Hollow fiber membrane, module thereof and method for selective separation, recovery and dissolution of gas

Abstract

An object of the present invention is to provide a hollow fiber membrane having high separation accuracy and high strength in a direction perpendicular to the fiber axis, a module thereof, and a method for using the same.SOLUTION: To provide a hollow fiber membrane having a support consisting of two or more kinds of polyolefin resins having different melting points and a separation functional layer of ≤5 μm laminated on the support, and to provide a module and a method for using the hollow fiber membrane.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hollow fiber membrane, a module thereof, and a method for selectively separating, recovering, and dissolving gases. [Background technology]

[0002] Hollow fiber membranes can be used to separate components from fluids and are used in a wide variety of applications, including medical devices, electrochemical devices, chemical processing devices, pharmaceutical equipment, and water purification.

[0003] Polyolefin hollow fiber membranes are produced by phase separation or dry stretching. The dry stretching method can be used to produce hollow fiber membranes without using solvents, and has the advantage of easily producing high-strength hollow fiber membranes.

[0004] However, with the dry stretching method, precise control of the pore size is difficult, and separation accuracy is an issue.

[0005] Therefore, Patent Document 1 discloses that a hollow fiber membrane with high separation accuracy can be produced by using a multi-cylindrical spinneret to perform melt conjugated spinning of two components, followed by stretching to make only one of the components porous. The hollow fiber membrane is made up of two layers, a porous layer and a non-porous layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-116483 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the hollow fiber membrane obtained in Patent Document 1 has high strength in the fiber axis direction but low strength in the direction perpendicular to the fiber axis, and has the problem of being easily damaged by bending deformation during advanced processing steps such as module production.

[0008] Therefore, an object of the present invention is to provide a hollow fiber membrane that has high separation accuracy and high strength in the direction perpendicular to the fiber axis. [Means for solving the problem]

[0009] As a result of intensive research aimed at solving the above problems, the present inventors have discovered that by forming a porous support with a composite cross section made of two or more polyolefin resins with different melting points, a hollow fiber membrane with high separation accuracy and high strength in the direction perpendicular to the fiber axis can be obtained, and have completed the present invention. That is, the present invention provides the following (1) to (6). (1) A hollow fiber membrane having, in its cross section, a porous support in which two or more polyolefin resins with different melting points are bonded together in a laminated or sea-island composite form, and a separation functional layer of 5 μm or less laminated thereon. (2) The hollow fiber membrane according to (1), wherein polymers having different melting points are alternately arranged and bonded together in the circumferential direction in the porous support, and the total number of segments is 4 or more and 40 or less. (3) The hollow fiber membrane according to (1), wherein the porous support has an island-in-a-sea structure with 3 to 100 islands. (4) The hollow fiber membrane according to any one of (1) to (3), wherein the separating functional layer contains poly-4-methyl-1-pentene and has a CO2 / N2 gas selectivity of 3.0 or more. (5) A separation membrane module comprising the hollow fiber membrane according to any one of (1) to (3). (6) A method for selectively separating and recovering a specific gas from a liquid or selectively dissolving a specific gas into a liquid, using the hollow fiber membrane according to any one of (1) to (3). [Effects of the Invention]

[0010] The hollow fiber membrane of the present invention has high separation accuracy and high strength in the direction perpendicular to the fiber axis, and therefore the module using the hollow fiber membrane and the method of use thereof can be used for a wide range of separation applications. [Brief explanation of the drawings]

[0011] [Figure 1]1 is a cross-sectional view of a hollow fiber membrane according to one embodiment of the present invention (polyolefin resins with different melting points bonded together (a total of five layers arranged alternately in the membrane thickness direction)). [Figure 2] 1 is a cross-sectional view of a hollow fiber membrane according to one embodiment of the present invention (polyolefin resins having different melting points bonded together (four pieces alternately arranged evenly in the circumferential direction)). [Figure 3] FIG. 1 is a cross-sectional view of a hollow fiber membrane according to one embodiment of the present invention (polyolefin resins with different melting points are bonded together in a sea-island composite configuration, with four islands evenly arranged (same distance between each island)). [Figure 4] An example of a die for producing hollow fiber membranes. [Figure 5] 1 shows an example of a die (only the portion of the polymer discharge hole 12) for producing the hollow fiber membrane of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will now be described in detail.

[0013] The hollow fiber membrane of the present invention contains at least two or more polyolefin resins with different melting points, such as polyethylene, polypropylene, polybutylene, poly(4-methyl-1-pentene), and copolymers thereof.

