JPH0592130A - Production of composite membrane for reverse osmosis method - Google Patents

Abstract

(57) [Summary] [Objective] To provide a composite membrane for reverse osmosis that uses a membrane-forming solvent having a low ozone layer depletion coefficient and has high performance in terms of the rejection rate and water permeability of the membrane. [Configuration] formula -Ph-SO ₂ -Ph-O- (where Ph represents a phenylene group.) Polyether having a repeating unit represented by - Terusuruhon More comprised porous support film, multifunctional In a method for producing a composite membrane for reverse osmosis having an active layer of a crosslinked polyamide obtained by polycondensing an amine and a polyfunctional acyl halide, 2,2-dichloro-1,1,1-tri is used as an active layer forming solvent. After forming the active layer, the composite film was treated with fluoroethane in an amount of 75-9.
A method for producing a composite membrane for a reverse osmosis method, which comprises hot water treatment in a temperature range of 5 ° C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a composite membrane used in a reverse osmosis method.

[0002]

2. Description of the Related Art Conventionally, as a membrane for a reverse osmosis method, a composite membrane having a polyamide as an active layer is most often used because of its high water permeability. For example, US Pat.
No. 7,344,072, a composite film having a crosslinked aromatic polyamide as an active layer, Japanese Patent Publication No. 56-500062.
There is a composite film having a cross-linked polymer containing a piperazine unit as an active layer, which is described in the specification. These composite membranes are produced by applying an aqueous solution containing a polyfunctional amino compound onto a porous polysulfone support membrane and then applying 1,1,2-trichloro-1,2,2-containing polyfunctional acyl halide.
Contacting with a trifluoroethane solution. Here, the polysulfone formula _{-Ph-C (CH 3) 2} -Ph-O-Ph-SO 2 -Ph-O- ( where Ph represents. A phenylene group) organic polymer having a repeating unit represented by the -, And the porous polysulfone support membrane is the same as the US Department of the Interior Salt Water Bureau Research and Development Report No. 35
Manufactured by the method described in No. 9. 1,1,2-trichloro- used in the production of these composite membranes
It has been pointed out that 1,2,2-trifluoroethane has a large property of depleting the ozone layer in the stratosphere and has an adverse effect on the global environment. The United Nations Environment Program (UNEP) states that the Vienna Convention for the Protection of the Ozone Layer (Adopted March 1985, 19
(Effective September 1988) and the Montreal Protocol on Substances that Deplete the Ozone Layer (Adopted September 1987, 198
Its use was restricted by January 9th), and the year 2000
It will be totally abolished in the year. 1,1,2-trichloro-1,2,
Even if an aliphatic hydrocarbon such as hexane that does not destroy the ozone layer is used in place of 2-trifluoroethane, practical membrane performance can be obtained, but these hydrocarbons are flammable and are not produced in industrial scale. Expensive equipment such as explosion-proof equipment is required, and its practicality is low.

[0003]

As a non-flammable film-forming solvent having a small ozone layer depletion coefficient and 2,2-dichloro-1,1,1-trifluoroethane, porous polysulfone is used as a supporting film. The cross-linked polyamide-based composite film described below can provide only low performance.

The inventors of the present invention previously made up a polyethersulfone having a repeating unit represented by the formula --Ph--SO ₂ --Ph--O-- (wherein Ph represents a phenylene group) as the porous support membrane. 2,2-dichloro-1, as a porous supporting membrane or a membrane forming solvent,
It was found that by using 1,1-trifluoroethane, a composite membrane having an active layer of crosslinked polyamide having high performance can be obtained, but the water permeation rate of the composite membrane was low in practical use.

[0005]

In order to solve the above problems, the present invention has the following constitution.

On a porous support membrane composed of a polyethersulfone having a repeating unit represented by the formula --Ph--SO ₂ --Ph--O-- (wherein Ph represents a phenylene group) as the porous support membrane. In the method for producing a composite membrane for reverse osmosis having an active layer of crosslinked polyamide obtained by polycondensing a polyfunctional amine and a polyfunctional acyl halide, 2,2-dichloro-1, Using 1,1-trifluoroethane, the composite film was formed with 75-9 after the formation of the active layer.
A method for producing a composite membrane for a reverse osmosis method, which comprises hot water treatment in a temperature range of 5 ° C.

In the present invention, the porous polyethylene sulfone support membrane is the same as the porous polysulfone support membrane in the Research and Development Report No. 359.

