JPH0380049B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a semipermeable composite membrane for reverse osmosis that can be used for desalination of seawater and can water, recovery of valuables, reuse of wastewater, production of ultrapure water, etc. Relating to a manufacturing method. [Prior Art] Conventionally, semipermeable membranes that have been used industrially include asymmetric membranes made from cellulose acetate, such as the lobe type membrane described in U.S. Pat. No. 3,133,132 and U.S. Pat. There is a membrane of However, this membrane has problems with hydrolysis resistance, microbial resistance, chemical resistance, etc. In particular, when trying to improve permeability, it is not possible to manufacture a membrane that has both pressure resistance and durability, so it is not used in some cases. However, it has not yet been put to practical use in a wide range of applications. Research into new materials that eliminate the drawbacks of these asymmetric cellulose acetate membranes is being actively conducted mainly in the United States and Japan, but aromatic polyamides, polyamide hydrazide (US Pat. No. 3,567,632), polyamic acid (Japanese Patent Publication) 55-37282), crosslinked polyamic acid (Japanese Patent Publication No. 56-3769), polyimidazopyrrolone, polysulfonamide, polybenzimidazole, polybenzimidazolone, polyarylene oxide, etc. Materials that improve some of their drawbacks. is inferior to cellulose acetate membranes in terms of selective separation and permeability. On the other hand, a composite membrane has been developed, which is a semipermeable membrane different from the lobe type, in which a porous support membrane is coated with an ultra-thin membrane that exhibits substantial membrane performance. For composite membranes, it becomes possible to select the optimal materials for each application for the ultra-thin membrane and porous support membrane, increasing the degree of freedom in membrane manufacturing technology. It also has the advantage of being able to be stored in a dry state, unlike the lobe type, which must be kept constantly moist. Among such composite membranes, ultra-thin composite membranes made of polyamide or polyurea have high membrane performance, particularly water permeability, and have therefore become the mainstream in the development of semipermeable composite membranes. The method for manufacturing the composite membrane is described in U.S. Patent No.
Specification No. 3191815, Specification No. 3744642, Specification No.
Carbonization containing an aqueous solution containing a compound having an amino group and a polyfunctional reaction reagent on a porous support as disclosed in Specification No. 4039440, Specification No. 4277344, and Japanese Patent Application Publication No. 56-500062. There is a method of forming an ultra-thin film through interfacial reaction by bringing it into contact with a hydrogen-based solution. [Problems to be Solved by the Invention] The present inventors have studied how to improve the performance of such semipermeable composite membranes, and have found that acyl They discovered that the performance of the composite membrane, especially water permeability, was improved by using a chemical catalyst, and the present invention was achieved based on this discovery. [Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration. ``When manufacturing a semipermeable composite membrane having an ultra-thin membrane made of a crosslinked aromatic polyamide obtained by interfacial reaction with a porous support membrane, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, pyridine, dimethylaminopyridine, etc. A method for producing a semipermeable composite membrane, characterized in that an interfacial reaction is carried out using at least one acylation catalyst selected from Support membranes having micropores of 10 to several thousand angstroms and known materials made of polysulfone, polyvinyl chloride, chlorinated vinyl chloride, polycarbonate, polyacrylonitrile, cellulose ester, etc. are included. Among these, porous polysulfone support membranes are particularly effective in the present invention. Porous polysulfone films are produced by casting polysulfone as a solution in an aprotic polar solvent such as dimethylformamide onto a woven or nonwoven fabric made of polyester fibers, and then coagulating (gelling) in a medium consisting essentially of water. ), or by so-called wet film forming. The porous polysulfone thus obtained has micropores on the surface having a size of several tens to several thousand angstroms and increasing in size from the front surface to the back surface. In the present invention, the ultra-thin film obtained by interfacial reaction is mainly composed of a crosslinked aromatic polyamide, and the crosslinked aromatic polyamide contains an aromatic amine having two or more reactive amino groups, It can be obtained by interfacial reaction of polyfunctional aromatic acid halides. In the present invention, aromatic amines having two or more reactive amine groups (hereinafter abbreviated as amino compounds)
