WO2024241110A1

WO2024241110A1 - Grafted articles derived from porous polymeric fibers and methods thereof

Info

Publication number: WO2024241110A1
Application number: PCT/IB2024/053792
Authority: WO
Inventors: Jinsheng Zhou; Chuntao Cao; Michael R. Berrigan; Jacob J. THELEN; John D. Stelter
Original assignee: 3M Innovative Properties Co
Current assignee: 3M Innovative Properties Co
Priority date: 2023-05-19
Filing date: 2024-04-18
Publication date: 2024-11-28
Anticipated expiration: 2025-11-19

Abstract

Described herein is a process for making an article and articles thereof. The process comprises: (i) providing porous polymeric fibers, wherein each porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; (ii) contacting the porous polymeric fibers with a polymerizable solution; and (iii) exposing the porous polymeric fibers to a controlled amount of ionizing radiation to form a grafted article. The grafted articles, which can include nonwovens, comprise a porous polymeric fiber, wherein the polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; and a plurality of polymer chains extending from the outer major surface of the porous polymeric fiber.

Description

GRAFTED ARTICLES DERIVED FROM POROUS POLYMERIC FIBERS AND METHODS THEREOF

TECHNICAL FIELD

[0001] Disclosed herein is a process for making a grafted article comprising a plurality of porous polymeric fibers with a plurality of polymer chains extending from the surface thereof. Such articles are described, which may be used, for example, in nonwoven substrates.

SUMMARY

[0002] Often, an article is made with a given polymer type due to cost and/or easy of processing. However, this first polymer may not be ideal from a use standpoint because it does not have the necessary properties. Thus, a second polymer may be grafted onto the first polymer. Polymer grafting by electron beam (EB) irradiation is one way to graft a polymer onto a relatively inert material like polyolefins. However, sometimes the grafting efficiency can be low. Thus, there is a desire to improve the grafting uptake.

[0003] In one aspect, a grafted fiber is discussed. The grafted fiber comprising a porous polymeric fiber, wherein the porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; and (b) a plurality of polymer chains extending from the outer major surface of the porous polymeric fiber.

[0004] In another aspect, a grafted nonwoven article is discussed. The grafted nonwoven article comprising a nonwoven substrate comprising (a) a plurality of porous polymeric fibers, wherein each porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; and (b) a plurality of polymer chains extending from the outer major surface of the porous polymeric fiber.

[0005] In one aspect, a method for making the grafted fiber is disclosed. The method comprising: (i) providing a porous polymeric fiber, wherein the porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; (ii) contacting the porous polymeric fiber with a polymerizable solution; and (iii) exposing the porous polymeric fiber to a controlled amount of ionizing radiation to form the grafted fiber.

[0006] In another aspect, a method for making the grafted nonwoven article is disclosed. The method comprising: (i) providing a nonwoven substrate comprising a plurality of porous polymeric fibers, wherein each porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; (ii) contacting the nonwoven substrate with a polymerizable solution; and (iii) exposing the nonwoven substrate to a controlled amount of ionizing radiation to form the grafted article.

[0007] 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.

DESCRIPTION OF THE FIGURES

[0008] Embodiments of the present disclosure are illustrated by way of example, and not limitation, in the accompanying drawings in which:

[0009] FIG. 1 is a scanning electron microscopy (SEM) image of Nonwoven 2;

[0010] Fig. 2 is an SEM of Comparative Example 2; and

[0011] Fig. 3 is an SEM of Example 2.

DETAILED DESCRIPTION

[0012] 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).

[0013] As used herein, the term “filament” refers to a continuous elongated strand of material, typically longer than 6 inches.

[0014] As used herein, the term “open celled porous structure” with respect to a fiber’s structure refers to a fiber that has a plurality of pores, at least some of which are connected to adjacent pores such that a fluid can pass from one major surface of a portion of the fiber to an opposing major surface of the fiber.

[0015] As used herein, the term “microfibril” refers to a portion of a porous structure of a fiber having a fibril in which each dimension is less than 1 micrometer in size.

[0016] As used herein, the term “lamellae” refer to crystal portions of semicrystalline polymeric material of a fiber.

[0017] As used herein, the term “continuous” with respect to a fiber refers to a fiber having a longest dimension that has a length of greater than 1 centimeter.

[0018] As used herein, the term “semicrystalline” refers to a polymer that beside an amorphous phase forms crystalline domains during solidification, plus exhibits a melting peak during heating and a crystallization peak during solidification as measured by dynamic scanning calorimetry (DSC).

