Pim-pi and pim-peg / ppg blending gas separation membranes and method thereof

Abstract

In order to improve the disadvantages of existing PIM-PI-PEG / PPG copolymer-based membranes, the present invention provides a mixed gas separation membrane comprising two polymers with different properties, namely intrinsic microporous polymer-polyimide (PIM-PI) and intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG).

Description

Technology Field

[0001] The present invention relates to a gas separation membrane comprising a mixture of PIM-PI and PIM-PEG / PPG, and a method for manufacturing the same. Background Technology

[0002] Currently, as the use of fossil fuels increases globally, the amount of greenhouse gases released into the atmosphere continues to rise. According to the 6th Assessment Report published by the Intergovernmental Panel on Climate Change (IPCC), the rise in the Earth's average temperature over the past five years (2016–2020) was the highest since 1850.

[0003] CO2, which accounts for the largest share of greenhouse gases, not only contributes significantly to global warming but also causes serious abnormal climate issues such as large-scale fires, heavy rainfall, and heatwaves. Therefore, to reduce the concentration of CO2 in the atmosphere, much research is being conducted to develop Carbon Capture Utilization & Storage (CCUS) technologies. These technologies involve selectively capturing and storing CO2 gas generated from fossil fuels through various methods, as well as converting it into new materials such as methanol or polymers.

[0004] Various methods, including cryogenic distillation, solvent absorption, adsorption, and membrane separation, have been studied for the separation of carbon dioxide. In particular, gas separation using polymer membranes is being extensively researched because it offers advantages such as lower cost, ease of scalability, and modularity compared to other processes. However, membrane-based separation technologies have weaknesses compared to other processes, such as low permeation selectivity and a short lifespan due to membrane aging effects. Therefore, to overcome these limitations, the development of gas separation membranes with excellent gas permeability, mechanical properties, and durability is essential.

[0005] In gas separation using membranes, important parameters are permeability and selectivity. Therefore, an ideal membrane—that is, a high-performance gas separation membrane—must possess excellent gas permeability and selectivity simultaneously. However, since permeability and selectivity are in a trade-off relationship, there are many difficulties in improving them at the same time, and this was confirmed in Robeson's plot, which investigates the permeability vs. selectivity trends of gas separation membranes. Various studies are being conducted to develop membranes with superior performance that surpass the upper bound, which is known as the limit in this graph.

[0006] Generally, glassy polymers used in gas separation membranes possess a high glass transition temperature. Additionally, they have an aligned packing structure between molecules, resulting in excellent thermal and mechanical stability. Thanks to this rigid molecular structure, gas permeability is relatively lower compared to rubber polymer-based membranes, but they offer the advantage of high diffusivity-selectivity.

[0007] In particular, polyimide-type polymers based on 6FDA (4,4′-(Hexafluoroisopropylidene)diphthalic anhydride) are widely used as gas separation membranes because they not only exhibit moderate CO2 permeability but also high thermal and chemical stability.

[0008] Despite these advantages of rigid polymer-based membranes, the high CO2 permeability or selectivity over other gases required for commercialization has not yet been achieved. In particular, the biggest disadvantage of rigid polymers with a high fractional free volume (FFV) is the decrease in gas permeability due to the decrease in free volume over time, i.e., the aging of the polymer membrane.

[0009] Meanwhile, rubbery polymers have a low glass transition temperature at room temperature. T g Because it possesses ), it exhibits high gas diffusivity through the active movement of the main chain. However, since it exhibits high diffusivity for all gases, it does not show diffusivity-selectivity based on the kinetic diameter of the gas. Instead, it exhibits solubility selectivity based on the difference in the relative affinity between the polymer matrix and the gas and the condensability of the gas. Therefore, the gas separation performance of rubber polymer-based membranes has been improved mainly by controlling the selective solubility of polymer materials.

[0010] Poly(ethylene glycol) (PEG), a representative rubbery polymer, possesses a structure in which ether groups are continuously repeated. Since carbon dioxide has higher condensability than other gases and exhibits strong quadrupole-quadrupole moment interactions between carbon dioxide and the ether groups present in PEG, PEG is known as a polymer with high solubility for CO2. However, as the molecular weight of PEG increases, crystallinity develops, which leads to a decrease in permeability and physical properties. Therefore, PEG isomers such as PPG and PEG / PPG (containing poly(propylene glycol)) have frequently been used as materials for gas separation membranes to increase gas permeability by reducing the crystallinity of PEG. However, because the low mechanical properties of such rubbery polymers are insufficient for fabricating self-standing membranes, they have been developed in forms such as copolymers with rigid polymers, cross-linked membranes, and blended polymer membranes.

[0011] Among them, blended membranes are an easy method for effectively forming membranes from polymers that cannot form a single membrane, such as PEG / PPG. In particular, because they exhibit the properties of different polymers mixed together, they are widely used in gas separation membranes. For example, in the case of a membrane formed by blending PEG with various molecular weights with PIM-1 polymer, the introduction of PEG resulted in an increase in CO2 / N2 gas selectivity compared to pristine PIM-1.

[0012] Meanwhile, polymers with intrinsic microporosity-polyimide (PIM-PI) are highly permeable polymer materials that have recently gained attention as membrane materials. This is because the packing of the polymer main chain is suppressed by the ladder-shaped twisted form created through the spiro structure of PIM. Consequently, it exhibits a high FFV, which contributes to the high gas permeability of the membrane. In addition, it possesses the excellent thermodynamic stability and high mechanical properties of PI. Despite these advantages, PIM-PI exhibits moderate gas selectivity and shows aging over time due to the shrinkage of free volume.

