JPH0314493B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a novel copolymer membrane having good selective permeability. More specifically, the present invention relates to a copolymer film mainly obtained from methacryloxy-modified polysiloxane and a vinyl compound having a hydrophobic group. (Prior Art) Recently, membrane separation methods using selectively permeable membranes have been desired in various fields. One is a membrane separation method that replaces the distillation method, which is a means of purifying liquid-liquid mixtures. In the distillation method, it is extremely difficult to separate azeotropic mixtures, near-boiling point mixtures, thermally decomposable compounds, etc.
It has been suggested that these separations are possible by membrane separation using polymer membranes. Mehta (Journal of membrane science, 12 , 1~
26 (1982) states that the membrane separation method is more cost-effective than the distillation method in the separation of aqueous alcohol solutions. The membrane separation method for liquids is not only advantageous for purifying substances that are difficult to separate by conventional distillation, but is also advantageous for energy saving since there is no need to heat the separation target to its boiling point. Another promising method is membrane separation as a means of enriching and separating specific gases from gas mixtures. for example,
These include the production of oxygen-enriched air for combustion and medical applications, the separation or recovery of helium from natural gas and other sources, and the separation of hydrogen from mixed gases in the field of _C1 chemistry. Many attempts have already been made to perform liquid-liquid separation and gas separation using polymer membranes. Kimura (Membrane, 8(3), 177 (1983)), Japanese Patent Application Laid-open No. 56-26504, describes Si(CH ₃ ) ₂ as a membrane for selectively separating alcohol from an aqueous alcohol solution.
A polydimethylsiloxane film consisting of -O- units has been proposed, and a similar polydimethylsiloxane film has been proposed as a film for enriching oxygen in air. However, since it is difficult to make the above-mentioned polydimethylsiloxane film thin, a new polymer film that can be thinned has been proposed as an alternative. For example, in JP-A-47-51715, a film using CH ₂ =CH-CH ₂ -SiR ₁ R ₂ R ₃ as a starting material is proposed as an oxidation-enriched film. However, this membrane is relatively brittle and has the disadvantage of not being suitable for practical use. (Objective of the Invention) In order to solve these problems, the present inventors have conducted intensive research and found that a copolymer based on methacryloxy-modified polysiloxane has mechanical strength that can withstand continuous use as a liquid separation and gas separation membrane. The present invention was achieved by discovering that the material has good selective permeability to gas and liquid mixtures. (Structure of the invention) That is, the present invention provides a vinyl compound () represented by the following general formula (A). [However, in the formula, R ₁ is a hydrogen atom or a methyl group, X is a divalent alkylene group, l, m, and n are each 1, or one of l, m, and n is a non-zero integer and 2
is 0. ] It is a membrane composed of a copolymer mainly composed of alkyl methacrylate and/or alkyl acrylate (), and has mechanical strength as a liquid and gas separation membrane and good selective permeability to gas and liquid mixtures. It is something. Examples of monomers for the vinyl compound () include tris(trimethylsiloxy)silylpropyl methacrylate, tris(trimethylsiloxy)silylpentyl methacrylate, tris(trimethylsiloxy)silylpropyl acrylate, tris(trimethylsiloxy)silylpentyl acrylate, and the like. On the other hand, vinyl compounds () having a hydrophobic group that can be copolymerized with vinyl compounds () include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate,
sec-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-
Methacrylates such as ethyl-hexyl methacrylate, iso-decyl methacrylate, lauryl methacrylate, stearyl methacrylate; methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, sec-butyl acrylate , tert-butyl acrylate, n-hexyl acrylate,
Examples include acrylates such as lauryl acrylate and stearyl acrylate. In this system, it is also possible to use vinyl compounds such as 2-vinylpyridine, 4-vinylpyridine, and styrene, and divinyl compounds such as polydimethylsiloxydimethacrylate. These monomers can be used alone or in combination of two. Copolymerization can be carried out by changing the ratio of the vinyl compound (2) to the vinyl compound (2) in the methacryloxy-modified polysiloxane copolymer of the present invention over a wide range. In order to provide good liquid and gas separation properties, the vinyl compound():vinyl compound() ratio may be selected from the range of 10:90 to 99:1, preferably from the range of 50:50 to 95:5. desirable. If the vinyl compound () content is less than 10%, good separation characteristics cannot be obtained because the Si(CH ₃ ) ₂ content in the obtained copolymer is low. Furthermore, if the vinyl compound () is 100%, the resulting polymer is viscous and has drawbacks such as not being able to form a good film. The copolymer of the present invention can also be used in a blend with other polymers such as olefin polymers, diene polymers, vinyl polymers, alkyl methacrylate polymers, polyethers, polyesters, polyamides, and the like. In the novel copolymer of the present invention, the vinyl compound () and the vinyl compound () are combined together with a polymerization initiator such as azobisisobutyronitrile or benzoyl peroxide at 50-90°C, preferably at 60-80°C.
