MXPA94009544A - Composite nonwoven fabric and articles produced therefrom - Google Patents

Abstract

The invention is directed to a composite nonwoven fabric (10) comprising first and second nonwoven webs (11, 13) of spunbonded substantially continuous thermoplastic filaments, and a nonwoven hydrophobic microporous web (12) of thermoplastic meltblown microfibers sandwiched between the first and second nonwoven webs. The filaments of the nonwoven spunbond webs are formed of continuous multiconstituent filaments which include a lower melting gamma radiation stable polyethylene polymer component and one or more higher melting gamma radiation stable polymer constituents, wherein a substantial portion of the surfaces of the multiconstituent filaments consists of the lower melting gamma radiation stable polyethylene constituent. The nonwoven hydrophobic microporous web is formed from a gamma radiation stable polyethylene polymer. The webs are bonded together to form the composite nonwoven fabric by discrete point bonds in which the polyethylene constituent of said multiconstituent filaments and the polyethylene of said third nonwoven web are fused together.

Description

MIXED NON-WOVEN FABRIC AND ARTICLES PRODUCED FROM THE SAME AND CROSS REFERENCE TO RELATED REQUESTS This application is a continuation-in-part of the co-pending United States Patent Application Serial No. 07 / A96,323, filed June 10, 1992 and a continuation-in-part of the Application for Co-pending patent of the United States with serial No. 08 / 093,7 ^ 6 filed on July 19, 1993.

FIELD OF THE INVENTION The invention relates to non-woven fabrics and more specifically, to mixed non-woven barrier fabrics particularly suitable for medical applications.

