Chemically functionalized nylon fibers and methods of making and using the same

Abstract

Described herein is a chemically functionalized fiber and a method of manufacture, wherein the core-in-sheath fiber comprises a nylon sheath layer that is chemically functionalized with an aqueous reaction mixture comprising an aminoalkyl (meth)acryl monomer. Such chemically functionalized fibers disclosed herein can be used to filter fluids.

Description

Technical Field

[0001] This disclosure relates to functionalized core-sheath fibers and methods for their preparation. This disclosure further relates to a filter using functionalized fibers in a nonwoven form and a method for filtering fluids. Functionalized fibers can be used to selectively filter and remove biological materials, such as biocontaminants, from biological samples. Summary of the Invention

[0002] Nonwovens have been grafted or derivatized with functional groups to enable the filtration of substances. See, for example, U.S. Patent No. 9,815,050 (Yavorsky et al.), which teaches the modification of nylon fibers with ion-exchange functionality. However, it is desirable to improve the functionalization of the substrate to achieve more effective capture of target molecules.

[0003] In one aspect, a chemically functionalized fiber comprises: A fiber comprising a core having a sheath thereon, wherein the sheath comprises nylon, and wherein the nylon is chemically functionalized by an aqueous reaction mixture comprising an aminoalkyl (meth)acryloyl monomer.

[0004] In one embodiment, the aqueous reaction mixture further comprises a hydrophilic monomer.

[0005] In one embodiment, the aqueous reaction mixture further comprises a (meth)acryloyl epoxide monomer.

[0006] On the other hand, a nonwoven fabric comprising chemically functionalized fibers is described, wherein the chemically functionalized fibers comprise: A fiber comprising a core having a sheath thereon, wherein the sheath comprises nylon, and wherein the nylon is chemically functionalized by an aqueous reaction mixture comprising an aminoalkyl (meth)acryloyl monomer.

[0007] In another aspect, a filter media comprising chemically functionalized fibers is described, the chemically functionalized fibers comprising: A fiber comprising a core having a sheath thereon, wherein the sheath comprises nylon, and wherein the nylon is chemically functionalized by an aqueous reaction mixture comprising an aminoalkyl (meth)acryloyl monomer.

[0008] In another aspect, a method for manufacturing chemically functionalized fibers is described, the method comprising: (i) Providing a fiber, wherein the fiber includes a core having a sheath disposed thereon, wherein the sheath comprises nylon; and (ii) Contacting the fiber with an aqueous reaction mixture containing an aminoalkyl (meth)acryloyl monomer; and (iii) Expose the fiber and aqueous reaction mixture to radiation.

[0009] The foregoing description is not intended to depict every embodiment. Details of one or more embodiments of the invention are also set forth in the following description. Other features, objectives, and advantages will become apparent from the specification and claims. Attached Figure Description

[0010] Embodiments of the present disclosure are illustrated by way of example in the accompanying drawings and schematic diagrams, which are for illustrative purposes only and are not drawn to scale.

[0011] Figure 1 This is a schematic diagram of an exemplary core-sheath fiber.

[0012] Figure 2 This is a schematic diagram of an exemplary chemically functionalized fiber according to an embodiment of the present disclosure.

[0013] Figure 3 This is a schematic diagram of an exemplary chemically functionalized fiber according to an embodiment of the present disclosure.

[0014] Figures 4 to 5 These are scanning electron microscope images of core-sheath fibers.

[0015] Figures 6 to 8 These are scanning electron microscope images of chemically functionalized fibers. Detailed Implementation

[0016] As used in this article, terminology

[0017] “a,” “an,” and “the” are used interchangeably and refer to one or more; and

[0018] "And / or" is used to indicate that one or both of the stated situations may occur, such as A and / or B including (A and B) and (A or B); "(Meth)acrylate" refers to compounds containing the structures of acrylate (CH2=CHCOOR) or methacrylate (CH2=CCH3COOR) or combinations thereof; and A monomer is a molecule that can be polymerized to form part of the basic structure of a polymer.

[0019] "Alkyl" refers to a saturated monovalent hydrocarbon with one to twelve carbon atoms, either straight-chain or branched, cyclic or acyclic, such as methyl, ethyl, 1-propyl, 2-propyl, pentyl, etc.

[0020] "alkylene" refers to a straight-chain saturated divalent hydrocarbon having one to twelve carbon atoms or a branched-chain saturated divalent hydrocarbon having three to twelve carbon atoms, such as methylene, ethylene, propylene, 2-methylpropylene, pentylene, hexylene, etc.

[0021] "Aryl" refers to a monovalent aromatic group, such as phenyl or naphthyl.

[0022] Similarly, in this article, the ranges expressed by the endpoints include all numbers contained within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0023] Similarly, in this article, the phrase “at least one” includes all numbers from one to larger (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0024] As used in this article, "including at least one of A, B, and C" means element A itself, element B itself, element C itself, A and B, A and C, B and C, and all combinations of the three.

[0025] In this disclosure, it has been discovered that when core-sheath fibers are chemically functionalized with the aqueous reaction mixtures disclosed herein, chemically functionalized fibers with unique morphology, improved grafting amounts, and / or improved target molecule capture can be obtained. Such fibers can be used in nonwoven form, and in some embodiments, they can be used as filter media.

[0026] The fibers disclosed herein are core-sheath fibers, and are also referred to herein simply as "fibers" or "multi-fibers". Reference now. Figure 1 The core-sheath fiber 10 includes a core 12, on which a sheath 14 is disposed. In some embodiments, such as Figure 1 As shown, the cortex 14 extends along the fiber length (except at the fiber ends). Although Figure 1 The core and sheath fibers shown have a circular cross-section, but other cross-sections can also be used, such as, for example, triangles, squares, rectangles, pentagons, hexagons, heptagons, octagons, stars, ellipses, trefoils, and tetralobes. Similarly, although... Figure 1 The core is shown in the center, but it can be located off-center.

[0027] In some embodiments, the core-sheath fibers are so-called “island-type” extruders in which multiple fiber cores (i.e., more than 1, 2, 4 or even 6 cores) are distributed within a polymer matrix that also forms a sheath.

[0028] The core of the fiber contains a thermoplastic resin, such as a polyolefin. Exemplary polyolefins include: poly(ethylene), poly(propylene), poly(1-butene), copolymers of ethylene and propylene, α-olefin copolymers (such as copolymers of ethylene or propylene with 1-butene, 1-hexene, 1-octene and 1-decene), poly(ethylene-co-1-butene) and poly(ethylene-co-1-butene-co-1-hexene) or copolymers or mixtures thereof.

