KR101929992B1 - Porous support for pressure retarded osmosis process, thin-film composite membrane containing the same and preparation method thereof - Google Patents

Abstract

TECHNICAL FIELD [0001] The present invention relates to a porous support for pressure delayed osmosis, an ultra-thin composite membrane comprising the same, and a method for producing the same, which comprises forming a porous support using a thermally converting poly (benzoxazole- imide) copolymer, The present invention relates to a technique for preparing a composite membrane including an active layer and applying it to a pressure delayed osmosis process.
The thin, porous, heat-converted poly (benzoxazole-imide) copolymer support prepared according to the present invention and the ultra-thin composite membrane comprising the same have excellent thermal and chemical stability and mechanical properties, But it can be applied to a pressure delay osmosis process or a positive osmosis process since the internal concentration polarization can be minimized to obtain a high water permeability and accordingly a high power density.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous support for pressure-delayed osmosis processes, an ultra-thin composite membrane including the porous support, and a method of manufacturing the same.

TECHNICAL FIELD [0001] The present invention relates to a porous support for pressure-delayed osmosis, an ultra-thin composite membrane comprising the same, and a method of manufacturing the same. More particularly, the present invention relates to a porous support for pressure- The present invention relates to a technique of preparing a composite membrane including a thin film active layer on a support and applying it to a pressure delayed osmosis process.

In recent years, salinity power generation which produces energy using osmotic pressure of sea water has been attracting attention, and studies on pressure retarded osmosis process have been actively carried out. The pressure-delayed osmosis process is a process in which the osmotic pressure difference of two solutions having a difference in salinity is used as a driving force to apply a pressure lower than the osmotic pressure to the opposite direction of the osmotic phenomenon through the separation membrane to delay water flow in the osmotic direction, It is a way to produce electricity.

As the separation membrane for the pressure delay osmosis process, a flat membrane or a hollow fiber membrane is a mainstream. Generally, a porous support of polysulfone (PS) or polyethylene terephthalate (PET) based on 100 to 200 탆 thickness and a polyamide PA) -based thin-film active layer (Patent Document 1).

However, in the conventional pressure-delayed osmosis membrane, when the water is permeated through the membrane, the concentration of the salt in the inlet solution is increased by increasing the salinity concentration at the interface between the active layer and the support, The density difference as a driving force of water permeability is reduced as a result, and ultimately the water permeability is lowered and the power density is lowered. As a result, it is recognized that the thickness of the support is as thick as 100 to 200 탆. In addition, the membrane used in the pressure-delayed osmosis process must be able to withstand high operating pressures, so that mechanical properties including thermal and chemical stability should be excellent.

On the other hand, attempts have been made to apply stiff glassy wholly aromatic organic polymers such as polybenzoxazole, polybenzimidazole, or polybenzthiazole, which have excellent thermal and chemical stability and mechanical properties, as gas separation membranes, It is difficult to prepare a film by a simple and practical solvent casting method because it is insoluble in an organic solvent. Therefore, the present inventors have recently found that the permeability of carbon dioxide is higher than that of conventional polybenzoxazole membranes prepared by the solvent casting method by preparing polybenzoxazole membranes by a method of converting polyimide having hydroxy groups at orthosial positions into heat, 100 times higher than that of the prior art (Non-Patent Document 1).

Accordingly, the inventors of the present invention have conducted studies to expand application fields of thermally-converting poly (benzoxazole-imide) copolymer films having excellent thermal and chemical stability and mechanical properties. As a result, they have found that heat- The present invention has been completed based on the fact that it is possible to form an ultra thin film composite membrane by forming a copolymer film on a porous support and forming a thin film active layer on the porous support, .

Patent Document 1 Korean Patent Publication No. 10-1391654

Non-Patent Document 1 Y.M. Lee et al., Science 318, 254-258 (2007)

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a polymer electrolyte membrane which is excellent in thermal and chemical stability and mechanical properties and can withstand high operating pressure, A porous support for a pressure-delayed osmosis process having a high porosity, an ultra-thin composite membrane including the porous support, and a method for producing the same.

In order to achieve the above object, the present invention provides a porous heat-converted poly (benzoxazole-imide) copolymer support for a pressure-delayed osmosis process having a repeating unit represented by the following formula (1).

≪ Formula 1 >

(Wherein Ar ₁ is an aromatic ring group selected from a substituted or unsubstituted quadrivalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted quadrivalent heterocyclic group having 4 to 24 carbon atoms, O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _p (1 ≦ _P ≦ ₁₀ ), or two or more of them form a condensed ring; ), (CF ₂ ) _q ( ₁ ? _Q ? 10), C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or CO-

Ar ₂ is an aromatic ring group selected from a substituted or unsubstituted divalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted divalent heterocyclic group having 4 to 24 carbon atoms and the aromatic ring group is present alone; Two or more of them form a condensed ring with each other; Two or more single bond, O, S, CO, SO 2, Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C _{(CH 3) 2, C (} CF 3) is connected to ₂ or CO-NH,

Q is a single bond; _{O, S, CO, SO 2} , Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C (CH 3) 2, C _{(CF 3) 2, CO-} NH, C (CH 3) (CF 3), or a substituted or unsubstituted phenylene ring, x, y is 0.1≤x≤0.9, 0.1≤y≤ a molar fraction within each repeating unit 0.9, x + y = 1)

In the above formula (1), Ar ₁ is any one selected from the following formulas.