BACKGROUND OF THE INVENTION / ^ Non-woven barrier fabrics have been developed which prevent the passage of bacteria or other contaminants and which are used for non-disposable medical articles, such as surgical garments, disposable gowns, and the like. For example, said barrier fabrics can be formed by sandwiching an inner fibrous web of blown thermoplastic microfibers under melting between two external nonwoven webs of substantially continuous thermoplastic spinning-bonded filaments. The fibrous web blown under melting provides a barrier to bacteria and other contaminants, while the outer spin bonded layers provide good strength and abrasion resistance to the mixed nonwoven fabric. Examples of such fabrics are described in the U.S.A. 4, 041, 203 and U.S. Patent No. 4, A63.7, 5. In the manufacture of this type of fabric, the respective non-woven layers are thermally bonded to form a unitary mixed fabric. Typically, thermal bonding involves passing the non-woven layers through a heated calender provided with pattern and partially melting the blown layer under internal melting in discrete areas to form fusion bonds that hold together the non-woven layers of the mixed material. Without melting and melting enough of the melt blown layer, the mixed fabric will have poor crease adhesion. However, unless the thermal bonding conditions are exactly controlled, there is a possibility that the "thermal bonding areas can become excessively hot, causing" tiny holes ", which can compromise or destroy the barrier properties of the blown layer under internal fusion.Thus, in practice, the thermal bonding conditions that are used represents a compromise between the required crevice resistance, on the one hand, and the required barrier properties that must be provided by the meltblown layer, on the other hand. Conventional spinning-bonding processes also have limitations on the types of sterilization process that may be used.For some applications, it is desired that the fabric or clothing be sterilized in the final stages of manufacture by exposing it to gamma radiation. fabric or clothing can be sealed first in a protective packaging, and then exposed to gamma radiation for sterilize the packaging and its contents. However, sterilization by gamma irradiation has been found to be unsuitable for many of the known medical barrier fabrics. Some of the polymers conventionally used in such medical barrier fabrics, such as conventional grades of polypropylene, for example, are especially sensitive to degradation by gamma irradiation. Fabrics produced from such polymers tend to lose strength over time, become brittle as a result of gamma irradiation. Also, the instability of the polymers towards irradiation gives as? result in the generation of unpleasant odors in the product that are unacceptable to the consumer. The conventional spin-blow-spin-spin-bonded spin-bond type barrier fabrics have limitations in the way they can be manufactured to a product, such as surgical draperies, surgical drapes, and the like. Typically, these types of fabrics do not tend by themselves to form seams in a fabric construction by thermal bonding to welding. In addition, such seams may be weak, and lack the integrity necessary to provide a complete barrier to the passage of contaminants. Fabrics formed from conventional spunblown-spunbonded fabrics can be constructed by baking, but this can be misleading, since punching the fabric with a needle results in holes in the fabric, which they damage the integrity of the fabric and the continuity of the barrier properties of the same. Several attempts have been made to overcome these limitations. For example, efforts have been made to make the polypropylene polymers more stable to gamma irradiation, such as by incorporating certain additives into the polymer to reduce the amount of degradation. For example, the patent of E.U.A. No. 4,622,666 discloses a polypropylene fabric stabilized with radiation wherein a long-chain aliphatic ester is added to the polymer, the U.S. No. 5,041,463 describes the incorporation of a colophonic ester into polypropylene to stabilize the polymer and reduce the tendency of odor generation after the * gamma irradiation. However, the use of such additives adds costs to the manufacturing process. In addition, polypropylene is difficult to make stable to gamma irradiation at normal commercial dose levels, even with the use of additives or stabilizers. The component layers of spunbonded meltblown-type spin-barrier barrier fabrics can also be formed of polymers that are stable to gamma irradiation. Such polymers include polyamides, polyesters, some polyolefins, such as polyethylene and the like. However, fabrics formed using high melting temperature polymers, such as polyamide and polyester, are not easily thermally bonded. The high temperatures that are required to sufficiently bind the fabric can destroy the meltblown barrier properties and the structure of the external spinbonded webs. Adhesives can be used to bond the high melting point temperature layers, but this can result in the resulting fabric stiffness and added costs. Therefore, it could be advantageous to provide a fabric that provides a barrier to the transmission of contaminants and that retains its resistance and does not create an unpleasant odor when sterilized in the presence of gamma radiation. It could also be advantageous to provide said fabric, which exhibits good aesthetic properties, such as desirable softness, covering and breathability, as well as good resistance and resistance to abrasion, and which can be easily constructed towards a product, such as a garment. surgical.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides mixed non-woven fabrics having desirable barrier properties and which are stable to gamma irradiation. The mixed nonwoven fabrics of the invention include first and second nonwoven webs bonded by spinning substantially continuous thermoplastic filaments, and a third nonwoven web sandwiched between the first and second webs and containing one or more hydrophobic microporous layers, which they form a barrier that is highly impermeable to bacteria but permeable to air. The nonwoven webs are formed of polymers that are stable to gamma irradiation. The spunbond webs are engineered so that the webs are bonded to form a mixed web without compromising the barrier properties of the microporous layer. More spunbond non-woven webs are formed from continuous filaments of multiple constituents that include a lower-melting gamma radiation stable polyethylene polymer component and one or more stable gamma point radiation polymer components. higher melting point, wherein the lower melting range stable polyethylene constituent is present on a substantial portion of the surface and the higher melting point polymer constituent is in a substantially continuous form along the length of the filaments. The non-woven microporous layer or layers may comprise a band of meltblown microfibers formed from a polyethylene polymer stable to gamma radiation. The webs are bonded to form the mixed nonwoven fabric by discrete knit ties, in which the polyethylene constituent of said multi-constituent filaments and the polyethylene microfibers of said third non-woven web is fused together.

The mixed nonwoven fabric of this invention is characterized by having an excellent balance of strength, breathability, and barrier properties, as well as stability to gamma radiation, such properties making the fabric particularly useful in medical and industrial applications. to be used as protective garments. The mixed non-woven fabrics of this invention have a tensile strength to the grip of at least o. To kg in the direction of crossing (DC) and 11.35 kg in the direction of machine (DM) and a Gurley air permeability of at least 35 cfm for fabrics that have a basis weight on the scale of 40 to 120 g.m18. The excellent barrier properties of the fabrics of this invention are illustrated by high hydrostatic column titrations, typically 35 cm or greater, and by bacterial filtration efficiency (EFB) ratings of 65% and more. In one embodiment of the invention, the continuous filaments of the spunbond non-woven webs have a two-component polymer structure. Such two-component polymer structures include sheath / core structures, collateral structures, and the like. Preferably, the two-component structure is a two-component sheath / core structure, wherein the sheath is formed from polyethylene and the core is formed from polyester. In another embodiment of the invention, the continuous filaments of spin-bonded nonwoven webs are formed by a combination of at least two different thermoplastic polymers. The polymer combination comprises a dominant phase and at least one phase dispersed therein. Illustrative of the combinations according to the invention are combinations wherein the dominant phase is a polymer selected from the group comprising polyamides and polyesters, and the dispersed phase is polyethylene. The composite fabrics of the present invention can be sealed or sewn by fusing the lower melting point polyethylene constituent by means of a hot heat, hot die sealer, ultrasonic sealer, RF sealer, or the like. This property is particularly advantageously for manufacturing products such as protective garments from mixed fabrics. Two or more pieces of the mixed fabric can be joined forming a continuous seam by fusion. The continuous fusion bonded seam maintains the protective barrier properties of the fabric along the seam, while other conventional methods, such as sewing, require the penetration of the non-woven barrier layer, and there may be a risk of this way, to break the barrier properties.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood from the detailed description that follows, and from the accompanying drawings, in which: Figure 1 is a diagrammatic cross-sectional view of a mixed non-woven fabric according to the invention; Figure 2 schematically illustrates one embodiment of a method for forming a mixed nonwoven fabric of the invention; Figure 3 illustrates a protective garment formed from mixed non-woven fabrics of the invention; and Figure 4 is a cross-sectional view taken along line 4-4 of Figure 3 and showing a seam bonded under melting of the garment.