[0029] The core can have any average diameter. For example, at least 1, 3, 5, 7 or even 10 micrometers and at most 100, 75, 50, 40, 25 or even 20 micrometers.

[0030] In this disclosure, the core is encapsulated by a sheath. The sheath comprises nylon. Exemplary nylons include: nylon 6; nylon 6,6; nylon 1,6; nylon 11; nylon 12; nylon 4,6; nylon 4; nylon 1,4; nylon 510; nylon TMDT (or nylon 6,3,T) or combinations thereof.

[0031] The sheath forms the outer surface of the fiber core, except for the ends of the fiber core, which may or may not be coated with the sheath. In some embodiments, the core is substantially covered by the sheath; in other words, it appears that there is no area of ​​the entire circumference of the core that is not covered by the sheath, and in some embodiments, it appears that there is no part of the core that is not covered by the sheath. While not mandatory, the sheath is preferably substantially uniform and intact. In one embodiment, the sheath may be thin, for example having a thickness of at least 0.5, 0.6, 0.7, 0.8, 0.9, or even 1 micrometer; and the average thickness is at most 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6.0, 8.0, or even 10.0 micrometers. In one embodiment, the core-to-sheath volume ratio is at least 95:5, 80:20, 75:25, 70:30, or even 60:40. In one embodiment, the core-to-sheath volume ratio is at most 20:80, 30:70, 40:60, or even 50:50. In one embodiment, the weight percentage of the sheath in the core-sheath fiber is at least 5, 8, 10, 15, or even 25 wt%. In another embodiment, the weight percentage of the sheath in the core-sheath fiber is at most 30, 40, 50, 60, or even 70 wt%.

[0032] The fibers used in the practice of this disclosure may have any average fiber diameter and may be continuous, random, and / or short fibers. For example, in some embodiments, the fibers (i.e., single fibers) may have an average fiber diameter of at least 5, 8, or even 10 micrometers and at most 12, 15, 18, 20, 22, or even 25 micrometers.

[0033] The diameter of the core and / or fibers can be measured using techniques known in the art. In some embodiments, the fiber diameter can be determined by microscopy (e.g., optical or scanning electron microscopy), where the fibers are cross-sectioned and observed under magnification to determine the fiber diameter, core diameter, and / or sheath thickness. In some embodiments, the fiber diameter can be calculated by measuring the pressure drop across the ends of the fiber web. The effective fiber diameter (EFD) can be calculated as described in the Examples section below. In practice, sheath thickness may exhibit some experimental variation due to routine experimental variations and the average nature of EFD.

[0034] Methods for manufacturing core-sheath fibers are well known and do not need to be described in detail herein. In one embodiment, the core-sheath fibers are manufactured by co-extrusion. For example, at least two polymers are extruded separately and fed into a polymer distribution system in which the polymers are introduced into segmented spinnerets. The polymers travel along different paths and combine in the spinneret orifices, thereby providing core-sheath fibers. See, for example, U.S. Patent Nos. 4,789,592 (Taniguchi et al.) and 5,336,552 (Strack et al.), both of which are incorporated herein by reference in their entirety. In another embodiment, a sheath is deposited onto the core fiber using deposition and coating techniques known in the art. For example, vapor deposition can be used to encapsulate the fiber core with a sheath material at a melting temperature above that of the resin. This technique may be more useful for a pure polymer resin sheath. See, for example, U.S. Patent No. 10,213,716 (Kitagawa et al.), which is incorporated herein by reference.

[0035] Coating techniques, such as spraying and dipping, can be used to coat a fiber core with a leather composition, thereby achieving a very thin leather. See, for example, WO Publication No. 201688692 (Kitagawa).

[0036] The fibers described herein can generally be manufactured using techniques known in the art for manufacturing filaments. Melt spinning is particularly advantageous for forming core-sheath fibers. In melt spinning, the polymer is heated, passed through a spinneret, and the fiber solidifies upon cooling. For example, melt spinning processes can be performed to collect multi-component fibers. As used herein, the term "melt spinning" refers to fibers formed by extruding molten fibers from a set of orifices and cooling and (at least partially) solidifying the fibers to form fibers, wherein the fibers pass through an air space (which may contain a moving airflow) to aid in cooling and solidifying the fibers, and the resulting fibers then pass through a drawing (i.e., stretching) unit to stretch the fibers.

[0037] In some embodiments, the core-sheath fibers are in a nonwoven form. As used herein, the term "nonwoven fabric" refers to a fabric having a structure of single fibers, which are randomly and / or unidirectionally interwoven in a pad-like manner. Nonwoven substrates can be manufactured using any process generally known for producing nonwoven webs. Typically, nonwoven fabrics are manufactured via a spunbond fiber process.

[0038] Spunbond nonwoven fiber webs can be formed according to known conventional methods, wherein melt-spun fibers are deposited on a moving belt, where they form a nonwoven continuous fiber web with interfiber adhesion.

[0039] In some embodiments, the nonwoven web can be made by air-forming fibers (e.g., core-sheath fibers and optional auxiliary fibers). Air-formed nonwoven webs can be prepared using equipment such as RANDO WEBBER, available for example from Rando Machine Company, Massand, New York. In some embodiments, an air-forming type called gravity web can be used, as described in, for example, U.S. Patent Publication No. 2011 / 0247839 (Lalouch et al.), the disclosure of which is incorporated herein by reference. The nonwoven web can be densified and strengthened, for example, by techniques such as cross-lapping, stitching, needle punching, hydroentangling, chemical bonding, and / or thermal bonding.

[0040] Unless otherwise stated, the nonwoven fiber webs according to this disclosure may have any basis weight, thickness, porosity, and / or density. In one embodiment, the core-sheath fibers have a basis weight of at least 50, 60, 80, or even 100 g / m²; and at most 150, 200, 225, 250, or even 275 g / m².

[0041] In this disclosure, the core-sheath fibers as described above are contacted with an aqueous reaction mixture and subjected to radiation to cause the monomers to react with the fibers.

[0042] In this disclosure, core-sheath fibers are exposed to an aqueous mixture of monomers, which are then reacted together to functionalize the fibers with amine groups (which may include quaternary ammonium groups).

[0043] The aqueous reaction mixture comprises an aminoalkyl (meth)acryloyl monomer; optionally, a hydrophilic monomer; and optionally, a (meth)acryloyl epoxide monomer.

