KR20150056331A - Method for preparation of crosslinked thermally rearranged poly(benzoxazole-co-imide) membranes for flue gas separation and membranes for flue gas separation prepared thereby - Google Patents

Abstract

The present invention is configured to manufacture a thermally rearranged poly(benzoxazole-imide) membrane with a crosslinked structure by crosslinking and thermal rearrangement at the same time by only thermally treating an ortho-hydroxy polyimide membrane having a carboxylic acid, and to apply the same to flue gas separation. According to the present invention, a thermally rearranged poly(benzoxazole-imide) membrane with a crosslinked structure for flue gas separation can be manufactured by only thermal treatment without undergoing a chemical method for forming the crosslinked structure and a complicated process such as UV irradiation, and a membrane for flue gas separation manufactured by the same not only has excellent transmissivity and selectivity, but also us able to be industrialized by mass production by a simple manufacturing process.

Description

TECHNICAL FIELD The present invention relates to a process for preparing a thermally-converting poly (benzoxazole-imide) membrane having a cross-linking structure for flue gas separation and a membrane for separating flue gas produced thereby flue gas separation < RTI ID = 0.0 > and membranes < / RTI &

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a heat-converted poly (benzoxazole-imide) film having a cross-linking structure for flue gas separation and a membrane for separating flue gas produced thereby, (Benzoxazole-imide) membrane having a cross-linking structure for flue gas separation by heat conversion at the same time as thermal cross-linking by directly heat-treating the hydroxypolyimide copolymer film and applying it to flue gas separation will be.

Recently, membrane-based gas separation has attracted attention as a rapidly growing separation technology in response to its importance. Gas separation using these membranes has several advantages, such as lower energy consumption and operating cost, but higher process availability than conventional separation processes. In particular, since the 1980s, a lot of basic research using organic polymer membranes has been conducted, but conventional polymers show relatively low mass transport rates due to the general properties of providing efficient packing in the polymer chain space with little micropores.

On the other hand, polymers with a high level of free volume, known as microporous organic polymers, are emerging as one of the strong candidates in the separation process due to their ability to adsorb to small gas molecules and their enhanced diffusion capability. Therefore, attention is focused on the fact that inherent microporous polymers based on a rigid ladder-like structure having a twisted region that prevents effective packing of the polymer chain space exhibit relatively high gas permeability and selectivity, and thus organic polymers Various researches are under way to develop.

Among these studies, attempts have been actively made to apply stiff glassy wholly aromatic organic polymers such as polybenzoxazole, polybenzimidazole, or polybenzthiazole, which have excellent thermal, mechanical and chemical properties, as gas separation membranes, Most of the polymers are insoluble in common organic solvents, and thus it has been difficult to prepare membranes by a simple and practical solvent casting method. Therefore, in order to overcome this difficulty, the present inventors have recently made a polybenzoxazole film by thermal conversion of a polyimide having a hydroxy group at orthosial position, and compared with the conventional polybenzoxazole film produced by the solvent casting method, , The selectivity of carbon dioxide / methane (CO ₂ / CH ₄ ) is still comparable to that of conventional commercialized cellulose acetate membranes, and there is room for improvement (see Non-Patent Document 1 ).

Further, in order to improve the selectivity of the polybenzoxazole film, a polybenzoxazole film is prepared by thermally converting a blend film of polyimide and poly (styrenesulfonic acid) having a hydroxyl group at the ortho position with the poly (styrenesulfonic acid) at 300 to 650 DEG C, The selectivity of carbon dioxide / methane (CO ₂ / CH ₄ ) was improved by up to 95% as compared with polybenzoxazole membranes prepared by heat conversion from hydroxypolyimide containing no sulfonic acid. However, the synthesis method of the polyimide which can ultimately be a precursor for producing the polybenzoxazole film has not been specifically disclosed. The method of imidization of the hydroxy polyimide, that is, the solution thermal imidization, Or free volume factor and gas separation performance of polybenzoxazole membranes thermally converted therefrom by azeotropic thermal imidization, solid state thermal imidization and chemical imidization, (See Patent Document 1).

Accordingly, the properties of the heat-converted polybenzoxazole are improved by various methods such as solution phase thermal imidization, solid-phase thermal imidization, and chemical imidization, based on the fact that the properties of the thermally- Polybenzimidazole membranes were prepared by thermal conversion of a polyimide having a hydroxyl group at the site of the polysaccharide. However, the polybenzimidazole membrane exhibited excellent separation characteristics due to its specific porous structure due to thermal conversion, The present invention is applied to a separation membrane for removing water from a solvent, and there is no description about the performance as a gas separation membrane (Patent Document 2).

