JP2508656B2 - Manufacturing method of gas separation membrane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a gas separation membrane. More specifically, it relates to a method for producing a gas separation membrane in which a gas separation thin film made of a plasma-polymerized membrane is formed on the surface of an organic porous membrane.

[Prior Art] A gas separation membrane used as an oxygen-enriched membrane is a thin film having excellent gas separation performance on the surface of a conventional organic porous membrane, for example, a thin film of polysiloxane, polycarbonate, polyvinylpyridine, polyester or the like. The casting method,
It is manufactured by forming by a water surface spreading method, a plasma polymerization method, a coating method or the like.

Although the performance of the gas separation membrane produced in this way is largely controlled by the thin film having gas separation performance, it is also affected by the properties of the organic porous membrane-like body which forms the thin film on the surface. In addition, the adhesion durability of the formed thin film to the organic porous film-like body is often insufficient, and therefore the surface of the organic porous film-like body is glow-discharged in the presence of argon gas in advance to perform plasma etching. However, in this case, there is a drawback that it is not effective unless the glow discharge time is extended.

[Problems to be Solved by the Invention] The present inventor has proposed a plasma etching pretreatment method for forming a gas-separable thin film by a plasma polymerization method.
As a result of various investigations for a method capable of improving the oxygen permeation rate, which is naturally required as an oxygen-enriched film with a short glow discharge time, it was found that plasma etching in the presence of argon gas was used instead of conventional plasma etching. It has been found that such problems can be effectively solved by performing plasma etching in the presence of fluorinated lower alkanes.

[Means for Solving Problems] Therefore, the present invention relates to a method for producing a gas separation membrane, in which a gas separation membrane is formed on the surface of an organic porous membrane to produce a gas separation membrane. At this time, the surface of the organic porous membrane is plasma-etched with a lower alkane or a fluorinated fluoride of a lower chlorinated alkane prior to the formation of the gas separating thin film.

The organic porous membrane is a porous body such as cellulose acetate, polypropylene, polycarbonate, polysulfone, or polyvinylidene fluoride, and has a flat membrane shape or a hollow fiber shape having a thickness capable of maintaining sufficient strength as a support. Membranes such as

These organic porous membranes are first plasma etched and then preferably plasma polymerized, but these plasma treatments are, for example, elongated on one end side, around which a coil connected to a high frequency oscillator is wound. It is carried out using a cylindrical plasma reactor.

Plasma etching was performed by exhausting the gas from the exhaust port on the other end of the reactor to reduce the pressure inside the reactor to the order of 10 ^-3 Torr, then using perfluoromethane CF ₄ and perfluoroethane C ₄ .
₂ F ₆ , perfluoropropane C ₃ F ₈ , trifluoromethane C
Fluoride of lower alkane such as HF ₃ or monochlorotrifluoromethane CClF ₃ , monochloropentafluoroethane C ₂ ClF ₅ , dichlorotetrafluoroethane C ₂ Cl ₂ F ₄
Fluorinated chlorinated lower alkanes such as 10 ^-2 to 10 ^-1 To
It is carried out by introducing a high frequency power of about 10 to 200 W for about 1/2 to 10 minutes and then performing glow discharge for about rr to rr.

Next, the plasma polymerization to be performed is carried out once in the reactor.
After exhausting to the order of ^-3 Torr, perfluorobenzene, perfluoroaromatic compounds such as perfluorotoluene, siloxane compounds such as hexamethyldisiloxane, organosilicon compounds such as trimethylvinylsilane, tetrafluoroethylene, etc. Glow discharge by introducing monomers such as fluorinated olefins into the equipment up to the order of 10 ^-2 to 10 ^-1 Torr and high frequency with output of about 10 to 200 W for about 1/5 to 10 minutes (when using perfluorobenzene) It is done by doing.

