JPS5962304A - Permselective hollow yarn membrane - Google Patents

Abstract

PURPOSE:To improve permeation performance by forming wrinkles on the surface of a hollow yarn membrane having permselectivity. CONSTITUTION:Wrinkles are formed in a longitudinal direction of the inside and/or outside surface of a hollow yarn membrane of which distribution of the part having permselectivity is restricted to the neighborhood of the surface layer, and the porous layer next to said layer has the permeation resistance extremely smaller than the permeation resistance of said permselective layer. If the surface area of the permselective layer is increased, the rate of permeation can be increased approximately proportionally to the increase in the surface area. The form of such membrane includes asymmetrical membranes consisting of a same material and a composite membrane consisting of a permselective layer and a porous layer made of a different material. With the asymmetrical membranes, the hollow yarn membrane of this invention is obtainable by a method of discharging a resin soln. to be formed into a hollow yarn membrane from a nozzle having ruggedness of a desired shape, immersing the same into a non-solvent and coagulating the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for improving the permeation performance of hollow fiber membranes. More specifically, it relates to improving the permeation performance by forming wrinkles on a surface having selective permeability and increasing the substantial surface rII+fall.

As a hollow fiber membrane whose cross section is not circular but irregularly shaped, Japanese Patent Application Laid-Open No. 48
-75481, JP-A No. 55-49107.

Various forms have already been proposed in various publications such as Japanese Patent Laid-Open No. 55-49108.

However, the purpose of these was to improve the permeation performance of the module by disrupting the flow of liquid and preventing close contact of the membrane surface when modularized. In these cases, the above-mentioned The hollow fiber membrane has a nearly homogeneous structure, and even if the surface area was increased, there was no significant change in permeation through the fiber.

On the other hand, if the area with selective permselectivity is limited to the vicinity of the surface layer, and the layer following this is a porous layer with significantly lower permeation resistance than the layer with selective permselectivity, then the surface of the surface with permselective ability They discovered that when the product is increased, the transmission cap increases approximately in proportion to the surface area, and the present invention was achieved.

That is, the present invention provides a permselective hollow fiber membrane characterized by having wrinkles along the longitudinal direction on its inner and/or outer surfaces, and having a permselective ability on the inner or outer surface having the wrinkles. According to the present invention, it is possible to increase the effective membrane area per unit volume, thereby increasing the membrane 1lI
It is possible to increase the amount of transmission as a module by the amount of increase in the I product.

Here, wrinkles along the longitudinal direction refer to irregularities that exist regularly or irregularly, continuously or discontinuously in the fiber axis direction. The first example of the cross section perpendicular to the fiber axis direction of the present invention is
As shown in FIG. Here, the circumference of a circle having an average radius of the radius (al) of the inscribed circle of the surface unevenness and the radius (b) of the circumscribed circle is expressed as (a + b) π.On the other hand, the entire circumference of the uneven surface In this case, the ratio of D to (a + b)π is 1.3 to 15, preferably 1.7 to 8.

If it is less than 1.3, the effect will not be much apparent, and if it is more than 15, the effect of concentration polarization will become large, which is not preferable.

A skin layer having selective permeability is a layer that selectively permeates or excludes a target substance in liquid separation, gas separation, etc. The thickness of this layer is 1/1o of the total thickness
It is more preferably 1150 or less. z/I
If it is 0 or more, the relationship between membrane area and permeation performance is no longer proportional, and the effect of increasing membrane area is not so noticeable.

The permeation rate of the intended treatment fluid through the porous layer in contact with the permselective layer is preferably at least 5 times the permeation rate of the permselective layer,
More preferably, it is 50 times on the eye. If it is 5 times or less, only a performance lower than the transmission performance originally possessed by the selectively permeable layer can be obtained.

Examples of such membranes include so-called asymmetric membranes made of the same material, and composite membranes in which the layer having selective permeability and the porous layer are made of different materials.

In the case of asymmetric membranes, the method for manufacturing the hollow fiber membrane of the present invention involves discharging a solution in which a resin, which is the material of the hollow fiber membrane, is dissolved in a solvent from a nozzle having irregularities of a desired shape, and immersing it in a non-solvent. However, there is a method of coagulating only the surface from the inside and then coagulating from the outside to cause the material to shrink and cause wrinkles on the inner surface.

In a composite membrane, the porous layer may be asymmetric or homogeneous; in the case of an asymmetric porous layer, the same method as for the asymmetric membrane described above can be used.

Homogeneous porous membranes include resin solutions and resin melts.

Examples include a method of discharging a glass melt, a metal melt, etc. from a mouthpiece of a desired shape, forming the molding, and then opening holes by methods such as L1 drawing, extraction 1 partial elution, and Y8 binding.

As a method for producing a thin film having selective permeability on the surface of such a porous body, methods such as a coating method, an interfacial polymerization method, a plasma polymerization method, an electron beam irradiation method, etc. can be used.

According to the present invention, in a hollow fiber module used for gas separation and liquid separation, the effective membrane area can be significantly increased without changing the average outer diameter and number of hollow fibers, compared to the case where a hollow fiber module with a circular cross section is used. This makes it possible to easily and significantly increase the transmission layer.

The hollow fiber membrane of the present invention can be used in a wide variety of applications, such as medical membranes such as ultra-C filter membranes for artificial kidneys used to recover valuable substances in aqueous solutions, and composite membranes used for gas or liquid separation. be able to.