- DETAILED DESCRIPTION OF THE INVENTION Figure 1 is a diagrammatic cross-sectional view of a mixed non-woven fabric according to one embodiment of the invention. The fabric, generally indicated at 10, is a 3-layer mixed material comprising an inner layer 12 sandwiched between the outer plates 11 and 13. The mixed fabric 10 has good strength, flexibility and drapery. The barrier properties of the fabric 10 make it particularly suitable for medical applications, such as surgical gowns, sterile wraps, surgical garments, caps, shoe covers, and the like, but the fabric is also useful for any other application where they are desirable. Barrier properties, such as work pants or other protective garments for industrial applications, for example. The outer layer 11 may suitably have a basis weight of at least about 3 g / p2 and preferably of about 10 g / m12 to about 30 g / m55. In the illustrated embodiment, the layer 11 is composed of continuous filaments of multiple constituents that have been formed into a nonwoven web by conventional spinning ligation techniques. Preferably, the filaments of the spin-linked fabric are pre-ligated at the filament crossing points to form a bonded band by unitary bonded spinning before being combined with the other bands of the mixed fabric. The outer layer 13 is also a non-woven band bonded <; - by spinning substantially continuous thermoplastic filaments. In the illustrated embodiment, the layer 13 is a nonwoven web of similar composition and with a basis weight as that of the outer layer 11. The multiple constituent filaments of the layer 11 have a lower melting point thermoplastic polymer constituent. and one or more thermoplastic constituents of higher melting point. For the purposes of this invention, it is important that a significant portion of the filament surface is formed by the lowest melting point polymer constituent, so that the lowest melting point constituent will be available for ligation, or is explained more fully below. At least one of the higher melting point constituents must be present in the filament of multiple constituents is a substantially continuous form along the length of the filament for good tensile strength. Preferably, the lower melting polymer constituent should have a melting point temperature of at least 5 ° C below that of the highest melting point constituent, so that at the temperatures used for the thermal ligation of the layers of the mixed fabric the higher melting point constituent retains its substantially continuous fibrous shape to provide a function of strength and reinforcement in the mixed fabric. The particular polymer compositions used in the higher and lower melting point constituents of the multi-constituent filaments can be selected from those range-stable polymers conventionally used in the formation of spun fibers under melting. Particularly preferred for the polymer constituent of the lower melting point is polyethylene, including polyethylene homopolymers, copolymers and terpolymers. Examples of polymers suitable for the higher melting point constituent include polyesters such as polyethylene terephthalate, polyamides such as poly (hexamethylene adipamide) and poly (caproamide), and copolymers and mixtures thereof. The filaments may also contain minor amounts of other polymers or additives without polymer, such as antistatic compositions, dirt release additives, water or alcohol repellents, and the like. In a preferred embodiment of the invention, the filaments are formed from a two-component polymer structure. The two-component polymer structure may be a sheath / core structure, a collateral structure, or other structures that provide that the lowest-melting gamma radiation stable polyethylene constituent is present on a substantial portion of the surface of filament and the higher melting polymer constituent is in a substantially continuous form along the length of the filaments. The two-component filaments can provide improved aesthetics such as softness based on the surface component of the two-component filaments, while providing good strength, resistance to breakage and the like, due to the stronger core component of filament. Preferred two-component filaments include sheath / core polyethylene / polyester filaments, such as sheath / core filaments of two-component polyethylene / polyethylene terephthalate. In another embodiment, the filaments are formed from a polymer mixture. In this embodiment of the invention, "E" c the dominant phase is a polymer selected from the group consisting of polyesters and polyamides, and the dispersed phase is a polyethylene.The dispersed base polymer is present in the mixture in an amount of about 1 to 203 »by weight, and preferably from about 5 to 15% by weight, of the polymer mixture, so that the polyethylene constituent stable to the lowest melting range gamma radiation is present on a portion of the filament surface and the higher melting polymer constituent is in a substantially continuous form along the length of the filaments The inner layer 12 comprises at least one microporous hydrophobic layer. understand a microporous film, a microporous sheet or band formed of thermally consolidated microfibers, or a microporous nonwoven web of microfibres. The