Nonwoven Fibrous Webs and Methods of Making and

Using Thereof

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No. 63/027,118, filed May 19, 2020, which is hereby incorporated herein by reference in its entirety.

BACKGROUND

Nonwoven fibrous webs have been used to produce absorbent or adsorbent articles useful, for example, as absorbent wipes for surface cleaning, as gas adsorbents and liquid absorbents, as fluid filtration media, and as absorptive barrier materials for use as an acoustic or thermal insulation. Nonwoven fibrous webs can be formed by a variety of techniques including carding, garneting, air-laying, wet-laying, melt blowing, spunbonding, electrospinning, and stitch bonding. Further processing of a nonwoven can be used to add properties such as strength, durability, and texture. Examples of further processing include calendering, hydroentangling, needle tacking, resin bonding, thermo-bonding, ultrasonic welding, embossing, and laminating.

While many nonwovens with varied characteristics have been prepared, there remains a need for improved nonwoven materials. In particular, there is a need for new nonwoven materials suitable for use in the preparation of personal protective equipment including facemasks.

SUMMARY

Provided herein nonwoven fibrous web comprising a population of fibers, wherein the fibers are formed from a composite that comprises: (i) a thermoplastic elastomeric polymer (TPE) component; (ii) a soft elastomeric polymer component that at ambient temperatures is above its glass transition temperature; and (iii) optionally a filler.

The TPE component can comprise a block copolymer having at least one elastomeric block. For example, the TPE component can comprise a polystyrene- polyisobutylene block copolymer, polystyrene-polybutadiene block copolymer, polystyrene-polyisoprene block copolymer, polystyrene-poly(ethylene-butylene block copolymer, polystyrene-poly(ethylene-propylene) block copolymer, a thermoplastic polyolefin (TPO), a dynamically vulcanized TPV, or a blend or copolymer thereof. In certain embodiments, the TPE component can comprise a polyisobutylene-based TPE, such as polystyrene-polyisobutylene-polystyrene (SIBS). The TPE component can have any suitable structure, such as a linear, star, arborescent, comb, brush, centipede, hyperbranched, or dendritic structure. In some embodiments, the TPE component can comprises a linear block copolymer, such as a linear triblock polystyrene-polyisobutylene- polystyrene copolymer (L SIBS).

The soft elastomeric polymer component can comprise, for example, polyisobutylene, a polyisobutylene-isoprene copolymer, a polyisobutylene-styrene copolymer, polyisobutylene-alkyl styrene copolymers, halogenated polyisobutylene-alkyl styrene terpolymers, polybutadiene, polyisoprene, polyethylene-propylene copolymers, polyethylene-propylene diene terpolymers, and combinations thereof. In certain embodiments, the soft elastomeric polymer component can comprise polyisobutylene, a polyisobutylene-isoprene copolymer (e.g., butyl rubber), or any combination thereof. As with the TPE component, the soft elastomeric polymer component can have any suitable structure, such as a linear, star, arborescent, comb, brush, centipede, hyperbranched, or dendritic structure.

In some embodiments, the TPE can be present in an amount from about 10% to about 90% by weight of the composite, and the soft elastomeric polymer component can be present in an amount from about 90 to about 10% by weight of the composite, based on the total weight of the composite. In certain embodiments, the TPE can be present in an amount from about 40% to about 60% by weight of the composite, and the soft elastomeric polymer component can be present in an amount from about 60 to about 40% by weight of the composite, based on the total weight of the composite.

The filler can comprise any suitable filler material. In some embodiments, the filler can comprise an antimicrobial filler. The antimicrobial filler can be an inorganic material that comprises one more more antimicrobial metals (e.g., silver, copper, zinc, and combinations thereof). In some examples, the antimicrobial filler can comprise zinc oxide, carbon black, or any combination thereof. In some embodiments, the filler can be present in an amount from about 2% to about 40% by weight of the composite, such as from about 5% to about 30% by weight, based on the total weight of the composite.

The population of fibers comprises population of fine fibers, a population of microfibers, a population of ultrafme microfibers, a population of sub-micrometer fibers, or any combination thereof. In some embodiments, the nonwoven fibrous web can be formed as a single layer.

In some embodiments, the nonwoven web can have a basis weight of at least 80 g/m ² , such as a basis weight of at least 100 g/m ² , at least 150 g/m ² , or at least 200 g/m ² . In certain embodiments, the nonwoven web can be self-supporting. The nonwoven fibrous web can be hydrophobic. In some embodiments, the nonwoven fibrous web can exhibit a water contact angle of at least 120°, as determined by goineometry.

In some embodiments, the nonwoven web can exhibit an average filtration efficiency relative to 20nm to 450 nm NaCl particles of at least 60%, as measured using the U.S. NIOSH (National Institute for Occupational Safety and Health) N95 Filtering Facepiece Respirator (FFR) certification method. In some embodiments, the nonwoven web can exhibit an average filtration efficiency relative to 300 nm NaCl particles of at least 50%, measured using the U.S. NIOSH (National Institute for Occupational Safety and Health) N95 Filtering Facepiece Respirator (FFR) certification method.

The nonwoven fibrous webs described herein can be used to construct a variety of articles, including gas filtration articles, liquid filtration articles, sound absorption articles, surface cleaning articles, cellular growth support articles, drug delivery articles, personal hygiene articles, and wound dressing articles. In some embodiments, the nonwoven fibrous webs described herein can be fashioned into facemasks.

Also provided are methods of making fibrous nonwoven webs. These methods can comprise forming a plurality of fibers from a composite comprising: (i) a thermoplastic elastomeric polymer (TPE) component; (ii) a soft elastomeric polymer component that at ambient temperatures is above its glass transition temperature; and (iii) optionally a filler; and collecting at least a portion of the fibers to form a nonwoven web. In some embodiments, the methods can further comprises combining (e.g., melt processing) the TPE component, the soft elastomeric polymer component, and the filler to form the composite.

The web can be formed using any suitable method, such as a melt-blowing, spun- bonding, or melt-spinning process. In some examples, the web can be formed using melt spinning, filament extrusion, electrospinning, gas jet fibrillation or combinations thereof. Optionally, methods can further comprise post heating the web, for example, by controlled heating or cooling of the web.

DESCRIPTION OF DRAWINGS

Figure 1 A shows the multilayer design of conventional surgical masks. As shown in Figure 1 A, conventional surgical masks employ a trilayer design that includes an outer (often polypropylene) spunbond nonwoven layer, a central (often polypropylene) meltblown layer which serves as the primary filter material, and an inner spunbond layer.

Figure IB shows the multilayer design of a conventional N95 mask. As shown in Figure IB, these masks include multiple meltblown nonwoven layers disposed between an inner and outer needle punched cotton layer.

Figure 2A is a photograph showing a nonwoven web formed by electrospinning Formulation 2.

Figure 2B is an electron micrograph of a nonwoven web formed by electrospinning Formulation 2.

Figure 3 A is a photograph showing a nonwoven web formed by electrospinning Formulation 1.

Figure 3B is an electron micrograph of a nonwoven web formed by electrospinning Formulation 1.

Figure 4 is a plot showing the filtration efficiency (in %, as measured using the NIOSHN95 Filtering Facepiece Respirator (FFR) certification method) of five example PIB-based nonwoven webs as a function of pressure drop (in Pa).

Figure 5 illustrates the measurement of the water contact angle of an example nonwoven web using goniometry.

Figure 6 illustrates an example facemask fabricated using a self-supporting nonwoven web prepared herein.

Figure 7 schematically illustrates the structure of various polymer architectures.

DETAILED DESCRIPTION

Definitions

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Methods and materials are described herein for use in the present invention; other, suitable methods and materials known in the art can also be used. The materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, sequences, database entries, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. “Nonwoven fibrous web” means an article or sheet having a structure of individual fibers or filaments, which are interlaid, but not in an identifiable manner as in a knitted fabric. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, and bonded carded web processes.

“Cohesive nonwoven fibrous web” means a fibrous web characterized by entanglement or bonding of the fibers sufficient to form a self-supporting web.

“Web” as used herein is a network of entangled fibers forming a sheet like or fabric like structure.

“Self-supporting” means a web having sufficient coherency and strength so as to be drapable and handleable without substantial tearing or rupture.

“Meltblowing” and “meltblown process” means a method for forming a nonwoven fibrous web by extruding a molten fiber-forming material through a plurality of orifices to form filaments while contacting the filaments with air or other attenuating fluid to attenuate the filaments into fibers, and thereafter collecting the attenuated fibers. An exemplary meltblowing process is taught in, for example, U.S. Pat. No. 6,607,624 (Berrigan et ah).

“Meltblown fibers” means fibers prepared by a meltblowing or meltblown process.

“Spunbonding” and “spun bond process” mean a method for forming a nonwoven fibrous web by extruding molten fiber-forming material as continuous or semi-continuous filaments from a plurality of fine capillaries of a spinneret, and thereafter collecting the attenuated fibers. An exemplary spunbonding process is disclosed in, for example, U.S. Pat. No. 3,802,817 (Matsuki et ah).

“Spun bond fibers” and “spunbonded fibers” mean fibers made using spunbonding or a spun bond process. Such fibers are generally continuous filaments and are entangled or point bonded sufficiently to form a cohesive nonwoven fibrous web such that it is usually not possible to remove one complete spun bond fiber from a mass of such fibers. The fibers may also have shapes such as those described, for example, in U.S. Pat. No. 5,277,976 (Hogle et ah), which describes fibers with unconventional shapes.

“Carding” and “carding process” mean a method of forming a nonwoven fibrous web webs by processing staple fibers through a combing or carding unit, which separates or breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction oriented fibrous nonwoven web. An exemplary carding process is taught in, for example, U.S. Pat. No. 5,114,787 (Chaplin et ah). “Bonded carded web” refers to nonwoven fibrous web formed by a carding process wherein at least a portion of the fibers are bonded together by methods that include for example, thermal point bonding, autogenous bonding, hot air bonding, ultrasonic bonding, needle punching, calendering, application of a spray adhesive, and the like.

“Autogenous bonding” means bonding between fibers at an elevated temperature as obtained in an oven or with a through-air bonder without application of solid contact pressure such as in point-bonding or calendering.

