber semipermeable membrane changes over a wide range from the ultrafilter field to the micro furnace field, and the water permeability also changes. It is large and strong enough to withstand practical use.

Table 2 Acrylic. Example 2260 shows the properties of nitrile-based hollow fibrous semipermeable membrane.
Dissolve dimethyl sulfoxy at a concentration of 1% by weight, uniformly disperse 1% by weight of chlorinated paraffin (chlorination rate 40%) in the polymer solution, and add 2% by weight in the same manner as in Example 1.
It was coagulated in water maintained at 0 CO to obtain a hollow fiber structure containing a dispersant.

Next, the hollow fiber structure was heat-treated with 40 oo hot water for 10 minutes, and the chlorinated paraffin present in the hollow fiber structure was extracted using carbon tetrachloride, and then soaked in water to obtain a hollow fiber semipermeable membrane. . The water permeability of the obtained hollow fiber-like semipermeable membrane was 0.50'/ground・min・a blood, and the furnace excess limit molecular weight was 1
It was 60,000.

The cross section of this hollow fiber had the structure shown in FIG. 3 as a model, and there were no cavities like in Example 1.

Example 3 The hollow fiber structure containing liquid paraffin produced in Example 1 was dried with 60q0 hot air, and then the liquid paraffin was extracted with dioxane.

Next, the hollow fiber semipermeable membrane is air-dried, and then the semipermeable membrane is soaked in water for 1 hour.
It was immersed for a time and the water permeability was measured. The results are shown in Table 4. Table 4 As shown in Table 4, the hollow fiber semipermeable membrane produced by adding the dispersant of the present invention has water permeability even after drying,
Its water permeability was 19-27% of the wet state.

This is due to the unique structure of the hollow fiber semipermeable membrane of the present invention. Example 4 After casting the membrane forming stock solution containing 15% by weight of liquid paraffin used in Example 1 onto a glass slope to a thickness of 0.3 skin,
It was immersed together with a glass plate in 200ml of water to solidify it.

Next, the liquid paraffin in the semipermeable membrane was extracted with tetrahydrofuran and soaked in water. The water permeability of the obtained flat semipermeable membrane was 18 min atm, and the molecular weight limit for the furnace was 16
It was 0.000. The cross-sectional surface structure of this flat semipermeable membrane is as shown in FIG. 2, with a mirror-oblique porous layer having a recessed portion on one side.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the cross-sectional structure of a film-like semipermeable membrane having a clique-type porous layer, and FIG. 2 is a schematic diagram showing the cross-sectional structure of the film-like semipermeable membrane of the present invention. FIG. 3 is a schematic diagram showing the cross-sectional structure of the hollow fiber semipermeable membrane of the present invention. FIG. 4 is a schematic diagram showing the cross-sectional structure of another hollow fiber semipermeable membrane of the present invention. FIG. 5 is a sectional view of an annular orifice nozzle for producing a hollow fiber semipermeable membrane. FIG. 6 is a schematic diagram of a hollow fiber semipermeable membrane paper thread device. FIG. 7 is a cross-sectional view of a hollow fiber semi-permeable water permeation measuring device. FIG. 8 is a cross-sectional view of a semi-transparent film-like permeated water amount measuring device. 1...Film-like semipermeable film-like porous layer, 2...Film-like semi-permeable film-like complex-type porous layer, surface recesses, 2'...Dispersion Cavity from which the agent escaped, 3... Inner inclined porous layer of hollow fiber semipermeable membrane, 4... Outer inclined porous layer of hollow fiber semipermeable membrane, 5...・Concavities on the inner surface of the hollow fiber semipermeable membrane,
6... Concavity on the outer surface of the hollow fiber semipermeable membrane, 5'.
...Cavity of hollow fiber-like semipermeable membrane where dispersant escapes, 7.
...Cavity not caused by dispersant in hollow fiber semipermeable membrane, 8
...Nozzle for producing hollow fibers, 9...Ga pump for membrane forming stock solution, 10...Ga pump for coagulation liquid, 11...Coagulation general, 12...・・Rewinder,
13...Hollow fiber bundle, 14...Hollow fiber east end joint, 15...Test liquid inlet, 16.
...Mesh diaphragm, 17...Film-like semipermeable membrane, 18...Porous plate. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. Having a graded porous layer on one or both surfaces, the average pore size of which decreases as it approaches the membrane surface;
In a film-like, tube-like, or hollow fiber-like semipermeable membrane having or including a network porous layer having a large number of cavities in the center, the inclined porous layer is provided with a surface of the inclined porous layer. 1. A semipermeable membrane having a large number of recesses having a depth larger than the pore diameter of the outermost surface of the porous layer and smaller than the thickness of the graded porous layer. 2. The semipermeable membrane according to claim 1, wherein the semipermeable membrane is formed of a polymer whose main component is an acrylonitrile residue. 3. A liquid dispersant having a solubility in the solvent of 5 or less is added to a membrane-forming stock solution consisting of a semipermeable membrane-forming polymer and its solvent.
Add and disperse in an amount up to 80% of the amount added to produce a continuous phase to form a uniform dispersed liquid phase, and coagulate this stock solution in a coagulating liquid that dissolves in the solvent but does not dissolve the dispersant. A method for producing a semipermeable membrane, which comprises forming a semipermeable membrane in the form of a film, a tube, or a hollow fiber, and then removing the dispersant. 4. The method for producing a semipermeable membrane according to claim 3, wherein the coagulating liquid is applied to both sides of the stock solution to form a film, tube, or hollow fiber. 5. The semipermeable membrane according to claim 3, in which a coagulating liquid is applied to only one side of the stock solution forming a film-shaped, tube-shaped or hollow fiber-shaped semipermeable membrane, and a non-coagulating liquid is applied to the other side. Method for producing a permeable membrane.