In addition, a polyimide having a hydroxy group at ortho position by a chemical imidization method is synthesized and thermally converted to obtain a polybenzoxazole film. Finally, ultraviolet light (UV) is irradiated to form a polybenzoxazole However, since the polyimide is prepared by the chemical imidization method, the thermal imidization process is omitted, and the polybenzoxazole film, which is thermally converted therefrom, has a cross-linking structure The permeability of carbon dioxide is still relatively low, and there is a disadvantage in the process of using an ultraviolet irradiation apparatus to form a crosslinked structure (Patent Document 3).

Therefore, the inventors of the present invention have focused on the gas transporting behavior of the thermally-converted polybenzoxazole film due to the imidization method of the polyimide, which can be referred to as a precursor, and the cross-linking structure of the polymer chain, A polyimide film having a hydroxy group and a carboxylic acid is synthesized and then subjected to heat treatment only to obtain a crosslinked structure and to obtain a polybenzoxazole film by heat conversion to obtain a crosslinked structure by chemical method and UV irradiation For flue gas separation without complicated process The present inventors have completed the present invention in view of the fact that the separation performance as a film will be remarkably improved.

Patent Document 1 Korean Patent Laid-Open No. 10-2012-0100920 Patent Document 2: US Patent Publication No. US 2012/0305484 Patent document 3 Japanese patent publication Patent specification 2012-521871

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 method for separating flue gas, which has excellent gas permeability and selectivity, without a chemical process for forming a cross- (Benzoxazole-imide) film having a crosslinked structure and a membrane for separating the flue gas produced therefrom.

In order to accomplish the above object, the present invention provides a method for producing a polyamic acid solution, comprising the steps of: i) reacting an acid anhydride, ortho-hydroxy diamine and a comonomer as a comonomer with 3, 5-diaminobenzoic acid to obtain a polyamic acid solution, Synthesizing an ortho-hydroxypolyimide copolymer having a carboxylic acid by the method of the present invention;

ii) forming an ortho-hydroxypolyimide copolymer having a carboxylic acid synthesized in the step i) in an organic solvent and casting it; And

and iii) heat-treating the film obtained in the step ii). The present invention also provides a method for producing a heat-converted poly (benzoxazole-imide) film having a crosslinked structure for separating flue gas.

The acid dianhydride in step i) is characterized by being represented by the following general formula (1).

≪ General Formula 1 &

(In the above general formula (1), Ar 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, and the aromatic ring group is 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-

The ortho-hydroxydiamine of the step i) is represented by the following general formula (2).

≪ General Formula 2 &

(Wherein Q is a single bond or O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _p (1 ≦ _P ≦ 10), (CF ₂ ) _{q q≤10), C (CH 3)} 2, C (CF 3) 2, is _{CO-NH, C (CH 3} ) (CF 3), or a substituted or unsubstituted phenylene ring)

In the azeotropic thermal imidization of step i), toluene or xylene is added to the polyamic acid solution, and the mixture is stirred to perform imidization reaction at 180 to 200 ° C for 6 to 12 hours.

The heat treatment in step iii) is performed by raising the temperature to 350 to 450 ° C at a rate of 1 to 20 ° C / min in an inert gas atmosphere of high purity, and then maintaining an isothermal state for 0.1 to 3 hours.

Further, the present invention provides a heat-converted poly (benzoxazole-imide) film having a crosslinked structure for separating flue gas produced by the above-mentioned production method.

The film is characterized by having a repeating unit represented by the following formula (1).

≪ Formula 1 >

Wherein Ar 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, Or two or more of them form a condensed ring or two or more of them are single bonds, 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 CO-

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,} and _{CO-NH, C (CH 3} ) (CF 3), or a substituted or unsubstituted phenylene ring,

x and y are molar ratios in the repeating unit, 0.75? x? 0.975, 0.025? y? 0.25, and x + y =

It characterized in that said film interplanar distance (d -spacing) of 0.62 ~ 0.67 nm.

Wherein the film has a density of 1.36 to 1.43 g / cm < ³ >.

The membrane is characterized in that the d ₃ average pore diameter is 4.0 Å and the d ₄ average pore diameter is 8.6 Å.

According to the present invention, a heat-converting poly (benzoxazole-imide) film having a cross-linking structure for flue gas separation can be produced only by a chemical process for forming a cross-linking structure and a complicated process such as UV irradiation For the separation of flue gas produced thereby The membrane is not only excellent in transparency and selectivity, but also has a simple manufacturing process and can be commercialized by mass production.

