MX2008001333A - Bicomponent sheet material having liquid barrier properties - Google Patents

Abstract

The invention provides a sheet material comprising bicomponent filaments having first and second polymer components that are arranged in substantially distinct zones within the filaments, with the first polymer component formed of a relatively lower melting polymer and the second component formed of a relatively higher melting polymer. The filaments of the nonwoven fabric layer are densely arranged and compacted against one another to form smooth, substantially nonporous opposite outer surfaces, and the nonwoven fabric layer are calendered such that the lower melting sheath polymer is fused to the contacting surface portions of adjacent filaments to impart strength and coherency to the nonwoven fabric layer. The sheet material has excellent breathability and liquid barrier properties and may be useful in house wrap, medical garments, and envelope applications.

Description

TWO COMPONENT PLATE MATERIAL WHICH HAS BARRIER TO LIQUID PROPERTIES FIELD OF THE INVENTION The invention relates generally to non-woven fabrics and more particularly to a non-woven sheet material having properties that include liquid barrier and ventilation properties, which make them useful in various applications including garments, wrappings it is used in the construction of buildings, wraps, printed media, filtration, labels and tags and cable wrapping, among other applications.

BACKGROUND OF THE INVENTION Non-woven fabrics are used in a wide variety of applications. For example, nonwoven materials of light weight and open structure are used in personal care articles such as disposable diapers. Higher weight nonwoven materials can be designed with pore structures that make them suitable for filtration or with barrier properties for applications such as sheaths used in the construction of buildings or protective garments for medical or industrial uses.

Various types of non-woven fabrics have been produced and commercially sold for use as a fabric that constitutes a liquid barrier in the construction of buildings or in protective garments. One such commercially available product is manufactured and sold by DuPont under the trademark Tyvek ™. This product is formed by instantaneous spinning of high density polyethylene fibers which are joined to form a nonwoven sheet material. Other commercially available products have been used as a nonwoven substrate with a film coating. For example, in Dunaway et al, Patent of E.U.A. No. 4,898,761 describes a barrier fabric in which a polymeric film is laminated to a non-woven fabric and the resulting composite sheet material is then perforated with a needle to provide micropores through the film. The non-woven fabric is a spin-bonded membrane that is formed of polyolefin filaments and the polymeric film can be applied to the non-woven membrane by hot-cast extrusion. The Patent Application of E.U.A. No. 2004/0029469 A1 discloses a waterproof, vapor permeable and moisture permeable composite sheet material which is suitable for use as a wrapping material that is used for the construction of buildings. The composite sheet material includes a non-woven substrate and a layer of film containing the filler material, extrusion coated which has become microporous by drawing.

The nonwoven liquid barrier materials usually available have various limitations. Some of the commercially available liquid barrier materials, when used as a wrapper used in building construction, can be easily torn during construction by manual ladders or by wind. Liquid barrier materials formed from laminates of a film with a non-woven substrate require a two-stage process which increases the expense. There is a need for an economical barrier material with superior strength as well as excellent water and air barrier properties.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a non-woven sheet material comprising a nonwoven fabric layer that includes two-component filaments having a first and second polymer components that are distributed in substantially different zones within the filaments, wherein the first polymeric component it is formed of a polymer with a relatively lower melting point and the second component is formed of a polymer with a relatively higher melting point. The filaments of the non-woven fabric layer are densely distributed and compacted together to form smooth opposed outer surfaces. The non-woven fabric layer is calendered so that the polymer with a point Minor melting is fused to the contact surface portions of adjacent filaments to impart strength and coherence to the non-woven fabric layer. As a result of calendering, the polymer of the lower melting point component has softened and flowed to form a film-like texture on at least one outer surface of the non-woven fabric layer. More particularly, the polymer with a lower melting point is fused to the contact surface portions of adjacent filaments to impart strength and coherence to the nonwoven fabric layer and where on the external surface substantially smooth the polymer with a point of Minor fusion forms a microporous film-like surface that allows vapor and moisture to be transmitted through the sheet material and at the same time serves as a barrier to the penetration of liquids. In one embodiment, the film-like texture is present on one of the outer surfaces of the non-woven fabric layer and the opposite outer surface of the non-woven fabric has a filamentary texture with the appearance of flattened filaments. In one embodiment, the two-component filaments have a sheath-core cross-sectional configuration wherein the first polymer with a higher melting point is located in the core and the second polymer with a lower melting point in the sheath. The first polymer component with a lower melting point preferably comprises polyethylene and the second polymer component is preferably selected from the group consisting of polypropylene, polyester and nylon.

The sheet material has excellent ventilation and liquid barrier properties. In an advantageous embodiment, the sheet material has a watertightness of at least 15 cm, more desirably at least 25 cm and a moisture vapor transmission rate of at least 62 g / m2 / 24 hours (4 g / 100 in2 / 24 hours). In one embodiment, the sheet material includes a first layer of the two-component filaments that are bonded to a second layer of two-component filaments that have a component dispersed in the sheath component of the filaments. The pigment results in the non-woven fabric having an opacity that is greater than 90%. In another embodiment, an antimicrobial agent is incorporated into the first polymer component. The antimicrobial agent is combined with the first polymer component before extrusion into the fibers so that it is present through the first polymer component. The antimicrobial agent may be present in the first polymer component in a concentration from about 0.01% to 5% by weight, based on the weight of the first polymer component. In yet another embodiment, the two-component filaments may be combined with one or more layers of melt-blown polyethylene fibers to form a composite membrane. The composite membrane can then be thermally calendered under high pressure to produce a sheet material having improved liquid barrier and ventilation properties.