“Calendering” means a process of passing a nonwoven fibrous web through rollers with application of pressure to obtain a compressed and bonded fibrous nonwoven web. The rollers may optionally be heated.

“Densification” means a process whereby fibers which have been deposited either directly or indirectly onto a filter winding arbor or mandrel are compressed, either before or after the deposition, and made to form an area, generally or locally, of lower porosity, whether by design or as an artifact of some process of handling the forming or formed filter. Densification also includes the process of calendering webs.

“Air-laying” is a process by which a nonwoven fibrous web layer can be formed. In the air-laying process, bundles of small fibers having typical lengths ranging from about 3 to about 52 millimeters (mm) are separated and entrained in an air supply and then deposited onto a forming screen, usually with the assistance of a vacuum supply. The randomly deposited fibers may then be bonded to one another using, for example, thermal point bonding, autogenous bonding, hot air bonding, needle punching, calendering, a spray adhesive, and the like. An exemplary air-laying process is taught in, for example, U.S. Pat. No. 4,640,810 (Laursen et ah).

“Wet-laying” is a process by which a nonwoven fibrous web layer can be formed. In the wet-laying process, bundles of small fibers having typical lengths ranging from about 3 to about 52 millimeters (mm) are separated and entrained in a liquid supply and then deposited onto a forming screen, usually with the assistance of a vacuum supply. Water is typically the preferred liquid. The randomly deposited fibers may by further entangled (e.g., hydro-entangled), or may be bonded to one another using, for example, thermal point bonding, autogeneous bonding, hot air bonding, ultrasonic bonding, needle punching, calendering, application of a spray adhesive, and the like. An exemplary wet-laying and bonding process is taught in, for example, U.S. Pat. No. 5,167,765 (Nielsen et ah). Exemplary bonding processes are also disclosed in, for example, U.S. Patent Application Publication No. 2008/0038976 A1 (Berrigan et al.).

To “co-form” or a “co-forming process” means a process in which at least one fiber layer is formed substantially simultaneously with or in-line with formation of at least one different fiber layer. Webs produced by a co-forming process are generally referred to as “co-formed webs.”

“Die” means a processing assembly for use in polymer melt processing and fiber extrusion processes, including but not limited to meltblowing and the spunbonding process.

“Particulate” and “particle” are used substantially interchangeably. Generally, a particulate or particle means a small distinct piece or individual part of a material in finely divided form. However, a particulate may also include a collection of individual particles associated or clustered together in finely divided form. Thus, individual particulates used in certain exemplary embodiments of the present disclosure may clump, physically intermesh, electro-statically associate, or otherwise associate to form particulates.

The term “median fiber diameter” means fiber diameter determined by producing one or more images of the fiber structure, such as by using a scanning electron microscope; measuring the fiber diameter of clearly visible fibers in the one or more images resulting in a total number of fiber diameters, x; and calculating the median fiber diameter of the x fiber diameters. Typically, x is greater than about 20, more preferably greater than about 50, and desirably ranges from about 50 to about 200.

“Effective Fiber Diameter” or “EFD” is the apparent diameter of the fibers in a fiber web based on an air permeation test in which air at 1 atmosphere and room temperature is passed through a web sample at a specified thickness and face velocity (typically 5.3 cm/sec), and the corresponding pressure drop is measured. Based on the measured pressure drop, the Effective Fiber Diameter is calculated as set forth in Davies, C. N., The Separation of Airborne Dust and Particulates, Institution of Mechanical Engineers, London Proceedings, IB (1952).

The term “fine fiber” generally refers to fibers having a median fiber diameter of no greater than about 50 micrometers (pm), preferably no greater than 25 pm, more preferably no greater than 20 pm, still more preferably no greater than 15 pm, even more preferably no greater than 10 pm, and most preferably no greater than 5 pm.

“Microfibers” are a population of fibers having a median fiber diameter of at least one pm but no greater than 100 pm. “Ultrafme microfibers” are a population of microfibers having a median fiber diameter of two pm or less.

“Sub-micrometer fibers” are a population of fibers having a median fiber diameter of no greater than one pm.

When reference is made herein to a batch, group, array, etc. of a particular kind of microfiber, e.g., “an array of sub-micrometer fibers,” it means the complete population of microfibers in that array, or the complete population of a single batch of microfibers, and not only that portion of the array or batch that is of sub-micrometer dimensions.

“Continuous oriented microfibers” means essentially continuous fibers issuing from a die and traveling through a processing station in which the fibers are permanently drawn and at least portions of the polymer molecules within the fibers are permanently oriented into alignment with the longitudinal axis of the fibers (“oriented” as used with respect to fibers means that at least portions of the polymer molecules of the fibers are aligned along the longitudinal axis of the fibers).

“Separately prepared microfibers” means a stream of microfibers produced from a microfiber-forming apparatus (e.g., a die) positioned such that the microfiber stream is initially spatially separate (e.g., over a distance of about 1 inch (25 mm) or more from, but will merge in flight and disperse into, a stream of larger size microfibers.

“Solidity” is a nonwoven web property inversely related to density and characteristic of web permeability and porosity (low Solidity corresponds to high permeability and high porosity), and is defined by the equation:

[3.937 * Web Basis Weight (g/m ² )] [Web Thickness (mils) * Bulk Density (g/cm ³ )]

“Web basis weight” is calculated from the weight of a 10 cmx 10 cm web sample, and is usually expressed in grams per square meter (gsm).

“Web thickness” is measured on a 10 cmx 10 cm web sample using a thickness testing gauge having a tester foot with dimensions of 5 cmx 12.5 cm at an applied pressure of 150 Pa.

“Bulk density” is the mass per unit volume of the bulk polymer or polymer blend that makes up the web, taken from the literature.

“Molecularly same” polymer means polymers that have essentially the same repeating molecular unit, but which may differ in molecular weight, method of manufacture, commercial form, and the like. “Fluid treatment unit,” “fluid filtration article,” or “fluid filtration system” means an article containing a fluid filtration medium, such as a porous nonwoven fibrous web. These articles typically include a filter housing for a fluid filtration medium and an outlet to pass treated fluid away from the filter housing in an appropriate manner. The term “fluid filtration system” also includes any related method of separating raw fluid, such as untreated gas or liquid, from treated fluid.

“Void volume” means a percentage or fractional value for the unfilled space within a porous body such as a web or filter, which may be calculated by measuring the weight and volume of a filter, then comparing the filter weight to the theoretical weight of a solid mass of the same constituent material of that same volume.

“Porosity” means a measure of void spaces in a material. Size, frequency, number, and/or interconnectivity of pores and voids contribute the porosity of a material.

“Layer” means a single stratum formed between two major surfaces. A layer may exist internally within a single web, e.g., a single stratum formed with multiple strata in a single web have first and second major surfaces defining the thickness of the web. A layer may also exist in a composite article comprising multiple webs, e.g., a single stratum in a first web having first and second major surfaces defining the thickness of the web, when that web is overlaid or underlaid by a second web having first and second major surfaces defining the thickness of the second web, in which case each of the first and second webs forms at least one layer. In addition, layers may simultaneously exist within a single web and between that web and one or more other webs, each web forming a layer.

“Adjoining” with reference to a particular first layer means joined with or attached to another, second layer, in a position wherein the first and second layers are either next to (i.e., adjacent to) and directly contacting each other, or contiguous with each other but not in direct contact (i.e., there are one or more additional layers intervening between the first and second layers).

As used herein, the term “soft elastomeric polymer” means a polymer that at ambient temperatures is above its glass transition temperature. In other words, this material is one which at ambient temperatures is a viscous material having an amorphous structure.

It is this component of the polymer matrix which is primarily responsible for the softness and high damping characteristics of the final composite.

As used herein, the term “thermoplastic elastomeric polymer (TPE)” means a thermoplastic polymer that at ambient temperatures exhibits a suitable degree of resilience and/or softness, but provides a thermolabile physical network so that the shape retention properties of the final polymer matrix are increased compared with those properties of the soft elastomeric polymer component alone. It is the thermoplastic nature of this second thermoplastic polymer component of the matrix of the composite which is primarily responsible for the shape retention and/or low compression creep properties of the final composite.

As used herein, the term “linear architecture” means a linear polymer chain.

As used herein, the term “star architecture” means a polymer having a core from which a number of arms (3 -infinite or as many as possible to fill the space) emanate.

As used herein, the term “arborescent architecture” means a randomly branched structure resembling a tree (branches on branches).

As used herein, the term “comb architecture” means a linear polymer chain to which a number of shorter linear chains are attached, with the structure resembling a comb.

HR is a commercial butyl elastomer, and SIBS is a commercial linear triblock polystyrene-polyisobutylene-polystyrene thermoplastic elastomer.

SBS means polystyrene-polybutadiene block copolymers.

SIS means polystyrene-polyisoprene block copolymers

SEBS and SEPS means the hydrogenated versions of SBS and SIS.

SEBS means poly styrene-poly(ethylene-butylene)-poly styrene.

SEPS means polystyrene-poly(ethylene-propylene)-polystyrene.

TPO means thermoplastic polyolefins.

TPV means dynamically vulcanized TPVs.

The above listed soft elastomer components and thermoplastic elastomer components can have various architectures (linear, star, arborescent, comb. etc).

Fibers and Nonwoven Fibrous Webs

Provided herein nonwoven fibrous web comprising a population of fibers, wherein the fibers are formed from a composite that comprises: (i) a thermoplastic elastomeric polymer (TPE) component; (ii) a soft elastomeric polymer component that at ambient temperatures is above its glass transition temperature; and (iii) optionally a filler.

The population of fibers comprises population of fine fibers, a population of microfibers, a population of ultrafme microfibers, a population of sub-micrometer fibers, or any combination thereof. In some embodiments, the nonwoven fibrous web can be formed as a single layer.

In some embodiments, the nonwoven web can have a basis weight of at least 80 g/m ² , such as a basis weight of at least 100 g/m ² , at least 150 g/m ² , or at least 200 g/m ² . In certain embodiments, the nonwoven web can be self-supporting. The nonwoven fibrous web can be hydrophobic. In some embodiments, the nonwoven fibrous web can exhibit a water contact angle of at least 120° (e.g., at least 125°, at least 130°, or at least 135°), as determined by goineometry.