[0014] The melting point is determined as follows. Different melting points refer to differences in melting points Tm determined as follows, with a difference of preferably 5° C. or more, and more preferably 10° C. or more. By using polyolefin resins with different melting points, a hollow fiber membrane with excellent strength in the direction perpendicular to the fiber axis can be obtained. (1) Approximately 5 mg of the sample is weighed using an electronic balance and set in a differential scanning calorimeter. The sample is heated under nitrogen at a heating rate of 10°C / min within a temperature range of 30 to 290°C, and then cooled at a heating rate of 10°C / min within a temperature range of 290 to 0°C, and differential scanning calorimetry is performed. (2) In the DSC curve obtained, the melting point Tm (°C) of the sample is determined from the peak-top temperature of the endothermic peak during the heating process, the heat of crystalline fusion ΔHm (J / g) is determined from the peak area, and the cold crystallization temperature Tc (°C) of the sample is determined from the peak-top temperature of the exothermic peak during the cooling process. If multiple endothermic peaks are observed, the waveforms are separated into single peaks and the peak-top temperature of each peak is determined.

[0015] The hollow fiber membrane of the present invention may contain a polymer other than polyolefin. Examples of polymers other than polyolefin include polyesters and polyamides. Examples of polyesters include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, as well as copolymers thereof. Examples of polyamides include polyε-capramide (nylon 6) and polyhexamethylene adipamide (nylon 66), as well as copolymers thereof.

[0016] The shape of the hollow fiber membrane is not particularly limited, but examples include a circular or elliptical cross section. When the hollow fiber membrane has a circular cross section, its inner diameter, outer diameter, and membrane thickness are not particularly limited. However, if the inner diameter is too small, the pressure loss when feeding air or liquid into the hollow fiber membrane increases, so the inner diameter is preferably 150 μm or more. On the other hand, as the inner diameter increases, the outer diameter of the hollow fiber membrane also increases. In other words, if the inner diameter is too large, the specific surface area decreases, hindering module miniaturization, so the inner diameter is preferably 300 μm or less. Furthermore, since the thinner the membrane thickness, the lower the mechanical strength, so the membrane thickness is preferably 15 μm or more. On the other hand, while the thicker the membrane thickness, the higher the mechanical strength, but a thicker membrane increases the resistance during fluid permeation and also increases the outer diameter of the hollow fiber membrane. Therefore, for the same reasons as when the inner diameter is too large, the membrane thickness is preferably 60 μm or less. In view of the relationship between the above-mentioned preferable range of the inner diameter and the preferable range of the membrane thickness, the outer diameter is preferably in the range of 200 to 500 μm.

[0017] Furthermore, the hollow ratio calculated using the following formula is preferably 30% or more. By using a hollow fiber membrane with a high hollow ratio, it is possible to reduce the membrane thickness of the hollow fiber membrane while suppressing pressure loss when a fluid is supplied to the hollow portion when used as a gas separation membrane, and a hollow fiber membrane that can contribute to making the module more compact can be obtained, so a hollow ratio of 40% or more is more preferable, and 50% or more is even more preferable. There is no particular upper limit to the hollow ratio, but 70% is preferable. A hollow fiber membrane with a high hollow ratio can be obtained by using a discharge nozzle having a structure that allows gas to be introduced into the interior as a core material, as described below. Hollow ratio (%) = {area of ​​hollow part / area of ​​entire hollow fiber membrane (membrane and hollow part)} x 100 When the cross section of the hollow fiber membrane is circular, the inner diameter, outer diameter and membrane thickness can be measured by observing the cross section with an optical microscope.

[0018] The hollow fiber membrane of the present invention has, in its cross section, a porous support in which two or more polyolefin resins with different melting points are bonded together in a laminated or sea-island composite configuration, and a separation functional layer of 5 μm or less laminated thereon. Here, the polyolefin resins constituting the porous support and the separation functional layer may be different.

[0019] The hollow fiber membrane of the present invention may also have a porous support or a separation functional layer in which a resin mixture of two or more polyolefin resins with different melting points is bonded together in a laminated or sea-island composite configuration. By disposing a resin mixture of two or more polyolefin resins with different melting points in the cross section, the interfacial strength in the composite cross section is improved, and a hollow fiber membrane with excellent passability in the stretching process and strength in the direction perpendicular to the fiber axis can be obtained.

[0020] When two or more polyolefin resins with different melting points are mixed, the ratio of the mixed component to the main component is preferably 3 to 25%. The higher the ratio of the mixed component to the main component, the more likely it is that the ease of passing through the stretching step and the strength in the direction perpendicular to the fiber axis will improve, so 5% or more is more preferable, and 10% or more is even more preferable. On the other hand, the higher the ratio of the mixed component to the main component, the more likely it is that the gas selectivity will decrease, so 20% or less is more preferable, and 15% or less is even more preferable.

