Porous solid fiber, fiber bundle, and purification column

Abstract

To provide a porous solid fiber, a fiber bundle, and a purification column incorporating the fiber bundle, that at the same time and at high efficiency can adsorb a plurality of removal object substances in which the molecular mass existing in a liquid to be processed is at the level of thousands to millions.SOLUTION: A porous solid fiber includes an area A1 where the average pore size is 4 nm to 50 nm, and an area A2 where the average pore size is 55 nm to 350 nm, at a cross section in a radial direction. The porosity of the area A1 is 10% to 95%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to porous solid fibers, fiber bundles and purification columns. [Background technology]

[0002] Many adsorbents that are incorporated into purification columns to remove target substances from the liquid to be treated by adsorption have a porous interior to increase the surface area that contributes to adsorption. Adsorbents are generally in the form of beads or fibers. Fiber-shaped adsorbents include hollow fibers, solid fibers, and knitted solid fibers. Among these, hollow fibers and solid fibers are superior in that they can ensure a sufficient flow path for the liquid to be treated when incorporated into a purification column. For example, Patent Document 1 discloses an invention relating to a porous fiber in which the cross-sectional shape in the radial direction of the fiber is irregular, thereby increasing the surface area per volume of the fiber and increasing the specific surface area of ​​the pores inside the fiber.

[0003] Patent Document 2 discloses a method for producing fibers that are made porous throughout the fiber in order to increase the porosity that contributes to the ability to adsorb substances.

[0004] Patent Document 3 discloses an invention relating to a solid fiber having powder particles inside a porous fiber for the purpose of simultaneously adsorbing a plurality of substances. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 067967 [Patent Document 2] Japanese Patent Application Publication No. 7-145512 [Patent Document 3] International Publication No. 2018 / 186210 [Non-patent literature]

[0006] [Non-Patent Document 1] Kazuhiko Ishikiriyama et al., "JOURNAL OF COLLOID AND INTERFACE SCIENCE", (1995), VOL.171, 103-111 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the substances to be removed by adsorbents used for blood purification include a variety of substances, including proteins, with molecular weights ranging from several thousand to several million, or molecular sizes ranging from 1 to 100 nm. However, because the porous structure inside the porous fiber described in Patent Document 1 is homogeneous, it has been difficult to simultaneously adsorb and remove substances of different sizes.

[0008] Patent Document 2 does not include any idea or description of simultaneously adsorbing and removing substances of different sizes.

[0009] In Patent Document 3, the powder particles inside the porous fiber selectively adsorb low molecular weight compounds with a molecular weight of less than 1000, and it was difficult to simultaneously and efficiently adsorb and remove multiple target substances with molecular weights of several thousand to several million.

[0010] Therefore, an object of the present invention is to provide a porous solid fiber, a fiber bundle, and a purification column incorporating a fiber bundle, which can simultaneously and efficiently adsorb multiple substances to be removed that have molecular weights of several thousand to several million and are present in the liquid to be treated. [Means for solving the problem]

[0011] The present invention has the following configurations for solving the above problems. (1) A porous solid fiber having, in a radial cross section, a region A1 having an average pore diameter of 4 nm or more and 50 nm or less and a region A2 having an average pore diameter of 55 nm or more and 350 nm or less, and the porosity of the region A1 is 10% or more and 95% or less. (2) The porous solid fiber according to (1) above, wherein the ratio of the region A2 to the outermost periphery of the radial cross section is 30% or more. (3) A porous solid fiber according to (1) or (2) above, in which the proportion of the region A1 in the entire radial cross section is 10% or more, and the proportion of the region A2 is 10% or more. (4) The porous solid fiber according to any one of (1) to (3) above, wherein the porosity of the region A2 is 10% or more and 95% or less. (5) Pore volume is 0.2 cm 3 / g or more 3.3cm 3 The porous solid fiber according to any one of (1) to (4) above, wherein the tensile strength is 1 / g or less. (6) The porous solid fiber according to any one of (1) to (5) above, having a surface porosity of 0.2% or more and 50.0% or less. (7) The porous solid fiber according to any one of (1) to (6) above, which has a dense layer on its surface, the thickness of which is 0.005 μm or more and 3.0 μm or less in the radial direction. (8) The porous solid fiber according to any one of (1) to (7) above, which contains an amorphous polymer. (9) The porous solid fiber according to (8) above, wherein the amorphous polymer is an ester group-containing polymer. (10) A porous solid fiber according to any one of (1) to (9) above, which has a negative charge. (11) A fiber bundle comprising the porous solid fiber according to any one of (1) to (10) above. (12) A purification column in which the fiber bundle described in (11) above is housed in a casing having ports at both ends that communicate with the interior. [Effects of the Invention]

[0012] The porous solid fiber, fiber bundle, and purification column incorporating the fiber bundle of the present invention make it possible to simultaneously and efficiently adsorb multiple substances to be removed, such as proteins, present in the liquid to be treated. DETAILED DESCRIPTION OF THE INVENTION

[0013] The porous solid fiber, fiber bundle, and purification column of the present invention will be described in detail below.

[0014] The present invention provides a porous solid fiber having, in a radial cross section, a region A1 having an average pore diameter of 4 nm or more and 50 nm or less and a region A2 having an average pore diameter of 55 nm or more and 350 nm or less, and the porosity of the region A1 is 10% or more.

[0015] Here, the term "radial cross section" refers to a plane perpendicular to the longitudinal direction of the porous solid fiber.

[0016] By controlling the sizes of regions A1 and A2 within the above ranges, multiple substances to be removed of different sizes can be adsorbed efficiently in the respective pores, while maintaining the mechanical strength of the porous solid fiber. The average pore diameters of regions A1 and A2 can be appropriately controlled within the above ranges depending on the size of the substances to be removed. However, to prevent clogging of the pores, it is preferable to make the average pore diameter larger than the size of the substances to be removed. The average pore diameters of regions A1 and A2 can be controlled by the concentration of the spinning dope, the temperature of the coagulation bath during spinning, etc.

[0017] Region A1 in the radial cross section of the porous solid fiber of the present invention is a region capable of adsorbing substances to be removed, such as cytokines and β2-microglobulin, which will be described later, having molecular weights of several thousand to several tens of thousands and sizes of about 1 to 10 nm. From the viewpoint of adsorbing substances of the above sizes, the average pore size is preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 14 nm or more. On the other hand, it is preferably 42 nm or less, more preferably 35 nm or less, and even more preferably 27 nm or less.

