JPS60255106A - Composite membrane for gas separation - Google Patents

Abstract

PURPOSE:To provide the titled composite membrane for gas separation having high permeability and selectivity and excellent mechanical strength, workability, resistance to chemicals, and durability by forming a thin film consisting of poly (perfluoro chemical) on the surface of a porous supporting membrane. CONSTITUTION:A porous supporting membrane is fixed on a rotary disk 1 of a plasma polymerization device. A monomer of a perfluoro chemical such as perfluorotributylamine is vaporized while evacuating the inside of a chamber 2 to fill the inside of the chamber with the vaporized monomer. Then glow discharge is generated between electrodes 3 while rotating the rotary disk 1, and a thin film of the poly(perfluoro chemical) is formed on the surface of the supporting membrane while plasma-polymerizing the perfluoro chemical to obtain the composite membrane for gas separation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite membrane that has selective permeability to a mixed gas and is capable of separating a specific gas. In particular, the present invention provides a gas separation composite that can be suitably used as a separation membrane that has a large amount of air permeation and excellent oxygen permselectivity when producing oxygen-enriched air from air using a membrane separation method. Regarding membranes.

In recent years, membrane separation technologies for separating specific gases from mixed gases have made remarkable progress, and some have even been put into practical use on an industrial scale.

On the other hand, obtaining oxygen-enriched air from the air can be used to treat cardiovascular diseases, strokes, chronic lung diseases, etc.
It is still extremely important in factories that require high heat such as cement production, fish farming, fermentation, and microbial treatment of wastewater.

Therefore, the membranes used for such gas separation have high permeability,
It has high selection and mechanical strength, processability, chemical resistance,
It is required to have excellent durability, etc.

Under these circumstances, many studies have been made to provide membranes meeting the above conditions, and many reports have already been made. Among these, composite membranes in which a thin film with high permeability and selectivity is formed on the surface of a porous support membrane are the mainstream. However, the thin films known so far have drawbacks such as insufficient permeability and selectivity, and poor bending strength, chemical resistance, etc., and are not necessarily satisfactory.

As a result of intensive research to overcome the above drawbacks, the present inventor discovered that a thin film of poly(perfluorochemical) obtained by polymerizing perfluorochemicals satisfies the above conditions. Completed the invention.

That is, the present invention provides a membrane for separating a specific gas from a mixed gas, which is formed from a porous support membrane and a thin film made of poly(perfluorochemical) formed on the surface or by filling the pores. The purpose of the present invention is to provide a composite membrane for gas separation consisting of a composite membrane comprising:

In the present invention, any porous support membrane commonly used in the art can be used. Examples of the material include polysulfone, polyethylene, polypropylene, poly7-tyrene,
Examples include polymer resins such as cellulose acetate and polycarbonate, Japanese paper, nonwoven fabric, synthetic paper, P paper, cloth, and mica. The thickness of the support film is not particularly limited as long as it has sufficient strength, but is generally preferably 1 μm to 1 mm. The porosity of the twisted support membrane is preferably 30 to 90, and the pore diameter is preferably 0.001 to 1 .mu.m. This porous support membrane may be a flat membrane or a hollow membrane, but particularly a hollow fiber membrane with an outer edge of 1 mm to 200 a gives good results.

The monomer used to produce the poly(perfluorochemical) that constitutes the thin film of the peritoneal membrane of the present invention, that is, the perfluorochemical, is a liquid with a molecular weight of 300 to 700 and has been studied as a material for artificial blood. It is extremely stable chemically and biologically, and typical examples include perfluorodecalin, perfluoroadamantane, perfluoro l-IJ furo-4-pyramine, perfluorotributylamine, and perfluorobutyltetrahydrofuran. Among these, perfluorotributylamine is particularly preferred.

Although poly(perfluorochemicals) can be produced by polymerizing these perfluorochemical monomers, it is preferred to use plasma polymerization methods. The composite membrane of the present invention is obtained by forming a poly(perfluorochemical) membrane layer on the surface of a porous support membrane and, if necessary, on the surface so as to fill the branch pores. Methods for forming a poly(perfluorochemical) film layer include coating, spray coating, electrostatic coating, dipping, rolling coating, and centrifugal force coating. Painting, ironing, roller coating, vacuum deposition coating, tampon coating, spatula coating, perfluorochemical monomers or low molecular weight polymers are evaporated by applying an appropriate temperature, and then glow discharge is applied. =5- Plasma vapor deposition coating method in which Zuma is vaporized and applied to the surface of the support film while polymerizing, but the porous support film is immersed in the above monomer or low molecular weight polymer liquid and the monomer etc. are added into the pores. A method of impregnation, plasma polymerization, and painting can be used. Considering the amount of gas permeation, the thickness of this poly(perfluorochemical) thin film is 1μ or less, especially 0.5μ or less.
The thickness is preferably 0.1 to 1.mu. or less, but if the thickness is reduced by thinning, pinholes will occur and strength problems will occur, so 01 to 1.mu. is preferable.

The above plasma polymerization method for perfluorochemicals was discovered by the present inventor. For example, plasma polymerization of perfluorotributylamine requires a discharge pressure of 0.03 mmHg, an output of 50 W, and
A thin film with the best oxygen permeation properties can be obtained when the distance between the electrodes is 6 crn and the discharge time is 25 minutes.

The composite membrane of the present invention thus obtained has an oxygen permeation rate of 2. IX]0-5(ec(stp
) 10h, sec, cmHg], the oxygen separation coefficient 6- (PO2/PN2) is extremely large at 36 or more, so
Using this, approximately 50% oxygen-enriched air can be obtained from air.