1 is a ¹ H-NMR spectrum of HPIDABA-15 synthesized according to Synthesis Example 4. Fig.
2 is an ATR-FTIR spectrum of HPIDABA-15, HPIDABA-20 and HPIDABA-25 membranes obtained according to Formulation Examples 4 to 6. FIG.
FIG. 3 is a graph showing the ATR-FTIR spectra of heat-converted poly (benzoxazole-imide) copolymer membranes having crosslinked structures prepared according to Examples 2 to 6
4 is a thermogravimetric-mass spectrometry (TG-MS) graph showing the thermogravimetric reduction characteristics of the HPIDABA-25 membrane obtained according to Formulation Example 6. Fig.
5 is a TGA and DTG graph of HPIDABA-5 and HPIDABA-25 obtained according to Formulation Examples 2 and 6, HPI formed according to Reference Example 1 and HPIMPD-5 prepared according to Reference Example 2, respectively.

The flue gas according to the present invention means a gas discharged from a part of the hydrocarbon fuel or from the complete combustion, and includes mainly carbon dioxide, water vapor and nitrogen, and in some cases, at least one hydrogen, oxygen, carbon monoxide, Sulfur oxides and fine particulate matter which are likely to be influenced by the exhaust gas. In the present invention, a method for producing such a flue gas separation membrane and a membrane for separating the flue gas produced thereby are provided will be.

The heat-converted poly (benzoxazole-imide) gas separation membrane having a crosslinked structure produced according to the present invention is based on the synthesis of polyimide prepared by imidizing a polyamic acid obtained by reacting an acid dianhydride with an anhydride. Furthermore, in order to have a cross-linking structure between polymer chains only by heat treatment, it is necessary to have a functional group such as a carboxylic acid in a repeating unit. Also, in the heat treatment process, the structure of polybenzoxazole is changed from polyimide to polyimide because the functional group such as a hydroxyl group at the ortho position of the aromatic imide linkage attacks the carbonyl group of the imide ring to form a carboxy-benzoxazole structure And then decarboxylation by subsequent thermal conversion. In the present invention, a thermally converting poly (benzoxazole-butadiene-styrene copolymer) having a cross-linking structure for flue gas separation is produced through a simple process as described below. Imide) film.

That is, in the present invention, i) a polyamic acid solution is obtained by reacting acid dianhydride, ortho-hydroxydiamine and 3, 5-diaminobenzoic acid as a comonomer, followed by azide thermal imidization, Synthesizing a saw-hydroxy polyimide copolymer;

ii) forming an ortho-hydroxypolyimide copolymer having a carboxylic acid synthesized in the step i) in an organic solvent and casting it; And

and iii) heat-treating the film obtained in the step ii). The present invention also provides a method for producing a heat-converted poly (benzoxazole-imide) film having a crosslinked structure for separating flue gas.

 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 1 is used as an acid anhydride.

≪ General Formula 1 &

(In the above general formula (1), Ar 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, and the aromatic ring group is 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-

As the monomers for synthesizing the polyimide, any of the acid anhydrides may be used as long as they are as defined in the general formula 1. However, considering the fact that the thermal and chemical properties of the polyimide synthesized can be further improved, Hexafluoroisopropylidene phthalic acid dianhydride (6FDA) is preferably used.

Further, in the present invention, in order to have a poly (benzoxazole-imide) copolymer structure, attention has been paid to the fact that polybenzoxazole units can be introduced by heat conversion of ortho-hydroxy polyimide, As the ortho-hydroxydiamine, a compound represented by the following general formula 2 is used to synthesize polyimide.

≪ General Formula 2 &

(Wherein Q is a single bond or O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _p (1 ≦ _P ≦ 10), (CF ₂ ) _{q q≤10), C (CH 3)} 2, C (CF 3) 2, is _{CO-NH, C (CH 3} ) (CF 3), or a substituted or unsubstituted phenylene ring)

As the ortho-hydroxydiamine, there can be used any of those as defined in the above-mentioned general formula 2. However, considering the fact that the thermal and chemical properties of the polyimide to be synthesized can be further improved, It is more preferable to use 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (bisAPAF).

In the present invention, since it is necessary to have a functional group such as carboxylic acid in the repeating unit in order to have a cross-linking structure between polymer chains only by a simple heat treatment process without going through a complicated process such as chemical crosslinking or UV irradiation, Diamino benzoic acid is reacted with the acid anhydride of the general formula 1 and the ortho-hydroxydaamine of the general formula 2 to synthesize an ortho-hydroxy polyimide copolymer having a carboxylic acid .

