A chemically-functionalized nylon fiber and methods of making and using the same

Abstract

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

Description

A CHEMICALLY-FUNCTIONALIZED NYLON FIBER AND METHODS OF MAKING AND USING THE SAME TECHNICAL FIELD

[0001] The present disclosure relates to functionalized sheath-core fibers, and methods for preparing the same. The present disclosure further relates to a filter using the functionalized fibers in a nonwoven format and a method of filtering a fluid. The functionalized fibers are useful in selectively filtering and removing biological materials, such as bio contaminates, from biological samples. SUMMARY

[0002] Nonwovens have been grafted or derivatized with functional groups to enable filtration of substances. See for example, U.S. Pat. No.9,815,050 (Yavorsky et al.) which teaches modification of nylon fibers with ion exchange functionality. However, there is a desire to improve the functionalization of substrates to achieve more efficient capture of targeted molecules.

[0003] In one aspect, a chemically-functionalized fiber comprising: a fiber wherein the fiber comprises a core having a sheath layer disposed thereon, wherein the sheath layer comprises nylon, and wherein the nylon is chemically-functionalized with 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] In another aspect, a non-woven is described comprising a chemically-functionalized fiber, wherein the chemically-functionalized fiber comprises: a fiber wherein the fiber comprises a core having a sheath layer disposed thereon, wherein the sheath layer comprises nylon, and wherein the nylon is chemically-functionalized with an aqueous reaction mixture comprising an aminoalkyl (meth)acryloyl monomer.

[0007] In yet another aspect, a filtration media is described comprising a chemically-functionalized fiber, which comprises: a fiber wherein the fiber comprises a core having a sheath layer disposed thereon, wherein the sheath layer comprises nylon, and wherein the nylon is chemically-functionalized with an aqueous reaction mixture comprising an aminoalkyl (meth)acryloyl monomer.

[0008] In still another aspect, a method of making a chemically-functionalized fiber is described, the method comprising: (i) providing a fiber wherein the fiber comprises a core having a sheath layer disposed thereon, wherein the sheath layer comprises nylon; and (ii)contacting the fiber with an aqueous reaction mixture comprising an aminoalkyl (meth)acryloyl monomer; and(iii) exposing the fiber and aqueous reaction mixture to radiation.

[0009] The above summary is not intended to describe each embodiment. The details of one or more embodiments of the invention are also set forth in the description below. Other features, objects, and advantages will be apparent from the description and from the claims. BRIEF DESCRIPTION OF FIGURES

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

[0011] Fig.1 is a schematic view of an exemplary sheath-core fiber.

[0012] Fig.2 is a schematic view of an exemplary chemically-functionalized fiber according to one embodiment of the present disclosure.

[0013] Fig.3 is a schematic view of an exemplary chemically-functionalized fiber according to one embodiment of the present disclosure.

[0014] Figs.4-5 are scanning electron microscopy images of sheath-core fibers.

[0015] Figs.6-8 are scanning electron microscopy images of chemically-functionalized fibers. DETAILED DESCRIPTION

[0016] As used herein, the term “a”, “an”, and “the” are used interchangeably and mean one or more; and “and / or” is used to indicate one or both stated cases may occur, for example A and / or B includes, (A and B) and (A or B); “(meth)acrylate” refers to compounds containing either an acrylate (CH2=CHCOOR) or a methacrylate (CH2=CCH3COOR) structure or combinations thereof; and “monomer” is a molecule which can undergo polymerization which then form part of the essential structure of a polymer. “Alkyl” means a linear or branched, cyclic or acyclic, saturated monovalent hydrocarbon having from one to about twelve carbon atoms, e.g., methyl, ethyl, 1-propyl, 2-propyl, pentyl, and the like. “Alkylene” means a linear saturated divalent hydrocarbon having from one to about twelve carbon atoms or a branched saturated divalent hydrocarbon having from three to about twelve carbon atoms, e.g., methylene, ethylene, propylene, 2-methylpropylene, pentylene, hexylene, and the like. “Aryl” means a monovalent aromatic, such as phenyl, naphthyl and the like.

[0017] Also herein, recitation of ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 10 includes 1.4, 1.9, 2.33, 5.75, 9.98, etc.).

[0018] Also herein, recitation of “at least one” includes all numbers of one and greater (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.).

[0019] As used herein, “comprises at least one of” A, B, and C refers to element A by itself, element B by itself, element C by itself, A and B, A and C, B and C, and a combination of all three.

[0020] In the present disclosure, it has been found that when chemically functionalizing a sheath-core fiber with an aqueous reaction mixture disclosed herein, chemically-functionalized fibers with unique morphologies, improved grafting amount, and / or improved capture of targeted molecules can be achieved. Such fibers may be used in a non-woven format, which in some embodiments, could be used as a filtration media.

[0021] The fibers of the present disclosure are sheath-core fibers and herein referred to also as simply “fiber” or “fibers”. Referring now to FIG.1, sheath-core fiber 10 comprises a core 12 having a sheath layer 14 disposed thereon. In some embodiments, as shown in Fig.1, sheath layer 14 is coextensive along the fiber length (fiber ends excluded). While the sheath-core fiber and the core shown in FIG.1 have circular cross-sections, other cross-sections may also be used such as, for example, triangular, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, star-shaped, oval, trilobal, and tetralobal. Likewise, while FIG.1 shows a centrally located core, the core may be located off-center.

[0022] In some embodiments, the sheath-core fibers are so called “islands-in-the-sea” extrudates, wherein multiple fiber cores (i.e., more than 1, 2, 4, or even 6 cores) are distributed within a polymer matrix, which also forms the sheath.

[0023] The core of the fiber comprises a thermoplastic resin such as a polyolefin. Exemplary polyolefin include: poly(ethylene), poly(propylene), poly(1-butene), copolymers of ethylene and propylene, alpha 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.

[0024] The core may 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.

[0025] In the present disclosure, the core is encapsulated by a sheath layer. The sheath layer comprises a 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.

[0026] The sheath layer forms the outer surface of the fiber core, exclusive of the ends of the fiber core which may or may not be coated with the sheath layer. In some embodiments, the core is substantially enclosed by the sheath, in other words, there does not appear to be any areas where the entire circumference of the core is not covered by a sheath, in some embodiments there does not appear to be any portion of the core not covered by a sheath. While not a requirement, the sheath layer is preferably substantially uniform and complete. In one embodiment, the sheath layer may be thin for example having a thickness of at least 0.5, 0.6, 0.7, 0.8, 0.9, or even 1 micron; and 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 microns in average thickness. In one embodiment, the volume ratio of the core to sheath is at least 95:5, 80:20, 75:25, 70:30, or even 60:40. In one embodiment, the volume ratio of the core to sheath is at most 20:80, 30:70, 40:60, or even 50:50. In one embodiment, the weight percent ofthe sheath layer in the sheath-core fiber is at least 5, 8, 10, 15, or even 25 wt%. In one embodiment, the weight percent of the sheath layer in the sheath-core fiber is at most 30, 40, 50, 60, or even 70 wt%.

