JPS5959214A - Gas separating composite membrane - Google Patents

Abstract

PURPOSE:To obtain a gas separating composite membrane good in oxygen separation capacity and capable of lasting said capacity for a long period of time, by laminating two layers of membranes each having gas separation capacity on a porous membrane having no gas separation capacity. CONSTITUTION:As an porous membrane having no gas separation capacity, one with an average pore size of 0.001-0.5mum and a porosity of 10-70% is used and the thickness thereof is pref. about 20-300mum. It is necessary that the gas separation capacity of first membrane is Po/Pn2=2-2.5 and the coefficient of gas permeation thereof is Po2=10<-8>-10<-7>cc.cm/cm<2>.sec.cmHg and the thickness thereof is pref. about 0.3-3mum. In addition, the material thereof is pref. polyorganosiloxane. Further, it is necessary that the gas separation capacity of a second membrane is Po2/PN2=3-6 and the coefficient of gas permeation thereof is Po2=10<-10>-10<-8>cc.cm/cm<2>.sec.cmHg and the material theeof comprises polyvinyl pivalate. By laminating three kinds of these membranes, an objective gas separation membrane is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite membrane for gas separation, particularly to a composite membrane for separating and concentrating oxygen in the air.

For example, medical oxygen is currently used in pure oxygen packed in cylinders and diluted as needed. However, since such pure oxygen is obtained by, for example, cryogenic separation, the production cost is generally high, and the purity is not very high.
Is high concentration of oxygen actually harmful to treatment? known to give.

In view of these circumstances, several so-called oxygen enrichment membranes that concentrate and separate only oxygen from the atmosphere have recently been proposed.

However, it is difficult to say that all of these proposed membranes have satisfactory performance, such as low oxygen separation performance, or insufficient sustainability even though the initial performance is high. It was something.

The inventor of the present invention has conducted various research and examinations with the aim of obtaining a composite family for gas separation that has sufficient oxygen separation performance and can maintain that performance for a long period of time. It has been found that by stacking the layers in a specific order, the above object can be achieved.

Thus, the present invention provides an oxygen permeability coefficient Po2 of 10-8 to 1 O-7 ct n-cm/6 with a gas separation performance PO□/PN2-2 to 25 on a porous membrane having no gas separation function;
1-sec -CrnHS'The first
layered with a film of
The object of the present invention is to provide a composite membrane for gas separation in which a second membrane made of a material having a total of -sec.tynHf is laminated.

In the present invention, the porous membrane having no gas separation function preferably has physical properties of an average pore diameter of 0.001 to 0.5 and a porosity of 10 to 70%. If these physical properties are less than the above range, the gas permeation resistance will be 9.
On the other hand, if it exceeds the above range, it becomes impossible to support the film laminated thereon, which is undesirable. Among these physical properties, when adopting an average pore diameter of 0001 to 0.05 and a porosity of 20 to 50%, the gas permeation resistance is small and it works effectively as a support for the membrane laminated on top. preferable.

Also, if the thickness of the porous membrane is too thin, the mechanical strength will be reduced, and conversely, if it is too thick, the gas permeation resistance will be low and the amount of gas permeation will be small, which is undesirable.
For this reason, it is generally appropriate to adopt a thickness of about 20 to 300μ.

Next, in the present invention, gas separation performance and gas permeability coefficient 'f
f: When specifying, oxygen and nitrogen will be used as the gases.

Thus, in the present invention, a first film having the above-mentioned physical properties is laminated on the porous film.

The gas separation performance of the first membrane is PO□/pH
It is necessary to have 222 to 2.5 total.

If the performance is less than the above range, the oxygen concentration in the gas obtained through the membrane will be extremely low, and if it exceeds the above range, it will be necessary to use a small material with a PO2 of 10-8 or less. Therefore, both are inappropriate.

In addition, the gas permeability coefficient of the first membrane is Po2=
10-8~1O-7cr: -Cm/crl -5e
It is necessary to have c-cmHy k. If the permeability coefficient is less than the above range, the amount of acid accumulation will be small,
Conversely, when the above range is exceeded, the separation factor is substantially 15.
Since there are only the following small materials, all of them are inappropriate.

