JPH041655B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a selectively permeable membrane for liquid or gaseous mixtures, and particularly relates to an oxygen membrane made of a styrene polymer having a silmethylene bond in its side chain, which is particularly effective for obtaining oxygen-enriched air from air. This relates to enriched membranes. Normal combustion systems (for example, boilers) use air in addition to 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 the amount of combustion gas and a reduction in the amount of combustion exhaust gas, which is expected to be effective in terms of 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: Separation coefficient = Oxygen gas permeability coefficient Po ₂ / Nitrogen gas permeability coefficient P _N2 (Hereinafter, unless otherwise specified,
The values of Po ₂ and P _N2 are the values when the film thickness is converted to 1 cm, and the unit is cm ³ (STP)・cm/cm ²・sec・cm
A polymer membrane with high Hg) and high oxygen permeability coefficient _Po2 is desirable. Furthermore, in actual membrane separation systems, in order to increase the oxygen permeation rate, ultra-thin membranes or composite membranes (ultra-thin membranes made of materials with excellent oxygen separation performance and laminated on a porous support to provide strength) are used. ) is used. Therefore, in addition to the above-mentioned 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 will not rupture due to pressure differences. It is necessary to have sufficient film strength to prevent this from occurring. (Prior Art) As a material for an oxygen enrichment membrane, a polymer having a structure in which polysiloxane segments with excellent gas permeability are reinforced with hard segments has been proposed.
One example is a polydimethylsiloxane-polycarbonate block copolymer, or a crosslinked copolymer obtained from a styrene polymer having an aromatic ring in the side chain and an α,ω-2 functional polysiloxane (Japanese Patent Application Laid-open No. 56-26506). However, the permeability coefficient of oxygen gas in the above membrane is 2×
10 ^-8 cm ² (STP)・cm/cm ²・sec・cmHg, which is on the same order as silicone rubber membranes, and is significantly improved compared to silicone rubber membranes in terms of thin film formability and film strength in the thin film state. However, it cannot be said that it is unsatisfactory because the separation coefficient is at a low level of 2.0 to 2.1. Therefore, when an oxygen enrichment system is assembled using these membrane materials, it becomes impractical because the driving energy of the vacuum pump required to obtain oxygen enriched air increases. As described above, it has been extremely difficult to create a membrane material with excellent oxygen permeability and separation coefficient using conventional techniques. (Objective of the present invention) An object of the present invention is to provide an oxygen-enriching membrane made of a styrene polymer having silmethylene bonds in its side chains, which is excellent in both oxygen permeability coefficient and separation coefficient. . (Structure of the present invention) In the present invention, the repeating unit mainly has the general formula

【formula】

[Formula] (where n is an integer of 2 or more, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are alkyl groups having 1 to 10 carbon atoms, substituted alkyl groups, phenyl groups, substituted phenyl groups) ,
i and j expressed as mole fractions are 0≦i(i+j)
The present invention relates to a selectively permeable membrane characterized by a relationship of ≦0.9 and a composite membrane characterized in that this membrane is provided on the surface of a porous membrane having fine pores continuous in the thickness direction. The composition ratio i/(i+j) in the sylmethylene 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 through the membrane will decrease, which is undesirable. More preferably, it is 0.5 or less, and the closer it is to 0, the more oxygen gas permeability is improved, which is preferable. The siloxane chain length n in the silmethylene bond-containing styrene polymer of the present invention is preferably 2 or more, more preferably 3 to 10. n is 20
If it exceeds 100%, the mechanical strength (breaking strength, Young's modulus) of the film tends to decrease, and the formability of the ultra-thin film tends to deteriorate. The sylmethylene bond-containing styrene polymer of the present invention can be synthesized by the following route. (1) Silmethylene oligomer with a Si-halogen bond at one end

