KR0123279B1 - Method for semipermeable composite membrane - Google Patents

Abstract

A complex semi-permeable membrane having an excellent salt removing function comprising the step adding 0.05~3wt% sulfonyl isophthatic chloride, isophthalic chloride, terephthalic chloride, 1,3,5-benzentricarbonylchloride or 5-chlorosufonyl isophthalic chloride of the mixed closslinker solution which is non-compound with water as polyfunctional crosslinker to normal hexane, cyclo hexane, heptane, octane, the step preparing the first crosslinker, the first crosslinking soluble polyfunctional amine therewith on the porous substrate to form the first of the semi-permeable active layer on porous substrate, and the step crosslinking non-reactive soluble polyfunctional amine with the second mixed crosslinker solution which is non-compound with the salt as polyfunctional amine to form a double active layer for forming the second semi-permeable active layer is disclosed.

Description

Composite semipermeable membrane with excellent salt removal ability and its manufacturing method

The figure is a sectional view of two types of composite semipermeable membranes produced by the present invention.

* Explanation of symbols for main parts of the drawings

1: porous support membrane 2: primary active layer

3: intermediate layer 4: secondary active layer

The present invention relates to a method for producing a composite semipermeable membrane, and more particularly to a method for producing a composite semipermeable membrane having excellent salt removal rate.

Currently, the semi-permeable membrane is S. S. Loed and S. Since the development of the cellulose acetate semipermeable membrane (US Pat. No. 3,133,132) having an asymmetric structure by S. Sourirajan, it has been widely used industrially, and has been widely used industrially, especially low molecular weight such as solution, emulsion and suspension. Membrane treatment techniques using semipermeable membranes have been widely used for the purpose of separating specific components in a mixture. However, semi-permeable membranes based on cellulose acetate such as Loed-Sourirajan type cellulose acetate and cellulose nitrate have problems with hydrolysis resistance, microbial resistance, and chemical resistance. In order to improve the permeability, a combination of pressure resistance and durability has to be manufactured, and some of them are used, but most of them are not practical for a wide range of uses.

In order to secure the shortcomings of the cellulose-based asymmetric membrane, various studies have been conducted in the United States or Japan, such as aromatic polyamide, polyamide hydrazide (US Pat. No. 3,567,632), polyamic acid (Japanese Patent 52-152879), crosslinked poly Although some materials, such as amic acid, polybenzimidazole, and polybenzimidazolone, were able to compensate for some disadvantages such as chemical resistance and microbial resistance, they could be obtained, but other problems that could not reach the cellulose acetate membrane in terms of selective permeability were generated. .

In addition, in a semipermeable membrane having a different form from a cellulose-based membrane, a composite membrane is developed in which an ultra-thin active layer is coated on a porous support which can substantially influence the performance of the membrane. In such composite membranes, an intermediate layer may be introduced onto the porous support membrane, and then the active layer of the ultrathin membrane may be covered, and there may be two cases in which the active layer is directly coated on the porous support. Such a composite membrane is capable of selecting an active layer and a support layer as an optimal material for each use, and has an advantage of being able to be stored in a dry state, unlike the cellulose acetate-based membrane, which should always be stored in a wet state. However, such a composite membrane has a limit in obtaining very high salt removal rate because the active layer having solute removal ability is very thin with a thickness of several tens of nanometers (nm) or less, but there is a slight damage to the active layer during elementization after film formation. In this case, the damage acts as a pinhole, so that the solute removal ability is fatally reduced, and the demineralization rate decreases again. Also, after forming the active layer, a technique of recoating the active layer with a material such as polyvinyl alcohol has been developed, but this is not intended to increase the salt removal rate, but merely to maintain the salt removal rate obtained as a protective layer protecting the active layer. Purpose.