In yet another embodiment, the two component filaments can be combined with one or more layers of very fine diameter fibers or nanofibers to form a composite membrane. The composite membrane can then be thermally calendered under high pressure to reduce the sheet material having increased opacity. The sheet material of the present invention has excellent liquid barrier and ventilation properties and is useful in a wide variety of applications including garments such as protective industrial clothing, aseptic room clothing, coverages or medical garments. , as filtration media for filtration, for a protective barrier such as casings that are used in the construction of buildings or underlying layer in the roof, in the manufacture of casings, labels and tags or printed media, such as a cable wrap and for industrial and consumer-related products where a quick release surface is needed.

BRIEF DESCRIPTION OF THE DRAWINGS Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: Figure 1 is a perspective view of a non-woven fabric comprising fibers of multiple components that are thermally bonded to forming a sheet material; Figures 2A and 2B are scanning electron microscope photographs of a cross-sectional view of the non-woven fabric; Figures 3A and 3B are scanning electron microscope photographs at two different magnifications of an external surface of the nonwoven sheet material produced according to one embodiment of the invention; Figures 4A and 4B are scanning electron microscope photographs at two different magnifications of the opposite external surface of the sheet material of Figures 3A and 3B; Figure 5 is a schematic illustration of a process line that is used to prepare the non-woven fabric of Figure 1; Figure 6A is a cross-sectional view of the two-component sheath-core fiber; and Figure 6B is a cross-sectional view of a two-component fiber side by side.