[0021] Examples of the laminated type include cross sections such as those shown in Figures 1 and 2, in which segments of different polyolefin resins are laminated together in the film thickness direction or circumferential direction. The cross section shown in Figure 2, in which different polyolefin resins are alternately arranged in the circumferential direction and laminated together, is preferred, as it can easily reduce resistance to fluid penetration in the film thickness direction. In the cross section shown in Figure 2, the greater the number of segments, the higher the strength in the direction perpendicular to the fiber axis tends to be. Therefore, the total number of segments is preferably 4 or more, and more preferably 8 or more. On the other hand, the greater the number of segments, the higher the resistance to fluid penetration in the film thickness direction tends to be. Therefore, the total number of segments is preferably 40 or less, and more preferably 30 or less. Furthermore, it is preferable that the areas of the same types of segments are the same.

[0022] An example of an island-sea composite type is a cross section as shown in Figure 3, which consists of island components surrounded by a sea component. Since the strength in the direction perpendicular to the fiber axis tends to increase as the number of islands increases, the number of islands is preferably 3 or more, and more preferably 10 or more. On the other hand, since the resistance to fluid permeation in the film thickness direction tends to increase as the number of islands increases, the number of islands is preferably 100 or less, more preferably 80 or less, and even more preferably 60 or less. It is preferable that the islands are evenly arranged (the distance between each island is the same).

[0023] The porous support in the present invention is a layer adjacent to the separation functional layer described below.

[0024] When the cross section of the hollow fiber membrane is circular, the composite cross-sectional morphology of the porous support can be evaluated by observing the cross section with an optical microscope or an electron microscope.

[0025] The separating functional layer in the present invention is a layer formed on one or both surfaces (inner and outer surfaces) of the hollow fiber membrane, and has a denser structure than the porous support.

[0026] The separation functional layer in the present invention preferably contains a polyolefin resin. Examples of polyolefin resins include polyethylene, polypropylene, polybutylene, and poly(4-methyl-1-pentene), as well as copolymers thereof. By containing a polyolefin resin in the separation functional layer, when a specific component is separated and recovered or separated and supplied from a liquid using the hollow fiber membrane of the present invention, the liquid is less likely to permeate into the hollow fiber membrane, and deterioration of performance over time can be suppressed.

[0027] Furthermore, when a polyolefin resin is contained, it is preferable to use a polyolefin resin having a lower crystallinity than the polyolefin resin forming the porous support. By using a polyolefin resin with a lower crystallinity for the separation functional layer, the occurrence of defective pores in the separation functional layer is suppressed, and a hollow fiber membrane with high separation accuracy can be obtained.

[0028] The separation functional layer of the present invention is formed by co-extruding a resin forming the porous support and a resin forming the separation functional layer through a die.

[0029] The thickness of the separation functional layer can be controlled by the amount of resin that forms the separation functional layer discharged from the spinneret and the spinning speed, and can also be controlled by the draw ratio when drawing is performed. The thickness of the separation functional layer in the hollow fiber membrane of the present invention is 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. The thinner the separation functional layer, the lower the resistance during fluid permeation, making it possible to obtain a hollow fiber membrane that is advantageous for module miniaturization. Note that, in the present invention, the thickness of the separation functional layer refers to the sum of the thicknesses of the separation functional layers on both surfaces when the separation functional layer is present on both surfaces of the hollow fiber membrane.

[0030] The thickness of the separation functional layer can be measured by observing the cross section of the hollow fiber membrane stained with ruthenium tetroxide or the like under an electron microscope and evaluating the thickness of the layer that contrasts differently with the support.

[0031] The hollow fiber membrane of the present invention preferably has slit-shaped micropores because the slit-shaped pores make it difficult for foreign matter to completely block the pores. In order to obtain slit-shaped micropores, it is preferable to perform stretching during the hollow fiber membrane production process, as described below. By forming pores while causing peeling between the laminated lamellae during the stretching process, small, uniform, slit-shaped micropores can be easily obtained.

[0032] The shape of the micropores can be evaluated by observing the inner wall surface of the hollow fiber membrane in a longitudinal cross section of the hollow fiber membrane.

[0033] The hollow fiber membrane of the present invention has excellent strength in the direction perpendicular to the fiber axis, and an excellent ratio of hook strength to tensile strength (hook strength / tensile strength).

