Method for manufacturing nonwoven fibrous web, nonwoven fibrous web, and multicomponent fiber

Abstract

A method for producing a nonwoven fibrous web, the method comprising: providing a meltblown nonwoven fibrous web comprising bonded primary fibers having an average fiber diameter of 2 to 100 microns, the primary fibers comprising a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units; opening at least a portion of the meltblown nonwoven fibrous web to provide relaxed primary fibers; combining the relaxed primary fibers with secondary fibers; and forming a secondary nonwoven fibrous web comprising the primary fibers and the secondary fibers. A fibrous web producible by this method, as well as a multicomponent fiber comprising a first phase comprising a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units and a second phase comprising a non-biodegradable polymer.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to fibers and nonwoven fibrous webs comprising same. [Background technology]

[0002] Highly hydrophilic, absorbent, and soluble fibers are useful as components of wound dressing materials. The most common materials used in these products are alginate and carboxymethylcellulose. Many wound care products utilize cationic antiseptics, which kill a wide variety of microorganisms but are sequestered and / or inactivated by anionic materials such as alginate and carboxymethylcellulose. Rayon, a highly hydrophilic material often used in wound care products, also binds cationic antimicrobial molecules.

[0003] Meltblowing is a method for forming nonwoven fibrous webs of thermoplastic multicomponent fibers. In a typical meltblowing process, streams of one or more thermoplastic (co)polymers are extruded through a die containing closely spaced orifices and attenuated with a converging stream of high-velocity, hot air to form microfibers, which are collected to form the meltblown nonwoven fibrous web. Multicomponent meltblown fibers, as well as various apparatus and methods for producing such fibers, are also known. Thermoplastic (co)polymers commonly used to form conventional meltblown nonwoven fibrous webs include polyethylene (PE) and polypropylene (PP). Meltblown nonwoven fibrous webs are used in a variety of applications, including acoustic and thermal insulation, filtration media, surgical drapes, and wipes, among others. Summary of the Invention

[0004] In view of the state of the art, it would be desirable to have fibers and nonwoven fibrous webs useful in wound care products (e.g., bandages) that avoid the aforementioned problems. The present disclosure provides nonionic fibrous materials suitable for use in wound dressings that avoid the inactivation of cationic antiseptics. Furthermore, these fibrous materials can be made nontoxic to human cells.

[0005] In a first aspect, the present disclosure provides a method for making a nonwoven fibrous web, comprising: a) providing a meltblown nonwoven fibrous web comprising bonded primary fibers having an average fiber diameter of 2 to 100 microns, the primary fibers comprising a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units; b) opening at least a portion of the meltblown nonwoven fibrous web to provide relaxed primary fibers; c) combining the relaxed primary fibers with secondary fibers; d) forming a secondary nonwoven fibrous web comprising the primary fibers and the secondary fibers.

[0006] In a second aspect, the present disclosure provides a secondary nonwoven fibrous web made by a method according to the present disclosure.

[0007] In a third aspect, the present disclosure provides a nonwoven fibrous web comprising a blend of at least primary fibers and secondary fibers, wherein the primary fibers comprise primary fibers having an average fiber diameter of 2 to 100 microns, and the primary fibers comprise a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units.

[0008] In a fourth aspect, the present disclosure provides a multicomponent fiber comprising a first phase comprising a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units, and a second phase comprising a non-biodegradable polymer.

[0009] As used herein, The term "monomer unit" refers to a residue in a polymer chain that corresponds to a monomer or a basic salt of a monomer (e.g., a conjugate base salt) used to form the polymer chain; The term "fiber" can refer to a fiber of finite length or a filament of infinite length; The term "nonwoven web" means a structure or web of material formed without the use of weaving or knitting processes to produce a structure of individual fibers or threads that are entangled but not in a discernible repeating manner. Nonwoven webs have been formed in the past by a variety of conventional processes, such as, for example, meltblowing and staple fiber carding.

[0010] The features and advantages of the present disclosure will be further understood by consideration of the detailed description and appended claims. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic perspective view of a nonwoven fibrous web 100 according to the present disclosure. [Figure 2] 2 is a schematic cross-sectional view of a multicomponent fiber 200 according to one embodiment of the present disclosure. [Figure 3A] 3 is a schematic cross-sectional view of a multicomponent fiber 300a according to various embodiments of the present disclosure. [Figure 3B] 3 is a schematic cross-sectional view of a multicomponent fiber 300b according to various embodiments of the present disclosure. [Figure 3C] 3 is a schematic cross-sectional view of a multicomponent fiber 300c according to various embodiments of the present disclosure.

[0012] Repeat use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the present disclosure. It is to be understood that those skilled in the art may devise numerous other modifications and embodiments that fall within the scope and spirit of the principles of the present disclosure. The figures may not be drawn to scale. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1, an exemplary nonwoven fibrous web 100 includes primary fibers 110 and secondary fibers 120. The primary fibers 110 have an average fiber diameter between 2 and 100 microns and include a copolymer including divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units.

