JPH0693975B2 - Method and apparatus for manufacturing semipermeable membrane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method and an apparatus for manufacturing a semipermeable membrane, and in particular,
The present invention relates to a method for uniformly, easily and continuously producing a semipermeable membrane in which a polymer layer is firmly bonded to a support, and an apparatus therefor.

[Prior Art] Conventionally, the semipermeable membrane used in the reverse osmosis method, the ultrafiltration method, and the microfiltration method is required to withstand practical use without causing membrane damage. Alternatively, a filter paper or other porous material is used as a backing material, or a material formed by directly applying a film forming solution to the surface of a porous material such as a woven fabric or a nonwoven fabric is used.

FIG. 8 is a cross-sectional view showing a conventional apparatus for directly applying a film forming solution to a membrane support such as a woven cloth or a nonwoven cloth to form a semipermeable membrane.

In the figure, 1 is a membrane support feeding roll, 2 to 11 are guide rolls, 12 is a membrane support take-up roll, 13 is a gelling bath, 14 is a membrane cleaning tank, 15 is a cast knife, and 20 is a membrane support. is there.
In this apparatus, the membrane support 20 is a membrane support delivery roll 1
While the film is being fed out from the membrane and guided by the guide rolls 2 to 11, and finally wound by the membrane support take-up roll 12, first, the membrane support is
A film forming solution is thinly coated on 20 with a cast knife 15, and then a gelling bath consisting of a non-solvent of a film forming polymer such as water.
Put in 13 and gel the film forming solution to make a semipermeable membrane. Then, the film is washed in the membrane cleaning tank 14 and wound. This method is widely used because not only the structure of the apparatus used is simple, but also the film thickness and film performance of the semipermeable membrane can be easily controlled and continuous film formation is possible.

By the way, among the above-mentioned conventional semipermeable membranes, those backed with a woven fabric or the like that serves as a support, in the case where the semipermeable membrane side is depressurized or pressure is applied from the support side, or the pressure during operation. When a vibration or the like is applied, the semipermeable membrane and the support are easily separated from each other, and the semipermeable membrane made of a material having relatively low strength is easily damaged. Generally, a semipermeable membrane that is used for a long period of time is liable to gradually peel off from the membrane support due to repeated pressurization and depressurization received during that period. A cloth-backed material cannot practically withstand long-term use.

On the other hand, as shown in FIG. 8, in the case where the membrane-forming solution is directly cast on the membrane support, a part of the membrane-forming solution enters into the mesh of a part of the membrane support, and the anchoring effect etc. The easiness of peeling between the membrane support and the polymer layer and some improvement are obtained. However, even a semipermeable membrane having an anchoring effect by directly casting a film forming solution on this support cannot be a fundamental solution to peeling of the polymer layer. That is, as shown in FIG. 9, the semipermeable membrane formed according to the method shown in FIG. 8 has the gelled semipermeable membrane polymer layer 2 on the membrane support 20 and a part of the polymer. Since the structure is such that it penetrates into a part of the support 20 and gels, the binding force between the polymer layer 21 and the membrane support 20 is not sufficient.

Therefore, in order to prevent the polymer layer and the membrane support from peeling off, several membrane production methods have been proposed for improving the binding force between the polymer layer and the membrane support.

One of these methods is that after the film-forming solution is directly cast on the film support, water or the polymer in the film-forming solution is not dissolved, but it is often used as a solvent or lubricant that constitutes the film-forming solution. Place the membrane support in a gelling bath composed of liquids that mix so that a part of the film-forming solution easily enters the membrane support before the polymer of the film-forming solution solidifies. By using it, the effect of anchoring the polymer layer to the membrane support is enhanced by increasing the permeation of the membrane forming solution into the membrane support, compared to the conventional one (Japanese Patent Publication Sho 62).
-30803).

Other methods include: using as a membrane support, a woven cloth partially woven with components that are soluble in a solvent forming the membrane forming solution (membrane forming solvent), fibers, yarns, or the like:
In this method, fibers that are not soluble in a film-forming solvent are previously coated with a polymer that is soluble in a film-forming solvent and used. In this method, the permeation of the membrane-forming solution into the membrane support is promoted during the production of the membrane, or the polymer previously coated on the fiber and the polymer in the membrane-forming solution are bound to each other, thereby binding the polymer layer to the membrane support. Strength is increased.
(Japanese Patent Publication No. 52-15398).

