JPH0214088B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF APPLICATION The present invention relates to a novel selectively permeable membrane for gas separation made of a polyurea-based polymer containing silicon in its main chain. Prior Art Various membranes have been proposed for use in separating oxygen and nitrogen in the atmosphere, that is, oxygen enrichment membranes, but among them, the one with the largest oxygen permeability coefficient is 6×10 ^{- 8} cc(STP)・cm/cm ²・sec・cm
It is silicone rubber that is Hg. However, silicone rubber has a low separation coefficient (oxygen permeation rate/nitrogen permeation rate) α of 2.0, and it is difficult to form a thin film. Therefore, it was proposed to produce a thin film of 0.1 μm or less by spreading a solution of polysiloxane-polycarbonate copolymer, which is a block copolymerization of polysiloxane and polycarbonate, on the water surface (Japanese Patent Laid-Open No. 51-89564). (see publication). However, the permeability coefficient of this membrane is 2×10 ^-8 cc (STP)・cm/cm ²・
sec・cmHg, which is lower than that of silicone rubber, and the separation coefficient (α) is also low, which is 2.2. Recently, a membrane has been proposed that has a separation coefficient (α) of 3 or more and can be formed into a thin film of 1.0 μm or less by crosslinking amino-modified silicone oil with acid chloride or the like (see JP-A-57-105203). ).
However, this membrane also had a relatively small separation coefficient (α) and insufficient permeation performance. OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a membrane with a high separation coefficient (α) and an excellent oxygen permeability coefficient. Structure of the invention The present invention is based on the following general formula (A) [However, in the formula, R ₁ and R ₂ are the same or different,
is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms; R ₃ , R ₄ , R ₅ and R ₆ are the same or different hydrocarbon groups having 1 to 10 carbon atoms; R ₀ is a different atom; Aromatic hydrocarbon group having a total number of carbon atoms of 6 to 14 or carbon atoms of 2 to 10, which may be bonded
is an alkylene group; p and q are the same or different and represent an integer of 2 to 10; ] A selectively permeable membrane for gas separation formed from a polymer consisting essentially of polyurea obtained by the reaction of a diamine represented by the above with a compound having at least two isocyanate groups, and a microporous support membrane for the above reaction. This is a method for producing a selectively permeable membrane for gas separation. Here, p and q in formula (A) may be the same or different, and are integers of 2 to 10, preferably 3 to 8.
is an integer. When p and q are 1, the raw material monomers are unstable and it is difficult to obtain a good polymer, and when p and q are 11 or more, the film forming property becomes poor, which is not preferable. Furthermore, R ₁ and R ₂ in formula (A) are each independently a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms, preferably a hydrogen atom or a methyl group. Further, R ₃ , R ₄ , R ₅ and R ₆ may be the same or different and are hydrocarbon groups having 1 to 10 carbon atoms. The hydrocarbon group means a substituted or unsubstituted, saturated or unsaturated aliphatic, alicyclic or aromatic hydrocarbon group, and preferred examples include a methyl group, an ethyl group, various propyl groups, and various butyl groups. , a vinyl group, an allyl group, a propenyl group, a phenyl group, a benzyl group, and other hydrocarbon groups having 1 to 7 carbon atoms, and particularly preferably an alkyl group having 1 or 2 carbon atoms and a phenyl group. R ₀ in formula (A) is an aromatic hydrocarbon group having 6 to 14 carbon atoms in total or an alkylene group having 2 to 10 carbon atoms, which may be bonded through different atoms, preferably bonded through different atoms. It is an aromatic hydrocarbon group having 6 to 12 carbon atoms in total or an alkylene group having 2 to 6 carbon atoms, which may be Total number of carbon atoms is 14
If it is more than that, the permeability decreases, which is not preferable. As a preferable example,