[0014] The copolymer may contain divalent hydroxyethylene monomer units (i.e., [ka] ) and divalent dihydroxybutylene monomer units. In a preferred embodiment, the divalent dihydroxybutylene monomer units are 3,4-dihydroxybutane-1,2-diyl monomer units (i.e., [ka] Optionally, but typically, the copolymer comprises acetoxyethylene divalent monomer units (i.e., [ka] The copolymer can be obtained by copolymerization of vinyl acetate and 3,4-dihydroxy-1-butene, followed by partial or complete saponification of the acetoxy groups to form hydroxyl groups. Alternatively, instead of 3,4-dihydroxy-1-butene, a carbonate, e.g. [ka] can also be used. After copolymerization, the carbonate can be hydrolyzed simultaneously with saponification of the acetate groups. In another embodiment, instead of 3,4-dihydroxy-1-butene, a compound of the formula: [ka] where each R is independently hydrogen or alkyl (e.g., methyl or ethyl). After copolymerization, the carbonate can be hydrolyzed simultaneously with or separately from saponification of the acetate groups. The copolymers can be prepared by known methods or obtained, for example, from commercial sources.

[0015] Commercially available copolymers include highly amorphous polyvinyl alcohols available under the trade name Nichigo G-Polymer (Nippon Gosei, Osaka), believed to have divalent monomer units of hydroxyethylene, 3,4-dihydroxybutane-1,2-diyl, and optionally acetoxyethylene. Nippon Gosei also refers to Nichigo G-Polymer by the chemical name butenediol vinyl alcohol (BVOH). Exemplary materials include Nichigo G-Polymer grades AZF8035W, OKS-1024, OKS-8041, OKS-8089, OKS-8118, OKS-6026, OKS-1011, OKS-8049, OKS-1028, OKS-1027, OKS-1109, OKS-1081, and OKS-1083. These copolymers are believed to have a degree of saponification of 80 to 97.9 mole percent and further comprise an alkylene oxide adduct of a polyhydric alcohol containing 5 to 9 moles of alkylene oxide per mole of polyhydric alcohol.

[0016] The meltblowing process is well known in the art. As used herein, the term "meltblowing" refers to a method of forming fibers by extruding a molten thermoplastic material through a plurality of fine, usually circular die capillaries into a high-velocity gas (e.g., air) stream, which attenuates the molten thermoplastic material to form fibers, which can have microfiber diameters, for example, diameters of less than 10 microns. The meltblown fibers are then carried by the gas stream and deposited on a collection surface, forming a web of irregular meltblown fibers. Such methods are disclosed, for example, in U.S. Patent Nos. 3,849,241 (Butin et al.), 4,307,143 (Meitner et al.), and 4,707,398 (Wisneski et al.). Advantageously and unexpectedly, at least for G polymer materials, the interfiber bond strength of the primary fibers in the meltblown fiber web is sufficiently low that the web can be mechanically opened to provide individual primary fibers.

[0017] The primary fibers according to the present disclosure may have circular and / or non-circular cross-sections. Likewise, they may be continuous or discontinuous (e.g., irregular or staple fibers). The average diameter of the primary fibers is between 2 and 100 microns, preferably between 3 and 60 microns, and more preferably between 5 and 20 microns.

[0018] The meltblown fibrous webs produced according to the present disclosure can be made in any basis weight and thickness, e.g., up to 1 g / m 2 (gsm) to 400 gsm, 1 gsm to 200 gsm, 10 gsm to 200 gsm, 50 gsm to about 200 gsm, or even 100 gsm to about 200 gsm.

[0019] Optionally, the meltblowing process may further include at least one of adding a plurality of staple fibers to the plurality of individual discontinuous multicomponent fibers or adding a plurality of particulates to the plurality of individual discontinuous multicomponent fibers to form a composite nonwoven fibrous web.

[0020] In some embodiments, a substantially uniform distribution of particles throughout the web is desired. There may be cases where a non-uniform distribution can be advantageous. In certain exemplary embodiments, a particulate density gradient is advantageously created within the composite nonwoven fibrous web. For example, a gradient through the depth of the web can result in a change in pore size distribution that can be used for depth filtration. A web with a surface loading of particles can be formed into a filter in which the fluid is exposed to the particles early in the flow path, with the remainder of the web providing a support structure and a means to prevent particle shedding. The flow paths may also be reversed so that the web can act as a pre-filter to remove some contaminants before the fluid reaches the active surfaces of the particles. Various methods are known for adding a flow of particulates to a nonwoven fiber stream. Suitable methods are described in U.S. Patent Nos. 4,118,531 (Hauser), 6,872,3115 (Koslow), and 6,494,974 (Riddell), and U.S. Patent Application Publication Nos. 2005 / 0266760 (Chhabra and Isele), 2005 / 0287891 (Park), and 2006 / 0096911 (Brey et al.). In other exemplary embodiments, the optional particulate can be added to the nonwoven fiber stream by air-laminating the fibrous web, adding the particulate to the fibrous web (e.g., by passing the web through a fluidized bed of particulate), and optionally post-heating the particulate-loaded web to bond the particulate to the fibers.