Also, if the first film is too thin, the mechanical strength will be weakened, and conversely, if it is too thick, the gas permeation resistance will be low and the amount of gas permeation will be small, so it is preferable. Therefore, it is generally appropriate to adopt a thickness of about 0.3 to 3μ.

Next, a second film having the above-mentioned physical properties is laminated on the first film.

The gas separation performance of the second membrane is Po2/PN
It is necessary to have 2-3 to 6. If the performance is less than the above range, the oxygen concentration in the gas obtained by passing through the membrane will be low, and if it exceeds the above range, there is only a small material with a Po2 of 10-10 or less. Therefore, both are inappropriate.

And within these ranges, PO2/PN2-35 to 50
It is particularly preferable to use this method because it has good oxygen separation performance and a large amount of oxygen permeation. Also, the gas permeability coefficient of the second membrane is Po2= 10-”'-
1O-scr, -cm/ca-sec-cmH? 'r
Must have.

If the permeability coefficient does not fall within the above range, the amount of oxygen permeation will be small, and if it exceeds the above range, there are essentially only materials with a small separation coefficient of 3 or less, so any material is unsuitable. be.

Among these ranges of transmission coefficients, PO2-5X 1
When adopting 0"-9 to 1O-8i, it is particularly preferable because the separation of oxygen and nitrogen is good and the amount of oxygen permeation is also small. Also, if the thickness of the second film is too thin (some mechanical On the other hand, if it is too thick, the gas permeation resistance will be low and the amount of permeation will be small, which is not preferable.For this reason, it is generally appropriate to use a thickness of about 001 to 0.1μ. .

As the material of the porous membrane without gas separation function used in the present invention, for example, cellulose acetate, cellulose 6-phosphate, polysulfone, polypropylene, cellulose ester, tetrafluoroethylene, polycarbonate, etc. can be used as appropriate. Of these, polysulfone is the most suitable.

Moreover, polyorganosiloxane is suitable as the material for the first film, and among these, polyorganosiloxane having an amine group is most preferable.

Specifically, the amino group-containing polysiloxane is as follows.

Regarding the types of polysiloxanes, do they have methyl groups, phenyl groups, or fluoroalkyl groups in their side chains? having a molecular weight of 50'0 to 50.000, preferably 1,0tJO to 1
0. OOO is suitable.

In addition, the amine group contained is 3-aminonolopyl<
(CH2)3NH2>, 3-7 chloroquinolaminopropyl<(CH2)3NH(◇>, aminomethyl (CH2NH2), dimethylamino〈-N(CH
3)2〉.

3-2-amineethylaminopropyl (-(CH2)3NH(CH2)2NH2)),
/ clohequinylami<-(CH2)3NNH>, etc.

(-) The material of the second film includes, for example, polyvinyl pivalate, polyarylene ether, polyacrylic acid alkyl ester, polymethacrylic acid alkyl ester, polyaromatic carbonate ester, polyα-olefin, trifluorochloroethylene Homopolymers and copolymers of the present invention can be employed as appropriate, but among them, polymers having pivalate groups are suitable, and among them, vinyl pivalate and trifluoroethylene chloride copolymer membrane The means for producing the composite membrane according to the present invention There are no particular restrictions on
For example, the surface of a porous membrane is coated with polyorganosiloxane by impregnating it in a solution of all-polyorganosiloxane, and a second membrane formed on the water surface is further laminated thereon. Can be adopted.

In the above explanation, oxygen and nitrogen were taken as an example, but the present invention is not limited to this system only, and may be used, for example, with oxygen and hydrogen, helium and hydrogen, fJl, carbon dioxide and hydrogen, or natural gas. It can also be applied to the recovery of helium from gas.

Next, the present invention will be explained by way of examples.

Example 1 A polysiloxane containing all amine groups was dissolved in tetrafluoroethane at a ratio of 3 parts by weight to a thickness of 60 μm.
After completely immersing the polysulfone porous membrane, it was heated at 100°C for 15
A polysulfone porous membrane was completely coated with a thin film of polysiloxane containing all amine groups by a heat treatment method for 1 minute.