[0019] As used herein, the term “porosity” with respect to fibers refers to a measurement of void spaces in a fiber that has an open celled porous structure, as determined by solvent absorption. One such solvent absorption method is described in the test method section of U.S. Prov. Pat. Appl. No. 63/422,139. [0020] As used herein, the term “porosity” with respect to a nonwoven fibrous web refers to a total volume of the void spaces between individual fibers of the web, as determined by measuring the solidity of the nonwoven fibrous web and subtracting the solidity from 100. Accordingly, the solidity represents the proportion of the total volume of a nonwoven fibrous web that is occupied by the fibers. Solidity is determined by dividing the measured bulk density of the nonwoven fibrous web by the density of the fibers. Bulk density of a web can be determined by first measuring the weight (e.g., of a 10-cm-by-10-cm section) of a web. Dividing the measured weight of the web by the web area provides the basis weight of the web, which is reported in g/m². The thickness of the web can be measured by obtaining (e.g., by die cutting) a 135 mm diameter disk of the web and measuring the web thickness with a 230 g weight of 100 mm diameter centered atop the web. The bulk density of the web is determined by dividing the basis weight of the web by the thickness of the web and is reported as g/m³. The solidity is then determined by dividing the bulk density of the nonwoven fibrous web by the density of the material (e.g., polymer) comprising the fibers of the web. The density of a bulk polymer can be measured by standard means if the supplier does not specify the material density. Solidity is a dimensionless fraction which is usually reported as a percentage.

[0021] As used herein, “thermoplastic” refers to a polymer that flows when heated sufficiently above its glass transition point and become solid when cooled. In contrast, “thermoset” refers to a polymer that permanently sets upon curing and does not flow upon subsequent heating. Thermoset polymers are typically crosslinked polymers.

[0022] As used herein, “(meth)” before a compound refers to the compound optionally being methylated. For example, (meth)acrylate includes both acrylate as well as methacrylate; and (meth)acrylamide includes both acrylamide and methacrylamide.

[0023] 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.).

[0024] 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.).

[0025] 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, or a combination of all three.

[0026] The present application is directed toward a grafted porous polymeric fiber. These grafted fibers can be used in a nonwoven and have been shown to have improved grafting yield.

[0027] The porous polymeric fibers disclosed herein comprise a plurality of pores. At least a portion of the pores are open along the outer major surface of the fiber and extend into the interior of the fiber. At least a portion of the pores in the fiber are fluidically connected in the axial direction (d_a) and/or radial direction (d_r) relative to the fiber. Shown in Fig. 1 is an SEM image of a portion of the outside of a porous fiber taken from Nonwoven 2 in the Example Section. Fig. 1 shows fiber 10, which comprises a plurality of pores 15, which extend into the fiber. [0028] The porous polymeric fibers (herein also referred to as porous fibers), may be made from polymers such as polyolefins including polypropylene (PP), polyethylene (PE), polymethyl pentene (PMP), or polybutene- 1; polyoxymethylene (POM); polyvinylidene fluoride (PVDF); or copolymers thereof. Optionally, each porous fiber may include a blend of at least two polymers, e.g., a blend of a first PP and a second PP. In some cases, one PP is preferred or two or more (e.g., different) PPs are preferred. For instance, the continuous fibers may comprise a PP having a number average molecular weight (Mn) of at least 250,000; 275,000; 300,000; 325,000; 350,000; 375,000; or even 400,000 grams per mole (g/mol); and at most 800,000; 775,000; 750,000; 725,000; 700,000; 675,000; 650,000; 625,000; 600,000; 575,000; 550,000; 525,000; 500,000; 475,000; 450,000; or even 425,000 g/mol. The porous fibers may comprise a PP having a number average molecular weight of 250,000 g/mol to 800,000 g/mol, inclusive. Exemplary PPs include for instance those polypropylenes commercially available under the trade designation “PPH3264” and “PPH3766” both from TotalEnergies Petrochemicals & Refining USA, Inc. (Houston, TX).

