KR20180122586A - Thin-film composite membrane for organic solvent nanofiltration and preparation method thereof - Google Patents

Abstract

The present invention relates to a thin film composite membrane for organic solvent nanofiltration and a method for manufacturing the same. The present invention relates to a composite membrane comprising a porous support formed of a heat-converted poly(benzoxazole-imide) copolymer and an active layer of a sulfonated polyarylene ether sulfone copolymer thin film having a crosslinked structure on the porous support. The thin film composite membrane manufactured according to the present invention has excellent chemical and thermal stability against organic solvents, is excellent in organic solvent nanofiltration performance, and can form a thin active layer by a simple and environmentally-friendly coating and heat treatment process, and thus can be applied as an organic solvent nanofiltration membrane in chemical, pharmaceutical or oil refining industries.

Description

TECHNICAL FIELD [0001] The present invention relates to a thin film composite membrane for organic solvent nanofiltration,

More particularly, the present invention relates to a thin film composite membrane for organic solvent nanofiltration, and more particularly to a thin film composite membrane for organic solvent nanofiltration which comprises a porous support formed of a thermally-converting poly (benzoxazole-imide) copolymer, The present invention relates to a technique for preparing a composite membrane containing an active layer of a sulfonated polyarylene ether sulfone copolymer thin film and applying it to an organic solvent nanofiltration process.

In general, the separation process required in the chemical industry and the pharmaceutical industry is carried out using almost organic solvents, including distillation, crystallization, adsorption, and extraction processes, and thus the demand for organic solvent separation membranes is steadily increasing. However, since most of the conventionally developed or commercialized membranes are manufactured for water treatment or gas separation, there is a limit to maintaining a stable chemical structure in an environment exposed to various organic solvents. Therefore, although there is an industrial demand for the organic solvent separator and its size is not so small, the organic solvent separator has not been developed so far.

However, a composite membrane obtained by forming a polyamide thin film layer on a polyimide support as an organic solvent nanofiltration membrane, a polybenzimidazole membrane and a polyether ether ketone membrane polymerized from tetraamine and dicarboxylic acid, and the like are known. In the case of the filtration membrane, the pore size is also important, but the interaction between the solvent or the solute and the separation membrane affects the performance of the separation membrane, so it is urgent to develop a material having excellent stability to the organic solvent. In addition, polyimide, crosslinked polybenzimidazole, polyetheretherketone membrane, etc., which are conventionally formed in the form of an asymmetric membrane, are often used in limited organic solvents and temperature ranges because they are difficult to obtain an excellent permeability even if they are stable to organic solvents Various types of separator materials, shapes, and improved separation performance are required (Patent Documents 1 and 2).

Further, a heat-converted poly (benzoxazole-imide) copolymer film is prepared by reacting an acid anhydride, ortho-hydroxyamine and an aromatic diamine to obtain a hydroxypolyimide-polyimide copolymer film and heat- , There is no disclosure about the chemical stability of the organic solvent as well as the separation performance of the organic solvent. Thus, application to the organic solvent nanofiltration membrane has not been considered (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- It is possible to prepare a composite membrane comprising an active layer of a sulfonated polyarylene ether sulfone copolymer thin film having a crosslinked structure formed by a simple coating and a thermal crosslinking method on the porous support, The present invention can be applied to an organic solvent nanofiltration membrane based on stability and separation performance of the organic solvent.

Patent Document 1: US Patent Application Publication No. US 2015/0231572 Patent Document 2 US Patent Publication No. US 2013/0118983

Non-Patent Document 1 Chul Ho Jung et al., J. Membr. Science 350, 301-309 (2010)

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 an organic solvent excellent in chemical and thermal stability, excellent in organic solvent nano filtration performance, simple and environmentally friendly coating and heat treatment And to provide a thin film composite membrane for organic solvent nanofiltration capable of forming a thin film active layer having a crosslinked structure, and a method for producing the same.

In order to accomplish the above object, the present invention provides a porous thermally-converting poly (benzoxazole-imide) copolymer support having a repeating unit represented by the following formula (1); And a sulfonated polyarylene ether sulfone copolymer thin film active layer having a cross-linked structure formed on the support. The present invention also provides a thin film composite membrane for organic solvent nanofiltration.

