JPH04145933A - Gas separation membrane - Google Patents

Abstract

PURPOSE:To reduce deterioration with time in gas transmitting property by making a subtd. polyacetylene membrane occlude a specified amt. of ditrimethylsilylfumalate. CONSTITUTION:The gas separation membrane is prepared by occluding ditrimethylsilylfumalate by 0.5-10.0wt.% in a subtd. polyacetylene polymer membrane expressed by formula I (R1 is hydrogen atom, halogen atom, alkyl group or halogenated alkyl group, and R2 is alkyl group, phenyl group or organosilyl group). This gas separation membrane is excellent in gas transmitting property and shows significant decrease in deterioration of gas transmission coefft with the lapse of time. Thereby, this membrane is very effective for manufacturing a composite with a super-thin film having enough selective transmitting function.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a gas separation membrane that selectively permeates a specific gas from a mixed gas. More specifically, the present invention relates to a separation membrane whose gas permeability characteristics are improved over time.

(Prior art) In recent years, there has been active development of technology for separating and concentrating specific gases from mixed gases.
The so-called oxygen-enriching membrane, which concentrates and separates microbial cells, is expected to be used in a variety of applications, including oxygen therapy in the medical field, energy saving in combustion systems, health equipment, and aerobic culture of bacterial cells.

Important characteristics required of an oxygen-enriched membrane are a large permeation amount of oxygen-enriched air and a high oxygen concentration. The amount of permeation of oxygen-enriched air is proportional to the oxygen permeability coefficient (PO2), which is a value unique to the material, and inversely proportional to the film thickness. In addition, the oxygen concentration is determined by the separation coefficient (PO2/PN2), which is the ratio of the oxygen permeability coefficient (PO2) and the nitrogen permeability coefficient (PN2).
Determined by

Therefore, an ideal oxygen-enriched membrane is one that uses a membrane material that has a large oxygen permeability coefficient and a high separation coefficient to form an ultra-thin membrane that is as thin as possible (preferably several tens of Å or less) and has no pinholes. be. However, such ultra-thin films usually have insufficient film strength, and if they are directly laminated onto a porous support material, the thin film will be destroyed during suction, resulting in a loss of practicality.

In order to solve this problem, a non-porous thin film having both reinforcement and cushioning properties may be interposed between the ultra-thin film and the porous support material. Such a non-porous membrane is required to have an extremely high oxygen permeability coefficient and, in addition, to have membrane strength necessary for thinning. This is because the thickness of a non-porous membrane must be thicker than the ultra-thin upper layer due to its nature, which means that the non-porous membrane tends to be rate-limiting for the amount of permeation. As long as the ultra-thin membrane has a sufficient oxygen enrichment function, a high separation coefficient is not necessarily required for a non-porous membrane as a reinforcing material. There is a strong desire to create a strong, thin film using as large a material as possible.

Polydimethylsiloxane is a known polymer membrane with a high oxygen permeability coefficient. Oxygen permeability coefficient is 6
X 1O-8L? n+3(STP)am/eTIl
"SeC" e+nHg is the highest among the rubbery polymers, but it is extremely flexible, so it is difficult to form a thin film of 25 μm or less, and it cannot be put to practical use. Also, the separation factor is 2
．． As low as 0.

For the purpose of improving the thin film properties of polydimethylsiloxane, polydimethylsiloxane/polycarbonate copolymers (U.S. Pat.
4) is known. Although the permeation flow rate was improved by achieving a thin thickness of 1 μm or less, the oxygen permeability coefficient was lower than that of polydimethylsiloxane, so
Practicality is not sufficient.

On the other hand, as a polymer membrane with a higher oxygen permeability coefficient than polydimethylsiloxane, poly(1-trimethyl, non-silyl 1-
Substituted polyacetylene compounds typified by PTMSP (hereinafter abbreviated as PTMSP) are known. (J, Am,
Chem, Soc, 105.7473 (1983)
) PTMS consists of bulky and highly mobile side chains of methyl and trimethylsilyl groups and a main chain of rigid double bonds.
Since the film density of P is very low and the free volume in the film is considerably larger than that of ordinary glassy polymers, the molecular structure of P immediately after film formation is considered to be very bulky. It is presumed that this results in a high gas permeability coefficient. This P.T.
A membrane made of MSP has a low separation coefficient of 1.4 to 2.0, but an oxygen permeability coefficient of 4 to IOX 10-7, which is an order of magnitude higher than that of polydimethylsiloxane, and has excellent membrane strength, making it easy to thin the membrane. It has the advantage of being easy to do. In that sense,
PTMSP is a preferred material.

