JPS61138516A - Permselective compound membrane for gas - Google Patents

Abstract

PURPOSE:To increase the affinity of the surface of a porous base body to a thin polymer film for facilitating the prepn. of a compound membrane, to improve the film forming property and to reduce deterioration of the compound membrane by providing a metal layer or a metal oxide layer between the porous base body and the thin polymer film. CONSTITUTION:A metal layer 2 such as Au layer, etc. is formed by sputtering vapor deposition on a porous base body 1 such as polypropylene, etc. A thin polymer film 3 of such as polyhydroxy styrene/polysulfone/polydimethyl siloxane copolymer, etc. is formed on the vapor-deposited metal layer by the film developing method on water surface to obtain a permselective compound membrane for gas. Metal oxide layer may be vapor-deposited in place of the metal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is particularly applicable to separation of gaseous systems among membrane separations, including the production of oxygen-enriched air with increased oxygen concentration in the air;
This invention relates to a selective gas permeable composite membrane that can be used for recovery of helium gas, etc.

Structure of conventional examples and their problems Selective gas permeable peritoneal membranes used for gas separation are composites in which a porous support and a thin film made of methylpentene polymer or organosiloxane-polycarbonate copolymer are laminated and integrated. Films (Japanese Unexamined Patent Publication No. 51-89564 and Unexamined Japanese Patent Application No. 54-40868) have been disclosed in the past. Polypropylene, polyethylene, polysulfone, cellulose ester, polycarbonate, Teflon, and the like are disclosed as materials for the porous support used in such composite membranes.

As a porous support for supporting a thin membrane having permselectivity as in the above example, a porous support that substantially provides resistance when the permeable substance that selectively permeates through the thin membrane permeates through the porous support. It is necessary to have a porous structure to a certain degree, to have a suitable affinity with thin films, and to not be deformed by pressure, temperature, etc. under actual usage conditions. However, the support material described above cannot be said to satisfy all of these characteristics.

For example, supports made of polyethylene and polypropylene have excellent chemical resistance and PH resistance, but since the polymer itself is non-polar, it lacks compatibility with thin films and causes problems in decoupling between the support and thin films. was there.

In the case of Teflon, it has excellent chemical resistance, PH resistance, and heat resistance, but since it is nonpolar, it lacks compatibility with thin films.

On the other hand, although polysulfone, polycarbonate, and cellulose ester dissolve in various solvents and have good moldability, they have a drawback of low porosity and low gas permeability when composited with a thin film.

Among these supports, polyethylene, polypropylene, etc. contain plasticizers, antioxidants, etc. to improve processability and provide heat resistance. Therefore, when a thin film is laminated on these supports, these additives affect the film properties and cause deterioration. This is because the polymer thin film is extremely active, so even a very small amount of additives in the support greatly affects the membrane properties, causing deterioration of the gas permeation properties of the composite membrane.

When considering gas permeation characteristics, polyethylene, polypropylene, and Teflon have higher porosity as a support and are advantageous when considering practical use, but as mentioned above, they have poor compatibility with polymer thin films and durability. This is a problem.

Purpose of the Invention The present invention solves the above-mentioned problems. By changing the surface of the porous support to one that has a high affinity with the thin film, it becomes easier to combine the thin film and the support, and at the same time improves film formability. The aim is to significantly improve the deterioration of composite membranes.

Structure of the Invention The present invention achieves the above object, and consists of a porous support for a selective gas permeable composite membrane formed by laminating a homogeneous thin polymer film on a porous support having micropores, and a thin polymer film. A selective gas permeable composite membrane is formed which is characterized by having a metal layer or a metal oxide layer provided in the middle.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

The figure shows a cross-sectional view of a selective gas permeable composite membrane in one embodiment of the present invention.

In this embodiment, a metal layer 2 is provided on a porous support 1 by sputter deposition, and a chicken bone thin film 3 is laminated thereon.

Comparative Example> Duraguard 2400 (manufactured by Polyplastic ■) was used as the porous support 1, and its surface was coated with polyhydroxystyrene (PH5)-polysulfone (ps)-polydimethylsiloxane (FDMS) (siloxane content). 6
Attempts were made to form a composite by spreading a copolymer thin film (0%) on the water surface and contacting it with a support, but the film had poor affinity and it was difficult to create a composite simply by contacting the support. Therefore, the thin film and support were combined by suction using a vacuum pump. The gas permeation properties of the composite membrane obtained in this way are such that the initial flow rate is 0.08 CC/960, (:j, IL tm,
The oxygen concentration was 33q6 (secondary pressure 170 mHg).

After operating for 1000 hours under these conditions, there is almost no change in oxygen concentration, but the permeation flow rate is o, o e cc.
/sec, d, atm, which decreased to 75% of the initial field.

<Example> As the porous support 1, Jura-do 24 was used as in the comparative example.
00 (manufactured by Polyplastic ■ Co., Ltd.), and MuU was vapor-deposited as a metal layer 2 on the surface thereof using an approximately 200X sputter deposition apparatus. On top of this, PH3-PS is used as a polymer thin film 3.
- When a thin film of FDMS (60% siloxane content) was formed by a water surface spreading method and a composite was attempted, the affinity improved and the thin film could be bonded to the support very easily. In addition, the initial characteristics of the composite membrane obtained in this way do not deteriorate, and the life characteristics of the composite membrane are greatly improved. After approximately 1000 hours of operation, there is no change in oxygen concentration, and the membrane flow rate remains at the initial value of 96. %
reached.

In the above embodiments, a case was described in which a metal layer was formed between the porous support and the polymer thin film, but the same effect can be obtained even if a metal oxide layer is used instead of the metal layer.

The thickness of such a metal layer or metal oxide is 100
0A or less is appropriate. This is because if it is thicker than this, it will cover the pores of the porous support, resulting in poor gas permeability. Further, as the metal or metal oxide to be vapor-deposited, in principle, any metal or metal oxide that can be vapor-deposited may be used, such as C, Si, Go, Sn, AI! , Ga
, In, Zn, Cu, Ag, Ni, Pd, C.

and their alloys and oxides.

Furthermore, as a thin polymer film, we conducted experiments using 4-methylpentene (manufactured by Cenelal Scie/Skobo Rayon ■), polyphenylene oxide, and polytrimethylnoryl globin, and the results showed that similar effects were obtained. Providing a vapor-deposited layer of material not only facilitates the production of a composite membrane of a porous support and a thin polymer film, but also provides excellent durability.

Effects of the Invention The present invention provides a selective gas permeable composite membrane comprising a porous support having fine pores and a homogeneous thin polymer film laminated thereon. This is a selective gas permeable composite membrane characterized by the provision of metal oxide 6. Composite membranes with such a structure have a porous support whose surface is Significantly improved affinity for polymer thin films,
This layer not only facilitates composite formation, but also has the advantage of eliminating interaction between the porous support and the polymer thin film, preventing deterioration of membrane properties, and significantly improving membrane life characteristics.

[Brief explanation of the drawing]

The figure is a sectional view of a selective gas permeable composite membrane in one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Porous support body, 2...Metal layer (metal oxide layer), 3-...Polymer thin film.

Claims (2)

[Claims] (1) It is characterized by comprising a porous support having micropores and a polymer thin film consisting of at least one layer provided on the porous support via a metal layer or a metal oxide layer. Selective gas permeable composite membrane. (2) The selective gas permeable composite membrane according to claim 1, wherein the metal layer or metal oxide layer has a thickness of 1000 Å or less.