[0044] The aminoalkyl (meth)acryloyl monomer is an amino (meth)acrylate or amino (meth)acrylamide of formula I or a quaternary ammonium salt thereof. I In equation I, R 1R is hydrogen or methyl, preferably methyl; L is —O— or —NH—; and Y is an alkylene group (e.g., an alkylene group having 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms). Each R 2 Independently hydrogen or alkyl, preferably C1-C4 alkyl. Alternatively, both R... 2 The groups, together with the nitrogen atoms to which they are attached, can form aromatic, partially unsaturated (i.e., unsaturated but non-aromatic) or saturated heterocyclic groups, wherein the heterocyclic groups may optionally be fused with a second ring, which is aromatic (e.g., benzene), partially unsaturated (e.g., cyclohexene), or saturated (e.g., cyclohexane). The counterions of quaternary ammonium salts are typically halides, sulfates, phosphates, nitrates, etc. Such grafted monomers can be quaternary ammonium monomers, i.e., those having -N(R) 2 )3 + X - Groups, wherein each R 2 As defined, and X - To counteract anions. Monomers with quaternary ammonium groups can react directly with fibers, or aminoalkyl (meth)acryloyl monomers with primary, secondary, or tertiary amine groups can react with fibers and subsequently be converted to quaternary ammonium groups via alkylation.

[0045] In some embodiments of Equation I, the two R 2 All groups are hydrogen. In other embodiments, one R 2 The group is hydrogen, and the other is an alkyl group having 1 to 10, 1 to 6, or 1 to 4 carbon atoms. In yet other embodiments, R 2 Groups combine with the nitrogen atoms to which they are attached to form heterocyclic groups. Heterocyclic groups include at least one nitrogen atom and may contain other heteroatoms such as oxygen or sulfur. Exemplary heterocyclic groups include, but are not limited to, imidazole groups. Heterocyclic groups may be fused with other rings such as benzene, cyclohexene, or cyclohexane. Exemplary heterocyclic groups fused with other rings include, but are not limited to, benzimidazole groups.

[0046] In one embodiment, the aminoalkyl (meth)acryloyl monomer of formula (I) is a quaternary ammonium salt as in formula (II): II Wherein R1 is hydrogen or methyl, preferably methyl; L is –O- or –NH-; and Y is an alkylene (e.g., an alkylene having 2 to 10 carbon atoms, 2 to 6 carbon atoms, or 2 to 4 carbon atoms). R2, R3, and R4 are independently aryl or alkyl, preferably C1-C4 alkyl; and X - To counteract anions.

[0047] Exemplary quaternary salts of aminoalkyl (meth)acryloyl monomers include, but are not limited to, (meth)acrylamidoalkyltrimethylammonium salts (e.g., 3-methacrylamidopropyltrimethylammonium chloride and 3-acrylamidopropyltrimethylammonium chloride) and (meth)acryloyloxyalkyltrimethylammonium salts (e.g., 2-acryloyloxyethyltrimethylammonium chloride, 2-methacryloyloxyethyltrimethylammonium chloride, 3-methacryloyloxy-2-hydroxypropyltrimethylammonium chloride, 3-acryloyloxy-2-hydroxypropyltrimethylammonium chloride and 2-acryloyloxyethyltrimethylmethylammonium sulfate).

[0048] In some embodiments, the aqueous reaction mixture comprises at least 10%, 20%, 25%, 30%, 40%, or even 50% by weight of aminoalkyl (meth)acryloyl monomers relative to the total monomers. In some embodiments, the aqueous reaction mixture comprises up to 55%, 60%, 70%, 80%, 90%, 95%, 98%, 99%, or even 100% by weight of aminoalkyl (meth)acryloyl monomers relative to the total monomers.

[0049] In some embodiments, the aqueous solution further includes a hydrophilic monomer, which is an olefinic unsaturated compound having hydrophilic characteristics. As used herein, a “hydrophilic monomer” is a polymerizable monomer having at least 1 wt.% and preferably at least 5 wt% water miscibility (water in the monomer) without reaching a cloud point, excluding poly(epoxide) monomers, and free of acidic functional groups or groups that would delay functionalization polymerization.

[0050] Examples of suitable hydrophilic monomers include 2-hydroxyethyl methacrylate (HEMA), 2-ethoxyethyl methacrylate (2-EOEMA), 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2,3-dihydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, N-vinylcaprolactam, N-vinylacetamide, N-vinylpyrrolidone, acrylonitrile, tetrahydrofurfuryl acrylate, acrylamide, mono- or di-N-alkyl substituted acrylamides, glyceryl methacrylates, and combinations thereof. Preferred polar monomers include 2-hydroxyethyl methacrylate (HEMA), N-vinylpyrrolidone, N-vinylacetamide, methacrylamide, and mixtures thereof.

[0051] In some embodiments, the aqueous reaction mixture comprises at least 0.5%, 1%, 2%, 10%, 20%, 25%, 30%, 40%, or even 50% hydrophilic monomers relative to the total monomers by weight. In some embodiments, the aqueous reaction mixture comprises up to 55%, 60%, 70%, 80%, 90%, or even 95% hydrophilic monomers relative to the total monomers by weight.

[0052] In some embodiments, the aqueous reaction mixture comprises a (meth)acryloyl epoxide monomer, in other words, a (meth)acrylate monomer having an epoxide substituent. Exemplary (meth)acryloyl epoxide monomers include glycidyl methacrylate and glycidyl acrylate.

[0053] In some embodiments, the aqueous reaction mixture comprises at least 0.1%, 0.5%, 1%, 1.5%, 2%, or even 2.5% (meth)acryloyl epoxide monomer relative to the total monomers by weight. In some embodiments, the aqueous reaction mixture comprises at most 20%, 15%, 10%, 5%, or even 3% (meth)acryloyl epoxide monomer relative to the total monomers by weight.

[0054] In some embodiments, the aqueous reaction mixture comprises a monofunctional olefinic unsaturated monomer having a poly(epoxide) group. Such a poly(epoxide) monomer may have the following formula: ZQ-(CH(R 5 )—CH2-Q) m -R 6 III Where Z represents the polymerizable unsaturated olefinic moiety, and R... 5 It is H or a C1 to C4 alkyl group, R 6 It is an H, C1 to C4 alkyl group, aryl group or combination thereof, and m is 2 to 100, preferably 5 to 20, and Q is selected from -O-, -NR. 1 —、—CO2— and —CONR 1 The divalent linker group.

[0055] In one embodiment, the poly(epoxyalkylene) group is a poly(ethylene oxide) (co)polymer. In another embodiment, the side poly(epoxyalkylene) groups are poly(ethylene oxide-co-propylene oxide) copolymers. Such copolymers can be block copolymers, random copolymers, or gradient copolymers.

[0056] The useful olefinic unsaturated moiety Z of the monomer may include:

[0057] Where R 3 It is H or -CH3 and r=1-10.

