JP3438278B2 - Semipermeable composite membrane and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high performance semipermeable composite membrane for selectively permeating and separating components of a liquid mixture and a method for producing the same. The semipermeable composite membrane obtained by the present invention can be used particularly for desalination of canned water, desalination of seawater, and production of ultrapure water used for production of semiconductors. Furthermore, from dyeing drainage, electrodeposition paint drainage, etc.
It is possible to selectively remove or recover pollutants or useful substances contained therein, and thus contribute to the closure of wastewater.

[0002]

2. Description of the Related Art Conventionally, an asymmetric membrane type cellulose acetate membrane has been used as a semipermeable membrane industrially used (for example, US Pat. Nos. 3,133,132 and 3,13).
3,137). However, this membrane has problems such as hydrolysis resistance and microbial resistance, and the salt rejection and water permeability were not sufficient. Therefore, although the cellulose acetate asymmetric membrane is used for some applications, it has not been put to practical use in a wide range of applications.

In order to make up for these drawbacks, a semipermeable membrane having a shape different from that of an asymmetric membrane is formed by coating a microporous support membrane with an ultrathin film (active layer) which substantially controls membrane separation performance with different materials. A permeable composite membrane was devised. In the semipermeable composite membrane, it is possible to select the most suitable material for each of the active layer and the microporous support membrane, and various membrane forming techniques can be selected.

Most of the semipermeable composite membranes currently on the market have a microporous support membrane having an active layer obtained by crosslinking a gel layer and a polymer, and an interfacial polycondensation of a monomer on the microporous support membrane. There are two types, one having an active layer. Specific examples of the former include Japanese Patent Laid-Open No. Sho 49-13282, Japanese Patent Publication No. Sho 55-38164, and PB Report 80-18.
2090, JP-B-59-27202, 61-2.
7102 and the like. Specific examples of the latter include US Pat. Nos. 3,744,942 and 3,926,926.
No. 798, No. 4,277,344, Japanese Patent Laid-Open No. 55-147106, No. 58-24303, No. 62-121603 and the like.

These semipermeable composite membranes have higher desalination performance than cellulose acetate asymmetric membranes. Further, these membranes are being improved in durability against chlorine and hydrogen peroxide used for sterilization, and are in the stage of expanding their applications. The disadvantage of this type of membrane is that when it is attempted to increase the water permeability (low pressure and high water production), the ultra-thin film (active layer) is applied very thinly, so that it may be caused by flaws in the microporous support membrane or foreign matter. In addition, it tends to cause defects, and in the case of flat membrane type composite membrane, when it is used as a spiral, plate and frame type element, the surface ultra-thin film (active layer) is scratched during the manufacturing process of the element. In many cases, the element's desalination performance deteriorated with respect to the membrane's original desalination performance. These are obstacles to the high exclusion property, which has recently been particularly desired. The former problem is being solved by improvements in manufacturing technology, and this type of membrane is in the stage of commercialization. As a means for solving the latter problem, a protective film has been proposed and results have been seen (for example, US Pat. No. 4,005,012, JP-A-56).
-15804 and JP-A-62-216604). This method requires insolubilization in water in order to prevent the protective film from falling off, and the applied polymer is thermally crosslinked or, if necessary, crosslinked in the presence of a catalyst. This is an effective means for covering a thin protective film without impairing the original performance in a composite film in which heat treatment is included in the manufacturing process of the film, but in a film manufactured without undergoing the heat treatment process, A new heat history was added, and the performance was degraded. (For example, PB Report PB8
5-247971).

Further, a proposal has been made to treat the membrane surface with a water-soluble compound having an amino group, and some results have been obtained (for example, Japanese Patent Laid-Open No. 2-115027). However, this treatment is a method of immersing the membrane in an amine aqueous solution and ionically adsorbing it to the acid component on the membrane surface, and the time required for the treatment is long and the process is difficult.