[0013] To address these shortcomings of PIM-PI, our previous study developed copolymers between PIM-PI and the rubbery polymer PEG / PPG. Through this, we succeeded in increasing gas selectivity by enhancing the CO2 solubility-selectivity attributed to PEG / PPG while maintaining the thermal and mechanical stability of PIM-PI. However, although these PIM-PI-PEG / PPG copolymer-based membranes exhibited high CO2 / N2 selectivity of 33.5–40.3, their CO2 permeability was significantly reduced to approximately 350–669 Barrer compared to pristine PIM-PI (2156 Barrer). This is because the PEG / PPG segments became entangled within the PIM-PI main chain, reducing the polymer's free volume (Fig. 1a). Prior art literature

[0015] Korean Registered Patent No. 10-1523263 The problem to be solved

[0016] In the present invention, to improve the disadvantages of existing PIM-PI-PEG / PPG copolymer-based membranes, a membrane was prepared by blending two polymers with different properties, PIM-PEG / PPG and PIM-PI. Through this, it was expected that the reduction in free volume caused by PIM-PEG / PPG would be minimized, and mechanical properties would be improved through microphase separation between the two polymers (Fig. 1b).

[0017] Furthermore, we sought to find the optimal mixture composition that could simultaneously enhance CO2 selectivity by PIM-PEG / PPG while minimizing the reduction in the high permeability of PIM-PI by varying the composition of PIM-PEG / PPG relative to PIM-PI. To this end, changes in thermal and mechanical properties, as well as morphology and gas permeability characteristics, were investigated in accordance with changes in the composition of the two polymers, PIM-PI and PIM-PEG / PPG.

[0018] The objectives of the present invention are not limited to those mentioned above. The objectives of the present invention will become more apparent from the following description and will be realized by the means and combinations thereof described in the claims. means of solving the problem

[0019] In the present invention, a PIM-PEG / PPG polymer exhibiting high CO2 selectivity is added to a PIM-PI polymer having high gas permeability at 1.5, 3, and 5 mol% relative to PIM-PI, respectively, so that regarding CO2 Blended membranes (PPB-1.5, PPB-3, and PPB-5) with high permeability and selectivity were fabricated. To maintain high permeability while minimizing the reduction in mechanical properties, the content of PIM-PEG / PPG was added up to a maximum of 5 mol%.

[0020] According to one embodiment of the present invention, a mixed gas separation membrane is provided comprising an intrinsic microporous polymer-polyimide (PIM-PI) having the structure of Formula 1 below and an intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) having the structure of Formula 2 below.

[0021] (Chemical Formula 1)

[0022]

[0023] (Chemical Formula 2)

[0024]

[0025] Here, m and n represent the final molar ratios of PIM-PI and PIM-PEG / PPG, respectively.

[0026] The above intrinsic microporous polymer-polyimide (PIM-PI) is characterized by being obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Chemical Formula 3 below and a diamine durene having the structure of Chemical Formula 4 below.

[0027] (Chemical Formula 3)

[0028]

[0029] (Chemical Formula 4)

[0030] .

[0031] The above intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) is characterized by being obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Chemical Formula 3 below and a diamine PEG / PPG (diamine PEG / PPG) having the structure of Chemical Formula 5 below.

[0032] (Chemical Formula 3)

[0033]

[0034] (Chemical Formula 5)

[0035]

[0036] (Here, x, y, and z in Chemical Formula 5 are the number of repeating units according to the molecular weight of PEG / PPG, each being an integer from 1 to 40).

[0037] The molar ratio of PIM-PEG / PPG relative to PIM-PI is characterized as being 1.5 to 5.0 mol%.

[0038] It is characterized in that as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases, the tensile strength and Young's modulus decrease, and the elongation at break increases.

[0039] The gas permeability of the membrane decreases and the selectivity for CO2 gas increases as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases.

[0040] According to another embodiment of the present invention, a method for manufacturing a mixed gas separation membrane is provided, comprising the steps of: preparing an intrinsic microporous polymer-polyimide (PIM-PI) having a structure of Formula 1 below; preparing an intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) having a structure of Formula 2 below; and mixing the intrinsic microporous polymer-polyimide (PIM-PI) and the intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG).

[0041] (Chemical Formula 1)

[0042]

[0043] (Chemical Formula 2)

[0044]

[0045] Here, m and n represent the final molar ratios of PIM-PI and PIM-PEG / PPG, respectively. Effects of the invention

[0047] As a result of analyzing the thermal characteristics of the obtained blended membranes using TGA, it was confirmed that they have thermal stability up to 300 ℃.

[0048] In addition, when an appropriate amount (5 mol%) of PIM-PEG / PPG was introduced, the microphase separation phenomenon between PIM-PI and PIM-PEG / PPG, which have different properties, was maximized, and the membrane (PPB-5) exhibited high mechanical properties, with the elongation at break value increasing by about 4.4 times (in the case of PPB-5) compared to pristine PIM-PI while maintaining the tensile stress level of non-blended pristine PIM-PI.

[0049] Morphological analyses observed using AFM and SEM clearly demonstrated the phase separation characteristics between the soft region of PIM-PEG / PPG and the hard region of PIM-PI. In particular, it was confirmed that the reduction in the free volume of the PIM-PI polymer caused by the addition of PIM-PEG / PPG was not significant, indicating that the decrease in the permeability of each gas relative to PIM-PI was not substantial.

[0050] When plotted on a Robeson plot, PPB-X demonstrated excellent performance, approaching the upper bound limit for CO2 / N2 of 2008. In particular, PPB-5, which exhibited the most distinct phase separation, showed excellent CO2 separation performance with P(CO2) = 1552.6 Barrer and CO2 / N2 = 29.3.

[0051] In addition, for blended membranes, PPB-X, it was confirmed that in mixed gas separation, similar to the gas permeability performance in single gas, as the content of PIM-PEG / PPG increases, the CO2 permeability decreases, but the CO2 / N2 gas selectivity increases from 9.05 (in the case of PPB-1.5) to 10.10 (in the case of PPB-5).

[0052] In particular, PPB-X, obtained by simply mixing PIM-PEG / PPG and PIM-PI, can be fabricated more easily and simply than existing PIM-PI-PEG / PPG copolymer-based membranes, and also exhibits significantly superior performance in CO2 separation (Copolymer membranes: 350~669 Barrer vs . Mixed polymer membranes: 1552~1620 Barrer).