In the technical background as described above, the present invention has been made to solve the problems of the prior art, and the object of the present invention is to provide a composite semipermeable membrane having excellent salt removal rate and excellent properties such as chemical resistance and microbial resistance, and a method of manufacturing the same. Have

In order to achieve the above object, the present invention provides a composite semipermeable membrane coated with an active layer that can substantially influence the performance of a membrane on a porous support, wherein the active layer is a mixture of a mixed crosslinker solution that is immiscible with water of the polyfunctional crosslinking agent. A semipermeable primary active layer (2) formed on the porous support (1) by the crosslinking reaction of the primary crosslinking agent and the water-soluble polyfunctional amine; The unreacted water-soluble polyfunctional amine remaining in the primary active layer 2 is semi-permeable secondary active layer formed on the primary active layer 2 by crosslinking again with the secondary crosslinking agent of the mixed crosslinking agent solution immiscible with water of the polyfunctional crosslinking agent. It provides a composite semipermeable membrane, characterized in that (4).

In addition, the present invention provides an intermediate layer (3) in which an unreacted water-soluble polyfunctional amine which does not react with the primary and secondary polyfunctional crosslinking agents between the primary active layer (2) and the secondary active layer (4) is always crosslinked. It provides a composite semipermeable membrane having the formed structure.

In the present invention, the porous support membrane may be polysulfone, polyethersulfone, polyvinyl chloride, polyamide, polyester, polycarbonate, etc., but because of excellent physical and chemical properties, polysulfone or polyethersulfone material Asymmetric porous membranes are preferred, and their preparation is shown in US Pat. No. 3,926,798 and US Pat. No. 3,615,627.

In addition, although the surface structure of the porous support membrane finally depends on the use of the membrane, it is preferable to have a pore size of 0.1 to 0.2 μm, more preferably, having a pore size of about 0.01 to 0.5 μm.

In the present invention, the multifunctional crosslinking agent is one or a mixture of two or more of the group consisting of 5-chlorosulfonyl isophthalic chloride, isophthalic chloride, terephthalic chloride, 1,3,5-benzenetricarbonyl chloride, The kind used for the first crosslinking reaction and the kind of the crosslinking agent used for the second crosslinking reaction may be the same or different, but the same kind is more preferable.

In the present invention, as the solvent for the multifunctional crosslinking agent, alkanes having 6 to 8 carbon atoms, such as normal hexane, cyclohexane, heptane, and octane, are preferred as organic solvents in the range of not dissolving the porous support membrane.

In addition, the water-soluble polyfunctional amine can be obtained as a polymer of ethylene imine as a polyetherene amine, and the distribution of amine groups is about 30% of primary amines, 40% of secondary amines, and 30% of tertiary amines, and has a molecular weight of 300 Although it is -100,000, in practice, the molecular weight of about 10,000-60,000 is suitable.

The intermediate layer 3 formed between the primary active layer 2 and the secondary active layer 4 smoothes the flow through the primary active layer 2 and strengthens the pressure resistance of the primary active layer 2.

The composite semipermeable membrane according to the present invention has excellent properties of permeation rate of 18 gpd or less and salt removal rate of 99% or more when the aqueous solution containing 35000 ppm NaCl at 1500 psi is permeated.

In order to obtain the composite semipermeable membrane according to the present invention, the present invention also provides a primary crosslinking reaction on a water-soluble polyfunctional amine and a porous support (1) by using a mixed crosslinking agent solution that is incompatible with water of the multifunctional crosslinking agent as the primary crosslinking agent. To form a semipermeable primary active layer (2) on the porous support, and the remaining unreacted water-soluble polyfunctional amine is further crosslinked with a solution of a second mixed crosslinker which is incompatible with water of the polyfunctional crosslinker. Provided is a method for producing a composite semipermeable membrane, wherein the double active layer forming the semipermeable secondary active layer 4 is formed.

In the present invention, the porous support membrane to be used may be polysulfone, polyethersulfone, polyvinyl chloride, polyamide, polyester or polycarbonate, and particularly preferably polysulfone having excellent physical and chemical properties. Or asymmetric porous membranes of polyester sulfone materials are preferred.

Asymmetric porous membranes of these polysulfone or polyester sulfone materials can be readily prepared by known methods disclosed in, for example, US Pat. Nos. 3,926,798 and 3,615,526.

For example, the polysulfone porous membrane can be easily manufactured by the following method.

In other words, after fixing the polyethylene terephthalate nonwoven fabric on a glass plate, a 15% by weight dimethylformamide solution of polysulfone was cast at room temperature in a thickness of 200 µm, and left for 5 minutes in 25 ° C pure water, followed by drying at 60 ° C for 12 hours. Polysulfone porous membranes reinforced with nonwoven fabrics are readily manufactured.