Hereinafter, a more detailed explanation will be given using examples.

In addition, "1 part" in the following examples means an overlapping part.

In the following examples, the permeation rate of pure water or air is 2
The amount of permeation when pure water or air permeates through the inner or outer surface of a hollow fiber at 5°C and a pressure of 0°skg/i is expressed with the surface area on the pressure side being h411, and is expressed in units of (
&/-・5ec-atm ) or (CC(STP)/c
r! -5ec-cInlly). The amount of permeation per unit volume is the permeation rate of pure water or air described above converted per volume occupied by the hollow fiber, and the volume of the hollow fiber is the average of the inscribed and circumscribed circles of the outer surface. Calculated as a cylinder with radius and the following unit ((!9/cnl・set
-atm ) or (cc (STP)/m ・sec-
CMlly) ).

Example] Polysulfone (8san Kagaku Kogyo ■UdelP3500) 1
5 parts, 3 parts of lithium chloride, 25 parts of methylcellosolve, N
A solution consisting of 57 parts of methyl 2-pyrrolidone was heated to a diameter of 3. O,
fi, the inner condensate was discharged as water from a concentric mouth with an orifice outer diameter of 2.4 gates, the free running distance was 5, and the inner surface was immersed in water, and the outer diameter was 50,071 m and the average inner diameter was 36 mm with wrinkles on the inner surface.
A 0 μm hollow fiber membrane was obtained.

The inner circumference of this membrane is 5.7 mm, which is 5.7 mm of the average inner diameter.
The permeation rate of pure water from the inside of the 258CK container of this membrane was s, o X + o = g /, 1-
sec-atm (based on actual internal area), and the amount of permeation per unit volume is 14,677/77-3eC-at
Met.

Comparative Example 1 In Example 1, the outer diameter of the cap was 1.0ItllJ7.
A membrane was formed in the same manner using a concentric ring having an inner diameter of 0.6vx to obtain a circular hollow fiber membrane with an outer diameter of 520 μm and an inner diameter of 380 μm. The inner circumference of this membrane was 1.2 gates.

The permeation rate of pure water from inside this membrane is 5.9×10 1
/c++1sec-atm (based on internal area), and the permeation amount per unit volume is 3.3317/tan・see・a
It was tm.

Examples Polyvinylidene fluoride (Penwalt Kynar3)
01) A solution consisting of 15 parts of dimethyl sulfoxide and 85 parts of dimethyl sulfoxide was prepared in exactly the same manner as in Example 1, except that the inner coagulation liquid was a solution of 50% water and 50% by weight of dimethylformamide, with an outer diameter of 740 μm and an average inner diameter. A hollow fiber membrane with wrinkles on the inner surface of 480 μm was obtained. The inner circumference of this membrane is 6.
9ii, which was 4.6 times the average radius of the inner surface.

The air permeation rate from inside this membrane is 1.5 x 10
-3CC(8TP)/crl・sec-cm) 1g (inner area basis *), and the permeation amount per unit volume is 0.7
cs 6 cc (STP)/cT7I-sec-crI
It was Lllg.

Comparative Example 2 Example 2 was carried out in exactly the same manner except that the same cap as that used in Comparative Example 1 was used, and the outer diameter was 720 mm.
A concentric hollow fiber membrane with an inner diameter of 470 μm was obtained. The inner circumference of this membrane is 1.5mm, and the air permeation rate from the inside is 1.6X10-3CO(S'rP)/nj-sec.
-cmllg (based on internal area), and the amount of permeation per unit volume is O:l 4 CC (STP), /cT+Lse
It was c-cml19.

Example 3 Using the hollow fiber membrane of Example 1, a solution of Hif, (aminopropyl)tetramethylsiloxane, and water/ethanol (50/50 ratio) was sent to the inner surface.
After extruding the excess liquid with nitrogen, 1% by weight of diphenylmethane diisocyne 7-1 was sent to the inner surface of the n-san solution to form a # film by interfacial polymerization.

The permeation rate of oxygen through this membrane at 25°C is 1.6
10' cc(STP)/c+4-4-5ee-c
ntl1 internal surface area basis) The amount of permeation per unit body is 4.
64 X I 0-3CC(STP)/cm-sec-
CrnIIg, and the oxygen to nitrogen permeability ratio is 4.゛) It was. On the other hand, when the hollow fiber membrane of Comparative Example 1 was formed in exactly the same manner as above, the oxygen permeation rate was 1.
,5 X 10-5(CC(STP)/crl ・se
c-crnllg (inner Thm & quasi)), the permeation amount per unit volume is 8.47 X s o cC (STP)/
a4-sec-cml19, and the ratio of oxygen to nitrogen selectivity was 4.6.

[Brief explanation of the drawing]

The attached FIGS. 1 and 2 schematically show a cross section of the hollow fiber membrane of the present invention in a direction perpendicular to the fiber axis direction. Patent Award - Dai Teidai Co., Ltd.

Claims (1)

[Claims] 1. A permselective hollow fiber membrane having wrinkles along the longitudinal direction on its inner and/or outer surfaces, and the wrinkled inner or outer membrane 11111 having permselective ability. 2. The hollow fiber membrane according to claim 1, comprising a skin layer having permselectivity and a porous layer in contact with the skin layer. 3. The hollow fiber membrane according to claim 1, wherein a thin film made of a composite material different from the porous layer and having selective permeation performance is formed on the wrinkled surface of the porous layer.