JPH03221130A - Fluorine separation membrane - Google Patents

Abstract

PURPOSE:To provide good oxygen-permeability, heat resistance, and chemical resistance by forming a separation membrane using a copolymer of perfluoro-(2,2-dimethyl-1,3-dioxole) and at least one kind of ethylenic unsaturated monomers. CONSTITUTION:A separation membrane is prepared using a copolymer of perfluoro-(2,2-dimethyl-1,3-dioxole) 'a first component' and at least one kind of ethylenic unsaturated monomers by a melting method, a solution method, etc. The obtained membrane is preferable to have at least oxygen permeability 1X10<-5>cm<3>/cm<2>.sec.cmHg at air permeating time in a temperature range from room temperature to 200 deg.C and at least 1.5 oxygen/nitrogen separation coefficient. The content of the first component of the copolymer is preferably at least about 50 mole % for improving the heat resistance. The obtained separation membrane has high gas permeability coefficient and separation coefficient in separation of high temperature gases.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention comprises a fluoropolymer. This invention relates to a separation membrane suitable for separating mixed gases, etc.

<Prior Art> In recent years, active consideration has been given to separating and purifying fluid mixtures using permselective models instead of energy-intensive processes involving phase changes such as distillation and deep cooling.

Among membrane separation and purification processes for fluid mixtures, the ones that have been put into practical use on an industrial scale are mainly liquid-liquid separation and liquid-solid separation, such as in water desalination and industrial wastewater treatment. However, very little work has been done on gas-gas separation. The reason why gas membrane separation is difficult to put into practical use is that there is no membrane that has low selective permselectivity, that is, it selectively allows certain gases to pass through while almost completely blocking other gases.
In order to obtain high purity '7) gas, VC needs to adopt a multi-stage method in which membrane separation is repeated several times, which requires a large device and a small amount of permeation, so a large amount of gas must be used. There are two main points that are difficult to handle.

However, from the point of view of selective permeation, the final use of gas does not necessarily require the supply of high-purity gas.
There are also many. For example, in the case of oxygen, high purity oxygen Fi is not necessarily required in applications such as high-temperature ventilation and combustion assistance. Not only that, X-purity stimulants may be inconvenient, such as damage to the furnace and the risk of fire. For these applications, the permeation rate for producing a large amount of electrolyte metal and the durability of the nitrogen equipment including the membrane, especially heat stability and chemical resistance, are more important than high selectivity.

Further, when removing dissolved oxygen from boiler water, N pure water, etc., it is necessary to use a membrane that is easily permeable to oxygen and difficult to permeate water vapor.

Conventionally, organosiloxane-polycarbonate copolymer, poly(4-methylpentene-1), has been known as a membrane material for obtaining a large amount of oxygen-enriched air of low to intermediate purity. ing.

In addition, fluorine-based copolymers consisting of barfluoro-(2,2-dimethyl-1,3-dioxole) and ethylenically unsaturated monomers are disclosed in U.S. Pat.
It is disclosed in Japanese Patent No. 8-38707.

[Problem to be solved by the invention]

However, the oxygen permeability coefficient of organosiloxane-polycarbonate is 1o-7 to 10-'-・α7 country 2.8Q
Although it has large C, tx, and Hg, it has poor chemical resistance and may be deteriorated by contaminated air, oil-filled pumps for depressurizing or pressurizing, or oil from condensers. Also, poly(4
-Methylpentene-1) has a high selectivity of 5 to 4, but an oxygen permeability coefficient of 1 (1' to 10-"am" ・e
xlon” ・sec ・3Hg, which is low, so it needs to be large area or #i/thin M.

That is, at present, 9H is not known to have sufficient oxygen permeability, heat resistance, and chemical resistance.

In addition, since the Mu water vapor permeability coefficient of polyorganosiloxane-based and poly(4-methylpentene-1) yarns is large lA,
When these membranes are used to deoxidize boiler water or the like by a reduced pressure method, problems arise such as increased power cost and water condensation on the secondary side.

