High-thermal-stability long-carbon-chain polyamide elastomer CO2 separation membrane as well as preparation method and application thereof

Abstract

The invention belongs to the field of polymer gas separation membranes, and discloses a high-thermal-stability long-carbon-chain polyamide elastomer CO2 separation membrane as well as a preparation method and application thereof. The CO2 separation membrane is prepared from an AABB type long-carbon-chain polyamide elastomer, and the AABB type long-carbon-chain polyamide elastomer is formed by condensation polymerization of a long-carbon-chain polyamide hard segment and a polyether soft segment, wherein the number of carbon atoms of diamine and the number of carbon atoms of binary acid are both even numbers. The preparation method of the CO2 separation membrane comprises one of extrusion calendaring and extrusion casting, or isothermal treatment on the basis of the extrusion calendaring and the extrusion casting. The melting film-forming method provided by the invention does not need a solvent, and the preparation process is simple and environment-friendly. The long-carbon-chain polyamide film prepared by the invention has the characteristics of high CO2 permeability, CO2 / N2 separability, high thermal stability, mechanical strength and the like, has a wide application prospect in the field of CO2 separation and recovery, and can be applied to CO2 / N2 separation occasions higher than 100 DEG C, such as thermal power plants, smelteries, large heat supply and heating systems and the like.

Description

Technical Field

[0001] The invention belongs to the field of polymer gas separation membranes, and in particular relates to a high-thermal-stability long-carbon-chain polyamide elastomer CO2 separation membrane and a preparation method and application thereof. Background Art

[0002] Energy and environment have always been issues of common concern to the world, among which CO2 separation is a major challenge facing human society in the 21st century. On the one hand, the rapid development of the world's industry and economy mainly relies on the intensified consumption of fossil energy. The large amount of CO2 emitted by its combustion poses a serious threat to the global ecological environment and may cause global climate deterioration. Therefore, it is particularly important to remove CO2 from flue gas, which requires a process with a high CO2 / N2 separation efficiency. On the other hand, CO2 is often associated with energy gases such as natural gas, oilfield gas, coalfield gas, and biogas. If carbon separation and purification are not carried out, the calorific value of the energy gas will be reduced, and the economy will be poor. Therefore, separating CO2 from energy gas is also an inevitable requirement for energy gas purification.

[0003] Polymer membrane separation technology is an important means of CO2 emission reduction and energy gas purification. It uses pressure difference as a driving force and uses the difference in the permeation rate of different gases in the membrane to achieve separation. This difference mainly comes from the different solubility, diffusivity and reactivity of different gases in the membrane. Compared with traditional absorption technology and amine solvent adsorption technology, membrane separation technology does not require chemical additives and has the advantages of low energy consumption, easy scalability and environmental friendliness. It has received widespread attention and rapid development in recent years. In the process of gas membrane separation, membrane materials are the key factors that determine the membrane separation process. The development of membrane materials with excellent performance has important industrial application significance.

[0004] Polymer separation membranes used for industrial gas separation and / or concentration can be divided into glassy polymers and rubbery polymers according to their mechanism of action. Glassy polymer separation membranes such as cellulose acetate (CA), polyimide (PI) and polysulfone (PSF) have high mechanical strength and thermal stability. They mainly rely on regulating free volume for selective gas permeation. Smaller gas molecules tend to be easier to permeate the separation membrane than larger molecules, so they have a higher CO2 / CH4 ideal separation factor. However, since glassy polymers are easily plasticized under high CO2 pressure or in the presence of a large number of high-grade hydrocarbon pollutants, their CO2 / CH4 mixed gas selectivity will decrease, and such membrane materials have extremely low CO2 permeability, which cannot meet some industrial requirements. Rubbery polymer separation membranes such as polydimethylsiloxane (PDMS) have strong polymer chain mobility, and the diffusion of gas molecules is not affected by size, so they have a higher CO2 permeability. However, since rubbery polymers do not have a size screening effect on gas molecules, their selectivity is not high. Using them for industrial gas separation requires multi-stage membrane separators in series, which has high production costs.

[0005] Long chain polyamide elastomer (LCPAE) is a copolymer formed by alternating the soft segments of polyether and the rigid hard segments of semi-crystalline long chain polyamide (LCPA). It has the characteristics of both rubber polymer and glass polymer and is a rational membrane material for separating CO2 from light gases. Series of elastomers [Energy & Fuels, 2021, 35 (21): 17085-17102]. On the one hand, the crystalline hard segment can serve as a physical crosslinking point to give the membrane material mechanical strength and thermal stability. The soft segment polyether has a low glass transition temperature and has a dipole-quadrupole moment interaction with CO2, giving the membrane material a certain flexibility and CO2 selective permeability; on the other hand, due to the thermodynamic incompatibility between the soft and hard segments of the copolymer, the crystalline and amorphous hard segments are often dispersed as dispersed phases in the amorphous matrix of the soft segment, and there is incomplete phase separation. In other words, there are a large number of amorphous hard segments in the amorphous phase region of the soft segment responsible for permeation. At this time, the crystalline region and the amorphous hard segment enriched region act as "obstacles" to gas permeation, giving the membrane material diffusion selectivity. Based on the affinity between ether oxygen groups and CO2, the solubility and permeability of the gas in the membrane can be effectively improved by increasing the fraction of polyether soft segments. However, the corresponding reduction in hard segment content will lead to a decrease in crystallinity and melting temperature, and cannot achieve a balance between permeation selectivity and thermal stability, which limits its application in high-temperature gas separation applications.