[Problems to be Solved by the Invention] In any of the above membrane production methods, the development of a special membrane support is indispensable in order to increase the bonding strength between the polymer layer and the membrane support. In addition to requiring a high degree of expertise in manufacturing, the new time and cost associated therewith are required.

Moreover, since the manufactured semipermeable membrane is basically bonded to the membrane support by the anchoring effect, the bonding strength between the polymer layer and the membrane support is 1.0 kg / cm ² to 2.0 kg / stress in terms of stress. Since it can be improved only up to about cm ² , for example, when the plate and frame system is used for a long period of time, it may not be possible to satisfy practical requirements regarding the bonding strength between the polymer layer and the membrane support.

In order to solve such a problem, a film forming solution is directly applied to the surface of the membrane support, the film forming solution permeates into the membrane support, and permeates from the surface of the membrane support to the back surface of the membrane support. The formed film forming solution forms a uniform layer on the back surface of the film support, and the film forming solution that has penetrated into the film support firmly connects the film forming solution layer on the front surface and the back surface of the film support, A semipermeable membrane having a structure in which the film forming solution is gelled is required. However, the semipermeable membrane having such a structure could not be easily and uniformly manufactured continuously by the conventional method.

The present invention solves the above-mentioned conventional problems and directly coats the surface of a porous support with a film-forming solution, and the film-forming solution penetrates into the support and further penetrates to the back side of the support. The film-forming solution forms a uniform layer on the back side of the support, and
The film-forming solution that has penetrated into the support has a structure in which the film-forming solution gels in a state where the film-forming solution layer on the front surface and the back surface of the support is firmly connected, and the polymer layer formed by gelation and the support are It is an object of the present invention to provide a method and a device therefor capable of easily, uniformly and continuously producing a strongly bonded semipermeable membrane.

[Means for Solving the Problem] In the method for producing a semipermeable membrane according to claim (1), the membrane forming solution is applied to the surface of the porous support and then immersed in a gelling bath to produce the semipermeable membrane. In the method described above, the thickness of the film-forming solution layer coated on the surface of the support and permeating the back surface of the support through the holes of the support is adjusted with an adjusting knife, and then immersed in a gelling bath. It is characterized by

The semipermeable membrane manufacturing apparatus according to claim (2) comprises means for applying a film forming solution to the surface of the porous support, and a gelling bath for immersing the porous support coated with the film forming solution. In the method for producing a semipermeable membrane, between the membrane forming solution coating means and the gelling bath, the back surface of the porous support is contacted, the support is coated on the surface of the support, and the solution is passed through the pores of the support. An adjusting knife for adjusting the thickness of the film-forming solution layer that has permeated the back surface of the support is provided.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the semipermeable membrane manufacturing apparatus of the present invention. In the apparatus of this embodiment, the guide roll 17 is provided between the guide rolls 2 and 3. The guide roll 2 and the guide rail 11 are lower rolls 2a and 11 respectively.
It is composed of a and upper rolls 2b and 11b. Further, between the guide rolls 3 and 4, there is provided an adjusting knife 16 which comes into contact with the back surface of the porous support (hereinafter sometimes referred to as “membrane support”). Other than this, the structure is basically the same as that of the apparatus shown in FIG. 8, and the members having the same functions are designated by the same reference numerals.

In the present invention, the surface of the membrane support refers to the surface on which the membrane-forming solution is applied to the membrane support, and the back surface of the membrane support refers to the surface opposite to the coating surface.

In the apparatus and method of the present embodiment, the membrane support 20 fed from the membrane support feeding roll 1 includes the guide rolls 2 (2a, 2b), 17, 3, 4, 5, 6, 7, 8, 9 , 10, 1
While being guided by 1 (11a, 11b) and being wound by the membrane support take-up roll 12, first, the film forming solution is applied to the front surface by the cast knife 15, and then the back surface is treated by the adjusting knife. The film-forming solution applied in the step of passing through the gelling bath 13 is gelled and then washed in the film washing tank 14 to form a semipermeable membrane.

In the present embodiment, the adjusting knife 16 is applied to the surface of the membrane support by the cast knife 15, and the film forming solution that has penetrated from the applied surface into the inside of the membrane support and reaches the back surface is applied to the entire back surface of the membrane support. And plays a role of uniformly adjusting the surface of the film-forming solution layer formed on the back surface.