It can be produced by polymerization at a temperature of °C. When the polymerization temperature is lower than 50°C, the polymerization rate is slow and it is economically disadvantageous. On the other hand, temperatures exceeding 90°C are not preferred because the initiator efficiency tends to deteriorate. The copolymer membranes of the present invention exhibit high selectivity for various liquid and gas mixtures. especially,
It has the characteristic of selectively permeating organic liquid compounds from a water/organic liquid compound mixture and oxygen from a nitrogen/oxygen gas mixture. The copolymer of the present invention is soluble in various solvents such as chloroform, toluene, benzenetetrahydrofuran, etc., and is extremely useful as a membrane material. When the copolymer of the present invention is used as a separation membrane, the amount of permeation is inversely proportional to the thickness of the membrane, so it does not substantially impair its inherent permselectivity and has the strength to withstand continuous use as a separation membrane. In order to obtain a high amount of transmission, it is desirable that the film be as thin as possible. For example, the preferred film thickness is 0.01 to 300μ. Examples of the form of the membrane include hollow fiber membranes, flat membranes, asymmetric membranes, and composite membranes in which the copolymer is coated on a porous support, and the membrane thickness is selected depending on the form of use. (Effects of the Invention) The permeable membrane thus obtained has excellent mechanical strength and good selective permeability to gas and liquid mixtures. (Example) Examples of the present invention will be described below, but the present invention is not limited thereto. Pervaporation Experimental Method The following pervaporation experiment was conducted under atmospheric pressure on the supply side of the water/water-soluble organic compound mixture and under reduced pressure of 0.3 mmHg or less on the permeation side. With the active layer side of the membrane facing the supply side, the feed liquid was added onto the membrane surface and stirred at a constant temperature. The effective area of the membrane at this time is 15.2 cm ² . The water and organic compounds that permeated the membrane were condensed with liquid nitrogen and collected. N-propanol was added to the permeate as an internal standard, and the permeation amount and separation coefficient were determined by TCD-gas chromatography. The separation coefficient α ^Et0H _H2O of ethanol with respect to water is defined as follows. α ^Et0H _H2O = YEt ₀ H/YH ₂ O/XEt ₀ H/XH ₂ O However, in the above formula, XEt ₀ H, XH ₂ O are the weight percent of ethanol and water in the feed solution, and YEt ₀ H, YH ₂ O represents the weight percent of ethanol and water in the permeate. Example 1 Benzene in a 100c.c. Pyrex ampoule
50c.c., Azobisisobutyronitrile (AIBN)
2.4×10 ^-3 mol/benzene, tris(trimethylsiloxy)silylpropyl methacrylate (SiMA) and methyl methacrylate (MMA) were added at a ratio of 1:2 to give 1.2 mol/benzene, and after sufficient nitrogen substitution, the mixture was sealed. The polymerization reaction was carried out in an oil bath at 65°C. After 16 to 40 hours, the ampoule was taken out and opened under nitrogen, and the reaction solution was poured into methanol to obtain a copolymer. After drying the obtained polymer under vacuum at room temperature, it was dissolved in deuterated chloroform, and the SiMA content in the copolymer was determined by H'-NMR.