EFFECTS OF THE INVENTION The gas separation membrane obtained by the method of the present invention can shorten the glow discharge time by plasma etching to less than half that in the case of using the conventional argon gas, and by this treatment, the organic porous membrane material Not only can the adhesion durability of the gas-separable thin film consisting of a plasma-polymerized film on the surface be improved, but also the improvement of the oxygen permeation rate can be achieved at the same time, further increasing the usefulness as an oxygen-enriched film. Will be done.

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

Example 1 A cellulose acetate-based porous membrane (Millipore filter manufactured by Japan Millipore Limited; pore diameter 0.05 μm) was placed in a cylindrical plasma reaction apparatus, and the inside of the apparatus was evacuated to 10 ⁻³ Torr. ^It was introduced to ^-1 Torr, a high frequency of 13.56 MHz was applied with an output of 50 W, and glow discharge was performed for 8 minutes.

Then, after exhausting once to 10 ^-3 Torr, perfluorobenzene was introduced up to 4 × 10 ^-1 Torr, high frequency was applied with an output of 100 W, glow discharge was performed for 1 minute, and plasma polymerization was performed.

A perfluorobenzene plasma polymerized film having a film thickness of 0.59 μm (measured using a film thickness meter DEKTAK-II-AV manufactured by Sloan Co., Ltd.) was formed on the surface of the porous film body. This plasma polymerized film-forming porous film was evaluated as a gas permeable film by the pressure method, and the oxygen permeation rate was 4.1 × 10 ^-5 c.
The value of m ³ · cm / cm ² · second · cmHg was obtained.

Example 2 In Example 1, the glow discharge time of perfluoromethane was changed to 3 minutes, and the plasma polymerization time of perfluorobenzene was changed to 45 seconds.

A 0.44 μm-thick plasma polymerized film was formed, and the oxygen permeability coefficient of this plasma polymerized film-formed porous film was 2.8 × 10 5.
^{It was -5} cm ³ · cm / cm ² · second · cmHg.

Comparative Example 1 In Example 1, argon gas was used instead of perfluoromethane at the same pressure, glow discharge was performed at an output of 50 W for 15 minutes, and then glow discharge of perfluorobenzene was performed for 30 seconds.

A plasma polymerized film with a thickness of 0.30 μm was formed, and the oxygen permeability coefficient of this plasma polymerized film-formed porous film was 2.3 × 10 5.
^{It was -5} cm ³ · cm / cm ² · second · cmHg.

Comparative Example 2 After evacuation to 10 ⁻³ Torr in Example 1, plasma polymerization of perfluorobenzene was carried out for 30 seconds without glow discharge in the presence of perfluoromethane gas.

A plasma polymerized film with a thickness of 0.33 μm was formed, and the oxygen permeability coefficient of this plasma polymerized film-formed porous film was 4.3 × 10.
^{It was −6} cm ³ · cm / cm ² · second · cmHg.

Example 3 In Example 1, another cellulose acetate-based porous membrane (Millipore filter manufactured by Japan Millipore Limited;
A pore diameter of 0.025 μm) was used, and the glow discharge time in the presence of perfluoromethane gas was variously changed.

Comparative Example 3 In Comparative Example 1, the cellulose acetate-based porous membrane used in Example 3 was used, and the glow discharge time in the presence of argon gas was variously changed.

The plasma polymerized film-forming porous membranes obtained in Example 3 and Comparative Example 3 above were subjected to a cellophane tape peeling test to evaluate the adhesion of the plasma polymerized membrane. The results obtained are shown in the following table.

Table Discharge time (minutes) Example 3 Comparative example 3 1 No peeling All peeling 3〃 〃 5〃 Partial peeling 8〃 〃 10〃 No peeling

Claims (1)

(57) [Claims] 1. A method for forming a gas-separating thin film made of a plasma-polymerized film on the surface of an organic porous film-like body, and producing the gas-separating film, prior to forming the gas-separating thin film, the organic porous film-like body. A method for producing a gas separation membrane, which comprises plasma-etching the surface of a substrate with a fluoride of a lower alkane or a chlorinated lower alkane.