In some embodiments, the nonwoven web can exhibit an average filtration efficiency relative to 20nm to 450 nm NaCl particles of at least 50% (e.g., at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%), as measured using the U.S. NIOSH (National Institute for Occupational Safety and Health) N95 Filtering Facepiece Respirator (FFR) certification method. In some embodiments, the nonwoven web can exhibit an average filtration efficiency relative to 300 nm NaCl particles of at least 50% (e.g., at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%), as measured using the U.S. NIOSH (National Institute for Occupational Safety and Health) N95 Filtering Facepiece Respirator (FFR) certification method.

The components of the composite are described in more detail below.

Thermoplastic Elastomeric Polymer (TPE) Components

A variety of suitable TPE components can be incorporated in the composites described herein. Examples of suitable TPEs include thermoplastic polyurethanes (TPU), styrenic block copolymers (TPS (TPE-s)), thermoplastic polyolefmelastomers (TPO (TPE- o)), thermoplastic vulcanizates (TPV (TPE-v or TPV)), thermoplastic copolyesters (TPC (TPE-E)), thermoplastic polyamides (TPA (TPE- A)), and copolymers and blends thereof. The TPE component can have any suitable structure, such as a linear, star, arborescent, comb, brush, centipede, hyperbranched, or dendritic structure.

In some embodiments, the TPE component can comprise a block copolymer having at least one elastomeric block. For example, the TPE component can comprise a polystyrene-polyisobutylene block copolymer, polystyrene-polybutadiene block copolymer, polystyrene-polyisoprene block copolymer, polystyrene-poly(ethylene-butylene block copolymer, polystyrene-poly(ethylene-propylene) block copolymer, a thermoplastic polyolefin (TPO), a dynamically vulcanized TPV, or a blend or copolymer thereof. In certain embodiments, the TPE component can comprise a polyisobutylene-based TPE (i.e., a block copolymer having at least one elastomeric polyisobutylene block). Examples of such polyisobutylene-based TPEs include polystyrene-polyisobutylene- polystyrene (SIBS). Linear triblock SIBS TPEs were introduced commercially in 2003 by Kaneka Co. of Japan. Such TPEs are described, for example, in U.S. Patent No. 4,946,899 and 4,946,899, each of which is hereby incorporated herein by reference in its entirety. Star-branched SIBS were subsequently developed, and considered the second generation with improved properties. The third generation, arborescent (dendritic, tree-like) SIBS TPEs were introduced in 2002. Such TPEs are described, for example, in U.S. Patent No. 6,747,098 and 8,748,530, each of which is hereby incorporated herein by reference in its entirety. A fourth generation of PIB-based TPEs (poly(alloocimene-isobutylene- alloocimene) or AIBA for short) have also been developed. Such TPEs are described, for example, in U.S. Patent No 9,790,301, which is hereby incorporated herein by reference in its entirety. Any of these polyisobutylene-based TPEs are suitable.

In some embodiments, the TPE component can comprise a linear polyisobutylene TPE, a star polyisobutylene TPE, or an arborescent polyisobutylene TPE.

In certain embodiments, the TPE component can comprise a linear polyisobutylene TPE that comprises an elastomeric midblock of polyisobutylene with a number average molecular weight of from about 10,000 to about 200,000 and a molecular weight distribution of from about 1.05 to about 1.6 and two plastomeric endblocks of at least one polymerized C8 to C12 monovinylidene aromatic monomer which may bear at least one Cl to C4 alkyl substituent or a bromine or chlorine atom on the aromatic ring comprising from about 5 to about 50 weight percent of a total of 100 weight percent of the linear triblock copolymer. In specific embodiments, the TPE component can comprise a linear polyisobutylene TPE that comprises an elastomeric midblock of polyisobutylene having a number average molecular weight of from about 35,000 to about 100,000 and a molecular weight distribution of from about 1.05 to about 1.6 and two plastomeric endbocks of polystyrene comprising from about 5 to about 50 weight percent of a total of 100 weight percent of the linear triblock copolymer.

In certain embodiments, the TPE component can comprise a star-shaped polyisobutylene TPE that comprises from three to six arms that comprise inner elastomeric blocks of polyisobutylene with a number average molecular weight of from about 10,000 to about 200,000 and outer plastomeric blocks of at least one polymerized C8 to C12 monovinylidene aromatic monomer which may bear at least one Cl to C4 alkyl substituent or a bromine or chlorine atom on the aromatic ring comprising from about 10 to about 55 weight percent of a total of 100 weight percent of the star-shaped block copolymer. In specific embodiments, the TPE component can comprise a star-shaped polyisobutylene TPE that comprises three arms that comprise inner elastomeric blocks of polyisobutylene with a number average molecular weight of from about 35,000 to about 100,000 and outer plastomeric blocks of polystyrene comprising from about 10 to about 55 weight percent of a total of 100 weight percent of the star-shaped block copolymer.

In some embodiments, the TPE component can comprise a linear polyisobutylene TPE, a star polyisobutylene TPE, an arborescent polyisobutylene TPE, a linear poly(isobutylene(OH)-b-(isobutylene-co-para-methylstyrene), a star poly(isobutylene(OH)- b-(isobutylene-co-para-methylstyrene), an arborescent poly(isobutylene(OH)-b- (isobutylene-co-para-methylstyrene), a linear poly(styrene-b-isobutylene-b-styrene), a star poly(styrene-b-isobutylene-b-styrene), an arborescent poly(styrene-b-isobutylene-b- styrene), a linear poly(isobutylene-OH-co-para-methyl styrene), a star poly(isobutylene-OH- co-para-m ethyl styrene), an arborescent poly(isobutylene-OH-co-para-methylstyrene), a linear poly(alloocimene-b-isobutylene-b-alloocimene), a star poly(alloocimene-b- isobutylene-b-alloocimene), or an arborescent poly(alloocimene-b-isobutylene-b- alloocimene). In one example, the TPE component can comprise an arborescent PIB-based TPE with poly (para-methyl styrene) end blocks (arbPIB-MS). In certain embodiments, the TPE component can comprises a linear triblock polystyrene-polyisobutylene-polystyrene copolymer (L SIBS).

In some embodiments, the TPE component can be present in the composite in an amount of at least about 10% by weight (e.g., at least about 15% by weight, at least about

20% by weight, at least about 25% by weight, at least about 30% by weight, at least about

35% by weight, at least about 40% by weight, at least about 45% by weight, at least about

50% by weight, at least about 55% by weight, at least about 60% by weight, at least about

75% by weight, at least about 80% by weight, or at least about 85% by weight), based on the total weight of the composite. In some embodiments, the TPE component can be present in the composite in an amount of about 90% by weight or less (e.g., about 85% by weight or less, about 80% by weight or less, about 75% by weight or less, about 70% by weight or less, about 65% by weight or less, about 60% by weight or less, about 55% by weight or less, about 50% by weight or less, about 45% by weight or less, about 40% by weight or less, about 35% by weight or less, about 30% by weight or less, about 25% by weight or less, about 20% by weight or less, or about 15% by weight or less), based on the total weight of the composite.

The TPE component can be present in the component in an amount ranging from any of the minimum values described above to any of the maximum values described above. For example, in some embodiments, the TPE component can be present in an amount from about 10% to about 90% by weight (e.g., from about 25% to about 90% by weight, from about 30% to about 65% by weight, or from about 40% to about 60% by weight), based on the total weight of the composite.

In one example, the composite can comprise a blend of butyl elastomers and block copolymers of polyisobutylene, such as the blends described in U.S. Patent No. 5,276,094, which is hereby incorporated herein by reference in its entirety.

Soft Elastomeric Polymer Components

Suitable polymers for use as the soft elastomeric polymer component include polyisobutylene, polyisobutylene-isoprene copolymers, polyisobutylene-styrene copolymers, polyisobutylene-alkyl styrene copolymers, halogenated polyisobutylene-alkyl styrene terpolymers, polybutadiene, polyisoprene, polyethylene-propylene copolymers, polyethylene-propylene diene terpolymers. Polyisobutylene, polyisobutylene-isoprene copolymers, particularly preferred. Selection of an optimum polymer may depend upon the exact mechanical properties required of it, which may depend to at least some extent on the amount of it to be incorporated in the composite and the relative physical properties of soft elastomeric polymer component and the TPE component, and possibly any other components of the composite which are present, including the filler.

In some embodiments, the soft elastomeric polymer component can comprise polyisobutylene, a polyisobutylene-isoprene copolymer, a polyisobutylene-styrene copolymer, polyisobutylene-alkyl styrene copolymers, halogenated polyisobutylene-alkyl styrene terpolymers, polybutadiene, polyisoprene, polyethylene-propylene copolymers, polyethylene-propylene diene terpolymers, and combinations thereof. In certain embodiments, the soft elastomeric polymer component can comprise polyisobutylene, a polyisobutylene-isoprene copolymer, or any combination thereof.

In certain embodiments, the soft elastomeric polymer component can comprise a butyl rubber. Butyl rubber is well known in the art and is a polymer of a C4 to Ce isoolefin, preferably isobutylene, and a C4 to Cx conjugated diolefin, preferably isoprene. A preferred butyl polymer contains from about 97 to 99.5 weight percent of isobutylene and from about 0.5 to about 3 weight percent of isoprene. Butyl rubber typically has a molecular weight expressed as the Mooney (MLl+8 at 125° C.), of from about 25 to about 65, preferably from about 40 to about 60.

In some embodiments, the soft elastomeric polymer component can be present in the composite in an amount of at least about 10% by weight (e.g., at least about 15% by weight, at least about 20% by weight, at least about 25% by weight, at least about 30% by weight, at least about 35% by weight, at least about 40% by weight, at least about 45% by weight, at least about 50% by weight, at least about 55% by weight, at least about 60% by weight, at least about 75% by weight, at least about 80% by weight, or at least about 85% by weight), based on the total weight of the composite. In some embodiments, the soft elastomeric polymer component can be present in the composite in an amount of about 90% by weight or less (e.g., about 85% by weight or less, about 80% by weight or less, about 75% by weight or less, about 70% by weight or less, about 65% by weight or less, about 60% by weight or less, about 55% by weight or less, about 50% by weight or less, about 45% by weight or less, about 40% by weight or less, about 35% by weight or less, about 30% by weight or less, about 25% by weight or less, about 20% by weight or less, or about 15% by weight or less), based on the total weight of the composite.