[0021] Alternatively, a preformed nonwoven fibrous web can be formed by spraying a preformed dispersion of particulates in a volatile fluid (e.g., an organic solvent, or even water), optionally after heating the particulate-loaded web, to remove the volatile fluid and bond the particulates to the fibers. In a further exemplary embodiment, the method further includes collecting the plurality of individual, discontinuous, multicomponent fibers as a nonwoven fibrous web on a collector. In certain such exemplary embodiments, the composite nonwoven fibrous web can be formed by depositing a population of fine, ultrafine, or sub-micrometer fibers directly onto a collector surface or onto an optional support layer on the collector surface, the support layer optionally comprising microfibers, so as to form a population of fine, ultrafine, or sub-micrometer fibers on the porous support layer.

[0022] A method for producing a meltblown fibrous web may include passing an optional support layer, which may optionally contain polymeric microfibers, through a fiber stream of fine, ultrafine, or sub-micrometer fibers. The fine, ultrafine, or sub-micrometer fibers may be deposited on the support layer so that they are temporarily or permanently bonded to the support layer while passing through the fiber stream. Once the fibers are deposited on the support layer, they may optionally bond to each other and may be further cured while on the support layer. In certain exemplary embodiments, the population of fine, ultrafine, or sub-micrometer fibers is combined with an optional porous support layer containing at least a portion of the population of coarse microfibers. In some exemplary embodiments, the microfibers forming the porous support layer are compositionally identical to the population of microfibers forming the first layer. In other presently preferred embodiments, the population of fine, ultrafine, or sub-micrometer fibers is combined with an optional porous support layer, followed by combination with at least a portion of the population of coarse microfibers. In some embodiments, the porous support layer is adjacent to a second layer opposite the first layer. In other exemplary embodiments, the porous support layer comprises a nonwoven fabric, a woven fabric, a knitted fabric, a foam layer, a screen, a porous film, a perforated film, an array of filaments, or a combination thereof. In some exemplary embodiments, the porous support layer comprises a thermoplastic mesh.

[0023] In some embodiments, the meltblown fibrous web manufacturing method further comprises treating the collected nonwoven fibrous web using a method selected from autogenous bonding (e.g., through-air bonding and / or calendaring), electret charging, embossing, needle tacking, or a combination thereof.

[0024] Depending on the state of the fibers and the relative proportions of microfibers and sub-micrometer fibers, some bonding may occur between the fibers themselves (e.g., self-bonding) and between the fibers and optional particulates before or during collection. However, additional bonding between the fibers themselves and between the fibers and optional particulates in the collected web may be desirable to provide a matrix of desired coherency, making the web more handleable and better able to hold any sub-micrometer fibers within the matrix ("bonding" the fibers to themselves means that the fibers are tightly adhered together so that they generally do not separate when the web is subjected to normal handling).

[0025] In certain exemplary embodiments, blends of microfibers and sub-micrometer fibers may be bonded together. Bonding can be achieved using, for example, thermal bonding, binder bonding, powder binder, needle tuck, calendaring, or a combination thereof. While conventional bonding techniques using heat and pressure applied in a point-bonding method or by smooth calendar rolls can be used, such methods may cause undesirable deformation of the fibers or excessive compression of the web. A presently preferred technique for bonding fibers, particularly microfibers, is the autogenous bonding method disclosed in U.S. Patent Application Publication No. 2008 / 0038976 A1 (Berrigan et al.).

[0026] In some specific embodiments, meltblown fibers may be advantageously electrostatically charged. Thus, in certain exemplary embodiments, meltblown fibers may be subjected to an electret charging process. An exemplary electret charging process is hydrocharging. Hydrocharging of fibers may be performed using various techniques, such as impinging, immersing, or concentrating a polar fluid onto the fibers, followed by drying, resulting in an electrostatic charge on the fibers. Representative patents describing hydrocharging include U.S. Pat. Nos. 5,496,507 (Angadjivand et al.), 5,908,598 (Rousseau et al.), 6,375,886 (Angadjivand et al.), 6,406,657 (B1) (Eitzman et al.), 6,454,986 (Eitzman et al.), and 6,743,464 (B1) (Insley et al.).

[0027] Apparatus useful for hydraulically entangling fibers is generally useful for hydro-charging, but hydro-charging generally operates at lower pressures than those used in hydroentangling. U.S. Patent No. 5,496,507 (Angadjivand et al.) describes an exemplary apparatus in which a jet or stream of water impinges on fibers in a web form at a pressure sufficient to impart a filtration-enhancing electret charging effect to the media, which is then dried.

