JPH05228345A - Preparation of membrane separation element - Google Patents

Abstract

PURPOSE:To obtain a membrane separation element in which separation membranes are uniformly dispersed even at various packing ratios by dissolving off a supporting structure by a specified solvent from a composite consisting of plural separation membranes and the supporting structure. CONSTITUTION:A stringy supporting structure 2 is set close to a hollow-fiber membrane 1 to constitute a bundled composite 3. The end of the composite 3 is treated with a solvent 4a incapable of dissolving the membrane 1 but capable of dissolving the structure 2 to expose the membrane 1. The membranes 1 at this part are substantially and separately dispersed in accordance with the mixing ratio of the membrane 1 to the structure 2. A binding resin is filled in the part to form fixed parts 5a and 5b at the ends of the membrane 1. The membranes except those at the fixed parts are left as the composite. This assembly is treated with a solvent 4b capable of dissolving the structure 2 but incapable of dissolving the other parts to remove the structure 2, and a membrane separation element in which the membranes 1 are uniformly dispersed is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a membrane separation element using a separation membrane for fluid treatment.

[0002]

2. Description of the Related Art A wide variety of methods are used for collecting and removing fine particles and microorganisms contained in fluids such as air and water, and for separating various colloids and other dissolved substances. In particular, the membrane separation treatment using a separation membrane is characterized in that the energy cost for the separation is basically low and the products are not affected by the treatment, and with the recent development of the polymer chemical industry, various functions have been developed. It has been used extensively, in part due to the development of a film having Among the separation membranes used in these membrane separation treatments, hollow fiber-shaped separation membranes have a relatively easy structure of the membrane separation element and can have a large membrane area per unit volume, and thus have been widely used in recent years. It has become to.

Generally, a membrane separation element using a hollow fiber-shaped separation membrane (hereinafter referred to as a hollow fiber membrane) is formed by bundling a plurality of hollow fiber membranes so that the hollow fiber membranes can be treated substantially as one unit, and the end portions of the bundles are treated. It is manufactured by filling various resins or the like as a fixing structure into and fixing each hollow fiber membrane in a liquid-tight manner. An opening of the hollow fiber membrane is formed in this resin fixing portion. In addition, a protective body having a shape that covers the outer periphery of the hollow fiber membrane bundle is integrally fixed to the resin fixing portion, or the casing of the membrane separation element is directly fixed.

[0004]

Since the hollow fiber membranes are liable and easily bent and easily broken or damaged when handled one by one, they are handled as a bundle as described above. Therefore, it is desirable that the bundle is firm and dense in handling. On the other hand, the resin fixing portion at the end needs to be configured such that the hollow fiber membranes are spaced from each other and the resin is allowed to enter. Therefore, at the time of manufacturing the membrane separation element, first, a dense bundle of hollow fiber membranes is made to facilitate handling and various operations are performed, and when fixing the resin at the end portions, the hollow fiber membranes are dispersed to leave a gap between the hollow fiber membranes. Is done.

At this time, the hollow fiber membranes other than the resin-fixed portions at the ends are used for separation so that the hollow fiber membranes are naturally dispersed inside the protective body and inside the casing. Generally, the filling rate of the hollow fiber membrane in the resin fixing portion at the end portion is around 40 to 50%, and the filling rate is equal to or higher than that in other portions.
(The filling factor in this case means that when the cross section of the hollow fiber membrane bundle in a dispersed state is viewed, the hollow fiber membrane actually occupies the area of the range in which the hollow fiber membrane is substantially dispersed. Area, that is, the sum of the areas inside the circle formed by the outer peripheries of the hollow fiber membranes.) With such a filling rate, the hollow fiber membranes are not so biased or bent. Although it is apparently evenly distributed, this distribution is left to the natural course and is not well controlled for each part of the film, and a considerable part of each film is in contact with and adheres to each other. .. These portions become portions that are not effectively used for filtration, and the higher the filling rate, the greater this tendency. Basically, it is desirable that each hollow fiber membrane is independent from the standpoint of effective use of the membrane area. However, depending on the object to be filtered, there may be a case in which an element having a space between the hollow fiber membranes is preferable for use.

If the filling rate is reduced, the hollow fiber membranes can be separated so that they do not adhere to each other, but this time it becomes difficult to maintain the bundle of hollow fiber membranes during the production of the membrane separation element, and each hollow fiber membrane becomes difficult to maintain. The yarn membrane is biased to one side, bent, or entangled with each other, so that the intervals cannot be uniformly maintained, and in extreme cases, it becomes difficult to manufacture the membrane separation element. After all, at present, it is not possible to freely produce a membrane separation element in which hollow fiber membranes are uniformly dispersed according to various filling rates, and it is possible to obtain a membrane separation element having the most desirable shape according to various purposes of use. Was difficult.