The soft elastomeric polymer component can be present in the component in an amount ranging from any of the minimum values described above to any of the maximum values described above. For example, in some embodiments, the soft elastomeric polymer component can be present in an amount from about 10% to about 90% by weight (e.g., from about 25% to about 90% by weight, from about 30% to about 65% by weight, or from about 40% to about 60% by weight), based on the total weight of the composite.

Fillers

The filler, when present, can comprise any suitable filler material. Examples of fillers include precipitated hydrated silica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate, zinc sulfate, barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates (e.g., calcium carbonate, zinc carbonate, barium carbonate, and magnesium carbonate), metals (e.g., titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, lead, copper, boron, cobalt, beryllium, zinc, and tin), metal alloys (e.g., steel, brass, bronze, boron carbide whiskers, and tungsten carbide whiskers), oxides (e.g., zinc oxide, tin oxide, iron oxide, calcium oxide, aluminum oxide, titanium dioxide, magnesium oxide, and zirconium oxide), particulate carbonaceous materials (e.g., graphite, carbon black, cotton flock, natural bitumen, cellulose flock, and leather fiber), microballoons (e.g., glass and ceramic), fly ash, regrind (i.e., core material that is ground and recycled), nanofillers and combinations thereof.

In some embodiments, the filler can comprise an antimicrobial filler. The antimicrobial filler can be an inorganic material that comprises one more more antimicrobial metals (e.g., silver, copper, zinc, and combinations thereof). In some examples, the antimicrobial filler can comprise zinc oxide, carbon black, or any combination thereof.

In some embodiments, the filler can be present in the composite in an amount of at least about 2% by weight (e.g., at least about 5% by weight, at least about 10% by weight, at least about 15% by weight, at least about 20% by weight, at least about 25% by weight, at least about 30% by weight, or at least about 35% by weight), based on the total weight of the composite. In some embodiments, the filler can be present in the composite in an amount of about 40% by weight or less (e.g., about 35% by weight or less, about 30% by weight or less, about 25% by weight or less, about 20% by weight or less, about 15% by weight or less, about 10% by weight or less, or about 5% by weight or less), based on the total weight of the composite.

The filler can be present in the component in an amount ranging from any of the minimum values described above to any of the maximum values described above. For example, in some embodiments, the filler can be present in an amount from about 2% to about 40% by weight (e.g., from about 2% to about 30% by weight, from about 5% to about 30% by weight, from about 5% to about 25% by weight, or from about 5% to about 20% by weight), based on the total weight of the composite.

Other Additives

The composite can optionally include one or more additional additives. Typically, the amount of additives other than the TPE component, soft elastomeric polymer component, and filler is no greater than about 25% by weight, desirably, no greater than about 10% by weight, or no greater than 5% by weight, based on the total weight of the composite. Suitable additives include, but are not limited to, stabilizers, plasticizers, tackifiers, flow control agents, cure rate retarders, adhesion promoters (for example, silanes and titanates), adjuvants, impact modifiers, expandable microspheres, thermally conductive particles, electrically conductive particles, colorants such as dyes and/or pigments, antioxidants, optical brighteners, antimicrobial agents, surfactants, wetting agents, fire retardants, and repellents such as hydrocarbon waxes, silicones, fluorochemicals, antistatic agents, odor control agents, perfumes and fragrances, combinations thereof, and the like.

One or more of the above-described additives may be used to reduce the weight and/or cost of the resulting fiber and layer, adjust viscosity, or modify the thermal properties of the fiber or confer a range of physical properties derived from the physical property activity of the additive including electrical, optical, density-related, liquid barrier or adhesive tack related properties.

In some embodiments, the composite can further comprise a plasticizer. In some cases, the plasticizer can comprise poly(ethylene glycol), oligomeric polyesters, fatty acid monoesters and di-esters, citrate esters, glycols such glycerin; propylene glycol, polyethoxylated phenols, mono or polysubstituted polyethylene glycols, higher alkyl substituted N-alkyl pyrrolidones, sulfonamides, triglycerides, citrate esters, esters of tartaric acid, benzoate esters, polyethylene glycols and ethylene oxide propylene oxide random and block copolymers having a molecular weight no greater than 10,000 Daltons (Da), preferably no greater than about 5,000 Da, more preferably no greater than about 2,500 Da; and combinations thereof.

In some embodiments, the composite can further comprise an antimicrobial agent (other than the filler described above). The antimicrobial agent may be added to impart antimicrobial activity to the fibers. The antimicrobial agent is the component that provides at least part of the antimicrobial activity, i.e., it has at least some antimicrobial activity for at least one microorganism. In some exemplary embodiments, a suitable antimicrobial agent may be selected from a fatty acid monoester, a fatty acid di-ester, an organic acid, a silver compound, a quaternary ammonium compound, a cationic (co)polymer, an iodine compound, or combinations thereof. Other examples of antimicrobial include those described in U.S. Patent Application Publication No. 2008/0142023, which is hereby incorporated by reference herein in its entirety.

Surface Treatment of Webs

The nonwoven fibrous webs described herein may be rendered more repellent by treatment with numerous compounds. For example, the nonwovens may be subjected to post web forming surface treatments which include paraffin waxes, fatty acids, bee's wax, silicones, fluorochemicals and combinations thereof. For example, the repellent finishes may be applied as disclosed in U.S. Pat. Nos. 5,027,803; 6,960,642; and 7,199,197, all of which are incorporated by reference herein in its entirety. Repellent finishes may also be melt additives such as those described in U.S. Pat. No. 6,262,180, which is incorporated by reference herein in its entirety.

Preferred fluorochemicals comprise a perfluoroalkyl group having at least 4 carbon atoms. These fluorochemicals may be small molecules, oligamers, or polymers. Silicone fluid repellents also may be suitable. In some instances hydrocarbon-type repellents may also be suitable.

Classes of fluorochemical agents or compositions useful in this invention include compounds and polymers containing one or more fluoroaliphatic radicals, Rf. In general, fluorochemical agents or compositions useful as a repellent additive comprise fluorochemical compounds or polymers containing fluoroaliphatic radicals or groups, Rf. The fluoroaliphatic radical, Rf, is a fluorinated, stable, inert, non-polar, preferably saturated, monovalent moiety which is both hydrophobic and oleophobic. It can be straight chain, branched chain, or, if sufficiently large, cyclic, or combinations thereof, such as alkylcycloaliphatic radicals. The skeletal chain in the fluoroaliphatic radical can include catenary divalent oxygen atoms and/or tri valent nitrogen atoms bonded only to carbon atoms. Generally Rf will have 3 to 20 carbon atoms, preferably 6 to about 12 carbon atoms, and will contain about 40 to 78 weight percent, preferably 50 to 78 weight percent, carbon- bound fluorine. The terminal portion of the Rf group has at least one trifluoromethyl group, and preferably has a terminal group of at least three fully fluorinated carbon atoms, e.g., CF3CF2CF2 — . The preferred Rf groups are fully or substantially fluorinated, as in the case where Rf is perfluroalkyl, CnF2n+l — .

Examples of such compounds include, for example, fluorochemical urethanes, ureas, esters, amines (and salts thereof), amides, acids (and salts thereof), carbodiimides, guanidines, allophanates, biurets, and compounds containing two or more of these groups, as well as blends of these compounds.

Useful fluorochemical polymers containing Rf radicals include copolymers of fluorochemical acrylate and/or methacrylate monomers with co-polymerizable monomers, including fluorine-containing and fluorine-free monomers, such as methyl methacrylate, butyl acrylate, octadecyl methacrylate, acrylate and methacrylate esters of poly(oxyalkylene) polyol oligomers and polymers, e.g., poly(oxy ethylene) glycol dimethacrylate, glycidyl methacrylate, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, vinylidene fluoride, acrylonitrile, vinyl chloroacetate, isoprene, chloroprene, styrene, butadiene, vinylpyridine, vinyl alkyl esters, vinyl alkyl ketones, acrylic and methacrylic acid, 2-hydroxyethyl acrylate, N-methylolacrylamide, 2-(N,N,N- trimethylammonium)ethyl methacrylate and the like.

The relative amounts of various comonomers which can be used with the fluorochemical monomer will generally be selected empirically, and will depend on the substrate to be treated, the properties desire from the fluorochemical treatment, i.e., the degree of oil and/or water repellency desired, and the mode of application to the substrate.

Useful fluorochemical agents or compositions include blends of the various classes of fluorochemical compounds and/or polymers described above. Also, blends of these fluorochemical compounds or polymers with fluorine-free compounds, e.g., N-acyl aziridines, or fluorine-free polymers, e.g., polyacrylates such as poly(methyl methacrylate) and poly(methyl methacrylate-co-decyl acrylate), polysiloxanes and the like.

The fluorochemical agents or compositions can include non-interfering adjuvants such as wetting agents, emulsifiers, solvents (aqueous and organic), dyes, biocides, fillers, catalysts, curing agents and the like. The final fluorochemical agent or composition should contain, on a solids basis, at least about 5 weight percent, preferably at least about 10 weight percent carbon-bound fluorine in the form of said Rf groups in order to impart the benefits described in this invention. Such fluorochemicals are generally known and commercially available as perfluoroaliphatic group bearing water/oil repellent agents which contain at least 5 percent by weight of fluorine, preferably 7 to 12 percent of fluorine in the available formulations.

By the reaction of the perfluoroaliphatic thioglycols with diisocyanates, there results perfluoroaliphatic group-bearing polyurethanes. These products are normally applied in aqueous dispersion for fiber treatment. Such reaction products are described in U.S. Pat. No. 4,054,592, incorporated herein by reference.

Another group of suitable compounds are perfluoroaliphatic group-bearing N- methylol condensation products. These compounds are described in U.S. Pat. No.

4,477,498, incorporated herein by reference where the emulsification of such products is dealt with in detail.