[0053] Therefore, through the present invention, it was confirmed that a separation membrane with excellent mechanical properties, outstanding gas permeability, and high selectivity can be obtained by blending a PIM-PI polymer with high gas permeability and a PIM-PEG / PPG polymer exhibiting high CO2 selectivity in an appropriate composition, thereby demonstrating the possibility of facilitating the commercialization and mass production of CO2 separation technology.

[0054] The effects of the present invention are not limited to those mentioned above. It should be understood that the effects of the present invention include all effects that can be inferred from the following description. Brief explanation of the drawing

[0055] Figure 1 is a schematic diagram of the expected PEG / PPG chain threading and the resulting free volume in the case of (a) PIM-(durene-PEG / PPG) copolymer, (b) mixed membrane, and PPB-X. Figure 2 shows (a) PIM-PI and (b) PIM-PEG / PPG. 1 This is the H NMR spectrum. Figure 3 shows the IR spectra of mixed membranes according to various PIM-PEG ratios. Figure 4 is a photograph of PIM-PI and PIM-PEG / PPG mixed membranes according to different PIM-PEG / PPG compositions ((a) PPB-1.5, (b) PPB-3 and (c) PPB-5). Figure 5 shows the WAXD spectra of PIM-PI and PPB-X (X= 1.5, 3, 5). Figure 6 shows (a) TGA analysis and (b) DTG graph of PPB-X and single polymers of PIM-PI and PIM-PEG / PPG. Figure 7 is a graph showing (a) the stress-strain curve of PPB-X and (b) the effect of PEG / PPG content on tensile strength, Young's modulus, and elongation at break. Figure 8 shows surface SEM images and EDS elemental mapping images (a'-c') of mixed separation membranes (ac) in (a) PPB-1.5, (b) PPB-3, and (c) PPB-5. Figure 9 shows AFM images of mixed membranes, (a) PPB-1.5, (b) PPB-3, and (c) PPB-5 (all AFM images were recorded at a 500 nm scale). Figure 10 is a graph showing (a) gas permeability and (b) selectivity of PPB-X. Figure 11 is a graph of the permeability-selectivity upper limit for (a) CO2 / N2 and (b) CO2 / CH4. Figure 12 shows (a) the mix-gas permeation and (b) the CO2 / N2 selectivity of PPB-X under conditions of 2 bar and 30 ℃. Specific details for implementing the invention

[0056] The above objects, other objects, features, and advantages of the present invention will be easily understood through the following preferred embodiments associated with the accompanying materials. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and that the spirit of the invention is sufficiently conveyed to a person skilled in the art.

[0057] In this specification, terms such as “comprising” or “having” are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0058] Unless otherwise specified, all numbers, values, and / or expressions representing ingredients and reaction conditions used herein shall be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among others. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including the maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to the maximum value including the maximum value, unless otherwise indicated.

[0060] According to one embodiment of the present invention, a mixed gas separation membrane is provided comprising an intrinsic microporous polymer-polyimide (PIM-PI) having the structure of Formula 1 below and an intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) having the structure of Formula 2 below.

[0061] (Chemical Formula 1)

[0062]

[0063] (Chemical Formula 2)

[0064]

[0065] Here, m and n represent the final molar ratios of PIM-PI and PIM-PEG / PPG, respectively.

[0066] The above intrinsic microporous polymer-polyimide (PIM-PI) is characterized by being obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Chemical Formula 3 below and a diamine durene having the structure of Chemical Formula 4 below.

[0067] (Chemical Formula 3)

[0068]

[0069] (Chemical Formula 4)

[0070] .

[0071] The above intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) is characterized by being obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Chemical Formula 3 below and a diamine PEG / PPG (diamine PEG / PPG) having the structure of Chemical Formula 5 below.

[0072] (Chemical Formula 3)

[0073]

[0074] (Chemical Formula 5)

[0075]

[0076] (Here, x, y, and z in Chemical Formula 5 are the number of repeating units according to the molecular weight of PEG / PPG, each being an integer from 1 to 40).

[0077] The molar ratio of PIM-PEG / PPG relative to PIM-PI is characterized as being 1.5 to 5.0 mol%.

[0078] It is characterized in that as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases, the tensile strength and Young's modulus decrease, and the elongation at break increases.

[0079] The gas permeability of the membrane decreases and the selectivity for CO2 gas increases as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases.

[0080] According to another embodiment of the present invention, a method for manufacturing a mixed gas separation membrane is provided, comprising the steps of: preparing an intrinsic microporous polymer-polyimide (PIM-PI) having a structure of Formula 1 below; preparing an intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) having a structure of Formula 2 below; and mixing the intrinsic microporous polymer-polyimide (PIM-PI) and the intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG).

[0081] (Chemical Formula 1)

[0082]

[0083] (Chemical Formula 2)

[0084]

[0085] Here, m and n represent the final molar ratios of PIM-PI and PIM-PEG / PPG, respectively.

[0087] 1. Results and Discussion

[0088] 1.1 Mixed Gas Separator PPB-X synthesis

[0089] The synthesis of the two polymers, namely PIM-PI (2) and PIM-PEG / PPG (3), was carried out by using PIM-dianhydride (4) to obtain precursor polymers 2 and 3 through condensation polymerization with durene-diamine (5) and PEG / PPG-diamine (6), respectively, following the method reported in the literature (Schematic Figure 1).