In the above-mentioned publication, the fluorine-based copolymer is only shown to be used as a window for a chemical reactor, and there is no mention of its application to separation or modeling.

Means for Solving Problem S> *The inventors have completed the present invention after intensive study to develop a gas valve aS that has excellent oxygen permeability, heat resistance, and chemical resistance.

That is, the gist of the present invention is a gas separation membrane comprising a copolymer of perfluoro-(2°2-dimethyl-1,3-dioxole) and at least one ethylenically unsaturated monomer.

The copolymer used in the separation WK of the present invention is perfluoro-
The copolymer has good heat resistance due to the ring structure of the first component. It is meant to show.

At least one ethylenically unsaturated monomer (hereinafter referred to as "second component") which is a constituent component of the copolymer pond includes olefins, vinyl It isomers, and bafluorofluorophores.

Examples of olefins include ethylene, 1-butene, imbutylene, trifluoropropene, and trifluoroethylene, and examples of vinyl polymers include vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene, and tetrafluoroethylene. can be mentioned. Also, the perfluoromonomer may have a different chemical structure, e.g.
-td, perfluoropropene, perfluoro(1,3
-dioxole), perfluoro(alkyl vinyl ether), methyl-3-[:1-(difluoro-[(trifluoroethylene)oxycomethyl)-1,2,2,
2-tetrafluoroethoxy]-2,2,3,3-tetrafluoropropanoate, CF2 = CFOCF2
CFOCF20F2 C00CH3CF.

and 2-C1-(difluoro-(: () +1fluoroethynyl)oxyne]methyl)-t2.2.2-tetrafluoroethoxy) -1,1,2,2-tetrafluoroethanesulfonyl fluoride CF2-C? OCF
! cFocy, CF2 S02 FC=.

Etc. are *excited.

As a constituent component of the copolymer, these second components may be used alone or in combination of two or more. Also, considering the heat resistance stability of the separation membrane and the fact that it can be supplied at low cost, it is preferable that the second component is tetrafluoroethylene! Yes.

The composition ratio of the constituent components of the copolymer is not particularly limited, but from the viewpoint of heat resistance, the first component is preferably 50 moles or more, and more preferably 75 moles or more.

The separation membrane of the present invention basically consists of only the above-mentioned copolymer, but it contains several N of polymers, oligomers, and a low amount of additive 1 for the purpose of improving mechanical strength. It may be.

The part 11I model of the present invention is a substantially non-porous sliding door, and can take the form of a flat membrane, a tubular membrane, or a hollow fiber membrane. or,
It may also be a composite membrane combined with a porous support.

The separation membrane of the present invention is exposed to a temperature range from room temperature to 200°C, and the permeability coefficient of hydrogen permeability to air (C) is usually IQ-'': 1
0-'cyd ・tx/czr? -QAC・c=++H
The value of g no-f- and the oxygen/nitrogen fraction x gA number have values on the t51 plate. The capacity of the separation membrane is not limited, but if it is 3 Qurn or less, the oxygen permeation rate should be 10-' cpnj/cm2 in the above temperature range.
It is possible to make it more than ssc ・tym Hg. IIIlidj It is more preferable that it is 5am or less1
It is particularly preferable that the weight is 10 weight meters or less. If the film thickness is less than one μm or less than several μm, the temperature range is set to the above temperature range, and the oxygen permeation rate is set to 10=cm”/>2・8'3C・
It is possible to make it more than a knockdown.

In addition, in the case of a membrane whose purpose is to remove dissolved oxygen from water, the aquatic air permeability coefficient 'oH26 and the oxygen permeability coefficient PO,
The ratio with pg2o/? 02 is preferably 15 or less, more preferably 10 or less. Also, in this case PO, I X i O-'α3・eya/lym2・
9QC-cyr Hcr or more is sufficient.