[0027] The fibers used in practice of the present disclosure may have any average fiber diameter, and may be continuous, random, and / or staple fibers. For example, in some embodiments, the fibers (i.e., individual 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.

[0028] The diameter of the core and / or fiber may be measured using techniques known in the art. In some embodiments, the diameter of the fiber can be determined by microscopy (e.g., optical or scanning electron microscopy), wherein the fiber is cross-sectioned and viewed under magnification to determine the diameter of the fiber, diameter of the core, and / or thickness of the sheath. In some embodiments, the diameter of the fiber can be calculated by measuring the pressure drop across a fiber web. The effective fiber diameter (EFD) can be calculated as described in the Example Section below. In practice, the sheath thickness may show some experimental variation as a result of routine experimental variation and the averaging nature of EFD.

[0029] Methods for making sheath-core fibers are well known and need not be described here in detail. In one embodiment, the sheath-core fibers are made by co-extrusion. For example, at least two polymers are extruded separately and fed to a polymer distribution system where the polymers are introduced into a segmented spinneret plate. The polymers follow separate paths and are combined in a spinneret hole thus providing a sheath-core type fiber. See, for example, U. S. Pat. 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, the sheath layer is deposited onto the core fiber, using deposition and coating techniques known in the art. For example, vapor deposition can be used to encase a fiber core with the sheath material above the melting temperature of the resin. Such a technique may be more useful with neat polymer resin sheaths. See for example, U.S. Pat. No.10,213,716 (Kitagawa et al.) are incorporated herein by reference.

[0030] Coating techniques, such as spray coating, dip coating, etc., can be used to coat fiber cores with the sheath composition enabling very thin sheaths. See for example, WO Publ. No.201688692 (Kitagawa).

[0031] Fibers described herein can generally be made using techniques known in the art for making filaments. Particularly advantageous to form sheath-core fibers is melt spinning. In melt spinning, a polymer is heated, passed through a spinneret, and fibers solidify upon cooling. For example, a melt spinning process can occur to collect the multicomponent fibers. The term "meltspun" as used herein refers to fibers that are formed by extruding molten fibers out of a set of orifices and allowing the fibers to cool and (at least partially) solidify to form fibers, with the fibers passing through an air space (which may contain streams of moving air) to assist in cooling and solidifying the fibers, and with the thus- formed fibers then passing through an attenuation (i.e., drawing) unit to draw the fibers.

[0032] In some embodiments, a sheath-core fibers are in a non-woven format. As used herein, the term “nonwoven” refers to a fabric that has a structure of individual fibers, which are randomly and / or unidirectionally interlaid in a mat-like fashion. The nonwoven substrate may be manufactured by any of the commonly known processes for producing nonwoven webs. Often, the non-woven is made via a spun bound fiber process.

[0033] Spunbonded nonwoven fibrous webs can be formed according to well-known conventional methods wherein meltspun fibers are deposited on a moving belt where they form a nonwoven continuous fiber web having interfiber bonds.

[0034] In some embodiments, a nonwoven web can be made by air-laying of fibers (e.g., sheath-core fibers and optional secondary fibers). Air-laid nonwoven fibrous webs may be prepared using equipment such as, for example, that available as a RANDO WEBBER from Rando Machine Company of Macedon, New York. In some embodiments, a type of air-laying may be used that is termed gravity-laying, as described, e.g., in U. S. Pat. Publ. No.2011 / 0247839 (Lalouch et al.) the disclosure of which is incorporated by reference herein. Nonwoven fibrous webs may be densified and strengthened, for example, by techniques such as crosslapping, stitchbonding, needletacking, hydroentangling, chemical bonding, and / or thermal bonding.

[0035] Nonwoven fibrous webs according to the present disclosure may have any basis weight, thickness, porosity, and / or density unless otherwise specified. In one embodiment, the sheath-core fibers have a basis weight of at least 50, 60, 80, or even 100 grams per square meter; and at most 150, 200, 225, 250, or even 275 grams per square meter.

[0036] In the present disclosure, sheath-core fibers such as described above, are contacted with an aqueous reaction mixture and subjected to radiation to react the monomers to the fiber.

[0037] In the present disclosure, the sheath-core fiber is exposed to an aqueous mixture of monomers, which are then reacted together to functionalize the fibers with amine groups, which can include quaternary ammonium groups.

[0038] The aqueous reaction mixture comprises an aminoalkyl (meth)acryloyl monomer; optionally, a hydrophilic monomer, and optionally, a (meth)acryloyl epoxide monomer.

[0039] The aminoalkyl (meth)acryloyl monomers are amino (meth)acrylates or amino (meth)acrylamides of Formula I or quaternary ammonium salts thereof I In Formula I, R1is hydrogen or methyl, preferably methyl; L is —O— or —NH—; and Y is an alkylene (e.g., an alkylene having 1 to 10 carbon atoms, 1 to 6, or 1 to 4 carbon atoms). Each R2is independently hydrogen or alkyl, preferably C1-C4 alkyl. Alternatively, the two R2groups taken together with the nitrogen atom to which they are attached can form a heterocyclic group that is aromatic, partiallyunsaturated (i.e., unsaturated, but not aromatic), or saturated, wherein the heterocyclic group can optionally be fused to a second ring that is aromatic (e.g., benzene), partially unsaturated (e.g., cyclohexene), or saturated (e.g., cyclohexane). The counter ions of the quaternary ammonium salts are often halides, sulfates, phosphates, nitrates, and the like. Such grafting monomers may be quaternary ammonium monomers, i.e., having a -N(R2)3+X−group, wherein each R2is as defined, and X−is the counter anion. Such monomers having a quaternary ammonium group may be directly reacted to the fiber or an aminoalkyl (meth)acryloyl monomer, having a primary, secondary or tertiary amine group, may be reacted to the fiber and subsequently converted to a quaternary ammonium group by alkylation.

[0040] In some embodiments of Formula I, both R2groups are hydrogen. In other embodiments, one R2group is hydrogen and the other is an alkyl having 1 to 10, 1 to 6, or 1 to 4 carbon atoms. In yet other embodiments, the R2groups combine with the nitrogen atom to which they are attached to form a heterocyclic group. The heterocyclic group includes at least one nitrogen atom and can contain other heteroatoms such as oxygen or sulfur. Exemplary heterocyclic groups include, but are not limited to imidazolyl. The heterocyclic group can be fused to an additional ring such as a benzene, cyclohexene, or cyclohexane. Exemplary heterocyclic groups fused to an additional ring include, but are not limited to, benzoimidazolyl.