[0090] (Schematic Diagram 1)

[0091]

[0092] The structural analysis of the two obtained polymers, namely PIM-PI and PIM-PEG / PPG, was confirmed using 1H NMR spectroscopy (Fig. 2). Specifically, in the case of PIM-PI (2), about 7.5 ppm (H a ), 7.3 ppm (H d ), 6.8 ppm (H b ), and 6.5 ppm (H c The integration ratios of the aromatic hydrogen peaks observed at ) were all observed to be 2:2:2:2, and 2.5~2.2 ppm(H g ,H h ), 2.0 ppm(H i ) and 1.5~1.2 ppm(H e ,H fThe structure of the polymer was confirmed by the fact that the integral ratio of the aliphatic hydrogen peaks observed in ) was 4:12:12. In addition, the relative integral ratio of the hydrogen peaks observed in PIM-dianhydride (4) and durene-diamine (5), that is, the methyl peak (H) in durene i Aromatic hydrogen peak (H) relative to ) a-d It was confirmed that PIM-PI (2) was successfully synthesized through the integration ratio of ) which came out to be about 12:8.

[0093] Also, in the case of PIM-PEG / PPG (3), similar to PIM-PI, 7.5 ppm (H a ), 7.3 ppm (H d ), 6.8 ppm (H b ), and 6.5 ppm (H c Along with the aromatic hydrogen peak observed at ), an aliphatic hydrogen peak originating from PEG appearing at 4.0–3.5 ppm and at 2.5–2.0 ppm (H f , H g ), 1.5~1.3 ppm(H e , H h The structure was confirmed through the hydrogen peak of the PIM structure observed in ).

[0094] The structures of PIM-PI and PIM-PEG / PPG were further confirmed using FT-IR spectroscopy (Fig. 3). Specifically, the characteristic peak of PIM-PI was found at 645 cm⁻¹. -1 Including the CN (CN out-of-plane bending) coming from, 744 cm -1 (imide ring deformation), 1097 cm -1 (COC symmetric stretching), 1356 cm -1(imide CN stretching), 1780 and 1720 cm -1 This was confirmed through peaks at (C=O imide asymmetric and symmetric stretching). Additionally, in the case of PIM-PEG / PPG, most absorption peaks appeared at lower frequencies than those of PIM-PI, specifically at 748 cm⁻¹. -1 (imide ring deformation), 944 cm -1 (CH2-O-CH2symmetric stretching), 1095 cm -1 (COC symmetric stretching), 1356 cm -1 (imide CN stretching), 1768 and 1710 cm -1 The structure was confirmed through absorption peaks at (C=O imide asymmetric and symmetric stretching).

[0096] 1.2 Mixed Gas Separator, PPB-X Manufacturing

[0097] PPB-x blended membranes were prepared by adding PIM-PEG / PPG at molar ratios of 1.5 mol%, 3 mol%, and 5 mol% relative to PIM-PI, respectively, blending the mixture, and then membrane casting. When the content of PIM-PEG / PPG increased to 5 mol% or more, the rigidity of the membrane decreased, preventing membrane casting. Therefore, in this invention, the composition of PIM-PEG / PPG was limited to a maximum of 5 mol%. All polymers were dissolved in chloroform solvent and membranes were prepared using a solvent drying method, yielding flexible membranes with a thickness of 40–50 μm (Fig. 4). The obtained blended membrane of PIM-PI and PIM-PEG / PPG was named PPB-X, where X represents the molar ratio of PIM-PEG / PPG to PIM-PI, and blended membranes with values ​​of 1.5, 3, and 5 were fabricated.

[0098] The structures of the obtained blended membranes, PPB-X, were confirmed using FT-IR spectroscopy. Characteristic peaks of PIM-PI were observed in blended membranes of all compositions, specifically at 645 cm⁻¹. -1 Including CN (CN out-of-plane bending), 744 cm -1 (imide ring bending), 1097 cm -1 (COC symmetric stretching), 1356 cm -1 (imide CN stretching), 1780 and 1720 cm -1Peaks were observed at (C=O imide asymmetric and symmetric stretching). Additionally, a peak attributed to PIM-PEG / PPG (CH2-O-CH2symmetric stretching at 944 cm⁻¹) was observed. -1 This was also observed in all PPB-X, and it was confirmed that the intensity of the corresponding peak increased as the content of PIM-PEG / PPG increased, thereby confirming that PIM-PEG / PPG was successfully blended within PIM-PI (Fig. 3).

[0100] 1.3 Physical Characteristics of PPB-X

[0101] The physical properties of the obtained blended membrane, PPB-X, were analyzed (Table 1). First, the density of PPB-X was measured. As a result, PPB-1.5 (1.335 g / cm³) -1 ) > PPB-3(1.269g / cm -1 ) > PPB-5(1.183g / cm -1 As the content of PIM-PEG / PPG increased, the density showed a tendency to decrease. This trend is attributed to the fact that PIM-PEG / PPG, which contains rubbery-type PEG / PPG with a flexible structure, has a lower density than PIM-PI, so the density of PPB-X decreased as the content of PIM-PEG / PPG increased.

[0102]

[0103] In addition, the fractional free volume (FFV) of the blended membranes was calculated based on these densities (Table 1). As a result, the FFV values ​​of PPB-X showed a decreasing trend as PPB-1.5 (0.212) > PPB-3 (0.211) > PPB-5 (0.210). Generally, FFV tends to increase as density decreases, but the opposite trend was observed in this experiment. It is believed that the decrease in FFV as the content of PIM-PEG / PPG increases is due to the soft PIM-PEG / PPG chains intermingling between the interchain spaces created by the rigid structure of PIM-PI, thereby increasing the occupied volume and consequently causing the FFV to decrease as the content of PIM-PEG / PPG increases.

[0104] Next, Wide Angle X-ray Diffraction (WAXD) spectra were measured on the fabricated polymer membranes in the range of 2θ = 5°–30°. As a result, it was confirmed that all PPB-X samples exhibited amorphousness with broad peaks within the measurement range. Furthermore, regarding the 2θ values ​​with maximum intensity, it was observed that the 2θ values ​​increased as the PIM-PEG / PPG content increased, in the order of PPB-1.5 (11.44°) < PPB-3 (11.56°) < PPB-5 (11.71°) (Fig. 5). This is related to Bragg's rule ( d = λ / 2 sin θ, where λ Using : wavelength of 1.789 Å and θ: scattering angle dWhen converted to spacing values, the values ​​were PPB-1.5 (7.73 Å) > PPB-3 (7.65 Å) > PPB-5 (7.55 Å), confirming that the spacing between polymer chains gradually decreases. This was consistent with the previous FFV trend, and through this, it can be confirmed that as the content of PIM-PEG / PPG increases, the interchain space attributable to PIM-PI decreases.