The perfluoroaliphatic group-bearing polycarbodimides are, e.g., obtained by reaction of perfluoroaliphatic sulfonamide alkanols with polyisocyanates in the presence of suitable catalysts. This class of compounds can be used by itself, but often is used with other Rf-group bearing compounds, especially with (co)polymers. Thus, another group of compounds which can be used in dispersions is mentioned. Among these compounds all known polymers bearing fluoroaliphatic residues can be used, also condensation polymers, such as polyesters and polyamides which contain the corresponding perfluoroaliphatic groups, are considered but especially (co)polymers on the basis of e.g. Rf-acrylates and Rf- methacrylates, which can contain different fluorine-free vinyl compounds as comonomers.

In DE-A 2310 801, these compounds are discussed in detail. The manufacture of Rf-group bearing polycarbodimides as well as the combination of these compounds with each other is also described in detail.

Besides the aforementioned perfluoroaliphatic group-bearing agents, further fluorochemical components may be used, for example, Rf-group-bearing guanidines, U.S. Pat. No. 4,540,479, Rf-group-bearing allophanates, U.S. Pat. No. 4,606,737 and Rf-group- bearing biurets, U.S. Pat. No. 4,668,406, the disclosures which are incorporated herein by reference. These classes are mostly used in combination. Others include fluoroalkyl- substituted siloxanes, e.g., CF3(CF2) ₆ CH20(CH2)3Si(0C2H5)3 — .

The useful compounds show, in general, one or more perfluoroaliphatic residues with preferably at least 4 carbon atoms, especially 4 to 14 atoms each. An exemplary fluorochemical is a formulation of 70% solvents and 30% emulsified solid fluorochemical polymers. The formulation includes as solvents 11% methyl isobutyl ketone, 6% ethylene glycol and 53% water. The fluorochemical polymers are a 50/50 blend of 5/95 copolymer of butyl acrylate and CsFnSC^CFE^FEC) — CCH=CH2 prepared as described in U.S. Pat.

No. 3,816,229, incorporated herein by reference (see especially column 3, lines 66-68 and column 4, lines 1-11) for a 10/90 copolymer. The second component of the 50/50 blend is a copolymer prepared from 1 mole of a tri -functional phenyl isocyanate (available from Upjohn Company under the name PAPI), 2 moles of CsFivN^FhCFbjCFhCFhOH and 1 mole of stearyl alcohol prepared as described in U.S. Pat. No. 4,401,780, incorporated herein by reference (see especially Table 1, C2 under footnote A). Emulsifiers used are conventional commercially available materials such as polyethoxylated quaternary ammonium compounds (available under the name 5% Ethoquad 18/25 from Akzo Chemie America) and 7.5% of a 50/50 mixture of C8Fi7S02NHC ₃ H6N(CH ₃ ) ₃ Cl and a polyethoxylated sorbitan monooleate (available from ICI Limited under the name TWEEN 80). Such fluorochemicals are non-yellowing and particularly non-irritating to the skin as well as providing articles that are stable having excellent long term aging properties. Exemplary fluorochemicals are available under the trade designations SCOTCHGARD, SCOTCH-RELEASE, and 3M BRAND TEXTILE CHEMICAL and are commercially from the 3M Company. Other commercially available materials include materials that use fluorotelomer chemistry materials provided by DuPont (available from duPont deNemours and Company, Wilmington, Del.).

Suitable silicones for use to obtain the low surface energy layers of the instant invention include any of the silicones known to those skilled in the art to provide water repellency and optionally oil repellency to fibers and films. Silicone fluids typically consist of linear polymers of rather low molecular weight, namely about 4000-25,000. Most commonly the polymers are polydimethylsiloxanes.

For use as fluids with enhanced thermal stability, silicones containing both methyl and phenyl groups are often used. Generally, the phenyl groups make up 10-45% of the total number of substituent groups present. Such silicones are generally obtained by hydrolysis of mixtures of methyl- and phenylchlorosilanes. Fluids for use in textile treatment may incorporate reactive groups so that they may be cross-linked to give a permanent finish. Commonly, these fluids contain Si — H bonds (introduced by including methyldichlorosilane in the polymerization system) and cross-linking occurs on heating with alkali.

Examples of suitable silicones are those available from Dow-Corning Corporation such as C2-0563 and from General Electric Corporation such as GE-SS4098. Especially preferred silicone finishes are disclosed in U.S. Pat. No. 5,045,387.

Methods of Forming Fibers and Webs

Also provided are methods of making fibrous nonwoven webs. These methods can comprise forming a plurality of fibers from a composite comprising: (i) a thermoplastic elastomeric polymer (TPE) component; (ii) a soft elastomeric polymer component that at ambient temperatures is above its glass transition temperature; and (iii) optionally a filler; and collecting at least a portion of the fibers to form a nonwoven web.

In some embodiments, the methods can further comprises combining (e.g., melt processing) the TPE component, the soft elastomeric polymer component, and the filler (when present) to form the composite. The composite may be manufactured by conventional methods well known in polymer technology, as are well known to the person skilled in the art and well described in the literature. For example, the TPE component, the soft elastomeric polymer component, and the filler (when present) can be combined in a standard type of mixer until a completely homogeneous matrix is formed, optionally with further heating if necessary. Then the composite may be cooled and passed to the next processing stage, which is preferably fiber formation. Alternatively, the composite can be formed into pellets, etc. which can be stored and subsequently processed into fibers.

Any suitable method of fiber formation may be used, such as a melt-blowing, spun- bonding, or melt-spinning process. The population of fibers comprises population of fine fibers, a population of microfibers, a population of ultrafme microfibers, a population of sub-micrometer fibers, or any combination thereof. Suitable methods of fiber formation can be selected, for example, based on the desired fiber dimensions. [In some examples, the web can be formed using melt-spinning, filament extrusion, electrospinning, gas jet fibrillation or combinations thereof.

In some embodiments, the nonwoven fibrous webs may include fine fibers that are substantially sub-micrometer fibers, fine fibers that are substantially microfibers, or combinations thereof. In some embodiments, a nonwoven fibrous web may be formed of sub-micrometer fibers commingled with coarser microfibers providing a support structure for the sub-micrometer nonwoven fibers. The support structure may provide the resiliency and strength to hold the fine sub-micrometer fibers in the preferred low solidity form. The support structure could be made from a number of different components, either singly or in concert. Examples of supporting components include, for example, microfibers, discontinuous oriented fibers, natural fibers, foamed porous cellular materials, and continuous or discontinuous non oriented fibers.

Sub-micrometer fibers are typically very long, though they are generally regarded as discontinuous. Their long lengths — with a length-to-diameter ratio approaching infinity in contrast to the finite lengths of staple fibers — causes them to be better held within the matrix of microfibers. They are usually organic and polymeric and often of the molecularly same polymer as the microfibers. As the streams of sub -micrometer fiber and microfibers merge, the sub-micrometer fibers become dispersed among the microfibers. A rather uniform mixture may be obtained, especially in the x-y dimensions, or plane of the web, with the distribution in the z dimension being controlled by particular process steps such as control of the distance, the angle, and the mass and velocity of the merging streams.

The relative amount of sub -micrometer fibers to microfibers included in a nonwoven fibrous web can be varied depending on the intended use of the web. An effective amount, i.e., an amount effective to accomplish desired performance, need not be large in weight amount. Usually the microfibers account for at least one weight percent and no greater than about 75 weight percent of the fibers of the web. Because of the high surface area of the microfibers, a small weight amount may accomplish desired performance. In the case of webs that include very small microfibers, the microfibers generally account for at least 5 percent of the fibrous surface area of the web, and more typically 10 or 20 percent or more of the fibrous surface area.

In one exemplary embodiment, a microfiber stream is formed and a sub-micrometer fiber stream is separately formed and added to the microfiber stream to form the nonwoven fibrous web. In another exemplary embodiment, a sub-micrometer fiber stream is formed and a microfiber stream is separately formed and added to the sub -micrometer fiber stream to form the nonwoven fibrous web. In these exemplary embodiments, either one or both of the sub-micrometer fiber stream and the microfiber stream is oriented. In an additional embodiment, an oriented sub-micrometer fiber stream is formed and discontinuous microfibers are added to the sub-micrometer fiber stream, e.g. using a process as described in U.S. Pat. No. 4,118,531 (Hauser).

In some exemplary embodiments, the method of making nonwoven fibrous web comprises combining the sub-micrometer fiber population and the microfiber population into a nonwoven fibrous web by mixing fiber streams, hydroentangling, wet forming, plexifilament formation, or a combination thereof. In combining the sub-micrometer fiber population with the microfiber population, multiple streams of one or both types of fibers may be used, and the streams may be combined in any order. In this manner, nonwoven composite fibrous webs may be formed exhibiting various desired concentration gradients and/or layered structures.

For example, in certain exemplary embodiments, the population of sub-micrometer fibers may be combined with the population of microfibers to form an inhomogenous mixture of fibers. In other exemplary embodiments, the population of sub-micrometer fibers may be formed as an overlayer on an underlayer comprising the population of microfibers.

In certain other exemplary embodiments, the population of microfibers may be formed as an overlayer on an underlayer comprising the population of sub-micrometer fibers

In other exemplary embodiments, the nonwoven fibrous article may be formed by depositing the population of sub-micrometer fibers onto a support layer, the support layer optionally comprising microfibers, so as to form a population of sub-micrometer fibers on the support layer or substrate. The method may comprise a step wherein the support layer, which optionally comprises polymeric microfibers, is passed through a fiber stream of sub- micrometer fibers having a median fiber diameter of no greater than 1 micrometer (mih). While passing through the fiber stream, sub-micrometer fibers may be deposited onto the support layer so as to be temporarily or permanently bonded to the support layer. When the fibers are deposited onto the support layer, the fibers may optionally bond to one another, and may further harden while on the support layer.

A number of processes may be used to produce and deposit sub-micrometer fibers, including, but not limited to melt blowing, melt spinning, or combination thereof. Particularly suitable processes include, but are not limited to, processes disclosed in U.S. Pat. No. 3,874,886 (Levecque et al.), U.S. Pat. No. 4,363,646 (Torobin), U.S. Pat. No. 4,536,361 (Torobin), U.S. Pat. No. 5,227,107 (Dickenson et al.), U.S. Pat. No. 6,183,670 (Torobin), U.S. Pat. No. 6,743,273 (Chung et al.), U.S. Pat. No. 6,800,226 (Gerking), and DE 19929709 C2 (Gerking), the entire disclosures of which are incorporated herein by reference.

