JPS60110303A - Permselective membrane and composite film - Google Patents

Abstract

PURPOSE:To obtain an oxygen enriched film excellent in oxygen permeability coefficient and separation coefficient, by providing side chains with predetermined siloxane bonds, in a film material based on styrene. CONSTITUTION:The permselective membrane consists of a polymer in which a main chain is based on polystyrene and which has 2-10 Si polyorganosiloxane groups as side chains. The polymer has, for example, a reccurring unit of formula I , wherein (n) is an integer of 2-10, each R is 1-10C alkyl or subst. alkyl, the groups R being identical or different, and (i) and (j) satisfy the relationship of formula II. The permselective membrane consisting of the polymer is provided on the surface of a porous film having micropores continuous in the thickness direction, whereby a composite film can be obtained.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a selectively permeable membrane for liquid or gaseous mixtures, which has a siloxane bond in its side chain that is particularly effective for obtaining oxygen-enriched air from air. This invention relates to an oxygen enrichment membrane made of a styrene polymer.

Normal combustion systems (boilers, for example) use air as fuel, but if oxygen-enriched air, which has an increased oxygen concentration in the air, is supplied to the combustion system instead of this air, fuel efficiency and combustion temperature can be improved. It is possible to achieve an improvement in fuel consumption and a reduction in the amount of combustion exhaust gas, and is expected to be effective in terms of both energy conservation and pollution prevention.

The heart of the oxygen enrichment system consists of an oxygen enrichment membrane. The material used for the oxygen enrichment membrane is the separation coefficient - oxygen gas permeability coefficient PO2/nitrogen gas permeability coefficient PH2 (
Below, unless otherwise specified, the values of PO2 and PH1 are the values when the film thickness is converted to IC11, and the units are aa
-011110+f -sea -cmt-1 (referred to as 1) is high, at least 2.5 or more, and a polymer membrane with a high oxygen permeability coefficient PO2 is desirable. Furthermore, in actual membrane separation systems, in order to increase the oxygen permeation rate, ultra-HM or composite membranes (layers with excellent oxygen separation performance are made into ultra-thin films and laminated on a porous support to provide strength). configuration) is used.

Therefore, in addition to the above-mentioned two parameters of separation coefficient and oxygen permeation rate, the performance required for an oxygen-enriched membrane is that even ultra-thin membranes of about 0.05 to 0.3μ can break due to pressure differences. It is not required to have sufficient membrane strength.

(Prior Art) A selective gas permeable membrane is characterized in that its main component is a crosslinked copolymer obtained from a styrene polymer having an aromatic ring in its side chain and an α,ω-2 functional polysiloxane. It has been proposed as a functional membrane for oxygen enrichment (Japanese Unexamined Patent Publication No. 56-26
"506). However, the permeability coefficient of oxygen gas in the above membrane is 1.8 x 100-8 cc (STP) a/cJ-
sec -clllH(+, which is high and on the same order as the silicone rubber family, but it has the disadvantage that the fractionation coefficient is 2.10, which is around 2, which is the same level as the silicone rubber membrane. Compared to silicone-based polymers, silicone-based polymers have been significantly improved in terms of thin film formability and film strength in the thin film state, but they still have insufficient performance in terms of oxygen permeability coefficient and separation coefficient. Ta.

As described above, in the prior art, it has been extremely difficult to create a styrene-based membrane material with excellent oxygen permeability and separation coefficient.

(Objective of the Invention) An object of the present invention is to provide an oxygen-enriching membrane made of a styrene polymer having siloxane bonds in its side chains, which is excellent in both oxygen permeability coefficient and separation coefficient.

(Structure of the invention) The present invention has the following configuration.

(1) The main chain is polystyrene-based, and the side chain is 3i
A permselective membrane comprising a polymer having a polyorganosiloxane group having 2 to 10 atoms.

(2) The permselective membrane according to claim (1), wherein the number of polyorganosiloxane groups is 0.1 to 1.0 relative to the number of repeating units of the polystyrene polymer.

(3) The main chain is polystyrene-based, and the side chain is S
A composite membrane characterized in that a permselective membrane made of a polymer having a polyorganosiloxane group having 2 to 10 atoms is stepped on the surface of a porous membrane having fine pores continuous in the thickness direction.

(Explanation of structure) As a preferred example of the polymer according to the present invention, repeating units mainly have the general formula (but
The integer R of ~10 is composed of an alkyl group or a substituted alkyl group having 1 to 10 carbon atoms, and each R may be the same or different and has a molar relationship.

The composition ratio i/(i+j) in the siloxane bond-containing styrene polymer of the present invention is preferably 0 or more and 0.9 or less. If this composition ratio exceeds 0.9, the permeability of oxygen gas to the membrane decreases, which is undesirable, and it is more preferably 0.5 or less, and the closer it is to 0, the more preferably the permeability of oxygen gas improves.