However, this PTMSP has a major drawback in that its oxygen permeability coefficient decreases significantly over time, and the speed of this deterioration tends to accelerate, especially under heating (
J, Appl, Po1m, Sci, 30. 1605
(1985)).

Although the cause of the decrease in gas permeability coefficient is not clear, it is thought to be due to a relaxation phenomenon of molecules that occurs over time, or the deposition of fine particles in the air. Therefore, PTM
A very important issue is how to measure the long-term stability of the SP membrane without reducing its oxygen permeability coefficient as much as possible.

In order to improve the instability of PTMSP's gas permeability over time, a method has been proposed in which dioctyl phthalate (hereinafter abbreviated as DOP), known as a PvC plasticizer, is adsorbed onto the PTMSP membrane (No. 24). Collection of abstracts from the water debate 1986). However, since this method adsorbs DOP at a high temperature of 100° C., it often accelerates the deterioration of the sludge permeation properties, and is therefore not a preferable method.

JP-A-62-110728 proposes a gas-permeable composite membrane in which PTMSP is impregnated with or adsorbed with a polysiloxane polymer, but although the separation coefficient is slightly higher, the oxygen permeability coefficient is lower than that of PTMSP alone. This is significantly lower than in the case, and it cannot be said to be suitable as a non-porous membrane used here.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned drawbacks, and provides a gas separation membrane that is excellent in gas permeability and whose oxygen permeability coefficient decreases little over time.

(Means and effects for solving the problems) The present invention
The purpose is to provide a polymer membrane that is stable over time without reducing the excellent oxygen permeability coefficient of substituted polyacetylene represented by MSP.
We discovered that by occluding ditrimethylsilyl fumarate (hereinafter abbreviated as DTMSF) monomers and/or oligomers on the surface or inside of a P membrane, it is possible to create a membrane material that has both excellent membrane strength and a high oxygen permeability coefficient. , we have completed the present invention.

That is, the present invention provides that ``the general formula is +C=C (where R1 is a hydrogen atom, a halogen atom, an alkyl group,
or a halogenated alkyl group, R2 is an alkyl group, a phenyl group, or an organosilyl group) A gas characterized by occluding 0.5 to lo, owt% of ditrimethylsilyl fumarate into a substituted polyacetylene polymer membrane. Its gist is ``separation membranes''.

Examples of the substituted polyacetylene used in the present invention include polymethylacetylene, polymethylacetylene, polypropylacetylene, polyt-butylacetylene, polytrimethylsilylpropylene, polyl,2-bis(trimethylsilyl)acetylene, polyphenylacetylene, and polyacetylene. Examples include, but are not limited to, 1-chloro2-phenylacetylene.

Among the substituted polyacetylenes, for example, P TMS P is
Conventionally known pressure increase etc. J, Am, Chem, Soc,
, 105.7473 (1983).

Using commercially available 1-trimethylsilyl-1-propyne as a raw material,
Tantalum pentachloride, niobium pentachloride, etc. are used as polymerization catalysts, and organic solvents (toluene, xylene, benzene, 1.2-
dichloroethane, carbon tetrachloride, etc.) at 80° C. for 12 to 24 hours. The produced polymer was precipitated in a large amount of methanol to form a white powder of PTM.
Purify to SP. The weight average molecular weight is 500,000 or more, preferably 1,000,000 or more as a styrene equivalent value determined by GPC method.

The substituted polyacetylene polymer used in the present invention (dissolved in an organic solvent such as toluene, xylene, benzene, n-hexane, etc.) can be easily formed into a thin film by commonly known casting methods, water surface development methods, etc., and is porous. It is laminated on a support material to form a composite membrane as a reinforcing layer for ultra-thin membranes.

As the porous support material, porous polymer membranes such as cellulose acetate, polycarbonate, polysulfone, polyethersulfone, and polyolefin can be used.

In order to understand the gas permeation characteristics of PTMSP alone over time, the present polymer was first dissolved in a benzene solvent, cast on a glass plate, and then dried at room temperature to form a film with a thickness of 80 to 150 μm. When the gas permeability was measured by a low pressure method, the initial value of the oxygen permeability coefficient of the PTMSP film was very high, 6 to 10 × 10-7, but it deteriorated over time, and the oxygen permeability coefficient of 100 When left in a heated atmosphere at ℃, the oxygen permeability coefficient becomes 1120 after 1 day and night.
It was found that it decreased below.

The DTMSF used in the present invention is obtained by reacting fumaric acid and hexamethyldisilazane on a 130°C oil bath for 8 hours, and then distilling the purified DTMSF under reduced pressure.
I got it. DTMSF is dissolved as a monomer or/and oligomer in an organic solvent such as methyl alcohol, ethyl alcohol, acetone, or ethyl acetate, and a substituted polyacetylene film including PTMSP is immersed in this solution. / and absorbed into the interior. Or DTMS
F can be occluded into substituted polyacetylene films as DTMSF vapor under reduced pressure. In either case, the occlusion temperature is set to 4
It is desirable to carry out the process at a temperature of 0 to 50°C or less, preferably at room temperature.