[0006] Freeman et al. [Journal of Polymer Science Part B: Polymer Physics, 2000, 38(15): 2051-2062] determined the phase separation of several polyether-b-polyamide block copolymers with different compositions. The permeability of H2, N2 and CO2 was studied. It was found that the permeability increased with the increase of polyether content. 1074, 4011), the copolymer containing PTMO with weaker polarity ( 2533, 4033) membrane material has a higher gas permeability. In copolymers with higher polar group concentrations, CO2 / N2 and CO2 / H2 selectivity is higher due to the good interaction between CO2 and ether oxygen groups. 2533 has low crystallinity and melting temperature, and is not suitable for gas separation in high-temperature environments. At the same time, the paper does not involve technical solutions for improving the thermal stability of long-chain polyamide elastomers.

[0007] Stribeck et al. [Macromolecules, 2003, 36(3):749-758] used small angle X-ray scattering (SAXS) to study a series of 1-butanol and cyclohexanol-based casts. The gas permeability of the film was studied. It was found that changing the solvent type can regulate the thickness of the amorphous region and the degree of microphase separation of the membrane material. With the increase of the thickness of the polyether phase region and the complete phase separation, the gas permeability improved. However, the paper does not involve the technical solution of how to improve the thermal stability of long carbon chain polyamide elastomers.

[0008] Baer et al. [Polymer, 2012, 53(6): 1383-1392] used a series of PTMO and PA12 with different compositions. Membrane materials, studied the effects of mechanical orientation and copolymer composition on gas permeability and morphology, and found that all PEBA copolymers showed a significant decrease in permeability in the oriented state. This is because the strain-induced crystallization of the polyether soft segment makes the gas diffusion path more tortuous. After annealing, all PTMO crystals melted and the permeability could be restored to a level comparable to that of unoriented membranes. However, the paper does not involve technical solutions for improving the thermal stability of long-chain polyamide elastomers.

[0009] CN114364716A introduces a copolymer having a hard polyamide block and containing polyethylene glycol (PEG), wherein the hard segment is PA6, PA11, PA12 and PA6 / 11, and the soft segment is a polyether derived from PEG and derived from PTMO. The membrane prepared by extrusion casting has good water vapor and carbon dioxide permeability and CO2 / O2 selectivity. At the same time, the mechanical properties before and after the water vapor transmission (MVTR) experiment show that it has good mechanical properties in a wet state. However, the patent does not involve a technical solution for improving the thermal stability of long carbon chain polyamide elastomers.

[0010] CN111032199A introduces a separation membrane cross-linked with poly(amide-b-ether) (PEBA) and diisocyanate polyether. The invention adopts a post-treatment method or a solution method to form a polymer cross-linked solution by dissolving diisocyanate polyether in a solvent. 2533 or 1657 is cross-linked, and the cross-linked film material has better mechanical properties and plasticization resistance and improved CO2 permeability. However, the introduction of more flexible propylene glycol segments reduces the glass transition temperature and melting point of the soft segment of the cross-linked film. At the same time, the chemical cross-linking method involves the use of multiple solvents; and the patent does not involve a technical solution for improving the thermal stability of long carbon chain polyamide elastomers.

[0011] KR102168152B1 introduces a polyethylene glycol-polyhedral oligomeric silsesquioxane (PEG-POSS) and polyether polyamide block copolymer ( 2533, 3533 and 1657, etc.) as the separation layer. First, the porous support layer is ultrasonically treated, and then the edge of the porous support membrane is foiled so that only one side of the porous support membrane is coated with polysiloxane (PDMS) and thermally cross-linked. Finally, the mixed solution constituting the separation layer is coated on the cross-linked PDMS layer. The porous support layer provides a channel for rapid gas permeation, thereby increasing the permeability of the membrane material, which is comparable to pure Compared with the composite membrane of 2533, the permeation-selectivity of the composite membrane with cage-like and polyether groups is further improved. However, the dispersion uniformity of nanofillers in the polymer matrix is ​​difficult to control, which often leads to a decrease in the thermal stability and mechanical properties of the copolymer film, and the patent does not involve a technical solution for improving the thermal stability of long carbon chain polyamide elastomers.

[0012] From the above research, it can be seen that the microstructure of the copolymer is the key factor in determining the gas permeation-separation performance. Through the design of the chain segment structure and the regulation of the condensed structure, separation membrane materials with both high permeability and high separation can be prepared. However, when the membrane separation reactor is used in the chemical process of flue gas decarbonization, such as decarbonization in thermal power plants, smelters and large heating systems, the temperature is generally greater than 100°C, which requires not only that the gas separation membrane has good permeation-separation performance for CO2 / N2, but also that the membrane material has good thermal stability.