[0029] Suitable crystalline thermoplastic polypropylene homopolymer resins are available from TotalEnergies Petrochemicals & Refining USA, Inc. (Houston, TX) such as, for example Homopolymer Polypropylene 3281, 3274, PPH3060, 3273, 3272, 3371, PPH4022, PPH4069, 3462, 3571, 3662, M3661, 3766, 3865, 3860. Other suitable polypropylene homopolymers are available from Lyondel-Basell Industries (Pasadena, TX) under the trade designation PRO-FAX such as, for example, PRO-FAX 1280 PRO-FAX 814, PRO-FAX 1282, PROFAX 1283 or under other trade designation such as ADFLUEX X500F, ADSYL 3C30F, HP403G, TOPPYL SP 2103. Additional suitable polypropylene homopolymers are available from INEOS Olefins & Polymers, USA (Carson, CA), for example INEOS H01-00, INEOS H02C-00, INEOS H04G-00, and INEOS H12G-00. Other suitable polypropylene homopolymers are available from Braskem Chemical and Plastics Company (LaPorte, TX), for example, F008, F013M, FF026, FF030F2. Further suitable polypropylene homopolymers are available from Exxon-Mobil Chemical Co. (Spring, TX), for example, PP1024E4, PP2252E3, PP4292E1, and PP4612E2, PP 4792. [0030] Suitable crystalline thermoplastic polyethylene (PE) homopolymer resins are available from Exxon-Mobil Chemical Co. Spring, TX), for example, HDPE 6908. Suitable polyethylene homopolymers are also available from TotalEnergies Petrochemicals& Refining USA, Inc. (Houston, TX), for example, High density polyethylene HDPE 56020, HDPE 55060, HDPE 5802, HDPE 51090, HDPE 5502. Other suitable polyethylene homopolymers are available from Braskem Chemical and Plastics Company (LaPorte, TX), for example, HF0144, HF0150, HF0147, and FH35; polyethylene polymer from NOVA Chemicals Corporation (Calgary, AB, Canada), for example, SUPRASS HPsl67- AB, HPs267-AB, HPs667-AB, SCLAIR 19E, SCLAIR99L, NOVAPOL HB-L354-A.

[0031] In some embodiments, the polymer resin can also include one or more poly(methyl)pentene (PMP) copolymer resins. Suitable grades of PMP copolymer resin having a low content of linear or branched alpha olefin comonomers are available from Mitsui Chemical (Minato-Ku, Tokyo, Japan) under the general trade designation TPX, for example resin grades DX470, RT18, DX820, and DX845. [0032] Suitable crystalline thermoplastic polybutene-1 (PB-1) homopolymer resins are available from Lyondel-Basell Industries (Pasadena, TX) for example Toppyl PB 0110M, Toppyl PB 8640M, Toppyl PB 8310, Toppyl PB 8340M.

[0033] The porous fibers of the present disclosure comprise a plurality of pores that interrupt the exterior surface of the porous fiber and extend inward in the fiber. In one embodiment, the pores have an average pore diameter along the outer surface of the porous fiber of at least 5, 10, 15, 20, 35, or even 30 nm; and at most 50, 60, 80, 100, 125, 150, 200, 300, 400, or even 500 nm assuming a circular cross-section. Such pore diameter may be determined using techniques known in the art, such as scanning electron microscopy (SEM).

[0034] The porous fibers comprise a plurality of pores. The plurality of pores results in the fibers having a higher surface area. For example, in one embodiment, the porous polymeric fibers have an average surface area of at least 5, 10, 15, 20, 35, 30, or even 40 m²/g as determined by BET (Brunauer Emmet Teller) nitrogen adsorption.

[0035] In one embodiment, the porous fibers have an open celled porous structure, typically, with a fiber porosity of at least 5, 0, 12, 15, 17, 20, 25, 30, 35, 40, or even 45 volume percent (vol %); and at most 50, 55, 60, 65, 70, 75, or even 80 vol %.

[0036] In one embodiment, the porous fibers have an average diameter of at least 6, 8, 10, 12, 15, 20, or even 25 micrometers. Typically, the porous fibers have an average diameter of less 200, 100, or even 50 micrometers. Such fiber diameter may be determined using techniques known in the art, such as scanning electron microscopy (SEM).

[0037] In one embodiment, the porous fibers described herein are made using a process as described in U.S. Prov. Pat. Appl. No. 63/422139 (Zhou et al.), herein incorporated by reference. Briefly, a polymeric material (such as a crystalline thermoplastic) is extruded to form fibers under well controlled process condition with air cooling. Crystal phases as rows are oriented in the fiber direction. Thus, when the fiber is subjected to a cold-hot-relaxation sequence while being stretched, pores form within the fiber. Fig. 1 was prepared according to the process as disclosed in U.S. Prov. Pat. Appl. No. 63/422139. Also shown in Fig. 1 is the plurality of microfibrils 12 extending between opposing lamellae microstructures 14. The microfibrils 12 and lamella micro structures 14 together define voids 15 of the porous fiber 10. The size of the microfibrils 12 can vary, typically including at least one dimension that has a length of 1 micrometer or smaller. In some cases, the lamella microstructures tend to have a non-row ordered configuration, but rather have been deformed during stretching to result in curved lamella microstructures.