5)11 of the present invention! The pattern can be manufactured by a known film forming method such as a melting method or a solution method, and as the solution method, a casting method, a water surface spreading method, a spin cord method, etc. can be adopted.

Further, examples of the solvent for dissolving the copolymer in the solution method include perfluoro(2-butyltetrahydrofuran).

When using a composite membrane, it is possible to apply a thin 5W separation membrane on the surface of a porous support, or to apply a polymer solution onto the porous support.

〔Example〕

The present invention will be further explained below with reference to Examples.

In addition, the unit of gas permeation rate in (Example) is (tys3
/lym' ・5ee-cnxFig), and the unit of gas permeability coefficient is [c1M3・Bi/Bi2・aec・m
It is 1 coffee.

Example 1 A 15-polymer fluorine-based copolymer consisting of 72 moles of perfluoro(2,2-methyl-1,3-dioxole) and 28 moles of tetrafluoroethylene was mixed with perfluoro(2-butyltetrahydrofuran) [ Manufactured by 3M,
A polymer solution for film formation was prepared by dissolving it in FC-75185 (trade name: Floriner).

This polymer solution was cast onto a smooth glass plate to a thickness of 150 μm using a doctor knife, and then cast in an atmosphere of 150°C for approximately 200 μm.
After drying for hours, a dense film with a thickness of 15 am was obtained.

Next, when the temperature was 25℃ and the gas permeability was evaluated using air as the raw material gas, the oxygen permeation rate QOxbal
5 X 10-5cm”/cnx2・sea -mHg
The oxygen/nitrogen separation coefficient was 2.7.

Converting this Qol to the oxygen permeation rate per film thickness (that is, oxygen permeation coefficient @POh) is a3XjO−'αゝ・B/
It was α2・39C・Bidg.

In addition, the tensile strength of this membrane is 370 kg/lx",
The elongation at break was 12.54.

Example 2 8 parts by weight of a copolymer consisting of 89 moles of perfluoro-(2,2-dimethyl-1,3-dioquinol) and 11 moles of tetrafluoroethylene were added to 92 parts by weight of perfluoro(2-butyltetrahydrofuran). A polymer solution for film formation was obtained by dissolving.

Subsequently, it was cast in the same manner as in Example 1 to obtain a dense pattern with a thickness of 10 μm. This membrane exhibited the oxygen permeation rate, minute M coefficient, and mechanical properties shown in Table 1.

Example 3 6 parts by weight of a copolymer consisting of 89 moles of barfluoro-(2,2-dimethyl-1,3-dioxole) and 11 moles of tetrafluoroethylene and perfluorobolyether (
Demnum S-200) (manufactured by Daikin) was dissolved in 92 parts by weight of perfluoro(2-butyltetrahydrofuran) to obtain a polymer solution for film formation.

Using this polymer solution, a dense film with a thickness of 10 μm was obtained in substantially the same manner as in Example 1. The characteristics of this film were evaluated and the first
Shown in the table.

Example 4 5 parts by weight of a copolymer consisting of 75 mol% of barfluoro-(2,2-dimethyl-1,3-dioxole) and 25 mols of tetrafluoroethylene were mixed with 95 parts by weight of barfluoro-(2-butyltetrahydrofuran). A polymer solution for film formation was obtained.

When 50 μL of this polymer solution was dropped onto the water surface, the droplet level spread on the water surface support to obtain a circular, extremely thin film.

Two of these extremely thin films were placed on a polytetrafluoroethylene porous film having an average pore diameter cL of 1 μm and a film thickness of 47 μm to prepare a composite film. For this composite membrane, the polarization is 25℃, 12
When the air permeation rate was measured at 0°C and 200°C, the oxygen permeation rate and separation coefficient showed the values shown in Table 2.