In addition, although the surface structure of the porous support membrane finally depends on the use of the membrane, it is preferable to have a pour size of about 0.01 to 0.5 mu m, more preferably 0.1 to 0.2 mu m.

A pore size of 0.5 μm or more is not desirable because it is difficult to withstand the physical properties as a support, and a pore size of 0.01 μm or less not only serves to limit the porosity of the final composite membrane and to lower permeate flow rate, It is not preferable because clogging may occur.

The polyfunctional crosslinking agent may be 5-chlorosulfonyl isophthalic chloride, isophthalic chloride, terephthalic chloride, 1,3,5-benzenetricarbonyl chloride, and the like. As a mixed crosslinking agent, 5-chlorosulfonyl isophthalic chloride and Isophthalic chloride can be used in a mixture. Most preferably, the mixture is used in a weight ratio of 3: 7 to 5: 5. Although the secondary polyfunctional crosslinking agent used for a secondary crosslinking reaction can use a different kind from the thing used for a primary crosslinking reaction, it is more preferable to use the same kind.

Normal hexane, cyclohexane, heptane, octane, etc. can be used for selecting the solvent of the polyfunctional crosslinking agent solution used for this invention from what cannot support | dissolve a support membrane. The content of the crosslinking agent in the solution is preferably 0.05 to 3% by weight, preferably 0.1 to 2% by weight.

As a method of applying the polyfunctional crosslinking agent solution onto the porous support, a deposition method, a casting method, a spray method, or the like may be used.

The water-soluble polyfunctional amine used in the present invention can be obtained as a polymer of ethylimine as polyethyleneimine, and it is known that the distribution of amine groups is approximately 30% primary amine, 40% secondary amine and 30% tertiary amine. . Although the molecular weight range suitable for the range of water-soluble polymer in composite film forming is known as about 300-100,000, it is preferable to use the thing of the molecular weight range of about 10,000-60,000 actually.

The solvent used to prepare the water-soluble polyfunctional amine solution may be water, ethanol, methanol or the like or a mixture thereof, but water is most suitable for the purposes of the present invention, the concentration of the water-soluble polyfunctional amine in the solution is 0.05 to 5% by weight. %, Preferably 0.2 to 2% by weight may be used.

Hydrogen halide generated in the reaction between the polyfunctional crosslinking agent and the water-soluble polyfunctional amine may be a water-soluble polyfunctional amine triethylamine or the like. Such a reaction accelerator (hydrogen halide acceptor) may be added directly to the aqueous aqueous polyfunctional amine solution before the crosslinking reaction or by a separate process after the crosslinking reaction.

Although the crosslinking reaction proceeds slowly even at low temperatures, it is preferable to perform drying and heat treatment in order to obtain good crosslinking density. Particularly, after the second crosslinking reaction, heat treatment is more effective. Heat treatment conditions are in the range of 30 to 150 ° C, more preferably in the range of 60 to 130 ° C. The heat treatment time is preferably 1 to 60 minutes, preferably about 5 to 30 minutes.

In the above heat treatment, the primary active layer formed by the primary crosslinking reaction between the primary polyfunctional crosslinking agent and the water-soluble polyfunctional amine, and the second polyfunctional crosslinking agent with the secondary polyfunctional crosslinking agent unreacted during the first crosslinking reaction An intermediate layer is formed between the primary active layer and the secondary active layer by self-crosslinking the unreacted water-soluble polyfunctional amine that does not react with the primary and secondary polyfunctional crosslinking agents between the secondary active layers formed by the primary crosslinking reaction. This intermediate layer facilitates the flow of permeated water through the primary active layer between the primary active layer and the secondary active layer and enhances the pressure resistance of the primary active layer.

In the following, preferred embodiments of the present invention are provided to make the present invention easier to understand. However, the present invention is not limited to these examples.

[Reference Example]

[Production of Porous Support Membrane]

The polyethylene terephthalate nonwoven fabric was fixed on the glass plate to obtain a porous support membrane. Next, a 15% by weight dimethylformamide solution of polysulfone (Udel P-3500) dimethylformamide was cast on the nonwoven fabric at a thickness of 200 µm at room temperature, and left for 5 minutes in 25 ° C pure water, followed by drying at 60 ° C for 12 hours. Reinforced polysulfone porous membranes were prepared.