[0013] In view of this, the present invention is proposed. Summary of the invention

[0014] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high thermal stability long carbon chain polyamide elastomer CO2 separation membrane and its preparation method and application. The CO2 separation membrane of the present invention is prepared by a melt film forming method using AABB type LCPAE as a resin, which can not only ensure good gas permeation and separation performance, but also have high thermal stability and mechanical strength, achieving a balance and unity between permeation selectivity and thermal stability, and has broad application prospects in the field of CO2 separation and recovery.

[0015] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0016] The invention provides a CO2 separation membrane made of a long carbon chain polyamide elastomer with high thermal stability. The CO2 separation membrane is prepared by adopting an AABB type long carbon chain polyamide elastomer. The long carbon chain polyamide elastomer is formed by condensation polymerization of a long carbon chain polyamide hard segment in which the carbon number of a diamine and the carbon number of a dibasic acid are both even numbers and a polyether soft segment.

[0017] The composition and structure of the soft segment and the hard segment in the AABB-type long-chain polyamide elastomer can be regulated, thereby achieving controllable gas permeation-separation performance and thermal stability of the long-chain polyamide elastomer film material.

[0018] The adjacent molecular chains of the long carbon chain polyamide hard segment will form a hydrogen bond surface structure through the interchain hydrogen bond force. Different arrangements make aliphatic polyamide have the characteristics of homogeneous polycrystal. The inventors of this application found in the experimental process that the hydrogen bond surface structure of the polyamide hard segment can be regulated by copolymerizing with different monomers and changing the thermal history of film processing, giving it adjustability in mechanical, thermal and other properties.

[0019] The Crystal Perfection Index (CPI) quantifies the changes in the hydrogen bond surface structure and is defined as:

[0020]

[0021] Where Ω is a constant related to the type of polyamide and is used to define the CPI of the perfect α phase obtained by slowly cooling the solution during film laying as 1. 100 represents the spacing of the (100) crystal plane, d 010 / 110 Represents the spacing between the (010) and (110) crystal planes, because the diffraction peaks of the (010) and (110) crystal planes are one and the spacing between them is equal.

[0022] On the basis of long carbon chain polyamide homopolymer, the introduction of polyether copolymer units can promote the reorganization of hydrogen bond surface structure of hard segment polyamide during melt cooling. The improvement of hydrogen bond surface structure between polyamide hard segment molecular chains will, on the one hand, make the long carbon chain polyamide elastomer film with high content and low hardness have higher modulus and melting temperature, and can withstand the harsh environment of high pressure and high temperature when treating a large amount of industrial waste gas; on the other hand, with the strengthening of hydrogen bond interaction between amide bonds, during melt cooling, the phase separation degree between soft and hard segments increases, and the hard segment content in the amorphous phase region of the soft segment decreases, which is conducive to the increase of gas permeability.

[0023] Further, according to certain embodiments, the long carbon chain polyamide hard segment is selected from at least one of polyamide 1416, polyamide 1214, polyamide 1212, polyamide 1012, polyamide 810, polyamide 612 or polyamide 610;

[0024] Preferably, the polyamide hard segment is selected from at least one of polyamide 1212, 1012 or 1010;

[0025] More preferably, the polyamide hard segment is polyamide 1012.

[0026] Further, according to certain embodiments, the long carbon chain polyamide hard segment and the polyether soft segment are connected by an ester bond or an amide bond;

[0027] The polyether soft segment is selected from one or more of polyoxyethylene ether, polyoxypropylene ether and polytetramethylene oxide ether;

[0028] Preferably, the polyether soft segment is polytetramethylene oxide.

[0029] Further, according to certain embodiments, the material of the CO2 separation membrane also includes a processing aid, and the processing aid is selected from one or more of a chain extender, an antioxidant, a nucleating agent or a lubricant;

[0030] Preferably, the processing aid is selected from chain extenders, antioxidants and nucleating agents.

[0031] Furthermore, in the present invention, the Shore hardness of the long-chain polyamide elastomer is lower than 50D, the flow temperature of the long-chain polyamide elastomer CO2 separation membrane is 110-160°C, the melting temperature is 120-180°C, the crystallization temperature is 80-150°C; and the crystal perfection index is 0.4-1.0.

[0032] Preferably, the long carbon chain polyamide elastomer CO2 separation membrane has a flow temperature of 130-160°C, a melting temperature of 130-170°C, a crystallization temperature of 90-120°C, and a crystal perfection index of 0.6-0.9.

[0033] Furthermore, in the present invention, the thickness of the CO2 separation membrane is 10-200 μm, the CO2 permeability coefficient of the CO2 separation membrane is ≥60 Barrer, and the CO2 / N2 ideal separation factor is ≥10.

[0034] Preferably, the CO2 separation membrane has a thickness of 10-80 μm, a CO2 permeability coefficient ≥ 80 Barrer, and a CO2 / N2 ideal separation factor ≥ 12.

