KR101743808B1 - Manufacturing Method of Polyamide-Based Composite Membrane - Google Patents

Abstract

The present invention relates to a process for producing a novel polyamide composite membrane applicable to hydrophobic supports, and has the advantage that the process is simple and the other power such as pressure is not used as compared with the conventional polyamide composite membrane production method.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide-based composite membrane,

The present invention relates to a process for producing a polyamide-based composite membrane.

Reverse osmosis technology is used to separate the dissolved material from the solution by reverse osmosis membrane (reverse osmosis membrane, RO membrane), which has a selective permeability to certain molecules by applying a pressure in excess of osmotic pressure to the solution. Reverse osmosis is therefore used extensively in water treatment where contaminants such as inorganic ions, bacteria, viruses, organic and colloidal substances need to be removed from raw water in order to purify and concentrate the liquid, in particular to obtain fixed wastewater .

The composite membrane is one of the reverse osmosis membranes including a porous support and a polyamide thin layer formed on the support.

Typically, the polyamide layer is formed by interfacial polymerization by immersing the microporous support in a polyfunctional amine aqueous solution, removing the excess solution, and contacting with an organic solution mixed with a polyfunctional acid halide compound [Non-Patent Document 1]

Interfacial polymerization is usually not used for hydrophobic supports because the conventional method of immersing in an aqueous amine solution can not be used. For this reason, polymers such as polyvinylidene fluoride (PVDF) have strong advantages in terms of chemical resistance, heat resistance, mechanical strength, etc., and have excellent advantages as a support in polymerization but they are not used because of hydrophobicity.

M. Mulder, Basic Principles of Membrane Technology Second Edition, Kluwer Academic Pub, 1996. F. Liu, N.A. Hashim, Y. Liu, M. Abed, K. Li, Progress in the production and modification of PVDF membranes, Journal of Membrane Science, 375 (2011) 1-27. Y. Sui, Z. Wang, X. Gao, C. Gao, Antifouling PVDF ultrafiltration membranes incorporating PVDF-PHEMA additive via atom transfer radical graft polymerizations, Journal of Membrane Science, 413

Accordingly, the present inventors have developed a method of forming a polyamide separator by interfacial polymerization by contacting an aqueous amine solution with a microporous support by immersing the microporous support in an organic tri chloride solution to form a polyamide separator by interfacial polymerization on the hydrophobic support Thereby completing the present invention.

Accordingly, the present invention aims to provide a method for producing a polyamide-based composite membrane on a hydrophobic support without complicated method.

As means for solving the above problems,

Immersing a microporous hydrophobic support in an organic solution mixed with a polyfunctional acid halide compound and then contacting a polyfunctional amine aqueous solution on the support to form a polyamide separation membrane by interfacial polymerization;

Based on the total weight of the polyamide-based composite membrane.

As another means for solving the above problems, the present invention provides a polyamide-based composite membrane produced by the above method.

As another means for solving the above problems, the present invention provides a nanofiltration (NF) membrane and / or a reverse osmosis (RO) membrane using a polyamide-based composite membrane produced by the above method.

The method of producing a polyamide composite membrane according to the present invention is advantageous compared with the existing method in which a polyamide separator is formed by interfacial polymerization by immersing a microporous support in an amine aqueous solution and then removing an excess solution and contacting the solution with an organic trichloride solution The process is simple and it is possible to manufacture without using any other forces such as pressure (contacting the amine aqueous solution without excess solution removal step).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view briefly showing a process for producing a polyamide composite membrane according to the present invention. FIG.
Fig. 2 shows FTIR results of the polyamide-based reverse osmosis composite membrane prepared in Example 1. Fig.
3 is an SEM photograph of the polyamide-based composite membrane prepared in Example 1. Fig.
FIG. 4 shows the removal rate and flux of 5000 ppm NaCl according to the reaction time of the polyamide composite membrane prepared in Example 1. FIG.
5 shows an apparatus for measuring NaCl removal rate and flux.

The present invention relates to a method for producing a polyamide-polyamide composite membrane, which comprises immersing a microporous hydrophobic support in an organic solution mixed with a polyfunctional acid halide compound, and then contacting a polyfunctional amine aqueous solution on the support to form a polyamide separation membrane by interfacial polymerization Based composite membrane.

The term " microporous support " as used herein refers to a support having a microporous structure. In particular, the support should have a pore size sufficient for permeation of permeated water. In order to function as a support, 500 nm. Pores larger than 500 nm can be expressed as defects in the final composite membrane due to depression during thin film formation. If it is less than 1 nm, the permeation flow rate is undesirably decreased.

First, a microporous hydrophobic support is prepared to prepare a polyamide composite membrane.

A hydrophobic polymer solution is applied on the nonwoven fabric to form a porous hydrophobic support layer. The application may be performed by casting, coating, or dipping, but is not limited thereto.