[0058] Monomers having poly(epoxide) groups can be prepared, for example, by reacting a monofunctional or difunctional epoxy (co)polymer (which is generally commercially available) with a reactive olefinic unsaturated compound (e.g., acrylate). The functional groups of the end-capped poly(epoxide) may include hydroxyl groups, amine groups, and carboxyl groups. Various reactive olefinic unsaturated compounds, such as acrylate derivatives, can be used, including but not limited to (meth)acrylic acid, (meth)acryloyl chloride, (meth)acrylic anhydride, and (meth)acrylic acid 2-isocyanate ethyl ester. Preferably, the monomer is prepared by reacting a monofunctional or difunctional epoxy (co)polymer with (meth)acrylic anhydride. Typically, 100% conversion to a monosubstituted product is obtained by combining stoichiometric amounts of the olefinic unsaturated reactant with a monofunctional epoxy (co)polymer (such as a monohydroxyl-terminated epoxy (co)polymer).

[0059] Examples of suitable monofunctional poly(epoxide) monomers include poly(ethylene oxide)(meth)acrylate, poly(propylene oxide)(meth)acrylate, poly(ethylene oxide-propylene oxide)(meth)acrylate, and combinations thereof. Such monomers preferably include a non-reactive end group, such as (C1-C4)alkoxy, aryloxy (e.g., phenoxy), and (C1-C4)alkylaryloxy. These groups can be linear or branched. These monomers can have a wide range of molecular weights and are commercially available from sources such as Sartomer Company of Exton, Pennsylvania; Shinnakamura Chemical Co., Ltd. of Tokyo, Japan; Aldrich of Milwaukee, Wisconsin; and Osaka Organic Chemical Ind., Ltd. of Osaka, Japan.

[0060] In some embodiments, the aqueous reaction mixture is substantially free of these monomers containing poly(epoxy) groups. As used herein, substantially free means less than 10, 8, 5, 2, 1, 0.5, or even 0.1% by weight or even free of these monomers relative to the total weight of the monomers.

[0061] The reaction mixture is aqueous, meaning the mixture contains water and / or a water-miscible organic solvent. In some embodiments, the water-miscible solvent is a proton-containing organic liquid, such as a lower alcohol having 1 to 4 carbon atoms, a lower glycol having 2 to 6 carbon atoms, and most preferably a lower glycol ether having 3 to 6 carbon atoms and 1 to 2 ether bonds. In some embodiments, higher glycols such as poly(ethylene glycol) may be used. Any such water-miscible organic solvent preferably does not have tertiary hydrogen atoms or other groups that would delay the polymerization of the monomer and the reaction of the monomer with the fiber. Exemplary water-miscible solvents include: methanol, ethanol, n-butanol, tert-butanol, ethylene glycol, methoxyethanol, ethoxyethanol, propoxyethanol, butoxyethanol, methyl carbitol, ethyl carbitol, and mixtures thereof. In some embodiments, aprotic water-miscible organic solvents, such as aliphatic esters and ketones, and sulfoxides, such as ethyl acetate, propyl acetate, butyl acetate, methoxyethyl acetate, ethoxyethyl acetate, propoxyethyl acetate, butoxyethyl acetate, triethyl phosphate, acetone, methyl ethyl ketone, methyl propyl ketone, and dimethyl sulfoxide, may also be used.

[0062] The ratio of water to organic solvent can vary, but is generally greater than 1:1 (v / v) water to organic solvent, preferably greater than 5:1, and more preferably greater than 7:1.

[0063] Typically, based on the total weight of the aqueous reaction mixture, the total concentration of monomers in the aqueous reaction mixture is in the range of at least 1, 2, 5 or even 10 wt% to at most 50, 45, 40, 30, 25, 20 or even 15 wt%.

[0064] In some embodiments, the amount of the aqueous reaction mixture is at least 30, 35, 40 or even 45 g to at most 100, 90, 80, 70, 60 or even 50 g per 100 g / m² (gsm) of core-sheath fiber substrate.

[0065] Irradiation is used to initiate the polymerization of the monomer reaction mixture and its reaction with nylon-containing leather.

[0066] The irradiation step includes ionizing the core-sheath fiber, preferably using an ionizing electron beam or gamma radiation to prepare radical reaction sites, followed by derivatization of the core-sheath fiber with an aqueous reaction mixture through these radical reaction sites. "Ionizing irradiation" means radiation with a dose and energy sufficient to form radical reaction sites on the base substrate. Ionizing radiation can include gamma rays, electron beams, X-rays, and other forms of electromagnetic radiation. In some cases, corona radiation can be sufficiently high-energy radiation. The radiation has sufficiently high energy that, when absorbed by the core-sheath fiber, enough energy is transferred to the fiber, causing the chemical bonds in the fiber to break and ultimately forming radical sites on the core-sheath fiber.

[0067] During the irradiation step, the core-sheath fibers are exposed to a sufficient amount of ionizing radiation to form free radicals within them. The chamber may contain at least one device capable of providing a sufficient dose of radiation. A single device can provide a sufficient dose of radiation, although two or more devices and / or multiple passes through a single device may be used. The environment containing the core-sheath fibers contains an inert atmosphere, such as nitrogen, carbon dioxide, helium, argon, etc., and a minimum amount of oxygen known to inhibit free radical polymerization.

[0068] Dose is the total amount of energy absorbed per unit mass. Dose is typically expressed in kilogras (kGy). A gray is defined as the amount of radiation required to provide one joule of energy per kilogram of mass. The total dose received by the core-sheath fiber depends on many parameters, including source activity, residence time (i.e., the total time the sample is irradiated), distance from the source, and attenuation through the intermediate cross-section of the material between the source and the sample. Dose is typically adjusted by controlling residence time, distance from the source, or both.

[0069] The total dose requirement for any given composition will vary depending on the desired monomers selected, the core-sheath fibers used, and the dose rate. In one embodiment, the dose range is about 20 to 40 kGy. Therefore, the dose rate can be selected based on the desired properties of the specified composition. Dose rates are typically in the range of 0.0005 kGy / second (gamma) to 200 kGy / second (electron beam).

[0070] Electron beams are a preferred method due to their readily available commercial sources. Electron beam generators are commercially available from a variety of sources, including the ESI “ELECTROCURE” EB system from Energy Sciences, Inc. (Wilmington, Massachusetts) and the BROADBEAM EB processor from PCT Engineered Systems, LLC (Davenport, Iowa). For any given equipment and irradiated sample location, the delivered dose can be measured according to ASTM E-1275, entitled “Practice for Use of a Radiochromic Film Dosimetry System.” Various dose rates can be obtained by varying the extractor grid voltage, beam diameter, and / or distance from the source.