[0041] In one embodiment, the aminoalkyl (meth)acryloyl monomers of formula (I) is a quaternary ammonium salt as in Formula II: II where 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, or 2 to 4 carbon atoms). R2, R3, and R4, are independently aryl or alkyl, preferably C1-C4 alkyl; and X- is the counter anion.

[0042] Exemplary quaternary salts of the aminoalkyl (meth)acryloyl monomers include, but are not limited to, (meth)acrylamidoalkyltrimethylammonium salts (e.g., 3- methacrylamidopropyltrimethylammonium chloride and 3-acrylamidopropyltrimethylammonium chloride) and (meth)acryloxyalkyltrimethylammonium salts (e.g., 2-acryloxyethyltrimethylammonium chloride, 2-methacryloxyethyltrimethylammonium chloride, 3-methacryloxy-2- hydroxypropyltrimethylammonium chloride, 3-acryloxy-2-hydroxypropyltrimethylammonium chloride, and 2-acryloxyethyltrimethylammonium methyl sulfate).

[0043] In some embodiments, the aqueous reaction mixture comprises at least 10, 20, 25, 30, 40, or even 50 % by weight of an aminoalkyl (meth)acryloyl monomer versus the total monomers. In some embodiments, the aqueous reaction mixture comprises at most 55, 60, 70, 80, 90, 95, 98, 99, or even 100% by weight of an aminoalkyl (meth)acryloyl monomer versus the total monomers.

[0044] In some embodiments, the aqueous solution also includes a hydrophilic monomer, which is an ethylenically-unsaturated compound that has hydrophilic character. As used herein “hydrophilic monomers” are those polymerizable monomers having a water miscibility (water in monomer) of at least 1 wt. %, preferably at least 5 weight % without reaching a cloud point, are exclusive of poly(alkylene oxide) monomers and contain no acidic functional groups or groups that would retard the functionalizing polymerization.

[0045] Examples of suitable hydrophilic monomers include 2-hydroxyethyl(meth)acrylate (HEMA), 2- ethoxyethyl methacrylate (2-EOEMA), 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate, N-vinyl caprolactam, N-vinyl acetamide, N-vinyl pyrrolidone, acrylonitrile, tetrahydrofurfuryl acrylate, acrylamide, mono- or di-N- alkyl substituted acrylamide, glycerol methacrylate, and combinations thereof. Preferred polar monomers include 2-hydroxyethyl(meth)acrylate (HEMA), N-vinyl pyrrolidone, N-vinyl acetamide, methylacrylamide, and mixtures thereof.

[0046] In some embodiments, the aqueous reaction mixture comprises at least 0.5, 1, 2, 10, 20, 25, 30, 40, or even 50 % by weight of a hydrophilic monomer versus the total monomers. In some embodiments, the aqueous reaction mixture comprises at most 55, 60, 70, 80, 90, or even 95 % by weight of a hydrophilic monomer versus the total monomers.

[0047] In some embodiments, the aqueous reaction mixture includes a (meth)acryloyl epoxide monomer, in other words a (meth)acrylate monomer with an epoxide substituent. Exemplary (meth)acryloyl epoxide monomers include: glycidyl methacrylate and glycidyl acrylate.

[0048] In some embodiments, the aqueous reaction mixture comprises at least 0.1, 0.5, 1, 1.5, 2, or even 2.5 % by weight of a (meth)acryloyl epoxide monomer versus the total monomers. In some embodiments, the aqueous reaction mixture comprises at most 20, 15, 10, 5, or even 3 % by weight of a (meth)acryloyl epoxide monomer versus the total monomers.

[0049] In some embodiments, the aqueous reaction mixture comprises a monofunctional ethylenically- unsaturated monomer having a poly(alkylene oxide) group. Such poly(alkylene oxide) monomer may be of the Formula: Z-Q-(CH(R5)—CH2-Q)m-R6, III wherein Z is a polymerizable ethylenically unsaturated moiety, R5is a H or a C1 to C4 alkyl group, R6is a H, a C1 to C4 alkyl group, aryl group, or combinations thereof and m is from 2 to 100, preferably 5 to 20, and Q is a divalent linking group selected from —O—, —NR1—, —CO2— and —CONR1.

[0050] In one embodiment, the poly(alkylene oxide) group is a poly(ethylene oxide) (co)polymer. In another embodiment, the pendent poly(alkylene oxide) group is a poly(ethylene oxide-co-propylene oxide) copolymer. Such copolymers may be block copolymers, random copolymers, or gradient copolymers.

[0051] Useful ethylenically unsaturated moiety, Z, of the monomer may include:wherein R3is H or -CH3 and r=1-10.

[0052] The monomer having a poly(alkylene oxide) group can be prepared, for example, by reacting mono- or di-functional alkylene oxide (co)polymers (which are typically commercially available) with reactive ethylenically unsaturated compounds (e.g., acrylates). The functional groups terminating the poly(alkylene oxide) may include hydroxy groups, amine groups and carboxy groups. A variety of reactive ethylenically unsaturated compounds such as acrylate derivatives can be used including, but not limited to, (meth)acrylic acid, (meth)acryloyl chloride, (meth)acrylic anhydride, and 2-isocyanatoethyl (meth)acrylate. Preferably, the monomer is prepared by reacting the mono- or di-functional alkylene oxide (co)polymer with (meth)acrylic anhydride. Typically, if a stoichiometric amount of the ethylenically unsaturated reactant is combined with the monofunctional alkylene oxide (co)polymer (such as a monohydroxy terminated alkylene oxide (co)polymer), 100% conversion to the monosubstituted product is obtained.

[0053] Examples of suitable monofunctional poly(alkylene oxide) 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 one nonreactive end group such as (C1-C4)alkoxy, aryloxy (e.g., phenoxy), and (C1-C4)alkaryloxy. These groups can be linear or branched. These monomers can be of a wide range of molecular weights and are commercially available from sources such as Sartomer Company, Exton, Pa.; Shinnakamura Chemical Co., Ltd., Tokyo, Japan; Aldrich, Milwaukee, Wis.; and Osaka Organic Chemical Ind., Ltd., Osaka, Japan.

[0054] In some embodiments, the aqueous reaction mixture is substantially free of these monomers comprising poly(alkylene oxide) groups. As used herein, substantially free means less than 10, 8, 5, 2, 1, 0.5, or even 0.1 weight % or even none versus the total weight of the monomers.