The siloxane chain length n in the siloxane bond-containing styrene polymer of the present invention is preferably from 2 to 10, more preferably from 2 to 5. n is 10
If it exceeds this value, there is a tendency that the mechanical strength (breaking strength, Young's modulus) of the film decreases, and the formability of the ultra-thin film deteriorates.

The silicon atom content in the polymer of the present invention is preferably at least 5% by weight, more preferably 10% by weight or more. If the silicon atom content is 5% by weight, the permeability coefficient of oxygen gas to the membrane is low and the membrane is impractical.

The substituent R is preferably an alkyl group having 1 to 10 carbon atoms, a phenyl group, a nuclear-substituted phenyl group, or a substituted alkyl group, and specific examples thereof include, but are not limited to, substituents having the following structure. It's not like I was given a break.

That is, methyl, ethyl, n-butyl, 5ec-butyl,
Alkyl groups such as tert-butyl, hexyl, octyl, cyclohexyl, cyclohexylenyl groups. Phenyl group, 4-methylphenyl group, 4-nitrophenyl group, 4-
A nuclear-substituted phenyl group such as a chlorophenyl group or a 4-methyl-xyphenyl group. Chlormethyl group, chloropropyl group, mercaptopropyl group, cyanoethyl group, benzyl group, 1
~A substituted alkyl group such as a lifluoroprobyl group, a methoxyethyl group, a nitropropyl group, a 2(carboxylic-1-xy)ethyl group, and a dichloromethyl group.

In order to manufacture a composite membrane for oxygen enrichment using the polymer of the present invention, it can be carried out by uniformly laminating a thin film made of the material of the present invention on a porous support. Examples of the lamination method include a method in which a dilute solution of the polymer is cast onto a water surface and the solvent is evaporated to laminate a polymer 'a film obtained on a porous support, or a method by coating. The thickness of the membrane is preferably larger than the pore diameter of the surface of the porous support, and is usually from 0.005 to
The thickness is preferably 10μ, preferably in the range of 0.05 to 0.5μ.

The size of the micropores of the porous support is 0.005 to 1.0μ, preferably 100 to 1000μ on one surface.
A 4μ support is preferred. The microporous support described above can be selected from a variety of commercially available filter materials, such as Millipore filters (VSWP), but typically are・Manufactured according to the method described in "Report" No. 359 (1968).The materials include polysulfone,
Homopolymers such as cellulose acetate, cellulose 21-cellulose, ethylcellulose, polyacrylonitrile, polypropylene, polyvinyl chloride, or blends of these polymers are usually used, but are not particularly limited thereto. The porous support is not limited to the above-mentioned flat membrane, and porous hollow fibers can also be used.

Examples of the solvent used in preparing the thin film of the styrene polymer having siloxane bonds in the side chain of the present invention include methylene chloride, tetrachloroethane, chloroform, dichloroethane, chlorobenzene, and dichlorobenzene. Chlorinated hydrocarbons, trifluoromonochloromethane,
fluorinated hydrocarbons, such as trifluorotrichloroethane,
Preferred examples include hydrocarbons such as bempine, toluene, xylene, and cyclohexane, and cyclic ether compounds such as detrahydrofuran and dioxane, singly or in mixtures.

(Effects of the Invention) In the present invention, by using a selectively permeable membrane composed of a polymer mainly composed of styrene having a short siloquinone chain having 1 to 10 silicon atoms on the pendant 1- This makes it possible to achieve both oxygen gas permeability and separation coefficient, which was difficult to achieve using conventional techniques.

EXAMPLES The present invention will be specifically explained below using Examples.

Example 1 Magnesium powder 9゜70 in a 300ml Mitsuro flask
Then, a solution of 31% ethyl bromide dissolved in 5% and 1% anhydrous tetrahydrofuran is added to activate the magnesium. To this mixture, 27% p-chlorostyrene is added.
A solution of 6 (7) dissolved in anhydrous tetrahydrofuran was gradually added dropwise over 40 minutes.

After the addition was complete, the reaction mixture was heated to reflux for 15 minutes, followed by 4
Stir for 45 minutes at 0°C.

1°1.
1.3.3-Pentamethyl-3-chloro-disiloxane and 100 ml of anhydrous tetrahydrofuran are charged, and while keeping the internal temperature at 65°C, the Grignard reagent from p-chlorostyrene synthesized earlier is gradually added dropwise. After the dropwise addition was completed, stirring was continued at 65° C. for another 2 hours. The reaction mixture is decomposed by pouring it into an ice/water mixture containing a small amount of ammonium chloride. Neutralize the ether layer, wash with water, Iil! Dry over magnesium chloride. After distilling off the ether, rectification was performed under reduced pressure to obtain a styrene monomer containing a siloxane bond shown below. Yield: 27.1g
The boiling point was 67-72°C and 10.18 g.