[0035] The present invention also provides a method for preparing the above-mentioned high thermal stability long carbon chain polyamide elastomer CO2 separation membrane, comprising:

[0036] (1) preparing an AABB type long carbon chain polyamide elastomer and drying it;

[0037] (2) mixing the pellets prepared in step (1) with a processing aid, and melt-extruding to form a film;

[0038] (3) The film prepared in step (2) is pulled and rolled up, and cooled and shaped to obtain a thin film.

[0039] Further, according to certain embodiments, the selected processing aid includes at least one of a chain extender, an antioxidant, a nucleating agent, or a lubricant;

[0040] Preferably, the processing aids are chain extenders, antioxidants and nucleating agents.

[0041] According to certain embodiments, the chain extender of the present invention comprises one or more of a styrene-acrylate copolymer containing a reactive epoxy group, triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane, styrene maleic anhydride or pyromellitic dianhydride;

[0042] The nucleating agent includes an inorganic nucleating agent and / or an organic nucleating agent, wherein the inorganic nucleating agent is selected from one or more of titanium dioxide, kaolin powder, montmorillonite powder, zinc oxide powder, calcium carbonate powder, talcum powder or silicon dioxide powder, and the organic nucleating agent is selected from one or more of fatty carboxylic acid metal compounds, isosorbide nucleating agents or rosin nucleating agents;

[0043] The antioxidant is selected from one or more of hindered phenol antioxidants, hindered amine antioxidants, phosphite antioxidants or sulfur antioxidants.

[0044] In the present invention, AABB type LCPAE is used as the resin to prepare the CO2 separation membrane by the melt film forming method, which can be prepared by calendering, casting and other methods, or further, isothermal heat treatment is performed on the prepared film.

[0045] Further, as an embodiment, in step (2), the method for preparing the film after melt extrusion includes a calendering method, and the calendering method includes the following steps:

[0046] The pellets are melted and plasticized and extruded through a twin-screw extruder, and then formed into a sheet film through a die. The temperatures of the barrel zone 1, barrel zone 2, die zone 1, and die zone 2 of the extruder are controlled at 180-250°C, and the screw speed is 10-100rpm. The obtained sheet film is extruded and calendered into a film through a twin-roll calender in a melt flow state. The temperature of the calender roll is 180-250°C, and then the film is directly laminated with the cloth base under the calender roll to form a film.

[0047] Preferably, in step (3), the traction speed of the traction machine is 1-100 rpm, and the winding speed of the winding machine is 1-100 rpm.

[0048] Further, as an embodiment, in step (2), the method for preparing the film after melt extrusion comprises a casting method, and the casting method comprises the following steps:

[0049] The pellets are plasticized and extruded by a twin-screw extruder, and then formed into a sheet film through a T-shaped forming die. The temperatures of the barrel zone 1, barrel zone 2, die zone 1, and die zone 2 of the extruder are 180-250°C, and the screw speed is 10-100rpm. The obtained sheet film is cast in a sheet shape onto the roller surface of a steadily rotating cooling roller in a melt flow state. The film is cooled and shaped on the cooling roller. There is an air knife on the side of the cooling roller with a nozzle length consistent with the roller surface width, the nozzle gap is 0.5-2mm, and the air knife wind pressure is 98-980kPa.

[0050] Furthermore, as a preferred embodiment, in step (2), after the film is formed, the film is also subjected to isothermal heat treatment;

[0051] Preferably, the isothermal heat treatment comprises annealing the film obtained by melt film formation, the annealing temperature is selected from any temperature value between 60-180° C., and the annealing time is 0.5-5 h.

[0052] Preferably, the annealing temperature is 90-150° C., and the annealing time is 0.5-2 h.

[0053] The above-mentioned thermal annealing treatment can promote the activation and rearrangement of the molecular chains, change the original crystal structure and microphase separation morphology of the polymer, and thus achieve the adjustability of the permeability and separation performance of the gas separation membrane without changing the composition of the copolymer.

[0054] The present invention also provides an application of a high thermal stability long carbon chain polyamide elastomer in the preparation of a CO2 separation membrane, wherein the high thermal stability long carbon chain polyamide elastomer is obtained by polycondensation of an AABB type long carbon chain polyamide hard segment in which the carbon number of the diamine and the carbon number of the dibasic acid are both even numbers and a polyether soft segment;

[0055] Preferably, the CO2 separation membrane is used for flue gas decarbonization and can withstand the high pressure generated when treating a large amount of industrial waste gas.

[0056] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0057] 1. The present invention provides a CO2 separation membrane of a long carbon chain polyamide elastomer with high thermal stability. The CO2 separation membrane of the present invention is prepared by a melt film forming method using AABB type LCPAE as a resin. The long carbon chain polyamide elastomer of the present invention is obtained by polycondensation of an AABB type polyamide hard segment and a polyether soft segment, and has a high flow temperature and melting temperature. By changing the composition and processing heat history of the copolymer, the hydrogen bond surface structure of the polyamide hard segment can be regulated, thereby promoting the increase in the degree of phase separation between the soft and hard segments, and giving the elastomer better gas permeability.

[0058] 2. The present invention improves the modulus and melting temperature of the long carbon chain polyamide elastomer film with high content and low hardness by enhancing the hydrogen bond interaction between the hard segment polyamide molecular chains, and can withstand the high pressure and high temperature harsh environment when treating a large amount of industrial waste gas. Therefore, the prepared CO2 separation membrane not only has good gas permeation and separation performance, but also has high thermal stability and mechanical strength, and achieves the balance and unity of permeation selectivity and thermal stability. It has broad application prospects in the field of CO2 separation and recovery, and can be applied to CO2 / N2 separation occasions above 100°C, such as thermal power plants, smelters and large heating systems.

[0059] 3. The method for preparing the high thermal stability long carbon chain polyamide elastomer CO2 separation membrane of the present invention adopts a melt film forming method that does not require a solvent, and the preparation process is simple and environmentally friendly. In addition, it does not require a large amount of additive components, which is more environmentally friendly and scientific.

[0060] 4. In the present invention, annealing can effectively regulate the aggregated structure of the film. By selecting the thermal annealing temperature, the permeability and separation performance of the gas separation membrane can be adjusted without changing the composition of the copolymer, and a CO2 separation membrane with more applicable scenarios can be prepared.

[0061] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the accompanying drawings:

[0063] Figure 1 These are the DSC graphs of the long carbon chain polyamide elastomer CO2 separation membranes prepared in Examples 1 and 2 of the present invention and Comparative Example 1, wherein they are the secondary heating (a) and primary cooling DSC curves (b) obtained by scanning LCPAE pellets at a fixed heating rate of 10°C / min in a nitrogen atmosphere.

[0064] Figure 2 DMA graphs of the long carbon chain polyamide elastomer CO2 separation membranes prepared in Examples 1 and 2 of the present invention and Comparative Example 1, wherein the DMA curves of the LCPAE film are: (a) storage modulus (G') and (b) loss factor (tanδ);

[0065] Figure 3 Engineering stress-strain curves of the long carbon chain polyamide elastomer CO2 separation membranes prepared in Examples 1 and 2 of the present invention and Comparative Example 1.

[0066] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0068] In the present invention, the parameter definitions and detection methods for measuring film performance are as follows:

[0069] The thickness of the film can be tested using the 543-791B digital height gauge.

[0070] The hydrogen bond surface structure can be quantified using the Crystallographic Perfection Index (CPI), defined as:

[0071] The thermal stability of the separation membrane can be expressed by the flow temperature (T flow ) characterization, which is defined as the temperature at which the storage modulus of the sample reaches 1MPa. The test method is as follows: The thermomechanical properties of the sample are characterized by using a TA Q800 thermomechanical analyzer, heating from -120°C to 180°C at a rate of 3°C / min, with a test frequency of 1Hz and a strain of 0.1%.

[0072] The CO2 permeability coefficient is used to characterize the speed of gas permeation through the film. The CO2 permeability coefficient and N2 permeability coefficient of the LCPAE-based film of the present invention are measured according to the method of GB / T 1038-2000. The test temperature and pressure are 35°C and 1 Barrer respectively. The ratio of the two gas permeability coefficients is the ideal separation factor.

[0073] The following examples 1-2 use a calendering method to prepare films:

[0074] Example 1

[0075] The pellets of AABB type long carbon chain polyamide elastomer A with an intrinsic viscosity of 175.8 dL / kg, a Shore hardness of 24D, PA1012 as a hard segment, and polytetramethylene ether glycol-3000 as a soft segment were selected for film preparation. The specific steps are as follows:

[0076] (1) drying pellets of the long carbon chain polyamide elastomer A in a vacuum oven;

[0077] (2) The dried pellets, 0.5% antioxidant 1098, 0.5% chain extender styrene-acrylate copolymer, and 0.5% silicon dioxide are mixed uniformly and plasticized and extruded through a twin-screw extruder. The hard segment melting point of the long carbon chain polyamide elastomer A is 176° C. When the tubular film blank is formed through the die, the temperatures of the extruder barrel zone 1, barrel zone 2, mold zone 1, and mold zone 2 are 210° C., 220° C., 250° C., and 250° C., respectively, and the screw speed is 10 rpm. The obtained tubular film blank is pressed by a calendering method in a melt-flowing state, the calendering roller temperature is 200° C., and then the film is directly bonded to the cloth base under the calendering roller;

[0078] (3) The membrane pressed out in step (2) is pulled and wound, the pulling speed of the pulling machine is 50 rpm, and the winding speed of the winding machine is 50 rpm. After cooling and shaping, an LCPAE separation membrane (A1) is obtained.

[0079] The film thickness of LCPAE separation membrane (A1) is 56 μm, and its flow temperature (Tflow ) is 157℃, the CO2 permeability coefficient is 103Barrer, and the ideal separation factor of CO2 / N2 is 17.