The nonwoven fabric is not particularly limited as long as the nonwoven fabric is generally a support for the membrane, but more preferably synthetic fibers selected from the group consisting of polyester, polypropylene, nylon and polyethylene; Or a cellulose-based natural fiber can be used. Such a nonwoven fabric can control the physical properties of the membrane according to porosity and hydrophilicity of the material. The thickness of the hydrophobic polymer layer in the nonwoven fabric is preferably in the range of 20 to 200 占 퐉. If the thickness of the hydrophobic polymer layer is less than 20 占 퐉, the strength and supportability of the entire membrane is insufficient.

The solvent for forming the polymer solution is not particularly limited as long as it can dissolve the polymer uniformly without forming precipitates, but is more preferably selected from the group consisting of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) Dimethylsulfoxide (DMSO) or dimethylacetamide (DMAc), or the like.

If the temperature is lower than 20 ° C, the polymer may not be dissolved and the membrane may not be produced. If the temperature is higher than 90 ° C, the viscosity of the polymer solution may become too thin, and thus the membrane may be difficult to produce .

The polymer forming the hydrophobic polymer solution is not particularly limited as long as it is a hydrophobic polymer capable of forming a polyamide-based composite membrane, but is more preferably polyvinylidene fluoride, polyisocyanate, polysulfone, polytetrafluoroethylene And polyethylene.

The polymer solution may preferably contain 7 to 35% by weight of the polymer. If the content of the polymeric substance is less than 7% by weight, the strength is lowered and the solution viscosity is low. Thus, the film is difficult to manufacture and has a problem. When it exceeds 35% by weight, the concentration of the polymer solution is too high.

Next, the microporous hydrophobic support prepared above is immersed in an organic solution mixed with a polyfunctional acid halide compound.

The polyfunctional acid halide compound reacts with the polyfunctional amine used in forming the polyamide layer of the present invention, and refers to a polyfunctional acyl halide. The polyfunctional acyl halide can be used alone or in a mixture of, for example, trimesoyl chloride, isophthaloyl chloride, terephthaloyl chloride, and the like. At this time, the use of the mixed form is most preferable in terms of the salt removal rate. The polyfunctional acyl halide may be dissolved in an aliphatic hydrocarbon solvent in an amount of 0.01 to 2% by weight, wherein the aliphatic hydrocarbon solvent is a mixture of n-alkanes having 5 to 12 carbon atoms and structural isomers of saturated or unsaturated hydrocarbons having 8 carbon atoms It is preferable to use a cyclic hydrocarbon having 5 to 7 carbon atoms. The polyfunctional acyl halide-containing solution preferably dissolves 0.01 to 2% by weight, more preferably 0.05 to 0.5% by weight, of the polyfunctional acyl halide in the aliphatic hydrocarbon solvent.

The time for immersing the support in the organic solution is preferably from 30 seconds to 5 minutes since it is a sufficient time for the organic solution to wet the support.

After the immersion, the organic solvent is directly contacted with the aqueous solution of the polyfunctional amine on the surface without directly removing the excessive organic solvent, so that the organic solvent is floated in the aqueous solution. Thus, polyamide formation and excess organic solvent Is performed at once.

The polyfunctional amine may be a polyamine having 2 to 3 amine functional groups per monomer and containing a primary amine or a secondary amine. Examples of the polyamines include aromatic primary diamines; Aromatic tertiary amine; Aliphatic primary diamine; Cycloaliphatic primary diamine; And cycloaliphatic secondary amine, and the aromatic primary diamine is m-phenylenediamine or paraphenylenediamine, and the aromatic primary amine is 1,3,5-triaminobenzene ego; The aliphatic primary diamine is ethylenediamine or propylenediamine; The cycloaliphatic primary diamine is cyclohexanediamine; The cycloaliphatic secondary amine may be piperazine and the like. More preferably, the polyfunctional amine is selected from the group consisting of metaphenylenediamine, and the concentration thereof is preferably in the form of an aqueous solution containing 0.5 to 10 wt% of metaphenylenediamine, more preferably 1 to 4 wt% % May be contained.

Further, the pH of the polyfunctional amine aqueous solution has a range of 7 to 13, and can be adjusted by adding 0.001 to 5% by weight of acid and base. In the acidic condition below pH 7, the polyfunctional amine is combined with the hydrogen ion to deteriorate the reactivity, which is undesirable. In strong base conditions exceeding pH 13, the acyl halide compound of the organic solution is hydrolyzed during the interfacial polymerization, As a result, the salt removal rate is low, which is not desirable. Examples of such acids and bases include hydroxides, carboxylates, carbonates, borates, phosphates of alkyl metals, trialkylamines, and the like. In addition, a basic acid such as caustic soda, calcium oxide, or magnesium oxide which can neutralize the acid (HCl) generated during the interfacial polymerization may be added to the aqueous solution of the polyfunctional amine, and dimethylsulfoxide (DMSO) A polar solvent, an amine salt, a polyfunctional tertiary amine, and the like may be added. As another additive, 2-ethyl-1,3-hexanediol, sodium dodecyl sulfate, dodecylammonium bromide and the like having a surfactant activity are added to prepare a polyamide-based composite membrane, To be uniformly applied to the surface of the substrate.