[0038] In one embodiment, the porous fibers are used in a non-woven substrate. As used herein, "nonwoven" generally refers to a fibrous web or material characterized by entanglement or point bonding of a plurality of fibers, wherein the fibers are interlaid, but not in an identifiable manner as in a knitted fabric. [0039] In one embodiment, at least 50, 60, 70 or even 75% by weight of the nonwoven substrate comprises the porous polymeric fiber. In one embodiment, at most 99, 98, 95, 90, 85 or even 80% by weight of the nonwoven substrate comprises the porous polymeric fiber. In some embodiments, the nonwoven substrate contains no other fibers other than the porous fibers.

[0040] In one embodiment, the nonwoven substrate of the present disclosure can be prepared as continuous fiber strands from melt processes as known in the art such as melt blowing processes, and spun bonding processes. In a melt blowing process, a nonwoven fibrous web is formed by extruding a fiber-forming material (e.g., the polyolefin-containing polymer) through one or more orifices to form filaments while contacting the filaments with air or other attenuating fluid to attenuate the filaments into discrete discontinuous fibers, and thereafter collecting a layer of the attenuated discrete discontinuous fibers. In a spunbound process, a molten fiber-forming material is extmded from a plurality of fine, usually circular, capillaries of a spinnerette with the diameter of the extruded fibers then being rapidly reduced as by, for example, drawing and/or other well-known spunbonding mechanisms. The spunbound fibers are collected onto a surface forming a web.

[0041] Alternatively, short lengths of the porous fibers may be made or chopped from continuous strands and bonded together using secondary bonding processes known in the art to form a nonwoven substrate of the present disclosure. Such bonding processes include the bonded carded process, through air bonding and pattern-roll bonding. In a bonded carded process, the small diameter fibers of the present disclosure are placed in a fiberizing unit/picker which separates the fibers. Next, the fibers are sent through a combining or carding unit which further breaks apart and aligns the staple fibers in the machine direction so as to form a machine direction-oriented fibrous non-woven web. Once the web has been formed, it is then bonded by one or more of several bonding methods. One bonding method is powder bonding wherein a powdered adhesive is distributed throughout the web and then activated, usually by heating the web and adhesive with hot air. Another bonding method is pattern bonding wherein heated calender rolls or ultrasonic bonding equipment is used to bond the fibers together, usually in a localized bond pattern through the web and or alternatively the web may be bonded across its entire surface if so desired. When using bi-component staple fibers, through-air bonding equipment is, for many applications, especially advantageous. Yet another bonding process includes a wet-laid process, which is analogous to a conventional papermaking process, where the small diameter fibers of the present disclosure along with optional other fibers and a binder are suspended in a fluid and the deposited onto a screen or porous surface to remove the fluid.

[0042] In yet another embodiment, the small diameter fibers may be made using a hydroentagling technique, wherein high-velocity waterjets are used to wrap or knot individual fibers in a web bonding process. Such techniques are known in the art. See for example, U.S. Pat. Nos. 7,981,336; 6,110,588; and 5,207,970.

[0043] In one embodiment, the porosity of the nonwoven fibrous web may be greater than 90, 91, 92, 93, 94, or greater than 95%. As the porosity of the nonwoven fibrous web is determined by measuring solidity and subtracting from 100, the measured solidity of the nonwoven fibrous web may be less than 10, 9, 8, 7, 6, or less than 5%.

[0044] Advantageously, the nonwoven substrate comprising a plurality of porous polymeric fibers may be produced in a roll-to-roll manner, in other words, the continuous processing of a substrate along a roller-based processing line.

[0045] The porous fibers (or the porous fibers in a nonwoven substrate format) of the present disclosure are grafted with a polymer.

[0046] Typically for grafting, the porous fibers or the nonwoven comprising the porous fibers is contacted with a polymerizable composition comprising monomers for grafting. Although not wanting to be limited by theory, it is believed that the monomers should be diffusible or of sufficiently small size to allow the monomers to diffuse into the pores of the porous fiber.

[0047] In some embodiments, the monomer for grafting comprises a functional moiety. In one embodiment, a monomer comprising an ethylenically unsaturated moiety and a functional moieties according to Formula I is used to graft functional moeities onto the surface of the porous fiber.