That is, in the step i), the acid dianhydride of the general formula 1, the ortho-hydroxydaramine of the general formula 2 and the 3,5-diaminobenzoic acid are dissolved in an organic solvent such as N-methylpyrrolidone (NMP) Followed by stirring to obtain a polyamic acid solution. Then, an ortho-hydroxypolyimide copolymer having a carboxylic acid represented by the following general formula (3) is synthesized by azeotropic thermal imidization.

≪ General Formula 3 &

(In the above general formula 3, Ar and Q are as defined in the general formulas 1 and 2, respectively, and x and y are respectively 0.75? X? 0.975 and 0.025? Y? 0.25 and x + y = 1 to be)

In the azeotropic thermal imidization, toluene or xylene is added to the polyamic acid solution, and the mixture is stirred at 180 to 200 ° C. for 6 to 12 hours to perform imidation reaction. During this period, Is separated as an azeotropic mixture of toluene or xylene.

Next, as a step ii), a polymer solution in which an ortho-hydroxypolyimide copolymer having a carboxylic acid in the step i) represented by the general formula 3 is dissolved in an organic solvent such as N-methylpyrrolidone (NMP) Cast on a glass plate to form an ortho-hydroxypolyimide copolymer film having a carboxylic acid.

Finally, the heat-converted poly (benzoxazole-imide) film of the bridged structure for separating flue gas having the repeating unit represented by the following formula (1), which is the final object, is prepared by simply heat-treating the film obtained in the step ii).

≪ Formula 1 >

Wherein Ar 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, Or two or more of them form a condensed ring or two or more of them are single bonds, 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 CO-

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,} and _{CO-NH, C (CH 3} ) (CF 3), or a substituted or unsubstituted phenylene ring,

x and y are molar ratios in the repeating unit, 0.75? x? 0.975, 0.025? y? 0.25, and x + y =

The heat treatment is completed by maintaining an isothermal state for 0.1 to 3 hours after raising the temperature to 350 to 450 DEG C at a rate of 1 to 20 DEG C / min in an inert gas atmosphere of high purity.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for producing a heat-converted poly (benzoxazole-imide) film having a cross-linking structure for separating flue gas according to the present invention will be described in detail with reference to the drawings.

[ Synthetic example  One] Carboxylic acid  Have Ortho - Synthesis of Hydroxypolyimide Copolymer

9.75 mmol of 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (bisAPAF) and 0.25 mmol of 3,5-diaminobenzoic acid (DABA) were dissolved in 10 ml of anhydrous NMP, , 10 mmol of 4,4'-hexafluoroisopropylidene phthalic anhydride (6FDA) 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 thus obtained brown solution was cooled to room temperature, immersed in a distillation shoe, washed several times with hot water, and dried in a convection oven at 120 ° C. for 12 hours to obtain an ortho-hydroxy compound having a carboxylic acid represented by the following formula Polyimide copolymer was synthesized and named HPIDABA-2.5.

(2)

It was confirmed by ¹ H-NMR and FT-IR data that the ortho-hydroxypolyimide copolymer having a carboxylic acid represented by the above-mentioned Synthesis Examples 1 to 2 was synthesized as follows. ^{1 H-NMR (300 MHz,} DMSO- d 6, ppm): 13.50 (s, -COOH), 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 = 8.3 Hz), 7.04 (d, H _ar , J = 8.3 Hz). FT-IR (film): v (OH) at 3400 cm ^-1 , v (C = O) at 1786 and 1716 cm ^-1 , Ar (CC) at 1619, 1519 cm ^-1 , imide v cm ^-1 , (CF) at 1299-1135 cm ^-1 , imide (CNC) at 1102 and 720 cm ^-1 .

[ Synthetic example  2 to 6] Carboxylic acid  Have Ortho - Synthesis of Hydroxypolyimide Copolymer

Also, 0.5 mmol, 1.0 mmol, 1.5 mmol, 2.0 mmol, and 2.5 mmol of bisAPAF, which is a reactant of Synthesis Example 1, were respectively used in the repeating units x and y were synthesized in the same manner as in Synthesis Example 1 [HPIDABA-Y (Y represents the mole fraction of DABA diamine introduced into the repeating unit (percent ), Y = 5, 10, 15, 20, 25).