The method for adjusting the stock solution for film formation is as follows. Polyether sulfone is mixed with an aprotic polar organic solvent and heated to 80 to 95 ° C. to completely dissolve it. Then, after cooling to room temperature, the film is provided for film formation.

When the reverse osmosis membrane according to the present invention is put to practical use, various usage forms generally called elements or modules are adopted in order to increase the filling area of the membrane per constant volume so that the treatment capacity can be increased. Be done. For example,
A tubular type in which the membrane is applied to the inner or outer wall of a thin porous tube, a flat plate type in which the membranes are supported and stacked with a porous plate, a spiral type in which the membranes are rolled and used, and a thin-walled membrane Although there are hollow fiber types and the like for forming hollow fibers, the spiral type is preferred in the present invention.

The composite membrane according to the present invention has a low mechanical strength, and as it is, the tension and the high pressure when the composite membrane is used in the manufacturing process of the composite membrane such as the continuous membrane which is a manufacturing method on an industrial scale. Can not stand,
It deforms or is destroyed and loses its original function. In order to solve such a problem, it is used as a so-called fiber-reinforced composite membrane in which a composite membrane is formed on a woven or non-woven fabric made of fibers. For the fiber-reinforced composite membrane, first, a fiber-reinforced porous support membrane is prepared, and an active layer is formed on the fiber-reinforced porous support membrane.

The fiber reinforced porous support membrane is formed by a wet film formation. That is, it is produced by casting a stock solution for film formation on a woven or non-woven fabric, and then coagulating (gelling) it in a medium (coagulation bath) consisting essentially of water. By this coagulation step, the solvent dissolves in the coagulation bath and is removed from the film, but if this is insufficient, a water washing step is provided to remove the solvent. The concentration of the polyether sulfone in the stock solution for film formation is preferably 14 to 20% by weight. Below this range, the rejection rate of the performance of the composite membrane will be low, and above this range, the water permeation rate will be low.

In the present invention, as the aprotic polar organic solvent used as a solvent for forming a porous polyethylene sulfone supporting membrane, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, 2-pyrrolidone, hexa There are methylphosphoric triamides and the like, but dimethylformamide is preferable.

In the present invention, the polyfunctional amine includes a compound which reacts with a polyfunctional acyl halide to form a polymer having a crosslinked structure. For example, the aliphatic amine is N, N-dimethylethylenediamine. , N, N-dimethylpropanediamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 1,3-bis (4
-Piperidyl) methane, 1,3-bis (4-piperidyl) propane and the like. The aromatic amine is preferably diamine or triamine, and aromatic diamine or aromatic triamine alone,
Alternatively, it is preferably used in the form of a mixture of aromatic diamine and aromatic triamine. Examples of aromatic diamines include m-phenylenediamine and p-phenylenediamine, but m-phenylenediamine is preferable because it can form a crosslinked polyamide ultrathin film having excellent water permeability. As the aromatic triamine, 1,3,5-triaminobenzene is preferable from the viewpoints of high desalination rate, elimination rate of organic substances, and structural stability of the ultrathin film layer due to high crosslinking density.

In the present invention, the polyfunctional acyl halide includes those which react with a polyfunctional amine to form a polymer having a crosslinked structure, and examples thereof include trimesic acid halide, benzophenone tetracarboxylic acid halide and trimellitate. Acid halide, pyromellitic acid halide, isophthalic acid halide, terephthalic acid halide, naphthalenedicarboxylic acid halide, diphenyldicarbic acid halide,
Pyridinedicarboxylic acid halide, 1,3,5-cyclohexanetricarboxylic acid halide, 1,3-cyclohexanedicarboxylic acid halide, 1,4-cyclohexanedicarboxylic acid halide and the like can be used. These polyfunctional acyl halides can be used alone or as a mixture. Considering the reactivity with a polyfunctional amine, the polyfunctional acyl halide is preferably a polyfunctional acyl chloride.

Next, a method of forming the active layer will be described.

In the present invention, the crosslinked polyamide active layer comprises an aqueous solution containing the above-mentioned polyfunctional amine and 2,2-dichloro-1, containing the polyfunctional acyl halide.
The 1,1-trifluoroethane solution is formed on the porous polyethersulfone support membrane by an interfacial polycondensation reaction, first the support membrane is coated with a polyfunctional amine.