The present invention has been made in view of the above problems, and provides a method capable of producing a membrane separation element in which a separation membrane is uniformly dispersed even at various filling rates, whereby the separation treatment can be further performed. It is intended to provide a membrane separation element that can be efficiently implemented.

[0008]

A method for manufacturing a membrane separation element according to the present invention comprises a plurality of separation membranes and a hybrid body in which a support structure supporting the separation membranes is installed in close proximity to each other and can be treated as substantially one body. Eggplant At least a part of the separation membrane is fixed with a resin adhesive which is a fixing structure. The support structure is dissolved and removed by a solvent in which the support structure is soluble and the others are not. Based on this, it is possible to provide an element that solves the above problems.

[0009]

FIG. 1 is a schematic view showing the principle of the method for producing a membrane separation element of the present invention, using a hollow fiber membrane as a separation membrane as an example. Based on this, the operation of the present invention will be described.
A filamentous support structure 2 is placed close to the hollow fiber membrane 1 to form a bundle-like hybrid body 3 as shown in FIG. 1a. Generally, the hybrid body 3 has a dense structure within a range in which the hybrid body 3 can be handled as a single body as in the case where the hollow fiber membranes are bundled. The end of this hybrid 3 is treated with a solvent 4a that does not dissolve the hollow fiber membrane 1 but dissolves the support structure 2 to expose the hollow fiber membrane 1 as shown in FIG. 1b. The hollow fiber membranes 1 in this portion are substantially individually dispersed according to the mixing ratio with the support structure 2. This portion is filled with a fixing resin to form fixing portions 5a and 5b at the ends of each hollow fiber membrane as shown in FIG. 1c. The hollow fiber membrane portion other than the fixed portion remains in the state of the hybrid 3,
This is a solvent 4 that dissolves the support structure 2 but not the others.
By treating with b and removing the support structure 2, a membrane separation element in which the hollow fiber membranes 1 are evenly dispersed is obtained as shown in FIG. 1d.

When the composite 3 is formed, the mixing ratio of the hollow fiber membrane 1 and the support structure 2, for example, when the above-mentioned thread-like support structure is used, it is possible to change the ratio of each number. The filling rate of the hollow fiber membrane can be set. Since the hybrid body 3 treated as a bundle can be a bundle having almost the same density regardless of the filling rate of the hollow fiber membranes,
There is no change in handling, the device can be manufactured in the same manner as before, and at any filling rate, a hollow fiber membrane is uniformly separated and a membrane separation element is obtained. ..

If, for example, a number corresponding to a filling rate of 15% for the hollow fiber membrane and a filling rate of 40% for the filamentous support structure is used, the filling rate of the entire bundle of hybrids will be 55%, which is usually The packing density is sufficient for handling when manufacturing a membrane separation element using the hollow fiber membrane. When this is treated by the method of the present invention, a hollow fiber membrane is uniformly dispersed without being entangled with each other to obtain a final membrane separation element having a packing density of 15%. In the conventional method, it is difficult to maintain the bundle at the packing density of this hollow fiber membrane, and each hollow fiber membrane is bent or biased, and it is not possible to obtain a membrane separation element that maintains an evenly dispersed state.

In the above example, when fixing the hollow fiber membrane,
The end portion of the hollow fiber membrane 1 was exposed as shown in FIG. 1b by treating the end portion of the bundle-like hybrid body 3. However, the hollow fiber membrane cut into a predetermined length and the filamentous support structure were used. Then, the hollow fiber membranes may be arranged in advance so as to be exposed for a predetermined length at the time of producing the bundle. In this case, the end portion of the hollow fiber membrane can be fixed immediately by using the prepared bundle of hybrids.

In addition, with the bundle of hybrid bodies 3 as shown in FIG. 1a, the hollow fiber membrane and the end portion of the support structure are fixed together with resin according to the conventional method, and then the support structure is dissolved and removed. It may be used as a membrane separation element. In this case, the fixed portion 5a,
The support structure 2 may remain on the surface 5b, but there is an advantage that the production is easier if the support structure 2 is used for a purpose in which there is no problem in use as a membrane separation element. Of course, it is also possible to dissolve and remove the support structure in the fixed portions 5a and 5b, and then fill this portion with a fixing resin to form a membrane separation element. In either case, basically, at least a part of the hollow fiber membrane 1 to be fixed should be fixed by a fixing part so as not to move, before completely dissolving and removing all the supporting structures 2 from the bundle of the hybrid body 3. Good.

