HK1124811B - Mechanically strong absorbent non-woven fibrous mats - Google Patents

Description

Mechanically strong absorbent nonwoven fibrous mat

Background

The present invention relates to mechanically strong absorbent materials. More specifically, such materials comprise at least one Hydrophilic Elastomeric Fibrous Component (HEFC) and at least one absorbent component. In addition, some embodiments may further include a viscous component (adhesive component). The HEFC can include a block copolymer, wherein the block includes an elastomeric block and a hydrophilic block. Alternatively, the HEFC may comprise a mixture or solid solution of a hydrophilic polymer and an elastomeric polymer. The absorbent component is generally in physical proximity to the HEFC so as to be in fluid communication therewith. Generally, the system operates as follows: HEFCs absorb and transfer liquid to the absorbent component, which liquid is captured and/or incorporated into the absorbent component. Embodiments that also include an adhesive component may be suitably secured to the location where the liquid is to be absorbed.

Various methods are known in the textile art for making fibers compatible with the present invention. Melt-blowing, gas-jet Nanofibers (NGJ), electrospinning (electrospinning) are non-limiting examples of such techniques. In melt-blown processes, a stream of molten polymer or other fiber-forming material is typically extruded into a gas nozzle to form fibers. The resulting fibers typically have diameters above 1,000 nanometers, and more typically diameters above 10,000 nanometers. Techniques and apparatus for forming fibers having diameters below 3,000 nanometers in accordance with NGJ techniques are described in U.S. patent nos. 6,382,526 and 6,520,425, and are hereby incorporated by reference in their entirety. This application is followed herein and throughout this application when there is a discrepancy between this application and the documents incorporated by reference.

Electrospinning (i.e., electrospinning) of liquids and/or solutions capable of forming fibers is well known in the art. Electrospinning has been described in a number of patents as well as in the scientific literature. Electrospinning methods generally involve the creation of an electric field across the surface of a liquid. The generated electricity produces a jet of charged liquid. Thus, the liquid jet can be attracted to other charged objects having a suitable potential. As the liquid jet elongates and travels, the fiber-forming material within the liquid jet dries and hardens. Hardening and drying of the elongated liquid jet can be facilitated by various means, including, without limitation: cooling the liquid; solvent evaporation (i.e., physically induced hardening); or by a curing mechanism (i.e., chemically induced hardening). The resulting charged fibers are collected on a suitably positioned, oppositely charged receptor (receiver) and subsequently removed therefrom as needed, or applied directly to an oppositely charged or grounded broad target area.

The fibers produced by this method have been used in a variety of applications and are known from U.S. Pat. No. 4,043,331 to be particularly useful in forming nonwoven pads suitable for use in wound dressings (Woulddressing). One of the main advantages of using electrospun fibers in wound dressings is: very fine fibers can be produced, typically on the order of about 50 nanometers to about 25 microns in diameter, and more advantageously, on the order of about 50 nanometers to about 5 microns. These fibers can be collected and formed into a nonwoven mat of any desired shape and thickness. It will be appreciated that because the fibers have very small diameters, mats can be produced having very small voids and large surface area per unit mass.

Medical dressings made using these non-woven mats of polymeric fibers, as disclosed in U.S. patent No. 4,043,331, can have particular advantages depending on the type of polymer or polymers used. Water wettable or hydrophilic polymers such as polyurethanes may be used. Alternatively, a polymer that is not water wettable or at least weakly hydrophobic, such as a saturated polyester, may be used. In the case of dressings made of wettable polymers, blood or serum that escapes from the wound tends to penetrate the dressing and the high surface area promotes clotting. Such a dressing may be used as an emergency dressing to stop bleeding. On the other hand, in the case where the dressing is made of a non-moist polymer and the interstices between the fibers are sufficiently small, i.e. on the order of about 100 nanometers or less, tissue fluids, including blood, tend not to penetrate into the dressing. Thus, the fluid is retained in the vicinity of the wound, where coagulation will occur. Subsequent removal of this dressing is facilitated by the absence of blood clotting that penetrates into the dressing material. In addition, U.S. Pat. No. 4,043,331 suggests that such a dressing has the advantages of: they are generally sufficiently porous to allow the exchange of oxygen and water vapor between the atmosphere and the wound surface.

In addition to having variability with respect to the diameter of the fibers or the shape, thickness, or porosity of any non-woven mat produced by the fibers, the ability to electrospin the fibers also allows for controlled variation in the composition of the fibers, their deposition density, and their inherent strength. The above-mentioned us patent shows that it is also possible to post-treat the nonwoven mat with other materials to alter its properties. For example, the strength of the pad can be enhanced using a suitable binder, or the water repellency can be enhanced by post-treating the pad with silicone or other water-repellent materials such as perfluoroalkyl methacrylates. Alternatively, strength may be enhanced by using Polytetrafluoroethylene (PTFE) fibers.

By varying the composition of the fibers to be formed, fibers having different physical or chemical properties can be obtained. This can be achieved: either by spinning a liquid containing multiple components, each of which can impart a desired characteristic to the finished product, or by simultaneously spinning fibers of different compositions from multiple liquid sources, which are then deposited simultaneously to form a mat. Also known in the prior art are: molecules, particles, droplets can be incorporated into electrospun nanofibers during the electrospinning process. The resulting mat, of course, is comprised of intimately mixed fibers of different materials.

Often, wetting the fibrous product compromises strength. This is particularly problematic in applications such as diapers, tampons, and the like, where both strength and absorbency are required. Prior patents and printed publications disclose various solutions to this absorption problem, but each is distinct from the present invention, as will be clearly explained herein.

For example, one option available in the art is to produce a mat having a plurality of layers of different material fibers. For example, wettable and non-wettable polymers provide different properties. Wettable polymers tend to be highly absorbent but provide relatively weak pads, while non-wettable polymers tend to be non-absorbent but provide relatively strong pads. The wettable polymer layer or layers impart a relatively high level of absorbency to the article, while the non-wettable polymer layer or layers impart a relatively high level of strength. The use of such a layered structure has the disadvantage that: the hydrophobic layer may form a barrier to liquid and impede liquid absorption by the wettable layer. Furthermore, upon absorption of the liquid, the wettable polymer layer will weaken and dislocation, relaxation or even separation of the layers may occur, possibly destroying the structure of the article.

U.S. Pat. No. 4,043,331 teaches that a strong non-woven mat of fibers comprising a plurality of organic materials, i.e. polymeric materials, can be produced by electrospinning the fibers from a liquid consisting of the materials or precursors thereof. The fibers are collected on a suitable charged receptacle. The pad or liner formed on the receptacle can then be transferred and used alone or with other previously constructed components, such as, for example, a woven fabric pad and a support layer, to impart desired characteristics to the wound dressing. For example, in the production of wound dressings, additional support or reinforcement, such as a fibrous pad or liner, or a support layer may be required to adhere the wound dressing to the skin and provide other desirable properties to the wound dressing. By way of example, a pad or liner of non-woven fibers may contain a material having bactericidal or wound healing properties. Surface treatment of the nonwoven mat already formed may also provide additional benefits in the production of such wound dressings. However, U.S. Pat. No. 4,043,331 does not provide a medical dressing that adheres only to intact skin. It also does not provide a single component dressing that can be adhered to a desired area of a patient, or a dressing comprised of composite fibers having a composition that varies along the length.

Electrospinning wound dressings in situ on wounds has also been described in PCT international publication number WO 98/03267. In such applications, the body itself is grounded and acts as a receptacle for the electrospun fibers. This method of synthesizing wound dressings allows the problems associated with the storage and preparation of bandages and gauze to be solved. It is well known that gauze and bandages, for example, must be stored and maintained in a sterile environment in order to give maximum protection in healing wounds. These products are hardly conducive to protecting the wound if the gauze or bandage is not sterile. Electrospinning a wound dressing in situ on a wound from a sterile liquid eliminates these problems.

International publication No. WO 01/27365, the disclosure of which is incorporated herein by reference in its entirety, describes electrospun fibers containing a substantially homogeneous mixture of a hydrophilic polymer, an at least weakly hydrophobic polymer, and an optional pH-adjusting compound. These fibers can be deposited directly onto the area they are intended to be used, rather than first applying the fibers to a temporary charged receptacle, or subjecting them to other intermediate manufacturing steps. However, the resulting fibers do not provide a dressing that adheres only to intact skin.