By the action of such an adjusting knife, not only the film forming solution layer that has penetrated to the back side of the membrane support becomes uniform,
The condition of permeation of the membrane-forming solution into the membrane support becomes uniform, and the membrane-forming solution sufficiently enters the membrane support, and the membrane-supporting solution is sufficiently impregnated into the membrane support. The body is wrapped by the film-forming solution. Then, as shown in FIG. 2, the film-forming solution that has penetrated into the membrane support 20 is gelled with the film-forming solution layers on the front and back surfaces of the membrane support being gelled to form the polymer 21. The semipermeable membrane 22 is manufactured.

In the present invention, the material of the adjusting knife does not damage the membrane support, has a coefficient of friction that does not hinder the winding of the membrane support, does not dissolve in the solvent of the film forming solution, and has a stress applied during film formation. Any material can be used as long as it can withstand, and for example, Teflon, aluminum, SUS steel, etc. can be used. Teflon or SUS steel is preferable. However, the material is not limited to the materials listed here, and any material having the above-described properties can be applied.

The shape of the adjusting knife is such that it does not damage the membrane support, does not hinder the winding of the membrane support, does not get damaged by the film forming solution, and withstands the stress applied during film formation. Any shape that can fulfill the role of, for example, the cross-sectional shape of the tip shown in FIG. 3 (a) is rectangular 16A, and the cross-sectional shape of the tip shown in FIG. 3 (b) is circular or elliptical. 16B, 16C and 16D having a trapezoidal cross section at the tip shown in FIGS. 3 (c) and 3 (d). The one shown in FIG. 3 (a) or FIG. 3 (c) is preferable. However, the shape of the adjusting knife is not necessarily limited to the shapes given here, and there is no particular limitation as long as it has the shape of the adjusting knife.

The width of the surface where the adjusting knife comes into contact with the membrane support (w in Figs. 3 (a) to (d)) is strong enough to withstand the stress applied during film formation and does not damage the membrane support. Any width may be used as long as it does not hinder the winding of the support and functions as the adjusting knife as described above. The width w of the adjusting knife is 0.1 to 10 mm, preferably 0.5 to 2 mm. However, the width does not necessarily have to be this width, and may be any width as long as it serves as an adjusting knife.

The material for the mounting portion of such an adjusting knife may have any strength as long as it can withstand the stress applied during film formation and does not dissolve in the solvent of the film forming solution, such as aluminum or SU.
Examples include S steel, Teflon, and iron. Preferably SUS
Steel and aluminum are good. However, the material is not necessarily limited to these materials, and any material may be used as long as it satisfies the required characteristics of the mounting portion of the adjusting knife.

In addition, the structure of the attachment part of the adjustment knife is such that the adjustment knife is firmly fixed, it is not damaged by the film forming solution, and it has the strength to withstand the stress applied during film formation. The movement of the adjustment knife can be adjusted freely, and the movement of the adjustment knife up and down (for example, in the vertical direction) can also be adjusted independently of the movement, and the angle at which the adjustment knife contacts the membrane support can be adjusted freely. Although the adjustable structure is preferable, one of them may be fixed, two of them may be fixed, or all of them may be fixed. 4 to 6 are exploded perspective views showing an embodiment of the attachment structure of the adjusting knife.

In FIG. 4, the mounting member 30 includes a horizontal portion 32 having a plurality of small holes 31 (four in FIG. 4) and the horizontal portion 32.
It consists of vertical parts 33 and 34 which are erected at both ends of 32.
Slots 35 and 36 are provided in 33 and 34, respectively. On the other hand, the adjusting knife 16E is provided with a plurality of elongated holes 37 (four in FIG. 4) in the lateral direction. In this mounting structure, the positions of the long hole 37 of the adjusting knife 16E and the small hole 31 of the horizontal portion 32 of the mounting member 30 are appropriately adjusted, and the adjusting knife 16E is mounted on the horizontal portion 32 of the mounting member 30 with the bolt 41 and the nut 42. The position of the adjusting knife 16E in the lateral direction (Z direction in FIG. 4) can be adjusted by attaching the adjusting knife 16E. Also,
The long hole 37 of the adjusting knife 16E and the small hole 3 of the horizontal portion 32 of the mounting member 30
By changing the combination with 1, the position of the adjusting knife 16E in the longitudinal direction (X direction in FIG. 4) can be adjusted. Further, by adjusting the positions of the long holes 35, 36 of the vertical portions 33, 34 of the mounting member 30 with respect to the device body (not shown) and attaching the mounting member 30 to the device body with the bolts 41 and the nuts 42, the adjustment knife is adjusted. The position of 16E in the vertical direction (Y direction in FIG. 4) can be adjusted.