Example 1

The nonwoven fabric-reinforced polysulfone porous membrane prepared in the reference example was reacted for 30 seconds at room temperature with a hexane solution containing 5-chlorosulfonyl isophthalic chloride and isophthalic chloride at a ratio of 5/5 by weight of 5/5, and then taken out. Next, the membrane treated with the polyfunctional crosslinking agent was immersed in a 1% by weight aqueous solution of polyethyleneimine (manufactured by Aldrich) having a molecular weight of 50,000 to 60,000 at room temperature for 60 seconds, and the membrane was taken out and dried for 10 minutes in a vertical state to remove excess polyethyleneimine. , 5-chlorosulfonyl isophthalic chloride mixture was immersed in a hexane solution containing 0.125% by weight (weight ratio 5/5) for 30 seconds and then taken out and heat-treated in an oven at 120 ℃ 5 to prepare a selective permeable composite semipermeable membrane.

Example 2-5

In Example 1, the composite semipermeable membrane was prepared by changing the concentration of the primary and secondary polyfunctional crosslinking agents and the mixing ratio between the crosslinking agents and changing the concentration of polyethyleneimine in the aqueous polyethyleneimine solution.

Comparative Example 1

The primary crosslinking reaction was omitted and only the second crosslinking reaction was carried out to the support membrane prepared in the above reference example. First, the support membrane was immersed for 60 seconds in an aqueous solution of 1% by weight of polyethyleneimine at room temperature, and then taken out and dried for 10 minutes in a vertical state. Excess polyethyleneimine was removed, and the hexane solution containing 0.250 wt% (weight ratio 5/5) of 5-chlorosulfonyl isophthalic chloride and isophthalic chloride mixture was immersed for 30 seconds, then taken out and heat-treated in an oven at 120 ° C. for 5 minutes. The selective permeable composite semipermeable membrane in which only the secondary active layer was formed was prepared.

Hereinafter, the results of measuring the permeation rate and salt removal rate of the selective permeable semipermeable membrane obtained in Examples according to the present invention by passing an aqueous solution containing 35000 ppm NaCl through the semipermeable membrane at 1500 psi are shown in the table.

As shown in the above table, the salt removal rate of the composite semipermeable membrane prepared according to the present invention has a high permeation rate. The composite semipermeable membrane prepared by the present invention also has high pressure resistance that does not rupture at a high pressure of 1500 psi or more, and thus may be usefully used as a salt separation membrane such as a reverse osmosis water purification treatment apparatus or a desalination apparatus requiring ultra high pressure conditions.

Claims (6)

5-chlorosulfonyl isophthalic chloride, isophthalic chloride, terephthalic chloride, 1,3,5-benzenetricarbonyl chloride or 5-chlorosulfonyl isophthalic chloride as a mixed crosslinker solution incompatible with water of the polyfunctional crosslinker And isophthalic chloride was added to 0.05 to 3% by weight in normal hexane, cyclohexane, heptane and octane to prepare a primary crosslinking agent, which was subjected to the primary crosslinking reaction on the water-soluble polyfunctional amine and the porous support (1). Forming a semi-permeable primary active layer (2) and secondarily crosslinking the remaining unreacted water-soluble polyfunctional amine with a secondary mixed crosslinker solution which is immiscible with water of the polyfunctional crosslinker to form a secondary active layer (4). A method for producing a composite semipermeable membrane, comprising forming a double active layer. The method of claim 1, wherein the mixing ratio of 5-chlorosulfonyl isophthalic chloride and isophthalic chloride in the primary crosslinking agent is weight ratio 3: 7 to 5: 5. The method of claim 1 wherein the concentration of the water soluble polyfunctional amine in the water soluble polyfunctional amine solution is 0.05 to 5% by weight. The method of claim 1 or 3, wherein the solvent of the water-soluble polyfunctional amine solution is water, methanol, ethanol alone or a mixture thereof. The rice process according to claim 1, wherein heat treatment is performed after the second crosslinking reaction. The method of claim 5, wherein the heat treatment is performed for 1 to 60 minutes at 30 to 150 ℃.