[0080] Example 2

[0081] Fixed copolymer composition: Select the pellets of AABB type long carbon chain polyamide elastomer B with an intrinsic viscosity of 211.6 dL / kg, a Shore hardness of 28D, PA1012 as the hard segment, and polytetramethylene ether glycol-2000 as the soft segment for film preparation. The specific steps are as follows:

[0082] (1) drying pellets of the long carbon chain polyamide elastomer B in a vacuum oven;

[0083] (2) The dried pellets, 0.5% antioxidant 1098, 0.5% chain extender styrene-acrylate copolymer, and 0.5% silicon dioxide are mixed uniformly and plasticized and extruded through a twin-screw extruder. The hard segment melting point of the long carbon chain polyamide elastomer B is 169° C. When the tubular film blank is formed through the die, the temperatures of the extruder barrel zone 1, barrel zone 2, mold zone 1, and mold zone 2 are 200° C., 220° C., 240° C., and 240° C., respectively, and the screw speed is 10 rpm. The obtained tubular film blank is pressed by a calendering method in a melt-flowing state, and the temperature of the calendering roller is 200° C., and then the film is directly bonded to the cloth base under the calendering roller;

[0084] (3) The membrane pressed out in step (2) is pulled and wound, the pulling speed of the pulling machine is 50 rpm, and the winding speed of the winding machine is 50 rpm. After cooling and shaping, an LCPAE separation membrane (B1) is obtained.

[0085] The film thickness of LCPAE separation membrane (B1) is 60 μm, and its flow temperature (T flow ) is 127℃, CO2 permeability coefficient is 84Barrer, and CO2 / N2 ideal separation factor is 18.

[0086] The following examples 3-4 use a casting method to prepare films:

[0087] Example 3

[0088] In this embodiment, the specific steps for preparing the long carbon chain polyamide elastomer CO2 separation membrane (A2) are as follows:

[0089] The long carbon chain polyamide elastomer A of Example 1 is used. Unlike Example 1, the melt extruded by the extruder is subjected to a film-forming method by a casting method. The nozzle gap is 0.5 mm, the air knife pressure is 98 kPa, the traction speed of the traction machine is 20 rpm, and the winding speed of the winder is 20 rpm. After cooling and shaping, an LCPAE separation membrane (A2) is obtained.

[0090] The film thickness of LCPAE separation membrane (A2) is 50 μm, and its flow temperature (T flow ) is 158℃, CO2 permeability coefficient is 98Barrer, and CO2 / N2 ideal separation factor is 19.

[0091] Example 4

[0092] In this embodiment, the specific steps for preparing the long carbon chain polyamide elastomer CO2 separation membrane (B2) are as follows:

[0093] The long carbon chain polyamide elastomer B of Example 2 is used. Unlike Example 2, the melt extruded by the extruder is subjected to film forming by a casting method. The nozzle gap is 0.5 mm, the air knife pressure is 98 kPa, the traction speed of the traction machine is 20 rpm, and the winding speed of the winder is 20 rpm. After cooling and shaping, an LCPAE separation membrane (B2) is obtained.

[0094] The film thickness of LCPAE separation membrane (B2) is 55 μm, and its flow temperature (T flow ) is 125℃, the CO2 permeability coefficient is 80Barrer, and the ideal separation factor of CO2 / N2 is 20.

[0095] Comparative Example 1

[0096] In this comparative example, the specific steps for preparing the long carbon chain polyamide elastomer CO2 separation membrane (C1) are as follows:

[0097] Commercially available Shore hardness 25D The PA12-based long carbon chain polyamide elastomer C of 2533 has a copolymer composition consistent with that of the embodiment, a tensile strength of 27.9±1.9 MPa, and an elongation at break of 3207±191%.

[0098] (1) drying pellets of the long carbon chain polyamide elastomer C in a vacuum oven;

[0099] (2) The dried pellets, 0.5% antioxidant 1098, 0.5% chain extender styrene-acrylate copolymer, and 0.5% silicon dioxide are mixed uniformly and plasticized and extruded through a twin-screw extruder, and the hard segment melting point of the long carbon chain polyamide elastomer C is 138° C. When the tubular film blank is formed through the die, the temperatures of the extruder barrel zone 1, barrel zone 2, mold zone 1, and mold zone 2 are 170° C., 190° C., 210° C., and 210° C., respectively, and the screw speed is 10 rpm. The obtained tubular film blank is pressed by a calendering method in a melt flow state, and the temperature of the calendering roller is 165° C., and then directly laminated with the cloth base under the calendering roller to form a film;

[0100] (3) The membrane pressed out in step (2) is pulled and wound, the pulling speed of the pulling machine is 50 rpm, and the winding speed of the winding machine is 50 rpm. After cooling and shaping, an LCPAE separation membrane (C1) is obtained.

[0101] The film thickness of LCPAE separation membrane (C1) is 57 μm, and its flow temperature (T flow ) is 120℃, the CO2 permeability coefficient is 114Barrer, and the ideal separation factor of CO2 / N2 is 17.

[0102] Comparative Example 2

[0103] In this embodiment, the specific steps for preparing the long carbon chain polyamide elastomer CO2 separation membrane (C2) are as follows:

[0104] The long carbon chain polyamide elastomer C of Comparative Example 1 is used. Unlike Comparative Example 1, the melt extruded by the extruder is subjected to a casting method to form a film. The nozzle gap is 0.5 mm, the air knife pressure is 98 kPa, the traction speed of the traction machine is 20 rpm, and the winding speed of the winder is 20 rpm. After cooling and shaping, an LCPAE separation membrane (C2) is obtained.