The mounting structure shown in FIGS. 5 and 6 is one in which the mounting members 38, 39 are directly erected and fixed to the adjusting knife 16F. In FIG. 5, the mounting members 38, 39 have elongated holes 43, 44. Since it is provided, the positions of the long holes 43 and 44 are adjusted with respect to the apparatus main body (not shown), and the mounting members 38 and 39 are fixed by the bolts 41 and the nuts 42.
The position of the adjusting knife 16F in the up-down direction (Y direction in FIG. 5) can be adjusted by attaching the. In the mounting structure shown in FIG. 5, the vertical position of the adjusting knife 16F can be continuously adjusted, whereas in the mounting structure shown in FIG.
Multiple small holes 45 and 46 in 8 and 39 (two in Fig. 6)
Since they are provided separately, the vertical position of the adjustment knife 16F can be adjusted stepwise.

In the present invention, the mounting structure shown in FIG. 4 is most preferable because the position of the adjusting knife can be adjusted in all directions. However, the attachment structure of the adjusting knife is not necessarily limited to those listed here, and any structure may be used as long as it can sufficiently exhibit the function of the adjusting knife as described above.

In the present invention, by adjusting the position of the adjusting knife, weakening the strength of the adjusting knife in contact with the membrane support,
It is formed on the back surface of the membrane support by strengthening or by changing the angle at which the adjustment knife and the membrane support contact, that is, the angle θ between the membrane support 20 and the adjustment knife 16 shown in FIG. The thickness of the polymer layer can be adjusted appropriately. (In FIG. 7, the arrow A indicates the traveling direction of the membrane support 20.) That is, when the adjustment knife is weakened in contact with the membrane support,
The thickness of the polymer layer on the back surface of the membrane support becomes thicker, and conversely, when it is made stronger, the thickness of the polymer layer on the back surface of the membrane support becomes thinner. The strength with which this adjusting knife contacts the membrane support is 0.05-2 kg / c.
The m ² is preferably 0.1 to 1 kg / cm ² .

Further, when the angle θ at which the adjusting knife contacts the membrane support is reduced, the polymer layer thickness on the back surface of the membrane support becomes thicker, and conversely, when it is increased, the polymer layer thickness on the back surface of the membrane support becomes thinner. The angle θ at which this adjusting knife contacts the membrane support is 5
It can be changed up to ~ 175 °, but preferably 60 ~ 90
゜ is good.

In the manufacturing method and apparatus of the present invention, the conditions such as the contact strength and the contact angle between the adjusting knife and the membrane support may be general conditions, and no special conditions are required.

That is, the polymer that constitutes the film forming solution, the solvent, the lubricant,
For the types of other additives and their concentrations in the film forming solution,
It can be one that is generally adopted and is not subject to any special restrictions.

The membrane support may be a commercially available one, or one usually used as a membrane support, and no special one is required. Examples of the membrane support include non-woven fabrics, woven fabrics, and other porous membrane supports, but those having an appropriately open mesh are preferable, for example, 50 to 300 mesh for a woven fabric. Things are good. Further, if it is a non-woven fabric or a porous membrane support, it is preferable that the air permeability is 3 ft ³ / min / ft ² or more.

[Operation] In the semipermeable membrane produced by the present invention, the membrane formation is such that the membrane support is wrapped with the membrane formation solution, and the membrane formation solution permeated into the membrane support is on the front surface and the back surface of the membrane support. Since it has a gelled structure with the solution layers still connected, the polymer layer formed by this gelation adheres firmly to the support and should be peeled off from the support even under severe use conditions or long-term use. There is no.

Thus, according to the manufacturing method and the manufacturing apparatus of the present invention, such a semipermeable membrane can be manufactured uniformly, continuously and easily.