The concentration of the amino compound in the polyfunctional amine aqueous solution is 0.1 to 10% by weight, preferably 0.5 to 1
It is 0% by weight, and the aqueous solution may contain a surfactant, an organic solvent, an antioxidant and the like as long as it does not hinder the interfacial polycondensation reaction.

The support membrane may be coated with the aqueous amine solution as long as the surface of the support membrane is uniformly and continuously coated, and known coating means such as coating the support membrane surface with the aqueous solution may be used. It can be carried out by a method, a method of immersing the supporting film in the aqueous solution, or the like.

Next, the excessively applied amine aqueous solution is removed by a draining process. As a method of draining, for example, there is a method of holding the surface of the supporting film in the vertical direction and allowing it to flow down naturally. Next, the 2,2-dichloro-1,1,1-trifluoroethane solution of the above-mentioned polyfunctional acyl halide is brought into contact with the surface of the supporting membrane coated with the polyfunctional amine aqueous solution. The concentration of polyfunctional acyl halide in the 2,2-dichloro-1,1,1-trifluoroethane solution is usually
It is 0.01 to 10% by weight, preferably 0.05 to 0.5% by weight. Below this range, the exclusion rate is insufficient,
Further, if it exceeds this range, the water permeation rate is low, and further, the supporting membrane may be damaged and the membrane performance of the composite membrane may become extremely low.

The method of contacting the polyfunctional acyl halide with the amino compound aqueous solution phase is the same as the method of coating the support film with the amino compound aqueous solution. After that, in order to remove the excessively attached polyfunctional acyl halide, the substrate is washed with an aqueous alkali solution such as sodium carbonate.

Next, the obtained composite membrane is subjected to hot water treatment in the temperature range of 75 to 95 ° C., more preferably in the temperature range of 85 to 95 ° C. The medium in the hot water treatment bath is preferably pure water,
A surfactant or the like may be contained as long as it does not adversely affect the film performance. The hot water treatment time is not particularly limited,
A sufficient effect is obtained in 2 to 5 minutes.

The composite membrane thus obtained exhibits a sufficiently good separation performance even by itself, but by further immersing the composite membrane in a chlorine-containing aqueous solution having a pH of 6 to 13, the separation performance, in particular, the exclusion rate is improved. , The water permeation rate can be improved. Typical examples of the chlorine generating reagent include chlorine gas, coconut powder, sodium hypochlorite, chlorine dioxide, chloramine B, chloramine T, halazone, dichlorodimethylhydantoin, chlorinated isocyanuric acid and salts thereof. It is preferable that the concentration is determined by the strength of the oxidizing power. Among the above chlorine generating reagents, an aqueous solution of sodium hypochlorite is preferable from the viewpoint of handleability. There is an important relationship between the oxidizing power of a chlorine-containing aqueous solution and pH, and when the pH is lower than 6, it does not show sufficient oxidizing power, and when the pH exceeds 13, hydrolysis of the amide bond occurs. Both are unsuitable because the ultra-thin layer is damaged. Therefore, it is preferable to immerse in a chlorine-containing aqueous solution at pH 6-13.

[0023]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

In the examples, the rejection rate was calculated by the following equation.

Exclusion rate [%] = (1-concentration of solute in membrane permeate / concentration of solute in membrane feed liquid) × 100 Example 1 Polyethersulfone (Victre manufactured by ICI Corporation)
x 4800) 18 parts by weight of dimethylformamide (hereinafter D
Abbreviated as MF. ) 82 parts by weight, and stirred at 90 ° C. for 60 minutes to be completely dissolved. The stock solution thus obtained was used for taffeta made of polyester fiber having a size of 30 cm in length and 20 cm in width (150 filament denier multi-filament yarn for both warp and weft, 90 wefts / inch vertical, 6 horizontal)
7 fibers / inch, thickness 160 μm) was fixed on a glass plate, cast at a thickness of 200 μm at room temperature (20 ° C.), immediately immersed in pure water and left for 5 minutes to leave a fiber reinforced polyethylene sulfone. A support film (hereinafter abbreviated as FR-PES support film) was prepared.

The FR-PES support film was made up of 1% by weight of 1,3,3.
It was immersed in an aqueous solution containing 5-triaminobenzene and 1% by weight of m-phenylenediamine for 1 minute. The supporting film was slowly pulled up vertically to remove excess aqueous solution from the surface of the supporting film, and then 2,2-dichloro containing 0.05% by weight of terephthalic acid chloride and 0.05% by weight of trimesic acid chloride. Apply -1,1,1-trifluoroethane solution so that the surface of the support membrane is completely wet.
Let stand for a minute. Next, the supporting film was made vertical and the excess solution was drained and removed, and then immersed in a 0.2 wt% aqueous solution of sodium carbonate for 5 minutes. After washing with water for 10 minutes, the composite membrane was placed in pure water at 90 ° C. and treated for 2 minutes.

The membrane thus obtained was treated with 1500 ppm saline adjusted to pH 6.5 as raw water to obtain 15 kg / c.
As a result of a reverse osmosis test under conditions of m ² and 25 ° C., the exclusion rate was 99.5% and the water permeation rate was 1.10 m ³ / m ² · day.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the composite membrane was not treated with hot water. As a result, the rejection rate was 99.5% and the water permeation rate was 0.66.
The film performance was m ³ / m ² · day.

Example 2 The FR-PES support film of Example 1 was added with 4% by weight of 1,3,5.
Immersed in an aqueous solution containing triaminobenzene for 1 minute. The support film was slowly pulled up in the vertical direction to remove excess aqueous solution from the surface of the support, and then a dichlorotrifluoroethane solution containing 0.1% by weight of isophthalic acid chloride was applied so that the surface was completely wet. Left for 1 minute. Next, the support was made vertical and the excess solution was drained and removed, and then immersed in a 0.2 wt% aqueous solution of sodium carbonate for 5 minutes. After washing with water for 10 minutes, the composite membrane is heated to 90 ° C.
It was put in pure water, and treated for 2 minutes. The obtained film was used in Example 1.
As a result of a reverse osmosis test under the conditions described above, the rejection rate was 99.2% and the water permeation rate was 1.04 m ³ / m ² · day.

Comparative Example 2 The same procedure as in Example 2 was carried out except that the composite membrane was not treated with hot water. As a result, the rejection rate was 99.1% and the water permeation rate was 0.63 m.
The membrane performance was ³ / m ² · day.

Example 3 2% by weight of the FR-PES support membrane of Example 1 was used in 1, 3, 5
Immersed in an aqueous solution containing triaminobenzene and 2% by weight of m-phenylenediamine for 1 minute. The supporting film was slowly pulled up vertically to remove excess aqueous solution from the surface of the supporting film, and then 2,2-dichloro containing 0.1% by weight of terephthalic acid chloride and 0.1% by weight of trimesic acid chloride. The -1,1,1-trifluoroethane solution was applied so that the surface of the supporting film was completely wet, and allowed to stand for 1 minute. Next, the supporting film was made vertical and the excess solution was drained and removed, and then immersed in a 0.2 wt% aqueous solution of sodium carbonate for 5 minutes. After washing with water for 10 minutes, the composite membrane is heated to 90 ° C.
It was put in pure water, and treated for 2 minutes.

The membrane thus obtained was treated with 3.5% saline adjusted to pH 6.5 as raw water to obtain 56 Kg / cm ² ,
As a result of reverse osmosis test under the condition of 25 ° C., the rejection rate was 99.
The membrane performance was 5% and the water permeability was 0.65 m ³ / m ² · day.

Comparative Example 3 The same procedure as in Example 3 was carried out except that the composite membrane was not treated with hot water. As a result, the rejection rate was 99.3% and the water permeation rate was 0.41 m.
The membrane performance was ³ / m ² · day.

[0034]

Industrial Applicability According to the present invention, a reverse osmosis composite membrane having a high rejection rate of membrane performance and a high water permeability is obtained by using a membrane-forming solvent having a small ozone layer depletion coefficient.

Claims (1)

[Claims] 1. A porous support membrane comprising a poly (ether sulfone) having a repeating unit represented by the formula: --Ph--SO ₂ --Ph--O-- (wherein Ph represents a phenylene group). In a method for producing a composite membrane for a reverse osmosis method having an active layer of crosslinked polyamide obtained by polycondensing a functional amine and a polyfunctional acyl halide, 2,2-dichloro-1,1,1 is used as an active layer forming solvent. -Using trifluoroethane, the composite membrane was made to have a thickness of 75-9 after formation of the active layer.
A method for producing a composite membrane for a reverse osmosis method, which comprises hot water treatment in a temperature range of 5 ° C.