The amount of occlusion of DTMSF in the substituted polyacetylene film is preferably 0.5 to 10 wt%, and 1.0 to 5.
It is more preferable if it is 0w%. If the amount of occlusion is within this range, the gas permeability will not be significantly impaired and the stability of the oxygen permeability coefficient over time can be maintained. When the amount of occlusion of DTMSF becomes 0.5wt% or less, untreated PTMS
As with the P film, a rapid decrease in the oxygen permeability coefficient over time was observed, and no occlusion effect of DTMSF was observed. On the other hand, if the amount of occlusion of DTMSF exceeds 10 wt %, the separation coefficient will be a little high, but the initial value of the oxygen permeability coefficient will be as low as 10-8, which is not preferable.

(Example) 1: The present invention will be explained in detail below with reference to Examples and Comparative Examples.
The present invention is not limited to this.

=12 Example-1 Preparation of PTMSP film 500 mmol of 1-trimethylsilyl-1-propyne (manufactured by Aldrich) was dissolved in 500 mmol of toluene, 5 mmol of tartarum pentachloride was added as a catalyst, and the mixture was polymerized at 80° C. for 24 hours. The resulting polymer was purified by dissolving it in toluene and precipitating it into a large amount of methanol.

The weight average molecular weight Mw of the polymer was measured by GPC method and was found to be 1,980,000.

2.0 g of the purified polymer was dissolved in 100 g of benzene, cast on a smooth glass plate, and the solvent was evaporated at room temperature and pressure to obtain a PTMSP film with a thickness of 120 μm.

1.0 mol of occluded fumaric acid of DTMSF was added to 1.1 mol of hexamethylsilazane, and the mixture was reacted at 130° C. for 8 hours. The product was distilled under reduced pressure to obtain purified DTMSF in the form of white crystals.

3.0 g of purified DTMSF was dissolved in methanol + 00 d, and the previously prepared PTMSP film was immersed in this solution for a day and night, and then dried at room temperature, and the amount of occlusion of DTMSF relative to PTMSP was 2.9 wt%. .

Example-2 6.0 g of purified DTMSF was dissolved in 100 ml of methanol, and a film with a thickness of 120 μm prepared in Example-1 was added to this solution.
When a PTMSP film of m was soaked for a day and night and dried, the amount of occlusion of DTMSF relative to PTMSP was 5.6w.
It was t%.

Comparative Example-1 The 120 μm thick PTMSP film prepared in Example-1 was used as it was.

Comparative Example-2 0.2 g of purified DTMSF was added to 100 g of methanol.
- and the film thickness 1 formed in Example-1 in this solution.
When a 20μm PTMSP film was soaked for one day and night and dried, the amount of DTMSF absorbed by PTMSP was 0.
．． It was 2wt%.

Comparative Example-3 15.0g of purified D TMS F was placed in methanol room.
9! When the PTMSP film having a thickness of 120 μm prepared in Example 1 was immersed in this solution for a day and night and dried, the amount of DTMSF occluded with respect to PTMSP was 14.3 wt%.

The films obtained in Examples 1 to 2 and Comparative Examples 1 to 3 were placed in a heated atmosphere at 100°C to accelerate deterioration over time, and the gas permeation characteristics were measured using a gas permeability measuring device (manufactured by Rika Seiki Kogyo Co., Ltd.). (used).

The results are shown in Table 1.

In all cases, separation membranes with high oxygen permeability coefficients and little deterioration over time were obtained.

(Blank below) +5- (Effects of the Invention) As described above, the present invention provides a gas separation membrane in which DTMSF is occluded on the surface and/or inside of a substituted polyacetylene membrane, which has excellent gas permeability and a low gas permeability coefficient. It is a very effective gas separation membrane when combined with an ultra-thin membrane that has a sufficient selective permeation function.

Claims (2)

[Claims] (1) The general formula is ▲ Numerical formula, chemical formula, table, etc. ▼ (However, R_1 is a hydrogen atom, halogen atom, alkyl group, or halogenated alkyl group, R_2 is an alkyl group,
1. A gas separation membrane characterized in that 0.5 to 10.0 wt % of ditrimethylsilyl fumarate is occluded in a substituted polyacetylene polymer membrane represented by a phenyl group or an organosilyl group. (2) The gas separation membrane according to claim 1, wherein the substituted polyacetylene polymer is poly(1-trimethylsilyl-1-propyne).