[0034] In the present invention, the snagging strength refers to the strength per unit weight against bending and tension when the hollow fiber membrane is bent at the snagging portion. The snagging strength can be measured, for example, in accordance with JIS L1013:2010 (Testing methods for chemical fiber filament yarns) 8.6.

[0035] In the present invention, the tensile strength refers to the tensile strength per unit weight when pulled in the longitudinal direction of the hollow fiber membrane. The tensile strength can be measured, for example, in accordance with JIS L1013:2010 (Testing methods for chemical fiber filament yarns) 8.5.1.

[0036] The hanging strength of the hollow fiber membrane of the present invention is not particularly limited, but the strength ratio (hanging strength / tensile strength), which is the ratio to the tensile strength described below, is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more. A larger strength ratio means that the membrane is less susceptible to breakage due to bending deformation, etc., and is more likely to pass through advanced processing steps such as module fabrication and to exhibit excellent performance even after advanced processing.

[0037] The tensile strength of the hollow fiber membrane of the present invention is preferably 0.5 cN / dtex or more, more preferably 1.2 cN / dtex or more, and even more preferably 1.5 cN / dtex or more. A higher tensile strength allows for a thinner membrane thickness of the hollow fiber membrane, which contributes to miniaturization of the module. On the other hand, although a higher tensile strength is preferable, toughness tends to decrease as the tensile strength increases, so the tensile strength is preferably 5.0 cN / dtex or less, and more preferably 3.0 cN / dtex or less.

[0038] The hollow fiber membrane of the present invention has gas selectivity and can be used as a gas separation membrane. Gas selectivity refers to the ratio of gas flux evaluated by a differential pressure method in accordance with JIS K7126-1:2006 (Plastics - Films and sheets - Gas permeability test method - Part 1: Differential pressure method).

[0039] The gases that can be separated by the hollow fiber membrane of the present invention are not particularly limited, but examples thereof include nitrogen and carbon dioxide, and nitrogen and oxygen.

[0040] The gas selectivity of the hollow fiber membrane of the present invention for carbon dioxide and nitrogen (carbon dioxide gas flux / nitrogen gas flux) is preferably 3.0 to 30.0, and more preferably 5.0 to 20.0. A higher gas selectivity value indicates better gas separation efficiency, which can contribute to module miniaturization when used as a gas separation module. On the other hand, in order to increase gas selectivity, it is necessary to increase the membrane thickness to reduce defects on the hollow fiber membrane surface, but increasing the membrane thickness increases gas permeation resistance. Therefore, in terms of the balance between gas selectivity and gas permeation resistance, a gas flux within the above range is preferred.

[0041] Next, the method for producing the hollow fiber membrane of the present invention will be described below.

[0042] The hollow fiber membrane of the present invention can be produced using a die having a gas outlet hole 11 and a polymer outlet hole 12, as shown in FIG.

[0043] The gas discharge hole is a cylindrical gap for discharging gas. Usually, the gas discharged from the gas discharge hole forms a cavity in the hollow fiber membrane.

[0044] The polymer discharge holes are gaps for discharging the polymer, and are arranged so as to surround the gas discharge holes. Usually, the polymer discharged from the polymer discharge holes becomes a hollow fiber membrane.

[0045] 5, the hollow fiber membrane can also be produced using a multi-hole spinneret in which a plurality of polymer discharge holes 13 and 14 are arranged inside a ring-shaped polymer discharge hole 12. By using a multi-hole spinneret, the hollow fiber membrane of the present invention having a highly complex cross section can be obtained relatively easily.

[0046] The hollow fiber membrane of the present invention can be produced, for example, by melt-spinning a polymer containing polyolefin, followed by heat treatment and stretching as necessary. The melt viscosity of the polymer is 1216 s at 280°C. -1 In this case, the melt viscosity is preferably 30 Pa·s or higher. A higher melt viscosity improves spinning stability and the mechanical properties of the resulting hollow fiber membrane, so the melt viscosity of the polymer is more preferably 50 Pa·s or higher. On the other hand, if the melt viscosity is too high, the polymer's deformation resistance during spinning becomes too high, making fiber breakage more likely, so the melt viscosity is preferably 500 Pa·s or lower, and more preferably 200 Pa·s or lower.

[0047] The gas discharged from the gas discharge holes is not particularly limited, but is preferably an inert gas such as nitrogen from the viewpoint of suppressing oxidation degradation of the polymer discharged from the polymer discharge holes.

[0048] The method for producing the hollow fiber membrane in the present invention is not particularly limited, but is preferably a production method using the above-mentioned nozzle.

[0049] The method for producing a hollow fiber membrane according to the present invention preferably comprises a spinning step, a heat treatment step, and a stretching step. The spinning step is a step in which a molten polymer is discharged from a nozzle and molded into a hollow fiber. The heat treatment step is a step in which the polymer molded into a hollow fiber is heat-treated for the purpose of increasing the order of the crystal structure. The stretching step is a step in which the polymer molded into a hollow fiber is uniformly stretched.

[0050] The longitudinal uniformity of the membrane thickness of a hollow fiber membrane can be affected not only by the nozzle but also by the spinning temperature, the cooling conditions of the extruded polymer, the heat treatment of the unstretched fiber obtained by spinning, and the stretching conditions. Because polyolefin-containing polymers have a low glass transition temperature, they solidify slowly when extruded from the nozzle and are subject to external disturbances before solidification, which tends to impair the longitudinal uniformity of the membrane thickness of the resulting hollow fiber membrane. Therefore, the longitudinal uniformity of the membrane thickness of a hollow fiber membrane is easily affected by the spinning temperature and the cooling conditions of the extruded polymer, which directly affect the solidification of the polymer extruded from the nozzle. Therefore, it is preferable to produce a hollow fiber membrane using the following spinning temperature and cooling conditions.

[0051] The spinning temperature is the temperature at which the polymer is melted in the spinning process, and is preferably 310°C or lower in order to prevent decomposition of the polymer. If the temperature is too low, the fluidity deteriorates and uneven discharge occurs at the nozzle, so the spinning temperature is preferably 240°C or higher. The spinning temperature is more preferably 250°C to 300°C.

[0052] In the spinning process, a heating cylinder may be provided immediately below the nozzle. The use of the heating cylinder can stabilize the ambient temperature immediately below the nozzle. Furthermore, by increasing the ambient temperature immediately below the nozzle, the melt extruded from the nozzle can be slowly cooled, thereby suppressing the concentration of strain stress when the melt undergoes severe deformation immediately below the nozzle. The length of the heating cylinder is preferably around 80 mm. The temperature of the heating cylinder is preferably 100 to 300°C, more preferably 120 to 280°C.

[0053] In the spinning process, a cooling section for cooling the discharged polymer with cooling air may be provided immediately below the nozzle or immediately below a heating barrel provided immediately below the nozzle. The temperature of the cooling air for cooling the discharged polymer is preferably 80°C or less from the viewpoint of suppressing delay in solidification of the discharged polymer. If the temperature of the cooling air is too low, strain stress will be concentrated when the molten polymer is highly deformed immediately below the nozzle, making fiber breakage more likely. Therefore, the temperature of the cooling air is preferably 10°C or more.

[0054] In the heat treatment step, the heat treatment temperature is preferably equal to or higher than the glass transition temperature and lower than the melting point of the polymer constituting the hollow fiber membrane, more preferably 80 to 220° C., and even more preferably 100 to 200° C. The heat treatment time is preferably 1 minute to 24 hours, and more preferably 5 minutes to 12 hours.

[0055] The stretching step may involve two-stage stretching, consisting of cold stretching and hot stretching. The cold stretching temperature is preferably near or below the glass transition temperature of the polymer constituting the hollow fiber membrane, more preferably -30 to 80°C, even more preferably -10 to 60°C, and most preferably 0 to 50°C. The stretch ratio in the cold stretching is preferably low, more preferably 1.05 to 1.6 times, even more preferably 1.1 to 1.5 times, and most preferably 1.2 to 1.4 times, from the viewpoint of forming small and uniform pores while causing delamination between the laminated lamellae. The hot stretching temperature is preferably above the glass transition temperature and below the melting point of the polymer constituting the hollow fiber membrane, more preferably 80 to 200°C, even more preferably 100 to 180°C, and most preferably 120 to 150°C. The stretching ratio in hot stretching is preferably 1.05 to 2.0 times, more preferably 1.1 to 1.8 times, and even more preferably 1.2 to 1.7 times, from the viewpoint of enlarging the pores formed by cold stretching while making the pores small and uniform in size.

[0056] The hollow fiber membrane of the present invention has properties suitable for gas separation membrane modules, and can be used, for example, as a degassing membrane or an oxygenator.

[0057] When the hollow fiber membrane of the present invention is incorporated into a gas separation membrane module, the hollow fiber membranes may be incorporated in a bundled state, or, if necessary, the hollow fiber membranes may be arranged in a sheet shape so that the spacing between the hollow fiber membranes is uniform.

[0058] The gas separation membrane module of the present invention preferably has hollow fiber membranes housed in a case. The method for housing the hollow fiber membranes in the case is not particularly limited, but an example is a method in which the hollow fiber membranes are cut to the required length, bundled together in the required number, and then housed in a cylindrical case, and a potting agent is poured into the case while rotating the module in a centrifuge. After the potting agent has solidified, both ends of the hollow fiber membranes are cut so that they are open, and headers are attached. [Example]

[0059] The present invention will be specifically explained below with reference to examples, but the present invention is not limited thereto.

[0060] (Evaluation method) A. Morphological observation of the holes The inner wall surface of the hollow fiber membrane was observed at 30,000 magnification in a longitudinal cross section to observe the pore morphology.

[0061] B. Thermal analysis Approximately 5 mg of sample was weighed and measured using a TA Instruments DSCQ2000 differential scanning calorimeter under nitrogen. The temperature was increased at a rate of 10°C / min from 30 to 290°C, and then decreased at a rate of 10°C / min from 290 to 0°C. The melting point (Tm) of the sample was determined from the peak-top temperature of the endothermic peak during the heating process (DSC curve). The heat of crystalline fusion (ΔHm) (J / g) was determined from the peak area. The cold crystallization temperature (Tc) of the sample was determined from the peak-top temperature of the exothermic peak during the cooling process. Table 1 shows the Tm, ΔHm, and Tc values ​​for the polymers used in the examples and comparative examples.

[0062] C. Evaluation of separation functional layer thickness The thickness of the separation functional layer at 20 randomly selected locations was evaluated from an electron microscope image of the cross section of the hollow fiber membrane stained with ruthenium tetroxide at 1500x magnification, and the arithmetic mean value was used.

[0063] D. Intensity ratio The ratio of the hook strength to the tensile strength (hook strength / tensile strength) was used as the strength ratio.

[0064] The snagging strength was evaluated in accordance with JIS L1013:2010 (Testing methods for synthetic fiber filament yarns) 8.6, using a Tensilon manufactured by Orientec Co., Ltd., with a sample length of 50 mm and a pulling speed of 50 mm / min. The measurement was carried out 10 times, and the arithmetic mean value of the measured values ​​was used.

[0065] The tensile strength was evaluated in accordance with JIS L1013:2010 (Testing method for chemical fiber filament yarn) 8.5.1, under the conditions of a sample length of 200 mm and a pulling speed of 200 mm / min using a Tensilon manufactured by Orientec Co., Ltd. The measurement was carried out 10 times, and the arithmetic mean value of the measured values ​​was used.

[0066] E. Gas selectivity The carbon dioxide and nitrogen gas fluxes of the hollow fiber membrane were evaluated according to JIS K7126-1:2006 (Plastics - Films and sheets - Gas permeability test methods - Part 1: Differential pressure method), and the ratio (carbon dioxide gas flux / nitrogen gas flux) was calculated. The measurement was performed five times, and the arithmetic mean of the measured values ​​was calculated and rounded to one decimal place.

[0067] Example 1 Poly(4-methyl-1-pentene) (Mitsui Chemicals, RT18) and poly(4-methyl-1-pentene) (Mitsui Chemicals, MX002) were used as the support, and poly(4-methyl-1-pentene) (Mitsui Chemicals, MX002) was used as the separation functional layer. Composite melt spinning was performed at 290°C using a double cylindrical spinneret with 130 holes for the support and 30 holes for the separation functional layer. For the composite melt spinning, melt extrusion was performed using a twin-screw extruder, and the resins forming the support and separation functional layer were extruded from the nozzle at a weight ratio of 92:8 while being metered using a gear pump. The running yarn extruded from the nozzle was wound at a spinning speed of 300 m / min to obtain an undrawn yarn. In a cooling section located below the nozzle, cooling air at 23°C and 50% relative humidity was used to cool the running yarn at a speed of 0.5 m / sec.

[0068] The unstretched yarn obtained was subjected to a heat treatment in an atmosphere of 185°C for 2 hours, then stretched 1.2 times at 30°C, and then further stretched 1.2 times at 120°C to obtain a hollow fiber membrane.

[0069] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane, in which four microporous segments formed from RT18 (area ratio of microporous segments in hollow fiber membrane: 85) and four non-microporous segments formed from MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were alternately and evenly arranged around the support in the circumferential direction, as shown in Figure 2 (segments of the same type had the same area; the same applies to the following examples).

[0070] Example 2 A hollow fiber membrane was produced in the same manner as in Example 1, except that polypropylene (S135, manufactured by Prime Polymer) and poly(4-methyl-1-pentene) (MX002, manufactured by Mitsui Chemicals) were used as the support.

[0071] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments formed with S135 (area ratio of microporous segments in hollow fiber membrane: 85) and four non-microporous segments formed with MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were arranged alternately in the circumferential direction on a support as shown in Figure 2.

[0072] Example 3 A hollow fiber membrane was produced in the same manner as in Example 1, except that a double cylindrical spinneret was used to form a sea-island composite cross section on the support.

[0073] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which 8 islands of non-microporous segments (area ratio of non-microporous segments in the hollow fiber membrane: 7) were evenly arranged among microporous segments (area ratio of microporous segments in the hollow fiber membrane: 85) on the support.

[0074] Example 4 A hollow fiber membrane was produced in the same manner as in Example 1, except that the composite ratio of the support and the separating functional layer was 95:5.

[0075] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments (area ratio of microporous segments in the hollow fiber membrane: 90) and four non-microporous segments (area ratio of non-microporous segments in the hollow fiber membrane: 5) were arranged alternately in the circumferential direction on the support.

[0076] Example 5 A hollow fiber membrane was produced in the same manner as in Example 1, except that the composite ratio of the support and the separating functional layer was 87:13.

[0077] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments (area ratio of microporous segments in the hollow fiber membrane: 76) and four non-microporous segments (area ratio of non-microporous segments in the hollow fiber membrane: 11) were arranged alternately in the circumferential direction on the support.

[0078] Example 6 A hollow fiber membrane was produced in the same manner as in Example 1, except that a double cylindrical die capable of obtaining supports with different numbers of segments was used.

[0079] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which 15 microporous segments formed from RT18 (area ratio of microporous segments in hollow fiber membrane: 85) and 15 non-microporous segments formed from MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were alternately arranged in the circumferential direction on the support.

[0080] Example 7 A hollow fiber membrane was produced in the same manner as in Example 1, except that a double cylindrical die capable of obtaining supports with different numbers of segments was used.

[0081] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which 25 microporous segments formed from RT18 (area ratio of microporous segments in hollow fiber membrane: 85) and 25 non-microporous segments formed from MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were alternately arranged in the circumferential direction on the support.

[0082] Example 8 A hollow fiber membrane was produced in the same manner as in Example 3, except that a double cylindrical die was used, which allows supports with different numbers of supporting islands to be obtained.

[0083] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which 20 islands of non-microporous segments (area ratio of non-microporous segments in the hollow fiber membrane: 7) were evenly arranged among microporous segments (area ratio of microporous segments in the hollow fiber membrane: 85) on a support.

[0084] Example 9 A hollow fiber membrane was produced in the same manner as in Example 3, except that a double cylindrical die was used, which allows supports with different island numbers to be obtained.

[0085] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which 60 islands of non-microporous segments (area ratio of non-microporous segments in the hollow fiber membrane: 7) were evenly arranged in two rows among microporous segments (area ratio of microporous segments in the hollow fiber membrane: 85) on a support.

[0086] Example 10 A hollow fiber membrane was produced in the same manner as in Example 3, except that a double cylindrical die was used, which allows supports with different island numbers to be obtained.

[0087] The evaluation results of the obtained hollow fiber membrane are shown in Table 2. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which 120 islands of non-microporous segments (area ratio of non-microporous segments in the hollow fiber membrane: 7) were evenly arranged in two rows among microporous segments (area ratio of microporous segments in the hollow fiber membrane: 85) on a support.

[0088] Example 11 A hollow fiber membrane was produced in the same manner as in Example 2, except that polypropylene (Prime Polymer, S135) and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in a weight ratio of 95 / 5 were used as the support, and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in a weight ratio of 95 / 5 were used as the separation functional layer. No sheath cracking was observed during stretching, and good processability was observed.

[0089] The evaluation results of the obtained hollow fiber membrane are shown in Table 3. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments formed with S135 (area ratio of microporous segments in hollow fiber membrane: 85) and four non-microporous segments formed with S135 and MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were arranged alternately in the circumferential direction on a support as shown in Figure 2.

[0090] Example 12 A hollow fiber membrane was produced in the same manner as in Example 2, except that polypropylene (Prime Polymer, S135) and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in a weight ratio of 90 / 10 were used as the support, and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in a weight ratio of 90 / 10 were used as the separation functional layer. No sheath cracking was observed during stretching, and good processability was observed.

[0091] The evaluation results of the obtained hollow fiber membrane are shown in Table 3. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments formed with S135 (area ratio of microporous segments in hollow fiber membrane: 85) and four non-microporous segments formed with S135 and MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were arranged alternately in the circumferential direction on a support as shown in Figure 2.