Suitable processes for forming sub-micrometer fibers also include electrospinning processes, for example, those processes described in U.S. Pat. No. 1,975,504 (Formhals), the entire disclosures of which are incorporated herein by reference. Other suitable processes for forming sub-micrometer fibers are described in U.S. Pat. No. 6,114,017 (Fabbricante et al.); U.S. Pat. No. 6,382,526 B1 (Reneker et al.); and U.S. Pat. No.

6,861,025 B2 (Erickson et al.), the entire disclosures of which are incorporated herein by reference.

The methods of making nonwoven fibrous webs may be used to form a sub micrometer fiber component containing fibers formed from any of the above-mentioned composites. Typically, the sub -micrometer fiber forming method step involves melt extruding a thermoformable material at a melt extrusion temperature ranging from about 130° C. to about 350° C. A die assembly and/or coaxial nozzle assembly (see, for example, the Torobin process referenced above) comprises a population of spinnerets and/or coaxial nozzles through which molten thermoformable material is extruded. In one exemplary embodiment, the coaxial nozzle assembly comprises a population of coaxial nozzles formed into an array so as to extrude multiple streams of fibers onto a support layer or substrate. See, for example, U.S. Pat. No. 4,536,361 (FIG. 2) and U.S. Pat. No. 6,183,670 (FIGS. 1-2).

A number of processes may be used to produce and deposit microfibers, including, but not limited to, melt blowing, melt spinning, filament extrusion, plexifilament formation, spunbonding, wet spinning, dry spinning, or a combination thereof. Suitable processes for forming microfibers are described in U.S. Pat. No. 6,315,806 (Torobin); U.S. Pat. No. 6,114,017 (Fabbricante et al.); U.S. Pat. No. 6,382,526 B1 (Reneker et al.); and U.S. Pat.

No. 6,861,025 B2 (Erickson et al.). Alternatively, a population of microfibers may be formed or converted to staple fibers and combined with a population of sub-micrometer fibers using, for example, using a process as described in U.S. Pat. No. 4,118,531 (Hauser), the entire disclosure of which is incorporated herein by reference. In certain exemplary embodiments, the population of microfibers comprises a web of bonded microfibers, wherein bonding is achieved using thermal bonding, adhesive bonding, powdered binder, hydroentangling, needlepunching, calendering, or a combination thereof, as described below.

A variety of equipment and techniques are known in the art for melt processing polymeric fine fibers. Such equipment and techniques are disclosed, for example, in U.S. Pat. No. 3,565,985 (Schrenk et al.); U.S. Pat. No. 5,427,842 (Bland et. al.); U.S. Pat. Nos. 5,589,122 and 5,599,602 (Leonard); and U.S. Pat. No. 5,660,922 (Henidge et al.). Examples of melt processing equipment include, but are not limited to, extruders (single and twin screw), Banbury mixers, and Brabender extruders for melt processing the inventive fine fibers.

The (BMF) meltblowing process is one particular exemplary method of forming a nonwoven web where a polymer fluid, either molten or as a solution, is extruded through one or more rows of holes then impinged by a high velocity gas jet. The gas jet, typically heated air, entrains and draws the polymer fluid and helps to solidify the polymer into a fiber. The solid fiber is then collected on solid or porous surface as a nonwoven web. This process is described by Van Wente in “Superfine Thermoplastic Fibers”, Industrial Engineering Chemistry, vol. 48, pp. 1342-1346. An improved version of the meltblowing process is described by Buntin et al. as described in U.S. Pat. No. 3,849,241, and incorporated by reference herein in its entirety.

Depending on the condition of the fibers, some bonding may occur between the fibers during collection. However, further bonding between the fibers in the collected web can be needed to provide a matrix of desired coherency, making the web more handleable and better able to hold the fibers within the matrix (“bonding” fibers means adhering the fibers together firmly, so they generally do not separate when the web is subjected to normal handling). Conventional bonding techniques using heat and pressure applied in a point-bonding process or by smooth calender rolls can be used, though such processes may cause undesired deformation of fibers or compaction of the web. Another technique for bonding the fibers is taught in U.S. Patent Application Publication No. 2008/0038976. Apparatus for performing this technique is illustrated in FIGS. 1, 5 and 6 of the drawings. In brief summary, as applied to the present disclosure, this preferred technique involves subjecting the collected web to a controlled heating and quenching operation that includes a) forcefully passing through the web a gaseous stream heated to a temperature sufficient to soften the fibers sufficiently to cause the fibers to bond together at points of fiber intersection (e.g., at sufficient points of intersection to form a coherent or bonded matrix), the heated stream being applied for a discrete time too short to wholly melt the fibers, and b) immediately forcefully passing through the web a gaseous stream at a temperature at least 50°C. no greater than the heated stream to quench the fibers (as defined in the above-mentioned U.S. Patent Application Publication No. 2008/0038976, “forcefully” means that a force in addition to normal room pressure is applied to the gaseous stream to propel the stream through the web; “immediately” means as part of the same operation, i.e., without an intervening time of storage as occurs when a web is wound into a roll before the next processing step). As a shorthand term this technique is described as the quenched flow heating technique, and the apparatus as a quenched flow heater.

Treatment of the collected web at such a temperature is found to cause the microfibers to become morphologically refined, which is understood as follows (we do not wish to be bound by statements herein of our “understanding,” which generally involve some theoretical considerations). As to the amorphous-characterized phase, the amount of molecular material of the phase susceptible to undesirable (softening-impeding) crystal growth is not as great as it was before treatment. The amorphous-characterized phase is understood to have experienced a kind of cleansing or reduction of molecular structure that would lead to undesirable increases in crystallinity in conventional untreated fibers during a thermal bonding operation. Treated fibers of certain exemplary embodiments of the present invention may be capable of a kind of “repeatable softening,” meaning that the fibers, and particularly the amorphous-characterized phase of the fibers, will undergo to some degree a repeated cycle of softening and resolidifying as the fibers are exposed to a cycle of raised and lowered temperature within a temperature region lower than that which would cause melting of the whole fiber. In practical terms, repeatable softening is indicated when a treated web (which already generally exhibits a useful bonding as a result of the heating and quenching treatment) can be heated to cause further autogenous bonding of the fibers. The cycling of softening and resolidifying may not continue indefinitely, but it is generally sufficient that the fibers may be initially bonded by exposure to heat, e.g., during a heat treatment according to certain exemplary embodiments of the present invention, and later heated again to cause re-softening and further bonding, or, if desired, other operations, such as calendering or re-shaping. For example, a web may be calendered to a smooth surface or given a nonplanar shape, e.g., molded into a face mask, taking advantage of the improved bonding capability of the fibers (though in such cases the bonding is not limited to autogenous bonding).

The diameters of the fibers can be tailored to provide needed filtration, acoustic absorption, and other properties. For example it may be desirable for the microfibers to have a median diameter of 5 to 50 micrometers (pm) and the sub-micrometer fibers to have a median diameter from 0.1 pm to no greater than 1 pm, for example, 0.9 pm. Preferably the microfibers have a median diameter between 5 pm and 50 pm, whereas the sub-micrometer fibers preferably have a median diameter of 0.5 pm to no greater than 1 pm, for example,

0.9 pm.

Various procedures are also available for electrically charging a dimensionally stable nonwoven fibrous web to enhance its filtration capacity: see e.g., U.S. Pat. No. 5,496,507 (Angadjivand).

In addition to the foregoing methods of making a nonwoven fibrous web, one or more of the following process steps may be carried out on the web once formed:

(1) advancing the nonwoven fibrous web along a process pathway toward further processing operations;

(2) bringing one or more additional layers into contact with an outer surface of the nonwoven web;

(3) calendering the nonwoven fibrous web;

(4) coating the nonwoven fibrous web with a surface treatment or other composition (e.g., a fire retardant composition, an adhesive composition, or a print layer);

(5) attaching the nonwoven fibrous web to a cardboard or plastic tube;

(6) winding-up the nonwoven fibrous web in the form of a roll; (7) slitting the nonwoven fibrous web to form two or more slit rolls and/or a plurality of slit sheets;

(8) placing the nonwoven fibrous web in a mold and molding the nonwoven fibrous web into a new shape;

(9) applying a release liner over an exposed optional pressure-sensitive adhesive layer, when present; and

(10) attaching the nonwoven fibrous web to another substrate via an adhesive or any other attachment device including, but not limited to, clips, brackets, bolts/screws, nails, and straps.

Articles Formed From Nonwoven Fibrous Webs

The present disclosure is also directed to methods of using the nonwoven fibrous webs of the present disclosure in a variety of applications. In a further aspect, the disclosure relates to an article comprising a nonwoven fibrous web according to the present disclosure. In exemplary embodiments, the article may be used as a gas filtration article, a liquid filtration article, a sound absorption article, a thermal insulation article, a surface cleaning article (e.g., wipe), a cellular growth support article, a drug delivery article, a personal hygiene article, a dental hygiene article, a surgical drape, a surgical equipment isolation drape, a medical isolation drape, a surgical gown, a medical gown, healthcare patient gowns and attire, an apron or other apparel, a sterilization wrap, a wipe, agricultural fabrics, food packaging, packaging, a tape backing, or a wound dressing article.

In certain embodiments, a nonwoven fibrous web of the present disclosure may be advantageous in gas filtration applications. Gas filters such as this may be particularly useful in personal protection respirators; heating, ventilation and air conditioning (HVAC) filters; automotive air filters (e.g., automotive engine air cleaners, automotive exhaust gas filtration, automotive passenger compartment air filtration); and other gas-particulate filtration applications.

