JPS5840127A - Gas-permeable membrane - Google Patents

Abstract

PURPOSE:To obtain a selective gas-permeable membrane having selective permeability and a large permeation coefficient, by using a siloxane-phenyl alternating copolymer with a specific structure as the main constituent. CONSTITUTION:As the main constituent of a gas-permeable membrane, a siloxane-phenyl alternating copolymer shown by the formula (wherein R1 and R2 are each a substituent such as alkyl or vinyl, X is a substituent such as hydrogen or alkyl, m is an integer of 1-4) is used. Because this copolymer wherein silicon and an org. group are alternately bonded to oxygen is excellent in selectivity and has sufficient permeation capacity, an excellent gas-permeable membrane is obtained from this copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas permeable membrane, and provides a selective gas permeable membrane having improved permselectivity and a large permeability coefficient.

Conventionally, there are methods for separating mixtures using membranes, but these use reverse osmosis membranes, ultrafiltration membranes, etc., and are mainly intended for liquids. On the other hand, with regard to the separation of mixed gases through membranes, the selectivity and amount of permeation were insufficient, so most of them were not used again, and on the contrary, the application of the gas permeation phenomenon in films was mainly focused on gas barrier films for packaging. It was.

Oxygen, which makes up 21% of the air's components, is used in internal combustion engines, iron and steel industry, and food industry.

Trowels are important raw materials for medical equipment, waste treatment, and other industrial applications, and therefore there has been a desire for a method to efficiently, inexpensively, and easily separate oxygen from air.

The conventional method of separating oxygen or nitrogen from the air without using a membrane is to pass the air through a separation agent made of zeolite or special carbon. There are known ways to do this. However, this method has the disadvantage that enriched oxygen or nitrogen cannot be supplied continuously.

On the other hand, the separation method using membranes has an extremely large industrial advantage because enriched oxygen or nitrogen can be continuously supplied.

For this reason, a separation membrane with high selective separation and a high permeation rate is desired, and several methods using thin polymer membranes have already been reported.

When separating oxygen or nitrogen from the air using a polymer thin film, important issues are the permeability coefficient of the polymer thin film for oxygen or nitrogen, the mechanical strength of the thin film, and the thin film technology. Become.

Currently reported materials with relatively good permeability include natural rubber, synthetic rubbers such as polybutadiene, and even more excellent materials such as silicone rubber. Among these, noricorn rubber shows superior permeability to almost all gases than any other polymer material, and although the separation ratio of each gas is small, it is considered to be a polymer material that is convenient for practical use. . Silicone, or polyorganosiloxane, has the property of low intermolecular interactions and high flexibility of siloxane bonds.
This is interpreted as a factor contributing to the excellent gas permeability. However, on the other hand, the above properties are closely related to a decrease in mechanical strength. It also causes a significant decrease in mechanical strength.Therefore, in the case of silicone, it can only be crosslinked through vulcanization and used for separation membranes as noricorn rubber.Silicone rubber, as a general structural material,
As is well known, it has excellent weather resistance and sufficient mechanical strength, but in order to use it as a thin film for gas permeation, the above-mentioned vulcanization treatment is a major drawback in the production of the thin film.

In order to overcome the above-mentioned drawbacks and to facilitate the film forming method, professional copolymers of silicone and other polymers, such as polydimethylsiloxane-polycarbonate, have been proposed. In such copolymers, other polymers are introduced into the polydimethylsiloxane alone, so the gas permeability is lower than that of silicone rubber, but the polymer as a whole remains stable even without vulcanization. Since it is a polymer that has mechanical strength that allows it to be made into a thin film and is soluble in organic solvents, it is very easy to make a thin film by using the casting method or other common methods.

However, its gas permeability is lower than that of silicone or corn rubber, and its selectivity for oxygen and nitrogen is low at about 2, which is about the same as that of silicone rubber, and its condensability is unpleasant.

The present inventors conducted various studies to improve the selectivity described above, and as a result, instead of using the block copolymer described above, we developed an alternating copolymer in which silicon atoms and organic groups are alternately bonded to oxygen atoms. It has been found that the polymer has excellent selectivity and sufficient permeability. That is, it has been found that a gas permeable membrane consisting essentially of an alternating copolymer represented by the general formula - exhibits excellent gas permeability and selectivity. Here, R, and R2 each represent a substituent selected from an alkyl group, a vinyl group, a halogen-substituted alkyl group, and a phenyl group, and X is hydrogen.

A substituent selected from an alkyl group, a sulfonic acid group, a carboxyl group, and a carboxylmethyl group, m is an integer of 1 to 4, and n represents the degree of polymerization.

The above compound can be easily obtained by condensing a silane compound having a difunctional group such as dichlorodimethylsilane or dianilinodiphenylsilane with a dihydroxyphenyl compound such as P-hydroquinone. The functional group of the bifunctional silane compound is a chlorine group.