[0018] Region A2 in the radial cross section of the porous solid fiber of the present invention is a region capable of adsorbing substances to be removed, such as LDL cholesterol, immune complexes, endotoxins, and proteoglycans, which have molecular weights of hundreds of thousands to millions and sizes of approximately 15 to 100 nm, as described below. From the viewpoint of adsorbing substances of the above sizes, the average pore size is preferably 65 nm or more, more preferably 75 nm or more, and even more preferably 85 nm or more. On the other hand, it is preferably 240 nm or less, more preferably 190 nm or less, and even more preferably 165 nm or less.

[0019] The above-mentioned area A1 and area A2 are determined by the "method of determining area A1 and area A2" described later.

[0020] The porous solid fiber of the present invention may have regions other than region A1 and region A2, such as a non-porous region for further strength enhancement. By having regions A1 and A2 with different average pore sizes, it is possible to simultaneously adsorb multiple target substances of different sizes, such as proteins, humic substances, sugars, or inorganic salts in water treatment and biopharmaceutical purification applications, or toxins, proteins, or drugs in medical applications. In particular, when used as a blood purification column for medical applications to adsorb pathogens from blood, it is necessary to minimize the amount of patient blood transported outside the body. The porous solid fiber of the present invention is suitable for use in blood purification columns because it can simultaneously adsorb and remove multiple target substances with high efficiency and can reduce the column volume. Examples of combinations of target substances of different sizes (small size / large size) that can be used in blood purification columns include inflammatory cytokines / immune complexes in autoimmune diseases, inflammatory cytokines / LDL cholesterol in arteriosclerosis, inflammatory cytokines / endotoxins in sepsis, and β2-microglobulin / proteoglycans in dialysis amyloidosis.

[0021] The porosity of region A1 must be 10% or more. Here, "porosity" refers to the proportion of pores in the radial cross section of the porous solid fiber. A high porosity allows the entire region to contribute to adsorption, improving adsorption performance. Therefore, the porosity of region A1 is preferably 14% or more, more preferably 18% or more, even more preferably 24% or more, and particularly preferably 35% or more. On the other hand, from the viewpoint of maintaining the mechanical strength of the fiber, the porosity of region A1 is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

[0022] In addition, in region A2, from the viewpoint of improving adsorption performance, the porosity is preferably 10% or more, more preferably 18% or more, even more preferably 32% or more, and particularly preferably 40% or more. On the other hand, from the viewpoint of maintaining the mechanical strength of the fiber, the porosity of region A2 is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. The porosity of region A1 and region A2 can be controlled by the concentration of the spinning dope and the temperature of the coagulation bath during spinning, etc. The porosity of region A1 and region A2 can be calculated by image analysis of images of the radial cross section of the fiber observed with a scanning electron microscope or the like.

[0023] The present invention relates to solid fibers, i.e., fiber shapes without hollow portions. Hollow fibers allow for control of cooling, coagulation liquid diffusion, and desolvation from both the inner and outer surfaces of the fiber during spinning, making it easy to achieve different average pore sizes on the inner and outer surfaces of the fiber. However, in the case of hollow fibers, if the liquid to be treated is brought into contact with only the inside or the outside of the hollow fiber, the surface area of ​​the fiber cannot be effectively utilized. While there are techniques for flowing the liquid to be treated on both the inside and outside of the hollow fiber, it is difficult to evenly distribute the flow rate between the inside and outside, which can easily result in uneven flow. For example, when blood is used as the liquid to be treated and then the remaining blood in the column is returned to the body using physiological saline (blood return), there is a concern that a large amount of blood may remain inside the hollow fiber, a phenomenon known as residual blood. On the other hand, in fiber shapes without hollow portions, i.e., solid fibers, the liquid to be treated is passed only on the fiber surface, making flow unevenness less likely to occur, thereby minimizing the above-mentioned concerns. Furthermore, because solid fibers have a continuous structure that is not divided by hollow portions, they have higher strength and elongation than hollow fibers for the same fiber volume, making them easier to thin. Therefore, when used as an adsorbent with the same surface area, solid fibers can have a smaller fiber volume than hollow fibers, allowing for the fiber bundle and purification column to be made smaller.

[0024] The porous solid fiber of the present invention may be a monofilament or a multifilament formed by entangling a plurality of porous solid fibers, but is preferably a monofilament, since it has fewer entangled portions, is more likely to come into contact with the liquid to be treated, and can effectively utilize its surface area for adsorption.

[0025] In the porous solid fiber of the present invention, the proportion of the region A2 in the outermost periphery of the radial cross section is preferably 30% or more. Here, "outermost periphery" refers to the portion adjacent to the fiber surface in the radial cross section of the fiber. Furthermore, if a dense layer (described later) is present on the fiber surface, the "outermost periphery" refers to the portion excluding the dense layer. When the region A2 with a large average pore size occupies the outermost periphery of the porous solid fiber, both the substances to be removed in region A1 and region A2 diffuse into the porous solid fiber, and the region present inside the porous solid fiber can also be effectively utilized for adsorption of the substances to be removed, thereby enabling simultaneous and highly efficient adsorption of multiple substances to be removed. Therefore, the proportion of the region A2 in the outermost periphery of the radial cross section of the fiber is more preferably 40% or more, even more preferably 60% or more, and particularly preferably 80% or more. For the same reasons, the proportion of the region A1 in the outermost periphery of the radial cross section of the fiber is preferably 30% or less, more preferably 15% or less, and even more preferably 5% or less.

[0026] It is preferable that the ratio of the region A1 to the entire radial cross section of the porous solid fiber of the present invention is 10% or more, and the ratio of the region A2 to the entire radial cross section is 10% or more. From the viewpoint of ensuring sufficient adsorption performance for multiple substances to be removed, the ratio of the region A2 to the entire radial cross section is more preferably 15% or more, even more preferably 25%, and particularly preferably 40% or more. Furthermore, the region A1 with a small average pore size is excellent not only in adsorption performance but also in stability during transportation and storage, which is advantageous in terms of fiber productivity and long-term stability, so the ratio of the region A1 to the entire radial cross section is more preferably 20% or more, even more preferably 30%, and particularly preferably 40% or more.

[0027] The ratio of the area A1 and the area A2 to the entire cross section in the radial direction can be calculated from the "ratio of each area to the entire cross section" described later.

[0028] The pore volume of the porous solid fiber of the present invention is 0.2 cm 3 / g or more 3.3cm 3 / g or less. Here, the "pore volume" refers to a value obtained by measuring the freezing point depression caused by capillary condensation of water in the pores using a differential scanning calorimeter (hereinafter referred to as "DSC").