【formula】

【formula】

[Formula] (X is -SO ₂ -,

[Formula] -O-, -CH ₂ -),

[Formula] (-CH ₂ )- _o (n is 2 to 5). Especially preferably

[Formula] - CH ₂ CH ₂ -. In the present invention, other diamine components can be copolymerized together with the diamine component represented by the general formula (A). Such diamines include aliphatic diamines having 2 to 12 carbon atoms, preferably 6 to 10 carbon atoms, alicyclic diamines having 6 to 13 carbon atoms, aromatic diamines having 6 to 13 carbon atoms, and polysiloxane-containing diamines. Preference is given to using diamines. Specific examples of these include aliphatic diamines such as ethylene diamine, tetramethylene diamine, hexamethylene diamine, and decamethylene diamine; alicyclic diamines such as cyclohexane diamine, 4,4'-diaminodicyclohexylmethane, and piperazine; and metaphenylene. Diamine, paraphenylene diamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminophenyl ether,
3,4'-diaminodiphenyl ether, N,N'-
Diphenyl metaphenylene diamine, N, N'-
Examples include aromatic diamines such as dimethyl metaphenylene diamine; polysiloxane-containing diamines such as bis(aminopropyl)tetramethyldisiloxane and bis(aminopropyl)octamethyltetrasiloxane. These can be used alone or in combination of two or more. The diisocyanate used in the present invention is not particularly limited, but preferably has 4 to 4 carbon atoms.
15, particularly preferably 6 to 13 diisocyanates, specific examples include aromatic diisocyanates such as toluylene diisocyanate, phenyl diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate. Aliphatic diisocyanate, cyclohexyl diisocyanate,
Alicyclic diisocyanates such as isophorone diisocyanate can be mentioned. These can be used singly or in a mixture of two or more. Further, a portion of a trifunctional or higher functional isocyanate may be mixed together with the diisocyanate. In order to form the membrane of the present invention from the diisocyanate component and diamine component, for example, both may be polymerized on a microporous support to form a thin film of polyurea on the support. However, a preferred method is to coat a solution of the diamine component on the microporous support membrane described below and advantageously react it with the diisocyanate component. This application method may be any method such as dipping method, roll coating method, wick coating method, spray coating method, etc., but the thickness of the applied diamine component layer is 0.01 to 2 μm, preferably 0.02 to 1 μm,
More preferably, the coating conditions should be controlled so that the thickness is 0.05 to 0.7 μm. If the coating thickness of the diamine layer is smaller than the above lower limit (ie, 0.01 μm), the active layer of the finally obtained composite membrane will be too thin and its mechanical strength will decrease. Furthermore, if the coating thickness is greater than 2 μm, the active layer becomes too thick and tends to impair the air permeability of the composite membrane. The diamine is preferably soluble, particularly in water, methanol, ethanol, isopropanol, methylcellosolve, dioxane ethylene glycol, diethylene glycol, triethylene glycol, glycerin, or a mixed solvent of two or more of these, preferably at least 0.1 g/100 ml. is 0.5g/
It is preferable that it is soluble in 100 ml or more. A solution of the diamine compound of the present invention dissolved in at least 0.1% in at least one solvent selected from these solvent groups is applied or impregnated onto a microporous membrane. As base materials for such membranes, glass porous materials, sintered metals, ceramics, cellulose esters, polystyrene, vinyl butyral, polysulfone,
Examples include organic polymers such as vinyl chloride. Polysulfone membranes have particularly excellent performance as substrates in the present invention, and polyvinyl chloride is also effective. The manufacturing method for polysulfone porous substrates is published in the U.S. Office of Salt Water Report (OSW Report)
It is also listed in No.359. Such substrates generally have a surface pore size of about 100
The surface pore size is preferably between ~1000 angstroms, but is not limited to this, depending on the final membrane application etc.
It can vary between 5000 Å. These substrates can be used in either symmetrical or asymmetrical structures, but asymmetrical structures are preferable. However, these base materials used have an air permeability of 20 to 3000 seconds, more preferably 50 to 1000 seconds, as measured by a JIS P8117 device. If the permeability is 20 seconds or less, the composite membrane obtained is likely to have defects and its selectivity may be reduced. Moreover, if the time is longer than 3000 seconds, only a composite membrane with a low air permeability can be obtained. Further, it is advantageous for the substrate (microporous membrane) to have a maximum pore size of 1 μ or less, preferably 0.5 μ or less. A polyurea thin film is formed on the substrate by bringing the substrate coated with the diamine described above into contact with a diisocyanate compound. The composite membrane of the present invention can be obtained by bringing the diamine described above into contact with a solution of the diisocyanate compound described above on the microporous membrane. The solvent used to dissolve the diisocyanate compound is one that is inert to the isocyanate and dissolves it, but does not substantially dissolve the diamine compound and the base material, and does not dissolve the formed polyurea. It is preferable to use one that hardly dissolves. Examples include hydrocarbon solvents such as n-hexane, n-heptane, n-octane, cyclohexane, n-nonane, n-decane, n-dodecane, and halogenated carbonaceous solvents such as carbon tetrachloride and trifluorotrichloroethylene. Examples include hydrogen solvents. Although the suitable concentration of the diisocyanate compound in the solvent may vary depending on the type of the compound, the solvent, the substrate, and other conditions, the optimum concentration can be determined by experiment. But generally about 0.1~5.0, preferably 0.5~
A sufficient effect can be exhibited at 3.0% by weight. Such interfacial reaction between the polyamine compound and the polyfunctional compound is carried out at room temperature to about 100°C, preferably at 20 to 50°C.
2 seconds to 10 minutes at a temperature of °C, preferably 10 seconds to
It can be done for 5 minutes. This interfacial reaction can be carried out so that it is mainly concentrated on the surface of the membrane. In this way, a composite membrane having a thin membrane of a polycondensate having permselectivity on the surface of a microporous substrate is obtained. The thickness of the permselective membrane in the membrane is not strictly defined, but can have a total thickness of at least 100 angstroms, usually from 300 to 4000 angstroms. The membrane of the present invention may be in any form such as a flat membrane or a hollow fiber, and the flat membrane may be a so-called plate-and-frame type module, a spiral type module, a tubular module, or in the case of hollow fibers, a hollow fiber type module having a membrane on the inside or outside of the fiber. , etc. can be put to practical use. Effects The selectively permeable membrane for gas separation of the present invention can be used, for example, in the following applications by utilizing its excellent gas permeability and selectivity, but is not necessarily limited thereto. For example, it can be incorporated into devices that produce oxygen-enriched air from air to improve the combustion efficiency of engines, heating equipment, etc., and can also be used as cleaner oxygen-enriched air, as nursery boxes for premature babies, and as treatment equipment for people with respiratory disorders. Alternatively, it can be used as an artificial lung or artificial gills. The present invention will be described below with reference to Examples, but the present invention is not limited thereto. In the examples, "parts" indicate parts by weight. Reference Example 1 Method for producing a nonwoven reinforced polysulfone porous membrane A densely woven Dacron nonwoven fabric (fabric weight 180 g/m ² ) was fixed on a glass plate. Next, a solution containing 12.5 wt% polysulfone, 12.5 wt% methylcellosolve, and the balance dimethylformamide is cast onto the nonwoven fabric in a layer having a thickness of about 0.2 μm, and the polysulfone layer is immediately gelled in a water bath at room temperature. As a result, a nonwoven reinforced porous polysulfone membrane was obtained. The porous polysulfone layer obtained in this way has a thickness of about 40 to 70μ, has an asymmetric structure, and has many micropores of about 50 to 600Å on the surface, as observed by electron micrographs. It was done. Furthermore, these porous substrates had an air permeability of 150 to 300 seconds using a JIS P8117 device. Example 1 1 part of bis(aminopropyldimethylsilyl)benzene was dissolved in a mixed solution of 49.5 parts of water and 49.5 parts of ethanol. After immersing the polysulfone microporous membrane obtained in Reference Example 1 in this solution for 5 minutes, the membrane was pulled out of the solution, held vertically, and drained for 10 minutes at room temperature. The thus drained membrane was drained in 4,
The sample was immersed in 100 ml of a 1% by weight solution of 4'-diphenylmethane diisocyanate in n-hexane for 3 minutes, and then air-dried at room temperature for 1 day. Table 1 shows the results of measuring the gas permeability of this membrane using a Seikaken type gas permeability meter manufactured by Rika Seiki Kogyo Co., Ltd. Example 2 0.5 part of bis(aminopropyldimethylsilyl)benzene was dissolved in a mixed solution of 50 parts of water and 50 parts of ethanol. After immersing the porous membrane in this solution and draining it in the same manner as in Example 1, 100 ml of a 0.5% by weight hexadecane-1 solution of isophorone diisocyanate was added.
After being immersed in the solution for 3 minutes, the sample was further immersed in an n-hexane solution for 30 seconds, taken out, and air-dried. The performance of this membrane is shown in Table 1. Example 3 A membrane was obtained in exactly the same manner as in Example 2 except that hexamethylene diisocyanate was used instead of isophorone diisocyanate. The performance of this membrane is shown in Table 1.