Various embodiments of the presently disclosed invention also provides useful articles made from fabrics and webs of fine fibers including medical drapes, medical gowns, aprons, filter media, industrial wipes and personal care and home care products such as diapers, facial tissue, facial wipes, wet wipes, dry wipes, disposable absorbent articles and garments such as disposable and reusable garments including infant diapers or training pants, adult incontinence products, feminine hygiene products such as sanitary napkins and panty liners and the like. The fibers and nonwoven webs described herein may also may be useful for producing clothing, thermal insulation for garments such as coats, jackets, gloves, cold weather pants, boots, and the like as well as acoustical insulation.

Other medical devices that may be made, in whole or in part, of the fibers and/or nonwoven webs described herein include: surgical mesh, slings, orthopedic pins (including bone filling augmentation material), adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, atrial septal defect repair devices, pericardial patches, bulking and filling agents, vein valves, bone marrow scaffolds, meniscus regeneration devices, ligament and tendon grafts, ocular cell implants, spinal fusion cages, skin substitutes, dural substitutes, bone graft substitutes, bone dowels, and hemostats.

It is believed that the nonwoven webs described herein can be sterilized by gamma radiation or electron beam without significant loss of physical strength (tensile strength for a 1 mil thick film does not decrease by more than 20% and preferably by not more than 10% after exposure to 2.5 Mrad gamma radiation from a cobalt gamma radiation source and aged at 23° C.-25° C. for 7 days). Similarly, it is expected that the nonwoven materials described herein can be sterilized by exposure to electron beam irradiation. Alternatively, the nonwoven webs described herein can be sterilized by gas or vapor phase antimicrobial agents such as ethylene oxide, hydrogen peroxide plasma, peracetic acid, ozone, and similar alkylating and/or oxidizing agents.

EXAMPLES

The invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of non- critical parameters which can be changed or modified to yield essentially the same results.

Overview

Since the breakout of COVID-19, there has been an increased interest in Personal Protective Equipment (PPE) such as face masks. At times, these materials have been in critical short supply. The currently available cloth face masks do not protect the wearer but mitigate the possibility of spreading the virus. N95 masks do protect the wearer but consistent supply has been problematic in the midst of the pandemic. In addition, existing masks are generally not very comfortable and absorb moisture from breath. We propose to develop a new technology for face mask manufacturing based on polymer (polyisobutylene-based) fiber mats. A polyisobutylene-based polymer (SIBS) forms the matrix of the drug eluting coating on coronary stents sold under the tradename TAXUS. These stents have a long history of clinical use; they were approved by the FDA for clinical use in 2004 and have since been implanted into over 6 million people. As described herein, SIBS can be combined with a filler (an antimicrobial filler) and processed into a nonwoven fiber mat using a suitable fiber-forming technology. For example, a polyisobutylene thermoplastic elastomer was combined with a zinc oxide filler and electrospun to form water-repellent rubbery mats. These mats were not cytotoxic and in principle could exhibit antimicrobial activity resulting from the ZnO loaded in the polymer fibers. These mats could be fashioned into facemasks and other PPE such as gowns etc.

Background

Electrospinning is a versatile and unique technique to produce fibers in the range of microns to nanometers from polymer solutions using electrostatic forces [1] These fibers with smaller pores and higher surface area have great potential in the biomedical industry because of the ease of fabrication of fibers from a wide array of polymers - biodegradable, non-degradable, synthetic, natural, or their blends. Some synthetic biocompatible polymers can be easily spun into fiber mats to make stretchable wound dressings, flexible scaffolds for cell growth and tissue engineering, and implantable membranes/coatings with the capability of controlled drug delivery.

Elastomers, which have the elasticity of natural rubber, are widely used in industry due to their durable and tough nature. Since elastomers have low glass transition temperature, it is very difficult to electrospin them into stable nanofibers. Also, the electrospun fibers on the collector may fuse quickly into large fibers or sometimes even a continuous film [2] Electrospinning of thermoplastic elastomers (TPEs) is easier since they can be processed as plastics but exhibit elastomeric properties. Various TPEs have been electrospun in the last two decades. Sencadas et al. studied the electrospinning of poly(styrene-Z>-butadiene-Z>-styrene) (SBS) TPE into fiber membranes and showed that the membranes were hydrophobic with a contact angle of 132° and the tensile strength was 0.525 MPa with 345% elongation at break [3] These authors also explained that the mechanical strength of the mat was lower than that of the bulk material (SBS) because of the higher porosity of the fibrous membrane. Since the fibers were not orderly arranged in the nonwoven membrane, and only a small portion of the fibers resisted to the applied mechanical loading which caused less chain entanglements per unit mass of the porous membrane. The electrospinning of poly(styrene-b-isoprene-b-styrene) TPEs was demonstrated by Supaphol et al. and they produced fibers in the range of 2.7-16 pm [4] Although electrospinning can produce ultrafme fibers, but their fibers were uncharacteristically large. They theorized that TPE molecules usually stretch while flowing through a restricted channel of the nozzle and after leaving recoiling occurs very fast which could prevent Coulombic stretching to decrease the fiber diameter. Similarly, larger fiber diameter (6 pm) was also found for poly(styrene-Z>-(ethylene-co-l-butene)-Z>-styrene) triblock copolymer (SEBS) fibers [5]

We have focused on polyisobutylene (PIB)-based TPEs because of the excellent bioinertness and biostability of PIB. A linear poly(styrene-/>-isobutylene-/>-styrene) triblock copolymer (L SIBS), a TPE is used in clinical practice as a polymer matrix of a drug eluting coating on the TAXUS coronary stent [6] Over 6 million patients have benefited from this device, emphasizing the significance of PIB-based biomaterials. Due to the unique low permeability of L SIBS, sustained drug delivery is achieved, but only approximately 10% of the encapsulated drug, Taxol, elutes from the coating, which is therapeutic for this application. After the success of L SIBS, we developed another TPE, Arbomatrix, comprising a branched {arborescent or dendritic) PIB core and end blocks of poly (71- methyl styrene) (PMS) [7,8] Arbomatrix and its carbon composite was also shown to be bioinert in a rabbit model [9] ElectroNanospray™, a technology of generating high velocity spray of nanoparticles, was used to coat several batches of Arbomatrix polymers loaded with Dexamethasone (DXM), a model drug, onto coronary stents. This particulate coating did not have an initial burst release but exhibited slow continuous release over time (20- 40% release in 28 days) [10] For biomedical applications requiring more release, we theorized that encapsulating drugs into electrospun fiber mats would provide high surface area to volume ratio to release more drug. However, Liu et al. [11] reported that neat L SIBS could not be electrospun, attributing this to the non-conductivity of the polymer solution. We reported conditions under which we electrospun neat L SIBS and Arbomatrix onto aluminum stubs [12] Subsequently we developed a new method that produced self- supporting fiber mats by electrospinning from a mixture of Arbomatrix and low molecular weight poly(ethylene glycol), PEG. The ratio of Arbomatrix to PEG was chosen to be 80/20 wt/wt based on scouting experiments. The fiber mats were highly water-repellent, with Water Contact Angles (WCA) > 120°. We successfully encapsulated a model drug, Zafirlukast, into the fibers, and demonstrated greater than 90% release [13] Although electrospinning can produce ultrafme fibers, the mean fiber size for Zafirlukast-loaded Arbomatrix/PEG fibers was larger (4.197 (±0.580) pm). However, this system showed higher doses and slower release rates than a recent study using poly(lactic-co-glycolic acid) polymer coating with a similar drug for reducing the capsular contracture (an inflammatory response around silicone rubber breast prostheses) in vivo [14] We also reported the electrospinning of a new linear PIB-based TPE, poly(alloocimene-Z>-isobutylene-Z>- alloocimene) or AIBA for short. It is also a triblock copolymer like L SIBS but contains polyalloocimene hard blocks instead of polystyrene. It is synthesized by the carbocationic copolymerization of isobutylene (IB) with alloocimene (Alio) [15, 16] AIBA is easier to synthesize than Arbomatrix [8] and it has higher tensile strength (15 MPa and 600% elongation at break) than Arbomatrix (5.6 MPa and 290% elongation at break). Electrospinning of non-polar and highly non-conductive materials such as AIBA is a challenge, because the process employs high voltage to electrically charge the polymer jets to produce ultrafme fibers [1] Therefore, the polymer was mixed with PEG to enhance the electrical conductivity in order to produce self-supporting fiber mats. AIBA is a candidate for drug delivery systems. Although AIBA is a highly hydrophobic material that is non polar and therefore has high electric resistivity, fiber mats with a proper morphology were still successfully obtained. We found that PEG was fully embedded into the electrospun fibers. The tensile strength measured on microdumbbells was 2.7 MPa at 537% elongation that is comparable to that of soft human tissues. These rubbery fiber mats were also found to be highly hydrophobic and cell culture studies showed their non-cytotoxicity [17] Based on these favorable properties, these fiber mats showed a great promise for tissue scaffold and drug delivery applications.

Fiber Mats

Electrospun fiber mats were formed for antibacterial and antiviral PPE applications. Specifically, these mats could be used to produce N95 equivalent masks with better sealing, no water absorption and better comfort. Two basic proprietary formulations were used.

Both included a polyisobutylene thermoplastic elastomer. The first (“white”) formulation included a zinc oxide filler. The second (“black”) formulation included a carbon filler (carbon black). Zinc oxide itself has wound healing and antibacterial properties so it is advantageous for wound healing applications. It also imparts UV stability to the mats. The addition of carbon increases conductivity and biocompatibility [9] It also makes the mats black (which may be aesthetically desirable in a certain situations).

Conventional N95 masks have high filtration efficiency but are thicker than surgical masks and rather uncomfortable for long-term use in daily life. N95 masks can impede breathing, and users experience problems due to the increase in temperature and humidity between the face and the mask. Masks fabricated from the fiber mats prepared herein can address these problems. Conventional face masks include a thin layer of electrospun or meltblown poly(vinylidene fluoride) (PVDF) or polycaprolactone (PCL or nylon) (basis weight of <10 g/square meter). These fiber mat filters are claimed to have a 99.9% barrier efficiency against viruses, but the mats are not self-supporting, so they must be incorporated into a self-supporting structure. Typically, this means that one or more layers of this material are combined with one or more thicker supporting layers to form a multilayer which has the structural integrity to be facbricated into a mask. In contrast, these

COVID-19 is about 0.125 micron in size, but often travels in biological aerosols from coughing or sneezing that are 0.5-3 micron in size and prefer hydrophilic surfaces. The fiber mats prepared herein are superhydrophobic, like lotus leaves from which water droplets roll off, can be made with pores smaller than COVID-19 virus particles, and are self-supporting at 100 g/m ² or more. The stretchable mats can be be attached to rubber frames, creating a tight fit around the nose and mouth. They can be sterilized by several methods, including ethylene oxide, low pressure plasma treatment or chi orodi oxide. If desired, they can also be recycled by simply dissolving them and re-spinning into a new fiber mat.