[0105] The film thickness of LCPAE separation membrane (C2) is 55 μm, and its flow temperature (T flow ) is 122℃, the CO2 permeability coefficient is 109Barrer, and the CO2 / N2 ideal separation factor is 19.

[0106] The film performance indicators of Examples 1-4 and Comparative Examples 1-2 are shown in Table 1.

[0107] Table 1 Performance of Examples 1-4 and Comparative Examples Films

[0108]

[0109] Figure 1 The DSC graphs of the long carbon chain polyamide elastomer CO2 separation membranes prepared in Examples 1 and 2 of the present invention and Comparative Example 1 show that the melting temperatures of the LCPAE-A and LCPAE-B membrane materials using polyamide PA1012 as the hard segment are 176 and 169°C, respectively, which are greater than the LCPAE-C membrane material using PA12 as the hard segment (138°C). Similarly, the crystallization temperature of the PA1012-based elastomer is also higher than that of the PA12-based elastomer.

[0110] Figure 2DMA graphs of the long carbon chain polyamide elastomer CO2 separation membranes prepared in Examples 1 and 2 of the present invention and Comparative Example 1. It can be seen that above the melting temperature of the soft segment, the storage modulus curve has a platform region, the temperature point at which the platform modulus of the PA1012-based elastomer decreases is higher than that of the PA12-based elastomer, and the flow temperatures are all greater than 120°C.

[0111] Figure 3 The engineering stress-strain curves of the long carbon chain polyamide elastomer CO2 separation membranes prepared in Examples 1 and 2 of the present invention and Comparative Example 1 show that the fracture strains of the three copolymers are all greater than 2000%, and the tensile strength is greater than 20 MPa, and they have good mechanical strength when prepared into thin films.

[0112] By comparing the gas permeability and separation properties of type A and B separation membranes with type C separation membrane, it can be seen that when the soft segment content is the same, the permeability of the LCPAE separation membrane with PA1012 as the hard segment is slightly lower than that of the LCPAE separation membrane with PA12 as the hard segment, but the separation performance is equivalent; and the higher the crystal perfection index, the better the gas permeability performance.

[0113] In summary, the number of methylene groups of the dibasic acid and diamine in the hard segment structure of the AABB type long carbon chain polyamide elastomer prepared by the present invention is equal, so that the amide bonds have stronger hydrogen bond interactions. When having the same high soft segment content, the flow temperature (T flow ), melting temperature (T m ) and crystallization temperature (T c ) is significantly higher than that of polyamide elastomers using PA12 as the hard segment, which enables the former to maintain dimensional stability at higher temperatures, cure faster during thermal processing, and have better processing efficiency. In addition, the increase in the length of the soft segment will increase the mobility of the chain segment, thereby promoting the improvement of the hydrogen bond surface structure of the hard segment during processing, thereby achieving improved thermal stability and gas permeability of the separation membrane.

[0114] The following Examples 5-17 are based on melt film formation and are isothermal treatment of the film.

[0115] Example 5

[0116] In this embodiment, the specific steps for preparing the long carbon chain polyamide elastomer CO2 separation membrane (A3) are as follows:

[0117] The separation membrane (A1) prepared in Example 1 was placed in a vacuum or nitrogen atmosphere and annealed at 70°C for 2 hours. The CO2 permeability coefficient was measured to be 97 Barrer and the CO2 / N2 ideal separation factor was 25.

[0118] Example 6

[0119] In this embodiment, the specific steps for preparing the long carbon chain polyamide elastomer CO2 separation membrane (B3) are as follows:

[0120] The separation membrane (B1) prepared in Example 2 was placed in a vacuum or nitrogen atmosphere and annealed at 70°C for 2 hours. The CO2 permeability coefficient was measured to be 78 Barrer and the CO2 / N2 ideal separation factor was 24.

[0121] The following are Examples 7-17. The operating steps are the same as in Examples 5 and 6. The specific process parameters and film performance indicators are shown in Table 2.

[0122] Table 2 Process parameters and film performance indicators of Examples 7-17

[0123]

[0124] In addition, through the heat treatment of the film in Examples 7-17, it can be found that, without changing the copolymer composition, selecting different annealing times and temperatures can further adjust the degree of perfection of the hydrogen bond surface, so that the thermal stability and selective permeability of the film can be balanced. When the annealing temperature is controlled at 90-150°C and the annealing time is 0.5-2h, the CO2 permeability coefficient and CO2 / N2 separation factor can be improved. When the temperature is controlled at 130°C and the annealing time is 2h, the best CO2 permeability coefficient and CO2 / N2 separation factor can be obtained, and the thermal stability is also at a high level.

[0125] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A high thermal stability long carbon chain polyamide elastomer CO2 separation membrane, characterized in that: The AABB type long carbon chain polyamide elastomer is prepared by polycondensation of a long carbon chain polyamide hard segment in which the carbon number of the diamine and the carbon number of the dibasic acid are both even numbers and a polyether soft segment.