CH₂=CXY (I) wherein X is H or CH?,, Y comprises a functional moiety. As used herein, a functional moiety refers to a group that introduces a new functionality to the porous fiber. The functional moiety is a group that provides a particular purpose. For example, the functional moiety could provide a site for additional reactions, add a property to the article such as wettability, or provide a site for interactions with a compound of interest. The functional moiety is located at the end of the grafted polymer either as a terminal group or in a sidechain depending on the polymer chemistry. In one embodiment, the monomer introduces ionic moieties, such as a sulfonic group, an amino group, a quaternary ammonium group, or combinations thereof.

[0048] One such ionic monomer is Formula II or salts thereof:

wherein R¹ is H or CH?,, and Z is a straight or branched alkylene having 1 to 10 carbon atoms. In one embodiment, Z is ~(CH?)_n~, where n is I, 2, 3. 4, 5, 6, 7, 8, 9, or 10 (more preferably I, 2, 3. 4, or 5); - CH2CH2-, -C(CI-I.j)?CH?-; -CH(CH?.)-; or -CH?CH(CIT;)-. Exempiaty salts of Formula TI include sodium salt, potassium salt, magnesium salt, calcium salt, ammonium salt, etc.

[0049] In another embodiment, the porous fiber or the nonwoven substrate comprising the porous fiber is treated to comprise a quaternary ammonium functional group, i.e., -NF R²R³R⁴ M" where M" is a counter ion group, often a halide (e.g., O'), a sulfate, a phosphate, a nitrate, and the like. In some embodiments, R², R³, and R⁴ of the ammonium functional group are all methyl. In other embodiments, one of the R², R³, and R⁴ groups is methyl and the other two are an alkyl having 2 to 18, 2 to 10, 2 to 6, or 2 to 4 carbon atoms. In other embodiments, two of the R², R³, and R⁴ groups are methyl and the other group is an alkyl having 2 to 18, 2 to 10, 2 to 6, or 2 to 4 carbon atoms. In yet other embodiments, at least two of the R², R³, and R⁴ groups 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, piperidinyl and morpholinyl. The heterocyclic group can be fused to an additional ring such as a benzene, cyclohexene, or cyclohexane.

[0050] In one embodiment, the quaternary ammonium salt of an aminoalkyl(meth)acryloyl monomer such as Formula (III) is used

straight or branched alkylene as described above. R⁵, R⁶, and R⁷, are independently aryl or alkyl, preferably C1-C4 alkyl; and M" is the counter anion group often a halide (e.g., O'), a sulfate, a phosphate, a nitrate, and the like.

[0051] Exemplary quaternary salts of the aminoalkyl (meth)acryloyl monomers of Formula (III) 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 -methacryloxy ethyltrimethylammonium chloride, 3 -methacryloxy -2- hydroxypropyltrimethylammonium chloride, 3 -acryloxy -2 -hydroxypropyltrimethylammonium chloride, and 2-acryloxyethyltrimethylammonium methyl sulfate). Such monomers having a quaternary ammonium group of Formula (III) may be directly grafted to the surface of the nonwoven substrate or a grafting aminoalkyl (meth)acryloyl monomer, having a primary, secondary or tertiary amine group, may be grafted and subsequently converted to a quaternary ammonium group by alkylation. Such manufacture of anion exchange nonwovens is described in U.S. Pat. No. 8,328,023 (Weiss et al.).

[0052] In one embodiment, the grafting monomer is N-vinylpyrrolidone, 4-hydroxybutyl methacrylate, 2 -hydroxylethyl (meth)acrylate, hydroxypropyl (meth)acrylate, (meth)acrylamide, N-methlolacrylamide, polyethylene glycol) mono(meth)acrylate, polypropylene glycol)mono(meth)acrylate, N- isopropylacrylamide, N-vinylcaprolactam, N-vinylformamide, N-vinyl-N-methacetamide, l-ethenyl-3- ethylurea, N-acryloylmorpholine, diethyl(meth)acrylamide, dimethyl(meth)acrylamide, glycerol mono(meth)acrylate, and tetrahydrofurfuryl acrylate.

[0053] Ionizing radiation can be used to initiate the grafting of the monomer or combinations of monomers onto the surface of the porous polymeric fibers.