[0007]

However, in the conventional method, it was difficult to control the charge characteristics of the membrane surface without impairing the separation performance of the semipermeable composite membrane.
The present invention solves these problems and at the same time prevents the defects of ultra-thin films to improve the separation performance and improve the uniformity of the membrane performance, which is difficult to achieve in the conventional semipermeable composite membrane. It is to solve the problem that was.

[0008]

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

[In a semipermeable composite membrane obtained by forming an ultrathin film on a microporous support membrane, a first porous membrane having two or more reactive groups in one molecule is provided on the microporous support membrane. A coating of an aqueous solution of a water-soluble compound is formed, and a solution of a polyfunctional reactive reagent capable of reacting with the first water-soluble compound is coated on the coating of the aqueous solution to react with the water-soluble compound. on the coating of a solution of a polyfunctional reagent in a molecule possess two or more reactive groups, and aromatic amines, aliphatic a
Mins, aliphatic alcohols and aromatic alcohols
A semipermeable composite membrane formed by coating an aqueous solution of a second water-soluble compound selected from the above and reacting with the polyfunctional reaction reagent remaining in the coating of the solution of the polyfunctional reaction reagent. "and,
“In a method for producing a semipermeable composite film for forming an ultrathin film on a microporous support film, the first water-soluble compound having two or more reactive groups in one molecule is formed on the microporous support film. A coating of an aqueous solution of a compound is formed, and a solution of a polyfunctional reaction reagent capable of reacting with the first water-soluble compound is coated on the coating of the aqueous solution to react with the water-soluble compound. possess two or more reactive groups on the coating of the solution of sexual reaction reagent in a molecule, and aromatic amines, aliphatic amines
From fatty acids, aliphatic alcohols and aromatic alcohols
A method for producing a semipermeable composite membrane, which comprises coating an aqueous solution of a selected second water-soluble compound and reacting with the polyfunctional reaction reagent remaining in the coating of the solution of the polyfunctional reaction reagent. In the present invention, the microporous support membrane is a layer having substantially no separation performance and is used for giving strength to an ultrathin film layer (active layer) having substantially separation performance. is there. The microporous support membrane has an asymmetric structure with uniform fine pores or dense and fine pores on one side and gradually larger fine pores on the other side. A structure having a thickness of 100 nm or less on the surface of is preferable. The thickness of the microporous support film is 1 μm to several mm, and preferably 10 μm or more from the viewpoint of film strength, and several 100 μm or less from the viewpoint of easy handling and module processing. The above microporous support membrane can be selected from various commercially available materials such as "Millipore Filter VSWP" (trade name) manufactured by Millipore and "Ultra Filter UK10" (trade name) manufactured by Toyo Roshi. ,Normally,
"Office of Saline Water Research and Development Progress Report" No. 359 (1968). The material of the microporous support membrane is a homopolymer or copolymer of polysulfone, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide, polyphenylene sulfide sulfone, etc. alone or a blend of these polymers. can do. Among these materials, polysulfone is generally used because it has high chemical, mechanical and thermal stability and is easy to mold. For example, a solution of polysulfone in dimethylformamide (DMF) is cast on a densely woven polyester cloth or non-woven cloth to a certain thickness, which is then poured into an aqueous solution containing 0.5% by weight of sodium dodecyl sulfate and 2% by weight of DMF. By wet coagulation, a microporous support membrane having most of the surface having fine pores having a diameter of several tens nm or less can be obtained.

An ultrathin film is formed on this microporous support film,
A composite semipermeable membrane is manufactured. The formation of the ultrathin film in the present invention involves forming a coating of an aqueous solution of a first water-soluble compound having two or more reactive groups in one molecule on a microporous support membrane, and coating the aqueous solution. A solution of a polyfunctional reaction reagent capable of reacting with the first water-soluble compound is coated on the above to react with the water-soluble compound, and the solution of the polyfunctional reaction reagent is further coated on one molecule. possess two or more reactive groups,
And aromatic amines, aliphatic amines, aliphatic alcohols
Of a second water-soluble compound selected from alcohols and aromatic alcohols and reacting with the polyfunctional reaction reagent remaining in the coating of the solution of the polyfunctional reaction reagent.