Also, a polyfunctional amine aqueous solution is brought into contact with the support for about 10 seconds to 3 minutes or 20 seconds to 1 minute to form a polyamide separation membrane by interfacial polymerization. If the contact time is less than 10 seconds, the interfacial polymerization reaction does not occur properly and a separation membrane is not formed. If the contact time exceeds 3 minutes, the polyamide layer becomes too thick and the flux and the removal rate are lowered . The contact may be carried out by, for example, a dipping method, a coating method, a spraying method, or the like, which is well known in the art, but is not limited thereto.

The support is then immersed in distilled water to remove residual aqueous polyfunctional amine. At this time, it is preferable to soak for 1 to 5 minutes.

This method not only facilitates the interfacial polymerization of polyamides on the hydrophobic support, but also removes the excess portion of the organic solvent remaining on the support, which is the most problematic in the interfacial polymerization using the hydrophobic support, after the interfacial polymerization is completed There is an advantage that the polyamide is formed without any drawbacks.

In addition, the polyamide-based composite membrane produced by this method can be used as a nanofiltration membrane or a reverse osmosis membrane because it can remove monovalent salts (removal rate of 88% or more) with a small particle size.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited by the following examples.

[ Example ]

Manufacturing example  1: Material preparation

The polymer concentration of the PVDF / DMAc solution was fixed at 13 wt% to prepare a PVDF support with a pore size of 50 nm. The polymer was prepared by casting 5 g of the polyester nonwoven fabric and then casting (thickness: 50 to 150 μm).

An organic solution in which TMC was mixed was prepared using 0.3 wt% of trimethoyl chloride (TMC) with heptane as a solvent. Heptane, which usually uses hexane as a solvent but is less evaporated due to the evaporative nature of organic solvents, was used.

The concentration of metaphenylenediamine (MPD), which is a polyfunctional amine aqueous solution, was 2 wt%.

0.05 wt% of NaOH was added to the MPD solution to neutralize the HCl generated by NH ₂ of the polyfunctional amine and Cl of the trimethoyl chloride reacted with NH + HCl.

Example  One: Polyamide series Composite membrane  Produce

A solution prepared by dissolving PVDF 13% in a solvent DMAc was cast on a PE support, immersed in water for 6 hours, and then taken out and dried to prepare a polymer scaffold.

TMC was precipitated in the polymer support in an organic solution containing 0.3 wt% of heptane. After immersing the substrate for 60 seconds on a glass plate, a solution of 2 wt% of MPD and 0.05 wt% of sodium hydroxide dissolved in distilled water was poured directly onto the surface of the polymer scaffold. After 20 seconds of reaction, the reaction mixture was taken out and precipitated in distilled water for 5 minutes. Unreacted MPD was diffused and removed, followed by drying.

Comparative Example  One: Polyamide series Composite membrane  Produce

PVDF was dissolved in a solution of DMF and acetone in a volume ratio of 6: 4 at 50 ° C. A support was prepared by electrospinning at a current of 13 kV using a 0.3 mm cylinder with an internal diameter of 50 urn and a spinning distance of 15 cm.

The support thus prepared was precipitated in an aqueous solution of piperazine and wetted with pressure. An excess amount of pyrazine aqueous solution on the surface was removed for 3 minutes, then precipitated in an organic solution of trimesoyl chloride for 1 minute and then dried at room temperature for 12 hours.

Comparative Example  2: Polyamide series Composite membrane  Produce

PVDF was dissolved in a solution of DMF and acetone in a volume ratio of 6: 4 at 50 ° C. A support was prepared by electrospinning at a current of 13 kV using a 0.3 mm cylinder with an internal diameter of 50 urn and a spinning distance of 15 cm.

The support thus prepared was soaked in a mixture of water and ethanol in a volume ratio of 2: 3 by volume for 4 minutes. An aqueous solution of piperazine mixed with excess water and ethanol on the surface was removed for 3 minutes, then precipitated in an organic solution of trimesoyl chloride for 1 minute and then dried at room temperature for 12 hours.

Comparative Example  3: Polyamide series Composite membrane  Produce

PVDF was dissolved in a solution of DMF and acetone in a volume ratio of 6: 4 at 50 ° C. A support was prepared by electrospinning at a current of 13 kV using a 0.3 mm cylinder with an internal diameter of 50 urn and a spinning distance of 15 cm.

