JP2926869B2 - Hollow fiber surface treatment method for hollow fiber module - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hollow fiber surface treatment method for a hollow fiber module. More specifically, the present invention relates to a method for performing a plasma polymerization treatment or a plasma etching treatment on the surface of a porous hollow fiber of a hollow fiber module.

[Conventional technology]

A fluid introduction and discharge header is provided at both ends, and a cylindrical body provided with a fluid introduction hole and a discharge hole in the body,
Hollow fiber modules containing a large number of porous hollow fiber groups are well known.

A porous hollow fiber housed in such a hollow fiber module is often used after forming a plasma polymerized film or a plasma etching film on the outer surface side of the hollow fiber in order to improve its surface characteristics. ing. For example, JP-A-63-59334: A gas separation membrane is formed by using a perfluoroaromatic compound, a siloxane compound, an organosilicon compound, a fluorinated olefin, etc. JP-A-62-23401: Saturated or unsaturated Patent Application Publication JP-A-62-68519: Using Bis (trimethylsilyl) acetamide to Form a Gas Separation Membrane such as an Oxygen-Enriched Membrane Publication No .: N-containing gas (N ₂ , NH ₃ , MeNH ₂ , Me ₂ NH, NO, NO ₂ etc.),
O-containing gas (O ₂ , CO, etc.) or S-containing gas (SO ₂ , H ₂ S
However, these plasma-treated porous hollow fibers are used in the production of a hollow fiber module after being subjected to plasma treatment in advance, and the processing surface is also generally a hollow fiber. Is limited to the outer surface side.

[Problems to be solved by the invention]

The hollow fiber module is used for various applications as described above, and hydrophilicity, hydrophobicity, or biocompatibility is required as a surface characteristic according to each application.

An object of the present invention is to provide a method for treating a hollow fiber surface of a hollow fiber module using a commercially available hollow fiber module and imparting these various surface characteristics to the inner surface, outer surface, or both surfaces of the porous hollow fiber. Is to provide.

[Means for solving the problem]

An object of the present invention is to provide a hollow fiber in which a large number of porous hollow fiber groups are accommodated in a cylindrical body provided with fluid introduction and discharge headers at both ends and a fluid introduction hole and a discharge hole at a body portion. A coil for discharge or a pair of counter electrodes is wound around the outer cylinder of the module. (1) The discharge header is connected to a vacuum pump with each hole of the body closed, and the internal space of the porous hollow fiber is depressurized. (2) Connect the body discharge hole to a vacuum pump with both end headers closed, and depressurize the porous hollow fiber external space in the cylindrical body, or (3) Discharge After connecting the header and the body discharge hole to a vacuum pump to reduce the pressure inside and outside of the porous hollow fiber, the gas introduced into the reduced pressure space is supplied with high-frequency power from the discharge coil or a pair of opposed electrodes. And apply The inner surface side of quality hollow fiber is achieved by forming the outer surface side or plasma treatment film on these both sides.

Since a large number of porous hollow fiber groups are subjected to plasma processing while being housed in the cylindrical body of the hollow fiber module,
A discharge coil or a pair of opposing electrodes (two pieces of label-like electrodes are placed separately at opposing positions of the outer cylindrical part of the cylindrical body) on the outer cylindrical part of a cylindrical body made of a non-conductive material such as plastic, glass, or ceramic. , And high frequency power is applied from there.

The plasma treatment is performed in the above-mentioned various modes depending on the application.For example, in the case of a polyvinylidene fluoride hollow fiber module, since the surface of the hollow fiber is hydrophobic, when it is used as an aqueous filter, it is hydrophilic. In order to achieve this, it is preferable that only the side in contact with the raw water is hydrophilic and the permeate side is hydrophobic. In this case, the plasma treatment is performed after reducing the pressure in (1) above. Will be

As the plasma processing gas, for example, O ₂ , NH ₃ , NO ₂ and the like are used for the hydrophilic treatment as described above, and CF ₄ and C are used for the hydrophobic treatment.
₂ F ₆ , C ₆ F ₆ , CF ₂ = CF ₂ , CF ₂ = CFCF _{3, and the} like, and an NH ₃ —O ₂ mixed gas or the like is used for the biocompatibility treatment. These plasma processing gases are as described in the above (1),
The fluid is introduced into the decompression space from the fluid introduction header, the body fluid introduction hole, or both, corresponding to the reduced pressure state of (2) or (3), respectively.

When the plasma treatment is performed on a module of a hollow fiber having a hydrophilic surface such as polysulfone, there is a problem that the air in the module cannot escape when wet with water. In such a case, as a method of making the surface of the hydrophilic polymer hydrophobic, there is a glow discharge treatment using a fluorine-based gas such as CF _{4 in} a dry method.