2. The high thermal stability long carbon chain polyamide elastomer CO2 separation membrane according to claim 1, characterized in that: The long carbon chain polyamide hard segment is selected from at least one of polyamide 1416, polyamide 1214, polyamide 1212, polyamide 1012, polyamide 1010, polyamide 810, polyamide 612 or polyamide 610; Preferably, the polyamide hard segment is selected from at least one of polyamide 1212, 1012 or 1010; More preferably, the polyamide hard segment is polyamide 1012.

3. The high thermal stability long carbon chain polyamide elastomer CO2 separation membrane according to claim 1, characterized in that: The long carbon chain polyamide hard segment and the polyether soft segment are connected by an ester bond or an amide bond; The polyether soft segment is selected from one or more of polyoxyethylene ether, polyoxypropylene ether and polytetramethylene oxide ether; Preferably, the polyether soft segment is polytetramethylene oxide.

4. The high thermal stability long carbon chain polyamide elastomer CO2 separation membrane according to any one of claims 1 to 3, characterized in that: The Shore hardness of the long carbon chain polyamide elastomer is lower than 50D, the flow temperature of the long carbon chain polyamide elastomer CO2 separation membrane is 110-160°C, the melting temperature is 120-180°C, the crystallization temperature is 80-150°C, and the crystal perfection index is 0.4-1.0; Preferably, the long carbon chain polyamide elastomer CO2 separation membrane has a flow temperature of 130-160°C, a melting temperature of 130-170°C, a crystallization temperature of 90-120°C, and a crystal perfection index of 0.6-0.

9.

5. The high thermal stability long carbon chain polyamide elastomer CO2 separation membrane according to any one of claims 1 to 3, characterized in that: The thickness of the CO2 separation membrane is 10-200 μm, the CO2 permeability coefficient of the CO2 separation membrane is ≥60 Barrer, and the CO2 / N2 ideal separation factor is ≥10; Preferably, the CO2 separation membrane has a thickness of 10-80 μm, a CO2 permeability coefficient ≥ 80 Barrer, and a CO2 / N2 ideal separation factor ≥ 12.

6. A method for preparing a CO2 separation membrane having a long carbon chain polyamide elastomer with high thermal stability as claimed in any one of claims 1 to 5, characterized in that: include: (1) preparing an AABB type long carbon chain polyamide elastomer and drying it; (2) mixing the pellets prepared in step (1) with a processing aid, and melt-extruding to form a film; (3) pulling and winding the film prepared in step (2), and cooling and shaping the film to obtain a thin film; Preferably, the selected processing aid includes at least one of a chain extender, an antioxidant, a nucleating agent or a lubricant; Preferably, the processing aids are chain extenders, antioxidants and nucleating agents.

7. The preparation method according to claim 6, characterized in that: In step (2), the method for preparing the film after melt extrusion includes a calendering method, and the calendering method includes the following steps: The pellets are melted and plasticized and extruded through a twin-screw extruder, and then formed into a sheet film through a die. The temperatures of the barrel zone 1, barrel zone 2, die zone 1, and die zone 2 of the extruder are controlled at 180-250°C, and the screw speed is 10-100rpm. The obtained sheet film is extruded and calendered into a film through a twin-roll calender in a melt flow state. The temperature of the calender roll is 180-250°C, and then the film is directly laminated with the cloth base under the calender roll to form a film. Preferably, in step (3), the traction speed of the traction machine is 1-100 rpm, and the winding speed of the winding machine is 1-100 rpm.

8. The preparation method according to claim 6, characterized in that: In step (2), the method for preparing the film after melt extrusion includes a casting method, and the casting method includes the following steps: The pellets are plasticized and extruded by a twin-screw extruder, and then formed into a sheet film through a T-shaped forming die. The temperatures of the barrel zone 1, barrel zone 2, die zone 1, and die zone 2 of the extruder are 180-250°C, and the screw speed is 10-100rpm. The obtained sheet film is cast in a sheet shape onto the roller surface of a steadily rotating cooling roller in a melt flow state. The film is cooled and shaped on the cooling roller. There is an air knife on the side of the cooling roller with a nozzle length consistent with the roller surface width, the nozzle gap is 0.5-2mm, and the air knife wind pressure is 98-980kPa.

9. The preparation method according to any one of claims 6 to 8, characterized in that: In step (2), after the film is formed, the film is also subjected to isothermal heat treatment; Preferably, the isothermal heat treatment comprises annealing the film obtained by melt film formation, the annealing temperature is selected from any temperature value between 60-180° C., and the annealing time is 0.5-5 h. Preferably, the annealing temperature is 90-150° C., and the annealing time is 0.5-2 h.

10. Application of a high thermal stability long carbon chain polyamide elastomer in the preparation of a CO2 separation membrane, characterized in that: The high thermal stability long carbon chain polyamide elastomer is obtained by polycondensation of an AABB type long carbon chain polyamide hard segment in which the carbon number of the diamine and the carbon number of the dibasic acid are both even numbers and a polyether soft segment; Preferably, the CO2 separation membrane is used for flue gas decarbonization.

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