[0071] Other radiation sources with similar derivatization properties can be used; desired ionizing radiation sources include electron beam sources because electron beams can produce high and rapid dose delivery rates. Electron beams (e-beams) are typically produced by applying a high voltage to a point maintained at approximately 10... -6Electrons are generated on a tungsten filament between a repulsion plate and an extractor grid within a vacuum chamber. The filament is heated under a high current to generate electrons. These electrons are guided and accelerated by the repulsion plate and the extractor grid to a thin window in the metal foil. The accelerated electrons travel at speeds exceeding 10... 7 Traveling at a speed of meters per second (m / sec) and possessing approximately 100 to 300 kiloelectron volts (keV), it exits the vacuum chamber through the foil window and penetrates any material placed immediately adjacent to the foil window.

[0072] The number of electrons produced is directly related to the current. As the extractor gate voltage increases, the acceleration or velocity of the electrons drawn from the tungsten filament increases. When under computer control, electron beam processing can be very precise, allowing for accurate electron dosage and dose rate targeting of the core-sheath fibers.

[0073] The temperature within the chamber is ideally maintained at ambient temperature using conventional methods. Without intending to be limited to any particular mechanism, it is believed that exposing the core-sheath fibers to an electron beam generates free radical sites in the substrate, which can then react with monomers in the aqueous reaction mixture.

[0074] The total dose received by the substrate primarily affects the number of free radical sites formed, and subsequently the extent of monomer-fiber reaction. The dose depends on several processing parameters, including voltage, web or line velocity, and beam current. The dose can be conveniently adjusted by controlling the line velocity (i.e., the speed at which the nonwoven substrate passes through the irradiation device) and the current supplied to the extractor grid. The target dose (e.g., <10 kGy) can be conveniently calculated to determine exposure by multiplying the experimentally measured coefficient (machine constant) by the beam current and dividing by the web velocity. The machine constant varies with the beam voltage.

[0075] While the controlled dose of electron beam radiation exposure depends on the dwell time, the controlled dose experienced by core-sheath fibers ranges from a minimum dose of about 1 kGy to a practical maximum dose of less than about 200 kGy, depending on the specific polymer. Higher doses, typically 10 to 70 kGy, can be used for less radiosensitive polymers such as nylon. Suitable gamma-ray sources typically emit gamma rays with energies of 400 keV or higher. Typically, suitable gamma-ray sources emit gamma rays with energies in the range of 500 keV to 5 MeV. Examples of suitable gamma-ray sources include cobalt-60 isotopes (which emit photons with energies of approximately 1.17 and 1.33 MeV in almost equal proportions) and cesium-137 isotopes (which emit photons with energies of approximately 0.662 MeV). The distance from the source can be fixed or can be varied by changing the location of the target or source. The flux of gamma rays emitted from a source typically decreases with the square of the distance from the source and the duration determined by the half-life of the isotope.

[0076] In this method, the irradiated fibers, which contain free radical sites, are contacted with an aqueous reaction mixture after, rather than simultaneously with, the irradiation step. The free radical sites generated in the core-sheath fibers have an average lifetime ranging from several minutes to several hours, and gradually decay to a low concentration over approximately ten hours at room temperature. Lower temperatures, such as dry ice temperatures, promote longer free radical lifetimes. Alternatively, humidification and nitrous oxide can increase the rate of matrix free radical formation by generating hydroxyl radicals.

[0077] Typically, the irradiated fibers are contacted with an aqueous reaction mixture immediately after the irradiation step. When using an electron beam, the irradiated fibers are typically absorbed within one hour, preferably within ten minutes.

[0078] The fibers can be contacted with the aqueous reaction mixture using techniques known in the art, including but not limited to spraying, overflow coating, doctor blade coating, Mayer rod coating, dip coating, and gravure coating.

[0079] The aqueous reaction mixture is kept in contact with the fiber for a sufficient time to allow free radical sites to initiate polymerization with the monomer. When in contact with the monomer solution, the reaction is mostly completed after 12 hours of exposure; typically around 90%+. Therefore, the fiber contains polymers and / or copolymers that adhere to the gaps, outer surface, and within the fiber.

[0080] Typically, the total monomer content functionalized onto the fiber can be 0.5 to 5 times the fiber weight.

[0081] Once the fibers have been in contact with the aqueous reaction mixture for the required time, the polymer-functionalized fibers may optionally be rinsed to remove residual monomers and / or dried.

[0082] In an optional rinsing step, the chemically functionalized fibers are washed or rinsed once or multiple times to remove any unreacted monomers, solvents, or other reaction byproducts. Typically, the functionalized fibers are washed or rinsed up to three times using water rinsing, alcohol rinsing, a combination of water and alcohol rinsing, and / or solvent rinsing (e.g., acetone, methyl ethyl ketone, etc.). When alcohol rinsing is used, the rinsing solution may include one or more alcohols, including but not limited to isopropanol, methanol, ethanol, or any other alcohol actually used, as well as an effective solvent for any residual monomers. In each rinsing step, the functionalized fibers may be rinsed through a rinsing bath or rinsing spray. In some embodiments, the rinsing solution may contain an ion buffer solution, which will reduce swelling of the resulting polymer, the amount of water retained, and also prevent the chemically functionalized fibers from being weakened during this rinsing step.

[0083] In an optional drying step, the functionalized fibers are dried to remove any rinsing solution. Typically, this involves drying the functionalized fibers in an oven at a relatively low temperature for a period of time (referred to herein as "oven dwell time"). Oven temperatures are typically in the range of about 60°C to about 120°C, while oven dwell times are typically in the range of about 8 to about 72 hours. Any conventional oven can be used in the optional drying step. It should also be noted that in other embodiments, the drying step may be performed prior to the rinsing step to remove volatile components before extraction of non-grafted residues. Following the optional drying step, the dried functionalized fibers can be wound into rolls for storage for future use.

[0084] When core-sheath fibers are functionalized with the aqueous reaction mixtures disclosed herein, unique morphologies emerge in some cases. For example, core-sheath fibers where the sheath is uniform and extends along the axial length of the fiber (e.g., as shown in the image). Figure 1 As shown), it can produce, during functionalization, such as Figure 2 The protrusions shown are illustrated in which the functionalized fiber 20 includes a sheath 24 enclosing the core 22, and protrusions 26 appear on the outside of the fiber, extending axially from the fiber and projecting radially along at least a portion of the fiber length. In some embodiments, the chemically functionalized fiber includes at least one protrusion; however, the fiber may include more protrusions, such as 2, 3, 4, 5, 6, 8, 10, or more. In another embodiment, the functionalized core-sheath fiber is shown... Figure 3 It includes a sheath 34 that encloses the core 32 and protrusions 36 extending from the fiber axis. Although Figure 2 and 3The illustration shows a sheath that directly contacts and wraps around the core, but in some embodiments, the sheath does not directly contact the core across the entire cross-section of the fiber as shown in some examples.