[0029] From the viewpoint of improving adsorption performance, it is preferable that the porous solid fiber of the present invention has a sufficient porous structure not only in the cross section but also in the entire fiber. Therefore, the pore volume of the porous solid fiber is 0.4 cm 3 / g or more is more preferable, and 0.8 cm 3 On the other hand, in order to maintain the strength of the porous solid fiber, the pore volume of the porous solid fiber is 3.0 cm 3 / g or less is more preferable, and 2.7 cm 3 The pore volume of the porous solid fiber can be controlled by the coagulation bath temperature during spinning.

[0030] The surface porosity of the porous solid fiber of the present invention is preferably 0.2% or more and 50.0% or less. Because this ensures sufficient diffusion of the target substance into the fiber, the surface porosity of the porous solid fiber is more preferably 0.6% or more, even more preferably 1.5% or more, and particularly preferably 3.0% or more. On the other hand, because this is expected to prevent a decrease in fiber strength, non-selective adsorption, and the outflow of fine particles generated inside the pores to the outside of the fiber, the surface porosity of the porous solid fiber is more preferably 45.0% or less, even more preferably 35.0% or less, and particularly preferably 30.0% or less. The surface porosity of the porous solid fiber can be controlled by, for example, the speed of the cold air in the idle section during spinning.

[0031] The surface porosity can be calculated by image analysis of an image of the fiber surface observed with a scanning electron microscope or the like.

[0032] The porous solid fiber of the present invention has a dense layer on its surface, and the thickness of the dense layer in the radial direction is preferably 0.005 μm or more and 3.0 μm or less. Here, the term "dense layer" refers to a region in the radial cross section of the fiber where no pores with a pore size of 4 nm or more exist, and refers to the distance from the fiber surface to the region. The dense layer has excellent mechanical strength and can particularly prevent damage to the porous solid fiber from external mechanical stress. Therefore, the thickness of the dense layer in the radial direction of the porous solid fiber is more preferably 0.02 μm or more, even more preferably 0.05 μm or more, and particularly preferably 0.10 μm or more. On the other hand, from the viewpoint of improving the diffusibility of the substance to be adsorbed into the fiber interior, the thickness of the dense layer in the radial direction of the porous solid fiber is more preferably 2.0 μm or less, even more preferably 1.0 μm or less, and particularly preferably 0.5 μm or less. The thickness of the dense layer on the surface of the porous solid fiber can be controlled by the idle running time during spinning.

[0033] The thickness of the dense layer can be calculated by image analysis of an image of a cross section of the fiber in the radial direction observed with a scanning electron microscope or the like.

[0034] The porous solid fiber of the present invention may contain a third component such as fine particles as a pore-forming agent or adsorbent inside the fiber. However, it is preferable that the porous solid fiber does not contain the third component, since this may result in a decrease in the strength of the porous solid fiber, a decrease in the efficiency of cleaning during spinning, or the third component may leach out from the inside of the porous solid fiber to the outside.

[0035] When the porous solid fiber of the present invention is used as an adsorbent, the adsorption principle may be any of hydrophobic interaction, electrostatic interaction, hydrogen bonding, etc., or a combination of these principles may be used. Hydrophobic interaction is particularly preferred because it has sufficient power to adsorb proteins and has little effect on blood cells and the like. These adsorption principles are basically determined by the fiber material, as described below. Multiple ligands that specifically interact with the target substance may be immobilized on the surface and within the pores of the porous solid fiber. However, it is difficult to simultaneously immobilize multiple ligands to the porous solid fiber, and even if immobilization is successful, competition between the ligands may reduce the amount of ligand immobilized and reduce adsorption performance. Therefore, it is preferable to immobilize only one type of ligand to the porous solid fiber.

[0036] From the viewpoint of achieving both blood compatibility and adsorption performance, the porous solid fiber of the present invention desirably has an appropriate degree of hydrophobicity on the outer surface of the fiber and on the surfaces of the pores inside the fiber. The hydrophobicity can be quantified by the dispersive component of the surface free energy, and specifically, the dispersive component of the surface free energy measured by inverse gas chromatography should be 5 to 100 mJ / m 2 is preferably 10 to 80 mJ / m 2 , and more preferably 20 to 70 mJ / m 2 is.

[0037] The materials of the regions A1 and A2 of the porous solid fiber of the present invention may be the same or different, but it is preferable that the materials of each region are the same in order to prevent peeling or deformation of the porous solid fiber due to differences in physical or chemical properties caused by the difference in materials.

[0038] Polymers are preferably used as the material for the porous solid fiber of the present invention from the viewpoints of moldability and cost. Examples of polymers include polymethyl methacrylate (hereinafter referred to as "PMMA"), polyacrylonitrile (hereinafter referred to as "PAN"), polysulfone, polyethersulfone, polyarylethersulfone, polypropylene, polystyrene, polycarbonate, polylactic acid, polyethylene terephthalate, cellulose, cellulose triacetate, ethylene-vinyl alcohol copolymer, polycaprolactam, polymethylpentene, polyvinylidene fluoride, polyester-based polymer alloys, and derivatives thereof. Among these, PMMA, PAN, polysulfone, polyethersulfone, polyester-based polymer alloys, polystyrene, and cellulose triacetate, which have moderate hydrophobic interactions, are preferably used. The porous solid fiber of the present invention preferably contains an amorphous polymer, and more preferably contains an amorphous polymer as the main component. Here, "mainly composed of an amorphous polymer" means that the amorphous polymer accounts for 50% by mass or more of the total components constituting the porous solid fiber. Amorphous polymers are particularly excellent in terms of moldability and cost. Furthermore, because they are composed only of amorphous portions, they have a uniform structure even from a microscopic perspective, and uniform adsorption reactions can be expected on the surface. Furthermore, compared to crystalline polymers, which have two domains, crystalline and amorphous, with significant differences in physical and chemical properties, amorphous polymers are easier to handle as materials. Among amorphous polymers, PMMA is particularly preferred because it has moderate hydrophobicity, excellent strength, and can withstand radiation sterilization when used in medical applications.

[0039] The amorphous polymer contained in the porous solid fiber of the present invention is preferably an ester group-containing polymer. Polymers containing ester groups, such as PMMA, are preferred because they have excellent blood compatibility and can easily exhibit functions by modifying the end groups.