[0028] The pressure required to achieve optimal results may vary depending on the type of sprayer used, the type of (co)polymer forming the fibers, the thickness and density of the web, and whether or not a pretreatment such as corona discharge is performed prior to hydrocharging.

[0029] Generally, pressures in the range of about 69 kPa to about 3450 kPa are suitable. Preferably, the water used to provide the droplets is relatively pure. Distilled or deionized water is preferred over tap water.

[0030] Fibers (e.g., fibers in a nonwoven fibrous web) may be subjected to other charging processing techniques in addition to or instead of electrostatic charging (e.g., as described in U.S. Pat. Nos. 4,215,682 (Kubik et al.), 5,401,446 (Tsai et al.), and 6,119,691 (Angadjivand et al.)), including hydrocharging, tribocharging (e.g., as described in U.S. Pat. No. 4,798,850 (Brown)), or plasma fluorination (e.g., as described in U.S. Pat. No. 6,397,458 (B1) (Jones et al.)). Corona discharge followed by hydrocharging and plasma fluorination followed by hydrocharging are particularly suitable charging processing techniques used in combination.

[0031] Various methods conventionally used to aid in fiber formation processes can be used on the fibers as they exit one or more orifices of the belt blowing die. These methods include spraying finishes, adhesives, or other materials onto the fibers, applying an electrostatic charge to the fibers, applying a water mist to the fibers, and the like. Additionally, various materials, such as binders, adhesives, finishes, and other webs or films, may be added to the collected web. For example, before collection, the extruded fibers or fibers may be subjected to several additional processing steps, such as further drawing, spraying, etc. Various fluids may be advantageously applied to the fibers before or during collection, including water sprayed onto the fibers, e.g., hot water or steam to heat the fibers, or cold water to quench the fibers.

[0032] After collection, the collected mass may additionally or alternatively be wound onto a storage roll for later processing, if desired. Generally, after collection, the collected meltblown nonwoven fibrous web may be transported to other equipment such as a calendering station, an embossing station, a laminator, a cutter, or may be passed through a drive roll and wound onto a storage roll.

[0033] The relaxed primary fibers can be combined with secondary fibers in any suitable manner to obtain a secondary fibrous web. Such methods are known in the nonwoven fibrous web art. For example, the primary and secondary fibers can be mechanically and / or air-mixed to form a nonwoven fibrous web.

[0034] Nonwoven fibrous webs can be produced, for example, by conventional airlaid, carded, stitchbonded, spunbonded, wetlaid, and / or meltblown procedures. In some embodiments, nonwoven webs can be produced by airlaying fibers. Airlaid nonwoven fibrous webs can be made using equipment such as that available from Rando Machine Company (Macedon, New York) under the name RANDO WEBBER. In some embodiments, a type of airlaying process known as gravity laying can be used, as disclosed, for example, in U.S. Patent Application Publication No. 2011 / 0247839 (Lalouch), the disclosure of which is incorporated herein by reference.

[0035] Nonwoven fibrous webs can be densified and strengthened by techniques such as, for example, cross-lapping, stitch-bonding, needle-tucking, chemical bonding, and / or thermal bonding.

[0036] Exemplary suitable secondary fibers may be continuous or staple. Secondary fibers may be uncrimped or crimped, irregular, and / or chopped. Secondary fibers may have a fiber diameter of up to about 500 microns, e.g., 0.5 denier to 100 denier, 0.5 denier to 50 denier, 0.5 denier to 25 denier, 0.5 denier to about 15 denier, or even 0.5 denier to about 10 denier for polymeric or natural fibers. Useful secondary fibers may be natural, synthetic, inorganic (glass fibers, metal fibers, and ceramic fibers), or combinations thereof.

[0037] As used herein, the term "denier" refers to an international unit of measurement for the thickness of fiber yarns, etc., which means the weight in grams of a fiber having a length of 9000 meters. If the denier of the fiber is less than 3, the fibers can easily break, making the nonwoven fiber web difficult to manufacture and handle. As used herein, basis weight refers to the weight (grams) of the nonwoven web 1 per unit area (sqm).

[0038] Exemplary synthetic fibers include polyolefins (e.g., polyethylene (HDPE, LDPE, LLDPE, VLDPE; ULDPE, UHMW-PE), polypropylene, poly(1-butene), polyisobutylene, poly(1-pentene), poly(4-methylpent-1-ene), polybutadiene, polyisoprene, styrene block copolymers (e.g., styrene-isoprene-styrene (SIS) block copolymer, styrene-ethylene-butadiene-styrene (SEBS) block copolymer, or styrene- butadiene-styrene (SBS) block copolymer) fibers, polyester (e.g., polylactic acid, polyethylene terephthalate, polytrimethylene terephthalate, polycaprolactone, polyethylene naphthalate, polylactic acid, polybutylene terephthalate) fibers, polyamide (e.g., polycaprolactam or nylon 6,6) fibers, acrylic (e.g., acrylonitrile) fibers, polyvinyl alcohol fibers, polycarbonate fibers, polystyrene fibers, polyphenylene sulfide fibers, polysulfone fibers, polyoxymethylene fibers, polyimide fibers, polyurea fibers, rayon fibers, or polyurethane fibers.