Example 5 Using eight composite M sheets obtained in the same manner as in Example 4, each of them was treated with an organic solvent of toluene, methylene chloride, hexane, ethanol, acetone, dimethylformamide, dimethylacetamide, or dimethylformoquine. After passing through the saturated air, the oxygen permeation rate and separation coefficient were measured, and no change in performance was observed in either case.

Example 6 Press film obtained by heating a fluorine-based copolymer consisting of 70 mol% of barfluoro-(2,2-dimethyl-1,5-diokasol) and 30 mol of tetrafluoroethylene to 270°C About / Evening O When the gas permeability coefficient was measured, PO2 was 1.
0-'PN2battf> OX 1 n-'
P'H20 is Z7X101, and pol/PNt is 2
．． 5, pEI, ○/po.

was mountain 5.

Implementation@7 Copolymer consisting of 62 mol% barfluoro-(2,2-dimethyl-1,3-dioquinol) and 38 mol width of tetrafluor 10 ethylene.
-Butyltetrahydrofuran) (manufactured by 3M, trade name: 70 Linate PC-75) was dissolved in 955 parts by weight to prepare a polymer solution for film formation.

When 50 ut of this polymer solution was dropped onto the water surface,
The droplet spread on the water surface support, and an extremely thin circular film was obtained. The average pore size (11 μm 1 film thickness 50
A composite membrane was prepared by taking it out onto a polytetrafluoroethylene porous membrane made by Am. Gas permeability coefficient P of this composite membrane
O2, PN.

and PH, 0 respectively j a 7 X 1O-944
X1 (r'' and I Z2 X 10-', po
Snow/PM was 2.4, and PH snow o/po was 1.6.

Comparative Example 1 Poly 4-methylbenzone-1 (Product name TPXMXOO1
, manufactured by Mitsui Petrochemical Industries, Ltd.) at a temperature of 260°C.
When I measured H Goose Q, it was PO.

is 19 X 10-10 PN, is 4.8 X j
The size of the controller was 415 x 10-10. That is, po, /Pwt Fi friend 9 and P
H1O/PO was 22, which was a fairly large value.

Comparative Examples 2 to 4 In Comparative Example 1, a film was prepared using the polymer shown in Table 1 instead of poly-4-methylbenzone-1, and its po, PM, PH, and O were measured. The results shown in 3 tables were obtained.

/ / / Table [Effects of the invention] The membrane of the present invention has excellent heat resistance and is effective in separating upper gases.
) exhibits excellent gas permeability and separation coefficients. In addition, it has excellent chemical resistance, and although it dissolves in certain fluorinated solvents, it is not affected by the four general solvents, and it has excellent alkali resistance, acid resistance, and oxidation resistance, so it can be used over a wide range of areas. It can be used in either environment.

Since the present invention has a relatively small water vapor permeability coefficient, it is applicable not only to the field of gas separation but also to the removal of dissolved oxygen from water.

Claims (5)

[Claims] (1) A separation membrane made of a copolymer of barfluoro-(2,2-dimethyl-1,3-dioxole) and at least one ethylenically unsaturated monomer. (2) The separation membrane according to claim 1, wherein the ethylenically unsaturated mer is tetrafluoroethylene. (3) Oxygen permeation rate during air permeation in the temperature range from room temperature to 200℃ is 1 x 10^-^5cm^3/cm^2
2. The separation membrane according to claim 1, which has an oxygen/nitrogen separation coefficient of 1.5 or more and sec.cmHg or more. (4) Oxygen permeation rate during air permeation in the temperature range from room temperature to 200℃ is 1 x 10^-^4cm^3/cm^2
The separation membrane according to claim 3, which has an oxygen/nitrogen separation coefficient of -sec.cmHg or more and an oxygen/nitrogen separation coefficient of 1.5 or more. (5) Water vapor permeability coefficient PH_2O and oxygen permeability coefficient PO_
2. The separation membrane according to claim 1, wherein the ratio PH_2O/PO_2 is 15 or less.