[0040] The porous solid fiber of the present invention preferably has a negative charge. Adding a material having a negatively charged functional group to the spinning dope can impart a negative charge to the porous solid fiber, and as described below, can also improve the porosity. Examples of negatively charged functional groups include sulfo groups, carboxyl groups, phosphate groups, phosphite groups, ester groups, sulfite groups, hyposulfite groups, and sulfide groups. The amount of negative charge per gram of dried porous solid fiber is preferably 5 μeq or more and 130 μeq or less. When the porous solid fiber has an appropriate negative charge, for example, sialic acid present on the surface of cells and albumin, a major negatively charged protein in blood, are repelled by the porous solid fiber, thereby suppressing fouling due to nonspecific adsorption.

[0041] The porous solid fiber of the present invention can be produced by either melt spinning or solution spinning. While it is possible to make composite fibers obtained by melt spinning porous by post-processing such as drawing or extraction, when attempting to obtain a porous solid fiber having multiple regions as in the present invention, delamination and breakage between the regions are likely to occur. Furthermore, controlling the average pore size for each region is difficult, and the porosity is likely to be low. On the other hand, solution spinning allows for the production of a porous fiber with sufficient pore volume and porosity by uniformly dissolving the fiber material in a solvent and then removing the solvent. Furthermore, by appropriately designing the spinning dope that forms each region, multiple regions with different average pore sizes can be easily formed within the porous solid fiber. Furthermore, since post-processing to make the fibers porous is not required, productivity is excellent and there is minimal risk of delamination or breakage. For these reasons, solution spinning is preferred as the method for producing porous solid fibers.

[0042] Hereinafter, a method for producing a porous solid fiber by solution spinning will be described, but the method is not limited to this.

[0043] First, to obtain a porous solid fiber having multiple regions with different average pore sizes, multiple spinning dope solutions with different compositions are simultaneously extruded from a spinneret. For example, when producing a porous solid fiber having regions A1 and A2, a spinning dope a1 for forming region A1 and a spinning dope a2 for forming region A2 are used. In this case, by reducing the difference in viscosity between the spinning dope a1 and a2, it is easier to maintain a balance in the flow rate when the dope solutions are extruded, and regions A1 and A2 can be formed into a continuous structure in the longitudinal direction of the fiber. In addition, the position of each region in the radial cross section of the fiber is constant, and so-called island merging is unlikely to occur. Furthermore, the fiber shape is also less likely to vary. On the other hand, if the viscosities of the spinning dope solutions are the same, adequate solvent exchange at the interface is unlikely to occur, and peeling is likely to occur at the boundary between the regions. Therefore, the value obtained by dividing the viscosity of the spinning dope with the higher viscosity by the viscosity of the spinning dope with the lower viscosity is preferably 1.1 or more, more preferably 1.3 or more, and even more preferably 1.5 or more. On the other hand, it is preferably 77.0 or less, more preferably 51.0 or less, and even more preferably 29.0 or less. For the purpose of controlling the viscosity, the molecular weight of the fiber-forming component may be adjusted, or a thickener, a surfactant, water, alcohol, or the like may be added to the spinning dope.

[0044] The solvent used in all spinning dope solutions is preferably the same. By using the same solvent, when removing the solvent in a coagulation bath or the like during spinning, it is not necessary to bring the dope into contact with another solvent having a different solubility, and therefore, changes in the pore structure can be suppressed.

[0045] After simultaneously discharging the spinning dope solutions a1 and a2 from the spinneret, they are preferably allowed to run idle for a certain period of time and then introduced into a coagulation bath containing a nonsolvent or poor solvent for the polymeric fiber material, where they are coagulated. It is also preferable to actively cool the fibers during this idle period. Cooling the fibers during this idle period quickly completes the formation of domains, continuous interfaces, and porous structures, resulting in fibers with a consistent structure in the longitudinal direction of the fibers. Specifically, cooling is preferably performed using cold air in the idle period. The cold air velocity is preferably 3.3 m / s or more, more preferably 4.6 m / s or more, and particularly preferably 5.2 m / s or more. Rapidly cooling the fibers after discharge by increasing the cold air velocity suppresses the aggregation of the fiber material, particularly on the fiber surface, and improves the surface open area ratio. The idle period after discharge is preferably 0.2 seconds to 2 seconds. Limiting the idle period to a certain period of time reduces the risk of fiber breakage. Furthermore, adjusting the idle period can control the dense layer thickness. The shorter the idle time, the more easily the fiber-forming components are precipitated on the fiber surface, and the thicker, denser layer can be formed.

[0046] The spinneret temperature during spinning is preferably 150° C. or less in order to ensure sufficient cooling of the fiber after extrusion.

[0047] The coagulation bath into which the spinning dope is immersed after being discharged from the spinneret usually contains a coagulant such as water or alcohol alone, or a mixture with the solvent that makes up the spinning dope. The average pore size, porosity, and pore volume of the porous solid fiber can be controlled by adjusting the coagulation bath temperature. In general, the average pore size can be increased by increasing the coagulation bath temperature. The mechanism behind this is unclear, but it is presumed to be as follows. When the spinning dope is immersed in the coagulation bath, desolvent removal and coagulation shrinkage occur in competition. At high temperatures, desolvent removal is faster, and the fiber solidifies and hardens before shrinking inside, resulting in a larger average pore size in the porous solid fiber.

[0048] The average pore size of regions A1 and A2 can be controlled by the concentration of each spinning solution, the addition of a pore-forming agent, and the position of each region in the radial cross section of the fiber. For example, the average pore size can be increased by decreasing the concentration of the spinning solution or adding a pore-forming agent. Furthermore, in the radial cross section of the fiber, the closer to the periphery, the faster the structure formation during free running and the desolvation in the coagulation bath, resulting in a larger average pore size. Therefore, it is preferable to position region A2 near the periphery of the fiber. In addition to the concentration of each spinning solution and the addition of a pore-forming agent, the porosity can be improved by incorporating positively and / or negatively charged functional groups into a portion of the polymer that forms the fiber material, thereby finely dispersing the polymer. Examples of positively charged functional groups include amino groups, guanidyl groups, and amidine groups. Examples of negatively charged functional groups include sulfo groups, carboxyl groups, phosphate groups, phosphite groups, ester groups, sulfite groups, hyposulfite groups, and sulfide groups.