[0039] Exemplary suitable natural fibers include cotton fibers, wool fibers, cashmere fibers, kenaf fibers, jute fibers, flax fibers, hemp fibers, cellulose fibers, sisal fibers, coir fibers, and combinations thereof.

[0040] Exemplary suitable metal fibers include stainless steel fibers, nickel fibers, titanium fibers, copper fibers, aluminum fibers, and combinations thereof.

[0041] Nonwoven fibrous webs according to the present disclosure can have any basis weight, thickness, porosity, and / or density unless otherwise specified. In some embodiments, the nonwoven fibrous web is a high loft open nonwoven fibrous web.

[0042] In addition to the methods for producing a nonwoven fibrous web and optionally bonding or electret charging the nonwoven fibrous web described above, after the nonwoven fibrous web is formed, the method further comprises the steps of: (1) advancing a nonwoven fibrous web along a process path toward further processing operations; (2) contacting one or more additional layers with the outer surface of the sub-micrometer fiber component, the microfiber component, and / or the optional support layer; (3) calendering the nonwoven fibrous web; (4) coating the nonwoven fibrous web with a surface treatment or other composition (e.g., a fire-resistant composition, an adhesive composition, or a printed layer); (5) attaching the nonwoven fibrous web to a cardboard or plastic tube; (6) winding 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 into a mold and forming the nonwoven fibrous web into a new shape; (9) applying a release liner over the exposed optional pressure-sensitive adhesive layer, if present.

[0043] While fiber blends of primary and secondary fibers are useful for producing nonwoven fibrous webs as described above, it is also possible to combine the primary and secondary fibrous materials in a single multicomponent fiber if the primary and secondary fibrous materials are extrudable. Nonwoven fibrous webs produced from these multicomponent fibers may have similar or superior properties compared to nonwoven fibrous blend webs of the same polymer.

[0044] Referring now to Figure 2, an exemplary multicomponent fiber 200 includes a first phase 210 and a second phase 220. The first phase 210 includes a copolymer including divalent hydroxyethylene and divalent dihydroxybutylene monomer units as described above. The second phase 220 includes a non-biodegradable polymer. Both the first and second phases can be either discontinuous or continuous.

[0045] The multicomponent fiber 200 shown in FIG. 2 has a circular cross-section, although other cross-sections, such as triangular, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, star-shaped, elliptical, trilobal, and tetralobal cross-sections, can also be used.

[0046] 3A-3C show various other exemplary configurations of the first and second phases (310a-c, 320a-c) within multicomponent fibers 300a-c. Other configurations not shown may also be used. For example, a core-sheath configuration, in which a BVOH polymer is included in the sheath and a non-biodegradable polymer is included in the fiber core, may be desirable in some situations.

[0047] Multicomponent fibers can be produced by known coextrusion techniques. For example, details regarding extrusion techniques for producing multicomponent fibers can be found in U.S. Patent Nos. 5,207,790 and 5,232,770 (Joseph et al.), the disclosures of which are incorporated herein by reference.

[0048] Non-biodegradable polymers are polymers that do not degrade under aerobic or anaerobic conditions as a result of microbial / enzymatic action.

[0049] Non-biodegradable polymers include polyolefins such as polyethylene (e.g., HDPE, LDPE, LLDPE, VLDPE; ULDPE, UHMW-PE grades), polypropylene, polybutylene, poly(ether ether ketone), and poly-4-methylpentene), certain polyesters (e.g., polyethylene terephthalate), polyvinyl chloride, certain acrylic polymers (e.g., polymethyl methacrylate, polyacrylonitrile), certain polyamides, polystyrene, styrene block copolymers (e.g., SIS, SEBS, SBS), polysulfones, and certain polyurethanes.

[0050] The multicomponent fibers may have any fiber diameter, with an average diameter of 2 to 100 microns, preferably 3 to 60 microns, and more preferably 5 to 20 microns, and may be continuous, irregular, or staple fibers. The multicomponent fibers may be uncrimped or crimped.