[ Coating Example  1 to 6] Carboxylic acid  Have Ortho - Preparation of Hydroxypolyimide Copolymer Membrane

HPIDABA-Y (Y = 2.5, 5, 10, 15, 20, 25) synthesized from Synthesis Examples 1 to 6 was dissolved in NMP to prepare a 15 wt% solution and cast on a glass plate. This was placed in a vacuum oven and the remaining NMP was evaporated and maintained at 100 ° C, 150 ° C, 200 ° C and 250 ° C for one hour, respectively, to obtain an ortho-hydroxypolyimide copolymer membrane having carboxylic acid, It was named in the same manner as in Examples 1 to 6.

[ Example  1 to 6] Cross-linking structure  Have Thermal Conversion Poly ( Benzoxazole - Imide ) Copolymer film

The defect-free film obtained from Film Formation Examples 1 to 6 was cut to a size of 3 cm x 3 cm and placed between quartz plates to prevent deformation of the film due to temperature rise in the muffle furnace. The sample was heated to 450 DEG C at a heating rate of 5 DEG C / min in a high-purity argon gas atmosphere, and maintained in an isothermal state for 1 hour. After the heat treatment, the muffle furnace was gradually cooled to room temperature at a cooling rate of less than 10 ° C / min to prepare a thermally-converting poly (benzoxazole-imide) copolymer film having a crosslinked structure represented by Chemical Formula 3. The PBODABA- Y (Y = 2.5, 5, 10, 15, 20, 25).

(3)

X and y in the formula 3 are x = 0.975, 0.95, 0.9, 0.85, 0.8, 0.75 and y = 0.025, 0.05, 0.1, 0.15, 0.2 and 0.25, respectively.

[ Reference example  One] Carboxylic acid  Do not have Ortho - Preparation of Hydroxypolyimide Homopolymer Membrane

An ortho-hydroxypolyimide homopolymer having no carboxylic acid was synthesized in the same manner as in Synthesis Example 1, except that 10 mmol of bisAPAF and 10 mmol of 6FDA were used instead of DABA as a reactant, 1, which was named HPI.

[ Reference example  2] Carboxylic acid  Do not have Ortho - Preparation of Hydroxypolyimide Copolymer Membrane

Hydroxypolyamide having no carboxylic acid was obtained in the same manner as in Synthesis Example 1, except that 9.5 mmol of bisAPAF, 0.5 mmol of meta-phenylenediamine and 10 mmol of 6FDA were used instead of DABA as a reactant. And then a membrane was obtained according to Formulation Example 1, which was named HPIMPD-5.

[ Comparative Example ] Cross-linking structure  Do not have Thermal Conversion Poly ( Benzoxazole - Imide ) Copolymer film

HPIMPD-5 obtained from Reference Example 2 was heat-treated in the same manner as in Example 1 to prepare a heat-converted poly (benzoxazole-imide) copolymer film having no crosslinked structure, which was named PBOMPD-5.

1 shows the synthesis of an ortho-hydroxypolyimide copolymer having carboxylic acid according to the present invention, and a ¹ H- NMR spectrum. From the characteristic peak of hydrogen in the repeating unit, which can be confirmed from the ¹ H-NMR spectrum of FIG. 1, it can be seen that an ortho-hydroxypolyimide copolymer having a carboxylic acid was synthesized.

2 shows the ATR-FTIR spectra of HPIDABA-15, HPIDABA-20 and HPIDABA-25 obtained according to Formulation Examples 4 to 6 among the film formulations of ortho-hydroxypolyimide copolymer membranes having a carboxylic acid according to the present invention Respectively. As shown in FIG. 2, broad stretching vibration peaks due to OH at around 3400 cm ^-1 , C = O stretching vibration peaks at 1786 cm ^-1 and 1716 cm ^-1 , 1619 cm ^-1 and 1519 cm ^-1 An aromatic CC absorption peak at 1377 cm ^-1 , a CN stretching vibration peak at imide, a CF absorption peak at 1299-1135 cm ^-1 , and a characteristic peak such as a CNC absorption peak of imide near 1102 cm ^-1 It was confirmed that an ortho-hydroxypolyimide copolymer film having a carboxylic acid was obtained.

3 shows a cross-sectional structure of a thermally-converted poly (benzoxazole-imide) copolymer film and a conventional polybenzoxazole film (FIG. 3) in accordance with the manufacturing methods of Examples 2 to 6 of the present invention, PBO). ≪ tb >< TABLE > The OH stretching peak appearing at around 3400 cm ^-1 disappears, and two distinct peaks due to the typical benzoxazole ring appear at about 1476 cm ^-1 and 1014 cm ^-1 , indicating that the benzoxazole ring was formed during the heat treatment Could know. In addition, the inherent absorption band of the imide was also found, and the thermal stability of the aromatic imide linkage was confirmed even at the heat treatment temperature up to 450 ° C.