microfibers are preferably manufactured according to the process described in the U.S.A. No. 3,976,185 of Butin et al. The inner layer 12 may suitably have a basis weight on a scale of about 10 to 80 g.m52 and preferably on the scale of approximately 10 to 30 g.m12. The microfibers preferably have a diameter of up to 50 microns, and desirably the fiber diameter is less than 10 microns. The polymer used to form the microporous layer or layers of layer 12 is also preferably selected for its stability to gamma irradiation. In addition, it must be selected so that it is thermally missible with the lowest melting point polyethylene constituent of the multi-constituent filaments. By "thermally misible", it is meant that polymers, when heated at thermal bonding temperatures, will be adherent and will join to form a single unitary bonding domain. Typically, to be "thermally miscible", the polymers will be of the same chemical composition or similar chemical composition that the copolymers are miscible with each other. If they are of different chemical compositions, the surface energies of the polymers are sufficiently similar so that they easily form an adherent bond when heated to a temperature of thermal activation. In contrast, polymers that are not thermally miscible with each other do not have such affinity between them to form adherent ligatures. Under conditions of thermal bonding, the polymers can be bound, but the binding mechanism is predominantly, if not exclusively, a mechanical bond resulting from mechanical work or encapsulation. The polymers do not form a unitary polymer domain but separate identifiable polymer phases remain. For purposes of the present invention, the microporous layer 12 is suitably formed of a polyethylene. In a preferred embodiment, meltblown thermoplastic microfibers comprise linear low density polyethylene (LLDPE), prepared by copolymerizing ethylene and an alpha-olefin having from 3 to 12 carbon atoms. More preferably, the polymer is LLDPE having a melting point of about 125 ° C. After the respective layers of the mixed non-woven fabric have been assembled, the layers are bonded together. The ligation can be achieved by heating the mixed fabric at a temperature sufficient to soften the polyethylene constiuent so that it fuses to the mixed nonwoven fabric to form a unitary structure. For example, when a two component filament is used, the mixed laminate is heat treated at a temperature sufficient to soften the lowest melting point polyethylene constituent thereof, so that it fuses with the nonwoven webs for * form a unitary mixed fabric. The layers can be ligated in any of the ways known in the art to achieve a thermal fusion ligation. Ligation can be achieved, for example, by the use of a heated calender, ultrasonic welding and similar means. The heated calender may include plain rolls or pattern or texturized rolls. In this way, the fabric can also be enhanced, if desired, through the use of textured or patterned rolls, to impart a desired surface texture and to improve or alter the tactile qualities of the mixed fabric. The pattern of the enhancement rollers can be any of those known in the art, including localized dot patterns, helical patterns, and the like. The enhancement may be in continuous or discontinuous patterns, uniform or random points or a Z? F combination thereof, all are well known in the art. Since a mixed fabric of three layers has been shown in the drawings, it should be understood that the number and arrangement of the layers may vary depending on the particular properties sought for the laminate. For example, several microporous layers may be employed in the invention and / or larger numbers of other fibrous webs may be used. In addition, at least one of the outer bands can be treated with a treatment agent to give the fabric one of the desired properties, such as flame retardation, hydrophilic properties, and the like. The presence of the lower melting point polyethylene constituent on the surface of the outer layers 11 and 13 spunbonded of the mixed fabric 10 allows the fabric to be sealed or sewn by fusing the lower melting point polyethylene constituent. means of a heat sealer, hot die, ultrasonic sealer, RF sealer, or the like. In this way, for example the edges of a fabric can be finished by fog a ligation of substantially continuous fusion by extending the peripheral edge, the fusion bond fog between the polyethylene constituent of the multi-constituent filaments of the outer layers. 11 and 13 linked by spinning and the polyethylene component of the inner band 12. This property is also advantageous for making products such as protective garments from the mixed fabric Two or more pieces of the mixed fabric can be joined together to form one Zjj f - continuous seam by fusion The continuous fusion bonded seam maintains the protective barrier properties of the fabric along the seam Figure 2 schematically illustrates a method for fog a mixed nonwoven fabric of the invention. conventional spinning ligation apparatus 20 forms a first layer 22 bonded by spinning of thermoplastic polymer filaments substantially almente continuous. The band 22 is deposited on the fog screen 24, which is driven in a longitudinal direction by the rollers 26.