【table】

Claims (1)

[Claims] 1 The following general formula (A) [However, in the formula, R ₁ and R ₂ are the same or different,
is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms; R ₃ , R ₄ , R ₅ and R ₆ are the same or different hydrocarbon groups having 1 to 10 carbon atoms; R ₀ is a different atom; Aromatic hydrocarbon group having a total number of carbon atoms of 6 to 14 or carbon atoms of 2 to 10, which may be bonded
is an alkylene group; p and q are the same or different and represent an integer of 2 to 10; ] A selectively permeable membrane for gas separation formed from a polymer consisting essentially of polyurea obtained by reacting a diamine represented by the following with a compound having at least two isocyanate groups. 2 General formula (A) below [However, in the formula, R ₁ and R ₂ are the same or different,
is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms; R ₃ , R ₄ , R ₅ and R ₆ are the same or different hydrocarbon groups having 1 to 10 carbon atoms; R ₀ is a different atom; An optionally bonded aromatic hydrocarbon group having a total number of carbon atoms of 6 to 14 or a number of carbon atoms of 2 to 10
is an alkylene group; p and q are the same or different and represent an integer of 2 to 10; ] A diamine component represented by the above and a compound having at least two isocyanate groups are polymerized on a microporous support membrane to form a polyurea membrane consisting essentially of polyurea on the support. A method for producing a selectively permeable membrane for gas separation.