In Table 1, densities and interplanar spacings ( d- spacings) of the samples prepared according to Formulation Examples 1 to 6, Examples 1 to 6, Reference Example 2 and Comparative Examples are shown. The interplanar distance of the thermally-converted poly (benzoxazole-imide) copolymer film having a crosslinked structure was 0.62 to 0.67 nm, and the interplanar distance (0.54 (m)) of the hydroxypolyimide copolymer film before heat conversion according to Formulation Examples 1 to 6 To 0.57 nm), the interplanar distance (0.53 nm) of the hydroxypolyimide copolymer film before thermal conversion without DABA according to Reference Example 2, and the heat-converted poly (benzoxazole -Imide) copolymer film is longer than the interplanar distance (0.59 nm) of the copolymer film, it is easy to see that the average interchain distance is remarkably increased. This is because the density of the thermally converted poly (benzoxazole-imide) 1.38 ~ 1.43 as g / cm ^3, before the thermal conversion Hydroxy polyimide is much reduced as a result in fact to be also consistent as compared to the copolymer film density ^{(1.50 ~ 1.52 g / cm 3} ).

Sample Density (g / cm ³⁾ d- spacing (nm) HPIDABA-2.5 1.51 0.54 HPIDABA-5 1.52 0.55 HPIDABA-10 1.51 0.55 HPIDABA-15 1.51 0.54 HPIDABA-20 1.52 0.57 HPIDABA-25 1.50 0.55 PBODABA-2.5 1.41 0.62 PBODABA-5 1.42 0.62 PBODABA-10 1.40 0.66 PBODABA-15 1.38 0.67 PBODABA-20 1.38 0.66 PBODABA-25 1.43 0.65 HPIMPD-5 1.50 0.53 PBOMPD-5 1.45 0.59

Therefore, the thermally-converting poly (benzoxazole-imide) copolymer membrane prepared according to the present invention has a structure in which the polymer chains are less packed and have a larger space, so that small molecules can permeate and diffuse It can be used as a gas separation membrane because of sufficient space.

In addition, decarboxylation in the course of preparing heat-converted polybenzoxazole from HPIDABA-5 and HPIDABA-25 according to Formulation Examples 2 and 6 of the present invention, HPI and HPIMPD-5 according to Reference Examples 1 and 2 decarboxylation was tested with a thermogravimetric analyzer (TGA). The results are shown in FIGS. 4 and 5, and other thermal properties including changes in glass transition temperature are shown in Table 2.

In Figure 4, there is a pronounced weight loss peak at 370-450 ° C. prior to the typical decomposition temperature of the polymer chain, 500-600 ° C. The release of CO ₂ during this initial weight loss phase is evidenced by a mass spectrometer, Which means that a thermal conversion process is involved. From FIG. 5, it can be clearly seen that the heat conversion temperature is influenced by the fluidity of the polymer chain depending on the degree of crosslinking. This is because the glass transition temperature changes as shown in Table 2 and the temperature change It is also confirmed from the tendency.

Sample Tg ^a
(° C) T _TR ^b
(° C) DABA CO ₂
Weight reduction ^c (%) Thermal Conversion Process CO ₂
Weight reduction ^d (%) Total CO ₂
Weight reduction ^d (%) Total CO ₂
Weight reduction ^e (%) HPI 300 407 - 11.36 11.36 11.25 HPIDABA-2.5 308 410 0.20 11.08 11.28 11.04 HPIDABA-5 305 417 0.39 10.79 11.18 11.04 HPIDABA-10 313 426 0.78 10.22 11.00 8.98 HPIDABA-15 314 430 1.18 9.66 10.84 8.87 HPIDABA-20 314 423 1.57 9.09 10.66 9.98 HPIDABA-25 300 429 1.96 8.52 10.48 8.80 HPIMPD-5 280 400 - 10.79 10.79 10.78

^a midpoint of the endothermic transition DSC secondary scan at a heating rate of 20 / min under ^a nitrogen atmosphere

^b Temperature at the maximum weight reduction point or maximum heat transfer rate to the PBO

^c Theoretical value of CO ₂ weight loss corresponding to removal of DABA carboxylic acid

^d theoretical value of the CO ₂ weight loss corresponding to the thermal conversion reaction

^e Experimental value of CO ₂ weight loss corresponding to the initial stage by TGA

PBODABA-5, PBODABA-10, PBODABA-15 and PBODABA-5 in a heat-converted poly (benzoxazole-imide) copolymer film PBODABA-Y having crosslinked structures prepared according to Examples 1 to 6 of the present invention, To quantitatively analyze the free volume and distribution of PBOMPD-5, a thermally-transforming poly (benzoxazole-imide) copolymer membrane prepared according to Comparative Example 20, PBODABA-25 and no crosslinked structure, a positron decay lifetime analyzer (PALS: positron annihilation lifetime spectroscopy). The results are shown in Table 3.