≪ 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)

The porous heat conversion poly (benzoxazole-imide) copolymer support is characterized by being an electrospray film.

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

The sulfonated polyarylene ether sulfone copolymer thin film active layer of the crosslinked structure has a repeating unit represented by the following general formula (2).

(2)

(Wherein Q is a single bond or O, S, C (= O), C (= O) NH, Si (CH ₃ ) ₂ , (CH ₂ ) _{p CF 2) q (1≤q≤10),} C (CH 3) 2, C (CF 3) 2, or _{C (CH 3) (CF 3} ) , n is 0, as a repeating unit, the molar ratio of structural unit I < n < 1)

The thin film active layer has a thickness of 50 nm to 1 占 퐉.

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 by dissolving the hydroxy group-containing polyimide-polyimide copolymer of step I) in an organic solvent by electrospinning;

III) obtaining a porous thermally-converting poly (benzoxazole-imide) copolymer support having the repeating units represented by Formula 1 by thermal conversion of the membrane obtained in the step II); And

IV) forming a sulfonated polyarylene ether sulfone copolymer thin film active layer having a crosslinked structure having the repeating unit represented by the formula (2) on the support, and a process for producing the thin film composite membrane for organic solvent nanofiltration .

The acid dianhydride in the step I) is characterized by being represented by the following formula (3).

(3)

(Wherein Ar ₁ is as defined in Formula 1)

The ortho-hydroxydiamine of the step I) is characterized by being represented by the following general formula (4).

&Lt; Formula 4 >

(Q in Formula 4 is the same as defined in Formula 1)

The aromatic diamine of the step I) is represented by the following general formula (5).

&Lt; Formula 5 >

(Ar ₂ in the formula (5) is the same as defined in the 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 formation of the sulfonated polyarylene ether sulfone copolymer thin film active layer having a crosslinked structure having the repeating unit represented by the general formula (2) in the step (IV) may be carried out by a) mixing 4,4'-dichlorodiphenyl sulfone or 4,4 ' -Difluorodiphenylsulfone, 4,4'-biphenol-based compound and sulfonated 4,4'-dichlorodiphenylsulfone or sulfonated 4,4'-difluorodiphenylsulfone to give sulfonated polyaryl Synthesizing a phenylene sulfone copolymer; And

b) spray coating and thermally crosslinking the polymer solution in which the sulfonated polyarylene ether sulfone copolymer is dissolved in dimethyl sulfoxide.

The 4,4'-biphenol compound is characterized by being represented by the following formula (6).

(6)

(Wherein Q is as defined in Formula 1)

The sulfonated polyarylene ether sulfone copolymer synthesized in the step a) has a repeating unit represented by the following general formula (7).

&Lt; Formula 7 >

(Wherein Q and n are the same as defined in Formula 1)

The thermal crosslinking in the step b) is performed by performing a heat treatment at 180 to 250 ° C for 1 to 12 hours.

The thin film composite membrane in which a sulfonated polyarylene ether sulfone copolymer thin film active layer of a crosslinked structure is formed on a porous thermally-converting poly (benzoxazole-imide) copolymer support prepared according to the present invention has chemical and thermal stability Is superior in organic solvent nanofiltration performance and can be used as an organic solvent nanofiltration membrane because a thin active layer can be formed by a particularly simple and environmentally friendly coating and heat treatment process.