The spinning bonding process involves * extruding a polymer through a generally linear die head or spinner 30 for spinning under melting the substantially continuous filaments 32. The spinner preferably produces the filaments in substantial and equally spaced arrangements and the holes in the die preferably have a diameter of about 0.00508 to about 0.116 cm. As shown in Figure 2, substantially continuous filaments 32 are extruded from the spinner 30 and extinguished by a supply of cooling air 34. The filaments are directed to an attenuator 36 after they are extinguished, and it is allowed therein an attenuation air supply. Although the extinguishing and attenuation zones separately are shown in the drawing, it will be apparent to one skilled in the art that the filaments can exit the spinner 30 directly into the attenuator 36 where the filaments can be extinguished, either by the supply of attenuation air or by a separate supply of extinguishing air. The attenuation air can be directed towards the attenuator 36 by a supply of air above the inlet end, by a vacuum located below a forming wire or by the use of integrally formed ejectors in the attenuator. The air continues down the attenuator 36, which is reduced in width in the direction away from the spinner 30, creating a nozzle effect by accelerating the air and causing attenuation of the filament. The air and the filaments exit the attenuator 36, and the filaments are collected on the collection screen 24. The attenuator 36 used in the spinning bonding process can be any of the suitable type known in the art, such as a towing apparatus. by slot or a tube type device (Lurgi). After the spin-bonded layer 22 is deposited on the screen 24, the web passes longitudinally below a conventional melt blowing apparatus 40. The melt blowing apparatus 40 forms a meltblown fibrous stream 42, which is deposited on the surface of the spunbonded web 22 to form a fibrous layer blown under melting. Melt blowing processes and apparatuses are known to those skilled in the art and are described in, for example, US Patents. 3,849,241 to Buntin, et al. And US patent. 4,048,364 to Hardipg, et al. The meltblown process involves extruding a molten polymeric material through fine capillaries into thin fi lament streams. The filamentary currents leave the face of the melting blow spinner where they find convergent streams of high velocity hot gas, typically air, supplied from nozzles 46 and 46. The convergent streams of high velocity heated gas attenuate the currents of polymer and break attenuated streams to microfibers blown under melting.