[0011] Here, the first water-soluble compound having two or more reactive groups in one molecule, an aliphatic having two or more reactive groups, an aromatic, or a compound of the heterocycle,
Any substance may be used as long as it is substantially soluble in water and reacts with a polyfunctional reaction reagent to form a water-insoluble cross-linked polymer, and the reactive group is an amino group, a hydroxyl group or the like and has two or more reactive groups. May be the same or different. Generally, for example, aromatic amines such as m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene and paraxylylenediamine, ethylenediamine, propylenediamine, dimethylethylenediamine, piperazine and aminomethylpiperidine. Aliphatic amines of
Aliphatic alcohols such as ethylene glycol, glycerin, propylene glycol, dihydroxybenzene,
Aromatic alcohols such as trihydroxybenzene are used. Among them, polyfunctional amino compounds, aromatic amines, especially m-phenylenediamine, p-phenylenediamine, in view of reactivity and performance of the obtained film,
1,3,5-triaminobenzene is preferred. These water-soluble compounds having two or more reactive groups in one molecule can be used alone or in combination. These water-soluble compounds are used as a 0.1 to 20% by weight aqueous solution. Other water-soluble compounds may be mixed with the aqueous solution as needed.

As the polyfunctional reaction reagent capable of reacting with the water-soluble compound, polyfunctional acid halides, polyfunctional isocyanate compounds and the like can be used. For example, examples of polyfunctional acid halides include trimesic acid halide, benzophenone tetracarboxylic acid halide, trimetic acid halide, pyrometic acid halide, isophthalic acid halide, terephthalic acid halide, naphthalenedicarboxylic acid halide, diphenyldicarboxylic acid halide, pyridinedicarboxylic acid halide. Aromatic polyfunctional acid halides such as benzenedisulfonic acid halide and chlorosulfonylisophthalic acid halide, and aromatic diisocyanate compounds such as toluene diisocyanate are used as the isocyanate compound. Among these compounds, aromatic acid chlorides, particularly isophthalic acid chloride, terephthalic acid chloride, trimesic acid chloride, and mixtures thereof are preferable from the viewpoints of easiness of reaction and separation performance of the obtained membrane. The solvent that dissolves the polyfunctional reaction reagent must be immiscible with water, and it must dissolve the polyfunctional reaction reagent and not destroy the microporous support membrane, forming a crosslinked polymer by interfacial polycondensation. Any one may be used as long as it can be obtained. Preferred examples include hydrocarbon compounds, cyclohexane, 1,1,2-trichloro-1,2,2 trifluoroethane, etc., but preferably n-hexane, heptane, in view of reaction rate and solvent volatility. Examples include octane, nonane, decane, undecane, dodecane, and 1,1,2-trichloro-1,2,2 trifluoroethane.

Further, the second water-soluble compound having two or more reactive groups in one molecule of the aqueous solution to be coated thereon is selected from the above-mentioned compounds and is the same as the first water-soluble compound. It doesn't matter if they are there or not. concrete
Include m-phenylenediamine and p-phenylenediamine.
1,3,5-triaminobenzene, paraxylylene
Aromatic amines such as diamines, ethylenediamine,
Ropylenediamine, dimethylethylenediamine, pipera
Aliphatic amines such as gin and aminomethylpiperidine,
Ethylene glycol, glycerin, propylene glycol
Fatty alcohols such as
Aromatic alcohol such as benzene and trihydroxybenzene
The one selected from the class is used. Among these
In terms of responsiveness and performance of the obtained film, polyfunctional amino compound,
Furthermore, aromatic amines, especially m-phenylenediamine,
p-phenylenediamine, 1,3,5-triaminoben
Zen is preferred. More than one reactivity in one molecule
Water-soluble compounds having groups are used alone or in combination.
You can These water-soluble compounds have a weight concentration of 0.
Used as a 1-20% aqueous solution. Required for aqueous solution
Other water-soluble compounds may be mixed accordingly.