[0051] Methods for producing multicomponent fibers are known and need not be described in detail herein. Forming the multicomponent fiber generally involves delivering first and second molten mixtures as separate liquid streams to at least one orifice to form at least one multicomponent molten filament comprised of the first (co)polymer component and the second (co)polymer component, applying a gas stream to the at least one multicomponent molten filament to attenuate the at least one multicomponent molten filament to form a plurality of individual, discontinuous multicomponent fibers; The plurality of individual, discontinuous multicomponent fibers are cooled to a temperature below the melting temperature of the first (co)polymer component mixture and the melting temperature of the second (co)polymer component to solidify the individual, discontinuous multicomponent fibers, thereby forming a nonwoven fibrous web.

[0052] In some exemplary embodiments, the individual discontinuous multicomponent fibers exhibit an axial cross-sectional structure selected from the group consisting of: a plurality of alternating layers of the first (co)polymer component and the second (co)polymer component; a plurality of alternating pie wedges of the first (co)polymer component and the second (co)polymer component; and a core / sheath structure in which the first (co)polymer component comprises substantially all of the sheath.

[0053] In some exemplary embodiments, applying a gas stream to at least one filament to attenuate the at least one filament to form a plurality of individual, discontinuous, multicomponent fibers is accomplished using a method selected from meltblowing, gas jet fibrillation, and combinations thereof. In some such exemplary embodiments, the method further includes at least one of adding a plurality of staple fibers to the plurality of individual, discontinuous, multicomponent fibers or adding a plurality of particulates to the plurality of individual, discontinuous, multicomponent fibers.

[0054] In further such exemplary embodiments, the method further includes collecting the plurality of individual, discontinuous, multicomponent fibers as a nonwoven fibrous web on a collector. In some such embodiments, the method further includes treating the collected nonwoven fibrous web using a method selected from autobonding, through-air bonding, electret charging, embossing, needlepunching, needletacking, or a combination thereof.

[0055] Numerous methods can be used to produce discrete multicomponent fibers. Suitable methods and apparatus for producing discrete multicomponent fibers include those described in U.S. Patent Nos. 5,698,322 (Tsai et al.), 7,008,207 (B2) (Bansal et al.), and 8,926,877 (B2) (Melik et al.). Particularly useful apparatus and methods, more specifically feedblocks for delivering multiple molten polymer streams to die orifices to produce discrete multicomponent meltblown fibers, are disclosed in U.S. Patent Nos. 5,207,970 (Joseph et al.), 5,258,220 (Joseph et al.), 5,238,733 (Joseph et al.), and 5,232,770 (Joseph et al.), each of which is incorporated herein by reference in its entirety.

[0056] Multicomponent fibers and nonwoven fibrous webs according to the present disclosure may be included in personal hygiene products, wound care products (eg, bandages), filtration media, and the like.

[0057] Selected embodiments of the present disclosure In a first embodiment, the present disclosure provides a method for making a nonwoven fibrous web, comprising: a) providing a meltblown nonwoven fibrous web comprising bonded primary fibers having an average fiber diameter of 2 to 100 microns, the primary fibers comprising a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units; b) opening at least a portion of the meltblown nonwoven fibrous web to provide relaxed primary fibers; c) combining the relaxed primary fibers with secondary fibers; d) forming a secondary nonwoven fibrous web comprising the primary fibers and the secondary fibers.

[0058] In a second embodiment, the present disclosure provides a method according to the first embodiment, wherein the copolymer further comprises a divalent acetoxyethylene monomer unit.

[0059] In a third embodiment, the present disclosure provides a method according to the first or second embodiment, wherein the divalent dihydroxybutylene monomer units comprise divalent 3,4-dihydroxybutane-1,2-diyl monomer units.

[0060] In a fourth embodiment, the present disclosure provides a method according to any of the first to third embodiments, wherein the secondary fibers comprise at least one of polyolefin fibers, polyester fibers, polyamide fibers, styrene block copolymer fibers, polyurethane fibers, metal fibers, ceramic fibers, or natural fibers.

[0061] In a fifth embodiment, the present disclosure provides a method according to any of the first to fourth embodiments, wherein forming the secondary nonwoven fibrous web comprises air-laying a fiber blend comprising relaxed primary fibers and secondary fibers.

[0062] In a sixth embodiment, the present disclosure provides a secondary nonwoven fibrous web produced according to any of the first to fifth embodiments.

[0063] In a seventh embodiment, the present disclosure provides a nonwoven fibrous web comprising a blend of at least primary fibers and secondary fibers, wherein the primary fibers comprise primary fibers having an average fiber diameter of 2 to 100 microns, and the primary fibers comprise a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units.

[0064] In an eighth embodiment, the present disclosure provides the nonwoven fibrous web according to the seventh embodiment, wherein the secondary fibers comprise at least one of polyolefin fibers, polyester fibers, polyamide fibers, polyurethane fibers, or natural fibers.

[0065] In a ninth embodiment, the present disclosure provides the nonwoven fibrous web according to the eighth embodiment, wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene, styrene block copolymers, and poly-4-methylpentene.

[0066] In a tenth embodiment, the present disclosure provides a multicomponent fiber comprising a first phase comprising a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units, and a second phase comprising a non-biodegradable polymer.