A meltblown / meltblown web structure 50 is thus formed. The structure 50 is then transported by the forming screen 24 in the longitudinal direction down to a point where a non-woven web of thermoplastic filaments is formed on the surface thereof. Figure 2 illustrates a spin-bonded layer formed by a second conventional spin-bonding apparatus 60. The spinning ligation apparatus 60 deposits a non-woven layer spinning on the TS ^ mixed structure 50 to thereby form a mixed structure 64 consisting of a spunbonded / meltblown / spunbond web. The mixed structure is then passed to a conventional thermal melt bonding station 70 to provide a mixed bonded nonwoven fabric 80. Here, the lower melting polyethylene constituent is softened so as to safely fuse the blown inner layer. under fusion to ß ^ - the external layers spin-linked while maintaining the integrity of the inner layer blown under melting. The resulting mixed web 70 leaves the heat fusion station 70 and is dened by conventional means onto the roller 90. The heat fusion station 70 is constructed in a conventional manner as is known to those skilled in the art, and is ventuously a calender having tie rolls 72 and 74 as illustrated in Figure 2. The tie rolls 72 and 74 may be smooth rolls, knit rolls, helical rolls, or the like.

Although the thermal fusion station is illustrated in Figure 2 in the form of a calender having ligation rollers, other heat treatment stations, such as air-binding, radiant or ultrasonic heaters, microwave treatments or other heat treatment RF that are capable of ligating the fabric according to the invention can be substituted for the calender of Figure 2. Such heating stations as conventional are known to those skilled in the art. The method illustrated in Figure 2 is susceptible to numerous variations. For example, although the schematic illustration of Figure 2 has been described in the formation of a spunbonded web directly during a continuous web process, it should be evident that spunbond webs can be preformed and supplied as preformed web rolls. Similarly, although the meltblown web 42 is shown to be formed directly on the spin-linked web 22, the melt blown web can be preformed and said preformed webs can be combined to form the mixed web, or they can be passed through the web. the heating rollers for further consolidation and then are passed over a spin-linked web or can be stored as a roll and fed from a preformed roll onto the spin-bonded layer 22. Similarly, the three layer web 64 can be formed and stored prior to bonding at station 70. In Figure 2, the reference character 95 indicates a surgical gown made of the mixed nonwoven fabric of the present invention. To use a surgical gown, the weight on the basis of the fabric is preferably within the range of 40 to 60 gsm, and very desirably within the range of 50 to 60 gsm. The fabric has a hydrostatic column rating of 35 cm or greater and a bacterial filtration efficiency rating (EFB) of 85% or greater. The gown 95 is manufactured by sewing panels or pre-cut pieces of the non-woven fabric together with a seam formed by fusion ligation. More particularly, as seen in Figure 4, one of the panels 96 has a portion placed in a face-to-face contact relationship with a portion of another of the panels 97, and a seam 98 joins the panels therebetween. along said contact portions. The seam 98 is a fused bond formed between the polyethylene constituent of the multi-constituent filaments of the panel 96 and the polyethylene constituent of the multi-constituent jV filaments of the other panel 97. The following examples serve to illustrate the invention but do not They intend to limit it.

EXAMPLE 1 Samples of a 3-ply composite fabric were prepared by combining 2 outer layers of a spin-bonded nonwoven fabric formed of two-component baine / polyethylene / polyester (PET) core filaments of 3 denier per filament, with a central inner layer of a blown band * Low melting formed from linear low density polyethylene. Samples were prepared using two weights on different bases of spin-linked 2-component filament fabric. The ligation was performed using a calender provided with heated standards. The physical properties of the fabric are shown in table 1 below.

TABLE 1 • - EXAMPLE 2 Additional samples were prepared as in Example 1, using a melt blown layer of linear low density polyethylene of 24 g. s and layers bonded by spinning 2 components of bain / polyethylene / polyester core (PET) 3 deniers per filament with weights in bases of 20 g.m2 and 15 g.m- respec ively. The physical properties are shown in pl table 2, TABLE 2 The invention has been described in considerable detail with reference to its preferred embodiments. However, it will be apparent that numerous variations and modifications can be made without departing from the spirit and scope of the invention as described in the specification detailed above and defined in the appended claims.

* F

Claims (3)