Sample τ ₃
(ns) I ₃
(%) τ ₄
(ns) I ₄
(%) pore
diameter
d ₃ (A) pore
diameter
d ₄ (A) PBOMPD-5 1.118 + 0.144 7.223 + - 0.936 3.750 + 0.046 12.987 + 0.369 3.69 ±
0.86 8.20 0.11 PBODABA-5 1.097 + - 0.112 7.040 + - 0.813 4.034 + 0.041 12.316 + 0.746 3.63 ±
0.68 8.52 ± 0.09 PBODABA-10 1.073 + - 0.054 6.165 + 0.416 4.146 + 0.030 10.342 + 0.097 3.55 ±
0.33 8.64 ± 0.06 PBODABA-15 1.194 + 0.053 6.655 ± 0.733 4.332 + 0.011 11.942 + 0.387 3.91 ±
0.30 8.84 ± 0.02 PBODABA-20 1.155 + 0.107 6.689 ± 0.770 4.198 ± 0.056 10.919 ± 0.332 3.80
0.62 8.69 ± 0.12 PBODABA-25 1.205 + 0.121 6.257 + 0.875 3.987 ± 0.037 11.887 ± 0.375 3.94 ±
0.67 8.47 ± 0.08

As can be seen in Table 3, the heat-converted poly (benzoxazole-imide) copolymer membrane PBODABA-Y having a crosslinked structure prepared according to an embodiment of the present invention has two o-Ps components:? ₃ and? ₄ , which means that there are two kinds of pores in the film. As a result of PALS analysis, micropores of τ ₃ ~1.2 ns corresponding to d ₃ average pore diameter of 4 Å and micropores of τ ₄ ~ 4 ns corresponding to d ₄ average pore diameter of 8.6 Å were confirmed, and PBODABA The d ₃ average pore diameter of PBODABA-15, PBODABA-20 and PBODABA-25 and the d ₄ average pore diameter of PBODABA-5, PBODABA-10, PBODABA-15, PBODABA-20 and PBODABA-25 were all Which is larger than the average pore diameter of PBOMPD-5.

In addition, the heat-converted poly (benzoxazole-imide) copolymer membrane PBODABA-Y having a crosslinked structure prepared according to Examples 1 to 6 of the present invention and the heat-converted poly (Benzoxazole-imide) copolymer membrane PBOMPD-5 were measured and the permeability and selectivity of various gases were measured. The results are shown in Tables 4 and 5, respectively.

Sample Gas permeability (barrer) ^a He H ₂ CO ₂ O ₂ N ₂ CH ₄ PBODABA-2.5 328 387 415 72 17 10.8 PBODABA-5 422 540 600 115 28.1 18.6 PBODABA-10 359 440 514 94 21.5 13.7 PBODABA-15 398 522 615 117 28.8 19.6 PBODABA-20 382 481 521 97.4 24.0 15.3 PBODABA-25 342 446 498 95 24.7 17.3 PBOMPD-5 427 469 358 82.5 20.5 13.0

^a 1 barrr = 10 ^-10 cm ³ (STP) cm / (s cm ² cmHg)

Sample Selectivity ^b O ₂ / N ₂ CO ₂ / N ₂ CO ₂ / CH ₄ CO ₂ / H ₂ H ₂ / CH ₄ N ₂ / CH ₄ PBODABA-2.5 4.2 24.4 38.4 1.1 35.8 1.6 PBODABA-5 4.1 21.3 32.3 1.1 29.0 1.5 PBODABA-10 4.4 23.9 37.5 1.2 32.1 1.6 XTR-PBOI-15 4.1 21.3 31.4 1.2 26.6 1.5 PBODABA-20 4.1 21.7 34.1 1.1 31.4 1.6 PBODABA-25 3.9 20.2 28.8 1.1 29.1 1.4 PBOMPD-5 4.0 17.4 27.3 0.8 35.8 1.6