In this case, F atoms are incorporated into the polymer surface,
While becoming hydrophobic, the hollow fiber polymer surface can be severely damaged due to the concurrent etching effect. In addition, the reduction of surface energy due to F atoms generated on the surface is not so effective because there is an increase in surface energy caused by the increase in surface roughness due to etching. As the time elapses, the polymer main chain is rotated inward by the rotation, thereby reducing the degree of surface hydrophobicity.

For that purpose, it is most effective to incorporate F atoms into the surface of the hollow fiber polymer and to make it hydrophobic by plasma treatment so that etching hardly occurs.
_{CF 4, CHF 3, C 2} F 6, C 3 rather than the fluorinated alkanes, such as _{F 8, C 2 H 2 F} 6, fluorinated such as _{CF 2 = CF 2, CF 2} = CFCF 3, CF 2 = CHF When an olefin is used as a plasma processing gas and an extremely thin fluoropolymer film is directly formed on the surface of the hollow fiber in a module state, the surface can be kept hydrophobic for a long period of time.

The discharge from the discharge coil or the pair of opposed electrodes for plasma treatment is performed by using a high frequency of about 10 to 100 W of effective power and discharging for about 1 to 5 minutes,
On the inner surface side, outer surface side or these both sides of the porous hollow fiber,
A plasma-polymerized film or a plasma-etched film having various surface characteristics is formed according to the type of the plasma processing gas used.

〔The invention's effect〕

 The following effects can be obtained by the method of the present invention.

(1) Since the surface modification of the porous hollow fiber forming the module is performed by plasma processing, dry and clean processing can be performed.

(2) By selecting the type of plasma processing gas, a porous hollow fiber having any of various surface states can be obtained.

(3) By changing the method of introducing the plasma processing gas, the surface modification can be easily performed only on the inner surface, only the outer surface, or both surfaces of the porous hollow fiber.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example 1 With the headers at both ends of the polysulfone hollow fiber module closed, the body discharge hole was connected to a vacuum pump, and the outer space of the porous hollow fiber in the cylindrical body was evacuated to 10 ^-3 Torr to reduce the pressure. After that, CF ₄ (60 SCCM) containing 5% O ₂ was introduced into the decompression space, and the internal pressure was set to 0.06 Torr, and a high frequency of 60 W was discharged from the discharge coil wound around the outer tube of the module. Discharged for 3 minutes. Further, after this space was evacuated to 10 ^-3 Torr, CF ₂ = CF ₂ was introduced into the reduced pressure space, and a high frequency of 50 W was discharged for 2 minutes with the internal pressure being 0.08 Torr. For each of the untreated, treated, and treated samples, the permeation amount (unit: cm ³ / cm ² / (kg / cm ² ) sec) after immersing each module in water was measured. . The results obtained are shown in the following table.

Claims (6)

(57) [Claims] 1. A hollow fiber module in which a plurality of porous hollow fiber groups are accommodated in a cylindrical body provided with fluid introduction and discharge headers at both ends and a fluid introduction hole and a discharge hole at a body. After winding a discharge coil or a pair of counter electrodes around the outer cylinder, connecting the discharge header to a vacuum pump with each hole of the body closed, and reducing the pressure inside the porous hollow fiber internal space, A high-frequency power is applied to the gas introduced into the reduced-pressure space from the discharge coil or the pair of opposed electrodes to form a plasma-treated film on the inner surface side of the porous hollow fiber, and the hollow fiber of the hollow fiber module is characterized in that Surface treatment method. 2. A hollow fiber module in which a plurality of porous hollow fiber groups are housed in a cylindrical body provided with fluid introduction and discharge headers at both ends and a fluid introduction hole and a discharge hole at a body portion. A discharge coil or a pair of counter electrodes is wound around the outer cylinder, and the body discharge hole is connected to a vacuum pump with both end headers closed, so that the outer space of the porous hollow fiber inside the cylinder is depressurized. And applying a high-frequency power to the gas introduced into the decompression space from the discharge coil or the pair of opposed electrodes to form a plasma treatment film on the outer surface side of the porous hollow fiber. Hollow fiber surface treatment method. 3. A hollow fiber module in which a plurality of porous hollow fiber groups are accommodated in a cylindrical body having fluid introduction and discharge headers at both ends and fluid introduction holes and discharge holes at a body. A discharge coil or a pair of counter electrodes is wound around the outer cylinder, the discharge header and the body discharge hole are connected to a vacuum pump, and the inside and outside space of the porous hollow fiber are reduced in pressure. A high-frequency power is applied to the introduced gas from the discharge coil or a pair of opposed electrodes to form a plasma-treated film on the inner surface and the outer surface of the porous hollow fiber. Surface treatment method. 4. The hollow fiber surface treatment method according to claim 1, wherein a fluorinated olefin is used as the plasma treatment gas. 5. The hollow fiber surface treatment method according to claim 1, wherein the plasma treatment film is a plasma etching film. 6. The hollow fiber surface treatment method according to claim 1, wherein the plasma treatment film is a plasma polymerized film.