The thread-like support structure shown in the above example has a shape particularly suitable as a support structure for a hollow fiber membrane, but is widely used for separation membranes of various shapes other than that. The shape of the support structure to be obtained is preferable. On the other hand, in addition to this thread-shaped support structure, a hollow fiber membrane may be arranged therein using a molded product having a wavy shape or a groove, and the hollow fiber membranes may be stacked to form a hybrid body. In this case, more reliable dispersion can be carried out more accurately than in the case of using the thread-shaped support structure. The granular support structure is also excellent in the degree of freedom in setting dispersion, and can be used for separation membranes having various shapes.

In the method of the present invention, various materials can be used as the materials for the separation membrane and the support structure by considering the combination of solvents used. Basically, since the support structure that supports the separation membrane is finally dissolved and removed, it is desirable that the support structure be made of a material that can be easily dissolved in various solvents. It is necessary to have such strength that the basic membrane performance as a separation membrane can be maintained against the treatment with the solvent. Further, the resin fixing portion also needs to be resistant to various treatments. Any combination of materials satisfying the above conditions may be used.

As the separation membrane, synthetic polymers, particularly polyolefin resins such as polypropylene (PP) and polyethylene (PE), and polytetrafluoroethylene (PTF).
Those using a fluorine-based resin such as E) are particularly suitable.
This is because these membranes are stable to various solvents and have high resistance and can be used in combination with various solvents.

The combination of each material and solvent is, for example, polyvinyl alcohol (PV
A), polyurethane (PU) as the fixing resin, and water as the solvent. In this case, any material can be used as the separation membrane as long as it is made of a water resistant material. As a similar combination, calcium alginate may be used for the support structure, and sodium carbonate solution may be used as the solvent. It is also possible to use ethyl cellulose as the support structure, epoxy resin as the fixing resin, and alcohol as the solvent. In this case, a separation membrane using the above-mentioned olefin-based or fluorine-based resin material is preferable.

In the example shown in FIG. 1, the solvent 4a, 4b is divided into two parts, the part shown in FIG. 1b and the part shown in FIG. 1d.
Although the support structure 2 is dissolved and removed by the above method, the same solvent may be used, or two different solvents may be used, and it may be appropriately selected according to each situation. From the standpoint of process, the use of the same solvent is advantageous in terms of cost.

[0019]

Example: As a separation membrane, 1000 polypropylene hollow fiber membranes (pore diameter 0.2 μm, outer diameter 500 μm) were used, and as a support structure, polyvinyl alcohol fiber (saponification degree 88%, average polymerization degree about 1600 PVA) 1 was dissolved in water to a concentration of 15% and then spun in a sodium sulfate solution to dry it.).
A membrane separation element was produced according to the method of the present invention shown in.
80 ° C. hot water was used as the solvent. The membrane separation element produced is shown in FIG. 2. Both ends of the hollow fiber membrane 1 are adhered with a fixing resin to form fixed portions 5a and 5b, and a protective body 6 having an inner diameter of 50 mm is integrally adhered and fixed to the fixed portions. Has been done. Although the filling rate of the hollow fiber membrane 1 was 10%, a membrane separation element in which each hollow fiber membrane was uniformly and neatly dispersed was obtained.

On the other hand, as a comparative example, the same number of hollow fiber membranes are used, and the same protector 6 as in the example is used. The bundle shape of the hollow fiber membranes 1 could not be maintained at the time of manufacturing the membrane separation element, and the hollow fiber membranes 1 were bent and only a state in which they were biased to one side of the protective body 6 was obtained.

An experimental example using the membrane separation element produced by the present invention is shown below. Experimental Example 1 500 porous hollow fiber membranes made of polypropylene having a pore diameter of 0.1 μm and an outer diameter of 500 μm were used, and the production method similar to that of the above-described example was used to obtain an effective membrane area of 1500 cm 2 shown in FIG.
A membrane separation element having the structure shown in was prepared. Using a protector having an inner diameter of 3 cm, the filling rate of the hollow fiber membrane in the filtration portion was about 15%. Since polypropylene is hydrophobic, surfactant (T
riton X100) was used for hydrophilic treatment. The membrane separation element was set in an experimental circuit as shown in FIG. 4, and a pressure filtration experiment was performed at a pressure of 2 kg / cm 2. The stock solution is a coagulation solution (SS concentration of about 2.5
%) Was used. The undiluted solution 11 in the undiluted solution tank 10 is pressure-fed by pressurized air 12 to a filtration tank 14 in which a membrane separation element 13 is installed, and is filtered at a predetermined filtration pressure. The resulting filtrate 15 is collected in the filtrate tank 16. As a comparative example, the same number of the same membranes was used to fabricate a membrane separation element having the same configuration as the above according to the method described above, and the same was used to perform filtration in the same manner. The results are shown in Fig. 5. Thirty minutes after the start of filtration, 1.2 l of filtrate was obtained in the example, but it was a low value of 0.7 l in the comparative example. It was clear that in the membrane separation element of the comparative example, a portion where the hollow fiber membranes were dense was formed, and the hollow fiber membranes inside this portion were not used effectively.