[0049] The adsorption performance of the porous solid fiber of the present invention can be measured, for example, by the amount of adsorption of the inflammatory cytokine IL-6 and LDL cholesterol. As mentioned above, these are factors in arteriosclerosis, and sufficient adsorption and removal of these substances is expected to improve the pathological condition. The amount of IL-6 adsorbed by the porous solid fiber was 0.04 μg / cm. 3 It is preferable that the concentration is equal to or higher than 0.06 μg / cm 3 More preferably, 0.09 μg / cm 3 The adsorption capacity of LDL cholesterol for porous solid fibers was 0.10 mg / cm 3 It is preferable that the concentration is equal to or higher than 0.15 mg / cm, and more preferably 0.15 mg / cm 3 More preferably, 0.30 mg / cm 3 That's all.

[0050] The fiber bundle of the present invention includes the porous solid fiber of the present invention. By forming a fiber bundle containing the porous solid fiber of the present invention, a fiber bundle that is easy to handle and exhibits high adsorption performance can be obtained. When forming the fiber bundle, in order to prevent the porous solid fibers from repelling each other due to static electricity or the like and from losing their cohesion, and to prevent adhesion between the single fibers, the fiber bundle may be wrapped in a film, net, mesh, nonwoven fabric, or the like, or a textured yarn such as a covering yarn may be spirally wrapped around one or more fibers.

[0051] The purification column of the present invention includes a casing having ports at both ends communicating with the interior, and the fiber bundle of the present invention is housed within the casing. Examples of the casing shape include a rectangular or hexagonal casing or a cylindrical casing with both ends open. Among these, a cylindrical casing, particularly a cylindrical casing with a perfectly circular cross section in the radial direction, is preferred. This is because the lack of corners in the casing can prevent blood from accumulating at the corners. Furthermore, by having open ends on both sides of the casing, the flow of the liquid to be treated is less likely to be disturbed, minimizing pressure loss. Materials such as plastics and metals can be used for the casing, with plastics being preferred from the standpoints of cost, moldability, mass, and blood compatibility. When plastics are used as the casing material, thermoplastic resins, which have excellent mechanical strength and thermal stability, are preferred. Examples of thermoplastic resins include polycarbonate resins, cellulose resins, polyester resins, polyarylate resins, polyimide resins, cyclic polysulfone resins, polyethersulfone resins, polyolefin resins, polystyrene resins, polyvinyl alcohol resins, ABS resins, and mixtures thereof. Among these, polypropylene, polystyrene, polycarbonate, ABS resin, or derivatives thereof are preferred from the viewpoint of moldability and radiation resistance required for the casing. In particular, resins with excellent transparency, such as polystyrene and polycarbonate, are advantageous in ensuring safety because, for example, the internal state can be observed during perfusion of the liquid to be treated.

[0052] Both ends of the casing are preferably physically sealed. Examples of sealing methods include placing a mesh or penetrating the partition wall with a resin or other material to provide through-holes that connect the inside and outside of the casing. Here, the term "through-hole" refers to an opening that penetrates the partition wall in the longitudinal direction of the porous solid fiber. In other words, the "through-hole" refers to a hole that exists in the partition wall and penetrates it, connecting the inside and outside of the casing separated by the partition wall. Here, the term "partition wall" refers to a portion at the end of the casing that separates the inside and outside of the casing, such as a resin that fixes the casing and the fiber. When using a resin as a partition wall, a resin liquid such as polyurethane is injected from both ends of the casing, and the resin liquid is hardened while flowing toward the end of the casing by centrifugal force, and then unnecessary portions are removed. Among the sealing methods, the method of placing a mesh is preferred because it is easier to process than the method of forming a partition wall and easily distributes the flow of the treated liquid uniformly within the column. In order to further improve the dispersibility of the liquid to be treated in the column, a mesh with a large pressure loss, a baffle plate, or a plate-like member for controlling the flow called a flow rectifier plate may be provided in part of the mesh.

[0053] Examples of fiber forms for incorporating a fiber bundle into a casing include finely chopped porous solid fibers and fibers processed to form knitted, woven, or nonwoven fabrics. Among these, a fiber bundle formed by bundling straight fibers is preferred, and it is preferable to insert the fiber bundle parallel to the longitudinal direction of the casing. A fiber bundle formed by bundling straight porous solid fibers easily ensures a flow path for the treated liquid, making it easier to evenly distribute the treated liquid within the casing. It also reduces turbulence and is advantageous in preventing increased pressure loss. Therefore, even when highly viscous blood is used as the treated liquid, the risk of coagulation within the casing can be minimized. Furthermore, particularly in the case of porous solid fibers having multiple regions with different average pore sizes, as in the present invention, a straight fiber bundle is preferred because it can reduce the risk of delamination at the interface between the regions due to pressure during the treatment liquid delivery. [Example]

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. First, measurement methods and evaluation methods are described below.

[0055] (Method for determining area A1 and area A2) First, a sufficiently moistened porous solid fiber was placed in a container filled with water and frozen with liquid nitrogen to obtain a block containing the embedded porous solid fiber. The block was sliced ​​at a temperature of -65°C and a thickness of 200 nm using an ultramicrotome equipped with a cryosystem to obtain a section exposing the radial cross section of the porous solid fiber (hereinafter referred to as the "fiber cross section"). The obtained section was freeze-dried in a vacuum dryer at 0.1 torr or less to sublimate the water, thereby obtaining a dried sample. Subsequently, a platinum-palladium (Pt-Pd) thin film was formed on the sample surface by sputtering to obtain a region observation sample. The fiber cross section of the sample was observed using a scanning electron microscope (S-5500, manufactured by Hitachi High-Technologies Corporation), and images were taken at arbitrary positions on the fiber cross section. The angle of view per photograph was 2 μm square (40,000x magnification) to ensure that the pores were clearly visible. When imaging multiple arbitrary positions, the imaging areas were prevented from overlapping. After capturing the images, the pores in each photograph were measured, and the average pore size and total area of ​​all pores were calculated. To determine the average pore size and total area of ​​all pores per photograph, the electron microscope images were binarized using the image analysis software "ImageJ" so that pores appeared black and non-pores appeared white. The resulting images were analyzed to calculate the average pore size and total area of ​​all pores. When binarization of pore and non-pore areas was difficult due to contrast differences in the electron microscope images, a transparent sheet was placed over the printout and the pores were filled in black using a black pen. The transparent sheet was then copied onto white paper, and the image was then binarized so that pores appeared black and non-pores appeared white, and analysis was then performed.