In this way, a second coating is formed on the second coating .
Of water-soluble compounds, by acting on the functional groups remaining unreacted polyfunctional reagents that give reacted with a second water-soluble compounds, the disadvantage of the membrane surface, reduce the wound. Further, it becomes possible to make the film thickness uniform and increase the crosslink density, and as a result, the separation performance is improved and the uniformity of the film properties is improved. Further, it becomes possible to eliminate, reduce or improve the influence of the unreacted functional group on the membrane performance.
For example , when a polyfunctional acid halide, a polyfunctional isocyanate compound or the like is used as the polyfunctional reaction reagent, unreacted functional groups of these polyfunctional reaction reagents remain, or hydrolysis is performed. When received, the film surface will
It has the property of negative charge. However, the unreacted functional group is reacted with the second water-soluble compound further coated thereon, or the functional group of the second water-soluble compound remains unreacted, so that the film surface is It becomes possible to modify it to be neutral or positively charged.

The membrane potential of the aromatic polyamide thus obtained is preferably -11 mV or higher, more preferably -8 mV or higher, even more preferably -4 mV or higher, much more preferably 0 mV or higher, more preferably +2 mV.
As described above, it is much more preferably +5 mV or more. Alternatively, an aromatic polyamide having a membrane potential of +8 mV or higher, further +11 mV or higher, or +14 mV or higher is also possible.

However, the term "membrane potential" as used herein means Japanese Patent Laid-Open No.
As described in JP-A-1-287492, at 25 ° C., the KCl aqueous solution has a membrane potential at a concentration of 10 ⁻³ mol / liter on the low concentration side and a concentration of 4 × 10 ⁻³ mol / liter on the high concentration side. .

The ultrathin film obtained has a thickness of 5 nm to 10 μm.
Although it is up to m, from the viewpoint of water permeability of the semipermeable composite membrane, 1
It is preferably not more than μm, and if it is thicker than this, water permeability may be lowered, which is not preferable.

Next, the film forming method will be described.

First, 2 reactive groups were formed on the microporous support membrane.
Coating the aqueous solution containing a first water-soluble compound having more than eight. After removing the excess aqueous solution , a solution of a polyfunctional reaction reagent in an organic solvent is then applied to coat the ultrathin film by an in situ interfacial polycondensation reaction. After removing the excess organic solvent solution and evaporating the organic solvent, immediately add two reactive groups.
An aqueous solution containing the above-mentioned second water-soluble compound is applied, reacted with the remaining polyfunctional reaction reagent or functional group, and further coated with an ultrathin film to obtain the semipermeable composite film of the present invention. The obtained semipermeable composite film may be washed with pure water or the like after this, if necessary.

As a method for coating the above aqueous solution , there are a coating method and a method of immersing the microporous support membrane in the aqueous solution. After coating the microporous support membrane with the aqueous solution ,
A liquid draining step is generally provided to remove the excess aqueous solution . As a liquid draining method, for example, there is a method of holding the film surface in a vertical direction and allowing it to flow down naturally.

After sufficient draining , two reactive groups are added.
An aqueous solution containing the above first water-soluble compound and a polyfunctional reaction
In situ interfacial polycondensation reaction respond reagent by covering the ultra-thin film. The polyfunctional reactive reagent is preferably a polyfunctional acid halide as indicated above. Further, the organic solvent is immiscible with water as described above, and it is necessary that it does not destroy the microporous support membrane by dissolving the reagent, and can form a crosslinked polymer by interfacial polycondensation. Either may be used.

The concentration of the polyfunctional reaction reagent is not particularly limited, but if it is too low, the formation of the ultrathin film which is the active layer may be insufficient, which may be a drawback, and if it is high, it is disadvantageous in terms of cost. Therefore, about 0.01 to 1.0% by weight is preferable.