Synthesis of [Formula]: The following compound () corresponding to R=CH ₃ , n=1 is It can be synthesized by Grignard coupling of chloromethyldimethylchlorosilane and trimethylchlorosilane according to the reaction formula below. The following compound () corresponding to R=CH ₃ and n=2 is: It can be synthesized according to the reaction formula below. (CH ₃ ) ₃ SiCH ₂ Cl＋Mg→(CH ₃ ) ₃ S
iCH ₂ MgCl……() Oligomers with n≧3 can be synthesized by Grignard coupling reaction using () or a similar compound thereof as a starting material. In addition to the above method of increasing the degree of polymerization sequentially, synthesis can also be performed by the following method. This method is suitable for synthesizing oligomers with a relatively high degree of polymerization. (2) Synthesis of styrene monomer containing a sylmethylene bond It can be synthesized by Grignard coupling reaction between p-chlorostyrene (or p-bromostyrene) and the above-mentioned sylmethylene oligomer having a Si-Cl bond at one end. . R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ each have 1 to 1 carbon atoms.
10 alkyl groups, phenyl groups, nuclear-substituted phenyl groups, and substituted alkyl groups are preferred, and specific examples thereof include substituents having the following structures, but are not limited to these. i.e. methyl, ethyl, n-propyl, i-
Propyl, n-butyl, sec-butyl, tert-
Alkyl groups such as butyl, hexyl, octyl, cyclohexyl, and cyclohexenyl groups. Nuclear substituted phenyl groups such as phenyl group, 4-methylphenyl group, 4-nitrophenyl group, 4-chlorophenyl group, 4-methoxyphenyl group. Chlormethyl group, chloropropyl group, mercaptopropyl group, cyanoethyl group, benzyl group, trichloropropyl group, methoxyethyl group, nitropropyl group, 2(carbomethoxy)ethyl group,
Substituted alkyl group such as dichloromethyl group. A composite membrane for oxygen enrichment using the polymer of the present invention can be produced 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 of laminating a thin polymer film obtained by casting a polymer and a dilute solution onto a water surface and evaporating the solvent on a porous support, or a method of coating. The thickness of the membrane is preferably larger than the pore diameter of the surface of the porous support, and is usually 0.005~
10μ, more 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 support with a structure such that The microporous support described above may be selected from a variety of commercially available filter materials, such as Millipore Filter (VSWP), but is typically manufactured by the Office of Water Research and Development Progress. It is manufactured according to the method described in "Report" No. 359 (1968).The materials include polysulfone, cellulose acetate, nitrocellulose, ethylcellulose,
Homopolymers such as polyacrylonitrile, polypropylene, polyvinyl chloride, or blends of these polymers are commonly used, but are not particularly limited thereto. The porous support is not limited to the above-mentioned flat membrane,
Porous hollow fibers can be used. The solvent used in preparing the thin film of the styrene polymer having silmethylene bonds in the side chain of the present invention includes chlorinated solvents such as methylene chloride, tetrachloroethane, chloroform, dichloroethane, chlorobenzene, and dichlorobenzene. Preferred examples include hydrocarbons, fluorinated hydrocarbons such as trifluoromonochloromethane and trifluorotrichloroethane, hydrocarbons such as benzene, tomeene, xylene, and cyclohexane, and cyclic ether compounds such as tetrahydrofuran and dioxane, alone or in mixtures. I can do it. (Effects of the present invention) In the present invention, by using a selectively permeable membrane composed of a polymer mainly composed of styrene having pendant short diorganosylmethylene chains having 1 to 20 silicon atoms, the present invention can overcome the conventional technology. This made it possible to achieve both oxygen gas permeability and separation coefficient, which was difficult to achieve in the above range. The present invention will be specifically explained below using Examples. Example 1 9.7 g of magnesium powder is placed in a 300 ml three-necked flask, and then a solution of 3 ml of ethyl bromide dissolved in 5 ml of anhydrous tetrahydrofuran is added to activate the magnesium. A solution of 27.6 g of p-chlorostyrene dissolved in 160 ml of anhydrous tetrahydrofuran was gradually added dropwise to this mixture over a period of 40 minutes. After the addition was completed, the reaction mixture was heated to reflux for 15 minutes.