It was 24.5 mol%. Then the obtained polymer
A 50wt% toluene solution was cast on a Teflon plate with a thickness of 2 mm, and a uniform film (thickness: 24.5 μm) having flexibility and mechanical strength was obtained by evaporation of the solvent. Using this homogeneous membrane, pervaporative separation experiments of various alcohol aqueous solutions were carried out. The results are shown in Table 1. Example 2 In the same manner as in Example 1, polymerization was carried out at a molar ratio of SiMA/MMA of 2/1, and the resulting polymer was applied onto a porous polyvinylidene fluoride (PVDF) membrane to synthesize a composite membrane. Using this composite membrane, pervaporation experiments of various alcohol aqueous solutions were conducted in the same manner as in Example 1, and the results shown in Table 2 were obtained. At this time, the SiMA content was 44 mol %, and the thickness of the coating layer was 106 μm. Example 3 Example 2 with SiMA/MMA charging molar ratio 5/1
An experiment similar to that was conducted and the results shown in Table 3 were obtained. Incidentally, the SiMA content at this time was 76 mol %, and the thickness of the coating layer was 239 μm. Example 4 In the same manner as in Example 1, copolymerization of SiMA and n-butyl methacrylate (n-BuMA) (charged molar ratio SiMA/n-BuMA = 1/7) was performed to improve flexibility and mechanical strength. A uniform film was obtained. The SiMA content was 9.3 mol% and the thickness was 89μ. Using this membrane, pervaporation separation experiments of various alcohol aqueous solutions were conducted, and the results shown in Table 4 were obtained. Example 5 A uniform film having flexibility and mechanical strength was obtained in exactly the same manner as in Example 4 except that the molar ratio of SiMA/n-BuMA was set to 1/1. The thickness and SiMA content of the uniform film obtained at this time were 135 μ and 56.3 mol.
It was %. Using this membrane, pervaporation separation experiments of various alcohol aqueous solutions were conducted, and the results shown in Table 5 were obtained. Example 6 In the same manner as in Example 1, copolymerization of SiMA and 2-ethylhexyl methacrylate (EHMA) (charged molar ratio SiMA/EHMA = 1/2) was carried out to form a uniform film having flexibility and mechanical strength. I got it. The SiMA content of the film is 35 mol% and the thickness is
It was 102μ. A pervaporation separation experiment of a methanol aqueous solution was conducted using the membrane, and the results shown in Table 6 were obtained. Example 7 SiMA/EHMA copolymer (charged molar ratio
A composite membrane of SiMA/EHMA=1) was prepared in the same manner as in Example 2, and pervaporation separation experiments of various alcohol aqueous solutions were conducted. At this time, the content of SiMA was 54.6 mol%, and the thickness of the coating layer was 100 μm. The results obtained are shown in Table 7. Example 8 Using the uniform SiMA/n-BuMA copolymer film obtained in Example 5, the permeability coefficients of various gases were measured, and the following results were obtained.

[Table] Example 9 When the permeability coefficients of oxygen and nitrogen were determined using the SiMA/n-BuMA copolymer uniform film obtained in Example 4, the following results were obtained. PO ₂ = 0.65cm ³・cm/cm ²・sec・cmHg (30℃), PN ₂ = 0.25cm ³・cm/cm ²・sec・cmHg (30℃), PO ₂ /PN ₂ = 2.58

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Claims (1)

[Claims] 1. A vinyl compound () represented by the following general formula (A) [However, in the formula, R ₁ is a hydrogen atom or a methyl group, X is a divalent alkylene group, l, m, and n are each 1, or one of l, m, and n is a non-zero integer and 2
is 0. ] and a selectively permeable membrane composed of a copolymer mainly consisting of alkyl methacrylate and/or alkyl acrylate (). 2 Vinyl compound (), R ₁ is a methyl group, X
The selectively permeable membrane according to claim 1, wherein is a trimethylene group, and l, m, and n are each 1.