1 is a process and a scanning electron microscope (SEM) image of a porous thermally-converting poly (benzoxazole-imide) copolymer support according to Examples 1-9.
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 a thermogravimetric analysis (TGA) graph showing the thermogravimetric reduction properties of the porous heat-converted poly (benzoxazole-imide) copolymer support prepared according to Example 1 according to the thermal conversion conditions.
4 is a graph showing the results of pure solvent permeability test results of a porous heat-converted poly (benzoxazole-imide) copolymer support prepared according to Example 1. Fig.
FIG. 5 is a graph showing changes in morphology and structure in a high-temperature DMF of a porous thermally-converting poly (benzoxazole-imide) copolymer support prepared according to Example 1 (a) a dimensional change graph, (C) scanning electron microscope (SEM) images].
6 is a graph showing the gel fraction (%) of a thin film composite membrane prepared by preparing a thin film composite membrane according to Example 10, but with different thermal crosslinking times.
7 is a thermogravimetric analysis (TGA) graph showing the thermogravimetric characteristics of a thin film composite membrane prepared according to Example 10, wherein the thin film composite membrane before and after the thermal crosslinking reaction.
8 is a scanning electron microscope (SEM) image of the morphology of the thin film composite film produced according to Example 10. FIG.
9 is a graph showing the THF permeability (a) and the rejection rate (b) of the thin film composite membrane produced according to Example 10. Fig.
10 is a graph showing the DMF permeability (a) and rejection rate (b) of the thin film composite membrane produced according to Example 10. Fig.
11 is a graph showing a self-wound healing phenomenon of a thin film composite film produced according to Example 10. FIG.

In the present invention, a porous heat-converted poly (benzoxazole-imide) copolymer support having a repeating unit represented by the following formula (1); And a sulfonated polyarylene ether sulfone copolymer thin film active layer having a cross-linked structure formed on the support. The present invention also provides a thin film composite membrane for organic solvent nanofiltration.

&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)

The porous thermally-converting poly (benzoxazole-imide) copolymer scaffold has excellent chemical and thermal stability in terms of the structure of the repeating units defined in the above formula (1).

The porous heat-converted poly (benzoxazole-imide) copolymer support is preferably an electrospun film. 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. Accordingly, in the present invention, when the porous thermally-converting poly (benzoxazole-imide) copolymer support is an electrorec- tric membrane, it may preferably have a thickness of 10 to 80 탆 and a porosity of 60 to 80%.

Therefore, in the present invention, the mass transport resistance can be minimized by using a very thin porous support having a thickness of 10 to 80 탆 and an extremely high porosity of 60 to 80% It can be applied to an organic solvent nanofiltration membrane in addition to its excellent chemical and thermal stability.

At this time, if the thickness of the porous support obtained from the electrospray is less than 10 탆, the thickness of the support may be too thin to reduce the mechanical properties, and if the thickness exceeds 80 탆, the mass transfer resistance may increase . If the porosity of the porous support is less than 60%, the separation efficiency of the organic solvent may be deteriorated. If the porosity exceeds 80%, the film formation is not smooth.

The sulfonated polyarylene ether sulfone copolymer thin film active layer having a crosslinked structure formed on the porous support may have a repeating unit represented by the following formula (2).

(2)

(Wherein Q is a single bond or O, S, C (= O), C (= O) NH, Si (CH ₃ ) ₂ , (CH ₂ ) _{p CF 2) q (1≤q≤10),} C (CH 3) 2, C (CF 3) 2, or _{C (CH 3) (CF 3} ) , n is 0, as a repeating unit, the molar ratio of structural unit I < n < 1)

If the thickness of the active layer is less than 50 nm, it is difficult to withstand a high operating pressure. If the thickness of the active layer is more than 1 탆, there is a problem in resistance to mass transfer have.

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, The present invention further provides a method for producing a thin film composite membrane for organic solvent nanofiltration comprising the following steps.

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 by dissolving the hydroxy group-containing polyimide-polyimide copolymer of step I) in an organic solvent by electrospinning;

III) obtaining a porous thermally-converting poly (benzoxazole-imide) copolymer support having the repeating units represented by Formula 1 by thermal conversion of the membrane obtained in the step II); And

IV) forming a sulfonated hydrocarbon-based polymer thin film active layer having a crosslinked structure having the repeating unit represented by the formula (2) on the support; and forming a thin film composite membrane for organic solvent nanofiltration.

In order to synthesize a polyimide, a polyamic acid must first be obtained by reacting an acid dianhydride with a diamine. In the present invention, a compound represented by the following formula 3 is used as an acid anhydride.

(3)

(Wherein Ar ₁ is as defined in Formula 1)

As the monomer for synthesizing the polyimide, any of the acid dianhydrides may be used as long as they are as defined in the above formula (3). However, considering the fact that the thermal and chemical properties of the polyimide synthesized can be further improved, 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-hydroxy diamine, a compound represented by the following formula (4) is used to synthesize hydroxy polyimide.