Then, vinyl pivalate and trifluorochloroethylene i50
: A drop (approximately 0.05 ct) of a solution prepared by dissolving a polymer polymerized at a ratio of 50 parts by weight in tetrafluoroethane at a ratio of 5 parts by weight is dropped on the entire water surface and spread on the water surface to form an ultra-thin film of the above polymer. This ultra-thin film was collected on the polysulfone porous membrane coated with the above-mentioned amino group-containing polysiloxane tV. This recovery operation was performed twice.

By the above method, a porous polysulfone with a thickness of 60μ) was obtained.
A composite film was obtained in which a borine O xane film containing an amine group of about 0.07 μm in thickness and a vinyl pivalate-trifluorochloride ethylene copolymer film of about 0.05 μm in thickness were laminated on the film. A test piece with a diameter of 10 cm cut out from this membrane was set in a measurement cell, and a pressure of 3
Pressurized air was passed through the thin film side using a kq/ca gauge at a temperature of 25°C, and the amount of gas passing through the skin and the oxygen concentration therein were examined.

As a result, the oxygen concentration was 412%, and the oxygen permeation rate was (147%).
7? '/n1''-11y atm.

Comparative Example 1 The same operation as in Example 1 was carried out except that polysiloxane 7 containing amine groups was coated on the polysulfone porous 11σ film, and vinyl pivalate with a thickness of about 01 μm was coated on the polysulfone porous film with a thickness of 60 μm. Fully manufactured composite membranes directly laminated with trifluorochloroethylene copolymer, 7111 Ushio IJ
When I performed the same measurements as in 1, the oxygen concentration was 35% and the oxygen permeation rate was 0.50 m3/n? kb ailT[l
Met.

Example 2 A polysiloxane containing an amine group was dissolved in tetrafluoroethane at a ratio of 4 parts by weight to a thickness of 60 μm.
On the polysulfone porous membrane, by a method of soaking the polysulfone porous membrane and then heat-treating it at 120°C for 10 minutes,
A thin film of amino group-containing polysiloxane was coated.

Next, a solution of poly4-methylpentene-1 dissolved in 6% by weight/chlorohexane was kept at 50°C, and one drop (approximately 0.05 ct) of this solution was dropped onto the water surface. An ultra-thin film of poly4-methylpente/-1 was completely formed by spreading the film, and this ultra-thin film was collected on the polysulfonoporous membrane coated with the above-mentioned amino group-containing polysiloxane. This recovery operation was performed twice.

By the above method, a composite film was obtained in which a polysulfone porous membrane having a thickness of 60 microns was laminated with a polysiloxane sample containing about 10 microns of amino groups and a poly-4-methylbenzone-1 film having a thickness of about 0.15 microns. A test piece with a diameter of 10 holes cut from this membrane was set in a measurement cell, and pressurized air was passed through the thin membrane side at a pressure of 3 kq/ca gauge and a temperature of 25°C to measure the amount of gas permeating through the skin and the oxygen concentration in it. I looked into it. As a result, the oxygen concentration was 396% and the oxygen permeation rate was 0.45 rr? /in ATM.

Claims (1)

[Claims] 1. In addition to the porous J which does not have a gas separation function, the gas separation performance P O2/P N 2 == 2 to 25 and the oxygen permeability coefficient Fo2 = ] ] O-8 to 1 O-7 cr knee cm
/cisec-cmHy 'l: Layer the first film made of the material, and further on top of it, F02/PN2:326
and P02== 10-10-10-8ct-cm/,
A composite membrane for gas separation in which the second membrane is made of a material containing J-5ec and CTnHyk. 2 Porous membranes without gas separation function have an average pore diameter of 0.
001 to 0.5μ and a porosity of 10 to 70. 3 Porous membranes that do not have a gas separation function include cellulose acetate, cellulose nitrate, and polysulfone. The membrane according to claim (1) or (2), which is phoriflopyrene, cellulose ester, IJjl fluorinated ethylene, or polycarbonate. 4. The membrane according to claim (1), wherein the first membrane C is polyorganosiloxane. 5 The second film is a homopolymer or copolymer of polyvinyl pivalate, polyarylene ether, polyacrylic acid alkyl ester, polymethacrylic acid alkyl ester, polyaromatic carbonate ester, polyα-onfin, trifluorochloroethylene. The membrane according to claim (1).