Example 2 Hollow fiber membrane 1000 made of regenerated cellulose having an outer diameter of 550 μm
Using a book and a cylindrical casing having an inner diameter of 3 cm, a membrane separation element having an effective membrane area of 3500 cm 2 was produced in the same manner as in Example 1. The filling factor of the hollow fiber membrane was about 34%. Openings of the hollow fiber membrane were provided in the fixing resin portions at both ends fixing the hollow fiber membrane. This membrane separation element was set in an experimental circuit as shown in FIG. 6, and a physiological saline solution containing creatinine at a concentration of 10 mg / dl was used as a stock solution and supplied to the membrane separation element at a flow rate of 100 ml / min. The stock solution 11 is introduced into the inlet 21 of the membrane separation element 13 by the pump 20a, passes through the inner diameter side of the hollow fiber membrane, and flows out from the outlet 22 of the membrane separation element. A physiological saline solution 23 was caused to flow outside the hollow fiber membrane at a rate of 500 ml per minute by a pump 20b, and creatinine was dialyzed and removed through the hollow fiber membrane. The creatinine concentration in the stock solution before and after the membrane separation element 13 was measured using the UV method (235 nm),
The removal rate was calculated. As a comparative example, the same number of separation membranes were used, and a membrane separation element having the same effective membrane area was produced by the conventional method, and the same experiment was conducted. As a result, in the example, the average removal rate of creatinine was about 55.
%, But about 40% in the comparative example. In the example, since the hollow fiber membranes were uniformly and neatly separated, the physiological saline solution flowing to the outer diameter side of the hollow fiber membranes was evenly distributed to each hollow fiber membrane, and was efficiently removed. It is considered that in the comparative example prepared by the usual method, the hollow fiber membrane was biased to one side, and therefore the flow of the physiological saline solution was lopsided and the removal was not performed efficiently.

Although the present invention has been described by taking the case where the hollow fiber membrane is used as an example, the present invention has the gist of the present invention with respect to the membrane separation element using the separation membrane of various shapes other than the hollow fiber membrane. Various application examples can be adopted without departing from the scope.

[0024]

As described above, according to the present invention, it becomes easy to freely produce a membrane separation element in which a separation membrane is uniformly dispersed at various packing densities, and the most suitable for various purposes of use. It is possible to provide a membrane separation element having a desired shape. As a result, the target separation process can be carried out more efficiently.

[Brief description of drawings]

FIG. 1 is a schematic view showing the principle of a method for producing a membrane separation element of the present invention, using a hollow fiber membrane as a separation membrane as an example.

FIG. 2 is a cross-sectional view of essential parts showing an example of a membrane separation element manufactured by using the method for manufacturing a membrane separation element of the present invention.

FIG. 3 is a cross-sectional view of an essential part showing an example of a membrane separation element manufactured by using a conventional general manufacturing method.

FIG. 4 is a schematic diagram showing an experimental circuit of Experimental Example 1.

FIG. 5 is a graph showing the results of Experimental Example 1.

6 is a schematic diagram showing an experimental circuit of Experimental Example 2. FIG.

[Explanation of Codes] 1 hollow fiber membrane 2 support structure 3 hybrid 4a, 4b solvent 5a, 5b fixed part 6 protector 10 stock solution tank 11 stock solution 12 pressurized air 13 membrane separation element 14 filtration tank 15 filtrate 16 filtrate tank 20a , 20b Pump 21 Inlet 22 Outlet 23 Saline solution

Claims (3)

[Claims] 1. A hybrid structure in which a plurality of separation membranes and a supporting structure for supporting the separation membranes are disposed in close proximity to each other and can be treated substantially as one body, and at least a part of the separation membranes is provided by a fixing structure. A method for producing a membrane separation element, which comprises fixing and further dissolving and removing the support structure from the hybrid by using a solvent in which the support structure can be dissolved and the others are insoluble. 2. The method for producing a membrane separation element according to claim 1, wherein the separation membrane is a hollow fiber-shaped separation membrane. 3. The method for producing a membrane separation element according to claim 1, wherein the support structure is a thread-like structure.