^b selectivity is the ratio of the permeability of the two gases

From Tables 4 and 5, the transmittance and selectivity of the heat-transferable poly (benzoxazole-imide) copolymer membrane PBODABA-Y having crosslinked structures prepared according to Examples 1 to 6 of the present invention were measured (Benzoxazole-imide) copolymer film PBOMPD-5 having no cross-linking structure is generally higher than that of the heat-converted poly (benzoxazole-imide) copolymer film PBOMPD-5. In general, it is known that the gas permeation characteristics of glassy polymers depend on the distribution and size of the free volume elements. The permeability coefficient of the PBODABA-Y membrane is greater than the permeability coefficient of the PBOMPD-5 membrane, Size pores. ≪ RTI ID = 0.0 >

The PBODABA-Y film of the present invention was excellent in both the transmittance and the selectivity, and was able to overcome the trade-off relationship of the general transmittance-selectivity. Particularly, it can be seen that the CO ₂ permeability of the CO ₂ / CH ₄ mixed gas is as high as 615 barrer and the selectivity is maintained at a high level.

Therefore, according to the production method of the present invention, the hydroxypolyimide copolymer film having carboxylic acid can be heat treated only by a chemical method for forming a crosslinked structure and a complicated process such as UV irradiation, (Benzoxazole-imide) membrane having a high catalytic activity can be produced. The membrane for separating the flue gas thus produced has excellent permeability and selectivity as well as a simple manufacturing process and can be commercialized by mass production .

Claims (10)

i) reacting an acid anhydride, ortho-hydroxydiamine and 3, 5-diaminobenzoic acid as a comonomer to obtain a polyamic acid solution, and then, by azeotropic thermal imidization, an ortho-hydroxypoly Methyl copolymer;
ii) forming an ortho-hydroxypolyimide copolymer having a carboxylic acid synthesized in the step i) in an organic solvent and casting it; And
and iii) heat-treating the film obtained in the step ii). The method for producing a heat-converted poly (benzoxazole-imide) film having a cross-linking structure for flue gas separation. The process for producing a heat-converted poly (benzoxazole-imide) membrane according to claim 1, wherein the acid dianhydride in step i) is represented by the following general formula (1).
≪ General Formula 1 &

(In the above general formula (1), Ar 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, and the aromatic ring group is 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- The process for producing a heat-converted poly (benzoxazole-imide) film according to claim 1, wherein the ortho-hydroxydiamine of the step i) is represented by the following general formula (2) Way.
≪ General Formula 2 &

(Wherein Q is a single bond or O, S, CO, SO ₂ , Si (CH ₃ ) ₂ , (CH ₂ ) _p (1 ≦ _P ≦ 10), (CF ₂ ) _{q q≤10), C (CH 3)} 2, C (CF 3) 2, is _{CO-NH, C (CH 3} ) (CF 3), or a substituted or unsubstituted phenylene ring) The azeotropic thermal imidization method according to claim 1, wherein the azeotropic thermal imidization is carried out by adding toluene or xylene to the polyamic acid solution and stirring the mixture at 180 to 200 ° C for 6 to 12 hours (Poly (benzoxazole - imide) film having a crosslinking structure for flue gas separation. The method according to claim 1, wherein the heat treatment in step iii) is performed by raising the temperature to 350 to 450 DEG C at a rate of 1 to 20 DEG C / min in an inert gas atmosphere of high purity, and then maintaining an isothermal state for 0.1 to 3 hours (Benzoxazole-imide) film having a cross-linking structure for separating flue gas. A heat-converted poly (benzoxazole-imide) film having a crosslinked structure for separating flue gas produced by the method of any one of claims 1 to 5. The thermally-converting poly (benzoxazole-imide) membrane according to claim 6, wherein the membrane has a repeating unit represented by the following formula (1).
≪ Formula 1 >

Wherein Ar 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, Or two or more of them form a condensed ring or two or more of them are single bonds, 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 CO-
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,} and _{CO-NH, C (CH 3} ) (CF 3), or a substituted or unsubstituted phenylene ring,
x and y are molar ratios in the repeating unit, 0.75? x? 0.975, 0.025? y? 0.25, and x + y = The method of claim 7, wherein the film interplanar distance (d -spacing) the thermal conversion polyester having a crosslinked structure for separating the flue gas, characterized in that 0.62 ~ 0.67 nm (benzoxazole-imide) film. The thermally-converting poly (benzoxazole-imide) membrane according to claim 7, wherein the membrane has a density of 1.36 to 1.43 g / cm ³ . The thermally-converting poly (benzoxazole-imide) resin composition according to claim 7, wherein the membrane has a d ₃ average pore diameter of 4.0 Å and a d ₄ average pore diameter of 8.6 Å. membrane.

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