The support thus prepared was soaked in the organic solution of trimesoyl chloride for 4 minutes. Excess trimethoyl chloride organic solution on the surface was removed for 5 seconds and then precipitated in aqueous piperazine solution for 1 minute. And dried at room temperature for 12 hours.

Experimental Example  One: Polyamide series Composite membrane  Check property

Example 1 of the polyamide composite membrane using the FTIR C = O peak at 1660 cm ^-1, it was confirmed the NH peak at 1547 cm ^-1. As a result, it was confirmed that PA (polyamide) was formed by the inverse interfacial polymerization method of the present invention (Fig. 2).

In addition, it was confirmed by SEM photograph that PA was formed on the polyamide composite membrane of Example 1 (Fig. 3).

The removal rate and flux of NaCl at a concentration of 5000 ppm according to the reaction time at a pressure of 30 atmospheric temperature of 25 ° C are shown in Table 1 and FIG.

The NaCl flux was measured over time using the apparatus of FIG. 5 and the NaCl removal rate was measured by measuring the NaCl concentration of the filtered water.

NaCl removal rate and flux Reaction time Removal rate (%) Flux (LMH) 10 90.64 24.67 20 92.06 25.81 30 91.02 25.13 40 90.54 24.81 60 90.01 22.37 80 89.75 20.32 100 88.82 17.66

As shown in Table 1, it was confirmed that the polyamide-based composite membrane of Example 1 had an excellent removal rate of NaCl with a very small particle size. This means that it can be used as a nanofiltration membrane or a reverse osmosis membrane because it can remove more than 90% of monovalent salts.

The polyamide based composite membranes prepared in Comparative Examples 1 to 3 were found to be capable of removing BSA (bovine serum albumin) having a larger particle size without removing NaCl having a small particle size as in the present invention. The BSA removal rate and flux 2 (Role of wettability in interfacial polymerization based on PVDF electrospun nanofibrous scaffolds, Journal of Membrane Science 442 (2013) 124-130).

division Comparative Example 1 Comparative Example 2 Comparative Example 3 BSA removal rate (%) - 93 98 Flux (LMH) - 40 66

BSA is usually not used when testing the performance of nanofiltration membranes or reverse osmosis membranes because the particles are too large. Therefore, the polyamide-based composite membranes prepared in Comparative Examples 1 to 3 can not be used as nanofiltration membranes or reverse osmosis membranes.

Claims (16)

Immersing a microporous hydrophobic support made of polyvinylidene fluoride in an organic solution mixed with a polyfunctional acid halide compound and then contacting a polyfunctional amine aqueous solution on the support to form a polyamide separation membrane by interfacial polymerization;
Based composite film.
delete The method according to claim 1,
Wherein the microporous hydrophobic support has a pore size of 1 to 500 nm.
The method according to claim 1,
Wherein the polyfunctional acid halide compound is a polyfunctional acyl halide.
5. The method of claim 4,
Wherein the polyfunctional acyl halide is at least one selected from the group consisting of trimesoyl chloride, isophthaloyl chloride and terephthaloyl chloride.
The method according to claim 1,
Wherein the organic solution in which the polyfunctional acid halide compound is mixed is a solution in which the polyfunctional acid halide compound is dissolved in an aliphatic hydrocarbon solvent.
The method according to claim 1,
And immersing the membrane in the organic solution for 30 seconds to 5 minutes.
The method according to claim 1,
Wherein the polyfunctional amine is a polyamine having a primary amine or secondary amine as a material having 2 to 3 amine functional groups per monomer.
The method according to claim 1,
The polyfunctional amine is an aromatic primary diamine; Aromatic tertiary amine; Aliphatic primary diamine; Cycloaliphatic primary diamine; And a cycloaliphatic secondary amine, in the presence of a catalyst.
10. The method of claim 9,
Wherein the aromatic primary diamine is m-phenylenediamine or p-phenylenediamine, the aromatic primary-triamine is 1,3,5-trinaminobenzene; The aliphatic primary diamine is ethylenediamine or propylenediamine; The cycloaliphatic primary diamine is cyclohexanediamine; Wherein the cycloaliphatic secondary amine is piperazine.
The method according to claim 1,
Wherein the polyfunctional amine aqueous solution is contacted for 10 seconds to 3 minutes.
The method according to claim 1,
After the formation of the separation membrane, washing with distilled water is further carried out.
A polyamide based composite membrane formed by interfacial polymerization by immersing an organic solution in which a polyfunctional acid halide compound is mixed with a microporous hydrophobic support made of polyvinylidene fluoride and bringing the aqueous solution of the polyfunctional amine into contact.
14. The method of claim 13,
A polyamide composite membrane capable of removing monovalent salts.
A nanofiltration membrane using the composite membrane according to claim 13.
A reverse osmosis membrane using the composite membrane according to claim 13.

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