JPH0368731B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for separating water from an aqueous solution of an organic substance or a mixed organic substance/water vapor. More specifically, the present invention relates to a membrane for separating and concentrating an organic substance aqueous solution by pervaporation or a mixed organic substance/water vapor by vapor permeation. (Prior Art) Regarding the concentration and separation of organic substance aqueous solutions using membranes, reverse osmosis has been put into practical use for concentrating some low-concentration organic substance aqueous solutions. however,
Since reverse osmosis requires applying pressure to the liquid to be separated that is higher than the osmotic pressure of the separation liquid, it cannot be applied to highly concentrated aqueous solutions where the osmotic pressure is high, and there is a limit to the concentration of the solution that can be separated. There is. In contrast, pervaporation and vapor permeation methods are attracting attention as new separation methods that are not affected by osmotic pressure. Regarding the pervaporation method, many research examples have been reported so far. For example, regarding the separation of aqueous ethanol solutions, there are examples of cellulose acetate homogeneous membranes in US Pat. No. 2,953,502 and polyvinyl alcohol in US Pat. No. 3,035,060. (Object of the Invention) When separating an organic aqueous solution or vapor using a pervaporation method and a vapor permeation method, separation performance as well as heat resistance and solvent resistance of the membrane are extremely important. In this respect, cellulose polymer membranes such as polyvinyl alcohol and cellulose acetate cannot be said to be suitable for separating a wide range of organic substances. Therefore, an object of the present invention is to provide sufficient durability and heat resistance for various organic substances and a wide range of concentration ranges when separating organic substance aqueous solutions or mixed vapors of organic substances and water by pervaporation and vapor permeation methods. The objective is to obtain a separation membrane having a high permeation rate and separation coefficient. (Structure of the Invention) As a result of intensive study on the above points, the present invention was arrived at. That is, in the present invention, the repeating unit is The m/n ratio of the polyamide-imide film expressed by
It is a water selective permeation membrane with a ratio of 10/0 to 3/7. As a separation membrane that requires heat resistance and solvent resistance,
As a result of searching for membranes that selectively permeate water from water/organic mixtures, mainly using condensed aromatic polymers, we found that m
- It has been found that a polyamide-imide membrane obtained by reacting phenylene diamine and p-phenylene diamine with trimellitic anhydride has significantly superior separation performance compared to other general-purpose heat-resistant polymer membranes. The present invention will be explained in more detail below. The polyamideimide in the present invention has the general formula: It is composed of repeating units represented by m:n=
A ratio of 10:0 to 3:7 (molar ratio) is suitable. When m/n is less than 3/7 (molar ratio), the water permeation rate becomes slow, which is not preferable. The method for producing the aromatic polyamideimide is not particularly limited, but for example, aromatic diamines such as m-phenylene diamine and p-phenylene diamine and trimellitic anhydride chloride are mixed with N-
Methylpyrrolidone, pyridine, N,N-dimethylacetamide, N,N-dimethylformamide,
It can be easily obtained by dissolving approximately equimolar amounts in an organic polar solvent such as dimethyl sulfoxide, polymerizing at around room temperature to obtain polyamic acid, which is a precursor of polyamide-imide, and imidizing this. The imidization reaction is carried out at 10 to 150°C in the presence of a tertiary amine compound such as trimethylamine, triethylamine, or pyridine, or an imidization promoter such as acetic anhydride before and after film formation, or
This can be carried out by heating the polyamic acid to 100 to 300°C, preferably 150 to 250°C, without adding an imidization promoter. The method for producing the permselective membrane of the present invention is not particularly limited, but any of flat membranes, tube membranes, hollow fiber membranes, uniform membranes, non-uniform membranes, etc. can be used using conventionally known techniques. Flat membranes can be laminated as they are, or they can be formed into pleats or spirals to form modules. Furthermore, by coating the composite membrane on a porous support, the membrane thickness can be reduced to about 0.1 μm. The membrane prepared in this manner can be used to prepare water/organic mixtures such as organic acids such as formic acid, acetic acid, propionic acid, butyric acid, alcohols such as methanol, ethanol, 1-propanol, 2-propanol, n-butanol, acetone, methyl ethyl ketone, etc. Separation of aqueous solutions or vapor mixtures with water containing one or more compounds from the group of ketones such as, ethers such as tetrahydrofuran and dioxane, aldehydes, aldehydes such as propionaldehyde, and amines such as pyridine and picoline. used for. (Effects of the Invention) The polyamide-imide membrane of the present invention has higher permeation rate and separation coefficient for separating water/organic mixtures than general-purpose heat-resistant polymers, and also has excellent solvent resistance and heat resistance. It is excellent and extremely effective for practical application of membrane separation processes. (Example) The present invention will be described in more detail with reference to Examples below. Example 1 0.02 mol of m-phenylenediamine and 2.8 ml of triethylamine are dissolved in 50 ml of dimethylacetamide, and while cooling externally with ice water, 0.02 mol of solid trimellitic anhydride chloride is added at once and stirring is continued. After 5 minutes, the cooling bath was removed and stirring was continued for 3 hours at room temperature to obtain a precursor polyamic acid. For film formation, the dope was separated, cast on a glass plate, dried at 100°C for 1 hour, peeled off from the glass plate, and vacuum-dried at 200°C for 6 hours to obtain a uniform polyamide-imide film. Table 1 shows the separation performance by the pervaporation method at 70°C using 80% acetic acid as the feed liquid. Comparative Example 1 The same polyamide-imide membrane as in Example except that m-phenylenediamine was p-phenylenediamine. The obtained separation performance is shown in Table 1. Comparative Example 2 300ml of m-phenylenediamine (0.02mol)
Add 60% dimethylacetamide to the reaction flask.
Dissolve in ml. After cooling this on ice, isophthaloyl chloride (0.015 mol) and terephthaloyl chloride (0.005 mol)
mol) was dissolved in 20 ml of chloroform and added all at once with good stirring. Stirring was continued for another 2 hours to obtain polyamide. Film formation was carried out in the same manner as in the examples. Separation performance is shown in Table 1. Comparative Example 3 A polyamide membrane was obtained which was the same as that of Comparative Example except that m-phenylenediamine was diaminodiphenyl ether. Separation performance is shown in Table 1. Comparative Example 4 A 300 ml three-necked flask is brought to an anhydrous state, and while nitrogen is being passed through the flask, diaminodiphenyl ether (0.03 mol) is placed in the flask, and 60 ml of dry dimethylacetamide is added thereto to dissolve it. While stirring this solution vigorously, add pyromellitic anhydride (0.03
mol) at once. When the acid anhydride is added, the internal temperature rises to around 40℃, but it quickly returns to room temperature. The reaction is continued for about 3 hours at room temperature to obtain polyamic acid, which is a precursor of polyimide. Film formation was carried out in the same manner as in Example 1. Separation performance is shown in Table 1. Comparative Example 5 Diaminodiphenyl ether (0.02 mol) is dissolved in 60 ml of dry dimethylacetamide and methylene bis(4-phenyl isocyanate) (0.02 mol) is added in one portion while stirring the solution vigorously. The reaction is continued for about 3 hours at room temperature to obtain polyurea. Film formation was carried out in the same manner as in Example 1. Separation performance is shown in Table 1. 【table】

Claims (1)

[Claims] 1. The repeating unit is The m/n ratio of the polyamide-imide film expressed by
A selectively permeable water membrane with a rating of 10/0 to 3/7. 2. The membrane according to claim 1, wherein the membrane is a separation membrane for pervaporation and vapor permeation.