[0067] In an eleventh embodiment, the present disclosure provides a multicomponent fiber according to the tenth embodiment, wherein the copolymer further comprises divalent acetoxyethylene monomer units.

[0068] In a twelfth embodiment, the present disclosure provides a multicomponent fiber according to the tenth or eleventh embodiment, wherein the divalent dihydroxybutylene monomer units comprise divalent 3,4-dihydroxybutane-1,2-diyl monomer units.

[0069] In a thirteenth embodiment, the present disclosure provides a multicomponent fiber according to any of the tenth to twelfth embodiments, wherein the non-biodegradable polymer comprises at least one of a polyolefin, a polyester, a polyamide, or a polyurethane.

[0070] In a fourteenth embodiment, the present disclosure provides a multicomponent fiber according to the thirteenth embodiment, wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene, styrene block copolymer, and poly-4-methylpentene.

[0071] In a fifteenth embodiment, the present disclosure provides a multicomponent fiber according to the fourteenth embodiment, wherein the polyolefin comprises polyethylene or polypropylene.

[0072] The objects and advantages of the present disclosure are further illustrated by the following non-limiting examples, but the specific materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed as unduly limiting the present disclosure. [Example]

[0073] Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and elsewhere in this specification are by weight.

[0074] Example 1 Meltblown (blown microfiber, BMF) nonwoven fibrous webs were produced using Nichigo G-Polymer butanediol vinyl alcohol copolymer (BVOH) pellets (obtained as Nichigo G-Polymer OKS8112) manufactured by Mitsubishi Chemical Corporation (Tokyo). A conventional meltblown process similar to that described by V. Wente in "Superfine Thermoplastic Fibers" (Industrial Engineering Chemistry, Vol. 48, pp. 1342 et seq. (1956) was used.

[0075] More specifically, the meltblowing die had circular, smooth-faced orifices spaced 10 to 10 centimeters apart with a length-to-diameter ratio of 5:1. The molten (co)polymer was delivered to the die by a 20 mm twin-screw extruder commercially available from STEER Co. (Uniontown, Ohio). The extruder was equipped with two weight-loss feeders to control the feeding of the (co)polymer resin into the extruder barrel and a gear pump to control the flow of the (co)polymer melt into the die. The extruder temperature was approximately 210°C, which fed the melt stream into the BMF die, which itself was maintained at 210°C. A (co)polymer throughput rate of 0.178 kg / hr / cm die (1.0 lb / hr / inch die width) was maintained at the die by adjusting the gear pump. The primary air temperature of the air knife adjacent to the die orifice was maintained at approximately 325°C. This produced a web on a rotating collector 18 cm from the die, with a collector speed of 5 ft / min (1.5 m / min). The web had a density of approximately 100 g / m 2 and comprised of fiber diameters ranging from 5 to 25 micrometers.

[0076] Example 2 A BMF web was produced as described in Example 1, except that the collector speed was reduced to 2.5 ft / min (0.076 m / min). The resulting web had a mass of 200 g / m 2 The paper had an apparent basis weight of 1.0001.

[0077] Example 3 The BVOH meltblown fibers from Example 1 were fed into a fiber opener and a "Roller-Doffed Card" carding machine obtained from Hergeth (Acahen, Germany) to form an unconsolidated mat. The opened BVOH fibers were then blended with opened rayon fibers in a 20:80 weight ratio. The rayon fibers had a fiber diameter of 1.7 decitex (dtex, 10-18 microns) and a length of 39 mm and were obtained as Lenzing viscose rayon fibers from the Lenzing Group (Lenzing, Austria).

[0078] The blended fibers were formed into a web using a conventional air-laid web former (available from Rando Machine Company, Macedon, NY, under the trade name "RANDO WEBBER") and had an apparent basis weight of 200 grams per square meter (gsm). The web was then needle-tacked to yield a fibrous web having a thickness of 4.2 mm.

[0079] Example 4 A nonwoven web was prepared as described in Example 3, except that meltable fibers were added to the composition. The resulting web was a blend of 75 parts by weight (pbw) rayon, 20 pbw BVOH fibers, and 5 pbw meltable fibers. The meltable fibers had a fiber diameter of 4 denier (4.4 decitex, 15-26 microns) and a length of 2 inches (5 cm) and were based on polyester (Tairilin polyester fiber type LML41, NanYa Plastics Corp., Kaohsiung City, Taiwan).

[0080] These webs were heat treated after the needle tucking process to further improve their mechanical properties. The webs were placed on a porous belt and sent through a heating device at 300°F (148°C), which drew hot air from top to bottom across the thickness of the collected fibers. The resulting fibrous webs had an apparent basis weight of 200 grams per square meter (gsm). The resulting webs had a thickness of 3.9 mm.