Dimethylamino group, diethylamino group, anilino group (phenylamino group), etc. are useful, and R4, R2
Suitable examples include a methyl group, an ethyl group, a propyl group, a vinyl group, a fluoropropyl group, and a phenyl group. On the other hand, the dihydroxyphenyl compounds that are alternately copolymerized with this are 2-methylhydro, quinone, and 2,6-dimethylhydroquinone.

2-methyl, 6-bropyrno-hydroquinone, etc. can be used, and after alternating copolymerization with P-hydroquinone, a substituent can be introduced by a Riedelkraff type reaction, and any alkyl group, sulfonic acid group, carboxyl group, carboxyl Methyl groups are useful.

The resulting alternating copolymer is tetrahydrofuran.

It is soluble in cyclic ethers such as 1.4 dioxane, and organic solvents such as dimethylformamide and dimethyl sulfoxide, and can be easily cast into films from these solutions. The gas permeable membrane made of alternating copolymers thus created is
Oxygen permeability is 10-8 to 1o-9 (CC-crn/Cr
18eC-crnHq), and the selectivity for oxygen and nitrogen showed a large value of 2 to 6.

Examples will be described below.

<Example-1> Method of J, E, Curry et al. (L Appl, P
o1y, Set.

9, 295, 1965), equimolar amounts of diphenyldianilinosilane and P-hydroquinone were heated and melted, and reacted for 6 hours while recovering the produced aniline under reduced pressure. The obtained polymer was dissolved in tetrahydrofuran, purified by reprecipitation with methanol, and then dissolved in tetrahydrofuran again.

When this was measured by GPC, the molecular weight was approximately 45,000.
It was. This solution was cast on a glass plate and dried to obtain a film. The gas permeability of this film is 4. + X + 0-9 (cc-Confucian/crl-s
The selectivity with respect to nitrogen (ea-cm Hg) was 4.2.

<Example-2> Methylhydroquinone was dissolved in tetrahydrofuran,
A solution of equimolar dimethyldichlorosilane in tetrahydrofuran was added dropwise and mixed, followed by heating and stirring at 60° C. for 1 hour. During this time, hydrochloric acid gas was generated quite violently. Gradually raise the temperature to evaporate the tetrahydrofuran and heat at approximately 100℃ for 6 hours.
The reaction was allowed to proceed for several hours, and the temperature was finally raised to 260°C.

The obtained solid was dissolved in tetrahydrofuran, washed and purified again with methanol, and measured by GPC, and the molecular weight was approximately 35,000. Based on this, a film was made in the same manner as in Example 1, and the gas permeability was measured.

Oxygen permeability 8.9 x 1O-9 (cc-cm/
The selectivity of crl ・5ec-cmHq) with nitrogen is 3.
It was 2.

<Example 3> Synthesis was performed according to the method of Example 1 using dimethyldiethylaminosilane instead of diphenyldianilinosilane. When the obtained polymer was measured by GPC, the molecular weight was about 60,000.

This polymer was dissolved in chloroform (partially swollen), and a chloroform solution of chlorosulfonic acid was added dropwise to the solution while stirring at room temperature. After stirring at room temperature for 2 hours, it was left at room temperature overnight. This solution was poured into methanol, and the resulting precipitate was filtered off.

The precipitate thus obtained was dissolved in 1,4 dioxane and cast on a glass plate to form a film.

The gas permeability of the film made of this polymer is 2 x 10 (cc-cm/crd, 5ec-cm) for oxygen.
cmHq), the selectivity with respect to nitrogen was 4.5.

Although typical examples have been shown above, the present invention can also be used to synthesize copolymers containing other substituents such as those described above by almost the same means. The oxygen permeability is 10-8 to 1o-9 < 0 cc-cm/cA 5een CrnH9),
Moreover, the selectivity of oxygen to nitrogen showed a high selectivity of 2 to 6.

As described above, the present invention is a gas permeable membrane consisting essentially of a siloxane/phenyl alternating copolymer represented by the general formula. Here, R4゜R2 each represents a substituent selected from the group consisting of an alkyl group, a vinyl group, a halogen-substituted group, an alkyl group, and a phenyl group, and X represents hydrogen, an alkyl group, a sulfonic acid group, a carboxyl group, and It represents a substituent selected from the group consisting of carboxylmethyl groups, and m is 1-4. The gas permeable membrane with such a structure has a high gas permeability of 4 or more compared to silicone rubber, and a high selectivity of 2 to 6, exhibiting excellent effects, and is particularly suitable for combustion, various industrial, medical, and other uses. is very useful for obtaining oxygen-enriched air.

Claims (1)

[Claims] A gas permeable membrane whose main constituent is a siloxane/phenyl alternating copolymer having the general formula shown below. (Here, R, and R2 each represent a substituent selected from an alkyl group, a vinyl group, a halogen-substituted alkyl group, and a phenyl group, and X represents hydrogen, an alkyl group, a sulfonic acid group, a carboxyl group, and a carboxylmethyl group. Indicates a carefully selected substituent, m indicates an integer from 1 to 4.)