10 g of the above monomer, 10 ml of anhydrous toluene, and 10 mg of azobisisobutyronitrile were placed in a Pyrex glass polymerization ampoule, and after purging with nitrogen, the mixture was frozen and degassed for 2 hours.
Repeated times. Polymerization was carried out at 80° C. for 10 hours in a nitrogen stream. After the polymerization was completed, the contents of the ampoule were diluted with 151 ml of toluene and poured into 500 ml of methanol to precipitate the polymer.

The recovered polymer was purified by dry contact and reprecipitation in a benzene-methanol system. Film cast from a cyclohexane solution of polymer (thickness: 48 μm)
), the permeability of oxygen gas and nitrogen gas was evaluated by gas chromatography, and the permeability coefficient of oxygen gas was 7.5X10= aK (STP) ・C11110
(-sec -c+n1-to, the permeability coefficient of nitrogen gas is 2.61X10-9cJ (STP) cm/a+f
-sec -Cl111-1(+, separation coefficient is 2.8
It was 7.

Example 2 0.5C1 of the siloxane-bonded metal-bearing tyrene polymer synthesized in Example 1 was uniformly dissolved in 50 ml of cyclohexane, and then 51 of tetrahydrofuran was added. A part of this polymer solution was cast on the free water surface and the solvent was volatilized at air temperature to obtain a thin film with an area of 48°.
025μ) to obtain a composite membrane. As a result of electron microscopy observation of an ultrathin section of this composite membrane, the thickness of the functional membrane was 1,550 mm. A sample piece with a diameter of 30 mm was cut out from this composite membrane and fixed in a permeation cell. 100 ml/1 liter of air at 1 atm was supplied to the primary side of the cell, and the secondary side of the cell was brought to 0.1 atm using a diaphragm vacuum pump. Upon evacuation, oxygen-enriched air with an oxygen temperature of 31% was obtained at a flow rate of 6.51/i+in (measured at 25° C.).

Example 3 1, 1. used in Example 1. 51.70 instead of 1.3.3-pentamethyl-3-chlorodisiloxane
A Grignard coupling reaction was carried out using dimethyldichlorosilane, and after the reaction was completed, the reaction mixture was extracted with ether. The ether solution was concentrated under reduced pressure and rectified under reduced pressure to obtain p-donylphenyldimethylchlorosilane. The peak is 21Q
1 boiling point is 61-b. Lithium 1-dimethylsilate and hexamethylcyclotrisilyloxyline were reacted at a molar ratio of 1:2 in anhydrous tetrahydrofuran under an argon atmosphere at ambient temperature for 18 hours.
Subsequently, an equimolar amount of p-vinylphenyldimethylchlorosilane and lithium trimethylsilate was added to the reaction mixture. The reaction mixture was purified by column chromatography to obtain the styrene derivative shown below.

The purity of the product was confirmed by liquid chromatography, and the structure was confirmed by I HNMR spectrum.

1,000 Q. of sutra in a Pyrex glass polymerization ampoule
, the above monomer 9. Ocr, 10ml anhydrous toluene, 8
111 (l) of azobisisobutyronitrile was charged, polymerization was carried out under the same conditions as in Example 1, and the polymer was isolated. A cast film (thickness: 42 μm) was prepared from a cyclohexane solution of the polymer. The permeability of oxygen gas and nitrogen gas was evaluated under the same conditions.The permeability coefficients of oxygen gas and nitrogen gas were 1.2X10-8cff, respectively.
l (STP)・cmlal-sac-ctnHo
,4. lx 10-9o+t (STP) ・cr
a/al-sea-cml-1g, separation factor is 2.
It was 92.

Comparative Example The reaction was carried out under the same conditions as in Example 3 except that the molar ratio of lithium trimethylsilate and hexamethylcyclotrisiloxane was 1:4, and a styrene derivative represented by the following structural formula was prepared. Synthesized.

The above monomer 109.101 was charged with anhydrous toluene, 2 m (l) of azobisisobutyronitrile, and polymerization was carried out under the same conditions as in Example 1, and the polymer was isolated. Polystyrene determined by gel permeation chromatography The converted weight average molecular weight was 1°21×105.The polymer was a viscous waxy substance, and it was impossible to prepare a self-supporting film by casting.

Patent applicant Higashi Shikikai Co., Ltd.

Claims (3)

[Claims] (1) The main chain is polystyrene-based, and the side chain is S1
A permselective membrane comprising a polymer having a polyorganosiloxane group having 2 to 10 atoms. (2) The permselective membrane according to claim 1, wherein the number of polyorganosiloxane groups is 0.1 to 1.0 relative to the number of repeating units of the polystyrene polymer. (3) The main chain is polystyrene-based, and the side chain is Si
1. A composite membrane characterized in that a permselective membrane made of a polymer having a polyorganosiloxane group having 2 to 10 atoms is provided on the surface of a porous membrane having fine pores continuous in the thickness direction.