DETAILED DESCRIPTION OF THE INVENTION The present inventions will now be described more fully in the following with reference to the accompanying drawings, in which some but not all embodiments of the inventions are shown. Actually, these inventions can be constituted in many ways different and should not be considered as limited to the modalities set forth herein; rather, these modalities are provided so that this description will satisfy applicable legal requirements. Similar numbers refer to similar elements in it. Referring to FIG. 1, a perspective view of a sheet material according to one embodiment of the present invention is illustrated and is generally referred to as the reference number 10. The sheet material includes a layer of non-woven fabric, spunbonded constituted of a plurality of continuous multicomponent filaments that are densely packed and densely packed against each other to form substantially smooth external surfaces for the nonwoven fabric layer. The multi-component fibers comprise at least two polymer components that are distributed in substantially different zones within the fibers and that extend continuously along the length of the filaments. The first polymer component has a melting temperature that is lower than the melting temperature of the second polymer component so that the first polymer component can serve as a binder to thermally bond the individual filaments together. The melting temperature of a polymer can be determined by differential scanning calorimetry (DSC). The fusion of a polymer generally occurs over a range of temperatures during which time heat is absorbed by the polymer as the crystal structure breaks and the chains Polymers lose their ordered distribution. DSC can be used to plot the amount of heat introduced into the system as the temperature increases. In the context of the present invention, the melting temperature of the polymer corresponds to the temperature at which the greatest amount of heat has been introduced into the polymer. In a DSC graph, generally the highest point of the graph is the fusion transition. Polymers suitable for the first component with a lower melting point include polyethylene, copolymers of propylene and ethylene, copolymers of ethylene with vinyl acetate (for example EVA) or with ethylene acrylates (for example EMA, EBA), ester terpolymers ethylene acrylic, ethylene and vinyl acetate terpolymerspolymers and copolymers of polylactic acid (PLA), polypropylene and polyester copolymers such as copolymers of polyethylene terephthalate / polyethylene isophthalate. Preferred polyethylene resins include linear low density polyethylene, low density polyethylene and high density polyethylene. In an alternative embodiment, the first component comprises high density polyethylene having a density greater than about 0.94 g / cc, preferably between and including 0.95 and 0.95 g / cc. Polymers suitable for the second component with a higher melting point include polypropylene, polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) and polyamides such as nylon-6 or nylon 6-6. In a particularly advantageous embodiment, the non-woven membrane comprises a high density polyethylene liner which surrounds a core of polyethylene terephthalate or polypropylene. Multicomponent filaments comprising a polyethylene component and a polyethylene terephthalate or polypropylene component may have many desirable characteristics. For example, polyethylene terephthalate has many desirable characteristics including strength, toughness, stiffness and resistance to heat and chemicals. Preferably, the polymers are selected to have a difference in melting points (as defined above) of at least 10 ° C, more desirably at least 30 ° C. In the embodiment illustrated, the spunbonded nonwoven fabric layer comprising two component filaments has a sheath-core cross sectional configuration wherein the sheath polymer has a lower melting temperature than the core polymer. However, other cross-sectional configurations may be advantageously used, including side by side, in the form of a slice of cake and configuration of islands in the sea. As can be seen in figure 1, on at least one of the outer surfaces of the non-woven fabric layer, the layer has an external surface 12 similar to a film formed by calendering the sheet material 10. In the calendering operation, the sheet material passes through the constriction of a pair of cooperating calendering rollers, under heat and pressure. The heat and pressure cause the polymer component of the sheath with a lower melting point to melt or soften or merge with the polymer component of the filament sheath adjacent to produce a strong and coherent nonwoven fabric. However, the fusion of the polymeric sheath component does not form a continuous monolithic structure. Through the thickness of the non-woven fabric layer there are many pore-like, randomly spaced, small openings 14 which allow moisture vapor to be transmitted through the fabric and at the same time substantially prevent liquids from passing in and through. the fabric On the outer surface 12 of the non-woven fabric layer, the film-like surface is microporous and allows moisture vapor to be transmitted through the sheet material and at the same time serves as a barrier for the penetration of liquids. The dense and compact structure of the non-woven fabric layer results in the sheet material having liquid barrier properties without sacrificing air permeability and moisture vapor. As a result, the sheet material can be used in a wide variety of applications where it may be desirable to have liquid barrier and ventilation (allow air passage) properties. These applications are described in more detail in the following. As can be seen from the scanning electron microscope photographs of Figures 2A and 2B, the two-component filaments are tightly packed together and form a dense sheet. The outer surface of the sheet material has a surface similar to flat film. It can also be seen that a substantial portion of the spaces between the adjacent fibers is occupied by the polymeric material of the sheath component that melts and flows together when the blade is subjected to calendering. However, the sheath-core structure of the filaments is still evident. In addition, the non-woven fabric still retains small intermittent openings between the filaments through which air and moisture vapor can be displaced. As a result, the sheet material provides liquid barrier properties and at the same time retains a desired degree of air and vapor permeability as well as flexibility. Figures 3 and 4 are scanning electron microscope photographs of the opposing outer surfaces of a sheet material according to one embodiment of the invention. The sample presented in these figures is subjected to a calendering operation in which one of the exposed surfaces makes contact with a smooth calendering roller internally heated, and the opposite exposed surface contacts an anvil, smooth and unheated calender roll. As a result, the sheet material presents a different appearance on its opposite external surfaces. In Figures 3A and 3B (at an enlargement of 50x and 500x, respectively), it can be seen that this outer surface of the fabric has a relatively smooth surface-like surface texture wherein a substantial portion of the sheath component has been fused and has fluidly joined as a result of contact of the heated surface of the calender roll. As can be seen from the photographs, the filaments have been flattened and compacted by bonding on the surface and the sheath polymer has flowed to form an almost continuous film-like surface. Do not However, the filamentous nature of the filaments can still be observed and the fabric still includes small random micro-apertures in part of the crossing locations of the filaments through which moisture vapor can pass through the fabric. In Figure 3B several micro openings can be observed, each having a maximum size of less than 10 μm. As described in the foregoing, these small spaces of micro openings allow the fabric to exhibit excellent ventilation and at the same time maintain the desired liquid barrier properties of the fabric. However, on the opposite surface of the sheet material, which is shown in Figures 4A and 4B, where the sheet material has made contact with the unheated surface of the anvil roller, the surface of the sheet material has an appearance significantly different and has a filamentous texture that presents the appearance of flattened filaments. In marked contrast to what is seen in Figure 3B, the filaments of the opposite surface shown in Figure 4B retain their individuality. The sheath polymer has not flowed to form a film-like surface and there are large spaces between the filaments communicating with the internal voids or passages within the thickness of the fabric. The non-woven fabric layer of sheet material 10 is produced by the well-known process for the manufacture of spunbond nonwoven materials. Examples of processes for manufacturing spunbond non-woven fabrics are described in the U.S. Patent. No. 3,338,992 for Kinney; the Patent of E.U.A. No. 3,802,817 for Matsuki, the Patent of E.U.A. No. 4,405,297 for Appel, the U.S. Patent. No. 4,812,112 to Balk and the U.S. Patent. No. 5,665,300 for Brignola et al. Figure 5 schematically illustrates an apparatus 30 for producing a thermally bonded, spin-bonded, non-woven fabric. More particularly, in this embodiment, the fabric is formed of randomly distributed two-component filaments 20 which are prepared by a pair of extruders 32 that supply two different polymeric materials 22, 24 from hoppers 34 to a two-component die 36. Preferably, the row 36 is distributed to produce two-component strands of the sheath-core or side-by-side type. Said configurations are shown in Figures 6A and 6B, respectively. The two polymeric components are combined in the row to form the two-component filaments having the two components which are located in two distinct zones within the cross section and which extend continuously along the length of the filaments. The rows for producing two-component filaments are well known in the art and are therefore not described in detail here. In a known embodiment, for example, the row includes a housing around a spin pack which includes a plurality of vertically stacked plates having an aperture pattern distributed to create flow paths to direct the two polymers separately to openings filament formers in the row. The filament forming fractures are distributed in one or more rows and the openings form a curtain extending downwardly of filaments 20 when the filaments are formed.