[0085] The aspect ratio of a protrusion can be determined by measuring its length and thickness. Figure 2 The aspect ratio is indicated by "l" and "t" respectively. Typically, the aspect ratio is the average value obtained by measuring various protrusions along multiple fibers. The aspect ratio can vary, especially if the chemically functionalized fibers exhibit "fin"-shaped protrusions rather than "fried dough stick" shaped morphology. Generally, the fin-shaped protrusions have a larger aspect ratio compared to the fried dough stick morphology. In some embodiments, the protrusions have a length-to-thickness aspect ratio of at least 0.5:1, 1:1, 1:1.5, or even 2:1, and at most 10:1, 8:1, 6:1, 5:1, 4:1, 3:1, or even 2.5:1.

[0086] While not wishing to be limited by theory, it is believed that because nylon is a hydrophilic substrate, the aqueous reaction mixture can absorb at least a portion of the nylon-containing skin, causing it to swell and / or the monomers to react into the bulk of the skin, thereby increasing the functionalized area.

[0087] In some embodiments, the mass of the chemically functionalized fibers as disclosed herein increases by at least 20%, 30%, 50%, 75%, 100%, 150%, 200%, or even 225%.

[0088] Due to the improved derivatization efficiency, in some embodiments, the chemically functionalized fibers disclosed herein possess an improved ability to capture analytes of interest. For example, when normalized for the surface area and total weight of the derivatized fibers, the chemically functionalized fibers of this disclosure can bind at least 30, 40, 50, 60, 70, 80, 90, or even 100 mg of analyte (e.g., BSA) / cm³. 2 Area / gram of total weight of the derived fibers.

[0089] In some embodiments, the functionalized fibers disclosed herein can be used, for example, in filtration applications, such as filtering macromolecules from fluids. For example, the purification or isolation of biological materials.

[0090] Example

[0091] Unless otherwise stated, all parts, percentages, ratios, etc., in the examples and the remainder of the instructions are by weight, and all reagents used in the examples are obtained from or available from general chemical suppliers, such as Sigma-Aldrich Company of St. Louis, Missouri, or can be synthesized by conventional methods.

[0092] The following abbreviations are used in the following examples: cm = centimeter, g = gram, gsm = gram per square meter, ghm = gram per pore per minute, hr = hour, oC = degree Celsius, in = inch, kV = kilovolt, lpm = liter per minute, mA = milliampere, mg = milligram, MRad = megarad, min = minute, m = meter, mm = millimeter, mM = millimole, mL = milliliter, nm = nanometer, Pa = pascal, psi = pound per square inch, ppm = part per million, oz = ounce, and sec = second.

[0093] Material

[0094] Method for manufacturing spunbond nonwovens containing fibers

[0095] Nonwoven media substrates were produced on a spunbond 0.5 m laboratory production line with 2 in (5.1 cm) and 2.5 in (6.35 cm) single-screw extruders, each with a planetary melt pump to meter the polymer flowing into the spinning assembly. Both monofilaments and core-sheath fibers were produced in a similar manner, differing only in the spinning assembly. The monofilament process was similar to that described in U.S. Patent No. 6,916,752 (Berrigan et al.). The core-sheath process was similar to that described in Example 4 of U.S. Patent No. 10,098,980 (Karls et al.). In monofilament or core-sheath fiber production, the polymer melt enters the assembly and is uniformly distributed and filtered before reaching the spinneret orifice for filament extrusion. In core-sheath fabrication, the melt converges in a composite plate immediately following the spinneret orifice to form a core / sheath structure.

[0096] As the polymer exits from the spinneret at the bottom of the assembly, it forms filaments (or fibers) and is vertically stretched through a quenching zone fed with cold air into a bundler supplied with compressed air. The filaments are then laid on a moving collector belt to form a nonwoven web, which is held in place by vacuum until it passes through a bonding zone, where the nonwoven web is wound onto a surface winding machine.

[0097] Pressure drop test

[0098] Operate the high-speed automated filter tester (8130 from TSI Corporation, Shorev, Minnesota) with particle generation and measurement off. Adjust the flow rate to 85 lpm and use a sample with a diameter of 5.25 in (13.34 cm). Place the sample on the lower circular pressurization opening and engage the tester. The pressure sensor within the device (MKS Instruments, Andover, Massachusetts) measures the pressure drop (ΔP) in mm water.

[0099] Methods for measuring effective fiber diameter (EFD)

[0100] The effective fiber diameter (EFD) was calculated based on the pressure drop (measured using the “pressure drop test” described herein), thickness, and a face velocity of 5.3 cm / sec. The sample thickness of a 5.25 in (13.34 cm) disc was measured using a thickness gauge with tester feet measuring 5 cm x 12.5 cm under an applied pressure of 150 Pa. The effective fiber diameter, in micrometers, was calculated based on the measured pressure drop, as described in CNDAvies, The Separation of Airborne Dust and Particulates, Proceedings of the Institution of Mechanical Engineers, London, IB (1952).

[0101] Scanning electron microscope (SEM)

[0102] The fiber dimensions and cross-section were examined using a scanning electron microscope (Hitachi TM4000Plus from NCI, Brooklyn Park, Minnesota). The cross-section was prepared by cryogenic fracturing of the sample with liquid nitrogen. A thin layer of gold was sputtered onto the sample to make it conductive.

[0103] The actual fiber diameter (or AFD) of the core-sheath fiber.

[0104] The AFD of the core-sheath filaments in nonwovens was determined by SEM of the nonwoven surface and by measuring the diameter of more than 50 individual fibers using measurement functions provided by the SEM instrument software.

[0105] AFD of monofilament

[0106] The fibers in the nonwoven fabric made of monofilaments were optically imaged using an optical microscope (Nikon ECLIPSEE 600POL, Tokyo, Japan) equipped with a digital camera (a DMC5400 from Leica Microsystems, Bloomington, Minnesota). For the conditions of interest, fiber bundles were collected below attenuators, cross-sections were prepared, and multifocal images were obtained using the optical microscope at 50x or 100x magnification (selecting the precise magnification as needed to obtain approximately 30 measurements from a single image). The fibers were then measured manually, with edge detection assisted by the associated Leica Applications Suite X v3.0.9.19082 software (from Leica Microsystems, Bloomington, Minnesota).

[0107] Electron beam (EB) derivatization process

[0108] The fibers were derivatized as follows: An aqueous reaction mixture (as described in the examples) was prepared in a 4 oz (118 mL) sealed wide-mouth flask to a total volume of 60 to 100 mL. After preparing the mixture, the flask was hand-shaken and bubbled with room nitrogen. The flask was then transferred to a nitrogen-containing glove box and left unsealed until the oxygen monitor reading in the glove box was < 20 ppm.

[0109] Nonwoven samples were prepared into 7 in x 9 in (17.8 cm x 22.9 cm) sheets and placed in 8 in x 10 in (20 cm x 25 cm) top-sealed plastic bags. The bags containing the samples were opened in a glove box and inertized with nitrogen until the glove box oxygen monitor reading was < 20 ppm. The bags were then opened, removed from the glove box, and attached to a PET carrier mesh, which was conveyed at 35 feet per minute (fpm) via an ElectroCure electron beam (Energy Sciences, Wilmington, MA). The samples were irradiated at 300 kV to a specified dose, typically 10 MRad. The resulting beam current was 55 mA.

[0110] After irradiation, the sample was removed and transferred back to the glove box. The oxygen monitor was allowed to reach <20 ppm before opening the bag. To deposit the monomer and initiate polymerization, the wide-mouth flask containing the aqueous reaction mixture was hand-shaken and then poured onto the nonwoven fabric inside the bag. To promote wetting of the entire sample, a hand roller was rolled over the sealed bag containing the nonwoven fabric and the aqueous reaction mixture. After 3 hours of reaction, the sample was removed from the glove box, exposed to the atmosphere, and placed in boiling deionized water for 1 hour to further saturate the reaction and remove residual monomers. Subsequently, the derivatized nonwoven fabric was dried overnight in ambient air on a polyethylene-lined aluminum tray, followed by further drying in a 70°C oven for 12 to 16 hours, followed by characterization and performance testing.

[0111] Basis weight

[0112] Cut a known sample size (e.g., a 5.25-inch disc) from the sample and weigh it to provide a basis weight in grams per square meter (gsm).

[0113] Evaluation of mass gain

[0114] The amount of monomer polymerized onto the fiber was determined by gravimetric analysis using the following equation: Quality gain % = [Final network quality - Initial network quality] / Initial network quality × 100 Static BSA combined Each disc sample (16 mm) was rolled in 4.5 mL of a buffer solution of 4 to 6 mg / mL BSA (25 mM Tris-HCl, 50 mM NaCl, pH 8) for 18 to 24 hours. Unbound BSA was then removed by washing the samples three times with rolling in fresh buffer solution for 30 minutes each. Bound BSA was then eluted into 3 mL of high-salt buffer (25 mM Tris-HCl, 1 M NaCl, pH 8) and rolled for 30 minutes. The amount of eluted BSA was measured using a UV / Vis spectrophotometer (Thermo Scientific NanoDrop, Thermo Fisher Scientific, Waltham, MA) with solution absorption at 280 nm. The amount of bound BSA was measured by transillumination through the disc area (mg / cm²). 2 After normalization, and after passing through the disc area and the weight of the grafted disc (mg / cm²) 2 / g) Report after normalization.

[0115] Preparation Examples 1 to 7 (PE01 to PE07)

[0116] Nonwoven media comprising core-sheath fibers with a nylon sheath content of 20 to 70 wt% were prepared using the method for manufacturing spunbond nonwovens as described above. PP polymer was used as the core, while nylon 1 was used as the sheath, with different target core / sheath (c / s) ratios and fiber diameters. Table 1 shows the die flow rate and drafting pressure used during processing, as well as the resulting basis weight, pressure drop (ΔP), effective fiber diameter, and actual fiber diameter measured on the resulting nonwovens.

[0117] Table 1 Using SEM measurement Preparation Examples 8 to 10 (PE08 to PE10) Using the method for manufacturing spunbond nonwovens described above, only nylon is used to prepare the nonwoven medium containing monofilaments. Table 2 shows the die flow rate and drafting pressure used during processing, as well as the resulting basis weight, pressure drop (ΔP), effective fiber diameter, and actual fiber diameter measured on the resulting nonwovens.

[0118] Table 2 Measurement using an optical microscope Examples 1 to 3 (EX01 to EX03) Nonwoven media containing core-sheath fibers were derivatized according to the EB derivatization procedure. The aqueous reaction mixture contained 12 wt% NVP, 10 wt% MAPTAC, and varying amounts of GMA (0 to 4 wt%) in aqueous solution. The mass gain of the resulting derivatized samples was evaluated. Table 3 shows the fiber type, amount of GMA used, and mass gain. The samples were analyzed by SEM. Table 3 also shows the visual observations of the resulting functionalized materials in SEM images. Figures 6 to 8 The various morphologies observed using the functionalizations disclosed herein are shown.

[0119] Figure 4 and 5 These are scanning electron micrographs of PE01 and PE02, respectively. The SEM images show a circular core surrounded by a ring-shaped skin, where the relative areas of the core and skin reflect their weight ratio at the time of manufacture. Figure 6 This is a scanning electron micrograph of EX01, showing the skin bending into a single large protrusion. In the following text, fibers with this type of structure will be referred to as "fins". Figure 7This is a scanning electron micrograph of EX02, showing the skin bending into multiple smaller protrusions at several points. In the following text, fibers with this structure will be referred to as "youtiao" (fried dough sticks). Figure 8 This is a scanning electron micrograph of EX03, showing the unbent skin, but appearing magnified and detached from most of the core. In the following text, fibers with this type of structure will be referred to as "rings".

[0120] Table 3

[0121] Examples 4 to 7 (EX04 to EX07)

[0122] The nonwoven media containing core-sheath fibers were derivatized according to the EB derivatization procedure. The aqueous reaction mixture contained 12 wt% NVP and 10 wt% MAPTAC in aqueous solution, but no GMA. The resulting derivatized samples were subjected to mass gain assessment and analyzed by SEM. The observed structures are reported in Table 4.

[0123] Examples 3 and 8 to 10 (EX03 and EX08 to EX10)

[0124] The nonwoven media containing core-sheath fibers were derivatized according to the EB derivatization procedure. The aqueous reaction mixture contained 12 wt% NVP, 10 wt% MAPTAC, and 4 wt% GMA in aqueous solution. The resulting derivatized samples were subjected to mass gain assessment and analyzed by SEM. The observed structures are reported in Table 4.

[0125] Sample discs (3 to 7 replicates) were cut from the selected samples, and BSA binding was tested. The results are shown in Table 4 below.

[0126] Table 4

[0127] NR = Not reported

[0128] Examples 11 to 12 (EX11 to EX12)

[0129] Nonwoven media with similar AFD but different percentages of sheath-to-core ratio were derivatized according to the EB derivatization procedure. The aqueous reaction mixture contained an aqueous solution of 12% NVP and 10% MAPTAC.

[0130] Imaging of the samples revealed that the fibers primarily exhibited a fin-like morphology, along with some rings. Circular discs (3 to 7 replicates) were cut from the grafted sheet, and static BSA bonding was tested. The average results are shown in Table 5.

[0131] Table 5

[0132] Examples 13 to 22 (EX13 to EX22)

[0133] The core-shell PE03 was derivatized according to the EB derivatization procedure. As shown in Table 6 below, the aqueous reaction mixture contained aqueous solutions of different monomer types and amounts. The resulting derivatized samples were subjected to mass gain assessment and analyzed by SEM; the observed structures are reported in Table 6.

[0134] Table 6

[0135] Comparative Examples 1 to 3 (CE01 to CE03)

[0136] Various nonwoven media containing monofilaments were derivatized according to the EB derivatization procedure. The aqueous reaction mixture contained an aqueous solution of 12 wt% NVP and 10 wt% MAPTAC. The mass gain of the resulting derivatized samples was evaluated. Discs (3 to 7 replicates) were cut from the grafted sheet and static BSA binding was tested. The results are shown in Table 6.

[0137] Table 6

[0138] The comparative examples have fibers with smaller diameters (AFD between 7 and 9 micrometers). Generally, smaller diameter fibers are considered to provide improved analyte (i.e., BSA) binding due to their higher surface area. In this disclosure, when considering the same derivatization solution, the comparative examples generally show lower BSA binding amounts normalized to area and mass compared to core-sheath fibers with larger diameters (see EX05 to EX07 and EX11 to EX12, which have AFDs varying from 12.5 to 15.7 micrometers).

[0139] Without departing from the scope and spirit of the invention, foreseeable modifications and alterations to the invention will be apparent to those skilled in the art. The invention should not be limited to the embodiments set forth in this application for illustrative purposes. In the event of any conflict or difference between the disclosure in this written specification and any document incorporated herein by reference, the written specification shall prevail.

Claims

1. A chemically functionalized fiber, comprising A fiber, wherein the fiber comprises a core having a sheath thereon, wherein the sheath comprises nylon, and wherein the nylon is chemically functionalized by an aqueous reaction mixture comprising an aminoalkyl (meth)acryloyl monomer.

2. The chemically functionalized fiber according to claim 1, wherein the core is substantially covered by the sheath.

3. The chemically functionalized fiber according to any one of the preceding claims, wherein the nylon comprises nylon 6; nylon 6,6; nylon 1,6; nylon 11; nylon 12; nylon 4,6; nylon 4; nylon 1,4; nylon 510; nylon TMDT; or combinations thereof.

4. The chemically functionalized fiber according to any one of the preceding claims, wherein the core comprises a polyolefin.

5. The chemically functionalized fiber according to claim 4, wherein the polyolefin is selected from poly(propylene), poly(ethylene), or copolymers or mixtures thereof.

6. The chemically functionalized fiber according to any one of the preceding claims, wherein the chemically functionalized fiber comprises at least one protrusion, wherein each protrusion extends axially and protrudes radially along at least a portion of the length of the chemically functionalized fiber when viewed in cross-section.

7. The chemically functionalized fiber according to claim 6, wherein each of the protrusions has a length-to-thickness ratio of at least 1:1 and at most 10:

1.

8. The chemically functionalized fiber according to any one of the preceding claims, wherein the fiber is a melt-spun fiber.

9. The chemically functionalized fiber according to any one of the preceding claims, wherein the aminoalkyl (meth)acryloyl monomer is an amino (meth)acrylate or amino (meth)acrylamide of formula I or a quaternary ammonium salt thereof. (I) Where R 1 It is hydrogen or methyl, preferably methyl; L is -O- or -NH-; and Y is alkylene and R is... 2 For (i) independently hydrogen or alkyl or (ii) two R 2 The groups, together with the nitrogen atoms to which they are attached, can form aromatic, partially unsaturated, or saturated heterocyclic groups, and optionally, said heterocyclic groups are fused with an aromatic, partially unsaturated, or saturated second ring.

10. The chemically functionalized fiber according to any one of the preceding claims, wherein the aqueous reaction mixture further comprises a hydrophilic monomer.

11. The chemically functionalized fiber according to claim 10, wherein the hydrophilic monomer comprises at least one of the following monomers: 2-hydroxyethyl methacrylate (HEMA), 2-ethoxyethyl methacrylate (2-EOEMA), 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2,3-dihydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, N-vinylcaprolactam, N-vinylacetamide, N-vinylpyrrolidone, acrylonitrile, tetrahydrofurfuryl acrylate, acrylamide, mono- or di-N-alkyl substituted acrylamide, glyceryl methacrylate, and combinations thereof.

12. The chemically functionalized fiber according to any one of the preceding claims, wherein the aqueous reaction mixture further comprises a (meth)acryloyl epoxide monomer.

13. The chemically functionalized fiber according to claim 12, wherein the (meth)acryloyl epoxide monomer comprises at least one of the following: glycidyl methacrylate or glycidyl acrylate.

14. A nonwoven fabric comprising chemically functionalized fibers according to any one of the preceding claims.

15. A filter medium comprising chemically functionalized fibers according to any one of claims 1 to 13.

16. A method for manufacturing chemically functionalized fibers, the method comprising: (i) Providing a fiber, wherein the fiber comprises a core having a sheath thereon, wherein the sheath comprises nylon; as well as (ii) Contacting the fibers with an aqueous reaction mixture, the aqueous reaction mixture comprising: Aminoalkyl (meth)acryloyl monomers; Optionally, hydrophilic monomers; and Optionally, (meth)acryloyl epoxide monomer; and (iii) Expose the fiber to radiation.

17. The method of claim 16, wherein the skin has a thickness of at least 0.5 micrometers and at most 5 micrometers.

18. The method according to any one of claims 16 to 17, wherein the fiber has a diameter of at least 5 micrometers and at most 25 micrometers.

19. The method according to any one of claims 16 to 18, wherein the fiber has a basis weight of at least 50 g / m² and at most 250 g / m².

20. The method according to any one of claims 16 to 19, wherein the volume ratio of the core to the sheath of the fiber is at least 95:5 to at most 20:80.

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