[0055] The reaction mixture is aqueous meaning that the mixture comprises water and / or water miscible organic solvents. In some embodiments, the water miscible solvents are protic group-containing organic liquids such as the lower alcohols having 1 to 4 carbon atoms, lower glycols having 2 to 6 carbon atoms, and most preferably lower glycol ethers having 3 to 6 carbon atoms and 1 to 2 ether linkages. In some embodiments higher glycols such as poly(ethylene glycol) may be used. Any such water miscible organic solvent preferably has no tertiary hydrogen atoms, or other groups that would retard the polymerization of the monomers and their reaction with the fiber. Exemplary water miscible solvents include: methanol,ethanol, n-butanol, t-butyl alcohol, ethylene glycol, methoxyethanol, ethoxyethanol, propoxyethanol, butoxyethanol, methyl carbitol, ethyl carbitol, and mixtures thereof. In some embodiments, non-protic water miscible organic solvents that can also be used 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.

[0056] The ratio of water to organic solvent can vary, but is typically greater than 1:1 (v / v) water to organic solvent, preferably greater than 5:1, and more preferably greater than 7:1.

[0057] Typically, the total concentration of the monomers in the aqueous reaction mixture ranges from at least 1, 2, 5, or even 10 wt % and at most 50, 45, 40, 30, 25, 20, or even 15 wt % based on a total weight of the aqueous reaction mixture.

[0058] In some embodiments, the amount of 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 grams per square meter (gsm) of sheath-core fiber substrate.

[0059] Irradiation is used to initiate the polymerization of the monomer reaction mixture and its reaction with the nylon-containing sheath.

[0060] The irradiation step comprises the ionizing irradiation of sheath-core fibers, preferably with ionizing e-beam or gamma radiation to prepare free radical reaction sites with which the sheath-core fibers are subsequently derivatized with the aqueous reaction mixture. “Ionizing irradiation” means radiation of a sufficient dosage and energy to cause the formation of free radical reaction sites the base substrate. Ionizing radiation may include gamma, electron-beam, x-ray and other forms of electromagnetic radiation. In some instances, corona radiation can be sufficiently high energy radiation. The radiation is sufficiently high energy, that when absorbed by the sheath-core fiber, sufficient energy is transferred to that sheath-core fiber to result in the cleavage of chemical bonds in that fiber and the resultant formation of free radical sites on the sheath-core fiber.

[0061] In the irradiation step, the sheath-core fiber is exposed to a sufficient quantity of ionizing radiation, so as to form free radicals in the sheath-core fiber. The chamber may contain at least one device capable of providing a sufficient dose of radiation. A single device is capable of providing 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 sheath-core fiber comprises an inert atmosphere such as nitrogen, carbon dioxide, helium, argon, etc. with a minimal amount of oxygen, which is known to inhibit free- radical polymerization.

[0062] Dose is the total amount of energy absorbed per mass unit. Dose is commonly expressed in kiloGrays (kGy). A Gray is defined as the amount of radiation required to supply 1 joule of energy per kilogram of mass. The total dose received by the sheath-core fiber depends on a number of parameters including source activity, residence time (i.e., the total time the sample is irradiated), the distance fromthe source, and attenuation by the intervening cross-section of materials between the source and sample. Dose is typically regulated by controlling residence time, distance to the source, or both.

[0063] Total dose requirement for any given composition will vary as a function of desired monomer selected, sheath-core fiber used, and the dose rate. In one embodiment, the doses ranged of about 20 to 40 kGy. Thus, a dose rate can be selected based on desired properties for a specified composition. The dose rate is typically in the range of 0.0005 kGy / sec (gamma) to 200 kGy / sec (E-beam).

[0064] Electron beam is one preferred method due to the ready-availability of commercial sources. Electron beam generators are commercially available from a variety of sources, including the ESI “ELECTROCURE” EB SYSTEM from Energy Sciences, Inc. (Wilmington, Mass.), and the BROADBEAM EB PROCESSOR from PCT Engineered Systems, LLC (Davenport, Iowa). For any given piece of equipment and irradiation sample location, the dosage delivered can be measured in accordance with ASTM E-1275 entitled “Practice for Use of a Radiochromic Film Dosimetry System.” By altering extractor grid voltage, beam diameter and / or distance to the source, various dose rates can be obtained.

[0065] Other sources of irradiation may be used with equal derivatizing performance, a desirable source of ionizing radiation comprises an electron beam source because the electron beam can produce high and fast dose delivery rates. Electron beams (e-beams) are generally produced by applying high voltage to tungsten wire filaments retained between a repeller plate and an extractor grid within a vacuum chamber maintained at about 10−6Torr. The filaments are heated at high current to produce electrons. The electrons are guided and accelerated by the repeller plate and extractor grid towards a thin window of metal foil. The accelerated electrons, traveling at speeds in excess of 107meters / second (m / sec) and possessing about 100 to 300 kilo-electron volts (keV), pass out of the vacuum chamber through the foil window and penetrate whatever material is positioned immediately beyond the foil window.

[0066] The quantity of electrons generated is directly related to the current. As extractor grid voltage is increased, the acceleration or speed of electrons drawn from the tungsten wire filaments increase. E-beam processing can be extremely precise when under computer control, such that an exact dose and dose rate of electrons can be directed against the sheath-core fiber.

[0067] The temperature within the chamber is desirably maintained at an ambient temperature by conventional means. Without intending to be limited to any particular mechanism, it is believed that the exposure of the sheath-core fiber to an electron beam results in free radical sites in the substrate which can then subsequently react with the monomers in the aqueous reaction mixture.

[0068] The total dose received by substrate primarily affects the number of radical sites formed and subsequently the extent to which the monomers are reacted with the fiber. Dose is dependent upon a number of processing parameters, including voltage, web- or line-speed and beam current. Dose can be conveniently regulated by controlling line speed (i.e., the speed with which the nonwoven substrate passes under the irradiation device), and the current supplied to the extractor grid. A target dose (e.g., <10kGy) can be conveniently calculated by multiplying an experimentally measured coefficient (a machine constant) by the beam current and dividing by the web speed to determine the exposure. The machine constant varies as a function of beam voltage.

[0069] While the controlled amount of electron beam radiation exposure is dependent upon the residence time, the sheath-core fiber is subjected to a controlled amount of dosage ranging from a minimum dosage of about 1 kilogray (kGy) to a practical maximum dosage of less than about 200 kGy, depending on the particular polymer. For less radiation sensitive polymers such as nylons, higher dosages, typically 10 to 70 kGy, may be used. Generally, suitable gamma ray sources emit gamma rays having energies of 400 keV or greater. Typically, suitable gamma ray sources emit gamma rays having energies in the range of 500 keV to 5 MeV. Examples of suitable gamma ray sources include cobalt-60 isotope (which emits photons with energies of approximately 1.17 and 1.33 MeV in nearly equal proportions) and cesium-137 isotope (which emits photons with energies of approximately 0.662 MeV). The distance from the source can be fixed or made variable by changing the position of the target or the source. The flux of gamma rays emitted from the source generally decays with the square of the distance from the source and duration of time as governed by the half-life of the isotope.

[0070] In the instant method, the irradiated fiber, having free radical sites in the fiber, are contacted with the aqueous reaction mixture subsequent to and not concurrent with, the irradiation step. The free radical sites generated in the sheath-core fiber have average lifetimes ranging from several minutes to several hours and progressively decay to a low concentration within about ten hours at room temperature. Lower temperatures, such as dry ice temperatures, promotes longer radical lifetimes. Alternatively, humidification and nitrous oxide can increase the rate of substrate radical formation via generation of hydroxyl radicals.

[0071] Generally, the irradiated fiber is contacted with the aqueous reaction mixture immediately after the irradiation step. Generally, when using E-beam the irradiated fiber is imbibed within an hour, preferably within ten minutes.

[0072] The fiber can be contacted with the aqueous reaction mixture using techniques known in the art including, but are not limited to, a spray coating, flood coating, knife coating, Meyer bar coating, dip coating, and gravure coating.

[0073] The aqueous reaction mixture remains in contact with the fiber for a time sufficient for the radical sites to initiate polymerization with the monomers. When contacted with a solution of monomers, reactions are mostly completed after 12 hours exposure; generally about 90+ percent. As a result, the fiber comprises polymers and / or copolymers attached to the interstitial, the outer surfaces, and within the fiber.

[0074] Generally, the total monomer content functionalized onto the fiber may be from 0.5 to 5 times the weight of the fiber.

[0075] Once the fiber has been contacted with the aqueous reaction mixture for a desired period of time, the fiber functionalized with the polymer groups may be optionally rinsed to remove residual monomer and / or dried.

[0076] In the optional rinsing step, the chemically-functionalized fiber is washed or rinsed one or more times to remove any unreacted monomers, solvent or other reaction by-products. Typically, the functionalized fiber is washed or rinsed up to three times using a water rinse, an alcohol rinse, a combination of water and alcohol rinses, and / or a solvent rinse (e.g., acetone, methyl ethyl ketone, etc.). When an alcohol rinse is used, the rinse may include one or more alcohols including, but not limited to, isopropanol, methanol, ethanol, or any other alcohol that is practical to use and an effective solvent for any residual monomer. In each rinse step, the functionalized fiber may pass through a rinse bath or a rinse spray. In some embodiments, the rinse may comprise an ionic buffer solution that would reduce swelling of the resulting polymer, the amount of retained water, and also avoiding weakening the chemically- functionalized fiber during this rinse step.

[0077] In the optional drying step, the functionalized fiber is dried to remove any rinse solution. Typically, the functionalized fiber is dried in oven having a relatively low oven temperature for a desired period of time (referred to herein as “oven dwell time”). Oven temperatures typically range from about 60°C to about 120°C, while oven dwell times typically range from about 8 to about 72 hours. Any conventional oven may be used in the optional drying step. It should also be noted that in other embodiments the drying step can proceed before the rinsing step to eliminate volatile components before extraction of non-grafted residue. Following the optional drying step, the dried functionalized fiber can be taken up in roll form to be stored for future use.

[0078] When the sheath-core fibers are functionalized with the aqueous reaction mixture disclosed here, in some instances unique morphologies appear. For example a sheath-core fiber, wherein the sheath is uniform and coextensive along the axial length of the fiber (as shown for example in Fig.1) may, upon functionalization, generate protuberances such as shown in Fig.2, where functionalized fiber 20 comprises sheath 24 encasing core 22, wherein perturbance 26 appears on the exterior of the fiber, extending axially from the fiber and protruding radially along at least a portion of the length of the fiber. In some embodiments, the chemically-functionalized fiber comprises at least one protuberance, however the fiber may comprise more perturbances such 2, 3, 4, 5, 6, 8, 10 or more. In another embodiment, a functionalized sheath—core fiber is shown in Fig.3 comprising sheath 34 encasing core 32 and protuberance 36 extending axially from the fiber. Although Figs.2 and 3 show the sheath directly contacting and encasing the core, in some embodiments, the sheath is not in direct contact with the core across the entire cross section of the fiber as shown in some of the examples.

[0079] The aspect ratio of the protuberances can be determined, by measuring the length of the protuberance versus the thickness of the protuberance, shown as “l” and “t”, respectively, in Fig.2. Generally, the aspect ratio is an average taken from measuring various protuberances along multiplefibers. The aspect ratio can vary, especially if the chemically-functionalized fibers show a “fin”-type protuberance versus a “churro”-type morphology. Typically, where fin-type have a larger aspect ratio versus churro-type. In some embodiments, the protuberance has an aspect ratio of length versus thickness 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.

[0080] Although not wanting to be limited by theory it is believed that since nylon is a hydrophilic substrate, the aqueous reaction mixture is able to imbibe at least a portion of the nylon-containing sheath, causing it to swell and / or the monomer reacts into the bulk of the sheath increasing the functionalized area.

[0081] In some embodiments, the chemically-functionalized fibers as disclosed herein gain in mass by at least 20, 30, 50, 75, 100, 150, 200, or even 225 %.

[0082] Due to the increase efficiency of derivatization, in some embodiments, the chemically- functionalized fibers as disclosed herein, have an improved ability to capture analytes of interest. For example, when normalized for surface area and total weight of derivatized fiber, the chemically- functionalized fibers of the present disclosure can bind at least 30, 40, 50, 60, 70, 80, 90 or even 100 mg of analyte (for example BSA) per cm2of area per gram of the total weight of the derivatized fiber.

[0083] In some embodiments, the functionalized fibers disclosed herein may be used for example, in filtration applications, such as filtering large molecules from fluids. For example, purification or isolation of biological materials. EXAMPLES

[0084] Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Missouri, or may be synthesized by conventional methods.

[0085] These abbreviations are used in the following examples: cm = centimeter, g = grams, gsm = grams per square meter, ghm = gram per hole per minute, hr = hour,oC = degrees Celsius, in = inch, kV = kiloVolt, lpm = liters per minute, mA = milliamp, mg = milligram, MRad = megaradian, min = minute, m = meter, mm = millimeter, mM = millimolar, mL = milliliter, nm = nanometer, Pa = Pascal, psi = pounds per square inch, ppm = parts per million, oz = ounce, and sec = second. Materials Name Description MAPTAC [3- (methacryloylamino)propyl] trimethylammonium chloride monomer obtained under the trade designation “Visiomer-MAPTAC ” from Evonik, Essen, DE. NVP N-vinylpyrrolidone monomer obtained under the trade designation “V3409”from Sigma-Aldrich Co. GMA Glycidyl methacrylate monomer obtained under the trade designation “141238” from Sigma-Aldrich Co. MAETAC [2-(Methacryloyloxy)ethyl]trimethylammonium chloride monomer at 80% in water obtained under the trade designation “408107” from Sigma-Aldrich Co. AETAC [2-(Acryloyloxy)ethyl]trimethylammonium chloride monomer at 80% in water obtained under the trade designation “496146” from Sigma-Aldrich Co. VBTAC (Vinylbenzyl)trimethylammonium chloride monomer obtained under the trade designation “458694” from Sigma-Aldrich Co. BSA Lyophilized powder of bovine serum albumin protein obtained under the trade designation “A2153” from Sigma-Aldrich Co. PP Polypropylene isotactic homopolymer resin obtained under the trade designation “M3766” from Total Petrochemicals & Refining, USA, Inc., Houston, TX. Nylon 1 Nylon 6 obtained under the trade designation “Ultramid B24 N 02” from BASF, Ludwigshafen, Germany. Nylon 2 Nylon 6 obtained under the trade designation “Ultramid B27 E” from BASF.

[0086] Method of Making a Spunbound Nonwoven Comprising Fibers

[0087] Nonwoven media substrate were produced on a spunbond 0.5 m lab line having 2 in (5.1 cm) and 2.5 in (6.35 cm) single screw extruders, each with planetary melt pumps to meter polymer flow to a spin pack assembly. Both monofilament and sheath-core fibers were produced similarly, differing only in the spin pack assembly. The monofilament process was similar to that described in U.S. Pat. No.6,916,752 (Berrigan et al.). The sheath-core process is similar to that described in Example 4 of U.S. Pat. No. 10,098,980 (Karls et al.). In either monofilament or sheath-core fiber production, polymer melt(s) entered the pack and were distributed evenly and filtered before reaching the spinneret orifices where the filaments were extruded. In making the sheath-core, the melts were brought together to form a sheath / core structure in a combination plate directly behind the spinneret orifices.

[0088] Filaments (or fibers) were formed as the polymer exited the spinneret at the bottom of the pack and were drawn vertically through a quench zone fed with chilled air into an attenuator supplied with compressed air. The filaments were then laid down on a moving collector belt forming a nonwoven web and held in place by vacuum until passing through a bonding zone where the nonwoven web was taken up on a surface winder.

[0089] Pressure Drop Test

[0090] A high-speed automated filter tester (8130 from TSI Inc., Shoreview, MN) was operated with particle generation and measurement turned off. Flowrate was adjusted to 85 lpm and a 5.25 in (13.34 cm) diameter sample was used. The sample was placed onto the lower circular plenum opening and thetester was engaged. A pressure transducer (MKS Instruments, Inc., Andover, MA) within the device measured the pressure drop (delta P) in mm water.

[0091] Method of Measuring Effective Fiber Diameter (EFD)

[0092] The EFD was calculated from a pressure drop (measured using the “Pressure Drop Test” described herein), a 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 testing gauge having a tester foot with dimensions of 5 cm x 12.5 cm at an applied pressure of 150 Pa. Based on the measured pressure drop, the Effective Fiber Diameter in microns was calculated as set forth in C.N. Davies, The Separation of Airborne Dust and Particulates, Institution of Mechanical Engineers, London Proceedings, IB (1952).

[0093] Scanning Electron Microscopy (SEM)

[0094] Fiber dimensions and cross sections were examined using a scanning electron microscope (Hitachi TM4000Plus from NCI Inc., Brooklyn Park, MN). Cross sections were prepared by freeze fracturing samples with liquid nitrogen. A thin layer of gold was sputter coated on the samples to make them conductive.

[0095] Actual Fiber Diameter (or AFD) for Sheath-Core Fiber

[0096] The AFD for the sheath-core filament in the nonwoven was determined from SEM of the nonwoven surface and using the measurement function provided by the SEM instrument software to measure the diameter of more than 50 individual fibers.

[0097] AFD for Monofilaments

[0098] An optical microscope (ECLIPSE E600POL from Nikon, Tokyo, Japan) with a digital camera (DMC5400 from Leica Microsystems, Bloomington, MN) was used for optically imaging the fibers in the nonwoven made with the monofilament. For conditions of interest, a fiber bundle was collected below the attenuator, a cross section prepared, and a multi-focus image was obtained with the optical microscope at 50 or 100x magnification (exact magnification was chosen as needed to obtain approximately 30 measurements from a single image). Fibers were then measured manually where edge detection was assisted by the associated Leica Application Suite X v3.0.9.19082 software (from Leica Microsystems, Bloomington, MN).

[0099] Electron Beam (EB) Derivatization Procedure

[0100] Fibers were derivatized as follows: Aqueous reaction mixtures (as described in the examples) were prepared in 4 oz (118 mL) tight-capped jars to a total volume of 60-100 mL. After the mixture was made, the jars were shaken by hand and sparged with house nitrogen. The jars were then transferred to the nitrogen-containing glove box and uncapped until the glove box oxygen monitor read < 20 ppm.

[0101] The nonwoven samples were prepared as 7 in x 9 in (17.8 cm x 22.9 cm) pieces and placed individually into 8 in x 10 in (20 cm x 25 cm) seal-top plastic bags. The sample-containing bags were opened inside a glove box with nitrogen for inerting until the glove box oxygen monitor read < 20ppm. The bags were then opened, removed from the glovebox and taped onto a PET carrier web being conveyed at 35 feet per minute (fpm) through an ElectroCure electron beam (Energy Sciences, Inc., Wilmington, MA). Samples were irradiated at 300 kV to a specified dose, typically 10 MRad. The resultant beam current was 55 mA.

[0102] After irradiation, the samples were removed and transferred back to the glove box. The oxygen monitor was allowed to reach < 20 ppm before the bags were opened. To deposit monomer and begin polymerization, the jar of aqueous reaction mixture was shaken by hand and then poured onto the nonwoven within the bag. To encourage wetting throughout the sample, a hand roller was rolled over the sealed bag containing nonwoven and aqueous reaction mixture. After 3 hr reaction, samples were taken from the glove box, exposed to atmosphere and placed into boiling deionized water for 1 hr to further saturate the reaction and remove residual monomer. After this, the derivatized nonwovens were dried on polyethylene-lined aluminum trays in an ambient environment overnight and then further dried in a 70°C oven for 12-16 hr before subsequent characterization and performance testing.

[0103] Basis Weight

[0104] A known sample size (for examples a 5.25 in disk) was cut from the sample and weighed to provide the basis weight in grams per square meter (gsm).

[0105] Evaluation of Mass Gain

[0106] The amount of monomer polymerized onto the fibers was determined by gravimetric analysis using the following equation: % ^^^^^^^^ ^^^^^^^^ = [^^^^^^^^^^ ^^^^^^ ^^^^^^^^ − ^^^^^^^^^^^^^^ ^^^^^^ ^^^^^^^^] / ^^^^^^^^^^^^^^ ^^^^^^ ^^^^^^^^ x 100

[0107] Static BSA Binding

[0108] Each disc sample (16 mm) was tumbled for 18 to 24 hr in 4.5 mL of 4-6 mg / mL BSA in a buffer solution (25mM Tris HCl, 50 mM NaCl, pH 8). The samples were then washed 3 times by tumbling for 30 min in fresh buffer solution to remove unbound BSA. Then, the bound BSA was eluted into 3mL high salt buffer (25mM Tris-HCl, 1M NaCl, pH 8) and tumbled for 30 min. The amount of eluted BSA was measured via a UV / Vis spectrophotometer (Thermo Scientific NanoDrop, ThermoFisher, Waltham, MA) using the solution absorption at wavelength 280 nm. The amount of bound BSA is reported after normalization by the disc area (mg / cm2) and also after normalization by disc area and grafted disc weight (mg / cm2 / g).

[0109] Preparatory Examples 1-7 (PE01-PE07)

[0110] Nonwoven media comprising sheath-core fibers with 20-70 wt% nylon sheath content were prepared using the Method of Making Spunbound Nonwoven as described above. PP polymer was used as the core while Nylon 1 was used as the sheath with varying targeted core / sheath (c / s) ratios and fiber diameters. Shown in Table 1 are the die flow rates and attenuation pressure used during processingand the resulting basis weight, pressure drop (delta P), effective fiber diameter and actual fiber diameter as measured on the resulting nonwovens. Table 1 Die Atten. Basis Average C / S Flow Delta P EFD Sample Press. weight AFD* Ratio Rate (mm water) (µm) (psi) (gsm) (µm) (ghm) PE01 80 / 20 0.25 11 102 3.1 15.0 12.5 PE02 30 / 70 0.15 8 123 2.5 15.8 12.0 PE03 80 / 20 0.15 8 108 2.5 17.6 13.4 PE04 70 / 30 0.15 8 114 2.9 16.1 14.1 PE05 50 / 50 0.15 8 118 2.6 16.5 12.8 PE06 70 / 30 0.25 8 112 2.2 19.2 15.7 PE07 50 / 50 0.25 8 114 1.6 20.7 15.6 *measured using SEM

[0111] Preparatory Examples 8-10 (PE08-10)

[0112] Nonwoven media comprising a monofilament was prepared using the Method of Making Spunbound Nonwoven as described above using only nylon. Shown in Table 2 are the die flow rates and attenuation pressure used during processing and the resulting basis weight, pressure drop (delta P), effective fiber diameter and actual fiber diameter as measured on the resulting nonwovens. Table 2 Die Atten. Basis Average Nylon Flow Delta P EFD Sample Press. weight AFD* type Rate (mm water) (µm) (psi) (gsm) (µm) (ghm) PE08 Nylon 2 0.09 5 122 5.0 10.7 8.1 PE09 Nylon 1 0.12 8 124 3.6 12.2 8.9 PE10 Nylon 1 0.10 8 124 5.1 10.9 7.1 *measured using an optical microscope

[0113] Examples 1-3 (EX01-03)

[0114] Nonwoven media comprising sheath-core fibers were derivatized following the EB Derivatization Procedure. The aqueous reaction mixture contained 12 wt% NVP, 10 wt% MAPTAC and varying amounts of GMA (0-4 wt%) in water. The resulting derivatized samples were evaluated for MassGain. Shown in Table 3 are the fiber type and GMA amounts used and the mass gain. The samples were analyzed by SEM. Also shown in Table 3 are visual observations of the resulting functionalized material as viewed in SEM images. Shown in Figs.6-8 are the various morphologies observed with the functionalization as disclosed herein.

[0115] Figs.4 and 5 are a scanning electron micrographs of PE01 and PE02, respectively. The SEM images show a circular core surrounded by an annular sheath, where the relative area of the core and sheath reflect the weight ratios at which they were made. Fig.6 is a scanning electron micrograph of EX01, which shows a sheath buckled into a single large protuberance. Going forward, fibers with such structures will be referred to as “fin”. Fig.7 is a scanning electron micrograph of EX02, which shows a sheath buckled at multiple points into multiple smaller protrusions. Going forward, fibers with such structures will be referred to as “churros”. Fig.8 is a scanning electron micrograph of EX03, which shows a sheath that did not buckle, but appears to be enlarged and detached from much of the core. Going forward, fibers with such structures will be referred to as “loops”. Table 3 Sample Fiber GMA used Mass Observed Final used (wt%) Gain (%) Structure EX01 PE01 0 80 Fin EX02 PE01 2 106 Churro EX03 PE02 4 238 Mostly thick l 2oo0ps, some stubby fins

[0116] Examples 4-7 (EX04-07)

[0117] Nonwoven media comprising sheath-core fibers were derivatized following the EB Derivatization Procedure. The aqueous reaction mixture contained 12 wt% NVP and 10 wt% MAPTAC with no GMA in water. The resulting derivatized samples were evaluated for Mass Gain and were analyzed by SEM and the observed structure is reported in Table 4.

[0118] Examples 3 and 8-10 (EX03 and EX08-10)

[0119] Nonwoven media comprising sheath-core fibers were derivatized following the EB Derivatization Procedure. The aqueous reaction mixture contained 12 wt% NVP and 10 wt% MAPTAC, and 4 wt% GMA in water. The resulting derivatized samples were evaluated for Mass Gain and were analyzed by SEM and the observed structure is reported in Table 4.

[0120] Sample discs (3-7 replicates) were cut out of selected samples were tested for BSA Binding and the results are shown in Table 4 below. Table 4Sample Fiber Target GMA Mass Observed Final BSA BSA / area / used Nylon (wt%) Gain Structure bound / mass (mg / % of (%) area 2 cm2 / g) sheath (mg / cm ) EX04 PE03 20 0 37 Fin NR NR EX05 PE04 30 0 59 Fin 2.2 57 EX06 PE05 50 0 166 Fin 4.4 67 EX07 PE02 70 0 192 Loop 4.3 59 Mostly churro, EX08 PE03 20 4 122 NR NR some loop Mix of fin and EX09 PE04 30 4 139 1.8 35 loop Mix of fin and EX10 PE05 50 4 209 2.9 36 loop Mostly thick EX03 PE02 70 4 238 loops, some 2.4 38 stubby fins NR= not reported

[0121] Examples 11-12 (EX11-12)

[0122] The nonwoven media having similar AFD but differing percents of sheath-core ratios were derivatized following the EB Derivatization Procedure. The aqueous reaction mixture contained 12% NVP and 10% MAPTAC in water.

[0123] Imaging of the samples showed fibers with mostly fin morphology along with some loop. Discs (3-7 replicates) were cut out of the grafted sheets and tested for Static BSA Binding. The averaged results are shown in Table 5.Table 5 Target Fiber Nylon Mass Observed BSA bound / area BSA / area / mass Sample used % of Gain Final Structure (mg / cm2) (mg / cm2 / g) sheath Mostly fin, EX11 PE06 30 79% 3.8 102 some loop Mostly fin, EX12 PE07 50 145% 4.5 71 some loop

[0124] Examples 13-22 (EX13-22)

[0125] Sheath-core PE03 was derivatized following the EB Derivatization Procedure. The aqueous reaction mixture contained varying monomer types and amounts in water as described in Table 6 below. The resulting derivatized samples were evaluated for Mass Gain and were analyzed by SEM and the observed structure is reported in Table 6. Table 6 Sample Mass Monomers (wt%) Gain Observed Final Structure (%) EX13 MAPTAC 10% 1 Sheath-core EX14 MAPTAC / GMA 10% / 2% 11 Sheath-core EX15 MAPTAC / NVP / GMA 10% / 12% / 2% 68 Churro, few loops EX16 MAPTAC / NVP 10% / 12% 28 Fin EX17 VBTAC / NVP / GMA 10% / 12% / 2% 50 Churro EX18 VBTAC / NVP 10% / 12% 22 Fins EX19 AETAC / NVP / GMA 10% / 12% / 2% 98 Churro EX20 AETAC / NVP 10% / 12% 88 Fin EX21 MAETAC / NVP / GMA 10% / 12% / 2% 178 Churro EX22 MAETAC / NVP 10% / 12% 56 Fin

[0126] Comparative Examples 1-3 (CE01-CE03

[0127] Various nonwoven media comprising monofilaments were derivatized following the EB Derivatization Procedure. The aqueous reaction mixture contained 12 wt% NVP and 10 wt% MAPTACin water. The resulting derivatized samples were evaluated for Mass Gain. Discs (3-7 replicates) were cut out of the grafted sheets and tested for Static BSA Binding. The results are shown in Table 6. Table 6 Sample Fiber Mass Basis BSA bound / area BSA bound / used Gain weight (mg / cm2) area / mass (%) (gsm) (mg / cm2 / g) CE01 PE08 267 473 2.7 28 CE02 PE09 201 466 4.9 52 CE03 PE10 201 448 3.1 34

[0128] The comparative examples had smaller diameter fibers (between 7-9 micron AFD). Typically, smaller diameter fibers are thought to give improved analyte (i.e., BSA) binding due to their higher surface area. In the present disclosure, the comparative examples in general showed lower BSA amount bound normalized for area and mass than the sheath-core fibers which had larger diameters (see EX05-EX07 and EX11-12, which had AFD that varied from 12.5 to 15.7 micrometers) when considering the same derivatizing solution.

[0129] Foreseeable modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. This invention should not be restricted to the embodiments that are set forth in this application for illustrative purposes. To the extent that there is any conflict or discrepancy between this specification as written and the disclosure in any document mentioned or incorporated by reference herein, this specification as written will prevail.

Claims

What is claimed is:

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

2. A chemically-functionalized fiber of claim 1, wherein the core is substantially enclosed by the sheath.

3. The chemically-functionalized fiber according to anyone of the previous 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 anyone of the previous 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 mixture thereof.

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

7. The chemically-functionalized fiber according to claim 6, wherein each of the protuberances have an aspect ratio of length versus thickness at least 1:1 and at most 10:

1.

8. The chemically-functionalized fiber according to any one of the previous claims, wherein the fiber is a meltspun fiber.

9. The chemically-functionalized fiber according to any one of the previous claims, wherein the aminoalkyl (meth)acryloyl monomers are amino (meth)acrylates or amino (meth)acrylamides of Formula I or quaternary ammonium salts thereofwherein R1is hydrogen or methyl, preferably methyl; L is —O— or —NH—; and Y is an alkylene and R2is (i) independently hydrogen or alkyl or (ii) the two R2groups taken together with the nitrogen atom to which they are attached can form a heterocyclic group that is aromatic, partially unsaturated, or saturated, and optionally, wherein the heterocyclic group is fused to a second ring that is aromatic, partially unsaturated, or saturated.

10. The chemically-functionalized fiber according to anyone of the previous 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(meth)acrylate (HEMA), 2- ethoxyethyl methacrylate (2-EOEMA), 2-hydroxypropyl(meth)acrylate, 3- hydroxypropyl(meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate, N-vinyl caprolactam, N-vinyl acetamide, N-vinyl pyrrolidone, acrylonitrile, tetrahydrofurfuryl acrylate, acrylamide, mono- or di-N-alkyl substituted acrylamide, glycerol methacrylate, and combinations thereof.

12. The chemically-functionalized fiber according to anyone of the previous 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)acyoloyl epoxide monomer comprises at least one of the following: glycidyl methacrylate, or glycidyl acrylate.

14. A non-woven comprising the chemically-functionalized fiber according to any one of the previous claims.

15. A filtration media comprising the chemically-functionalized fiber according to any one of claims 1- 13.

16. A method of making a chemically-functionalized fiber, the method comprising: (i) providing a fiber wherein the fiber comprises a core having a sheath layer disposed thereon, wherein the sheath layer comprises nylon; and (ii) contacting the fiber with an aqueous reaction mixture comprising: an aminoalkyl (meth)acryloyl monomer; optionally, a hydrophilic monomer; and optionally, a (meth)acryloyl epoxide monomer; and (iii) exposing the fiber to radiation.

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

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

19. The method of any one of claims 16-18, wherein the fiber has a basis weight of at least 50 grams per square meter and at most 250 grams per square meter.

20. The method of any one of claims 16-19, 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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