The excess organic solvent solution of the polyfunctional reaction reagent is removed by a draining process, and the organic solvent is generally volatilized during this period. At this time, the polyfunctional reaction reagent is not completely removed from the film surface, but is partially left on the film surface. Further, by positively volatilizing the organic solvent by applying wind or the like, depending on the concentration of the solution to be applied, 0.01 to 0.1 g / m ² of multifunctional
It is possible to leave the sexual reaction reagent on the membrane surface. The feature of the production method of the present invention is to utilize this residual polyfunctional reaction reagent. It is also possible that some of the functional groups of the polyfunctional reaction reagent remain unreacted, and the utilization of this is also included in the present invention. With the polyfunctional reaction reagent remaining on the membrane surface, an aqueous solution containing a water-soluble compound having two or more reactive groups in one molecule diluted in concentration is coated,
The ultra-thin film is further coated by the n situ interface reaction,
Similarly, the liquid is drained to obtain a composite semipermeable membrane having a target composite structure ultrathin film layer.

The first has two or more reactive groups in a molecule
The aqueous solution containing the second water-soluble compound may be a solution of the same compound as the first water-soluble compound or a solution of a different water-soluble compound. From the viewpoint of film performance, polyfunctional amino compounds, and aromatic amines, particularly m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferable. The concentration of the second solution is preferably 1/100 or more and 1/10 or less of the concentration of the first aqueous solution in consideration of the amount of the polyfunctional reaction reagent remaining on the membrane surface. When the reactivity is low, the higher the concentration is, the more preferable it is. However, if an excessive amount of the water-soluble compound remains, it is difficult to wash it. On the other hand, if the concentration is too low, the reaction is not sufficiently performed.

The composite semipermeable membrane obtained as described above can be used as it is, but it is preferable to remove unreacted residue by washing with water or the like before use.

Further, the form of the composite membrane of the present invention may be a flat membrane or a hollow fiber. In addition, the obtained composite membrane can be used by incorporating the flat membrane into a spiral, tubular, or plate-and-frame module, or by bundling the hollow fibers and incorporating them into the module.
The present invention does not depend on the usage of these membranes.

[0027]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 Taffeta made of polyester fiber having a size of 30 cm in the vertical direction and 20 cm in the horizontal direction (multifilament yarn of 150 denier for both vertical and horizontal threads, weaving density vertical 90 threads / inch, horizontal 67 threads / inch, 160 μm thick was fixed on a glass plate, and polysulfone (Udel P manufactured by Amoco Co., Ltd.) was placed on the glass plate.
3500) 15 wt% dimethylformamide (DM
F) The solution was cast at a thickness of 200 μm at room temperature (20 ° C.), immediately immersed in pure water and left for 5 minutes to prepare a fiber-reinforced polysulfone support membrane (hereinafter abbreviated as FR-PS support membrane). FR-obtained in this way
The pure water permeability coefficient of the PS support membrane (thickness 210 to 215 μm) is 0.005 when measured at a pressure of 1 kg / cm ² and a temperature of 25 ° C.
It was ~ 0.01 g / cm ² · sec · atm.

The FR-PS support membrane was immersed in a 2 wt% aqueous solution of metaphenylenediamine for 2 minutes. After removing the excess aqueous solution from the surface of the FR-PS supporting membrane, a solution of 0.1% by weight of trimesic acid chloride in 1,1,2-trichloro-1,2,2-trifluoroethane was completely dissolved on the surface. It was coated so as to be wet and left still for 1 minute. Next, the membrane was made vertical and excess solution was drained off to remove, and then 0.1 wt% metaphenylenediamine aqueous solution was coated on the membrane surface so that the surface was completely wet, and the membrane was allowed to stand for 30 seconds. The film thus formed was placed vertically and drained, and then dried at room temperature.
The osmotic pressure of the composite membrane thus obtained was 28 kg / cm ²
As a result of performing a reverse osmosis test on 10 sheets under the conditions of 56 kg / cm ² and 25 ° C. using 3.5% NaCl, stable membrane performance as shown in Table 1 was obtained. At this time, the average value is 99.78% salt rejection, water permeability 0.66 m ³ / m
^The standard deviation value on the ^2nd day was a salt rejection rate of 0.0066%, and a water permeation rate of 0.0102m ³ / m ² · day.