[0054] The irradiation step involves the irradiation of substrate surfaces with ionizing radiation to prepare free radical reaction sites on such surfaces upon which the grafting monomer or combination of grafting monomers are subsequently grafted. "Ionizing radiation" means e-beam, gamma, and x-ray radiation of a sufficient dose and energy to cause the formation of free radical reaction sites on the surface(s) of the porous fibers. The radiation is of sufficiently high energy that when absorbed by the porous fibers, chemical bonds in the porous fibers are cleaved and free radical sites generated. Free radical sites on the surface of the porous fibers can react with the carbon-carbon double bond of grafting monomer, which can continue to add grafting monomer via a free radical, addition (or chain) polymerization. Other reactions are also possible. For example, when the grafting monomers and porous fibers are in contact during the irradiation step, free radicals can be generated at both the monomer and the porous fiber. Free radicals in the grafting composition can initiate polymerization of the grafting monomers, and the resultant monomeric, oligomeric, and polymeric active free radical species can couple with free radical sites on the porous fiber as known in the art.

[0055] In the present disclosure, the ionizing radiation is selected from e-beam, x-ray, and/or gamma radiation. These radiation sources are able to penetrate through solids, such that the porous fibers would not act as a mask during the irradiation. This is particularly advantageous when surface-treating a nonwoven substrate comprising a plurality of porous fibers comprising a complicated network of pores. The radiation source maybe selected depending on the application. For example, e-beam uses accelerated electrons while gamma irradiation uses radioisotope-generated gamma rays in a continuous exposure mode. Thus, gamma is more penetrating in irradiation than e-beam and is more suited for irradiating denser materials. As e-beam is powered by electricity, it can provide significantly higher irradiation dose rate and therefore require significantly less time. E-beam is perhaps better suited for continuous or semi- continuous web-based process while gamma can treat dense and bulky materials. X-ray is similar to gamma although the radiation is generated in a different manner. Gamma involves radioactive decay while x-rays are Bremstrahlung radiation generated from accelerating electrons into a metal target. X-ray tubes generally emit slightly longer wavelengths and lower photon energies than a gamma source. Depending on product density, product packaging, and/or desired processing mode, one irradiation method may be selected over the other. For example, e-beam irradiation provides significantly higher dose rates and therefore requires significantly less irradiation time than gamma irradiation. Thus, e-beam irradiation is more suited for continuous or semi-continuous web-based processes than gamma irradiation. Gamma irradiation may be more suited for batch processes and the surface treatment of large objects or a collection of objects that is voluminous.

[0056] In the irradiation step, the porous fibers or nonwoven substrate comprising porous fibers is exposed to ionizing radiation inside a chamber. The chamber may contain at least one source capable of providing a sufficient dose of radiation. A single source is typically capable of providing a sufficient dose of radiation, although two or more sources and/or multiple passes through a single source may be used. 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.

[0057] In one embodiment, the porous fibers (or nonwoven comprising the porous fibers) is first exposed to a controlled amount of ionizing radiation followed by contact with the graftable monomers. Alternatively, the porous fibers (or nonwoven comprising the porous fibers) is first contacted with the graftable monomers, followed by exposure to a controlled amount of ionizing radiation to generate the grafted fibers.

[0058] Typically, the grafting of the porous fibers occurs across a majority of the porous fiber exposed surface. In one embodiment, the plurality of polymer chains extending from the outer major surface of the porous polymeric fiber covers on average at least 50, 60, 70 or even 80 % of the surface of the plurality of porous polymeric fibers.

[0059] In one embodiment, the plurality of porous polymeric fibers has an average first fiber diameter and the plurality of polymer chains extending from the outer major surface of the porous polymeric fiber results in an average second fiber diameter, wherein the average second fiber diameter is at least 10, 20, or even 30 % larger than the average first fiber diameter.

[0060] Although not wanting to be limited by theory, it is believed that the larger surface area afforded by the porous nature enables grafting propagation into the interior of the porous fibers, even given the pore’s small size, allowing for large grafting yields. In one embodiment, the porous fibers gain at least 100, 150, or even 200% in weight.

[0061] In one embodiment, the grafted porous fibers as disclosed herein can be used in nonwoven substrates to provide recovery of analytes of interest from fluids. Such fluids can include gas or liquids. Such recovery can include the adsorption or absorption of the analyte of interest (such as a biopharmaceutical compound) with the grafted polymer layer.

[0062] Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

EXAMPLES

[0063] 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.