[0081] Example 5 Multicomponent BMF webs were produced using a meltblowing process similar to that described by VA Wente in "Superfine Thermoplastic Fibers" (Industrial Engineering Chemistry, Vol. 48, pp. 1342 et seq. (1956). The extruder supplying the molten (co)polymer to the meltblowing die was a STEER 20 mm twin-screw extruder commercially available from STEER Co., equipped with two weight-loss feeders to control the extruder barrel for controlling the (co)polymer melt flow to the meltblowing die and the supply of the (co)polymer resin to the melt pump. The die had a plurality of circular, smooth-faced orifices (10 orifices / cm) in a 5:1 weight ratio, as generally described, for example, in U.S. Pat. No. 5,232,770 (Joseph et al.).

[0082] All web examples discussed below were produced using an apparatus equipped with a multilayer feedblock configured to produce multicomponent fibers exhibiting an axial cross-sectional structure when viewed in axial cross-section, consisting of two layers (side-by-side). A first BMF web was produced with each fiber having two parallel layers. One layer of fiber was produced with BVOH, and the second layer was produced using Dow DNDB 1077 linear low-density polyethylene (LLDPE) manufactured by Dow Chemical Company (Midland, Michigan). The two extruders were maintained at the same temperature of 210°C to deliver the melt stream to the BMF die (maintained at 210°C). The gear pump was adjusted to produce a 50 / 50 ratio of BVOH / LLDPE, and a total polymer throughput rate of 0.178 kg / hr / cm of die width (1.0 lb / hr / in. of die width) was maintained at the BMF die. The primary air temperature was maintained at approximately 325°C. The resulting web was collected at a distance of 7 inches (18 cm) from the BMF die to the collector and a collection speed of 5 feet / minute (1.5 m / minute). The resulting meltblown fiber web had a weight of 195 g / m 2 The resulting fibers had fiber diameters in the range of 5 to 30 micrometers.

[0083] Example 6 A multicomponent BMF fibrous web was prepared as described in Example 5, except for the following changes: First layer: 75% BVOH; Second layer: 25% LLDPE. The resulting web was collected at a die-to-collector distance of 7 inches (18 cm) and a collection speed of 5 feet / minute (1.5 m / minute). The resulting meltblown fibrous web had a mass of 203 g / m 2 The resulting fibers had fiber diameters in the range of 5 to 30 micrometers.

[0084] Example 7 A multicomponent BMF fibrous web was prepared as described in Example 5, except for the following changes: First layer: 25% BVOH; Second layer: 75% LLDPE. The resulting web was collected at a die-to-collector distance of 7 inches (18 cm) and a collection speed of 5 feet / minute (1.5 m / minute). The resulting meltblown fibrous web had a mass of approximately 215 g / m 2 The resulting fibers had fiber diameters in the range of 5 to 30 micrometers.

[0085] All references, patents, and patent applications cited in this application that are incorporated by reference are incorporated in a consistent manner. In the event of a conflict or inconsistency between any portion of an incorporated reference and this application, the information in this application shall prevail. The foregoing description is intended to enable one skilled in the art to practice the disclosure as set forth in the claims, and should not be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereof.

Claims

1. A method for producing a nonwoven fibrous web, comprising: a) providing a meltblown nonwoven fibrous web comprising bonded primary fibers having an average fiber diameter of 2 to 100 μm, the primary fibers comprising a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units; b) opening at least a portion of the meltblown nonwoven fibrous web to provide relaxed primary fibers; c) combining the relaxed primary fibers with secondary fibers; d) forming a secondary nonwoven fibrous web comprising said primary fibers and said secondary fibers.

2. The method of claim 1 , wherein the copolymer further comprises a divalent acetoxyethylene monomer unit.

3. The method of claim 1 , wherein the divalent dihydroxybutylene monomer units comprise divalent 3,4-dihydroxybutane-1,2-diyl monomer units.

4. The method of claim 1 , wherein the secondary fibers comprise at least one of polyolefin fibers, polyester fibers, polyamide fibers, styrene block copolymer fibers, polyurethane fibers, metal fibers, ceramic fibers, or natural fibers.

5. The method of claim 1 , wherein forming the secondary nonwoven fibrous web comprises air-laying a fiber blend comprising the relaxed primary fibers and the secondary fibers.

6. A nonwoven fibrous web comprising a blend of at least primary fibers and secondary fibers, wherein the primary fibers have an average fiber diameter of 2 to 100 μm, and the primary fibers comprise a copolymer comprising divalent hydroxyethylene monomer units and divalent dihydroxybutylene monomer units.

7. 7. The nonwoven fibrous web of claim 6, wherein the secondary fibers comprise at least one of polyolefin fibers, polyester fibers, polyamide fibers, polyurethane fibers, or natural fibers.

8. 8. The nonwoven fibrous web of claim 7, wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene, styrene block copolymers, and poly-4-methylpentene.

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