International patent application WO 2005/016205 provides an absorbent core made from a fibrous substrate, wherein the substrate is reinforced with a retractable reinforcing member, such as scrims, wherein the fibres are fixed to the reinforcing member. This is in part different from the present invention because the reinforcing member is a completely separate component from the fibrous matrix. In contrast, the present invention in this respect is self-reinforcing, which incorporates hydrophilic and elastic characteristics into a fibrous mat. The strength of the fibrous pad of the present invention is not dependent on the fixation of the separating body, such as a scrim. In addition, the' 205 publication does not disclose the use of an absorbent component separate from the fibrous component as in the present invention.

Accordingly, there is a need in the art for an absorbent, liquid-entrapping device comprising a hydrophilic, elastomeric fibrous component that is physically adjacent to the absorbent component such that fluid communication occurs therewith. Furthermore, there is a need for an arrangement in which one or more liquids enter the fibrous component which transfers the liquid to the absorbent component, thereby capturing the liquid.

Summary of The Invention

The present invention relates generally to absorbent materials (absorbent materials) that retain mechanical strength when wet. More specifically, such materials comprise at least one Hydrophilic Elastic Fibrous Component (HEFC) and at least one absorbent component. In some embodiments, the present invention may further comprise a viscous component. The HEFC can include a block copolymer, wherein the block includes an elastomeric block and a hydrophilic block. In still other embodiments, the HEFC can include a mixture or solid solution of a hydrophilic polymer and an elastomeric polymer. The absorbent component is generally in physical proximity to the HEFC so that fluid communication therewith occurs. The HEFC and absorbent component combination may be disposed onto a woven or non-woven mat or any other suitable form. The adhesive composition may be placed on one or more surfaces of the pad, thus enabling it to be secured to an object, such as a wound of a patient.

In one embodiment, the present invention relates to a liquid entrapping device comprising: an absorbing component; and a hydrophilic elastic fibrous component, wherein the absorbent component and the hydrophilic elastic fibrous component are in physical proximity such that fluid communication occurs, and wherein the absorbent component has a greater absorbent capacity than the hydrophilic elastic fibrous component.

In another embodiment, the present invention relates to a method of making a liquid entrapping device comprising: spinning at least one fiber from a solution comprising a hydrophilic elasticity-producing component (hydrophthalic elastogenic component) and an absorbent component, wherein the fiber comprises the absorbent component in physical proximity to the hydrophilic elasticity-producing component so as to be in fluid communication therewith.

In another embodiment, the invention relates to a method of using a liquid entrapping device comprising the step of placing the liquid entrapping device in contact with at least one liquid.

In another embodiment, the invention relates to a liquid absorbing mechanism comprising a fluid conducting mechanism and an absorbing mechanism, wherein the absorbing mechanism maintains resistance to tensile stress after absorption of one or more liquids.

In another embodiment, the present invention is also directed to a nonwoven fibrous component comprising one or more fibers, wherein the fibers comprise: a viscous component, an elastic component, and a hydrophilic component.

In yet another embodiment, the present invention is directed to a method of making a nonwoven fibrous component, the method comprising: providing at least one fiber-forming material; and forming at least one fiber from the at least one fiber-forming material, wherein the at least one fiber-forming material comprises a viscous component, an elastic component, and a hydrophilic component.

In yet another embodiment, the invention relates to a method of treating a patient comprising: applying a non-woven fibrous assembly to a predetermined area of a patient, wherein the non-woven fibrous assembly contains one or more fibers comprising an adhesive component, an elastic component, and a hydrophilic component.

In yet another embodiment, the present invention is directed to an apparatus for forming at least one composite fiber comprising a hydrophilic component, an elastic component, and an adhesive component, wherein the apparatus comprises: a plurality of reservoirs for holding a plurality of fiber-forming materials; a plurality of valves, each independently in communication with the reservoir; and a fiberizing apparatus selected from the group consisting of spinnerets, NGJ nozzles, and electrospinning apparatuses in communication with the valve.

Drawings

FIG. 1 is a schematic view of an apparatus for making composite fibers according to the present invention;

FIG. 2 is a drawing of a tensile test specimen;

FIG. 3 is an electron micrograph of a fiber mat prior to wetting;

FIG. 4 is an electron micrograph of the fiber mat after wetting and redrying;

FIG. 5 is a graph of equilibrium absorbent capacity versus percent absorbent in the case where the liquid is water or urine;

FIG. 6 is a graph of wet/dry area ratio and thickness ratio versus percent absorbent;

FIG. 7 is a graph of stress versus strain for various percent absorbers;

FIG. 8 is a graph of stress versus strain for an elastic fiber mat in wet and dry states;

FIG. 9 is a schematic view of an apparatus for forming composite fibers according to an embodiment of the present invention;

FIG. 10 is a graph showing the absorbency of the nanofiber assembly of the present invention; and

fig. 11 is a stress-strain curve of a nanofiber assembly according to the present invention.

Detailed Description

The present invention relates generally to absorbent materials that retain mechanical strength when wet. More specifically, such materials comprise at least one Hydrophilic Elastic Fibrous Component (HEFC) and at least one absorbent component. In some embodiments, the present invention may further comprise a viscous component. The HEFC can include a block copolymer, wherein the block includes an elastomeric block and a hydrophilic block. Alternatively, the HEFC may comprise a mixture or solid solution of a hydrophilic polymer and an elastomeric polymer. The absorbent component is generally in physical proximity to the HEFC so as to be in fluid communication therewith. The HEFC and absorbent component combination may be disposed onto a woven or non-woven mat or any other suitable form.

In one embodiment, the HEFC of the present invention may function as a conduit that transports liquid to the absorbent component where it will be captured. Thus, the HEFC acts in the manner of a wick (wick) in that it provides a fluid flow means. This wicking characteristic, along with the difference in absorbent capacity and velocity between the HEFC and the absorbent component, results in a net fluid flow to the absorbent component. That is, because the HEFC both absorbs faster and has a smaller volume than the absorbent component, it tends to reach its volume more quickly. Thus, there tends to be a net fluid flow from the fibers to the absorbent component.

In general, the present invention operates in the following manner. A fibrous pad comprising the HEFC and absorbent component is placed in fluid communication with a liquid to be absorbed. The HEFC absorbs the liquid and transfers it to the absorbing component of the current-collecting body. The elastic properties of the fibrous component serve to contain the expansion of the absorbent component without causing rupture of the fibrous component. According to the invention, the fibrous component is elongated to allow for dimensional changes due to the absorption of liquid by the absorbent component. In addition, some embodiments may include an adhesive component to secure the fibrous mat to an object from which one or more liquids are to be absorbed.

As used herein, the term absorbent includes compounds/substances that are capable of being wetted with a liquid. As used herein, the term elastomer includes any polymeric material that is capable of elastically deforming under load and returning substantially to its original shape when the load is removed. As used herein, the term hydrophilic includes the ability to absorb aqueous or otherwise polar liquids. The material may be both elastomeric, hydrophilic and absorbent. As used herein, the term super-absorbent includes any material that is capable of absorbing about 50 times its own weight of liquid or more. Without limitation, the superabsorbent may be organic polymers and porous clays. As used herein, the term "absorbent capacity" refers to the mass of liquid retained by an absorbent device per unit mass, including structural and absorbent components. Generally, the absorption capacity referred to herein is the equilibrium value. As used herein, the term "absorb" includes the amount of liquid absorbed. As used herein, a "fiber assembly" includes at least one fiber that is in fluid communication with at least one absorbent component.

As used herein, elastomeric refers to the ability of a compound to form an elastomer. Similarly, as used herein, to produce hydrophilic (hydrophthalenic) refers to the ability of a compound to form a hydrophilic polymer. Although the terms elastic-producing and hydrophilic-producing describe the elastic and hydrophilic properties of materials downstream from themselves, the elastic-producing and hydrophilic-producing materials may also be hydrophilic and/or elastic. For example, the material that creates hydrophilicity may itself be hydrophilic; however, the material that generates hydrophilicity is not required to be hydrophilic. The same is true for the materials that give rise to elasticity.