[0092] Example 13 A hollow fiber membrane was produced in the same manner as in Example 2, except that polypropylene (Prime Polymer, S135) and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in a weight ratio of 85 / 15 were used as the support, and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in a weight ratio of 85 / 15 were used as the separation functional layer. No sheath cracking was observed during stretching, and good processability was observed.

[0093] The evaluation results of the obtained hollow fiber membrane are shown in Table 3. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments formed with S135 (area ratio of microporous segments in hollow fiber membrane: 85) and four non-microporous segments formed with S135 and MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were arranged alternately in the circumferential direction on a support as shown in Figure 2.

[0094] Example 14 A hollow fiber membrane was produced in the same manner as in Example 2, except that polypropylene (Prime Polymer, S135) and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in an 80 / 20 weight ratio were used as the support, and a resin obtained by mixing polypropylene (Prime Polymer, S135) and poly4-methyl-1-pentene (Mitsui Chemicals, MX002) in an 80 / 20 weight ratio was used as the separation functional layer. No sheath cracking was observed during stretching, and good processability was observed.

[0095] The evaluation results of the obtained hollow fiber membrane are shown in Table 3. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments formed with S135 (area ratio of microporous segments in hollow fiber membrane: 85) and four non-microporous segments formed with S135 and MX002 (area ratio of non-microporous segments in hollow fiber membrane: 7) were arranged alternately in the circumferential direction on a support as shown in Figure 2.

[0096] (Comparative Example 1) A hollow fiber membrane was produced in the same manner as in Example 1, except that only poly(4-methyl-1-pentene) (manufactured by Mitsui Chemicals, RT18) was used as the support.

[0097] The evaluation results of the obtained hollow fiber membrane are shown in Table 4. The cross section of the obtained hollow fiber membrane was a hollow fiber membrane in which the entire support was made up of microporous segments (area ratio of the microporous segments in the hollow fiber membrane: 92).

[0098] (Comparative Example 2) A hollow fiber membrane was produced in the same manner as in Example 1, except that the composite ratio of the support and the separating functional layer was set to 20:80.

[0099] The evaluation results of the obtained hollow fiber membrane are shown in Table 4. The cross section of the obtained hollow fiber membrane was a composite cross-section hollow fiber membrane in which four microporous segments (area ratio of microporous segments in hollow fiber membrane: 61) and four non-microporous segments (area ratio of non-microporous segments in hollow fiber membrane: 19) were arranged alternately in the circumferential direction on the support, and the separation function layer was 9.6 μm.

[0100] (Comparative Example 3) A hollow fiber membrane was produced in the same manner as in Example 1, except that only poly(4-methyl-1-pentene) (manufactured by Mitsui Chemicals, RT18) was used as the support and the separation functional layer.

[0101] The evaluation results of the obtained hollow fiber membrane are shown in Table 4. The cross section of the obtained hollow fiber membrane was entirely microporous segments, and the hollow fiber membrane had no separation function layer.

[0102] [Table 1]

[0103] [Table 2]

[0104] [Table 3]

[0105] [Table 4] [Industrial Applicability]

[0106] The hollow fiber membrane of the present invention has high separation accuracy and high strength in the direction perpendicular to the fiber axis, and therefore the module using the hollow fiber membrane and the method of use thereof can be suitably used for a wide range of separation applications. [Explanation of symbols]

[0107] 1: Separation functional layer 2: Porous support A 3: Porous support B 10: Discharge nozzle 11: Gas outlet hole 12: Polymer discharge hole 13: Polymer discharge hole A 14: Polymer discharge hole B

Claims

1. A hollow fiber membrane having a porous support in which two or more polyolefin resins having different melting points are bonded together in a laminated or sea-island composite manner in a cross section, and a separation functional layer having a thickness of 5 μm or less laminated thereon.

2. 2. The hollow fiber membrane according to claim 1, wherein polymers having different melting points are alternately arranged and bonded together in the circumferential direction of the porous support, and the total number of segments is 4 or more and 40 or less.

3. 2. The hollow fiber membrane according to claim 1, wherein the porous support has an island-in-a-sea structure with 3 to 100 islands.

4. The hollow fiber membrane according to any one of claims 1 to 3, wherein the separation functional layer contains poly 4-methyl-1 pentene and has a CO2 / N2 gas selectivity of 3.0 or more.

5. A separation membrane module comprising the hollow fiber membrane according to any one of claims 1 to 3.

6. A method for selectively separating and recovering a specific gas from a liquid or selectively dissolving a specific gas into a liquid, using the hollow fiber membrane according to any one of claims 1 to 3.

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