[0106] 1.4 Thermal Characteristics of PPB-X

[0107] The thermal properties of the blended membrane, PPB-X, were observed via Thermo Gravimetric Analysis (TGA), and the TGA results of PPB-X were compared with the thermal properties of PIM-PI and PIM-PEG / PPG homopolymers (Fig. 6a and Table 2).

[0108] As a result, PPB-X exhibited a two-step thermal degradation peak. In contrast, a one-step mass reduction was observed for the two homopolymers (PIM-PI and PIM-PEG / PPG). The mass reduction of PIM-PI is caused by the decomposition of the polymer backbone and the onset thermal decomposition temperature (T d2 ) is 497℃, and the maximum weight loss temperature (T) confirmed by derivative thermogravimetry (DTG) is max2 It exhibited very high thermal stability at 544 ℃ (Fig. 6b and Table 2).

[0109] In the case of PIM-PEG / PPG, lower thermal stability was observed compared to PIM-PI, and the polymer main chain decomposition onset temperature (T d1 ) is 342 ℃, and the maximum weight loss temperature (Tmax1 ) also showed high thermal stability at 408 ℃.

[0110] Meanwhile, in the case of the blended membrane, PPB-X, a two-step mass reduction was observed. The onset decomposition temperature (T) was 342 °C. d1 The first mass loss observed is due to the degradation of the main chain of the PIM-PEG / PPG polymer. Additionally, it was confirmed via DTG that the weight loss percentage of the corresponding portion increased as the content of PIM-PEG / PPG increased.

[0111] T d2 = 342 ℃, T max2 The second mass loss occurring at 544 ℃ is caused by the decomposition of the PIM-PI polymer main chain and exhibited the same degradation temperature as the PIM-PI homopolymer, and it was confirmed that as the composition of PIM-PEG / PPG increased, the weight loss % of the corresponding peak decreased, and at the same time, the residue at 800 ℃ also decreased.

[0112] As such, it can be seen that PPB-X is a membrane obtained by simply physically mixing two homopolymers, and possesses the thermal degradation characteristics of PIM-PI and PIM-PEG / PPG simultaneously. In addition, it was confirmed that the PPB-X polymer membrane developed in this invention has stable thermal characteristics for use as a gas separation membrane.

[0113]

[0115] 1.5 Mechanical Properties

[0116] To verify the mechanical properties of the blended gas membrane, PPB-X, a strain-stress curve was measured (Fig. 7 and Table 2). As a result, it was confirmed that as the content of the elastic PIM-PEG / PPG increased, the tensile strength and Young's modulus of PPB-X decreased, while the elongation at break increased.

[0117] That is, in blended membranes of all compositions, the tensile strength value gradually decreased from 66.9 Mpa (for pristine PIM-PI) to 62.2 Mpa (for PPB-1.5), 59.9 Mpa (for PPB-3), and 54.0 Mpa (for PPB-5), and also Young's modulus decreased in the order of pristine PIM-PI (1.72 GPa) to PPB-1.5 (1.33 GPa) > PPB-3 (1.3 GPa) > PPB-5 (1.23 GPa).

[0118] However, as the content of PIM-PEG / PPG increased, the elongation at break value increased in the order of 8% (for pure (Pristine) PIM-PI), 24.6% (for PPB-1.5), 31.6% (for PPB-3), and 35.5% (for PPB-5).

[0119] In particular, the elongation at break value of PPB-5 increased by about 4.4 times compared to pristine PIM-PI (8%).

[0120] It is believed that the elastic polymer PIM-PEG / PPG intersects between the free volumes of the main chains formed by the rigid polymer PIM-PI, resulting in well-developed microphase separation between the segments of polymers with different properties, and due to this phase separation, the blended membranes exhibit the rigidity of PIM-PI and the elasticity of PIM-PEG / PPG simultaneously, thereby possessing excellent mechanical properties.

[0122] 1.6 Morphological Analysis

[0123] The morphology of the blended membranes, PPB-X, was analyzed using a scanning electron microscope (SEM) and an atomic force microscope (AFM) (Fig. 8).

[0124] First, surface image analysis using SEM revealed that in all three PPB-X membranes, a dark and dense surface image attributed to the PIM-PI polymer was clearly separated from a bright surface image attributed to PIM-PEG / PPG.

[0125] In other words, it can be seen that phase separation occurred between the hard phase unit formed by PIM-PI and the soft phase unit formed by PIM-PEG / PPG. Furthermore, it was confirmed that this phase separation tended to increase significantly as the content of PIM-PEG / PPG increased (Figs. 8a-8c).

[0126] In addition, it was confirmed that PIM-PI and PIM-PEG / PPG, which have different properties, were successfully blended by observing that PIM-PEG / PPG was evenly distributed in blended membranes of all compositions.

[0127] Additionally, the elemental dispersion and relative content of each membrane were observed through Energy Dispersive Spectroscopy (EDS) analysis. As a result, it was confirmed that the bright regions observed in Figures 9a-9c corresponded to the distribution of O atoms in the EDS mapping images. Furthermore, the oxygen atomic percentage of each polymer membrane was PPB-1.5 (25.48%) < PPB-3 (26.03%) < PPB-5 (26.75%), confirming that the oxygen atomic percentage increased as the content of PIM-PEG / PPG increased (Figures 8a'-8c' and Table 3).

[0128]

[0129] In addition, changes in the morphology of blended membranes as the content of PIM-PEG / PPG increased were further confirmed using AFM. In the AFM images, the dark areas correspond to the relatively soft PIM-PEG / PPG segments, and the bright areas correspond to the hard PIM-PI segments. As shown in Figure 9, it can be confirmed that all three polymer membranes have distinct phase separation between the hard segments and the soft segments.

[0130] It is noteworthy that in the copolymer membranes of PIM-PI and PIM-PEG / PPG used in prior studies, there was no significant change in morphology up to a PEG / PPG content of 15 mol%, whereas in the blended membranes of the present invention, distinct phase separation can be observed even when only a relatively small amount of PIM-PEG / PPG is added, which is 1.5 mol%. This is believed to be because PIM-PEG / PPG can more easily intrude into the interchain space, or free space, created by the backbone of PIM-PI, thereby further increasing the phase separation of the polymer.

[0131] In particular, when the content of PIM-PEG / PPG is 3 mol% or more (PPB-3 and PPB-5), it can be observed that soft PIM-PEG / PPG segments are continuously connected. Based on these results, it is expected that as the amount of PIM-PEG / PPG increases in blended membranes, the microphase separation of the membrane increases, and gas permeability characteristics will be improved through the phase separation created by the connection of these hard segments and soft segments.

[0133] 1.7 Gas Separation Characteristics

[0134] To verify the gas separation characteristics of blended membranes and PPB-X according to PIM-PEG / PPG content, single gas permeability for N2, CH4, and CO2 was measured at 2 atm and 30 °C, and these results were compared with pristine PIM-PI as well as PIM-(durene-PEG / PPG) block-type copolymer membranes from previous studies (Table 4 and Fig. 10). As a result, in all polymer membranes including PIM-PI, gas permeability decreased in the order of P(CO2) > P(CH4) > P(N2), which is a general permeability trend observed in most gas separation membranes.

[0135] In the case of the blended membrane, PPB-X, the permeability for all measured gases tended to decrease as the content of PIM-PEG / PPG increased.

[0136] This is attributed to the fact that the content of ether oxygen included in PIM-PEG / PPG increased, which in turn increased the interaction between polymer main chains and reduced the d-spacing between polymers. This reduction in d-spacing resulted in a decrease in gas permeability. Specifically, the N2 permeability showed a decrease of approximately 64%, from P(N2) = 148 barrer (for PIM-PI) to P(N2) = 53 barrer (for PPB-5), and the CH4 permeability showed a decrease of approximately 55%, from P(CH4) = 209 barrer (for PIM-PI) to P(CH4) = 93.1 barrer (for PPB-5).

[0137] Meanwhile, regarding the permeability to CO2, PPB-5 showed a decrease of approximately 28% compared to the control group, PIM-PI [P(CO2) = 2156 barrer for PIM-PI; P(CO2) = 1552.6 barrer for PPB-5]. In other words, it can be seen that the decrease in permeability to CO2 for blended membranes is not significant compared to other gases. Furthermore, despite this decrease in permeability, the selectivity for CO2 gas increased as the content of PIM-PEG / PPG increased.

[0138] That is, CO2 / N2 increased by about 100% from 14.6 (for PIM-PI) to 29.3 (for PPB-5), and the selectivity of CO2 / CH4 increased by about 62% from 10.3 (for PIM-PI) to 16.7 (for PPB-5).

[0139]

[0140] Next, the diffusivity coefficient and solubility coefficient for each gas of the blended membranes, PPB-X, were calculated (Table 5). For all measured membranes, the diffusivity coefficient decreased in the order of D(CO2) > D(N2) > D(CH4). This order tended to follow the order of the kinetic diameter of the gases (CO2 (3.30 Å) < N2 (3.64 Å) < CH4 (3.8 Å)), and such diffusion behavior is commonly observed in rigid polymer membranes. Through these results, it was confirmed that the blended membranes, PPB-X, with three different compositions still possess the size-sieving property characteristic of rigid polymer membranes, despite the introduction of elastic PEG / PPG.

[0141] In addition, it can be seen that the diffusivity coefficient gradually decreases as the content of PIM-PEG / PPG increases (20.6 (PPB-1.5) > 19.1 (PPB-3) > 18.5 (PPB-5)). This is because the total free volume decreases as PIM-PEG / PPG intercalates between the free volumes attributed to PIM-PI, and it is believed that the diffusivity of the blended membranes for each gas decreases due to this decrease in free volume.

[0143]

[0145] However, it can be seen that the rate of decrease in permeability is not significant compared to the rate of decrease in diffusivity of the mixed polymer membrane. This is because the solubility for CO2 increases with the introduction of PIM-PEG / PPG.

[0146] In other words, solubility in all mixed polymer membranes shows a trend of CO2 > CH4 > N2, because CO2 (304.2 K), which has a higher critical temperature than non-polar gases such as CH4 or N2, exhibits high condensability and solubility coefficients.

[0147] Accordingly, as the content of PIM-PEG / PPG increased, the solubility coefficient of CO2 gas increased from 0.79 (for PPB-1.5) to 0.84 (for PPB-5), and the solubility-selectivity of CO2 for non-polar gases such as N2 also increased.

[0148] The high CO2 solubility observed in blended membranes as described above is due to the interaction between CO2 gas, which possesses a quadrupole moment, and the ether oxygen of PIM-PEG / PPG regarding CO2. This is because the affinity increases. In addition, it can be seen that as the PEG / PPG content increases, the CO2 / N2 selectivity increases faster than the CO2 / CH4 selectivity. This is because PEG / PPG has a low affinity for N2, and N2 is a gas with low condensability, so the solubility for N2 has decreased relatively.

[0149] One thing to note is that when comparing the gas permeability characteristics of the blended membranes between PIM-PI and PIM-PEG / PPG developed in the present invention with the block copolymer of PIM-PI and PIM-PEG / PPG developed in previous studies, it can be seen that the blended membranes, PBB-X, have a higher gas permeability with the same PEG / PPG composition.

[0150] More specifically, in the case of the copolymer co(1:0.05) having a molar ratio of 1:0.05 between durene and PEG / PPG, the CO2 permeability is 669 Barrer, which is about 40% of the CO2 permeability of PPB-5, a blended membrane with the same composition, which is 1552.6 Barrer. These results are due to the fact that, in the case of the copolymer, the PIM-PI and PIM-PEG / PPG units exist simultaneously within a single polymer backbone, causing the soft PEG / PPG molecules to become entangled in the W-shaped polymer backbone formed by PIM-PI, thereby reducing the free volume of the entire polymer.

[0151] However, in the case of blended membranes, since polymers of different properties are mixed, the degree of entanglement is not severe, and therefore micro phase separation occurs between PIM-PI and PIM-PEG / PPG. As a result, the reduction in the free volume of PIM-PI is not significant and remains, which is why it is judged to show higher permeability compared to the copolymer (co(1:0.05)).

[0152] This can be seen from the well-developed micro-separation between the hard segment and the soft segment observed in blended membranes, specifically PPB-X, as confirmed by SEM and AFM.

[0154] 1.8 Transmittance vs. Selectivity

[0155] Next, the separation performance for CO2, such as the selectivity of blended membranes and PPB-X gas membranes for CO2 / N2 (Fig. 11a) and CO2 / CH4 (Fig. 11b), was compared with the upper bound of the Robeson value.

[0156] In addition, the separation performance of PPB-X was compared and analyzed with the gas separation performance of blended membranes mixed with PEG / PPG polymers and rigid type polymers, such as PIM-1 / PEG-PPG, Matrimid / PEG, CA-PEG, PEBAX / PEG, PPO, polycarbonate, 6FDA-DAM, PEG / PPG-based polyimides such as 6FDA-durene / PEG-PPG, BPDA-ODA / PEG-PI, and 9FDA-OBDA / PPG-PI, as well as rigid type polymers such as PIM-1 / PEG-PPG, Matrimid / PEG, CA-PEG, PEBAX / PEG, and PIM-(durene-PEG / PPG) copolymer.

[0157] As shown in Fig. 11a, all three blended membranes developed in the present invention exhibited high CO2 / N2 selectivity along with high permeability. In other words, all three blended membranes demonstrated separation performance approaching the upper bound for CO2 / N2. In particular, PPB-5 exhibited higher selectivity while having similar permeability compared to the other two polymers.

[0158] In addition, it can be confirmed that PPB-X membranes have superior separation performance for CO2 (especially CO2 permeability: 1552 to 1620 barrer) when compared to other commercially available polymers, including PIM-1 / PEG-PPG, Matrimid / PEG, CA-PEG, and PEBAX / PEG, which are polymers blended with PEG and various rigid polymers.

[0159] In addition, it can be seen that it is superior in terms of permeability compared to the PIM-(durene-PEG / PPG) copolymer previously developed by the inventors.

[0160] In addition, it can be seen that the three blended polymer membranes also exhibit excellent separation performance for CO2 / CH4. Specifically, PPB-X exceeds the 1991 upper-bound and approaches the 2008 upper-bound for CO2 / CH4. This is a significantly superior result compared to PEG-based blended membranes such as PIM-1 / PEG-PPG, Matrimid / PEG, CA-PEG, PEBAX / PEG, as well as PIM-(durene-PEG / PPG) copolymer previously developed by the inventors.

[0161] Through this, it was confirmed that the blended gas separation membrane, PPB-X, developed in this invention, possesses high CO2 permeability along with high CO2 / N2 and CO2 / CH4 selectivity by mixing PIM-PI, which has high permeability, and PIM-PEG / PPG, which is CO2-affinity (CO2-philc).

[0163] 1.9 Mixed Gas Separation Characteristics

[0164] Finally, the CO2 / N2 (10 vol% : 90 vol%) mixed-gas permeation of the blended membranes, PPB-X membrane, was evaluated at 2 bar and 30 ℃ (Fig. 12).

[0165] As a result, the mix-gas permeation of all three PPB-X membranes showed a similar trend to the pure gas permeability. That is, as the content of PIM-PEG / PPG increased, the CO2 permeance gradually decreased in the order of PPB-1.5 (19.07 GPU) > PPB-3 (17.51 ​​GPU) > PPB-5 (16.05 GPU) (Fig. 12a and Table 6).

[0166] On the other hand, CO2 / N2 selectivity increased as the PIM-PEG / PPG content increased, with PPB-1.5 (9.05) > PPB-3 (9.84) > PPB-5 (10.10) (Fig. 12b). This trend is consistent with that of pure gas. However, compared to pure gas, selectivity decreased in all polymer membranes, which is due to the composition of the mixed gas used in the experiment being CO2 (10 vol%) and N2 (90 vol%), compared to CO2 This is because N2 has a relatively larger amount.

[0167] In addition, unlike pure gas, mixed gas is considered to have low permeability and selectivity because the two gases engage in competitive adsorption.

[0168]

[0170] 2. Conclusion

[0171] In the present invention, a PIM-PEG / PPG polymer exhibiting high CO2 selectivity is added to a PIM-PI polymer having high gas permeability at 1.5, 3, and 5 mol% relative to PIM-PI, respectively, so that regarding CO2 Blended membranes (PPB-1.5, PPB-3, and PPB-5) with high permeability and selectivity were fabricated. To maintain high permeability while minimizing the reduction in mechanical properties, the content of PIM-PEG / PPG was added up to a maximum of 5 mol%.

[0172] As a result of analyzing the thermal characteristics of the obtained blended membranes using TGA, it was confirmed that they have thermal stability up to 300 ℃.

[0173] In addition, when an appropriate amount (5 mol%) of PIM-PEG / PPG was introduced, the microphase separation phenomenon between PIM-PI and PIM-PEG / PPG, which have different properties, was maximized, and the membrane (PPB-5) exhibited high mechanical properties, with the elongation at break value increasing by about 4.4 times (in the case of PPB-5) compared to pristine PIM-PI while maintaining the tensile stress level of non-blended pristine PIM-PI.

[0174] Morphological analyses observed via AFM and SEM clearly demonstrated phase separation characteristics between the soft region of PIM-PEG / PPG and the hard region of PIM-PI. In particular, it was confirmed that the reduction in the free volume of the PIM-PI polymer caused by the addition of PIM-PEG / PPG was not significant, resulting in minimal decrease in the permeability of each gas compared to PIM-PI. When plotted on a Robeson's plot, all blended membranes, including PPB-X, exhibited excellent performance approaching the 2008 upper bound limit for CO2 / N2. Notably, PPB-5, which exhibited the most distinct phase separation, demonstrated excellent CO2 separation performance with P(CO2) = 1552.6 Barrer and CO2 / N2 = 29.3.

[0175] In addition, for blended membranes, PPB-X, it was confirmed that in mixed gas separation, similar to the gas permeability performance in single gas, as the content of PIM-PEG / PPG increases, the CO2 permeability decreases, but the CO2 / N2 gas selectivity increases from 9.05 (in the case of PPB-1.5) to 10.10 (in the case of PPB-5).

[0176] In particular, PPB-X, obtained by simply mixing PIM-PEG / PPG and PIM-PI, can be fabricated more easily and simply than existing PIM-PI-PEG / PPG copolymer-based membranes, and also demonstrated significantly superior performance in CO2 separation (Copolymer membranes: 350~669 Barrer vs . Mixed polymer membranes: 1552~1620 Barrer).

[0177] Therefore, through the present invention, it was confirmed that a separation membrane with excellent mechanical properties, superior gas permeability, and high selectivity can be obtained by blending a PIM-PI polymer with high gas permeability and a PIM-PEG / PPG polymer exhibiting high CO2 selectivity in an appropriate composition, thereby demonstrating the possibility of facilitating the commercialization and mass production of CO2 separation technology.

[0179] The present invention described above is not limited to the aforementioned embodiments, as various substitutions and modifications are possible within the scope of the technical concept of the present invention without departing from the technical spirit of the present invention for those skilled in the art to which the present invention belongs.

Claims

Claim 1 A mixed gas separation membrane characterized by mixing an intrinsic microporous polymer-polyimide (PIM-PI) having the structure of Chemical Formula 1 below and an intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) having the structure of Chemical Formula 2 below, wherein the molar ratio of PIM-PEG / PPG relative to PIM-PI is 1.5 to 5.0 mol%, (Chemical Formula 1) (Chemical Formula 2) Here, m and n represent the final molar ratios of PIM-PI and PIM-PEG / PPG, respectively, and x, y, and z are the number of repeating units according to the molecular weight of PEG / PPG, each being integers from 1 to 40. Claim 2 A mixed gas separation membrane according to claim 1, wherein the intrinsic microporous polymer-polyimide (PIM-PI) is obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Formula 3 below and a diamine durene having the structure of Formula 4 below (Formula 3). (Chemical Formula 4) . Claim 3 A mixed gas separation membrane according to claim 1, wherein the intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) is obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Formula 3 below and a diamine PEG / PPG (diamine PEG / PPG) having the structure of Formula 5 below (Formula 3). (Chemical Formula 5) (Here, x, y, and z in Chemical Formula 5 are the number of repeating units according to the molecular weight of PEG / PPG, each being an integer from 1 to 40). Claim 4 delete Claim 5 A mixed gas separation membrane according to claim 1, characterized in that as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases, the tensile strength and Young's modulus decrease, and the elongation at break increases. Claim 6 A mixed gas separation membrane according to claim 1, characterized in that as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases, the gas permeability of the separation membrane decreases and the selectivity for CO2 gas increases. Claim 7 A method for manufacturing a mixed gas separation membrane comprising: a step of preparing an intrinsic microporous polymer-polyimide (PIM-PI) having the structure of Chemical Formula 1 below; a step of preparing an intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) having the structure of Chemical Formula 2 below; and a step of mixing the intrinsic microporous polymer-polyimide (PIM-PI) and the intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG); wherein the molar ratio of PIM-PEG / PPG to PIM-PI is 1.5 to 5.0 mol%, (Chemical Formula 1) (Chemical Formula 2) Here, m and n represent the final molar ratios of PIM-PI and PIM-PEG / PPG, respectively, and x, y, and z are the number of repeating units according to the molecular weight of PEG / PPG, each being integers from 1 to 40. Claim 8 A method for manufacturing a mixed gas separation membrane according to claim 7, wherein the intrinsic microporous polymer-polyimide (PIM-PI) is obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Chemical Formula 3 below and a diamine durene having the structure of Chemical Formula 4 below, (Chemical Formula 3) (Chemical Formula 4) . Claim 9 A method for manufacturing a mixed gas separation membrane according to claim 7, wherein the intrinsic microporous polymer-polyethylene glycol / polypropylene glycol (PIM-PEG / PPG) is obtained by the condensation polymerization of an intrinsic microporous polymer-dianhydride (PIM-dianhydride) having the structure of Chemical Formula 3 below and a diamine PEG / PPG (diamine PEG / PPG) having the structure of Chemical Formula 5 below, (Chemical Formula 3) (Chemical Formula 5) (Here, x, y, and z in Chemical Formula 5 are the number of repeating units according to the molecular weight of PEG / PPG, each being an integer from 1 to 40). Claim 10 delete Claim 11 A method for manufacturing a mixed gas separation membrane according to claim 7, characterized in that as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases, the tensile strength and Young's modulus decrease, and the elongation at break increases. Claim 12 A method for manufacturing a mixed gas separation membrane according to claim 7, characterized in that as the molar ratio of PIM-PEG / PPG relative to PIM-PI increases, the gas permeability of the separation membrane decreases and the selectivity for CO2 gas increases.

Images