The polymers are extruded through the row 36. As the filaments 20 exit the row 36, they come in contact with a cooling gas 40, which is typically air, from one or both sides of the filament curtain, which at least partially cools the filament. In addition, a fiber drawing unit or vacuum cleaner 42 is placed below the die 36 to extract and thin the filaments 20. The filaments 20 are deposited in a substantially random manner on a mobile carrier band 46 that is driven on a set of rollers. 48 by a conventional drive source (not shown) to form a loose membrane of randomly deposited filaments. In some embodiments an appropriate suction means 49 may be present under the carrier band 46 to assist in depositing the filaments 20. It should be noted that although a single row assembly and a single layer filament membrane are shown., it is possible to supply additional row assemblies in-line to produce a thicker membrane or a multi-layer non-woven fabric. In the distribution shown in Figure 5, the advancing nonwoven web 10 passes from the carrier web 46 and is directed into the interior through a pressure constriction 50 formed by the calendering rollers 52 comprising a heated roller 54. and a hard surface anvil roll 56. The roller 54 can be heated internally in a conventional manner, for example by circulating a heat transfer fluid through the interior of the roller. The anvil roller 56 can also be heat in a similar way. The time, temperature and pressure conditions in the calendering constriction are sufficient to heat the filaments to cause the first polymer component, with a lower melting point, to melt and flow together so that the filaments fuse together in a it is compacted and densely distributed and that the polymer with a lower melting point forms a film-like surface. In one embodiment, the pressure narrowing applies a pressure of approximately 2627 N / cm (1500 pounds per linear inch) to 5254 N / cm (3000 pounds per linear inch), more specifically, approximately 3152 N / cm (1800 pounds) per linear inch) at approximately 4378 N / cm (2500 pounds per linear inch) and heated to a temperature between approximately 116 ° C (240 ° F) and 130 ° C (265 ° F). The non-woven fabric 10 is then directed from the calendering rolls 52 to a suitable take-up roll 58. In an alternative distribution, the calendering step can be carried out off-line, as a separate step. In this case, the filament membrane will initially be bonded in-line during the manufacturing process to form a coherent non-woven fabric and then collected on a winding roll. The bond can be made by bonding points at separate sites through the fabric or through the entire fabric in places where the filaments are in contact with each other (bonding area). In the case of spot bonding, the calender 52 shown in Figure 5 may include a properly engraved roll that have a pattern of projections or valleys and a cooperating anvil roller. One or more layers of the non-woven fabric formed in this way can subsequently be subjected to an off-line calendering operation. The offline calendering apparatus can have various configurations. A possible configuration includes two heated steel calendering rollers and a roller covered in unheated cotton cloth. The fabric is directed so that it performs a displacement in s by the lower steel roller in the lower part and is compressed against the roller covered with cotton by the upper and lower steel rollers. When more than one layer of non-woven fabric is directed through the calender, the calendering operation joins the layers to form a unitary composite sheet material. The combination of two or more layers advantageously increases the point-to-point uniformity of the final sheet material in thickness and strength. If a smoother or more film-like surface is desired, additional polyethylene can be provided on one or both surfaces by combining an additional non-woven layer of polyethylene fibers or filaments, such as a nonwoven layer bonded by joining from filaments monocomponent of polyethylene or a meltblown layer formed of polyethylene fibers. If additional opacity is required, an additional opacity enhancer layer can be incorporated within the sheet material 10. In one embodiment, for example, a non-woven opacity improver layer is produced by incorporating a carbon black filler material into the sheath of a non-woven fabric joined by two-component PE / PP spinning. This layer Improved opacity can be combined with another non-woven fabric bonded by PE / PP two-component yarn pigmented with T02 to form a composite non-woven sheet material with a white appearance on a surface and a dark appearance on the opposite surface. Alternatively, the improved opacity layer can be buried between two white nonwoven layers pigmented with Ti02 so that the sheet material exhibits the same white appearance on both surfaces. Another way to increase the opacity is to laminate or extrude onto the surface of the spin-bonded nonwoven layer a polymeric film containing an opacifying pigment such as TiO2 or carbon black. Depending on the calendering operation, the fabric can be produced with a two-sided appearance, as shown in Figures 3 and 4, or both surfaces can be brought into contact with a heated calendering roll to produce a film-like texture on both of the exposed surfaces of the sheet material. The desired level of ventilation and liquid barrier properties of the sheet material will of course depend on the proposed use and the conditions to which it can be exposed. For example, in wrapping applications used in building construction, it may be desirable for the sheet material to have high liquid barrier and ventilation properties, whereas in a wrapping application, the properties of a high liquid barrier It may not be so crucial. The liquid barrier properties and the ventilation of the sheet material are affected with the thermal bonding conditions, thickness, filament diameter, calendering conditions and base weight of the membrane. In an alternative embodiment, the sheet material may have a thickness of 0.4 to 0.9 millimeters. The sheet material of the present invention can provide high liquid barrier properties without sacrificing the desired level of ventilation. In an alternative embodiment, the sheet material may have a seal of at least about 15 cm. Preferably, the sheet material has a watertightness of at least 25 cm, a watertightness exceeding 45 cm being preferred. For wrapping applications used in the construction of buildings, the