indicates an amino compound having two or more amino groups directly connected to an aromatic ring, such as metaphenylenediamine, paraphenylenediamine, 3,5-
Diaminobenzoic acid, 2,5-diaminobenzenesulfonic acid, 4,4'-diaminobenzanilide,
3,3',5,5'-tetraaminobenzanilide,
Examples include 1,3,5-triaminobenzene. These amino compounds are generally subjected to the interfacial reaction in the form of an aqueous solution, and the concentration of the amino compound in the aqueous amino compound solution is 0.1 to 10% by weight, preferably 0.5 to 5.0% by weight. Further, the amino compound aqueous solution may contain a surfactant, an organic solvent, etc. as long as they do not interfere with the reaction between the amino compound and the polyfunctional reaction reagent. The aqueous solution of the amino compound may be coated on the surface of the porous support membrane as long as the aqueous solution is uniformly and continuously coated on the surface. This may be carried out by a method such as immersing a porous support membrane in the aqueous solution. The polyfunctional aromatic acid halide in the present invention refers to a compound having two or more acyl halide groups directly connected to an aromatic ring (hereinafter referred to as a polyfunctional reaction reagent), such as trimesic acid chloride, benzophenonetetracarboxylic acid Examples include chloride, trimellitic acid chloride, pyromellitic acid chloride, isophthalic acid chloride, terephthalic acid chloride, naphthalenedicarboxylic acid chloride, diphenyldicarboxylic acid chloride, pyridinedicarboxylic acid chloride, benzenedisulfonic acid chloride, etc., but their solubility in the membrane forming solvent In consideration of the performance of the semipermeable composite membrane, trimesic acid chloride, isophthalic acid chloride, and terephthalic acid chloride are preferred. These polyfunctional reaction reagents are generally dissolved in a water-immiscible solvent and subjected to an interfacial reaction, and the solvent is inert to the amino compound and the polyfunctional reaction reagent and water It must be insoluble or poorly soluble in Furthermore, it is preferable that the solvent is inert to the porous support membrane. Typical examples of such solvents include liquid hydrocarbons and halogenated hydrocarbons, such as pentane, hexane, heptane, 1,1,2-trichloro-1,2,2-
There's trifluoroethane. The concentration of the polyfunctional reaction reagent is preferably 0.01 to 10% by weight, more preferably 0.02 to 2% by weight. The method for contacting the polyfunctional reaction reagent with the aqueous amino compound solution phase may be carried out in the same manner as the method for coating the porous support membrane with the aqueous amino compound solution. When such an aqueous solution of an amino compound and a solution of a polyfunctional reaction reagent are brought into contact with each other on a porous support membrane, an ultra-thin film of crosslinked Yokozaki polyamide is formed at the interface due to an interfacial reaction. Generally, an aqueous solution of an amino compound is applied, excess aqueous solution is removed, and then a solution of a polyfunctional reaction reagent is brought into contact to perform an interfacial reaction. At this time, if an acylation catalyst is added to one or both of the solutions, the performance of the resulting semipermeable composite membrane, especially water permeability, will be improved. As the acylation catalyst, at least one selected from dimethylformamide, dimethylacetamide, N-methylpyrrolidone, pyridine, and dimethylaminopyridine can be used, and the amount added can be determined depending on its strength as a catalyst. preferable. Among the acylation catalysts, amide solvents such as dimethylformamide and dimethylacetamide are preferred from the viewpoint of ease of handling, and among these, dimethylformamide is preferred from the viewpoint of catalytic ability. When an interfacial reaction is carried out using an acylation catalyst, water permeability improves, but conversely, the solute exclusion rate tends to decrease slightly. The reason for this is that the produced crosslinked aromatic polyamide is completely composed of amide bonds and does not have aromatic rings bonded, and some amine terminal groups (-NH ₂ ) and carboxylic acid terminals (-COOH) are formed. This is thought to be due to the ionization of the terminal group, and since the acylation catalyst activates the reactivity of the acid halide, it normally contributes to the progress of imidization by reaction with the amine, but in the present invention, interfacial polycondensation is used. , activates not only the reaction with amines but also the reaction with water. Then,