Wherein X ₁ , X ₂ , X ₃ and X ₄ are the same or different and each independently represents O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _{p ), (CF 2) q (} 1≤q≤10), C (CH 3) 2, C (CF 3) 2, or a CO-NH, W ₁ and W ₂ are the same or different, and independently O , S, or CO and Z ₁ is O, S, CR ₁ R ₂ or NR ₃ wherein R ₁ , R ₂ and R ₃ are the same or different and each independently is hydrogen or an alkyl group having 1 to 5 carbon atoms , Z ₂ and Z ₃ are the same or different and are each independently N or CR ₄ (R ₄ is hydrogen or an alkyl group having 1 to 5 carbon atoms) or is not CR ₄ at the same time.

And Ar < _{1 >} is any one selected from the following formulas.

In the formula (1), Ar ₂ is any one selected from the following formulas.

Wherein X _1, X _2, X ₃ and X ₄ are the same or different, each independently represent _{O, S, CO, SO 2} , Si (CH 3) 2, (CH 2) p (1 = p = 10 _{), (CF 2) q (} 1 = q = 10), C (CH 3) 2, C (CF 3) 2, or a CO-NH, W ₁ and W ₂ are the same or different, and independently O , S, or CO and Z ₁ is O, S, CR ₁ R ₂ or NR ₃ wherein R ₁ , R ₂ and R ₃ are the same or different and each independently is hydrogen or an alkyl group having 1 to 5 carbon atoms , Z ₂ and Z ₃ are the same or different and are each independently N or CR ₄ (R ₄ is hydrogen or an alkyl group having 1 to 5 carbon atoms) or is not CR ₄ at the same time.

And Ar < ₂ > is any one selected from the following formulas.

The porous thermally-converting poly (benzoxazole-imide) copolymer support is characterized by being an electrospray membrane or a hollow fiber membrane.

The thickness of the electrodisplacive film is 10 to 80 탆 and the porosity is 60 to 80%.

The present invention also relates to a porous heat-converted poly (benzoxazole-imide) copolymer support having a repeating unit represented by the above formula (1); And an active layer of a thin film formed on the porous support. The present invention also provides an ultra thin composite membrane for a pressure delayed osmosis process.

Wherein the active layer of the thin film is an aromatic polyamide having a crosslinked structure having a repeating unit represented by the following formula (2).

(2)

The active layer of the thin film has a thickness of 50 to 300 nm.

The present invention also provides a process for preparing a polyimide-polyimide copolymer, which comprises: (I) synthesizing a hydroxy group-containing polyimide-polyimide copolymer by reacting an acid dianhydride, ortho-hydroxy diamine and an aromatic diamine to obtain a polyamic acid solution, followed by azeotropic thermal imidization;

II) forming a polymer solution obtained by dissolving the hydroxyl group-containing polyimide-polyimide copolymer of step I) in an organic solvent by a conventional electrospinning or non-solvent-induced phase separation; And

III) preparing a porous thermally-converting poly (benzoxazole-imide) copolymer support for a pressure-delayed osmosis process having a repeating unit represented by the above-mentioned formula (1) ≪ / RTI >

The ortho-hydroxydiamine of the step I) is characterized by being represented by the following general formula (3).

(3)

(Wherein Q in the above formula (3) is the same as defined in the above formula (1)

In the azeotropic thermal imidation of the step I), toluene or xylene is added to the polyamic acid solution, and the mixture is stirred to perform imidization reaction at 160 to 200 ° C for 6 to 24 hours.

The heat conversion in step III) is performed by raising the temperature to 300 to 400 ° C at a rate of 1 to 20 ° C / min in an inert gas atmosphere of high purity, and then maintaining the isothermal state for 1 to 2 hours.

The present invention also provides an aromatic polyamide thin film having a crosslinked structure having a repeating unit represented by the above formula (2) on a porous thermally-converting poly (benzoxazole-imide) copolymer support having a repeating unit represented by the above formula The method comprising the steps of: (a) forming a pressure-reduced osmosis membrane;

The active layer of the aromatic polyamide thin film having the crosslinked structure is characterized in that it is formed by the interfacial polymerization reaction of meta-phenylenediamine and trimethoyl chloride.

Treating the ultra-thin composite membrane with an aqueous sodium hypochlorite solution.

The present invention also relates to a porous heat-converted poly (benzoxazole-imide) copolymer support having a repeating unit represented by the above formula (1); And an active layer of a thin film formed on the porous support. The present invention also provides an ultra thin composite membrane for a positive osmosis process.

The thin, porous, heat-converted poly (benzoxazole-imide) copolymer support prepared according to the present invention and the ultra-thin composite membrane comprising the same have excellent thermal and chemical stability and mechanical properties, But it can be applied to a pressure delay osmosis process or a positive osmosis process since the internal concentration polarization can be minimized to obtain a high water permeability and accordingly a high power density.

1 is a process and a scanning electron microscope (SEM) image of a porous thermally-converting poly (benzoxazole-imide) copolymer support (electrospray membrane) according to Examples 1 to 9;
Figure 2 is an ATR-IR spectrum of a porous heat-converted poly (benzoxazole-imide) copolymer support prepared according to Examples 1-9.
3 is an ATR-IR spectrum of a porous thermally-converting poly (benzoxazole-imide) copolymer support (a) prepared according to Example 1 and an ultra-thin composite membrane (b) prepared according to Example 11.
4 is a thermogravimetric analysis (TGA) graph showing the thermogravimetric reduction characteristics of the porous heat-converted poly (benzoxazole-imide) copolymer support prepared according to Example 1 according to the thermal conversion conditions.
5 is a photograph showing the stability of the porous heat-converted poly (benzoxazole-imide) copolymer support prepared according to Example 1 to an organic solvent.
6 is a scanning electron microscope (SEM) image of a conventional polysulfone-based asymmetric composite membrane (a) and an ultrathin composite membrane (b) prepared according to Example 10 of the present invention.
FIG. 7 is a graph showing the water permeability before and after the treatment (500 ppm NaOCl, 1000 ppm NaOCl) and the salt rejection rate of the ultra-thin composite membrane prepared according to Example 10 [feed solution: 2000 ppm NaCl (20 ° C)].
8 is a graph showing the water permeation amount and power density of an ultra-thin composite membrane for a pressure-delayed osmosis process according to an embodiment of the present invention (inductive solution: 1M NaCl (20 ° C), feed solution: deionized water (20 ° C)].

In the present invention, there is provided a porous heat-converted poly (benzoxazole-imide) copolymer support for a pressure-delayed osmosis process having a repeating unit represented by the following formula (1).

≪ Formula 1 >

(Wherein Ar ₁ is an aromatic ring group selected from a substituted or unsubstituted quadrivalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted quadrivalent heterocyclic group having 4 to 24 carbon atoms, O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _p (1 ≦ _P ≦ ₁₀ ), or two or more of them form a condensed ring; ), (CF ₂ ) _q ( ₁ ? _Q ? 10), C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or CO-

Ar ₂ is an aromatic ring group selected from a substituted or unsubstituted divalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted divalent heterocyclic group having 4 to 24 carbon atoms and the aromatic ring group is present alone; Two or more of them form a condensed ring with each other; Two or more single bond, O, S, CO, SO 2, Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C _{(CH 3) 2, C (} CF 3) is connected to ₂ or CO-NH,

Q is a single bond; _{O, S, CO, SO 2} , Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C (CH 3) 2, C _{(CF 3) 2, CO-} NH, C (CH 3) (CF 3), or a substituted or unsubstituted phenylene ring, x, y is 0.1≤x≤0.9, 0.1≤y≤ a molar fraction within each repeating unit 0.9, x + y = 1)

In Formula 1, Ar ₁ may be any one selected from the following formulas.

Wherein X ₁ , X ₂ , X ₃ and X ₄ are the same or different and each independently represents O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _{p ), (CF 2) q (} 1≤q≤10), C (CH 3) 2, C (CF 3) 2, or a CO-NH, W ₁ and W ₂ are the same or different, and independently O , S, or CO and Z ₁ is O, S, CR ₁ R ₂ or NR ₃ wherein R ₁ , R ₂ and R ₃ are the same or different and each independently is hydrogen or an alkyl group having 1 to 5 carbon atoms , Z ₂ and Z ₃ are the same or different and are each independently N or CR ₄ (R ₄ is hydrogen or an alkyl group having 1 to 5 carbon atoms) or is not CR ₄ at the same time.

Specific examples of the above-mentioned Ar ₁ are preferably those represented by the following structural formulas.

In Formula 1, Ar ₂ may be any one selected from the following formulas.

Wherein X ₁ , X ₂ , X ₃ and X ₄ are the same or different and each independently represents O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _{p ), (CF 2) q (} 1≤q≤10), C (CH 3) 2, C (CF 3) 2, or a CO-NH, W ₁ and W ₂ are the same or different, and independently O , S, or CO and Z ₁ is O, S, CR ₁ R ₂ or NR ₃ wherein R ₁ , R ₂ and R ₃ are the same or different and each independently is hydrogen or an alkyl group having 1 to 5 carbon atoms , Z ₂ and Z ₃ are the same or different and are each independently N or CR ₄ (R ₄ is hydrogen or an alkyl group having 1 to 5 carbon atoms) or is not CR ₄ at the same time.

Specific examples of the above-mentioned Ar ₂ are preferably those represented by the following structural formulas.

The porous thermally-converting poly (benzoxazole-imide) copolymer support is preferably an electrospray membrane or a hollow fiber membrane in the form of a flat membrane. Generally, electrospinning can deposit hundreds of nano-sized fibers in a bottom-up manner by electrospinning to form a porous support with a thin thickness and interconnected pore structure with high porosity. Therefore, in the present invention, when the porous thermally-converting poly (benzoxazole-imide) copolymer support is an electrospun film in the form of a flat membrane, it preferably has a thickness of 10 to 80 μm and a porosity of 60 to 80% have.

Since the polysulfone-based or polyethylene terephthalate-based porous support of the ultra-thin composite membrane used as a conventional water treatment membrane is thick with a thickness of 100 to 200 탆, it can be used for a pressure delayed osmosis process for energy production or a cleansing process When used as a separator, internal concentration polarization is generated inside a thick porous support, and the concentration difference, which is the driving force of water permeability, is reduced. As a result, water permeability is lowered and power density is lowered accordingly.

Therefore, according to the present invention, the thickness of the porous support obtained from the flat membrane-type electrospray membrane is as thin as 10 to 80 탆, and the porosity is as high as 60 to 80%, thereby minimizing internal concentration polarization, And thus it can be applied to the pressure delay osmosis process or the positive osmosis process.

If the thickness of the porous support obtained from the flat membrane-type electrospacer membrane is less than 10 탆, the thickness of the support may be too thin, which may degrade mechanical properties. If the thickness exceeds 80 탆, concentration polarization may occur within the support. If the porosity of the porous support is less than 60%, the water permeability may be lowered. If the porosity exceeds 80%, the film formation is not smooth.

The present invention also relates to a porous heat-converted poly (benzoxazole-imide) copolymer support having a repeating unit represented by the above formula (1); And an active layer of a thin film formed on the porous support. The present invention also provides an ultra thin composite membrane for a pressure delayed osmosis process.

At this time, the active layer of the thin film formed on the porous support may be a crosslinked aromatic polyamide having a repeating unit represented by the following formula (2).

(2)

The active layer of the thin film preferably has a thickness of 50 to 300 nm. When the thickness of the active layer is less than 50 nm, it is difficult to withstand a high operating pressure when applied to a pressure delay osmosis process. If the thickness exceeds 300 nm, There is a problem in resistance.

The structure of the poly (benzoxazole-imide) copolymer represented by the above formula (1) is based on the synthesis of a polyimide prepared by imidizing a polyamic acid obtained by reacting an acid dianhydride with a diamine. In addition, the thermally-modified polybenzoxazole can be prepared by a method in which a functional group such as a hydroxyl group in the ortho-position of the aromatic imido linkage attacks an imine ring carbonyl group to form an intermediate of the carboxy- benzoxazole structure, In the present invention, the porous heat-converted poly (benzoxazol-imide) for pressure-sensitive delayed osmosis process having the repeating unit represented by the above-mentioned formula (1), including the following steps, is synthesized by decarboxylation ) Copolymer < / RTI > support.

That is, in the present invention, a process for preparing a polyamic acid solution by reacting an acid dianhydride, an ortho-hydroxydiamine and an aromatic diamine, followed by synthesis of a hydroxy group-containing polyimide-polyimide copolymer by an azeotropic thermal imidization process;

II) forming a polymer solution obtained by dissolving the hydroxyl group-containing polyimide-polyimide copolymer of step I) in an organic solvent by a conventional electrospinning or non-solvent-induced phase separation; And

III) preparing a porous thermally-converting poly (benzoxazole-imide) copolymer support for a pressure-delayed osmosis process having a repeating unit represented by the above-mentioned formula (1) ≪ / RTI >

Generally, in order to synthesize polyimide, a polyamic acid is to be obtained by first reacting an acid dianhydride with a diamine. In the present invention, a compound represented by the following formula is used as an acid anhydride.

≪

(Ar ₁ in the formula is as defined in formula (I))

As the monomer for synthesizing the polyimide, any of the acid dianhydrides may be used without limitation as long as they are as defined in the above formula. However, considering the fact that the thermal and chemical properties of the polyimide synthesized can be further improved, 4,4'-hexafluoroisopropylidene phthalic acid dianhydride (6FDA), or 4,4'-oxydiphthalic acid dianhydride (ODPA) is preferably used.

In addition, since the present invention ultimately has a poly (benzoxazole-imide) copolymer structure, attention has been paid to the fact that polybenzoxazole units can be introduced by thermal conversion of ortho-hydroxypolyimide, As the ortho-hydroxydiamine, a compound represented by the following formula (3) is used to synthesize hydroxypolyimide.

(3)

(Wherein Q in the above formula (3) is the same as defined in the above formula (1)

As the ortho-hydroxydiamine, there can be used any one as long as it is as defined in the above formula (3). However, considering the fact that the thermal and chemical properties of the polyimide to be synthesized can be further improved, 2,2 (3-amino-4-hydroxyphenyl) hexafluoropropane (APAF) or 3,3'-diamino-4,4'-dihydroxybiphenyl (HAB) .

In the present invention, a hydroxy group-containing polyimide-polyimide copolymer is synthesized by reacting an acid anhydride of the above formula and an ortho-hydroxy diamine of the formula (3) using an aromatic diamine represented by the following formula (4) as a comonomer .

≪ Formula 4 >

(Ar ₂ in the formula (4) is the same as defined in the formula (1)

As the aromatic diamine, any of the aromatic diamines may be used as long as they are as defined in the above formula (4), but 4,4'-oxydianiline (ODA) or 2,4,6-trimethylphenylenediamine (DAM) .

That is, in step I), the acid dianhydride of the above formula, the ortho-hydroxydaramine of formula (III) and the aromatic diamine of formula (IV) are dissolved in an organic solvent such as N-methylpyrrolidone (NMP) After the solution is obtained, the hydroxy group-containing polyimide-polyimide copolymer represented by the following general formula (1) is synthesized by azeotropic thermal imidization.

≪ General Formula 1 &

(Ar ₁ , Ar ₂ , Q, x and y in the general formula (1) are the same as defined in the general formula (1)

At this time, in the azeotropic thermal imidization method, toluene or xylene is added to the polyamic acid solution, and the imidization reaction is carried out at 160 to 200 ° C for 6 to 24 hours. During this period, the imide ring is generated and water Is separated as an azeotropic mixture of toluene or xylene.

Next, a polymer solution obtained by dissolving the hydroxy group-containing polyimide-polyimide copolymer of the step I) represented by the general formula 1 in an organic solvent such as N-methylpyrrolidone (NMP) is subjected to ordinary electrospinning, Or by nonsolvent induced phase separation to obtain an electrospun film or a hollow fiber membrane in the form of a flat membrane as a support.

Next, the porous heat-converted poly (meth) acrylate polymer having a repeating unit represented by the above formula (1) as a target by thermally converting the hydroxyl group-containing polyimide-polyimide copolymer electrospray membrane or the hollow fiber membrane as the support, Benzoxazole-imide) copolymer support.

At this time, the heat conversion is performed by raising the temperature to 300-400 DEG C at a rate of 1 to 20 DEG C / min in an inert gas atmosphere of high purity, and then maintaining the isothermal state for 1 to 2 hours.

Further, in the present invention, an aromatic polyamide thin film having a crosslinked structure having the repeating unit represented by the above formula (2) on a porous thermally-converting poly (benzoxazole-imide) copolymer support having the repeating unit represented by the above formula The method comprising the steps of: (a) forming a pressure-reduced osmosis membrane;

At this time, it is preferable that the active layer of the aromatic polyamide thin film having the crosslinked structure is formed by interfacial polymerization of meta-phenylenediamine (MPD) and trimethoyl chloride (TMC) according to the following Reaction Scheme 1.

<Reaction Scheme 1>

The method may further include post-treating the ultra-thin composite membrane with an aqueous solution of sodium hypochlorite (NaOCl) in the method of manufacturing the ultra-thin composite membrane for the pressure delayed osmosis process, A polyamide thin film having a partially crosslinked structure causes decomposition of polyamide as shown in the following reaction formula (2).

<Reaction Scheme 2>

Meanwhile, although the pressure delay osmosis and positive osmosis are processes for producing energy (electric power) and water, respectively, there is a difference in the purpose thereof, but there is a common point that osmosis phenomenon is used. According to the present invention, Porous thermally-exchangeable poly (benzoxazole-imide) copolymer supports having units; And an active layer of a thin film formed on the porous support. The present invention also provides an ultra thin composite membrane for a positive osmosis process. At this time, the active layer of the thin film may be a crosslinked aromatic polyamide having a repeating unit represented by the above-mentioned formula (2), and the thickness thereof is preferably 50 to 300 nm as described above.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

[Synthesis Example 1] Synthesis of hydroxy group-containing polyimide-polyimide copolymer

5.0 mmol of 3,3'-diamino-4,4'-dihydroxybiphenyl (HAB) and 5.0 mmol of 4,4'-oxydianiline (ODA) were dissolved in 10 ml of anhydrous NMP, 10.0 mmol of 4,4'-oxydiphthalic acid dianhydride (ODPA) dissolved in 10 ml of anhydrous NMP was added thereto. The reaction mixture was stirred at 0 占 폚 for 15 minutes, then allowed to warm to room temperature and allowed to stand overnight to obtain a polyamic acid viscous solution. Next, 20 ml of ortho-xylene was added to the polyamic acid solution, followed by vigorous stirring and heating to carry out imidization at 180 ° C for 6 hours. In this process, the water released by the formation of the imide ring was isolated as the xylene azeotropic mixture. The resulting brown solution was cooled to room temperature, immersed in distilled water, washed several times with hot water, and dried in a convection oven at 120 ° C. for 12 hours to obtain a hydroxy group-containing polyimide-polyimide copolymer represented by the following formula And named it ODPA-HAB ₅ -ODA ₅ .

&Lt; Formula 5 >

It was confirmed by ¹ H-NMR and FT-IR data that the hydroxy group-containing polyimide-polyimide copolymer of Synthesis Example 1 to 5 was synthesized as follows. ^{1 H-NMR (300 MHz,} DMSO- d 6, ppm): 10.41 (s, -OH), 8.10 (d, H ar, J = 8.0Hz), 7.92 (d, H ar, J = 8.0Hz), _{7.85 (s, H ar),} 7.80 (s, H ar), 7.71 (s, H ar), 7.47 (s, H ar), 7.20 (d, H ar, J = 8.3Hz), 7.04 (d, H _ar , J = 8.3 Hz). FT-IR (film): ν (OH) at 3400 cm ^-1 , ν (C═O) at 1786 and 1705 cm ^-1 , Ar (CC) at 1619, 1519 cm ^-1 , imide ν (CN) at 1377 cm ^-1 , imide (CNC) at 1102 and 720 cm ^-1 .

[Synthesis Examples 2 to 9] Synthesis of hydroxy group-containing polyimide-polyimide copolymer

A polyimide-polyimide copolymer containing a hydroxy group was prepared in the same manner as in Synthesis Example 1, and various acid dianhydrides, ortho-hydroxydiamine and aromatic diamines shown in Table 1 below were used as reactants, Was named in the same manner as in Example 1.

Synthetic example Sample name Mole fraction Synthesis Example 2 ODPA-HAB ₈ -ODA ₂ x = 0.8, y = 0.2 Synthesis Example 3 6FDA-APAF ₈ -ODA ₂ x = 0.8, y = 0.2 Synthesis Example 4 6FDA-APAF ₅ -DAM ₅ x = 0.5, y = 0.5 Synthesis Example 5 6FDA-HAB ₅ -ODA ₅ x = 0.5, y = 0.5 Synthesis Example 6 6FDA-HAB ₈ -ODA ₂ x = 0.8, y = 0.2 Synthesis Example 7 6FDA-HAB ₅ -DAM ₅ x = 0.5, y = 0.5 Synthesis Example 8 6FDA-APAF ₂ -ODA ₈ x = 0.2, y = 0.8 Synthesis Example 9 6FDA-APAF ₅ -ODA ₅ x = 0.5, y = 0.5

6FDA (4,4'-hexafluoroisopropylidene phthalic acid dianhydride)

APAF (2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane)

DAM (2,4,6-trimethylphenylenediamine)

[ Example  One] Thermal Conversion Poly ( Benzoxazole - Imide ) Copolymer support ( An electric room )

ODPA-HAB ₅ -ODA ₅ obtained from Synthesis Example 1 was dissolved in dimethylacetamide (DMAc) to prepare a 10 wt% solution. 6 ml of the polymer solution was charged into a 10 ml syringe equipped with a 23 G needle and then mounted on a syringe pump of an electrospinning device (ES-robot, NanoNC, Korea) HPI). The obtained electrospun film was put between an alumina plate and a carbon cloth and heated to 400 DEG C at a rate of 3 DEG C / min in a high purity argon gas atmosphere. Thereafter, the isotropic state was maintained at 400 DEG C for 2 hours, (Benzoxazole - imide) copolymer electrospray membrane (PBO) represented by the formula (6) was prepared.

(6)

[ Example  2 to 9] Thermal Conversion Poly ( Benzoxazole - Imide ) Copolymer support ( An electric room )

Thermosetting poly (benzoxazole-imide) copolymer electrospun films were prepared in the same manner as in Example 1 using the samples obtained in Synthesis Examples 2 to 9, and the porosity It can be seen that a nanofiber porous electrodisplacive film was prepared from the manufacturing process of a thermally converted poly (benzoxazole-imide) copolymer support (electrospray membrane) and a scanning electron microscope (SEM) image.

[ Example  10] Thermal Conversion Poly ( Benzoxazole - Imide ) Preparation of Copolymer Support (Hollow Fiber Membrane)

A dope solution for the hollow fiber formation was obtained from the ODPA-HAB ₅ -ODA ₅ sample obtained according to Synthesis Example 1 (composition of the dope solution: 25% by weight of ODPA-HAB ₅ -ODA ₅ , N-methylpyrrolidone ) And propionic acid (PA) (NMP: PA = 50:50 mol%, 65 wt%, ethylene glycol 10 wt%), the dope solution was fed with a bore solution (water) Gap: 5 cm) to obtain a hollow fiber membrane according to a conventional nonsolvent induced phase separation (NIPS) method. The resultant hollow fiber membrane was heated to 400 DEG C at a rate of 10 DEG C / min in a high-purity argon gas atmosphere, and then maintained at 400 DEG C for 2 hours in an isothermal state to obtain a heat conversion poly (benzoxazole- imide) copolymer hollow The desert was prepared.

[Example 11] Preparation of an ultra-thin composite membrane comprising a heat-converted poly (benzoxazole-imide) copolymer support

The thermosensitive poly (benzoxazole-imide) copolymer electrospun film prepared from Example 1 was immersed in an aqueous solution of meta-phenylenediamine (MPD) of 3.5% by weight, the excess solution was removed, and 0.15 After the interfacial polymerization reaction was carried out by pouring a weight% solution of trimesoyl chloride in hexane, the hexane was washed and allowed to stand in the air and cured in an oven at 90 ° C to obtain a thermally-converted poly (benzoxazole-imide) copolymer support Thin film composite membrane on which a polyamide thin film active layer of crosslinked structure was formed.

[Example 12] Preparation of an ultra-thin composite membrane comprising a thermally-converting poly (benzoxazole-imide) copolymer support

An aqueous solution of 3.5% by weight of meta-phenylenediamine (MPD) was flowed into the hollow fiber using the heat-converted poly (benzoxazole-imide) copolymer hollow fiber membrane prepared in Example 10 as a support, After the reaction, 0.15% by weight of trimesoyl chloride hexane solution was poured into the hollow fiber to carry out an interfacial polymerization reaction. Then, an excess amount of the solution was removed, and the solution was allowed to stand in the air and dried to obtain thermally converted poly (benzoxazol-imide) Thin composite membrane having a polyamide thin film active layer of crosslinked structure formed on a coalesced support (hollow fiber membrane).

FIG. 2 shows the ATR-IR spectra of the porous heat-converted poly (benzoxazole-imide) copolymer supports prepared according to Examples 1 to 9. The OH stretching peak near 3400 cm ^-1 disappears and two distinct peaks due to the typical benzoxazole ring near 1480 cm ^-1 and 1054 cm ^-1 appear, indicating that the benzoxazole ring was formed during the heat treatment Could know. In addition, the inherent absorption band of the imide is found around 1784 cm ^-1 and 1717 cm ^-1 , and the thermal stability of the aromatic imide linkage ring can be confirmed even at the thermal conversion temperature reaching 400 ° C.

Table 2 shows mechanical properties, average pore size, porosity and water permeability according to various thicknesses of the thermally-converting poly (benzoxazole-imide) copolymer support (electrospray membrane) prepared in Example 1 above.

Thickness (㎛) Mechanical properties (MD / TD) Average pore size (占 퐉) Porosity (%) Water Transmission (LMH) Tensile Strength (Mpa) Elongation (%) 20 35/51 11/28 0.22 75 8541 40 23/29 6/13 0.20 64 3304 60 23/34 5/12 0.12 61 2334

Machine direction (MD), transverse direction (TD)

From Table 2, it can be seen that the thermally-converting poly (benzoxazole-imide) copolymer support prepared according to the present invention is much thinner than the thickness of the porous support (100 ~ 200 탆) And the porosity is also very high, which shows that the resulting water permeability is greatly improved.

3 shows the ATR-IR spectra of the porous heat-converted poly (benzoxazole-imide) copolymer support (a) prepared according to Example 1 and the ultra-thin composite membrane (b) prepared according to Example 11 Respectively. As shown in FIG. 3, in the case of the ultra-thin composite membrane (b) prepared according to Example 11, unlike the porous heat conversion poly (benzoxazole-imide) copolymer support (a) prepared according to Example 1 , 3444 cm ^-1 and 3310 cm ^-1 , respectively. The stretching vibration and the hydrogen bonding of the NH group were confirmed at 1667 cm ^-1 and 1542 cm ^-1 , and the stretching vibration of the C═O group and the plane bending of the NH group were confirmed there was.

4 shows the results of various thermal conversion conditions (375 DEG C for 0.5 hour, 375 DEG C for 1 hour, 375 DEG C for 2 hours, 400 DEG C) for the porous thermally-converting poly (benzoxazole- imide) copolymer support prepared according to Example 1 Deg.] C for 2 hours) as a thermogravimetric analysis (TGA) graph. The thermogravimetric analysis was carried out at a heating rate of 10 ° C / min to 400 ° C, followed by heating at 400 ° C for 2 hours and then heating to 800 ° C again. The weight reduction due to heat conversion is theoretically about 9% when 100% heat conversion is performed, and the weight reduction of pristine is 10% between 40 and 160 minutes as shown in FIG. It can be seen that the heat conversion has proceeded smoothly and the degree of thermal conversion can be calculated inversely from the quantitative weight loss data of the support treated in each heat conversion condition.

FIG. 5 is a photograph showing the stability of the porous heat-converted poly (benzoxazole-imide) copolymer support prepared according to Example 1 with respect to an organic solvent. As a result of the chemical stability experiment using dimethylacetamide (DMAc), an organic solvent used in the film formation, the support (HPI) after heat conversion was dissolved in the organic solvent, whereas the support (PBO) And it was confirmed that it maintained its shape without melting.

6 shows a scanning electron microscope (SEM) image of a conventional polysulfone-based asymmetric composite membrane (a) and an ultra-thin composite membrane (b) prepared according to Example 11 of the present invention. According to Example 11 of the present invention, it is possible to observe an ultra-thin composite film in which a polyamide thin film layer is well formed. The thickness of the formed polyamide thin film layer (61 nm) is about three times thinner than the conventional polysulfone asymmetric composite film (209 nm) . Further, it was confirmed that the total thickness of the membrane was also significantly thinner (16 탆) than the conventional polysulfone-based asymmetric composite membrane (204 탆) by 12 times or more.

7 shows the water permeability before and after the post-treatment (500 ppm NaOCl, 1000 ppm NaOCl) of the ultra-thin composite membrane prepared according to Example 11 of the present invention in order to confirm whether the ultra- (water permeability) and salt rejection (supply solution: 2000 ppm NaCl (20 ° C)). It can be seen that the NaOCl treatment improves the water permeability by a factor of about 2 without significantly deteriorating the salt rejection rate.