[0056] After the above measurements, if there was at least one photograph showing an average pore size of 4 nm or more and 50 nm or less, the porous solid fiber was determined to belong to region A1. If there was at least one photograph showing an average pore size of 55 nm or more and 350 nm or less, the porous solid fiber was determined to belong to region A2. To calculate the average pore size of region 1 and region A2, 20 photographs each were randomly selected from those judged to be region A1 or region A2, and the average pore size per photograph was averaged and rounded to the nearest tenth. If the area of ​​the region was small and there were fewer than 20 photographs judged to be region A1 or region A2, the average pore size was calculated according to the number of photographs judged to be region A1 or region A2, and the value rounded to the nearest tenth was used as the average pore size of region A1 and region A2.

[0057] (Porosity of Area A1 and Area A2) Twenty photographs were randomly selected from those judged to be in region A1 or region A2 using the above-mentioned "method for judging region A1 and region A2." The porosity of each photograph judged to be in region A1 or region A2 was calculated using the total area of ​​all holes per photograph calculated using the above-mentioned "method for judging region A1 and region A2" using the following formula (1).

[0058] Porosity (%) of each photograph = total area of ​​all pores (μm 2 ) / 4μm 2 ×100...Equation (1) The porosity of each photograph determined to be region A1 or region A2 was averaged and rounded to the nearest tenth to obtain the porosity of region A1 and region A2. If the area of ​​the region was small and there were fewer than 20 photographs determined to be region A1 or region A2, the porosity was calculated based on the number of photographs determined to be region A1 or region A2, and the porosity of region A1 and region A2 was obtained by averaging the porosity of region A1 and region A2 based on the number of photographs determined to be region A1 or region A2, and rounding to the nearest tenth to obtain the porosity of region A1 and region A2.

[0059] (Proportion of each area to the entire cross section) The ratio of the area A1 and the area A2 to the entire cross section in the radial direction of the porous solid fiber was determined by photographing an arbitrary position on the fiber cross section, in the same manner as in the "method for determining the area A1 and the area A2" described above, and determining the area of ​​4 μm per photograph in the photographs determined to be the area A1 or A2. 2 The area ratio of region A1 was calculated using the following formula (2), and the area ratio of region A2 was calculated using the following formula (3), and the values ​​were rounded off to the first decimal place.

[0060] Area ratio of area A1 (%) = (number of photos of area A1 × 4 μm 2 ) / fiber cross-sectional area (μm 2 )×100...Equation (2) Area ratio of area A2 (%) = (number of photos of area A2 × 4 μm 2 ) / fiber cross-sectional area × (μm 2 )100...Equation (3) If the area ratio reached 10% before determining the areas A1 and A2 for the entire fiber cross section, the area ratio was determined to be 10% or more. Area ratios of 15% or more, 20% or more, 25% or more, 30% or more, and 40% or more were also determined in the same manner.

[0061] The fiber cross-sectional area was determined by photographing the above-mentioned area observation sample using a scanning electron microscope (S-5500, manufactured by Hitachi High-Technologies Corporation) so that the entire fiber cross-section was captured, and then using the image analysis software "ImageJ" to determine the area of ​​the fiber cross-section.

[0062] (Surface porosity) A thoroughly moistened porous solid fiber was frozen in liquid nitrogen and freeze-dried in a vacuum dryer at or below 0.1 torr for 24 hours to sublimate the water, yielding a dried sample. A platinum-palladium (Pt-Pd) thin film was then formed on the sample surface by sputtering, creating a surface observation sample. The fiber surface of the surface observation sample was observed using a scanning electron microscope (Hitachi High-Technologies Corporation, S-5500), and images were taken of random locations on the fiber surface. The field of view per photograph was set to 6 μm square (10,000x magnification), allowing for sufficient visibility of pores. After imaging, the pores in each photograph were counted, and the total area of ​​all pores was calculated. The electron microscope images were binarized using the image analysis software "ImageJ" so that pores were black and non-pores were white. The resulting images were then analyzed to calculate the total area of ​​all pores. When it was difficult to binarize the porous and non-porous areas due to differences in contrast in the electron microscope image, a transparent sheet was placed over the printout and the porous areas were filled in black using a black pen or similar. The transparent sheet was then copied onto a blank piece of paper, and the image was used for binarization so that the porous areas were black and the non-porous areas were white, and then analysis was performed. The surface porosity was calculated from the total area of ​​all the obtained pores using the following formula (4). This measurement was performed at 40 locations, and the values ​​were averaged and rounded to the nearest tenth.

[0063] Surface porosity (%) = total area of ​​all pores (μm 2 ) / 36μm 2 ×100...Equation (4) (Dense layer thickness) The fiber cross-sections of the region observation samples prepared using the "Method for Determining Regions A1 and A2" described above were observed using a scanning electron microscope (S-5500, Hitachi High-Technologies Corporation). Images were taken of the outermost periphery of the fiber cross-section, with a field of view of 4 μm square (magnification 20,000x) around the entire fiber periphery. If the entire dense layer could not be captured in the outermost periphery, photographs of adjacent areas could be taken and combined to capture the entire dense layer. The pore diameters of all pores in each photograph were measured. To measure pore diameters, the electron microscope images were binarized using the image analysis software "ImageJ" so that pores were black and non-pores were white. The resulting images were analyzed to calculate the average pore diameter and the total area of ​​all pores. If binarization of pore and non-pore areas was difficult due to contrast differences in the electron microscope images, a transparent sheet was placed over the printed image and pores were blacked out using a black pen. The transparent sheet was then copied onto a blank sheet, and the image was binarized so that the pores were black and the non-pores were white. In the binarized image, the area that did not contain pores with a diameter of 4 nm or more and was in contact with the outermost surface of the fiber was defined as the dense layer, and the distance that this dense layer continued from the outermost surface toward the center of the fiber was defined as the dense layer thickness.

[0064] (Ratio of area A1 and area A2 at the outermost periphery) A region observation sample was prepared using the same method as in the "Method for determining regions A1 and A2" described above. The fiber cross section of the sample was observed using a scanning electron microscope (S-5500, manufactured by Hitachi High-Technologies Corporation), and the position of the outermost periphery of the fiber cross section was photographed around the entire circumference of the fiber. The angle of view per photograph was 2 μm square, so that the holes could be clearly seen. The determination of whether it was region A2 was performed as described in the "Method for determining regions A1 and A2" described above. If a dense layer was present on the fiber surface, the dense layer was removed by image processing, and the determination was made using the image. The ratio of region A1 to region A2 at the outermost periphery was calculated using the following formula (5) or (6), and the value rounded to one decimal place was used.