Incidentally, in the conventional film forming method, the bonding strength between the polymer layer and the membrane support could be improved only to about 1.0 to 2.0 kg / cm ² as stress, but according to the present invention, the polymer layer and the membrane support are A semipermeable membrane having a bond strength improved to ⁴ to 7 kg / cm ² as a stress can be manufactured uniformly, continuously and easily.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

In the following, the semipermeable membrane was manufactured using the apparatus shown in FIG. 1 in the examples and the apparatus shown in FIG. 8 in the comparative examples.

Examples 1 to 4 Commercially available polysulfone P-3500, polyvinylpyrrolidone and dimethylformamide were uniformly dissolved in the composition shown in Table 1, and the film-forming solution prepared by defoaming was prepared as a membrane support shown in Table 1. A semipermeable membrane was manufactured by casting directly on the surface of the above with a cast knife and treating the backside with an adjusting knife. In addition,
The contact angle θ and the contact strength of the adjusting knife with the membrane support were as shown in Table 1.

As a result of examining the cross-sectional structure of the obtained semipermeable membrane using a scanning electron microscope, it was confirmed that each had a structure as shown in FIG.

The pure water permeation amount at an operating pressure of 1 kg / cm ² and an operating temperature of 25 ° C. and the molecular weight cut off measured using a dextran aqueous solution were as shown in Table 1. Further, the bond strength between the semipermeable membrane polymer layer and the membrane support was the value shown in Table 1 in terms of stress, and it was confirmed that the bond was extremely strong.

Comparative Examples 1 to 3 With the formulation shown in Table 1, a membrane-forming solution prepared in the same manner as in Example 1 was directly cast on the surface of the membrane support shown in Table 1 to produce a semipermeable membrane.

As a result, in any case, not only the thickness of the polymer layer-forming solution that had permeated from the surface of the membrane support to the back of the membrane support was uneven, but also the contraction force of the membrane-forming solution was lost during the gelation process. The entire polymer layer contracted and wrinkles did not become more uniform, resulting in a non-uniform semipermeable membrane. Also, the bond strength between the polymer layer and the membrane support was examined by selecting a part of this semipermeable membrane which was as uniform as possible.
It turned out to be very weak.

[Effects of the Invention] As described in detail above, according to the semipermeable membrane manufacturing method of claim (1) and the semipermeable membrane manufacturing apparatus of claim (2), excellent durability and harsh operating conditions are provided. A semipermeable membrane that can withstand long-term use can be easily and uniformly produced continuously with high productivity.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a semipermeable membrane manufacturing apparatus manufactured by the present invention, FIG. 2 is a schematic perspective view showing an embodiment of a semipermeable membrane of the present invention, and FIG. Is a cross-sectional view showing an embodiment of the adjusting knife, FIGS. 4, 5 and 6 are exploded perspective views showing an embodiment of the adjusting knife mounting structure, and FIG. 7 is the contact between the adjusting knife and the membrane support. FIG. 8 is a schematic view showing an angle, FIG. 8 is a sectional view showing a conventional semipermeable membrane manufacturing apparatus, and FIG. 9 is a schematic perspective view showing a conventional semipermeable membrane. 1 ... Membrane support feeding roll, 12 ... Membrane support winding roll, 13 ... Gelling bath, 14 ... Membrane cleaning tank, 15 ... Cast knife, 16 ... Adjusting knife, 20 ... Membrane support Body, 21 …… Polymer layer, 22 …… Semipermeable membrane.

Claims (2)

[Claims] 1. A method for producing a semipermeable membrane by applying a film-forming solution to the surface of a porous support and then dipping it in a gelling bath, wherein the semi-permeable membrane is applied to the surface of the support to form pores in the support. A method for producing a semipermeable membrane, comprising adjusting the thickness of a film-forming solution layer that has permeated the back surface of the support through an adjusting knife and then immersing it in a gelling bath. 2. An apparatus for producing a semipermeable membrane, comprising: a means for applying a film-forming solution on the surface of a porous support; and a gelling bath for immersing the porous support coated with the film-forming solution. Between the film-forming solution coating means and the gelling bath, the back surface of the porous support was brought into contact with the surface of the support, and the solution was applied to the back surface of the support through the pores of the support. An apparatus for producing a semipermeable membrane, comprising an adjusting knife for adjusting the thickness of a film forming solution layer.