Subsequently, stir at 40°C for 45 minutes. 42.1g of 1,1,1, in a 500ml three-necked flask
Prepare 3,3-pentamethyl-3-chloro-disylmethylene and 100 ml of anhydrous tetrahydrofuran.
While maintaining the internal temperature at 65°C, the Grignard reagent from p-chlorostyrene synthesized earlier was gradually added dropwise. After the dropwise addition was completed, stirring was continued at 65°C for an additional 2 hours. The reaction mixture is decomposed by pouring it into an ice/water mixture containing a small amount of ammonium chloride. The ether layer is neutralized, washed with water and dried over magnesium sulfate. After distilling off the ether, rectification was performed under reduced pressure to obtain a styrene monomer containing a siloxane bond shown below. Yield: 25.5g, boiling point:
The temperature was 71.5-73.0°C/0.12mmHg. A polymerization ampoule made of Pyrex glass was charged with 10 g of the above monomer, 10 ml of anhydrous toluene, and 10 mg of azobisisobutyronitrile, and after purging with nitrogen, freezing-degassing was repeated twice. Polymerization was carried out in a nitrogen stream at 80
It was carried out for 10 hours at ℃. After polymerization, the contents of the ampoule are
It was diluted with 15 ml of toluene and poured into 500 ml of methanol to precipitate the polymer. The recovered polymer was dried and purified by reprecipitation using a benzene-methanol system. When the permeability of oxygen gas and nitrogen gas was evaluated using gas chromatography for a film cast from a cyclohexane solution of the polymer (thickness: 42μ), the permeability coefficient for oxygen gas was 3.1×10 ^-9 cm ³ (STP) cm /cm ²・sec・cm
The permeability coefficient of Hg and nitrogen gas is 9.7×10 ¹⁰ cm ³
(STP)・cm/cm ²・sec・cmHg, and the separation coefficient was 3.20. Example 2 0.5 g of the silmethylene bond-containing styrene polymer synthesized in Example 1 was uniformly dissolved in 50 ml of cyclohexane, and then 5 ml of tetrahydrofuran was added. Pour this polymer solution onto the free water surface.
A thin film with an area of 48 cm ² was obtained by casting 0.1 ml and volatilizing the solvent at room temperature. This thin film was laminated on a Millipore filter VSWP (average pore size 0.025μ) to obtain a composite film. As a result of electron microscopy observation of an ultrathin section of this composite membrane, the thickness of the functional membrane was 1450 mm. A sample piece of 30 mmφ was cut from this composite membrane, and air at 1 atm was supplied at 100 ml/min to the primary side of the cell fixed in a permeation cell, and the secondary side of the cell was evacuated to 0.1 atm using a diaphragm type vacuum pump. , oxygen enriched air with an oxygen concentration of 44% is 2.7
obtained at a flow rate of ml/min (measured at 25°C). Example 3 Styrene in Pyrex glass polymerization ampoule
1.0 g, 8.0 g of styrene monomer containing the following silmethylene bond, 10 ml of anhydrous toluene, Prepare 8 mg of azobisisobutyronitrile,
Polymerization was carried out under the same conditions as in Example 1, and the polymer was isolated. A cast film (thickness: 51 μm) was prepared from a cyclohexane solution of the polymer, and its permeability to oxygen gas and nitrogen gas was evaluated under the same conditions as in Example 1. The permeability coefficients of oxygen gas and nitrogen gas are 1.7×10 ^-8 cm ³ (STP)・cm/cm ²・sec・
cmHg, 5.6×10 ^-9 cm ² (STP)・cm/cm ²・sec・cm
Hg, separation coefficient was 3.03.

Claims (1)

[Scope of Claims] 1 The repeating unit mainly has the general formula [Formula] [Formula] (where n is an integer of 2 or more, and R ₁ , R ₂ , R ₃ , R ₄ and R ₅ have 1 to 10 carbon atoms) alkyl group, substituted alkyl group, phenyl group, substituted phenyl group),
i and j expressed as mole fractions are 0≦i/(i+
j) A selectively permeable membrane characterized by a relationship of ≦0.9. 2 The repeating units are mainly [Formula] [Formula] (where n is an integer of 2 or more, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are alkyl groups having 1 to 10 carbon atoms, substituted alkyl groups, phenyl group, substituted phenyl group),
i and j expressed as mole fractions are 0≦i/(i+
j) A composite membrane characterized in that a permselective membrane having a relationship of ≦0.9 is provided on the surface of a porous membrane having fine pores continuous in the thickness direction.