As used herein, hydrophilic elastic fibrous components refer to liquid-wicking members (liquid-wicking members) that have the ability to absorb liquids and act as conduits to transport such liquids to another material. The word order of the term "HEFC" has no meaning. In particular, it does not indicate whether the material is predominantly hydrophilic or predominantly elastic. For example, the phrase elastic hydrophilic fibrous component is equivalent to a hydrophilic elastic fibrous component. Every other permutation of the word order is also possible. Likewise, the term producing hydrophilicity producing elastic components is equivalent to producing elasticity producing hydrophilic components.

The HEFC may comprise any hydrophilic elastomeric material as long as it is capable of: (1) spun into fibers, and (2) absorb and wick liquids. Advantageously, such materials are also able to withstand the strain created by the dimensional change of the absorbing component. Materials within the scope of the present invention may be blends, mixtures or solid solutions that produce an elastic subcomponent(s) and that produce a hydrophilic subcomponent(s). Alternatively, such materials may be copolymers of elastomeric matrices (mers) and hydrophilic matrices, such as random copolymers, block copolymers, and the like. In another embodiment, the present invention may also include copolymers that include a tacky component(s) in addition to the elastomeric and hydrophilic components.

Also, materials used to form the HEFC within the scope of the present invention include homopolymers in which the components are both hydrophilic and elastomeric. Specific materials within the scope of the present invention include, without limitation: zein, polyester elastomers, polydimethylsiloxane, hydrophilic ether ester copolymer elastomers, silicone-co-polyethylene glycol copolymers (silicone-co-polyethylene glycol) elastomers, polyacrylates, thermoplastic polyurethanes, ether-urethane copolymers (poly (ether-co-urethanes)), and polyurethanes. Particularly advantageous materials include, but are not limited to, ether urethane copolymers and polyurethanes.

Any absorbent material may be used as the absorbent component of the present invention so long as it is in physical proximity to the HEFC so as to be in fluid communication therewith. Generally, this means that the material must be wettable by aqueous or otherwise polar liquids. More specifically, materials within the scope of the present invention advantageously have a greater liquid volume per unit mass than HEFCs. In contrast to the HEFC, a specific morphology is not necessary for the efficacy of the absorbing component. By way of example, the absorbent component may be, without limitation, irregular, amorphous, spherical, elongated, fibrous, azimuthal, ellipsoidal, or spherical. Furthermore, a specific stress-strain relationship is not necessary for the performance of the absorbing material. Thus, the absorbent material may be, without limitation, substantially rigid, pliable, elastic, gelatinous, fluid, or frangible. The absorbent material includes, but is not limited to: polyesters, polyethers, polyester-polyethers, polymers with pendant acid groups (pendant acid) or pendant hydroxyl groups (pendant hydroxyl), polysiloxanes, polyacrylamides, kaolins, serpentines, smectites, glauconite, chlorite, vermiculite, attapulgite, sepiolite, allophane and imogolite (imogolite), sodium polyacrylate and 2-acrylamide/2-propenoic acid copolymer (2-propenamide-co-2-propenoic acid). Particularly advantageous materials include, but are not limited to, sodium polyacrylate and 2-acrylamide/2-acrylic acid copolymer.

The absorbent material may have any of a variety of absorbent capacities; advantageously, however, the absorbent material has a greater absorbent capacity than the HEFC. More advantageously, the absorbent material is superabsorbent.

The absorbent component may be distributed in any manner so long as it is in physical proximity to the HEFC so as to be in fluid communication therewith. For example, the absorbent material may be coated onto a surface of the HEFC. More specifically, it may be physisorbed or chemisorbed onto the HEFC surface, or it may be affixed to the surface in any other suitable manner. In another embodiment, the absorbent material may be mechanically trapped or entangled within the hydrophilic elastomeric fibers. Alternatively, the absorbent component may be embedded in the HEFC. Additionally, any combination of the foregoing arrangements is also within the scope of the present invention.

Any of the foregoing distributions may be advantageous depending on the physical characteristics of the absorbing component. For example, if the absorbent component has a tendency to fall off, it may be advantageous to embed it in the HEFC rather than fix it to the fiber surface. On the other hand, if the absorbent material can be firmly fixed to the outer surface of the hydrophilic elastic fiber, the fiber can be coated with the absorbent instead of embedding it in the fiber. Furthermore, if the mass transfer rate from the fibers to the absorbent material is so slow that absorption is unacceptably hindered, it may be advantageous to apply the absorbent component to the fibers as opposed to embedding. Further, one or more of any of the foregoing distributions may be used in any combination thereof.

In one embodiment, a solution of a hydrophilic material is mixed with a solution of an elastomeric material, and then the mixture of the two is spun, producing a fiber that includes both materials. The fibers prepared in this manner can have a uniform composition in which the elastic and hydrophilic materials are uniformly distributed. Alternatively, the fibers may include well-defined phases, or a portion of the fibers may be a homogeneous solid solution and a portion may be phase separated. In another embodiment, the fiber may comprise a block copolymer, wherein the block further comprises an elastomeric block and a hydrophilic block. These blocks may be arranged irregularly or in any of a variety of suitable ways.

As described above, embodiments of the present invention may provide a nonwoven fibrous component that includes at least one fiber and contains an optional adhesive component, an elastic component, and a hydrophilic component. The at least one fiber may comprise a series of segments, such as segments that are primarily or even entirely viscous components, segments that are primarily or entirely elastomeric components, and segments that are primarily or entirely hydrophilic components. When the at least one fiber has such an arrangement of constituents, the different segments may be arranged in any of a number of orders, as desired for a particular application. It is envisioned that a particularly useful arrangement will include a segment of at least predominantly a tacky component located adjacent to a segment of at least predominantly a hydrophilic component, which in turn is located adjacent to a segment of at least predominantly an elastomeric component. The composite fiber may also include two or more components located in the fiber segment. The composition of each segment and the number of segments may also vary over the length of the fiber. Furthermore, the transition between segments may be gradual or abrupt. Alternatively, the composition of the fibers may be constant over the length of the fibers. The nonwoven fibrous component may also comprise a plurality of fibers, wherein different fibers provide each component, either alone or in combination.

According to embodiments of the present invention having a tacky component, a method of making a nonwoven fibrous component includes the following steps. Forming at least one fiber comprising a viscous component, an elastic component, and a hydrophilic component. The at least one fiber may be formed by any technique compatible with each component of the fiber or fibers. It is envisioned that melt-blowing, NGJ techniques, and electrospinning are suitable methods of forming fibers according to binder-containing embodiments of the present invention. Electrospinning provides particular benefits. The fibers may also be formed by other techniques, including phase separation, casting in holes (potting), and slitting of membranes (slitting of a film).

When fibers having a small diameter are formed, a fiber mat having small voids and a high surface area is produced. The nonwoven fibrous components according to the present invention may be used in, but are not limited to, medical dressings, diapers, feminine hygiene products, absorbent towels or wipes for skin use, and transdermal or oral delivery systems for therapeutic and prophylactic substances. It is also envisioned that the nonwoven fiber assembly may also be used for other purposes such as spill containment in fuel cells, water transport and handling, and for collecting and transporting water or other fluids from coalescing filters.

When the nonwoven fibrous component is formed into a medical dressing, the resulting medical dressing is microporous and breathable, but resistant to high air flow. These are important and desirable characteristics of medical dressings. Typically, medical dressings produced using such techniques have pore sizes in the range of about 50nm to about 1000nm, or 100nm to 750nm, or 250nm to 500nm, or even 300nm to 400 nm. Here, as in various places of the specification, these ranges may be combined. In some embodiments, the pores of the invention are small enough to protect the wound from bacterial invasion by aerosol particle capture mechanisms. Furthermore, in some embodiments, such pores may also impede the passage of viral particles through the dressing into the wound.

The nonwoven or fibrous pad of the present invention advantageously has a thickness of at least about 5m for effective fluid absorption and transdermal transport²A high surface area per gram, andmore advantageously, about 100m²(ii) in terms of/g. The high surface area may also impart high hemostatic potential to the dressing.