[0065] Ratio (%) of area A1 in the outermost periphery = number of photos in area A1 / number of photos in the outermost periphery × 100... Equation (5) Ratio (%) of area A2 in the outermost periphery = number of photos in area A2 / number of photos in the outermost periphery × 100... Equation (6) (pore volume) The pore volume of the porous solid fiber was calculated by measuring the freezing point depression due to capillary coagulation of water in the pores using DSC. Specifically, the adsorbent material was rapidly cooled to -55°C, then heated to 5°C at a rate of 0.3°C / min, and the volume was calculated from the resulting curve. For details, see Non-Patent Document 1. The pore volume was calculated using equation

[10] on page 104, and the value was rounded to one decimal place.

[0066] (amount of negative charge) 0.02 g of the dried porous solid fiber was weighed and washed with 20 mL of 0.1 mol / L aqueous sodium hydroxide solution, followed by distilled water. After washing, 1% by mass phenolphthalein solution was added dropwise to the distilled water, and washing with distilled water was repeated until the color disappeared. After washing, the porous solid fiber was freeze-dried for 24 hours in a vacuum dryer at 0.1 torr or less. The porous solid fiber was then placed in a test tube, 20 mL of 0.001 mol / L aqueous sodium hydroxide solution was added, and the mixture was shaken at 30°C at 150 rpm for 24 hours. After shaking, 10 mL of the supernatant was collected and titrated with 0.001 mol / L hydrochloric acid. Two drops of 0.1% by mass methyl red were added as an indicator. The negative charge was calculated using the following formula (7), rounded to the nearest whole number.

[0067] Amount of negative charge (μeq / g) = {Volume of supernatant used in titration (mL) × Normality of sodium hydroxide (μeq / mL) – Titration volume (mL) × Normality of hydrochloric acid (μeq / mL)} / Dry mass of porous solid fiber (g) Equation (7) (dispersion component of surface free energy) The freeze-dried porous solid fiber was packed into a glass column, and the dispersive component of the surface free energy was measured and calculated using a surface free energy analyzer (iGC-SEA) manufactured by Japan Science Core Co., Ltd., following the method described in "Inverse gas chromatography applications: A review" Adv. Colloid Interface Sci., 212, 21-44 (2014). Specifically, linear alkanes with 6 to 9 carbon atoms were used as the test solvent, and the retention volume was calculated from the resulting chromatogram. The dispersive component of the surface free energy was calculated from the retention volume of each alkane.

[0068] (Adsorption performance of porous solid fiber) First, human IL-6 was added to commercially available human plasma to an initial concentration of 25 ng / mL, and the mixture was stirred. 3 The plasma was placed in a 15 mL centrifuge tube so that the concentration was 0.01%. 2.6 mL of the human plasma was added and the mixture was shaken at 37°C for 2 hours using a seesaw shaker (Wave-SI, TAITEC) set to 38 and the maximum angle (one cycle per 1.7 seconds). 1 mL of human plasma was sampled before and after contact with the porous solid fiber. IL-6 was measured by ELISA (HUMAN IL-6 QUANTIKINE QUICKKIT, R&D), and LDL cholesterol was measured by the direct method. IL-6 concentrations C1 and D1 in the human plasma before contact with the porous solid fiber, and IL-6 concentrations C2 and D2 after contact were determined. The adsorption amount per fiber volume was calculated using the following formula (8) or (9). Each measurement was performed three times, and the average was calculated. The values ​​were rounded to the nearest tenth.

[0069] IL-6 adsorption per fiber volume (μg / cm 3 )=(C1-C2)×2.6 / 0.19...Equation (8) Amount of LDL cholesterol adsorbed per fiber volume (mg / cm 3 )=(D1-D2)×2.6 / 0.19...Equation (9) Example 1 To obtain a PMMA concentration of 21% by mass, 31.7 parts by mass of syn-PMMA with a weight average molecular weight of 400,000, 31.7 parts by mass of syn-PMMA with a weight average molecular weight of 1.4 million, 16.7 parts by mass of iso-PMMA with a weight average molecular weight of 500,000, 20 parts by mass of PMMA copolymer with a molecular weight of 300,000 containing 1.5 mol% of sodium parastyrene sulfonate having a sulfo group exhibiting a negative charge, and 376 parts by mass of dimethyl sulfoxide (hereinafter referred to as "DMSO") were mixed and stirred at 110 ° C. for 8 hours to prepare a spinning solution a1 for forming region A1. The viscosity of the obtained spinning solution a1 at 110 ° C. was 4230 poise.

[0070] In addition, 40.9 parts by mass of syn-PMMA with a weight-average molecular weight of 1.4 million, 6.8 parts by mass of iso-PMMA with a weight-average molecular weight of 500,000, and 428 parts by mass of DMSO were mixed so that the PMMA concentration was 10% by mass, and the mixture was stirred at 110°C for 8 hours to prepare spinning solution a2 for forming region A2. The viscosity of the obtained spinning solution a2 at 110°C was 190 poise.

[0071] Using a concentric core-sheath spinneret, spinning solution a1 was simultaneously extruded into the air at a rate of 1.0 cc / min, with spinning solution a2 forming the core and sheath. The spinneret temperature was 99°C. The length of the free-running section was 550 mm, and the free-running time was 0.72 seconds. The fiber was cooled with cold air at a speed of 7.5 m / sec during free-running. The fiber was then introduced into a coagulation bath containing a 20% by mass DMSO aqueous solution at a temperature of 43°C. The resulting porous solid fiber was washed in a 40°C water bath, then introduced into a bath containing a 70% by mass glycerin aqueous solution for moisture retention, and wound up at 46 m / min to obtain porous solid fiber 1.

[0072] Using this porous solid fiber 1, the determination of regions A1 and A2, the porosity of regions A1 and A2, the proportion of each region in the entire cross section, the surface porosity, the thickness of the dense layer, the proportion of region A2 in the outermost periphery, the pore volume, the amount of negative charge, the dispersion component of the surface free energy, and the adsorption performance were measured, and the results are shown in Table 1.

[0073] Example 2 The same operations as in Example 1 were carried out, except that the coagulation bath temperature was set to 60°C, to obtain porous solid fiber 2. Using this porous solid fiber 2, the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance were measured, and the results are shown in Table 1.

[0074] Example 3 The same operations as in Example 1 were carried out except that the coagulation bath temperature was set to 70°C, thereby obtaining a porous solid fiber 3. Using this porous solid fiber 3, the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance were measured, and the results are shown in Table 1.