1. WHAT WE ARE CLAIMING IS: i.- A mixed non-woven fabric with gamma radiation characterized in that you comprise first and second nonwoven webs formed by spinning formed from filaments of continuous multiple constituents, said first and second non-woven webs spun by defining opposite outer surfaces of the mixed non-woven fabric, the multi-constituent yarns of said first and second bands including a constituent of polyethylene polymer stable to the lowest melting point range radiation and a stable polymer constituent in the gamma-ray range radiation. higher melt, the radiation-stable polyethylene constituent stable to the lowest melting point range radiation being present on a substantial portion of the filament surface and the higher melting point polymer constituent being in a substantially continuous form throughout of the length of the filaments; a third nonwoven web sandwiched between said first and second nonwoven spunbond webs, said third nonwoven web comprising at least one microporous hydrophobic layer formed from a polyethylene polymer stable to gamma radiation; and a multitude of discrete stitch ties throughout the mixed fabric linking said first, second and third bands to form the mixed nonwoven fabric, said # discrete point ligatures comprising areas where the polyethylene constituent of said multi-constituent filaments and the polyethylene polymer of said third non-woven web is fused.
2. 2. The mixed non-woven fabric according to claim 1, further characterized in that it has a resistance to grip tension of at least 6.81 kg in the direction of crossing (DC) and at least 11.35 kg in the direction of machine (DM), and an air permeability of * Gurley of at least 35 cfm, and a base weight on the scale of 400 to 120 g.mi2.
3. 3. The mixed non-woven fabric according to claim 2, further characterized in that it has a basis weight on the scale of 50 to 60 g.m52 and a hydrostatic column rating of 35 cm or greater. 4.- The mixed nonwoven fabric in accordance with the *? claim 1, further characterized in that it has a bacterial filtration efficiency (EFB) rating of 85.% or higher. 5. The mixed non-woven fabric according to claim 1, further characterized in that said higher melting polymer constituent of said multi-constituent filaments is a polyester. 6. The mixed non-woven fabric according to claim 1, further characterized in that the higher melting polymer constituent of said multi-constituent filaments is a polyamide. V f * 7.- The mixed non-woven fabric according to claim 1, further characterized in that said multiple constituent filaments of said first and second webs comprise structured two sheath / core filaments having a polyester core and a polyethylene sheath. & . - The mixed nonwoven web according to claim 1, further characterized in that said filaments? ^ 'Of multiple constituents of said first and second webs comprise collateral structured two-component filaments having a polyester component and a polyethylene component. 9. The mixed nonwoven fabric according to claim 1, further characterized in that said filaments of multiple constituents of said first and second bands comprise filaments of an unstructured mixture of a There is polyamide polymer and a polyethylene polymer. 10. The mixed non-woven fabric according to claim 1, further characterized in that at least one hydrophobic microporous layer comprises a nonwoven web of blown microfibers under melting. 11. The mixed nonwoven fabric according to claim 1, further characterized in that it includes a substantially continuous seal extending along at least a peripheral edge portion of the fabric, said seal comprising a fusion bond formed between the polyethylene constituent of the multiple constituent filaments of said first and second bands. 12. An article of manufacture characterized in that it comprises two pieces of mixed non-woven fabric according to claim 1, and a seam joining the two fabrics, said seam comprising a fusion ligature formed between the polyethylene constituent of the filaments of multiple constituents of said part and the polyethylene constituent of the multiple constituent filaments of the other part. 13. A mixed non-woven fabric that is ilishable with gamma radiation, characterized in that it comprises; first and second spunbonded nonwoven webs formed of continuous multiple constituent filaments, said first and second nonwoven webs spunbonded defining opposing outer surfaces of the mixed nonwoven web, multiple constituent filaments of said first and second webs including a constituent of polyethylene polymer stable to the lowest melting point range radiation present on the surface of the filaments and a constituent of polyester polymer stable to the highest melting point range radiation, the stable polyethylene constituent the lower melting point range radiation being present on a substantial portion of the filament surface and the higher melting point polymer constituent being in a substantially continuous form along the length of the filaments; a third nonwoven web of microfibers sandwiched between said first and second spunbond nonwoven webs, said third nonwoven web comprising at least one microporous hydrophobic layer formed from a polyethylene polymer stable to gamma radiation; a multiplicity of discrete point ligatures throughout the mixed fabric linking said first, second and third bands to form the mixed nonwoven fabric, said discrete point ties comprising areas wherein the polyethylene constituent of said multi-constituent filaments and the polyethylene microfibers of said third nonwoven web are fused; and said mixed fabric having a tensile strength at grip of at least 6.61 kg in the cross direction (DC) and at least 11.35 kg in the machine direction ^ Wf (DM), and an air permeability of Gurley of at least 35 cfm, a hydrostatic column rating of 35 cm or greater, and a bacterial filtration efficiency (EFB) rating of 85% or greater. 