[0064] Test methods

[0065] BET Surface Area

[0066] BET Surface area was measured by gas sorption experiments performed using a Micromeritics Instrument Corporation (Norcross, GA) accelerated surface area and porosimetry (ASAP) 2020 Plus system instrument. In a Micromeritics half inch diameter sample tube, 50-250 milligrams of sample was degassed by first heating under high vacuum (500 micrometers of Hg) on the degas port for 3 hours at 80 °C. At the end of this degassing step, the sample tube was backfilled with nitrogen, and the sample tube was moved over to the analysis port. The sample was then further degassed by heating under ultra-high vacuum (3-7 micrometers Hg) on the analysis port of the instrument for 3 hours at 80 °C. Nitrogen sorption isotherms at 77 K were obtained using low pressure dosing (5 cm³/g) at a relative pressure (p/p°) less than 0.1 and a pressure table of linearly spaced pressure points for a p/p° from 0.1 to 0.998. The method for all isotherms made use of the following equilibrium intervals: 90 seconds at p/p° less than 10’ ⁵, 40 seconds at p/p° in a range of 10'⁵ to 0.1, and 20 seconds at p/p° greater than 0.1. Helium was used for the free space determination, after nitrogen sorption analysis, both at ambient temperature and at 77 K. BET specific surface areas (SABET) were calculated from nitrogen adsorption data by multipoint Brunauer-Emmett-Teller (BET) analysis. Apparent micropore distributions were calculated from nitrogen adsorption data by density functional theory (DFT) analysis using the standard nitrogen at 77 K density functional theory (DFT) model. Total pore volume was calculated from the total amount of nitrogen adsorbed at a p/p° equal to approximately 0.98. BET, DFT and total pore volume analyses were performed using Micromeritics MicroActive Version 5.02 software.

[0067] Scanning Electron Microscopy (SEM)

[0068] High magnification images were obtained using a field emission SEM(FE-SEM) (Model Hitachi S-4700, obtained from Hitachi High-Tech Corporations, Japan).

[0069] Nonwoven 1: non-porous fiber nonwoven prepared according to PE5 in U.S. Prov. Pat. Appl. No. 63/422, 139 (filed 11/03/2022). This nonwoven had a BET surface area of 4.0 m²/g.

[0070] Nonwoven 2: porous fiber nonwoven formed after cold/hot stretching of Nonwoven 1, prepared according to E5 in U.S. Prov. Pat. Appl. No. 63/422,139. This nonwoven had a BET surface area of 48.2 m²/g. [0071] Example 1

[0072] Three 4 inch x 6 inch (10 cm x 15 cm) samples were cut and weighed from Nonwovens 1 and 2. The nonwoven samples were placed into a glove box under nitrogen environment and oxygen was purged out for typically 30 minutes to 2 hours until the oxygen level inside the box was at 20ppm (parts per million) or below. While inside the glove box, each of the nonwovens was placed into a separate seal top plastic bags and sealed before removing them from the glove box. Each of the nonwoven samples was irradiated in their plastic bag with an electron beam (available from Energy Sciences Inc., Wilmington, MA) having an electron accelerating voltage of 300kV by a single pass. The irradiation dosage was set at lOMrad. The irradiated plastic bags were returned to the glove box and the glove box with samples was purged of oxygen as described above. Then, each nonwoven sample was removed from their plastic bag and placed in a new seal top plastic bag.

Table 1. Chemical compositions of polymerizable monomer solutions

[0073] Monomer Solutions 1, 2, and 3 each were prepared in glass bottles using the wt% of materials as described in Table 1. Monomer Solutions 1 and 2 appeared opaque as emulsions while Monomer Solution 3 was clear. Each of the Monomer Solutions were purged with nitrogen gas before sealing their respective bottles. All bottles were moved in the same glove box where the irradiated samples in new seal top plastic bags were kept. The Monomer Solutions were further purged for 1-10 min with caps off. Then the designated Monomer Solution (weight ratio of 20 to 30 Monomer Solution: 1 nonwoven) was added to each of the plastic bags containing the irradiated nonwoven sample. The Monomer Solutions were spread in the plastic bag to saturate the nonwoven sample. The plastic bags were sealed and the sample was allowed to react for 3 hours.

[0074] Each of the grafted nonwoven samples was removed from their plastic bag and held in boiling water for one hour. Then, the grafted nonwoven samples were soaked in deionized water for another hour, followed by drying at ambient temperature for at least 48 hours. The grafted nonwoven samples were weighed again and the % weight gain was calculated (i.e., (final weight - initial weight)/initial). The results are shown in Table 2. Table 2, Grafting yield of nonwoven samples

[0075] Fig. 2 is an SEM of Comparative Example 2 and Fig. 3 an SEM of Example 2.

[0076] 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 grafted article comprising: a nonwoven substrate comprising a plurality of porous polymeric fibers, wherein each porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; and a plurality of polymer chains grafted to the outer major surface of the porous polymeric fiber.