[0075] Example 4 The same operation as in Example 1 was carried out, except that the spinning dope a1 was used as the sheath and the spinning dope a2 was used as the core, to obtain a porous solid fiber 4. Using this porous solid fiber 4, the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance were measured, and the results are shown in Table 1.

[0076] Example 5 To obtain a PMMA concentration of 15% by mass, 31.7 parts by mass of syn-PMMA with a weight average molecular weight of 400,000, 31.7 parts by mass of syn-PMMA with a weight average molecular weight of 1.4 million, 16.7 parts by mass of iso-PMMA with a weight average molecular weight of 500,000, 20 parts by mass of PMMA copolymer with a molecular weight of 300,000 containing 1.5 mol% of sodium parastyrene sulfonate having a negatively charged sulfo group, and 567 parts by mass of DMSO were mixed and stirred at 110 ° C. for 8 hours to prepare spinning solution a3 for forming region A2. The viscosity of the resulting spinning solution a3 at 110 ° C. was 102 poise.

[0077] The same operation as in Example 1 was carried out, except that the spinning dope a1 was used as the sheath, the spinning dope a3 was used as the core, and the coagulation bath temperature was set to 61° C., to obtain porous solid fiber 5. Using this porous solid fiber 5, the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance were measured, and the results are shown in Table 2.

[0078] Example 6 The same operation as in Example 1 was carried out, except that the discharge rates of the spinning dope a1 and the spinning dope a2 were set to 1.8 cc / min and 0.2 cc / min, respectively, to obtain a porous solid fiber 6. Using this porous solid fiber 6, the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance were measured, and the results are shown in Table 2.

[0079] (Comparative Example 1) The same operation as in Example 1 was carried out except that only the spinning dope a1 was used, a circular (single-nozzle) spinneret was used, and the discharge rate was set to 2.0 cc / min, to obtain fiber 1. Using this fiber, the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance were measured, and the results are shown in Table 2.

[0080] (Comparative Example 2) The same operation as in Example 1 was carried out except that only spinning solution a2 was used, a circular (single-nozzle) spinneret was used, and the discharge rate was set to 2.0 cc / min, to obtain fiber 2. Measurements were made of the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance, and the results are shown in Table 2.

[0081] (Comparative Example 3) To obtain a PMMA concentration of 18% by mass, 31.7 parts by mass of syn-PMMA with a weight average molecular weight of 400,000, 31.7 parts by mass of syn-PMMA with a weight average molecular weight of 1.4 million, 16.7 parts by mass of iso-PMMA with a weight average molecular weight of 500,000, 20 parts by mass of PMMA copolymer with a molecular weight of 300,000 containing 1.5 mol% of sodium parastyrene sulfonate having a negatively charged sulfo group, and 456 parts by mass of DMSO were mixed and stirred at 110 ° C. for 8 hours to prepare spinning solution a4 for forming region A2. The viscosity of the resulting spinning solution a4 at 110 ° C. was 590 poise.

[0082] Fiber 3 was obtained in the same manner as in Example 1, except that the spinning dope a1 was used as the core, the spinning dope a4 was used as the sheath, and the coagulation bath temperature was set to 43° C. Using this fiber 3, the determination of region A1 and region A2, the porosity of region A1 and region A2, the ratio of each region to the entire cross section, the surface porosity, the dense layer thickness, the ratio of region A2 in the outermost periphery, the pore volume, and the adsorption performance were measured, and the results are shown in Table 2.

[0083] (Reference example 1) The same operation as in Example 1 was carried out except that only the spinning solution a2 was used, a circular (single nozzle) spinneret was used, and the discharge rate was set to 1.0 cc / min. As a result, thread breakage occurred frequently, and fibers could not be obtained.

[0084] [Table 1]

[0085] [Table 2]

[0086] Examples 1 to 3 and Comparative Examples 1 to 3 show that the porous solid fibers of the present invention having regions A1 and A2 can simultaneously adsorb both LDL cholesterol and IL-6 with high efficiency, compared to the fibers of Comparative Example 1 consisting only of region A1 and Comparative Example 2n consisting only of region A2.

[0087] Examples 1, 4, and 5 show that increasing the ratio of region A2 at the outermost periphery of the radial cross section of the porous solid fiber improves diffusivity to region A1 inside the fiber, making it easier to achieve a balance between the adsorption amounts of LDL cholesterol and IL-6.

[0088] Examples 1 and 6 show that by making the ratio of region A1 and region A2 to the entire cross section of the porous solid fiber 10% or more, it is possible to easily adsorb both LDL cholesterol and IL-6 simultaneously with high efficiency.

[0089] From Examples 1 and 4 and Reference Example 1, it can be seen that, although the spinning solution a2 for forming the region A2 having a large average pore size alone has low mechanical strength and is difficult to spin, spinning can be ensured by simultaneously extruding the spinning solution a1 for forming the region A1 having a small average pore size and excellent mechanical strength, thereby forming a form having both the region A1 and the region A2.

Claims

1. In the radial cross section, A region A1 having an average pore diameter of 4 nm or more and 50 nm or less; A region A2 having an average pore diameter of 55 nm or more and 350 nm or less; The porous solid fiber has a porosity of 10% or more and 95% or less in the region A1.

2. 2. The porous solid fiber according to claim 1, wherein the ratio of the area A2 to the outermost periphery of the cross section in the radial direction is 30% or more.

3. 3. The porous solid fiber according to claim 1, wherein the ratio of the region A1 to the entire cross section in the radial direction is 10% or more, and the ratio of the region A2 to the entire cross section in the radial direction is 10% or more.

4. The porous solid fiber according to claim 1 or 2, wherein the porosity of the region A2 is 10% or more and 95% or less.

5. Pore ​​volume is 0.2 cm ３ / g or more 3.3cm ３ 3. The porous solid fiber according to claim 1, wherein the tensile strength is 1 / g or less.

6. 3. The porous solid fiber according to claim 1, wherein the surface porosity is 0.2% or more and 50.0% or less.

7. 3. The porous solid fiber according to claim 1, which has a dense layer on its surface, the thickness of which is 0.005 μm or more and 3.0 μm or less in the radial direction.

8. The porous solid fiber according to claim 1 or 2, which contains an amorphous polymer.

9. The porous solid fiber according to claim 8, wherein the amorphous polymer is an ester group-containing polymer.

10. 3. The porous solid fiber of claim 1 or 2, which has a negative charge.

11. A fiber bundle comprising the porous solid fiber according to claim 1 or 2.

12. A purification column comprising the fiber bundle according to claim 11 housed in a casing having ports at both ends communicating with the interior.

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