[0030]

[Table 1] Comparative Example 1 In the same manner as in Example 1, except that the 0.1 wt% meta-phenylenediamine aqueous solution was not coated,
As a result of the single reverse osmosis test, the membrane performance as shown in Table 2 was obtained. At this time, the average value is salt exclusion rate: 99.3.
It was 8% and the water permeation rate was 0.81 m ³ / m ² · day. The standard deviation values are as follows: salt rejection rate: 0.071%, water permeation rate: 0.
It was 0403 m ³ / m ² · day.

[0031]

[Table 2] Example 2 In Example 1, 0.05 wt% was used instead of the coating of 0.1 wt% meta-phenylenediamine aqueous solution.
As a result of carrying out in the same manner except that the 1,3,5-triaminobenzene aqueous solution was used, an exclusion rate of 99.7% and a water permeation rate of 0.69 m ³ / m ² · day were obtained.

As shown in the above examples, in the present invention, the salt rejection rate is improved by 0.3% or more and the uniformity of the film is improved as compared with the conventional composite membrane and the method for producing the composite membrane. .

[0033]

Industrial Applicability According to the present invention, a semipermeable composite membrane having an improved salt rejection of 0.3% or more and improved membrane uniformity as compared with the conventional composite membrane and the method for producing the composite membrane is provided. can do.

Claims (9)

(57) [Claims] 1. A semipermeable composite membrane comprising an ultrathin film formed on a microporous support membrane, the first porous membrane having two or more reactive groups in one molecule on the microporous support membrane. And forming a coating of an aqueous solution of the water-soluble compound, and coating the solution of the polyfunctional reactive reagent capable of reacting with the first water-soluble compound on the coating of the aqueous solution to react with the water-soluble compound. possess the polyfunctional reagent solution 2 or more reactive groups in a molecule on the coating, and aromatic amines, aliphatic a
Mins, aliphatic alcohols and aromatic alcohols
A semipermeable composite membrane formed by coating an aqueous solution of a second water-soluble compound selected from the above and reacting with the polyfunctional reaction reagent remaining in the coating of the solution of the polyfunctional reaction reagent. 2. The semipermeable composite membrane according to claim 1, wherein the solvent of the solution of the polyfunctional reaction reagent comprises a solvent immiscible with water. 3. The semipermeable composite membrane according to claim 1, wherein the reactive group contains two or more amino groups. 4. The semipermeable composite membrane according to claim 1, wherein the polyfunctional reaction reagent is an acid halide. 5. A method for producing a semipermeable composite membrane, which comprises forming an ultrathin film on a microporous support membrane, wherein the microporous support membrane has two or more reactive groups in one molecule. 1. Forming a coating of an aqueous solution of a water-soluble compound, and coating a solution of a polyfunctional reactive reagent capable of reacting with the first water-soluble compound on the coating of the aqueous solution to react with the water-soluble compound. further the multi-functional reagent on the coating solution possess two or more reactive groups in a molecule, and aromatic amines,
Aliphatic amines, fatty alcohols and aromatic alcohols
A method for producing a semipermeable composite membrane, which comprises coating an aqueous solution of a second water-soluble compound selected from coals and reacting it with the polyfunctional reaction reagent remaining in the coating of the solution of the polyfunctional reaction reagent. 6. A solvent for a solution of a polyfunctional reaction reagent,
The method for producing a semipermeable composite membrane according to claim 5, wherein a solvent immiscible with water is used. 7. The concentration of the aqueous solution of the second water-soluble compound is
1/100 or more of the concentration of the aqueous solution of the first water-soluble compound 1
The method for producing a semipermeable composite membrane according to claim 5, wherein the range is / 10 or less. 8. The method for producing a semipermeable composite membrane according to claim 5, wherein a compound having a reactive group containing two or more amino groups is used as the first and second water-soluble compounds. 9. The method for producing a semipermeable composite membrane according to claim 5, wherein an acid halide is used as the polyfunctional reaction reagent.