14. A mixed non-woven fabric sterilizable with gamma radiation characterized in that it comprises: first and second spunbonded nonwoven webs formed of filaments of multiple constituents, said first and second spunbond non-woven webs defining the opposite outer surfaces of the web; mixed non-woven fabric, the multi-component filaments of said first and second bands including a polyethylene polymer constituent stable to the low melting radiation range present on the surface of the filaments and a polyester polymer constituent stable to high radiation gamma fusion, the polyethylene constiuent stable to the low melting radiation range being present on a substantial portion of the filament surface and the high melting polymer constituent being in a substantially continuous form along the filaments; a third nonwoven web of melt blown microfibers sandwiched between said first and second spunbonded nonwoven webs, said microfibers having a fiber diameter of less than 50 microns and being formed of a linear low density polyethylene polymer stable to the gamma radiation; a multiplicity of discrete knit ligatures through the entire mixed fabric linking said first, second and third bands to form the mixed nonwoven fabric, said discrete knit ligatures comprising areas wherein the polyethylene constituent of said filaments of multiple constituents and the polyethylene microfibers of said third nonwoven web are fused; and said mixed fabric having a grip strength of at least 6.81 kg in the crossover direction (DC) and at least 11.35 kg in the machine direction (DM), a Gurley air permeability of at least minus 35 ae cfm, and one base on the scale of 40 to 120 g.m'U 15.- A protective garment esteri 1 izable with gamma radiation characterized in that it comprises: first and second non-woven bands linked by spinning formed of filaments substantially continuous formed from a polymer mixture comprising a dominant phase of polyester or polyamide and a polyethylene phase dispersed therein, the polyethylene phase stable to the low range melting radiation being present on a substantial FX portion of the filament surface and the high melting polyester or polyamide phase being present in a substantially continuous form along the filaments; and a third nonwoven web of meltblown polyethylene microfibers formed of a thermoplastic polymer composition stable to gamma radiation sterilization and having a fiber diameter of 50 microns, said third nonwoven web sandwiched between said first and second nonwoven webs to form a nonwoven mixed web; a multiplicity of discrete knit ligatures through the entire mixed fabric linking said first, second and third bands to form the mixed nonwoven fabric, said discrete knit ligatures comprising areas wherein the polyethylene constituent of said filaments of multiple constituents and the polyethylene microfibers of said third nonwoven web are fused; and said mixed fabric having a tensile strength to the grip of at least 6.81 kg in the direction of / < »Fe crossing (DC) and at least 11.35 kg in the machine direction T (DM), a Gurley air permeability of at least 35 cfm, and a base weight on the scale of 40 to 120 g.mU 16 .- A protective garment sterilizable with gamma radiation characterized by comprising: at least two panels of a nonwoven mixed fabric sterilizable with gamma radiation, said mixed nonwoven fabric comprising first and second spunbonded nonwoven webs formed of composite filaments. Multiple continuous W-shaped materials, said first and second nonwoven webs spunbonded defining opposing outer surfaces of the mixed non-woven fabric, the multi-constituent filaments of said first and second webs including a stable, low-down polyethylene polymer constituent. Fusion radiation range and a polymer constituent stable to high gamma radiation, the constituent of polyethylene stable to low radiation melting ga ma being present on a substantial portion of the filament surface and the high melt polymer constituent being in a substantially continuous form along the length of the filaments; a third nonwoven web sandwiched between said first and second nonwoven spunbond webs, said third nonwoven web comprising at least one microporous hydrophobic layer formed from a polyethylene polymer stable to gamma radiation; and a multiplicity of discrete knots throughout the mixed fabric by ligating said first, second and third bands to form the mixed nonwoven fabric, said discrete knots comprising areas where the polyethylene constituent of said filaments of multiple constituents and the polyethylene polymer of said third nonwoven web are fused; one of said panels having a portion placed in a face-to-face contact relationship with a portion of another of said panels; and a seam that joins said panels between them to the * length of the contact portions, said seam comprising a fusion bond formed between the polyethylene constituent of the multi-constituent filaments of said panel and the polyethylene constituent of the multi-constituent filaments of the other panel. 17. The protective garment according to claim 16, further characterized in that said panels of mixed non-woven cloth sterilizable with gamma radiation have a resistance to grip tension of at least 6.81 kg in the direction of crossing (DC) and at least 11.35 kg in the machine direction (DM), a Gurley air permeability of at least 35 cfm, and a basis weight on the scale of 40 to 120 g. m12. NON-WOVEN FABRIC "* MIXED AND ARTICLES PRODUCED FROM THE SAME" EXTRACT OF THE INVENTION The invention is directed to a mixed non-woven fabric comprising first and second non-woven webs of substantially continuous thermoplastic filaments spin-bonded, and a hydrophobic non-woven microporous web of thermoplastic microfibers blown under melt sandwiched between the webs. * first and second non-woven bands. The filaments of the non-woven spunbond webs are formed of continuous filaments of multiple constituents that include a polyethylene polymer component stable to the lowest melting point gamma radiation and one or more other polymer constituents stable to the gamma radiation. higher melting point, wherein a substantial portion of the surfaces of the multi-constituent filaments consists of the polyethylene constituent stable to the lowest melting range gamma radiation. The non-woven hydrophobic microporous band is formed from a polyethylene polymer stable to gamma radiation. The webs are bonded to form the mixed nonwoven fabric by discrete knit links where the polyethylene constituent of said multiple constituent filaments and the polyethylene of said third nonwoven web are fused together.