sheet material preferably has a watertightness of at least 25 cm and preferably a watertightness varying between 100 and 900 cm. For wrapping applications and other applications where properties of a high liquid barrier are not critical, the sheet material typically has a watertightness of at least 10 cm, and a watertightness varying between 25 and 300 cm is additionally preferred. Ventilation of the sheet material can be assessed by determining its moisture vapor transmission rate (MVTR) and permeability. The desired MVTR will of course depend on its end use. Preferably, the sheet material has an MVTR of 62 g / m2 / 24 hours at 4650 g / m2 / 24 hours (4 to 300 g / 100 inches2 / 24 hours). As discussed in the above, ventilation in wrapping applications used for the construction of buildings is important for the proper functioning of the building. sheet material. In wrapping applications used in building construction, the sheet material preferably has an MVTR between 62 g / m2 / 24 hours and 4650 g / m2 / 24 hours (4-300 g / 100 inches2 / 24 hours) for Wrap applications and other applications where ventilation is not critical, the sheet material typically has an MVTR of at least 15.5 g / m2 / 24 hours (1 g / 100 inches2 / 24 hours), with an MVTR interval preferred between 62 g / m2 / 24 hours and 4650 g / m2 / 24 hours (4-300 g / 100 inches2 / 24 hours). The permeability of the sheet material can be conveniently determined by measuring its air permeability using a commercially available air permeability instrument. Such as the Textest air permeability instrument, according to the air permeability test procedures established in ASTM D-11 test method 17. Of course, the desired air permeability will depend on the end use. Preferably, the sheet material has an air permeability, measured by this method, of 0 to 1.5 m 3 / m2 / min (0 to 5 cfm / ft 2 / min). As stated in the above, ventilation in wrapping applications used for the construction of buildings is important for the proper functioning of the envelope. In wrapping applications that are used for building construction, the sheet material preferably has an air permeability between 0 and 1.5 m3 / m2 / min (0 and 5 cfm / ft2 / min). Figures 6A and 6B illustrate a cross-sectional view of two exemplary multiple component filaments of the invention. As illustrated in Figure 6A, the filaments 20 may comprise two-component filaments having an inner core polymer domain 22 and a surrounding sheath polymer domain 24. In an alternative embodiment, the first and second polymer components 22, 24 may be distributed in a side-by-side array, as shown in Figure 6B. As used herein, the term "multi-component filaments" includes continuous filaments prepared from two or more polymers present in separate structured domains in the filament, as opposed to combinations wherein the domains tend to be dispersed, randomized or unstructured For purposes of illustration only, the present invention is generally described in terms of a two-component filament comprising two components. However, it should be understood that the scope of the present invention encompasses the inclusion of filaments with two or more structured components. In general, the polymer domains or components are distributed in substantially constant zones, placed differently across the cross section of the multicomponent filament and extend continuously along the length of the multicomponent filament. A suitable configuration is a sheath / core distribution, wherein a first component, the sheath, substantially surrounds a second component, the core. Other structured configurations may be used, as are known in the art, such as, but not limited to, side by side, in the form of pie slice, islands in the sea or multi-lobed structures with tip. The weight ratio of the polymer domains or components may vary. Typically, the weight ratio of the first polymer component to the second polymer component ranges from about 20:80 to about 50:50, although the weight ratio may be outside this range as well. In a preferred embodiment, the ratio of the first polymer component to the second polymer component is about 30:70. By using polyethylene or polypropylene as the first polymeric component, many thermally sensitive melt tives are allowed to enter through the thickness of the polyethylene during the extrusion process without degradation or loss of the desired activity. For example, certain organic antimicrobial agents could be thermally degraded at the temperatures that are needed to extrude PET. By incorporating the antimicrobial agent into a polyethylene or polypropylene sheath component surrounding a PET core component, the antimicrobial sheet material can be produced to include many of the physical properties commonly associated with polyethylene terephthalate. . The antimicrobial agent can be suitably combined with the polymer of the component with a melting point lower than a concentration from 0.01% to 5% by weight, based on the weight of the first polymeric component. The specific concentration used is determined by the type of antimicrobial agent used and the target organisms, and can be easily determined without undue experimentation using systematic screening tests. In an alternative embodiment, the antimicrobial may comprise a broad spectrum antimicrobial agent that is effective against most of the harmful bacteria found in water. In particular, various organic antimicrobial and antifungal agents such as triclosan antimicrobial fusion tive are available from Microban ™. For example, an antimicrobial agent such as 2,4,4'-trichloro-2'-hydroxydiphenol ether or 5-chloro-2-phenol compounds (2,4-dichlorophenoxy) commonly sold under the trade name MICROBAN RB by Microban Products Company , Huntersville, North Carolina are the ones that can be used. However, it will be understood that various tional antimicrobial agents that are harmless, non-toxic and substantially insoluble in water can be used in the present invention. The presence of the antimicrobial agent in the first polymeric component 24 effectively inhibits the growth of microorganisms in the non-woven fabric. Because the antimicrobial agent is dispersed through the non-woven fabric, it provides antimicrobial activity to the surface of the entire fiber. In tion, by incorporating the antimicrobial agent in the first polymer component, such as the sheath, the first polymer component can serve as a reservoir for sustained diffusion and release of the antimicrobial agent.