Next, an example will be given and explained.

Example 1 Commercially available porous polypropylene film (thickness 25μ,
Maximum pore diameter: 0.2 p x 0.02
It is fixed on the rotating disk (1) of CRN. Total volume approximately 59t
The inside of the chamber (2) was evacuated and the previously set monomer perfluorotributylamine [N(C
4F9) 3-Molecular weight 6711 Vapor pressure 1. ] 4 mm
Hg (37℃) Production 7 Luca, sold by Wako Tsumugi Pharmaceutical] was vaporized and the chamber was filled with steam, ultimately reaching a height of 0.03 m.
The pressure is n+Hg. Then, while rotating the rotating disk to which the film was fixed at a rotational speed of 1 rps, the output was 5.
Under the conditions of 0W electrode distance of 6 m and electrode area of 15 cm x 15 squares], glow discharge of OKH2 was generated and discharged for 7 to 25 minutes. However, the actual time that the film is charged during the discharge frame between the electrodes is considered to be about 6 hours of discharge time. Therefore, if the film were to remain stationary during the discharge frame, the net optimum residence time would be about 2y4 minutes, or about 375 seconds.

As a result, a thin film obtained from perfluorotributylamine with good oxygen permeability and pinholes was formed on a porous polypropylene film, and a composite film was obtained.

Example 2 Commercially available cellulose acetate ultrafiltration membrane (thickness 0.1
The following Example 1 was carried out using Millipore VS (product name: Millipore VS, manufactured by Nippon Millipore Co., Ltd.) with an average pore diameter of 0.025 # and a porosity of so.
A composite membrane was obtained using the same operations and conditions as above.

Example 3 Using the composite membrane prepared in Example 1, a performance test was conducted to determine the membrane properties. First, scanning electron microscopy (SE)
M) Photographs were taken and the state of the film was observed. As a result, the film thickness was approximately 1 μm and no pinholes were observed.

Next, the gas permeation rate of the composite membrane was measured using a conventional volumetric method and a pressure method. The results are shown in Table 1.

Table 1 Gas permeation characteristics of composite membrane 9- As is clear from Table 1, the oxygen permeation rate is 2, I
10-5 ['cc (stp)/+cJ sec cm
l(g), that of nitrogen is 5.8 X 10″Ccc
(stp)/d sec cmHg) and the separation coefficient (PO2/PN2) was 3.6. Therefore, theoretically, 49.6% oxygen enriched air can be obtained.

In addition, the surface of the composite film was analyzed by X-ray photoelectron spectroscopy. As a result, the polymer film (thin film) contained C, F, 0. N
It consisted of the following elements and contained the structure of CF2-1CFs.

Furthermore, using the cylindrical closed system permeability measurement cell with the composite membrane set as is, air (21% oxygen,
The oxygen-enriched air that has passed through the composite membrane is separated from the other side, and the oxygen-enriched air is collected using a Cassu quadrupole mass spectrometer (Ga
Results of analysis using s-Mass 5pect, ) 4
1% oxygen enriched air was obtained. The difference between this and the theoretical value is due to measurement error.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a bell 10-jar type plasma polymerization apparatus for producing the composite membrane of the present invention. Applicant: Nippon Chemifa Co., Ltd. 11- Figure 1 1, Rotating disk 2, Chamber 3, Electrode 4, Monomer 5, Pump 6, High frequency power procedure amendment (voluntary) August 29, 1985 Commissioner of the Patent Office Michibu Uga 1981 Patent Application No. 111562 2 Name of the invention Composite membrane for gas separation 3 Relationship to the case of the person making the amendment Applicant address 2-2-3 Iwamoto-cho, Chiyoda-ku, Tokyo Name Name
Nippon Chemifa Co., Ltd. Representative Keizo Ushiyama 4 Agent Voluntary 6 Column 7 “Detailed Description of the Invention” of the specification subject to amendment Contents of the amendment (1) In the specification, page 4, line 2 “?” After ``Lisulfone,'' insert ``-Riethersulfone.'' (2) Page 6, line 16, “In case” [In case, also 1: L 56 M
l (under the discharge of z, the discharge pressure is 0.04 mmHf,
When the output is 50W, the distance between the electrodes is 6cIL, and the discharge time is 150 seconds.'' (3) On page 8, line 16, which says ``A composite membrane was obtained,'' change the next line and insert the text. [Example 3 Commercially available? Risulfone hollow fiber (diameter 240μ, wall thickness 8
0μ) into the cross tube type Zolazma polymerization apparatus.
Fluorotributylamine vapor at a pressure of 0.04 mm
Filled with Hf, a glow discharge of 13.56 MHz was generated under the conditions of an output of 50 W, an inter-electrode distance of 6 cx, and an electrode area of 14 m (XX 11 m), and discharged for 150 seconds. Good oxygen permeability properties [separation coefficient 02/N2
= 2.7) composite membrane was obtained. (4) On page 8, line 17, "Example 3" is corrected to "Example 4." (5) Page 10, lines 17-18, 3--Delete the statement ``This and 111.'' 4-

Claims (1)

[Scope of Claims] 1. A membrane for separating a specific gas from a gas mixture, comprising a porous support membrane and a thin film made of poly(perfluorochemical) formed on the surface of the porous support membrane and its surface or pores filled with 1-. Composite membranes for gas separation. 2. The composite membrane for gas separation according to claim 1, wherein the poly(perfluorochemical) is poly(perfluorotributylamine). 3. The composite membrane for gas separation according to claim 1 or 2, which is obtained by plasma polymerizing poly(perfluorochemical) or perfluorochemical.