When used as a medical dressing, the nonwoven fibrous component of the present invention provides a greater water vapor transmission rate, expressed as water vapor flux (water vapor flux), than commercial barrier film dressings. In one embodiment, the electrospun fiber mat forms a medical dressing having a water vapor flux that is at least about ten times greater than a solid film barrier dressing. Advantageously, the medical dressing provides a water vapor flux that is at least about 30 times greater than commercial barrier membranes. More advantageously, the medical dressing provides a water vapor flux that is at least about 30 times greater than commercial barrier membranes.

The appropriate thickness of the fibers of the dressing depends on such factors as the fiber-forming material used, the diameter of the fibers, the structural arrangement of the fibers, the size of the pores formed by the fibers, and the desired degree of air penetration and protection from contamination. For example, when the concentration is as small as about 0.1g/m²When applied at the coating level of (a), the fibers can form a medical dressing. The fibers may also be in the range of about 0.1 to about 100g/m²Is applied at the coating level of (1). At one thickness, the fibers of the medical dressing provide a filtration efficiency of 97% or more for aerosols having a diameter between about 0.5 μm and about 20 μm. At another thickness, the fibers provide a filtration efficiency of 97% or more for aerosols having a diameter between about 0.1 μm and about 20 μm. The fibers may also be used at thicknesses that provide substantially complete filtration for aerosols having diameters between about 0.5 μm and about 20 μm, or even aerosols having diameters between about 0.1 μm and about 20 μm.

While the medical dressing provides an effective barrier to contamination, it also allows for air circulation. This allows oxygen to permeate the dressing and contact the wound, burn or other protected area, thereby accelerating healing and reducing the likelihood of infection, compared to wound dressings that do not allow airflow into the protected area. In one example, the medical dressing has a size of about 5 x 10⁹m^-1The following airflow resistance. Advantageously, the medical dressing has a size of about 2 x 10⁸m^-1The following airflow resistance. In another example, the medical dressing has a size of about 2 x 10⁷m^-1The following airflow resistance.

The fibers and resulting medical dressings and other nonwoven fibrous components described herein are lightweight, oxygen and moisture permeable, yet protected from airborne contaminants such as dust, microorganisms, and/or other infectious materials. The ability of the fiber mat fibers to deliver therapeutic additives to the wound site is also important. This ability to transport and deliver additives can be controlled by the selection of the polymer carrier, the density and thickness of the nonwoven fibrous sheet, and/or the layering of the different fibrous mat fibers.

With respect to the fibers used in medical dressings, it should be understood that the fibers may be dry and form a strong fiber mat. However, in some cases, wet fibers may be used. While wet fibers may be strong, wet fibers are generally softer than dry fibers and conform better to the surface of the substrate to which they are applied. Other advantages may include those previously described in the discussion related to U.S. patent No. 4,043,331 above. In any case, the ability to form the fibers of the present invention directly onto the wound surface can increase the flexibility of the fiber composition, improve the porosity of the fiber mat, and improve its strength, all in a cheap and timely manner. Furthermore, by applying the fibers directly to the wound, advantageously, the fibers can be placed in intimate and shaped contact with the entire wound surface, even if healthy tissue is located deep within the wound. This enables efficient removal of dead cells, fluids or bacteria from deep within the wound when the dressing is replaced, thus reducing or eliminating the need for wound debridement. Direct contact with the wound surface will also result in improved drug delivery to the wound. Finally, it will be appreciated that direct application provides improved and in fact inherent sterility to the fibres and hence the dressing, thereby eliminating the need for gamma irradiation or other treatment to sterilise the dressing material. In addition, controlled ozone generation and other active species may be used to assist in sterilization.

Electrospinning a wound dressing in situ on a wound, however, limits the types of solvents that can be used to only those that are compatible with the skin or other tissue to which the dressing is applied. Examples of such solvents include water, alcohols, and acetone. Likewise, because the types of solvents that can be used are limited, the types of additives that can be used with the polymer, such as absorbents, biocides, and antibiotics, are also limited to those additives that are soluble in the particular solvent used or that form a stable dispersion. Similarly, the types of polymers that can be used are also limited to those that are soluble in skin or tissue-compatible solvents. Biocompatible polymer/solvent combinations include, for example, polyethylenimine/ethanol, polyvinylpyrrolidone/ethanol, polyethylene oxide/water, and poly (2-hydroxymethacrylate)/ethanolic acid plus (poly (2-hydroxymethacrylate)/ethanol plus acid). Although the fibers from such a combination are non-reactive in their woven state, exposure of the fibers to fluids from a wound or external source may change the pH there from a neutral or near neutral pH to an acidic or basic pH, depending on the composition of the fibers. For example, when a polyethylenimine fiber is exposed to a fluid, it will participate in proton transfer, resulting in a basic pH in the fluid contacting the polymer.

In one embodiment, the dressing also includes a closed cell foam to protect the treatment area from mechanical disturbances and/or to provide thermal insulation.

Embodiments of the present invention that include an adhesive component may include at least one fiber formed from a mixture of any of a variety of hydrophilic polymers, elastomeric polymers, and polymers having adhesive properties. The fiber-forming material may optionally be blended with any of a variety of medically important wound treatment drugs, including analgesics and other pharmaceutical or therapeutic additives. Such polymeric materials suitable for electrospinning into fibers may include, for example, those inert polymeric materials that are absorbable or biodegradable, that react well with the selected organic or aqueous solvent, or that dry quickly. Essentially any organic or water-soluble polymer, or dispersion of such a polymer with soluble or insoluble additives suitable for topical treatment of wounds, can be used. Other additives may be used when used in applications other than medical dressings. For example, in leak treatment applications, particles for absorbing a particular type of compound may be encapsulated in one such polymer composition. For example, a nonwoven fibrous component for controlling the leakage of hydrophobic compounds may contain a hydrophobic compound-absorbing compound encapsulated in a polymeric component of the component.

The dressing of the present invention may comprise a mixture of nanofibers that are elastic and hydrophilic or hydrophobic with hydrophilic particles adhered thereto. For example, WaterlockPolymers (gain Processing corp., Muscarine, IA) can be incorporated into highly hydrophilic bandages that can account for 60 times or more of their dry weight in water. Such elastic, water-containing wound dressings may provide a reservoir for water and support fluid flow driven by alternating compression and expansion of the bandage. Such dressing materials may also provide for the delivery of therapeutic substances to the wound site, as well as the delivery of soluble or water-deliverable healing by-products away from the wound.

It is envisioned that the proportions of each component in the nonwoven fibrous component may vary depending on the particular requirements of a particular type of application. It is also envisioned that the proportions of each component in the dressing may vary within the nonwoven fibrous component itself such that the composition of the component on one surface is different from the composition of the component on the other surface. For example, one or more fibers made primarily of an elastic polymer may form the surface of the dressing furthest from the wound. In this portion of the dressing, the percentage of elastic polymer present in the fibers may be close to and include 100%. Inside the dressing, one or more fibres containing an increased amount of hydrophilic polymer may be present. In this portion of the dressing, the percentage of hydrophilic polymer present in the fibers may be close to and include 100%. The thickness of the portion of the dressing may also vary depending on the desired needs of a particular application. The fiber(s) on the surface of the dressing to be placed in contact with the patient may contain an increased amount of polymer with adhesive properties. The percentage of adhesive polymer used in the fibers of this portion of the dressing will vary with the need for dry adhesion (adhesive attachment) or non-adhesive attachment (non-adhesive attachment), but is accessible and 100% included. The transition from one type of polymer to another can be gradual, without creating a distinct fiber type layer within the dressing, or abrupt, thus creating distinct layers within the dressing. The polymer fibers can be used under aseptic conditions. Alternatively, the composition of the at least one fiber may be constant along the length of the fiber.

As described more fully below, the hydrophilic component is believed to absorb water and swell when contacted by water, thus surrounding the adhesive component so that the adhesive does not adhere to the wound surface. The hydrophilic component also keeps the dressing moist, facilitating the movement of water to the outer surface of the dressing, and facilitating the movement of the therapeutic substance throughout the dressing. Examples of suitable hydrophilic polymers include, but are not limited to, linear polyethylenimines, cellulose acetate and other grafted cellulosics, polyhydroxyethylmethacrylate, polyethylene oxide, polyvinylpyrrolidone, polyurethane, polypropylene oxide, and mixtures and copolymers thereof. The hydrophilic component may also be a water-absorbing gel, such as a WaterlockA polymer or carboxymethyl cellulose. The hydrophilic component may be incorporated into the fibers, adhered to the surface of the fibers, or physically retained between fibers.

The elastic component of the present invention provides mechanical strength to the dressing and the ability to accommodate stretching of the skin. Mechanical strength is required not only to hold the assembly in place during use, but also to facilitate removal of the dressing when it needs to be replaced. Examples of suitable elastomeric polymers include, but are not limited to, polyurethanes, polyesters, polyanhydrides, polyamides, polyimides, and mixtures and copolymers thereof.

Some embodiments may also include one or more adhesive components for adhering the assembly to a substrate. Suitable polymers having adhesive properties include, but are not limited to, homopolymers and copolymers of acrylates, polyvinylpyrrolidones, and silicones, and mixtures thereof. The adhesive may be a fiber forming an open network that adheres the dressing to the wound at many points, but allows fluid to necessarily pass through the voids in the adhesive network.

The polymer contained in the fiber may also contribute to more than one type of ingredient. For example, acrylate block copolymers may be used. In this case, the acrylate block provides adhesive properties while the copolymer block contributes hydrophilic properties.

While not wishing to be bound by any one theory, it is believed that the constituents of the fiber-forming polymer produce structures within the fibers by phase separation, which are in the form of rods, granules, flakes, or other geometric shapes. It is also believed that the hydrophilic component may swell and expand upon wetting in a manner that physically prevents the viscous component from coming into contact with the substrate surface. Thus, the medical dressing according to the invention will adhere to intact skin, since the hydrophilic polymer has not yet contacted water and has not yet swelled to surround the adhesive component. In the early stages of healing, the dressing will not adhere to the wound or tissue, on the other hand, because moisture from the wound contacts the hydrophilic component, swelling it and preventing the adhesive from adhering to the wound.

Likewise, a portion of the dressing is intentionally wetted, which would otherwise adhere to the skin, which would cause the hydrophilic region to swell. This wetting and swelling allows for easy removal of the bandage. Advantageously, inadvertent wetting should be avoided to hold the bandage in place.

The nonwoven fibrous component may also be used for other purposes. For example, the fiber assembly may be used to deliver pesticides, nutrients, or other desired compounds to crops. The fibrous assembly may adhere to the crop when dry, but can be easily removed by washing with water. The assembly may also be used as a type of sponge or wall-less bottle to absorb or contain water or other liquids. The fibrous assembly can thus be used in diapers, personal hygiene products, absorbent towels and the like.

The present invention also provides a method of making a nonwoven fibrous component comprising the steps of: at least one fiber-forming material is provided that contains a viscous component, an elastic component, and a hydrophilic component, and at least one fiber is made from the fiber-forming material. The fiber assembly of the present invention may be made from polymers that are soluble in organic or aqueous solvents. The fiber-forming material may be provided in a solvent such as, for example, an alcohol, ethyl acetate, acetone, or Tetrahydrofuran (THF). Optionally, the solvent may be biocompatible.

The method of the present invention may optionally include a treatment step to provide one or more desired properties of the dressing after the fibers are formed. For example, fibers containing water soluble materials can be crosslinked to form water insoluble fibers. In another embodiment, the fibers may be treated to include therapeutic or pharmaceutical products. For example, linear polyethylenimines can be treated with nitrogen oxide to form polyethylenimine diazeniumdiolates(polyethyleniminediazeniumdiolate)。

As noted above, the relative amounts of the viscous component, elastic component, and hydrophilic component may vary over time during fiber formation. This time-dependent variation can produce a nonwoven fibrous assembly in which the composition on the first surface is different from the composition on the second surface. For example, one or more fibers may be electrospun primarily from an elastic polymer to form a surface of the medical dressing that will not contact the patient. When fibers are electrospun to form the interior of the dressing, an increased amount of hydrophilic polymer may be used to form the fibers. After a sufficient amount of fibers containing hydrophilic polymers are incorporated into the dressing, an increased amount of polymers with adhesive properties may be used to form the fibers of the dressing.

The transition from one type of polymer to another may be gradual (i.e., the gradient between polymer types does not change), which does not create a distinct fiber type layer within the dressing. Alternatively, the transition may be abrupt, thus creating a distinct layer within the dressing. Such abrupt transitions can be accomplished by a step-wise concentration gradient from one polymer to another or a complete transition from one polymer to another in a single step. The transition between regions of the dressing may also be the result of a gradient between polymer types that is not constant or "skewed". Other variations or combinations of transitions may also be used in this method. Also, the layers at the center of the dressing may be different from those in the rest of the bandage, for example, by controlling the position of the fiber jets with an electric field or air flow.

In one embodiment, a medical dressing is prepared according to the following method. At least one fiber is electrospun from an elastic polymer, such as an elastic polyurethane, under conditions that produce a fiber (i.e., a wet fiber) containing an excess of solvent, either throughout the fiber or only on the surface of the fiber. The wet fiber or fibers are collected in a receptacle such as a non-adhesive film. At high temperatures, the collected wet fibers will melt at the intersections to form a fibrous membrane with high water vapor transmission rate and air permeability. The conditions of electrospinning are then changed so that the dry fibers are received over the wet fibers. This can be achieved, for example, by increasing the distance between the electrospinning apparatus and the receptacle. When a layer of dry fibers is placed on the wet fibers, the composition of the polymer becomes a hydrophilic polymer, such as a hydrophilic polyurethane. The second polymer may be introduced in a step gradient, a constant gradient, a skewed gradient, or any combination thereof. The concentration of hydrophilic polymer may approach and/or be equal to 100%. A predetermined amount of fibers is deposited and then the composition of the fibers is changed to a viscous polymer. As with the transition between the previous polymer types, the transition may occur through a step gradient, a constant gradient, a skewed gradient, or any combination thereof. The composition of this portion of the dressing may be close to and/or equal to 100% of the adhesive polymer. The adhesive polymer forms a dressing surface that is applied to a patient.

In one embodiment, the present invention provides a method of treating a patient comprising applying a medical dressing to a predetermined area of the patient. The dressing contains one or more fibers and contains an adhesive component, an elastic component, and a hydrophilic component. Such a method may be used to apply one or more fibers to a burn, wound, or another area in need of protection from contamination, or an area in need of treatment with a therapeutic or pharmaceutical compound. The method may include forming the at least one fiber on a separate receptacle and transferring the at least one fiber to a predetermined area of a patient. Optionally, the method may comprise applying the at least one fibre directly to the predetermined area, for example by electrospinning the fibre onto the wound.

As indicated above, other additives, soluble additives or insoluble particulates may also be included in the liquid(s) from which the at least one fiber is to be formed. In one embodiment, these additives are medically important topical additives that are provided in at least therapeutically effective amounts to treat a patient. The specific amount defining an effective amount depends on the type of additive, as well as the wound and physical characteristics of the patient. In general, however, such additives may be incorporated into the fibers in amounts ranging from trace amounts (less than 0.1 parts by weight per 100 parts of polymer) to 500 parts by weight or more per 100 parts of polymer. Examples of such therapeutic additives include, but are not limited to: antimicrobial additives, such as silver-containing antimicrobials and antimicrobial polypeptides; analgesics, such as lidocaine (lidocaine); soluble or insoluble antibiotics, such as neomycin; thrombin haemagglutinin combinationSubstances (thrombogenic compounds); nitric oxide-releasing compounds that promote wound healing, such as sydnonimines and diazeniumdiolates(diazeniumdiolate); a bactericidal compound; a fungicidal compound; an antiviral compound; a bacteriostatic compound; an anti-inflammatory compound; an anthelmintic compound; an antiarrhythmic compound; an antidepressant; an antidiabetic agent; anti (epileptic) epileptic drugs (anti-epilietics); anti-muscarinic drugs (antimuscarinics); an anti-mycobacterial compound; an anti-tumor compound; an immunosuppressant; anxiolytic sedatives (anxiolyticsedatives); an astringent; a beta-adrenoceptor blocking compound; a corticosteroid; a cough suppressant; a diagnostic compound; a diuretic; an anti-parkinson's disease compound; an immunizing compound; a muscle relaxant; vasodilators (vasodialators); hormones, including steroids; a parasympathomimetic functional compound; a radiopharmaceutical agent; antihistamines and other anti-allergic compounds; anti-inflammatory compounds, such as PDE IV inhibitors; neurohormonal inhibitors, such as NK3 inhibitors; inhibitors of emergency proteins, such as p38/NK/CSBP/mHOGl inhibitors; antipsychotic agents; xanthine; nucleic acids such as deoxyribonucleic acid, ribonucleic acid, and nucleotide analogs; enzymes and other proteins and growth factors. Furthermore, the embodiments of the present invention also include non-therapeutic or inert ingredients such as adhesives, fragrance and/or odor absorbing compounds.

In yet another embodiment, additives that impart structural properties to the article may be included. These additives include small solid particles; dispersed droplets of immiscible liquid in which other substances can be dissolved; a crosslinking compound; a blowing agent to produce a foam; a binder; elastomers and the like. Such components may be selected for their function in protecting and healing wounds.

It will be appreciated that many different types of fibre mats may be produced according to the invention, depending on how the fibres are produced and deposited. In one embodiment, the liquid to form the fibers is a mixture of a viscous polymer, a hydrophilic polymer, and an elastomeric polymer. Thus, one fluid provides the entire fiber mat. However, it is also envisioned that composite fibers of different compositions may be woven together or in a continuous layer to provide a suitable fiber mat.

Methods of using the medical dressings of the present invention may include applying at least one fiber to a predetermined location to form a fibrous, non-woven matrix. The predetermined site may be one or more of a wound, an area in need of protection from contamination, or an area in need of treatment with a therapeutic or pharmaceutical compound. The dressing may include a hydrophilic component, an elastic component, and an adhesive component.

In another embodiment, the dressing of the invention additionally comprises at least one pharmaceutical or therapeutic agent selected from antibiotic compounds, such as bactericidal and fungicidal compounds; a bacteriostatic compound; a crosslinking compound; an analgesic compound; a thrombin haemagglutinin compound; nitric oxide releasing compounds, e.g. sydnonimines and diazeniumdiolates(diazeniumdiolate), which promotes wound healing; other pharmaceutical compounds; and nucleic acids, regardless of solubility in biocompatible solvents. In addition, such embodiments may contain non-therapeutic or inert ingredients such as adhesives, fragrances, odor-absorbing compounds. In contrast to previous electrospun fibers, the additives are not limited to those that are soluble in the polymer/solvent combination. In some embodiments, an insoluble additive is combined with the polymer/solvent combination of the present invention and incorporated into the fiber substantially unchanged from its form when added.

Finally, the present invention also provides an apparatus for forming at least one composite fiber. The apparatus is capable of forming at least one fiber comprising a hydrophilic component, an elastic component, and optionally an adhesive component. The apparatus comprises a plurality of reservoirs for containing more than one type of fibre-forming material; a plurality of valves, each independently in communication with the reservoir; and a fiberizing apparatus selected from the group consisting of spinnerets, NGJ nozzles, and electrospinning apparatuses in communication with the valve.

With reference to fig. 1, an embodiment of the device of the present invention can be described. The device 10 includes a first reservoir 12, a second reservoir 16, and a third reservoir 20. The first reservoir 12 is in fluid communication with a first valve 14. Likewise, second reservoir 16 is in fluid communication with second valve 18, and third reservoir 20 is in fluid communication with third valve 22. The first, second, and third valves 14, 18, 22 may be manually controlled or they may be placed in communication with a controller 24 for automatic control. First, first valve 14, second valve 18, and third valve 22 are optionally in communication with a mixing tank 26, which mixing tank 26 is in turn in communication with a fiberizing apparatus 28. Alternatively, a fiber-forming apparatus (spinneret, NGJ nozzle, electrospinning apparatus) may be connected to each reservoir. The rate at which the fibers are produced from each apparatus can be adjusted to supply a particular polymer in the amount required to produce the desired spatially variable structure. When the fiber-forming apparatus is an electrospinning apparatus, a power source is in electrical communication with the electrospinning apparatus.

The device 10 may be used to form fibers according to the present invention by placing an elastic component, a hydrophilic component, and optionally a viscous component, in each of the reservoirs 12, 16, and 20. The relative amounts of each component fed to the fiberizing apparatus 28 is controlled by selectively opening or closing each of the valves 14, 18 and 22. The relative amounts of each component control the composition of the fibers produced by the fiberizing apparatus 28.

The fibers of the present invention can be made according to various methods known in the art, including electrospinning, wet spinning, dry spinning, melt spinning, and gel spinning. Electrospinning is particularly suitable for making the fibers of the present invention because it tends to produce the finest (i.e., finest denier) fibers of any of the foregoing methods. Typically, electrospun fibers can be produced having very small diameters, typically on the order of about 1 to about 3000 nanometers, or from about 10 to about 2000 nanometers, or from about 25 to about 1000 nanometers, or from about 50 to about 500 nanometers, or even from about 5 to about 100 nanometers. As elsewhere in this specification and claims, individual ranges therein may be combined.

Another particularly effective method for producing the nanofibers of the present invention includes nanofibers made by a gas jet process (i.e., NGJ process). Such methods have been previously described and are known in the art. Briefly, the method involves the use of an apparatus having an inner tube and a coaxial outer tube with a side feeder arm (sidearm). The inner tube is recessed from the outer tube edge, thus creating a thin film-forming region. Fluid polymer is fed through the side feed arms and fills the empty space between the inner and outer tubes. The polymer melt continues to flow toward the outflow end of the inner tube until it contacts the effluent gas jet. The gas jets on the melt surface collide to produce a thin film of polymer melt that travels to the outflow end of the tube where it is ejected forming turbulent cloud nanofibers.

Electrospinning and NGJ techniques allow the processing of polymers from organic and aqueous solvents. Moreover, with electrospinning and NGJ techniques, the addition of particle dispersions and soluble non-fiber-forming additives (i.e., spinning additives) to the fluid to be spun does not prevent the formation of a fibrous mat. Thus, a wide variety of additives may be incorporated into the fibers and devices described herein. Thus, the absorbent additive may be included, for example, sodium polyacrylate or 2-acrylamide/2-acrylic acid copolymer, and the like.

Examples

The following examples have been set forth in order to demonstrate the practice of the invention. From the container containing WaterlockA-180 and TecophilicElectrospinning of polymers in THF/ethanol solution (30: 70)The fibers are combined to form a nonwoven fiber assembly or mat. WaterlockThe polymer is a corn starch/acrylamide/sodium acrylate copolymer, available from Grain Processing Corp. (Muscatine, IA). WaterlockThe polymer provides a hydrophilic component to the resulting fibrous assembly. TecophilicIs an aliphatic polyether-based polyurethane available from Thermedics Polymer products (Wilmington, Mass.), said TecophilicThe fibrous component is provided with an elastic component and a hydrophilic component.

The polymer solution was spun from a conical metal reservoir and the spacing was varied with a laboratory jack. The metal cone is suspended by a metal wire connected to a high voltage power supply. The voltage and spacing were varied to produce the best fibers at the highest speed. An aluminum foil was covered over the target plate and a square polyester mesh was placed over the aluminum foil, collecting the fibers thereon. The diameter of the hole at the tip of the metal reservoir is in the range of about 0.5mm to about 1.5 mm. For higher viscosity solutions, larger pores are selected. The polymer solution is slightly more viscous than water to enable spinning. In some embodiments, the reservoir is conical. However, many shapes work equally well. Likewise, in some embodiments, the aperture at the tip of the reservoir is circular. However, various shapes work equally well.

The base polymer solution was 14% (w/w) Tecophilic in ethanol and THF (80: 20)A polymer solution. This solution was prepared as follows. First the TecophilicDissolved in excess THF and then concentrated by evaporation. Ethanol is then added to the solution to provide the desired concentration. The next step is to incorporate the absorbent polymer, WaterlockOr sodium (poly) acrylate (SPA) -suspended in ethanol and the Tecophilic was addedAnd (3) solution. The absorbent needs to be re-suspended periodically, for example by inverting or shaking the container several times. Using WaterlockIn TecophilicI.e. 0, 7, 30, 47, 71, 85 and 95%, wherein each percentage is calculated on a weight to weight (w/w) meter basis. 50: 50(w/w) SPA/Tecophilic was also preparedAnd (3) solution.

The Waterlock/TecophilicThe viscosity of the solution is such that the metallic conical reservoir used can have a hole of about 1mm in diameter. All examples were spun at room temperature at a 37cm pitch and a voltage of 37 kV. SPA/Tecophilic using a cone with a hole of about 1.5mm in diameter at a voltage of 30kV and a spacing of 30cmThe solution is spun. 25 to 30 g of fiber-forming solution are requiredParts, to produce a fiber mat having dimensions of about 1mm x 10cm and a dry weight of about 2 grams. The fibers were then removed from the polyester web and cut into 1.5cm squares to test their absorbency and tensile strength. The diameter of the nanofiber segments can vary, between about 500 to 1500 nm. The thickness of the nonwoven sheet is also varied, but in most cases, a sample of about 1mm thickness is used.

Relative to the content without WaterlockThe absorbent capacity of the mat of fibers of (1), containing 7, 30, 50, 70 or 85% WaterlockThe fibrous mat of (WL) was tested for its absorbent capacity for water and urine. Synthetic urine was prepared by adding the following to distilled water: 25g urea, 9g sodium chloride, 2.5g sodium phosphate, 3g ammonium chloride and 3g sodium sulphate. Once all the material was dissolved, additional distilled water was added until the total volume was equal to 1L.

The test method is to first weigh the fiber sample and record its dry weight and starting dimensions. The fiber sample was then placed in a beaker containing water or synthetic urine and removed after five seconds. The wet sample was placed on a paper towel and the excess water was allowed to drain gradually. The sample is then weighed and measured. The process continues with the weight and size being measured after 0.16, 0.5, 1, 2,5 and 10 minutes of immersion. Finally, the fibers were submerged for at least 24 hours to reach an equilibrium absorption state. The absorption capacity is defined as:

Q＝(W₂-W₁)/W₁

wherein Q is the absorption capacity, W₁Is the initial weight, W₂Is the weight of the fiber mat when wet. The percent absorbent capacity of each sample is graphically represented in fig. 5. FIG. 5 shows WaterlockThe addition of the polymer increases the absorbent capacity of the resulting fibrous assembly. Absorbency can also be determined by any of a variety of methods known in the art, such as Absorbency Under Load (abl underload (AUL)) or Gravimetric Absorbency Analysis System (GATS).

Each Waterlock/TecophilicFour samples in combination were tested and the average absorbent capacity of the four samples at equilibrium was calculated. FIG. 6 shows a Waterlock containing 0% to 85% by weight(WL) graph of equilibrium/initial absorbency ratio of nanofibers to water.

The fibrous mat absorbs 400% to 6000% when placed in water and 500% to 1250% in synthetic urine. FIG. 5 shows the results when only Tecophilic is usedNanofibers made of polymer (identified in the figure as Waterlock)At TecophilicMedium 0%) the nanofibers containing 7% absorbent had very similar results. For synthetic urine, the increase in absorbent capacity is not as great as for water as the amount of absorbent increases. Fig. 5 shows a comparison between the absorption capacity in water and in synthetic urine. As the amount of absorbent increases, the difference between the absorption capacity in water and the absorption capacity in synthetic urine also increases.

WaterlockProducers of absorbents point out that up to 160mL of water can be absorbed per gram of polymer. Containing HEFC (e.g. Tecophilic)) And an absorbent component (e.g. Waterlock)) The nano-fiber of (a) absorbs less moisture than pure Waterlock in powder formMuch more absorbed. The experimental data showed only 90mL of water per gram of polymer, a 44% reduction. While not wishing to be bound by any one theory, it is believed that this decrease may be attributed to the mechanical binding of the HEFC to the absorbent component, which limits swelling.

The absorption rate is determined by calculating the percentage of absorption at a known time. The percent absorption is the ratio of the liquid weight gain at any time to the liquid weight gain at equilibrium. Waterlock at 0%, 7%, and 30% in 5 secondsThe sample almost reached its maximum absorption. With WaterlockThe rate of absorption by the fiber decreases with increasing amounts. After 5 seconds 50% and 70% of the samples absorbed more than 75% of their maximum absorption. 85% of the samples took 2 minutes to reach 73% of their maximum absorption.

Containing 85% WaterlockThe nonwoven sheet sample of (1) was thicker than the others. Samples of nonwoven sheets used for the absorption test are typically about 1.0mm thick. At 85% WaterlockOnly one of the four samples of (a) was 1.0mm thick. The thicknesses of the other three are 15mm, 20mm and 25 mm. It was observed that the time required for the thicker sheet to reach maximum absorption was longer than for the thinner sheet. This variation in sheet thickness allows for large differences in the observed absorption rates.

The size of each sample was measured when dry and when saturated with water. The dimensions were analyzed by calculating the wet/dry area ratio and the wet/dry thickness ratio. When Waterlock in the sampleAs the amount of (a) increases, the wet/dry area ratio also increases. Wet/dry thickness ratio with WaterlockThe concentration did not change significantly. This indicates the absence of WaterlockThe nanofibers of (a) expand the most in the length and width dimensions. The addition of the absorbent increases the length, width and thickness of the nanofibers in the wet state.

Scanning electron micrographs (SEM's) were obtained of the fiber mat according to the invention, wherein the mat was in two different states. The first micrograph (shown in FIG. 3) shows the original electrospun fiber gel, i.e., before wetting. The second micrograph (fig. 4) shows the fiber gel after the water has been absorbed and then removed by vacuum. The broken and entangled film in fig. 4 indicates the location of the absorbent particles, which are not present after wetting and drying. It appears that the entangled film contains the absorbent particles, which may have been removed by wetting. This result is consistent with particles embedded in HEFC. More particularly, it appears that the particles expand to the point of fracturing the HEFC, leaving only a hollow membrane surrounding the particles. Alternatively, the dry particles of absorbent may become sheet-like structures once wetted and remain trapped in that form after drying.

Ideally isThe absorbent not only can rapidly absorb fluid, but also can resist mechanical force in a wet state. Mechanical testing was performed which measured the amount of stress and strain that the fiber mat could withstand before it broke. An Instron 5567 mechanical tester was used. Dumbbell-shaped pieces conforming to ASTM 5-D638 were cut from the fiber mat and are shown in FIG. 2. The thickness of the fiber mat was measured in three places, which are identified in fig. 2 by the numbers 1, 2 and 3. The two black lines are spaced 10cm apart and mark the area where the stretch is measured. Since the absorption capacity test showed that after 5 seconds a total water increase of 95% was reached, the area between the two black lines was wetted with water for at least 1 minute before the test was performed. Dumbbell parts 1 and 3 were not wetted and served as attachments to the tensile tester grips. Thickness measurements were made on the dry sample at dumbbell portion 2. Waterlock at each different concentration/TecophilicThree samples (0%, 7%, 30%, 50%, 70% and 85%) were tested. All tensile measurements were taken when the clamps were separated at 50 mm/min.

These samples were stretched at a speed of 50 mm/min. FIG. 7 shows a Waterlock containing 7, 30, 50, 70, or 85% WaterlockStress-strain characteristics of the sample of (WL). According to this data, these samples can absorb deformation amounts (i.e. strain) exceeding 500% in each case. Containing 7% WaterlockThe tensile strength of the fibre assembly of (a) is maximal, which is also greater than TecophilicSample (0% WL) is large.

The TecophilicThe polymer provides strength and elasticity to the nanofiber, while WaterlockNone. WaterlockThe higher the concentration of (a), the weaker the nanofiber becomes, as shown in fig. 7. Contains high content of WaterlockThe nanofibers of (1), i.e. 70% and 80%, are not mechanically strong, they break below 0.5 MPa. Those completely free of WaterlockOr only contains 7 percent of nano-fiber, and the nano-fiber is not broken until the stress reaches 2-3 MPa. 70% and 80% WaterlockThe sample also had the lowest strain at its fracture point.

According to these data, the deformation (i.e., strain) that these samples can withstand before breaking was over 500% in all samples. Containing 7% WaterlockThe tensile strength of the fibre assembly of (a) is maximal, which is also greater than that of the fibre assembly essentially consisting of TecophilicPolymer composition and being substantially free of WaterlockThe tensile strength of the sample (2) is high. Waterlock for 70% and 80% WaterlockFor the sample, the strain at the break point was about 600%. Has low content ofConcentration WaterlockThe samples of (a) all broke at about 850% to 900%.

The total amount of absorbent material lost from the nanofiber matrix was measured. Samples were taken from the fiber mat, weighed, and placed in a container of known mass. The sample was then immersed in a quantity of water for about 24 hours, after which the sample was removed and the residual solution was evaporated. The amount of residual material left after evaporation was measured and compared to the starting mass of the fiber mat:

the percentage of leachable species is in the range of about 1.58% to about 4.46%, which is acceptable.

The importance of the percentage of leachable substances is based on the fact that: the absorbent is generally embedded to some extent in the fibrous component. If the fibrous material is strong enough, the absorbent will resist rupturing when it swells due to liquid absorption. Conversely, if it is not sufficiently strong, the fibrous material will likely rupture and release the absorbent. In fact, it is difficult to completely eliminate the breakages, however, formulations exhibiting better strength tend to exhibit fewer breakages, and therefore fewer leachable substances.

One embodiment of the present invention includes a bandage that is highly absorbent and strong even when wet. Another embodiment of the present invention includes a diaper that is highly absorbent and strong even when wet. Yet another embodiment of the present invention comprises a highly absorbent and robust means for absorbing spilled liquids. Such liquids include, but are not limited to: harmful chemicals, biologically harmful substances, household goods, food and household or industrial cleaning agents. Yet another embodiment of the present invention includes a cleaning device, such as a mop head, a dishwashing cloth, a sanitary wipe, or a floor waxing device. Still another embodiment of the present invention includes a cosmetic or personal hygiene product including, but not limited to, a sanitary napkin, a tampon, or a sponge for washing.

In this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Unless defined otherwise, 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.

It is to be understood that any variations which would be apparent to one of ordinary skill in the art are intended to be within the scope of the claimed invention and, thus, the selection of specific component elements may be determined without departing from the spirit of the invention disclosed and described herein. Furthermore, the present invention is not limited to the examples and embodiments set forth herein, which are intended to be illustrative only. Rather, the scope of the invention is to be determined solely by the claims.

Claims (30)

1. A liquid entrapping device comprising: an absorbing component; and a hydrophilic elastic fibrous component, wherein the absorbent component and the hydrophilic elastic fibrous component are in physical proximity such that fluid communication occurs, and wherein the absorbent component has a greater absorbent capacity than the hydrophilic elastic fibrous component, and wherein the liquid entrapping device comprising the hydrophilic elastic fibrous component is formed from at least one nanofiber, wherein the at least one nanofiber comprises the absorbent component and the hydrophilic elastic fibrous component in a nanofiber body.

2. The liquid entrapping device of claim 1, wherein the absorbent component is distributed in an embedded manner within the hydrophilic elastomeric fibrous component.

3. The liquid entrapping device of claim 1, wherein the absorbent component is selected from the group consisting of polyesters, polyethers, polyester-polyethers, polymers having pendant carboxylic or hydroxyl groups, polysiloxanes, polyacrylamides, kaolins, serpentines, smectites, glauconite, chlorite, vermiculite, attapulgite, sepiolite, allophane and imogolite, sodium polyacrylate, 2-acrylamide/2-acrylic acid copolymer, and any combination thereof.

4. The liquid entrapping device of claim 1, wherein the hydrophilic elastomeric fibrous component is selected from the group consisting of zein, polyester elastomers, polydimethylsiloxanes, hydrophilic ether ester copolymer elastomers, elastomeric copolymers of silicone and polyethylene glycol, polyacrylates, thermoplastic polyurethanes, ether urethane copolymers, and any combination thereof.

5. The liquid entrapping device of claim 1, wherein the absorbent component is present in an amount of 1% (w/w) to 85% (w/w).

6. The liquid entrapping device of claim 1, wherein the absorbent component is present in an amount of 5% (w/w) to 50% (w/w).

7. The liquid entrapping device of claim 1, wherein the absorbent component is present in an amount of 30% (w/w) to 50% (w/w).

8. The liquid entrapping device of claim 1, wherein the hydrophilic elastomeric fibrous component is selected from the group consisting of polyurethanes, ether urethane copolymers, and any combination thereof.

9. The liquid entrapping device of claim 1, wherein the liquid entrapping device comprises a device selected from the group consisting of: diapers, cotton balls, sanitary napkins, sanitary wipes, spill absorbers, mop heads, and floor waxing devices.

10. The liquid entrapping device of claim 1, wherein the liquid entrapping device further comprises: an absorption capacity for water of 400% to 6000%, wherein the absorption capacity is defined as Q ═ W (W)₂-W₁)/W₁。

11. The liquid entrapping device of claim 10, wherein the liquid entrapping device further comprises: the absorption capacity for water is 500% to 5500%.

12. The liquid entrapping device of claim 1, wherein the liquid entrapping device further comprises: an absorption capacity for urine of 500% to 1250%, wherein the absorption capacity is defined as Q ═ W (W)₂-W₁)/W₁。

13. The liquid entrapping device of claim 12, wherein the liquid entrapping device further comprises: the absorption capacity for urine is 500% to 1000%.

14. The liquid entrapping device of claim 13, wherein the liquid entrapping device further comprises: an absorption capacity for urine of 600% to 1000%, wherein the absorption capacity is defined as Q ═ W (W)₂-W₁)/W₁。

15. The liquid entrapping device of claim 1, wherein the liquid entrapping device further comprises: the capacity of 100% of its equilibrium capacity can be absorbed in 5 seconds.

16. The liquid entrapping device of claim 15, wherein the liquid entrapping device further comprises: can absorb over 73% of the balance capacity in 5 seconds.

17. The liquid entrapping device of claim 16, wherein the liquid entrapping device further comprises: the capacity of more than 75% of the equilibrium capacity can be absorbed within 2 minutes.

18. The liquid entrapping device of claim 1, wherein the liquid entrapping device further comprises: the tensile strength when the device is wetted with water is 0 to 3.0 MPa.

19. The liquid entrapping device of claim 18, wherein the liquid entrapping device further comprises: the tensile strength when the device is wetted with water is 0.25 to 3.0 MPa.

20. The liquid entrapping device of claim 18, wherein the liquid entrapping device further comprises: the tensile strength when the device is wetted with water is 0 to 2.8 MPa.

21. The liquid entrapping device of claim 20, wherein the liquid entrapping device further comprises: the tensile strength when the device is wetted with water is 0.25 to 2.8 MPa.

22. The liquid entrapping device of claim 1, wherein the liquid entrapping device further comprises a breaking point at 850% to 900% strain.

23. The liquid entrapping device of claim 1, wherein the liquid entrapping device further comprises a breaking point at 600% strain.

24. The liquid entrapping device of claim 1, wherein the liquid entrapping device further comprises: 1% (w/w) to 5% (w/w) of a leachable substance.

25. The liquid entrapping device of claim 24, wherein the liquid entrapping device further comprises: 1.6% (w/w) to 4.5% (w/w) of leachable substance.

26. The liquid entrapping device of claim 24, wherein the liquid entrapping device further comprises: 1% (w/w) to 4% (w/w) of leachable substances.

27. A method of making a liquid entrapping device comprising: spinning at least one fiber from a solution comprising a hydrophilic elasticity-producing component and an absorbent component, wherein the fiber comprises an absorbent component that is physically proximal to the hydrophilic elasticity-producing component so as to be in fluid communication therewith, and wherein the absorbent component has a greater absorbent capacity than the hydrophilic elastic fibrous component, and wherein the liquid entrapping device comprising the hydrophilic elastic fibrous component is formed from at least one nanofiber, wherein the at least one nanofiber comprises the absorbent component and the hydrophilic elastic fibrous component in a nanofiber body.

28. The method of claim 27, wherein the product comprises a product selected from the group consisting of diapers, bandages, devices for absorbing chemical spills, devices for absorbing biohazard spills, mop heads, dish cloths, sanitary wipes, floor waxing devices, sanitary napkins, cotton balls, and sponges,

29. a method of using a liquid entrapping device prepared according to claim 28, comprising: the liquid entrapping device is contacted with at least one absorbable liquid.

30. A product prepared according to the method of claim 27.