The density and composition of the first polymeric component can be selected to control the rate at which the antimicrobial agent travels to the surface of the fibers of the non-woven fabric. In general, many antimicrobial agents can have a certain degree of mobility in polyolefin polymers. In an alternative embodiment, the density and / or composition of the first polymeric component can be selected such that the antimicrobial agent diffuses through the polymer at a desired rate. In one embodiment, the diffusion rate of the antimicrobial agent can be controlled by the selection of the composition of the first polymeric component. For example, the first polymer component may comprise a combination of one or more polymers, such as polyethylene, polypropylene, polybutylene and copolymers thereof, wherein the composition of the combination and the proportions of each polymer in the combination are selected in a manner that the antimicrobial agent diffuses at the desired speed. further, the antimicrobial agent typically has little or no affinity for polyesters, such as polyethylene terephthalate. As a result, a non-woven fabric can be prepared in which the antimicrobial agent diffuses to the surface of each fiber at a desired rate without significant displacement of the anti-microbial agent in the core of the fiber. Non-woven fabrics can be prepared in this manner wherein the first polymeric component serves as a reservoir for controlled diffusion and release of the antimicrobial agent. In an alternative embodiment, the sheet material may comprising two or more layers of two-component filaments that are stretched together to form a non-woven membrane. In some embodiments, each layer may contain various additives in the polymer components that may be the same or different from each other. In some preferred embodiment, the sheet material may comprise a first layer of two component filaments and a second layer of two component filaments having one or more additives that have been incorporated into the first polymer component. This embodiment may be particularly useful for preparing casings having a desired level of opacity. In one embodiment, an envelope having a desired level of opacity can be prepared by combining a first layer of two-component filaments having a relatively white appearance and a second layer of two-component filaments having a pigment, such as incorporated carbon in the pod component. The two non-woven fabric layers are then calendered to form a sheet material of the invention. The first layer will typically comprise the outer surface of the envelope. The presence of the pigment in the second layer imparts to the envelope the desired level of opacity. In wrapping applications, the opacity level typically varies between 75 and 100%, as measured by the Byk-Gardner colorimeter. Preferably, the envelope has an opacity of greater than about 80% and more preferably greater than about 90% reflectance. In an alternative embodiment, the sheet material may comprise a combination of one or more membranes joined by spinning two components of the present invention with a membrane comprising meltblown fibers. In some embodiments, the meltblown fibers may comprise polyethylene. Meltblown membranes can be prepared using methods known in the art such as the method described in the U.S. Patent. No. 3,849,241. The spunbond and meltblown layers can be processed separately and subsequently joined together in an off-line process to form a multi-layer sheet material. In an advantageous embodiment, the meltblown fibers are deposited directly on a spunbonded layer of multiple components of the present invention, in an on-line process. Spunbond or meltblown layers can be thermally bonded together, for example with a spunbond layer interposed between two meltblown layers. In other embodiments, the sheet material may comprise a single layer bonded by spinning, directly attached to a single meltblown layer. As described above, the bonding is preferably carried out in a manner such that both ventilation and barrier properties of the fabric are retained. Alternative methods for joining the layers of the composite sheet include through-air bonding, vapor bonding and adhesive bonding. For example, an adhesive can be applied in a defined pattern between adjacent layers or as a continuous layer if the adhesive is an adhesive that allows air to pass through. The composite sheet material of the present invention preferably has a basis weight of between about 10 and 150 g / m2, more preferably between about 34 and 100 g / m2, and more preferably between about 54 and 68 g / m2, with a permeability to air Frazier preferably in the range of about 3 to 21 cm3 / min / cm2, more preferably in the range of 4 to 12 cm3 / min / cm2 and much more preferably in the range of 5 to 11 cm3 / min / cm2 and a head hydrostatic preferably of at least 15 cm with a range of about 35 to 150 cm of H20 as most preferable. In some embodiments, the composite sheet material may have a hydrostatic head in the range of about 45 to 120 cm of H20 or in the range of 55 to 100 cm of H20. In some embodiments, stabilizers and antioxidants can also be added to the polymer components. Other additives may also be added according to the present invention. The inorganic additives are for example such as titanium dioxide, talc, fumed silica or carbon black. The polymeric resin may also contain other additives such as other polymers, diluents, compatibilizers, antiblocking agents, impact modifiers, plasticizers, UV stabilizers, pigments, delusterants, lubricants, wetting agents, antistatic agents, nucleating agents, rheology modifiers, repellents. water and alcohol and the like. It is also anticipated that the additive materials which have an effect on the processing or on the product properties such as extrusion, quenching, stretching, laying, properties Static and / or electrical, bonding, wetting properties or repellency properties can also be used in combination with the polymeric components. In particular, polymeric additives that impart specific benefits to either processing and / or end use can also be used. The following examples are included to show the invention and should not be considered as limiting the scope of the invention.

Test Methods In the above description and in the non-limiting examples that follow, the following test methods are used to determine different reported characteristics and properties. ASTM refers to the American Society for Testing and Materials, AATCC refers to the American Association of Textile Chemists and Colorists, INDA refers to the Association of the Nonwovens Fabrics Industry and TAPPI refers to the Technical Association of Pulp and Paper Industry. The basis weight is a measure of the mass per unit area of a cloth or sheet and is determined by ASTM D-3776-96, which is incorporated herein by reference, and reported in units of g / m2. Resistance to clamping tension is a measure of the breaking strength of a fabric when it is subjected to unidirectional tension.

This test is carried out in a known manner in accordance with ASTM D 4632 -. 4632 - Standard Test Method for Grab Breaking Load and Elongation of Geotextiles, 1991 (approved again in 1996) and reported in pounds. The Resistance to clamping tension is reported in the examples in the machine direction (MD) and in a transverse direction (XD). The elongation percentage is measured at the point where the sample initially fails and its elongation at which it reaches the maximum load during the measurement of clamping tension. The percent elongation is reported in the examples for the machine direction (MD) and for the cross direction (XD). The hydrostatic head (watertightness) is a measure of the resistance of a sheet to penetration by liquid water under a static pressure. The test is carried out in accordance with AATCC-127, which is incorporated herein by reference, and reported in centimeters. The moisture vapor transmission rate (MVTR) is determined by ASTM E 96, Standard Test Methods for Water Vapor Transmission of Materials; 1995, procedure A with a relative humidity of 50% (RH) and 23 ° C (73 ° F) and reported in grams per 100 inches2 per 24 hours. The Mullen discharge resistance is determined by ASTM D3786, Standard Test Method for Hydraulic Bursting Strength of Textile Fabrics - Diaphragm Bursting Strength Method. Air permeability, unless otherwise stated, is measured with a Textest air permeability instrument, in accordance with ASTM D-11 test method 17, which is incorporated herein by reference and reported in cfm / ft2 / min.

The air permeability Frazier is a measure of the air flow that passes through a sheet under a pressure differential established between the surfaces of the sheet and is carried out in accordance with ATSM D-737, which is incorporated in the present as reference and is reported in (m3 / min) / m2. The thickness of the fabric or sheet is determined in accordance with ASTM D-1777-96 - Standard Test Method for Thickness of Textile Materials, which is incorporated herein by reference and reported in thousandths of an inch (1 thousandth of an inch = 0.001 of an inch). Opacity is a measure of the amount of light obscured or prevented from passing through the sheet material and measured with a Byk-Gardner colorimeter and determined according to the TAPPI method T425 and expressed in%. Opacity (89% support reflectance) is sometimes referred to as the contrast ratio, C..89 is defined as 100 times the diffuse reflectance ratio, R0 of a specimen baked in a black body of 0.5% reflectance or less respect to the diffuse reflectance, R ..., of the same sample baked with a white body having an absolute reflectance of 0.89; therefore C0 89 = (Ro / Ro.ß.) - EXAMPLE 1 Fifteen non-woven fabrics joined by different spinning are prepared according to the invention. The fabric samples comprise filaments of two substantially continuous components that are thermally bonded together. The two-component filaments have a sheath / core configuration wherein the weight ratio of the sheath component to the core component ranges from 50:50 to about 30:70. The two-component filaments are thermally bonded with a calender under a pressure of 4.4 x 105 N / m (2500 pounds per inch) and a temperature of 129 ° C (265 ° F); wherein: PE is a polyethylene having a density of 0.89 to 0.96 g / cm 3 and a melt index of 6 to 40. PP is a polypropylene having a density of about 0.90 g / cm 3. PET is a poly (ethylene terephthalate) that has an intrinsic viscosity of 0.5 to 0.9. The physical properties of the resulting non-woven fabrics are presented in Tables 2 and 3 below.

TABLE 1 TABLE 2 TABLE 3 In samples 11 and 12, two layers of a spunbonded nonwoven fabric formed from polyethylene monocomponent filaments are interposed between outer layers of a nonwoven fabric joined by spinning two.

PE / PET core / sheath components and are calendered to produce a composite sheet material. From the above data, it can be seen that the non-woven fabrics prepared according to the invention can be produced to have excellent tension, ventilation and liquid barrier properties.

EXAMPLE 2 In the following example a sheet material is prepared which can be particularly useful in wrapping applications. The sheet material is comprised of two layers of two-component filaments having a sheath / core configuration wherein the weight ratio of the sheath component to the core component is about 70:30. The sheath component is made of polyethylene and the core is made of polypropylene, both mentioned in the above, in Example 1. The two-component filaments are thermally bonded with a calender under a pressure of 4.4 x 105 N / m (2500 pounds per inch) and a temperature of 129 ° C (265 ° F). The first layer has a relatively white appearance and comprises the outer surface of the envelope. The second layer includes a carbon pigment that is incorporated into the sheath and has a relatively darker color than the first layer. The properties of the resulting fabric are summarized in the Table 4 below.

TABLE 4 From the data in Table 4, it can be seen that incorporating a pigment in the second layer substantially increases the opacity of the resulting sheet material. In contrast, sample 9, which has been described above and does not include a colored pigment, has an opacity of approximately 51%. Many modifications and other embodiments of the invention set forth herein will occur to those skilled in the art to which these inventions pertain by having the benefit of the teachings presented in the foregoing descriptions and the related drawings. Therefore, it should be understood that the inventors are not limited to the specific embodiments described and that said modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (24)

NOVELTY OF THE INVENTION CLAIMS

1. - A non-woven sheet material comprising a layer of non-woven fabric including two-component filaments having a first and a second polymer component that are distributed in substantially different zones within the filaments, wherein the first polymeric component formed of a polymer with a relatively low melting point and the second component formed of a polymer with a relatively high melting point, the filaments of the non-woven fabric layer form a substantially smooth external surface on at least one side of sheet material non-woven, wherein the filaments are densely distributed and compacted together by calendering under heat and pressure to cause the polymeric component with a lower melting point to fuse to the contact surface portions of the adjacent filaments to impart strength and coherence to the nonwoven fabric layer, and where on the external surface substantially While a smooth portion, a substantial portion of the polymeric sheath component with lower melting point has flowed together to form an almost continuous film-like surface with small random micro-openings through which moisture vapor can be transmitted through the sheet material while It works as a barrier to the penetration of liquids.

2. - The non-woven sheet material according to claim 1, further characterized in that the film-like texture is present on one of the outer surfaces of the non-woven fabric layer and wherein the opposite outer surface of the non-woven fabric has a filamentous texture that has the appearance of flattened filaments.

3. The non-woven sheet material according to claim 1 or 2, further characterized in that the polymer of the lower melting point component comprises polyethylene and the polymer with the higher melting point component is selected from the group consisting of polypropylene, polyester and nylon.

4. The non-woven sheet material according to any of claims 1 to 3, further characterized in that it has a hydrostatic head of at least 15 cm.

5. The non-woven sheet material according to any of claims 1 to 4, further characterized by having air permeability, measured according to the ASTM D-1 117 test method, or 0 and 1.5 m3 / m2 / min (0 to 5 cfm / ft2 / min).

6. The non-woven sheet material according to any of claims 1 to 5, further characterized in that it has a moisture vapor transmission rate of at least 62 g / m2 / 24 hours (4 g / 100 inches2 / 24 hours) at a relative humidity (RH) of 50% and 23 ° C (73 ° F).

7. - The non-woven sheet material according to any of claims 1 to 6, further characterized in that it has a basis weight in the range of 10 to 150 gsm.

8. The non-woven sheet material according to any of claims 1 to 7, further characterized in that the filaments of the components are of a cross-sectional configuration of sheath-core, the filaments have a core component formed of a polymer with higher melting point and a sheath component formed of a polymer with lower melting point.

9. The non-woven sheet material according to any of claims 1 to 8, further characterized in that the polymer of the sheath component is polyethylene.

10. The non-woven sheet material according to claim 9, further characterized in that the polyethylene sheath component includes an antimicrobial agent incorporated therein.

11. The nonwoven sheet material according to claim 10, further characterized in that the antimicrobial agent comprises a thermally sensitive organic compound having a degradation temperature that is lower than the melting point temperature of the core and greater than the temperature of the core. melting point temperature of the pod.

12. The non-woven sheet material according to claim 10, further characterized in that the antimicrobial agent is selected from the group consisting of 2,4,4'-trichloro-2-hydroxydiphenol ether and 5-chloro-2-phenol (2,4-dichlorophenoxy) compounds.

13. The non-woven sheet material according to any of the preceding claims, further characterized in that it comprises a layer of meltblown polyethylene fibers superimposed on an outer surface of the nonwoven fabric layer and adhered thereto.

14. The non-woven sheet material according to any of claims 1 to 12, further characterized in that the sheet material comprises a first layer of the two-component filaments and a second layer of the two-component filaments wherein the filaments of components of the second layer include one or more pigments incorporated in the sheath polymer.

15. The non-woven sheet material according to claim 14, further characterized in that the sheet material has an opacity of at least 90 percent.

16. The non-woven sheet material according to any of claims 1 to 12, further characterized in that it comprises a layer of nanofibers superimposed on a surface of the non-woven fabric layer and adhered to it.

17. An envelope used in the construction of buildings, which is formed of the fabric of any of claims 1 to 12.

18. - A protective garment that is formed of the fabric according to any of claims 1 to 12.

19. A non-woven sheet material composed of multiple layers, comprising the non-woven sheet material in accordance with any of claims 1 to 12 laminated to at least one additional nonwoven fabric layer.

20. The multi-layer composite nonwoven sheet material according to claim 19, further characterized in that at least one additional nonwoven fabric layer is selected from the group consisting of a spunbonded nonwoven fabric and a fabric non-woven blown by fusion.

21. A ventilated nonwoven fabric having liquid barrier properties, comprising the non-woven sheet material according to any of claims 1 to 16, wherein the filaments have a sheath-core configuration, wherein the The sheath component comprises polyethylene or a copolymer thereof and the core component comprises polyester, polypropylene or copolymer thereof having a melting temperature greater than the sheath component.

22. The non-woven fabric according to claim 21, further characterized in that the fabric has a watertightness of at least 15 cm and a moisture vapor transmission rate of at least 20 g / m2 / 24 hours at a time. relative humidity (RH) of 50% and 23 ° C (73 ° F).

23. - The non-woven fabric according to claim 21 or 22, further characterized in that the sheath comprises from about 30 to 50% by weight of polyethylene and from about 50 to 70 weight percent of polyethylene terephthalate.

24. The non-woven fabric according to claim 21 or 22, further characterized in that the sheath comprises from about 30 to 50 weight percent polyethylene and from about 50 to 70 weight percent polypropylene.