&Lt; Formula 4 >

(Q in Formula 4 is the same as defined in Formula 1)

As the ortho-hydroxydiamine, there can be used any of those as defined in Chemical Formula 4 above. However, considering 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) .

The present invention also provides a process for producing a hydroxy group-containing polyimide-polyimide copolymer by reacting an acid dianhydride represented by Chemical Formula 3 and an ortho-hydroxy diamine represented by Chemical Formula 4 with an aromatic diamine represented by Chemical Formula 5 as a comonomer, can do.

&Lt; Formula 5 >

(Ar ₂ in the formula (5) 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 (5), but 4,4'-oxydianiline (ODA) or 2,4,6-trimethylphenylenediamine (DAM) .

That is, in step I), the acid dianhydride of Chemical Formula 3, the ortho-hydroxydaramine of Chemical Formula 4, and the aromatic diamine of Chemical Formula 5 are dissolved and stirred 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.

&Lt; General Formula 1 &

(In the general formula 1, Ar ₁ , Ar ₂ , Q, x and y are 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 above step I) represented by the above-mentioned general formula 1 in an organic solvent such as N-methylpyrrolidone (NMP) is subjected to electrospinning I need to make a film.

Subsequently, the hydroxy group-containing polyimide-polyimide copolymer electrospun film is thermally converted to obtain a porous thermally-converting poly (benzoxazole-imide) copolymer support having the repeating unit represented by the above formula (1).

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.

Finally, a sulfonated polyarylene ether sulfone copolymer having a crosslinked structure having a repeating unit represented by the above-mentioned formula (2) was coated on a porous thermally-converting poly (benzoxazole-imide) copolymer support having a repeating unit represented by the above formula Thereby forming a thin film composite membrane for organic solvent nanofiltration, which is the object of the present invention.

At this time, the formation of the sulfonated polyarylene ether sulfone copolymer thin film active layer having a crosslinked structure having the repeating unit represented by the formula (2) in the step IV) may be carried out by a) mixing 4,4'-dichlorodiphenyl sulfone or 4,4'- 4'-difluorodiphenylsulfone, 4,4'-biphenol-based compound and sulfonated 4,4'-dichlorodiphenylsulfone or sulfonated 4,4'-difluorodiphenylsulfone to give sulfonated Synthesizing a polyarylene ether sulfone copolymer; And

b) spray coating and thermally crosslinking the polymer solution in which the sulfonated polyarylene ether sulfone copolymer is dissolved in dimethyl sulfoxide.

The 4,4-biphenol compound used as a monomer for synthesizing the sulfonated polyarylene ether sulfone copolymer in the step a) may be a compound represented by the following formula (6), in which bisphenol A is more preferably used do.

(6)

 (Wherein Q is as defined in Formula 1)

The sulfonated polyarylene ether sulfone copolymer synthesized in the step a) may have a repeating unit represented by the following general formula (7).

&Lt; Formula 7 >

(Wherein Q and n are the same as defined in Formula 1)

Preferably, in step a), 4,4'-dichlorodiphenyl sulfone (DCDPS) or 4,4'-difluorodiphenyl sulfone (DFDPS), 4,4'-biphenol compound Sulfonated 4,4'-dichlorodiphenylsulfone (SDCDPS) or sulfonated 4,4'-difluorodiphenylsulfone (SDFDPS) is reacted with a polymerization solvent such as N-methylpyrrolidone (NMP) in the presence of potassium carbonate The sulfonated polyarylene ether sulfone copolymer can be synthesized by direct polycondensation reaction at 190 DEG C for 16 hours. The sulfonated polyarylene ether sulfone copolymer can be synthesized according to an example of the following reaction formula, And thus the description thereof is omitted in the present invention (F Wang et al., J. Membr. Sci., 197 (2002), p. 231, F Wang et al., Macromol. Symp., 175 (2001), p. 387].

<Reaction Scheme>

Next, a thin film is formed by spray coating a polymer solution prepared by dissolving the sulfonated polyarylene ether sulfone copolymer synthesized in step a) in dimethyl sulfoxide (DMSO) on a support. The spray coating method of the present invention can be easily commercialized in the form of a continuous process together with an IR lamp, and since dimethylsulfoxide (DMSO), which is a relatively environmentally friendly organic solvent, is used as a solvent for forming a thin film by spray coating, Process. Further, the amount of the polymer used is smaller than that of the non-solvent induced phase separation (NIPS) or thermally induced phase separation (TIPS) conventionally used in the separation membrane production method, Because it is simple and short, it has advantages in its manufacturing cost.

As described above, a thin film of a sulfonated polyarylene ether sulfone copolymer having a repeating unit represented by the above formula (7) was formed on a porous thermally-converting poly (benzoxazole-imide) copolymer support by spray coating Finally, the thin film is thermally crosslinked to prepare an organic solvent nanofiltration composite membrane according to the present invention.

The thermal crosslinking is carried out by heat treating the coated thin film at 180-250 ° C. for 1 to 12 hours. When the thermally activated sulfonic acid group reacts with the benzene ring of the main chain of the copolymer at 180-250 ° C., As a result, the crosslinking of the polymer proceeds. Particularly, no additives or catalysts are required, and dimethylsulfoxide (DMSO) used for obtaining a coating solution plays a role and function as a crosslinking reaction promoter. As the crosslinking reaction progresses and the sulfonic acid group disappears, the ion exchange capacity (IEC), which is an ion transporting ability, is lost. However, since the chemical resistance is improved, the gel fraction is increased in proportion to the increase of the crosslinking reaction time.

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 .

(8)

It was confirmed by ¹ H-NMR and FT-IR data that the hydroxy group-containing polyimide-polyimide copolymer represented by formula (8) 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  1] Porous 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 (9) was prepared.

&Lt; Formula 9 >

[ Example  2 to 9] Porous 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.

[Synthesis Example 10] Synthesis of sulfonated polyarylene ether sulfone copolymer

As the monomer, there was used a known method [F (4-dichloro-4-methoxyphenyl) Wang et al., J. Membr. Sci., 197 (2002), p. 231, F Wang et al., Macromol. Symp., 175 (2001), p. 387), a copolymer of sulfonated polyarylene ether sulfone represented by the following formula (10) was synthesized (with a degree of sulfonation of 60%) and confirmed to be synthesized by ¹ H-NMR and FT-IR. As a result, And it was found that it coincided with the described data.

&Lt; Formula 10 >

A sulfonated polyarylene ether sulfone copolymer having a sulfonation degree of 40% was also prepared by varying the molar ratio of the above monomers.

[ Example  10] Thin film Composite membrane  Produce

A porous heat conversion poly (benzoxazole-imide) copolymer support (electrospray membrane) prepared from Example 1 was prepared (film area: 6 cm x 6 cm). 2 mL of a polymer solution obtained by dissolving a sulfonated polyarylene ether sulfone copolymer (sulfonation degree: 60%, 40%) obtained in Synthesis Example 10 in dimethylsulfoxide (DMSO) was spray-coated on the porous support (electrospray membrane) . The thin film was subjected to heat treatment at 180 ° C for 5 hours to have a crosslinked structure to form a sulfonated polyarylene ether sulfone copolymer thin film having a crosslinked structure on a porous heat converting poly (benzoxazole-imide) copolymer support A thin film composite film having an active layer was formed (sample name: X60, X40).

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

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

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.

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.

3 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 heat conversion 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 carried out. As shown in FIG. 3, the weight reduction of pristine (pre-thermal conversion support) is 10% between 40 and 160 minutes 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. 4 is a graph showing the results of pure solvent permeability test of the porous heat-converted poly (benzoxazole-imide) copolymer support prepared according to Example 1. FIG. As shown in FIG. 4, it is preferable to use an alcohol such as isopropyl alcohol (IPA), distilled water, chloroform, dimethylformamide, tetrahydrofuran, toluene, Heptane), it exhibits high pure solvent permeability from not only the chemical resistance of the support but also the high porosity. Therefore, it plays a role as a supporter for organic solvent nanofiltration, and has a chemical resistance and heat resistance It can be applied to organic solvent nanofiltration membrane.

Further, the morphology and structural change of the porous thermally-converting poly (benzoxazole-imide) copolymer support prepared according to Example 1 of FIG. 5 in high temperature DMF was observed [(a) (30 ° C, 60 ° C, 90 ° C, 120 ° C), which is the most deteriorated condition, in the DMF solvent, the heat resistance and chemical resistance of the substrate Is not numerically changed, and it can be seen that there is no significant change even with the naked eye and the scanning electron microscope (SEM) image.

FIG. 6 shows the gel fraction (%) of the thin film composite membrane prepared by preparing the thin film composite membrane according to Example 10, but with different thermal crosslinking times, according to the Soxhlet method (Reference: Polymer testing 22 (2003), p. (W / W ₀ ) X 100, W: weight of dry insoluble portion, W ₀ : initial weight of sample], thermal crosslinking When the reaction time exceeds 5 hours, the gel fraction exceeds 90%. When the reaction time reaches 10 hours, the gel fraction reaches 98% or more, and the crosslinking reaction is stably performed. Thus, it is confirmed that the gel fraction is insoluble in ordinary organic solvents there was.

In addition, FIG. 7 shows a thermogravimetric analysis (TGA) graph of the thermogravimetric characteristics of the thin film composite membrane before and after the thermal crosslinking reaction according to Example 10, wherein 800 ° C. at a heating rate of 5 ° C./min (Sulfonation degree of 40%) and 60 (degree of sulfonation of 60%), respectively, since the decomposition starts at 250 DEG C, The degradation of the sulfonic acid group was observed. However, since the weight change was not observed in the X40 and X60 samples after crosslinking, it can be confirmed that the thin film was thermally softened.

8 shows a scanning electron microscope (SEM) image of the morphology of the thin film composite membrane produced according to Example 10. FIG. As shown in FIG. 8, it can be seen that the thickness of the entire thin film composite film is within 35 μm, and the thickness of the thin film active layer is within 1 μm. In addition, since it was confirmed that no peeling and permeation phenomenon occurred between the thin film and the support during the spray coating and the thermal crosslinking process, it was possible to apply the organic solvent nanofiltration membrane together with the chemical stability as described above.

9 shows the THF permeability (a) and rejection rate (b) of the thin film composite membrane prepared in Example 10 as a graph. The THF permeability (a) and rejection rate (b) hr using a volumetric cylinder. The volume of the permeate was measured for a certain period of time. The permeate and the feed were sampled in the same manner and the rejection rate was measured using HPLC-UV / Vis. As shown in FIG. 9, it can be seen that the rejection ratio of polystyrene having a molecular weight of 236 to 1600 g / mol and a permeability of 0.05 LMH / bar is 99% or more.

10 shows the DMF permeability (a) and rejection rate (b) of the thin film composite membrane prepared in Example 10 as a graph. As a result, it was confirmed that the membrane permeability at 30 ° C, 30 bar and 50 L / hr. &lt; / RTI &gt; In the measurement, the permeation rate was calculated by measuring the volume of the permeate for a certain period of time, and the rejection rate was measured. As a result, the permeation rate was about 0.4 LMH / bar and the polystyrene having a molecular weight of 236 to 1600 g / molecular weight cut off, 90%) of 600 g / mol.

11 is a graph showing a self-wound healing phenomenon of the thin film composite film produced according to Example 10. FIG. 11, it can be seen that the thin film composite membrane of the present invention exhibits much higher permeability when operated in the DMF solvent, while the rejection rate is somewhat lower. As a result, the chemical structure of the active layer in the DMF solvent is loosened High permeability and loose rejection rate curves. Further, in the case of a separator having a high permeability and a low rejection rate when measuring the THF solvent as in the case of a conventional defect, the permeability and rejection ratio of the DMF solvent return to similar to those of the other separators, It can be said that the chemical structures are rearranged by the interaction between the active layer and the DMF solvent to complement small defects on the molecular scale.

As described above, the thin film composite membrane having a sulfonated polyarylene ether sulfone copolymer thin film active layer having a crosslinked structure formed on the porous thermally-converting poly (benzoxazole-imide) copolymer support prepared according to the present invention, In addition to excellent chemical and thermal stability and excellent organic solvent nano filtration performance, it is possible to form a thin film active layer by a particularly simple and environmentally friendly coating and heat treatment process, so that it can be used as an organic solvent nanofiltration membrane in chemical, pharmaceutical or refining industries have.

Claims (11)

A porous thermally-converting poly (benzoxazole-imide) copolymer support having a repeating unit represented by the following formula (1); And a sulfonated polyarylene ether sulfone copolymer thin film active layer having a crosslinked structure having a repeating unit represented by the following formula (2) formed on the 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)

(Wherein Q is a single bond or O, S, C (= O), C (= O) NH, Si (CH ₃ ) ₂ , (CH ₂ ) _{p CF 2) q (1≤q≤10),} C (CH 3) 2, C (CF 3) 2, or _{C (CH 3) (CF 3} ) , n is 0, as a repeating unit, the molar ratio of structural unit I < n &lt; 1) The thin film composite membrane for organic solvent nanofiltration according to claim 1, wherein the porous heat conversion poly (benzoxazole-imide) copolymer support is an electroreson film. The thin film composite membrane for organic solvent nanofiltration according to claim 2, wherein the thickness of the electrodisplacive film is 10 to 80 탆 and the porosity is 60 to 80%. The thin film composite membrane for organic solvent nanofiltration according to claim 1, wherein the thin film active layer has a thickness of 50 nm to 1 占 퐉. I) reacting an acid dianhydride, ortho-hydroxydiamine and an aromatic diamine to obtain a polyamic acid solution, and then synthesizing a hydroxy group-containing polyimide-polyimide copolymer by an azeotropic thermal imidization process;
II) forming a polymer solution by dissolving the hydroxy group-containing polyimide-polyimide copolymer of step I) in an organic solvent by electrospinning;
III) obtaining a porous heat-converted poly (benzoxazole-imide) copolymer support having a repeating unit represented by the general formula (1) according to claim 1 by thermally converting the membrane obtained in the step (II); And
IV) forming a thin film active layer of a sulfonated polyarylene ether sulfone copolymer having a crosslinked structure having a repeating unit represented by the general formula (2) described in claim 1 on the support; and a step of preparing a thin film composite membrane for organic solvent nanofiltration As a method,
The formation of the sulfonated polyarylene ether sulfone copolymer thin film active layer having a crosslinked structure having the repeating unit represented by the general formula (2) described in the above (1) in the step (IV) is carried out by a) dissolving 4,4'- 4,4'-difluorodiphenylsulfone, 4,4'-biphenol compound and sulfonated 4,4'-dichlorodiphenylsulfone or sulfonated 4,4'-difluorodiphenylsulfone are subjected to condensation polymerization reaction Synthesizing a sulfonated polyarylene ether sulfone copolymer; And
b) spray-coating and thermally crosslinking the polymer solution obtained by dissolving the sulfonated polyarylene ether sulfone copolymer in dimethylsulfoxide, thereby forming a thin film composite membrane for organic solvent nanofiltration. [6] The method according to claim 5, wherein the acid dianhydride of step I) is represented by the following formula (3).
(3)

(In the general formula Ar ₁ 3 are as defined in formula (I) of claim 1) [Claim 5] The method according to claim 5, wherein the ortho-hydroxydiamine of the step I) is represented by the following formula (4).
&Lt; Formula 4 >

(Wherein Q in the formula (4) is the same as defined in the formula (1) 6. The method according to claim 5, wherein the aromatic diamine in step I) is represented by the following formula (5).
&Lt; Formula 5 >

(Wherein Ar &lt; ₂ &gt; in the general formula (5) is the same as defined in the general formula (1) The method of claim 5, wherein 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 a high purity, and maintaining an isothermal state for 1 to 2 hours Wherein the organic solvent nanofiltration membrane is a porous membrane. 6. The method according to claim 5, wherein the 4,4'-biphenol compound is represented by the following formula (6).
(6)

(In the above formula (6), Q is as defined in formula (1) 6. The method according to claim 5, wherein the sulfonated polyarylene ether sulfone copolymer synthesized in step a) has a repeating unit represented by the following formula (7).
&Lt; Formula 7 >

(Wherein, in the above formula (7), Q and n are the same as defined in the formula (1)

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