Example Fiber Mats

A linear poly(styrene-/>-isobutylene-/>-styrene) triblock copolymer (L SIBS), sold under the tradename SIB STAR, was obtained from Kaneka Co. of Japan. Butyl rubber (HR) was obtained from ExxonMobil (commercially available under the tradename ExxonMobil 268).

A base formulation was prepared containing L SIBS/IIR 50/50 by weight was prepared. Varying concentrations of filler (ranging from 5% to 20% by weight) were then added to this blend to form composites for use in fiber formation. For initial proof of principle studies, a composite containing 5% by weight zinc oxide (Formulation 1) and a composite containing 5% by weight carbon black (Formulation 2) were prepared. A series of 24 different fiber mats were prepared by electrospinning either Formulation 1 (47.5% by weight L_SIBS/47.5% by weight IIR/5% by weight ZnO) or Formulation 2 (47.5% by weight L_SIBS/47.5% by weight IIR/5% by weight carbon black) to form nonwoven webs having various basis weights ranging from 13.8 g/m ² to 121.8 g/m ² . The basis weight of the Formulation 1 samples were as follows: 24.5; 84.0; 67.9;

85.6; 60.4; 24.9; 24.5; 25.8; 38.7; 35.5; 16.6; 14.8; 13.8; and 15.4 g/m ² . The basis weight of the Formulation 2 samples were as follows: 121.8; 51.8; 26.4; 21.8; 42.2; 42.6; 42.3; 42.4; 82.8; and 101.2 g/m ² .

Fiber diameter was kept as a constant to evaluate the effect of web thickness on filtration efficiency. Fiber diameter was evaluated with optical microscopy and it was concluded that the mean fiber diameter is around 1 micrometer in all webs. Material samples were collected on a PP substrate.

Figures 2A and 3 A show a photograph of example nonwoven webs prepared by electrospinning Formulation 2 and Formulation 1, respectively . As shown in Figures 2B and 3B, these nonwovens include a plurality randomly oriented individual fine fibers interlaid to produce self-supporting cohesive nonwoven webs.

Five samples with different basis weights were selected, and the filtration efficiency and corresponding pressure drop were evaluated using standard methods set forth in the U.S. NIOSH (National Institute for Occupational Safety and Health) N95 Filtering Facepiece Respirator (FFR) certification method. The filtration efficiency was measured with NaCl particles ranging from 20nm - 450 nm. Filtration efficiency is presented both on average and also at 300nm particles only.

Table 1. Summary of properties of example nonwoven webs. Figure 4 shows a plot of the filtration efficiency as a function of pressure drop for example webs 1-5. As shown in Figure 4, filtration efficiency increased as pressure drop increased, suggesting that webs meeting the N95 standard could be generated by increasing the basis weight of the webs.

Figure 5 shows an example water contact measurement performed on the surface of an example web. As shown in Figure 5, these example webs exhibited water contact angles of greater that 130°, indicating that these webs are strongly hydrophobic. This suggests that face masks fabricated from these webs would be water repellant, improving comfort for wearers — in particular, for those wearing masks for long periods of time, for those wearing masks in high humidity environments, for those wearing masks when breathing heavily, or any combination thereof.

Example webs having basis weights of 100 g/m ² or more were found to be self- supporting. As shown in Figure 6, such example webs could be formulated into face masks without needed to be combined with additional nonwoven layer (e.g., there was no need for an outer and/or inner spunbond layer to support the nonwoven web).

In a further proof of principle studies, formulations containing higher filler loadings were prepared and electrospun as described above to form webs of varying basis weight (see Table 2 below). These formulations also generated high quality self-supporting nonwoven fibrous webs.

Table 2. Additional nonwoven webs prepared using higher filler loadings.

References

[1] Doshi, J.; Reneker, D.H. Electrospinning Process and Applications of Electrospun Fibers. J. Electrostat. 1995, 35, 151-160. DOI: 10.1016/0304-3886(95)00041-8.

[2] Choi, S.-S.; Hong, J.-P.; Seo, Y. S.; Chung, S. M.; Nah, C. Fabrication and Characterization of Electrospun Polybutadiene Fibers Crosslinked by UV Irradiation. J.

Appl. Polym. 2006, 101, 2333-2337. DOE 10.1002/app.23764. [3] Duong, H.C., Chuai, D., Woo, Y.C., Shon, H.K., Nghiem, L.D. and Sencadas, V. A Novel Electrospun, Hydrophobic, and Elastomeric Styrene-Butadiene-Styrene Membrane for Membrane Distillation Applications. J. Membrane Sci. 2018, 549, 420-427. DOI:

10.1016/j.memsci.2017.12.024.

[4] Chuangchote, S., Sirivat, A., Supaphol, P. Electrospinning of Styrene-Isoprene Copolymeric Thermoplastic Elastomers. Polym. J. 2006, 38, 961-969. DOE

10.1295/polymj .PJ2005234.

[5] Rungswang, W., Kotaki, M., Shimojima, T., Kimura, G., Sakurai, S., Chirachanchai, S. Existence of Microdomain Orientation in Thermoplastic Elastomer Through a Case Study of SEBS Electrospun Fibers. Polymer 2011, 52, 844-853. DOI:

10.1016/j.polymer.2010.12.019.

[6] Kamath, K.R., Barry, J.J., Miller, K.M. The Taxus™ Drug-eluting Stent: A New Paradigm in Controlled Drug Delivery, Adv. Drug. Deliver. Rev. 2006, 58, 412-436, DOI: 10.1016/j.addr.2006.01.023.

[7] Puskas, J.E., Dos Santos, L.M., Orlowski, E. Polyisobutylene-based Thermoplastic Biorubbers. Rubber Chem. Technol. 2010, 83, 235-246. DOI: 10.5254/1.3525683.

[8] Puskas, J.E., Kwon Y., Anthony P., Bhowmick, A.K. Synthesis and Characterization of Novel Dendritic (Arborescent, Hyperbranched) Polyisobutylene-Polystyrene Block Copolymers. J. Polym. Sci. Al. 2005, 43, 1811-1826. DOI: 10.1002/pola.20638.

[9] Lim, G.T., Valente, S.A., Hart-Spicer, C.R., Evancho-Chapman, M.M., Puskas, J.E., Horne, W.I., Schmidt S.P. New Biomaterial as a Promising Alternative to Silicone Breast Implants, J. Mech. Behav. Biomed. Mater. 2013, 21, 47-56. DOI: 10.1016/j.jmbbm.2013.01.025.

[10] Puskas, J.E., Hoerr, R.A. Drug Release from Novel Rubbery Coatings. Macromol. Sy. 2010, 291-292, 326-329. DOI: 10.1002/masy.201050538.

[11] Liu, Y., Liu, X., Chen, J. Gilmore, K.J., Wallace G.G. 3D Bio-nanofibrous PPy/SIBS Mats as Platforms for Cell Culturing, Chem. Commun. 2008, 323729-3731. DOI: 10.1039/b804283g.

[12] Lim, G.T., Puskas, J.E., Reneker, D.H., Jakli, A., Horton, W.E. Highly Hydrophobic Electrospun Fiber Mats from Polyisobutylene-Based Thermoplastic Elastomers. Biomacromolecules. 2011, 12, 1795-1799, DOI: 10.1021/bm200157b.

[13] Jindal, A., Puskas, J.E., McClain, A., Nedic, K., Luebbers, M.T., Baker Jr, J.R., Dos Santos, B.P., Camassola M., Jennings, W., Einspom, R.L., Leipzig, N.D. Encapsulation and Release of Zafirlukast from Electrospun Polyisobutylene-based Thermoplastic Elastomeric Fiber Mat, Eur. Polym. J. 2018, 98, 254-261, DOE 10.1016/j.eurpolymj.2017.11.012.

[14] Kim, B.H., Park, M., Park, H.J., Lee, S.H., Choi, S.Y., Park, C.G., Han, S.M., Heo, C.Y., Choy, Y.B. Prolonged Acute Suppression of Cysteinyl Leukotriene to Reduce Capsular Contracture Around Silicone Implants, Acta Biomater. 2017, 51, 209-219. DOE 10.1016/j.actbio.2017.01.033.

[15] Gergely, A.L., Puskas, J.E. Synthesis and Characterization of Thermoplastic Elastomers with Polyisobutylene and Polyalloocimene Blocks. J. Polym. Sci. Al. 2015, 53, 1567-1574. DOE 10.1002/pola.27587.

[16] Puskas, J.E.; Terpene/isoolefm copolymers having substantially heterogeneous compositional distribution and displaying thermoplastic elastomeric properties. U.S. Patent 9,790,301 (2017).

[17] Puskas, J.E.; Molnar, K.; Jindal, A. Electrospun Fiber Mats from Poly(alloocimene- isobutylene-alloocimene) Thermoplastic Elastomer. International Journal of Polymeric Materials and Polymeric Biomaterials. Published online: 2019 Feb 01. DOI: 10.1080/00914037.2018.1563083.

The compositions, devices, and methods of the appended claims are not limited in scope by the specific compositions, devices, and methods described herein, which are intended as illustrations of a few aspects of the claims. Any compositions, devices, and methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the compositions, devices, and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative compositions, devices, and methods steps disclosed herein are specifically described, other combinations of the compositions, devices, and methods steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein or less, however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated.

The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various embodiments, the terms “consisting essentially of’ and “consisting of’ can be used in place of “comprising” and “including” to provide for more specific embodiments of the invention and are also disclosed. Other than where noted, all numbers expressing geometries, dimensions, and so forth used in the specification and claims are to be understood at the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, to be construed in light of the number of significant digits and ordinary rounding approaches.

Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference.