JPH0596141A - Production of composite membrane for reverse osmotic method - Google Patents

Abstract

PURPOSE:To obtain a composite membrane having stable membrane performances by using polyether sulfone as a polymer, ehtylene glycol as an additive, non-proton polar org. solvent as a solvent, and 2,2-dichloro-1,1,1- trifluoroethane as a solvent for the formation of an active layer. CONSTITUTION:A soln. incorporating polyether sulfone with the repeating unit expressed by formula Ph-SO2-Ph-O (wherein Ph is a phenylene group) as a polymer, ethylene glycol and/or glycerol as an additive, and non-proton polar org. solvent such as dimethylformamide, etc., as a solvent is used as the source liquid to form the membrane Rs a solvent 2,2-dichloro-1,1,1-trifulroethane is used for forming an active layer. Thereby, the membrane having high membrane performances, especially, high removing rate and stable property is obtd. by using the solvent for formation of membrane having a small coefft. for breaking an ozone layer.

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 has the formula _{-Ph-C (CH 3) 2} -Ph-O-Ph-SO 2
It is an organic polymer having a repeating unit represented by -Ph-O- (wherein Ph represents a phenylene group), and the porous polysulfone supporting membrane is 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 above obtained 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 a high performance of a crosslinked polyamide having an active layer can be obtained, but when further studies were conducted, the composite membrane showed that the membrane performance, particularly It has been found that it is difficult to manufacture industrially stably because the fluctuation of the exclusion rate is large.

An object of the present invention is to solve these problems and obtain a composite membrane having stable membrane performance in the production of a porous support membrane composed of polyethersulfone.

[0006]

To achieve the above object, the present invention has the following constitution.

In the method for producing a composite membrane for the reverse osmosis method having a cross-linked polyamide obtained by polycondensing a polyfunctional amine and a polyfunctional acyl halide on a porous support membrane as an active layer, the polymer represented by formula -Ph is used. -SO ₂ -Ph-O- (wherein Ph represents a phenylene group), a polyether sulfone having a repeating unit, ethylene glycol or / and glycerin as an additive, and an aprotic polar solvent. A porous membrane obtained by wet film formation is used as a solution for forming a film containing a solution containing an organic solvent, and 2,2-dichloro-1,1,1-trifluoroethane is used as an active layer forming solvent. Method for producing composite membrane for reverse osmosis method.

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.

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

The method for adjusting the stock solution for film formation is as follows. First, ethylene glycol and / or glycerin is dissolved in an aprotic polar organic solvent, and then polyether sulfone is mixed with this solution 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 In the case of the present invention, there are hollow fiber types and the like for making hollow fibers. The spiral type is preferable.

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 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 and the lithium salt are dissolved in the coagulation bath and removed from the film. If this is insufficient, a water washing step is provided to remove the solvent and the lithium salt. The concentration of the polyethersulfone in the stock solution for film formation is 14 to
20% by weight is preferred. Below this range, the rejection rate of the composite membrane performance is low, and above this range, the water permeation rate is low. The amount of ethylene glycol and / or glycerin used is in the range of 2 to 50% by weight relative to the polyether sulfone. Below this range, the effect of the present invention is insufficient, and above this range, there is a problem in solubility in a solvent.

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

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 by a known coating means, for example, the surface of the support membrane is coated with the aqueous solution. It can be carried out by a method, a method of immersing the supporting film in the aqueous solution, or the like.

Then, the excessively applied aqueous amine 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.

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-Solute concentration in membrane permeate / Solute concentration in membrane feed) × 100 Example 1 3.6 parts by weight of ethylene glycol was added to dimethylformamide (hereinafter abbreviated as DMF). .) 78.4 parts by weight and stirred at room temperature for 30 minutes to completely dissolve it. To this solution,
Tersulphone (Victrex 4800 manufactured by ICI Corporation)
18 parts by weight of was added and completely stirred by stirring at 90 ° C. for 60 minutes. 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 (multi-filament yarn of 150 denier for both warp and weft yarns, weaving density 90 warp / inch, weft 67 200 / μm by fixing a book / inch, thickness 160μm) on a glass plate.
It is cast at room temperature (20 ° C.) with a thickness of m, immediately immersed in pure water and left for 5 minutes to obtain fiber-reinforced polyethylene.
Tersulphone support membrane (hereinafter abbreviated as FR-PES support membrane)
Was produced.

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 support membrane was made vertical and the excess solution was drained and removed, and then immersed in a 0.2 wt% sodium carbonate aqueous solution for 5 minutes to obtain a composite membrane.

The above-mentioned formation of the FR-PES support membrane and formation of a composite membrane were repeated 5 times.

The composite membrane thus obtained was sampled at 3 points each for a number of times of film formation, for a total of 15 points, and 1500 ppm saline adjusted to pH 6.5 was used as raw water to obtain 15 kg /
As a result of reverse osmosis test under the conditions of cm ² and 25 ° C., the exclusion rate was 99.1 to 99.6% (average value: 99.4%), the water permeation rate was 0.58 to 0.70 m ³ / m ² · day. (Average value; 0.
The film performance was 64 m ³ / m ² · day).

Example 2 In Example 1, glycerin 3.6 was used instead of ethylene glycol in the stock solution for forming the FR-PES support film.
As a result of performing the same except that the weight part is used, the rejection rate is 9
9.0 to 99.6% (average value; 99.3%), water permeation rate 0.57 to 0.71 m ³ / m ² · day (average value; 0.63)
The film performance was m ³ / m ² · day).

Comparative Example 1 The same procedure as in Example 1 was carried out except that ethylene glycol was not added to the stock solution for forming the FR-PES support film, and the exclusion rate was 95.6 to 99.46%. (Average value: 9
8.4%), water permeation rate 0.61 to 0.72 m ³ / m ² ·
The film performance was one day (average value: 0.67 m ³ / m ² · day).

Example 3 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 vertically to remove excess aqueous solution from the surface of the support, and then 1,2-dichloro-1, containing 0.1% by weight of isophthalic acid chloride,
The 1,1-trifluoroethane solution was applied so that the surface was completely wet, and allowed to stand 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.

The production of the FR-PES support membrane and the formation of a composite membrane were repeated 5 times.

The composite membrane thus obtained was subjected to reverse osmosis test under the conditions of Example 1 as a result of 15 samplings, 3 points each for each number of times of film formation, and a rejection rate of 98.6 to 99.2%.
(Average value; 99.0%) Water permeability 0.63 to 0.71 m ³
The film performance was / m ² · day (average value: 0.67 m ³ / m ² · day).

COMPARATIVE EXAMPLE 2 The same procedure as in Example 3 was repeated except that ethylene glycol was not added to the stock solution for forming the FR-PES support film, resulting in an exclusion rate of 92.3 to 99.0%. (Average value: 9
The membrane performance was a water permeability of 0.65 to 0.74 m ³ / m ² · day (average value: 0.70 m ³ / m ² · day).

[0035]

According to the present invention, a film-forming solvent having a small ozone layer depletion coefficient is used, and film performance, particularly a high rejection rate and stable performance can be obtained.

Claims (1)

[Claims] 1. A method for producing a composite membrane for a reverse osmosis method, comprising a crosslinked polyamide obtained by polycondensing a polyfunctional amine and a polyfunctional acyl halide on a porous support membrane as an active layer, wherein the polymer is used as a polymer. -Ph-SO ₂ -Ph-O- polyether (where Ph represents a phenylene group.) having a repeating unit represented by - Terusuruhon, ethylene glycol as an additive - le and / or glycerol, and as solvents aprotic It is characterized in that a solution containing a polar organic solvent is used as a stock solution for film formation and a porous film obtained by wet film formation is used, and 2,2-dichloro-1,1,1-trifluoroethane is used as a solvent for forming an active layer. A method for producing a composite membrane for reverse osmosis.