2. The grafted article of claim 1, wherein at least a portion of the polymer chains comprise a functional end group.

3. The grafted article of claim 2, wherein the functional end group is an analyte binding group.

4. The grafted article of claim 2, wherein the functional end group comprises an ionic group, optionally, wherein the ionic group comprises a sulfonic acid, an amino group, a quaternary ammonium group, or combinations thereof.

5. The grafted article of any one of the previous claims, wherein the plurality of porous polymeric fibers has an average first fiber diameter and the plurality of polymer chains extending from the outer major surface of the porous polymeric fiber results in an average second fiber diameter, wherein the average second fiber diameter is at least 10% larger than the average first fiber diameter.

6. The grafted article of any one of the previous claims, the plurality of polymer chains extending from the outer major surface of the porous polymeric fiber covers on average at least 50 % of the surface of the plurality of porous polymeric fibers.

7. The grafted article of any one of the previous claims, wherein the porous polymeric fiber exhibits a porosity of 5 volume percent to 80 volume percent.

8. The grafted article of any one of the previous claims, wherein the plurality of pores has an average pore diameter of 5 to 500 nm assuming a circular cross-section.

9. The grafted article of any one of the previous claims, wherein the porous polymeric fiber comprises one or more semicrystalline polymers.

10. The grafted article of any one of the previous claims, wherein the porous polymeric fiber comprises at least one of a polypropylene, a polyethylene, a polymethyl pentene, a polyoxymethylene, polybutene- 1, polyvinylidene fluoride, or copolymers thereof.

11. The grafted article of any one of the previous claims, wherein the porous polymeric fiber comprises polypropylene.

12. The grafted article of claim 11, wherein the porous polymeric fiber comprising polypropylene has a number average molecular weight of 250,000 grams per mole or greater to 800,000 grams per mole or less.

13. The grafted article of any one of the previous claims, wherein the porous polymeric fiber comprises microfibrils that connect lamellae micro structures.

14. The grafted article of any one of the previous claims, wherein at least 50% by weight of the nonwoven substrate comprises the porous polymeric fiber.

15. The grafted article of any one of the previous claims, wherein the porous polymeric fibers have an average surface area of at least 5 m²/g.

16. The grafted article of any one of the previous claims, wherein the porous polymeric fibers have an average surface area of at least 40 m²/g.

17. A method of making a grafted article, the method comprising:

(i) providing a nonwoven substrate comprising a plurality of porous polymeric fibers, wherein each porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected;

(ii) contacting the nonwoven substrate with a polymerizable solution; and

(iii) exposing the nonwoven substrate to a controlled amount of ionizing radiation to form the grafted article.

18. The method of claim 17, wherein the nonwoven substrate is first exposed to the controlled amount of ionizing radiation followed by contacting with the polymerizable solution.

19. The method of claim 17, wherein the nonwoven substrate is first contacted with the polymerizable solution followed by exposing to the controlled amount of ionizing radiation.

20. The method of any one of claims 17-19, wherein the ionizing radiation comprising e-beam, x-ray, or gamma radiation.

21. The method of any one of claims 17-19, wherein the polymerizable solution comprises a monomer comprising an ethylenically unsaturated moiety and a functional moiety according to Formula I:

CH₂=CXY (I) wherein X is H or CHj, and Y comprises a functional end group.

22. The method of any one of claims 19-21, wherein the polymerizable solution comprises an ionic monomer according to Formula II or salts thereof:

wherein R^! is H or CH;. and Z is a straight or branched alkylene having 1 io 10 carbon atoms.

23. The method of any one of claims 19-22, wherein the polymerizable solution comprises an ionic monomer according to Formula (III):

where R¹ is H or CHj; L is -O- or -NH-; Z is a straight or branched alkylene having 1 to 10 carbon atoms. R⁵, R⁶, and R⁷ are independently aryl or alkyl group; and M" is a counter anion.

24. The method of any one of claims 19-23, wherein the ionizing radiation induces radical polymerization of the polymerizable solution.

25. A grafted fiber comprising: a porous polymeric fiber, wherein the porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected; and a plurality of polymer chains grafted to the outer major surface of the porous polymeric fiber.

26. A method of making a grafted fiber, the method comprising: (i) providing a porous polymeric fiber, wherein the porous polymeric fiber comprises an outer major surface and a plurality of pores, wherein at least a portion of the pores are open to the outer major surface extending therefrom to an interior portion of the porous polymeric fiber and wherein at least a portion of the pores are fluidically connected;

(ii) contacting the porous fiber with a polymerizable solution; and

(iii) exposing the porous fiber to a controlled amount of ionizing radiation to form the grafted fiber.