FIG. 8 is a graph showing the water flux and power density of an ultra-thin composite membrane for a pressure-delayed osmosis process according to an embodiment of the present invention (inductive solution: 1M NaCl (20 ° C) : Ultra-thin composite membrane TR40 (thickness 40 占 퐉), TR60 (thickness 60 占 퐉), TR40 _NaOCl (thickness: 40 占 퐉) manufactured by Hydration Technology Innovations Co., 40 [micro] m, NaOCl 1000 ppm for 10 minutes]. As shown in FIG. 8, the conventional HTI exhibits a low power density of 5 W / m ² while the ultra-thin composite membrane (TR40 _NaOCl ) It was achieved by high power densities up to 21 W / m ^2. in the present invention, as a result, TR40 this reduces the mass transfer resistance indicates a higher power density compared to TR40 and TR60 to evaluate the resistance according to the thickness of the support .

As described above, the thin, porous, heat-converted poly (benzoxazole-imide) copolymer support prepared according to the present invention and the ultra-thin composite membrane comprising the same have excellent thermal and chemical stability and mechanical properties, It is possible to apply the present invention to a pressure-delayed osmosis process or a positive osmosis process because it can obtain a high water permeability and accordingly a high power density by minimizing internal concentration polarization.

Claims (20)

delete delete delete delete delete delete delete A porous thermally-converting poly (benzoxazole-imide) copolymer support having a repeating unit represented by the following formula (1); And
An active layer of a cross-linked aromatic polyamide thin film having a repeating unit represented by the following formula (2) formed on the porous thermally-converting poly (benzoxazole-imide) copolymer support.
&Lt; Formula 1 >

(Wherein Ar ₁ is an aromatic ring group selected from a substituted or unsubstituted quadrivalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted quadrivalent heterocyclic group having 4 to 24 carbon atoms, O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _p (1 ≦ _P ≦ ₁₀ ), or two or more of them form a condensed ring; ), (CF ₂ ) _q ( ₁ ? _Q ? 10), C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or CO-
Ar ₂ is an aromatic ring group selected from a substituted or unsubstituted divalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted divalent heterocyclic group having 4 to 24 carbon atoms and the aromatic ring group is present alone; Two or more of them form a condensed ring with each other; Two or more single bond, O, S, CO, SO 2, Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C _{(CH 3) 2, C (} CF 3) is connected to ₂ or CO-NH,
Q is a single bond; _{O, S, CO, SO 2} , Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C (CH 3) 2, C _{(CF 3) 2, CO-} NH, C (CH 3) (CF 3), or a substituted or unsubstituted phenylene ring, x, y is 0.1≤x≤0.9, 0.1≤y≤ a molar fraction within each repeating unit 0.9, x + y = 1)
(2)

delete The ultra-thin composite membrane for a pressure-delayed osmosis process according to claim 8, wherein the active layer of the thin film has a thickness of 50 to 300 nm. delete delete delete delete A porous thermally-converting poly (benzoxazole-imide) copolymer support having a repeating unit represented by the general formula (1) as set forth in claim 8, which has a crosslinked structure having a repeating unit represented by the general formula (2) And forming an active layer of the amide thin film. 16. The method of claim 15, wherein the active layer of the aromatic polyamide thin film having a crosslinked structure is formed by interfacial polymerization between meta-phenylenediamine and trimethoyl chloride. 16. The method of claim 15, further comprising post-treating the ultra-thin composite membrane with an aqueous sodium hypochlorite solution. A porous thermally-converting poly (benzoxazole-imide) copolymer support having a repeating unit represented by the following formula (1); And
An active layer of a cross-linked aromatic polyamide thin film having a repeating unit represented by the following formula (2) formed on the porous thermally-converting poly (benzoxazole-imide) copolymer support.
&Lt; Formula 1 >

(Wherein Ar ₁ is an aromatic ring group selected from a substituted or unsubstituted quadrivalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted quadrivalent heterocyclic group having 4 to 24 carbon atoms, O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _p (1 ≦ _P ≦ ₁₀ ), or two or more of them form a condensed ring; ), (CF ₂ ) _q ( ₁ ? _Q ? 10), C (CH ₃ ) ₂ , C (CF ₃ ) ₂ or CO-
Ar ₂ is an aromatic ring group selected from a substituted or unsubstituted divalent arylene group having 6 to 24 carbon atoms and a substituted or unsubstituted divalent heterocyclic group having 4 to 24 carbon atoms and the aromatic ring group is present alone; Two or more of them form a condensed ring with each other; Two or more single bond, O, S, CO, SO 2, Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C _{(CH 3) 2, C (} CF 3) is connected to ₂ or CO-NH,
Q is a single bond; _{O, S, CO, SO 2} , Si (CH 3) 2, (CH 2) p (1≤P≤10), (CF 2) q (1≤q≤10), C (CH 3) 2, C _{(CF 3) 2, CO-} NH, C (CH 3) (CF 3), or a substituted or unsubstituted phenylene ring, x, y is 0.1≤x≤0.9, 0.1≤y≤ a molar fraction within each repeating unit 0.9, x + y = 1)
(2)

delete The ultra-thin composite membrane for a positive osmosis process according to claim 18, wherein the active layer of the thin film has a thickness of 50 to 300 nm.

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