If any amino groups remain, amidation of these groups will reduce the number of amine ends, and reaction with water will increase the number of carboxylic acid ends. Therefore, it is thought that the solute exclusion rate decreases slightly and the water permeation system improves. When dimethylformamide is used as an acylation catalyst, it is preferably in the range of 0.1 to 10% when added to an aqueous solution of an amino compound, and in the range of 0.2 to 5% considering the balance of membrane performance. When added to a solution of 10 to 1000 ppm,
Considering the balance of membrane performance, a range of 20 to 500 ppm is preferable. As mentioned above, in the case of dimethylformamide, it is quantitatively more economical to add it to the solution of the polyfunctional reaction reagent. [Example] The present invention will be specifically described below with reference to Examples. Examples 1 to 2, Comparative Example 1 Taffeta made of polyester fibers with a length of 30 cm and a width of 20 cm (multifilament yarn of 150 denier for both warp and weft, weaving density of 90 pieces/width)
67 wires/inch, 160μ thick) was fixed on a glass plate, and 15% by weight of polysulfone (Udel P3500 manufactured by Union Carboid) was placed on top of the glass plate.
A fiber-reinforced polysulfone support (hereinafter abbreviated as FR-PS support) was prepared by casting dimethylformamide (DMF) solution to a thickness of 200μ at room temperature (20°C), immediately immersing it in pure water, and leaving it for 5 minutes. ). FR− obtained in this way
The pure water permeability coefficient of the PS support (thickness 210-215μ) is
0.005 to 0.01 when measured at a pressure of 1Kg/cm ² and a temperature of 25℃
g/mm ²・sec・atm. The FR-PS support was immersed for 2 minutes in a 2% by weight aqueous solution of metaphenylenediamine as an amino compound. After removing the excess aqueous solution from the surface of the FR-PS support, 1,1,2-triclo-1,2,2
- A solution prepared by dissolving 0.1% by weight of trimesic acid chloride as a polyfunctional reaction reagent and dimethylformamide shown in Table 1 in trifluoroethane was coated so that the surface was completely wetted and allowed to stand for 1 minute. Next, the membrane was turned vertically and excess solution was removed by draining. The composite membrane obtained in this way
As a result of a reverse osmosis test using 1500 ppm saline as raw water at 15 kg/cm ² and 25°C, the membrane performance shown in Table 1 was obtained. Examples 3 to 4, Comparative Example 2 In Examples 1 to 2 and Comparative Example 1, an aqueous mixed solution of 1% by weight of metaphenylenediamine and 1% by weight of 1,3,5-triaminobenzene was used as the amino compound, As a polyfunctional reaction reagent, 1,1,2-trichloro-1, 0.05% by weight of trimesic acid chloride and 0.05% by weight of terephthalic acid chloride;
A composite membrane was obtained in the same manner except for using a 2,2-trifluoroethane solution. Membrane performance is shown in Table 2. Example 5 In Comparative Example 2, 0.65% by weight of dimethylformamide was added to the aqueous solution of the amino compound, and the membrane performance of a composite membrane obtained in the same manner as above was as follows: salt rejection rate of 99.64%;
Water permeability was 0.62 m ³ /m ² ·d. Examples 6 to 9 In Comparative Example 2, the acylation catalyst shown in Table 3 was added to the polyfunctional reaction reagent, and the performance of composite membranes obtained in the same manner as above is shown.

【table】

【table】

[Table] [Effects of the Invention] As explained above, in the present invention, it is possible to obtain a composite membrane whose water permeation rate is improved by 1 to 40% compared to conventional composite membrane manufacturing methods. The reason for this appears to be that carboxylic acid terminals are introduced into the crosslinked aromatic polyamide forming the ultra-thin film.

Claims (1)

[Claims] 1 When producing a semipermeable composite membrane having an ultra-thin membrane made of a crosslinked aromatic polyamide obtained by interfacial reaction with a porous support membrane, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, pyridine, dimethylaminopyridine A method for producing a semipermeable composite membrane, comprising carrying out an interfacial reaction using at least one acylation catalyst selected from the following.